WO2011108143A1 - Display control device and display control method - Google Patents

Display control device and display control method Download PDF

Info

Publication number
WO2011108143A1
WO2011108143A1 PCT/JP2010/069838 JP2010069838W WO2011108143A1 WO 2011108143 A1 WO2011108143 A1 WO 2011108143A1 JP 2010069838 W JP2010069838 W JP 2010069838W WO 2011108143 A1 WO2011108143 A1 WO 2011108143A1
Authority
WO
WIPO (PCT)
Prior art keywords
light emission
emission amount
amount
backlight
display control
Prior art date
Application number
PCT/JP2010/069838
Other languages
French (fr)
Japanese (ja)
Inventor
哲也 大歳
輝彦 上林
武生 松本
志都香 根元
Original Assignee
富士通テン株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2010045824A external-priority patent/JP5604136B2/en
Priority claimed from JP2010045825A external-priority patent/JP5649832B2/en
Application filed by 富士通テン株式会社 filed Critical 富士通テン株式会社
Publication of WO2011108143A1 publication Critical patent/WO2011108143A1/en

Links

Images

Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/0646—Modulation of illumination source brightness and image signal correlated to each other
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/021—Power management, e.g. power saving
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2354/00—Aspects of interface with display user
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2380/00—Specific applications
    • G09G2380/10—Automotive applications

Definitions

  • the present invention relates to a display control device and a display control method.
  • 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.
  • 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 image. 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.
  • a luminance distribution histogram
  • the technique described in Patent Document 1 has a problem that it is difficult to sufficiently reduce power consumption by the backlight.
  • the technique described in Patent Document 1 has a problem that the power saving effect is reduced when a bright image is input. This is because, in the case of a bright image, the amount of power consumption is reduced as a result of setting a larger amount of backlight emission.
  • Such a problem is particularly noticeable in an in-vehicle device that displays many bright images such as navigation images.
  • the present invention has been made to solve the above-described problems caused by the prior art, and an object of the present invention is to provide a display control device and a display control method that can further reduce power consumption by a backlight.
  • a display control device is a display control device that controls the amount of light emitted from a backlight that irradiates light to a display panel.
  • the counting means for counting the pixels constituting the image data in descending order of the luminance value, and the luminance value when the cumulative number of pixels counted by the counting means reaches a predetermined number Comparison between the provisional light emission amount determining means for determining the provisional light emission amount of the backlight, comparison means for comparing the provisional light emission amount determined by the provisional light emission amount determination means with a predetermined threshold, and comparison by the comparison means
  • a definite light emission amount determination that determines a light emission amount smaller than the provisional light emission amount as the definite light emission amount of the backlight. Characterized by comprising a stage.
  • the display control device is a display control device that controls the light emission amount of the backlight that irradiates light to the display panel, and the target light emission of the backlight based on the luminance value of the input image data.
  • a target light emission amount determining means for determining an amount, and a change amount from the current light emission amount according to a difference value between the target light emission amount determined by the target light emission amount determination means and the current light emission amount of the backlight.
  • the display control device is a display control device that controls the amount of light emitted from a backlight that irradiates light to the display panel, and the number of pixels constituting the image data with respect to input image data.
  • the cumulative addition means for cumulatively adding in order from the highest brightness value
  • the partial average brightness calculation means for calculating the average brightness of the pixels that have been cumulatively added by the cumulative addition means
  • the partial average brightness calculation means for calculating the average brightness of the pixels that have been cumulatively added by the cumulative addition means.
  • the back-up is performed based on the minimum brightness value.
  • a light emission amount determining means for determining the light emission amount of the light.
  • the display control method is a display control method for controlling the light emission amount of the backlight that irradiates light to the display panel, and for the input image data, the pixels constituting the image data are changed.
  • Counting step for counting in descending order of luminance value, and provisional light emission for determining the provisional light emission amount of the backlight based on the luminance value when the cumulative number of pixels counted in the counting step reaches a predetermined number
  • a definite light emission amount determining step of determining a light emission amount smaller than the provisional light emission amount as a definite light emission amount of the backlight.
  • the display control method is a display control method for controlling a light emission amount of a backlight that irradiates light to a display panel, and is based on a luminance value of input image data.
  • the amount of change from the current light emission amount is determined in accordance with a target light emission amount determination step for determining the amount, and a difference value between the target light emission amount determined in the target light emission amount determination step and the current light emission amount of the backlight
  • a light emission amount determination step of determining a light emission amount obtained by changing the current light emission amount by the change amount determined in the change amount determination step as a light emission amount of the backlight.
  • the display control method 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.
  • the partial average luminance calculation step of calculating the average luminance of the pixels cumulatively added in the cumulative addition step as the partial average luminance
  • the partial average luminance calculation step When the difference between the partial average brightness and the minimum brightness value of the brightness values of the pixels cumulatively added in the cumulative addition step is equal to or greater than a predetermined threshold value, the backlight emits light based on the minimum brightness value.
  • a light emission amount determining step for determining the amount.
  • the pixels constituting the image data are counted in descending order of luminance value, and the luminance value when the cumulative number of counted pixels reaches a predetermined number is obtained.
  • the provisional light emission amount of the backlight is determined, the provisional light emission amount is compared with a predetermined threshold value, and if the result of comparison indicates that the provisional light emission amount exceeds the predetermined threshold value, the provisional light emission amount Since the amount of light emission smaller than the amount of light is determined as the definite amount of light emission of the backlight, it is possible to suppress the reduction in the amount of reduction in backlight power consumption when a bright image is input. Play.
  • the target light emission amount of the backlight is determined based on the luminance value of the input image data, and according to the difference value between the determined target light emission amount and the current light emission amount of the backlight.
  • the amount of change from the current amount of light is determined, and the amount of light that has been changed by the amount of change determined is determined as the amount of light emitted from the backlight.
  • the number of pixels constituting the image data is cumulatively added to the input image data in descending order of the luminance value, and the average luminance of the accumulated pixels is set as the partial average luminance.
  • the difference between the calculated partial average brightness and the minimum brightness value of the cumulatively added pixel brightness values is equal to or greater than a predetermined threshold, the light emission amount of the backlight is calculated based on the minimum brightness value. Since the determination is made, when high-luminance pixels are included in a part of the overall dark image, there is an effect that the visibility of the high-luminance pixels can be improved while suppressing power consumption by the backlight.
  • FIG. 1 is a diagram illustrating an overview of a display control method according to the first embodiment.
  • FIG. 2 is a block diagram illustrating the configuration of the display control apparatus according to the first embodiment.
  • FIG. 3 is a block diagram illustrating the configuration of the histogram analysis unit according to the first embodiment.
  • FIG. 4 is a diagram illustrating an operation example of the histogram analysis unit according to the first embodiment.
  • FIG. 5 is a diagram illustrating an example of RGB conversion information.
  • FIG. 6 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the first embodiment.
  • FIG. 7 is a diagram illustrating an outline of the halation avoidance technique according to the second embodiment.
  • FIG. 8 is a block diagram illustrating the configuration of the histogram analysis unit according to the second embodiment.
  • FIG. 1 is a diagram illustrating an overview of a display control method according to the first embodiment.
  • FIG. 2 is a block diagram illustrating the configuration of the display control apparatus according to the first embodiment.
  • FIG. 9 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the second embodiment.
  • FIG. 10 is a diagram for explaining a halation avoidance function and an H offset setting change.
  • FIG. 11 is a diagram for explaining a case where the L offset is set.
  • FIG. 12 is a diagram illustrating an overview of the display control method according to the third embodiment.
  • FIG. 13 is a block diagram illustrating the configuration of the display control apparatus according to the third embodiment.
  • FIG. 14 is a diagram illustrating an operation example of the histogram analysis unit.
  • FIG. 15 is a block diagram illustrating the configuration of the light emission amount changing unit according to the third embodiment.
  • FIG. 16 is a diagram illustrating an example of the change amount setting information.
  • FIG. 10 is a diagram for explaining a halation avoidance function and an H offset setting change.
  • FIG. 11 is a diagram for explaining a case where the L offset is set.
  • FIG. 12 is a diagram illustrating an overview of the
  • FIG. 17 is a diagram illustrating an operation example of the change amount determination unit and the light emission amount determination unit.
  • FIG. 18 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the third embodiment.
  • FIG. 19 is a diagram illustrating another operation example of the change amount determination unit.
  • FIG. 20 is a diagram illustrating another operation example of the change amount determination unit.
  • FIG. 21 is a diagram illustrating an overview of the display control method according to the fourth embodiment.
  • FIG. 22 is a block diagram illustrating a configuration of the histogram analysis unit.
  • FIG. 23 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. 24 is a diagram illustrating another operation example of the light emission amount determination unit.
  • FIG. 24 is a diagram illustrating another operation example of the light emission amount determination unit.
  • FIG. 25 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the fourth embodiment.
  • FIG. 26 is a diagram for describing a case where AVEDIS is changed according to the value of partial average luminance.
  • FIG. 27 is a diagram illustrating another operation example of the cumulative addition unit.
  • FIG. 28 is a diagram illustrating another operation example of the light emission amount determination unit.
  • FIG. 1 is a diagram illustrating an overview of a display control method according to the first embodiment. Note that (A) in the figure shows a case where a light emission amount lower than the provisionally determined light emission amount is determined as a definite light emission amount when a bright image is input. Further, (B) of FIG. 5 shows a case where the light emission amount tentatively determined is determined as a definite light emission amount when a dark image is input.
  • the display control method when the amount of light emitted from the backlight is controlled according to the brightness of the image, the amount of light emitted from the backlight is fixed even when a bright image is input.
  • the main feature is that an upper limit is set for the amount of light emitted from the backlight so as not to exceed the fixed amount.
  • the display control method according to the first embodiment first, when image data is input, the pixels constituting the image data are counted in descending order of luminance value. That is, the display control method according to the first embodiment generates a luminance distribution (hereinafter, referred to as “histogram”) of the pixels constituting the image data as shown in FIG. The pixels are counted in order.
  • a luminance distribution hereinafter, referred to as “histogram”.
  • the luminance value of the pixel takes a value from 0 to 255, and the light emission amount of the backlight is 0% when the luminance value is 0, and 255 The value of 0 to 100% is taken as 100%.
  • the light emission amount of the backlight is associated with the luminance value in advance.
  • the backlight is temporarily set based on the luminance value when the accumulated number of counted pixels (hereinafter referred to as “accumulated pixel number”) reaches a predetermined number.
  • accumulated pixel number the accumulated number of counted pixels
  • Determine the amount of luminescence Specifically, as shown in (A) of the figure, a position where the cumulative number of pixels exceeds a predetermined number on the histogram is set as a calculation point, and a light emission amount corresponding to the calculation point is set as a temporary light emission of the backlight. It is determined as an amount (hereinafter referred to as “provisional luminescence amount”).
  • the provisional light emission amount is compared with a predetermined threshold (hereinafter referred to as “H offset”).
  • H offset a predetermined threshold
  • the light emission amount smaller than the provisional light emission amount is determined as a definite light emission amount (hereinafter referred to as “determined light emission amount”). Determine as.
  • the display control method determines the H offset as the final light emission amount.
  • the light emission amount of the backlight is set to be relatively large, but the H offset located on the lower luminance side than the calculation point is set as the final light emission amount.
  • the light emission amount of the backlight can be reduced as compared with the case where the light emission amount corresponding to the calculation point is set as the fixed light emission amount. Therefore, it is possible to increase the power consumption reduction amount as compared with the case where the light emission amount at the calculation point is set as the fixed light emission amount.
  • the display control method according to the first embodiment by introducing the H offset as the upper limit value of the light emission amount of the backlight, even when a bright image is input, the determined light emission amount is equal to or higher than the H offset. It was decided to restrict so that it would not. Therefore, according to the display control method according to the first embodiment, it is possible to suppress a reduction in the amount of reduction in the power consumption of the backlight when a bright image is input.
  • the provisional emission amount is determined as the definite emission amount of the backlight. For example, as shown in FIG. 5B, when a dark image is input, the number of pixels positioned on the low luminance side of the histogram increases, and as a result, the calculation point is positioned on the low luminance side of the H offset. Will be. In such a case, since the provisional light emission amount is smaller than the H offset, the provisional light emission amount is determined as the determined light emission amount.
  • halation a phenomenon that the color of a particularly bright part in the image appears to be crushed. This may cause image quality degradation. Therefore, when there is a possibility that halation will occur, a process of avoiding the occurrence of halation by determining a light emission amount larger than the H offset as the determined light emission amount may be performed. The specific contents of the halation avoidance will be described in the second embodiment.
  • the provisional light emission amount is larger than the H offset and the H offset is set as the fixed light emission amount has been described so far, but the present invention is not limited to this.
  • a value obtained by converting the provisional emission amount by a predetermined conversion formula may be determined as the determined emission amount. This point will also be described later.
  • 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.
  • the display control device according to the present invention is not limited to this, and various types of display units that perform display using a backlight, such as a mobile terminal device, a PC (Personal Computer), or a TV (Television). It can be applied to other devices.
  • FIG. 2 is a block diagram illustrating the configuration of the display control apparatus according to the first 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.
  • the display control device 10 is a device that performs display control of the liquid crystal display 20 mounted on the in-vehicle device.
  • 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.
  • the display control apparatus 10 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 125.
  • the control unit 11 is a processing unit that executes processing such as acquisition of image data from the in-vehicle device, sub-sampling of the acquired image data, generation and analysis of a histogram, light emission amount change processing, PWM generation, or RGB conversion processing.
  • 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.
  • sub-sampling indicates a process of thinning out pixels from 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.
  • the image data of WVGA size 800 ⁇ 480
  • the image data of WVGA size 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.
  • the histogram is information representing the luminance distribution of the pixels constituting the image data.
  • 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 determined light emission amount of the backlight module 22 by analyzing the histogram generated by the histogram generation unit 11c using the threshold information 12a.
  • FIG. 3 is a block diagram illustrating the configuration of the histogram analysis unit 11d according to the first embodiment.
  • the histogram analysis unit 11d includes a provisional light emission amount determination unit 111a, a comparison unit 111b, and a fixed light emission amount determination unit 111c.
  • the threshold information 12a includes a DNUM 121 and an H offset 122.
  • the provisional emission amount determination unit 111a is a processing unit that determines the provisional emission amount using the histogram acquired from the histogram generation unit 11c and the DNUM 121 included in the threshold information 12a.
  • the DNUM 121 is information indicating a threshold value for the cumulative number of pixels.
  • the provisional light emission amount determination unit 111a 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 121. The amount is determined as the provisional light emission amount. In addition, when the provisional light emission amount determination unit 111a determines the provisional light emission amount, the provisional light emission amount determination unit 111a also performs a process of passing the determined provisional light emission amount to the comparison unit 111b.
  • the comparison unit 111b is a processing unit that compares the provisional emission amount determined by the provisional emission amount determination unit 111a with the H offset 122 stored in the storage unit 12.
  • the H offset 122 is threshold information indicating the upper limit value of the light emission amount of the backlight module 22.
  • the comparison unit 111b also performs a process of passing the comparison result between the provisional light emission amount and the H offset to the fixed light emission amount determination unit 111c.
  • the determined light emission amount determination unit 111c is a processing unit that determines the determined light emission amount according to the comparison result by the comparison unit 111b.
  • the determined light emission amount determining unit 111c also performs a process of passing the determined determined light emission amount to the light emission amount changing unit 11e.
  • FIG. 4 is a diagram illustrating an operation example of the histogram analysis unit 11d according to the first embodiment. Note that (A) in the figure shows an operation example of the provisional light emission amount determination unit 111a, and (B) and (C) in the same figure show operation examples of the comparison unit 111b and the fixed light emission amount determination unit 111c. Each is shown.
  • the provisional light emission amount determination unit 111a sets the position of the luminance value “255” in the histogram as the counting start point.
  • the provisional light emission amount determination unit 111a sequentially counts the number of pixels corresponding to each luminance value from the counting start point toward the low luminance side. Then, the provisional light emission amount determination unit 111a determines the position where the cumulative number of pixels reaches DNUM 121 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.
  • the provisional light emission amount determination unit 111a sets the light emission amount “78%” corresponding to the luminance value “200” to provisional light emission. Determine as quantity.
  • the comparison unit 111b compares the provisional light emission amount determined by the provisional light emission amount determination unit 111a with the H offset 122, and passes the comparison result to the fixed light emission amount determination unit 111c. Then, as shown in (B) of the figure, when the provisional emission amount is equal to or less than the H offset, the determined emission amount determination unit 111c determines the provisional emission amount as the fixed emission amount. On the other hand, when the provisional light emission amount exceeds the H offset, the determined light emission amount determination unit 111c determines the H offset as the determined light emission amount.
  • the calculation point when the calculation point is located on the lower luminance side than the H offset, such as the calculation point a and the calculation point b, that is, the input image is a dark image.
  • the light emission amount (provisional light emission amount) corresponding to each calculation point is the determined light emission amount.
  • the calculated points are located on the higher luminance side than the H offset as in the calculation points c to e, that is, when the input image is a bright image, the determined light emission amount corresponds to each calculated point.
  • the H offset is a light emission amount smaller than the light emission amount (provisional light emission amount).
  • the H offset that is a light emission amount smaller than the provisional light emission amount is set as the definite light emission amount, thereby inputting a bright image. Even if it exists, the reduction amount of the power consumption of the backlight module 22 can be increased as much as possible.
  • the light emission amount changing unit 11e emits light based on the difference between the determined 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 processing unit for performing a light emission amount changing process for limiting the amount of change in the amount.
  • 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.
  • the light emission amount changing unit 11e will be described more specifically in the third embodiment.
  • 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 125, and passes the determined RGB conversion coefficient to the RGB conversion unit 11g. Do.
  • the contents of the RGB conversion information 125 will be described with reference to FIG.
  • FIG. 5 is a diagram illustrating an example of the RGB conversion information 125.
  • the RGB conversion information 125 is information in which “RGB conversion coefficient” is associated with each “changed light emission amount”.
  • “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.
  • 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.
  • 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.
  • R, G, and B components are respectively multiplied by RGB conversion coefficients.
  • the RGB conversion information 125 is set so that the RGB conversion coefficient increases as the light emission amount after change decreases, that is, as the light emission amount of the backlight module 22 decreases and the screen becomes darker.
  • 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 125, and passes the extracted RGB conversion coefficient to the RGB conversion unit 11g.
  • the PWM generation unit 11f 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 generator 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.
  • VSYNC Very Synchronizing signal
  • 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.
  • the RGB conversion unit 11g 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.
  • FIG. 6 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the first embodiment. In the figure, only the processing procedure related to the light emission amount control of the backlight among the processing procedures executed by the display control device 10 is shown.
  • the display control apparatus 10 when the image data acquisition unit 11a acquires image data (step S101), the sub-sampling unit 11b performs sub-sampling on the acquired image data (step S102). ). Subsequently, in the display control device 10, the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S103), and the temporary light emission amount determination unit 111a uses the histogram and the DNUM 121 to generate a temporary light emission amount. Is determined (step S104).
  • the comparison unit 111b compares the provisional light emission amount with the H offset 122 (step S105), and the determined light emission amount determination unit 111c determines whether or not the provisional light emission amount is larger than the H offset 122. Is determined (step S106). Then, when the provisional emission amount is larger than the H offset (Yes in step S106), the determined emission amount determination unit 111c sets the H offset as the decision emission amount (step S107), and the provisional emission amount is equal to or less than the H offset. In this case (No at Step S106), the provisional light emission amount is set as the fixed light emission amount (Step S108).
  • the light emission amount changing unit 11e performs a light emission amount changing process to determine the changed light emission amount (step S109).
  • 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).
  • 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.
  • the provisional light emission amount determination unit counts pixels constituting the image data in descending order of luminance value for the input image data, and accumulates the counted pixels.
  • the provisional light emission amount of the backlight is determined based on the luminance value when the number reaches the predetermined number, the comparison unit compares the temporary light emission amount with a predetermined threshold value, and the determined light emission amount determination unit As a result of comparison by the comparison unit, when the provisional light emission amount exceeds a predetermined threshold, the light emission amount smaller than the provisional light emission amount is determined as the definite light emission amount of the backlight. Accordingly, it is possible to suppress a reduction in the amount of reduction in power consumption of the backlight when a bright image is input.
  • the image quality deterioration is prevented by performing the correction for increasing the RGB value by the RGB conversion processing.
  • Example 2 it is determined whether there is a possibility that halation will occur when the provisional light emission amount is larger than the H offset, and when it is determined that there is a possibility that it will occur, it is larger than the H offset. By determining the light emission amount as the definite light emission amount, the occurrence of halation was avoided.
  • FIG. 7 is a diagram illustrating an outline of the halation avoidance technique according to the second embodiment.
  • (A) of the figure shows the situation where halation occurs
  • (B) of the figure shows an outline of the halation avoidance technique.
  • the RGB conversion coefficient is “1.00” (see FIG. 5). That is, when the input RGB value is “255”, the output RGB value is also “255”.
  • the RGB conversion coefficient is “2.05” (see FIG. 5).
  • the output RGB values are all “255” (that is, the output RGB value is “255”).
  • the output RGB value should be “410”.
  • the limit value of the RGB value is “255”
  • the output RGB value is “255”. It becomes.
  • the image data includes a pixel having a large RGB value
  • the converted RGB value output RGB value
  • portions that should originally be expressed with different RGB values are all expressed with the same RGB value (255) by the RGB conversion processing. May deteriorate.
  • the display control apparatus 10 determines whether or not there is a possibility of halation when a bright image is input, that is, when the provisional light emission amount is larger than the H offset, When it is determined that there is a risk of occurrence, the light emission amount larger than the H offset is determined as the determined light emission amount.
  • the display control apparatus 10 calculates the average luminance of the image data after sub-sampling as shown in (B) of the figure, and the average luminance corresponds to the H offset. If it is higher than that, it is determined that halation may occur.
  • the display control device 10 determines that there is a high possibility that halation will occur, the display control device 10 does not set the H offset as the fixed light emission amount, but sets the light emission amount corresponding to the average luminance as the fixed light emission. Amount.
  • the RGB conversion coefficient may be reduced and the output RGB value may reach a peak by setting the determined light emission amount to be higher than the H offset. Since it is suppressed, the occurrence of halation can be avoided.
  • the histogram analysis unit 11d 'according to the second embodiment further includes an average luminance calculation unit 111d in addition to the configuration of the histogram analysis unit 11d described in the first embodiment.
  • the average luminance calculation unit 111d is a processing unit that acquires a histogram from the histogram generation unit 11c and calculates the average luminance of the subsampled image data using the acquired histogram.
  • the average luminance calculation unit 111d also performs a process of passing the calculated average luminance to the comparison unit 111b.
  • the comparison unit 111b further compares the average luminance acquired from the average luminance calculation unit 111d with the luminance value corresponding to the H offset. In addition, the comparison unit 111b also performs a process of passing this comparison result to the determined light emission amount determination unit 111c.
  • the determined light emission amount determination unit 111c determines whether or not the average luminance is higher than the luminance value corresponding to the H offset. Then, when it is determined that the average luminance is higher than the luminance value corresponding to the H offset, the determined light emission amount determination unit 111c determines the light emission amount corresponding to the average luminance as the determined light emission amount.
  • FIG. 9 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the second embodiment. In the figure, only the processing procedure related to the light emission amount control of the backlight among the processing procedures executed by the display control device 10 is shown.
  • the sub-sampling unit 11b performs sub-sampling on the acquired image data (step S202). ).
  • the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S203), and the average luminance calculation unit 111d uses the histogram to output the image data after sub-sampling. Is calculated (step S204).
  • the provisional light emission amount determining unit 111a determines the provisional light emission amount using the histogram and the DNUM 121 (step S205).
  • the comparison unit 111b compares the provisional light emission amount with the H offset 122 (step S206), and the determined light emission determination unit 111c determines whether or not the provisional light emission amount is larger than the H offset 122. Is determined (step S207). Subsequently, when the provisional light emission amount is larger than the H offset (step S207, Yes), the determined light emission amount determination unit 111c further determines whether or not the average luminance is higher than the luminance value corresponding to the H offset. (Step S208).
  • the determined emission amount determining unit 111c determines the emission amount corresponding to the average luminance as the determined emission amount. (Step S209).
  • the determined light emission amount determining unit 111c determines the H offset as the determined light emission amount (Step S210). In step S207, if the provisional light emission amount is not greater than the H offset (No in step S207), the provisional light emission amount is determined as the determined light emission amount (step S211).
  • the light emission amount changing unit 11e performs a light emission amount changing process based on the difference between the determined light emission amount acquired from the determined light emission amount determining unit 111c and the current light emission amount, and determines the changed light emission amount (step S212).
  • the PWM generation unit 11f generates a PWM signal corresponding to the changed light emission amount and outputs the PWM signal to the backlight module 22 (step S213).
  • 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 S214). Then, the RGB conversion unit 11g outputs the image data after the RGB conversion processing to the liquid crystal panel 21 (step S215), and ends the processing.
  • the average luminance calculation unit calculates the average luminance of the image data
  • the comparison unit further compares the average luminance calculated by the average luminance calculation unit with the H offset and confirms it. If the provisional light emission amount exceeds the H offset and the average luminance exceeds the H offset as a result of the comparison by the comparison unit, the light emission amount determination unit determines the average luminance as the definite light emission amount of the backlight. It was.
  • the second embodiment when a bright image is input, it is possible to prevent image quality deterioration due to the occurrence of halation while suppressing a reduction in power consumption of the backlight module 22 from being reduced.
  • FIG. 10 is a diagram for explaining a halation avoidance function and an H offset setting change.
  • image quality emphasis mode the state where the halation avoidance function is ON
  • power saving mode the case where it is OFF
  • the liquid crystal panel 21 displays a mode selection button 21a, a “dark” button 21c and a “bright” button 21d for adjusting the screen brightness.
  • the liquid crystal panel 21 displays the current power consumption reduction rate 21b.
  • “image quality emphasis mode” is selected, and “brightness” is set to 4 out of 7 levels.
  • “30%” is displayed as the current power consumption reduction rate.
  • the user can select either the image quality emphasis mode or the power saving mode according to his / her preference by pressing the mode selection button 21a while confirming the image displayed on the liquid crystal panel 21. .
  • the image quality emphasis mode in the image quality emphasis mode, the image quality is improved because halation is prevented, and the light emission amount less than the provisional light emission amount is emitted from the backlight module 22. Since it is used as a quantity, it has a high power saving effect. On the other hand, in the power saving mode, there is a possibility that halation may occur. Therefore, although the image quality is inferior to that in the image quality emphasis mode, the light emission amount of the backlight module 22 is further reduced. Compared to higher.
  • a user who thinks that the image quality is high enough to recognize characters can improve the power saving effect by selecting the power saving mode.
  • the user can confirm the image quality of the image displayed on the liquid crystal panel 21 and the power consumption reduction rate 21b, and press the “dark” button 21c and the “bright” button 21d, so that the brightness according to the user's preference can be obtained. Can be adjusted.
  • the value of the H offset is set so as to decrease as the “dark” button 21c is pressed and increase as the “bright” button 21d is pressed. Has been.
  • the “dark” button 21c is pressed to reduce the value of the H offset, the upper limit value of the light emission amount of the backlight module 22 is lowered, and the power saving effect is further enhanced.
  • the value of the H offset may be extremely lowered to greatly increase the power saving effect.
  • a line-of-sight detection sensor is provided on the liquid crystal display 20.
  • the gaze detection sensor is a sensor that detects the gaze direction of the user, and outputs the detection result to the display control device 10.
  • control unit 11 of the display control apparatus 10 determines whether or not the user's line of sight is on the liquid crystal panel 21, and detects the viewer of the image when determining that the user's line of sight is on the liquid crystal panel 21. And the control part 11 of the display control apparatus 10 reduces the value of H offset significantly, when the viewer of an image is not detected.
  • control unit 11 of the display control apparatus 10 functions as a viewer detection unit to detect a viewer of an image displayed on the liquid crystal panel 21. Further, the control unit 11 of the display control device 10 functions as a threshold value changing unit, so that when the image viewer is not detected, the value of the H offset is compared with the case where the image viewer is detected. Lower.
  • the upper limit value of the light emission amount of the backlight module 22 is greatly reduced, so that a power saving effect is achieved. It can be further increased.
  • the definite amount of light emission is 0% regardless of what image data is input.
  • the power consumption of the module 22 can be reduced to the maximum.
  • the present invention is not limited to this.
  • a value obtained by converting the provisional emission amount by a predetermined conversion formula may be determined as the determined emission amount.
  • the determined emission amount determination unit 111c obtains a value obtained by converting the provisional emission amount using the above conversion formula. Is determined as the definite light emission amount.
  • the deterministic light emission amount determination unit 111c uses, for example, a linear function that obtains a definite light emission amount smaller than the provisional light emission amount by multiplying the provisional light emission amount by a coefficient larger than 0 and smaller than 1 as a conversion equation. be able to.
  • the determined light emission amount becomes smaller than the provisional light emission amount, and the fixed light emission amount changes depending on the provisional light emission amount, so that the reduction in the amount of power consumption of the backlight is reduced.
  • the backlight can be emitted with a fixed light emission amount suitable for each image.
  • the conversion expression may be any conversion expression as long as the value before conversion is smaller than the value after conversion.
  • FIG. 11 is a diagram for explaining a case where the L offset is set.
  • the provisional light emission amount determination unit 111a sequentially counts the number of pixels from the high luminance side of the histogram, and corresponds to the position (luminance value) on the histogram when the cumulative number of pixels exceeds DNUM 121. The amount of light emitted is determined as the provisional light emission amount. Subsequently, the comparison unit 111b compares the provisional light emission amount with another threshold value (L offset) set on the lower luminance side than the H offset.
  • L offset another threshold value
  • the determined emission amount determination unit 111c determines the provisional emission amount as it is as the fixed emission amount.
  • the determined light emission amount determining unit 111c determines the L offset as the determined light emission amount.
  • Patent Document 1 has a problem that flicker may occur on the screen displayed on the liquid crystal display when the brightness of the image changes frequently. This is because a dark portion of an image is easily affected by luminance due to a change in the amount of backlight emission, and a sudden change in the amount of backlight emission causes flickering.
  • the backlight emission amount is set to be large even though the scene is dark, or conversely, even though the scene is bright.
  • the amount of light emitted from the backlight may be set to be small, which causes flickering on the screen.
  • Example 3 when the target light emission amount of the backlight is determined based on the luminance distribution of the input image, the determined light emission amount is obtained by changing the current light emission amount step by step over a plurality of frames. To match.
  • Example 3 will be described with reference to FIGS.
  • the same reference numerals as those in the first or second embodiment are used for the same functions as those of the display control apparatus 10 according to the first or second embodiment, and the description thereof is omitted. To do.
  • FIG. 12 is a diagram illustrating an overview of the display control method according to the third embodiment.
  • (A) in the figure shows an outline of a conventional display control technique
  • (B) in the figure shows an outline of a display control technique according to the third embodiment.
  • the graph shown to (A) and (B) of the figure represents the time-dependent change of the emitted light quantity of a backlight. Times t0 to t3 attached to the horizontal axis represent frame update timings.
  • the target light emission amount is determined based on the luminance distribution of a certain frame
  • the determined target light emission amount is directly adopted as the light emission amount of the backlight in the next frame.
  • the target light emission amount determined based on the luminance distribution of the frame updated at time t0 is used as the light emission amount of the backlight at time t1.
  • the target light emission amount determined based on the luminance distribution of the frame updated at time t0 is used as the light emission amount of the backlight at time t1.
  • the target light emission amount when the target light emission amount is immediately reflected as the backlight light emission amount, when the actual light emission amount and the target light emission amount are greatly different, the backlight light emission amount changes abruptly. There is a risk of flickering. In particular, when a bright image and a dark image are alternately repeated, the difference between the light emission amount to be applied and the light emission amount actually applied tends to increase, and the flickering of the screen becomes remarkable.
  • the current light emission amount is changed stepwise over a plurality of frames. It is characterized in that it matches the determined light emission amount.
  • the current light emission amount is not changed linearly, but is increased as the difference from the target light emission amount is increased, and the change amount is reduced as the target light emission amount is approached. It also has a feature in that it can be changed.
  • the amount of change from the current light emission amount is Determine the amount of change (large).
  • the light emission amount obtained by changing the current light emission amount by the change amount (large) is applied to the frame updated at t1.
  • the amount of change (large) is an amount of change that does not cause screen flickering.
  • the difference value between the light emission amount (current light emission amount) and the target light emission amount at time t1 is smaller than the difference value between the light emission amount (current light emission amount) and the target light emission amount at time t0. For this reason, in the display control method according to the third embodiment, a change amount (medium) is determined as a change amount from the current light emission amount. In the display control method according to the third embodiment, the light emission amount obtained by changing the current light emission amount by the change amount (medium) is applied to the frame updated at t2.
  • the difference value between the light emission amount (current light emission amount) and the target light emission amount at time t2 is smaller than the difference value between the light emission amount (current light emission amount) and the target light emission amount at time t1.
  • the change amount (small) is determined as the change amount from the current light emission amount.
  • the light emission amount obtained by changing the current light emission amount by the change amount (small) is applied to the frame updated at t3.
  • the actual light emission amount of the backlight coincides with the target light emission amount determined based on the luminance distribution of the frame updated at time t0 at time t3.
  • the change is made stepwise over a plurality of frames. As a result, flickering of the screen can be prevented.
  • the current light emission amount is greatly changed with a change amount that does not cause flickering of the screen.
  • the difference value decreases, the amount of change is also reduced, so that the current light emission amount is smoothly converged to the target light emission amount.
  • the light emission amount of the backlight can be brought close to the target light emission amount as quickly as possible, so that the color collapse that tends to occur when the difference between the light emission amount of the backlight and the target light emission amount is large can be prevented.
  • the screen may flicker. Therefore, if the difference value between the target light emission amount and the current light emission amount is a predetermined value or less, the light emission amount of the backlight may not be changed. Accordingly, it is possible to prevent screen flickering caused by a slight change in the light emission amount of the backlight.
  • the amount of change from the current light emission amount may be reduced. As a result, it is possible to reduce the processing load caused by frequently changing the light emission amount of the backlight in a short period.
  • 12A and 12B illustrate the case where the light emission amount of the backlight is increased toward the target light emission amount, but in the display control method according to the third embodiment, the light emission amount of the backlight is the target. Similarly, in the case of decreasing toward the light emission amount, the light emission amount of the backlight is changed stepwise.
  • the light emission amount of the backlight when the light emission amount of the backlight is decreased, the amount of change may be larger than when the light emission amount of the backlight is increased. Thereby, when reducing the light emission amount of the backlight, the light emission amount of the backlight module 22 can be brought closer to the target light emission amount without causing the viewer to feel the flickering of the screen.
  • FIGS. 12A and 12B the case where the actual light emission amount of the backlight is changed in three stages has been described.
  • the present invention is not limited to this. There is no problem.
  • the display control apparatus includes a display unit that performs display using a backlight, such as a mobile terminal device, a PC (Personal Computer), or a TV (Television).
  • a display unit that performs display using a backlight, such as a mobile terminal device, a PC (Personal Computer), or a TV (Television).
  • the present invention can be applied to various devices.
  • FIG. 13 is a block diagram illustrating the configuration of the display control apparatus according to the third embodiment.
  • the display control apparatus 10 according to the third embodiment includes a storage unit 12 ′ instead of the storage unit 12 in the display control apparatus 10 according to the first embodiment.
  • the storage unit 12 ' stores a DNUM 121 and setting information 12b. The specific contents of the setting information 12b will be described later.
  • the histogram analysis unit 11d is a processing unit that determines the definite light emission amount of the backlight module 22 by analyzing the histogram generated by the histogram generation unit 11c using the DNUM 121.
  • the DNUM 121 is information indicating a threshold value for the cumulative number of pixels as described above.
  • FIG. 14 is a diagram illustrating an operation example of the histogram analysis unit 11d.
  • (A) in the figure shows an operation example of the cumulative pixel counting process using the histogram
  • (B) in the figure shows an operation example of the target light emission amount determination process. .
  • the luminance value of the pixel takes a value from 0 to 255.
  • the light emission amount of the backlight is associated with the luminance value in advance so as to take a value of 0 to 100%, with 0% when the luminance value is 0 and 100% when the luminance value is 255.
  • the histogram analysis unit 11d acquires the histogram from the histogram generation unit 11c, first, the histogram analysis unit 11d performs a counting process of counting the number of pixels in order from the high luminance side of the histogram. Specifically, as illustrated in (A) of FIG. 11, the histogram analysis unit 11 d uses 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 as the counting start point. Counts in order from the low brightness side.
  • the position corresponding to the luminance value being analyzed is referred to as “calculation point”.
  • the histogram analysis unit 11 d calculates a calculation point (luminance value) when the accumulated number of counted pixels (hereinafter referred to as “accumulated pixel number”) reaches DNUM 121. ) Is determined as the target light emission amount.
  • the histogram analysis unit 11d sets the light emission amount “78%” corresponding to the luminance value “200” as the target light emission amount. decide.
  • the histogram generation unit 11c and the histogram analysis unit 11d function as an example of target light emission amount determining means for determining the target light emission amount of the backlight based on the luminance distribution of the input image data.
  • the display control apparatus 10 according to the third embodiment includes the histogram analysis unit 11d according to the first embodiment
  • the present invention is not limited thereto, and the histogram control unit 11d ′ according to the second embodiment is provided. It is good as well.
  • the light emission amount changing unit 11e is a processing unit that determines the light emission amount of the backlight module 22 based on the difference between the target light emission amount acquired from the histogram analysis unit 11d and the current light emission amount.
  • the configuration of the light emission amount changing unit 11e will be described with reference to FIG.
  • FIG. 15 is a block diagram illustrating a configuration of the light emission amount changing unit 11e according to the third embodiment.
  • the light emission amount change unit 11e includes a difference value calculation unit 112a, a change amount determination unit 112b, a light emission amount determination unit 112c, and a conversion coefficient determination unit 112d.
  • the setting information 12b stores light emission amount history information 123, change amount setting information 124, and RGB conversion information 125.
  • the light emission amount history information 123 is history information of the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c.
  • the light emission amount history information 123 includes the current light emission amount of the backlight module 22 as history information.
  • the change amount setting information 124 is information used when determining the change amount of the light emission amount of the backlight module 22.
  • the light emission amount history information 123 will be described later with reference to FIG.
  • the RGB conversion information 125 is information in which “RGB conversion coefficient” is associated with each light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c.
  • the “RGB conversion coefficient” is a coefficient that is multiplied with the values (RGB values) of R, G, and B components.
  • the RGB conversion information 125 is set so that the RGB conversion coefficient increases as the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c decreases, that is, as the screen becomes darker.
  • the difference value calculation unit 112a is a processing unit that calculates a difference value between the target light emission amount acquired from the histogram analysis unit 11d and the current light emission amount. Specifically, when obtaining the target light emission amount from the histogram analysis unit 11d, the difference value calculation unit 112a extracts the current light emission amount included in the light emission amount history information 123 and subtracts the current light emission amount from the target light emission amount. The absolute value is the difference value.
  • the difference value calculation unit 112a is information indicating whether the value obtained by subtracting the current light emission amount from the target light emission amount is a positive value or a negative value, that is, the current light emission amount should be increased or decreased. A process of passing information indicating whether or not to be performed to the change amount determination unit 112b together with the calculated difference value is also performed.
  • the change amount determination unit 112b is a processing unit that determines a change amount from the current light emission amount according to the difference value acquired from the difference value calculation unit 112a. Specifically, the change amount determination unit 112b uses the change amount setting information 124 for the change amount associated with the range to which the difference value acquired from the difference value calculation unit 112a belongs among the ranges divided by a plurality of threshold values. The determined change amount is determined as a change amount from the current light emission amount.
  • FIG. 16 is a diagram illustrating an example of the change amount setting information 124.
  • the change amount setting information 124 is information in which a change amount is associated with each range divided by a plurality of threshold values (threshold value L1 and threshold value L2) having different sizes. Specifically, the change amount setting information 124 is information in which “change amount (increase)” and “change amount (decrease)” are associated with each “range” delimited by the threshold L1 and the threshold L2. .
  • range includes ranges “A1” to “A3”. Specifically, the range “A1” indicates a range where “threshold L1 ⁇ difference value”, the range “A2” indicates a range where “threshold L2 ⁇ difference value ⁇ threshold L1”, and the range “A3” indicates “ A range where difference value ⁇ threshold value L2 ”is shown. As shown in the figure, the threshold value L1 is assumed to be larger than the threshold value L2.
  • “change amount (when increased)” is information indicating a change amount applied when the light emission amount of the backlight module 22 is increased.
  • “HI_1” is stored in association with the range “A1”
  • “MID_1” is stored in association with the range “A2”
  • “LOW_1” is stored in association with the range “A3”.
  • the amount of change (at the time of increase) is “HI_1” is the largest and “LOW_1” is the smallest among “HI_1”, “MID_1”, and “LOW_1”.
  • the change amount “HI — 1” is a change amount that does not cause screen flicker in the liquid crystal display 20.
  • “change amount (at the time of decrease)” is information indicating the change amount used when the light emission amount of the backlight module 22 is reduced.
  • “HI_2” is stored in association with the range “A1”
  • “MID_2” is stored in association with the range “A2”
  • “LOW_2” is stored in association with the range “A3”.
  • the amount of change (at the time of decrease) is “HI_2” is the largest and “LOW_2” is the smallest among “HI_2”, “MID_2”, and “LOW_2”.
  • “HI_2” of the amount of change (when decreasing) is larger than “HI_1” of the amount of change (when increasing).
  • the change amount setting information 124 associates a larger change amount with a range delimited by a threshold having a larger value among ranges delimited by a plurality of threshold values.
  • the change amount setting information 124 is first change amount setting information used when the target light emission amount is larger than the current light emission amount, and second change information used when the target light emission amount is smaller than the current light emission amount. Change amount setting information.
  • the change amount determination unit 112b determines the change amount corresponding to the range to which the difference value acquired from the difference value calculation unit 112a belongs as the change amount of the backlight module 22 by referring to the change amount setting information 124. Further, the change amount determination unit 112b also performs a process of passing the determined change amount and information indicating whether the current light emission amount should be increased or decreased to the light emission amount determination unit 112c.
  • the difference value calculation unit 112a and the change amount determination unit 112b are based on the difference value between the target light emission amount determined by the target light emission amount determination unit and the current light emission amount of the backlight. It functions as an example of a change amount determining means for determining a change amount.
  • the light emission amount determination unit 112c is a processing unit that determines the light emission amount obtained by changing the current light emission amount by the change amount determined by the change amount determination unit 112b as the light emission amount of the backlight module 22. Specifically, the light emission amount determination unit 112c performs a process of taking out the current light emission amount from the light emission amount history information 123 and changing the extracted current light emission amount by the change amount acquired from the change amount determination unit 112b.
  • the light emission amount determination unit 112c uses the current light emission amount extracted from the light emission amount history information 123.
  • a value obtained by adding the change amounts acquired from the change amount determination unit 112b is determined as the light emission amount of the backlight module 22.
  • the light emission amount determination unit 112c changes with respect to the current light emission amount extracted from the light emission amount history information 123. A value obtained by subtracting the change amount acquired from the amount determination unit 112b is determined as the light emission amount of the backlight module 22.
  • the light emission amount determination unit 112c determines the light emission amount of the backlight module 22
  • the light emission amount determination unit 112c passes the determined light emission amount to the PWM generation unit 11f and the conversion coefficient determination unit 112d.
  • the light emission amount determination unit 112c determines the light emission amount of the backlight module 22
  • the light emission amount determination unit 112c also performs a process of storing the determined light emission amount in the light emission amount history information 123.
  • FIG. 17 is a diagram illustrating an operation example of the change amount determination unit 112b and the light emission amount determination unit 112c.
  • 2A shows an operation example when the light emission amount of the backlight module 22 is increased
  • FIG. 2B shows an operation example when the light emission amount of the backlight module 22 is decreased. Respectively.
  • the target light emission amount shown in (A) of the figure is a target light emission quantity based on the histogram of the frame (image data) updated at time t0, and the target light emission quantity shown in (B) of FIG. It is assumed that the target light emission amount is based on the histogram of the frame updated at time t4.
  • the difference value D1 between the light emission amount (current light emission amount) applied to the frame updated at time t0 and the target light emission amount is within the range “A1” shown in FIG. ".
  • the change amount determination unit 112b extracts the change amount (in the increase) “HI_1” corresponding to the range “A1” from the change amount setting information 124, and passes the extracted change amount “HI_1” to the light emission amount determination unit 112c. .
  • the light emission amount determination unit 112c acquires the change amount “HI_1” from the change amount determination unit 112b, the light emission amount determination unit 112c extracts the current light emission amount from the light emission amount history information 123, and the change amount “HI_1” with respect to the extracted current light emission amount. ] Is determined as the backlight module 22. As a result, the light emission amount of the backlight module 22 is increased by the change amount “HI_1” at the time t1.
  • the change amount determining unit 112b extracts the change amount (when increasing) “MID_1” corresponding to the range “A2” from the change amount setting information 124, and passes the extracted change amount “MID_1” to the light emission amount determining unit 112c.
  • the change amount “MID_1” is a value smaller than the change amount “HI_1”.
  • the light emission amount determination unit 112c acquires the change amount “MID_1” from the change amount determination unit 112b, the light emission amount determination unit 112c extracts the current light emission amount from the light emission amount history information 123, and the change amount “MID_1” with respect to the extracted current light emission amount. ] Is determined as the backlight module 22. As a result, the light emission amount of the backlight module 22 is increased by the change amount “MID_1” at the time t2.
  • the change amount determination unit 112b extracts the change amount (when increasing) “LOW_1” corresponding to the range “A3” from the change amount setting information 124, and passes the extracted change amount “LOW_1” to the light emission amount determination unit 112c. .
  • the change amount “LOW_1” is smaller than the change amount “MID_1”.
  • the light emission amount determination unit 112c acquires the change amount “LOW_1” from the change amount determination unit 112b, the light emission amount determination unit 112c extracts the current light emission amount from the light emission amount history information 123, and the change amount “LOW_1” with respect to the extracted current light emission amount. ] Is determined as the backlight module 22. As a result, the light emission amount of the backlight module 22 is increased by the change amount “LOW_1” at time t3.
  • the light emission amount of the backlight module 22 when the light emission amount of the backlight module 22 is matched with the target light emission amount, the light emission amount of the backlight module 22 is not changed suddenly in one frame, but is stepped over a plurality of frames. It was decided to make it correspond with the target light emission amount by changing it periodically. Therefore, a rapid change in the light emission amount of the backlight module 22 can be suppressed, and as a result, flickering of the screen can be prevented.
  • Example 3 when the difference value between the current light emission amount and the target light emission amount is large, the current light emission amount is largely changed by a change amount that does not cause flickering of the screen, while the difference value is small. As the amount of change gradually decreases, the current light emission amount is gradually converged to the target light emission amount. As a result, the light emission amount of the backlight module 22 can be brought close to the target light emission amount as soon as possible, so that color collapse that is likely to occur when the difference between the light emission amount of the backlight module 22 and the target light emission amount is large can be prevented. .
  • the change amount determination unit 112b extracts the change amount (when reduced) “HI_2” corresponding to the range “A1” from the change amount setting information 124, and passes the extracted change amount “HI_2” to the light emission amount determination unit 112c. .
  • the light emission amount determination unit 112c acquires the change amount “HI_2” from the change amount determination unit 112b
  • the light emission amount determination unit 112b extracts the current light emission amount from the light emission amount history information 123, and the change amount “HI_2” with respect to the extracted current light emission amount.
  • the value obtained by subtracting “ is determined as the backlight module 22.
  • the light emission amount of the backlight module 22 is reduced by the change amount “HI_2” at time t5.
  • the amount of change “HI_2” used when the backlight module 22 is decreased is larger than the amount of change “HI_1” used when the backlight module 22 is increased. Value. This is because the viewer is less likely to recognize when the screen is darkened instantaneously than when the screen is brightened instantaneously.
  • the maximum light emission amount when the light emission amount of the backlight module 22 is decreased larger than the maximum light emission amount when the light emission amount of the backlight module 22 is increased the viewer feels flickering on the screen. Without this, the light emission amount of the backlight module 22 can be brought closer to the target light emission amount more quickly.
  • the amount of power consumption reduction by the backlight module 22 increases, so that the power saving effect can be further enhanced.
  • the difference value D5 between the light emission amount applied to the frame updated at time t5 and the target light emission amount belongs to the range “A2”
  • the light emission amount of the backlight module 22 changes at time t6. It will decrease by “MID_2”.
  • the difference value D6 between the light emission amount applied to the frame updated at time t6 and the target light emission amount belongs to the range “A3”
  • the light emission amount of the backlight module 22 changes at time t7. It will decrease by “LOW_2”.
  • the value of the change amount stored as the light emission amount history information 123 can be arbitrarily set. For example, by setting each change amount (for example, “HI — 1”, “MID — 1”, etc.) to be a little smaller as a whole, the light emission amount of the backlight module 22 gradually changes toward the target light emission amount. For this reason, it is possible to more reliably prevent the occurrence of screen flicker.
  • each change amount for example, “HI — 1”, “MID — 1”, etc.
  • halation refers to a phenomenon in which the color of a particularly bright portion in an image appears to be crushed by causing the backlight module 22 to emit light with a small amount of light emission when a bright image is input.
  • each change amount stored as the light emission amount history information 123 is set to be a large amount as a whole, the actual light emission amount quickly follows the target light emission amount, thereby preventing the occurrence of halation. it can. However, in such a case, the amount of change in the actual light emission amount increases, and thus the screen flickers easily. Considering such circumstances, if the value of the change amount stored as the light emission amount history information 123 is set to an appropriate value according to the device characteristics of the liquid crystal display 20, the occurrence of halation and the screen It is possible to prevent the occurrence of flickering with a good balance.
  • the values of the threshold value L1 and the threshold value L2 stored as the light emission amount history information 123 can be arbitrarily set.
  • the set number of thresholds can be arbitrarily changed. In particular, when the number of thresholds is set to 0, the target light emission amount can be immediately reflected on the actual light emission amount.
  • the conversion coefficient determination unit 112d is a processing unit that determines the RGB conversion coefficient corresponding to the acquired light emission amount using the RGB conversion information 125 when the light emission amount of the backlight module 22 is acquired from the light emission amount determination unit 112c. .
  • the conversion coefficient determination unit 112d also performs a process of passing the determined RGB conversion coefficient to the RGB conversion unit 11g.
  • the PWM generation unit 11f is a processing unit that generates a PWM signal whose pulse width is adjusted so that the light emission amount of the backlight module 22 becomes the light emission amount acquired from the light emission amount determination unit 112c, and outputs the PWM signal to the backlight module 22. is there. Note that the PWM generator 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 multiplies the R, G, B component values included in the image data acquired from the image data acquisition unit 11a by the RGB conversion coefficient acquired from the conversion coefficient determination unit 112d. 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.
  • the RGB conversion unit 11g 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.
  • the RGB conversion information 125 is set such that the RGB conversion coefficient increases as the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c decreases. Therefore, the RGB conversion unit 11g corrects the RGB value to be larger as the light emission amount of the backlight module 22 is smaller.
  • the RGB conversion unit 11g corrects the RGB value to be larger as the light emission amount of the backlight module 22 is smaller.
  • the RGB brightness is increased by the RGB conversion unit 11g, so that the apparent brightness is kept constant and the image quality is improved. Deterioration is to be prevented.
  • FIG. 18 is a flowchart illustrating a processing procedure executed by the display control apparatus 10 according to the third embodiment.
  • the figure shows a processing procedure of the display control apparatus 10 when the light emission amount of the backlight module 22 is increased.
  • the change amount determination unit 112b of the display control apparatus 10 determines whether to increase or decrease the light emission amount of the backlight module 22 based on information from the difference value calculation unit 112a.
  • the sub-sampling unit 11b performs sub-sampling on the image data acquired by the image data acquisition unit 11a (step S301).
  • the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S302), and the histogram analysis unit 11d determines the target light emission amount using the histogram and DNUM 121. (Step S303).
  • the difference value calculation unit 112a calculates a difference value between the target light emission amount and the current light emission amount (step S304), and the change amount determination unit 112b has the calculated difference value in the range “ It is determined whether it belongs to “A1” (step S305). If it is determined that the difference value belongs to the range “A1” (step S305, Yes), the change amount determination unit 112b selects the change amount “HI_1” with reference to the change amount setting information 124 (step S305). S306).
  • the change amount determination unit 112b determines whether or not the calculated difference value belongs to the range “A2”. Determination is made (step S307).
  • the change amount determination unit 112b selects the change amount “MID_1” with reference to the change amount setting information 124 (step S307). S308).
  • the change amount determination unit 112b refers to the change amount setting information 124 and sets the change amount “LOW_1”. Select (step S309).
  • the light emission amount determination unit 112c adds a value obtained by adding the amount of change selected in any of steps S306, 308, and 309 to the current light emission amount extracted from the light emission amount history information 123. Is determined (step S310). Further, the light emission amount determination unit 112c stores the determined light emission amount in the light emission amount history information 123 (step S311).
  • the PWM generation unit 11f generates a PWM signal corresponding to the changed light emission amount and outputs the PWM signal to the backlight module 22 (step S312).
  • the RGB converter 11g multiplies 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 corresponding to the changed light emission amount. Processing is performed (step S313).
  • the RGB conversion unit 11g outputs the image data after the RGB conversion processing to the liquid crystal panel 21 (step S314), and ends the processing.
  • the histogram analysis unit determines the target light emission amount of the backlight based on the luminance value of the input image data, and the change amount determination unit determines the determined target light emission amount.
  • the amount of change from the current light emission amount is determined according to the difference value between the current light emission amount of the backlight and the backlight, and the light emission amount determination unit changes the current light emission amount by the determined change amount.
  • the amount of light emitted from the backlight was determined. Therefore, according to the third embodiment, it is possible to reduce screen flicker that occurs when the brightness of an image frequently changes while suppressing power consumption by the backlight.
  • the light emission amount of the backlight module 22 is changed even when the difference between the light emission amount of the backlight module 22 and the target light emission amount is small.
  • the screen may flicker even if the light emission amount of the backlight module 22 is slightly changed.
  • FIG. 19 is a diagram illustrating another operation example of the change amount determination unit 112b. Note that (A) in the figure shows another example of the change amount setting information 124, and (B) in the figure shows another example of operation when the light emission amount of the backlight module 22 is increased. Show.
  • the change determining unit 112b changes when the difference value at the time t2 belongs to the range “A3”, that is, when the difference value at the time t2 falls below the threshold value L2.
  • the amount of change “0” is selected with reference to the amount setting information 124 and passed to the light emission amount determination unit 112c.
  • the light emission amount determination unit 112c determines the current light emission amount extracted from the light emission amount history information 123 as the light emission amount of the backlight module 22. . As a result, the light emission amount of the backlight module 22 does not change despite a difference from the target light emission amount.
  • the amount of change from the current light emission amount of the backlight module 22 is set to 0, thereby the backlight module.
  • the flickering of the screen caused by a slight change in the light emission amount 22 can be prevented.
  • threshold value L2 has been described as a predetermined value here, the present invention is not limited to this, and a value smaller than the threshold value L2 may be separately provided as the predetermined value.
  • the light emission amount of the backlight module 22 is changed one by one as in the above-described embodiment.
  • a large processing load is applied to the liquid crystal display 20.
  • the change amount determination unit 112 b determines that the screen is blinking based on the light emission amount history of the backlight module 22 stored as the light emission amount history information 123.
  • the change amount is reduced by multiplying the change amount extracted from the change amount setting information 124 by a predetermined coefficient (or 0). And).
  • FIG. 20 is a diagram illustrating another operation example of the change amount determination unit 112b.
  • (A) in the figure shows a state in which a bright image and a dark image are alternately repeated
  • (B) in the figure shows a history of the light emission amount of the backlight module 22
  • (C) shows a change amount of the light emission amount of the backlight module 22 determined by the change amount determination unit 112b.
  • each determined light emission amount is stored in the storage unit 12 ′ as the light emission amount history information 123 each time. To go.
  • the storage unit 12 ′ stores the light emission amount “E1” determined in the frame F1, the light emission amount “E2” determined in the frame F2, and the frame F3.
  • the emitted light amount “E3” and the light amount “E4” determined in the frame F4 are stored as the light amount history information 123.
  • the change amount setting information 124 determines that the screen is blinking based on the light emission amount history of the backlight module 22. Specifically, the change amount determination unit 112b determines that the screen is blinking when all the difference values of the light emission amounts between adjacent frames are equal to or greater than a predetermined value.
  • the change amount determination unit 112b determines that the screen is blinking.
  • the change amount determination unit 112b determines that the screen is blinking
  • the change amount extracted from the change amount setting information 124 is multiplied by a predetermined coefficient. To reduce the amount of change (or 0).
  • the change amount determination unit 112b extracts the change amount “HI_1” from the change amount setting information 124, and multiplies the extracted change amount “HI_1” by a predetermined coefficient “0” to thereby change the backlight module 22.
  • the change amount of the light emission amount is set to “0”.
  • the light emission amount of the backlight module 22 is the same as that of the frame F5 in the frame F6.
  • the storage unit 12 ′ stores the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c for a predetermined frame
  • the change amount determination unit 112b stores the light emission amount stored in the storage unit 12 ′.
  • the light emission amount determination unit 112 c calculates the backlight module 22 by multiplying the change amount extracted from the change amount setting information 124 by the daytime coefficient. Is determined as the amount of change.
  • the light emission amount determination unit 112c is obtained by multiplying the change amount extracted from the change amount setting information 124 by the night coefficient, and the backlight module 22. Is determined as the amount of change.
  • the daytime coefficient is larger than the nighttime coefficient.
  • the amount of change from the current light emission amount is determined in accordance with the light emission amount of the backlight module 22, the target light emission amount, and the difference value.
  • the light emission amount of the module 22 may be forcibly changed to a designated light emission amount.
  • Patent Document 1 has a problem that the visibility of the high-luminance pixel is lowered when the high-luminance pixel is included in a part of the overall 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. .
  • Example 4 when a high-luminance pixel is included in a part of an overall dark image, the light emission amount of the backlight is not reduced too much.
  • Example 4 will be described with reference to FIGS.
  • Example 4 shown below, about the thing which exhibits the same function as the display control apparatus 10 which concerns on said Example 1, 2, or 3, the same code
  • FIG. 21 is a diagram illustrating an overview of the display control method according to the fourth embodiment.
  • (A) in the figure shows a state in which high luminance pixels are included in a part of an overall dark image
  • (B) in the figure shows the image shown in (A) in the figure. The luminance distribution is shown.
  • 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.
  • the light emission amount of the backlight is set to be small. Since the number of pixels located on the high luminance side is large, a large amount of light emitted from the backlight is set.
  • the amount of light emitted from the backlight is not reduced too much.
  • the light emission amount of the backlight is not simply set to the light emission amount according to the high luminance pixel, but the light emission is also considered in consideration of the power consumption reduction by the backlight. The amount was decided.
  • the display control method according to the fourth embodiment when image data is input, the number of pixels constituting the image data is changed from those having a high luminance value. Cumulative addition in order.
  • 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 from the calculation start point toward the lower luminance side.
  • the number of pixels of the value is sequentially accumulated and added (see (B-1) in the figure).
  • the re-high brightness value on the histogram changes according to the resolution.
  • the average luminance (hereinafter referred to as “partial average”) of pixels that have been cumulatively added (hereinafter referred to as “cumulative pixels”). (Refer to (B-2) in the figure).
  • 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.
  • 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 ((B-4) in the figure). reference). Specifically, in the display control method according to the fourth embodiment, the light emission amounts from 0% to 100% are associated in advance with the luminance values from 0 to 255, respectively. In the display control method according to the fourth embodiment, the light emission amount corresponding to the luminance value of the calculation point is determined as the light emission amount of the backlight.
  • the display control method when a high-luminance pixel is included in a part of an overall dark image, the amount of light emitted from the backlight is not reduced too much in accordance with the low-luminance pixel.
  • the visibility of high-luminance pixels can be improved.
  • 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.
  • the cumulative pixel number 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 The light emission amount of the backlight is determined based on the calculation point when the predetermined 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.
  • the difference between the calculation point and the partial average luminance is a predetermined threshold value.
  • 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.
  • 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.
  • the display control method according to the fourth embodiment is applied to a display control device that performs display control of a liquid crystal display mounted on an in-vehicle device.
  • the display control apparatus according to the fourth embodiment is not limited to this, and includes a display unit that performs display using a backlight, such as a mobile terminal device, a PC (Personal Computer), or a TV (Television).
  • a backlight such as a mobile terminal device, a PC (Personal Computer), or a TV (Television).
  • the present invention can be applied to various devices.
  • 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.
  • the display control apparatus 10 according to the fourth embodiment includes a histogram analysis unit 11d ′′ instead of the histogram analysis unit 11d in the display control apparatus 10 according to the first embodiment. Further, the display control apparatus 10 according to the fourth embodiment stores threshold information 12a ′ instead of the threshold information 12 in the display control apparatus 10 according to the first embodiment.
  • 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 ′.
  • FIG. 22 is a block diagram illustrating a configuration of the histogram analysis unit 11d ′′ according to the first embodiment.
  • the histogram analysis unit 11d ′′ includes a cumulative addition unit 113a, a partial average luminance calculation unit 113b, and a light emission amount determination unit 113c.
  • the threshold information 12a ′ includes a DNUM 121 and an AVEDIS 126.
  • the histogram generation unit 11c passes the generated histogram to the cumulative addition unit 113a and the partial average luminance calculation unit 113b.
  • the cumulative addition unit 113a 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 113a also performs a process of passing the cumulative number of pixels, which is the cumulative number of pixels, and the current calculation point to the light emission amount determination unit 113c.
  • the cumulative addition unit 113a 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 transferred to the light emission amount determination unit 113c.
  • the cumulative addition unit 113a also performs a process of passing the current calculation point to the partial average luminance calculation unit 113b.
  • the partial average luminance calculation unit 113b is a processing unit that calculates the average luminance of the pixels that have been cumulatively added by the cumulative addition unit 113a as the partial average luminance. That is, when the partial average luminance calculation unit 113b receives the calculation point from the cumulative addition unit 113a, the partial average luminance calculation unit 113b calculates the partial average luminance of pixels included from the calculation start point to the calculation point.
  • the partial average luminance is expressed by ⁇ ⁇ (calculation point) ⁇ (number of pixels) ⁇ / (cumulative number of pixels). 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.
  • the luminance value “255” has one pixel
  • the luminance value “254” has two pixels
  • the luminance value “253” has three pixels
  • the current calculation point is “253”.
  • the partial average luminance is ⁇ (255 ⁇ 1) + (254 ⁇ 2) + (253 ⁇ 3) ⁇ / 6 ⁇ 254.
  • the partial average luminance calculation unit 113b After calculating the partial average luminance, the partial average luminance calculation unit 113b passes the calculated partial average luminance to the light emission amount determination unit 113c.
  • the light emission amount determination unit 113c is a processing unit that determines the light emission amount of the backlight module 22 using the information received from the cumulative addition unit 113a and the partial average luminance calculation unit 113b, and the DNUM 121 and the AVEDIS 126 that are threshold information 12a ′. is there.
  • DNUM 121 is information indicating a threshold value for the cumulative number of pixels.
  • AVEDIS 126 is information indicating a threshold value of a difference between the partial average luminance and the current calculation point.
  • the light emission amount determination unit 113c 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 126 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 c determines the light emission amount corresponding to the calculation point when the cumulative number of pixels received from the cumulative addition unit 113 a reaches DNUM 121 as the light emission amount of the backlight module 22.
  • FIG. 23 is a diagram illustrating an operation example of the light emission amount determination unit 113c when a high-luminance pixel is included in an overall dark image.
  • the luminance difference value increases as the calculation point shifts to the low luminance side, and becomes AVEDIS 126 or more at a certain calculation point ( (See (B-1) in the figure).
  • the light emission amount determination unit 113c sets the light emission amount corresponding to this calculation point as the light emission amount of the backlight module 22.
  • FIG. 24 is a diagram illustrating another operation example of the light emission amount determination unit 113c. In the figure, a histogram in which pixels are evenly distributed is shown.
  • the cumulative addition unit 113a sequentially adds the number of pixels by sequentially shifting the calculation point to the low luminance side until the cumulative number of pixels reaches DNUM 121 (see FIG. (See (A-1)).
  • the light emission amount determination unit 113 c 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.
  • 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.
  • 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 processing 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 used as the light emission amount of the backlight module 22 as usual.
  • the light emission amount changing unit 11e and the current light emission amount acquired from the histogram analysis unit 11d '' are used to prevent screen flickering caused by a sudden change in the light emission amount of the backlight module 22. It is a processing unit that performs a light emission amount change process for limiting the amount of change in the light emission amount based on the difference from the amount. Specifically, the light emission amount changing unit 11e limits the amount of change in the light emission amount according to the processing procedure shown in the third embodiment.
  • FIG. 25 is a flowchart illustrating a processing procedure executed by the display control apparatus 10 according to the fourth 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.
  • the sub-sampling unit 11b performs sub-sampling on the image data acquired by the image data acquisition unit 11a (step S401). Further, in the display control apparatus 10, the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S402), and passes the generated histogram to the cumulative addition unit 113a and the partial average luminance calculation unit 113b.
  • the cumulative addition unit 113a starts a cumulative addition process of sequentially adding the number of pixels from the calculation start point using the histogram received from the histogram generation unit 11c (step S403).
  • the partial average luminance calculation unit 113b calculates partial average luminance that is the average luminance of the pixels that have been cumulatively added by the cumulative addition unit 113a (step S404).
  • the light emission amount determination unit 113c determines whether or not the cumulative pixel number has reached the DNUM 121 (step S405), and when the cumulative pixel number is less than the DNUM 121 (step S405, No), the luminance difference value. Is determined to be equal to or greater than AVEDIS 126 (step S406).
  • the light emission amount determination unit 113c determines the light emission amount corresponding to the calculated point when the luminance difference value is equal to or greater than AVEDIS 126 to the backlight module. The amount of light emission 22 is determined (step S407). On the other hand, when the luminance difference value is less than AVEDIS 126 (No in step S406), the light emission amount determination unit 113c repeats the processes in steps S404 to S406.
  • the light emission amount determination unit 113c sets the light emission amount corresponding to the calculated point when the cumulative pixel number has reached DNUM 121 as the backlight.
  • the amount of light emitted by the module 22 is determined (step S408).
  • step S407 or step S408 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 113c to determine the changed light emission amount (step S409).
  • 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 S410).
  • 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 S411). Then, the RGB converter 11g outputs the image data after the RGB conversion process to the liquid crystal panel 21 (step S412), and ends the process.
  • the cumulative addition unit cumulatively adds the number of pixels constituting the image data to the input image data in descending order of the 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.
  • 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 an example.
  • the present invention is not limited to this.
  • 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.
  • the cumulative number of pixels may reach DNUM 121 before the luminance difference value becomes equal to or greater than AVEDIS 126, 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 AVEDIS 126 may be made smaller than when the luminance value of the high-luminance pixel is high.
  • FIG. 26 is a diagram for explaining a case where the AVEDIS 126 is changed according to the value of the partial average luminance.
  • (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.
  • (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
  • (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.
  • the light emission amount determination unit 113c compares the luminance difference value with AVEDIS (large), and the luminance difference value is 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.
  • the light emission amount determination unit 113c 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.
  • the partial average luminance calculated by the partial average luminance calculation unit 113b 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 larger than AVEDIS 126. As a result, the high luminance pixel is visually recognized. sexually can be improved appropriately.
  • AVEDIS (large) and AVEDIS (small) stored as AVEDIS 126 can be arbitrarily changed as long as AVEDIS (small) does not exceed AVEDIS (large).
  • a method has been described in which the visibility of a high-brightness pixel is improved when a high-brightness pixel is included in a part of an overall dark image by introducing the AVEDIS 126.
  • This method can also improve the visibility of high-luminance pixels. For example, when all the pixels included in the image data are classified into two, a high luminance pixel and a low luminance pixel, and the cumulative addition unit 113a 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.
  • FIG. 27 is a diagram illustrating another operation example of the cumulative addition unit 113a.
  • (A) in the figure shows a normal operation example of the cumulative addition unit 113a
  • (B) in the same figure shows another operation example of the cumulative addition unit 113a.
  • the value of DNUM 121 will be described as “60”.
  • pixels with luminance values “200” to “255” are high luminance pixels
  • pixels with luminance values “0” to “199” are low luminance pixels.
  • Shall be classified as
  • the cumulative addition unit 113a 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.
  • the cumulative adder 113a is classified into low luminance pixels when the cumulative number of high luminance pixels is “15”. A value obtained by adding “15” to the number of pixels of the luminance value is cumulatively added. For example, the cumulative addition unit 113a cumulatively adds a value “16” obtained by adding “15” to the number of pixels “1” of the luminance value “199”.
  • 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.
  • the visibility of the high-luminance pixels can be enhanced 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.
  • the predetermined light emission amount may be determined as the light emission amount of the backlight module 22.
  • FIG. 28 is a diagram illustrating another operation example of the light emission amount determination unit 113c.
  • the partial average luminance calculation unit 113b calculates the overall average luminance which is the average luminance of all the pixels of the image data, and passes it to the light emission amount determination unit 113c.
  • the cumulative addition unit 113a passes the cumulative number of high luminance pixels to the light emission amount determination unit 113c.
  • 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”).
  • the light emission amount determining unit 113c receives the overall average brightness from the partial average brightness calculating unit 113b, it determines whether or not the overall average brightness is less than the threshold value B (see (1) in the figure). In addition, the light emission amount determination unit 113c 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). If the light emission amount determination unit 113c 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, the light emission amount determination unit 113c adds a part of the dark image. It is determined that a high-luminance pixel is included (see (3) in the figure).
  • the light emission amount determination unit 113c determines a predetermined light emission amount as the light emission amount of the backlight module 22 (see (4) in FIG. 4).
  • the predetermined light emission amount is a light emission amount larger than the light emission amount corresponding to the overall average luminance.
  • the predetermined threshold value 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.
  • the display control device and the display control method according to the present invention are useful when it is desired to further reduce the power consumption by the backlight, and are particularly suitable for the case where it is desired to reduce the power consumption of the liquid crystal display of the in-vehicle device. Yes.

Abstract

In order to control power consumption of a backlight, a display control device counts the number of pixels constituting input image data in descending order of brightness value, determines a provisional amount of emission of the backlight on the basis of the brightness value when the cumulative number of the counted pixels reaches a predetermined number, compares the provisional amount of emission with a predetermined threshold, and determines an amount of emission less than the provisional amount of emission as a determinate amount of emission of the backlight when the provisional amount of emission exceeds the predetermined threshold as a result of the comparison.

Description

表示制御装置および表示制御方法Display control apparatus and display control method
　本発明は、表示制御装置および表示制御方法に関する。 The present invention relates to a display control device and a display control method.
　近年、カーナビゲーションの普及に伴い、自動車には液晶ディスプレイを有する車載装置が搭載されることが一般的となってきている。 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.
　液晶ディスプレイは、バックライトから照射された光を部分的に遮ったり透過させたりすることによって映像の表示を行っているが、バックライトによる消費電力の高さが省電力化の妨げとなっている。そこで、近年では、バックライトによる消費電力を削減するための様々な試みがなされている。 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.
　たとえば、特許文献１には、映像の明るさに応じてバックライトの発光量を制御することで、バックライトによる消費電力を削減する技術が開示されている。具体的には、特許文献１に記載の技術では、映像に含まれる画素の輝度分布（ヒストグラム）を作成し、作成したヒストグラムを用いて高輝度側から累積画素数を計数していき所定の画素数に達した位置の輝度値をバックライト発光量として決定する。 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 image. 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.
　これにより、特許文献１に記載の技術では、暗い映像の場合には、高輝度側に位置する画素数が少ないためバックライトの発光量が少なく設定され、明るい映像の場合には、高輝度側に位置する画素数が多いためバックライトの発光量が多く設定されることとなる。 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.
特開２００７－２１９４７７号公報JP 2007-219477 A
　しかしながら、特許文献１に記載の技術には、バックライトによる消費電力を十分に抑えることが難しいという問題があった。たとえば、特許文献１に記載の技術には、明るい映像が入力された場合に、省電力効果が低くなるという問題があった。これは、明るい映像の場合には、バックライトの発光量が多めに設定される結果、消費電力の削減量が少なくなるためである。 However, the technique described in Patent Document 1 has a problem that it is difficult to sufficiently reduce power consumption by the backlight. For example, the technique described in Patent Document 1 has a problem that the power saving effect is reduced when a bright image is input. This is because, in the case of a bright image, the amount of power consumption is reduced as a result of setting a larger amount of backlight emission.
　このような問題は、特に、ナビゲーション画像などの明るい映像が多く表示される車載装置において顕著である。 Such a problem is particularly noticeable in an in-vehicle device that displays many bright images such as navigation images.
　これらのことから、バックライトによる消費電力をより抑えることができる表示制御装置あるいは表示制御方法をいかにして実現するかが大きな課題となっている。 For these reasons, it has become a major issue how to realize a display control device or a display control method that can further reduce the power consumption of the backlight.
　本発明は、上述した従来技術による問題点を解消するためになされたものであって、バックライトによる消費電力をより抑えることができる表示制御装置および表示制御方法を提供することを目的とする。 The present invention has been made to solve the above-described problems caused by the prior art, and an object of the present invention is to provide a display control device and a display control method that can further reduce power consumption by a backlight.
　上述した課題を解決し、目的を達成するために、本発明に係る表示制御装置は、表示パネルへ光を照射するバックライトの発光量を制御する表示制御装置であって、入力された画像データに対して、当該画像データを構成する画素を輝度値の高いものから順に計数する計数手段と、前記計数手段によって計数された画素の累積数が所定数に達した場合の輝度値に基づいて前記バックライトの暫定的な発光量を決定する暫定発光量決定手段と、前記暫定発光量決定手段によって決定された暫定的な発光量と所定の閾値とを比較する比較手段と、前記比較手段による比較の結果、前記暫定的な発光量が前記所定の閾値を超える場合に、前記暫定的な発光量よりも少ない発光量を前記バックライトの確定的な発光量として決定する確定発光量決定手段とを備えたことを特徴とする。 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. On the other hand, the counting means for counting the pixels constituting the image data in descending order of the luminance value, and the luminance value when the cumulative number of pixels counted by the counting means reaches a predetermined number Comparison between the provisional light emission amount determining means for determining the provisional light emission amount of the backlight, comparison means for comparing the provisional light emission amount determined by the provisional light emission amount determination means with a predetermined threshold, and comparison by the comparison means As a result, when the provisional light emission amount exceeds the predetermined threshold value, a definite light emission amount determination that determines a light emission amount smaller than the provisional light emission amount as the definite light emission amount of the backlight. Characterized by comprising a stage.
　また、本発明に係る表示制御装置は、表示パネルへ光を照射するバックライトの発光量を制御する表示制御装置であって、入力された画像データの輝度値に基づいて前記バックライトの目標発光量を決定する目標発光量決定手段と、前記目標発光量決定手段によって決定された目標発光量と前記バックライトの現在の発光量との差分値に応じて前記現在の発光量からの変化量を決定する変化量決定手段と、前記変化量決定手段によって決定された変化量だけ前記現在の発光量を変化させた発光量を前記バックライトの発光量として決定する発光量決定手段とを備えたことを特徴とする。 The display control device according to the present invention is a display control device that controls the light emission amount of the backlight that irradiates light to the display panel, and the target light emission of the backlight based on the luminance value of the input image data. A target light emission amount determining means for determining an amount, and a change amount from the current light emission amount according to a difference value between the target light emission amount determined by the target light emission amount determination means and the current light emission amount of the backlight. A change amount determining means for determining, and a light emission amount determining means for determining the light emission amount obtained by changing the current light emission amount by the change amount determined by the change amount determining means as the light emission amount of the backlight. It is characterized by.
　また、本発明に係る表示制御装置は、表示パネルへ光を照射するバックライトの発光量を制御する表示制御装置であって、入力された画像データに対して当該画像データを構成する画素の数を輝度値の高いものから順に累積加算する累積加算手段と、前記累積加算手段によって累積加算済みの画素の平均輝度を部分平均輝度として算出する部分平均輝度算出手段と、前記部分平均輝度算出手段によって算出された部分平均輝度と、前記累積加算手段によって累積加算済みの画素の輝度値のうちの最低輝度値との差が所定の閾値以上となった場合に、当該最低輝度値に基づいて前記バックライトの発光量を決定する発光量決定手段とを備えたことを特徴とする。 The 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 the display panel, and the number of pixels constituting the image data with respect to input image data. By the cumulative addition means for cumulatively adding in order from the highest brightness value, the partial average brightness calculation means for calculating the average brightness of the pixels that have been cumulatively added by the cumulative addition means, and the partial average brightness calculation means. When the difference between the calculated partial average brightness and the minimum brightness value of the brightness values of the pixels that have been cumulatively added by the cumulative addition means is equal to or greater than a predetermined threshold value, the back-up is performed based on the minimum brightness value. And a light emission amount determining means for determining the light emission amount of the light.
　また、本発明に係る表示制御方法は、表示パネルへ光を照射するバックライトの発光量を制御する表示制御方法であって、入力された画像データに対して、当該画像データを構成する画素を輝度値の高いものから順に計数する計数工程と、前記計数工程において計数した画素の累積数が所定数に達した場合の輝度値に基づいて前記バックライトの暫定的な発光量を決定する暫定発光量決定工程と、前記暫定発光量決定工程において決定した暫定的な発光量と所定の閾値とを比較する比較工程と、前記比較工程における比較の結果、前記暫定的な発光量が前記所定の閾値を超える場合に、前記暫定的な発光量よりも少ない発光量を前記バックライトの確定的な発光量として決定する確定発光量決定工程とを含んだことを特徴とする。 The display control method according to the present invention is a display control method for controlling the light emission amount of the backlight that irradiates light to the display panel, and for the input image data, the pixels constituting the image data are changed. Counting step for counting in descending order of luminance value, and provisional light emission for determining the provisional light emission amount of the backlight based on the luminance value when the cumulative number of pixels counted in the counting step reaches a predetermined number An amount determination step, a comparison step of comparing the provisional light emission amount determined in the provisional light emission amount determination step with a predetermined threshold value, and a result of comparison in the comparison step, the provisional light emission amount becomes the predetermined threshold value. A definite light emission amount determining step of determining a light emission amount smaller than the provisional light emission amount as a definite light emission amount of the backlight.
　また、本発明に係る表示制御方法は、表示パネルへ光を照射するバックライトの発光量を制御する表示制御方法であって、入力された画像データの輝度値に基づいて前記バックライトの目標発光量を決定する目標発光量決定工程と、前記目標発光量決定工程において決定した目標発光量と前記バックライトの現在の発光量との差分値に応じて前記現在の発光量からの変化量を決定する変化量決定工程と、前記変化量決定工程において決定した変化量だけ前記現在の発光量を変化させた発光量を前記バックライトの発光量として決定する発光量決定工程とを含んだことを特徴とする。 The display control method according to the present invention is a display control method for controlling a light emission amount of a backlight that irradiates light to a display panel, and is based on a luminance value of input image data. The amount of change from the current light emission amount is determined in accordance with a target light emission amount determination step for determining the amount, and a difference value between the target light emission amount determined in the target light emission amount determination step and the current light emission amount of the backlight And a light emission amount determination step of determining a light emission amount obtained by changing the current light emission amount by the change amount determined in the change amount determination step as a light emission amount of the backlight. And
　また、本発明に係る表示制御方法は、表示パネルへ光を照射するバックライトの発光量を制御する表示制御方法であって、入力された画像データに対して当該画像データを構成する画素の数を輝度値の高いものから順に累積加算する累積加算工程と、前記累積加算工程において累積加算した画素の平均輝度を部分平均輝度として算出する部分平均輝度算出工程と、前記部分平均輝度算出工程において算出した部分平均輝度と、前記累積加算工程において累積加算した画素の輝度値のうちの最低輝度値との差が所定の閾値以上となった場合に、当該最低輝度値に基づいて前記バックライトの発光量を決定する発光量決定工程とを含んだことを特徴とする。 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. Are calculated in the partial average luminance calculation step, the partial average luminance calculation step of calculating the average luminance of the pixels cumulatively added in the cumulative addition step as the partial average luminance, and the partial average luminance calculation step. When the difference between the partial average brightness and the minimum brightness value of the brightness values of the pixels cumulatively added in the cumulative addition step is equal to or greater than a predetermined threshold value, the backlight emits light based on the minimum brightness value. And a light emission amount determining step for determining the amount.
　本発明によれば、入力された画像データに対して、当該画像データを構成する画素を輝度値の高いものから順に計数し、計数した画素の累積数が所定数に達した場合の輝度値に基づいてバックライトの暫定的な発光量を決定し、暫定的な発光量と所定の閾値とを比較し、比較の結果、暫定的な発光量が所定の閾値を超える場合に、暫定的な発光量よりも少ない発光量をバックライトの確定的な発光量として決定することとしたので、明るい映像が入力された場合に、バックライトの消費電力の削減量が少なくなることを抑制できるという効果を奏する。 According to the present invention, with respect to input image data, the pixels constituting the image data are counted in descending order of luminance value, and the luminance value when the cumulative number of counted pixels reaches a predetermined number is obtained. Based on this, the provisional light emission amount of the backlight is determined, the provisional light emission amount is compared with a predetermined threshold value, and if the result of comparison indicates that the provisional light emission amount exceeds the predetermined threshold value, the provisional light emission amount Since the amount of light emission smaller than the amount of light is determined as the definite amount of light emission of the backlight, it is possible to suppress the reduction in the amount of reduction in backlight power consumption when a bright image is input. Play.
　また、本発明によれば、入力された画像データの輝度値に基づいて前記バックライトの目標発光量を決定し、決定された目標発光量とバックライトの現在の発光量との差分値に応じて現在の発光量からの変化量を決定し、決定された変化量だけ現在の発光量を変化させた発光量をバックライトの発光量として決定することとしたので、バックライトによる消費電力を抑えつつ、画像の明るさが頻繁に変化した場合に生じる画面のちらつきを低減することができるという効果を奏する。 Further, according to the present invention, the target light emission amount of the backlight is determined based on the luminance value of the input image data, and according to the difference value between the determined target light emission amount and the current light emission amount of the backlight. The amount of change from the current amount of light is determined, and the amount of light that has been changed by the amount of change determined is determined as the amount of light emitted from the backlight. On the other hand, it is possible to reduce the flickering of the screen that occurs when the brightness of the image changes frequently.
　また、本発明によれば、入力された画像データに対して当該画像データを構成する画素の数を輝度値の高いものから順に累積加算し、累積加算済みの画素の平均輝度を部分平均輝度として算出し、算出した部分平均輝度と累積加算済みの画素の輝度値のうちの最低輝度値との差が所定の閾値以上となった場合に、当該最低輝度値に基づいてバックライトの発光量を決定することとしたため、全体的に暗い画像の一部に高輝度の画素が含まれる場合に、バックライトによる消費電力を抑えつつ、高輝度画素の視認性を高めることができるという効果を奏する。 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 the average luminance of the accumulated pixels is set as the partial average luminance. When the difference between the calculated partial average brightness and the minimum brightness value of the cumulatively added pixel brightness values is equal to or greater than a predetermined threshold, the light emission amount of the backlight is calculated based on the minimum brightness value. Since the determination is made, when high-luminance pixels are included in a part of the overall dark image, there is an effect that the visibility of the high-luminance pixels can be improved while suppressing power consumption by the backlight.
図１は、実施例１に係る表示制御手法の概要を示す図である。FIG. 1 is a diagram illustrating an overview of a display control method according to the first embodiment. 図２は、実施例１に係る表示制御装置の構成を示すブロック図である。FIG. 2 is a block diagram illustrating the configuration of the display control apparatus according to the first embodiment. 図３は、実施例１に係るヒストグラム解析部の構成を示すブロック図である。FIG. 3 is a block diagram illustrating the configuration of the histogram analysis unit according to the first embodiment. 図４は、実施例１に係るヒストグラム解析部の動作例を示す図である。FIG. 4 is a diagram illustrating an operation example of the histogram analysis unit according to the first embodiment. 図５は、ＲＧＢ変換情報の一例を示す図である。FIG. 5 is a diagram illustrating an example of RGB conversion information. 図６は、実施例１に係る表示制御装置が実行する処理手順を示すフローチャートである。FIG. 6 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the first embodiment. 図７は、実施例２に係るハレーション回避手法の概要を示す図である。FIG. 7 is a diagram illustrating an outline of the halation avoidance technique according to the second embodiment. 図８は、実施例２に係るヒストグラム解析部の構成を示すブロック図である。FIG. 8 is a block diagram illustrating the configuration of the histogram analysis unit according to the second embodiment. 図９は、実施例２に係る表示制御装置が実行する処理手順を示すフローチャートである。FIG. 9 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the second embodiment. 図１０は、ハレーション回避機能およびＨオフセットの設定変更について説明するための図である。FIG. 10 is a diagram for explaining a halation avoidance function and an H offset setting change. 図１１は、Ｌオフセットを設定する場合について説明するための図である。FIG. 11 is a diagram for explaining a case where the L offset is set. 図１２は、実施例３に係る表示制御手法の概要を示す図である。FIG. 12 is a diagram illustrating an overview of the display control method according to the third embodiment. 図１３は、実施例３に係る表示制御装置の構成を示すブロック図である。FIG. 13 is a block diagram illustrating the configuration of the display control apparatus according to the third embodiment. 図１４は、ヒストグラム解析部の動作例を示す図である。FIG. 14 is a diagram illustrating an operation example of the histogram analysis unit. 図１５は、実施例３に係る発光量変更部の構成を示すブロック図である。FIG. 15 is a block diagram illustrating the configuration of the light emission amount changing unit according to the third embodiment. 図１６は、変化量設定情報の一例を示す図である。FIG. 16 is a diagram illustrating an example of the change amount setting information. 図１７は、変化量決定部および発光量決定部の動作例を示す図である。FIG. 17 is a diagram illustrating an operation example of the change amount determination unit and the light emission amount determination unit. 図１８は、実施例３に係る表示制御装置が実行する処理手順を示すフローチャートである。FIG. 18 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the third embodiment. 図１９は、変化量決定部の他の動作例を示す図である。FIG. 19 is a diagram illustrating another operation example of the change amount determination unit. 図２０は、変化量決定部の他の動作例を示す図である。FIG. 20 is a diagram illustrating another operation example of the change amount determination unit. 図２１は、実施例４に係る表示制御手法の概要を示す図である。FIG. 21 is a diagram illustrating an overview of the display control method according to the fourth embodiment. 図２２は、ヒストグラム解析部の構成を示すブロック図である。FIG. 22 is a block diagram illustrating a configuration of the histogram analysis unit. 図２３は、全体的に暗い画像の中に高輝度画素が含まれる場合における発光量決定部の動作例を示す図である。FIG. 23 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. 図２４は、発光量決定部の他の動作例を示す図である。FIG. 24 is a diagram illustrating another operation example of the light emission amount determination unit. 図２５は、実施例４に係る表示制御装置が実行する処理手順を示すフローチャートである。FIG. 25 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the fourth embodiment. 図２６は、部分平均輝度の値に応じてＡＶＥＤＩＳを変更する場合について説明するための図である。FIG. 26 is a diagram for describing a case where AVEDIS is changed according to the value of partial average luminance. 図２７は、累積加算部の他の動作例を示す図である。FIG. 27 is a diagram illustrating another operation example of the cumulative addition unit. 図２８は、発光量決定部の他の動作例を示す図である。FIG. 28 is a diagram illustrating another operation example of the light emission amount determination unit.
　以下に添付図面を参照して、本発明に係る表示制御装置および表示制御方法の実施例を詳細に説明する。 Hereinafter, embodiments of a display control device and a display control method according to the present invention will be described in detail with reference to the accompanying drawings.
　まず、実施例１の詳細な説明に先立って、実施例１に係る表示制御手法の概要について図１を用いて説明する。図１は、実施例１に係る表示制御手法の概要を示す図である。なお、同図の（Ａ）には、明るい画像が入力された場合に、暫定的に決定された発光量よりも低い発光量が確定的な発光量として決定される場合を示している。また、同図の（Ｂ）には、暗い画像が入力された場合に、暫定的に決定された発光量がそのまま確定的な発光量として決定される場合を示している。 First, prior to detailed description of the first embodiment, an outline of a display control method according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an overview of a display control method according to the first embodiment. Note that (A) in the figure shows a case where a light emission amount lower than the provisionally determined light emission amount is determined as a definite light emission amount when a bright image is input. Further, (B) of FIG. 5 shows a case where the light emission amount tentatively determined is determined as a definite light emission amount when a dark image is input.
　同図に示すように、実施例１に係る表示制御手法では、画像の明るさに応じてバックライトの発光量を制御する場合に、明るい画像が入力されたとしてもバックライトの発光量が所定量を超えないようにバックライトの発光量に上限値を設けた点に主たる特徴を有する。 As shown in the figure, in the display control method according to the first embodiment, when the amount of light emitted from the backlight is controlled according to the brightness of the image, the amount of light emitted from the backlight is fixed even when a bright image is input. The main feature is that an upper limit is set for the amount of light emitted from the backlight so as not to exceed the fixed amount.
　具体的には、実施例１に係る表示制御手法では、まず、画像データが入力されると、画像データを構成する画素を輝度値の高いものから順に計数する。すなわち、実施例１に係る表示制御手法では、同図の（Ａ）に示したように、画像データを構成する画素の輝度分布（以下、「ヒストグラム」と記載する）を生成し、高輝度側から順に画素を計数していく。 Specifically, in the display control method according to the first embodiment, first, when image data is input, the pixels constituting the image data are counted in descending order of luminance value. That is, the display control method according to the first embodiment generates a luminance distribution (hereinafter, referred to as “histogram”) of the pixels constituting the image data as shown in FIG. The pixels are counted in order.
　ここで、同図の（Ａ）に示したように、画素の輝度値は、０～２５５までの値を取り、バックライトの発光量は、輝度値が０のときを０％、２５５のときを１００％として、０～１００％の値を取る。このように、バックライトの発光量は、輝度値と予め対応付けられている。 Here, as shown in FIG. 6A, the luminance value of the pixel takes a value from 0 to 255, and the light emission amount of the backlight is 0% when the luminance value is 0, and 255 The value of 0 to 100% is taken as 100%. Thus, the light emission amount of the backlight is associated with the luminance value in advance.
　つづいて、実施例１に係る表示制御手法では、計数した画素の累積数（以下、「累積画素数」と記載する）が所定数に達した場合の輝度値に基づいてバックライトの暫定的な発光量を決定する。具体的には、同図の（Ａ）に示したように、ヒストグラム上において累積画素数が所定数を超える位置を算出ポイントとし、かかる算出ポイントに対応する発光量をバックライトの暫定的な発光量（以下、「暫定発光量」と記載する）として決定する。 Subsequently, in the display control method according to the first embodiment, the backlight is temporarily set based on the luminance value when the accumulated number of counted pixels (hereinafter referred to as “accumulated pixel number”) reaches a predetermined number. Determine the amount of luminescence. Specifically, as shown in (A) of the figure, a position where the cumulative number of pixels exceeds a predetermined number on the histogram is set as a calculation point, and a light emission amount corresponding to the calculation point is set as a temporary light emission of the backlight. It is determined as an amount (hereinafter referred to as “provisional luminescence amount”).
　つづいて、実施例１に係る表示制御手法では、暫定発光量と所定の閾値（以下、「Ｈオフセット」と記載する）とを比較する。そして、実施例１に係る表示制御手法では、暫定発光量がＨオフセットよりも多い場合に、暫定発光量よりも少ない発光量を確定的な発光量（以下、「確定発光量」と記載する）として決定する。 Subsequently, in the display control method according to the first embodiment, the provisional light emission amount is compared with a predetermined threshold (hereinafter referred to as “H offset”). In the display control method according to the first embodiment, when the provisional light emission amount is larger than the H offset, the light emission amount smaller than the provisional light emission amount is determined as a definite light emission amount (hereinafter referred to as “determined light emission amount”). Determine as.
　たとえば、同図の（Ａ）に示したように、明るい画像が入力された場合には、ヒストグラムの高輝度側に位置する画素が多くなる結果、算出ポイントがＨオフセットよりも高輝度側に位置することとなる。かかる場合、暫定発光量がＨオフセットよりも多くなるため、実施例１に係る表示制御手法では、Ｈオフセットを確定発光量として決定する。 For example, as shown in FIG. 5A, when a bright image is input, the number of pixels positioned on the high luminance side of the histogram increases, and as a result, the calculation point is positioned on the high luminance side of the H offset. Will be. In such a case, since the provisional light emission amount is larger than the H offset, the display control method according to the first embodiment determines the H offset as the final light emission amount.
　このように、明るい画像が入力された場合には、バックライトの発光量が比較的多めに設定されることとなるが、算出ポイントよりも低輝度側に位置するＨオフセットを確定発光量とすることで、算出ポイントに対応する発光量を確定発光量とする場合と比較してバックライトの発光量を少なくすることができる。したがって、算出ポイントにおける発光量を確定発光量とした場合と比較して消費電力の削減量を多くすることができる。 As described above, when a bright image is input, the light emission amount of the backlight is set to be relatively large, but the H offset located on the lower luminance side than the calculation point is set as the final light emission amount. As a result, the light emission amount of the backlight can be reduced as compared with the case where the light emission amount corresponding to the calculation point is set as the fixed light emission amount. Therefore, it is possible to increase the power consumption reduction amount as compared with the case where the light emission amount at the calculation point is set as the fixed light emission amount.
　このように、実施例１に係る表示制御手法では、バックライトの発光量の上限値としてＨオフセットを導入することで、明るい画像が入力された場合であっても、確定発光量がＨオフセット以上とならないように制限することとした。したがって、実施例１に係る表示制御手法によれば、明るい画像が入力された場合に、バックライトの消費電力の削減量が少なくなることを抑制することができる。 As described above, in the display control method according to the first embodiment, by introducing the H offset as the upper limit value of the light emission amount of the backlight, even when a bright image is input, the determined light emission amount is equal to or higher than the H offset. It was decided to restrict so that it would not. Therefore, according to the display control method according to the first embodiment, it is possible to suppress a reduction in the amount of reduction in the power consumption of the backlight when a bright image is input.
　なお、暫定発光量がＨオフセットよりも少ない場合には、暫定発光量をバックライトの確定的な発光量として決定する。たとえば、同図の（Ｂ）に示したように、暗い画像が入力された場合には、ヒストグラムの低輝度側に位置する画素が多くなる結果、算出ポイントがＨオフセットよりも低輝度側に位置することとなる。かかる場合には、暫定発光量がＨオフセットよりも少なくなるため、暫定発光量が確定発光量として決定される。 If the provisional emission amount is smaller than the H offset, the provisional emission amount is determined as the definite emission amount of the backlight. For example, as shown in FIG. 5B, when a dark image is input, the number of pixels positioned on the low luminance side of the histogram increases, and as a result, the calculation point is positioned on the low luminance side of the H offset. Will be. In such a case, since the provisional light emission amount is smaller than the H offset, the provisional light emission amount is determined as the determined light emission amount.
　ところで、明るい画像が入力された場合に、少ない発光量でバックライトを発光させると、画像中の特に明るい部分の色がつぶれたように見える現象（以下、「ハレーション」と記載する）が発生するおそれがあり、画質劣化の原因となる。そこで、ハレーションが発生する可能性がある場合には、Ｈオフセットよりも多い発光量を確定発光量として決定することによってハレーションの発生を回避する処理も併せて行ってもよい。なお、かかるハレーション回避の具体的な内容については、実施例２において説明することとする。 By the way, when a bright image is input, if a backlight emits light with a small amount of light emission, a phenomenon that the color of a particularly bright part in the image appears to be crushed (hereinafter referred to as “halation”) occurs. This may cause image quality degradation. Therefore, when there is a possibility that halation will occur, a process of avoiding the occurrence of halation by determining a light emission amount larger than the H offset as the determined light emission amount may be performed. The specific contents of the halation avoidance will be described in the second embodiment.
　また、これまでは、暫定発光量がＨオフセットよりも多い場合に、Ｈオフセットを確定発光量とする場合について説明したが、これに限ったものではない。たとえば、暫定発光量がＨオフセットよりも多い場合に、暫定発光量を所定の変換式で変換した値を確定発光量として決定することとしてもよい。かかる点についても後述する。 In addition, the case where the provisional light emission amount is larger than the H offset and the H offset is set as the fixed light emission amount has been described so far, but the present invention is not limited to this. For example, when the provisional emission amount is larger than the H offset, a value obtained by converting the provisional emission amount by a predetermined conversion formula may be determined as the determined emission amount. This point will also be described later.
　以下では、図１を用いて説明した表示制御手法を適用した表示制御装置についての実施例１を詳細に説明する。なお、以下に示す実施例１では、車載装置に搭載される液晶ディスプレイの表示制御を行う表示制御装置に対して本発明を適用する場合について説明する。ただし、本発明にかかる表示制御装置は、これに限ったものではなく、携帯端末装置やＰＣ（Personal Computer）あるいはＴＶ（Television）のように、バックライトを用いて表示を行う表示部を備える各種の装置に対して適用することができる。 Hereinafter, the first embodiment of the display control apparatus to which the display control method described with reference to FIG. 1 is applied will be described in detail. In the first embodiment described below, a case where 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 will be described. However, the display control device according to the present invention is not limited to this, and various types of display units that perform display using a backlight, such as a mobile terminal device, a PC (Personal Computer), or a TV (Television). It can be applied to other devices.
　図２は、実施例１に係る表示制御装置の構成を示すブロック図である。なお、同図には、表示制御装置の特徴を説明するために必要な構成要素のみを示しており、一般的な構成要素についての記載を省略している。 FIG. 2 is a block diagram illustrating the configuration of the display control apparatus according to the first 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.
　同図に示すように、実施例１に係る表示制御装置１０は、車載装置に搭載される液晶ディスプレイ２０の表示制御を行う装置である。ここで、液晶ディスプレイ２０は、液晶パネル２１と、バックライトモジュール２２とを備えている。液晶パネル２１は、表示制御装置１０から出力される画像データを表示する表示部である。また、バックライトモジュール２２は、液晶パネル２１の背面側に設けられた照明装置であり、液晶パネル２１に対して背面側から光を照射する。かかるバックライトモジュール２２による消費電力の高さが省電力化の妨げとなっている。 As shown in the figure, the display control device 10 according to the first embodiment is a device that performs display control of the liquid crystal display 20 mounted on the 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.
　つづいて、実施例１に係る表示制御装置１０の構成について説明する。実施例１に係る表示制御装置１０は、制御部１１と、記憶部１２とを備えている。また、制御部１１は、画像データ取得部１１ａと、サブサンプリング部１１ｂと、ヒストグラム生成部１１ｃと、ヒストグラム解析部１１ｄと、発光量変更部１１ｅと、ＰＷＭ（Pulse Width Modulation）生成部１１ｆと、ＲＧＢ変換部１１ｇとを備えている。また、記憶部１２は、閾値情報１２ａと、ＲＧＢ変換情報１２５とを記憶している。 Subsequently, the configuration of the display control apparatus 10 according to the first embodiment will be described. The display control apparatus 10 according to the first 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 125.
　制御部１１は、車載装置からの画像データの取得、取得した画像データのサブサンプリング、ヒストグラムの生成および解析、発光量の変更処理、ＰＷＭの生成あるいはＲＧＢ変換処理といった処理を実行する処理部である。画像データ取得部１１ａは、ナビゲーション画像等の画像データを車載装置から取得する処理部である。また、画像データ取得部１１ａは、取得した画像データをサブサンプリング部１１ｂおよびＲＧＢ変換部１１ｇへ渡す処理も併せて行う。 The control unit 11 is a processing unit that executes processing such as acquisition of image data from the in-vehicle device, sub-sampling of the acquired image data, generation and analysis of a histogram, light emission amount change processing, PWM generation, or RGB conversion processing. . 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.
　サブサンプリング部１１ｂは、画像データ取得部１１ａから画像データを取得した場合に、取得した画像データに対してサブサンプリングを行う処理部である。また、サブサンプリング部１１ｂは、サブサンプリング後の画像データをヒストグラム生成部１１ｃへ渡す処理も併せて行う。 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.
　ここで、サブサンプリングとは、取得した画像データから画素を間引く処理を示す。このように、取得した画像データに対してサブサンプリングを行うことによって、後述するヒストグラム生成部１１ｃやヒストグラム解析部１１ｄといった処理部の処理速度を高めることができる。なお、ここでは、ＷＶＧＡサイズ（８００×４８０）の画像データが１２８×６４のサイズに縮小されるものとする。 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.
　ヒストグラム生成部１１ｃは、サブサンプリング部１１ｂから取得したサブサンプリング後の画像データを用いてヒストグラムを生成する処理部である。ヒストグラムとは、上述したように、画像データを構成する画素の輝度分布をあらわす情報である。ここで、ヒストグラム生成部１１ｃは、画像データに含まれるＲ，Ｇ，Ｂの各成分うち、最も値の大きい成分を用いてヒストグラムを生成する。また、ヒストグラム生成部１１ｃは、生成したヒストグラムをヒストグラム解析部１１ｄへ渡す処理も併せて行う。 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.
　ヒストグラム解析部１１ｄは、ヒストグラム生成部１１ｃによって生成されたヒストグラムを閾値情報１２ａを用いて解析することによって、バックライトモジュール２２の確定発光量を決定する処理部である。 The histogram analysis unit 11d is a processing unit that determines the determined light emission amount of the backlight module 22 by analyzing the histogram generated by the histogram generation unit 11c using the threshold information 12a.
　ここで、かかるヒストグラム解析部１１ｄの具体的な構成について図３を用いて説明する。図３は、実施例１に係るヒストグラム解析部１１ｄの構成を示すブロック図である。同図に示すように、ヒストグラム解析部１１ｄは、暫定発光量決定部１１１ａと、比較部１１１ｂと、確定発光量決定部１１１ｃとを備えている。また、閾値情報１２ａは、ＤＮＵＭ１２１と、Ｈオフセット１２２とを含んでいる。 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 11d includes a provisional light emission amount determination unit 111a, a comparison unit 111b, and a fixed light emission amount determination unit 111c. The threshold information 12a includes a DNUM 121 and an H offset 122.
　暫定発光量決定部１１１ａは、ヒストグラム生成部１１ｃから取得したヒストグラムと閾値情報１２ａに含まれるＤＮＵＭ１２１とを用いて暫定発光量を決定する処理部である。ＤＮＵＭ１２１とは、累積画素数の閾値を示す情報である。 The provisional emission amount determination unit 111a is a processing unit that determines the provisional emission amount using the histogram acquired from the histogram generation unit 11c and the DNUM 121 included in the threshold information 12a. The DNUM 121 is information indicating a threshold value for the cumulative number of pixels.
　具体的には、暫定発光量決定部１１１ａは、ヒストグラムの高輝度側から順に画素数を計数していき、累積画素数がＤＮＵＭ１２１を超えた場合におけるヒストグラム上の位置（輝度値）に対応する発光量を暫定発光量として決定する。また、暫定発光量決定部１１１ａは、暫定発光量を決定すると、決定した暫定発光量を比較部１１１ｂへ渡す処理も併せて行う。 Specifically, the provisional light emission amount determination unit 111a 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 121. The amount is determined as the provisional light emission amount. In addition, when the provisional light emission amount determination unit 111a determines the provisional light emission amount, the provisional light emission amount determination unit 111a also performs a process of passing the determined provisional light emission amount to the comparison unit 111b.
　比較部１１１ｂは、暫定発光量決定部１１１ａによって決定された暫定発光量と記憶部１２に記憶されたＨオフセット１２２とを比較する処理部である。ここで、Ｈオフセット１２２は、バックライトモジュール２２の発光量の上限値を示す閾値情報である。また、比較部１１１ｂは、暫定発光量とＨオフセットとの比較結果を確定発光量決定部１１１ｃへ渡す処理も併せて行う。 The comparison unit 111b is a processing unit that compares the provisional emission amount determined by the provisional emission amount determination unit 111a with the H offset 122 stored in the storage unit 12. Here, the H offset 122 is threshold information indicating the upper limit value of the light emission amount of the backlight module 22. The comparison unit 111b also performs a process of passing the comparison result between the provisional light emission amount and the H offset to the fixed light emission amount determination unit 111c.
　確定発光量決定部１１１ｃは、比較部１１１ｂによる比較結果に応じて確定発光量を決定する処理部である。また、確定発光量決定部１１１ｃは、決定した確定発光量を発光量変更部１１ｅへ渡す処理も併せて行う。 The determined light emission amount determination unit 111c is a processing unit that determines the determined light emission amount according to the comparison result by the comparison unit 111b. The determined light emission amount determining unit 111c also performs a process of passing the determined determined light emission amount to the light emission amount changing unit 11e.
　ここで、かかるヒストグラム解析部１１ｄの動作例について図４を用いて説明する。図４は、実施例１に係るヒストグラム解析部１１ｄの動作例を示す図である。なお、同図の（Ａ）には、暫定発光量決定部１１１ａの動作例を、同図の（Ｂ）および（Ｃ）には、比較部１１１ｂおよび確定発光量決定部１１１ｃの動作例を、それぞれ示している。 Here, an example of the operation of the histogram analysis unit 11d will be described with reference to FIG. FIG. 4 is a diagram illustrating an operation example of the histogram analysis unit 11d according to the first embodiment. Note that (A) in the figure shows an operation example of the provisional light emission amount determination unit 111a, and (B) and (C) in the same figure show operation examples of the comparison unit 111b and the fixed light emission amount determination unit 111c. Each is shown.
　同図の（Ａ）に示したように、暫定発光量決定部１１１ａは、ヒストグラムにおける輝度値「２５５」の位置を計数開始ポイントとする。また、暫定発光量決定部１１１ａは、各輝度値に対応する画素数を計数開始ポイントから低輝度側へ向かって順に計数していく。そして、暫定発光量決定部１１１ａは、累積画素数がＤＮＵＭ１２１に達した位置を算出ポイントとして定め、かかる算出ポイントの輝度値に対応する発光量を暫定発光量として決定する。 As shown in (A) of the figure, the provisional light emission amount determination unit 111a sets the position of the luminance value “255” in the histogram as the counting start point. The provisional light emission amount determination unit 111a sequentially counts the number of pixels corresponding to each luminance value from the counting start point toward the low luminance side. Then, the provisional light emission amount determination unit 111a determines the position where the cumulative number of pixels reaches DNUM 121 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.
　たとえば、暫定発光量決定部１１１ａは、累積画素数がＤＮＵＭ１２１に達した位置の輝度値が「２００」である場合には、かかる輝度値「２００」に対応する発光量「７８％」を暫定発光量として決定する。 For example, if the luminance value at the position where the cumulative number of pixels has reached DNUM 121 is “200”, the provisional light emission amount determination unit 111a sets the light emission amount “78%” corresponding to the luminance value “200” to provisional light emission. Determine as quantity.
　また、比較部１１１ｂは、暫定発光量決定部１１１ａによって決定された暫定発光量とＨオフセット１２２との比較を行い、比較結果を確定発光量決定部１１１ｃへ渡す。そして、確定発光量決定部１１１ｃは、同図の（Ｂ）に示したように、暫定発光量がＨオフセット以下である場合には、暫定発光量を確定発光量として決定する。一方、確定発光量決定部１１１ｃは、暫定的発光量がＨオフセットを超える場合には、Ｈオフセットを確定発光量として決定する。 Further, the comparison unit 111b compares the provisional light emission amount determined by the provisional light emission amount determination unit 111a with the H offset 122, and passes the comparison result to the fixed light emission amount determination unit 111c. Then, as shown in (B) of the figure, when the provisional emission amount is equal to or less than the H offset, the determined emission amount determination unit 111c determines the provisional emission amount as the fixed emission amount. On the other hand, when the provisional light emission amount exceeds the H offset, the determined light emission amount determination unit 111c determines the H offset as the determined light emission amount.
　たとえば、同図の（Ｃ）に示したように、算出ポイントａや算出ポイントｂのように、算出ポイントがＨオフセットよりも低輝度側に位置する場合、すなわち、入力された画像が暗めの画像である場合には、各算出ポイントに対応する発光量（暫定発光量）が確定発光量となる。一方、算出ポイントｃ～ｅのように算出ポイントがＨオフセットよりも高輝度側に位置する場合、すなわち、入力された画像が明るめの画像である場合の確定発光量は、各算出ポイントに対応する発光量（暫定発光量）よりも少ない発光量であるＨオフセットとなる。 For example, as shown in FIG. 5C, when the calculation point is located on the lower luminance side than the H offset, such as the calculation point a and the calculation point b, that is, the input image is a dark image. In the case of, the light emission amount (provisional light emission amount) corresponding to each calculation point is the determined light emission amount. On the other hand, when the calculated points are located on the higher luminance side than the H offset as in the calculation points c to e, that is, when the input image is a bright image, the determined light emission amount corresponds to each calculated point. The H offset is a light emission amount smaller than the light emission amount (provisional light emission amount).
　このように、実施例１では、暫定発光量がＨオフセットを超える場合には、暫定発光量よりも少ない発光量であるＨオフセットを確定発光量とすることによって、明るい画像が入力された場合であっても、バックライトモジュール２２の消費電力の削減量を極力多くすることができる。 As described above, in the first embodiment, when the provisional light emission amount exceeds the H offset, the H offset that is a light emission amount smaller than the provisional light emission amount is set as the definite light emission amount, thereby inputting a bright image. Even if it exists, the reduction amount of the power consumption of the backlight module 22 can be increased as much as possible.
　図２に戻り、制御部１１の説明を続ける。発光量変更部１１ｅは、バックライトモジュール２２の発光量の急激な変化によって生じる画面のちらつきを防止するため、ヒストグラム解析部１１ｄから取得した確定発光量と現在の発光量との差分に基づいて発光量の変化量を制限する発光量変更処理を行う処理部である。 Referring back to FIG. 2, the description of the control unit 11 is continued. The light emission amount changing unit 11e emits light based on the difference between the determined 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 processing unit for performing a light emission amount changing process for limiting the amount of change in the amount.
　具体的には、発光量変更部１１ｅは、確定発光量と現在の発光量との差分が所定の閾値よりも大きい場合に、変化量の上限値として予め決められた値を現在の発光量に対して加算（あるいは減算）した値を最終的な発光量として決定する。また、発光量変更部１１ｅは、最終的な発光量（以下、「変更後発光量」と記載する）を決定すると、この変更後発光量をＰＷＭ生成部１１ｆへ渡す。なお、発光量変更部１１ｅについては、実施例３においてより具体的に説明する。 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. The light emission amount changing unit 11e will be described more specifically in the third embodiment.
　また、発光量変更部１１ｅは、変更後発光量を決定すると、ＲＧＢ変換情報１２５を用いて変更後発光量に対応するＲＧＢ変換係数を決定し、決定したＲＧＢ変換係数をＲＧＢ変換部１１ｇへ渡す処理も行う。ここで、ＲＧＢ変換情報１２５の内容について図５を用いて説明する。図５は、ＲＧＢ変換情報１２５の一例を示す図である。 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 125, and passes the determined RGB conversion coefficient to the RGB conversion unit 11g. Do. Here, the contents of the RGB conversion information 125 will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of the RGB conversion information 125.
　同図に示したように、ＲＧＢ変換情報１２５は、「変更後発光量」ごとに「ＲＧＢ変換係数」を対応付けた情報である。ここで、「変更後発光量」は、発光量変更部１１ｅによって決定された変更後発光量を示す。また、「ＲＧＢ変換係数」は、Ｒ，Ｇ，Ｂの各成分の値（ＲＧＢ値）に対して掛け合わせる係数である。 As shown in the figure, the RGB conversion information 125 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.
　たとえば、変更後発光量が「１００％」である場合には、ＲＧＢ変換係数は「１．００」となる。これは、入力データのＲＧＢ値が、そのまま出力データのＲＧＢ値となることを示している。また、変更後発光量が「５０％」である場合には、ＲＧＢ変換係数は「１．２６」となる。これは、入力データのＲＧＢ値を１．２６倍した値が出力データのＲＧＢ値となることを示している。なお、ここでは、Ｒ，Ｇ，Ｂの各成分に対してＲＧＢ変換係数をそれぞれに掛け合わせるものとする。 For example, when the light emission after 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. When the light emission after 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.
　このように、ＲＧＢ変換情報１２５では、変更後発光量が少なくなるほど、すなわち、バックライトモジュール２２の発光量が少なくなり画面が暗くなるほど、ＲＧＢ変換係数が高くなるように設定されている。なお、発光量変更部１１ｅは、変更後発光量を決定すると、決定した変更後発光量と対応付けられたＲＧＢ変換係数をＲＧＢ変換情報１２５から取り出し、取り出したＲＧＢ変換係数をＲＧＢ変換部１１ｇへ渡す。 As described above, the RGB conversion information 125 is set so that the RGB conversion coefficient increases as the light emission amount after change 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 125, and passes the extracted RGB conversion coefficient to the RGB conversion unit 11g.
　ＰＷＭ生成部１１ｆは、発光量変更部１１ｅから変更後発光量を取得すると、バックライトモジュール２２の発光量が変更後発光量となるようにパルス幅が調整されたＰＷＭ信号を生成してバックライトモジュール２２へ出力する処理部である。なお、ＰＷＭ生成部１１ｆは、ＶＳＹＮＣ（Vertical Synchronizing signal：垂直同期信号）が１回出力されるごとに、デフォルトでは、ＰＷＭ信号を４回出力することとしている。ただし、ＶＳＹＮＣの単位出力当たりのＰＷＭ信号の出力回数は、レジスタにより適宜調整可能である。 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 generator 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.
　ＲＧＢ変換部１１ｇは、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値に対して、発光量変更部１１ｅから取得したＲＧＢ変換係数を掛け合わせるＲＧＢ変換処理を行う処理部である。また、ＲＧＢ変換部１１ｇは、ＲＧＢ変換処理後の画像データを液晶パネル２１へ出力する処理も併せて行う。 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.
　たとえば、ＲＧＢ変換部１１ｇは、ＲＧＢ変換係数「１．２６」を取得した場合、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値を１．２６倍する。そして、ＲＧＢ変換部１１ｇは、Ｒ，Ｇ，Ｂの各成分の値を１．２６倍した画像データを液晶パネル２１へ出力する。 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.
　次に、実施例１に係る表示制御装置１０の具体的動作について図６を用いて説明する。図６は、実施例１に係る表示制御装置が実行する処理手順を示すフローチャートである。なお、同図においては、表示制御装置１０が実行する処理手順のうち、バックライトの発光量制御に関する処理手順のみを示す。 Next, a specific operation of the display control apparatus 10 according to the first embodiment will be described with reference to FIG. FIG. 6 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the first embodiment. In the figure, only the processing procedure related to the light emission amount control of the backlight among the processing procedures executed by the display control device 10 is shown.
　同図に示すように、表示制御装置１０では、画像データ取得部１１ａが、画像データを取得すると（ステップＳ１０１）、サブサンプリング部１１ｂが、取得した画像データに対してサブサンプリングを行う（ステップＳ１０２）。つづいて、表示制御装置１０では、ヒストグラム生成部１１ｃが、サブサンプリング後の画像データを用いてヒストグラムを生成し（ステップＳ１０３）、暫定発光量決定部１１１ａが、ヒストグラムおよびＤＮＵＭ１２１を用いて暫定発光量を決定する（ステップＳ１０４）。 As shown in the figure, in the display control apparatus 10, when the image data acquisition unit 11a acquires image data (step S101), the sub-sampling unit 11b performs sub-sampling on the acquired image data (step S102). ). Subsequently, in the display control device 10, the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S103), and the temporary light emission amount determination unit 111a uses the histogram and the DNUM 121 to generate a temporary light emission amount. Is determined (step S104).
　つづいて、表示制御装置１０では、比較部１１１ｂが、暫定発光量とＨオフセット１２２とを比較し（ステップＳ１０５）、確定発光量決定部１１１ｃが、暫定発光量がＨオフセット１２２よりも多いか否かを判定する（ステップＳ１０６）。そして、確定発光量決定部１１１ｃは、暫定発光量がＨオフセットよりも多い場合には（ステップＳ１０６、Ｙｅｓ）、Ｈオフセットを確定発光量とし（ステップＳ１０７）、暫定発光量がＨオフセット以下である場合には（ステップＳ１０６、Ｎｏ）、暫定発光量を確定発光量とする（ステップＳ１０８）。 Subsequently, in the display control device 10, the comparison unit 111b compares the provisional light emission amount with the H offset 122 (step S105), and the determined light emission amount determination unit 111c determines whether or not the provisional light emission amount is larger than the H offset 122. Is determined (step S106). Then, when the provisional emission amount is larger than the H offset (Yes in step S106), the determined emission amount determination unit 111c sets the H offset as the decision emission amount (step S107), and the provisional emission amount is equal to or less than the H offset. In this case (No at Step S106), the provisional light emission amount is set as the fixed light emission amount (Step S108).
　つづいて、発光量変更部１１ｅは、発光量変更処理を行って変更後発光量を決定する（ステップＳ１０９）。つづいて、ＰＷＭ生成部１１ｆは、変更後発光量に応じたＰＷＭ信号を生成してバックライトモジュール２２へ出力する（ステップＳ１１０）。 Subsequently, the light emission amount changing unit 11e performs a light emission amount changing process 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).
　また、ＲＧＢ変換部１１ｇは、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値に対して、変更後発光量に対応するＲＧＢ変換係数を掛け合わせるＲＧＢ変換処理を行う（ステップＳ１１１）。そして、ＲＧＢ変換部１１ｇは、ＲＧＢ変換処理後の画像データを液晶パネル２１へ出力して（ステップＳ１１２）、処理を終了する。 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.
　上述してきたように、実施例１では、暫定発光量決定部が、入力された画像データに対して、当該画像データを構成する画素を輝度値の高いものから順に計数し、計数した画素の累積数が所定数に達した場合の輝度値に基づいてバックライトの暫定的な発光量を決定し、比較部が、暫定的な発光量と所定の閾値とを比較し、確定発光量決定部が、比較部による比較の結果、暫定的な発光量が所定の閾値を超える場合に、暫定的な発光量よりも少ない発光量をバックライトの確定的な発光量として決定することとした。したがって、明るい映像が入力された場合に、バックライトの消費電力の削減量が少なくなることを抑制することができる。 As described above, in the first embodiment, the provisional light emission amount determination unit counts pixels constituting the image data in descending order of luminance value for the input image data, and accumulates the counted pixels. The provisional light emission amount of the backlight is determined based on the luminance value when the number reaches the predetermined number, the comparison unit compares the temporary light emission amount with a predetermined threshold value, and the determined light emission amount determination unit As a result of comparison by the comparison unit, when the provisional light emission amount exceeds a predetermined threshold, the light emission amount smaller than the provisional light emission amount is determined as the definite light emission amount of the backlight. Accordingly, it is possible to suppress a reduction in the amount of reduction in power consumption of the backlight when a bright image is input.
　ところで、上述した実施例１では、バックライトモジュール２２の発光量を少なくする場合であっても、ＲＧＢ変換処理によってＲＧＢ値を高める補正を行うことで、画質劣化を防止することとした。 Incidentally, in the above-described first embodiment, even when the light emission amount of the backlight module 22 is reduced, the image quality deterioration is prevented by performing the correction for increasing the RGB value by the RGB conversion processing.
　ところが、実施例１で説明したように、明るい画像が入力された場合に、暫定発光量よりも少ない発光量でバックライトモジュール２２を発光させることとすると、ＲＧＢ値の補正量が頭打ちとなり、ハレーションが発生するおそれがある。そこで、実施例２では、暫定発光量がＨオフセットよりも多い場合に、ハレーションが発生するおそれがあるか否かを判定し、発生するおそれがあると判定した場合には、Ｈオフセットよりも多い発光量を確定発光量として決定することで、ハレーションの発生を回避することとした。 However, as described in the first embodiment, when a bright image is input, if the backlight module 22 is caused to emit light with a light emission amount smaller than the provisional light emission amount, the correction amount of the RGB value reaches a peak, and halation occurs. May occur. Therefore, in Example 2, it is determined whether there is a possibility that halation will occur when the provisional light emission amount is larger than the H offset, and when it is determined that there is a possibility that it will occur, it is larger than the H offset. By determining the light emission amount as the definite light emission amount, the occurrence of halation was avoided.
　以下では、かかる実施例２について説明する。まず、ハレーション回避手法の概要について図７を用いて説明する。図７は、実施例２に係るハレーション回避手法の概要を示す図である。なお、同図の（Ａ）には、ハレーションが発生する状況を示し、同図の（Ｂ）には、ハレーション回避手法の概要を示している。 Hereinafter, the second embodiment will be described. First, the outline of the halation avoidance technique will be described with reference to FIG. FIG. 7 is a diagram illustrating an outline of the halation avoidance technique according to the second embodiment. In addition, (A) of the figure shows the situation where halation occurs, and (B) of the figure shows an outline of the halation avoidance technique.
　また、以下に示す実施例２では、上記の実施例１に係る表示制御装置１０と同様の機能を発揮するものについては実施例１と同一の符号を付してその説明を省略する。 Also, in the second embodiment shown below, those that exhibit the same functions as those of the display control apparatus 10 according to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and description thereof is omitted.
　同図の（Ａ）に示したように、発光量変更部１１ｅによって変更後発光量が「１００％」に決定された場合には、ＲＧＢ変換係数は「１．００」となる（図５参照）。すなわち、入力ＲＧＢ値が「２５５」である場合は、出力ＲＧＢ値も「２５５」となる。 As shown in FIG. 5A, when the light emission amount after change is determined to be “100%” by the light emission amount changing unit 11e, the RGB conversion coefficient is “1.00” (see FIG. 5). . That is, when the input RGB value is “255”, the output RGB value is also “255”.
　一方、発光量変更部１１ｅによって変更後発光量が「１２．５％」に決定された場合、ＲＧＢ変換係数は「２．０５」となる（図５参照）。 On the other hand, when the changed light emission amount is determined to be “12.5%” by the light emission amount changing unit 11e, the RGB conversion coefficient is “2.05” (see FIG. 5).
　かかる場合において、同図の（Ａ）に示したように、入力ＲＧＢ値が「１２４」以上である場合には、出力ＲＧＢ値が全て「２５５」となる（すなわち、出力ＲＧＢ値が「２５５」で頭打ちとなる）。たとえば、入力ＲＧＢ値が「２００」である場合、本来ならば、出力ＲＧＢ値を「４１０」となるべきところが、ＲＧＢ値の限界値が「２５５」であるために、出力ＲＧＢ値は「２５５」となる。 In this case, as shown in FIG. 5A, when the input RGB value is “124” or more, the output RGB values are all “255” (that is, the output RGB value is “255”). ) For example, when the input RGB value is “200”, the output RGB value should be “410”. However, since the limit value of the RGB value is “255”, the output RGB value is “255”. It becomes.
　このように、画像データにＲＧＢ値の大きい画素が含まれる場合には、ＲＧＢ変換処理を行うことによって変換後のＲＧＢ値（出力ＲＧＢ値）が頭打ちとなるおそれがある。この結果、本来ならば異なるＲＧＢ値（たとえば、１２４～２５５）で表現されるべき部分が、ＲＧＢ変換処理によって全て同じＲＧＢ値（２５５）で表現されることとなるため、ハレーションが発生し、画質が劣化するおそれがある。 As described above, when the image data includes a pixel having a large RGB value, there is a possibility that the converted RGB value (output RGB value) reaches a peak by performing the RGB conversion process. As a result, portions that should originally be expressed with different RGB values (for example, 124 to 255) are all expressed with the same RGB value (255) by the RGB conversion processing. May deteriorate.
　そこで、実施例２に係る表示制御装置１０は、明るい画像が入力された場合、すなわち、暫定発光量がＨオフセットよりも多い場合には、ハレーションが発生するおそれがあるか否かを判定し、発生するおそれがあると判定した場合には、Ｈオフセットよりも多い発光量を確定発光量として決定することとした。 Therefore, the display control apparatus 10 according to the second embodiment determines whether or not there is a possibility of halation when a bright image is input, that is, when the provisional light emission amount is larger than the H offset, When it is determined that there is a risk of occurrence, the light emission amount larger than the H offset is determined as the determined light emission amount.
　ここで、ハレーションが発生する可能性は、ＲＧＢ値の大きい画素が多く含まれる画像データほど高い。このため、実施例２に係る表示制御装置１０は、同図の（Ｂ）に示したように、サブサンプリング後の画像データの平均輝度を算出し、かかる平均輝度がＨオフセットに対応する輝度値よりも高い場合に、ハレーションが発生する可能性があると判定する。 Here, the possibility that halation will occur is higher for image data containing many pixels with large RGB values. For this reason, the display control apparatus 10 according to the second embodiment calculates the average luminance of the image data after sub-sampling as shown in (B) of the figure, and the average luminance corresponds to the H offset. If it is higher than that, it is determined that halation may occur.
　そして、実施例２に係る表示制御装置１０は、ハレーションが発生する可能性が高いと判定した場合には、Ｈオフセットを確定発光量とするのではなく、平均輝度に対応する発光量を確定発光量とする。 When the display control apparatus 10 according to the second embodiment determines that there is a high possibility that halation will occur, the display control device 10 does not set the H offset as the fixed light emission amount, but sets the light emission amount corresponding to the average luminance as the fixed light emission. Amount.
　このように、実施例２では、ハレーションが発生する可能性がある場合には、確定発光量をＨオフセットよりも高くすることによって、ＲＧＢ変換係数が小さくなり、出力ＲＧＢ値が頭打ちとなることが抑制されるため、ハレーションの発生を回避することができる。 As described above, in the second embodiment, when there is a possibility that halation may occur, the RGB conversion coefficient may be reduced and the output RGB value may reach a peak by setting the determined light emission amount to be higher than the H offset. Since it is suppressed, the occurrence of halation can be avoided.
　次に、実施例２に係るヒストグラム解析部１１ｄ’の構成について図８を用いて説明する。ここで、実施例１において説明した機能と同一の機能を有するものについては、同一の符号を付し、その説明を省略することとする。同図に示すように、実施例２に係るヒストグラム解析部１１ｄ’は、実施例１において説明したヒストグラム解析部１１ｄの構成に加えて、平均輝度算出部１１１ｄをさらに備えている。 Next, the configuration of the histogram analysis unit 11d 'according to the second embodiment will be described with reference to FIG. Here, components having the same functions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. As shown in the figure, the histogram analysis unit 11d 'according to the second embodiment further includes an average luminance calculation unit 111d in addition to the configuration of the histogram analysis unit 11d described in the first embodiment.
　平均輝度算出部１１１ｄは、ヒストグラム生成部１１ｃからヒストグラムを取得し、取得したヒストグラムを用いてサブサンプリング後の画像データの平均輝度を算出する処理部である。また、平均輝度算出部１１１ｄは、算出した平均輝度を比較部１１１ｂへ渡す処理も併せて行う。 The average luminance calculation unit 111d is a processing unit that acquires a histogram from the histogram generation unit 11c and calculates the average luminance of the subsampled image data using the acquired histogram. The average luminance calculation unit 111d also performs a process of passing the calculated average luminance to the comparison unit 111b.
　また、比較部１１１ｂは、平均輝度算出部１１１ｄから取得した平均輝度とＨオフセットに対応する輝度値とをさらに比較する。また、比較部１１１ｂは、この比較結果を確定発光量決定部１１１ｃへ渡す処理も併せて行う。 Further, the comparison unit 111b further compares the average luminance acquired from the average luminance calculation unit 111d with the luminance value corresponding to the H offset. In addition, the comparison unit 111b also performs a process of passing this comparison result to the determined light emission amount determination unit 111c.
　また、確定発光量決定部１１１ｃは、暫定発光量がＨオフセットよりも多い場合に、平均輝度がＨオフセットに対応する輝度値よりも高いか否かを判定する。そして、確定発光量決定部１１１ｃは、平均輝度がＨオフセットに対応する輝度値よりも高いと判定した場合には、平均輝度に対応する発光量を確定発光量として決定する。 Further, when the provisional light emission amount is larger than the H offset, the determined light emission amount determination unit 111c determines whether or not the average luminance is higher than the luminance value corresponding to the H offset. Then, when it is determined that the average luminance is higher than the luminance value corresponding to the H offset, the determined light emission amount determination unit 111c determines the light emission amount corresponding to the average luminance as the determined light emission amount.
　次に、実施例２に係る表示制御装置１０の具体的動作について図９を用いて説明する。図９は、実施例２に係る表示制御装置が実行する処理手順を示すフローチャートである。なお、同図においては、表示制御装置１０が実行する処理手順のうち、バックライトの発光量制御に関する処理手順のみを示す。 Next, a specific operation of the display control apparatus 10 according to the second embodiment will be described with reference to FIG. FIG. 9 is a flowchart illustrating a processing procedure executed by the display control apparatus according to the second embodiment. In the figure, only the processing procedure related to the light emission amount control of the backlight among the processing procedures executed by the display control device 10 is shown.
　同図に示すように、表示制御装置１０では、画像データ取得部１１ａが、画像データを取得すると（ステップＳ２０１）、サブサンプリング部１１ｂが、取得した画像データに対してサブサンプリングを行う（ステップＳ２０２）。つづいて、表示制御装置１０では、ヒストグラム生成部１１ｃが、サブサンプリング後の画像データを用いてヒストグラムを生成し（ステップＳ２０３）、平均輝度算出部１１１ｄが、ヒストグラムを用いてサブサンプリング後の画像データの平均輝度を算出する（ステップＳ２０４）。また、暫定発光量決定部１１１ａは、ヒストグラムおよびＤＮＵＭ１２１を用いて暫定発光量を決定する（ステップＳ２０５）。 As shown in the figure, in the display control apparatus 10, when the image data acquisition unit 11a acquires image data (step S201), the sub-sampling unit 11b performs sub-sampling on the acquired image data (step S202). ). Subsequently, in the display control device 10, the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S203), and the average luminance calculation unit 111d uses the histogram to output the image data after sub-sampling. Is calculated (step S204). Further, the provisional light emission amount determining unit 111a determines the provisional light emission amount using the histogram and the DNUM 121 (step S205).
　つづいて、表示制御装置１０では、比較部１１１ｂが、暫定発光量とＨオフセット１２２とを比較し（ステップＳ２０６）、確定発光量決定部１１１ｃが、暫定発光量がＨオフセット１２２よりも多いか否かを判定する（ステップＳ２０７）。つづいて、確定発光量決定部１１１ｃは、暫定発光量がＨオフセットよりも多い場合には（ステップＳ２０７、Ｙｅｓ）、平均輝度がＨオフセットに対応する輝度値よりも高いか否かをさらに判定する（ステップＳ２０８）。そして、平均輝度がＨオフセットに対応する輝度値よりも高いと判定した場合には（ステップＳ２０８、Ｙｅｓ）、確定発光量決定部１１１ｃは、平均輝度に対応する発光量を確定発光量として決定する（ステップＳ２０９）。 Subsequently, in the display control device 10, the comparison unit 111b compares the provisional light emission amount with the H offset 122 (step S206), and the determined light emission determination unit 111c determines whether or not the provisional light emission amount is larger than the H offset 122. Is determined (step S207). Subsequently, when the provisional light emission amount is larger than the H offset (step S207, Yes), the determined light emission amount determination unit 111c further determines whether or not the average luminance is higher than the luminance value corresponding to the H offset. (Step S208). Then, when it is determined that the average luminance is higher than the luminance value corresponding to the H offset (step S208, Yes), the determined emission amount determining unit 111c determines the emission amount corresponding to the average luminance as the determined emission amount. (Step S209).
　一方、平均輝度がＨオフセットに対応する輝度値よりも高くない場合には（ステップＳ２０８、Ｎｏ）、確定発光量決定部１１１ｃは、Ｈオフセットを確定発光量として決定する（ステップＳ２１０）。また、ステップＳ２０７において、暫定発光量がＨオフセットよりも多くない場合には（ステップＳ２０７、Ｎｏ）、暫定発光量を確定発光量として決定する（ステップＳ２１１）。 On the other hand, when the average luminance is not higher than the luminance value corresponding to the H offset (No at Step S208), the determined light emission amount determining unit 111c determines the H offset as the determined light emission amount (Step S210). In step S207, if the provisional light emission amount is not greater than the H offset (No in step S207), the provisional light emission amount is determined as the determined light emission amount (step S211).
　つづいて、発光量変更部１１ｅは、確定発光量決定部１１１ｃから取得した確定発光量と現在の発光量との差分に基づく発光量変更処理を行って変更後発光量を決定する（ステップＳ２１２）。つづいて、ＰＷＭ生成部１１ｆは、変更後発光量に応じたＰＷＭ信号を生成してバックライトモジュール２２へ出力する（ステップＳ２１３）。 Subsequently, the light emission amount changing unit 11e performs a light emission amount changing process based on the difference between the determined light emission amount acquired from the determined light emission amount determining unit 111c and the current light emission amount, and determines the changed light emission amount (step S212). Subsequently, the PWM generation unit 11f generates a PWM signal corresponding to the changed light emission amount and outputs the PWM signal to the backlight module 22 (step S213).
　また、ＲＧＢ変換部１１ｇは、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値に対して、変更後発光量に対応するＲＧＢ変換係数を掛け合わせるＲＧＢ変換処理を行う（ステップＳ２１４）。そして、ＲＧＢ変換部１１ｇは、ＲＧＢ変換処理後の画像データを液晶パネル２１へ出力して（ステップＳ２１５）、処理を終了する。 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 S214). Then, the RGB conversion unit 11g outputs the image data after the RGB conversion processing to the liquid crystal panel 21 (step S215), and ends the processing.
　上述してきたように、実施例２では、平均輝度算出部が、画像データの平均輝度を算出し、比較部が、平均輝度算出部によって算出された平均輝度とＨオフセットとをさらに比較し、確定発光量決定部が、比較部による比較の結果、暫定発光量がＨオフセットを超え、かつ、平均輝度がＨオフセットを超える場合には、平均輝度をバックライトの確定的な発光量として決定することとした。 As described above, in the second embodiment, the average luminance calculation unit calculates the average luminance of the image data, and the comparison unit further compares the average luminance calculated by the average luminance calculation unit with the H offset and confirms it. If the provisional light emission amount exceeds the H offset and the average luminance exceeds the H offset as a result of the comparison by the comparison unit, the light emission amount determination unit determines the average luminance as the definite light emission amount of the backlight. It was.
　したがって、実施例２によれば、明るい画像が入力された場合に、バックライトモジュール２２の消費電力の削減量が少なくなることを抑制しつつ、ハレーションの発生による画質劣化を防止することができる。 Therefore, according to the second embodiment, when a bright image is input, it is possible to prevent image quality deterioration due to the occurrence of halation while suppressing a reduction in power consumption of the backlight module 22 from being reduced.
　ところで、上述したハレーション回避機能をユーザの操作に応じてＯＮ／ＯＦＦの切り替え可能としてもよい。また、Ｈオフセットの値をユーザの操作に応じて変更することとしてもよい。以下では、これらの点について図１０を用いて説明する。図１０は、ハレーション回避機能およびＨオフセットの設定変更について説明するための図である。ここでは、ハレーション回避機能がＯＮの状態を「画質重視モード」と呼び、ＯＦＦの場合を「省電力モード」と呼ぶこととする。 By the way, the above-described halation avoidance function may be switched on / off in accordance with a user operation. Also, the value of the H offset may be changed according to the user's operation. Hereinafter, these points will be described with reference to FIG. FIG. 10 is a diagram for explaining a halation avoidance function and an H offset setting change. Here, the state where the halation avoidance function is ON is referred to as “image quality emphasis mode”, and the case where it is OFF is referred to as “power saving mode”.
　なお、同図の（Ａ）には、液晶パネル２１に表示される画面の一例を示し、同図の（Ｂ）には、各モード時の画質および省電力効果について示し、同図の（Ｃ）には、Ｈオフセットと省電力効果との関係を示している。なお、同図の（Ａ）に示した液晶パネル２１は、タッチパネルであるとする。 Note that (A) in the figure shows an example of a screen displayed on the liquid crystal panel 21, (B) in the figure shows image quality and power saving effect in each mode, and (C) in FIG. ) Shows the relationship between the H offset and the power saving effect. It is assumed that the liquid crystal panel 21 shown in FIG.
　同図の（Ａ）に示したように、液晶パネル２１には、モード選択ボタン２１ａ、画面の明るさを調整するための「暗」ボタン２１ｃおよび「明」ボタン２１ｄが表示されている。また、液晶パネル２１には、現在の消費電力削減率２１ｂが表示されている。たとえば、同図の（Ａ）では、「画質重視モード」が選択されており、「明るさ」が７段階中の４に設定されている。また、同図の（Ａ）では、現在の消費電力削減率として「３０％」が表示されている。 As shown in FIG. 5A, the liquid crystal panel 21 displays a mode selection button 21a, a “dark” button 21c and a “bright” button 21d for adjusting the screen brightness. The liquid crystal panel 21 displays the current power consumption reduction rate 21b. For example, in FIG. 5A, “image quality emphasis mode” is selected, and “brightness” is set to 4 out of 7 levels. Moreover, in (A) of the figure, “30%” is displayed as the current power consumption reduction rate.
　ここで、ユーザは、液晶パネル２１に表示される画像を確認しつつモード選択ボタン２１ａを押下することによって、画質重視モードあるいは省電力モードのいずれかのモードを好みに応じて選択することができる。 Here, the user can select either the image quality emphasis mode or the power saving mode according to his / her preference by pressing the mode selection button 21a while confirming the image displayed on the liquid crystal panel 21. .
　ここで、同図の（Ｂ）に示したように、画質重視モードでは、ハレーションの発生が防止されるため画質が高くなり、また、暫定発光量よりも少ない発光量をバックライトモジュール２２の発光量として用いるため省電力効果も高い。一方、省電力モードでは、ハレーションが発生する可能性があるため、画質重視モードと比較して画質は劣るものの、バックライトモジュール２２の発光量がさらに少なくなるため、省電力効果が画質重視モードと比較してより高くなる。 Here, as shown in FIG. 5B, in the image quality emphasis mode, the image quality is improved because halation is prevented, and the light emission amount less than the provisional light emission amount is emitted from the backlight module 22. Since it is used as a quantity, it has a high power saving effect. On the other hand, in the power saving mode, there is a possibility that halation may occur. Therefore, although the image quality is inferior to that in the image quality emphasis mode, the light emission amount of the backlight module 22 is further reduced. Compared to higher.
　たとえば、ナビゲーション画像が表示されている場合に、文字が認識できる程度の画質でよいと考えるユーザは、省電力モードを選択することによって、省電力効果を高めることができる。 For example, when a navigation image is displayed, a user who thinks that the image quality is high enough to recognize characters can improve the power saving effect by selecting the power saving mode.
　また、ユーザは、液晶パネル２１に表示される画像の画質や消費電力削減率２１ｂを確認しつつ、「暗」ボタン２１ｃや「明」ボタン２１ｄを押下することで、ユーザの好みに合った明るさに調整することができる。 In addition, the user can confirm the image quality of the image displayed on the liquid crystal panel 21 and the power consumption reduction rate 21b, and press the “dark” button 21c and the “bright” button 21d, so that the brightness according to the user's preference can be obtained. Can be adjusted.
　ここで、同図の（Ｃ）に示したように、Ｈオフセットの値は、「暗」ボタン２１ｃが押下されるに従って小さくなり、「明」ボタン２１ｄが押下されるにしたがって大きくなるように設定されている。特に、「暗」ボタン２１ｃを押下してＨオフセットの値を小さくすることで、バックライトモジュール２２の発光量の上限値が下がる結果、省電力効果が一層高まることとなる。 Here, as shown in FIG. 10C, the value of the H offset is set so as to decrease as the “dark” button 21c is pressed and increase as the “bright” button 21d is pressed. Has been. In particular, when the “dark” button 21c is pressed to reduce the value of the H offset, the upper limit value of the light emission amount of the backlight module 22 is lowered, and the power saving effect is further enhanced.
　ところで、液晶ディスプレイ２０に表示される画像を誰も見ていない場合には、Ｈオフセットの値を極端に下げて省電力効果を大幅に高めることとしてもよい。具体的には、液晶ディスプレイ２０に視線検知センサを設ける。ここで、視線検知センサは、ユーザの視線方向を検知するセンサであり、検知結果を表示制御装置１０へ出力する。 By the way, when no one is looking at the image displayed on the liquid crystal display 20, the value of the H offset may be extremely lowered to greatly increase the power saving effect. Specifically, a line-of-sight detection sensor is provided on the liquid crystal display 20. Here, the gaze detection sensor is a sensor that detects the gaze direction of the user, and outputs the detection result to the display control device 10.
　また、表示制御装置１０の制御部１１は、ユーザの視線が液晶パネル２１上にあるか否かを判定し、液晶パネル２１上にあると判定した場合に、画像の閲覧者を検出する。そして、表示制御装置１０の制御部１１は、画像の閲覧者が検出されなかった場合に、Ｈオフセットの値を大幅に下げる。 Further, the control unit 11 of the display control apparatus 10 determines whether or not the user's line of sight is on the liquid crystal panel 21, and detects the viewer of the image when determining that the user's line of sight is on the liquid crystal panel 21. And the control part 11 of the display control apparatus 10 reduces the value of H offset significantly, when the viewer of an image is not detected.
　このように、表示制御装置１０の制御部１１は、閲覧者検出手段として機能することによって、液晶パネル２１に表示される画像の閲覧者の検出を行う。また、表示制御装置１０の制御部１１は、閾値変更手段として機能することによって、画像の閲覧者が検出されなかった場合に、画像閲覧者が検出された場合と比較してＨオフセットの値を下げる。 As described above, the control unit 11 of the display control apparatus 10 functions as a viewer detection unit to detect a viewer of an image displayed on the liquid crystal panel 21. Further, the control unit 11 of the display control device 10 functions as a threshold value changing unit, so that when the image viewer is not detected, the value of the H offset is compared with the case where the image viewer is detected. Lower.
　すなわち、画像の閲覧者がいない場合（すなわち、液晶パネル２１に画像を表示する必要がない場合）には、バックライトモジュール２２の発光量の上限値を大幅に下げることとしたため、省電力効果をより一層高めることができる。 That is, when there is no image viewer (that is, when there is no need to display an image on the liquid crystal panel 21), the upper limit value of the light emission amount of the backlight module 22 is greatly reduced, so that a power saving effect is achieved. It can be further increased.
　なお、画像の閲覧者が検出されなかった場合に、Ｈオフセットの値を０とすれば、どのような画像データが入力された場合であっても確定発光量が０％となるため、バックライトモジュール２２の消費電力を最大限に削減することができる。 If no image viewer is detected, if the value of the H offset is set to 0, the definite amount of light emission is 0% regardless of what image data is input. The power consumption of the module 22 can be reduced to the maximum.
　また、上述してきた各実施例では、暫定発光量がＨオフセットよりも多い場合に、Ｈオフセットを確定発光量とする場合について説明したが、これに限ったものではない。たとえば、暫定発光量がＨオフセットよりも多い場合に、暫定発光量を所定の変換式で変換した値を確定発光量として決定することとしてもよい。 Further, in each of the embodiments described above, the case where the H offset is set as the fixed light emission amount when the provisional light emission amount is larger than the H offset has been described, but the present invention is not limited to this. For example, when the provisional emission amount is larger than the H offset, a value obtained by converting the provisional emission amount by a predetermined conversion formula may be determined as the determined emission amount.
　具体的には、確定発光量決定部１１１ｃは、比較部１１１ｂによる比較の結果、暫定発光量がＨオフセットを超える場合に、上記の変換式を用いて暫定発光量を変換することによって得られる値を確定発光量として決定する。 Specifically, when the provisional emission amount exceeds the H offset as a result of comparison by the comparison unit 111b, the determined emission amount determination unit 111c obtains a value obtained by converting the provisional emission amount using the above conversion formula. Is determined as the definite light emission amount.
　ここで、確定発光量決定部１１１ｃは、たとえば、０よりも大きく１よりも小さい係数を暫定発光量に対して乗じることによって暫定発光量よりも少ない確定発光量を得る一次関数を変換式として用いることができる。 Here, the deterministic light emission amount determination unit 111c uses, for example, a linear function that obtains a definite light emission amount smaller than the provisional light emission amount by multiplying the provisional light emission amount by a coefficient larger than 0 and smaller than 1 as a conversion equation. be able to.
　これにより、確定発光量が暫定発光量よりも少なくなり、かつ、確定発光量が暫定発光量に依存して変化することとなるため、バックライトの消費電力の削減量が少なくなることを抑制しつつ、画像ごとに適した確定発光量でバックライトを発光させることができる。なお、変換式は、変換前の値が変換後の値よりも小さくなるものであればどのような変換式であってもよい。 As a result, the determined light emission amount becomes smaller than the provisional light emission amount, and the fixed light emission amount changes depending on the provisional light emission amount, so that the reduction in the amount of power consumption of the backlight is reduced. On the other hand, the backlight can be emitted with a fixed light emission amount suitable for each image. The conversion expression may be any conversion expression as long as the value before conversion is smaller than the value after conversion.
　また、上述してきた各実施例では、バックライトモジュール２２の発光量に対して上限値のみを定める場合について説明してきたが、バックライトモジュール２２の発光量に対して下限値も定めてもよい。以下、かかる点について図１１を用いて説明しておく。図１１は、Ｌオフセットを設定する場合について説明するための図である。 In each of the embodiments described above, the case where only the upper limit value is determined for the light emission amount of the backlight module 22 has been described. However, the lower limit value may be determined for the light emission amount of the backlight module 22. Hereinafter, this point will be described with reference to FIG. FIG. 11 is a diagram for explaining a case where the L offset is set.
　同図に示すように、暫定発光量決定部１１１ａは、ヒストグラムの高輝度側から順に画素数を計数していき、累積画素数がＤＮＵＭ１２１を超えた場合におけるヒストグラム上の位置（輝度値）に対応する発光量を暫定発光量として決定する。つづいて、比較部１１１ｂは、暫定発光量と、Ｈオフセットよりも低輝度側に設定された他の閾値（Ｌオフセット）とを比較する。 As shown in the figure, the provisional light emission amount determination unit 111a sequentially counts the number of pixels from the high luminance side of the histogram, and corresponds to the position (luminance value) on the histogram when the cumulative number of pixels exceeds DNUM 121. The amount of light emitted is determined as the provisional light emission amount. Subsequently, the comparison unit 111b compares the provisional light emission amount with another threshold value (L offset) set on the lower luminance side than the H offset.
　そして、確定発光量決定部１１１ｃは、暫定発光量がＬオフセットよりも多い場合には、暫定発光量をそのまま確定発光量として決定する。一方、確定発光量決定部１１１ｃは、Ｌオフセットが暫定発光量よりも多い場合には、Ｌオフセットを確定発光量として決定する。これにより、画面が暗くなり過ぎることが防止されるため、画面の視認性を高めることができる。 Then, when the provisional emission amount is larger than the L offset, the determined emission amount determination unit 111c determines the provisional emission amount as it is as the fixed emission amount. On the other hand, when the L offset is larger than the provisional light emission amount, the determined light emission amount determining unit 111c determines the L offset 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.
　ところで、特許文献１に記載の技術には、画像の明るさが頻繁に変化した場合に、液晶ディスプレイに表示される画面にちらつきが発生するおそれがあるという問題もあった。これは、映像の暗部がバックライト発光量の変化によって輝度への影響を受けやすく、急激なバックライト発光量の変化がちらつきの原因となるためである。 By the way, the technique described in Patent Document 1 has a problem that flicker may occur on the screen displayed on the liquid crystal display when the brightness of the image changes frequently. This is because a dark portion of an image is easily affected by luminance due to a change in the amount of backlight emission, and a sudden change in the amount of backlight emission causes flickering.
　このため、特に、暗いシーンと明るいシーンとが交互に繰り返される場合には、暗いシーンであるにも関わらずバックライトの発光量が多めに設定されたり、逆に、明るいシーンであるにも関わらずバックライトの発光量が少なめに設定されたりする場合があり、これによって画面にちらつきが発生することとなる。 For this reason, in particular, when a dark scene and a bright scene are alternately repeated, the backlight emission amount is set to be large even though the scene is dark, or conversely, even though the scene is bright. In some cases, the amount of light emitted from the backlight may be set to be small, which causes flickering on the screen.
　これらのことから、バックライトによる消費電力を抑えつつ、画像の明るさが頻繁に変化した場合に生じる画面のちらつきを低減することができる表示制御装置あるいは表示制御方法をいかにして実現するかも大きな課題となっている。 Therefore, how to realize a display control device or a display control method that can reduce screen flicker that occurs when the brightness of an image frequently changes while suppressing power consumption by the backlight is also significant. It has become a challenge.
　そこで、実施例３では、入力画像の輝度分布に基づいてバックライトの目標発光量が決定された場合に、現在の発光量を複数フレームかけて段階的に変化させることによって、決定された発光量と一致させることとした。以下では、かかる実施例３について図１２～２０を用いて説明する。 Therefore, in Example 3, when the target light emission amount of the backlight is determined based on the luminance distribution of the input image, the determined light emission amount is obtained by changing the current light emission amount step by step over a plurality of frames. To match. Hereinafter, Example 3 will be described with reference to FIGS.
　なお、以下に示す実施例３では、上記の実施例１または２に係る表示制御装置１０と同様の機能を発揮するものについては実施例１または２と同一の符号を付してその説明を省略する。 In the third embodiment shown below, the same reference numerals as those in the first or second embodiment are used for the same functions as those of the display control apparatus 10 according to the first or second embodiment, and the description thereof is omitted. To do.
　まず、実施例３の詳細な説明に先立って、実施例３に係る表示制御手法の概要について図１２を用いて説明する。図１２は、実施例３に係る表示制御手法の概要を示す図である。ここで、同図の（Ａ）には、従来の表示制御手法の概要を、同図の（Ｂ）には、実施例３に係る表示制御手法の概要を、それぞれ示している。なお、同図の（Ａ）および（Ｂ）に示したグラフは、バックライトの発光量の経時変化をあらわしている。また、横軸に付した時刻ｔ０～ｔ３は、フレームの更新タイミングをあらわしている。 First, prior to detailed description of the third embodiment, an overview of a display control method according to the third embodiment will be described with reference to FIG. FIG. 12 is a diagram illustrating an overview of the display control method according to the third embodiment. Here, (A) in the figure shows an outline of a conventional display control technique, and (B) in the figure shows an outline of a display control technique according to the third embodiment. In addition, the graph shown to (A) and (B) of the figure represents the time-dependent change of the emitted light quantity of a backlight. Times t0 to t3 attached to the horizontal axis represent frame update timings.
　従来の表示制御手法では、あるフレームの輝度分布に基づいて目標発光量が決定された場合に、決定された目標発光量をそのまま次のフレームにおけるバックライトの発光量として採用していた。たとえば、同図の（Ａ）に示したように、従来の表示制御手法では、時刻ｔ０において更新されたフレームの輝度分布に基づいて決定された目標発光量を、時刻ｔ１におけるバックライトの発光量として決定していた。 In the conventional display control method, when the target light emission amount is determined based on the luminance distribution of a certain frame, the determined target light emission amount is directly adopted as the light emission amount of the backlight in the next frame. For example, as shown in FIG. 6A, in the conventional display control method, the target light emission amount determined based on the luminance distribution of the frame updated at time t0 is used as the light emission amount of the backlight at time t1. Was determined as.
　このように、目標発光量をバックライトの発光量として即反映することとすると、実際の発光量と目標発光量とが大きく異なる場合に、バックライトの発光量が急激に変化することによって画面のちらつきが発生するおそれがある。特に、明るい画像と暗い画像とが交互に繰り返された場合に、適用すべき発光量と実際に適用される発光量との差が大きくなりやすく、画面のちらつきが顕著となる。 As described above, when the target light emission amount is immediately reflected as the backlight light emission amount, when the actual light emission amount and the target light emission amount are greatly different, the backlight light emission amount changes abruptly. There is a risk of flickering. In particular, when a bright image and a dark image are alternately repeated, the difference between the light emission amount to be applied and the light emission amount actually applied tends to increase, and the flickering of the screen becomes remarkable.
　そこで、実施例３に係る表示制御手法では、入力画像の輝度分布に基づいてバックライトの目標発光量が決定された場合に、現在の発光量を複数フレームかけて段階的に変化させることによって、決定された発光量と一致させる点に特徴を有する。また、実施例３に係る表示制御手法では、現在の発光量を直線的に変化させるのではなく、目標発光量との差が大きいほど大きく変化させ、目標発光量に近づくにつれて変化量が少なくなるように変化させる点にも特徴を有する。 Therefore, in the display control method according to the third embodiment, when the target light emission amount of the backlight is determined based on the luminance distribution of the input image, the current light emission amount is changed stepwise over a plurality of frames. It is characterized in that it matches the determined light emission amount. In the display control method according to the third embodiment, the current light emission amount is not changed linearly, but is increased as the difference from the target light emission amount is increased, and the change amount is reduced as the target light emission amount is approached. It also has a feature in that it can be changed.
　具体的には、同図の（Ｂ）に示したように、実施例３に係る表示制御手法では、目標発光量と現在の発光量との差分値に応じて現在の発光量からの変化量を決定し、決定した変化量だけ現在の発光量を変化させた発光量をバックライトの発光量として採用する。 Specifically, as shown in FIG. 5B, in the display control method according to the third embodiment, the amount of change from the current light emission amount according to the difference value between the target light emission amount and the current light emission amount. And the light emission amount obtained by changing the current light emission amount by the determined change amount is employed as the light emission amount of the backlight.
　たとえば、同図の（Ｂ）に示したように、時刻ｔ０における発光量（現在の発光量）と目標発光量との差分値が比較的大きい場合には、現在の発光量からの変化量として変化量（大）を決定する。そして、実施例３に係る表示制御手法では、現在の発光量を変化量（大）だけ変化させた発光量をｔ１において更新されるフレームに適用する。ここで、変化量（大）は、画面のちらつきが発生しない程度の変化量とする。 For example, as shown in FIG. 5B, when the difference value between the light emission amount (current light emission amount) at time t0 and the target light emission amount is relatively large, the amount of change from the current light emission amount is Determine the amount of change (large). In the display control method according to the third embodiment, the light emission amount obtained by changing the current light emission amount by the change amount (large) is applied to the frame updated at t1. Here, the amount of change (large) is an amount of change that does not cause screen flickering.
　また、時刻ｔ１における発光量（現在の発光量）と目標発光量との差分値は、時刻ｔ０における発光量（現在の発光量）と目標発光量との差分値よりも小さくなる。このため、実施例３に係る表示制御手法では、現在の発光量からの変化量として変化量（中）を決定する。そして、実施例３に係る表示制御手法では、現在の発光量を変化量（中）だけ変化させた発光量をｔ２において更新されるフレームに適用する。 The difference value between the light emission amount (current light emission amount) and the target light emission amount at time t1 is smaller than the difference value between the light emission amount (current light emission amount) and the target light emission amount at time t0. For this reason, in the display control method according to the third embodiment, a change amount (medium) is determined as a change amount from the current light emission amount. In the display control method according to the third embodiment, the light emission amount obtained by changing the current light emission amount by the change amount (medium) is applied to the frame updated at t2.
　同様に、時刻ｔ２における発光量（現在の発光量）と目標発光量との差分値は、時刻ｔ１における発光量（現在の発光量）と目標発光量との差分値よりも小さくなる。このため、実施例３に係る表示制御手法では、現在の発光量からの変化量として変化量（小）を決定する。そして、実施例３に係る表示制御手法では、現在の発光量を変化量（小）だけ変化させた発光量をｔ３において更新されるフレームに適用する。 Similarly, the difference value between the light emission amount (current light emission amount) and the target light emission amount at time t2 is smaller than the difference value between the light emission amount (current light emission amount) and the target light emission amount at time t1. For this reason, in the display control method according to the third embodiment, the change amount (small) is determined as the change amount from the current light emission amount. In the display control method according to the third embodiment, the light emission amount obtained by changing the current light emission amount by the change amount (small) is applied to the frame updated at t3.
　これによって、バックライトの実際の発光量は、時刻ｔ０において更新されたフレームの輝度分布に基づいて決定された目標発光量と時刻ｔ３において一致することとなる。 Thus, the actual light emission amount of the backlight coincides with the target light emission amount determined based on the luminance distribution of the frame updated at time t0 at time t3.
　このように、実施例３に係る表示制御手法では、現在の発光量を目標発光量まで変化させる場合に、複数フレームかけて段階的に変化させることとしたため、バックライトの発光量の急激な変化を抑えることができ、この結果、画面のちらつきを防止することができる。 As described above, in the display control method according to the third embodiment, when the current light emission amount is changed to the target light emission amount, the change is made stepwise over a plurality of frames. As a result, flickering of the screen can be prevented.
　しかも、実施例３に係る表示制御手法では、現在の発光量と目標発光量との差分値が大きい場合には、画面のちらつきが発生しない程度の変化量で現在の発光量を大きく変化させる一方、差分値が小さくなるにつれて変化量も少なくしていくことによって現在の発光量を目標発光量へなだらかに収束させることとした。これによって、バックライトの発光量を極力早く目標発光量に近づけることができるため、バックライトの発光量と目標発光量との差が大きい場合に生じやすい色つぶれを防ぐことができる。 In addition, in the display control method according to the third embodiment, when the difference value between the current light emission amount and the target light emission amount is large, the current light emission amount is greatly changed with a change amount that does not cause flickering of the screen. As the difference value decreases, the amount of change is also reduced, so that the current light emission amount is smoothly converged to the target light emission amount. As a result, the light emission amount of the backlight can be brought close to the target light emission amount as quickly as possible, so that the color collapse that tends to occur when the difference between the light emission amount of the backlight and the target light emission amount is large can be prevented.
　ところで、使用する液晶ディスプレイによっては、バックライトの発光量をわずかに変化させただけでも画面にちらつきが生じる場合がある。そこで、目標発光量と現在の発光量との差分値が所定値以下であるならば、バックライトの発光量を変化させないこととしてもよい。これによって、バックライトの発光量のわずかな変化によって生じる画面のちらつきを防止することができる。 By the way, depending on the liquid crystal display used, even if the amount of light emitted from the backlight is changed slightly, the screen may flicker. Therefore, if the difference value between the target light emission amount and the current light emission amount is a predetermined value or less, the light emission amount of the backlight may not be changed. Accordingly, it is possible to prevent screen flickering caused by a slight change in the light emission amount of the backlight.
　また、暗い画像と明るい画像とが交互に繰り返される場合には、現在の発光量からの変化量を少なくすることとしてもよい。これによって、バックライトの発光量を短期間で頻繁に変化させることによる処理負荷を低減することができる。 In addition, when a dark image and a bright image are alternately repeated, the amount of change from the current light emission amount may be reduced. As a result, it is possible to reduce the processing load caused by frequently changing the light emission amount of the backlight in a short period.
　また、図１２（Ａ）および（Ｂ）では、バックライトの発光量を目標発光量へ向かって増加させる場合について説明したが、実施例３に係る表示制御手法では、バックライトの発光量を目標発光量へ向かって減少させる場合も同様に、バックライトの発光量を段階的に変化させる。 12A and 12B illustrate the case where the light emission amount of the backlight is increased toward the target light emission amount, but in the display control method according to the third embodiment, the light emission amount of the backlight is the target. Similarly, in the case of decreasing toward the light emission amount, the light emission amount of the backlight is changed stepwise.
　ここで、ハレーションは、バックライト制御を暗→明へ変化させた場合に発生し易く、逆に、明→暗へ変化させた場合には発生し難い。そこで、バックライトの発光量を減少させる場合には、バックライトの発光量を増加させる場合よりも変化量を多くしてもよい。これによって、バックライトの発光量を減少させる場合に、視認者に画面のちらつきを感じさせることなく、バックライトモジュール２２の発光量をより早く目標発光量へ近づけることができる。 Here, halation is likely to occur when the backlight control is changed from dark to light, and conversely, it is difficult to occur when the backlight control is changed from light to dark. Therefore, when the light emission amount of the backlight is decreased, the amount of change may be larger than when the light emission amount of the backlight is increased. Thereby, when reducing the light emission amount of the backlight, the light emission amount of the backlight module 22 can be brought closer to the target light emission amount without causing the viewer to feel the flickering of the screen.
　なお、図１２（Ａ）および（Ｂ）では、バックライトの実際の発光量を３段階で変化させる場合について説明したが、これに限ったものではなく、多段階であれば３段階より多くても少なくても構わない。 In FIGS. 12A and 12B, the case where the actual light emission amount of the backlight is changed in three stages has been described. However, the present invention is not limited to this. There is no problem.
　以下では、図１２を用いて説明した表示制御手法を適用した表示制御装置についての実施例３を詳細に説明する。なお、実施例３では、実施例１および２と同様、車載装置に搭載される液晶ディスプレイの表示制御を行う表示制御装置に対して実施例３に係る表示制御手法を適用する場合について説明する。ただし、実施例３にかかる表示制御装置は、これに限ったものではなく、携帯端末装置やＰＣ（Personal Computer）あるいはＴＶ（Television）のように、バックライトを用いて表示を行う表示部を備える各種の装置に対して適用することができる。 Hereinafter, a third embodiment of the display control apparatus to which the display control method described with reference to FIG. 12 is applied will be described in detail. In the third embodiment, as in the first and second embodiments, a case where the display control method according to the third embodiment is applied to a display control device that performs display control of a liquid crystal display mounted on an in-vehicle device will be described. However, the display control apparatus according to the third embodiment is not limited to this, and includes a display unit that performs display using a backlight, such as a mobile terminal device, a PC (Personal Computer), or a TV (Television). The present invention can be applied to various devices.
　図１３は、実施例３に係る表示制御装置の構成を示すブロック図である。同図に示すように、実施例３に係る表示制御装置１０は、実施例１に係る表示制御装置１０における記憶部１２に代えて記憶部１２’を備えている。記憶部１２’は、ＤＮＵＭ１２１と、設定情報１２ｂとを記憶している。なお、設定情報１２ｂの具体的な内容については、後述する。 FIG. 13 is a block diagram illustrating the configuration of the display control apparatus according to the third embodiment. As shown in the figure, the display control apparatus 10 according to the third embodiment includes a storage unit 12 ′ instead of the storage unit 12 in the display control apparatus 10 according to the first embodiment. The storage unit 12 'stores a DNUM 121 and setting information 12b. The specific contents of the setting information 12b will be described later.
　ヒストグラム解析部１１ｄは、ヒストグラム生成部１１ｃによって生成されたヒストグラムをＤＮＵＭ１２１を用いて解析することによって、バックライトモジュール２２の確定発光量を決定する処理部である。ＤＮＵＭ１２１とは、上述したように累積画素数の閾値を示す情報である。 The histogram analysis unit 11d is a processing unit that determines the definite light emission amount of the backlight module 22 by analyzing the histogram generated by the histogram generation unit 11c using the DNUM 121. The DNUM 121 is information indicating a threshold value for the cumulative number of pixels as described above.
　ここで、ヒストグラム解析部１１ｄの動作例について図１４を用いて説明しておく。図１４は、ヒストグラム解析部１１ｄの動作例を示す図である。ここで、同図の（Ａ）には、ヒストグラムを用いた累積画素の計数処理の動作例を、同図の（Ｂ）には、目標発光量の決定処理の動作例を、それぞれ示している。 Here, an operation example of the histogram analysis unit 11d will be described with reference to FIG. FIG. 14 is a diagram illustrating an operation example of the histogram analysis unit 11d. Here, (A) in the figure shows an operation example of the cumulative pixel counting process using the histogram, and (B) in the figure shows an operation example of the target light emission amount determination process. .
　なお、同図の（Ａ）および（Ｂ）に示したように、画素の輝度値は、０～２５５までの値を取る。また、バックライトの発光量は、輝度値が０のときを０％、２５５のときを１００％として、０～１００％の値を取るように輝度値と予め対応付けられている。 In addition, as shown in (A) and (B) of the figure, the luminance value of the pixel takes a value from 0 to 255. Further, the light emission amount of the backlight is associated with the luminance value in advance so as to take a value of 0 to 100%, with 0% when the luminance value is 0 and 100% when the luminance value is 255.
　ヒストグラム解析部１１ｄは、ヒストグラム生成部１１ｃからヒストグラムを取得すると、まず、ヒストグラムの高輝度側から順に画素数を計数する計数処理を行う。具体的には、同図の（Ａ）に示したように、ヒストグラム解析部１１ｄは、ヒストグラムにおける輝度値「２５５」の位置を計数開始ポイントとし、各輝度値に対応する画素数を計数開始ポイントから低輝度側へ向かって順に計数していく。なお、ここでは、同図の（Ａ）に示したように、解析中の輝度値に対応する位置を「算出ポイント」と記載する。 When the histogram analysis unit 11d acquires the histogram from the histogram generation unit 11c, first, the histogram analysis unit 11d performs a counting process of counting the number of pixels in order from the high luminance side of the histogram. Specifically, as illustrated in (A) of FIG. 11, the histogram analysis unit 11 d uses 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 as the counting start point. Counts in order from the low brightness side. Here, as shown in FIG. 5A, the position corresponding to the luminance value being analyzed is referred to as “calculation point”.
　そして、ヒストグラム解析部１１ｄは、同図の（Ｂ）に示したように、計数した画素の累積数（以下、「累積画素数」と記載する）がＤＮＵＭ１２１に達した場合における算出ポイント（輝度値）に対応する発光量を目標発光量として決定する。 Then, as shown in (B) of FIG. 11, the histogram analysis unit 11 d calculates a calculation point (luminance value) when the accumulated number of counted pixels (hereinafter referred to as “accumulated pixel number”) reaches DNUM 121. ) Is determined as the target light emission amount.
　たとえば、ヒストグラム解析部１１ｄは、累積画素数がＤＮＵＭ１２１に達した位置の輝度値が「２００」である場合には、かかる輝度値「２００」に対応する発光量「７８％」を目標発光量として決定する。 For example, when the luminance value at the position where the cumulative number of pixels reaches DNUM 121 is “200”, the histogram analysis unit 11d sets the light emission amount “78%” corresponding to the luminance value “200” as the target light emission amount. decide.
　このように、ヒストグラム生成部１１ｃやヒストグラム解析部１１ｄは、入力された画像データの輝度分布に基づいてバックライトの目標発光量を決定する目標発光量決定手段の一例として機能する。 As described above, the histogram generation unit 11c and the histogram analysis unit 11d function as an example of target light emission amount determining means for determining the target light emission amount of the backlight based on the luminance distribution of the input image data.
　なお、ここでは、実施例３に係る表示制御装置１０が、実施例１に係るヒストグラム解析部１１ｄを備える場合について説明するが、これに限らず、実施例２に係るヒストグラム解析部１１ｄ’を備えることとしてもよい。 In addition, although the case where the display control apparatus 10 according to the third embodiment includes the histogram analysis unit 11d according to the first embodiment will be described here, the present invention is not limited thereto, and the histogram control unit 11d ′ according to the second embodiment is provided. It is good as well.
　図１３に戻り、発光量変更部１１ｅについて説明する。発光量変更部１１ｅは、ヒストグラム解析部１１ｄから取得した目標発光量と現在の発光量との差分に基づいてバックライトモジュール２２の発光量を決定する処理部である。ここで、発光量変更部１１ｅの構成について図１５を用いて説明する。図１５は、実施例３に係る発光量変更部１１ｅの構成を示すブロック図である。 Returning to FIG. 13, the light emission amount changing unit 11e will be described. The light emission amount changing unit 11e is a processing unit that determines the light emission amount of the backlight module 22 based on the difference between the target light emission amount acquired from the histogram analysis unit 11d and the current light emission amount. Here, the configuration of the light emission amount changing unit 11e will be described with reference to FIG. FIG. 15 is a block diagram illustrating a configuration of the light emission amount changing unit 11e according to the third embodiment.
　同図に示すように、発光量変更部１１ｅは、差分値算出部１１２ａと、変化量決定部１１２ｂと、発光量決定部１１２ｃと、変換係数決定部１１２ｄとを備えている。また、設定情報１２ｂは、発光量履歴情報１２３と、変化量設定情報１２４と、ＲＧＢ変換情報１２５とを記憶している。 As shown in the figure, the light emission amount change unit 11e includes a difference value calculation unit 112a, a change amount determination unit 112b, a light emission amount determination unit 112c, and a conversion coefficient determination unit 112d. The setting information 12b stores light emission amount history information 123, change amount setting information 124, and RGB conversion information 125.
　ここで、設定情報１２ｂについて説明しておく。発光量履歴情報１２３は、発光量決定部１１２ｃによって決定されたバックライトモジュール２２の発光量の履歴情報である。かかる発光量履歴情報１２３には、バックライトモジュール２２の現在の発光量も履歴情報として含まれている。また、変化量設定情報１２４は、バックライトモジュール２２の発光量の変化量を決定する際に用いられる情報である。かかる発光量履歴情報１２３については、図１６を用いて後述する。 Here, the setting information 12b will be described. The light emission amount history information 123 is history information of the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c. The light emission amount history information 123 includes the current light emission amount of the backlight module 22 as history information. The change amount setting information 124 is information used when determining the change amount of the light emission amount of the backlight module 22. The light emission amount history information 123 will be described later with reference to FIG.
　また、ＲＧＢ変換情報１２５は、発光量決定部１１２ｃによって決定されるバックライトモジュール２２の発光量ごとに、「ＲＧＢ変換係数」を対応付けた情報である。「ＲＧＢ変換係数」とは、Ｒ，Ｇ，Ｂの各成分の値（ＲＧＢ値）に対して掛け合わせる係数である。ここで、ＲＧＢ変換情報１２５は、発光量決定部１１２ｃによって決定されるバックライトモジュール２２の発光量が少ないほど、すなわち、画面が暗くなるほど、ＲＧＢ変換係数が高くなるように設定されている。 The RGB conversion information 125 is information in which “RGB conversion coefficient” is associated with each light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c. The “RGB conversion coefficient” is a coefficient that is multiplied with the values (RGB values) of R, G, and B components. Here, the RGB conversion information 125 is set so that the RGB conversion coefficient increases as the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c decreases, that is, as the screen becomes darker.
　差分値算出部１１２ａは、ヒストグラム解析部１１ｄから取得した目標発光量と現在の発光量との差分値を算出する処理部である。具体的には、差分値算出部１１２ａは、ヒストグラム解析部１１ｄから目標発光量を取得すると、発光量履歴情報１２３に含まれる現在の発光量を取り出し、目標発光量から現在の発光量を減算した値の絶対値を差分値とする。 The difference value calculation unit 112a is a processing unit that calculates a difference value between the target light emission amount acquired from the histogram analysis unit 11d and the current light emission amount. Specifically, when obtaining the target light emission amount from the histogram analysis unit 11d, the difference value calculation unit 112a extracts the current light emission amount included in the light emission amount history information 123 and subtracts the current light emission amount from the target light emission amount. The absolute value is the difference value.
　また、差分値算出部１１２ａは、目標発光量から現在の発光量を減算した値が正の値であるか負の値であるか示す情報、すなわち、現在の発光量を増加させるべきか減少させるべきかを示す情報を、算出した差分値とともに変化量決定部１１２ｂへ渡す処理も併せて行う。 Further, the difference value calculation unit 112a is information indicating whether the value obtained by subtracting the current light emission amount from the target light emission amount is a positive value or a negative value, that is, the current light emission amount should be increased or decreased. A process of passing information indicating whether or not to be performed to the change amount determination unit 112b together with the calculated difference value is also performed.
　変化量決定部１１２ｂは、差分値算出部１１２ａから取得した差分値に応じて現在の発光量からの変化量を決定する処理部である。具体的には、変化量決定部１１２ｂは、複数の閾値によって区切られる範囲のうち、差分値算出部１１２ａから取得した差分値が属する範囲に対応付けられた変化量を変化量設定情報１２４を用いて特定し、特定した変化量を現在の発光量からの変化量として決定する。 The change amount determination unit 112b is a processing unit that determines a change amount from the current light emission amount according to the difference value acquired from the difference value calculation unit 112a. Specifically, the change amount determination unit 112b uses the change amount setting information 124 for the change amount associated with the range to which the difference value acquired from the difference value calculation unit 112a belongs among the ranges divided by a plurality of threshold values. The determined change amount is determined as a change amount from the current light emission amount.
　ここで、変化量設定情報１２４の内容について図１６を用いて説明する。図１６は、変化量設定情報１２４の一例を示す図である。 Here, the content of the change amount setting information 124 will be described with reference to FIG. FIG. 16 is a diagram illustrating an example of the change amount setting information 124.
　同図に示すように、変化量設定情報１２４は、大きさの異なる複数の閾値（閾値Ｌ１および閾値Ｌ２）によって区切られる範囲ごとに変化量を対応付けた情報である。具体的には、変化量設定情報１２４は、閾値Ｌ１および閾値Ｌ２によって区切られる「範囲」ごとに、「変化量（増加時）」および「変化量（減少時）」を対応付けた情報である。 As shown in the figure, the change amount setting information 124 is information in which a change amount is associated with each range divided by a plurality of threshold values (threshold value L1 and threshold value L2) having different sizes. Specifically, the change amount setting information 124 is information in which “change amount (increase)” and “change amount (decrease)” are associated with each “range” delimited by the threshold L1 and the threshold L2. .
　ここで、「範囲」は、範囲「Ａ１」～「Ａ３」を含んでいる。具体的には、範囲「Ａ１」は「閾値Ｌ１≦差分値」である範囲を示し、範囲「Ａ２」は「閾値Ｌ２≦差分値＜閾値Ｌ１」である範囲を示し、範囲「Ａ３」は「差分値＜閾値Ｌ２」である範囲を示している。なお、同図に示したように、閾値Ｌ１は閾値Ｌ２よりも大きいものとする。 Here, “range” includes ranges “A1” to “A3”. Specifically, the range “A1” indicates a range where “threshold L1 ≦ difference value”, the range “A2” indicates a range where “threshold L2 ≦ difference value <threshold L1”, and the range “A3” indicates “ A range where difference value <threshold value L2 ”is shown. As shown in the figure, the threshold value L1 is assumed to be larger than the threshold value L2.
　また、「変化量（増加時）」は、バックライトモジュール２２の発光量を増加させる場合に適用される変化量を示す情報である。同図では、範囲「Ａ１」と対応付けて「HI_1」が記憶され、範囲「Ａ２」と対応付けて「MID_1」が記憶され、範囲「Ａ３」と対応付けて「LOW_1」が記憶されている。ここで、変化量（増加時）は、「HI_1」，「MID_1」，「LOW_1」のうち、「HI_1」が最も大きく、「LOW_1」が最も小さいものとする。また、変化量「HI_1」は、液晶ディスプレイ２０に画面のちらつきが生じない程度の変化量であるものとする。 Also, “change amount (when increased)” is information indicating a change amount applied when the light emission amount of the backlight module 22 is increased. In the figure, “HI_1” is stored in association with the range “A1”, “MID_1” is stored in association with the range “A2”, and “LOW_1” is stored in association with the range “A3”. . Here, it is assumed that the amount of change (at the time of increase) is “HI_1” is the largest and “LOW_1” is the smallest among “HI_1”, “MID_1”, and “LOW_1”. Further, it is assumed that the change amount “HI — 1” is a change amount that does not cause screen flicker in the liquid crystal display 20.
　また、「変化量（減少時）」とは、バックライトモジュール２２の発光量を減少させる場合に用いられる変化量を示す情報である。同図では、範囲「Ａ１」と対応付けて「HI_2」が記憶され、範囲「Ａ２」と対応付けて「MID_2」が記憶され、範囲「Ａ３」と対応付けて「LOW_2」が記憶されている。ここで、変化量（減少時）は、「HI_2」，「MID_2」，「LOW_2」のうち、「HI_2」が最も大きく、「LOW_2」が最も小さいものとする。また、変化量（減少時）の「HI_2」は、変化量（増加時）の「HI_1」よりも大きい値であるものとする。 Also, “change amount (at the time of decrease)” is information indicating the change amount used when the light emission amount of the backlight module 22 is reduced. In the figure, “HI_2” is stored in association with the range “A1”, “MID_2” is stored in association with the range “A2”, and “LOW_2” is stored in association with the range “A3”. . Here, it is assumed that the amount of change (at the time of decrease) is “HI_2” is the largest and “LOW_2” is the smallest among “HI_2”, “MID_2”, and “LOW_2”. Further, it is assumed that “HI_2” of the amount of change (when decreasing) is larger than “HI_1” of the amount of change (when increasing).
　このように、変化量設定情報１２４は、複数の閾値によって区切られる範囲のうち、より値の大きい閾値によって区切られる範囲ほど大きい変化量を対応付けている。また、変化量設定情報１２４は、目標発光量が現在の発光量よりも多い場合に用いられる第１の変化量設定情報と、目標発光量が現在の発光量よりも少ない場合に用いられる第２の変化量設定情報とを含んでいる。 As described above, the change amount setting information 124 associates a larger change amount with a range delimited by a threshold having a larger value among ranges delimited by a plurality of threshold values. The change amount setting information 124 is first change amount setting information used when the target light emission amount is larger than the current light emission amount, and second change information used when the target light emission amount is smaller than the current light emission amount. Change amount setting information.
　変化量決定部１１２ｂは、かかる変化量設定情報１２４を参照することによって、差分値算出部１１２ａから取得した差分値が属する範囲に対応する変化量をバックライトモジュール２２の変化量として決定する。また、変化量決定部１１２ｂは、決定した変化量と、現在の発光量を増加させるべきか減少させるべきかを示す情報とを発光量決定部１１２ｃへ渡す処理も併せて行う。 The change amount determination unit 112b determines the change amount corresponding to the range to which the difference value acquired from the difference value calculation unit 112a belongs as the change amount of the backlight module 22 by referring to the change amount setting information 124. Further, the change amount determination unit 112b also performs a process of passing the determined change amount and information indicating whether the current light emission amount should be increased or decreased to the light emission amount determination unit 112c.
　このように、差分値算出部１１２ａや変化量決定部１１２ｂは、目標発光量決定手段によって決定された目標発光量とバックライトの現在の発光量との差分値に応じて現在の発光量からの変化量を決定する変化量決定手段の一例として機能する。 As described above, the difference value calculation unit 112a and the change amount determination unit 112b are based on the difference value between the target light emission amount determined by the target light emission amount determination unit and the current light emission amount of the backlight. It functions as an example of a change amount determining means for determining a change amount.
　発光量決定部１１２ｃは、変化量決定部１１２ｂによって決定された変化量だけ現在の発光量を変化させた発光量をバックライトモジュール２２の発光量として決定する処理部である。具体的には、発光量決定部１１２ｃは、発光量履歴情報１２３から現在の発光量を取り出し、取り出した現在の発光量を変化量決定部１１２ｂから取得した変化量だけ変化させる処理を行う。 The light emission amount determination unit 112c is a processing unit that determines the light emission amount obtained by changing the current light emission amount by the change amount determined by the change amount determination unit 112b as the light emission amount of the backlight module 22. Specifically, the light emission amount determination unit 112c performs a process of taking out the current light emission amount from the light emission amount history information 123 and changing the extracted current light emission amount by the change amount acquired from the change amount determination unit 112b.
　より具体的には、発光量決定部１１２ｃは、現在の発光量を増加させるべき旨の情報を変化量決定部１１２ｂから取得した場合には、発光量履歴情報１２３から取り出した現在の発光量に対して変化量決定部１１２ｂから取得した変化量を加算した値をバックライトモジュール２２の発光量として決定する。また、発光量決定部１１２ｃは、現在の発光量を減少させるべき旨を示す情報を変化量決定部１１２ｂから取得した場合には、発光量履歴情報１２３から取り出した現在の発光量に対して変化量決定部１１２ｂから取得した変化量を減算した値をバックライトモジュール２２の発光量として決定する。 More specifically, when the information indicating that the current light emission amount should be increased is acquired from the change amount determination unit 112b, the light emission amount determination unit 112c uses the current light emission amount extracted from the light emission amount history information 123. On the other hand, a value obtained by adding the change amounts acquired from the change amount determination unit 112b is determined as the light emission amount of the backlight module 22. In addition, when the information indicating that the current light emission amount should be reduced is acquired from the change amount determination unit 112b, the light emission amount determination unit 112c changes with respect to the current light emission amount extracted from the light emission amount history information 123. A value obtained by subtracting the change amount acquired from the amount determination unit 112b is determined as the light emission amount of the backlight module 22.
　また、発光量決定部１１２ｃは、バックライトモジュール２２の発光量を決定すると、決定した発光量をＰＷＭ生成部１１ｆおよび変換係数決定部１１２ｄへ渡す。また、発光量決定部１１２ｃは、バックライトモジュール２２の発光量を決定すると、決定した発光量を発光量履歴情報１２３へ記憶する処理も行う。 In addition, when the light emission amount determination unit 112c determines the light emission amount of the backlight module 22, the light emission amount determination unit 112c passes the determined light emission amount to the PWM generation unit 11f and the conversion coefficient determination unit 112d. In addition, when the light emission amount determination unit 112c determines the light emission amount of the backlight module 22, the light emission amount determination unit 112c also performs a process of storing the determined light emission amount in the light emission amount history information 123.
　ここで、変化量決定部１１２ｂおよび発光量決定部１１２ｃの動作例について図１７を用いて説明する。図１７は、変化量決定部１１２ｂおよび発光量決定部１１２ｃの動作例を示す図である。なお、同図の（Ａ）には、バックライトモジュール２２の発光量を増加させる場合の動作例を、同図の（Ｂ）には、バックライトモジュール２２の発光量を減少させる場合の動作例を、それぞれ示している。 Here, operation examples of the change amount determination unit 112b and the light emission amount determination unit 112c will be described with reference to FIG. FIG. 17 is a diagram illustrating an operation example of the change amount determination unit 112b and the light emission amount determination unit 112c. 2A shows an operation example when the light emission amount of the backlight module 22 is increased, and FIG. 2B shows an operation example when the light emission amount of the backlight module 22 is decreased. Respectively.
　また、同図の（Ａ）に示した目標発光量は、時刻ｔ０において更新されたフレーム（画像データ）のヒストグラムに基づく目標発光量であり、同図の（Ｂ）に示した目標発光量は、時刻ｔ４において更新されたフレームのヒストグラムに基づく目標発光量であるとする。 Further, the target light emission amount shown in (A) of the figure is a target light emission quantity based on the histogram of the frame (image data) updated at time t0, and the target light emission quantity shown in (B) of FIG. It is assumed that the target light emission amount is based on the histogram of the frame updated at time t4.
　同図の（Ａ）に示したように、時刻ｔ０において更新されたフレームに適用された発光量（現在の発光量）と目標発光量との差分値Ｄ１が、図１６に示した範囲「Ａ１」に属するとする。かかる場合、変化量決定部１１２ｂは、変化量設定情報１２４から範囲「Ａ１」に対応する変化量（増加時）「HI_1」を取り出し、取り出した変化量「HI_1」を発光量決定部１１２ｃへ渡す。 As shown in FIG. 16A, the difference value D1 between the light emission amount (current light emission amount) applied to the frame updated at time t0 and the target light emission amount is within the range “A1” shown in FIG. ". In this case, the change amount determination unit 112b extracts the change amount (in the increase) “HI_1” corresponding to the range “A1” from the change amount setting information 124, and passes the extracted change amount “HI_1” to the light emission amount determination unit 112c. .
　そして、発光量決定部１１２ｃは、変化量決定部１１２ｂから変化量「HI_1」を取得すると、発光量履歴情報１２３から現在の発光量を取り出し、取り出した現在の発光量に対して変化量「HI_1」を加算した値をバックライトモジュール２２として決定する。これによって、バックライトモジュール２２の発光量は、時刻ｔ１において変化量「HI_1」だけ増加することとなる。 When the light emission amount determination unit 112c acquires the change amount “HI_1” from the change amount determination unit 112b, the light emission amount determination unit 112c extracts the current light emission amount from the light emission amount history information 123, and the change amount “HI_1” with respect to the extracted current light emission amount. ] Is determined as the backlight module 22. As a result, the light emission amount of the backlight module 22 is increased by the change amount “HI_1” at the time t1.
　また、時刻ｔ１において更新されたフレームに適用された発光量（現在の発光量）と目標発光量との差分値Ｄ２が、図１６に示した範囲「Ａ２」に属するとする。かかる場合、変化量決定部１１２ｂは、変化量設定情報１２４から範囲「Ａ２」に対応する変化量（増加時）「MID_1」を取り出し、取り出した変化量「MID_1」を発光量決定部１１２ｃへ渡す。なお、上述したように、変化量「MID_1」は、変化量「HI_1」よりも小さい値である。 Further, it is assumed that the difference value D2 between the light emission amount (current light emission amount) applied to the frame updated at time t1 and the target light emission amount belongs to the range “A2” shown in FIG. In such a case, the change amount determining unit 112b extracts the change amount (when increasing) “MID_1” corresponding to the range “A2” from the change amount setting information 124, and passes the extracted change amount “MID_1” to the light emission amount determining unit 112c. . As described above, the change amount “MID_1” is a value smaller than the change amount “HI_1”.
　そして、発光量決定部１１２ｃは、変化量決定部１１２ｂから変化量「MID_1」を取得すると、発光量履歴情報１２３から現在の発光量を取り出し、取り出した現在の発光量に対して変化量「MID_1」を加算した値をバックライトモジュール２２として決定する。これによって、バックライトモジュール２２の発光量は、時刻ｔ２において変化量「MID_1」だけ増加することとなる。 When the light emission amount determination unit 112c acquires the change amount “MID_1” from the change amount determination unit 112b, the light emission amount determination unit 112c extracts the current light emission amount from the light emission amount history information 123, and the change amount “MID_1” with respect to the extracted current light emission amount. ] Is determined as the backlight module 22. As a result, the light emission amount of the backlight module 22 is increased by the change amount “MID_1” at the time t2.
　また、時刻ｔ２において更新されたフレームに適用された発光量（現在の発光量）と目標発光量との差分値Ｄ３が、図１６に示した範囲「Ａ３」に属するとする。かかる場合、変化量決定部１１２ｂは、変化量設定情報１２４から範囲「Ａ３」に対応する変化量（増加時）「LOW_1」を取り出し、取り出した変化量「LOW_1」を発光量決定部１１２ｃへ渡す。なお、上述したように、変化量「LOW_1」は、変化量「MID_1」よりも小さい値である。 Further, it is assumed that the difference value D3 between the light emission amount (current light emission amount) applied to the frame updated at time t2 and the target light emission amount belongs to the range “A3” shown in FIG. In such a case, the change amount determination unit 112b extracts the change amount (when increasing) “LOW_1” corresponding to the range “A3” from the change amount setting information 124, and passes the extracted change amount “LOW_1” to the light emission amount determination unit 112c. . As described above, the change amount “LOW_1” is smaller than the change amount “MID_1”.
　そして、発光量決定部１１２ｃは、変化量決定部１１２ｂから変化量「LOW_1」を取得すると、発光量履歴情報１２３から現在の発光量を取り出し、取り出した現在の発光量に対して変化量「LOW_1」を加算した値をバックライトモジュール２２として決定する。これによって、バックライトモジュール２２の発光量は、時刻ｔ３において変化量「LOW_1」だけ増加することとなる。 When the light emission amount determination unit 112c acquires the change amount “LOW_1” from the change amount determination unit 112b, the light emission amount determination unit 112c extracts the current light emission amount from the light emission amount history information 123, and the change amount “LOW_1” with respect to the extracted current light emission amount. ] Is determined as the backlight module 22. As a result, the light emission amount of the backlight module 22 is increased by the change amount “LOW_1” at time t3.
　このように、実施例３では、バックライトモジュール２２の発光量を目標発光量と一致させる場合に、バックライトモジュール２２の発光量を１フレームで急激に変化させるのではなく、複数フレームかけて段階的に変化させることによって目標発光量と一致させることとした。したがって、バックライトモジュール２２の発光量の急激な変化を抑えることができ、この結果、画面のちらつきを防止することができる。 As described above, in the third embodiment, when the light emission amount of the backlight module 22 is matched with the target light emission amount, the light emission amount of the backlight module 22 is not changed suddenly in one frame, but is stepped over a plurality of frames. It was decided to make it correspond with the target light emission amount by changing it periodically. Therefore, a rapid change in the light emission amount of the backlight module 22 can be suppressed, and as a result, flickering of the screen can be prevented.
　しかも、実施例３では、現在の発光量と目標発光量との差分値が大きい場合には、画面のちらつきが発生しない程度の変化量で現在の発光量を大きく変化させる一方、差分値が小さくなるにつれて変化量も少なくしていくことによって現在の発光量を目標発光量へなだらかに収束させることとした。これによって、バックライトモジュール２２の発光量を極力早く目標発光量に近づけることができるため、バックライトモジュール２２の発光量と目標発光量との差が大きい場合に生じやすい色つぶれを防ぐことができる。 In addition, in Example 3, when the difference value between the current light emission amount and the target light emission amount is large, the current light emission amount is largely changed by a change amount that does not cause flickering of the screen, while the difference value is small. As the amount of change gradually decreases, the current light emission amount is gradually converged to the target light emission amount. As a result, the light emission amount of the backlight module 22 can be brought close to the target light emission amount as soon as possible, so that color collapse that is likely to occur when the difference between the light emission amount of the backlight module 22 and the target light emission amount is large can be prevented. .
　一方、同図の（Ｂ）に示したように、時刻ｔ４において更新されたフレームに適用された発光量（現在の発光量）と目標発光量との差分値Ｄ４が、図１６に示した範囲「Ａ１」に属するとする。かかる場合、変化量決定部１１２ｂは、変化量設定情報１２４から範囲「Ａ１」に対応する変化量（減少時）「HI_2」を取り出し、取り出した変化量「HI_2」を発光量決定部１１２ｃへ渡す。 On the other hand, as shown in FIG. 16B, the difference value D4 between the light emission amount (current light emission amount) applied to the frame updated at time t4 and the target light emission amount is within the range shown in FIG. It belongs to “A1”. In such a case, the change amount determination unit 112b extracts the change amount (when reduced) “HI_2” corresponding to the range “A1” from the change amount setting information 124, and passes the extracted change amount “HI_2” to the light emission amount determination unit 112c. .
　そして、発光量決定部１１２ｃは、変化量決定部１１２ｂから変化量「HI_2」を取得すると、発光量履歴情報１２３から現在の発光量を取り出し、取り出した現在の発光量に対して変化量「HI_2」を減算した値をバックライトモジュール２２として決定する。これによって、バックライトモジュール２２の発光量は、時刻ｔ５において変化量「HI_2」だけ減少することとなる。 Then, when the light emission amount determination unit 112c acquires the change amount “HI_2” from the change amount determination unit 112b, the light emission amount determination unit 112b extracts the current light emission amount from the light emission amount history information 123, and the change amount “HI_2” with respect to the extracted current light emission amount. The value obtained by subtracting “is determined as the backlight module 22. As a result, the light emission amount of the backlight module 22 is reduced by the change amount “HI_2” at time t5.
　ここで、実施例３では、上述したように、バックライトモジュール２２を減少させる場合に用いられる変化量「HI_2」は、バックライトモジュール２２を増加させる場合に用いられる変化量「HI_1」よりも大きな値としている。これは、画面が瞬間的に明るくなる場合よりも瞬間的に暗くなる場合の方が視認者によって認識され難いためである。 In the third embodiment, as described above, the amount of change “HI_2” used when the backlight module 22 is decreased is larger than the amount of change “HI_1” used when the backlight module 22 is increased. Value. This is because the viewer is less likely to recognize when the screen is darkened instantaneously than when the screen is brightened instantaneously.
　このように、バックライトモジュール２２の発光量を減少させる場合の最大発光量をバックライトモジュール２２の発光量を増加させる場合の最大発光量よりも大きくすることで、視認者に画面のちらつきを感じさせることなく、バックライトモジュール２２の発光量をより早く目標発光量へ近づけることができる。 In this way, by making the maximum light emission amount when the light emission amount of the backlight module 22 is decreased larger than the maximum light emission amount when the light emission amount of the backlight module 22 is increased, the viewer feels flickering on the screen. Without this, the light emission amount of the backlight module 22 can be brought closer to the target light emission amount more quickly.
　また、バックライトモジュール２２の発光量の最大減少量を多くすることによって、バックライトモジュール２２による消費電力の削減量が増えるため、省電力効果をより一層高めることができる。 Also, by increasing the maximum reduction amount of the light emission amount of the backlight module 22, the amount of power consumption reduction by the backlight module 22 increases, so that the power saving effect can be further enhanced.
　なお、時刻ｔ５において更新されたフレームに適用された発光量と目標発光量との差分値Ｄ５が、範囲「Ａ２」に属する場合には、バックライトモジュール２２の発光量は、時刻ｔ６において変化量「MID_2」だけ減少することとなる。また、時刻ｔ６において更新されたフレームに適用された発光量と目標発光量との差分値Ｄ６が、範囲「Ａ３」に属する場合には、バックライトモジュール２２の発光量は、時刻ｔ７において変化量「LOW_2」だけ減少することとなる。 When the difference value D5 between the light emission amount applied to the frame updated at time t5 and the target light emission amount belongs to the range “A2”, the light emission amount of the backlight module 22 changes at time t6. It will decrease by “MID_2”. When the difference value D6 between the light emission amount applied to the frame updated at time t6 and the target light emission amount belongs to the range “A3”, the light emission amount of the backlight module 22 changes at time t7. It will decrease by “LOW_2”.
　ところで、発光量履歴情報１２３として記憶される変化量の値は任意に設定可能である。たとえば、各変化量（たとえば、「HI_1」や「MID_1」など）を全体的に少なめに設定することによって、バックライトモジュール２２の発光量が目標発光量へ向かってなだらかに変化することとなる。このため、画面のちらつきの発生をより確実に防止することができる。 Incidentally, the value of the change amount stored as the light emission amount history information 123 can be arbitrarily set. For example, by setting each change amount (for example, “HI — 1”, “MID — 1”, etc.) to be a little smaller as a whole, the light emission amount of the backlight module 22 gradually changes toward the target light emission amount. For this reason, it is possible to more reliably prevent the occurrence of screen flicker.
　ただし、かかる場合には、実際の発光量が目標発光量に対してゆっくり追従していくこととなるため、ハレーションが発生しやすくなる。ここで、ハレーションとは、明るい画像が入力された場合に、少ない発光量でバックライトモジュール２２を発光させることによって画像中の特に明るい部分の色がつぶれたように見える現象を示す。 However, in such a case, since the actual light emission amount slowly follows the target light emission amount, halation is likely to occur. Here, halation refers to a phenomenon in which the color of a particularly bright portion in an image appears to be crushed by causing the backlight module 22 to emit light with a small amount of light emission when a bright image is input.
　一方、発光量履歴情報１２３として記憶される各変化量を全体的に多めに設定した場合には、実際の発光量が目標発光量に対して素早く追従するため、ハレーションの発生を防止することができる。しかし、かかる場合には、実際の発光量の変化量が多くなるため、画面のちらつきが発生しやすくなる。このような事情を考慮して、発光量履歴情報１２３として記憶される変化量の値を液晶ディスプレイ２０のデバイス特性等に応じた適切な値に設定することとすれば、ハレーションの発生と画面のちらつきの発生をバランスよく防止することが可能となる。 On the other hand, when each change amount stored as the light emission amount history information 123 is set to be a large amount as a whole, the actual light emission amount quickly follows the target light emission amount, thereby preventing the occurrence of halation. it can. However, in such a case, the amount of change in the actual light emission amount increases, and thus the screen flickers easily. Considering such circumstances, if the value of the change amount stored as the light emission amount history information 123 is set to an appropriate value according to the device characteristics of the liquid crystal display 20, the occurrence of halation and the screen It is possible to prevent the occurrence of flickering with a good balance.
　また、発光量履歴情報１２３として記憶される閾値Ｌ１および閾値Ｌ２の値も任意に設定可能である。また、閾値の設定数も同様に、任意に変更することができる。特に、閾値の数を０とした場合には、目標発光量を実際の発光量に対して即反映させることができる。 Also, the values of the threshold value L1 and the threshold value L2 stored as the light emission amount history information 123 can be arbitrarily set. Similarly, the set number of thresholds can be arbitrarily changed. In particular, when the number of thresholds is set to 0, the target light emission amount can be immediately reflected on the actual light emission amount.
　図１５に戻り、変換係数決定部１１２ｄについて説明する。変換係数決定部１１２ｄは、発光量決定部１１２ｃからバックライトモジュール２２の発光量を取得した場合に、取得した発光量に対応するＲＧＢ変換係数をＲＧＢ変換情報１２５を用いて決定する処理部である。また、変換係数決定部１１２ｄは、決定したＲＧＢ変換係数をＲＧＢ変換部１１ｇへ渡す処理も併せて行う。 Returning to FIG. 15, the conversion coefficient determination unit 112d will be described. The conversion coefficient determination unit 112d is a processing unit that determines the RGB conversion coefficient corresponding to the acquired light emission amount using the RGB conversion information 125 when the light emission amount of the backlight module 22 is acquired from the light emission amount determination unit 112c. . The conversion coefficient determination unit 112d also performs a process of passing the determined RGB conversion coefficient to the RGB conversion unit 11g.
　図１３に戻り、ＰＷＭ生成部１１ｆについて説明する。ＰＷＭ生成部１１ｆは、バックライトモジュール２２の発光量が発光量決定部１１２ｃから取得した発光量となるようにパルス幅が調整されたＰＷＭ信号を生成してバックライトモジュール２２へ出力する処理部である。なお、ＰＷＭ生成部１１ｆは、ＶＳＹＮＣ（Vertical Synchronizing signal：垂直同期信号）が１回出力されるごとに、デフォルトでは、ＰＷＭ信号を４回出力することとしている。ただし、ＶＳＹＮＣの単位出力当たりのＰＷＭ信号の出力回数は、レジスタにより適宜調整可能である。 Returning to FIG. 13, the PWM generator 11f will be described. The PWM generation unit 11f is a processing unit that generates a PWM signal whose pulse width is adjusted so that the light emission amount of the backlight module 22 becomes the light emission amount acquired from the light emission amount determination unit 112c, and outputs the PWM signal to the backlight module 22. is there. Note that the PWM generator 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.
　ＲＧＢ変換部１１ｇは、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値に対して、変換係数決定部１１２ｄから取得したＲＧＢ変換係数を掛け合わせるＲＧＢ変換処理を行う処理部である。また、ＲＧＢ変換部１１ｇは、ＲＧＢ変換処理後の画像データを液晶パネル２１へ出力する処理も併せて行う。 The RGB conversion unit 11g multiplies the R, G, B component values included in the image data acquired from the image data acquisition unit 11a by the RGB conversion coefficient acquired from the conversion coefficient determination unit 112d. 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.
　たとえば、ＲＧＢ変換部１１ｇは、ＲＧＢ変換係数「１．２６」を取得した場合、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値を１．２６倍する。そして、ＲＧＢ変換部１１ｇは、Ｒ，Ｇ，Ｂの各成分の値を１．２６倍した画像データを液晶パネル２１へ出力する。 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.
　なお、上述したように、ＲＧＢ変換情報１２５は、発光量決定部１１２ｃによって決定されるバックライトモジュール２２の発光量が少ないほど、ＲＧＢ変換係数が高くなるように設定されている。したがって、ＲＧＢ変換部１１ｇは、バックライトモジュール２２の発光量が少ないほどＲＧＢ値を大きく補正することとなる。このように、実施例３では、バックライトモジュール２２の発光量を少なくする場合であっても、ＲＧＢ変換部１１ｇによってＲＧＢ値を高める補正を行うことで、見た目の明るさを一定に保ち、画質劣化を防止することとしている。 Note that, as described above, the RGB conversion information 125 is set such that the RGB conversion coefficient increases as the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c decreases. Therefore, the RGB conversion unit 11g corrects the RGB value to be larger as the light emission amount of the backlight module 22 is smaller. As described above, in the third embodiment, even when the light emission amount of the backlight module 22 is reduced, the RGB brightness is increased by the RGB conversion unit 11g, so that the apparent brightness is kept constant and the image quality is improved. Deterioration is to be prevented.
　次に、実施例３に係る表示制御装置１０の具体的動作について図１８を用いて説明する。図１８は、実施例３に係る表示制御装置１０が実行する処理手順を示すフローチャートである。ここで、同図には、バックライトモジュール２２の発光量を増加させる場合における表示制御装置１０の処理手順を示している。なお、表示制御装置１０の変化量決定部１１２ｂは、上述したように、バックライトモジュール２２の発光量を増加させるかあるいは減少させるかを差分値算出部１１２ａからの情報に基づいて判定する。 Next, a specific operation of the display control apparatus 10 according to the third embodiment will be described with reference to FIG. FIG. 18 is a flowchart illustrating a processing procedure executed by the display control apparatus 10 according to the third embodiment. Here, the figure shows a processing procedure of the display control apparatus 10 when the light emission amount of the backlight module 22 is increased. Note that, as described above, the change amount determination unit 112b of the display control apparatus 10 determines whether to increase or decrease the light emission amount of the backlight module 22 based on information from the difference value calculation unit 112a.
　同図に示すように、表示制御装置１０では、サブサンプリング部１１ｂが、画像データ取得部１１ａによって取得された画像データに対してサブサンプリングを行う（ステップＳ３０１）。つづいて、表示制御装置１０では、ヒストグラム生成部１１ｃが、サブサンプリング後の画像データを用いてヒストグラムを生成し（ステップＳ３０２）、ヒストグラム解析部１１ｄが、ヒストグラムおよびＤＮＵＭ１２１を用いて目標発光量を決定する（ステップＳ３０３）。 As shown in the figure, in the display control device 10, the sub-sampling unit 11b performs sub-sampling on the image data acquired by the image data acquisition unit 11a (step S301). Subsequently, in the display control device 10, the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S302), and the histogram analysis unit 11d determines the target light emission amount using the histogram and DNUM 121. (Step S303).
　つづいて、表示制御装置１０では、差分値算出部１１２ａが、目標発光量と現在の発光量との差分値を算出し（ステップＳ３０４）、変化量決定部１１２ｂが、算出した差分値が範囲「Ａ１」に属するか否かを判定する（ステップＳ３０５）。そして、差分値が範囲「Ａ１」に属すると判定した場合には（ステップＳ３０５、Ｙｅｓ）、変化量決定部１１２ｂは、変化量設定情報１２４を参照して変化量「HI_1」を選択する（ステップＳ３０６）。 Subsequently, in the display control apparatus 10, the difference value calculation unit 112a calculates a difference value between the target light emission amount and the current light emission amount (step S304), and the change amount determination unit 112b has the calculated difference value in the range “ It is determined whether it belongs to “A1” (step S305). If it is determined that the difference value belongs to the range “A1” (step S305, Yes), the change amount determination unit 112b selects the change amount “HI_1” with reference to the change amount setting information 124 (step S305). S306).
　一方、差分値算出部１１２ａによって算出した差分値が範囲「Ａ１」に属さない場合（ステップＳ３０５、Ｎｏ）、変化量決定部１１２ｂは、算出した差分値が範囲「Ａ２」に属するか否かを判定する（ステップＳ３０７）。そして、差分値が範囲「Ａ２」に属すると判定した場合には（ステップＳ３０７、Ｙｅｓ）、変化量決定部１１２ｂは、変化量設定情報１２４を参照して変化量「MID_1」を選択する（ステップＳ３０８）。 On the other hand, when the difference value calculated by the difference value calculation unit 112a does not belong to the range “A1” (step S305, No), the change amount determination unit 112b determines whether or not the calculated difference value belongs to the range “A2”. Determination is made (step S307). When it is determined that the difference value belongs to the range “A2” (step S307, Yes), the change amount determination unit 112b selects the change amount “MID_1” with reference to the change amount setting information 124 (step S307). S308).
　一方、差分値算出部１１２ａによって算出した差分値が範囲「Ａ２」に属さない場合（ステップＳ３０７、Ｎｏ）、変化量決定部１１２ｂは、変化量設定情報１２４を参照して変化量「LOW_1」を選択する（ステップＳ３０９）。 On the other hand, when the difference value calculated by the difference value calculation unit 112a does not belong to the range “A2” (No in Step S307), the change amount determination unit 112b refers to the change amount setting information 124 and sets the change amount “LOW_1”. Select (step S309).
　つづいて、発光量決定部１１２ｃは、発光量履歴情報１２３から取り出した現在の発光量に対して、ステップＳ３０６，３０８，３０９の何れかにおいて選択された変化量を加算した値をバックライトモジュール２２の発光量として決定する（ステップＳ３１０）。また、発光量決定部１１２ｃは、決定した発光量を発光量履歴情報１２３へ記憶する（ステップＳ３１１）。 Subsequently, the light emission amount determination unit 112c adds a value obtained by adding the amount of change selected in any of steps S306, 308, and 309 to the current light emission amount extracted from the light emission amount history information 123. Is determined (step S310). Further, the light emission amount determination unit 112c stores the determined light emission amount in the light emission amount history information 123 (step S311).
　つづいて、ＰＷＭ生成部１１ｆは、変更後発光量に応じたＰＷＭ信号を生成してバックライトモジュール２２へ出力する（ステップＳ３１２）。つづいて、ＲＧＢ変換部１１ｇは、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値に対して、変更後発光量に対応するＲＧＢ変換係数を掛け合わせるＲＧＢ変換処理を行う（ステップＳ３１３）。そして、表示制御装置１０では、ＲＧＢ変換部１１ｇは、ＲＧＢ変換処理後の画像データを液晶パネル２１へ出力して（ステップＳ３１４）、処理を終了する。 Subsequently, the PWM generation unit 11f generates a PWM signal corresponding to the changed light emission amount and outputs the PWM signal to the backlight module 22 (step S312). Subsequently, the RGB converter 11g multiplies 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 corresponding to the changed light emission amount. Processing is performed (step S313). Then, in the display control device 10, the RGB conversion unit 11g outputs the image data after the RGB conversion processing to the liquid crystal panel 21 (step S314), and ends the processing.
　上述してきたように、実施例３では、ヒストグラム解析部が、入力された画像データの輝度値に基づいて前記バックライトの目標発光量を決定し、変化量決定部が、決定された目標発光量とバックライトの現在の発光量との差分値に応じて現在の発光量からの変化量を決定し、発光量決定部が、決定された変化量だけ現在の発光量を変化させた発光量をバックライトの発光量として決定することとした。したがって、実施例３によれば、バックライトによる消費電力を抑えつつ、画像の明るさが頻繁に変化した場合に生じる画面のちらつきを低減することができる。 As described above, in the third embodiment, the histogram analysis unit determines the target light emission amount of the backlight based on the luminance value of the input image data, and the change amount determination unit determines the determined target light emission amount. The amount of change from the current light emission amount is determined according to the difference value between the current light emission amount of the backlight and the backlight, and the light emission amount determination unit changes the current light emission amount by the determined change amount. The amount of light emitted from the backlight was determined. Therefore, according to the third embodiment, it is possible to reduce screen flicker that occurs when the brightness of an image frequently changes while suppressing power consumption by the backlight.
　ところで、上述してきた実施例では、バックライトモジュール２２の発光量と目標発光量と差がわずかな場合であっても、バックライトモジュール２２の発光量を変化させることとした。しかしながら、液晶ディスプレイ２０の性能によっては、バックライトモジュール２２の発光量をわずかに変化させただけでも画面にちらつきが生じる場合がある。 By the way, in the embodiment described above, the light emission amount of the backlight module 22 is changed even when the difference between the light emission amount of the backlight module 22 and the target light emission amount is small. However, depending on the performance of the liquid crystal display 20, the screen may flicker even if the light emission amount of the backlight module 22 is slightly changed.
　そこで、バックライトモジュール２２の発光量と目標発光量との差分値が所定値を下回る場合には、バックライトモジュール２２の発光量を変化させないこととしてもよい。以下では、かかる場合について図１９を用いて説明する。図１９は、変化量決定部１１２ｂの他の動作例を示す図である。なお、同図の（Ａ）には、変化量設定情報１２４の他の一例を、同図の（Ｂ）には、バックライトモジュール２２の発光量を増加させる場合の他の動作例を、それぞれ示している。 Therefore, when the difference value between the light emission amount of the backlight module 22 and the target light emission amount is below a predetermined value, the light emission amount of the backlight module 22 may not be changed. Hereinafter, such a case will be described with reference to FIG. FIG. 19 is a diagram illustrating another operation example of the change amount determination unit 112b. Note that (A) in the figure shows another example of the change amount setting information 124, and (B) in the figure shows another example of operation when the light emission amount of the backlight module 22 is increased. Show.
　同図の（Ａ）に示したように、変化量設定情報１２４には、範囲「Ａ３」に対して変化量（増加時）および変化量（減少時）ともに「０」が対応付けられている（同図の（Ａ－1）参照）。 As shown in FIG. 6A, in the change amount setting information 124, “0” is associated with both the change amount (when increasing) and the change amount (when decreasing) with respect to the range “A3”. (See (A-1) in the figure).
　同図の（Ｂ）に示したように、変化量決定部１１２ｂは、時刻ｔ２における差分値が範囲「Ａ３」に属する場合、すなわち、時刻ｔ２における差分値が閾値Ｌ２を下回る場合には、変化量設定情報１２４を参照して変化量「０」を選択して発光量決定部１１２ｃへ渡す。 As shown in FIG. 5B, the change determining unit 112b changes when the difference value at the time t2 belongs to the range “A3”, that is, when the difference value at the time t2 falls below the threshold value L2. The amount of change “0” is selected with reference to the amount setting information 124 and passed to the light emission amount determination unit 112c.
　そして、発光量決定部１１２ｃは、変化量決定部１１２ｂから取得した変化量が「０」であるため、発光量履歴情報１２３から取り出した現在の発光量をバックライトモジュール２２の発光量として決定する。これによって、バックライトモジュール２２の発光量は、目標発光量との間に差があるにもかかわらず変化しないこととなる。 Then, since the change amount acquired from the change amount determination unit 112b is “0”, the light emission amount determination unit 112c determines the current light emission amount extracted from the light emission amount history information 123 as the light emission amount of the backlight module 22. . As a result, the light emission amount of the backlight module 22 does not change despite a difference from the target light emission amount.
　このように、バックライトモジュール２２の発光量と目標発光量との差分値が所定値を下回る場合に、バックライトモジュール２２の現在の発光量からの変化量を０とすることによって、バックライトモジュール２２の発光量のわずかな変化によって生じる画面のちらつきを防止することができる。 As described above, when the difference value between the light emission amount of the backlight module 22 and the target light emission amount is lower than the predetermined value, the amount of change from the current light emission amount of the backlight module 22 is set to 0, thereby the backlight module. The flickering of the screen caused by a slight change in the light emission amount 22 can be prevented.
　なお、ここでは、閾値Ｌ２を所定値として説明したが、これに限ったものではなく、閾値Ｌ２よりも小さい値を所定値として別途設けることとしてもよい。 Although the threshold value L2 has been described as a predetermined value here, the present invention is not limited to this, and a value smaller than the threshold value L2 may be separately provided as the predetermined value.
　ところで、点滅シーンのように暗い画像と明るい画像とが交互に繰り返される場合に、上述してきた実施例のように、バックライトモジュール２２の発光量を逐一変更していたのでは、制御部１１や液晶ディスプレイ２０に対して大きな処理負荷がかかることとなる。 By the way, when the dark image and the bright image are alternately repeated as in the blinking scene, the light emission amount of the backlight module 22 is changed one by one as in the above-described embodiment. A large processing load is applied to the liquid crystal display 20.
　そこで、暗い画像と明るい画像とが交互に繰り返される場合には、現在の発光量からの変化量を少なくするまたは０とすることとしてもよい。具体的には、変化量決定部１１２ｂは、発光量履歴情報１２３として記憶されたバックライトモジュール２２の発光量履歴に基づき、画面が点滅していることを判定する。そして、変化量決定部１１２ｂは、画面が点滅していると判定した場合に、変化量設定情報１２４から取り出した変化量に対して所定の係数を乗じることによってかかる変化量を少なくする（または０とする）。 Therefore, when a dark image and a bright image are alternately repeated, the amount of change from the current light emission amount may be reduced or set to zero. Specifically, the change amount determination unit 112 b determines that the screen is blinking based on the light emission amount history of the backlight module 22 stored as the light emission amount history information 123. When the change amount determination unit 112b determines that the screen is blinking, the change amount is reduced by multiplying the change amount extracted from the change amount setting information 124 by a predetermined coefficient (or 0). And).
　以下では、かかる場合について図２０を用いて説明する。図２０は、変化量決定部１１２ｂの他の動作例を示す図である。なお、同図の（Ａ）には、明るい画像と暗い画像とが交互に繰り返される様子を示し、同図の（Ｂ）には、バックライトモジュール２２の発光量の履歴を示し、同図の（Ｃ）には、変化量決定部１１２ｂによって決定されるバックライトモジュール２２の発光量の変化量を示している。 Hereinafter, such a case will be described with reference to FIG. FIG. 20 is a diagram illustrating another operation example of the change amount determination unit 112b. In addition, (A) in the figure shows a state in which a bright image and a dark image are alternately repeated, and (B) in the figure shows a history of the light emission amount of the backlight module 22. (C) shows a change amount of the light emission amount of the backlight module 22 determined by the change amount determination unit 112b.
　同図の（Ａ）に示したように、明るいフレームＦ１，Ｆ３と暗いフレームＦ２，Ｆ４とが、Ｆ１→Ｆ２→Ｆ３→Ｆ４の順で表示されたとする。かかる場合、発光量決定部１１２ｃは、各フレームＦ１～Ｆ４のそれぞれにおいてバックライトモジュール２２の発光量を決定すると、決定した各発光量を発光量履歴情報１２３としてその都度記憶部１２’に記憶していく。 Suppose that bright frames F1 and F3 and dark frames F2 and F4 are displayed in the order of F1, F2, F3, and F4 as shown in FIG. In such a case, when the light emission amount determination unit 112c determines the light emission amount of the backlight module 22 in each of the frames F1 to F4, each determined light emission amount is stored in the storage unit 12 ′ as the light emission amount history information 123 each time. To go.
　これによって、同図の（Ｂ）に示したように、記憶部１２’には、フレームＦ１において決定された発光量「Ｅ１」、フレームＦ２において決定された発光量「Ｅ２」、フレームＦ３において決定された発光量「Ｅ３」およびフレームＦ４において決定された発光量「Ｅ４」が発光量履歴情報１２３として記憶される。 As a result, as shown in FIG. 6B, the storage unit 12 ′ stores the light emission amount “E1” determined in the frame F1, the light emission amount “E2” determined in the frame F2, and the frame F3. The emitted light amount “E3” and the light amount “E4” determined in the frame F4 are stored as the light amount history information 123.
　そして、変化量設定情報１２４は、これらバックライトモジュール２２の発光量履歴に基づいて画面が点滅していることを判定する。具体的には、変化量決定部１１２ｂは、隣接するフレーム間の発光量の差分値が全て所定値以上である場合に、画面が点滅していると判定する。 Then, the change amount setting information 124 determines that the screen is blinking based on the light emission amount history of the backlight module 22. Specifically, the change amount determination unit 112b determines that the screen is blinking when all the difference values of the light emission amounts between adjacent frames are equal to or greater than a predetermined value.
　すなわち、フレームＦ１およびフレームＦ２間の発光量の差分値「Ｅ１－Ｅ２」（絶対値）、フレームＦ２およびフレームＦ３間の発光量の差分値「Ｅ２－Ｅ３」（絶対値）、フレームＦ３およびフレームＦ４間の発光量の差分値「Ｅ３－Ｅ４」（絶対値）が全て所定値以上である場合、変化量決定部１１２ｂは、画面が点滅していると判定する。 That is, the difference value “E1-E2” (absolute value) of the light emission amount between the frames F1 and F2, the difference value “E2-E3” (absolute value) of the light emission amount between the frames F2 and F3, the frame F3 and the frame When the difference values “E3-E4” (absolute values) of the light emission amounts between F4 are all equal to or greater than the predetermined value, the change amount determination unit 112b determines that the screen is blinking.
　そして、同図の（Ｃ）に示したように、変化量決定部１１２ｂは、画面が点滅していると判定すると、変化量設定情報１２４から取り出した変化量に対して所定の係数を乗じることによってかかる変化量を少なくする（または０とする）。 Then, as shown in FIG. 5C, when the change amount determination unit 112b determines that the screen is blinking, the change amount extracted from the change amount setting information 124 is multiplied by a predetermined coefficient. To reduce the amount of change (or 0).
　たとえば、フレームＦ５のヒストグラムに基づいて決定された目標発光量が、フレームＦ５における実際の発光量よりも閾値Ｌ１以上多いとする。かかる場合、変化量決定部１１２ｂは、変化量設定情報１２４から変化量「HI_1」を取り出すとともに、取り出した変化量「HI_1」に対して所定の係数「０」を乗じることによってバックライトモジュール２２の発光量の変化量を「０」とする。これによって、バックライトモジュール２２の発光量は、フレームＦ６においてもフレームＦ５と同一の発光量となる。 For example, it is assumed that the target light emission amount determined based on the histogram of the frame F5 is more than the threshold L1 than the actual light emission amount in the frame F5. In this case, the change amount determination unit 112b extracts the change amount “HI_1” from the change amount setting information 124, and multiplies the extracted change amount “HI_1” by a predetermined coefficient “0” to thereby change the backlight module 22. The change amount of the light emission amount is set to “0”. As a result, the light emission amount of the backlight module 22 is the same as that of the frame F5 in the frame F6.
　このように、記憶部１２’が、発光量決定部１１２ｃよって決定されたバックライトモジュール２２の発光量を所定フレーム分記憶し、変化量決定部１１２ｂが、記憶部１２’に記憶された発光量に基づいて画面が点滅していると判定した場合に、画像が点滅していない場合と比較して現在の発光量からの変化量を少なくする。これによって、バックライトモジュール２２の発光量を短期間で頻繁に変化させることによる処理負荷を低減することができる。なお、ここでは、所定の係数を「０」として説明したが、これに限ったものではなく、所定の係数は、０以上かつ１を超えない範囲で任意に設定することができる。 In this way, the storage unit 12 ′ stores the light emission amount of the backlight module 22 determined by the light emission amount determination unit 112c for a predetermined frame, and the change amount determination unit 112b stores the light emission amount stored in the storage unit 12 ′. When it is determined that the screen is blinking based on the above, the amount of change from the current light emission amount is reduced compared to the case where the image is not blinking. As a result, the processing load caused by frequently changing the light emission amount of the backlight module 22 in a short period can be reduced. Although the predetermined coefficient is described as “0” here, the present invention is not limited to this, and the predetermined coefficient can be arbitrarily set within a range of 0 or more and not exceeding 1.
　また、昼間と夜間とで変化量を変えることとしてもよい。たとえば、発光量決定部１１２ｃは、昼間（たとえば、午前９～午後５時）の場合には、変化量設定情報１２４から取り出した変化量に対して昼用係数を乗じた値をバックライトモジュール２２の変化量として決定する。また、発光量決定部１１２ｃは、夜間（たとえば、午後５～午前９時）の場合には、変化量設定情報１２４から取り出した変化量に対して夜用係数を乗じた値をバックライトモジュール２２の変化量として決定する。ここで、昼用係数は、夜用係数よりも大きな値とする。これによって、画像の明るさだけでなく周囲の明るさも考慮してバックライトモジュール２２の発光量を変更させることができる。 It is also possible to change the amount of change between daytime and nighttime. For example, in the case of daytime (for example, from 9 am to 5 pm), the light emission amount determination unit 112 c calculates the backlight module 22 by multiplying the change amount extracted from the change amount setting information 124 by the daytime coefficient. Is determined as the amount of change. Further, in the case of nighttime (for example, from 5 pm to 9 am), the light emission amount determination unit 112c is obtained by multiplying the change amount extracted from the change amount setting information 124 by the night coefficient, and the backlight module 22. Is determined as the amount of change. Here, the daytime coefficient is larger than the nighttime coefficient. As a result, the light emission amount of the backlight module 22 can be changed in consideration of not only the brightness of the image but also the brightness of the surroundings.
　なお、上述してきた実施例では、バックライトモジュール２２の発光量と目標発光量と差分値に応じて現在の発光量からの変更量を決定することとしたが、差分値に関係なく、バックライトモジュール２２の発光量を指定した発光量に強制的に変更するようにしてもよい。 In the embodiment described above, the amount of change from the current light emission amount is determined in accordance with the light emission amount of the backlight module 22, the target light emission amount, and the difference value. The light emission amount of the module 22 may be forcibly changed to a designated light emission amount.
　ところで、特許文献１に記載の技術には、全体的に暗い映像の一部に高輝度画素が含まれる場合に、かかる高輝度画素の視認性が低下するという問題もあった。これは、映像が全体的に暗い場合には、バックライトの発光量が少なめに設定される結果、多めの発光量を必要とする高輝度画素にとって適切なバックライトの発光量とならないためである。 By the way, the technique described in Patent Document 1 has a problem that the visibility of the high-luminance pixel is lowered when the high-luminance pixel is included in a part of the overall 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. .
　また、バックライトの発光量が暗めに設定された場合には、映像自体の明るさを高める補正がなされるため、高輝度画素によって表示される部分（元々明るい部分）に色つぶれが生じ、視認性が低下するという問題もある。 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.
　これらのことから、全体的に暗い画像の一部に高輝度の画素が含まれる場合に、バックライトによる消費電力を抑えつつ、高輝度画素の視認性を高めることができる表示制御装置あるいは表示制御方法をいかにして実現するかも大きな課題となっている。 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 also a big issue.
　そこで、実施例４では、全体的に暗い画像の一部に高輝度画素が含まれる場合には、バックライトの発光量を少なくしすぎないこととした。以下では、かかる実施例４について図２１～２８を用いて説明する。 Therefore, in Example 4, when a high-luminance pixel is included in a part of an overall dark image, the light emission amount of the backlight is not reduced too much. Hereinafter, Example 4 will be described with reference to FIGS.
　なお、以下に示す実施例４では、上記の実施例１，２または３に係る表示制御装置１０と同様の機能を発揮するものについてはこれらと同一の符号を付してその説明を省略する。 In addition, in Example 4 shown below, about the thing which exhibits the same function as the display control apparatus 10 which concerns on said Example 1, 2, or 3, the same code | symbol is attached | subjected to these, and the description is abbreviate | omitted.
　まず、実施例４の詳細な説明に先立って、実施例４に係る表示制御手法の概要について図２１を用いて説明する。図２１は、実施例４に係る表示制御手法の概要を示す図である。ここで、同図の（Ａ）には、全体的に暗い画像の一部に高輝度画素が含まれる様子を示し、同図の（Ｂ）には、同図の（Ａ）に示した画像の輝度分布を示している。 First, prior to detailed description of the fourth embodiment, an overview of a display control method according to the fourth embodiment will be described with reference to FIG. FIG. 21 is a diagram illustrating an overview of the display control method according to the fourth embodiment. 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.
　なお、実施例４に係る表示制御手法では、入力された画像データの輝度値分布（以下、「ヒストグラム」と記載する）に基づいてバックライトの発光量を決定することとしている。具体的には、実施例４に係る表示制御手法では、暗い画像の場合には、低輝度側に位置する画素の数が多いためバックライトの発光量を少なく設定し、明るい画像の場合には、高輝度側に位置する画素の数が多いためバックライトの発光量を多く設定する。 In the display control method according to the fourth embodiment, 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 fourth embodiment, 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 to be small. Since the number of pixels located on the high luminance side is large, a large amount of light emitted from the backlight is set.
　このため、同図の（Ａ）に示したように、全体的に暗い画像の一部に高輝度画素が含まれる場合には、低輝度画素の数が多いためバックライトの発光量が少なく設定される。しかしながら、バックライトの発光量が少なめに設定されると、高輝度画素によって表示される部分に色つぶれ現象（以下、「ハレーション」と記載する）が発生し、かかる部分の視認性が低下するおそれがある。 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.
　そこで、実施例４に係る表示制御手法では、全体的に暗い画像の一部に高輝度画素が含まれる場合には、バックライトの発光量を少なくしすぎないこととした。また、実施例４に係る表示制御手法では、かかる場合に、バックライトの発光量を単純に高輝度画素に合わせた発光量とするのではなく、バックライトによる消費電力の削減も考慮して発光量を決定することとした。 Therefore, in the display control method according to the fourth embodiment, when high luminance pixels are included in a part of an overall dark image, the amount of light emitted from the backlight is not reduced too much. In the display control method according to the fourth embodiment, 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 the light emission is also considered in consideration of the power consumption reduction by the backlight. The amount was decided.
　具体的には、同図の（Ｂ）に示したように、実施例４に係る表示制御手法では、画像データが入力されると、画像データを構成する画素の数を輝度値の高いものから順に累積加算する。すなわち、実施例４に係る表示制御手法では、ヒストグラム上の最高輝度値（たとえば、８ｂｉｔ分解能の場合には、「２５５」）を算出開始ポイントとし、算出開始ポイントから低輝度側へ向かって各輝度値の画素数を順次累積加算していく（同図の（Ｂ－１）参照）。なお、ヒストグラム上の再高輝度値は、分解能に応じて変化するものである。 Specifically, as shown in (B) of the figure, in the display control method according to the fourth embodiment, when image data is input, the number of pixels constituting the image data is changed from those having a high luminance value. Cumulative addition in order. In other words, in the display control method according to the fourth embodiment, 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 from the calculation start point toward the lower luminance side. The number of pixels of the value is sequentially accumulated and added (see (B-1) in the figure). The re-high brightness value on the histogram changes according to the resolution.
　また、実施例４に係る表示制御手法では、各輝度値の画素数を累積加算するごとに、累積加算済みの画素（以下、「累積画素」と記載する）の平均輝度（以下、「部分平均輝度」と記載する）を算出する（同図の（Ｂ－２）参照）。 In the display control method according to the fourth embodiment, every time the number of pixels of each luminance value is cumulatively added, the average luminance (hereinafter referred to as “partial average”) of pixels that have been cumulatively added (hereinafter referred to as “cumulative pixels”). (Refer to (B-2) in the figure).
　すなわち、現在累積加算中の輝度値、言い換えれば、累積加算済みの画素の輝度値のうちの最低輝度値（以下、「算出ポイント」と記載する）は、画素数を累積加算するごとに低輝度側へ向かって遷移していく。また、これに伴い、部分平均輝度も低輝度側へ遷移していくこととなる。 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.
　ここで、全体的に暗い画像の一部に明るい部分が含まれる場合には、同図の（Ｂ）に示したように、高輝度側に少数の画素が存在し、残り大多数の画素が低輝度側に存在するヒストグラムとなる。このため、このようなヒストグラムを用いて高輝度側から画素数を累積加算していくと、高輝度画素の数を累積加算し終えた時点で累積画素数がほとんど増えない状態となり、これに伴い、部分平均輝度もほとんど変化しなくなる。 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.
　すなわち、全体的に暗い画像の一部に明るい部分が含まれる場合には、算出ポイントが低輝度側へ遷移するほど、部分平均輝度と算出ポイントとの間に大きな差が生じることとなる。そこで、実施例４に係る表示制御手法では、部分平均輝度と算出ポイントとの差が所定の閾値以上となった場合に（同図の（Ｂ－３）参照）、全体的に暗い画像の一部に高輝度画素が含まれると判定することとした。 That is, when a bright part is included in a part of an overall dark image, a larger difference occurs between the partial average luminance and the calculated point as the calculated point shifts to the lower luminance side. Therefore, in the display control method according to the fourth embodiment, 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 same figure), an entire dark image is displayed. It was decided that a high-luminance pixel was included in the part.
　そして、実施例４に係る表示制御手法では、部分平均輝度との差が所定の閾値以上となった場合における算出ポイントに基づいてバックライトの発光量を決定する（同図の（Ｂ－４）参照）。具体的には、実施例４に係る表示制御手法では、０から２５５までの輝度値に対してそれぞれ０％から１００％までの発光量があらかじめ対応付けられている。そして、実施例４に係る表示制御手法では、上記算出ポイントの輝度値に対応する発光量をバックライトの発光量として決定する。 In the display control method according to the fourth embodiment, 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 ((B-4) in the figure). reference). Specifically, in the display control method according to the fourth embodiment, the light emission amounts from 0% to 100% are associated in advance with the luminance values from 0 to 255, respectively. In the display control method according to the fourth embodiment, the light emission amount corresponding to the luminance value of the calculation point is determined as the light emission amount of the backlight.
　このように、実施例４に係る表示制御手法では、全体的に暗い画像の一部に高輝度画素が含まれる場合に、バックライトの発光量を低輝度画素に合わせて下げすぎないようにしたため、高輝度画素の視認性を高めることができる。 As described above, in the display control method according to the fourth embodiment, when a high-luminance pixel is included in a part of an overall dark image, the amount of light emitted from the backlight is not reduced too much in accordance with the low-luminance pixel. The visibility of high-luminance pixels can be improved.
　しかも、かかる場合に、バックライトの発光量を単純に高輝度画素に合わせた発光量とするのではなく、高輝度画素と低輝度画素との間（ここでは、算出ポイント）の輝度値に対応する発光量をバックライトの発光量とすることとした。したがって、バックライトによる消費電力を抑えつつ、高輝度画素の視認性を高めることができる。 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.
　なお、実施例４に係る表示制御手法では、算出ポイントと部分平均輝度との差が所定の閾値以上となる前に、累積画素数が所定の画素数を超えた場合には、累積画素数が所定の画素数を超えた時点の算出ポイントに基づいてバックライトの発光量を決定する。これにより、全体的に暗い画像の一部に高輝度画素が含まれるような特殊なケースでない場合には、通常通り、入力画像全体の明るさに応じた発光量をバックライトの発光量とすることができる。 In the display control method according to the fourth embodiment, 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 The light emission amount of the backlight is determined based on the calculation point when the predetermined 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.
　ところで、同図の（Ｂ）に示したヒストグラムにおいて高輝度画素の分布と低輝度画素の分布とが比較的近い位置に存在する場合には、算出ポイントと部分平均輝度との差が所定の閾値以上となる前に、累積画素数が所定の画素数を超えてしまう場合がある。このような場合には、全体的に暗い画像の一部に高輝度画素が含まれているにもかかわらず、高輝度画素の視認性を適切に高めることができない。 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.
　そこで、実施例４に係る表示制御手法では、部分平均輝度の値に応じて所定の閾値を変更することによって上記のような状況を回避することとしている。かかる点の詳細については、実施例において後述する。 Therefore, in the display control method according to the fourth embodiment, 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.
　以下では、図２１を用いて説明した表示制御手法を適用した表示制御装置についての実施例４を詳細に説明する。なお、以下に示す実施例４では、実施例１～３と同様、車載装置に搭載される液晶ディスプレイの表示制御を行う表示制御装置に対して実施例４に係る表示制御手法を適用する場合について説明する。ただし、実施例４にかかる表示制御装置は、これに限ったものではなく、携帯端末装置やＰＣ（Personal Computer）あるいはＴＶ（Television）のように、バックライトを用いて表示を行う表示部を備える各種の装置に対して適用することができる。 Hereinafter, a fourth embodiment of the display control apparatus to which the display control method described with reference to FIG. 21 is applied will be described in detail. In the fourth embodiment shown below, as in the first to third embodiments, the display control method according to the fourth embodiment is applied to a display control device that performs display control of a liquid crystal display mounted on an in-vehicle device. explain. However, the display control apparatus according to the fourth embodiment is not limited to this, and includes a display unit that performs display using a backlight, such as a mobile terminal device, a PC (Personal Computer), or a TV (Television). The present invention can be applied to various devices.
　また、以下では、全体的に暗い画像の一部に高輝度画素が含まれる場合にヒストグラム上に形成される２つの分布のうち（図２１参照）、高輝度側の分布に属する画素を高輝度画素と呼び、低輝度側の分布に属する画素を低輝度画素と呼ぶこととする。 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. 21), 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.
　実施例４に係る表示制御装置１０は、実施例１に係る表示制御装置１０におけるヒストグラム解析部１１ｄに代えてヒストグラム解析部１１ｄ''を備えている。また、実施例４に係る表示制御装置１０は、実施例１に係る表示制御装置１０における閾値情報１２に代えて閾値情報１２ａ’を記憶している。 The display control apparatus 10 according to the fourth embodiment includes a histogram analysis unit 11d ″ instead of the histogram analysis unit 11d in the display control apparatus 10 according to the first embodiment. Further, the display control apparatus 10 according to the fourth embodiment stores threshold information 12a ′ instead of the threshold information 12 in the display control apparatus 10 according to the first embodiment.
　ヒストグラム解析部１１ｄ''は、ヒストグラム生成部１１ｃによって生成されたヒストグラムを閾値情報１２ａ’を用いて解析することによって、バックライトモジュール２２の発光量を決定する処理部である。 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 ′.
　ここで、かかるヒストグラム解析部１１ｄ''の具体的な構成について図２２を用いて説明する。図２２は、実施例１に係るヒストグラム解析部１１ｄ''の構成を示すブロック図である。同図に示すように、ヒストグラム解析部１１ｄ''は、累積加算部１１３ａと、部分平均輝度算出部１１３ｂと、発光量決定部１１３ｃとを備えている。また、閾値情報１２ａ’は、ＤＮＵＭ１２１と、ＡＶＥＤＩＳ１２６とを含んでいる。なお、同図に示したように、ヒストグラム生成部１１ｃは、生成したヒストグラムを累積加算部１１３ａおよび部分平均輝度算出部１１３ｂへ渡す。 Here, a specific configuration of the histogram analysis unit 11d ″ will be described with reference to FIG. FIG. 22 is a block diagram illustrating a configuration of the histogram analysis unit 11d ″ according to the first embodiment. As shown in the figure, the histogram analysis unit 11d ″ includes a cumulative addition unit 113a, a partial average luminance calculation unit 113b, and a light emission amount determination unit 113c. The threshold information 12a ′ includes a DNUM 121 and an AVEDIS 126. As shown in the figure, the histogram generation unit 11c passes the generated histogram to the cumulative addition unit 113a and the partial average luminance calculation unit 113b.
　累積加算部１１３ａは、ヒストグラム生成部１１ｃから取得したヒストグラムを用いて輝度値の高いものから順に画素数を累積加算する処理部である。また、累積加算部１１３ａは、画素数を累積加算するごとに、累積加算した画素数である累積画素数および現在の算出ポイントを発光量決定部１１３ｃへ渡す処理も併せて行う。 The cumulative addition unit 113a 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 113a also performs a process of passing the cumulative number of pixels, which is the cumulative number of pixels, and the current calculation point to the light emission amount determination unit 113c.
　たとえば、輝度値「２５５」の画素数が１個であり、輝度値「２５４」の画素数が２個であり、輝度値「２５３」の画素数が３個であるとする。かかる場合、累積加算部１１３ａは、輝度値「２５３」までの画素数を累積加算したならば、累積画素数「６」および現在の算出ポイント「２５３」を発光量決定部１１３ｃへ渡す。 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, when the cumulative addition unit 113a 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 transferred to the light emission amount determination unit 113c.
　また、累積加算部１１３ａは、現在の算出ポイントを部分平均輝度算出部１１３ｂへ渡す処理も行う。 Further, the cumulative addition unit 113a also performs a process of passing the current calculation point to the partial average luminance calculation unit 113b.
　部分平均輝度算出部１１３ｂは、累積加算部１１３ａによって累積加算済みの画素の平均輝度を部分平均輝度として算出する処理部である。すなわち、部分平均輝度算出部１１３ｂは、累積加算部１１３ａから算出ポイントを受け取ると、算出開始ポイントから算出ポイントまでに含まれる画素の部分平均輝度を算出する。 The partial average luminance calculation unit 113b is a processing unit that calculates the average luminance of the pixels that have been cumulatively added by the cumulative addition unit 113a as the partial average luminance. That is, when the partial average luminance calculation unit 113b receives the calculation point from the cumulative addition unit 113a, the partial average luminance calculation unit 113b calculates the partial average luminance of pixels included from the calculation start point to the calculation point.
　ここで、部分平均輝度は、Σ{（算出ポイント）×（画素数）}／（累積画素数）によってあらわされる。すなわち、部分平均輝度は、各算出ポイント（輝度値）と当該算出ポイントの画素数とを乗じた値を算出開始ポイントから現在の算出ポイントまで総和し、総和した値を累積画素数で除算することによって求められる。 Here, the partial average luminance is expressed by Σ {(calculation point) × (number of pixels)} / (cumulative number of pixels). 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.
　たとえば、輝度値「２５５」の画素数が１個、輝度値「２５４」の画素数が２個、輝度値「２５３」の画素数が３個であり、現在の算出ポイントが「２５３」であるとする。かかる場合、部分平均輝度は、{（２５５×１）＋（２５４×２）＋（２５３×３）}／６≒２５４となる。 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.
　部分平均輝度算出部１１３ｂは、部分平均輝度を算出すると、算出した部分平均輝度を発光量決定部１１３ｃへ渡す。 After calculating the partial average luminance, the partial average luminance calculation unit 113b passes the calculated partial average luminance to the light emission amount determination unit 113c.
　発光量決定部１１３ｃは、累積加算部１１３ａおよび部分平均輝度算出部１１３ｂから受け取った情報と、閾値情報１２ａ’であるＤＮＵＭ１２１およびＡＶＥＤＩＳ１２６とを用いてバックライトモジュール２２の発光量を決定する処理部である。ここで、ＤＮＵＭ１２１とは、累積画素数の閾値を示す情報である。また、ＡＶＥＤＩＳ１２６は、部分平均輝度と現在の算出ポイントとの差の閾値を示す情報である。 The light emission amount determination unit 113c is a processing unit that determines the light emission amount of the backlight module 22 using the information received from the cumulative addition unit 113a and the partial average luminance calculation unit 113b, and the DNUM 121 and the AVEDIS 126 that are threshold information 12a ′. is there. Here, DNUM 121 is information indicating a threshold value for the cumulative number of pixels. AVEDIS 126 is information indicating a threshold value of a difference between the partial average luminance and the current calculation point.
　具体的には、発光量決定部１１３ｃは、累積画素数がＤＮＵＭ１２１に達する前に、部分平均輝度と現在の算出ポイントとの差（以下、「輝度差分値」と記載する）がＡＶＥＤＩＳ１２６以上となった場合に、現在の算出ポイントに対応する発光量をバックライトモジュール２２の発光量として決定する。また、発光量決定部１１３ｃは、累積加算部１１３ａから受け取った累積画素数がＤＮＵＭ１２１に達した場合の算出ポイントに対応する発光量をバックライトモジュール２２の発光量として決定する。 Specifically, the light emission amount determination unit 113c 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 126 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 c determines the light emission amount corresponding to the calculation point when the cumulative number of pixels received from the cumulative addition unit 113 a reaches DNUM 121 as the light emission amount of the backlight module 22.
　ここで、発光量決定部１１３ｃの動作例について図２３を用いて説明する。図２３は、全体的に暗い画像の中に高輝度画素が含まれる場合における発光量決定部１１３ｃの動作例を示す図である。 Here, an operation example of the light emission amount determination unit 113c will be described with reference to FIG. FIG. 23 is a diagram illustrating an operation example of the light emission amount determination unit 113c when a high-luminance pixel is included in an overall dark image.
　同図の（Ａ）に示すように、全体的に暗い画像の一部に明るい部分が含まれる場合には、高輝度側に少数の画素が存在し、残り大多数の画素が低輝度側に存在するようなヒストグラムとなる。ここで、同図の（Ａ）に示したように、累積加算部１１３ａによって高輝度側の画素数を累積加算している場合、すなわち、現在の算出ポイントが高輝度側に位置する場合には、部分平均輝度と現在の算出ポイントとの差はあまり開かない。したがって、算出ポイントおよび部分平均輝度は、輝度差分値がＡＶＥＤＩＳ１２６未満の状態で低輝度側へ遷移していく（同図の（Ａ－１）参照）。 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. 6A, when the cumulative addition unit 113a 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 calculated point and the partial average luminance shift to the low luminance side in a state where the luminance difference value is less than AVEDIS 126 (see (A-1) in the figure).
　一方、同図の（Ｂ）に示したように、累積加算部１１３ａが高輝度画素の画素数を累積加算し終えると、算出ポイントが低輝度側へ到達するまで累積画素数がほとんど増えない状態となる。これは、高輝度画素および低輝度画素間の輝度値に対応する画素数が少ないためである。これに伴い、部分平均輝度もほとんど変化しなくなる。 On the other hand, as shown in FIG. 5B, when the cumulative addition unit 113a 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.
　したがって、全体的に暗い画像の一部に明るい部分が含まれる場合には、算出ポイントが低輝度側へ遷移するにしたがって、輝度差分値が大きくなっていき、ある算出ポイントにおいてＡＶＥＤＩＳ１２６以上となる（同図の（Ｂ－１）参照）。かかる場合に、発光量決定部１１３ｃは、この算出ポイントに対応する発光量をバックライトモジュール２２の発光量とする。 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 126 or more at a certain calculation point ( (See (B-1) in the figure). In such a case, the light emission amount determination unit 113c sets the light emission amount corresponding to this calculation point as the light emission amount of the backlight module 22.
　一方、発光量決定部１１３ｃは、累積画素数がＤＮＵＭ１２１に達した場合には、かかる場合の算出ポイントに対応する発光量をバックライトモジュール２２の発光量とする。かかる場合について図２４を用いて説明する。また、図２４は、発光量決定部１１３ｃの他の動作例を示す図である。なお、同図には、画素が満遍なく分布したヒストグラムを示している。 On the other hand, when the accumulated number of pixels reaches DNUM 121, the light emission amount determination unit 113c sets the light emission amount corresponding to the calculation point in this case as the light emission amount of the backlight module 22. Such a case will be described with reference to FIG. FIG. 24 is a diagram illustrating another operation example of the light emission amount determination unit 113c. In the figure, a histogram in which pixels are evenly distributed is shown.
　同図の（Ａ）に示したように、累積加算部１１３ａは、累積画素数がＤＮＵＭ１２１に達するまで、算出ポイントを順次低輝度側へ遷移させて画素数を累積加算していく（同図の（Ａ－１）参照）。 As shown in FIG. 5A, the cumulative addition unit 113a sequentially adds the number of pixels by sequentially shifting the calculation point to the low luminance side until the cumulative number of pixels reaches DNUM 121 (see FIG. (See (A-1)).
　ここで、同図の（Ｂ）に示したように、画素が満遍なく分布している場合には、算出ポイントおよび部分平均輝度は、輝度差分値がＡＶＥＤＩＳ１２６未満の状態で共に低輝度側へ遷移していくこととなる（同図の（Ａ－２）および（Ｂ－１）参照）。このような場合には、輝度差分値がＡＶＥＤＩＳ１２６以上となることなく累積画素数がＤＮＵＭ１２１に達することとなる（同図の（Ｂ－２）参照）。したがって、発光量決定部１１３ｃは、累積画素数がＤＮＵＭ１２１に達した場合の算出ポイントに対応する発光量をバックライトモジュール２２の発光量として決定する。 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 AVEDIS 126. (Refer to (A-2) and (B-1) in the figure). In such a case, the number of accumulated pixels reaches DNUM 121 without the luminance difference value becoming AVEDIS 126 or more (see (B-2) in the figure). Therefore, the light emission amount determination unit 113 c 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.
　このように、実施例４では、累積画素数がＤＮＵＭ１２１に達する前に、輝度差分値がＡＶＥＤＩＳ１２６以上となった場合に、かかる場合の算出ポイントに基づいてバックライトモジュール２２の発光量を決定することとした。したがって、累積画素数がＤＮＵＭ１２１に達した場合の算出ポイントに対応する発光量よりも多い発光量がバックライトモジュール２２の発光量として決定されることとなる。このため、全体的に暗い画像の一部に高輝度画素が含まれる場合に、かかる高輝度画素の視認性を高めることができる。 As described above, in the fourth embodiment, when the luminance difference value is equal to or greater than AVEDIS 126 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.
　また、実施例４では、累積画素数がＤＮＵＭ１２１に達した場合には、累積画素数がＤＮＵＭ１２１に達した場合の算出ポイントに基づいてバックライトモジュール２２の発光量を決定することとした。したがって、高輝度画素の視認性を高める処理が必要ない場合には、通常通り、画像全体の輝度値に応じた発光量をバックライトモジュール２２の発光量とすることができる。 In the fourth 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 processing 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 used as the light emission amount of the backlight module 22 as usual.
　なお、閾値情報１２ａ’として記憶されるＤＮＵＭ１２１およびＡＶＥＤＩＳ１２６の値は、任意に変更することができる。 Note that the values of DNUM 121 and AVEDIS 126 stored as threshold information 12a 'can be arbitrarily changed.
　また、実施例４において、発光量変更部１１ｅは、バックライトモジュール２２の発光量の急激な変化によって生じる画面のちらつきを防止するため、ヒストグラム解析部１１ｄ''から取得した発光量と現在の発光量との差分に基づいて発光量の変化量を制限する発光量変更処理を行う処理部である。具体的には、発光量変更部１１ｅは、実施例３に示した処理手順により発光量の変化量を制限する。 In the fourth embodiment, the light emission amount changing unit 11e and the current light emission amount acquired from the histogram analysis unit 11d '' are used to prevent screen flickering caused by a sudden change in the light emission amount of the backlight module 22. It is a processing unit that performs a light emission amount change process for limiting the amount of change in the light emission amount based on the difference from the amount. Specifically, the light emission amount changing unit 11e limits the amount of change in the light emission amount according to the processing procedure shown in the third embodiment.
　次に、実施例４に係る表示制御装置１０の具体的動作について図２５を用いて説明する。図２５は、実施例４に係る表示制御装置１０が実行する処理手順を示すフローチャートである。なお、同図においては、表示制御装置１０が実行する処理手順のうち、バックライトモジュール２２の発光量制御に関する処理手順のみを示している。 Next, specific operations of the display control apparatus 10 according to the fourth embodiment will be described with reference to FIG. FIG. 25 is a flowchart illustrating a processing procedure executed by the display control apparatus 10 according to the fourth 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.
　同図に示すように、表示制御装置１０では、サブサンプリング部１１ｂが、画像データ取得部１１ａによって取得された画像データに対してサブサンプリングを行う（ステップＳ４０１）。また、表示制御装置１０では、ヒストグラム生成部１１ｃが、サブサンプリング後の画像データを用いてヒストグラムを生成し（ステップＳ４０２）、生成したヒストグラムを累積加算部１１３ａおよび部分平均輝度算出部１１３ｂへ渡す。 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 S401). Further, in the display control apparatus 10, the histogram generation unit 11c generates a histogram using the image data after sub-sampling (step S402), and passes the generated histogram to the cumulative addition unit 113a and the partial average luminance calculation unit 113b.
　つづいて、累積加算部１１３ａは、ヒストグラム生成部１１ｃから受け取ったヒストグラムを用いて算出開始ポイントから画素数を順次累積加算する累積加算処理を開始する（ステップＳ４０３）。つづいて、部分平均輝度算出部１１３ｂは、累積加算部１１３ａによって累積加算済みの画素の平均輝度である部分平均輝度を算出する（ステップＳ４０４）。 Subsequently, the cumulative addition unit 113a starts a cumulative addition process of sequentially adding the number of pixels from the calculation start point using the histogram received from the histogram generation unit 11c (step S403). Subsequently, the partial average luminance calculation unit 113b calculates partial average luminance that is the average luminance of the pixels that have been cumulatively added by the cumulative addition unit 113a (step S404).
　つづいて、発光量決定部１１３ｃは、累積画素数がＤＮＵＭ１２１に達したか否かを判定し（ステップＳ４０５）、累積画素数がＤＮＵＭ１２１未満である場合には（ステップＳ４０５、Ｎｏ）、輝度差分値がＡＶＥＤＩＳ１２６以上となったか否かを判定する（ステップＳ４０６）。 Subsequently, the light emission amount determination unit 113c determines whether or not the cumulative pixel number has reached the DNUM 121 (step S405), and when the cumulative pixel number is less than the DNUM 121 (step S405, No), the luminance difference value. Is determined to be equal to or greater than AVEDIS 126 (step S406).
　そして、輝度差分値がＡＶＥＤＩＳ１２６以上となったと判定した場合（ステップＳ４０６、Ｙｅｓ）、発光量決定部１１３ｃは、輝度差分値がＡＶＥＤＩＳ１２６以上となった時点の算出ポイントに対応する発光量をバックライトモジュール２２の発光量として決定する（ステップＳ４０７）。一方、輝度差分値がＡＶＥＤＩＳ１２６未満である場合には（ステップＳ４０６、Ｎｏ）、発光量決定部１１３ｃは、ステップＳ４０４～Ｓ４０６の処理を繰り返す。 If it is determined that the luminance difference value is equal to or greater than AVEDIS 126 (step S406, Yes), the light emission amount determination unit 113c determines the light emission amount corresponding to the calculated point when the luminance difference value is equal to or greater than AVEDIS 126 to the backlight module. The amount of light emission 22 is determined (step S407). On the other hand, when the luminance difference value is less than AVEDIS 126 (No in step S406), the light emission amount determination unit 113c repeats the processes in steps S404 to S406.
　また、累積画素数がＤＮＵＭ１２１に達したと判定した場合には（ステップＳ４０５、Ｙｅｓ）、発光量決定部１１３ｃは、累積画素数がＤＮＵＭ１２１に達した時点の算出ポイントに対応する発光量をバックライトモジュール２２の発光量として決定する（ステップＳ４０８）。 When it is determined that the cumulative number of pixels has reached DNUM 121 (step S405, Yes), the light emission amount determination unit 113c sets the light emission amount corresponding to the calculated point when the cumulative pixel number has reached DNUM 121 as the backlight. The amount of light emitted by the module 22 is determined (step S408).
　ステップＳ４０７またはステップＳ４０８の処理を終えると、発光量変更部１１ｅは、発光量決定部１１３ｃによって決定された発光量に対して発光量変更処理を行って変更後発光量を決定する（ステップＳ４０９）。つづいて、ＰＷＭ生成部１１ｆは、変更後発光量に応じたＰＷＭ信号を生成してバックライトモジュール２２へ出力する（ステップＳ４１０）。 When the processing of step S407 or step S408 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 113c to determine the changed light emission amount (step S409). 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 S410).
　また、ＲＧＢ変換部１１ｇは、画像データ取得部１１ａから取得した画像データに含まれるＲ，Ｇ，Ｂの各成分の値に対して、変更後発光量に対応するＲＧＢ変換係数を掛け合わせるＲＧＢ変換処理を行う（ステップＳ４１１）。そして、ＲＧＢ変換部１１ｇは、ＲＧＢ変換処理後の画像データを液晶パネル２１へ出力して（ステップＳ４１２）、処理を終了する。 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 S411). Then, the RGB converter 11g outputs the image data after the RGB conversion process to the liquid crystal panel 21 (step S412), and ends the process.
　上述してきたように、実施例４では、累積加算部が、入力された画像データに対して当該画像データを構成する画素の数を輝度値の高いものから順に累積加算し、部分平均輝度算出部が、累積加算済みの画素の平均輝度を部分平均輝度として算出し、発光量決定部が、算出した部分平均輝度と累積加算済みの画素の輝度値のうちの最低輝度値との差が所定の閾値以上となった場合に、当該最低輝度値に基づいてバックライトの発光量を決定することとした。したがって、全体的に暗い画像の一部に高輝度の画素が含まれる場合に、バックライトによる消費電力を抑えつつ、高輝度画素の視認性を高めることができる。 As described above, in the fourth embodiment, the cumulative addition unit cumulatively adds the number of pixels constituting the image data to the input image data in descending order of the 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.
　ところで、上述してきた実施例４では、画像中の暗い部分と明るい部分との輝度差が大きい場合、すなわち、ヒストグラムにおいて高輝度画素の分布と低輝度画素の分布とが大きく離れている場合を例として説明してきた。しかしながら、これに限ったものではなく、たとえば、画像中の明るい部分の輝度値があまり高くない場合のように、高輝度画素の分布と低輝度画素の分布とが比較的近い位置に存在する場合もある。 By the way, in the fourth 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 an example. As 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.
　かかる場合には、全体的に暗い画像の一部に高輝度画素が含まれているにもかかわらず、輝度差分値がＡＶＥＤＩＳ１２６以上となる前に、累積画素数がＤＮＵＭ１２１に達してしまうおそれがある。そこで、高輝度画素の輝度値が比較的低い場合には、高輝度画素の輝度値が高い場合と比較してＡＶＥＤＩＳ１２６の値を小さくすることとしてもよい。 In such a case, the cumulative number of pixels may reach DNUM 121 before the luminance difference value becomes equal to or greater than AVEDIS 126, 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 AVEDIS 126 may be made smaller than when the luminance value of the high-luminance pixel is high.
　以下では、かかる場合について図２６を用いて説明する。図２６は、部分平均輝度の値に応じてＡＶＥＤＩＳ１２６を変更する場合について説明するための図である。なお、同図の（Ａ）には、部分平均輝度と閾値Ａとの大小関係に応じて異なるＡＶＥＤＩＳ１２１が対応付けられる様子を示している。また、同図の（Ｂ）には、部分平均輝度が閾値Ａ以上である場合にＡＶＥＤＩＳ（大）が適用される様子を、同図の（Ｃ）には、部分平均輝度が閾値Ａ未満である場合にＡＶＥＤＩＳ（小）が適用される様子を、それぞれ示している。 Hereinafter, such a case will be described with reference to FIG. FIG. 26 is a diagram for explaining a case where the AVEDIS 126 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.
　同図の（Ａ）に示したように、実施例４に係る記憶部１２には、ＡＶＥＤＩＳ１２６として、ＡＶＥＤＩＳ（大）と、ＡＶＥＤＩＳ（大）よりも値の小さいＡＶＥＤＩＳ（小）とが記憶されている。 As shown to (A) of the figure, in the memory | storage part 12 which concerns on Example 4, AVEDIS (large) and AVEDIS (small) whose value is smaller than AVEDIS (large) are memorize | stored as AVEDIS126. Yes.
　そして、発光量決定部１１３ｃは、部分平均輝度算出部１１３ｂによって算出された部分平均輝度が閾値Ａ以上である場合には、輝度差分値とＡＶＥＤＩＳ（大）とを比較し、輝度差分値がＡＶＥＤＩＳ（大）以上となったか否かを判定する（同図の（Ｂ）参照）。これは、部分平均輝度が閾値Ａ（「所定の輝度値」に相当）以上である場合には、低輝度画素と高輝度画素との輝度差が大きいと見なすことができるためである。 When the partial average luminance calculated by the partial average luminance calculation unit 113b is greater than or equal to the threshold A, the light emission amount determination unit 113c compares the luminance difference value with AVEDIS (large), and the luminance difference value is 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.
　一方、発光量決定部１１３ｃは、部分平均輝度が閾値Ａ未満となった場合には、輝度差分値とＡＶＥＤＩＳ（小）とを比較し、輝度差分値がＡＶＥＤＩＳ（小）以上となったか否かを判定する（同図の（Ｃ）参照）。これは、部分平均輝度が閾値Ａ未満となった場合には、低輝度画素と高輝度画素との輝度差が小さいと見なすことができるためである。 On the other hand, when the partial average luminance is less than the threshold A, the light emission amount determination unit 113c 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.
　このように、部分平均輝度算出部１１３ｂによって算出された部分平均輝度が所定の輝度値未満である場合には、部分平均輝度が所定の輝度値以上である場合と比較してＡＶＥＤＩＳを小さくすることとした。したがって、高輝度画素と低輝度画素との輝度差が小さい場合に、輝度差分値がＡＶＥＤＩＳ１２６以上となる前に、累積画素数がＤＮＵＭ１２１に達してしまうことが防止される結果、高輝度画素の視認性を適切に高めることができる。 As described above, when the partial average luminance calculated by the partial average luminance calculation unit 113b 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 larger than AVEDIS 126. As a result, the high luminance pixel is visually recognized. Sexually can be improved appropriately.
　なお、ＡＶＥＤＩＳ１２６として記憶されるＡＶＥＤＩＳ（大）およびＡＶＥＤＩＳ（小）の値は、ＡＶＥＤＩＳ（小）がＡＶＥＤＩＳ（大）を超えない範囲であれば、任意に設定変更可能である。 Note that the values of AVEDIS (large) and AVEDIS (small) stored as AVEDIS 126 can be arbitrarily changed as long as AVEDIS (small) does not exceed AVEDIS (large).
　ところで、上述してきた実施例４では、ＡＶＥＤＩＳ１２６を導入することによって、全体的に暗い画像の一部に高輝度画素が含まれる場合における高輝度画素の視認性を高める方式について説明してきたが、他の方式によっても高輝度画素の視認性を高めることができる。たとえば、画像データに含まれる全画素を高輝度画素および低輝度画素の２つに分類し、累積加算部１１３ａによって画素数の累積加算を行う場合に、高輝度画素の累積画素数を低輝度画素の各輝度値の画素数へ加算しながら順次累積加算していくことによって、累積画素数を通常よりも早くＤＮＵＭ１２１に到達させるようにしてもよい。 By the way, in the fourth embodiment described above, a method has been described in which the visibility of a high-brightness pixel is improved when a high-brightness pixel is included in a part of an overall dark image by introducing the AVEDIS 126. This method can also improve the visibility of high-luminance pixels. For example, when all the pixels included in the image data are classified into two, a high luminance pixel and a low luminance pixel, and the cumulative addition unit 113a 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.
　以下では、かかる場合について図２７を用いて説明する。図２７は、累積加算部１１３ａの他の動作例を示す図である。ここで、同図の（Ａ）には、累積加算部１１３ａの通常の動作例を示し、同図の（Ｂ）には、累積加算部１１３ａの他の動作例を示している。なお、ここでは、ＤＮＵＭ１２１の値を「６０」として説明する。また、同図の（Ｂ）に示したように、ここでは、輝度値「２００」～「２５５」までの画素を高輝度画素とし、輝度値「０」～「１９９」の画素を低輝度画素として分類するものとする。 Hereinafter, such a case will be described with reference to FIG. FIG. 27 is a diagram illustrating another operation example of the cumulative addition unit 113a. Here, (A) in the figure shows a normal operation example of the cumulative addition unit 113a, and (B) in the same figure shows another operation example of the cumulative addition unit 113a. Here, the value of DNUM 121 will be described as “60”. Further, 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
　同図の（Ａ）に示したように、通常の動作において、累積加算部１１３ａは、算出開始ポイントから低輝度へ向かって画素数を順次累積加算していく。そして、累積画素数がＤＮＵＭ１２１を超えた時点の算出ポイント（ここでは、輝度値「１００」）に対応する発光量「３９％」をバックライトモジュール２２の発光量として決定する。 As shown in FIG. 5A, in a normal operation, the cumulative addition unit 113a 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.
　一方、他の動作において、累積加算部１１３ａは、同図の（Ｂ）に示したように、高輝度画素の累積画素数が「１５」である場合には、低輝度画素に分類される各輝度値の画素数に対してそれぞれ「１５」を加算したものを累積加算していく。たとえば、累積加算部１１３ａは、輝度値「１９９」の画素数「１」に対して「１５」を加算した値「１６」を累積加算する。 On the other hand, in other operations, as shown in (B) of the figure, the cumulative adder 113a is classified into low luminance pixels when the cumulative number of high luminance pixels is “15”. A value obtained by adding “15” to the number of pixels of the luminance value is cumulatively added. For example, the cumulative addition unit 113a cumulatively adds a value “16” obtained by adding “15” to the number of pixels “1” of the luminance value “199”.
　このように、低輝度画素に分類される各輝度値の画素数に対して高輝度画素の累積画素数を加算したものを順次累積加算していくことによって、累積画素数は、同図の（Ａ）に示した場合よりも早くＤＮＵＭ１２１に達することとなる。すなわち、かかる処理によって、累積画素数がＤＮＵＭ１２１に達した時点における算出ポイント（ここでは、輝度値「１９７」）を同図の（Ａ）に示した場合よりも高くすることができ、結果として、バックライトモジュール２２の発光量も同図の（Ａ）に示した場合よりも多くすることができる。 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.
　したがって、かかる方式を用いた場合であっても、全体的に暗い画像の一部に高輝度画素が含まれる場合に、高輝度画素の視認性を高めることができる。なお、高輝度画素と低輝度画素との境界値は、任意に設定変更可能である。 Therefore, even when such a method is used, the visibility of the high-luminance pixels can be enhanced 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.
　また、その他の方式として、全体平均輝度が所定の閾値以下であり、かつ、高輝度画素の累積画素数が所定数以上である場合に、暗い画像の一部に高輝度画素が含まれると判定し、既定の発光量をバックライトモジュール２２の発光量として決定してもよい。以下では、かかる場合について図２８を用いて説明する。図２８は、発光量決定部１１３ｃの他の動作例を示す図である。 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. 28 is a diagram illustrating another operation example of the light emission amount determination unit 113c.
　同図に示したように、部分平均輝度算出部１１３ｂは、画像データの全画素の平均輝度である全体平均輝度を算出し、発光量決定部１１３ｃへ渡す。また、累積加算部１１３ａは、高輝度画素の累積画素数を発光量決定部１１３ｃへ渡す。なお、高輝度画素の累積画素数とは、輝度値「２５５」から所定の輝度値（たとえば、「２００」）までの画素の累積数を示す。 As shown in the figure, the partial average luminance calculation unit 113b calculates the overall average luminance which is the average luminance of all the pixels of the image data, and passes it to the light emission amount determination unit 113c. In addition, the cumulative addition unit 113a passes the cumulative number of high luminance pixels to the light emission amount determination unit 113c. 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”).
　また、発光量決定部１１３ｃは、部分平均輝度算出部１１３ｂから全体平均輝度を受け取ると、全体平均輝度が閾値Ｂ未満であるか否かを判定する（同図の（１）参照）。また、発光量決定部１１３ｃは、高輝度画素の累積画素数が所定数以上であるか否かを判定する（同図の（２）参照）。そして、発光量決定部１１３ｃは、全体平均輝度が閾値Ｂ未満であると判定し、かつ、高輝度画素の累積画素数が所定数以上であると判定した場合には、暗い画像の一部に高輝度画素が含まれると判定する（同図の（３）参照）。 Further, when the light emission amount determining unit 113c receives the overall average brightness from the partial average brightness calculating unit 113b, it determines whether or not the overall average brightness is less than the threshold value B (see (1) in the figure). In addition, the light emission amount determination unit 113c 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). If the light emission amount determination unit 113c 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, the light emission amount determination unit 113c adds a part of the dark image. It is determined that a high-luminance pixel is included (see (3) in the figure).
　そして、暗い画像の一部に高輝度画素が含まれると判定すると、発光量決定部１１３ｃは、既定の発光量をバックライトモジュール２２の発光量として決定する（同図の（４）参照）。ここで、既定の発光量とは、全体平均輝度に対応する発光量よりも多い発光量とする。 If it is determined that a high-luminance pixel is included in a part of the dark image, the light emission amount determination unit 113c determines a predetermined light emission amount as the light emission amount of the backlight module 22 (see (4) in FIG. 4). Here, the predetermined light emission amount is a light emission amount larger than the light emission amount corresponding to the overall average luminance.
　このように、全体平均輝度が所定の閾値以下であり、かつ、高輝度画素の累積画素数が所定数以上である場合に、既定の発光量をバックライトモジュール２２の発光量として決定する方式を用いた場合であっても、全体的に暗い画像の一部に含まれる高輝度画素の視認性を高めることができる。なお、上記の所定数や閾値Ｂの値は、任意に変更することができる。 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.
　以上のように、本発明に係る表示制御装置および表示制御方法は、バックライトによる消費電力をより抑えたい場合に有用であり、特に、車載装置の液晶ディスプレイの消費電力を抑えたい場合に適している。 As described above, the display control device and the display control method according to the present invention are useful when it is desired to further reduce the power consumption by the backlight, and are particularly suitable for the case where it is desired to reduce the power consumption of the liquid crystal display of the in-vehicle device. Yes.
　　１０　　　表示制御装置
　　１１　　　制御部
　　１１ａ　　画像データ取得部
　　１１ｂ　　サブサンプリング部
　　１１ｃ　　ヒストグラム生成部
　　１１ｄ　　ヒストグラム解析部
　１１１ａ　　暫定発光量決定部
　１１１ｂ　　比較部
　１１１ｃ　　確定発光量決定部
　　１１ｄ’　ヒストグラム解析部
　１１１ｄ　　平均輝度算出部
　　１１ｄ''　ヒストグラム解析部
　１１３ａ　　累積加算部
　１１３ｂ　　部分平均輝度算出部
　１１３ｃ　　発光量決定部
　　１１ｅ　　発光量変更部
　１１２ａ　　差分値算出部
　１１２ｂ　　変化量決定部
　１１２ｃ　　発光量決定部
　１１２ｄ　　変換係数決定部
　　１１ｆ　　ＰＷＭ生成部
　　１１ｇ　　ＲＧＢ変換部
　　１２　　　記憶部
　　１２ａ　　閾値情報
　１２１　　　ＤＮＵＭ
　１２２　　　Ｈオフセット
　　１２ｂ　　設定情報
　１２３　　　発光量履歴情報
　１２４　　　変化量設定情報
　１２５　　　ＲＧＢ変換情報
　　１２’　　記憶部
　１２６　　　ＡＶＥＤＩＳ
　　２０　　液晶ディスプレイ
　　２１　　液晶パネル
　　２１ａ　モード選択ボタン
　　２１ｃ　「暗」ボタン
　　２１ｄ　「明」ボタン
　　２２　　バックライトモジュール 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 111a Temporary light emission amount determination part 111b Comparison part 111c Determining light emission amount determination part 11d 'Histogram analysis part 111d Average brightness calculation part 11d '' Histogram analysis unit 113a Cumulative addition unit 113b Partial average luminance calculation unit 113c Light emission amount determination unit 11e Light emission amount change unit 112a Difference value calculation unit 112b Change amount determination unit 112c Light emission amount determination unit 112d Conversion coefficient determination unit 11f PWM generation unit 11g RGB conversion unit 12 storage unit 12a threshold information 121 DNUM
122 H offset 12b Setting information 123 Light emission amount history information 124 Change amount setting information 125 RGB conversion information 12 'Storage unit 126 AVEDIS
20 Liquid crystal display 21 Liquid crystal panel 21a Mode selection button 21c “Dark” button 21d “Bright” button 22 Backlight module

Claims (17)

  1. 　表示パネルへ光を照射するバックライトの発光量を制御する表示制御装置であって、
    　入力された画像データに対して、当該画像データを構成する画素を輝度値の高いものから順に計数する計数手段と、
    　前記計数手段によって計数された画素の累積数が所定数に達した場合の輝度値に基づいて前記バックライトの暫定的な発光量を決定する暫定発光量決定手段と、
    　前記暫定発光量決定手段によって決定された暫定的な発光量と所定の閾値とを比較する比較手段と、
    　前記比較手段による比較の結果、前記暫定的な発光量が前記所定の閾値を超える場合に、前記暫定的な発光量よりも少ない発光量を前記バックライトの確定的な発光量として決定する確定発光量決定手段と
    　を備えたことを特徴とする表示制御装置。     A display control device for controlling a light emission amount of a backlight that irradiates light to a display panel,
    Counting means for counting the pixels constituting the image data in order from the highest luminance value for the input image data;
    Provisional light emission amount determining means for determining a provisional light emission amount of the backlight based on a luminance value when the cumulative number of pixels counted by the counting means reaches a predetermined number;
    A comparison means for comparing the provisional light emission amount determined by the provisional light emission amount determination means with a predetermined threshold;
    If the provisional light emission amount exceeds the predetermined threshold as a result of the comparison by the comparison means, the definite light emission that determines a light emission amount smaller than the temporary light emission amount as the definite light emission amount of the backlight A display control apparatus comprising: a quantity determining unit.
  2. 　前記確定発光量決定手段は、
    　前記比較手段による比較の結果、前記暫定的な発光量が前記所定の閾値を超える場合に、前記所定の閾値を前記バックライトの確定的な発光量として決定することを特徴とする請求項１に記載の表示制御装置。     The determined light emission amount determining means includes
    The predetermined threshold value is determined as a definite light emission amount of the backlight when the provisional light emission amount exceeds the predetermined threshold value as a result of comparison by the comparison unit. The display control apparatus described.
  3. 　前記画像データの平均輝度を算出する平均輝度算出手段
    　をさらに備え、
    　前記比較手段は、
    　前記平均輝度算出手段によって算出された平均輝度と前記所定の閾値とをさらに比較し、
    　前記確定発光量決定手段は、
    　前記比較手段による比較の結果、前記暫定的な発光量が前記所定の閾値を超え、かつ、前記平均輝度が前記所定の閾値を超える場合には、前記平均輝度を前記バックライトの確定的な発光量として決定することを特徴とする請求項１に記載の表示制御装置。     Average luminance calculating means for calculating an average luminance of the image data;
    The comparison means includes
    Further comparing the average brightness calculated by the average brightness calculation means and the predetermined threshold,
    The determined light emission amount determining means includes
    As a result of the comparison by the comparison means, when the provisional light emission amount exceeds the predetermined threshold value and the average luminance exceeds the predetermined threshold value, the average luminance is determined as the definite light emission of the backlight. The display control apparatus according to claim 1, wherein the display control apparatus determines the quantity.
  4. 　前記表示パネルに表示される画像の閲覧者を検出する閲覧者検出手段と、
    　前記閲覧者検出手段によって前記画像の閲覧者が検出されなかった場合に、前記閲覧者検出手段によって前記画像の閲覧者が検出された場合と比較して前記所定の閾値を下げる閾値変更手段と
    　をさらに備えたことを特徴とする請求項１に記載の表示制御装置。     A viewer detecting means for detecting a viewer of an image displayed on the display panel;
    A threshold value changing means for lowering the predetermined threshold value when a viewer of the image is not detected by the viewer detecting means compared to a case where a viewer of the image is detected by the viewer detecting means; The display control apparatus according to claim 1, further comprising:
  5. 　前記確定発光量決定手段は、
    　前記比較手段による比較の結果、前記暫定的な発光量が前記所定の閾値を超える場合に、変換前の値が変換後の値よりも小さくなる変換式を用いて前記暫定的な発光量を変換することによって得られる値を前記確定的な発光量として決定することを特徴とする請求項１に記載の表示制御装置。     The determined light emission amount determining means includes
    If the provisional light emission amount exceeds the predetermined threshold as a result of the comparison by the comparison means, the provisional light emission amount is converted using a conversion formula in which the value before conversion is smaller than the value after conversion. The display control apparatus according to claim 1, wherein a value obtained by performing the determination is determined as the definite light emission amount.
  6. 　表示パネルへ光を照射するバックライトの発光量を制御する表示制御装置であって、
    　入力された画像データの輝度値に基づいて前記バックライトの目標発光量を決定する目標発光量決定手段と、
    　前記目標発光量決定手段によって決定された目標発光量と前記バックライトの現在の発光量との差分値に応じて前記現在の発光量からの変化量を決定する変化量決定手段と、
    　前記変化量決定手段によって決定された変化量だけ前記現在の発光量を変化させた発光量を前記バックライトの発光量として決定する発光量決定手段と
    　を備えたことを特徴とする表示制御装置。     A display control device for controlling a light emission amount of a backlight that irradiates light to a display panel,
    Target light emission amount determining means for determining the target light emission amount of the backlight based on the luminance value of the input image data;
    Change amount determining means for determining a change amount from the current light emission amount in accordance with a difference value between the target light emission amount determined by the target light emission amount determining means and the current light emission amount of the backlight;
    A display control apparatus comprising: a light emission amount determining unit that determines a light emission amount obtained by changing the current light emission amount by a change amount determined by the change amount determining unit as a light emission amount of the backlight.
  7. 　大きさの異なる複数の閾値によって区切られる範囲ごとに変化量を対応付けた変化量設定情報を記憶する変化量記憶手段
    　をさらに備え、
    　前記変化量決定手段は、
    　前記複数の閾値によって区切られる範囲のうち前記差分値が属する範囲に対応付けられた変化量を前記変化量設定情報を用いて特定し、特定した変化量を前記現在の発光量からの変化量として決定する
    　ことを特徴とする請求項６に記載の表示制御装置。     A change amount storage means for storing change amount setting information in which a change amount is associated with each range divided by a plurality of thresholds having different sizes;
    The change amount determining means includes
    A change amount associated with a range to which the difference value belongs among the ranges divided by the plurality of threshold values is specified using the change amount setting information, and the specified change amount is set as a change amount from the current light emission amount. The display control device according to claim 6, wherein the display control device is determined.
  8. 　前記変化量記憶手段は、
    　前記複数の閾値によって区切られる範囲のうち、より値の大きい閾値によって区切られる範囲ほど大きい変化量を対応付けた変化量設定情報を記憶することを特徴とする請求項７に記載の表示制御装置。     The change amount storage means includes:
    The display control apparatus according to claim 7, wherein change setting information in which a larger change amount is associated with a range delimited by a threshold having a larger value among the ranges delimited by the plurality of threshold values is stored.
  9. 　前記変化量決定手段は、
    　前記差分値が所定の値を下回る場合に、前記現在の発光量からの変化量を０とすることを特徴とする請求項６に記載の表示制御装置。     The change amount determining means includes
    The display control apparatus according to claim 6, wherein when the difference value is less than a predetermined value, the change amount from the current light emission amount is set to zero.
  10. 　前記発光量決定手段によって決定された前記バックライトの発光量を所定フレーム分記憶する発光量履歴記憶手段
    　をさらに備え、
    　前記変化量決定手段は、
    　前記発光量履歴記憶手段に記憶された発光量に基づいて画面が点滅していると判定した場合には、画像が点滅していない場合と比較して前記現在の発光量からの変化量を少なくすることを特徴とする請求項６に記載の表示制御装置。     A light emission amount history storage unit for storing the light emission amount of the backlight determined by the light emission amount determination unit for a predetermined frame;
    The change amount determining means includes
    When it is determined that the screen is blinking based on the light emission amount stored in the light emission amount history storage unit, the amount of change from the current light emission amount is smaller than when the image is not blinking. The display control apparatus according to claim 6.
  11. 　前記変化量記憶手段は、
    　前記目標発光量が前記バックライトの現在の発光量よりも多い場合に用いられる第１の変化量設定情報と、前記目標発光量が前記バックライトの現在の発光量よりも少ない場合に用いられる第２の変化量設定情報とを記憶し、
    　前記変化量決定手段は、
    　前記目標発光量が前記バックライトの現在の発光量よりも多い場合には、前記第１の変化量設定情報を用いて前記現在の発光量からの変化量を決定し、前記目標発光量が前記バックライトの現在の発光量よりも少ない場合には、前記第２の変化量設定情報を用いて前記現在の発光量からの変化量を決定することを特徴とする請求項７に記載の表示制御装置。     The change amount storage means includes:
    First change amount setting information used when the target light emission amount is larger than the current light emission amount of the backlight, and a first change amount setting information used when the target light emission amount is smaller than the current light emission amount of the backlight. 2 change amount setting information,
    The change amount determining means includes
    When the target light emission amount is larger than the current light emission amount of the backlight, the change amount from the current light emission amount is determined using the first change amount setting information, and the target light emission amount is 8. The display control according to claim 7, wherein when the amount of light emitted from the backlight is smaller than the current light emission amount, a change amount from the current light emission amount is determined using the second change amount setting information. apparatus.
  12. 　表示パネルへ光を照射するバックライトの発光量を制御する表示制御装置であって、
    　入力された画像データに対して当該画像データを構成する画素の数を輝度値の高いものから順に累積加算する累積加算手段と、
    　前記累積加算手段によって累積加算済みの画素の平均輝度を部分平均輝度として算出する部分平均輝度算出手段と、
    　前記部分平均輝度算出手段によって算出された部分平均輝度と、前記累積加算手段によって累積加算済みの画素の輝度値のうちの最低輝度値との差が所定の閾値以上となった場合に、当該最低輝度値に基づいて前記バックライトの発光量を決定する発光量決定手段と
    　を備えたことを特徴とする表示制御装置。     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;
    Partial average luminance calculating means for calculating the average luminance of the pixels that have been cumulatively added by the cumulative addition means as 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 A display control apparatus comprising: a light emission amount determining unit that determines a light emission amount of the backlight based on a luminance value.
  13. 　前記発光量決定手段は、
    　前記部分平均輝度算出手段によって算出された部分平均輝度が所定の輝度値未満である場合には、前記部分平均輝度が前記所定の輝度値以上である場合と比較して前記所定の閾値を小さくすることを特徴とする請求項１２に記載の表示制御装置。     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 12.
  14. 　前記発光量決定手段は、
    　前記累積加算手段によって累積加算された画素の数が所定数に達した場合の輝度値に基づいて前記バックライトの発光量を決定する一方、前記累積加算手段によって累積加算された画素の数が前記所定数に達する前に、前記部分平均輝度と前記最低輝度値との差が前記所定の閾値以上となったならば、当該最低輝度値に基づいて前記バックライトの発光量を決定することを特徴とする請求項１２に記載の表示制御装置。     The light emission amount determining means includes
    While determining the amount of light emission of the backlight based on the luminance value when the number of pixels cumulatively added by the cumulative addition means reaches a predetermined number, the number of pixels cumulatively added by the cumulative addition means Before the predetermined number is reached, if the difference between the partial average luminance and the minimum luminance value is equal to or greater than the predetermined threshold value, the light emission amount of the backlight is determined based on the minimum luminance value. The display control device according to claim 12.
  15. 　表示パネルへ光を照射するバックライトの発光量を制御する表示制御方法であって、
    　入力された画像データに対して、当該画像データを構成する画素を輝度値の高いものから順に計数する計数工程と、
    　前記計数工程において計数した画素の累積数が所定数に達した場合の輝度値に基づいて前記バックライトの暫定的な発光量を決定する暫定発光量決定工程と、
    　前記暫定発光量決定工程において決定した暫定的な発光量と所定の閾値とを比較する比較工程と、
    　前記比較工程における比較の結果、前記暫定的な発光量が前記所定の閾値を超える場合に、前記暫定的な発光量よりも少ない発光量を前記バックライトの確定的な発光量として決定する確定発光量決定工程と
    　を含んだことを特徴とする表示制御方法。     A display control method for controlling a light emission amount of a backlight that irradiates light to a display panel,
    A counting step for counting the pixels constituting the image data in order from the highest luminance value for the input image data;
    A provisional light emission amount determining step of determining a provisional light emission amount of the backlight based on a luminance value when the cumulative number of pixels counted in the counting step reaches a predetermined number;
    A comparison step of comparing the provisional light emission amount determined in the provisional light emission amount determination step with a predetermined threshold;
    As a result of the comparison in the comparison step, when the provisional light emission amount exceeds the predetermined threshold value, the definite light emission that determines a light emission amount smaller than the temporary light emission amount as the definite light emission amount of the backlight A display control method comprising: a quantity determining step.
  16. 　表示パネルへ光を照射するバックライトの発光量を制御する表示制御方法であって、
    　入力された画像データの輝度値に基づいて前記バックライトの目標発光量を決定する目標発光量決定工程と、
    　前記目標発光量決定工程において決定した目標発光量と前記バックライトの現在の発光量との差分値に応じて前記現在の発光量からの変化量を決定する変化量決定工程と、
    　前記変化量決定工程において決定した変化量だけ前記現在の発光量を変化させた発光量を前記バックライトの発光量として決定する発光量決定工程と
    　を含んだことを特徴とする表示制御方法。     A display control method for controlling a light emission amount of a backlight that irradiates light to a display panel,
    A target light emission amount determination step for determining a target light emission amount of the backlight based on the luminance value of the input image data;
    A change amount determining step of determining a change amount from the current light emission amount according to a difference value between the target light emission amount determined in the target light emission amount determination step and the current light emission amount of the backlight;
    A display control method comprising: a light emission amount determination step of determining a light emission amount obtained by changing the current light emission amount by the change amount determined in the change amount determination step as a light emission amount of the backlight.
  17. 　表示パネルへ光を照射するバックライトの発光量を制御する表示制御方法であって、
    　入力された画像データに対して当該画像データを構成する画素の数を輝度値の高いものから順に累積加算する累積加算工程と、
    　前記累積加算工程において累積加算した画素の平均輝度を部分平均輝度として算出する部分平均輝度算出工程と、
    　前記部分平均輝度算出工程において算出した部分平均輝度と、前記累積加算工程において累積加算した画素の輝度値のうちの最低輝度値との差が所定の閾値以上となった場合に、当該最低輝度値に基づいて前記バックライトの発光量を決定する発光量決定工程と
    　を含んだことを特徴とする表示制御方法。     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;
    A partial average luminance calculation step of calculating the average luminance of the pixels cumulatively added in the cumulative addition step 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 cumulatively added in the cumulative addition step is equal to or greater than a predetermined threshold value, the minimum luminance value And a light emission amount determining step for determining the light emission amount of the backlight based on the display control method.
PCT/JP2010/069838 2010-03-02 2010-11-08 Display control device and display control method WO2011108143A1 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP2010-045824 2010-03-02
JP2010-045823 2010-03-02
JP2010045824A JP5604136B2 (en) 2010-03-02 2010-03-02 Display control apparatus and display control method
JP2010045823 2010-03-02
JP2010-045825 2010-03-02
JP2010045825A JP5649832B2 (en) 2010-03-02 2010-03-02 Display control apparatus and display control method

Publications (1)

Publication Number Publication Date
WO2011108143A1 true WO2011108143A1 (en) 2011-09-09

Family

ID=44541819

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2010/069838 WO2011108143A1 (en) 2010-03-02 2010-11-08 Display control device and display control method

Country Status (1)

Country Link
WO (1) WO2011108143A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105590599A (en) * 2014-11-07 2016-05-18 乐金显示有限公司 Method and device for clipping a gray scale level of pixels during the dimming of the backlight of a display device
CN108282922A (en) * 2018-02-13 2018-07-13 上海艾为电子技术股份有限公司 A kind of audio sound phototiming lamp effect dynamic Enhancement Method and device
CN114495858A (en) * 2022-02-09 2022-05-13 Tcl华星光电技术有限公司 Image display method, device and storage medium
CN115035865A (en) * 2022-05-05 2022-09-09 石家庄市京华电子实业有限公司 Partition dimming method of light valve assembly based on LED backlight
TWI797785B (en) * 2021-10-20 2023-04-01 茂達電子股份有限公司 Method of improving performance of averager

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006284982A (en) * 2005-04-01 2006-10-19 Seiko Epson Corp Dimming information generation device, method thereof, program thereof, recording medium with program recorded therein, and image display device
JP2006285064A (en) * 2005-04-04 2006-10-19 Matsushita Electric Ind Co Ltd Image display apparatus
JP2008111886A (en) * 2006-10-27 2008-05-15 Digital Electronics Corp Automatic door, screen display apparatus, screen display control program, and computer readable recording medium recorded with the program
JP2008209828A (en) * 2007-02-28 2008-09-11 Epson Imaging Devices Corp Image display device and electronic apparatus
JP2009003188A (en) * 2007-06-21 2009-01-08 Renesas Technology Corp Display device drive circuit, display device and electronic equipment
JP2009098617A (en) * 2007-06-22 2009-05-07 Renesas Technology Corp Display device and display device driving circuit
JP2009271104A (en) * 2008-04-30 2009-11-19 Seiko Epson Corp Image processor, integrated circuit device and electronic apparatus

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006284982A (en) * 2005-04-01 2006-10-19 Seiko Epson Corp Dimming information generation device, method thereof, program thereof, recording medium with program recorded therein, and image display device
JP2006285064A (en) * 2005-04-04 2006-10-19 Matsushita Electric Ind Co Ltd Image display apparatus
JP2008111886A (en) * 2006-10-27 2008-05-15 Digital Electronics Corp Automatic door, screen display apparatus, screen display control program, and computer readable recording medium recorded with the program
JP2008209828A (en) * 2007-02-28 2008-09-11 Epson Imaging Devices Corp Image display device and electronic apparatus
JP2009003188A (en) * 2007-06-21 2009-01-08 Renesas Technology Corp Display device drive circuit, display device and electronic equipment
JP2009098617A (en) * 2007-06-22 2009-05-07 Renesas Technology Corp Display device and display device driving circuit
JP2009271104A (en) * 2008-04-30 2009-11-19 Seiko Epson Corp Image processor, integrated circuit device and electronic apparatus

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105590599A (en) * 2014-11-07 2016-05-18 乐金显示有限公司 Method and device for clipping a gray scale level of pixels during the dimming of the backlight of a display device
US10720112B2 (en) 2014-11-07 2020-07-21 Lg Display Co., Ltd. Method and device for clipping a gray scale level of pixels during the dimming of the backlight of a display device
CN108282922A (en) * 2018-02-13 2018-07-13 上海艾为电子技术股份有限公司 A kind of audio sound phototiming lamp effect dynamic Enhancement Method and device
CN108282922B (en) * 2018-02-13 2020-03-10 上海艾为电子技术股份有限公司 Audio acousto-optic synchronous lamp effect dynamic enhancement method and device
TWI797785B (en) * 2021-10-20 2023-04-01 茂達電子股份有限公司 Method of improving performance of averager
CN114495858A (en) * 2022-02-09 2022-05-13 Tcl华星光电技术有限公司 Image display method, device and storage medium
CN114495858B (en) * 2022-02-09 2024-03-08 Tcl华星光电技术有限公司 Image display method, device and storage medium
CN115035865A (en) * 2022-05-05 2022-09-09 石家庄市京华电子实业有限公司 Partition dimming method of light valve assembly based on LED backlight

Similar Documents

Publication Publication Date Title
US8552946B2 (en) Display device, display driver and image display method
JP5508679B2 (en) Low power drive apparatus and method
US7554535B2 (en) Display apparatus, image display system, and terminal using the same
KR102143656B1 (en) Display unit, image processing unit, and display method
US9495921B2 (en) Video display device and television receiving device with luminance stretching
US20090274389A1 (en) Image processor, integrated circuit device, and electronic apparatus
US20100214325A1 (en) Image display
JP2010533305A (en) Video management technology
WO2011108143A1 (en) Display control device and display control method
JPWO2006049058A1 (en) Video signal converter, video display device
KR20080042722A (en) Image display control device
JP2009002976A (en) Display driving circuit
JP5604136B2 (en) Display control apparatus and display control method
JP2015099181A (en) Display device
JP4854431B2 (en) Image processing apparatus and method
JP2008258925A (en) Gamma correction circuit and method
JP6180135B2 (en) Image display apparatus and control method thereof
JP5687908B2 (en) Display control apparatus and display control method
JP2012173576A (en) Display controller and display control method
US20120262503A1 (en) Monitor and method of displaying pixels on displaying device
EP2190195A2 (en) Moving-image processing apparatus and method therefor
JP5649832B2 (en) Display control apparatus and display control method
JP5331020B2 (en) Display control apparatus, display system, and display control method
JP5828648B2 (en) Display control apparatus and display control method
JP5331019B2 (en) Display control apparatus, display system, and display control method

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 10847040

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 10847040

Country of ref document: EP

Kind code of ref document: A1