JP2006091727A - Color separating and mixing optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color separating and mixing optical system which is more lightweight than a conventional color separating and mixing optical system using four polarization beam splitters, prevents birefringence due to heat absorption of a polarization beam splitter, can make a display image high in luminance by relaxing restrictions on an optical system F value, and prevents an increase in back focus of a projection optical system and an increase in size (volume) of the whole optical system. <P>SOLUTION: The color separating and mixing optical system has a condenser lens 4, a concave lens 5a on which luminous flux having passed through the condenser lens 4 is incident, a color splitting means having at least a wire grid polarizing plate 7, a 1st field lens 5b on which 1st and 2nd color component light beams having passed through the color splitting means are incident, and a 2nd field lens 5c on which a 3rd color component light beam having passed through the color splitting means is incident. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color separation / synthesis optical system that separates an incident light beam into three primary colors, combines them again, and emits them in an image display device or the like.

  Conventionally, an image display apparatus using a reflective spatial light modulator has been proposed. Such an image display device is configured as a projector for a so-called home theater or a presentation device, and its usage frequency is increasing year by year. Further, in such an image display device, the image quality of the display image is improved, and the device configuration is reduced in size and weight.

  In such an image display apparatus, as described in Patent Document 1, a color separation / synthesis optical system configured using a polarization beam splitter is used. This color separation / synthesis optical system separates an incident light beam from a light source into three primary colors, illuminates a reflective spatial light modulation element for each color with these three primary color lights, and reflects the reflected light beam from these reflective spatial light modulation elements. It is an optical system that combines again and emits it toward the imaging system.

  FIG. 4 is a plan view showing a configuration of a conventional color separation / synthesis optical system used in the image display apparatus.

  In this color separation / synthesis optical system, as shown in FIG. 4, the light beam emitted from the light source 101 is incident on the condenser lens 104 through the pair of fly-eye lens arrays 102 and 103. The light beam that has passed through the condenser lens 104 is incident on the first wavelength selective polarization conversion element 106 through the field lens 105.

  The first wavelength-selective polarization conversion element 106 is an optical element configured by laminating retardation plates, and is a filter that rotates the direction of the polarization plane of only a specific wavelength band by 90 °. In the light beam transmitted through the first wavelength selective polarization conversion element 106, the polarization plane of the blue component light B is orthogonal to the polarization planes of the red component light R and the green component light G (yellow component light Y). ing.

  The light beam that has passed through the first wavelength selective polarization conversion element 106 is incident on the first polarization beam splitter 107. In the first polarization beam splitter 107, the blue component light B is S-polarized light, the red component light R, and the green component light G (yellow component light Y) is P-polarized light with respect to the polarization separation film 107a. Accordingly, in the first polarization beam splitter 107, the blue component light B is reflected by the polarization separation film 107a, and the red component light R and the green component light G (yellow component light Y) are transmitted through the polarization separation film 107a.

  The red component light R and the green component light G (yellow component light Y) emitted from the first polarization beam splitter 107 are incident on the second wavelength selective polarization conversion element 108. The second wavelength-selective polarization conversion element 108 sets the polarization plane of the red component light R orthogonal to the polarization plane of the green component light G, and uses the red component light R and the green component light G (yellow component light). Y) is transmitted.

  The light beam that has passed through the second wavelength selective polarization conversion element 108 is incident on the second polarization beam splitter 109. In the second polarization beam splitter 109, the red component light R is P-polarized light and the green component light G is S-polarized light with respect to the polarization separation film 109a. The red component light R is transmitted through the polarization separation film 109 a, is emitted from the second polarization beam splitter 109, and enters the red reflective spatial light modulation element 110. Further, the green component light G is reflected by the polarization separation film 109 a, is emitted from the second polarization beam splitter 109, and enters the green reflective spatial light modulator 111.

  The red reflective spatial light modulator 110 and the green reflective spatial light modulator 111 are so-called reflective liquid crystal display devices, which respectively modulate the polarization of incident light according to the red and green components of the display image. Reflect.

  The first modulated light modulated and reflected by the red reflective spatial light modulator 110 is incident on the second polarization beam splitter 109 again. Since the first modulated light is S-polarized with respect to the polarization separation film 109 a, it is reflected by the polarization separation film 109 a and is transmitted from the second polarization beam splitter 109 to the first polarization beam splitter 107. The light is emitted in a direction different from the returning direction.

  The second modulated light modulated and reflected by the green reflective spatial light modulator 111 is incident on the second polarization beam splitter 109 again. Since the second modulated light is P-polarized with respect to the polarization separation film 109a, the second modulated light is transmitted through the polarization separation film 109a and is transmitted from the second polarization beam splitter 109 to the first polarization beam splitter 107. The light is emitted in a direction different from the direction returning to.

  On the other hand, the blue component light B emitted from the first polarization beam splitter 107 is incident on the third polarization beam splitter 112. In the third polarization beam splitter 112, the blue component light B is S-polarized with respect to the polarization separation film 112a. The blue component light B is reflected by the polarization separation film 112a, is emitted from the third polarization beam splitter 112, and enters the blue reflective spatial light modulator 113. The blue reflective spatial light modulator 113 is a so-called reflective liquid crystal display device, and reflects incident light by polarization-modulating it according to the blue component of the display image.

  The third modulated light modulated and reflected by the blue reflective spatial light modulator 113 is incident on the third polarization beam splitter 112 again. Since the third modulated light is P-polarized with respect to the polarization separation film 112a, the third modulation light is transmitted through the polarization separation film 112a and is transmitted from the third polarization beam splitter 112 to the first polarization beam splitter 107. The light is emitted in a direction different from the direction returning to.

  The first and second modulated lights emitted from the second polarization beam splitter 109 are incident on the third wavelength selective polarization conversion element 114. The third wavelength-selective polarization conversion element 114 rotates the polarization plane of the first modulated light by 90 °, transmits the first and second modulated lights, and enters the fourth polarization beam splitter 115. At this time, the polarization planes of the first and second modulated lights are in the same direction.

  Further, the third modulated light emitted from the third polarizing beam splitter 112 is incident on the fourth polarizing beam splitter 115.

  In the fourth polarization beam splitter 115, the first and second modulated lights are P-polarized light and the third modulated light is S-polarized light with respect to the polarization separation film 115a. The first and second modulated lights pass through the polarization separation film 115a and are emitted from the fourth polarization beam splitter 115. The third modulated light is reflected by the polarization separation film 115 a and is emitted from the fourth polarization beam splitter 115. In this way, the first and second modulated light and the third modulated light are combined.

The first to third modulated lights emitted from the fourth polarization beam splitter 115 enter the projection optical system 116. The projection optical system 116 projects the first to third modulated light onto the screen and displays an image.
JP 2000-284228 A

  Incidentally, the image display apparatus using the conventional color separation / synthesis optical system shown in FIG. 4 has the following problems because the color separation / synthesis optical system uses four polarization beam splitters. It was. That is, the polarization separation film of the polarization beam splitter is formed of a multilayer film, and the optical characteristics depend on the incident angle of incident light. Therefore, in order to maintain good color reproducibility in this color separation / synthesis optical system, it is necessary to limit the incident angle range of incident light to each polarization beam splitter. Therefore, the optical system F value is limited, and it is difficult to increase the brightness of the display image.

  Further, in this image display device, in the glass prism constituting the polarization beam splitter, a temperature distribution due to heat absorption occurs and birefringence occurs, so that there is a possibility that the image quality and contrast of the display image are lowered.

  Further, in this image display device, it is necessary to form the glass prism with a glass material having a small photoelastic coefficient in order to reduce the influence of birefringence in the glass prism constituting the polarizing beam splitter. A glass material having a small photoelastic coefficient contains a large amount of lead and has a large specific gravity, which increases the weight of the entire color separation / synthesis optical system.

  Here, as shown in FIG. 5, it is conceivable to replace three of the four polarizing beam splitters with wire grid polarizers. In other words, the first to third polarization beam splitters 107, 109, and 112 are replaced with the wire grid polarizers 107b, 109b, and 112b that are disposed at an inclination of 45 ° with respect to the incident optical axis, whereby the above-described color separation / synthesis is performed. The same action as that of the optical system can be obtained. This is because the wire grid polarizer exhibits the same action as the polarization separation film of the polarization beam splitter in that it transmits only the P-polarized light component of the incident light and reflects the S-polarized light component.

  However, in the color separation / synthesis optical system using three wire grid polarizers as described above, the following problems occur. That is, when the polarizing beam splitter disposed in the vicinity of the reflective spatial light modulator is replaced with a wire grid polarizing plate, the portion of the polarizing beam splitter that is a glass material becomes air having a refractive index of 1. Then, the optical distance to the projection optical system becomes longer corresponding to the ratio of the refractive index of air and glass material, and as a required performance for the projection optical system, it is necessary to increase the back focus. It becomes difficult to design.

  In this color separation / synthesis optical system, the wire grid polarizing plate is disposed at an angle of 45 ° with respect to the optical axis on the optical path from the reflective spatial light modulator to the projection optical system. It has been found that astigmatism occurs in the grid polarizing plate and the resolution of the displayed image is significantly deteriorated. This is because the wire grid polarizing plate exerts the same optical action on transmitted light as a plane parallel plate inclined with respect to the optical axis.

  Furthermore, in this color separation / synthesis optical system, it is possible to reduce the weight by replacing the polarizing beam splitter with a wire grid polarizing plate, but the size (volume) of the entire optical system is rather increased. It is had.

  Therefore, as shown in FIG. 6, it is conceivable to replace only one of the four polarizing beam splitters in FIG. 4 with a wire grid polarizer. That is, a color separation / synthesis optical system in which only the first polarizing beam splitter 107 is replaced with the wire grid polarizing plate 107b and the other polarizing beam splitters are used as they are can be considered. In this color separation / synthesis optical system, there is no wire grid polarizer on the optical path from the reflective spatial light modulator to the projection optical system, so there is no need to lengthen the back focus of the projection optical system. The display image resolution does not deteriorate due to astigmatism.

  However, this color separation / synthesis optical system has the following problems. That is, the first polarizing beam splitter 107 into which the light beam from the light source is incident is replaced with a wire grid polarizing plate, so that the ratio of the refractive index of air and the glass material is adjusted to the wire grid polarizing plate. The incident angle of incident light must be increased. The wire grid polarizer has no dependency on optical characteristics with respect to the incident angle of incident light. However, this incident light may interfere with the third polarizing beam splitter 112 close to the optical path.

  In this color separation / synthesis optical system, the field lens 105 and the first wavelength-selective polarization conversion element 106 have to be enlarged.

  In order to eliminate such interference of the incident light from the light source with respect to the polarization beam splitter, as shown in FIG. 7, between the second polarization beam splitter and the fourth polarization beam splitter, and third It is also conceivable to insert a spacer 117 between the polarizing beam splitter and the fourth polarizing beam splitter.

  However, when the spacer 117 is inserted between the polarization beam splitters as described above, problems such as an increase in the back focus of the projection optical system and an increase in the size (volume) of the entire optical system occur as described above.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and can be reduced in weight as compared with a conventional color separation / synthesis optical system using four polarization beam splitters. Generation of birefringence due to heat absorption is prevented, the image quality and contrast of the display image in the image display device are maintained, and further, the restriction on the optical system F value is relaxed, and the display image can be brightened. However, an increase in the back focus of the projection optical system and an increase in the overall size (volume) of the optical system are prevented, and there is no possibility that incident light from the light source interferes with the polarization beam splitter close to the optical path. An object is to provide a synthesis optical system.

  In order to solve the above-described problems, a color separation / synthesis optical system according to the present invention includes a condenser lens that receives a white light beam emitted from a light source, a concave lens that receives a light beam that has passed through the condenser lens, and at least a wire. The optical path of the first and second color component light and the optical path of the third color component light of the red component light, the green component light, and the blue component light of the light beam having a grid polarizing plate and passing through the concave lens. Color dividing means for branching to optical paths orthogonal to each other, a first field lens to which the first and second color component lights having passed through the color dividing means are incident, and third color component light having passed through the color dividing means The incident second field lens, the first and second color component lights that have passed through the first field lens are incident, and the polarization plane of the first color component light and the polarization plane of the second color component light are Wavelengths that are orthogonal to each other The first color is obtained by having a selective polarization conversion element and a polarization separation film on which a light beam having passed through the wavelength selective polarization conversion element is incident, and transmitting the P polarization component and reflecting the S polarization component with respect to the polarization separation film. The optical path of the component light and the optical path of the second color component light are branched, the first color component light is incident on the first spatial light modulation element, and the second color component light is incident on the second spatial light modulation element A first polarization separation element that causes the third color component light that has passed through the second field lens to enter, and a second polarization separation element that causes the third color component light to enter the third spatial light modulation element. The first and second modulated lights that have passed through the first and second spatial light modulators and the third modulated light that has passed through the third spatial light modulators are incident, and these modulated lights are combined to form imaging optics. And a polarization beam combining element that emits light toward the system.

  By having such a configuration, the color separation / synthesis optical system according to the present invention can be miniaturized while maintaining the F number as the illumination optical system.

  In this color separation / synthesis optical system, as a color dividing means, a wire grid polarizing plate in which a light beam that has passed through a wavelength-selective polarization conversion element arranged orthogonal to the optical axis is inclined with respect to the optical axis. Incident on the dichroic mirror disposed obliquely with respect to the optical axis, or inclined with respect to the optical axis The two light fluxes that have passed through the dichroic mirror arranged in this manner can be made incident on two wire grid polarizers arranged orthogonal to the optical axis.

  In the color separation / combination optical system according to the present invention, the white light beam emitted from the light source passes through the condenser lens, the concave lens, and the color splitting means having at least the wire grid polarizing plate. The light is branched into an optical path of component light and an optical path of third color component light. The first and second color component lights are incident on the first field lens, and the third color component light is incident on the second field lens.

  Therefore, in this color separation / synthesis optical system, it is not necessary to increase the diameter of the field lens while maintaining the F number as the illumination optical system, so that the size can be reduced.

  In addition, this color separation / synthesis optical system is lighter than the conventional color separation / synthesis optical system using four polarization beam splitters, and the incident light from the light source may be incident on the polarization beam splitter first. Therefore, the occurrence of birefringence due to the heat absorption of the polarizing beam splitter is prevented.

Furthermore, in this color separation / synthesis optical system, there is no possibility that the incident light from the light source interferes with the polarization beam splitter close to the optical path. That is, the present invention is a conventional color separation / synthesis optical system using four polarization beam splitters. The weight can be reduced as compared with the system, the occurrence of birefringence due to the heat absorption of the polarization beam splitter is prevented, the image quality and contrast of the display image in the image display device are maintained, and the optical system F Although the limit of the value is relaxed and the brightness of the display image can be increased, the back focus of the projection optical system and the size (volume) of the entire optical system are prevented from increasing, and the incident light from the light source Therefore, it is possible to provide a color separation / combination optical system that does not interfere with the polarization beam splitter close to the optical path.

  Embodiments of the present invention will be described below with reference to the drawings.

  In this embodiment, an image display apparatus is configured using the color separation / synthesis optical system according to the present invention.

[First Embodiment]
FIG. 1 is a plan view showing a first embodiment of a color separation / synthesis optical system according to the present invention.

  In this color separation / synthesis optical system, as shown in FIG. 1, a light beam emitted from a light source 1 is incident on a condenser lens 4 via a pair of fly-eye lens arrays 2 and 3. The light beam that has passed through the condenser lens 4 passes through the concave lens 5a and enters the first wavelength selective polarization conversion element 6 that constitutes the color dividing means. The first wavelength selective polarization conversion element 6 is disposed orthogonal to the optical axis of the incident light beam.

  The first wavelength-selective polarization conversion element 6 is an optical element formed by laminating retardation plates, and is a filter that rotates the direction of the polarization plane of only a specific wavelength band by 90 °. As such a wavelength-selective polarization conversion element, for example, “Color Select” manufactured by Color Link can be used. In the light flux that has passed through the first wavelength selective polarization conversion element 6, the polarization planes of the red component light R and the green component light G (yellow component light Y) that are the first and second color component lights are It is orthogonal to the plane of polarization of the blue component light B, which is the third color component light.

  The light beam that has passed through the first wavelength-selective polarization conversion element 6 is incident on the wire grid polarizer 7 that constitutes the color dividing means. The wire grid polarizer 7 is disposed at an angle of 45 ° with respect to the optical axis of the incident light beam.

  In this wire grid polarizer 7, the blue component light B is S-polarized light, the red component light R and the green component light G (yellow component light Y) are P-polarized light. Therefore, in this wire grid polarizing plate 7, the blue component light B is reflected and the red component light R and the green component light G (yellow component light Y) are transmitted.

  The red component light R and the green component light G (yellow component light Y) transmitted through the wire grid polarizer 7 are incident on the second wavelength selective polarization conversion element 8 via the first field lens (convex lens) 5b. The The second wavelength-selective polarization conversion element 8 sets the polarization plane of the red component light R orthogonal to the polarization plane of the green component light G, and uses the red component light R and the green component light G (yellow component light). Y) is transmitted.

  The light beam that has passed through the second wavelength-selective polarization conversion element 8 is incident on the first polarization beam splitter 9 serving as the first polarization separation element. In the first polarization beam splitter 9, the red component light R is P-polarized light and the green component light G is S-polarized light with respect to the polarization separation film 9a. The red component light R passes through the polarization separation film 9a, is emitted from the first polarization beam splitter 9, and is incident on the red reflective spatial light modulator 10 serving as the first spatial light modulator. The green component light G is reflected by the polarization separation film 9a, is emitted from the first polarization beam splitter 9, and is incident on the green reflective spatial light modulator 11 serving as the second spatial light modulator.

  The red reflective spatial light modulator 10 and the green reflective spatial light modulator 11 are so-called reflective liquid crystal display devices, which respectively modulate the polarization of incident light according to the red and green components of the display image. Reflect. Information of the display image is supplied to the red reflective spatial light modulator 10 and the green reflective spatial light modulator 11 from the outside.

  The first modulated light modulated and reflected by the red reflective spatial light modulator 10 is incident on the first polarization beam splitter 9 again. Since the first modulated light is S-polarized with respect to the polarization separation film 9 a, the first modulated light is reflected by the polarization separation film 9 a and returns from the first polarization beam splitter 9 to the wire grid polarization plate 7. And emit in a different direction.

  The second modulated light that has been modulated and reflected by the green reflective spatial light modulator 11 is incident on the first polarization beam splitter 9 again. Since the second modulated light is P-polarized with respect to the polarization separation film 9 a, the second modulated light is transmitted through the polarization separation film 9 a and returned from the first polarization beam splitter 9 to the wire grid polarization plate 7. The light is emitted in a direction different from the direction.

  On the other hand, the blue component light B reflected by the wire grid polarizing plate 7 is incident on the second polarization beam splitter 12 serving as the second polarization separation element through the second field lens (convex lens) 5c. In the second polarization beam splitter 12, the blue component light B is S-polarized with respect to the polarization separation film 12a. The blue component light B is reflected by the polarization separation film 12a, is emitted from the second polarization beam splitter 12, and is incident on the blue reflective spatial light modulator 13 serving as a third spatial light modulator. The blue reflective spatial light modulator 13 is a so-called reflective liquid crystal display device that reflects incident light by polarization-modulating the incident light according to the blue component of the display image. Information of the display image is supplied from the outside to the blue reflective spatial light modulator 13.

  The third modulated light modulated and reflected by the blue reflective spatial light modulator 13 is incident on the second polarization beam splitter 12 again. Since the third modulated light is P-polarized with respect to the polarization separation film 12a, it passes through the polarization separation film 12a and returns to the wire grid polarizer 7 from the second polarization beam splitter 12. The light is emitted in a direction different from the direction.

  The first and second modulated lights emitted from the first polarization beam splitter 9 are incident on the third wavelength selective polarization conversion element 14. The third wavelength-selective polarization conversion element 14 rotates the polarization plane of the first modulated light by 90 ° to transmit the first and second modulated lights, and becomes a third polarization beam splitter serving as a polarization combining element. 15 is incident. At this time, the polarization planes of the first and second modulated lights are in the same direction.

  Further, the third modulated light emitted from the second polarizing beam splitter 12 is incident on the third polarizing beam splitter 15.

  In the third polarization beam splitter 15, the first and second modulated lights are P-polarized and the third modulated light is S-polarized with respect to the polarization separation film 15a. The first and second modulated lights pass through the polarization separation film 15 a and are emitted from the third polarization beam splitter 15. The third modulated light is reflected by the polarization separation film 15 a and is emitted from the third polarization beam splitter 15. In this way, the first and second modulated light and the third modulated light are combined.

  The first to third modulated lights emitted from the third polarization beam splitter 15 enter the imaging optical system 16. The projection optical system 16 projects the first to third modulated light onto the screen and displays an image.

  In this color separation / synthesis optical system, the light beam from the light source 1 is converged by passing through the condenser lens 4, and the convergence angle is relaxed by passing through the concave lens 5a, so that the first wavelength-selective polarization conversion element 6 and the wire. Incident on the grid polarizer 7. Moreover, since the wire grid polarizing plate 7 does not depend on the incident angle of incident light for optical characteristics, the incident angle of illumination light incident on the concave lens 5a from the light source 1 can be increased. That is, in this color separation / synthesis optical system, the F-number as the illumination optical system can be reduced, the luminous flux from the light source 1 can be used efficiently, and the illumination brightness of each spatial light modulator can be improved. .

  In this color separation / synthesis optical system, the concave lens 5a and the first field lens 5b, and the concave lens 5a and the second field lens 5c are each designed to function as one field lens. .

  In this color separation / synthesis optical system, the light beam from the light source 1 passes through the condenser lens 4 and then passes through the concave lens 5a so that the convergence angle is relaxed and is incident on the first wavelength selective polarization conversion element 6. Therefore, there is no interference with the second polarization beam splitter 12 disposed in the vicinity of the first wavelength selective polarization conversion element 6.

[Second Embodiment]
In this embodiment, as the color dividing means, a wire grid polarizing plate arranged orthogonal to the optical axis of the incident light, and an inclination arranged with respect to the optical axis of the light beam passing through the wire grid polarizing plate. Used dichroic mirror.

  FIG. 2 is a plan view showing a second embodiment of the color separation / synthesis optical system according to the present invention.

  That is, in this color separation / synthesis optical system, as shown in FIG. 2, the light beam emitted from the light source 1 is incident on the condenser lens 4 through the pair of fly-eye lens arrays 2 and 3. The light beam that has passed through the condenser lens 4 is incident on the wire grid polarizing plate 7 constituting the color dividing means through the concave lens 5a. The wire grid polarizing plate 7 is disposed orthogonal to the optical axis of the incident light beam. In the light flux that has passed through the wire grid polarizer 7, the light flux of each color component is all linearly polarized light in the same direction.

  The light beam that has passed through the wire grid polarizer 7 is incident on a dichroic mirror 17 that constitutes a color dividing means. The dichroic mirror 17 is disposed with an inclination of 45 ° with respect to the optical axis of the incident light beam. The dichroic mirror 17 reflects only the blue component light B and transmits the red component light R and the green component light G (yellow component light Y).

  The red component light R and the green component light G (yellow component light Y) transmitted through the dichroic mirror 17 are incident on the second wavelength-selective polarization conversion element 8 through the first field lens (convex lens) 5b. The second wavelength-selective polarization conversion element 8 sets the polarization plane of the red component light R orthogonal to the polarization plane of the green component light G, and uses the red component light R and the green component light G (yellow component light). Y) is transmitted.

  The light beam that has passed through the second wavelength-selective polarization conversion element 8 is incident on the first polarization beam splitter 9 serving as the first polarization separation element. In the first polarization beam splitter 9, the red component light R is P-polarized light and the green component light G is S-polarized light with respect to the polarization separation film 9a. The red component light R passes through the polarization separation film 9a, is emitted from the first polarization beam splitter 9, and is incident on the red reflective spatial light modulator 10 serving as the first spatial light modulator. The green component light G is reflected by the polarization separation film 9a, is emitted from the first polarization beam splitter 9, and is incident on the green reflective spatial light modulator 11 serving as the second spatial light modulator.

  The red reflective spatial light modulator 10 and the green reflective spatial light modulator 11 are so-called reflective liquid crystal display devices, which respectively modulate the polarization of incident light according to the red and green components of the display image. Reflect. Information of the display image is supplied to the red reflective spatial light modulator 10 and the green reflective spatial light modulator 11 from the outside.

  The first modulated light modulated and reflected by the red reflective spatial light modulator 10 is incident on the first polarization beam splitter 9 again. Since the first modulated light is S-polarized with respect to the polarization separation film 9 a, the first modulated light is reflected by the polarization separation film 9 a and returns from the first polarization beam splitter 9 to the wire grid polarization plate 7. And emit in a different direction.

  The second modulated light that has been modulated and reflected by the green reflective spatial light modulator 11 is incident on the first polarization beam splitter 9 again. Since the second modulated light is P-polarized with respect to the polarization separation film 9 a, the second modulated light is transmitted through the polarization separation film 9 a and returned from the first polarization beam splitter 9 to the wire grid polarization plate 7. The light is emitted in a direction different from the direction.

  On the other hand, the blue component light B reflected by the dichroic mirror 17 passes through the second field lens (convex lens) 5c and enters the second polarization beam splitter 12 serving as the second polarization separation element. In the second polarization beam splitter 12, the blue component light B is S-polarized with respect to the polarization separation film 12a. The blue component light B is reflected by the polarization separation film 12a, is emitted from the second polarization beam splitter 12, and is incident on the blue reflective spatial light modulator 13 serving as a third spatial light modulator. The blue reflective spatial light modulator 13 is a so-called reflective liquid crystal display device that reflects incident light by polarization-modulating the incident light according to the blue component of the display image. Information of the display image is supplied from the outside to the blue reflective spatial light modulator 13.

  The third modulated light modulated and reflected by the blue reflective spatial light modulator 13 is incident on the second polarization beam splitter 12 again. Since the third modulated light is P-polarized with respect to the polarization separation film 12a, it passes through the polarization separation film 12a and returns to the wire grid polarizer 7 from the second polarization beam splitter 12. The light is emitted in a direction different from the direction.

  The first and second modulated lights emitted from the first polarization beam splitter 9 are incident on the third wavelength selective polarization conversion element 14. The third wavelength-selective polarization conversion element 14 rotates the polarization plane of the first modulated light by 90 ° to transmit the first and second modulated lights, and becomes a third polarization beam splitter serving as a polarization combining element. 15 is incident. At this time, the polarization planes of the first and second modulated lights are in the same direction.

  Further, the third modulated light emitted from the second polarizing beam splitter 12 is incident on the third polarizing beam splitter 15.

  In the third polarization beam splitter 15, the first and second modulated lights are P-polarized and the third modulated light is S-polarized with respect to the polarization separation film 15a. The first and second modulated lights pass through the polarization separation film 15 a and are emitted from the third polarization beam splitter 15. The third modulated light is reflected by the polarization separation film 15 a and is emitted from the third polarization beam splitter 15. In this way, the first and second modulated light and the third modulated light are combined.

  The first to third modulated lights emitted from the third polarization beam splitter 15 enter the imaging optical system 16. The projection optical system 16 projects the first to third modulated light onto the screen and displays an image.

  In this color separation / synthesis optical system, the light beam from the light source 1 is converged by passing through the condenser lens 4, and the convergence angle is relaxed by passing through the concave lens 5 a and is incident on the wire grid polarizer 7 and the dichroic mirror 17. The Moreover, since the wire grid polarizing plate 7 does not depend on the incident angle of incident light for optical characteristics, the incident angle of illumination light incident on the concave lens 5a from the light source 1 can be increased. That is, in this color separation / synthesis optical system, the F-number as the illumination optical system can be reduced, the luminous flux from the light source 1 can be used efficiently, and the illumination brightness of each spatial light modulator can be improved. .

  Also in this color separation / synthesis optical system, the concave lens 5a and the first field lens 5b, and the concave lens 5a and the second field lens 5c are each designed to function as one field lens. .

  In this color separation / synthesis optical system, the light beam from the light source 1 passes through the condenser lens 4 and then passes through the concave lens 5a so that the convergence angle is relaxed and is incident on the wire grid polarizer 7. There is no interference with the second polarizing beam splitter 12 arranged in the vicinity of the grid polarizer 7.

[Third Embodiment]
In this embodiment, as the color splitting means, a dichroic mirror arranged to be inclined with respect to the optical axis of the incident light, and two pieces arranged orthogonal to the optical axis of the light beam passing through the dichroic mirror The wire grid polarizer is used.

  FIG. 3 is a plan view showing a third embodiment of the color separation / synthesis optical system according to the present invention.

  That is, in this color separation / synthesis optical system, as shown in FIG. 3, the light beam emitted from the light source 1 enters the condenser lens 4 through the pair of fly-eye lens arrays 2 and 3. The light beam that has passed through the condenser lens 4 is incident on the dichroic mirror 17 that constitutes the color dividing means, through the concave lens 5a. The dichroic mirror 17 is disposed with an inclination of 45 ° with respect to the optical axis of the incident light beam. The dichroic mirror 17 reflects only the blue component light B and transmits the red component light R and the green component light G (yellow component light Y).

  The red component light R and the green component light G (yellow component light Y) transmitted through the dichroic mirror 17 pass through the first field lens (convex lens) 5b and enter the first wire grid polarizer 7a constituting the color dividing means. Incident. The first wire grid polarizer 7a is disposed orthogonal to the optical axis of the incident light beam. In the light beam transmitted through the first wire grid polarizer 7a, the red component light R and the green component light G are linearly polarized light in the same direction.

  Then, the light beam transmitted through the first wire grid polarizer 7 a is incident on the second wavelength selective polarization conversion element 8. The second wavelength-selective polarization conversion element 8 sets the polarization plane of the red component light R orthogonal to the polarization plane of the green component light G, and uses the red component light R and the green component light G (yellow component light). Y) is transmitted.

  The light beam that has passed through the second wavelength-selective polarization conversion element 8 is incident on the first polarization beam splitter 9 serving as the first polarization separation element. In the first polarization beam splitter 9, the red component light R is P-polarized light and the green component light G is S-polarized light with respect to the polarization separation film 9a. The red component light R passes through the polarization separation film 9a, is emitted from the first polarization beam splitter 9, and is incident on the red reflective spatial light modulator 10 serving as the first spatial light modulator. The green component light G is reflected by the polarization separation film 9a, is emitted from the first polarization beam splitter 9, and is incident on the green reflective spatial light modulator 11 serving as the second spatial light modulator.

  The red reflective spatial light modulator 10 and the green reflective spatial light modulator 11 are so-called reflective liquid crystal display devices, which respectively modulate the polarization of incident light according to the red and green components of the display image. Reflect. Information of the display image is supplied to the red reflective spatial light modulator 10 and the green reflective spatial light modulator 11 from the outside.

  The first modulated light modulated and reflected by the red reflective spatial light modulator 10 is incident on the first polarization beam splitter 9 again. Since the first modulated light is S-polarized with respect to the polarization separation film 9 a, the first modulated light is reflected by the polarization separation film 9 a and returns from the first polarization beam splitter 9 to the wire grid polarization plate 7. And emit in a different direction.

  The second modulated light that has been modulated and reflected by the green reflective spatial light modulator 11 is incident on the first polarization beam splitter 9 again. Since the second modulated light is P-polarized with respect to the polarization separation film 9 a, the second modulated light is transmitted through the polarization separation film 9 a and returned from the first polarization beam splitter 9 to the wire grid polarization plate 7. The light is emitted in a direction different from the direction.

  On the other hand, the blue component light B reflected by the dichroic mirror 17 passes through the second field lens (convex lens) 5c and enters the second wire grid polarizing plate 7b constituting the color dividing means. The second wire grid polarizer 7b is disposed perpendicular to the optical axis of the incident light beam. In the light beam that has passed through the second wire grid polarizer 7b, the blue component light B is linearly polarized light.

  Then, the light beam that has passed through the second wire grid polarizer 7b is incident on the second polarization beam splitter 12 serving as the second polarization separation element. In the second polarization beam splitter 12, the blue component light B is S-polarized with respect to the polarization separation film 12a. The blue component light B is reflected by the polarization separation film 12a, is emitted from the second polarization beam splitter 12, and is incident on the blue reflective spatial light modulator 13 serving as a third spatial light modulator. The blue reflective spatial light modulator 13 is a so-called reflective liquid crystal display device that reflects incident light by polarization-modulating the incident light according to the blue component of the display image. Information of the display image is supplied from the outside to the blue reflective spatial light modulator 13.

  The third modulated light modulated and reflected by the blue reflective spatial light modulator 13 is incident on the second polarization beam splitter 12 again. Since the third modulated light is P-polarized with respect to the polarization separation film 12a, it passes through the polarization separation film 12a and returns to the wire grid polarizer 7 from the second polarization beam splitter 12. The light is emitted in a direction different from the direction.

  The first and second modulated lights emitted from the first polarization beam splitter 9 are incident on the third wavelength selective polarization conversion element 14. The third wavelength-selective polarization conversion element 14 rotates the polarization plane of the first modulated light by 90 ° to transmit the first and second modulated lights, and becomes a third polarization beam splitter serving as a polarization combining element. 15 is incident. At this time, the polarization planes of the first and second modulated lights are in the same direction.

  Further, the third modulated light emitted from the second polarizing beam splitter 12 is incident on the third polarizing beam splitter 15.

  In the third polarization beam splitter 15, the first and second modulated lights are P-polarized and the third modulated light is S-polarized with respect to the polarization separation film 15a. The first and second modulated lights pass through the polarization separation film 15 a and are emitted from the third polarization beam splitter 15. The third modulated light is reflected by the polarization separation film 15 a and is emitted from the third polarization beam splitter 15. In this way, the first and second modulated light and the third modulated light are combined.

  The first to third modulated lights emitted from the third polarization beam splitter 15 enter the imaging optical system 16. The projection optical system 16 projects the first to third modulated light onto the screen and displays an image.

  In this color separation / synthesis optical system, the light beam from the light source 1 is converged by passing through the condenser lens 4 and is incident on the dichroic mirror 17 with the convergence angle relaxed by passing through the concave lens 5a. The incident angle of the illumination light incident on the concave lens 5a can be increased. That is, in this color separation / synthesis optical system, the F value as the illumination optical system can be reduced, the luminous flux from the light source 1 can be used efficiently, and the illumination brightness of each spatial light modulator can be improved. .

  Also in this color separation / synthesis optical system, the concave lens 5a and the first field lens 5b, and the concave lens 5a and the second field lens 5c are each designed to function as one field lens. .

  In this color separation / combination optical system, the light flux from the light source 1 passes through the condenser lens 4 and then passes through the concave lens 5a so that the convergence angle is relaxed and is incident on the dichroic mirror 17. Therefore, the dichroic mirror 17 Is not interfered with the second polarizing beam splitter 12 arranged in the vicinity of.

  Further, the color separation / synthesis optical system in the third embodiment has wire grid polarizers 7a and 7b closer to the spatial light modulator than the color separation / synthesis optical system in the second embodiment. Since the light beams that have passed through the wire grid polarizers 7a and 7b reach the respective spatial light modulators, the polarization state is hardly disturbed, and the performance of polarization separation is improved. Contrast can be improved.

1 is a plan view showing a first embodiment of a color separation / synthesis optical system according to the present invention. FIG. It is a top view which shows 2nd Embodiment of the color separation / synthesis optical system which concerns on this invention. It is a top view which shows 3rd Embodiment of the color separation / synthesis optical system which concerns on this invention. It is a top view which shows the structure of the conventional color separation / synthesis optical system used in an image display apparatus. It is a top view which shows the other example of a structure of the conventional color separation synthetic | combination optical system. It is a top view which shows the further another example of a structure of the conventional color separation / synthesis optical system. It is a top view which shows the further another example of a structure of the conventional color separation / synthesis optical system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2, 3 Fly eye lens array 4 Condenser lens 5a Concave lens 6 1st wavelength selective polarization conversion element 7 Wire grid polarizing plate 7a 1st wire grid polarizing plate 7b 2nd wire grid polarizing plate 8 2nd wavelength Selective polarization conversion element 9 First polarization beam splitter 10 Red reflective spatial light modulator 11 Green reflective spatial light modulator 5b First field lens 5c Second field lens 12 Second polarization beam splitter 13 Reflective spatial light modulator for blue 14 Third wavelength selective polarization conversion element 15 Third polarization beam splitter 16 Projection optical system 17 Dichroic mirror

Claims (1)

A condenser lens to which a white light beam emitted from a light source is incident;
A concave lens into which the light beam having passed through the condenser lens is incident;
An optical path of the first and second color component light of the red component light, the green component light, and the blue component light of the light beam passing through the concave lens, and a third color component; Color dividing means for branching the optical path of light into optical paths orthogonal to each other;
A first field lens on which the first and second color component lights having passed through the color dividing means are incident;
A second field lens on which the third color component light having passed through the color dividing means is incident;
Wavelength selection in which the first and second color component lights having passed through the first field lens are incident and the polarization planes of the first color component light and the polarization plane of the second color component light are orthogonal to each other A polarizing conversion element,
An optical path of the first color component light by having a polarization separation film on which a light beam having passed through the wavelength-selective polarization conversion element is incident, and transmitting a P-polarized component and reflecting an S-polarized component with respect to the polarization separation film And the optical path of the second color component light are branched, the first color component light is incident on the first spatial light modulation element, and the second color component light is incident on the second spatial light modulation element A first polarization separation element;
A second polarization separation element that receives the third color component light that has passed through the second field lens, and that makes the third color component light incident on the third spatial light modulation element;
The first and second modulated light that has passed through the first and second spatial light modulation elements and the third modulated light that has passed through the third spatial light modulation element are incident, and these modulated lights are combined, A color separation / synthesis optical system comprising: a polarization synthesis element that emits light toward an imaging optical system.

Images