JPH09101414A - Liquid crystal video projector using holographic color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector large n the quantity of projection light which can make a bright full-color image formed on a screen observable, by making the full-color image formed by a color filter and a liquid crystal panel incident in a proper direction. SOLUTION: A hologram panel 6 formed by longitudinally and laterally arraying hologram cells which are formed out of volume transmission type holograms having diffraction wavelength selectivity and transmit and diffract respective colors of red, green, and blue is used as a holographic color filter, and the transmission and diffraction directions of the respective hologram cells are so designed that light transmitted through the color filter 6 and liquid crystal panel 4 is converged on a projection lens 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color filter using a hologram, and more particularly to a liquid crystal video projector using a color filter for improving the utilization efficiency of illumination light by using the hologram.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal video projector using a color filter has been used, and FIG. 8 shows an outline of its configuration example. Illumination light (white light) 1 emitted from a light source such as a light bulb (not shown) passes through a condenser lens 2 and color filters 3 (cells of respective colors of red, green, and blue are arranged in a matrix, and the periphery of each cell is The light that has passed through the color filter 3 and the liquid crystal panel 4 is illuminated by the black matrix (which is a light-shielding portion) and is projected onto a screen (not shown) by the projection lens 5, and the light is emitted by the color filter 3 and the liquid crystal panel 4. The constructed full-color image is imaged on the screen and viewed.

In the liquid crystal video projector, illumination light for projection display is indispensable. However, if white light is emitted from the back of the liquid crystal video projector as it is, its utilization efficiency is very low. The main reasons are listed below.

The black matrix occupies a large area and the light impinging on it is wasted. Since the color component of the white light incident on each cell is limited to any one of red, green, and blue, the other complementary color components are wasted. There is a loss due to absorption in each color filter.

In order to solve such a problem, JP-A-6-
The proposal of 308332 publication is known. The above suggestions
The color filter itself is configured by a hologram, and is characterized in that incident light is diffracted and dispersed by the hologram to emit light having different wavelengths at a predetermined position in a predetermined spatial cycle. (Refer to FIG. 9) According to the above proposal, it is not necessary to pass through the color filter, loss due to absorption (above) is eliminated, and bright display / imaging becomes possible. In addition, since it is possible to focus the light that has been dispersed efficiently at a predetermined position (resolving the above), it is possible to use each wavelength component of the backlight for color filters without waste (resolving the above), and the utilization efficiency is greatly improved. Can be improved.

However, in the above proposal, it is not easy in terms of alignment to cause the light of each color component that has passed through the hologram to accurately enter the liquid crystal cell (of the liquid crystal panel) of the corresponding color component. Further, since the liquid crystal cell has a certain area (width), strictly speaking, light of only the required color (wavelength) is not incident on the liquid crystal cell, but a component having a wavelength distribution of a certain width. Light (not a single wavelength) will be incident. Further, the light of each color component that has passed through the hologram cannot be vertically incident on the liquid crystal cell, and thus the light of the component that is obliquely incident is inevitably present. Therefore, the light passing through each liquid crystal cell does not exhibit the optimum polarization rotation property, and is perceived by the observer as a decrease in brightness. In addition, the product according to the above proposal is not necessarily related to a so-called liquid crystal video projector of a type in which a produced full-color image is projected on a screen for observation. That is, when the product according to the above proposal is applied to a liquid crystal video projector, since light of each color component enters each liquid crystal cell at different angles, all the light that has passed through the liquid crystal cell is incident on the projection lens. This is because the efficiency of use of light that contributes to projection onto the screen is low, not necessarily incident light.

According to the improvement of the liquid crystal video projector,
As a proposal by the present applicant, Japanese Patent Laid-Open No. 5-232319 is known. The above proposal is to configure each color cell of the color filter itself with a hologram,
It has a hologram panel (color filter) consisting of holograms of minute dots corresponding to each color of red, green and blue, so that each diffracted light corresponding to each color from the hologram panel is condensed, This is a liquid crystal video projector in which a slit provided with a light transmitting portion is arranged and the light passing through the slit is imaged as red, green, and blue dots on a screen. In the above proposal, nothing is considered about making the light of each color component that has passed through the hologram panel incident on the liquid crystal cell (of the liquid crystal panel) of the corresponding color component.

[0008]

DISCLOSURE OF THE INVENTION The present invention is intended to cause the light of each color component of red, green, and blue that has passed through a hologram to enter the liquid crystal cell (of the liquid crystal panel) of the corresponding color component with high accuracy. , A full-color image composed of a color filter and a liquid crystal panel, using a color filter having a structure in which a hologram cell having a color (wavelength) that is transmitted and diffracted for each cell is associated with the liquid crystal cell 1: 1 An object of the present invention is to provide a liquid crystal video projector in which (projection light) is incident in an appropriate direction and a bright full-color image with a high projection light amount formed on a screen can be observed.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a liquid crystal video projector for projecting a full-color image composed of a color filter and a liquid crystal panel on a screen by a projection lens, and a volume transmission hologram having a diffraction wavelength selectivity. A holographic panel composed of vertically and horizontally arranged hologram cells for transmitting and diffracting each color of red, green and blue is used as a holographic color filter and passed through the color filter and the liquid crystal panel. It is characterized in that the transmission diffraction direction of each hologram cell is designed so that the light is condensed on the projection lens. As a preferred mode for realizing the above design, the center of each hologram cell, the center of the corresponding liquid crystal cell, and the center of the projection lens are arranged so as to be substantially linear.

[0010]

[Function] Since the color filter composed of the hologram cell composed of the transmission type hologram having the diffraction wavelength selectivity for transmitting and diffracting each color of red, green and blue is used, the spatial frequency of the hologram cell is Diffraction efficiency close to 100% can be obtained at the central wavelength, and the color purity in each cell is high. Also, by controlling the spatial frequency of the hologram cell, it is possible to select any center wavelength in each color of red, green, and blue, and by adjusting the thickness of the hologram, the wavelength band (bandwidth) Can also be adjusted.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a main part of a liquid crystal video projector to which a holographic color filter according to the present invention is applied. The same parts as those in FIG. 8 are designated by the same reference numerals, and the description thereof will be omitted. Only the part will be described. That is, the liquid crystal video projector according to the present embodiment includes the condenser lens 2 shown in FIG.
Is omitted, and a hologram panel 6 is provided instead of the color filter 3.

The hologram panel 6 is a holographic color filter having the structure shown in FIG. 2, and has hologram cells for transmitting and diffracting each color of red, green and blue arranged in a matrix. These hologram cells have the center of the corresponding color component (of the liquid crystal panel).
It is arranged at a position on an extension of a line connecting the center of the liquid crystal cell and the projection lens.

The hologram cells 6R, 6G, and 6B are preferably volume-transmission type cells that transmit and diffract only specific wavelengths and do not transmit and diffract other wavelengths (absorption or reflection), and red and green, respectively.・ Has wavelength selectivity as shown in Fig. 3 so that only light of wavelength corresponding to blue is transmitted and diffracted.

Also, the hologram cells 6R, 6G, 6B
For example, in one of 6R, 6R1, the diffracted light from is projected by the transmitted diffracted light when focused by the red laser light corresponding to the center wavelength of the 6R1 at approximately the center of the corresponding liquid crystal cell 4R1. The light is incident near the center of the lens 5.

In order to design the transmission / diffraction direction of each hologram cell so that the light passing through the holographic color filter 6 and the liquid crystal panel 4 is condensed on the projection lens 5, the following is performed. Then, the holographic color filter 6 is manufactured.

First, using the optical system as shown in FIG. 5, master holograms corresponding to red, green and blue are produced by laser lights of respective colors (wavelengths). A parallel laser beam 7 emitted from a laser light source (not shown) passes through a lens 9 that focuses on a dry plate (photosensitive material) 8, then illuminates a microlens array 10, and passes through the microlens array 10. Illuminates the plate 8. At this time, the focus of each lens of the microlens array 10 on the dry plate 8 is the projection lens 5 and the liquid crystal panel 4 in FIG.
It should be tied to the position of the liquid crystal cell of the corresponding color depending on the distance. On the other hand, the parallel laser light 11 emitted from a laser light source of the same wavelength (not shown) illuminates the dry plate 8 from an oblique direction and interferes with the laser light that has passed through the microlens array to cause the dry plate 8 to have a desired color (wavelength). The master hologram of is recorded. The above operation is performed for each of the colors red, green, and blue to produce master holograms for three colors.

Next, using the obtained master hologram, a hologram panel 6 is produced by the optical system shown in FIG. The dry plate 13 is arranged at a position corresponding to the microlens array 10 in FIG. 5 with respect to the master hologram 12 (made of the dry plate 8). A parallel laser beam 14 emitted from a laser light source (not shown) having the same wavelength as that of the master hologram is incident on the master hologram 12 from the opposite (conjugate) direction to the parallel laser beam 11 of the master hologram. Let Diffracted light from the master hologram 12 reaches the dry plate 13. On the other hand, a parallel laser beam 15 emitted from a laser light source of the same wavelength (not shown) is obliquely fed to the dry plate 1
3 and the hologram is recorded on the dry plate 13 by the interference with the diffracted light from the master hologram 12. The above operation is performed for each color of red, green, and blue to produce hologram panels for three colors. In this case, holograms of three colors may be recorded on the same dry plate 13, or holograms recorded on three different dry plates may be superposed.

Next, the operation of the liquid crystal video projector constructed as shown in FIG. 1 using the hologram panel will be described. In FIG. 1, illumination light (white light) 1 emitted from a light source such as a light bulb (not shown) illuminates a hologram panel (holographic color filter) 6,
The light that has been transmitted and diffracted by the hologram panel 6 and has passed through the liquid crystal panel 4 enters the projection lens 5 and is projected on a screen (not shown) by the projection lens 5 to be composed of the hologram panel 6 and the liquid crystal panel 4. A full color image is formed on the screen and viewed. FIG. 7 shows an optical path of incident white light with respect to one specific cell (red hologram cell). Due to the design of the hologram panel, only red light is transmitted and diffracted, enters the corresponding liquid crystal cell so as to be converged, and then enters the projection lens while expanding. The light emitted from the projection lens will be projected as a red cell on a screen (not shown).

[0019]

[Effect of the invention] Like the existing color filters,
It is not necessary for the green and blue color cells to be arranged in a matrix without overlapping, and even if the hologram cells of each color overlap, there is no problem due to the diffraction wavelength selectivity. Therefore, the hologram cell may be made large, the black matrix is not necessary, and in addition, since the diffraction efficiency close to 100% is exhibited at the center wavelength of each color, the utilization efficiency of the illumination light is significantly increased. In addition, since a full-color image composed of a color filter and a liquid crystal panel is designed to be incident in an appropriate direction, a liquid crystal capable of observing a bright full-color image with a high projected light amount imaged on the screen. A video projector is provided.

[0020]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a main part of a liquid crystal video projector of the present invention.

FIG. 2 is an explanatory diagram showing a configuration example of a hologram panel.

FIG. 3 is an explanatory view showing the diffraction wavelength selectivity of the hologram panel.

FIG. 4 is an explanatory diagram showing optical characteristics of a hologram panel.

FIG. 5 is an explanatory view showing an optical system used for manufacturing a hologram panel.

FIG. 6 is an explanatory view showing an optical system used for manufacturing a hologram panel.

FIG. 7 is an explanatory diagram showing optical characteristics of a hologram panel.

FIG. 8 is a schematic diagram showing a main part of a conventional liquid crystal video projector using a color filter.

FIG. 9 is an explanatory diagram showing a configuration example of a conventional hologram panel.

[Explanation of symbols]

 1 ... Illumination light (white light) 2 ... Lens 3 ... Color filter 4 ... Liquid crystal panel 5 ... Projection lens 6 ... Hologram panel

Claims (2)

[Claims] 1. A liquid crystal video projector for projecting a full-color image composed of a color filter and a liquid crystal panel onto a screen by means of a projection lens. A hologram panel consisting of vertically and horizontally arranged hologram cells that transmit and diffract each blue color is used as a holographic color filter, and the light that has passed through the color filter and liquid crystal panel is focused on a projection lens. As described above, the liquid crystal video projector using the holographic color filter is characterized in that the transmission diffraction direction of each hologram cell is designed. 2. The structure according to claim 1, wherein the center of each hologram cell, the center of the corresponding liquid crystal cell, and the center of the projection lens are arranged so as to be substantially straight. A liquid crystal video projector using the described holographic color filter.