JP2011164464A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve display quality by securing brightness of a video image including high saturation primary colors such as R, G and B, in a display device for displaying multi-primary colors such as RGBY or RGBW. <P>SOLUTION: The display device includes: a display panel (a color filter 7 and a liquid crystal panel body 8) for displaying the video image by a pixel including sub-pixels, which is constituted with primary colors of four colors or more; a backlight light source 9 for irradiating light from a rear face of the display panel; a video processing circuit 3 for detecting a primary color pixel having predetermined primary colors (R, G and B etc.) for each frame of an input video signal, or for each block in which the input video signal is divided; and a light source control circuit 5 which controls so that brightness of the backlight source 9 is high in the frame or the block when primary color pixel having a fixed saturation or more is included in the frame or the block in which the primary color pixel is detected by the video processing circuit 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a display device that supports multi-primary color displays such as RGBY and RGBW.

  2. Description of the Related Art Conventionally, various types of displays that form images with pixels have been commercialized as display means for displaying information and video. For example, one pixel is generally composed of sub-pixels (sub-pixels) of three primary colors composed of red (R), green (G), and blue (B), and thus color display is generally performed. Color filters are usually used to realize these subpixels. In such color display technology, in recent years, it has been studied to expand the color reproduction range in order to improve display quality.

  On the other hand, by increasing the number of primary colors to four or more primary colors using new colors other than the three primary colors, the area on the chromaticity diagram is expanded (in the case of chromatic colors), or the luminance efficiency is improved ( So-called multi-primary displays have been developed that can (when white). For example, Patent Document 1 describes an RGBW liquid crystal display device that can display an image with appropriate luminance. According to this, when determining the luminance of the liquid crystal panel, the luminance of the pixel of the transparent filter unit corresponding to white (W) is independently and appropriately controlled under a predetermined calculation, and output from the liquid crystal panel. The brightness of the image is improved.

JP 2001-154636 A

  However, according to the RGBW type liquid crystal display device described in Patent Document 1, white luminance can be increased by adding W to the three primary colors of RGB. Since the brightness per hit decreases, the brightness of the RGB three primary colors decreases. The problem of luminance reduction of this multi-primary color display will be described below.

  There are two main reasons for the decrease in luminance in multi-primary color displays. First, since the area per subpixel decreases as the aperture ratio decreases, that is, the number of primary colors increases, the luminance per subpixel accordingly. Decreases. In this case, the luminance can be improved by supplying a large amount of current to each primary color sub-pixel. Second, if the change in white balance, that is, the number of primary colors increases, the contribution ratio to white per primary color decreases, and the luminance per subpixel decreases accordingly.

  For example, in the RGB three-color system, assuming that the maximum white luminance is 100, the luminance of each primary color is, for example, R: 20, G: 70, B: 10 (R + G + B = 100). On the other hand, in the case of the RGBW four-color system, assuming that the maximum white luminance is 100, for example, R: 10, G: 35, B: 5, W: 50 (R + G + B + W = 100), and the ratio of each primary color to white decreases. The primary color becomes dark. Also, the color of the mixed color is different from the color intended in the video signal. That is, the balance between white and primary colors changes, and the luminance per subpixel decreases.

FIG. 7 is a diagram for explaining the difference in primary color luminance between the RGB liquid crystal display device and the RGBY liquid crystal display device. In this example, for convenience of explanation, the L ^* a ^* b ^* color space is combined with the chromaticity coordinates of u′v ′ defined by the CIE (International Commission on Illumination), and the vertical axis represents L ^* ( (Luminance) and u ′ (chromaticity coordinates) on the horizontal axis. Note that u ′ on the horizontal axis is obtained by taking the RG of the display color gamut on the left and right of the u′v ′ plane, and is set as u ′ for convenience of explanation. Figure 7 (A) is 'shows the relationship, FIG. 7 (B) ^{L * -u'v} of RGBY type liquid crystal display device' ^{L * -u'v} of RGB type liquid crystal display device showing a relation. Both ends of the color space shown in FIGS. 7A and 7B are R and G. When the luminances of R and G are compared, the RGBY liquid crystal display device is lower than the RGB liquid crystal display device. Recognize.

FIG. 8 is a diagram for explaining a difference in primary color luminance between the RGB liquid crystal display device and the RGBW liquid crystal display device. Figure 8 (A) is 'shows the relationship, FIG. 8 (B) ^{L * -u'v} the RGBW-type liquid crystal display device' ^{L * -u'v} of RGB type liquid crystal display device showing a relation. Although the same as the example of FIG. 7 above, both ends of the color space shown in FIGS. 8A and 8B are R and G. When the luminances of R and G are compared, the RGB type liquid crystal display device It can be seen that the RGBW liquid crystal display device is lower than that of the liquid crystal display device.

  As described above, in a multi-primary color display, sufficient luminance cannot be obtained with high-saturation primary colors such as R, G, and B (particularly R, G) due to the second cause described above, and these high-saturation primary colors are included. There has been a problem of degrading the display quality of the displayed video.

  The present invention has been made in view of the above circumstances, and in a display device that supports multi-primary color displays such as RGBY and RGBW, ensures the brightness of an image including primary colors with high chroma such as R, G, and B. The purpose is to improve display quality.

  In order to solve the above-mentioned problem, the first technical means of the present invention is a display panel that displays an image by pixels including sub-pixels composed of four or more primary colors, and irradiates light from the back surface of the display panel. A primary color pixel detecting means for detecting a primary color pixel having a predetermined primary color for each frame of the input video signal or for each block obtained by dividing the input video signal, and the primary color pixel detection Light source luminance control for controlling the luminance of the backlight light source to be higher with respect to the frame or block when the primary color pixel having a certain saturation or higher is included in the frame or block in which the primary color pixel is detected by the means And means.

  According to a second technical means, in the first technical means, the light source luminance control means is configured such that a primary color pixel having a certain saturation or more is constant in a frame or block in which the primary color pixel is detected by the primary color pixel detection means. In the case where the number is more than one, the luminance of the backlight light source is controlled to be high with respect to the frame or block.

  According to a third technical means, in the first technical means, the light source luminance control means includes a primary color pixel having a saturation and luminance of a certain level or more in a frame or block in which the primary color pixel is detected by the primary color pixel detection means. Is included, the luminance of the backlight light source is controlled to be high with respect to the frame or block.

  According to a fourth technical means, in the first technical means, the light source luminance control means includes a primary color pixel having a saturation and luminance of a certain level or more in a frame or block in which the primary color pixel is detected by the primary color pixel detection means. Is included, the luminance of the backlight light source is controlled to be high with respect to the frame or block.

  According to a fifth technical means, in any one of the first to fourth technical means, the primary color pixel detecting means has a predetermined hue or higher with respect to a frame or block of the input video signal. A saturation is designated, a luminance histogram in a range corresponding to the designated hue and saturation is calculated, and a primary color pixel having a certain saturation or more is detected based on the calculation result. It is.

  The sixth technical means is the frame or block according to any one of the first to fifth technical means, wherein the luminance of the pixel in the low saturation portion of the frame or block in which the luminance of the backlight light source is controlled to be high is determined. It is characterized by comprising gain control means for lowering the luminance gain of the low chroma portion by lowering.

  According to a seventh technical means, in any one of the first to sixth technical means, the backlight light source is an LED.

  According to an eighth technical means, in any one of the first to seventh technical means, the predetermined primary color is one or more of red, green, and blue.

  According to the present invention, in a display device that supports multi-primary color display, high-saturation primaries such as R, G, and B are detected from an input video signal, and the backlight luminance is reduced only in the case of an image that includes these high-saturation primaries. By increasing the brightness, it is possible to secure the brightness of the image and improve the display quality.

It is a block diagram which shows the structural example of the display apparatus which concerns on one Embodiment of this invention. It is the figure which showed the structural example of the display part typically. It is a figure which shows the structural example of each subpixel formation part shown in FIG. It is a figure which shows an example of the input video signal divided | segmented into the some block. It is a figure for demonstrating an example of the detection process of the primary color pixel by a video processing circuit. It is a figure for demonstrating an example of the method of lowering | hanging the luminance gain of the low chroma part by the liquid crystal display device of this invention. It is a figure for demonstrating the difference of the primary color brightness | luminance in a RGB type liquid crystal display device and a RGBY type liquid crystal display device. It is a figure for demonstrating the difference of the primary color brightness | luminance in a RGB type liquid crystal display device and a RGBW type liquid crystal display device.

  Hereinafter, preferred embodiments according to a display device of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram illustrating a configuration example of a display device according to an embodiment of the present invention. In this example, an RGBW liquid crystal display device is described as a representative example of the display device, but the basic configuration is the same even for other multi-primary color displays such as the RGBY type. This liquid crystal display device is roughly composed of a drive control circuit 1, an input unit 2, a video processing circuit 3, a control unit 4, a light source control circuit 5, and a display unit 6. The display unit 6 includes an active matrix type color display panel, and the drive control circuit 1 generates a drive signal for driving the display unit 6.

  The input unit 2 is an interface for inputting a video signal such as a digital broadcast signal. Hereinafter, the video signal input from the input unit 2 is referred to as an input video signal. The video processing circuit 3 is a circuit that executes various types of signal processing on the input video signal from the input unit 2. The control unit 4 includes a CPU and a memory that control the operation of the liquid crystal display device. The light source control circuit 5 adjusts the luminance of the backlight light source by controlling the power supplied to the backlight light source constituting the display unit 6 in accordance with a control command from the control unit 4.

  The display unit 6 includes a color filter 7, a liquid crystal panel body 8, and a backlight light source 9. As shown in FIG. 3 to be described later, the liquid crystal panel main body 8 is formed with a plurality of data signal lines Ls and a plurality of scanning signal lines Lg intersecting the plurality of data signal lines Ls. The liquid crystal panel body 8 and the color filter 7 constitute a color liquid crystal panel including a plurality of pixel forming portions arranged in a matrix. For example, an LED (Light Emitting Diode) or a cold cathode ray tube (CCFL) can be considered as the backlight light source 9, but it is desirable to use an LED for control in units of blocks described later.

  FIG. 2 is a diagram schematically illustrating a configuration example of the display unit 6. Each pixel forming unit 62 in the display unit 6 includes an R subpixel forming unit 61, a G subpixel forming unit 61, and a B subcorresponding to red (R), green (G), blue (B), and white (W), respectively. Each pixel of the color image displayed by the display unit 6 includes an R sub-pixel, a G sub-pixel, and a B sub-pixel corresponding to red, green, blue, and white, respectively. It consists of subpixels and W subpixels. Note that the sub-pixel and the sub-pixel are synonymous.

  FIG. 3 is a diagram illustrating a configuration example of each sub-pixel forming unit illustrated in FIG. FIG. 3A is a diagram showing an electrical configuration of one sub-pixel forming unit 61 in the display unit 6, and FIG. 3B is an equivalent circuit diagram showing an electrical configuration of the sub-pixel forming unit 61. As shown in FIGS. 2 and 3, each pixel forming unit 62 includes a number of sub-pixel forming units 61 equal to the number of primary colors for displaying a color image, and each sub-pixel forming unit 61 includes a plurality of sub-pixel forming units 61. The data signal line Ls and the plurality of scanning signal lines Lg are provided corresponding to the intersections. In addition, an auxiliary capacitance line Lcs arranged in parallel with each scanning signal line Lg is provided, and a common electrode Ecom common to all the sub-pixel forming portions 61 is provided.

  In FIG. 3, each sub-pixel forming unit 61 includes a switching element having a gate terminal connected to the scanning signal line Lg passing through the corresponding intersection and a source terminal connected to the data signal line Ls passing through the intersection. Thin film transistor (TFT) 61a, a pixel electrode 61b connected to the drain terminal of the TFT 61a, and an auxiliary electrode 61c arranged so that an auxiliary capacitor Ccs is formed between the pixel electrode 61b. Including. In addition, each subpixel forming unit 61 includes a common electrode Ecom provided in common to all the subpixel forming units 61, and a pixel electrode 61b and a common electrode Ecom provided in common to all the subpixel forming units 61. A liquid crystal layer Clc is formed by the pixel electrode 61b, the common electrode Ecom, and the liquid crystal layer sandwiched between them, including a liquid crystal layer as an electro-optical element sandwiched therebetween.

  The drive control circuit 1 includes a display control circuit 11, a data signal line drive circuit 13, and a scanning signal line drive circuit 14. The display control circuit 11 receives the data signal DAT (Ri, Gi, Bi) from the video processing circuit 3 and the timing control signal TS from a timing controller (not shown), and receives the digital video signal DV (Ro, Go, Bo, Wo), data A start pulse signal SSP, a data clock signal SCK, a latch slope signal LS, a gate start pulse signal GSP, a gate clock signal GCK, and the like are output.

  As shown in FIG. 2, each pixel forming unit 61 of the display unit 6 includes an R subpixel forming unit, a G subpixel forming unit, a B subpixel forming unit, and a W subpixel corresponding to red, green, blue, and white, respectively. The data signal DAT includes three primary color signals (Ri, Gi, Bi) corresponding to the three primary colors of red, green, and blue. The display control circuit 11 converts an input primary color signal (Ri, Gi, Bi) corresponding to the three primary colors of RGB into an output primary color signal (Ro, Go, Bo, Wo) corresponding to the four primary colors of RGBW. Is provided. The digital video signal DV is an output primary color signal (Ro, Go, Bo, Wo) output from the conversion circuit 12, and thereby displays a color image to be displayed on the display unit 6.

  The data start pulse signal SSP, the data clock signal SCK, the latch strobe signal LS, the gate start pulse signal GSP, the gate clock signal GCK, and the like are timing signals for controlling the timing for displaying an image on the display unit 6. It is.

  The data signal line driving circuit 13 receives the digital image signal DV (Ro, Go, Bo, Wo), the data start pulse signal SSP, the data clock signal SCK, and the latch strobe signal LS output from the display control circuit 11 and displays them. The data signal voltage Vs is applied as a drive signal to each data signal line Ls in order to charge the pixel capacitance (Clc + Ccs) in each sub-pixel forming unit 61 in the unit 6. At this time, the data signal line driving circuit 13 sequentially holds the digital video signal DV indicating the voltage to be applied to each data signal line Ls at the timing when the pulse of the data clock signal SCK is generated. At the timing when the pulse of the latch strobe signal LS is generated, the held digital video signal DV is converted into an analog voltage and applied to all the data signal lines Ls in the display unit 6 as the data signal voltage Vs at the same time. .

  Here, the data signal line driving circuit 13 generates an analog voltage corresponding to the primary color signals Ro, Go, Bo, Wo constituting the digital video signal DV as the data signal voltage Vs, and is connected to the R subpixel forming unit 61. A data signal voltage Vs corresponding to the red primary color signal Ro is applied to the data signal line Ls, and a data signal voltage corresponding to the green primary color signal Go is applied to the data signal line Ls connected to the G subpixel forming unit 61. A data signal voltage Vs corresponding to the blue primary color signal Bo is applied to the data signal line Ls connected to the B subpixel forming unit 61 by applying Vs, and the data signal line connected to the W subpixel forming unit 61 A data signal voltage Vs corresponding to the white primary color signal Wo is applied to Ls.

  Based on the gate start pulse signal GSP and the gate clock signal GCK output from the display control circuit 11, the scanning signal line driving circuit 14 scans the scanning signal line Lg in the display unit 6 with an active scanning signal (TFT 61 a turned on). Signal voltage Vg) is applied sequentially.

  The drive control circuit 1 also includes an auxiliary electrode drive circuit and a common electrode drive circuit (not shown). A predetermined auxiliary electrode voltage Vcs is applied to each auxiliary capacitance line Lcs from the auxiliary electrode drive circuit, and a predetermined common voltage Vcom is applied to the common electrode Ecom from the common electrode drive circuit. The auxiliary electrode voltage Vcs and the common voltage Vcom may be the same voltage, and the auxiliary electrode driving circuit and the common electrode driving circuit may be shared.

  As described above, in the display unit 6, the data signal voltage Vs is applied to the data signal line Ls, the scanning signal voltage Vg is applied to the scanning signal line Lg, the common voltage Vcom is applied to the common electrode Ecom, and the auxiliary capacitance line Lcs is applied. The auxiliary electrode voltage Vcs is applied. As a result, a voltage corresponding to the digital video signal DV is held in the pixel capacitance of each sub-pixel forming unit 61 and applied to the liquid crystal layer. As a result, a color image represented by the digital video signal DV is displayed on the display unit 6. Is done.

  At this time, each R sub-pixel forming unit 61 controls the amount of red light transmitted according to the voltage held in the internal pixel capacitance, and each G sub-pixel forming unit 61 has its internal pixel capacitance. Each B subpixel forming unit 61 controls the amount of blue light transmitted according to the voltage held in its internal pixel capacitance, and each W The sub-pixel forming unit 61 controls the amount of white light transmitted according to the voltage held in the internal pixel capacitance.

  The main characteristic part of the present invention is to ensure the luminance of an image including high-saturated primary colors such as R, G, B and improve the display quality in a liquid crystal display device supporting multi-primary colors such as RGBY and RGBW. is there. As a configuration for this, a liquid crystal display device includes a display panel that displays an image with pixels including sub-pixels (sub-pixels) formed of four or more primary colors, and a backlight light source that emits light from the back of the display panel. 9. This display panel corresponds to a color liquid crystal panel including a color filter 7 and a liquid crystal panel body 8.

  In addition, the liquid crystal display device includes a video processing circuit 3 corresponding to primary color pixel detecting means for detecting primary color pixels having a predetermined primary color for each frame of the input video signal or for each block obtained by dividing the input video signal, and the video processing circuit 3. The light source luminance control means for controlling the luminance of the backlight light source 9 higher than the frame or block when the primary color pixel having a certain saturation or higher is included in the frame or block in which the primary color pixel is detected. With. The light source luminance control means includes a control unit 4 and a light source control circuit 5.

  In the following description, the case where the luminance of the backlight light source 9 is controlled in units of frames of the input video signal will be described as an example, but the same luminance control of the backlight light source 9 can be performed even in units of blocks. In addition, when controlling the brightness | luminance of the backlight light source 9 per block, it is desirable to use LED as a light source.

  The video processing circuit 3 detects, for example, primary color pixels having one or more primary colors of red, green, and blue as predetermined primary colors from the frame of the input video signal, and outputs the detection result to the control unit 4. . Then, the control unit 4 determines whether or not the frame in which the primary color pixel is detected by the video processing circuit 3 includes a primary color pixel having a certain saturation or higher (that is, a primary pixel with high saturation). The hue, saturation, and brightness of each pixel of the input video signal may be obtained, for example, as the YCbCr signal of the input video signal, or the value (0 to 255) of the YCbCr signal of the input video signal is possessed. It can also be obtained by converting into an RGB signal and further converting the converted RGB signal into u′v ′ chromaticity coordinates using a known conversion formula. In addition, a reference value used for determination of saturation above a certain level may be set in advance and stored in the memory of the control unit 4.

  When the control unit 4 determines that a high-saturation primary color pixel is included in the frame as a result of the determination, the control unit 4 outputs a control command to the light source control circuit 5 so that the luminance of the backlight light source 9 is increased. Control. On the other hand, if it is determined that a high-saturation primary color pixel is not included in the frame, the luminance of the backlight source 9 is maintained at the current luminance. Here, how much the luminance of the backlight light source 9 is adjusted is not particularly limited. For example, a luminance adjustment amount is set in advance by, for example, setting a predetermined percentage higher than the current backlight luminance by a user setting. It is possible to keep it. For example, in order to realize the intended R primary color luminance of the broadcast signal, the predetermined ratio is about 60% up in RGBY and about twice in RGBW. In addition, in order to achieve an appropriate appearance based on the subjective evaluation results of RGBY, the image quality should be improved by about 5% for images with relatively low saturation and about 30% for images with high saturation. Can do.

  Then, the light source control circuit 5 determines the luminance of the backlight light source 9 based on a control command from the control unit 4, and controls a control value (for example, PWM control) of power supplied to the backlight light source 9 according to the determined luminance. Determine the duty ratio). Then, the light source control circuit 5 supplies power corresponding to the determined control value to the backlight light source 9 and controls the backlight light source 9 to have high luminance. By controlling the luminance of the backlight light source 9 in this way, it is possible to compensate for a decrease in the primary color luminance in the RGBW liquid crystal display device, to ensure the luminance of the video, and to improve the display quality.

  Here, according to the above method, for example, when primary color pixels having high saturation R and G are detected from the frame of the input video signal, the luminance of the backlight light source 9 is always controlled to be high. In such a broadcast signal, there are many achromatic colors and relatively few high chromatic colors. Therefore, it is considered that the power consumption by the backlight light source 9 does not extremely increase even with such control. However, for the purpose of reducing the power consumption in the liquid crystal display device, when a predetermined number or more of primary color pixels having a certain saturation or more are included in the frame in which the primary color pixels are detected by the video processing circuit 3, or The brightness of the backlight source 9 is controlled to be high when primary color pixels having a certain saturation and brightness are included, or when a certain number or more of primary color pixels having a certain saturation and brightness are included. May be.

  That is, even when the number of primary color pixels is high, the number is small, or even when the primary color pixel is low (dark) even when the primary color pixel is high saturation, or even when the primary color pixel is high saturation and high brightness. When there is little, control which makes the brightness | luminance of the backlight light source 9 high is not performed. By controlling the luminance of the backlight light source 9 in this way, power consumption in the liquid crystal display device can be reduced, so that energy saving can be achieved while improving display quality.

  The video processing circuit 3 in the above example detects the primary color pixels for each frame of the input video signal. However, the input video signal is divided into a plurality of blocks as shown in FIG. It may be detected. In this case, when the primary color pixel having a certain saturation or higher is included in the block in which the primary color pixel is detected by the video processing circuit 3, the control unit 4 performs the backlight light source 9 on the block. The brightness of the can be controlled high. In FIG. 4, B <b> 1 indicates a block including primary pixels with high saturation. The luminance of the backlight light source 9 is controlled to be higher than that of the block B <b> 1. As described above, light source luminance control in units of blocks can be easily performed by using the backlight light source 9 as an LED.

  FIG. 5 is a diagram for explaining an example of primary color pixel detection processing by the video processing circuit 3. High-saturated primary color pixels can be detected by a known method using the hue circle shown in FIG. In the figure, the vertical axis indicates the color difference Cr and the horizontal axis indicates the color difference Cb. The saturation is set from the point P of the hue ring toward the outer periphery, and the saturation becomes higher toward the outer periphery. Further, hues are set along the circumferential direction of the hue circle, R, G, and B are primary colors, and C, M, and Y are intermediate colors. The video processing circuit 3 designates a certain saturation or higher for a predetermined primary color hue for a frame or block of the input video signal, and calculates a luminance histogram in a range corresponding to the designated hue and saturation. Then, based on the calculation result of the luminance histogram, primary color pixels having a certain saturation or more are detected.

  Specifically, as a hue of a predetermined primary color, for example, a saturation (for example, 80% or more) of a certain level or higher is designated for the hues of red (R) and green (G). That is, a range 15 in which the saturation including R and G of the hue circle shown in FIG. 5 is a certain level of saturation (80% or more) is designated, and a luminance histogram of the designated range 15 is obtained. When the luminance histogram of R and G with high saturation (80% or more) is calculated, it is determined that R or G with high saturation is included in the frame or block of the input video signal, and the frame unit or block The brightness of the backlight source 9 is controlled to be high in units.

  According to the method of FIG. 5, it is possible to designate a hue and saturation range on the hue ring and calculate a luminance histogram of the designated range according to an operation by the user, so that not only a high-saturation primary color pixel but also a high saturation In addition, high-luminance primary color pixels can be detected.

  Here, by controlling the luminance of the backlight light source 9 to be high, the luminance of pixels of other colors other than the primary color pixels also increases at the same time. In particular, if the brightness of a low-saturation white pixel increases, it may be brighter than necessary, giving the viewer a sense of discomfort. Therefore, the luminance of the pixels in the low chroma portion of the frame or block in which the luminance of the backlight light source 9 is controlled to be high may be lowered by lowering the luminance gain of the low chroma portion of the frame or block. Specifically, the luminance gain of a specific hue can be reduced by the method described in FIG.

  FIG. 6 is a diagram for explaining an example of a method for reducing the luminance gain of the low saturation portion by the liquid crystal display device of the present invention. FIG. 6A shows the luminance characteristic of the input video signal before and after controlling the light source luminance, Yl is the luminance characteristic of the input video signal before the light source luminance is controlled to be high, and Yh is after the light source luminance is controlled to be high. The luminance characteristic of the input video signal, ΔY represents the luminance gain adjustment amount, the vertical axis represents luminance (Y), and the horizontal axis represents saturation (S: Saturation). FIG. 6B shows a hue circle corresponding to the luminance characteristics shown in FIG. In the hue circle of FIG. 6B, S (saturation) = 0 indicates white (W), and S (saturation) = 1 indicates the maximum saturation of primary colors (C1, C2) such as R, G, B, and the like. This corresponds to S = 0 and S = 1 in FIG.

  The liquid crystal display device in this example lowers the luminance of the pixels in the low saturation portion of the frame or block in which the luminance of the backlight light source 9 is controlled to be high, and decreases the gain (luminance gain) in the low saturation portion of the frame or block. Gain control means for lowering is provided. This gain control means includes the video processing circuit 3 and the control unit 4. That is, the light source control circuit 5 controls the luminance of the backlight light source 9 to be high according to a control command from the control unit 4 for a frame or block including high-saturation primary color pixels, and the video processing circuit 3 In accordance with the control command from, control for lowering the luminance gain in the low saturation portion is performed.

Specifically, the luminance gain of the low saturation portion is lowered by video processing on the input video signal using the following equation (1).
ΔY = (Yh−Yl) × (1−Saturation) (1)
Where Yl is the luminance characteristic of the input video signal before the light source luminance is controlled to be high, Yh is the luminance characteristic of the input video signal after the light source luminance is controlled to be high, ΔY is the luminance gain adjustment amount, and Saturation is an arbitrary value of the input video signal The saturation of.

  In FIG. 6A, since the luminance of each color is raised by controlling the luminance of the backlight light source 9 to be higher than the input video signal having the luminance characteristic Yl, the luminance characteristic Yl changes to the luminance characteristic Yh. To do. Then, with respect to the raised luminance characteristic Yh, the luminance gain of the low-saturation portion including white is lowered using the above equation (1). Specifically, if S = 0 corresponding to white (W) is substituted for “Saturation” in Expression (1), ΔY = Yh−Yl, and white (in the luminance characteristic Yl before controlling the light source luminance high) ( The brightness is adjusted to W ′). In addition, the saturation increases from S = 0 to S = 1, and S = 1 is the maximum saturation of the primary colors C1 and C2, respectively. However, the primary colors (C1, C2) are added to “Saturation” in Expression (1). When S = 1 corresponding to) is substituted, ΔY = 0, and the luminance is maintained as the luminance characteristic Yh after the light source luminance is controlled to be high.

  That is, according to Equation (1), as the saturation increases from S = 0 (white) to S = 1 (high saturation primary color), the luminance gain adjustment amount ΔY continues in the low saturation portion including white. The luminance gain adjustment amount ΔY becomes 0 for the primary color with the maximum saturation, and the luminance is maintained as it is. The luminance characteristic of the input video signal after adjusting the gain of the low saturation portion in this way is as shown by the luminance characteristic Y ′ shown in FIG. Thereby, even when the luminance of the backlight light source 9 is controlled to be high, the primary pixels of high saturation are maintained at high luminance, and only the luminance of the pixels in the low saturation portion including white can be lowered, so that the viewer can Natural images with reduced white luminance can be provided.

  In this way, in a display device that supports multi-primary color displays such as RGBW and RGBY, high-saturation primary colors such as R, G, and B are detected from the input video signal, and only in the case of an image that includes these high-saturation primary colors. By increasing the light brightness and lowering the gain of the low-saturation part of the input video signal, the brightness of the low-saturation part can be lowered while increasing the brightness of the primary color of high saturation, ensuring the display brightness of the video. The quality can be improved.

DESCRIPTION OF SYMBOLS 1 ... Drive control circuit, 2 ... Input part, 3 ... Image processing circuit, 4 ... Control part, 5 ... Light source control circuit, 6 ... Display part, 7 ... Color filter, 8 ... Liquid crystal panel main body, 9 ... Backlight light source, DESCRIPTION OF SYMBOLS 11 ... Conversion circuit, 12 ... Display control circuit, 13 ... Data signal line drive circuit, 14 ... Scanning signal line drive circuit

Claims (8)

A display device comprising: a display panel that displays an image with pixels including sub-pixels composed of four or more primary colors; and a backlight light source that emits light from the back of the display panel,
In primary color pixel detection means for detecting primary color pixels having a predetermined primary color for each frame of the input video signal or for each block obtained by dividing the input video signal, and in the frame or block in which the primary color pixels are detected by the primary color pixel detection means, A display device comprising light source luminance control means for controlling the luminance of the backlight light source to be high with respect to the frame or block when primary color pixels having a certain saturation or higher are included.   2. The display device according to claim 1, wherein the light source luminance control unit includes a predetermined number or more of primary color pixels having a certain saturation or more in a frame or block in which the primary color pixels are detected by the primary color pixel detection unit. In this case, the display device is characterized in that the luminance of the backlight light source is controlled to be higher than the frame or block.   2. The display device according to claim 1, wherein the light source luminance control unit includes a primary color pixel having a saturation and luminance of a certain level or more in a frame or block in which the primary color pixel is detected by the primary color pixel detection unit. Furthermore, the brightness of the backlight light source is controlled to be higher for the frame or block.   2. The display device according to claim 1, wherein the light source luminance control unit includes a predetermined number or more of primary color pixels having a certain saturation and luminance in a frame or block in which the primary color pixels are detected by the primary color pixel detection unit. If included, the display device controls the luminance of the backlight light source to be higher with respect to the frame or block.   5. The display device according to claim 1, wherein the primary color pixel detection unit designates a predetermined saturation or higher with respect to a hue of the predetermined primary color with respect to a frame or a block of the input video signal. Then, a luminance histogram in a range corresponding to the designated hue and saturation is calculated, and a primary color pixel having a certain saturation or more is detected based on the calculation result.   The display device according to any one of claims 1 to 5, wherein the luminance of a pixel in a low chroma portion of a frame or block in which the luminance of the backlight light source is controlled to be high is set to be low chroma of the frame or block. A display device comprising gain control means for lowering the luminance gain of a portion by lowering.   The display device according to claim 1, wherein the backlight light source is an LED.   8. The display device according to claim 1, wherein the predetermined primary color is one or more of red, green, and blue.