U.S. patent application number 12/805038 was filed with the patent office on 2011-01-27 for image displaying apparatus and optical apparatus.
This patent application is currently assigned to Sony Corporation. Invention is credited to Kazuma Aiki, Katsuyuki Akutsu.
Application Number | 20110019250 12/805038 |
Document ID | / |
Family ID | 43497097 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110019250 |
Kind Code |
A1 |
Aiki; Kazuma ; et
al. |
January 27, 2011 |
Image displaying apparatus and optical Apparatus
Abstract
The image displaying apparatus includes an image production
apparatus, a first light conduction section and a second light
conduction section. The first light conduction section includes a
first light conduction plate which propagates part of incident
light thereto by total reflection in the inside thereof and emits
the propagated light, and a reflection type volume hologram
diffraction grating disposed on the first light conduction plate.
The second light conduction section includes a second light
conduction plate, a first deflection section and a second
deflection section.
Inventors: |
Aiki; Kazuma; (Tokyo,
JP) ; Akutsu; Katsuyuki; (Kanagawa, JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING, 1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
Sony Corporation
Tokyo
JP
|
Family ID: |
43497097 |
Appl. No.: |
12/805038 |
Filed: |
July 8, 2010 |
Current U.S.
Class: |
359/15 ; 359/633;
359/861 |
Current CPC
Class: |
G02B 5/32 20130101; G02B
6/0038 20130101; G02B 27/0172 20130101; G02B 6/00 20130101; G02B
5/1828 20130101; G02B 2027/0174 20130101; G02B 2027/0125
20130101 |
Class at
Publication: |
359/15 ; 359/861;
359/633 |
International
Class: |
G02B 27/01 20060101
G02B027/01; G02B 5/32 20060101 G02B005/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2009 |
JP |
2009-170730 |
Apr 27, 2010 |
JP |
2010-101615 |
Jun 30, 2010 |
JP |
2010-149346 |
Claims
1. An image displaying apparatus, comprising: (A) an image
production apparatus; (B) first light conduction means for
receiving, conducting and emitting a light emitted from said image
production apparatus; and (C) second light conduction means for
receiving and conducting light emitted from said first light
conduction means and then emitting the light toward the pupil of an
observer; said first light conduction means including (B-1) a first
light conduction plate for propagating part of the incident light
by total reflection in the inside thereof and emitting the light
therefrom, and (B-2) a reflection type volume hologram diffraction
grating disposed on said first light conduction plate, said second
light conduction means including (C-1) a second light conduction
plate configured to propagate incoming light in the inside thereof
by total reflection and then emit the light, (C-2) first deflection
means disposed in said second light conduction plate and adapted to
deflect light incident to said second light conduction plate such
that the light introduced to said second light conduction plate is
totally reflected in the inside of said second light conduction
plate, and (C-3) second deflection means disposed in said second
light conduction plate and adapted to deflect the light propagated
in the inside of said second light conduction plate by total
reflection over a plural number of times in order to emit the light
propagated in the inside of said second light conduction plate by
total reflection from said second light conduction plate.
2. The image displaying apparatus according to claim 1, wherein
said image production apparatus includes: (A-1) an image formation
apparatus having a plurality of pixels arrayed in a two-dimensional
matrix; and (A-2) a collimate optical system for converting light
emitted from the pixels of said image formation apparatus into
parallel light, and a light flux of the parallel light obtained by
the conversion by said collimate optical system is introduced to
said first light conduction means.
3. The image displaying apparatus according to claim 1, wherein
said image production apparatus includes: (A-1) a light source;
(A-2) a collimate optical system for converting light emitted from
said light source into parallel light; (A-3) scanning means for
scanning the parallel light emitted from said collimate optical
system; and (A-4) a relay optical system for relaying the parallel
light scanned by said scanning means, and a light flux of the
parallel light obtained by the conversion by said relay optical
system is introduced to said first light conduction means.
4. The image displaying apparatus according to claim 1, wherein,
where the light propagation direction by the total reflection in
the inside of said second light conduction plate is represented as
Y direction and the thicknesswise direction of said second light
conduction plate is represented as X direction, the light
propagation direction by the total reflection in the inside of said
first light conduction plate is a Z direction and the thicknesswise
direction of said first light conduction plate is the X direction,
and the beam diameter along the Z direction of the light emitted
from said first light conduction plate is greater than the beam
diameter along the'Z direction of the light incident to said first
light conduction plate.
5. The image displaying apparatus according to claim 1, wherein
said reflection type volume hologram diffraction grating is
disposed on a face of said first light conduction plate opposing to
said second light conduction plate, and part of the light incident
to said first light conduction plate is diffracted by said
reflection type volume hologram diffraction grating, totally
reflected once in the inside of said first light conduction plate,
totally reflected once on the surface of said reflection type
volume hologram diffraction grating, diffracted by said reflection
type volume hologram diffraction grating and then emitted from said
first light conduction plate while the remaining part of the light
incident to said first light conduction plate is emitted from said
first light conduction plate after passing through said first light
conduction plate and said reflection type volume hologram
diffraction grating.
6. The image displaying apparatus according to claim 1, wherein
said first light conduction means has a structure wherein said
first light conduction plate, said reflection type volume hologram
diffraction grating and a transparent parallel flat plate are
laminated in order from the light incidence side.
7. The image displaying apparatus according to claim 1, wherein
said first deflection means is configured from a diffraction
grating element.
8. The image displaying apparatus according to claim 7, wherein
said first deflection means is configured from a reflection type
volume hologram diffraction grating, and where the light
propagation direction by the total reflection in the inside of said
second light conduction plate is represented a Y direction and the
thicknesswise direction of said second light conduction plate is
represented as X direction, the diffraction direction by said
reflection type volume hologram diffraction grating which
configures said first deflection means is the Y direction and the
diffraction direction by said reflection type volume hologram
diffraction grating which configures said first light conduction
means is a Z direction.
9. The image displaying apparatus according to claim 8, further
comprising a phase difference plate disposed between the first
light conduction plate and the second light conduction plate and
configured to vary a phase difference of polarization components
outputted from said first light conduction plate.
10. The image displaying apparatus according to claim 9, wherein
the polarization components of the light passing through said phase
difference plate are in parallel to the Z direction.
11. The image displaying apparatus according to claim 1, wherein
said first deflection means diffracts the light incident to said
second light conduction plate, and said second deflection means
diffracts the light propagated in the inside of the second light
conduction plate by total reflection over a plural number of
times.
12. The image displaying apparatus according to claim 11, wherein
said first deflection means and said second deflection means are
individually configured from a diffraction grating element.
13. The image displaying apparatus according to claim 12, wherein
said diffraction grating element is configured from a reflection
type diffraction grating element.
14. The image displaying apparatus according to claim 12, wherein
said diffraction grating element is configured from a transmission
type diffraction grating element.
15. The image displaying apparatus according to claim 12, wherein
one of the diffraction grating elements is configured from a
reflection type diffraction grating element and the other one of
the diffraction grating elements is configured from a transmission
type diffraction grating element.
16. The image displaying apparatus according to claim 1, wherein
said first deflection means reflects the light incident to said
second light conduction plate; and said second deflection means
transmits and reflects the light propagated in the inside of said
second light conduction plate by total reflection over a plural
number of times.
17. The image displaying apparatus according to claim 16, wherein
said first deflection means functions as a reflecting mirror, and
said second deflection means functions as a half-mirror.
18. An optical apparatus, comprising: first light conduction means
for receiving, conducting and emitting a light flux; and second
light conduction means for receiving and conducting the light flux
emitted from said first light conduction means and then emitting
the light, said first light conduction means including (a-1) a
first light conduction plate for propagating part of the incident
light by total reflection in the inside thereof and emitting the
light therefrom, and (a-2) a reflection type volume hologram
diffraction grating disposed on said first light conduction plate,
said second light conduction means including (b-1) a second light
conduction plate configured to propagate incoming light in the
inside thereof by total reflection and then emit the light, (b-2)
first deflection means disposed in said second light conduction
plate for deflecting light incident to said second light conduction
plate such that the light introduced to said second light
conduction plate is totally reflected in the inside of said second
light conduction plate, and (b-3) second deflection means disposed
in said second light conduction plate for deflecting the light
propagated in the inside of said second light conduction plate by
total reflection over a plural number of times in order to emit the
light propagated in the inside of said second light conduction
plate by total reflection from said second light conduction
plate.
19. An image displaying apparatus, comprising: (A) an image
production apparatus; and (B) light conduction means for receiving
and conducting light outputted from said image production apparatus
and then emitting the light toward the pupil of an observer, said
light conduction means including (B-1) a light conduction plate for
propagating the incident light by total reflection in the inside
thereof and emitting the light therefrom, (B-2) first deflection
means disposed in said light conduction plate and adapted to
deflect the light incident to said light conduction plate so that
the light incident to said light conduction plate is totally
reflected in the inside of said light conduction plate, and (B-3)
second deflection means disposed in said light conduction plate and
adapted to deflect the light propagated in the inside of said light
conduction plate by total reflection over a plural number of times
in order to emit the light propagated in the inside of said light
conduction plate by total reflection from said light conduction
plate, said image displaying apparatus further comprising beam
expansion means for expanding, where an entering direction of the
light into said light conduction plate and a propagation direction
of the light in said light conduction plate are defined as an X
direction and a Y direction, respectively, the light emitted from
said image production apparatus along a Z direction and emitting
the expanded light to said light conduction means.
20. The image displaying apparatus according to claim 19, wherein
said beam expansion means is configured from a first reflecting
mirror and a second reflecting mirror, said first reflecting mirror
is positioned on the opposite side to said image production
apparatus with said light conduction means sandwiched therebetween,
and said second reflecting mirror is positioned adjacent said image
production apparatus with respect to said light conduction
means.
21. The image displaying apparatus according to claim 20, wherein
part of the light outputted from said image production apparatus
repetitively undergoes, in order by a predetermined number of
times, passage through said light conduction plate and said first
deflection means, reflection by said first reflecting mirror,
passage through said light conduction plate and said first
deflection means, reflection by said second reflecting mirror, and
passage of part of the light through said light conduction plate
and said first deflection means.
22. The image displaying apparatus according to claim 21, wherein
each of light reflecting faces of said first and second light
conduction plates which configure said beam expansion section has a
plurality of convex and concave portions which extend in planes
parallel to a plane defined by an X axis and a Z axis and have a
shape of a combination of adjacent sides to the right angle of a
right-angled triangle along the Y direction when it is assumed to
cut said concave and convex portions in planes defined by normal
lines to said first reflecting mirror and said second reflecting
mirror and a Y axis.
23. The image displaying apparatus according to claim 19, wherein
said beam expansion means is configured from a half-mirror and a
reflecting mirror, and said half-mirror and said reflecting mirror
are positioned adjacent said image production apparatus with
respect to said light conduction means.
24. The image displaying apparatus according to claim 23, wherein
part of the light emitted from said image production apparatus
passes through said half-mirror and introduced into said light
conduction plate and the remaining part of the light is reflected
on said half-mirror and introduced into said reflecting mirror, and
part of the light reflected on said reflecting mirror passes
through said half-mirror and introduced into said light conduction
plate while the remaining part of the light is reflected on said
half-mirror and introduced into said reflecting mirror, the passage
and reflection actions being repetitively carried out by a
predetermined number of times.
25. An optical apparatus, comprising: light conduction means for
receiving, conducting and emitting a light flux, said light
conduction means including a light conduction plate for propagating
the incident light by total reflection in the inside thereof and
emitting the light therefrom, first deflection means disposed in
said light conduction plate for deflecting the light incident to
said light conduction plate so that the light incident to said
light conduction plate is totally reflected in the inside of said
light conduction plate, and second deflection means disposed in
said light conduction plate for deflecting the light propagated in
the inside of said light conduction plate by total reflection over
a plural number of times in order to emit the light propagated in
the inside of said light conduction plate by total reflection from
said light conduction plate, said optical apparatus further
comprising beam expansion means for expanding, where an entering
direction of the light flux into said light conduction plate and a
propagation direction of the light in said light conduction plate
are defined as an X direction and a Y direction, respectively, the
light flux along a Z direction and emitting the expanded light to
said light conduction means.
26. An image displaying apparatus, comprising: (A) an image
production apparatus; (B) first light conduction means for
receiving, conducting and emitting a light emitted from said image
production apparatus; and (C) second light conduction means for
receiving and conducting light emitted from said first light
conduction means and then emitting the light toward the pupil of an
observer, said first light conduction means including (B-1) a first
light conduction plate for propagating part of the incident light
by total reflection in the inside thereof and emitting the light
therefrom, and (B-2) a reflection type volume hologram diffraction
grating disposed on said first light conduction plate, said second
light conduction means including (C-1) a second light conduction
plate configured to propagate incoming light in the inside thereof
by total reflection and then emit the light, (C-2) first deflection
means disposed in said second light conduction plate and adapted to
deflect light incident to said second light conduction plate, and
(C-3) second deflection means disposed in said second light
conduction plate and adapted to deflect the light propagated in the
inside of the second light conduction plate by total
reflection.
27. The image displaying apparatus according to claim 26, wherein
said reflection type volume hologram diffraction grating is
disposed on the face of said first light conduction plate opposing
to said second light conduction plate.
28. An image displaying apparatus, comprising: (A) an image
production apparatus; and (B) light conduction means for receiving
and conducting light outputted from said image production apparatus
and then emitting the light toward the pupil of an observer, said
light conduction means including (B-1) a light conduction plate for
propagating the incident light by total reflection in the inside
thereof and emitting the light therefrom, (B-2) first deflection
means disposed in said light conduction plate and adapted to
deflect light incident to said light conduction plate, and (B-3)
second deflection means disposed in said light conduction plate and
adapted to deflect the light propagated in the inside of said light
conduction plate by total reflection over a plural number of times,
said image displaying apparatus further comprising beam expansion
means for expanding, where an entering direction of the light into
said light conduction plate and a propagation direction of the
light in said light conduction plate are defined as a first
direction and a second direction, respectively, the light emitted
from said image production apparatus along a third direction
different from the first direction and the second direction and
emitting the expanded light to said light conduction means.
29. The image displaying apparatus according to claim 28, wherein
said beam expansion means is configured from at least two
reflecting mirrors positioned with said light conduction means
sandwiched therebetween.
30. An optical apparatus, comprising: a first light conduction
section configured to receive, conduct and emit a light flux; and a
second light conduction section configured to receive and conduct a
light flux emitted from said first light conduction section and
then emit the light, said first light conduction section including
(a-1) a first light conduction plate for propagating part of the
incident light by total reflection in the inside thereof and
emitting the light therefrom, and (a-2) a reflection type volume
hologram diffraction grating disposed on said first light
conduction plate, said second light conduction section including
(b-1) a second light conduction plate adapted to propagate incoming
light in the inside thereof by total reflection and then emit the
light, (b-2) a first deflection section disposed in said second
light conduction plate for deflecting light incident to said second
light conduction plate such that the light introduced to said
second light conduction plate is totally reflected in the inside of
said second light conduction plate, and (b-3) a second deflection
section disposed in said second light conduction plate for
deflecting the light propagated in the inside of said second light
conduction plate by total reflection over a plural number of times
in order to emit the light propagated in the inside of said second
light conduction plate by total reflection from said second light
conduction plate.
31. An optical apparatus, comprising: a light conduction section
configured to receive, conduct and emit a light flux, said light
conduction section including a light conduction plate for
propagating the incident light by total reflection in the inside
thereof and emitting the light therefrom, a first deflection
section disposed in said light conduction plate for deflecting the
light incident to said light conduction plate so that the light
incident to said light conduction plate is totally reflected in the
inside of said light conduction plate, and a second deflection
section disposed in said light conduction plate for deflecting the
light propagated in the inside of said light conduction plate by
total reflection over a plural number of times in order to emit the
light propagated in the inside of said light conduction plate by
total reflection from said light conduction plate, said optical
apparatus further comprising a beam expansion section configured to
expand, where an entering direction of the light flux into said
light conduction plate and a propagation direction of the light in
said light conduction plate are defined as an X direction and a Y
direction, respectively, the light flux along a Z direction and
emit the expanded light to said light conduction section.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an optical apparatus and an image
displaying apparatus in which the optical apparatus is
incorporated.
[0003] 2. Description of the Related Art
[0004] A virtual image displaying apparatus as an image displaying
apparatus wherein a virtual image optical system allows a
two-dimensional image formed by an image formation apparatus to be
observed as an enlarged virtual image by an observer is well known,
for example, from JP-T-2005-521099 and Japanese Patent Laid-Open
No. 2006-162767.
[0005] As conceptually illustrated in FIG. 25, the image displaying
apparatus 900 mentioned includes an image formation apparatus 911
including a plurality of pixels arranged in a two-dimensional
matrix, a collimate optical system 912 for converting light emitted
from the pixels of the image formation apparatus 911 into parallel
light and a light conduction section 930 for receiving, conducting
and emitting the parallel light from the collimate optical system
912. The light conduction section 930 includes a light conduction
plate 931 for propagating incident light in the inside thereof by
total reflection and then emitting the propagated light therefrom,
a first deflection section 940 formed, for example, from a
single-layer light reflecting film for reflecting the light
incident to the light conduction plate 931 such that the light
incident to the light conduction plate 931 is totally reflected in
the inside of the light conduction plate 931 and a second
deflection section 950 formed, for example, from a light reflecting
multi-layer film having a multi-layer lamination structure for
emitting the light propagated in the inside of the light conduction
plate 931 by total reflection from the light conduction plate 931.
If, for example, a head-mounted display (HMD) unit is formed from
such an image displaying apparatus 900 as described above, then
reduction in weight and size of the apparatus can be achieved.
[0006] Alternatively, a virtual image displaying apparatus as an
image displaying apparatus in which a hologram diffraction grating
is used in order to allow an observer to observe a two-dimensional
image formed by an image formation apparatus as an enlarged virtual
image by a virtual image optical system is known, for example, from
Japanese Patent Laid-Open No. 2007-094175 and Japanese Patent
Laid-Open No. 2007-012530.
[0007] As conceptually illustrated in FIGS. 26 and 27, the image
displaying apparatus 1000 mentioned above includes, as basic
components thereof, an image formation apparatus 1011 for
displaying an image, a collimate optical system 1012 and a virtual
image optical system or light conduction section 1030 which
receives light displayed by the image formation apparatus 1011 and
conducts the inputted light to the pupil 41 of an observer. The
light conduction section 1030 includes a light conduction plate
1031, and a first diffraction grating member 1040 and a second
diffraction grating member 1050 provided on the light conduction
plate 1031 and individually formed from a reflection type volume
hologram diffraction grating. Light emitted from pixels of the
image formation apparatus 1011 is inputted to the collimate optical
system 1012, and parallel light is produced by the collimate
optical system 1012 and then is introduced to the light conduction
plate 1031. The parallel light enters and outgoes from a first face
1032 of the light conduction plate 1031. Meanwhile, the first
diffraction grating member 1040 and the second diffraction grating
member 1050 are mounted on a second face 1033 of the light
conduction plate 1031 which extends in parallel to the first face
1032 of the light conduction plate 1031.
SUMMARY OF THE INVENTION
[0008] On an XY plane shown in FIG. 26, image displaying light
emitted from the image formation apparatus 1011 is converted into a
parallel light flux group wherein the angles of view, that is, the
outgoing angles of light emitted from the pixels of the image
formation apparatus 1011, are different from each other by the
collimate optical system 1012. The parallel light flux group is
converted into a light flux group wherein the angles of view are
different from each other on an XZ plane orthogonal to the XY plane
and is introduced to the light conduction plate 1031. It is to be
noted that, in FIG. 26, representative parallel light fluxes on the
XY plane are indicated by parallel light fluxes r.sub.1 represented
by a solid line, r.sub.2 represented by an alternate long and short
dash line and r.sub.3 represented by a broken line. Further, in
FIG. 27, representative parallel fluxes on the XZ plane are
indicated by parallel light fluxes R.sub.1 represented by a solid
line, R.sub.2 represented by an alternate long and short dash line
and R.sub.3 represented by a broken line.
[0009] In the image displaying apparatus 1000 shown in FIGS. 26 and
27, a leftward and rightward, that is, horizontal, direction and an
upward and downward, that is, vertical, direction are defined as a
Y direction and a Z direction, respectively. In particular, image
displaying light for displaying an image, various kinds of
information and so forth is conducted from a transverse direction
to the pupil 41 of an observer and enters the pupil 41. It is to be
noted that, where the image displaying apparatus 1000 is applied to
a head-mounted type display (HMD) unit, the image formation
apparatus and so forth are disposed not above the pupil 41 but in a
transverse direction with respect to the pupil 41 so that good
observation of the external world can be implemented.
[0010] On the other hand, with such a configuration as described
above, since the propagation distance of the light conducted in the
inside of the light conduction plate 1031 becomes comparatively
long, a problem given below appears.
[0011] Here, in the configuration described above, the image
displaying light inputted from the first face 1032 of the light
conduction plate 1031 is inputted to the first diffraction grating
member 1040 formed from a reflection type volume hologram
diffraction grating disposed on the second face 1033 which is a
position opposing to the first face 1032. It is to be noted that
the reflection type volume hologram diffraction grating has a
configuration having a uniform interference fringe pitch on the
hologram surface irrespective of a position.
[0012] Regarding an X direction component on the XY plane, the
light fluxes r.sub.1, r.sub.2 and r.sub.3 of the light diffraction
reflected by the first diffraction grating member 1040 in the light
conduction plate 1031 are conducted as parallel light fluxes while
repetitively totally reflecting between the first face 1032 and the
second face 1033, and advances in a Y direction toward the second
diffraction grating member 1050 formed from a reflection type
volume hologram diffraction grating and provided on the other end
of the light conduction plate 1031. Here, since the light
conduction plate 1031 is thin and a path of the light which
advances in the light conduction plate 1031 is comparatively long
as described above, the number of times of total reflection to the
second diffraction grating member 1050 is different depending upon
a horizontal angle of view as shown in FIG. 26. Therefore, the
number of times of reflection of the parallel light r.sub.3
inputted while inclining to the second diffraction grating member
1050 (that is, whose horizontal angle of view is positive) from
among the parallel light r.sub.1, r.sub.2 and r.sub.3 inputted to
the light conduction plate 1031 is smaller than the number of times
of reflection of the parallel light r.sub.1 inputted to the light
conduction plate 1031 with an angle in the opposite direction to
the direction of the parallel light r.sub.3 (that is, whose
horizontal angle of view is negative). In particular, since the
interference fringe pitch on the hologram surface of the first
diffraction grating member 1040 is uniform, regarding the outgoing
angle of diffraction reflection in the first diffraction grating
member 1040, the parallel light r.sub.3 whose horizontal angle of
view is positive is greater than the parallel light r.sub.1 whose
horizontal angle of view is negative. Then, the parallel light of
angles of view inputted to the second diffraction grating member
1050 goes beside from the total reflection condition by the
diffraction reflection, and is emitted from the light, conduction
plate 1031 and then inputted to the pupil 41 of the observer.
[0013] In this manner, in the advancing direction of the parallel
light fluxes, the number of times of reflection in the light
conduction plate 1031 is different depending upon the horizontal
angle of view. In other words, the optical path length is
different. However, since all of the propagated light fluxes are
parallel light fluxes, as it were, a light flux group advances in
such a manner as to be folded. As it is apparent if inverse ray
tracing is carried out in the configuration shown in FIG. 14 of
Japanese Patent Laid-Open No. 2007-12530, there exists a light flux
which is returned and reflected at a position extending over the
edge portion of the first diffraction grating member 1040 and the
second face 1033 from within the light flux group. If the inverse
ray tracing is carried out, then part of the light fluxes (that is,
a portion reflected on the second face 1033) is repetitively
reflected to be diffracted at a different position of the first
diffraction grating member 1040 to reach the collimate optical
system 1012. On the other hand, the remaining light fluxes are
diffracted at an end portion of the first diffraction grating
member 1040 to reach the collimate optical system 1012 as they are.
In particular, while the light fluxes are parallel light fluxes
emitted from the same pixel and having the same angles of view,
there exists a light flux which is diffraction reflected at a
different portion of the first diffraction grating member 1040 to
be multiplexed in the light conduction plate 1031 to propagate.
[0014] In this manner, the width regarding the Y direction of a
necessary light flux in such an optical system as described above,
that is, an aperture stop width in the Y direction, is determined
by an end point at which the light flux is folded. On the light
conduction plate 1031, the position of the first diffraction
grating member 1040 on which the parallel light flux group emitted
from the collimate optical system 1012 and inputted to the light
conduction plate 1031 is diffraction reflected is determined as the
aperture stop position in the Y direction.
[0015] On the other hand, regarding the incoming light R.sub.1,
R.sub.2 and R.sub.3 whose horizontal angles of view are different
from each other on the XZ plane, while the X direction component is
repetitively reflected in the light conduction plate 1031, the Z
direction component reaches an emerging portion without being
reflected. In particular, the light emitted from the collimate
optical system 1012 is converged and inputted from the first face
1032 on the XZ plane and then advances in the Y direction in the
light conduction plate 1031. Then, the light fluxes advance while
being reflected on the first face 1032 and the second face 1033 of
the light conduction plate 1031 so as to spread in the Z direction
until they come to the second diffraction grating member 1050.
Then, the light fluxes are reflected and diffracted by and then
emitted from the diffraction grating member 1050 so that they are
introduced to the pupil 41 of the observer. In this manner, in the
image displaying apparatus 1000, the necessary width of the light
fluxes in the Z direction, that is, the aperture stop width in the
Z direction, is determined depending upon the position of the pupil
41 of the observer.
[0016] Since the aperture stop position in the Z direction is the
position of the pupil 41 of the observer, the distance from the
collimate optical system 1012 to the aperture stop position in the
Z direction is equal to the sum of the distance over which the
light is repetitively totally reflected and propagated in the
inside of the light conduction plate 1031 and the distance from the
light conduction plate 1031 to the pupil 41 of the observer.
Therefore, the distance is very long. On the other hand, since the
aperture stop position in the Y direction is the position of the
first diffraction grating member 1040 disposed on the light
conduction plate 1031, the distance to the aperture stop position
in the Y direction can be made smaller than that to the aperture
stop position in the Z direction. In this manner, since the
distance to the aperture stop position is great in the Z direction,
the diameter of the collimate optical system 1012 in the Z
direction must be set greater than the diameter in the Y
direction.
[0017] Further, where the diameter of the aperture stop in the Z
direction in the image formation apparatus 911 and 1011 is set
great, the light ray angle of the peripheral angle of view becomes
great in an image emitted from the image formation apparatus 911
and 1011. As a result, the display contrast in a liquid crystal
display apparatus or the like used in the image formation apparatus
911 and 1011 decreases and makes a cause of degradation of the
picture quality.
[0018] Accordingly, it is desirable to provide an image displaying
apparatus which allows an observer to observe a two-dimensional
image formed by an image formation apparatus as an enlarged virtual
image by means of a virtual image optical system and wherein there
is no necessity to use a lens of a large diameter in the image
formation apparatus and an optical apparatus suitable to
incorporate in the image displaying apparatus.
[0019] According to a first mode of the present invention, there is
provided an image displaying apparatus including:
[0020] (A) an image production apparatus;
[0021] (B) a first light conduction section adapted to receive,
conduct and emit a light emitted from the image production
apparatus; and
[0022] (C) a second light conduction section adapted to receive and
conduct light emitted from the first light conduction section and
then emit the light toward the pupil of an observer,
[0023] the first light conduction section including [0024] (B-1) a
first light conduction plate for propagating part of the incident
light by total reflection in the inside thereof and emitting the
light therefrom, and [0025] (B-2) a reflection type volume hologram
diffraction grating disposed on the first light conduction
plate,
[0026] the second light conduction section including [0027] (C-1) a
second light conduction plate adapted to propagate incoming light
in the inside thereof by total reflection and then emit the light,
[0028] (C-2) a first deflection section disposed in the second
light conduction plate and adapted to deflect light incident to the
second light conduction plate such that the light introduced to the
second light conduction plate is totally reflected in the inside of
the second light conduction plate, and [0029] (C-3) a second
deflection section disposed in the second light conduction plate
and adapted to deflect the light propagated in the inside of the
second light conduction plate by total reflection over a plural
number of times in order to emit the light propagated in the inside
of the second light conduction plate by total reflection from the
second light conduction plate.
[0030] It is to be noted that the term "total reflection" is used
here and hereafter to signify internal total reflection or total
reflection in the inside of the first light conduction plate or of
the second light conduction plate.
[0031] According to the first mode of the present invention, there
is provided an optical apparatus including:
[0032] a first light conduction section configured to receive,
conduct and emit a light flux; and
[0033] a second light conduction section configured to receive and
conduct the light flux emitted from the first light conduction
section and then emit the light toward the pupil of an
observer,
[0034] the first light conduction section including [0035] (a-1) a
first light conduction plate for propagating part of the incident
light by total reflection in the inside thereof and emitting the
light therefrom, and [0036] (a-2) a reflection type volume hologram
diffraction grating disposed on the first light conduction
plate,
[0037] the second light conduction section including [0038] (b-1) a
second light conduction plate adapted to propagate incoming light
in the inside thereof by total reflection and then emit the light,
[0039] (b-2) first deflection section disposed in the second light
conduction plate for deflecting light incident to the second light
conduction plate such that the light introduced to the second light
conduction plate is totally reflected in the inside of the second
light conduction plate, and [0040] (b-3) second deflection section
disposed in the second light conduction plate for deflecting the
light propagated in the inside of the second light conduction plate
by total reflection over a plural number of times in order to emit
the light propagated in the inside of the second light conduction
plate by total reflection from the second light conduction
plate.
[0041] According to a second mode of the present invention, there
is provided an image displaying apparatus including:
[0042] (A) an image production apparatus; and
[0043] (B) a light conduction section configured to receive and
conduct light outputted from the image production apparatus and
then emit the light toward the pupil of an observer,
[0044] the light conduction section including [0045] (B-1) a light
conduction plate for propagating the incident light by total
reflection in the inside thereof and emitting the light therefrom,
[0046] (B-2) a first deflection section disposed in the light
conduction plate and adapted to deflect the light incident to the
light conduction plate so that the light incident to the light
conduction plate is totally reflected in the inside of the light
conduction plate, and [0047] (B-3) a second deflection section
disposed in the light conduction plate and configured to deflect
the light propagated in the inside of the light conduction plate by
total reflection over a plural number of times in order to emit the
light propagated in the inside of the light conduction plate by
total reflection from the light conduction plate,
[0048] the image displaying apparatus further including
[0049] a beam expansion section configured to expand, where an
entering direction of the light into the light conduction plate and
a propagation direction of the light in the light conduction plate
are defined as an X direction and a Y direction, respectively, the
light emitted from the image production apparatus along a Z
direction and emit the expanded light to the light conduction
section.
[0050] According to the second mode of the present invention, there
is provided an optical apparatus including:
[0051] a light conduction section configured to receive, conduct
and emit a light flux, [0052] the light conduction section
including a light conduction plate for propagating the incident
light by total reflection in the inside thereof and emitting the
propagated light therefrom, [0053] a first deflection section
disposed in the light conduction plate for deflecting the light
incident to the light conduction plate so that the light incident
to the light conduction plate is totally reflected in the inside of
the light conduction plate, and [0054] a second deflection section
disposed in the light conduction plate for deflecting the light
propagated in the inside of the light conduction plate by total
reflection over a plural number of times in order to emit the light
propagated in the inside of the light conduction plate by total
reflection from the light conduction plate,
[0055] the optical apparatus further including
[0056] beam expansion section configured to expand, where an
entering direction of the light flux into the light conduction
plate and a propagation direction of the light in the light
conduction plate are defined as an X direction and a Y direction,
respectively, the light flux along a Z direction and emit the
expanded light to the light conduction means.
[0057] According to another mode of the present invention, there is
provided an image displaying apparatus, including:
[0058] (A) an image production apparatus;
[0059] (B) a first light conduction section configured to receive,
conduct and emit a light emitted from the image production
apparatus; and
[0060] (C) a second light conduction section configured to receive
and conduct light emitted from the first light conduction section
and then emit the light toward the pupil of an observer,
[0061] the first light conduction section including [0062] (B-1) a
first light conduction plate for propagating part of the incident
light by total reflection in the inside thereof and emitting the
light therefrom, and [0063] (B-2) a reflection type volume hologram
diffraction grating disposed on the first light conduction
plate,
[0064] the second light conduction section including [0065] (C-1) a
second light conduction plate configured to propagate incoming
light in the inside thereof by total reflection and then emit the
light; [0066] (C-2) a first deflection section disposed in the
second light conduction plate and configured to deflect light
incident to the second light conduction plate, and [0067] (C-3) a
second deflection section disposed in the second light conduction
plate and configured to deflect the light propagated in the inside
of the second light conduction plate by total reflection.
[0068] According to a further mode of the present invention, there
is provided an image displaying apparatus, including:
[0069] (A) an image production apparatus; and
[0070] (B) a light conduction section configured to receive and
conduct light outputted from the image production apparatus and
then emit the light toward the pupil of an observer,
[0071] the light conduction section including [0072] (B-1) a light
conduction plate for propagating the incident light by total
reflection in the inside thereof and emitting the light therefrom,
[0073] (B-2) a first deflection section disposed in the light
conduction plate and configured to deflect light incident to the
light conduction plate, and [0074] (B-3) a second deflection
section disposed in the light conduction plate and configured to
deflect the light propagated in the inside of the light conduction
plate by total reflection over a plural number of times,
[0075] the image displaying apparatus further including
[0076] a beam expansion section configured to expand, where an
entering direction of the light into the light conduction plate and
a propagation direction of the light in the light conduction plate
are defined as a first direction and a second direction,
respectively, the light emitted from the image production apparatus
along a third direction different from the first direction and the
second direction and emit the expanded light to the light
conduction section.
[0077] It is to be noted that the "second light conduction section"
in the image displaying apparatus and the optical apparatus
according to the first mode of the present invention and the "light
conduction section" in the image displaying apparatus and the
optical apparatus according to the second mode of the present
invention are substantially same as each other. Thus, in the
description given hereinbelow, the "light conduction section" in
the image display apparatus and the optical apparatus according to
the second mode of the present invention is referred to as "second
light conduction section" for the convenience of description.
Similarly, the "second light conduction plate" in the image
displaying apparatus and the optical apparatus according to the
first mode of the present invention and the "light conduction
plate" in the image displaying apparatus and the optical apparatus
according to the second mode of the present invention are
substantially same as each other. Thus, in the description given
hereinbelow, the "light conduction plate" in the image display
apparatus and the optical apparatus according to the second mode of
the present invention is referred to as "second light conduction
plate" for the convenience of description.
[0078] In the image displaying apparatus and the optical apparatus
according to the first mode of the present invention, the first
light conduction section is disposed between the image production
apparatus and the second light conduction section and is configured
from the first light conduction plate and the reflection type
volume hologram diffraction grating. Accordingly, the first light
conduction section functions as a kind of beam expander, that is,
as a kind of beam expansion means, and the shape of a light flux
emitted from the image production apparatus and introduced into the
first light conduction section is expanded along the light
propagation direction by the internal total reflection in the first
light conduction plate by the reflection type volume hologram
diffraction grating. Then, the light flux of the expanded form is
introduced into the second light conduction section. On the other
hand, the image displaying apparatus and the optical apparatus
according to the second mode of the present invention include the
beam expansion section for expanding light or a light flux in the Z
direction and introducing the expanded light or light flux to the
light conduction section. Therefore, the necessity for setting the
diameter of the aperture stop in the Z direction of the image
production apparatus to a large diameter is eliminated, and the
necessity to use a lens of a large diameter in the image production
apparatus is eliminated. Consequently, reduction in size and weight
of the image displaying apparatus can be anticipated, and such a
situation that the display contrast drops and the picture quality
is deteriorated is prevented. Further, while the first light
conduction section is formed from the reflection type volume
hologram diffraction grating, since interference fringes formed on
the reflection type volume hologram diffraction grating have a
uniform angle and exhibit uniform refractive index modulation over
the entirety thereof, there is no necessity for alignment which is
difficult and a dispersion is less likely to occur.
[0079] The above and other objects, features and advantages of the
present invention will become apparent from the following
description and the appended claims, taken in conjunction with the
accompanying drawings in which like parts or elements denoted by
like reference symbols.
BRIEF DESCRIPTION OF THE DRAWINGS
[0080] FIG. 1 is a schematic view conceptually showing an image
displaying apparatus of an embodiment 1;
[0081] FIG. 2 is a similarly view but conceptually showing an image
displaying apparatus of an embodiment 2;
[0082] FIG. 3A is a view conceptually showing an image displaying
apparatus of an embodiment 3, and FIG. 3B is an enlarged schematic
sectional view showing part of a reflection type volume hologram
diffraction grating of the image displaying apparatus of FIG.
3A;
[0083] FIG. 4 is a schematic view conceptually showing an image
displaying apparatus of an embodiment 4;
[0084] FIG. 5A is a view schematically showing an arrangement state
of an image production apparatus, a first light conduction section
and a second light conduction section, and FIG. 5B is a schematic
view conceptually showing the first light conduction section in
section;
[0085] FIG. 6 is a schematic view of a head-mounted type display
unit of an embodiment 5 as viewed from the front;
[0086] FIG. 7 is a schematic view of the head-mounted type display
unit of FIG. 6 as viewed from the front with a frame removed;
[0087] FIG. 8 is a schematic view of the head-mounted type display
unit of FIG. 6 as viewed from above;
[0088] FIG. 9 is a schematic view, as viewed from above, of the
head-mounted type display unit of FIG. 6 mounted on the head of an
observer showing only the image displaying apparatus with the frame
omitted;
[0089] FIG. 10 is a schematic view of a head-mounted type display
unit of an embodiment 6 as viewed from the front;
[0090] FIG. 11 is a schematic view of the head-mounted type display
unit of FIG. 10 as viewed from the front with a frame removed;
[0091] FIG. 12 is a schematic view of the head-mounted type display
unit of FIG. 10 as viewed from above;
[0092] FIGS. 13A and 13B are views schematically showing
arrangement states of an image production apparatus, a beam
expansion section and a light conduction section in an embodiment 7
and an embodiment 8;
[0093] FIG. 14 is a schematic view conceptually showing an image
displaying apparatus of the embodiment 7;
[0094] FIG. 15 is a schematic view conceptually showing a
modification to the image displaying apparatus of FIG. 14;
[0095] FIG. 16 is a schematic view conceptually showing an image
displaying apparatus of the embodiment 8;
[0096] FIGS. 17, 18 and 19 are similar views but showing different
modifications to the image displaying apparatus of FIG. 16;
[0097] FIG. 20 is a view of a modification to an image formation
apparatus suitable for use in image displaying apparatus of FIG. 1
or FIG. 3A;
[0098] FIGS. 21, 22, 23 and 24 are similar views but showing
several modifications to the image formation apparatus suitable of
FIG. 20;
[0099] FIG. 25 is a schematic view conceptually showing a
conventional image displaying apparatus;
[0100] FIG. 26 is a schematic view conceptually showing another
conventional image displaying apparatus;
[0101] FIG. 27 is a view of the conventional image displaying
apparatus of FIG. 25 as viewed from a direction different from that
in FIG. 26;
[0102] FIGS. 28A and 28B are schematic views of an arrangement
state of an image production apparatus, a beam expansion section
and a light conduction section in a working example 9 as viewed in
a Y direction and a Z direction, respectively;
[0103] FIGS. 29A and 29B are schematic partial sectional views of
the beam expansion section in the working example 9 and FIG. 29C is
a schematic view illustrating a state in which light is reflected
by the beam expansion section in the working example 9; and
[0104] FIGS. 30A and 30B are schematic views illustrating an
arrangement state of the image production apparatus, the beam
expansion section and the light conduction section in the working
example 7 as viewed in a Y direction and a Z direction,
respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0105] In the following, the present invention is described in
detail in connection with several embodiments thereof with
reference to the accompanying drawings. It is to be noted, however,
that the present invention is not limited to the embodiments and
various numerical values and materials applied in the embodiments
are given for illustrative purpose only. It is to be noted that the
description is given in the following order.
1. General Description of the Image Displaying Apparatus, Optical
Apparatus and Head-Mounted Type Display Unit of the Invention
[0106] 2. Embodiment 1 (image displaying apparatus and optical
apparatus according to the first mode of the invention) 3.
Embodiment 2 (modification to the embodiment 1) 4. Embodiment 3
(different modification to the embodiment 1) 5. Embodiment 4
(modification to the embodiment 3) 6. Embodiment 5 (head-mounted
type display unit) 7. Embodiment 6 (modification to the
head-mounted type display unit) 8. Embodiment 7 (image displaying
apparatus and optical apparatus according to the second mode of the
invention) 9. Embodiment 8 (modification to the embodiment 7) 10.
Embodiment 9 (modification to the Embodiment 7) and others
General Description of the Image Displaying Apparatus and the
Optical Apparatus of the Invention
[0107] The image display apparatus according to the first mode or
the second mode of the present invention may be configured such
that the image production apparatus includes:
[0108] (A-1) an image formation apparatus having a plurality of
pixels arrayed in a two-dimensional matrix; and
[0109] (A-2) a collimate optical system for converting light
emitted from the pixels of the image formation apparatus into
parallel light; and
[0110] a light flux of the parallel light obtained by the
conversion by the collimate optical system is introduced to the
first light conduction section or the beam expansion section. It is
to be noted that the image production apparatus having such a
configuration as just described is hereinafter referred to as
"image production apparatus of the first form."
[0111] Alternatively, the image display apparatus according to the
first mode or the second mode of the present invention may be
configured such that the image production apparatus includes:
[0112] (A-1) a light source;
[0113] (A-2) a collimate optical system for converting light
emitted from the light source into parallel light;
[0114] (A-3) a scanning section for scanning the parallel light
emitted from the collimate optical system; and
[0115] (A-4) a relay optical system for relaying the parallel light
scanned by the scanning section; and
[0116] a light flux of the parallel light obtained by the
conversion by the relay optical system is introduced to the first
light conduction section or the beam expansion section. It is to be
noted that the image production apparatus having such a
configuration as just described is hereinafter referred to as
"image production apparatus of the second form."
[0117] The image displaying apparatus according to the first mode
of the present invention including the image production apparatus
of the first form and the image production apparatus of the second
form (such image displaying apparatus may be hereinafter referred
to generally as "image displaying apparatus according to the first
mode") may be configured such that, where the light propagation
direction by the total reflection in the inside of the second light
conduction plate is represented as Y direction and the
thicknesswise direction of the second light conduction plate is
represented as X direction, the light propagation direction by the
total reflection in the inside of the first light conduction plate
is a Z direction and the thicknesswise direction of the first light
conduction plate is the X direction, and the beam diameter along
the Z direction of the light emitted from the first light
conduction plate is greater than the beam diameter along the Z
direction of the light incident to the first light conduction
plate. It is to be noted that, where an optically reflecting
element such as a mirror is disposed between the first light
conduction plate and the second light conduction plate so that
light emitted from the first light conduction plate is introduced
in a variously varied direction to the second light conduction
plate, the relationship of the X, Y and Z directions of the first
light conduction plate to those of the second light conduction
plate should be determined based on the behavior of light when it
is assumed that the optical reflecting element such as a mirror is
removed. This similarly applies also to the description given
below. Also in the image displaying apparatus according to the
second mode of the present invention including the image production
apparatus of the first form and the image production apparatus of
the second form (such image displaying apparatus may be hereinafter
referred to generally as "image displaying apparatus according to
the second mode"), the beam diameter along the Z direction of light
emitted from the entire beam expansion section is greater than the
beam diameter in the Z direction of light incident to the beam
expansion section.
[0118] The image display apparatus and so forth according to the
first mode of the present invention including the preferred forms
described above may be configured such that the reflection type
volume hologram diffraction grating is disposed on a face of the
first light conduction plate opposing to the second light
conduction plate; and part of the light incident to the first light
conduction plate is diffracted by the reflection type volume
hologram diffraction grating, totally reflected once in the inside
of the first light conduction plate, totally reflected once on the
surface of the reflection type volume hologram diffraction grating,
diffracted by the reflection type volume hologram diffraction
grating and then emitted from the first light conduction plate
while the remaining part of the light incident to the first light
conduction plate is emitted from the first light conduction plate
after passing through the first light conduction plate and the
reflection type volume hologram diffraction grating. It is to be
noted that such a behavior of light in the first light conduction
section as described above is hereinafter referred to as "emission
of the light from the first light conduction section by two times
of total reflection" for the convenience of description. The
interference fringes formed on the reflection type volume hologram
diffraction grating should be optimized so that such a Bragg
condition that part of the light incident to the first light
conduction plate is diffracted by the reflection type volume
hologram diffraction grating, totally reflected once in the inside
of the first light conduction plate, totally reflected once on the
surface of the reflection type volume hologram diffraction grating,
diffracted by the reflection type volume hologram diffraction
grating and then emitted from the first light conduction plate may
be satisfied.
[0119] However, the configuration of the reflection type volume
hologram diffraction grating is not limited to that described
above. In other words, the configuration the reflection type volume
hologram diffraction grating is not limited to the configuration
wherein all of part of the light incident to the first light
conduction plate is emitted from the first light conduction section
by the emission of the light from the first light conduction
section by two times of total reflection. In particular, the
reflection type volume hologram diffraction grating may be
configured otherwise such that the light is totally reflected in
the inside of the first light conduction plate, totally reflected
on the surface of the reflection type volume hologram diffraction
grating, totally reflected in the inside of the first light
conduction plate again, totally reflected on the surface of the
reflection type volume hologram diffraction grating again,
diffracted by the reflection type volume hologram diffraction
grating and then emitted from the first light conduction plate. In
other words, the reflection type volume hologram diffraction
grating may be configured such that part of the part of the light
incident to the first light conduction plate is emitted by the
"emission of the light from the first light conduction plate by two
times of total reflection" and the remaining part of the part of
the light incident to the first light conduction plate is emitted
by "emission of the light from the first light conduction section
by four times of total reflection." Further, the reflection type
volume hologram diffraction grating may be configured otherwise
such that emission of the light from the first light conduction
section by a greater plural number of times of total reflection may
occur.
[0120] Where all of the part of the light entering the first light
conduction plate by the emission of the light from the first light
conduction section by two times of total reflection" is emitted,
preferably the light amount of the part of the light and the light
amount of the remaining part of the light in the first light
conduction plate is equal to each other from the point of view of
achieving uniformity in intensity distribution of light emitted
from the entire first light conduction section. To this end,
preferably
T(1-.eta.)=(T.eta.).sup.2
where .eta. is the reflection efficiency of the reflection type
volume hologram diffraction grating which composes the first light
conduction section and T is the light transmission factor of the
reflection type volume hologram diffraction grating. In particular,
where T=1, preferably
.eta.=0.62
is satisfied. In order to achieve this, optimization of selection
of a material for forming the reflection type volume hologram
diffraction grating, optimization of the thickness of the
reflection type volume hologram diffraction grating and
optimization of the refractive index modulation degree .DELTA.n of
the reflection type volume hologram diffraction grating should be
carried out.
[0121] Further, the image displaying apparatus and so forth
according to the first mode of the present invention including the
preferred forms and configurations described above may be
structured such that the first light conduction section has a
structure wherein the first light conduction plate, the reflection
type volume hologram diffraction grating and a transparent parallel
flat plate are laminated in order from the light incidence side. In
particular, that the reflection type volume hologram diffraction
grating is sandwiched by the first light conduction plate and the
transparent parallel flat plate is preferable from the point of
view of protection of the reflection type volume hologram
diffraction grating, prevention of scattering of light and
prevention of a drop of the contract and deterioration of the
resolution.
[0122] Alternatively, the image displaying apparatus and so forth
according to the first mode of the present invention including the
preferred forms and configurations described above may be
configured such that the first deflection section is configured
from a diffraction grating element. In this instance, the image
displaying apparatus may be configured such that the first
deflection section is configured from a reflection type volume
hologram diffraction grating; and where the light propagation
direction by the total reflection in the inside of the second light
conduction plate is represented a Y direction and the thicknesswise
direction of the second light conduction plate is represented as X
direction, the direction in which the interference fringes of the
reflection type volume hologram diffraction grating which
configures the first deflection section are juxtaposed, that is,
the diffraction direction, is the Y direction and the direction in
which the interference fringes of the reflection type volume
hologram diffraction grating which configures the first light
conduction section are juxtaposed, that is, the diffraction
direction, is a Z direction. Further, in this instance or in such a
configuration as just described, image displaying apparatus and so
forth may further include a phase difference plate disposed between
the first light conduction plate and the second light conduction
plate and adapted to vary a phase difference of polarization
components outputted from the first light conduction plate.
Furthermore, the image displaying apparatus may be configured such
that the polarized light components of the light passing through
the phase difference plate are parallel to the Z direction, that
is, the phase difference plate is disposed such that a polarized
light component of the light to enter the first deflection section
becomes parallel to the Z direction. Further, the image displaying
apparatus may be configured such that a second phase difference
plate for varying the phase difference of polarized light
components emitted from the collimate optical system or the relay
optical system is disposed between the collimate optical system or
the relay optical system and the first light conduction plate.
Furthermore, the image displaying apparatus may be configured such
that the polarized light components of the light passing through
the second phase difference plate are parallel to the Y direction,
that is, the second phase difference plate is disposed such that a
polarized light component of the light to enter the first light
conduction plate becomes parallel to the Y direction.
[0123] Alternatively, the image display apparatus and so forth
according to the first mode or the second mode of the present
invention including the preferred forms and configurations
described above may be configured such that the first deflection
section diffracts the light incident to the second light conduction
plate; and the second deflection section diffracts the light
propagated in the inside of the second light conduction plate by
total reflection over a plural number of times. In this instance,
the image displaying apparatus and so forth may be configured such
that the first deflection section and the second deflection section
are individually configured from a diffraction grating element.
Furthermore, the image displaying apparatus and so forth may be
configured such that the diffraction grating element is configured
from a reflection type diffraction grating element, or the
diffraction grating element is configured from a transmission type
diffraction grating element, or else one of the diffraction grating
elements is configured from a reflection type diffraction grating
element and the other one of the diffraction grating elements is
configured from a transmission type diffraction grating
element.
[0124] Or, the image display apparatus and so forth according to
the first mode or the second mode of the present invention
including the preferred forms and configurations described above
may be configured such that the first deflection section reflects
the light incident to the second light conduction plate; and the
second deflection section transmits and reflects the light
propagated in the inside of the second light conduction plate by
total reflection over a plural number of times. In this instance,
the image display apparatus and so forth may be configured such
that the first deflection section functions as a reflecting mirror;
and the second deflection section functions as a half-mirror.
[0125] Meanwhile, the image display apparatus or the optical
apparatus according to the second mode of the present invention
including the preferred forms and configurations described above
may be configured such that the beam expansion section is
configured from a first reflecting mirror and a second reflecting
mirror;
[0126] the first reflecting mirror is positioned on the opposite
side to the image production apparatus with the light conduction
section sandwiched therebetween (in other words, positioned on the
opposite side to the light incidence side of the light conduction
section); and
[0127] the second reflecting mirror is positioned adjacent the
image production apparatus with respect to the light conduction
section (in other words, positioned on the light incidence side of
the light conduction section). Further, in this instance, the image
display apparatus or the optical apparatus may be configured such
that part of the light emerging from the image production apparatus
repetitively undergoes, in order by a predetermined number of
times, passage through the light conduction plate and the first
deflection section, reflection by the first reflecting mirror,
passage through the light conduction plate and the first deflection
section, reflection by the second reflecting mirror, and passage of
part of the light through the light conduction plate and the first
deflection section.
[0128] Here, each of light reflecting faces of the first and second
reflecting mirrors which configure the beam expansion section may
be smooth or may have a plurality of convex and concave portions.
In the latter case, preferably the convex and concave portions
extend in planes parallel to a plane defined by an X axis and a Z
axis and have a shape of a combination of adjacent sides to the
right angle of a right-angled triangle (such adjacent sides are
hereinafter referred to merely as "adjacent sides") along the Y
direction when it is assumed to cut the concave and convex portions
in planes defined by normal lines to the first reflecting mirror
and the second reflecting mirror and a Y axis. In particular, each
of the convex and concave portions preferably extends in parallel
to the plane defined by the X axis and the Z axis and has a shape
of a right-angular prism having a vertical angle of 90 degrees. It
is to be noted that a reflecting mirror of the type described is
also called reversal mirror. The right-angle triangle may be a
right-angled isosceles triangle having adjacent sides which are
equal in length to each other or a right-angled triangle having
adjacent sides which are different from each other. In particular,
adjacent sides of right-angled triangles of the same shape may be
juxtaposed along the Y direction or adjacent sides of right-angled
triangles of different shapes may be juxtaposed along the Y
direction. In particular, in the former case, each of the convex
and concave portions may be configured such that, for example, the
adjacent sides of the right-angled isosceles triangles are
juxtaposed. On the other hand, in the latter case, each of the
convex and concave portions may be configured such that, for
example, the adjacent sides of each right-angled isosceles triangle
are juxtaposed on the central region of the light reflecting face,
the adjacent sides of each right-angled scalene triangle are
juxtaposed on the right side of a central region of the light
reflecting face while the adjacent sides of each of the
right-angled scalene triangles symmetrical to those on the right
side of the central region of the light reflecting face are
juxtaposed on the left side of the central region of the light
reflecting face.
[0129] Here, an edge line of the light reflecting face
corresponding to the right angle of the right-angled triangle
extends in parallel to the plane defined by the X axis and the Z
axis. For the convenience of description, the two inclined faces of
the light reflecting face corresponding to the adjacent sides to
the right angle of a right-angled triangle are hereinafter referred
to individually as "first inclined face" and "second inclined
face." Light incoming to the first reflecting mirror collides with
and is reflected by the first inclined face and then collides with
and is reflected by the second inclined face, whereafter it emerges
from the first reflecting mirror. Or, light incoming to the first
reflecting mirror collides with and is reflected by the second
inclined face and then collides with and is reflected by the first
inclined face, whereafter it emerges from the first reflecting
mirror. The light incoming to the first inclined face and the light
emerging from the second inclined face are parallel. Similarly,
light incoming to the second reflecting mirror collides with and is
reflected by the first inclined face and then collides with and is
reflected by the second inclined face, whereafter it emerges from
the second reflecting mirror. Or, light incoming to the first
reflecting mirror collides with and is reflected by the second
inclined face and then collides with and is reflected by the first
inclined face, whereafter it emerges from the first reflecting
mirror. The light incoming to the first inclined face and the light
emerging from the second inclined face are parallel. Although
reflection of light is repeated between the first reflecting mirror
and the second reflecting mirror, the colliding point of the light
flux with the first reflecting mirror and the colliding point of
the light flux with the second reflecting mirror do not move in the
Y direction in principle but merely move in the X direction and the
Z direction. Therefore, the necessity to set the diameter of the
aperture stop in the Y direction of the image production apparatus
to a great diameter is eliminated.
[0130] It is to be noted that, where the light reflecting faces of
the first reflecting mirror and the second reflecting mirror are
smooth, a light reflecting layer is provided on the light
reflecting faces. Meanwhile, where each of the light reflecting
faces of the first reflecting mirror and the second reflecting
mirror has a plurality of convex and concave portions, a light
reflecting layer may be or may not be provided on the light
reflecting face. In the former case, light can be reflected without
allowing the light to be admitted into the inside of the first
reflecting mirror and the second reflecting mirror. Alternatively,
light can be reflected by allowing the light to be admitted into
the inside of the first reflecting mirror and the second reflecting
mirror. On the other hand, in the latter case, light should be
introduced into the inside of the first reflecting mirror and the
second reflecting mirror so that light is totally reflected by the
first inclined face and the second inclined face.
[0131] Alternatively, the image display apparatus or the optical
apparatus according to the second mode of the present invention
including the preferred forms and configurations described above
may be configured such that the beam expansion section is
configured from a half-mirror and a reflecting mirror; and the
half-mirror and the reflecting mirror are positioned adjacent the
image production apparatus with respect to the light conduction
section (in other words, positioned on the light incidence side of
the light conduction section). Further, in this instance, the image
displaying apparatus or the optical apparatus may be configured
such that part of the light emitted from the image production
apparatus passes through the half-mirror and introduced into the
light conduction plate and the remaining part of the light is
reflected on the half-mirror and introduced into the reflecting
mirror, and part of the light reflected on the reflecting mirror
passes through the half-mirror and introduced into the light
conduction plate while the remaining part of the light is reflected
on the half-mirror and introduced into the reflecting mirror; the
passage and reflection actions being repetitively carried out by a
predetermined number of times.
[0132] The image formation apparatus of the image production
apparatus in the first mode may be, for example, an image formation
apparatus which includes a reflection type spatial light modulation
apparatus and a light source, another image information apparatus
which includes a transmission type spatial light modulation
apparatus and a light source or a further image formation apparatus
which includes light emitting elements such as organic EL (Electro
Luminescence) elements, inorganic EL elements or light emitting
diodes (LEDs). Among them, the image formation apparatus which
includes a reflection type spatial light modulation apparatus and a
light source is used preferably. The spatial light modulation
apparatus may be, for example, a liquid crystal display apparatus
of the transmission type or the reflection type which includes
light valves such as, for example, LCOS (Liquid Crystal On Silicon)
light valves or a digital micromirror device (DMD), and the light
source may be a light emitting element. Further, the reflection
type spatial light modulation apparatus may include a liquid
crystal display apparatus, and a beam splitter for reflecting part
of light from a light source so as to be introduced to the liquid
crystal display apparatus and passing part of the light reflected
by the liquid crystal display apparatus therethrough so as to be
introduced to the collimator optical system. The light emitting
element which forms the light source may be a red light emitting
element, a green light emitting element, a blue light emitting
element or a white light emitting element. Further, the light
emitting element may be, for example, a semiconductor laser
element, a solid-state laser or an LED. The number of pixels may be
determined based on specifications required for the image
displaying apparatus. The particular value of the number of pixels
may be 320.times.240, 432.times.240, 640.times.480, 854.times.480,
1024.times.768 or 1920.times.1080. The collimate optical system has
a function of converting position information of a pixel into angle
information of the optical system of the second light conduction
section. The collimate optical system may be a convex lens, a
concave lens, a free-form surface prism or a hologram lens which
are used singly or in combination so that the optical system may
have a positive optical power as a whole.
[0133] Meanwhile, the light source of the image production
apparatus in the second mode may be a light emitting element and
particularly a red light emitting element, a green light emitting
element, a blue light emitting element or a white light emitting
element. Further, the light emitting element may be, for example, a
semiconductor laser element, a solid-state laser or an LED. The
number of pixels or virtual pixels of the image displaying
apparatus of the second mode may be determined based on
specifications required for the image displaying apparatus. The
particular value of the number of pixels or virtual pixels may be
320.times.240, 432.times.240, 640.times.480, 854.times.480,
1024.times.768 or 1920.times.1080. Where the light source is formed
from a red light emitting element, a green light emitting element
and a blue light emitting element, preferably, for example, a cross
prism is used to carry out color synthesis. The scanning section
carries out horizontal scanning and vertical scanning of the light
emitted from the light source. For example, a MEMS (Micro Electro
Mechanical System) having micromirrors rotatable in two-dimensional
directions or a galvano mirror may be used. The relay optical
system may be formed from a well-known relay optical system.
[0134] For example, as an image formation apparatus or a light
source which is configured from a light emitting element and a
light valve, the following configurations may be applied in
addition to a backlight which generally emits white light and a
liquid crystal display apparatus which includes red light emitting
elements, green light emitting elements and blue light emitting
elements.
Image Formation Apparatus A
[0135] The image formation apparatus A includes:
(.alpha.) a first image formation apparatus which includes a first
light emitting panel wherein a plurality of first light emitting
elements for emitting blue light are arrayed in a two-dimensional
matrix; (.beta.) a second image formation apparatus which includes
a second light emitting panel wherein a plurality of second light
emitting elements for emitting green light are arrayed in a
two-dimensional matrix; (.gamma.) a third image formation apparatus
which includes a third light emitting panel wherein a plurality of
third light emitting elements for emitting red light are arrayed in
a two-dimensional matrix; and (.delta.) a section configured to
integrate light emitting from the first, second and third image
formation apparatus into a single light flux (such means may be a
dichroic prism; this similarly applies also in the following
description), and
[0136] the light emitting/no-light emitting state of each of the
first, second and third light emitting elements is controlled.
Image Formation Apparatus B
[0137] The image formation apparatus B includes:
(.alpha.) a first image formation apparatus which includes a first
light emitting element for emitting blue light, and a first light
passage controlling apparatus for controlling passage/non-passage
therethrough of the emitted light emitted from the first light
emitting element for emitting blue light (the first light passage
controlling apparatus is a kind of light valve which is formed, for
example, from a liquid crystal display device, a digital
micromirror device (DMD) or an LCOS device; this similarly applies
also in the following description); (.beta.) a second image
formation apparatus which includes a second light emitting element
for emitting green light, and a second light passage controlling
apparatus (light valve) for controlling passage/non-passage
therethrough of the emitted light emitted from the second light
emitting element for emitting green light; (.gamma.) a third image
formation apparatus which includes a third light emitting element
for emitting red light, and a third light passage controlling
apparatus (light valve) for controlling passage/non-passage
therethrough of the emitted light emitted from the third light
emitting element for emitting red light; and (.delta.) a section
configured to integrate the light passing through the first, second
and third light passage controlling apparatus into a single light
flux, and
[0138] the passage/non-passage of the emitted light emitted from
the light emitting elements is controlled by the light passage
controlling apparatus to display an image. As a section (material)
for conducting the emitted light emitted from the first, second and
third light emitting elements to the light passage controlling
apparatus, a light conduction member, a microlens array, a mirror,
a reflecting plate or a condensing lens may be used.
Image Formation Apparatus C
[0139] The image formation apparatus C includes:
(.alpha.) a first image formation apparatus which includes a first
light emitting panel wherein a plurality of first light emitting
elements for emitting blue light are arrayed in a two-dimensional
matrix and a blue light passage controlling apparatus (light valve)
for controlling passage/non-passage of the emitted light emitted
from the first light emitting panel; (.beta.) a second image
formation apparatus which includes a second light emitting panel
wherein a plurality of second light emitting elements for emitting
green light are arrayed in a two-dimensional matrix and a green
light passage controlling apparatus (light valve) for controlling
passage/non-passage of the emitted light emitted from the second
light emitting panel; (.gamma.) a third image formation apparatus
which includes a third light emitting panel wherein a plurality of
third light emitting elements for emitting red light are arrayed in
a two-dimensional matrix and a red light passage controlling
apparatus (light valve) for controlling passage/non-passage of the
emitted light emitted from the third light emitting panel; and
(.delta.) a section configured to integrate the light passing
through the blue, green and red light passage controlling apparatus
into a single light flux, and
[0140] the passage/non-passage of the emitted light emitted from
the first, second and third light emitting panels is controlled by
the light passage controlling apparatus (light valve) to display an
image.
Image Formation Apparatus D
[0141] The image formation apparatus D is a color display image
formation apparatus of the field sequential type and includes:
(.alpha.) a first image formation apparatus including a first light
emitting element for emitting blue light; (.beta.) a second image
formation apparatus including a second light emitting element for
emitting green light; (.gamma.) a third image formation apparatus
including a third light emitting element for emitting red light;
(.delta.) a section configured to integrate the light emitted from
the first, second and third image formation apparatus into a single
light flux; and (.di-elect cons.) a light passage controlling
apparatus (light valve) for controlling passage/non-passage of the
emitted light emitted from the integrating section, and
[0142] the passage/non-passage of the emitted light emitted from
the light emitting elements is controlled by the light passage
controlling apparatus to display an image.
Image Formation Apparatus E
[0143] Also the image formation apparatus E is a color display
image formation apparatus of the field sequential type and
includes:
(.alpha.) a first image formation apparatus including a first light
emitting panel wherein a plurality of first light emitting elements
for emitting blue light are arrayed in a two-dimensional matrix;
(.beta.) a second image formation apparatus including a second
light emitting panel wherein a plurality of second light emitting
elements for emitting green light are arrayed in a two-dimensional
matrix; (.gamma.) a third image formation apparatus including a
third light emitting panel wherein a plurality of third light
emitting elements for emitting red light are arrayed in a
two-dimensional matrix; (.delta.) a section configured to integrate
the light emitted from the first, second and third image formation
apparatus into a single light flux; and (.di-elect cons.) a light
passage controlling apparatus (light valve) for controlling
passage/non-passage of the emitted light emitted from the
integrating section, and
[0144] the passage/non-passage of the emitted light emitted from
the light emitting panels is controlled by the light passage
controlling apparatus to display an image.
Image Formation Apparatus F
[0145] The image formation apparatus F is a color display image
formation apparatus of the passive matrix type or the active matrix
type wherein the light emission/no-light emission state of each of
first, second and third light emitting elements is controlled to
display an image.
Image Formation Apparatus G
[0146] The image information apparatus G is a color display image
formation apparatus of the field sequential type which includes a
light passage controlling apparatus (light valve) for controlling
passage/non-passage of emitted light emitted from light emitting
element units arrayed in a two-dimensional matrix. The light
emission/no-light emission state of each of first, second and third
light emitting elements in each light emitting element unit is
time-divisionally controlled. Further, the light passage
controlling apparatus controls passage/non-passage of the emitted
light emitted from the first, second and third light emitting
elements to display an image.
[0147] In a preferred configuration of the image production
apparatus in the first or second form, the first deflection section
functions as a reflecting mirror and the second deflection section
functions as a half-mirror as described hereinabove. In such a form
as just described, the first deflection section, or the reflecting
mirror which forms the beam expansion section, can be formed from a
light reflecting film, which is a kind of mirror, made of, for
example, a metal including an alloy for reflecting light incident
to the second light conduction plate or a diffraction grating (for
example, a hologram diffraction grating film) for diffracting light
incident to the second light conduction plate. Meanwhile, the
second deflection section, or the half-mirror which forms the beam
expansion section, can be formed, for example, from a dielectric
multilayer film, a half-mirror, a polarized light beam splitter or
a hologram diffraction grating film. The first and second defection
sections are disposed in the inside of the second light conduction
plate, that is, incorporated in the inside of the second light
conduction plate. Thus, the first defection section reflects or
diffracts parallel light incident to the second light conduction
plate so that the parallel light incident to the second light
conduction plate is totally reflected in the inside of the second
light conduction plate. Meanwhile, the second deflection section
reflects or diffracts the parallel light propagated in the inside
of the second light conduction plate by total reflection by a
plural number of times and emits the reflected or diffracted light
in the form of parallel light from the second light conduction
plate.
[0148] Alternatively, in another preferred configuration of the
image production apparatus in the first or second form, the first
and second deflection sections are formed, for example, from a
reflection type diffraction grating element, particularly, for
example, from a reflection type volume hologram diffraction grating
as described hereinabove. It is to be noted that the first
deflection section formed from a reflection type volume hologram
diffraction grating is hereinafter referred to sometimes as "first
diffraction grating member" and the second deflection section
formed from a reflection type volume hologram diffraction grating
is hereinafter referred to sometimes as "second diffraction grating
member" for the convenience of description.
[0149] In order to make the first or second diffraction grating
member ready for diffraction reflection of P (here P=3 for red,
green and blue) different kinds of light having P different
wavelength bands or wavelengths, it can be formed by laminating P
diffraction grating layers each formed from a reflection type
volume hologram diffraction grating. In each diffraction grating
layer, interference fringes corresponding to one frequency band or
frequency are formed. Alternatively, in order to make the first or
second diffraction grating member ready for diffraction reflection
of P different kinds of light having P different wavelength bands
or wavelengths, it may be configured such that the first or second
diffraction grating member formed from a single diffraction grating
layer has p kinds of interference fringes formed therein. Or it is
possible to adopt a different configuration wherein an angle of
view is divided, for example, equally into three angles and the
first or second diffraction grating member is formed by laminating
diffraction grating layers corresponding to the divisional angles
of view. By adopting any of the configurations described, it is
possible to achieve increase of the diffraction efficiency,
increase of the diffraction reception angle and optimization of the
diffraction angle when light having each wavelength band or
wavelength is diffracted and reflected by the first or second
diffraction grating member. Also the reflection type volume
hologram diffraction grating of the first light conduction section
may be configured similarly.
[0150] The first and second diffraction grating members may be
formed from a photopolymer material. The material and the basic
structure of the first and second diffraction grating members each
formed from a reflection type volume hologram diffraction grating
may be same as those of an existing reflection type volume hologram
diffraction grating. The reflection type volume hologram
diffraction grating signifies a hologram diffraction grating which
diffracts and reflects only + first order diffraction light. While
the diffraction grating member has interference fringes formed from
the inside to the surface thereof, the formation method of such
interference fringes may be same as a traditional formation method.
In particular, for example, object light is irradiated upon a
member of a photopolymer material, which forms the diffraction
grating member, from a first predetermined direction on one side
while reference light is simultaneously irradiated upon the member,
which forms the diffraction grating member, from a second
predetermined direction on the opposite side. Then, interference
fringes formed by the object light and the reference light are
recorded in the inside of the member which forms the diffraction
grating member. If the first predetermined direction, the second
predetermined direction and the wavelengths of the object light and
the reference light are selected appropriately, then a desired
pitch of the interference fringes on the surface of the diffraction
grating member and a diffraction inclination angle or slant angle
of the interference fringes can be obtained. The inclination angle
of interference fringes signifies an angle defined by the surface
of the diffraction grating member or diffraction grating layer and
the interference fringes. Where the first and second diffraction
grating members are formed from a lamination structure of P
diffraction grating layers each formed from a reflection type
volume hologram diffraction grating, the P diffraction grating
layers may first be produced separately from each other and then
laminated or adhered using, for example, an ultraviolet curing
bonding agent. Or, the P diffraction grating layers may be produced
otherwise by producing a single diffraction grating layer using a
photopolymer material having self-bonding properties and then
successively adhering a photopolymer material having self-bonding
properties. The reflection type volume hologram diffraction grating
which forms the first light conduction section may be configured
similarly.
[0151] While, in the image production apparatus of the first or
second form, light formed as a plurality of parallel light fluxes
by the collimate optical system or the relay optical system is
introduced into the second light conduction plate, the request for
such parallel light is based on the fact that light wave
information when such light is introduced into the second light
conduction plate need to be maintained also after the light is
emitted from the second light conduction plate through the first
and second deflection sections. It is to be noted that, in order to
produce a plurality of parallel light fluxes, particularly a light
emitting portion of the image formation apparatus should be
positioned at the position of a focal length of, for example, the
collimate optical system or the relay optical system. The collimate
optical system has a function of converting position information of
a pixel into angle information in the optical system of the optical
apparatus.
[0152] In the image display apparatus, the second light conduction
plate has two parallel faces, that is, a first face and a second
face, extending in parallel to the light propagation direction,
that is, to the Y direction, by internal total reflection in the
second light conduction plate. Where the face of the second light
conduction plate through which light enters is a second light
conduction plate incidence face and the face of the second light
conduction plate from which light emerges is a second light
conduction plate emergence face, the second light conduction plate
incidence face and the second light conduction plate emergence face
may be formed from the first face. Or, the second light conduction
plate incidence face may be formed from the first face while the
second light conduction plate emergence face is formed from the
second face.
[0153] The second light conduction plate, first light conduction
plate or transparent parallel flat plate may be formed from any of
such materials as glass including quartz glass and optical glass
such as BK7, and plastics materials such as PMMA, polycarbonate
resins, acrylic-based resins, amorphous polypropylene-based resins
and styrene-based resins including AS resins. The shape of the
second light conduction plate is not limited to the flat shape but
may be a curved shape.
[0154] The image display apparatus of the present invention can be
used to configure, for example, a head-mounted type display (HMD)
unit and is effective to achieve reduction in weight and size of
the apparatus. Further, a disagreeable feeling when the apparatus
is mounted can be reduced significantly, and besides the production
cost can be reduced.
[0155] The head-mounted type display unit includes:
[0156] (1) a frame of the glasses type for being mounted on the
head of an observer; and
[0157] (2) an image display apparatus of the present invention.
The head-mounted type display unit may include one image display
apparatus of the present invention (monocular type) or two image
display apparatus of the present invention (binocular type).
[0158] The frame includes a front portion disposed in front of the
observer, two temple portions attached for pivotal motion to the
opposite ends of the front portion by hinges, and two modern
portions attached to end portions of the temple portions, and
further includes nose pads. Where the entire head-mounted type
display unit is viewed, the assembly of the frame and the nose pads
has a structure substantially same as that of ordinary glasses
except that it does not have a rim. The frame may be formed from a
material same as that used for configuration of ordinary glasses
such as a metal, an alloy, a plastic material or a suitable
combination of such materials. Also the nose pads may be formed in
a well-known configuration and structure.
[0159] Further, from a point of view of the design of the
head-mounted type display unit or of easiness of mounting of the
head-mounted type display unit, the head-mounted type display unit
is formed preferably such that wiring lines such as a signal line
and a power supply line from one or two image production apparatus
extend through the temple portions and the inside of the modern
portions and outwardly from the end portions of the modern portions
and are connected to an external circuit which may be a controlling
circuit. Further, each image production apparatus includes a
headphone section, and the head-mounted type display unit is
configured further preferably such that headphone wiring lines from
the image production apparatus extend through the temple portions
and the inside of the modern portions and further from the end
portions of the modern portions to the headphone sections. The
headphone sections may be, for example, those of the inner ear type
or those of the canal type. More particularly, the headphone
section wiring lines are preferably configured such that they
extend from the end portions of the modern portions to the
headphone sections in such a manner as to go round the rear side of
the auricles or ear capsules.
[0160] The head-mounted type display unit may be formed such that
an image pickup apparatus is attached to a central portion of the
front portion. The image pickup apparatus particularly includes a
solid-state image pickup element formed, for example, from a CCD
sensor or a CMOS sensor, and a lens. Wiring lines from the image
pickup apparatus may, for example, extend along the rear face of
the front portion and be connected to one of the image displaying
apparatus. Further, the wiring lines may be included in the wiring
lines extending from the image production apparatus.
[0161] Where the head-mounted type display unit is formed as that
of the binocular type, preferably it is configured such that
[0162] the second light conduction section is disposed as a whole
on the center side of the face of the observer with respect to the
image production apparatus; that
[0163] the head-mounted type display unit further includes a
coupling member for coupling the two image displaying apparatus to
each other; that
[0164] the coupling member is attached to the side, which opposes
to the observer, of a central portion of the frame positioned
between the two pupils of the observer; and that
[0165] a projection image of the coupling member is included in a
projection image of the frame.
[0166] If the head-mounted type display unit is structured such
that the coupling member is attached to the central portion of the
frame positioned between the two pupils of the observer in this
manner, that is, where the image display apparatus are not attached
directly to the frame, then when the observer mounts the frame on
the head thereof, the temple portions are placed into an outwardly
expanded state. As a result, even if the frame is deformed, such
deformation of the frame does not cause displacement or positional
variation of the image reproduction apparatus or of the second
light conduction section, or even if the deformation causes such
displacement, the amount of such displacement is very small.
Therefore, such a situation that the angle of convergence of the
left and right images varies can be prevented with certainty.
Besides, since there is no necessity to raise the rigidity of the
front portion of the frame, increase in weight of the frame,
degradation in design performance and increase of the cost are not
encountered. Further, since the image displaying apparatus are not
attached directly to the frame of the glasses type, the design,
color and so forth of the frame can be selected freely depending
upon the liking of the observer, and also the restriction to the
design of the frame is little and the degree of freedom in design
is high. In addition, the coupling member is disposed between the
observer and the frame, and besides a projection image of the
coupling member is included in a projection image of the frame. In
other words, when the head-mounted type display unit is observed
from the front of the observer, the coupling member is hidden by
the frame. Accordingly, high design performances can be provided to
the head-mounted type display unit.
[0167] It is to be noted that the coupling member is attached
preferably to the face of the central portion of the front portion
thereof which is positioned between the two pupils of the observer.
The central portion of the front portion corresponds to a bridging
portion of ordinary glasses.
[0168] Although the two image displaying apparatus are coupled to
each other by the coupling member, particularly the image
production apparatus are attached preferably to end portions of the
coupling member such that the attachment state thereof can be
adjusted. In this instance, each image production apparatus is
preferably positioned on the outer side with respect to the pupils
of the observer. Further, in such a configuration as just
described, where the distance between the attached portion center
of one of the image production apparatus and an end portion of the
frame is represented by .alpha., the distance from the center of
the coupling member to the end portion of the frame by .beta., the
distance between the attached portion center of the other image
production apparatus and the end portion of the frame by .gamma.,
and the length of the frame by L,
0.01.times.L.ltoreq..alpha..ltoreq.0.30.times.L is satisfied.
Preferably, 0.05.times.L.ltoreq..alpha..ltoreq.0.25.times.L is
satisfied. Further, 0.35.times.L.ltoreq..beta..ltoreq.0.65.times.L
is satisfied, and preferably,
0.45.times.L.ltoreq..beta..ltoreq.0.55.times.L is satisfied.
Furthermore, 0.70.times.L.ltoreq..gamma..ltoreq.0.99.times.L is
satisfied, and preferably,
0.75.times.L.ltoreq..gamma..ltoreq.0.95.times.L is satisfied. The
attachment of the image production apparatus to the opposite end
portions of the coupling member is carried out in the following
manner. In particular, for example, three through-holes are
provided at different locations of each end portion of the coupling
member, and threaded portions corresponding to the through-holes
are provided on each image production apparatus. Then, a screw is
inserted into each through-hole and screwed into a corresponding
one of the threaded portions provided on the image production
apparatus. A spring is inserted in advance between the screw and
the threaded-portion. Thus, the mounted state of the image
production apparatus, that is, the inclination of the image
production apparatus with respect to the coupling member, can be
adjusted by the tightened state of the screws.
[0169] Here, the attachment portion center of an image production
apparatus is a bisecting point, along an axial direction of the
frame, of a portion of a projection image of the frame with which a
projection image of the image production apparatus which is
obtained when the image production apparatus and the frame are
projected to a virtual plane in a state wherein the image
production apparatus is attached to the coupling member overlaps.
Further, the center of the coupling member is a bisecting point,
along the axial direction of the frame, of a portion of the
coupling member at which the coupling member contacts with the
frame in the state wherein the coupling member is attached to the
frame. The length of the frame where the frame is curved is a
length of the projection image of the frame. It is to be noted that
the projection direction is a perpendicular direction to the face
of the observer.
[0170] Alternatively, the head-mounted type display unit may be
formed such that, although the two image displaying apparatus are
coupled to each other by the coupling member, particularly the
coupling member couples the two second light conduction sections to
each other. It is to be noted that the two second light conduction
sections are sometimes produced as a unitary member. In such an
instance, the coupling member is attached to the integrally
produced second light conduction sections, and also this coupling
form is included in the form wherein the coupling member couples
the two second light conduction sections to each other. Where the
distance between the center of one of the image production
apparatus and one end portion of the frame is represented by
.alpha.' and the distance between the center of the other image
production apparatus and the one end portion of the frame is
represented by .gamma.', also the values of .alpha.' and .gamma.'
are preferably equal to those of .alpha. and .gamma. specified
hereinabove, respectively. It is to be noted that the center of an
image production apparatus is a bisecting point, along an axial
direction of the frame, of a portion of a projection image of the
frame with which a projection image of the image production
apparatus which is obtained when the image production apparatus and
the frame are projected to a virtual plane in a state wherein the
image production apparatus is attached to the second light
conduction section overlaps.
[0171] The shape of the coupling member can essentially be
determined arbitrarily as far as the projection image of the
coupling member is included in the projection image of the frame,
and, for example, the coupling member may have a shape of a bar or
an elongated plate. Also the material of the coupling member may be
a metal, an alloy, a plastic material or a suitable combination of
such materials.
Embodiment 1
[0172] An embodiment 1 relates to the image displaying apparatus
according to the first mode of the present invention and the
optical apparatus according to the first mode of the present
invention and further relates to the image production apparatus of
the first form. The image displaying apparatus according to the
embodiment 1 and embodiments 2 to 4 hereinafter described are
conceptually shown in FIGS. 1, 2, 3A and 4, respectively. Further,
an arrangement state of the image production apparatus, a first
light conduction section and a second light conduction section is
schematically shown in FIG. 5A, and a concept when the first light
conduction section is cut is illustrated in FIG. 5B.
[0173] The image displaying apparatus 100, 200, 300 or 400
according to the embodiment 1 or any of the embodiments 2 to 4
hereinafter described includes
[0174] (A) an image production apparatus 110 or 210;
[0175] (B) a first light conduction section 120 adapted to receive,
conduct and emit the light emitted from the image production
apparatus 110 or 210; and
[0176] (C) a second light conduction section 130 or 330 adapted to
receive and conduct light emitted from the first light conduction
section 120 and then emit the light toward the pupil 41 of an
observer 40. The first light conduction section 120 includes:
[0177] (B-1) a first light conduction plate 121 for propagating
part of the incident light by total reflection in the inside
thereof and emitting the propagated light therefrom;
[0178] (B-2) a reflection type volume hologram diffraction grating
122 disposed on the first light conduction plate 121. Meanwhile,
the second light conduction section 130 or 330 includes:
[0179] (C-1) a second light conduction plate 131 or 331 adapted to
propagate incoming light in the inside thereof by total reflection
and then emit the light;
[0180] (C-2) a first deflection section 140 or 340 disposed on the
second light conduction plate 131 or 331 and adapted to deflect
light incident to the second light conduction plate 131 or 331 such
that the light introduced to the second light conduction plate 131
or 331 is totally reflected in the inside of the second light
conduction plate 131 or 331; and
[0181] (C-3) a second deflection section 150 or 350 disposed on the
second light conduction plate 131 or 331 and adapted to deflect the
light propagated in the inside of the second light conduction plate
131 or 331 by total reflection over a plural number of times in
order to emit the light propagated in the inside of the second
light conduction plate 131 or 331 by total reflection from the
second light conduction plate 131 or 331. It is to be noted that
the second light conduction section 130 or 330 is of the
see-through type or half-transmission type.
[0182] Meanwhile, the optical apparatus in the embodiment 1 or any
of the embodiments 2 to 4 hereinafter described includes:
[0183] a first light conduction section 120 adapted to receive,
conduct and emit a light flux; and
[0184] a second light conduction section 130 or 330 adapted to
receive and conduct the light flux emitted from the first light
conduction section 120 and then emit the light.
[0185] The first light conduction section 120 includes:
[0186] (a-1) a first light conduction plate for propagating part of
the incident light by total reflection in the inside thereof and
emitting the propagated light therefrom; and
[0187] (a-2) a reflection type volume hologram diffraction grating
122 disposed on the first light conduction plate 121, and
[0188] the second light conduction section 130 or 330 includes:
[0189] (b-1) a second light conduction plate 131 or 331 adapted to
propagate incoming light in the inside thereof by total reflection
and then emit the light;
[0190] (b-2) a first deflection section 140 or 340 disposed on the
second light conduction plate 131 or 331 and adapted to deflect
light incident to the second light conduction plate 131 or 331 such
that the light introduced to the second light conduction plate 131
or 331 is totally reflected in the inside of the second light
conduction plate 131 or 331; and
[0191] (b-3) a second deflection section 150 or 350 disposed on the
second light conduction plate 131 or 331 and adapted to deflect the
light propagated in the inside of the second light conduction plate
131 or 331 by total reflection over a plural number of times in
order to emit the light propagated in the inside of the second
light conduction plate 131 or 331 by total reflection from the
second light conduction plate 131 or 331.
[0192] Here, in the image displaying apparatus 100 or 300 of the
embodiment 1 or the embodiment 3 which is hereinafter described,
the image production apparatus 110 includes:
[0193] (A-1) an image formation apparatus 111 having a plurality of
pixels arrayed in a two-dimensional matrix; and
[0194] (A-2) a collimate optical system 112 for converting light
emitted from the pixels of the image formation apparatus 111 into
parallel light; and
[0195] a light flux of the parallel light obtained by the
conversion by the collimate optical system 112 is introduced to the
first light conduction section 120.
[0196] The first deflection section 140 and the second deflection
section 150 are disposed in the inside of the second light
conduction plate 131. The first deflection section 140 reflects
light entering the second light conduction plate 131, and the
second deflection section 150 passes and reflects the light
propagated in the inside of the second light conduction plate 131
by total reflection by a plural number of times. In other words,
the first deflection section 140 functions as a reflecting mirror,
and the second deflection section 150 functions as a half mirror.
More particularly, the first deflection section 140 provided in the
inside of the second light conduction plate 131 is formed from a
light reflecting mirror which is a kind of mirror made of aluminum
for reflecting light entering the second light conduction plate
131. Meanwhile, the second deflection section 150 provided in the
inside of the second light conduction plate 131 is formed from a
multilayer laminated structure wherein a large number of dielectric
laminate films are laminated. The dielectric laminate films are
formed, for example, from a TiO.sub.2 film as a high dielectric
constant material and a SiO.sub.2 film as a low dielectric constant
material. A multilayer laminated structure wherein a large number
of dielectric laminate films are laminated is disclosed in
JP-T-2005-521099. While, in FIGS. 1 and 2, a dielectric laminate
film of six layers is shown, the number of layers of the dielectric
laminate film is not limited to this. Between adjacent ones of the
dielectric laminate films, a thin piece made of a material same as
that of the second light conduction plate 131 is sandwiched. It is
to be noted that, by the first deflection section 140, parallel
light entering the second light conduction plate 131 is reflected
or refracted so that the incident parallel light may be totally
reflected in the inside of the second light conduction plate 131.
On the other hand, by the second deflection section 150, parallel
light propagated in the inside of the second light conduction plate
131 by total reflection is reflected or diffracted by a plural
number of times and emitted in the form of parallel light from the
second light conduction plate 131.
[0197] The first deflection section 140 may be formed by cutting
away a portion 134 of the second light conduction plate 131 at
which the first deflection section 140 is to be provided to provide
an inclined face at which the first deflection section 140 is to be
formed on the second light conduction plate 131, forming a light
reflecting film on the inclined face by vapor deposition and
adhering the cut away portion 134 of the second light conduction
plate 131 back to the first deflection section 140. Meanwhile, the
second deflection section 150 may be formed by producing a
multilayer laminate structure wherein a large number of layers of a
material such as the material of the second light conduction plate
131 such as, for example, glass and a large number of dielectric
laminated films, which can be formed, for example, by vapor
deposition, are laminated, cutting away a portion 135 of the second
light conduction plate 131 at which the second deflection section
150 is to be provided to form an inclined face, adhering the
multilayer laminate structure to the inclined face, and carrying
out polishing to put the profile in order. The second light
conduction section 130 wherein the first deflection section 140 and
the second deflection section 150 are provided in the second light
conduction plate 131 can be obtained in this manner.
[0198] In the embodiment 1 or the embodiment 3 which is hereinafter
described, the image formation apparatus 111 includes a reflection
type spatial optical modulation apparatus 160 and a light source
163 which is formed from a light emitting diode which emits white
light. More particularly, the reflection type spatial optical
modulation apparatus 160 includes a liquid crystal display (LCD)
apparatus 161 formed from an LCOS as a light valve, and a polarized
light beam splitter 162 for reflecting a part of the light from the
light source 163 to introduce the light to the liquid crystal
display apparatus 161, and passing part of the light reflected by
the liquid crystal display apparatus 161 therethrough so as to be
introduced to the collimate optical system 112. The liquid crystal
display apparatus 161 includes a plurality of, for example,
320.times.240, pixels or liquid crystal cells arrayed in a
two-dimensional matrix. The polarized light beam splitter 162 has a
known configuration and structure. Non-polarized light emitted from
the light source 163 collides with the polarized light beam
splitter 162. The polarized light beam splitter 162 passes a P
polarized light component of the incident light therethrough and
emits the same to the outside of the system. On the other hand, an
S polarized light component of the incident light is reflected by
the polarized light beam splitter 162 and enters the liquid crystal
display apparatus 161. Then, the S polarized light component is
reflected in the inside of the liquid crystal display apparatus 161
and then emitted from the liquid crystal display apparatus 161.
Here, of the light emitted from the liquid crystal display
apparatus 161, light emitted from a pixel which displays "white"
includes much P polarized light component, and light emitted from
another pixel which displays "black" includes much S polarized
light component. Accordingly, the P polarized light component from
within the light emitted from the liquid crystal display apparatus
161 and colliding with the polarized light beam splitter 162 passes
through the polarized light beam splitter 162 and are introduced to
the collimate optical system 112. Meanwhile, the S polarized light
component is reflected by the polarized light beam splitter 162 and
returned to the light source 163. The liquid crystal display
apparatus 161 includes a plurality of, for example, 320.times.240,
pixels (the number of liquid crystal cells is equal to three times
the number of pixels) arrayed in a two-dimensional matrix. The
collimate optical system 112 is formed, for example, from a convex
lens, and the image formation apparatus 111, more particularly, the
liquid crystal display apparatus 161, is disposed at the position
of a focal length of the collimate optical system 112 in order to
produce parallel light. Meanwhile, one pixel is formed from a red
light emitting subpixel for emitting red light, a green light
emitting subpixel for emitting green light and a blue light
emitting subpixel for emitting blue light.
[0199] Here, in the embodiment 1 or in any of the embodiments 2 to
4, the second light conduction plate 131 or 331 made of an optical
glass or plastic material has two parallel faces (first face 132 or
332 and second face 133 or 333) extending in parallel to a light
propagation direction, that is, in a Y direction, by internal total
reflection of the second light conduction plate 131 or 331. The
first face 132 or 332 and the second face 133 or 333 oppose to each
other. Parallel light enters through the first face 132 or 332
which corresponds to a light incident face and propagates by total
reflection in the inside of the second light conduction plate 131
or 331, whereafter it is emitted from the first face 132 or 332
which corresponds to a light emergent face. It is to be noted that
the light incident face and the light emergent face are not limited
to them but the light incident face may be formed from the second
face 133 or 333 and the light emergent face may be formed from the
first face 132 or 332.
[0200] In order to make the reflection type volume hologram
diffraction grating 122, which forms the first light conduction
section 120, ready for diffraction reflection of P (here P=3 for
red, green and blue) different kinds of light having P different
wavelength bands or wavelengths, the reflection type volume
hologram diffraction grating 122 is formed by laminating P
diffraction grating layers each formed from a reflection type
volume hologram diffraction grating. It is to be noted that, in
each diffraction grating layer made of a photopolymer material,
interference fringes corresponding to one frequency band or
frequency are formed, and the diffraction grating layers are
produced by a hitherto known method. More particularly, the
reflection type volume hologram diffraction grating 122 has a
structure wherein a diffraction grating layer for diffracting and
reflecting red light, another diffraction grating layer for
diffracting and reflecting green light and a further diffraction
grating layer for diffracting and reflecting blue light are
laminated. The pitch of the interference fringes formed on the
diffraction grating layers or diffraction optical elements is
fixed, and the interference fringes have a linear form and extend
in parallel to the Y direction. It is to be noted that the
reflection type volume hologram diffraction grating 122 is shown
with a single layer. Adoption of such a configuration as just
described can achieve increase of the diffraction efficiency,
increase of the diffraction reception angle and optimization of the
diffraction angle when light having the frequency bands or
frequencies is diffracted and reflected by the reflection type
volume hologram diffraction grating 122. It is to be noted that
also a first diffraction grating member 340 and a second
diffraction grating member 350 hereinafter described may be
configured similarly.
[0201] Here, where the light propagation direction by internal
total reflection in the second light conduction plate 131 or 331 is
defined as Y direction and the thicknesswise direction of the
second light conduction plate 131 or 331 is defined as X direction,
the light propagation direction by internal total reflection of the
first light conduction plate 121 is a Z direction and the
thicknesswise direction of the first light conduction plate 121 is
the X direction. Then, the beam diameter along the Z direction of
light emitted from the first light conduction plate 121 is greater
than the beam diameter along the Z direction of light incident to
the first light conduction plate 121.
[0202] FIG. 5B shows the inside of the reflection type volume
hologram diffraction grating 122 in an enlarged scale. Referring to
FIG. 5B, the reflection type volume hologram diffraction grating
122 is disposed on a face 121A of the first light conduction plate
121 which opposes to the second light conduction plate 131 or 331.
Thus, part of light incident to the first light conduction plate
121 is diffracted by the reflection type volume hologram
diffraction grating 122 and is totally reflected once in the inside
the first light conduction plate 121. Then, the light is totally
reflected by the surface 122A of the reflection type volume
hologram diffraction grating 122 and diffracted by the reflection
type volume hologram diffraction grating 122, whereafter it is
emitted from the first light conduction plate 121. Meanwhile, the
remaining part of the light incident to the first light conduction
plate 121 passes through and is emitted from the first light
conduction plate 121 and the reflection type volume hologram
diffraction grating 122. In particular, in the embodiments 1 to 4,
"emission of light from the first light conduction section by two
times of total reflection" is adopted. Then, in order to make the
light amount of the part and the light amount of the remaining part
of the light in the first light conduction plate 121 equal to each
other to establish uniformity of the intensity distribution of the
light to be emitted from the entire first light conduction section
120, where the reflection efficiency of the reflection type volume
hologram diffraction grating 122 is represented by .eta. and the
light transmission factor T is T=1, the reflection efficiency .eta.
is set to 0.62.
[0203] Further, by adopting such a configuration as described
above, it is possible to make the beam diameter along the Z
direction of light to be emitted from the first light conduction
plate 121 greater by twice than the beam diameter along the Z
direction of light to be incident to the first light conduction
plate 121. In other words, the first light conduction section 120
functions as a kind of expander. Accordingly, the shape of a light
flux emitted from the image production apparatus 110 to enter the
first light conduction section 120 is deformed appropriately by the
first light conduction section 120, and the light flux of the
deformed shape enters the second light conduction section 130 or
330. Therefore, there is no necessity to set the diameter of the
aperture stop in the Z direction in the image formation apparatus
111 to a great diameter. In other words, there is no necessity to
increase the diameter of the lens provided in the collimate optical
system 112 provided in the image formation apparatus 111, and
reduction in size and weight of the image displaying apparatus can
be anticipated. Further, such a problem that the display contrast
drops and the picture quality is deteriorated does not occur.
[0204] If the surface 122A of the reflection type volume hologram
diffraction grating 122 is not sufficiently smooth or flat, then
the light may be scattered or drop of the contrast or deterioration
of the resolution may occur. From a point of view of prevention of
occurrence of such a problem as just described and also of
protection of the reflection type volume hologram diffraction
grating 122, the first light conduction section 120 may otherwise
be configured such that the first light conduction plate 121,
reflection type volume hologram diffraction grating 122 and
transparent parallel flat plat are laminated in order from the
light incidence side. This also applies similarly to the other
embodiments described below.
Embodiment 2
[0205] The embodiment 2 is a modification to the embodiment 1 and
relates to the image production apparatus 210 of the second mode.
The image displaying apparatus 200 of the embodiment 2 or an image
displaying apparatus 400 of the embodiment 4 hereinafter described
includes, as shown in FIG. 2 or 4,
[0206] (A-1) a light source 261;
[0207] (A-2) a collimate optical system 262 for converting light
emitted from the light source 261 into parallel light;
[0208] (A-3) a scanning section 263 for scanning the parallel light
emitted from the collimate optical system 262; and
[0209] (A-4) a relay optical system 264 for relaying the parallel
light scanned by the scanning section 263; and
[0210] a light flux of the parallel light obtained by the
conversion by the relay optical system 264 is introduced to the
first light conduction section 120.
[0211] The first light conduction section 120 and the second light
conduction section 130 have a configuration and a structure similar
to those of the first light conduction section 120 and the second
light conduction section 130 described hereinabove in connection
with the embodiment 1, respectively, and therefore, overlapping
description of them is omitted herein to avoid redundancy.
[0212] A light source 261 includes a red light emitting element
261R for emitting red light, a green light emitting element 261G
for emitting green light and a blue light emitting element 261B for
emitting blue light, each formed from a semiconductor laser
element. Light of the three primary colors emitted from the light
source 261 passes through a cross prism 265, whereupon color
synthesis is carried out to form a single light flux. The resulting
light enters a collimate optical system 262 which generally has a
positive optical power and emerges as parallel light from the
collimate optical system 262. The parallel light is reflected by a
total reflection mirror 266 and then subjected to horizontal
scanning and vertical scanning by a scanning section 263 formed
from an MEMS which includes micromirrors disposed for rotation in
two-dimensional directions and can scan the incoming parallel light
two-dimensionally so that the parallel light is converted into a
kind of a two-dimensional image and virtual pixels are produced.
Then, light from the virtual pixels passes through a relay optical
system 264 formed from a well-known relay optical system, and a
light flux in the form of parallel light enters the first light
conduction section 120 and the second light conduction section
130.
Embodiment 3
[0213] Also the embodiment 3 is a modification to the embodiment 1.
Referring to FIG. 3A, the image formation apparatus 111 and
collimate optical system 112 and the first light conduction section
120 in the image displaying apparatus 300 of the embodiment 3 have
a configuration and a structure same as those of the image
formation apparatus 111 and collimate optical system 112 and the
first light conduction section 120 described hereinabove in
connection with the embodiment 1, respectively. Although the second
light conduction section 330 is different in the configuration and
structure of the first and second deflection sections, also it has
a basic configuration and structure similar to those of the second
light conduction section 130 in the embodiment 1. In particular,
the second light conduction section 330 includes
[0214] (C-1) a second light conduction plate 331 adapted to
propagate incoming light in the inside thereof by total reflection
and then emit the light;
[0215] (C-2) a first deflection section 340 disposed on the second
light conduction plate 331 and adapted to deflect light incident to
the second light conduction plate 331 such that the light
introduced to the second light conduction plate 331 is totally
reflected in the inside of the second light conduction plate 331;
and
[0216] (C-3) a second deflection section 350 disposed on the second
light conduction plate 331 and adapted to deflect the light
propagated in the inside of the second light conduction plate 331
by total reflection over a plural number of times in order to emit
the light propagated in the inside of the second light conduction
plate 331 by total reflection from the second light conduction
plate 331.
[0217] In the embodiment 3, the first and second deflection
sections are disposed on the surface of the second light conduction
plate 331, particularly on the second face 333 of the second light
conduction plate 331. The first deflection section diffracts light
entering the second light conduction plate 331, and the second
deflection section diffracts light, which has propagated in the
inside of the second light conduction plate 331, by total
reflection, over a plural number of times. Each of the first and
second deflection sections is formed from a diffraction grating
element, particularly a reflection type diffraction grating
element, more particularly a reflection type volume hologram
diffraction grating. In the following description, the first
deflection section formed from a reflection type volume hologram
diffraction grating is referred to as "first diffraction grating
member 340" for the convenience of description, and the second
deflection section formed from a reflection type volume hologram
diffraction grating is referred to as "second diffraction grating
member 350" for the convenience of description.
[0218] In the embodiment 3 or the embodiment 4 hereinafter
described, in order to make the first diffraction grating member
340 and the second diffraction grating member 350 ready for
diffraction reflection of P (here P=3 for red, green and blue)
different kinds of light having P different wavelength bands or
wavelengths, the first diffraction grating member 340 and the
second diffraction grating member 350 are formed by laminating P
diffraction grating layers each formed from a reflection type
volume hologram diffraction grating. It is to be noted that, in
each diffraction grating layer made of a photopolymer material,
interference fringes corresponding to one frequency band or
frequency are formed, and the diffraction grating layers are
produced by a hitherto known method. More particularly, the first
diffraction grating member 340 and the second diffraction grating
member 350 have a structure wherein a diffraction grating layer for
diffracting and reflecting red light, another diffraction grating
layer for diffracting and reflecting green light and a further
diffraction grating layer for diffracting and reflecting blue light
are laminated. The pitch of the interference fringes formed on the
diffraction grating layers or diffraction optical elements is
fixed, and the interference fringes have a linear form and extend
in parallel to the Z direction. It is to be noted that, in FIGS. 3A
and 4, the first diffraction grating member 340 and the second
diffraction grating member 350 are shown with a single layer.
Adoption of such a configuration as just described can achieve
increase of the diffraction efficiency, increase of the diffraction
reception angle and optimization of the diffraction angle when
light having the frequency bands or frequencies is diffracted and
reflected by the first diffraction grating member 340 and the
second diffraction grating member 350.
[0219] FIG. 3B shows an enlarged schematic partial section of a
reflection type volume hologram diffraction grating. Referring to
FIG. 3B, the reflection type volume hologram diffraction grating
has interference fringes having an inclination angle .phi. formed
therein. Here, the inclination angle .phi. is defined by the
surface and the interference fringes of the reflection type volume
hologram diffraction grating. The interference fringes are formed
from the inside to the surface of the reflection type volume
hologram diffraction grating. The interference fringes satisfy the
Bragg condition. The Bragg condition is a condition which satisfies
the following expression (A):
m.lamda.=2dsin(.theta.) (A)
where m is a positive integer, .lamda. a wavelength, d the pitch of
the grating face, that is, the distance in a normal direction of a
virtual plane including the interference fringes, and .theta. the
complementary angle to the angle at which light enters the
interference fringes. Meanwhile, the relationship between the
inclination angle .phi. and the incidence angle .psi. where light
enters the diffraction grating member at the incidence angle .psi.
is given by the following expression (B):
.theta.=90.degree.-(.phi.+.psi.) (B)
[0220] The first diffraction grating member 340 is disposed on,
that is, adhered to, the second face 333 of the second light
conduction plate 331 as described hereinabove, and diffracts and
reflects parallel light entering the second light conduction plate
331 from the first face 332 so as to be totally reflected in the
inside of the second light conduction plate 331. Further, the
second diffraction grating member 350 is disposed on or adhered to
the second face 333 of the second light conduction plate 331 as
described hereinabove, and diffracts and reflects the parallel
light, which has propagated in the inside of the second light
conduction plate 331 by total reflection, by a plural number of
times such that the light is emitted from the first face 332 of the
second light conduction plate 331 while it remains in the form of
parallel light. However, the configuration of the incident and
emergent faces is not limited to this, but the second light
conduction plate incidence face may be formed from the second face
333 and the second light conduction plate emergence face may be
formed from the first face 332.
[0221] Also the second light conduction plate 331 is configured
such that parallel light of the three colors of red, green and blue
propagates in the inside thereof by total reflection and then
emerges therefrom. At this time, since the second light conduction
plate 331 is thin and the light path of light advancing in the
inside of the second light conduction plate 331 is long, the number
of times of total reflection to the second diffraction grating
member 350 differs depending upon the angle of view, that is, the
horizontal angle of view. More particularly, the number of times of
reflection of parallel light entering with an angle, that is, a
horizontal angle of view, of a direction in which it approaches the
second diffraction grating member 350 from within parallel light
which enters the second light conduction plate 331 is smaller than
the number of times of reflection of parallel light which enters
the second light conduction plate 331 with a horizontal angle of
view of a direction in which it is spaced away from the second
diffraction grating member 350. This is because the angle which is
defined by the parallel light diffracted and reflected by the first
diffraction grating member 340 and entering the second light
conduction plate 331 with a horizontal angle of view of a direction
in which it approaches the second diffraction grating member 350
and a normal to the second light conduction plate 331 when light
propagating in the inside of the second light conduction plate 331
collides with the inner face of the second light conduction plate
331 is smaller than the angle which is defined by the parallel
light entering the second light conduction plate 331 with a
horizontal angle of view of the opposite direction and the normal
to the second light conduction plate 331. Further, the shape of the
interference fringes formed in the inside of the second diffraction
grating member 350 and the shape of the interference fringes formed
in the inside of the first diffraction grating member 340 have a
symmetrical relationship to each other with respect to the XZ plane
of the second light conduction plate 331.
[0222] Also the second light conduction plate 331 in the embodiment
4 described subsequently has a configuration and a structure
basically same as those of the second light conduction plate 331
described above.
[0223] In the embodiment 3, where the light propagation direction
by internal total reflection in the second light conduction plate
331 is defined as Y direction and the thicknesswise direction of
the second light conduction plate 331 is defined as X direction,
the direction in which the interference fringes in the first
diffraction grating member 340 and the second diffraction grating
member 350 are juxtaposed, that is, the diffraction direction, is
the Y direction. Further, the direction in which the interference
fringes in the reflection type volume hologram diffraction grating
122 which forms the first light conduction section 120, that is,
the diffraction grating of the reflection type volume hologram
diffraction grating 122, is the Z direction.
[0224] In the embodiment 3, the distance between the centers of the
first deflection section, that is, the first diffraction grating
member 340, and the second defection section, that is, the second
diffraction grating member 350, is 30 mm, and the wavelength of the
incident light is 522 nm. Further, the diffraction angle of
incident light entering at 0 degree into the second light
conduction plate 331, that is, the total reflection angle in the
second light conduction plate 331, is 59 degrees. Further, the
thickness of the second light conduction plate 331 is 1.5 mm and
the refractive index is 1.52 while the eye relief is 15 mm. At this
time, the distance from an incident point to the second light
conduction plate 331 of light which collides with the center of the
first diffraction grating member 340 (such incident point is
hereinafter referred to as "light incident point") to the pupil of
the observer is 40 mm in the air conversion length. Then, when the
horizontal angle of view is in the negative, the distance from the
light incident point to the pupil 41 of the observer is greatest.
Here, if the horizontal angle of view is .+-.11 degrees and the
vertical angle of view is .+-.8.3 degrees, then the air conversion
length of the distance from the light incident point of a ray of
light having a horizontal angle of view of -11 degrees to the pupil
41 of the observer is 47 mm. It is necessary to assure an aperture
stop (clear aperture) of the vertical angle of view of .+-.8.3
degrees at the distance of 48 mm. Accordingly, the aperture of the
projection optical system necessary in the vertical direction is,
where the diameter of the pupil of the observer is 3 mm, 17 mm.
This aperture corresponds to the length of the light emerging
region of the first light conduction section 120 along the Z
direction. Where the thickness of the first light conduction plate
121 is 3 mm, the refractive index is 1.52, the wavelength of
incidence light is 522 nm and the diffraction angle of 0-degree
incidence light, that is, the total reflection angle in the first
light conduction plate 121, is 59 degrees, the diffractive angle
corresponding to the angle of view of -8.3 degrees is 49.7 degrees,
and the distance over which the light advances by one time of total
reflection (refer to "L" in FIG. 5B) is 7.1 mm. Through such a
procedure of calculation as described above, the aperture of the
lens provided in the image formation apparatus which is necessary
to introduce parallel light into the first light conduction section
120 is determined to be 10.5 mm.
[0225] As described above, in the embodiment 3, where the light
propagation direction by internal total reflection in the second
light conduction plate 331 is defined as Y direction and the
thicknesswise direction of the second light conduction plate 331 is
defined as X direction, the diffraction direction by the first
diffraction grating member 340 and the second diffraction grating
member 350 is the Y direction and the diffraction direction by the
reflection type volume hologram diffraction grating 122 which forms
the first light conduction section 120 is the Z direction. In this
instance, a phase difference plate for varying the phase difference
of a polarized light component emitted from the first light
conduction plate 121 may be disposed between the first light
conduction plate 121 and the second light conduction plate 331. It
is to be noted that preferably the polarized light component
emitted from the first light conduction plate 121 is made parallel
to the Z direction. In other words, the phase difference plate may
be disposed such that the polarized light component to enter the
first diffraction grating member 340 may be parallel to the Z
direction. Here, the phase difference plate may be a half-wave
plate or two quarter-wave plates, and an S polarized light
component should be introduced into the first diffraction grating
member 340. Further, a second phase difference plate for varying
the phase difference of a polarized light component emitted from
the collimate optical system or the relay optical system may be
disposed between the collimate optical system or the relay optical
system and the first light conduction plate 121. In this instance,
preferably the second phase plate is disposed such that the
polarized light component to enter the first light conduction plate
121 becomes parallel to the Y direction. Here, the phase difference
plate may be a half-wave plate or two quarter-wave plates, and an S
polarized light component should be introduced into the reflection
type volume hologram diffraction grating 122. This similarly
applies also to the embodiment 4 described below, and a second
phase difference plate may be disposed also in the embodiment 1 or
the embodiment 2. Although preferably a polarized light component
of light passing through the phase difference plate is parallel to
the Z direction as described above, the reason is such as described
below. In particular, an incident light ray is reflected and Bragg
diffracted by the interference fringes, and the diffracted light
emerges (refer to FIG. 3B which is an enlarged schematic partial
sectional view of a reflection type volume hologram diffraction
grating). Here, the "polarized light component which is parallel to
the plane of the figure and perpendicular to the incident light" is
considered to enter as "p polarized light" into the interference
fringes. On the other hand, the "polarized light component
perpendicular to the plane of the figure" is considered to enter as
"s polarized light" to the interference fringes. The diffraction
efficiency of the reflection type volume hologram diffraction
grating has a polarization dependency, and the diffraction
efficiency of "p polarized light" is lower than that of "s
polarized light." Accordingly, from a point of view of raising the
light utilization efficiency, preferably the polarized light to be
introduced into the reflection type volume hologram diffraction
grating is "s polarized light."
Embodiment 4
[0226] The embodiment 4 is a modification to the embodiment 3. The
image displaying apparatus of the embodiment 4 is conceptually
shown in FIG. 4. The light source 261, collimate optical system
262, scanning section 263, relay optical system 264 and so forth of
the image displaying apparatus of the embodiment 4 have a
configuration and a structure same as those of the embodiment 2.
Further, the second light conduction section 330 in the embodiment
4 has a configuration and a structure same as those of the second
light conduction section 330 in the embodiment 3.
Embodiment 5
[0227] The embodiment 5 relates to the image displaying apparatus
according to the first mode of the present invention, and more
particularly to a head-mounted type display unit in which any one
of the image displaying apparatus 100, 200, 300 and 400 described
hereinabove in connection with the embodiments 1 to 4,
respectively. A schematic view of the head-mounted type display
unit of the embodiment 5 as viewed from the front is shown in FIG.
6, and a schematic view of the head-mounted type display unit of
the embodiment 5 as viewed from the front where a frame is removed
is shown in FIG. 7. Further, a schematic view of the head-mounted
type display unit of the embodiment as viewed from above is shown
in FIG. 8, and a view of the head-mounted type display unit of the
embodiment 5 in a state wherein it is mounted on the head of an
observer 40 as viewed from above is shown in FIG. 9. It is to be
noted that FIG. 9 only shows the image displaying apparatus for the
convenience of description while the frame is omitted. Further,
while, in the following description, the image display apparatus
described is represented by the image displaying apparatus 100, it
is a matter of course that it is possible to apply the image
displaying apparatus 200, 300 and 400.
[0228] The head-mounted type display unit of the embodiment 5
includes:
[0229] (A) a frame 10 of the glasses type adapted to be mounted on
the head of an observer 40; and
[0230] (B) two image display apparatus 100. It is to be noted that
the head-mounted type display unit in the present embodiment 5 or
the embodiment 6 hereinafter described is of the both-eye type
including two image display apparatus 100.
[0231] The head-mounted type display unit of the embodiment 5
further includes a coupling member 20 for coupling the two image
display apparatus 100. The coupling member 20 is attached to the
side, which opposes to the observer, of a central portion 10C of a
frame 10 positioned between the two pupils 41 of the observer 40,
that is, to a location between the observer 40 and the frame 10,
for example, using a screw not shown. Further, a projection image
of the coupling member 20 is included in a projection image of the
frame 10. In particular, when the head-mounted type display unit is
viewed from the front of the observer 40, the coupling member 20 is
hidden by the frame 10 and cannot be visually observed. Further,
while the two image display apparatus 100 are connected to each
other by the coupling member 20, particularly image reproduction
apparatus 110A and 110B are attached to the opposite end portions
of the coupling member 20 such that the attached state thereof can
be adjusted. The image reproduction apparatus 110A and 110B are
positioned on the outer side with respect to the pupils 41 of the
observer 40. In particular, where the distance between the attached
portion center 110A.sub.c of the image production apparatus 110A
and an end portion 10A of the frame 10 is represented by .alpha.,
the distance from the center 20.sub.c of the coupling member 20 to
the end portion 10A of the frame 10 by .beta., the distance between
the attached portion center 110B.sub.c of the other image
production apparatus 110B and the end portion 10A of the frame 10
by .gamma., and the length of the frame 10 b L, the following
expressions are satisfied:
.alpha.=0.1.times.L
.beta.=0.5.times.L
.gamma.=0.9.times.L
[0232] Attachment of the image production apparatus, particularly
the image reproduction apparatus 110A and 110B, to the opposite end
portions of the coupling member 20 is carried out in the following
manner. In particular, for example, through holes (not shown) are
provided in three portions at each end of the coupling member, a
tapped hole corresponding to a through-hole, that is, a threaded
portion not shown, is provided in the image reproduction apparatus
110A and 110B, and a screw not shown is inserted into each of the
through-holes and screwed into the tapped hole provided in each of
the image reproduction apparatus 110A and 110B. A spring is
inserted between the screw and the tapped hole in advance. Thus,
the attachment state of each image production apparatus, that is,
the inclination of each image production apparatus with respect to
the coupling member, can be adjusted by the tightened state of the
screw. After the attachment, the screws are hidden by lids not
shown. It is to be noted that, in FIGS. 7 and 11, slanting lines
are applied to the coupling members 20 and 30 in order to clearly
indicate the coupling members 20 and 30, respectively.
[0233] The frame 10 includes a front portion 10B disposed in front
of the observer 40, two temple portions 12 pivotally attached to
the opposite ends of the front portion 10B through hinges 11, and
two modern portions (also called end cells or ear pads) attached to
end portions of the temple portions 12. The coupling member 20 is
attached to the central portion 100 of the front portion 10B
positioned between the two pupils 41 of the observer 40. The
central portion 10C corresponds to a bridge in ordinary glasses.
Nose pads 14 are attached to, the side of the coupling member 20
opposing to the observer 40. It is to be noted that, in FIGS. 8 and
12, the nose pads 14 are omitted. The frame 10 and the coupling
member 20 are made of a metal or plastic material, and the coupling
member 20 has shape of a curved bar.
[0234] Further, a wiring line 15 including a signal line and a
power supply line and extending from the image production apparatus
110A extends from an end portion of the corresponding modern
section 13 to the outside through the inside of the corresponding
temple section 12 and the modern section 13. Further, the image
reproduction apparatus 110A and 110B have a headphone section 16,
and a headphone section wiring line 17 extending from each of the
image reproduction apparatus 110A and 110B extends from an end
portion of the corresponding modern section 13 to the corresponding
headphone section 16 through the inside temple section 12 and the
inside of the modern section 13. More particularly, the headphone
section wiring line 17 extends from an end portion of the modern
section 13 to the headphone section 16 such that it goes round the
rear side of the auricle. By such a configuration as just
described, the head-mounted type display unit does not give such an
impression that the headphone sections 16 and the headphone section
wiring lines 17 are disposed disorderly to the observer but gives a
fine feeling.
[0235] To the central portion 10C of the front portion 10B, an
image pickup apparatus 18 is attached which includes a solid-state
image pickup element formed from CCD (Charge coupled device) or
CMOS (Complementary metal oxide semiconductor) sensors and a lens
all not shown. In particular, a through-hole is formed at the
central portion 10C of the frame 10, and a recessed portion is
provided at a portion of the coupling member 20 opposing to the
through-hole provided at the central portion 10C. The image pickup
apparatus 18 is disposed in the recessed portion. Light entering
through the through-hole provided in the central portion 10C is
focused on the solid-state image pickup element by the lens. A
signal from the solid-state image pickup element is sent to the
image production apparatus 110A through a wiring line not shown
extending from the image pickup apparatus 18 and further to an
external circuit. It is to be noted that the wiring line passes
between the coupling member 20 and the front portion 10B and is
connected to the image production apparatus 110A. By the
configuration described, the user is less likely to visually
confirm that the image pickup apparatus 18 is incorporated in the
head-mounted type display unit.
[0236] In this manner, in the head-mounted type display unit (HMD)
of the embodiment 5, the coupling member 20 couples the two image
display apparatus 100 to each other, and this coupling member 20 is
attached to the central portion 100 of the frame 10 positioned
between the two pupils 41 of the observer 40. In particular, each
of the image display apparatus 100 is not structured such that it
is attached directly to the frame 10. Accordingly, when the
observer 40 mounts the frame 10 on the head thereof, the temple
portions 12 are placed into an outwardly expanded state, and as a
result, even if the frame 10 is deformed, no displacement or
positional variation of the image reproduction apparatus 110A and
110B occurs, and even if such displacement occurs, the amount
thereof is very small. Therefore, the convergence angle of the left
and right images can be prevented from varying with certainty.
Besides, since there is no necessity to raise the rigidity of the
front portion 10B of the frame 10, increase in weight of the frame
10, degradation in design property and increase in cost are not
caused. Further, since the image displaying apparatus 100 is not
attached directly to the frame 10 of the glasses type, it is
possible to freely select the design, color and so forth of the
frame 10 in accordance with the liking of the observer and the
degree of freedom in design is high with the restriction to the
design of the frame 10 reduced. In addition, when the head-mounted
type display unit is viewed from the front of the observer, the
coupling member 20 is hidden by the frame 10. This can provide a
high design property to the head-mounted type display unit.
Embodiment 6
[0237] The embodiment 6 is a modification to the embodiment 5. A
schematic view of the head-mounted type display unit of the
embodiment 6 as viewed from the front is shown in FIG. 10, and
another schematic view of the head-mounted type display unit of the
embodiment as viewed from the front where a frame is removed is
shown in FIG. 11. A further schematic view of the head-mounted type
display unit of the embodiment 6 as viewed from above is shown in
FIG. 12.
[0238] In the head-mounted type display unit of the embodiment 6, a
coupling member 30 in the form of a bar is different from that in
the embodiment 5 in that it couples two second light conduction
sections 130 to each other in place of coupling the two image
reproduction apparatus 110A and 110B to each other. It is to be
noted that it is possible to produce the two second light
conduction sections 130 integrally with each other and attach the
coupling member 30 to the integrated second light conduction
sections 130.
[0239] Also in the head-mounted type display unit of the embodiment
6, the coupling member 30 is attached to the central portion 10C of
the frame 10 positioned between the two pupils 41 of the observer
40, for example, using a screw, and the image production apparatus
110 are positioned on the outer sides with respect to the pupils
41. It is to be noted that the image production apparatus 110 are
attached to the opposite end portions of the second light
conduction section 130. Where the distance from the center 30.sub.c
of the coupling member 30 to one end portion of the frame 10 is
represented by .beta. and the length of the frame 10 by L,
.beta.=0.5.times.L is satisfied. It is to be noted that, also in
the embodiment 6, the value of .alpha.' and the value of .gamma.'
are equal to the values of .alpha. and .gamma. in the embodiment 5,
respectively.
[0240] In the embodiment 6, the frame 10 and the image displaying
apparatus have a configuration and a structure same as those of the
frame 10 and the image displaying apparatus described hereinabove
in connection with the embodiment 5, respectively. Therefore,
detailed description of them is omitted herein to avoid redundancy.
Also the head-mounted type display unit of the embodiment 6 has a
configuration and a structure substantially same as those of the
head-mounted type display unit of the embodiment 5 except the
differences described above, and therefore, overlapping description
of the same is omitted hereinto avoid redundancy.
Embodiment 7
[0241] The embodiment 7 relates to an image display apparatus
according to the second mode of the present invention and an
optical apparatus according to the second mode of the present
invention and further to the image production apparatus according
to the first or second form of the present invention. The image
display apparatus in the embodiment 7 is conceptually shown in FIG.
14 or 15, and an arrangement state of the image production
apparatus, beam expansion section and light conduction section
(referred to as "second light conduction section" from a
relationship to the other embodiments) is schematically illustrated
in FIG. 13A. It is to be noted that the image displaying apparatus
shown in FIG. 14 is configured such that the beam expansion section
in the embodiment 7 is applied to the image displaying apparatus of
the embodiment 3 shown in FIGS. 3A and 3B. Meanwhile, the image
displaying apparatus shown in FIG. 15 is configured such that the
beam expansion section in the embodiment 7 is applied to the image
displaying apparatus of the embodiment 4 shown in FIG. 4.
[0242] The image displaying apparatus 700 or 800 according the
embodiment 7 or an embodiment 8 hereinafter described includes:
[0243] (A) an image production apparatus 110 or 210; and
[0244] (B) a light conduction section (second light conduction
section 130 or 330) adapted to receive and conduct light outputted
from the image production apparatus 110 or 210 and then emit the
light toward the pupil 41 of an observer 40. The light conduction
section (second light conduction section 130 or 330) includes:
[0245] (B-1) a light conduction plate (second light conduction
plate 131 or 331) for propagating the incident light by total
reflection in the inside thereof and emitting the propagated light
therefrom;
[0246] (B-2) a first deflection section 140 or 340 disposed on the
light conduction plate (second light conduction plate 131 or 331)
and adapted to deflect the light incident to the light conduction
plate (second light conduction plate 131 or 331) so that the light
incident to the light conduction plate (second light conduction
plate 131 or 331) is totally reflected in the inside of the light
conduction plate (second light conduction plate 131 or 331);
and
[0247] (B-3) a second deflection section 150 or 350 disposed on the
light conduction plate (second light conduction plate 131 or 331)
and adapted to deflect the light propagated in the inside of the
light conduction plate (second light conduction plate 131 or 331)
by total reflection over a plural number of times in order to emit
the light propagated in the inside of the light conduction plate
(second light conduction, plate 131 or 331) by total reflection
from the light conduction plate (second light conduction plate 131
or 331). It is to be noted that the second light conduction section
130 or 330 is of the sea-through type or half-transmission
type.
[0248] Meanwhile, the optical apparatus according to the embodiment
7 or the embodiment 8 hereinafter described includes a light
conduction section (second light conduction section 130 or 330)
adapted to receive, conduct and emit a light flux. The light
conduction section (second light conduction section 130 or 330)
includes:
[0249] a light conduction plate (second light conduction plate 131
or 331) for propagating the incident light by total reflection in
the inside thereof and emitting the propagated light therefrom;
[0250] a first deflection section 140 or 340 disposed on the light
conduction plate (second light conduction plate 131 or 331) and
adapted to deflect the light incident to the light conduction plate
(second light conduction plate 131 or 331) so that the light
incident to the light conduction plate (second light conduction
plate 131 or 331) is totally reflected in the inside of the light
conduction plate (second light conduction plate 131 or 331);
and
[0251] a second deflection section 150 or 350 disposed on the light
conduction plate (second light conduction plate 131 or 331) and
adapted to deflect the light propagated in the inside of the light
conduction plate (second light conduction plate 131 or 331) by
total reflection over a plural number of times in order to emit the
light propagated in the inside of the light conduction plate
(second light conduction plate 131 or 331) by total reflection from
the light conduction plate (second light conduction plate 131 or
331).
[0252] Further, in the embodiment 7 or the embodiment 8 hereinafter
described, the image displaying apparatus or the optical apparatus
further includes a beam expansion section 710 or 810 adapted to
expand, where an entering direction of the light flux into the
light conduction plate (second light conduction plate 131 or 331)
and a propagation direction of the light in the light conduction
plate (second light conduction plate 131 or 331) are defined as an
X direction (in the drawings, indicated by a -X direction) and a Y
direction, respectively, the light along a Z direction different
from the X and Y directions and emit the expanded light to the
light conduction section.
[0253] In the embodiment 7, as shown in FIG. 13A, the beam
expansion section 710 includes a first reflecting mirror 711 and a
second reflecting mirror 712. The first reflecting mirror 711 is
positioned on the opposite side to the image production apparatus
with respect to the light conduction section, that is, with respect
to the second light conduction section 330, that is, positioned on
the opposite side to the light entering side of the light
conduction section, while the second reflecting mirror 712 is
positioned adjacent the image production apparatus with respect to
the light conduction section, that is, positioned on the light
entering side of the light conduction section. Then, part of the
light emitted from the image production apparatus passes through
the light conduction plate and first deflection section, that is,
the second light conduction section 330. Thereafter, a series of
operations that the light passing through the second light
conduction section 330 is reflected by the first reflecting mirror
711 and passes through the light conduction plate and the first
deflection section, that is, the second light conduction section
330, and then is reflected by the second reflecting mirror 712,
whereafter part of the reflected light passes through the light
conduction plate and the first deflection section, that is, the
second light conduction section 330, is repeated by a predetermined
number of times. In the example illustrated in FIG. 13A, the light
is reflected twice by the second reflecting mirror 712. Where the
first reflecting mirror 711 and the second reflecting mirror 712
extend in parallel to each other and light is reflected twice by
the second reflecting mirror 712, the light which begins to
propagate in the inside of the light conductor plate, that is, the
second light conduction plate 331, is finally elongated by
approximate three times in the Z direction of the light which first
enters the light conduction plate, that is, the second light
conduction plate 331.
[0254] Here, the first reflecting mirror 711 and the second
reflecting mirror 712 preferably extend in parallel to each other.
Further, the light entering the light conduction plate, that is,
the second light conduction plate 331, may first be incident
perpendicularly to the light conduction plate, that is, to the
second light conduction plate 331, or may enter at a certain
incident angle other than 0 degrees.
[0255] Meanwhile, where the first diffraction grating member 340 is
formed from a reflection type volume hologram diffraction grating,
the light transmission factor T of the reflection type volume
hologram diffraction grating can be set, for example, to 0.1 to 0.9
by selection of the material to be used for the reflection type
volume hologram diffraction grating, optimization of the thickness
of the reflection type volume hologram diffraction grating and
optimization of the refractive index modulation degree. .DELTA.n of
the reflection type volume hologram diffraction grating. The light
transmission factor T may be determined, for example, by carrying
out various tests. Or, the light transmission factor T may be
varied along the Z direction. By the countermeasures, the
difference in brightness in the Z direction of the light which
propagates in the inside of the light conduction plate, that is, of
the second light conduction plate 331, can be reduced.
[0256] Where light which first enters the light conduction plate,
that is, the second light conduction plate 331, enters
perpendicularly into the light conduction plate, that is, into the
second light conduction plate 331, and the first reflecting mirror
711 and the second reflecting mirror 712 extend in parallel to each
other and besides the distance between the first reflecting mirror
711 and the second reflecting mirror 712, that is, the length of a
normal to the first reflecting mirror 711 when the normal crosses
with the second reflecting mirror 712, is represented by L.sub.0,
the angle defined by the first reflecting mirror 711 and the
conduction plate, that is, the second light conduction plate 331,
is represented by .theta..sub.d, the incidence angle when the light
enters the first reflecting mirror 711 is represented by
.theta..sub.in and besides the length in the Z direction of the
light when the light first enters the first reflecting mirror 711
is represented by Z.sub.0, L.sub.0, .theta..sub.d, .theta..sub.in
and Z.sub.0 may have a relationship given by the following
expression:
Z.sub.0=2.times.L.sub.0.times.tan(.theta..sub.in).times.cos(.theta..sub.-
d)
[0257] By adopting such a configuration as described above, the
beam diameter in the Z direction of light to emerge from the beam
expansion section 710 can be made greater than the beam diameter
along the Z direction of the light incident to the beam expansion
section 710. Accordingly, the shape of the light flux emitted from
the image production apparatus to enter the beam expansion section
710 is deformed appropriately by the beam expansion section 710 and
then introduced into the second light conduction section 330.
Therefore, there is no necessity to set a great diameter of the
aperture stop in the Z direction in the image formation apparatus.
In other words, there is no necessity to increase the diameter of
the lens provided in the collimate optical system or the like
provided in the image formation apparatus, and reduction in size
and weight of the image displaying apparatus can be anticipated.
Further, such a problem that the display contrast drops and the
picture quality deteriorates does not occur. This similarly applies
also to the embodiment 8 hereinafter described.
[0258] In the image displaying apparatus 700 of the embodiment 7,
the image production apparatus 110 includes, similarly as in the
embodiment 1:
[0259] (A-1) an image formation apparatus 111 having a plurality of
pixels arrayed in a two-dimensional matrix; and
[0260] (A-2) a collimate optical system 112 for converting light
emitted from the pixels of the image formation apparatus 111 into
parallel light; and
[0261] a light flux of the parallel light obtained by the
conversion by the collimate optical system 112 is introduced to the
beam expansion section 710.
[0262] Alternatively, in the image displaying apparatus 700 of the
embodiment 7, the image production apparatus 210 includes,
similarly as in the embodiment 2:
[0263] (A-1) a light source 261;
[0264] (A-2) a collimate optical system 262 for converting light
emitted from the light source 261 into parallel light;
[0265] (A-3) a scanning section 263 for scanning the parallel light
emitted from the collimate optical system 262; and
[0266] (A-4) a relay optical system 264 for relaying the parallel
light scanned by the scanning section 263; and
[0267] a light flux of the parallel light obtained by the
conversion by the relay optical system 264 is introduced to the
beam expansion section 710.
[0268] It is to be noted that the light conduction section, that
is, the second light conduction section 330, may be configured
similarly to the second light conduction section 330 described
hereinabove in connection with the embodiment 3, and therefore,
overlapping description the same is omitted hereinto avoid
redundancy. Further, the image displaying apparatus of the
embodiment 7 described hereinabove and the image displaying
apparatus of the embodiment 8 which is hereinafter described can
naturally be applied to the head-mounted type display units
described hereinabove in connection with the embodiments 5 and
6.
Embodiment 8
[0269] The embodiment 8 is a modification to the embodiment 7.
Image display apparatus according to the embodiment 8 are
conceptually shown in FIGS. 16 to 19, and an arrangement state of
the image production apparatus, beam expansion section and light
conduction section (hereinafter referred to as "second conduction
section" similarly as in the description of the embodiment 7) is
schematically illustrated in FIG. 13B. It is to be noted that the
image displaying apparatus shown in FIG. 16 is an application of
the beam expansion section in the embodiment 8 to the image
displaying apparatus of the embodiment 3 described hereinabove with
reference to FIG. 3A. Meanwhile, the image displaying apparatus
shown in FIG. 17 is an application of the beam expansion section in
the embodiment 8 to the image displaying apparatus of the
embodiment 4 described hereinabove with reference to FIG. 4.
Further, the image displaying apparatus shown in FIG. 18 is an
application of the beam expansion section in the embodiment 8 to
the image displaying apparatus of the embodiment 1 described
hereinabove with reference to FIG. 1. Furthermore, the image
displaying apparatus shown in FIG. 19 is an application of the beam
expansion section in the embodiment 8 to the image displaying
apparatus of the embodiment 2 described hereinabove with reference
to FIG. 2.
[0270] In the embodiment 8, the beam expansion section 810 includes
a half-mirror 811 and a reflecting mirror 812 which are positioned
adjacent the image production apparatus with reference to the light
conduction section, that is, on the light incidence side of the
light conduction section. Part of light emitted from the image
production apparatus passes through the half-mirror 811 and enters
the light conduction section, that is, the second light conduction
section 130 or 330, while the remaining part of the light is
reflected by the half-mirror 811 and enters the reflecting mirror
812. Then, a series of operations that part of the light reflected
by the reflecting mirror 812 passes through the half-mirror 811 and
enters the light conduction, that is, the second light conduction
section 130 or 330 while the remaining part of the light is
reflected by the half-mirror 811 and comes to the reflecting mirror
812 is repeated by a predetermined number of times. In the example
shown in FIG. 13B, the light is reflected twice by the reflecting
mirror 812. Where the half-mirror 811 and the reflecting mirror 812
extend in parallel to each other and light is reflected twice by
the reflecting mirror 812, the light which begins to propagate in
the inside of the light conduction plate, that is, of the second
light conduction plate 131 or 331, is finally expanded by
approximately three times in the Z direction of the light which
first enters the light conduction plate, that is, the second light
conduction plate 131 or 331.
[0271] Preferably the half-mirror 811 and the reflecting mirror 812
extend in parallel to each other. Further, the light which first
enters the light conduction plate, that is, the second light
conduction plate 131 or 331, may be incident perpendicularly to the
light conduction plate, that is, to the second light conduction
plate 131 or 331 or may be incident at a certain incidence angle
other than 0 degrees.
[0272] Meanwhile, where the first diffraction section 340 is formed
from a reflection type volume hologram diffraction grating, the
light transmission factor T of the reflection type volume hologram
diffraction grating can be set, for example, to 0.1 to 0.9 by
selection of the material to be used for the reflection type volume
hologram diffraction grating, optimization of the thickness of the
reflection type volume hologram diffraction grating and
optimization of the refractive index modulation degree .DELTA.n of
the reflection type volume hologram diffraction grating. The light
transmission factor T may be determined, for example, by carrying
out various tests. Alternatively, the light transmission factor T
of the half-mirror 811 may be varied along the Z direction. By the
countermeasures, the difference in brightness in the Z direction of
the light which propagates in the inside of the light conduction
plate, that is, of the second light conduction plate 331, can be
reduced.
[0273] Where light which first enters the light conduction plate,
that is, the second light conduction plate 331, enters
perpendicularly into the light conduction plate, that is, into the
second light conduction plate 331, and the half-mirror 811 and the
reflecting mirror 812 extend in parallel to each other and besides
the distance between the half-mirror 811 and the reflecting mirror
812, that is, the length of a normal to the half-mirror 811 when
the normal crosses with the reflecting mirror 812, is represented
by L.sub.0, the angle defined by the half-mirror 811 and the
conduction plate, that is, the second light conduction plate 331,
is represented by .theta..sub.d, the incidence angle when the light
enters the half-mirror 811 is represented by .theta..sub.in and
besides the length in the Z direction of the light when the light
first enters the half-mirror 811 is represented by Z.sub.0, a
relationship of L.sub.0, .theta..sub.d, .theta..sub.in and Z.sub.0
may have given by the following expression:
Z.sub.0=2.times.L.sub.0.times.tan(.theta..sub.in).times.cos(.theta..sub.-
d)
[0274] It is to be noted that, in the image displaying apparatus
800 of the embodiment 8, the image production apparatus 110 may be
configured similarly to that in the embodiment 1 and the image
production apparatus 210 may be configured similarly to that in the
embodiment 2. Further, the light conduction section, that is, the
second light conduction section 130 or 330, may be configured
similarly to the second light conduction section 130 described
hereinabove in connection with the embodiment 1 or the second light
conduction section 330 described hereinabove in connection with the
embodiment 3. Therefore, detailed description of them is omitted
herein to avoid redundancy.
Embodiment 9
[0275] Also the embodiment 9 is a modification to the embodiment 7.
Arrangement states of the image production apparatus, beam
expansion section and light conduction section in the embodiment 9
as viewed in the Y direction and the X direction are schematically
illustrated in FIGS. 28A and 28B, respectively. It is to be noted
that the second conduction plate 331 is not shown in FIG. 28B, and
the second conduction plate 331 is not shown in FIG. 30B.
[0276] In the beam expansion section 710 described hereinabove in
the description of the embodiment 7, light which begins to
propagate in the inside of the light conduction plate, that is, the
second light conduction plate 331, is finally expanded, for
example, to approximately three times in the Z direction of the
light incident first to the light conduction plate, that is, to the
second light conduction plate 331. However, according to
circumstances, there is the possibility that it may become
necessary to set the diameter of the aperture stop in the Y
direction of the image formation apparatus to a great diameter. A
light flux is supposed whose horizontal angle of view assumes a
negative maximum value in the collimate optical system 112 or the
relay optical system 264. A behavior of the light flux in the beam
expansion section 710 when the light flux enters the beam expansion
section 710 is schematically illustrated in FIGS. 30A and 30B.
Here, FIGS. 30A and 30B illustrate the arrangement states of the
image production apparatus, beam expansion section and light
conductor section in the embodiment 7 as viewed in the Y direction
and the Z direction, respectively.
[0277] As seen from FIGS. 30A and 30B, a light flux which is
repetitively reflected between the first reflecting mirror 711 and
the second reflecting mirror 712 gradually moves in the -Y
direction. For example, in FIGS. 30A and 30B, a light flux denoted
by reference character a whose horizontal angle of view assumes a
negative maximum angle collides with and is reflected by the first
reflecting mirror 711 at a point "b" and then collides with and is
reflected by the second reflecting mirror 712 at another point "c."
Thereafter, the light flux collides with and is reflected by the
first reflecting mirror 711 at a further point "d," and then
collides with and is reflected by the second reflecting mirror 712
at a still further point "e," whereafter it enters and is
diffracted and reflected by an end portion "f" in the Y direction
of the second light conduction section 330. In this instance, the
light flux entering the end portion "f" in the Y direction of the
second light conduction section 330 is displaced by .DELTA.Y' in
the -Y direction with reference to the emerging position "a" from
the collimate optical system 112 or the relay optical system 264.
Similarly, when another light flux whose horizontal angle of view
assumes a positive maximum value is supposed, the light flux is
displaced by .DELTA.Y' in the +Y direction with reference to the
emerging position from the collimate optical system 112 or the
relay optical system 264.
[0278] Here, the position of the first deflection section 340 which
diffracts and reflects a parallel light flux group emerging from
the collimate optical system 112 or the relay optical system 264
and incoming to the second light conduction section 330 becomes the
aperture stop position in the Y direction. Accordingly, it
sometimes becomes necessary to set the diameter in the Y direction
of the collimate optical system 112 or the relay optical system 264
to a great diameter. In particular, in the example shown in FIGS.
30A and 30B, the diameter in the Y direction of the collimate
optical system 112 or the relay optical system 264 must have a
value equal to the sum of the length in the Y direction of the
first deflection section 340 and 2.times..DELTA.Y'.
[0279] In the working example 9, as seen in FIGS. 29A and 29B which
show the beam expansion section in an enlarged scale, the light
reflecting faces of a first reflecting mirror 721 and a second
reflecting mirror 722 which configure a beam expansion section 720
have a plurality of concave and convex portions 723 and 724,
respectively. Here, the concave and convex portions 723 and 724
extend in planes parallel to a plane defined by the X axis and the
Z axis and have a shape of a combination of adjacent sides to the
right angle of a right-angled triangle along the Y direction when
it is assumed to cut the concave and convex portions 723 and 724 in
planes defined by normal lines to the first reflecting mirror 2721
and the second reflecting mirror 2722 and the Y axis. In
particular, each of the concave and convex portions 723 and 724 has
a shape of a rectangular prism whose axial line extends in parallel
to a plane defined by the X axis and the Z axis and whose vertical
angle is 90 degrees. While, in the working example 9, the
right-angled triangle is an isosceles triangle having adjacent
sides which are equal in length to each other and the adjacent
sides of the right-angled triangles of the same shape along the Y
direction are juxtaposed with each other, the configuration of the
concave and convex portions 723 and 724 is not limited to this. It
is to be noted that a point at which a center light flux emerging
from the center of the collimate optical system 112 or the relay
optical system 264 and passing through an image formation apparatus
side nodal point enters the first reflecting mirror 721 is defined
as a reflecting mirror central point. Further, an axial line which
passes the center of the first reflecting mirror and extends in
parallel to the X direction is defined as an X axis while another
axial line which passes the first reflecting mirror central point
and extends in parallel to the Y direction is defined as a Y axis
and a further axis parallel to the Z direction is defined as a Z
axis.
[0280] Two inclined faces of a light reflecting face corresponding
to adjacent sides to the right angle of a write-angled triangle are
individually referred to as a first inclined face 723A or 724A and
a second inclined face 723B or 724B for the convenience of
description. As seen from FIG. 29C which shows an enlarged
schematic partial sectional view, light incident to the first
reflecting mirror 721 collides, for example, with the first
inclined face 723A and is reflected by the first inclined face
723A, and then collides with and is reflected by the second
inclined face 723B, whereafter it is emitted from the first
reflecting mirror 721. The light incident to the first inclined
face 723A and the light emerging from the second inclined face 723B
are parallel to each other. Similarly, light incident to the second
reflecting mirror 722 collides, for example, with and is reflected
by the first inclined face 724A and then collides with and is
reflected by the second inclined face 724B, whereafter it is
emitted from the second reflecting mirror 722. The light incident
to the first inclined face 724A and the light emerging from the
second inclined face 724B are parallel to each other. It is to be
noted that light reflecting layers 725 and 726 made of a light
reflecting material such as, for example, aluminum are provided on
the light reflecting faces of the first reflecting mirror 721 and
the second reflecting mirror 722, respectively.
[0281] A light flux whose horizontal angle of view assumes a
maximum value in the collimate optical system 112 or the relay
optical system 264 is supposed. A behavior of the beam expansion
section 720 when such a light flux as just described enters the
beam expansion section 2720 is schematically illustrated in FIGS.
28A and 28B.
[0282] As seen from FIGS. 28A and 28B, reflection of light is
repeated between the first reflecting mirror 721 and the second
reflecting mirror 722. However, a colliding point of a light flux
with the first reflecting mirror 721 and a colliding point of the
light flux with the second reflecting mirror 722 do not move in the
Y direction but merely move in the X direction and the Y direction
in principle. For example, in the example illustrates in FIGS. 28A
and 28B, a light flux denoted by "a" whose horizontal angle of view
assumes a negative maximum value collides with and is reflected by
the first reflecting mirror 721 at a point "b," and then collides
with and is reflected by the second reflecting mirror 722 at
another point "c." Thereafter, the light flux collides with and is
reflected by the first reflecting mirror 721 at a further point
"d," and then collides with and is reflected by the second
reflecting mirror 722 at a still further point "e," and then enters
and is diffracted and reflected by a Y direction end portion "f" of
the second light conduction section 330. In this instance, the
light flux entering the Y direction end portion "f" of the second
light conduction section 330 is displaced by .DELTA.Y in the -Y
direction with reference to the emerging position "a" from the
collimate optical system 2112 or the relay optical system 264.
Similarly, when another light flux whose horizontal angle of view
assumes a positive maximum value is assumed, the light flux
incident to the Y direction end portion "f" is displaced by
.DELTA.Y in the +Y direction with reference to the emerging
position from the collimate optical system 112 or the relay optical
system 264. However, the value of the displacement amount .DELTA.Y
is lower than the value of the displacement amount .DELTA.Y' shown
in FIG. 30B.
[0283] Here, as described hereinabove, the position of the first
deflection section 340 which diffracts and reflects a parallel
light flux group emerging from the collimate optical system 112 or
the relay optical system 264 and incoming to the second light
conduction section 330 becomes the aperture stop position in the Y
direction. In particular, in the example shown in FIGS. 28A and
28B, the diameter in the Y direction of the collimate optical
system 112 and the relay optical system 264 must be set to a value
equal to the sum of the length in the Y direction of the first
deflection section 340 and 2.times..DELTA.Y. However, the value of
the displacement amount .DELTA.Y is lower than the value of the
displacement amount .DELTA.Y' described hereinabove with reference
to FIG. 30B with certainty. Therefore, there is no necessity to
form the first reflecting mirror 2721 and the second reflecting
mirror 2722 as reversal mirrors to set the diameter of the
collimate optical system 2112 or the relay optical system 2264 in
the Y direction to a great value or, even if the diameter is set to
a great value, there is no necessity to make the diameter in the Y
direction very much.
[0284] Further, in the second light conduction section in the
embodiment 3 or 4, such a configuration that the first deflection
section formed from a transmission type hologram is disposed on the
first face 332 of the second light conduction plate 331 and a
second deflection section formed from a reflection type hologram is
disposed on the second face 333 may be adopted.
[0285] As a modification to the image forming apparatus suitable
for use with the embodiment 1, 3, 7 or 8, for example, such an
image formation apparatus of the active matrix type as conceptually
shown in FIG. 20 may be used. Referring to FIG. 20, the image
formation apparatus includes a light emitting panel wherein a
plurality of light emitting elements 501 each formed from a
semiconductor light emitting element are arrayed in a
two-dimensional matrix. The light emitting/no-light emitting state
of each of the light emitting elements 501 is controlled so that
the light emitting state of the light emitting element 501 is
directly visually observed to display an image. Light emitted from
the image formation apparatus enters the second light conduction
plate 131 or 331 through the collimate optical system 112.
[0286] Alternatively, the image formation apparatus may be formed
as an image formation apparatus for color display which includes,
as conceptually shown in FIG. 21,
[0287] (.alpha.) a red light emitting panel 511R wherein a
plurality of red light emitting elements 501R for emitting red
light are arrayed in a two-dimensional matrix;
[0288] (.beta.) a green light emitting panel 511G wherein a
plurality of green light emitting elements 501G for emitting green
light are arrayed in a two-dimensional matrix;
[0289] (.gamma.) a blue light emitting panel 511B wherein a
plurality of blue light emitting elements 501B for emitting blue
light are arrayed in a two-dimensional matrix; and
[0290] (.delta.) a member such as, for example, a dichroic prism
503, for integrating the light emitted from the red light emitting
panel 511R, green light emitting panel 511G and blue light emitting
panel 511B into a single light flux, and
[0291] the light emitting/no-light emitting state of the red light
emitting elements 501R, green light emitting element 501G and blue
light emitting elements 501B is individually controlled. Also the
light emitted from this image formation apparatus is introduced to
the second light conduction plate 131 or 331 through the collimate
optical system 112. It is to be noted that reference numeral 512
denotes a microlens element for condensing the light emitted from
the light emitting elements.
[0292] An image formation apparatus including light emitting panels
511R, 511G and 511B in which such light emitting elements 501R,
501G and 501B as described above are arrayed in a two-dimensional
matrix, respectively, is conceptually shown in FIG. 22. Referring
to FIG. 22, light emitted from the light emitting panels 511R, 511G
and 511B is controlled to pass or not pass by light passage
controlling apparatus 504R, 504G and 504B, respectively, and enters
the dichroic prism 503 by which it is integrated into a single
light flux. The light flux is introduced into the second light
conduction plate 131 or 331 through the collimate optical system
112.
[0293] Meanwhile, an image formation apparatus which includes light
emitting panels 511R, 511G and 511B in which the light emitting
elements 501R, 501G and 501B are arrayed in a two-dimensional
matrix, respectively, is shown conceptually shown in FIG. 23.
Referring to FIG. 23, light emitted from the light emitting panels
511R, 511G and 511B enters the dichroic prism 503, by which fluxes
of the light are integrated into a single light flux. Then, the
light emitted from the dichroic prism 503 is controlled to pass or
not pass by a light passage controlling apparatus 504 and is
introduced to the second light conduction plate 131 or 331 through
the collimate optical system 112.
[0294] Alternatively, the image information apparatus may have such
a configuration as shown in FIG. 24. Referring to FIG. 24, the
image formation apparatus includes a red light emitting element
501R for emitting red light and a light passage controlling
apparatus such as, for example, a liquid crystal display apparatus
504R which is a kind of light valve for controlling
passage/non-passage of light emitted from the red light emitting
element 501R, a green light emitting element 501G for emitting
green light and a light passage controlling apparatus such as, for
example, a liquid crystal display apparatus 504G which is a kind of
light valve for controlling passage/non-passage of light emitted
from the green light emitting element 501G, and a blue light
emitting element 501B for emitting blue light and a light passage
controlling apparatus such as, for example, a liquid crystal
display apparatus 504B which is a kind of light valve for
controlling passage/non-passage of light emitted from the blue
light emitting element 501B. The image formation apparatus further
includes a light conduction member 502 for conducting light emitted
from each of the light emitting elements 501R, 501G and 501B, which
are made of a GaN-based semiconductor, and a member such as, for
example, a dichroic prism 503 for integrating the light conducted
by the light conduction member 502 into a single light flux.
[0295] The present application contains subject matter related to
that disclosed in Japanese Priority Patent Applications JP
2009-170730 filed in the Japan Patent Office on Jul. 22, 2009, JP
2010-101615 filed in the Japan Patent Office on Apr. 27, 2010 and
JP 2010-149346 filed in the Japan Patent Office on Jun. 30, 2010,
the entire contents of which is hereby incorporated by
reference.
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