JPH04306639A - Projection type image display device and adjustment thereof - Google Patents

Abstract

PURPOSE:To eliminate the dispersion of white balance for the dispersion of the chromaticity of three primary colors by selecting the chromaticity and luminance of three primary colors which pass through a liquid crystal panel and adjusting the transmissivity of each liquid crystal panel on the basis of the result of measurement. CONSTITUTION:The radiation light supplied from a lamp 1 of a light source is color-analyzed into three primary colors of RGB by dichroic filters 2 and 3 through a total reflection mirror 8, and introduced into the liquid crystal panels 6(R)-(B) installed in a light passage of each primary color of RGB. The light which passes through the liquid crystal panels 6(R)-(B) is color-synthesized by a dichroic filter 5, and projected on a screen by a projection lens 7. A sensor 9 for measuring the chromaticity and luminance of three primary colors as transmission light is installed on each liquid crystal panel 6(R)-(B), and the measurement data is inputted into a control circuit 11, and the transmissivity of each liquid crystal panel 6 is adjustment-controlled. Accordingly, the synthesis ratio of RGB for obtaining a prescribed white balance is adjusted according to the chromaticity of three primary colors of RGB.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display apparatus, and more particularly to white balance adjustment thereof.

0002

BACKGROUND OF THE INVENTION In recent years, there has been a tendency for television receivers with larger screen sizes to be preferred. Its weight has increased dramatically, exceeding 80 kg for a 37-inch size. If a larger screen size is desired, the screen will become too large for general home use. Therefore, projection-type image display devices (projectors), which are much lighter than direct-view CRTs, are attracting attention, and research and development of projection-type image display devices using liquid crystal panels (LCD projectors) is particularly active. It is becoming.

The general configuration of this type of projection type image display device will be explained below with reference to the drawings.

FIG. 8 is a block diagram of a projection type image display device viewed from the side. In the figure, white light emitted from a lamp 1 (for example, a metal halide lamp) that is a light source is passed through dichroic filters 2 and 3 to R (red), G (green), B (
The colors are separated into the wavelengths of the three primary colors (blue), and then passed through the R, G, and B liquid crystal panels 6 and then passed through the dichroic filters 4 and 5 again.
The colors are combined and projected onto a screen (not shown) by a projection lens 7.

[0005]

[Problems to be Solved by the Invention] In such a conventional projection type image display device, in principle, the lamp 1 which is a light source and the white light emitted from this lamp 1 are color separated and synthesized into three primary color wavelengths of RGB. dichroic filters 2 to 5
Variations in the spectral characteristics of the liquid crystal panel 6 and variations in the gamma characteristics (voltage-transmittance characteristics) of the liquid crystal panel 6 that functions as an optical shutter are large and unavoidable. These directly affect image quality performance, such as brightness, color reproduction, white balance,
Although there will be variations in gradation, etc., the degree of variation is much greater than that of CRT. In particular, variations in the spectral characteristics of the light source and dichroic filter lead to variations in the chromaticity of the three primary colors, and the white balance used to synthesize the three primary colors varies greatly. Therefore, white balance adjustment is an effective means of absorbing such variations (CRTs emit phosphor, so there is little variation in color in principle). Unlike CRTs, the RGB composition ratio is fixed. If left as is, the degree of variation would increase, and no countermeasures have been taken in conventional projection type image display apparatuses in this respect.

The present invention is intended to solve the above-mentioned problems, and provides a projection type image display device that can eliminate variations in white balance with respect to variations in chromaticity of three primary colors.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the projection type image display device of the present invention has sensor means for measuring the chromaticity and brightness or tristimulus values of the projected light from the shutter means, the projection lens, etc. and a control circuit that adjusts the transmittance of the shutter means based on the measured results.

[0008]

[Operation] With the above-described configuration, the present invention adjusts the synthesis ratio of the three primary color lights of RGB according to the chromaticity thereof.

[0009]

Embodiments Hereinafter, embodiments of the projection type image display apparatus of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a liquid crystal projection type projector according to a first embodiment of the present invention, viewed from the side. Note that the same components as those in the conventional example shown in FIG. 8 are given the same reference numerals and detailed explanations will be omitted.

In the figure, the emitted light (white light) from a lamp 1 that is a light source is reflected by a total reflection mirror 8 into green (G) light.
dichroic filter 2 that transmits only the color components of
The dichroic filter 3 transmits only the blue (B) color component, which separates the light into the three primary colors of RGB.
Liquid crystal panel 6 (R) provided in the optical path of each primary color light of GB
~(B) through field lenses. The liquid crystal panel 6 works as a light shutter,
It is controlled pixel by pixel according to an input image signal (input means not shown). Each LCD panel 6 (R)
, (G), and (B) are color-combined by a dichroic filter 5 that transmits only the blue (B) color component, and projected onto a screen (not shown) by a projection lens 7.

Further, each of the liquid crystal panels 6 (R) to (B) is provided with a color luminance sensor 9 (R, G, B) for measuring the chromaticity and luminance of the three primary color lights that are transmitted therethrough. The measured data is input to a control circuit 11 via a transmission line 10 (for example, an optical fiber). Control circuit 11
is the transmittance of each liquid crystal panel 6 based on the input data (
(brightness modulation degree).

(Embodiment 2) FIG. 2 shows a second embodiment of the present invention, in which the chromatic luminance sensor 9, which was provided near the liquid crystal panel 6 in FIG. 1, is provided in front of the projection lens 7.
The other configurations are completely the same as the first embodiment.

In the configurations of the first and second embodiments described above, the white balance adjustment algorithm and the control circuit 11
More specific block diagrams of the system are shown in FIGS. 3 and 4, and the operation thereof will be explained in more detail with reference to FIG. 4 according to the flow of FIG. 3.

In steps 1 and 2, the liquid crystal panel 6 is fully opened simultaneously or sequentially by the adjustment switch 12 via the microprocessor 13, gain adjustment circuit 14, and video signal generation circuit 18. That is, its transmittance is maximized.

Note that in the second embodiment, the color luminance sensor 9
is provided in front of the projection lens 7, so each liquid crystal panel 6 is fully opened in the order of R, G, and B, for example, and the chromatic luminance sensor 9 detects each of the three primary colors of R, G, and B instead of composite light. Light is sequentially guided and the chromaticity and brightness of each is measured.

The chromaticity and luminance of the three primary color lights transmitted through each liquid crystal panel 6 whose transmittance has reached the maximum in step 3 are measured by the chromatic luminance sensor 9, and transmitted through the transmission line 10 composed of optical fibers. , G, and B are input to the control circuit 11. The input data (optical signal) is converted into an analog electrical signal by a photoelectric conversion circuit 15, further converted into a digital signal by an AD (Analog Digital) conversion circuit 16, and inputted to the microprocessor 13. Microprocessor 13
calculates the RGB synthesis ratio and the adjusted brightness for each signal level in order to obtain a predetermined white balance in accordance with the input digital signal.

Note that if the color luminance sensor 9 outputs an electrical signal instead of an optical signal, the transmission line 10 does not need to be an optical fiber, and of course the photoelectric conversion circuit 15
is not required either.

Based on the measurement data, the microprocessor 13 determines the RGB mixed luminance ratio (RGB synthesis ratio) and the RGB
Adjusted brightness (target brightness for lowlights and highlights) is calculated (see steps 4 and 5), and a method for calculating the actual RGB mixed brightness ratio and RGB adjusted brightness will be described later.

Next, in step 6, the microprocessor 13
, the video signal generation circuit 18 generates a video signal of a predetermined level (for example, highlight IRE=80), and inputs this to each liquid crystal panel 6 via the gain adjustment circuit 14. Then, in steps 7 and 8, the microprocessor 13
The gain adjustment circuit 14 is controlled by the microprocessor 13 so that the RGB mixed brightness ratio calculated by
The transmittance of each of the R, G, and B liquid crystal panels 6 is controlled in a closed loop while increasing or decreasing the gain of the liquid crystal panel 6 and measuring the brightness. desired R
The voltage control data for the gain adjustment circuit 14 when the GB mixed brightness ratio and adjusted brightness are reached is stored in the memory 17 in step 9. Here, the microprocessor 13 reads data from the memory 17 and adjusts the white balance every time the power of the main body of the apparatus is turned on.

Although not shown in the algorithm of FIG. 3, the adjustment for low lights (IRE=20) is the same as for highlights, except that a video signal of IRE=20 level is generated in step 6. This is an adjustment operation. In addition,
In this embodiment, brightness adjustment (gamma adjustment) for each signal level is performed simultaneously with white balance adjustment.

As described above, white balance adjustment and gamma adjustment are performed for each product according to the chromaticity of the three primary color lights.Next, a method for calculating the RGB mixed brightness ratio and RGB adjusted brightness will be explained.

As already mentioned, when adjusting the white balance of a projection type image display device, the liquid crystal method and the CRT method are used.
The biggest difference between the three primary colors is that the variation in chromaticity of the three primary colors (variation in the spectral characteristics of the light source and dichroic filter) cannot be ignored. Therefore, in the liquid crystal system, if the RGB composition ratio is set to a fixed ratio like in the CRT system, the variation will become larger.
The GB composition ratio is changed.

[0024] Also, regarding gamma correction, liquid crystal method and C
A different way of thinking from the RT method is required, and like the CRT method, a reference light is determined and low light (for example, IRE = 20
), if the target brightness of highlights (for example, IRE=80) is fixed, the brightness of the light source will vary, resulting in gradation defects such as lack of color coverage due to crushed whites and floating low lights, and crushed blacks. Therefore, in the liquid crystal method, it is necessary to change the adjustment target (set it as a constant percentage of the brightness obtained by the optical system for each product) in accordance with the variation in brightness, as in the case of chromaticity. For these reasons, in this embodiment, the RGB composition ratio and target brightness are calculated as follows, and white balance adjustment and gamma adjustment are performed.

(1) Measure the spectral characteristics of the optical system (luminance and chromaticity of each RGB raster when the liquid crystal transmittance is at its maximum) for each product.

(2) Find the RGB combination ratio from the above chromaticity data, and calculate the target brightness of lowlights and highlights from the maximum brightness data and the combination ratio.

Note that in the first embodiment, the liquid crystal panel 6 is simply
Although the color and luminance sensor 9 measures the light that passes through the LCD panel 6, it is of course possible to set a photometric window outside the effective display area of the liquid crystal panel 6 and measure the light that passes through the window. The window here may be a liquid crystal pixel provided separately from the liquid crystal pixels in the effective display area, or may simply be a hole formed in the outer frame of the panel.

[0028] Also, the concept of tristimulus values is well known as one of the color expression methods for expressing colors. The relationship is as follows, and the chromaticity coordinates (x, y) are the stimulus values (X, Y
) is normalized by the stimulus sum S. Therefore, the color luminance sensor 9 may be configured to measure the tristimulus values.

Chromaticity (x, y), luminance Y←−→tristimulus values X, Y, Z relational expressions x=X/S y=Y/S z=X/
SS=X+Y+Z (stimulus sum) The chromaticity coordinate of white, which is a composite of the three primary colors RGB on the xy chromaticity coordinates, is obtained by weighting and adding each coordinate of RGB with each stimulus sum. That is, the sum of each RGB stimulus is Sr, Sg, Sb
Then, the chromaticity coordinates (xw, yw) of white can be calculated as follows.

xw=(Sr・xr+Sg・xg+Sb・xb)/
(Sr+Sg+Sb) yw=(Sr・yr+Sg・
yg+Sb・yb)/(Sr+Sg+Sb) Divide the denominator and numerator on the right side of the above equation by Sg and solve for the stimulus sum ratio of Sr/Sg and Sb/Sg.

[0031]

[Math 1]

[0032] Here, each luminance of RGB is Yr, Y
If g and Yb are used, then from the color system relationship Yr=Sr・yr Yg=Sg・yg
Yb=Sb・yb

[0033]

[Math 2]

Therefore, by substituting (Equation 1) into (Equation 2), RGB can be obtained from each RGB chromaticity coordinate and the target white chromaticity coordinate.
The brightness ratio (composition ratio) when compositing can be calculated. This is the principle of white balance adjustment in this embodiment (Reference: "How to use optical components and points to note for utilizing optronics", p. 132 to p. 172, written by Tetsuo Sueda, published by Optronics Co., Ltd.).

Furthermore, while maintaining the white balance, the gamma characteristic (γ=2.2) included in the broadcast signal and the gamma characteristic (voltage-transmittance characteristic) of the liquid crystal panel are corrected to obtain linear characteristics. In this embodiment, good gradation characteristics can be obtained by setting the white luminance Yw of the low light and highlight to 4% and 70% of the maximum luminance of the optical system using the gain adjustment circuit 14. The RGB target brightness Yr, Yg, and Yb of the low lights and highlights are calculated and adjusted from the following.

Yw=Yr+Yg+Yb

...(3) Yr: Yg: Yb is the above (Math. 1), (Math. 2)
Low light (IRE = 20); Yw = 4% of maximum brightness Highlight (IRE = 80); same 70% In this example, white balance adjustment is performed at the signal level of two points, low light and highlight. and gamma adjustment, but it is not limited to this and can be performed at any signal level.

(Embodiment 3) FIG. 5 shows a third embodiment of the present invention, in which the chromatic luminance sensor 9 provided inside the projector in the first and second embodiments is attached to the protective cap 19 of the projection lens 7. It was established. Furthermore, in this embodiment, the control circuit 11 that adjusts and controls the transmittance of the liquid crystal panel 6 is of a separate type for the inside and outside of the projector.

(Embodiment 4) FIG. 6 shows a fourth embodiment of the present invention, in which a separate control circuit 11 is used as in the third embodiment.
It uses In this embodiment, in particular, color luminance sensors 9 are provided at the four corners and the center of the screen 20.

A concrete block diagram of such a separate type control circuit 11 is shown in FIG.
The operation of the fourth embodiment will be explained. As is clear from FIG. 7, in this embodiment, the external control circuit 11A and the internal control circuit 11A
B is provided with microprocessors 13A and 13B, respectively. The adjustment algorithm in this embodiment is almost the same as in the first and second embodiments,
The chromaticity and luminance of the three primary color lights transmitted through the liquid crystal panel 6 are sequentially measured by the adjustment switch 12 and the like when the transmittance reaches the maximum, and the first The microprocessor 13A calculates the RGB mixed brightness ratio (RGB synthesis ratio) and the RGB adjusted brightness (target brightness of lowlights and highlights). Also,
The video signal generation circuit 18 generates a predetermined level (IRE=20, I
A video signal of RE=80) is generated, and the transmittance of the liquid crystal panel 6 is controlled in a closed loop so that the video signal has a desired RGB mixed brightness ratio and RGB adjusted brightness.

As described above, according to this embodiment, the control circuit 1
1 is separated into the inside and outside of the projector, and white balance adjustment etc. are adjusted at the time of shipment from the factory. Compared to the first and second embodiments, the cost borne by the user is only for the internal control circuit 11B, which is more useful. Become something.

Furthermore, although the projected light from the projection lens 7 is enlarged and projected on the screen 20, the brightness level and chromaticity level are slightly different between the central part and the peripheral part of the enlarged image. By installing the color brightness sensor 9 at the four corners and the center of the screen 20 as shown in 4, the average chromaticity of the entire screen can be measured with high precision, allowing for more detailed white balance correction that corresponds to the actual enlarged image. etc. can be done.

In each of the first to fourth embodiments, the adjustment switch 12 is used to fully open the liquid crystal panel 6 sequentially or simultaneously. Mechanical optical shutter means (mechanical) that is electrically controlled to open and close (with respect to the direction of approach)
It goes without saying that the same effect can be obtained by providing a structure in which the liquid crystal panel 6 is fully opened at the same time, and then the adjustment switch 12 is used to fully open R, G, and B sequentially, for example.

Furthermore, instead of the liquid crystal panel as the shutter means, an oil film type image display element of a schlieren optical system used in large-sized image display devices may be used.

[0044]

[Effects of the Invention] As is clear from the above description, according to the present invention, the composition ratio of the three primary color lights of RGB can be adjusted according to the chromaticity of the three primary color lights, so white balance can be adjusted without variation between products. It can be performed.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a liquid crystal projection type image display device according to a first embodiment of the present invention.

[Figure 2] Configuration diagram of the second embodiment

[Figure 3] Adjustment algorithm for white balance and gamma correction in the first and second embodiments

[Fig. 4] Block diagram of the control circuit 3 in the first and second embodiments.

FIG. 5 is a configuration diagram of a liquid crystal projection type image display device according to a third embodiment of the present invention.

[Fig. 6] Configuration diagram of the fourth embodiment

[Fig. 7] External control circuit 3 in the third and fourth embodiments
A. Block diagram of internal control circuit 3B

[Figure 8] Configuration diagram of a conventional liquid crystal projection type image display device

[Explanation of symbols]

6.LCD panel 9 Color brightness sensor 11 Control circuit 12 Switch 13. Microprocessor 14 Gain adjustment circuit 18 Video signal generation circuit 19 Protective cap 20 Screen

Claims (9)

[Claims] 1. A light source, a filter means for separating the emitted light from the light source into three primary color lights of RGB, a shutter means for transmitting or blocking the three primary color lights of RGB based on an image signal, and an adjustment mode. a switch means for fully opening the shutter means to transmit the RGB three primary color lights; a sensor means for measuring and outputting the chromaticity, luminance or tristimulus value of the transmitted RGB three primary color lights; A projection type image display device comprising: a control circuit that adjusts the transmittance of the filter means based on the output of the sensor means. 2. The projection type image display device according to claim 1, wherein a liquid crystal panel is used as the shutter means. 3. The projection according to claim 2, wherein a photometric window is provided outside the effective display area of the liquid crystal panel, and the chromaticity, luminance, or tristimulus value of the RGB three primary color lights transmitted through the window is measured by the sensor means. type image display device. 4. A light source, a first filter means for separating the emitted light from the light source into three primary color lights of RGB, and a shutter means for transmitting or blocking the three primary color lights of RGB based on an image signal. , a switch means for fully opening the shutter means to transmit the three primary color lights of RGB when in the adjustment mode; and a second switch means for color-synthesizing the transmitted three primary color lights.
, a sensor means for measuring and outputting the chromaticity, brightness or tristimulus value of the combined light, and a control circuit for adjusting the transmittance of the filter means based on the output of the sensor means. type image display device. 5. Each of the light beam paths of the three primary color lights of RGB has a mechanical light shutter means that is electrically controlled to open and close;
5. A projection type image display apparatus according to claim 1, wherein the mechanical optical shutter means are sequentially opened in the adjustment mode. 6. The projection type image display device according to claim 4, wherein the sensor means is provided in a protective cap of a projection lens that projects the combined light onto the screen. 7. The projection type image display device according to claim 4, wherein the sensor means is provided on the screen side. 8. The projection type image display device according to claim 4, wherein the sensor means is provided upstream of a projection lens that projects the combined light onto the screen. 9. The first step to fully open the shutter method of transmitting or blocking the three primary colors of RGB based on the image signal, and the RGB three -primary color of the RGB, the color of the three primary colors, brightness, or three stimuli that has been transmitted through the shutter means. a second step of measuring the value; a third step of calculating a combination ratio of the three primary color lights of RGB based on the measured data; and a step of adjusting the gain of the three primary color lights of RGB so as to achieve the combination ratio. A method for adjusting a projection type image display device, which comprises a fourth step and adjusting white balance in the above-described order.