JPH08194272A - Liquid crystal video projector - Google Patents

Abstract

PURPOSE: To set the optical path length of the light of three primary colors to be equal to each other while restraining the increase of the number of optical parts to the minimum. CONSTITUTION: This projector is constituted of a light source 101, 1st and 2nd dichroic mirrors 102 and 106 separating the light of three primary colors, 1st, 2nd, 3rd and 4th total reflection mirrors 115, 116, 117 and 118, 1st, 2nd and 3rd liquid crystal display panels 104, 107 and 110, a dichroic prism 105 synthesizing the light of three primary colors, and a projection lens 111. The 1st dichroic mirror 102 and the 1st total reflection mirror 115 are set so that the incident angle to incident light may be an angle α smaller than 45 deg. so as to reflect the incident light obliquely backward with respect to the advancing direction of the incident light. The optical path length of the light of primary colors from the 1st dichroic mirror 102 to the display panels 104, 107 and 110 is all 156mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates light from a light source into three primary color lights using a color separation optical system, guides each of these primary color lights to a liquid crystal display panel, and modulates the brightness using a video signal. The present invention relates to a liquid crystal video projector that synthesizes by a dichroic prism and magnifies and projects the synthesized light onto a predetermined screen. More specifically, the present invention relates to an improvement in a mirror arrangement configuration of a color separation optical system including a dichroic mirror and a reflection mirror.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal video projector in which color-separated three primary color lights are modulated by a predetermined video signal using a liquid crystal display panel, the modulated lights are combined by a dichroic prism, and then enlarged and projected on a predetermined screen. Is widely known.

Such a liquid crystal video projector is composed of two dichroic mirrors and a plurality of reflecting mirrors for separating light from a light source into three primary color lights and guiding each primary color light to a corresponding liquid crystal display panel. Equipped with color separation optical system.

By the way, in such a color separation optical system, since the optical path lengths of the primary color lights from the light source to the respective liquid crystal display panels are not set to be equal to each other, the intensity distribution of the primary color lights on the screen is They do not match, resulting in color unevenness in the projected image, which causes deterioration of the image quality of the projected image.

Under these circumstances, in recent years, a liquid crystal video projector having a color separation optical system as shown in FIG. 3 has been disclosed in order to set all the optical path lengths of respective primary color lights to be equal (Japanese Patent Laid-Open Publication No. HEI 5-1993). No. 107658).

That is, to explain this prior art with reference to FIG. 3, first, the light from the light source 1 is separated by the first dichroic mirror 2 into the first primary color light R and the remaining primary color light. The first primary color light R is reflected at a right angle by the first dichroic mirror 2, and then the first reflection mirror 1
3, the second reflection mirror 14 and the third reflection mirror 15 sequentially make a right-angle reflection, and enter the first liquid crystal display panel 4.

On the other hand, the remaining primary color light is reflected at a right angle by the fourth reflecting mirror 16 and then separated into the second primary color light G and the third primary color light B by the second dichroic mirror 6.
The second primary color light G is reflected at a right angle by the second dichroic mirror 6. The second primary color light G is a fifth reflection mirror arranged on the back surface of the first reflection mirror 13.
The light is reflected at a right angle at 17 and enters the second liquid crystal display panel 7.
Further, the third primary color light B is reflected at a right angle by the sixth reflection mirror 18 and enters the third liquid crystal display panel 10. After that, the primary color lights transmitted through the respective liquid crystal display panels 4, 7, 10 are combined by the dichroic prism 5, and the combined primary color lights are enlarged and projected on the screen 12 by the projection lens 11.

In this prior art, two dichroic mirrors 2, 6 and six reflective mirrors 13, 14, 15, 1 are used.
Since 6, 17, 18 are arranged as described above and the optical path lengths of the primary color lights R, G, B from the light source 1 to the liquid crystal display panels 4, 7, 10 are set equal to each other, It is possible to avoid the occurrence of color unevenness.

[0009]

By the way, in the above-mentioned prior art shown in FIG. 3, in order to set the optical path length of each primary color light to be equal to each other, six reflecting mirrors are used in addition to two dichroic mirrors. However, if such a large number of reflecting mirrors are used, the cost required for the optical component increases, the number of assembling steps also increases, and the manufacturing cost eventually increases. Moreover, since the space for disposing the optical components is increased, it is against the demand for downsizing the device.

The present invention has been made in view of the above circumstances, and provides a liquid crystal video projector capable of setting the optical path lengths of three primary color lights to be equal to each other while suppressing an increase in the number of optical components to a minimum. That is the purpose.

[0011]

In the liquid crystal video projector of the present invention, light reflection by at least one dichroic mirror and at least one reflection mirror is changed to oblique reflection other than right angle reflection, and two dichroic mirrors and four reflections are used. By configuring the color separation optical system with mirrors, 3
The feature is that the optical path lengths of the three primary color lights are set to be equal to each other.

That is, the liquid crystal video projector of the present invention separates the light from the light source into three primary color lights and irradiates the liquid crystal display panels corresponding to the respective primary color lights, and in each of these liquid crystal display panels, the respective primary color lights are emitted. In the liquid crystal video projector, luminance is modulated by a video signal corresponding to the primary color light, the modulated primary color lights are combined by a dichroic prism, and the combined three primary color lights are enlarged and projected on a predetermined screen. Dichroic mirror for separating the light from the first primary color light and the remaining primary color light, a reflection mirror for reflecting the remaining primary color light, and the remaining primary color reflected from this reflection mirror A second dichroic mirror that separates light into a second primary color light and a third primary color light, and a first dichroic mirror that separates the light. And three reflection mirrors for reflecting the primary color light and the second primary color light and the third primary color light separated by the second dichroic mirror to irradiate the liquid crystal display panel corresponding to each primary color light. , The first dichroic mirror so that the light incident on the first dichroic mirror and the first primary color light incident on a reflection mirror that reflects the first primary color light are reflected in an oblique direction, respectively. , And the reflection mirror for reflecting the first primary color light is set at a predetermined angle,
It is characterized in that the optical path lengths of the three primary color lights are substantially equal to each other.

The term "obliquely reflected" means that incident light is reflected in an angle direction other than 90 ° and 180 °.

Further, the dichroic mirror and the reflection mirror mean means having a dichroic mirror surface and a reflection mirror surface, and include a dichroic prism and a reflection prism, respectively.

[0015]

In the color separation optical system of the conventional liquid crystal video projector, the light reflections at the dichroic mirror and the reflection mirror are all set to right angle reflection as shown in FIG. In the system, if the optical path lengths of the three primary color lights are set equal to each other, the number of reflection mirrors will inevitably increase.

The present inventor has made it possible to minimize the number of reflection mirrors by changing the concept of changing the light reflection in at least a part of the dichroic mirror and the reflection mirror to oblique reflection other than right angle reflection.

As described above, the present inventor has been able to change the above-mentioned idea because the method of assembling the optical system is different from the conventional method of fixing each optical component on the optical substrate while positioning and holding the optical component. In recent years, there has been a change to a method of fitting corresponding optical components on a molded substrate provided with grooves.
It is based on the technical background that the assembling work does not become troublesome even if the mirror member is not arranged at an angle of 45 ° with respect to the incident light, that is, at an angle that achieves right angle reflection.

That is, the present inventor has, based on the above knowledge and a change of idea, reflect the first dichroic mirror of the color separation optical system and the first primary color light from the first dichroic mirror to the first liquid crystal display panel. By setting the arrangement angle of the reflecting mirrors to a predetermined angle at which the incident light is obliquely reflected, it becomes possible to omit the two reflecting mirrors conventionally arranged between these two mirrors, and It is possible to make the optical path lengths of the three primary color lights equal to each other while minimizing the increase in the number of parts.

As a result, it is possible to prevent the occurrence of color unevenness in the projected image on the screen while suppressing an increase in manufacturing cost.

[0020]

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

FIG. 1 is a schematic diagram showing a liquid crystal video projector according to a first embodiment of the present invention. The liquid crystal video projector shown in FIG. 1 includes a light source 101 and first and second dichroic mirrors 102, 10 for separating light of three primary colors.
6 and the first, second, third and fourth total reflection mirrors 115
, 116, 117, 118, first, second and third liquid crystal display panels 104, 107, 110, a dichroic prism 105 for combining light of the three primary colors, and a projection lens 111.

The light source 101 is a high brightness white light source such as a halogen lamp or a metal halide lamp, and its output light 103 is made into a parallel light flux by an optical system (not shown).

A UV / IR cut filter for cutting ultraviolet light and infrared light is usually arranged on the light emitting side of the light source 101, and a cooling means for cooling the light source 101 and its vicinity by air cooling or the like. Is provided.

The first dichroic mirror 102 and the second dichroic mirror 106 are each provided with a dichroic film made of a dielectric multilayer film having spectral characteristics as a red light reflection mirror and a green light reflection mirror on a glass substrate. Has been formed.

The three liquid crystal display panels 104, 107,
Each of 110 is composed of a twisted nematic (TN) type liquid crystal display element, displays an image in accordance with a corresponding image signal from a liquid crystal driver (not shown), and modulates the intensity of each incident primary color light.

Further, the dichroic prism 105 is
It is formed by joining four right-angled prisms, and two orthogonally joined surfaces are provided with a dichroic film composed of a dielectric multilayer film having spectral characteristics as a red light reflection mirror and a blue light reflection mirror, respectively. And red, blue,
It is possible to combine the three primary color lights of green into one light beam of white light.

Further, the projection lens 211 is constructed so that the combined three primary color lights can be projected on a screen arranged at a predetermined distance, and a full color image can be enlarged and projected on this screen.

By the way, the second dichroic mirror 10
6 and the second, third and fourth total reflection mirrors 116, 117,
118 is arranged at an angle of 45 ° with respect to the incident light (incident angle is 45 °), and is set to reflect the incident light in a direction at right angles, the first dichroic mirror 102 and the first dichroic mirror 102 The total reflection mirror 115 has an incident angle with respect to each incident light.
It is set so that the angle α is smaller than 45 °,
This incident light is reflected obliquely backward with respect to the traveling direction of the incident light.

The operation of the liquid crystal video projector configured as described above will be described below.

Light (white light) 103 output from the light source 101
Is separated into red light R and the remaining primary color light by the first dichroic mirror 102. Since the first dichroic mirror 102 has the spectral characteristic of reflecting the red light R as described above, and is set so that its incident angle with respect to the light 103 is an angle α smaller than 45 °, Red light R
Is reflected obliquely backward, and the remaining primary color light is transmitted.

The first total reflection mirror 115 is arranged so as to be parallel to the first dichroic mirror 102, and the red light R reflected by the first dichroic mirror 102 is 45 ° above. The red light R is set so as to enter at a smaller angle α, and is reflected toward the first liquid crystal display panel 104.

On the other hand, the remaining primary color light transmitted from the first dichroic mirror 102 is reflected at a right angle by the second total reflection mirror 116 and separated into green light G and blue light B by the second dichroic mirror 106. .

The second dichroic mirror 106 is
As described above, it has the spectral characteristic of reflecting the green light G, and since the incident angle is set to 45 ° with respect to the remaining primary color light, the green light G is reflected at right angles, The blue light B is transmitted.

The green light G reflected by the second dichroic mirror 106 is reflected at a right angle by the third total reflection mirror 117 and guided to the second liquid crystal display panel 107, while
The blue light B transmitted through the second dichroic mirror 106 is reflected at a right angle by the fourth total reflection mirror 118 and guided to the third liquid crystal panel 110.

In this way, the corresponding liquid crystal display panel
The respective primary color lights R, G, B incident on the 104, 107, 110 are brightness-modulated by the video signals corresponding to the primary color lights R, G, B in the liquid crystal display panels 104, 107, 110, and thereafter, The dichroic mirror 105 combines the light into a single white light, which is enlarged by the projection lens 111 and projected on a predetermined screen. As a result, the image displayed on each of the liquid crystal display panels 104, 107 and 110 is projected as a full color image on the screen.

FIG. 1 shows the distance on the optical axis between the optical members in the apparatus of this embodiment. That is, the distance between the first dichroic mirror 102 and the first total reflection mirror 115 is 116 mm, the distance between the first total reflection mirror 115 and the first liquid crystal display panel 104 is 40 mm, and the first dichroic mirror 102 is The distance between the second total reflection mirrors 116 is 46 mm,
Second total reflection mirror 116 and second dichroic mirror
The distance between 106 is 40 mm, the second dichroic mirror 106
And the distance between the third total reflection mirror 117 and the third total reflection mirror 117 is 50 mm, and the distance between the third total reflection mirror 117 and the second liquid crystal display panel 107 is 20 mm.
mm, the distance between the second dichroic mirror 106 and the fourth total reflection mirror 118 is set to 50 mm, and the distance between the fourth total reflection mirror 118 and the third liquid crystal display panel 110 is set to 20 mm. Thereby, the optical path length of the red light R from the first dichroic mirror 102 to the first liquid crystal display panel 104,
Dichroic mirror 102 to second LCD display panel
The optical path length of the green light G up to 107 and the optical path length of the blue light G from the first dichroic mirror 102 to the third liquid crystal display panel 110 are all equal to 156 mm.

Next, a liquid crystal video projector according to the second embodiment of the present invention will be described with reference to FIG. Note that FIG.
The numbers given to the respective optical members are shown by adding 100 to the numbers given to the corresponding members of the first embodiment device, and in the following description, they are the same as those of the first embodiment device. The description of the optical members is omitted.

The apparatus of the second embodiment has the spectral characteristics of the first dichroic mirror 202 and the second total reflection mirror 216.
The arrangement angle is different from that in the first embodiment.

That is, the first dichroic mirror 202 has a spectral characteristic of reflecting the green light G and the blue light B and transmitting the red light R.
Only the red light R out of the white light 203 from is transmitted and the remaining primary color light is reflected.

The second total reflection mirror 216 reflects the remaining primary color light in the direction of the second dichroic mirror 206, and the incident angle is larger than 45 ° with respect to the remaining primary color light. Light from light source 201
203 is a part of this second total reflection mirror 216 and is designed so as not to be vignetted.

Note that FIG. 2 shows the distances on the optical axis between the optical members in the apparatus of the second embodiment, as in FIG. That is, the distance between the first dichroic mirror 202 and the first total reflection mirror 215 is 120 mm, and the distance between the first total reflection mirror 215 and the first liquid crystal display panel 204 is 40 m.
m, the distance between the first dichroic mirror 202 and the second total reflection mirror 216 is 50 mm, the distance between the second total reflection mirror 216 and the second dichroic mirror 206 is 40 mm, and the distance between the second dichroic mirror 206 and the second dichroic mirror 206 is The distance between the third total reflection mirror 217 is 50 mm, the distance between the third total reflection mirror 217 and the second liquid crystal display panel 207 is 20 mm, and the distance between the second dichroic mirror 206 and the fourth total reflection mirror 218. Is set to 50 mm, and the distance between the fourth total reflection mirror 218 and the third liquid crystal display panel 210 is set to 20 mm. Thereby, the optical path length of the red light R from the first dichroic mirror 202 to the first liquid crystal display panel 204, the first dichroic mirror 202
To the second liquid crystal display panel 207 and the optical path length of the blue light G from the first dichroic mirror 202 to the third liquid crystal display panel 210 are 160 mm, which are equal lengths.

The liquid crystal video projector of the present invention is not limited to the above embodiment, and various modifications can be made.

For example, it is possible to select values other than those shown in the figures for the arrangement positions and angles of the first dichroic mirror and the first total reflection prism.
The positions and angles of the other mirrors can be set so that the incident angle of the incident light is an angle other than 45 °.

The distance between the optical members is not limited to that in the above embodiment.

Further, in the above embodiment, the total reflection mirror is used as the reflection mirror, but it is also possible to replace some of the reflection mirrors with half mirrors and adjust the light amount between the primary color lights.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a liquid crystal video projector according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a liquid crystal video projector according to a second embodiment of the present invention.

FIG. 3 is a schematic view showing a conventional liquid crystal video projector.

[Explanation of symbols]

1, 101, 201 Light source 103, 203 Light 2, 6, 102, 106, 202, 206 Dichroic mirror 13, 14, 15, 16, 17, 18, 115, 116, 117, 118, 21
5, 216, 217, 218 Reflection mirror (total reflection mirror) 4, 7, 10, 104, 107, 110, 204, 207, 210
Liquid crystal display panel 5,105,205 Dichroic prism 11,111,211 Projection lens 12 Screen

Claims (1)

[Claims] 1. A light source separates light into three primary color lights and irradiates the liquid crystal display panels corresponding to the respective primary color lights, and in each of these liquid crystal display panels, the respective primary color lights are image signals corresponding to the primary color lights. In the liquid crystal video projector, the light from the light source is first modulated by the brightness modulation, the modulated primary colors are combined by a dichroic prism, and the combined three primary colors are enlarged and projected on a predetermined screen. A first dichroic mirror that separates the light and the remaining primary color light, a reflection mirror that reflects the remaining primary color light, and a second dichroic mirror that reflects the remaining primary color light reflected from the reflection mirror.
Second dichroic mirror for separating the primary color light and the third primary color light, and a first dichroic mirror for separating the primary color light by the first dichroic mirror.
And the three reflection mirrors that reflect the second primary color light and the third primary color light separated by the second dichroic mirror and irradiate the liquid crystal display panel corresponding to the respective primary color lights. The first dichroic so that the light incident on the first dichroic mirror and the first primary color light incident on a reflection mirror that reflects the first primary color light are reflected in an oblique direction. A liquid crystal video projector, characterized in that a mirror and a reflection mirror for reflecting the first primary color light are set at a predetermined angle, and optical path lengths of the three primary color lights are substantially equal to each other.