JPH0854596A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To provide a high-luminance and high-resolution liquid crystal projector capable of reducing the number of parts, simplifying structure and making the entire device compact. CONSTITUTION:Since the same optical images are formed on optical address system liquid crystal display panels 7 to 9 by image light displayed on respective CRTs 19 to 21 for red, green and blue writing and projected by projected light from a light source 2, the image having high luminance and high resolution is obtained. Furthermore, the projected light from the light source 2 is selected as the light of specified polarization component by one polarizing beam splitter 1 and one dichroic prism 4. The selected light of the specified polarization component is separated to specified wavelength regions and the reflected light, which is the projected light reflected, is synthesized in accordance with the optical images on the display panels 7 to 9. The polarization component of the synthesized image light is selected and projected, so that the number of parts is extremely small, the structure is simple and the entire device is made compact in comparison with the conventional projector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector.

[0002]

2. Description of the Related Art Generally, a projector forms an image by an image forming means and enlarges and projects the image on a screen by a projection lens. Such projectors include those using a CRT or a transmissive liquid crystal display panel as an image forming means. The former projector that uses a CRT has a structure in which an image created by the CRT is enlarged and projected on a screen by a projection lens. Therefore, the brighter the image, the larger the beam current is required, and the higher brightness is required. Accordingly, there is a problem that the resolution is reduced. The latter projector using a transmissive liquid crystal display panel has a structure in which the back surface of the liquid crystal display panel is irradiated with light from a light source, and an image created by the liquid crystal display panel is enlarged and projected onto a screen by a projection lens. Therefore, as the resolution is increased, the aperture ratio (light transmittance) is decreased and the brightness is decreased, and it is difficult to use a high-output light source due to heat generated by heat absorption of the polarizing plate. There is a problem.

Therefore, in the past, high brightness,
In order to achieve high resolution, a liquid crystal projector using an optically addressed liquid crystal display panel and a writing CRT as image forming means has been developed. In this type of liquid crystal projector, light from a light source is divided into three wavelength regions of red, green and blue by three dichroic filters and incident on red, green and blue optical addressing liquid crystal display panels. In addition to the above, on the back of each liquid crystal display panel, for red, green,
Image light created by each CRT for blue is projected by a projection lens for writing, an optical image corresponding to each of these images is created on each liquid crystal display panel, and each liquid crystal display is created according to these optical images. The structure is such that the light incident on the panel is reflected and is enlarged and projected onto one screen by each projection lens.

[0004]

However, in such a conventional liquid crystal projector, the light from the light source is decomposed into three kinds of wavelength regions by using three dichroic filters, and the decomposed light in each wavelength region is decomposed. Must be led to each liquid crystal display panel for red, green and blue, and for red,
Since it is necessary to create an optical image corresponding to the image light of each CRT for green and blue on each liquid crystal display panel, and combine these optical images on one screen by each projection lens to project them in an enlarged manner, There is a problem that the number of parts is very large, the structure is complicated, and the entire device becomes large. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a high-luminance, high-resolution liquid crystal projector having a small number of parts, a simple structure, and a compact size of the entire device. .

[0005]

According to the present invention, there is provided a light source, a polarization beam splitter for selecting a polarization component of light from the light source, and for selecting again a polarization component of reflected light of the selected and emitted light. , A dichroic prism that decomposes light of a predetermined polarization component selected by the polarization beam splitter into three wavelength regions of red, green, and blue, and emits each light, and combines reflected light of the emitted light, and this dichroic prism The red, green, and blue photo-addressed liquid crystal display panels provided corresponding to the respective exit surfaces, and the liquid crystal display panels are irradiated with red, green, and blue image lights, respectively. Each display device for writing is provided. In this case, as described in claim 2,
A liquid crystal display panel has a liquid crystal layer, a dielectric mirror layer, a light-shielding layer, and a photoconductive layer laminated between a pair of transparent electrode substrates. It is desirable that the impedance of the photoconductive layer is changed so that the same optical image as that of the photoconductive layer is formed on the liquid crystal layer. Further, as described in claim 3, the liquid crystal layer of the liquid crystal display panel is 1 / It is desirable to have the same function as a four-wave plate.

[0006]

According to the present invention, the polarization component of the light from the light source is selected by the polarization beam splitter, and the light of the selected predetermined polarization component, for example, the light of the S polarization component of the P polarization component and the S polarization component is made into one dichroic. It is divided into three wavelength regions of red, green and blue by a prism and is made incident on each liquid crystal display panel of the red, green and blue photo-addressing system, and for the red displayed on each display device for writing. , Green and blue image lights are respectively projected onto the respective liquid crystal display panels to form optical images, and the reflected lights from the respective liquid crystal display panels corresponding to the respective optical images are combined by one dichroic prism. , The polarized light component is again selected by the polarized beam slitter and projected. Therefore, the same optical image is created on each liquid crystal display panel of the optical addressing system by the image light of each display device for writing, and each of these optical images is projected by the projection light from the light source. In addition, the projection light from the light source is selected as the light of the specific polarization component by the one polarization beam slitter and the one dichroic prism, and the light of the selected specific polarization component is selected in the predetermined wavelength range. In addition to disassembling into, the projected light is reflected according to the optical image of each liquid crystal display panel, and the reflected light is combined, and the polarized component of this combined image light is selected again and projected. Therefore, the number of parts is very small, the structure is simple, and the entire apparatus can be made compact.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid crystal projector of the present invention will be described below with reference to FIGS. FIG.
FIG. 1 is a schematic configuration diagram of a liquid crystal projector of the present invention. This liquid crystal projector includes a polarization beam splitter 1. The polarization beam splitter 1 is for selecting and emitting the polarization component of the light from the light source 2, and the light from the light source 2 is incident from the incident surface 1a on the right side. Of the left emission surface 1b through which the light of
The splitter surface 3 that emits light from the light source 2 and reflects the light of the S-polarized component and emits it from the lower emission surface 1c.
It has a structure in which it is arranged at an angle of about 45 ° with respect to.

The exit surface 1 below the polarization beam splitter 1
A dichroic prism 4 is arranged in the vicinity of c correspondingly. The dichroic prism 4 has an upper surface 4a through which the light of the S-polarized component from the polarization beam splitter 1 is transmitted.
Of the incident light, and transmits or reflects light in a specific wavelength range. That is, in this embodiment, light in the red wavelength region is reflected toward the left surface 4b, and light of other wavelengths is transmitted through the first dichroic surface 5 and light in the blue wavelength region is reflected toward the right surface 4c. , And a second dichroic surface 6 through which other light is transmitted, and the first and second dichroic surfaces 5 and 6 are provided orthogonal to each other, whereby wavelength regions other than the red wavelength region and the blue wavelength region, that is, Light in the green wavelength region is emitted from the lower surface 4d, and the reflected light of each emitted light is combined as described later.

Both left and right side surfaces 4 of the dichroic prism 4
b and 4c and the lower surface 4d in the vicinity thereof, the respective surfaces 4b to 4d.
Corresponding to the above, liquid crystal display panels 7 to 9 of red, green and blue photo-addressing systems are respectively arranged. As shown in FIG. 2, each of the photo-addressable liquid crystal display panels 7 to 9 includes a liquid crystal layer 12, a dielectric mirror layer 13, a light shielding layer 14, and a photoconductive layer between a pair of transparent electrode substrates 10 and 11. 1
5 has a laminated structure. Then, the photoconductive layer 15
As shown in FIG. 2, a voltage is applied in series to the liquid crystal layer 12. The photoconductive layer 15 has an extremely high resistance when no light is incident thereon. Therefore, almost no voltage is applied to the liquid crystal layer 12, and an optical image is formed on the photoconductive layer 15. When formed, the resistance of the photoconductive layer 15 changes according to the brightness and darkness, and the same optical image as the photoconductive layer 15 is formed on the liquid crystal layer 12. On the other hand, the dielectric mirror layer 13 reflects almost 100% of the light incident on the liquid crystal layer 12. The liquid crystal layer 12 is a TN type having the same function as a quarter-wave plate by twisting the liquid crystal molecules at a predetermined angle. That is, the liquid crystal layer 12 rotates the light of the S-polarized component that is incident when no voltage is applied by 45 °, and the dielectric mirror layer 13
The light reflected by is further rotated by 45 °, so that it is emitted as the light of the P-polarized component, and the light of the S-polarized component that is incident when a voltage is applied is directly reflected by the dielectric mirror layer 13 to convert the light of the S-polarized component. It has a structure that allows light to be emitted.

On the back surface of each liquid crystal display panel 7-9, FIG.
As shown in FIG.
Each CRT 19 for writing for red, green, and blue via 8
21 are arranged respectively. That is, the CRT 19 for red is disposed correspondingly on the rear surface of the liquid crystal display panel 7 for red on the left side, and the CRT 20 for blue is disposed correspondingly on the rear surface of the liquid crystal display panel 8 for blue on the right side. On the back surface of the lower liquid crystal display panel 9 for green, a CRT 21 for green is arranged correspondingly. And each CRT 19-21
An image corresponding to each color of red, green, and blue is displayed, and each image light thereof is written in each photoconductive layer 15 of the liquid crystal display panels 7 to 9 by each projection lens 16 to 18.

A projection lens 22 is arranged in the vicinity of the exit surface 1d on the upper side of the polarization beam splitter 1 corresponding thereto. The projection lens 22 is for enlarging and projecting a combined image of the P-polarized light components which are combined by the dichroic prism 4 and whose polarization components are selected by the polarization beam splitter 1, onto a screen (not shown).

In such a liquid crystal projector, the light source 2
From the right side of the polarization beam splitter 1
When incident on the splitter surface 3, only the S-polarized component light is reflected by the splitter surface 3 and is emitted from the lower emission surface 1c, and the P-polarized component light is transmitted through the splitter surface 3 and emitted from the left emission surface 1b. . When the light of the S-polarized component emitted from the lower emission surface 1c enters the dichroic prism 4 from the upper surface 4a, the light in the red wavelength region of the incident light is reflected by the first dichroic surface 5 toward the left surface 4b. The light in the blue wavelength region is reflected by the second dichroic surface 6 toward the right surface 4c and is incident on the liquid crystal display panel 8 for blue. The light in the area is transmitted through the first and second dichroic surfaces and is incident on the liquid crystal display panel 9 for green from the lower surface 4d.

In this state, each CRT for red, green and blue
When an image is displayed on 19 to 21, each image light is applied to each photoconductive layer 15 of each liquid crystal display panel 7 to 9 by the writing projection lenses 16 to 18, respectively. Then
An optical image is formed on each photoconductive layer 15, the resistance of the photoconductive layer 15 changes according to the brightness and darkness, and the same optical image as the photoconductive layer 15 is formed on the liquid crystal layer 12. As described above, in the liquid crystal layer 12 on which the optical image is formed, the portion corresponding to the optical image is in the voltage non-applied state, and the other portions are in the voltage applied state. Therefore, the dichroic prism 4
Of the light in the specific wavelength region incident on the liquid crystal layer 12 of each of the liquid crystal display panels 7 to 9, the S-polarized component light incident on the portion corresponding to the optical image of the liquid crystal layer 12 is 45
The light is rotated by ° and reflected by the dielectric mirror layer 13, and is again rotated by 45 ° in the liquid crystal layer 12 to become the light of the P-polarized component and is incident on the dichroic prism 4. In addition, the S-polarized component light incident on a portion that does not correspond to the optical image passes through the liquid crystal layer 12 as it is, and the dielectric mirror layer 13
The reflected light is incident on the dichroic prism 4 with the S-polarized component being reflected.

The lights in the red, green, and blue wavelength regions that have entered the dichroic prism 4 are combined by the first and second dichroic surfaces 5 and 6, and the combined image light is a splitter of the polarization beam splitter 1. The polarization component is again selected at surface 3. That is, the light of the S-polarized component of the composite image is reflected by the splitter surface 3 toward the light source 2 side, the light of the P-polarized component of the composite image is transmitted, and enlarged and projected as a color image on the screen by the projection lens 22. become.

Thus, in this liquid crystal projector,
Since the same optical image is created on each of the liquid crystal display panels 7-9 of the optical addressing system by the image light of each CRT 19-21 for writing, and this optical image is projected by the light (projection light) from the light source 2, a high brightness is obtained. In addition, it is possible to obtain a high resolution one, and the projection light from the light source 2 is selected as the light of the specific polarization component by the one polarization beam slitter 1 and the one dichroic prism 4, and the selected specific polarization component The light is decomposed into predetermined wavelength regions, and the reflected light obtained by reflecting the projection light according to the optical image of each liquid crystal display panel 7 to 9 is synthesized, and the polarization component of the synthesized image light is selected again. Therefore, the number of parts is much smaller than the conventional one, the structure is simple, and the entire apparatus can be made compact.

In the above embodiment, the case where the CRTs 19 to 21 are used as the display devices for writing has been described, but it is not necessarily a CRT and a liquid crystal display panel with a backlight may be used. Further, in the above-described embodiment, S is used on the splitter surface 3 of the polarization beam splitter 1.
Although the light of the polarization component is reflected and the light of the P polarization component is transmitted, the invention is not limited to this. For example, the light of the P polarization component is reflected and S
The polarization beam splitter 1 having a splitter surface that transmits the light of the polarization component may be used.

[0017]

As described above, according to the present invention, the same optical image is formed on each liquid crystal display panel of the optical address system by the image light of each writing display device, and this optical image is emitted from the light source. Since it is projected by the projection light, high brightness,
It is possible to obtain a high-resolution one, and the projection light from the light source is selected as the light of the specific polarization component by one polarization beam slitter and one dichroic prism, and the light of the selected specific polarization component is set to a predetermined value. Since the reflected light is decomposed into wavelength regions and the projected light is reflected according to the optical image of each liquid crystal display panel, and the polarized component of the combined image light is selected again and projected, Compared with, the number of parts is very small, the structure is simple, and the entire apparatus can be made compact.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a liquid crystal projector of the present invention.

FIG. 2 is a cross-sectional view showing a photo-addressing type liquid crystal display panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polarization beam splitter 2 Light source 4 Dichroic prism 7-9 Optical addressless liquid crystal display panel 11 Transparent electrode substrate 12 Liquid crystal layer 13 Dielectric mirror layer 14 Light-shielding layer 15 Photoconductive layer 16-18 Writing projection lens 19-21 CRT 22 projection lens for writing

Claims (6)

[Claims] 1. A light source, a polarization beam splitter that selects a polarization component of light from the light source, and again selects a polarization component of reflected light of light that is selected and emitted, and a polarization beam splitter that is selected by the polarization beam splitter. Corresponding to a dichroic prism that decomposes light of a predetermined polarization component into three wavelength regions of red, green, and blue and emits each light, and combines reflected light of each emitted light, and each emission surface of the dichroic prism And liquid crystal display panels of the red, green, and blue optical addressing systems, and writing displays for irradiating the liquid crystal display panels with red, green, and blue image lights, respectively. A liquid crystal projector comprising: a device. 2. The liquid crystal display panel, wherein a liquid crystal layer, a dielectric mirror layer, a light shielding layer, and a photoconductive layer are laminated between a pair of transparent electrode substrates, and an optical image is formed on the photoconductive layer. ,
2. The liquid crystal projector according to claim 1, wherein the impedance of the photoconductive layer is changed according to the brightness and darkness, and the same optical image as that of the photoconductive layer is formed on the liquid crystal layer. 3. The liquid crystal projector according to claim 2, wherein the liquid crystal layer has the same function as a quarter-wave plate. 4. The liquid crystal projector according to claim 1, wherein the writing display device is a CRT display. 5. The projection lens for projecting an image on a screen is arranged on the exit surface side of the polarization beam splitter located on the side opposite to the dichroic prism. LCD projector. 6. The front surface of each display device for writing,
6. The liquid crystal projector according to claim 1, wherein each writing projection lens for projecting an image is arranged on each of the liquid crystal display panels.