JP2014052549A - Image display device, control method of image display device, control program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress local breakdown of a display video.SOLUTION: An image display device includes: an LED data calculation unit 22 that specifies an approximation pattern in which brightness distribution of an input image is approximated and the amount of change is equal to or less than a predetermined value, and calculates LED data on the basis of the specified approximation pattern; and a liquid crystal transmittance calculation unit 23 that calculates the liquid crystal transmittance on the basis of the input image and the approximation pattern specified by the LED data calculation unit 22.

Description

  The present invention relates to an image display device having a function of controlling the luminance of a backlight (backlight dimming function), a control method for the image display device, a control program, and a recording medium.

  In an image display device having a backlight, such as a liquid crystal display device, the backlight power consumption is controlled based on the input image, thereby suppressing the power consumption of the backlight or improving the image quality of the display image. it can. 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 an image 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. The luminance of the LED corresponding to each area (luminance at the time of light emission) is obtained based on the maximum value or the average value of the luminance of the pixels in each area, and is provided as LED data to the backlight drive circuit. Further, display data (in the case of a liquid crystal display device, 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 a display panel drive circuit. Given to. In the case of a liquid crystal display device, the luminance of each pixel on the screen is the product of the luminance of light from the backlight and the light transmittance based on the display data.

  Incidentally, light emitted from an LED in a certain area not only irradiates the area but also irradiates surrounding areas. In other words, a certain area is irradiated not only with the light emitted from the LEDs in the area but also with the light emitted from the LEDs in the surrounding area. Therefore, the luminance displayed in each area must be calculated in consideration of the diffusion (spreading) of the light emitted from each LED.

  Therefore, conventionally, there is a method of avoiding the breakdown of the output image by actually measuring the actual luminance distribution, generating a correction table, and correcting the display data. For example, Patent Document 1 describes that for each area, the light transmittance of the display element is calculated based on an input image and display brightness corrected in consideration of diffusion from LED data. Patent Document 2 describes that in area active driving, an input image is corrected and light transmittance is calculated in order to eliminate uneven luminance in adjacent areas.

JP 2009-192963 A (released August 27, 2009) JP 2010-256912 A (published November 11, 2010)

  However, in the conventional technology as described above, it is difficult to completely quantify the actually measured luminance distribution obtained by actual measurement. For this reason, a mismatch between the corrected display luminance and the actually measured luminance may occur, and an appropriate light transmittance may not be calculated. Therefore, the output image may break down.

  Specifically, problems of the prior art will be described with reference to FIGS.

  When the input image 61 shown in FIG. 10 is input, the conventional technology generates LED data shown in FIG. In FIG. 10, the point A is the center point of the white circle, the point B is the right end point of the input image 61, and the point C is the boundary between the white circle (80%) and the background (20%) on the line AB. Point D is a boundary point of the backlight control area on the line AB.

  FIG. 22 shows the liquid crystal transmittance obtained by dividing the LED data from the input image based on the input image 61 and the LED data shown in FIG. However, as described above, when the LED is driven based on the LED data shown in FIG. 21, the luminance distribution is actually as shown in FIG. Therefore, in this case, as shown in FIG. 23, the luminance distribution of the output image is broken in the vicinity of point D.

  Therefore, the above-described conventional technique avoids the breakdown of the luminance distribution of the output image by actually measuring the actual luminance distribution shown in FIG. 24, generating a correction table, and correcting the liquid crystal transmittance with the correction table. is there. The liquid crystal transmittance at this time is shown in FIG. However, it is difficult to completely quantify the luminance distribution shown in FIG. For this reason, the liquid crystal transmittance cannot be appropriately corrected, and the luminance distribution of the output image may break as shown in FIG. In particular, in the prior art, since the LED data and the liquid crystal transmittance of each area are independently controlled, a display video failure occurs locally, such as a halo between CDs as shown in FIG. Sometimes.

  Further, when the measured luminance distribution is reproduced with high accuracy in order to avoid this problem, there arises a problem that the circuit scale for executing the calculation process increases and the cost increases.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to realize an image display device, a control method for the image display device, a control program, and a recording medium that suppress local display video failure. There is.

  In order to solve the above problems, an image display device according to the present invention is an image display device in which a plurality of light sources are arranged along one or two sides of a display panel. Based on the approximate pattern specified by the pattern specifying means, the pattern specifying means for specifying the approximate pattern approximating the luminance distribution of the light source array direction component of the input image from the approximate patterns that are equal to or less than the predetermined value, Light source data calculating means for calculating light source data for controlling the output of the light source, and light transmission for controlling the light transmittance of the display panel based on the input image and the approximate pattern specified by the pattern specifying means A light transmittance calculating means for calculating a rate, a light source driving means for driving the plurality of light sources based on the light source data calculated by the light source data calculating means, and the light transmittance Based on the light transmission rate calculating means has calculated, it is characterized by comprising a display panel driving means for driving the display panel.

  In addition, a method for controlling an image display device according to the present invention is a method for controlling an image display device in which a plurality of light sources are arranged along one or two sides of a display panel in order to solve the above-described problem. A pattern specifying step that specifies an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image from the approximate patterns that are configured with straight lines and whose variation is equal to or less than a predetermined value, and that is specified in the pattern specifying step Based on the approximate pattern, the light source data calculating step for calculating the light source data for controlling the output of the plurality of light sources, and the input image and the approximate pattern specified in the pattern specifying step, Calculated in the light transmittance calculating step for calculating the light transmittance for controlling the light transmittance and the light source data calculating step. A light source driving step for driving the plurality of light sources based on the light source data, and a display panel driving step for driving the display panel based on the light transmittance calculated in the light transmittance calculating step. It is characterized by.

  According to the above configuration, the light source data calculation means is an approximate pattern that is configured by a straight line and whose variation is equal to or less than a predetermined value, and is based on an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image. To calculate light source data. The light transmittance calculating unit calculates the light transmittance based on the same approximate pattern. Since the amount of change between light sources adjacent to each other is less than or equal to a predetermined value, the luminance distribution indicated by the light source data and the actual luminance distribution when the plurality of light sources are driven based on the light source data are greatly different locally. Can be prevented. Therefore, compared to the conventional case, there is an effect that it is possible to prevent the failure of the display image that occurs locally.

  Further, the image display device according to the present invention divides the input image into a plurality of areas, specifies evaluation values indicating the luminance levels of the respective areas, and sets the evaluation values of the respective areas in order. The pattern specifying means refers to pattern specifying information in which a correspondence relationship between the evaluation value sequence and the approximate pattern that is closest to the evaluation value sequence is predetermined, It is preferable to specify an approximate pattern corresponding to the evaluation value sequence generated by the image evaluation unit.

  According to said structure, the said pattern specific | specification means selects the pattern most approximated with an input image from the predetermined approximate patterns. Thus, by approximating the input image to an approximate pattern with a limited number of types, the light source data and liquid crystal transmittance calculation processing can be simplified, and the circuit scale can be reduced.

  In the image display device according to the present invention, it is preferable that the image evaluation unit specifies a maximum value of pixels or picture elements included in the area as an evaluation value of the area.

  In the image display device according to the present invention, it is preferable that the image evaluation unit specifies an average value of pixels or picture elements included in the area as an evaluation value of the area.

  Further, in the image display device according to the present invention, the image evaluation means takes a histogram of pixel values or pixel values included in the area, and determines the largest number of pixel values or pixel values as the evaluation value of the area. It is preferable to specify as.

  Further, in the image display device according to the present invention, the light source data calculating unit specifies the pattern specifying unit when an inversion flag is added to the approximate pattern specified by the pattern specifying unit in the pattern specifying information. It is preferable to calculate the light source data based on a pattern obtained by inverting the approximate pattern.

  According to the above configuration, since an approximate pattern obtained by inverting a certain approximate pattern can be selected by the inversion flag, the type of approximate pattern to be set in advance without reducing the number of applicable approximate pattern types The number can be reduced. Therefore, it is possible to suppress an increase in circuit scale while maintaining the degree of freedom of application.

  In the image display device according to the present invention, the image evaluation unit further specifies an overall evaluation value indicating a luminance level of the entire input image, and the light source data calculation unit includes the pattern specifying unit. Preferably, the light source data is calculated by correcting the offset of the approximate pattern specified by the means based on the overall evaluation value.

  According to the above configuration, an approximate pattern obtained by increasing or decreasing the entire value of a certain approximate pattern can be derived by the offset correction. Therefore, the approximate pattern should be set in advance without reducing the number of applicable approximate patterns. The number of types of approximate patterns can be reduced. Therefore, it is possible to suppress an increase in circuit scale while maintaining the degree of freedom of application.

  The light transmittance calculating means preferably calculates the light transmittance based on the following equation.

LCD_rate (i, j) = Offset + Pat_Max-LCD_Pat_ # j if (revers = '0')
= Offset + LED_Pat_ # n if (revers = '1')
Assist (i, j, c) = (1-Cin (i, j, c)) * LCD_rate (i, j) * K
Cout (i, j, c) = Cin (i, j, c) + (Cin (i, j, c) * Assist (i, j, c))
Cin (i, j, c): Pixel value of pixel in i row and j column of the input image
Cout (i, j, c): Light transmittance of picture element of pixel in i row and j column
K: Any value
Offset: Overall evaluation value indicating the brightness of the entire input image
Pat_Max: Maximum value of approximate pattern
LCD_Pat_ # j: Output value of pixels in column j in the approximate pattern
revers: reversal flag In order to solve the above-mentioned problem, the image display device according to the present invention is an image display device in which a plurality of light sources are arranged in a matrix on the back surface of the display panel, each of which is configured by a straight line. The horizontal component approximate pattern that approximates the luminance distribution of the horizontal component of the input image and the vertical component that approximates the luminance distribution of the vertical component of the input image from among the horizontal component approximate pattern and vertical component approximate pattern whose variation is equal to or less than a predetermined value Light source data for calculating light source data for controlling the outputs of the plurality of light sources based on a pattern specifying unit for specifying each component approximate pattern and a horizontal component approximate pattern and a vertical component approximate pattern specified by the pattern specifying unit Near the horizontal component approximate pattern and vertical component specified by the calculating means, the input image and the pattern specifying means Based on the similar pattern, the light transmittance calculating means for calculating the light transmittance for controlling the light transmittance of the display panel, and the plurality of light sources based on the light source data calculated by the light source data calculating means. A light source driving unit for driving and a display panel driving unit for driving the display panel based on the light transmittance calculated by the light transmittance calculating unit are provided.

  The image display device may be realized by a computer. In this case, a control program for causing the image display device to be realized by the computer by causing the computer to operate as each unit of the image display device, and A computer-readable recording medium on which it is recorded also falls within the scope of the present invention.

  As described above, the image display device according to the present invention specifies an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image from the approximate patterns that are configured with straight lines and whose variation is equal to or less than a predetermined value. A light source data calculating means for calculating light source data for controlling the outputs of the plurality of light sources based on the approximate pattern specified by the pattern specifying means, the input image and the pattern specifying means. Based on the identified approximate pattern, the light transmittance calculating means for calculating the light transmittance for controlling the light transmittance of the display panel, and the light source data calculated by the light source data calculating means, Light source driving means for driving the light source, and display panel driving means for driving the display panel based on the light transmittance calculated by the light transmittance calculating means. And is a configuration that.

  In addition, the control method for the image display device according to the present invention specifies an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image from the approximate patterns that are configured with straight lines and whose variation is equal to or less than a predetermined value. A pattern specifying step, a light source data calculating step for calculating light source data for controlling outputs of the plurality of light sources based on the approximate pattern specified in the pattern specifying step, and the input image and the pattern specifying step. On the basis of the approximate pattern identified in step, based on the light transmittance calculation step for calculating the light transmittance for controlling the light transmittance of the display panel, and on the light source data calculated in the light source data calculation step, Light calculated in the light source driving step for driving the plurality of light sources and the light transmittance calculating step Based on the excessive rate, and a display panel driving step of driving the display panel.

  Therefore, compared to the conventional case, there is an effect that it is possible to prevent the failure of the display image that occurs locally.

1, showing an embodiment of the present invention, is a block diagram illustrating a main configuration of a liquid crystal display device. FIG. It is a flowchart which shows an example of the display process which the said liquid crystal display device performs. It is a figure which shows the outline | summary of the example of a process of the image evaluation part of the said liquid crystal display device. It is a figure which shows an example of an approximate pattern. It is a figure which shows an example of the pattern specific information which shows the correspondence of an evaluation value sequence (Index) and an approximate pattern. It is a figure which shows the output value of each LED in an approximate pattern. It is a figure which shows a certain approximate pattern and the approximate pattern which reversed the said approximate pattern. It is a figure which shows a certain approximate pattern and the approximate pattern which carried out the offset correction | amendment of the said approximate pattern. It is a figure which shows the relationship between the pixel value of an input image, and a liquid crystal transmittance. It is a figure which shows an example of an input image. It is a figure which shows an example of the LED data which the LED data calculation part calculated when the input image shown in FIG. 10 is input. It is a figure which shows actual luminance distribution when an LED driver drives LED based on the LED data shown in FIG. FIG. 11 is a diagram illustrating a liquid crystal transmittance calculated by a liquid crystal transmittance calculating unit when the input image shown in FIG. 10 is input. It is a figure which shows display luminance distribution when a LED driver drives LED based on the LED data shown in FIG. 11, and a liquid crystal driver drives a liquid crystal panel based on the liquid crystal transmittance shown in FIG. It is a figure which shows LED arranged on 2 sides of a liquid crystal panel. It is a figure which shows two types of evaluation areas (a horizontal component evaluation area and a vertical component evaluation area). It is a figure which shows an example of an input image. It is a figure which shows an example of the approximate pattern of the horizontal component specified from the input image shown in FIG. 17, and the approximate pattern of a vertical component. It is a figure which shows LED arranged in the matrix form on the back surface of a liquid crystal panel. It is a figure which shows the time change of each LED data with respect to the several input image input continuously. It is a figure which shows a prior art and shows an example of LED data when the input image shown in FIG. 10 is input. It is a figure which shows a prior art and shows the liquid-crystal transmittance | permeability at the time of the input image shown in FIG. 10 being input. FIG. 21 shows a conventional technique, and shows a display luminance distribution when the LED driver drives an LED based on the LED data shown in FIG. 21 and the liquid crystal driver drives a liquid crystal panel based on the liquid crystal transmittance shown in FIG. FIG. It is a figure which shows a prior art and shows actual luminance distribution when an LED driver drives LED based on the LED data shown in FIG. It is a figure which shows a prior art and shows the liquid-crystal transmittance | permeability correct | amended in consideration of actual luminance distribution, when the input image shown in FIG. 10 is input. FIG. 21 shows a conventional technique, and shows a display luminance distribution when the LED driver drives an LED based on the LED data shown in FIG. 21 and the liquid crystal driver drives a liquid crystal panel based on the liquid crystal transmittance shown in FIG. FIG. It is a figure which shows an example of LED element information with which the approximate pattern and the element information for calculating the output value corresponding to each LED were matched. It is a figure which shows an example of the LCD element information with which the approximate pattern and the element information for calculating the output value corresponding to each pixel were matched.

  An embodiment of the present invention will be described below with reference to FIGS.

[Configuration of liquid crystal display device]
FIG. 1 is a block diagram illustrating an example of a main configuration of a liquid crystal display device (image display device) 1. As shown in FIG. 1, the liquid crystal display device 1 includes a control unit 11, a liquid crystal panel (display panel) 12, an LED (light source) 13, a liquid crystal driver (display panel driving unit) 14, and an LED driver (light source driving unit) 15. I have.

  The liquid crystal panel 12 is a liquid crystal display element in which pixels are arranged in a matrix. Each pixel includes a sub-pixel (sub-pixel) provided with a color filter that transmits red (R), green (G), and blue (B) light. The liquid crystal panel 12 has a display surface on which an image can be displayed.

  Note that the number of colors of the color filter arranged in the sub-pixel is not limited to the above-described three colors, and may be two colors or four colors, for example. In the present embodiment, the number of pixels of the liquid crystal panel 12 is assumed to be 1920 × 1080 (full HD). However, the present invention is not limited to this, and the number of pixels of the liquid crystal panel 12 may be arbitrary.

  The LED 13 irradiates light from the back surface (surface opposite to the image display surface) side of the liquid crystal panel 12 through the light guide plate. That is, the LED 13 functions as a backlight. The LED 13 is disposed along one long side of the liquid crystal panel 12 as shown in FIG. In the present embodiment, it is assumed that 48 LEDs are arranged.

  The light source used as the backlight of the liquid crystal display device 1 is not limited to the LED, and may be an arbitrary light source. In this embodiment, the edge light method is adopted and the LEDs 13 are arranged only on one long side of the liquid crystal panel 12, but the present invention is not limited to this. For example, you may arrange | position LED13 along two sides of the long side of the liquid crystal panel 12, and a short side. Further, a direct type may be adopted and the LED 13 may be disposed on the back side of the liquid crystal panel 12. In the present embodiment, 48 LEDs 13 are arranged, but the number of LEDs 13 to be used may be arbitrary.

  The liquid crystal driver 14 is a drive circuit that drives the liquid crystal panel 12 based on an instruction from the control unit 11. Specifically, the liquid crystal driver 14 applies a voltage to each pixel (each subpixel) of the liquid crystal panel 12 and controls the liquid crystal transmittance of each pixel (each subpixel).

  The LED driver 15 is a drive circuit that drives each LED 13 based on an instruction (LED data) from the control unit 11. That is, the LED driver 15 controls the intensity of light emitted from each LED 13. More specifically, the LED driver 15 acquires an LED data string from the control unit 11, and controls the output of each LED 13 based on the acquired LED data string. Here, the LED data string is an array of LED data indicating the output of each LED 13 in the order in which the LEDs 13 are arranged. That is, in the present embodiment, the LED data string is an array of 48 LED data.

  The control unit 11 includes a microcomputer and controls the entire liquid crystal display device 1 by controlling each unit included in the liquid crystal display device 1. In the present embodiment, the control unit 11 includes, as functional blocks, an image evaluation unit (image evaluation unit) 21, an LED data calculation unit (pattern specifying unit, light source data calculation unit) 22, and a liquid crystal transmittance calculation unit (light transmittance calculation). Means) 23 is provided. Each functional block (21 to 23) of the control unit 11 includes a CPU (central processing unit) that stores a program stored in a storage device realized by a ROM (read only memory) or the like (RAM (random access memory)). It may be realized by reading out to a temporary storage unit realized by the above or the like and executing it. Each functional block (21 to 23) may be realized not by software but by hardware.

  The image evaluation unit 21 acquires an input image from the outside of the liquid crystal display device 1 and analyzes the acquired input image. Specifically, the image evaluation unit 21 divides the input image into a plurality of areas, specifies the evaluation values of each area, and generates an evaluation value sequence in which the evaluation values of each area are arranged in order. At the same time, the image evaluation unit 21 specifies the evaluation value of the entire input image. Here, the evaluation value is an index indicating the luminance level of a certain area. The image evaluation unit 21 outputs the evaluation value sequence to the LED data calculation unit 22 and outputs the evaluation value of the entire input image to the liquid crystal transmittance calculation unit 23. The image evaluation unit 21 may further output an evaluation value of the entire input image to the LED data calculation unit 22. Hereinafter, the evaluation value of the entire input image is referred to as an overall evaluation value.

  The LED data calculation unit 22 calculates LED data (light source data) based on the analysis result of the image evaluation unit 21. Specifically, the LED data calculation unit 22 acquires an evaluation value sequence from the image evaluation unit 21, identifies an approximate pattern (details will be described later) corresponding to the evaluation value sequence, and obtains LED data from the identified approximate pattern. calculate. The LED data calculation unit 22 outputs the calculated LED data to the LED driver 15. Further, the LED data calculation unit 22 outputs the specified approximate pattern to the liquid crystal transmittance calculation unit 23.

  In addition, when acquiring the evaluation value sequence and the overall evaluation value from the image evaluation unit 21, the LED data calculation unit 22 specifies an approximate pattern corresponding to the evaluation value sequence, and offset-corrects the approximate pattern based on the overall evaluation value. LED data is calculated.

  The liquid crystal transmittance calculation unit 23 acquires an input image from the outside of the liquid crystal display device 1, acquires an overall evaluation value from the image evaluation unit 21, and acquires an approximate pattern from the LED data calculation unit 22. Then, the liquid crystal transmittance calculating unit 23 calculates a correction coefficient from the acquired input image, approximate pattern, and overall evaluation value, and based on the acquired input image and the calculated correction coefficient, the liquid crystal transmittance (light transmittance). Is calculated. The liquid crystal transmittance calculating unit 23 outputs the calculated liquid amount transmittance to the liquid crystal driver 14.

  Note that the image evaluation unit 21 and the liquid crystal transmittance calculation unit 23 acquire an input image from the outside of the liquid crystal display device 1, but are not limited thereto. When the liquid crystal display device 1 includes a storage unit (not shown), the image evaluation unit 21 and the liquid crystal transmittance calculation unit 23 may read an image from the storage unit and acquire an input image.

[Display processing of liquid crystal display devices]
Next, an example of display processing executed by the liquid crystal display device 1 will be described with reference to FIG. FIG. 2 is a flowchart illustrating an example of display processing executed by the liquid crystal display device 1.

  As shown in FIG. 2, first, the image evaluation unit 21 and the liquid crystal transmittance calculation unit 23 acquire an input image from the outside of the liquid crystal display device 1 (S1). Next, the image evaluation unit 21 divides the acquired input image into a plurality of areas (S2). And the image evaluation part 21 specifies the evaluation value of each area, respectively, and produces | generates the evaluation value row | line | column which arranged the evaluation value of each area in order (S3). Further, the image evaluation unit 21 specifies an overall evaluation value from the input image (S4).

  Next, the LED data calculation unit 22 specifies an approximate pattern corresponding to the evaluation value sequence generated by the image evaluation unit 21 (S5), and calculates LED data from the specified approximate pattern (S6).

  Further, the liquid crystal transmittance calculation unit 23 calculates a correction coefficient from the acquired input image, the approximate pattern specified by the LED data calculation unit 22 and the overall evaluation value specified by the image evaluation unit 21, and calculates the acquired input image. The liquid crystal transmittance is calculated based on the correction coefficient (S7).

  The LED driver 15 drives the LED 13 based on the LED data calculated by the LED data calculation unit 22, and the liquid crystal driver 14 drives the liquid crystal panel 12 based on the liquid crystal transmittance calculated by the liquid crystal transmittance calculation unit 23. Drive (S8).

  If there is a next input image (YES in S9), the above S1 to S8 are repeated, and if there is no next input image (NO in S9), the display process is terminated.

〔Example〕
Next, more specific processing examples of the image evaluation unit 21, the LED data calculation unit 22, and the liquid crystal transmittance calculation unit 23 will be described with reference to FIGS.

  Here, it is assumed that the input image has 0 to 255 (8 bit) gradation, the pixel is one pixel including RGB, and the picture element is an R, G, B subpixel. The value of the LED data is assumed to be 10 bits from 0 to 1023.

(Example of processing by the image evaluation unit)
First, a processing example of the image evaluation unit 21 will be described with reference to FIG. FIG. 3 is a diagram illustrating an outline of a processing example of the image evaluation unit 21.

  As shown in FIG. 3B, the image evaluation unit 21 divides the input image 41 shown in FIG. 3A into five areas 41a to 41e perpendicular to the long side direction. However, the method of dividing the input image is not limited to this. In the present embodiment, since the LEDs 13 are arranged along the long side direction of the liquid crystal panel 12, the input image 41 is divided perpendicularly to the long side direction. For example, when the LEDs 13 are arranged along the short side direction of the liquid crystal panel 12, the input image 41 is divided perpendicularly to the short side direction.

  Further, if the input image is divided perpendicularly to the direction in which the LEDs 13 are arranged, the number of areas, the area, and the like may be arbitrary. For example, in the example shown in FIG. 3B, the area is divided into five areas 41a to 41e, but may be a plurality of areas. In the example shown in FIG. 3B, the input image 41 is divided into five equal parts, but the five areas 41a to 41e may be different from each other. The number of areas is desirably an odd number in order to obtain an evaluation value at the center of the input image. Further, the accuracy of evaluation increases as the number of areas increases. However, if the number of areas exceeds the number of LEDs 13, the accuracy of evaluation is not improved.

  Next, a method for specifying the evaluation value will be described. In this embodiment, first, the image evaluation unit 21 extracts the maximum value of the pixel values in the area for each of the areas 41a to 41e and sets it as a representative value. For example, if there are n pixels in the area 41a and R1, G1, B1 = (10, 20, 30),..., Rn, Gn, Bn = (100, 150, 100), the maximum value is obtained. 150 is a representative value of the area 41a.

  Here, the representative value extraction method is not limited to the above-described example. For example, the pixel value in the area may be referred to instead of the pixel value in the area. Further, an average value of pixel values or pixel values in the area may be used as the representative value. In addition, a histogram of pixel values or pixel values in the area may be taken, and the largest number of pixel values or pixel values may be used as representative values. In addition, the value of an arbitrary pixel or picture element in the area may be used as the representative value.

  Next, the image evaluation unit 21 does not use the extracted representative value as it is as the evaluation value, but divides 0 to 255 into a plurality of levels and sets the value of the level corresponding to the representative value as the evaluation value. Specifically, 0 to 255 are divided into four equal parts, 0 to 63 are “level 0”, 64 to 127 are “level 1”, 128 to 191 are “level 2”, and 192 to 255 are “level 3”. To do. For example, since the representative value of the area 41a is 150, the evaluation value of the area 41a is “2”.

  In this way, the image evaluation unit 21 specifies the evaluation values of the areas 41a to 41e, and generates the evaluation value string (Index) by arranging the specified evaluation values in order. Here, it is assumed that the evaluation value sequence is “2, 3, 3, 3, 2” as shown in FIG.

  Note that the level classification method described above may be arbitrary. In this embodiment, 0 to 255 is divided into four equal parts, but the number of levels, the level range, etc. may be arbitrary. Also, the representative value may be used as the evaluation value as it is without being divided into levels.

  Finally, the image evaluation unit 21 specifies the maximum value of the picture elements included in the input image 41 as the overall evaluation value (Frame Level). Here, it is assumed that the overall evaluation value is “200”. The method for specifying the overall evaluation value may be the same as the method for extracting the representative value.

  As described above, the image evaluation unit 21 divides and evaluates the input image 41 into predetermined areas, and digitizes the input image 41 in the form of an evaluation value sequence. With respect to the direction in which the LEDs 13 are arranged, the luminance distribution of the input image 41 can be grasped as a large tendency such as rising to the right, rising to the left, partial or uniform, and can be handled as a numerical value. That is, the image evaluation unit 21 approximates and digitizes the luminance distribution of the input image 41 with respect to the direction in which the LEDs 13 are arranged. Note that the luminance distribution of the input image 41 is a distribution of luminance magnitude when the input image 41 is displayed, and corresponds to a distribution of pixel values or pixel values of the input image 41.

(Processing example of LED data calculation unit)
First, the approximate pattern will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of the approximate pattern. An approximate pattern is composed of straight lines and the amount of change is not more than a predetermined value. In addition, as shown in FIG. 4, a plurality of types of approximate patterns are set in advance. In this embodiment, the approximate pattern is composed of four straight lines, and the inclination of each straight line is equal to or less than a predetermined value.

  Further, as shown in FIG. 5, the correspondence between the evaluation value sequence (Index) and the approximate pattern is set in advance. The LUT (Look Up Table) indicating the correspondence between the evaluation value string (Index) and the approximate pattern shown in FIG. 5 is referred to as pattern specifying information. In FIG. 5, an evaluation value string and an identification number (type number) indicating the type of the approximate pattern are associated with each other. Further, “Revers” shown in FIG. 5 means upside down of the approximate pattern, which will be described in detail later.

  Here, for each evaluation value string (“00000” to “33333”), the pattern specifying information is set by associating the approximate pattern that most closely approximates the shape obtained by connecting the values of the evaluation value string with a straight line. In other words, the pattern specifying information is set by associating each evaluation value sequence (“00000” to “33333”) with the approximate pattern that most closely approximates the graph shape.

  That is, the LED data calculation unit 22 identifies an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image from the approximate patterns that are configured with straight lines and whose variation is equal to or less than a predetermined value. In the present embodiment, the light source arrangement direction component is the long side direction (horizontal direction).

  The number of types of approximate patterns and the number of straight lines constituting the approximate pattern may be arbitrary. In this embodiment, the approximate pattern is composed of four straight lines, and each straight line is a “straight line having 0 slope”, a “right-up line”, and a “right-up line”. In this case, 81 types of approximate patterns can be prepared, and all or some of them are adopted as approximate patterns. By increasing the number of types of approximate patterns, dimming suitable for an input image (video) becomes possible.

  However, if the number of types of approximate patterns is increased, matching with the evaluation value sequence (Index) becomes difficult, and the circuit scale increases. In addition, if the number of straight lines that make up the approximate pattern increases, more complex patterns are used, and complex and large luminance changes are likely to occur in a narrow range, and the backlight light appears to have uneven luminance. There is. Furthermore, when the number of types of approximate patterns is increased, there is a higher risk that the video will fail due to the occurrence of incompatibility with the liquid crystal correction. For these reasons, it is appropriate that the number of straight lines constituting the approximate pattern is 3 to 5.

  As described above, the LED data calculation unit 22 predetermines the approximate pattern and the pattern specifying information indicating the correspondence between the evaluation value sequence and the approximate pattern. Then, the LED data calculation unit 22 refers to the pattern identification information and identifies an approximate pattern corresponding to the evaluation value sequence acquired from the image evaluation unit 21. In the pattern specifying information, when the reverse flag is added to the approximate pattern (when “Revers” is “1”), the LED data calculation unit 22 determines the shape of the approximate pattern corresponding to the evaluation value sequence. It is assumed that the approximate pattern obtained by vertically inverting is specified.

  A specific example in which the LED data calculation unit 22 calculates LED data (LED data string) from the specified approximate pattern will be described below.

  The LED data calculation unit 22 refers to the LED element information in which the approximate pattern and the element information for calculating the output value corresponding to each LED 13 are associated, and approximates from the element information corresponding to the identified approximate pattern. The output value of each LED 13 in the pattern is calculated.

  The LED data calculation unit 22 sets LED element information in advance. Here, the element information for calculating the output value of each LED 13 is an approximate pattern when the shape of the approximate pattern is applied to a graph in which the horizontal axis indicates the LED number and the vertical axis indicates the output value of each LED 13. These are the starting point and inclination of each straight line that constitutes, and the maximum value of the approximate pattern. For example, the LED element information may be an LUT as shown in FIG.

  In this embodiment, the approximate pattern is composed of four straight lines (Line_A to Line_D), so as shown in FIG. The maximum value (Pat_Max) is described as element information.

  In addition, said LED number shows the order from the end (this embodiment left end of FIG. 1) in which LED13 is arranged. In addition, it is assumed that the correspondence relationship between the straight line constituting the approximate pattern and the LED number is set in advance. In this embodiment, since the approximate pattern is composed of four straight lines, each LED 13 is equally classified into four groups A to D in the arrangement order. That is, the LED # 0 to # 11, LED # 12 to # 23, LED # 24 to # 35, and LED # 36 to # 47 are classified. LED # n indicates the LED number, and in this embodiment, the head is “0”.

  In this embodiment, the LEDs 13 are classified equally, but the present invention is not limited to this, and the number of LEDs 13 included in the group may be arbitrary.

  As shown in FIG. 6, the LED data calculation unit 22 calculates the output value of each LED 13 in the approximate pattern based on the element information (start points 51 to 54 and inclinations 55 to 58) associated with the identified approximate pattern. To do.

  Specifically, the output value corresponding to each LED 13 in the approximate pattern is calculated for each group as follows.

LED_Pat_ # n = Start + Step × LED_Group_ # m
Here, “LED_Pat_ # n” indicates the output value of the nth LED 13 in the approximate pattern. LED_Group_ # m indicates the order from the end of the LED in the group, and the head is 0th.

For example, as shown in FIG. 6, when the value of the starting point 51 of group A is “0” and the slope is “512/12”, the output value of the LED 13 with LED number # 6 is
LED_Pat_ # 6 = 0 + 512/12 × 6 = 256
It becomes. If the value of the start point 52 of the group B is “512” and the inclination is “0”, the output value of the LED 13 with the LED number # 14 is the third in the group B.
LED_Pat_ # 14 = 512 + 0 × 3 = 512
It becomes.

  When the inversion flag is not added to the approximate pattern, the LED data calculation unit 22 uses the output value of each LED 13 in the approximate pattern as LED data as it is. That is, LED_Data_ # n = LED_Pat_ # n. Here, “LED_Data_ # n” indicates the LED data of the nth LED 13.

  In addition, in the pattern specifying information, when an inversion flag is added to the approximate pattern, the LED data calculation unit 22 calculates the LED data of each LED 13 as follows (see FIG. 7). Specifically, LED_Data_ # n = Pat_Max−LED_Pat_ # n.

  Moreover, when acquiring the evaluation value sequence and the overall evaluation value from the image evaluation unit 21, the LED data calculation unit 22 performs the offset correction on the output value of each LED 13 in the approximate pattern as follows to calculate the LED data ( (See FIG. 8). Specifically, LED_Data_ # n = LED_Pat_ # n + (Offset−Pat_Max). Here, “Offset” is a value obtained by converting an 8-bit overall evaluation value (Frame Level) to 10 bits.

  Thus, by setting the output value of each LED 13 corresponding to the approximate pattern with the above LED element information, the circuit scale can be reduced as compared with the case where each value is held in the LUT. Even if the number of LEDs 13 increases, the scale of element information does not increase.

  In addition, an approximate pattern obtained by inverting an approximate pattern vertically and an approximate pattern obtained by increasing or decreasing the entire value of the approximate pattern are obtained by calculation. Thereby, the number of types of approximate patterns can be reduced, and the scale of the LED element information can be reduced.

  In the present invention using the approximate pattern, the degree of freedom of backlight control is reduced as compared with the conventional method. However, the above-described device can improve the degree of freedom while suppressing an increase in circuit scale.

  As described above, by calculating the LED data based on the approximate pattern that most closely approximates the luminance distribution of the input image and the change amount is equal to or less than a predetermined value, it is possible to prevent the failure of the display video that occurs locally. In addition, an approximate pattern is selected according to a large tendency of the luminance distribution of the input image, and the degree of freedom of the LED data is lowered, that is, the LED data is limited. Thereby, calculation of the output (LED data) of the LED actually output can be simplified, and the circuit scale can be reduced.

  Furthermore, by changing the approximate pattern to be set according to the model of the liquid crystal display device 1, various requests can be flexibly met. In general, the luminance diffusion filter used in the prior art needs to be recreated if the optical system is different. By using the present invention, an optical simulation for each liquid crystal display device and a luminance diffusion filter for each optical system are used. Is no longer necessary.

  In other words, the LED data calculation unit 22 specifies and specifies an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image from the approximate patterns that are configured with straight lines and the change amount is equal to or less than a predetermined value. It can be said that LED data for controlling the outputs of the plurality of LEDs 13 is calculated based on the approximate pattern.

(Processing example of liquid crystal transmittance calculation unit)
Next, a processing example of the liquid crystal transmittance calculating unit 23 will be described. The liquid crystal transmittance calculation unit 23 calculates the liquid crystal transmittance as follows based on the input image, the overall evaluation value, and the approximate pattern.

  First, an output value corresponding to each pixel is calculated in the approximate pattern. Specifically, the liquid crystal transmittance calculating unit 23 refers to the LCD element information in which the approximate pattern and the element information for calculating the output value corresponding to each pixel are associated, and corresponds to the identified approximate pattern. The output value of each pixel in the approximate pattern is calculated from the element information.

  The liquid crystal transmittance calculating unit 23 sets LCD element information in advance. Here, the element information for calculating the output value corresponding to each pixel is an approximation when the shape of the approximate pattern is applied to a graph in which the horizontal axis is the pixel number and the vertical axis is the output value of each pixel. The starting point and inclination of each straight line constituting the pattern, and the maximum value of the approximate pattern. For example, the LCD element information may be an LUT as shown in FIG.

  In the present embodiment, since the approximate pattern is composed of four straight lines (Line_A to Line_D), as shown in FIG. The maximum value (Pat_Max) is described as element information.

  In addition, said pixel number shows the order from the end in which the pixel is arranged. In this embodiment, since the approximate pattern is approximated by the horizontal component of the input image, the pixel number is a column number starting from the left end of FIG. Also, it is assumed that the correspondence between the straight lines constituting the approximate pattern and the pixel numbers is set in advance. In this embodiment, since the approximate pattern is composed of four straight lines, each horizontal component pixel (1920 pixels) is equally classified into four groups A to D in the arrangement order.

  In this embodiment, the pixels are equally classified, but the present invention is not limited to this, and the number of pixels included in the group may be arbitrary.

  Specifically, the output value corresponding to each pixel in the approximate pattern is calculated for each group as follows.

LCD_Pat_ # j = Start + Step × LCD_Group_ # m
Here, “LCD_Pat_ # j” indicates an output value corresponding to the j columns of pixels in the approximate pattern. LCD_Group_ # m indicates the order from the end of the pixel in the group.

  In this way, the liquid crystal transmittance calculating unit 23 calculates the output value of each pixel in the approximate pattern, and based on the calculated output value, the input image, and the overall evaluation value, the liquid crystal transmittance is as follows. Is calculated.

LCD_rate (i, j) = Offset + Pat_Max-LCD_Pat_ # j if (revers = '0')
= Offset + LCD_Pat_ # j if (revers = '1')
Assist (i, j, c) = (1-Cin (i, j, c)) * LCD_rate (i, j) * K
Cout (i, j, c) = Cin (i, j, c) + (Cin (i, j, c) * Assist (i, j, c))
Here, “Cin (i, j, c)” is a pixel value (c = R or G or B) of a pixel in i row and j column of the input image. “Cout (i, j, c)” is the liquid crystal transmittance of the pixel (c = R or G or B) of the pixel in i row and j column. “Assist (i, j, c)” is a correction coefficient. “K” is the correction intensity. “LCD_rate (i, j)” is an intermediate value for deriving a correction coefficient.

  In addition, in order to make “Cout (i, j, c)” take a value of 0 to 1, “Cin (i, j, c)” and “LCD_rate (i, j)” are standardized and “ “K” is an arbitrary value from 0 to 1. FIG. 9 shows the relationship between “Cout (i, j, c)” and “Cin (i, j, c)” in the present embodiment. FIG. 9 is a diagram illustrating the relationship between the pixel value of the input image and the liquid crystal transmittance. In FIG. 9, the horizontal axis is “Cin (i, j, c)” and the vertical axis is “Cout (i, j, c)”. In addition, “if (revers = '0')” is a case where the inversion flag is not added to the approximate pattern in the pattern identification information, and “if (revers = '1')” is in the pattern identification information, A case where an inversion flag is added to the approximate pattern is shown.

  As shown in FIG. 11 described later, in order to reduce the LED data in accordance with the luminance distribution of the input image, the display luminance is lowered when the liquid crystal transmittance is not corrected. Therefore, it is possible to prevent a decrease in luminance by correcting the liquid crystal transmittance. As shown in FIG. 9, gradation correction can be prevented by increasing halftone correction and reducing correction at low gradations and high gradations.

(Effect of the present invention)
Finally, when the input image 61 shown in FIG. 10 is input, the output result of each unit is shown below.

  First, FIG. 11 shows the LED data calculated by the LED data calculation unit 22 when the input image 61 shown in FIG. 10 is input. In FIG. 11, the horizontal axis represents LEDs corresponding to the positions from point A to point B in FIG. 10, and the vertical axis represents LED data values. FIG. 12 shows an actual luminance distribution when the LED driver 15 drives the LED 13 based on the LED data shown in FIG.

  Next, FIG. 13 shows the liquid crystal transmittance calculated by the liquid crystal transmittance calculator 23 when the input image 61 shown in FIG. 10 is input. In FIG. 13, the horizontal axis represents picture elements (pixels) located from point A to point B in FIG. 10, and the vertical axis represents the liquid crystal transmittance value.

  14 shows the display luminance distribution when the LED driver 15 drives the LED 13 based on the LED data shown in FIG. 11 and the liquid crystal driver 14 drives the liquid crystal panel 12 based on the liquid crystal transmittance shown in FIG. Show.

  As described above, in the present invention, the LED data and the liquid crystal transmittance are calculated based on the approximate pattern that approximates the luminance distribution of the input image and the change amount is equal to or less than the predetermined value. Compared with the conventional dimming method shown in FIG. 26, it is possible to prevent the local video from being broken. To be precise, as shown in FIG. 14, the display luminance distribution is deviated from the luminance distribution of the input image in the vicinity of the point D. However, this difference is not visually perceived because it is a gradual change, not a local sudden change.

  Further, by selecting any one of the approximate patterns that most closely approximates the input image, it is possible to reduce the circuit scale while suppressing deterioration in display quality.

[Modification 1]
In the present embodiment, the LEDs 13 are arranged only on the long side of the liquid crystal panel 12, but the present invention is not limited to this. For example, as shown in FIG. 15, the LEDs 13 may be arranged along the long side and the short side of the liquid crystal panel 12. That is, it is good also as 2 side incident light to the liquid crystal panel 12.

  In this case, the image evaluation unit 21 sets two types of evaluation areas (horizontal component evaluation area and vertical component evaluation area) as shown in FIG. Specifically, the image evaluation unit 21 divides the input image into five evaluation areas (horizontal component evaluation areas) perpendicular to the long side direction (horizontal direction) as shown in FIG. At the same time, as shown in FIG. 16B, the image evaluation unit 21 divides the input image into three evaluation areas (vertical component evaluation areas) perpendicular to the short side direction (vertical direction).

  Then, the image evaluation unit 21 specifies an evaluation value for each horizontal component evaluation area, and generates a horizontal component evaluation value sequence. At the same time, the image evaluation unit 21 specifies an evaluation value for each vertical component evaluation area, and generates a vertical component evaluation value sequence. Further, the image evaluation unit 21 specifies an overall evaluation value.

  Next, the LED data calculation unit 22 specifies a horizontal component approximate pattern (horizontal component approximate pattern) corresponding to the horizontal component evaluation value sequence, and calculates horizontal component LED data from the horizontal component approximate pattern. At the same time, the LED data calculation unit 22 specifies a vertical component approximate pattern (vertical component approximate pattern) corresponding to the vertical component evaluation value sequence, and calculates vertical component LED data from the vertical component approximate pattern. Here, the LED data of the horizontal component is LED data of the LED 13 on the long side, and the LED data of the vertical component is LED data of the LED 13 on the short side.

  For example, when the input image shown in FIG. 17 is input, the LED data calculation unit 22 specifies the approximate pattern of the horizontal component and the approximate pattern of the vertical component shown in FIG.

  Next, the liquid crystal transmittance calculator 23 calculates the liquid crystal transmittance as follows based on the input image, the overall evaluation value, and the approximate pattern of the horizontal component and the approximate pattern of the vertical component.

LCD_rate_h (j) = Offset + Pat_Max-LCD_Pat_h_ # j if (revers = '0')
= Offset + LED_Pat_h_ # n if (revers = '1')
LCD_rate_v (i) = Offset + Pat_Max-LCD_Pat_v_ # i if (revers = '0')
= Offset + LED_Pat_v_ # n if (revers = '1')
LCD_rate_f (i, j) = (LCD_rate_h (j) + LCD_rate_v (i)) / 2
Assist (i, j, c) = (1-Cin (i, j, c)) * LCD_rate_f (i, j) * K
Cout (i, j, c) = Cin (i, j, c) + (Cin (i, j, c) * Assist (i, j, c))
Here, “LCD_Pat_h_ # j” indicates an output value corresponding to a pixel in column j in the horizontal component approximate pattern, and “LCD_Pat_v_ # i” indicates an output value corresponding to a pixel in column i in the approximate vertical component pattern. Indicates. Each output value is the LCD horizontal component element information in which the horizontal component approximate pattern and the element information for calculating the output value corresponding to each pixel in the j column are associated, or the vertical component approximate pattern and the i column. It is calculated with reference to LCD vertical component element information associated with element information for calculating an output value corresponding to each pixel.

  In addition, “LCD_rate_f (i, j)”, “LCD_rate_h (j)”, and “LCD_rate_v (i)” are intermediate values for deriving a correction coefficient.

  In addition, in order to make “Cout (i, j, c)” take a value of 0 to 1, “Cin (i, j, c)”, “LCD_rate_f (i, j)”, “LCD_rate_h (j ) ”And“ LCD_rate_v (i) ”, and“ K ”is an arbitrary value between 0 and 1.

The above "LCD_rate_f (i, j)"
LCD_rate_f (i, j) = LCD_rate_h (j) * LCD_rate_v (i)
May be calculated as

[Modification 2]
In the present embodiment, the LEDs 13 are arranged on the long side of the liquid crystal panel 12, but the present invention is not limited to this. For example, as shown in FIG. 19, the LEDs 13 may be arranged in a matrix on the back surface of the liquid crystal panel 12. Here, 27 rows and 48 columns of LEDs 13 are arranged.

  In this case, the image evaluation unit 21 sets two types of evaluation areas (horizontal component evaluation area and vertical component evaluation area) in the same manner as the first modification described above, and sets the horizontal component evaluation value sequence and the vertical component evaluation value. Generate a column. Further, the image evaluation unit 21 specifies an overall evaluation value.

  Next, the LED data calculation unit 22 includes a horizontal component approximate pattern (horizontal component approximate pattern) and a vertical component approximate pattern (vertical component approximate pattern) respectively corresponding to the horizontal component evaluation value sequence and the vertical component evaluation value sequence. Is identified. Then, the horizontal component LED data and the vertical component LED data are respectively calculated from the horizontal component approximate pattern and the vertical component approximate pattern.

Here, assuming that the LED data of the horizontal component and the LED data of the vertical component are “LED_data_h_ # n” and “LED_data_v_ # m”, respectively, the LED data of the LED 13 of m rows and n columns is
LED_data_f (m, n) = (LED_data_h_ # n + LED_data_v_ # m) / 2
Or
LED_data_f (m, n) = LED_data_h_ # n * LED_data_v_ # m
Calculate as

  Next, the liquid crystal transmittance calculating unit 23 calculates the liquid crystal transmittance in the same manner as in the first modification based on the input image, the overall evaluation value, and the approximate pattern of the horizontal component and the approximate pattern of the vertical component.

[Modification 3]
In the present embodiment, in the pattern specifying information, the evaluation value sequence and the approximate pattern are associated in advance. However, when the number of evaluation areas, levels, approximate patterns, and the like increases, it becomes difficult to associate the two with the LUT. For example, there are nine evaluation areas and levels 0-24.

  Therefore, in such a case, the difference between the evaluation value sequence and each approximate pattern may be calculated, and the approximate pattern with the smallest difference may be selected. However, an approximate pattern having a smaller value in the evaluation value sequence is selected so that insufficient luminance does not occur.

[Modification 4]
In this embodiment, the approximate pattern is defined by the start point of each group, the slope of the straight line of each group, and the maximum output value, but is not limited to this. For example, all output values of the LEDs 13 in the approximate pattern may be defined as numerical values.

[Modification 5]
In the present embodiment, the change amount in the LED data is set to a predetermined value or less in the physical dimension, but the change amount in the LED data may be set to a predetermined value or less in the temporal dimension.

Specifically, as shown in FIG. 20, when displaying a moving image, the LED data is determined so that the difference between the LED data for a certain input image and the LED data for the next input image is less than or equal to a predetermined value. May be. For example, LED data (LED_out) for an input image is
LED_out = Pre_LED + (New_LED- Pre_LED) * T
You may ask as. Here, “Pre_LED” is LED data for the input image immediately before the certain input image (“LED_out” for the previous input image). “New_LED” is LED data calculated from an approximate pattern corresponding to an evaluation value sequence generated from a certain input image. “T” is a correction coefficient, and is an arbitrary value between 0 and 1.

  Thereby, since the luminance of the LED 13 changes gradually, it is possible to prevent the occurrence of flicker or the like during a sudden video change such as a scene change.

  In the present embodiment, the amount of change in the intermediate value for deriving the liquid crystal correction coefficient in the physical dimension is set to a predetermined value or less. Further, in the temporal dimension, the liquid crystal correction coefficient for deriving the correction coefficient The amount of change in the intermediate value may be a predetermined value or less.

Specifically, as with the above LED data, when displaying a moving image, an intermediate value for deriving a liquid crystal correction coefficient for a certain input image and a liquid crystal correction coefficient for the next input image are derived. The intermediate value may be determined so that the difference from the intermediate value is equal to or less than a predetermined value. For example, the intermediate value (LCD_rate) for deriving the liquid crystal correction coefficient for a certain input image is:
LCD_rate = Pre_LCD_rate + (New_LCD_rate-Pre_LCD_rate) * T
You may ask as. Here, “Pre_LCD_rate” is an intermediate value (“LCD_rate” for the previous input image) for deriving a liquid crystal correction coefficient for the previous input image of the certain input image. “New_LCD_rate” is an intermediate value for deriving a liquid crystal correction coefficient calculated from an approximate pattern corresponding to an evaluation value sequence generated from a certain input image. “T” is a correction coefficient, and is an arbitrary value between 0 and 1.

  Thereby, since the brightness of the intermediate value for deriving the correction coefficient of the liquid crystal gradually changes, it is possible to prevent occurrence of flicker or the like when a sudden video change such as a scene change occurs.

[Modification 6]
In the present embodiment, a liquid crystal display device mounted with a liquid crystal panel is exemplified as the display device, but the present invention is not limited to this. The display device only needs to have a backlight and can set the light transmittance of the display panel. For example, the display device may be a signboard such as a color corton.

[Supplement]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  Finally, each block of the liquid crystal display device 1, particularly the control unit 11, may be configured by hardware logic, or may be realized by software using a CPU as follows.

  That is, the liquid crystal display device 1 includes a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and a RAM (random access memory) that expands the program. And a storage device (recording medium) such as a memory for storing the program and various data. An object of the present invention is a recording medium in which a program code (execution format program, intermediate code program, source program) of a control program of the liquid crystal display device 1 which is software for realizing the above-described functions is recorded so as to be readable by a computer. This can also be achieved by supplying the liquid crystal display device 1 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM (registered trademark) / flash ROM.

  The liquid crystal display device 1 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Further, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The present invention can be used for an image display device having a function of controlling the luminance of a backlight based on an input image.

1 Liquid crystal display device (image display device)
11 Control unit 12 Liquid crystal panel (display panel)
13 LED (light source)
14 Liquid crystal driver (display panel drive means)
15 LED driver (light source drive means)
21 Image evaluation unit (image evaluation means)
22 LED data calculation unit (pattern identification means, light source data calculation means)
23 Liquid crystal transmittance calculation unit (light transmittance calculation means)

Claims (12)

An image display device in which a plurality of light sources are arranged along one or two sides of a display panel,
Pattern specifying means for specifying an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image from the approximate pattern that is configured by a straight line and the change amount is equal to or less than a predetermined value;
Light source data calculating means for calculating light source data for controlling the outputs of the plurality of light sources based on the approximate pattern specified by the pattern specifying means;
A light transmittance calculating means for calculating a light transmittance for controlling the light transmittance of the display panel based on the input image and the approximate pattern specified by the pattern specifying means;
Light source driving means for driving the plurality of light sources based on the light source data calculated by the light source data calculating means;
An image display device comprising: display panel driving means for driving the display panel based on the light transmittance calculated by the light transmittance calculating means. Further comprising image evaluation means for dividing the input image into a plurality of areas, specifying an evaluation value indicating the magnitude of luminance of each area, and generating an evaluation value sequence in which the evaluation values of each area are arranged in order,
The pattern specifying means refers to the evaluation value string generated by the image evaluation means with reference to pattern specifying information in which a correspondence relationship between the evaluation value string and the approximate pattern closest to the evaluation value string is predetermined. The image display apparatus according to claim 1, wherein an approximate pattern corresponding to is specified.   The image display device according to claim 2, wherein the image evaluation unit specifies a maximum value of a pixel value or a pixel value included in the area as an evaluation value of the area.   The image display device according to claim 2, wherein the image evaluation unit specifies an average value of pixel values or picture element values included in the area as an evaluation value of the area.   3. The image evaluation means takes a histogram of pixel values or pixel values included in the area, and specifies the largest number of pixel values or pixel values as an evaluation value of the area. The image display device described in 1.   In the pattern specifying information, the light source data calculating means, when an inversion flag is added to the approximate pattern specified by the pattern specifying means, based on a pattern obtained by inverting the approximate pattern specified by the pattern specifying means, 6. The image display device according to claim 2, wherein light source data is calculated. The image evaluation means further specifies an overall evaluation value indicating a luminance level of the entire input image,
7. The light source data calculating means calculates the light source data by offset-correcting the approximate pattern specified by the pattern specifying means based on the overall evaluation value. The image display device described in 1. The image display device according to claim 2, wherein the light transmittance calculating unit calculates the light transmittance based on the following expression.
LCD_rate (i, j) = Offset + Pat_Max-LCD_Pat_ # j if (revers = '0')
= Offset + LED_Pat_ # n if (revers = '1')
Assist (i, j, c) = (1-Cin (i, j, c)) * LCD_rate (i, j) * K
Cout (i, j, c) = Cin (i, j, c) + (Cin (i, j, c) * Assist (i, j, c))
Cin (i, j, c): Pixel value of pixel in i row and j column of the input image
Cout (i, j, c): Light transmittance of picture element of pixel in i row and j column
K: Any value
Offset: Overall evaluation value indicating the brightness of the entire input image
Pat_Max: Maximum value of approximate pattern
LCD_Pat_ # j: Output value of pixels in column j in the approximate pattern
revers: Reverse flag An image display device in which a plurality of light sources are arranged in a matrix on the back surface of a display panel,
The horizontal component approximate pattern that approximates the luminance distribution of the horizontal component of the input image and the luminance of the vertical component of the input image from among the horizontal component approximate pattern and vertical component approximate pattern that are each composed of straight lines and whose variation is less than a predetermined value Pattern specifying means for specifying each vertical component approximate pattern approximating the distribution;
Light source data calculating means for calculating light source data for controlling the outputs of the plurality of light sources based on the horizontal component approximate pattern and the vertical component approximate pattern specified by the pattern specifying means;
Light transmittance calculating means for calculating light transmittance for controlling the light transmittance of the display panel based on the input image and the horizontal component approximate pattern and vertical component approximate pattern specified by the pattern specifying means; ,
Light source driving means for driving the plurality of light sources based on the light source data calculated by the light source data calculating means;
An image display device comprising: display panel driving means for driving the display panel based on the light transmittance calculated by the light transmittance calculating means. A control method for an image display device in which a plurality of light sources are arranged along one or two sides of a display panel,
A pattern specifying step for specifying an approximate pattern that approximates the luminance distribution of the light source array direction component of the input image from among the approximate patterns that are configured with straight lines and whose variation is equal to or less than a predetermined value;
A light source data calculating step for calculating light source data for controlling the outputs of the plurality of light sources based on the approximate pattern specified in the pattern specifying step;
A light transmittance calculating step for calculating a light transmittance for controlling the light transmittance of the display panel based on the input image and the approximate pattern specified in the pattern specifying step;
A light source driving step for driving the plurality of light sources based on the light source data calculated in the light source data calculating step;
A display panel driving step for driving the display panel based on the light transmittance calculated in the light transmittance calculating step.   A control program for operating the image display apparatus according to any one of claims 1 to 9, wherein the control program causes a computer to function as each of the means.   The computer-readable recording medium which recorded the control program of Claim 11.

Images