JP5828648B2 - Display control apparatus and display control method - Google Patents

Description

  The present invention relates to a display control device and a display control method.

  In recent years, with the spread of car navigation, it has become common for automobiles to be equipped with in-vehicle devices having a liquid crystal display panel.

  Liquid crystal display panels display images by partially blocking or transmitting light emitted from the backlight, but the high power consumption by the backlight hinders power saving. Yes.

  Therefore, in recent years, various attempts have been made to reduce power consumption by the backlight. For example, Patent Document 1 discloses a technique for reducing the power consumption of a backlight by controlling the light emission amount of the backlight according to the luminance of the video.

  In the technique described in Patent Document 1, a luminance distribution of pixels included in an image is created, and using this luminance distribution, the cumulative number of pixels is counted from the high luminance side, and the luminance value at a position where the predetermined number of pixels is reached. Based on the above, the luminance of the video is increased and the light emission amount of the backlight is reduced. Thereby, the power consumption by the backlight is reduced.

JP 2007-219477 A

  However, for example, in an in-vehicle device such as a car navigation, an image having a tendency of different distributions of luminance and color of pixels constituting the image is selectively displayed on the display device. For example, distribution trends such as brightness and color of pixels differ between a video such as a movie recorded on a DVD (Digital Versatile Disc) or the like and a navigation video.

  Therefore, for example, if the power consumption of the backlight is effectively reduced with respect to the DVD video, the power consumption of the backlight may not be effectively reduced with respect to the navigation video.

  The present invention has been made in view of the above, and an object thereof is to provide a display control device and a display control method capable of appropriately reducing the power consumption of a backlight.

  In order to solve the above-described problems and achieve the object, the display control device according to the present invention controls the light emission amount of the backlight that irradiates the display panel with light according to the luminance of the image, and the light emission of the backlight. A display control apparatus that displays the video with the luminance corrected according to the amount on the display panel, a storage unit that stores a plurality of control parameters in association with video types, and a video that is displayed on the display panel And a determining unit that reads out a control parameter corresponding to the type of the backlight from the storage unit and determines a light emission amount of the backlight corresponding to the luminance of the video according to the read control parameter.

  In the display control method of the present invention, the amount of light emitted from the backlight that irradiates the display panel with light is controlled according to the luminance of the image, and the image with the luminance corrected according to the amount of light emitted from the backlight is displayed. A display control method for displaying on a panel, the step of reading a control parameter according to the type of video to be displayed on the display panel from a storage unit that stores a plurality of control parameters in association with the type of video, And a step of determining a light emission amount of the backlight according to the luminance of the video according to the read control parameter.

  According to the present invention, since the amount of backlight emission according to the brightness of the video is determined by the control parameter according to the type, it is possible to appropriately reduce the power consumption of the backlight according to the type. .

FIG. 1 is a diagram showing an overview of a display control method according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the configuration of the display system including the display control apparatus according to the embodiment. FIG. 3 is a block diagram illustrating the configuration of the display control apparatus according to the embodiment. FIG. 4 is a diagram illustrating an example of the control parameter table. FIG. 5 is a diagram illustrating application timing of control parameters. FIG. 6 is a block diagram illustrating the configuration of the light emission amount determination unit according to the embodiment. FIG. 7 is a diagram illustrating an operation example of the light emission amount determination unit. FIG. 8 is a diagram illustrating an example of RGB conversion information. FIG. 9 is a flowchart illustrating the processing procedure of the display control apparatus according to the embodiment.

  Exemplary embodiments of a display control device and a display control method according to embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  First, prior to detailed description of examples, an outline of a display control method according to an embodiment of the present invention will be described. FIG. 1 is a diagram showing an overview of a display control method according to an embodiment of the present invention.

  The display control method according to the present embodiment controls the light emission amount of the backlight and the luminance correction amount of the video based on the video information acquired from the video source and the source type. In the following, an example in which the video type is determined based on the video source type is shown, but the video type may be determined by other methods.

  In such a display control method, as shown in FIG. 1, information indicating the source type of video to be displayed on the display device by the control unit of the display control device (hereinafter referred to as “source type information”) is displayed. Obtain (step S1).

  Here, the video source type is a type of video source that generates video information (hereinafter referred to as “video information”) to be displayed on the display device. In the example illustrated in FIG. 1, the type of the video source that generates the video information is “source type 1”.

  When the display device is a vehicle-mounted display device, examples of the video source include a DVD (Digital Versatile Disc), a navigation video source, a TV (Television), and a camera. For example, the source type of DVD is “source type 1”, the source type of navigation video source is “source type 2”, the source type of TV is “source type 3”, and the source type of camera is “source type 4”. Is assigned.

  The source type information is acquired from the video source, but the acquisition source of the source type information is not limited to this. For example, when there is a video output device that inputs video information from a plurality of sources and outputs video information selected from the video information to the display control device, the control unit of the display control device The video source type may be obtained from the video source. Here, since the video type is determined by the video source type, a video processing circuit or the like is not required, and the video type can be easily determined.

  Next, the control unit of the display control apparatus acquires a control parameter corresponding to the video source type based on the source type information acquired in step S1 (step S2). The storage unit of the display control device stores a plurality of control parameters according to the video source type, and the control unit of the display control device stores the control parameter according to the source type information acquired in step S1. By reading from, control parameters corresponding to the video source type are acquired.

  Since the source type information acquired in step S1 is information indicating “source type 1”, the control unit of the display control apparatus acquires a control parameter corresponding to “source type 1” from the storage unit.

  Next, the control unit of the display control apparatus acquires video information from the video source (step S3). And the control part of a display control apparatus determines the light emission amount of a backlight using the control parameter read by step S2, and correct | amends the brightness | luminance of an image | video (step S4).

  Specifically, the control unit of the display control device determines the luminance of the video based on the luminance of the pixels constituting the video information. Then, the control unit determines the light emission amount of the backlight according to the luminance of the video using the control parameter of “source type 1” read out in step S2.

  The video source of “source type 1” is a DVD, and the video information acquired from the DVD is video information such as a movie. Such videos are often relatively complex and often have a complicated distribution of pixel brightness and color. However, when a small value is determined as the amount of light emitted from the backlight for such an image and correction is performed to greatly increase the luminance of the image, a color collapse phenomenon (hereinafter, referred to as “color loss phenomenon”) occurs in a portion displayed by high luminance pixels. (Described as “halation”), and visibility may be reduced.

  Therefore, the control unit of the display control apparatus acquires a control parameter of “source type 1” for which a large value is determined as the light emission amount of the backlight from the storage unit for the video whose video source is DVD. The light emission amount of the backlight is determined by the control parameter of “source type 1”.

  On the other hand, the video with the video source as the navigation video source is a video with a simple distribution of pixel brightness, color, etc., such as a map video, so even if the number of high-luminance pixels increases, Less likely to cause halation problems.

  That is, in a video having a video source as a navigation video source, there are many areas where pixels of the same color and the same luminance are adjacent to each other, and the color difference between the areas is large, so that the boundary between the areas is clearly distinguished. Therefore, even when the number of high-luminance pixels increases, the problem of halation hardly occurs.

  Therefore, the control unit of the display control apparatus acquires, from the storage unit, a control parameter of “source type 2” in which a small value is determined as the backlight emission amount for the video having the video source as the navigation video source. Then, the light emission amount of the backlight is determined by the control parameter of “source type 2”.

  Therefore, it is possible to appropriately correct the amount of light emitted from the backlight and the luminance of the video having the video source for navigation as the video source.

  The control parameter is a parameter that associates the brightness of the video with the light emission amount of the backlight. For example, for each video luminance, a table in which the backlight emission amount is associated with the video luminance can be used as a control parameter, or a parameter for determining the video luminance can be used as a control parameter.

  Next, the control unit of the display control device causes the backlight of the display device to emit light with the light emission amount of the backlight determined in step S4 (step S5), and corrects the luminance according to the determined light emission amount of the backlight. The information of the video image is output to the display panel (step S6).

  As described above, in the display control method according to the present embodiment, the backlight emission amount is determined and the luminance correction of the video is performed according to the control parameter corresponding to the video source type, so that the power consumption of the backlight is appropriately reduced. be able to.

  Below, the Example about the display control apparatus to which the display control method demonstrated using FIG. 1 is applied is described in detail. In the following embodiment, a case will be described in which the present display control technique is applied to a display control device that controls a vehicle-mounted display device. However, the display control device according to the present invention is not limited to this, and various devices including a display device that performs display using a backlight, such as a portable terminal device, a PC (Personal Computer), or a TV. It can be applied to.

  FIG. 2 is a diagram illustrating a configuration of a display system including the display control apparatus according to the present embodiment. As shown in FIG. 2, the display control device 10 according to the present embodiment is a device that acquires video information from the video information output device 30 and performs display control of the display device 20. Note that the video information output from the video information output device 30 is, for example, video information in the RGB444 format.

  The display device 20 includes a display panel 21 and a backlight 22. The display panel 21 is a display unit such as a liquid crystal display panel that displays video according to video information output from the display control device 10. The backlight 22 is a lighting device provided on the back side of the display panel 21 and irradiates the display panel 21 with light from the back side.

  The video information output device 30 outputs the video information to the display control device 10. The video information output to the display control device 10 is selected by the source selection unit 31. That is, the source selection unit 31 controls the selector 32 to select one video source from a plurality of video sources, and outputs video information output from the selected video source to the display control device 10. The video information output device 30 is provided with an operation unit (not shown), and the source selection unit 31 selects a video source by a user operation on the operation unit.

  Here, the video source includes a navigation video (daytime) source, a navigation video (night) source, a DVD video source, a camera video source, and a TV video source. The navigation video (daytime) is a navigation video for daytime, and the navigation video (night) is a navigation video for night. Information on the navigation video is output from the car navigation device.

  The DVD video is a video such as a movie stored on the DVD, and information on the DVD video is output from the DVD playback device. The camera video is a video of a vehicle-mounted camera that images the periphery of the vehicle, and the TV video is a TV (Television) video output from the digital television broadcast receiver.

  In addition, the source selection unit 31 outputs source type information, which is type information of the selected video source, to the display control device 10. For example, when the source selection unit 31 selects the source of the navigation video (daytime), the source selection unit 31 outputs the source type information indicating that the source type is the source of the navigation video (daytime) to the display control device 10. The source selection unit 31 selects the navigation video (daytime) when the day / night discrimination unit 33 determines that it is daytime, and selects the navigation video (night) when the day / night discrimination unit 33 determines that the day is night.

  The video information output device 30 includes a day / night discrimination unit 33 that discriminates whether the current time zone is daytime or night and outputs day / night information for distinguishing between daytime and night to the display control device 10. Yes. For example, when the illuminance value output from an illuminance sensor (not shown) is a predetermined or higher illuminance value, the day / night determination unit 33 determines that the current time zone is daytime, and the illuminance value is less than the predetermined illuminance value. If there is, it is determined that the current time zone is night. Note that the day / night determination unit 33 can determine that the current time zone is night even if the illuminance value is equal to or greater than a predetermined illuminance value when a headlight such as a headlight is lit. .

  The day / night determination unit 33 determines that the current time zone is night when the headlamp is turned on by a headlight switch (not shown), and if the headlamp is turned off, the current time You may determine that the belt is daytime. In this case, the small light may be turned on when the vehicle is traveling in a place where the surrounding vehicle is relatively bright, such as a short tunnel or dense fog, but the oncoming vehicle is aware of the vehicle or the driver wants to ensure visibility. Then, when the headlamp switch is turned on, the day / night discriminating unit 33 determines that it is night. For example, in the case of a navigation video, the navigation video (daytime) is switched to the navigation video (night). When the surroundings are bright, it may be desirable to maintain the navigation video (daytime) without switching to the navigation video (night) even if the headlight switch is turned on. For that purpose, it is determined whether it is day or night according to the illuminance value and time around the vehicle, and when it is determined that it is daytime, it is determined that it is daytime even if the headlight is lit, and the navigation video ( Switching to night) should be prohibited.

  Next, the configuration of the display control apparatus 10 according to the present embodiment will be described. FIG. 3 is a block diagram illustrating a configuration of the display control apparatus 10 according to the present embodiment. Note that FIG. 3 shows only the components necessary for explaining the characteristics of the display control apparatus 10, and omits descriptions of general components. Further, the display control device 10 can be configured by, for example, an ASIC (Application Specific Integrated Circuit).

  The display control apparatus 10 according to the present embodiment includes a control unit 11 and a storage unit 12. The control unit 11 includes a video information acquisition unit 11a, a source type information acquisition unit 11b, a day / night information acquisition unit 11c, a sub-sampling unit 11d, a histogram generation unit 11e, a light emission amount determination unit 11f, and a light emission amount regulation unit. 11g, a PWM (Pulse Width Modulation) generation unit 11h, and an RGB conversion unit 11i. The storage unit 12 stores a control parameter table 12a and RGB conversion information 12b.

  The control unit 11 performs processing such as acquisition of video information from the video information output device 30, sub-sampling of the acquired video information, generation and analysis of a histogram, emission amount regulation processing, PWM generation, or RGB conversion processing. Part. The video information acquisition unit 11 a is a processing unit that acquires video information from the video information output device 30. The video information acquisition unit 11a also performs a process of passing the acquired video information to the sub-sampling unit 11d and the RGB conversion unit 11i.

  The source type information acquisition unit 11b is a processing unit that acquires source type information from the video information output device 30, and also performs a process of passing the acquired source type information to the light emission amount determination unit 11f. The day / night information acquisition unit 11c is a processing unit that acquires day / night information from the video information output device 30, and also performs a process of passing the acquired day / night information to the light emission amount determination unit 11f.

  The subsampling unit 11d is a processing unit that performs subsampling on the acquired video information when the video information is acquired from the video information acquisition unit 11a. In addition, the sub-sampling unit 11d also performs processing for passing the sub-sampled video information to the histogram generation unit 11e.

  Here, subsampling indicates a process of thinning out pixels from acquired video information. Thus, by performing sub-sampling on the acquired video information, the processing speed of processing units such as a histogram generation unit 11e and a light emission amount determination unit 11f described later can be increased.

  The histogram generation unit 11e is a processing unit that generates a histogram using the video information after sub-sampling acquired from the sub-sampling unit 11d. The histogram is information representing the luminance distribution of the pixels constituting the video information. The histogram generation unit 11e generates a histogram using the component having the largest value among the R, G, and B components included in the video information. The histogram generation unit 11e also performs a process of passing the generated histogram to the light emission amount determination unit 11f.

  The light emission amount determination unit 11f is a processing unit that determines the determined light emission amount of the backlight 22 by analyzing the histogram generated by the histogram generation unit 11e using control parameters.

  The light emission amount determination unit 11f acquires the source type information from the source type information acquisition unit 11b, acquires the day / night information from the day / night information acquisition unit 11c, and stores the control parameters corresponding to the information in the storage unit 12. Is read from the control parameter table 12a. And the histogram produced | generated by the histogram production | generation part 11e is analyzed using the read control parameter. Here, the contents of the control parameter table 12a will be described. FIG. 4 is a diagram illustrating an example of the control parameter table 12a.

  As illustrated in FIG. 4, the control parameter table 12 a is information in which control parameters such as DNUM, H offset, and L offset are associated with each pattern 1 to 4. As the pattern 1 moves from the pattern 1 to the pattern 4, the ratio of giving priority to the power consumption reduction amount increases.

  That is, the control parameter of pattern 1 is the control parameter that gives the highest priority to the image quality of the video, and the control parameter of pattern 4 is the control parameter that gives the highest priority to the power consumption reduction amount. The control parameter of pattern 2 is a control parameter that prioritizes the reduction amount of power consumption over pattern 1, and the control parameter of pattern 3 is a control parameter that prioritizes the reduction amount of power consumption over pattern 2.

  Here, pattern 1 is a pattern selected when the source video is a DVD video, a TV video, or a camera video, and the day / night information is information indicating the daytime. Pattern 2 is a pattern that is selected when the source video is a DVD video or a TV video and the day / night information is information indicating the night.

  Pattern 3 is a pattern that is selected when the source video is a navigation video and the day / night information is information indicating daytime. Pattern 4 is a navigation video and the day / night information is information indicating night. Is the pattern that is selected when Each control parameter (DNUM, H offset, L offset) will be described in detail later.

  DVD video, TV video, and camera video are relatively complex video, and are often video with a complicated distribution of pixel brightness, color, etc., so in order to avoid visibility degradation due to halation, Pattern 1 and pattern 2 having a high degree of priority are assigned.

  On the other hand, navigation video is a video with a simple distribution of pixel brightness, color, etc., so even if the number of high-brightness pixels increases, halation problems are unlikely to occur, so priority is given to reducing power consumption. Pattern 3 and pattern 4 having a high degree of being assigned are assigned.

  Also, the DVD video, TV video, and camera video are output and controlled by the video information output device 30 so that they are darker at night than at daytime. For this reason, the pattern is changed depending on whether it is day or night. For example, in the case of a DVD video or a TV video, pattern 1 is selected at daytime and pattern 2 is selected at night. In the case of a navigation video, the pattern 3 is selected at daytime, and the pattern 4 is selected at night.

  Here, the same pattern is assigned to the DVD video, TV video, and camera video in the daytime, and the same pattern is assigned to the DVD video and TV video in the night time. Different patterns may be assigned to the videos.

  As described above, the storage unit 12 stores the control parameter table 12a in which a plurality of control parameters are associated with the video source type and day / night information, and the light emission amount determination unit 11f stores the video source type and day / night. Select control parameters according to the information.

  In the example shown in FIG. 4, the pattern corresponding to the source type information and the day / night information is selected and the control parameter corresponding to the selected pattern is used. However, the control parameter table 12a is not limited to this. Absent.

  For example, two control parameter tables in which a plurality of control parameters are associated with source types may be provided for daytime and nighttime. In this case, one of a plurality of control parameter tables is selected based on the day / night information, and a control parameter is selected from the selected control parameter table based on the source type information.

  Alternatively, a control parameter corresponding to the source type may be selected only for one of daytime and nighttime. In this case, for example, at night, the same control parameter is used regardless of the source type, and during the day, a control parameter corresponding to the source type is selected from the control parameter table.

  Further, the control parameter may be changed according to the illuminance value output from the illuminance sensor, instead of dividing into day and night. In this case, for example, the control parameter table is stored in the storage unit 12 for each illuminance value within a predetermined range, and the control parameter table is selected according to the illuminance value output from the illuminance sensor. Then, a control parameter corresponding to the source type is selected from the selected control parameter table.

  Returning to FIG. 3, the description of the control unit 11 is continued. The light emission amount determination unit 11f synchronizes the timing at which the selected control parameter is applied to the histogram analysis with VSYNC (Vertical Synchronizing signal). VSYNC is a signal included in video information output from the display control device 10 to the display device 20.

  Here, the timing relationship between the video input to the video information acquisition unit 11a (hereinafter referred to as “input video”), the VSYNC output to the display device 20, and the applied control parameters will be described. FIG. 5 is a diagram illustrating application timing of control parameters.

  In the example illustrated in FIG. 5, the input video input as video information to the video information acquisition unit 11 a is switched from the camera video to the navigation video (daytime). When detecting that the input video is switched from the camera video to the navigation video (daytime), the light emission amount determination unit 11f selects the control parameter of the pattern 3 corresponding to the navigation video (daytime) from the control parameter table 12a. .

  Thereafter, the light emission amount determination unit 11f applies the control parameter of the pattern 3 to the histogram analysis at the timing when the next VSYNC appears. In this way, it is possible to appropriately set the application timing of the control parameter for the input video to be switched. That is, the control parameter can be applied in accordance with frame switching.

  Here, a specific configuration of the light emission amount determination unit 11f will be described. FIG. 6 is a block diagram illustrating a configuration of the light emission amount determination unit 11f according to the present embodiment. As illustrated in FIG. 6, the light emission amount determination unit 11 f includes a provisional light emission amount determination unit 111, a comparison unit 112, and a determined light emission amount determination unit 113.

  The provisional light emission amount determination unit 111 is a processing unit that determines the provisional light emission amount using the histogram and DNUM acquired from the histogram generation unit 11e. DNUM is a control parameter indicating a threshold value for the cumulative number of pixels.

  Specifically, the provisional light emission amount determination unit 111 sequentially counts the number of pixels from the high luminance side of the histogram, and the light emission corresponding to the position (luminance value) on the histogram when the cumulative pixel number exceeds DNUM. The amount is determined as the provisional light emission amount. In addition, when the provisional light emission amount determination unit 111 determines the provisional light emission amount, the provisional light emission amount determination unit 111 also performs a process of passing the determined provisional light emission amount to the comparison unit 112.

  The comparison unit 112 is a processing unit that compares the provisional emission amount determined by the provisional emission amount determination unit 111 with the H offset and the L offset stored in the storage unit 12. The comparison unit 112 also performs a process of passing the comparison result between the temporary light emission amount and the H offset and L offset to the fixed light emission amount determination unit 113. The H offset is a control parameter indicating an upper limit value of the light emission amount of the backlight 22, and the L offset is a control parameter indicating a lower limit value of the light emission amount of the backlight 22.

  Here, an operation example of the light emission amount determination unit 11f will be described. FIG. 7 is a diagram illustrating an operation example of the light emission amount determination unit 11f. 7A illustrates an operation example of the provisional light emission amount determination unit 111, and FIG. 7B illustrates an operation example of the comparison unit 112 and the fixed light emission amount determination unit 113.

  As shown in FIG. 7A, the provisional light emission amount determination unit 111 sets the position of the luminance value “255” in the histogram as the counting start point, and sets the number of pixels corresponding to each luminance value from the counting start point to the low luminance side. Count in order toward. Then, the provisional light emission amount determination unit 111 determines the position where the cumulative number of pixels has reached DNUM as a calculation point, and determines the light emission amount corresponding to the luminance value of the calculation point as the provisional light emission amount.

  For example, the provisional light emission amount determination unit 111 determines “200” as the provisional light emission amount when the luminance value at the position where the cumulative number of pixels has reached DNUM is “200”.

  Further, the comparison unit 112 compares the temporary light emission amount determined by the temporary light emission amount determination unit 111 with the H offset and the L offset, and passes the comparison result to the fixed light emission amount determination unit 113. Then, as shown in FIG. 7B, when the provisional emission amount is equal to or smaller than the H offset, the determined emission amount determination unit 113 determines the provisional emission amount as the fixed emission amount.

  On the other hand, when the provisional emission amount exceeds the H offset, the fixed emission amount determination unit 113 determines the H offset as the decision emission amount, and when the provisional emission amount is less than the L offset, determines the L offset. Determine as quantity.

  Here, for example, when the source type is a video source of DVD video and the day / night information is information indicating daytime, pattern 1 is selected. As shown in FIG. 4, DNUM is “100”, and H offset is “ 215 "and the L offset is" 100 ".

  Therefore, for example, when the luminance value at the position where the cumulative number of pixels reaches DNUM is “220”, the provisional light emission amount is “220”, and thus the fixed light emission amount is “215” with an H offset. Further, for example, when the luminance value at the position where the cumulative number of pixels reaches DNUM is “95”, the provisional light emission amount is “95”, and thus the fixed light emission amount is “100” of the L offset.

  Thus, when the provisional emission amount exceeds the H offset, the H offset, which is an emission amount smaller than the provisional emission amount, is set as the fixed emission amount, so that even if a bright image is input, The amount of power consumption reduction of the light 22 can be increased as much as possible.

  Further, when the L offset is larger than the provisional light emission amount, an L offset larger than the provisional light emission amount is determined as the determined light emission amount. Thereby, since it is prevented that a screen becomes too dark, the visibility of a screen can be improved.

  As can be seen from the above control, the smaller the DNUM is, and the larger the H offset is, the larger the determined emission amount tends to be. Therefore, the reduction rate of the light emission amount of the backlight 22 is lowered by reducing DNUM and increasing the H offset. On the other hand, the reduction rate of the light emission amount of the backlight 22 is increased by increasing DNUM and reducing the H offset.

  Therefore, for example, as shown in FIG. 4, by configuring the control parameter table 12a, the reduction rate of the light emission amount of the backlight can be increased with respect to the navigation video in which halation is difficult to occur compared to other videos. it can.

  In other words, when control parameters such as DNUM and H offset are made common to all images, the control parameters are such that halation does not occur in DVD images and TV images. It cannot be reduced more effectively.

  However, in this embodiment, since the control parameter can be applied in correspondence with the source type, it is possible to more effectively reduce the backlight emission amount for the navigation video. In particular, the display device 20 is for in-vehicle use and has a long effect of displaying navigation images, so that the effect of reducing power consumption is high.

  Returning to FIG. 3, the description of the control unit 11 is continued. The light emission amount restricting unit 11g emits light based on the difference between the determined light emission amount acquired from the light emission amount determining unit 11f and the current light emission amount in order to prevent screen flickering caused by a sudden change in the light emission amount of the backlight 22. A light emission amount regulation process for limiting the amount of change is performed.

  Specifically, when the difference between the determined light emission amount and the current light emission amount is greater than a predetermined threshold, the light emission amount regulating unit 11g sets a predetermined value as the upper limit value of the change amount to the current light emission amount. A value obtained by adding (or subtracting) to the final light emission amount. On the other hand, when the difference between the determined light emission amount and the current light emission amount is less than the predetermined threshold value, the light emission amount regulating unit 11g sets the determined light emission amount as the final light emission amount. When the final light emission amount (hereinafter referred to as “final final light emission amount”) is determined, the light emission amount regulation unit 11g passes this final final light emission amount to the PWM generation unit 11h.

  Further, when determining the final determined light emission amount, the light emission amount regulating unit 11g determines the RGB conversion coefficient corresponding to the final determined light emission amount using the RGB conversion information 12b, and passes the determined RGB conversion coefficient to the RGB conversion unit 11i. Processing is also performed. Here, the contents of the RGB conversion information 12b will be described. FIG. 8 is a diagram illustrating an example of the RGB conversion information 12b.

  As illustrated in FIG. 8, the RGB conversion information 12b is information in which “RGB conversion coefficient” is associated with each “final determined emission amount”. Here, the “final final emission amount” indicates the final final emission amount determined by the emission amount regulating unit 11g. The “RGB conversion coefficient” is a coefficient to be multiplied with the values (RGB values) of R, G, and B components.

  For example, when the final determined light emission amount is “255 (100%)”, the RGB conversion coefficient is “1.00”. This indicates that the RGB value of the input data becomes the RGB value of the output data as it is. When the final determined light emission amount is “240 (93.75%)”, the RGB conversion coefficient is “1.03”. This indicates that a value obtained by multiplying the RGB value of the input data by 1.03 becomes the RGB value of the output data.

  As described above, the RGB conversion information 12b is set so that the RGB conversion coefficient increases as the final determined light emission amount decreases, that is, as the light emission amount of the backlight 22 decreases and the screen becomes darker. When the final determined light emission amount is determined, the light emission amount regulation unit 11g reads the RGB conversion coefficient associated with the determined final determined light emission amount from the RGB conversion information 12b, and the read RGB conversion coefficient to the RGB conversion unit 11i. hand over.

  When acquiring the final determined light emission amount from the light emission amount regulating unit 11g, the PWM generation unit 11h generates a PWM signal whose pulse width is adjusted so that the light emission amount of the backlight 22 becomes the final determined light emission amount, and the backlight 22 Is a processing unit that outputs to Note that the PWM generator 11h outputs the PWM signal four times each time VSYNC is output once.

  The RGB conversion unit 11i multiplies the R, G, and B component values included in the video information acquired from the video information acquisition unit 11a by the RGB conversion coefficient acquired from the light emission amount regulation unit 11g. I do. The RGB converter 11i also performs a process of outputting the video information after the RGB conversion process to the display panel 21.

  For example, when the RGB conversion unit 11i acquires the RGB conversion coefficient “1.26”, the R, G, and B component values included in the video information acquired from the video information acquisition unit 11a are multiplied by 1.26. . Then, the RGB converter 11i outputs video information obtained by multiplying the values of the R, G, and B components by 1.26 to the display panel 21.

  Next, a specific operation of the display control apparatus 10 according to the present embodiment will be described. FIG. 9 is a flowchart illustrating the processing procedure of the display control apparatus 10 according to the present embodiment. In FIG. 9, the control parameter selection procedure is mainly shown among the processing procedures executed by the display control apparatus 10. This processing procedure is started when video source information of a new source type is acquired from the video information output device 30 or when day / night information is acquired.

  As shown in FIG. 9, in the display control device 10, when the light emission amount determination unit 11f acquires the video source information from the video information output device 30, it determines whether or not the source type is a camera video (step S10). . When determining that the video type is not a camera video (No in step S10), the light emission amount determination unit 11f determines whether the source type is a TV video (step S11).

  If it is determined that the source type is not a TV video (No at Step S11), the light emission amount determination unit 11f determines whether the source type is a DVD video (Step S12). When it is determined that the source type is not a DVD video (step S12, No), the light emission amount determination unit 11f determines whether the source type is a navigation video (step S13).

  If it is determined that the source type is navigation video (step S13, Yes), the light emission amount determination unit 11f determines whether the day / night information acquired from the video information output device 30 is information indicating daytime (step). S14).

  When it is determined that the day / night information is information indicating daytime (step S14, Yes), the light emission amount determination unit 11f reads the control parameter of the pattern 3 from the control parameter table 12a stored in the storage unit 12 (step S14). S15).

  On the other hand, when it is determined that the day / night information is not information indicating daytime (No in step S14), the light emission amount determination unit 11f reads the control parameter of the pattern 4 from the control parameter table 12a stored in the storage unit 12 ( Step S16).

  If it is determined in step S11 that the source type is TV video (step S11, Yes), or if it is determined in step S12 that the source type is DVD video (step S12, Yes), the light emission amount determination unit 11f determines whether the day / night information acquired from the video information output device 30 is information indicating daytime (step S17).

  When it is determined that the day / night information is information indicating daytime (step S17, Yes), the light emission amount determination unit 11f reads the control parameter of the pattern 1 from the control parameter table 12a stored in the storage unit 12 (step S17). S18).

  On the other hand, when it is determined that the day / night information is not information indicating daytime (No in step S17), the light emission amount determination unit 11f reads the control parameter of the pattern 2 from the control parameter table 12a stored in the storage unit 12 ( Step S19).

  When it is determined in step S10 that the source type is camera video (step S10, Yes), the light emission amount determination unit 11f determines whether the day / night information acquired from the video information output device 30 is information indicating daytime. Determination is made (step S20).

  When it is determined that the day / night information is information indicating daytime (step S20, Yes), the light emission amount determination unit 11f reads the control parameter of the pattern 3 from the control parameter table 12a stored in the storage unit 12 (step S20). S21).

  When the control parameter selection process described above is completed, that is, when the processes of steps S15, S16, S18, S19, and S21 are completed, the light emission amount determining unit 11f reads the read control parameters (DNUM, H offset, L offset). ) To determine the light emission amount (determined light emission amount) of the backlight 22 (step S22). Thereafter, the control unit 11 controls the backlight 22 and adjusts the luminance of the video based on the determined light emission amount of the backlight 22.

  In Step S20, when it is determined that the day / night information is not information indicating daytime (No in Step S20), the control unit 11 stops the backlight control without determining the light emission amount of the backlight 22. .

  That is, the light emission amount of the backlight 22 is set to 100%. This is because the camera video is dark at night, and performing backlight control deteriorates the video quality and reduces the visibility. Note that the light emission amount determination unit 11f stops the backlight control by fixing the determined light emission amount to “255”. As a method of fixing the fixed light emission amount to “255”, for example, there is a method of setting the H offset to “255”.

  When it is determined that the source type is not the navigation video (No at Step S13), the light emission amount determination unit 11f ends the process.

  As described above, in the display control apparatus 10 according to the present embodiment, the control parameter corresponding to the source type of the video to be displayed on the display panel 21 is read from the storage unit 12, and the luminance of the video is based on the read control parameter. The light emission amount determining unit 11f that determines the light emission amount of the backlight 22 according to the light source is provided, and the power consumption of the backlight 22 can be appropriately reduced according to the source type.

  Further, in the display control apparatus 10 according to the present embodiment, the control parameter is changed depending on whether it is day or night in addition to the source type of the video displayed on the display panel 21. Therefore, for example, at night, the image displayed on the display panel 21 can be made less visible and the image can be viewed more easily. At noon, the image displayed on the display panel 21 can be brightened.

  In this embodiment, paying attention to the fact that the distribution of the luminance and color of the pixels constituting the video is simple, control parameters that can more effectively reduce the light emission amount of the backlight 22 are set. Although an example of setting is shown, it is not limited to this.

  That is, any control parameter may be used as long as the control parameter corresponding to the video type is set based on the characteristics of each video type. For example, different control parameters may be set for a video source with a relatively large number of videos with high luminance and a video source with a relatively large number of videos with low luminance.

  Further, in this embodiment, the light emission amount determination unit 11f stops the backlight control when the day / night information is night and the source type is camera video. The backlight control may be stopped in the case of video or TV video.

  In this embodiment, the control parameters are set according to the source type and day / night information. Further, the power consumption of an in-vehicle device (for example, a car navigation device) (not shown) and the battery voltage supplied to the in-vehicle device. The control parameters may be changed according to the above.

  For example, in addition to the source type and day / night information, a control parameter table including control parameters according to the power consumption of the in-vehicle device is stored in the storage unit 12. The light emission amount determination unit 11f then determines the light emission amount of the backlight 22 in accordance with the power consumption of the in-vehicle device in addition to the source type and day / night information.

  In addition, when there are a plurality of in-vehicle cameras such as a front camera and a back camera, the control parameters may be changed for each camera.

  As described above, the display control device and the display control method according to the present invention are useful when it is desired to increase the reduction amount of the power consumption of the backlight. For example, when the power consumption of the liquid crystal display of the in-vehicle device is desired to be suppressed. Is suitable.

DESCRIPTION OF SYMBOLS 10 Display control apparatus 11 Control part 11a Image | video information acquisition part 11b Source type information acquisition part 11c Day / night information acquisition part 11d Subsampling part 11e Histogram generation part 11f Light emission amount determination part 11g Light emission amount regulation part 11h PWM generation part 11i RGB conversion part 12 Storage unit 12a Control parameter table 12b RGB conversion information 20 Display device 30 Video information output device

Claims (5)

A display control device that controls a light emission amount of a backlight that irradiates light to a display panel according to a luminance of an image, and displays the video whose luminance is corrected according to the light emission amount of the backlight on the display panel. ,
A storage unit for storing a plurality of control parameters in association with a source type indicating a video source type of the video,
A control parameter corresponding to a source type indicating a video source type of a video to be displayed on the display panel is read from the storage unit, and a light emission amount of the backlight corresponding to the luminance of the video is determined by the read control parameter. and a determination unit that,
The type of the video source is
A source of at least one of a camera image, a DVD image and a TV image, and a source of a navigation image;
The display control device according to claim 1, wherein among the plurality of control parameters, a control parameter corresponding to a source of the navigation video is set so that a light emission amount of the backlight is minimized . The determination unit
The display control apparatus according to claim 1, wherein when the source type is a specific type, the determination of the light emission amount of the backlight according to the luminance of the video is stopped. The determination unit
It has acquisition means to acquire day and night information that distinguishes day and night,
According to the control parameters corresponding to the source type and the day / night information acquired by the acquisition means, the luminance of the video is changed so that the amount of light emitted from the backlight changes depending on the type of the video source depending on whether it is daytime or nighttime. The display control apparatus according to claim 1, wherein the amount of light emitted from the backlight is determined accordingly. The control parameter is:
Including a first parameter and a second parameter;
The determination unit
The pixels constituting the video are counted in descending order of luminance value, and the provisional light emission amount of the backlight is based on the luminance value when the cumulative number of counted pixels reaches the value of the first parameter. Provisional light emission amount determining means for determining
Comparison means for comparing the provisional light emission amount determined by the provisional light emission amount determination means with the value of the second parameter;
As a result of the comparison by the comparison means, when the provisional light emission amount exceeds the value of the second parameter, the light emission amount smaller than the provisional light emission amount is determined as the definite light emission amount of the backlight. The display control apparatus according to claim 1, further comprising: a definite light emission amount determining unit. A display control method for controlling a light emission amount of a backlight that irradiates light to a display panel according to a luminance of an image, and displaying the video whose luminance is corrected according to the light emission amount of the backlight on the display panel. ,
A step of reading a control parameter corresponding to a source type indicating a video source type of a video to be displayed on the display panel from a storage unit that stores a plurality of control parameters in association with a source type indicating a video source type. When,
By the read control parameter look including the step of determining a light emission amount of the backlight in accordance with the brightness of the image,
The type of the video source is
A source of at least one of a camera image, a DVD image and a TV image, and a source of a navigation image;
The display control method according to claim 1, wherein among the plurality of control parameters, a control parameter corresponding to a source of the navigation video is set so that a light emission amount of the backlight is minimized .

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