Display device and control method thereof

Abstract

A display device capable of performing optimal picture quality setting according to each scene included in content and a control method thereof are provided. The display device includes a display panel that displays an image, a backlight that irradiates light to the display panel to cause the display panel to light up, a scene determination section that performs determination of a scene related to an input image based on a light-up rate of the backlight, a parameter setting section that sets a parameter of a luminance value applied to a plurality of regions of the backlight based on the scene determined by the scene determination section, and a local dimming control section that performs local dimming control of the backlight for each region of the plurality of regions based on the set parameter.

Description

Technical Field

[0001] This invention relates to a display device and a control method thereof. Background Technology

[0002] Japanese Patent Application Publication No. 2010-283790 discloses a technique for determining the category of acquired content images in a content reproduction device and selecting display parameters for a display based on the determined content category. Summary of the Invention The technical problem to be solved by the present invention

[0003] Content playback devices such as television receivers sometimes manage picture and sound quality settings as audio-visual modes in conjunction with the audio-visual settings, based on the audio-visual environment and image source.

[0004] By preparing such a complex audiovisual mode, it is possible to cope with various audiovisual environments and scenarios. On the other hand, for users, the options for setting when reproducing images increase, making operation more complicated.

[0005] Regarding this point, if the structure described in Japanese Patent Application Publication No. 2010-283790 is adopted, the content reproduction device can determine the type of content image and provide an appropriate audiovisual mode. However, for example, film content may include various scenes, and depending on the scene, the picture quality in the audiovisual mode may not be optimal.

[0006] As an aspect, the purpose of this disclosure is to provide a display device and its control method capable of setting optimal image quality according to the various scenes contained in the content.

[0007] One aspect of the present invention relates to a display device comprising: a display panel displaying an image; a backlight illuminating the display panel to illuminate it; a scene determination unit determining a scene related to the input image based on the backlight's illumination rate; a parameter setting unit setting parameters for 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 performing local dimming control of the backlight for each of the multiple areas based on the set parameters. Attached Figure Description

[0008] Figure 1 This is a block diagram illustrating an example of a television set according to the first embodiment. Figure 2A This is a schematic diagram of the image displayed on the screen of the television set according to the first embodiment. Figure 2B yes Figure 2A The image shown is a histogram of brightness values. Figure 3AThis is a schematic diagram showing the grayscale distribution of a region on the display of a television set according to the first embodiment. Figure 3B This is a schematic diagram illustrating the concept of a method for determining the backlight grayscale in a television set according to the first embodiment. Figure 4 This is a flowchart illustrating an example of the processing flow of a television set according to the first embodiment. Figure 5A This is a schematic diagram of the image displayed on the screen of the television set according to the second embodiment. Figure 5B for Figure 5A The image shown is a histogram of brightness values. Figure 6 This is a flowchart illustrating an example of the processing flow of a television set according to the second embodiment. Figure 7A This is a schematic diagram of the image displayed on the screen of the television set according to the third embodiment. Figure 7B yes Figure 8A The image shown is a histogram of brightness values. Figure 8A This is a schematic diagram of the image displayed on the screen of the television set according to the third embodiment. Figure 8B yes Figure 8A The image shown is a histogram of brightness values. Figure 9 This is a flowchart illustrating an example of the processing flow of a television set according to the third embodiment. Figure 10 This is a schematic diagram illustrating the concept of blur used in a television set, as shown in variations of the first to third embodiments. Figure 11 This is a schematic diagram illustrating the concept of backlight gamma used in a television set, which is a variation of the first to third embodiments. Figure 12 This is a flowchart illustrating an example of the processing flow of a television set, representing a variation of the first to third embodiments. Detailed Implementation

[0009] <First Implementation Method> The first embodiment will be described below. Figure 1 This diagram illustrates an example of a television set 100 according to the first embodiment. The television set 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 set 100 may have other configurations, or these configurations may be omitted. Figure 1 It is a part of the composition.

[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 executes various processes in each embodiment. The processing unit 101 has a processor and a memory. By executing multiple instruction sets (programs) stored in the memory by the processor of the processing unit 101, the processing unit 101 functions as the scene determination unit 111, the parameter setting unit 112, and the local dimming control unit 113, enabling various controls in each embodiment. The processor can be any processor such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), or FPGA (Field Programmable Gate Array).

[0011] The aforementioned program is stored, for example, in a non-transitory recording medium such as a semiconductor medium, an optical recording medium, or an opto-magnetic recording medium. Then, by executing the program stored in the recording medium through the processing unit 101, various controls in each embodiment can be implemented. Furthermore, the aforementioned program can also be obtained by the television set 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 broadcasting equipment from one or more broadcasting operators and performs prescribed signal processing. The broadcast waves may include multiple programs distributed by the broadcasting operators. The receiving unit 102 receives the broadcast waves wirelessly or via wired connection. Furthermore, the broadcast waves are terrestrial broadcasts (terrestrial digital television broadcasts), satellite broadcasts, etc. Satellite broadcasts include BS (Broadcasting Satellites) broadcasts, CS (Communication Satellites) broadcasts, and new 4K / 8K satellite broadcasts, etc.

[0013] Storage unit 103 stores various types of information. For example, storage unit 103 stores image quality information, i.e., image quality parameters, related to image quality settings suitable for display on display unit 106. Storage unit 103 may also store other information.

[0014] The connection part 104 is connected to the external storage device 200. The external storage device 200 is a recording device that records data (program data) of programs received by the television set 100. The external storage device 200 is a USB (Universal Serial Bus) hard drive, recorder, etc.

[0015] The processing unit 101 can record program data received by the receiving unit 102 to the external storage device 200 via the connection unit 104. Furthermore, the processing unit 101 can read the program data recorded in the external storage device 200 via the connection unit 104 and reproduce the read program data. The external storage device 200 may, for example, be a recording device built into the television set 100.

[0016] Speaker 105 is a device that outputs sound.

[0017] The backlight 107, for example, has multiple LEDs (Light Emitting Diodes). Furthermore, the backlight 107 illuminates the display unit 106 with light output from the LEDs. This controls the brightness of the image displayed on the display unit 106. In this embodiment, the backlight 107 can divide the display unit 106 into multiple regions to control brightness. That is, the backlight 107, for example, includes nine regions L1 to L9 (3×3), and the intensity of light illuminating the display unit 106 from each region L1 to L9 can be controlled independently. This technique is known as local dimming. Furthermore, in Figure 1 In the example, backlight 107 represents the case of (3×3)9 regions L1 to L9, but the number of regions and the method of region division can be appropriately selected.

[0018] Display unit 106 is a display panel such as a liquid crystal display (LCD). Display unit 106 displays images based on image signals provided from processing unit 101. Furthermore, as described above, display unit 106 is illuminated by backlight 107, thereby controlling the brightness of the images displayed by display unit 106. At this time, regions L1 to L9 of backlight 107 are controlled independently of each other. Therefore, the brightness of regions P1 to P9 of display unit 106 corresponding to these regions L1 to L9 is also controlled independently of regions 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 image received from the receiving unit 102 or the input image 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 image and the illumination rate of the backlight 107 when the input image is displayed on the display unit 106. The scene determination unit 111 determines whether the scene of the input image is a scene with bright areas scattered throughout an overall dark image. Specifically, the scene determination unit 111 determines whether the scene is a scene where the proportion of areas with brightness values ​​of a predetermined value X1 (first brightness value) or less is R1 or more, and the proportion of areas with brightness values ​​of a predetermined value X2 (second brightness value) or more is R2 or more. The method for determining this scene will be explained later. A scene that satisfies this condition is a scene where bright areas are scattered throughout an overall dark image. Examples of such scenes include a nighttime starry sky. Based on the scene determined by the scene determination unit 111, the parameter setting unit 112 determines the parameters for the brightness value applied to the backlight 107. This will be described later.

[0020] The parameter setting unit 112 sets parameters related to the brightness values ​​applied to the multiple regions L1 to L9 in the backlight 107 based on the scene determined by the scene determination unit 111. These parameters are, for example, parameters used to determine the backlight grayscale in each of the regions L1 to L9, and their details will be described in detail later.

[0021] The local dimming control unit 113 controls the backlight 107 for each region L1 to L9 based on the parameters set by the parameter setting unit 112. In addition, the local dimming control unit 113 controls the display unit 106 to send the image signal received from the receiving unit 102 or the external storage device 200 to the display unit 106 and display the image based on the image signal.

[0022] Next, an overview of the scene determination method for the input image and the backlight control method based on the scene determination result of this embodiment will be described. In this embodiment, as an example of a scene, a method for determining a scene that is generally dark but has scattered bright areas, such as the image of the starry sky described above, will be used as an example for explanation.

[0023] Figure 2A This is an example of a screen displaying an image of the starry sky on the display unit 106. As shown, bright, small dots are displayed in several areas, while other areas are mostly black. Figure 2B Is with Figure 2A The corresponding brightness histogram. As shown in the figure, in the case of images like the starry sky, the histogram is divided into low-brightness regions and high-brightness regions, with almost no intermediate brightness. Additionally, in images containing... Figure 2BIn the subsequent brightness histogram, the brightness increases in the direction of the arrow on the horizontal axis, and the number of pixels increases in the direction of the arrow on the vertical axis.

[0024] Therefore, the scene determination unit 111 first confirms the overall illumination rate of the backlight 107. That is, the scene determination unit 111 confirms the proportion of illuminated areas in the (3×3) = 9 areas L1 to L9 of the backlight 107. Then, it determines whether the illumination rate is above a predetermined value. This is because, if Figure 2A As shown, in the case of images with stars scattered everywhere, the backlight illumination rate should be above a certain level in order for these stars to shine brightly.

[0025] Next, the scene determination unit 111 determines whether the proportion of the high-brightness area, that is, the area equivalent to the star-shaped image, relative to the entire screen is above a certain level. This is because, in the case of star-shaped dispersion, such as Figure 2B As shown in the histogram, areas of high brightness should exist to a certain extent. Furthermore, the scene determination unit 111 determines whether the proportion of low-brightness areas, i.e., areas comparable to dark areas, relative to the entire image is to a certain extent. This is because, in the case of an image of the starry sky, most areas are like... Figure 2B The histogram shows areas with low brightness.

[0026] Furthermore, when the scene determination unit 111 determines that the input image is as follows: the backlight brightness rate is above a certain level, the proportion of high-brightness areas relative to the entire screen is above a certain level, and the proportion of low-brightness areas relative to the entire screen is above a certain level. Figure 2A as well as Figure 2B The image shown is of the starry sky.

[0027] If the scene determination unit 111 determines that the input image is a starry sky image, the parameter setting unit 112 sets the backlight grayscale to a high level. More specifically, it increases the ratio α of the maximum brightness to the average brightness in each area. Figure 3A as well as Figure 3B Explain the proportion α. Figure 3A This represents the grayscale distribution of a certain region L of the display unit 106. Figure 3B This schematically illustrates the method for determining the backlight grayscale in this area.

[0028] in the case of Figure 3A In the example shown, the dotted white areas within the region are bright and have the highest brightness, while other areas have approximately the lowest brightness. The backlight grayscale level in this region is based on the maximum brightness in that region, i.e. Figure 3A The brightness value of the dotted white area shown, the average brightness of that area, i.e. Figure 3AThe brightness is determined by both the brightness value of the dotted white area shown and the average brightness of the entire area, which includes the approximate lowest brightness value of other areas. Figure 3B This situation is illustrated schematically.

[0029] like Figure 3B As shown, the backlight grayscale in this region is obtained by mixing the maximum brightness in this region with the average brightness in this region. This mixture can also be called a blend, for example. The ratio for this blending is the ratio α mentioned above. Therefore, the brightness value (backlight grayscale) of this region can be expressed by the following equation (1) if the ratio α is used. α×(MAX_TONE)+(1-α)×(AVE_TONE)…(1) Where (MAX_TONE) is the maximum brightness of the region, and (AVE_TONE) is the average brightness of the region.

[0030] As shown in equation (1) above, by increasing the ratio α, the brightness value of the area increases. When the parameter setting unit 112 determines that the input image is a starry sky image, it increases the ratio α. For example, it sets it to the maximum settable value. Then, the local dimming control unit 113 controls the backlight 107 according to the set ratio α. As a result, the area is brightly illuminated by the backlight 107, and the star pattern in the display unit 106 is also brightly and brilliantly displayed. In addition, the ratio α set by the parameter setting unit 112 is applied to all areas L1 to L9 within the backlight 107. That is, the ratio α is a value shared by the entire area.

[0031] Furthermore, (MAX_TONE) is not necessarily limited to the maximum brightness in that area. For example, any brightness value above a predetermined value is acceptable. That is, the ratio α can be defined as the ratio of the brightness value above the predetermined value in each of the multiple areas to the average brightness value in that area.

[0032] Figure 4 This indicates the use of the above. Figure 2A , Figure 2B , Figure 3A as well as Figure 3B The flowchart illustrates the process of scene determination and backlight control based on the scene determination results.

[0033] As shown in the figure, firstly, in step S10, the scene determination unit 111 confirms the overall illumination rate of the backlight 107. That is, if it is... Figure 1For example, the scene determination unit 111 determines whether the proportion of illuminated areas in the (3×3) = 9 regions L1 to L9 of the backlight 107 is greater than or equal to a preset value R0. The preset value R0 can be appropriately selected according to the scene to be determined. In the case of a starry sky image, for example, it can be set to 60% to 80%. However, the preset value R0 depends not only on the scene but also on the number of regions in the backlight. That is, in the case of a starry sky image, the more regions there are, in other words, the smaller the area of ​​one region, the smaller the preset value R0. This is because the more regions there are, the higher the probability that there are more regions that do not contain star shapes.

[0034] Next, in step S11, the scene determination unit 111 determines whether the proportion of areas with brightness values ​​below a predetermined value X1 (first brightness value) is R1 or higher. This step is equivalent to... Figure 2B The histogram illustrates whether the proportion of low-brightness areas, i.e., dark areas, is above a certain level. Therefore, as... Figure 2B As shown, the specified value X1 is the value at which areas with a brightness value of X1 or less can be considered dark areas. Furthermore, in the case of images of the starry sky, a considerable area should be considered dark, so the ratio R1 can be set to a relatively high value, such as 70-90%.

[0035] Next, in step S12, the scene determination unit 111 determines whether the proportion of areas with a brightness value of a predetermined value X2 (second brightness value) or higher is R2 or higher. This step is equivalent to... Figure 2B The histogram illustrates whether the proportion of high-brightness areas, i.e., star-shaped areas, reaches a certain level. Therefore, as... Figure 2B As shown, the specified value X2 is the value at which areas with a brightness value of X2 or higher can be identified as stars. Furthermore, in the case of starry sky images, a considerable area should appear dark; therefore, the ratio R2 can be set to a relatively low value, such as 10-30%. Thus, regarding brightness values, the relationship X2 > X1 holds true, and regarding the ratio of the area, the relationship R1 > R2 holds true.

[0036] If all 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. Therefore, in step S14, the parameter setting unit 112 sets the ratio α to a large value. Then, the local dimming control unit 113 sets the backlight grayscale to a high value, and the display unit 106 is illuminated by the backlight 107. This step is performed as before. Figure 3A as well as Figure 3B As explained.

[0037] On the other hand, if the conditions in any of steps S10, S11, and S12 are not met, in step S15, the scene determination unit 111 determines that the input image is not a scene like a starry sky but a general image. In this case, compared to the case in step S14, the parameter setting unit 112 sets the ratio α to a smaller value. In this case, the ratio α is, for example, the default adjusted value, where, as an example, the ratio of maximum brightness and the ratio of average brightness are each set to 50% (α = 0.5). Of course, this is not limited to this case; the value of α can be selected in various ways, but it is set to a lower value than that for a scene like a starry sky. Then, the backlight grayscale 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 image based on the brightness distribution of the input image and the illumination rate of the backlight 107. Then, based on the scene determined by the scene determination unit 111, a parameter α is determined for setting (e.g., increasing or decreasing the overall grayscale) the grayscale of a region of the backlight 107. Then, the local dimming control unit 113 performs local dimming control using this parameter α. For example, if the overall scene is dark, but bright areas like star-shaped areas are illuminated with higher brightness light, optimal local dimming corresponding to the scene can be achieved.

[0039] <Second Implementation Method> Next, the second embodiment will be described. This embodiment relates to a scenario where an overall bright (high brightness) scene is detected instead of a starry sky scene as described in the first embodiment. Hereinafter, only the differences from the first embodiment will be described.

[0040] The scene determination method for the input image and the backlight control method based on the scene determination result of this embodiment will be described in summary. As an example of a scene, the scene determination unit 111 of this embodiment determines a scene that is generally bright.

[0041] Figure 5A This is an example of a scene displayed on the display unit 106 when the entire scene is bright. As shown in the figure, if it is... Figure 5A In the example, the hills are shown in the foreground, with the blue sky and sun behind them. The area P3, showing the sun, is particularly bright. On the other hand, the area P7, showing the hills, is less bright than other areas due to factors such as the presence of shadows. Figure 5B Is with Figure 5A The corresponding brightness histogram. As shown in the figure, it is consistent with the one described in the first embodiment. Figure 3A as well as Figure 3BThe situation differs; pixels are distributed more widely from areas of low to high brightness. Furthermore, the number of pixels is higher in areas of high brightness. Moreover, in this example, the average brightness value of the overall image displayed by the display unit 106 is as follows: Figure 5B The example shown is set to Xave1.

[0042] Figure 6 This indicates the use of the above. Figure 5A and Figure 5B The flowchart illustrates the scene determination method and the backlight control method based on the scene determination result. This embodiment differs from the one described in the first embodiment. Figure 4 The difference lies in that the illumination rate of the backlight 107 is not considered when the scene determination unit 111 performs scene determination. Moreover, in this embodiment, the scene determination unit 111 performs scene determination based on the average picture level (APL) of the input image.

[0043] like Figure 6 As shown, firstly, in step S20, the scene determination unit 111 determines whether the APL of the input image is greater than or equal to a predetermined value Xref1. For example, in Figure 5B In the example, the average brightness value Xave1 is equivalent to APL, and Xave1 is greater than Xref1. The specified value Xref1 can be appropriately set according to the desired brightness of the scene. If the value of Xref1 is set to a small value, even a relatively dark scene can be judged as a bright scene overall. Conversely, if the value of Xref1 is set to a large value, if the APL is not sufficiently high, it will not be judged as a bright scene.

[0044] In step S20, if APL is above a predetermined value Xrefl, the scene determination unit 111 determines in step S21 that the input image is a scene that is bright overall. Therefore, in step S22, the parameter setting unit 112 sets the ratio α to a value near the average. That is, as described in equation (1) of the first embodiment and... Figure 3B In this process, the contribution of increasing the average brightness (AVE_TONE) is increased. More specifically, the value of the ratio α is set to a small value, such as around 0.3 to 0.4. Of course, the ratio α is not limited to these values; it can also be a value larger or smaller than these values. Then, using the set ratio α, the local dimming control unit 113 controls the backlight 107.

[0045] On the other hand, in step S20, if APL is less than the predetermined value Xref1, the scene determination unit 111 determines in step S23 that the input image is not a brightly lit scene but a general image. Therefore, in step S24, the parameter setting unit 112 sets the ratio α to, for example, a default value. This process is the same as step S16 described in the first embodiment. At this time, for example, the value of the ratio α set in step S24 (e.g., 0.5) is larger than the ratio α set in step S22. Then, using the set ratio α, the local dimming control unit 113 controls the backlight.

[0046] According to this embodiment, in the case of an input image that is generally bright, the value of the ratio α is set to be smaller compared to a less bright situation. By setting the value of the ratio α to be smaller, the backlight grayscale is set to be darker. This effect is significant in low-grayscale or medium-grayscale areas of the image, where the brightness is relatively low. On the other hand, even when using the same ratio α, the effect of setting the ratio α to be smaller in high-grayscale areas is small, and the brightness of these areas remains high. Furthermore, since the brightness values ​​in low-grayscale or medium-grayscale areas are small, the power used in these areas is suppressed. Therefore, the local dimming control unit 113 can use the power suppressed in low-grayscale or medium-grayscale areas for high-grayscale areas. More specifically, by using the power in high-grayscale areas, the brightness of these areas can be further increased. As a result, since the brightness values ​​in low-grayscale or medium-grayscale areas are low, the brightness values ​​in high-grayscale areas can be increased, thereby improving the contrast of the image.

[0047] <Third Implementation Method> Next, the third embodiment will be described. In this embodiment, when a scene such as a starry sky is determined as the input image, the density of brighter areas is determined, and a ratio α is determined based on the result. Hereinafter, only the differences from the first embodiment will be described.

[0048] After implementing the first embodiment Figure 4 Based on the processing described above, it can be determined that the next two cases are scenarios like the starry sky. First, for Figure 7A as well as Figure 7B The case shown. Figure 7A This shows an example of the screen displayed on the display unit 106. Figure 7B yes Figure 7A Brightness histograms of regions P1 to P9 in the image.

[0049] like Figure 7AAs shown, in this case, the image is dark overall, but bright, star-shaped areas are prevalent in regions P1 to P9. Furthermore, in this situation, the brightness histograms of each region P1 to P9 are... Figure 7B The shape shown indicates that there are a large number of low-brightness pixels and a very small number of high-brightness pixels.

[0050] The following case is Figure 8A and Figure 8B The scene shown. Figure 8A This indicates an example of the screen displayed on display unit 106. Figure 8B yes Figure 8A Brightness histograms of regions P1 to P9 in the image.

[0051] like Figure 8A As shown, in this case, the image as a whole is dark and... Figure 7A The same applies, but the bright, star-shaped area is concentrated only in region P5. This example is, for instance, an image of the moon taken using a telephoto lens. Furthermore, in this case, such as... Figure 8B As shown, the brightness histograms of regions P1–P4 and P6–P9 only contain pixels with low brightness. Furthermore, even if small star-shaped patterns exist, their pixel count is as low as... Figure 7B As shown, there are far fewer. In contrast, in the brightness histogram of region P5, the number of high-brightness pixels becomes very large.

[0052] In this embodiment, as described above, in Figure 7A Cases and Figure 8A In the case, the proportion α is used separately. Figure 9 This is a flowchart illustrating the processing flow of the scene determination method and the backlight control method based on the scene determination result in this embodiment, corresponding to the one described in the first embodiment. Figure 4 .

[0053] like Figure 9 As shown, the first implementation is carried out in the first embodiment. Figure 4 The processing steps S10 to S13 and S15 are described below. Then, in step S13, if the scene determination unit 111 determines that the input image is a scene like a starry sky, then in step S30, the scene determination unit 111 continues to determine whether the maximum value of the average brightness of each region in the input image is below a predetermined value Xref2 (third brightness value).

[0054] The third brightness value is determined based on how dense the illuminated area is within a given region. Figure 8AThe scene is determined by the density of bright areas shown. For example, when the APL of the entire screen is determined by the number of areas and the overall screen size, and the bright areas are densely concentrated in one area, the situation can be determined by the following formula (2). In addition, XX represents a value between 0 and 100. Xref2 = (APL of the entire screen) × (number of regions × (XX) / 100)……(2) However, the method for determining the third brightness value is not limited to this; other methods can also be used.

[0055] For example, when such as Figure 8A When the illuminated areas are concentrated in one area, assuming it's a case of "densely bright areas," the value of XX in equation (2) above is, for example, 100. Therefore, the value of Xref2 is ((APL of the entire screen) × 9). If Figure 7A and Figure 7B In the example, only a small number of small star-shaped features exist in each region, so the maximum average brightness of each region is relatively low. Furthermore, as... Figure 7B As shown, the maximum average brightness of each region P1 to P9 is Xave_max, which is less than the predetermined value Xref2. Therefore, in this case, in step S31, the scene determination unit 111 determines it as a scene where bright areas are sparsely present, i.e. Figure 7A The scene shown. Then, similar to step S14 described in the first embodiment, in step S32, the parameter setting unit 112 sets the ratio α to the maximum, and the local dimming control unit 113 sets the backlight brightness to a higher level to illuminate the display unit 106.

[0056] On the other hand, if Figure 8A as well as Figure 8B In the example, region P5 has densely packed bright areas, therefore the maximum average brightness of region P5 is relatively high. Figure 8B In the example, the maximum value of the average brightness of each region P1~P4 and P6~P9 is, for example, compared with... Figure 7B The situation is the same, but the maximum value of the average brightness of region P5 is Xave_max as shown in the figure, which is greater than the specified value Xref2. Therefore, in this case, in step S33, the scene determination unit 111 determines it as a scene where bright areas are densely concentrated, i.e. Figure 8A The scenario is as shown. Then, similar to step S16 described in the first embodiment, in step S34, the parameter setting unit 112 sets the ratio α to a default value, for example, 0.5, and the local dimming control unit 113 sets the backlight brightness to a default value to illuminate the display unit 106.

[0057] According to this embodiment, in the first embodiment described above, a determination is made as to whether the brighter areas are dense. If the bright areas are dense, sufficient brightness can be obtained even without increasing the grayscale of the backlight. Therefore, power consumption can be reduced.

[0058] <Variations, etc.> As described above, the display device and its control method according to the first to third embodiments determine what kind of scene the input image is, and can perform optimal local dimming control based on the determination result. Furthermore, the embodiments are not limited to the methods described above, and various modifications can be made. Each embodiment can be implemented independently, or multiple embodiments can be combined.

[0059] For example, in the second embodiment described above, if the input image is a scene that is generally bright, the blurring effect on objects can be reduced by illuminating the backlight around the brightest areas. Hereinafter, in this specification, the process of blurring objects will be referred to simply as "blurring". Figure 10 A simple explanation of paste.

[0060] Figure 10 This is a schematic diagram of the backlight 107, which contains (5×5) = 25 areas. The intensity of the illumination light can be adjusted for each area, and the numbers recorded in each area represent the illumination rate of that area. Figure 10 The left image shows the case where blur is off, assuming that only the central area of ​​backlight 107 is lit, for example, with a lighting rate of 100%. In contrast, Figure 10 The right image illustrates the case where blur is enabled. In this example, in... Figure 10 In the left figure, eight adjacent areas are illuminated around the area with a 100% illuminance, which is, for example, 75%. Furthermore, which area is newly illuminated and its illuminance can be appropriately selected, for example, by the parameter setting unit 112 and the local dimming control unit 113.

[0061] As described above, blurring refers to the function of expanding the illuminated area by illuminating the backlight of areas adjacent to the illuminated area. When blurring is enhanced, i.e., by increasing the number of illuminated areas and / or increasing the illumination rate of the illuminated areas, although the contrast between light and dark decreases, the drawbacks caused by extreme brightness differences become less noticeable. This drawback refers to the phenomenon where, when a displayed object is shown at a high brightness and the surrounding brightness is very low, the periphery of the object, i.e., the area with extreme brightness differences, appears darker to the viewer compared to other areas, such as the center of the object. On the other hand, if blurring is weakened, i.e., by decreasing the increase in the number of illuminated areas and / or decreasing the illumination rate of the illuminated areas, conversely, the aforementioned drawback becomes more noticeable, but the contrast between light and dark increases.

[0062] Furthermore, in the second embodiment described above, when the input image is a generally bright scene, the strength of the gamma correction can be reduced. In other words, correction can be performed by reducing the intermediate value within the brightness distribution of the backlight. Regarding this, using... Figure 11 To explain, Figure 11 The brightness curve represents the backlight. The horizontal axis represents the input (before correction) brightness value, and the vertical axis represents the output (after correction) brightness value. The brightness value ranges from zero (black) to 255 (white). The higher the brightness value, the brighter the light.

[0063] As shown in the figure, the distribution of the output relative to the input can be represented by the following equation (3). y=255×(x / 255)(1 / γ)…(3) Where y is the output (corrected brightness value), x is the input (brightness value before correction), and γ is the γ correction value, representing the case where the minimum brightness value is zero and the maximum value is 255. For example, when γ is 1, the input brightness value and the output brightness value are the same, and the input and output have a linear relationship. Conversely, when γ has a value greater than 1, the brightness curve becomes an upward convex shape, and the output brightness value becomes a larger value relative to the input brightness value through correction. That is, the brightness value of the backlight 107 is greater 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 becomes a downward convex (concave) shape, and the output brightness value becomes a smaller value relative to the input brightness value through correction. That is, the brightness value of the backlight 107 is less than the input value. For example, such gamma correction is performed by the parameter setting unit 112 and the local dimming control unit 113 to control the backlight 107. Furthermore, as Figure 5A In the case of the image shown, the local dimming control unit 113 sets γ to a small value near 1, thus darkening the overall tone of the image. This enhances the contrast between bright and dark areas.

[0064] Figure 12 This indicates that the application uses the above. Figure 10 and Figure 11 The flowchart illustrating the backlight control method during blur and gamma correction corresponds to the one described in the second embodiment. Figure 6 As shown in the figure, in Figure 6 After the processing described in steps S20 to S22, 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... Figure 11The brightness curve described herein sets the brightness value of the input image to a value around 1, for example, in the range of (1 / 1.2) to 1.2, and then corrects the brightness value. Of course, the value of γ can also be adjusted outside of this setting. Additionally, in Figure 12 The illustration is omitted, but in step S23, when it is determined to be a general image, the blur in the backlight 107 can be set to be stronger than in step S40, and the brightness value of the input image can be set to... Figure 11 The brightness curve described herein is larger than that in the linear curve, i.e., it bulges upwards and is a larger value compared to the case in step S40, thereby correcting the brightness value. Alternatively, γ can be set to be less than 1, but a value larger than that in step S40. These values ​​can be preset as default values, for example.

[0065] Furthermore, in the first and third embodiments described above, examples of starry sky images were given. However, scenes that are generally dark but have bright areas scattered throughout could also be images with fluorescent light, night scenes, or images of light from windows of buildings such as skyscrapers. In addition, the above embodiments used starry sky scenes and generally bright scenes as examples. However, the scenes determined by the scene determination unit 111 are not limited to these. The scene determination unit 111 can pre-store features of various scenes and, based on these features, make various changes to the reference values ​​X1, X2, Xref1, Xref2 of the pixel values ​​of the input image, the regions R1, R2 with specific pixel values, and the brightness rate R0 of the backlight 107. It can also further determine the scene based on features in the distribution of pixel values ​​as a whole of the image, the average brightness level, etc. Furthermore, the parameter setting unit 112 can pre-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 the scaling factor α, blur, or gamma correction value; any parameter related to the brightness in the display unit 106 is acceptable. Furthermore, these benchmark values ​​used to determine the scene (e.g.) Figure 4 The specified values ​​(R0-R2, brightness values ​​X1, X2, etc.) can be maintained. Figure 1 The television set 100, which is not shown in the figure, includes storage devices such as ROM and RAM. Of course, the processing unit 101, which is a processor, can also perform various calculations based on the scene to be determined, and calculate the reference values ​​required for scene determination.

[0066] Furthermore, in the above embodiments, image quality adjustments corresponding to the content category can also be performed. That is, in the multiplexed broadcast wave, category information indicating the content category of the program is transmitted along with the program's image data. At this time, the parameter setting unit 112 of the television set 100 can determine basic image quality adjustments (backlight adjustments) based on the content category, and use the methods described in the first to third embodiments and their variations as a reference for these basic image quality adjustments. For example, even for the same starry sky scene, the specified values ​​R0 to R2 and specified values ​​X1 and X2 may differ depending on the content category of the program, such as whether it is a movie or a documentary. In addition, depending on the situation, Figure 4 In this embodiment, steps S14 and S16 may be interchanged. This also applies to the second and third embodiments.

[0067] This disclosure is not limited to the embodiments described above, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of this invention. Moreover, by combining the technical solutions disclosed in each embodiment, new technical features can be formed. Furthermore, the processing order of the flowcharts described in the above embodiments can be changed as much as possible.

[0068] The program that implements the functions of each embodiment is stored in a non-transitory recording medium such as a semiconductor medium, an optical recording medium, or an optical-magnetic recording medium. For example, a non-volatile memory card can be used as a semiconductor medium. For optical or optical-magnetic recording media, CDs (Compact Dicks) and DVDs (Digital Versatile Disks) can be used. Furthermore, the program can also be provided to a computer via any transmittable medium.

Claims

1. A display device, characterized in that, It includes: Display panel, which displays images; A backlight illuminates the display panel, causing it to light up. The scene determination unit determines the scene related to the input image based on the brightness distribution of the input image and the illumination rate of the backlight. The parameter setting unit sets parameters for the brightness values ​​applied to multiple areas of the backlight based on the scene determined by the scene determination unit. as well as The local dimming control unit performs local dimming control on the backlight for each of the plurality of regions based on the set parameters. The parameter setting unit determines, based on the determined scene, the ratio of the brightness value above a predetermined value in each of the plurality of regions to the average brightness value of each of the plurality of regions, and uses the determined ratio to set the parameter applied to each of the plurality of regions. The parameter setting unit further determines the parameter by increasing the ratio of brightness values ​​above the predetermined value to a ratio greater than the average brightness value when the following conditions are met: The scene determination unit determines that the input image is a scene that includes a dark background with a brightness value below a first brightness value and a bright area with a brightness value above a second brightness value, wherein the second brightness value is greater than the first brightness value, and in the scene, the ratio of areas with brightness values ​​below the first brightness value is greater than the ratio of areas with brightness values ​​above the second brightness value.

2. The display device according to claim 1, characterized in that, The same value of the parameter is applied to all of the plurality of regions of the backlight.

3. The display device according to claim 1, characterized in that, If the scene determination unit determines, for the input image, that the scene consists of a dark background with a brightness value below a first brightness value and bright illuminated parts with a brightness value above a second brightness value that is higher than the first brightness value, then... Furthermore, if it is determined that the illuminated portion is densely packed within the image displayed on the display panel, The parameter setting unit sets the ratio of brightness values ​​above the specified value to be the same as or less than the ratio of the average brightness value, and determines the parameter.

4. The display device according to claim 1 or 2, characterized in that, The parameter setting unit changes the relationship between the brightness value of the output image and the brightness value of the input image based on the scene determined by the scene determination unit.

5. The display device according to claim 1 or 2, characterized in that, The parameter setting unit increases or decreases the intensity of blur in the backlight based on the scene determined by the scene determination unit.

6. A method for controlling a display device, the display device comprising a backlight that illuminates a display panel displaying an image and lights the display panel, the method being characterized in that it comprises: Based on the brightness distribution of the input image and the illumination rate of the backlight, a scene determination is made regarding the input image. Based on the determined scenario, parameters related to the brightness values ​​applied to multiple areas of the backlight are set. as well as Based on the set parameters, local dimming control is performed on the backlight for each of the plurality of regions. Based on the determined scenario, a ratio is determined between the brightness value above a predetermined value in each of the plurality of regions and the average brightness value of each of the plurality of regions, and the determined ratio is used to set the parameters applied to each of the plurality of regions. Furthermore, the parameter is determined by increasing the ratio of brightness values ​​above the specified value to a ratio greater than the average brightness value when the following conditions are met: The input image is determined to be a scene comprising a dark background with a brightness value below a first brightness value and a bright area with a brightness value above a second brightness value, wherein the second brightness value is greater than the first brightness value, and wherein the ratio of areas with brightness values ​​below the first brightness value is greater than the ratio of areas with brightness values ​​above the second brightness value in the scene.

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