U.S. patent application number 16/941724 was filed with the patent office on 2021-02-04 for light emitting device and projector.
The applicant listed for this patent is Seiko Epson Corporation. Invention is credited to Yoshitaka ITOH.
Application Number | 20210033955 16/941724 |
Document ID | / |
Family ID | 1000005341259 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210033955 |
Kind Code |
A1 |
ITOH; Yoshitaka |
February 4, 2021 |
LIGHT EMITTING DEVICE AND PROJECTOR
Abstract
A light emitting device includes resonant parts constituted by a
photonic crystal structure, and rows each of which includes the
resonant parts arranged along a first direction, wherein light
resonating in the resonant part resonates in a first resonant
direction and a second resonant direction, the rows are arranged
along a second direction, the rows include a first row, and a
second row, a distance between the resonant part located furthest
at one side of the first direction in the first row and the
resonant part located furthest at the one side of the first
direction in the second row is different from a distance between
the resonant part located furthest at the one side of the first
direction and the resonant part located furthest at another side of
the first direction in the first row, the first and second resonant
directions are along the first and second axes respectively, and in
a plan view a length along the first direction of the resonant part
and a length along the second direction of the resonant part are
equal to each other.
Inventors: |
ITOH; Yoshitaka; (Matsumoto,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seiko Epson Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
1000005341259 |
Appl. No.: |
16/941724 |
Filed: |
July 29, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03B 21/2013 20130101;
G03B 21/2033 20130101; H04N 9/3161 20130101; H04N 9/3164
20130101 |
International
Class: |
G03B 21/20 20060101
G03B021/20; H04N 9/31 20060101 H04N009/31 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2019 |
JP |
2019-139486 |
Claims
1. A light emitting device comprising: a plurality of resonant
parts constituted by a photonic crystal structure, and a plurality
of rows each of which includes the resonant parts arranged along a
first direction, wherein light resonating in the resonant part
resonates in a first resonant direction and a second resonant
direction intersecting the first resonant direction, the rows are
arranged along a second direction intersecting the first direction,
p represents number of the resonant parts, q represents number of
the rows, and r represents number of the resonant parts in each
rows, p, q, and r, are satisfy p=q.times.r, the rows include a
first row located furthest at one side of the second direction
among the rows, and a second row located furthest at the other side
of the second direction among the rows, a distance between the
resonant part located furthest at one side of the first direction
in the first row and the resonant part located furthest at the one
side of the first direction in the second row is different from a
distance between the resonant part located furthest at the one side
of the first direction and the resonant part located furthest at
another side of the first direction in the first row, the first
resonant direction is along the first direction and the second
resonant direction is along the second direction, and in a plan
view viewed from a direction along a third direction perpendicular
to a plane including the first direction and the second direction,
a length along the first direction of the resonant part and a
length along the second direction of the resonant part are equal to
each other.
2. The light emitting device according to claim 1, wherein the
resonant part includes a plurality of nano-structures, the
nano-structures are arranged so as to form a square lattice, the
first direction and the second direction are perpendicular to each
other
3. The light emitting device according to claim 1, wherein the
resonant part includes a plurality of nano-structures, the
nano-structures are arranged so as to form an
equilateral-triangular lattice, light resonating in the resonant
part resonates in a fourth resonant direction, the second direction
is tilted 120.degree. with respect to the first direction, and the
third resonant direction is tilted 60.degree. with respect to the
first resonant direction, and the third direction is tilted
60.degree. with respect to the second resonant direction.
4. A projector comprising: the light emitting device according to
claim 1.
5. The projector according to claim 4, further comprising: a light
collection optical system configured to collect light emitted from
the light source device; and a phosphor to be excited by light
emitted from the light collection optical system.
Description
[0001] The present application is based on, and claims priority
from JP Application Serial Number 2019-139486, filed Jul. 30, 2019,
the disclosure of which is hereby incorporated by reference herein
in its entirety.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a light emitting device
and a projector.
2. Related Art
[0003] A projector using a semiconductor laser element as a light
source has been put into practical use.
[0004] In JP-A-2013-190591, for example, there is described a
projector provided with a red light source device, a blue light
source device, and a green light source device formed of a
fluorescence emitting device which is excited by outgoing light
from an excitation light source device.
[0005] As a light source of such a projector as described above,
there is demanded a light emitting device for emitting light having
an isotropic light distribution angle. When using the light
emitting device for emitting the light having the isotropic light
distribution angle, since the cross-sectional shape is a circular
shape, and thus, the light having a homogenous intensity
distribution can be obtained, it is possible to efficiently excite
a phosphor when, for example, exciting the phosphor.
SUMMARY
[0006] A light emitting device according to an aspect of the
present disclosure includes p resonators each having a resonant
part constituted by a photonic crystal structure, wherein light
resonating in the resonant part resonates in a plurality of
resonant directions, in the resonant part, lengths in the plurality
of resonant directions are all equal to each other, q of the
resonant parts are arranged along a first direction to form a row,
the rows are arranged along a second direction as much as r,
p=q.times.r is true, a distance between the resonant part located
furthest at one side of the first direction in the row located
furthest at one side of the second direction of the r rows and the
resonant part located furthest at the one side of the first
direction in the row located furthest at another side of the second
direction of the r rows is different from a distance between the
resonant part located furthest at the one side of the first
direction and the resonant part located furthest at another side of
the first direction in the row located furthest at the one side of
the second direction of the r rows, the plurality of resonant
directions includes a direction along the first direction and a
direction along the second direction, and in a plan view viewed
from a direction along a third direction perpendicular to a plane
including the first direction and the second direction, a length
along the first direction of the resonant part and a length along
the second direction of the resonant part are equal to each
other.
[0007] In the light emitting device according to the above aspect,
nano-structures of the photonic crystal structure may be arranged
so as to form a square lattice, the first direction and the second
direction may be perpendicular to each other, and the plurality of
resonant directions may correspond to the direction along the first
direction and the direction along the second direction.
[0008] In the light emitting device according to the above aspect,
nano-structures of the photonic crystal structure may be arranged
so as to form an equilateral-triangular lattice, the second
direction may be tilted 120.degree. with respect to the first
direction, and the plurality of resonant directions may correspond
to a direction along the first direction, a direction along the
second direction, and a direction along a fourth axis tilted
60.degree. with respect to the first direction.
[0009] A projector according to another aspect of the present
disclosure includes the light emitting device according to one of
the above aspects.
[0010] The projector according to the above aspect may further
include a light collection optical system configured to collect
light emitted from the light source device, and a phosphor to be
excited by light emitted from the light collection optical
system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a plan view schematically showing a light emitting
device according to a first embodiment.
[0012] FIG. 2 is a plan view schematically showing the light
emitting device according to the first embodiment.
[0013] FIG. 3 is a cross-sectional view schematically showing the
light emitting device according to the first embodiment.
[0014] FIG. 4 is a diagram for explaining light emitted from the
light emitting device according to the first embodiment.
[0015] FIG. 5 is a plan view schematically showing a light emitting
device according to a second embodiment.
[0016] FIG. 6 is a plan view schematically showing the light
emitting device according to the second embodiment.
[0017] FIG. 7 is a plan view schematically showing a light sources
module of a projector according to a third embodiment.
[0018] FIG. 8 is a cross-sectional view schematically showing the
light sources module of the projector according to the third
embodiment.
[0019] FIG. 9 is a diagram schematically showing the projector
according to the third embodiment.
[0020] FIG. 10 is a diagram schematically showing a projector
according to a modified example of the third embodiment.
[0021] FIG. 11 is a diagram for explaining light emitted from a
light collection optical system of the projector according to the
modified example of the third embodiment.
[0022] FIG. 12 is a diagram for explaining the light emitted from
the light collection optical system of the projector according to
the modified example of the third embodiment.
[0023] FIG. 13 is a diagram schematically showing a phosphor of the
projector according to the modified example of the third
embodiment.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0024] Some preferred embodiments of the present disclosure will
hereinafter be described in detail using the drawings. It should be
noted that the embodiments described hereinafter do not
unreasonably limit the contents of the present disclosure as set
forth in the appended claims. Further, all of the constituents
described hereinafter are not necessarily essential elements of the
present disclosure.
1. First Embodiment
1.1. Light Emitting Device
[0025] Firstly, a light emitting device according to a first
embodiment will be described with reference to the drawings. FIG. 1
is a plan view schematically showing the light emitting device 100
according to the first embodiment, namely the present embodiment.
It should be noted that in FIG. 1, a first direction A1, a second
direction A2, and a third direction A3 are shown as three axes
crossing each other. In the illustrated example, the first
direction A1, the second direction A2, and the third direction A3
are perpendicular to each other.
[0026] As shown in FIG. 1, the light emitting device 100 has
resonators 12 each having a resonant part 10. The light emitting
device 100 has p pieces of the resonators 12. In other words, the
light emitting device 100 has p pieces of the resonant parts 10. In
the illustrated example, the light emitting device 100 has 64
resonant parts 10. The resonant part 10 is a part where the light
resonates.
[0027] A row 11 of the resonant parts 10 is formed by q of the
resonant parts 10 arranged along the first direction A1. In the
illustrated example, the row 11 of the resonant parts 10 is formed
by 16 of the resonant parts 10 arranged along the first direction
A1. There are arranged the rows as much as r along the second
direction A2. In the illustrated example, there are arranged the
rows 11 as much as 4 along the second direction A2. It should be
noted that p=q.times.r is true. In the illustrated example, the p
resonant parts 10 are arranged in a matrix in a direction along the
first direction A1 and a direction along the second direction A2.
The p resonant parts 10 are, for example, the same in shape and
size.
[0028] A row 11a is a first row which is one of the r rows 11, and
is located the furthest at one side (in the +A2 axis direction in
the illustrated example) of the second direction A2. A resonant
part 10a is one of the resonant parts 10, and is located the
furthest at one side (in the +A1 axis direction in the illustrated
example) of the first direction A1 in the row 11a. A resonant part
10b is one of the resonant parts 10, and is located the furthest at
the other side (in the -A1 axis direction in the illustrated
example) of the first direction A1 in the row 11a.
[0029] A row 11b is a second row which is one of the r rows 11, and
is located the furthest at the other side (in the -A2 axis
direction in the illustrated example) of the second direction A2. A
resonant part 10c is one of the resonant parts 10, and is located
the furthest at the one side (in the +A1 axis direction in the
illustrated example) of the first direction A1 in the row 11b.
[0030] A distance D1 between the resonant part 10a and the resonant
part 10c and a distance D2 between the resonant part 10a and the
resonant part 10b are different from each other. In a plan view
(hereinafter simply referred to as "in the plan view") viewed from
a direction along the third direction A3 perpendicular to a plane
including the first direction A1 and the second direction A2, a
distance between the center of the resonant part 10a and the center
of the resonant part 10c is different from a distance between the
center of the resonant part 10a and the center of the resonant part
10b. In the illustrated example, the distance D1 between the
resonant part 10a and the resonant part 10c is shorter than the
distance D2 between the resonant part 10a and the resonant part
10b.
[0031] Here, FIG. 2 is the plan view schematically showing the
light emitting device 100 according to the first embodiment, namely
the present embodiment. FIG. 3 is a cross-sectional view along the
line III-III shown in FIG. 2, and schematically shows the light
emitting device 100 according to the first embodiment, namely the
present embodiment.
[0032] As shown in FIG. 2 and FIG. 3, the light emitting device 100
has, for example, a substrate 102, a stacked body 103 disposed on
the substrate 102, a first electrode 122, and a second electrode
124. The stacked body 103 has a reflecting layer 104, a buffer
layer 106, a photonic crystal structure 108, and a semiconductor
layer 120. It should be noted that in FIG. 1, the light emitting
device 100 is illustrated in a simplified manner for the sake of
convenience. Further, in FIG. 2, the illustration of members other
than columnar parts 110 of the photonic crystal structure 108 is
omitted.
[0033] The substrate 102 is, for example, an Si substrate, a GaN
substrate, or a sapphire substrate.
[0034] The reflecting layer 104 is disposed on the substrate 102.
The reflecting layer 104 is, for example, a DBR (distributed Bragg
reflector) layer. The reflecting layer 104 is, for example, what is
obtained by alternately stacking AlGaN layers and GaN layers at one
another or what is obtained by alternately stacking AlInN layers
and GaN layers on one another. The reflecting layer 104 reflects
the light generated by a light emitting layer 114 of each of
columnar parts 110 of the photonic crystal structure 108 toward the
second electrode 124.
[0035] It should be noted that in the present specification, when
taking the light emitting layer 114 as a reference in the stacking
direction (hereinafter also referred to simply as a "stacking
direction") of the stacked body 103, the description will be
presented assuming a direction from the light emitting layer 114
toward a semiconductor layer 116 as an "upward direction," and a
direction from the light emitting layer 114 toward a semiconductor
layer 112 as a "downward direction." Further, the "stacking
direction of the stacked body" denotes a stacking direction of the
semiconductor layer 112 and the light emitting layer 114.
[0036] The buffer layer 106 is disposed on the reflecting layer
104. The buffer layer 106 is a layer made of semiconductor such as
an Si-doped n-type GaN layer. In the illustrated example, on the
buffer layer 106, there is disposed a mask layer 128 for growing
the columnar parts 110. The mask layer 128 is, for example, a
silicon oxide layer or a silicon nitride layer.
[0037] The photonic crystal structure 108 is disposed on the buffer
layer 106. The photonic crystal structure 108 has, for example, the
columnar parts 110 and light propagation layers 118.
[0038] The photonic crystal structure 108 can develop an effect of
the photonic crystal, and the light emitted by the light emitting
layers 114 of the photonic crystal structure 108 is confined in an
in-plane direction of the substrate 102, and is emitted in the
stacking direction. Here, the "in-plane direction of the substrate
102" denotes a direction perpendicular to the stacking
direction.
[0039] The columnar parts 110 are disposed on the buffer layer 106.
The planar shape of the columnar part 110 is a polygonal shape such
as a regular hexagon, a circle, or the like. In the example shown
in FIG. 2, the planar shape of the columnar part 110 is a regular
hexagon. The diametrical size of the columnar part 110 is, for
example, in a nanometer-order range, and is specifically not
smaller than 10 nm and not larger than 500 nm. The columnar part
110 is a nano-structure constituting the photonic crystal structure
108. The size in the stacking direction of the columnar part 110
is, for example, not smaller than 0.1 .mu.m and not larger than 5
.mu.m.
[0040] It should be noted that when the planar shape of the
columnar part 110 is a circle, the "diametrical size" denotes the
diameter of the circle, and when the planar shape of the columnar
part 110 is not a circle, the "diametrical size" denotes the
diameter of a minimum enclosing circle. For example, when the
planar shape of the columnar part 110 is a polygonal shape, the
diametrical size of the columnar part 110 is the diameter of a
minimum circle including the polygonal shape inside, and when the
planar shape of the columnar part 110 is an ellipse, the
diametrical size of the columnar part 110 is the diameter of a
minimum circle including the ellipse inside. Further, when the
planar shape of the columnar part 110 is a circle, the "center of
the columnar part 110" denotes the center of the circle, and when
the planar shape of the columnar part 110 is not a circle, the
"center of the columnar part 110" denotes the center of the minimum
enclosing circle. For example, when the planar shape of the
columnar part 110 is a polygonal shape, the center of the columnar
part 110 is the center of a minimum circle including the polygonal
shape inside, and when the planar shape of the columnar part 110 is
an ellipse, the center of the columnar part 110 is the center of a
minimum circle including the ellipse inside.
[0041] The number of the columnar parts 110 disposed is more than
one. An interval between the columnar parts 110 adjacent to each
other is, for example, not smaller than 1 nm and not larger than
500 nm. The columnar parts 110 are periodically disposed in a
predetermined direction at a predetermined pitch.
[0042] In the example shown in FIG. 2, the columnar parts 110 are
arranged so as to form a square lattice. In the illustrated
example, the columnar parts 110 are arranged along the first
direction A1 at a predetermined pitch, and are arranged along the
second direction A2 at a predetermined pitch. The pitch along the
first direction A1 of the columnar parts 110 and the pitch along
the second direction A2 of the columnar parts 110 are equal to each
other. The pitch along the first direction A1 of the columnar parts
110 mentioned here is a distance between the centers of the
columnar parts 110 adjacent to each other along the first direction
A1. The pitch along the second direction A2 of the columnar parts
110 means a distance between the centers of the columnar parts 110
adjacent to each other along the second direction A2.
[0043] As shown in FIG. 3, the columnar parts 110 each have the
semiconductor layer 112, the light emitting layer 114, and the
semiconductor layer 116.
[0044] The semiconductor layer 112 is disposed on the buffer layer
106. The semiconductor layer 112 is, for example, the Si-doped
n-type GaN layer.
[0045] The light emitting layer 114 is disposed on the
semiconductor layer 112. The light emitting layer 114 is disposed
between the semiconductor layer 112 and the semiconductor layer
116. The light emitting layer 114 has a quantum well structure
constituted by, for example, a GaN layer and an InGaN layer. The
light emitting layer 114 is a layer capable of emitting light in
response to injection of an electrical current.
[0046] The semiconductor layer 116 is disposed on the light
emitting layer 114. The semiconductor layer 116 is a layer
different in conductivity type from the semiconductor layer 112.
The semiconductor layer 116 is, for example, an Mg-doped p-type GaN
layer. The semiconductor layers 112, 116 are cladding layers having
a function of confining the light in the light emitting layer
114.
[0047] The light propagation layer 118 is disposed between the
columnar parts 110 adjacent to each other. In the illustrated
example, the light propagation layers 118 are disposed on the mask
layer 128. The refractive index of the light propagation layer 118
is lower than, for example, the refractive index of the light
emitting layer 114. The light propagation layer 118 is, for
example, a silicon oxide layer, an aluminum oxide layer, or a
titanium oxide layer. The light generated in the light emitting
layer 114 can propagate through the light propagation layer
118.
[0048] The resonant part 10 is constituted by the photonic crystal
structure 108. The p resonant parts 10 are separated from each
other. In the illustrated example, the columnar part 110 is not
disposed between the resonant parts 10 adjacent to each other. The
p resonant parts 10 have a single substrate 102 as a common
substrate. In the resonant parts 10 adjacent to each other, the
light resonating in one of the resonant parts 10 does not reach the
other of the resonant parts 10. The distance between the resonant
parts 10 adjacent to each other is longer than the wavelength of
the light generated in the light emitting layer 114. Thus, in the
resonant parts 10 adjacent to each other, it is possible to prevent
the light resonating in one of the resonant parts 10 from reaching
the other of the resonant parts 10.
[0049] It should be noted that although not shown in the drawings,
it is possible to dispose a light absorption part for absorbing
light between the resonant parts 10 adjacent to each other. The
light absorption part is formed of a substance having a narrower
bandgap than the light resonating in the resonant part 10. As the
substance, there can be cited, for example, InGaN and InN. The
light absorption part is, for example, a crystalline body having a
columnar shape or a wall-like shape. Thus, in the resonant parts 10
adjacent to each other, it is possible to prevent the light
resonating in one of the resonant parts 10 from reaching the other
of the resonant parts 10.
[0050] Further, although not shown in the drawings, it is possible
to dispose a light reflection part for reflecting light between the
resonant parts 10 adjacent to each other. For example, by disposing
the columnar parts 110 smaller in pitch and diametrical size than
the columnar parts 110 constituting the resonant part 10 between
the resonant parts 10 adjacent to each other, it is possible to
form the light reflection part. Thus, in the resonant parts 10
adjacent to each other, it is possible to prevent the light
resonating in one of the resonant parts 10 from reaching the other
of the resonant parts 10.
[0051] In the plan view, a length L1 along the first direction A1
of the resonant part 10 and a length L2 along the second direction
A2 of the resonant part 10 are equal to each other. Since the
length L1 and the length L2 are equal to each other, as shown in
FIG. 4, in the light emitted from the resonant part 10, a light
distribution angle .theta.1 along the first direction A1 and a
light distribution angle .theta.2 along the second direction A2
become equal to each other. As described above, it is possible to
check whether or not the length L1 and the length L2 are equal to
each other based on the light distribution angle of the light
emitted from the resonant part 10.
[0052] In the plan view, the shape of the resonant part 10 is, for
example, a square. In the plan view, a diagram formed of straight
lines connecting the centers of the columnar parts 110 located at
the outermost circumference out of the plurality of columnar parts
110 constituting the resonant part 10 is, for example, a square.
When the diagram is a square or a regular hexagon, the light
emitted from the resonant part 10 becomes to have a light
distribution angle which is rotational symmetry with respect to an
emission axis a as shown in FIG. 4. In the illustrated example, the
emission axis a is an axis parallel to the third direction A3.
[0053] The light resonating in the resonant part 10 resonates in a
plurality of resonant directions. In the resonant part 10, the
lengths in the plurality of resonant directions are all equal to
each other. It is possible to check whether or not the lengths in
the resonant directions in the resonant part 10 are all equal to
each other based on the light distribution angle of the light
emitted from the resonant part 10. The plurality of resonant
directions includes a first resonant direction along the first
direction A1 and a second resonant direction along the second
direction A2. In the illustrated example, the plurality of resonant
directions comprises the direction along the first direction A1 and
the direction along the second direction A2. In the plan view, for
example, in the resonant part 10, a distance between the center of
the columnar part 110 located the furthest at the one side of the
first direction A1 and the center of the columnar part 110 located
the furthest at the other side of the first direction A1 is equal
to a distance between the center of the columnar part 110 located
the furthest at the one side of the second direction A2 and the
center of the columnar part 110 located the furthest at the other
side of the second direction A2.
[0054] For example, as shown in FIG. 1, a distance between the
center of the columnar part 110 located the furthest in the -A2
axis direction out of the plurality of columnar parts 110
constituting the resonant part 10a and the center of the columnar
part 110 located the furthest in the +A2 axis direction out of the
plurality of columnar parts 110 constituting the resonant part 10c
is different from a distance between the center of the columnar
part 110 located the furthest in the -A1 axis direction out of the
plurality of columnar parts 110 constituting the resonant part 10a
and the center of the columnar part 110 located the furthest in the
+A1 axis direction out of the plurality of columnar parts 110
constituting the resonant part 10b.
[0055] In the light emitting device 100, the p-type semiconductor
layer 116, the light emitting layer 114 with no impurity doped, and
the n-type semiconductor layer 112 constitute a pin diode. The
semiconductor layers 112, 116 are layers larger in bandgap than the
light emitting layer 114. In the light emitting device 100, when
applying a forward bias voltage of the pin diode between the first
electrode 122 and the second electrode 124 to inject a current,
there occurs recombination of electrons and holes in the light
emitting layer 114. The recombination causes light emission. The
light generated in the light emitting layer 114 propagates through
the light propagation layer 118 in the in-plane direction of the
substrate 102 due to the semiconductor layers 112, 116 to form a
standing wave due to the effect of the photonic crystal in the
photonic crystal structure 108, and is confined in the in-plane
direction of the substrate 102. The light thus confined causes
laser oscillation with the gain in the light emitting layer 114. In
other words, the light generated in the light emitting layer 114
resonates in the in-plane direction of the substrate 102 due to the
photonic crystal structure 108 to cause the laser oscillation.
Specifically, the light generated in the light emitting layer 114
resonates in the in-plane direction of the substrate 102 in the
resonant part 10 of the resonator 12 constituted by the photonic
crystal structure 108 to cause the laser oscillation. Then,
positive first-order diffracted light and negative first-order
diffracted light proceed in the stacking direction as a laser
beam.
[0056] The laser beam proceeding toward the reflecting layer 104
out of the laser beam having proceeded in the stacking direction is
reflected by the reflecting layer 104, and proceeds toward the
second electrode 124. Thus, it is possible for the light emitting
device 100 to emit the light from the second electrode 124
side.
[0057] The semiconductor layer 120 is disposed on the photonic
crystal structure 108. The semiconductor layer 120 is, for example,
an Mg-doped p-type GaN layer.
[0058] The first electrode 122 is disposed on the buffer layer 106.
It is also possible for the buffer layer 106 to have ohmic contact
with the first electrode 122. In the illustrated example, the first
electrode 122 is electrically coupled to the semiconductor layer
112 via the buffer layer 106. The first electrode 122 is one of the
electrodes for injecting the electrical current into the light
emitting layer 114. As the first electrode 122, there is used, for
example, what is obtained by stacking a Ti layer, an A1 layer, and
an Au layer in this order from the buffer layer 106 side.
[0059] The second electrode 124 is disposed on the semiconductor
layer 120. It is also possible for the semiconductor layer 120 to
have ohmic contact with the second electrode 124. The second
electrode 124 is electrically coupled to the semiconductor layer
116. In the illustrated example, the second electrode 124 is
electrically coupled to the semiconductor layer 116 via the
semiconductor layer 120. The second electrode 124 is the other of
the electrodes for injecting the electrical current into the light
emitting layer 114. As the second electrode 124, there is used, for
example, ITO (Indium Tin Oxide). The second electrode 124 disposed
in one of the photonic crystal structures 108 adjacent to each
other and the second electrode 124 disposed in the other of the
photonic crystal structure are electrically coupled to each other
with an interconnection not shown.
[0060] It should be noted that although the light emitting layer
114 of the InGaN type is described above, any types of material
capable of emitting light in response to an electrical current
injected in accordance with the wavelength of the light emitted can
be used as the light emitting layer 114. It is possible to use
semiconductor materials such as an AlGaN type, an AlGaAs type, an
InGaAs type, an InGaAsP type, an InP type, a GaP type, or an AlGaP
type. Further, it is also possible to change the size and the pitch
of the arrangement of the columnar parts 110 in accordance with the
wavelength of the light emitted.
[0061] Further, although the photonic crystal structure 108 has the
columnar parts 110 disposed periodically in the above description,
it is also possible to have hole parts disposed periodically as a
nano-crystal structure in order to develop the photonic crystal
effect.
[0062] The light emitting device 100 has, for example, the
following advantages.
[0063] In the light emitting device 100, there are provided the
resonators 12 each having the resonant part 10 constituted by the
photonic crystal structure 108, and in the plan view, the length L1
along the first direction A1 of the resonant part 10 and the length
L2 along the second direction A2 of the resonant part 10 are equal
to each other. Therefore, in the light emitting device 100, it is
possible to make the light distribution angle along the first
direction A1 and the light distribution angle along the second
direction A2 equal to each other in the light to be emitted from
the resonant part 10. Thus, in the light emitting device 100, it is
possible to emit the light having the isotropic light distribution
angle in the direction along the first direction direction A1 and
the direction along the second direction A2 compared to when the
length L1 and the length L2 are different from each other.
[0064] Further, in the light emitting device 100, the distance D1
between the resonant parts 10a, 10c and the distance D2 between the
resonant parts 10a, 10b are different from each other (e.g., the
area where the plurality of resonant parts 10 is disposed has a
substantially rectangular shape). Therefore, it is easy to increase
the ratio (the length of the circumferential side to the area in an
area where the plurality of resonant parts 10 is disposed) of the
circumference of the light emitting device 100 compared to when the
distance D1 and the distance D2 are equal to each other. The
luminous efficiency lowers when the resonant part 10 is heated, but
in the light emitting device 100, since a substantially rectangular
shape is adopted as the shape of the area where the plurality of
resonant parts 10 is arranged, it becomes easy for the resonant
part 10 to release the heat, and thus, high light output can be
obtained.
1.2. Method of Manufacturing Light Emitting Device
[0065] Then, a method of manufacturing the light emitting device
100 according to the first embodiment will be described with
reference to the drawings.
[0066] As shown in FIG. 3, the reflecting layer 104 and the buffer
layer 106 are grown epitaxially on the substrate 102 in this order.
As the method of achieving the epitaxial growth, there can be
cited, for example, an MOCVD (Metal Organic Chemical Vapor
Deposition) method and an MBE (Molecular Beam Epitaxy) method.
[0067] Then, the mask layer 128 is formed on the buffer layer 106
using the MOCVD method or the MBE method. Then, the semiconductor
layer 112, the light emitting layer 114, and the semiconductor
layer 116 are grown epitaxally on the buffer layer 106 in this
order using the mask layer 128 as a mask. As the method of
achieving the epitaxial growth, there can be cited, for example,
the MOCVD method and the MBE method. Due to the present process, it
is possible to form the columnar parts 110. Then, the light
propagation layers 118 are formed between the columnar parts 110
adjacent to each other using a spin coat method or the like. Due to
the present process, it is possible to form the photonic crystal
structure 108.
[0068] Then, the semiconductor layer 120 is formed on the columnar
parts 110 and the light propagation layers 118 using, for example,
the MOCVD method or the MBE method.
[0069] Subsequently, the first electrode 122 and the second
electrode 124 are formed using, for example, a vacuum evaporation
method.
[0070] According to the process described hereinabove, it is
possible to manufacture the light emitting device 100.
2. Second Embodiment
2.1. Light Emitting Device
[0071] Then, a light emitting device according to a second
embodiment will be described with reference to the drawings. FIG. 5
and FIG. 6 are each a plan view schematically showing the light
emitting device 200 according to the second embodiment. It should
be noted that in FIG. 5, the light emitting device 200 is
illustrated in a simplified manner for the sake of convenience.
Further, in FIG. 6, the illustration of members other than columnar
parts 110 of the photonic crystal structure 108 is omitted.
Further, in FIG. 5 and FIG. 6, the first direction A1, the second
direction A2, the third direction A3, and a fourth axis A4 are
shown as four axes crossing each other.
[0072] Hereinafter, in the light emitting device 200 according to
the second embodiment, the members having substantially the same
functions as those of the constituent members of the light emitting
device 100 according to the first embodiment described above will
be denoted by the same reference symbols, and the detailed
descriptions thereof will be omitted.
[0073] In the light emitting device 100 described above, the
columnar parts 110 are arranged so as to form the square lattice as
shown in FIG. 2. Further, in the light emitting device 100, q of
the resonant parts 10 are arranged along the first direction A1 to
form the row 11, and the rows 11 are arranged as much as r along
the second direction A2 perpendicular to the first direction
A1.
[0074] In contrast, in the light emitting device 200, a plurality
of columnar parts 110 is arranged so as to form an
equilateral-triangular lattice as shown in FIG. 6.
[0075] In the light emitting device 200, the second direction A2 is
tilted 120.degree. with respect to the first direction A1 as shown
in FIG. 5 and FIG. 6. In other words, the rows 11 are arranged as
much as r along the second direction tilted 120.degree. with
respect to the first direction A1. The fourth axis A4 is tilted
60.degree. with respect to the first direction A1. The fourth axis
A4 is tilted 60.degree. with respect to the second direction A2.
The third direction A3 is perpendicular to a plane including the
first direction A1, the second direction A2, and the fourth axis
A4.
[0076] As shown in FIG. 6, a columnar part 110a out of the
plurality of columnar parts 110 is the columnar part 110 adjacent
to a columnar part 110b in a direction along an axis obtained by
rotating the first direction A1 clockwise as much as 30.degree.. A
columnar part 110c out of the plurality of columnar parts 110 is
the columnar part 110 adjacent to the columnar part 110b in a
direction along an axis obtained by rotating the first direction A1
counterclockwise as much as 30.degree.. A diagram formed of a
straight line connecting the center of the columnar part 110a and
the center of the columnar part 110b, a straight line connecting
the center of the columnar part 110b and the center of the columnar
part 110c, and a straight line connecting the center of the
columnar part 110c and the center of the columnar part 110a is an
equilateral triangle.
[0077] In the light emitting device 200, the plurality of resonant
directions comprises a direction along the first direction A1, a
direction along the second direction A2, and a direction along the
fourth axis A4. In the resonant part 10, the lengths in the
direction along the first direction A1, the direction along the
second direction A2, and the direction along the fourth axis A4 are
all equal to each other. In the plan view, for example, in the
resonant part 10, a distance between the center of the columnar
part 110 located the furthest at the one side of the first
direction A1 and the center of the columnar part 110 located the
furthest at the other side of the first direction A1, a distance
between the center of the columnar part 110 located the furthest at
the one side of the second direction A2 and the center of the
columnar part 110 located the furthest at the other side of the
second direction A2, and a distance between the center of the
columnar part 110 located the furthest at one side of the fourth
axis A4 and the center of the columnar part 110 located the
furthest at the other side of the fourth axis A4 are equal to each
other. In the plan view, the shape of the resonant part 10 is, for
example, a regular hexagon. In the plan view, a diagram formed of
straight lines connecting the centers of the columnar parts 110
located at the outermost circumference out of the plurality of
columnar parts 110 constituting the resonant part 10 is, for
example, a regular hexagon.
2.2. Method of Manufacturing Light Emitting Device
[0078] Then, a method of manufacturing the light emitting device
200 according to the second embodiment will be described. The
method of manufacturing the light emitting device 200 according to
the second embodiment is basically the same as the method of
manufacturing the light emitting device 100 according to the first
embodiment described above. Therefore, the detailed description
thereof will be omitted.
3. Third Embodiment
3.1. Projector
[0079] Then, a projector according to a third embodiment will be
described with reference to the drawings. Firstly, a light source
module provided to the projector according to the third embodiment
will be described. FIG. 7 is a plan view schematically showing the
light source module 310 of the projector 300 according to the third
embodiment. FIG. 8 is a cross-sectional view along the line
VIII-VIII shown in FIG. 7 schematically showing the light source
module 310 of the projector 300 according to the third
embodiment.
[0080] As shown in FIG. 7 and FIG. 8, the light source module 310
is provided with, for example, the light emitting devices 100, a
base member 312, a frame member 314, a lid member 316, and
sub-mounts 318. It should be noted that in FIG. 7, the illustration
of the lid member 316 is omitted for the sake of convenience.
Further, in FIG. 7 and FIG. 8, the light emitting devices 100 are
illustrated in a simplified manner.
[0081] The base member 312 is, for example, a plate-like member. It
is preferable for the base member 312 to be high in thermal
conductivity. Thus, it is possible to release the heat generated in
the light emitting devices 100. The material of the base member 312
is, for example, copper, kovar (an alloy obtained by combining
nickel and cobalt with iron), or aluminum nitride.
[0082] As shown in FIG. 8, the frame member 314 couples the base
member 312 and the lid member 316 to each other. The frame member
314 is disposed along the outer circumference of the base member
312 in the plan view. It is preferable for the thermal expansion
coefficient of the frame member 314 to be approximate to the
thermal expansion coefficient of the lid member 316. Thus, it is
possible to reduce the stress caused in the light source module 310
by a difference in thermal expansion coefficient between the frame
member 314 and the lid member 316. The material of the frame member
314 is, for example, kovar.
[0083] The frame member 314 is provided with terminals 315. In the
illustrated example, the terminals 315 each penetrate the frame
member 314. The terminals 315 are electrically coupled to the light
emitting devices 100 via interconnections not shown.
[0084] The lid member 316 is a sealing member for closing an
opening of a recessed part defined by the base member 312 and the
frame member 314. The lid member 316 transmits the light emitted
from the light emitting devices 100. As the lid member 316, there
is used, for example, a sapphire substrate. The light emitting
devices 100 are disposed in a space 2 formed by the base member
312, the frame member 314, and the lid member 316. The space 2 can
be set as a nitrogen atmosphere.
[0085] The sub-mounts 318 are disposed on the base member 312. The
sub-mounts 318 are respectively disposed between the base member
312 and the light emitting devices 100. The plurality of sub-mounts
318 is disposed so as to correspond to the plurality of light
emitting devices 100.
[0086] It is preferable for the sub-mounts 318 to be high in
thermal conductivity. Thus, it is possible to release the heat
generated in the light emitting devices 100. It is preferable for
the thermal expansion coefficient of the sub-mounts 318 to be
approximate to the thermal expansion coefficient of the base member
312 and the thermal expansion coefficient of the light emitting
devices 100. Thus, it is possible to reduce the stress caused in
the light source module 310 due to a difference in thermal
expansion coefficient between the sub-mounts 318 and the base
member 312, and a difference in thermal expansion coefficient
between the sub-mounts 318 and the light emitting devices 100. The
material of the sub-mounts 318 is, for example, aluminum nitride or
aluminum oxide.
[0087] The light emitting devices 100 are respectively disposed on
the sub-mounts 318. The number of the light emitting devices 100
disposed is, for example, more than one. In the illustrated
example, the plurality of light emitting devices 100 is arranged in
a matrix in a direction along the first direction A1 and a
direction along the second direction A2. A distance D3 between the
light emitting devices 100 adjacent to each other in the direction
along the first direction A1 and a distance D4 between the light
emitting devices 100 adjacent to each other in the direction along
the second direction A2 are, for example, equal to each other. It
should be noted that a first distance between areas where the
plurality of resonant parts 10 is disposed in the light emitting
devices 100 adjacent to each other in the direction along the first
direction A1 can be equal to a second distance between areas where
the plurality of resonant parts 10 is disposed in the light
emitting devices 100 adjacent to each other in the direction along
the second direction A2. Further, a third distance between
substantially centers of the areas where the plurality of resonant
parts 10 is disposed in the light emitting devices 100 adjacent to
each other in the direction along the first direction A1 can be
equal to a fourth distance between substantially centers of the
areas where the plurality of resonant parts 10 is disposed in the
light emitting devices 100 adjacent to each other in the direction
along the second direction A2. Since it is possible for the light
emitting devices 100 to emit the light having the isotropic light
distribution angle, by realizing D3=D4, it is possible to obtain
illumination light having a substantially homogenous intensity
distribution on an illumination target distant as much as a
predetermined distance L from the light emitting devices 100.
Depending on a magnitude relationship between the size of the area
where the plurality of resonant parts 10 is disposed and the
distance L, it is possible to obtain the effect described above
when realizing (the first distance)=(the second distance), and it
is possible to obtain the effect described above when realizing
(the third distance)=(the fourth distance).
[0088] Then, a configuration of the projector 300 will be
described. FIG. 9 is a diagram schematically showing the projector
300 according to the third embodiment.
[0089] As shown in FIG. 9, the projector 300 has, for example,
light source modules 310R, 310G, and 310B, diffusion elements 320,
first polarization plates 330, second polarization plates 340,
light modulation elements 350, a colored light combining prism 360,
and a projection lens 370. It should be noted that in FIG. 9, the
light source modules 310R, 310G, and 310B are illustrated in a
simplified manner for the sake of convenience.
[0090] The light source module 310R emits red light. The light
source module 310G emits green light. The light source module 310B
emits blue light. The light source modules 310R, 310G, and 310B are
each, for example, a light source module 310 having the light
emitting devices 100. In the illustrated example, on one surface of
each of the light source modules 310R, 310G, and 310B, there is
disposed a radiator fin 302. The radiator fins 302 radiate the heat
generated in the light source modules 310R, 310G, and 310B. Thus,
it is possible to suppress heating in the light source modules
310R, 310G, and 310B to enhance the luminous efficiency.
[0091] The light emitted from the light source modules 310R, 310G,
and 310B enters the diffusion elements 320, respectively. The
diffusion elements 320 homogenize the intensity distributions of
the light emitted from the light source modules 310R, 310G, and
310B, respectively.
[0092] The light modulation elements 350 modulate the light emitted
from the light source modules 310R, 310G, and 310B, respectively,
in accordance with image information. The light modulation elements
350 are, for example, transmissive liquid crystal light valves for
transmitting the light emitted from the light source modules 310R,
310G, and 310B, respectively. The projector 300 is an LCD (liquid
crystal display) projector.
[0093] On the incident side of each of the light modulation
elements 350, there is disposed the first polarization plate 330.
The first polarization plates 330 adjust polarization directions
and polarization degrees of the light emitted from the light source
modules 310R, 310G, and 310B, respectively. Specifically, the first
polarization plates 330 are each an optical element for
transmitting only the linearly polarized light in a specific
direction. Due to the first polarization plate 330, it is possible
to uniform the polarization direction of the light entering the
light modulation element 350.
[0094] On the exit side of each of the light modulation elements
350, there is disposed the second polarization plate 340. The
second polarization plates 340 function as analyzers with respect
to the light emitted from the light source modules 310R, 310G, and
310B, respectively. The light emitted from the second polarization
plate 340 enters the colored light combining prism 360.
[0095] The colored light combining prism 360 combines the light
emitted from the light source module 310R and then transmitted
through the light modulation element 350, the light emitted from
the light source module 310G and then transmitted through the light
modulation element 350, and the light emitted from the light source
module 310B and then transmitted through the light modulation
element 350 with each other. The colored light combining prism 360
is, for example, a cross dichroic prism which is formed by bonding
four rectangular prisms to each other, and is provided with a
dielectric multilayer film for reflecting the red light and a
dielectric multilayer film for reflecting the blue light disposed
on the inside surfaces thereof.
[0096] The projection lens 370 projects the light combined by the
colored light combining prism 360, namely image light formed by the
light modulation elements 350, on a screen not shown. An enlarged
image is displayed on the screen.
[0097] The projector 300 has the light emitting devices 100 which
can emit the light having the isotropic light distribution angle,
and is easy to release the heat, and can therefore achieve
high-intensity display. Therefore, it is possible to realize a high
display performance.
[0098] It should be noted that although not shown in the drawings,
the projector 300 can be an LCoS (Liquid Crystal on Silicon)
projector having reflective liquid crystal light valves for
reflecting the light emitted from the light source modules 310R,
310G, and 310B.
3.2. Modified Example of Projector
[0099] Then, a projector according to a modified example of the
third embodiment will be described with reference to the drawing.
FIG. 10 is a diagram schematically showing the projector 400
according to the modified example of the third embodiment.
[0100] Hereinafter, in the projector 400 according to the modified
example of the third embodiment, the members having substantially
the same functions as those of the constituent members of the
projector 300 according to the third embodiment described above
will be denoted by the same reference symbols, and the detailed
descriptions thereof will be omitted.
[0101] The projector 300 described above has the light source
modules 310R, 310G, and 310B as shown in FIG. 9.
[0102] In contrast, the projector 400 has the light source module
310B, but does not have the light source modules 310R, 310G as
shown in FIG. 10.
[0103] As shown in FIG. 10, the projector 400 has a light source
410, a color separation optical system 420, light modulation
elements 430R, 430G, and 430B, the colored light combining prism
360, and the projection lens 370.
[0104] The light source 410 has the light source module 310B, a
light collection optical system 411, a phosphor 412, a collimating
optical system 413, lens arrays 414, 415, a polarization conversion
element 416, and a superimposing lens 417.
[0105] The light emitted from the light source module 310B enters
the light collection optical system 411. The light collection
optical system 411 collects the light emitted from the light source
module 310B. The light collection optical system 411 is formed of,
for example, a convex lens. The light emitted from the light
collection optical system 411 enters the phosphor 412. Since the
focus of the light collection optical system 411 is substantially
set on the phosphor 412, the cross-sectional shape and the
intensity distribution of the light entering the phosphor 412
become those reflecting the light distribution angle of the light
emitted from the light source module 310B.
[0106] When exciting the phosphor to generate the fluorescence, the
fluorescence generation efficiency is basically proportional to the
intensity of the excitation light, but degrades when exceeding a
predetermined intensity. Therefore, when exciting the phosphor, it
is desirable to use the light having a substantially homogenous
intensity distribution approximate to a top hat type not having a
sharp peak in the intensity of the light.
[0107] Since the light emitted from the light emitting devices 100
of the light source module 310B has the isotropic light
distribution angle as described above, it is possible to obtain the
excitation light having the intensity distribution approximate to
the top hat type with, for example, the simple light collection
optical system 411 provided with few refractive surfaces. Thus, in
the projector 400, it is possible to realize the high fluorescence
generation efficiency, and it is possible to obtain high light
output. Therefore, it is possible to realize a high-intensity
projector. On the other hand, when the light emitted is not
isotropic, it is necessary to use a light collection optical system
provided with, for example, a number of refractive surfaces or
toric surfaces, and the light collection optical system becomes
complicated in some cases.
[0108] FIG. 11 and FIG. 12 are diagrams for explaining the
intensity distribution of the light emitted from the light
collection optical system 411. It should be noted that in FIG. 11,
there is shown the fact that the brighter a portion is, the higher
the intensity of the light in that portion is. Further, FIG. 12 is
a cross-sectional view along the line XII-XII shown in FIG. 11. The
cross-sectional surface along the XIIa-XIIa line shown in FIG. 11
also has substantially the same intensity distribution as shown in
FIG. 12. As shown in FIG. 11 and FIG. 12, it is possible for the
light emitted from the light collection optical system 411 to have
the intensity distribution approximate to the top hat type.
[0109] FIG. 13 is a diagram schematically showing the phosphor 412.
The phosphor 412 shown in FIG. 10 corresponds to the
cross-sectional view along the line X-X shown in FIG. 13.
[0110] As shown in FIG. 10 and FIG. 13, the phosphor 412 is
disposed on a circular disk 412b which can be rotated by a motor
412a. The phosphor 412 is disposed along a circumferential
direction of the circular disk 412b. The phosphor 412 is excited by
the light emitted from the light collection optical system 411 to
emit the fluorescence consisting of the red light and the green
light, namely the fluorescence consisting of yellow light. The
phosphor 412 transmits a part of the blue light emitted from the
light collection optical system 411. The phosphor 412 is, for
example, a Ce:YAG (Yttrium Aluminum Garnet) type phosphor including
cerium as an activator agent.
[0111] The circular disk 412b transmits the blue light emitted from
the light source module 310B. The material of the circular disk
412b is, for example, quartz glass, quartz crystal, sapphire, or
resin.
[0112] As shown in FIG. 10, the collimating optical system 413 has
a lens 413a for suppressing spread of the light emitted from the
phosphor 412, and a lens 413b for collimating the light emitted
from the lens 413a, and collimates the light emitted from the
phosphor 412 as a whole. The lenses 413a, 413b are each formed of a
convex lens.
[0113] The lens array 414 has a plurality of lenses 414a, the lens
array 415 has a plurality of lenses 415a, and the lenses 414a and
the lenses 415a are set so as to correspond one-to-one to each
other. The light having entered the lens array 414 is divided by
the plurality of lenses 414a into a plurality of light beams, and
then enters the corresponding lenses 415a of the lens array
415.
[0114] The polarization conversion element 416 uniforms the
polarization state of the light beams emitted from the plurality of
lenses 415a of the lens array 415 to output the result as, for
example, P-polarized light.
[0115] The superimposing lens 417 changes the proceeding directions
of the plurality of light beams emitted from the polarization
conversion element 416 to converge the plurality of light beams on
the illumination target area of each of the light modulation
elements 430. Due to the process described above, the light emitted
from the collimating optical system 413 is uniformed in the
polarization state of the light and at the same time converted into
the light having the homogenous intensity distribution on the
illumination target area of each of the light modulation elements
430 by the lens arrays 414, 415, the polarization conversion
element 416, and the superimposing lens 417.
[0116] The color separation optical system 420 has dichroic mirrors
421, 422, mirrors 423, 424, and 425, relay lenses 426, 427, and
field lenses 428R, 428G, and 428B. The dichroic mirrors 421, 422
are each formed by, for example, stacking a dielectric multilayer
film on a glass surface. The dichroic mirrors 421, 422 have a
property of selectively reflecting the colored light in a
predetermined wavelength band, and transmitting the colored light
in the other wavelength band. Here, the dichroic mirror 421
reflects the green light and the blue light. The dichroic mirror
422 reflects the green light.
[0117] The light emitted from the superimposing lens 417 is white
light including the red light R, the green light G, and the blue
light B, and enters the dichroic mirror 421.
[0118] The red light R included in the white light passes through
the dichroic mirror 421 to enter the mirror 423, and is then
reflected by the mirror 423 to enter the field lens 428R. The red
light R is collimated by the field lens 428R, and then enters the
light modulation element 430R.
[0119] The green light G included in the white light is reflected
by the dichroic mirror 421, and is then further reflected by the
dichroic mirror 422 to enter the field lens 428G. The green light G
is collimated by the field lens 428G, and then enters the light
modulation element 430G.
[0120] The blue light B included in the white light is reflected by
the dichroic mirror 421, then passes through the dichroic mirror
422 and the relay lens 426, and is then reflected by the mirror
424, and is further transmitted through the relay lens 427, and
then reflected by the mirror 425 to enter the field lens 428B. The
blue light B is collimated by the field lens 428B, and then enters
the light modulation element 430B.
[0121] The light modulation elements 430R, 430G, and 430B are each,
for example, a transmissive liquid crystal light valve. The light
modulation elements 430R, 430G, and 430B are electrically coupled
to a signal source such as a PC (Personal Computer) for supplying
an image signal including the image information. The light
modulation elements 430R, 430G, and 430B each modulate the incident
light pixel by pixel to form an image based on the image signal
thus supplied. The light modulation elements 430R, 430G, and 430B
form a red image, a green image, and a blue image, respectively.
The image light modulated by the light modulation elements 430R,
430G, and 430B enters the colored light combining prism 360.
[0122] In the colored light combining prism 360, the three colors
of image light are superimposed on each other to thereby be
combined with each other, and the color image light thus combined
is projected by the projection lens 370 on a screen 440 in an
enlarged manner to form a color image.
[0123] In the present disclosure, some of the constituents can be
omitted, or the embodiments and the modified example can be
combined with each other within a range in which the features and
the advantages described in the specification are provided.
[0124] The present disclosure is not limited to the embodiments
described above, but can further variously be modified. For
example, the present disclosure includes substantially the same
configuration as the configurations described in the embodiments.
Substantially the same configuration denotes a configuration
substantially the same in, for example, function, way, and result,
or a configuration substantially the same in object and advantage.
Further, the present disclosure includes configurations obtained by
replacing a non-essential part of the configuration explained in
the above description of the embodiments. Further, the present
disclosure includes configurations providing the same functions and
the same advantages or configurations capable of achieving the same
object as that of the configurations explained in the description
of the embodiments. Further, the present disclosure includes
configurations obtained by adding a known technology to the
configuration explained in the description of the embodiments.
* * * * *