JP2844871B2 - Projection display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection type liquid crystal display device.

[Conventional technology]

The conventional optical system has a color synthesizing dichroic mirror between the liquid crystal panel and the projection lens for synthesizing three primary colors inclined at 45 ° to the optical axis.

[Problems to be solved by the invention]

In a conventional optical system, light transmitted through a liquid crystal panel and transmitted through a synthetic dichroic mirror enters a projection lens and forms an image of the liquid crystal panel on a screen or the like. However, at this time, astigmatism occurs due to the combined dichroic mirror. This astigmatism is caused by the difference in the optical path of light passing through the dichroic mirror between the image plane in the radiation direction (sagittal direction) and the image plane in the annular line direction (meridional direction). Is the imaging position in the radiation direction, the imaging position in the annular line direction, and 2
There will be one. Therefore, the optimal image in this optical system is a blurred image by observing the minimum circle of confusion between the two. Correcting this astigmatism with a projection lens system significantly increases the performance and price of the projection lens, and is not realistic. Therefore, the present invention solves such a problem, and an object of the present invention is to provide a projection-type liquid crystal display device that obtains an image without blur by making the optical paths in the radiation direction and the annular line direction equivalent. Is what you do.

[Means for solving the problem]

The present invention provides a plurality of light valves that respectively modulate a plurality of color lights, a color combining unit that combines the color lights modulated by the plurality of light valves, and a projection unit that projects the light combined by the color combining unit. Wherein the color synthesizing means includes a dichroic mirror, and the dichroic mirror is provided in an optical path between the light valve that modulates color light transmitted through the dichroic mirror and the dichroic mirror. A light-transmissive plate member optically equivalent to a mirror, wherein the dichroic mirror is disposed so as to have a predetermined inclination with respect to a plane perpendicular to a plane defined by the optical axis of each color light, and Plate material is disposed so as to have the predetermined inclination with respect to a plane defined by the optical axis of each color light. Characterized by the symptoms.

〔Example〕

FIG. 1A is an arrangement diagram of an optical system according to an embodiment of the present invention. A light beam emitted from a light source 1 is reflected by a green reflecting dichroic mirror 3 and a red reflecting dichroic mirror 4.
It is decomposed into three primary colors of red, green and blue. Red, green,
Light transmitted through the transmissive liquid crystal panels 5, 6, 7 for blue is combined by combining dichroic mirrors 11, 12 which are perpendicular to the horizontal plane (paper surface) including the optical axis and inclined at 45 ° to the optical axis. The image is projected on a screen or the like by the projection lens 13. At this time, the green light transmitted through the synthetic dichroic mirror 11 is perpendicular to the vertical plane (the plane perpendicular to the paper surface) including the optical axis between the green transmission type liquid crystal panel 6 and the synthetic dichroic mirror 11. A compensating glass 9 inclined at 45 ° to the optical axis is arranged, and a synthetic dichroic mirror 12
Is transmitted between the blue transmissive liquid crystal panel 7 and the synthetic dichroic mirror 12 at a right angle to the vertical plane (the plane perpendicular to the paper surface) including the optical axis and at 45 ° to the optical axis. The correction glass 10 is disposed at an angle. The correction glasses 9 and 10 are colorless and transparent plate glasses having the same refractive index and thickness as the synthetic dichroic mirrors 11 and 12, respectively, or color filters of green and blue, respectively.

FIG. 1B is a perspective view of the arrangement of the synthetic dichroic mirrors 11 and 12 and the correction glasses 9 and 10. The light travels from the right to the left of the figure, and the compensating glasses 9 and 10 are inclined at 45 ° to the horizontal plane 14 and the composite dichroic mirror 1 is inclined at 45 ° to the vertical plane 15
It is composed of 1,12. The angle with respect to the optical axis of each of the synthetic dichroic mirror and the correction glass in the embodiment is 45.
However, depending on the configuration of the optical system, it may be set to an angle that matches the imaging conditions of the optical system.

FIG. 2 is an exploded view of astigmatism in a radiation direction and an annular line direction of transmission through a combined dichroic mirror in a conventional optical system. Assuming that the inclination of the principal ray of the projection lens is θ, the difference Δf between f _{1 and} f _{2 in} the figure is the difference between the image forming position in the radiation direction and the annular line direction due to astigmatism.

FIG. 3 is an analysis diagram of astigmatism due to the correction glass arrangement of the present invention. Imaging position f ₁ and the image forming position f ₂ annular line direction of the radiation directions are equal, the astigmatism is eliminated. Thereby, the image of the liquid crystal panel is formed at one point, and an image without blur is obtained.

In addition, it is possible to arrange a liquid crystal panel other than the embodiment.
In an optical system that transmits through a synthetic dichroic mirror in one liquid crystal panel, the same correction glass as described above may be provided.

〔The invention's effect〕

As described above, according to the present invention, by arranging the correction glass in the optical path, astigmatism due to transmission of the synthetic dichroic mirror can be easily eliminated, and an in-focus image without blur can be obtained. Having.

[Brief description of the drawings]

FIG. 1 (a) is an optical system layout diagram of the present invention. FIG. 1B is a perspective view showing the arrangement of a synthetic dichroic mirror and correction glass. FIG. 2 is an analysis diagram of astigmatism transmitted through a synthetic dichroic mirror. FIG. 3 is an analysis diagram of astigmatism due to a correction glass arrangement. DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Heat ray reflection filter 3 ... Green reflection dichroic mirror 4 ... Red reflection dichroic mirror 5 ... Red transmissive liquid crystal panel 6 ... Green transmissive liquid crystal panel 7 ... Blue transmissive liquid crystal Panel 8 Aluminum reflective mirror 9 Compensating glass 10 Compensating glass 11 Synthetic dichroic mirror 12 Synthetic dichroic mirror 13 Projection lens 14 Horizontal plane 15 Vertical plane

Claims (1)

(57) [Claims] A plurality of light valves respectively modulating a plurality of color lights; a color synthesizing means for synthesizing the color lights modulated by the plurality of light valves; and a projection for projecting the light synthesized by the color synthesizing means. And a projection type display device comprising: a light valve that modulates color light transmitted through the dichroic mirror, wherein the color synthesizing means includes a dichroic mirror, and in the optical path between the dichroic mirror, A light transmitting plate member optically equivalent to a dichroic mirror, wherein the dichroic mirror is disposed so as to have a predetermined inclination with respect to a plane perpendicular to a plane defined by an optical axis of each color light; The transmissive plate member is arranged so as to have the predetermined inclination with respect to a plane defined by the optical axis of each color light. And a projection display device.