DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] A color separating and mixing element according to an embodiment of the present invention will be described on the basis of FIGS. 1 and 2 .

[0051] As shown in FIG. 1 , a color separating and mixing element 50 comprises, in its transparent glass cube, a first optical function surface 50 a composed of a multilayer dielectric film or the like formed on a dividing surface for dividing the cube into two triangular prisms, and a second optical function surface 50 b composed of a multilayer dielectric film or the like formed on another dividing surface. For example, the first optical function surface 50 a is arranged so as to connect an upper side on the innermost side of the transparent cube and a lower side on the front side thereof to each other, as shown in FIG. 2 ( a ). The first optical function surface 50 a has the function of transmitting both P-polarized light and S-polarized light with respect to red light, has the function of transmitting both P-polarized light and S-polarized light with respect to green light, and has the function of transmitting P-polarized light and reflecting S-polarized light with respect to blue light. On the other hand, the second optical function surface 50 b is arranged so as to connect a longitudinal side on the left innermost side of the transparent cube and a longitudinal side on the right front side thereof to each other, as shown in FIG. 2 ( b ). The second optical function surface 50 b has the function of transmitting P-polarized light and reflecting S-polarized light with respect to red light, has the function of transmitting P-polarized light and reflecting S-polarized light with respect to green light, and has the function of transmitting both P-polarized light and S-polarized light with respect to blue light.

[0052] In FIG. 1 , the color separating and mixing element 50 respectively takes a first face (bottom face in the drawing) and a second face (right face) of the cube as light incidence surfaces, respectively takes a third face (top face), a fourth face (left face), and a fifth face (innermost face) of the cube as surfaces opposite to three reflection type liquid crystal display panels 31 , and takes a sixth face (front face) of the cube as a light output surface.

[0053] The reflection type liquid crystal display panel for blue color 31 B is arranged opposite to the third face (top face) of the cube. The reflection type liquid crystal display panel is so configured that a pixel in its portion to be displayed rotates the direction of polarization of incident light (illuminating light) by 90° and reflects (modulates) the rotated incident light. Blue light which is P-polarized light is incident on the first face (bottom face) of the cube. The incident blue light which is P-polarized light passes through the first optical function surface 50 a to lead to the reflection type liquid crystal display panel 31 B, and is reflected after being changed into modulated blue light which is S-polarized light after the direction of polarization thereof is rotated by 90° by the reflection type liquid crystal display panel 31 B. The modulated blue light which is S-polarized light is reflected by the first optical function surface 50 a , and is emitted from the light output surface.

[0054] The reflection type liquid crystal display panel for red color 31 R is arranged opposite to the fourth face (left face) of the cube, and the reflection type liquid crystal display panel for green color 31 G is arranged opposite to the fifth face (innermost face) of the cube. Yellow light (Red light which is P-polarized light and green light which is S-polarized light) is incident on the second face (right face) of the cube.

[0055] The red light which is P-polarized light of the incident yellow light which is P-polarized light passes through the second optical function surface 50 b to lead to the reflection type liquid crystal display panel for red color 31 R, and is reflected after being changed into modulated red light which is S-polarized light after the direction of polarization thereof is rotated by 90° by the reflection type liquid crystal display panel 31 R. The modulated red light which is S-polarized light is reflected by the second optical function surface 50 b , and is emitted from the light output surface. The green light which is S-polarized light is reflected by the second optical function surface 50 b to lead to the reflection type liquid crystal display panel for green color 31 G, and is reflected after being changed into modulated green light which is P-polarized light after the direction of polarization thereof is rotated by 90° by the reflection type liquid crystal display panel 31 G. The modulated green light which is P-polarized light passes through the second optical function surface 50 b , and is emitted from the light output surface.

[0056] FIG. 3 is an explanatory view showing an optical system for a liquid crystal projector comprising the above-mentioned color separating and mixing element 50 . In FIG. 3 , a reflection type liquid crystal display panel for green color 31 G is arranged at the back of the color separating and mixing element 50 , a surface at the front of the color separating and mixing element 50 is a light output surface, and a projection lens (not shown) is arranged on the light output surface.

[0057] A light emitter 2 in a light source 1 is composed of a ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, or the like, and its irradiated light is emitted after being changed into parallel lights by a parabolic reflector 3 , and is introduced into an integrator lens 4 .

[0058] The integrator lens 4 is composed of pairs of lenses (a pair of fly's eye lenses), and each of the pairs of lenses introduces the light emitted from the light source 1 into the whole surface of the reflection type liquid crystal display panel 31 . The light which has passed through the integrator lens 4 is introduced into a dichroic mirror 6 through a polarization conversion system 5 .

[0059] The polarization conversion system 5 is composed of a polarizing beam splitter array (hereinafter referred to as a PBS array) The PBS array comprises a polarized light separating surface and a retardation plate (½λ plate). The polarized light separating surface in the PBS array passes P-polarized light and changes the optical path of S-polarized light by 90° in the light from the integrator lens 4 . The S-polarized light whose optical path has been changed is reflected by an adjacent polarized light separating surface and is emitted. On the other hand, the P-polarized light which has passed through the polarized light separating surface is converted into S-polarized light by the retardation plate provided on the front side (on the light exit side) and is emitted. That is, almost all lights are converted into S-polarized lights.

[0060] The dichroic mirror 6 transmits yellow light (red light and green light), while reflecting blue light. The blue light reflected by the dichroic mirror 6 is reflected by a total reflection mirror 7 so that the optical path thereof is changed. The blue light which is P-polarized light reflected by the total reflection mirror 7 is incident on the first face of the cube of the color separating and mixing element 50 .

[0061] On the other hand, the yellow light which has passed through the dichroic mirror 6 is reflected by a total reflection mirror 8 , and is introduced into a narrow-band retardation plate 9 . The narrow-band retardation plate 9 changes only the green light into P-polarized light by rotating the direction of polarization thereof by 90°. The narrow-band retardation plate 9 may be replaced with a combination of a dichroic mirror and a retardation plate. S (S-polarized light) in FIG. 3 is S-polarized light based on the polarization conversion system 5 . On the other hand, each of P-polarized light and S-polarized light in FIG. 1 is P-polarized light and S-polarized light respectively based on the first optical function surface 50 a and the second optical function surface 50 b in the color separating and mixing element 50 . The first optical function surface 50 a and the second optical function surface 50 b in FIG. 1 are directed toward the twisted direction by 90° with respect to the polarization conversion system 5 , the dichroic mirror 6 , and the total reflection mirror 7 and 8 in FIG. 3 . Therefore, S-polarized light in FIG. 3 is P-polarized light for the color separating and mixing element 50 .

[0062] FIG. 4 is an explanatory view showing another optical system for a reflection type liquid crystal projector comprising the color separating and mixing element 50 . In FIG. 4 , a reflection type liquid crystal display panel for green color 31 G is arranged at the back of the color separating and mixing element 50 , a surface at the front of the color separating and mixing element 50 is a light output surface, and a projection lens (not shown) is arranged on the light output surface.

[0063] The liquid crystal projector comprises three illuminating devices 11 R, 11 G, and 11 B (a reference numeral “ 11 ” is used when each of the illuminating devices is not specified). The illuminating device 11 R emits red light, the illuminating device 11 G emits green light, and the illuminating device 11 B emits blue light. The illuminating devices 11 R, 11 G, and 11 B differ in color of emitted light but are approximately the same in configuration. Therefore, only constituent elements in the illuminating device 11 G are assigned reference numerals, and reference numerals to be assigned to constituent elements in the other illuminating devices 11 R and 11 B are omitted.

[0064] The illuminating device 11 comprises a light source having LED chips 12 arranged therein in an array shape and having lens cells 13 arranged therein on the light output side of the LED chips 12 , and an integrator lens 14 for integrating (superimposing) lights emitted from the LED chips 12 and parallelized by the lens cells 13 and introducing the lights into the reflection type liquid crystal display panel 31 . The integrator lens 14 is composed of pairs of lenses (a pair of fly's eye lenses), and each of the pairs of lenses introduces the light emitted from the corresponding LED chip 12 into the whole surface of the reflection type liquid crystal display panel 31 . The lights emitted from the LED chips 12 are thus integrated and introduced into the reflection type liquid crystal display panel 31 , thereby making it possible to prevent the intensity distribution of lights introduced onto the reflection type liquid crystal display panel 31 (onto a screen video) from being non-uniform.

[0065] A polarization conversion system 15 is provided between the integrator lens 14 and a condenser lens 16 . Although the polarization conversion system 15 has the same configuration as that of the above-mentioned polarization conversion system 5 , the emitted light is converted into P-polarized light in the illuminating device for green color 11 G.

[0066] The illuminating devices 11 R and 11 G are arranged such that the optical axes of the respective emitted lights cross each other at an angle of 90°. A polarizing beam splitter 17 is provided at the above-mentioned crossing position. A light output surface of the polarizing beam splitter 17 is opposed to the yellow light incidence surface (the second face of the cube) in the color separating and mixing element 50 . The red light which is S-polarized light emitted from the illuminating device 11 R and the green light which is P-polarized light emitted from the illuminating device 11 G are mixed by the polarizing beam splitter 17 to be yellow light, and the yellow light is incident on the yellow light incidence surface in the color separating and mixing element 50 .

[0067] The illuminating device 11 B is opposed to the blue light incidence surface (the first face of the cube) in the color separating and mixing element 50 , and the blue light which is S-polarized light emitted from the illuminating device 11 B is incident on the blue light incidence surface in the color separating and mixing element 50 .

[0068] The polarizing beam splitter 17 can be also replaced with a wire grid having a configuration in which line-shaped members each having a width which is approximately equal to or less than the wavelength of object color light are arranged with spacing which is approximately equal to or less than the wavelength. A dichroic prism for mixing red light and green light may be used. Further, an illuminating device for emitting yellow light which is P-polarized light may be provided in place of the illuminating devices 11 R and 11 G, and a narrow-band retardation plate for changing only red light into S-polarized light may be further provided on the optical path of the yellow light. Each of P (P-polarized light) and S (S-polarized light) in FIG. 4 is P-polarized light and S-polarized light based on the polarizing beam splitter 17 (which may be the polarization conversion system 15 ). On the other hand, each of P-polarized light and S-polarized light in FIG. 1 is P-polarized light and S-polarized light respectively based on the first optical function surface 50 a and the second optical function surface 50 b in the color separating and mixing element 50 . The first optical function surface 50 a and the second optical function surface 50 b in FIG. 1 are directed toward the twisted direction by 90° with respect to the polarization conversion system 15 in FIG. 4 . Therefore, P-polarized light in FIG. 4 is S-polarized light for the color separating and mixing element 50 , and S-polarized light in FIG. 4 is P-polarized light for the color separating and mixing element 50 .

[0069] FIGS. 5 ( a ) and 5 ( b ) are explanatory views showing the relationship between an illuminating system using an integrator lens 4 and a color separating and mixing element 50 . The relationship occurs between blue light and a second optical function surface 50 b and between yellow light and a first optical function surface 50 a . FIG. 5 ( b ) simply illustrates the relationship among a light source 1 , the color separating and mixing element 50 , and a reflection type liquid crystal display panel 31 (a retardation plate or the like is also omitted), and FIG. 5 ( a ) illustrates the relationship between reflected light (modulated light) by the reflection type liquid crystal display panel 31 B and the second optical function surface 50 b in the color separating and mixing element

[0070] Light incident on one of convex lenses composing an incidence-side lens array in the integrator lens 4 is focused in the vicinity of a corresponding convex lens in an output-side lens array, is refracted toward the center by condenser lenses 21 and 22 , and is obliquely introduced into the liquid crystal display panel 31 , and the light reflected by the liquid crystal display panel 31 is obliquely incident on the color separating and mixing element 50 .

[0071] However, the second optical function surface 50 b in the color separating and mixing element 50 is arranged parallel to the direction of light output/incidence of the liquid crystal display panel for blue color 31 B, and reflects a part of modulated light reflected by the reflection type liquid crystal display panel for blue color 31 B and obliquely incident thereon. As shown in FIG. 5 ( c ), light which reaches the second optical function surface 50 b after being reflected by the reflection type liquid crystal display panel 31 B is totally reflected, and is focused at a corresponding position on a screen as if light modulated at a point a on the panel came from a point b on the panel. Further, as shown in FIG. 5 ( a ), light which does not reach the optical function surface 50 b after being reflected by the reflection type liquid crystal display panel 31 B and is modulated as it is at the point b on the panel is focused at a corresponding position on the screen. Consequently, lights from two points, i.e., the points a and b on the panel are superimposed and focused at a position corresponding to the point b on the screen, thereby producing a double image.

[0072] An illuminating optical system capable of overcoming the disadvantages of such a double image will be then described on the basis of FIGS. 6 to 8 . FIG. 6 is a perspective view showing the relationship between the second optical function surface 50 b in the color separating and mixing element 50 and the reflection type liquid crystal display panel for blue color 31 B, where the illustration of a color light separation optical system for yellow light and its optical guiding system is omitted. The color light separation optical system for yellow light and the optical guiding system are illustrated in FIG. 9 .

[0073] In the present embodiment, each of the liquid crystal display panels 31 is obliquely arranged such that the center line thereof is parallel to the optical function surfaces 50 a and 50 b . The reflection type liquid crystal display panel 31 is divided into areas using as a boundary a horizontal center line (which can be also a vertical center line) thereof. One of the areas is taken as a first irradiation area, and the other area is taken as a second irradiation area. Letting A:B be an aspect ratio in the reflection type liquid crystal display panel 31 , each of the first irradiation area and the second irradiation area is divided at a ratio of A:B/2. A first light flux from the light source 1 is introduced into the first irradiation area, and a second light flux from the light source 1 is introduced into the second irradiation area.

[0074] FIG. 6 is an explanatory view showing the outline of an optical system for a reflection type liquid crystal projector according to the present embodiment. FIG. 6 ( b ) simply illustrates the relationship among a light source 1 , a color separating and mixing element 50 , and a reflection type liquid crystal display panel 31 B (a retardation plate or the like is also omitted), and FIG. 6 ( a ) illustrates the relationship between reflected light (modulated light) by a reflection type liquid crystal display panel 31 B and a second optical function surface 50 b in the color separating and mixing element 50 .

[0075] A first integrator lens 41 and a second integrator lens 42 for averaging partial nonuniformity of luminance which exists in light are arranged on the light output side of the light source 1 . A first light flux is produced by the first integrator lens 41 , and a second light flux is produced by the second integrator lens 42 .

[0076] The first integrator lens 41 comprises a pair of lens arrays (a pair of fly's eye lenses) 41 a and 41 b , and each of convex lenses (irrespective of whether the convex lens is directed toward the light incidence side or the light output side) composing each of the lens arrays irradiates the first irradiation area of the reflection type liquid crystal display panel 31 B. That is, in the first integrator lens 41 , light incident on one of the convex lenses composing the incidence-side lens array 41 a is focused in the vicinity of the corresponding convex lens in the output-side lens array 41 b , is refracted by a condenser lens 21 , and is introduced into the reflection type liquid crystal display panel 31 B in such a manner as to cross the second optical function surface 50 b in the color separating and mixing element 50 .

[0077] The second integrator lens 42 comprises a pair of lens arrays (a pair of fly's eye lenses) 42 a and 42 b , and each of convex lenses (irrespective of whether the convex lens is directed toward the light incidence side or the light output side) composing each of the lens arrays irradiates the second irradiation area of the reflection type liquid crystal display panel 31 B. That is, in the second integrator lens 42 , light incident on one of the convex lenses composing the incidence side lens array 42 a is focused in the vicinity of the corresponding convex lens in the output-side lens array 42 b , is refracted by the condenser lens 21 , and is introduced into the reflection type liquid crystal display panel 31 B in such a manner as to cross the second optical function surface 50 b in the color separating and mixing element 50 .

[0078] Light from the light source 1 is thus changed into two light fluxes by the first integrator lens 41 and the second integrator lens 42 . The two light fluxes cross each other on the second optical function surface 50 b in the color separating and mixing element 50 , to be respectively introduced into the first irradiation area and the second irradiation area of the reflection type liquid crystal display panel 31 B. The shapes of convex lens portions in the integrator lenses are respectively similar to the shapes of the first and second irradiation areas.

[0079] By such a configuration, reflected light modulated by the reflection type liquid crystal display panel 31 B is reflected in a direction away from the second optical function surface 50 b in the color separating and mixing element 50 , not to cross the second optical function surface 50 b in the color separating and mixing element 50 . Accordingly, a double image is prevented from being formed by total reflection and transmission on the second optical function surface 50 b in the color separating and mixing element 50 . Although transmission and total reflection occur when the two light fluxes are incident on the second optical function surface 50 b , total reflection on one surface of the optical function surface before being incident on the liquid crystal display panel is canceled by total reflection on the other surface, not to lead to imbalance in brightness between the first and second irradiation areas of the liquid crystal display panel.

[0080] Assuming that the two light fluxes are respectively introduced into the first irradiation area and the second irradiation area of the reflection type liquid crystal display panel 31 B, light is not sufficiently introduced into the boundary between the first irradiation area and the second irradiation area so that a dark line may, in some cases, appear at the center of the panel.

[0081] A perspective view of FIG. 7 illustrates a projection type video display comprising a mechanism for canceling the above-mentioned dark line. In a configuration shown in FIG. 7 , condenser lenses 21 A and 21 B are respectively provided on the light output side of output-side lens arrays 41 b and 42 b in the first and second integrator lenses 41 and 42 , and are individually provided such that the movements thereof are respectively adjustable in directions perpendicular to their optical axes. The direction perpendicular to the optical axis is a direction perpendicular to the optical function surface. Although a mechanism for moving each of the condenser lenses 21 A and 21 B can be realized by constituent elements such as a lens supporting frame, a guide for guiding the lens supporting frame, and a screw member for pushing and pulling the lens supporting frame along the guide, the present invention is not limited to such a mechanism. Further, a portion between the condenser lenses 21 A and 21 B is shaded.

[0082] Furthermore, the first integrator lens 41 and the condenser lens 21 A are integrated to form a set, and the second integrator lens 42 and the condenser lens 21 B are integrated to form a set. The positions of the sets can be individually shifted. Although a mechanism for shifting the position of each of the sets can be realized by constituent elements such as a frame for supporting each set, a guide for guiding the frame for supporting each set, and a screw member for pushing and pulling the frame for supporting each set along the guide, the present invention is not limited to such a mechanism.

[0083] Irradiation areas on the liquid crystal display panel by the sets are respectively made slightly larger than the first and second irradiation areas. Since the irradiation areas are respectively made slightly larger than the first and second irradiation areas, the irradiation of the first and second irradiation areas can be maintained even if the positions of the respective sets are shifted. In addition thereto, a non-irradiation area can be prevented from appearing in the boundary therebetween. These circumstances will be described on the basis of FIG. 8 . The irradiation area is shifted (the position thereof is shifted), so that the irradiation area on the panel is enlarged, as indicated by {circle over (2)} from an irradiated state indicated by {circle over (1)} in FIG. 8 . Accordingly, the amount of irradiated light onto the center of the panel is increased so that the dark line at the center is removed.

[0084] Only by shifting the irradiation area (shifting the position thereof), the light flux crosses the second optical function surface 50 b , as indicated by {circle over (2)} in FIG. 8 . At this time, each of the condenser lenses 21 A and 21 B is moved, as shown in FIG. 7 , so that the angle of incidence of the light flux can be increased (refraction increases toward the periphery of the lens), thereby making it possible to prevent the light flux from crossing the optical function surface 50 b , as indicated by {circle over (3)} in FIG. 8 .

[0085] In the configuration shown in FIG. 6 (the configuration using the two integrator lenses), lights (secondary lights), out of lights emitted from the one convex lens in the lens array 42 a , introduced into the convex lenses other than the corresponding convex lens in the lens array 42 b cannot cross the second optical function surface 50 b in the color separating and mixing element 50 , to be introduced into the reflection type liquid crystal display panel 31 B, for example, as indicated by a dotted line in FIG. 6 , thereby making it impossible to reliably prevent the double image from being produced.

[0086] A configuration capable of overcoming the disadvantages which occur in the configuration shown in FIG. 6 or the like will be then described on the basis of FIGS. 9 to 11 .

[0087] FIG. 9 is an explanatory view showing the outline of an optical system for a reflection type liquid crystal projector. In FIG. 9 , a color light separation optical system for not only blue light but also yellow light and its light guiding system are also illustrated.

[0088] On the light output side of a light source 1 , a first light flux producer 62 for producing a first light flux and a second light flux producer 63 for producing a second light flux are arranged. The first light flux producer 62 comprises a condenser lens 62 a , a rod integrator 62 b , and a pair of lenses 62 c nd 62 d . On the other hand, the second light flux producer 63 comprises a condenser lens 63 a , a rod integrator 63 b , and a pair of lenses 63 c and 63 d . Since the first light flux producer 62 and the second light flux producer 63 have the same configuration, the first light flux producer 62 will be mainly described.

[0089] The condenser lens 62 a is arranged by occupying the half of a light output area of the light source 1 , and is obtained by cutting a circular lens larger than the half of the area in conformity with the half of the area. The center of an optical axis of the condenser lens 62 a is at a position intermediate between the center of the optical axis of the light source 1 and an edge of the light source 1 . Light condensed by the condenser lens 62 a is incident on a light incidence end surface of the rod integrator 62 b . Light incident on the rod integrator 62 b is repeatedly reflected inside the rod integrator 62 b , and is emitted from an output surface of the rod integrator 62 b . The shapes of the end surfaces on the output side of the rod integrators 62 b and 63 b are similar to the shapes of the first and second irradiation areas.

[0090] The pair of lenses 62 c and 62 d corresponds to a pair of lenses in a pair of fly's eye lenses. Light passing through the incidence-side lens 62 c is focused in the vicinity of the output-side lens 62 d , and light emitted from the output-side lens 62 d is refracted by a condenser lens 65 A and condenser lenses 66 A and 66 B, and is introduced into a first area of the reflection type liquid crystal display panel 31 in such a manner as to cross the optical function surface in the color separating and mixing element 50 . Similarly, the pair of lenses 63 c and 63 d corresponds to a pair of lenses in a pair of fly's eye lenses. Light passing through the incidence-side lens 63 c is focused in the vicinity of the output-side lens 63 d , and light emitted from the output-side lens 63 d is refracted by a condenser lens 65 B and the condenser lenses 66 A and 66 B, and is introduced into a second area of the reflection type liquid crystal display panel 31 in such a manner as to cross the optical function surface in the color separating and mixing element 50 . The condenser lenses 66 A and 66 B exist as a simple substance (a common for the first and second light fluxes) at a position on the light incidence side of the color separating and mixing element 50 , and receives two light fluxes which arrive in a crossing shape to refract the light fluxes.

[0091] The output-side lens 62 d in the pair of lenses 62 c and 62 d and the output-side lens 63 d in the pair of lenses 63 c and 63 d are respectively mounted on openings formed in a shading plate 64 , and prevent lights other than lights passing through the lenses from being introduced into the reflection type liquid crystal display panel 31 .

[0092] The light from the light source 1 is thus completely separated into independent two light fluxes, respectively, by the first light flux producer 62 and the second light flux producer 63 . The two light fluxes cross each other on the optical function surface in the color separating and mixing element 50 , and are respectively introduced into the first irradiation area and the second irradiation area of the reflection type liquid crystal display panel 31 . That is, reflected light modulated by the reflection type liquid crystal display panel 31 is reflected in a direction away from the optical function surface in the color separating and mixing element 50 , not to cross the optical function surface in the color separating and mixing element 50 . Accordingly, a double image is prevented from being formed by total reflection and transmission on the optical function surface in the color separating and mixing element 50 . Further, light is not changed into two light fluxes using a pair of integrator lenses each composed of a lot of pairs of convex lenses, as shown in FIG. 6 , and the two light fluxes are completely separated by the two rod integrators, thereby reliably preventing the double image.

[0093] In a projection type video display shown in FIG. 10 ( a ), a light source 1 ′ comprises a parabolic reflector, and emits approximately parallel lights. The shape of an opening on the light output side of the light source 1 ′ is set to an approximately square shape (similar to an aspect ratio in a liquid crystal display panel 31 ), the half thereof (corresponding to first and second irradiation areas of the liquid crystal display panel 31 ) being occupied to position a light incidence end surface of a first rod integrator 67 A, and the other half thereof being occupied to position a light incidence end surface of a second rod integrator 67 B. The sizes of output surfaces of the first and second rod integrators 67 A and 67 B and the positional relationship therebetween are the same as the sizes of the output surfaces of the rod integrators 62 b and 63 b and the positional relationship therebetween shown in FIG. 9 . Further, the same configuration as that shown in FIG. 9 is applicable to an optical system in a stage succeeding output surfaces of the first and second rod integrators 67 A and 67 B.

[0094] In the configuration shown in FIG. 10 ( a ), the necessity of the condenser lenses 62 a and 63 a shown in FIG. 9 can be eliminated, thereby reducing the number of parts in an optical system.

[0095] In a projection type video display shown in FIG. 10 ( b ), a light source 1 ″ comprises a two-focuses elliptic reflector. The two-focuses elliptic reflector is so configured that two light converging points can be formed with respect to one light emitting point, and has a first elliptic reflector area where a first light converging point is formed from one light emitting point and a second elliptic reflector area where a second light converging point is formed from the one light emitting point, for example. A light incidence end surface of a first rod integrator 68 A is positioned at the first light converging point, and a light incidence end surface of a second rod integrator 68 B is positioned at the second light converging point. The arrangement relationship between the first and second rod integrators 68 A and 68 B is the same as the arrangement relationship between the rod integrators 62 b and 63 b shown in FIG. 9 . Further, the same configuration as that shown in FIG. 9 is applicable to an optical system in a stage succeeding output surfaces of the first and second rod integrators 68 A and 68 B.

[0096] In the configuration shown in FIG. 10 ( b ), the necessity of the condenser lenses 62 a and 63 a shown in FIG. 9 can be eliminated, thereby reducing the number of parts in an optical system. Although the cone angle of light fluxes which have been emitted from each of the rod integrators 67 A and 67 B is increased because its output surface is smaller than its light incidence end surface in the configuration shown in FIG. 10 ( a ), the sizes of the light incidence end surface and the output surface of the rod integrator are made the same, thereby making it possible to prevent the cone angle from being enlarged in the configuration shown in FIG. 10 ( b ).

[0097] A reflector may be provided in an area other than the positions of two light converging points in the light source 1 ″, to return unnecessary light toward the light source 1 ″ to achieve effective utilization of light. Further, predetermined polarized light is introduced into the color separating and mixing element 50 . A polarization conversion system used therefor may be provided on the output surface of the rod integrator, as shown in FIG. 10 ( c ), rather than being provided on the light incidence side of the rod integrator. Of course, the polarization conversion system may be arranged on an optical path in a stage succeeding the output surface of the rod integrator, it is desirably arranged at a position short of the light incidence side of the dichroic mirror 6 . The polarization conversion system shown in FIG. 10 ( c ) is composed of a polarizing beam splitter (hereinafter referred to as PBS). The PBS comprises a polarized light separating surface and a retardation plate (1/2 λ plate). The polarized light separating surface in the PBS passes P-polarized light and changes the optical path of S-polarized light by 90°, for example, in the incident light. The S-polarized light whose optical path has been changed is reflected by an adjacent total reflection mirror (which may be a prism) and is emitted. On the other hand, the P-polarized light which has passed through the polarized light separating surface is converted into S-polarized light by the retardation plate (1/2 λ plate) provided on the front side (on the light exit side) and is emitted. That is, in this example, almost all lights are converted into S-polarized lights.

[0098] In a projection type video display shown in FIG. 11 ( a ), first and second rod integrators 67 A and 67 B are arranged such that their optical axes (center lines) cross each other. The crossing arrangement of the optical axes makes it possible to eliminate the necessary of the condenser lens 65 for crossing and refraction shown in FIG. 9 . Light sources 69 A and 69 B each composed of solid-state light emitting elements (e.g., LEDs (light emitting diodes)) arranged in an array shape are respectively provided on light incidence end surfaces of the rod integrators 67 A and 67 B. Although the intensity distribution of lights from the light sources 69 A and 69 B is nonuniform due to the array-shaped arrangement, the lights are superimposed (integrated) by passing through the rod integrators 67 A and 67 B, and the lights whose intensity distribution is made uniform are respectively emitted from output surfaces of the rod integrators 67 A and 67 B.

[0099] In a projection type video display shown in FIG. 11 ( b ), a light incidence end surface of a first rod integrator 68 A is positioned at a first light converging point of a light source 1 ″, and a light incidence end surface of a second rod integrator 68 B is positioned at a second light converging point. The first and second rod integrators 68 A and 68 B are arranged such that their optical axes (center lines) cross each other. The crossing arrangement of the optical axes makes it possible to eliminate the necessary of the condenser lens 65 for crossing and refraction shown in FIG. 9 .

[0100] In a configuration other than the configuration shown in FIG. 11 ( a ), a solid-state light source (an LED, a semiconductor laser, etc.) may be also used.

[0101] As described in the foregoing, the color separating and mixing element according to the present invention has two optical function surfaces formed in its cubic shape, which is a simple configuration comprising a combination of four optical parts. Therefore, the manufacture thereof is easier than that of a conventional configuration comprising six tetrahedrons, and an optical function surface for reflecting video light so as to twist the video light is eliminated, thereby making it possible to also avoid a reduction in contrast. In a video light producing device having a configuration in which lights are introduced so as to cross each other on an optical function surface, a double image can be reliably prevented from being produced. If a configuration using two rod integrators is used as the configuration in which lights are introduced so as to cross each other on an optical function surface, the double image can be reliably prevented from being produced.

[0102] Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.