JP2009175421A - Liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal projector capable of obtaining a high gradation projection image. <P>SOLUTION: The liquid crystal projector includes: reflection type liquid crystal panels 21 to 23 that modulate illumination light from a light source 1 according to input image information and emit the modulated light; lenses 31 and 32 that image the modulated light from the reflection type liquid crystal panels 21 to 23; transmission type liquid crystal panels 41 to 43 that are disposed in conjugate position relative to the reflection type liquid crystal panels 21 to 23, modulate imaged light according to the input image information and emit the modulated light; polarizors 51 to 53 that are disposed on the light emission side of the reflection type liquid crystal panels 41 to 43 and align the polarization direction of the modulated light to a prescribed direction; and a projection lens 54 that projects modulation light from the transmission type liquid crystal panels 41 to 43 as image light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal projector that displays a projected image by enlarging and projecting image light on a screen.

  As a conventional liquid crystal projector, light emitted from a light source lamp is separated into three color lights (blue light, green light, red light) according to the wavelength of light by a dichroic mirror, and each of the separated lights is converted into image information according to color. A liquid crystal panel that is driven accordingly is illuminated, the image light of each color emitted from the illuminated liquid crystal panel is synthesized, and the synthesized color image is projected onto a screen at an appropriate magnification by a projection lens. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 2-118624

  In recent years, it has been demanded to obtain an image with high gradation as the performance of display elements such as liquid crystal devices (higher pixels). However, in order to obtain a high gradation, high precision is required for gradation adjustment, and complicated control for precisely operating the display element is required, which raises the problem of increasing the cost of the device.

  The present invention has been made in view of such a problem, and an object thereof is to provide a liquid crystal projector capable of obtaining a projection image having a high gradation.

  According to an embodiment of the present invention, a first liquid crystal panel that modulates illumination light from a light source according to input image information and emits modulated light, and relay optics that forms an image of the modulated light from the first liquid crystal panel A second liquid crystal panel which is arranged at a position conjugate with the first liquid crystal panel and which modulates image light imaged by the relay optical system according to input image information and emits modulated light; A polarizing unit that is disposed on the light exit side of the panel and aligns the polarization direction of the modulated light from the second liquid crystal panel in a predetermined direction, and a projection optical system that projects the modulated light from the second liquid crystal panel as image light. A liquid crystal projector is provided.

  According to the present invention, it is possible to provide a liquid crystal projector capable of obtaining a projected image with high gradation by performing two-step light intensity modulation on the first liquid crystal panel and the second liquid crystal panel.

  Embodiments of the present invention will be described below with reference to the drawings. The liquid crystal projector of this embodiment projects an optical image formed by modulating the light intensity of a light beam emitted from a light source with a liquid crystal panel on a screen.

  First, the liquid crystal projector of the first embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram illustrating the liquid crystal projector according to the first embodiment. The liquid crystal projector includes a light source 1 that generates illumination light, a relay lens 2, dichroic mirrors 3 to 6, condenser lenses 7 to 9, polarization beam splitters (hereinafter referred to as PBS) 11 to 13, and a reflection type that is a kind of light valve. Liquid crystal panels 21 to 23, lenses 31 to 36, transmissive liquid crystal panels 41 to 43 which are a kind of light valves, polarizers 51 to 53, and a projection lens 54 are provided.

  The white light emitted from the light source 1 passes through the relay lens 2 and then enters the first dichroic mirror 3 on the optical path. As the first color light among the three primary colors of blue light LB, green light LG, and red light LR, for example blue The light LB is reflected by changing the direction by approximately 90 °, and, for example, green light LG and red light LR are transmitted as the second and third color lights. The separated blue light LB passes through the condenser lens 7 and enters the PBS 11. The green light LG and the red light LR are further incident on the second dichroic mirror 4 to reflect the green light LG while changing its direction by approximately 90 ° and transmit the red light LR. The separated green light LG passes through the condenser lens 8 and then enters the PBS 12, and the separated red light LR passes through the condenser lens 9 and then enters the PBS 13.

  The light incident on the PBSs 11, 12, and 13 is separated into S-polarized light and P-polarized light by the polarization separation film. The polarization separation film is configured to transmit P-polarized light and reflect S-polarized light, and the P-polarized light of each color light LB, LG, and LR transmitted through the PBSs 11, 12, and 13 is a reflective liquid crystal panel. Incident on 21, 22 and 23, respectively.

  The reflective liquid crystal panels 21, 22, 23 perform spatial light modulation according to input image information, and reflect and emit as modulated light. In each pixel of the reflective liquid crystal panels 21, 22, and 23, the arrangement of liquid crystal molecules changes according to the applied voltage, and the liquid crystal layer serves as a phase plate. The reflective liquid crystal panels 21, 22, and 23 control the applied voltage according to the input image information for each P-polarized light incident from the PBSs 11, 12, and 13, so that the pixel units constituting the liquid crystal panel are used. The polarization state is modulated (brightness modulation) and again incident on the PBSs 11, 12, and 13, respectively.

  The P-polarized light included in the modulated light emitted from the reflective liquid crystal panel 21 passes through the PBS 11 and returns to the light source 1, and part of it is used again as illumination light. On the other hand, the S-polarized light included in the modulated light emitted from the reflective liquid crystal panel 21 is reflected by the polarization separation film of the PBS 11 while changing its direction by approximately 90 °, and is parallel by the lens 31 as shown in FIG. After being converted to light, the light is projected onto the image forming area of the transmissive liquid crystal panel 41 disposed at a position optically conjugate with the reflective liquid crystal panel 21 by the lens 32.

  The transmissive liquid crystal panel 41 performs spatial light modulation in accordance with the input image information and transmits the incident light as modulated light. In each pixel of the transmissive liquid crystal panel 41, the arrangement of liquid crystal molecules changes according to the applied voltage, and the liquid crystal layer serves as a phase plate. The transmissive liquid crystal panel 41 modulates the polarization state in units of pixels constituting the liquid crystal panel (brightness modulation) by controlling the applied voltage according to the image information inputted with the S-polarized light incident from the lens 32. And output to the polarizer 51.

  Here, the image pattern formed in the image forming area of the transmissive liquid crystal panel 41 according to the image information is overlapped with the optical image of the reflective liquid crystal panel 21 projected onto the image forming area by the lenses 31 and 32. ing. That is, if the imaging magnification by the lenses 31 and 32 is β, the optical image formed in the image forming area of the reflective liquid crystal panel 21 is projected on the image forming area of the transmissive liquid crystal panel 41 at a magnification of β times. Therefore, the shape of the image forming area of the transmissive liquid crystal panel 41 is β times so as to be similar to the shape of the image forming area of the reflective liquid crystal panel 21 so that the enlarged optical image and the image pattern overlap. And the pixel pitch of the transmissive liquid crystal panel 41 is set to be β times the pixel pitch of the reflective liquid crystal panel 21 and the number of pixels constituting the transmissive liquid crystal panel 41 and the pixels constituting the reflective liquid crystal panel 21. The number is set to match. As a result, the pixels of the transmissive liquid crystal panel 41 and the reflective liquid crystal panel 21 are enlarged and projected on the image forming area of the transmissive liquid crystal panel 41 at a magnification β with a one-to-one correspondence.

  Although detailed illustration and description are omitted, the green and red light LG and LR (P-polarized light) transmitted through the PBSs 12 and 13 are incident on the transmissive liquid crystal panels 42 and 43 from the reflective liquid crystal panels 22 and 23, respectively. The optical projection formed by the reflective liquid crystal panels 22 and 23 has the same image size as that of the optical image formed by the reflective liquid crystal panel 21, so that the transmissive liquid crystal panels 42, The image is enlarged and projected at the same magnification β on the 43 image forming areas. That is, the pixels of the reflective liquid crystal panels 22 and 23 and the transmissive liquid crystal panels 42 and 43 are enlarged and projected at a magnification β on the image forming area of the transmissive liquid crystal panels 42 and 43 in a one-to-one correspondence. The

  In this way, the modulated light whose light intensity is modulated by the reflective liquid crystal panels 21, 22, and 23 is further modulated by the transmissive liquid crystal panels 41, 42, 43. The image light of each color emitted from the panels 41, 42, 43 has high gradation.

  The image light of each color emitted from the transmissive liquid crystal panels 41, 42, 43 is aligned in the polarization direction by the polarizers 51, 52, 53, and then the third dichroic mirror 5 and the fourth dichroic on the optical path. The synthesized light is synthesized by the mirror 6, and this synthesized light is enlarged and projected onto a screen (not shown) via the projection lens 54, and a color image is displayed.

  As described above, in the liquid crystal projector according to the first embodiment, the modulated light whose light intensity is modulated by the reflective liquid crystal panels 21, 22, and 23 according to the input image information is further transmitted to the transmissive liquid crystal panels 41, 42, and 43. Therefore, the image light of each color emitted from the transmissive liquid crystal panels 41, 42, and 43 is subjected to two-stage modulation and has a high gradation. As a result, an image projected on the screen is also obtained. An image having a very high gradation can be obtained.

  In the above-described first embodiment, the case where the reflection intensity liquid crystal panel and the transmissive liquid crystal panel are used as the light intensity modulation unit has been described as being configured to perform two-stage modulation. However, in the second embodiment, the transmissive liquid crystal is used. A case where two-stage modulation is performed between panels will be described with reference to FIG. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and differences from the first embodiment will be mainly described.

  In the first embodiment, the transmissive liquid crystal panels 41, 42, and 43 are respectively arranged at positions optically conjugate with the reflective liquid crystal panels 21, 22, and 23. In the second embodiment, the transmissive liquid crystal panels are arranged. Transmission type liquid crystal panels 41, 42, and 43 (only 41 is shown in FIG. 3) are arranged at optically conjugate positions with the panels 71, 72, and 73 (only 71 is shown in FIG. 3). ing.

  In the first embodiment, the PBSs 11, 12, and 13 are provided. In the second embodiment, the polarizing plates 81, 82, and 83 (FIG. 3) are arranged so as to sandwich the transmissive liquid crystal panels 71, 72, and 73. , Only 81 is shown).

  Of the light emitted from the light source 1, the blue light LB passes through the condenser lens 7, and then the polarization direction of the illumination light incident on the transmissive liquid crystal panel 71 is adjusted by the polarizing plate 81 and is incident on the transmissive liquid crystal panel 71. To do.

  The transmissive liquid crystal panel 71 performs spatial light modulation according to input image information, and transmits and transmits the incident light as modulated light. In each pixel of the transmissive liquid crystal panel 71, the arrangement of the liquid crystal molecules is changed by controlling the applied voltage, and the liquid crystal layer serves as a phase plate. The transmissive liquid crystal panel 71 modulates the polarization state (brightness modulation) in units of pixels constituting the liquid crystal panel and outputs the incident light by controlling the applied voltage in accordance with the input image information.

  Only the modulated light in a predetermined polarization direction is extracted from the transmissive liquid crystal panel 71 by the polarizing plate 81, and is transmitted at a position optically conjugate with the transmissive liquid crystal panel 71 by the lenses 31 and 32. Is projected onto the image forming area of the liquid crystal panel 41.

  Here, the image pattern formed in the image forming area of the transmissive liquid crystal panel 41 in accordance with the image information overlaps the optical image of the transmissive liquid crystal panel 71 projected on the image forming area by the lenses 31 and 32. ing. That is, if the imaging magnification by the lenses 31 and 32 is β, the optical image formed in the image forming area of the transmissive liquid crystal panel 71 is enlarged and projected by β times on the image forming area of the transmissive liquid crystal panel 41. Therefore, the shape of the image forming area of the transmissive liquid crystal panel 41 is β times so as to be similar to the shape of the image forming area of the transmissive liquid crystal panel 71 so that the enlarged optical image and the image pattern overlap. And the pixel pitch of the transmissive liquid crystal panel 41 is set to be β times the pixel pitch of the transmissive liquid crystal panel 71 and the number of pixels constituting the transmissive liquid crystal panel 41 and the pixels constituting the transmissive liquid crystal panel 71. The number is set to match. As a result, the pixels of the transmissive liquid crystal panel 41 and the transmissive liquid crystal panel 71 are enlarged and projected on the image forming area of the transmissive liquid crystal panel 41 at a magnification β with a one-to-one correspondence.

  Although detailed illustration and description are omitted, image projection from the transmissive liquid crystal panels 72 and 73 into which the green and red lights LG and LR are respectively incident to the transmissive liquid crystal panels 42 and 43 is the same. The optical images formed by the transmissive liquid crystal panels 72 and 73 have the same image size as that of the optical image formed by the transmissive liquid crystal panel 71 and are the same on the image forming areas of the transmissive liquid crystal panels 42 and 43, respectively. Magnified and projected at a magnification β.

  In this way, the transmissive liquid crystal panels 41, 42, 43 modulate the light intensity modulated by the transmissive liquid crystal panels 71, 72, 73, and the transmissive liquid crystal panels 41, 42, 43 further modulate the light intensity. The image light of each color emitted from the panels 41, 42, 43 has a high gradation.

  As described above, in the liquid crystal projector according to the second embodiment, the modulated light whose light intensity has been modulated by the transmissive liquid crystal panels 71, 72, 73 according to the input image information is further converted into the transmissive liquid crystal panels 41, 42, 43. Since the light intensity modulation is performed, the image projected on the screen can be an image having a very high gradation as in the case of the first embodiment.

It is a figure which shows the structure of the liquid crystal projector which concerns on 1st Embodiment. It is a figure explaining the relationship between the reflective liquid crystal panel used for 1st Embodiment, and a transmissive liquid crystal panel. It is a figure for demonstrating the relationship between the transmissive liquid crystal panels used for 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light sources 11-13 Polarization beam splitters 3 and 4 Dichroic mirror (color light separation part)
5,6 Dichroic mirror (color light synthesis part)
21-23 Reflective liquid crystal panel (first liquid crystal panel)
31-36 Lens (Relay optical system)
41 to 43 Transmission type liquid crystal panel (second liquid crystal panel)
51-53 Polarizer (Polarizing part)
54 Projection lens (projection optical system)
71-73 Transmission type liquid crystal panel (first liquid crystal panel)
81-83 Polarizing plate

Claims (6)

A first liquid crystal panel that modulates illumination light from a light source according to input image information and emits modulated light;
A relay optical system for imaging the modulated light from the first liquid crystal panel;
A second liquid crystal panel that is arranged at a position conjugate with the first liquid crystal panel and that modulates image light imaged by the relay optical system according to input image information and emits modulated light;
A polarizing unit disposed on the light output side of the second liquid crystal panel, and aligning the polarization direction of the modulated light from the second liquid crystal panel in a predetermined direction;
A liquid crystal projector comprising: a projection optical system that projects modulated light from the second liquid crystal panel as image light.   2. The liquid crystal according to claim 1, wherein the pixel pitch of the second liquid crystal panel is a pixel pitch obtained by multiplying the pixel pitch of the first liquid crystal panel by a predetermined magnification equal to the imaging magnification of the relay optical system. projector. The outer shape of the effective pixel region of the second liquid crystal panel is a similar shape with the predetermined magnification with respect to the outer shape of the effective pixel region of the first liquid crystal panel,
3. The liquid crystal projector according to claim 1, wherein the number of pixels in the effective pixel area of the second liquid crystal panel is the same as the number of pixels in the effective pixel area of the first liquid crystal panel. The first liquid crystal panel comprises a reflective liquid crystal panel;
The second liquid crystal panel comprises a transmissive liquid crystal panel;
The polarizing beam splitter is provided on a light incident side of the reflective liquid crystal panel, and has a polarization plane that reflects or transmits illumination light from the light source and reflected light from the reflective liquid crystal panel. The liquid crystal projector according to any one of 1 to 3. The first liquid crystal panel and the second liquid crystal panel are both transmissive liquid crystal panels,
4. The liquid crystal projector according to claim 1, further comprising polarizing plates for aligning a polarization direction of the modulated light in a predetermined direction on the light incident side and the light emitting side of the first liquid crystal panel. 5. The first liquid crystal panel is composed of a plurality of first color liquid crystal panels that respectively modulate first to third color lights,
The second liquid crystal panel is composed of a plurality of second color liquid crystal panels that modulate the first to third color lights,
A color light separating unit that separates illumination light from the light source into first to third color light, and a color light combining unit that combines the modulated light of each color modulated by the second color liquid crystal panel. The liquid crystal projector according to claim 1.

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