Light source device and projector

Abstract

To increase the wavelength conversion efficiency of a wavelength conversion element.SOLUTION: A light source device comprises: a plurality of light-emitting elements that each emit first light having a first wavelength range; 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; and an angle conversion member that converts the angle distribution of the second light emitted from the wavelength conversion element. The wavelength conversion element has a first surface that is directed in a longitudinal direction and emits the second light toward the angle conversion member, 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 first light is incident. The concentration of a fluorescent emission point of the phosphor reduces toward the first surface from the second 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 wavelength conversion member. Furthermore, fluorescence emitted from various parts of the wavelength conversion member is collected on the exit surface of the wavelength conversion device before being emitted to the outside of the wavelength conversion device. Therefore, the phosphor closer to the exit surface absorbs more fluorescence. As a result, if the temperature of the part of the wavelength conversion member facing the exit surface becomes too high, there is a risk that thermal quenching of fluorescence in the part of the wavelength conversion member facing the exit surface will increase. This may result in a decrease in the wavelength conversion efficiency, which is the efficiency with which the wavelength conversion member converts excitation light into fluorescence. [Means for solving the problem]

[0005] One embodiment of the light source device of the present invention comprises a plurality of light-emitting elements that emit first light having a first wavelength band, 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, and an angle conversion member that converts the angular distribution of the second light emitted from the wavelength conversion element, wherein the wavelength conversion element has a first surface that faces in the longitudinal direction and emits the second light toward the angle conversion member, a second surface that faces opposite to the first surface, and a third surface that intersects both the first surface and the second surface and onto which the first light is incident, and the concentration of fluorescent emission points of the phosphor decreases from the second surface toward the first 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] 5A and 5B are diagrams showing the distribution of the concentration of fluorescence-emitting points and the distribution of the intensity of the first light in the longitudinal direction of the wavelength conversion element of the first embodiment. [Figure 4] FIG. 4 is a schematic configuration diagram of a first illumination device according to a modified example of the first embodiment. [Figure 5] FIG. 10 is a schematic configuration diagram of a first lighting device according to a second embodiment. [Figure 6] FIG. 10 is a schematic configuration diagram of a first lighting device according to a third 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 schematic diagram 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 multiple 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. The projection optical device 6 projects the light LR, LG, and LB modulated by the light modulation devices 4R, 4G, and 4B, respectively. This causes a color image to be displayed on the screen SCR.

[0022] 2 is a schematic configuration diagram of the first illumination device 20 of this embodiment. As shown in FIG. 2, the first illumination device 20 includes a 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 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 reflector 40.

[0024] The wavelength conversion element 30 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 longitudinal direction is also the direction in which the wavelength conversion element 30 emits the second light L2. 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 rectangular. In the following description, the Y-axis direction may be referred to as the incident direction. The incident direction is the direction in which the first light L1 is incident on the wavelength conversion element 30.

[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 face in the longitudinal direction (X-axis direction) and are located on opposite sides of each other in the longitudinal direction. The second surface 30b is located away from the first surface 30a in the longitudinal direction. The second surface 30b faces in the opposite direction to the first surface 30a. The longitudinal dimension Sx of the wavelength conversion element 30 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 face the incident direction (Y-axis direction) and are located on opposite sides of the incident direction. The fourth surface 30d is spaced apart from the third surface 30c in the incident 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. The wavelength conversion element 30 has a fifth surface 30e and a sixth surface 30f that face the Z-axis direction and are located on opposite sides of each other in the Z-axis direction. In the following description, the third surface 30c, the fourth surface 30d, the fifth surface 30e, and the sixth surface 30f may each be referred to as a "side surface."

[0026] The wavelength conversion element 30 converts first light L1 having a first wavelength band into 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 third surface 30c. The second light L2 is guided inside the wavelength conversion element 30, and then emitted from the first surface 30a toward the angle conversion member 38. That is, the first surface 30a emits the second light L2 toward the angle conversion member 38.

[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 concentration Dp of the fluorescence-emitting points in the longitudinal direction (X-axis direction) changes continuously. Therefore, it is desirable to form the wavelength conversion element 30 by the Czochralski method (CZ method). This makes it possible to smoothly change the concentration Dp of the fluorescence-emitting points in the longitudinal 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. As a result, 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 wavelength band of 490 nm to 750 nm. When the phosphor 33 absorbs the first light L1, the phosphor 33 generates heat. Furthermore, a portion of the second light L2 guided inside the wavelength conversion element 30 is absorbed by the phosphor 33. When the phosphor 33 absorbs the second light L2, the phosphor 33 generates heat.

[0030] The light source section 34 emits a first light L1 to the wavelength conversion element 30. The light source section 34 is disposed opposite to the third surface 30c 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, on a surface facing the third surface 30c of the wavelength conversion element 30 in the incident 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 having a first wavelength band toward the third surface 30c of the wavelength conversion element 30. As a result, the first light L1 is incident on the third surface 30c. The first light L1 enters the wavelength conversion element 30 from the third surface 30c. 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. That is, the light source device 21 includes a plurality of light emitting elements 36. In this embodiment, the light source unit 34 has seven 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 third surface 30c 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 six or less, or eight or more. The plurality of light-emitting elements 36 include a first light-emitting element 36a and a second light-emitting element 36b.

[0033] The first light-emitting element 36a is any one of the multiple light-emitting elements 36. The second light-emitting element 36b is any one of the multiple light-emitting elements 36 that is arranged closer to the first surface 30a of the wavelength conversion element 30 than the first light-emitting element 36a. In this embodiment, the intensity P1 of the first light L1 emitted by the second light-emitting element 36b is greater than the intensity P1 of the first light L1 emitted by the first light-emitting element 36a. Therefore, in this embodiment, the light-emitting element 36 that is closer to the first surface 30a emits a first light L1 with a higher intensity. As a result, the intensity P1 of the first light L1 emitted to the third surface 30c increases from the second surface 30b toward the first surface 30a. Therefore, the intensity P1 of the first light L1 incident on the third surface 30c increases from the second surface 30b toward the first surface 30a. As a result, the intensity P1 of the first light L1 incident from the third surface 30c into the wavelength conversion element 30 increases from the second surface 30b toward the first surface 30a.

[0034] 2, the reflecting portion 40 is provided on the second surface 30b of the wavelength conversion element 30. That is, the reflecting portion 40 is provided on the second surface 30b. The reflecting portion 40 reflects the second light L2 that has been guided inside the wavelength conversion element 30 and reached the second surface 30b. The reflecting portion 40 is made of a metal film or a dielectric multilayer film formed on the second surface 30b.

[0035] The first light L1 emitted from each light-emitting element 36 toward the third surface 30c enters the wavelength conversion element 30 from the third surface 30c. 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 is emitted radially from the fluorescence-emitting point. The second light L2 traveling toward the four side surfaces 30c, 30d, 30e, and 30f of the wavelength conversion element 30 is repeatedly totally reflected by the side surfaces 30c, 30d, 30e, and 30f and travels toward the first surface 30a or the second surface 30b. The second light L2 traveling toward the second surface 30b is reflected by the reflector 40 and travels toward the first surface 30a. As a result, the second light L2 emitted at the fluorescence-emitting point travels toward the first surface 30a, passes through the first surface 30a, and enters the angle conversion member 38. Therefore, in the wavelength conversion element 30 of this embodiment, the intensity P2 of the second light L2 increases from the second surface 30b toward the first surface 30a.

[0036] The angle conversion member 38 is provided on the light emission side of the first surface 30a of the wavelength conversion element 30. The second light L2 emitted from the first surface 30a 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 emitted from the wavelength conversion element 30 is incident, an emission surface 38b from which the second light L2 exits, and a reflective side surface 38c that reflects the second light L2 toward the emission surface 38b. The incident surface 38a faces the first surface 30a in the longitudinal direction (X-axis direction).

[0037] 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.

[0038] 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 angular distribution of the second light L2 emitted from the wavelength conversion element 30. Generally, the etendue of light, which is defined as the product of the area of ​​the light emission region and the solid angle (maximum emission angle) of the 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.

[0039] In this embodiment, the incident surface 38a of the angle conversion member 38 is fixed to the first surface 30a 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.

[0040] 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.

[0041] 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 distribution of intensity P2 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Next, the concentration Dp of the fluorescence-emitting points of the wavelength conversion element 30 will be described. Note that in the following description, the amount of absorption of the first light L1 by the phosphor 33 may be simply referred to as the "absorption amount of the first light L1." The absorption amount of the first light L1 correlates with both the intensity P1 of the first light L1 and the concentration Dp of the fluorescence-emitting points. The absorption amount of the first light L1 increases as the intensity P1 of the first light L1 increases. The absorption amount of the first light L1 decreases as the concentration Dp of the fluorescence-emitting points decreases. As described above, when the phosphor 33 absorbs the first light L1, the phosphor 33 generates heat. Therefore, the amount of heat generated by the phosphor 33 increases as the absorption amount of the first light L1 increases.

[0046] As described above, a portion of the second light L2 guided through the wavelength conversion element 30 is absorbed by the phosphor 33. In the following description, the amount of second light L2 absorbed by the phosphor 33 may be simply referred to as the "absorption amount of second light L2." The absorption amount of second light L2 correlates with both the intensity P2 of the second light L2 and the concentration Dp of the fluorescence-emitting points. The absorption amount of second light L2 increases as the intensity P2 of the second light L2 increases. The absorption amount of second light L2 decreases as the concentration Dp of the fluorescence-emitting points decreases. When the phosphor 33 absorbs the second light L2, the phosphor 33 generates heat. Therefore, the amount of heat generated by the phosphor 33 increases as the absorption amount of second light L2 increases.

[0047] FIG. 3 is a diagram showing the distribution of the concentration Dp of the fluorescence-emitting points and the distribution of the intensity P1 of the first light L1 in the longitudinal direction (X-axis direction) of the wavelength conversion element 30 of this embodiment. The horizontal axis of FIG. 3 is the distance Dx from the second surface 30b in the longitudinal direction. The origin of the horizontal axis of FIG. 3 is the position of the second surface 30b in the longitudinal direction. As described above, the longitudinal dimension Sx of the wavelength conversion element 30 is the distance between the first surface 30a and the second surface 30b. On the horizontal axis of FIG. 3, the first surface 30a is located at Sx. The first vertical axis of FIG. 3 is the concentration Dp of the fluorescence-emitting points. The second vertical axis of FIG. 3 is the intensity P1 of the first light L1. The intensity P1 of the first light L1 shown in FIG. 3 is the intensity of the first light L1 incident on the third surface 30c.

[0048] As described above, in this embodiment, the second light L2 emitted from the fluorescence-emitting point travels toward the first surface 30a, passes through the first surface 30a, and enters the angle conversion member 38. Therefore, the intensity P2 of the second light L2 in the wavelength conversion element 30 increases from the second surface 30b toward the first surface 30a. Also, as described above, the amount of second light L2 absorbed by the phosphor 33 increases as the intensity P2 of the second light L2 increases. Furthermore, as described above, the amount of heat generated by the phosphor 33 increases as the amount of absorption of the second light L2 increases. For these reasons, when the concentration Dp of the fluorescence-emitting points in the longitudinal direction (X-axis direction) is uniform, the amount of absorption of the second light L2 increases from the second surface 30b toward the first surface 30a, and therefore the amount of heat generated by the phosphor 33 increases from the second surface 30b toward the first surface 30a. Therefore, when the concentration Dp of the fluorescence emission points in the longitudinal direction is uniform, the temperature of the portion of the wavelength conversion element 30 on the first surface 30a side becomes high. If the temperature of the portion of the wavelength conversion element 30 on the first surface 30a side becomes too high, thermal quenching of the second light L2 in the portion of the wavelength conversion element 30 on the first surface 30a side is likely to increase. Therefore, when the concentration Dp of the fluorescence emission points in the longitudinal direction is uniform, there is a risk of a decrease in the wavelength conversion efficiency, which is the efficiency with which the wavelength conversion element 30 converts the first light L1 into the second light L2. In the following description, the portion of the wavelength conversion element 30 on the first surface 30a side may be simply referred to as the "portion on the first surface 30a side." In the following description, the portion of the wavelength conversion element 30 on the second surface 30b side may be simply referred to as the "portion on the second surface 30b side."

[0049] In contrast, in this embodiment, as shown in FIG. 3, the concentration Dp of the fluorescence-emitting points of the phosphor 33 in the longitudinal direction (X-axis direction) decreases from the second surface 30b toward the first surface 30a. More specifically, the concentration Dp of the fluorescence-emitting points continuously decreases from the second surface 30b toward the first surface 30a. In this embodiment, the concentration Dp of the fluorescence-emitting points decreases approximately linearly from the second surface 30b toward the first surface 30a. Therefore, in this embodiment, an increase in the amount of absorption of the second light L2 in the portion on the first surface 30a side can be suppressed. Note that the concentration Dp of the fluorescence-emitting points may decrease curvilinearly from the second surface 30b toward the first surface 30a.

[0050] 3, in this embodiment, the intensity P1 of the first light L1 incident on the third surface 30c increases from the second surface 30b toward the first surface 30a. Therefore, the intensity P1 of the first light L1 incident on the portion on the second surface 30b side can be reduced. Therefore, in this embodiment, even though the concentration Dp of the fluorescence-emitting points on the second surface 30b is high, the amount of absorption of the first light L1 in the portion on the second surface 30b side can be reduced. This prevents the temperature of the portion on the second surface 30b side from becoming too high, thereby suppressing thermal quenching of the second light L2 in the portion of the wavelength conversion element 30 on the second surface 30b side.

[0051] According to this embodiment, the light source device 21 includes a plurality of light-emitting elements 36 that emit first light L1 having a first wavelength band, a wavelength conversion element 30 that contains a phosphor 33 and 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, and an angle conversion member 38 that converts the angular distribution of the second light L2 emitted from the wavelength conversion element 30. The wavelength conversion element 30 has a first surface 30a that faces the longitudinal direction (X-axis direction) and emits the second light L2 toward the angle conversion member 38, a second surface 30b that faces the opposite side to the first surface 30a, and a third surface 30c that intersects both the first surface 30a and the second surface 30b and on which the first light L1 is incident, and a concentration Dp of fluorescence emission points of the phosphor 33 decreases from the second surface 30b toward the first surface 30a. As described above, in this embodiment, the second light L2 emitted from the fluorescence-emitting points is transmitted through the first surface 30a and enters the angle conversion member 38. Therefore, the intensity P2 of the second light L2 guided inside the wavelength conversion element 30 increases from the second surface 30b toward the first surface 30a. Therefore, as described above, when the concentration Dp of the fluorescence-emitting points in the longitudinal direction is uniform, the absorption amount of the second light L2 increases from the second surface 30b toward the first surface 30a. That is, the absorption amount of the second light L2 in the portion on the first surface 30a side increases. In contrast, in this embodiment, the concentration Dp of the fluorescence-emitting points of the phosphor 33 decreases from the second surface 30b toward the first surface 30a, so that an increase in the absorption amount of the second light L2 in the portion of the wavelength conversion element 30 on the first surface 30a side can be suppressed. Therefore, the amount of the second light L2 emitted from the first surface 30a can be increased, and the wavelength conversion efficiency of the wavelength conversion element 30 can be increased.

[0052] Furthermore, in this embodiment, as described above, an increase in the amount of absorption of the second light L2 in the portion of the wavelength conversion element 30 on the first surface 30a side can be suppressed, and therefore the amount of heat generated by the phosphor 33 in the portion on the first surface 30a side can be suppressed. This prevents the temperature of the portion on the first surface 30a side from becoming too high. Therefore, temperature quenching of the second light L2 in the portion on the first surface 30a side can be reduced, and the wavelength conversion efficiency of the wavelength conversion element 30 can be more suitably improved.

[0053] Furthermore, in this embodiment, as described above, the concentration Dp of the fluorescence emission points of the phosphor 33 decreases from the second surface 30b toward the first surface 30a, so that the amount of absorption of the first light L1 in the portion of the wavelength conversion element 30 on the first surface 30a side can be suppressed. This makes it possible to more effectively suppress the amount of heat generated by the phosphor 33 in the portion on the first surface 30a side. Therefore, it is possible to more effectively prevent the temperature of the portion on the first surface 30a side from becoming too high, and therefore it is possible to more effectively suppress the temperature quenching of the second light L2 in the portion on the first surface 30a side. Therefore, it is possible to more effectively increase the wavelength conversion efficiency of the wavelength conversion element 30.

[0054] According to this embodiment, each of the multiple light-emitting elements 36 faces the third surface 30c and is arranged side by side in the longitudinal direction (X-axis direction). The multiple light-emitting elements 36 include a first light-emitting element 36a and a second light-emitting element 36b arranged closer to the first surface 30a than the first light-emitting element 36a. The intensity P1 of the first light L1 emitted by the second light-emitting element 36b is greater than the intensity P1 of the first light L1 emitted by the first light-emitting element 36a. As described above, in this embodiment, the concentration Dp of the fluorescence emission points of the phosphor 33 decreases from the second surface 30b toward the first surface 30a, so the concentration Dp of the fluorescence emission points in the portion of the wavelength conversion element 30 on the second surface 30b side increases. Therefore, when the intensities P1 of the first light L1 emitted by the light-emitting elements 36 are the same, the amount of first light L1 absorbed by the phosphor 33 in the portion on the second surface 30b side increases. As a result, the amount of heat generated by the phosphor 33 in the portion on the second surface 30b side increases, and the temperature of the portion on the second surface 30b side tends to rise. Therefore, thermal quenching of the second light L2 in the portion on the second surface 30b side tends to increase. In contrast, in this embodiment, the intensity P1 of the first light L1 incident on the portion on the second surface 30b side of the wavelength conversion element 30 can be reduced. This reduces the amount of absorption of the first light L1 in the portion on the second surface 30b side, and therefore prevents the temperature of the portion on the second surface 30b side from becoming too high. Therefore, thermal quenching of the second light L2 in the portion on the second surface 30b side of the wavelength conversion element 30 can be suppressed. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be more suitably improved.

[0055] Furthermore, in this embodiment, as described above, the concentration Dp of the fluorescent light-emitting points in the portion of the wavelength conversion element 30 on the first surface 30a side is low, making it difficult to increase the amount of light emitted by the second light L2 in the portion on the first surface 30a side. In contrast, in this embodiment, the intensity P1 of the first light L1 incident on the portion on the first surface 30a side can be increased. This makes it possible to increase the amount of light emitted by the second light L2 in the portion of the wavelength conversion element 30 on the first surface 30a side. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be more suitably improved.

[0056] According to this embodiment, the second surface 30b is provided with a reflecting portion 40 that reflects the second light L2. Therefore, the second light L2 emitted from the fluorescence emission point and traveling toward the second surface 30b can be reflected toward the first surface 30a by the reflecting portion 40. This makes it possible to prevent the second light L2 from leaking out of the wavelength conversion element 30 from the second surface 30b, thereby more preferably increasing the amount of second light L2 emitted from the first surface 30a. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be more preferably increased.

[0057] 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 decreases from the second surface 30b toward the first surface 30a. As described above, this can suppress an increase in the amount of absorption of the second light L2 in the portion of the wavelength conversion element 30 on the first surface 30a side, and can suppress thermal quenching of the second light L2 in the portion on the first surface 30a side. Therefore, the wavelength conversion efficiency of the wavelength conversion element 30 can be improved. This can reduce the amount of first light L1 required to emit a predetermined amount of second light L2 toward the angle conversion member 38. Therefore, the amount of first light L1 emitted by each light-emitting element 36 can be reduced, thereby reducing the power consumed by the projector 1.

[0058] (Modification of the first embodiment) A projector 101 according to a modification of the first embodiment will be described below. The basic configuration of projector 101 of this modified example is similar to that of projector 1 of the first embodiment, and projector 101 of this modified example includes a reflecting element 142. In the following description, components that are the same as those of projector 1 of the first embodiment described above are given the same reference numerals, and descriptions thereof will be omitted.

[0059] FIG. 4 is a schematic diagram of a first illumination device 120 of this modified example. 4, the first illumination device 120 includes a light source device 121, 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 modified example 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.

[0060] The light source device 121 of this modification converts the first light L1 into the yellow second light L2 and emits the second light L2 toward the integrator optical system 50. The light source device 121 includes a wavelength conversion element 30, a light source unit 34, an angle conversion member 38, a reflecting unit 40, and a reflecting element 142.

[0061] The reflecting element 142 is provided on a portion of the fourth surface 30d of the wavelength conversion element 30 on the first surface 30a side. The reflecting element 142 reflects the first light L1 that has been guided inside the wavelength conversion element 30 in the incident direction (Y-axis direction) and reached the fourth surface 30d. When viewed from the incident direction, the end of the reflecting element 142 on the first surface 30a side overlaps the first surface 30a. The end of the reflecting element 142 on the first surface 30a side may be located closer to the second surface 30b than the first surface 30a. The end of the reflecting element 142 on the second surface 30b side is located near the center of the fourth surface 30d in the longitudinal direction (X-axis direction). In this modification, the reflecting element 142 is made of a metal film or a dielectric multilayer film formed on the fourth surface 30d. The reflecting element 142 may be a mirror made of metal, for example. The reflecting element 142 may also be located away from the fourth surface 30d in the incident direction. Other configurations of the light source device 121 of this modified example are similar to other configurations of the light source device 21 of the above-described first embodiment.

[0062] According to this modification, a reflecting element 142 that reflects the first light L1 is provided on a portion of the fourth surface 30d on the first surface 30a side. As in the first embodiment described above, the concentration Dp of fluorescent light-emitting points on the first surface 30a side of the wavelength conversion element 30 of this modification is small. Therefore, the first light L1 that enters the inside of the wavelength conversion element 30 from the third surface 30c is less likely to be absorbed by the phosphor 33 and more likely to reach the fourth surface 30d. Furthermore, because the angle of incidence of the first light L1 on the fourth surface 30d is small, the first light L1 is more likely to leak from the fourth surface 30d to the outside of the wavelength conversion element 30. In contrast, in this modification, the first light L1 that reaches the fourth surface 30d can be reflected by the reflecting element 142 and returned to the inside of the wavelength conversion element 30. This increases the intensity P1 of the first light L1 guided to the portion of the wavelength conversion element 30 on the first surface 30a side, thereby increasing the amount of second light L2 emitted from the portion on the first surface 30a side, thereby more suitably improving the wavelength conversion efficiency of the wavelength conversion element 30.

[0063] (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 light source unit 234. 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 the description thereof will be omitted.

[0064] FIG. 5 is a schematic diagram of the first illumination device 220 of this embodiment. 5, 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.

[0065] The light source device 221 of this embodiment converts the first light L1 into 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 30, a light source unit 234, an angle conversion member 38, and a reflecting unit 40.

[0066] The light source section 234 emits a first light L1 to the wavelength conversion element 30. The light source section 234 is disposed opposite to the third surface 30c of the wavelength conversion element 30 in the incident direction (Y-axis direction). The light source section 234 includes a substrate 35 and a light emitting element 236. That is, the light source device 21 includes the light emitting element 236.

[0067] The light emitting element 236 is configured by, for example, a light emitting diode. The light emitting element 236 emits first light L1 having a first wavelength band toward the third surface 30c of the wavelength conversion element 30. As a result, the first light L1 enters the wavelength conversion element 30 from the third surface 30c. The light source section 234 has a plurality of light emitting elements 236. That is, the light source device 221 includes a plurality of light emitting elements 236. In this embodiment, the light source section 234 has seven light emitting elements 236. The light emitting elements 236 are arranged side by side in the longitudinal direction (X-axis direction). Each light emitting element 236 faces the third surface 30c in the incident direction (Y-axis direction). The plurality of light emitting elements 236 includes a first light emitting element 236a and a second light emitting element 236b.

[0068] The first light-emitting element 236a is any one of the multiple light-emitting elements 236. The second light-emitting element 236b is any one of the multiple light-emitting elements 236 that is arranged closer to the first surface 30a of the wavelength conversion element 30 than the first light-emitting element 236a. In this embodiment, the intensity P1 of the first light L1 emitted by the second light-emitting element 236b is smaller than the intensity P1 of the first light L1 emitted by the first light-emitting element 236a. Therefore, in this embodiment, the light-emitting element 236 that is closer to the first surface 30a emits the first light L1 with a lower intensity. As a result, the intensity P1 of the first light L1 emitted to the third surface 30c decreases from the second surface 30b toward the first surface 30a. Therefore, the intensity P1 of the first light L1 incident on the third surface 30c decreases from the second surface 30b toward the first surface 30a. As a result, the intensity P1 of the first light L1 incident from the third surface 30c into the wavelength conversion element 30 decreases from the second surface 30b toward the first surface 30a. Other configurations of the light source device 221 of this embodiment are similar to other configurations of the light source device 21 of the first embodiment described above. Note that a reflecting element 142 may be provided on the portion of the fourth surface 30d of the wavelength conversion element 30 on the first surface 30a side, as in the modified example of the first embodiment described above.

[0069] According to this embodiment, each of the plurality of light-emitting elements 236 faces the third surface 30c and is arranged side by side in the longitudinal direction (X-axis direction). The plurality of light-emitting elements 236 includes a first light-emitting element 236a and a second light-emitting element 236b arranged closer to the first surface 30a than the first light-emitting element 236a. The intensity P1 of the first light L1 emitted by the second light-emitting element 236b is smaller than the intensity P1 of the first light L1 emitted by the first light-emitting element 236a. Therefore, the intensity P1 of the first light L1 guided to the portion of the wavelength conversion element 30 on the first surface 30a side can be reduced, thereby reducing the amount of first light L1 absorbed in the portion on the first surface 30a side. This reduces the amount of heat generated by the phosphor 33 in the portion on the first surface 30a side, thereby preventing the temperature of the portion on the first surface 30a side from becoming too high. Therefore, the temperature quenching of the second light L2 in the portion on the first surface 30a side can be reduced, and the wavelength conversion efficiency of the wavelength conversion element 30 can be more suitably improved.

[0070] Furthermore, similarly to the first embodiment described above, the concentration Dp of the fluorescent light-emitting points in the portion of the wavelength conversion element 30 on the second surface 30b side of this embodiment is high. Furthermore, in this embodiment, the intensity P1 of the first light L1 guided to the portion of the wavelength conversion element 30 on the second surface 30b side can be increased. As a result, in this embodiment, the amount of second light L2 emitted in the portion on the second surface 30b side can be increased. Therefore, the amount of second light L2 emitted from the first surface 30a can be more suitably increased, and the wavelength conversion efficiency of the wavelength conversion element 30 can be more suitably increased.

[0071] (Third embodiment) A projector 301 according to the third embodiment will be described below. The basic configuration of the projector 301 of this embodiment is similar to that of the projector 1 of the first embodiment, and the projector 301 of this embodiment includes a wavelength conversion element 330. 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 the description thereof will be omitted.

[0072] FIG. 6 is a schematic diagram of the first illumination device 320 of this embodiment. 6, the first illumination device 320 includes a light source device 321, 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.

[0073] The light source device 321 of this embodiment converts the first light L1 into yellow second light L2 and emits the second light L2 toward the integrator optical system 50. The light source device 321 includes a wavelength conversion element 330, a light source unit 34, an angle conversion member 38, and a reflector 40. Note that the light source unit 34 may be the light source unit 234 of the second embodiment described above, in which the intensity of the first light L1 emitted by the second light emitting element 236b is smaller than the intensity of the first light L1 emitted by the first light emitting element 236a.

[0074] The wavelength conversion element 330 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 330 has a rectangular prism shape extending in the X-axis direction. The dimension of the wavelength conversion element 330 in the X-axis direction is greater than the dimensions in the Y-axis direction and the Z-axis direction. The wavelength conversion element 330 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 face in the longitudinal direction (X-axis direction) and are located on opposite sides of each other in the longitudinal direction. The first surface 30a emits the second light L2 toward the angle conversion member 38. The third surface 30c intersects with both the first surface 30a and the second surface 30b, and the first light L1 is incident on the third surface 30c. In this embodiment, the third surface 30c is perpendicular to both the first surface 30a and the second surface 30b.

[0075] In this embodiment, the wavelength conversion element 330 is composed of a plurality of laminated sections 331 laminated in the longitudinal direction (X-axis direction). Each laminated section 331 has a substantially rectangular parallelepiped shape extending in the longitudinal direction. In this embodiment, the wavelength conversion element 330 is composed of four laminated sections 331. The four laminated sections 331 include laminated section 331a, laminated section 331b, laminated section 331c, and laminated section 331d. The four laminated sections 331 are arranged in the order of laminated section 331a, laminated section 331b, laminated section 331c, and laminated section 331d from the second surface 30b side. The laminated sections 331 are fixed to each other via an optical adhesive. The number of laminated sections 331 constituting the wavelength conversion element 330 is not limited to four, and may be three or less, or five or more.

[0076] In this embodiment, the first surface 30a is a surface of the outer surface of the laminated portion 331d that faces the angle conversion member 38 in the longitudinal direction (X-axis direction). The second surface 30b is a surface of the outer surface of the laminated portion 331a 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 laminated portion 331 that faces the light source unit 34 in the incident direction (Y-axis direction). The fourth surface 30d is formed by a surface of the outer surface of each laminated portion 331 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 laminated portion 331 that faces one side in the Z-axis direction. The sixth surface 30f is formed by a surface of the outer surface of each laminated portion 331 that faces the other side in the Z-axis direction.

[0077] In this embodiment, the concentration Dp of the fluorescent light-emitting substance contained in the laminated portion 331b is smaller than the concentration Dp of the fluorescent light-emitting substance contained in the laminated portion 331a. The concentration Dp of the fluorescent light-emitting substance contained in the laminated portion 331c is smaller than the concentration Dp of the fluorescent light-emitting substance contained in the laminated portion 331b. The concentration Dp of the fluorescent light-emitting substance contained in the laminated portion 331d is smaller than the concentration Dp of the fluorescent light-emitting substance contained in the laminated portion 331c. Therefore, the concentration Dp of the fluorescent light-emitting points contained in each of the multiple laminated portions 331 is smaller than the concentration Dp of the fluorescent light-emitting points contained in the other laminated portions 331 arranged on the second surface 30b side. As a result, the concentration Dp of the fluorescent light-emitting points of the phosphor 333 of the wavelength conversion element 330 decreases from the second surface 30b toward the first surface 30a. More specifically, the concentration Dp of the fluorescent light-emitting points of the phosphor 333 of the wavelength conversion element 330 decreases stepwise from the second surface 30b toward the first surface 30a. Other configurations of the wavelength conversion element 330 of this embodiment are similar to other configurations of the wavelength conversion element 30 of the above-described first embodiment. Note that a reflecting element 142 may be provided on a portion of the fourth surface 30d of the wavelength conversion element 330 on the first surface 30a side, as in the modified example of the above-described first embodiment.

[0078] According to this embodiment, the concentration Dp of the fluorescence emission points of the phosphor 333 of the wavelength conversion element 330 decreases from the second surface 30b toward the first surface 30a. Therefore, similar to the first embodiment described above, it is possible to suppress an increase in the amount of absorption of the second light L2 in the portion of the wavelength conversion element 330 on the first surface 30a side, and to suppress temperature quenching of the second light L2 in the portion on the first surface 30a side. Therefore, it is possible to improve the wavelength conversion efficiency of the wavelength conversion element 330.

[0079] According to this embodiment, the wavelength conversion element is configured with multiple stacked portions 331 stacked in the longitudinal direction (X-axis direction), and the concentration Dp of fluorescence emission points included in each of the multiple stacked portions 331 is smaller than the concentration Dp of fluorescence emission points included in other stacked portions 331 arranged on the second surface 30b side. Therefore, since the wavelength conversion element 330 can be configured with multiple stacked portions 331 whose fluorescence emission point concentrations Dp are known in advance, the distribution of the fluorescence emission point concentrations Dp in the longitudinal direction can be more easily stabilized compared to when the wavelength conversion element 330 is configured integrally. This makes it easier to stably decrease the fluorescence emission point concentration Dp of the phosphor 333 of the wavelength conversion element 330 from the second surface 30b toward the first surface 30a. Therefore, it is possible to more effectively suppress an increase in the amount of absorption of the second light L2 in the portion of the wavelength conversion element 330 on the first surface 30a side, and to more effectively suppress temperature quenching of the second light L2 in the portion on the first surface 30a side. Therefore, the wavelength conversion efficiency of the wavelength conversion element 330 can be more suitably improved.

[0080] 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.

[0081] 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.

[0082] A summary of this disclosure is provided below.

[0083] (Appendix 1) 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; and an angle conversion member that converts the angular distribution of the second light emitted from the wavelength conversion element, wherein the wavelength conversion element has a first surface that faces in a longitudinal direction and emits the second light toward the angle conversion member, a second surface that faces opposite to the first surface, and a third surface that intersects with both the first surface and the second surface and into which the first light is incident, and a concentration of fluorescent emission points of the phosphor decreases from the second surface to the first surface.

[0084] According to the light source device having the configuration of Supplementary Note 1, it is possible to suppress an increase in the amount of absorption of the second light in the portion on the first surface side of the wavelength conversion element, and to suppress temperature quenching of the second light in the portion on the first surface side, thereby improving the wavelength conversion efficiency of the wavelength conversion element 30.

[0085] (Appendix 2) The light source device described in Appendix 1, wherein each of the plurality of light-emitting elements faces the third surface and is arranged side by side in the longitudinal direction, the plurality of light-emitting elements includes a first light-emitting element and a second light-emitting element arranged closer to the first surface than the first light-emitting element, and the intensity of the first light emitted by the second light-emitting element is greater than the intensity of the first light emitted by the first light-emitting element.

[0086] According to this configuration, the intensity of the first light incident on the second surface side of the wavelength conversion element can be reduced. This reduces the amount of first light absorbed in the second surface side, preventing the temperature of the second surface side from becoming too high. This prevents thermal quenching of the second light in the second surface side of the wavelength conversion element. This can more effectively improve the wavelength conversion efficiency of the wavelength conversion element.

[0087] (Appendix 3) The light source device described in Appendix 1, wherein each of the plurality of light-emitting elements faces the third surface and is arranged side by side in the longitudinal direction, the plurality of light-emitting elements includes a first light-emitting element and a second light-emitting element arranged closer to the first surface than the first light-emitting element, and the intensity of the first light emitted by the second light-emitting element is smaller than the intensity of the first light emitted by the first light-emitting element.

[0088] According to this configuration, the intensity of the first light guided to the first surface side portion of the wavelength conversion element can be reduced, thereby reducing the amount of first light absorbed in the first surface side portion. This reduces the amount of heat generated in the first surface side portion, thereby preventing the temperature of the first surface side portion from becoming too high. Therefore, thermal quenching of the second light in the first surface side portion can be reduced, thereby more suitably improving the wavelength conversion efficiency of the wavelength conversion element.

[0089] (Appendix 4) The wavelength conversion element has a fourth surface facing the opposite side to the third surface, and a reflective element that reflects the first light is provided on a portion of the fourth surface facing the first surface.

[0090] According to this configuration, the first light that reaches the fourth surface can be reflected by the reflecting element and returned to the inside of the wavelength conversion element. This increases the intensity of the first light guided to the portion of the wavelength conversion element on the first surface side, thereby increasing the amount of second light emitted from the portion on the first surface side. Therefore, the wavelength conversion efficiency of the wavelength conversion element can be more suitably improved.

[0091] (Appendix 5) 5. The light source device according to claim 1, wherein the second surface is provided with a reflecting portion that reflects the second light.

[0092] According to this configuration, the second light traveling toward the second surface can be reflected toward the first surface by the reflecting portion. This allows the second light to leak out of the wavelength conversion element from the second surface, thereby more preferably increasing the amount of second light emitted from the first surface. Therefore, the wavelength conversion efficiency of the wavelength conversion element can be more preferably increased.

[0093] (Appendix 6) 6. The light source device according to claim 1, wherein the wavelength conversion element is configured by a plurality of laminated portions stacked in the longitudinal direction, and the concentration of the fluorescent emission points included in each of the plurality of laminated portions is smaller than the concentration of the fluorescent emission points included in other laminated portions arranged on the second surface side.

[0094] According to this configuration, the wavelength conversion element can be constructed using multiple laminated sections whose concentrations of fluorescent emission points are known in advance, making it easier to stabilize the distribution of the concentration of fluorescent emission points in the longitudinal direction. This makes it easier to stably decrease the concentration of fluorescent emission points in the phosphor of the wavelength conversion element from the second surface toward the first surface. Therefore, it is possible to more effectively suppress an increase in the amount of absorption of the second light in the portion of the wavelength conversion element on the first surface side, and to more effectively suppress temperature quenching of the second light in the portion of the wavelength conversion element on the first surface side. Therefore, it is possible to more effectively increase the wavelength conversion efficiency of the wavelength conversion element.

[0095] (Appendix 7) A projector comprising: a light source device according to any one of Supplementary Note 1 to Supplementary Note 6; 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.

[0096] According to a projector having this configuration, the wavelength conversion efficiency of the wavelength conversion element can be increased, so the amount of first light required to emit a predetermined amount of second light can be reduced, and therefore the amount of first light emitted by each light-emitting element can be reduced, so the power consumed by the projector can be reduced. [Explanation of symbols]

[0097] 1,101,201,301...projector, 4R,4G,4B...light modulation device, 6...projection optical device, 21,121,221,321...light source device, 30,330...wavelength conversion element, 30a...first surface, 30b...second surface, 30c...third surface, 30d...fourth surface, 33,333...phosphor, 36,236...light-emitting element, 36a,236a...first light-emitting element, 36b,236b...second light-emitting element, 38...angle conversion member, 40...reflecting portion, 142...reflecting element, 331...laminated portion, Dp...concentration of fluorescent light-emitting point, L1...first light, L2...second light.

Claims

1. a plurality of light-emitting elements that emit 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; an angle conversion member that converts the angular distribution of the second light emitted from the wavelength conversion element; Equipped with the wavelength conversion element has a first surface facing a longitudinal direction and through which the second light is emitted toward the angle conversion member, 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 on which the first light is incident, the concentration of the fluorescent points of the phosphor decreases from the second surface toward the first surface; Light source device.

2. each of the plurality of light-emitting elements is arranged opposite the third surface and aligned in the longitudinal direction; the plurality of light-emitting elements include a first light-emitting element and a second light-emitting element disposed closer to the first surface than the first light-emitting element, The intensity of the first light emitted from the second light-emitting element is greater than the intensity of the first light emitted from the first light-emitting element. The light source device according to claim 1 .

3. each of the plurality of light-emitting elements is arranged opposite the third surface and aligned in the longitudinal direction; the plurality of light-emitting elements include a first light-emitting element and a second light-emitting element disposed closer to the first surface than the first light-emitting element, an intensity of the first light emitted from the second light-emitting element is smaller than an intensity of the first light emitted from the first light-emitting element; The light source device according to claim 1 .

4. the wavelength conversion element has a fourth surface facing the opposite side to the third surface, a reflecting element that reflects the first light is provided on a portion of the fourth surface on the first surface side; The light source device according to claim 1 .

5. The second surface is provided with a reflecting portion that reflects the second light. The light source device according to claim 1 .

6. the wavelength conversion element is configured by a plurality of laminated portions laminated in the longitudinal direction, the concentration of the fluorescent light emitting points included in each of the plurality of laminated portions is lower than the concentration of the fluorescent light emitting points included in the other laminated portions arranged on the second surface side; The light source device according to claim 1 .

7. The light source device according to any one of claims 1 to 3; 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; A projector equipped with

Images