具体实施方式：
[0032]The following describes embodiments of the present disclosure in detail with reference to the drawings. The following description is a specific example of the present disclosure, but the present disclosure is not limited to the following embodiments. In addition, the present disclosure is not limited to arrangement, dimensions, dimensional ratios, and the like of the constituent elements illustrated in the drawings. It is to be noted that description is given in the following order.
[0033]1. First Embodiment (an example in which a plurality of heat dissipation members each having heat dissipation performance different from each other depending on a distance from a phosphor layer is disposed on a back surface of a wheel substrate)[0034]1-1. Configurations of Phosphor Wheel and Its Surroundings[0035]1-2. Method of Manufacturing Phosphor Wheel[0036]1-3. Configuration of Light Source Apparatus[0037]1-4. Workings and Effects
[0038]2. Second Embodiment (an example of a phosphor wheel including a plurality of heat dissipation members each having a fin whose thickness is different from each other)
[0039]3. Third Embodiment (an example of a phosphor wheel including a plurality of heat dissipation members each having a fin whose length and thickness are different from each other)
[0040]4. Modification Examples[0041]4-1. Modification Example 1 (an example in which a plurality of heat dissipation members is formed in an integrated manner)[0042]4-2. Modification Example 2 (an example in which an outermost heat dissipation member is provided integrally with a wheel substrate)[0043]4-3. Modification Example 3 (an example in which a plurality of heat dissipation members is formed in an integrated manner with a wheel substrate)[0044]4-4. Modification Example 4 (an example in which another heat dissipation member is further provided on an inner circumference as compared to a phosphor layer)[0045]4-5. Modification Example 5 (an example in which a sloping surface is provided on a peripheral edge portion of a housing)[0046]4-6. Modification Example 6 (an example in which other heat dissipation members are further provided on a front surface of a wheel substrate)[0047]4-7. Modification Example 7 (an example of a transmissive phosphor wheel)[0048]4-8. Modification Example 8 (another configuration example of a light source apparatus)
[0049]5. Application Examples (projection display apparatuses)
1. First Embodiment
[0050]FIG. 1 schematically illustrates an example of cross-sectional configurations of a wavelength converter (a phosphor wheel 10A) and a housing 20 included in a light source apparatus (a light source apparatus 1) according to a first embodiment of the present disclosure. FIG. 2A schematically illustrates a planar configuration, seen from a front surface side, of a phosphor wheel 10A illustrated in FIG. 1. FIG. 2B schematically illustrates a planar configuration, seen from a back surface side, of the phosphor wheel 10A illustrated in FIG. 1. FIG. 1 illustrates a cross-sectional configuration taken along a line I-I illustrated in FIGS. 2A and 2B. Further, FIGS. 2A and 2B each illustrate portions of respective fins 132a, 132b, and 132c of heat dissipation members 13A, 13B, and 13C. The phosphor wheel 10A is to be used as, for example, a light-emitting device (a wavelength converter) included in a light source apparatus (e.g., a light source apparatus 1) of a projection display apparatus (a projector 1000) to be described later (e.g., see FIGS. 6 and 18).
[0051]The light source apparatus 1 according to the present embodiment includes: the phosphor wheel 10A that converts a wavelength of excitation light EL (e.g., blue light) outputted from a light source unit 1110 to be described later into a wavelength of fluorescence FL (e.g., yellow light) and outputs the wavelength-converted light; and a housing 20 that contains the phosphor wheel 10A. The phosphor wheel 10A has a phosphor layer 12 fixed to, for example, a front surface (one surface; a surface 1151) of a wheel substrate 11 having a circular planar shape. On a back surface (another surface; a surface 11S2) is provided with a plurality of concentric heat dissipation members 13 centered on a center (O) of rotation of the wheel substrate 11. A plurality of heat dissipation members (a plurality of fins 221) is provided inside the housing 20. The plurality of heat dissipation members (the plurality of fins 221) is disposed in a nested manner with the plurality of heat dissipation members 13. In the present embodiment, three heat dissipation members 13A, 13B, and 13C each having heat dissipation performance different from each other are provided, as the plurality of heat dissipation members 13, on the back surface (the surface 11S2) of the wheel substrate 11 depending on the distances from the phosphor layer 12. It should be noted that FIGS. 1, 2A, and 2B each schematically illustrate configurations of the phosphor wheel 10A and the housing 20, and may differ from actual dimensions and shapes.
1-1. Configurations of Phosphor Wheel and its Surroundings
[0052]As described above, in the phosphor wheel 10A, the phosphor layer 12 is provided on the front surface (the surface 11S1) of the circular wheel substrate 11, and the two heat dissipation members 13A, 13B, and 13C are provided on the back surface (the surface 11S2) of the circular wheel substrate 11. The phosphor layer 12 is formed in an annular shape, for example, around a center O of rotation of the wheel substrate 11. The wheel substrate 11 is fixed to a motor 14, and is rotatable, for example, in an arrow C direction about an axis J14A passing through the center (O) of rotation, for example, during an operation of the light source apparatus 1. The phosphor wheel 10A is rotated in order to prevent a decrease in light conversion efficiency while suppressing a local increase in temperature with application of the excitation light EL and maintaining structure stability.
[0053]The wheel substrate 11 serves as a substrate that supports the phosphor layer 12, and also serves as a heat dissipation member. The wheel substrate 11 includes, for example, an inorganic material such as a metal material and a ceramic material. As a constituent material of the wheel substrate 11, a material having high heat conductivity is preferable. Specifically, examples of the metal material included in the wheel substrate 11 include simple substances of metals such as aluminum (Al), copper (Cu), molybdenum (Mo), tungsten (W), cobalt (Co), chromium (Cr), platinum (Pt), tantalum (Ta), lithium (Li), zirconium (Zr), ruthenium (Ru), rhodium (Rh) and palladium (Pd) or an alloy including one or more of the metals. Alternatively, as the metal material included in the wheel substrate 11, it is possible to use an alloy such as CuW containing 80 at % or more of W and CuMo containing 40 at % or more of Mo. Examples of the ceramic material include a ceramic material including silicon carbide (SiC), aluminum nitride (AlN), beryllium oxide (BeO), a composite material of Si and SiC, or a composite material of SiC and Al (in which the content of SiC is 50% or more). Moreover, in addition to a simple substance of Si, SiC, and a crystal material such as diamond or sapphire, it is also possible to use quartz and glass. In particular, as the constituent element of the wheel substrate 11, the simple substances of Mo, Si, and W are preferable, which have high heat conductivity.
[0054]The phosphor layer 12 the phosphor layer 12 includes a plurality of phosphor particles, and is fixed to the front surface (the surface S1) of the wheel substrate 11. The phosphor layer 12 is preferably formed in a plate-like shape, for example, and includes a so-called ceramic phosphor or a binder-type porous phosphor. The binder binds one phosphor particle to another phosphor particle adjacent to the one phosphor particle. The binder includes, for example, a cross-linked body of an inorganic material such as water glass. The water glass indicates a silicate compound that is also referred to as sodium silicate, potassium silicate, or silicate soda, and indicates a liquid in which anhydrous silicic acid (SiO2) and sodium oxide (Na2O) or potassium oxide (K2O) are mixed at a predetermined ratio. Water glass is represented by a molecular formula of Na2O·nSiO2.
[0055]The phosphor particles include a particulate phosphor that absorbs the excitation light EL (for example, laser light) applied from outside to emit fluorescence FL. For example, the phosphor particles include a fluorescent material that is excited by blue laser light having a wavelength in a blue wavelength range (for example, from 400 nm to 470 nm) to emit yellow fluorescence (light in a wavelength range between a red wavelength range and a green wavelength range). As such a fluorescent material, for example, YAG (yttrium aluminum garnet)-based material is used.
[0056]It is to be noted that, as illustrated in FIG. 3, the phosphor layer 12 may be fixed to the wheel substrate 11 with a reflection film 15 interposed therebetween, for example. The reflection film 15 functions to reflect the excitation light EL applied from outside and the fluorescence FL emitted from the phosphor layer 12, thereby enhancing light emission efficiency in the phosphor wheel 10A. The reflection film 15 includes, in addition to a dielectric multilayer film, a metal film including a metal element such as aluminum (Al), silver (Ag), or titanium (Ti), etc., for example. It is to be noted that in a case where the wheel substrate 11 includes a material having light reflectivity, the reflection film 15 may be omitted where appropriate.
[0057]As described above, in the phosphor wheel 10A, the three heat dissipation members 13A, 13B, and 13C are disposed, for example, as the plurality of heat dissipation members 13, on the back surface (the surface 1152) of the wheel substrate 11. The heat dissipation members 13A, 13B, and 13C each correspond to a specific example of a “first heat dissipation member” of the present disclosure. As described above, the heat dissipation members 13A, 13B, and 13C each have heat dissipation performance different from each other, and are disposed depending on the distances from the phosphor layer 12. Specifically, the heat dissipation member 13A has the highest heat dissipation performance, the heat dissipation member 13B has the next highest heat dissipation performance, and the heat dissipation member 13C has the lowest heat dissipation performance. In the present embodiment, the heat dissipation member 13A having the highest heat dissipation performance is disposed nearest to the phosphor layer 12 that is to be a heat source, e.g., immediately below the phosphor layer 12 as illustrated in FIG. 1, and the heat dissipation member 13C having the lowest heat dissipation performance is disposed furthest from the phosphor layer 12, e.g., on a peripheral edge portion of the wheel substrate 11, as illustrated in FIG. 1. The heat dissipation members 13A, 13B, and 13C are disposed in this order from the center (O) of rotation of the wheel substrate 11.
[0058]The heat dissipation members 13A, 13B, and 13C include stationary portions 131 (131a, 131b, and 131c) bonded to the back surface (the surface 11S2) of the wheel substrate 11, and fins 132 (132a, 132b, and 132c) bent substantially parallel to a rotation axis J14 of the phosphor wheel 10A from the stationary portions 131. The heat dissipation members 13A, 13B, and 13C are bonded to the wheel substrate 11 via the stationary portion 131a, 131b, and 131c, respectively. As a result, the heat dissipation members 13A, 13B, and 13C are rotatable about the axis J14A, for example, together with the wheel substrate 11 during the operation of the light source apparatus 1. The fins 132a, 132b, and 132c are each bent in the direction substantially parallel to the rotation axis J14 of the phosphor wheel 10A, and each form a cylindrical surface substantially parallel to the rotation axis J14, as described above. The cylindrical surface is preferably formed as a continuous surface around the rotation axis J14 as a center, but may have, for example, an incision extending in a rotation axis direction at one or more spots.
[0059]In the present embodiment, the heat dissipation performance of each of the heat dissipation members 13A, 13B, and 13C is adjusted by the respective lengths of the fins 132a, 132b, and 132c, for example. Specifically, the heat dissipation members 13A, 13B, and 13C have the fin 132a having a length l1, the fin 132b having a length l2, and the fin 132c having a length l3, respectively, and a relationship of the lengths l1>l2>l3 is satisfied. Thus, the length of the fin 132a of the heat dissipation member 13A disposed closest to the phosphor layer 12 is made the longest and the lengths of the fins 132b and 132c are made shorter as the distance from the phosphor layer 12 increases. This makes it possible to reduce a weight of the phosphor wheel 10A while maintaining cooling efficiency of a heat generator (the phosphor layer 12) by the heat dissipation members 13A, 13B, and 13C.
[0060]The heat dissipation members 13A, 13B, and 13C each preferably include a material having high heat conductivity. Specifically, the heat dissipation members 13A, 13B, and 13C each desirably include, for example, pure aluminum, an aluminum alloy, a copper alloy such as beryllium copper, a carbon material, graphite, etc. It is to be noted that the heat dissipation members 13A, 13B, and 13C may include the same material, or may each include a material different from each other.
[0061]The housing 20 contains the phosphor wheel 10A including the heat dissipation members 13 and prevents dust from being attached to the phosphor wheel 10A. The housing 20 has a front face portion 21, a back face portion 22, and a side face portion 23. On the front face portion 21, a lens 24 is disposed at a position directly opposed to the phosphor layer 12 as a transmission section through which the excitation light EL and the fluorescence FL are transmitted. The back face portion 22 is provided with, for example, two fins 221a and 221b as the plurality of concentric fins 221 centered on, for example, the center (O) of rotation of the wheel substrate 11. That is, the back face portion 22 of the housing 20 corresponds to a “first supporting member” of the present disclosure, and the fins 221a and 221b each correspond to a specific example of a “second heat dissipation member” of the present disclosure.
[0062]The fins 221a and 221b are each formed integrally with the back face portion 22 in the same length and each form a cylindrical surface substantially parallel to the rotation axis J14 of the phosphor wheel 10A. The cylindrical surfaces of the fins 221a and 221b are each preferably formed as a continuous surface around the rotation axis J14 as a center in a similar manner as the fins 132a, 132b, and 132c of the heat dissipation members 13A, 13B, and 13C, but may have, for example, an incision extending in the rotation axis direction at one or more spots. That is, the fins 132a 132b, 132c of the heat dissipation members 13A, 13B, and 13C and the fins 221a and 221b have surfaces that are opposed to each other and are substantially parallel to each other.
[0063]In the present embodiment, the fins 221a and 221b are disposed in a nested manner with the fins 132a, 132b, and 132c of the heat dissipation members 13A, 13B, and 13C. Specifically, the fins 132a, 132b, and 132c and the fins 221a and 221b are disposed in the order of the fin 132a, the fin 221a, the fin 132b, the fin 221b, and the fin 132c from the center (O) of rotation of the wheel substrate 11.
[0064]The positions of the fins 132a 221a, 132b, 221b, and 132c are preferably disposed in such a manner that, for example, an aspect ratio (AB) of a distance (A) to a distance (B) is 2 or greater. The distance (A) is a distance of a portion of the respective surfaces of the fin 132a and the fin 221a that are opposed to each other and the distance (B) is a distance between the fin 132a and the fin 221a. Similarly, it is preferable that the aspect ratio of a distance of a portion of the respective surfaces of the fin 132b and the fin 221b that are opposed to each other to a distance between the fin 132b and the fin 221b be 2 or greater. As for the fin 132c, it is preferable that a distance of a portion of the respective surfaces of the fin 132c and the side face portion 23 of the housing 20 and a distance between the fin 132c and the side face portion 23 have a similar configuration.
[0065]As a result, when the phosphor wheel 10A is rotationally driven, a Taylor vortex is generated in fluid (for example, air) between the fin 132a and the fin 221a, between the fin 132b and the fin 221b, and between the fin 132c and the side face portion 23. The Taylor vortex is generated by the centrifugal force acting on the gas. For this reason, in the present embodiment, the fins combined to have the above-described aspect ratio have such a configuration that the fins (the fins 221) on the outer peripheral side are fixed and the fins (the fins 132) on the inner peripheral side are rotationally driven. Accordingly, the heat generated in the phosphor layer 12 and transferred from the wheel substrate 11 to the heat dissipation member 13 is efficiently transferred to the fins 221a and 221b, which makes it possible to efficiently cool the phosphor layer 12.
[0066]It is to be noted that an upper limit of the aspect ratio is preferably 10 or less, for example. This is because in a case where the aspect ratio exceeds 10, an effect of improving cooling performance is reduced. Moreover, this is because in a case where the aspect ratio is 10 or more, that is, a portion corresponding to the fin becomes larger, a level of difficulty in manufacturing the heat dissipation members 13A, 13B, and 13C and the housing 20 becomes higher.
[0067]It is preferable that the housing 20 include a material having high heat conductivity. Specifically, the housing 20 desirably includes, for example, pure aluminum, an aluminum alloy, a copper alloy such as beryllium copper or the like, etc.
[0068]It is to be noted that FIG. 1 illustrates, as the housing 20, a sealed housing in which the front face portion 21, the back face portion 22, and the side face portion 23 are bonded to each other and completely isolated from the outside; however, the housing 20 may be an open housing in which the front surface (surface 11S1) side of the wheel substrate 11 is opened. Further, in the present embodiment, the side face portion 23 is used as the surface opposed to the fin 132c of the heat dissipation member 13C disposed on the peripheral edge portion of the wheel substrate 11; however, another fin may be separately provided on the back face portion 22 as the surface opposed to the fin 132c.
[0069]In a case where the housing 20 has a sealed structure, the housing 20 may be filled with a gas having higher heat conductivity than air, in addition to air as fluid. Specifically, the housing 20 is preferably filled with a gas having higher heat conductivity than heat conductivity (heat conductivity of 0.0257 W/mK in an environment at 20° C.) of air. Examples of such a gas include helium (He). Not only the gas but also a liquid may be sealed in the housing 20. Examples of the liquid sealed in the housing 20 include water, a silicon oil, etc., and a liquid having lowest possible viscosity is preferably selected. It is to be noted that in a case where the liquid is sealed in the housing 20, it is possible to rotate the phosphor wheel 10A with use of magnet-driving.
[0070]Moreover, for example, a heat dissipation structure 30 may be provided outside the housing 20, as illustrated in FIG. 1. This makes it possible to improve heat exhaust efficiency in the housing 20. The heat dissipation structure 30 includes, for example, a supporting member 31 bonded to the back face (the surface S2) of the housing 20, and a plurality of fins 32 is mounted on the supporting member 31. The heat transferred from the phosphor wheel 10A to the housing 20 is diffused into air.
[0071]The heat dissipation structure 30 may have a configuration in which a plurality of heat pipes is mounted on the back face (the surface S2) of the housing 20, and a heat sink is coupled to ends of the heat pipes. Examples of other heat dissipation structures include a liquid cooling system. In the liquid cooling system, a pipe is mounted on, for example, a surface or a side surface of the housing 20, and a cooling medium flows in the pipe, which causes heat of the housing 20 to be transferred to the cooling medium, thereby cooling the housing 20. The heat transferred to the cooling medium is diverged into air by a radiator, etc.
1-2. Method of Manufacturing Phosphor Wheel
[0072]The phosphor wheel 10A according to the present embodiment is manufacturable, for example, as follows. FIG. 4A and FIG. 4B are each a schematic view of a process of manufacturing the phosphor wheel 10A illustrated in FIG. 1.
[0073]First, as illustrated in FIG. 4A, the heat dissipation members 13A, 13B, and 13C are bonded to the back surface (the surface 11S2) of the wheel substrate 11. Thereafter, as illustrated in FIG. 4B, the phosphor layer 12 is bonded to the front surface (the surface 11S1) of the wheel substrate 11.
[0074]FIG. 5 illustrates warpage of the wheel substrate 11. Here, an aluminum substrate having a diameter of 95 mm and a thickness of 0.8 mm is used as the wheel substrate 11 and a sintered phosphor is used as the phosphor layer 12. In a case where the phosphor layer 12 was fixed to the aluminum wheel substrate 11 using a thermosetting adhesive, the warpage of the wheel substrate 11 after thermal curing was 0.4. In contrast, as in the present embodiment, in a case where the plurality of concentric heat dissipation members 13 was fixed to the back surface (the surface 11S2) of the wheel substrate 11 following which the phosphor layer 12 was fixed to the front surface (the surface 11S1) of the wheel substrate 11, the warpage of the wheel substrate 11 after thermal curing was about 0.07. As described above, the bonding of the phosphor layer 12 after the bonding of the heat dissipation member 13 to the back surface of the wheel substrate 11 makes it possible to reduce the warpage to about ⅙ of the warpage of the wheel substrate 11.
1-3. Configuration of Light Source Apparatus
[0075]FIG. 6 is a schematic view of an entire configuration of the light source apparatus 1. It is to be noted that, in FIG. 6, the phosphor wheel 10A is illustrated in a simplified manner together with the housing 20. The light source apparatus 1 includes: the phosphor wheel 10A as a wavelength converter; a light source unit 1110; a polarization beam splitter PBS 1112; a quarter-wave plate 1113; and a light-condensing optical system 1114 (1114A and 1114B). The members included in the light source apparatus 1 are disposed on an optical path of white light (multiplexed light Lw) outputted from the phosphor wheel 10A in the order of the light-condensing optical system 1114, the quarter-wave plate 1113, the PBS 1112, and the light source unit 1110, from the side of the phosphor wheel 10A.
[0076]The light source unit 1110 includes a solid-state light-emitting device that outputs light having a predetermined wavelength. In the present embodiment, as the solid-state light-emitting device, a semiconductor laser device that oscillates the excitation light EL (e.g., blue laser light having a wavelength of 445 nm or 455 nm) is used, and the excitation light EL of linearly polarized light (e.g., S-polarized light) is outputted from the light source unit 1110.
[0077]It is to be noted that, in a case where the light source unit 1110 includes the semiconductor laser device, the excitation light EL of a predetermined output may be obtained by one semiconductor laser device, or the excitation light EL of the predetermined output may be obtained by multiplexing the light outputted from a plurality of semiconductor laser devices. Further, a wavelength of the excitation light EL is not limited to the numerical values described above, and it is possible to use any wavelength as long as the wavelength is within the wavelength band of light that is referred to as blue light.
[0078]The PBS 1112 separates the excitation light EL entering from the light source unit 1110 and the multiplexed light Lw entering from the phosphor wheel 10A. Specifically, the PBS 1112 transmits the excitation light EL entering from the light source unit 1110 toward the quarter-wave plate 1113. Further, the PBS 1112 reflects the multiplexed light Lw entering from the phosphor wheel 10A and transmitted through the light-condensing optical system 1114 and the quarter-wave plate 1113. The reflected multiplexed light Lw enters an illumination optical system 2 (to be described later).
[0079]The quarter-wave plate 1113 is a phase difference device that causes a phase difference of π/2 with respect to incident light. In a case where the incident light is linearly polarized light, the quarter-wave plate 1113 converts the linearly polarized light into circularly polarized light, and in a case where the incident light is the circularly polarized light, the quarter-wave plate 1113 converts the circularly polarized light into the linearly polarized light. In the present embodiment, the excitation light EL that is the linearly polarized light outputted from the PBS 1112 is converted into the excitation light EL that is the circularly polarized light by the quarter-wave plate 1113. Further, an excitation light component of the circularly polarized light included in the multiplexed light Lw outputted from the phosphor wheel 10A is converted into the linearly polarized light by the quarter-wave plate 1113.
[0080]The light-condensing optical system 1114 (1114A and 1114B) condenses the excitation light EL outputted from the quarter-wave plate 1113 to have a predetermined spot diameter, and outputs the condensed excitation light EL toward the phosphor wheel 10A. Further, the light-condensing optical system 1114 converts the multiplexed light Lw outputted from the phosphor wheel 10A into parallel light, and outputs the parallel light toward the quarter-wave plate 1113. It is to be noted that the light-condensing optical system 1114, for example, may include a single collimating lens, may be configured to convert the incident light into the parallel light using a plurality of lenses.
[0081]A configuration of an optical member that separates the excitation light EL entering from the light source unit 1110 and the multiplexed light Lw outputted from the phosphor wheel 10A is not limited to the PBS 1112, and it is possible to use any optical member as long as the optical member has a configuration that enables the above-described light separating operation.
1-4. Workings and Effects
[0082]The light source apparatus 1 according to the present embodiment includes the phosphor wheel 10A in which, on the back surface (the surface 11S2) of the wheel substrate 11 provided with the phosphor layer 12, the three heat dissipation members 13A, 13B, and 13C each having the heat dissipation performance different from each other are concentrically disposed depending on the distances from the phosphor layer 12. The heat dissipation performance of each of the heat dissipation members 13A, 13B, and 13C is as follows: the heat dissipation member 13A>the heat dissipation member 13B>the heat dissipation member 13C. The heat dissipation member 13A having the highest heat dissipation performance is disposed nearest to (e.g., immediately below) the phosphor layer 12, the heat dissipation member 13B is disposed next, and the heat dissipation member 13C having the lowest heat dissipation performance is disposed at a position furthest from the phosphor layer 12 (e.g., on the peripheral edge portion of the wheel substrate 11). This makes it possible to efficiently diffuse the heat generation of the phosphor layer 12 caused by application of the excitation light EL while suppressing an increase in the weight of the phosphor wheel 10A. This will be described below.
[0083]In recent years, a laser light source having a small size, a long life, and a fast rise and fall has been widely used as a white light source. Although a semiconductor laser is mainly used as the laser, the semiconductor laser has low light emission efficiencies of GB light sources out of RGB light sources that are necessary for the white light source. For this reason, widely used is a light source apparatus (a phosphor laser light source) of a laser-phosphor system that generates the white light by synthesizing blue laser light and yellow fluorescence extracted by exciting the phosphor with the blue laser light.
[0084]However, there is an issue of temperature quenching that the light emission efficiency of the phosphor decreases as temperature rises. Accordingly, having been adopted is a method of suppressing the temperature rise of the phosphor by using a rotary phosphor wheel and diffusing heat generated by laser excitation. Such a light source apparatus may be lowered in the light emission efficiency or may be damaged due to the attachment of dust to the phosphor wheel. Thus, in an actual product, the phosphor wheel is disposed in a sealed space. As a heat dissipation technique of the phosphor wheel disposed in the sealed space, as described above, there is a method of providing concentric fins that are nested with each other on the back surface of the wheel substrate and on the surface of the sealed housing that is opposed to the back surface of the wheel substrate, and improving cooling efficiency of the light emission unit of the phosphor by utilizing the Taylor vortex generated between the fins when the wheel substrate is rotationally driven.
[0085]However, in the light source apparatus having the above-described heat dissipation structure, balancing between the heat dissipation efficiency and the weight of the phosphor wheel is cited as an issue. It is possible to improve the heat dissipation efficiency of the above-described light source apparatus by increasing the number of fins and increasing lengths of the fins, but in this case, the weight increases, resulting in issues of an increase in a size and an increase in a cost of a drive motor.
[0086]In contrast, the light source apparatus 1 according to the present embodiment includes, for example, three heat dissipation members 13A, 13B, and 13C each having heat dissipation performance different from each other depending on the distance from the phosphor layer 12 are provided on the back surface (the surface 11S2) of the wheel substrate 11 on which the phosphor layer 12 is provided. Specifically, the heat dissipation member (the heat dissipation member 13A) having higher heat dissipation performance is disposed as the distance from the phosphor layer 12 decreases, and the heat dissipation member (the heat dissipation member 13C) having lower heat dissipation performance is disposed as the distance from the phosphor layer 12 increases. This makes it possible to efficiently lower the temperature of the phosphor layer 12 increased by application of the excitation light EL while suppressing the increase in the weight of the phosphor wheel 10A.
[0087]As described above, in the present embodiment, on the back surface (the surface 11S2) of the wheel substrate 11 on which the phosphor layer 12 is provided, the heat dissipation member (the heat dissipation member 13A) having higher heat dissipation performance is disposed as the distance from the phosphor layer 12 decreases, and the heat dissipation member (the heat dissipation member 13C) having lower heat dissipation performance is disposed as the distance from the phosphor layer 12 increases. This makes it possible to efficiently cool the phosphor layer 12 that has generated heat by application of the excitation light EL while suppressing the increase in the weight of the phosphor wheel 10A. That is, it is possible to improve the heat dissipation efficiency.
[0088]Further, in the present embodiment, the three heat dissipation members 13A, 13B, and 13C are concentrically disposed on the back surface (the surface 11S2) of the wheel substrate 11, for example. Thus, it becomes possible to reduce the warpage of the wheel substrate 11 when fixing the phosphor layer 12 to the front surface (the surface 11S1). This suppresses deflection of a phosphor surface, and allows stable power to be outputted as a light source. That is, it leads to restr