JP2010054729A - Liquid crystal display device and color processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device and the like which can reduce color smear caused by the angle viewing a display surface, where an image is displayed. <P>SOLUTION: It is determined whether the color of a pixel is a color within a specified color region RN (S112). The specified color region RN is a region including a plurality of colors such that when a color is displayed on the display surface, a color, displayed on the display surface, that a person feels on an axis perpendicular to the display surface and a color, displayed on the display surface, that the person feels on an axis inclined at a predetermined angle have a difference larger than a predetermined value. Based upon the position of the color of a pixel to be processed which is a pixel determined to have a color within the specified color region RN, a first color which is a color not within the specified color region RN and has lower color saturation than the color of the pixel to be processed and a second color which is a color within the specified color region RN and has higher color saturation than the color of the pixel to be processed are computed (S114, S116). The color of the pixel to be processed is changed to one of the first color and second color, and the color of a pixel nearby the pixel to be processed is changed to the other of the first color and second color (S117). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device and a color processing method, and more particularly to a liquid crystal display device and a color processing method for performing processing for changing the color of a pixel of an image.

In recent years, liquid crystal display devices using a VA (Vertical Alignment) type liquid crystal panel are becoming widespread. The VA liquid crystal panel has a feature of high contrast because of less leakage light when displaying black. Therefore, the VA liquid crystal panel is used in many liquid crystal televisions because the optical change of the viewing angle is smaller than that of a TN (Twisted Nematic) liquid crystal panel. Non-Patent Document 1 discloses the principle of the VA method, the principle of viewing angle expansion, and the like.
A. Takeda, S. Kataoka, tea. T. Sasaki, H. H. Chida, Kei. K. Ohmura, tea. T. Sasabayashi, Wai. Y. Koike and Kay. “A Super-High-Image-Quality Multi-Domain Vertical Alignment LCD by New Rubbing-Less” by K. Okamoto, “A Super-High-Image-Quality Multi-Domain Vertical Alignment LCD” Technology), SID (SID) '98 Digest, 1998, p.1077-1080

  However, the VA liquid crystal panel may point out a color change when viewed from an oblique direction. Actually, in the VA liquid crystal panel, although the brightness is reduced when moving away from the front, the tone (tone) of the image does not change, so there are few indications of the brightness reduction, but the viewing angle is narrow due to the color change. Is often pointed out.

  FIG. 14 is a diagram illustrating characteristics of a VA liquid crystal panel. In FIG. 14, the vertical axis indicates the relative value of luminance. The value shown on the vertical axis is a relative value when the maximum luminance value is “1”. The value shown on the horizontal axis is a relative value when the maximum value of the input level is “1”.

  Hereinafter, a display surface that displays an image included in the VA liquid crystal display device is referred to as a VA display surface. In the following, an axis that is perpendicular to the VA system display surface and that has one end in contact with the center position of the VA system display surface is referred to as a display surface vertical axis. In the following description, when the user views the VA display surface on the display surface vertical axis inclined in the horizontal direction by K (real number less than 0 to 180), K degrees on the display surface vertical axis inclined by K degrees. Is called the viewing angle.

  Here, it is assumed that a predetermined color (for example, white) is displayed on the VA system display surface. In this case, in FIG. 14, a characteristic curve L0 indicates the brightness characteristic of the VA system display surface as perceived by the user (human) on the display surface vertical axis. That is, the characteristic curve L0 indicates the brightness characteristic of the VA system display surface that the user (human) feels when the user (human) views the VA system display surface from the front.

  The characteristic curve L0 is a curve when the gamma value is “2.2”. A characteristic curve L30 indicates the brightness characteristic of the VA system display surface as perceived by the user (human) on the vertical axis of the display surface tilted 30 degrees in the horizontal direction. A characteristic curve L60 indicates the brightness characteristic of the VA system display surface as perceived by the user (human) on the vertical axis of the display surface tilted 60 degrees in the horizontal direction.

  As shown in FIG. 14, the luminance value increases in the halftone as the display surface vertical axis, which is the position where the user views the VA display surface, is tilted by 30 degrees and 60 degrees. That is, even with signals having the same input level, the luminance shifts as the viewing angle increases.

  Even when a luminance shift occurs, the R, G, and B primary colors are not mixed, so no color shift occurs. However, in the mixed color that is slightly inside the primary color on the chromaticity diagram, the ratio of the other colors changes, resulting in a color shift.

  For example, in FIG. 14, when the input level is “0.9”, the luminances indicated by the characteristic curve L0 and the characteristic curve L60 are A1 and A2, respectively. When the input level is “0.4”, the luminances indicated by the characteristic curve L0 and the characteristic curve L60 are B1 and B2, respectively.

  In this case, when the viewing angle is 0 degrees, a vermilion color CA0 described later is generated from the R (red) color of the luminance A1, the G (green) color of the luminance B1, and the B (blue) color of the luminance B1. To do. In addition, when the viewing angle is 60 degrees, a red CA30, which will be described later, is generated from the R (red) color of luminance A2, the G (green) color of luminance B2, and the B (blue) color of luminance B2. . In this case, when the viewing angle changes from 0 degree to 60 degrees, the mixing ratio of the primary color (R) and the secondary color (G, B) is changed from A1 / B1 to A2 / B2.

  That is, the mixing ratio of the primary color (R) and the secondary color (G, B) changes in the direction in which the color becomes lighter. Therefore, as the viewing angle changes from 0 degrees to 60 degrees, the vermilion displayed on the VA display surface is identified so as to become lighter. This phenomenon was perceived as image quality degradation by viewers (users).

  FIG. 15 shows the above phenomenon on a chromaticity diagram. FIG. 15 is a CIE 1976 UCS (Uniform Color Scale) chromaticity diagram. In FIG. 15, a color area RA is an area showing all colors that can be displayed by the liquid crystal display device. As described above, the color area line LA0 is generated from the R (red) color of the luminance A1, the G (green) color of the luminance B1, and the B (blue) color of the luminance B1 when the viewing angle is 0 degree. It is a line which shows the intermediate color containing the vermilion color CA0 made. The color area line LA30 is a line indicating an intermediate color including the vermilion CA30 when the viewing angle is 30 degrees. The color C0 is an achromatic color. The position of the achromatic color C0 is the position of the origin of the achromatic color when the color temperature is 6500 degrees in the television standard. In FIG. 15, a primary color CP is an example of a primary color of red (R). In FIG. 15, a line segment connecting the achromatic color C0 and the primary color CP is defined as a line segment L0P.

  As shown in FIG. 15, the positions of R, G, and B primary colors (for example, primary color CP) hardly change even when the viewing angle changes. The position of the intermediate color (for example, vermilion CA0) whose saturation is lower than that of the primary color moves greatly inward according to the change in the viewing angle (for example, vermilion CA30). As described above, in the VA liquid crystal display device, there is a problem in that the intermediate color changes depending on the viewing angle of the display surface on which the image is displayed. That is, the VA liquid crystal display device has a problem in that color misregistration occurs depending on an angle at which a display surface on which an image is displayed is viewed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device that can reduce color misregistration caused by an angle of viewing a display surface on which an image is displayed. Etc. is to provide.

  In order to solve the above-described problem, according to one aspect of the present invention, a VA (Vertical Alignment) type liquid crystal display device having a display surface for displaying an image constitutes an image and an acquisition unit. A color for performing color determination processing for determining whether or not the color of each pixel is a color within a specific color region on a chromaticity diagram indicating all colors that can be displayed by the liquid crystal display device A determination unit. When a color is displayed on the display surface, the specific color area is displayed on the display surface that is perceived by humans on an axis that is perpendicular to the display surface and on the display surface that is perceived by humans on an axis that is tilted at a predetermined angle. This is an area on the chromaticity diagram including a plurality of colors having a difference from a color to be set to a predetermined value or more. The liquid crystal display device has a color outside the specific color area based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color area by the color determination unit, and the processing target pixel A color calculation process for calculating a first color having a lower saturation than the color of the first color and a second color having a color outside the specific color area and having a higher saturation than the color of the processing target pixel; A color change process in which the color is changed to one of the first color and the second color and the color of the pixel in the vicinity of the process target pixel is changed to the other of the first color and the second color. And a display unit for displaying an image including all the processing target pixels processed by the color processing unit.

  That is, it is determined whether or not the color of the pixel is a color within the specific color region. When a color is displayed on the display surface, the specific color area is displayed on the display surface that is perceived by humans on an axis that is perpendicular to the display surface and on the display surface that is perceived by humans on an axis that is tilted at a predetermined angle. This is an area including a plurality of colors having a difference from a given color equal to or greater than a predetermined value. A first color that is outside the specific color area and lower in saturation than the color of the processing target pixel based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color area A color and a second color that is outside the specific color region and has a higher saturation than the color of the processing target pixel are calculated. The color of the processing target pixel is changed to one of the first color and the second color, and the color of the pixel near the processing target pixel is changed to the other of the first color and the second color.

  That is, the color of the pixel in the specific color region including a plurality of colors having a large degree of color change depending on the angle at which the human views the display surface is expressed by two colors outside the specific color region and two pixels.

  Therefore, the color misregistration caused by the angle at which the image display surface on which the image is displayed is viewed can be greatly reduced.

  According to another aspect of the present invention, a color processing method performed by a VA (Vertical Alignment) type liquid crystal display device having a display surface for displaying an image includes an acquisition step of acquiring an image, and a plurality of pixels constituting the image A color determination step of performing color determination processing for determining whether or not the color of the pixel is a color within a specific color region on the chromaticity diagram showing all colors that can be displayed by the liquid crystal display device Is provided. When a color is displayed on the display surface, the specific color area is displayed on the display surface that is perceived by humans on an axis that is perpendicular to the display surface and on the display surface that is perceived by humans on an axis that is tilted at a predetermined angle. This is an area on the chromaticity diagram including a plurality of colors having a difference from a color to be set to a predetermined value or more. The color processing method includes a color outside the specific color area based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color area by the color determination step, and the processing target pixel. A color calculation process for calculating a first color having a lower saturation than the color of the first color and a second color having a color outside the specific color area and having a higher saturation than the color of the processing target pixel; A color change process in which the color is changed to one of the first color and the second color and the color of the pixel in the vicinity of the process target pixel is changed to the other of the first color and the second color. And a display step for displaying an image including all the processing target pixels processed in the color processing step.

  That is, it is determined whether or not the color of the pixel is a color within the specific color region. When a color is displayed on the display surface, the specific color area is displayed on the display surface that is perceived by humans on an axis that is perpendicular to the display surface and on the display surface that is perceived by humans on an axis that is tilted at a predetermined angle. This is an area including a plurality of colors having a difference from a given color equal to or greater than a predetermined value. A first color that is outside the specific color area and lower in saturation than the color of the processing target pixel based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color area A color and a second color that is outside the specific color region and has a higher saturation than the color of the processing target pixel are calculated. The color of the processing target pixel is changed to one of the first color and the second color, and the color of the pixel near the processing target pixel is changed to the other of the first color and the second color.

  That is, the color of the pixel in the specific color region including a plurality of colors having a large degree of color change depending on the angle at which the human views the display surface is expressed by two colors outside the specific color region and two pixels.

  Therefore, the color misregistration caused by the angle at which the image display surface on which the image is displayed is viewed can be greatly reduced.

  Note that the present invention can also be realized as a program that causes a computer to execute processing performed by the color processing method. The present invention can also be realized as a computer-readable recording medium and an integrated circuit for storing the program.

  According to the present invention, it is determined whether or not the color of a pixel is a color within a specific color region. When a color is displayed on the display surface, the specific color area is displayed on the display surface that is perceived by humans on an axis that is perpendicular to the display surface and on the display surface that is perceived by humans on an axis that is tilted at a predetermined angle. This is an area including a plurality of colors having a difference from a given color equal to or greater than a predetermined value. A first color that is outside the specific color area and lower in saturation than the color of the processing target pixel based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color area A color and a second color that is outside the specific color region and has a higher saturation than the color of the processing target pixel are calculated. The color of the processing target pixel is changed to one of the first color and the second color, and the color of the pixel near the processing target pixel is changed to the other of the first color and the second color.

  That is, the color of the pixel in the specific color region including a plurality of colors having a large degree of color change depending on the angle at which the human views the display surface is expressed by two colors outside the specific color region and two pixels.

  Therefore, it is possible to greatly reduce the color shift caused by the angle at which the image display surface on which the image is displayed is viewed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a liquid crystal display device 1000 according to the first embodiment. As shown in FIG. 1, the liquid crystal display device 1000 includes a signal processing circuit 100, a data driving circuit 210, a scanning driving circuit 220, and a liquid crystal panel 230.

  The liquid crystal display device 1000 also includes a backlight unit, a power supply unit, and the like not shown. When the liquid crystal display device 1000 is a television receiver, the liquid crystal display device 1000 further includes a tuner, a decoding circuit, and the like that are not shown.

  The signal processing circuit 100 is a circuit dedicated to image processing, such as a DSP (Digital Signal Processor) and an ASIC (Application Specific Integrated Circuit). The signal processing circuit 100 is not limited to a DSP, ASIC, or the like, and may be another arithmetic circuit.

  An image signal IMG is input to the signal processing circuit 100. The signal processing circuit 100 performs image processing such as color processing (for example, color shift reduction processing described later) and gamma correction on the input image signal IMG. The signal processing circuit 100 transmits the image signal subjected to the image processing to the data driving circuit 210. The data driving circuit 210 transmits the received image signal to the liquid crystal panel 230.

  The liquid crystal panel 230 is a VA (Vertical Alignment) type liquid crystal panel. The liquid crystal panel 230 has an image display surface for displaying an image.

  Further, the signal processing circuit 100 transmits a scanning signal synchronized with the image signal subjected to image processing to the scanning driving circuit 220. The scan drive circuit 220 drives the liquid crystal panel 230 according to the received scan signal. By the operations of the data driving circuit 210 and the scanning driving circuit 220, an image based on the image signal is displayed on the image display surface of the liquid crystal panel 230. Note that the processing for displaying an image on the image display surface of the liquid crystal panel 230 is the same as the processing of a general VA liquid crystal display device, and therefore will not be described in detail.

  In the following, an axis that is perpendicular to the image display surface and whose one end is in contact with the center of the image display surface is referred to as a display surface vertical axis. In the following, when the user views the image display surface on the display surface vertical axis inclined by K (real number less than 0 to 180) degrees, the K degree on the display surface vertical axis inclined by K degrees in the horizontal direction. The angle is called the viewing angle.

  FIG. 2 is a diagram for explaining the color misregistration for each viewing angle from the achromatic color to the primary color on the UCS chromaticity diagram. Specifically, FIG. 2 is a diagram showing the color shift for each viewing angle as an actual measurement value when the color on the line segment L0P connecting the achromatic color C0 and the primary color CP in FIG. 15 is displayed on the image display surface. is there. The actual measurement value is a value measured by a device such as a color meter.

  In FIG. 2, the horizontal axis represents a relative value when the distance from the achromatic color C0 to the primary color CP in FIG. 15 is “1”. 2 represents a value (Δu ′) obtained by measuring the color displayed on the image display surface from the front of the image display surface when the color on the line segment L0P is displayed on the image display surface. v ′ “0”). That is, when a color on the line segment L0P is displayed on the image display surface and the user views the image display surface from the vertical axis of the display surface, the user does not feel a color shift.

  The characteristic curve LC15 is a display that is tilted by 15 degrees in the horizontal direction with the color displayed on the image display surface measured by the colorimeter from the vertical axis of the display surface when the color on the line segment L0P is displayed on the image display surface. The characteristic of the difference (deviation) from the color displayed on the image display surface measured with the colorimeter from the surface vertical axis | shaft is shown. The characteristic curve LC30 is a display tilted 30 degrees in the horizontal direction with the color displayed on the image display surface measured by the colorimeter from the vertical axis of the display surface when the color on the line segment L0P is displayed on the image display surface. The characteristic of the difference (deviation) from the color displayed on the image display surface measured with the colorimeter from the surface vertical axis | shaft is shown.

  The characteristic curve LC45 is a display inclined at 45 degrees in the horizontal direction with the color displayed on the image display surface measured by the colorimeter from the vertical axis of the display surface when the color on the line L0P is displayed on the image display surface. The characteristic of the difference (deviation) from the color displayed on the image display surface measured with the colorimeter from the surface vertical axis | shaft is shown.

  The characteristic curve LC30 is displayed on the image display screen when the color at a distance of about 0.8 distance from the position of the achromatic color C0 on the line segment L0P in FIG. 15 is displayed on the display screen vertical axis. This shows that the difference (deviation) between the color displayed on the image display surface perceived by the user and the color displayed on the image display surface perceived by the user on the display surface vertical axis inclined by 30 degrees in the horizontal direction is the largest.

  As shown in FIG. 2, in each of the characteristic curves LC15, LC30, and LC45, the value of Δu′v ′ corresponding to the range of 0.7 to 0.95 on the horizontal axis corresponds to the other range. It is particularly larger than the value of Δu′v ′.

  In the present invention, the color displayed on the image display surface perceived by the user on the display surface vertical axis and the image display surface perceived by the user on the display surface vertical axis inclined by a predetermined angle (for example, 30 degrees) in the horizontal direction. An area including a plurality of colors having a difference (Δu′v ′) from the displayed color equal to or greater than a predetermined value is referred to as a specific color area RN.

  The characteristics indicated by the characteristic curves LC15, LC30, and LC45 are characteristics of some of the colors shown in the USC chromaticity diagram. Therefore, in the present invention, in consideration of color characteristics other than those corresponding to FIG. 2, a region including a plurality of colors in which the value of the horizontal axis in FIG. The specific color region RN is assumed. Therefore, in FIG. 2, as an example, the specific color region RN is a range of about 80% of the value of Δu′v ′ indicated by the characteristic curve LC30 of about 0.02 or more. The range of values for determining the specific color region RN is not limited to 0.6 to 0.9, but may be a range of other values (for example, 0.7 to 0.92).

  In the present invention, the specific color region RN is intended to cope with color misregistration when the viewing angle is within 30 degrees, for example. Note that the viewing angle for dealing with the color shift of the specific color region RN is not limited to within 30 degrees.

  The specific color region RN shown in FIG. 2 includes skin color. Therefore, when an image showing a human face is displayed on the image display surface, the skin color changes as the viewing angle increases.

  FIG. 3 is a diagram illustrating the specific color region RN in the UCS chromaticity diagram. In FIG. 3, portions denoted by the same reference numerals as those shown in FIG. 15 are the same as those described with reference to FIG. 15, and thus detailed description thereof will not be repeated. The color area RA shown in FIG. 3 is an area showing all colors that can be displayed on the liquid crystal panel 230 of the liquid crystal display device 1000. The specific color area RN is an area arranged in the color area RA.

  In FIG. 3, a region boundary line LR1 is a line indicating an inner boundary in the specific color region RN. The region boundary line LR2 is a line indicating the outer boundary in the specific color region RN. Hereinafter, a line indicating the boundary of the color area RA is referred to as an all color area boundary line. The primary color CP is arranged on the all color region boundary line.

  In the present invention, when an image is displayed on the image display surface, when the color of the pixel of the image to be displayed is a color within the specific color region RN, a plurality of colors outside the specific color region RN, and a plurality of colors It is an invention of expressing a color in a specific color region RN using pixels.

(Processing for color shift reduction)
Next, processing for reducing color misregistration that occurs according to the viewing angle (hereinafter referred to as color misregistration reduction processing) will be described.

  FIG. 4 is a flowchart of the color misregistration reduction process. As shown in FIG. 4, first, in the color misregistration reduction process, the process of step S111 is performed.

  In step S111, the signal processing circuit 100 in FIG. 1 acquires an image from the outside. Specifically, the signal processing circuit 100 acquires an image signal indicating an image from the outside. Hereinafter, the image indicated by the image signal acquired by the signal processing circuit 100 is referred to as an acquired image. Here, the size of the acquired image is assumed to be a size of horizontal 1920 pixels and vertical 1080 pixels as an example.

  In step S112, the signal processing circuit 100 determines whether or not the color of the S (natural number) pixel among the plurality of pixels constituting the acquired image is a color in the specific color region RN shown in FIG. To do. It is assumed that the initial value of S is “1”.

  In the acquired image, the 1st to 1920th pixels are a pixel in the first row and the first column to a pixel in the first row and the 1920th column, respectively. In the acquired image, the 1921st pixel is the pixel in the second row and the first column. That is, the S-th pixel becomes an adjacent right pixel every time the value of S increases by one. In the acquired image, when there is no right pixel adjacent to the S-th pixel, the S + 1-th pixel is the pixel in the first column below the first row. Finally, the S-th pixel is a pixel of 1080 rows and 1920 columns.

  If YES in step S112, the process proceeds to step S113. On the other hand, if NO at step S112, the process proceeds to the process at step S112A. In the following, a pixel whose pixel color is determined to be a color within the specific color region RN is referred to as a processing target pixel. Here, assuming that NO is determined in step S112, the process of step S112A is performed.

In step S112A, the signal processing circuit 100 increments the value of S by “1”.
In step S112B, it is determined whether or not the determination process in step S112 has been completed for all pixels constituting the acquired image. Specifically, the signal processing circuit 100 determines whether or not the value of S is larger than the number of pixels constituting the acquired image (1080 × 1920 = 2073600).

  If YES in step S112B, the signal processing circuit 100 sets the value of S to “1”, and the process proceeds to the process of step S119 described later. On the other hand, if NO at step S112B, the process at step S112 is performed again. Here, it is determined as NO and the process of step S112 is performed.

  Here, it is assumed that the acquired image is the following acquired image G100. Here, it is assumed that the Sth pixel is the pixel PX shown in the acquired image G100.

  FIG. 5 is a diagram illustrating an acquired image G100 as an example. In FIG. 5, the pixels PN1 and PN2 will be described later.

  Further, it is assumed that the S-th pixel as the pixel PX in FIG. 5 is the pixel PX shown in FIG. That is, it is assumed that the color of the Sth pixel PX is a color within the specific color region RN shown in FIG. In this case, it is determined as YES in Step S112, and the process proceeds to Step S113. In this case, the pixel PX is a processing target pixel.

  In step S113, a coordinate conversion process is performed. In the coordinate conversion process, the signal processing circuit 100 performs processing of the pixel to be processed in the line segment connecting from the position of the achromatic color C0 in FIG. 3 to the color region boundary line described above via the color position of the pixel to be processed. Calculate the position of the color. The calculated color position is a position on the UCS chromaticity diagram. In the following, a line segment from the position of the achromatic color C0 in FIG. 3 to the above-described all color region boundary line via the color position of the processing target pixel is referred to as a color calculation line segment. In the following description, the position on the color calculation line segment is the position on the UCS chromaticity diagram.

  FIG. 6 is a diagram for describing processing for expressing the color of a pixel determined to be a color in the specific color region RN using a plurality of colors outside the specific color region RN.

  FIG. 6A shows a color calculation line segment. Here, it is assumed that the processing target pixel is the pixel PX shown in FIG. In this case, in FIG. 6A, the color CX is assumed to be the color of the pixel PX as the processing target pixel. In this case, the position of the processing target pixel in the color calculation line segment is calculated as the position of the color CX by the process in step S113.

  In FIG. 4 again, in step S114, the signal processing circuit 100 calculates an out-of-region high saturation color. As shown in FIG. 6A, the out-of-region high saturation color is a color Y outside the specific color region RN on the color calculation line segment and closest to the region boundary line LR2. That is, the out-of-region high saturation color Y is a color at a position between the region boundary line LR2 and the all-color region boundary line. That is, the out-of-region high saturation color Y is a color at a position between the specific color region RN and the all-color region boundary line.

  In step S115, the signal processing circuit 100 calculates a distance between the position of the color CX and the position of the out-of-region high saturation color Y (hereinafter referred to as CX-Y distance).

  In step S116, the signal processing circuit 100 calculates an out-of-region low saturation color. As shown in FIG. 6A, the out-of-region low chroma color is a color outside the specific color region RN on the color calculation line segment, and from the position of the color CX toward the achromatic color C0. , Color Z at a position separated by CX-Y distance (L1). That is, the out-of-region low saturation color Z is a color at a position between the position of the achromatic color C0 and the region boundary line LR1. That is, the out-of-region low saturation color Z is a color at a position between the position of the achromatic color C0 and the specific color region RN.

  Further, the distance (L1) between the position of the color CX of the processing target pixel and the position of the out-of-region low saturation color Z is the distance (L1) between the position of the color CX of the processing target pixel and the position of the out-of-region high saturation color Y. Is the same. In the color calculation line segment, the distance from the position of the achromatic color C0 to the specific color region RN (region boundary line LR1) is longer than the distance from the entire color region boundary line to the specific color region RN (region boundary line LR2). .

  In step S117, color change processing is performed. In the color change process, the signal processing circuit 100 changes the color of the processing target pixel PX to the calculated out-of-region low saturation color Z, and the pixel PN (see FIG. 5) is changed to an out-of-region high saturation color Y (see FIG. 6B).

  Note that when changing the color of a pixel in the color change process, in the UCS chromaticity diagram, the color space in which the data driving circuit 210 can process the position of the color to be changed (for example, the out-of-region low saturation color Z). Inverse coordinate conversion processing is performed for conversion to a position in (for example, the RGB color space). That is, the color of the pixel whose color is to be changed (for example, the processing target pixel PX) is changed to the color to be changed (for example, the low saturation color Z outside the region in the RGB color space) that has been subjected to the inverse coordinate conversion process. The

  FIG. 6B is a diagram for explaining that a target color (color CX) is displayed by two pixels. This coincides with the fact that the color information of a normal television signal is transmitted as a color difference signal, and the frequency component is half that of the luminance signal, that is, only the same color information exists in two pixels adjacent in the horizontal direction. This means that this method of realizing a desired signal with an average of two pixels has an advantage that the resolution is not reduced. Note that the color change is the value of Δu′v ′ in FIG. 2, and the limit value that can be identified by a general human being is said to be around 0.01. If the color is corrected with an error within this range, Good.

  As shown in FIG. 6B, when the user (human) views the processing target pixel PX indicating the out-of-region low saturation color Z and the pixel PN indicating the out-of-region high saturation color Y, the user performs processing. The colors of the two pixels of the target pixel PX and the pixel PN are perceived as a color CX by the characteristics of the eyes. This is because the average color of the out-of-region low saturation color Z and the out-of-region high saturation color Y is the color CX. That is, by this process, the color of the pixel determined to be a color in the specific color region RN can be expressed using a plurality of colors outside the specific color region RN and a plurality of pixels.

  As illustrated in FIG. 5, the pixel PN may be a pixel adjacent to the left of the processing target pixel PX instead of the pixel adjacent to the right of the processing target pixel PX. Note that when the processing target pixel PX is the rightmost pixel in the acquired image G100, the pixel PN is a pixel on the left side of the processing target pixel PX. The pixel PN may be a pixel adjacent above or below the processing target pixel PX.

  In FIG. 7 again, after the process of step S117, the process of step S112B described above is performed.

  The pixels in which the acquired image G100 is determined to be a color in the specific color region RN in the acquired image G100 by repeatedly performing the processes in steps S112 to S117 described above until it is determined YES in step S112B. Is changed to an image (hereinafter referred to as a color-changed image) expressed by two pixels respectively indicating the colors Z and Y.

  When the process of step S112 is performed on all the pixels constituting one image, YES is determined in step S112B, the signal processing circuit 100 sets the value of S to “1”, and the process of step S119. Is done.

  In step S119, an image display process is performed. In the image display process, the signal processing circuit 100 transmits the color change image to the scan driving circuit 220. Then, the signal processing circuit 100 transmits a scanning signal for displaying the color-changed image on the image display surface of the liquid crystal panel 230 to the scanning driving circuit 220. By this process, the color change image is displayed on the image display surface of the liquid crystal panel 230.

Then, the process of step S111 is performed again.
As described above, according to the first embodiment, it is determined for each of a plurality of pixels constituting the acquired image whether or not the color of the pixel is a color within the specific color region RN. The specific color region RN is displayed on the image display surface that the user feels on the display surface vertical axis that is inclined by a predetermined angle in the horizontal direction and the color that is displayed on the image display surface that the user feels on the display surface vertical axis. It is an area including a plurality of colors whose difference from the color is a predetermined value or more.

  Then, based on the position of the pixel (processing target pixel) determined to be a color within the specific color region RN, the color is outside the specific color region RN on the color calculation line segment, and the region boundary line LR2 The out-of-region high saturation color Y most adjacent to is calculated. Further, based on the position of the processing target pixel, the color is outside the specific color region RN on the color calculation line segment, and is separated from the position of the color CX by the CX-Y distance in the direction of the achromatic color C0. A low saturation color Z outside the region of the position is calculated.

  In addition, the color of the processing target pixel is changed to the calculated out-of-region low saturation color Z, and the color of the pixel PN adjacent to the processing target pixel in the horizontal direction is changed to the out-of-region high saturation color Y. The change process is performed on all the processing target pixels.

  The color-changed image generated by the above processing is displayed on the image display surface of the liquid crystal panel 230. That is, the color-changed image displayed on the image display surface does not use the color in the specific color region RN that has a relatively large color change depending on the angle at which the user views the image display surface. In other words, the color of the pixel determined to be the color of the image is expressed using a plurality of pixels and an out-of-region high chroma color Y and an out-of-region low chroma color Z outside the specific color region RN. Therefore, the change in the color of the image due to the viewing angle can be greatly reduced. That is, the color shift caused by the angle at which the image display surface on which the image is displayed is viewed can be greatly reduced.

  Note that the processing described in the first embodiment greatly reduces the change in the color of the image due to the viewing angle by using only the signal processing without using a liquid crystal panel having a different driving method from the VA method. That is, the change in the color of the image due to the viewing angle can be greatly reduced without changing manufacturing equipment, processes, and the like.

<Modification of the first embodiment>
In the color misregistration reduction process according to the first embodiment, when the position of the color of the processing target pixel in the specific color area RN is closer to the area boundary line LR2 than to the area boundary line LR1, the position of the color Z Is within the specific color region RN. In this case, there arises a problem that the color of the processing target pixel is changed to a color that causes a color shift depending on the viewing angle.

  Further, when the position of the color of the processing target pixel in the specific color area RN is closer to the area boundary line LR2 than to the area boundary line LR1, the position of the color Z is set to a position outside the specific color area RN. In addition, when the process for determining the position of the color Y is performed, the color Y may be the primary color. In this case, there arises a problem that a desired color cannot be displayed.

  Next, in order to solve the above problem, a process for expressing the color of the pixel in the specific color region RN with four pixels will be described. Although details will be described later, in a natural picture displayed by a television receiver, there is almost no fine pattern in color information, that is, there is almost no high frequency component. Is less affected. In this case, since the specific color region RN can be divided into four equal parts, by using the weighting of 1: 3, it is possible to realize the expression of the color of the region that was difficult with the above-described two-pixel method.

  Since the configuration and function of the liquid crystal display device according to the modification of the first embodiment are the same as those of liquid crystal display device 1000 of FIG. 1, detailed description will not be repeated.

(Processing for color shift reduction)
Next, processing for reducing color misregistration that occurs according to the viewing angle (hereinafter referred to as color misregistration reduction processing A) will be described.

  FIG. 7 is a flowchart of the color misregistration reduction process A. In FIG. 7, the process with the same step number as the step number of FIG. 4 is performed in the same way as the process described in the first embodiment, and therefore detailed description will not be repeated.

  In steps S111, S112, and S113 of the color misregistration reduction process A, the same processes as those described in the first embodiment are performed.

  In step S113A, the signal processing circuit 100 determines whether or not the position of the color of the processing target pixel is a position in a color area RY described later.

  FIG. 8 is a diagram for describing processing for expressing the color of a pixel determined to be a color in the specific color region RN using a plurality of colors outside the specific color region RN.

  FIG. 8A is a diagram illustrating the color calculation line segments described in the first embodiment. In FIG. 8A, the color region RY is a region adjacent to the region boundary line LR2 among the four regions obtained by dividing the specific color region RN on the color calculation line segment into four equal parts. That is, the color region RY is a region in the specific color region RN on the color calculation line segment, and is a region closer to the region boundary line LR2 than the region boundary line LR1.

  In FIG. 7 again, if YES in step S113A, the process proceeds to step S214A described later. On the other hand, if NO at step S113A, the process proceeds to the process at step S113B. Here, assuming that the color position of the pixel to be processed is a position in the color region RY, the process proceeds to the process of step S214A.

  In step S113B, the signal processing circuit 100 determines whether the color position of the processing target pixel is closer to the region boundary line LR1 than to the region boundary line LR2. If YES in step S113B, the process proceeds to the process in step S114. If it is determined as YES in step S113B, the position of the color of the processing target pixel is a position in the specific color area RN and a position on the achromatic color C0 side from the middle of the specific color area RN.

  On the other hand, if NO at step S113B, the process proceeds to the process at step S214A. If it is determined as NO in step S113B, the position of the color of the processing target pixel is a position in the specific color area RN and a position between the middle of the specific color area RN and the color area RY. is there.

  Since the processing of steps S114 to S117 has been described in the first embodiment, detailed description thereof will not be repeated.

  In step S214A, the signal processing circuit 100 calculates a low saturation color outside the first region. As shown in FIG. 8A, the low saturation color outside the first region is a color outside the specific color region RN on the color calculation line segment and closest to the region boundary line LR1. It is.

  In step S215A, the signal processing circuit 100 calculates the distance between the position of the color CX and the position of the low saturation color Z outside the first region (hereinafter referred to as CX-Z distance).

  In step S216A, the signal processing circuit 100 calculates a high saturation color outside the second region. As shown in FIG. 8A, the high saturation color outside the second region is a color outside the specific color region RN on the color calculation line segment, and from the position of the color CX toward the primary color CP. The color Y is located at a distance (L2B) that is 1/3 times the CX-Z distance (L1A). That is, as shown in FIG. 8A, the ratio of the CX-Z distance (L1A) and the distance (L2B) between the position of the color CX and the high saturation color Y outside the second region is 3: 1.

  Note that when the process of step S216A is performed after NO is determined in step S113B, the second outside high-saturation color is a color in the specific color area RN. In this case, the signal processing circuit 100 sets the calculated second outside high-saturation color as a color Y that is outside the specific color region RN on the color calculation line segment and closest to the region boundary line LR2. .

  In step S217A, color change processing A is performed. In the color change processing A, the signal processing circuit 100 changes the color of the processing target pixel PX to the calculated low saturation color Z outside the first region and is a pixel adjacent to the processing target pixel PX in the horizontal direction. The color of PN (see FIG. 5) is changed to the high saturation color Y outside the second region (see FIG. 8B). In addition, the signal processing circuit 100 changes the color of the pixel PN1 and the color of the pixel PN2 to the high saturation color Y outside the second region (see FIG. 8B). When the color of the pixel is changed in the color change processing A, the data driving circuit 210 can process the position of the color to be changed (for example, the low saturation color Z outside the first region) in the UCS chromaticity diagram. Inverse coordinate conversion processing is performed for conversion to a position in a simple color space (for example, RGB color space). That is, the color of the pixel whose color is to be changed (for example, the processing target pixel PX) is changed to the color to be changed (for example, the low saturation color Z outside the first region in the RGB color space) that has been subjected to inverse coordinate conversion processing. Be changed.

  The image processing performed in the color change processing A is a dither method for color intensity. In the color changing process A, the error diffusion method as image processing may be performed without being limited to the dither method.

  The pixel PN1 is a pixel adjacent to the processing target pixel PX in the vertical direction. Note that when the processing target pixel PX is the lowermost pixel in the acquired image G100 in FIG. 5, the pixel PN1 is a pixel adjacent to the processing target pixel PX. The pixel PN2 is a pixel adjacent to the pixel PN in the vertical direction and adjacent to the pixel PN1 in the horizontal direction.

  As shown in FIG. 8B, the user (human) views the processing target pixel PX indicating the first out-of-region low saturation color Z and the pixels PN, PN1, and PN2 indicating the out-of-region high saturation color Y. Then, the user feels the color of the four pixels of the processing target pixel PX and the pixels PN, PN1, and PN2 as the color CX due to the eye characteristics. That is, by this process, the color of the pixel determined to be a color in the specific color region RN can be expressed using a plurality of colors outside the specific color region RN and a plurality of pixels.

  As described above, when the processing target pixel PX is the rightmost pixel in the acquired image G100, the pixel PN is a pixel adjacent to the left of the processing target pixel PX. In this case, the pixel PN2 is a pixel adjacent to the left of the pixel PN1. That is, the position of the pixel PN2 varies depending on the positions of the pixels PN and PN1.

After step S217A, step S112B is performed.
The process of steps S214A to S217A and the process of steps S112 to S117 described in the first embodiment described above are repeated until YES is determined in step S112B, whereby the acquired image G100 is changed in color. It is changed to image A. The color change image A is expressed by four pixels in which the color of one pixel in the color area RY in the specific color area RN in the acquired image G100 is composed of a pixel indicating the color Z and three pixels indicating the color Y. It is an image that was made. The color-changed image A is also an image in which the color of the pixel determined to be a color in the specific color region RN in the acquired image G100 is expressed by two pixels that respectively indicate the colors Z and Y.

  When the process of step S112 is performed on all the pixels constituting one image, YES is determined in step S112B, the signal processing circuit 100 sets the value of S to “1”, and the process of step S119A Is done.

  In step S119A, image display processing A is performed. In the image display process A, the signal processing circuit 100 transmits the signal of the color changed image A to the data driving circuit 210. The data driving circuit 210 transmits the received image signal to the liquid crystal panel 230. Then, the signal processing circuit 100 transmits a scanning signal for displaying the color-changed image A on the image display surface of the liquid crystal panel 230 to the scanning driving circuit 220. By this processing, the color change image A is displayed on the image display surface of the liquid crystal panel 230.

Then, the process of step S111 is performed again.
As described above, according to the modification of the first embodiment, the four pixels using the color outside the specific color region RN as the color of the processing target pixel according to the color position of the processing target pixel. Or the color of the pixel to be processed is expressed by two pixels using colors outside the specific color area RN.

  Therefore, in the process according to the modification of the first embodiment, the change in the color of the image due to the viewing angle can be further reduced more than in the first embodiment. That is, the color shift caused by the angle at which the image display surface on which the image is displayed is viewed can be further greatly reduced.

<Second Embodiment>
Next, a process for reducing a change in the color of an image due to a viewing angle will be described by using a plurality of continuous images (frames), as compared with the modification of the first embodiment.

  FIG. 9 is a block diagram illustrating a configuration of a liquid crystal display device 1000B according to the second embodiment. As shown in FIG. 9, the liquid crystal display device 1000B is different from the liquid crystal display device 1000 of FIG. 1 in that the liquid crystal display device 1000B further includes a frame buffer 240B. The rest of the configuration is the same as that of the liquid crystal display device 1000, and the detailed description will not be repeated.

  The frame buffer 240B is a memory that temporarily stores an image. As an example, it is assumed that the frame buffer 240B can store four images (frames). Note that the frame buffer 240B is not limited to four, and may store five or more images (frames).

  The signal processing circuit 100 performs image processing such as color processing (for example, color shift reduction processing B described later) and gamma correction on the input image signal IMG, and the image signal subjected to the image processing is converted into a frame. Transmit to buffer 240B. When the frame buffer 240B stores four images and receives a new image signal from the signal processing circuit 100, the frame buffer 240B outputs the image signal stored most quickly among the four images as data. Transmit to the drive circuit 210. Note that even when only one image is stored in the frame buffer 240B, the stored image signal is transmitted to the data driving circuit 210 when it is time to display the stored image. To do.

The data driving circuit 210 transmits the received image signal to the liquid crystal panel 230.
The signal processing circuit 100 also displays an image based on the image signal received by the liquid crystal panel 230 on the image display surface of the liquid crystal panel 230 at a timing when the liquid crystal panel 230 receives the image signal transmitted from the frame buffer 240B. A control signal for display is transmitted. The processing for displaying an image on the image display surface of the liquid crystal panel 230 is the same as that of a general VA liquid crystal display device, and therefore will not be described in detail.

(Processing for color shift reduction)
Next, processing for reducing color misregistration that occurs according to the viewing angle (hereinafter referred to as color misregistration reduction processing B) will be described. It is assumed that the signal processing circuit 100 holds the value of the frame counter n. It is assumed that the initial value of the frame counter n is “0”. Note that the signal processing circuit 100 acquires a plurality of images (frames) for continuous display in a predetermined order one by one from the outside.

  FIG. 10 is a flowchart of the color misregistration reduction process B. In FIG. 10, the processing with the same step number as that of FIG. 7 is performed in the same manner as the processing described in the first embodiment and the modification of the first embodiment, so that detailed description will be repeated. Absent.

  In step S111B, the signal processing circuit 100 acquires an image from the outside. Specifically, the signal processing circuit 100 acquires an image signal indicating an image from the outside. Hereinafter, the image indicated by the image signal acquired by the signal processing circuit 100 is referred to as an acquired image. Here, it is assumed that the acquired image is the acquired image G100 in FIG. As an example, the size of the acquired image G100 is assumed to be 1920 pixels wide and 1080 pixels vertical.

  In addition, when the image is acquired, the signal processing circuit 100 increments the frame counter n by “1”.

  In step S111C, the signal processing circuit 100 determines whether or not the value of the frame counter n is “1”. If YES in step S111C, the process proceeds to step S112. On the other hand, if NO at step S111C, the process proceeds to step S321B described later. Here, it is assumed that the value of the frame counter n is “1”, and the process proceeds to step S112.

  In steps S112 and S113 of color misregistration reduction processing B, processing similar to the processing described in the first embodiment is performed.

  In step S113N, the signal processing circuit 100 determines whether or not the position of the color of the processing target pixel is a position in a color area RYB described later.

  FIG. 11 is a diagram for describing processing for expressing the color of a pixel determined to be a color within the specific color region RN using a plurality of colors outside the specific color region RN.

  FIG. 11A is a diagram illustrating the color calculation line segment described in the first embodiment. FIG. 11A is an enlarged view of the specific color region RN in FIG. In FIG. 11A, since the color region RY has been described with reference to FIG. 8A, detailed description will not be repeated.

  In FIG. 11A, the color region RYB is a region adjacent to the region boundary line LR2 among four regions obtained by dividing the color region RY on the color calculation line segment into four equal parts. That is, the color region RYB is a region in the specific color region RN on the color calculation line segment and is closer to the region boundary line LR2 than the region boundary line LR1.

  In FIG. 10 again, if YES in step S113N, the process proceeds to a process in step S314B described later. On the other hand, if NO at step S113N, the process proceeds to step S113A. Here, it is assumed that the color position of the processing target pixel is a position in the color region RYB, and the process proceeds to the process of step S314B.

  In step S113A, step S113B, step S114 to S117, and step S214A to S217A, the same processes as those described in the first embodiment and the modified example of the first embodiment are performed, and thus detailed description will be given. Does not repeat.

  In step S314B, a process similar to that in step S214A is performed, and thus detailed description will not be repeated. By this process, the low saturation color outside the first region is calculated. As shown in FIG. 11A, the low saturation color outside the first region is a color outside the specific color region RN on the color calculation line segment and closest to the region boundary line LR1. It is.

  In step S315B, a process similar to the process of step S215A is performed, and thus detailed description will not be repeated. With this processing, the distance between the position of the color CX and the position of the low saturation color Z outside the first region (hereinafter referred to as CX-Z distance) is calculated.

  In step S316B, the signal processing circuit 100 calculates a high saturation color outside the third region. As shown in FIG. 11A, the high saturation color outside the third region is a color outside the specific color region RN on the color calculation line segment, and from the position of the color CX toward the primary color CP. The color Y is located at a distance (L2D) that is 1/15 times the CX-Z distance (L1C). That is, as shown in FIG. 11A, the ratio of the CX-Z distance (L1C) and the distance (L2D) between the position of the color CX and the high saturation color Y outside the third region is 15: 1.

  In step S317B, color change processing AB is performed. The color change process AB is a process in which the second outside high-saturation color is replaced with the third outside-high color saturation color in the description of the color change process A in step S217A of FIG. With this processing, when the frame counter n is “1”, the colors set to the four pixels in the acquired image are the four pixels indicated by the n frame shown in FIG. 11B. Hereinafter, the four pixels whose color has been changed by the process of step S317B are referred to as a color-changed pixel group.

After the process of step S317B, the process proceeds to the process of step S318B.
In step S318B, the signal processing circuit 100 stores color change information indicating the coordinates of each of the four pixels that form the color-changed pixel group and the calculated high saturation color Y outside the third region. The high saturation color Y outside the third region indicated by the color change information is a color expressed in a color space (for example, an RGB color space) that can be processed by the data driving circuit 210.

  Each time the process of step S318B is repeated, the signal processing circuit 100 further stores color change information. That is, when the process of step S318B is repeated a plurality of times, the signal processing circuit 100 stores a plurality of pieces of color change information.

After the process of step S318B, the process of step S112B is performed.
Then, the above-described steps S112, S113, S113N, S113A, S113B, S114 to S117, steps S214A to S217A, and steps S314B to S318B are repeatedly performed until YES is determined in step S112B. The image G100 is changed to the color change image A described above.

  When the process of step S112 is performed on all the pixels constituting one image, YES is determined in step S112B, the signal processing circuit 100 sets the value of S to “1”, and the process of step S119B. Is done.

  In step S119B, image display processing B is performed. In the image display process B, the signal processing circuit 100 transmits the generated latest image (for example, the color-changed image A) to the frame buffer 240B. The frame buffer 240B transmits a signal of the received image (for example, the color-changed image A) to the data driving circuit 210. The data driving circuit 210 transmits the received image signal to the liquid crystal panel 230.

  In addition, the signal processing circuit 100 transmits a scanning signal for displaying an image (for example, the color change image A) received by the liquid crystal panel 230 on the image display surface of the liquid crystal panel 230 to the scanning driving circuit 220. With this process, the latest image (for example, color-changed image A) is displayed on the image display surface of the liquid crystal panel 230.

  Then, the process of step S111B is performed again. By the process of step S111B, an acquired image to be displayed next to the acquired image when the frame counter n is “1” is obtained. Further, the frame counter n is set to “2” by the process of step S111B.

  Then, it is determined NO in step S111C, and the process proceeds to step S321B.

  In the following, in the acquired image when the frame counter n is any of “2” to “4”, a pixel group consisting of four pixels at the same position as the color-changed pixel group described above is subject to color change. It is called a pixel group.

  In step S321B, the signal processing circuit 100 determines whether or not the value of the frame counter n is 5. If YES in step S321B, the process proceeds to step S330B described later. On the other hand, if NO at step S321B, the process proceeds to step S327B. Here, it is assumed that the value of the frame counter n is “2”, and the process proceeds to step S327B.

  In step S327B, color change processing B is performed. In the color change process B, the signal processing circuit 100 converts one or more color change target pixel groups in the latest acquired image into the corresponding high saturation color outside the third region based on the stored one or more color change information. Change to Y. Hereinafter, a pixel group including four pixels whose color has been changed by the process of step S327B is also referred to as a color-changed pixel group.

  For example, when one color change information indicates the coordinates of each of the four pixels constituting the color-changed pixel group in the acquired image G100 in FIG. 5 and the high saturation color Y outside the third region, the color change process B Then, the colors of the four pixels at the same positions as the positions of the four pixels shown in FIG. 5 in the latest acquired image are changed to the high saturation color Y outside the third region.

  In this case, the colors set for the four pixels constituting the color change target pixel group in the acquired image are the four pixels indicated by the n + 1 frame shown in FIG. 11B. If there are a plurality of pieces of color change information, the colors of the plurality of color change target pixel groups in the latest acquired image are changed to the high saturation color Y outside the third region indicated by the corresponding color change information.

  In step S328B, the signal processing circuit 100 deletes one or more stored color change information. Then, the process of step S119B is performed again. By this process, the image whose color has been changed by the process of step S327B is displayed on the image display surface of the liquid crystal panel 230.

Then, the process of step S111B is performed again.
If YES in step S321B, the process proceeds to step S330B.

  In step S330B, the signal processing circuit 100 sets the value of the frame counter n to “1”. Then, the process of step S112B is performed again.

  By repeating the process described above, the first image displayed on the image display surface of the liquid crystal panel 230 is the color change process in step S117, the color change process A in step S217A, and the color change process in step S317B. The image is changed in color by at least one process of AB. In addition, the second to fourth images displayed on the image display surface of the liquid crystal panel 230 are images whose colors have been changed by the color change process B in step S327B.

  That is, the first image displayed on the image display surface indicates one or more color-changed pixel groups indicated by the n frame in FIG. The second image displayed on the image display surface indicates one or more color-changed pixel groups indicated by the (n + 1) th frame in FIG. The third image displayed on the image display surface indicates one or more color-changed pixel groups indicated by the n + 2 frame in FIG. The fourth image displayed on the image display surface indicates one or more color-changed pixel groups indicated by the n + 3 frame in FIG. That is, in the color misregistration reduction process B, the color of the processing target pixel is expressed by 16 pixels using colors outside the specific color region RN.

  As shown in FIG. 11B, when the user (human) views the image display surface on which the first to fourth images are continuously displayed, the color-changed pixel group at the same position in the image. The color of the four pixels constituting the color CX is perceived as a color CX by the characteristics of the eyes.

  As described above, according to the second embodiment, according to the position of the color of the processing target pixel, the color of the processing target pixel is changed using four images (frames) that are displayed in succession. It is expressed by 16 pixels using colors outside the specific color area RN. Note that the color misregistration reduction processing B also performs processing included in the modification of the first embodiment in accordance with the color position of the processing target pixel.

  Therefore, in the process according to the second embodiment, the change in the color of the image due to the viewing angle can be further reduced as compared with the modification of the first embodiment. That is, the color shift caused by the angle at which the image display surface on which the image is displayed is viewed can be further greatly reduced.

  Note that the processing of the second embodiment is performed as long as the same processing as the image display processing A in step S119A in FIG. 7 is performed in the color misregistration reduction processing B in FIG. 10 instead of the image display processing B in step S119B. The liquid crystal display device 1000 in FIG. 1 can also be executed.

  In the second embodiment, the color of the processing target pixel is assigned as in the four color-changed pixel groups shown in FIG. 11B. However, the present invention is not limited to this. The present invention can be implemented even if the Y and color Z assignments are other than those shown in FIG.

  In the second embodiment, four consecutive images (frames) are used. However, more than five consecutive images are used to represent the color within the specific color region RN more accurately. May be. Of course, the present invention can be implemented in combinations other than 4 pixels × 4 frames. For example, the present invention can be implemented by a combination of 2 pixels × 4 frames, 4 pixels × 2 frames, and the like.

  In the second embodiment, it is expressed by 16 pixels using colors outside the specific color area RN. That is, when the color density is reduced to 1/16 unit, the color Z and the color Y may be a sufficient number of colors in a general image even if they are fixed discrete colors adjacent to the boundary of the region. Many. Therefore, in the present invention, the color Y may be a fixed discrete color adjacent to the region boundary line LR2 without calculating the third region high saturation color Y according to the color position of the processing target pixel. .

  Further, according to the present invention, the high-saturation color Y outside the third region is not calculated according to the color position of the processing target pixel, and the color position of the processing target pixel is close to a discrete position within the specific color region RN. By determining whether or not the number of colors Y and Z to be used is calculated, the color of the processing target pixel may be expressed by the calculated number of colors Y and Z.

  Note that even moving images that move violently are not recognized by the user until the nuances of fine colors are included, and switching between multiple frames (still images / fine colors) and single frames (moving images / somewhat rough colors) while incorporating the video detection algorithm. Such processing may be performed.

  In the present invention, it is of course desirable to shift the position by round-robbing the color on the minority side in order to avoid a specific dot pattern.

(Experimental result)
Next, in the inventors' experiments, it has been found that the first color that the majority of general viewers point out color changes is a skin color. Other primary color systems were insensitive or tolerant of some color change. Specifically, in the UCS chromaticity diagram, when the value of Δu′v ′ is 0.008, skin color is pointed out as a color change, whereas red and blue have a value of Δu′v ′ of 0. In the case of 0.03 or 0.04, there was an indication of a color change. Therefore, it has been found that the circuit scale can be reduced by applying the present invention only to the skin color. In the following, in the UCS chromaticity diagram, an area showing the skin color is referred to as a skin color area RM.

  FIG. 12 is a diagram for explaining a skin color region RM in the UCS chromaticity diagram. In FIG. 12, the skin color region RM is a region connecting the position of u ′ = 0.2, v ′ = 0.46 and the position of u ′ = 0.32, v ′ = 0.54. The length of the skin color region RM is Δu′v′0.03. The inventors have found that the vicinity of the skin color region RM is recognized as a skin color by the above experiment.

  A simple processing circuit such as a look-up table can be used as long as the skin color region RM is sized. In FIG. 12, the color DS indicates the coordinates of the Dark Skin of the Macbeth chart. The Macbeth chart is a reference color chart for adjusting the color balance of a camera, a photographing device or the like when photographing a movie. The color LS indicates the coordinates of the Light Skin of the Macbeth chart. This area is a typical skin color. Note that the colors DS and LS are included in the specific color region RN.

(Function block diagram)
FIG. 13 is a functional block diagram of the signal processing circuit 100 in the first embodiment, a modification of the first embodiment, and the second embodiment.

  As illustrated in FIG. 13, the signal processing circuit 100 includes an acquisition unit 101, a color determination unit 102, a color processing unit 103, and a position determination unit 104.

  The acquisition unit 101 acquires an image. For each of the plurality of pixels constituting the image, the color determination unit 102 determines whether the color of the pixel is a color within a specific color region on the chromaticity diagram indicating all colors that can be displayed by the liquid crystal display device. A color determination process is performed to determine whether or not.

  The color processing unit 103 is a color outside the specific color region based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color region by the color determination unit 102 and is processed. A color calculation process for calculating a first color having a lower saturation than the color of the target pixel and a second color having a color outside the specific color area and having a higher saturation than the color of the processing target pixel; A color changing process for changing the color of the pixel to one of the first color and the second color and changing the color of the pixel in the vicinity of the pixel to be processed to the other of the first color and the second color. This is performed for the target pixel.

  The position determination unit 104 indicates the boundary of the entire color region including all colors from the position of the achromatic color on the chromaticity diagram via the position of the color of the processing target pixel. Whether the position is within a specific color area on a line connecting all the color area boundary lines, and within a predetermined area that is closer to the second boundary line position than the first boundary line position Determine whether or not.

  When the position determination unit 104 determines that the color position of the processing target pixel is a position within the predetermined area, the color processing unit 103 changes the color calculation process and the color of the processing target pixel to the first color, In addition, a plurality of color change processing for changing the color of a plurality of pixels in the vicinity of the processing target pixel to the second color is performed for all the processing target pixels for which the color position is determined to be a position within the predetermined area. Do.

  Note that all or part of the acquisition unit 101, the color determination unit 102, the color processing unit 103, and the position determination unit 104 included in the signal processing circuit 100 may be configured by hardware. Further, all or part of the acquisition unit 101, the color determination unit 102, the color processing unit 103, and the position determination unit 104 may be a module of a program executed by the signal processing circuit 100.

  The present invention can also be realized as a program that causes a computer to execute the steps shown in the flowcharts of FIGS. 4, 7, and 10. The present invention can also be realized as a computer-readable recording medium and an integrated circuit for storing the program.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the color processing in the present invention, it is possible to reduce the change in the color of the image due to the viewing angle by the VA liquid crystal display device, and it is possible to realize high image quality.

It is a block diagram which shows the structure of the liquid crystal display device in 1st Embodiment. It is a figure for demonstrating the color shift for every viewing angle from the achromatic color to a primary color on a UCS chromaticity diagram. In a UCS chromaticity diagram, it is a diagram showing a specific color region RN. It is a flowchart of a color misregistration reduction process. It is a figure which shows the acquired image as an example. It is a figure for demonstrating the process for expressing the color of the pixel determined to be the color in the specific color area | region RN using the several color outside the specific color area | region RN. 5 is a flowchart of color misregistration reduction processing A. It is a figure for demonstrating the process for expressing the color of the pixel determined to be the color in the specific color area | region RN using the several color outside the specific color area | region RN. It is a block diagram which shows the structure of the liquid crystal display device in 2nd Embodiment. 10 is a flowchart of color misregistration reduction processing B. It is a figure for demonstrating the process for expressing the color of the pixel determined to be the color in the specific color area | region RN using the several color outside the specific color area | region RN. In the UCS chromaticity diagram, it is a diagram for explaining a skin color region RM. It is a functional block diagram of a signal processing circuit in a 1st embodiment, a modification of the 1st embodiment, and a 2nd embodiment. It is a figure which shows the characteristic of the liquid crystal panel of a VA system. It is a figure for demonstrating the change of a color.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Signal processing circuit 230 Liquid crystal panel 1000,1000B Liquid crystal display device

Claims (18)

A VA (Vertical Alignment) type liquid crystal display device having a display surface for displaying an image,
An acquisition unit for acquiring images;
For each of a plurality of pixels constituting the image, it is determined whether or not the color of the pixel is a color within a specific color region on a chromaticity diagram indicating all colors that can be displayed by the liquid crystal display device. A color determination unit that performs color determination processing,
When the color is displayed on the display surface, the specific color area includes a color displayed on the display surface that a human feels on an axis perpendicular to the display surface, and a human being on the axis inclined by a predetermined angle. A region on the chromaticity diagram including a plurality of colors having a difference from a color displayed on the display surface to be felt is a predetermined value or more;
Based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color region by the color determination unit, the color is outside the specific color region, and the processing target pixel A color calculation process for calculating a first color having a saturation lower than that of the color, and a second color having a color outside the specific color area and having a saturation higher than that of the pixel to be processed; A color change process for changing a color of a pixel to one of the first color and the second color and changing a color of a pixel in the vicinity of the processing target pixel to the other of the first color and the second color; A color processing unit that performs the processing on all the pixels to be processed;
A liquid crystal display device further comprising: a display unit that displays an image including all the processing target pixels processed by the color processing unit. The specific color area is arranged in an entire color area including all the colors indicated by the chromaticity diagram,
The position of the achromatic color in a line segment connecting from the position of the achromatic color on the chromaticity diagram to the whole color area boundary line indicating the boundary of the whole color area via the color position of the pixel to be processed The distance from the specific color region is longer than the distance from the all color region boundary line to the specific color region,
The first color is a color at a position between the position of the achromatic color and the specific color region in the line segment,
The second color is a color at a position between the specific color region and the all-color region boundary line in the line segment.
The liquid crystal display device according to claim 1. In the line segment, the distance between the color position of the processing target pixel and the position of the first color is the same as the distance between the color position of the processing target pixel and the position of the second color.
The liquid crystal display device according to claim 2. The line segment passes through first and second boundary positions on an area boundary line indicating a boundary of the specific color area,
The position on the first boundary line is a position closer to the achromatic position than the position on the second boundary line,
A predetermined area in which the color position of the processing target pixel is an area in the specific color area on the line segment and is closer to the second boundary line position than the first boundary line position A position determination unit that determines whether or not the position is within,
The color processing unit determines the color calculation process and the color of the processing target pixel when the position determination unit determines that the position of the color of the processing target pixel is a position within the predetermined region. And changing the color of the plurality of pixels in the vicinity of the processing target pixel to the second color, and determining that the color position is a position in the predetermined area. For all the pixels to be processed,
The liquid crystal display device according to claim 2. The acquisition unit acquires a plurality of images for continuous display in a predetermined order,
The color determination unit performs the color determination process on any one of the plurality of images acquired by the acquisition unit,
When the position determination unit determines that the color position of the pixel to be processed is a position in the predetermined area, the color processing unit performs the color calculation process and the multiple color change process, The process is performed for all the processing target pixels included in the image subjected to the color determination process, which is determined to be a position in the predetermined area, and the color determination process is performed among the plurality of images. For an image to be displayed after the processed image, the color of the pixel at the same position as the position of the pixel to be processed on which the color calculation process and the multiple color change process have been performed, and a plurality of pixels in the vicinity of the pixel Changing the color of the pixel to the second color;
The liquid crystal display device according to claim 4. The processing target pixel and a pixel in the vicinity of the processing target pixel are adjacent in the horizontal direction.
The liquid crystal display device according to claim 1.   The liquid crystal display device according to claim 1, wherein the color changing process performed by the color processing unit is a process based on a dither method or an error diffusion method. The specific color region is a region including skin color.
The liquid crystal display device according to claim 1. The chromaticity diagram is a UCS (Uniform Color Scale) chromaticity diagram.
The liquid crystal display device according to claim 1. A color processing method performed by a VA (Vertical Alignment) liquid crystal display device having a display surface for displaying an image,
An acquisition step of acquiring an image;
For each of a plurality of pixels constituting the image, it is determined whether or not the color of the pixel is a color within a specific color region on a chromaticity diagram indicating all colors that can be displayed by the liquid crystal display device. A color determination step for performing color determination processing,
When the color is displayed on the display surface, the specific color area includes a color displayed on the display surface that a human feels on an axis perpendicular to the display surface, and a human being on the axis inclined by a predetermined angle. A region on the chromaticity diagram including a plurality of colors having a difference from a color displayed on the display surface to be felt is a predetermined value or more;
Based on the position of the color of the processing target pixel that is a pixel determined to be a color within the specific color area by the color determination step, the color is outside the specific color area and the processing target pixel A color calculation process for calculating a first color having a saturation lower than that of the color, and a second color having a color outside the specific color area and having a saturation higher than that of the pixel to be processed; A color change process for changing a color of a pixel to one of the first color and the second color and changing a color of a pixel in the vicinity of the processing target pixel to the other of the first color and the second color; A color processing step for performing all of the processing target pixels;
A color processing method, further comprising: a display step of displaying an image including all the processing target pixels processed by the color processing step. The specific color area is arranged in an entire color area including all the colors indicated by the chromaticity diagram,
The position of the achromatic color in a line segment connecting from the position of the achromatic color on the chromaticity diagram to the whole color area boundary line indicating the boundary of the whole color area via the color position of the pixel to be processed The distance from the specific color region is longer than the distance from the all color region boundary line to the specific color region,
The first color is a color at a position between the position of the achromatic color and the specific color region in the line segment,
The second color is a color at a position between the specific color region and the all-color region boundary line in the line segment.
The color processing method according to claim 10. In the line segment, the distance between the color position of the processing target pixel and the position of the first color is the same as the distance between the color position of the processing target pixel and the position of the second color.
The color processing method according to claim 11. The line segment passes through first and second boundary positions on an area boundary line indicating a boundary of the specific color area,
The position on the first boundary line is a position closer to the achromatic position than the position on the second boundary line,
A predetermined area in which the color position of the processing target pixel is an area in the specific color area on the line segment and is closer to the second boundary line position than the first boundary line position A position determination step for determining whether or not the position is within,
In the color processing step, when the position determination step determines that the color position of the processing target pixel is a position within the predetermined region, the color calculation process and the color of the processing target pixel are set to the first color. And changing the color of the plurality of pixels in the vicinity of the processing target pixel to the second color, and determining that the color position is a position in the predetermined area. For all the pixels to be processed,
The color processing method according to claim 11. The obtaining step obtains a plurality of images for continuous display in a predetermined order,
The color determination step performs the color determination process on any one of the plurality of images acquired by the acquisition step,
In the color processing step, when the position determination step determines that the color position of the processing target pixel is a position in the predetermined area, the color calculation process and the multiple color change process are performed. The process is performed for all the processing target pixels included in the image subjected to the color determination process, which is determined to be a position in the predetermined area, and the color determination process is performed among the plurality of images. For an image to be displayed after the processed image, the color of the pixel at the same position as the position of the pixel to be processed on which the color calculation process and the multiple color change process have been performed, and a plurality of pixels in the vicinity of the pixel Changing the color of the pixel to the second color;
The color processing method according to claim 13. The processing target pixel and a pixel in the vicinity of the processing target pixel are adjacent in the horizontal direction.
The color processing method according to claim 10.   The color processing method according to claim 10, wherein the color changing process performed by the color processing step is a process based on a dither method or an error diffusion method. The specific color region is a region including skin color.
The color processing method according to claim 10. The chromaticity diagram is a UCS (Uniform Color Scale) chromaticity diagram.
The color processing method according to claim 10.

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