JPH0561129A - Projection type display device - Google Patents

Abstract

PURPOSE:To stably provide the small-sized liquid crystal projection type display device of a large screen having decreased unequal colors and high image quality. CONSTITUTION:White light is first made incident on a dichroic mirror 2 from a light source 1. Green light and red light transmits this mirror. The reflected blue light is changed in progressing direction by a mirror 5 and is made incident on a liquid crystal light valve 9 for blue light. This light transmits dichroic prisms 6 and 7 and is made incident on a projecting lens 8 after modulation. The red light is reflected by the dichroic mirror 3 and is made incident on a liquid crystal light valve 10 for red light. This light is reflected by the joint surface of the dichroic prism 6 after modulation, transmits the dichroic prism 7 and is made incident on the projecting lens 8. The green light transmits the dichroic mirror 3, is made incident on a liquid crystal light valve 11 for green light, is changed in the progressing direction by the mirror 4 after modulation, is reflected by the joint surface of the dichroic prism 7 and is made incident on the projecting lens 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for projecting an image of each color light passing through a liquid crystal light valve in color, and more specifically, a device which is inserted into three optical paths in which white light is separated into three color lights. The present invention relates to a display device that combines and projects three color lights modulated by a single liquid crystal light valve.

[0002]

2. Description of the Related Art In recent years, projection-type display devices have tended to be compact, low-priced, and have a large screen with a short projection distance. As a result, liquid crystal light valves have become smaller and lenses have wider angles. There is.

Conventionally, as shown in FIGS. 7 and 8, projection type display devices have been roughly classified into two types of optical arrangements. FIG. 8 shows an optical path from a light source to each liquid crystal light valve surface. By making the lengths equal or nearly equal,
Care is taken to prevent the occurrence of color unevenness. 7 and 8, 1 is a white light source, 2 and 3 are dichroic mirrors, 4 and 5 are mirrors, 8 is a projection lens, and 9,
Reference numerals 10 and 11 are liquid crystal light valves, 14 and 15 are dichroic prisms, and 16 and 17 are dichroic mirrors.

[0004]

In the optical arrangement as shown in FIG. 8, when a plane-parallel plate is obliquely inserted into an outgoing ray bundle as a device for synthesizing light components, a light component passing through the plane-parallel plate is obtained. Aberrations similar to astigmatism (hereinafter referred to as astigmatism) occur in the image, and the phenomenon that the point image is disturbed occurs, resulting in deterioration of the image quality of the projected image. In the case of the configuration of FIG. 7, there is no influence of asbestos, but it becomes expensive in terms of production cost and other aspects,
The configuration of FIG. 8 is advantageous for economically suppressing the occurrence of color unevenness. Therefore, as a method of reducing the astigmatism generated in the projection type display device shown in FIG. The thickness of the plane-parallel plate used as the light component synthesizer is reduced. 2. Reduce the aperture ratio of the projection optical device (projection lens). The method such as is conceivable.

However, the above 1. The method of reducing the thickness of the plane-parallel plate is limited in terms of strength, and the distortion of the plane-parallel plate due to the holding mechanism adversely affects the projection screen. 2. The method of reducing the diameter of the projection lens is to increase the depth of field to capture the disturbance of the point image due to the ass within the range of the depth of field. It has the harmful effect of becoming dark.

When the size of the liquid crystal light valve is reduced by keeping the number of pixels of the liquid crystal light valve constant, the area of each pixel becomes small. Therefore, when an image of the liquid crystal light valve is projected by the projection lens having the same aperture ratio, the downsized depth of field is obtained in the downsized liquid crystal light valve. Further, in order to obtain a projection screen of the same size at the same projection distance, if the liquid crystal light valve size is reduced, the projection lens must be widened. Furthermore, between the optical path from each liquid crystal light valve to the projection lens,
There is a problem that the distance from each liquid crystal light valve to the projection lens becomes very long because a member for synthesizing light of three colors of red component, green component and blue component is included.

A projection type display device using three liquid crystal light valves is required to have small distortion, small chromatic aberration of magnification, and near telecentricity. However, from the liquid crystal light valve to the projection lens. If the distance is increased, it becomes more difficult to widen the angle of the projection lens, which causes a cost increase.

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection type display device having a small image size, a high image quality, a small size and a large screen at low cost.

[Means for Solving the Problems]

The present invention is intended to solve these problems, and is a member for decomposing white light generated from a light source into three-color light of a red component, a green component, and a blue component, and a member of the decomposed three-color light. It is composed of three liquid crystal light valves inserted in the optical path for the purpose of modulating each of them, a combining member for combining the modulated three color lights, and a projection optical member for projecting the combined lights, each of which is a liquid crystal from a light source. Red component up to the light valve,
In a projection type display device in which optical paths of green component and blue component are equal or substantially equal to each other, a dichroic coating is applied to a joint surface of the composite member.
It is characterized by using one or two synthetic prisms.

The composite prism is preferably a pair of right-angled isosceles triangular prisms, each of which is a rectangular parallelepiped or a rectangular parallelepiped whose oblique sides are joined to each other and whose joint surface is dichroic coated.

Further, the composite prism is composed of a pair of parallelogram prisms and one right-angled isosceles triangular prism, and each pair of parallelogram prisms has two sets of diagonals of 135 ° and 45 °, respectively. Select a quadrangular prism composed of parallelograms of 0 °, join them so that their optical axes are at right angles to each other, and apply a dichroic coating to the joining surface and a total reflection mirror coating to one of the surfaces facing the joining surface. It is desirable that one surface including the hypotenuse of a right-angled isosceles triangular prism is joined to the other surface and dichroic coating is applied to the joined surface.

Further, the synthesizing member is composed of an optical system using one synthesizing prism composed of the pair of right-angled isosceles triangular prisms and one parallel plane plate having a dichroic coating. In this case, the dichroic coating is applied. You may arrange | position so that the light component which permeate | transmits the parallel plane plate may become a blue component.

[0013]

Next, the synthesizing action of the light components having the above-mentioned structure will be described with reference to the drawings. Fig. 8 shows a structure that has less color unevenness and is advantageous in terms of cost. Two parallel dichroic plates with dichroic coating are used for combining light components. By replacing with the synthetic prism described above, the amount of generated astigmatism is suppressed. For example, as shown in FIGS. 2 and 3, when one synthetic prism in which right-angled isosceles triangular prisms are joined and one parallel plane plate having a dichroic coating are used, the amount of generated ashes is halved. .. Further, by using such a prism, excellent flatness and sufficient mechanical strength can be secured.

In this case, if the light component transmitted through the plane-parallel plate having the dichroic coating is arranged so as to have the blue component, the human eye has a low resolving power for the blue light, so that it is difficult to recognize the deterioration of the projected image.

Further, as shown in FIGS. 1 and 4, when two composite prisms in which right-angled isosceles triangular prisms are joined are used (FIG. 1) and when a parallelogram prism is used (FIG. 4). There is no generation of asbestos. Therefore, it is possible to obtain a small-sized projection type display device with little color unevenness and high image quality.

In FIG. 5, a is a liquid crystal light valve surface 2
Let 0 be the physical length from the projection lens 8, b be the physical length of the optical axis passing through the prism, and N be the refractive index.
Assuming that the refractive index of the prism is n and the refractive index of air is 1, the length L converted from the liquid crystal light valve surface 20 to the projection lens 8 by the refractive index of air is L = ab (1-1 / n). ). Here, since n> 1, L <a holds, and the synthetic prism used as a synthetic member for the light components acts to substantially reduce the distance from each liquid crystal light valve to the projection lens. It is easy to downsize and widen the angle.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings. The same reference numerals are used for common elements in the drawings. FIG. 1 shows a first embodiment according to the present invention. White light emitted from the light source 1 first enters the dichroic mirror 2 and transmits green light and red light. The reflected blue light has its traveling direction changed by the mirror 5, enters the blue light liquid crystal light valve 9, is modulated, passes through the dichroic prisms 6 and 7, and enters the projection lens 8. The red light and the green light transmitted through the dichroic mirror 2 enter the dichroic mirror 3. The red light is reflected and enters the liquid crystal light valve 10 for red light, and after being modulated,
The light is reflected by the cemented surface of the dichroic prism 6, passes through the dichroic prism 7, and enters the projection lens 8.
The green light transmitted through the dichroic mirror 3 enters the liquid crystal light valve 11 for green light and is modulated, and then the mirror 4
The direction of travel is changed by the dichroic prism 7
It is reflected by the cemented surface of and enters the projection lens 8. Here, each color light does not generate ashes after passing through the liquid crystal light valve. Each of the dichroic prisms 6 and 7 is a rectangular parallelepiped prism in which a pair of right-angled isosceles triangular prisms are attached to each other at a surface including the oblique sides thereof.
The joint surface is dichroic coated.

The light combined as described above is projected by the projection lens 8
Is enlarged and projected on the screen by. Here, the arrangement of the liquid crystal light valves 9, 10, 11 is arbitrarily exchanged, and each dichroic mirror and dichroic prism is arranged so that each color light is incident on the projection lens 8 after passing through each color light liquid crystal light valve. However, the same effect can be obtained.

2 and 3 show second and third embodiments according to the present invention. That is, in the projection type display device having the structure described in the first embodiment shown in FIG. 1, the second embodiment has a structure in which the dichroic mirror 12 is arranged instead of the dichroic prism 6.

The third embodiment has a structure in which a dichroic mirror 13 is arranged instead of the dichroic prism 7 having the structure described in the first embodiment.

In the second and third embodiments, the colored light passing through the dichroic mirror 12 or 13 produces astigmatism, but other colored light does not produce astigmatism. Therefore, when the respective color lights are combined and enlarged and projected on the screen by the projection lens 8, the influence of astigmatism is smaller than that of the conventional configuration shown in FIG. 8, and there is no practical problem.

In the second and third embodiments, the arrangement of the liquid crystal light valves 9, 10 and 11 is arbitrarily exchanged, and each dichroic mirror and dichroic prism is replaced by a liquid crystal light valve for each color light. The same effect can be obtained by arranging the dichroic mirror 12 or 13 so that it enters the projection lens 8 after passing through the dichroic mirror 12, the dichroic mirror, the liquid crystal light valve so that the color light passing through the dichroic mirror 12 or 13 becomes blue. By arranging, the influence of ass is further reduced.

FIG. 4 shows a fourth embodiment according to the present invention.
In the fourth embodiment, a dichroic prism 18 is provided instead of the mirror 4 and the dichroic prisms 6 and 7 in the projection type display device having the configuration of the first embodiment.

FIG. 6 shows the structure of the dichroic prism 18. The dichroic prism 18 is the prism 18
The three prisms a, 18b and 18c are joined together. Each of the prisms 18a and 18b is a prism having a shape of a parallelepiped having two parallel diagonals of 135 ° and 45 °, and the prism 18c is a right-angled isosceles triangular prism.

As shown in the drawing, the prism 18a and the prism 18b are joined so that the optical axes thereof are perpendicular to each other, and the hypotenuse of the prism 18c is attached to the opposite side of the joint surface of the prism 18b so that the optical axis thereof coincides. .. Prism 18
A total reflection mirror coating is applied to the opposite side of the joining surface of a. Further, dichroic coating is applied to each of the two joining surfaces. The fourth embodiment is substantially similar in effect to the first embodiment.

The present invention is not limited to the above-mentioned embodiments, and modifications can be made in details without departing from the scope of the claims.

[0027]

As described above, according to the projection type display device of the present invention, the cost is suppressed and the red component is added to the color separation system.
By making the optical path length of each color light of the green component and the blue component equal and making the intensity of each color light equal, it is possible to obtain the desired combined light and suppress astigmatism as much as possible to prevent deterioration of the image quality of the displayed image. In addition, the liquid crystal light valve can be downsized together with the downsizing of the projection lens, and a large screen and high image quality of the displayed image can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a configuration of a first embodiment of a projection type display device according to the present invention.

FIG. 2 is an explanatory view schematically showing the configuration of a second embodiment of the projection type display device according to the present invention.

FIG. 3 is an explanatory view schematically showing the configuration of a third embodiment of the projection type display device according to the present invention.

FIG. 4 is an explanatory view schematically showing a configuration of a fourth embodiment of the projection type display device according to the present invention.

FIG. 5 is an explanatory diagram showing the principle of the projection type display device according to the present invention.

FIG. 6 is an explanatory view schematically showing the structure of a compound prism in a fourth embodiment of the projection type display device according to the present invention.

FIG. 7 is an explanatory view schematically showing a first example of a conventional projection display device.

FIG. 8 is an explanatory view schematically showing a second example of the conventional projection display device.

[Explanation of symbols]

 1 White light source 2 Dichroic mirror 3 Dichroic mirror 4 Mirror 5 Mirror 6 Dichroic prism 7 Dichroic prism 8 Projection lens 9 Liquid crystal light valve 10 Liquid crystal light valve 11 Liquid crystal light valve 12 Dichroic mirror 13 Dichroic prism 16 Dichroic prism 16 Dichroic prism 15 Dichroic prism Dichroic mirror 18 Dichroic prism

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyoguchi Toruguchi, Omiya City, Saitama Prefecture, 195 Kazawano, Kazawano Kuwatono Grove 116

Claims (4)

[Claims] 1. A member for decomposing white light generated from a light source into three-color light of red component, green component, and blue component, and three members inserted in an optical path for modulating each of these decomposed three-color light. It is composed of a liquid crystal light valve, a combining member for combining these modulated three-color lights, and a projection optical member for projecting the combined light. The red component, the green component, and the blue component from the light source to the liquid crystal light valve, respectively. In a projection type display device having equal or substantially equal optical path lengths, two synthetic prisms having dichroic coating on the joint surfaces are used as the synthetic members for synthesizing the three color lights, and the synthetic prisms form a pair of right angles. A projection display device characterized by being a rectangular parallelepiped or a rectangular parallelepiped in which isosceles triangular prisms are joined. 2. A member for decomposing white light generated from a light source into three-color light of red component, green component, and blue component, and three members inserted in an optical path for modulating each of these decomposed three-color light. It is composed of a liquid crystal light valve, a combining member for combining these modulated three-color lights, and a projection optical member for projecting the combined light. The red component, the green component, and the blue component from the light source to the liquid crystal light valve, respectively. In a projection type display device having equal or substantially equal optical path lengths, a combining member for combining the three color lights, a combining prism having a dichroic coating on a joint surface, and a parallel plane plate 1 having a dichroic coating. A projection type display device characterized in that the composite prism is a rectangular parallelepiped or a rectangular parallelepiped in which a pair of right-angled isosceles triangular prisms are joined. 3. A member for decomposing white light emitted from a light source into three color lights of red component, green component and blue component, and three members inserted in an optical path for modulating each of these decomposed three color lights. It is composed of a liquid crystal light valve, a combining member for combining these modulated three-color lights, and a projection optical member for projecting the combined light. The red component, the green component, and the blue component from the light source to the liquid crystal light valve, respectively. In a projection type display device having equal or substantially equal optical path lengths, a combining member for combining the three color lights is a pair of parallelogram prisms and a pair of parallelogram prisms.
It is composed of right-angled isosceles triangular prisms, and each of the pair of parallelogram prisms is a quadrangular prism composed of two parallelograms with diagonals of 135 ° and 45 °, respectively. They are joined at right angles to each other, and a dichroic coating is applied to the joining surface and a total reflection mirror coating is applied to one of the surfaces facing this joining surface, and the other surface is made up of one right-angled isosceles triangular prism. A projection type display device characterized in that a surface including a hypotenuse is cemented and a dichroic coating is applied to the cemented surface. 4. The composite member is constituted by an optical system using one composite prism composed of the pair of right-angled isosceles triangular prisms and one parallel plane plate having a dichroic coating, and the dichroic coating is provided. The projection type display device according to claim 2, wherein the projection-type display device is arranged such that a light component that passes through the parallel plane plate is a blue component.