Patent Publication Number: US-2023147140-A1

Title: Light source device and projector

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-184054, filed Nov. 11, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a light source device and a projector. 
     2. Related Art 
     As a light source device used in a projector, there is a technique for generating bright illumination light by making excitation light emitted from a plurality of light emitting elements incident on a fluorescent unit and increasing a light emission amount of fluorescent light (see, for example, JP-A-2016-66061). 
     In recent years, a further reduction in the size of a projector has been requested. A further reduction in size has also be desired for a light source device used in the projector. However, in the light source device, since brightness of illumination light is regarded as important and the number of light emitting elements is increased, the light source device tends to be increased in size as the outer diameter of a condensing lens for condensing excitation light on a phosphor unit increases. 
     SUMMARY 
     According to a first aspect of the present disclosure, there is provided a light source device including: a light source unit including: a first mounting substrate on which a first light emitting element is mounted; a second mounting substrate that is disposed in parallel to the first mounting substrate and on which a second light emitting element is mounted; and a base member on which the first mounting substrate and the second mounting substrate are placed; a wavelength conversion unit including: a wavelength conversion wheel configured to emit, from a second surface opposite to a first surface, wavelength-converted light obtained by wavelength-converting light emitted from the first light emitting element and the second light emitting element and made incident from the first surface; and a wheel housing configured to house the wavelength conversion wheel; and an optical unit including: a condensing optical system configured to condense the light emitted from the first light emitting element and the second light emitting element on the wavelength conversion wheel; a pickup optical system configured to pick up the wavelength-converted light; and an optical housing configured to hold the condensing optical system and the pickup optical system to locate the wavelength conversion wheel on an optical path between the condensing optical system and the pickup optical system. The condensing optical system includes: a first lens on which the light emitted from the first light emitting element is directly made incident; and an optical-path changing member including a first reflection surface and a second reflection surface and configured to reflect, with the first reflection surface, the light emitted from the second light emitting element in a direction in which the light is brought closer to the light emitted from the first light emitting element and reflect, with the second reflection surface, the light reflected by the first reflection surface and make the light incident on the first lens. The optical housing includes: a first supporting section formed to recess to the wavelength conversion wheel side with respect to a holding surface for holding the light source unit and configured to support the optical-path changing member; and a second supporting section formed to recess to the wavelength conversion wheel side with respect to a bottom surface of the first supporting section and configured to support the first lens. The holding surface of the optical housing and the base member are fixed. 
     According to a second aspect of the present disclosure, there is provided a projector including: the light source device according to the first aspect; an image forming device configured to form light output from the light source device into image light; and a projection optical device configured to project the image light output from the image forming device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram showing an overall configuration of a projector in a first embodiment. 
         FIG.  2    is an exploded perspective view showing an attachment state of a light source device. 
         FIG.  3    is an exploded perspective view showing the configuration of the light source device. 
         FIG.  4    is a sectional view showing the configuration of the light source device. 
         FIG.  5    is a perspective view showing the configuration of a wavelength conversion unit. 
         FIG.  6 A  is a diagram showing the configuration on a light incident surface side of a wavelength conversion wheel. 
         FIG.  6 B  is a diagram showing the configuration on a light emission surface side of the wavelength conversion wheel. 
         FIG.  7    is a perspective view showing the configuration of an optical housing. 
         FIG.  8 A  is a side view of the optical housing viewed from a −X side. 
         FIG.  8 B  is a side view of the optical housing viewed from a +X side. 
         FIG.  9    is a sectional view by a XI-XI line arrow view of  FIG.  4   . 
         FIG.  10    is a perspective view showing the configuration of a cross section by a surface including a X-X line in  FIG.  4   . 
         FIG.  11    is a perspective view showing a schematic configuration of a light source device in a second embodiment. 
         FIG.  12    is a plan view showing the configuration of a light source device in a modification of the second embodiment. 
         FIG.  13    is a perspective view showing a schematic configuration of a light source device in a third embodiment. 
         FIG.  14    is an exploded perspective view showing the configuration of the light source device in the third embodiment. 
         FIG.  15 A  is a bottom view of an optical housing in the third embodiment viewed from a −Z side. 
         FIG.  15 B  is a bottom view of the optical housing in the third embodiment viewed from a +Z side. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Embodiments of the present disclosure are explained in detail below with reference to the drawings. 
     In the drawings referred to in the following explanation, characteristic portions are sometimes enlarged and shown for convenience in order to clearly show characteristics. Dimension ratios and the like of components are not always the same as actual dimension ratios and the like. 
     First Embodiment 
       FIG.  1    is a diagram showing an overall configuration of a projector in a first embodiment. 
     A projector  1  in this embodiment modulates illumination light emitted from a light source device  2  to generate image light corresponding to image information and enlarges and projects the formed image light onto a projection surface such as a screen. 
     As shown in  FIG.  1   , the projector  1  includes a light source device  2 , an image forming device  3 , a projection optical device  6 , and an exterior housing  7 . 
     The light source device  2  supplies white illumination light WL to the image forming device  3 . The light source device  2  in this embodiment generates the illumination light WL including fluorescent light generated by wavelength-converting, with a phosphor, excitation light emitted from a light source module including a semiconductor laser. The configuration of the light source device  2  is explained below. 
     The image forming device  3  includes light modulation panels  10 R,  10 G, and  10 B and a cross dichroic prism  11 . Each of the light modulation panels  10 R,  10 G, and  10 B modulates color light made incident thereon according to image information to form image light. Each of the light modulation panels  10 R,  10 G, and  10 B is configured by a light transmissive liquid crystal panel. 
     The cross dichroic prism  11  combines image lights emitted from the light modulation panels  10 R,  10 G, and  10 B. The cross dichroic prism  11  is formed in a substantially square shape in a plane view obtained by pasting together four right-angle prisms. A dielectric multilayer film is provided on a substantially X-shaped interface where the right-angle prisms are pasted together. 
     Based on such a configuration, the image forming device  3  in this embodiment combines the image lights of the colors to generate full-color image light. 
     In this embodiment, field lenses  12 R,  12 G, and  12 B are provided on light incident sides of the respective light modulation panels  10 R,  10 G, and  10 B. 
     Although not illustrated, incident side polarization plates are disposed between the light modulation panels  10 R,  10 G, and  10 B and the field lenses  12 R,  12 G, and  12 B and emission side polarization plates are disposed between the light modulation panels  10 R,  10 G, and  10 B and the cross dichroic prism  11 . 
     In this embodiment, the image forming device  3  further includes a color separation optical system  4  and a uniform illumination optical system  5 . 
     The illumination light WL emitted from the light source device  2  is made incident on the uniform illumination optical system  5 . 
     The uniform illumination optical system  5  includes a first lens array  5   a , a second lens array  5   b , a polarization conversion element  5   c , and a superimposition lens  5   d.    
     The first lens array  5   a  includes a plurality of first small lenses for dividing the illumination light WL made incident from the light source device  2  into a plurality of partial light beams. The plurality of first small lenses are arrayed in a matrix shape in a plane orthogonal to an optical axis AX 1  of the illumination light WL. 
     The second lens array  5   b  includes a plurality of second small lenses corresponding to the plurality of first small lenses of the first lens array  5   a . The plurality of second small lenses are arrayed in a matrix shape in a plane orthogonal to the optical axis AX 1 . 
     The second lens array  5   b  forms, in conjunction with the superimposition lens  5   d , images of the first small lenses of the first lens array  5   a  respectively in the vicinities of image forming regions of the light modulation panels  10 R,  10 G, and  10 B. 
     The polarization conversion element  5   c  converts light emitted from the second lens array  5   b  into linearly polarized light in one direction. The polarization conversion element  5   c  includes, for example, a polarization separation film and a phase difference plate not shown in  FIG.  1   . 
     The superimposition lens  5   d  condenses the partial light beams emitted from the polarization conversion element  5   c  and superimposes the partial light beams respectively in the vicinities of the image forming regions of the light modulation panels  10 R,  10 G, and  10 B. 
     The color separation optical system  4  separates the illumination light WL passed through the uniform illumination optical system  5  into red light LR, green light LG, and blue light LB and guides the red light LR, the green light LG, and the blue light LB to the light modulation panels  10 R,  10 G, and  10 B. The color separation optical system  4  includes a first dichroic mirror  41 , a second dichroic mirror  42 , a first reflection mirror  43 , a second reflection mirror  44 , a third reflection mirror  45 , a first relay lens  46 , and a second relay lens  47 . 
     The first dichroic mirror  41  reflects the red light LR and transmits the green light LG and the blue light LB. Of the green light LG and the blue light LB transmitted through the first dichroic mirror  41 , the second dichroic mirror  42  reflects the green light LG and transmits the blue light LB. The first reflection mirror  43  reflects the red light LR. The second reflection mirror  44  and the third reflection mirror  45  reflect the blue light LB. The first relay lens  46  is disposed between the second dichroic mirror  42  and the second reflection mirror  44 . The second relay lens  47  is disposed between the second reflection mirror  44  and the third reflection mirror  45 . 
     The projection optical device  6  includes a projection lens group. Image light combined by the cross dichroic prism  11  of the image forming device  3  is made incident on the projection optical device  6 . Although not illustrated, a lens shift mechanism for shifting an optical axis AX 2  of the projection optical device  6  may be provided in a connecting portion of the projection optical device  6  and the cross dichroic prism  11  of the image forming device  3 . 
     Based on such a configuration, the projector  1  in this embodiment can enlarge and project the image light generated by the image forming device  3  toward a projection surface such as a screen. Consequently, an enlarged color video is displayed on the screen. 
     The exterior housing  7  houses the light source device  2  and the image forming device  3  on the inside and configures the exterior of the projector  1 . 
     Light Source Device 
     Subsequently, the configuration of the light source device  2  is explained. 
       FIG.  2    is an exploded perspective view showing an attachment state of the light source device  2  to the exterior housing  7 . In  FIG.  2   , a bottom plate section  17 , which is a part of the exterior housing  7 , is shown in order to show the internal structure of the projector  1 . 
     In the following explanation concerning the light source device, an XYZ orthogonal coordinate system is used according to necessity. 
     In the drawings, a Y axis is an axis along the optical axis AX 1  of the illumination light WL emitted from the light source device  2  toward the image forming device  3  shown in  FIG.  1   . A Z axis is an axis orthogonal to the Y axis and orthogonal to a plate surface of the bottom plate section  17  of the exterior housing  7 . An X axis is an axis orthogonal to the Y axis and the Z axis. 
     In the following explanation in this embodiment, for example, a direction along the Z axis is referred to as “up-down direction Z” in the light source device  2 , +Z is referred to as “upper side”, −Z is referred to as “lower side”, a direction along the X axis is referred to as “left-right direction X” in the light source device  2 , +X that is a rear side opposite to the front of the projector  1  in which the projection optical device  6  is provided is referred to as “right side”, −X that is the front side of the projector  1  is referred to as “left side”, a direction along the Y axis is referred to as “front-rear direction Y” in the light source device  2 , +Y is referred to as “front side”, and −Y is referred to as “rear side”. 
     The up-down direction Z, the left-right direction X, and the front-rear direction Y are simply names for explaining a disposition relation among constituent members of the light source device  2  and do not define actual setting postures and directions in the light source device  2  and the projector  1 . 
     As shown in  FIG.  2   , the light source device  2  in this embodiment is held on the bottom plate section  17  of the exterior housing  7  via screw members  9 . The bottom plate section  17  includes a light source holding member  18  for holding the light source device  2 . The light source holding member  18  includes a plurality of screw fastening sections  18   a  projecting from the bottom plate section  17  to the upper side +Z and a plurality of positioning sections  18   b  projecting from the bottom plate section  17  to the upper side +Z. The plurality of screw fastening sections  18   a  are parts where the screw members  9  are fastened. The plurality of positioning sections  18   b  are pins for positioning the light source device  2  in a predetermined position with respect to the bottom plate section  17 . At least two positioning sections  18   b  are provided. The numbers and disposition of the screw fastening sections  18   a  and the positioning sections  18   b  are not limited to the form shown in  FIG.  2    and can be changed as appropriate according to the configuration of the light source device  2 . 
     The light source device  2  in this embodiment includes a light source unit  20 , a wavelength conversion unit  30 , a cooling unit  50 , and an optical unit  40 . The cooling unit  50  includes a first cooling section  50 A that cools the light source unit  20  and a second cooling section  50 B that cools the optical unit  40 . 
     The first cooling section  50 A includes a first heat radiating section  51   a  and a first heat conducting section  52   a . The second cooling section  50 B includes a second heat radiating section  51   b  and a second heat conducting section  52   b . In this embodiment, the first heat radiating section  51   a  and the second heat radiating section  51   b  are collectively referred to as heat radiating section  51  and the first heat conducting section  52   a  and the second heat conducting section  52   b  are collectively referred to as heat conducting section  52 . That is, the cooling unit  50  includes the heat radiating section  51  disposed in parallel to the optical unit  40  and the heat conducting section  52  that conducts heat received by a base member  23  of the light source unit  20  to the heat radiating section  51 . 
     In this embodiment, the heat radiating section  51  is disposed in parallel to the left side −X of the light source unit  20  when viewed from a position on the +Y side. 
     The first heat conducting section  52   a  thermally connects the first heat radiating section  51   a  and the base member  23  of the light source unit  20 . The thermally connecting means a state in which two members are connected to be capable of transferring heat. Another member may be interposed between the two members if the heat transfer is possible between the two members. 
     The heat received by the base member  23  is conducted to the first heat radiating section  51   a  via the first heat conducting section  52   a . The first heat radiating section  51   a  is configured by a heat sink including a plurality of heat radiation fins and emits heat conducted from the first heat conducting section  52   a . As the first heat conducting section  52   a , for example, other than graphite, copper, and the like, a heat pipe, a vapor chamber, and the like that make use of evaporation and condensation of a coolant can also be used. In the case of this embodiment, the first heat conducting section  52   a  is configured by a heat pipe. 
     The second heat radiating section  51   b  is disposed in parallel to the left side −X of the light source unit  20  and the upper side +Z of the first heat radiating section  51   a  when viewed from a position on the +Y side. 
     The second heat conducting section  52   b  thermally connects the second heat radiating section  51   b  and a lid body  53  provided in the optical unit  40 . The lid body  53  is configured by a sheet metal member made of metal excellent in thermal conductivity. 
     Heat received by the lid body  53  is conducted to the second heat radiating section  51   b  via the second heat conducting section  52   b . The second heat radiating section  51   b  is configured by a heat sink including a plurality of heat radiation fins and emits heat conducted from the second heat conducting section  52   b . As the second heat conducting section  52   b , for example, other than graphite, copper, and the like, a heat pipe, a vapor chamber, and the like that make use of evaporation and condensation of a coolant can also be used. In the case of this embodiment, the second heat conducting section  52   b  is configured by a heat pipe. 
       FIG.  3    is an exploded perspective view showing the configuration of the light source device  2 .  FIG.  4    is a sectional view showing the configuration of the light source device  2 .  FIG.  4    is a sectional view in the left-right direction X on an optical axis AX 3  of a condensing optical system  60  explained below. 
     As shown in  FIGS.  3  and  4   , the light source device  2  in this embodiment includes the light source unit  20 , the optical unit  40 , and the wavelength conversion unit  30 . In  FIGS.  3  and  4   , the cooling unit  50  is not shown in order to clearly show the figures. 
     Light source unit 
     First, the configuration of the light source unit  20  is explained. 
     As shown in  FIGS.  3  and  4   , the light source unit  20  includes a plurality of light emitting elements  21 , a plurality of mounting substrates  22 , and the base member  23 . The plurality of light emitting elements  21  include first light emitting elements  211  and second light emitting elements  212 . The plurality of mounting substrates  22  include first mounting substrates  221  on which the first light emitting elements  211  are mounted and second mounting substrates  222  on which the second light emitting elements  212  are mounted. 
     The base member  23  is fixed to the optical unit  40  by screw members  24 . The base member  23  includes a fixed section  23   a  fixed to the light source unit  20  and a recess  23   b  formed to recess to the rear side −Y from the surface of the fixed section  23   a . In the case of this embodiment, the fixed section  23   a  is disposed to be separated into two in the left-right direction X by the recess  23   b.    
     In the base member  23 , the first mounting substrates  221  and the second mounting substrates  222  are placed in the recess  23   b . The base member  23  in this embodiment includes the recess  23   b  to secure a space for mounting the first mounting substrates  221  and the second mounting substrates  222  between the base member  23  and the optical unit  40 . 
     In the case of this embodiment, as shown in  FIG.  3   , two first mounting substrates  221  and two second mounting substrates  222  are placed on the base member  23 . The two first mounting substrates  221  are placed on the base member  23  side by side in the up-down direction Z. The two second mounting substrates  222  are placed on the base member  23  side by side in the up-down direction Z. The first mounting substrates  221  and the second mounting substrates  222  are placed on the base member  23  to be adjacent to each other in the left-right direction X. 
     On each of the first mounting substrates  221 , two first light emitting elements  211  are mounted side by side in the left-right direction X. The number of the first light emitting elements  211  mounted on the first mounting substrate  221  is not limited to this. 
     As shown in  FIG.  4   , the first light emitting element  211  includes, for example, a plurality of laser elements and a collimator lens. The first light emitting element  211  emits excitation light B 1  formed by blue light having a peak wavelength within a range of, for example, 380 nm to 495 nm. 
     On each of the second mounting substrates  222 , one second light emitting element  212  is mounted. The number of the second light emitting elements  212  mounted on the second mounting substrate  222  is not limited to this. 
     The second light emitting element  212  has the same configuration as the configuration of the first light emitting element  211 . The second light emitting element  212  includes, for example, a plurality of laser elements and a collimator lens. Like the first light emitting element  211 , the second light emitting element  212  emits excitation light B 2  formed by blue light having a peak wavelength within a range of, for example, 380 nm to 495 nm. 
     Based on such a configuration, the light source unit  20  emits excitation light B including a plurality of excitation lights B 1  and B 2  toward the optical unit  40 . 
     As shown in  FIG.  3   , the recess  23   b  pierces through the base member  23  in the up-down direction Z. In the light source unit  20  in this embodiment, the end portions in the upper side +Z and the lower side −Z of the recess  23   b  are respectively closed by a pair of plate materials  26 . The plate materials  26  are fixed to, for example, the upper end face and the lower end face of a light-source fixing section  70  via the screw members  24 . 
     In this embodiment, a sheet-like sealing member  27  is provided between the plate materials  26  and the base member  23 . In the case of this embodiment, as shown in  FIG.  4   , a plate-like sealing member  27  is disposed between the base member  23  of the light source unit  20  and a holding surface  71  of the light-source fixing section  70 . That is, an optical housing  62  of the light source unit  20  and the base member  23  of the optical unit  40  are fixed in a sealed state. Accordingly, dust is prevented from intruding into the recess  23   b  of the base member  23  from a gap between the optical housing  62  and the base member  23 . Accordingly, a deficiency such as heat generation or the like due to adhesion of dust to the first light emitting elements  211  and the second light emitting elements  212  mounted in the recess  23   b  is prevented from occurring. 
     Optical Unit 
     Subsequently, the configuration of the optical unit  40  is explained. 
     As shown in  FIG.  4   , the optical unit  40  includes a condensing optical system  60 , a pickup optical system  61 , an optical housing  62  that holds the condensing optical system  60  and the pickup optical system  61 , a diffusion plate  65 , and a lid body  53 . 
     The condensing optical system  60  includes a plurality of lenses. The condensing optical system  60  in this embodiment is configured by two convex lenses including a first lens  60   a  and a second lens  60   b . The number of lenses configuring the condensing optical system  60  is not particularly limited. 
     The first lens  60   a  is disposed to be opposed to the light source unit  20 . That is, the first lens  60   a  is a lens located closest to the light incident side in the condensing optical system  60 . 
     The second lens  60   b  is disposed on the opposite side of the light source unit  20  in the first lens  60   a , that is, a light emission side of the first lens  60   a.    
     In the condensing optical system  60  in this embodiment, the diameter of the second lens  60   b  located on a wavelength conversion wheel  31  side is smaller than the diameter of the first lens  60   a  located closer to the light incident side than the second lens  60   b . That is, the lenses  60   a  and  60   b  configuring the condensing optical system  60  have a larger outer diameter in a radial direction orthogonal to the optical axis AX 3  of the condensing optical system  60  as the lenses  60   a  and  60   b  are further away from the wavelength conversion unit  30 . The optical axis AX 3  coincides with the optical axis of the first lens  60   a  and the second lens  60   b  configuring the condensing optical system  60 . As shown in  FIG.  3   , the optical axis AX 3  of the condensing optical system  60  coincides with the optical axis AX 1  of the illumination light WL emitted from the light source device  2 . 
     The condensing optical system  60  in this embodiment further includes a prism member  63 , which is an optical-path changing member. The prism member  63  is disposed in a position opposed to the second light emitting element  212  and not opposed to the first light emitting element  211  with respect to the light source unit  20 . 
     In the case of this embodiment, the wavelength conversion unit  30  is disposed on the left side −X, which is one side in the left-right direction X, with respect to the optical housing  62  when viewed from a position on the +Y side in the left-right direction X, which is a first direction, crossing the optical axis AX 3  of the condensing optical system  60  including the first lens  60   a . The prism member  63  is disposed on the right side +X, which is the other side in the left-right direction X, in the optical housing  62 . 
     That is, in the case of this embodiment, the wavelength conversion unit  30  is disposed, with respect to the optical housing  62 , on the left side −X opposite to the right side +X where the prism member  63  is provided in the optical housing  62 . 
     In this embodiment, the excitation light B 1  emitted from the first light emitting element  211  is directly made incident on the first lens  60   a  of the condensing optical system  60  as shown in  FIG.  4   . That is, the excitation light B 1  is made incident on the first lens  60   a  of the condensing optical system  60  without being made incident on the prism member  63 . On the other hand, the excitation light B 2  emitted from the second light emitting element  212  is made incident on the first lens  60   a  through the prism member  63 . 
     The prism member  63  is a member that changes an optical path of the excitation light B 2  emitted from the second light emitting element  212 . 
     The prism member  63  in this embodiment is configured by a prism member, a plane shape of which is a parallelogram. 
     The prism member  63  includes a first reflection surface  63   a  and a second reflection surface  63   b  separated in the left-right direction X in which the first light emitting element  211  and the second light emitting element  212  are arranged. The first reflection surface  63   a  is disposed on the optical axis of the excitation light B 2  emitted from the second light emitting element  212 . The first reflection surface  63   a  reflects the excitation light B 2  emitted from the second light emitting element  212  to the left side −X. That is, the first reflection surface  63   a  reflects the excitation light B 2  emitted from the second light emitting element  212  in a direction in which the excitation light B 2  is brought closer to the excitation light B 1  emitted from the first light emitting element  211 . The excitation light B 2  reflected on the first reflection surface  63   a  is made incident on the second reflection surface  63   b.    
     The second reflection surface  63   b  reflects, along the optical axis of the first light emitting element  211 , the excitation light B 2  reflected from the first reflection surface  63   a  and makes the excitation light B 2  incident on the first lens  60   a.    
     The optical path of the excitation light B 2  passed through the prism member  63  in this way is shifted to the left side −X compared with before the excitation light B 2  passes through the prism member  63 . Accordingly, the prism member  63  is capable of reducing a light beam width in the left-right direction X in the excitation light B including the plurality of excitation lights B 1  and B 2 . 
     The second reflection surface  63   b  of the prism member  63  is located between the first lens  60   a  and the first mounting substrate  221  in the front-rear direction Y extending along the optical axis AX 3  of the first lens  60   a  of the condensing optical system  60 . That is, the second reflection surface  63   b  of the prism member  63  is disposed to overlap the first mounting substrate  221  when being viewed in a plane view along the front-rear direction Y. Consequently, the second reflection surface  63   b  of the prism member  63  is disposed in a position closer to the optical axis of the first lens  60   a . Since the second reflection surface  63   b  does not planarly overlap the first light emitting element  211 , the second reflection surface  63   b  does not block the excitation light B 1  made incident on the first lens  60   a.    
     A case is examined in which the second reflection surface  63   b  is disposed in a position overlapping the second mounting substrate  222  in the front-rear direction Y or a position overlapping a gap between the first mounting substrate  221  and the second mounting substrate  222 . 
     In this case, since the second reflection surface  63   b  of the prism member  63  is disposed in a position further apart from the optical axis of the first lens  60   a , a light beam width of the excitation light B cannot be sufficiently reduced. Accordingly, it is necessary to increase the lens diameter of the first lens  60   a  because the light beam width of the excitation light B increases. As a result, an increase in the size of the light source device  2  is caused. 
     In contrast, in the case of this embodiment, as explained above, the second reflection surface  63   b  of the prism member  63  is disposed in the position closer to the optical axis of the first lens  60   a . Therefore, the lens diameter of the first lens  60   a  on which the excitation light B is made incident decreases. It is possible to achieve a reduction in the size of the light source device  2 . 
     Based on such a configuration, the condensing optical system  60  in this embodiment can condense the excitation light B emitted from the light source unit  20  and make the excitation light B incident on the wavelength conversion wheel  31  of the wavelength conversion unit  30 . The configuration of the wavelength conversion unit  30  is explained below. 
     In the case of this embodiment, the diffusion plate  65  is disposed between the condensing optical system  60  and the wavelength conversion unit  30  on an optical path of the excitation light B. The diffusion plate  65  diffuses the excitation light B and uniformizes a light intensity distribution of the excitation light B on the wavelength conversion wheel  31 . As the diffusion plate  65 , it is possible to use a publicly-known diffusion plate, for example, ground glass, a holographic diffuser, a diffusion plate obtained by applying blasting to the surface of a transparent substrate, or a diffusion plate obtained by dispersing a scattering material such as beads on the inside of the transparent substrate to scatter light with the scattering material. 
     The wavelength conversion unit  30  emits fluorescent light YL as wavelength-converted light obtained by wavelength-converting the excitation light B. The fluorescent light YL emitted from the wavelength conversion unit  30  is made incident on the pickup optical system  61 . 
     The pickup optical system  61  picks up wavelength-converted light emitted from the wavelength conversion wheel  31  and converts the wavelength-converted light into parallel light. 
     The pickup optical system  61  in this embodiment includes a plurality of lenses. The pickup optical system  61  in this embodiment is configured by three convex lenses including a third lens  61   a , a fourth lens  61   b , and a fifth lens  61   c . The number of lenses configuring the pickup optical system  61  is not particularly limited. 
     The third lens  61   a  is disposed to be opposed to the wavelength conversion unit  30 . That is, the third lens  61   a  is a lens located closest to the light incident side in the pickup optical system  61 . 
     The fourth lens  61   b  is disposed on the opposite side of the light source unit  20  in the third lens  61   a , that is, a light emission side of the third lens  61   a.    
     The fifth lens  61   c  is disposed on the opposite side of the light source unit  20  in the fourth lens  61   b , that is, the light emission side of the fourth lens  61   b.    
     In the pickup optical system  61  in this embodiment, the diameter of the third lens  61   a  located on the wavelength conversion wheel  31  side is smaller than the diameter of the fourth lens  61   b  located closer to the light emission side than the third lens  61   a . The diameter of the fourth lens  61   b  is smaller than the diameter of the fifth lens  61   c  located closer to the light emission side than the fourth lens  61   b . That is, the lenses  61   a ,  61   b , and  61   c  configuring the pickup optical system  61  have a larger outer diameter in the radial direction orthogonal to the optical axis of the pickup optical system  61  as the lenses  61   a ,  61   b , and  61   c  are further away from the wavelength conversion unit  30 . The optical axis of the pickup optical system  61  coincides with the optical axis AX 3  of the condensing optical system Wavelength conversion unit 
     Subsequently, the configuration of the wavelength conversion unit  30  is explained.  FIG.  5    is a perspective view showing the configuration of the wavelength conversion unit  30 .  FIG.  6 A  is a diagram showing the configuration on a light incident surface side of the wavelength conversion wheel  31 .  FIG.  6 B  is a diagram showing the configuration on a light emission surface side of the wavelength conversion wheel  31 . 
     As shown in  FIG.  5   , the wavelength conversion unit  30  includes the wavelength conversion wheel  31  and a wheel housing  32 . 
     As shown in  FIGS.  6 A and  6 B , the wavelength conversion wheel  31  includes a wheel substrate  311 , a wavelength conversion element  312 , and a rotation driving section  313 . The rotation driving section  313  is configured by, for example, a motor. Electric power is supplied to the rotation driving section  313  via a flexible cable  316 . The rotation driving section  313  includes a rotation supporting section  313   a  capable of rotating centering on a center axis O. The rotation supporting section  313   a  supports the wheel substrate  311  to be capable of rotating centering on the center axis O. 
     The wheel substrate  311  is configured from an annular metal plate excellent in heat dissipation such as aluminum or copper. 
     The wavelength conversion element  312  is provided along the outer circumference of the wheel substrate  311 . The wavelength conversion element  312  is formed in a ring shape around the center axis O and has an annular shape projecting in a brim shape from the outer circumference of the wheel substrate  311  toward the radial direction outer side. The radial direction outer side means a direction that is orthogonal to the center axis O and away from the center axis O. 
     As shown in  FIG.  5   , the wavelength conversion element  312  makes the excitation light B emitted from the light emitting element  21  of the light source unit  20  incident from a rear surface  312   a  and emits, from a front surface  312   b , yellow fluorescent light YL obtained by wavelength-converting the excitation light B. That is, the wavelength conversion element  312  is a light transmissive wavelength conversion element that makes the excitation light B incident from the first surface  312   a  and emits the wavelength-converted light YL from the second surface  312   b.    
     As the wavelength conversion element  312 , YAG:Ce obtained by adding cerium ions, for example, Ce3+ to, for example, a garnet crystal (YAG) of Y 3 Al 5 O 12 . A not-shown appropriate scattering element may be included in the wavelength conversion element  312 . 
     The wavelength conversion wheel  31  in this embodiment is a so-called transmissive phosphor wheel. Specifically, the wavelength conversion element  312  transmits a part of the excitation light B made incident from the rear surface  312   a  and emits the part of the excitation light B from the front surface  312   b  together with the fluorescent light YL. Accordingly, the wavelength conversion element  312  emits the white illumination light WL obtained by combining blue component light BB, which is a part of the excitation light B, and the fluorescent light YL. 
     As shown in  FIG.  6 B , the wheel substrate  311  in this embodiment includes a plurality of fins  314  provided on the rear surface  312   a  side of the wavelength conversion element  312  on which the excitation light B is made incident. The plurality of fins  314  are provided on a rear surface  311   b  of the wheel substrate  311 . The plurality of fins  314  are disposed around the center axis O to radially extend. 
     As shown in  FIG.  6 A , the wheel substrate  311  in this embodiment includes a plurality of fins  315  provided on the front surface  312   b  side of the wavelength conversion element  312  that emits the excitation light B. The plurality of fins  315  are provided on a front surface  311   a  of the wheel substrate  311 . The fins  315  are radially provided around the center axis O. In the case of this embodiment, temperature easily rises on the light incident side of the wheel substrate  311  compared with the light emission side. Therefore, a size of the fins  314  on the light incident side is set larger than a size of the fins  315  on the light emission side. A size relation between the fins  314  and  315  is not limited to this. The fins  314  and  315  may have the same size or the fins  315  may be larger than the fins  314 . 
     With the wavelength conversion wheel  31  in this embodiment, it is possible to generate an air current around the wavelength conversion element  312  at a rotation time with the fins  314  and  315  provided on both the surfaces of the wheel substrate  311  and cool the wavelength conversion element  312 . Consequently, it is possible to generate bright fluorescent light YL by improving wavelength conversion efficiency of the wavelength conversion element  312 . 
     The wheel housing  32  houses the wavelength conversion wheel  31  as shown in  FIG.  3   . The wheel housing  32  includes a first housing  321 , a second housing  322 , and a wheel sealing member  323  disposed between the first housing  321  and the second housing  322 . The first housing  321  and the second housing  322  are fixed to each other in a sealed state via the wheel sealing member  323 . The first housing  321  and the second housing  322  are configured by a metal member excellent in heat dissipation such as aluminum or stainless steel. 
     The first housing  321  is a plate-like member and includes a plurality of heat radiation fins  120  provided on a surface  321   a  and a coupling section  121  extending to the second housing  322  side and coupled to the second housing  322 . The first housing  321  is fixed to the second housing  322  via the screw members  24 . Screw holes  321 H for inserting the screw members  24  are provided at four corners of the first housing  321 . A cutout  121   a  is provided at the outer edge on the right side +X when viewed from a position on the +Y side. The cutout  121   a  has a substantially chevron shape. 
     The second housing  322  holds the wavelength conversion wheel  31 . The wavelength conversion wheel  31  is, for example, fixed to a bottom plate section  122  of the second housing  322  via not-shown screw members. 
     The second housing  322  includes the bottom plate section  122  that holds the wavelength conversion wheel  31 , a side plate section  123  surrounding the outer edge portions in three directions of the bottom plate section  122 , a flange section  124  provided on the opposite side of the bottom plate section  122  in the side plate section  123 , a screw fastening section  125 , and an attaching section  126 . In the second housing  322 , as shown in  FIGS.  3  and  10   , a plurality of heat radiation fins  130  are provided on the surface of the bottom plate section  122 . Specifically, the wheel housing  32  in this embodiment includes the plurality of heat radiation fins  130  provided in a position not overlapping the optical housing  62  in the front-rear direction Y extending along the optical axis AX 3  on the surface of the bottom plate section  122  of the second housing  322  facing the light source unit  20  side. Consequently, it is possible to improve the heat dissipation of the wheel housing  32  while preventing interference of the heat radiation fins  130  and the optical housing  62 . 
     As shown in  FIG.  3   , in the bottom plate section  122 , a cutout  122   a  is provided at the outer edge not surrounded by the side plate section  123 . The cutout  122   a  has a substantially chevron shape. The shape of the cutout  122   a  of the bottom plate section  122  corresponds to the shape of the cutout  121   a  of the first housing  321 . That is, the cutouts  121   a  and  122   a  are formed to overlap each other when the wheel housing  32  is viewed in a plane view. 
     The flange section  124  is a part opposed to the first housing  321  and has a substantially C-shaped plane shape. Overhanging sections overhanging to the inner side and overlapping the external shape of the bottom plate section  122  in a plane view are respectively provided at both distal ends of the flange section  124 . The wheel sealing member  323  is provided along the shape of the flange section  124 . 
     The screw fastening section  125  is a part to which the screw members  24  for fixing the first housing  321  to the second housing  322  are fastened. The screw fastening section  125  is provided integrally with a part of the flange section  124 . 
     As shown in  FIG.  3   , the attaching section  126  is a member for fixing the wavelength conversion wheel  31  of the wavelength conversion unit  30  to the optical housing  62  of the optical unit  40  with the screw members  24 . 
     As shown in  FIG.  5   , the attaching section  126  includes a front side attaching section  127 , which is a first attaching section, and a rear side attaching section  128 , which is a second attaching section. 
     The front side attaching section  127  includes a pair of front side attachment plates  127   a  provided in overhanging sections  124   a  of the flange section  124 . In the front side attachment plates  127   a , screw holes  127   b  for inserting the screw members  24  are provided. The front side attachment plates  127   a  are provided to be orthogonal to the overhanging sections  124   a  and to be opposed to an attachment plate  83  of an attaching section  80  of the optical housing  62 . The front side attachment plates  127   a  are arranged in a row in the up-down direction Z. Specifically, the positions in the left-right direction X of the screw holes  127   b  of the front side attachment plates  127   a  are equal. 
     The rear side attaching section  128  is provided on the rear side −Y, which is the opposite side of the first housing  321  in the bottom plate section  122  of the second housing  322 . The rear side attaching section  128  includes a pair of rear side attachment plates  128   a . In the rear side attachment plates  128   a , screw holes  128   b  for inserting the screw members  24  are provided. 
     The rear side attachment plates  128   a  are provided to be orthogonal to the bottom plate section  122  and to be opposed to the attachment plate  83  of the attaching section  80  of the optical housing  62 . The rear side attachment plates  128  are arranged in a row in the up-down direction Z. Specifically, positions in the left-right direction X of the screw holes  128   b  of the rear side attachment plates  128   a  are equal. 
     Positions in the up-down direction Z of the front side attachment plates  127   a  and the rear side attachment plates  128   a  arranged in the front-rear direction Y are equal. Specifically, positions in the up-down direction Z of the screw holes  127   b  of the front side attachment plates  127   a  and the screw holes  128   b  of the rear side attachment plates  128   a  are equal. 
     As shown in  FIG.  5   , the wheel housing  32  in this embodiment houses the wavelength conversion wheel  31  to expose a part of the wavelength conversion wheel  31 . The wheel housing  32  includes a wheel opening section  33 , which is a first opening section, for exposing a part of the wavelength conversion wheel  31 . 
     The wheel opening section  33  is configured by at least one of the first housing  321  and the second housing  322 . The wheel opening section  33  is configured by an end face of a portion where the cutout  121   a  is formed in the first housing  321 , an end face of the overhanging section  124   a  in the second housing  322 , an end face of the side plate section  123 , and an end face of a portion where the cutout  122   a  is formed in the bottom plate section  122 . That is, in the case of this embodiment, the wheel opening section  33  is configured by the first housing  321  and the second housing  322 . In the following explanation, end faces of the first housing  321  and the second housing  322  configuring the wheel opening section  33  are referred to as “wheel opening end face  32   a”.    
     As shown in  FIGS.  5  and  6 A , the wavelength conversion element  312 , which is a part of the wavelength conversion wheel  31 , is projected further to the outer side than the wheel opening end face  32   a  of the wheel housing  32  via the wheel opening section  33 . 
     Subsequently, a specific configuration of the optical housing  62  is explained. 
       FIG.  7    is a perspective view showing a configuration on the rear side −Y of the optical housing  62 . 
       FIGS.  8 A and  8 B  are side views showing a main part configuration of the optical housing  62 .  FIG.  8 A  is a side view of the optical housing  62  viewed from the −X side.  FIG.  8 B  is a side view of the optical housing  62  viewed from the +X side. 
       FIG.  9    is a sectional view by a XI-XI line arrow view of  FIG.  4   .  FIG.  10    is a perspective view showing a configuration in a cross section by a surface including a X-X line in  FIG.  4   . 
     As shown in  FIG.  7   , the optical housing  62  includes the attaching section  80 , a first member  85 , and a second member  86 . In this embodiment, the attaching section  80 , the first member  85 , and the second member  86  are integrally formed. That is, the optical housing  62  in this embodiment is configured by a single member. As shown in  FIGS.  3  and  4   , the first member  85  is a member that holds the condensing optical system  60  and the second member  86  is a member that holds the pickup optical system  61 . 
     As shown in  FIG.  2   , the optical housing  62  includes a holding section  64  held by the light source holding member  18  of the exterior housing  7  via the screw members  9 . As shown in  FIG.  2   , the holding section  64  includes screw fixing holes  64   a  into which the screw members  9  fastened to the screw fastening sections  18   a  of the light source holding member  18  are inserted and positioning holes  64   b  into which the positioning sections  18   b  of the light source holding member  18  are inserted. 
     As shown in  FIGS.  8 A and  8 B , the first member  85  includes a light-source fixing section  70  and a first tubular section  90 . The light source unit  20  is fixed to the light-source fixing section  70  via the screw members  24  (see  FIG.  3   ). 
     As shown in  FIG.  7   , the light-source fixing section  70  includes a holding surface  71 , screw fastening sections  72 , and a pair of positioning pins  73 . The holding surface  71  holds the base member  23  of the light source unit  20  as shown in  FIGS.  3  and  4   . The screw fastening sections  72  are parts that are provided at four corners of the holding surface  71  having a rectangular shape and to which the screw members  24  for fixing the light source unit  20  are fastened. The pair of positioning pins  73  is respectively provided in positions equivalent to both the sides in the left-right direction X and the center in the up-down direction Z on the holding surface  71 . As shown in  FIGS.  3  and  4   , the pair of positioning pins  73  is inserted into positioning holes  23   a   1  formed in the fixing section  23   a  of the base member  23  to position the base member  23  of the light source unit  20  with respect to the light-source fixing section  70 . 
     As shown in  FIGS.  4  and  7   , the optical housing  62  in this embodiment includes a prism supporting section  74 , which is a first supporting section that supports the prism member  63  of the condensing optical system  60 . The prism supporting section  74  is provided in the light-source fixing section  70 . 
     The prism supporting section  74  is formed to recess to the wavelength conversion wheel  31  side from the holding surface  71  that holds the light source unit  20 . The prism supporting section  74  includes a supporting surface  74   a  that supports the prism member  63 . In the case of this embodiment, a pair of supporting members  74   b  that supports the prism member  63  is provided on the supporting surface  74   a  of the prism supporting section  74 . The pair of supporting members  74   b  is respectively plate-like parts extending in the left-right direction X and is provided on the supporting surface  74   a  to be spaced in the up-down direction Z. Based on such a configuration, the prism supporting section  74  can stably support the prism member  63  in a predetermined position on the supporting surface  74   a  via the pair of supporting members  74   b.    
     As shown in  FIG.  4   , the prism member  63  is disposed on the right side +X with respect to the optical axis AX 3  of the condensing optical system  60  when viewed from a position on the +Y side. The center of the light source unit  20  is located closer to the right side +X than the optical axis AX 3 . Accordingly, in the left-right direction X, the distance from the optical axis AX 3  to the end face on the left side −X of the light-source fixing section  70  of the optical housing  62  is shorter than the distance from the optical axis AX 3  to the end face on the right side +X of the light-source fixing section  70  of the optical housing  62 . That is, a projection amount of the optical housing  62  with respect to the optical axis AX 3  is larger on the left side −X than the right side +X. 
     The first tubular section  90  of the optical housing  62  includes a lens supporting section  91 , which is a second supporting section, and a diffusion-plate supporting section  92 . The lens supporting section  91  is provided on the inner surface side of the first tubular section  90  and is formed to recess to the wavelength conversion wheel  31  side from the supporting surface  74   a  of the prism supporting section  74 . 
     The lens supporting section  91  includes a first step section  91   a  that supports the first lens  60   a  and a second step section  91   b  that supports the second lens  60   b.    
     The first step section  91   a  is configured by a step between a first inner circumferential surface  90   a  of the first tubular section  90  and a second inner circumferential surface  90   b  having a smaller inner diameter than the first inner circumferential surface  90   a . The first lens  60   a  is supported in the lens supporting section  91  by the first step section  91   a . The first lens  60   a  may be fit in the first step section  91   a  and fixed or may be fixed via a not-shown adhesive. 
     The second step section  91   b  is a step between a third inner circumferential surface  90   c  having a smaller inner diameter than the second inner circumferential surface  90   b  and a fourth inner circumferential surface  90   d  having a smaller inner diameter than the third inner circumferential surface  90   c . The second lens  60   b  is supported in the lens supporting section  91  by the second step section  91   b . The second lens  60   b  may be fit in the second step section  91   b  and fixed or may be fixed via a not-shown adhesive. 
     The diffusion-plate supporting section  92  is formed to recess to the wavelength conversion wheel  31  side from the bottom surface of the lens supporting section  91 . The diffusion-plate supporting section  92  includes a supporting surface  92   a  that supports the diffusion plate  65  and an opening  92   b  provided on the supporting surface  92   a . The opening  92   b  makes the excitation light B transmitted through the diffusion plate  65  incident on the wavelength conversion wheel  31 . 
     The second member  86  of the optical housing  62  includes a connecting section  99  and a second tubular section  95 . As shown in  FIG.  7   , the connecting section  99  is provided to overhang to, from the outer edge of the distal end on the front side +Y of the second tubular section  95 , the radial direction outer side to which the connecting section  99  separates in a direction orthogonal to the optical axis AX 3 . The connecting section  99  is a member that connects the light source device  2  to the uniform illumination optical system  5  shown in  FIG.  1   . 
     Based on such a configuration, the light source device  2  in this embodiment can efficiently make the illumination light WL incident on the uniform illumination optical system  5  via the connecting section  99  of the optical housing  62 . 
     The second tubular section  95  mainly configured by a lens supporting section  96  that supports the pickup optical system  61 . The lens supporting section  96  is provided on the inner surface of the second tubular section  95 . The lens supporting section  96  includes a third step section  96   a  that supports the third lens  61   a , a fourth step section  96   b  that supports the fourth lens  61   b , and a fifth step section  96   c  that supports the fifth lens  61   c.    
     The fifth step section  96   c  is configured by a step between a fifth inner circumferential surface  95   a  located closest to the front side +Y in the second tubular section  95  and a sixth inner circumferential surface  95   b  located closer to the rear side −Y and having a smaller inner diameter than the fifth inner circumferential surface  95   a . The fifth lens  61   c  is supported in the lens supporting section  96  by the fifth step section  96   c . The fifth lens  61   c  may be fit in the fifth step section  96   c  and fixed or may be fixed via a not-shown adhesive. 
     The fourth step section  96   b  is configured by a step between a seventh inner circumferential surface  95   c  located closer to the rear side −Y and having a smaller inner diameter than the sixth inner circumferential surface  95   b  and an eighth inner circumferential surface  95   d  located closer to the rear side −Y and having a smaller inner diameter than the seventh inner circumferential surface  95   c . In the case of this embodiment, a ninth inner circumferential surface  95   e  connecting the sixth inner circumferential surface  95   b  and the seventh inner circumferential surface  95   c  is formed as a taper surface narrowed in an inner diameter toward the rear side −Y. 
     The fourth lens  61   b  is supported in the lens supporting section  96  by the fourth step section  96   b . The fourth lens  61   b  may be fit in the fourth step section  96   b  and fixed or may be fixed via a not-shown adhesive. 
     The third step section  96   a  is configured by a step between a tenth inner circumferential surface  95   f  located closer to the rear side −Y and having a smaller inner diameter than the eighth inner circumferential surface  95   d  and an eleventh inner circumferential surface  95   g  located closer to the rear side −Y and having a smaller inner diameter than the tenth inner circumferential surface  95   f.    
     In the case of this embodiment, the eighth inner circumferential surface  95   d  is formed as a taper surface narrowed in an inner diameter stepwise toward the rear side −Y. 
     The third lens  61   a  is supported in the lens supporting section  96  by the third step section  96   a . The third lens  61   a  may be fit in the third step section  96   a  and fixed or may be fixed via a not-shown adhesive. 
     In this embodiment, the outer diameters of the lenses configuring the condensing optical system  60  and the pickup optical system  61  decrease as the lenses are closer to the wavelength conversion unit  30 . 
     Consequently, in the optical housing  62  in this embodiment, a diameter-reduced section  69  is provided in a position corresponding to the second lens  60   b  of the condensing optical system  60  and the third lens  61   a  of the pickup optical system  61 . The diameter-reduced section  69  is a part having a relatively smaller outer diameter than the other portions in the optical housing  62 . 
     In this embodiment, the wavelength conversion unit  30  is disposed in the diameter-reduced section  69  of the optical housing  62 . Since the wavelength conversion unit  30  is attached to the optical housing  62  from the radial direction outer side, an increase in the dimension in the radial direction of the light source device  2  is prevented by disposing the wavelength conversion unit  30  in the diameter-reduced section  69 . 
     As shown in  FIGS.  8 A and  8 B , the attaching section  80  is a part for attaching the wavelength conversion unit  30  to the optical housing  62 . In this embodiment, by using the attaching section  80 , the wavelength conversion unit  30  including the wavelength conversion wheel  31  can be attached to the optical housing  62  from a plurality of directions with respect to the optical axis AX 3  of the condensing optical system  60 . 
     The attaching section  80  includes a first attachment structure  81 , a second attachment structure  82 , and an attachment plate  83  extending along a YZ plane. The attachment plate  83  connects the first tubular section  90  and the second tubular section  95 . 
     As shown in  FIGS.  7  to  8 B , the attachment plate  83  includes a first attachment surface  83   a  extending along the optical axis AX 3  of the condensing optical system  60  and facing the left side −X when viewed from a position on the +Y side, a second attachment surface  83   b  extending along the optical axis AX 3  of the condensing optical system  60  and facing the right side +X opposite to the first attachment surface  83   a  when viewed from a position on the +Y side, and a through-hole  84 . 
     The attachment plate  83  is located on the optical axis AX 3  of the condensing optical system  60 . 
     In this embodiment, the attachment plate  83  being located on the optical axis AX 3  of the condensing optical system  60  refers to a state in which the optical axis AX 3  overlaps the first attachment surface  83   a  or the second attachment surface  83   b  or a state in which the optical axis AX 3  is located between the first attachment surface  83   a  and the second attachment surface  83   b.    
     In the case of this embodiment, in the attachment plate  83 , the optical axis AX 3  is located in the middle between the first attachment surface  83   a  and the second attachment surface  83   b . That is, in the attachment plate  83  in this embodiment, the distance from the optical axis AX 3  to the first attachment surface  83   a  and the distance from the optical axis AX 3  to the second attachment surface  83   b  are equal. 
     The through-hole  84  pierces through the attachment plate  83  in the plate thickness direction. A plane shape of the through-hole  84  is a rectangle. When the wavelength conversion unit  30  is attached to the attaching section  80 , a part of the wavelength conversion wheel  31  is projected from one side to the other side of the attachment plate  83  through the through-hole  84 . 
     The first attachment structure  81  enables the wavelength conversion unit  30  to be attached to the first attachment surface  83   a . As shown in  FIG.  3   , in the light source device  2  in this embodiment, when viewed from a position on the +Y side, the wavelength conversion unit  30  is attached to the left side −X of the optical housing  62  via the first attachment structure  81 . In the case of this embodiment, the wavelength conversion unit  30  is disposed between the heat radiating section  51  and the optical unit  40 . 
     As shown in  FIG.  8 A , the first attachment structure  81  is provided on the first attachment surface  83   a . The first attachment structure  81  includes a plurality of screw fastening sections  81   a  and a pair of pedestals  81   b  projecting from the first attachment surface  83   a . In the case of this embodiment, four screw fastening sections  81   a  are provided. As shown in  FIG.  3   , the screw members  24  for attaching the wavelength conversion unit  30  are respectively fastened to the screw fastening sections  81   a . The pair of pedestals  81   b  is disposed to be separated in the front-rear direction Y. As shown in  FIG.  9   , the pedestals  81   b  are seats having a trapezoidal plane shape when viewed from a direction extending along the optical axis AX 3  and function as seats for setting the wavelength conversion unit  30 . The pedestals  81   b  have an external shape corresponding to the wheel opening end face  32   a  of the wheel housing  32 . 
     In the case of this embodiment, the width in the front-rear direction Y of the pedestal  81   b  on the rear side −Y is larger than the width in the front-rear direction Y of the pedestal  81   b  on the front side +Y. This is because of a difference due to the width of contact with the wavelength conversion unit  30 . Depending on the shape on the wavelength conversion unit  30  side, the widths of the pedestals  81   b  may be set the same or the width on the front side +Y may be set larger than the width on the rear side −Y. 
     The optical housing  62  in this embodiment includes a left side opening section  87 , which is a second opening section, provided on the first attachment surface  83   a  side of the attaching section  80 . The left side opening section  87  is an opening defined by a boundary between a space sandwiched by the pair of pedestals  81   b  and the outside of the space. 
     As shown in  FIGS.  3  and  5   , when the wavelength conversion unit  30  is attached to the optical housing  62 , the front side attachment plates  127   a  of the front side attaching section  127  and the rear side attachment plates  128   a  of the rear side attaching section  128  and the screw fastening sections  81   a  of the first attachment structure  81  are fixed by the screw members  24 . As shown in  FIG.  8 A , in the wheel housing  32 , the wheel opening end face  32   a  of the wheel housing  32  configuring the wheel opening section  33  collides with the pedestals  81   b  and the attachment plate  83  of the first attachment structure  81  such that the wheel opening section  33  planarly surrounds the left side opening section  87 . 
     In the wavelength conversion unit  30 , the wavelength conversion element  312 , which is a part of the wavelength conversion wheel  31 , is located on an optical path between the condensing optical system  60  and the pickup optical system  61  in a state in which the wavelength conversion unit  30  is attached to the attaching section  80  of the optical housing  62  of the optical unit  40 . 
     That is, in this embodiment, in the optical unit  40  and the wavelength conversion unit  30 , the wavelength conversion element  312 , which is a part of the wavelength conversion wheel  31  exposed via the wheel opening section  33  of the wheel housing  32 , is disposed on the optical path between the condensing optical system  60  and the pickup optical system  61  via the left side opening section  87  of the optical housing  62 . 
     In the case of this embodiment, as shown in FIGS.  5  and  6 A, the wavelength conversion element  312 , which is a part of the wavelength conversion wheel  31 , projects further to the outer side than the wheel opening end face  32   a  of the wheel housing  32  via the wheel opening section  33 . Accordingly, when the wavelength conversion unit  30  is attached to the optical housing  62 , the wavelength conversion element  312  projecting from the wheel opening end face  32   a  is likely to interfere with the attachment plate  83 . 
     In contrast, in the attaching section  80  in this embodiment, as shown in  FIGS.  5  and  10   , the through-hole  84  is provided in a position corresponding to the wavelength conversion element  312  projecting from the wheel opening end face  32   a  to locate the wavelength conversion element  312  projecting from the wheel opening end face  32   a  on the opposite side of the attachment plate  83  via the through-hole  84 . In this way, the wavelength conversion element  312  is disposed on the optical axis AX 3  of the condensing optical system  60 . Therefore, it is possible to efficiently make the excitation light B incident on the wavelength conversion element  312  via the condensing optical system  60 . 
     In the case of this embodiment, since the optical axis of the pickup optical system  61  coincides with the optical axis AX 3  of the condensing optical system  60 , the illumination light WL emitted from the wavelength conversion element  312  can be efficiently taken into the pickup optical system  61 . Accordingly, it is possible to improve light use efficiency of the illumination light WL. 
     In this embodiment, as shown in  FIG.  3   , a first sealing member  55  is disposed between the wavelength conversion unit  30  and the optical housing  62 . The wavelength conversion unit  30  is fixed to the first attachment structure  81  of the optical housing  62  by the screw members  24 . 
     As shown in  FIG.  9   , the first sealing member  55  is pressed between the wheel opening end face  32   a  of the wheel housing  32  and the pedestal  81   b  and the first attachment surface  83   a  of the first attachment structure  81 . A gap between the left side opening section  87  of the optical housing  62  and the wheel opening section  33  of the wheel housing  32  is satisfactorily closed by the first sealing member  55 . 
     In this way, the optical unit  40  and the wavelength conversion unit  30  are fixed in a state in which the left side opening section  87  of the optical housing  62  and the wheel opening section  33  of the wheel housing  32  are sealed. 
     The second attachment structure  82  enables the wavelength conversion unit  30  to be attachable to the second attachment surface  83   b . As shown in  FIG.  8 B , the second attachment structure  82  includes a plurality of screw fastening sections  82   a  and a pair of pedestals  82   b  provided on the second attachment surface  83   b . In the case of this embodiment, four screw fastening sections  82   a  are provided. 
     The second attachment structure  82  has the same configuration as the configuration of the first attachment structure  81 . Accordingly, in the optical housing  62 , the wavelength conversion unit  30  can be attached to the second attachment structure  82  by changing an attaching direction of the wavelength conversion unit  30 . 
     In the case of this embodiment, as explained above, the wavelength conversion unit  30  is attached to the optical housing  62  using the first attachment structure  81 . Therefore, the second attachment structure  82  is not used to attach the wavelength conversion unit  30 . 
     The optical housing  62  in this embodiment includes a right side opening section  88 , which is a third opening section, provided on the second attachment surface  83   b  side of the attaching section  80 . The right side opening section  88  is an opening defined by a boundary between a space sandwiched by the pair of pedestals  82   b  and the outside of the space. The right side opening section  88  is opposed to the left side opening section  87  across the attachment plate  83  of the attaching section  80 . 
     The condensing optical system  60  and the pickup optical system  61  on which the excitation light B is made incident generate heat. In the light source device  2  in this embodiment, as shown in  FIG.  2   , the lid body  53  thermally connected to the second heat conducting section  52   b  of the second cooling section  50 B is attached to the second attachment structure  82 . Consequently, cooling performance of the condensing optical system  60  and the pickup optical system  61  is improved by radiating heat received from the optical housing  62 . 
     As shown in  FIG.  3   , the lid body  53  includes a lid main body section  53   a  and an attaching section  53   b . The lid main body section  53   a  of the lid body  53  has an external shape corresponding to the pedestals  82   b  of the second attachment structure  82  and the pedestals  81   b  having the same shape as the pedestals  82   b.    
     When the lid body  53  is attached to the optical housing  62 , the attaching section  53   b  of the lid body  53  and the screw fastening sections  82   a  of the second attachment structure  82  are fixed by the screw members  24 . At this time, as shown in  FIG.  8 B , the lid main body section  53   a  of the lid body  53  collides with the pedestals  82   b  and the attachment plate  83  of the second attachment structure  82  to close the right side opening section  88 . 
     In this embodiment, as shown in  FIG.  3   , a second sealing member  56  is disposed between the lid body  53  and the optical housing  62 . The lid body  53  is fixed to the second attachment structure  82  of the optical housing  62  by the screw members  24 . Consequently, a gap between the right side opening section  88  of the optical housing  62  and the lid main body section  53   a  of the lid body  53  is satisfactorily closed by the second sealing member  56 . Accordingly, as shown in  FIG.  8 B , the lid body  53  is fixed to the optical housing  62  in a state in which the lid body  53  covers the right side opening section  88  of the optical housing  62  in a sealed state. 
     As explained above, the light source device  2  in this embodiment includes the prism member  63  that changes the optical path of the excitation light B 2  emitted from the second light emitting element  212  to bring the excitation light B 2  closer to the excitation light B 1  emitted from the first light emitting element  211  and makes the excitation light B 2  incident on the first lens  60   a  of the condensing optical system  60 . The optical housing  62  includes the prism supporting section  74  that supports the prism member  63  and the lens supporting section  91  that supports the condensing optical system  60 . The holding surface  71  of the optical housing  62  and the base member  23  are fixed. 
     The light source device  2  in this embodiment is configured by the three units, that is, the light source unit  20 , the wavelength conversion unit  30 , and the optical unit  40 . The prism member  63  that changes the optical path of the excitation light B 2  emitted from the second light emitting element  212  and makes the excitation light B 2  incident on the condensing optical system  60  is disposed in the optical housing  62  together with the condensing optical system  60 . Therefore, it is possible to generate bright illumination light WL while reducing the device configuration of the light source device  2  in size. 
     In the case of this embodiment, the second reflection surface  63   b  of the prism member  63  is located between the first lens  60   a  and the first mounting substrate  221  in the front-rear direction Y extending along the optical axis AX 3  of the condensing optical system  60 . Therefore, it is possible to prevent an increase in the size of the light source device  2  in the left-right direction X, which is an arranging direction of the first mounting substrate  221  and the second mounting substrate  222 . 
     In the case of this embodiment, the base member  23  includes the recess  23   b . The first mounting substrate  221  and the second mounting substrate  222  are set in the recess  23   b.    
     With this configuration, when the holding surface  71  of the optical housing  62  and the base member  23  of the light source unit  20  are fixed, a housing space for the light emitting element  21  can be secured in the recess  23   b.    
     In the case of this embodiment, in the left-right direction X crossing the optical axis AX 3  of the condensing optical system  60 , when viewed from a position on the +Y side, the wavelength conversion unit  30  is disposed on the left side −X in the left-right direction X with respect to the optical housing  62  and the prism member  63  is disposed on the right side +X in the left-right direction X with respect to the optical axis AX 3  in the optical housing  62 . 
     With this configuration, a space can be secured on the right side +X, which is the opposite side of the wavelength conversion unit  30  with respect to the optical unit  40 . Accordingly, it is possible to reduce the size of the device configuration of the projector  1  by, for example, disposing the projector components in the space on the right side +X of the optical unit  40 . 
     In the case of this embodiment, the wheel housing  32  includes the plurality of heat radiation fins  130  in the position not overlapping the optical housing  62  in the front-rear direction Y extending along the optical axis AX 3  on the surface of the second housing  322  facing the light source unit  20  side. 
     With this configuration, it is possible to improve heat dissipation of the wheel housing  32  while effectively using a space not overlapping the optical housing  62  on the surface of the second housing  322 . 
     In the light source device  2  in this embodiment, the light source unit  20  and the optical unit  40  are fixed in the sealed state. In the optical unit  40  and the wavelength conversion unit  30 , a part of the wavelength conversion wheel  31  exposed via the wheel opening section  33  of the wheel housing  32  is disposed on the optical path between the condensing optical system  60  and the pickup optical system  61  via the left side opening section  87  of the optical housing  62 . The left side opening section  87  of the optical housing  62  and the wheel opening section  33  of the wheel housing  32  are fixed in the sealed state. 
     With the light source device  2  in this embodiment, it is possible to provide a light source device having a sealed structure in which the wavelength conversion wheel  31  is disposed on the optical path between the condensing optical system  60  and the pickup optical system  61  and the three units, that is, the light source unit  20 , the wavelength conversion unit  30 , and the optical unit  40  are fixed in the sealed state. Consequently, since intrusion of dust into the inside of the light source device  2  is prevented, it is possible to prevent occurrence of deficiencies such as deterioration and heat generation of components caused by dust adhering to the lenses and the wavelength conversion wheel  31 . Since the light source device  2  is configured by the three units, it is possible to provide the light source device  2  excellent in assemblability. 
     In the case of this embodiment, in the optical housing  62 , the wavelength conversion unit  30  is disposed in the diameter-reduced section  69  having the smaller outer diameter than the other portions. Accordingly, a projection amount of the wavelength conversion unit  30  from the optical housing  62  is reduced. It is possible to prevent an increase in the size of the light source device  2 . 
     In the case of this embodiment, the optical housing  62  of the optical unit  40  and the base member  23  of the light source unit  20  are fixed in the sealed state. 
     With this configuration, in the light source unit  20 , not the mounting substrate  22  on which the light emitting element  21  is mounted but the optical housing  62  is fixed to the base member  23 . Therefore, the sealed state can be easily realized. 
     In the case of this embodiment, the optical path of the excitation light B 2  emitted from the second light emitting element  212  can be changed by the prism member  63  to reduce the light beam width of the excitation light B made incident on the condensing optical system  60 . Accordingly, it is possible to generate the bright fluorescent light YL by increasing a light amount of the excitation light B while preventing an increase in the size of the condensing optical system  60  on which the excitation light B is made incident. 
     In the case of this embodiment, in the first cooling section  50 A that cools the optical unit  40 , the heat of the base member  23  is conducted to the first heat radiating section  51   a  via the first heat conducting section  52   a . With this configuration, flexibility of disposition of the first heat radiating section  51   a  is improved by changing routing of the first heat conducting section  52   a . Accordingly, it is possible to provide the light source device  2  in which a layout change is easy. 
     In the case of this embodiment, the wheel housing  32  of the wavelength conversion unit  30  is configured by the first housing  321  and the second housing  322 . The wheel opening section  33  of the wheel housing  32  is configured by the first housing  321  and the second housing  322 . 
     With this configuration, the wheel housing  32  including the wheel opening section  33  can be configured by the two housings. Therefore, it is possible to improve assemblability of the wavelength conversion unit  30 . 
     In the case of this embodiment, in the optical housing  62 , the first member  85  that holds the condensing optical system  60  and the second member  86  that holds the pickup optical system  61  are integrally formed. Therefore, the number of components can be reduced. If the optical housing  62  is configured by a plurality of components, adjustment is necessary because of tolerance of the components. However, in this embodiment, since the optical housing  62  is configured by one component, the adjustment is unnecessary. It is possible to improve assemblability. 
     In the case of this embodiment, the optical unit  40  further includes the lid body  53  that covers, in the sealed state, the right side opening section  88  opposed to the left side opening section  87  of the optical housing  62 . 
     With this configuration, the wavelength conversion unit  30  can be attached to the right side opening section  88  of the optical housing  62  as well. Accordingly, the wavelength conversion unit  30  can be attached to the optical housing  62  from both the sides in the left-right direction X. Therefore, flexibility of the layout of the wavelength conversion unit  30  is improved. 
     It is possible to maintain the sealed state in the light source device  2  by closing, with the lid body  53 , an opening section not used to attach the wavelength conversion unit  30 . 
     In the case of this embodiment, in the second cooling section  50 B, heat received by the lid body  53  from the wavelength conversion unit  30 , the condensing optical system  60 , the pickup optical system  61 , or the light source unit  20  via the optical housing  62  can be conducted to the second heat radiating section  51   b  via the second heat conducting section  52   b . Accordingly, it is possible to improve cooling performance while simplifying a device configuration of the light source device  2 . 
     In the light source device  2  in this embodiment, to enable the wavelength conversion wheel  31  to be disposed from two directions with respect to the optical axis AX 3  of the condensing optical system  60 , the optical unit  40  includes the attaching section  80  to which the wavelength conversion unit  30  is attached. 
     With the light source device  2  in this embodiment, the wavelength conversion wheel  31  can be disposed from two directions with respect to the optical housing  62  of the optical unit  40 . Therefore, flexibility of the layout of the light source device  2  can be improved. Accordingly, the light source device  2  in which a layout change corresponding to specifications can be easily performed is provided. 
     In the case of this embodiment, the attaching section  80  includes the attachment plate  83  including the first attachment surface  83   a  extending along the optical axis AX 3  of the condensing optical system  60  and the second attachment surface  83   b  opposite to the first attachment surface  83   a . The wavelength conversion unit  30  is attached to one of the first attachment surface  83   a  and the second attachment surface  83   b.    
     With this configuration, it is possible to realize, with the attachment plate  83 , a configuration in which the wavelength conversion unit  30  is symmetrically disposed with respect to the optical axis AX 3 . 
     In the case of this embodiment, the attachment plate  83  is located on the optical axis AX 3  of the condensing optical system  60 . 
     With this configuration, the distance from the wavelength conversion unit  30  attached to the first attachment surface  83   a  to the optical axis AX 3  and the distance from the wavelength conversion unit  30  attached to the second attachment surface  83   b  to the optical axis AX 3  are the same. Accordingly, it is easy to align the wavelength conversion unit  30  and the optical axis AX 3  and assemblability is improved. 
     In the case of this embodiment, the attaching unit  80  includes the first attachment structure  81  that enables the wavelength conversion unit  30  to be attached to the first attachment surface  83   a  and the second attachment structure  82  that enables the wavelength conversion unit  30  to be attached to the second attachment surface  83   b  and having the same configuration as the configuration of the first attachment structure  81 . 
     With this configuration, it is possible to attach the wavelength conversion units  30  having the same structure to both the surfaces of the attachment plate  83 . Accordingly, it is possible to provide a light source device in which a layout change can be easily performed while reducing cost by using the wavelength conversion units  30  in common irrespective of attaching directions. 
     In the case of this embodiment, the wavelength conversion wheel  31  makes the excitation light B incident from the rear surface  312   a  and emits the yellow fluorescent light YL obtained by wavelength-converting the excitation light B from the front surface  312   b . Further, in the state in which the wavelength conversion unit  30  is attached to the attaching section  80  of the optical unit  40 , a part of the wavelength conversion wheel  31  is located on the optical path between the condensing optical system  60  and the pickup optical system  61 . 
     With this configuration, in the transmissive wavelength conversion wheel  31 , it is possible to improve flexibility of the layout of the light source device  2 . 
     In the case of this embodiment, the cooling unit  50  includes the heat radiating section  51  disposed in parallel to the optical unit  40  and the heat conducting section  52  that conducts heat received by the base member  23  of the light source unit  20  to the heat radiating section  51 . 
     With this configuration, it is possible to efficiently cool the light emitting element  21  of the light source unit  20 . 
     In the case of this embodiment, the wavelength conversion unit  30  is disposed between the heat radiating section  51  and the optical unit  40 . Therefore, a space can be secured on the opposite side of the wavelength conversion unit  30  (the right side +X) with respect to the optical unit  40 . Accordingly, for example, it is possible to reduce the size of a device configuration of the projector  1  by disposing the projector components in the space on the right side +X of the optical unit  40 . 
     The projector  1  in this embodiment includes the light source device  2  with improved flexibility of the layout. Therefore, it is possible to provide a projector having high flexibility of the layout of an internal configuration. Accordingly, a projector having a high added value for facilitating a layout change corresponding to specifications is provided. 
     The projector  1  in this embodiment includes the light source device  2 , the image forming device  3  that forms light output from the light source device  2  into image light, and the projection optical device  6  that projects the image light output from the image forming device  3 . 
     The projector  1  in this embodiment includes the light source device  2  with improved flexibility of the layout. Therefore, it is possible to provide a projector having high flexibility of the layout of an internal configuration. Accordingly, a projector having a high added value for facilitating a layout change corresponding to specifications is provided. 
     According to this embodiment, since the projector  1  includes the light source device  2  that prevents intrusion of dust, it is possible to provide a projector having high reliability by preventing an operation failure of the light source device  2  due to dust. Since a dust collecting filter for preventing intrusion of dust into the light source device  2  can be omitted, the device configuration of the projector  1  can be simplified. 
     According to this embodiment, the projector  1  includes the light source device  2  that generates the bright illumination light WL while being reduced in the size of the device configuration. Therefore, it is possible to provide a projector that is small in size and displays a bright image. 
     Second Embodiment 
     Subsequently, a light source device in a second embodiment is explained. 
     The light source device in this embodiment is different from the light source device in the first embodiment in an attaching direction of the wavelength conversion unit  30  to the optical unit  40 . Components and members common to the first embodiment are denoted by the same reference numerals and signs and explanation is omitted about details of the components and the members. 
       FIG.  11    is a perspective view showing a schematic configuration of a light source device  2 A in this embodiment. 
     As shown in  FIG.  11   , in the light source device  2 A in this embodiment, when viewed from a position on the +Y side, the wavelength conversion unit  30  is attached to the right side +X of the optical unit  40 . 
     In this embodiment, when the wavelength conversion unit  30  is attached to the right side +X of the optical housing  62 , that is, when the wavelength conversion unit  30  is attached to the opposite side of the cooling unit  50  with respect to the condensing optical system  60 , the attaching section  126  of the wavelength conversion unit  30  and the screw fastening sections  82   a  of the second attachment structure  82  are fixed by the screw members  24 . Since the second attachment structure  82  has the same configuration as the configuration of the first attachment structure  81 , it is possible to attach the wavelength conversion unit  30  to the second attachment structure  82  by rotating the wavelength conversion unit  30  180° around the optical axis AX 3 . 
     In this embodiment, as shown in  FIG.  3   , the wavelength conversion unit  30  and the prism member  63  are respectively disposed on the right side +X, which is one side in the left-right direction X crossing the optical axis AX 3  of the first lens  60   a  of the condensing optical system  60 , with respect to the optical housing  62 . That is, the wavelength conversion unit  30  and the prism member  63  are located on the same right side +X with respect to the optical axis AX 3 . A part of the wavelength conversion unit  30  overlaps the prism member  63  in the front-rear direction Y extending along the optical axis AX 3 . 
     In the case of this embodiment, the wavelength conversion unit  30  is attached to the optical housing  62  using the second attachment structure  82 . Therefore, the first attachment structure  81  is not used to attach the wavelength conversion unit  30 . 
     In the light source device  2 A in this embodiment, when viewed from a position on the +Y side, the lid body  53  thermally connected to the second heat conducting section  52   b  of the second cooling section  50 B is attached to the left side −X of the optical unit  40  using the first attachment structure  81 . 
     In this embodiment, when the lid body  53  is attached to the left side −X of the optical housing  62 , the attaching section  53   b  of the lid body  53  and the screw fastening sections  81   a  of the first attachment structure  81  are fixed by the screw members  24 . 
     In this way, in the light source device  2 A in this embodiment, when viewed from a position on the +Y side, the wavelength conversion unit  30  is disposed on the right side +X in the left-right direction X in which the external shape of the optical housing  62  further projects with respect to the optical axis AX 3 . 
     With the light source device  2 A in this embodiment, when the wavelength conversion unit  30  is attached to the optical housing  62 , the width of the wavelength conversion unit  30  projecting in the left-right direction X from the end face of the light-source fixing section  70  of the optical housing  62  can be reduced to be smaller than the width in the configuration of the light source device  2  in the first embodiment. Therefore, with the light source device  2 A in this embodiment, it is possible to achieve a reduction in the size of a device configuration of the light source device  2 A by further reducing the size in the left-right direction X. 
     In this embodiment, the wavelength conversion unit  30  is disposed on the right side +X, which is the opposite side of the heat radiating section  51  with respect to the optical unit  40 . In this case, compared with a configuration in which the wavelength conversion unit  30  is disposed on the same side as the heat radiating section  51  with respect to the optical unit  40  as in the first embodiment, a space is formed between the light source unit  20  and the heat radiating section  51 . Therefore, it is desirable to effectively use this excess space. 
       FIG.  12    is a plan view showing the configuration of a light source device in a modification in which the excess space is effectively used. In  FIG.  12   , illustration of a heat conducting section connected to the lid body  53  is omitted in order to clearly show the figure. 
     As shown in  FIG.  12   , a first heat radiating section  151   a  and a second heat radiating section  151   b  in a heat radiating section  151  respectively include extending portions  150   a  and  150   b  extending to a portion overlapping the excess space SP. With the heat radiating section  151 , it is possible to improve heat radiation performance by enlarging the area of the heat radiating section  151  and prevent an increase in the size of the device configuration of the light source device by using the excess space SP. 
     Third Embodiment 
     Subsequently, a light source device in a third embodiment is explained. 
     The light source device in this embodiment is different from the light source devices in the first embodiment and the second embodiment in the configuration of an optical unit. Components and members common to the embodiments explained above are denoted by the same reference numerals and signs and explanation is omitted about details of the components and the members. 
       FIG.  13    is a perspective view showing a schematic configuration of a light source device  2 B in this embodiment. 
     As shown in  FIG.  13   , the light source device  2 B in this embodiment includes the light source unit  20 , an optical unit  140 , the wavelength conversion unit  30 , and the cooling unit  50 . 
       FIG.  14    is an exploded perspective view showing the configuration of the light source device  2 B. 
     As shown in  FIG.  14   , the optical unit  140  in the light source device  2 B in this embodiment includes an optical housing  162  different in a shape from the embodiments explained above. The optical housing  162  includes an attaching section  180 , the first member  85 , and the second member  86 . 
     The optical housing  162  in this embodiment is different from the optical housing  62  in the first and second embodiments in that the attaching section  180  is rotated 90° around the optical axis AX 3  of the condensing optical system  60  shown in  FIG.  3    with respect to the first member  85  and the second member  86 . The configuration other than the layout of the attaching section  180  in the optical housing  162  is generally common to the optical housing  62  in the first and second embodiments. Therefore, explanation is omitted about details of the configuration. 
     In the case of this embodiment, the wavelength conversion unit  30  can be attached from a plurality of directions, specifically, two directions in the up-down direction Z with respect to the optical axis AX 3  by using the attaching section  180  of the optical housing  162 . In this embodiment, the wavelength conversion unit  30  is disposed, with respect to the optical unit  140 , in the up-down direction Z crossing the left-right direction X in which the optical unit  140  and the heat radiating section  51  are adjacent to each other. 
     Specifically, in the light source device  2 B in this embodiment, when viewed from a position on the +Y side, the wavelength conversion unit  30  is attached to the lower side −Z of the optical unit  140  via the first sealing member  55  by the screw members  24  and the lid body  53  is attached to the upper side +Z of the optical unit  140  via the second sealing member  56  by the screw members  24 . 
       FIGS.  15 A and  15 B  are side views showing a main part configuration of the optical housing  162 .  FIG.  15 A  is a bottom view of the optical housing  162  viewed from the −Z side.  FIG.  15 B  is a top view of the optical housing  162  viewed from the +Z side. 
     As shown in  FIGS.  15 A and  15 B , in the optical housing  162  in this embodiment, the attaching section  180  includes the first attachment structure  81 , the second attachment structure  82 , and an attachment plate  183  extending along an XY plane. The attachment plate  183  in this embodiment includes a first attachment surface  183   a  extending along the optical axis AX 3  of the condensing optical system  60  and facing the lower side −Z, a second attachment surface  183   b  extending along the optical axis AX 3  of the condensing optical system  60  and facing the upper side +Z opposite to the first attachment surface  183   a , and the through-hole  84 . The attachment plate  183  is located on the optical axis AX 3  of the condensing optical system  60 . 
     The optical housing  162  enables, with the first attachment structure  81 , the wavelength conversion unit  30  to be attached to the lower side −Z. 
     The optical housing  162  in this embodiment includes a lower side opening section  187 , which is a second opening section, provided on the first attachment surface  183   a  side of the attaching section  180 . The lower side opening section  187  is an opening defined by a boundary between a space sandwiched by the pair of pedestals  81   b  and the outside of the space. 
     As shown in  FIG.  14   , when the wavelength conversion unit  30  is attached to the lower side −Z of the optical housing  162 , the attaching section  126  of the wavelength conversion unit  30  and the screw fastening sections  81   a  of the first attachment structure  81  shown in  FIG.  15 A  are fixed by the screw members  24 . At this time, as shown in  FIG.  15 A , in the wheel housing  32 , the wheel opening end face  32   a  of the wheel housing  32  configuring the wheel opening section  33  collides with the pedestals  81   b  and the attachment plate  183  of the first attachment structure  81  such that the wheel opening section  33  planarly surrounds the lower side opening section  187 . 
     In this embodiment as well, the wavelength conversion element  312 , which is a part of the wavelength conversion wheel  31  exposed via the wheel opening section  33  of the wheel housing  32 , is disposed on the optical path between the condensing optical system  60  and the pickup optical system  61  via the lower side opening section  187  of the optical housing  162  in a state in which the wavelength conversion unit  30  is attached to the attaching section  180  of the optical housing  162  of the optical unit  40 . 
     As shown in  FIG.  14   , in the optical unit  40  and the wavelength conversion unit  30 , the lower side opening section  187  of the optical housing  162  and the wheel opening section  33  of the wheel housing  32  are fixed in a sealed state by the first sealing member  55 . 
     In the optical housing  162 , the wavelength conversion unit  30  can be attached to the upper side +Z as well by the second attachment structure  82 . However, as explained above, the wavelength conversion unit  30  is attached to the lower side −Z of the optical housing  162  using the first attachment structure  81 . Accordingly, in this embodiment, the second attachment structure  82  is not used to attach the wavelength conversion unit  30 . 
     The optical housing  162  in this embodiment includes an upper side opening section  188 , which is a third opening section, provided on the second attachment surface  183   b  side of the attaching section  180 . The upper side opening section  188  is an opening defined by a boundary between a space sandwiched by the pair of pedestals  82   b  and the outside of the space. The upper side opening section  188  is opposed to the lower side opening section  187  across the attachment plate  183  of the attaching section  180 . 
     As shown in  FIG.  14   , when the lid body  53  is attached to the optical housing  162 , the attaching section  53   b  of the lid body  53  and the screw fastening sections  82   a  of the second attachment structure  82  are fixed by the screw members  24 . At this time, as shown in  FIG.  15 B , in the lid body  53 , the lid main body section  53   a  collides with the pedestals  82   b  and the attachment plate  83  of the second attachment structure  82  to close the upper side opening section  188 . 
     In the optical unit  40  and the lid body  53 , the upper side opening section  188  of the optical housing  162  and the lid body  53  are fixed in a sealed state by the second sealing member  56 . 
     In this way, with the light source device  2 B in this embodiment, it is possible to provide a light source device having a sealed structure that enables the wavelength conversion unit  30  to be attached to the optical unit  140  from the two directions in the up-down direction Z. 
     The embodiment of the present disclosure is explained above as an example. However, the present disclosure is not always limited to the embodiment. Various changes can be applied without departing from the gist of the present disclosure. 
     For example, in the first embodiment, as an example, the first member  85  and the second member  86  are integrally formed in the optical housing  62 . However, the first member  85  and the second member  86  may be formed by separate bodies. For example, the optical housing  62  may be configured by coupling, with the attachment plate  83 , the first member  85  and the second member  86  formed by the separate bodies. With this configuration, since the first member  85  and the second member  86  are configured by separate members, it is easy to incorporate the condensing optical system  60  and the pickup optical system  61  in the first member  85  and the second member  86 . 
     In the embodiment, as an example, the wheel opening section  33  of the wheel housing  32  is configured by the first housing  321  and the second housing  322 . However, the wheel opening section  33  may be configured by only one of the first housing  321  and the second housing  322 . 
     In the embodiment, as an example, the attachment section  80  of the optical housing  62  is located on the optical axis AX 3  of the condensing optical system  60 . However, the attachment plate  83  may be disposed to deviate in any one direction in the left-right direction X with respect to the optical axis AX 3 . 
     In each of the optical housings  62  and  162  in the embodiments explained above, the two opening sections are provided to enable the wavelength conversion unit  30  to be attached from the two directions. The opening section to which the wavelength conversion unit  30  is not attached is covered by the lid body  53 . However, only one opening section to which the wavelength conversion unit  30  is attached may be provided. 
     In the light source device  2  in the first embodiment, when viewed from a position on the +Y side, the wavelength conversion unit  30  is disposed on the left side −X in the left-right direction X in which a projection amount of the external shape of the optical housing  62  is small with respect to the optical axis AX 3 . Therefore, when the wavelength conversion unit  30  is attached to the optical housing  62 , overlap in the left-right direction X of the second housing  322  of the wheel housing  32  of the wavelength conversion unit  30  and the optical housing  62  decreases. 
     That is, compared with when the wavelength conversion unit  30  is attached to the right side +X of the optical housing  62 , the surface area of the second housing  322  exposed from the optical housing  62  increases. Therefore, if the wavelength conversion unit is not used in common in the embodiments, about the wavelength conversion unit  30  attached to the left side −X of the optical housing  62  as in the first embodiment, the heat dissipation of the wheel housing  32  may be further improved by increasing the size of the heat radiation fins  130  provided on the surface of the second housing  322  exposed from the optical housing  62 . 
     A light source device according to an aspect of the present disclosure may include the following configuration. 
     The light source device according to the aspect of the present disclosure includes: a light source unit including: a first mounting substrate on which a first light emitting element is mounted; a second mounting substrate that is disposed in parallel to the first mounting substrate and on which a second light emitting element is mounted; and a base member on which the first mounting substrate and the second mounting substrate are placed; a wavelength conversion unit including: a wavelength conversion wheel configured to emit, from a second surface opposite to a first surface, wavelength-converted light obtained by wavelength-converting light emitted from the first light emitting element and the second light emitting element and made incident from the first surface; and a wheel housing configured to house the wavelength conversion wheel; and an optical unit including: a condensing optical system configured to condense the light emitted from the first light emitting element and the second light emitting element on the wavelength conversion wheel; a pickup optical system configured to pick up the wavelength-converted light; and an optical housing configured to hold the condensing optical system and the pickup optical system to locate the wavelength conversion wheel on an optical path between the condensing optical system and the pickup optical system. The condensing optical system includes: a first lens on which the light emitted from the first light emitting element is directly made incident; and an optical-path changing member including a first reflection surface and a second reflection surface and configured to reflect, with the first reflection surface, the light emitted from the second light emitting element in a direction in which the light is brought closer to the light emitted from the first light emitting element and reflect, with the second reflection surface, the light reflected by the first reflection surface and make the light incident on the first lens. The optical housing includes: a first supporting section formed to recess to the wavelength conversion wheel side with respect to a holding surface for holding the light source unit and configured to support the optical-path changing member; and a second supporting section formed to recess to the wavelength conversion wheel side with respect to a bottom surface of the first supporting section and configured to support the first lens. The holding surface of the optical housing and the base member are fixed. 
     In the light source device according to the aspect of the present disclosure, the second reflection surface of the optical-path changing member may be located between the first lens and the first mounting substrate in a direction extending along an optical axis of the first lens. 
     In the light source device according to the aspect of the present disclosure, the base member may include a recess, and the first mounting substrate and the second mounting substrate may be set in the recess. 
     In the light source device according to the aspect of the present disclosure, the condensing optical system and the pickup optical system may be respectively configured by pluralities of lenses, in the condensing optical system, a diameter of a second lens located closer to the wavelength conversion wheel side than the first lens may be smaller than a diameter of the first lens, in the pickup optical system, a diameter of a third lens located on the wavelength conversion wheel side may be smaller than a diameter of a fourth lens located closer to a light emission side than the third lens, the optical housing may include a diameter-reduced section having a smaller outer diameter than other portions in a position corresponding to the second lens of the condensing optical system and the third lens of the pickup optical system, and the wavelength conversion unit may be disposed in the diameter-reduced section. 
     In the light source device according to the aspect of the present disclosure, the wavelength conversion unit may be disposed, in a first direction crossing an optical axis of the first lens, on one side in the first direction with respect to the optical housing, and the optical-path changing member may be disposed on another side in the first direction with respect to the optical axis in the optical housing. 
     In the light source device according to the aspect of the present disclosure, the wavelength conversion unit and the optical-path changing member may be respectively disposed on one side in a first direction crossing an optical axis of the first lens with respect to the optical housing, and a part of the wavelength conversion unit may overlap the optical-path changing member in a second direction extending along the optical axis. 
     In the light source device according to the aspect of the present disclosure, the wheel housing may include a plurality of heat radiation fins provided in a position not overlapping the optical housing in a direction extending along an optical axis of the first lens on a surface facing the light source unit side. 
     A projector according to an aspect of the present disclosure may include the following configuration. 
     The projector according to the aspect of the present disclosure includes: the light source device according to the aspect explained above; an image forming device configured to form light output from the light source device into image light; and a projection optical device configured to project the image light output from the image forming device.