Abstract:
An illumination apparatus includes a light source, a polarization splitter disposed facing the light source at about 45 degrees with respect to its light emission direction, a first reflector reflecting and condensing one of the polarization light components polarized and split by the polarization splitter, a quarter wave plate disposed between the polarization splitter and the first reflector, a second reflector reflecting and condensing the other of the polarization light components polarized and split by the polarization splitter, a third reflector disposed around the light source and reflecting the other polarization light reflected by the second reflector and the polarization splitter and proceeding in the light source direction, and a quarter wave plate disposed between the polarization splitter and the third reflector and around the light source, the light reflected at the first reflector and reflected at the polarization splitter being used to illuminate a predetermined surface.

Description:
TECHNICAL FIELD 
     The present invention relates to an illumination apparatus and projector provided with a polarization conversion function. 
     BACKGROUND ART 
     A projector projecting a projection-use image displayed on a liquid crystal device is known in the art (for example, Japanese Patent Laid-open Publication No. 2005-250392A). In this projector, only a specific polarization component of light is used for projection of the projection-use image, so only half of the amount of light emitted from a light source can be utilized. Therefore, a projector using a polarization conversion device to align the light emitted from a light source in polarization direction with a certain polarization direction and thereby increase the amount of light able to be used for projection by the projector has been proposed (for example, Japanese Patent Laid-open Publication No. 2006-227361A). 
     SUMMARY OF INVENTION 
     However, in the above-mentioned projector, when aligning the polarization directions, a polarization conversion device is used, so there was the problem of the apparatus becoming larger in size. 
     An object of the present invention is to provide an illumination apparatus and projector providing a small sized, compact polarization conversion function and enabling light emitted from a light source to be efficiently utilized. 
     The illumination apparatus of the present invention is comprised of a light source, a polarization splitter disposed facing the light source at about 45 degrees with respect to its light emission direction, a first reflector reflecting and condensing one of the polarization light components polarized and split by the polarization splitter, a quarter wave plate disposed between the polarization splitter and the first reflector, a second reflector reflecting and condensing the other of the polarization light components polarized and split by the polarization splitter, a third reflector disposed around the light source and reflecting the other polarization light reflected by the second reflector and the polarization splitter and proceeding in the light source direction, and a quarter wave plate disposed between the polarization splitter and the third reflector and around the light source, the light reflected at the first reflector and reflected at the polarization splitter being used to illuminate a predetermined surface. 
     Further, the projector of the present invention is comprised of a light source, a display displaying a projection-use image, a polarization splitter disposed facing the light source at about 45 degrees with respect to its light emission direction, a first reflector reflecting and condensing one of the polarization light components polarized and split by the polarization splitter, a quarter wave plate disposed between the polarization splitter and the first reflector, a second reflector reflecting and condensing the other of the polarization light components polarized and split by the polarization splitter, a third reflector disposed around the light source and reflecting the other polarization light reflected by the second reflector and the polarization splitter and proceeding in the light source direction, and a quarter wave plate disposed between the polarization splitter and the third reflector and around the light source, the light reflected at the first reflector and reflected at the polarization splitter being used to illuminate the display. 
     According to the illumination apparatus and projector of the present invention, a small in size and compact polarization conversion function is provided, so light emitted from the light source can be efficiently utilized. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view showing the configuration of a projector according to a first embodiment of the present invention. 
         FIG. 2  is a view showing a light path in a projector according to a first embodiment of the present invention. 
         FIG. 3  is a view showing a light path in a projector according to a first embodiment of the present invention. 
         FIG. 4  is a view showing a light path in a projector according to a first embodiment of the present invention. 
         FIG. 5  is a view showing a light path in a projector according to a first embodiment of the present invention. 
         FIG. 6  is a view showing the configuration of a projector according to a second embodiment of the present invention. 
         FIG. 7  is a view showing a light path in a projector according to a second embodiment of the present invention. 
         FIG. 8  is a view showing a light path in a projector according to a second embodiment of the present invention. 
         FIG. 9  is a view showing a light path in a projector according to a second embodiment of the present invention. 
         FIG. 10  is a view showing a modification of a projector unit according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Below, referring to the drawings, a projector according to a first embodiment of the present invention will be explained.  FIG. 1  is a view showing the configuration of a projector according to a first embodiment of the present invention. A projector  2  is provided with a light source comprised of an LED (light emitting diode)  4 , a wire grid  6  disposed facing the LED  4  at about 45 degrees with respect to its light emission direction, passing a P polarization component of light, and reflecting an S polarization component of light so as to split the striking light into the P polarization component of light and the S polarization component of light, a mirror  8  having a concave shaped reflecting surface and reflecting and condensing the P polarization component of light split by the wire grid, a mirror  10  having a circumferential shaped concave shape and reflecting and condensing the S polarization component of light split by the wire grid, and a mirror  12  disposed around the light source and having a circumferential shape. Further, between the wire grid  6  and mirror  8 , a quarter wave plate  20  is provided, while between the wire grid  6  and mirror  12  and around the LED  4 , a quarter wave plate  22  having a circumferential shape is provided. Furthermore, a wire grid  14  disposed facing the wire grid  6  at about 45 degrees with respect to the direction of progression of the reflected light, passing the S polarization component of light, and reflecting the P polarization component of light, a LCOS (reflection type liquid crystal device)  16  displaying a projection-use image, and a projection lens  18  projecting the projection-use image are provided. 
     Next, referring to  FIG. 2  to  FIG. 5 , the path of the light emitted from the LED according to the first embodiment will be explained. The light emitted from the LED  4  strikes the wire grid  6  and is split into the P polarization component of light and the S polarization component of light. As shown in  FIG. 2 , the P polarization component of light passes through the wire grid  6  and proceeds in the mirror  8  direction. The P polarization component of light passing through the wire grid  6  passes through the quarter wave plate  20  and is reflected and condensed at the mirror  8  to become substantially parallel light which again passes through the quarter wave plate  20  to thereby be converted to the S polarization component of light. The S polarization component of light again strikes the wire grid  6 , is reflected by the wire grid  6 , passes through the wire grid  14 , and illuminates the LCOS  16 . 
     Further, in the light emitted from the LED  4  and striking the wire grid  6 , the S polarization component of light, as shown in  FIG. 3 , is reflected by the wire grid  6 , proceeds toward the mirror  10 , and strikes the mirror  10 . In the S polarization component of light striking the mirror  10 , since the mirror  10  has a circumferential concave shape, the light striking near the center of the mirror  10  is reflected outward. Therefore, the cross-section of the S-polarization light reflected by the mirror  10  is a circular or elliptical shape with the center portion missing, that is, a ring shape. The light proceeds in the wire grid  6  direction, is reflected at the wire grid  6 , and proceeds in the LED  4  direction. 
     The S polarization component of light reflected at the wire grid  6  and proceeding in the LED  4  direction, as shown in  FIG. 4 , passes through the quarter wave plate  22  having the circumferential shape, is reflected at the mirror  12  having the circumferential shape, and, as shown in  FIG. 5 , again passes through the quarter wave plate  22  to thereby be converted to the P polarization component of light. At this time, the mirror  12  is formed so as to be slanted in the peripheral edge direction so that the reflected light strikes the outer circumference of the mirror  8 . Therefore, as shown in  FIG. 5 , the light reflected by the mirror  12  is emitted somewhat outward. The light reflected by the mirror  12  and converted to the P polarization component of light passes through the wire grid  6  and proceeds in the mirror  8  direction. The P polarization component of light passing through the wire grid  6  passes through the quarter wave plate  20 , is reflected and condensed at the mirror  8 , again passes through the quarter wave plate  20 , and thereby is converted to the S polarization component of light. The light converted to the S polarization component of light again strikes the wire grid  6 , is reflected by the wire grid  6 , passes through the wire grid  14 , and illuminates the LCOS  16 . 
     That is, the light emitted from the LED  4  is split by the wire grid  6  into the P polarization component and the S polarization component, but both the P polarization component and S polarization component strike the LCOS  16  as the S polarization component of light. 
     The S polarization component of light striking the LCOS  16  proceeds through the liquid crystal layer of the LCOS  16 , is reflected at a not shown reflection film, then proceeds through the liquid crystal layer of the LCOS  16  in the opposite direction and is emitted from the LCOS  16 . The light emitted from the LCOS  16  again strikes the wire grid  14 . When voltage is applied to the liquid crystal layer of the LCOS  16 , the LCOS functions as a phase plate and converts the S polarization component of light to the P polarization component of light. Therefore, the light again striking the wire grid  14  becomes the mixed S polarization component of light and P polarization component. The wire grid  14  reflects, in the again striking light, only the P polarization component of light. The reflected P polarization component of light strikes the projection lens  18 . Therefore, the projection-use image is projected through the projection lens  18  on to a not shown screen. 
     According to the projector of the present embodiment, it is possible to effectively utilize the light emitted from the light source for projection of a projection-use image. 
     Note that even if configuring the wire grid  6  to reflect the P polarization component of light and pass the S polarization component of light and configuring the wire grid  14  to reflect the S polarization component of light and pass the P polarization component of light, a similar function can be exhibited. In this case, the light path of the P polarization component in above-mentioned first embodiment becomes the light part of the S polarization component and the light path of the S polarization component becomes the light path of the P polarization component. 
     Next, a projector according to a second embodiment of the present invention will be explained. Note that, the configuration of the projector according to this second embodiment changes the layout of the mirrors of the projector according to the first embodiment. Therefore, a detailed explanation of the same configurations as the first embodiment will be omitted and only the different parts will be explained in detail. Further, parts of the configuration the same as in the first embodiment will be explained assigned the same reference numerals. 
       FIG. 6  is a view showing the configuration of a projector according to a second embodiment of the present invention. A projector  23  is comprised of an LED  4  as a light source, a wire grid  6  arranged facing the LED  4  at about 45 degrees with respect to its light emission direction, reflecting the S polarization component of light, and passing the P polarization component of light, a mirror  24  having a concave shaped reflecting surface and reflecting and condensing the S polarization component of light split by the wire grid, a mirror  26  having a circumferential shaped concave shape and reflecting and condensing the P polarization component of light split by the wire grid, and a mirror  12  arranged around the light source and having a circumferential shape. Further, between the wire grid  6  and mirror  24 , a quarter wave plate  28  is provided, while between the wire grid  6  and mirror  12  and around the LED  4 , a quarter wave plate  22  having a circumferential shape is provided. Furthermore, a wire grid  15  arranged facing the wire grid  6  at about 45 degrees with respect to the direction of progression of the reflected light, reflecting the S polarization component of light, and passing the P polarization component of light, a LCOS (reflection type liquid crystal device)  16  displaying a projection-use image, and a projection lens  18  projecting the projection-use image are provided. 
     Next, referring to  FIG. 7  to  FIG. 9 , the path of the light emitted from the LED according to the second embodiment will be explained. The light emitted from the LED  4  strikes the wire grid  6  and is split into the P polarization component of light and the S polarization component of light. In the light striking the wire grid  6 , the S polarization component of light, as shown in  FIG. 7 , is reflected at the wire grid  6 , proceeds toward the mirror  24 , passes through the quarter wave plate  28 , is reflected and condensed at the mirror  24  to become substantially parallel light, again passes through the quarter wave plate  28 , and thereby is converted to the P polarization component of light. The light converted to the P polarization component of light again strikes the wire grid  6  to pass through the wire grid  6 . Further, it passes through the wire grid  15  and illuminates the LCOS  16 . 
     Further, in the light emitted from the LED  4  and striking the wire grid  6 , the P polarization component of light passes through the wire grid  6  and, as shown in  FIG. 8 , proceeds toward the mirror  26  and strikes the mirror  26 . In the P polarization component of light striking the mirror  26 , since the mirror  26  has a circumferential shaped concave shape, the light striking near the center of the mirror  26  is reflected outward. Therefore, the cross-section of the P-polarization light reflected by the mirror  26  is a circular or elliptical shape with the center portion missing, that is, a ring shape. The light proceeds in the wire grid  6  direction, is reflected at the wire grid  6 , and proceeds in the LED  4  direction. 
     The P polarization component of light passing through the wire grid  6  and proceeding in the LED  4  direction, as shown in  FIG. 9 , passes through the quarter wave plate  22  having the circumferential shape to be reflected by the mirror  12  having the circumferential shape and, as shown in  FIG. 9 , again passes through the quarter wave plate  22 , so is converted to the S polarization component of light. At this time, the mirror  12  is formed to slant in the peripheral edge direction so that the reflected light strikes the outer circumference of the mirror  24 . Therefore, as shown in  FIG. 9 , the light reflected by the mirror  12  is emitted somewhat outward. The light reflected by the mirror  12  and converted to the S polarization component of light is reflected at the wire grid  6  and proceeds in the mirror  24  direction. The S polarization component of light reflected at the wire grid  6  passes through the quarter wave plate  28 , is reflected and condensed at the mirror  24 , again passes through the quarter wave plate  28 , and thereby is converted to the P polarization component of light. The light converted to the P polarization component of light again strikes the wire grid  6  and passes through the wire grid  6 . Further, it passes through the wire grid  15  and illuminates the LCOS  16 . 
     That is, the light emitted from the LED  4  is split by the wire grid  6  into the P polarization component and the S polarization component. Both the P polarization component and S polarization component strike the LCOS  16  as the P polarization component of light. 
     The P polarization component of light striking the LCOS  16  proceeds through the liquid crystal layer of the LCOS  16 , is reflected by a not shown reflection film, then proceeds through the liquid crystal layer of the LCOS  16  in the opposite direction and is emitted from the LCOS  16 . The light emitted from the LCOS  16  again strikes the wire grid  15 . When voltage is applied to the liquid crystal layer of the LCOS  16 , the LCOS functions as a phase plate and converts the P polarization component of light to the S polarization component of light. Therefore, the light again striking the wire grid  15  becomes a mix of the S polarization component and P polarization component. The wire grid  15  reflects, in the again striking light, only the S polarization component of light at the polarization splitter. The reflected S polarization component of light strikes the projection lens  18 . Therefore, the projection-use image is projected through a projection lens  18  on to a not shown screen. 
     According to the projector of the second embodiment, even when changing the layout of the mirrors, the projector can function in the same way as the first embodiment and efficiently utilize light emitted from a light source for projecting a projection-use image. 
     Note that, in the second embodiment, the wire grid  6  and the wire grid  15  were both explained using ones which reflect the S polarization component of light and pass the P polarization component of light, but even if configuring both the wire grid  6  and the wire grid  15  to reflect the P polarization component of light and pass the S polarization component of light, a similar function can be exhibited. In this case, the light path of the P polarization component in the above-mentioned second embodiment becomes the light path of the S polarization component and the light path of the S polarization component becomes the light path of the P polarization component. 
     Further, as shown in  FIG. 10 , instead of the reflection type liquid crystal device, a transmission type liquid crystal device  30  may also be used. Further, it is also possible not to use a mirror having a circumferential shaped concave shape. In this case, light reflected without being reflected in a ring shape will also strike the LED  4 . The light reflected at the mirror  12  at the outer circumference of the LED  4  can increase the amount of light illuminating the LCOS  16 . Further, instead of the wire grid, it is also possible to use a polarization beam splitter superior in angle characteristics. 
     Note that, this disclosure relates to the content contained in Japanese Patent Application No. 2007-296640 filed on Apr. 7, 2008, the entire disclosure of which is clearly incorporated by reference here. 
     {INDUSTRIAL APPLICABILITY} 
     The present invention can be utilized for an illumination apparatus and projector provided with a polarization conversion function.