WO2012164678A1

WO2012164678A1 - Display device and display method

Info

Publication number: WO2012164678A1
Application number: PCT/JP2011/062451
Authority: WO
Inventors: 勝之松井
Original assignee: Ｎｅｃディスプレイソリューションズ株式会社
Priority date: 2011-05-31
Filing date: 2011-05-31
Publication date: 2012-12-06
Also published as: JPWO2012164678A1; JP5791130B2

Abstract

A display device (1) wherein a plurality of backlights (12) of different primary colors are provided and said backlights (12) illuminate a liquid-crystal panel from behind to display color images. Said display device is characterized by having the following: a target color-gamut storage unit (21) that stores information representing a target color gamut; a detection unit (13) that detects the white point of the backlights; estimation units (18, 19, 20) that estimate the color gamut of the display device (1) on the basis of said white point; a color-correction unit (22) that compares said estimated color gamut with the aforementioned target color gamut and corrects a video signal; and a display unit (23) that displays images on the basis of the video signal outputted by the color-correction unit (22).

Description

Display device and display method

The present invention relates to a display device and a display method provided with a plurality of primary color backlights of different colors.

When performing graphic design using a display device, the white balance (white point chromaticity) of the display device is often determined according to the illumination color in the viewing environment. This is for the purpose of color matching with printed matter. That is, in an industrial field where strict color reproduction is required, a commercial display device is required to have a wide white point chromaticity, high color display accuracy, and a wide and stable color gamut.

Further, cited document 1 discloses a technique related to a high-quality liquid crystal display device in consideration of crosstalk between the liquid crystal panel and the backlight.

JP 2008-102379 A

A display device having a primary color backlight usually adjusts the chromaticity of a white point by changing the light output of each color of the backlight. In a display device having such a primary color backlight, a wide color gamut can be obtained, but when the chromaticity adjustment range by the backlight is expanded, there is a problem that the display color gamut fluctuates or is reduced.
FIG. 9 is a diagram illustrating an example of the color gamut change by the backlight white point chromaticity setting. As shown in this figure, the color gamut differs depending on the white point setting.

This problem is noticeable when setting a white point where the drive level difference between the backlight colors is large. Even when the drive level is kept constant, the chromaticity shift of the backlight due to the temperature change and aging deterioration occurs, so that the display color gamut varies and is reduced.

This problem is unique to the primary color backlight. In a conventional general display device, that is, a display device having a white backlight, the display color gamut is a display device specific value independent of the white setting.
The above-mentioned problems cause image quality degradation such as a decrease in color matching accuracy, but cannot be detected by the backlight sensor (inside the display device) because it occurs on the display panel surface. Therefore, it is necessary to narrow the adjustment range of the backlight chromaticity in advance.
That is, it is difficult to satisfy both the degree of freedom of white point chromaticity and display accuracy (color gamut stability).

On the other hand, the above-mentioned Patent Document 1 considers crosstalk, but does not disclose a specific procedure for calculating the coefficient of the transformation matrix based on the measurement of the display device.
Further, unless the backlight and data related to the wavelength distribution of the sub-pixel color filter are transmitted from the display panel to the personal computer, signal processing related to the wavelength distribution such as crosstalk correction processing cannot be performed (Patent Document 1). (See paragraph 0086).
As described above, in the cited document 1, it is necessary to measure or calculate the wavelength distribution of the display device using the spectrophotometer. However, spectrometers are generally expensive and low speed, and are difficult to apply to practical products.

Therefore, the present invention provides a display device and a display method that can perform chromaticity correction with a simple configuration.

In order to solve the above-described problem, the present invention is a display device that is provided with a plurality of backlights of different primary colors and that displays a color image by irradiating a liquid crystal panel from the back of the display with the backlight. A target color gamut storage unit that stores a target color gamut that is information representing a color gamut, a detection unit that detects white point chromaticity of a backlight, and a color gamut of a display device is estimated based on the white point chromaticity A color correction unit that compares the estimated color gamut with the target color gamut to correct a video signal, and a display that displays an image based on the video signal output from the color correction unit And a portion.

The present invention also provides a display method in a display device in which a plurality of backlights of different primary colors are provided, and a liquid crystal panel is illuminated from the back of the display by the backlight to display a color image, and the white point chromaticity of the backlight And based on the white point chromaticity, the color gamut of the display device is estimated, and the estimated color gamut is compared with the target color gamut, which is information representing the target color gamut. , And an image is displayed based on the corrected video signal.

According to the present invention, chromaticity correction based on the color gamut can be performed with a simple configuration. In addition, according to the present invention, in a display device having a primary color backlight, the color gamut variation of the liquid crystal panel that occurs when the backlight chromaticity changes can be suppressed by correcting the video signal, thereby improving the color display accuracy. Wide white point setting and high color gamut stability.

It is a schematic block diagram showing the function of the display apparatus 1 in this invention. It is a figure showing an example of a color filter characteristic. It is a figure showing the cross section for 1 pixel of a liquid crystal panel. It is a figure showing the cross section for 1 pixel of a liquid crystal panel, and explaining the ideal characteristic at the time of displaying green among panel color gamuts. It is a figure showing the display characteristic in the actual case which displays green. It is a figure showing the case where the chromaticity of a backlight is changed. The cross section for 1 pixel of a liquid crystal panel is represented. The cross section for 1 pixel of a liquid crystal panel is represented. It is a figure showing the example of the color gamut change by backlight white point chromaticity setting.

Hereinafter, a display device according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing functions of the display device 1 according to the present invention.
In this figure, a display device 1 is provided with a plurality of backlights of different primary colors, and a color image is displayed by irradiating a liquid crystal panel from the back of the display with the backlight.

Here, the cause of the color gamut variation with respect to the backlight white point is due to the color filter characteristics (FIG. 2) and the pixel structure of the display device (FIG. 3; sectional view of one pixel). Details are described below.
FIG. 2 is a diagram illustrating an example of color filter characteristics. The vertical axis is the light transmittance, and the horizontal axis is the wavelength. In this figure, reference numeral 201 represents the transmittance of light having a blue wavelength, reference numeral 202 represents the transmittance of light having a green wavelength, and reference numeral 203 represents the transmittance of light having a red wavelength. To express. Here, for each color (blue, green, and red), it is desirable that only the target color to be transmitted is transmitted, but not only the target color is necessarily transmitted, but part of other colors are transmitted.

FIG. 3 is a diagram showing a cross section of one pixel of the liquid crystal panel. As shown in this figure, light emitted from each light source (LED) of the red backlight 301, the green backlight 302, and the blue backlight 303 provided on the back plate 300 is converted into an optical diffusion plate 304 and a TFT (thin film transistor). The light transmitted through the element illuminates the liquid crystal panel from the back. Further, in this figure, a case where white is displayed is illustrated, and the amount of light transmitted through the red pixel 305, the green pixel 306, and the blue pixel 307 is the same amount. Here, for each pixel, one set of red backlight 301, green backlight 302, and blue backlight 303 is provided, and one set of red pixel 305, green pixel 306, and blue pixel 307 is provided. Is configured.

FIG. 4 shows a cross section of one pixel of the liquid crystal panel, and is a diagram for explaining ideal characteristics when displaying green in the panel color gamut. As shown in this figure, as an ideal state, only green light is transmitted from the green pixel 402. Light is not transmitted from the red pixel 401 and the blue pixel 303.

FIG. 5 is a diagram showing display characteristics in the actual case of displaying green. From the green pixel 501, in addition to green light, part of red and blue light that should be blocked is transmitted. This is because leakage light having a cutoff wavelength is not zero from the color filter characteristics shown in FIG.

FIG. 6 is a diagram illustrating a case where the chromaticity of the backlight is changed. By changing the chromaticity of the backlight, the balance of red, green, and blue light transmitted through the green pixel changes, that is, the chromaticity (color gamut) of green changes.
Therefore, in the present invention, the panel color gamut is calculated using this leakage light characteristic, and the video signal is corrected so that the color gamut characteristic maintains the target.

Returning to FIG. 1, the white spot setting information storage unit 10 stores target luminance and chromaticity. Here, the luminance is 70 cd / m ² and the chromaticity is 9300K.
The backlight drive circuit 11 drives the primary color backlight 12. The backlight drive circuit 11 individually controls and drives each color backlight of the primary color backlight 12. There are various driving methods. For example, there is a method of driving the power supplied to the backlight by PWM (pulse width modulation).

The primary color backlight 12 is driven in accordance with a drive signal from the backlight drive circuit 11 and emits light. The primary color backlight 12 is, for example, an LED (light emitting diode) corresponding to each color of R (red), G (green), and B (blue).

The backlight emission color detection unit 13 is, for example, a backlight sensor, detects light emitted from the primary color backlight 12, and detects white point chromaticity of the backlight from the detected light. In addition, when not using a backlight sensor, the information memorize | stored in the white setting information storage part 10 can be used.

The backlight single color luminance calculation unit 14 calculates the luminance for each color of the backlight based on the detection result detected by the backlight emission color detection unit 13. Here, for example, in the state where only the red color of the primary color backlight 12 is turned on by the backlight drive circuit 11, the backlight emission color detection unit 13 detects light, and the backlight monochromatic luminance calculation unit 14 detects the light. The brightness for the red color of the backlight is obtained using the result. Then, the backlight monochromatic luminance calculation unit 14 outputs the red color filter transmitted light amount calculation unit 15, the green color filter transmitted light amount calculation unit 16, and the blue color filter transmitted light amount calculation unit 17. Further, the backlight single color luminance calculation unit 14 detects light with the backlight emission color detection unit 13 in a state where only the green color of the primary color backlight 12 is lit, obtains the luminance about the green color of the backlight, and Output to the color filter transmitted light amount calculation unit 15, the green color filter transmitted light amount calculation unit 16, and the blue color filter transmitted light amount calculation unit 17.

Further, the backlight single color luminance calculation unit 14 detects light with the backlight emission color detection unit 13 in a state where only the blue color of the primary color backlight 12 is lit, obtains the luminance of the backlight blue, Output to the color filter transmitted light amount calculation unit 15, the green color filter transmitted light amount calculation unit 16, and the blue color filter transmitted light amount calculation unit 17.

The red color filter transmitted light amount calculation unit 15 is input from the backlight luminance selection unit 14, the luminance when the red color of the backlight is lit, the luminance when the green color of the backlight is lit, and the backlight Based on the brightness when the blue light is turned on, the amount of light transmitted through the red pixel of the backlight is calculated and summed for each color pixel.

The green color filter transmitted light amount calculation unit 16 is input from the backlight luminance selection unit 14, the luminance when the backlight red is turned on, the luminance when the backlight green is turned on, and the backlight Based on the brightness when the blue light is turned on, the amount of light transmitted through the green pixels of the backlight is calculated and summed for each color pixel.

The blue color filter transmitted light amount calculation unit 17 is input from the backlight luminance selection unit 14, the luminance when the red color of the backlight is lit, the luminance when the green color of the backlight is lit, and the backlight Based on the brightness when the blue light is turned on, the amount of light transmitted through the blue pixels of the backlight is calculated and summed for each color pixel.

Here, the red color filter transmitted light amount calculation unit 15, the green color filter transmitted light amount calculation unit 16, and the blue color filter transmitted light amount calculation unit 17 calculate the luminance when the red light of the backlight is turned on according to a predetermined formula. Alternatively, the amount of light transmitted through the pixels of each color of the backlight may be calculated by substituting the luminance when the backlight green is turned on and the luminance when the backlight blue is turned on. In addition, the luminance when the backlight red is turned on, the luminance when the backlight green is turned on, the luminance when the backlight blue is turned on, and the amount of light transmitted through the pixels of each color A table representing the relationship may be stored, and the amount of light transmitted through each color pixel may be calculated by referring to this table.

The red primary color panel chromaticity estimation unit 18 estimates the chromaticity of the pixel based on the ratio of the light amount added by the red color filter transmitted light amount calculation unit 15. Here, the light amount ratio is a ratio of the amount of red light transmitted through the red pixel, the amount of green light transmitted through the red pixel, and the amount of blue light transmitted through the red pixel. By using this ratio and the amount of light, the chromaticity of the light transmitted through the red pixel is specified.

The green primary color panel chromaticity estimation unit 19 estimates the chromaticity of the pixel based on the ratio of the light amount added by the green color filter transmitted light amount calculation unit 16. As described above, the green primary color panel chromaticity estimation unit 19 uses the amount of red light transmitted through the green pixel, the amount of green light transmitted through the green pixel, and the amount of blue light transmitted through the green pixel. The chromaticity of the light transmitted through the green pixel is specified by using the ratio and the amount of light.

The blue primary color panel chromaticity estimation unit 20 estimates the chromaticity of the pixel based on the ratio of the light amount added by the blue color filter transmitted light amount calculation unit 17. As described above, the blue primary color panel chromaticity estimation unit 20 includes the amount of red light transmitted through the blue pixel, the amount of green light transmitted through the blue pixel, and the amount of blue light transmitted through the blue pixel. The chromaticity of the light transmitted through the blue pixel is specified by using the ratio and the amount of light.

The color gamut setting information storage unit 21 stores a target color gamut that is information representing a target color gamut.

The LCD panel color correction circuit 22 includes a color gamut estimated by the red primary color panel chromaticity estimation unit 18, a green primary color panel chromaticity estimation unit 19, and a blue primary color panel chromaticity estimation unit 20, and a color gamut setting information storage unit 21. The video signal output to the display unit 23 is corrected by comparing with the target color gamut stored in.

The display unit 23 includes an LCD panel driver and an LCD panel, and displays an image on the LCD panel based on the video signal output from the LCD panel color correction circuit 22.

In the above-described configuration, the panel color gamut prediction based on the backlight emission color will be further described. First, LCD panel characteristics are calculated in the reference state. At this time, the backlight single color is turned on, and the leakage light of each backlight in each cell is obtained based on the white and primary color luminance measured on the panel surface.
For example, as shown in FIG. 7 and FIG. 8, when the amount of light when displaying blue is GBL_Bcell, and the amount of light when displaying white is GBL_RGBcell, by calculating according to the equation (GBL_Bcell) / (GBL_RGBcell), The amount of leakage light of the green backlight in the blue cell can be obtained. These leakage lights are usually 2 to 3% with respect to the amount of light of the color desired to be transmitted.
In this way, all backlight colors (red, green, blue) are performed on all pixels.

Next, whenever necessary, the light emission amount of each color of the target or current backlight is detected, and the chromaticity of the RGB pixel is obtained based on the leaked light component. At this time, since the chromaticity is a calculated value using the reference characteristic, it is not necessary to actually measure the panel surface.
Note that a general correction method can be used for video correction based on the calculated panel color gamut. For example, correction is performed using an LUT (LookUpTable).

According to the embodiment described above, the correction characteristic automatically follows by detecting an optical characteristic change due to individual difference / aging. For this reason, there is little individual difference, and a stable image quality deterioration suppressing effect can be expected for a long period of time. Moreover, since the measured value of the panel color gamut is not required when used by the user, the user can operate the display device without complicated manual measurement.

Further, according to the above-described embodiment, correction can be performed without performing wavelength distribution measurement or calculation. For example, the image signal can be multiplied by an RGB determinant to correct backlight crosstalk with the LCD. That is, since the matrix coefficient can be calculated by short-time measurement using an inexpensive color luminance meter (a few tens of seconds at the maximum), adjustment for each individual can be performed during mass production.

Further, the program for realizing the function of the display device 1 in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into the computer system and executed, thereby executing chromaticity correction. May be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM or a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” includes a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. Alternatively, the program may be stored in a predetermined server, and the program may be distributed (downloaded or the like) via a communication line in response to a request from another device.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within the scope not departing from the gist of the present invention.

The present invention is a display device that performs high-precision color reproduction, and is particularly effective in the fields of graphic design, printing shops, medical displays, and the like.

DESCRIPTION OF SYMBOLS 1 Display apparatus 10 White point setting information storage part 11 Backlight drive circuit 12 Primary color backlight 13 Backlight emission color detection part 14 Backlight single color brightness | luminance calculation part 15 Red color filter transmitted light amount calculation part 16 Green color filter transmitted light amount calculation part 17 Blue color filter transmitted light amount calculation unit 18 Red primary color panel chromaticity estimation unit 19 Green primary color panel chromaticity estimation unit 20 Blue primary color panel chromaticity estimation unit 21 Color gamut setting information storage unit 22 LCD panel color correction circuit 23 Display unit

Claims

A display device provided with a plurality of backlights of different primary colors and displaying a color image by irradiating a liquid crystal panel from the back of the display with the backlight,
A target color gamut storage unit for storing a target color gamut, which is information representing the target color gamut;
A detection unit for detecting the white point chromaticity of the backlight;
An estimation unit that estimates a color gamut of the display device based on the white point chromaticity;
A color correction unit that compares the estimated color gamut with the target color gamut to correct a video signal;
A display unit for displaying an image based on a video signal output from the color correction unit;
A display device comprising:
The estimation unit includes
Calculate the amount of light that passes through each color pixel for each backlight color,
Total the amount of transmitted backlight for each color pixel,
The display device according to claim 1, wherein the chromaticity of the pixel is estimated based on a ratio of the total light amount.
A display method in a display device in which a plurality of backlights of different primary colors are provided, and a liquid crystal panel is irradiated from the back of the display by the backlight to display a color image,
Detect the white point chromaticity of the backlight,
Based on the white point chromaticity, the color gamut of the display device is estimated,
A video signal is corrected by comparing the estimated color gamut with a target color gamut, which is information representing the target color gamut,
A display method, comprising: displaying an image based on the corrected video signal.