JP7595814B1 - Image display device, image display method, and image display program - Google Patents

Abstract

An image display device, an image display method, and an image display program capable of displaying an image with gradation characteristics conforming to desired gradation characteristics are provided. The image display device includes a luminance acquisition unit, a gradation characteristic acquisition unit, and a display unit. The luminance acquisition unit acquires a first luminance value as an output luminance value by predicting an output luminance value at a maximum output gradation value of the image display device at a first timing. The gradation characteristic acquisition unit acquires a first gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that the display unit should output according to the input gradation value based on the first luminance value as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance. The display unit displays an image using the first gradation characteristic. The luminance acquisition unit acquires a second luminance value as the output luminance value by predicting an output luminance value that is an output luminance value at a maximum output gradation value of the image display device at a second timing after the first timing and that has changed over time since the first timing. The gradation characteristic acquisition unit acquires, as a gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance, a second gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that should be output by the display unit in accordance with the input gradation value, based on the second luminance value. The display unit displays the image using the second gradation characteristic.

Description

The present invention relates to an image display device, an image display method, and an image display program.

Display devices capable of displaying images with a wider dynamic range than the conventional dynamic range (the range of brightness that the human eye can perceive) have appeared. The dynamic range that can be expressed by conventional display devices is called SDR (Standard Dynamic Range), and those with a wider dynamic range than conventional display devices are called HDR (High Dynamic Range). For example, Patent Document 1 discloses a technology for comparatively displaying an HDR image with a wide dynamic range and an SDR image with a narrow dynamic range.

In order to display HDR images correctly, it is important not only to increase brightness, but also to express "color" and "gradation" that matches the characteristics of human vision. This color and gradation are influenced by the input/output characteristic "gamma (EOTF: Electro Optical Transfer Function)" of each input/output device. The international HDR standard "ITU-R BT.2100" establishes two gamma curves (PQ method and HLG method) to suit different applications.

The PQ (Perceptual Quantization) method uses gamma that matches the characteristics of human vision, making it suitable for the production of movies and web-based content, where reproducibility is important. On the other hand, the HLG (Hybrid Log Gamma) method is suitable for television broadcasting and live coverage, as it emphasizes that the image can be displayed naturally on conventional SDR televisions.

In the case of the PQ method, the peak luminance (maximum brightness) is specified as 10,000 cd/ ^m2 , and the same gamma curve (PQ curve) is always drawn up to the luminance that can be reproduced by the display device, so that in the gradation range up to the peak luminance of the display device, an HDR image that accurately reproduces the PQ curve can be displayed. On the other hand, in the case of the HLG method, the peak luminance coincides with the maximum luminance of the display device. In other words, since the gamma curve changes depending on the maximum luminance of the display device, an HDR image can be displayed without significant image degradation even when displayed on a conventional SDR television.

In recent years, technological developments in the display field have progressed, and display devices with high display quality have been proposed that use self-luminous elements such as organic light-emitting diodes (OLEDs) as light sources. However, the lifespan of self-luminous elements is short, and in display devices that use self-luminous elements as light sources, for example, the peak luminance decreases with an increase in the light-emitting time of the self-luminous elements (specifically, the current (load current) flowing through the self-luminous elements and the cumulative amount of time the current flows), and the output luminance value of the display device corresponding to each input gradation value of the displayed image also decreases relatively. For this reason, it has been difficult to display HDR images with gradation characteristics that comply with the PQ method, that is, gradation characteristics that require the display device to always draw the same gamma curve in the gradation range up to the peak luminance.

JP 2017-181762 A

The object of the present invention is to provide an image display device, an image display method, and an image display program capable of displaying an image with gradation characteristics conforming to desired gradation characteristics.

According to the present invention, there is provided an image display device having the following configuration.
[1] An image display device including a luminance acquisition unit, a gradation characteristic acquisition unit, and a display unit, wherein the luminance acquisition unit acquires a first luminance value as an output luminance value by predicting an output luminance value at a maximum output gradation value of the image display device at a first timing, and the gradation characteristic acquisition unit acquires a first luminance value as the output luminance value, as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the first gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that should be output by the display unit in accordance with the input gradation value based on the first luminance value, and the display unit displays an image using the first gradation characteristic, the unit acquires a second luminance value as the output luminance value by predicting an output luminance value that has changed over time since the first timing, which is an output luminance value at a maximum output luminance value of the image display device, at a second timing after the first timing; the gradation characteristic acquisition unit acquires a second luminance value as the output luminance value, as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the second luminance characteristic indicating a correspondence between an input gradation value of an image displayed by the display unit and, based on the second luminance value, an output luminance value that the display unit should output in accordance with the input gradation value; and the display unit displays an image using the second gradation characteristic.

According to the present invention, at the second timing, a second luminance value that has changed over time since the first timing is acquired, and instead of the first gradation characteristic, an image is displayed using the second gradation characteristic that indicates the correspondence between the input gradation value of the image displayed by the display unit and the output luminance value that the display unit should output in accordance with the input gradation value based on the second luminance value, as a gradation characteristic that conforms to the gradation characteristic defined by the absolute value of luminance. Therefore, even at the second timing after the first timing, an image can be displayed with gradation characteristics that conform to the desired gradation characteristic.

Various embodiments of the present invention will be described below. The embodiments described below can be combined with each other.
[2] The image display device according to [1], wherein the gradation characteristic defined by the absolute value of the luminance is a gradation characteristic that satisfies a PQ curve standard.
[3] The image display device according to [1], wherein the gradation characteristic defined by the absolute value of the luminance is a gradation characteristic that satisfies the Grayscale Standard Display Function (GSDF) of the DICOM standard.
[4] An image display device as described in any of [1] to [3], wherein the luminance acquisition unit acquires a third luminance value as the output luminance value by actually measuring an output luminance value at a maximum output luminance value of the image display device at a third timing different from the first and second timings, the gradation characteristic acquisition unit acquires a third luminance value as the output luminance value, as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the third gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that should be output by the display unit in accordance with the input gradation value based on the third luminance value, and the display unit displays an image using the third gradation characteristic.
[5] An image display device according to any one of [1] to [4], wherein the luminance acquisition unit acquires the output luminance value at a frequency equal to or greater than that of a case where an image is displayed using gradation characteristics conforming to gradation characteristics defined by an absolute value of luminance when the image is displayed using gradation characteristics conforming to gradation characteristics defined by a relative value of luminance.
[6] An image display device according to any one of [1] to [5], wherein the luminance acquisition unit reduces the frequency of acquisition of the output luminance value as the time for which the image is displayed by the display unit becomes longer.
[7] The image display device according to any one of [1] to [6], wherein the display unit is a self-luminous type.
[8] An image display method having a luminance acquisition step, a gradation characteristic acquisition step, and a display step, wherein in the luminance acquisition step, a first luminance value is acquired as the output luminance value by predicting an output luminance value at a maximum output gradation value of the image display device at a first timing, and in the gradation characteristic acquisition step, a first gradation characteristic is acquired as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the first gradation characteristic indicating a correspondence relationship between an input gradation value of an image to be displayed in the display step and an output luminance value to be output in the display step according to the input gradation value based on the first luminance value, and in the display step, an image is displayed using the first gradation characteristic, an image display method in which, in the luminance acquisition step, at a second timing after the first timing, a second luminance value is acquired as the output luminance value by predicting an output luminance value that has changed over time since the first timing, and, in the gradation characteristic acquisition step, a second luminance characteristic is acquired as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the second gradation characteristic indicating a correspondence between an input gradation value of an image to be displayed in the display step and, based on the second luminance value, an output luminance value to be output in the display step in accordance with the input gradation value, and, in the display step, an image is displayed using the second gradation characteristic.
[9] An image display program that causes a processor to execute the image display method described in [8].

According to the present invention, an image can be displayed using desired gradation characteristics.

1 is a block diagram showing a functional configuration of an image display device 10 according to an embodiment of the present invention. FIG. 13 is a diagram showing an example of a PQ curve. Fig. 3A is a diagram showing an example of a gradation characteristic curve of the display unit 3 when the output luminance value (peak luminance value) of the display unit 3 is 300. Fig. 3B is a diagram showing an example of a gradation characteristic curve of the display unit 3 when the output luminance value of the display unit 3 is 1000. Fig. 3C is a diagram showing an example of a gradation characteristic curve of the display unit 3 when the output luminance value of the display unit 3 is 4000. 1 is a diagram showing an example of a deterioration characteristic curve of a self-luminous element; Fig. 5A is a diagram showing an example of a gradation characteristic curve 25 showing the first gradation characteristic when the first luminance value is 300. Fig. 5B is a diagram showing an example of a gradation characteristic curve 26 showing the first gradation characteristic when the first luminance value is 1000. Fig. 6A is a diagram showing an example of a gradation characteristic curve 27 showing the first gradation characteristic when the first luminance value is 4000. Fig. 6B is a diagram showing an example of a gradation characteristic curve 28 showing the first gradation characteristic when the first luminance value is 10000. 4 is a flowchart showing an example of an image display process performed by the image display device 10. Fig. 8A is a diagram showing an example of a gradation characteristic curve 33 showing a first gradation characteristic when the first luminance value is 1000. Fig. 8B is a diagram showing an example of a gradation characteristic curve 34 showing a second gradation characteristic when the second luminance value is 800. FIG. 9 is a diagram showing an example of a gradation characteristic curve 36 of the display unit 3 when the first luminance value of the display unit 3 is 1000, and an example of a gradation characteristic curve 37 of the display unit 3 when the second luminance value of the display unit 3 is 800. 5A and 5B are diagrams illustrating an example of predicted timing and actual measurement timing of an output luminance value by a luminance acquisition unit 5.

Below, an embodiment of the present invention will be described with reference to the drawings. The features shown in the following embodiment can be combined with each other. In addition, each feature can be an invention independently.

Figure 1 is a block diagram showing the functional configuration of an image display device 10 according to an embodiment of the present invention. As shown in Figure 1, the image display device 10 is, for example, a color image display device using three colors, RGB, and includes an image acquisition unit 1, a display control unit 2, a display unit 3, a luminance acquisition unit 5, a gradation characteristic acquisition unit 8, a memory unit 9, and an operation reception unit 11.

Each component of the image display device 10 may be realized by software or by hardware. When realized by software, various functions can be realized by the CPU executing a computer program. The program may be stored in a built-in memory unit or a non-transitory computer-readable recording medium. In addition, the program stored in an external memory unit may be read and realized by so-called cloud computing. When realized by hardware, it can be realized by various circuits such as ASIC, FPGA, or DRP (Dynamically Reconfigurable Processor). In this embodiment, various information and concepts that include it are handled, but these are represented by the high and low signal values as a binary bit collection consisting of 0 or 1, and communication and calculation can be performed by the above software or hardware aspects.

The image display device 10 is a display device capable of displaying images in a wider dynamic range than the conventional dynamic range (the range of brightness that the human eye can perceive). The dynamic range that can be expressed by conventional display devices is called SDR (Standard Dynamic Range), and a dynamic range that can be expressed wider than that of conventional display devices is called HDR (High Dynamic Range).

In order to properly display HDR images (hereafter referred to as "HDR images"), it is important not only to increase brightness but also to express "color" and "gradation" that matches the characteristics of human vision. This color and gradation are influenced by the input/output characteristic "gamma (EOTF: Electro Optical Transfer Function)" that each input/output device possesses. The international HDR standard "ITU-R BT.2100" establishes two gamma curves (PQ method and HLG method) to suit different applications.

The PQ (Perceptual Quantization) method uses gamma that matches the characteristics of human vision, making it suitable for the production of movies and web-based content, where reproducibility is important. On the other hand, the HLG (Hybrid Log Gamma) method is suitable for television broadcasting and live coverage, as it emphasizes that the image can be displayed naturally on conventional SDR televisions.

In the case of the PQ method, the peak luminance (maximum brightness) is specified as 10,000 cd/ ^m2, and the luminance value of the HDR image is treated as an absolute value (constant regardless of the display device), and the same gamma curve (PQ curve) is always drawn up to the luminance that can be reproduced by the display unit 3, so that in the gradation range up to the peak luminance of the display unit 3, an HDR image that accurately reproduces the PQ curve can be displayed.

Fig. 2 is a diagram showing an example of a PQ curve 20. As shown in Fig. 2, the PQ curve 20 is a fixed curve in which luminance ^up to a maximum of 10000 cd/m2 is specified as an absolute value in a predetermined gradation range (gradation value: 0 to 1023).

FIG. 3A is a diagram showing an example of a gradation characteristic curve 22 of the display unit 3 when the peak luminance value of the display unit 3 is 300. FIG. 3B is a diagram showing an example of a gradation characteristic curve 23 of the display unit 3 when the peak luminance value of the display unit 3 is 1000. FIG. 3C is a diagram showing an example of a gradation characteristic curve 24 of the display unit 3 when the peak luminance value of the display unit 3 is 4000. In FIGS. 3A, 3B, and 3C, the curve indicated by the reference numeral 21 is a PQ curve in which the luminance up to 10000 cd/m ² is specified by an absolute value in a predetermined gradation range (gradation value: 0 to 1023). Note that the peak luminance value of the display unit 3 is an output luminance value at the maximum output gradation value of the image display device 10. For example, the peak luminance value is an output luminance value that the image display device 10 can output when a specific area (for example, a rectangular area) on an image is displayed at the maximum output gradation value.

As shown in the gradation characteristic curve 22 of FIG. 3A, in the case of the PQ method, the same gamma curve (PQ curve) is always drawn up to the luminance that can be reproduced by the display unit 3, so in the gradation range up to the peak luminance value (300) of the display unit 3, an HDR image that accurately reproduces the PQ curve 21 can be displayed on the display unit 3. Similarly, as shown in the gradation characteristic curve 23 of FIG. 3B, in the gradation range up to the peak luminance value (1000) of the display unit 3, an HDR image that accurately reproduces the PQ curve 21 can be displayed on the display unit 3. Also, as shown in the gradation characteristic curve 24 of FIG. 3C, in the gradation range up to the peak luminance value (4000) of the display unit 3, an HDR image that accurately reproduces the PQ curve 21 can be displayed on the display unit 3.

On the other hand, in the case of the HLG method, the luminance value of the HDR image is treated as a relative value (varies depending on the display device), and the peak luminance value coincides with the maximum luminance value of the display device. In other words, because the gamma curve changes depending on the maximum luminance value on the display device side, HDR images can be displayed without significant image distortion even when displayed on a conventional SDR image display device (for example, a television).

The functional configuration of the image display device 10 is described below.

The image acquisition unit 1 acquires HDR image data (input image data) from an input device (not shown), performs predetermined image processing on the acquired HDR image data to generate display image data, and outputs the generated display image data to the display control unit 2. The input device is, for example, an information processing device such as a personal computer, and is configured to be able to output various data such as image data including HDR image data.

The display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to cause the display unit 3 to display an image corresponding to the display image data.

The display unit 3 includes a display panel including a plurality of pixels arranged on a substrate, and an optical sensor 4, and displays an image corresponding to the display image data output from the display control unit 2 under the control of the display control unit 2. The images displayed by the display unit 3 include still images and moving images. In this embodiment, each of the plurality of pixels includes a self-luminous element such as an organic light-emitting diode (OLED). In other words, the display unit 3 is a self-luminous display device (e.g., an OLED display, a MicroLED display) that does not require a backlight.

The optical sensor 4 measures (actually measures) the output luminance value (peak luminance value) that the display unit 3 can output when the display unit 3 displays an image at the maximum output gradation value (maximum output gradation value of the image display device 10), and outputs the measurement result to the luminance actual measurement unit 7 (luminance acquisition unit 5). The optical sensor 4 is provided in a frame-shaped portion surrounding the display panel of the housing of the display unit 3. For example, the optical sensor 4 can be configured to move in and out from within the housing onto the display surface of the display panel in response to the operation of an actuator or motor, etc., and the optical sensor 4 can be configured to move onto the display surface when the luminance actual measurement unit 7 measures the output luminance value.

The optical sensor 4 may be configured to be detachably connected to the display unit 3 via a signal line or the like, and when measuring the output luminance value, the user may attach the optical sensor 4 to the display surface of the display panel and connect the signal line or the like to the display unit 3. Note that in this embodiment, the optical sensor 4 is configured to measure the output luminance value as a display characteristic value of the display unit 3, but is not limited thereto, and may be configured to measure other display characteristic values such as chromaticity, for example.

Although it is ideal to provide the optical sensor 4 on the display surface of the display panel, the optical sensor 4 may be provided near the display panel other than the display surface, and the output luminance value on the display surface of the display panel may be estimated from the luminance measured by the optical sensor 4. The output luminance value on the display surface of the display panel may also be estimated from the drive amount of the display panel.

The luminance acquisition unit 5 includes a luminance prediction unit 6 and a luminance measurement unit 7, and acquires an output luminance value that the display unit 3 can output when the display unit 3 displays an image (HDR image) at the maximum output gradation value. Note that the output luminance value that the display unit 3 can output is a value that can change due to various factors (e.g., over time), and the luminance acquisition unit 5 acquires the output luminance in response to changes in the output luminance value.

The luminance prediction unit 6 predicts an output luminance value that the display unit 3 can output when the display unit 3 displays an image (HDR image) at the maximum output gradation value at the first timing, thereby acquiring a first luminance value as the output luminance value. This allows the luminance prediction unit 6 to easily acquire the first luminance value without using the optical sensor 4. The luminance prediction unit 6 then outputs the acquired first luminance value to the gradation characteristic acquisition unit 8. Note that the luminance prediction unit 6 may predict a luminance range centered on the output luminance value at the first timing. In this case, the luminance prediction unit 6 acquires an average luminance value, for example, obtained by averaging the luminance values included in the predicted luminance range, as the first luminance value.

In addition, the luminance prediction unit 6 predicts an output luminance value that the display unit 3 can output when the display unit 3 displays an image (HDR image) with the maximum output gradation value at a second timing after the first timing and that has changed over time since the first timing, thereby acquiring a second luminance value as the output luminance value. The second timing is, for example, a timing at which a predetermined time has elapsed since the first timing. This allows the luminance prediction unit 6 to easily acquire the second luminance value without using the optical sensor 4. Then, the luminance prediction unit 6 outputs the acquired second luminance value to the gradation characteristic acquisition unit 8. Note that the output luminance value that has changed over time since the first timing includes an output luminance value that has risen, fallen, or been maintained since the first timing. In addition, the luminance prediction unit 6 may predict a luminance range centered on the output luminance value at the second timing. In this case, the luminance prediction unit 6 acquires an average luminance value obtained by, for example, averaging the luminance values included in the predicted luminance range as the second luminance value.

In this embodiment, the luminance prediction unit 6 predicts the output luminance value that the display unit 3 can output when displaying an image at the maximum output gradation value, based on the degradation characteristic that the output luminance value (peak luminance value) at the maximum output gradation value of the image display device 10 decreases in accordance with an increase in the light-emitting time of the self-luminous elements used as pixels of the display panel (specifically, the current (load current) flowing through the self-luminous elements and the cumulative amount of time the current flows).

Figure 4 is a diagram showing an example of a deterioration characteristic curve 30 of a self-luminous element. As shown in Figure 4, the deterioration characteristic curve 30 is a curve that corresponds the light emission time of the self-luminous element (horizontal axis in Figure 4) to the output luminance value (vertical axis in Figure 4) that the display unit 3 can output when the display unit 3 displays an image at the maximum output gradation value, and shows that the output luminance value at the maximum output gradation value of the image display device 10 deteriorates (decreases) as the light emission time of the self-luminous element increases. Here, the output luminance value is normalized, and the maximum value of the output luminance value is 1 and the minimum value of the output luminance value is 0. It can be seen that the deterioration rate of the output luminance value is faster when the light emission time of the self-luminous element is short (for example, as shown in range 31) than when the light emission time of the self-luminous element is long (for example, as shown in range 32).

Note that the light emission time of the self-luminous elements, specifically the current (load current) flowing through the self-luminous elements and the cumulative amount of time the current flows, differ for each self-luminous element, and the output luminance value is calculated for each self-luminous element. For example, in an OLED display (self-luminous display device), although the degradation (reduction) of the output luminance value differs for each display area, burn-in correction is generally performed so that the degradation of the output luminance value does not differ for each display area. Therefore, by calculating the light emission time of the self-luminous elements for a portion of the display area of the display screen, the output luminance value corresponding to the calculated light emission time can be obtained as the output luminance value for the entire display screen.

The luminance measurement unit 7 acquires the third luminance value as the output luminance value by measuring the output luminance value that the display unit 3 can output when the display unit 3 displays an image (HDR image) at the maximum output gradation value at a third timing different from the first and second timings (prediction timings). In this embodiment, the luminance measurement unit 7 acquires the third luminance value by inputting the measurement result output from the optical sensor 4 at the third timing. As a result, the luminance measurement unit 7 can acquire the third luminance value easily and accurately without performing a prediction calculation process by itself, compared to when predicting the output luminance value at the maximum output gradation value of the image display device 10. The luminance measurement unit 7 then outputs the acquired third luminance value to the gradation characteristic acquisition unit 8. In addition, the brightness measurement unit 7 may obtain the third brightness value as the output brightness value by actually measuring the output brightness value that the display unit 3 is capable of outputting when the display unit 3 displays an image (HDR image) at the maximum output gradation value at a third timing that is after the first and second timings (predicted timings), and by measuring the output brightness value that has changed over time from the predicted timing.

In addition, the brightness measurement unit 7 acquires a fourth brightness value as the output brightness value by measuring an output brightness value that the display unit 3 can output when the display unit 3 displays an image (HDR image) at the maximum output gradation value at a fourth timing that is different from the first and second timings (prediction timings) and is later than the third timing. The fourth timing is, for example, a timing at which a predetermined time has elapsed since the third timing. In this embodiment, the brightness measurement unit 7 acquires the fourth brightness value by inputting the measurement result output from the optical sensor 4 at the fourth timing. As a result, the brightness measurement unit 7 can acquire the fourth brightness value easily and accurately without performing a prediction calculation process by itself, compared to when predicting the output brightness value. Then, the brightness measurement unit 7 outputs the acquired third brightness value to the gradation characteristic acquisition unit 8.

The gradation characteristic acquisition unit 8 acquires a first gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the first luminance value output from the luminance prediction unit 6. For example, the gradation characteristic acquisition unit 8 refers to the storage unit 9 and acquires the first gradation characteristic based on gradation characteristic information (LUT: Look Up Table) on which the first gradation characteristic is based. Then, the gradation characteristic acquisition unit 8 outputs first gradation characteristic information indicating the acquired first gradation characteristic to the display control unit 2. In this embodiment, the gradation characteristic defined by the absolute value of luminance is a gradation characteristic that satisfies the PQ curve standard. Note that the gradation characteristic acquisition unit 8 may acquire the first gradation characteristic by calculating the first gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the first luminance value output from the luminance prediction unit 6.

The first gradation characteristic indicates the correspondence between the input gradation value of the image displayed by the display unit 3 and the output luminance value that the display unit 3 should output in accordance with the input gradation value based on the first luminance value output from the luminance prediction unit 6, and is a gradation characteristic for reproducing the PQ curve in the gradation range up to the first luminance value.

Figure 5A is a diagram showing an example of gradation characteristic information (LUT) on which the first gradation characteristic (the same applies to the second, third, and fourth gradation characteristics below) is based when the first luminance value (the same applies to the second, third, and fourth luminance values below) is 300. Here, the output gradation value (shown by curve 25) to be output by the display unit 3 is normalized, with the maximum value of the output gradation value (maximum output gradation value) being 1 and the minimum value of the output gradation value being 0. If the output gradation is, for example, 8 bits, the maximum output gradation value is 255.

Figure 5B is a diagram showing an example of gradation characteristic information (LUT) on which the first gradation characteristic (the same applies to the second, third, and fourth gradation characteristics below) is based when the first luminance value (the same applies to the second, third, and fourth luminance values below) is 1000. Here, the output gradation value (shown by curve 26) to be output by the display unit 3 is normalized, with the maximum value of the output gradation value (maximum output gradation value) being 1 and the minimum value of the output gradation value being 0. If the output gradation is, for example, 8 bits, the maximum output gradation value is 255.

Figure 6A is a diagram showing an example of gradation characteristic information (LUT) on which the first gradation characteristic (the same applies to the second, third and fourth gradation characteristics below) is based when the first luminance value (the same applies to the second, third and fourth luminance values below) is 4000. Here, the output gradation value (shown by curve 27) to be output by the display unit 3 is normalized, with the maximum value of the output gradation value (maximum output gradation value) being 1 and the minimum value of the output gradation value being 0. If the output gradation is, for example, 8 bits, the maximum output gradation value is 255.

Figure 6B is a diagram showing an example of gradation characteristic information (LUT) on which the first gradation characteristic (the same applies to the second, third and fourth gradation characteristics below) is based when the first luminance value (the same applies to the second, third and fourth luminance values below) is 10,000. Here, the output gradation value (shown by curve 28) to be output by the display unit 3 is normalized, with the maximum value of the output gradation value (maximum output gradation value) being 1 and the minimum value of the output gradation value being 0. If the output gradation is, for example, 8 bits, the maximum output gradation value is 255.

The gradation characteristics defined by the absolute value of luminance may be gradation characteristics that satisfy the Grayscale Standard Display Function (GSDF) of the DICOM standard instead of gradation characteristics that satisfy the PQ curve standard. In this case, the input gradation value of the image displayed by the display unit 3 is JND (Just-Noticeable Difference).

When first gradation characteristic information is output from the gradation characteristic acquisition unit 8, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data on the display unit 3 using the first gradation characteristic indicated by the first gradation characteristic information.

The gradation characteristic acquisition unit 8 acquires a second gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the second luminance value output from the luminance prediction unit 6. For example, the gradation characteristic acquisition unit 8 refers to the storage unit 9 and acquires the second gradation characteristic based on gradation characteristic information (LUT) on which the second gradation characteristic is based. The gradation characteristic acquisition unit 8 then outputs second gradation characteristic information indicating the acquired second gradation characteristic to the display control unit 2. The gradation characteristic acquisition unit 8 may acquire the second gradation characteristic by calculating the second gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the second luminance value output from the luminance prediction unit 6.

The second gradation characteristic indicates the correspondence between the input gradation value of the image displayed by the display unit 3 and the output luminance value that the display unit 3 should output in accordance with the input gradation value based on the second luminance value output from the luminance prediction unit 6, and is a gradation characteristic for reproducing the PQ curve in the gradation range up to the second luminance value.

When second gradation characteristic information is output from the gradation characteristic acquisition unit 8, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data on the display unit 3 using the second gradation characteristics indicated by the second gradation characteristic information.

The gradation characteristic acquisition unit 8 acquires a third gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the third luminance value output from the luminance measurement unit 7. For example, the gradation characteristic acquisition unit 8 refers to the storage unit 9 and acquires the third gradation characteristic based on the gradation characteristic information (LUT) on which the third gradation characteristic is based. The gradation characteristic acquisition unit 8 then outputs third gradation characteristic information indicating the acquired third gradation characteristic to the display control unit 2. The gradation characteristic acquisition unit 8 may acquire the third gradation characteristic by calculating the third gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the third luminance value output from the luminance prediction unit 6.

The third gradation characteristic indicates the correspondence between the input gradation value of the image displayed by the display unit 3 and the output luminance value that the display unit 3 should output in accordance with the input gradation value based on the third luminance value output from the luminance measurement unit 7, and is a gradation characteristic for reproducing the PQ curve in the gradation range up to the third luminance value.

When the third gradation characteristic information is output from the gradation characteristic acquisition unit 8, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data on the display unit 3 using the third gradation characteristic indicated by the third gradation characteristic information.

The gradation characteristic acquisition unit 8 acquires a fourth gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the fourth luminance value output from the luminance measurement unit 7. For example, the gradation characteristic acquisition unit 8 refers to the storage unit 9 and acquires the fourth gradation characteristic based on gradation characteristic information (LUT) on which the fourth gradation characteristic is based. The gradation characteristic acquisition unit 8 then outputs fourth gradation characteristic information indicating the acquired fourth gradation characteristic to the display control unit 2. The gradation characteristic acquisition unit 8 may acquire the fourth gradation characteristic by calculating the fourth gradation characteristic conforming to the gradation characteristic defined by the absolute value of luminance based on the fourth luminance value output from the luminance prediction unit 6.

The fourth gradation characteristic indicates the correspondence between the input gradation value of the image displayed by the display unit 3 and the output luminance value that the display unit 3 should output in accordance with the input gradation value based on the fourth luminance value output from the luminance measurement unit 7, and is a gradation characteristic for reproducing the PQ curve in the gradation range up to the fourth luminance value.

When the fourth gradation characteristic information is output from the gradation characteristic acquisition unit 8, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data on the display unit 3 using the fourth gradation characteristic indicated by the fourth gradation characteristic information.

The storage unit 9 stores degradation characteristic information indicating the degradation characteristics of each pixel (self-luminous element) of the plurality of pixels included in the display panel of the display unit 3. The storage unit 9 also stores gradation characteristic information indicating the correspondence between the input gradation value of the image displayed by the display unit 3 and the output gradation value that should be output by the display unit 3 in accordance with the input gradation value for each of the plurality of luminance values (the above-mentioned first luminance value, second luminance value, third luminance value, and fourth luminance value) that can be output from the luminance prediction unit 6 and the luminance actual measurement unit 7.

Part of the memory unit 9 is composed of, for example, RAM (Random Access Memory) or DRAM (Dynamic Random Access Memory), and is used as a work area when executing processes based on various programs. Part of the memory unit 9 is, for example, non-volatile memory such as ROM (Read Only Memory) or HDD (Hard Disk Drive), and stores various data and programs used for various processes. The memory unit 9 can hold a database including one or more tables for recording various information and processing results.

The operation reception unit 11 is composed of, for example, a keyboard and a mouse, and receives input of various operations by the user. In this embodiment, the operation reception unit 11 receives a setting operation for displaying an image corresponding to the display image data on the display unit 3 in the PQ method or the HLG method. The operation reception unit 11 then outputs setting operation information indicating the content of the received setting operation (PQ method or the HLG method) to the display control unit 2.

When the setting operation information output from the operation reception unit 11 indicates that the content of the setting operation is the PQ method, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data in the PQ method on the display unit 3. When the setting operation information output from the operation reception unit 11 indicates that the content of the setting operation is the HLG method, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data in the HLG method on the display unit 3.

Figure 7 is a flowchart showing an example of an image display process (corresponding to the "image display method" of the present invention) performed by the image display device 10 in this embodiment.

First, the brightness acquisition unit 5 determines whether or not it is a predicted timing (the first timing or the second timing described above) at which the output brightness value that the display unit 3 can output when the display unit 3 displays an image (HDR image) with the maximum output gradation value (step S100).

If the result of the judgment is that it is the prediction timing (step S100, YES), the luminance prediction unit 6 obtains the output luminance value (the above-mentioned first luminance value or the second luminance value) by predicting the output luminance value that the display unit 3 can output when the display unit 3 displays an image with the maximum output gradation value (step S110). Then, the luminance prediction unit 6 outputs the obtained output luminance value to the gradation characteristic acquisition unit 8.

Next, the gradation characteristic acquisition unit 8 acquires gradation characteristics (the above-mentioned first gradation characteristic or the second gradation characteristic) that conform to the gradation characteristic defined by the absolute value of luminance based on the output luminance value output from the luminance prediction unit 6 (step S120). Then, the gradation characteristic acquisition unit 8 outputs gradation characteristic information (the above-mentioned first gradation characteristic information or the second gradation characteristic information) indicating the acquired gradation characteristic to the display control unit 2.

Finally, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data on the display unit 3 using the gradation characteristics indicated by the gradation characteristic information output from the gradation characteristic acquisition unit 8 (step S130). When the process of step S130 is completed, the image display device 10 ends the image display process shown in FIG.

Returning to the judgment process of step S100, if it is not the predicted timing (step S100, NO), the luminance acquisition unit 5 judges whether it is the actual measurement timing (the third timing or the fourth timing described above) at which the display unit 3 actually measures the output luminance value that can be output when the display unit 3 displays an image with the maximum output gradation value (step S140). If the result of the judgment is that it is not the actual measurement timing (step S140, NO), the image display device 10 ends the image display process shown in FIG.

On the other hand, if it is the actual measurement timing (step S140, YES), the brightness measurement unit 7 acquires the output brightness value (the above-mentioned third brightness value or fourth brightness value) by measuring the output brightness value that the display unit 3 can output when the display unit 3 displays an image with the maximum output gradation value (step S150). Then, the brightness measurement unit 7 outputs the acquired output brightness value to the gradation characteristic acquisition unit 8.

Next, the gradation characteristic acquisition unit 8 acquires gradation characteristics (the above-mentioned third gradation characteristic or fourth gradation characteristic) that conform to the gradation characteristics defined by the absolute value of luminance based on the output luminance value output from the luminance actual measurement unit 7 (step S160). Then, the gradation characteristic acquisition unit 8 outputs gradation characteristic information (the above-mentioned third gradation characteristic information or fourth gradation characteristic information) indicating the acquired gradation characteristic to the display control unit 2.

Finally, the display control unit 2 outputs the display image data output from the image acquisition unit 1 to the display unit 3 and controls the display unit 3 to display an image corresponding to the display image data on the display unit 3 using the gradation characteristics indicated by the gradation characteristic information output from the gradation characteristic acquisition unit 8 (step S170). When the process of step S170 is completed, the image display device 10 ends the image display process shown in FIG.

As described above in detail, in this embodiment, the image display device 10 includes a luminance acquisition unit 5, a gradation characteristic acquisition unit 8, and a display unit 3. The luminance acquisition unit 5 acquires a first luminance value as the output luminance value by predicting an output luminance value at the maximum output gradation value of the image display device 10 at a first timing. The gradation characteristic acquisition unit 8 acquires a first gradation characteristic that indicates a correspondence between an input gradation value of an image displayed by the display unit 3 and an output luminance value that the display unit 3 should output in accordance with the input gradation value based on the first luminance value, as a gradation characteristic that conforms to a gradation characteristic (PQ curve standard) defined by an absolute value of luminance. The display unit 3 displays an image using the first gradation characteristic.

Furthermore, the luminance acquisition unit 5 acquires a second luminance value as the output luminance value at the maximum output luminance value of the image display device 10 at a second timing after the first timing by predicting an output luminance value that has changed over time since the first timing. The gradation characteristic acquisition unit 8 acquires a second gradation characteristic that indicates a correspondence between an input gradation value of an image displayed by the display unit 3 and an output luminance value that the display unit 3 should output in accordance with the input gradation value based on the second luminance value, as a gradation characteristic that conforms to a gradation characteristic (PQ curve standard) defined by an absolute value of luminance. The display unit 3 displays an image using the second gradation characteristic.

According to the present embodiment configured as described above, at the second timing, the second luminance value that has changed over time since the first timing is acquired, and instead of the first gradation characteristic, an image is displayed using the second gradation characteristic that indicates the correspondence between the input gradation value of the image displayed by the display unit 3 and the output luminance value that the display unit 3 should output according to the input gradation value based on the second luminance value as a gradation characteristic that conforms to the gradation characteristic defined by the absolute value of luminance. Therefore, even at the second timing after the first timing, an HDR image can be displayed with gradation characteristics conforming to the PQ method, that is, gradation characteristics that are required to always draw the same gamma curve in the gradation range up to the output luminance value (peak luminance value) at the maximum output gradation value of the image display device 10, and thus an image can be displayed with gradation characteristics conforming to the desired gradation characteristics.

For example, if a first luminance value (e.g., 1000) is acquired at the first timing, and a second luminance value (e.g., 800) that has changed over time since the first timing is acquired at the second timing, instead of the first luminance value-based first gradation characteristic, an image is displayed using a second gradation characteristic that indicates a correspondence between the input gradation value of the image displayed by the display unit 3 and the output luminance value that the display unit 3 should output according to the input gradation value based on the second luminance value, as a gradation characteristic that conforms to the gradation characteristic defined by the absolute value of luminance. Therefore, even at the second timing after the first timing, an HDR image can be displayed with gradation characteristics that conform to the PQ method, that is, gradation characteristics that are required to always draw the same gamma curve in the gradation range up to the output luminance value (peak luminance value, e.g., 800) at the maximum output gradation value of the image display device 10.

Figure 8A is a diagram showing an example of gradation characteristic information (LUT) on which the first gradation characteristic is based when the first luminance value is 1000. Here, the output gradation value (shown by curve 33) to be output by the display unit 3 is normalized, with the maximum value of the output gradation value (maximum output gradation value) being 1 and the minimum value of the output gradation value being 0. Figure 8B is a diagram showing an example of gradation characteristic information (LUT) on which the second gradation characteristic is based when the second luminance value is 800. Here, the output gradation value (shown by curve 34) to be output by the display unit 3 is normalized, with the maximum value of the output gradation value (maximum output gradation value) being 1 and the minimum value of the output gradation value being 0.

9 is a diagram showing an example of a gradation characteristic curve 36 of the display unit 3 when the first luminance value at the maximum output gradation value of the image display device 10 is 1000, and a gradation characteristic curve 37 of the display unit 3 when the second luminance value at the maximum output gradation value of the image display device 10 is 800. In FIG. 9, the curve indicated by the reference numeral 35 is a PQ curve in which the luminance up to 10000 cd/m ² is specified by an absolute value in a predetermined gradation range (gradation value: 0 to 1023). As shown in the gradation characteristic curves 36 and 37 of FIG. 9, when the second luminance value at the maximum output gradation value of the image display device 10 is 800, the gradation region in which an HDR image accurately reproducing the PQ curve 35 can be displayed on the display unit 3 becomes smaller than when the first luminance value at the maximum output gradation value of the image display device 10 is 1000.

Furthermore, in this embodiment, the luminance acquisition unit 5 acquires a third luminance value as the output luminance value by actually measuring the output luminance value at the maximum output luminance value of the image display device 10 at a third timing different from the first and second timings. The gradation characteristic acquisition unit 8 acquires a third gradation characteristic that indicates a correspondence between an input gradation value of an image displayed by the display unit 3 and an output luminance value that the display unit 3 should output in accordance with the input gradation value based on the third luminance value, as a gradation characteristic that conforms to a gradation characteristic (PQ curve standard) defined by an absolute value of luminance. The display unit 3 displays an image using the third gradation characteristic.

The luminance acquisition unit 5 acquires a fourth luminance value as an output luminance value at the maximum output luminance value of the image display device 10 at a fourth timing that is different from the first and second timings and is later than the third timing, by actually measuring the output luminance value that has changed over time since the third timing. The gradation characteristic acquisition unit 8 acquires a fourth luminance characteristic that indicates a correspondence between an input luminance value of an image displayed by the display unit 3 and an output luminance value that the display unit 3 should output in accordance with the input luminance value based on the fourth luminance value, as a gradation characteristic that conforms to a gradation characteristic (PQ curve standard) defined by an absolute value of luminance. The display unit 3 displays an image using the fourth luminance characteristic.

According to the present embodiment configured as described above, at the fourth timing, a fourth luminance value that has changed over time since the third timing is acquired, and instead of the third gradation characteristic, an image is displayed using a fourth gradation characteristic that indicates a correspondence between the input gradation value of the image displayed by the display unit 3 and the output luminance value that the display unit 3 should output according to the input gradation value based on the fourth luminance value as a gradation characteristic that conforms to the gradation characteristic defined by the absolute value of luminance. Therefore, even at the fourth timing after the third timing, an HDR image can be displayed with gradation characteristics conforming to the PQ method, that is, gradation characteristics that are required to always draw the same gamma curve in the gradation range up to the output luminance value (peak luminance value) at the maximum output gradation value of the image display device 10, and thus an image can be displayed with gradation characteristics conforming to the desired gradation characteristics.

In the above embodiment, the luminance acquisition unit 5 performs both prediction and actual measurement of the output luminance value at the maximum output gradation value of the image display device 10. However, the timing of prediction and actual measurement may be set arbitrarily. For example, the luminance acquisition unit 5 may perform more precise prediction of the output luminance value at the maximum output gradation value of the image display device 10 than actual measurement. FIG. 10 is a diagram showing an example of the prediction timing and actual measurement timing of the output luminance value by the luminance acquisition unit 5. As shown in FIG. 10, the luminance acquisition unit 5 predicts the output luminance value at times T1, T2, T4, T5, and T7, and the luminance acquisition unit 5 actually measures the output luminance value at times T3 and T6. That is, in the example shown in FIG. 10, the luminance acquisition unit 5 predicts the output luminance value twice, and then the luminance acquisition unit 5 actually measures the output luminance value once.

In addition, in the above embodiment, the brightness acquisition unit 5 may only predict or only measure the output brightness value that the display unit 3 can output, rather than both predicting and measuring the output brightness value at the maximum output gradation value of the image display device 10.

In addition, in the above embodiment, when an image is displayed on the display unit 3 using gradation characteristics conforming to gradation characteristics defined by an absolute value of luminance, the luminance acquisition unit 5 may acquire the output luminance value at a frequency equal to or greater than that when the image is displayed on the display unit 3 using gradation characteristics conforming to gradation characteristics defined by a relative value of luminance (e.g., the HLG curve standard). This is because when an image is displayed using gradation characteristics conforming to gradation characteristics defined by an absolute value of luminance, there is a greater need to switch the gradation characteristics used by the display unit 3 when displaying an image due to a decrease in the output luminance value at the maximum output gradation value of the image display device 10, compared to when an image is displayed using gradation characteristics conforming to gradation characteristics defined by a relative value of luminance.

Furthermore, in the above embodiment, the luminance acquisition unit 5 may reduce the frequency of acquisition of the output luminance value at the maximum output gradation value of the image display device 10 as the time for which the image is displayed by the display unit 3 becomes longer (i.e., the deterioration rate of the self-luminous elements becomes slower). This is because, as the deterioration rate of the self-luminous elements becomes slower, the need to switch the gradation characteristics used by the display unit 3 when displaying an image due to a decrease in the output luminance value at the maximum output gradation value of the image display device 10 becomes smaller.

In the above embodiment, the display unit 3 is a self-luminous display device that does not require a backlight, but the present invention is not limited to this. For example, the display unit 3 may be a display device that requires a backlight (e.g., a liquid crystal display device).

Although various embodiments of the present invention have been described above, these are presented as examples and are not intended to limit the scope of the invention. The novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. The embodiments and their variations are included within the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

1: Image acquisition unit, 2: Display control unit, 3: Display unit, 4: Light sensor, 5: Brightness acquisition unit, 6: Brightness prediction unit, 7: Brightness actual measurement unit, 8: Gradation characteristic acquisition unit, 9: Memory unit, 10: Image display device, 11: Operation reception unit, 20, 21, 35: PQ curve, 22, 23, 24, 36, 37: Gradation characteristic curve, 25, 26, 27, 28, 33, 34: Curve, 30: Deterioration characteristic curve, 31, 32: Range

Claims (9)

An image display device including a luminance acquisition unit, a gradation characteristic acquisition unit, and a display unit,
the luminance acquisition unit, at a first timing, predicts an output luminance value at a maximum output gradation value of the image display device, and acquires a first luminance value as the output luminance value;
the gradation characteristic acquisition unit acquires a first gradation characteristic that is specified by an absolute value of luminance and conforms to a gradation characteristic that satisfies a PQ curve standard , the first gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that should be output by the display unit in response to the input luminance value, based on the first luminance value, and for reproducing a PQ curve at input gradation values corresponding to luminance values equal to or less than the first luminance value, excluding input gradation values corresponding to luminance values greater than the first luminance value ;
the display unit displays an image using the first gradation characteristic;
the luminance acquisition unit acquires a second luminance value as the output luminance value by predicting an output luminance value that is an output luminance value at a maximum output gradation value of the image display device at a second timing that is later than the first timing, and that has changed over time since the first timing;
the gradation characteristic acquisition unit acquires a second gradation characteristic that is specified by an absolute value of luminance and conforms to a gradation characteristic that satisfies a PQ curve standard , the second gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that should be output by the display unit in response to the input gradation value, based on the second luminance value, and for reproducing a PQ curve at input gradation values corresponding to luminance values equal to or less than the second luminance value, excluding input gradation values corresponding to luminance values greater than the second luminance value ;
the display unit displays an image using the second gradation characteristic.
Image display device. The image display device according to claim 1 ,
the luminance acquisition unit acquires a third luminance value as the output luminance value by actually measuring an output luminance value at a maximum output gradation value of the image display device at a third timing different from the first and second timings;
the gradation characteristic acquisition unit acquires a third gradation characteristic that is specified by an absolute value of luminance and conforms to a gradation characteristic that satisfies a PQ curve standard , the third gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that should be output by the display unit in response to the input gradation value, based on the third luminance value, and for reproducing a PQ curve at input gradation values corresponding to luminance values equal to or less than the third luminance value, excluding input gradation values corresponding to luminance values greater than the third luminance value ;
the display unit displays an image using the third gradation characteristic.
Image display device. 3. The image display device according to claim 1,
the luminance acquisition unit acquires the output luminance value at a frequency equal to or greater than that of a case where an image is displayed using gradation characteristics conforming to gradation characteristics defined by an absolute value of luminance when the image is displayed using gradation characteristics conforming to gradation characteristics defined by a relative value of luminance.
Image display device. 3. The image display device according to claim 1,
the luminance acquisition unit decreases the frequency of acquisition of the output luminance value as the display time of the image on the display unit becomes longer.
Image display device. 3. The image display device according to claim 1,
The display unit is a self-luminous display device.
Image display device. An image display method having a luminance acquisition step, a gradation characteristic acquisition step, and a display step,
In the luminance acquisition step, a first luminance value is acquired as the output luminance value by predicting an output luminance value at a maximum output gradation value of the image display device at a first timing;
In the gradation characteristic acquisition step, a first gradation characteristic is acquired, which is defined by an absolute value of luminance and conforms to a gradation characteristic satisfying a PQ curve standard , and indicates a correspondence relationship between an input gradation value of an image to be displayed in the display step and an output luminance value to be output in the display step according to the input luminance value based on the first luminance value, and which reproduces a PQ curve at input gradation values corresponding to luminance values equal to or less than the first luminance value, excluding input gradation values corresponding to luminance values greater than the first luminance value ;
In the display step, an image is displayed using the first gradation characteristic;
In the luminance acquisition step, a second luminance value is acquired as the output luminance value by predicting an output luminance value at a maximum output gradation value of the image display device at a second timing that is later than the first timing, the output luminance value having changed over time since the first timing;
In the gradation characteristic acquisition step , a correspondence relationship between an input gradation value of an image to be displayed in the display step and an output luminance value to be output in the display step according to the input luminance value based on the second luminance value is shown as a gradation characteristic that is specified by an absolute value of luminance and conforms to a gradation characteristic that satisfies a PQ curve standard , and a second gradation characteristic is acquired for reproducing a PQ curve at an input gradation value corresponding to a luminance value equal to or less than the second luminance value, excluding an input gradation value corresponding to a luminance value greater than the second luminance value;
In the display step, an image is displayed using the second gradation characteristic.
Image display method. An image display device including a luminance acquisition unit, a gradation characteristic acquisition unit, and a display unit,
the luminance acquisition unit, at a first timing, predicts an output luminance value at a maximum output gradation value of the image display device, and acquires a first luminance value as the output luminance value;
the gradation characteristic acquisition unit acquires a first gradation characteristic that indicates a correspondence relationship between an input gradation value of an image to be displayed by the display unit and an output luminance value that should be output by the display unit in response to the input gradation value, based on the first luminance value, as a gradation characteristic that conforms to a gradation characteristic defined by an absolute value of luminance;
the display unit displays an image using the first gradation characteristic between the first timing and a second timing that is a predetermined time after the first timing ;
the luminance acquisition unit acquires a second luminance value as the output luminance value by predicting an output luminance value that is an output luminance value at a maximum output gradation value of the image display device at the second timing and that has changed over time since the first timing;
the gradation characteristic acquisition unit acquires, as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, a second gradation characteristic indicating a correspondence relationship between an input gradation value of an image displayed by the display unit and an output luminance value that should be output by the display unit in response to the input gradation value, based on the second luminance value;
the display unit displays an image using the second gradation characteristic between the second timing and a timing a predetermined time after the second timing, the timing being a timing at which the luminance acquisition unit predicts or actually measures an output luminance value at a maximum output gradation value of the image display device ;
the luminance acquisition unit acquires a third luminance value as the output luminance value by actually measuring an output luminance value at a maximum output gradation value of the image display device at a third timing different from the first and second timings;
the gradation characteristic acquisition unit acquires a third gradation characteristic that indicates a correspondence relationship between an input gradation value of an image to be displayed by the display unit and an output luminance value that should be output by the display unit in response to the input gradation value, based on the third luminance value, as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance;
the display unit displays an image using the third gradation characteristic between the third timing and a timing a predetermined time after the third timing, the timing being a timing at which the luminance acquisition unit predicts or actually measures an output luminance value at a maximum output gradation value of the image display device.
Image display device. An image display method having a luminance acquisition step, a gradation characteristic acquisition step, and a display step,
In the luminance acquisition step, a first luminance value is acquired as the output luminance value by predicting an output luminance value at a maximum output gradation value of the image display device at a first timing;
In the gradation characteristic acquisition step, a first gradation characteristic is acquired as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the first gradation characteristic indicating a correspondence relationship between an input gradation value of an image to be displayed in the display step and an output luminance value to be output in the display step according to the input gradation value based on the first luminance value;
In the display step, an image is displayed using the first gradation characteristic between the first timing and a second timing that is a predetermined time after the first timing ;
In the luminance acquisition step, a second luminance value is acquired as the output luminance value by predicting an output luminance value at a maximum output gradation value of the image display device at a second timing that is later than the first timing, the output luminance value having changed over time since the first timing;
In the gradation characteristic acquisition step, a second gradation characteristic is acquired as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the second gradation characteristic indicating a correspondence relationship between an input gradation value of an image to be displayed in the display step and an output luminance value to be output in the display step according to the input gradation value based on the second luminance value;
In the display step, an image is displayed using the second gradation characteristic between the second timing and a timing when a predetermined time has elapsed since the second timing, and the luminance acquisition step predicts or actually measures an output luminance value at a maximum output gradation value of the image display device ,
In the luminance acquisition step, an output luminance value at a maximum output gradation value of the image display device is actually measured at a third timing different from the first and second timings to acquire a third luminance value as the output luminance value;
In the gradation characteristic acquisition step, a third gradation characteristic is acquired as a gradation characteristic conforming to a gradation characteristic defined by an absolute value of luminance, the third gradation characteristic indicating a correspondence relationship between an input gradation value of an image to be displayed in the display step and an output luminance value to be output in the display step according to the input gradation value based on the third luminance value;
In the display step, an image is displayed using the third gradation characteristic between the third timing and a timing when a predetermined time has elapsed since the third timing, and the luminance acquisition step predicts or actually measures an output luminance value at a maximum output gradation value of the image display device.
Image display method. An image display program that causes a processor to execute the image display method according to claim 6 or 8 .