WO2012114989A1

WO2012114989A1 - Image display device and image display method

Info

Publication number: WO2012114989A1
Application number: PCT/JP2012/053764
Authority: WO
Inventors: 勝照橋本; 克也乙井
Original assignee: シャープ株式会社
Priority date: 2011-02-25
Filing date: 2012-02-17
Publication date: 2012-08-30

Abstract

An image display device for performing an area-active drive, wherein less electric power is consumed while the occurrence of brightness defects in a region for a high-gradation display is suppressed. A data comparator (154) compares the brightness of each in-area pixel with a data assessment threshold (Sd) for each area and computes, as a count value (Cnt), the number of pixels having a brightness at or above the data assessment threshold (Sd). A count extractor/comparator (156) compares the count value (Cnt) for each area with a count assessment threshold (Sc). A LED output value calculator (158) computes an LED output value for every area in accordance with a comparison result (35) produced by the count extractor/comparator (156). In the process, the LED output value is determined on the basis of the maximum brightness value of pixels in an area where the count value (Cnt) is at or above the count assessment threshold (Sc), and the LED output value is determined on the basis of the mean brightness value of pixels in the other areas.

Description

Image display device and image display method

The present invention relates to an image display device, and more particularly to an image display device having a function of controlling the brightness of a backlight (backlight dimming function).

In an image display device having a backlight, such as a liquid crystal display device, by controlling the luminance of the backlight based on the input image, the power consumption of the backlight can be suppressed and the image quality of the display image can be improved. In particular, by dividing the screen into a plurality of areas and controlling the luminance of the backlight light source corresponding to the area based on the input image in the area, it is possible to further reduce power consumption and improve image quality. Hereinafter, such a method of driving the display panel while controlling the luminance of the backlight light source based on the input image in the area is referred to as “area active driving”.

In a liquid crystal display device that performs area active drive, for example, RGB three-color LEDs (Light Emitting Diodes) or white LEDs are used as a backlight light source. Conventionally, the following two methods are known as typical methods for determining the brightness of these LEDs. The first method is a method of determining the luminance of the LED corresponding to the area based on the maximum luminance value of the pixels in the area (hereinafter referred to as “Max method”). The second method is a method of determining the luminance of the LED corresponding to the area based on the average value of the luminance of the pixels in the area (hereinafter referred to as “Mean method”). The luminance of the LED corresponding to each area is obtained by the above-described method and the like, and is given as LED data to the backlight driving circuit. Further, display data (data for controlling the light transmittance of the liquid crystal) is generated based on the LED data and the input image, and the display data is supplied to a driving circuit for the liquid crystal panel.

According to the liquid crystal display device as described above, suitable display data and LED data are obtained based on the input image, the light transmittance of the liquid crystal is controlled based on the display data, and each area is handled based on the LED data. By controlling the luminance of the LED, an image corresponding to the input image can be displayed on the liquid crystal panel. When the luminance of the pixels in the area is small, the power consumption of the backlight can be reduced by decreasing the luminance of the LED corresponding to the area.

Incidentally, Japanese Unexamined Patent Publication No. 2007-183608 discloses the following liquid crystal display device. The gradation of each region based on the maximum gradation value for each unit pixel (for example, the maximum value is 255 if the respective values of R, G, and B are 255, 240, and 245) The average value of the values (the average value for each area equal to the number of the divided areas) is calculated. Then, the maximum average value (maximum value of the average value for each region), the minimum average value (the minimum value of the average value for each region), and the overall average value (the average value for each region) An average value) is obtained, and a dimming curve is generated so that the luminance of the backlight light is adjusted by these values and the minimum and maximum dimming values set from the outside. Thus, it is described that there are effects such as image quality improvement and power consumption reduction.

Japanese Unexamined Patent Publication No. 2007-183608

However, according to the Max method, the problem of insufficient luminance does not occur, but the power consumption increases. On the other hand, according to the Mean method, power consumption is reduced, but there is a problem of insufficient luminance. These will be described below with reference to FIGS. FIG. 40 is a diagram schematically illustrating an example of an input image. In FIG. 40, it is assumed that an area indicated by an arrow 81 is an area where high gradation display is to be performed, and an area indicated by an

arrow

82 and 83 is an area where low gradation display is to be performed.

When the brightness of each area (LED) is determined using the Max method for the input image shown in FIG. 40, the brightness distribution in the entire screen is as shown in FIG. Here, when attention is paid to the regions indicated by

arrows

82 and 83 in FIG. 41, the luminance is relatively high regardless of the region where low gradation display is to be performed. This is because the luminance of the LED is determined based on the maximum value of the luminance of the pixels in the area, and therefore the luminance of the LED increases if even one pixel data of high gradation is included in the area. . For this reason, if high tone noise data is included in the input image, the luminance of the LED is unnecessarily increased, and the power consumption increases.

On the other hand, when the luminance of each area is determined using the Mean method for the input image shown in FIG. 40, the luminance distribution in the entire screen is as shown in FIG. Here, when attention is paid to the area indicated by the arrow 81 in FIG. 42, the luminance is intermediate although it is an area where high gradation display is to be performed. This is because the brightness of the LED is determined based on the average value of the brightness of the pixels in the area, and therefore if the high gradation pixel data and the low gradation pixel data are mixed in the area, the LED brightness This is because the luminance is equivalent to that when the entire area has a middle gradation. For this reason, insufficient luminance occurs in an area where high gradation display is to be performed, and image quality is degraded.

In the liquid crystal display device disclosed in Japanese Unexamined Patent Application Publication No. 2007-183608, the luminance of the LED is determined based on the average value for each region. Insufficient brightness occurs when pixel data is mixed. Further, when the average value for each region is increased by noise data, the dimming value increases, and the effect of reducing power consumption cannot be sufficiently obtained.

Therefore, an object of the present invention is to realize low power consumption while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed in an image display device that performs area active driving.

A first aspect of the present invention is an image display device having a function of controlling the luminance of a backlight,
A display panel including a plurality of display elements;
A backlight including a plurality of light sources;
A backlight data processing unit that divides the input image into a plurality of areas and obtains backlight data indicating the luminance of the light source corresponding to each area based on the input image;
A display data calculation unit for obtaining display data for controlling the light transmittance of the display element based on the input image and the backlight data;
A panel drive circuit that outputs a signal for controlling the light transmittance of the display element to the display panel based on the display data;
A backlight driving circuit that outputs a signal for controlling the luminance of the light source to the backlight based on the backlight data;
The backlight data processing unit
An area data extraction unit that extracts a plurality of pixel data included in each area from the input image as area data;
Based on the area data, an area maximum value detection unit that detects the maximum value of the plurality of pixel data values as an area maximum value;
Based on the area data, an area average value calculation unit that calculates an average value of the values of the plurality of pixel data as an area average value;
The backlight data is obtained using the value obtained based on the value of each pixel data included in the area data or the value of each pixel data included in the area data as a first comparison value for the pixel data. A first comparison unit that compares with a first threshold value provided for the purpose, and obtains the number of pixel data for which a predetermined relationship is established as a count value;
A second threshold value provided for obtaining the backlight data using a value obtained based on the count value for each area or the count value itself for each area as a second comparison value for each area. A second comparison unit for comparing with,
And a backlight data calculation unit for obtaining the backlight data in accordance with a comparison result by the second comparison unit for each area.

According to a second aspect of the present invention, in the first aspect of the present invention,
The area data extraction unit extracts the area data from an image after a process for reducing the resolution is performed on the input image.

According to a third aspect of the present invention, in the first aspect of the present invention,
The pixel data is data representing a gradation value or a luminance value.

According to a fourth aspect of the present invention, in the first aspect of the present invention,
The first comparison unit obtains, as the count value, the number of pixel data in which the first comparison value is greater than or equal to the first threshold value, or the first comparison value is greater than the first threshold value. The number of pixel data having a larger value is obtained as the count value.

According to a fifth aspect of the present invention, in the first aspect of the present invention,
For the area where the second comparison value is equal to or greater than the second threshold, the backlight data calculation unit sets the value corresponding to the area maximum value as the backlight data, or the second comparison For an area having a value larger than the second threshold value, a value corresponding to the maximum area value is used as the backlight data.

According to a sixth aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit sets a constant value as the backlight data for an area where the second comparison value is greater than or equal to the second threshold value, or the second comparison value is the second comparison value. For areas larger than the threshold, a constant value is used as the backlight data.

A seventh aspect of the present invention is the sixth aspect of the present invention,
The constant value is a maximum value that the pixel data can take.

According to an eighth aspect of the present invention, in the first aspect of the present invention,
For the area where the second comparison value is less than or equal to the second threshold, the backlight data calculation unit sets the value corresponding to the area average value as the backlight data, or the second comparison For an area whose value is smaller than the second threshold value, a value corresponding to the area average value is used as the backlight data.

According to a ninth aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit sets a constant value as the backlight data for an area where the second comparison value is equal to or less than the second threshold value, or the second comparison value is the second comparison value. For areas smaller than the threshold value, a constant value is used as the backlight data.

According to a tenth aspect of the present invention, in a ninth aspect of the present invention,
The constant value is a minimum value that the pixel data can take.

According to an eleventh aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is smaller than the second threshold value. For the area, the value corresponding to the area average value is the backlight data, or
For an area where the second comparison value is larger than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is equal to or less than the second threshold value. For the area, a value corresponding to the area average value is used as the backlight data.

According to a twelfth aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, the maximum possible value of the pixel data is the backlight data, and the second comparison value is greater than the second threshold value. For a small area, the value corresponding to the area average value is the backlight data, or
For an area where the second comparison value is larger than the second threshold value, the maximum value that the pixel data can take is the backlight data, and the second comparison value is less than or equal to the second threshold value. For a certain area, a value corresponding to the average area value is used as the backlight data.

According to a thirteenth aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is smaller than the second threshold value. For the area, the minimum value that the pixel data can take is the backlight data, or
For an area where the second comparison value is larger than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is equal to or less than the second threshold value. For the area, the minimum value that the pixel data can take is the backlight data.

In a fourteenth aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit obtains an area where the second comparison value is greater than or equal to the second threshold based on at least the area maximum value, the maximum value that the pixel data can take, and the count value. A value to be obtained as the backlight data, or at least the area maximum value, the maximum possible value of the pixel data, and the count value for an area where the second comparison value is larger than the second threshold value A value obtained based on the above is used as the backlight data.

A fifteenth aspect of the present invention is the fourteenth aspect of the present invention,
The backlight data calculation unit calculates the backlight data for the area where the second comparison value is greater than or equal to the second threshold by the following equation.
E1 = (Ma · (Da-Cnt) + Dmax · (Cnt-Sc)) / (Da-Sc)
Here, E1 represents the value of the backlight data, Ma represents the maximum area value, Da represents the number of pixel data in the area, Cnt represents the count value, and Dmax represents the capture of the pixel data. Represents the maximum value obtained, and Sc represents the second threshold.

A sixteenth aspect of the present invention is the fourteenth aspect of the present invention,
The backlight data calculation unit calculates the backlight data by the following formula for an area where the second comparison value is larger than the second threshold.
E1 = (Ma · (Da-Cnt) + Dmax · (Cnt-Sc-1)) / (Da-Sc-1)
Here, E1 represents the value of the backlight data, Ma represents the maximum area value, Da represents the number of pixel data in the area, Cnt represents the count value, and Dmax represents the capture of the pixel data. Represents the maximum value obtained, and Sc represents the second threshold.

According to a seventeenth aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit calculates a value obtained based on at least the area maximum value, the area average value, and the count value for an area in which the second comparison value is equal to or less than the second threshold value. For the area where the second comparison value is smaller than the second threshold, a value obtained based on at least the area maximum value, the area average value, and the count value is used as the write data. It is characterized by write data.

According to an eighteenth aspect of the present invention, in an seventeenth aspect of the present invention,
For the area where the second comparison value is smaller than the second threshold value, the backlight data is calculated by the following equation.
E2 = (Ma · Cnt + Me · (Sc-Cnt)) / Sc
Here, E2 represents the value of the backlight data, Ma represents the area maximum value, Cnt represents the count value, Me represents the area average value, and Sc represents the second threshold value.

According to a nineteenth aspect of the present invention, in a seventeenth aspect of the present invention,
The backlight data calculation unit calculates the backlight data for the area where the second comparison value is less than or equal to the second threshold by the following formula.
E2 = (Ma · Cnt + Me · (Sc + 1-Cnt)) / (Sc + 1)
Here, E2 represents the value of the backlight data, Ma represents the area maximum value, Cnt represents the count value, Me represents the area average value, and Sc represents the second threshold value.

According to a twentieth aspect of the present invention, in the first aspect of the present invention,
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, a value obtained based on at least the area maximum value, the maximum value that can be taken by the pixel data, and the count value is used as the backlight data. In addition, for an area where the second comparison value is smaller than the second threshold value, a value obtained based on at least the area maximum value, the area average value, and the count value is used as the backlight data. Or
For an area where the second comparison value is larger than the second threshold value, a value obtained based on at least the area maximum value, the maximum value that can be taken by the pixel data, and the count value is used as the backlight data. In addition, for an area where the second comparison value is equal to or less than the second threshold value, a value obtained based on at least the area maximum value, the area average value, and the count value is used as the backlight data. It is characterized by.

According to a twenty-first aspect of the present invention, in the first aspect of the present invention,
The first comparison unit is characterized in that a value obtained by subtracting the area average value from a value of each pixel data included in the area data is used as the first comparison value.

According to a twenty-second aspect of the present invention, in the first aspect of the present invention,
The second comparison unit is characterized in that a value obtained by dividing the count value by the number of pixel data included in each area is used as the second comparison value.

According to a twenty-third aspect of the present invention, in the first aspect of the present invention,
The first comparison unit generates a histogram indicating a distribution of appearance frequencies of values that can be taken by the pixel data based on the area data, and obtains the first threshold value based on the histogram. To do.

According to a twenty-fourth aspect of the present invention, in the first aspect of the present invention,
The second comparison unit generates a histogram showing a distribution of appearance frequencies of each count value obtained by the first comparison unit, and obtains the second threshold based on the histogram. .

According to a 25th aspect of the present invention, in the first aspect of the present invention,
A first threshold setting unit for setting the first threshold from the outside is further provided.

According to a twenty-sixth aspect of the present invention, in the first aspect of the present invention,
A second threshold setting unit for setting the second threshold from the outside is further provided.

A twenty-seventh aspect of the present invention is an image display method in an image display device including a display panel including a plurality of display elements and a backlight including a plurality of light sources,
A backlight data processing step of dividing an input image into a plurality of areas and obtaining backlight data indicating luminance of a light source corresponding to each area based on the input image;
A display data calculation step for obtaining display data for controlling light transmittance of the display element based on the input image and the backlight data;
A panel driving step for outputting a signal for controlling the light transmittance of the display element to the display panel based on the display data;
A backlight driving step for outputting a signal for controlling the luminance of the light source to the backlight based on the backlight data;
The backlight data processing step includes
An area data extraction step of extracting a plurality of pixel data included in each area from the input image as area data;
An area maximum value detecting step for detecting a maximum value of the values of the plurality of pixel data as an area maximum value based on the area data;
An area average value calculating step for calculating an average value of the values of the plurality of pixel data as an area average value based on the area data;
The backlight data is obtained using the value obtained based on the value of each pixel data included in the area data or the value of each pixel data included in the area data as a first comparison value for the pixel data. A first comparison step for comparing the first threshold value provided for the purpose and determining the number of pixel data for which a predetermined relationship is established as a count value;
A second threshold value provided for obtaining the backlight data using a value obtained based on the count value for each area or the count value itself for each area as a second comparison value for each area. A second comparison step for comparing with
A backlight data calculation step for obtaining the backlight data in accordance with a comparison result in the second comparison step for each area.

According to the first aspect of the present invention, for each area, a count value is obtained by comparing a value (first comparison value) based on each pixel data with a predetermined threshold (first threshold), Backlight data for controlling the luminance of the light source of the backlight is obtained according to the comparison result between the value based on the count value (second comparison value) and a predetermined threshold value (second threshold value). For this reason, unlike the prior art, the backlight data can be obtained by a different method for each area. This makes it possible to effectively emit the backlight according to the image to be displayed for each area.

According to the second aspect of the present invention, since the number of pixel data included in one area is reduced, the processing burden on the backlight data processing unit is reduced.

According to the third aspect of the present invention, an effect similar to that of the first aspect of the present invention can be obtained in an image display device in which data representing gradation values or luminance values is used as pixel data.

According to the fourth aspect of the present invention, it is possible to effectively emit the backlight according to the image to be displayed for each area without complicating the processing.

According to the fifth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value higher than the threshold value provided for comparison, the backlight emits light based on the maximum value of the pixel data in the area. . For this reason, by setting the threshold value to a suitable value, occurrence of insufficient luminance in an area where high gradation display is to be performed is suppressed.

According to the sixth aspect of the present invention, the backlight emits light based on the constant value in an area that includes a relatively large amount of pixel data having a value higher than the threshold value provided for comparison. For this reason, by setting the threshold value and the constant value to suitable values, occurrence of insufficient luminance in an area where high gradation display is to be performed is suppressed.

According to the seventh aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value higher than the threshold value provided for comparison, the backlight emits light based on the maximum value that the pixel data can take. For this reason, by setting the threshold value to a suitable value, occurrence of insufficient luminance in an area where high gradation display is to be performed is suppressed.

According to the eighth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value lower than the threshold value provided for comparison, the backlight emits light based on the average value of the pixel data in the area. . For this reason, by setting the threshold value to a suitable value, it is possible to suppress the LED from emitting light with an unnecessarily high luminance and to reduce power consumption.

According to the ninth aspect of the present invention, the backlight emits light based on the constant value in an area that includes a relatively large amount of pixel data having a value lower than the threshold value provided for comparison. For this reason, by setting the threshold value and the constant value to suitable values, it is possible to suppress the LED from emitting light with an unnecessarily high luminance, and to reduce power consumption.

According to the tenth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value lower than the threshold value provided for comparison, the backlight emits light based on the minimum value that the pixel data can take. For this reason, by setting the threshold value to a suitable value, it is possible to suppress the LED from emitting light with an unnecessarily high luminance and to reduce power consumption.

According to the eleventh aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value higher than the threshold value provided for comparison, the backlight emits light based on the maximum value of the pixel data in the area. In an area that includes a relatively large amount of pixel data having a value lower than the threshold, the backlight emits light based on the average value of the pixel data in the area. For this reason, by setting the threshold value to a suitable value, it is possible to reduce power consumption while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed.

According to the twelfth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value higher than the threshold value provided for comparison, the backlight emits light based on the maximum value that the pixel data can take. In an area that includes a relatively large amount of pixel data having a lower value, the backlight emits light based on the average value of the pixel data in the area. For this reason, by setting the threshold value to a suitable value, it is possible to reduce power consumption while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed.

According to the thirteenth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value higher than the threshold value provided for comparison, the backlight emits light based on the maximum value of the pixel data in the area. In an area that includes a relatively large amount of pixel data having a value lower than the threshold, the backlight emits light based on the minimum value that the pixel data can take. For this reason, by setting the threshold value to a suitable value, it is possible to reduce power consumption while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed.

According to the fourteenth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value higher than a threshold value provided for comparison, the maximum value of pixel data in the area and the maximum value that can be taken by the pixel data And the backlight emits light based on the count value described above. That is, in this area, the maximum value that can be taken by the pixel data is reflected in the light emission luminance of the backlight. For this reason, by setting the threshold value to a suitable value, occurrence of insufficient luminance in an area where high gradation display is to be performed is suppressed.

According to the fifteenth aspect of the present invention, as in the fourteenth aspect of the present invention, the occurrence of insufficient luminance in the area where high gradation display is to be performed is suppressed.

According to the sixteenth aspect of the present invention, as in the fourteenth aspect of the present invention, the occurrence of insufficient luminance in the area where high gradation display is to be performed is suppressed.

According to the seventeenth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value lower than the threshold value provided for comparison, the maximum value of the pixel data in the area, the pixel data in the area The backlight emits light based on the average value and the number of pixel data having a value higher than the threshold value. That is, in the area, the average value of the pixel data is reflected on the light emission luminance of the backlight. For this reason, by setting the threshold value to a suitable value, it is possible to suppress the LED from emitting light with an unnecessarily high luminance and to reduce power consumption.

According to the eighteenth aspect of the present invention, as in the seventeenth aspect of the present invention, the LED is prevented from emitting light with an unnecessarily high luminance, and the power consumption is reduced.

According to the nineteenth aspect of the present invention, as in the seventeenth aspect of the present invention, the LED is prevented from emitting light with an unnecessarily high luminance, and the power consumption is reduced.

According to the twentieth aspect of the present invention, in an area that includes a relatively large amount of pixel data having a value higher than the threshold value provided for comparison, the maximum value of the pixel data in the area, the maximum value that the pixel data can take , And the number of pixel data having a value higher than the threshold value, the backlight emits light. That is, in this area, the maximum value that can be taken by the pixel data is reflected in the light emission luminance of the backlight. On the other hand, in an area that includes a relatively large amount of pixel data having a value lower than the threshold, the maximum value of the pixel data in the area, the average value of the pixel data in the area, and the pixel data having a value higher than the threshold The backlight emits light based on the number. That is, in the area, the average value of the pixel data is reflected on the light emission luminance of the backlight. As described above, by setting the threshold value to a suitable value, it is possible to reduce power consumption while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed.

According to the twenty-first aspect of the present invention, when the value obtained by subtracting the area average value from the pixel data value is used as the subtraction result value, the subtraction result value is higher than the threshold value provided for comparison. The backlight data can be obtained by a method different between an area including a relatively large number of pixels and an area including a relatively large number of pixels whose subtraction result value is lower than the threshold value. For areas containing noise data, the difference between the value of each pixel data and the area average value is relatively small.For example, in areas containing relatively many pixels whose subtraction result value is higher than the threshold value, the luminance of the backlight is set. In areas that contain relatively many pixels that are relatively high and have a subtraction result value lower than the threshold value, the luminance of the backlight is relatively low, resulting in insufficient luminance in areas where high gradation display is to be performed. And an unnecessary increase in power consumption due to the presence of noise data can be suppressed.

According to the twenty-second aspect of the present invention, according to the comparison result between the ratio of the count value to the number of pixel data included in each area and a predetermined threshold value (second threshold value), Backlight data for controlling the luminance is required. For this reason, there is no variation in how to obtain backlight data between a plurality of areas having different numbers of pixels. Thereby, even when the number of pixels included in one area is not constant, the backlight can be effectively emitted according to the image to be displayed for each area.

According to the twenty-third aspect of the present invention, based on a histogram generated from pixel data of each area, a threshold value (first threshold value) to be compared with a value (first comparison value) based on each pixel data ) Is required. For this reason, the threshold value is set to a suitable value according to the content of the input image. Thereby, it becomes possible to emit the backlight more effectively according to the image to be displayed for each area.

According to the twenty-fourth aspect of the present invention, based on the histogram generated from the comparison result by the first comparison unit, the comparison target with the value (second comparison value) based on the count value described above for each area A threshold value (second threshold value) is obtained. For this reason, the threshold value is set to a suitable value according to the content of the input image. Thereby, it becomes possible to emit the backlight more effectively according to the image to be displayed for each area.

According to the twenty-fifth aspect of the present invention, a threshold value (first threshold value) to be compared with a value (first comparison value) based on each pixel data can be set from the outside.

According to the twenty-sixth aspect of the present invention, it is possible to externally set a threshold value (second threshold value) that is to be compared with a value (second comparison value) based on the count value described above for each area. It becomes.

According to the twenty-seventh aspect of the present invention, the same effect as in the first aspect of the present invention can be achieved in the image display method in the image display device.

It is a block diagram which shows the detailed structure of the area active drive process part in the 1st Embodiment of this invention. It is a block diagram which shows the structure of the liquid crystal display device which concerns on the said 1st Embodiment. It is a figure which shows the detail of the backlight shown in FIG. 6 is a flowchart illustrating a processing procedure of an area active drive processing unit in the first embodiment. FIG. 3 is a diagram showing a luminance diffusion filter in the first embodiment. It is a figure which shows progress until liquid crystal data and LED data are obtained in the said 1st Embodiment. In the said 1st Embodiment, it is a figure which shows the relationship between the count value about each area, and LED output value. In the said 1st Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 1st Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 1st Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 1st Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 1st Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 1st Embodiment, it is a figure for demonstrating how to obtain | require LED output value. It is a figure for demonstrating the effect in the said 1st Embodiment. In the 1st modification of the said 1st Embodiment, it is a figure which shows the relationship between the count value about each area, and LED output value. It is a figure for demonstrating how to obtain | require LED output value in the 1st modification of the said 1st Embodiment. It is a figure for demonstrating how to obtain | require LED output value in the 1st modification of the said 1st Embodiment. In the 2nd modification of the said 1st Embodiment, it is a figure which shows the relationship between the count value about each area, and LED output value. It is a figure for demonstrating how to obtain | require LED output value in the 2nd modification of the said 1st Embodiment. It is a figure for demonstrating how to obtain | require LED output value in the 2nd modification of the said 1st Embodiment. It is a figure which shows the relationship between the count value about each area, and LED output value in the 3rd modification of the said 1st Embodiment. It is a figure for demonstrating how to obtain | require LED output value in the 3rd modification of the said 1st Embodiment. It is a block diagram which shows the detailed structure of the area active drive process part in the 2nd Embodiment of this invention. It is a figure for demonstrating the effect in the said 2nd Embodiment. It is a figure for demonstrating the effect in the said 2nd Embodiment. In the said 2nd Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 2nd Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 2nd Embodiment, it is a figure for demonstrating how to obtain | require LED output value. It is a block diagram which shows the detailed structure of the area active drive process part in the 3rd Embodiment of this invention. In the said 3rd Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 3rd Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 3rd Embodiment, it is a figure for demonstrating how to obtain | require LED output value. In the said 3rd Embodiment, it is a figure for demonstrating how to obtain | require LED output value. It is a block diagram which shows the detailed structure of the area active drive process part in the 4th Embodiment of this invention. In the said 4th Embodiment, it is a figure for demonstrating how to obtain | require the determination threshold value for data. In the said 4th Embodiment, it is a figure for demonstrating how to obtain | require the determination threshold value for a count. It is a figure for demonstrating how to obtain | require the determination threshold value for data in the 1st modification of the said 4th Embodiment. It is a figure for demonstrating how to obtain | require the determination threshold value for counting in the 2nd modification of the said 4th Embodiment. It is a block diagram which shows the detailed structure of the area active drive process part in the 5th Embodiment of this invention. It is a figure which shows the example of an input image typically. It is a figure which shows typically the luminance distribution in the whole screen when the brightness | luminance of LED is determined based on the maximum brightness | luminance of each area. It is a figure which shows typically the luminance distribution in the whole screen when the luminance of LED is determined based on the average luminance of each area.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<1. First Embodiment>
<1.1 Overall configuration and operation overview>
FIG. 2 is a block diagram showing a configuration of the liquid crystal display device 10 according to the first embodiment of the present invention. The liquid crystal display device 10 shown in FIG. 2 includes a liquid crystal panel 11, a panel drive circuit 12, a backlight 13, a backlight drive circuit 14, an area active drive processing unit 15, and an RGB signal processing unit 18. The liquid crystal display device 10 performs area active drive for driving the liquid crystal panel 11 while dividing the screen into a plurality of areas and controlling the luminance of the backlight light source based on the input image in each area. Hereinafter, m and n are integers of 2 or more, p and q are integers of 1 or more, and at least one of p and q is an integer of 2 or more.

The liquid crystal display device 10 receives an RGB image signal 30 including an R image, a G image, and a B image. Each of the R image, the G image, and the B image includes the luminance of (m × n) pixels. The RGB signal processing unit 18 separates the RGB image signal 30 into R, G, and B color components and inputs an input image (for each of R, G, and B color components) to the area active drive processing unit 15. Give as 31. Based on the input image 31, the area active drive processing unit 15 displays data for driving the liquid crystal panel 11 (hereinafter referred to as liquid crystal data 32) and backlight control data for driving the backlight 13 (hereinafter referred to as LED). Data 33) (details will be described later).

The liquid crystal panel 11 includes (m × n × 3) display elements 21. The display elements 21 are arranged two-dimensionally as a whole, 3 m in the row direction (horizontal direction in FIG. 2) and n in the column direction (vertical direction in FIG. 2). The display element 21 includes an R display element that transmits red light, a G display element that transmits green light, and a B display element that transmits blue light. The R display element, the G display element, and the B display element are arranged side by side in the row direction. These three display elements 21 form one pixel. The arrangement of the display elements 21 is not limited to this format.

The panel drive circuit 12 is a drive circuit for the liquid crystal panel 11. The panel drive circuit 12 outputs a signal (voltage signal) for controlling the light transmittance of the display element 21 to the liquid crystal panel 11 based on the liquid crystal data 32 output from the area active drive processing unit 15. The voltage output from the panel drive circuit 12 is written to the pixel electrode in the display element 21, and the light transmittance of the display element 21 changes according to the voltage written to the pixel electrode.

The backlight 13 is provided on the back side of the liquid crystal panel 11 and irradiates the back light of the liquid crystal panel 11 with backlight light. FIG. 3 is a diagram showing details of the backlight 13. As illustrated in FIG. 3, the backlight 13 includes (p × q) LED units 22. The LED units 22 are two-dimensionally arranged as a whole, p in the row direction and q in the column direction. The LED unit 22 includes one red LED 23, one green LED 24, and one blue LED 25. Light emitted from the three LEDs 23 to 25 included in one LED unit 22 hits a part of the back surface of the liquid crystal panel 11.

The backlight drive circuit 14 is a drive circuit for the backlight 13. The backlight drive circuit 14 outputs a signal (voltage signal or current signal) for controlling the luminance of the LEDs 23 to 25 to the backlight 13 based on the LED data 33 output from the area active drive processing unit 15. The brightness of the LEDs 23 to 25 is controlled independently of the brightness of the LEDs inside and outside the unit.

The screen of the liquid crystal display device 10 is divided into (p × q) areas, and one LED unit 22 is associated with one area. For each of the (p × q) areas, the area active drive processing unit 15 obtains the luminance (luminance during light emission) of the red LED 23 corresponding to the area based on the R image in the area. Similarly, the luminance of the green LED 24 is determined based on the G image in the area, and the luminance of the blue LED 25 is determined based on the B image in the area. The area active drive processing unit 15 calculates the luminance of all the LEDs 23 to 25 included in the backlight 13, and outputs LED data 33 representing the calculated luminance to the backlight driving circuit 14.

Further, the area active drive processing unit 15 displays the brightness of the backlight light in all the display elements 21 included in the liquid crystal panel 11 based on the LED data 33 (displayed by the backlight light in a portion corresponding to each display element 21). Brightness). Further, the area active drive processing unit 15 obtains the light transmittance of all the display elements 21 included in the liquid crystal panel 11 based on the input image 31 and the luminance of the backlight light, and the liquid crystal data representing the obtained light transmittance. 32 is output to the panel drive circuit 12.

In the liquid crystal display device 10, the luminance of the R display element is the product of the luminance of the red light emitted from the backlight 13 and the light transmittance of the R display element. The light emitted from one red LED 23 hits a plurality of areas around the corresponding one area. Accordingly, the luminance of the R display element is the product of the total luminance of the light emitted from the plurality of red LEDs 23 and the light transmittance of the R display element. Similarly, the luminance of the G display element is the product of the total luminance of light emitted from the plurality of green LEDs 24 and the light transmittance of the G display element, and the luminance of the B display element is emitted from the plurality of blue LEDs 25. This is the product of the total light luminance and the light transmittance of the B display element.

According to the liquid crystal display device 10 configured as described above, the liquid crystal data 32 and the LED data 33 which are data for displaying an image on the liquid crystal panel 11 are obtained based on the input image 31. The luminance of the LEDs 23 to 25 is controlled based on the LED data 33, and the light transmittance of the display element 21 is controlled based on the liquid crystal data 32, thereby corresponding to the RGB image signal 30 sent from the outside. The image to be displayed is displayed on the liquid crystal panel 11.

<1.2 Configuration and Operation of Area Active Drive Processing Unit>
FIG. 1 is a block diagram showing a detailed configuration of the area active drive processing unit 15 in the present embodiment. The area active drive processing unit 15 includes a backlight data processing unit 150 and a liquid crystal data calculation unit 159. The backlight data processing unit 150 divides the input image 31 into a plurality of areas, and based on the input image 31, brightness at the time of light emission of LEDs corresponding to each area (hereinafter also referred to as “LED output value”). LED data 33 is obtained. The liquid crystal data calculation unit 159 obtains liquid crystal data 32 representing the light transmittance of all the display elements 21 included in the liquid crystal panel 11 based on the input image 31 and the LED data 33.

The backlight data processing unit 150 includes, as constituent elements for executing predetermined processing, a region data extraction unit 151, a region maximum value detection unit 152, a region average value calculation unit 153, a data comparison unit 154, and a count extraction / comparison. A data determination threshold storage unit 155 and a count determination threshold storage unit 157 as constituent elements for storing predetermined data.

The area data extraction unit 151 extracts pixel data of each area from the input image 31. Hereinafter, the extracted pixel data for one area is referred to as “extracted pixel data”. The area maximum value detection unit 152 detects the maximum value of the luminance of the pixels in the area based on the extracted pixel data 34 for each area. The detected maximum value is output from the region maximum value detection unit 152 as a region maximum value (area maximum value) Ma. The area average value calculation unit 153 calculates the average value of the luminance of the pixels in the area based on the extracted pixel data 34 for each area. The calculated average value is output from the region average value calculation unit 153 as a region average value (area average value) Me.

The data determination threshold storage unit 155 stores a data determination threshold Sd that is data for comparison with the luminance of each pixel. For each area, the data comparison unit 154 compares the luminance of each pixel in the area with the data determination threshold Sd, and counts the number of pixels having a luminance equal to or higher than the data determination threshold Sd. By this processing by the data comparison unit 154, the count value Cnt is obtained for each area. The count determination threshold value storage unit 157 stores a count determination threshold value Sc that is data for comparison with the count value Cnt described above. The count extraction / comparison unit 156 compares the count value Cnt of each area with the count determination threshold value Sc, and gives a comparison result 35 for each area to the LED output value calculation unit 158. The data determination threshold value Sd and the count determination threshold value Sc need to be set to suitable values so that the backlight 13 (LEDs 23 to 25) is lit efficiently.

The LED output value calculation unit 158 obtains an LED output value according to the comparison result 35 by the count extraction / comparison unit 156 for each area. At this time, for each area, if the comparison result 35 indicates that the count value Cnt is greater than or equal to the count determination threshold value Sc, a value corresponding to the region maximum value Ma (for example, the value of the region maximum value Ma itself) is obtained. LED output value. On the other hand, for each area, if the comparison result 35 indicates that the count value Cnt is less than the count determination threshold value Sc, the value corresponding to the region average value Me (for example, the value of the region average value Me itself) is LED. Output value.

As described above, in the present embodiment, an area in which the number of pixels having a luminance equal to or higher than the predetermined data determination threshold Sd is equal to or higher than the predetermined determination threshold Sc is set in the area. The LED output value is determined based on the maximum luminance value of the pixel. On the other hand, for an area where the number of pixels having a luminance equal to or higher than the data determination threshold Sd is less than the counting determination threshold Sc, the LED output value is determined based on the average value of the luminance of the pixels in the area.

In this embodiment, the area data extraction unit 151 realizes an area data extraction unit, the region maximum value detection unit 152 realizes an area maximum value detection unit, and the region average value calculation unit 153 realizes an area average value calculation unit. Is realized, the data comparison unit 154 implements a first comparison unit, the count extraction / comparison unit 156 implements a second comparison unit, the LED output value calculation unit 158 implements a backlight data calculation unit, A display data calculation unit is realized by the liquid crystal data calculation unit 159. The first threshold is realized by the data determination threshold Sd, the second threshold is realized by the count determination threshold Sc, and the area data is realized by the extracted pixel data.

In this embodiment, the number of pixels having a luminance equal to or higher than the data determination threshold Sd is used as the count value Cnt. However, the number of pixels having a luminance higher than the data determination threshold Sd may be used as the count value Cnt. Further, in the present embodiment, the method for obtaining the LED output value is different depending on whether or not the count value Cnt is equal to or greater than the count determination threshold Sc, but whether or not the count value Cnt is greater than the count determination threshold Sc. The LED output value may be obtained in different ways.

<1.3 Processing procedure of area active drive processing unit>
FIG. 4 is a flowchart showing a processing procedure of the area active drive processing unit 15. An image of a certain color component (hereinafter referred to as color component C) included in the input image 31 is input to the area active drive processing unit 15 (step S11). The input image of the color component C includes the luminance of (m × n) pixels.

Next, the area active drive processing unit 15 performs sub-sampling processing (averaging processing) on the input image of the color component C, and the luminance of (sp × sq) (s is an integer of 2 or more) pixels. A reduced image is obtained (step S12). In step S12, the input image of the color component C is reduced by (sp / m) times in the horizontal direction and (sq / n) times in the vertical direction. Next, the area active drive processing unit 15 divides the reduced image into (p × q) areas (step S13). Each area includes the luminance of (s × s) pixels.

Next, the area active drive processing unit 15 obtains the maximum luminance value (region maximum value) Ma of the pixels in the area for each of the (p × q) areas (step S14). Further, the area active drive processing unit 15 obtains an average value (region average value) Me of the luminance of the pixels in the area for each of (p × q) areas (step S15).

Next, the area active drive processing unit 15 counts the number of pixels having a luminance equal to or higher than the data determination threshold value Sd held in the data determination threshold value storage unit 155 for each of (p × q) areas. Is obtained as a count value Cnt (step S16). Further, the area active drive processing unit 15 determines the count determination threshold Sc held in the count determination threshold storage unit 157 and the count value Cnt obtained in Step S16 for each of (p × q) areas. Are compared (step S17). Then, the area active drive processing unit 15 determines the LED output value E for each of (p × q) areas according to the comparison result in step S17 (step S18). At this time, a value corresponding to the region maximum value Ma is set as the LED output value E for an area where the number of pixels having a luminance equal to or greater than the data determination threshold Sd is equal to or greater than the count determination threshold Sc. On the other hand, for an area where the number of pixels having a luminance equal to or higher than the data determination threshold Sd is less than the count determination threshold Sc, a value corresponding to the region average value Me is set as the LED output value E.

Next, the area active drive processing unit 15 applies (tp × tq) pieces of luminance diffusion filters (point diffusion filters) to the (p × q) pieces of LED output values E obtained in step S18. First backlight luminance data including luminance (t is an integer of 2 or more) is obtained (step S19). In step S19, (p × q) LED output values E are enlarged t times in the horizontal direction and the vertical direction, respectively. For example, as shown in FIG. 5, the luminance diffusion filter diffuses light in order to calculate the display luminance of each area (the luminance estimated to be displayed in each area when all LEDs emit light). PSF data (Point Spread Filter Data), which is data representing the way of the above in numerical values, is stored.

Next, the area active drive processing unit 15 obtains second backlight luminance data including (m × n) luminances by performing linear interpolation processing on the first backlight luminance data (Step S1). S20). In step S20, the first backlight luminance data is enlarged (m / tp) times in the horizontal direction and (n / tq) times in the vertical direction. The second backlight luminance data indicates that (m × n) color components C are displayed when (p × q) color component C LEDs emit light at the luminance of the LED output value E obtained in step S18. This represents the luminance of the backlight of the color component C incident on the element 21.

Next, the area active drive processing unit 15 determines the luminance of (m × n) pixels included in the input image of the color component C, respectively (m × n) included in the second backlight luminance data. The light transmittance T of the display element 21 of (m × n) color components C is obtained by dividing by the luminance of (step S21).

Finally, the area active drive processing unit 15 for the color component C, the liquid crystal data 32 representing the (m × n) light transmittances T obtained in step S21 and the (p × q) pieces obtained in step S18. LED data 33 representing the LED output value E is output (step S22). At this time, the liquid crystal data 32 and the LED data 33 are converted into values in a suitable range according to the specifications of the panel drive circuit 12 and the backlight drive circuit 14.

The area active drive processing unit 15 performs the processing shown in FIG. 4 on the R image, the G image, and the B image, thereby based on the input image 31 including the luminance of (m × n × 3) pixels. Liquid crystal data 32 representing (m × n × 3) light transmittances and LED data 33 representing (p × q × 3) LED output values are obtained.

FIG. 6 is a diagram showing a process until liquid crystal data 32 and LED data 33 are obtained in the case of m = 1920, n = 1080, p = 32, q = 16, s = 10, and t = 5. As shown in FIG. 6, a sub-sampling process is performed on the input image of the color component C including the luminance of (1920 × 1080) pixels, thereby reducing the image including the luminance of (320 × 160) pixels. Is obtained. The reduced image is divided into (32 × 16) areas (area size is (10 × 10) pixels). The maximum value data including (32 × 16) area maximum values and the average value including (32 × 16) area average values by obtaining the maximum value Ma and the average value Me of the luminance of the pixels for each area. Data.

Then, the count value Cnt of each area is obtained by comparing the luminance of each pixel with the data determination threshold value Sd. Furthermore, the count value Cnt of each area is compared with the determination threshold value Sc, and the LED output value of each area is obtained as described above according to the comparison result. Thereby, the LED data 33 of the color component C representing (32 × 16) LED output values is obtained.

Next, by applying a luminance diffusion filter to the LED data 33 of the color component C, first backlight luminance data including (160 × 80) luminances is obtained. Further, by performing a linear interpolation process on the first backlight luminance data, second backlight luminance data including (1920 × 1080) luminances is obtained. Finally, by dividing the luminance of the pixels included in the input image by the luminance included in the second backlight luminance data, the liquid crystal data 32 of the color component C including (1920 × 1080) light transmittances is obtained. .

In FIG. 4 and FIG. 6, the area active drive processing unit 15 sequentially performs the process for each color component image for ease of explanation. However, the process for each color component image is performed in a time-sharing manner. May be. 4 and 6, the area active drive processing unit 15 performs sub-sampling processing on the input image for noise removal, and performs area active drive based on the reduced image. A configuration in which area active driving is performed based on an image may be employed. Furthermore, regarding FIG. 4, the order of the process of step S14 and the process of step S15 may be interchanged. Furthermore, with reference to FIG. 4, the processing of step S14 and step S15 may be performed between the processing of step S17 and the processing of step S18.

<1.4 Effect>
According to this embodiment, in the liquid crystal display device that performs area active driving, the LED output value in each area is determined as follows. For an area in which the number of pixels having a luminance equal to or higher than the data determination threshold Sd is equal to or higher than the counting determination threshold Sc, the LED output value is based on the maximum luminance (region maximum value Ma) of the pixels in the area. It is determined. On the other hand, for an area where the number of pixels having a luminance equal to or higher than the data determination threshold Sd is less than the determination threshold Sc for counting, the LED output value is the average value of the luminance of the pixels in the area (region average value Me). To be determined. Thereby, the relationship between the count value Cnt and the LED output value for each area is as shown in FIG. Here, by setting the data determination threshold value Sd and the count determination threshold value Sc to suitable values, in an area where there are relatively many pixels on which high gradation display is to be performed, the LED output value is the region maximum value Ma. In the area where the occurrence of insufficient brightness is suppressed and the number of pixels for which high gradation display is to be performed is relatively small, the LED output value is determined based on the area average value Me. Power consumption is reduced.

For example, in a liquid crystal display device in which the screen is divided into (3 × 5) areas, the area average value Me of each area is as shown in FIG. 8, and the area maximum value Ma of each area is shown in FIG. Assume that it is as shown. Further, it is assumed that the data determination threshold Sd is set to “150” and the count determination threshold Sc is set to “3”. Further assume that each area is composed of (3 × 3) pixels. In FIGS. 8 and 9, reference numerals 61 to 66 are assigned to areas where the area average value Me and the area maximum value Ma are different.

Here, for example, when the luminance of each pixel in the area 62 is as shown in FIG. 10, since there are six pixels having a luminance of 150 or more, the count value Cnt of the area 62 is “6”. For example, when the luminance of each pixel in the area 66 is as shown in FIG. 11, there are two pixels having a luminance of 150 or more, and the count value Cnt of the area 66 is “2”. Assume that the count value Cnt of each area as described above is as shown in FIG.

Under the conditions as described above, the count value Cnt is 3 or more for the

areas

61 and 62 among the areas where the area maximum value Ma and the area average value Me are different. Therefore, for the

areas

61 and 62, the area maximum value Ma is set as the LED output value. On the other hand, of the areas where the region maximum value Ma and the region average value Me are different, the count value Cnt is less than 3 in the areas 63 to 66. Therefore, for the areas 63 to 66, the area average value Me is the LED output value. As a result, the LED output values for all areas are determined as shown in FIG.

Next, the luminance distribution on the entire screen obtained when the input image 31 as shown in FIG. 40 is given to the area active drive processing unit 15 will be described. Focusing on the area indicated by the arrow 81, each area in the area contains a relatively large amount of high gradation pixel data, and therefore the LED output value is determined based on the area maximum value Ma. For this reason, the LED in the region emits light with high luminance. On the other hand, focusing on the areas indicated by the

arrows

82 and 83, the LED output value is based on the area average value Me because it is mainly composed of low gradation pixel data and does not contain much high gradation pixel data. It is determined. For this reason, the LED in the region emits light with low luminance. As a result, the luminance distribution on the entire screen is as shown in FIG.

As described above, according to the present embodiment, the LED emits light with high brightness in an area where high gradation display is to be performed, and the LED emits light with appropriate brightness without emitting light with unnecessary high brightness in other areas. Emits light. Thus, in an image display apparatus that performs area active drive, low power consumption is realized while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed.

<1.5 Modification>
In the first embodiment, the LED output value of each area is set to the region maximum value Ma according to the comparison result 35 between the count value Cnt representing the number of pixels with relatively high luminance and the determination threshold value Sc. A corresponding value or a value corresponding to the region average value Me is set. However, the present invention is not limited to this. Hereinafter, a modified example regarding the method of obtaining the LED output value of each area based on the comparison result 35 will be described.

<1.5.1 First Modification>
In this modification, the LED output value of each area is determined as follows. For an area where the number of pixels having a luminance equal to or higher than the data determination threshold Sd (count value Cnt) is equal to or higher than the determination threshold Sc for counting, the LED output value is the maximum value that can be taken as the luminance of the pixel (hereinafter referred to as “data It is determined on the basis of “maximum value”). On the other hand, for an area where the number of pixels having a luminance equal to or higher than the data determination threshold value Sd (count value Cnt) is less than the determination threshold value Sc for counting, the LED output value is the average value of the luminance of the pixels in the area (area It is determined on the basis of the average value Me). As a result, the relationship between the count value Cnt and the LED output value for each area is as shown in FIG.

Here, it is assumed that the area average value Me of each area is as shown in FIG. 8, and the result of obtaining the count value Cnt of each area is as shown in FIG. Since the maximum data value is the same value (here, “255”) in all areas, the maximum data value in each area is as shown in FIG. Further, it is assumed that the count determination threshold value Sc is set to “3”. Under the above conditions, for example, for the area 62, the count value Cnt is 3 or more, so the maximum data value is the LED output value. For example, for the area 66, the count value Cnt is less than 3, so the area average value Me is used as the LED output value. When the LED output values for all areas are obtained as described above, the result shown in FIG. 17 is obtained.

<1.5.2 Second Modification>
In this modification, the LED output value of each area is determined as follows. For an area where the number of pixels having a luminance equal to or higher than the data determination threshold Sd (count value Cnt) is equal to or higher than the determination threshold Sc for counting, the LED output value is the maximum luminance (region maximum value) of the pixels in the area. Determined based on Ma). On the other hand, for an area where the number of pixels having a luminance equal to or higher than the data determination threshold Sd (count value Cnt) is less than the determination threshold Sc for counting, the LED output value is the minimum value that can be taken as the luminance of the pixel (hereinafter, It is determined on the basis of “data minimum value”). As a result, the relationship between the count value Cnt and the LED output value for each area is as shown in FIG.

Here, it is assumed that the area maximum value Ma of each area is as shown in FIG. 9, and the result of obtaining the count value Cnt of each area is as shown in FIG. Since the minimum data value is the same for all areas (here, “0”), the minimum data value for each area is as shown in FIG. Further, it is assumed that the count determination threshold value Sc is set to “3”. Under the above conditions, for example, for the area 62, the count value Cnt is 3 or more, so the region maximum value Ma is set as the LED output value. For example, for area 66, the count value Cnt is less than 3, so the minimum data value is the LED output value. When the LED output values for all areas are obtained as described above, the results shown in FIG. 20 are obtained.

<1.5.3 Third Modification>
In this modification, the LED output value of each area is determined as follows. For an area where the number of pixels having a luminance equal to or greater than the data determination threshold Sd (count value Cnt) is equal to or greater than the count determination threshold Sc, the LED output value is a value between the data maximum value and the region maximum value Ma. It is determined based on a predetermined calculation formula. On the other hand, for an area where the number of pixels having a luminance equal to or higher than the data determination threshold value Sd (count value Cnt) is less than the determination threshold value Sc for counting, the LED output value is between the region maximum value Ma and the region average value Me. It is determined based on a predetermined calculation formula so as to be a value of. Thus, the relationship between the count value Cnt and the LED output value for each area is as shown in FIG.

Next, a specific example of a calculation formula for obtaining the LED output value will be described. When the LED output value in the area where the count value Cnt is greater than or equal to the count determination threshold Sc is “E1” and the LED output value in the area where the count value Cnt is less than the count determination threshold Sc is “E2”, E1 is It calculates | requires by following Formula (1) and calculates | requires E2 by following Formula (2). Da represents the number of pixels in the area, and Dmax represents the maximum data value.
E1 = (Ma · (Da−Cnt) + Dmax · (Cnt−Sc)) / (Da−Sc) (1)
E2 = (Ma ・ Cnt + Me ・ (Sc−Cnt)) / Sc (2)

Here, the area average value Me of each area is as shown in FIG. 8, the area maximum value Ma of each area is as shown in FIG. 9, and the data maximum value of each area is shown in FIG. It is assumed that the result of obtaining the count value Cnt of each area is as shown in FIG. Further, it is assumed that the count determination threshold value Sc is set to “3”. Under the above conditions, for example, for the area 62, the count value Cnt is 3 or more, so the LED output value E1 is obtained as follows.
E1 = (192 ・ (9−6) +255 ・ (6−3)) / (9−3)
= 224
Further, for example, for the area 66, since the count value Cnt is less than 3, the LED output value E2 is obtained as follows.
E2 = (192.2 + 128. (3-2)) / 3
= 171
In the above calculation results, values after the decimal point are rounded off.
As described above, the LED output values for all areas are determined as shown in FIG.

By the way, the calculation formula for obtaining the LED output value is not limited to that described above. For example, the LED output value E1 in an area where the count value Cnt is larger than the counting determination threshold value Sc is obtained by the following equation (3), and the LED output value E2 in the area where the count value Cnt is equal to or less than the counting determination threshold value Sc is You may make it obtain | require by Formula (4).
E1 = (Ma · (Da-Cnt) + Dmax · (Cnt-Sc-1)) / (Da-Sc-1) (3)
E2 = (Ma · Cnt + Me · (Sc + 1-Cnt)) / (Sc + 1) (4)

<2. Second Embodiment>
<2.1 Configuration and operation>
Next, a second embodiment of the present invention will be described. The overall configuration and the operation outline are the same as those in the first embodiment, and a description thereof will be omitted (see FIGS. 2 and 3). FIG. 23 is a block diagram showing a detailed configuration of the area active drive processing unit 15 in the present embodiment. In this embodiment, the region average value Me obtained by the region average value calculation unit 153 is provided not only to the LED output value calculation unit 158 but also to the data comparison unit 154. Other configurations are the same as those in the first embodiment.

In the present embodiment, the data comparison unit 154 determines, for each area, a value obtained by subtracting the region average value Me from the luminance of each pixel in the area (hereinafter referred to as “subtraction result value”). Compared with the threshold value Sd, the number of pixels whose subtraction result value is equal to or greater than the data determination threshold value Sd is counted. This process is associated with the process of step S16 in FIG. Based on the comparison result 35 between the count value Cnt obtained as described above and the determination threshold value Sc, the LED output value of each area is obtained in the same manner as in the first embodiment.

<2.2 Effect>
According to the present embodiment, in addition to the same effects as those of the first embodiment, an effect of suppressing the luminance of the backlight from becoming unnecessarily high in an area including noise data can be obtained. This will be described below.

Image data that includes pixel data that should be displayed with high gradation and that should be prevented from being deficient in luminance typically spreads over a relatively wide area as shown in FIG. Image data in which pixel data of high gradation exists in a relatively narrow area among pixel data of low gradation. As noise data, typically, as shown in FIG. 25, image data in which high gradation pixel data and low gradation pixel data are irregularly mixed can be cited. Note that the image data shown in FIGS. 24 and 25 is image data of one area, respectively.

Here, for the image data as shown in FIG. 24, the region average value Me is a low value. On the other hand, for the image data as shown in FIG. 25, the region average value Me is an intermediate value. Therefore, the subtraction result value for each pixel tends to be larger in the image data as shown in FIG. 24 than in the image data as shown in FIG. Therefore, the image data as shown in FIG. 24 and the image data as shown in FIG. 25 can be distinguished based on the number of pixels whose subtraction result value is equal to or greater than the data determination threshold value Sd.

Therefore, in the present embodiment, the count value Cnt is obtained by comparing the value (subtraction result value) obtained by subtracting the region average value Me from the luminance of each pixel with the data determination threshold Sd, and the count value Cnt LED output values are determined based on the region maximum value Ma for areas where the count is equal to or greater than the determination threshold value Sc, and LED outputs are determined based on the region average value Me for areas where the count value Cnt is less than the count determination threshold Sc. The value is determined. Thus, by setting the data determination threshold value Sd and the count determination threshold value Sc to suitable values in advance, in the area of the image data as shown in FIG. 24, the LED output value is based on the region maximum value Ma. Thus, the occurrence of insufficient luminance is suppressed, and in the area of the image data as shown in FIG. 25, the LED output value is determined based on the area average value Me, thereby reducing the power consumption.

For example, the area average value Me of each area is as shown in FIG. 8, the luminance of each pixel in the area 62 is as shown in FIG. 10, and the luminance of each pixel in the area 66 is shown in FIG. Assuming that Further, it is assumed that the data determination threshold Sd is set to “50”. Under the above conditions, for example, the subtraction result value for the area 62 is as shown in FIG. Since there are six pixels with a subtraction result value of 50 or more, the count value Cnt of the area 62 is “6”. Further, for example, the subtraction result value for the area 66 is as shown in FIG. Since there is no pixel whose subtraction result value is 50 or more, the count value Cnt of the area 66 is “0”. When the count value Cnt for all areas is obtained as described above, for example, a result as shown in FIG. 28 is obtained. Thereafter, for each area, the count value Cnt is compared with the count determination threshold value Sc, and the LED output value is determined based on the comparison result 35.

As described above, in the present embodiment, the area average value Me is determined from the luminance of each pixel in consideration of the fact that the difference between the luminance value of each pixel and the area average value Me is relatively small for an area including noise data. The count value Cnt is obtained by comparing the value obtained by subtracting (subtraction result value) with a predetermined data determination threshold value Sd, and the count value Cnt and the predetermined determination threshold value Sc The LED output value is determined according to the comparison result 35. At this time, for the area where the count value Cnt is less than the count determination threshold value Sc, the LED output value is determined based on the region average value Me. Thereby, it is suppressed that the brightness | luminance of a backlight becomes unnecessarily high in the area containing noise data, and power consumption is reduced effectively.

In the present embodiment as well, as in the first embodiment, various methods (first to third modifications of the first embodiment) can be used for obtaining the LED output value of each area based on the comparison result. (See example).

<3. Third Embodiment>
<3.1 Configuration and operation>
Next, a third embodiment of the present invention will be described. The overall configuration and the operation outline are the same as those in the first embodiment, and a description thereof will be omitted (see FIGS. 2 and 3). FIG. 29 is a block diagram showing a detailed configuration of the area active drive processing unit 15 in the present embodiment. In the present embodiment, a count ratio calculation / comparison unit 161 is provided instead of the count extraction / comparison unit 156 in the first embodiment, and instead of the count determination threshold storage unit 157 in the first embodiment. A count ratio determination threshold value storage unit 162 is provided. Other configurations are the same as those in the first embodiment.

The count ratio calculation / comparison unit 161 obtains the count ratio for each area by multiplying the value obtained by dividing the count value Cnt obtained by the data comparison unit 154 by the number of pixels in the area by “100”. . Further, the count ratio calculation / comparison unit 161 compares the count ratio of each area with the count ratio determination threshold value Sr, and provides the LED output value calculation unit 158 with the comparison result 35 for each area. The above processing by the count ratio calculation / comparison unit 161 is associated with the processing in step S17 in FIG. The LED output value calculation unit 158 obtains the LED output value of each area based on the comparison result 35 in the same manner as in the first embodiment. The count ratio determination threshold value storage unit 162 stores a count ratio determination threshold value Sr, which is data for comparison with the above-described count ratio. The count ratio determination threshold value Sr needs to be set to a suitable value so that the backlight 13 (LEDs 23 to 25) is lit efficiently. In this embodiment, the count ratio is expressed as a percentage by the process of multiplying “100” as described above, but the count ratio may be expressed as a value of 0 or more and 1 or less.

In the present embodiment, the second comparison unit is realized by the count ratio calculation / comparison unit 161, and the second threshold is realized by the count ratio determination threshold Sr.

<3.2 Effects>
According to the present embodiment, even when the number of pixels included in one area is not constant, low power consumption can be realized while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed. In addition, the LEDs 23 to 25 are lit with suitable luminance in all areas. This will be described below.

When dividing the screen into a plurality of areas, it is preferable that the number of pixels included in each area is constant. However, the number of pixels included in each area may not be constant depending on the number of vertical and horizontal areas when the screen is divided and the resolution of the screen. For example, it is conceivable that the number of pixels in the area located at the edge of the screen is smaller than the number of pixels in other areas. Here, as shown in FIG. 30, it is assumed that the number of pixels in the column area indicated by reference numeral 6b is smaller than the number of pixels in the column area indicated by reference numeral 6a. Further, the area 62 is composed of nine pixels (3 rows × 3 columns of pixels) as shown in FIG. 10, and the area 66 is composed of 6 pixels (3 rows × 2 columns) as shown in FIG. Pixel). Further, it is assumed that the count value Cnt of each area is obtained as shown in FIG. 32, and the count ratio determination threshold Sr is set to “15%”.

Under the above conditions, for example, the count ratio of the area 62 is obtained by multiplying the value obtained by dividing the count value “6” by the number of pixels “9” in the area by “100”. As a result, the count ratio of the area 62 is “67%”. For example, the count ratio of the area 66 is obtained by multiplying a value obtained by dividing the count value “1” by the number of pixels “6” in the area by “100”. As a result, the count ratio of the area 66 is “17%”. In the above calculation results, values after the decimal point are rounded off. When the count ratios for all areas are obtained as described above, the result shown in FIG. 33 is obtained. Thereafter, the count ratio is compared with the count ratio determination threshold value Sr for each area, and the LED output value is determined based on the comparison result 35.

As described above, in the present embodiment, the method of obtaining the LED output value for each area is determined according to the ratio of pixels having a luminance equal to or higher than the data determination threshold Sd. For this reason, there is no variation in the method of obtaining the LED output value between a plurality of areas having different numbers of pixels. Therefore, even when the number of pixels included in one area is not constant, it is possible to suppress the occurrence of an area with insufficient luminance or an area with excessive luminance.

Also in this embodiment, as in the first and second embodiments, there are various methods for obtaining the LED output value of each area based on the comparison result (the first to the first embodiments of the first embodiment). 3) can be adopted.

<4. Fourth Embodiment>
<4.1 Configuration and operation>
Next, a fourth embodiment of the present invention will be described. The overall configuration and the operation outline are the same as those in the first embodiment, and a description thereof will be omitted (see FIGS. 2 and 3). FIG. 34 is a block diagram showing a detailed configuration of the area active drive processing unit 15 in the present embodiment. In the present embodiment, a data histogram extraction / comparison unit 163 is provided instead of the data comparison unit 154 in the first embodiment, and a count histogram extraction is performed instead of the count extraction / comparison unit 156 in the first embodiment. A comparison unit 164 is provided. Other configurations are the same as those in the first embodiment.

The data histogram extraction / comparison unit 163 generates, for each area, a histogram indicating the distribution of the appearance frequency of each luminance value based on the extracted pixel data (pixel data extracted by the region data extraction unit 151). The data histogram extraction / comparison unit 163 also obtains the data determination threshold Sd based on the histogram, and stores the obtained data determination threshold Sd in the data determination threshold storage unit 155. At this time, the luminance value having the highest appearance frequency among the luminance values that can be taken by the extracted pixel data is set as the data determination threshold value Sd. For example, it is assumed that the histogram 40 as shown in FIG. 35 is generated by the data histogram extraction / comparison unit 163. At this time, since the luminance value with the highest appearance frequency (see the portion indicated by reference numeral 71) is “50”, the data determination threshold Sd is “50”. Further, for each area, the data histogram extraction / comparison unit 163 compares the luminance of the pixels in the area with the data determination threshold Sd, and counts the number of pixels having a luminance equal to or higher than the data determination threshold Sd. Through the above processing by the data histogram extraction / comparison unit 163, the count value Cnt is obtained for each area.

The count histogram extraction / comparison unit 164 generates a histogram indicating the distribution of the appearance frequency of each count value based on the count value Cnt for each area obtained by the data histogram extraction / comparison unit 163. The count histogram extraction / comparison unit 164 also obtains the count determination threshold Sc based on the histogram, and stores the obtained count determination threshold Sc in the count determination threshold storage unit 157. At this time, the count value with the highest appearance frequency is set as the count determination threshold value Sc. For example, it is assumed that the histogram 41 as shown in FIG. 36 is generated by the count histogram extraction / comparison unit 164. At this time, since the count value having the highest appearance frequency is “50”, the determination threshold value Sc for counting is set to “50”. The count histogram extraction / comparison unit 164 further compares the count value Cnt of each area with the count determination threshold value Sc, and provides the LED output value calculation unit 158 with the comparison result 35 for each area. The LED output value calculation unit 158 obtains the LED output value of each area based on the comparison result 35 in the same manner as in the first embodiment.

In the present embodiment, the first comparison unit is realized by the data histogram extraction / comparison unit 163, and the second comparison unit is realized by the count histogram extraction / comparison unit 164.

<4.2 Effects>
According to the present embodiment, the histogram 40 is generated based on the extracted pixel data, and the luminance value having the highest appearance frequency is set as the data determination threshold value Sd. Further, a histogram 41 is generated based on the count value Cnt for each area, and the count value Cnt having the highest appearance frequency is set as the count determination threshold Sc. Thus, the threshold value used for the comparison process in the backlight data processing unit 150 is obtained based on the input image 31. That is, the threshold values (data determination threshold value Sd, count determination threshold value Sc) dynamically change according to the content of the input image 31. As a result, low power consumption can be achieved while suppressing the occurrence of insufficient luminance in an area where high gradation display is to be performed more effectively.

Also in this embodiment, as in the first to third embodiments, there are various methods for obtaining the LED output value of each area based on the comparison result (the first to the first embodiments of the first embodiment). 3) can be adopted.

<4.3 Modification>
Hereinafter, a modified example regarding how to determine the data determination threshold value Sd and how to determine the count determination threshold value Sc will be described.

<4.3.1 First Modification>
In the present modification, the area active drive processing unit 15 is configured as shown in FIG. 34 as in the fourth embodiment. However, the method for obtaining the data determination threshold value Sd in the data histogram extraction / comparison unit 163 is different from that in the fourth embodiment. In the present modification, an appearance frequency parameter F1 is provided as a parameter used when determining the data determination threshold value Sd.

The data histogram extraction / comparison unit 163 extracts data whose appearance frequency is equal to or greater than the value of the appearance frequency parameter F1 based on the histogram 40 generated based on the extracted pixel data. Next, the data histogram extraction / comparison unit 163 obtains the average value of the luminance values of the extracted data. The average value thus obtained is set as the data determination threshold value Sd. For example, assume that a histogram 40 as shown in FIG. 37 is generated based on the extracted pixel data. At this time, first, data of portions indicated by

reference numerals

72 and 73 in FIG. 37 is extracted. Next, an average value of luminance values of the extracted data is calculated. The calculation result “140” is set as the data determination threshold value Sd. As described above, according to this modification, the histogram 40 is generated based on the extracted pixel data, and the average value of the luminance value data appearing at a predetermined frequency or more is set as the data determination threshold value Sd.

<4.3.2 Second Modification>
In the present modification, the area active drive processing unit 15 is configured as shown in FIG. 34 as in the fourth embodiment. However, the counting histogram extraction / comparison unit 164 differs from the fourth embodiment in how to determine the counting determination threshold value Sc. In this modification, an appearance frequency parameter F2 is provided as a parameter used when determining the count determination threshold value Sc.

The count histogram extraction / comparison unit 164 extracts data whose appearance frequency is equal to or greater than the value of the appearance frequency parameter F2 based on the histogram 41 generated based on the count value Cnt for each area. Next, the count histogram extraction / comparison unit 164 obtains the average value of the count values for the extracted data. The average value obtained in this way is set as the count determination threshold value Sc. For example, it is assumed that a histogram 41 as shown in FIG. 38 is generated based on the count value Cnt for each area. At this time, first, data of portions indicated by

reference numerals

74 and 75 in FIG. 38 is extracted. Next, an average value of the count values of the extracted data is calculated. Then, “10” as the calculation result is set as the count determination threshold value Sc. As described above, according to this modification, the histogram 41 is generated based on the count value Cnt for each area, and the average value of the count value data that appears at a predetermined frequency or more is set as the determination threshold value Sc for counting. The

<5. Fifth Embodiment>
<5.1 Configuration and operation>
Next, a fifth embodiment of the present invention will be described. The overall configuration and the operation outline are the same as those in the first embodiment, and a description thereof will be omitted (see FIGS. 2 and 3). FIG. 39 is a block diagram showing a detailed configuration of the area active drive processing unit 15 in the present embodiment. In the present embodiment, as shown in FIG. 39, the data determination threshold value setting unit 171 for setting the data determination threshold value Sd from the outside of the area active drive processing unit 15 and the count from the outside of the area active drive processing unit 15 are counted. And a counting judgment threshold value setting unit 172 for setting the judgment threshold value Sc. Other configurations are the same as those in the first embodiment.

The data determination threshold setting unit 171 outputs a data setting signal S1 according to the state of the liquid crystal display device 10 (mode set by the user). Based on the data setting signal S1, the data determination threshold value Sd stored in the data determination threshold value storage unit 155 is set. The count determination threshold setting unit 172 outputs a count setting signal S <b> 2 according to the state of the liquid crystal display device 10. Based on the count setting signal S2, the count determination threshold value Sc stored in the count determination threshold value storage unit 157 is set. As described above, in the present embodiment, the data determination threshold Sd and the count determination threshold Sc are set by the signals (the data setting signal S1 and the count setting signal S2) given from the outside of the area active drive processing unit 15. Is done.

In the present embodiment, a first threshold setting unit is realized by the data determination threshold setting unit 171, and a second threshold setting unit is realized by the counting determination threshold setting unit 172.

<5.2 Control example>
Here, a control example in which the data determination threshold Sd and the count determination threshold Sc are set in accordance with the AV position mode (a mode provided for adjusting the image quality according to the user's preference) will be described. For example, it is assumed that the liquid crystal display device 10 is provided with four modes of “dynamic mode”, “standard mode”, “movie mode”, and “PC mode” as AV position modes. Then, it is assumed that the four modes are associated with the data determination threshold Sd in advance as follows.
Dynamic mode: 50, standard mode: 100, movie mode: 150, PC mode: 255 (maximum value).
Furthermore, it is assumed that the above four modes are associated with the count determination threshold value Sc in advance as follows. Here, it is assumed that each area includes 25 pixels.
Dynamic mode: 5, standard mode: 10, movie mode: 15, PC mode: 25 (maximum value).
At this time, if the movie mode is selected by the user, the following operation is performed. The data determination threshold setting unit 171 outputs the data setting signal S1 so that the data determination threshold Sd is set to “150” that is a value associated with the movie mode. Based on the data setting signal S1, the value “150” is stored in the data determination threshold storage unit 155 as the data determination threshold Sd. The count determination threshold value setting unit 172 outputs the count setting signal S2 so that the count determination threshold value Sc is set to “15” that is a value associated with the movie mode. Based on the count setting signal S2, the value “15” is stored in the count determination threshold storage unit 157 as the count determination threshold Sc.

As described above, according to the present embodiment, the data determination threshold Sd and the count determination threshold Sc are set according to the mode selected by the user (indicating the state of the liquid crystal display device 10).

Also in this embodiment, as in the first to fourth embodiments, there are various methods for obtaining the LED output value of each area based on the comparison result (the first to first embodiments of the first embodiment). 3) can be adopted.

<5.3 Modification>
In the present modification, the area active drive processing unit 15 is configured as shown in FIG. 39 as in the fifth embodiment. In this modification, the data determination threshold setting unit 171 outputs a data setting signal S1 according to the content set by the user using a remote controller or the like. Similarly, the count determination threshold setting unit 172 outputs the count setting signal S2 according to the content set by the user using a remote controller or the like.

For example, it is assumed that the liquid crystal display device 10 is provided with a function of selecting (by the user) the peak luminance from four options of “high”, “medium”, “low”, and “off”. Then, it is assumed that the above four options and the data determination threshold Sd are associated in advance as follows.
High: 50, Medium: 100, Low: 200, Off: 255.
Furthermore, it is assumed that the above four options are associated with the count determination threshold value Sc in advance as follows. Here, it is assumed that each area includes 25 pixels.
High: 5, Medium: 10, Low: 15, Off: 25.
At this time, if the option “high” is selected by the user, the following operation is performed. The data determination threshold setting unit 171 outputs the data setting signal S1 so that the data determination threshold Sd is set to “50”, which is a value associated with the option “high”. Based on the data setting signal S1, the value “50” is stored in the data determination threshold storage unit 155 as the data determination threshold Sd. The count determination threshold value setting unit 172 outputs the count setting signal S2 so that the count determination threshold value Sc is set to “5” that is a value associated with the option “high”. Based on the count setting signal S2, the value “5” is stored in the count determination threshold storage unit 157 as the count determination threshold Sc.

As described above, according to the present modification, the data determination threshold Sd and the count determination threshold Sc are set according to the content set by the user using a remote controller or the like.

<6. Other>
In the above embodiments, the liquid crystal display device has been described as an example, but the present invention is not limited to this. In any image display device that includes a backlight and performs area active drive, the same effect as that of a liquid crystal display device can be obtained by obtaining the LED output value of each area as described above.

Further, in each of the above embodiments, the process for calculating the LED output value using the maximum value or the average value of the luminance data is performed, but the present invention is not limited to this, and the gradation is not limited to this. Processing for calculating the LED output value may be performed using the maximum value, the average value, or the like for the data.

Furthermore, in each of the above embodiments, it is assumed that three colors of RGB LEDs (red LED 23, green LED 24, and blue LED 25 in FIG. 3) are used as the backlight 13. However, the present invention can also be applied to a configuration in which a white LED is used as the backlight 13. In this case, there are two possible methods for obtaining the LED data 33 to be given to the backlight drive circuit 14. The first method is a method in which LED output values are obtained for each of the R image, G image, and B image, and the maximum value among the obtained three LED output values is used as the LED data 33. In the second method, the maximum value of the RGB data is extracted for each pixel (for each unit pixel), and the LED output value obtained using the extracted maximum value (for all pixels) is set as the LED data 33. It is a method to do. The first method is preferable from the viewpoint of versatility, and the second method is preferable from the viewpoint of circuit scale and cost.

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 11 ... Liquid crystal panel 12 ... Panel drive circuit 13 ... Backlight 14 ... Backlight drive circuit 15 ... Area active drive processing part 16 ... RGB signal processing part 31 ... Input image 32 ... Liquid crystal data 33 ... LED data 35 ... Comparison results 40, 41 ... Histogram 150 ... Backlight data processing section 151 ... Area data extraction section 152 ... Area maximum value calculation section 153 ... Area average value calculation section 154 ... Data comparison section 155 ... Data determination threshold storage section 156 ... Count extraction / comparison unit 157 ... Count determination threshold storage unit 158 ... LED output value calculation unit 159 ... Liquid crystal data calculation unit Ma ... Area maximum value Me ... Area average value Sc ... Count determination threshold Sd ... Data determination threshold

Claims

An image display device having a function of controlling the brightness of a backlight,
A display panel including a plurality of display elements;
A backlight including a plurality of light sources;
A backlight data processing unit that divides the input image into a plurality of areas and obtains backlight data indicating the luminance of the light source corresponding to each area based on the input image;
A display data calculation unit for obtaining display data for controlling the light transmittance of the display element based on the input image and the backlight data;
A panel drive circuit that outputs a signal for controlling the light transmittance of the display element to the display panel based on the display data;
A backlight driving circuit that outputs a signal for controlling the luminance of the light source to the backlight based on the backlight data;
The backlight data processing unit
An area data extraction unit that extracts a plurality of pixel data included in each area from the input image as area data;
Based on the area data, an area maximum value detection unit that detects the maximum value of the plurality of pixel data values as an area maximum value;
Based on the area data, an area average value calculation unit that calculates an average value of the values of the plurality of pixel data as an area average value;
The backlight data is obtained using the value obtained based on the value of each pixel data included in the area data or the value of each pixel data included in the area data as a first comparison value for the pixel data. A first comparison unit that compares with a first threshold value provided for the purpose, and obtains the number of pixel data for which a predetermined relationship is established as a count value;
A second threshold value provided for obtaining the backlight data using a value obtained based on the count value for each area or the count value itself for each area as a second comparison value for each area. A second comparison unit for comparing with,
An image display device comprising: a backlight data calculation unit that obtains the backlight data according to a comparison result by the second comparison unit for each area.
2. The image display device according to claim 1, wherein the area data extraction unit extracts the area data from an image after a process for reducing the resolution is performed on the input image.
2. The image display device according to claim 1, wherein the pixel data is data representing a gradation value or a luminance value.
The first comparison unit obtains, as the count value, the number of pixel data in which the first comparison value is greater than or equal to the first threshold value, or the first comparison value is greater than the first threshold value. The image display device according to claim 1, wherein the number of pixel data having a larger value is obtained as the count value.
For the area where the second comparison value is equal to or greater than the second threshold, the backlight data calculation unit sets the value corresponding to the area maximum value as the backlight data, or the second comparison The image display apparatus according to claim 1, wherein a value corresponding to the area maximum value is set as the backlight data for an area whose value is larger than the second threshold value.
The backlight data calculation unit sets a constant value as the backlight data for an area where the second comparison value is greater than or equal to the second threshold value, or the second comparison value is the second comparison value. The image display device according to claim 1, wherein a constant value is used as the backlight data for an area larger than a threshold value.
The image display device according to claim 6, wherein the constant value is a maximum value that the pixel data can take.
For the area where the second comparison value is less than or equal to the second threshold, the backlight data calculation unit sets the value corresponding to the area average value as the backlight data, or the second comparison The image display apparatus according to claim 1, wherein a value corresponding to the area average value is used as the backlight data for an area having a value smaller than the second threshold value.
The backlight data calculation unit sets a constant value as the backlight data for an area where the second comparison value is equal to or less than the second threshold value, or the second comparison value is the second comparison value. The image display device according to claim 1, wherein a constant value is used as the backlight data for an area smaller than a threshold value.
10. The image display device according to claim 9, wherein the constant value is a minimum value that can be taken by the pixel data.
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is smaller than the second threshold value. For the area, the value corresponding to the area average value is the backlight data, or
For an area where the second comparison value is larger than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is equal to or less than the second threshold value. The image display device according to claim 1, wherein a value corresponding to the area average value is used as the backlight data for the area.
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, the maximum possible value of the pixel data is the backlight data, and the second comparison value is greater than the second threshold value. For a small area, the value corresponding to the area average value is the backlight data, or
For an area where the second comparison value is larger than the second threshold value, the maximum value that the pixel data can take is the backlight data, and the second comparison value is less than or equal to the second threshold value. The image display device according to claim 1, wherein a value corresponding to the area average value is set as the backlight data for a certain area.
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is smaller than the second threshold value. For the area, the minimum value that the pixel data can take is the backlight data, or
For an area where the second comparison value is larger than the second threshold value, a value corresponding to the area maximum value is used as the backlight data, and the second comparison value is equal to or less than the second threshold value. The image display device according to claim 1, wherein a minimum value that the pixel data can take for the area is the backlight data.
The backlight data calculation unit obtains an area where the second comparison value is greater than or equal to the second threshold based on at least the area maximum value, the maximum value that the pixel data can take, and the count value. A value to be obtained as the backlight data, or at least the area maximum value, the maximum possible value of the pixel data, and the count value for an area where the second comparison value is larger than the second threshold value The image display device according to claim 1, wherein a value obtained based on the above is used as the backlight data.
15. The image according to claim 14, wherein the backlight data calculation unit calculates the backlight data by the following formula for an area where the second comparison value is equal to or greater than the second threshold value. Display device.
E1 = (Ma · (Da-Cnt) + Dmax · (Cnt-Sc)) / (Da-Sc)
Here, E1 represents the value of the backlight data, Ma represents the maximum area value, Da represents the number of pixel data in the area, Cnt represents the count value, and Dmax represents the capture of the pixel data. Represents the maximum value obtained, and Sc represents the second threshold.
15. The image according to claim 14, wherein the backlight data calculation unit calculates the backlight data by the following formula for an area where the second comparison value is larger than the second threshold value. Display device.
E1 = (Ma · (Da-Cnt) + Dmax · (Cnt-Sc-1)) / (Da-Sc-1)
Here, E1 represents the value of the backlight data, Ma represents the maximum area value, Da represents the number of pixel data in the area, Cnt represents the count value, and Dmax represents the capture of the pixel data. Represents the maximum value obtained, and Sc represents the second threshold.
The backlight data calculation unit calculates a value obtained based on at least the area maximum value, the area average value, and the count value for an area in which the second comparison value is equal to or less than the second threshold value. For the area where the second comparison value is smaller than the second threshold, a value obtained based on at least the area maximum value, the area average value, and the count value is used as the write data. The image display device according to claim 1, wherein the image display device is write data.
The image display device according to claim 17, wherein the backlight data is calculated by the following formula for an area where the second comparison value is smaller than the second threshold value.
E2 = (Ma · Cnt + Me · (Sc-Cnt)) / Sc
Here, E2 represents the value of the backlight data, Ma represents the area maximum value, Cnt represents the count value, Me represents the area average value, and Sc represents the second threshold value.
The image according to claim 17, wherein the backlight data calculation unit calculates the backlight data by the following formula for an area where the second comparison value is equal to or less than the second threshold value. Display device.
E2 = (Ma · Cnt + Me · (Sc + 1-Cnt)) / (Sc + 1)
Here, E2 represents the value of the backlight data, Ma represents the area maximum value, Cnt represents the count value, Me represents the area average value, and Sc represents the second threshold value.
The backlight data calculation unit
For an area where the second comparison value is equal to or greater than the second threshold value, a value obtained based on at least the area maximum value, the maximum value that can be taken by the pixel data, and the count value is used as the backlight data. In addition, for an area where the second comparison value is smaller than the second threshold value, a value obtained based on at least the area maximum value, the area average value, and the count value is used as the backlight data. Or
For an area where the second comparison value is larger than the second threshold value, a value obtained based on at least the area maximum value, the maximum value that can be taken by the pixel data, and the count value is used as the backlight data. In addition, for an area where the second comparison value is equal to or less than the second threshold value, a value obtained based on at least the area maximum value, the area average value, and the count value is used as the backlight data. The image display device according to claim 1, wherein:
The said 1st comparison part makes the value obtained by subtracting the said area average value from the value of each pixel data contained in the said area data a said 1st comparison value, The said 1st comparison value is characterized by the above-mentioned. The image display device described.
2. The second comparison unit according to claim 1, wherein the second comparison unit uses a value obtained by dividing the count value by the number of pixel data included in each area as the second comparison value. Image display device.
The first comparison unit generates a histogram indicating a distribution of appearance frequencies of values that can be taken by the pixel data based on the area data, and obtains the first threshold value based on the histogram. The image display device according to claim 1.
The second comparison unit generates a histogram showing a distribution of appearance frequencies of each count value obtained by the first comparison unit, and obtains the second threshold based on the histogram. The image display device according to claim 1.
2. The image display device according to claim 1, further comprising a first threshold value setting unit for setting the first threshold value from the outside.
The image display device according to claim 1, further comprising a second threshold value setting unit for setting the second threshold value from the outside.
An image display method in an image display device comprising a display panel including a plurality of display elements and a backlight including a plurality of light sources,
A backlight data processing step of dividing an input image into a plurality of areas and obtaining backlight data indicating luminance of a light source corresponding to each area based on the input image;
A display data calculation step for obtaining display data for controlling light transmittance of the display element based on the input image and the backlight data;
A panel driving step for outputting a signal for controlling the light transmittance of the display element to the display panel based on the display data;
A backlight driving step for outputting a signal for controlling the luminance of the light source to the backlight based on the backlight data;
The backlight data processing step includes
An area data extraction step of extracting a plurality of pixel data included in each area from the input image as area data;
An area maximum value detecting step for detecting a maximum value of the values of the plurality of pixel data as an area maximum value based on the area data;
An area average value calculating step for calculating an average value of the values of the plurality of pixel data as an area average value based on the area data;
The backlight data is obtained using the value obtained based on the value of each pixel data included in the area data or the value of each pixel data included in the area data as a first comparison value for the pixel data. A first comparison step for comparing the first threshold value provided for the purpose and determining the number of pixel data for which a predetermined relationship is established as a count value;
A second threshold value provided for obtaining the backlight data using a value obtained based on the count value for each area or the count value itself for each area as a second comparison value for each area. A second comparison step for comparing with
And a backlight data calculation step for obtaining the backlight data in accordance with a comparison result of the second comparison step for each area.