Patent Application
20240169934
The present disclosure relates to a display apparatus, a display control method, and the like.
Various methods for controlling display apparatuses are known. For example, a conventionally known method switches, depending on the brightness of the surroundings of an apparatus, control curves to use that each define the relationship between a brightness-related index and a stretching amount by which the luminance of a backlight in the apparatus is stretched.
This known method can only determine Max luminance (maximum luminance of the backlight) based on the brightness of the surroundings of the apparatus, because the method is intended to control the stretching amount. For example, according to this known method, the relative relationship between the illumination ratio of the backlight corresponding to a high-luminance portion of an input image and the illumination ratio of the backlight corresponding to a darker portion of the input image is invariable regardless of the brightness of the surroundings.
According to some aspects of the present disclosure, it is possible to provide a display apparatus, a display control method, and the like for flexibly controlling the illumination ratio of a backlight depending on signal values corresponding to an input image and a surrounding environmental light condition.
An aspect of the present disclosure relates to a display apparatus including: a display that displays an image; a receiver that receives input signals corresponding to an input image; a surrounding environmental data processor that determines a surrounding environmental light condition including information representing a brightness of surroundings of the display apparatus; a backlight illumination ratio determiner that determines, for each of a plurality of areas set on the display, an illumination ratio of a backlight of the display based on the input signals and the surrounding environmental light condition; and a display controller that causes the display to display the input image by illuminating the backlight of the display based on the illumination ratio, wherein the backlight illumination ratio determiner determines the illumination ratio so that areas corresponding to a high tone range are assigned an illumination ratio of greater than or equal to an illumination ratio threshold value, the high tone range including input signals having a signal value of greater than or equal to a first signal threshold value.
Another aspect of the present disclosure relates to a display control method including: receiving input signals corresponding to an input image; determining a surrounding environmental light condition including information representing a brightness of surroundings of a display apparatus; determining, for each of a plurality of areas set on a display of the display apparatus, an illumination ratio of a backlight of the display based on the input signals and the surrounding environmental light condition; and causing the display to display the input image by illuminating the backlight of the display based on the illumination ratio, wherein in the determining the illumination ratio of the backlight, the illumination ratio is determined so that areas corresponding to a high tone range are assigned an illumination ratio of greater than or equal to an illumination ratio threshold value, the high tone range including input signals having a signal value of greater than or equal to a first signal threshold value.
The following describes an embodiment of the present disclosure with reference to the accompanying drawings. In the drawings, the same or equivalent elements are labeled with the same reference numerals, and description thereof is not repeated. It should be noted that the embodiment described below does not unreasonably limit what is defined in the appended claims. In addition, not all of elements of configuration described in the present embodiment are requirements of the present disclosure.
The receiver 110 receives input signals corresponding to an input image. The input image herein represents an image to be displayed on the display 150. The receiver 110 may be, for example, a tuner that receives signals corresponding to broadcast waves for television broadcast from an antenna and outputs input signals based on the received signals. The tuner includes, for example, an interface for receiving broadcast waves for television broadcast at a specific frequency and circuitry that performs processing on the received broadcast waves. In this case, the input signals may be those in accordance with Rec.709 (BT.709), which is a standard related to coding and the like in high-definition television broadcast. Rec.709 specifies, for example, RGB color space parameters.
Alternatively, the receiver 110 may be implemented by a communication interface other than the tuner. For example, the communication interface is an interface for acquiring video signals from a Blu-ray Disc (BD, registered trademark) player or recorder, and may be a port to which a high-definition multimedia interface (HDMI) cable can be connected. In this case, the input signals may be signals corresponding to data stored on an optical storage medium such as a BD, or signals corresponding to data stored on a storage medium such as a hard disk drive (HDD) or a solid state drive (SSD). The communication interface may be an interface defined by an established standard such as IEEE 802.3 or IEEE 802.11. In this case, the input signals may be those obtained by the communication interface from a content server via a public communication network such as the Internet.
The surrounding environmental data processor 120 determines a surrounding environmental light condition including information representing the brightness of the surroundings of the display apparatus 100. For example, the surrounding environmental data processor 120 may determine the surrounding environmental light condition based on a sensor value from a brightness sensor. The brightness sensor herein is an illuminance meter, which may be implemented by, for example, a photoelectric conversion element such as a photodiode. However, the brightness sensor in the present embodiment may be any sensor that detects the brightness of the surroundings of the display apparatus 100, and may be implemented by an element other than a photodiode. The brightness sensor is provided, for example, on a front side of the display apparatus 100 (side where the display 150 can be viewed). However, the brightness sensor may be provided at another location on the display apparatus 100. Alternatively, the brightness sensor may be provided externally to the display apparatus 100, and the surrounding environmental data processor 120 may acquire sensor values by communicating with the brightness sensor. The surrounding environmental data processor 120 may also determine the surrounding environmental light condition based on information from an image sensor (camera) that can determine saturation and hue in addition to brightness (lightness). The image sensor herein may be provided in the display apparatus 100, or may be an external camera provided externally to the display apparatus 100. For example, the display apparatus 100 may acquire information from the external camera via a network (in a narrow sense, a home LAN). Sensors provided externally to the display apparatus 100 may include a motion sensor. That is, various modifications can be made to the specific form of the present embodiment.
The surrounding environmental data processor 120 determines, for example, a parameter representing the brightness by performing a process for comparing the sensor value with predetermined threshold values, and a process for outputting the parameter as the surrounding environmental light condition to the backlight illumination ratio determiner 130. The surrounding environmental light condition is not limited to such brightness information, but may also include other information related to the surrounding environmental light, such as color temperature. The details of the processes will be described below using some drawings including
Based on the input signals and the surrounding environmental light condition, the backlight illumination ratio determiner 130 performs a process for determining the illumination ratio of a backlight of the display 150 for each of a plurality of areas set on the display 150. For example, the display apparatus 100 according to the present embodiment is capable of performing so-called local dimming, in which the backlight of the display 150 is divided into a plurality of areas and the brightness of the backlight is controlled on an area-by-area basis. The backlight illumination ratio determiner 130 determines the illumination ratio of the backlight for each area in the local dimming based on the surrounding environmental light condition. The details of processes to be performed by the backlight illumination ratio determiner 130 will be described below.
The display controller 140 performs control to cause the display 150 to display an input image by illuminating the backlight of the display 150 based on the illumination ratio determined by the backlight illumination ratio determiner 130.
The surrounding environmental data processor 120, the backlight illumination ratio determiner 130, and the display controller 140 of the present embodiment may be implemented by a processor. As this processor, various processors are usable, such as a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The processor may include hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).
The display 150 displays images. The display 150 is, for example, a liquid-crystal display. However, the display 150 of the present embodiment may be any other type of display having a backlight.
The display apparatus 100 may also include memory and an operation interface not shown in
The video tone determiner 160 performs a process for correcting the signal values (tone values) of the input signals based on the illumination ratio determined by the backlight illumination ratio determiner 130. For example, the video tone determiner 160 may determine the corrected signal values based on Equation (1) shown below.
Corrected signal value=(signal value of input signal)/(illumination ratio of backlight) (1)
The signal values of the input signals herein refer to, for example, the luminance values of respective pixels of the input image. In a case where the signal values are 8-bit data, the signal values are between 0 and 255. The illumination ratio of the backlight refers to a numerical value that represents the degree of illumination of the backlight. For example, the illumination ratio of the backlight is a numerical value of greater than or equal to 0 and less than or equal to 1 (greater than or equal to 0% and less than or equal to 100%) that represents a ratio of an actual luminous intensity to the maximum luminous intensity (for example, a numerical value expressed in units of cd/m2) that the backlight can output. In the present embodiment, the local dimming is performed in which the illumination ratio is determined for each of the plurality of areas. Accordingly, the signal value of each pixel is corrected based on the illumination ratio of the area to which the pixel belongs.
In the example using Equation (1) above, the signal value is not changed if the illumination ratio of the backlight is maximum (illumination ratio=100%), and is corrected in such a manner that the signal value increases with a decrease in the illumination ratio. However, because of light leakage that can occur in a configuration in which a liquid-crystal panel is used as the display 150, increasing the illumination ratio of the backlight makes a screen appear brighter. Conversely, decreasing the illumination ratio of the backlight increases the signal value of the input signal and contributes to opening a liquid-crystal shutter, allowing more light leakage from the backlight, but contributes to dimming the backlight, making the screen appear darker. Consequently, even after the correction has been made by the video tone determiner 160, areas with a higher illumination ratio of the backlight are displayed brighter and areas with a low illumination ratio of the backlight are displayed darker.
The luminance stretcher 170 performs a correction process on the illumination ratio determined by the backlight illumination ratio determiner 130. For example, the luminance stretcher 170 of the present embodiment can perform the same control as in the aforementioned known method, in which the Max luminance is controlled based on the brightness of the surroundings.
As shown in
In Step S102, the surrounding environmental data processor 120 obtains a sensor value from the brightness sensor. For example, the brightness sensor detects light around the display apparatus 100 and outputs the detection result as a sensor value to the surrounding environmental data processor 120.
In Step S103, the surrounding environmental data processor 120 determines the surrounding environmental light condition based on the sensor value.
For example, threshold values may be prestored in the memory of the display apparatus 100. The threshold values herein are for use in comparison with the sensor value from the brightness sensor. In the example shown in
The surrounding environmental data processor 120 determines the parameter that represents the surrounding environmental light condition based on the comparison between the sensor value and the threshold values. For example, the surrounding environmental data processor 120 determines the parameter to be P0 if the sensor value is less than TH1. The surrounding environmental data processor 120 determines the parameter to be P1 if the sensor value is greater than or equal to TH1 and less than TH2. Likewise, the surrounding environmental data processor 120 determines the parameter to be P2 if the sensor value is greater than or equal to TH2 and less than TH3, determines the parameter to be P3 if the sensor value is greater than or equal to TH3 and less than TH4, and determines the parameter to be P4 if the sensor value is greater than or equal to TH4. The example in which the parameter is set in discrete levels has been described so far. However, the parameter may be continuous values. For example, the surrounding environmental data processor 120 may determine the parameter based on the sensor value and a prestored continuous function that associates the sensor value and the parameter. For example, the sensor value and the parameter may have a linear relationship, as indicated by a dashed line in
Next, the backlight illumination ratio determiner 130 determines the illumination ratio of the backlight for each of the plurality of areas based on the input signals and the surrounding environmental light condition. For example, the backlight illumination ratio determiner 130 may determine, based on the surrounding environmental light condition, association information indicating the association between the signal values of the input signals and the illumination ratio. The backlight illumination ratio determiner 130 then determines the illumination ratio of the backlight for each of the plurality of areas based on the determined association information and the input signals of the area. In this way, the illumination ratio can be appropriately determined based on the surrounding environmental light condition and the input signals. The following describes detailed processes.
First, in Step S104, the backlight illumination ratio determiner 130 determines a backlight gamma (also referred to below as a BL gamma) based on the surrounding environmental light condition. The BL gamma is a function that determines the relationship between an input illumination ratio and an output illumination ratio. Specifically, the BL gamma may be a gamma curve given by “output illumination ratio=(input illumination ratio) γ”. The input illumination ratio is an illumination ratio of the backlight determined based on the signal values of the input signals for each area in the local dimming. That is, the BL gamma is information that associates the signal values of the input signals with the output illumination ratio, and is therefore included in the association information according to the present embodiment. However, the association information in the present embodiment is not limited to gamma curves, and may be other information that defines the association between the input signals and the illumination ratio.
In Step S105, for each of the plurality of areas, the backlight illumination ratio determiner 130 determines the input illumination ratio based on the signal values of the input signals, and determines the output illumination ratio based on the input illumination ratio and the BL gamma determined in Step S104. For example, the backlight illumination ratio determiner 130 may calculate a maximum value and an average value of the signal values (luminance values) of multiple pixels included in an area of interest and determine an area signal value based on Equation (2) shown below. In Equation (2), a is a variable of greater than or equal to 0 and less than or equal to 1.
Area signal value=α×maximum value+(1−α)×average value (2)
For example, in a case where the signal value of each pixel is greater than or equal to 0 and less than or equal to 255, the area signal value is also greater than or equal to 0 and less than or equal to 255. The backlight illumination ratio determiner 130 determines the input illumination ratio based on the area signal value. For example, the area signal value and the input illumination ratio may have a linear relationship as represented by Equation (3) shown below. However, the specific relationship therebetween is not limited to Equation (3) as long as the input illumination ratio increases with an increase in the area signal value.
Input illumination ratio=(area signal value/255)×100(%) (3)
As mentioned above, the BL gamma is information that defines the relationship between the input illumination ratio and the output illumination ratio. Once the input illumination ratio is determined for each area, the output illumination ratio is determined for each area based on the input illumination ratio and the BL gamma. Since the BL gamma is determined depending on the surrounding environmental light condition in the present embodiment, the output illumination ratio is a value that takes into account the input signal and the surrounding environmental light condition.
The following describes the processes in Steps S104 and S105 in detail using a specific example.
In the BL gammas, as can be appreciated from the example shown in
The backlight illumination ratio determiner 130 may set the illumination ratio to a higher value for areas corresponding to an intermediate tone range, which includes input signals having a signal value of greater than a second signal threshold value and less than the first signal threshold value, in a case where the surroundings of the display apparatus 100 are determined to be bright based on the surrounding environmental light condition than in a case where the surroundings of the display apparatus 100 are determined to be dark. For example, in a case where gamma curves are used to associate the signal value (input illumination ratio) and the illumination ratio (output illumination ratio), the brighter the surroundings of the display apparatus 100 are, the smaller the value of γ is set. The intermediate tone range may be, for example, a range excluding input signals having the minimum and maximum values. In this case, the first signal threshold value is, for example, 255, and the second signal threshold value is, for example, 0. However, the signal threshold values are not limited as such, and the intermediate tone range may be narrower.
For example, three gamma curves are set as shown in
According to the method of the present embodiment, the illumination ratio can be set to a value close to 100% for areas where the signal value is larger, i.e., areas desired to be displayed brighter, thus ensuring the brightness of such areas. Furthermore, with respect to the intermediate tone range, the illumination ratio of the backlight is adjusted depending on the brightness of the surroundings of the display apparatus 100, making it possible to display video suitable for the surrounding environment. For example, in a case where the surroundings of the display apparatus 100 are bright, the BL gamma curve having a smaller value of γ is used, resulting in a higher illumination ratio even in areas corresponding to the intermediate tone range than in a case where the surroundings of the display apparatus 100 are dark. As a result, the representation quality in a darker portion of the input image is improved. In a case where the surroundings of the display apparatus 100 are dark, the illumination ratio corresponding to the intermediate tone range is lower than in a case where the surroundings of the display apparatus 100 are bright, allowing reduction of black blooming. Furthermore, the illumination ratio corresponding to the high tone range is maintained at a high value even in a case where the surroundings of the display apparatus 100 are dark, preventing a decrease in the representation quality in a brighter portion of the input image.
Returning to
In Step S107, the luminance stretcher 170 performs a luminance stretching process.
For example, a plurality of characteristic curves may be stored in the memory of the display apparatus 100. In this case, the luminance stretcher 170 selects one of the characteristic curves based on various information, and determines the maximum illumination ratio of the backlight based on the selected characteristic curve and the APL of one frame of input image. The luminance stretcher 170 may select a characteristic curve using the setting value of the brightness, which is one of user-configurable setting items of the display apparatus 100, or using the surrounding environmental light condition.
For example, in a case where a characteristic curve S-1 in
In Step S108, the display controller 140 performs control to cause the display 150 to display the input image by controlling the display 150 based on the signal value determined in Step S106 and the illumination ratio determined in Step S107.
The following describes the method according to the present embodiment using specific examples of the signal value and the illumination ratio.
If the display apparatus 100 is determined to be in a dark room based on the surrounding environmental light condition, for example, the BL gamma curve G-3 in
According to a method in which the characteristic curves for luminance stretching are changed depending on the brightness of the surroundings, such as the aforementioned known method, the maximum illumination ratio of the backlight is adjusted. Reducing the brightness of areas corresponding to the intermediate tone range for black blooming reduction can therefore lead to a reduction in the illumination ratio corresponding to the high tone range. In other words, according to such a conventional method, the relative relationship between the illumination ratio corresponding to the high tone range and the illumination ratio corresponding to the intermediate tone range is invariable regardless of the brightness of the surroundings of the apparatus (for example, the BL gamma curve to use is fixed to one of G-1 to G-3), and it may not be easy to flexibly adjust the relative relationship. In this regard, according to the method of the present embodiment described above, it is possible to adjust the illumination ratio corresponding to the intermediate tone range depending on the brightness of the surroundings while maintaining the illumination ratio corresponding to the high tone range, and thus it is possible to flexibly change the relative relationship therebetween depending on the surrounding environmental light condition.
It should be noted that even in the method of the present embodiment, the processing by the luminance stretcher 170 may be performed as shown in
Some or all of the processes to be performed by the display apparatus 100 according to the present embodiment may be implemented using a program. The processes to be performed by the display apparatus 100 may be, for example, processes to be performed by the processor of the display apparatus 100, or in a narrow sense, processes to be performed by the surrounding environmental data processor 120, the backlight illumination ratio determiner 130, and the display controller 140.
The program according to the present embodiment may be stored in, for example, a non-transitory computer-readable information storage medium (information storage device). The information storage medium may be implemented by, for example, an optical disk, a memory card, an HDD, or semiconductor memory. The semiconductor memory is, for example, ROM. The display apparatus 100 performs the various processes according to the present embodiment based on the program stored in the information storage medium. That is, the information storage medium stores therein a program for causing a computer to function as the components of the display apparatus 100. The computer refers to a device including an inputter, a processor, a storage, and an outputter. Specifically, the program according to the present embodiment causes the computer to execute the steps described above with reference to some drawings including
Specifically, the program causes the computer to function as the surrounding environmental data processor 120 that determines the surrounding environmental light condition including information representing the brightness of the surroundings based on the sensor value from the brightness sensor, the backlight illumination ratio determiner 130 that determines the illumination ratio of the backlight of the display 150 for each of a plurality of areas set on the display 150 based on input signals corresponding to an input image and the surrounding environmental light condition, and the display controller 140 that causes the display 150 to display the input image by illuminating the backlight of the display 150 based on the illumination ratio. As described above, the backlight illumination ratio determiner 130 determines the illumination ratio so that areas corresponding to the high tone range, which includes input signals having a signal value of greater than or equal to the first signal threshold value, are assigned an illumination ratio of greater than or equal to the illumination ratio threshold value. The program may also cause the computer to function as the video tone determiner 160 and the luminance stretcher 170.
Furthermore, the method of the present embodiment may be applied to a display control method. The display control method includes: receiving input signals corresponding to an input image; determining the surrounding environmental light condition based on data representing the brightness of the surroundings of the display apparatus; determining the illumination ratio of the backlight of the display 150 for each of a plurality of areas set on the display 150 based on the input signals and the surrounding environmental light condition; and causing the display 150 to display the input image by illuminating the backlight of the display 150 based on the illumination ratio. In the determining the illumination ratio of the backlight, the illumination ratio is determined so that areas corresponding to the high tone range, which includes input signals having a signal value of greater than or equal to the first signal threshold value, are assigned an illumination ratio of greater than or equal to the illumination ratio threshold value.
The following describes some modification examples.
The surrounding environmental data processor 120 may perform a process for reducing fluctuations in the surrounding environmental light condition.
In the example shown in
The surrounding environmental data processor 120 may therefore correct use cases determined based on the sensor value by applying a debouncing filter to the use cases. For example, “Use Case A” in
The surrounding environmental data processor 120 may also change the process for determining the environmental light condition, based on the genre of the input image. For example, the surrounding environmental data processor 120 may change the process to be performed based on the sensor value from the brightness sensor. The genre of the input image may be obtained by the receiver 110 as information accompanying the input signals, may be inputted by a user, or may be determined through image processing on the input signals. This configuration makes it possible to display video by taking into account the genre of the input signals as well as the surrounding environmental light condition.
For example, in a case where the genre of the input image is movies, users tend to prefer darker video to be displayed. In a case where the genre of the input image is sports, users tend to prefer brighter video to be displayed, so that it is easier for the users to see fast or vigorous actions of players. For example, the memory of the display apparatus 100 may store therein information indicating the association between the genre of the input image and preferred video. Based on such information and the genre of the input image, the surrounding environmental data processor 120 changes the process for determining the surrounding environmental light condition.
For example, upon determining that the genre of the input image is movies or any other genre that suggests a preference for darker video, the surrounding environmental data processor 120 may determine the parameter based on the relationship shown in
For another example, upon determining that the genre of the input image is sports or any other genre that suggests a preference for brighter video, the surrounding environmental data processor 120 may determine the parameter based on the relationship shown in
For another example, upon determining that the genre of the input image is one that suggests a preference for video with intermediate brightness, the surrounding environmental data processor 120 may determine the parameter based on the relationship shown in
The surrounding environmental data processor 120 may consider the source of the input signals to change the process for determining the surrounding environmental light condition to be performed based on the sensor value. The source of the input signals is an object from which the receiver 110 acquires the input signals. Examples thereof include a facility that transmits broadcast waves for television broadcast (for example, a broadcast tower), a BD player, and a gaming device.
In a case where the input signals are supplied from a gaming device, for example, a game screen is to be displayed. It is therefore highly probable that the user prefers brighter video to be displayed. In this case, therefore, the surrounding environmental data processor 120 determines the parameter based on the relationship shown in
For another example, the receiver 110 may additionally receive information about the video frame rate when obtaining the input signals. In this case, the surrounding environmental data processor 120 may acquire such frame rate information and perform the process for determining the surrounding environmental light condition based on the acquired frame rate. For example, in a case where the frame rate is 24 fps, it is highly probable that the input signals correspond to a movie. This suggests a preference for darker video, and thus the surrounding environmental data processor 120 may determine the parameter based on the relationship shown in
The surrounding environmental data processor 120 may consider an image quality setting in the display apparatus 100 to change the process for determining the surrounding environmental light condition to be performed based on the sensor value. Examples of possible image quality settings include “standard” and “dynamic” for displaying vivid video. Furthermore, settings suitable for the genre and the source of the input signals may be available as items of the image quality settings. Examples of such image quality settings include “movies”, “sports”, and “games”.
In the case of the image quality setting “standard”, the surrounding environmental data processor 120 determines the parameter based on the relationships shown in
With respect to the settings such as “movies”, for example, the surrounding environmental data processor 120 may perform the process in the same manner as in the examples in which the genre or the source of the input signals is considered. For example, the surrounding environmental data processor 120 determines the parameter based on the relationship shown in
As described above, considering information such as the genre, the source of the input signals, or the image quality setting in addition to the surrounding environmental light condition makes it possible to display video that is more preferable for the user on the display 150.
As described above with reference to
For example, the luminance stretcher 170 may consider the setting value of the brightness determined through a user's operation to perform the correction process on the illumination ratio determined by the backlight illumination ratio determiner 130. For example, setting items of the display apparatus 100 include “brightness setting”, and the user enters a setting value of this setting item. In this example, the setting value may be a specific numerical value such as 0 to 100, or may be one of discrete levels such as bright, standard, or dark. The luminance stretcher 170 determines the characteristic curves shown in
The luminance stretcher 170 may consider the surrounding environmental light condition to perform the correction process on the illumination ratio determined by the backlight illumination ratio determiner 130. For example, the luminance stretcher 170 determines the characteristic curves shown in
In a configuration in which the luminance stretcher 170 performs the correction process as described above, the backlight illumination ratio determiner 130 may determine the output illumination ratio by considering what is done in the correction process. Specifically, the backlight illumination ratio determiner 130 may determine the BL gamma based on the settings of the luminance stretcher 170.
If the setting value of the brightness is greater than the threshold value (No in Step S201), the luminance stretcher 170 determines whether or not a brightness sensor linkage setting is on. The brightness sensor linkage setting represents a setting for causing the luminance stretcher 170 to perform the correction process depending on the sensor value from the brightness sensor (surrounding environmental light condition). That is, the luminance stretcher 170 performs the correction process depending on the surrounding environmental light condition if the brightness sensor linkage setting is on, and does not if the brightness sensor linkage setting is off. It should be noted that the term on/off herein can be rephrased as active/inactive.
If the setting value of the brightness is less than or equal to the threshold value (Yes in Step S201) or the brightness sensor linkage setting is on (Yes in Step S202), the backlight illumination ratio determiner 130 determines whether or not the use case corresponds to a dark room based on the surrounding environmental light condition in Step S203. In the example shown in
Upon determining that the use case corresponds to a dark room (Yes in Step S203), the backlight illumination ratio determiner 130 adjusts the BL gamma. Specifically, the backlight illumination ratio determiner 130 adjusts the BL gamma so that the output illumination ratio corresponding to at least a portion of the intermediate tone range is higher in accordance with the adjusted gamma than in accordance with the BL gamma corresponding to the dark room case (parameter=P0). For example, the backlight illumination ratio determiner 130 may perform a process for decreasing the value of γ in Step S204. For example, if the BL gamma corresponding to P0 is linear (γ=1), the BL gamma is corrected to an upward convex shape through the process in Step S204. Alternatively, the backlight illumination ratio determiner 130 may perform a process for selecting a BL gamma corresponding to any of P1 to P4 (in a narrow sense, the BL gamma corresponding to P1) even if the parameter is P0.
If the setting value of the brightness is greater than the threshold value (No in Step S201) and the brightness sensor linkage setting is off (No in Step S202), the backlight illumination ratio determiner 130 determines the BL gamma depending on the surrounding environmental light condition (parameter) in Step S205.
As described above, the backlight illumination ratio determiner 130 may set the illumination ratio to a higher value for areas where the input signals have a signal value of less than the first signal threshold value in a case where the setting value of the brightness, which is used in the luminance stretcher 170, is less than or equal to the predetermined threshold value (Yes in Step S201, S204) than in a case where the setting value of the brightness is greater than the predetermined threshold value (No in Step S201, S205). In a case where the setting value of the brightness is less than or equal to the threshold value, the luminance stretching process works to set the maximum illumination ratio of the backlight to a lower value, which may result in displaying darker video. In this regard, according to the method of the present embodiment, the BL gamma is adjusted so as to increase the illumination ratio corresponding to the intermediate tone range. As a result, the representation quality in a darker portion of the input image can be improved.
Similarly, the backlight illumination ratio determiner 130 may set the illumination ratio to a higher value for areas where the input signals have a signal value of less than the first signal threshold value in a case where the correction process in the luminance stretcher 170 based on the surrounding environmental light condition is active (Yes in Step S202, S204) than in a case where the correction process is inactive (No in Step S202, S205). In a case where the brightness sensor linkage setting is on, the luminance stretching process for the use case corresponding to a dark room works to set the maximum illumination ratio of the backlight to a lower value, which results in displaying darker video. In this regard, according to the method of the present embodiment, the BL gamma is adjusted so as to increase the illumination ratio corresponding to the intermediate tone range. As a result, the representation quality in a darker portion of the input image can be improved.
The backlight illumination ratio determiner 130 may acquire the brightness of the surroundings and information representing the color temperature of surrounding environmental light as the surrounding environmental light condition. For example, in addition to the illuminance meter (photodiode, for example) that detects the brightness, the display apparatus 100 may include an RGB sensor that detects light in different wavelength bands corresponding to RGB. The RGB sensor herein may be an image sensor included in a camera. The surrounding environmental data processor 120 determines the color temperature based on an output form the RGB sensor and outputs the determination result to the backlight illumination ratio determiner 130 as the surrounding environmental light condition. It should be noted that a known method is employed for determining the color temperature based on the output from the RGB sensor, and therefore detailed description thereof is omitted. The backlight illumination ratio determiner 130 according to the present embodiment may determine the illumination ratio of the backlight based on the brightness and the color temperature.
For example, warm-color lighting is likely to be used in a home theater, while cool-color lighting is likely to be used in a living room. Thus, if the surrounding environmental light is determined to be resulting from warm-color lighting based on the color temperature, the display apparatus 100 can be presumed to be located in a home theater. In this case, it is highly probable that darker video is preferred because a movie is displayed on the display apparatus 100. If the surrounding environmental light is determined to be resulting from cool-color lighting based on the color temperature, the display apparatus 100 can be presumed to be located in a living room. In this case, it is highly probable that brighter video is preferred compared to the case of a home theater. Considering the color temperature therefore allows for control of the backlight in a way that suits the environment in which the display apparatus 100 is placed.
Cool-color lighting is more likely to seem brighter to the user's eyes than warm-color lighting even at the same luminous intensity. Considering the color temperature therefore allows for control of the backlight in a way that suits the brightness as perceived subjectively by the user even if the detection result from the illuminance meter is the same. For example, in the case of a room with cool-color lighting, the representation quality in a darker portion of the input image can be improved by displaying relatively bright video. In the case of a room with warm-color lighting, black blooming can be reduced by displaying relatively dark video.
For example, the backlight illumination ratio determiner 130 may first determine a BL gamma based on the brightness, and then correct the BL gamma based on the color temperature. Specifically, in the case of a lower color temperature (in the case of warm-color lighting), the backlight illumination ratio determiner 130 performs a correction process for increasing the value of γ determined based on the brightness. In the case of a higher color temperature (in the case of cool-color lighting), the backlight illumination ratio determiner 130 performs a correction process for decreasing the value of γ determined based on the brightness.
However, the processing with the use of the brightness and the color temperature is not limited as such. For example, the surrounding environmental data processor 120 may pre-set a function f having both the brightness and the color temperature as variables, and perform a process for determining the surrounding environmental light condition (parameter) based on the function f. Various other modifications may be made to the processing based on the color temperature.
The backlight illumination ratio determiner 130 may determine the illumination ratio of the backlight based on the input signals, the surrounding environmental light condition, and information representing time of day in which the display apparatus 100 is used. This configuration allows for control of the backlight that takes into account the characteristics of the time of day in which the display apparatus 100 is used.
In the example shown in
The following discusses, for example, a configuration in which the brightness sensor is provided on the front side of the display apparatus 100 and a window is provided on the back side of the display apparatus 100. In this case, the user viewing the display 150 of the display apparatus 100 can recognize outside light (referred to below as “outdoor light”) through the window because the window at the back is in view. During daytime hours (for example, from the 9 o'clock hour to the 15 o'clock hour), the outdoor light is stronger, and consequently the surroundings of the display apparatus 100 seem brighter to the user. As a result, the viewability may decrease unless brighter video is displayed. However, in the configuration in which the brightness sensor is located on the front side, the outdoor light may not adequately reach the brightness sensor. In this case, the sensor value from the brightness sensor can fail to reflect the actual brightness of the surroundings of the display apparatus 100, which seem bright to the user, providing information mainly corresponding to indoor light.
In this regard, as long as the information shown in
The outdoor brightness varies depending on the weather. For example, even during the same daytime hours, the influence of sunlight is greater on sunny days than cloudy or rainy days. Accordingly, the backlight illumination ratio determiner 130 may adjust the BL gamma based on weather information in addition to the information representing time of day. For example, the backlight illumination ratio determiner 130 may set the weighting of change to a higher value in a case where the weather is determined to be sunny than in a case where the weather is determined to be cloudy or rainy. The weather information may be obtained from the Internet or other sources via a communication interface (receiver) or based on data broadcasting included in broadcast waves.
Furthermore, according to the present embodiment, the illumination ratio of the backlight may be controlled depending on the user's daily rhythm (biological clock). For example, the backlight illumination ratio determiner 130 sets the illumination ratio of the backlight to a higher value in a case where the time of day in which the display apparatus 100 is used corresponds to the user's wake-up time than in a case where the time of day in which the display apparatus 100 is used corresponds to the user's bedtime. The wake-up time herein may be a specific wake-up clock time or a certain length of period of time. The same is true for the bedtime. The wake-up time and the bedtime may be settable on a user-by-user basis.
For example, the backlight illumination ratio determiner 130 may set a magnification factor to be applied to the BL gamma to a relatively high value for a time of day corresponding to the wake-up time and to a relatively low value for a time of day corresponding to the bedtime. This configuration makes it possible to display brighter video at or during the wake-up time to encourage the user to wake up smoothly. This configuration also makes it possible to display darker video at or during the bedtime to avoid interfering with the user's ability to fall asleep.
As described above, the backlight illumination ratio determiner 130 may perform a process for determining a signal value of the input signals for each of the plurality of areas based on the maximum value and the average value of the input signals in the area. For example, the backlight illumination ratio determiner 130 determines the area signal value based on Equation (2) shown again below.
Area signal value=α×maximum value+(1−α)×average value (2)
In this example, the backlight illumination ratio determiner 130 may determine the illumination ratio of the backlight based on the relationship between the priority of the maximum value and the priority of the average value in the process for determining the signal value. The priority herein is, for example, the contribution of the maximum value and the contribution of the average value to the signal value to be determined, and may be information to be determined using a in Equation (2) shown above. For example, the priority of the maximum value is a, and the priority of the average value is 1−α.
For example, the backlight illumination ratio determiner 130 may perform a process for setting the illumination ratio corresponding to the intermediate tone range to a lower value in a case where the priority of the maximum value is greater than or equal to a predetermined threshold value than in a case where the priority of the maximum value is less than this threshold value. For example, the backlight illumination ratio determiner 130 selects a linear BL gamma regardless of the surrounding environmental light condition if the priority of the maximum value is greater than or equal to the threshold value, and selects a BL gamma out of BL gammas that are determined depending on the surrounding environmental light condition if the priority of the maximum value is less than the threshold value.
For example, the following discusses an example in which low-luminance pixels account for a large portion of an area of interest in the local dimming and the area has only one pixel having a high luminance value. In this case, the maximum value is large and the average value is sufficiently small in comparison. In this example, giving high priority to the maximum value results in a large area signal value and a high input illumination ratio, and consequently tends to result in a high output illumination ratio. In this case, the portion with a large signal value is properly displayed, but black blooming can occur in the other portion, which is a darker portion, due to the high illumination ratio of the backlight. In this regard, according to the method of the present embodiment, the output illumination ratio corresponding to the intermediate tone range is adjusted to a lower value (the value of γ of the BL gamma is set to a larger value) in a situation where the maximum value takes priority, so that black blooming can be reduced.
So far, the BL gammas have been described as a specific example of the association information indicating the association between the signal value and the illumination ratio, and a linear shape (G-1 in
The association information shown in
Consequently, in a case where the surroundings of the display apparatus 100 are dark, a brighter portion is more illuminated to be more viewable while a darker portion is prevented from causing black blooming, thus allowing for an improvement in contrast.
As described above, the association information (BL gamma) is determined based on the surrounding environmental light condition and is information that is applied to the entirety of a single input image. For example, the backlight illumination ratio determiner 130 determines the output illumination ratio for each area by selecting one of G-1 to G-3 in
For example, the backlight illumination ratio determiner 130 may perform a process for determining area association information in addition to the process for determining the association information common to the plurality of areas based on the surrounding environmental light condition. The association information is as described above. The area association information refers to information that indicates the association between the signal value of the input signals and the illumination ratio in each of the plurality of areas, and is determined for each individual area.
For example, the backlight illumination ratio determiner 130 may determine the area association information for an area of interest based on the signal value of the area among the input signals. For example, the backlight illumination ratio determiner 130 may determine the area association information based on the signal value acquired at a single point in time or based on time-series signal values acquired in different points in time. For example, the backlight illumination ratio determiner 130 determines the area signal value based on Equation (2) and determines the area association information based on the area signal value acquired at a single point in time or the time-series area signal values. For example, the backlight illumination ratio determiner 130 determines the area association information so that the output illumination ratio corresponding to the intermediate tone range is higher (the value of γ is smaller) in a case where the area signal value is large than in a case where the area signal value is small.
The backlight illumination ratio determiner 130 then determines the output illumination ratio for each of the plurality of areas based on the second association information and the signal value of the area. This configuration makes it possible to determine the output illumination ratio based on a plurality of pieces of association information obtained from different perspectives.
In the configuration in which the association information is obtained for each area, however, illumination ratio differences may occur at boundaries between areas, which can give the user a feeling of strangeness. The backlight illumination ratio determiner 130 may therefore obtain the second association information by applying a spatial filter as shown in
Although the present embodiment has been described above in detail, those skilled in the art will easily understand that a number of modifications can be made within a range not substantially departing from the novelties and effects of the present embodiment. Therefore, all such modifications are included in the scope of the present disclosure. For example, a term described in the specification or drawings at least once together with a term having a broader meaning or the same meaning may be replaced with the different term anywhere in the specification or drawings. All combinations of the present embodiment and modifications are also included in the scope of the present disclosure. The configuration, operation, and the like, of the display apparatus are also not limited to those described in the present embodiment, and various modifications can be made thereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-183765 | Nov 2022 | JP | national |
