WO2014208383A1 - 表示装置、及び表示装置の制御方法 - Google Patents
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- WO2014208383A1 WO2014208383A1 PCT/JP2014/065897 JP2014065897W WO2014208383A1 WO 2014208383 A1 WO2014208383 A1 WO 2014208383A1 JP 2014065897 W JP2014065897 W JP 2014065897W WO 2014208383 A1 WO2014208383 A1 WO 2014208383A1
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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
- G09G3/2007—Display of intermediate tones
- G09G3/2018—Display of intermediate tones by time modulation using two or more time intervals
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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
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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
- G09G2310/00—Command of the display device
- G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
- G09G2310/0243—Details of the generation of driving signals
- G09G2310/0248—Precharge or discharge of column electrodes before or after applying exact column voltages
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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
- G09G2320/0252—Improving the response speed
-
- 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
- G09G2320/0271—Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
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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
- G09G2320/0285—Improving the quality of display appearance using tables for spatial correction of 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
- 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
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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
- G09G2340/00—Aspects of display data processing
- G09G2340/16—Determination of a pixel data signal depending on the signal applied in the previous frame
Definitions
- the present invention relates to a display device that displays an image using a liquid crystal panel, and a control method for the display device.
- the response of the brightness change is slow depending on the amount of change in the brightness of the pixel, and the image quality of the moving image may deteriorate. For example, so-called tailing occurs in which a moving object in a moving image is displayed as if it is tailed. Therefore, the display device changes the brightness of the pixel by changing the brightness of the pixel by a change amount that makes the response of the brightness change faster, and then changes the brightness to the target brightness, thereby changing the brightness.
- Overdrive control is performed to improve the response.
- Patent Document 1 discloses a technique for appropriately determining parameters for overdrive control.
- a liquid crystal is oriented vertically with respect to a display surface to express a light non-transmission state, and a light transmission state is expressed using a refractive index that changes by tilting the liquid crystal by applying a voltage.
- Virtical (alignment) type liquid crystal panel is used.
- a display device provided with a VA liquid crystal panel has a problem that a response is slow when the brightness of a pixel greatly changes. Therefore, in a display device including a VA liquid crystal panel, when changing the brightness of a pixel from the minimum displayable brightness value to the maximum value or a value close to the maximum value, the brightness of the pixel is set to the minimum value.
- Overdrive control is performed to control the liquid crystal panel so as to change to a brightness between the brightness to be displayed and then to a maximum value or a value close to the maximum value. For example, when the brightness is controlled with 256 gradations, the liquid crystal panel is changed so that the gradation value representing the brightness of the pixel is changed from the gradation value 0 to the gradation value 244 and then to the gradation value 255. Control.
- the display device stores image data for each frame, compares the brightness of each pixel between the frame to be displayed and the previous frame, and performs overdrive control according to the difference in brightness.
- the brightness of the pixel may be misidentified due to compression / decompression errors. For example, the minimum brightness may be mistaken for a greater brightness.
- appropriate overdrive control cannot be performed. For example, if the brightness of a pixel is mistaken as a larger brightness even though it is the minimum value one frame before, the brightness of the pixel is the maximum value or a value close to the maximum value in one frame to be displayed. When this happens, proper overdrive control is not performed.
- the present invention has been made in view of such circumstances, and the object of the present invention is to reduce the image quality of moving images by reliably performing overdrive control even when the brightness of a pixel is mistaken. It is an object of the present invention to provide a display device that can be prevented and a method for controlling the display device.
- a display device sequentially stores a liquid crystal panel that sequentially displays a plurality of images each consisting of a plurality of pixels, and image data representing each of the images, so that one image before the image to be displayed is displayed.
- a storage unit that reads out image data representing the image of the image, and for each pixel included in the image, the brightness of the pixel in the image represented by the image data read out by the storage unit is a value included in a predetermined range, and is displayed.
- the brightness of the pixel in the power image is equal to or higher than a predetermined setting value, the brightness of the pixel is displayed as the brightness value in the image represented by the image data from the brightness in the previous image.
- the brightness of the pixels included in the image displayed by the liquid crystal panel so as to change to a halfway value between the brightness value in the power image and then to the brightness value in the image to be displayed.
- the control means exceeds the minimum brightness value that can be displayed when the brightness of the pixels included in the image represented by the image data read by the storage unit is less than the set value.
- the display device is characterized in that the set value is a maximum value of displayable brightness.
- the brightness of the pixels included in the image represented by the image data read by the storage unit is greater than the first threshold value, and less than the set value.
- the threshold value is less than or equal to a predetermined second threshold value
- the intermediate value is determined to be larger as the brightness value of the pixel is larger than the constant value.
- the storage unit includes a unit that compresses and stores image data, and a unit that reads and expands the image data, and the first threshold value is an image read by the storage unit.
- the brightness of a pixel included in an image represented by data is an upper limit value that can be mistaken for the minimum value due to a compression / decompression algorithm.
- the storage unit includes a unit that compresses and stores image data, and a unit that reads and expands the image data, and the first threshold value is an image read by the storage unit.
- the brightness of the pixels included in the image represented by the data is a value that is less than the upper limit value that can be mistaken for the minimum value due to the compression / decompression algorithm, and the second threshold value is a value that is greater than or equal to the upper limit value. It is characterized by that.
- control means stores a correspondence table in which the halfway value is associated with a brightness value of a pixel, and image data read by the storage unit based on the correspondence table The halfway value according to the brightness of the pixel included in the image represented by is defined.
- a liquid crystal panel that sequentially displays a plurality of images each having a plurality of pixels, and image data representing each image are sequentially stored, and an image to be displayed is displayed.
- a display device including a storage unit that reads image data representing the previous image, and the brightness of the pixel in the image represented by the image data read by the storage unit is within a predetermined range for each pixel included in the image.
- An image that is included in the image data and represents the brightness of the pixel from the brightness of the previous image when the brightness of the pixel in the image to be displayed is equal to or higher than a predetermined setting value.
- the liquid crystal panel displays so as to change to a halfway value between the brightness value in the image to be displayed and the brightness value in the image to be displayed, and then to the brightness value in the image to be displayed.
- the minimum brightness that can be displayed when the brightness of the pixels included in the image represented by the image data read by the storage unit is less than the set value When the value is equal to or less than a predetermined first threshold value exceeding the value, the midway value is set to a predetermined constant value exceeding the first threshold value.
- the display device sequentially displays images on the liquid crystal panel, sequentially stores image data representing the images in the storage unit, and reads out image data representing the image immediately before the image to be displayed.
- the display device obtains the brightness of the pixel from the brightness in the previous image by using the read image data. Control the brightness of the pixel so that it changes once to a halfway value between the brightness of the pixel in the previous image and the brightness in the image to be displayed, and then changes to the brightness in the image to be displayed.
- the set value is, for example, the maximum value of displayable brightness or a value close to the maximum value.
- the display device When the brightness of the pixel in the previous image is equal to or less than the first threshold value, the display device performs control with the midway value as a constant value. Even if the brightness of the pixel in the previous image is a value that exceeds the minimum value of the displayable brightness, if the display device is equal to or less than the first threshold value, the display device displays the pixel in the previous image. The same control is performed as when the brightness of the is the minimum value.
- the set value is the maximum value that can be displayed. For this reason, when the brightness of the pixel in the image to be displayed is the maximum value, the display device temporarily changes the brightness of the pixel from the brightness in the previous image to the midway value, and then the maximum value. The brightness of the pixel is controlled so as to change the value.
- the display device also has a pixel brightness that is greater than the first threshold value and less than or equal to the second threshold value in the previous image and greater than or equal to the set value in the image to be displayed.
- the brightness is changed from the brightness in the previous image to the midway value, and then changed to a brightness equal to or higher than the set value.
- the midway value a value that is larger than the midway value when the pixel brightness in the previous image is equal to or less than the first threshold value and increases as the brightness of the previous image increases is used.
- the first threshold value is an upper limit value in which the brightness of a pixel in the previous image may be mistaken from the minimum value due to an error in image compression / expansion in the storage unit. It is. Even when the brightness of the pixel in the previous image that should be the minimum value is erroneously recognized, the same control as that in the case where the brightness of the previous image is the minimum value is reliably performed.
- the first threshold value is an upper limit value in which the brightness of a pixel in the previous image may be mistaken from the minimum value due to an error in image compression / expansion in the storage unit. Is less than.
- the display device stores a correspondence table in which the halfway value is associated with the brightness value of the pixel, and determines the halfway value according to the correspondence table.
- the display device performs overdrive control similar to the case of changing the pixel brightness from the minimum value even if the brightness of the pixel in the previous frame is mistaken from the minimum value to another value. I do. Therefore, the present invention has an excellent effect that the display device can surely execute overdrive control even when the brightness of a pixel is mistakenly recognized and prevent deterioration of the image quality of a moving image.
- FIG. 10 is a conceptual diagram illustrating an example of contents of a lookup table according to Embodiment 2.
- FIG. 10 is a conceptual diagram illustrating an example of contents of a lookup table according to Embodiment 3.
- FIG. 10 is a conceptual diagram illustrating an example of contents of a lookup table according to Embodiment 3.
- FIG. 1 is a block diagram showing an internal functional configuration of the display device of the present invention.
- the display device includes a liquid crystal panel 3 and displays an image composed of a plurality of pixels using the liquid crystal panel 3.
- the display device is a television receiver or a monitor device.
- the display device includes an input unit 5 for inputting data from the outside.
- the input unit 5 is an interface unit for data input or a tuner to which broadcast data is input.
- An image generation unit 4 is connected to the input unit 5.
- the image generation unit 4 generates image data representing an image to be displayed using the liquid crystal panel 3 based on the data input to the input unit 5.
- the image generation unit 4 sequentially generates a plurality of image data representing a plurality of images constituting the moving image.
- An overdrive unit 1 is connected to the image generation unit 4.
- the image generation unit 4 sequentially inputs a plurality of image data to the overdrive unit 1.
- the overdrive unit 1 sequentially generates image signals for displaying an image on the liquid crystal panel 3 while performing overdrive control.
- a display control unit 2 is connected to the overdrive unit 1 and the liquid crystal panel 3.
- the display control unit 2 performs processing for sequentially displaying images on the liquid crystal panel 3 according to the image signals sequentially generated by the overdrive unit 1. Each image corresponds to each frame of the video.
- a moving image is displayed on the liquid crystal panel 3 by sequentially displaying a plurality of images.
- FIG. 2 is a block diagram showing an internal configuration of the overdrive unit 1.
- the overdrive unit 1 includes a color conversion unit 11, a quantization unit 12, a frame memory 13, an inverse quantization unit 14, and a color inverse conversion unit 15.
- the frame memory 13 includes a RAM (Random Access Memory).
- the image data for one frame generated by the image generation unit 4 is input to the color conversion unit 11, and the color conversion unit 11 performs color conversion for compressing the image data.
- the quantization unit 12 compresses the image data by quantizing the image data after color conversion.
- the frame memory 13 stores compressed image data representing one frame.
- the inverse quantization unit 14 reads image data from the frame memory 13 and inversely quantizes the read image data.
- the color inverse transform unit 15 decompresses the image data stored in the frame memory 13 by performing color inverse transform on the inversely quantized image data.
- the color conversion unit 11, the quantization unit 12, the frame memory 13, the inverse quantization unit 14, and the color inverse conversion unit 15 correspond to a storage unit in the present invention.
- the image data sequentially generated by the image generation unit 4 is sequentially stored and read.
- the overdrive unit 1 includes an LUT (Look Up Table) unit 16.
- the LUT unit 16 sets the brightness target value to be temporarily changed from the brightness one frame before the frame in which the pixel brightness is to be displayed by overdrive control, based on the brightness of the pixel in the two frames.
- a lookup table recorded in association with a combination of values is stored in advance. The lookup table corresponds to the correspondence table in the present invention.
- FIG. 3 is a conceptual diagram showing an example of the contents of the lookup table according to the first embodiment.
- the brightness of the pixel is represented by any one of gradation values from 0 to 255.
- the gradation value 0 is the minimum displayable brightness value
- the gradation value 255 is the maximum brightness value.
- a gradation value indicating the target value is recorded.
- the gradation value 244 is recorded in association with the gradation value 0 in the previous frame and the gradation value 255 in the current frame.
- a target value less than the gradation value 255 associated with the gradation value 255 in the current frame corresponds to a halfway value in the present invention.
- the value recorded in the lookup table is determined in advance.
- the LUT unit 16 determines a target value in overdrive control according to the stored lookup table.
- a color reverse conversion unit 15 and an interpolation unit 17 are connected to the LUT unit 16.
- the interpolation unit 17 calculates the target value of the pixel brightness by interpolation according to the combination not recorded in the lookup table among the combinations of the pixel brightness values in the two frames.
- the calculation of the interpolation unit 17 determines a brightness target value that should temporarily change the brightness of each pixel included in the image from the brightness in the previous frame.
- a processing unit 18 is connected to the interpolation unit 17.
- the processing unit 18 temporarily changes the brightness of the pixels from the brightness in the previous frame to the target value determined for each pixel, and then changes the brightness to the brightness in the current frame that is an image to be displayed next. Is generated.
- the LUT unit 16, the interpolation unit 17, the processing unit 18, and the display control unit 2 correspond to control means in the present invention.
- the image data sequentially input from the image generation unit 4 to the overdrive unit 1 is input in parallel to the color conversion unit 11, the LUT unit 16, and the processing unit 18.
- the image data is compressed by the color conversion unit 11 and the quantization unit 12 and stored in the frame memory 13.
- Image data representing the previous frame stored in the frame memory 13 is read from the frame memory 13, decompressed by the inverse quantization unit 14 and the color inverse transform unit 15, and input to the LUT unit 16.
- the LUT unit 16 specifies the brightness value of each pixel in the two frames based on the image data representing the current frame and the image data representing the previous frame.
- the LUT unit 16 refers to the stored look-up table and identifies a brightness target value corresponding to the combination of brightness values of the identified pixels.
- the interpolation unit 17 calculates the target value of the brightness according to the combination of the brightness of the pixels not recorded in the lookup table by interpolation, and determines the target value of the brightness of each pixel.
- the interpolation unit 17 inputs the determined brightness target value of each pixel to the processing unit 18.
- the processing unit 18 temporarily changes the brightness of each pixel from the brightness in the previous frame to the target value based on the input image data representing the current frame and the brightness target value of each pixel.
- An image signal for changing to the brightness in the frame is generated and input to the display control unit 2.
- the overdrive unit 1 generates an image signal by the processing unit 18 and inputs it to the display control unit 2 every time image data is sequentially input from the image generation unit 4.
- the display control unit 2 displays an image on the liquid crystal panel 3 based on the input image signal. At this time, the display control unit 2 controls the brightness of the pixels included in the image based on the image signal generated by the overdrive unit 1. Accordingly, an image on which overdrive control has been performed is displayed.
- FIG. 4 is a characteristic diagram showing an example of overdrive control.
- FIG. 4 shows an example in which the brightness of a pixel is changed from a gradation value 0 to a gradation value 255.
- the horizontal axis represents time
- the vertical axis represents pixel brightness in terms of gradation values.
- the lookup table associates the gradation value 0 in the previous frame with the gradation value 255 in the current frame, and uses the gradation as a target value for temporarily changing the brightness of the pixel.
- a value 244 is recorded.
- the overdrive unit 1 generates an image signal for temporarily changing the brightness of the pixel from the gradation value 0 to the gradation value 244 and then to the gradation value 255, and sends it to the display control unit 2. input.
- the display control unit 2 displays an image on the liquid crystal panel 3 according to the input image signal.
- the response of the brightness of the pixel when overdrive control is performed is indicated by a solid line.
- the brightness of the pixel rises once toward the gradation value 244 and then changes so as to approach the gradation value 255.
- the response of the brightness of the pixel when overdrive control is not performed is indicated by a broken line. Compared with the case where overdrive control is not performed, when overdrive control is performed, the brightness of the pixel changes from the gradation value 0 to the gradation value 255 in a shorter time.
- the brightness of the pixel in the current frame is the gradation value 255 that is the maximum displayable brightness
- the brightness of the pixel should be temporarily changed from the brightness in the previous frame.
- the target brightness value is an intermediate value between the brightness value of the pixel and the maximum value in the previous frame.
- the gradation value 244 is associated with the gradation value 0 in the previous frame and the gradation value 255 in the current frame as the target value (intermediate value).
- the target value is set to a value that exceeds the gradation value 0 in the previous frame and is equal to or less than the gradation value 128 and the gradation value 255 in the current frame.
- the same gradation value 244 as the gradation value 0 in the frame is associated.
- the gradation value 128 in the previous frame corresponds to the first threshold value in the present invention.
- the halfway value in the overdrive control is determined to be a constant gradation value 244. .
- the brightness of the pixel in the previous frame exceeds the gradation value 0 but is below the gradation value 128, the brightness of the pixel is changed when the brightness of the pixel is changed to the gradation value 255.
- the same overdrive control as when changing the gradation value from the gradation value 0 to the gradation value 255 is performed.
- the gradation value 244 corresponds to a constant value in the present invention.
- the overdrive control similar to the case where the pixel brightness in the previous frame has the gradation value 0 is performed. It was not done.
- the gradation value 255 is associated with the value exceeding the gradation value 0 in the previous frame and the gradation value 255 in the current frame, and the brightness of the pixel is adjusted. There is no influence of overdrive control when changing to the adjustment value 255.
- the image data representing one frame is compressed by the color conversion unit 11 and the quantization unit 12 and expanded by the inverse quantization unit 14 and the color inverse conversion unit 15. The brightness may be mistaken for other values.
- the brightness of the pixel in the previous frame has a gradation value of 0, as a result of compressing and expanding the image data, the brightness of the pixel is erroneously changed to the gradation value 32, and the brightness of the pixel in the previous frame May be mistaken for a gradation value of 32.
- misperception occurs, conventionally, even when the brightness of a pixel is changed from a gradation value 0 to a gradation value 255, the brightness of the pixel is changed from a gradation value 32 to a gradation value 255.
- the process for changing is performed, and the overdrive control that should be originally performed is not performed. For this reason, the response of the change in the brightness of the pixel becomes slow, and the image quality of the moving image deteriorates.
- the brightness of a pixel is changed from a brightness exceeding the gradation value 0 to the gradation value 255, the brightness of the pixel is changed from the gradation value 0 to the gradation value 255.
- the same overdrive control as in the case of changing is performed. For this reason, even if the brightness of the pixel in the previous frame having a gradation value of 0 is mistaken for another value, the same as when changing the brightness of the pixel from the gradation value 0 to the gradation value 255.
- overdrive control By performing overdrive control, overdrive control that should be performed is performed.
- the display device can reliably perform overdrive control even when the brightness of a pixel is mistakenly recognized, and can prevent deterioration in the image quality of a moving image. For example, even when a moving image in which an extreme change in brightness occurs, such as a moving image in which a mixed-color square figure moves in the horizontal direction on a white background, deterioration of the image quality of the moving image is prevented.
- a display device using a VA liquid crystal panel can prevent deterioration of moving image quality.
- the brightness value of the pixel that exceeds the gradation value 0 and is equal to or less than the first threshold value is the brightness of the pixel in the previous frame that should be the gradation value 0 that is the minimum brightness value. It is a value that can be mistaken.
- the first threshold value is the gradation value 128, and the gradation value 128 is the upper limit value of the brightness of pixels that may possibly be mistaken for the brightness of the pixel with the gradation value 0 in the previous frame.
- the first threshold is determined based on the premise that there is.
- the first threshold value is appropriately determined according to the compression / decompression algorithm for image data.
- the first threshold value may be a value other than the gradation value 128 according to the compression / decompression algorithm.
- ⁇ Misunderstanding of pixel brightness in the previous frame may occur when an image that is not assumed in the compression / decompression algorithm is generated.
- the display device is a television receiver
- a compression / decompression algorithm suitable for an image showing nature is often adopted, and when an image for a monitor device including a geometric pattern is generated.
- pixel brightness may be misidentified due to compression error.
- the display device can display a moving image without deteriorating the image quality.
- FIG. 5 is a conceptual diagram illustrating an example of the contents of a lookup table according to the second embodiment.
- the look-up table associates the gradation value 128 exceeding the gradation value 128 in the previous frame with the gradation value 240 or less and the gradation value 255 in the current frame, and the gradation value 255 as the target value. Less than halftone values are recorded in association with each other. These target values are determined in advance according to the brightness value of the pixel in the previous frame, and correspond to the midway value in the present invention.
- the overdrive unit 1 allows the brightness of the pixel in the previous frame to exceed the gradation value 128 and be equal to or less than the gradation value 240.
- the brightness is the gradation value 255
- the brightness of the pixel is temporarily changed from the brightness in the previous frame to a predetermined halfway value, and then an image signal for changing to the gradation value 255 is generated.
- the halfway value when the brightness of the pixel in the previous frame exceeds the gradation value 128 and is equal to or less than 240 is the brightness of the pixel in the previous frame according to the brightness value of the pixel in the previous frame.
- the larger the value the larger the predetermined value.
- the gradation value 240 corresponds to the second threshold value in the present invention.
- a gradation value 255 is associated as a target value with a value of gradation value 144 or more in the previous frame and a gradation value 255 in the current frame. For this reason, when the brightness of the pixel is changed from a value equal to or higher than the gradation value 144 to the gradation value 255, there is no influence by the overdrive control.
- Embodiment 1 when changing the brightness of a pixel from the gradation value 128 to the gradation value 255, the brightness of the pixel is temporarily changed from the gradation value 128 to the gradation value 144, and then Overdrive control for changing the gradation value to 255 is performed.
- a pixel whose brightness in the previous frame has a gradation value of 128 has a slower response to brightness change than when there is no overdrive control.
- a pixel whose brightness in the previous frame has a gradation value of 144 is not affected by the overdrive control when the brightness is changed to the gradation value of 255, and thus the response to the brightness change is delayed. There is nothing. Therefore, there is a possibility that the image quality deteriorates, such as a difference in response of pixel brightness change in the image and local tailing.
- the brightness of the pixel in the previous frame is changed.
- Overdrive control is performed to temporarily change from brightness to an intermediate value less than the gradation value 255 and then to the gradation value 255. For this reason, a pixel whose brightness in the previous frame exceeds the gradation value 128 is delayed in response to the brightness change by overdrive control, similarly to a pixel whose brightness is the gradation value 128 or less. Differences in the response of pixel brightness changes occurring in the image are reduced, local tailing becomes inconspicuous, and deterioration in image quality is prevented.
- the brightness of a pixel that is not likely to be a value in which the brightness of a pixel having a gradation value of 0 is mistakenly recognized due to an error in compression / expansion is set to a halfway value.
- the halfway value corresponding to the brightness of the pixel that has exceeded the first threshold in the previous frame is set to a larger value as the brightness value of the pixel in the previous frame is larger.
- the pixel brightness is temporarily changed to the halfway value and then changed to the gradation value 255.
- Drive control can be performed.
- the halfway value approaches the gradation value 255 as the brightness value of the pixel in the previous frame increases. Will be less affected and the response to brightness changes will be improved.
- the display device can prevent the occurrence of a large difference in the response of the brightness change between the pixels. In addition, it is possible to suppress the deterioration of the response of the brightness change.
- the second threshold value is the gradation value 240, but the second threshold value may be any other value.
- FIG. 6 is a conceptual diagram illustrating an example of the contents of a lookup table according to the third embodiment.
- the first threshold value has a gradation value of 80. That is, the gradation value 244 that is the same as the gradation value 0 in the previous frame is associated with the gradation value 255 in the previous frame and the gradation value 255 in the current frame as an intermediate value.
- the overdrive unit 1 temporarily changes the brightness of the pixel from a value equal to or less than the gradation value 80 to the gradation value 244, and then the gradation value 255. An image signal for changing to is generated.
- the halfway value associated with the gradation value 0 in the previous frame as the halfway value to the value exceeding the gradation value 80 in the previous frame and the gradation value 255 in the current frame. Values that exceed are associated.
- the halfway value in the case where the brightness of the pixel in the previous frame exceeds the gradation value 80 and is equal to or less than 240 is the brightness of the pixel in the previous frame according to the brightness value of the pixel in the previous frame.
- the value is set to a predetermined value that increases as the value of the height increases.
- the overdrive unit 1 exceeds the gradation value 244 from the value that exceeds the gradation value 80 and is equal to or less than the gradation value 240.
- An image signal for changing to a halfway value and then to a gradation value 255 is generated.
- the upper limit value of the value in which the pixel brightness in the previous frame may be erroneously recognized from the gradation value 0 due to the compression / decompression error is the gradation value 128.
- the first threshold value is a gradation value 80 less than the gradation value 128.
- the brightness of the pixel in the previous frame is a value that may be mistaken from the gradation value 0
- a value close to the upper limit value is unlikely to be a value that misrecognized the gradation value 0.
- the brightness of the pixel is changed from the value of the gradation value 128 or less in the previous frame to the gradation in the current frame.
- the response to the brightness change is delayed.
- the intermediate value is set closer to the gradation value 255. is there.
- the halfway value is closer to the gradation value 255, the response of the brightness change becomes faster. Therefore, the display device suppresses the deterioration of the response of the brightness change while preventing the deterioration of the image quality due to the compression / decompression error. can do.
- the display device can prevent deterioration in the image quality of the moving image. If the effect of preventing the deterioration of the image quality of the movie is weakened, the image quality of the movie frequently deteriorates because the probability that the brightness of the pixel with the gradation value 0 in the previous frame is mistaken for the value close to the upper limit is low. There is nothing.
- the overdrive unit 1 sets the pixel brightness to the previous frame. Then, an image signal is generated for changing from the brightness at 1 to the halfway value and then to the gradation value 255. For this reason, the difference in the response of the brightness change of the pixel generated in the image becomes small, the local tail becomes inconspicuous, and the deterioration of the image quality of the moving image is prevented.
- the halfway value corresponding to the brightness of the pixel that has exceeded the first threshold in the previous frame is determined to be a value that increases as the brightness value of the pixel in the previous frame increases. Therefore, the greater the brightness value of the pixel in the previous frame, the faster the response to the brightness change. Therefore, the display device can suppress the deterioration of the brightness change response while preventing a large difference in the brightness change response between the pixels.
- the first threshold value is not limited to the gradation value 80, but exceeds the gradation value 0, and the upper limit of the brightness of the pixel in which the brightness of the pixel having the gradation value 0 in the previous frame may be mistaken. Other values may be used as long as they are less than the value. Further, the second threshold value may be a value other than the gradation value 240.
- the setting value in the present invention is the gradation value 255 that is the maximum value of displayable brightness.
- the display device of the present invention can perform display. A form in which a value less than the maximum value of brightness is set as the set value may be used. In this mode, the display device performs overdrive control when the pixel brightness in the previous frame is equal to or lower than the first threshold value or the second threshold value and the pixel brightness in the current frame is equal to or higher than the set value. .
- the gradation value in the previous frame and the gradation value in the current frame are set to the gradation value that is lower than the first threshold value or the second threshold value in the previous frame and the gradation value that is larger than the set value in the current frame.
- the display device has a pixel brightness that is equal to or less than the first threshold value or the second threshold value in the previous frame, and the maximum value or maximum value in the current frame
- the brightness of the pixel is changed so that the brightness of the pixel is temporarily changed from the brightness in the previous frame to the midway value and then changed to the maximum value or a value close to the maximum value. Control.
- the display device can reliably perform overdrive control even when the brightness of a pixel is mistakenly recognized, and can prevent deterioration in the image quality of a moving image.
- the example in which the brightness of the pixel is expressed in 256 gradations is shown.
- the display device expresses in 256 gradations, such as a method of expressing the pixel brightness in 512 gradations.
- a form in which the brightness of the pixel is expressed by a method different from the method may be used.
- the example in which the overdrive unit 1 is configured by hardware has been described.
- the display device executes part of the processing in the overdrive unit 1 using software. Form may be sufficient.
Abstract
Description
(実施の形態1)
図1は、本発明の表示装置の内部の機能構成を示すブロック図である。表示装置は、液晶パネル3を備えており、複数の画素から構成される画像を液晶パネル3を用いて表示する。例えば、表示装置は、テレビジョン受像機又はモニタ装置である。表示装置は、外部からデータを入力される入力部5を備えている。入力部5は、データ入力用のインタフェース部、又は放送されたデータを入力されるチューナである。入力部5には、画像生成部4が接続されている。画像生成部4は、入力部5に入力されたデータに基づいて、液晶パネル3を用いて表示するための画像を表す画像データを生成する。動画が表示される場合は、画像生成部4は、動画を構成する複数の画像を表す複数の画像データを順次生成する。画像生成部4には、オーバードライブ部1が接続されている。画像生成部4は、複数の画像データを順次オーバードライブ部1へ入力する。オーバードライブ部1は、オーバードライブ制御を行いながら液晶パネル3に画像を表示させるための画像信号を順次生成する。オーバードライブ部1及び液晶パネル3には、表示制御部2が接続されている。表示制御部2は、オーバードライブ部1が順次生成した画像信号に従って、液晶パネル3に画像を順次表示させる処理を行う。夫々の画像は動画の夫々のフレームに対応する。複数の画像が順次表示されることで、液晶パネル3には動画が表示される。
図5は、実施の形態2に係るルックアップテーブルの内容例を示す概念図である。表示装置のその他の構成は実施の形態1と同様である。実施の形態2では、ルックアップテーブルは、前フレームでの階調値128を超過し階調値240以下の値及び現フレームでの階調値255に対応づけて、目標値として階調値255未満の階調値を対応づけて記録している。これらの目標値は、前フレームでの画素の明るさの値に応じて予め定められており、本発明における中途値に相当する。このようにルックアップテーブルが定められていることによって、オーバードライブ部1は、前フレームでの画素の明るさが階調値128を超過し階調値240以下であり、現フレームでの画素の明るさが階調値255である場合に、画素の明るさを、前フレームでの明るさから所定の中途値へ一旦変化させ、次に階調値255へ変化させるための画像信号を生成する。前フレームでの画素の明るさが階調値128を超過し階調値240以下である場合の中途値は、前フレームでの画素の明るさの値に応じて、前フレームでの画素の明るさの値が大きいほど大きい所定の値に定められている。また、階調値240は、本発明における第2閾値に対応する。
図6は、実施の形態3に係るルックアップテーブルの内容例を示す概念図である。表示装置のその他の構成は実施の形態1と同様である。実施の形態3では、第1閾値は階調値80となっている。即ち、前フレームでの階調値80以下の値及び現フレームでの階調値255に、中途値として、前フレームでの階調値0と同一の階調値244が対応づけられている。このようにルックアップテーブルが定められていることによって、オーバードライブ部1は、画素の明るさを、階調値80以下の値から、階調値244へ一旦変化させ、次に階調値255へ変化させるための画像信号を生成する。
11 色変換部
12 量子化部
13 フレームメモリ
14 逆量子化部
15 色逆変換部
16 LUT部
17 補間部
18 処理部
2 表示制御部
3 液晶パネル
Claims (7)
- 夫々に複数の画素からなる複数の画像を順次的に表示する液晶パネルと、夫々の画像を表す画像データを順次的に記憶し、表示すべき画像の一つ前の画像を表す画像データを読み出す記憶部と、画像に含まれる夫々の画素について、前記記憶部が読み出した画像データが表す画像における前記画素の明るさが所定範囲に含まれる値であり、表示すべき画像における前記画素の明るさが所定の設定値以上である場合に、前記画素の明るさを、一つ前の画像における明るさから、前記画像データが表す画像における明るさの値と表示すべき画像における明るさの値との間の中途値まで変化させ、次に、表示すべき画像における明るさの値まで変化させるように、前記液晶パネルが表示する画像に含まれる画素の明るさを制御する制御手段とを備える表示装置において、
前記制御手段は、
前記記憶部が読み出した画像データが表す画像に含まれる画素の明るさが、前記設定値未満で表示可能な明るさの最小値超の所定の第1閾値以下である場合に、前記中途値を前記第1閾値超の所定の定数値に定める手段を有すること
を特徴とする表示装置。 - 前記設定値は、表示可能な明るさの最大値であること
を特徴とする請求項1に記載の表示装置。 - 前記制御手段は、
前記記憶部が読み出した画像データが表す画像に含まれる画素の明るさが、前記第1閾値超であり、前記設定値未満で前記第1閾値超の所定の第2閾値以下である場合に、前記中途値を、前記定数値超で前記画素の明るさの値が大きいほど大きい値に定める手段を有すること
を特徴とする請求項1又は2に記載の表示装置。 - 前記記憶部は、
画像データを圧縮して記憶する手段と、
画像データを読み出して伸張する手段とを有し、
前記第1閾値は、前記記憶部が読み出した画像データが表す画像に含まれる画素の明るさが圧縮・伸張アルゴリズムに起因して前記最小値から誤認され得る値の上限値であること
を特徴とする請求項1から3までの何れか一つに記載の表示装置。 - 前記記憶部は、
画像データを圧縮して記憶する手段と、
画像データを読み出して伸張する手段とを有し、
前記第1閾値は、前記記憶部が読み出した画像データが表す画像に含まれる画素の明るさが圧縮・伸張アルゴリズムに起因して前記最小値から誤認され得る値の上限値未満の値であり、
前記第2閾値は前記上限値以上の値であること
を特徴とする請求項3に記載の表示装置。 - 前記制御手段は、
前記中途値を画素の明るさの値に対応づけた対応表を記憶してあり、
該対応表に基づいて、前記記憶部が読み出した画像データが表す画像に含まれる画素の明るさに応じた前記中途値を定めるように構成してあること
を特徴とする請求項1から5までの何れか一つに記載の表示装置。 - 夫々に複数の画素からなる複数の画像を順次的に表示する液晶パネルと、夫々の画像を表す画像データを順次的に記憶し、表示すべき画像の一つ前の画像を表す画像データを読み出す記憶部とを備える表示装置で、画像に含まれる夫々の画素について、前記記憶部が読み出した画像データが表す画像における前記画素の明るさが所定範囲に含まれる値であり、表示すべき画像における前記画素の明るさが所定の設定値以上である場合に、前記画素の明るさを、一つ前の画像における明るさから、前記画像データが表す画像における明るさの値と表示すべき画像における明るさの値との間の中途値まで変化させ、次に、表示すべき画像における明るさの値まで変化させるように、前記液晶パネルが表示する画像に含まれる画素の明るさを制御する表示装置の制御方法において、
前記記憶部が読み出した画像データが表す画像に含まれる画素の明るさが、前記設定値未満で表示可能な明るさの最小値超の所定の第1閾値以下である場合に、前記中途値を前記第1閾値超の所定の定数値に定めること
を特徴とする表示装置の制御方法。
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