JP4487006B2 - Image display device and image display method - Google Patents

Description

  The present invention relates to an image display apparatus and an image display method for controlling a light source that emits light to a display unit and displaying an image on the display unit.

  A liquid crystal display device displays an image by allowing a liquid crystal panel to transmit or block light emitted from a backlight. The color reproducibility, contrast performance, and power consumption in a liquid crystal display device depend mainly on the performance or control of the liquid crystal panel and the backlight. In recent years, there has been proposed a drive method (hereinafter referred to as area active drive) in which a backlight is divided into a plurality of regions and the light emission rate is controlled for each region.

  In the area active drive, when a part of the displayed image has low luminance, the light emission rate of the backlight region corresponding to the part is lowered, and the transmittance of the liquid crystal panel is set according to the light emission rate. As described above, since the light emission rate of the backlight can be optimized for each region, the power consumption of the entire backlight can be reduced. In addition, by reducing the light emission rate for each area, it is possible to reduce black floating in the liquid crystal display (for example, the state where black on the screen appears brightly when the illumination is turned off), and the contrast and image quality are improved. can do.

  In this area active drive, an RGB-LED light source composed of LEDs (Light-Emitting Diodes) of three colors of red (R), green (G), and blue (B) can be used for the backlight. In this case, it is necessary not only to increase or decrease the light emission rate for each region, but also to control each of the three color LEDs in the region. Specifically, when a display image corresponding to a certain region is composed of only blue, a red (R) LED (hereinafter referred to as R-LED) and a green (G) LED (hereinafter referred to as G-LED). Is turned off, only the blue (B) LED (hereinafter referred to as B-LED) is turned on, and the transmittance of the liquid crystal display panel is set in accordance with the light emission rate of the B-LED. Thereby, an image with high color purity of only blue is displayed. In this way, since only the necessary LEDs are controlled from among the LEDs in the region, the effect of reducing the power consumption can be made higher than in the case of a white light source. Furthermore, the color gamut of the display image can be increased by increasing the color purity of each primary color.

In the area active drive as described above, Patent Document 1 describes an apparatus and a method that can perform local luminance control and color characteristic control of a backlight. In the apparatus and method described in Patent Document 1, the liquid crystal display panel is divided into a plurality of regions, and the backlight is configured by a plurality of LEDs that irradiate each region with light. And the light emission rate of LED is controlled according to the peak value of the gradation in each area | region of a liquid crystal display panel.
JP 2005-338857 A

  By the way, in the area active drive using the RGB-LED light source, a problem may occur depending on the characteristics of the color filter of the liquid crystal panel. FIG. 9 is a schematic diagram showing the relationship between the transmission characteristics of the color filter of the liquid crystal panel and the wavelengths of the LEDs of RGB. For example, the characteristic of a blue (B) color filter (hereinafter referred to as B-CF) has a portion overlapping the wavelength of the G-LED. For this reason, even when it is desired to transmit only the light from the B-LED through the B-CF, the light from the G-LED transmits through the B-CF, resulting in extra light leakage from the LED. When the light emission rate of each LED is the same and fixed, the ratio of the light transmission amount of the B-LED and the light transmission amount of the G-LED with respect to the B-CF is always constant. Light leakage does not occur by incorporating the leakage amount of the G-LED with respect to the CF.

  However, when the light emission rate of each LED changes dynamically, the amount of light leakage also changes dynamically. FIG. 10 is a schematic diagram for explaining light leakage caused by a change in the light emission rate. In FIG. 10, a green rectangular image 101 is displayed on a blue background image 100 on the screen. Further, the screen is divided into a plurality of areas including area A and area B, and the rectangular image 101 is displayed in area A and has a size slightly smaller than the size of area A. Also, the backlight is divided so as to correspond to each area of the screen, and light emission is controlled for each area.

  In this case, since only the blue background image 100 is displayed in area B, only the B-LED emits light. For this reason, in area B, light from other than the B-LED does not pass through the B-CF, no light leakage occurs, and a high-purity blue color is displayed. On the other hand, in the area A, since the blue background image 100 and the green rectangular image 101 are displayed, the B-LED and the G-LED emit light. Therefore, light from the G-LED passes through the B-CF, and light leakage occurs in the area A. When this amount of light leakage is large, a blue image is displayed with a significantly higher luminance than originally. For this reason, on the screen, the contour 102 along the contour of the rectangular image 101 and the periphery thereof become a bright blue color due to green light leakage (a phenomenon in which a ring of light can be seen faintly. Hereinafter, a halo phenomenon). The image quality will be impaired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image display device and an image display method that reduce the risk of impairing image quality by reducing light leakage. is there.

The image display device according to the present invention controls the light emission rate of each of the light sources of a plurality of colors that irradiates light to a display panel having a color filter for each light source based on the gradation of an image displayed on the display panel. In the image display device, a halo phenomenon occurs due to light leakage from a light source of a color other than a light source of a color corresponding to a color filter generated in an outline of an image in a partial region of the display panel on which the image is displayed. a determining means for determining whether it has an acquisition unit for acquiring light emission rate of each of the light sources, based on the obtained result by the acquisition unit, in a region where the determining means determines that the halo phenomenon has occurred the light emission of the light source of the corresponding backlight and a control means for controlling the light emission rate of the light source so close to white light, the determining means is halo for each frame of the image It is determined whether or not a phenomenon has occurred, and the control means gradually emits light from the light source toward the area from the periphery of the area determined by the determination means that the halo phenomenon has occurred. The light emission rate of the light source is controlled so as to be close to light, and the light emission rate of the light source is controlled when the determination unit determines that a halo phenomenon has occurred in a plurality of consecutive frames. Features.

  The image display device according to the present invention is characterized in that the control means controls the light emission rate of the light source so that the light from the light source is additively mixed and brought close to white.

  The image display apparatus according to the present invention is characterized in that the control means maintains the brightness of the light source having the maximum brightness acquired by the acquisition means and controls the brightness of other light sources.

The image display device according to the present invention is characterized in that the control means is adapted to bring the color of the synthesized light closer to white at a speed based on a determination result by the determination means.

  The image display device according to the present invention is characterized in that the control means is configured to gradually bring the color synthesized by the light source closer to white.

The image display device according to the present invention determines whether or not the control unit terminates the control based on a detection result by the detection unit when the control unit controls the light emission rate of the light source. and hand stage that, wherein if it is determined that the to exit, the color of the synthesized light, so as to control the light emission rate of the light source so away from the white at a slower rate than that close to white It is characterized by being.

In the image display method according to the present invention, the light emission rate of each of the light sources of a plurality of colors for irradiating light to a display panel having a color filter is controlled for each light source based on the gradation of an image displayed on the display panel. In the image display method, a halo phenomenon occurs due to light leakage from a light source of a color other than a light source of a color corresponding to a color filter generated in an outline of an image in a partial region of the display panel on which the image is displayed. determining step of determining whether it has the step of obtaining the light emission rate of each of the light sources, and, based on the acquired light emission rate, the backlight light source corresponding to the area where the halo phenomenon is determined to have occurred emission has a control step of controlling the light emission rate of the light source so close to white light, the determination step, the halo phenomenon occurs for each frame of the image The control step determines whether the light emission of the light source gradually approaches white light from the periphery of the region determined to have a halo phenomenon in the determination step toward the region. The light emission rate of the light source is controlled when the light emission rate of the light source is controlled and it is determined in the determination step that a halo phenomenon has occurred in a plurality of frames .

  In the present invention, when luminance unevenness or color unevenness in the direction of increasing luminance occurs in the image displayed on the display unit, each light source is controlled so that the color of light combined by a plurality of light sources approaches white. Light from the light source passes through the color filter of the display unit, but the color filter has a property of passing only light having a necessary wavelength and blocking other light. For this reason, even if the light sources of a plurality of colors emit light, white light can be blocked by the color filter by using the combined light as white light. As a result, it is possible to reduce the possibility that unnecessary light from the light source is transmitted and the quality of the image displayed on the display unit is impaired.

  Further, by controlling the light emission rate of the light source in accordance with the number of areas where luminance unevenness or color unevenness is detected, there is a case where the possibility of impairing the color purity of the display portion may be reduced. For example, when the number of areas in which luminance unevenness or color unevenness is detected is large, there is a possibility that luminance unevenness or color unevenness has occurred in almost all of the display unit. At this time, the viewer may recognize that the original image includes luminance unevenness or color unevenness. In such a case, the viewer does not care about the brightness unevenness or color unevenness of the image. There is a case. Therefore, by not controlling the light emission rate, priority can be given to controlling the light emission rate to prevent a decrease in color purity.

  In the present invention, by making the light emission of the light source closer to white light step by step, the abrupt change in light emission at the boundary of the region where the luminance unevenness or color unevenness occurs is reduced, thereby making the viewer feel uncomfortable. The risk of being held can be suppressed.

  In the present invention, white light can be obtained by mixing light of each color in equal amounts using light sources of three colors of red, green, and blue.

  In the present invention, by controlling to maintain the light emission rate of the light source having the maximum light emission rate, the generated luminance unevenness or color unevenness can be eliminated without lowering the original color purity, and the displayed image The risk of damaging the quality of the product can be reduced.

  In the present invention, when an image composed of a plurality of regions is displayed, if the luminance unevenness or the color unevenness occurs continuously for a plurality of frames, each light source is controlled. Thereby, by controlling the light source more than necessary, the color purity can be reduced, and the possibility of impairing the image quality can be reduced. Note that a frame refers to an image displayed on one screen. For example, if two fields are sequentially displayed, the R (red), G (green), and B (blue) colors of the three fields are combined. It is an image. Further, in the case of the interlace method, it means an image obtained by combining the scan image in the odd-numbered row and the scan image in the even-numbered row, and in the case of the non-interlace method, it means an image displayed by vertical scanning.

  In the present invention, the color can be changed according to the content of the image by making the color close to white at a speed based on the result of detecting the luminance unevenness or the color unevenness. For example, if an image that does not bother brightness unevenness or color unevenness is displayed and the degree of detection is low, the color is given to a viewer who is viewing the image displayed on the display unit by slightly bringing it closer to white. It is possible to prevent the user from feeling uncomfortable with the changes. Further, when an image in which brightness unevenness or color unevenness is anxious is displayed, the brightness unevenness or color unevenness can be immediately eliminated by making the light almost white, and the quality of the image can be maintained.

  In the present invention, it is possible to prevent the viewer from feeling uncomfortable that the color has changed by making the synthesized light color gradually approach white.

  In the present invention, when the control of the light emission rate is terminated, the light source is controlled so as to keep the synthesized color away from white at a slower speed than when white is set. Thereby, it is possible to prevent the viewer from feeling uncomfortable because the color changes rapidly.

  In the present invention, when luminance unevenness or color unevenness in the direction of increasing luminance occurs in the image displayed on the display unit, each light source is controlled so that the color of light combined by a plurality of light sources approaches white. Light from the light source passes through the color filter of the display unit, but the color filter has a property of passing only light having a necessary wavelength and blocking other light. For this reason, even if the light sources of a plurality of colors emit light, white light can be blocked by the color filter by using the combined light as white light. As a result, it is possible to reduce the possibility that unnecessary light from the light source is transmitted and the quality of the image displayed on the display unit is impaired.

  Further, by controlling the light emission rate of the light source in accordance with the number of areas where luminance unevenness or color unevenness is detected, there is a case where the possibility of impairing the color purity of the display portion may be reduced. For example, when the number of areas in which luminance unevenness or color unevenness is detected is large, there is a possibility that luminance unevenness or color unevenness has occurred in almost all of the display unit. At this time, the viewer may recognize that the original image includes luminance unevenness or color unevenness. In such a case, the viewer does not care about the brightness unevenness or color unevenness of the image. There is a case. Therefore, by not controlling the light emission rate, priority can be given to controlling the light emission rate to prevent a decrease in color purity.

  Preferred embodiments of the present invention will be described below with reference to the drawings. The liquid crystal display device according to this embodiment is an image display device of the present invention, and displays an image based on an RGB video signal input from the outside. The RGB video signal may be received by television radio waves, read from a recording medium such as a DVD (Digital Versatile Disc), or input via a network. May be.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the liquid crystal display device according to the present embodiment.

  The liquid crystal display device includes a control unit 1, a video processing unit 2, an area active processing unit 3, a display panel unit 10, and a drive unit 4 that drives a backlight 11. The display panel unit 10 is provided with a backlight 11 on the back side, and includes a display unit on the front side for displaying an image based on the input RGB video signal. The display panel unit 10 includes a display element having a number of pixels corresponding to the screen display resolution. The display element has a color filter that transmits only necessary light (wavelength) and blocks other light (wavelength), and has three colors of red (R), green (G), and blue (B). Any light is transmitted. A color image is displayed on the display unit as light passes through the display element. Note that the amount of light transmitted through the display element is determined by the transmittance of the display element. The transmittance is a ratio at which the liquid crystal panel can pass the light irradiated by the backlight 11.

  The backlight 11 is a light source that emits light from the back side of the display panel unit 10. FIG. 2 is a diagram schematically illustrating the configuration of the backlight 11. The backlight 11 is entirely divided into a plurality of rectangular regions 110, and each region 110 is provided with an R-LED 11a, a G-LED 11b, and a B-LED 11c. The backlight 11 is controlled to emit light for each area 110. In FIG. 2, one LED 11a, 11b, and 11c is provided in the region 110, but a plurality of LEDs may be provided. For example, when a light amount is necessary, two or more LEDs of the same color may be provided.

  The video processing unit 2 performs various signal processing on the input RGB video signal. For example, the video processing unit 2 acquires image data (hereinafter also referred to as a frame) extracted from the RGB video signal at a certain time interval, acquires the gradation of the image data, and adjusts the size of the image data. The various information is output to the control unit 1 and the area active processing unit 3. The video processing unit 2 also generates RGB signals, digital conversion processing, color space conversion processing, scaling processing, color correction processing, synchronization detection processing, gamma correction processing, OSD (On-Screen Display) display processing, and the like. The signal processing is appropriately executed.

  The area active processing unit 3 determines the peak value of each color component of one frame corresponding to the region 110 based on the gradation of the image data input from the video processing unit 2 and a mix ratio described later input from the control unit 1. The optimum light emission rate of each LED 11a, 11b, 11c is determined according to the above. For example, in the area active processing unit 3, the peak value of each color component of RGB of one frame is 10% for the red (R) component, 60% for the green (G) component, and 30 for the blue (B) component compared to the dynamic range. %, The light emission rates of the LEDs 11a, 11b, and 11c are also 10%, 60%, and 30%. The area active processing unit 3 determines the light emission rate for all the regions 110 in units of frames.

  Further, the area active processing unit 3 determines a transmittance control value (voltage value) for controlling the transmittance of the display element of the display panel unit 10 for each frame based on the gradation of the image data and the determined light emission rate. . The area active processing unit 3 outputs the determined light emission rate and transmittance control value (voltage value) to the control unit 1 and the drive unit 4.

  The light transmission amount from the display element of the display panel unit 10 is obtained by multiplying the light emission rate of the color LED corresponding to the display element by the transmittance of the display element. By determining the light emission rate and the transmittance control value based on the gradation level of the image data, for example, when the gradation level of the image data in a certain area of the display panel unit 10 is small, in the area 110 corresponding to that area. By reducing the light emission rate of the LED, the power consumption of the backlight 11 can be reduced.

  The drive unit 4 includes a panel drive unit 41 and a backlight drive unit 42. The panel drive unit 41 is a drive circuit for the display panel unit 10 and controls the transmittance of the display elements of the display panel unit 10 based on the transmittance control value input from the area active processing unit 3. The transmittance control value (voltage value) output from the panel drive unit 41 is charged to the electrodes in each display element of the display panel unit 10. Then, the tilt amount of the liquid crystal related to the display element changes according to the charged voltage, and as a result, the transmittance of the display element is controlled. The backlight drive unit 42 is a drive circuit for the backlight 11, and controls the light emission rates of the LEDs 11 a, 11 b, and 11 c of the backlight 11 based on the light emission rate input from the area active processing unit 3. The backlight drive unit 42 controls the LEDs 11a, 11b, and 11c for each region 110.

  The control unit 1 is a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and the like, and controls each part of the liquid crystal display device to control the entire liquid crystal display device. For example, the control unit 1 acquires the transmittance control value (voltage value), the light emission rates of the LEDs 11a, 11b, and 11c from the area active processing unit 3. Based on the information acquired from the video processing unit 2 and the area active processing unit 3, the control unit 1 determines the possibility that a halo phenomenon (luminance unevenness or color unevenness) has occurred in each region 110. When there is a possibility that the halo phenomenon has occurred, the control unit 1 changes the mix rate in order to reduce the halo phenomenon.

  Next, a method for determining whether or not a halo phenomenon has occurred will be described.

  As described above, the halo phenomenon is a phenomenon in which light from an LED is generated by light leakage that passes through a filter of a color that is not supported, and a contour of the image and a circle of light can be seen in the periphery of the image. The control unit 1 detects the occurrence of the halo phenomenon by the balance of the light emission rates of the LEDs 11a, 11b, and 11c and the balance of the transmittance of the display elements. In order to explain specifically, as a premise, in the area A of FIG. 10, the light emission rates of the LEDs 11a, 11b, and 11c are set to 0%, 80%, and 20%, and in the area B, 0%, 0%, and 20%. %, And the transmittance of the display element is 100%. The light leakage from the G-LED 11b to blue (B) is 10% of the G-LED 11b, and the allowable value of light leakage is less than 20% with respect to the transmission amount of blue (B). The allowable value of light leakage is a limit value of the amount of light leakage that may impair image quality.

  In this case, since the light emission rate of the G-LED 11b is 80%, the light leakage amount is 8%. Further, since the light emission rate of the B-LED 11c is 20%, the allowable value of the light leakage amount is 4%. Since the light leakage amount of the G-LED 11b is 8%, the light leakage amount of the B-LED 11c is larger than the allowable value. That is, since the light from the G-LED 11b is mixed with the light from the B-LED 11c at the contour 102 and its surroundings, the blue image around the contour 102 and its surroundings is displayed as brighter than the original blue. . Therefore, the video processing unit 2 calculates the light leakage amount, and determines the possibility that the halo phenomenon has occurred based on the result.

  The video processing unit 2 performs the above-described determination of the possibility of the halo phenomenon on a pixel-by-pixel basis for each display element. Next, the video processing unit 2 also performs determination on pixels that are adjacent in the vertical and horizontal directions of a pixel that may have a halo phenomenon, and detects the continuity of pixels that may have a halo phenomenon. When there is a possibility of occurrence of a halo phenomenon in a plurality of vertical and horizontal pixels, in other words, the video processing unit 2 may cause a halo phenomenon of a predetermined area (for example, 50% of an area) within one frame. If there is a possibility, it is determined that there is a possibility of occurrence of a halo phenomenon in the frame. Then, the control unit 1 determines the continuity of the frames determined to have the possibility of the halo phenomenon. For example, when it is determined that there is the possibility of the halo phenomenon for four consecutive frames, the control unit 1 reduces the halo phenomenon. Determine the execution.

  In the present embodiment, only an example of a method for determining the possibility of occurrence of the halo phenomenon is shown, and the detection method of the halo phenomenon, conditions for determining that the halo phenomenon has occurred, and the like can be changed as appropriate.

  Next, a method for reducing the generated halo phenomenon will be described.

  When reducing the halo phenomenon, the area active processing unit 3 brings the combined light emission of the LEDs 11a, 11b, and 11c closer to white light by additive color mixing. Since white light has the same light emission rate of each color LED, the area active processing unit 3 controls the light emission rates of the LEDs 11a, 11b, and 11c to be the same so as to approach white light. In the present embodiment, the LED having the maximum light emission rate is not controlled, and control is performed so that the light emission rates of the other LEDs are close to the maximum light emission rate. For example, when the light emission rate of the G-LED 11b is the maximum, the area active processing unit 3 brings the light emission rates of the R-LED 11a and the B-LED 11c closer to the light emission rate of the G-LED 11b.

  The control unit 1 determines the mix rate in order to bring the combined light emission of the LEDs 11a, 11b, and 11c closer to white light. A mix rate is a ratio at the time of changing the light emission rate of each LED11a, 11b, 11c. For example, when the light emission rates of the LEDs 11a, 11b, and 11c are optimal light emission rates for the respective color components of the image data determined by the area active processing unit 3, the mix rate is 0. In other words, when the mix rate is 0, the control unit 1 does not control the light emission rates of the LEDs 11a, 11b, and 11c. Further, when the light emission rates of the LEDs 11a, 11b, and 11c are adjusted to the maximum light emission rate, that is, when the backlight 11 is a white light source, the mix rate is 1.

The mix rate can be determined by a predetermined function. For example, when the light emission rates of the mix rate “0” are r1, g1, b1, the light emission rates of the white light source are r2, g2, b2, and the mix rate is m (0 ≦ m ≦ 1), light emission by the mix rate The rates rm, gm, and bm are as follows.
rm = (r2-r1) * m + r1
gm = (g2−g1) × m + g1
bm = (b2−b1) × m + b1

  FIG. 3 is a schematic diagram showing the light emission rates of LEDs of different colors at different mix rates, where (a) is a mix rate of 0, (b) is a mix rate of 1, and (c) is a mix rate of 0.4. Show the case. When the mix rate is 0, the light emission rates of the LEDs 11a, 11b, and 11c are 10%, 60%, and 30% (see FIG. 3A). When the mix rate is 1, the light emission rates of the LEDs 11a, 11b, and 11c are all 60% (see FIG. 3B). When the mix rate is 0.4, the light emission rates of the LEDs 11a, 11b, and 11c are 30%, 60%, and 42% (see FIG. 3C).

  The control unit 1 determines the optimum mix rate according to the detection result of the video processing unit 2, so that the light leakage amount of one color LED is less than the allowable value of the light leakage amount of the other color LED, The halo phenomenon can be reduced. For example, in the case of the example using FIG. 10 described above, the mix rate is determined to be 33%.

  FIG. 4 is a schematic diagram showing the light emission rate when the light emission rates of the LEDs 11a, 11b, and 11c are changed at a mix rate of 33%, where (a) shows the case before the change, and (b) shows the case after the change. In the case of area A, the light emission rates of the LEDs 11a, 11b, and 11c are 26%, 80%, and 40%, and in the case of area B, they are 6%, 6%, and 20%. In this case, the amount of light leakage of the G-LED 11b having a light emission rate of 80% is 8%. Further, the light leakage amount of the B-LED 11c having a light emission rate of 40% is 4%, and its allowable value is doubled to 8%. Since the light leakage amount of the G-LED 11b is 8%, the light leakage amount of the B-LED 11c is less than the allowable value. As a result, the halo phenomenon occurring in the contour portion 102 and its periphery is reduced.

  The control unit 1 may control only the LEDs 11a, 11b, and 11c included in the region 110 where the halo phenomenon occurs based on the determined mix ratio, or the LEDs 11a, 11a, 11b and 11c may be controlled. When controlling only the LEDs 11a, 11b, and 11c in the region 110 where the halo phenomenon occurs, the display screen corresponding to the region 110 is controlled by controlling the LEDs 11a, 11b, and 11c in the region 110 where the halo phenomenon does not occur. It can prevent that the color purity of this falls. Moreover, the power consumption of the backlight 11 can be reduced by keeping the light emission rate low. On the other hand, when the LEDs 11a, 11b, and 11c in all the regions 110 are controlled, the color purity of the entire screen can be made uniform and the processing can be simplified, so that the circuit scale can be reduced. it can.

  The control unit 1 may change the mix ratio of the LEDs 11a, 11b, and 11c included in the area where the halo phenomenon occurs and the surrounding area. FIG. 5 is a diagram showing the mix ratio of the LEDs 11a, 11b, and 11c determined for each region 110 in the frame. FIG. 5 shows the mix ratio of the LEDs 11a, 11b, and 11c in each area 110 into which the backlight 11 is divided. In FIG. 5, a region where the halo phenomenon occurs is a region 120.

  For example, as illustrated in FIG. 5A, when the control unit 1 sets the mix ratio of the LEDs 11a, 11b, and 11c in the region 120 to 1, the LEDs 11a, 11b, and 4 in the four regions 110 that are adjacent to the region 120 vertically and horizontally. The mix ratio of 11c is determined to be 0.5. And the control part 1 determines the mix rate of LED11a, 11b, 11c of the other area | region 110 to 0. That is, the mix rate of the LEDs 11a, 11b, and 11c approaches 1 stepwise from the region 110 where the mix rate is 0 toward the region 120. Thereby, it is possible to prevent the viewer from feeling uncomfortable that the light emission colors of the LEDs 11a, 11b, and 11c are changed from the surroundings by only the region 120.

  As shown in FIG. 5B, when the mix ratio of the LEDs 11a, 11b, and 11c in the region 120 is 0.5, the control unit 1 mixes the LEDs 11a, 11b, and 11c in the region 110 adjacent to the region 120. The rate is determined to be 0.25, and the mix rate of the LEDs 11a, 11b, and 11c in the other regions is determined to be 0. Thereby, the mix rate of LED11a, 11b, 11c is approaching 0.5 in steps toward the area | region 120 from the area | region 110 of 0 mix ratios.

  As shown in FIG. 5 (c), when the mix rate of the LEDs 11a, 11b, and 11c included in the region 120 is 1, the control unit 1 is 0.25 in order from the region of the mix rate 0 toward the region 120. 0.5 and 0.75 are determined. In this case, the color purity can be changed more smoothly in comparison with the cases of FIGS. 5 (a) and 5 (b).

  Furthermore, when changing the determined mix ratio, the control unit 1 may continuously cause the light emission of the LEDs 11a, 11b, and 11c to approach white light or gradually. For example, the color purity can be changed smoothly by continuously changing the color purity, and the color purity can be changed without a sense of incongruity by changing it step by step at a timing that the viewer does not notice. Moreover, you may make it the control part 1 change suitably the speed which approaches white light. For example, the viewer may not care about the halo phenomenon depending on the generation position or generation size of the halo phenomenon. In this case, by slowly approaching white, it is possible to prevent the viewer from noticing that the color of the image displayed on the display panel unit 10 has changed. Further, when the halo phenomenon is eliminated by bringing the color closer to white earlier, an image that does not impair the quality of the image can be displayed.

  In the liquid crystal display device configured as described above, an operation when displaying an input RGB video signal on the screen will be described. FIG. 6 is a flowchart illustrating processing executed by the control unit 1 and the video processing unit 2.

  The video processing unit 2 acquires an RGB video signal input from the outside (S1), and acquires the light emission rate and transmittance control values in one frame of the RGB video signal (S2). The video processing unit 2 acquires or estimates the light emission rate and transmittance control value determined by the area active processing unit 3 or inside the video processing unit 2. The video processing unit 2 detects whether or not a halo phenomenon may occur in one pixel of the display element (S3), and determines whether or not the continuity of pixels that may cause a halo phenomenon has reached a predetermined value. Detect (S4). From the result, the presence / absence of occurrence of the halo phenomenon in the frame is detected (S5). Specifically, as described above, the video processing unit 2 calculates the light leakage amount of the LED, and detects the presence or absence based on the calculation result.

  The control unit 1 determines whether there is a possibility of occurrence of a halo phenomenon in the frame from the detection result of S5 (S6). When there is no possibility of occurrence of the halo phenomenon (S6: NO), the control unit 1 ends the process in this frame and executes the same process for the next frame. When there is a possibility of occurrence of the halo phenomenon (S6: YES), the control unit 1 determines whether or not the frames determined to have the possibility of occurrence of the halo phenomenon continue for four or more frames (S7). When it is not continuous (S7: NO), the control unit 1 ends the process in this frame and executes the same process for the next frame.

  When four or more frames are continued (S7: YES), the control unit 1 executes a process for reducing the halo phenomenon (S8). Specifically, the control unit 1 determines the optimal mix ratio, and reduces the halo phenomenon by setting the light leakage amount of one color LED to be equal to or less than the allowable value of the light leakage amount of another color LED. To do. At this time, the control unit 1 may control only the LEDs 11a, 11b, and 11c included in the region 110 where the halo phenomenon occurs, or may control the LEDs 11a, 11b, and 11c in all the regions 110. It may be. Then, the control part 1 complete | finishes this process.

  In addition, the control part 1 complete | finishes control of the mix rate of LED, when the possibility of a halo phenomenon generate | occur | producing is lose | eliminated when controlling the mix rate of LED11a, 11b, 11c. That is, the control unit 1 performs control to keep the light emission of the LEDs 11a, 11b, and 11c approaching white light away from the white light.

  As described above, the liquid crystal display device according to the present embodiment determines the possibility of occurrence of the halo phenomenon in the RGB video signal in units of frames, and the LEDs 11a, 11b, The light emission of 11c is brought close to white light. Accordingly, white light can be blocked by the color filter of the display element, and the amount of light leakage from the backlight 11 can be reduced. As a result, it is possible to reduce the possibility that unnecessary light from the backlight 11 is transmitted and the quality of the image displayed on the display panel unit 10 is impaired.

  In the present embodiment, when it is determined that the halo phenomenon may occur for four consecutive frames, the halo phenomenon is reduced. However, the number of consecutive frames can be changed as appropriate. For example, the continuous number may be determined according to the time interval at which the frames are extracted. Further, as described above, the LEDs 11a, 11b, and 11c may be controlled only for the region 110 where the halo phenomenon occurs, or the LEDs 11a, 11b, and 11c in all the regions 110 may be controlled. Good.

(Embodiment 2)
Next, Embodiment 2 according to the present invention will be described. In the first embodiment, only whether or not there is a possibility of occurrence of a halo phenomenon is determined, but in this embodiment, the degree of possibility of occurrence of a halo phenomenon is determined. And according to the degree, the speed which controls the mix rate of LED is changed. Only the differences will be described below.

  The control unit 1 of the liquid crystal display device according to the present embodiment evaluates the possibility of occurrence of the halo phenomenon in 10 stages based on the amount of light leakage, and mixes the LEDs 11a, 11b, and 11c at a speed based on the evaluation result. Change the rate. Here, the change in the mix ratio includes a case where the light emission of the LEDs 11a, 11b, and 11c is brought close to white light and a case where the light emission is kept away from the white light. Further, the case of moving away from white light means that the halo phenomenon is eliminated (reduced) as a result of controlling the mix ratio of the LEDs 11a, 11b, and 11c at a certain mix ratio, and then the mix ratio is returned to 0 (closed). Refers to cases. The control unit 1 sets a level 0 when there is no light leakage and no halo phenomenon occurs, for example, a level 10 when there is a light leakage amount twice the allowable value of the light leakage amount, and a level according to the light leakage amount. decide.

  When the light emission of the LEDs 11a, 11b, and 11c is brought close to white light, the control unit 1 spends about 60 msec to shift the level by one step. For example, when the possibility of occurrence of the halo phenomenon is level 4, in order to shift to control of the mix ratio determined to reduce the halo phenomenon, the control unit 1 takes 240 (60 × 4) msec, The light emission of 11b and 11c is brought close to white light.

  When the light emission of the LEDs 11a, 11b, and 11c is kept away from the white light, the control unit 1 spends about 250 msec to shift the level by one step. For example, if the possibility of occurrence of the halo phenomenon is evaluated as level 4 and then the halo phenomenon disappears (becomes level 0), the control unit 1 shifts to control with a mix rate of 0, so 1000 (250 X4) The light emitted from the LEDs 11a, 11b, and 11c is kept away from the white light over msec.

  In this way, by executing the speed at which the light emitted from the LEDs 11a, 11b, and 11c approaches white light in a short time, it is possible to display an image so that the viewer does not notice the occurrence of the halo phenomenon. Further, when moving away from white light, the speed of the image is changed more rapidly than when moving closer, so that it is possible to suppress the possibility that the color of the image changes suddenly and the viewer feels uncomfortable.

  As described above, the liquid crystal display device according to the present embodiment reduces the halo phenomenon by causing the light emission of the LEDs 11a, 11b, and 11c to approach white light in a short time when the halo phenomenon occurs. Further, when the halo phenomenon is eliminated (reduced), the liquid crystal display device keeps the light emission of the LEDs 11a, 11b, and 11c away from the white light at a speed slower than the speed close to the white light.

  In addition, the speed which changes the mix rate of LED11a, 11b, 11c can be changed suitably. For example, in the case of an image that is worrisome even if the halo phenomenon occurs, the light emission of the LEDs 11a, 11b, and 11c may be brought closer to white light slowly. In this case, it is possible to prevent the viewer from feeling uncomfortable that the color has changed. Further, in the case of an image that is worried about the occurrence of the halo phenomenon, the halo phenomenon can be quickly eliminated by bringing it closer to white light earlier, and the quality of the image can be maintained.

(Embodiment 3)
Next, Embodiment 3 according to the present invention will be described. In the first and second embodiments, if there is a possibility of occurrence of a halo phenomenon, processing for reducing the halo phenomenon is performed. In this embodiment, the halo phenomenon is reduced depending on the degree of occurrence of the halo phenomenon. The difference is that no processing is performed. Only the differences will be described below.

  The video processing unit 2 of the liquid crystal display device according to the present embodiment determines the possibility of occurrence of the halo phenomenon on a pixel-by-pixel basis, and the pixels determined to have the possibility of occurrence of the halo phenomenon are, for example, more than half of one frame If it occupies an area, the frame is not subjected to processing for reducing the halo phenomenon. When the halo phenomenon occurs in more than half the area in one frame, the viewer may not be concerned about the occurrence of the halo phenomenon.

  FIG. 7A shows an example of a design that does not reduce the halo phenomenon, and FIG. 7B shows an example of a design that reduces the halo phenomenon. FIG. 7 shows a case where a plurality of leaf images are displayed against a blue sky.

  For example, when the symbol in FIG. 7A is displayed on the display panel unit 10 and the halo phenomenon has occurred in all the leaf images, the halo phenomenon has occurred in substantially the entire screen. For this reason, the viewer may feel the display as if the halo phenomenon was an original image. Therefore, the control unit 1 does not perform a process of reducing the halo phenomenon when the halo phenomenon occurs in an area of half or more of one frame. As a result, it is possible to display an image in which the original color is prioritized, so that the quality of the image can be improved.

  On the other hand, when the symbol in FIG. 7B is displayed on the display panel unit 10 and the halo phenomenon occurs in all the leaf images, the halo phenomenon occurs only in a part of the screen. For this reason, the viewer may feel uncomfortable with the halo phenomenon. Therefore, the control unit 1 performs a process of reducing the halo phenomenon when the halo phenomenon occurs in an area of half or less of one frame.

  FIG. 8 is a flowchart illustrating processing executed by the control unit 1 and the video processing unit 2.

  The video processing unit 2 acquires an RGB video signal input from the outside (S11), and acquires the light emission rate and transmittance control value in one frame of the RGB video signal (S12). The presence or absence of the possibility of occurrence of a halo phenomenon in one pixel is detected (S13), and it is detected whether or not the continuity of pixels that may cause a halo phenomenon has become a predetermined value (S14). Specifically, as described above, the video processing unit 2 calculates the light leakage amount of the LED and detects it based on the calculation result.

  The control unit 1 detects the halo phenomenon in the frame (S15), and determines whether there is a possibility of occurrence of the halo phenomenon (S16). When there is no possibility of occurrence of the halo phenomenon (S16: NO), the control unit 1 ends the process in this frame and executes the same process for the next frame. If there is a possibility of occurrence of a halo phenomenon (S16: YES), whether the total of pixels that the control unit 1 has determined that a halo phenomenon may have occurred occupies an area of 50% of one frame so far It is determined whether or not (S17). For example, when the halo phenomenon occurs in substantially the entire screen, the viewer may determine that the halo phenomenon is included in the original image and may not be concerned about the halo phenomenon. On the other hand, when a halo phenomenon occurs in a part of the screen, the viewer may feel uncomfortable with the display content.

  When the total number of pixels determined to have the possibility of occurrence of the halo phenomenon is not 50% or less of the area (S17: NO), the halo phenomenon has occurred in more than half of the screen. It is determined that the viewer does not care about the halo phenomenon, and the process ends without performing the process of reducing the halo phenomenon. When it is 50% or less of the area (S17: YES), the control unit 1 determines that there is a possibility of occurrence of the halo phenomenon in this frame, and subsequently, there are four frames that are determined to have the possibility of occurrence of the halo phenomenon. It is determined whether or not the frames are continuous (S18).

  When four frames are not continuous (S18: NO), the control unit 1 ends the process in this frame, and executes the same process for the next frame. Depending on the continuity of frames that have been determined to cause the halo phenomenon, the process of reducing the halo phenomenon is not executed, and controlling the light source more than necessary reduces the color purity and impairs the image quality. The fear can be reduced. When four frames are continued (S18: YES), the control unit 1 executes a process for reducing the halo phenomenon (S19). Specifically, the control unit 1 determines the optimal mix ratio, and reduces the halo phenomenon by setting the light leakage amount of one color LED to be equal to or less than the allowable value of the light leakage amount of another color LED. To do. At this time, the control unit 1 may control only the LEDs 11a, 11b, and 11c included in the region 110 where the halo phenomenon occurs, or may control the LEDs 11a, 11b, and 11c in all the regions 110. It may be. Then, the control part 1 complete | finishes this process.

  As described above, the liquid crystal display device according to the present embodiment does not perform the process of reducing the halo phenomenon when a pixel that may cause the halo phenomenon occupies a predetermined area, and the pixel is less than the predetermined area. In some cases, processing is performed to reduce the halo phenomenon. As a result, even if a halo phenomenon occurs in the case of a complex pattern, the viewer does not care about the halo phenomenon, so by not performing processing to reduce the halo phenomenon, an image display that maintains the original color purity can be achieved. It becomes possible.

  Note that, as in the first embodiment, the control unit 1 may perform the process of reducing the halo phenomenon when the frames to be subjected to the process of reducing the halo phenomenon are continuous, or the halo phenomenon for each frame. You may make it perform the process which reduces. Further, the area occupied by a pixel that may cause a halo phenomenon is 50% of the frame, but can be changed as appropriate. For example, the processing for reducing the halo phenomenon may not be performed when the number of pixels with the possibility of the halo phenomenon occupying a predetermined ratio or more with respect to the total number of pixels.

  The preferred embodiments of the present invention have been specifically described above, but each configuration, operation, and the like can be appropriately changed and are not limited to the above-described embodiments.

It is a block diagram which shows the structure of the liquid crystal display device which concerns on embodiment. It is a figure which shows the structure of a backlight typically. It is a schematic diagram which shows the light emission rate of LED of each color in a different mix rate, (a) is a mix rate 0, (b) is a mix rate 1, (c) shows the case where a mix rate is 0.4. It is a schematic diagram which shows the light emission rate in the case of changing the light emission rate of LED by the mix rate 33%, (a) shows the case before a change, (b) shows the case after a change. It is a figure which shows the mix rate of LED determined for every area | region in a flame | frame. It is a flowchart which shows the process which a control part and a video process part perform. (A) shows an example of a design that does not reduce the halo phenomenon, and (b) shows an example of a design that reduces the halo phenomenon. It is a flowchart which shows the process which a control part and a video process part perform. It is a schematic diagram which shows the relationship between the transmission characteristic of the color filter of a liquid crystal panel, and the wavelength of each LED of RGB. It is a schematic diagram for demonstrating the light leakage which arises when a luminous rate changes.

Explanation of symbols

1 Control unit ( determination means, control means, acquisition means)
2 Video processing unit (control means)
3 Area active processing unit 4 Drive unit 10 Display panel unit 11 Backlight 11a R-LED
11b G-LED
11c B-LED

Claims (7)

In the image display device that controls the light emission rate of each of the light sources of the plurality of colors that irradiates the display panel having the color filter for each light source based on the gradation of the image displayed on the display panel .
Whether or not a halo phenomenon has occurred due to light leakage from a light source of a color other than a light source of a color corresponding to a color filter generated in the contour of the image in a partial area of the display panel on which the image is displayed. and determination means for determining,
Obtaining means for obtaining the light emission rate of each of the light sources;
Control means for controlling the light emission rate of the light source so as to make the light emission of the backlight light source corresponding to the area determined by the determination means that the halo phenomenon has occurred closer to white light based on the acquisition result by the acquisition means It equipped with a door,
The determination means includes
Determine whether a halo phenomenon occurs for each frame of the image,
The control means includes
The light emission rate of the light source is controlled so that the light emission of the light source gradually approaches white light from the periphery of the region where the determination unit determines that the halo phenomenon has occurred to the region, and the determination An image display apparatus characterized in that the means controls the light emission rate of the light source when the means determines that a halo phenomenon has occurred in a plurality of consecutive frames . The control means includes
The image display apparatus according to claim 1 , wherein the light emission rate of the light source is controlled so that light from the light source is additively mixed to approach white. The control means includes
The image display apparatus according to claim 1 or 2 , wherein the luminance of the light source having the maximum luminance acquired by the acquisition unit is maintained and the luminance of another light source is controlled. The control means includes
Wherein at a rate based on the determination result by the determination means, the image display apparatus according to the color of the synthesized light in any one of claims 1, wherein the 3 that you have to approach to white. The control means includes
The image display device according to claim 4 , wherein a color synthesized by the light source is made to gradually approach white. When said control means controls the light emission rate of the light source, based on a detection result by the detecting means, and hand stage you determine whether to terminate the control to the control means,
The control means includes
If it is determined that terminates, the color of the synthesized light, according to claim 4 or 5, characterized in that at a slower than the speed as close to white speed are so as to control the light emission rate of the light source so away from white The image display device described in 1. In the image display method for controlling the light emission rate of each of the light sources of a plurality of colors for irradiating the display panel having a color filter for each light source based on the gradation of the image displayed on the display panel .
Whether or not a halo phenomenon has occurred due to light leakage from a light source of a color other than a light source of a color corresponding to a color filter generated in the contour of the image in a partial area of the display panel on which the image is displayed. decision determining step,
Obtaining a luminous rate of each of the light sources; and
A control step of controlling the light emission rate of the light source so that the light emission of the backlight corresponding to the region determined by the determination means that the halo phenomenon has occurred is brought close to white light based on the acquired light emission rate; And
The determination step includes
Determine whether a halo phenomenon occurs for each frame of the image,
The control step includes
The light emission rate of the light source is controlled so that the light emission of the light source gradually approaches white light from the periphery of the region where the halo phenomenon is determined to occur in the determination step, and the determination An image display method , comprising: controlling a light emission rate of the light source when it is determined in a step that a halo phenomenon occurs in a plurality of frames continuously .

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