γ-curve setting device, γ-curve setting method, and display device

Abstract

To provide a γ-curve setting device capable of handling image variations caused by reflection of light on a display unit.SOLUTION: A γ-curve setting device (10) is provided, comprising a first acquisition unit (15) for acquiring luminance information (LU) in an environment of a display unit (13), a second acquisition unit (16) for acquiring reflection handling information corresponding to light reflectance on a display area of the display unit, and a setting unit (17) configured to set a γ-curve based on the luminance information and the reflection handling information.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gamma curve setting device, a gamma curve setting method, and a display device. [Background technology]

[0002] There is known a technique for converting the luminance of an image by using a gamma curve generated in accordance with the luminance histogram of the input image (see Patent Document 1). With this technique, the image can be adjusted in accordance with the luminance histogram of the image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-017200 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, it was found that the image changes not only depending on the image itself, but also on the brightness of the environment in which the image is viewed, and further on the display device that displays the image. That is, two different types of display devices were placed in a relatively bright environment and a relatively dark environment, and the images displayed were compared. As a result, both of them were able to display images with high contrast and subdued blacks in the dark environment. However, in a bright environment, while the image of one display device was as good as in the dark environment, the image of the other display device had floating blacks and a poor sense of contrast.

[0005] As a result of the inventors' investigation, it was found that this black floating is caused by the reflection of light on the display area of ​​the display device. However, with the above-mentioned technology, it is difficult to deal with the change in image caused by the reflection of light on the display unit.

[0006] An object of one embodiment of the present invention is to provide a gamma curve setting device, a gamma curve setting method, and a display device that can accommodate changes in an image caused by reflection of light on a display unit. [Means for solving the problem]

[0007] In order to solve the above problems, a gamma curve setting device according to one embodiment of the present invention includes a first acquisition unit that acquires illuminance information in an environment of a display unit for displaying an image, a second acquisition unit that acquires reflection correspondence information corresponding to the reflectance of light on a display area of ​​the display unit, and a setting unit that sets a gamma curve for converting the gradation of a video signal for display on the display unit based on the illuminance information and the reflection correspondence information. Effect of the Invention

[0008] According to one aspect of the present invention, it is possible to provide a gamma curve setting device, a gamma curve setting method, and a display device that are capable of dealing with changes in an image caused by reflection of light on a display unit. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram illustrating a configuration of a display device according to an embodiment of the present invention. [Diagram 2] FIG. 11 is a flowchart showing a process flow in a gamma curve setting method. [Diagram 3] FIG. 11 is a diagram illustrating an example of a determined gamma curve. [Figure 4] FIG. 13 is a diagram illustrating an example of an adjusted gamma curve. [Diagram 5] FIG. 11 is a flowchart showing a process flow in a gamma curve setting method. [Figure 6] FIG. 13 is a diagram showing the relationship between a table and an image quality mode. [Figure 7] FIG. 13 is a diagram showing the relationship between a table and illuminance. [Figure 8] FIG. 11 is a flowchart showing a process flow in a gamma curve setting method. [Figure 9] FIG. 13 is a diagram illustrating an example of an intermediate gamma curve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [First embodiment] A first embodiment of the present invention will be described in detail below. Fig. 1 is a block diagram showing the configuration of a display device 10 according to the first embodiment. The display device 10 has a video signal processing unit 11, a driver 12, a display unit 13, a storage unit 14, an illuminance information acquisition unit 15, a reflection correspondence information acquisition unit 16, and a gamma curve setting unit 17. Of these, the storage unit 14, the illuminance information acquisition unit 15, the reflection correspondence information acquisition unit 16, and the gamma curve setting unit 17 function as a gamma curve setting device 20 that sets a gamma curve.

[0011] The display device 10 displays an image based on the video signal on the display unit 13. The display unit 13 is driven by a drive signal DS to display an image (e.g., a moving image or a still image) represented by the video signal ISo. Examples of the display unit 13 include a liquid crystal display device, an organic electroluminescent (EL) display device, and an organic light-emitting diode (OLED) display device.

[0012] It has been found that the reflection of light (e.g., lighting, sunlight) on the display area of ​​the display unit 13 can reduce the contrast of the image displayed on the display unit 13, particularly in a bright environment. In other words, the addition of reflected light to an image area that is originally close to black (low gradation) makes the original black color appear slightly whitish, resulting in black floating.

[0013] It has been found that this black floating changes depending on (i) the brightness (illuminance) of the environment in which the display unit 13 is placed, and (ii) the reflectance of the display area of ​​the display unit 13.

[0014] (i) Since black floating occurs due to reflection of external light, it varies depending on the brightness of the environment in which the display unit 13 is placed. That is, black floating does not occur in a dark environment, but can occur in an environment that is brighter than a certain level. (ii) Black floating also varies depending on the reflectance in the display area of ​​the display unit 13. If this reflectance is small, black floating does not substantially occur, but if the reflectance becomes large enough, black floating can occur.

[0015] The reflectance of the display area of ​​the display unit 13 varies depending on the type of the display unit. For this reason, it is preferable to consider the difference in reflectance due to the type of the display unit 13. For example, a quantum dot organic light emitting diode (QD-OLED) display device does not have a polarizing plate, so the reflectance of external light at the quantum dot (QD) color conversion layer is high. As a result, the QD-OLED display device is more likely to have black floating than a normal organic light emitting diode (OLED) display device. When the two were compared in a dark environment, both were able to display images with high contrast and with low black. On the other hand, when the two were compared in a bright environment, the normal OLED display device was able to display images with high contrast and low black, as in a dark environment, but the QD-OLED display device sometimes had black floating and looked poor in contrast.

[0016] In this embodiment, the gamma curve is set taking into consideration the brightness of the environment in which the display unit 13 is placed and the reflectance on the display area of ​​the display unit 13, thereby suppressing changes in the image caused by light reflection on the display unit 13 (for example, the occurrence of black floating in the image).

[0017] For this purpose, the display unit 13 holds the reflection association information RI. That is, the display unit 13 has, for example, a storage unit that stores the reflection association information RI.

[0018] The reflection correspondence information RI is information corresponding to the reflectance of light on the display area of ​​the display unit 13. The reflection correspondence information RI does not need to include numerical information of the reflectance, etc., as long as it can be associated with the reflectance of light on the display area of ​​the display unit 13. For example, the reflection correspondence information RI may include model information for identifying the model and type of the display unit 13, and ID information for identifying the display unit 13. As described later, the reflection correspondence information RI is acquired from the display unit 13 by the reflection correspondence information acquisition unit 16, and is used by the gamma curve setting unit 17 to set the gamma curve. That is, as long as it can be associated with the reflectance of the display unit 13 in some sense in the gamma curve setting unit 17, the reflection correspondence information RI itself may be in various formats.

[0019] The video signal processing unit 11 processes the video signal ISi (input video signal) based on the γ curve and outputs it to the driver 12 as a video signal ISo (output video signal). The driver 12 generates a drive signal DS for driving the display unit 13 based on the processed output video signal ISo. The video signal processing unit 11 may have a histogram generating unit that generates a histogram of gradations on an image (e.g., a frame image) represented by the video signal ISi. This gradation histogram can be used in the γ curve adjustment process (step S12) described later.

[0020] The video signal processing unit 11 functions as a video signal conversion unit that converts the gradation of the video signal IS based on the gamma curve set by the gamma curve setting unit 17. That is, the video signal ISi input to the video signal processing unit 11 has its gradation value converted based on the gamma curve, and is output as the video signal ISo. The conversion of the gradation value is performed to optimize the image generated by the video signal ISo. The gamma curve is used to convert the gradation of the video signal, and is an index (for example, a kind of table) that indicates the relationship between the gradation before conversion (input gradation Gi) and the gradation after conversion (output gradation Go).

[0021] The storage unit 14 can store one or more gamma curves or parameters representing these gamma curves. The storage unit 14 may store only one standard gamma curve, or may store multiple switchable gamma curves.

[0022] Switching between multiple gamma curves may be based on (i) a user's selection, or, as described below, may be based on (ii) illuminance information, or (iii) video genre information and illuminance information. When the user selects a gamma curve, the display device 10 preferably has an input unit through which the user inputs information for selecting a gamma curve.

[0023] When the gamma curve is switched based on the illuminance information, it is preferable that the storage unit 14 stores a table T that indicates the relationship between the illuminance of the environment in which the image represented by the video signal is displayed (i.e., the environment around the display unit 13) and the gamma curve. In this case, the table T may continuously associate the illuminance information with the gamma curve, or may associate the illuminance information with the gamma curve in stages. For example, the illuminance information may be divided into several stages (for example, nine stages), and a gamma curve may be associated with each of the divided illuminance ranges. Instead of the gamma curve itself, the table T may associate a parameter that defines the gamma curve with the illuminance. In this case, a parameter that defines the gamma curve is identified from the illuminance, and the gamma curve is further identified from this parameter.

[0024] The illuminance information acquisition unit 15 acquires illuminance information in the environment of the display unit 13, and functions as a first acquisition unit that acquires illuminance information LU in the environment of the display unit 13 for displaying an image. The illuminance information acquisition unit 15 may be either (i) an illuminance sensor that measures illuminance, or (ii) an interface that receives information on illuminance measured by the illuminance sensor. This illuminance is, for example, illuminance caused by light incident on the display unit 13. This incident light is, for example, illumination light or sunlight that illuminates the environment in which the display unit 13 is placed. The incident light may also include light that is emitted from the display unit 13 and reflected by something and re-enters the display unit 13. Note that the illuminance is not limited to illuminance in the strict sense, but refers to the general brightness of the environment in which the image is displayed.

[0025] The reflection association information acquisition unit 16 acquires the reflection association information RI from the display unit 13. As described above, the reflection association information RI can be in various formats as long as it can be associated with the reflectance of light on the display area of ​​the display unit 13.

[0026] In order to diversify the reflection correspondence information RI, it is preferable that the storage unit 14 stores a table T0 that associates the reflection correspondence information RI with reflectance. In this case, the table T0 may associate a parameter for adjusting the gamma curve with the reflection correspondence information RI instead of the reflectance. As will be described later, the reflectance functions as a parameter for adjusting the gamma curve in the adjustment process (step S12). For this reason, if the reflectance can be associated with a parameter for adjusting the gamma curve, it will be associated with the reflectance, at least indirectly.

[0027] The gamma curve setting unit 17 (setting unit) sets a gamma curve based on the illuminance information LU and the reflection correspondence information RI. The gamma curve is an index for converting the gradation of a video signal for display on the display unit 13. The gamma curve setting unit 17 can be configured by a CPU (Central Processing Unit). In this case, the storage unit 14 can store a program for driving the CPU.

[0028] (Gamma curve setting method S10) The following describes the setting of a gamma curve by the gamma curve setting device 20. Fig. 2 is a flow chart showing the process flow of a gamma curve setting method S10, which is an example of a gamma curve setting method by the gamma curve setting device 20. The gamma curve setting method S10 will be described in detail below.

[0029] As shown in Fig. 2, the gamma curve setting unit 17 executes a determination process (step S11), an adjustment process (step S12), and a setting process (step S13). The determination process (step S11) is a process for determining a gamma curve. The adjustment process (step S12) is a process for adjusting the gamma curve determined in the determination process (step S11) based on illuminance information and reflection correspondence information. The setting process (step S13) is a process for setting the gamma curve adjusted in the adjustment process (step S12) as the gamma curve for the video signal ISi.

[0030] As described above, the determination process (step S11) can be various processes. For example, it may be fixed to one standard γ curve stored in the storage unit 14. That is, the determination process (step S11) also includes a case where the γ curve to be determined is specified.

[0031] The gamma curve to be determined may be selected from a plurality of gamma curves stored in the storage unit 14. This selection may be based on any of (i) the user, (ii) illuminance information, or (iii) video genre information and illuminance information. In the following, determination of a gamma curve based on illuminance will be described as an example.

[0032] When determining the gamma curve based on the illuminance, the gamma curve setting device 20 determines the gamma curve to be set based on the illuminance information LU acquired by the illuminance information acquisition unit 15. The gamma curve setting unit 17, for example, (1) moves the gamma curve closer to a linear curve L described below as the illuminance decreases, and (2) moves the gamma curve away from the linear curve L as the illuminance increases. Moving the gamma curve away from the linear curve L may include increasing the gradient of the gamma curve at gradations lower than a predetermined gradation value as the illuminance increases. In this determination process, a table T (a table showing the relationship between illuminance and gamma curve) stored in the storage unit 14 can be used.

[0033] As described above, in the determination process (step S11), the gamma curve to be set is determined based on the illuminance (brightness of the environment around the display unit 13) acquired by the illuminance information acquisition unit 15. As a result, an appropriate gamma curve can be set according to the illuminance of the environment around the display unit 13, thereby improving the image.

[0034] FIG. 3 is a diagram showing an example of a gamma curve determined in the determination process (step S11). Gamma curves C0 and C1 are shown, which are selected according to the magnitude of illuminance. The gamma curve C0 is selected when the illuminance is relatively low, and is relatively close to the linear curve L (a straight line where the input gradation Gi and the output gradation Go are equal). On the other hand, the gamma curve C1 is selected when the illuminance is relatively high, and is relatively far from the linear curve L. In this way, when the illuminance is relatively high, the gamma curve is moved away from the linear curve to prevent the contrast from being lost due to the brightness of the external light. In other words, the intermediate gradations are raised to expand the dynamic range.

[0035] As described above, in the adjustment process (step S12), the gamma curve determined in the determination process (step S11) is adjusted based on the illuminance information and the reflection correspondence information. By adjusting the determined gamma curve based on a combination of the illuminance information and the reflection correspondence information, it is possible to reduce black floating that occurs in an image due to reflected light when the surroundings of the display unit 13 are relatively bright and the reflectance of the display unit 13 is relatively high.

[0036] The gamma curve setting unit 17 may multiply the illuminance represented by the illuminance information LU by the reflectance corresponding to the reflection correspondence information RI, and determine the amount of adjustment of the gamma curve based on the multiplication value Vm. For example, the larger the multiplication value Vm, the larger the amount of adjustment. Also, when the multiplication value Vm is larger than a reference value, the gamma curve may be adjusted according to the multiplication value Vm, and when the multiplication value Vm is equal to or smaller than the reference value, the gamma curve may not be adjusted.

[0037] The same applies to the reflection correspondence information RI. For example, in the adjustment process (step S12), if the illuminance represented by the illuminance information LU is greater than the reference illuminance, the gamma curve setting unit 17 adjusts the gamma curve determined in the determination process (step S11), and if the illuminance represented by the illuminance information is equal to or less than the reference illuminance, the gamma curve does not need to be adjusted. This allows the gamma curve to be appropriately adjusted when the illuminance in the environment of the display unit 13 is high and the reflection of light from the display unit 13 affects the image.

[0038] The same can be said about the illuminance information LU. For example, in the adjustment process (step S12), if the illuminance represented by the illuminance information LU is greater than the reference illuminance, the gamma curve setting unit 17 adjusts the gamma curve determined in the determination process (step S11), and if the illuminance represented by the illuminance information is equal to or less than the reference illuminance, the gamma curve setting unit 17 does not need to adjust the gamma curve determined in the determination process. This allows the gamma curve to be appropriately adjusted when the reflectance of the display unit 13 is high and the reflection of light from the display unit 13 affects the image.

[0039] As described above, based on a combination of the illuminance information LU and the reflection correspondence information RI, or on either one of them, it is possible to switch ON / OFF (presence or absence of adjustment) of the gamma curve adjustment and the amount of adjustment stepwise and continuously.

[0040] Fig. 4 shows an example of gamma curves before and after adjustment. Graph G1 shows an enlarged low gradation range of the gamma curve C1 before adjustment in Fig. 3. Graph G2 shows an enlarged low gradation range of both the gamma curve C1 before adjustment and the gamma curve C2 after adjustment. Here, the relatively low gradation range of 0 to 50 out of the total gradation range of 0 to 255 has been enlarged.

[0041] As shown in graph G2, the input gradation Gi is converted into output gradations G01 and Go2 by the γ curves C1 and C2 respectively. In the gradation range where the input gradation Gi is lower than the reference gradation Gi0 (Gi < Gi0), the output gradation Go2 is smaller than the output gradation Go1. Thus, by adjusting the γ curve so that the output gradation decreases in the low gradation region, it is possible to suppress the black floating in the low gradation region caused by the reflected light.

[0042] The γ curve is an index for converting the gradation of a video signal from the input gradation to the output gradation. As shown in FIG. 4, the γ curve after being adjusted in the adjustment process (step S12) may have the following predetermined input gradation range including at least a part of the input gradation range lower than the reference gradation Gi0. That is, the first output gradation (for example, output gradation Go2) converted from the input gradation (for example, input gradation Gi) within this predetermined input gradation range by the γ curve (for example, γ curve C2) after being adjusted in the adjustment process is smaller than the second output gradation (for example, output gradation Go1) converted from this input gradation (for example, input gradation Gi) by the γ curve (for example, γ curve C1) before being adjusted in the adjustment process. Note that the predetermined input gradation range only needs to include at least a part of the input gradation range lower than the reference gradation, and does not necessarily need to include the entire input gradation range lower than the reference gradation.

[0043] In other words, the γ curve after being adjusted has a lower output gradation within the predetermined input gradation range compared to the γ curve before being adjusted. By reducing the output gradation, it is possible to suppress the occurrence of black floating within the predetermined input gradation range (for example, the low gradation region) due to the reflected light. Here, the reference gradation defining the predetermined input gradation range can be, for example, in the range of about 0% to 25% of the full gradation (as an example, 5%), or when the full gradation is 0 to 255, in the range of 0 to 64 (as an example, 13).

[0044] At this time, in the adjustment process, the gamma curve setting unit 17 (setting unit) may obtain the minimum gradation in the image represented by the video signal, and adjust the determined gamma curve so that the output gradation converted by the gamma curve becomes smaller than the minimum gradation, with the minimum gradation as the input gradation. For example, if the minimum gradation is 16, the gamma curve is adjusted so that when the input gradation Gi is 16, the output gradation Go becomes smaller than 16 (for example, 0).

[0045] Here, when the gradation range of the video signal is limited, it is preferable to adjust the output gradation Go (gamma curve) within the limited gradation range. For example, assume that the gradation range of the video signal is limited to 16 to 235, and the minimum gradation of the input video signal ISi is 30. In this case, it is preferable to adjust the output gradation Go (gamma curve) within a range smaller than 30, with 16 as the limit.

[0046] As described above, by adjusting the gamma curve so that the output grayscale when the minimum grayscale is the input grayscale is smaller than the minimum grayscale, the output grayscale in the low grayscale range can be lowered. This makes it possible to suppress black floating in the low grayscale range caused by reflected light and to further expand the dynamic range of grayscale.

[0047] The minimum gradation can be obtained from a gradation histogram generated by a histogram generating unit of the video signal processing unit 11. If the video signal Gi has a gradation range (minimum gradation, maximum gradation) specified for use, the minimum gradation used in the adjustment process (step S12) can be identified based on this video signal Gi. The maximum gradation can also be identified based on the gradation histogram or the video signal Gi, similar to the minimum gradation.

[0048] In addition to the minimum gradation, the gamma curve setting unit 17 (setting unit) may obtain the maximum gradation in the image represented by the video signal in the adjustment process, and adjust the determined gamma curve so that the output gradation converted by the gamma curve with the maximum gradation as the input gradation is greater than the maximum gradation. For example, if the maximum gradation is 235, the gamma curve is adjusted so that when the input gradation Gi is 235, the output gradation Go is greater than 235 (for example, 255).

[0049] As described above, when the gradation range of the video signal is limited, it is preferable to adjust the output gradation Go (gamma curve) within the limited gradation range. For example, assume that the gradation range of the video signal is limited to 16 to 235, and the maximum gradation of the input video signal ISi is 200. In this case, it is preferable to adjust the output gradation Go (gamma curve) within a range greater than 200, with 235 as the limit.

[0050] As described above, by adjusting the gamma curve so that the output grayscale, with the maximum grayscale as the input grayscale, becomes greater than the maximum grayscale, the dynamic range of the grayscale can be further expanded.

[0051] The setting process is a process for setting the gamma curve adjusted in the adjustment process as the gamma curve of the video signal. By setting the adjusted gamma curve as the gamma curve, the signal processing unit 11 processes the video signal IS using an appropriate gamma curve.

[0052] As described above, the gamma curve setting device 20 according to this embodiment includes an illuminance information acquiring unit 15 (first acquiring unit) that acquires illuminance LU in the environment of the display unit 13 for displaying an image, a reflection correspondence information acquiring unit 16 (second acquiring unit) that acquires reflection correspondence information RI corresponding to the reflectance of light on the display area of ​​the display unit 13, and a gamma curve setting unit 17 (setting unit) that sets a gamma curve for converting the gradation of the video signal ISi for display on the display unit 13, based on the illuminance information LU and the reflection correspondence information RI. By setting the gamma curve based on the illuminance information LU in the environment of the display unit 13 and the reflection correspondence information RI corresponding to the reflectance of light on the display area of ​​the display unit 13, it becomes possible to respond to changes in an image caused by reflection of light on the display unit 13.

[0053] Second Embodiment A second embodiment of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0054] (Gamma curve setting method S20) 5 is a flow diagram showing the flow of processing in the gamma curve setting method S20 by the gamma curve setting device 20. In the gamma curve setting method S20, a determination process (step S21) is executed instead of the determination process (step S11) in the gamma curve setting method S10. This determination process (step S21) is a process for determining a gamma curve based on the type of image and illuminance information.

[0055] The input video signal ISi has genre information that identifies the genre of the video, and the gamma curve setting unit 17 determines the gamma curve to be set based on the video genre information and environmental illuminance information.

[0056] Before this determination process (step S21), a first acquisition process and a second acquisition process are executed. The first acquisition process is a process for acquiring illuminance information LU in the environment of the display unit 13 for displaying an image, and is executed by the illuminance information acquisition unit 15. The second acquisition process is a process for acquiring reflection correspondence information RI corresponding to the reflectance of light on the display area of ​​the display unit 13, and is executed by the reflection correspondence information acquisition unit 16.

[0057] This determination process (step S21) can be performed using table T stored in storage unit 14. In this case, table T preferably represents the relationship between the genre of the video, the illuminance, and the gamma curve. More specifically, video signal IS includes genre information for identifying the genre of the video and format information for identifying the format of the video content, and table T represents the relationship between the image quality mode (corresponding to the genre of the video), the format, and the environmental illuminance, and the gamma curve.

[0058] 6 and 7 are diagrams showing an example of this table T. Table T is divided into a plurality of tables corresponding to image quality modes 1 to 9. Here, image quality modes 1 to 9 are divided into sports, movies, standard (e.g., news), etc., and are further divided into three corresponding to the formats of video content (SDR, HLG, PQ). As a result, the table is divided into 27 tables ij (1-1 to 1-3, 2-1 to 2-3, ..., 9-1 to 9-3) (1: integers from 1 to 9, j: integers from 1 to 3). As shown in FIG. 6, each table ij is divided into nine setting tables ij-1 to ij-9 according to illuminance information (e.g., illuminance value). In this way, table T essentially represents the relationship between the genre and format of the video, the illuminance of the environment, and the gamma curve.

[0059] The gamma curve setting unit 17 acquires the genre information and the format information from the video signal ISi, determines the image quality mode corresponding to the genre information, and selects the table ij corresponding to the image quality mode and the format. For example, when the genre is sports and the format is SDR, table 1-1 is selected, and when the genre is movies and the format is HLG, table 2-2 is selected.

[0060] Then, parameters ij-1 to ij-9 are selected based on the table ij selected corresponding to the genre and format and the illuminance information, and the gamma curve is determined. The adjustment process (step S12) and the setting process (step S13) are the same as those in the first embodiment, and therefore detailed explanations are omitted.

[0061] According to the gamma curve setting method S20, an appropriate gamma curve is determined (step S21) without the user being aware of the genre of the video, and the gamma curve is adjusted based on the illuminance information LU and the reflection correspondence information RI (step S12). For example, when a "sports" broadcast is being received, the gamma curve T1-1 is determined and adjusted, and a vivid and dynamic video appears.

[0062] As described above, in the gamma curve setting device 20 according to this embodiment, the gamma curve setting unit 17 determines a gamma curve based on the genre information and illuminance information of the video, and adjusts and sets the gamma curve based on the illuminance information LU and the reflection correspondence information RI. This makes it possible to respond to changes in the video caused by the genre of the video, the brightness of the environment, and the reflection of light on the display unit 13.

[0063] Third embodiment A third embodiment of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0064] (Gamma curve setting method S30) Fig. 8 is a flow diagram showing the flow of processing in the gamma curve setting method S30 by the gamma curve setting device 20. The determination process (step S31), adjustment process (step S32), and setting process of the adjusted gamma curve (step S36) are substantially similar to the determination process (step S11), adjustment process (step S12), and setting process (step S13) in Fig. 2, so their explanations are omitted. Between the adjustment process (step S32) and the setting process of the adjusted gamma curve (step S36), a setting process of an intermediate gamma curve (steps S33 to S35) is executed.

[0065] The gamma curve setting unit 17 (setting unit) may gradually switch the gamma curve set in the setting process (step S36) from the (current) gamma curve that was set before the adjustment process (step S32) to the gamma curve adjusted in the adjustment process.

[0066] The gamma curve may have been set before the adjustment process (step S32). In this case, the gamma curve is switched from the (current) gamma curve (1) that was set before the adjustment process to the adjusted gamma curve (2). The gamma curve (1) is set when the display device 10 is started up or in the previous setting process (step S36). For example, the gamma curve may change over time due to a change in the amount of external light reflected by the display unit 13 caused by a change in the brightness of the environment.

[0067] Here, before switching the setting from the current gamma curve (1) to the adjusted gamma curve (2) (step S36), gamma curves (1) and (2) are compared (steps S33, S34) to determine whether or not it is necessary to set to a gamma curve intermediate between gamma curves (1) and (2).This is because if there is a large difference between the gamma curves before and after the switching, the switching of the gamma curve may give the viewer a sense of discomfort.

[0068] Instead of comparing the γ curves (1) and (2) themselves, for example, parameters defining the γ curves (1) and (2) may be compared, or the corresponding illuminances of the γ curves (1) and (2) may be compared. For example, the need for an intermediate γ curve may be determined based on the difference in the corresponding illuminances.

[0069] 9 is a diagram showing an example of an intermediate gamma curve. Before the gamma curve is switched from the current gamma curve Ca to the adjusted gamma curve Cb, an intermediate gamma curve Cc between the gamma curves Ca and Cb is set. That is, the gamma curves are set in the order of the gamma curves Ca, Cc, and Cb.

[0070] Here, a case where one intermediate gamma curve Cc is set is shown, but (one) or multiple intermediate gamma curves may be set in sequence, and then gamma curve (2) may be set. In other words, the gamma curve to be set may be switched in stages from gamma curve (1) to gamma curve (2).

[0071] In this case, the number of intermediate gamma curves and the time intervals to be set can be set appropriately. For example, the number of intermediate gamma curves can be increased according to the magnitude of the difference between the gamma curves (1) and (2) based on the parameters. The time intervals can be constant or can be varied according to the number of intermediate gamma curves.

[0072] As described above, in the gamma curve setting device 20 according to this embodiment, the gamma curve setting unit 17 gradually switches the gamma curve to be set from the (current) gamma curve set before the adjustment process (step S32) to the gamma curve adjusted in the adjustment process. This makes it possible to make changes in the image caused by changes in the gamma curve settings less noticeable.

[0073] [Software implementation example] The functions of the display device 10 or the gamma curve setting device 20 (hereinafter referred to as the "device") can be realized by a program for causing a computer to function as the device, and a program for causing a computer to function as each control block of the device (in particular, each part included in the gamma curve setting unit 17).

[0074] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each function described in each of the above embodiments.

[0075] The program may be non-transitory and may be recorded in one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be provided to the device via any wired or wireless transmission medium.

[0076] In addition, some or all of the functions of each of the control blocks can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of each of the control blocks can be realized by, for example, a quantum computer.

[0077] 〔summary〕 A gamma curve setting device (20) according to a first aspect of the present invention includes a first acquisition unit (15) that acquires illuminance information (LU) in the environment of a display unit (13) for displaying an image, a second acquisition unit (16) that acquires reflection correspondence information (RI) that corresponds to the reflectance of light on a display area of ​​the display unit, and a setting unit (17) that sets a gamma curve for converting the gradation of a video signal for display on the display unit based on the illuminance information and the reflection correspondence information. Thus, by setting the gamma curve based on the illuminance information and the reflection correspondence information, it becomes possible to respond to changes in an image caused by light reflection on the display unit.

[0078] In a gamma curve setting device according to aspect 2 of the present invention, in aspect 1, the setting unit executes a determination process (S11) for determining the gamma curve, an adjustment process (S12) for adjusting the gamma curve determined in the determination process based on the illuminance information and the reflection correspondence information, and a setting process (S13) for setting the gamma curve adjusted in the adjustment process as a gamma curve for the video signal. By adjusting the gamma curve based on the illuminance information and the reflection correspondence information, it is possible to further reduce changes in an image caused by light reflection on a display unit, compared to a gamma curve before adjustment.

[0079] A gamma curve setting device according to a third aspect of the present invention is in the second aspect, wherein in the adjustment process, if the illuminance represented by the illuminance information is greater than a reference illuminance, the setting unit adjusts the gamma curve determined in the determination process, and if the illuminance is equal to or less than the reference illuminance, the setting unit does not adjust the gamma curve determined in the determination process. If the illuminance represented by the illuminance information is equal to or less than the reference illuminance, the determined gamma curve is not adjusted, thereby optimizing the adjustment of the gamma curve based on the reflection correspondence information.

[0080] A gamma curve setting device according to a fourth aspect of the present invention is in accordance with the second or third aspect, wherein the gamma curve is an index for converting the gradation of a video signal from an input gradation to an output gradation, the gamma curve after adjustment in the adjustment process has a predetermined input gradation range including at least a part of an input gradation range lower than a reference gradation, and a first output gradation converted from an input gradation within the predetermined input gradation range by the gamma curve after adjustment in the adjustment process is smaller than a second output gradation converted from the input gradation by the gamma curve before adjustment in the adjustment process. This reduces gradation in a predetermined input gradation range (e.g., a low gradation region) lower than the reference gradation, and prevents dark areas of an image from becoming whitish due to reflected light.

[0081] A gamma curve setting device according to a fifth aspect of the present invention is any one of the second to fourth aspects, in which the setting unit, in the adjustment process, obtains a minimum gradation in an image represented by the video signal, and adjusts the gamma curve determined in the determination process so that, with the minimum gradation as an input gradation, an output gradation converted by the gamma curve becomes smaller than the minimum gradation. This makes it possible to suppress changes in an image caused by light reflection on a display unit, improve contrast, and increase the dynamic range of gradations.

[0082] A gamma curve setting device according to a sixth aspect of the present invention is any one of the second to fifth aspects, in which the setting unit, in the adjustment process, obtains a maximum gradation in an image represented by the video signal, and adjusts the gamma curve determined in the determination process so that an output gradation converted by the gamma curve using the maximum gradation as an input gradation becomes larger than the maximum gradation. This makes it possible to further increase the dynamic range of gradations.

[0083] A gamma curve setting device according to aspect 7 of the present invention is any one of aspects 1 to 6, in which the setting unit gradually switches the gamma curve set in the setting process from the gamma curve set before the adjustment process to the gamma curve adjusted in the adjustment process. This makes it possible to make changes in an image caused by switching of the gamma curve less noticeable.

[0084] A gamma curve setting device according to an eighth aspect of the present invention is any one of the second to seventh aspects, wherein the setting unit determines a gamma curve based on the illuminance information in the determination process. This makes it possible to suppress changes in a displayed image due to environmental illuminance by determining a gamma curve based on illuminance information.

[0085] A gamma curve setting device according to a ninth aspect of the present invention is the same as in the eighth aspect, wherein the video signal has genre information identifying a genre of the video, and the setting unit determines a gamma curve based on the genre information of the video and the illuminance information in the determination process. Thus, by determining a gamma curve based on the genre information and the illuminance information, it is possible to adapt the displayed video to the genre of the video and the illuminance of the environment.

[0086] A gamma curve setting method according to a tenth aspect of the present invention includes a first acquisition process for acquiring illuminance information under an environment of a display unit for displaying an image, a second acquisition process for acquiring reflection correspondence information corresponding to the reflectance of light on a display area of ​​the display unit, and a setting process for setting a gamma curve for converting the gradation of a video signal for display on the display unit based on the illuminance information and the reflection correspondence information. As a result, by setting the gamma curve based on the illuminance information and the reflection correspondence information, it becomes possible to respond to changes in an image caused by light reflection on the display unit.

[0087] A display device according to an eleventh aspect of the present invention includes the gamma curve setting device according to any one of aspects 1 to 9, a video signal conversion unit that converts the video signal based on the gamma curve set by the gamma curve setting device, and a display unit that displays an image based on the converted video signal. This makes it possible to realize a display device that can handle changes in an image caused by light reflection on the display unit by setting a gamma curve based on illuminance information and reflection correspondence information.

[0088] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Furthermore, new technical features can be formed by combining the technical means disclosed in the respective embodiments. [Explanation of symbols]

[0089] 10 Display device 11 Video signal processing section 12 Drivers 13 Display section 14 Storage section 15 Illuminance information acquisition section 16 Reflection correspondence information acquisition section 17 Gamma curve setting section 20 Gamma curve setting device

Claims

1. A first acquisition unit that acquires illuminance information in an environment of a display unit for displaying an image; a second acquisition unit that acquires reflection correspondence information corresponding to a reflectance of light on a display area of ​​the display unit; a setting unit that sets a gamma curve for converting a gray scale of a video signal for display on the display unit based on the illuminance information and the reflection correspondence information; A gamma curve setting device comprising:

2. The setting unit is A determination process for determining the gamma curve; an adjustment process for adjusting the gamma curve determined in the determination process based on the illuminance information and the reflection correspondence information; a setting process for setting the gamma curve adjusted in the adjustment process as a gamma curve for the video signal; The gamma curve setting device according to claim 1, further comprising:

3. In the adjustment process, the setting unit If the illuminance represented by the illuminance information is greater than a reference illuminance, the gamma curve determined in the determination process is adjusted, and if the illuminance is equal to or less than the reference illuminance, the gamma curve determined in the determination process is not adjusted.

3. The gamma curve setting device according to claim 2.

4. the gamma curve is an index for converting the gradation of the video signal from an input gradation to an output gradation, the gamma curve after being adjusted in the adjustment process has a predetermined input tone range including at least a portion of the input tone range lower than the reference tone; a first output gradation converted from an input gradation within the predetermined input gradation range by the gamma curve after adjustment in the adjustment process is smaller than a second output gradation converted from the input gradation by the gamma curve before adjustment in the adjustment process; 4. The gamma curve setting device according to claim 2 or 3.

5. In the adjustment process, the setting unit Obtaining a minimum gray scale on an image represented by the video signal; adjusting the gamma curve determined in the determination process so that an output grayscale converted by the gamma curve, with the minimum grayscale being an input grayscale, is smaller than the minimum grayscale; 4. The gamma curve setting device according to claim 2 or 3.

6. In the adjustment process, the setting unit Obtaining a maximum gray scale on an image represented by the video signal; adjusting the gamma curve determined in the determination process so that an output grayscale converted by the gamma curve using the maximum grayscale as an input grayscale is greater than the maximum grayscale; 6. The gamma curve setting device according to claim 5.

7. 4. The gamma curve setting device according to claim 2, wherein the setting unit gradually switches the gamma curve set in the setting process from a gamma curve set before the adjustment process to a gamma curve adjusted in the adjustment process.

8. The gamma curve setting device according to claim 2 , wherein the setting unit determines the gamma curve based on the illuminance information in the determination process.

9. the video signal has genre information for identifying a genre of the video; The gamma curve setting device according to claim 8 , wherein the setting section determines the gamma curve based on genre information of the video and the illuminance information in the determination process.

10. A first acquisition process for acquiring illuminance information in an environment of a display unit for displaying an image; A second acquisition process for acquiring reflection correspondence information corresponding to a reflectance of light on a display area of ​​the display unit; a setting process for setting a gamma curve for converting a gradation of a video signal for display on the display unit based on the illuminance information and the reflection correspondence information; A gamma curve setting method including:

11. A gamma curve setting device according to any one of claims 1 to 3, a video signal conversion unit that converts the video signal based on the gamma curve set by the gamma curve setting device; a display unit that displays an image based on the image signal converted by the image signal conversion unit; A display device comprising:

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