JP2000035612A - Color image projector - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To eliminate the need for a lens with a long back focus and to enlarge and project a high-quality color image without increasing the size of a projection lens group. A three-color projection device for projecting illumination light beams corresponding to three colors.
Three light beam splitting members 3, 8, and 10, three image display means 4, 9, 11 radiated through the light beam splitting members, and respective light beams reflected from the image display means and transmitted through the light beam splitting members A first projection lens system 20a, 20b, 20c for projecting as a parallel light beam, a color combining prism 5 for guiding each light beam from the first projection lens system along the same axis optical axis, 3 from the color combining prism
A pair of second projection lens systems 20d for superimposing and projecting the respective luminous fluxes of the colors onto the screen 15; Is not required, and a high-quality color image can be enlarged and projected without increasing the size of the projection lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image projection apparatus which uses a reflection type liquid crystal display device and enlarges and projects a color video signal on a screen.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional color image projector using a reflection type liquid crystal display device.

A light source 1 emits white light including red, green, and blue light, reflects only blue light having a blue wavelength component on the optical axis of the light source 1, and emits green light of other wavelength components. A first dichroic mirror 2 transmitting red light is provided, and a first deflecting beam splitter 3 having a deflecting / reflecting surface on a reflection optical axis of the first dichroic mirror 2 is provided. A blue reflection type liquid crystal display element 4 is provided on the optical axis so as to face the first deflection beam splitter 3, and a color combining prism 5 is provided on the reflection optical axis of the blue reflection type liquid crystal display element 4.

A reflection mirror 6 is provided on the transmission optical axis of the first dichroic mirror 2 and reflects only green light having a green wavelength component on the reflection optical axis of the reflection mirror 6 to reduce the red wavelength component. A second dichroic mirror 7 that transmits only the red light is provided, and a second deflecting beam splitter 8 having a deflecting / reflecting surface on the reflection optical axis of the second dichroic mirror 7 is provided. The second deflection beam splitter 8
The green reflection type liquid crystal display element 9 is disposed on the reflection optical axis of (1).
The color synthesizing prism 5 is arranged on the reflection optical axis of the green reflection type liquid crystal display element 9.

A third deflecting beam splitter 1 having a deflecting / reflecting surface on the transmission optical axis of the second dichroic mirror 7
0, a red reflective liquid crystal display element 11 is provided on the reflected optical axis of the third deflection beam splitter 10, and the color combining prism 5 is provided on a reflected optical axis of the red reflective liquid crystal display element 11. It is arranged.

The color synthesizing prism 5 has a reflecting surface 5a and a reflecting surface 5b, and the reflecting surface 5a reflects only blue light.
The reflection surface 5b reflects only red light. Therefore, the blue light reflected by the blue reflective liquid crystal display element 4 and the green light reflected by the green reflective liquid crystal display element 9 in the color combining prism 5, and the blue light reflected by the red reflective liquid crystal display element 11. The red light is synthesized and radiated toward the screen 15.

On the light irradiation side of the color synthesizing prism 5, a convex lens 16, a concave lens 17, a convex lens 18, and a concave lens 19 are provided.
Is provided.

The white light emitted from the light source 1 is first reflected by a first dichroic mirror 2 in blue light, and further reflected by a first deflecting beam splitter 3 to irradiate the blue reflective liquid crystal display element 4. The blue reflective liquid crystal display element 4
In the example, an image is displayed based on a blue video signal, and the blue image is reflected by the blue reflective liquid crystal display element 4. The reflected light from the blue reflective liquid crystal display element 4 has a phase rotated by 90 ° with respect to the incident light, and passes through the first deflecting beam splitter 3 to reach the color combining prism 5.

The green light transmitted through the first dichroic mirror 2 is reflected by the reflection mirror 6, then reflected by the second dichroic mirror 7, further reflected by the second deflection beam splitter 8, and reflected by the green light. The reflection type liquid crystal display element 9 is irradiated. The green reflective liquid crystal display element 9 displays an image based on a green video signal, and the green reflective liquid crystal display element 9 reflects a green image. The phase of the reflected light of the green reflective liquid crystal display element 9 is rotated by 90 ° with respect to the incident light, and the second deflecting beam splitter 8
And reaches the color synthesizing prism 5.

The red light transmitted through the second dichroic mirror 7 is reflected by the third deflection beam splitter 10 and further reflected by the red reflective liquid crystal display element 11. As described above, the red reflective liquid crystal display element 11
In the example, an image is displayed based on a red video signal, and the red image is reflected. The reflected light of the red reflective liquid crystal display element 11 has a phase rotated by 90 ° with respect to the incident light, and passes through the third deflection beam splitter 10 to reach the color combining prism 5.

The blue light reflected from the blue reflective liquid crystal display element 4 is reflected by the reflective surface 5a, the green light reflected from the green reflective liquid crystal display element 9 is transmitted through the color synthesizing prism 5, and the red light is reflected. The reflected red light from the liquid crystal display element 11 is reflected by the reflection surface 5b, and the three colors are combined by the color combining prism 5. The synthesized light is formed as an image having a natural color on the screen 15 by the projection lens group 20.

[0012]

In the projection lens group 20 used in the above-mentioned conventional color image projection apparatus, the distance from the last lens (convex lens 16) surface to each of the reflection type liquid crystal display elements 4, 9, 11 is set. Since the optical elements such as the respective deflection beam splitters 3, 8, 10 or the color synthesizing prism 5 are disposed, a long back focus is required.

In general, the projection lens group 20 is often of a retrofocus type in which a lens group having a negative refractive power is arranged in advance. In particular, in the case of a rear projection type projector, the projection distance of the projection lens needs to be shorter than that of the front projection type in order to reduce the size of the entire apparatus. The fact that the magnification is the same when the image is enlarged and projected on the screen 15 and the projection distance is short means that the focal length of the projection lens group 20 is short and the angle of view is large. However, since the required length of the flange back is the same, in the retrofocus type projection lens group 20, a negative lens group having remarkably strong refracting power must be arranged beforehand. When the negative refractive power becomes strong, the asymmetry of the lens group becomes strong, and the occurrence of various aberrations of the lens, especially negative distortion, becomes large, and the quality of the projected image is remarkably deteriorated. Further, since the angle of view is large, it becomes difficult to increase the F value. If the quality of the projected image is improved and the F value is made brighter, the number of lenses increases, and the size of the projection lens group 20 increases.

In view of such circumstances, the present invention makes it possible to eliminate the need for a long back-focus lens and to enlarge and project a high-quality color image without increasing the size of the projection lens group. is there.

[0015]

According to the present invention, there are provided three light beam splitting members for projecting illumination light beams corresponding to three colors, three image display means irradiated through the light beam splitting members,
Three first projection lens systems for projecting each light beam reflected from each image display means and transmitted through the light beam splitting member as a parallel light beam, and each light beam from the first projection lens system being coaxially optical axis The present invention relates to a color image projecting apparatus comprising a color combining prism for guiding the light beams along the image plane, and a set of second projection lens systems for projecting the light beams of the three colors from the color combining prism onto a screen in a superimposed manner. Further, the image display means is related to a color image projection apparatus which is a reflection type liquid crystal display means, and the light beam splitting member is related to a color image projection apparatus which is a deflection beam splitter. By arranging between the projection lens systems, a projection lens with a long back focus is not required, so even a projection lens with a large F value and a wide angle of view can achieve high image quality without increasing the size of the projection lens. It can be maintained.

[0016]

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

In FIG. 1, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the details will not be described.

A first dichroic mirror 2 is disposed on the optical axis of a light source 1 that emits white light, and a first deflection beam splitter 3 is disposed on a reflection optical axis of the first dichroic mirror 2. A blue reflective liquid crystal display element 4 is provided on the reflection optical axis of the deflection beam splitter 3 so as to face the first deflection beam splitter 3, and a reflection surface 5a is provided on the reflection optical axis of the blue reflection liquid crystal display element 4. A color combining prism 5 having a reflecting surface 5b is provided.

A reflection mirror 6 is provided on the transmission optical axis of the first dichroic mirror 2, a second dichroic mirror 7 is provided on the reflection optical axis of the reflection mirror 6, and a second dichroic mirror 7 is provided. The second deflection beam splitter 8 is provided on the reflected optical axis. The second deflection beam splitter 8
The green reflection type liquid crystal display element 9 is disposed on the reflection optical axis of (1).
The color synthesizing prism 5 is arranged on the reflection optical axis of the green reflection type liquid crystal display element 9.

A third deflecting beam splitter 10 is disposed on the transmission optical axis of the second dichroic mirror 7, and a red reflective liquid crystal display element 11 is disposed on a reflection optical axis of the third deflecting beam splitter 10. The color synthesizing prism 5 is arranged on the reflection optical axis of the red reflection type liquid crystal display element 11.

A first projection lens system 20a comprising a convex lens 16 and a concave lens 17 is disposed between the color synthesizing prism 5 and the first deflection beam splitter 3, and the second deflection beam splitter 8 and the color synthesis prism are arranged. 5, a first projection lens system 20b including a convex lens 16 and a concave lens 17 is provided, and the third deflection beam splitter 10
A first projection lens system 20c including a convex lens 16 and a concave lens 17 is provided between the first projection lens system 20c and the color combining prism 5. On the screen 15 side of the color synthesizing prism 5, a second projection lens system 20d including a convex lens 18 and a concave lens 19 is provided. The second projection lens system 20d and the first projection lens system 20a, the second projection lens system 20d and the first projection lens system 20b, the second projection lens system 20d
The first projection lens system 20c and the first projection lens system 20c are paired to form three sets of projection lens systems 21a, 21b, and 21c equivalent to the projection lens group 20 shown in FIG.

The white light emitted from the light source 1 is first reflected by the first dichroic mirror 2 into blue light, and the blue light reflected by the first deflecting beam splitter 3 is passed through the blue reflection type liquid crystal display element 4. Irradiate. The blue reflective liquid crystal display element 4 displays an image of a blue component, and the blue image is reflected by the blue reflective liquid crystal display element 4. The reflected light of the blue reflective liquid crystal display element 4 has a phase of 9 with respect to the incident light.
The reflected light is transmitted through the deflecting / reflecting surface of the first deflecting beam splitter 3 and is further rotated by 0 °.
The light is collimated at a and reaches the color combining prism 5. The blue reflected light is reflected by the reflecting surface 5a of the color synthesizing prism 5, and is transmitted through the second projection lens system 20d to be projected on the screen 15 as a light beam having a predetermined angle of view.

The green light transmitted through the first dichroic mirror 2 is reflected by the reflecting mirror 6, then reflected by the second dichroic mirror 7, further reflected by the second deflecting beam splitter 8, and The reflection type liquid crystal display element 9 is irradiated. The green reflection type liquid crystal display element 9 displays a green component image, and the green reflection type liquid crystal display element 9 reflects the green component image. The reflected light of the green reflective liquid crystal display element 9 is rotated by 90 ° in phase with respect to the incident light, the reflected green light is transmitted through the deflecting and reflecting surface of the second deflecting beam splitter 8, and System 2
0b, and reaches the color synthesizing prism 5 with a parallel light flux. The green reflected light is transmitted through the reflection surfaces 5a and 5b, and is transmitted through the second projection lens system 20d to be projected on the screen 15 as a light beam having a predetermined angle of view.

The red light transmitted through the second dichroic mirror 7 is reflected by the third deflecting beam splitter 10 and further enters the red reflective liquid crystal display device 11. As described above, the red reflective liquid crystal display element 11
Displays an image of a red component, and the red reflective liquid crystal display element 11 reflects the image of the red component. The phase of the reflected light of the red reflective liquid crystal display element 11 is rotated by 90 ° with respect to the incident light, and the third deflecting beam splitter 1
0 through the first projection lens system 20c.
, And reaches the color synthesizing prism 5.
The reflected red light is reflected by the reflection surface 5b of the color synthesizing prism 5, is converted into a light beam having a predetermined angle of view by the second projection lens system 20d, and is projected on the screen 15.

As described above, between the first projection lens system 20a and the second projection lens system 20d, between the first projection lens system 20b and the second projection lens system 20d, and between the first projection lens system 20c and the second projection lens system 20d. Since there is a parallel light flux (including a substantially parallel light flux), spherical aberration does not occur when the light passes through the color combining prism 5. Therefore, the first projection lens systems 20a, 20b, and 20c do not need to correct spherical aberration, and the first projection lens systems 20a, 20b, and 20c do not need to correct spherical aberration.
The configuration of b and 20c is light and the configuration is simple.

The blue light, green light and red light projected from the color synthesizing prism 5 are superimposed on the same optical axis,
The image is enlarged and projected on the screen 15 by the projection lens system 20d.

In the above-described embodiment, the three primary colors are separated in the order of blue, green, and red. However, the order is not limited thereto. For example, the order of blue, red, green, or red, The order of green and blue may be used. Further, the deflection beam splitter is not a solid prism having a polarization splitting surface inside,
A liquid polarization beam splitter in which a glass plate having a polarization separation surface is put in a liquid may be used.

[0028]

As described above, according to the present invention, since the color combining prism is disposed between the projection lens systems, a projection lens having a long back focus is not required.
Even with a projection lens having a large value and a wide angle of view, excellent effects such as high image quality can be maintained without increasing the size of the projection lens.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a main part of an optical system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a main part of a conventional optical system.

[Explanation of symbols]

 Reference Signs List 1 light source 2 first dichroic mirror 3 first deflecting beam splitter 4 blue reflective liquid crystal display element 5 color combining prism 7 second dichroic mirror 8 second deflecting beam splitter 9 green reflective liquid crystal display element 10 third deflecting beam splitter 11 red Reflective liquid crystal display device 20 Projection lens system 21 Projection lens system

Claims (3)

[Claims] 1. A light beam splitting member for projecting illumination light beams corresponding to three colors, three image display means illuminated through the light beam splitting member, and the light flux reflected from each image display means. Three first projection lens systems for projecting each light beam transmitted through the splitting member as a parallel light beam, and a color combining prism for guiding each light beam from the first projection lens system along the same axis optical axis And a pair of second projection lens systems for superimposing and projecting the three color light beams from the color synthesizing prism onto a screen. 2. The color image projection apparatus according to claim 1, wherein said image display means is a reflection type liquid crystal display means. 3. The color image projection apparatus according to claim 1, wherein said light beam splitting member is a deflection beam splitter.