JP5649832B2 - Display control apparatus and display control method - Google Patents

Description

  The present invention relates to a display control device and a display control method, and in particular, when high luminance pixels are included in a part of an overall dark image, the visibility of high luminance pixels is improved while suppressing power consumption by a backlight. The present invention relates to a display control apparatus and a display control method that can perform the same.

  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.

  LCDs display images by partially blocking or transmitting light emitted from the backlight, but the high power consumption of the backlight hinders power saving . 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 brightness of the video. Specifically, in the technique described in Patent Document 1, a luminance distribution (histogram) of pixels included in a video is created, and the cumulative number of pixels is counted from the high luminance side using the created histogram. The luminance value at the position reaching the number is determined as the backlight emission amount.

  As a result, in the technique described in Patent Document 1, in the case of a dark image, the number of pixels positioned on the high luminance side is small, so that the light emission amount of the backlight is set small. In the case of a bright image, the high luminance side is set. Since the number of pixels located at is large, the light emission amount of the backlight is set to be large.

  In the technique described in Patent Document 1, even when the amount of light emitted from the backlight is reduced, the brightness of the image is maintained by correcting the RGB values to increase the brightness of the video itself.

JP 2007-219477 A

  However, the technique described in Patent Document 1 has a problem that visibility of a high-luminance pixel is lowered when a high-luminance pixel is included in a part of an entirely dark image. This is because when the image is entirely dark, the backlight emission amount is set to be small, so that the backlight emission amount is not appropriate for a high-luminance pixel that requires a larger amount of emission. .

  In addition, when the amount of light emitted from the backlight is set to be dark, correction is made to increase the brightness of the image itself, so that the portion displayed by the high-intensity pixels (originally bright portion) is crushed and visually There is also a problem that the performance decreases.

  For these reasons, when high-luminance pixels are included in a part of an overall dark image, a display control device or display control that can increase the visibility of high-luminance pixels while suppressing power consumption by the backlight How to realize the method is a big issue.

  The present invention has been made to solve the above-described problems caused by the prior art, and suppresses power consumption by a backlight when high-luminance pixels are included in a part of an overall dark image. An object of the present invention is to provide a display control device and a display control method that can improve the visibility of high-luminance pixels.

In order to solve the above-described problems and achieve the object, a display control device according to the present invention is a display control device that controls the amount of light emitted from a backlight that irradiates light to a display panel. A cumulative addition means for cumulatively adding the number of pixels constituting the image data in descending order of luminance value, and every time the number of pixels is cumulatively added by the cumulative addition means, A partial average luminance calculating unit that calculates the average luminance of the partial average luminance, a partial average luminance calculated by the partial average luminance calculating unit, and a minimum luminance among the luminance values of the pixels that have been cumulatively added by the cumulative adding unit If the difference between the value is equal to or greater than a predetermined threshold value, and a light emission amount determination means for determining the associated in advance with the light emission amount to the minimum luminance value as the emission amount of the backlight It is characterized in.

The display control method according to the present invention is a display control method for controlling the light emission amount of a backlight that irradiates light to a display panel, and the number of pixels constituting the image data with respect to input image data. a cumulative addition step of cumulatively adding the descending order of the luminance values, the each time the number of the pixels by cumulative addition process is cumulatively added, partial average of calculating the average luminance of the pixels already accumulating as a partial average brightness When the difference between the luminance calculation step, the partial average luminance calculated in the partial average luminance calculation step, and the minimum luminance value of the luminance values of the pixels already accumulated in the cumulative addition step is equal to or greater than a predetermined threshold value And a light emission amount determining step of determining a light emission amount associated with the minimum luminance value in advance as the light emission amount of the backlight.

According to the present invention, the number of pixels constituting the image data is cumulatively added to the input image data in descending order of the luminance value, and every time the number of pixels is cumulatively added , When the average luminance of the pixel is calculated as the partial average luminance, and the difference between the calculated partial average luminance and the luminance value of the cumulatively added pixels is equal to or greater than a predetermined threshold value, the minimum luminance value to advance the associated light emission amount was to be determined as a light emission amount of the backlight, when including the pixels of the high luminance part of the overall dark image, while suppressing the power consumption by the backlight, high There is an effect that the visibility of the luminance pixel can be enhanced.

FIG. 1 is a diagram showing an overview of a display control method according to the present invention. FIG. 2 is a block diagram illustrating the configuration of the display control apparatus according to the present embodiment. FIG. 3 is a block diagram illustrating a configuration of the histogram analysis unit. FIG. 4 is a diagram illustrating an operation example of the light emission amount determination unit when a high-luminance pixel is included in an overall dark image. FIG. 5 is a diagram illustrating another operation example of the light emission amount determination unit. FIG. 6 is a flowchart illustrating a processing procedure of the display control apparatus. FIG. 7 is a diagram for explaining a case where AVEDIS is changed according to the value of partial average luminance. FIG. 8 is a diagram illustrating another operation example of the cumulative addition unit. FIG. 9 is a diagram illustrating another operation example of the light emission amount determination unit.

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

  First, prior to detailed description of the embodiment, an outline of a display control method according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an overview of a display control method according to the present invention. Here, (A) in the figure shows a state in which high luminance pixels are included in a part of an overall dark image, and (B) in the figure shows the image shown in (A) in the figure. The luminance distribution is shown.

  In the display control method according to the present invention, the light emission amount of the backlight is determined based on the luminance value distribution (hereinafter referred to as “histogram”) of the input image data. Specifically, in the display control method according to the present invention, in the case of a dark image, since the number of pixels located on the low luminance side is large, the light emission amount of the backlight is set small, and in the case of a bright image, Since the number of pixels located on the high luminance side is large, a large amount of backlight emission is set.

  For this reason, as shown in FIG. 5A, when a high-luminance pixel is included in a part of an overall dark image, the number of low-luminance pixels is large, so that the backlight emission amount is set to be small. Is done. However, if the amount of light emitted from the backlight is set to be small, a color collapse phenomenon (hereinafter referred to as “halation”) may occur in a portion displayed by high luminance pixels, and the visibility of the portion may be reduced. There is.

  Therefore, in the display control method according to the present invention, when high luminance pixels are included in a part of an overall dark image, the light emission amount of the backlight is not reduced too much. Further, in such a case, the display control method according to the present invention does not simply set the backlight emission amount to match the high-luminance pixel, but considers reduction of power consumption by the backlight. It was decided to decide.

  Specifically, as shown in (B) of the figure, in the display control method according to the present invention, when image data is input, the number of pixels constituting the image data is set in descending order of luminance value. Cumulative addition. In other words, in the display control method according to the present invention, the highest luminance value on the histogram (for example, “255” in the case of 8-bit resolution) is used as the calculation start point, and each luminance value from the calculation start point toward the lower luminance side. Are sequentially accumulated and added (see (B-1) in the figure). The re-high brightness value on the histogram changes according to the resolution.

  Further, in the display control method according to the present invention, every time the number of pixels of each luminance value is cumulatively added, the average luminance (hereinafter referred to as “partial average luminance”) of pixels that have been cumulatively added (hereinafter referred to as “cumulative pixels”). (Refer to (B-2) in the figure).

  That is, the luminance value currently being cumulatively added, in other words, the lowest luminance value (hereinafter referred to as “calculation point”) among the luminance values of the pixels that have already been cumulatively added is reduced with each cumulative addition of the number of pixels. Transition to the side. As a result, the partial average luminance also shifts to the low luminance side.

  Here, when a bright part is included in a part of an overall dark image, a small number of pixels exist on the high luminance side and the remaining majority of pixels are present as shown in FIG. The histogram is present on the low luminance side. For this reason, if the number of pixels is cumulatively added from the high luminance side using such a histogram, the cumulative number of pixels hardly increases when the cumulative addition of the number of high luminance pixels is completed. The partial average luminance hardly changes.

  That is, when a bright part is included in a part of an overall dark image, the larger the calculated point shifts to the lower luminance side, the greater the difference between the partial average luminance and the calculated point. Therefore, in the display control method according to the present invention, when the difference between the partial average luminance and the calculation point is equal to or greater than a predetermined threshold (see (B-3) in the figure), a part of the image that is entirely dark. Is determined to contain a high-luminance pixel.

  In the display control method according to the present invention, the light emission amount of the backlight is determined based on the calculated points when the difference from the partial average luminance is equal to or greater than a predetermined threshold (see (B-4) in the figure). ). Specifically, in the display control method according to the present invention, light emission amounts of 0% to 100% are associated in advance with luminance values of 0 to 255, respectively. In the display control method according to the present invention, the light emission amount corresponding to the luminance value of the calculation point is determined as the light emission amount of the backlight.

  In this way, in the display control method according to the present invention, when high luminance pixels are included in a part of an overall dark image, the light emission amount of the backlight is not reduced too much in accordance with the low luminance pixels. The visibility of high-luminance pixels can be increased.

  Moreover, in such a case, the light emission amount of the backlight is not simply set to the light emission amount according to the high luminance pixel, but corresponds to the luminance value between the high luminance pixel and the low luminance pixel (here, the calculation point). The amount of emitted light was determined as the amount of emitted light from the backlight. Therefore, it is possible to improve the visibility of the high-luminance pixels while suppressing power consumption by the backlight.

  In the display control method according to the present invention, when the cumulative pixel number exceeds the predetermined pixel number before the difference between the calculation point and the partial average luminance exceeds the predetermined threshold value, the cumulative pixel number is predetermined. The amount of light emitted from the backlight is determined based on the calculated points at the time when the number of pixels is exceeded. As a result, if it is not a special case in which high luminance pixels are included in a part of the overall dark image, the light emission amount according to the brightness of the entire input image is used as the backlight light emission amount as usual. be able to.

  By the way, when the distribution of the high luminance pixels and the distribution of the low luminance pixels are located at relatively close positions in the histogram shown in FIG. 5B, the difference between the calculation point and the partial average luminance is a predetermined threshold value. Before the above is reached, the cumulative number of pixels may exceed a predetermined number of pixels. In such a case, the visibility of the high-luminance pixels cannot be appropriately improved even though the high-luminance pixels are included in a part of the overall dark image.

  Therefore, in the display control method according to the present invention, the above situation is avoided by changing the predetermined threshold according to the value of the partial average luminance. Details of this point will be described later in Examples.

  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 embodiment described below, a case will be described in which the present invention is applied to a display control device that performs display control of a liquid crystal display mounted on an in-vehicle device. However, the display control device according to the present invention is not limited to this, and various types of display units that display using a backlight, such as a portable terminal device, a PC (Personal Computer), or a TV (Television). It can be applied to other devices.

  In the following, among the two distributions formed on the histogram when high luminance pixels are included in a part of an overall dark image (see FIG. 1), pixels belonging to the distribution on the high luminance side are set to high luminance. The pixel belonging to the distribution on the low luminance side is called a low luminance pixel.

  FIG. 2 is a block diagram illustrating the configuration of the display control apparatus according to the present embodiment. In the figure, only components necessary for explaining the characteristics of the display control device are shown, and descriptions of general components are omitted.

  As shown in the figure, a display control device 10 according to the present embodiment is a device that performs display control of a liquid crystal display 20 mounted on an in-vehicle device. Here, the liquid crystal display 20 includes a liquid crystal panel 21 and a backlight module 22. The liquid crystal panel 21 is a display unit that displays image data output from the display control device 10. The backlight module 22 is a lighting device provided on the back side of the liquid crystal panel 21 and irradiates the liquid crystal panel 21 with light from the back side. The high power consumption by the backlight module 22 hinders power saving.

  Next, the configuration of the display control apparatus 10 according to the present embodiment will be described. 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 an image data acquisition unit 11a, a sub-sampling unit 11b, a histogram generation unit 11c, a histogram analysis unit 11d, a light emission amount change unit 11e, a PWM (Pulse Width Modulation) generation unit 11f, RGB conversion unit 11g. The storage unit 12 stores threshold information 12a and RGB conversion information 12b.

  The image data acquisition unit 11a is a processing unit that acquires image data such as navigation images from the in-vehicle device. The image data acquisition unit 11a also performs a process of passing the acquired image data to the sub-sampling unit 11b and the RGB conversion unit 11g.

  The sub-sampling unit 11b is a processing unit that performs sub-sampling on the acquired image data when the image data is acquired from the image data acquisition unit 11a. Further, the sub-sampling unit 11b also performs a process of passing the image data after sub-sampling to the histogram generation unit 11c.

  Here, sub-sampling indicates a process of thinning out pixels from acquired image data. Thus, by performing subsampling on the acquired image data, the processing speed of processing units such as a histogram generation unit 11c and a histogram analysis unit 11d described later can be increased. Here, it is assumed that the image data of WVGA size (800 × 480) is reduced to a size of 128 × 64.

  The histogram generation unit 11c is a processing unit that generates a histogram using the image data after sub-sampling acquired from the sub-sampling unit 11b. As described above, the histogram is information representing the luminance distribution of the pixels constituting the image data. Here, the histogram generation unit 11c generates a histogram using the component having the largest value among the R, G, and B components included in the image data. The histogram generation unit 11c also performs a process of passing the generated histogram to the histogram analysis unit 11d.

  The histogram analysis unit 11d is a processing unit that determines the light emission amount of the backlight module 22 by analyzing the histogram generated by the histogram generation unit 11c using the threshold information 12a.

  Here, a specific configuration of the histogram analysis unit 11d will be described with reference to FIG. FIG. 3 is a block diagram illustrating the configuration of the histogram analysis unit 11d according to the first embodiment. As shown in the figure, the histogram analysis unit 11 d includes a cumulative addition unit 111, a partial average luminance calculation unit 112, and a light emission amount determination unit 113. The threshold information 12a includes a DNUM 121 and an AVEDIS 122.

  The cumulative addition unit 111 is a processing unit that cumulatively adds the number of pixels in descending order of luminance value using the histogram acquired from the histogram generation unit 11c. In addition, every time the number of pixels is cumulatively added, the cumulative addition unit 111 also performs a process of passing the cumulative number of pixels that are cumulatively added and the current calculation point to the light emission amount determination unit 113.

  For example, it is assumed that the number of pixels of the luminance value “255” is one, the number of pixels of the luminance value “254” is two, and the number of pixels of the luminance value “253” is three. In this case, if the cumulative addition unit 111 cumulatively adds the number of pixels up to the luminance value “253”, the cumulative number of pixels “6” and the current calculation point “253” are passed to the light emission amount determination unit 113.

  The cumulative addition unit 111 also performs a process of passing the current calculation point to the partial average luminance calculation unit 112.

  The partial average luminance calculation unit 112 is a processing unit that calculates the average luminance of the pixels that have been cumulatively added by the cumulative addition unit 111 as the partial average luminance. That is, when the partial average luminance calculation unit 112 receives the calculation point from the cumulative addition unit 111, the partial average luminance calculation unit 112 calculates the partial average luminance of pixels included from the calculation start point to the calculation point.

  Here, the partial average luminance is expressed by Σ {(calculation point) × (number of pixels)} / (cumulative pixel number). That is, the partial average luminance is obtained by summing a value obtained by multiplying each calculation point (luminance value) and the number of pixels of the calculation point from the calculation start point to the current calculation point, and dividing the total value by the cumulative number of pixels. Sought by.

  For example, the luminance value “255” has one pixel, the luminance value “254” has two pixels, the luminance value “253” has three pixels, and the current calculation point is “253”. And In such a case, the partial average luminance is {(255 × 1) + (254 × 2) + (253 × 3)} / 6≈254.

  When the partial average luminance is calculated, the partial average luminance calculation unit 112 passes the calculated partial average luminance to the light emission amount determination unit 113.

  The light emission amount determination unit 113 is a processing unit that determines the light emission amount of the backlight module 22 using the information received from the cumulative addition unit 111 and the partial average luminance calculation unit 112, and the DNUM 121 and the AVEDIS 122 that are threshold information 12a. . Here, DNUM 121 is information indicating a threshold value for the cumulative number of pixels. AVEDIS 122 is information indicating a threshold value of a difference between the partial average luminance and the current calculation point.

  Specifically, the light emission amount determination unit 113 determines that the difference between the partial average luminance and the current calculation point (hereinafter referred to as “luminance difference value”) is equal to or greater than AVEDIS 122 before the cumulative number of pixels reaches DNUM 121. In this case, the light emission amount corresponding to the current calculation point is determined as the light emission amount of the backlight module 22. In addition, the light emission amount determination unit 113 determines the light emission amount corresponding to the calculation point when the cumulative number of pixels received from the cumulative addition unit 111 reaches DNUM 121 as the light emission amount of the backlight module 22.

  Here, an operation example of the light emission amount determination unit 113 will be described with reference to FIG. FIG. 4 is a diagram illustrating an operation example of the light emission amount determination unit 113 when a high-luminance pixel is included in an overall dark image.

  As shown in FIG. 5A, when a part of a dark image as a whole includes a bright part, a small number of pixels exist on the high luminance side, and the majority of the remaining pixels appear on the low luminance side. Histogram that exists. Here, as shown in FIG. 5A, when the cumulative addition unit 111 cumulatively adds the number of pixels on the high luminance side, that is, when the current calculation point is located on the high luminance side. The difference between the partial average luminance and the current calculation point is not so wide. Therefore, the calculation point and the partial average luminance shift to the low luminance side in a state where the luminance difference value is less than AVEDIS 122 (see (A-1) in the figure).

  On the other hand, as shown in FIG. 5B, when the cumulative addition unit 111 finishes cumulatively adding the number of high luminance pixels, the cumulative number of pixels hardly increases until the calculation point reaches the low luminance side. It becomes. This is because the number of pixels corresponding to the luminance value between the high luminance pixel and the low luminance pixel is small. Along with this, the partial average luminance hardly changes.

  Therefore, when a bright part is included in a part of the overall dark image, the luminance difference value increases as the calculation point shifts to the low luminance side, and becomes AVEDIS 122 or more at a certain calculation point ( (See (B-1) in the figure). In such a case, the light emission amount determination unit 113 sets the light emission amount corresponding to this calculation point as the light emission amount of the backlight module 22.

  On the other hand, when the cumulative number of pixels reaches DNUM 121, the light emission amount determination unit 113 sets the light emission amount corresponding to the calculation point in such a case as the light emission amount of the backlight module 22. Such a case will be described with reference to FIG. FIG. 5 is a diagram illustrating another operation example of the light emission amount determination unit 113. In the figure, a histogram in which pixels are evenly distributed is shown.

  As shown in FIG. 6A, the cumulative addition unit 111 sequentially shifts the calculation point to the low luminance side and cumulatively adds the number of pixels until the cumulative number of pixels reaches DNUM 121 (see FIG. (See (A-1)).

  Here, as shown in (B) of the figure, when the pixels are evenly distributed, the calculation point and the partial average luminance are both shifted to the low luminance side when the luminance difference value is less than AVEDIS122. (See (B-1) in the figure). In such a case, the accumulated pixel number reaches DNUM 121 without the luminance difference value being equal to or greater than AVEDIS 122 (see (B-2) in the figure). Therefore, the light emission amount determination unit 113 determines the light emission amount corresponding to the calculation point when the cumulative number of pixels reaches DNUM 121 as the light emission amount of the backlight module 22.

  As described above, in this embodiment, when the luminance difference value is equal to or greater than AVEDIS 122 before the cumulative number of pixels reaches DNUM 121, the light emission amount of the backlight module 22 is determined based on the calculation point in such a case. It was. Therefore, the light emission amount larger than the light emission amount corresponding to the calculation point when the cumulative number of pixels reaches DNUM 121 is determined as the light emission amount of the backlight module 22. For this reason, when a high-intensity pixel is included in a part of an entirely dark image, the visibility of the high-intensity pixel can be enhanced.

  In this embodiment, when the cumulative number of pixels reaches DNUM 121, the light emission amount of the backlight module 22 is determined based on the calculation point when the cumulative number of pixels reaches DNUM 121. Therefore, when a process for increasing the visibility of high-luminance pixels is not necessary, the light emission amount corresponding to the luminance value of the entire image can be set as the light emission amount of the backlight module 22 as usual.

  The values of DNUM 121 and AVEDIS 122 stored as threshold information 12a can be arbitrarily changed.

  Returning to FIG. 2, the description of the control unit 11 will be continued. The light emission amount changing unit 11e is based on the difference between the light emission amount acquired from the histogram analysis unit 11d 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 module 22. It is a process part which performs the light emission amount change process which restrict | limits the variation | change_quantity.

  Specifically, when the difference between the determined light emission amount and the current light emission amount is greater than a predetermined threshold value, the light emission amount changing unit 11e sets a predetermined value as the upper limit value of the change amount to the current light emission amount. A value obtained by addition (or subtraction) is determined as a final light emission amount. Further, when the light emission amount changing unit 11e determines the final light emission amount (hereinafter referred to as “changed light emission amount”), it passes this changed light emission amount to the PWM generation unit 11f.

  In addition, when the changed light emission amount is determined, the light emission amount changing unit 11e also determines an RGB conversion coefficient corresponding to the changed light emission amount using the RGB conversion information 12b, and passes the determined RGB conversion coefficient to the RGB conversion unit 11g. Do.

  Here, the RGB conversion information 12b is information in which “RGB conversion coefficient” is associated with each “changed light emission amount”. Here, “changed emission amount” indicates the changed emission amount determined by the emission amount changing unit 11e. 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 light emission amount after the change is “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. Further, when the light emission amount after the change is “50%”, the RGB conversion coefficient is “1.26”. This indicates that a value obtained by multiplying the RGB value of the input data by 1.26 becomes the RGB value of the output data. Here, it is assumed that R, G, and B components are respectively multiplied by RGB conversion coefficients.

  As described above, the RGB conversion information 12b is set so that the RGB conversion coefficient increases as the light emission amount after light emission decreases, that is, as the light emission amount of the backlight module 22 decreases and the screen becomes darker. When the light emission amount changing unit 11e determines the light emission amount after change, the light emission amount changing unit 11e extracts the RGB conversion coefficient associated with the determined light emission amount after change from the RGB conversion information 12b, and passes the extracted RGB conversion coefficient to the RGB conversion unit 11g.

  When the changed light emission amount is acquired from the light emission amount changing unit 11e, the PWM generation unit 11f generates a PWM signal whose pulse width is adjusted so that the light emission amount of the backlight module 22 becomes the changed light emission amount, and the backlight module 22 It is a processing part which outputs to. Note that the PWM generation unit 11f outputs the PWM signal four times by default every time VSYNC (Vertical Synchronizing signal) is output once. However, the number of output of the PWM signal per unit output of VSYNC can be appropriately adjusted by a register.

  The RGB conversion unit 11g performs an RGB conversion process of multiplying the R, G, and B component values included in the image data acquired from the image data acquisition unit 11a by the RGB conversion coefficient acquired from the light emission amount change unit 11e. Is a processing unit. The RGB converter 11g also performs a process of outputting the image data after the RGB conversion process to the liquid crystal panel 21.

  For example, when the RGB conversion unit 11g acquires the RGB conversion coefficient “1.26”, the RGB conversion unit 11g multiplies the values of the R, G, and B components included in the image data acquired from the image data acquisition unit 11a by 1.26. . The RGB converter 11g outputs image data obtained by multiplying the values of the R, G, and B components by 1.26 to the liquid crystal panel 21.

  Next, a specific operation of the display control apparatus 10 according to the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart illustrating the processing procedure of the display control apparatus 10 according to the present embodiment. In the figure, only the processing procedure related to the light emission amount control of the backlight module 22 among the processing procedures executed by the display control device 10 is shown.

  As shown in the figure, in the display control apparatus 10, the sub-sampling unit 11b performs sub-sampling on the image data acquired by the image data acquisition unit 11a (step S101). In the display control apparatus 10, the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S102), and passes the generated histogram to the cumulative addition unit 111 and the partial average luminance calculation unit 112.

  Subsequently, the cumulative addition unit 111 starts a cumulative addition process of sequentially cumulatively adding the number of pixels from the calculation start point using the histogram received from the histogram generation unit 11c (step S103). Subsequently, the partial average luminance calculation unit 112 calculates partial average luminance that is the average luminance of the pixels that have been cumulatively added by the cumulative addition unit 111 (step S104).

  Subsequently, the light emission amount determination unit 113 determines whether or not the cumulative number of pixels has reached the DNUM 121 (step S105), and when the cumulative number of pixels is less than the DNUM 121 (step S105, No), the luminance difference value. Is determined to be greater than or equal to AVEDIS 122 (step S106).

  If it is determined that the luminance difference value is equal to or greater than AVEDIS 122 (step S106, Yes), the light emission amount determination unit 113 determines the light emission amount corresponding to the calculated point when the luminance difference value is equal to or greater than AVEDIS 122. The amount of light emission 22 is determined (step S107). On the other hand, when the luminance difference value is less than AVEDIS 122 (No in step S106), the light emission amount determining unit 113 repeats the processes in steps S104 to S106.

  If it is determined that the cumulative number of pixels has reached DNUM 121 (step S105, Yes), the light emission amount determination unit 113 sets the light emission amount corresponding to the calculated point when the cumulative number of pixels has reached DNUM 121 to the backlight. The amount of light emitted by the module 22 is determined (step S108).

  When the process of step S107 or step S108 is completed, the light emission amount changing unit 11e performs a light emission amount changing process on the light emission amount determined by the light emission amount determining unit 113 to determine the changed light emission amount (step S109). Subsequently, the PWM generator 11f generates a PWM signal corresponding to the changed light emission amount and outputs the PWM signal to the backlight module 22 (step S110).

  Further, the RGB conversion unit 11g performs an RGB conversion process of multiplying R, G, and B component values included in the image data acquired from the image data acquisition unit 11a by an RGB conversion coefficient corresponding to the changed light emission amount. Is performed (step S111). Then, the RGB conversion unit 11g outputs the image data after the RGB conversion processing to the liquid crystal panel 21 (step S112), and ends the processing.

  As described above, in this embodiment, the cumulative addition unit cumulatively adds the number of pixels constituting the image data to the input image data in order from the highest luminance value, and the partial average luminance calculation unit Calculates the average luminance of the accumulated pixels as the partial average luminance, and the light emission amount determination unit determines that the difference between the calculated partial average luminance and the lowest luminance value of the accumulated luminance values of the pixels is a predetermined value. When the threshold value is exceeded, the light emission amount of the backlight is determined based on the minimum luminance value. Therefore, when high-luminance pixels are included in a part of an overall dark image, it is possible to increase the visibility of the high-luminance pixels while suppressing power consumption by the backlight.

  By the way, in the embodiment described above, the case where the luminance difference between the dark portion and the bright portion in the image is large, that is, the case where the distribution of the high luminance pixels and the distribution of the low luminance pixels are largely separated in the histogram is taken as an example. I have explained. However, the present invention is not limited to this. For example, when the luminance value of the bright portion in the image is not so high, the distribution of the high luminance pixels and the distribution of the low luminance pixels are relatively close to each other. There is also.

  In such a case, there is a possibility that the cumulative number of pixels may reach DNUM 121 before the luminance difference value becomes equal to or greater than AVEDIS 122, even though high luminance pixels are included in a part of the overall dark image. . Therefore, when the luminance value of the high luminance pixel is relatively low, the value of the AVEDIS 122 may be reduced as compared with the case where the luminance value of the high luminance pixel is high.

  Hereinafter, such a case will be described with reference to FIG. FIG. 7 is a diagram for explaining a case where the AVEDIS 122 is changed according to the value of the partial average luminance. Note that (A) in the figure shows a state in which different AVEDIS 121 are associated according to the magnitude relationship between the partial average luminance and the threshold A. Further, (B) in the figure shows a state in which AVEDIS (large) is applied when the partial average luminance is equal to or higher than the threshold A, and (C) in the same figure shows that the partial average luminance is less than the threshold A. Each of them shows how AVEDIS (small) is applied in some cases.

  As shown in FIG. 5A, the storage unit 12 stores AVEDIS (large) and AVEDIS (small) having a value smaller than AVEDIS (large) as AVEDIS122.

  Then, when the partial average luminance calculated by the partial average luminance calculation unit 112 is equal to or greater than the threshold A, the light emission amount determination unit 113 compares the luminance difference value with AVEDIS (large), and the luminance difference value is determined to be AVEDIS. It is determined whether or not (large) or more (see (B) of the figure). This is because when the partial average luminance is equal to or greater than the threshold value A (corresponding to “predetermined luminance value”), it can be considered that the luminance difference between the low luminance pixel and the high luminance pixel is large.

  On the other hand, when the partial average luminance is less than the threshold A, the light emission amount determination unit 113 compares the luminance difference value with AVEDIS (small), and determines whether the luminance difference value is equal to or greater than AVEDIS (small). (See (C) of the figure). This is because when the partial average luminance is less than the threshold value A, it can be considered that the luminance difference between the low luminance pixel and the high luminance pixel is small.

  As described above, when the partial average luminance calculated by the partial average luminance calculation unit 112 is less than the predetermined luminance value, AVEDIS is reduced as compared with the case where the partial average luminance is equal to or higher than the predetermined luminance value. It was. Therefore, when the luminance difference between the high luminance pixel and the low luminance pixel is small, the cumulative number of pixels is prevented from reaching DNUM 121 before the luminance difference value becomes equal to or greater than AVEDIS 122. As a result, the high luminance pixel is visually recognized. Sexually can be improved appropriately.

  The values of AVEDIS (large) and AVEDIS (small) stored as AVEDIS 122 can be arbitrarily changed as long as AVEDIS (small) does not exceed AVEDIS (large).

  By the way, in the above-described embodiments, a method has been described in which the visibility of a high-luminance pixel is increased when a high-luminance pixel is included in a part of an overall dark image by introducing the AVEDIS 122. The visibility of high-luminance pixels can also be improved by the method. For example, when all the pixels included in the image data are classified into two, high luminance pixels and low luminance pixels, and the cumulative addition unit 111 performs cumulative addition of the number of pixels, the cumulative number of high luminance pixels is set to the low luminance pixel. The cumulative number of pixels may reach the DNUM 121 earlier than usual by sequentially performing cumulative addition while adding to the number of pixels of each luminance value.

  Hereinafter, such a case will be described with reference to FIG. FIG. 8 is a diagram illustrating another operation example of the cumulative addition unit 111. Here, (A) in the figure shows a normal operation example of the cumulative addition unit 111, and (B) in the same figure shows another operation example of the cumulative addition unit 111. Here, the value of DNUM 121 will be described as “60”. Also, as shown in FIG. 5B, here, pixels with luminance values “200” to “255” are high luminance pixels, and pixels with luminance values “0” to “199” are low luminance pixels. Shall be classified as

  As shown in FIG. 6A, in a normal operation, the cumulative addition unit 111 sequentially adds the number of pixels from the calculation start point toward the low luminance. Then, the light emission amount “39%” corresponding to the calculation point when the cumulative number of pixels exceeds DNUM 121 (here, the luminance value “100”) is determined as the light emission amount of the backlight module 22.

  On the other hand, in other operations, as shown in (B) of the figure, the cumulative addition unit 111, when the cumulative number of high luminance pixels is “15”, is classified as a low luminance pixel. A value obtained by adding “15” to the number of pixels of the luminance value is cumulatively added. For example, the cumulative addition unit 111 cumulatively adds a value “16” obtained by adding “15” to the number of pixels “1” of the luminance value “199”.

  As described above, the cumulative number of pixels is obtained by sequentially adding the sum of the cumulative number of high luminance pixels to the number of pixels of each luminance value classified as the low luminance pixel. The DNUM 121 is reached earlier than in the case shown in A). That is, by this processing, the calculation point (in this case, the luminance value “197”) at the time when the cumulative number of pixels reaches DNUM 121 can be made higher than the case shown in FIG. The amount of light emitted from the backlight module 22 can also be increased as compared with the case shown in FIG.

  Therefore, even when such a method is used, the visibility of the high-luminance pixels can be improved when the high-luminance pixels are included in a part of the overall dark image. The boundary value between the high luminance pixel and the low luminance pixel can be arbitrarily set and changed.

  As another method, when the overall average brightness is equal to or less than a predetermined threshold and the cumulative number of high-luminance pixels is equal to or greater than the predetermined number, it is determined that a high-luminance pixel is included in a part of a dark image. Then, the predetermined light emission amount may be determined as the light emission amount of the backlight module 22. Hereinafter, such a case will be described with reference to FIG. FIG. 9 is a diagram illustrating another operation example of the light emission amount determination unit 113.

  As shown in the figure, the partial average luminance calculation unit 112 calculates the overall average luminance that is the average luminance of all the pixels of the image data, and passes it to the light emission amount determination unit 113. Further, the cumulative addition unit 111 passes the cumulative number of high luminance pixels to the light emission amount determination unit 113. The cumulative number of high-luminance pixels indicates the cumulative number of pixels from the luminance value “255” to a predetermined luminance value (for example, “200”).

  Further, when the light emission amount determination unit 113 receives the overall average brightness from the partial average brightness calculation unit 112, the light emission amount determination unit 113 determines whether the overall average brightness is less than the threshold B (see (1) in the figure). In addition, the light emission amount determination unit 113 determines whether or not the cumulative number of high-luminance pixels is greater than or equal to a predetermined number (see (2) in the figure). Then, if the light emission amount determination unit 113 determines that the overall average luminance is less than the threshold B and determines that the cumulative number of high-luminance pixels is greater than or equal to a predetermined number, It is determined that a high-luminance pixel is included (see (3) in the figure).

  When it is determined that a high-luminance pixel is included in a part of the dark image, the light emission amount determination unit 113 determines a predetermined light emission amount as the light emission amount of the backlight module 22 (see (4) in the figure). Here, the predetermined light emission amount is a light emission amount larger than the light emission amount corresponding to the overall average luminance.

  As described above, when the overall average luminance is equal to or less than the predetermined threshold value and the cumulative number of high luminance pixels is equal to or greater than the predetermined number, a method for determining the predetermined light emission amount as the light emission amount of the backlight module 22 is provided. Even when it is used, it is possible to improve the visibility of high-luminance pixels included in a part of a dark image as a whole. Note that the predetermined number and the value of the threshold value B can be arbitrarily changed.

  As described above, the display control device and the display control method according to the present invention reduce the power consumption of the backlight and suppress the power consumption by the backlight when a high-luminance pixel is included in a part of the overall dark image. This is useful when it is desired to improve the visibility, and is particularly suitable when it is desired to suppress the power consumption of the liquid crystal display of the in-vehicle device.

DESCRIPTION OF SYMBOLS 10 Display control apparatus 11 Control part 11a Image data acquisition part 11b Subsampling part 11c Histogram generation part 11d Histogram analysis part 111 Cumulative addition part 112 Partial average brightness | luminance calculation part 113 Light emission amount determination part 11e Light emission amount change part 11f PWM generation part 11g RGB Conversion unit 12 Storage unit 12a Threshold information 121 DNUM
122 AVEDIS
12b RGB conversion information 20 Liquid crystal display 21 Liquid crystal panel 22 Backlight module

Claims (4)

A display control device for controlling a light emission amount of a backlight that irradiates light to a display panel,
Cumulative addition means for cumulatively adding the number of pixels constituting the image data to the input image data in order from the highest luminance value;
Each time the number of pixels is cumulatively added by the cumulative addition means, a partial average luminance calculation means for calculating the average luminance of the accumulated pixels as a partial average luminance;
When the difference between the partial average luminance calculated by the partial average luminance calculation unit and the minimum luminance value of the luminance values of the pixels that have been cumulatively added by the cumulative addition unit is equal to or greater than a predetermined threshold, the minimum display control device is characterized in that a light emission amount determination means for determining an amount of light emission that is related in advance to the luminance value as a light emission amount of the backlight. The light emission amount determining means includes
When the partial average luminance calculated by the partial average luminance calculation means is less than a predetermined luminance value, the predetermined threshold is made smaller than when the partial average luminance is equal to or higher than the predetermined luminance value. The display control apparatus according to claim 1. The light emission amount determining means includes
While determining the light emission amount pre-associated with the luminance value when the number of pixels cumulative addition by the accumulative adding means reaches a predetermined number as a light emission amount of the backlight is cumulatively added by the cumulative addition means If the difference between the partial average luminance and the minimum luminance value is equal to or greater than the predetermined threshold before the number of pixels reaches the predetermined number, the light emission amount associated with the minimum luminance value is set in advance. The display control apparatus according to claim 1, wherein the display control apparatus determines the light emission amount of the backlight. A display control method for controlling a light emission amount of a backlight that irradiates light to a display panel,
A cumulative addition step of cumulatively adding, in order from the highest luminance value, the number of pixels constituting the image data to the input image data;
Each time the number of the pixels by the cumulative addition process is cumulatively added, and the partial average luminance calculating step of calculating an average luminance of the pixels already accumulating as a partial average luminance,
When the difference between the partial average luminance calculated in the partial average luminance calculation step and the minimum luminance value of the luminance values of the pixels already accumulated in the cumulative addition step is equal to or greater than a predetermined threshold, the minimum luminance And a light emission amount determining step of determining a light emission amount previously associated with the value as a light emission amount of the backlight.

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