JP3074831B2 - LCD projection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projection device, and more particularly to a structure for separating or synthesizing light using a dichroic element.

[0002]

2. Description of the Related Art FIG. 7 shows a structural example of a conventional liquid crystal projection device.

[0003] Irradiation light emitted from a light source 1 using a metal halide lamp or the like is collected forward by a converging reflection mirror 2 and is red or red by dichroic mirrors 3 and 4.
It is separated into three primary colors, green and blue. Then, the respective lights enter the transmissive liquid crystal plates 6r, 6g, 6b.

Light transmitted through the liquid crystal plates 6r, 6g, and 6b is image light that captures an image of each liquid crystal plate, is combined with a color image by dichroic mirrors 8, 9, and is enlarged and projected by a projection lens 10. .

At this time, in order to widen the viewing angle characteristics to the left and right, the polarizing direction of the polarizing plate is attached to the liquid crystal plate by rotating the polarizing direction obliquely 45 degrees from the vertical. Therefore, as shown in FIG. 8, the polarization direction of the light incident on the dichroic mirror for synthesizing the image light is also inclined at 45 degrees. The light incident on the dichroic mirror that separates the light is unpolarized light. However, since the polarization direction of the polarizing plate is 45 degrees, the light incident on the liquid crystal plate from the dichroic mirror for separation is oblique. This means that 45-degree polarized light is used, which is the same as when 45-degree polarized light is incident on the dichroic mirror for separation.

[0006]

The spectral characteristics of a dichroic mirror differ between p-polarized light and s-polarized light as shown in FIG. Compared to s-polarized light, p-polarized light has a small change in spectral characteristics when the incident angle of light is shifted, and has a good transmittance of unnecessary colors as shown in FIG. It is advantageous. The spectral characteristic of polarized light in the oblique 45 degree direction is p
This is the average of polarized light and s-polarized light. In addition to the above-mentioned points, the wavelength range where the transmittance becomes maximum to minimum is widened as shown in FIG. Efficiency, color purity and light utilization are not good.

[0007] The polarization direction of the polarizing plate is set at an angle of 45 with respect to the liquid crystal plate.
In the case where the angle is set in the degree direction, in the conventional optical system, a polarized light beam in the diagonal direction of 45 degrees is incident on the dichroic mirror, and the color purity and the light utilization rate are deteriorated.

An object of the present invention is to provide a liquid crystal projection apparatus for separating and synthesizing light using a dichroic element, in which the efficiency of the separation and synthesis of the light is high, the color purity and the light utilization rate are good. It is in.

[0009]

In order to achieve the above object, according to the present invention, a first dichroic element for separating light from a light source into three primary color lights and a polarizing direction of a polarizing plate are set to be vertical.
A liquid crystal projection device comprising: three transmission liquid crystal units rotated by 45 degrees more; and a second dichroic element that combines light transmitted through each transmission liquid crystal unit and guides the light to a projection lens. The liquid crystal unit has a configuration in which polarization rotating means for rotating the polarization direction is provided on the light incident side and the light emission side.

[0010]

The polarization rotating means rotates the polarization direction of light.

[0011]

An embodiment using p-polarized light will be described below.

FIG. 1 shows a first embodiment of a liquid crystal projection device according to the present invention.

The irradiation light emitted from the lamp 1 is collected forward by the condensing reflecting mirror 2 and becomes almost parallel light.

The irradiation light then enters the red reflecting dichroic mirror 3. The red light in the irradiation light is reflected at right angles by the dichroic mirror 3, further reflected by the total reflection mirror 7, passes through the half-wave plate 5r, and enters the liquid crystal plate 6r.

The irradiation light transmitted through the dichroic mirror 3 is incident on a green reflecting dichroic mirror 4, and the green light is reflected in a right angle direction, transmitted through a half-wave plate 5 g and transmitted through a liquid crystal plate 6.
g.

The light transmitted through the dichroic mirror 4 is blue light, transmitted through the half-wave plate 5b, and enters the liquid crystal plate 6b.

As shown in FIG. 2, the light incident on each liquid crystal plate is rotated by 45 degrees by the half-wave plates 5r, 5g, and 5b, so that the light incident on the dichroic mirror for light separation is changed. The polarized light enters the liquid crystal plates 6r, 6g, 6b as polarized light inclined at 45 degrees. The image light transmitted through each liquid crystal plate is again rotated by 45 degrees by the half-wave plates 5r, 5b, and 5g to become p-polarized light.
The light enters the dichroic mirrors 8 and 9 and is synthesized. Then, the synthesized image light is enlarged and projected on the screen by the projection lens 10.

FIG. 3 shows a second embodiment of the liquid crystal projection device according to the present invention, which has a configuration using a cross dichroic mirror 12 for synthesizing image light. The image light transmitted through each liquid crystal plate is divided into half-wave plates 5r, 5g,
After the polarization is rotated by 45 degrees by b, it becomes p-polarized light, is synthesized into a color image by the cross dichroic mirror 12, and is enlarged and projected by the projection lens 10.

FIG. 4 shows a third embodiment of the liquid crystal projection device according to the present invention. The light emitted from the lamp 1 is collected by the condensing reflection mirror 2 and separated into three primary colors by dichroic mirrors 8 and 11, and then the p-polarized light in the light is changed to a half-wave plate 5r, 5g, 5b. Is rotated by 45 degrees, and the liquid crystal plates 6r, 6g,
6b. Light transmitted through each liquid crystal plate is enlarged and projected on a screen by three projection lenses 10.

FIG. 5 shows a fourth embodiment of the liquid crystal projection device according to the present invention. Emit red, green and blue light
The light emitted from the three lamps 13, 14, and 15 is transmitted through the respective liquid crystal plates, and then the polarization is rotated by 45 degrees by a half-wave plate, turned into p-polarized light, and converted into a color image by the cross dichroic mirror 12. And the image is enlarged and projected on the screen by the projection lens 10.

[0021]

According to the present invention, the spectral efficiency of light is improved, and the color purity and light utilization are improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a polarization direction of light of a part of FIG.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

FIG. 6 is a diagram showing the spectral reflectance of a dichroic mirror at p and s polarizations.

FIG. 7 is a diagram showing a configuration of a conventional liquid crystal projection device.

FIG. 8 is a diagram illustrating a polarization direction of light of a part of FIG. 7;

[Description of Signs] 4 ... Green reflection dichroic mirror, 5 ... 1/2 wavelength plate, 6 ... Liquid crystal plate, 7 ... Total reflection mirror, 8 ... Green reflection dichroic mirror.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 27/28 G02F 1/13 505

Claims (1)

(57) [Claims] A first light source for separating light from a light source into three primary color lights;
Dichroic element and the polarizing direction of the polarizing plate
A liquid crystal projection device comprising: three transmissive liquid crystal units rotated by 45 degrees; and a second dichroic element that combines light transmitted through each of the transmissive liquid crystal units and guides the light to a projection lens. A liquid crystal projection device, comprising: a polarization rotation unit for rotating a polarization direction on a light incident side and a light output side of the unit.