Abstract:
A projector apparatus comprises: a light modulation optical system which separates white light into a plurality of light components with respective wavelength bands, controls the intensity of each of the plurality of light components, and then composes the controlled plurality of light components; a projection lens for projecting the light composed in the light modulation optical system; a light source optical system for permitting the white light to exit therefrom, the light source optical system being disposed so that the optical axis of the light source optical system is displaced relative to the optical axis of the light modulation optical system; and a focusing lens which is disposed so that the optical axis of the focusing lens is coincident with the optical axis of the light modulation optical system, for focusing the light output from the light source optical system and inputting the focused light into the light modulation optical system. By virtue of this construction, the projector apparatus can realize a small apparatus size, a thin apparatus thickness and projected images which have high illuminance and have no significant color shading.

Description:
FIELD OF THE INVENTION 
     The invention relates to a projector apparatus, and more particularly to a projector apparatus which separates white light into light components of the primary colors, modulates the separated light components, and then composes the modulated light components. 
     BACKGROUND OF THE INVENTION 
     There are various conventional projector apparatuses for projecting images according to image signals. These projector apparatuses are classified into a system wherein white light from a light source is passed through a full-color light modulator followed by projection, and a system wherein white light from a light source is separated into light components or the three primary colors which are passed through respective light modulators and then composed, followed by projection. The invention belongs to the latter system. 
     Japanese Patent Laid-Open No. 171045/1998 discloses a projector apparatus which separates light using two dichroic mirrors and composes the separated light components using a cross-dichroic prism. Technique described in this publication will be explained as a first example of prior art. 
     FIG. 3 is a side view illustrating the structure of the first example of the conventional projector apparatus. 
     The projector apparatus shown in FIG. 3 comprises a light source optical system  600 , a light separating optical system  700 , a light guide optical system  720 , a light composing optical system  780 , an projection lens  770 . 
     Light having random polarization components emitted from a light source  611  is reflected from a concave mirror  612  and then enters first and second integrators  620 ,  630 . 
     The first and second integrators  620 ,  630  each comprise a number of minute rectangular lenses, which have been continuously arranged in a planar matrix form, and function to homogenize the illuminance distribution of the incident light and then to output the homogenized light. 
     The polarization light converter  640  arranges the light, output from the first and second integrator, in a specific linear polarization direction and outputs the arranged light. This light from the light source  611  is then passed through a focusing lens  650  and a reflecting mirror  660  and is applied to irradiation areas near light valves  750 ,  752  and a light guide lens  730 . 
     A first dichroic mirror  710  reflects red light and green light components among the components of the incident light, and permits only a blue light component to be passed therethrough. The transmitted blue light component is passed through a reflecting mirror  718 , a condenser lens  744 , and a light valve  750  in that order, and then enters a cross-dichroic prism  760 . 
     The second dichroic mirror  712  permits the transmission of only the red light component out of the red light and green light components as the incident light, and reflects only the green light component. The reflected green light component is passed through the condenser lens  742  and the light valve  752  in that order, and then enters the cross-dichroic prism  760 . 
     On the other hand, the red light component passed through the second dichroic mirror  720  is passed through a light guide lens  730 , a reflecting mirror  722 , a light guide lens  734  a reflecting mirror  724 , a condenser lens  744 , and a light valve  754  in that order, and then enters the cross-dichroic prism  760 . 
     The red light, green light, and blue light components input into the cross-dichroic prism  760  are composed to form a full-color image which is then projected in an enlarged manner onto a projection screen  800  through a projection lens  770 . 
     Thus, the projector apparatus as the first example of the prior art has a structure such that light components of the three primary colors are introduced into the second cross-dichroic prism  760  from three sides around the second cross dichroic prism  760  to compose the introduced light components. 
     Japanese Patent Laid-Open No. 158167/1993 discloses a projector apparatus which separates light using a cross-dichroic mirror and composes the separated light components using another cross-dichroic mirror. The technique described in this publication will be explained as a second example of prior art. 
     FIG. 4 is a perspective view illustrating the structure of the second example of the conventional projector apparatus. 
     The projector apparatus shown in FIG. 4 comprises a light source  911 , a concave mirror  933 , a first cross-dichroic mirror  931 , reflecting mirrors  934 ,  935 ,  937 ,  938 ,  940 ,  941 , liquid crystal panels  936 ,  939 ,  942 , a second cross-dichroic mirror  932 , and a projection lens  943 . 
     Light having random polarization components emitted from the light source  911  is reflected from the concave mirror  933  and then enters the first cross-dichroic mirror  931 . 
     The first cross-dichroic mirror  931  comprises a combination of a red transmission cross-dichroic mirror and a blue transmission cross-dichroic mirror which each are disposed on the optical axis  911   x  of the light source  911  so as to be inclined at 45 degrees to the optical axis  911   x  and to be orthogonal to each other and functions to separate white light from the light source  911  into light components of the three primary colors, red light, green light, and blue light components. 
     A pair of reflecting mirrors  934  and  935 , a pair of reflecting mirrors  937  and  938 , and a pair of reflecting mirrors  940  and  941  are disposed respectively on the optical paths of green light, red light, and blue light components to bend each of the optical paths to form a “⊃” shape. 
     The second cross-dichroic mirror  932  comprises a combination of a red reflection dichroic mirror and a blue reflection dichroic mirror which each are disposed so as to be inclined at 45 degrees to the output optical axis and to be disposed orthogonal to each other. The second cross-dichroic mirror  932  is disposed just under and adjacent to the first cross-dichroic mirror  931 , and composes the green light, red light, and blue light components reflected by the reflecting mirrors  935 ,  938 ,  941  to form a full-color light which is then output. 
     The full-color light composed by the second cross-dichroic mirror  932  is projected as a projection image by the projection lens  943  onto the projection screen  944 . 
     Thus, in the projector apparatus according to the second example of the prior art, the adoption of a structure, wherein the first and second cross-dichroic mirrors  931 ,  932  are put on top of the other respectively as upper and lower cross-dichroic mirrors so as to be adjacent to each other, has eliminated the need to provide the light guide optical system  720  in the projector apparatus according to the first example of the prior art. 
     The projector apparatuses according to the above examples of the prior art, however, had the following problems. 
     In the projector apparatus according to the first example or the prior art, the light components of the three primary colors should be introduced from the three sides around the second cross-dichroic prism  760 . Therefore, the provision of the light guide optical system  720  is indispensable for the structure. 
     Since, however, the optical path length of the red light component passed through the light guide optical system  720  is different from the optical path lengths of the green light and blue light components not passed through the light guide optical system  720 , the illuminance distribution on a light valve  733  on the optical path of the red light component is unfavorably different from the illuminance distributions on light valves  731 ,  732  on the light paths of the green light and blue light components. Consequently, when white is displayed on the whole projection screen, a problem of color shading occurs, that is, there is a difference in color between the center portion of the projected image on the projection screen  800  and the periphery of the projected image. 
     Likewise, since the quantity of the red light component incident to the projection lens  770  is different from the quantity of the green light and blue light components, when white is displayed on the whole projection screen  800 , a problem of color shading occurs in the projected image on the projection screen  800 . 
     Unlike the first example of the prior art, the projector apparatus as the second example of the prior art does not have the light guide optical system  720  and thus does not pose the above problem. Instead, however, since the structure, wherein the first and second cross-dichroic mirror  931 ,  932  are vertically put on top of the other, is indispensable for the projector apparatus as the second example of the prior art, a light source having a large volume should be disposed adjacent to these cross-dichroic mirrors. This poses a problem of an increased height of the projector apparatus. 
     Further, since the projector apparatus as the second example of the prior art does not have any optical device for homogenizing the illuminance distribution, such as integrators, in the light source section, the illuminance distribution of the projection screen  944  is heterogeneous, that is, such that the center portion is bright while the peripheral portion is dark. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a projector apparatus which is small and thin and can produce projected images having high illuminance and having no significant color shading. 
     The above object can be attained by the following features. 
     According to the first feature of the invention, a projector apparatus comprises: 
     a light modulation optical system ( 1  in FIG. 2) which separates white light into a plurality of light components with respective wavelength bands, controls the intensity of each of said plurality of light components, and then composes the controlled plurality of light components; 
     a projection lens ( 460 ) for projecting the light composed in the light modulation optical system ( 1 ); 
     a light source optical system ( 100 ) for permitting the white light to exit therefrom, the light source optical system ( 100 ) being disposed so that the optical axis ( 10   x ) of the light source optical system ( 100 ) is displaced relative to the optical axis ( 200   x ) of the light modulation optical system ( 1 ); and 
     a focusing lens ( 150 ) which is disposed so that the optical axis ( 150   x ) of the focusing lens is coincident with the optical axis ( 200   x ) of the light modulation optical system ( 1 ), for focusing the light output from the light source optical system ( 100 ) and inputting the focused light into the light modulation optical system ( 1 ). 
     According to the second feature of the invention, a projector apparatus comprises; 
     a light separating optical system ( 200  in FIG. 2) which separates white light into a plurality of light components with respective wavelength bands; 
     a light guide optical system ( 250 ) for bending the optical paths of said plurality of light components, which have been output from the light separating optical system ( 200 ), so as to form a “⊃” shape; 
     a light composing optical system ( 400 ) which is disposed adjacent to the light separation optical system ( 200 ) and composes the plurality of light components output from the light guide optical system ( 250 ); 
     light modulators ( 431  to  433 ) which are disposed respectively on optical paths between the light separating optical system ( 200 ) and the light composing optical system ( 400 ) to control the intensity of the plurality of light components; 
     a projection lens ( 460 ) for projecting the light composed in the light composing optical system ( 400 ); 
     a light source optical system ( 100 ) for permitting the white light, which has been polarized in a specific polarization direction, to exit therefrom, the light source optical system being disposed so that the optical axis ( 100   x ) of the light source optical system ( 100 ) is displaced relative to the optical axis ( 200   x ) of the light separating optical system ( 200 ); and 
     a focusing lens ( 150 ) which is disposed so that the optical axis ( 150   x ) of the focusing lens is coincident with the optical axis ( 200   x ) of the light separating optical system ( 200 ), for focusing the light output from the light source optical system ( 100 ) and inputting the focused light into the light separating optical system ( 200 ). Preferably, the projector apparatus may further comprise: a first relay lens ( 510 ) disposed between the focusing lens ( 150 ) and the light separating optical system ( 200 ); and a second relay lens ( 521  to  523 ) disposed between the light separating optical system ( 200 ) and the light modulators ( 431  to  433 ). 
     Thus, according to the projector apparatus of the invention, the light guide optical system is provided on all the optical paths of the three primary colors so that, for all the three primary colors, the optical path length and the structure of the optical systems on the optical paths are identical Therefore, the occurrence of color shading can be prevented even at the time of the display of white on the whole projection screen. 
     The provision of the relay optical system can enhance the efficiency for light utilization, and thus can enhance the illuminance of projected images as compared with the projector apparatus according to the first example of the prior art. 
     The vertical displacement of the optical axis of the light source optical system relative to the optical axis of the light separating optical system enables the height of the projector apparatus to be reduced to the sum of the height of the light separating optical system and the height of the light composing optical system, and thus can significantly reduce the thickness of the projector apparatus as compared with the projector apparatus according to the second example of the prior art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in more detail in conjunction with the appended drawings, wherein; 
     FIG. 1 is a perspective view illustrating the structure of the projector apparatus according to one preferred embodiment of the invention; 
     FIG. 2 is a partial side view illustrating the structure of the projector apparatus according to the preferred embodiment shown in FIG. 1; 
     FIG. 3 is a side view illustrating the structure of the projector apparatus according to a first example of the prior art; and 
     FIG. 4 is a perspective view illustrating the structure of the projector apparatus according to a second example of the prior art. 
    
    
     REFERENCE NUMERALS IN DRAWING 
     B: BLUE LIGHT 
     D: DISPLACEMENT 
     G: GREEN LIGHT 
     I: LIGHT MODULATION OPTICAL SYSTEM 
     R: RED LIGHT 
     T: THICKNESS 
       100 : OPTICAL SYSTEM FOR LIGHT SOURCE 
       100   x:  OPTICAL AXIS 
       110 : OPTICAL SYSTEM FOR LIGHT SOURCE 
       111 : LIGHT SOURCE 
       112 . CONCAVE MIRROR 
       120 : 1ST INTEGRATOR 
       130 : 2ND INTEGRATOR 
       140 : POLARIZATION LIGHT CONVERTER 
       150 : FOCUSING LENS 
       150   x:  OPTICAL AXIS 
       171 : REFLECTING PRISM 
       172 : REFLECTING PRISM 
       200 : COLOR SEPARATING OPTICAL SYSTEM 
       200   x.  OPTICAL AXIS 
       240 : CROSS DICHROIC MIRROR 
       250 : LIGHT GUIDE OPTICAL SYSTEM 
       253 : REFLECTING MIRROR 
       254 : REFLECTING MIRROR 
       261 : REFLECTING PRISM 
       262 : REFLECTING PRISM 
       263 : REFLECTING PRISM 
       400 : COLOR COMPOSING OPTICAL SYSTEM 
       411 : CONDENSER LENS 
       412 : CONDENSERLENS 
       413 : CONDENSERLENS 
       421 : POLARIZER 
       422 : POLARIZER 
       423 : POLARIZER 
       431 : LIGHT VALVE 
       432 : LIGHT VALVE 
       433 : LIGHT VALVE 
       441 : ANALYZER 
       442 : ANALYZER 
       443 : ANALYZER 
       450 : CROSS DICHROIC: PRISM 
       460 : PROJECTION LENS 
       460   p:  ENTRANCE PUPL 
       500 : RELAY OPTICAL SYSTEM 
       510 : 1ST RELAY LENS 
       522 : 2ND RELAY LENS 
       523 : 2ND RELAY LENS 
       600 : OPTICAL SYSTEM FOR LIGHT SOURCE 
       611 . LIGHT SOURCE 
       612 : CONCAVE MIRROR 
       620 : 1ST INTEGRATOR 
       630 : 2ND INTEGRATOR 
       640 : POLARIZATION LIGHT CONVERTER 
       650 : FOCUSING LENS 
       660 : REFLECTING MIRROR 
       700 : COLOR SEPARATING OPTICAL SYSTEM 
       710 : 1ST DICHROIC MIRROR 
       712 : 2ND DICHROIC MIRROR 
       718 : REFLECTING MIRROR 
       720 : LIGHT GUIDE OPTICAL SYSTEM 
       722 : REFLECTING MIRROR 
       724 : REFLECTING MIRROR 
       730 : LIGHT GUIDE LENS 
       732 : LIGHT GUIDE LENS 
       740 : CONDENSER LENS 
       742 : CONDENSER LENS 
       744 : CONDENSER LENS 
       750 : LIGHT VALVE 
       752 : LIGHT VALVE 
       754 : LIGHT VALVE 
       760 : CROSS DICHROIC PRISM 
       770 : PROJECTION LENS 
       780 : LIGHT COMPOSING OPTICAL SYSTEM 
       800 : PROJECTION SCREEN 
       911 : LIGHT SOURCE 
       911   x:  OPTICAL AXIS 
       931 : 1ST CROSS DICHROIC MIRROR 
       932 : 2ND CROSS DICHROIC MIRROR 
       933 : CONCAVE MIRROR 
       934 : REFLECTING MIRROR 
       935 : REFLECTING MIRROR 
       936 : LIQUID CRYSTAL PANEL 
       937 : REFLECTING MIRROR 
       938 : REFLECTING MIRROR 
       939 : LIQUID CRYSTAL PANEL 
       940 : REFLECTING MIRROR 
       941 : REFLECTING MIRROR 
       942 : LIQUID CRYSTAL PANEL 
       943 : PROJECTION LENS 
       944 : PROJECTION SCREEN 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view illustrating the structure of the projector apparatus according to one preferred embodiment of the invention, and FIG. 2 a partial side view illustrating the structure of the projector apparatus according to the preferred embodiment shown in FIG.  1 . In FIG. 2, for facilitating the understanding of the invention, only the optical path of the green light component among the light components of the three primary colors is shown, and, in addition, reflecting prisms  171 ,  172  are not shown. 
     The projector apparatus shown in FIGS. 1 and 2 comprises a light source optical system  100  (FIG.  2 ), a focusing lens  150 , a light separating optical system  200  (FIG.  2 ), a light guide optical system  250  (FIG.  2 ), light valves  431  to  433 , a light composing optical system  400  (FIG.  2 ), a projection lens  460 , and a relay optical system  500  (FIG.  2 ). 
     Among these elements, the light separating optical system  200  (FIG.  2 ), the light guide optical system  250  (FIG.  2 ). the light valves  431  to  433 , the light composing optical system  400  (FIG.  2 ), and the relay optical system  500  (FIG. 2) constitute a light modulation optical system  1  as a whole. 
     The light source optical system  100  comprises: a light source  111 , such as a halogen lamp; a concave mirror  112  for reflecting the light, emitted from the light source  111 , in a specific direction; first and second integrators  120 ,  130  comprising a large number of minute rectangular lenses arranged in a planar matrix form; and a polarization light converter  140  which arranges the polarization direction of the incident light in a specific linear polarization direction and outputs the arranged light. 
     The focusing lens  150  is a lens which is disposed so that the optical axis  150   x  thereof is displaced vertically and downward by D relative to the optical axis  100   x  of the light source optical system  100 . The focusing lens  150  transfers and applies the light from the light source optical system  100  to a first relay lens  511  in the relay optical system  500  which will be described below in more detail. 
     As shown in FIG. 1, a reflecting prism  171  is disposed between the first and second integrators  120 ,  130 , and a reflecting prism  172  is disposed between the focusing lens  150  and the first relay lens  510 . The reflecting prisms  171 ,  172  function to bend the optical paths to reduce the bottom area of the optical system. Reflecting mirrors may be substituted for these reflecting prisms  171 ,  172 . 
     The light separating optical system  200  is disposed so that the incident light axis  200   x  thereof is coincident with the optical axis  150   x  of the focusing lens  150 . The light separating optical system  200  comprises a cross-dichroic mirror  240  which separates the white light from the focusing lens  150  into light components of the three primary colors, that is, red light, green light, and blue light components. The cross-dichroic mirror  240  comprises a combination of a red reflection dichroic mirror and a blue reflection dichroic mirror which each are disposed so as to be inclined at 45 degrees to the input optical axis  200   x  and to be disposed orthogonal to each other. 
     The light guide optical system  250  is disposed on each of the optical paths of the light components of the three primary colors, and comprises reflecting prisms  261  to  263  which totally reflect upward the respective light components of the three primary colors output from the cross-dichroic mirror  240  disposed in a crossed form. The reflecting prisms  261  to  263  respectively comprise a pair of reflecting mirrors  251  and  252 , a pair of reflecting mirrors  253  and  254 , and a pair of reflecting mirrors  255  and  256 . 
     According to input image signals, light valves  431  to  433  modulate, pixel by pixel, the transmission intensity of the incident light for each of the light components of the three primary colors, that is, the red light, green light, and blue light components. 
     Further, condenser lenses  411  to  413  are disposed on the incident aide of the light valves  431  to  433  in order to input the light, incident to the light valves  431  to  433 , into an entrance pupil  460   p  of the projection lens  460  without any loss. 
     Polarizers  421  to  423  and analyzers  441  to  443  for inhibiting unnecessary polarized light components are disposed so as to sandwich the light valves  431  to  433  between the polarizers  421  to  423  and the analyzers  441  to  443 . 
     The light composing optical system  400  comprises a cross-dichroic prism  450  for composing the light components modulated by the light valves  431  to  433 . The cross-dichroic prism  450  comprises a combination of a prism having a red reflection dichroic mirror face and a prism having a blue reflection dichroic mirror face which are disposed so as to be inclined at 45 degrees to the incident optical axis and to be orthogonal to each other. 
     This cross-dichroic prism  450  in the light composing optical system  400  is disposed just above and adjacent to the cross-dichroic prism  240  in the light separating optical system  200 . 
     The projection lens  460  projects the light composed in the cross-dichroic prism  450  onto a projection screen  470 . 
     The relay optical system  500  comprises a first relay lens  510  and a second relay lens  521  to  523 . 
     The first relay lens  510  is disposed in a first irradiation region between the focusing lens  150  and the cross-dichroic prism  240 , and the white light output from the focusing lens  150  is transferred and applied to the first relay lens  510 . 
     The second relay lenses  521  to  523  (the second relay lens  521  not shown) are disposed respectively on the optical paths of the light components or the three primary colors to transfer and apply the image formed on the first relay lens  510  as the first irradiation region to the light valves  431  to  433  as the second irradiation region, 
     The features of this preferred embodiment are as follows. 
     (1) The optical axes  150   x,    200   x  of the optical systems provided behind the focusing lens  150  are displaced vertically and downward by D relative to the optical axis  100   x  of the light source optical system  100 . 
     (2) The first relay lens  510  is provided in the first irradiation region for the focusing lens  150 . 
     (3) the second relay lenses  521  to  523  are provided for transferring applying the optical image in the first irradiation region near the first relay lens  510  onto the second irradiation region near the light valves  431  to  433 . 
     Next, the principle of the operation of the projector apparatus according to the preferred embodiment will be described. 
     In the projector apparatus shown in FIGS. 1 and 2, light emitted from the light source  111  as a point light source and having heterogeneous illuminance distribution and random polarization components is focused on the concave mirror  112  and then enters the first integrator  120 . 
     The light incident to the first integrator  120  are converted by a large number of minute rectangular lenses constituting the first integrator  120  to light components of a large number of minute rectangular regions which are then output. 
     The light output from the first integrator  120  is input into the second integrator  130  which applies the light to the first irradiation region near the first relay lens  510 . 
     The light, which is random in polarization direction, output from the second integrator  130  enters the polarization light converter  140 , where the light is arranged in a specific linear polarization direction and is then output. 
     The focusing lens  150  puts the illuminance distribution of the minute regions cut off in the first integrator  120  onto the first irradiation region near the first relay lens  510 . 
     Thus, the light output from the light source  111  is homogeneously applied to the first irradiation region near the first relay lens  510  through the first and second integrators  120 ,  130  and the focusing lens  150 . 
     Here the focusing lens  150  is disposed so that the optical axis  150   x  of the focusing lens  150  is displaced vertically and downward by D relative to the optical axis  100   x  of the light source optical system  100 . More specifically, a satisfactory level of displacement D is provided which meets a relationship represented by formula D≦T wherein D represents the level of displacement of the optical axis  150   x  of the focusing lens  150  relative to the optical axis  100   x  of the light source optical system  100 ; and T represents the thickness of the polarization light converter  140 . 
     Thus, as shown in FIG. 2, in the focusing lens  150  having an outer shape such that a part of a circle has been cut off, the optical path of the light from the light source  111  is refracted downward when it passes through the focusing lens  150  in its upper end, while the optical path passed through the focusing lens  150  in its lower end is not refracted. Therefore, the whole luminous flux can be applied without any loss to the incident face of the cross-dichroic prism  240  having a smaller area than the output face of the concave mirror  112 . 
     According to this construction, the outer dimension of the first and second relay lenses  510  and  521  to  523  can be reduced by at least 50% as compared with the outer dimension of the focusing lens  150 . 
     The white light from the first relay lens  510  enters the first cross-dichroic mirror  240 , and is separated into light components of the three primary colors, that is, red light, green light, and blue light components. 
     The separated light components of the three primary colors are reflected by the reflecting prisms  261  to  253 , and are applied by the second relay lenses  521  to  523  to the light valves  431  to  433  in the second irradiation region. 
     For the light components incident to the light valves  431  to  433 , that is, the red light, green light, and blue light components, the transmission intensity is modulated, pixel by pixel, according to image signals, followed by light composing in the cross-dichroic prism  450 . 
     The composed light is projected as a full-color image onto the projection screen  470  through the projection lens  460 . 
     Here the condenser lenses  411  to  413  disposed on the incident side of the light valves  431  to  433  for the respective colors focus the incident light on the entrance pupil  460   p  of the projection lens  460  without any loss to enhance the illuminance of the projected image on the projection screen  470 . 
     Further, for the polarizers  421  to  423  and the analyzers  441  to  443  disposed so as co sandwich the light valves  431  to  433  for the respective colors between the polarizers  421  to  423  and the analyzers  441  to  443 , the coincidence of the polarization direction of the incident light to the polarization direction of the light valves  431  to  433  can enhance the illuminance of the projected image on the projection screen  470 . 
     Thus, in the projector apparatus of the invention, the vertical height of the projector apparatus can be reduced to the sum of the height of the light separating optical system and the height of the light composing optical system. 
     Further, in the examples of the prior art, the distance between the first and second integrators is unconditionally determined by the dimension of the minute rectangular lenses of the first and second integrators. Therefore, in this case, the small-size construction of the first and second integrators and the efficiency for light utilization are traded off against each other. By contrast, according to the invention, by virtue of the provision of the first and second relay lenses to perform transfer and application of light, the distance between the first and second integrators is not limited. Therefore, both the small-size construction and the high efficiency for light utilization can be realized. 
     Transmission liquid crystal light valves have been used as the light modulator in the above preferred embodiment. Instead of the transmission liquid crystal light valve, it is possible to use liquid crystal light valves of types other than the transmission type or transmission light valves of types other than the liquid crystal type. 
     Further, in the above preferred embodiment, a cross-dichroic mirror has been used for light separation purposes, while a cross-dichroic prism has been used for light composing purposes. However, conversely, the crossdichroic mirror may be used for light composing purposes with the cross-dichroic prism being used for light separation purposes. Further, either a plurality of cross-dichroic mirrors or a plurality of cross-dichroic prisms may be used. 
     As is apparent from the forgoing description, the projector apparatus according to the invention has the following effects. 
     First, the size and thickness of the projector apparatus can be advantageously reduced. 
     This is because the adoption of a structure, wherein the light separating optical system and the light composing optical system have been put on top of the other vertically adjacent to each other, can reduce the bottom area of the whole optical system and can reduce the area necessary for installing the projector apparatus per se and, in addition, can reduce the height, for example, to about two-third of the liquid crystal projector apparatus according to the second example of the prior art. 
     The second advantage is that the illuminance of the projected image can be enhanced. 
     More specifically, the provision of the first and second relay leases enables the image formed on the first relay lens to be transferred and applied onto the light valves through the second relay lenses. Therefore, the distance between the focusing lens and the first relay lens can be set as desired independently of the outer dimension of the light valves. Thus, the first and second integrators can be disposed at any desired position, and the conversion efficiency of the polarization light converter can be enhanced. 
     The third advantage is to eliminate color shading of projected images. 
     This advantage is attributable to the fact that the optical path lengths for the three primary colors are identical to one another and, in addition, the construction of the optical systems provided on the respective optical paths are identical to one another. 
     The invention has been described in detail with particular reference to preferred embodiments, but it will be understood that variations and modifications can be effected within the scope of the invention as oat forth in the appended claims.