JP4894149B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device such as a liquid crystal television or a liquid crystal monitor using a liquid crystal display panel having a backlight capable of changing luminance and chromaticity.

  In a non-light emitting display device such as a liquid crystal display device, an illumination device called a backlight for irradiating the image display element with uniform light from the back surface is arranged. As this backlight, a side-light type has been used with the thinning of liquid crystal display devices, etc., but in recent years, with the increase in screen size and definition of liquid crystal display devices, backlights with higher brightness have been used. It has come to be requested. For this reason, a direct-type backlight is used in which a light source such as a fluorescent tube is arranged directly under the image display device to obtain a planar light source, and RGB is used as the light source for lightening and low power consumption. LEDs capable of emitting light of the three primary colors have been used.

  With the increase in size of liquid crystal display devices, the size of lamps and liquid crystal panels has also increased, so that many lamps and LEDs with the same brightness and color temperature can be used in backlights, and large-area liquid crystal panels can be used. Therefore, it is very difficult to manufacture a liquid crystal display device that does not have uneven brightness or chromaticity on the display screen of the liquid crystal display device.

As a method for solving such a problem, for example, in Japanese Patent Application Laid-Open No. 8-313879, a non-uniformity of a display image is detected by a detector, and signal processing is performed so that there is no non-uniformity in an image to be displayed. A technique for performing unevenness correction is disclosed. The conventional unevenness correction method disclosed in this publication divides the screen displayed on the liquid crystal display panel into a plurality of parts, detects the brightness and chromaticity of each area with a detector, and determines the brightness of each area. Unevenness is corrected by correcting the display video in each area by performing video signal processing so that the chromaticity is the same.
JP-A-8-313879

  However, in the past, when correcting the unevenness, the video signal is corrected based on the unevenness detection result of the display screen to make the display image uniform. For example, when the video signal is black, the video signal If the unevenness correction is performed in, the video signal cannot be further lowered because the brighter area than the average luminance of the display screen is adjusted to the average luminance. Therefore, the video signal is inevitably raised rather than the darkest part of each detected area. Corrections must be made for bright spots. That is, in a certain area, it is necessary to raise the level of the video signal to be brighter than the black luminance that can be originally displayed. Similarly, when displaying white, the brightness cannot be adjusted to the brightest part of each area in order to correct unevenness, so the video signal is lowered and corrected to the darkest part of each detected area. Must be done. That is, in a certain area, the level of the video signal must be lowered and displayed darker than the white luminance that can be originally displayed. As a result, the average luminance of the display screen is increased in black, and the average luminance of the display screen is decreased in white, so that the contrast is lowered.

In order to solve this problem, the present invention stores a liquid crystal display panel for displaying a video signal, a backlight capable of changing the luminance and chromaticity of a partial portion of the display screen, and a plurality of pieces of information. And a backlight control means for controlling the backlight according to the value of the memory,
A liquid crystal display device that adjusts brightness and chromaticity of a display screen of a liquid crystal display panel based on a correction amount stored in the memory

  If the liquid crystal display device according to the first invention of the present application is used, a liquid crystal display having a backlight capable of changing the luminance and chromaticity of a partial portion of the display screen and a memory capable of storing a plurality of information. In the device, the brightness and chromaticity of the partial part of the backlight are changed by the information stored in the memory regardless of the video signal, and the unevenness of the brightness and chromaticity of the display screen is corrected. It is possible to correct unevenness of the display screen with respect to the signal and display a uniform image. In the production of liquid crystal display devices, the defective rate of liquid crystal display panels and backlights can be reduced to improve production efficiency.

  If the liquid crystal display device according to the second invention of the present application is used, a correction amount for correcting the unevenness is obtained each time from information obtained by a detector for detecting unevenness of luminance and chromaticity of the display screen, and stored in the memory. By changing the correction amount, it is possible to correct unevenness of the liquid crystal display screen that changes under various circumstances and display a uniform image.

  If the liquid crystal display device according to the third invention of the present application is used, the average luminance of the input video signal is detected, and the luminance and chromaticity of the partial portion of the backlight are changed according to the detected value, and the luminance of the display screen or Since chromaticity unevenness correction is performed, it is possible to correct display screen unevenness for various video signals and display a uniform image.

  If the liquid crystal display device according to the fourth aspect of the present invention is used, the average luminance of the input video signal is detected, and the luminance and chromaticity of a partial portion of the display screen on which the backlight and the video signal are displayed according to the detected value. Since the display screen brightness and chromaticity unevenness are corrected by changing the display, the display screen unevenness is corrected for various video signals to display a uniform image and reduce power consumption. It becomes possible to do.

A liquid crystal display panel for displaying video signals, a backlight for changing the luminance and chromaticity of a part of the display screen, a memory for storing a plurality of pieces of information, and a backlight for controlling the backlight according to the value of the memory In a liquid crystal display device provided with a control means,
The liquid crystal display device is characterized in that brightness and chromaticity of a display screen of the liquid crystal display panel are adjusted based on a correction amount stored in the memory.

  An embodiment of the first invention of the present application will be described below with reference to FIG.

  This liquid crystal display device 100 shown in FIG. 1 includes a liquid crystal display panel 51 that displays a video signal, a backlight 52 that changes the luminance and chromaticity of a portion of the display screen, a memory 10 that stores a plurality of pieces of information, A backlight control circuit 11 that controls the backlight according to the value of the memory is provided.

  In the liquid crystal display device configured as described above, for example, a video signal a having a video signal level (r1, g1, b1) = (10%, 10%, 10%) is displayed on the liquid crystal panel 51 as a video signal. Consider the case where it is displayed entirely.

  First, details of the conventional method for correcting the unevenness of the liquid crystal display screen are described in Japanese Patent Application Laid-Open No. 8-313879, and will be briefly described with reference to FIG. The configuration of the liquid crystal display device shown in FIG. 2 has the same basic structure as that of the liquid crystal display device of the present invention, and the backlight control circuit of the present invention is a signal control circuit, thereby correcting unevenness by correcting the video signal. It is carried out. When the video signal a is displayed on the liquid crystal panel 51 of the liquid crystal display device shown in FIG. 2A, for example, when the display screen is divided into four as shown in FIG. As the inherent unevenness, if the luminance ratio of each area is (A: B: C: D) = (1: 1.1: 0.9: 1), the memory 10 is used to correct this unevenness. The correction amount is stored. The signal control circuit 500 performs signal processing on the areas B and C so as to lower the luminance of the area B and increase the luminance of the area C by this correction amount. That is, video signals having different luminance ratios for each area of the liquid crystal display panel 51 are displayed so that the display image becomes uniform. Further, correction is performed by the signal control circuit 500 so as to match the average luminance of the entire video signal screen. Thereby, unevenness in luminance can be corrected. Similarly, the chromaticity unevenness can be corrected by changing the RGB ratio of the signal.

  However, when a black video signal b such as a video signal level (r1, g1, b1) = (0%, 0%, 0%) is displayed on the entire screen as a video signal, each area unique to the liquid crystal panel 51 is displayed. When the luminance ratio of (A: B: C: D) = (1: 1.1: 0.9: 1) is similarly corrected, the luminance of area B further decreases the video signal level. Therefore, a uniform display without unevenness cannot be achieved. Further, in order to perform uniform display without unevenness, it is necessary to perform correction in accordance with the luminance of area B, which is the maximum luminance in the area. As a result, the average luminance of the entire screen increases and the contrast deteriorates. Similarly, in the case of white display where the video signal level is (r1, g1, b1) = (100%, 100%, 100%), the average luminance of the entire screen is lowered for uniform display without unevenness. There must be.

  Therefore, the operation of the liquid crystal display device of the present invention will be described with reference to FIG. 1 when such a video signal b is input. First, in the case of the liquid crystal device of the present invention, a backlight capable of changing the luminance and chromaticity of a partial portion of the display screen is used. As a backlight driving method capable of changing the luminance and chromaticity of a partial portion of the display screen, there is an LED backlight as described in JP-A-8-152856. Detailed description is omitted here. Accordingly, the unevenness of the display screen can be corrected by correcting the luminance of the backlight for each area without being affected by the video signal level. More specifically, when a black video signal b such as the video signal level (r1, g1, b1) = (0%, 0%, 0%) is displayed on the entire screen, If the luminance ratio of each area is (A: B: C: D) = (1: 1.1: 0.9: 1), the luminance of area B based on the correction amount stored in the memory 51 By controlling the backlight so that the brightness of area C is increased and the brightness of area C is increased, the video signal is not affected, and uniform display without unevenness can be achieved without deteriorating the contrast.

  According to a second aspect of the present invention, the memory value of the first aspect includes a luminance / chromaticity detection means for detecting the luminance and chromaticity distribution of the display screen, and the luminance and chromaticity of the liquid crystal display screen from the detection means. A liquid crystal display device that stores a plurality of correction amounts obtained by correction amount detection means for detecting a correction amount for correcting.

  Since the method of correcting the unevenness of the liquid crystal display device of the present invention is the same as that described in the first embodiment, description of the correction method is omitted, and a method of detecting data stored in the memory will be described with reference to FIG. . The luminance and chromaticity distribution of the display screen of the liquid crystal panel 51 is detected by the luminance / chromaticity detector 80, and a correction amount for correcting the unevenness is calculated by the unevenness feature amount detection circuit 81 from the detected data. The calculated unevenness correction amount is stored in the memory 10. By obtaining the correction amount stored in the memory each time and changing the correction amount stored in the memory as needed, it is possible to correct unevenness of the liquid crystal display screen that changes under various circumstances, and display a uniform image. It becomes possible.

  The third invention of the present application is a liquid crystal display panel for displaying a video signal, a backlight capable of changing the luminance and chromaticity of a part of the display screen, and a memory capable of storing a plurality of pieces of information. Luminance detection means for detecting luminance information of an image displayed on the liquid crystal display panel from the input video signal, a correction amount stored in the memory and luminance information obtained from the luminance detection means. In the liquid crystal display device having control means for controlling the backlight, the control means extracts the optimum correction amount stored in the memory in accordance with the luminance information obtained from the luminance information detecting means, and the liquid crystal A liquid crystal display device that adjusts the luminance and chromaticity of a display screen of a display panel.

  The liquid crystal display device of the present invention extracts an appropriate correction amount from the memory 10 based on the luminance detection means 12 for detecting the luminance of the video signal I input to the liquid crystal display device described in the first embodiment and the obtained luminance information. Thus, a control means 13 for controlling the backlight control means 11 is added. For this reason, the description of the unevenness correction method is the same as that described in the first embodiment, and a description thereof will be omitted.

  The unevenness displayed on the liquid crystal screen is various such as unevenness caused by manufacturing a liquid crystal panel and unevenness caused by unevenness of light emission characteristics of lamps and LEDs used for a light source. Among them, some commonly used liquid crystal display panels change the distribution of display screen unevenness depending on the level of a video signal to be displayed. In the case of such a liquid crystal display panel, the unevenness can be corrected by the liquid crystal display device according to the present invention. As a method for this, a correction amount for correcting unevenness that occurs when images of various signal levels are displayed in the memory 10 is stored in advance. Information on the luminance of the input video signal I is detected by the luminance detection circuit 12. Based on the detected luminance information, the control means 13 extracts a backlight correction amount from the memory so that the average luminance of each area becomes the detected luminance. It is possible to control the backlight by this extracted correction amount and display a uniform image. That is, even in the case of a liquid crystal display panel in which the distribution of unevenness changes due to a change in the signal level of the input video signal I, it is possible to perform uniform display on various video signals I.

  The fourth invention of the present application can change the luminance and chromaticity of a part of the display screen, a video conversion means for converting the input video signal, a liquid crystal display panel for displaying the converted video signal Backlight, a memory capable of storing a plurality of pieces of information, luminance detection means for detecting luminance information of an image displayed on the liquid crystal display panel from an input video signal, and stored in the memory In a liquid crystal display device comprising a control means for controlling a backlight control means and a video signal conversion means based on a correction amount and brightness information obtained from the brightness detection means, the control means is obtained from the brightness information detection means. In accordance with brightness information to be extracted, an optimal correction amount stored in the memory is extracted, and the backlight control means and the video signal conversion means are controlled in conjunction with each other, and the liquid crystal display A liquid crystal display device and adjusting the brightness and chromaticity of the display screen of the panel.

The liquid crystal display device of the present invention is obtained by adding video signal conversion means 14 for converting an input video signal to the configuration of the liquid crystal display device described in the third embodiment. Therefore, the same parts as those described in Example 1 or Example 3 in the description of the operation of the liquid crystal display device of the present invention are omitted. The operation of the liquid crystal display device of the present invention will be described with reference to FIG. In the third embodiment, the control means 13 extracts an appropriate correction amount from the memory 10 based on the luminance information obtained by the luminance detection means 12, and controls the backlight based on the correction amount. The control means 13 of the present invention extracts an appropriate correction amount from the memory 10 based on the luminance information obtained by the luminance detection means 12, and the backlight control means 11 and the video signal based on the correction amount and the luminance information. Uniform video display is realized by controlling the conversion means 14 in conjunction with each other. A specific operation will be described with reference to FIG. FIG. 6 shows a portion where a liquid crystal display screen is divided into four areas. As a characteristic peculiar to the liquid crystal display panel, the luminance ratio of each area is (A: B: when the signal level of the video signal a is black display of (r1, g1, b1) = (0%, 0%, 0%). When C: D) = (1: 1.1: 0.9: 1) and the signal level of the video signal c is (r1, g1, b1) = (10%, 10%, 10%) Suppose that the luminance ratio of each area is (A: B: C: D) = (1: 1.1: 1: 0.9). In the liquid crystal display device described in Example 3,
When the video signal a is input, the backlight is controlled so as to decrease the luminance of the area B and increase the luminance of the area A, thereby correcting unevenness. When the video signal b is input, the backlight is controlled so as to decrease the luminance of the area B and increase the luminance of the area D, thereby correcting unevenness. In the liquid crystal display device according to the fourth aspect of the present invention, when the video signal a is inputted, the backlight of the area B is lowered and the luminance of the area A is raised as in the first or third embodiment. Is controlled to correct unevenness, but different control is performed when the video signal b is input. When the video signal b is input, first, the brightness of the backlight of the area B is lowered so as to lower the brightness of the area B, but the gain of the video signal of the area D is raised so that the brightness of the area D is increased in the area D. Control to increase the brightness. Thereby, without increasing the luminance of the backlight of the area D, it is possible to increase the luminance by increasing the gain of the video signal and perform uniform display. Furthermore, normally, in area D, the brightness of the backlight was increased to correct the unevenness, but the image signal was raised without increasing the brightness of the backlight, and the backlight and the video signal were linked to correct the unevenness. By doing so, the backlight power can be reduced.

  The liquid crystal display device according to the present invention is a liquid crystal display device having a backlight capable of changing the luminance and chromaticity of a partial portion of the display screen, and a memory capable of storing a plurality of pieces of information. Regardless of the video signal, the brightness and chromaticity of the partial part of the backlight are changed by the information stored in the memory, and the unevenness of the brightness and chromaticity of the display screen is corrected. LCD screens and LCD monitors that use a liquid crystal display panel with a backlight that can change the brightness and chromaticity. This is useful in liquid crystal display devices.

The figure explaining the circuit operation | movement for correcting the nonuniformity in Example 1 of this invention. The figure explaining the circuit operation for performing the conventional nonuniformity correction The figure explaining the circuit operation | movement for correcting the nonuniformity in Example 2 of this invention. The figure explaining the circuit operation | movement for correcting the nonuniformity in Example 3 of this invention. The figure explaining the circuit operation | movement for correcting the nonuniformity in Example 4 of this invention. Reference diagram for explaining the circuit operation in the fourth embodiment of the present invention

Explanation of symbols

10 Memory 11 Backlight Control Circuit 12 Luminance Detection Circuit 13 CPU
14 Video Signal Conversion Circuit 51 Liquid Crystal Panel 52 Backlight 80 Luminance / Chromaticity Distribution Detector 81 Uneven Feature Detection Circuit

Claims (1)

A liquid crystal display panel for displaying video signals;
A backlight for changing the brightness of each area of the display screen of the liquid crystal display panel;
Luminance detection means for detecting the luminance of the video signal;
Unevenness of the display screen generated by the luminance correction amount and the video signal for correcting the unevenness of the display screen that occurs when displaying the video signal by the luminance ratio between the liquid crystal display panel-specific of each area in the correction amount for correcting the variation of the distribution, and a memory for storing a plurality of correction amount of backlight for correcting the average brightness of each area to the luminance of the video signal,
Control means for extracting a correction amount of the backlight from the memory based on the luminance of the video signal, and controlling the backlight based on the extracted correction amount;
A liquid crystal display device.

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