Abstract:
A projection type display apparatus includes: a reflection type light valve; a polarization beam splitter that emits light obtained through polarization split executed thereat on light from a light source toward the reflection type light valve, analyzes light modulated at the reflection type light valve and includes a light blocking portion disposed near an outer edge of an exit surface through which the analyzed light exits; and a projection lens through which the analyzed light is projected.

Description:
INCORPORATION BY REFERENCE 
   The disclosure of the following priority application is herein incorporated by reference:
         Japanese Patent Application No. 2003-194976 filed Jul. 10, 2003       

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a projection type display apparatus. 
   2. Description of the Related Art 
   There are projection type display apparatuses disclosed in the related art in which light from a light source undergoes color separation to be separated into blue color light, red color light and green color light, with each of the different colors of light radiated onto a reflection type light valve disposed in correspondence to the specific color of light via a polarization beam splitter, the individual colors of light modulated at the corresponding reflection type light valves reenter the polarization beam splitters where they are analyzed before they exit the polarization beam splitters and then the different colors of light undergo color composition at a color composition optical system so as to project a full-color image onto a screen through a projection lens (for instance, see Japanese Laid Open Patent Publication No. H 11-38365). 
   SUMMARY OF THE INVENTION 
   In the projection type display apparatus disclosed in the example of the related art described above, diffracted light exiting an end of a reflection type light valve enters the polarization beam splitter, is reflected at a side surface of the polarization beam splitter to advance via the color composition optical system and enters the projection lens as a light beam within the NA of the aperture stop in the projection lens, which is projected onto the screen as a ghost image. 
   According to the 1st aspect of the invention, a projection type display apparatus comprises: a reflection type light valve; a polarization beam splitter that emits light obtained through polarization split executed thereat on light from a light source toward the reflection type light valve, analyzes light modulated at the reflection type light valve and includes a light blocking portion disposed near an outer edge of an exit surface through which the analyzed light exits; and a projection lens through which the analyzed light is projected. 
   According to the 2nd aspect of the invention, in the projection type display apparatus according to the 1st aspect, it is preferred that the light blocking portion comprises a light absorbing member. 
   According to the 3rd aspect of the invention, in the projection type display apparatus according to the 1st aspect, it is preferred that the light blocking portion is formed by processing a surface of the polarization beam splitter near the outer edge of the exit surface so as to achieve a light scattering state. 
   According to the 4th aspect of the invention, in the projection type display apparatus according to the 1st aspect, it is preferred that the light blocking portion is formed by cutting off a corner near the outer edge of the exit surface at the polarization beam splitter. 
   According to the 5th aspect of the invention, in the projection type display apparatus according to the 4th aspect, it is preferred that a surface of the light blocking portion is processed so as to achieve a light scattering state. 
   According to the 6th aspect of the invention, a projection type display apparatus comprises: a color separation optical system that executes color separation to separate light from a light source into individual colors of light that are first color light, second color light and third color light; reflection type light valves, each disposed in correspondence to one of the individual colors of light; polarization beam splitters each of which is disposed in correspondence to one of the individual colors of light, outputs light obtained through polarization split executed thereat on a corresponding color of light resulting from the color separation at the color separation optical system toward the reflection type light valve disposed in correspondence to the corresponding color of light, and analyzes light modulated at the reflection type light valve; a color composition optical system that executes color composition of the individual colors of analyzed light; spacer members which are disposed in correspondence to the individual colors of light between the polarization beam splitters and the color composition optical system, with a spacer member disposed for at least one of the individual colors of light having a light blocking portion near an outer edge of an entry surface through which the analyzed light enters; and a projection lens through which light resulting from the color composition is projected. 
   According to the 7th aspect of the invention, in the projection type display apparatus according to the 6th aspect, it is preferred that the light blocking portion comprises a light absorbing member. 
   According to the 8th aspect of the invention, in the projection type display apparatus according to the 6th aspect, it is preferred that the light blocking portion is formed by processing a surface of the spacer member near the outer edge of the entry surface through which the analyzed light enters so as to achieve a light scattering state. 
   According to the 9th aspect of the invention, in the projection type display apparatus according to the 6th aspect, it is preferred that the light blocking portion is formed by cutting off a corner of the spacer member near the outer edge of the entry surface. 
   According to the 10th aspect of the invention, in the projection type display apparatus according to the 9th aspect, it is preferred that a surface of the light blocking portion is processed so as to achieve a light scattering state. 
   According to the 11th aspect of the invention, in the projection type display apparatus according to the 6th aspect, it is preferred that: the color composition optical system comprises a first dichroic film that reflects the first color light and a second dichroic film that is disposed substantially orthogonally to the first dichroic film and reflects the second color light; and the projection type display apparatus further comprises a third dichroic film disposed in the spacer member in an optical path of the third color light which reflects the first color light. 
   According to the 12th aspect of the invention, in the projection type display apparatus according to the 11th aspect, it is preferred that the light blocking portion comprises a light absorbing member. 
   According to the 13th aspect of the invention, in the projection type display apparatus according to the 11th aspect, it is preferred that the light blocking portion is formed by processing a surface of the spacer member near the outer edge of the entry surface through which the analyzed light enters so as to achieve a light scattering state. 
   According to the 14th aspect of the invention, in the projection type display apparatus according to the 11th aspect, it is preferred that the light blocking portion is formed by cutting off a corner of the spacer member near the outer edge of the entry surface. 
   According to the 15th aspect of the invention, in the projection type display apparatus according to the 14th aspect, it is preferred that a surface of the light blocking portion is processed so as to achieve a light scattering state. 
   According to the 16th aspect of the invention, a projection type display apparatus comprises: a reflection type light valve; a polarization beam splitter that emits light obtained through polarization split executed thereat on light from a light source toward the reflection type light valve, analyzes light modulated at the reflection type light valve and includes an nonreflecting portion disposed at a surface facing opposite an entry surface through which the light from the light source enters; and a projection lens through which the analyzed light is projected. 
   According to the 17th aspect of the invention, in the projection type display apparatus according to the 16th aspect, it is preferred that the nonreflecting portion is constituted by processing the surface facing opposite the entry surface so as to achieve a light scattering state. 
   According to the 18th aspect of the invention, in the projection type display apparatus according to the 16th aspect, it is preferred that the nonreflecting portion is constituted as an indented portion formed at the surface facing opposite the entry surface. 
   According to the 19th aspect of the invention, in the projection type display apparatus according to the 16th aspect, it is preferred that the nonreflecting portion is constituted with a light absorbing member disposed at the surface facing opposite the entry surface. 
   According to the 20th aspect of the invention, a projection type display apparatus, comprises: a color separation optical system that executes color separation to separate light from a light source into individual colors of light that are first color light, second color light and third color light; reflection type light valves, each disposed in correspondence to one of the individual colors of light; polarization beam splitters each of which is disposed in correspondence to one of the individual colors of light, outputs light obtained through polarization split executed thereat on a corresponding color of light resulting from the color separation at the color separation optical system toward the reflection type light valve disposed in correspondence to the corresponding color of light, and analyzes light modulated at the reflection type light valve; a color composition optical system that comprises a first dichroic film that reflects the first color light and a second dichroic film that is disposed substantially orthogonally to the first dichroic film and reflects the second color light and executes color composition of the individual colors of analyzed light; spacer members which are disposed in correspondence to the individual colors of light between the polarization beam splitters and the color composition optical system, with a spacer member disposed for at least one of the individual colors of light having a light blocking portion near an outer edge of an entry surface through which the analyzed light enters; a third dichroic film disposed in the spacer member in an optical path of the second color light which reflects the first color light; and a projection lens through which light resulting from the color composition is projected. 
   According to the 21th aspect of the invention, in the projection type display apparatus according to the 20th aspect, it is preferred that the light blocking portion comprises a light absorbing member. 
   According to the 22th aspect of the invention, in the projection type display apparatus according to the 20th aspect, it is preferred that the light blocking portion is formed by processing a surface of the spacer member near the outer edge of the entry surface through which the analyzed light enters so as to achieve a light scattering state. 
   According to the 23th aspect of the invention, in the projection type display apparatus according to the 20th aspect, it is preferred that the light blocking portion is formed by cutting off a corner of the spacer member near the outer edge of the entry surface. 
   According to the 24th aspect of the invention, in the projection type display apparatus according to the 20th aspect, it is preferred that a surface of the light blocking portion is processed so as to achieve a light scattering state. 
   According to the 25th aspect of the invention, in the projection type display apparatus according to the 20th aspect, it is preferred that there is further provided halfwave phase plates that are disposed in correspondence to the individual colors of light between the polarization beam splitters and the color composition optical system, and the analyzed light enters the color composition optical system as S polarized light. 
   According to the 26th aspect of the invention, a projection type display apparatus, comprises: a color separation optical system that executes color separation to separate light from a light source into individual colors of light that are first color light, second color light and third color light; reflection type light valves, each disposed in correspondence to one of the individual colors of light; polarization beam splitters each of which outputs light obtained through polarization split executed thereat on a corresponding color of light resulting from the color separation at the color separation optical system toward the reflection type light valve, analyzes light modulated at the reflection type light valve, and includes an nonreflecting portion disposed at a surface facing opposite an entry surface through which the light from the light source enters; a color composition optical system that comprises a first dichroic film that reflects the first color light and a second dichroic film that is disposed substantially orthogonally to the first dichroic film and reflects the second color light and executes color composition of the individual colors of analyzed light; spacer members which are disposed in correspondence to the individual colors of light between the polarization beam splitters and the color composition optical system; a third dichroic film disposed in the spacer member in an optical path of the second color light which reflects the first color light; and a projection lens through which light resulting from the color composition is projected. 
   According to the 27th aspect of the invention, in the projection type display apparatus according to the 26th aspect, it is preferred that the nonreflecting portion is constituted by processing the surface facing opposite the entry surface so as to achieve a light scattering state. 
   According to the 28th aspect of the invention, in the projection type display apparatus according to the 26th aspect, it is preferred that the nonreflecting portion is constituted as an indented portion formed at the surface facing opposite the entry surface. 
   According to the 29th aspect of the invention, in the projection type display apparatus according to the 26th aspect, it is preferred that the nonreflecting portion is constituted with a light absorbing member disposed at the surface facing opposite the entry surface. 
   According to the 30th aspect of the invention, in the projection type display apparatus according to the 26th aspect, it is preferred that there is further provided halfwave phase plates that are disposed in correspondence to the individual colors of light between the polarization beam splitters and the color composition optical system, and the analyzed light enters the color composition optical system as S polarized light. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic plan view of the structure adopted in a first embodiment of the projection type display apparatus according to the present invention; 
       FIG. 2  is a schematic plan view of the structure adopted in a second embodiment of the projection type display apparatus according to the present invention; 
       FIG. 3  is a schematic plan view of the structure adopted in a third embodiment of the projection type display apparatus according to the present invention; 
       FIG. 4  is a schematic plan view of the structure adopted in a fourth embodiment of the projection type display apparatus according to the present invention; 
       FIG. 5  is a schematic plan view of the structure adopted in a fifth embodiment of the projection type display apparatus according to the present invention; 
       FIG. 6  is a schematic plan view of the structure adopted in a variation example of the second embodiment of the projection type display apparatus according to the present invention; and 
       FIG. 7  is a schematic plan view of the structure adopted in a variation example of the second embodiment of the projection type display apparatus according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following is an explanation of the embodiments of the present invention, given in reference to the drawings. 
     FIG. 1  is a schematic plan view showing the structure adopted in the first embodiment of the projection type display apparatus according to the present invention.  FIG. 2  is a schematic plan view showing the structure adopted in the second embodiment of the projection type display apparatus according to the present invention.  FIG. 3  is a schematic plan view showing the structure adopted in the third embodiment of the projection type display apparatus according to the present invention.  FIG. 4  is a schematic plan view showing the structure adopted in the fourth embodiment of the projection type display apparatus according to the present invention.  FIG. 5  is a schematic plan view showing the structure adopted in the fifth embodiment of the projection type display apparatus according to the present invention. In each of the figures, an X axis, a Y axis and a Z axis extending perpendicular to one another are defined. It is to be noted that the Z axis extends perpendicular to the drawing sheet surface. 
   First Embodiment 
   In  FIG. 1 , light emitted along the Y axis from a light source  10  constituted with a lamp  10   a  and a concave mirror  10   b  assuming a parabolic surface contour travels through a polarization conversion device  11  where it is converted to linearly polarized light vibrating along the Z axis perpendicular to the drawing sheet surface. 
   The light exiting the polarization conversion device  11  enters a cross dichroic mirror  12  which is achieved by disposing a dichroic mirror  12 B having characteristics whereby blue color light (hereafter referred to as B light) is reflected and a dichroic mirror  12 RG having characteristics whereby red color light (hereafter referred to as R light) and green light (hereafter referred to as G light) are reflected so that the dichroic mirrors intersect each other orthogonally and undergoes color separation to be separated into B light that advances along the X axis and mixed light containing R light and G light that advances along the −X axis. 
   The B light resulting from the color separation changes its advancing direction at a mirror  13  to advance along the Y axis and enters a polarization beam splitter  16 B for B light. The mixed light containing the R light and the G light resulting from the color separation changes its advancing direction at a mirror  14  to advance along the Y axis, enters a dichroic mirror  15  disposed on the optical axis and having G light reflecting characteristics where it undergoes color separation to be separated into R light, which is transmitted through the dichroic mirror  15  and advances along the Y axis and G light, which is reflected at the dichroic mirror  15 , changes its advancing direction and advances along the X axis, and the R light and the G light respectively enter polarization beam splitters  16 R and  16 G for R light and G light. The color separation optical system is thus achieved. 
   Since the B light, the G light and the R light entering the polarization beam splitters  16 B,  16 G and  16 R have been polarized along the directions with which they are substantially reflected at polarization split portions  16 BP,  16 GP and  16 RP (perpendicular to the XY plane and each forming an angle of approximately 45° relative to the incident light optical axis) (namely, they have been S polarized relative to the polarization split portions), they are reflected at the corresponding polarization split portions  16 BP,  16 GP and  16 RP, exit the polarization beam splitters  16 B,  16 G and  16 R and enter reflection type light valves  17 B,  17 G and  17 R disposed so as to constitute integrated units together with the polarization beam splitters  16 B,  16 G and  16 R by using integrating members  18 B,  18 G and  18 R respectively. 
   The reflection type light valves  17 B,  17 G and  17 R each modulate the incident light by using a corresponding color signal, i.e., a B light color signal, a G light color signal or an R light color signal, and emit reflected light (modulated light exits as P polarized light, whereas unmodulated light exits as the initial S polarized light). The B light, the G light and the R light having exited the corresponding light valves reenter the polarization beam splitters  16 B,  16 G and  16 R respectively. The modulated light in the B light, the G light and the R light having reentered the polarization beam splitters is transmitted (analyzed) through the corresponding polarization split portions  16 BP,  16 GP and  16 RP and then exits the polarization split portions. The B light, the G light and the R light having exited the polarization beam splitters  16 B,  16 G and  16 R then travel through spacer members (e.g., glass substrates)  19 B,  19 G and  19 R disposed between the exit planes at the polarization beam splitters  16 B,  16 G and  16 R and entry planes of a cross dichroic prism  20  constituting the color composition optical system and enter the cross dichroic prism  20  through different entry planes. 
   The R light and the B light having entered the cross dichroic prism  20  are respectively reflected at an R light reflecting dichroic film  20 R and a B light reflecting dichroic film  20 B disposed inside the cross dichroic prism  20  so as to intersect each other orthogonally, the G light having entered the cross dichroic prism  20  is transmitted through the R light reflecting dichroic film  20 R and the B light reflecting dichroic film  20 B, the B light, the G light and the R light become combined, the composite light exits along the Y axis through the exit surface of the cross dichroic prism  20  and enters a projection lens  21  which then projects a full-color projected image onto a screen (not shown). The projection type display apparatus in the embodiment is achieved by adopting the structure described above. 
   In the first embodiment, the spacer members  19 B,  19 G and  19 R comprise cut portions  19 Ba,  19 Ga and  19 Ra formed by grinding off the peripheral corners at the surfaces thereof toward the polarization beam splitters  16 B,  16 G and  16 R. The cut portions  19 Ba,  19 Ga and  19 Ra are formed with a roughly ground finish (ground glass finish) so as to cause the light to scatter. As a result, the diffracted light (indicated with the dotted line in the figure) from the end portion of, for instance, the reflection type light valve  17 G, which becomes ghost light in the related art, is caused to enter the polarization beam splitter  16 G, is reflected at a side surface of the polarization beam splitter  16 G, exits the polarization beam splitter  16 G, enters and is scattered at the cut portion  19 Ga of the spacer member  19 G. Thus, it is not projected as ghost light through the projection lens  21 . In addition, similar diffracted light beams exiting the reflection type light valves  17 R and  17 G for the other colors of light, i.e., R light and B light, too, are blocked at the cut portions  19 Ra and  19 Ba of the spacer members  19 R and  19 B adopting structures identical to that of the spacer member  19 G, and thus, they are not projected as ghost light. 
   It is to be noted that a similar effect can be achieved by disposing a light absorbing member that absorbs incident light at the cut portions. In addition, the specific spacer member corresponding to a given color of light at which a cut portion must be formed should be determined based upon the conditions under which ghost light occurs, and such cut portions do not need to be formed in correspondence to all the colors of light, i.e., R light, B light and G light. It is to be noted that the term of “color of light” may be referred to as the term of “colored light”. 
   While the cut portions are formed by grinding the corners of the spacer members in the embodiment, light blocking portions may be formed at the polarization beam splitters without grinding the spacer members. In such a case, the ghost phenomenon can be prevented equally effectively by disposing a light blocking member such as a light absorbing member at the periphery of the exit surface facing opposite the cut portion of the spacer member. As an alternative, the corners of the exit surfaces at the polarization beam splitters may be ground off as at the spacer members instead of providing light blocking members. 
   Second Embodiment 
   Next, the projection type display apparatus achieved in the second embodiment of the present invention is explained. The explanation is given by assigning the same reference numerals to components adopting structures similar to those in the first embodiment. 
   In  FIG. 2 , light emitted along the Y axis from a light source  10  constituted with a lamp  10   a  and a concave mirror  10   b  assuming a parabolic surface contour travels through a polarization conversion device  11  where it is converted to linearly polarized light vibrating along the Z axis perpendicular to the drawing sheet surface. 
   The light exiting the polarization conversion device  11  enters a cross dichroic mirror  12 , which is achieved by disposing a dichroic mirror  12 B having characteristics whereby B light is reflected and a dichroic mirror  12 RG having characteristics whereby R light and G light are reflected so that the dichroic mirrors intersect each other orthogonally and undergoes color separation to be separated into B light, which advances along the X axis and mixed light containing R light and G light that advances along the −X axis. 
   The B light resulting from the color separation changes its advancing direction at a mirror  13  to advance along the Y axis and enters a polarization beam splitter  16 B for B light. The mixed light containing the R light and the G light resulting from the color separation changes its advancing direction at a mirror  14  to advance along the Y axis, enters a dichroic mirror  15  disposed on the optical axis and having G light reflecting characteristics where it undergoes color separation to be separated into R light, which is transmitted through the dichroic mirror  15  and advances along the Y axis and G light, which is reflected at the dichroic mirror  15 , changes its advancing direction and advances along the X axis, and the R light and the G light respectively enter polarization beam splitters  16 R and  16 G for R light and G light. The color separation optical system is thus achieved. 
   Since the B light, the G light and the R light entering the polarization beam splitters  16 B,  16 G and  16 R have been polarized along the directions with which they are substantially reflected at polarization split portions  16 BP,  16 GP and  16 RP (perpendicular to the XY plane and each forming an angle of approximately 45° relative to the incident optical axis) (namely, they have been S polarized relative to the polarization split portions), they are reflected at the corresponding polarization split portions  16 BP,  16 GP and  16 RP, exit the polarization beam splitters  16 B,  16 G and  16 R and enter reflection type light valves  17 B,  17 G and  17 R disposed so as to constitute integrated units together with the polarization beam splitters  16 B,  16 G and  16 R by using integrating members  18 B,  18 G and  18 R respectively. 
   The reflection type light valves  17 B,  17 G and  17 R each modulate the incident light by using a corresponding color signal, i.e., a B light color signal, a G light color signal or an R light color signal and emit reflected light (modulated light exits as P polarized light, whereas unmodulated light exits as the initial S polarized light) . The B light, the G light and the R light having exited the corresponding light valves reenter the polarization beam splitters  16 B,  16 G and  16 R respectively. The modulated light in the B light, the G light and the R light having reentered the polarization beam splitters is transmitted (analyzed) through the corresponding polarization split portions  16 BP,  16 GP and  16 RP and then exits the polarization split portions. 
   The R light and the B light respectively travel through halfwave phase plates  24 R and  24 B and spacer members  19 R′ and  19 B′ disposed between the exit surfaces of the polarization beam splitters  16 R and  16 B and the corresponding entry surfaces of a cross dichroic prism  20  constituting the color composition optical system, become converted to S polarized light and separately enter the dichroic prism  20 . The G light, on the other hand, passes through a spacer member  19 G′ disposed between the exit surface of the polarization beam splitter  16 G and the cross dichroic prism  20  and formed by tilting an R light reflecting dichroic film  25  relative to the optical axis and then enters the cross dichroic prism  20 . It is to be noted that a halfwave phase plate  24 G may be disposed in the optical path of the G light as shown in  FIG. 7 . In this case, the G light is converted to S polarized light and enters the cross dichroic prism  20 . However, in this implementation, an R light reflecting dichroic film is not disposed in the spacer member  19 G for the G light. 
   The R light and the B light having entered the cross dichroic prism  20  are respectively reflected at an R light reflecting dichroic film  20 R and a B light reflecting dichroic film  20 B disposed inside the cross dichroic prism  20  so as to intersect each other orthogonally, the G light having entered the cross dichroic prism  20  is transmitted through the R light reflecting dichroic film  20 R and the B light reflecting dichroic film  20 B, the B light, the G light and the R light become combined, the composite light exits along the Y axis through an exit surface of the cross dichroic prism  20  and enters a projection lens  21  via a quarterwave phase plate  23 . The projection lens  21  then projects a full-color projected image onto a screen (not shown). The projection type display apparatus in the embodiment is achieved by adopting the structure described above. 
   The R light reflecting dichroic film  25  disposed inside the spacer member  19 G′ is explained. Light having been transmitted through the quarterwave phase plate  23  and reflected at a lens surface in the projection lens  21  is then retransmitted through the quarterwave phase plate  23  and becomes converted to P polarized light. R light in this P polarized light enters the dichroic prism  20  and a portion of the R light is transmitted through the R light reflecting dichroic film  20 R to advance ahead. The transmitted R light is guided out of the optical path at the dichroic film  25 . Namely, the R light having been transmitted through the dichroic film  20 R exits the cross dichroic prism  20 , is reflected at the dichroic film  25  and thus does not enter the polarization beam splitter  16 G. Thus, no R light is allowed to enter the reflection type light valve  17 G to become reflected and advance as ghost light to the projection lens  21  through the cross dichroic prism  20 . 
   In case that the halfwave phase plate  24 G is disposed in the optical path of the G light and the G light enters the color composition optical system as the S polarized light, following ghost light is generated. The R light exiting the reflection type light valve  17 R for R light enters the cross dichroic prism  20  as the S polarized light. A portion of the R light is transmitted through the R light reflecting dichroic film  20 R to advance toward the reflection type light valve  17 B for B light, then is converted to P polarized light at the halfwave phase plate  24 B, then is transmitted through the polarization split portion of the polarization beam splitter  16 B, and then enters the reflection type light valve  17 B for B light. The R light entering the reflection type light valve  17 B for B light is reflected to advance in the reverse direction, then is transmitted through the polarization split portion of the polarization beam splitter  16 B again, and then is converted to S polarized light at the halfwave phase plate  24 B to enter the cross dichroic prism  20 . A portion of the light entering the cross dichroic prism  20  is reflected at the B light reflecting dichroic film  20 B of the cross dichroic prism  20  to enter the projection lens  21 , and then becomes the ghost light. 
   R light, which is reflected at the reflection type light valve  17 B for B light to enter the cross dichroic prism  20  again and then is transmitted through the B light reflecting dichroic film  20 B, is reflected at the R light reflecting dichroic film  20 R to advance toward the reflection type light valve  17 G for G light, then becomes P polarized light at the halfwave phase plate  24 G, then is transmitted through the polarization split portion of the polarization beam splitter  16 G, and then enters the reflection type light valve  17 G for G light. The R light entering the reflection type light valve  17 G for G light is reflected to advance in the reverse direction, then is transmitted through the polarization split portion of the polarization beam splitter  16 G again, and then is converted to S polarized light at the halfwave phase plate  24 G for G light to enter the cross dichroic prism  20  again. A portion of the R light entering the cross dichroic prism  20  is transmitted through the dichroic films  20 B and  20 R to enter the projection lens  21 , and then become the ghost light. In order to prevent the ghost light, by disposing and tilting the R light reflecting dichroic film  25  relative to the optical axis in the spacer member  19 B, the R light which is transmitted through the cross dichroic prism  20  is reflected at the R light reflecting dichroic film  25  to be discarded out of the optical axis. As a result, unnecessary R light is prevented from entering the reflection type light valve  17 B for B light. 
   In the second embodiment, a surface  16 RS facing opposite the surface at which the R light resulting from color separation enters the polarization beam splitter  16 R is formed with a roughly ground finish. Consequently, diffracted light (indicated by the dotted line in the figure) exiting, for instance, the reflection type light valve  17 R for R light, which would become ghost light in the related art, enters the polarization beam splitter  16 R, is reflected and is scattered at the roughly ground side surface  16 RS in the second embodiment to ensure that it is not projected as ghost light through the projection lens  21 . 
   If the side surface  16 RS had a polished finish instead of a roughly ground finish, the diffracted light (indicated by the dotted line in  FIG. 2 ) from the reflection type light valve  17 R would be reflected at a side surface  16 RS and a portion of the reflected light would be reflected at the B light reflecting dichroic film  20 B of the cross dichroic prism  20  to advance toward the reflection type light valve  17 G for G light. This R light would then enter the dichroic film  25  at the spacer member  19 G′, be reflected to reenter and exit the cross dichroic prism  20 , and enter the projection lens  21  to be projected as ghost light. The phenomenon of such ghost light, too, can be prevented by forming the side surface  16 RS with a roughly ground finish. 
   In addition, the light exiting, for instance, the reflection type light valve  17 R, which enters the polarization beam splitter  16 R, advances substantially parallel to the optical axis, is transmitted through the two dichroic films  20 R and  20 B in the cross dichroic prism  20  and exits the cross dichroic prism  20 , then enters the polarization beam splitter  16 B, is transmitted through the polarization beam splitter  16 B, enters the reflection type light valve  17 B, is reflected at the R light reflecting dichroic film  20 R at the cross dichroic prism  20 , is reflected at the R light reflecting dichroic film  25  in the spacer member  19 G′ to advance ahead, enters the polarization beam splitter  16 R through the surface at which the analyzed light exits and enters the side surface  16 RS near the analyzed light exit surface at the polarization beam splitter  16 R from the inside. However, since the side surface is formed with a roughly ground finish, this light is scattered and thus, it is not projected through the projection lens  21  as ghost light. 
   If the side surface  16 RS was not formed with a roughly ground finish, the R light reflected at the dichroic film  25  to reenter the polarization beam splitter  16 R and then enter the side surface  16 RS would be reflected at a side surface  16 RS to advance through the polarization beam splitter  16 R, enter the side surface facing opposite the side surface  16 Rs, be reflected at the side surface, be reflected at the surface facing opposite the reflection type light valve  17 R, reenter the side surface  16 Rs, be reflected, exit the polarization beam splitter  16 R, reenter the dichroic film  25  in the spacer member  19 G′, be reflected at the dichroic film  25  and be transmitted through the cross dichroic prism  20  to enter the projection lens  21 . Such R light might be projected as ghost light. 
   It is to be noted that a similar effect can be achieved by disposing a light absorbing member that absorbs incident light at the side surface  16 RS of the polarization beam splitter  16 R, as well. 
   While ghost light resulting from diffracted light exiting the reflection type light valve  17 R for R light, which is reflected at a side surface  16 RS of the polarization beam splitter  16 R, is reflected at the dichroic film  20 B in the cross dichroic prism  20  and is reflected at the dichroic film  25  in the spacer member  19 G′, is prevented by adopting the embodiment, light other than this diffracted light may be prevented from becoming ghost light according to the present invention. It goes without saying that the present invention may be adopted to prevent the phenomenon of ghost light resulting from diffracted light exiting the reflection type light valves  17 R,  17 G and  17 B provided in correspondence to the individual colors of light, which then enters the corresponding polarization beam splitters, is reflected at the surfaces facing opposite the surface through which the light in the specific colors resulting from the color separation has entered, exits the polarization beam splitter to advance ahead, enters the cross dichroic prism  20  where R light is reflected at the dichroic film  20 R, B light is reflected at the dichroic film  20 B, G light is transmitted through the two films to advance ahead and the R light, the B light and the G light thus undergo color composition to enter the projection lens as composite light. The advantage of the present invention may be achieved by forming side surfaces of the other polarization beam splitters  16 G and  16 B facing opposite the entry surfaces through which the individual colors of light resulting from the color separation enter with a roughly ground finish as well as the side surface at the R light polarization beam splitter  16 R or by providing a light absorbing member at the side surfaces of the polarization beam splitter  16 G and  16 B as well as the side surface at the R light polarization beam splitter  16 R. 
   Alternatively, as shown in  FIG. 6 , an indented portion may be formed at the side surface  16 RS facing opposite the entry surface of the polarization beam splitter. This indented portion should be formed at the side surface  16 RS of the polarization beam splitter  16 R along the direction perpendicular to the drawing sheet surface. The size of the indented portion should be determined in correspondence to the size of the polarization beam splitter  16 R and the diameter of the light flux exiting the reflection type light valve  17 R. At the indented portion formed at the side surface  16 Rs, as described above, light entering the side surface  16 RS is scattered and thus it does not become ghost light projected through the projection lens  21 . It is to be noted that a similar effect may be achieved by forming a similar indented portion at the side surfaces of the polarization beam splitters  16 G and  16 B for the other colors of light as well as at the side surface of the R light polarization beam splitter  16 R. 
   Third Embodiment 
   Next, the projection type display apparatus achieved in the third embodiment of the present invention is explained. The same reference numerals are assigned to components adopting structures similar to those in the second embodiment to preclude the necessity for a repeated explanation thereof. 
   In  FIG. 3 , the R light and the B light respectively travel through halfwave phase plates  24 R and  24 B and spacer members  29 R and  19 B′ disposed between the exit surfaces of the polarization beam splitters  16 R and  16 B and the corresponding entry surfaces of a cross dichroic prism  20  constituting the color composition optical system, and separately enter the dichroic prism  20 . The G light, on the other hand, passes through a spacer member  19 G′ disposed between the exit surface of the polarization beam splitter  16 G and the cross dichroic prism  20  and formed by tilting an R light reflecting dichroic film  25  relative to the optical axis and then enters the cross dichroic prism  20 . Since other structural features and functions are similar to those of the second embodiment, their explanation is omitted. 
   The spacer member  29 R in the third embodiment forms a cut portion  30 R at a side surface thereof facing opposite the entry surface through which the R light resulting from the color separation enters the polarization beam splitter  16 R, on the outer edge toward the polarization beam splitter  16 R. The cut portion  30 R is formed with a roughly ground finish. As a result, diffracted light (indicated with the dotted line in the figure) exiting, for instance, the reflection type light valve  17 R for R light, which would become ghost light in the related art after entering the polarization beam splitter  16 R, being reflected at a side surface thereof, exiting the polarization beam splitter  16 R through the exit surface and entering the cut portion  30  at the spacer member  29 , is instead scattered at the cut portion  30 R with a roughly ground finish. Thus, the phenomenon of ghost light is prevented, as in the preceding embodiments. 
   In addition, a portion of the R light exiting the reflection type light valve  17 R for R light, which would then be transmitted through the dichroic films  20 R and  20 B at the cross dichroic prism  20 , enter the reflection type light valve  17 B for B light, be reflected at the reflection type light valve  17 B for B light, be reflected at the dichroic film  20 R in the cross dichroic prism  20 , enter the spacer member  19 G′, be reflected at the R light reflecting dichroic film  25 , reflected at the dichroic film  20 R in the cross dichroic prism  20  again and enter the polarization beam splitter  17 R through the analyzed light exit surface, is instead scattered at the cut portion  30 R with a roughly ground finish at the spacer member  29 R. As a result, the light does not enter the polarization beam splitter  17 R through the analyzed light exit surface and ultimately does not enter the projection lens  21  as ghost light. 
   It is to be noted that a similar effect can be achieved by disposing a light absorbing member that absorbs incident light at the cut portion  30 R, as well. Also, the halfwave phase plate  24 G may be disposed in the spacer members  19 B as shown in the second embodiment. 
   Fourth Embodiment 
   Next, the projection type display apparatus achieved in the fourth embodiment of the present invention is explained. 
   In  FIG. 4 , light emitted along the Y axis from a light source  10  constituted with a lamp  10   a  and a concave mirror  10   b  assuming a parabolic surface contour travels through a polarization conversion device  11  where it is converted to linearly polarized light vibrating along the Z axis perpendicular to the drawing sheet surface. 
   The light having exited the polarization conversion device  11  enters a time-series color separation optical system  32  and undergos color separation to be separated into R light, G light and B light in time series (time domain). The individual colors of light then exit the time-series color separation optical system  32  in time series. The time-series color separation optical system  32  is constituted by disposing three different types of filters used to extract R light, G light and B light transmitted through them at a substantially disk-shaped member that rotates around a central axis O over substantially uniform intervals along the circumference. 
   The different colors of light resulting from the color separation at the time-series color separation optical system  32  enter a polarization beam splitter  33  along a single optical axis, are reflected at a polarization split portion  33 P, exit the polarization beam splitter  33 , enter a reflection type light valve  34  in time series, undergo the process of modulation achieved by using color signals corresponding to the individual colors of light at the reflection type light valve  34 , are reflected and reenter the polarization beam splitter  33 . The modulated light resulting from the modulation at the reflection type light valve  34  corresponding to the individual colors having entered the polarization beam splitter  33  is analyzed and extracted as transmitted light transmitted through the polarization split portion  33 P and the extracted light is then allowed to enter the projection lens  35  to be projected in an enlargement onto a screen (not shown). The projection type display apparatus in the embodiment is achieved by adopting the structure as described above. 
   The polarization beam splitter  33  used in the fourth embodiment forms a cut portion (chamfered portion)  33   a  at the outer edges of the exit surface through which the light having been analyzed at the polarization split portion  33 P exits, and the surface of the cut portion  33   a  has a roughly ground finish. As a result, diffracted light (indicated by the dotted line in the figure) from, for instance, the reflection type light valve  34 , which would become ghost light in the related art after entering the polarization beam splitter  33 , being reflected at a side surface of the polarization beam splitter  33  to advance ahead and exiting through the exit surface, is instead scattered at the cut portion  33   a  and thus, the light is not projected through the projection lens  35  as ghost light. 
   It is to be noted that a light absorbing member may be disposed at the beveled portion  33   a  to achieve a similar effect by absorbing the light which would become ghost light. In addition, as in the second embodiment, a light blocking portion may be disposed at a surface of the polarization beam splitter facing opposite the surface through which color light from the time-series color separation optical system enters to achieve a similar effect. 
   Fifth Embodiment 
   Next, the projection type display apparatus achieved in the fifth embodiment of the present invention is explained. The projection type display apparatus in the fifth embodiment differs from the projection type display apparatus in the fourth embodiment in that a member that cuts off ghost light is provided at the exit surface of the polarization beam splitter, and for this reason, the same reference numerals are assigned to components identical to those in the fourth embodiment to preclude the necessity for a repeated explanation thereof. 
     FIG. 5  shows light blocking members  36  disposed at the outer edges of the exit surface through which the light having been analyzed at a polarization split portion  33 ′P of a polarization beam splitter  33 ′ exits so as to cut off ghost light. Thus, diffracted light (indicated by the dotted line in the figure) exiting the reflection type light valve  34 , for instance, that would become ghost light in the related art after entering the polarization beam splitter  33 ′, being reflected at a side surface of the polarization beam splitter  33 ′ to advance ahead and exiting the exit surface of the polarization beam splitter  33 ′ is instead cut off at the light blocking members  36 , and ultimately, it is not projected through the projection lens  35  as ghost light. 
   It is to be noted that the light blocking members  36  may be light absorbing members that absorb light or they may be metal plate members or organic members having surfaces thereof formed with a roughly ground finish so as to scatter light. 
   By adopting any of the embodiments described above, it becomes possible to cut superfluous light that would become ghost light and thus to provide a projection type display apparatus in which projection of ghost light is prevented. 
   The above described embodiments are examples, and various modifications can be made without departing from the spirit and scope of the invention.