Image display device and image display method

Abstract

To provide an image display device capable of displaying an image with high picture quality even if a pixel of high luminance that an original image does not have is included in a frame of a video signal.SOLUTION: A maximum luminance information acquisition section 1 extracts meta data indicating a maximum luminance value and acquires maximum luminance information. A cumulative histogram generation section 10 divides a range from lightness corresponding to a minimum pixel value determined by a bit number of a video signal to lightness corresponding to a maximum pixel value into a plurality of lightness levels and, while defining lightness of a pixel having lightness equal to or higher than a threshold which is set based on lightness indicated by the maximum luminance information as 0, generates a cumulative histogram indicating a ratio of cumulative pixel numbers equal to or lower than each lightness level on one or more frames basis. A gradation curve setting section 4 sets a gradation curve formed from an input pixel value and an output pixel value in accordance with a lightness level having maximum lightness indicated by the cumulative histogram, and the input pixel value is converted into the output pixel value in accordance with the gradation curve and supplied to a drive section 5.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image display device and an image display method.

Background Art

[0002] In a projector as an example of an image display device, it may be configured to change a tone curve according to the maximum luminance value of pixels for each frame of an image to be projected based on an input video signal.

[0003] Specifically, it is controlled as follows. A frame may have a wide tone from a minimum luminance value corresponding to a minimum pixel value determined by the number of bits of a video signal to a maximum luminance value corresponding to a maximum pixel value determined by the number of bits of the video signal. At this time, the projector displays an image of a frame having such a wide tone using a wide dynamic range from the minimum brightness to the maximum brightness of projection light by a tone curve suitable for displaying a frame having a wide tone.

[0004] Also, a frame may have a narrow tone of a low tone from a minimum luminance value corresponding to a minimum pixel value determined by the number of bits of a video signal to a predetermined luminance value of a low luminance as a maximum luminance value. At this time, the projector displays an image of a frame having such a narrow tone using a similar wide dynamic range by a tone curve suitable for displaying a frame having a narrow tone.

[0005] As described above, when the projector displays an image while changing the tone curve according to the maximum luminance value of pixels for each frame, even when displaying a frame having a narrow tone of a low tone as described above, an image can be displayed with high image quality without black crushing.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] If a frame of a video signal input to a projector contains high - brightness pixels that the original image (the original pattern of the image), such as a telop, does not have, the high - brightness pixels are detected as the maximum brightness value of the pixels in that frame. Then, even a frame with a narrow range of low - gradation tones as described above is misjudged as a frame with a wide range of tones, and the image is displayed using a tone curve corresponding to a frame with a wide range of tones. As a result, black crush occurs in the image with a narrow range of low - gradation tones, and the image quality deteriorates.

[0008] In addition, when switching from a frame without a telop inserted to a frame with a telop inserted, and when switching from a frame with a telop inserted to a frame without a telop inserted, the image quality changes, so that the user feels a visual discomfort.

[0009] An object of the present invention is to provide an image display apparatus and an image display method that can display a high - quality image even if a frame of a video signal contains high - brightness pixels that the original image does not have, and that can prevent a user from feeling a visual discomfort when the state of the video signal frame changes from a state without high - brightness pixels that the original image does not have to a state with such pixels, or vice versa.

Means for Solving the Problems

[0010] The present invention provides an image display device including: a maximum luminance information acquisition unit that extracts metadata indicating a maximum luminance value added to a video signal to be displayed and acquires maximum luminance information of the video signal; a cumulative histogram generation unit that divides a range from a luminance corresponding to a minimum pixel value determined by the number of bits of the video signal to a luminance corresponding to a maximum pixel value into a plurality of luminance levels, and for each one or more frames of the video signal, after regarding the luminance of pixels having a luminance equal to or higher than a threshold set based on the luminance indicated by the maximum luminance information as 0, generates a cumulative histogram indicating a ratio of the cumulative number of pixels below each luminance level among the plurality of luminance levels; and a tone curve setting unit that, for each frame of the video signal, sets a tone curve formed by an input pixel value and an output pixel value of the video signal according to a luminance level having the maximum luminance indicated by the cumulative histogram, converts the input pixel value into the output pixel value according to the tone curve, and supplies the output pixel value to a driving unit that drives a display unit to display the video signal.

[0011] The present invention provides an image display method including: extracting metadata indicating a maximum luminance value added to a video signal to be displayed and acquiring maximum luminance information of the video signal; dividing a range from a luminance corresponding to a minimum pixel value determined by the number of bits of the video signal to a luminance corresponding to a maximum pixel value into a plurality of luminance levels; for each frame of the video signal, after regarding the luminance of pixels having a luminance equal to or higher than a threshold set based on the luminance indicated by the maximum luminance information as 0, generating a cumulative histogram indicating a ratio of the cumulative number of pixels below each luminance level among the plurality of luminance levels; for each frame of the video signal, setting a tone curve formed by an input pixel value and an output pixel value of the video signal according to a luminance level having the maximum luminance indicated by the cumulative histogram; converting the input pixel value into the output pixel value according to the tone curve for each frame; and supplying the output pixel value to a driving unit that drives a display unit to display the video signal.

Advantages of the Invention

[0012] According to the image display device and the image display method of the present invention, even if a frame of a video signal includes high-luminance pixels that the original image does not have, a high-quality image can be displayed, and when the state changes from a state where a frame of a video signal does not include high-luminance pixels that the original image does not have to a state where it does, or vice versa, the user does not feel a visual discomfort.

Brief Description of the Drawings

[0013]

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Embodiments for Carrying Out the Invention

[0014] Hereinafter, the image display device and the image display method according to each embodiment will be described with reference to the accompanying drawings.

[0015] <First Embodiment> FIG. 1 shows an image display device 100 according to the first embodiment. The image display device 100 includes a maximum luminance information acquisition unit 1, an original cumulative histogram generation unit 2, a cumulative histogram correction unit 3, a gradation curve setting unit 4, a driving unit 5, and a liquid crystal display element 6. The image display device 100 may be a projector. The original cumulative histogram generation unit 2 and the cumulative histogram correction unit 3 constitute a cumulative histogram generation unit 10 that generates the final cumulative histogram to be supplied to the gradation curve setting unit 4.

[0016] When the image display device 100 is a projector, typically, the liquid crystal display element 6 includes a liquid crystal display element for red (R), a liquid crystal display element for green (G), and a liquid crystal display element for blue (B). When the image display device 100 is a projector, the image display device 100 includes an illumination optical system and a projection optical system (not shown). The liquid crystal display element 6 is an example of a display unit that displays a video signal.

[0017] In FIG. 1, the maximum luminance information acquisition unit 1, the original cumulative histogram generation unit 2, and the gradation curve setting unit 4 are input with the video signal displayed on the liquid crystal display element 6. The video signal is, for example, a reproduction signal of a video signal recorded on an optical disc called Ultra HD Blu-ray (hereinafter, UHDBD). The video signal recorded on the UHDBD has metadata called MaxCLL (Maximum Content Light Level) that indicates the maximum luminance value of each content based on the HDR10 standard. The maximum luminance information acquisition unit 1 extracts MaxCLL from the video signal to acquire the maximum luminance information of the content.

[0018] When the HDR10+ standard is adopted for the UHDBD, the video signal has metadata indicating the maximum luminance value of the frame or scene recorded for each frame or scene. The metadata indicating the maximum luminance value of the frame or scene is also referred to as MaxCLL. The maximum luminance information acquisition unit 1 may extract the MaxCLL for each frame or scene from the video signal to acquire the maximum luminance information for each frame or scene. The maximum luminance information acquisition unit 1 supplies the acquired maximum luminance information to the cumulative histogram correction unit 3.

[0019] The original cumulative histogram generation unit 2 generates an original cumulative histogram for each frame based on the luminance values of all pixels constituting the frame. The original cumulative histogram is an initial cumulative histogram before being corrected by the cumulative histogram correction unit 3. However, since the cumulative histogram correction unit 3 may not correct the original cumulative histogram, there may be a case where the original cumulative histogram is the same as the final cumulative histogram output from the cumulative histogram correction unit 3. The original cumulative histogram generation unit 2 may generate an original cumulative histogram for every plurality of frames. In this case, the original cumulative histogram is updated for every plurality of frames.

[0020] The original cumulative histogram before correction shown in FIG. 2 shows an example of the original cumulative histogram generated by the original cumulative histogram generation unit 2. Assuming that the video signal is, for example, 10 bits, the luminance values corresponding to the minimum pixel value of 0 to the maximum pixel value of 1023 determined by the number of bits of the video signal are associated with, for example, 0 nit to 1000 nit as the brightness of the displayed pixels.

[0021] As an example, the original cumulative histogram generation unit 2 classifies the brightness of pixels into 10 brightness levels: 0 nit or more and 100 nit or less, exceeding 100 nit and 200 nit or less, exceeding 200 nit and 300 nit or less,..., exceeding 800 nit and 900 nit or less, exceeding 900 nit. The brightness of pixels may be classified into any plurality of brightness levels. The numerical value of each brightness level of the original cumulative histogram indicates the ratio of the cumulative number of pixels below each brightness level to the total number of pixels in the frame.

[0022] In the example shown in FIG. 2, since the value is 0 at a brightness level of 0 nit or more and 100 nit or less, it indicates that there are no pixels with a brightness level of 0 nit or more and 100 nit or less. Since the value is 10 at a brightness level exceeding 100 nit and 200 nit or less, it indicates that, with respect to the total number of pixels in the frame, the cumulative number of pixels with a brightness level of 0 nit or more and 100 nit or less and exceeding 100 nit and 200 nit or less is 10%. Here, since the value at a brightness level of 0 nit or more and 100 nit or less is 0, the number of pixels exceeding 100 nit and 200 nit or less is 10%.

[0023] Since the value is 80 at a brightness level exceeding 200 nit and 300 nit or less, it indicates that, with respect to the total number of pixels in the frame, the cumulative number of pixels with a brightness level of 0 nit or more and 100 nit or less, exceeding 100 nit and 200 nit or less, and exceeding 200 nit and 300 nit or less is 80%.

[0024] Suppose the maximum brightness information acquired by the maximum brightness information acquisition unit 1 is, for example, 300 nit. If the maximum brightness information is 300 nit, then at brightness levels of 300 nit or more and 400 nit or less and subsequent levels, since the original image does not have pixels corresponding to each brightness level, the value remains 80 up to brightness levels of 300 nit or more and 400 nit or less and up to 700 nit or more and 800 nit or less.

[0025] However, the value is 90 at a brightness level of 800 nit or more and 900 nit or less, and the value is 100 at a brightness level exceeding 900 nit. This indicates that the frame for which the original cumulative histogram generation unit 2 generates the original cumulative histogram contains high-brightness pixels that the original image such as a telop does not have. Hereinafter, it is assumed that the high-brightness pixels are telops. From the original cumulative histogram generated by the original cumulative histogram generation unit 2 shown in FIG. 2, it can be seen that the ratio of the number of pixels constituting the telop is 20%.

[0026] Returning to FIG. 1, the original cumulative histogram generation unit 2 supplies the generated original cumulative histogram to the cumulative histogram correction unit 3. The cumulative histogram correction unit 3 corrects the original cumulative histogram as will be described later and supplies the corrected cumulative histogram to the tone curve setting unit 4. The tone curve setting unit 4 sets a tone curve corresponding to the input corrected cumulative histogram for the input video signal. The tone curve setting unit 4 converts the input pixel value into an output pixel value corresponding to the tone curve and supplies it to the driving unit 5. The driving unit 5 drives the liquid crystal display element 6 with the pixel value supplied from the tone curve setting unit 4 and displays the image of each frame on the liquid crystal display element 6.

[0027] Here, with reference to FIG. 3, the basic operation of the tone curve setting unit 4 will be described. Based on the input cumulative histogram, if the maximum luminance value of all the pixels constituting the frame is 1000 nit, the tone curve setting unit 4 sets the PQ curve PQ1000 as the tone curve. Setting the PQ curve means selecting one of a plurality of PQ curves. The PQ curve is a so-called gamma curve, which is a tone curve for determining the relationship between the input pixel value and the output pixel value. The minimum value 0 of the output pixel value corresponds to the minimum brightness of the projected light, and the maximum value corresponds to the maximum brightness of the projected light.

[0028] Therefore, if the tone curve setting unit 4 converts each input pixel value in the input frame into the output pixel value set by the PQ curve PQ1000 and supplies it to the driving unit 5, a frame having a wide tone range from 0 nit to 1000 nit is displayed using a wide dynamic range from the minimum brightness to the maximum brightness of the projected light.

[0029] Based on the input cumulative histogram, if the maximum luminance value of all pixels constituting the frame is 800 nit, the tone curve setting unit 4 sets the PQ curve PQ800 as the tone curve. If the tone curve setting unit 4 converts each input pixel value in the input frame into the output pixel value set by the PQ curve PQ800 and supplies it to the driving unit 5, a frame having tones from 0 nit to 800 nit is similarly displayed using a wide dynamic range from the minimum brightness to the maximum brightness of the projected light.

[0030] Based on the input cumulative histogram, if the maximum luminance value of all pixels constituting the frame is 500 nit, the tone curve setting unit 4 sets the PQ curve PQ500 as the tone curve. If the tone curve setting unit 4 converts each input pixel value in the input frame into the output pixel value set by the PQ curve PQ500 and supplies it to the driving unit 5, a frame having tones from 0 nit to 500 nit is similarly displayed using a wide dynamic range from the minimum brightness to the maximum brightness of the projected light.

[0031] In this way, the tone curve setting unit 4 sets a PQ curve according to the brightness level including the maximum luminance value of all pixels constituting the frame based on the input cumulative histogram. The tone curve setting unit 4 converts the input pixel value of the video signal into the output pixel value according to the PQ curve. The tone curve setting unit 4 supplies the output pixel value to the driving unit 5.

[0032] Suppose that the tone curve setting unit 4 is supplied with the original cumulative histogram generated by the original cumulative histogram generation unit 2 shown in FIG. 2 as it is, instead of the cumulative histogram corrected by the cumulative histogram correction unit 3. Since the original cumulative histogram before correction shown in FIG. 2 shows that there are pixels with a brightness level exceeding 900 nit, as shown in FIG. 4, the tone curve setting unit 4 sets the PQ curve PQ1000 as the tone curve. That is, although the target frame originally contains tones only from 0 nit to 300 nit as an original image, the PQ curve PQ1000 suitable for a frame having a wide tone from 0 nit to 1000 nit is set.

[0033] Therefore, as can be seen from FIG. 4, an image having gradations from 0 nit to 300 nit is displayed with a very narrow dynamic range. Thus, black crush occurs and the image quality deteriorates.

[0034] Therefore, the cumulative histogram correction unit 3 corrects the original cumulative histogram to generate the corrected cumulative histogram shown in FIG. 2. Since the number of pixels constituting the telop is 20%, the cumulative histogram correction unit 3 regards the pixel values of the pixels constituting the telop as 0 and distributes 20% of the number of pixels to the brightness levels from 0 nit to 100 nit. Then, the value is 20 at the brightness level from 0 nit to 100 nit, 30 at the brightness level exceeding 100 nit and below 200 nit, and 100 at the brightness level exceeding 200 nit and below 300 nit.

[0035] The corrected cumulative histogram indicates that the target frame includes gradations from 0 nit to 300 nit. The corrected cumulative histogram shown in FIG. 2 is supplied to the gradation curve setting unit 4. Therefore, as shown in FIG. 5, the gradation curve setting unit 4 sets a PQ curve PQ300 suitable for a frame having gradations from 0 nit to 300 nit instead of the PQ curve PQ1000 indicated by the two-dot chain line. Since an image having gradations from 0 nit to 300 nit is displayed using a wide dynamic range from the minimum brightness to the maximum brightness of the projection light, a high-quality image can be displayed without black crush of the image.

[0036] In FIG. 1, the cumulative histogram correction unit 3 may correct the original cumulative histogram by regarding pixels having a brightness equal to or higher than a threshold set based on the brightness indicated by the maximum brightness information input from the maximum brightness information acquisition unit 1 as telops. It is preferable to set the threshold to the brightness obtained by adding a predetermined margin value to the brightness indicated by the maximum brightness information. As an example, the margin value is 50 nit. If the brightness indicated by the maximum brightness information is 300 nit, the cumulative histogram correction unit 3 regards pixels of 350 nit or higher as telops.

[0037] As described above, the image display device 100 includes a maximum luminance information acquisition unit 1, an integrated histogram generation unit 10, and a tone curve setting unit 4. The maximum luminance information acquisition unit 1 extracts metadata indicating the maximum luminance value added to the video signal to be displayed and acquires the maximum luminance information of the video signal. The integrated histogram generation unit 10 divides the range from the brightness corresponding to the minimum pixel value determined by the number of bits of the video signal to the brightness corresponding to the maximum pixel value into a plurality of brightness levels.

[0038] The integrated histogram generation unit 10 generates an integrated histogram indicating the ratio of the integrated number of pixels below each brightness level among the plurality of brightness levels for each one or more frames of the video signal. At this time, the integrated histogram generation unit 10 generates an integrated histogram in which the brightness of pixels having a brightness equal to or higher than a threshold set based on the brightness indicated by the maximum luminance information is regarded as 0. The integrated histogram generation unit 10 generates an integrated histogram in which the brightness of pixels having a brightness equal to or higher than a threshold is regarded as 0 by the original integrated histogram generation unit 2 generating the original integrated histogram and the integrated histogram correction unit 3 correcting the original integrated histogram.

[0039] The tone curve setting unit 4 sets a tone curve formed by the input pixel value and the output pixel value of the video signal according to the brightness level having the maximum brightness indicated by the integrated histogram for each frame of the video signal. The tone curve setting unit 4 converts the input pixel value into the output pixel value according to the tone curve and supplies the output pixel value to the driving unit 5.

[0040] Suppose that in the corrected cumulative histogram shown in FIG. 2, the numerical value is 99 at a brightness level exceeding 200 nit and not exceeding 300 nit, and the numerical value is 100 at a brightness level exceeding 300 nit and not exceeding 400 nit. In this case, the ratio of the number of pixels included in the brightness level exceeding 300 nit and not exceeding 400 nit is 1%. In such a case, the 1% of the pixels may be noise. Therefore, when the ratio of the number of pixels included in a certain brightness level is extremely small, such as less than 1%, it may be better not to set that brightness level as the brightness level having the maximum brightness.

[0041] The gradation curve setting unit 4 may set, as the brightness level having the maximum brightness, the brightness level including pixels having, for example, 99% brightness among the pixels from the minimum brightness to the maximum brightness. Instead of 99%, it may be 99.5%, and there is no limitation on what percentage of bright-level pixels are regarded as noise. The brightness level including the pixel having the maximum brightness in each frame may be the brightness level including the pixel having the maximum brightness after excluding the brightness levels with an extremely small ratio so as to remove noise.

[0042] According to the image display device 100, even if a frame of a video signal includes high-brightness pixels that the original image such as a telop does not have, a high-quality image can be displayed.

[0043] <Second Embodiment> FIG. 6 shows an image display device 200 according to the second embodiment. In FIG. 6, the same parts as those of the image display device 100 according to the first embodiment are denoted by the same reference numerals, and the description thereof may be omitted. The image display device 200 includes a maximum luminance information acquisition unit 1, an integrated histogram generation unit 20, a gradation curve setting unit 4, a driving unit 5, and a liquid crystal display element 6.

[0044] In FIG. 6, the maximum luminance information acquisition unit 1 supplies the acquired maximum luminance information to the cumulative histogram generation unit 20. In the image display device 100, the cumulative histogram correction unit 3 collectively corrects the cumulative histogram generated by the original cumulative histogram generation unit 2 based on the maximum luminance information supplied from the maximum luminance information acquisition unit 1. On the other hand, in the image display device 200, the cumulative histogram generation unit 20 generates a cumulative histogram after replacing the pixel values of the pixels determined to be the pixels constituting the telop with 0 based on the maximum luminance information.

[0045] When the cumulative histogram generation unit 20 generates a cumulative histogram by replacing the pixel values of the pixels determined to be the pixels constituting the telop with 0, the same cumulative histogram as the corrected cumulative histogram shown in FIG. 2 is generated. The gradation curve setting unit 4 sets a PQ curve according to the brightness level including the maximum luminance value in all the pixels constituting the frame based on the cumulative histogram generated by the cumulative histogram generation unit 20. The operations after the driving unit 5 are the same as those in the image display device 100.

[0046] As described above, the cumulative histogram generation unit 20 generates a cumulative histogram after regarding the brightness of the pixels having a brightness equal to or higher than the threshold set based on the brightness indicated by the maximum luminance information as 0. The cumulative histogram generation unit 20 directly generates a cumulative histogram in which the brightness of the pixels having a brightness equal to or higher than the threshold is regarded as 0. According to the image display device 200, even if the frame of the video signal includes high-brightness pixels that the original image such as a telop does not have, a high-quality image can be displayed.

[0047] Using FIGS. 7 to 10, the operation and effect of the image display devices 100 and 200, in which the image quality does not change when switching from a frame without a telop inserted to a frame with a telop inserted, or vice versa, will be further described.

[0048] As shown in FIG. 7, no caption is inserted in frame F1. In the next frame F2 of frame F1, a caption TL2 is inserted. Here, the caption TL2 is characters composed of high-brightness pixels of "Tokyo Tower". The brightness of the pixels in the original image at the position where the caption TL2 is inserted exceeds 100 nit and is 200 nit or less, and the number of pixels is 20% of the total number of pixels in the frame.

[0049] Taking the operation of the image display device 100 according to the first embodiment as an example, the original cumulative histogram generation unit 2 generates an original cumulative histogram as shown in FIG. 8, for example, in frame F1. In frame F2, since the area of the pixels with a brightness exceeding 100 nit and being 200 nit or less and having 20% of the number of pixels becomes the high-brightness caption TL2, the original cumulative histogram generation unit 2 generates an original cumulative histogram as shown in FIG. 8 in frame F2.

[0050] Suppose that the original cumulative histograms generated by the original cumulative histogram generation unit 2 in frames F1 and F2 shown in FIG. 8 are supplied to the tone curve setting unit 4 as they are. Then, as shown in FIG. 9, the tone curve setting unit 4 sets the PQ curve PQ300 in frame F1 and the PQ curve PQ1000 in frame F2. Therefore, when the frame of the projected image is switched from frame F1 to frame F2, the image quality changes abruptly, and the user feels a visual discomfort.

[0051] Similarly, when the frames with the caption TL2 inserted are consecutive and switched from the last frame with the caption TL2 inserted to the frame without the caption TL2 inserted, the user also feels a visual discomfort.

[0052] In the image display device 100, the cumulative histogram correction unit 3 corrects the original cumulative histogram as shown in FIG. 8 in frame F2. The cumulative histogram correction unit 3 regards the pixel values of 20% of the pixels at the position where the telop TL2 is inserted as 0 and distributes 20% of the number of pixels to the brightness levels of 0 nit or more and 100 nit or less. Therefore, the value is 20 at the brightness level of 0 nit or more and 100 nit or less, the value is 30 at the brightness level exceeding 100 nit and 200 nit or less, and the value is 100 at the brightness level exceeding 200 nit and 300 nit or less and subsequent levels.

[0053] The cumulative histogram correction unit 3 supplies the corrected cumulative histogram shown in FIG. 8 in frame F2 to the tone curve setting unit 4. Therefore, as shown in FIG. 10, since the tone curve setting unit 4 sets the PQ curve PQ300 in frame F1 and also sets the PQ curve PQ300 in frame F2, the image quality does not change even when switching from frame F1 to frame F2, and the user does not feel a visual discomfort.

[0054] In the image display device 200 according to the second embodiment, the cumulative histogram generation unit 20 generates the same cumulative histogram as the original cumulative histogram shown in FIG. 8 in frame F1 and generates the same cumulative histogram as the corrected cumulative histogram shown in FIG. 8 in frame F2. Therefore, also in the image display device 200, the tone curve setting unit 4 sets the PQ curve PQ300 in frame F1 and also sets the PQ curve PQ300 in frame F2. Also in the image display device 200, similarly, the image quality does not change even when switching from frame F1 to frame F2, and the user does not feel a visual discomfort.

[0055] The present invention is not limited to the first or second embodiment described above, and various modifications can be made without departing from the gist of the present invention. For example, another display element such as a DMD display element may be used instead of the liquid crystal display element 6.

Description of Reference Numerals

[0056] 1 Maximum luminance information acquisition unit 2 Original cumulative histogram generation unit 3 Cumulative histogram correction unit 4 Tone curve setting unit 5 Driving unit 6 Liquid crystal display element 10,20 Cumulative histogram generation unit 100,200 Image display device

Claims

1. a maximum luminance information acquisition unit that extracts metadata indicating a maximum luminance value added to a video signal to be displayed and acquires maximum luminance information of the video signal; a cumulative histogram generating unit that divides a range of brightness from a minimum pixel value determined by a bit number of the video signal to a maximum pixel value into a plurality of brightness levels, and generates a cumulative histogram indicating a ratio of a cumulative number of pixels that are equal to or lower than each brightness level in the plurality of brightness levels, while regarding a brightness of a pixel having a brightness equal to or higher than a threshold value set based on the brightness indicated by the maximum luminance information as 0 for one or more frames of the video signal; a gradation curve setting unit that sets a gradation curve formed by input pixel values ​​and output pixel values ​​of the video signal according to a brightness level having a maximum brightness indicated by the cumulative histogram for each frame of the video signal, converts the input pixel values ​​to the output pixel values ​​according to the gradation curve, and supplies the output pixel values ​​to a drive unit that drives a display unit to display the video signal; An image display device comprising:

2. The image display device according to claim 1 , wherein the cumulative histogram generating section regards the brightness of pixels constituting a telop inserted in the frame as zero.

3. the metadata is added to each content of the video signal, each scene of the content, or each frame of the video signal; The maximum luminance information acquisition unit acquires the maximum luminance information for each of the contents if the metadata is added for each of the contents, acquires the maximum luminance information for each of the scenes if the metadata is added for each of the scenes, and acquires the maximum luminance information for each of the frames if the metadata is added for each of the scenes.

3. The image display device according to claim 1 or 2.

4. extracting metadata indicating a maximum luminance value added to a video signal to be displayed, and acquiring maximum luminance information of the video signal; a range of brightness levels from a minimum pixel value determined by the number of bits of the video signal to a maximum pixel value; and, for each frame of the video signal, a brightness level of a pixel that is equal to or greater than a threshold value set based on the brightness level indicated by the maximum luminance information is regarded as 0, and a cumulative histogram is generated that indicates a ratio of a cumulative number of pixels that are equal to or less than each brightness level among the plurality of brightness levels; setting a gradation curve formed by input pixel values ​​and output pixel values ​​of the video signal according to a brightness level having a maximum brightness indicated by the cumulative histogram for each frame of the video signal; converting the input pixel values ​​to the output pixel values ​​according to the tone curve for each of the frames; The output pixel value is supplied to a driver that drives a display unit to display the video signal. Image display method.

Images