JP2005070690A - Liquid crystal display - Google Patents

Abstract

In an image in which regions having greatly different luminance levels are mixed, it is difficult to increase the contrast only by dynamic control of a light source.
Light sources 4a to 4d are installed on the back surface of a liquid crystal panel 6, and a feature detection unit 1 receives a video signal, and average luminance levels (5) to 5d corresponding to the light sources 4a to 4d respectively. The light control unit 2 receives the APL and obtains light control data for controlling the light source based on a difference from a predetermined reference luminance level. The light source control unit 3 performs dimming control on the drive currents of the light sources 4a to 4d based on the dimming control data. Thus, by optimally dimming the light source for each image display area, it is possible to display an image with a more contrast feeling and to reduce power consumption.
[Selection] Figure 1

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that individually controls the brightness (light quantity) of a plurality of light sources in accordance with an input video signal.

  As is well known, a device for displaying an image using a liquid crystal panel as a light receiving type light modulating means (hereinafter referred to as a liquid crystal display device) is widely used as an image display device such as a television receiver or a computer device. Since the liquid crystal display device is a non-self-luminous type, in order to make it easy to see an image displayed on the liquid crystal panel, a light source is generally provided to increase the visual brightness of the display screen by irradiating light from the back of the liquid crystal panel.

  Basically, the brightness of the light source is fixedly set to the content manually adjusted by the user. However, in recent years, various methods have been proposed for dynamically adjusting the brightness of a light source (hereinafter referred to as dimming) in accordance with an input video signal that changes as needed in order to make the image easier to see.

  As a conventional method for dimming the brightness of the light source, for example, there is one disclosed in Japanese Patent Laid-Open No. 2001-27889 “Image Display Device and Image Display Method”. The conventional light control method disclosed in this publication will be briefly described below with reference to FIG.

FIG. 4 shows a feature detection unit 1 that detects a feature amount of an input video signal, for example, an average luminance level (hereinafter referred to as APL), and dimming that controls a light source based on a difference between a predetermined reference luminance level and APL. The light control unit 2 includes a light control unit 2 that obtains control data, a light source control unit 3 that controls the light source based on the light control data, a light source 4, and a liquid crystal panel 6. The dimming control unit generates dimming control data for dynamically controlling the driving current of the light source based on the reference dimming control data that maximizes the light emission efficiency of the light source. According to this method, the luminance level of the light source can certainly be changed according to the APL of the input video signal, and the light emission efficiency of the light source can be improved.
JP 2001-27889 A

  By the way, even in a video signal having a certain APL value, there are a case where the gradation is composed only of pixels in the vicinity of the APL and a case where the gradation is composed only of pixels that vary greatly. In the case where only pixels in the vicinity of the APL are formed, the gradation of each pixel is almost the same as that of the APL, so that when the light source is dynamically controlled based on the APL, the image is displayed at an ideal luminance level.

  On the other hand, as shown in FIG. 5, when displaying an image in which the gradation of each pixel greatly varies from the APL and the pixels having similar gradations are displayed together, the light source is dynamically dimmed according to the APL. When controlled, for example, when the light source becomes brighter, the high gradation display pixel (right half of the screen) becomes brighter, so the contrast is improved, but the low gradation display pixel (left half of the screen) also slightly increases. The brightness increases and works in the direction of deteriorating contrast. Therefore, strictly speaking, it is impossible to improve the contrast only by dimming control of the light source. In addition, unlike CRT, even in a low gradation display pixel, the light source side emits light with a constant brightness, so it is difficult to improve and reduce power consumption.

  A first aspect of the present invention is a liquid crystal display device having a plurality of light sources that can be dimmed independently, and a plurality of image display areas corresponding to each of the plurality of light sources on a liquid crystal panel and a video signal are input, Feature detecting means for obtaining feature data corresponding to the feature amount of the video displayed in each of the plurality of image display areas, and a plurality of dimming controls for inputting the feature data and obtaining dimming control data for controlling the corresponding light source And a plurality of light source control means for dynamically adjusting the brightness by driving a corresponding light source according to the light control data.

  A second invention is a liquid crystal display device having a plurality of light sources that can be dimmed and controlled independently, wherein a plurality of image display areas corresponding to each of the plurality of light sources on the liquid crystal panel, video signals are input, and luminance is When the video type is known in advance to have an image display area with almost no level fluctuation, the video type determining means for outputting the video type information and the video type information are input, and the corresponding light source is controlled. A plurality of dimming control means for obtaining the dimming control data to be performed, and a light source control means for driving the corresponding light source according to the dimming control data and dimming and controlling the brightness according to the dimming control data.

  A third invention is an invention subordinate to the first or second invention, wherein the light source includes a fluorescent lamp.

  A fourth invention is an invention dependent on the first or second invention, wherein the light source comprises a light emitting diode.

  As described above, according to the first invention, the display screen is divided into a plurality of image display areas, and the feature amount of the video is obtained for each image display area. The backlight is composed of a plurality of light sources, and performs dimming control of the corresponding light sources in accordance with the feature amount of the video for each image area. As a result, the light source can be optimally dimmed for each image display area, an image display with a higher contrast can be achieved, and power consumption can be reduced.

  As described above, according to the second invention, when the display screen is considered to be divided into a plurality of image display areas and it is known in advance that there is an image display area in which there is almost no change in luminance level, Dimming control is performed on the light source corresponding to the display area. As a result, even if the brightness level of other image display areas varies, it is possible to display an optimal image without being affected, and to reduce power consumption.

  As described above, the third and fourth inventions show light emitting devices used as light sources in the first or second invention.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the liquid crystal display device according to the first embodiment of the present invention. 1, the liquid crystal display device according to the first embodiment of the present invention includes a feature detection unit 1, a dimming control unit 2, a light source control unit 3, light sources 4a, 4b, 4c, and 4d, and a liquid crystal panel. 6.

  Video signals output from a signal processing circuit (not shown) such as a television receiver or a computer device are input to the feature detection unit 1 and the liquid crystal panel 6, respectively. Light sources 4a to 4d equipped with light emitting devices such as fluorescent lamps and light emitting diodes are installed on the back surface of the liquid crystal panel 6 so that the video signals input to the corresponding image display areas 5a to 5d on the liquid crystal panel can be easily viewed. indicate.

  The feature detection unit 1 detects an average luminance level (hereinafter referred to as APL) of an input video signal.

  The dimming control unit 2 inputs the APL detected by the feature detection unit 1 and, based on the difference between the predetermined reference luminance level and the APL, darkens the light source when the APL is larger than the reference luminance level, and when it is smaller Dimming control data for separately controlling the light sources 4a to 4d is obtained so as to brighten the light source.

  The light source control unit 3 dynamically controls the brightness of the light sources 4a to 4d by controlling the value of the drive current i of the light sources 4a to 4d according to the dimming control data output from the dimming control unit 2. To do.

  As described above, according to the liquid crystal display device according to the first embodiment of the present invention, the liquid crystal panel is virtually divided into a plurality of image display areas, and the video APL and the reference luminance level in each image display area. Based on the difference, the dimming control is dynamically performed on a plurality of corresponding light sources. As a result, a constant display luminance can be obtained for each image display area, and the corresponding light source is individually controlled for dimming, so that an image display with higher contrast can be performed and power consumption can be reduced. it can.

  In this embodiment, the dimming control of four light sources has been described. However, as the number of light sources is larger and the area of the image display area corresponding to one light source is smaller, the dimming control can be performed more finely, and thus the contrast feeling. It is considered that power consumption can be reduced.

(Embodiment 2)
FIG. 2 is a block diagram showing a configuration of a liquid crystal display device according to the second embodiment of the present invention. In FIG. 2, the liquid crystal display device according to the second embodiment of the present invention includes a video type determination unit 7, a dimming control unit 2, a light source control unit 3, light sources 4a, 4b, and 4c, and a liquid crystal panel 6. With.

  Video signals output from a signal processing circuit such as a television receiver or a computer device are input to the video type determination unit 7 and the liquid crystal panel 6, respectively. On the back of the liquid crystal panel, light sources 4a to 4c equipped with light emitting devices such as fluorescent lamps and light emitting diodes are installed. The liquid crystal panel easily displays video signals input to the corresponding image display areas 5a to 5c. To do.

  The video type determination unit 7 determines whether or not a black display display area that does not need to be displayed at the top, bottom, left or right at the time of video display is inserted in the input video signal, as shown in FIG. Output insertion range data for the display area. An example where black display areas are inserted above and below the video display section is a signal called letterbox, which is output when movie software is played back and displayed on popular video playback devices. Often done. There is a case where a signal that indicates letterbox display is superimposed on the video signal itself, or a case where a control signal is provided in addition to the video signal.

  The dimming control unit 2 obtains dimming control data for controlling the light sources 4 a to 4 c in accordance with the insertion range data output from the video type determination unit 7.

  The light source control unit 3 controls the value of the drive current i of the light sources 4a to 4c in accordance with the dimming control data output from the dimming control unit 2.

  As described above, according to the liquid crystal display device according to the second embodiment of the present invention, when it is found that the black display areas are inserted above and below or left and right of the video signal, it corresponds to the black display area. Dimming control is performed so as to reduce the drive current i of the light source. Thereby, without affecting the luminance level of the video display area, it is possible to prevent black floating in the black display area, display an image with higher contrast, and reduce power consumption.

  As described above, the liquid crystal display device according to the present invention performs optimal dimming control of the light source for each image display area, and is also applicable to applications that require more contrast-sensitive image display and lower power consumption. it can.

Block diagram illustrating Embodiment 1 of the present invention Block diagram illustrating Embodiment 2 of the present invention The figure which shows the picture where the black indication is inserted in the top and bottom or the right and left of the picture display Block diagram illustrating a conventional liquid crystal display device The figure which shows the image | video pattern from which the luminance level of the pixel varied greatly from APL

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Feature detection part 2 Dimming control part 3 Light source control part 4a, 4b, 4c, 4d Light source 5a, 5b, 5c, 5d Image display area 6 Liquid crystal panel 7 Image | video classification determination part

Claims (4)

A liquid crystal display device having a plurality of light sources capable of independently dimming control, wherein a plurality of image display areas corresponding to each of the plurality of light sources on the liquid crystal panel, and a plurality of image display areas are input. Feature detection means for obtaining feature data corresponding to the feature amount of each displayed video, a plurality of dimming control means for obtaining dimming control data for controlling the corresponding light source based on the feature data, and the dimming control A liquid crystal display device comprising: a plurality of light source control means for driving a corresponding light source in accordance with light control data to dynamically control light intensity. A liquid crystal display device having a plurality of light sources that can be dimmed and controlled independently, wherein a plurality of image display areas corresponding to each of the plurality of light sources on the liquid crystal panel and video signals are input, and there is almost no fluctuation in luminance level When the video type is known in advance as having an image display area, video type determination means for outputting video type information, and dimming control data for inputting the video type information and controlling the corresponding light source A liquid crystal display device comprising: a plurality of dimming control units to be obtained; and a light source control unit that drives a corresponding light source according to the dimming control data and performs dimming control of brightness according to the dimming control data. The liquid crystal display device according to claim 1, wherein the light source includes a fluorescent lamp. The liquid crystal display device according to claim 1, wherein the light source includes a light emitting diode.

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