JP2011242690A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of saving power as much as possible while suppressing uneven luminance on the entire screen in a configuration that luminance of each light source mounted on a backlight device is gradually decreased from the center portion to the outer periphery.SOLUTION: Luminance of each light source is inclined to gradually decrease from the center portion of a liquid crystal panel to the outer periphery when the liquid crystal panel is illuminated from the back by a plurality of the light sources arranged in the vertical direction and/or the horizontal direction of the liquid crystal panel. The luminance of each light source is controlled so that luminance inclination becomes smaller when an amount of change in one frame of a displayed image on the liquid crystal panel is small (refer to FIG.3B) and the luminance inclination becomes larger when the amount of change is large (refer to FIG.3C).

Description

  The present invention relates to a liquid crystal display device having a backlight device that illuminates the liquid crystal panel from behind by a plurality of light sources arranged in a vertical direction or a horizontal direction on the back side of the liquid crystal panel, and in particular, tilts the luminance of each of the light sources. The present invention relates to a liquid crystal display device.

Liquid crystal display devices such as liquid crystal television receivers and liquid crystal monitor devices include a backlight device that illuminates a liquid crystal panel from behind. This backlight device has a plurality of light sources arranged in a vertical direction or a horizontal direction of a liquid crystal panel. A cold cathode tube or LED is used as the light source.
Conventionally, in a liquid crystal display device, it has been proposed to incline the luminance of each light source of the backlight device so as to gradually decrease from the central portion of the liquid crystal panel toward the outer periphery (see, for example, Patent Document 1).
By the way, since power saving performance is becoming important in recent liquid crystal display devices, it is desirable to reduce power consumption of a backlight device that occupies most of the power consumption in the liquid crystal display device. Here, as described above, the luminance of each light source of the backlight device is gradually decreased from the central portion toward the outer periphery, thereby reducing power consumption compared to the case where the entire device emits light with the same luminance as the central portion. can do. And the greater the slope at which the brightness of each light source is reduced, the smaller the power consumption of the light source near the outer periphery, so the power saving effect is enhanced.

JP-A-6-75216

However, when the slope of the brightness of each light source increases in the backlight device, the difference in brightness between the light sources is recognized by the user as brightness unevenness, and the display quality may deteriorate. In particular, when the amount of change in one frame of the display image on the liquid crystal panel is large, it is difficult to understand the difference in luminance of the light source, but the amount of change in the overall gradation is small like the solid image of the one frame. If it is, the luminance unevenness due to the difference in the luminance of the light source becomes conspicuous, and the display quality deteriorates.
Therefore, the present invention has been made in view of the above circumstances, and the object of the present invention is to reduce power consumption as much as possible while suppressing luminance unevenness of the entire screen in a configuration in which the luminance of each light source of the backlight device is inclined. An object is to provide a liquid crystal display device that can be realized.

In order to achieve the above object, the present invention provides a backlight device that illuminates a liquid crystal panel from behind by a plurality of light sources arranged in a vertical direction or a horizontal direction of the liquid crystal panel, and a luminance gradient that inclines the luminance of each of the light sources. And the brightness tilting means controls the brightness tilt of each of the light sources in accordance with the feature quantity of the display image on the liquid crystal panel. It is characterized by being. Here, the brightness tilting means controls the brightness tilt of each of the light sources so as to gradually decrease from the central part of the liquid crystal panel toward the outer periphery, for example.
As a result, the magnitude of the luminance gradient of each of the light sources can be adjusted in accordance with the feature quantity of the display image on the liquid crystal panel, so that power saving can be achieved within a range where luminance unevenness in the display image can be prevented. Can be achieved.
For example, the feature amount may be a change amount in one frame of the display image of the liquid crystal panel. The brightness tilting means increases the brightness tilt of each of the light sources such that the smaller the change amount in one frame of the display image of the liquid crystal panel, the smaller the tilt, and the greater the change amount, the greater the tilt. It is conceivable that it controls the thickness. As a result, when the amount of change in one frame is large and luminance unevenness is difficult to see, the inclination can be increased to increase the power saving effect, and the amount of change in one frame of the display image of the liquid crystal panel is small and luminance unevenness is small. When is conspicuous, the inclination can be reduced to prevent uneven brightness.
Specifically, a histogram indicating the frequency distribution (color distribution, etc.) of the video signal for each frame of the video displayed on the whole or a part of the liquid crystal panel is acquired, and the liquid crystal panel is obtained based on the histogram. It is conceivable to determine the amount of change in one frame of the displayed video. In particular, a histogram is obtained for the whole and part of the liquid crystal panel, and a change amount in one frame of the display image of the liquid crystal panel is determined based on the histogram of the whole and part of the liquid crystal panel. Is desirable.
As a more specific configuration of the present invention, it further comprises filter storage means for storing a plurality of preset brightness gradient filters for changing the brightness of each light source at different slopes, and the brightness slope means The brightness gradient filter stored in the filter storage means is selected in accordance with the amount of change in one frame of the display image of the liquid crystal panel, and the brightness of each of the light sources is changed using the brightness gradient filter. It is possible that
Further, the backlight device has a plurality of LEDs arranged in a matrix behind the liquid crystal panel, and the brightness tilting means tilts the brightness of each of the LEDs in the vertical direction and the horizontal direction. It can be considered a thing. Thereby, since the brightness | luminance of LED can be made low as it leaves | separates from the center part of the said backlight apparatus to the left-right direction or an up-down direction, the high power saving effect can be acquired.
In the backlight device, since adjacent light sources supplement each other in luminance, when the luminance of the light sources around the central portion of the liquid crystal panel is reduced, the display luminance in the central portion is reduced. Therefore, the brightness tilting means has a reduction amount of the brightness of the light source corresponding to a position around the center portion so as to keep the brightness of the center portion of the liquid crystal panel constant before and after the brightness tilt of each light source. It is desirable to control the luminance of each of the light sources so that the luminance of the light source corresponding to the central portion increases as the value increases. Thereby, the luminance of the backlight device can be inclined while maintaining the luminance of the central portion constant.

  According to the present invention, since the magnitude of the luminance gradient of each of the light sources can be adjusted according to the feature amount of the display image on the liquid crystal panel, the luminance unevenness in the display image can be prevented. It is possible to save power. In particular, the brightness of each of the light sources is controlled such that the greater the amount of decrease in the brightness of the light source corresponding to the position around the center of the liquid crystal panel, the higher the brightness of the light source corresponding to the center. It is desirable to be. Thereby, the luminance of the backlight device can be inclined while maintaining the luminance of the central portion constant.

1 is a block diagram showing a main part configuration of a liquid crystal display device according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating an example of a backlight device provided in the liquid crystal display device according to the embodiment of the present invention. The schematic diagram which shows an example of the inclination of the display luminance of the liquid crystal panel by the backlight apparatus provided in the liquid crystal display device which concerns on embodiment of this invention. 6 is a flowchart for explaining an example of a procedure of backlight control processing executed in the liquid crystal display device according to the embodiment of the present invention. The figure for demonstrating an example of the histogram utilized by the backlight control process performed with the liquid crystal display device which concerns on embodiment of this invention. The figure for demonstrating an example of the histogram utilized by the backlight control process performed with the liquid crystal display device which concerns on an Example. The figure for demonstrating an example of the histogram utilized by the backlight control process performed with the liquid crystal display device which concerns on an Example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
As shown in FIG. 1, a liquid crystal display device X according to an embodiment of the present invention includes a display control unit 11, a liquid crystal panel 21, a liquid crystal drive unit 22, a backlight device 31, a backlight control unit 32, and the like. Yes.
The liquid crystal display device X is, for example, a liquid crystal television receiver or a liquid crystal monitor device. In the present embodiment, description of other components that do not directly affect the present invention included in a general liquid crystal television receiver or liquid crystal monitor device is omitted.

The display control unit 11 includes control devices such as an MPU, a RAM, and a ROM, and the MPU executes processing according to a predetermined control program stored in the ROM, whereby the liquid crystal driving unit 22 and the A control instruction is given to the backlight control unit 32 to control the operation of the liquid crystal panel 21 and the backlight device 31.
Specifically, the display control unit 11 receives a video signal included in a television broadcast received by an antenna (not shown) or a video content input from an external input terminal (not shown), and the video signal is converted into the video signal. Based on this, a vertical synchronizing signal, a horizontal synchronizing signal, etc. are generated. The display control unit 11 inputs the video signal, the vertical synchronization signal, and the horizontal synchronization signal to the liquid crystal driving unit 22.
Here, the display control unit 11 generates a vertical synchronizing signal having a driving frequency of 120 Hz, which is a double speed of 60 Hz, which is a frequency of a video signal of television broadcasting. Therefore, the display control unit 11 outputs one frame image in the video signal to the liquid crystal drive unit 22 twice, or generates an interpolated image from two consecutive frames in the video signal, Inserted and output to the liquid crystal drive unit 22.

The display control unit 11 calculates a luminance histogram by counting the number of pixels for each luminance level based on the input video signal, and determines the luminance of the video signal and the backlight device 31 based on the luminance histogram. adjust.
Specifically, the display control unit 11 reduces the luminous intensity of the backlight device 31 as much as possible within a range in which display luminance necessary for displaying an image based on a video signal on the liquid crystal panel 21 can be realized. The brightness signal corresponding to each LED 31a (described later) provided in the backlight device 31 is adjusted. As a result, the light intensity of the backlight device 31 is reduced as much as possible, so that power saving is achieved.
The display control unit 11 corrects the video signal based on the light intensity of the backlight device 31. That is, the display control unit 11 corrects the gradation signal of the video signal so as to have a higher value than the original video signal when the luminous intensity of the backlight device 31 is lowered.
Thereby, the light intensity of the backlight device 31 becomes as low as possible, and the power consumption in the backlight device 31 can be reduced as much as possible.

The liquid crystal panel 21 is formed of a liquid crystal layer, a scan electrode and a data electrode for applying a scan signal and a data signal to the liquid crystal layer, and includes a plurality of liquid crystal elements whose transmittance varies depending on an applied voltage. This is an active matrix type liquid crystal panel.
The liquid crystal driving unit 22 sets the scan electrode (gate electrode) and the data electrode (source electrode) of the liquid crystal panel 21 based on the video signal, the vertical synchronization signal, and the horizontal synchronization signal input from the display control unit 11. Drive. Specifically, after receiving the vertical synchronizing signal, the liquid crystal driving unit 22 outputs a gate signal to the scanning electrode in accordance with the horizontal synchronizing signal corresponding to the first line and also outputs the video signal corresponding to the first line as data. Output sequentially to the electrodes. As a result, the first line image is displayed. Thereafter, when the horizontal synchronizing signal corresponding to the second line is input, the liquid crystal driving unit 22 outputs a gate signal to the scanning electrode of the second line and sequentially applies the video signal corresponding to the second line to the data electrode. Output. Thereafter, the same processing is repeated to display an image on the full screen of the liquid crystal panel 21.

The backlight device 31 illuminates the liquid crystal panel 21 from behind by a plurality of light sources arranged on the back side of the liquid crystal panel 21. FIG. 2 is a schematic diagram showing an example of the structure of the backlight device 31. As shown in FIG.
As shown in FIG. 2, the backlight device 31 has a plurality of LEDs 31 a arranged in a matrix in the vertical direction and the horizontal direction behind the liquid crystal panel 21.
The backlight control unit 32 blinks each LED 31a of the backlight device 31 individually according to the luminance signal input from the display control unit 11. At this time, the light emission luminance of the LED 31a varies depending on the supply power determined by the duty ratio of the luminance signal. Of course, the LED 31a may be grouped every predetermined number, and the LED 31a may be blinked for each group. The number of the LEDs 31 a is not limited to that shown in FIG. 2, and the design may be appropriately changed according to the size of the liquid crystal panel 21.

By the way, also in the backlight device 31, as described above, it is possible to save power by inclining the brightness of each of the LEDs 31 a so as to gradually decrease from the central portion toward the outer periphery. For example, the backlight control unit 32 applies a luminance gradient filter that is set in advance so that the attenuation rate increases from the central portion toward the outer periphery with respect to the luminance signal of each of the LEDs 31a. Can be inclined.
However, when the luminance is inclined in the backlight device 31, the inclination is large, and the amount of change in one frame (an example of the characteristic amount of the display image) is such that the display image on the liquid crystal panel 21 is a solid image. If it is small, the gradient of the luminance is conspicuous, resulting in luminance unevenness and being easily recognized by the user, and the display quality deteriorates. On the other hand, when the luminance gradient of the backlight device 31 is small, or when the amount of change in one frame of the display image on the liquid crystal panel 21 is large, the luminance gradient is less noticeable. It is difficult to recognize and the deterioration of display quality can be suppressed.

Therefore, the display control unit 11 executes a backlight control process (see FIG. 4), which will be described later, so that the luminance of each LED 31a of the backlight device 31 gradually decreases from the central part toward the outer periphery. In addition to tilting, the degree of brightness tilt is changed according to the display image of the liquid crystal panel 21. Specifically, the display control unit 11 determines the brightness of each of the LEDs 31a so that the smaller the change amount in one frame of the display image of the liquid crystal panel 21, the smaller the inclination, and the larger the change amount, the larger the inclination. To control. Here, the display control unit 11 when executing such processing corresponds to the luminance tilting means.
In the present embodiment, as a method for changing the degree of luminance gradient in the backlight device 31, the backlight control unit 32 uses the luminance signal duty ratio of each LED 31a of the backlight device 31 as the luminance gradient. An example will be described in which a change is made using any one of the luminance gradient filters F1 and F2 having different degrees of. The luminance gradient filters F1 and F2 are stored in advance in a storage memory (an example of a filter storage unit) provided in the backlight control unit 32, the display control unit 11, and the like. Of course, a larger number of luminance gradient filters may be stored and the luminance gradient filters may be selectively used. In addition, inclining the brightness of each of the LEDs 31a by a predetermined arithmetic expression can be considered as another embodiment.

3B and 3C, the display brightness of the liquid crystal panel 21 when the brightness gradient filters F1 and F2 are not applied as shown in FIG. When the luminance gradient filter F1 is applied, the display luminance gradient result of the liquid crystal panel 21 when the luminance gradient filter F2 is applied is shown. FIG. 3 schematically shows the display brightness of the liquid crystal panel 21 divided into regions H1 to H9 at predetermined intervals in the horizontal direction and regions V1 to V5 at predetermined intervals in the vertical direction. .
As shown in FIG. 3B, the luminance gradient filter F1 has a luminance of a part of the central portion of the display image of the liquid crystal panel 21 being 100 (%), but the luminance of the outer peripheral portion is vertical and The duty ratio of the luminance signal corresponding to each of the LEDs 31a is inclined so that the luminance gradually decreases toward the four corners in the horizontal direction, and the luminance decreases to about 93 (%) at the ends of the four corners.
In addition, as shown in FIG. 3C, the luminance gradient filter F2 has a partial luminance of 100 (%) in the central portion of the display image of the liquid crystal panel 21, but the luminance of the outer peripheral portion thereof. The luminance signal corresponding to each of the LEDs 31a gradually decreases toward the four corners in the vertical direction and the horizontal direction at a gradient larger than that of the luminance gradient filter F1 and decreases to about 78 (%) at the ends of the four corners. The duty ratio is inclined.
However, in general, in the backlight device 31, which is a so-called direct type LED backlight having a large number of LEDs 31 a, the display brightness of the liquid crystal panel 21 is increased by mutually supplementing the brightness of the adjacent LEDs 31 a (brightness assist). Determined. Therefore, when the luminance gradient filters F1 and F2 are used to incline the luminance of each of the LEDs 31a, if only the luminance around the central portion is reduced, the luminance at the central portion is also lowered accordingly. Therefore, the brightness gradient filters F1 and F2 have the brightness of the LED 31a corresponding to the position around the center portion so as to maintain the display brightness of the center portion of the liquid crystal panel 21 constant (for example, 100 (%)). The duty ratio of the luminance signal corresponding to each LED 31a is set in advance so that the luminance of the LED 31a corresponding to the position of the central portion increases as the amount of decrease increases.

Hereinafter, an example of the procedure of the backlight control process executed by the display control unit 11 will be described with reference to the flowchart of FIG. 4, S1, S2,... Represent processing procedure (step) numbers.
The backlight control process is executed as needed by the display control unit 11 when video is displayed on the liquid crystal panel 21 in the liquid crystal display device X. In addition, a configuration in which the display control unit 11 can switch the execution / non-execution of the backlight control processing (presence / absence of luminance tilt) according to a remote control operation by the user is also considered as another embodiment.

<Step S1>
First, in step S1, the display control unit 11 acquires a histogram (color histogram or the like) that is a frequency distribution of video signals in one frame of video displayed on the entire liquid crystal panel 21. For example, the histogram shows the number of pixels for each gradation (color) component within a predetermined range in one frame. Specifically, when the gradation of each pixel is expressed by 256 gradations, it is conceivable to count the number of pixels every 16 gradations or every 32 gradations. Here, the display control unit 11 when executing such processing corresponds to a histogram acquisition means.
Here, FIG. 5A shows an example of a histogram when the change amount of one frame of the display image is small, and FIG. 5B shows an example of a histogram when the change amount of one frame of the display image is large.
As shown in FIG. 5A, when the number of pixels for every 16 gradations included in one frame is biased, it is determined that the image of the one frame is close to a solid image and the amount of change is small. If the number of pixels for each of the 16 gradations contained in one frame is dispersed as shown in FIG. 5B, it is determined that the amount of change in the image in that one frame is large. Is possible.

<Steps S2 to S3>
In steps S2 to S3, the display control unit 11 determines the degree of change in one frame of the display image on the liquid crystal panel 21 based on the histogram acquired in step S1, and branches the process.
Specifically, the display control unit 11 has a case where any value of the number of pixels for each of 16 gradations included in one frame is equal to or larger than a first threshold value K1 (%) set in advance (for example, FIG. 5 (a)), that is, when the amount of change in one frame of the display image is small (Yes in S2), the process proceeds to step S21.
Further, the display control unit 11 is configured such that when all the values of the number of pixels for every 16 gradations included in one frame are less than the first threshold value K1 (%) (see, for example, FIG. 5B) That is, when the amount of change in one frame of the display image is large (No side of S2), the process proceeds to step S3.
In this embodiment, the case where the gradation change amount of all pixels included in one frame image of the display image is used as the feature amount of the display image will be described as an example. It is also conceivable to use another index that can determine whether or not the image is conspicuous as the feature amount of the display image.

<Step S21>
In step S21, the display control unit 11 gives a control instruction to the backlight device 31 so that each LED 31a emits light with the same luminance without using the luminance gradient filters F1 and F2. Thereby, uneven brightness in the display image of the liquid crystal panel 21 is prevented.

<Step S3>
On the other hand, in step S3, the display control unit 11 sets a preset second threshold value K2 in which any value of the number of pixels for each of 16 gradations included in one frame is smaller than the first threshold value K1. If it is equal to or greater than (%), that is, if the amount of change in one frame of the display image is relatively small (Yes side of S3), the process proceeds to step S31, and is less than the second threshold value K2 (%). In some cases, that is, when the amount of change in one frame of the display image is relatively large (No side of S3), the process proceeds to step S32.

<Step S31>
In step S31, the display control unit 11 selects the luminance gradient filter F1 according to the amount of change in one frame of the display image being relatively small, and the luminance gradient filter F1 is transmitted to the backlight control unit 32. A control instruction is given to convert the luminance of each of the LEDs 31a.
In this case, the luminance of each of the LEDs 31a is partially attenuated by the luminance gradient filter F1 in the backlight control unit 32. Thereby, for example, as shown in FIG. 3B, the luminance of each of the LEDs 31a is inclined from the central portion toward the outer peripheral portion, and further power saving can be achieved. Further, in this case, since the amount of change in one frame of the display image is large to some extent, even if the luminance of each LED 31a is inclined, the uneven brightness in the display image of the liquid crystal panel 21 is not easily recognized by the user. Degradation can be suppressed.
Furthermore, although the display control unit 11 adjusts the luminance of each of the LEDs 31a using the luminance gradient filter F1, the luminance of the LED 31a corresponding to the position around the central portion of the liquid crystal panel 21 decreases. The brightness of the LED 31a located at the center of the liquid crystal panel 21 is adjusted to be high so as to offset the decrease in display brightness at the center of the liquid crystal panel 21 due to the decrease in brightness. The display brightness at the center is kept constant (for example, 100 (%)) (see FIG. 3B).

<Step S32>
On the other hand, in step S32, the display control unit 11 selects the luminance gradient filter F2 whose luminance gradient is steeper than that of the luminance gradient filter F1 in accordance with a relatively large change amount in one frame of the display image. Then, a control instruction is given to the backlight control unit 32 so as to convert the luminance of each of the LEDs 31a using the luminance gradient filter F2.
In this case, the brightness of each of the LEDs 31a is partially attenuated by the brightness gradient filter F2 in the backlight control unit 32. As a result, for example, as shown in FIG. 3C, the luminance of each of the LEDs 31a is inclined from the central portion toward the outer peripheral portion with a larger inclination than in the case shown in FIG. 3B. Thus, further power saving can be achieved as compared with the case where the brightness gradient filter F1 is used. In addition, in this case, since the amount of change in one frame of the display image is sufficiently large, even if the luminance of each of the LEDs 31a is steeply inclined, uneven brightness in the display image of the liquid crystal panel 21 is recognized by the user. It is difficult to suppress the deterioration of display quality.
Furthermore, although the display control unit 11 adjusts the luminance of each of the LEDs 31a using the luminance gradient filter F2, the luminance of the LED 31a corresponding to the position around the central portion of the liquid crystal panel 21 decreases. The brightness of the LED 31a located at the center of the liquid crystal panel 21 is adjusted to be high so as to offset the decrease in display brightness at the center of the liquid crystal panel 21 due to the decrease in brightness. The display luminance at the center is kept constant (for example, 100 (%)) (see FIG. 3C).

As described above, in the liquid crystal display device X, when the display control unit 11 executes the backlight control process (see FIG. 4), the amount of change in one frame of the display image on the liquid crystal panel 21 is changed. When it is difficult to see uneven brightness, the brightness of each LED 31a can be increased to increase the power saving effect, and the amount of change in one frame of the display image on the liquid crystal panel 21 is small and the uneven brightness is noticeable. Therefore, it is possible to save power within a range in which the luminance gradient of each LED 31a can be reduced to prevent luminance unevenness.
Further, the display control unit 11 uses the brightness gradient filters F1 and F2, and the larger the amount of decrease in the brightness of the LED 31a corresponding to the position around the center of the liquid crystal panel 21, the more the center corresponds to the center. Since the brightness of each of the LEDs 31a is controlled so that the brightness of the LED 31a increases, the display brightness at the center of the liquid crystal panel 21 is kept constant before and after the brightness gradient filters F1 and F2 are applied. Is possible.
In the present embodiment, the luminance gradient filters F1 and F2 are described as an example in which the luminance of each of the LEDs 31a in the backlight device 31 is inclined in both the vertical direction and the horizontal direction of the liquid crystal panel 21. However, the present invention is not limited to this, and inclining in only one direction is also conceivable as another embodiment. Therefore, in the case of tilting only in one direction, a plurality of cold cathode tubes (fluorescent tubes) arranged in the vertical direction or the horizontal direction can be used as the light source instead of the LED 31a of the backlight device 31. .

In the embodiment, the method of selecting the degree of the luminance gradient in the backlight device 31 according to the histogram (see FIG. 5) calculated for the entire frame of the display image of the liquid crystal panel 21 has been described. In the present embodiment, another example of a method for selecting the degree of luminance gradient in the backlight device 31 will be described.
In general, it is the central part of the liquid crystal panel 21 that is easily noticeable by the user who views the video on the liquid crystal display device X. Therefore, the display control unit 11 obtains histograms of the entire one frame of the display image of the liquid crystal panel 21 and the predetermined region in the central part in the backlight control process (S1), and based on the two histograms. It is conceivable to determine the amount of change in one frame of the display image on the liquid crystal panel 21 (S2 to S3).

6 and 7, (a) covers the entire frame of the display image of the liquid crystal panel 21, and (b) covers only a predetermined area in the center of the frame of the display image of the liquid crystal panel 21. Shows an example of the calculated histogram.
As shown in FIG. 6, even when the amount of change is small in the entire frame of the display image of the liquid crystal panel 21 (FIG. 6A), the amount of change is large in the center (FIG. 6B). ) In this case, since the amount of change in the central portion that is easily noticeable by the user is large, even if the luminance gradient in the backlight device 31 is increased, the user hardly perceives luminance unevenness. Further, there is a possibility that black belt portions are formed on the top and bottom or the left and right of the display image of the liquid crystal panel 21 due to a difference in aspect ratio such as a movie.
Therefore, in such a case, the display control unit 11 gives priority to the degree of change in the central part, and increases the degree of luminance inclination in the backlight device 31 in accordance with the large amount of change in the central part. It is possible.
On the other hand, as shown in FIG. 7, the change amount is large in one frame of the display image of the liquid crystal panel 21 (FIG. 7A), but the change amount is small in the central portion (FIG. 7B). Conceivable. In this case, since the amount of change in the central portion, which is easily noticeable by the user, is small, when the luminance gradient in the backlight device 31 is increased, the user tends to feel luminance unevenness.
Therefore, in such a case, the display control unit 11 prioritizes the degree of change in the central part, and reduces the degree of luminance inclination in the backlight device 31 in accordance with the small change in the central part. It is possible to do.
In addition, a histogram is calculated for only the central region of the display image on the liquid crystal panel 21, the amount of change in one frame of the display image on the liquid crystal panel 21 is determined based on the histogram, and the backlight It is also conceivable to select the degree of brightness gradient in the device 31.

  The present invention can be applied to a liquid crystal display device such as a liquid crystal television receiver or a liquid crystal monitor device.

11: Display control unit 21: Liquid crystal panel 22: Liquid crystal drive unit 31: Backlight device 31a: LED (an example of a light source)
32: Backlight control units S1, S2,...: Processing procedure (step) number X: Liquid crystal display device

Claims (8)

A liquid crystal display device comprising: a backlight device that illuminates the liquid crystal panel from behind by a plurality of light sources arranged in the vertical direction and / or horizontal direction of the liquid crystal panel; and a luminance tilting unit that tilts the luminance of each of the light sources. Because
The liquid crystal display device, wherein the brightness tilting means controls the brightness tilt of each of the light sources in accordance with a feature amount of a display image on the liquid crystal panel.   The brightness tilting means adjusts the brightness slope of each of the light sources such that the smaller the change amount in one frame of the display image of the liquid crystal panel, the smaller the tilt, and the greater the change amount, the greater the tilt. The liquid crystal display device according to claim 1, which is to be controlled.   The luminance gradient means controls the magnitude of the luminance gradient of each of the light sources so as to gradually decrease from the center of the liquid crystal panel toward the outer periphery. Liquid crystal display device. A histogram acquisition means for acquiring a histogram indicating the frequency distribution of the video signal for each frame of the video displayed on the whole and / or part of the liquid crystal panel;
4. The liquid crystal display device according to claim 2, wherein the luminance inclination unit determines a change amount in one frame of a display image of the liquid crystal panel based on a histogram acquired by the histogram acquisition unit. . The histogram acquisition means acquires a histogram for the whole and a part of the liquid crystal panel;
The liquid crystal display device according to claim 4, wherein the brightness tilting unit determines a change amount in one frame of a display image of the liquid crystal panel based on a histogram of the entire liquid crystal panel and a partial region. Filter storage means for storing a plurality of brightness gradient filters set in advance to change the brightness of each of the light sources at different slopes;
The luminance gradient means selects one of the luminance gradient filters stored in the filter storage means according to the amount of change in one frame of the display image of the liquid crystal panel, and uses the luminance gradient filter to select the light source The liquid crystal display device according to claim 2, wherein each luminance is changed. The backlight device has a plurality of LEDs arranged in a matrix behind the liquid crystal panel,
The liquid crystal display device according to claim 1, wherein the brightness tilting unit tilts the brightness of each of the LEDs in a vertical direction and a horizontal direction.   In order for the brightness tilting means to keep the brightness of the central portion of the liquid crystal panel constant before and after the brightness tilt of each of the light sources, as the amount of decrease in the brightness of the light source corresponding to the position around the center portion increases. The liquid crystal display device according to claim 1, wherein the luminance of each of the light sources is controlled so that the luminance of the light source corresponding to the central portion is increased.

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