Display device and its control method
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SHARP KK
- Filing Date
- 2022-06-30
- Publication Date
- 2026-08-03
Smart Images
Figure 0007898799000001 
Figure 0007898799000002 
Figure 0007898799000003
Abstract
Description
Technical Field
[0001] The present invention relates to a display device and a control method thereof.
Background Art
[0002] Patent Document 1 discloses a technique in a content playback device for identifying the type of acquired content video and selecting display parameters for a display according to the identified content type.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Content playback devices such as television receivers may collectively manage profile settings of image quality and sound quality as viewing modes according to the viewing environment and video source. By preparing such a complex viewing mode, it is possible to cope with various viewing environments and scenes. On the other hand, for the user, the number of options for setting during video playback increases, and the operation tends to become complicated.
[0005] In this regard, with the configuration described in Patent Document 1, the content playback device can identify the type of content video and provide an appropriate viewing mode. However, for example, a movie content includes various scenes, and depending on the scene, the image quality setting in the viewing mode may not be optimal.
[0006] As one aspect, an object of the present disclosure is to provide a display device and a control method thereof that enable optimal image quality setting according to each scene included in content.
Means for Solving the Problems
[0007] A display device according to one aspect of the present invention comprises a display panel on which an image is displayed, a backlight that illuminates the display panel by irradiating it with light, a scene determination unit that determines a scene for an input video based on the brightness distribution of the input video and the illumination rate of the backlight, a parameter setting unit that sets parameters relating to brightness values applied to multiple areas of the backlight based on the scene determined by the scene determination unit, and a local dimming control unit that controls the backlight for each of the multiple areas based on the set parameters. [Brief explanation of the drawing]
[0008] [Figure 1] A block diagram showing an example of a television according to the first embodiment. [Figure 2A] A schematic diagram of an image displayed on the television screen according to the first embodiment. [Figure 2B] Histogram of brightness values for the image shown in Figure 2A. [Figure 3A] A schematic diagram showing the grayscale distribution of one area in the display of a television according to the first embodiment. [Figure 3B] A schematic diagram illustrating the concept of a method for determining backlight gradation in a television according to the first embodiment. [Figure 4] A flowchart showing an example of the processing flow of a television according to the first embodiment. [Figure 5A] A schematic diagram of an image displayed on the television screen according to the second embodiment. [Figure 5B] Histogram of brightness values for the image shown in Figure 5A. [Figure 6] A flowchart showing an example of the processing flow of a television according to the second embodiment. [Figure 7A] A schematic diagram of an image displayed on the television screen according to the third embodiment. [Figure 7B] Histogram of brightness values for the image shown in Figure 8A. [Figure 8A] A schematic diagram of an image displayed on the television screen according to the third embodiment. [Figure 8B] Histogram of brightness values for the image shown in Figure 9A. [Figure 9] A flowchart showing an example of the processing flow of a television according to the third embodiment. [Figure 10] A schematic diagram illustrating the concept of blur used in a television according to a modified example of the first to third embodiments. [Figure 11] A schematic diagram illustrating the concept of backlight gamma used in a television according to a modified example of the first to third embodiments. [Figure 12] A flowchart showing an example of the processing flow of a television according to a modified version of the first to third embodiments. [Modes for carrying out the invention]
[0009] <First Embodiment> The first embodiment will be described below. Figure 1 shows an example of a television 100 according to the first embodiment. The television 100 (display device) includes a processing unit 101, a receiving unit 102, a storage unit 103, a connection unit 104, a speaker 105, a display unit (display panel) 106, and a backlight 107. The television 100 may have other configurations, and some of the configurations in Figure 1 may be omitted.
[0010] The processing unit 101 includes a scene determination unit 111, a parameter setting unit 112, and a local dimming control unit 113. The processing unit 101 is a computer that performs various processes in each embodiment. The processing unit 101 has a processor and memory. By executing a plurality of instruction sets (programs) stored in the memory, the processor of the processing unit 101 functions as the scene determination unit 111, the parameter setting unit 112, and the local dimming control unit 113, and various controls in each embodiment can be realized. Any processor such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), or FPGA (Field Programmable Gate Array) can be used as the processor.
[0011] The above program is stored in a non-transitory recording medium such as a semiconductor medium, an optical recording medium, a magneto-optical recording medium, etc. And by executing the program stored in the recording medium by the program of the processing unit 101, various controls of each embodiment can be realized. Further, the above program may be acquired by the TV 100 from an external server via a network.
[0012] The receiving unit 102 includes, for example, a tuner. The receiving unit 102 receives broadcast waves distributed by broadcast equipment of one or more broadcasters and performs predetermined signal processing. The broadcast waves may include a plurality of programs distributed by broadcasters. The receiving unit 102 receives the broadcast waves wirelessly or by wire. Also, the broadcast waves are broadcast waves such as terrestrial wave broadcasting (terrestrial digital TV broadcasting) and satellite broadcasting. Satellite broadcasting includes BS (Broadcasting Satellites) broadcasting, CS (Communication Satellites) broadcasting, new 4K8K satellite broadcasting, etc.
[0013] The storage unit 103 stores various kinds of information. The storage unit 103 stores, for example, image quality parameters as image quality information regarding an image quality setting suitable for the image displayed by the display unit 106. The storage unit 103 may store other information.
[0014] The connection unit 104 is connected to the external storage device 200. The external storage device 200 is a recording device that records program data (program data) of the program received by the TV 100. The external storage device 200 is a USB (Universal Serial Bus) hard disk, a recorder, or the like.
[0015] The processing unit 101 can record the program data received by the receiving unit 102 in the external storage device 200 via the connection unit 104. Also, the processing unit 101 reads out the program data recorded in the external storage device 200 via the connection unit 104 and reproduces the read program data. The external storage device 200 may be, for example, a recording device built in the TV 100.
[0016] Speaker 105 is a device that outputs sound.
[0017] The backlight 107 includes, for example, multiple LEDs (Light Emitting Diodes). The backlight 107 illuminates the display unit 106 with the light emitted by the LEDs. This controls the brightness of the image displayed on the display unit 106. In this embodiment, the backlight 107 can control the brightness of the display unit 106 by dividing it into multiple areas. That is, the backlight 107 includes, for example, nine (3x3) areas L1 to L9, and the intensity of the light emitted by each area L1 to L9 onto the display unit 106 can be controlled independently of each other. This technique is known as local dimming. In the example in Figure 1, the backlight 107 is shown to include nine (3x3) areas L1 to L9, but the number of areas and the way the areas are divided can be selected as appropriate.
[0018] The display unit 106 is a display panel such as a liquid crystal display (LCD). The display unit 106 displays an image based on the video signal provided by the processing unit 101. As mentioned above, the brightness of the image displayed on the display unit 106 is controlled by the illumination of the backlight 107. In this case, the backlight 107 is controlled independently for areas L1 to L9. Therefore, the brightness of areas P1 to P9 of the display unit 106 corresponding to these areas L1 to L9 is also controlled independently by areas L1 to L9.
[0019] Next, the processing unit 101 will be described. The scene determination unit 111 of the processing unit 101 performs scene determination on the input video received from the receiving unit 102 or the input video received from the external storage device 200 via the connection unit 104. The scene determination unit 111 performs scene determination based on the brightness distribution of the input video and the illumination rate of the backlight 107 when the input video is displayed on the display unit 106. The scene determination unit 111 determines whether the scene of the input video is a scene in which bright areas are scattered within an overall dark image. Specifically, the scene determination unit 111 determines whether the above scene is a scene in which the proportion of areas having a brightness value of a predetermined value X1 (first brightness value) or less is R1 or more, and the proportion of areas having a brightness value of a predetermined value X2 (second brightness value) or more is R2 or more. The method for determining the scene will be described later. A scene that satisfies these conditions is a scene in which bright areas are scattered within an overall dark image. An example of such a scene is a scene of a starry night sky. The parameter setting unit 112 determines the parameters applied to the brightness value of the backlight 107 according to the scene determined by the scene determination unit 111. This will be explained later.
[0020] The parameter setting unit 112 sets parameters related to the brightness values applied to multiple areas L1 to L9 in the backlight 107, based on the scene determined by the scene determination unit 111. These parameters are, for example, parameters for determining the backlight gradation in each of the areas L1 to L9, and their details will be described later.
[0021] The local dimming control unit 113 controls the backlight 107 for each area L1 to L9 based on the parameters set in the parameter setting unit 112. The local dimming control unit 113 also transmits the video signal received from the receiving unit 102 or the external storage device 200 to the display unit 106 and controls the display unit 106 to display the video based on the video signal.
[0022] Next, an overview of the scene determination method for input video according to this embodiment and the backlight control method based on the result of the scene determination will be described. In this embodiment, as an example of a scene, a method for determining a scene that is generally dark but has bright areas scattered throughout, such as the starry sky video mentioned above, will be explained.
[0023] Figure 2A shows an example screen when displaying a starry sky image on the display unit 106. As shown, several bright, small dots are displayed in multiple areas, while the rest of the area is almost black. Figure 2B is the luminance histogram corresponding to Figure 2A. As shown, in the case of an image like a starry sky, the histogram is divided into low-luminance and high-luminance regions, with almost no intermediate luminance. In the luminance histograms from this point onward, including Figure 2B, the horizontal axis represents increasing luminance in the direction of the arrow, and the vertical axis represents increasing pixel count in the direction of the arrow.
[0024] The scene determination unit 111 first checks the illumination rate of the entire backlight 107. That is, the scene determination unit 111 checks the proportion of illuminated areas among the (3 x 3) = 9 areas L1 to L9 of the backlight 107. Then it determines whether the illumination rate is above a predetermined value. As shown in Figure 2A, in the case of an image where stars are scattered everywhere, the illumination rate of the backlight should be above a certain level in order to make those stars shine brightly.
[0025] The scene determination unit 111 then determines whether the proportion of the high-luminance areas, i.e., areas corresponding to the image of stars, is above a certain level relative to the entire screen. This is because, when stars are scattered, there should be a certain or greater proportion of high-luminance areas, as shown in the histogram in Figure 2B. Furthermore, the scene determination unit 111 determines whether the proportion of the low-luminance areas, i.e., areas corresponding to darkness, is above a certain level relative to the entire screen. This is because, in the case of an image of a starry sky, most of the area should be a low-luminance area, as shown in the histogram in Figure 2B.
[0026] The scene determination unit 111 then determines that the input video is a starry sky video as shown in Figures 2A and 2B if the backlight illumination rate is above a certain level, the proportion of the high-brightness area to the entire screen is above a certain level, and the proportion of the low-brightness area to the entire screen is above a certain level.
[0027] If the scene determination unit 111 determines that the input image is a starry sky, the parameter setting unit 112 sets the backlight gradation to a higher level. More specifically, it increases the ratio α of the maximum brightness to the average brightness in each area. This ratio α will be explained using Figures 3A and 3B. Figure 3A shows the gradation distribution of a certain area L in the display unit 106, and Figure 3B schematically shows the method for determining the backlight gradation in that area.
[0028] In the example shown in Figure 3A, the dotted white areas in the area have the highest brightness, while the other areas have the lowest brightness. The backlight gradation in this area is determined based on both the maximum brightness in that area, i.e., the brightness value of the dotted white areas shown in Figure 3A, and the average brightness in that area, i.e., the brightness value of the dotted white areas shown in Figure 3A, and the average brightness of the entire area, including the lowest brightness value of the other areas. This is schematically illustrated in Figure 3B.
[0029] As shown in Figure 3B, the backlight gradation in the area is obtained by mixing the maximum brightness and the average brightness in the area. This mixing is sometimes referred to as blending. The ratio used in this blending is the ratio α mentioned above. Therefore, the brightness value (backlight gradation) of the area can be expressed by the following equation (1) using the ratio α. α×(MAX_TONE)+(1-α)×(AVE_TONE)…(1) However, (MAX_TONE) is the maximum brightness of the area, and (AVE_TONE) is the average brightness of the area.
[0030] As shown in equation (1) above, increasing the ratio α increases the brightness value of the area in question. The parameter setting unit 112 increases this ratio α when it determines that the input image is a starry sky. For example, it sets it to the maximum possible value. The local dimming control unit 113 then controls the backlight 107 based on the set ratio α. As a result, the area in question is brightly illuminated by the backlight 107, and the stars on the display unit 106 are displayed to shine brightly. The ratio α set by the parameter setting unit 112 is applied to all areas L1 to L9 within the backlight 107. In other words, the ratio α is a common value for all areas.
[0031] Note that (MAX_TONE) is not necessarily limited to the maximum brightness in the area in question. For example, any brightness value above a predetermined value is acceptable. In other words, the ratio α can be defined as the ratio of the brightness values above a predetermined value in each of the multiple areas to the average brightness value in that area.
[0032] Figure 4 is a flowchart showing the processing flow of the scene determination method and the backlight control method based on the scene determination results, as explained using Figures 2A, 2B, 3A, and 3B above.
[0033] As shown in the diagram, in step S10, the scene determination unit 111 first checks the illumination rate of the entire backlight 107. That is, in the example in Figure 1, the scene determination unit 111 determines whether the proportion of illuminated areas among the (3 x 3) = 9 areas L1 to L9 in the backlight 107 is equal to or greater than a predetermined value R0. The predetermined value R0 can be appropriately selected depending on the scene to be determined, and in the case of a starry sky image, it may be set to, for example, 60-80%. However, the predetermined value R0 may be based not only on the scene but also on the number of areas in the backlight. That is, in the case of a starry sky image, the more areas there are, in other words, the smaller the area of one area, the smaller the predetermined value R0 can be. This is because the more areas there are, the more likely it is that there will be areas that do not contain stars.
[0034] Next, in step S11, the scene determination unit 111 determines whether the proportion of areas with a brightness value of X1 (first brightness value) or less is greater than or equal to R1. This step corresponds to the determination of whether the proportion of low-brightness areas, i.e., dark areas, is above a certain level, as explained in the histogram in Figure 2B. Therefore, the predetermined value X1 is a value that allows areas with a brightness value of X1 or less to be recognized as dark, as shown in Figure 2B. Also, in the case of a starry sky image, a considerable area should be dark, so the proportion R1 can be set to a relatively high value, for example, 70-90%.
[0035] Next, in step S12, the scene determination unit 111 determines whether the proportion of areas having a brightness value of a predetermined value X2 (second brightness value) or higher is R2 or higher. This step corresponds to the determination of whether the proportion of areas with high brightness, i.e., areas of stars, is above a certain level, as explained in the histogram in Figure 2B. Therefore, the predetermined value X2 is a value in which areas with a brightness value of X2 or higher can be recognized as stars, as shown in Figure 2B. Also, in the case of a starry sky image, a considerable area should be dark, so the proportion R2 can be set to a relatively low value, for example, 10-30%. Therefore, the relationship X2 > X1 holds true for brightness values, and the relationship R1 > R2 holds true for the proportion of areas.
[0036] If all the conditions in steps S10, S11, and S12 are met, the scene determination unit 111 determines in step S13 that the input image is a scene that is generally dark, like a starry sky, but with scattered bright areas. Then, in step S14, the parameter setting unit 112 sets the ratio α to a large value. The local dimming control unit 113 then sets the backlight gradation to a high value, and the display unit 106 is brightly illuminated by the backlight 107. This step is as previously explained using Figures 3A and 3B.
[0037] On the other hand, if the conditions are not met in any of steps S10, S11, or S12, the scene determination unit 111 determines in step S15 that the input image is not a scene like a starry sky, but a general image. In this case, the parameter setting unit 112 sets the ratio α to a smaller value than in step S14. In this case, the ratio α is, for example, the value adjusted by default, one example being a value where the ratio of the maximum brightness and the ratio of the average brightness are set to 50% each (α=0.5). Of course, it is not limited to this case, and various values of α can be selected, but it is set to a lower value than in the case of a scene like a starry sky. Then, the backlight gradation is set lower by the local dimming control unit 113.
[0038] As described above, in this embodiment, the scene determination unit 111 determines the scene of the input video based on the brightness distribution of the input video and the illumination rate of the backlight 107. Based on the scene determined by the scene determination unit 111, a parameter α is determined for setting the gradation of the entire area of the backlight 107 (for example, whether to increase or decrease the overall gradation). The local dimming control unit 113 then performs local dimming control using this parameter α, so that, for example, even if the entire scene is dark, bright areas such as stars are illuminated with light of higher brightness, making it possible to perform optimal local dimming according to the scene.
[0039] <Second Embodiment> Next, a second embodiment will be described. This embodiment relates to the detection of a generally bright (high-luminance) scene instead of a scene like a starry sky, as in the first embodiment described above. Below, only the differences from the first embodiment will be described.
[0040] This section will describe the scene determination method for input video according to this embodiment and the outline of the backlight control method based on the result of the scene determination. The scene determination unit 111 according to this embodiment determines a scene that is generally bright as an example of a scene.
[0041] Figure 5A shows an example screen when the display unit 106 displays an overall bright scene. As shown in the figure, in the example of Figure 5A, a hill is displayed in the foreground, and a blue sky and sun are displayed behind it. Area P3, where the sun is displayed, has particularly high brightness. On the other hand, area P7, where the hill is displayed, has lower brightness compared to other areas, for example, due to reflections of shadows. Figure 5B is a brightness histogram corresponding to Figure 5A. As shown in the figure, unlike the cases of Figures 3A and 3B described in the first embodiment, pixels are widely distributed from low to high brightness levels. And the number of pixels is relatively large in the high brightness levels. In this example, the average brightness value of the entire image displayed on the display unit 106 is set to Xave1, as shown in Figure 5B.
[0042] Figure 6 is a flowchart illustrating the processing flow of the scene determination method described using Figures 5A and 5B above, and the backlight control method based on the result of the scene determination. The difference between this embodiment and Figure 4 described in the first embodiment is that the scene determination unit 111 does not consider the illumination rate of the backlight 107 when performing scene determination. In this embodiment, the scene determination unit 111 performs scene determination based on the average picture level (APL) of the input image.
[0043] As shown in Figure 6, in step S20, the scene determination unit 111 first determines whether the APL of the input video is greater than or equal to a predetermined value Xref1. For example, in the example of Figure 5B, the average brightness value Xave1 corresponds to the APL, and Xave1 is greater than Xref1. The predetermined value Xref1 can be set appropriately according to the desired brightness of the scene. If the value of Xref1 is set small, even a relatively dark scene will be judged as a bright scene overall, and conversely, if the value of Xref1 is set large, the scene will not be judged as bright unless the APL is quite high.
[0044] In step S20, if APL is greater than or equal to the specified value Xref1, the scene determination unit 111 determines in step S21 that the input image is a bright scene overall. Then, in step S22, the parameter setting unit 112 sets the ratio α to a value closer to the average. That is, in equation (1) and Figure 3B described in the first embodiment, the contribution of average brightness (AVE_TONE) is increased. More specifically, the value of ratio α is set to a relatively small value, for example, a value of about 0.3 to 0.4. Of course, the ratio α is not limited to these values; it may be a larger or smaller value. Then, the local dimming control unit 113 controls the backlight 107 using the set ratio α.
[0045] On the other hand, if APL is less than the specified value Xref1 in step S20, the scene determination unit 111 determines in step S23 that the input image is a general video and not an overall bright scene. Then, in step S24, the parameter setting unit 112 sets the ratio α to, for example, the default value. This process is the same as step S16 described in the first embodiment. In this case, for example, the value of ratio α (for example, 0.5) set in step S24 is greater than the ratio α set in step S22. Then, the local dimming control unit 113 controls the backlight using the set ratio α.
[0046] According to this embodiment, when the input video is a generally bright scene, the value of ratio α is set smaller than when it is not. By setting the value of ratio α smaller, the backlight gradation is set to be relatively darker. This effect is particularly noticeable in the low-gradation and medium-gradation regions of the video, and the brightness in these regions becomes relatively low. On the other hand, even when using the same ratio α, the effect of setting ratio α smaller is small in the high-gradation region, and the brightness in these regions remains high. As a result, the brightness values in the low-gradation and medium-gradation regions can be kept low, and the power used in these regions is suppressed. Therefore, the local dimming control unit 113 can use the power suppressed in the low-gradation and medium-gradation regions for the high-gradation regions. More specifically, by using this power for the high-gradation regions, the brightness in these regions can be further increased. As a result, the brightness values in the low-gradation and medium-gradation regions can be kept low, and the brightness values in the high-gradation regions can be kept high, making it possible to enhance the contrast of the video.
[0047] <Third Embodiment> Next, a third embodiment will be described. In this embodiment, if the input image is determined to be a scene like a starry sky, the density of the brighter areas is further determined, and the ratio α is determined according to the result. Below, only the differences from the first embodiment will be described.
[0048] When the process described in Figure 4 of the first embodiment is performed, the following two cases can be determined to be scenes resembling a starry sky. First, there are the cases shown in Figures 7A and 7B. Figure 7A shows an example of a screen displayed on the display unit 106, and Figure 7B is a luminance histogram for each area P1 to P9 in Figure 7A.
[0049] As shown in Figure 7A, in this case, although the overall image is dark, bright regions representing stars are evenly distributed across areas P1 to P9. In this case, the brightness histograms for each area P1 to P9 all have the shape shown in Figure 7B. That is, there are a very large number of pixels with low brightness and a very small number of pixels with high brightness.
[0050] The following case is the scene shown in Figures 8A and 8B. Figure 8A shows an example of the screen displayed on the display unit 106, and Figure 8B is the luminance histogram for each area P1 to P9 in Figure 8A.
[0051] As shown in Figure 8A, in this case, the overall image is dark, similar to Figure 7A, but the bright regions containing stars are concentrated only in area P5. This case applies, for example, to images of the moon taken with a telephoto lens. In this case, as shown in Figure 8B, the luminance histograms of areas P1-P4 and P6-P9 contain only low-luminance pixels, and even if small stars are present, their number of pixels is small, as shown in Figure 7B. In contrast, the luminance histogram of area P5 has a very large number of high-luminance pixels.
[0052] As described above, this embodiment uses different ratios α for the case shown in Figure 7A and the case shown in Figure 8A. Figure 9 is a flowchart showing the processing flow of the scene determination method and the backlight control method based on the result of the scene determination according to this embodiment, and corresponds to Figure 4 described in the first embodiment.
[0053] As shown in Figure 9, first the processes of steps S10 to S13 and S15 described in Figure 4 of the first embodiment are performed. Then, in step S13, if the scene determination unit 111 determines that the input video is a scene like a starry sky, in step S30 the scene determination unit 111 continues to determine whether the maximum average brightness value for each area in the input video is less than or equal to a predetermined value Xref2 (third brightness value).
[0054] The third luminance value is determined by how densely the illuminated areas must be concentrated in one area for it to be judged as a scene with densely packed bright areas, as shown in Figure 8A. For example, if it is determined that there is a dense concentration of bright areas when (XX)% or more of the illuminated areas of the entire screen are concentrated in one area, using the number of areas and the APL of the entire screen, it can be determined by equation (2) below, for example. Note that XX is a value between 0 and 100. Xref2 = (APL of the entire screen) × (Number of areas × (XX) / 100) ... (2) However, the method for determining the third luminance value is not limited to this method; other methods may also be used.
[0055] For example, when the illuminated areas are concentrated in one area as in Figure 8A, and this is assumed to be a case of "densely packed bright areas," the value of XX in equation (2) above is, for example, 100. Therefore, the value of Xref2 becomes ((APL of the entire screen) × 9). In this respect, in the examples of Figures 7A and 7B, since there are only a few small stars in each area, the maximum average brightness of each area is relatively low. As shown in Figure 7B, the maximum average brightness of each area P1 to P9 is Xave_max shown in the figure, and this value is smaller than the specified value Xref2. Therefore, in this case, in step S31, the scene determination unit 111 determines that it is a scene with sparsely distributed bright areas, that is, a scene like the one shown in Figure 7A. After that, similar to step S14 described in the first embodiment, in step S32, the parameter setting unit 112 sets the ratio α closer to the maximum, and the local dimming control unit 113 sets the brightness of the backlight to a high level to illuminate the display unit 106.
[0056] On the other hand, in the examples of Figures 8A and 8B, since bright areas are densely concentrated in area P5, the maximum average brightness of area P5 is relatively high. In the example of Figure 8B, the maximum average brightness of areas P1 to P4 and P6 to P9 is the same as in the case of Figure 7B, for example, but the maximum average brightness of area P5 is Xave_max shown in the figure, and this value is greater than the default value Xref2. Therefore, in this case, in step S33, the scene determination unit 111 determines that it is a scene in which bright areas are densely concentrated, that is, a scene like the one shown in Figure 8A. After that, in step S34, similar to step S16 described in the first embodiment, the parameter setting unit 112 sets the ratio α to the default value, for example, 0.5, and the local dimming control unit 113 sets the brightness of the backlight to the default value and illuminates the display unit 106.
[0057] According to this embodiment, in the first embodiment described above, a determination is made as to whether or not there are densely packed bright areas. If there are densely packed bright areas, sufficient brightness can be obtained without increasing the gradation of the backlight. Therefore, power consumption can be reduced.
[0058] <Examples of variations, etc.> As described above, the display device and control method according to the first to third embodiments determine what kind of scene the input video is and enables optimal local dimming control according to the determination result. The embodiments are not limited to the forms described above, and various modifications are possible. Each embodiment may be implemented independently, or multiple embodiments may be combined and implemented.
[0059] For example, in the second embodiment described above, if the input video is a bright scene overall, the blurring effect on the object may be reduced by illuminating the backlight around the high-brightness areas. Hereafter, this process of blurring the object will be simply referred to as "blur" in this specification. Blur will be briefly explained using Figure 10.
[0060] Figure 10 is a schematic diagram of a backlight 107 containing (5 x 5) = 25 areas, where the illumination light intensity can be adjusted for each area. The numbers written within each area indicate the illumination rate of that area. The left side of Figure 10 shows the case where the blur is off, and only the central area of the backlight 107 is illuminated, with an illumination rate of 100%. In contrast, the right side of Figure 10 shows the case where the blur is on. In this example, eight areas adjacent to the area with a 100% illumination rate in the left side of Figure 10 are illuminated, with an illumination rate of, for example, 75%. Note that which areas to illuminate and their illumination rates can be appropriately selected, for example, by the parameter setting unit 112 or the local dimming control unit 113.
[0061] As described above, blur is a function that expands the illuminated area by illuminating the backlight in areas adjacent to the illuminated area. When the blur is increased, that is, when the number of illuminated areas is increased and / or the illumination rate of the illuminated areas is increased, the contrast between light and dark decreases, but the negative effects of extreme brightness differences become less noticeable. This negative effect occurs when an object is displayed at high brightness and the surrounding brightness is very low, causing the periphery of the object, that is, the area with an extreme brightness difference, to appear darker to the viewer compared to other areas, such as the center of the object. On the other hand, when the blur is decreased, that is, when the increase in the number of illuminated areas is reduced and / or the illumination rate of the illuminated areas is reduced, the above negative effect becomes more noticeable, but the contrast between light and dark increases.
[0062] Furthermore, in the second embodiment described above, if the input video is a generally bright scene, the gamma correction intensity may be reduced. In other words, correction may be performed such that the midpoint value in the backlight luminance distribution becomes smaller. This point will be explained using Figure 11. Figure 11 shows the backlight luminance curve, where the horizontal axis is the input (before correction) luminance value and the vertical axis is the output (after correction) luminance value. The luminance values are distributed from zero (black) to 255 (white), and the brighter the value, the higher the luminance value.
[0063] As shown in the figure, the distribution of output with respect to input can be expressed by equation (3) below. y = 255 × (x / 255) (1 / γ) …(3) However, y is the output (corrected brightness value), x is the input (uncorrected brightness value), and γ is the γ correction value, and the case shown is when the minimum brightness value is zero and the maximum brightness value is 255. For example, when γ is 1, the input brightness value is the same as the output brightness value, and the input and output have a linear relationship. In contrast, when γ has a value greater than 1, the brightness curve takes on an upward convex shape, and the output brightness value is made larger than the input brightness value due to the correction. That is, the brightness value of the backlight 107 becomes larger than the input value, and the display unit 106 is illuminated with brighter light. On the other hand, when γ has a value less than 1, the brightness curve takes on a downward convex (concave) shape, and the output brightness value is made smaller than the input brightness value due to the correction. That is, the brightness value of the backlight 107 becomes smaller than the input value. Such gamma correction may be performed by, for example, the parameter setting unit 112 or the local dimming control unit 113 to control the backlight 107. Then, in the case of an image like the one shown in Figure 5A, the local dimming control unit 113 sets γ to a small value around 1, thereby darkening the overall color tone of the image. This makes it possible to increase the contrast between bright and dark areas.
[0064] Figure 12 is a flowchart showing the processing flow of the backlight control method when blur and gamma correction described using Figures 10 and 11 above are applied, and corresponds to Figure 6 described in the second embodiment. As shown in the figure, after the processing of steps S20 to S22 described in Figure 6, for example, the parameter setting unit 112 and the local dimming control unit 113 reduce the intensity of the blur in the backlight 107 or turn off the blur in step S40, and correct the brightness value of the input video by setting the γ value to around 1, for example, in the range of (1 / 1.2) to 1.2 in the brightness curve described in Figure 11. Of course, the γ value may be adjusted outside of this setting. Although not shown in Figure 12, if it is determined in step S23 that it is a general image, the blur in the backlight 107 may be set stronger than in the case of step S40, and further, the brightness value of the input video may be corrected by setting it to a value greater than linear, i.e., convex upwards, and greater than in the case of step S40, in the brightness curve described in Figure 11. Alternatively, γ may be less than 1, but it should be a larger value than in the case of step S40. These values may be pre-set as default values, for example.
[0065] Furthermore, in the first and third embodiments described above, examples of images of a starry sky were explained. However, scenes in which bright areas are scattered within an overall dark image may include, for example, images of fireflies or nightscapes with scattered lights from the windows of buildings. Also, in the embodiments described above, the cases of a starry sky scene and an overall bright scene were explained as examples. However, the scenes that the scene determination unit 111 determines are not limited to these, and the scene determination unit 111 may, in advance, store characteristics of various scenes and, based on these characteristics, change the reference values X1, X2, Xref1, Xref2 of the input image's pixel values, the regions R1, R2 having specific pixel values, and the illumination rate R0 of the backlight 107 in various ways. Furthermore, scene determination can be performed based on characteristics of the pixel value distribution and average brightness level of the image as a whole. The parameter setting unit 112 may, in advance, store various setting values for each scene that can be determined by the scene determination unit 111. Examples of setting values are not limited to ratio α, blur, and gamma correction value, but are not limited to any parameter related to brightness in the display unit 106. These reference values for determining the scene (for example, the specified values R0 to R2 and brightness values X1, X2 in Figure 4) can be stored in a storage device such as ROM or RAM provided by the television 100, which is not shown in Figure 1. Of course, a processing unit 101, for example, a processor, may perform various calculations according to the scene to be determined to calculate the reference values necessary for scene determination.
[0066] Furthermore, in the above embodiments, image quality adjustments may also be performed according to the content type. That is, in the multiplexed broadcast wave, genre information indicating the content type of the program is transmitted along with the video data of the program. In this case, the parameter setting unit 112 of the television 100, for example, determines basic image quality adjustments (backlight adjustments) according to the content type, and the method described in the first to third embodiments and their modifications may be used as the basis for these basic image quality adjustments. For example, even for the same starry sky scene, the predetermined values R0 to R2 and predetermined values X1 and X2 may differ depending on whether the content type of the program is, for example, a movie or a documentary. Also, in some cases, the processing of steps S14 and S16 may be swapped in Figure 4. The same applies to the second and third embodiments.
[0067] This disclosure is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. In addition, the processing order of the flowcharts described in the embodiments described above can be changed as much as possible.
[0068] The program that implements the functions of each embodiment is stored in a non-temporary recording medium such as a semiconductor medium, an optical recording medium, or a magneto-optical recording medium. For example, a non-volatile memory card may be used as the semiconductor medium. For example, a CD (Compact Dick) or DVD (Digital Versatile Disk) may be used as the optical recording medium or magneto-optical recording medium. Furthermore, the program may be supplied to a computer via any transmission medium capable of transmission. [Explanation of symbols]
[0069] 100...Television, 101...Processing unit, 102...Receiving unit, 103...Storage unit, 104...Connection unit, 105...Speaker, 106...Display unit, 107...Backlight, 111...Scene determination unit, 112...Parameter setting unit, 113...Local dimming control unit, 200...External storage device
Claims
1. A display panel where images are displayed, A backlight that illuminates the display panel by shining light on the display panel, A scene determination unit that determines the scene of the input video based on the illumination rate of the backlight, A parameter setting unit sets parameters relating to the brightness values applied to multiple areas of the backlight based on the scene determined by the scene determination unit, A local dimming control unit that performs local dimming control of the backlight for each of the multiple areas based on the set parameters, It is equipped with, The parameter setting unit is, Depending on the scene determined above, the ratio between one luminance value in the plurality of areas that is greater than or equal to a predetermined value and the average luminance value in the plurality of areas is determined. Using the determined ratio, set the parameter to be applied to each of the multiple areas. Display device.
2. The display device according to claim 1, wherein the same value of the parameter is applied to all of the plurality of areas of the backlight.
3. If the scene determination unit determines that the input video is a scene composed of a dark background with a first brightness value or less and a bright area with a second brightness value or more that is higher than the first brightness value, The parameter setting unit determines the parameters by making the ratio of one luminance value greater than or equal to the predetermined value greater than the ratio of the average luminance values. The display device according to claim 1.
4. When the scene determination unit determines that the input video is a scene composed of a dark background with a first brightness value or less and a bright illuminated area with a second brightness value or higher than the first brightness value, Furthermore, if the parameter setting unit determines that the illuminated portions are densely clustered in the image displayed on the display panel, it determines the parameters by setting the ratio of one brightness value greater than or equal to the ratio of the average brightness values to be the same as or less than the ratio of the average brightness values. The display device according to claim 1.
5. A display panel on which an image is displayed, A backlight that illuminates the display panel by shining light on the display panel, A scene determination unit that determines the scene of the input video based on the illumination rate of the backlight, A parameter setting unit sets parameters relating to the brightness values applied to multiple areas of the backlight based on the scene determined by the scene determination unit, A local dimming control unit that performs local dimming control of the backlight for each of the multiple areas based on the set parameters, It is equipped with, The parameter setting unit changes the relationship between the brightness value of the output video and the brightness value of the input video based on the scene determined by the scene determination unit. Display device.
6. The display device according to claim 1, wherein the parameter setting unit increases or decreases the blur intensity in the backlight based on the scene determined by the scene determination unit.
7. The scene determination unit determines the scene of the input video based on the brightness distribution of the input video and the illumination rate of the backlight. The display device according to claim 1.
8. A control method for a display device equipped with a backlight that illuminates a display panel on which an image is displayed by irradiating the panel with light, Based on the illumination rate of the aforementioned backlight, the scene of the input video is determined, Based on the determined scene, parameters relating to the brightness values applied to multiple areas of the backlight are set. Based on the parameters set above, the backlight is to be locally dimmed for each of the multiple areas. It is equipped with, In setting the aforementioned parameters, Depending on the scene determined above, the ratio between one luminance value in the plurality of areas that is greater than or equal to a predetermined value and the average luminance value in the plurality of areas is determined. Using the determined ratio, set the parameter to be applied to each of the multiple areas. A method for controlling a display device.
9. In determining the scene, the scene is determined for the input video based on the brightness distribution of the input video and the illumination rate of the backlight. A method for controlling a display device according to claim 8.