U.S. patent application number 11/405546 was filed with the patent office on 2006-08-17 for display apparatus.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Youichi Horii, Takeshi Hoshino, Rieko Otsuka.
Application Number | 20060181688 11/405546 |
Document ID | / |
Family ID | 33100344 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060181688 |
Kind Code |
A1 |
Hoshino; Takeshi ; et
al. |
August 17, 2006 |
Display apparatus
Abstract
A display apparatus is provided which can display different
text/image information depending on the viewing angle and the
viewer, display a high reality three-dimensional image viewable
from any direction and realize stereoscopic viewing without glasses
or the like. The display apparatus includes a display unit having a
view angle-limiting filter on its surface, a rotary mechanism to
rotate the display unit and a control unit which implements control
so that when the display unit, rotated by the rotary mechanism, is
faced to each of plural directions, the display unit displays a
different text/image content associated with the direction.
Inventors: |
Hoshino; Takeshi; (Kodaira,
JP) ; Horii; Youichi; (Mitaka, JP) ; Otsuka;
Rieko; (Kokubunji, JP) |
Correspondence
Address: |
REED SMITH LLP;Suite 1400
3110 Fairview Park Drive
Falls Church
VA
22042
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
33100344 |
Appl. No.: |
11/405546 |
Filed: |
April 18, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10785051 |
Feb 25, 2004 |
7059733 |
|
|
11405546 |
Apr 18, 2006 |
|
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Current U.S.
Class: |
353/122 ; 353/10;
359/446 |
Current CPC
Class: |
G03B 37/04 20130101;
G09F 19/14 20130101; H04N 13/302 20180501; G03B 21/28 20130101;
H04N 13/393 20180501; H04N 13/307 20180501; G03B 35/24 20130101;
G03B 21/60 20130101; H04N 13/218 20180501; H04N 13/207 20180501;
G03B 21/14 20130101 |
Class at
Publication: |
353/122 ;
359/446; 353/010 |
International
Class: |
G03B 21/00 20060101
G03B021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2003 |
JP |
2003-073371 |
Feb 5, 2004 |
JP |
2004-028798 |
Claims
1. A display apparatus, comprising: a screen having a view
angle-limiting filter on a surface thereof; a rotary mechanism
which rotates the screen; and an electronic projector which, when
the screen being rotated by the rotary mechanism is faced to each
of a plurality of rotation directions, projects each of mutually
different projection images including information or image
corresponding to each of the plurality of rotation directions to
the screen.
2. The display apparatus according to claim 1, wherein the
electronic projector is comprised by arranging with plural around
the screen so as to project each of the mutually different
projection images from each of the plurality of rotation directions
to the screen.
3. The display apparatus according to claim 1, wherein the mutually
different projection images form a three-dimensional image.
4. The display apparatus according to claim 2, wherein the mutually
different projection images form a three-dimensional image.
5. The display apparatus according to claim 1, further comprising a
acquiring unit which acquires the projection images to be projected
from the electronic projector and stores the projection images in a
memory unit; wherein the acquiring unit reads out the projection
images stored in the memory unit so as to supply the projection
images to the electronic projector.
6. The display apparatus according to claim 2, further comprising
each of image pickup devices being arranged by combining with each
of the electronic projectors so that each of the image pickup
devices pickups each of images of an object provided in stead of
the screen at a location being provided the screen on the rotary
mechanism.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation application of U.S.
application Ser. No. 10/785,051 filed Feb. 25, 2004. Priority is
claimed based on U.S. application Ser. No. 10/785,051 filed Feb.
25, 2004, which claims the priority dates of Japanese Patent
Application Nos. 2003-073371 and 2004-028798 filed Mar. 18, 2003
and Feb. 5, 2004, respectively, all of which is incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a display apparatus which
is intended for use in stations, shopping centers and other public
spaces and provides information viewable from any direction and
relates to a display apparatus which provides an image viewable as
a three-dimensional image by persons moving around the
apparatus.
[0003] Information provided from conventional display apparatus
placed in public and other sites can be viewed only from specific
directions.
[0004] In Japanese Patent Laid-open No. 6-301019, a display
apparatus is described wherein a single filter having both a view
angle-limiting function and a heating function is introduced to
minimize the deterioration of display elements in brightness.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a
display apparatus capable of displaying different text or image
information depending on the viewing angle and the viewer.
[0006] It is another object of the present invention to provide a
display apparatus capable of providing a high reality
three-dimensional image to persons therearound.
[0007] It is yet another object of the present invention to provide
a display apparatus capable of realizing stereoscopic viewing
without the necessity of wearing glasses, etc.
[0008] It is still another object of the present invention to
provide an image pickup apparatus capable of picking up images of
an object from a plurality of directions at a time for use in
display apparatus and provide a display apparatus capable of
three-dimensional image communication with this image pickup
apparatus.
[0009] It is still another object of the present invention to
provide a display apparatus having such interacting capabilities as
to change the displayed image if a person approaches or moves a
hand.
[0010] According to an aspect of the present invention, there is
provided a display apparatus comprising: a display unit having a
view angle-limiting filter on a surface thereof; a rotary mechanism
which rotates the display unit; and control unit for implementing
control so that when the display unit, rotated by the rotary
mechanism, is faced to each of plural directions, the display unit
displays a different text or image content associated with the
direction.
[0011] According to another aspect of the present invention, there
is provided a display apparatus comprising: a display unit having a
view angle-limiting filter on a surface thereof; a rotary mechanism
which rotates the display unit; a detection unit for detecting a
direction extending through a viewer; and a control unit for
implementing control so that when the display unit, rotated by the
rotary mechanism, is faced to the detected direction extending
through a viewer, the display unit displays a text or image content
associated with the direction.
[0012] In the above-mentioned display apparatus, the display unit
may be a display or a screen to which text or image information is
projected by an electronic projector and the control unit may have
a memory unit in which the text or image information to be
displayed by the display unit is stored.
[0013] According to yet another aspect of the present invention,
there is provided a display apparatus comprising: a screen having a
view angle-limiting filter on a surface thereof; a rotary mechanism
which rotates the screen; and an electronic projector which when
the screen, rotated by the rotary mechanism, is faced to each of
plural directions, projects a different text or image content
associated with the direction to the screen.
[0014] According to still another aspect of the present invention,
there is provided a display apparatus comprising: a screen having a
view angle-limiting filter on a surface thereof; a rotary mechanism
which rotates the screen; an electronic projector which projects an
image comprising a plurality of different text or image contents;
and a projection optical system by which the image projected from
the electronic projector is divided into the plurality of different
text or image contents and each of the plurality of different text
or contents is projected to the screen when the screen, rotated by
the rotary mechanism, is faced to the associated one of plural
directions.
[0015] The present invention is characterized in that a
three-dimensional image is formed by the plurality of different
text or image contents.
[0016] The present invention is characterized by providing an
acquiring unit for acquiring the content to be projected from the
electronic projector so as to store the content in a memory unit,
wherein the acquiring unit reads out the content stored in the
memory unit so as to supply to the electronic projector.
[0017] The present invention is characterized in that the image
pickup apparatus includes a reflection optical system comprising
plural mirrors arranged circularly; and an image pickup device such
as a camera is set up above the center of the mirror circle;
wherein an object is placed within the mirror circle, plural images
of the object viewed from plural directions are reflected by the
corresponding mirrors and picked up by the image pickup device as a
circular array of images.
[0018] According to still another aspect of the present invention,
there is provided a display apparatus characterized by comprising
sensors such as proximity sensors set up around the apparatus; and
a detection unit for detecting the position and movement of a
viewer according to changes in the states of sensors through a
control unit; wherein an image associated with the detected
position or movement is read out from a memory unit and supplied to
an electronic projector.
[0019] According to the present invention, it is possible to
display different text/image contents to different directions.
[0020] According to the present invention, it is possible to
display an image of an object according to each view direction. For
example, it is possible to view its rear image if the viewer goes
round to the rear of the display apparatus.
[0021] According to the present invention, it is possible to
provide information in an intuitively easy-to-understand style. For
example, in the case of road/passage guidance, information given to
a person is consistent with his traveling direction at that
time.
[0022] According to the present invention, it is also possible to
provide a stereoscopic effect. The viewer can have stereoscopic
vision without wearing glasses. A three-dimensional image can be
viewed from any direction with this stereoscopic effect. This
effect also functions when the image source is moving images
obtained from a memory unit and can be enjoyed by plural persons
simultaneously.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a perspective view of a display apparatus
according to a first embodiment of the present invention;
[0024] FIG. 2 is a general block diagram of the display apparatus
of the first embodiment;
[0025] FIG. 3 is a diagram for explaining the passage guidance;
[0026] FIG. 4 illustrates the guidance contents output from the
display unit;
[0027] FIG. 5 shows a view angle-limiting filter attached to the
surface of the display unit;
[0028] FIGS. 6(a) and 6(b) are perspective views showing concrete
examples of view angle-limiting filters attached to display
surfaces;
[0029] FIGS. 7(a) and 7(b) exaggeratedly show a view angle
limiting-filter whose functional perpendicular direction is
increasingly tilted as the periphery nears; in FIG. 7(a), the
display screen is being viewed by a person right ahead of the
display screen; and in FIG. 7(b), the person is viewing the display
screen which has rotated a little;
[0030] FIGS. 8(a), 8(b) and 8(c) are diagrams for explaining a case
where a maximum view angle is .+-.22.5 degrees, in which FIG. 8(a)
shows the same case, FIG. 8(b) shows display intervals and off
intervals, and FIG. 8(c) shows contents a to d viewable ranges;
[0031] FIGS. 9(a), 9(b) and 9(c) are diagrams for explaining a case
where a maximum view angle is .+-.45 degrees, in which FIG. 9(a)
shows the same case, FIG. 9(b) shows display intervals and off
intervals, and FIG. 9(c) shows contents a to d viewable ranges;
[0032] FIG. 10 is a flowchart showing a control flow for the
display apparatus according to the first embodiment;
[0033] FIG. 11 shows a display unit constructed by bonding two view
angle-limiting filter-attached displays back to back;
[0034] FIG. 12 shows the principle of a display apparatus according
to a second embodiment of the present invention;
[0035] FIG. 13 is a perspective view of the display apparatus
according to the second embodiment;
[0036] FIG. 14 is a general block diagram of the display apparatus
according to the second embodiment;
[0037] FIG. 15 is a diagram showing 16 image divisions projected to
a rotating screen from an electronic projector;
[0038] FIG. 16 is a diagram showing 16 directions a to p from which
projection is made to the rotating screen;
[0039] FIG. 17 is a diagram showing 16 image divisions Ga.about.Gp
which constitutes a three-dimensional image viewed by a person who
moves around the screen;
[0040] FIG. 18 is a diagram for explaining the maximum view
angle;
[0041] FIG. 19 is a diagram for explaining a view angle-limiting
filter-attached screen;
[0042] FIG. 20 is a perspective view showing an example of a view
angle-limiting filter-attached screen;
[0043] FIG. 21 is a perspective view of an acquiring unit for
acquiring (obtaining) image divisions included in the display
apparatus according to the second embodiment;
[0044] FIG. 22 is a general block diagram of the acquiring unit for
acquiring image divisions included in the display apparatus
according to the second embodiment;
[0045] FIGS. 23(a) and 23(b) are diagrams for explaining a
stereoscopic display apparatus according to a third embodiment of
the present invention;
[0046] FIG. 24 is a perspective view of a display apparatus
according to a fourth embodiment of the present invention;
[0047] FIG. 25 is a general block diagram of the display apparatus
of the fourth embodiment;
[0048] FIG. 26 shows the general configuration of another example
of a view angle-limiting filter-attached screen;
[0049] FIG. 27 is a perspective view showing the configuration of a
directional reflection screen;
[0050] FIG. 28 is a perspective view of a modified display
apparatus of the display apparatus according to the fourth
embodiment of the present invention;
[0051] FIG. 29 is a perspective view of an image pickup apparatus
according to a fifth embodiment of the present invention;
[0052] FIG. 30 is a general block diagram of a three-dimensional
image transmission system employed in the image pickup apparatus
according to the fifth embodiment of the present invention;
[0053] FIG. 31 is an oblique perspective view of another image
pickup apparatus according to the fifth embodiment of the present
invention;
[0054] FIG. 32 is a perspective view of a display apparatus
provided with an interaction function according to a sixth
embodiment of the present invention;
[0055] FIG. 33 is a perspective view of a display apparatus
according to a seventh embodiment of the present invention;
[0056] FIG. 34 is a general side view of the display apparatus of
the seventh embodiment;
[0057] FIG. 35 shows eight image divisions projected to a rotating
screen from an electronic projector included in the display
apparatus of the seventh embodiment;
[0058] FIG. 36 is a diagram showing the feature of the Fresnel
lens;
[0059] FIG. 37 shows types of Fresnel lenses;
[0060] FIG. 38 shows a configuration to realize vertical diffusive
reflection by using a Fresnel lens; and
[0061] FIG. 39 is a general side view showing the configuration of
a screen employed in the display apparatus of the seventh
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0062] Preferred embodiments of display apparatus according to the
present invention will be described with reference to the
drawings.
First Embodiment
[0063] Firstly, by using FIGS. 1 to 11, the following describes a
first embodiment of a display apparatus according to the present
invention, which is intended for use in public spaces, such as
stations and shopping centers, for providing information viewable
from any direction. FIG. 1 is a perspective view of the display
apparatus according to the first embodiment of the present
invention. In the first embodiment, text or image (graphic)
information is displayed by a view angle-limited display unit 1
composed of a liquid crystal, plasma or some other thin-shaped
display rotated by a rotary shaft 3 of a rotary mechanism 2. Text
or image (graphic) information displayed at a time can be viewed
only by the people who exist in front of the screen at that time.
That is, the first embodiment is configured such that the display
unit 1 provides different text or image information to individual
viewers depending on the direction from which they view the display
unit 1. Note that although in FIG. 1 the display unit 1 is shown as
a single-display unit composed of a view angle-limited thin-shaped
display, such as a liquid crystal or plasma display, it may also be
configured by uniting two thin-shaped displays back to back.
Further, three, four or more thin-shaped displays may also be
united so as to form three, four or more-sided polygons rotated
around the rotary drive shaft 3 when viewed from the direction of
the rotary drive shaft 3. Although increasing the number of
thin-shaped displays makes the cost higher, this brings about
improvement in brightness and visibility since the same image can
be viewed more than once per revolution. In addition, even if the
screen switching speed is slow as is often the case with liquid
crystal screens, visibility deterioration can be prevented.
Further, this makes it possible to reduce the rotation speed of the
display unit 1.
[0064] In the case of a liquid crystal display, it comprises a
liquid crystal panel and a backlight.
[0065] FIG. 2 is a general block diagram of the display apparatus
according to the first embodiment of the present invention. On the
surface of the display unit 1 composed of a liquid crystal display
or the like, a view angle-limiting filter (view angle-limiting
optical component) is attached as described later. In addition, the
display unit 1 is configured so as to be rotated continuously by
the rotary drive shaft 3 of the rotary mechanism (rotary drive
source) 2. A rotation angle sensor (detecting means) 4 detects the
rotation angle of the display unit 1 (display direction of the
display unit 1) by detecting, for example, the rotation angle of
the rotary drive shaft 3. Besides, the display apparatus may also
be provided with a detection unit (not shown in the figure) to
sense a direction extending through a viewer (or the viewer) by
using an infrared ray sensor or the like. A drive circuit 5 is a
circuit to drive the rotary mechanism (rotary drive source) 2. A
memory unit 7 stores text or image information which is to be
displayed selectively depending on the display direction. FIG. 3
shows that the display apparatus of the first embodiment is set up
where passages are intersected. Passages A, B, C and D respectively
lead to an emergency exit, a stairway, an elevator and a toilet. In
this case, the memory unit 7 stores text or image information a to
d (as shown in FIG. 4) to be displayed respectively when the
display unit 1 is faced to passages A to D.
[0066] A control unit 6 has a radio transmitter (not shown in the
figure) whereas the display unit 1 has a radio receiver (not shown
in the figure). Thus, according to the rotation angle of the
display unit 1 (display direction of the display unit 1) detected
by the rotation angle sensor 4, the control unit 6 can select and
read out an appropriate text or image information content from the
memory unit 7 and send it wirelessly to the display unit 1. This
allows the displayed content to be switched depending on the
display direction of the display unit 1. The control unit 6 may
also be modified in such a manner that if a viewer is detected in
some direction by the aforementioned detection unit, a text/image
information content associated with the direction is selected and
read out from the memory unit 6 so as to display it on the display
unit 1 when the display direction of the display unit 1 is detected
as equal to the direction of the viewer by the rotation angle
sensor 4. For the control unit 6 to select and read out appropriate
text/image information for display on the display unit 1 according
to the rotary drive shaft 3, the rotary mechanism 2 must have a
slip ring, blush or some other signal propagation means.
[0067] DC power can be supplied from the rotary unit 1 to the
conductors of the drive shaft 3 via a slip ring, brush or the like
and then to the display unit 1.
[0068] Assume that the display unit 1 displays a different content
to each of four directions as shown in FIG. 3. The following
describes how its maximum view angle is related with the interval
(off interval). During each interval, a single color such as black
is fully displayed. Alternatively, the backlight may be turned off
if the display unit 1 is a liquid crystal display. To prevent two
different contents from being viewed at the same time, a view
angle-limiting filter (view angle-limiting optical component) 12
must be attached to the surface of a display 11 constituting the
display unit 1 as shown in FIG. 5. The view angle-liming filter 12
is configured as an array of shielding fins 121 as shown in FIG.
6(a). Fins of 100 to 200 .mu.m in thickness are arranged with a
pitch of about 1 to 3 mm equal to the pixel size. The maximum view
angle (viewable range) is dependent on the height of the fins. The
height is about 1 to 3 mm for a maximum view angle of .+-.45
degrees and about 2 to 5 mm for maximum view visibility angle of
about .+-.22.5 degrees. Alternatively, as shown in FIG. 6(b), 50 to
100 .mu.m thickness shielding dividers 122, which have the same
function as the fins 121, may be embedded with a pitch of about 1
to 3 mm equal to the pixel size in the transparent film or sheet
123 whose thickness is about 1 to 3 mm for a maximum view angle of
about .+-.45 degrees and about 2 to 5 mm for a maximum view angle
of about .+-.22.5 degrees. Also note that as shown exaggeratedly in
FIGS. 7(a) and 7(b), the angle formed at a point on the screen of
the display unit 1 between the line of sight and the display
direction of the screen becomes larger as the point goes from the
center to the periphery. To minimize the shielding due to these
angles, fins of the view angle-limiting filter 12 must be slightly
angled. In FIG. 7(a), the screen of the display 11 is being viewed
by a person who exists right ahead of the display 11. In FIG. 7(b),
the display 11 has been rotated a little and the screen is being
viewed from a slightly oblique direction by the person. The same
function of the view angle-limiting filter 12 may also be
implemented by an array of cylindrical lenses each of which
converges light so as to limit the view angle.
[0069] To prevent two different contents from being viewable
concurrently when viewed from any direction, intervals (off
intervals or no-content on intervals) substantially equal to the
maximum view angle must be set as shown in FIGS. 8(a) to 8(c) and
FIGS. 9(a) to 9(c). In each off interval, the display 11 must be
either entirely filled with a single color such as black or remain
turned off (the backlight must remain turned off in the case of a
liquid crystal display). It is also necessary to make the sides and
rear of the display 11 invisible by blackening them (in the case of
one display having one screen) . As a result, persons who view the
display 11 from any direction are given only the text/image
information to be delivered to that direction without noticing the
probably strange movement of the display 11.
[0070] In the case of FIGS. 8(a), 8(b) and 8(c), the maximum view
angle by the view angle-limiting filter 12 is .+-.22.5 degrees when
the display unit 1 is viewed from four directions. To prevent two
different contents from being viewable concurrently when viewed
from any direction, the viewable ranges of contents a, b, c and d
must be set as shown in FIG. 8(c) by imposing off intervals of 45
degrees each as shown in FIG. 8(b) if the view maximum angle is set
to about .+-.22.5 degrees. This means that when the display unit 1
begins/ends a display interval, the view angle is about .+-.22.5
degrees. In this case, each of contents a, b, c and d is displayed
during an interval of .+-.22.5 degrees.
[0071] In the case of FIGS. 9(a), 9(b) and 9(c) the maximum view
angle by the view angle-limiting filter 12 is about .+-.45 degrees
when the display unit 1 is viewed from four directions. To prevent
two different contents from being viewable concurrently when viewed
from any direction, the viewable ranges of contents a, b, c and d
must be set as shown in FIG. 9(c) by imposing off intervals of
about 90 degrees each as shown in FIG. 8(b) if the maximum view
angle is set to .+-.45 degrees. This means that when the display
unit 1 begins/ends a display interval, the view angle is about
.+-.45 degrees. In this case, each of contents a, b, c and d is
displayed for a moment.
[0072] As described so far, by imposing off intervals or no-content
intervals according to the maximum view angle determined by the
view angle-limiting filter 12 attached to the surface of the
display 11, it is possible to prevent two different contents from
being viewable concurrently when the display 11 is viewed from any
direction. This makes it possible to display such guide information
as shown in FIG. 4.
[0073] Then, the following describes how the first embodiment is
controlled with reference to FIG. 10. Firstly, after the control is
started, the rotation angle sensor 4 detects the rotation angle of
the display unit 1 rotated by the rotary mechanism 2 (Step S101).
The control unit 6 refers to a rotation angle-video database stored
in the memory unit 7 (Step S102), reads out text/image information
which is associated with the detected rotation angle of the display
unit 1 and sends the information to the display unit 1. The display
unit 1 is driven by an internal IC driver to display the
information. During an off interval, however, the display unit 1
outputs fully a single color such as black or controls a backlight
driver circuit to turn off the backlight (Step S103). This sequence
is initiated repeatedly in Step S104 so that different text/image
contents are displayed to the respective directions as shown in
FIG. 4.
[0074] Specifically, assume that the display unit 1 is a
single-screen display capable of displaying 60 frames per second
and is controlled so as to deliver information to four directions
and impose off or no-content intervals of 45 degrees each. In this
case, if the off intervals is implemented by turning off the
backlight, each content can be displayed 15 times per second since
the content has only to be switched 4 times per revolution. In
addition, if each off interval is considered one content, each
content is displayed 7.5 times per second since the content is
switched 8 times per revolution. The number of times each content
is displayed per second to the corresponding direction can further
be increased by raising the rotation speed combined with a
high-speed response display. It is also possible to display moving
images as well as still text/image information. Also note that
although equally distant four directions are assumed in the
description of the first embodiment, it is also possible to display
information to unequally distant four directions or display
different pieces of information to five or more directions.
[0075] By the way, if the rotary drive shaft 3 is aligned to the
center of the screen of the display unit 1, points of the screen
near the center line look stationary. However, as the points go
toward the periphery, they look to be more moving while the display
unit 1 is rotating. To provide a stationary text/image content to
persons right ahead of the display unit 1, a plurality of
text/image contents designed to produce the stationary text/image
content during the display interval must be prepared and stored in
the memory unit 7. Making the displayed content look stationary can
also be achieved by minimizing the on time of the display unit if
it provides sufficient brightness.
Second Embodiment
[0076] With reference to FIGS. 12 to 23, the following describes a
display apparatus according to a second embodiment of the present
invention capable of providing a three dimensional image to a
viewer who moves around the display apparatus.
[0077] FIG. 12 shows the principle of the display apparatus
implemented as the second embodiment. A view angle-limiting
filter-attached screen (display unit) 20 is rotated continuously or
stepwise. Around it, a plurality of image pick up devices (CCD
cameras) 22 each combined with an electronic projector 21, such as
a liquid crystal-used one, are placed. The number of image pickup
devices 22 is equal to the number of image divisions to constitute
a three dimensional image of an object. Each electronic projector
21 reads out an image division (for example, one of images Ga to Gp
in FIG. 17) corresponding to its angular position from such a
memory unit 31 as shown in FIG. 14 and projects the frame to the
screen 20. Viewers at any positions around the view angle-limiting
filter-attached screen 20 feel as if the object actually was
present there.
[0078] Image divisions to be projected can be picked up by pick up
devices (CCD cameras) 22. In this case, a three-dimensional object
35 is placed at the position of the screen 20 and shot with the
plural image pickup devices 22. The obtained image divisions are
stored in such a memory unit 31 as shown in FIG. 31. The image
divisions can be stored as still images if the object is not
moving. It is also possible to store them as moving images if the
object is moving.
[0079] In the above description of the principle of the second
embodiment, a plurality of electronic projectors 21 are set up
around the screen 20. As compared with another example described
later, this configuration provides higher image quality although it
is a more complicated and larger-scale implementation. In addition,
since each electronic projector 21 has a light source, illumination
can be raised sufficiently. It is therefore possible for each
electronic projector 21 to display a more definite image if the
projector is turned on momentarily only when the screen is right
ahead of it (remained turned off or displays fully a single color
such as black while the screen is not faced to it) . In this case,
however, means (a detection unit such as a sensor) to detect the
angle of the screen is required (not shown in the figure).
[0080] As such, the following describes another example of the
second embodiment with reference to FIGS. 13 to 22. FIG. 13 shows a
perspective view of the display apparatus of this second
embodiment. A view angle-limiting filter-attached screen 20 is
rotated continuously or stepwise by a rotary mechanism (rotary
drive source) 23. Reference numeral 25 denotes a cylindrical
internally polyhedral mirror (mirror group). 26 is a conical
externally polyhedral mirror (mirror group). These mirrors 25 and
26 form a projection optical system. Reference numeral 27 is an
electronic projector such as a liquid crystal projector. According
to the input image data, it projects such image divisions Ga to Gp
(which constitute a three-dimensional image of an object when
viewed around the object and are arranged circularly in a ring
area) as shown in FIG. 15. Reference numeral 28 is a general
control section comprising a drive circuit 29, a control unit 30
and a memory unit 31. The control unit 30 controls the drive
circuit 29 to drive the rotary mechanism 23 and the electronic
projector 27. The memory unit 31 stores image divisions of a
three-dimensional image Ga to Gp to be projected by the electronic
projector 27. The series data Ga to Gp to be stored in the memory
unit 31 may be either created by computer graphics or the like or
shot by a CCD camera or the like as described later. When a CCD
camera is picked up an object, it is also possible to receive the
three-dimensional image from the remote place and to store it in
the memory unit 31.
[0081] In this configuration, the control unit 30 reads out image
data, such as those shown in FIG. 15, from the memory unit 31 and
sends them to the electronic projector 27. The electronic projector
27 displays the received image data on a liquid crystal panel or
the like. The displayed image data is projected onto the screen 20.
In more detail, the image divisions Ga to Gp arranged in a ring
area are sequentially are projected to the corresponding faces of
the conical externally polyhedral mirror 26 and, reflected there,
projected to the corresponding faces of the cylindrical internally
polyhedral mirror 25 which in turn reflects/projects the image
divisions Ga to Gp of FIG. 17 from respective directions to the
screen 20 as shown in FIG. 16. Each side of the rotating screen 20
comprises a screen plate 20a having each side provided with a view
angle-limiting filter (optical component) 20b (as shown in FIG.
20). This filter limits the maximum view angle (viewable range) to,
e.g., .+-.5.6 degrees (360 degrees/(16.times.4) for 16 image
divisions) from its normal direction. Therefore, only one image
division is viewable from each direction a to p as shown in FIG. 16
since the projected adjacent image divisions are shielded. As a
result, a person moving around across the directions a to p can
view a three-dimensional image of an object, composed of image
divisions Ga to Gp shown in FIG. 17. This method is advantageous in
that plural persons lying at respective locations can
simultaneously enjoy the image. On the other hand, it is
disadvantageous in that each image division is not displayed during
97% ( 31/32) of the display time when 16 image divisions are
displayed per revolution.
[0082] To cope with this disadvantage, the control unit 30 controls
the drive circuit 29 to drive the rotary mechanism 23 so as to face
the screen toward a viewer. The direction of the viewer, one of
directions a to p, is detected by using a detection unit such as an
infrared ray sensor (not shown in the figure) or receiving a radio
directional signal from the viewer (via a remote switch or the
like). For the control unit 30 to control the rotary drive so as to
face the screen 20 toward a viewer, it is necessary to detect the
rotation angle of the screen 20 by a rotation angle-detecting
sensor (not shown in the figure). If the viewer moves around, the
control unit 30 controls the rotation so as to keep the screen 20
faced toward the viewer. This allows the viewer to always view some
image division projected to the screen 20 facing the viewer. In
addition, if only an image division which was shot from the current
direction of the viewer is projected to the screen 20 from the
electronic projector 27, it is possible to eliminate the view
angle-limiting filter 20b. If there are plural viewers, it is
preferable to rotate the screen in steps so as to maximize the
respective periods during which the screen is faced to the viewers.
To prevent each image division from looking blurred, it may be
preferable to momentarily display each image division only when the
screen is just faced to its shot direction. In this case, the lamp
in the projector is implemented by a stroboscopic lamp or a shutter
is used to shield the projection light except when the screen is
just faced to each shot direction. In either method, the sensor
(not shown in the figure) to detect the rotation angle of the
screen is used to detect the moments when the screen is just faced
to the respective directions from which the image divisions were
shot.
[0083] The view angle-liming filter 20b is configured as an array
of shielding fins 211 as shown in FIGS. 19 and 20. Fins of about
100 to 200 .mu.m in thickness are arranged with a pitch of about
0.5 to 2 mm. The maximum view angle (viewable range) is dependent
on the height of the fins. The height is about 5 to 20 mm for a
maximum view angle of .+-.5.6 degrees (in the case of 16 image
divisions) and about 3.2 to 13 mm for maximum view visibility angle
about .+-.9.0 degrees (in the case of 10 image divisions).
Alternatively, about 50 to 200 .mu.m thickness shielding dividers
(not shown in the figure), which have the same function as the
above-mentioned fins, may be embedded with a pitch of about 0.3 to
2 mm in the transparent film or sheet (not shown in the figure)
whose thickness is set to about 3 to 20 mm for a maximum view angle
of about .+-.5.6 degrees (in the case of 16 image divisions) and
about 1.9 to 13 mm for a maximum view angle .+-.9.0 degrees (in the
case of 10 image divisions). The same function of the view
angle-limiting filter 20b may also be implemented by an array of
cylindrical lenses each of which converges light so as to limit the
view angle.
[0084] With reference to FIG. 21, the following describes how to
prepare the image divisions Ga to Gp shown in FIG. 15. That is, the
acquiring unit (apparatus) to acquire the image divisions Ga to Gp
is configured by adding a switching mirror 37 and an image pickup
device (CCD camera) 36 to the apparatus shown in FIG. 13. Firstly,
the view angle-limiting filter-attached screen 20 is removed from
the rotary mechanism 23 and an object 35 is placed where the view
angle-limiting filter-attached screen 20 was mounted. Then, the
image divisions of the stationary object 35, viewed from the
respective directions a to p as shown in FIG. 16, are reflected by
the faces of the cylindrical internally polyhedral mirror 25, the
faces of the conical externally polyhedral mirror 26 and the
switching mirror 37 to the CCD camera 36. The image divisions Ga to
Gp picked up by the CCD camera 36 as shown in FIG. 17 are stored in
the memory unit 31. That is, the image divisions are obtained from
the respective corresponding faces of the cylindrical internally
polyhedral mirror 25 or those of the conical externally polyhedral
mirror 26. To display a moving object, they are stored as moving
images.
[0085] If illumination is required by the CCD camera 36 to pick up
the image divisions Ga to Gp of the object 35 viewed from
directions a to p, for example, a half mirror (not shown in the
figure) is set up between the switching mirror 37 and the CCD
camera 36 so that the half mirror, illuminated by the light source,
illuminates the object 35 sequentially from the directions a to
p.
[0086] Needless to say, when the image divisions Ga to Gp are
projected and displayed on the rotating screen 20, the screen 20 is
mounted on the rotary mechanism 26 after the object 35 is removed,
and the switching mirror 37 is switched before the apparatus is
started.
[0087] As described so far, the image divisions Ga to Gp can be
picked up by the CCD camera 36 that has substantially the same view
angle as the electronic projector 27. Thus, since the image
divisions picked up can directly be used by the electronic
projector 27, the system can be implemented as a compact and
inexpensive one. It is also possible to exchange three-dimensional
images between two systems. One system is set up to use the camera
to pick up images and send them to the other system that is set up
to use the electronic projector.
Third Embodiment
[0088] With reference to FIG. 23, the following describes a
stereoscopic display apparatus according to a third embodiment.
[0089] Assume that the display of the first embodiment or the
screen of the second embodiment is viewed from an arbitrary
position by two eyes as shown in FIG. 23(a). If the apparatus is
configured so that the two eyes respectively view the different
adjacent image divisions due to the limited view angle,
stereoscopic viewing can be realized without wearing glasses, etc.
as shown in FIG. 23(b). Since the left and right eyes are 6 to 7 cm
distant from each other, if the viewer is about 30 cm distant from
the center of the screen, the viewing angle of each eye is about 6
to 7 degrees. In this case, such a display apparatus can be
implemented by setting the number of image divisions to about 25 to
30 and the maximum view angle determined by the view angle-limiting
filter to about 3 to 3.5 degrees.
[0090] According to the third embodiment described above, it is
possible to realize stereoscopic viewing if the angular resolution
is high enough to allow the left and right eyes to view different
image divisions without wearing glasses, etc. This stereoscopic
effect can be enjoyed from any direction between 0 and 360 degrees.
In addition, this effect can be enjoyed by plural viewers
regardless of whether the image source from the memory unit 7 or 31
is still images or moving images.
[0091] In addition, the stereoscopic effect can directly be
obtained from the image divisions of an object which are picked up
by a camera under the above-mentioned condition in the same system
as the second embodiment. The three-dimensional image of the object
can easily be reproduced with the stereoscopic effect in the same
system.
Fourth Embodiment
[0092] With reference to FIGS. 15 to 20 and FIGS. 24 to 28, the
following describes a display apparatus according to a fourth
embodiment of the present invention capable of providing a
three-dimensional image to a viewer who moves around the display
apparatus.
[0093] FIG. 24 is a perspective view of the display apparatus of
the fourth embodiment. A view angle-limiting filter-attached screen
39 is rotated continuously or stepwise by a rotary mechanism
(rotary drive source) 41. Reference numeral 40 denotes a
cylindrical internally polyhedral mirror (mirror group). Reference
numeral 38 is a mirror attached to the inner side of the ceiling of
the display apparatus. These mirrors 38 and 40 form a projection
optical system. Reference numeral 42 is an electronic projector
such as a liquid crystal projector. According to the input image
data, it projects such image divisions Ga to Gp (which constitute a
three-dimensional image of an object when viewed around the object
and are arranged circularly in a ring area) as shown in FIG.
15.
[0094] FIG. 25 is a total block diagram of the display apparatus of
the fourth embodiment. The display apparatus comprises a drive
circuit 44, a control unit 43 to control the drive circuit 44 to
drive a rotary mechanism 41, and an electronic projector 42 and a
memory unit 45 to store image divisions of a three dimensional
image Ga to Gp to be projected by the electronic projector 42. The
series data of the three-dimensional image Ga to Gp to be stored in
the memory unit 45 may be either created by computer graphics or
the like or shot by a CCD camera or the like as described later.
When a CCD camera is picked up an object, it is also possible to
receive, for example, the image data as shown in FIG. 15 from a
remote place and to store it in the memory unit 45.
[0095] In this configuration, the control unit 43 reads out image
data, such as those shown in FIG. 15, from the memory unit 45 and
sends them to the electronic projector 42. The electronic projector
42 projects the image data toward the screen 39. In more detail,
such image divisions Ga through Gp as shown in FIG. 17 are
sequentially projected to the ceiling mirror 38 and, reflected
there, projected to the corresponding faces of the conical
externally polyhedral mirror 40 and, reflected again there,
projected to the screen 39 from directions a to p as shown in FIG.
16.
[0096] Besides the method shown in FIG. 20, the rotating screen 39
can also use a directional reflection screen material as described
in Japanese Patent Laid-open No. 11-258697. FIG. 26 shows how the
screen 39 is configured by using a directional reflection material.
FIG. 27 shows how the directional reflection material is
configured. The directional reflection screen material 46 is
composed of a corner mirror sheet 46a and a lenticular sheet 46b.
To incident light, the directional reflection screen material 46
shows horizontal retroreflection and vertical diffuse reflection.
Incident light is reflected to the incident direction if the angle
of incidence is not larger than .+-.45 degrees. That is, the viewer
continues to view the same image until the directional reflection
screen 46 rotates .+-.45 degrees leftward or rightward after the
screen is just faced to the viewer. Therefore, as compared with
that shown in FIG. 20, the directional reflection screen 46
reflects a larger amount of light since the wider range of angles
of incidence causing reflection to the viewer. As a result, the
displayed image is brighter than that by the screen shown in FIG.
20.
[0097] However, since some of the incident light is reflected to
other directions depending on the angle of incidence, image
divisions to be viewed only from the corresponding directions may
be viewed simultaneously from a signal direction. Accordingly, a
view angle-liming filter 47 (shown in FIG. 26) is used to prevent
the viewer from receiving reflected light from other directions so
that the viewer views only the image division to be rendered to the
direction of the viewer. Similar to that shown in FIGS. 19 and 20,
this view angle-limiting filter 47 is an array of pitches arranged
with a fine pitch. For example, if a view angle-limiting filter
that limits the view angle (viewable range) to .+-.24 degrees from
the normal direction is attached to the surface of the directional
reflection screen 46, reflected light from adjacent image divisions
can be shielded, allowing the viewer to view only a single image
division from the corresponding direction, one of a to p shown in
FIG. 16. As a result, one or more persons moving around across the
directions a to p can view a three-dimensional image of an object,
composed of image divisions Ga to Gp shown in FIG. 17. In addition,
it is also possible to form a both-sided screen by bonding two
directional reflection screens back to back. A lenticular sheet and
a view angle-limiting filter are attached to each side. When using
the both-sided screen, unlike a single-sided screen, each image
division projected from the corresponding mirror is reflected twice
per resolution by the front and rear sides. Therefore, each image
division can be viewed for a longer time while the screen is
rotating.
[0098] FIG. 28 is a block diagram of a display apparatus having a
projection optical system configured differently from that shown in
FIG. 24. Although such components as a view angle-limiting
filter-attached screen 51, an electronic projector 48, a rotary
mechanism 50, a control unit 49 to control the electronic projector
48, cylindrical internally polyhedral mirror 52 and others are
configured in the same manner, the electronic projector 48 is fixed
to the ceiling and the rotary mechanism 50 and screen 51 are set up
right below the electronic projector 48. Such image divisions Ga to
Gp as shown in FIG. 17 are sequentially projected from the
electronic projector 48 to the corresponding faces of the
cylindrical internally polyhedral mirror 52 and, reflected there,
projected to the screen 51 from directions a to p as shown in FIG.
16.
[0099] Either the fourth embodiment or second embodiment allows
more than one persons to simultaneously enjoy a three-dimensional
image from any direction. However, the second embodiment must be
adjusted so that the faces of the cylindrical internally polyhedral
mirror (mirror group) are accurately faced to the corresponding
facets of the conical. externally polyhedral mirror. In the case of
the fourth embodiment, such adjustment is not required and errors
due to subtle deviations of the mirror in position and attitude is
small. The second embodiment is characterized in that since nothing
is set up above the screen, the image is more felt as floating
there. However, since both internal and external mirror groups
require considerably large diameters, the second embodiment
occupies a larger space and imposes a larger distance between the
screen and the viewers than the fourth embodiment.
[0100] As understood from the two examples of the fourth embodiment
mentioned above, the electronic projector may be set up either
above or below the rotary shaft of the screen. In the former case,
projection is made downward from the projector while projection is
made upward in the latter case. In addition, its vertical positions
in the figures merely show its altitudinal relations with the
rotary shaft and image for the purpose of facilitating
understanding. Further, its vertical position is not restricted by
the altitudinal relation between the floor and ceiling where the
display apparatus is set up.
Fifth Embodiment
[0101] With reference to FIGS. 15, 16 and 29 to 31, the following
describes a fifth embodiment of the present invention, an image
pickup device capable of shooting an object from plural directions
at once. For example, such image divisions Ga to Gp shown in FIG.
15 are created at once. FIG. 29 shows the principle of the image
pickup method. A cylindrical internally polyhedral mirror 55 is
arranged circularly in the same manner as the cylindrical
internally polyhedral mirror 40 of the second embodiment. An
optical image pickup device (CCD camera) 55 is set up above the
cylindrical internally polyhedral mirror 55. An object 54 is placed
within the circle of the cylindrical internally polyhedral mirror
55. Then, the image divisions of the object 54, viewed from the
respective directions a to p as shown in FIG. 16, are reflected by
the faces of the cylindrical internally polyhedral mirror 55 and
picked up by the CCD camera 53. The image divisions picked up by
the CCD camera 53 are as shown in FIG. 15. Either still or moving
images can be picked up by the CCD camera 53.
[0102] In FIG. 31, the apparatus is configured so as to pick up a
whole image of a human body. In this configuration, a cylindrical
internally polyhedral mirror 64, a CCD camera 63 and a ceiling
mirror 62 are set up as shown in FIG. 31 and a human being or the
object of image pickup enters into the circle of the cylindrical
internally polyhedral mirror 64. Then, the image divisions of the
object 54, viewed from the respective directions a to p as shown in
FIG. 16, are reflected by the faces of the cylindrical internally
polyhedral mirror 25 and reflected again by the ceiling mirror 62
before picked up by the CCD camera 53. The image divisions are
picked up by the CCD camera 53 are as shown in FIG. 15. In this
case, any number of objects of any kinds can be shot as long as
they can be entered into the circle of the cylindrical internally
polyhedral mirror 64.
[0103] FIG. 30 is a block diagram of real-time three-dimensional
image transmission between the CCD camera 53 in the above-mentioned
image pickup apparatus and the electronic projector 61 in a display
apparatus. From a communication unit of the image pickup apparatus,
images picked up by the CCD camera are sent in the NTSC/PAL or
other formats to the projector 61. Either cable or radio
communication is possible. It is also possible to send acquired
images to a remote place via a network. A display apparatus in the
remote place can display the received images. In addition, the
received images can be displayed as moving images if they were
picked up as moving images.
[0104] Further, the principle of this image pickup apparatus allows
its size to be adapted to the size of the object. That is, the
image apparatus can be optimized to the object by designing the
size of each face of the cylindrical internally polyhedral mirror
and the diameter of the mirror according to the size of the object.
To pick up such image divisions as shown in FIG. 15 from the
cylindrical internally polyhedral mirror, the height of the CCD
camera is adjusted so as to fully cover the mirror.
Sixth Embodiment
[0105] With reference to FIGS. 15 to 17 and 32, the following
describes an interaction function of a display apparatus according
to a sixth embodiment of the present invention. FIG. 32 is a
perspective view of the display apparatus provided with the
interaction function. As shown in FIG. 32, it is possible to detect
an approaching person if proximity sensors are mounted on the outer
surface of the display apparatus or mat switches are laid out on
the floor. It is also possible to detect the direction of the
viewer (for example, one of a to p as shown in FIG. 16) by using as
many sensors, such as infrared ray sensors, proximity sensors and
microphones, as the directions to be detected (for example, 16
directions a to p). In this case, the movement of the viewer can be
detected roughly from the differences among the signals acquired
from adjacent sensors.
[0106] Signals from sensors 65 are processed by a control unit 66.
Images responding to the viewer's movement are sent by the control
unit 66 to an electronic projector 67. For example, it is possible
to provide such an interaction that a character projected to the
screen is turned to face an approaching person according to his
approaching direction detected from sensor signals. The image of
the character, such as that shown in FIG. 15, can be turned by
successively shifting its image divisions Ga to Gp such as those of
FIG. 17 stored in the control unit 66 one or more divisions
circularly at a time before they are projected by the electronic
projector 67. It is also possible to display its front image
division to the direction of the detected person according to the
stored directional information about the image divisions.
[0107] In addition, it is possible to provide such an interaction
that the direction of the character is changed in response to the
direction and the movement to which, for example, the viewer's hand
moved and which are detected from the differences among the signals
from adjacent sensors. Further, it is also possible to detect
approaching plural persons and their motions and generate images in
response to them if more sensors are set.
Seventh Embodiment
[0108] With reference to FIGS. 15 to 17 and 33 to 35, the following
describes a semi-cylindrical display apparatus according to a
seventh embodiment of the present invention capable of displaying a
three-dimensional image.
[0109] FIG. 33 is a perspective view of the semi-cylindrical
display apparatus. FIG. 34 is a general side view of the display
apparatus. A view angle-limiting filter-attached screen 69 is
rotated continuously or stepwise by a rotary mechanism (rotary
drive source) 70. Reference numeral 73 denotes a semi-cylindrical
internally polyhedral mirror (mirror group) . Reference numeral 68
is a mirror attached to the inner side of the ceiling of the
display apparatus. These mirrors 68 and 73 form a projection
optical system. Reference 71 is an electronic projector which
projects such image data as shown in FIG. 35. Reference numeral 72
is a control unit that stores image data and sends image data to
the electronic projector 71.
[0110] FIG. 35 shows image divisions Gb to Gi (those shown in FIG.
17) which constitute a three-dimensional image of an object viewed
around the object. They are arranged semi-circularly in a ring
area. The images in FIG. 35 may be either created freely by
computer graphics or the like or shot (pick up) by a CCD camera or
the like as described in the fifth embodiment.
[0111] In this configuration, the control unit 72 reads out and
sends image data, such as those shown in FIG. 35, to the electronic
projector 71. The electronic projector 71 projects the received
image data so that they are displayed on the screen 69. The image
divisions Gb through Gi projected from the ring area are reflected
by the ceiling mirror 68 to the corresponding faces of the
semi-cylindrical internally polyhedral mirror (mirror group) 73
and, reflected again there, projected to the screen 69 respectively
from the corresponding directions b to i as shown in FIG. 16. The
rotary screen 69 has the property of transmitting an image
projected to the rear surface. To allow a different image to be
viewed depending on the viewing direction, its horizontal view
angle should be limited and it should have a vertically wide range
of viewing angles. Therefore, the screen is made of such a
semi-transmitting diffusion film as used by rear projection
displays.
[0112] The screen 69 may be implemented by using a Fresnel lens.
FIG. 36 shows the feature of the Fresnel lens. The Fresnel lens has
not a continuously curved surface but a stepped surface. As shown
in FIG. 36, light is refracted by stepped parts to condense
transmitted light to the same direction as the incident direction
of light. In the viewing angle, commercially available Fresnel
lenses vary up to about .+-.60 degrees. If a Fresnel lens screen is
used, since light is transmitted to the same direction as the
incident direction and condensed to a predetermined position, the
viewer can view an image being projected to a face of the
semi-cylindrical inner polyhedral mirror 73 when he is at a
position along the line connecting the face and the Fresnel lens
screen. That is, similar to the retroreflection described with the
fourth embodiment, using a Fresnel lens allows the viewer to view
the image corresponding to the viewing direction. In addition, the
viewer can continue to view the same image while the angle of the
Fresnel lens screen is within a certain range (of viewing angle)
relative to the viewing direction. FIG. 37 shows two types of
Fresnel lenses. Reference numeral 74a is the most popular and has a
surface cut concentrically. The lens 74a condenses light both
horizontally and vertically. Thus if this lens is used as the
screen 69 in the display apparatus of the seventh embodiment, the
image reflected by each face of the internally polyhedral mirror 73
can be viewed only within the view angle range of the Fresnel lens
both horizontally and vertically. Therefore, using a Fresnel lens
74b having a surface cut only horizontally is considered
appropriate as the material of the screen 69 since it condenses
light only horizontally.
[0113] To suppress the vertical condensing in order to allow an
image to be viewed from a wider range, the screen is configured so
as to vertically cause diffusive reflection. FIG. 38 is a structure
to let the Fresnel lens perform diffusive reflection vertically. By
attaching (sticking) a lenticular sheet 75, which is similar to the
lenticular sheet 46b shown in FIG. 27, to the surface of the
Fresnel, vertical diffusive reflection can be realized. This makes
the whole screen uniformly bright in the vertical direction,
resulting in an easier-to-view image displayed.
[0114] FIG. 39 is a structure (top view) of the screen 69 using a
Fresnel lens. The lenticular sheet 75 shown in FIG. 38 is attached
to the Fresnel lens in order to cause diffusive reflection
vertically. Further, in order to limit the viewing angle, fins are
attached in the same manner as the view angle-limiting filter shown
in FIG. 20 or such a view angle-limiting filter as used for the
liquid crystal displays of PCs, mobile phones is attached.
[0115] Unlike in the first, second and fourth embodiments, the
image to be viewed is projected from the rear in the seventh
embodiment described so far. Therefore, flickering is suppressed
since fin edges in the view angle-limiting filter are not directly
lit up. This results in a high contrast image displayed. In
addition, although the viewer cannot fully moves around the seventh
embodiment, the viewer can get closer to the screen since the
internally polyhedral mirror is semi-cylindrical as compared with
the cylindrical display apparatus of the first, second and fourth
embodiments. To enlarge the screen and the image displayed on the
screen in the cylindrical display apparatus of each of the first,
second and fourth embodiments, the scale of the whole apparatus
must be enlarged, resulting in a longer distance between the user
and the screen. In the case of the seventh embodiment, the scale of
the whole apparatus can be enlarged without making longer the
distance between the viewer and the screen.
[0116] In the first, second and fourth embodiments, image divisions
such as Ga to Gp (16 divisions) shown in FIG. 15 are arranged
circularly in a ring area and projected from an electronic
projector. In the seventh embodiment, image divisions such as those
(8 divisions) shown in FIG. 35 are arranged semi-circularly in a
ring area and projected. Therefore, if both are projected with the
same resolution, the number of image divisions required in the
seventh embodiment is half that required in the other embodiments.
This means that since the resolution of each image division
projected by the electronic projector in seventh embodiment is four
times as high as that in the first, second and fourth embodiments,
the seventh embodiment has higher power of expression.
[0117] Note that although the internally polyhedral mirror is
assumed to form half of a circle in the above description of the
seventh embodiment, it may also be extended or reduced so as to
form a larger or smaller part of the circle. The angular range of
the three dimensional image which can be viewed is determined by
the angular range covered by the mirror arranged cylindrically. By
using a light transmittance low reflection screen, it is also
possible to form a fully cylindrical display apparatus like in the
second and fourth embodiments.
* * * * *