WO2009096068A1 - 画像表示装置および画像表示方法 - Google Patents
画像表示装置および画像表示方法 Download PDFInfo
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- WO2009096068A1 WO2009096068A1 PCT/JP2008/068366 JP2008068366W WO2009096068A1 WO 2009096068 A1 WO2009096068 A1 WO 2009096068A1 JP 2008068366 W JP2008068366 W JP 2008068366W WO 2009096068 A1 WO2009096068 A1 WO 2009096068A1
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- limit value
- upper limit
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- 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
- G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
- G09G3/3426—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines the different display panel areas being distributed in two dimensions, e.g. matrix
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- 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
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0238—Improving the black level
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- 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
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
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- 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
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0261—Improving the quality of display appearance in the context of movement of objects on the screen or movement of the observer relative to the screen
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- 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
- G09G2320/04—Maintaining the quality of display appearance
- G09G2320/041—Temperature compensation
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- 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
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- 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
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- 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
- G09G2360/14—Detecting light within display terminals, e.g. using a single or a plurality of photosensors
- G09G2360/144—Detecting light within display terminals, e.g. using a single or a plurality of photosensors the light being ambient light
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- 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
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- 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
- G09G3/36—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 using liquid crystals
- G09G3/3611—Control of matrices with row and column drivers
- G09G3/3648—Control of matrices with row and column drivers using an active matrix
Definitions
- the present invention relates to an image display device, and more particularly to an image display device having a function of controlling the brightness of a backlight (backlight dimming function).
- an image display device having a backlight such as a liquid crystal display device
- a backlight such as a liquid crystal display device
- the power consumption of the backlight can be suppressed and the image quality of the display image can be improved.
- by dividing the screen into a plurality of areas and controlling the luminance of the backlight light source corresponding to the area based on the input image in the area it is possible to further reduce power consumption and improve image quality.
- area active driving such a method of driving the display panel while controlling the luminance of the backlight light source based on the input image in the area.
- RGB three-color LEDs Light Emitting Diodes
- white LEDs are used as a backlight light source.
- the luminance of the LED corresponding to each area is obtained based on the maximum value or the average value of the luminance of the pixels in each area, and is given as LED data to the backlight driving circuit.
- display data (data for controlling the light transmittance of the liquid crystal) is generated based on the LED data and the input image, and the display data is supplied to a driving circuit for the liquid crystal panel.
- the luminance of each pixel on the screen is the product of the luminance of light from the backlight and the light transmittance based on the display data.
- the light emitted from one LED hits a plurality of areas around the corresponding area. Accordingly, the luminance of each pixel is the product of the total luminance of light emitted from the plurality of LEDs and the light transmittance based on the display data.
- suitable display data and LED data are obtained based on the input image, the light transmittance of the liquid crystal is controlled based on the display data, and the LED corresponding to each area based on the LED data.
- the input image can be displayed on the liquid crystal panel.
- the power consumption of the backlight can be reduced by decreasing the luminance of the LED corresponding to the area.
- Japanese Laid-Open Patent Publication No. 2002-108305 discloses an invention of a liquid crystal display device having a backlight dimming control and a limiter taking into account the average luminance of an input signal and a gamma adjustment value.
- Japanese Patent Application Laid-Open No. 2002-333858 discloses an invention of an image display device that adjusts a dynamic range of an image signal displayed on a display unit according to an average signal level of input pixel signals.
- 2007-140436 discloses an invention of a liquid crystal display device that changes a luminance control characteristic that defines light emission luminance of a light source with respect to a feature amount of an input video signal in accordance with a tone mode.
- Japanese Unexamined Patent Publication No. 2002-108305 Japanese Unexamined Patent Publication No. 2002-333858 Japanese Unexamined Patent Publication No. 2007-140436
- the number of LEDs included in the backlight is smaller than the number of pixels of the display panel. For this reason, when a moving image is displayed by area active driving, the maximum value (or average value) of the luminance of the pixels in the area changes for each frame, the luminance of the LED changes for each frame, and flickers on the screen. May occur. This flicker becomes more prominent when the screen is darker than when the screen is bright. Hereinafter, the flicker will be described.
- an object of the present invention is to provide an image display device that performs area active driving and can suppress the occurrence of flicker when displaying a moving image.
- a first aspect of the present invention is an image display device having a function of controlling the luminance of a backlight,
- a display panel including a plurality of display elements;
- a backlight including a plurality of light sources;
- a signal processing unit for obtaining display data and backlight control data based on the input image;
- a luminance range determining unit for determining an upper limit value and a lower limit value of the luminance of the light source;
- a panel drive circuit that outputs a signal for controlling the light transmittance of the display element to the display panel based on the display data;
- a backlight driving circuit that outputs a signal for controlling the luminance of the light source to the backlight based on the backlight control data;
- the signal processing unit divides the input image into a plurality of areas, and within each range within an upper limit value and a lower limit value determined by the luminance range determination unit. The luminance of the corresponding light source is obtained.
- An average luminance calculating unit for calculating an average luminance of the input image for one screen;
- the luminance range determining unit determines an upper limit value and a lower limit value of the luminance of the light source based on the calculated average luminance that is the average luminance calculated by the average luminance calculating unit.
- the luminance range determination unit determines the lower limit value such that the lower limit value of the luminance of the light source increases as the calculated average luminance increases.
- the luminance range determination unit determines the upper limit value so that the upper limit value of the luminance of the light source decreases as the calculated average luminance increases.
- An illuminance detector that detects the illuminance received by the display panel;
- the luminance range determining unit determines an upper limit value and a lower limit value of luminance of the light source based on detected illuminance that is illuminance detected by the illuminance detecting unit.
- a sixth aspect of the present invention is the fifth aspect of the present invention.
- the luminance range determination unit determines the lower limit value so that the lower limit value of the luminance of the light source increases as the detected illuminance increases.
- the luminance range determination unit determines the upper limit value so that the upper limit value of the luminance of the light source decreases as the detected illuminance decreases.
- the luminance range determining unit determines the upper limit value so that the upper limit value of the luminance of the light source decreases as the detected illuminance decreases when the detected illuminance is less than or equal to a predetermined illuminance, and the detection
- the lower limit value is determined such that the lower limit value of the luminance of the light source increases as the illuminance increases.
- a temperature detection unit for detecting the temperature of the backlight determines an upper limit value and a lower limit value of luminance of the light source based on a detected temperature that is a temperature detected by the temperature detecting unit.
- the luminance range determining unit determines the upper limit value so that the upper limit value of the luminance of the light source decreases as the detected temperature increases when the detected temperature is equal to or higher than a predetermined temperature.
- a moving image rate that determines whether each area is a moving image or a still image based on the input image, and calculates a ratio of the number of areas determined to be moving images to the number of the plurality of areas as a screen moving image rate A calculation unit;
- the luminance range determining unit determines an upper limit value and a lower limit value of luminance of the light source based on a calculated screen moving image rate that is a screen moving image rate calculated by the moving image rate calculating unit.
- a twelfth aspect of the present invention is the eleventh aspect of the present invention.
- the luminance range determining unit determines the lower limit value so that the lower limit value of the luminance of the light source increases as the calculated screen moving image rate increases when the calculated screen moving image rate is equal to or less than a predetermined value, and the calculation When the screen moving image rate is equal to or higher than the predetermined value, the upper limit value is determined so that the upper limit value of the luminance of the light source decreases as the calculated screen moving image rate increases.
- a histogram generation unit that generates a histogram indicating the luminance distribution of the input image;
- the luminance range determining unit determines an upper limit value and a lower limit value of the luminance of the light source based on the histogram generated by the histogram generating unit.
- a fourteenth aspect of the present invention is an image display method in an image display device including a display panel including a plurality of display elements and a backlight including a plurality of light sources, A signal processing step for obtaining display data and backlight control data based on the input image; A luminance range determining step for determining an upper limit value and a lower limit value of the luminance of the light source; A panel driving step for outputting a signal for controlling the light transmittance of the display element to the display panel based on the display data; A backlight driving step for outputting a signal for controlling the luminance of the light source to the backlight based on the backlight control data;
- the signal processing step when obtaining the backlight control data, the input image is divided into a plurality of areas, and within each range within the range between the upper limit value and the lower limit value determined in the luminance range determination step. The luminance of the corresponding light source is required.
- the image display device that controls the luminance of the light source for each area
- the upper limit value and the lower limit value of the luminance are determined in advance. For this reason, by setting the upper limit value of the luminance lower than the maximum luminance or by setting the lower limit value of the luminance higher than the minimum luminance, the luminance difference between the areas becomes smaller than that in the past. Thereby, even if the luminance of the light source in each area changes for each frame due to the moving image display, the occurrence of flicker is suppressed.
- the upper limit value and the lower limit value of the luminance of the light source are determined based on the average luminance of the image. For this reason, it is possible to determine the upper limit value and the lower limit value of the luminance of the light source in consideration of the overall brightness of the image, so that it is possible to suppress the occurrence of flicker during moving image display while suppressing the decrease in luminance. Can do.
- the lower limit of the luminance of the light source is increased as the average luminance of the image increases. For this reason, when a bright image is displayed as a whole, the luminance difference between the areas is reduced, and the occurrence of flicker is effectively suppressed. Further, when a dark image is displayed as a whole, the luminance difference between areas becomes large, so that high contrast can be obtained.
- the upper limit value of the luminance of the light source is lowered as the average luminance of the image increases. For this reason, when an overall bright image is displayed, generation of flicker is effectively suppressed by reducing the luminance difference between the areas, and the upper limit value of the luminance of the light source is reduced. Electric power and heat generation are reduced. Further, when a dark image is displayed as a whole, the luminance difference between areas becomes large, so that high contrast can be obtained.
- the upper limit value and the lower limit value of the luminance of the light source are determined based on the illuminance received by the display panel. For this reason, it is possible to determine the upper and lower limits of the brightness of the light source in consideration of the brightness of the usage environment, so that flickering during video display is suppressed while taking into consideration the dazzling feeling that people feel can do.
- the lower limit of the luminance of the light source is increased as the illuminance increases. For this reason, when the image display apparatus is used in a bright environment, the luminance difference between the areas is reduced, and the occurrence of flicker is effectively suppressed. In addition, when the image display device is used in a dark environment, the luminance difference between the areas becomes large, so that high contrast can be obtained.
- the upper limit value of the luminance of the light source is lowered as the illuminance decreases. For this reason, when the image display apparatus is used in a dark environment, the occurrence of flicker is effectively suppressed by reducing the luminance difference between areas, and the upper limit value of the luminance of the light source is reduced. The feeling of dazzling is alleviated.
- the luminance difference between areas is reduced by making the upper limit value of the luminance of the light source lower than the maximum luminance or making the lower limit value of the luminance of the light source higher than the minimum luminance. The occurrence of flicker when displaying a moving image is suppressed.
- the upper limit value and the lower limit value of the luminance of the light source are determined based on the temperature of the backlight. For this reason, it is possible to determine the upper limit value and the lower limit value of the luminance of the light source while taking into account thermal runaway caused by the rise in the temperature of the backlight.
- the upper limit value of the luminance of the light source is lowered as the backlight temperature increases. For this reason, thermal runaway due to an increase in the temperature of the backlight is suppressed, and power consumption is reduced.
- the upper limit value and the lower limit value of the luminance of the light source are determined based on the ratio of the moving image included in the image. For this reason, generation
- the luminance difference between areas decreases as the ratio of moving images included in images increases. For this reason, flicker at the time of moving image display is effectively suppressed.
- the upper limit value and the lower limit value of the luminance of the light source are determined based on the luminance distribution of the image. For this reason, since the upper limit value and the lower limit value of the luminance of the light source can be determined according to the overall tendency of the image, the luminance difference between the areas is reduced when an image in which flicker is easily visible is displayed. Thus, the occurrence of flicker can be suppressed.
- FIG. 1 is a block diagram illustrating a configuration of a liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows the detail of the backlight shown in FIG. 4 is a flowchart showing processing of an area active drive processing unit in the first embodiment.
- the said 1st Embodiment it is a figure which shows the correspondence of APL and the upper limit / lower limit of LED brightness. It is a figure which shows progress until liquid crystal data and LED data are obtained in the said 1st Embodiment.
- the said 1st Embodiment it is a figure which shows the 1st modification of the correspondence of APL and the upper limit / lower limit of LED brightness.
- the said 1st Embodiment it is a figure which shows the 2nd modification of the correspondence of APL and the upper limit / lower limit of LED brightness. It is a block diagram which shows the structure of the liquid crystal display device which concerns on the 2nd Embodiment of this invention.
- the second embodiment it is a flowchart showing the processing of the area active drive processing unit.
- the said 2nd Embodiment it is a figure which shows the correspondence of ambient illumination intensity and the upper limit / lower limit of LED brightness.
- the said 2nd Embodiment it is a figure which shows the 1st modification of the correspondence of ambient illuminance and the upper limit / lower limit of LED brightness.
- the said 2nd Embodiment it is a figure which shows the 2nd modification of the correspondence of ambient illuminance and the upper limit / lower limit of LED brightness. It is a block diagram which shows the structure of the liquid crystal display device which concerns on the 3rd Embodiment of this invention.
- the third embodiment it is a flowchart showing the processing of the area active drive processing unit.
- the said 3rd Embodiment it is a figure which shows the example of the correspondence of BLU temperature and the upper limit / lower limit of LED brightness.
- the said 4th Embodiment it is a flowchart which shows the process of an area active drive process part. It is a flowchart which shows the process of an MPL calculation part in the said 4th Embodiment. In the said 4th Embodiment, it is a figure which shows the example of the correspondence of MPL and the upper limit / lower limit of LED brightness. It is a block diagram which shows the structure of the liquid crystal display device which concerns on the 5th Embodiment of this invention. In the said 5th Embodiment, it is a flowchart which shows the process of an area active drive process part. In the said 5th Embodiment, it is a figure for demonstrating the example of analysis of a histogram (1st example).
- SYMBOLS 10 Liquid crystal display device 11 ... Liquid crystal panel 12 ... Panel drive circuit 13 ... Backlight 14 ... Backlight drive circuit 15 ... Area active drive process part 16 ... APL calculation part 21 ... Display element 22 ... LED unit 23 ... Red LED 24 ... Green LED 25 ... Blue LED DESCRIPTION OF SYMBOLS 31 ... Input image 32 ... Liquid crystal data 33 ... LED data 34 ... APL data 41 ... Ambient illuminance detection part 42 ... BLU temperature detection part 43 ... MPL calculation part 44 ... Histogram generation part 51 ... Detection illuminance data 52 ... Detection temperature data 53 ... MPL data 54 ... Histogram analysis result data
- FIG. 1 is a block diagram showing a configuration of a liquid crystal display device 10 according to the first embodiment of the present invention.
- the liquid crystal display device 10 shown in FIG. 1 includes a liquid crystal panel 11, a panel drive circuit 12, a backlight 13, a backlight drive circuit 14, an area active drive processing unit 15, and an APL calculation unit 16.
- the area active drive processing unit 15 includes a luminance range determination unit 151.
- the liquid crystal display device 10 divides the screen into a plurality of areas, and performs area active driving for driving the liquid crystal panel 11 while controlling the luminance of the backlight light source based on the input image in the area.
- m and n are integers of 2 or more
- p and q are integers of 1 or more
- at least one of p and q is an integer of 2 or more.
- An input image 31 including an R image, a G image, and a B image is input to the liquid crystal display device 10.
- Each of the R image, the G image, and the B image includes the luminance of (m ⁇ n) pixels.
- the input image 31 is given to the area active drive processing unit 15 and the APL calculation unit 16.
- the APL calculation unit 16 obtains APL data 34 representing the average luminance level of the image for one frame (hereinafter referred to as “APL” or “screen average luminance”).
- the luminance range determination unit 151 determines the upper limit value and the lower limit value of the luminance of the LEDs 23 to 25 described later based on the data value (calculated average luminance) of the APL data 34.
- the area active drive processing unit 15 displays data for use in driving the liquid crystal panel 11 (hereinafter referred to as liquid crystal data 32) and backlight control data for use in driving the backlight 13 (hereinafter referred to as LED data). 33) (details will be described later).
- the data value of the APL data 34 is simply referred to as “APL value”.
- the liquid crystal panel 11 includes (m ⁇ n ⁇ 3) display elements 21.
- the display elements 21 are arranged two-dimensionally as a whole, 3 m in the row direction (horizontal direction in FIG. 1) and n in the column direction (vertical direction in FIG. 1).
- the display element 21 includes an R display element that transmits red light, a G display element that transmits green light, and a B display element that transmits blue light.
- the R display element, the G display element, and the B display element are arranged side by side in the row direction, and three pixels form one pixel.
- the panel drive circuit 12 is a drive circuit for the liquid crystal panel 11.
- the panel drive circuit 12 outputs a signal (voltage signal) for controlling the light transmittance of the display element 21 to the liquid crystal panel 11 based on the liquid crystal data 32 output from the area active drive processing unit 15.
- the voltage output from the panel drive circuit 12 is written to a pixel electrode (not shown) in the display element 21, and the light transmittance of the display element 21 changes according to the voltage written to the pixel electrode.
- the backlight 13 is provided on the back side of the liquid crystal panel 11 and irradiates the back light of the liquid crystal panel 11 with backlight light.
- FIG. 2 is a diagram showing details of the backlight 13.
- the backlight 13 includes (p ⁇ q) LED units 22.
- the LED units 22 are two-dimensionally arranged as a whole, p in the row direction and q in the column direction.
- the LED unit 22 includes one red LED 23, one green LED 24, and one blue LED 25. Light emitted from the three LEDs 23 to 25 included in one LED unit 22 hits a part of the back surface of the liquid crystal panel 11.
- the backlight drive circuit 14 is a drive circuit for the backlight 13.
- the backlight drive circuit 14 outputs a signal (voltage signal or current signal) for controlling the luminance of the LEDs 23 to 25 to the backlight 13 based on the LED data 33 output from the area active drive processing unit 15.
- the brightness of the LEDs 23 to 25 is controlled independently of the brightness of the LEDs inside and outside the unit.
- the screen of the liquid crystal display device 10 is divided into (p ⁇ q) areas, and one LED unit 22 is associated with one area.
- the area active drive processing unit 15 obtains the luminance of the red LED 23 corresponding to each area based on the R image in each area for each of (p ⁇ q) areas. Similarly, the luminance of the green LED 24 is determined based on the G image in the area, and the luminance of the blue LED 25 is determined based on the B image in the area.
- the area active drive processing unit 15 calculates the brightness of all the LEDs 23 to 25 included in the backlight 13 and outputs LED data 33 representing the calculated LED brightness to the backlight drive circuit 14.
- the area active drive processing unit 15 obtains the luminance of the backlight light in all the display elements 21 included in the liquid crystal panel 11 based on the LED data 33. Further, the area active drive processing unit 15 obtains the light transmittance of all the display elements 21 included in the liquid crystal panel 11 based on the input image 31 and the luminance of the backlight light, and the liquid crystal data representing the obtained light transmittance. 32 is output to the panel drive circuit 12.
- the luminance of the R display element is the product of the luminance of the red light emitted from the backlight 13 and the light transmittance of the R display element.
- the light emitted from one red LED 23 hits a plurality of areas around the corresponding one area.
- the luminance of the R display element is the product of the total luminance of the light emitted from the plurality of red LEDs 23 and the light transmittance of the R display element.
- the luminance of the G display element is the product of the total luminance of light emitted from the plurality of green LEDs 24 and the light transmittance of the G display element
- the luminance of the B display element is emitted from the plurality of blue LEDs 25. This is the product of the total light luminance and the light transmittance of the B display element.
- suitable liquid crystal data 32 and LED data 33 are obtained based on the input image 31, the light transmittance of the display element 21 is controlled based on the liquid crystal data 32, and the LED data
- the input image 31 can be displayed on the liquid crystal panel 11 by controlling the luminances of the LEDs 23 to 25 based on FIG.
- the power consumption of the backlight 13 can be reduced by reducing the luminance of the LEDs 23 to 25 corresponding to the area.
- the luminance of the display element 21 corresponding to the area is switched between a smaller number of levels, so that the resolution of the image can be increased and the image quality of the display image can be improved.
- FIG. 3 is a flowchart showing the processing of the area active drive processing unit 15.
- An image of a certain color component (hereinafter referred to as color component C) included in the input image 31 is input to the area active drive processing unit 15 (step S11).
- the input image of the color component C includes the luminance of (m ⁇ n) pixels.
- the area active drive processing unit 15 performs sub-sampling processing (averaging processing) on the input image of the color component C, and the luminance of (sp ⁇ sq) (s is an integer of 2 or more) pixels.
- a reduced image is obtained (step S12).
- the input image of the color component C is reduced by (sp / m) times in the horizontal direction and (sq / n) times in the vertical direction.
- the area active drive processing unit 15 divides the reduced image into (p ⁇ q) areas (step S13). Each area includes the luminance of (s ⁇ s) pixels.
- the area active drive processing unit 15 obtains the maximum luminance value Ma of the pixels in the area and the average luminance Me of the pixels in the area (step S14).
- the luminance range determination unit 151 in the area active drive processing unit 15 determines the upper limit value and the lower limit value of the LED luminances based on the data value of the APL data 34 obtained by the APL calculation unit 16 (step S15). .
- the APL and the upper limit value / lower limit value of LED luminances are associated in advance as shown in FIG.
- the upper limit value of the LED luminance is constant (maximum luminance) regardless of the level of the APL value.
- the lower limit value of the LED luminance is a value that changes according to the APL value. Specifically, when the APL is minimum, the lower limit value of the LED luminance is gradually increased from the minimum luminance as the APL value increases.
- the area active drive processing unit 15 obtains the LED brightness for each of (p ⁇ q) areas (step S16).
- a method of determining the LED luminance for example, a method of determining based on the maximum luminance value Ma of the pixels in the area, a method of determining based on the average luminance Me of the pixels in the area, There is a method in which the maximum value Ma and the average value Me are determined by weighted averaging.
- the LED luminance is a luminance (value) within the range between the upper limit value and the lower limit value obtained in step S15. Therefore, for example, when the LED luminance obtained by the method based on the maximum luminance value Ma of the pixels in the area is lower than the lower limit value obtained in step S15, in step S16, the lower limit value is set as the LED luminance. Is done.
- the area active drive processing unit 15 applies (tp ⁇ tq) (t ⁇ tq) pieces (t) by applying a luminance diffusion filter (point diffusion filter) to the (p ⁇ q) pieces of LED luminance obtained in step S16.
- First backlight luminance data including luminance of 2 is obtained (step S17).
- step S ⁇ b> 17 (p ⁇ q) LED luminances are enlarged t times in the horizontal direction and the vertical direction, respectively.
- the area active drive processing unit 15 obtains second backlight luminance data including (m ⁇ n) luminances by performing linear interpolation processing on the first backlight luminance data (Step S1). S18).
- the first backlight luminance data is enlarged (m / tp) times in the horizontal direction and (n / tq) times in the horizontal direction.
- the second backlight luminance data is incident on the display element 21 of (m ⁇ n) color components C when the (p ⁇ q) color component C LEDs emit light with the luminance obtained in step S16. Represents the luminance of the backlight of the color component C to be reproduced.
- the area active drive processing unit 15 determines the luminance of (m ⁇ n) pixels included in the input image of the color component C, respectively (m ⁇ n) included in the second backlight luminance data.
- the light transmittance T of the display element 21 of (m ⁇ n) color components C is obtained by dividing by the luminance of (step S19).
- the area active drive processing unit 15 for the color component C the liquid crystal data 32 representing the (m ⁇ n) light transmittance obtained in step S19 and the (p ⁇ q) pieces of liquid crystal data 32 obtained in step S16.
- LED data 33 representing the LED brightness is output (step S20). At this time, the liquid crystal data 32 and the LED data 33 are converted into values in a suitable range according to the specifications of the panel drive circuit 12 and the backlight drive circuit 14.
- the area active drive processing unit 15 performs the processing shown in FIG. 3 on the R image, the G image, and the B image, and based on the input image 31 including the luminance of (m ⁇ n ⁇ 3) pixels ( Liquid crystal data 32 representing m ⁇ n ⁇ 3) transmittance and LED data 33 representing (p ⁇ q ⁇ 3) LED luminances are obtained.
- a sub-sampling process is performed on the input image of the color component C including the luminance of (1920 ⁇ 1080) pixels, thereby reducing the image including the luminance of (320 ⁇ 160) pixels. Is obtained.
- the reduced image is divided into (32 ⁇ 16) areas (area size is (10 ⁇ 10) pixels).
- the maximum value data including (32 ⁇ 16) maximum values and the average value data including (32 ⁇ 16) average values are obtained.
- an upper limit value and a lower limit value of LED luminances are determined based on the APL value. Then, considering the upper limit value / lower limit value, based on the maximum value data, based on the average value data, or based on the maximum value data and the average value data, (32 ⁇ 16) pieces LED data of the color component C representing the LED luminance is obtained.
- first backlight luminance data including (160 ⁇ 80) luminances is obtained, and linear interpolation processing is performed on the first backlight luminance data.
- second backlight luminance data including (1920 ⁇ 1080) luminances is obtained.
- the liquid crystal data of the color component C including (1920 ⁇ 1080) light transmittances is obtained.
- the area active drive processing unit 15 sequentially performs processing for each color component image. However, the processing for each color component image may be performed in a time-sharing manner. . In FIG. 3, the area active drive processing unit 15 performs sub-sampling processing on the input image to remove noise, and performs area active drive based on the reduced image, but based on the original input image. Area active drive may be performed.
- the upper limit value / lower limit value of the LED luminance is determined in advance based on the average luminance level of the image.
- the lower the APL value, the lower the lower limit value of the LED brightness, and the higher the APL value the higher the lower limit value of the LED brightness.
- the lower limit value of the LED luminance gradually increases from the minimum luminance as the APL value increases. Therefore, the maximum and minimum values of the LED luminance that can appear in one frame as the entire screen becomes brighter. The brightness difference is reduced.
- FIG. 6 is a diagram illustrating a first modification of the correspondence relationship between APL and the upper limit value / lower limit value of LED luminances.
- the lower limit value of the LED luminance is constant (minimum luminance) regardless of the level of the APL value.
- the upper limit value of the LED luminance is a value that changes according to the APL value. Specifically, when the APL is the minimum, the upper limit value of the LED luminance is gradually decreased from the maximum luminance as the APL value increases. That is, the upper limit value of the LED brightness gradually decreases as the screen becomes brighter as a whole.
- the brightness difference between the maximum value and the minimum value of the LED brightness that can appear in one frame becomes smaller as the screen becomes brighter as a whole.
- the occurrence of flicker is suppressed during moving image display.
- the upper limit value of the LED luminances decreases as the screen becomes brighter as a whole, the power consumption is reduced and the heat generation amount is also reduced.
- the dazzling feeling when displaying a bright image as a whole is alleviated.
- the APL value is low, the brightness difference between the maximum value and the minimum value of the LED brightness that can appear in one frame becomes large, so that an overall dark image is displayed as in the first embodiment. High contrast can be obtained.
- FIG. 7 is a diagram illustrating a second modification of the correspondence relationship between APL and the upper limit value / lower limit value of LED luminances.
- the lower limit value of the LED luminance is increased from the minimum luminance at a relatively high rate as the APL value increases.
- the increase in APL is slight.
- the correspondence between the APL and the upper limit value / lower limit value of the LED luminances is as shown in FIG. 4, the luminance difference between the areas is not so small.
- the luminance difference between areas is effectively reduced by increasing the lower limit value of the LED luminance, and the occurrence of flicker is effectively suppressed.
- the upper limit value of the LED luminance is gradually lowered from the maximum luminance as the APL value increases.
- effects such as a reduction in power consumption, a reduction in the amount of heat generation, and a reduction in glare can be obtained.
- FIG. 8 is a block diagram showing the configuration of the liquid crystal display device 10 according to the second embodiment of the present invention.
- an ambient illuminance detector 41 is provided in place of the APL calculator 16 in the first embodiment. Since the configuration other than the ambient illuminance detection unit 41 is the same as that of the first embodiment, description thereof is omitted.
- the ambient illuminance detection unit 41 detects the brightness (illuminance) around the liquid crystal display device 10 and outputs a value indicating the detected illuminance as detected illuminance data 51.
- the brightness range determination unit 151 determines the upper limit value and the lower limit value of the LED brightness based on the data value of the detected illuminance data 51. In the following, the data value of the detected illuminance data 51 is simply referred to as “detected illuminance”.
- FIG. 9 is a flowchart showing the processing of the area active drive processing unit 15 in the present embodiment.
- the luminance range determination unit 151 in the area active drive processing unit 15 determines the LED luminance based on the data value (detected illuminance) of the detected illuminance data 51 output from the ambient illuminance detection unit 41. Determine the upper and lower limits. Note that the processing contents in steps other than step S15 are the same as those in the first embodiment, and a description thereof will be omitted.
- the ambient illuminance and the upper limit value / lower limit value of LED luminances are associated in advance as shown in FIG.
- the upper limit value of the LED luminance is constant (maximum luminance) regardless of the detected illuminance level.
- the lower limit value of the LED luminance is a value that changes according to the detected illuminance. Specifically, when the ambient illuminance is minimum, the lower limit value of the LED luminance is gradually increased from the minimum luminance as the detected illuminance increases.
- the lower limit value of the LED brightness increases as the detected illuminance increases, so that the brightness between the maximum value and the minimum value of the LED brightness that can appear in one frame as the surroundings of the liquid crystal display device become brighter.
- the difference becomes smaller.
- the occurrence of flicker during moving image display is suppressed.
- the surroundings (use environment) of the liquid crystal display device is dark, the brightness difference between the maximum value and the minimum value of the LED brightness that can appear in one frame becomes large, so that high contrast can be obtained.
- FIG. 11 is a diagram illustrating a first modification of the correspondence relationship between ambient illuminance and the upper limit value / lower limit value of LED luminances.
- the lower limit value of the LED luminance is constant (minimum luminance) regardless of the detected illuminance level.
- the upper limit value of the LED luminance is a value that changes according to the detected illuminance. Specifically, when the ambient illuminance is maximum, the upper limit value of the LED luminance is gradually decreased from the maximum luminance as the detected illuminance decreases.
- the upper limit value of the LED luminance decreases as the ambient illuminance decreases, so that the luminance between the maximum value and the minimum value of the LED luminance that can appear in one frame as the periphery of the liquid crystal display device becomes darker.
- the difference becomes smaller.
- FIG. 12 is a diagram illustrating a second modification of the correspondence relationship between ambient illuminance and the upper limit value / lower limit value of LED luminances.
- the upper limit value / lower limit value of the LED brightness is a value that changes according to the detected illuminance, and when the ambient illuminance is greater than or equal to the predetermined value, / The lower limit is fixed regardless of the detected illuminance.
- the upper limit value of the LED luminance is gradually decreased from the maximum luminance as the detected illuminance decreases, when the ambient illuminance is the predetermined value.
- the lower limit value of the LED luminance is gradually increased from the minimum luminance as the detected illuminance increases until the detected illuminance reaches the predetermined value when the ambient illuminance is minimum.
- the brightness difference between the maximum value and the minimum value of LED brightness that can appear in one frame is made smaller than before, regardless of the ambient illuminance. For this reason, the occurrence of flicker during moving image display is suppressed regardless of the usage environment of the liquid crystal display device. Also.
- the upper limit value of the LED luminance is low, so that the dazzling feeling when the liquid crystal display device is used in a dark environment is reduced.
- the lower limit value of the LED luminance is low when the detected illuminance is low, high contrast can be obtained when the liquid crystal display device is used in a dark environment.
- FIG. 13 is a block diagram showing the configuration of the liquid crystal display device 10 according to the third embodiment of the present invention.
- a BLU temperature detector 42 is provided in place of the APL calculator 16 in the first embodiment. Since the configuration other than the BLU temperature detection unit 42 is the same as that of the first embodiment, description thereof is omitted.
- the BLU temperature detection unit 42 detects the temperature of the backlight 13 provided in the liquid crystal display device 10 (hereinafter referred to as “BLU temperature”), and outputs a value indicating the detected temperature as detected temperature data 52. To do.
- the brightness range determination unit 151 determines the upper limit value and the lower limit value of the LED brightness based on the data value of the detected temperature data 52. In the following, the data value of the detected temperature data 52 is simply referred to as “detected temperature”.
- FIG. 14 is a flowchart showing processing of the area active drive processing unit 15 in the present embodiment.
- the luminance range determining unit 151 in the area active drive processing unit 15 determines the LED luminance based on the data value (detected temperature) of the detected temperature data 52 output from the BLU temperature detecting unit 42. Determine the upper and lower limits. Note that the processing contents in steps other than step S15 are the same as those in the first embodiment, and a description thereof will be omitted.
- the BLU temperature and the upper limit value / lower limit value of LED luminances are associated in advance as shown in FIG.
- the lower limit value of LED luminance is constant (minimum luminance) regardless of the detected temperature.
- the upper limit value of the LED luminance is constant (maximum luminance) when the BLU temperature is equal to or lower than a predetermined value, and is changed according to the detected temperature when the BLU temperature is equal to or higher than the predetermined value. Specifically, when the BLU temperature is the predetermined value, the upper limit value of the LED luminance is gradually lowered as the detected temperature increases.
- the upper limit value of the LED luminance is lowered as the backlight temperature increases. For this reason, thermal runaway due to an increase in the temperature of the backlight is suppressed, and power consumption is reduced. Further, when the backlight temperature is low, the upper limit value of the LED luminance is increased, so that insufficient luminance is suppressed.
- FIG. 16 is a block diagram showing a configuration of a liquid crystal display device 10 according to the fourth embodiment of the present invention.
- an MPL calculation unit 43 is provided instead of the APL calculation unit 16 in the first embodiment. Since the configuration other than the MPL calculation unit 43 is the same as that of the first embodiment, description thereof is omitted.
- the MPL calculation unit 43 determines whether each area is a moving image or a still image based on the input image 31, and the ratio of the number of moving image areas to the total number of areas (hereinafter referred to as "MPL" or "screen moving image rate”). ) MPL data 53 is obtained.
- the brightness range determination unit 151 determines the upper limit value and the lower limit value of the LED brightness based on the data value (calculated screen moving image rate) of the MPL data 53. In the following, the data value of the MPL data 53 is simply referred to as “MPL value”.
- FIG. 17 is a flowchart showing the process of the area active drive processing unit 15 in the present embodiment.
- the luminance range determination unit 151 in the area active drive processing unit 15 determines the upper limit value and the lower limit value of LED luminances based on the MPL value obtained by the MPL calculation unit 43. Note that the processing contents in steps other than step S15 are the same as those in the first embodiment, and a description thereof will be omitted.
- FIG. 18 is a flowchart showing the processing of the MPL calculation unit 43.
- the MPL calculation unit 43 obtains the average value Me of the luminance of the pixels in the area for one of the (p ⁇ q) areas described above (step S31). As will be described later, by repeating the processing from step S31 to step S35, when proceeding to step S36, the average value Me is obtained for all (p ⁇ q) areas.
- the average value obtained during the processing of the current frame is indicated by “Me (n)”, and the average value obtained during the processing one frame before (previous frame) is represented by “Me (n)”. -1) ".
- the MPL calculation unit 43 determines whether or not the difference between the average value Me (n) in the current frame and the average value Me (n ⁇ 1) in the previous frame is greater than a predetermined threshold Th (Step S1). S32). As a result, if the difference between Me (n) and Me (n ⁇ 1) is larger than the threshold Th, the MPL calculation unit 43 determines that the area is a moving image area (step S33). On the other hand, if the difference between Me (n) and Me (n ⁇ 1) is less than or equal to the threshold Th, the MPL calculation unit 43 determines that the area is a still image area (step S34).
- the threshold value Th can be arbitrarily set.
- the MPL calculation unit 43 determines whether or not the determination as to whether the area is a moving image area or a still image area has been completed for all (p ⁇ q) areas. As a result, if completed, the process proceeds to step S36, and if not completed, the process returns to step S31. In this way, the processing from step S31 to step S35 is repeated (p ⁇ q) times.
- step S36 the MPL calculating unit 43 calculates the MPL (screen moving image rate) by dividing the number of areas determined to be moving image areas by the total number of areas.
- step S15 shown in FIG. 17 the upper limit value and the lower limit value of the LED luminances are determined based on the MPL calculated in this way.
- the MPL and the upper limit value / lower limit value of the LED luminances are associated in advance as shown in FIG.
- the upper limit value of LED luminances is constant (maximum luminance) when the MPL value is equal to or less than a predetermined value, and is a value that changes according to the MPL value when the MPL value is equal to or greater than the predetermined value. Specifically, when the MPL is the above predetermined value, the upper limit value of the LED luminance is gradually lowered from the maximum luminance as the MPL value increases.
- the lower limit value of the LED brightness is constant when the MPL value is equal to or greater than the predetermined value, and is a value that changes according to the MPL value when the MPL value is equal to or smaller than the predetermined value. Specifically, when the MPL is the minimum, the lower limit value of the LED luminance is gradually increased from the minimum luminance as the MPL value increases until the MPL value reaches the predetermined value.
- FIG. 20 is a block diagram showing a configuration of a liquid crystal display device 10 according to the fifth embodiment of the present invention.
- a histogram generation unit 44 is provided instead of the APL calculation unit 16 in the first embodiment. Since the configuration other than the histogram generation unit 44 is the same as that of the first embodiment, description thereof is omitted.
- the histogram generation unit 44 generates a histogram indicating the luminance distribution of the image for one frame based on the input image 31. Then, the histogram generation unit 44 analyzes image tendencies (for example, “entirely bright image”, “entirely dark image”, “high and low luminance mixed image”, etc.) based on the histogram. The analysis result is output as histogram analysis result data 54.
- the brightness range determination unit 151 determines the upper limit value and the lower limit value of the LED brightness based on the histogram analysis result data 54.
- FIG. 21 is a flowchart showing the process of the area active drive processing unit 15 in the present embodiment.
- the luminance range determination unit 151 in the area active drive processing unit 15 sets the upper limit value and the lower limit value of the LED luminances based on the histogram analysis result data 54 output from the histogram generation unit 44. decide. Note that the processing contents in steps other than step S15 are the same as those in the first embodiment, and a description thereof will be omitted.
- the relationship between the histogram generated by the histogram generation unit 44 and the upper limit value / lower limit value of LED luminances will be described with an example.
- the histogram is as shown in FIG. 22 (first example)
- the lower limit value of the LED luminance is set to a low value.
- the histogram is as shown in FIG. 23 (second example)
- the luminance difference between the areas is relatively small, flicker due to moving image display is not easily recognized. Therefore, the lower limit value of the LED luminance is set to a low value.
- the histogram is as shown in FIG. 24 (third example), it is understood that there are a relatively large number of high-luminance images when high-luminance images and low-luminance images are mixed. At this time, the luminance difference between the areas is relatively large, but since a bright image is displayed as a whole, flicker due to moving image display is difficult to be visually recognized. Therefore, the lower limit value of the LED luminance is set to a low value.
- the histogram is as shown in FIG. 25 (fourth example), it is understood that there are a relatively large number of low-brightness images when high-brightness images and low-brightness images are mixed. At this time, the luminance difference between the areas becomes relatively large, and since a dark image is displayed as a whole, flicker due to moving image display is easily visible. Therefore, the lower limit value of the LED luminance is set to a high value.
- the upper limit value / lower limit value of LED luminances are determined based on the luminance distribution of the input image. That is, as in the first to fourth examples, the upper limit value / lower limit value of the LED luminance can be changed according to the overall tendency of the image. For this reason, when an image in which flicker is easily visible is displayed, the upper limit value / lower limit value of the LED luminance can be determined in advance so that the luminance difference between the areas becomes small, and the occurrence of flicker is effectively achieved. It is suppressed.
- the backlight 13 is configured by the red LED 23, the green LED 24, and the blue LED 25.
- the backlight may be configured by a white LED, a cold cathode fluorescent lamp (CCFL), or the like.
- the area active drive processing unit 15 When the backlight is configured with white LEDs, the area active drive processing unit 15 generates a Y image (luminance image) based on, for example, the R image, the G image, and the B image, and performs steps in the processing illustrated in FIG. S11 to S18 may be performed on the Y image, and step S19 may be performed on the combination of each of the three color images and the Y image.
- the LED unit 22 includes one red LED 23, one green LED 24, and one blue LED 25.
- the number of three color LEDs included in the LED unit 22 may be other than this.
- the LED unit 22 may include one red LED 23 and one blue LED 25 and two green LEDs 24.
- the backlight drive circuit 14 may control the two green LEDs 24 so that the total luminance of the two green LEDs 24 becomes the LED luminance determined in step S16.
- the frame rate in the liquid crystal display device may be arbitrary, for example, 30 Hz, 60 Hz, 120 Hz, or higher.
- the higher the frame rate the less the flicker becomes noticeable because the brightness of the LED changes in smaller units.
- the upper limit value and the lower limit value of the LED luminance as described above in an arbitrary image display device provided with a backlight, the same effect as in the case of the liquid crystal display device can be obtained.
Abstract
Description
複数の表示素子を含む表示パネルと、
複数の光源を含むバックライトと、
入力画像に基づき、表示用データとバックライト制御データを求める信号処理部と、
前記光源の輝度の上限値および下限値を決定する輝度範囲決定部と、
前記表示用データに基づき、前記表示パネルに対して前記表示素子の光透過率を制御する信号を出力するパネル駆動回路と、
前記バックライト制御データに基づき、前記バックライトに対して前記光源の輝度を制御する信号を出力するバックライト駆動回路とを備え、
前記信号処理部は、前記バックライト制御データを求めるときに、前記入力画像を複数のエリアに分割し、前記輝度範囲決定部によって決定された上限値と下限値との範囲内で、各エリアに対応した光源の輝度を求めることを特徴とする。
1画面分の前記入力画像の平均輝度を算出する平均輝度算出部を更に備え、
前記輝度範囲決定部は、前記平均輝度算出部によって算出された平均輝度である算出平均輝度に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする。
前記輝度範囲決定部は、前記算出平均輝度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定することを特徴とする。
前記輝度範囲決定部は、前記算出平均輝度が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする。
前記表示パネルの受ける照度を検出する照度検出部を更に備え、
前記輝度範囲決定部は、前記照度検出部によって検出された照度である検出照度に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする。
前記輝度範囲決定部は、前記検出照度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定することを特徴とする。
前記輝度範囲決定部は、前記検出照度が低くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする。
前記輝度範囲決定部は、前記検出照度が所定の照度以下であるときに、前記検出照度が低くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定し、かつ、前記検出照度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定することを特徴とする。
前記バックライトの温度を検出する温度検出部を更に備え、
前記輝度範囲決定部は、前記温度検出部によって検出された温度である検出温度に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする。
前記輝度範囲決定部は、前記検出温度が所定の温度以上であるときに、前記検出温度が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする。
前記入力画像に基づき、エリア毎に動画であるか静止画であるかを判定し、動画であると判定されたエリアの数の前記複数のエリアの数に対する割合を画面動画率として算出する動画率算出部を更に備え、
前記輝度範囲決定部は、前記動画率算出部によって算出された画面動画率である算出画面動画率に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする。
前記輝度範囲決定部は、前記算出画面動画率が所定値以下であるときには、前記算出画面動画率が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定し、前記算出画面動画率が前記所定値以上であるときには、前記算出画面動画率が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする。
前記入力画像の輝度の分布を示すヒストグラムを生成するヒストグラム生成部を更に備え、
前記輝度範囲決定部は、前記ヒストグラム生成部によって生成されたヒストグラムに基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする。
入力画像に基づき、表示用データとバックライト制御データを求める信号処理ステップと、
前記光源の輝度の上限値および下限値を決定する輝度範囲決定ステップと、
前記表示用データに基づき、前記表示パネルに対して前記表示素子の光透過率を制御する信号を出力するパネル駆動ステップと、
前記バックライト制御データに基づき、前記バックライトに対して前記光源の輝度を制御する信号を出力するバックライト駆動ステップとを備え、
前記信号処理ステップでは、前記バックライト制御データを求めるときに、前記入力画像が複数のエリアに分割され、前記輝度範囲決定ステップで決定された上限値と下限値との範囲内で、各エリアに対応した光源の輝度が求められることを特徴とする。
11…液晶パネル
12…パネル駆動回路
13…バックライト
14…バックライト駆動回路
15…エリアアクティブ駆動処理部
16…APL算出部
21…表示素子
22…LEDユニット
23…赤色LED
24…緑色LED
25…青色LED
31…入力画像
32…液晶データ
33…LEDデータ
34…APLデータ
41…周囲照度検出部
42…BLU温度検出部
43…MPL算出部
44…ヒストグラム生成部
51…検出照度データ
52…検出温度データ
53…MPLデータ
54…ヒストグラム解析結果データ
<1.1 全体的な構成および動作概要>
図1は、本発明の第1の実施形態に係る液晶表示装置10の構成を示すブロック図である。図1に示す液晶表示装置10は、液晶パネル11、パネル駆動回路12、バックライト13、バックライト駆動回路14、エリアアクティブ駆動処理部15、および、APL算出部16を備えている。エリアアクティブ駆動処理部15には、輝度範囲決定部151が含まれている。液晶表示装置10は、画面を複数のエリアに分割し、エリア内の入力画像に基づきバックライト光源の輝度を制御しながら、液晶パネル11を駆動するエリアアクティブ駆動を行う。以下、mとnは2以上の整数、pとqは1以上の整数、pとqのうち少なくとも一方は2以上の整数であるとする。
図3は、エリアアクティブ駆動処理部15の処理を示すフローチャートである。エリアアクティブ駆動処理部15には、入力画像31に含まれるある色成分(以下、色成分Cという)の画像が入力される(ステップS11)。色成分Cの入力画像には(m×n)個の画素の輝度が含まれる。
本実施形態によれば、エリアアクティブ駆動を行う液晶表示装置において各エリアに対応したLEDの輝度を求める際に、画像の平均輝度レベルに基づいて、予めLED輝度の上限値/下限値が決定される。詳しくは、図4に示すように、APL値が低いほどLED輝度の下限値も低い値とされ、APL値が高いほどLED輝度の下限値も高い値とされる。このように、APL値が高くなるにつれてLED輝度の下限値が最小輝度から徐々に上昇するので、画面が全体的に明るくなるにつれて、1フレーム中に現れ得るLED輝度の最大値と最小値との輝度差が小さくなる。これにより、動画表示によって各エリアのLEDの輝度がフレーム毎に変化しても、エリア間の輝度差が従来よりも小さくなるので、フリッカの発生が抑制される。また、APL値が低い時には、1フレーム中に現れ得るLED輝度の最大値と最小値との輝度差が大きくなる。このため、全体的に暗い画像の表示が行われるときには、高いコントラストが得られる。
上記第1の実施形態においては、APLとLED輝度の上限値/下限値との対応関係は図4に示すようになっていたが、本発明はこれに限定されない。以下、上記対応関係の変形例を示す。
図6は、APLとLED輝度の上限値/下限値との対応関係の第1の変形例を示す図である。本変形例では、LED輝度の下限値については、APL値の高低にかかわらず一定(最小輝度)とされる。一方、LED輝度の上限値については、APL値に応じて変化する値とされる。詳しくは、APLが最小のときを基準とすると、APL値が高くなるに従って、LED輝度の上限値は最大輝度から徐々に低くされる。すなわち、画面が全体的に明るくなるにつれて、LED輝度の上限値は徐々に低下する。
図7は、APLとLED輝度の上限値/下限値との対応関係の第2の変形例を示す図である。本変形例では、APLが低い時(参照符号71で示す範囲にある時)には、APL値が高くなるに従って、LED輝度の下限値が比較的高い割合で最小輝度から高められる。例えば、真っ暗の画像が表示されている状態から図26に示したような白いバーが表示される状態に移るような場合には、APLの上昇は僅かである。このため、APLとLED輝度の上限値/下限値との対応関係が図4に示したようなものである場合には、エリア間の輝度差はあまり小さくはならない。一方、図7に示した対応関係であれば、LED輝度の下限値が高められることによりエリア間の輝度差が効果的に小さくされ、フリッカの発生が効果的に抑制される。
<2.1 全体構成および処理手順>
図8は、本発明の第2の実施形態に係る液晶表示装置10の構成を示すブロック図である。本実施形態においては、上記第1の実施形態におけるAPL算出部16に替えて、周囲照度検出部41が設けられている。なお、周囲照度検出部41以外の構成については、上記第1の実施形態と同様であるので、説明を省略する。
本実施形態によれば、検出照度が高くなるにつれてLED輝度の下限値は上昇するので、液晶表示装置の周囲が明るくなるにつれて、1フレーム中に現れ得るLED輝度の最大値と最小値との輝度差が小さくなる。これにより、液晶表示装置が明るい環境下で使用されている時に、動画表示の際のフリッカの発生が抑制される。また、液晶表示装置の周囲(使用環境)が暗い時には、1フレーム中に現れ得るLED輝度の最大値と最小値との輝度差が大きくなるので、高いコントラストが得られる。
上記第1の実施形態においては、周囲照度とLED輝度の上限値/下限値との対応関係は図10に示すようになっていたが、本発明はこれに限定されない。以下、上記対応関係の変形例を示す。
図11は、周囲照度とLED輝度の上限値/下限値との対応関係の第1の変形例を示す図である。本変形例では、LED輝度の下限値については、検出照度の高低にかかわらず一定(最小輝度)とされる。一方、LED輝度の上限値については、検出照度に応じて変化する値とされる。詳しくは、周囲照度が最大のときを基準とすると、検出照度が低くなるに従って、LED輝度の上限値は最大輝度から徐々に低くされる。
図12は、周囲照度とLED輝度の上限値/下限値との対応関係の第2の変形例を示す図である。本変形例では、周囲照度が所定値以下であるときには、LED輝度の上限値/下限値は検出照度に応じて変化する値とされ、周囲照度が所定値以上であるときには、LED輝度の上限値/下限値は検出照度にかかわらず一定とされる。詳しくは、LED輝度の上限値については、周囲照度が上記所定値のときを基準とすると、検出照度が低くなるに従って最大輝度から徐々に低くされる。一方、LED輝度の下限値については、周囲照度が最小のときを基準とすると、検出照度が上記所定値になるまでは、検出照度が高くなるに従って最小輝度から徐々に高くされる。
<3.1 全体構成および処理手順>
図13は、本発明の第3の実施形態に係る液晶表示装置10の構成を示すブロック図である。本実施形態においては、上記第1の実施形態におけるAPL算出部16に替えて、BLU温度検出部42が設けられている。なお、BLU温度検出部42以外の構成については、上記第1の実施形態と同様であるので、説明を省略する。
本実施形態によれば、バックライトの温度が所定温度以上になれば、バックライトの温度が高くなるにつれてLED輝度の上限値が低くされる。このため、バックライトの温度の上昇に起因する熱暴走が抑制されるとともに、消費電力が低減される。また、バックライトの温度が低い時にはLED輝度の上限値が高くされるので、輝度不足が抑制される。
<4.1 全体構成および処理手順>
図16は、本発明の第4の実施形態に係る液晶表示装置10の構成を示すブロック図である。本実施形態においては、上記第1の実施形態におけるAPL算出部16に替えて、MPL算出部43が設けられている。なお、MPL算出部43以外の構成については、上記第1の実施形態と同様であるので、説明を省略する。
本実施形態によれば、MPL値が高くなるにつれて、1フレーム中に現れ得るLED輝度の最大値と最小値との輝度差が小さくなる。すなわち、画面中に動画像が多くなるほどエリア間の輝度差は小さくなる。このため、動画表示の際のフリッカが効果的に抑制される。
<5.1 全体構成および処理手順>
図20は、本発明の第5の実施形態に係る液晶表示装置10の構成を示すブロック図である。本実施形態においては、上記第1の実施形態におけるAPL算出部16に替えて、ヒストグラム生成部44が設けられている。なお、ヒストグラム生成部44以外の構成については、上記第1の実施形態と同様であるので、説明を省略する。
本実施形態によれば、入力画像の輝度の分布に基づいて、LED輝度の上限値/下限値が決定される。すなわち、上記第1~第4の例のように、画像の全体的な傾向に応じて、LED輝度の上限値/下限値を変化させることができる。このため、フリッカが視認されやすい画像が表示される際に、エリア間の輝度差が小さくなるように予めLED輝度の上限値/下限値を定めておくことができ、フリッカの発生が効果的に抑制される。
上記各実施形態では、バックライト13は赤色LED23、緑色LED24および青色LED25で構成されているが、バックライトを白色LEDや冷陰極管(CCFL:Cold Cathode Fluorescent Lamp )などで構成してもよい。バックライトを白色LEDで構成した場合には、エリアアクティブ駆動処理部15は、例えば、R画像、G画像およびB画像に基づきY画像(輝度画像)を生成し、図3に示す処理のうちステップS11~S18をY画像に対して行い、ステップS19を3色の画像のそれぞれとY画像の組合せに対して行えばよい。
Claims (26)
- バックライトの輝度を制御する機能を有する画像表示装置であって、
複数の表示素子を含む表示パネルと、
複数の光源を含むバックライトと、
入力画像に基づき、表示用データとバックライト制御データを求める信号処理部と、
前記光源の輝度の上限値および下限値を決定する輝度範囲決定部と、
前記表示用データに基づき、前記表示パネルに対して前記表示素子の光透過率を制御する信号を出力するパネル駆動回路と、
前記バックライト制御データに基づき、前記バックライトに対して前記光源の輝度を制御する信号を出力するバックライト駆動回路とを備え、
前記信号処理部は、前記バックライト制御データを求めるときに、前記入力画像を複数のエリアに分割し、前記輝度範囲決定部によって決定された上限値と下限値との範囲内で、各エリアに対応した光源の輝度を求めることを特徴とする、画像表示装置。 - 1画面分の前記入力画像の平均輝度を算出する平均輝度算出部を更に備え、
前記輝度範囲決定部は、前記平均輝度算出部によって算出された平均輝度である算出平均輝度に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする、請求項1に記載の画像表示装置。 - 前記輝度範囲決定部は、前記算出平均輝度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定することを特徴とする、請求項2に記載の画像表示装置。
- 前記輝度範囲決定部は、前記算出平均輝度が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする、請求項2に記載の画像表示装置。
- 前記表示パネルの受ける照度を検出する照度検出部を更に備え、
前記輝度範囲決定部は、前記照度検出部によって検出された照度である検出照度に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする、請求項1に記載の画像表示装置。 - 前記輝度範囲決定部は、前記検出照度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定することを特徴とする、請求項5に記載の画像表示装置。
- 前記輝度範囲決定部は、前記検出照度が低くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする、請求項5に記載の画像表示装置。
- 前記輝度範囲決定部は、前記検出照度が所定の照度以下であるときに、前記検出照度が低くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定し、かつ、前記検出照度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定することを特徴とする、請求項5に記載の画像表示装置。
- 前記バックライトの温度を検出する温度検出部を更に備え、
前記輝度範囲決定部は、前記温度検出部によって検出された温度である検出温度に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする、請求項1に記載の画像表示装置。 - 前記輝度範囲決定部は、前記検出温度が所定の温度以上であるときに、前記検出温度が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする、請求項9に記載の画像表示装置。
- 前記入力画像に基づき、エリア毎に動画であるか静止画であるかを判定し、動画であると判定されたエリアの数の前記複数のエリアの数に対する割合を画面動画率として算出する動画率算出部を更に備え、
前記輝度範囲決定部は、前記動画率算出部によって算出された画面動画率である算出画面動画率に基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする、請求項1に記載の画像表示装置。 - 前記輝度範囲決定部は、前記算出画面動画率が所定値以下であるときには、前記算出画面動画率が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値を決定し、前記算出画面動画率が前記所定値以上であるときには、前記算出画面動画率が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値を決定することを特徴とする、請求項11に記載の画像表示装置。
- 前記入力画像の輝度の分布を示すヒストグラムを生成するヒストグラム生成部を更に備え、
前記輝度範囲決定部は、前記ヒストグラム生成部によって生成されたヒストグラムに基づいて、前記光源の輝度の上限値および下限値を決定することを特徴とする、請求項1に記載の画像表示装置。 - 複数の表示素子を含む表示パネルと複数の光源を含むバックライトとを備えた画像表示装置における画像表示方法であって、
入力画像に基づき、表示用データとバックライト制御データを求める信号処理ステップと、
前記光源の輝度の上限値および下限値を決定する輝度範囲決定ステップと、
前記表示用データに基づき、前記表示パネルに対して前記表示素子の光透過率を制御する信号を出力するパネル駆動ステップと、
前記バックライト制御データに基づき、前記バックライトに対して前記光源の輝度を制御する信号を出力するバックライト駆動ステップとを備え、
前記信号処理ステップでは、前記バックライト制御データを求めるときに、前記入力画像が複数のエリアに分割され、前記輝度範囲決定ステップで決定された上限値と下限値との範囲内で、各エリアに対応した光源の輝度が求められることを特徴とする、画像表示方法。 - 1画面分の前記入力画像の平均輝度を算出する平均輝度算出ステップを更に備え、
前記輝度範囲決定ステップでは、前記平均輝度算出ステップで算出された平均輝度である算出平均輝度に基づいて、前記光源の輝度の上限値および下限値が決定されることを特徴とする、請求項14に記載の画像表示方法。 - 前記輝度範囲決定ステップでは、前記算出平均輝度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値が決定されることを特徴とする、請求項15に記載の画像表示方法。
- 前記輝度範囲決定ステップでは、前記算出平均輝度が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値が決定されることを特徴とする、請求項15に記載の画像表示方法。
- 前記表示パネルの受ける照度を検出する照度検出ステップを更に備え、
前記輝度範囲決定ステップでは、前記照度検出ステップで検出された照度である検出照度に基づいて、前記光源の輝度の上限値および下限値が決定されることを特徴とする、請求項14に記載の画像表示方法。 - 前記輝度範囲決定ステップでは、前記検出照度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値が決定されることを特徴とする、請求項18に記載の画像表示方法。
- 前記輝度範囲決定ステップでは、前記検出照度が低くなるに従って前記光源の輝度の上限値が低くなるように該上限値が決定されることを特徴とする、請求項18に記載の画像表示方法。
- 前記輝度範囲決定ステップでは、前記検出照度が所定の照度以下であるときに、前記検出照度が低くなるに従って前記光源の輝度の上限値が低くなるように該上限値が決定され、かつ、前記検出照度が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値が決定されることを特徴とする、請求項18に記載の画像表示方法。
- 前記バックライトの温度を検出する温度検出ステップを更に備え、
前記輝度範囲決定ステップでは、前記温度検出ステップで検出された温度である検出温度に基づいて、前記光源の輝度の上限値および下限値が決定されることを特徴とする、請求項14に記載の画像表示方法。 - 前記輝度範囲決定ステップでは、前記検出温度が所定の温度以上であるときに、前記検出温度が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値が決定されることを特徴とする、請求項22に記載の画像表示方法。
- 前記入力画像に基づき、エリア毎に動画であるか静止画であるかを判定し、動画であると判定されたエリアの数の前記複数のエリアの数に対する割合を画面動画率として算出する動画率算出ステップを更に備え、
前記輝度範囲決定ステップでは、前記動画率算出ステップで算出された画面動画率である算出画面動画率に基づいて、前記光源の輝度の上限値および下限値が決定されることを特徴とする、請求項14に記載の画像表示方法。 - 前記輝度範囲決定ステップでは、前記算出画面動画率が所定値以下であるときには、前記算出画面動画率が高くなるに従って前記光源の輝度の下限値が高くなるように該下限値が決定され、前記算出画面動画率が前記所定値以上であるときには、前記算出画面動画率が高くなるに従って前記光源の輝度の上限値が低くなるように該上限値が決定されることを特徴とする、請求項24に記載の画像表示方法。
- 前記入力画像の輝度の分布を示すヒストグラムを生成するヒストグラム生成ステップを更に備え、
前記輝度範囲決定ステップでは、前記ヒストグラム生成ステップで生成されたヒストグラムに基づいて、前記光源の輝度の上限値および下限値が決定されることを特徴とする、請求項14に記載の画像表示方法。
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JP2009551396A JP4979776B2 (ja) | 2008-01-31 | 2008-10-09 | 画像表示装置および画像表示方法 |
US12/681,756 US20100225574A1 (en) | 2008-01-31 | 2008-10-09 | Image display device and image display method |
EP08871823A EP2237258A4 (en) | 2008-01-31 | 2008-10-09 | IMAGE DISPLAY DEVICE AND IMAGE DISPLAY METHOD |
CN200880116524.XA CN101861618B (zh) | 2008-01-31 | 2008-10-09 | 图像显示装置和图像显示方法 |
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CN101861618B (zh) | 2012-10-31 |
US20100225574A1 (en) | 2010-09-09 |
CN101861618A (zh) | 2010-10-13 |
JPWO2009096068A1 (ja) | 2011-05-26 |
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