Patent Publication Number: US-9410678-B2

Title: Illumination apparatus light source apparatus using illumination apparatus and image display apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of co-pending U.S. patent application Ser. No. 14/611028 filed Jan. 30, 2015, which claims foreign priority benefit of Japanese Patent Application No. 2014-018956 filed Feb. 3, 2014. The disclosures of the above-named applications are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an illumination apparatus, a light source apparatus using the illumination apparatus, and an image display apparatus. In particular, the present invention relates to a light source apparatus using a laser diode (LD) light source and a projector using the light source such as a projection display apparatus. 
     2. Description of the Related Art 
     In recent years, a projector capable of displaying a color image by using a fluorescent member (phosphor) that can convert blue light emitted from an LD light source into green light and red light has been developed. 
     The above-described projector is discussed in U.S. Patent Application Publication No. US2010/0328632 and U.S. Patent Application Publication No. US2011/0292349. 
     In the technique discussed in U.S. Patent Application Publication No. US2010/0328632, a color image is displayed by using blue light emitted from an LD light source in addition to green light and red light emitted as fluorescence light (phosphor light). In the technique, a fluorescence wheel having a diffusion layer capable of transmitting the blue light emitted from the LD light source and a fluorescent layer functioning as a fluorescent member is rotated. When the diffusion layer is irradiated with the blue light emitted from the LD light source, the blue light passes through the fluorescent layer, so as to be guided to an illumination optical system by a reflection mirror. On the other hand, when the fluorescent layer is irradiated with the blue light emitted from the LD light source, green light and red light are emitted in the light source direction, so as to be guided to the illumination optical system by a dichroic mirror. 
     In the technique discussed in U.S. Patent Application Publication No. US2011/0292349, blue light emitted from a blue light-emitting diode (LED) disposed separately from an LD light source is used in addition to green light and red light emitted as fluorescence light. As described above, the techniques for displaying a color image have been discussed. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, an illumination apparatus includes a wavelength conversion element configured to convert at least part of light emitted from a light source into converted light having a wavelength different from a wavelength of the light emitted from the light source and to emit the converted light and unconverted light having the same wavelength as the wavelength of the light emitted from the light source, a first optical element including a first region configured to guide the light emitted from the light source to the wavelength conversion element and a second region configured to prevent the unconverted light from traveling to the light source, and a second optical element configured to guide the converted light in a direction different from a direction of the light source while guiding the light emitted from the light source to the wavelength conversion element, wherein the second optical element is disposed in an optical path between the first optical element and the wavelength conversion element, and the light emitted from the light source is incident on the first region of the first optical element and the unconverted light is incident on both the first region and the second region of the first optical element. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an schematic diagram illustrating a configuration of a projection display apparatus on which an illumination apparatus according to exemplary embodiments of the present invention can be mounted. 
         FIGS. 2A and 2B  are schematic diagrams illustrating a configuration of an illumination apparatus according to a first exemplary embodiment of the present invention. 
         FIGS. 3A and 3B  are graphs illustrating spectral characteristics of light emitted from the light source and fluorescence light according to the first exemplary embodiment of the present invention. 
         FIG. 4  is a graph illustrating a spectral reflectance characteristic of a dichroic mirror according to the first exemplary embodiment of the present invention. 
         FIG. 5  is a schematic diagram illustrating a light shielding member according to the first exemplary embodiment of the present invention. 
         FIG. 6  is a schematic diagram illustrating a configuration of an illumination apparatus according to a second exemplary embodiment of the present invention. 
         FIG. 7  is a schematic diagram illustrating a configuration of an illumination apparatus according to a third exemplary embodiment of the present invention. 
         FIG. 8  is a graph illustrating a spectral reflectance characteristic of a dichroic mirror according to the third exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Although a fluorescent member can convert a wavelength of blue light emitted from an LD light source into wavelengths of green light and red light, not all the wavelength of the blue light is converted thereby. In practice, there is unconverted light returning to the LD light source from the fluorescent member, the wavelength of which is not converted by the fluorescent member. 
     The unconverted light returning to the LD light source may lower the luminous efficiency of the LD light source by increasing the temperature thereof. Therefore, an amount of the unconverted light returning to the LD light source may desirably be reduced as much as possible. 
     The present invention is directed to a light source apparatus capable of reducing the amount of unconverted light returning to the light source from a wavelength conversion element and projecting a brighter image. 
     Exemplary embodiments of the present invention will be described below with reference to appended drawings. Herein, shapes and relative alignment of the constituent elements described in the present exemplary embodiments can be changed as appropriate according to a configuration and various conditions of the apparatus the present invention is applied to. In other words, the shapes of the constituent elements illustrated herein are not intended to limit the scope of the invention to the exemplary embodiments described below. 
     &lt;Configuration of Projection Display Apparatus&gt; 
     First, with reference to  FIG. 1 , a configuration of a projection display apparatus  100  on which a light source apparatus according to exemplary embodiments of the present invention can be mounted will be described. 
     The display apparatus (projection display apparatus)  100  includes a light source apparatus  21 , a polarization plate  20 , a dichroic mirror  22 , a phase difference plate (wavelength-selective phase difference plate)  23 , and polarization beam splitters (PBS)  10  ( 10   a  and  10   c ). 
     Further, the display apparatus  100  includes ¼π plates  24  (¼π red plate  24   r,  ¼π green plate  24   g,  and ¼π blue plate  24   b ). 
     The display apparatus  100  further includes liquid crystal panels (reflective liquid crystal panels)  25 , i.e., a red liquid crystal panel  25   r,  a green liquid crystal panel  25   g,  and a blue liquid crystal panel  25   b,  serving as light modulation elements. 
     Furthermore, the display apparatus  100  includes a dichroic prism  26  and a projection lens  30 . In other words, the display apparatus  100  is a so-called reflective liquid crystal projector. 
     The light source apparatus  21  is a light source apparatus described in any one of exemplary embodiments of the present invention described below. 
     The polarization plate  20  transmits only s-polarized light  12  (s-polarized red light  12   r,  s-polarized green light  12   g,  and s-polarized blue light  12   b ) from among white light  11  (red light  11   r,  green light  11   g,  and blue light  11   b ) emitted from the light source apparatus  21 . 
     The dichroic mirror  22  has a reflectance characteristic of reflecting light in a green wavelength band while transmitting light in red and blue wavelength bands. 
     The phase difference plate  23  transmits polarized light in a blue wavelength band without converting the polarization direction. On the other hand, the phase difference plate  23  converts the polarization direction of polarized light in a red wavelength band by 90-degree. 
     The PBSs  10  each reflect s-polarized light and transmit p-polarized light. 
     The ¼π plates  24  each apply a phase difference of π/2 to obliquely incident light when transmitting through and back through the ¼π plate  24 , so as to increase analysis efficiency of the PBSs  10  with respect to the obliquely incident light. 
     The liquid crystal panels  25  convert the polarization direction of the light incident on the liquid crystal panels  25  according to an image signal. Further, the liquid crystal panels  25  emit image light  13  (red image light  13   r,  green image light  13   g,  and blue image light  13   b ) in which the polarization directions thereof has been converted by the liquid crystal panels  25 . 
     The dichroic prism  26  has a reflectance characteristic of reflecting the light in a green wavelength band while transmitting the light in red and blue wavelength bands. 
     The projection lens  30  guides the light combined by the dichroic prism  26  to a screen. 
     A process until the white light  11  emitted from the light source apparatus  21  reaches the projection lens  30  will be described. 
     Of the white light  11  emitted from the light source apparatus  21 , only the s-polarized light passes through the polarization plate  20 , so as to be guided to the dichroic mirror  22 . Of the s-polarized light  12  guided thereto, the s-polarized green light  12   g  is reflected and guided to the PBS  10   a,  while the s-polarized red light  12   r  and the s-polarized blue light  12   b  pass through the dichroic mirror  22 , so as to be guided to the PBS  10   c.    
     The s-polarized green light  12   g  guided to the PBS  10   a  is reflected by the PBS  10   a,  so as to be guided to the ¼π green plate  24   g.  The polarization direction of the s-polarized green light  12   g  is converted by the green liquid crystal panel  25   g,  so that the s-polarized green light  12   g  reflects thereon. Of the light reflected on the green liquid crystal panel  25   g,  the p-polarized light is guided to the dichroic prism  26  as the green image light  13   g.    
     Similar to the above-described s-polarized green light  12   g,  the s-polarized red light  12   r  and the s-polarized blue light  12   b  guided to the PBS  10   c  are also guided to the dichroic prism  26  as the red image light  13   r  and the blue image light  13   b.    
     The respective colors of image light  13   g,    13   r,  and  13   b  guided to the dichroic prism  26  are combined with each other, and the combined image light  13  is guided to the projection lens  30 . Through this processes, a color image can be projected and displayed on the screen. 
     Hereinafter, a configuration applicable to the light source apparatus  21  will be described. 
     The light source apparatus according to the present exemplary embodiment includes a light source unit (light source)  11 , a collimator lens unit  22 , a compression lens unit (second lens unit)  3 , and a light shielding member (first optical element)  4 . The light source according to the present exemplary embodiment further includes a mirror (second optical element)  5 , a collective lens unit (first lens unit)  6 , and a fluorescent member (wavelength conversion element)  7 . 
     In addition, the illumination apparatus according to the present exemplary embodiment includes the fluorescent member  7 , the light shielding member  4 , and the mirror  5 . 
     The light source unit  11  includes a plurality of light sources (a plurality of light emitting points)  1 . In the present exemplary embodiment, the light sources  1  are LD light sources. As illustrated in  FIG. 3A , the light sources  1  emit blue light having a wavelength of  448  nm. Therefore, according to the present exemplary embodiment, the light emitted from the light sources  1  is blue light. 
     The fluorescent member  7  converts the light emitted from the light sources  1  into fluorescence light (converted light) having a wavelength different from that of the light emitted from the light sources  1 , and emits the fluorescence light and unconverted light having a same wavelength as that of the light emitted from the light sources  1 . As illustrated in  FIG. 3B , the fluorescence light mainly consists of green light and red light. 
     The light shielding member  4  is an optical element including a region  41  (first region) having a characteristic of guiding the light emitted from the light sources  1  to the fluorescent member  7  and a region  42  (second region) having a characteristic of preventing the unconverted light from proceeding toward the light sources  1 . 
     The mirror  5  is an optical element having a characteristic of guiding the light emitted from the light sources  1  to the florescent member  7  while guiding the fluorescence light to a direction different from a direction of the light sources  1 . 
     The collimator lens unit  22  is configured of a plurality of collimator lenses  2 , and substantially collimates the light emitted from the light source unit  11 . 
     The condenser lens unit  6  has positive power in order to guide the light emitted from the light source unit to the fluorescent member  7  while guiding the fluorescence light and the unconverted light to the mirror  5 . According to the present exemplary embodiment, the condenser lens unit  6  is configured of four lenses in total. 
     The compression lens unit  3  compresses the light emitted from the light source unit  11  so as to guide the light to the region  41 . 
       FIG. 2  is a schematic diagram illustrating a configuration of the light source apparatus according to a first exemplary embodiment of the present invention. 
     Starting from the light source unit  11 , each of the constituent elements is aligned in a line in order of the light source unit  11 , the collimator lens unit  22 , the compression lens unit  3 , the light shielding member  4 , the mirror  5 , the condenser lens unit  6 , and the fluorescent member  7 . Thus, the fluorescent member  7  is disposed on a position in a direction toward the mirror  5  from the light source unit  11 . More specifically, the compression lens unit  3  is disposed on a position between the light source unit  11  and the mirror  5 , and the condenser lens unit  6  is disposed on a position between the mirror  5  and the fluorescent member  7 . 
     First, a process until the light emitted from the light source unit  11  reaches the mirror  5  will be described below with reference to  FIG. 2A . Blue light B 1  emitted from the light source unit  11  is substantially collimated by the collimator lens unit  22 , so as to be incident on the compression lens unit  3 . As illustrated in  FIG. 2A , the compression lens unit  3  is configured of a total of two lenses, i.e., a lens  3   a  disposed closer to the light source unit  11  and a lens  3   b  disposed farther from the light source unit  11 . The lens  3   a  is a positive-power lens for refracting the collimated light emitted through the collimator lens unit  22  to cause the collimated light to be incident on the lens  3   b.  The lens  3   b  substantially collimates the light emitted from the lens  3   a  to guide the collimated light to the mirror  5 . In other words, the compression lens unit  3  functions as an afocal optical system capable of guiding the blue light B 1  to the mirror  5  by reducing the light flux diameter thereof. 
     Subsequently, a process until the blue light B 1  reaches the fluorescent member  7  from the mirror  5  will be described below. As illustrated in  FIG. 4 , the mirror  5  is a dichroic mirror having a reflectance characteristic of transmitting the blue light B 1  while reflecting the visible light having a wavelength longer than that of the blue light B 1 . Accordingly, the blue light B 1  incident on the mirror  5  passes through the mirror  5 , so as to be guided to the condenser lens unit  6 . The blue light B 1  incident on the condenser lens unit  6  reaches the fluorescent member  7  by being guided and collected onto a surface of the fluorescent member  7  by the condenser lens unit  6  to form a light source image. 
     Next, description will be given to a process in which the fluorescent member  7  converts a part of the blue light B 1  into fluorescence light having a wavelength different from that of the blue light B 1  to emit the fluorescence light and unconverted light having a same wavelength as that of the blue light B 1 . The fluorescent member  7  is mainly formed of a Yttrium-Aluminum-Garnet (YAG) based material, and emits light having a spectrum illustrated in  FIG. 3B  as fluorescence light by using the blue light B 1  as excitation light. In other words, in the present exemplary embodiment, the fluorescence light consists of green light and red light. In addition, not all the blue light B 1  incident on the fluorescent member  7  is converted into the fluorescence light, and unconverted light of the wavelength of which has not been converted also exists. Therefore, in the present exemplary embodiment, the unconverted light consists of blue light. Because the fluorescent member  7  is fixed to a mirror or a metallic component, all the light does not pass through the fluorescent member  7  but reflects thereon. 
     Next, with reference to  FIG. 2B , description will be given to a process until the fluorescence light emitted from the fluorescent member  7  reaches the mirror  5  so as to be guided to the illumination optical system. The fluorescent member  7  emits the fluorescence light and the unconverted light to the condenser lens unit  6  in a random direction without determining the emission direction. The condenser lens unit  6  is disposed on a position between the fluorescent member  7  and the mirror  5  in order to collimate the fluorescence light and the unconverted light emitted in a random direction to guide the fluorescence light and unconverted light to the mirror  5  from the fluorescent member  7 . As described above, fluorescence light RG 5  guided to the mirror  5  from the fluorescent member  7  consists of green light and red light. Further, as described above, the mirror  5  is a dichroic mirror having a reflectance characteristic of transmitting the blue light B 1  while reflecting the visible light having a wavelength longer than that of the blue light B 1 . Accordingly, the fluorescence light RG 5  is reflected by the mirror  5  because the wavelength thereof is longer than that of the blue light B 1 . In the present exemplary embodiment, the illumination optical system (not illustrated) is disposed on a position to which the fluorescence light RG 5  is guided by the mirror  5 . 
     Next, a process until the unconverted light emitted from the fluorescent member  7  reaches the light shielding member  4  to return to the light source unit  11  and a process until that reached unconverted light is shielded by the light shielding member  4  will be described with reference to  FIGS. 2B and 5 . As described above, the unconverted light is substantially collimated by and emitted through the condenser lens unit  6 . At this time, the unconverted light is emitted from the condenser lens unit  6  with the cross-sectional area larger than that of the blue light B 1 . More specifically, as illustrated in  FIG. 5 , a cross-sectional area S OUT  is larger than a cross-sectional area S IN . The cross-sectional area S OUT  represents a cross-sectional area of the light flux (fluorescence light and unconverted light) emitted through the condenser lens unit  6  on a plane S perpendicular to an optical axis of the condenser lens unit  6  (i.e., plane S is parallel to the sheet surface in  FIG. 5 ). Further, the cross-sectional area S IN  represents a cross-sectional area of the light flux emitted through the light shielding member  4  on the plane S. In other words, as illustrated in  FIG. 5 , the unconverted light is incident on the region  41  (first region) and the region  42  (second region). A configuration of the light shielding member  4  will be described below. 
     The unconverted light emitted from the fluorescent member  7  passes through the mirror  5  to reach the light shielding member  4  because the wavelength thereof is the same as that of the blue light B 1 . Herein, a configuration of the light shielding member  4  will be described with reference to  FIG. 5 . As illustrated in  FIG. 5 , the light shielding member  4  includes the region  41  (first region) having a characteristic of guiding the blue light B 1  to the fluorescent member  7  and the region  42  (second region) having a characteristic of preventing the unconverted light from proceeding toward the light source unit  11 . In the present exemplary embodiment, an opening portion is provided on the region  41 , and the lens  3   b  of the above-described compression lens unit  3  is arranged in the opening portion. The lens  3   b  does not have the dichroic mirror characteristic as described in the above-described mirror  5 , so as to transmit light regardless of the wavelength thereof. Further, a light shielding glass for shielding at least the light having a same wavelength as that of the blue light B 1  is arranged on the region  42 . 
     In the light shielding member  4 , a projection area S 41 , which is the projection of the region  41  perpendicularly projected on the plane S, is larger than the cross-sectional area S IN . Therefore, of the unconverted light incident on the light shielding member  4 , unconverted light B 41  incident on the region  41  passes through the region  41  to return to the light source unit  11 . Likewise, a projection area S 42 , which is the projection of the region  42  perpendicularly projected on the plane S, is larger than the cross-sectional area S OUT . Therefore, of the unconverted light incident on the light shielding member  4 , unconverted light B 42  incident on the region  42  is shielded by the light shielding glass arranged on the region  42 . As described above, the light shielding member  4  having the regions  41  and  42  can guide the blue light B 1  to the fluorescent member  7  while preventing the unconverted light B 42  from returning to the light source unit  11 . 
     As described above, in the present exemplary embodiment, because the cross-sectional area S OUT  is larger than the cross-sectional area S IN , an amount of the unconverted light returning to the light source unit  11  from the fluorescent member  7  can be reduced. In order to reduce the amount of the unconverted light returning to the light source unit  11  from the fluorescent member  7 , it is preferable that the cross-sectional area S OUT  and the cross-sectional area S IN  satisfy the formula “S IN /S OUT  &lt;0.8”. 
     Further, it is more preferable if the cross-sectional area S OUT  and the cross-sectional area S IN  satisfy the formula “S IN /S OUT  &lt;0.5”. 
       FIG. 6  is a diagram illustrating a configuration of a light source apparatus according to a second exemplary embodiment of the present invention. The present exemplary embodiment is different from the first exemplary embodiment in that the light source further includes a folding mirror (third optical element)  8  disposed in the middle of the optical path from the light shielding member  4  to the mirror  5 . In other words, the folding mirror  8  is disposed on a position between the light shielding member  4  and the mirror  5 . As illustrated in  FIG. 5 , the folding mirror  8  includes a region (transmissive region)  81  transmitting the light having a same wavelength as that of the blue light B 1  and a region (reflection region)  82  reflecting the light having a same wavelength as that of the blue light B 1 . 
     The unconverted light emitted from the fluorescent member  7  reaches the mirror  5  similarly as described in the first exemplary embodiment. In the present exemplary embodiment, the unconverted light passing through the mirror  5  reaches the folding mirror  8 . Of the unconverted light incident on the folding mirror  8 , unconverted light B 81  incident on the region  81  passes through the region  81  and the region  41  of the light shielding member  4 , so as to return to the light source unit  11 . On the other hand, of the unconverted light incident on the folding mirror  8 , unconverted light B 82  incident on the region  82  is incident on the fluorescent member  7  again due to the mirror arranged on the region  82 , so as to be able to excite the fluorescent member  7 . 
     As described above, the light source according to the present exemplary embodiment further includes the folding mirror  8  disposed in the middle of the optical path from the light shielding member  4  to the mirror  5 . With this configuration, a part of the unconverted light can be reused as an excitation light, and thus the light use efficiency can be further improved in comparison to the above-described first exemplary embodiment. 
       FIG. 7  is a diagram illustrating a configuration of a light source apparatus according to a third exemplary embodiment of the present invention. Similar to the light source described in the first exemplary embodiment of the present invention, the light source according to the present exemplary embodiment includes a light source unit  11 , a collimator lens unit  22 , a compression lens unit  3 , a light shielding member  4 , a mirror  5 , a condenser lens unit  6 , and a fluorescent member  7 . 
     The present exemplary embodiment and the first exemplary embodiment are different in the positional relationship between the light source unit  11  and the fluorescent member  7 . In the first exemplary embodiment, the light source unit  11 , the mirror  5 , and the fluorescent member  7  are aligned in a line. On the other hand, in the present exemplary embodiment, the light source unit  11 , the mirror  5 , and the fluorescent member  7  are not aligned in a line. More specifically, the fluorescent member  7  is disposed on a position to which the blue light B 1  is reflected by the mirror  5 . 
     First, a process until the blue light B 1  reaches the fluorescent member  7  will be described with reference to  FIG. 7 . The blue light B 1  reaches the mirror  5  similarly as described in the first exemplary embodiment. However, in the present exemplary embodiment, as illustrated in  FIG. 8 , the mirror  5  is a dichroic mirror having a reflectance characteristic of reflecting the blue light B 1  while transmitting the visible light having a wavelength longer than that of the blue light B 1 . Accordingly, similar to the above-described first exemplary embodiment, the blue light B 1  is guided to the condenser lens unit  6  by reflecting on the mirror  5 , so as to be collected on a surface of the fluorescent member  7  by the condenser lens unit  6 . 
     Similar to the above-described first exemplary embodiment, the fluorescent member  7  converts a part of the blue light B 1  into fluorescence light having a wavelength different from that of the blue light B 1 , so as to emit the fluorescence light and unconverted light having a same wavelength as that of the blue light B 1 . 
     Next, a process until the fluorescence light emitted from the fluorescent member  7  reaches the mirror  5  so as to be guided to the illumination optical system will be described with reference to  FIG. 7 . The fluorescence light proceeds to the mirror  5  from the condenser lens unit  6  similarly as described in the first exemplary embodiment. However, as described above, in the present exemplary embodiment, the mirror  5  has a reflectance characteristic of reflecting the blue light B 1  while transmitting the visible light having a wavelength longer than that of the blue light B 1 . Therefore, the fluorescence light passes through the mirror  5 , so as to be guided to the illumination optical system. 
     Next, a process until the unconverted light emitted from the fluorescent member  7  reaches the light shielding member  4  to return to the light source unit  11  and a process until that reached unconverted light is shielded by the light shielding member  4  will be described. The unconverted light proceeds to the mirror  5  from the condenser lens unit  6  similarly as described in the first exemplary embodiment. However, as described above, in the present exemplary embodiment, the mirror  5  has a reflectance characteristic of reflecting the blue light B 1  while transmitting the visible light having a wavelength longer than that of the blue light B 1 . Therefore, the unconverted light is reflected on the mirror  5 , so as to reach the light shielding member  4 . In the present exemplary embodiment, similar to the above-described first exemplary embodiment, of the unconverted light incident on the light shielding member  4 , the unconverted light B 41  incident on the region  41  passes through the region  41  to return to the light source unit  11 . Further, similar to the above-described first exemplary embodiment, in the present exemplary embodiment, of the unconverted light incident on the light shielding member  4 , the unconverted light B 42  incident on the region  42  is shielded by the light shielding glass disposed on the region  42 . 
     As described above, similar to the above-described first exemplary embodiment, in the present exemplary embodiment, the blue light B 1  can be guided to the fluorescent member  7  by the light shielding member  4  having the regions  41  and  42 . Furthermore, it is possible to prevent the unconverted light B 42  from returning to the light source unit  11 . 
     In the above-described exemplary embodiments, a configuration of the reflective liquid crystal projector has been described as an example of the image display apparatus on which the light source apparatus according to the exemplary embodiments of the present invention can be mounted. However, the present invention is not limited thereto. For example, the image display apparatus can be a projector using a transmissive liquid crystal panel. 
     Further, in the above-described exemplary embodiments, a configuration in which the light emitted from the light source apparatus is firstly incident on the polarization plate has been described as a configuration of the projection display apparatus on which the light source apparatus according to the exemplary embodiments can be mounted. However, the present invention is not limited thereto. For example, an integrator using fly-eye lenses and a polarization conversion element for converting unpolarized light into linearly-polarized light may be disposed as a configuration of the projection display apparatus instead of using the polarization plate. 
     Further, in the above-described exemplary embodiments, a configuration including a projection lens has been described as a configuration of the projection display apparatus on which the light source apparatus according to the exemplary embodiments can be mounted. However, the present invention is not limited thereto. For example, a configuration including a detachable projection lens may be employed as a configuration of the projection display apparatus. 
     Furthermore, in the above-described exemplary embodiments, although a configuration of the light source apparatus using the LD light source emitting blue light has been described as an example, the present invention is not limited thereto. Any light source such as a blue LED light source may be employed therefor as long as the light source can emit light in a blue wavelength band. Further, for example, an LD light source emitting green light or red light may be employed as long as the light source can display a color image. 
     Further, in the above-described exemplary embodiments, configurations of the light source apparatus and the projection display apparatus configured to guide white light (visible light) to the illumination optical system have been described as examples. However, the present invention is not limited thereto. The present invention is applicable not only to a projection display apparatus projecting visible light but also to a projection display apparatus projecting only infrared light and ultraviolet light or a projection display apparatus projecting visible light in addition to the infrared light and the ultraviolet light. Furthermore, the present invention is applicable to a light source apparatus mounted on the projection display apparatus configured as the above. 
     Furthermore, in the above-described exemplary embodiments, a configuration of the light source apparatus using the light shielding member having the opening portion and the light shielding glass has been described as an example. However, the present invention is not limited thereto. For example, the light source may include a light shielding member having an opening portion and a mirror as long as the light source is configured to reduce the amount of the unconverted light returning thereto. Similar to the second exemplary embodiment, by employing the light shielding member having the opening portion and the mirror, a part of the unconverted light can be reused as excitation light. 
     In addition, in the above-described exemplary embodiments, a configuration of the light source apparatus using a dichroic mirror having a characteristic of transmitting the blue light while reflecting the visible light having a wavelength longer than that of the blue light has been described as an example. However, the present invention is not limited thereto. The reflectance characteristic of the dichroic mirror may be changed as appropriate according to the wavelength of the light emitted from the light source as long as an amount of the unconverted light returning to the light source can be reduced. Further, a configuration using the PBS instead of the dichroic mirror may be employed. In the configuration using the PBS instead of the dichroic mirror, light in the first polarization direction from among the light emitted from the light source can be guided to the fluorescent member, while light in the second polarization direction different from the first polarization direction from among the unconverted light can be guided to a direction different from a direction of the light source. Through the above-described configuration, a part of the unconverted light can be guided to the illumination optical system. 
     Furthermore, in the above-described exemplary embodiments, a compression lens unit configured of four lenses has been described as an example of the compression lens unit having positive power. However, the present invention is not limited thereto. The compression lens unit may be configured of more than four or less than four lenses as long as the compression lens unit has positive power as a whole unit. In other words, in a case where the compression lens unit includes a single compression lens, the compression lens unit is configured of a single compression lens instead of a compression lens group consisting of a plurality of compression lenses. 
     Further, in the above-described exemplary embodiments, a configuration of the projection display apparatus on which the light source apparatus according to the exemplary embodiments of the present invention can be mounted has been described as an example. However, the present invention is not limited thereto. For example, the light source apparatus according to the exemplary embodiments of the present invention may be mounted on a liquid crystal display or an electronic viewfinder as a backlight. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.