Light source device and projector

Abstract

To increase the wavelength conversion efficiency of a wavelength conversion element.SOLUTION: A light source device comprises: a light-emitting element that emits first light having a first wavelength range; and a wavelength conversion element that includes a phosphor, converts the first light into second light having a second wavelength range different from the first wavelength range, and emits the second light. The wavelength conversion element has a first surface on which the first light is incident, a second surface that is directed to the opposite side of the first surface, and a third surface that intersects both the first surface and the second surface, and on which the second light is incident. The concentration of a fluorescent emission point of the phosphor increases toward the second surface from the first surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a light source device and a projector. [Background technology]

[0002] As a light source device used in a projector, a light source device has been proposed that emits fluorescence from a phosphor when the phosphor is irradiated with excitation light emitted from a light-emitting element. Patent Document 1 listed below discloses a light source device that includes a light source element that emits excitation light and a wavelength conversion member that contains a phosphor that converts the excitation light into fluorescence. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-108325 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the concentration of fluorescent emission points of the phosphor contained in the wavelength conversion member is uniform throughout the entire wavelength conversion member. Therefore, among the multiple outer surfaces of the wavelength conversion member, the phosphor located closer to the incident surface where excitation light is incident absorbs more excitation light. As a result, if the temperature of the incident surface side of the wavelength conversion member becomes too high, there is a risk that thermal quenching of fluorescence on the incident surface side of the wavelength conversion member will increase. As a result, there is a risk that the wavelength conversion efficiency, which is the efficiency with which the wavelength conversion member converts excitation light into fluorescence, will decrease. [Means for solving the problem]

[0005] One embodiment of the light source device of the present invention comprises a light-emitting element that emits first light having a first wavelength band, and a wavelength conversion element that contains a phosphor and converts the first light into second light having a second wavelength band different from the first wavelength band and emits the second light, wherein the wavelength conversion element has a first surface onto which the first light is incident, a second surface facing opposite to the first surface, and a third surface that intersects both the first surface and the second surface and emits the second light, and the concentration of fluorescent emission points of the phosphor increases from the first surface toward the second surface.

[0006] A projector according to one embodiment of the present invention comprises the above-described light source device, a light modulation device that modulates light including the second light emitted from the light source device, and a projection optical device that projects the light modulated by the light modulation device. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a projector according to a first embodiment. [Figure 2] FIG. 2 is a schematic configuration diagram of a first lighting device according to the first embodiment. [Figure 3] 3 is a cross-sectional view of the light source device taken along line III-III in FIG. 2. FIG. [Figure 4] 4 is a diagram showing the distribution of the concentration of fluorescence emission points in the incident direction of the wavelength conversion element of the first embodiment. FIG. [Figure 5] 4 is a diagram showing the intensity distribution of a first light in the incident direction of the wavelength conversion element of the first embodiment. FIG. [Figure 6] FIG. 3 is a diagram showing a heat generation distribution in the incident direction of the wavelength conversion element of the first embodiment. [Figure 7] FIG. 10 is a schematic configuration diagram of a first lighting device according to a second embodiment. [Figure 8] FIG. 10 is a diagram showing the distribution of the concentration of fluorescence emission points in the incident direction of the wavelength conversion element of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention will be described with reference to the drawings. In the drawings referred to in the following description, each layer or each member may be shown at a different scale to make it easier to see each layer or each member.

[0009] In the following drawings, an XYZ Cartesian coordinate system will be used as necessary for explanation. The Z axis is an axis along the vertical direction of the projector. The X axis is an axis parallel to the first optical axis J1, which is the optical axis of the first lighting device. The Y axis is an axis perpendicular to both the X axis and the Z axis.

[0010] (First embodiment) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a projector 1 according to this embodiment. The projector 1 according to this embodiment is an example of a projector that uses a liquid crystal panel as a light modulation device. As shown in FIG. 1, the projector 1 is a projection-type image display device that displays a color image on a screen SCR, which is a projection surface. The projector 1 includes three light modulation devices 4R, 4G, and 4B corresponding to red light LR, green light LG, and blue light LB. The projector 1 also includes a first illumination device 20, a second illumination device 80, a color separation optical system 3, the light modulation devices 4R, 4G, and 4B, a light combining element 5, and a projection optical device 6.

[0011] The first illumination device 20 emits yellow second light L2 toward the color separation optical system 3. The second illumination device 80 emits blue light LB toward the light modulation device 4B. Detailed configurations of the first illumination device 20 and the second illumination device 80 will be described later.

[0012] The color separation optical system 3 separates the yellow second light L2 emitted from the first illumination device 20 into red light LR and green light LG. The color separation optical system 3 has a dichroic mirror 7, a first reflecting mirror 8a, and a second reflecting mirror 8b.

[0013] The dichroic mirror 7 separates the second light L2 into red light LR and green light LG. The dichroic mirror 7 transmits the red light LR and reflects the green light LG. The second reflecting mirror 8b is disposed in the optical path of the green light LG. The second reflecting mirror 8b reflects the green light LG reflected by the dichroic mirror 7 toward the optical modulation device 4G. The first reflecting mirror 8a is disposed in the optical path of the red light LR. The first reflecting mirror 8a reflects the red light LR transmitted through the dichroic mirror 7 toward the optical modulation device 4R.

[0014] The blue light LB emitted from the second illumination device 80 is reflected by a reflecting mirror 9 toward the light modulation device 4B. The second illumination device 80 has a second light source unit 81, a condenser lens 82, a diffuser plate 83, a rod lens 84, and a relay lens 85. The second light source unit 81 is composed of at least one semiconductor laser. The second light source unit 81 emits blue light LB composed of laser light toward the condenser lens 82. Note that the second light source unit 81 is not limited to being a semiconductor laser, and may be composed of a light emitting diode (LED) that emits blue light.

[0015] The condenser lens 82 is made of a convex lens. The condenser lens 82 condenses the blue light LB emitted from the second light source unit 81 and makes the condensed light incident on the diffuser plate 83. The diffuser plate 83 diffuses the blue light LB emitted from the condenser lens 82 with a predetermined diffusion degree, thereby generating blue light LB having a uniform light distribution. The diffuser plate 83 is made of, for example, frosted glass made of optical glass.

[0016] The blue light LB diffused by the diffuser plate 83 enters the rod lens 84. The rod lens 84 has a rectangular columnar shape extending along the second optical axis J2. The rod lens 84 has a light incident end surface 84a at one end and a light exit end surface 84b at the other end. The diffuser plate 83 is fixed to the light incident end surface 84a of the rod lens 84 with an optical adhesive (not shown). It is desirable that the refractive index of the diffuser plate 83 and the refractive index of the rod lens 84 match as closely as possible. The second optical axis J2 is the central axis of the blue light LB emitted from the second lighting device 80.

[0017] The blue light LB propagates through the rod lens 84 while being totally reflected inside the rod lens 84, and is emitted from the light emitting end surface 84b with an increased uniformity of illuminance distribution. The blue light LB emitted from the rod lens 84 is incident on the relay lens 85. The relay lens 85 causes the blue light LB, whose uniformity of illuminance distribution has been increased by the rod lens 84, to be incident on the reflecting mirror 9.

[0018] The light modulation device 4R modulates the red light LR according to image information to form image light corresponding to the red light LR. The light modulation device 4G modulates the green light LG according to image information to form image light corresponding to the green light LG. The light modulation device 4B modulates the blue light LB according to image information to form image light corresponding to the blue light LB. Each of the light modulation devices 4R, 4G, and 4B can be, for example, a transmissive liquid crystal panel. Polarizing plates (not shown) are disposed on the entrance and exit sides of each of the light modulation devices 4R, 4G, and 4B. The polarizing plates allow only linearly polarized light of a specific direction to pass through. As described above, the red light LR and the green light LG are light obtained by separating the second light L2 by the dichroic mirror 7. Therefore, the light modulation devices 4R, 4G, and 4B modulate light including the second light L2.

[0019] A field lens 10R is disposed on the incident side of the optical modulation device 4R. The field lens 10R collimates the chief ray of the red light LR incident on the optical modulation device 4R. A field lens 10G is disposed on the incident side of the optical modulation device 4G. The field lens 10G collimates the chief ray of the green light LG incident on the optical modulation device 4G. A field lens 10B is disposed on the incident side of the optical modulation device 4B. The field lens 10B collimates the chief ray of the blue light LB incident on the optical modulation device 4B.

[0020] The light combining element 5 combines the image light modulated by the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, and emits the combined image light toward the projection optical device 6. As the light combining element 5, for example, a cross dichroic prism can be used.

[0021] The projection optical device 6 is composed of a plurality of projection lenses (not shown). The projection optical device 6 enlarges and projects the image light combined by the light combining element 5 onto the screen SCR. As a result, a color image is displayed on the screen SCR.

[0022] Fig. 2 is a schematic configuration diagram of the first illumination device 20 of this embodiment. Fig. 3 is a cross-sectional view of the light source device 21 taken along line III-III in Fig. 2. As shown in Fig. 2, the first illumination device 20 includes the light source device 21, an integrator optical system 50, a polarization conversion element 55, and a superimposing optical system 56.

[0023] The light source device 21 converts the first light L1 into a yellow second light L2 and emits the second light L2 toward the integrator optical system 50. The light source device 21 includes a wavelength conversion element 30, a light source unit 34, an angle conversion member 38, and a mirror 40. As shown in FIG. 3 , the light source device 21 includes a support member 41 and a pressing member 45.

[0024] The wavelength conversion element 30 shown in FIG. 2 has a rectangular prism shape extending in the X-axis direction. The dimension of the wavelength conversion element 30 in the X-axis direction is larger than the dimensions in the Y-axis direction and the Z-axis direction. In this embodiment, the X-axis direction is the longitudinal direction of the wavelength conversion element 30. In the following description, the X-axis direction may be referred to as the longitudinal direction. The longitudinal direction is parallel to the direction in which the first optical axis J1 extends. The dimensions of the wavelength conversion element 30 in the Y-axis direction and the Z-axis direction are approximately the same. Therefore, the cross-sectional shape of the wavelength conversion element 30 cut along a plane perpendicular to the longitudinal direction is approximately square. The cross-sectional shape of the wavelength conversion element 30 cut along a plane perpendicular to the longitudinal direction may be other shapes, such as a rectangle. In the following description, the Y-axis direction may be referred to as the incident direction. As will be described later, the incident direction is the direction in which the first light L1 is incident on the wavelength conversion element 30. The incident direction is also the direction in which the light source unit 34 emits the first light L1.

[0025] The wavelength conversion element 30 has six surfaces. The wavelength conversion element 30 has a first surface 30a and a second surface 30b that are perpendicular to the incident direction (Y-axis direction) and located on opposite sides of the incident direction. The second surface 30b is located away from the first surface 30a in the incident direction. The second surface 30b faces in the opposite direction to the first surface 30a. The dimension Sy of the wavelength conversion element 30 in the incident direction is the distance between the first surface 30a and the second surface 30b. The wavelength conversion element 30 has a third surface 30c and a fourth surface 30d that are perpendicular to the longitudinal direction (X-axis direction) and located on opposite sides of each other in the longitudinal direction. The fourth surface 30d is spaced apart from the third surface 30c in the longitudinal direction. The fourth surface 30d faces the opposite side of the third surface 30c. Each of the third surface 30c and the fourth surface 30d intersects with both the first surface 30a and the second surface 30b. In this embodiment, each of the third surface 30c and the fourth surface 30d is perpendicular to both the first surface 30a and the second surface 30b. 3, the wavelength conversion element 30 has a fifth surface 30e and a sixth surface 30f that are perpendicular to the Z-axis direction and located on opposite sides of each other in the Z-axis direction. In the following description, the first surface 30a, the second surface 30b, the fifth surface 30e, and the sixth surface 30f may each be referred to as a "side surface."

[0026] 2, the wavelength conversion element 30 converts a first light L1 having a first wavelength band into a second light L2 having a second wavelength band different from the first wavelength band. The wavelength conversion element 30 emits the second light L2 toward the angle conversion member 38. The first light L1 is emitted from the light source unit 34 in the incident direction (Y-axis direction) and enters the wavelength conversion element 30 from the first surface 30a. The second light L2 is guided inside the wavelength conversion element 30 and then emitted from the third surface 30c toward the angle conversion member 38. That is, the third surface 30c emits the second light L2.

[0027] The wavelength conversion element 30 includes a phosphor 33. The phosphor 33 converts the first light L1 into the second light L2. In this embodiment, the wavelength conversion element 30 is made of, for example, fluorescent glass in which rare earth ions are dispersed in glass, a ceramic phosphor made of a single crystal phosphor or a polycrystalline phosphor, or a material in which the phosphor 33 is dispersed in a binder such as a resin. As the fluorescent glass, Lumiras (trade name, manufactured by Sumita Optical Glass Co., Ltd.) or the like can be used. The phosphor 33 is, for example, a phosphor in which any of Ce, Pr, Eu, and Cr is dispersed as an activator (Y 1-x-y ,Gd x ,Lu y )3(Al,Ga)5O 12 The wavelength conversion element 30 includes a YAG-based phosphor (one of Ce:YAG, Pr:YAG, Eu:YAG, and Cr:YAG). The activator absorbs the first light L1 and emits a second light L2, which is yellow fluorescence. The activator may include one or more of Ce, Pr, Eu, and Cr. The wavelength conversion element 30 is made of a material in which a large number of phosphor particles are dispersed in a binder. In the following description, the activator contained in the phosphor 33 may be referred to as a fluorescence emission point. In the following description, the atomic ratio (atomic percent, at%) of the activator to the wavelength conversion element 30 is referred to as the fluorescence emission point concentration Dp. The fluorescence emission point concentration Dp of the wavelength conversion element 30 will be described in detail later.

[0028] As will be described later, in the wavelength conversion element 30 of this embodiment, the density Dp of the fluorescence emission points in the incident direction (Y-axis direction) changes continuously. Therefore, it is desirable that the wavelength conversion element 30 be formed by the Czochralski method (CZ method). This makes it possible to smoothly change the density Dp of the fluorescence emission points in the incident direction. Note that the wavelength conversion element 30 may also be formed by the floating zone method (FZ method).

[0029] When the first light L1 is incident on the wavelength conversion element 30, the phosphor 33 absorbs the first light L1 and emits second light L2 having a second wavelength band. In this way, the wavelength conversion element 30 converts the first light L1 into the second light L2. In this embodiment, the second light L2 is yellow fluorescence containing a red light component and a green light component. The second wavelength band of the second light L2 is, for example, a yellow light wavelength band of 490 nm to 750 nm. When the phosphor 33 absorbs the first light L1, the phosphor 33 generates heat.

[0030] The light source section 34 irradiates the wavelength conversion element 30 with the first light L1. The light source section 34 is disposed opposite to the first surface 30a of the wavelength conversion element 30 in the incident direction (Y-axis direction). The light source section 34 includes a substrate 35 and a light-emitting element 36. That is, the light source device 21 includes the light-emitting element 36. The light source section 34 may include other optical members such as a light guide plate, a diffusion plate, a lens, etc.

[0031] The substrate 35 supports the light emitting element 36. The light emitting element 36 is provided on one of the outer surfaces of the substrate 35, facing the first surface 30a of the wavelength conversion element 30 in the incident direction (Y-axis direction).

[0032] The light emitting element 36 is formed of, for example, a light emitting diode. The light emitting element 36 emits first light L1 in a first wavelength band toward the first surface 30a of the wavelength conversion element 30. As a result, the first light L1 is incident on the first surface 30a. The first light L1 enters the wavelength conversion element 30 from the first surface 30a. In this embodiment, the first wavelength band is, for example, a wavelength band of 400 nm to 480 nm spanning from blue to purple. The peak wavelength of the first light L1 is, for example, 445 nm. The light source unit 34 has a plurality of light emitting elements 36. In this embodiment, the light source unit 34 has two light emitting elements 36. The light emitting elements 36 are arranged side by side in the longitudinal direction (X-axis direction). Each light emitting element 36 faces the first surface 30a in the incident direction (Y-axis direction). The number of light emitting elements 36 included in the light source unit 34 is not particularly limited and may be one, three or more.

[0033] As shown in FIG. 3 , the support member 41 surrounds the wavelength conversion element 30. The support member 41 supports the second surface 30b of the wavelength conversion element 30 in the incident direction (Y-axis direction). Heat generated in the wavelength conversion element 30 is transferred to the support member 41, and the heat is dissipated to the outside of the light source device 21. Therefore, it is desirable that the support member 41 be made of a material having a predetermined strength and high thermal conductivity. For example, metals such as aluminum and stainless steel can be used as the material of the support member 41. It is particularly desirable to use an aluminum alloy such as a 6061 series aluminum alloy as the material of the support member 41. In this embodiment, the thermal conductivity of the support member 41 is higher than that of the wavelength conversion element 30. The support member 41 has a first wall surface 41a, a second wall surface 41b, a support surface 41d, and an accommodating recess 41h.

[0034] The accommodating recess 41h is a recess recessed in the incident direction from a surface of the outer surface of the support member 41 that faces the light source unit 34 in the incident direction (Y-axis direction). The wavelength conversion element 30 is accommodated in the accommodating recess 41h.

[0035] The support surface 41d is the bottom surface of the accommodating recess 41h. The support surface 41d supports the second surface 30b of the wavelength conversion element 30 in the incident direction. This allows the support member 41 to support the wavelength conversion element 30. Note that heat-conductive grease may be disposed between the support surface 41d and the second surface 30b. This reduces the thermal resistance between the wavelength conversion element 30 and the support member 41, thereby increasing the amount of heat transferred from the wavelength conversion element 30 to the support member 41. This prevents the temperature of the wavelength conversion element 30 from becoming too high.

[0036] The first wall surface 41a is one side surface of the accommodating recess 41h. The first wall surface 41a faces the fifth surface 30e of the wavelength conversion element 30 in the Z-axis direction with a gap therebetween. The second wall surface 41b is the other side surface of the accommodating recess 41h. The second wall surface 41b faces the sixth surface 30f of the wavelength conversion element 30 in the Z-axis direction with a gap therebetween.

[0037] The first wall surface 41a has a first portion 41a1 located farther from the support surface 41d and a second portion 41a2 located closer to the support surface 41d. The first portion 41a1 extends in a direction perpendicular to the support surface 41d. The second portion 41a2 extends in a direction inclined with respect to the support surface 41d. The second portion 41a2 is an inclined surface that approaches the wavelength conversion element 30 as it approaches the support surface 41d.

[0038] The second wall surface 41b has a third portion 41b1 located on the side farther from the support surface 41d and a fourth portion 41b2 located on the side closer to the support surface 41d. The third portion 41b1 extends in a direction perpendicular to the support surface 41d. The fourth portion 41b2 extends in a direction inclined with respect to the support surface 41d. The fourth portion 41b2 is an inclined surface that approaches the wavelength conversion element 30 as it approaches the support surface 41d. In this embodiment, the shape of the second wall surface 41b is plane-symmetrical to the shape of the first wall surface 41a, with a plane that extends in a direction perpendicular to the Z-axis direction as the plane of symmetry.

[0039] Of the first light L1 emitted from the light-emitting element 36, the first light L11 that enters the gap between the wavelength conversion element 30 and the first wall surface 41a is reflected by the first portion 41a1 and enters the fifth surface 30e of the wavelength conversion element 30. Furthermore, of the first light L1 emitted from the light-emitting element 36, the first light L12 that enters the gap between the wavelength conversion element 30 and the first wall surface 41a is reflected by the second portion 41a2 and enters the fifth surface 30e of the wavelength conversion element 30. Although not shown in the figures, similarly, of the first light L1 emitted from the light-emitting element 36, the first light that enters the gap between the wavelength conversion element 30 and the second wall surface 41b is reflected by the third portion 41b1 or the fourth portion 41b2 and enters the sixth surface 30f of the wavelength conversion element 30. As a result, the amount of first light L1 that is reflected by the support surface 41d and returns to the light source unit 34 can be reduced, thereby improving the utilization efficiency of the first light L1.

[0040] It is desirable that each of the first wall surface 41a and the second wall surface 41b be a mirror-finished surface. This increases the reflectance of the first wall surface 41a and the second wall surface 41b. Therefore, the first light L1 incident on the first wall surface 41a and the second wall surface 41b can be suitably reflected toward the wavelength conversion element 30, thereby increasing the utilization efficiency of the first light L1.

[0041] The pressing member 45 presses the wavelength conversion element 30 against the support member 41. More specifically, the pressing member 45 presses the wavelength conversion element 30 against the support surface 41d. The pressing member 45 is configured of, for example, an elastic member such as a leaf spring. One end of the pressing member 45 is connected to the support member 41. The other end of the pressing member 45 abuts against the first surface 30a of the wavelength conversion element 30. The wavelength conversion element 30 is pressed against the support surface 41d by the elastic force of the pressing member 45. This improves adhesion between the wavelength conversion element 30 and the support surface 41d, thereby reducing thermal resistance between the wavelength conversion element 30 and the support surface 41d. Therefore, heat generated in the wavelength conversion element 30 can be more effectively transferred to the support member 41. This more effectively prevents the temperature of the wavelength conversion element 30 from becoming too high.

[0042] 2, the mirror 40 is provided on the fourth surface 30d of the wavelength conversion element 30. The mirror 40 reflects the second light L2 that has been guided inside the wavelength conversion element 30 and reached the second surface 30b. The mirror 40 is made of a metal film or a dielectric multilayer film formed on the second surface 30b.

[0043] The first light L1 emitted from the light-emitting element 36 toward the first surface 30a enters the wavelength conversion element 30 from the first surface 30a. When the first light L1 enters the wavelength conversion element 30, the phosphor 33 is excited, causing the second light L2 to be emitted at the fluorescence-emitting point. The second light L2 propagates radially from the fluorescence-emitting point. The second light L2 propagates toward the four side surfaces 30a, 30b, 30e, and 30f of the wavelength conversion element 30, undergoing repeated total reflection at each of the side surfaces 30a, 30b, 30e, and 30f, and proceeding toward the third surface 30c or the fourth surface 30d. The second light L2 propagating toward the fourth surface 30d is reflected by the mirror 40 and proceeds toward the third surface 30c. As a result, all of the second light L2 emitted at the fluorescence-emitting point propagates toward the third surface 30c, passes through the third surface 30c, and enters the angle conversion member 38.

[0044] A part of the second light L2 is emitted from the first surface 30a to the outside of the wavelength conversion element 30. A part of the second light L2 emitted from the first surface 30a to the outside of the wavelength conversion element 30 is reflected by members surrounding the wavelength conversion element 30 including the light source unit 34, enters the inside of the wavelength conversion element 30 from the first surface 30a, etc., and is emitted from the third surface 30c. Note that the intensity of the second light L2 emitted from the third surface 30c is greater than the intensity of the second light L2 emitted from the first surface 30a.

[0045] The angle conversion member 38 is provided on the light exit side of the third surface 30c of the wavelength conversion element 30. The second light L2 exiting from the third surface 30c is incident on the angle conversion member 38. The angle conversion member 38 is made of a light-transmitting member such as a tapered rod. The angle conversion member 38 has an incident surface 38a on which the second light L2 exiting from the wavelength conversion element 30 is incident, an exit surface 38b from which the second light L2 exits, and a reflective side surface 38c that reflects the second light L2 toward the exit surface 38b. The incident surface 38a faces the third surface 30c in the longitudinal direction (X-axis direction).

[0046] The angle conversion member 38 has a truncated quadrangular pyramid shape, and the cross-sectional area of ​​the cross section perpendicular to the first optical axis J1 increases along the traveling direction of the second light L2. Therefore, the area of ​​the exit surface 38b is larger than the area of ​​the entrance surface 38a. In this embodiment, the optical axis of the angle conversion member 38 coincides with the first optical axis J1. However, the optical axis of the angle conversion member 38 does not have to coincide with the first optical axis J1.

[0047] The second light L2 incident on the angle conversion member 38 changes its traveling direction each time it is reflected by the reflective side surface 38c so as to approach a direction parallel to the first optical axis J1. In this way, the angle conversion member 38 converts the emission angle distribution of the second light L2 emitted from the wavelength conversion element 30. Generally, the etendue of light, which is defined by the product of the area of ​​the light emission region and the solid angle (maximum emission angle) of light, is preserved, so the etendue of the second light L2 is preserved before and after passing through the angle conversion member 38. As described above, the area of ​​the emission surface 38b is larger than the area of ​​the incident surface 38a. Therefore, from the viewpoint of etendue conservation, the maximum emission angle of the second light L2 at the emission surface 38b is smaller than the maximum incident angle of the second light L2 incident on the incident surface 38a.

[0048] In this embodiment, the incident surface 38a of the angle conversion member 38 is fixed to the third surface 30c of the wavelength conversion element 30 via an optical adhesive (not shown). Therefore, the angle conversion member 38 and the wavelength conversion element 30 are in contact with each other via the optical adhesive, and no gap is provided between them. When a gap is provided between the angle conversion member 38 and the wavelength conversion element 30, the second light L2 that reaches the incident surface 38a of the angle conversion member 38 and is incident on the incident surface 38a at an angle equal to or greater than the critical angle is totally reflected by the incident surface 38a and cannot enter the angle conversion member 38. In contrast, when no gap is provided between the angle conversion member 38 and the wavelength conversion element 30, as in this embodiment, the second light L2 that cannot enter the angle conversion member 38 can be reduced. It is desirable to match the refractive index of the angle conversion member 38 with that of the wavelength conversion element 30 as closely as possible.

[0049] The configuration of the angle conversion member 38 is not limited to that of this embodiment, and may be, for example, a compound parabolic concentrator (CPC). Even when a CPC is used as the angle conversion member 38, the same effect as when the tapered rod described above is used can be obtained. Furthermore, the light source device 21 does not necessarily have to include the angle conversion member 38.

[0050] The integrator optical system 50 has a first lens array 52 and a second lens array 53. The integrator optical system 50 and the superimposing optical system 56 constitute a uniform illumination optical system that uniformizes the intensity distribution of the second light L2 emitted from the light source device 21 in each of the light modulation devices 4R and 4G, which are the illuminated areas. The second light L2 emitted from the emission surface 38b of the angle conversion member 38 is incident on the first lens array 52.

[0051] The first lens array 52 has a plurality of first small lenses 52a. Each of the first small lenses 52a splits the second light L2 emitted from the angle conversion member 38 into a plurality of partial light beams. The first small lenses 52a are arranged in a matrix on a plane perpendicular to the first optical axis J1. The shape of each of the first small lenses 52a is substantially similar to the shape of the image forming areas of the light modulation devices 4R, 4G. This allows the partial light beams emitted from the first lens array 52 to efficiently enter the image forming areas of the light modulation devices 4R, 4G.

[0052] The second lens array 53 is disposed on the light exit side of the first lens array 52. ​​The second light L2 exiting from the first lens array 52 is incident on the second lens array 53. The second lens array 53 has a plurality of second small lenses 53a corresponding to the plurality of first small lenses 52a, respectively. The second lens array 53, together with the superimposing optical system 56, forms an image of the partial light beams exiting from each of the first small lenses 52a near the image forming areas of the light modulation devices 4R, 4G.

[0053] The polarization conversion element 55 converts the polarization direction of the second light L2 emitted from the second lens array 53. More specifically, the polarization conversion element 55 converts each partial beam of the second light L2, which is split by the first lens array 52 and emitted from the second lens array 53, into linearly polarized light. The second light L2 emitted from the second lens array 53 is incident on the superimposing optical system 56. The superimposing optical system 56 causes the second light L2 to be incident on the color separation optical system 3.

[0054] Next, the concentration Dp of the fluorescence emission points of the wavelength conversion element 30 will be described. The distribution of the concentration Dp of the fluorescence emission points of the wavelength conversion element 30 of this embodiment can be the same as the distribution of the concentration Dp of the fluorescence emission points of Examples 1 to 3 shown in FIG. 4 (described later). In the distributions of the concentration Dp of the fluorescence emission points of Examples 1 to 3 and the comparative example shown in FIG. 4 (described later), the integrated heat generation amount, which is the heat generation amount obtained by integrating the heat generation amount Ah of the wavelength conversion element 30 in the incident direction (Y-axis direction) shown in FIG. 6 (described later), is the same. In the following description, the distribution of the concentration Dp of the fluorescence emission points of Examples 1 to 3 and the comparative example will be described, as well as the heat generation amount distribution of the wavelength conversion element 30 in the incident direction. In the following description, the wavelength conversion elements 30 of Examples 1 to 3 will sometimes be simply referred to as Examples 1 to 3. In the following description, the wavelength conversion element 30 of the comparative example will sometimes be simply referred to as the comparative example. In the following description, the amount of absorption of the first light L1 by the phosphor 33 will sometimes be simply referred to as the "absorption amount of the first light L1." The amount of absorption of the first light L1 correlates with both the intensity of the first light L1 and the concentration Dp of the fluorescence-emitting points. The amount of absorption of the first light L1 increases as the intensity of the first light L1 increases. The amount of absorption of the first light L1 increases as the concentration Dp of the fluorescence-emitting points increases.

[0055] FIG. 4 is a diagram showing the distribution of the concentration Dp of the fluorescence emission points in the incident direction (Y-axis direction) of the wavelength conversion element 30 of this embodiment. The horizontal axis of FIG. 4 is the distance Dt from the first surface 30a in the incident direction. In the following description, the distance Dt from the first surface 30a in the incident direction will be simply referred to as the "distance Dt from the first surface 30a." The origin of the horizontal axis of FIG. 4 is the position of the first surface 30a in the incident direction. The first light L1 is incident on the wavelength conversion element 30 at the origin of the horizontal axis of FIG. 4. As described above, the dimension Sy of the wavelength conversion element 30 in the incident direction is the distance between the first surface 30a and the second surface 30b. On the horizontal axis of FIG. 4, the second surface 30b is located at Sy. The vertical axis of FIG. 4 is the concentration Dp of the fluorescence emission points.

[0056] The concentration Dp of the fluorescence-emitting points in Example 1 increases from the first surface 30a toward the second surface 30b. The concentration Dp of the fluorescence-emitting points in Example 1 increases continuously from the first surface 30a toward the second surface 30b. More specifically, the concentration Dp of the fluorescence-emitting points in Example 1 increases linearly from the first surface 30a toward the second surface 30b. The concentration Dp of the fluorescence-emitting points in the comparative example is uniform in the incident direction.

[0057] FIG. 5 is a diagram showing the intensity distribution of the first light L1 in the incident direction (Y-axis direction) of the wavelength conversion element 30 of this embodiment. The horizontal axis of FIG. 5 represents the distance Dt from the first surface 30a. The vertical axis of FIG. 5 represents the intensity Lp of the first light L1. The intensity Lp of the first light L1 shown in FIG. 5 is normalized based on the intensity of the first light L1 at the first surface 30a. As described above, the first light L1 incident on the wavelength conversion element 30 is absorbed by the phosphor 33 and converted into the second light L2. Therefore, the intensity Lp of the first light L1 of the comparative example and the intensity Lp of the first light L1 of Example 1 each decrease from the first surface 30a to the second surface 30b. More specifically, the intensity Lp of the first light L1 of the comparative example decreases significantly on the first surface 30a side and decreases gradually on the second surface 30b side. That is, in the wavelength conversion element 30 of the comparative example, the absorption amount of the first light L1 is greater in the portion located closer to the first surface 30a. In contrast, in the wavelength conversion element 30 of Example 1, the intensity Lp of the first light L1 decreases more linearly from the first surface 30a to the second surface 30b than in the comparative example. This is because the concentration Dp of the fluorescence-emitting points on the first surface 30a side, where the intensity Lp of the first light L1 is greater, is small, thereby reducing the absorption amount of the first light L1 on the first surface 30a side. Furthermore, the concentration Dp of the fluorescence-emitting points on the second surface 30b side, where the intensity Lp of the first light L1 is smaller, is large, thereby increasing the absorption amount of the first light L1 on the second surface 30b side. As a result, Example 1 can reduce the variation in the absorption amount of the first light L1 in the incident direction compared to the comparative example. In particular, Example 1 can reduce the absorption amount of the first light L1 on the first surface 30a side compared to the comparative example.

[0058] FIG. 6 is a diagram showing the heat generation distribution in the incident direction (Y-axis direction) of the wavelength conversion element 30 of this embodiment. The horizontal axis in FIG. 6 represents the distance Dt from the first surface 30a. The vertical axis in FIG. 6 represents the heat generation amount Ah of the wavelength conversion element 30. As described above, the integrated heat generation amounts of Example 1 and the Comparative Example are the same. As described above, the phosphor 33 generates heat when absorbing the first light L1 and emitting the second light L2. Therefore, the heat generation amount Ah increases in the portion of the wavelength conversion element 30 that absorbs more of the first light L1. As shown in FIG. 6, the heat generation amount Ah of the Comparative Example increases from the second surface 30b toward the first surface 30a. This is because, in the Comparative Example, the portion closer to the first surface 30a absorbs more of the first light L1. As described above, in the Comparative Example, the heat generation amount Ah of the portion closer to the first surface 30a is larger, and therefore the temperature of the portion closer to the first surface 30a becomes too high. Therefore, in the comparative example, the temperature quenching of the second light L2 is likely to increase in the portion on the first surface 30a side of the wavelength conversion element 30. Therefore, in the comparative example, there is a risk of a decrease in wavelength conversion efficiency, which is the efficiency with which the wavelength conversion element 30 converts the first light L1 into the second light L2.

[0059] Compared to the comparative example, in Example 1, the variation in the heat generation amount Ah in the incident direction (Y-axis direction) can be reduced. This is because, compared to the comparative example, in Example 1, the variation in the absorption amount of the first light L1 in the incident direction is smaller. As a result, in Example 1, it is possible to prevent the temperature of the phosphor 33 in the portion on the first surface 30a side of the wavelength conversion element 30 from becoming too high, and therefore it is possible to reduce temperature quenching of the second light L2 in that portion.

[0060] 4, the concentration Dp of the fluorescence-emitting spots in Example 2 increases continuously from the first surface 30a toward the second surface 30b. More specifically, the concentration Dp of the fluorescence-emitting spots in Example 2 increases superlinearly from the first surface 30a toward the second surface 30b. In this embodiment, the superlinear increase means that the slope of the distribution curve of the concentration Dp of the fluorescence-emitting spots increases from the first surface 30a toward the second surface 30b.

[0061] As shown in FIG. 5, in Example 2, the first light L1 decreases more linearly from the first surface 30a toward the second surface 30b compared to Example 1. This is because, compared to Example 1, Example 2 can suppress an increase in the ratio of the concentration Dp of fluorescence-emitting points at the center in the incident direction (Y-axis direction) to the concentration Dp of fluorescence-emitting points on the first surface 30a, and can more suitably increase the concentration Dp of fluorescence-emitting points near the second surface 30b. Therefore, compared to Example 1, Example 2 can reduce the variation in the absorption amount of the first light L1 in the incident direction. In particular, compared to Example 1, Example 2 can reduce the absorption amount of the first light L1 near the center in the incident direction. Therefore, as shown in FIG. 6, in Example 2, the variation in the heat generation amount Ah in the incident direction can be reduced compared to Example 1. As a result, Example 2 can prevent the temperature of a portion of the wavelength conversion element 30 from becoming too high, thereby more suitably reducing the thermal quenching of the second light L2.

[0062] As shown in Fig. 4, the concentration Dp of the fluorescence-emitting points in Example 3 increases continuously from the first surface 30a toward the second surface 30b. The concentration Dp of the fluorescence-emitting points in Example 3 increases superlinearly from the first surface 30a toward the second surface 30b. More specifically, the concentration Dp of the fluorescence-emitting points included in the second surface 30b is two or more times and nine or less times the concentration Dp of the fluorescence-emitting points included in the central portion in the incident direction (Y-axis direction) in Example 3. Note that the concentration Dp of the fluorescence-emitting points included in the second surface 30b is less than two times the concentration Dp of the fluorescence-emitting points included in the central portion in the incident direction in Example 2.

[0063] As shown in FIG. 5, in Example 3, the concentration Dp of the fluorescent light-emitting points on the second surface 30b side can be increased compared to Example 2, and therefore the amount of decrease in the intensity Lp of the first light L1 on the second surface 30b side can be increased. That is, in Example 3, the amount of absorption of the first light L1 in the portion on the second surface 30b side can be increased. Therefore, as shown in FIG. 6, in Example 3, compared to Example 2, the amount of heat generated in the central portion of the wavelength conversion element 30 in the incident direction (Y-axis direction) can be reduced and the amount of heat generated in the portion on the second surface 30b side of the wavelength conversion element 30 can be increased. As described above, since the second surface 30b is supported by the support member 41, heat generated in the portion on the second surface 30b side of the wavelength conversion element 30 is easily transferred to the support member 41. Therefore, in Example 3, the amount of heat transferred from the wavelength conversion element 30 to the support member 41 can be suitably increased. Therefore, in Example 3, the temperature of the wavelength conversion element 30 can be easily reduced, and therefore the thermal quenching of the second light L2 can be more suitably reduced.

[0064] According to this embodiment, the light source device 21 includes a light emitting element 36 that emits first light L1 having a first wavelength band, and a wavelength conversion element 30 that contains a phosphor 33, converts the first light L1 into second light L2 having a second wavelength band different from the first wavelength band, and emits the second light L2. The wavelength conversion element 30 has a first surface 30a on which the first light L1 is incident, a second surface 30b facing the opposite side to the first surface 30a, and a third surface 30c that intersects with both the first surface 30a and the second surface 30b and emits the second light L2, and a density Dp of fluorescence emission points of the phosphor 33 increases from the first surface 30a toward the second surface 30b. Therefore, as described above, the concentration Dp of the fluorescence-emitting points on the first surface 30a side, where the intensity Lp of the first light L1 is high, can be reduced, and the concentration Dp of the fluorescence-emitting points on the second surface 30b side, where the intensity Lp of the first light L1 is low, can be increased, thereby reducing the amount of absorption of the first light L1 on the first surface 30a side. As a result, as described above, it is possible to prevent the temperature of the phosphor 33 in the portion of the wavelength conversion element 30 on the first surface 30a side from becoming too high, thereby reducing temperature quenching of the second light L2 in that portion. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be improved.

[0065] Furthermore, in this embodiment, as described above, the variation in the heat generation amount Ah in the incident direction (Y-axis direction) can be reduced. This makes it possible to suppress the temperature variation of the wavelength conversion element 30 in the incident direction, thereby reducing the difference in the amount of thermal expansion between the portion on the first surface 30a side of the wavelength conversion element 30 and the portion on the second surface 30b side. Therefore, deformation of the wavelength conversion element 30, such as warping, can be suppressed.

[0066] According to this embodiment, the concentration Dp of the fluorescence emission points continuously increases from the first surface 30a toward the second surface 30b. Therefore, it is possible to reduce variations in the amount of absorption of the first light L1 in the incident direction (Y-axis direction). This makes it easy to prevent a local increase in the amount of heat generated in a part of the wavelength conversion element 30. Therefore, it is possible to prevent the temperature of a part of the wavelength conversion element 30 from becoming too high, and therefore it is possible to more suitably reduce the temperature quenching of the second light L2 in the wavelength conversion element 30. Therefore, it is possible to more suitably increase the wavelength conversion efficiency of the wavelength conversion element 30.

[0067] According to this embodiment, the concentration Dp of the fluorescence-emitting points increases superlinearly from the first surface 30a toward the second surface 30b. Therefore, as described above, it is possible to prevent the ratio of the concentration Dp of the fluorescence-emitting points at the center in the incident direction (Y-axis direction) to the concentration Dp of the fluorescence-emitting points on the first surface 30a from increasing, and it is possible to more suitably increase the concentration Dp of the fluorescence-emitting points near the second surface 30b. Therefore, it is possible to more suitably decrease the first light L1 in a linear manner from the first surface 30a toward the second surface 30b. This makes it possible to more suitably reduce the variation in the amount of absorption of the first light L1 in the incident direction, as described above. Therefore, it is possible to more suitably prevent the temperature of a portion of the wavelength conversion element 30 from becoming too high, thereby more suitably reducing the temperature quenching of the second light L2 in the wavelength conversion element 30. Therefore, it is possible to more suitably increase the wavelength conversion efficiency of the wavelength conversion element 30.

[0068] According to this embodiment, the concentration Dp of the fluorescence emission points included in the second surface 30b of the wavelength conversion element 30 is two to nine times higher than the concentration Dp of the fluorescence emission points included in the central portion of the wavelength conversion element 30 in the incident direction (Y-axis direction). Therefore, as described above, the concentration Dp of the fluorescence emission points on the second surface 30b side can be more suitably increased, thereby increasing the amount of absorption of the first light L1 on the second surface 30b side. As a result, as described above, the heat generation amount Ah in the central portion of the wavelength conversion element 30 in the incident direction can be reduced, and the heat generation amount Ah in the portion on the second surface 30b side can be increased. Therefore, as described above, the amount of heat transferred from the wavelength conversion element 30 to the support member 41 can be suitably increased. This makes it easier to reduce the temperature of the wavelength conversion element 30, thereby more suitably reducing the thermal quenching of the second light L2 in the wavelength conversion element 30. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be more suitably improved.

[0069] According to this embodiment, the light source device 21 further includes a support member 41 that supports the second surface 30b, and the thermal conductivity of the support member 41 is greater than that of the wavelength conversion element 30. Therefore, the amount of heat transferred from the wavelength conversion element 30 to the support member 41 can be more preferably increased. Also, the amount of heat radiated from the support member 41 to the outside of the light source device 21 can be more preferably increased. As a result, the amount of heat radiated from the wavelength conversion element 30 to the outside of the light source device 21 via the support member 41 can be more preferably increased. Therefore, the temperature of the wavelength conversion element 30 can be more preferably prevented from becoming too high, and therefore, the thermal quenching of the second light L2 in the wavelength conversion element 30 can be more preferably reduced. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be more preferably improved.

[0070] According to this embodiment, the light source device 21 further includes a pressing member 45 that presses the wavelength conversion element 30 against the support member 41. When the wavelength conversion element 30 is fixed to the support member 41 with an adhesive, the reflectance of the second light L2 at the second surface 30b decreases, and the amount of the second light L2 that transmits through the second surface 30b and leaks out of the wavelength conversion element 30 increases. This reduces the wavelength conversion efficiency of the wavelength conversion element 30. In contrast, in this embodiment, the pressing member 45 presses the wavelength conversion element 30 toward the support member 41 to fix the wavelength conversion element 30 to the support member 41, thereby preventing a decrease in the reflectance of the second light L2 at the second surface 30b. This makes it easy to reduce the amount of the second light L2 that transmits through the second surface 30b and leaks out of the wavelength conversion element 30, thereby improving the wavelength conversion efficiency of the wavelength conversion element 30.

[0071] Furthermore, when the wavelength conversion element 30 is fixed to the support member 41 with an adhesive, the wavelength conversion element 30 is unlikely to deform even if temperature variations occur in the wavelength conversion element 30. Therefore, the thermal stress applied to the wavelength conversion element 30 is likely to increase, which may result in damage to the wavelength conversion element 30. In contrast, in this embodiment, when temperature variations occur in the wavelength conversion element 30, the wavelength conversion element 30 can easily deform in response to the thermal stress. Therefore, the increase in thermal stress applied to the wavelength conversion element 30 can be suppressed, and therefore damage to the wavelength conversion element 30 can be suppressed.

[0072] Furthermore, in this embodiment, the pressing member 45 presses the second surface 30b of the wavelength conversion element 30 against the support member 41, thereby reducing the thermal resistance between the second surface 30b and the support member 41. This makes it possible to more suitably increase the amount of heat transferred from the wavelength conversion element 30 to the support member 41. Therefore, it is possible to more suitably prevent the temperature of the wavelength conversion element 30 from becoming too high, thereby more suitably reducing the thermal quenching of the second light L2 in the wavelength conversion element 30. Therefore, it is possible to more suitably increase the wavelength conversion efficiency of the wavelength conversion element 30.

[0073] According to this embodiment, the light source device 21 further includes an angle conversion member 38 onto which the second light L2 emitted from the third surface 30c is incident. The angle conversion member 38 has an incident surface 38a onto which the second light L2 is incident and an exit surface 38b from which the second light L2 is emitted. The maximum exit angle of the second light L2 emitted from the exit surface 38b is smaller than the maximum incident angle of the second light L2 incident on the incident surface 38a. This increases the directivity of the second light L2 emitted from the angle conversion member 38, allowing the second light L2 to efficiently enter the integrator optical system 50 located downstream. This increases the amount of second light L2 emitted from the first illumination device 20 toward the color separation optical system 3 and the light modulation devices 4R and 4G. This improves the quality of the image displayed on the screen SCR.

[0074] According to this embodiment, the intensity of the second light L2 emitted from the third surface 30c is greater than the intensity of the second light L2 emitted from the first surface 30a. This increases the amount of second light L2 emitted from the third surface 30c toward the color separation optical system 3 and the light modulation devices 4R and 4G. This improves the quality of the image displayed on the screen SCR.

[0075] According to this embodiment, the projector 1 includes a light source device 21, light modulation devices 4R, 4G, and 4B that modulate light including the second light L2 emitted from the light source device 21, and a projection optical device 6 that projects the light modulated by the light modulation devices 4R, 4G, and 4B. As described above, in this embodiment, the density Dp of the fluorescence emission points of the phosphor 33 increases from the first surface 30a toward the second surface 30b. As described above, this prevents the temperature of the phosphor 33 in the portion of the wavelength conversion element 30 on the first surface 30a side from becoming too high, thereby improving the wavelength conversion efficiency of the wavelength conversion element 30. This reduces the amount of first light L1 required to emit a predetermined amount of second light L2. Therefore, the amount of first light L1 emitted by the light-emitting element 36 can be reduced, thereby reducing the power consumed by the projector 1.

[0076] (Second embodiment) A projector 201 according to the second embodiment will be described below. The basic configuration of the projector 201 of this embodiment is similar to that of the projector 1 of the first embodiment, and the projector 201 of this embodiment includes a wavelength conversion element 230 configured by a plurality of laminated plates 231 stacked in the incident direction (Y-axis direction). In the following description, the same components as those of the projector 1 of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

[0077] FIG. 7 is a schematic diagram of the first illumination device 220 of this embodiment. 7, the first illumination device 220 includes a light source device 221, an integrator optical system 50, a polarization conversion element 55, and a superimposing optical system 56. The configurations of the integrator optical system 50, the polarization conversion element 55, and the superimposing optical system 56 of this embodiment are similar to the configurations of the integrator optical system 50, the polarization conversion element 55, and the superimposing optical system 56 of the first embodiment described above.

[0078] The light source device 221 converts the first light L1 into a yellow second light L2 and emits the second light L2 toward the integrator optical system 50. The light source device 221 includes a wavelength conversion element 230, a light source unit 34, an angle conversion member 38, a mirror 40, a support member 41 (see FIG. 3), and a pressing member 45 (see FIG. 3).

[0079] The wavelength conversion element 230 converts the first light L1 having a first wavelength band into the second light L2 having a second wavelength band different from the first wavelength band. The wavelength conversion element 230 has a rectangular prism shape extending in the X-axis direction. The dimension of the wavelength conversion element 230 in the X-axis direction is larger than the dimensions in the Y-axis direction and the Z-axis direction. The wavelength conversion element 230 has a first surface 30a, a second surface 30b, a third surface 30c, a fourth surface 30d, a fifth surface 30e, and a sixth surface 30f. The first surface 30a and the second surface 30b are perpendicular to the incident direction (Y-axis direction) and are located on opposite sides of the incident direction. The third surface 30c intersects both the first surface 30a and the second surface 30b. In this embodiment, the third surface 30c is perpendicular to both the first surface 30a and the second surface 30b. The third surface 30c emits the second light L2 toward the angle conversion member .

[0080] In this embodiment, the wavelength conversion element 230 is composed of a plurality of laminate plates 231 stacked in the incident direction (Y-axis direction). Each laminate plate 231 has a plate shape extending in the longitudinal direction (X-axis direction). The plate surface of each laminate plate 231 faces the incident direction. Although not shown, when viewed from the incident direction, each laminate plate 231 has a substantially rectangular shape with its long side extending in the longitudinal direction. In this embodiment, the wavelength conversion element 230 is composed of five laminate plates 231. The five laminate plates 231 include a laminate plate 231a, a laminate plate 231b, a laminate plate 231c, a laminate plate 231d, and a laminate plate 231e. The five laminate plates 231 are arranged in the order of laminate plate 231a, laminate plate 231b, laminate plate 231c, laminate plate 231d, and laminate plate 231e from the light source unit 34 side. The laminate plates 231 are fixed to each other via an optical adhesive. The number of laminated plates 231 constituting the wavelength conversion element 230 is not limited to five, but may be four or less, or six or more.

[0081] In this embodiment, the first surface 30a is a surface of the outer surface of the laminate plate 231a that faces the light source unit 34 in the incident direction. The second surface 30b is a surface of the outer surface of the laminate plate 231e that faces the opposite side from the first surface 30a. The third surface 30c is formed by a surface of the outer surface of each laminate plate 231 that faces the angle conversion member 38 in the longitudinal direction. The fourth surface 30d is formed by a surface of the outer surface of each laminate plate 231 that faces the opposite side from the surface that forms the third surface 30c. The fifth surface 30e is formed by a surface of the outer surface of each laminate plate 231 that faces one side in the Z-axis direction. The sixth surface 30f is formed by a surface of the outer surface of each laminate plate 231 that faces the other side in the Z-axis direction.

[0082] In this embodiment, the concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231b is greater than the concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231a. The concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231c is greater than the concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231b. The concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231d is greater than the concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231c. The concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231e is greater than the concentration Dp of the fluorescent light-emitting material contained in the laminate plate 231d. Therefore, the concentration Dp of the fluorescent light-emitting points contained in each of the multiple laminate plates 231 is greater than the concentration Dp of the fluorescent light-emitting points contained in the other laminate plates 231 arranged on the first surface 30a side. As a result, as shown in FIG. 8, the concentration Dp of the fluorescent light-emitting points of the phosphor 233 of the wavelength conversion element 230 increases from the first surface 30a toward the second surface 30b. More specifically, the concentration Dp of the fluorescent light emitting points of the phosphor 233 of the wavelength conversion element 230 increases stepwise from the first surface 30a toward the second surface 30b. Other configurations of the wavelength conversion element 230 of this embodiment are similar to those of the wavelength conversion element 30 of the first embodiment described above.

[0083] According to this embodiment, the concentration Dp of the fluorescence emission points of the phosphor 233 of the wavelength conversion element 230 increases from the first surface 30a toward the second surface 30b. Therefore, although not shown, similar to the first embodiment described above, the concentration Dp of the fluorescence emission points on the first surface 30a side, where the intensity Lp of the first light L1 is high, can be reduced, and the concentration Dp of the fluorescence emission points on the second surface 30b side, where the intensity Lp of the first light L1 is low, can be increased. This reduces the amount of absorption of the first light L1 on the first surface 30a side. This prevents the temperature of the phosphor 233 in the portion of the wavelength conversion element 230 on the first surface 30a side from becoming too high, thereby reducing temperature quenching of the second light L2 in that portion. This therefore increases the wavelength conversion efficiency of the wavelength conversion element 230.

[0084] According to this embodiment, the wavelength conversion element 230 is configured with multiple laminated plates 231 stacked in the incident direction (Y-axis direction), and the concentration Dp of fluorescence emission points included in each of the multiple laminated plates 231 is greater than the concentration Dp of fluorescence emission points included in other laminated plates 231 arranged on the first surface 30a side. Therefore, since the wavelength conversion element 230 can be configured with multiple laminated plates 231 whose fluorescence emission point concentrations Dp are known in advance, the concentration distribution of fluorescence emission points in the incident direction can be more easily stabilized compared to when the wavelength conversion element 230 is configured integrally. This makes it easier to stably increase the concentration Dp of fluorescence emission points in the phosphor 233 of the wavelength conversion element 230 from the first surface 30a toward the second surface 30b. Therefore, excessive temperature rise of the phosphor 233 in the portion of the wavelength conversion element 230 on the first surface 30a side can be more effectively prevented, thereby more effectively reducing temperature quenching of the second light L2 in that portion. Therefore, the wavelength conversion efficiency of the wavelength conversion element 230 can be more suitably improved.

[0085] Although the embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Furthermore, one aspect of the present invention can be a configuration in which the characteristic portions of the above-described embodiments are appropriately combined.

[0086] For example, the concentration distribution of the fluorescent emission points in the incident direction of the wavelength conversion element is not limited to the above-described embodiment, and may be another concentration distribution, such as a concentration distribution curve in which the gradient of the concentration curve of the fluorescent emission points increases sublinearly from the first surface to the second surface. Even with such a distribution of the concentration of the fluorescent emission points, it is possible to prevent the temperature of the phosphor in the portion of the wavelength conversion element on the first surface side from becoming too high, thereby improving the wavelength conversion efficiency of the wavelength conversion element.

[0087] The shape, number, arrangement, and materials of the components of the light source device and the projector are not limited to those of the above-described embodiment and can be modified as appropriate. In the above-described embodiment, an example was shown in which a light source device is mounted in a projector using a liquid crystal panel. However, a light source device may also be mounted in a projector using a digital micromirror device as a light modulation device. Furthermore, a projector does not necessarily have to have multiple light modulation devices, and may have only one light modulation device. Furthermore, the light source device can also be used as a light source device for lighting fixtures, automobile headlights, and the like.

[0088] A summary of this disclosure is provided below.

[0089] (Appendix 1) 1. A light source device comprising: a light-emitting element that emits first light having a first wavelength band; and a wavelength conversion element that includes a phosphor and converts the first light into second light having a second wavelength band different from the first wavelength band and emits the second light, wherein the wavelength conversion element has a first surface onto which the first light is incident, a second surface facing the opposite side to the first surface, and a third surface that intersects with both the first surface and the second surface and emits the second light, and wherein a concentration of fluorescent emission points of the phosphor increases from the first surface toward the second surface.

[0090] According to the light source device having the configuration of Supplementary Note 1, the concentration of fluorescent emission points on the first surface side where the intensity of the first light is high can be reduced, and the concentration of fluorescent emission points on the second surface side where the intensity of the first light is low can be increased, thereby reducing the amount of absorption of the first light on the first surface side. This prevents the temperature of the phosphor in the portion of the wavelength conversion element on the first surface side from becoming too high, thereby reducing temperature quenching of the second light in that portion. Therefore, the wavelength conversion efficiency of the wavelength conversion element can be improved.

[0091] (Appendix 2) 2. The light source device according to claim 1, wherein the density of the fluorescent light emitting points increases continuously from the first surface toward the second surface.

[0092] According to this configuration, the variation in the absorption amount of the first light in the incident direction can be reduced, which makes it easier to prevent a local increase in the amount of heat generated in a part of the wavelength conversion element. Therefore, the temperature of a part of the wavelength conversion element can be prevented from becoming too high, which makes it possible to more effectively reduce the temperature quenching of the second light in the wavelength conversion element. Therefore, it is possible to more effectively improve the wavelength conversion efficiency of the wavelength conversion element.

[0093] (Appendix 3) 3. The light source device according to claim 2, wherein the density of the fluorescent light emitting points increases superlinearly from the first surface toward the second surface.

[0094] This configuration can prevent the ratio of the concentration of fluorescence-emitting points at the center in the incident direction to the concentration of fluorescence-emitting points on the first surface from becoming large, and can more suitably increase the concentration of fluorescence-emitting points near the second surface, thereby more suitably reducing the variation in the absorption amount of the first light in the incident direction. Therefore, it can more suitably prevent the temperature of part of the wavelength conversion element from becoming too high. Therefore, it can more suitably increase the wavelength conversion efficiency of the wavelength conversion element.

[0095] (Appendix 4) the second surface is disposed apart from the first surface in an incident direction, which is a direction in which the first light is incident on the wavelength conversion element, and a concentration of the fluorescent emission points included in the second surface of the wavelength conversion element is two to nine times higher than a concentration of the fluorescent emission points included in a central portion of the wavelength conversion element in the incident direction.

[0096] According to this configuration, the concentration of fluorescent light-emitting points on the second surface side can be more preferably increased, thereby increasing the amount of first light absorbed on the second surface side. This increases the amount of heat generated in the portion on the second surface side. Therefore, the amount of heat transferred from the wavelength conversion element 30 to the support member 41 can be preferably increased, making it easier to reduce the temperature of the wavelength conversion element 30. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be more preferably increased.

[0097] (Appendix 5) The light source device described in Appendix 1, wherein the wavelength conversion element is composed of a plurality of laminated plates stacked in an incident direction, which is the direction in which the first light is incident on the wavelength conversion element, and the concentration of the fluorescent emission points contained in each of the plurality of laminated plates is greater than the concentration of the fluorescent emission points contained in other laminated plates arranged on the first surface side.

[0098] According to this configuration, the wavelength conversion element can be constructed using a plurality of laminated plates whose concentrations of fluorescent emission points are known in advance, so that the concentration of fluorescent emission points can be easily increased from the first surface toward the second surface. Therefore, it is possible to more effectively prevent the temperature of the phosphor in the portion of the wavelength conversion element on the first surface side from becoming too high. Therefore, it is possible to more effectively improve the wavelength conversion efficiency of the wavelength conversion element.

[0099] (Appendix 6) 6. The light source device according to claim 1, further comprising a support member that supports the second surface, wherein the thermal conductivity of the support member is greater than the thermal conductivity of the wavelength conversion element.

[0100] According to this configuration, the amount of heat dissipated from the wavelength conversion element to the outside of the light source device via the support member can be further increased, and the temperature of the wavelength conversion element can be more effectively prevented from becoming too high, thereby more effectively improving the wavelength conversion efficiency of the wavelength conversion element.

[0101] (Appendix 7) 7. The light source device according to claim 6, further comprising a pressing member that presses the wavelength conversion element against the support member.

[0102] According to this configuration, the wavelength conversion element is fixed to the support member by pressing the wavelength conversion element toward the support member with the pressing member, so that it is possible to suppress a decrease in the reflectance of the second light on the second surface, and therefore it is easy to reduce the second light that passes through the second surface and leaks out of the wavelength conversion element, thereby improving the wavelength conversion efficiency of the wavelength conversion element.

[0103] (Appendix 8) 8. The light source device of claim 1, further comprising an angle conversion member onto which the second light emitted from the third surface is incident, the angle conversion member having an incident surface onto which the second light is incident and an exit surface from which the second light is emitted, wherein a maximum emission angle of the second light emitted from the exit surface is smaller than a maximum incidence angle of the second light incident on the incident surface.

[0104] This configuration can increase the directivity of the second light emitted from the angle conversion member, thereby increasing the amount of second light incident from the first illumination device to the color separation optical system and the light modulation device, thereby improving the quality of the image displayed on the screen.

[0105] (Appendix 9) 9. The light source device according to claim 1, wherein the intensity of the second light emitted from the third surface is greater than the intensity of the second light emitted from the first surface.

[0106] This configuration increases the amount of second light incident on each of the color separation optical system and the light modulation device from the third surface, thereby improving the quality of the image displayed on the screen.

[0107] (Appendix 10) A projector comprising: a light source device according to any one of Supplementary Note 1 to Supplementary Note 9; a light modulation device that modulates light including the second light emitted from the light source device; and a projection optical device that projects the light modulated by the light modulation device.

[0108] According to a projector having this configuration, the wavelength conversion efficiency of the wavelength conversion element can be increased, and therefore the amount of first light required to emit a predetermined amount of second light can be reduced. Therefore, the amount of first light emitted from the light emitting element toward the wavelength conversion element can be reduced, and the power consumed by the projector can be reduced. [Explanation of symbols]

[0109] 1,201...projector, 4R, 4G, 4B...light modulation device, 6...projection optical device, 21,221...light source device, 30,230...wavelength conversion element, 30a...first surface, 30b...second surface, 30c...third surface, 33,233...phosphor, 36...light-emitting element, 38...angle conversion member, 38a...incident surface, 38b...exit surface, 41...support member, 45...pressing member, 231...laminated plate, Dp...concentration of fluorescent emission point, L1...first light, L2...second light.

Claims

1. a light emitting element that emits first light having a first wavelength band; a wavelength conversion element that includes a phosphor, converts the first light into second light having a second wavelength band different from the first wavelength band, and emits the second light; Equipped with the wavelength conversion element has a first surface onto which the first light is incident, a second surface facing an opposite side to the first surface, and a third surface intersecting both the first surface and the second surface and from which the second light exits, the concentration of the fluorescent light emitting points of the phosphor increases from the first surface toward the second surface; Light source device.

2. the concentration of the fluorescent light emitting points increases continuously from the first surface toward the second surface; The light source device according to claim 1 .

3. the concentration of the fluorescent light emitting spots increases superlinearly from the first surface toward the second surface; The light source device according to claim 2 .

4. the second surface is disposed apart from the first surface in an incident direction in which the first light is incident on the wavelength conversion element, a concentration of the fluorescence emission points included in the second surface of the wavelength conversion element relative to a concentration of the fluorescence emission points included in a central portion of the wavelength conversion element in the incident direction is 2 times or more and 9 times or less; The light source device according to claim 2 .

5. the wavelength conversion element is configured by a plurality of laminated plates stacked in an incident direction, which is a direction in which the first light is incident on the wavelength conversion element, the concentration of the fluorescent emission points included in each of the plurality of laminated plates is greater than the concentration of the fluorescent emission points included in the other laminated plates arranged on the first surface side; The light source device according to claim 1 .

6. Further provided is a support member that supports the second surface, The thermal conductivity of the support member is greater than the thermal conductivity of the wavelength conversion element. The light source device according to claim 1 .

7. Further provided is a pressing member that presses the wavelength conversion element against the support member. The light source device according to claim 6 .

8. an angle conversion member onto which the second light emitted from the third surface is incident, the angle conversion member has an incident surface onto which the second light is incident and an exit surface from which the second light exits, a maximum emission angle of the second light emitted from the emission surface is smaller than a maximum incidence angle of the second light incident on the incidence surface; The light source device according to claim 1 .

9. an intensity of the second light emitted from the third surface is greater than an intensity of the second light emitted from the first surface; The light source device according to claim 1 .

10. The light source device according to claim 1 , a light modulation device that modulates light including the second light emitted from the light source device; a projection optical device that projects the light modulated by the light modulation device; Equipped with projector.

Images