JP2008090076A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which is capable of controlling brightness and tint in a partial region of an image, has a high response speed and can suppress electric current consumption. <P>SOLUTION: An image dividing circuit 18 divides an image signal into blocks 32 by using a timing pulse which divides a vertical image period into (n) pieces and a horizontal image period into (m) pieces in accordance with the size of LED unit 31 of RGB. An image analyzing circuit 19 analyzes the image into respective blocks 32. A microcomputer 21 determines brightness of each LED as a backlight 25 based on the image signal of the image dividing circuit 18 and the result analyzed by the image analyzing circuit 19. Based on the determined brightness, a control signal is outputted to an LED driving control circuit 22 and, based on the control signal, the LED driving control circuit 22 drives each LED unit 31 of forming the backlight 25 via LED drive circuits 23, 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device that improves the image quality (contrast, color reproduction range) and reduces power consumption by controlling the backlight luminance of a liquid crystal panel.

  In recent years, television receivers using a liquid crystal panel, computer monitors, and the like have become widespread. In such a liquid crystal display device, since the liquid crystal itself does not emit light, a backlight such as a cold cathode tube, LED, EL or the like is disposed behind the liquid crystal panel, and high luminance display is achieved by the irradiation light.

  In general, the screen contrast of the liquid crystal display device and the brightness of the backlight can be adjusted by the operator to make the screen easier to see. However, it may be difficult to see the screen contrast and brightness adjusted by the content received by a television receiver or the like. For example, in the case of a daytime outdoor video, the entire display screen becomes too bright, and in the case of a night view video, the entire display screen becomes too dark. In addition, some images may be too bright or too dark.

  Therefore, there is a technique disclosed in Patent Document 1 as a technique that can improve these and display an easily viewable video. As shown in FIG. 9, the liquid crystal panel 100 is divided into two regions in the horizontal direction and two regions in the vertical direction, and one fluorescent tube 101, 102, 103, 104 is arranged in each of the divided regions. To do. These fluorescent tubes are arranged at the edge of each region by an edge light method, and guide light to each region by a light guide plate.

  This liquid crystal display device divides the video signal into 2 × 2 horizontally and vertically, detects the average DC voltage level of the average luminance in the video signal of each video region, and sends the detection result to the signal processing circuit 106. input. Depending on the detection result and the correlation between the video areas, the signal processing circuit 106 reduces the overall gain when the average luminance is high so that a white-side gradation can be produced, and the average luminance is low. Performs an operation to increase the overall gain so that a black gradation is produced, and outputs a control signal to the inverter control circuit 105. The inverter control circuit 105 controls the duty ratio of the inverters of the fluorescent tubes 101, 102, 103, and 104 to adjust the brightness. In this example, the video signal is divided into 2 × 2 areas, but it is also possible to divide it into m × n and arrange fluorescent tubes in the respective video display areas.

In this way, the brightness can be controlled for each of the divided areas while taking into account the correlation of the entire screen, so that an image with a sense of contrast can be generated.
JP 2000-321571 A

  However, in the invention of Patent Document 1, it is not possible to control the hue by simply controlling the brightness. For example, in a certain part, it is not possible to generate an image with a more contrast feeling by making the hues of white, red, etc. vivid as well as the brightness of the brightness.

  A device using a cold cathode tube backlight is always lit regardless of the image. Since it is lit even when no luminance is required, there are problems such as black level floating and increased power consumption. Even if the brightness is changed by controlling the cold-cathode tube backlight, there is a limit to reducing the size of a single cold-cathode tube, and since the response speed is slow, Does not provide the desired effect.

  In view of such circumstances, the present invention is intended to provide a liquid crystal display device that can control luminance and hue in a partial region of an image, has a high response speed, and can suppress current consumption.

  The present invention relates to a liquid crystal display device having a liquid crystal panel for displaying an input video signal and a backlight in which RGB backlight member units are arranged vertically and horizontally, and the video signal has the same size as the RGB backlight member unit. Video dividing means for dividing the block into corresponding blocks, video analyzing means for analyzing the luminance and RGB component video data of the block, and a backlight for setting the luminance correction amount of the RGB backlight member based on the analyzed video data result And a light control means.

Further, the video analysis means obtains each difference of the analyzed RGB components,
The backlight control means increases the luminance of the larger RGB backlight when one or two of the RGB component differences exceed a predetermined value.

The video analysis means analyzes the video signal of the inner peripheral portion of the block, and analyzes the video signal of the video area of the inner peripheral portion of the adjacent block adjacent to the inner peripheral portion,
The backlight control means includes a difference between the luminance correction amount of the RGB backlight member in the target block and the luminance correction amount of the RGB backlight member in the adjacent block, the peripheral video data of the target block, and the peripheral video data of the adjacent block. Further, when the absolute value of the difference between the correction amount difference and the difference between the peripheral video data exceeds a predetermined value, the correction for reducing the difference in luminance correction amount between the target block and the backlight member of the adjacent block It is characterized by performing.

When the absolute value of the difference between the correction amount difference and the difference between the peripheral video data exceeds a predetermined value, the backlight control means determines that the correction amount based on the peripheral region is the correction amount of the target block− (correction of the target block). Amount−correction amount of adjacent block) × z%, and the luminance correction amount of the backlight member is an average of the correction amounts obtained for each peripheral region.
In addition, it is preferable that the said backlight member is LED.

  According to the present invention, the luminance data of the block and the RGB component video data are analyzed, and the luminance correction amount of the RGB backlight member is set based on the result, so that the bright image is brighter and darker. The darker and more vivid colors are displayed more vividly, and a high-contrast image can be obtained. In addition, when multiple screens such as two screens are used, each screen can be provided with an optimum backlight that is not affected by other screens and that matches the video on each screen.

  Further, the difference between the luminance correction amount of the RGB backlight member in the target block and the luminance correction amount of the RGB backlight member in the adjacent block, and the difference between the peripheral video data of the target block and the peripheral video data of the adjacent block are calculated. In addition, when an absolute value of the difference between the correction amount difference and the difference between the peripheral video data exceeds a predetermined value, if one object image is displayed across a plurality of blocks, a difference in luminance between the blocks is displayed. Is adjusted so as not to increase. Therefore, it is possible to display an image that does not feel strange when viewed from the viewer.

  Moreover, since the backlight member is an LED, it is not necessary to turn on a portion that is lit unnecessarily in a dark image such as a sidebar when a 4: 3 image is displayed, thereby reducing power consumption. Become. In addition, since the range in which the LED brightness can be controlled can be reduced compared to a fluorescent tube, the brightness can be finely adjusted. For example, even in a multi-screen display, each screen is not affected by other screens. Optimal backlight adjustment is possible according to the screen image.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an example of a television receiver which is a liquid crystal display device according to the present invention. FIG. 2 is a schematic diagram showing the relationship between the LEDs arranged behind the liquid crystal panel and the video area of the liquid crystal panel.

  The liquid crystal display device 10 includes A / D converters 11 and 12, a video processing circuit 13, a first memory 14, a liquid crystal drive control circuit 15, a liquid crystal drive circuit 16, a liquid crystal panel 17, and a video dividing circuit 18. A video analysis circuit 19, a second memory 20, a microcomputer (abbreviation for microcomputer) 21, an LED drive control circuit 22, LED drive circuits 23 and 24, and a backlight 25.

  In the liquid crystal display device 10, as shown in FIG. 2, the backlight 25 is disposed behind the liquid crystal panel 17. The backlight 25 includes an LED unit 31 in which three LEDs, which are RGB backlight members, are arranged in a horizontal row. The LED units 31 are arranged in the vertical direction and m in the horizontal direction and n in the horizontal direction behind the liquid crystal panel 17. Is done. An image displayed on the liquid crystal panel 17 is divided into a vertical m × horizontal n region, and a block 32 as the video region corresponds to the RGB LED unit 31.

Next, an outline of the operation of the liquid crystal display device 10 will be described.
The received video data of the television broadcast is input to the A / D converter 11, and the A / D converter 11 converts the analog signal into a digital signal. In addition, when performing the two-screen display simultaneously displaying another channel video, the A / D converter 12 is further provided, and the A / D converter 12 converts the analog signal of the video data of the television broadcast of the other channel into a digital signal. To do. The video processing circuit 13 temporarily stores the digital signal in the first memory 14, reads out the digital video signal from the first memory 14, performs video processing for display on the liquid crystal panel 17, and sends it to the liquid crystal drive control circuit 15. send. The liquid crystal drive control circuit 15 displays the video on the liquid crystal panel 17 by controlling the liquid crystal drive circuit 16 based on the video signal from the video processing circuit 13.

  Further, the video processing circuit 13 sends the generated video signal to the video dividing circuit 18. As shown in FIG. 2, the video dividing circuit 18 converts the video signal into a block 32 by timing pulses that divide the vertical video period into n and the horizontal video period into m according to the size of the RGB LED unit 31. To divide. The video analysis circuit 19 temporarily stores the divided video signal in the second memory 20 and analyzes the image for each block 32. The average of the luminance of the video signal and the level of the RGB component is obtained and simultaneously compared between the blocks. The analysis result is stored in the second memory 20.

  The microcomputer 21 serving as the control unit obtains the luminance correction amount of each LED that is the backlight 25 based on the video signal of the video dividing circuit 18 and the analysis result of the video analysis circuit 19. Based on this, a control signal is issued to the LED drive control circuit 22, and based on this control signal, the LED drive control circuit 22 sends the individual LED units 31 forming the backlight 25 via the LED drive circuits 23 and 24. To drive.

  The contents analyzed by the video analysis circuit 19 are the average luminance for each block 32 and the average level of the RGB components. Furthermore, the difference between the video data of the inner periphery of the target block and the inner periphery of the adjacent block is compared with the difference between the correction amount of the target block and the correction amount of the adjacent block. Correction is performed to correct the LED brightness so that the connection between the blocks does not become unnatural.

  Now, as an example of the LED luminance correction algorithm of the microcomputer 21, the LED correction range is limited (for example, correction is made in the range of 60 to 100%). That is, since the LED is a backlight, it always emits light with a basic light emission amount. In the present embodiment, the brightness is increased by adding a correction amount to the basic light emission amount to obtain a high-contrast image. Therefore, if the maximum luminance of the LED is 100% and the basic light emission amount (minimum luminance) is 60%, the remaining 40% is adjusted as the correction amount. The luminance correction of the LED is performed within the range of the correction amount according to the respective levels of the RGB LEDs.

The following conversion formulas are established between the luminance Y and RGB components E _R , E _G , E _R.
Y = 0.299 × E _R + 0.587 × E _G + 0.114 × E _R
Accordingly, the luminance correction of the LED also obtains a desired luminance by setting each luminance of the RGB-LED based on the above conversion formula.

FIG. 3 is a flowchart showing a procedure for correcting the luminance of the LED unit 31, and FIG. 4 is a flowchart of a subroutine in step S6.
As shown in FIG. 2, for the (xn, ym) block 32 divided by the video dividing circuit 18, the video analyzing circuit 19 obtains the average of the luminance and RGB component levels of each block from the video signal (step S1). . Based on the analysis result of the (xn, ym) block 32, the microcomputer 21 provisionally sets the LED correction amount (light emission amount added to the basic light emission amount) for each RGB (step S2). This is provided with a data table in which analysis values and LED correction amounts are associated with each other, and each RGB-LED correction amount is set based on this table.

  Next, as shown in FIG. 5, the video analysis circuit 19 obtains the average of the luminance and the RGB component levels of the video signal around the four sides of the (xn, ym) block 32 (step S3). For example, the average of the luminance and RGB levels of the surrounding areas 1, 2, 3, and 4 in the four sides of the block 32 shown in FIG. Here, the surrounding area of the block 32 is about 25% at the maximum with respect to the area of the whole block.

  Then, as shown in FIG. 5, the video analysis circuit 19 includes video data (luminance, RGB component levels) in the peripheral area in the (xn, ym) block 32 and blocks 32-1, 32-2, The difference between the video data (luminance, RGB component levels) in the peripheral areas in 32-3 and 32-4 is obtained (step S4). For example, in FIG. 5, the peripheral region 3 of the block 32-1 for the peripheral region 1 of the block 32, the peripheral region 4 of the block 32-2 for the peripheral region 2 of the block 32, and the peripheral region 3 of the block 32. The difference between the peripheral region 1 of the block 32-3 and the peripheral region 2 of the block 32-4 with respect to the peripheral region 4 of the block 32 are obtained.

  The microcomputer 21 calculates the difference between the correction amount of the LED of the LED unit 31 corresponding to the (xn, ym) block 32 and the correction amount of the LED of the blocks 32-1, 32-2, 32-3, and 32-4 adjacent thereto. Obtained (step S5).

  Next, when the image is vivid in the primary color, RGB correction of the LED is performed so that the primary color looks more vivid (step S6). Detailed processing contents of step S6 will be described below.

  In step S21, the video analysis circuit 19 obtains a difference between the RGB level values of the video signal in each block. That is, RG, GB, and BR are obtained. If there is one or two of the three differences whose absolute value of the difference exceeds the predetermined value E (positive number) (step S22), this corresponds to the larger RGB level exceeding E. The luminance correction amount of the RGB LED is added by α (step S23).

"
If the absolute value of the RGB difference exceeds the predetermined value E (positive number) is 0 or 3, no processing is performed and the process proceeds to step S7.

A specific example of LED luminance correction will be described.
FIG. 6 is a diagram showing an image to be processed. 7A is a diagram showing an image on a liquid crystal panel, and FIG. 7B is a diagram showing luminance of RGB-LEDs.

  In FIG. 6, 51 is a yellow sun, 52 is a white cloud, 53 is a red balloon, 54 is a blue sky, and 55 is a green mountain. In particular, the mountain 55 becomes greener as it goes to the right, and the lower right end 56 is darkest and darkest.

  As shown in FIG. 7A, the video displayed on the liquid crystal panel 17 is divided into blocks by the video dividing circuit 18, and the LED unit corresponding to this block is turned on as shown in FIG. 7B. Is done. The video analysis circuit 19 performs video analysis for each video block 32. Based on this, the microcomputer 21 enhances the brightness of the sun 51, the cloud 52, and the balloon 53 so that the LED unit 55 is yellow, the LED unit 58 is red, and the LED units 56 and 57 are white. Further, the dark green portion 56 of the mountain has a lower brightness as it goes to the right side and the lower side of the LED units 59, 60, 61, 62, but the brighter portion is more emphasized. In particular, a portion where the luminance is low is perceived to be lower than the actual luminance by the viewer.

Next, in step S7, the microcomputer 21
If the absolute value of [(difference in LED correction amount between target block and adjacent block) − (difference in video data between peripheral area of target block and peripheral area of adjacent block)] exceeds positive predetermined value D, step The process proceeds to S8, and if it is equal to or less than the positive predetermined value D, the process proceeds to Step 9.

  When the color and brightness of the target block and the adjacent block are completely different, or when the color and brightness are almost the same, the difference between the LED correction amount difference of the adjacent block and the video data difference of the surrounding area The absolute value of does not exceed the positive predetermined value D. On the other hand, when there is an image that covers a part of a block adjacent to the target block, the difference in the LED correction amount between the adjacent blocks and the difference in the video data in the surrounding area may become large. In this case, the fact that the brightness of the LED greatly differs from the adjacent block gives an unnatural feeling to the viewer, and thus correction is performed.

In step S8, the LED correction amounts C1 to C4 set by paying attention to the peripheral area 1 of the target block and the peripheral area of the block adjacent thereto are set as in the following formula.
C1 to C4 = target block correction amount− (target block correction amount−adjacent block correction amount) × z%

In step S9, the LED correction amount C1 remains the set luminance value A.
The average of C1 to C4 thus obtained is defined as C as the LED luminance value. This luminance value is obtained for RGB (step S10).

  For example, as shown in FIG. 8A, the target block is 32b, and there is an adjacent block 32a next to it. A cloud image 35 is displayed on the target block 32b and a part of the target block 32a. If it is the brightness | luminance of normal backlight, as shown in FIG.8 (b), the LED unit 31a will become darker than the LED unit 31b. However, since the cloud exists in a part of the target block 32b and the target block 32a, if the luminance of the LED is too different between the block 32b and the block 32a, the viewer will feel a sense of discomfort in the cloud image. Therefore, the above process is performed to reduce the luminance difference between the blocks 31a and 31b by reducing the luminance of the LED unit 31c, thereby alleviating the uncomfortable feeling of the image.

  Even in the case of a multi-screen display such as a two-screen display, the range in which the brightness of the LED can be controlled can be made smaller than that of a fluorescent tube, so that each screen is not affected by other screens. The optimal backlight adjustment is possible according to the video.

It is a block diagram which shows an example of the television receiver which is a liquid crystal display device which concerns on this invention. It is the schematic which shows the relationship between LED arrange | positioned behind a liquid crystal panel, and the video area | region of a liquid crystal panel. 6 is a flowchart showing a procedure for correcting the luminance of the LED unit 31. It is a flowchart of the subroutine in step S6. It is an external view of the surrounding area of an object block, and the block adjacent to it. It is a figure which shows the image | video which should be processed. (A) is a figure which shows the image | video of a liquid crystal panel, (b) is a figure which shows the brightness | luminance of RGB-LED. It is explanatory drawing which shows the brightness correction of a target block and an adjacent block. It is a block diagram which shows an example of the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 and 12 A / D converter 13 Image processing circuit 14 1st memory 15 Liquid crystal drive control circuit 16 Liquid crystal drive circuit 17 Liquid crystal panel 18 Image dividing circuit 19 Image analysis circuit 20 Second memory 21 Microcomputer 22 Drive control circuit 23 , 24 Drive circuit 25 Backlight 31 LED unit 32 Video block

Claims (5)

A liquid crystal display device having a liquid crystal panel for displaying an input video signal and a backlight in which RGB backlight member units are arranged vertically and horizontally,
Video dividing means for dividing the video signal into blocks corresponding to the sizes of the RGB backlight member units;
Video analysis means for analyzing video data of luminance and RGB components of the block;
A liquid crystal display device comprising: backlight control means for setting luminance correction amounts of RGB backlight members based on the analyzed video data results. The video analysis means obtains each difference of the analyzed RGB components,
2. The liquid crystal display according to claim 1, wherein the backlight control unit increases the luminance of the larger RGB backlight when one or two of the differences between the RGB components exceed a predetermined value. apparatus. The video analysis means analyzes the video signal of the inner peripheral part of the block, and analyzes the video signal of the video area of the inner peripheral part of the adjacent block adjacent to the inner peripheral part,
The backlight control means includes a difference between the luminance correction amount of the RGB backlight member in the target block and the luminance correction amount of the RGB backlight member in the adjacent block, the peripheral video data of the target block, and the peripheral video data of the adjacent block. When the absolute value of the difference between the correction amount difference and the difference between the peripheral video data exceeds a predetermined value, the difference in luminance correction amount between the target block and the backlight member of the adjacent block is reduced. The liquid crystal display device according to claim 1, wherein correction is performed.   When the absolute value of the difference between the correction amount difference and the difference between the peripheral video data exceeds a predetermined value, the backlight control means determines that the correction amount based on the peripheral region is the correction amount of the target block− (correction of the target block). 4. The liquid crystal display according to claim 3, wherein the luminance correction amount of the backlight member is an average of the correction amounts obtained for each peripheral region. apparatus.   The liquid crystal display device according to claim 1, wherein the backlight member is an LED.