JPH04255839A - Liquid crystal projection device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal projection device which enables a natural- color image to be observed under electric control. CONSTITUTION:First liquid crystal panels 6a, 6b, and 6c are provided for image formation and video signals of R, G, and B are inputted thereto. On the same optical paths, 2nd liquid crystal panels 7a, 7b, and 7c are arranged and a control signal generated by a control circuit 9 by detecting reflected light from a screen 13 by a photodetection sensor 10 is inputted to them. With this control signal, the light transmissivity of the 2nd liquid crystal panels is controlled and the brightness and white balance of images of the 1st liquid crystal panels are adjusted.

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 function for responding to changes in brightness in a liquid crystal projection system that projects images formed on a liquid crystal panel.

0002

2. Description of the Related Art Liquid crystal panels obtain a light modulation function by applying a voltage above a threshold value between electrodes that sandwich a liquid crystal layer, and have recently been widely used as various display devices. Since liquid crystal panels have light modulation properties, they are used not only as display devices but also as optical filters. One of them is a liquid crystal projection system. This device is configured as a system in which the image formed on the liquid crystal panel is not directly viewed as it is, but is enlarged and projected onto a projection surface such as a screen through the liquid crystal panel, and the projected image is observed.

0003

A liquid crystal projection system forms an observable projected image on a screen by reflecting or transmitting light from a light source through a liquid crystal panel on which an image is formed. Therefore, as an observer, you see the image as an image on a screen, and the image you are observing may not necessarily have the same white balance and brightness due to various factors such as the light source condition, but also the reflection characteristics of the screen and extraneous light. The situation was less than optimal. In particular, depending on the aging of the light source, the surface condition of the screen on which it is projected, or extraneous light, the image may be observed in colors that are significantly different from the original image. Conventionally, measures such as changing the brightness of the light source lamp or interposing a filter have been taken to solve this problem. However, there is a problem that when the brightness of the lamp is changed, the color temperature also changes, and when a filter is used, it cannot be controlled electrically.

The present invention was made in view of the above-mentioned problems with the conventional liquid crystal projection system, and includes a second liquid crystal panel separate from the liquid crystal panel for forming images to adjust white balance, brightness, etc. The object of the present invention is to provide a liquid crystal projection device that allows viewing images in natural colors through electrical control.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a liquid crystal projection device that projects an image formed on a liquid crystal panel. This is a liquid crystal projection device that includes a second liquid crystal panel disposed on an optical path for a second liquid crystal display, and a control circuit that controls light modulation of the second liquid crystal panel. Further, the control circuit is a liquid crystal projection device that includes a sensor that detects reflected light from the projection surface, and controls light transmission of the second liquid crystal panel using a light modulation signal formed based on the sensor output. Further, the second liquid crystal panel includes three first liquid crystal panels provided for each of R, G, and B.
This is a liquid crystal projection device that is arranged on the side opposite to the light source of each first liquid crystal panel with respect to the liquid crystal panel.

[0006]

[Function] Brightness and white balance can be adjusted electrically and automatically by controlling the light modulation using the second liquid crystal panel, and the control signal for adjustment is output from the optical sensor. It can be created by In addition, by detecting the reflected light from the screen with a sensor and controlling the light modulation of the second LCD panel, the brightness and white balance can be adjusted regardless of the screen condition or without affecting the color temperature of the light source. Can be adjusted.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a color liquid crystal projection system according to an embodiment of the present invention. In FIG. 1, an image projected from a liquid crystal projection device main body 1 is projected onto a screen 13. As shown in FIG. The liquid crystal projection device main body 1 has an R
, G, B, three first liquid crystal panels 6a, 6b, 6
c is placed. The first liquid crystal panel 6a, 6b,
6c is connected to a video signal processing circuit 8, and is provided with a video signal for color display, as has been conventionally practiced in this type of device.

[0008] Of the light emitted from the light source 3, for example, only the R color component is reflected by the dichroic mirror 4a.
The rest will be transparent. The transmitted light is dichroic mirror 4b
is incident on the The R color component separated by the dichroic mirror 4a enters the first liquid crystal panel 6a that shares the R color, is optically modulated by the video signal applied to the liquid crystal panel 6a, and is sent to the second liquid crystal panel 7a. It is incident. That is, in this liquid crystal projection device, a second liquid crystal panel 7a is provided on the opposite side of the light source 3 in addition to the first liquid crystal panel 6a that forms an image for projection, and the R component light separated from the light source 3 is transmitted to the second liquid crystal panel 7a. Following the first liquid crystal panel 6a, the second liquid crystal panel 7a is transmitted. The second liquid crystal panel 7a is connected to a control circuit 9, and is given a control signal for controlling the light transmittance as described later.

The light transmitted through the dichroic mirror 4a and incident on the dichroic mirror 4b reflects the G color component and transmits the remaining B color component to be separated. Of the separated light, the G color component is incident on the first liquid crystal panel 6b which shares the G color, and the B color component is incident on the first liquid crystal panel 6c which is responsible for the B color. Video signals of each color component formed by the video signal processing circuit 8 as described above are input to the R, G, and B first liquid crystal panels 6a, 6b, and 6c according to the color components of each liquid crystal panel. , modulates the incident light of each color component in accordance with the video signal to form output light. For the G and B first liquid crystal panels 6b and 6c, second liquid crystal panels 7b and 7c are provided as a pair on the side opposite to the light source 3, similarly to the R first liquid crystal panel 6a. It is connected to a control circuit 9 and is supplied with a control signal.

In the liquid crystal projection system of this embodiment, the light receiving sensor 10 is located at a position where the reflected light from the screen 13 can enter through the optical system 11.
Place. The output of the light receiving sensor 10 is input to the control circuit 9, and the control circuit 9 forms brightness and white balance control signals from the color temperature information and the like of the detected light. Since this control signal is formed based on the output of the light receiving sensor 10, it is a signal that comprehensively takes into account the conditions of the light source 3, screen 13, external light, etc. The second liquid crystal panels 7a, 7b, 7c to which the control signal for light modulation formed by the control circuit 9 is input, output the respective colors of R, G, and B transmitted through the first liquid crystal panels 6a, 6b, 6c. The transmittance of each light is further adjusted, and light with automatically adjusted brightness and white balance is output. The R color output light exiting the second liquid crystal panel 7a is reflected by the total reflection mirror 5a,
The dichroic mirror 4c combines the light with the G color output light output from the second liquid crystal panel 7b. Furthermore, dichroic mira 4d
It is combined with the B color output light exiting the second liquid crystal panel 7c, and is enlarged and projected onto the screen 13 by the projection lens 12.

Since the first liquid crystal panels 6a, 6b, and 6c play the role of forming images, they each have a panel structure capable of providing desired light modulation for each pixel, such as active drive elements such as TFTs and MIMs. A liquid crystal panel provided for each image pixel is used. The second liquid crystal panels 7a, 7b, 7c are
Although it is possible to adopt a panel with the same structure as the liquid crystal panels 6a, 6b, and 6c, since it is not directly related to image formation, it is possible to use a liquid crystal panel with a simple structure in which the liquid crystal layer is sandwiched between mutually opposing electrodes. You can also. However, if the sensor that receives the reflected light from the projection surface is divided into multiple sections and is equipped with a sensor that forms a control signal for light modulation according to the area, the sensor will not be able to handle multiple areas. A liquid crystal projection device is configured using the divided second liquid crystal panel. Then, in response to the output of each region of the sensor, light transmission through the corresponding region of the second liquid crystal panel is controlled to perform optimal light modulation.

[0012] In the above embodiment, the device was constructed by incorporating three liquid crystal panels for color, but the device may be constructed using a liquid crystal panel in which multiple color filters are formed in one panel for colorization. You can also do that. In this structure as well, a second liquid crystal panel for adjusting light transmission is arranged separately from the first liquid crystal panel for forming images.

Furthermore, the installation of the second liquid crystal panel is not limited to the side opposite to the light source of the first liquid crystal panel, but as shown in FIG. It can also be constructed by arranging a liquid crystal panel 7. Second
The light transmittance of the liquid crystal panel 7 can be controlled by a configuration in which a brightness adjustment input that can be set manually is given to the control circuit 9, and the brightness and white balance can be set to the viewer's preference from the outside. can. In FIG. 2, 14 is a polarizing plate, and 15 is a condenser lens that has been conventionally used in constructing this type of device.

[0014]

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a projection image in which the brightness and white balance are automatically adjusted regardless of the state of the light source or the projection surface, and the projection image quality of liquid crystal projection can be improved. It is possible to obtain a projection device that is improved and is not subject to restrictions due to changes in the light source or changes in the installation location. In particular, LCD projection devices are portable and do not necessarily need to be projected onto a screen to observe the projected image; even when projected onto any surface, a projected image suitable for the situation can be obtained. The scope of application can be significantly expanded.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing essential parts of a liquid crystal projection according to an embodiment of the present invention.

FIG. 2 is a diagram showing main parts of a liquid crystal projection according to another embodiment of the present invention.

[Explanation of symbols]

3 light sources 6a, 6b, 6c, 6 first liquid crystal panel 7a, 7b,
7c, 7 Second liquid crystal panel 8 Video signal processing circuit 9 Control circuit 10 Light receiving sensor

Claims (3)

[Claims] Claim 1: A liquid crystal projection device that projects an image formed on a liquid crystal panel, comprising: a first liquid crystal panel that forms an image for projection; a second liquid crystal panel disposed on an optical path for projection; , and a control circuit that controls light modulation of the second liquid crystal panel. 2. The control circuit includes a sensor that detects reflected light from the projection surface, and supplies a light modulation signal formed based on the sensor output to the second liquid crystal panel. The liquid crystal projection device described in . 3. The second liquid crystal panel is located on the side opposite to the light source of each of the three first liquid crystal panels provided for each of R, G, and B for color images. 3. The liquid crystal projection device according to claim 2, wherein the liquid crystal projection device is arranged as follows.