U.S. patent application number 16/168714 was filed with the patent office on 2019-05-02 for lighting device and projection display apparatus.
The applicant listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to YUSAKU NISHIKAWA, SHIGEKAZU YAMAGISHI.
Application Number | 20190129287 16/168714 |
Document ID | / |
Family ID | 66243769 |
Filed Date | 2019-05-02 |
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United States Patent
Application |
20190129287 |
Kind Code |
A1 |
YAMAGISHI; SHIGEKAZU ; et
al. |
May 2, 2019 |
LIGHTING DEVICE AND PROJECTION DISPLAY APPARATUS
Abstract
A lighting device of the present disclosure includes an
excitation light source, a phosphor, a spreader, a reflective
layer, and a reflective region. The excitation light source emits a
polarized light. The phosphor receives the light as an excitation
light from the excitation light source, and emits a fluorescent
light, the phosphor including a plurality of phosphor pieces
adjacently disposed on the reflective layer, the plurality of
phosphor pieces having a same characteristic. The spreader supports
the phosphor. The reflective layer is disposed between the phosphor
and the spreader, and reflects the fluorescent light. The
reflective region is disposed between the plurality of phosphor
pieces, the reflective region reflecting the received excitation
light while keeping a polarization characteristic of the received
excitation light.
Inventors: |
YAMAGISHI; SHIGEKAZU;
(Osaka, JP) ; NISHIKAWA; YUSAKU; (Osaka,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
66243769 |
Appl. No.: |
16/168714 |
Filed: |
October 23, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03B 21/16 20130101;
F21V 29/70 20150115; G03B 21/2013 20130101; H04N 9/3167 20130101;
G03B 33/12 20130101; G03B 21/204 20130101; F21K 9/64 20160801; H04N
9/3161 20130101; G03B 21/2073 20130101; H04N 9/3164 20130101; F21V
7/30 20180201 |
International
Class: |
G03B 21/20 20060101
G03B021/20; G03B 33/12 20060101 G03B033/12; H04N 9/31 20060101
H04N009/31; F21K 9/64 20060101 F21K009/64 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2017 |
JP |
2017-210680 |
Jul 27, 2018 |
JP |
2018-140792 |
Claims
1. A lighting device comprising: an excitation light source
configured to emit a polarized light; a phosphor configured to
receive the polarized light as an excitation light from the
excitation light source, and emit a fluorescent light, the phosphor
including a plurality of phosphor pieces adjacently disposed on the
reflective layer, the plurality of phosphor pieces having a same
characteristic; a spreader configured to support the phosphor; a
reflective layer disposed between the phosphor and the spreader,
and configured to reflect the fluorescent light; and a reflective
region disposed between the plurality of phosphor pieces, the
reflective region reflecting the received excitation light while
keeping a polarization characteristic of the received excitation
light.
2. The lighting device according to claim 1, further comprising,
between the excitation light source and the phosphor: an afocal
optical system configured to convert the excitation light received
from the excitation light source into collimated light; a diffuser
panel configured to diffuse the received excitation light while
keeping the polarization characteristic; a dichroic mirror disposed
obliquely with respect to the received excitation light, and
configured to reflect an S-polarized light of a waveform of the
excitation light source and transmit a P-polarized light of the
waveform of the excitation light source; a quarter wavelength plate
configured to receive the excitation light from the excitation
light source; and a condenser lens configured to collect the
received excitation light onto the phosphor to form a spot.
3. The lighting device according to claim 1, the light device
further comprises: an adhesive layer disposed between the
reflective layer and the spreader, wherein the reflective layer is
disposed on a face of the phosphor.
4. The lighting device according to claim 1, the light device
further comprises: a light-transmitting adhesive layer is disposed
between the phosphor and the reflective layer, wherein the
reflective layer is disposed on a face of the spreader.
5. The lighting device according to claim 4, wherein the reflective
layer includes a reflective material in a light-transmitting
adhesive material.
6. The lighting device according to claim 1, wherein the phosphor
includes an inorganic material.
7. The lighting device according to claim 6, wherein the phosphor
includes a ceramic plate including the inorganic material.
8. The lighting device according to claim 1, wherein the spreader
includes one of an aluminum material, a copper material, and a
silicon carbide.
9. The lighting device according to claim 1, wherein the excitation
light source includes a blue laser, and the phosphor receives the
excitation light and emits an yellow light.
10. The lighting device according to claim 1, wherein the phosphor
is fixed to the spreader via the reflective layer by diffusion
bonding.
11. The lighting device according to claim 1, wherein the spreader
is fixed, and includes a cooling means inside the spreader or on a
surface of the spreader, the phosphor being not on the surface.
12. The lighting device according to claim 1, wherein a reflective
surface of the reflective region configured to receive the
excitation light has an uneven shape.
13. The lighting device according to claim 1, wherein the
reflective region includes: a light-transmitting member; and the
reflective layer disposed between the light-transmitting member and
the spreader.
14. The lighting device according to claim 1, wherein a reflective
surface of the reflective region configured to receive the
excitation light has a fine uneven portion on a projecting or
recessed reference surface.
15. The lighting device according to claim 1, wherein the
reflective region includes a reflective surface configured to
receive the excitation light, the plurality of phosphor pieces
include phosphor surfaces configured to receive the excitation
light, and an area ratio of the reflective surface to the phosphor
surfaces is 10-20 to 100.
16. The lighting device according to claim 1, wherein the
reflective region includes a reflective surface configured to
receive the excitation light, the plurality of phosphor pieces
include phosphor surfaces configured to receive the excitation
light, and when an area change rate of an effective range of the
excitation light received by the phosphor is .+-.20% or less, a
change rate of an area ratio of the reflective surface to the
phosphor surfaces in the effective range is a half or less of the
area change rate.
17. The lighting device according to claim 2, wherein the quarter
wavelength plate is disposed so that the polarized light
perpendicularly enters the quarter wavelength plate, and an angle
of a phase axis with respect to a polarization axis of the
polarized light is adjustable.
18. The lighting device according to claim 2, wherein a distance
from the phosphor to the condenser lens is adjustable.
19. A projection display apparatus comprising: the lighting device
according to claim 1; an image display element configured to
modulate a light outgoing from the lighting device in response to a
image signal, and generate an image light; and a projection lens
configured to enlarge and project the image light generated by the
image display element.
Description
BACKGROUND
1. Field of the Invention
[0001] The present disclosure relates to a lighting device using a
phosphor, and a projection display apparatus using the lighting
device as a light source.
2. Description of the Related Art
[0002] Patent Literature 1 (Unexamined Japanese Patent Publication
No. 2012-129135) discloses that the directivity of light emission
is controlled by blocking the gaps between divided phosphors with
light absorbing materials. When the light emission intensity
estimated for illumination or the like is used, however, the light
absorbing materials generate a remarkably large amount of heat.
This method is not practical in consideration of the temperature
quenching characteristic of phosphors. Patent Literature 2
(Unexamined Japanese Patent Publication No. 2013-102078) discloses
a technology in which a more effective wall is disposed on the
interface between phosphors and this wall is used as a metal
reflective face. Also in this technology, the interface between
adjacent phosphors has a specific property. Furthermore, metals
having different thermal expansions are disposed on the interface,
so that the reliability is reduced.
[0003] In either technology, different materials are disposed
between phosphors and the excitation light entering the materials
is wasted. Therefore, the efficiency is obviously reduced.
SUMMARY
[0004] The present disclosure provides a lighting device that can
generate, with a simple configuration, a combined color from the
color light of excitation light and the fluorescent light.
Furthermore, by dividing a phosphor into a plurality of phosphor
pieces, this lighting device can achieve a high reliability at
which a delamination fracture does not occur even when the phosphor
has received strong excitation energy.
[0005] A lighting device of the present disclosure includes an
excitation light source, a phosphor, a spreader, a reflective
layer, and a reflective region. The excitation light source emits a
polarized light. The phosphor receives the light as an excitation
light from the excitation light source, and emits a fluorescent
light, the phosphor including a plurality of phosphor pieces
adjacently disposed on the reflective layer, the plurality of
phosphor pieces having a same characteristic. The spreader supports
the phosphor. The reflective layer is disposed between the phosphor
and the spreader, and reflects the fluorescent light. The
reflective region is disposed between the plurality of phosphor
pieces, the reflective region reflecting the received excitation
light while keeping a polarization characteristic of the received
excitation light.
[0006] In a lighting device of the present disclosure, a combined
color (for example, white color) can be generated from the color
light of excitation light and the fluorescent light in a simple
configuration. Furthermore, by dividing a phosphor into a plurality
of phosphor pieces, a high reliability at which a delamination
fracture does not occur even when the phosphor has received strong
excitation energy can be achieved.
BRIEF DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a diagram showing a projection display apparatus
using a phosphor light-source lighting device in accordance with an
exemplary embodiment;
[0008] FIG. 2 is a diagram showing the spectral characteristic of a
dichroic mirror;
[0009] FIG. 3 is a front view of a phosphor device used for the
phosphor light-source lighting device;
[0010] FIG. 4 is a side view of the phosphor device shown in FIG.
3;
[0011] FIG. 5 is a diagram showing a configuration of a reflective
region of the phosphor device;
[0012] FIG. 6 is a diagram showing modified example 1 of the
reflective region of the phosphor device;
[0013] FIG. 7 is a diagram showing modified example 2 of the
reflective region of the phosphor device;
[0014] FIG. 8 is a front view showing the phosphor device in
accordance with modified example 3; and
[0015] FIG. 9 is a side view of the phosphor device shown in FIG.
8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Hereinafter, exemplary embodiments are described in detail
appropriately with reference to the accompanying drawings. Here,
unnecessarily detailed descriptions are sometimes omitted. For
example, the detailed descriptions of well-known items or the
redundant descriptions of substantially the same configuration are
sometimes omitted. The objective of the omission is to avoid
unnecessary redundancy of the following descriptions and to allow
persons skilled in the art to easily understand the present
disclosure.
[0017] The accompanying drawings and the following descriptions are
provided to allow the persons skilled in the art to sufficiently
understand the present disclosure. The drawings and descriptions
are not intended to restrict the subjects described in the
claims.
EXEMPLARY EMBODIMENT
[0018] Hereinafter, an exemplary embodiment of a phosphor
light-source lighting device is described with reference to FIG. 1
to FIG. 9.
[0019] FIG. 1 is a diagram showing the configuration of a
projection display apparatus using the phosphor light-source
lighting device. FIG. 2 is a spectral characteristic diagram of a
dichroic mirror. FIG. 3 is a front view of a phosphor device used
for the phosphor light-source lighting device. FIG. 4 is a side
view of the phosphor device shown in FIG. 3. FIG. 5 is a partially
enlarged view of an A arrow part of the phosphor device of FIG. 3.
FIG. 6 and FIG. 7 are partially enlarged views showing the
configurations of the reflective regions of the phosphor devices in
accordance with modified examples 1 and 2, respectively. FIG. 8 is
a front view of the phosphor device in accordance with modified
example 3. FIG. 9 is a side view of the phosphor device of FIG. 8.
Here, the hatching in the drawings of FIG. 3 to FIG. 9 allows the
configuration to be understood, and does not show cross
sections.
[0020] In FIG. 1, blue laser diode unit 101 for light sources
includes: a plurality of blue laser diodes; and collimating lenses
disposed on the outgoing side of the blue laser diode unit
correspondingly to respective blue laser diodes. Blue laser diode
unit 101 can output light while suppressing the spread of laser
beams. Light coming from blue laser diode unit 101 is radiated in
the +X direction, is converted into a substantially telecentric
light (collimated light) by lens 102 and lens 103, and enters
diffuser 104. In other words, lens 102 and lens 103 constitute an
afocal optical system. Diffuser 104 includes an endless number of
fine protrusions on its surface, and can control the outgoing angle
of the incident light after the diffuser panel between the
Y-direction and the direction perpendicular to the paper plane in
FIG. 1. The light having entered diffuser 104 travels in the +X
direction while keeping the polarization characteristic, and enters
dichroic mirror 105 inclined with respect to the principal beam of
the incident light.
[0021] Dichroic mirror 105 has a spectral characteristic shown in
FIG. 2. Incidentally, the light outgoing from blue laser diode unit
101 is polarized (namely, polarized light). In the present
exemplary embodiment, the outgoing light is configured to enter
dichroic mirror 105 as P-polarized light. The perpendicular broken
line in FIG. 2 shows 455 nm, which is the center wavelength of the
light outgoing from blue laser diode unit 101. Blue laser diode
unit 101 is an example of the excitation light source.
[0022] Thus, the incident light to dichroic mirror 105 passes
through it, and then enters .lamda./4 plate 106, which is a quarter
wavelength plate. Here, .lamda./4 plate 106 is set so that a
linearly-polarized incident light perpendicularly enters it. The
phase axis of .lamda./4 plate 106 is set so as to satisfy the
following condition: [0023] the light entering .lamda./4 plate 106
is linearly polarized; but [0024] the light having passed through
.lamda./4 plate 106 is circularly polarized. Generally, the phase
axis with respect to the polarization axis of the incident light is
set at 45.degree.. In this case, however, .lamda./4 plate 106 is
supported so that, around this angle, the angle of the phase axis
can be adjusted with respect to the polarization axis of the
incident light.
[0025] The light having passed through .lamda./4 plate 106 enters
condenser lenses 107 and 108, and then is collected onto a phosphor
of phosphor device 110 to form a spot pattern. Condenser lenses 107
and 108 are integrally stored in barrel 109, and are movable on the
optical axis together with barrel 109. Thus, the distance from the
condenser lenses to the phosphor of phosphor device 110 can be
adjusted. Therefore, the excitation light collected onto the
phosphor is within the range (light collection range 112) shown by
the broken line in FIG. 3. Light collection range 112 is determined
on the basis of: the spread angle of the light coming from blue
laser diode unit 101; the light flux diameter; the specification of
diffuser 104; and the distance from the condenser lenses 107 and
108 to the phosphor. Here, as shown in FIG. 3, the phosphor
includes six phosphor pieces 111a, 111b, 111c, 111d, 111e, and
111f. In some cases, a plurality of phosphor pieces are
collectively called phosphor 111.
[0026] In phosphor device 110, as shown in FIG. 3 and FIG. 4,
phosphor 111 (phosphor pieces 111a, 111b, 111c, 111d, 111e, and
111f) and reflective layer 113 disposed on the back side thereof
are fixed to spreader 115 via light-transmitting adhesive layer
114. Here, spreader 115 is made of a material having a high thermal
conductivity, such as copper. In the present exemplary embodiment,
heat sink 116 as a heat dissipating means is integrally formed.
Spreader 115 is generally called a heat spreader.
[0027] Phosphor 111 receives light as the excitation light from
blue laser diode unit 101, and emits fluorescent light. Phosphor
111 is formed of a ceramic plate made of an inorganic material.
Reflective layer 113 disposed between phosphor 111 and spreader 115
has a property of reflecting the light of a fluorescent wavelength
at which phosphor 111 emits light.
[0028] Phosphor 111 utilizes about half of the incident light as
the excitation light for wavelength conversion, and about half of
the remaining incident light becomes heat. When the temperature
excessively increases, a phenomenon that is called temperature
quenching and decreases the conversion efficiency occurs.
Therefore, in order to prevent the reduction in output and the
increase in generated heat, an appropriate heat dissipation is
required. Therefore, reflective layer 113 is produced as a very
thin layer by vapor deposition or the like, and the influence on
the thermal conductivity is set small. Adhesive layer 114 is
preferably made of a material having a high thermal conductivity,
and its thickness is set also small (for example, 20.mu. or less).
When the phosphor is formed integrally and the excitation energy is
high, there is the following risk: [0029] the phosphor breaks due
to the difference between the amount of thermal expansion generated
by increase in phosphor temperature and the amount of thermal
expansion of fixed spreader 115. Because the absolute amount of the
thermal expansion is small, however, this risk can be suppressed by
forming a slight gap between each of the phosphor pieces and a
different material disposed among them. Here, the gap is originally
required for assembling. This phenomenon is remarkable especially
when the phosphor is made of ceramic.
[0030] As shown in FIG. 3, and as shown in FIG. 5 showing a part of
the A arrow view of FIG. 3, reflective regions 117a and 117b are
disposed among phosphor pieces 111a, 111b, 111c, 111d, 111e, and
111f. As shown in FIG. 5, each of the reflective regions disposed
on spreader 115 as a substrate is configured so as to satisfy the
following conditions: [0031] the surface (reflective surface 117s)
of the reflective region has a zigzag shape or an uneven shape; and
[0032] the incident light is regularly reflected with a certain
diffusion width kept. Reflective surface 117s of the reflective
region is formed on a projecting reference sphere used for
enlarging and reflecting the light coming from the front side.
Here, the reference sphere is the dashed-dotted line shown in FIG.
5, and is an example of a reference surface. Thus, the light is
regularly reflected with a spread kept. Thus, the incident blue
light arrives at the reference sphere through .lamda./4 plate 106
in the state of circularly polarized light, but becomes a
circularly polarized light of reverse rotation after reflection by
reflective surface 117s. That is because the polarization
characteristic is kept even when the circularly polarized light is
reflected by reflective surface 117s. Then, the circularly
polarized light of reverse rotation returns to condenser lenses 107
and 108 with a certain spread angle kept.
[0033] Reflective regions 117a and 117b occupy a surface area of
about 20% of light collection range 112. As discussed above, it is
preferable that the surface area percentage of reflective regions
117a and 117b does not significantly change even when variation in
components related to light collection range 112 somewhat changes
the magnification or position. Specifically, the following
configurations are not preferable: [0034] the surface area
percentage rapidly changes at a center part or in a peripheral
part; and [0035] the surface area significantly changes in a
boundary part in design of light collection range 112. Phosphor 111
has a property of receiving blue light (excitation light) and
emitting yellow light. The ratio between the quantity of the yellow
light emitted in the phosphor region and that of the blue light
reflected in the reflective regions is determined mainly by the
area ratio between the following factors: [0036] the phosphor
surface of phosphor 111 into which the excitation light comes; and
[0037] the total reflective surface of reflective regions 117a and
117b. Therefore, when the area ratio changes significantly, the
white quality of the white light cannot be kept.
[0038] It is preferable that, in light collection range 112 on the
light collection surface of the excitation light, the design center
is defined so that the area ratio of the reflective surface of the
reflective region to the phosphor surface is 10-20 to 100. When the
percentage of the phosphor surface decreases, the brightness is
affected, the surface state and polarization characteristic of the
reflective region vary--not zero --, and the influence on the
amount of loss of the blue light becomes significant. Therefore,
the area percentage of the reflective surface is set at 20 or less.
Furthermore, it is desirable that, when the light collection spot
size (light collection range 112) varies at an area change rate of
.+-.20% or less due to optical variation, the following condition
is satisfied: [0039] the change rate of the area ratio between the
reflective surface of the reflective region and the phosphor
surface is a half or less of the area change rate (for example, 25%
when the ratio between the reflective region and the phosphor
surface is 20:100). Here, the light collection spot size means an
effective range of the excitation light that is formed on the
reflective surface and phosphor surface.
[0040] In the example shown in FIG. 3, reflective region 117a is
disposed between phosphor piece 111a and phosphor piece 111c.
However, a reflective region may be formed between phosphor piece
111a and phosphor piece 111b.
[0041] Thus, the blue light having been reflected by the reflective
surface of reflective regions 117a and 117b comes into .lamda./4
plate 106 again as a circularly polarized light of reverse
rotation, and passes through it. After that, this circularly
polarized light becomes S-polarized light orthogonal to the
polarization direction at the incident time, and enters dichroic
mirror 105. As shown in FIG. 2, the S-polarized blue light of a
center wavelength of 455 nm,--the same as that of the P-polarized
blue light --, is reflected by dichroic mirror 105 and hence
travels in the +Y-direction. The blue light passes through lens
118, mirror 119, and lens 120, and is collected to the incident
surface of rod integrator 121 having a rectangular opening.
[0042] Upon receiving the blue light as the excitation light, a
phosphor 111 part in light collection range 112 emits an yellow
fluorescent light. In the present exemplary embodiment, as the
phosphor, a YAG phosphor that has a relatively high conversion
efficiency and achieves widespread use in a light source market is
employed. The generated yellow light returns to condenser lenses
107 and 108 again similarly to the blue light. The fluorescent
light that has passed through the condenser lenses enters .lamda./4
plate 106, and then enters dichroic mirror 105 without being
affected by the polarization characteristic in .lamda./4 plate 106.
That is because the polarization characteristic of the fluorescent
light is eliminated. Dichroic mirror 105 has a property of
reflecting the light of 440 nm or more regardless of the
polarization characteristic as shown in FIG. 2. Therefore,
similarly to the blue light, the incident yellow light passes
through lens 118, mirror 119, and lens 120, and is collected to the
incident surface of rod integrator 121 having the rectangular
opening.
[0043] The light outgoing from rod integrator 121 enters relay
optical system 122, passes through relay lenses 123 and 124, is
reflected by return mirror 125, passes through field lens 126, and
then enters total internal reflection prism 127. Total internal
reflection prism 127 is formed by fixing first prism 128 to second
prism 129 while keeping a slight gap. The light having entered
total internal reflection prism 127 is totally reflected by total
reflection surface 130, and then enters color prism unit 131.
[0044] Color prism unit 131 is formed by bonding and fixing the
following prisms to each other: [0045] first prism 133 including
dichroic mirror surface 132 having a property of reflecting blue
light; [0046] second prism 135 including dichroic mirror surface
134 having a property of reflecting red light; and [0047] third
prism 136. End surfaces of respective prisms include digital
micro-mirror devices (DMDs) 137, 138, and 139 as shown in FIG. 1.
In these DMDs, very small mirrors are disposed two-dimensionally,
and the falling direction is controlled in two directions in
response to an image signal from the outside. At the falling angle
during the ON signal, the reflected light having been reflected by
a very small mirror returns to color prism unit 131 at an incident
angle of 0.degree.. During the OFF signal, the reflected light
enters color prism unit 131 again at a wide angle. DMD 137 is used
for blue light modulation, DMD 138 is used for red light
modulation, and DMD 139 is used for green light modulation. Each
DMD is an example of an image display element that modulates the
light outgoing from the lighting device in response to the image
signal and generates image light.
[0048] Thus, in the pixel of each of DMDs 137, 138, and 139, color
display can be achieved in the following processes: [0049] the
image light corresponding to the white display mode (ON signal)
returns to color prism unit 131 again; [0050] the image light
passes through first prism 128 and second prism 129 of total
internal reflection prism 127, and then enters projection lens 140;
and [0051] the image light arrives at a screen (not shown).
[0052] In such configuration, phosphor light-source lighting device
100 can process yellow light and blue light on the same optical
path with one block, so that a simple and small system can be
achieved. In the present exemplary embodiment, phosphor
light-source lighting device 100 is used in projection display
apparatus 10, and a DMD is used as the image display element.
However, the present disclosure is not limited to this. The image
display element can be replaced with liquid crystal or the like as
long as it can modulate the incident light.
[0053] Phosphor light-source lighting device 100 of the present
exemplary embodiment is an example of a lighting device. Not an
image display element but a lens group for enlarging and lighting a
forward image is disposed on the outgoing side, and the lens group
can be naturally developed as a lighting apparatus. The phosphor
light-source lighting device of the present disclosure is available
as a lighting device as long as the phosphor light-source lighting
device is formed of an excitation light source, a phosphor device,
and a minimum required optical system disposed between them.
Therefore, rod integrator 121 is not essential, for example.
[0054] In the present exemplary embodiment, reflective regions 117a
and 117b having zigzag shapes or uneven shapes are disposed, on a
substrate, among phosphor pieces 111a, 111b, 111c, 111d, 111e, and
111f. However, any configuration can be employed as long as the
incident light is reflected without affecting the polarization
characteristic. In other words, the same effect can be produced
even when the reference sphere of reflective surface 117s shown in
FIG. 5 has not a projecting shape but a recessed shape. Thus, a
fine uneven portion is disposed on this reference sphere.
[0055] As shown in modified example 1 of FIG. 6, a reflective
region may be formed by fixing transparent member 142 (a part of
light-transmitting member) to spreader 115 via adhesive layer 144.
Here, transparent member 142 includes: diffusing means 141 having a
light-transmitting characteristic on its reflective surface; and
reflective layer 143 on the surface facing the reflective surface.
Here, naturally, the reference sphere can be disposed on the
reflective surface side, the reflective layer 143 side, or both of
them.
[0056] As shown in modified example 2 of FIG. 7, a reflective
region may be formed by mixing beads 146 having different
refractive indices into transparent material 145 to provide a
diffusing function. Also in this case, transparent material 145 is
fixed to spreader 115 via refractive layer 143 using adhesive layer
144. When the diffusivity becomes high in accordance with a set
amount of beads or set refractive indices, however, the
polarization characteristic is difficult to be kept and the
available light quantity decreases. Therefore, the diffusivity must
be suppressed to a level allowing the polarization characteristic
to be kept.
[0057] FIG. 8 is a front view of the phosphor device 210 in
accordance with modified example 3. In FIG. 8, the shapes of the
refractive surfaces of reflective regions 147a, 147b, 147c, and
147d and the shapes of the phosphor surfaces of phosphor pieces
148a, 148b, 148c, and 148d are changed. This case is desirable
because the change in the area ratio between the refractive
surfaces and phosphor surfaces due to the change of the light
collection spot size (light collection range 112) can be
suppressed. FIG. 9 is a side view of phosphor device 210 shown in
FIG. 8. In this case, each refractive surface is formed by
producing the surface of spreader 115 using a partially uneven
material or by producing the surface of spreader 115 in a
saw-tooth-like zigzag shape.
[0058] In this case, the reflective region may be produced in the
following methods: [0059] as shown in modified example 1 of FIG. 6,
an uneven portion is disposed on the front surface of a
light-transmitting member, and a reflective layer is disposed on
the back surface; and [0060] as shown in modified example 2 of FIG.
7, beads having different refractive indices are mixed into a
light-transmitting material to provide a diffusing function, and a
reflective layer is disposed on the back surface.
[0061] In the present exemplary embodiment, a phosphor is made of
an inorganic phosphor, especially ceramic, and is bonded to a
spreader via an adhesive layer. However, some inorganic phosphors
capable of being produced directly on the spreader, or organic
phosphors or the like capable of being mixed with the binder and
being directly applied to the spreader do not require an adhesive
layer. Therefore, only a reflective layer may be formed between the
phosphor and the spreader.
[0062] In the present exemplary embodiment, in phosphor devices 110
and 210, phosphor 111 and reflective layer 113 disposed on the back
surface thereof are fixed to spreader 115 via adhesive layer 114
and integrated with heat sink 116. Here, spreader 115 is made of a
material (copper material) such as copper having a high thermal
conductivity. However, phosphor 111 and reflective layer 113 are
not limited to these. As a reflective layer, a phosphor may be
fixed to a spreader via a light-transmitting adhesive material
including a reflective material. Furthermore, the following method
is also allowed: a reflective layer is disposed between the
phosphor and the spreader without an adhesive layer, and the
phosphor is fixed to a spreader via a reflective layer by diffusion
bonding. Thus, heat dissipation can be performed efficiently
without heat resistance in the adhesive layer. This configuration
can be applied to the reflective regions shown in FIG. 6 and FIG.
7.
[0063] The present exemplary embodiment has shown an example in
which a copper material is used as spreader 115. It is desirable
that first and second essential factors as the spreader are a high
thermal conductivity and a low thermal expansion coefficient,
respectively. Therefore, when the excitation energy is low, the
cost can be reduced using an aluminum material, especially using a
pure aluminum material. While, when the excitation energy is high,
the problem can be addressed by producing the spreader using
ceramic such as silicon carbide having both a high thermal
conductivity and a low thermal expansion coefficient. Thus, the
spreader is fixed in the projection display apparatus differently
from a phosphor wheel, and includes a cooling means inside the
spreader or on a surface of the spreader being where a portion
provided with the phosphor is excluded. In the present exemplary
embodiment, heat sink 116 is used as a cooling means. However,
naturally, it can be changed to another means such as a liquid
cooling means.
[0064] Furthermore, a configuration using a YAG phosphor having a
high conversion efficiency in a visible region has been described.
This configuration is applicable to a lighting device that obtains
output light by finally mixing the light having the wavelength of
excitation light and the light having the wavelength of the
fluorescent light, or to a projection display apparatus.
INDUSTRIAL APPLICABILITY
[0065] The present disclosure is applicable to a lighting device
using a phosphor, or a projection display apparatus.
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