JP2002051353A - Image display system and chrominance signal adjusting used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve displayable luminance, without excessively deteriorating the color balance. SOLUTION: When an input chrominance signal, indicating an achromatic color of 100% level is inputted, a chrominance signal adjusting device outputs an output chrominance signal of 100% level, and when an input chrominance signal indicating an achromatic signal at 0% level is inputted, the chrominance signal adjusting device outputs an output chrominance signal at 0% level. When an input chrominance signal indicating an achromatic color in at least one intermediate level which excludes 100% level or the 0% level is inputted, the chrominance signal adjusting device outputs an output chrominance signal, so that the chromaticity point of an image to be displayed at an image display device can be turned so as to be almost the same as a prescribed white point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display system for displaying a color image and a color signal adjusting device used for the system.

[0002]

2. Description of the Related Art In a projector (projection display device) as an image display system, in order to correct a nonlinear input / output characteristic (voltage light response characteristic) of a display device or to arbitrarily adjust a color tone, A color signal adjustment device is provided. In this color signal adjustment device, red (R), green (G),
A lookup table representing each input / output characteristic of blue (B) is used.

[0003]

FIG. 3 is an explanatory diagram showing a problem of color signal adjustment in a conventional projector. CR, CG, and CB in FIG. 3 respectively indicate input / output characteristics of each color of R, G, and B in the color signal adjustment device.
Note that the input tone levels in FIG. 3 are expressed as a ratio (percentage) to the maximum input tone level. The output signal level in FIG. 3 is expressed as a ratio (percentage) to the maximum signal level that can be output. In addition, each characteristic CR,
The shapes of CG and CB are represented by simple curved shapes for easy explanation, but actually have more complicated curved shapes. Note that the shape of this characteristic is the same throughout this specification.

In a projector for projecting a color image,
A method of generating a color component image of each color using three liquid crystal panels corresponding to each color of R, G, and B, and combining the generated color component images of each color to display a color image (called a three-panel method) ) Is often used. When the input / output characteristics (voltage light response characteristics) of the three liquid crystal panels are the same, the input / output characteristics C for each of the R, G, and B colors are set as shown in FIG.
The look-up table of the color signal adjusting device is set so that R, CG, and CB are the same. However, the actual input / output characteristics of the three liquid crystal panels are often not the same, and the input / output characteristics CR, CG, and CB of each color are, for example, as shown in FIG.
They are set so as to have different characteristics as shown in FIG. That is, these characteristics CR, CG, CB
Are set so that when an input signal of the same level is given to each color, the projector projects an achromatic synthesized light corresponding to a predetermined white point on the chromaticity diagram.

When the input / output characteristics CR, CG, and CB of each of R, G, and B are set as shown in FIG. 3B, the output signal level B of B with respect to the input color signal of the maximum gradation level is set.
Although max is the maximum level that can be output, the R and G output signal levels Rmax and Gmax are not the maximum levels.

[0006] Since it is desired that the brightness of the image projected by the projector is as bright as possible, the higher the brightness, the better. However, as described above, in the conventional projector, even when the input signal level of each color is 100%, the output signals of some colors take values smaller than 100%, so that the maximum luminance level that can be displayed is reduced. However, there is a problem that an image cannot be displayed. On the other hand, if you try to increase the brightness as much as possible,
As shown in FIG. 3A, three input / output characteristics CR, CG, and CB
Are desirably set to be the same, but in this case, there is a problem that the color balance of the displayed image is deteriorated.

[0007] The above-mentioned problem is not limited to the liquid crystal panel but is common to display systems using various display devices.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and it is an object of the present invention to increase the displayable luminance without excessively deteriorating the color balance in an image display system such as a projector. The purpose is to provide technology that can

[0009]

In order to solve at least a part of the above problems, a first apparatus of the present invention is an image display system, which is an image display apparatus for displaying a color image. And a color signal adjustment device that converts input color signals of a plurality of color components representing a color image into output color signals supplied to the image display device,
The color signal adjusting device outputs a 100% level output color signal when an input color signal representing a 100% level achromatic color is input, and receives an input color signal representing a 0% level achromatic color. When this is done, the output color signal of the 0% level is output, and when the input color signal representing the achromatic color of at least one intermediate level excluding the 100% level and the 0% level is input, the image display device outputs the signal. An output color signal is output such that the chromaticity point of the displayed image is substantially the same as a predetermined white point.

According to the above configuration, in an image display system such as a projector, displayable luminance can be increased without excessively deteriorating color balance.

In this case, the color signal adjusting device may have a maximum luminance level that can be displayed by the image display device by 40% to 40%.
When displaying an achromatic image with a luminance level of 60%,
It is preferable to output an output color signal such that the chromaticity point of the achromatic image is substantially the same as the predetermined white point.

This makes it possible to further suppress the color balance of the halftone image from being excessively deteriorated.

A second device of the present invention is a color signal adjusting device for converting input color signals of a plurality of color components representing a color image into output color signals supplied to a predetermined image display device, respectively. When an input color signal representing an achromatic color at a 100% level is input, an output color signal at a 100% level is output. When an input color signal representing an achromatic color at a 0% level is input, a 0% level is output. And when an input color signal representing an achromatic color of at least one intermediate level other than the 100% level and the 0% level is input, the chromaticity of the image displayed on the image display device is output. An output color signal whose point is substantially the same as a predetermined white point is output.

By applying the color signal adjusting device of the present invention to an image display system, the image display device of the present invention can be configured.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the following procedures based on examples. A. Configuration of Projector: Setting of input / output characteristics: Modification:

A. Configuration of Projector: FIG. 1 is a block diagram showing the configuration of a projector as one embodiment of the image display system of the present invention. The projector includes an AD conversion circuit 10, a video processor 20, and an image memory 30 which constitute an image processing apparatus;
0 and a liquid crystal panel drive circuit 50 constituting the image display device
And a liquid crystal panel 60, a controller 70 and a ROM 80 which constitute a control device of the projector. The video processor 20 and the color signal adjustment circuit 40 are connected to a controller 70 via a bus 70b. The controller 70 includes a CPU and the like,
The operation of the video processor 20 and the color signal adjustment circuit 40 is controlled according to data and programs stored in the ROM 80. Further, various settings of the video processor 20 and the color signal adjustment circuit 40 are executed in accordance with data and programs stored in the ROM 80.

The image display device further includes an illuminating device 90 for illuminating the liquid crystal panel 60 and a screen SC that emits an image emitted from the liquid crystal panel 60.
And a projection optical system 100 for projecting upward.

The liquid crystal panel 60 has three liquid crystal panels 60R, 60G and 60B for R, G and B. Each of the liquid crystal panels 60R, 60G, and 60B is used as a light valve (light modulator) that modulates illumination light emitted from the illumination device 90.

The illumination device 90 has a color light separation optical system for separating light emitted from the light source lamp into light of three colors.
The projection optical system 100 has a combining optical system that combines light of three colors from the liquid crystal panel 60.

The configuration of the optical system of the projector as described above is described in detail in, for example, Japanese Patent Application Laid-Open No. Hei 10-171445 disclosed by the present applicant.
Here, the description is omitted.

The AD conversion circuit 10 converts the R, G, and B color signals contained in the input analog image signal AV into digital color signals.

The video processor 20 includes an AD conversion circuit 1
The digital color signals input from 0 are temporarily written to the image memory 30 and the data written in the image memory 30 are read out as color signals of the respective colors. At this time, various image processing such as enlargement / reduction of an image is executed.

The color signal adjusting circuit 40 has a look-up table (LUT) 40R, 40G, 4 for each of R, G, and B colors.
0B is stored. The contents of the lookup tables 40R, 40G, and 40B for each of the R, G, and B colors are registered in a memory (not shown) in the color signal adjustment circuit 40 by the controller 70.

The input color signals of R, G, and B input from the video processor 20 to the color signal adjustment circuit 40 are converted into corresponding output color signals in accordance with the corresponding look-up tables 40R, 40G, and 40B. . The output color signals of the R, G, and B colors output from the color signal adjustment circuit 40 are supplied to the liquid crystal panel drive circuit 50. The liquid crystal panel driving circuit 50 controls the liquid crystal panel 60 (60R, 60G, 60R) in accordance with the given color signals of R, G, and B colors.
A drive signal for driving B) is generated. R, G, B
The liquid crystal panels 60R, 60G, and 60B of each color modulate the light of each color of R, G, and B by the lighting device 90 according to the drive signal. The modulated R, G, B light (R, G, B)
The light representing the color component image of each of the G and B colors) is emitted from the projection optical system 10.
0 is projected on the screen SC. As a result, a color image is displayed on the screen SC.

B. Setting of input / output characteristics: FIG. 2 is an explanatory diagram showing input / output characteristics in the color signal adjustment circuit 40 of the present embodiment. FIG. 2 shows the input gradation level Vi as an 8-bit gradation and the corresponding output signal level Lo as a 10-bit gradation. Note that the maximum value of the input gradation level Vi is 255. The maximum value of the output signal level Lo is 1023.

The input / output characteristics CI indicated by broken lines indicate theoretical ideal input / output characteristics (hereinafter, referred to as "reference input / output characteristics").

The input / output characteristics CR, CG, R, G, B of each color
CB is set to have the characteristics described below.
Values ViR, Vi of input tone levels Vi of R, G, B colors
When G and ViB are the maximum values (100% level), that is, when ViR = ViG = ViB = 255,
Values LoR, Lo of output signal levels Lo of R, G, B colors
G and LoB are their maximum values (100% level), LoR = LoG = LoB = 1023. on the other hand,
Values ViR, Vi of input tone levels Vi of R, G, B colors
G and ViB are minimum values (0% level), that is, ViR
= ViG = ViB = 0, the output signal level Lo
Are LoR = LoG = LoB = 0, which are the minimum values (0% level) that can be output. Thereby, when the input color signal of the maximum level is input, an image of the maximum displayable luminance level is displayed, and when the input color signal of the minimum level is input, the image of the minimum displayable luminance level is displayed. be able to. As a result, the contrast of the displayed image can be increased as much as possible.

However, when such a setting is made, the chromaticity point of the achromatic image having the maximum and minimum luminance levels is generally shifted from the target predetermined chromaticity point (white point). . In FIG. 2, the xy chromaticity points of the images at the maximum and minimum luminance levels are F (x, y) = (0.289, 0.36).
9), which is a predetermined white point W (x, y) =
It is slightly greener than (0.291, 0.354). By the way, in the conventional image display system, a target white point is determined in advance, and the input / output characteristics CR, CG, and CB are determined so that almost the same chromaticity as the white point can be reproduced at any gradation level. Was normal. For example, the white point W (x, y) shown in FIG.
91, 0.354) is such a target white point. In contrast, the input / output characteristics shown in FIG.
The colors of the images displayed for the% level and 0% level inputs correspond to chromaticity points that deviate from the target white point.

At the input gradation level Vi corresponding to the achromatic image of all halftone levels except the maximum and minimum, the chromaticity point F (x, y) of the displayed image is set to the predetermined white point W ( x, y), so that R, G, B
The input / output characteristics CR, CG, and CB of each color are set. For example, input / output characteristics CR, CG, CB of each color of R, G, B
Is the value ViR of the input gradation level Vi of each of the R, G, and B colors.
ViG and ViB are, for example, ViR = ViG = ViB =
At 192, the output signal level Lo of each of R, G, and B colors
R, LoG, and LoB are LoR = 593 and LoG, respectively.
= 503, LoB = 558. The chromaticity point F (x, y) of the displayed image is (2.29)
1, 0.354), which is almost the same as the predetermined white point W (x, y). Here, “the chromaticity point of the displayed image is substantially the same as the predetermined white point” means that the deviation of the chromaticity coordinates between the chromaticity point and the white point of the displayed image is ± about each of x and y. It means within the range of 0.005. Specifically, the chromaticity coordinates (x, y) of the white point W are (0.29
In this case, the chromaticity coordinates of the chromaticity point F of the displayed image are (0.291 ± 0.005, 0.35).
54 ± 0.005).

As a result, in the projector of this embodiment, the color reproducibility of a halftone image other than the maximum and minimum is not reduced.

As described above, in the projector of the present embodiment, the maximum level of the achromatic image can be obtained without deteriorating the color reproducibility of the halftone level image except for the maximum and minimum input tone levels. When an input color signal corresponding to is input, an achromatic image having the maximum displayable luminance level can be displayed. Therefore, the luminance level of the image displayed for the maximum level achromatic input color signal is set to the maximum luminance level that can be displayed on the image display device, and the input / output characteristics of the image display system are the same as in the past. It can be adjustable. That is, the luminance of a displayable image can be increased without excessively deteriorating the color balance of the displayed image.

In the projector of the above embodiment, the input / output characteristics CR, CG, CB of each of R, G, B colors are
The chromaticity point F (x, y) of the image corresponding to the halftone input gradation level excluding the maximum and minimum input gradation levels is substantially the same as the predetermined white point W (x, y). The case where the adjustment is performed is shown as an example, but the present invention is not limited to this. The chromaticity point of the displayed image may be adjusted to be substantially the same as the predetermined white point with respect to the input tone level corresponding to the at least one halftone achromatic image. . This makes it possible to display an image without deteriorating the color reproducibility of the image corresponding to the adjusted input tone level. However, when displaying an achromatic image having a luminance level of 40% to 60% of the maximum luminance level to be displayed, the chromaticity point F (x, y) of the achromatic image of each luminance level to be displayed is displayed. ) Is a predetermined white point W
Preferably, it is adjusted so as to be substantially the same as (x, y). In this way, images can be displayed without reducing the color reproducibility of many displayed halftone images. Further, when an achromatic image having a luminance level of 20% to 80% of the displayed maximum luminance level is displayed, the chromaticity point F (x, x) of the achromatic image at each luminance level is displayed.
Preferably, y) is adjusted so as to be substantially the same as the predetermined white point W (x, y). If you do this,
Images can be displayed without deteriorating the color reproducibility of more halftone images to be displayed.

C. Modifications: The present invention is not limited to the above-described examples and embodiments, and can be carried out in various modes without departing from the gist thereof. For example, the following modifications are also possible. is there.

C1. Modification Example 1 In the above-described embodiment, the configuration in which the lookup tables 40R, 40G, and 40B for the respective colors of R, G, and B are used as the color signal adjustment circuit 40 has been described as an example. However, the configuration is not limited thereto. For example, R.
G. FIG. A configuration using a multiplication circuit provided for each B color may be used. In this case, the input / output characteristics CR, CG, and CB of each of the R, G, and B colors are adjusted by respectively adjusting the multiplication coefficients according to the gradation levels of the input color signals of the R, G, and B colors.
Can be adjusted. In addition, R. G. FIG. A configuration using an addition circuit provided for each of the B colors may be used. In this case, by adjusting the offsets according to the gradation levels of the input color signals of the R, G, and B colors, the R, G, and B colors are adjusted.
The input / output characteristics CR, CG, and CB of each color of G and B can be adjusted.

C2. Modification 2 In the above embodiment, the configuration of the projector using the transmission type liquid crystal panel as the image display device has been described, but the present invention is applicable to other types of projectors. Other types of projectors include those using a reflective liquid crystal panel, those using a digital micromirror device (trademark of Texas Instruments), and those using a CRT.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a projector as one embodiment of an image display system.

FIG. 2 is an explanatory diagram showing input / output characteristics in a color signal adjustment circuit 40.

FIG. 3 is an explanatory diagram showing a problem of color signal adjustment in a conventional projector.

[Explanation of symbols]

Reference Signs List 10 AD conversion circuit 20 Video processor 30 Image memory 40 Color signal adjustment circuit 40R, 40G, 40B Look-up table (LU
T) 50: liquid crystal panel drive circuit 60: liquid crystal panel 60R, 60G, 60B: liquid crystal panel 70b: bus 70: controller 80: ROM 90: lighting device 100: projection optical system SC: screen

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[Procedure amendment]

[Submission date] September 11, 2001 (2001.9.1
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

At the input gradation level Vi corresponding to the achromatic image of all halftone levels except the maximum and minimum, the chromaticity point F (x, y) of the displayed image is set to the predetermined white point W ( x, y), so that R, G, B
The input / output characteristics CR, CG, and CB of each color are set. For example, input / output characteristics CR, CG, CB of each color of R, G, B
Is the value ViR of the input gradation level Vi of each of the R, G, and B colors.
When ViG and ViB are, for example, ViR = ViG = ViB =
At 192, the output signal level Lo of each of R, G, and B colors
R, LoG, and LoB are LoR = 593 and LoG, respectively.
= 503, LoB = 558. The chromaticity point F (x, y) of the displayed image is ( 0.29
1 , 0.354), which is almost the same as the predetermined white point W (x, y). Here, “the chromaticity point of the displayed image is substantially the same as the predetermined white point” means that the deviation of the chromaticity coordinates between the chromaticity point and the white point of the displayed image is ± about each of x and y. It means within the range of 0.005. Specifically, the chromaticity coordinates (x, y) of the white point W are (0.29
In this case, the chromaticity coordinates of the chromaticity point F of the displayed image are (0.291 ± 0.005, 0.35).
54 ± 0.005).

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

C1. Modification Example 1 In the above-described embodiment, the configuration in which the lookup tables 40R, 40G, and 40B for the respective colors of R, G, and B are used as the color signal adjustment circuit 40 has been described as an example. However, the configuration is not limited thereto. For example, R,
A configuration using a multiplication circuit provided for each of the G and B colors may be used. In this case, the input / output characteristics CR, CG, and CB of each of the R, G, and B colors are adjusted by respectively adjusting the multiplication coefficients according to the gradation levels of the input color signals of the R, G, and B colors.
Can be adjusted. Further, a configuration using an adder circuit provided for each of R, G, and B colors may be adopted. In this case, by adjusting the offsets according to the gradation levels of the input color signals of the R, G, and B colors, the R, G, and B colors are adjusted.
The input / output characteristics CR, CG, and CB of each color of G and B can be adjusted.

Claims (4)

[Claims] 1. An image display system, comprising: an image display device for displaying a color image; and an input color signal of a plurality of color components representing the color image, each being converted to an output color signal supplied to the image display device. A color signal adjusting device that outputs a 100% level output color signal when an input color signal representing an achromatic color at a 100% level is input, and outputs a 0% level When an input color signal representing an achromatic color is input, an output color signal of a 0% level is output, and an input color signal representing an achromatic color of at least one intermediate level excluding the 100% level and the 0% level is output. An image display system which, when input, outputs an output color signal such that a chromaticity point of an image displayed on the image display device is substantially the same as a predetermined white point. 2. The image display system according to claim 1, wherein the color signal adjustment device is an achromatic color having a luminance level of 40% to 60% of a maximum luminance level that can be displayed by the image display device. An image display system that outputs an output color signal such that a chromaticity point of the achromatic image is substantially the same as the predetermined white point when displaying an image. 3. A color signal adjusting device for converting input color signals of a plurality of color components representing a color image into output color signals supplied to a predetermined image display device, wherein the color signal adjusting device converts 100% level achromatic color. When an input color signal representing an achromatic color is input, an output color signal at a 100% level is output. When an input color signal representing an achromatic color at a 0% level is input, an output color signal at a 0% level is output. In addition, when an input color signal representing an achromatic color of at least one intermediate level other than the 100% level and the 0% level is input, the chromaticity point of the image displayed on the image display device is a predetermined white point. A color signal adjustment device that outputs output color signals that are almost the same. 4. The color signal adjusting device according to claim 3, wherein the image display device displays an achromatic image having a luminance level of 40% to 60% of a maximum luminance level that can be displayed. A color signal adjustment device that outputs an output color signal such that the chromaticity point of the achromatic image is substantially the same as the predetermined white point.