JP2011221112A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve display quality, in a display device compatible with multi-primary color display such as RGBY and RGBW, by securing luminance of a video including primary colors with high saturation, such as R, G, B, according to an image quality mode.SOLUTION: A display device comprises: a display panel (a color filter 7 and a liquid crystal panel body 8) which displays a video with pixels each including a sub-pixel consisting of four or more primary colors; a backlight source 9 which irradiates light from a back face of the display panel; a video processing circuit 3 which detects a primary color pixel having a primary color (R, G, B, etc.) predetermined for each frame of an input video signal or each block of a divided input video signal; and a light source control circuit 5 which, when a primary color pixel having saturation higher than a predetermined level is included in the frame or the block where the primary color pixel is detected by the video processing circuit 3, controls to increase the luminance of the backlight source 9 according to an image quality mode set in the display device with respect to the frame or the block.

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.

  On the other hand, there is known a liquid crystal display device in which a plurality of image quality modes for adjusting the image quality of a display image can be set. In such image quality modes, for example, there are modes set in consideration of the viewing environment of the liquid crystal display device, user requirements, and the like. For example, “dynamic (storefront) mode”, “standard (standard) mode”, “movie mode”, “game mode”, and the like are set. These image quality modes and the purpose of setting the modes are determined for each manufacturer of the liquid crystal display device, for example, and the names of the modes are not unified, and various mode names are used for each manufacturer. . Then, the light emission luminance of the backlight light source is controlled in accordance with the image quality mode, so that an image can be displayed with an optimum brightness according to the image quality mode.

  In the above-mentioned multi-primary color display, it is conceivable to increase the brightness of the backlight light source in order to solve the problem of degrading the display quality of the image including the primary color of high saturation. There are modes in which it is not necessary to increase the luminance of the backlight light source much, and conversely, it is better to increase the luminance of the backlight light source to some extent. For example, in the “game mode”, the video of a game has a relatively small number of colors and many low-saturation colors, so that a decrease in luminance of high-saturation colors is not a problem. For this reason, it is not necessary to increase the luminance of the backlight light source more than necessary. On the other hand, in the “movie mode”, it is desirable that the movie image can faithfully express the saturation in order to obtain a higher sense of reality. For this reason, it is better to increase the luminance of the backlight light source to some extent.

  Thus, in a multi-primary color display, it is desirable that the luminance of the backlight light source can be adjusted according to the image quality mode set in the display when the luminance of the backlight light source is increased for an image including a primary color with high saturation. However, such a technique has not been realized so far.

  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, high-saturated primary colors such as R, G, and B are included depending on the image quality mode. The purpose is to secure the brightness of the image and improve the 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 When the frame or block in which the primary color pixel is detected by the means includes a predetermined number or more of primary color pixels having at least a certain saturation, the image quality set in the display device for the frame or block And a light source luminance control means for controlling the luminance of the backlight light source to be high according to the mode.

  A second technical means includes a luminance control table storing an adjustment amount of luminance of the backlight light source for each image quality mode that can be set in the display device in the first technical means, and the light source luminance control means includes: Based on the image quality mode set in the display device, the brightness control table is referred to determine the brightness adjustment amount of the backlight light source.

  According to a third technical means, in the second technical means, an initial setting value of the luminance of the backlight light source is associated in advance with each image quality mode that can be set in the display device. Is controlled so that the luminance of the backlight light source becomes higher than the initial setting value based on the adjustment amount of the luminance of the backlight light source determined by the luminance control table. .

  A fourth technical means is the first technical means according to any one of the first to third technical means, wherein the light source luminance control means includes a predetermined color or more in a frame or block in which the primary color pixels are detected by the primary color pixel detection means. When a predetermined number or more of primary color pixels having a degree and brightness are included, the brightness of the backlight light source is controlled to be high for the frame or block according to the image quality mode set in the display device. It is a feature.

  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 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, Thus, by increasing the backlight luminance, it is possible to ensure the luminance of the video 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 connects a tuner that receives a digital broadcast signal and inputs a video signal included in the digital broadcast signal, or an external device such as a game machine, a player, or a recorder, and inputs the video signal from the external device. It is an external interface. 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 feature of the present invention is that a liquid crystal display device that supports multi-primary color displays such as RGBY and RGBW secures and displays the luminance of video including high-saturated primary colors such as R, G, and B according to the image quality mode. It is to improve the quality. 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. In the frame or block in which the primary color pixel is detected in the above, when a certain number of primary color pixels having a saturation of at least a certain level or more (this constant number is an integer of 1 or more) are included, Light source luminance control means for controlling the luminance of the backlight light source 9 high according to the image quality mode set in the liquid crystal display device. The light source luminance control means includes a control unit 4 and a light source control circuit 5.

  The liquid crystal display device includes a remote control light receiving unit 15 for receiving a remote control signal transmitted from the remote control device R. The remote control light receiving unit 15 is composed of a light receiving LED for receiving a remote control operation signal using infrared rays, for example. The remote control operation signal received by the remote control light receiving unit 15 is input to the control unit 4, and the control unit 4 performs predetermined control according to the remote control operation signal. For example, in the present embodiment, the user can select a desired image quality mode from the image quality modes prepared in advance using the remote control device R, and can perform setting control on the liquid crystal display device.

  In addition, the liquid crystal display device includes a luminance control table 16 that stores an adjustment amount of the luminance of the backlight light source 9 for each image quality mode that can be set in the liquid crystal display device. The control unit 4 constituting the light source luminance control means determines the luminance adjustment amount of the backlight light source 9 with reference to the luminance control table 16 based on the image quality mode set in the liquid crystal display device.

  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 pixels are detected by the video processing circuit 3 includes a predetermined number or more of primary color pixels having a certain saturation or higher (that is, high saturation primary color pixels). . 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.

  If 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 and determines the backlight light source 9 according to the image quality mode. Control to increase the brightness. On the other hand, when it is determined that a high-saturation primary color pixel is not included in the frame, the luminance of the backlight source 9 is controlled based on the initial setting value of the luminance of the backlight source 9 preset in each image quality mode. Is done.

  Here, how high the luminance of the backlight light source 9 is adjusted when a high-saturation primary color pixel is included in the frame differs depending on the image quality mode set in the liquid crystal display device. When the image quality modes that can be set in the liquid crystal display device are the dynamic (storefront) mode, the standard (standard) mode, the movie mode, the game mode, and the eco (energy saving) mode, the luminance of the backlight light source 9 for each image quality mode An adjustment example will be described.

  The brightness adjustment amount of the backlight light source 9 for each image quality mode is stored in advance in the brightness control table 16, but each image quality mode is associated with an initial setting value of the brightness of the backlight light source 9 in advance. Yes. The control unit 4 controls the luminance of the backlight light source 9 to be higher than the initial setting value based on the adjustment amount of the luminance of the backlight light source 9 determined by the luminance control table 16. Here, the luminance of the backlight light source 9 is expressed in%, 100% when it is brightest, and 0% when it is extinguished. For example, the initial setting value of “shop front mode” is 100% and the initial value of “standard mode” The setting value is 50%, the initial setting value of “movie mode” is 20%, and the initial setting value of “game mode” is 20%.

  The “storefront mode” is a mode that is considered to be used in a bright environment such as a store, or in an environment where many people view for demonstration purposes. When the image quality mode is the “shop front mode”, the initial setting value of the luminance of the backlight light source 9 is set to the maximum luminance (100%), so the luminance adjustment of the backlight light source 9 is not performed.

  The “standard mode” is a mode set in consideration of use in a standard viewing environment such as a home living room. When the image quality mode is “standard mode”, the luminance adjustment amount is set so that the luminance of the backlight light source 9 becomes a target luminance higher than the initial setting value of “standard mode”. As a specific example, when the initial setting value of the luminance of the backlight light source 9 is 50% of the maximum luminance, if the luminance adjustment amount is increased by 60% with respect to the initial setting value (50%), 50% × 1. 6 = 80%, which is 80% of the maximum luminance. However, in this “standard mode”, it is desirable to suppress the up rate to about 30% from the viewpoint of energy saving. When the up rate is 30%, 50% × 1.3 = 65%. In this way, by suppressing the backlight luminance to about 60 to 70% of the maximum luminance, the primary color luminance of high saturation is increased to some extent while saving energy.

  The “movie mode” is a mode set for viewing movie content, and it is necessary to faithfully reproduce the saturation. When the image quality mode is “movie mode”, the luminance adjustment amount is set so that the luminance of the backlight light source 9 becomes a target luminance higher than the initial setting value of “movie mode”. As a specific example, when the initial setting value of the luminance of the backlight light source 9 is 20% of the maximum luminance, if the luminance adjustment amount is increased by 60% with respect to the initial setting value (20%), 20% × 1. 6 = 32%, which is 32% of the maximum luminance. In this “movie mode”, in order to increase the luminance of the backlight light source 9 as much as possible, the up rate is set to 60%, and the backlight luminance is increased to 30 to 35% of the maximum luminance. As a result, the primary color luminance of high saturation is increased and the saturation is faithfully reproduced.

  The “game mode” is a mode used when the viewer plays a game. However, in the case of game content, there are many relatively low saturation colors, so even if the saturation cannot be faithfully reproduced, it becomes a problem. I don't think it will happen. When the image quality mode is “game mode”, the luminance adjustment amount is set so that the luminance of the backlight light source 9 becomes a target luminance higher than the initial setting value of “game mode”. As a specific example, when the initial setting value of the luminance of the backlight light source 9 is 50% of the maximum luminance, if the luminance adjustment amount is increased by 20% with respect to the initial setting value (50%), 50% × 1. 2 = 60%, which is 60% of the maximum luminance. In this “game mode”, since the content is CG (computer graphic), it is considered that the fidelity of saturation is not a problem. For this reason, the luminance adjustment amount may be set small. Alternatively, the luminance adjustment amount may be set to 0 and the initial setting value may be maintained.

  The “eco mode” is a mode in which on / off is set for the purpose of reducing power consumption (energy saving) with respect to the “standard mode”, “movie mode”, and “game mode”. When the “eco mode” is turned on for each image quality mode, the brightness adjustment amount when increasing the brightness of the backlight light source 9 is made lower than the brightness adjustment amount in each image quality mode described above to save energy. Try to figure it out.

  In FIG. 1, 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 power control value (for example, power supplied to the backlight light source 9 according to the determined luminance). , Duty ratio in PWM control) is determined. Then, the light source control circuit 5 supplies power corresponding to the determined control value to the backlight light source 9 so that the luminance of the backlight light source 9 increases according to the image quality mode set in the liquid crystal display device. Control. In this way, by controlling the luminance of the backlight light source 9 according to the image quality mode, it is possible to compensate for the 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 even one primary color pixel having high saturation R and G is detected from the frame of the input video signal, the luminance of the backlight light source 9 is always in accordance with the image quality mode. However, it is considered that the power consumption by the backlight light source 9 does not increase extremely even in such a control because normal broadcast signals have many achromatic colors and relatively few high chromatic colors. However, for the purpose of reducing the power consumption in the liquid crystal display device, the frame in which the primary color pixels are detected by the video processing circuit 3 includes a predetermined number or more (for example, 10 or more) of primary color pixels having a certain saturation or more. Or the luminance of the backlight source 9 set in advance for each image quality mode when there are more than a certain number of primary color pixels (a certain number is an integer greater than or equal to 1). The luminance of the backlight light source 9 may be controlled to be higher than the initial setting value.

  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 the amount of light is small, the luminance of the backlight light source 9 is controlled based on the initial setting value of the luminance of the backlight light source 9 preset for each image quality mode. As described above, since the power consumption of the liquid crystal display device can be reduced by controlling the luminance of the backlight light source 9 according to the image quality mode, it is possible to save energy while improving the 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, if the block in which the primary color pixel is detected by the video processing circuit 3 includes a certain number of high-saturation primary color pixels having a certain saturation or higher, the control unit 4 applies liquid crystal to the block. The luminance of the backlight light source 9 can be controlled to be high according to the image quality mode set in the display device. In FIG. 4, B1 indicates a block including high-saturation primary color pixels, and the luminance of the backlight light source 9 is controlled to be higher for this block B1 according to the image quality mode. 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 17 in which the saturation including R and G in 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 17 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 in accordance with the image quality mode, 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 saturation portion of the frame or block in which the luminance of the backlight light source 9 is controlled to be high according to the image quality mode is reduced by reducing the luminance gain of the low saturation portion of the frame or block. It may be. 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 according to the image quality mode, and Yh is the light source luminance. The luminance characteristic of the input video signal after high control according to the image quality mode, 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.

  In the liquid crystal display device in this example, the luminance of the low saturation portion of the frame or block in which the luminance of the backlight light source 9 is controlled to be high in accordance with the image quality mode, and the gain (luminance of the low saturation portion of the frame or block) are determined. Gain control means for lowering the gain). 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 the image quality mode in accordance with the control command from the control unit 4 for the frame or block including the primary color pixels with high saturation, and the video processing circuit 3 Performs control to lower the luminance gain of the low saturation portion in accordance with a control command from the control unit 4.

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)
However, Yl is the luminance characteristic of the input video signal before the light source luminance is controlled to be high according to the image quality mode, Yh is the luminance characteristic of the input video signal after the light source luminance is controlled to be high according to the image quality mode, and ΔY is the luminance gain. The adjustment amount, Saturation, indicates an arbitrary saturation of the input video signal.

  In FIG. 6A, since the luminance of each color is raised by controlling the luminance of the backlight light source 9 to be high according to the image quality mode with respect to the input video signal having the luminance characteristic Yl, the luminance characteristic Yl is The luminance characteristic changes to Yh. 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 into “Saturation” in Expression (1), ΔY = Yh−Yl, and the luminance before the light source luminance is controlled to be high according to the image quality mode. The luminance is adjusted to white (W ′) in the characteristic Yl. 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 according to the image quality mode.

  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 according to the image quality mode, the primary color pixels with high saturation are maintained at high luminance, and only the luminance of the pixels in the low saturation portion including white can be lowered. Therefore, it is possible to provide the viewer with a natural image with reduced white luminance.

  In this way, in a display device that supports multi-primary color displays such as RGBW and RGBY, high-saturated primary colors such as R, G, and B are detected from the input video signal, and image quality is only available for images that include these high-saturated primary colors. Depending on the mode, by increasing the backlight brightness and decreasing the gain of the low saturation part of the input video signal, the brightness of the low saturation part can be reduced while increasing the high saturation primary color brightness. It is possible to improve the display quality by ensuring the brightness of the video for each mode.

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, 15 ... Remote control light-receiving part, 16 ... Luminance control table

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, When a predetermined number or more of primary color pixels having a certain saturation or higher are included, the luminance of the backlight light source is controlled to be high for the frame or block according to the image quality mode set in the display device. And a light source luminance control means.   The display device according to claim 1, further comprising: a luminance control table storing an adjustment amount of the luminance of the backlight light source for each image quality mode that can be set in the display device, wherein the light source luminance control unit includes the display device. A display device that determines an adjustment amount of luminance of the backlight light source by referring to the luminance control table on the basis of the image quality mode set to 1.   3. The display device according to claim 2, wherein an initial setting value of the luminance of the backlight light source is associated with each image quality mode that can be set in the display device in advance, A display device that controls the brightness of the backlight light source to be higher than the initial setting value based on an adjustment amount of the brightness of the backlight light source determined by a control table.   4. The display device according to claim 1, wherein the light source luminance control unit has 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. When a predetermined number or more of primary color pixels are included, the luminance of the backlight light source is controlled to be high for the frame or block according to the image quality mode set in the display device. apparatus.   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.