Display device

Abstract

A first-half subframe luminance determination unit (16) determines the luminance level of a target pixel in an image in the first-half subframe on the basis of first conversion data that defines a correspondence of an input luminance level and a first coefficient to an output luminance level. A second-half subframe luminance determination unit (18) determines the luminance level of the target pixel in the image in the second-half subframe on the basis of second conversion data that defines a correspondence of an input luminance level and a second coefficient to an output luminance level. As an identical first coefficient and second coefficient increase, the difference increases between the output luminance level corresponding to the input luminance level in the first conversion data and the output luminance level corresponding to the same input luminance level in the second conversion data.

Description

[Technical field]

[0001] The following disclosure relates to display devices. [Background technology]

[0002] Patent Document 1 discloses an image display device that divides one frame period into a plurality of subframe periods, determines the grayscale level of each subframe according to the grayscale level of an input image signal, supplies the determined grayscale level to an image display unit, and displays an image, and is equipped with a display control means that supplies subframes with increasing grayscale levels in order from the subframe at or close to the temporal center of the one frame period. According to Patent Document 1, it is possible to suppress the motion blur that occurs when displaying moving images in a hold-type image display device, while suppressing the decrease in maximum brightness and contrast.

[0003] Patent Document 2 discloses an image display device which divides one frame into a plurality of subframe periods, and when an image of one frame is input in which an area displayed by a certain image signal α or an image signal close to the image signal α is adjacent to an area displayed by another image signal β or an image signal close to the image signal β, changes and displays an image signal in at least one subframe period A near the boundary between the area of ​​the image signal α and the area of ​​the image signal β such that the difference with the image signal of the other area is reduced, and changes and displays an image signal in at least one other subframe period B such that the difference with the image signal of the other area is emphasized. According to Patent Document 2, it is possible to improve the moving image quality of a hold-type display device without causing a decrease in luminance or the occurrence of flicker in the image display device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-173574 [Patent Document 2] International Patent Publication No. WO2007 / 052441 Summary of the Invention [Problem to be solved by the invention]

[0005] The techniques of Patent Documents 1 and 2 leave room for further improvement in the display quality of moving images.

[0006] An aspect of the present disclosure aims to further improve the display quality of moving images. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, a display device according to one embodiment of the present disclosure is a display device that divides one frame into a first subframe and a second subframe, and displays an image in each of the first subframe and the second subframe, and includes a pixel of interest specifying unit that specifies one of a plurality of pixels constituting the image of the one frame as a pixel of interest, a first peripheral pixel specifying unit that specifies a plurality of first peripheral pixels arranged around the pixel of interest in the image, a first difference coefficient determination unit that determines a plurality of first difference coefficients based on differences between pixel values ​​of the pixel of interest and the plurality of first peripheral pixels in the image of the one frame, and a pixel value of the pixel of interest in the image of the one frame, a first coefficient determination unit that determines a first coefficient by performing an operation using a first filter on each of the plurality of first difference coefficients, and a pair between an input pixel value, and the first coefficient and an output pixel value. a second surrounding pixel specifying unit that specifies a plurality of second surrounding pixels arranged around the pixel of interest in the image; a second difference coefficient determination unit that determines a plurality of second difference coefficients based on differences between each pixel value of the pixel of interest and each of the second surrounding pixels in an image of a frame following the one frame, and each pixel value of the pixel of interest and each of the second surrounding pixels in the image of the one frame; a second coefficient determination unit that determines a second coefficient by performing an operation using a second filter on each of the plurality of second difference coefficients; and a second pixel value determination unit that determines the pixel value of the pixel of interest in the image of the latter subframe based on second conversion data that specifies a correspondence between an input pixel value and the second coefficient, and an output pixel value, Before The larger the first and second coefficients are, the larger the difference between the output pixel value corresponding to the input pixel value in the first transformed data and the output pixel value corresponding to the same input pixel value in the second transformed data. Effect of the Invention

[0008] According to one aspect of the present disclosure, the display quality of moving images can be further improved. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a configuration of a display device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing names of luminance levels of pixels in images of three frames constituting input image data in one embodiment of the present invention. [Diagram 3] FIG. 11 is a diagram showing names of luminance levels of pixels in six subframe images constituting output image data in one embodiment of the present invention. [Figure 4] FIG. 13 is a diagram showing a filter for determining the luminance level of each pixel in the first half subframe. [Diagram 5] FIG. 13 is a diagram showing a filter for determining the luminance level of each pixel in the latter half subframe. [Figure 6] FIG. 2 is a diagram showing actual luminance levels of pixels in three frame images constituting input image data in one embodiment of the present invention. [Figure 7] FIG. 2 is a diagram showing the actual luminance levels of pixels in six sub-frame images constituting the converted display data in one embodiment of the present invention. [Figure 8] 5A to 5C are diagrams showing specific examples of filter values ​​included in a filter in one embodiment of the present invention. [Figure 9] 5A to 5C are diagrams showing specific examples of filter values ​​included in a filter in one embodiment of the present invention. [Figure 10] FIG. 13 shows the luminance levels of a predetermined number of pixels of an nth frame used to determine the luminance levels of pixels of the nth first half subframe. [Figure 11] FIG. 11 is a diagram showing the luminance levels of a predetermined number of pixels in frame n and the luminance levels of a predetermined number of pixels in frame n+1 used to determine the luminance levels of pixels in the nth latter subframe. [Figure 12] 11 is a graph showing a correspondence relationship between an input luminance level and an output luminance level in converted data. [Figure 13]FIG. 13 is a diagram showing values ​​of first-half subframe coefficients and second-half subframe coefficients determined for each pixel in each subframe. [Figure 14] 13A and 13B are diagrams showing the distribution of luminance levels of each pixel in L rows of an nth first half subframe and the distribution of luminance levels of each pixel in L rows of an nth latter half subframe. [Figure 15] FIG. 11 is a diagram showing the luminance level of each pixel visually recognized by a user when a moving image is displayed without being driven at double speed. [Figure 16] FIG. 11 is a diagram showing the luminance level of each pixel visually recognized by a user when a moving image is displayed at double speed. [Figure 17] FIG. 13 is a diagram showing a moving image blur waveform visually recognized by a user. [Figure 18] FIG. 11 is a diagram showing the actual brightness levels of pixels in three frame images constituting input image data (moving image) in one embodiment of the present invention, and the brightness levels of each pixel as viewed by a user when the images are displayed without double-speed driving. [Figure 19] FIG. 11 is a diagram showing the actual brightness levels of pixels in six subframe images constituting converted display data in one embodiment of the present invention, and the brightness levels of each pixel as viewed by a user when the image is displayed at double speed. [Figure 20] 13A and 13B are diagrams showing the distribution of luminance levels of each pixel in L rows of an nth first half subframe and the distribution of luminance levels of each pixel in L rows of an nth latter half subframe. [Figure 21] FIG. 13 is a diagram showing a moving image blur waveform visually recognized by a user. [Figure 22] FIG. 11 is a diagram showing the actual brightness levels of pixels in the images of six subframes constituting the converted display data in a modified example of the present invention, and the brightness levels of each pixel as viewed by a user when the images are displayed at double speed. [Diagram 23] 13A and 13B are diagrams showing the distribution of luminance levels of each pixel in L rows of an nth first half subframe and the distribution of luminance levels of each pixel in L rows of an nth latter half subframe. [Figure 24] FIG. 13 is a diagram showing a moving image blur waveform visually recognized by a user. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Configuration of display device 1) FIG. 1 is a block diagram showing a configuration of a display device 1 according to an embodiment of the present invention. As shown in this figure, the display device 1 includes an image data conversion unit 2, a line memory 3, a frame memory 4, a data selector 5, a luminance gradation conversion unit 6, and an image display unit 7. The image data conversion unit 2 includes a timing controller 12, a line memory controller 13 (a pixel of interest specification unit, a second peripheral pixel specification unit), a frame memory controller 14 (a pixel of interest specification unit, a first peripheral pixel specification unit), a first half subframe coefficient determination unit 15 (a first difference coefficient determination unit, a first coefficient determination unit), a first half subframe luminance determination unit 16 (a first pixel value determination unit), a second half subframe coefficient determination unit 17 (a second difference coefficient determination unit, a second coefficient determination unit), and a second half subframe luminance determination unit 18 (a second pixel value determination unit). The image display unit 7 includes a panel drive unit 21 and an OLED panel 22.

[0011] The display device 1 is realized as various devices having a function of displaying moving images, such as a PC monitor, a television device, a smartphone, etc. The OLED panel 22 is a panel capable of displaying moving images at a high frame rate such as 120 Hz or 144 Hz and with high-speed response.

[0012] (Definition of terms) The display device 1 can display a moving image on the OLED panel 22 by displaying each image included in the moving image on the OLED panel 22 for each corresponding frame. In this embodiment, the current frame (current frame) on the display device 1 is referred to as the nth frame. The frame immediately before the current frame (previous frame) is referred to as the n-1th frame, and the frame immediately following the current frame (next frame) is referred to as the n+1th frame.

[0013] The display device 1 improves the moving image display performance by driving the OLED panel 22 at double speed. Specifically, the display device 1 divides each frame when displaying a moving image into two subframes and sequentially displays images in each of the two subframes, thereby doubling the number of display frames of the moving image. This allows the display device 1 to convert a moving image with a frame rate of 60 Hz into a moving image with a frame rate of 120 Hz and display it on the OLED panel 22.

[0014] In this embodiment, of the two subframes obtained by dividing one frame, the subframe for displaying an image first within the same frame is referred to as the first half subframe. Furthermore, the subframe for displaying an image next within the same frame is referred to as the second half subframe. That is, the display device 1 divides one frame into the first half subframe that occupies the first half of the frame and the second half subframe that occupies the second half of the frame.

[0015] In this embodiment, two subframes obtained by dividing an n frame are referred to as the n first subframe and the n second subframe. Also, two subframes obtained by dividing an n-1 frame are referred to as the n-1 first subframe and the n-1 second subframe. Also, two subframes obtained by dividing an n+1 frame are referred to as the n+1 first subframe and the n+1 second subframe.

[0016] FIG. 2 is a diagram showing the names of the luminance levels (pixel values) of pixels in three frame images constituting input image data (moving image) in one embodiment of the present invention. FIG. 2 shows the names of the luminance levels of five pixels in the same L (L is a natural number) rows contained in the three frame images. X1 to X5 shown in FIG. 2 indicate the positions of five consecutive pixels contained in the L row of the image. More generally, in this embodiment, the position of the i-th pixel (i is a natural number) contained in the L row is referred to as Xi. That is, "pixel Xi" in this embodiment refers to the i-th pixel contained in the L row in the image.

[0017] In FIG. 2, I1(n) to I5(n) indicate the luminance levels of the five pixels X1 to X5 included in the L row in the nth frame image. In general, in this embodiment, the luminance level of the i-th pixel included in the L row in the nth frame image is referred to as Ii(n). In more general, in this embodiment, the luminance level of the i-th pixel included in the L row in the kth frame image (k is a natural number) is referred to as Ii(k). Therefore, in FIG. 2, I1(n-1) to I5(n-1) are the luminance levels of the five pixels X1 to X5 included in the L row in the n-1th frame image. Also, in FIG. 2, I1(n+1) to I5(n+1) are the luminance levels of the five pixels X1 to X5 included in the L row in the n+1th frame image.

[0018] Fig. 3 is a diagram showing the names of the luminance levels of pixels in six subframe images constituting output image data (moving image) in one embodiment of the present invention. Fig. 3 shows the names of the luminance levels of five pixels included in L rows of six subframe images obtained by dividing three frames respectively.

[0019] In FIG. 3, F1(n) to F5(n) indicate the luminance levels of the five pixels X1 to X5 included in row L of the image of the nth first half subframe. In general, in this embodiment, the luminance level of the i-th pixel included in row L of the image of the nth first half subframe is referred to as Fi(n). More generally, in this embodiment, the luminance level of the i-th pixel included in row L of the image of the first half subframe divided from the kth frame is referred to as Ii(k). Therefore, in FIG. 3, F1(n-1) to F5(n-1) are the luminance levels of the five pixels X1 to X5 included in row L of the image of the n-1th first half subframe. Also, in FIG. 3, F1(n+1) to F5(n+1) are the luminance levels of the five pixels X1 to X5 included in row L of the image of the n+1th first half subframe.

[0020] In FIG. 3, S1(n) to S5(n) indicate the luminance levels of the five pixels X1 to X5 included in the L row of the image of the nth latter subframe. In general, in this embodiment, the luminance level of the i-th pixel included in the L row of the image of the nth latter subframe is referred to as Si(n). In more general, in this embodiment, the luminance level of the i-th pixel included in the L row of the image of the latter subframe divided from the kth frame is referred to as Si(k). Therefore, in FIG. 3, S1(n-1) to S5(n-1) are the luminance levels of the five pixels X1 to X5 included in the L row of the image of the n-1th latter subframe. Also, in FIG. 3, S1(n+1) to S5(n+1) are the luminance levels of the five pixels X1 to X5 included in the L row of the image of the n+1th latter subframe.

[0021] The image data conversion unit 2 converts the image of each frame included in the input image data into an image of a first subframe and an image of a second subframe. In this case, the image data conversion unit 2 converts the luminance level of pixel Xi included in the image of the kth frame into the luminance level Fi(k) of pixel Xi in the kth first subframe and the luminance level Si(k) of pixel Xi in the kth second subframe. For example, the image data conversion unit 2 converts the luminance level I5(n) of pixel X5 included in the image of the nth frame into the luminance level F5(n) of pixel X5 included in the image of the nth first subframe and the luminance level S5(n) of pixel X5 included in the image of the nth second subframe. Furthermore, the image data conversion unit 2 converts the luminance level I3(n+1) of pixel X3 included in the image of the n+1th frame into the luminance level F3(n+1) of pixel X3 included in the image of the n+1th first subframe and the luminance level S5(n) of pixel X3 included in the image of the n+1th second subframe. 3 and the luminance level S3(n+1).

[0022] FIG. 4 is a diagram showing a filter 31 for determining the luminance level of each pixel of the first half subframe. The image data conversion unit 2 determines the luminance level of each pixel of the first half subframe using the filter 31 (first filter) shown in FIG. 4. The filter 31 is a planar filter having a plurality of filter values ​​(first filter values) arranged two-dimensionally. In FIG. 4, the filter 31 has a total of 81 filter values ​​arranged in a square shape of 9 rows and 9 columns. In FIG. 4, the filter value arranged in the xth row and yth column (x and y are integers not less than 1 and not more than 9) of the filter 31 is referred to as Axy. Therefore, A11 is the filter value arranged in the 1st row and the 1st column of the filter 31, and A55 is the filter value arranged in the 5th row and the 5th column of the filter 31.

[0023] FIG. 5 is a diagram showing a filter 32 for determining the luminance level of each pixel of the latter subframe. The image data conversion unit 2 determines the luminance level of each pixel of the latter subframe using the filter (second filter) 32 shown in FIG. 5. The filter 32 is a planar filter having a plurality of filter values ​​(second filter values) arranged two-dimensionally. In FIG. 5, the filter 32 has a total of 25 filter values ​​arranged in a square shape of 5 rows and 5 columns. In FIG. 5, the filter value arranged in the xth row and yth column (x and y are integers not less than 1 and not more than 5) of the filter 32 is referred to as Bxy. For example, B11 is a filter value arranged in the 1st row and 1st column of the filter 32, and B33 is a filter value arranged in the 3rd row and 3rd column of the filter 32.

[0024] 4 and 5, the size of filter 31 is larger than the size of filter 32. In particular, the number of filter values ​​arranged in the horizontal direction in filter 31 is greater than the number of filter values ​​arranged in the horizontal direction in filter 32. Furthermore, the number of filter values ​​arranged in the vertical direction in filter 31 is greater than the number of filter values ​​arranged in the vertical direction in filter 32.

[0025] (Example of image brightness levels) Fig. 6 is a diagram showing the actual luminance levels of pixels in images of three frames constituting input image data (moving image) in one embodiment of the present invention. An example in which the image data conversion unit 2 processes an image having each luminance level shown in Fig. 6 will be described below. This image includes an edge at a predetermined position in the row direction of the image. An edge is a location where a first region in the image where the same first luminance level continues meets a second region in the image where a second luminance level different from the first luminance level continues.

[0026] In the example of FIG. 6, an edge exists between an area in an image where the luminance level is 0.25 and an area where the luminance level is 0.5. For example, in an image of the n-1th frame, an edge exists between pixel X15 and pixel X16. In an image of the next nth frame, an edge exists between pixel X11 and pixel X12. In an image of the next n+th frame, an edge exists between pixel X15 and pixel X16. 1 In the frame image, an edge exists between pixel X7 and pixel X8. That is, if each image shown in Fig. 6 is displayed as is at a frame rate of 60 Hz, the edge existing in row L is displayed as if it moves by four pixels from right to left on the screen of the OLED panel 22 for each frame.

[0027] Fig. 7 is a diagram showing actual luminance levels of pixels in images of six subframes constituting converted display data in one embodiment of the present invention. The image data conversion unit 2 converts the images of the frames shown in Fig. 6 into the images of the subframes shown in Fig. 7. For example, the image data conversion unit 2 converts the luminance level "0.5" of pixel X12 in the nth frame into the luminance level "0" of pixel X12 in the first half of the nth subframe and the luminance level "0.8" of pixel X12 in the second half of the nth subframe. The conversion procedure will be described in detail later.

[0028] (Examples of filter values) FIG. 8 shows the present invention Kazumi8 is a diagram showing a specific example of each filter value included in the filter 31 in the embodiment. In this embodiment, the image data conversion unit 2 uses the filter 31 shown in FIG. 8 when determining the luminance level of each pixel in the n-th first half subframe. In the filter 31, the filter values ​​A11, A19, A91, and A99 are all 4. The filter values ​​A21, A31, ..., A 8 1 is always 8. Filter value A 29 , A 39 , A 89 are all 8. Filter values ​​A12 to A18 are all 8. Filter values ​​A92 to A98 are all 8. The remaining filter values ​​are all 16. Thus, with filter 31, the closer to the center of filter 31 the filter value is, the larger it tends to be, and the closer to the corners of the filter, the smaller the filter value is.

[0029] FIG. 9 shows the present invention Kazumi 9 is a diagram showing a specific example of each filter value included in the filter 32 in the embodiment. In this embodiment, the image data conversion unit 2 uses the filter 32 shown in FIG. 9 when determining the luminance level of each pixel in the latter subframe. In the filter 32, the filter values ​​B11, B15, B51, and B 55 The filter value B is 4. 2 Filter values ​​B1, B31, and B41 are all 8. Filter values ​​B25, B35, and B45 are all 8. Filter values ​​B12, B13, and B14 are all 8. Filter values ​​B52, B53, and B54 are all 8. The remaining filter values ​​are all 16. Thus, filter 32 tends to have larger filter values ​​closer to the center of filter 32 and smaller filter values ​​closer to the corners of the filter.

[0030] (Processing flow) The following describes a series of processing steps performed when the display device 1 displays a moving image, focusing in particular on the conversion processing performed by the image data converter 2. The following describes an example in which the display device 1 converts an image of n frames into an image of the n first half subframe and an image of the n second half subframe, and displays them in sequence on the OLED panel 22.

[0031] In the display device 1, a moving image to be displayed is input as an input image signal to the image data conversion unit 2. Each image included in the input image signal is Raw The value is specified as a gradation level, not a luminance level. Therefore, the gradation / luminance conversion unit 11 converts the gradation level of each pixel in the input image signal into a luminance level. The luminance level here means a normalized luminance level. Therefore, the luminance level after conversion takes any value within the range of 0 to 1. 0 corresponds to the darkest color (black) in the image, and 1 corresponds to the brightest color (white) in the image. The gradation / luminance conversion unit 11 outputs the converted input image signal to the frame memory controller 14 for each frame at regular intervals. The frame memory controller 14 stores the input image of one frame in the frame memory 4. Here, it is assumed that n frames of images are stored in the frame memory 4.

[0032] (Conversion process for the first half of n subframes) Immediately after the start of the nth frame, timing controller 12 outputs a trigger signal for the image of the first half subframe to frame memory controller 14 and data selector 5. In response to the trigger signal, frame memory controller 14 reads out from frame memory 4 the luminance levels of a predetermined number of pixels included in the image of the nth frame, which are necessary for determining the luminance level of each pixel included in the image of the nth first half subframe, and outputs the luminance levels to first half subframe coefficient determination unit 15 and first half subframe luminance determination unit 16.

[0033] In the following, an example will be described in which the image data conversion unit 2 converts the luminance level I12(n) of pixel X12 in the nth frame into the luminance level F12(n) of pixel X12 in the nth first half subframe and the luminance level S12(n) of pixel X12 in the nth latter half subframe.

[0034] FIG. 10 is a diagram showing the luminance levels of a predetermined number of pixels in the nth frame used to determine the luminance level of pixel X12 in the nth first subframe. The frame memory controller 14 specifies pixel X12 as a pixel of interest to be processed. Next, the frame memory controller 14 specifies a plurality of pixels that overlap the periphery of the filter 31 in the row direction when pixel X12 is overlapped on the center A55 of the filter 31 in L rows of the image of the nth frame as peripheral pixels (first peripheral pixels) of pixel X12. Here, pixels X8 to X11 and pixels X13 to X16 are specified as peripheral pixels (first peripheral pixels) of pixel X12. The frame memory controller 14 reads out the luminance levels I8(n) to I16(n) of the pixel of interest X12 and the peripheral pixels X8 to X11 and X13 to 16 from the frame memory 4, and outputs them to the first-half subframe coefficient determination unit 15. Frame memory controller 14 further outputs the luminance level I12(n) of pixel X12 to first-half subframe luminance determination unit 16. As shown in Fig. 10, I8(n) to I11(n) are 0.25, and I12(n) to I16(n) are 0.5.

[0035] (Calculation of the difference coefficient) The first-half subframe coefficient determination unit 15 determines difference coefficients (first difference coefficients) D1-D9 based on the input luminance levels I8(n)-I16(n), respectively. Specifically, the first-half subframe coefficient determination unit 15 first calculates, as difference coefficients D1-D9, individual differences between the luminance level of pixel X12 in the nth frame image and each of pixels X8-X16, including the pixel of interest X12 and its surrounding pixels, in the nth frame image, and the luminance level of pixel X12 in the nth frame image, as follows: D1= I8(n)-I12(n)=0.25-0.5=-0.25 D2= I9(n)-I12(n)=0.25-0.5=-0.25 D3=I10(n)-I12(n)=0.25-0.5=-0.25 D4=I11(n)-I12(n)=0.25-0.5=-0.25 D5=I12(n)-I12(n)=0.5-0.5=0 D6 = I13(n) - I12(n) = 0.5 - 0.5 = 0 D7=I14(n)-I12(n)=0.5-0.5=0 D8=I15(n)-I12(n)=0.5-0.5=0 D9 = I16(n) - I12(n) = 0.5 - 0.5 = 0.

[0036] Next, the first-half subframe coefficient determination unit 15 converts the calculated difference coefficients D1 to D9 to 1 if the calculated values ​​are other than 0, and 0 If there is, it is maintained as 0. In this way, the difference coefficients D1 to D9 are determined as follows.

[0037] D1=1 *Converted from -0.25 to 1 D2=1 *Converted from -0.25 to 1 D3=1 *Converted from -0.25 to 1 D4=1 *Converted from -0.25 to 1 D5=0 D6=0 D7=0 D8=0 D9=0.

[0038] The first-half subframe coefficient determination unit 15 determines the first-half subframe coefficient Pf by performing a calculation using the filter 31 on each of the determined difference coefficients D1 to D9. The first-half subframe coefficient determination unit 15 first multiplies each of the difference coefficients D1 to D9 individually by filter values ​​A15, A25, . . . A95 that are respectively superimposed on the pixels X8 to X16 in the filter 31. As a result, the difference coefficients D1 to D9 are converted as follows: D1=1×A15=1×8=8 D2=1×A25=1×16=16 D3=1×A35=1×16=16 D4=1×A45=1×16=16 D5=0×A55=0×16=0 D6=0×A65=0×16=0 D7=0×A75=0×16=0 D8=0×A85=0×16=0 D9=0×A95=0×8=0.

[0039] Next, the first half subframe coefficient determination unit 15 calculates the sum Dsum of the converted difference coefficients D1 to D9. That is, Dsum=8+16+16+16+0+0+0+0 +0 =56. First-half subframe coefficient determination unit 15 finally determines a first-half subframe coefficient (first coefficient) Pf based on the sum Dsum and a predetermined threshold Th. Here, threshold Th is assumed to be 40. First-half subframe coefficient determination unit 15 determines the first-half subframe coefficient Pf by dividing the sum Dsum by threshold Th. However, if the value after division exceeds 1, it is converted to 1. Here, Pf=56÷40=1.4. Therefore, since Pf exceeds 1, it is converted to Pf=1. In this way, first-half subframe coefficient determination unit 15 finally determines Pf=1.

[0040] (Determining the brightness level) First-half subframe coefficient determination unit 15 outputs the determined first-half subframe coefficient Pf to first-half subframe luminance determination unit 16. First-half subframe luminance determination unit 16 determines the luminance level (first pixel value) F12(n) of pixel X12 of the nth first half subframe based on the luminance level I12(n) of pixel X12 of interest and the input first-half subframe coefficient Pf. In this case, first-half subframe luminance determination unit 16 determines F12(n) based on conversion data (first conversion data) that defines the correspondence between both the input luminance level (input pixel value) and the first-half subframe coefficient Pf and the output luminance level (output pixel value). In this embodiment, when the input luminance level is In and the output luminance level is Fn, the conversion data for the nth first half subframe is defined as the following arithmetic expression: Fn = (-1 × In) × Pf + In (when In is 0.5 or less) Fn=(In-1)×Pf+In (when In is greater than 0.5).

[0041] The first-half subframe luminance determination unit 16 determines F12(n) as Fn by substituting I12(n) for In defined in the conversion data. Here, since I12(n)=0.5 and Pf=1, Fn=(-1×0.5)×1+0.5=0. As a result, the first-half subframe luminance determination unit 16 determines F12(n)=0.

[0042] The first half subframe luminance determination unit 16 outputs the determined luminance level F12(n) to the data selector 5. The data selector 5 stores the input luminance level F12(n) in a memory (not shown). When the luminance levels of a certain number of pixels included in the image of the n first half subframe are stored in the memory, the data selector 5 outputs the luminance levels of those pixels to the luminance gradation conversion unit 6. For example, when the luminance levels of all pixels of the image of the n first half subframe are stored in the memory, the data selector 5 reads out all the luminance levels of all the pixels from the memory and outputs them to the luminance gradation conversion unit 6. The luminance gradation conversion unit 6 generates an output image signal corresponding to the image of the n first half subframe by converting the luminance levels of all the input pixels into gradation levels. The luminance gradation conversion unit 6 outputs the generated output image signal to the image display unit 7. The panel drive unit 21 of the image display unit 7 drives each pixel of the OLED panel 22 by outputting the input image signal as a source signal to the OLED panel 22. This allows the image of the n-th first half subframe to be displayed on the OLED panel 22.

[0043] (Conversion process for the nth subframe) After determining the luminance levels of all pixels in the n first half subframe, timing controller 12 immediately outputs a trigger signal for the image of the latter half subframe to line memory controller 13, frame memory controller 14, and data selector 5. In response to the trigger signal, frame memory controller 14 reads out from frame memory 4 the luminance levels of a predetermined number of pixels included in the image of the n frame, which are necessary for determining the luminance level of each pixel included in the image of the n second half subframe, and outputs the luminance levels to latter half subframe coefficient determination unit 17 and latter half subframe luminance determination unit 18.

[0044] FIG. 11 is a diagram showing the luminance levels of a predetermined number of pixels in the nth frame and the luminance levels of a predetermined number of pixels in the n+1th frame, which are used to determine the luminance level of pixel X12 in the nth latter subframe. The frame memory controller 14 specifies pixel X12 as a pixel of interest to be processed. Next, the frame memory controller 14 specifies each pixel that is superimposed on the periphery in the row direction of the filter 32 when pixel X12 is superimposed on the center B33 of the filter 32 in the Lth row of the image of the nth frame as peripheral pixels (second peripheral pixels) of pixel X12. Here, pixels X10 and X11, as well as pixels X13 and X14 are specified as peripheral pixels of pixel X12. The frame memory controller 14 specifies a total of five pixels X10 to X12 including pixel X12 and its peripheral pixels. 14 The frame memory controller 14 reads out the luminance levels I10(n) to I14(n) of the pixel X12 from the frame memory 4 and outputs them to the latter subframe coefficient determination unit 17. The frame memory controller 14 further outputs the luminance level I12(n) of the pixel X12 to the latter subframe luminance determination unit 18. 1 As shown in the figure, I10(n) and I11(n) are 0.25, and I12(n) to I14(n) are 0.5.

[0045] In parallel, the line memory controller 13 specifies pixel X12 as a pixel of interest to be processed. Next, the line memory controller 13 specifies each pixel that overlaps with the center B33 of the filter 32 in the row direction as a peripheral pixel of pixel X12 when pixel X12 is overlapped with the center B33 of the filter 32 in the L row of the image of the n+1 frame. Here, pixels X10 and X11, and pixels X13 and X14 are specified as peripheral pixels of pixel X12. The line memory controller 13 requests the luminance levels I10(n+1) to I14(n+1) of pixel X12 and each of its peripheral pixels of the image of the n+1 frame from the gradation and luminance conversion unit 11. In response to this request, the gradation and luminance conversion unit 11 outputs the luminance levels I10(n+1) to I14(n+1) to the line memory controller 13. The line memory controller 13 stores each input luminance level in the line memory 3 in sequence. When the line memory controller 13 completes storing the input luminance levels, it reads out the luminance levels I10(n+1) to I14(n+1) from the line memory 3 and outputs them to the latter half subframe coefficient determination unit 17. 1 As shown in the figure, I10(n+1) to I14(n+1) are 0.5.

[0046] (Calculation of the difference coefficient) The latter half subframe coefficient determination unit 17 determines difference coefficients (second difference coefficients) D1 to D5 based on the input luminance levels I10(n) to I14(n) and I10(n+1) to I14(n+1), respectively. Specifically, the latter half subframe coefficient determination unit 17 first calculates, as difference coefficients D1 to D5, differences between the luminance levels I10(n+1) to I14(n+1) of the n+1 frame and the luminance levels I10(n) to I14(n) of the n frame for each of the pixels X10 to X14, respectively, as follows: D1=I10(n)-I10(n+1)=0.5-0.25=0.25 D2=I11(n)-I11(n+1)=0.5-0.25=0.25 D3 = I12(n) - I12(n+1) = 0.5 - 0.5 = 0 D4 = I13(n) - I13(n+1) = 0.5 - 0.5 = 0 D5 = I14(n) - I14(n+1) = 0.5 - 0.5 = 0 Next, the latter subframe coefficient determination unit 17 converts the calculated difference coefficients D1 to D5 to 1 if the calculated values ​​are other than 0, and 0 If there is, it is maintained as 0. In this way, the difference coefficients D1 to D5 are determined as follows.

[0047] D1=1 *Converted from 0.25 to 1 D2=1 *Converted from 0.25 to 1 D3=0 D4=0 D5=0.

[0048] The latter subframe coefficient determination unit 17 determines a latter subframe coefficient Ps by performing a calculation using the filter 32 on each of the determined difference coefficients D1 to D5. First, for each of the difference coefficients D1 to D5, the latter subframe coefficient determination unit 17 calculates filter values ​​B13, B23,..., B 53 are multiplied individually. This converts the difference coefficients D1 to D5 as follows: D1=1×B13=1×8=8 D2=1×B23=1×16=16 D3=0×B33=0×16=0 D4=0×B43=0×16=0 D5=0×B53=0×8=0.

[0049] Next, the second-half subframe coefficient determination unit 17 calculates the sum Dsum of the converted difference coefficients D1 to D5. That is, Dsum=8+16+0+0+0=24. Finally, the second-half subframe coefficient determination unit 17 determines the second-half subframe coefficient (second coefficient) Ps based on the sum Dsum and a predetermined threshold Th. Here, the threshold Th is assumed to be 40. The second-half subframe coefficient determination unit 17 determines the second-half subframe coefficient Ps by dividing the sum Dsum by the threshold Th. However, if the value after division exceeds 1, it is converted to 1. Here, Ps=24÷40=0.6. In this manner, the second-half subframe coefficient determination unit 17 finally determines Ps. s Determine = 0.6.

[0050] (Determining the brightness level) Second-half subframe coefficient determination unit 17 outputs the determined second-half subframe coefficient Ps to second-half subframe luminance determination unit 18. Second-half subframe luminance determination unit 18 determines the luminance level (second pixel value) S12(n) of pixel X12 in the nth second-half subframe based on the luminance level I12(n) of pixel X12 and the input second-half subframe coefficient Ps. At that time, second-half subframe luminance determination unit 18 determines S12(n) based on conversion data (second conversion data) that defines the correspondence between both the input luminance level and the second-half subframe coefficient Ps and the output luminance level. In this embodiment, when the input luminance level is In and the output luminance level is Sn, the conversion data for the nth second-half subframe is defined as the following arithmetic expression: Sn=In×Ps+In (when In is 0.5 or less) Sn=(1-In)×Ps+In (when In is greater than 0.5).

[0051] The latter-half subframe luminance determination unit 18 determines S12(n) as Sn by substituting I12(n) for In defined in the conversion data. Here, I12(n)=0.5 and Ps=0.6, so Sn=0.5×0.6+0.5=0.8. As a result, the latter-half subframe luminance determination unit 18 determines S12(n)=0.8.

[0052] The latter half subframe luminance determination unit 18 outputs the determined luminance level S12(n) to the data selector 5. The data selector 5 stores the input luminance level S12(n) in a memory (not shown). When the luminance levels of a certain number of pixels included in the image of the nth latter half subframe are stored in the memory, the data selector 5 outputs the luminance levels of those pixels to the luminance gradation conversion unit 6. For example, when the luminance levels of all pixels of the image of the nth latter half subframe are stored in the memory, the data selector 5 reads out all the luminance levels of all the pixels from the memory and outputs them to the luminance gradation conversion unit 6. The luminance gradation conversion unit 6 generates an output image signal corresponding to the image of the nth latter half subframe by converting the luminance levels of all the input pixels into gradation levels. The luminance gradation conversion unit 6 outputs the generated output image signal to the image display unit 7. The panel drive unit 21 of the image display unit 7 drives each pixel of the OLED panel 22 by outputting the input image signal as a source signal to the OLED panel 22. This allows the image of the nth latter subframe to be displayed on the OLED panel 22.

[0053] (Properties of converted data) Fig. 12 is a graph showing the correspondence relationship between input luminance levels and output luminance levels in converted data. In Fig. 12, graphs 41 to 43 show the correspondence relationship between input luminance levels and output luminance levels in converted data for determining the luminance level of the first half subframe. Graphs 51 to 53 show the correspondence relationship between input luminance levels and output luminance levels in converted data for determining the luminance level of the second half subframe.

[0054] Graph 41 is a graph when the first-half subframe coefficient Pf is 1, graph 42 is a graph when the first-half subframe coefficient Pf is 0.5, and graph 43 is a graph when the first-half subframe coefficient Pf is 0. In this way, the conversion data for determining the luminance level of the first-half subframe has a different correspondence relationship between the input luminance level and the output luminance level depending on the value of the first-half subframe coefficient Pf.

[0055] Graph 51 is a graph when the latter subframe coefficient Ps is 1, graph 52 is a graph when the latter subframe coefficient Ps is 0.5, and graph 53 is a graph when the latter subframe coefficient Ps is 0. In this way, the conversion data for determining the luminance level of the latter subframe has a correspondence relationship between the input luminance level and the output luminance level that differs depending on the value of the latter subframe coefficient Ps.

[0056] 12, the greater the mutually identical first-half subframe coefficient Pf and second-half subframe coefficient Ps, the greater the difference between the output luminance level corresponding to the input luminance level in the converted data for the n first-half subframe and the output luminance level corresponding to the same input luminance level in the second converted data for the n second-half subframe. More specifically, in a range in which the input luminance level is greater than 0 and less than 1, the output luminance level corresponding to the input luminance level in the converted data for the n second-half subframe is greater than the output luminance level corresponding to the same input luminance level in the converted data for the n first-half subframe.

[0057] In detail, as shown in graph 43, when Pf=0, the output luminance level is the same as the input luminance level over the entire range of input luminance levels. Similarly, as shown in graph 53, when Ps=0, the output luminance level is the same as the input luminance level over the entire range of input luminance levels. As shown in graphs 41 and 51, when Pf=1 and Ps=1, the difference between the output luminance level of the first subframe and the output luminance level of the second subframe for the same input luminance level is the largest. More specifically, the larger Pf and Ps are, the larger the difference between the output luminance level of the first subframe and the output luminance level of the second subframe for the same input luminance level is.

[0058] Fig. 13 is a diagram showing values ​​of a first half subframe coefficient Pf and a second half subframe coefficient Ps determined for each pixel X1 to X20 in each subframe. Fig. 13 shows first half subframe coefficients Pf of pixels X1 to X20 in the n-1 first half subframe and second half subframe coefficients Ps of pixels X1 to X20 in the n-1 second half subframe, determined from the luminance levels of pixels X1 to X20 in the n-1 frame shown in Fig. 6. Fig. 13 further shows first half subframe coefficients Pf of pixels X1 to X20 in the n first half subframe and second half subframe coefficients Ps of pixels X1 to X20 in the n second half subframe, determined from the luminance levels of pixels X1 to X20 in the n frame shown in Fig. 6.

[0059] When determining the n-th first half subframe coefficient Pf, the image data conversion unit 2 calculates difference coefficients D1 to D9 based on the differences between the luminance levels of the pixel of interest in the n-th frame image and its peripheral pixels and the luminance level of the pixel of interest in the n-th frame image. In this way, the image data conversion unit 2 determines the first half subframe coefficient Pf=1 for pixels in the n-th first half subframe image that are centered on the same position as the position of the edge included in the n-th frame image and within a certain range determined according to the horizontal size of filter 31. Therefore, as shown in FIG. 13, the image data conversion unit 2 can set the position of the edge included in the n-th first half subframe image to the same position as the edge included in the original n-th frame image.

[0060] When determining the n-th latter subframe coefficient Ps, the image data conversion unit 2 calculates difference coefficients D1 to D5 based on differences between the luminance levels of the pixel of interest in the image of the n+1 frame and its peripheral pixels and the luminance levels of the pixel of interest in the image of the n frame and its peripheral pixels. In this way, the image data conversion unit 2 determines the latter subframe coefficient Ps=1 for pixels in the image of the n-th latter subframe that are centered on the midpoint between the position of an edge included in the image of the n frame and the position of an edge included in the image of the n+1 frame and that are within a certain range determined according to the horizontal size of the filter 32. Therefore, as shown in FIG. 13, the image data conversion unit 2 can set the position of the edge included in the image of the n-th latter subframe to a position between the position of the edge of the n-th first half subframe and the position of the edge of the n+1-th first half subframe.

[0061] The first half subframe coefficient Pf and the second half subframe coefficient Ps each approach 1 the closer the pixel is to an edge, and approach 0 the farther the pixel is from an edge. Therefore, in FIG. 13, the position of a pixel where Pf or Ps is 1 corresponds to an edge, and the position of a pixel where Pf or Ps is 0 corresponds to a solid part in an image. As shown in FIG. 13, the range of pixels where Ps=1 in the n-1 second half subframe (X12 to X15) is closer to the range of pixels where Ps=1 in the n first half subframe (X10 to X13) than the range of pixels where Pf=1 in the n-1 first half subframe (X14 to X17). Although not shown, the range of pixels where Ps=1 in the n second half subframe (X8 to X11) is closer to the range of pixels where Ps=1 in the n+1 first half subframe (X6 to X9) than the range of pixels where Pf=1 in the n first half subframe (X10 to X13). As a result, when the OLED panel 22 is driven at double speed, the edge present in row L is displayed to move by two pixels for each subframe from right to left on the screen of the OLED panel 22. As a result, the edge can be displayed to move stepwise for each subframe, allowing the user to correctly view the position of the edge when driven at double speed.

[0062] The range of pixels in which the latter subframe coefficient Ps becomes 1 in the image of the n latter subframes is determined according to the moving speed of the edge and the size of the filter 32. The faster the moving speed of the edge, the wider the range in which the difference corresponding to each peripheral pixel superimposed on the filter value in the horizontal range of the filter 32 takes a value other than 0, and therefore the frequency with which the latter subframe coefficient Ps becomes 1 increases. As a result, the range of pixels in which the latter subframe coefficient Ps becomes 1 becomes wider the faster the moving speed of the edge and the larger the size of the filter 32. On the other hand, the range of pixels in which the latter subframe coefficient Ps becomes 1 in the image of the n first half subframes is determined only by the size of the filter 31, regardless of the moving speed of the edge. Therefore, the faster the moving speed of the edge, the wider the difference between the range of pixels in which the latter subframe coefficient Ps becomes 1 and the range of pixels in which the first half subframe coefficient Ps becomes 1 becomes.

[0063] Therefore, by making the size of filter 31 larger than the size of filter 32, regardless of the moving speed of the edge, the range of pixels in which the latter subframe coefficient Ps is 1 can be limited to a maximum of the size of filter 32. This makes it possible to prevent the range of pixels in which the latter subframe coefficient Ps is 1 from becoming wider than the range of pixels in which the first subframe coefficient Pf is 1, so that the coefficient Ps=1 indicating an edge can be set in an appropriate range in the image of the nth latter subframe, as shown in Fig. 13.

[0064] Fig. 14 is a diagram showing the distribution of luminance levels of each pixel in L rows of the nth first half subframe and the distribution of luminance levels of each pixel in L rows of the nth latter half subframe. In Fig. 14, graph 61 shows the distribution of luminance levels of each pixel in L rows of the nth first half subframe shown in Fig. 7. Graph 62 shows the distribution of luminance levels of each pixel in L rows of the nth latter half subframe shown in Fig. 7. In Fig. 14, the horizontal axis shows the position of each pixel in L rows, and the vertical axis shows the output luminance level after conversion.

[0065] As shown in FIG. 7 and graph 61 in FIG. 14, pixels X10 to X13 Each brightness level F10(n)~F 13 ( n ) are all 0. That is, in the image of the nth first half subframe, black display is inserted at the edge position existing in the vicinity of pixel X12. Furthermore, as shown in FIG. 7 and graph 62 of FIG. 14, the luminance levels S10(n) to S14( n ) are all equal to or greater than 0.5. That is, in the image of the nth latter subframe, the luminance level of the edge position present in the vicinity of pixel X12 is emphasized.

[0066] As a result, the user can see pixels X10 to X1 3 The luminance level at which the black display is inserted in the n-th subframe is offset by the emphasized luminance levels of the pixels X10 to X14 in the n-th latter subframe, and the luminance level is perceived as the luminance level of each of the pixels X10 to X14. This allows the user to correctly view the edge present at the position of the pixel X12 even during double-speed driving.

[0067] As shown in graphs 61 and 62 in Fig. 7 and Fig. 14, in an area away from an edge, the luminance level of the nth first subframe and the luminance level of the nth latter subframe at the same pixel position are the same value. For example, in an area to the left of an edge, the luminance level is 0.25 in both the nth first subframe and the nth latter subframe. Also, in an area to the right of an edge, the luminance level is 0.5 in both the nth first subframe and the nth latter subframe. In this way, the position where black display is inserted in the nth first subframe is limited to the position where an edge exists.

[0068] Therefore, the display device 1 can display edges more sharply by inserting black display, thereby improving the display quality of moving images. Furthermore, because black display is inserted only near edges, even if flicker occurs in moving images displayed at 120 Hz, the position where the flicker occurs is limited to the edge vicinity where black display is inserted. This makes it possible to keep the position where flicker occurs in moving images to a minimum range, thereby preventing a decrease in the display quality of moving images in areas other than edges.

[0069] (Blurred video waveform) FIG. 15 is a diagram showing the luminance level of each pixel visually recognized by a user when an image is displayed without double-speed driving. When an edge included in an image is displayed moving to the left of the screen as shown in FIG. 15, the user's eyes visually recognize the image by tracking the movement of the edge in each frame. In this case, the user sequentially tracks and visually recognizes the luminance level of each pixel at the destination of the line of sight, and ultimately visually recognizes the integral value (average value) of each visually recognized luminance level as the actual luminance level. In FIG. 15, the edge moves at a speed of 4 pixels per frame. Therefore, for example, in the n-1 frame, the user visually recognizes the luminance levels of the four pixels X14 to X17, and in the next n frame, the user visually recognizes the luminance levels of the four pixels X10 to X13 to the left, and finally, the four pixels X6 to X8 to the left. 9 The user then visually recognizes the luminance levels of pixel X. 7 As a result, the user perceives the pixel X as an actual luminance level. 7 As a result of the user's gaze tracking, the image appears blurred at the edge position that is visually perceived by the user. This phenomenon is called motion blur.

[0070] In the example of Fig. 15, the image of each frame has only two pixels that form an edge: a pixel with a luminance level of 0.25 and a pixel with a luminance level of 0.5 that is located next to it. On the other hand, in the luminance level that is visually recognized by the user, the pixels that form the edge are pixel X with a luminance level of 0.25 and pixel X with a luminance level of 0.5. 5 and pixel X with a brightness level of 0.5 9 and for each pixel X with luminance levels of 0.31, 0.38, and 0.44, respectively. 6 ~X 8 Therefore, the user will visually recognize the range of five pixels consisting of pixels X4 to X8 as an edge. As a result, the width of the edge visually recognized by the user is larger than the width of the edge contained in the original image, and the edge appears blurred to the user.

[0071] FIG. 16 is a diagram showing the luminance level of each pixel as viewed by a user when an image is displayed by driving at double speed. When an edge included in an image is displayed moving to the left of the screen as shown in FIG. 16, the user's eyes view the image by following the movement of the edge in each subframe. In this case, the user sequentially views the luminance level of each pixel at the destination of the line of sight by following it, and ultimately views the integral value (average value) of each viewed luminance level as the actual luminance level. In FIG. 16, the edge moves at a speed of 2 pixels per subframe. Therefore, for example, in the n-1 first half subframe, the user views the luminance levels of two pixels X17 and X18, and in the next n-1 second half subframe, the user views the luminance levels of two pixels X15 and X16. 6The user visually recognizes the luminance levels of the two pixels X13 and X14 in the next n first half subframe, and the luminance levels of the two pixels X11 and X12 in the next n second half subframe. Finally, the user visually recognizes the luminance levels of the two pixels X9 and X10 in the next n+1 first half subframe, and the luminance levels of the two pixels X7 and X8 in the next n+1 second half subframe. The user then visually recognizes the average value of these 12 luminance levels as the actual luminance level of pixel X7. As a result, the user visually recognizes 0.38 as the luminance level of pixel X7. Even when a video is displayed by driving it at double speed at 120 Hz, the user's line of sight tracking results in blurring of the image at the edge position visually recognized by the user.

[0072] In the example of FIG. 16, at the brightness level visually recognized by the user, the pixels constituting the edge are only pixel X7 with a brightness level of 0.38, located between pixel X6 with a brightness level of 0.25 and pixel X8 with a brightness level of 0.5. Therefore, the user visually recognizes the range of three pixels consisting of pixels X6 to X8 as an edge. As a result, the width of the edge visually recognized by the user is larger than the width of the edge contained in the original image, and the edge appears blurred to the user. However, the degree of blurring is smaller than that of a moving image displayed at 60 Hz.

[0073] Fig. 17 is a diagram showing a moving image blur waveform visually recognized by a user. Graph 71 is a graph showing the distribution of luminance levels actually visually recognized by a user when a moving image is displayed at 60 Hz as shown in Fig. 15. Graph 72 is a graph showing the distribution of luminance levels actually visually recognized by a user when a moving image is displayed at double speed driving of 120 Hz as shown in Fig. 16. In Fig. 17, the horizontal axis indicates the position of each pixel in row L of an image, and the vertical axis indicates the luminance level actually visually recognized by a user.

[0074] Graph 71 corresponds to the moving image blur waveform when moving images are displayed at 60 Hz, and graph 72 corresponds to the moving image blur waveform when moving images are displayed at double speed at 120 Hz. As shown in FIG. 17, the width of the edge of the luminance level included in graph 72 is narrower than the width of the edge of the luminance level included in graph 71. In this way, the display device 1 can suppress the degree of moving image blur that occurs at the edges when moving images are displayed at 120 Hz, thereby improving the display quality of the moving images. quality can be improved.

[0075] 18 is a diagram showing the actual luminance levels of pixels in images of three frames constituting input image data (moving image) in one embodiment of the present invention, and the luminance levels of each pixel visually recognized by a user when the image is displayed without double-speed driving. An example in which the image data conversion unit 2 processes an image having each luminance level shown in FIG. 18 will be described below. In the example of FIG. 18, an edge exists between an area in the image where luminance level 0 continues and an area where luminance level 1 continues. The position of the edge is the same as the position of the edge of the intermediate luminance level shown in FIG. 6.

[0076] Fig. 19 is a diagram showing the actual luminance levels of pixels in six subframe images constituting converted display data in one embodiment of the present invention, and the luminance levels of each pixel as viewed by a user when the image is displayed at double speed. The image data conversion unit 2 converts the luminance levels of each pixel shown in Fig. 18 into the images of each subframe shown in Fig. 19 by the above-mentioned method. The values ​​of the first half subframe coefficient Pf and second half subframe coefficient Ps of each pixel determined by this are the same as those shown in Fig. 7.

[0077] 12, regardless of the values ​​of the first-half subframe coefficient Pf and the second-half subframe coefficient Ps, the output luminance level corresponding to the minimum input luminance level in the converted data corresponding to the n first half subframes is the same as the output luminance level corresponding to the minimum input luminance level in the converted data corresponding to the second half subframes. Moreover, the output luminance level corresponding to the maximum input luminance level in the converted data corresponding to the first half subframes is the same as the output luminance level corresponding to the maximum input luminance level in the converted data corresponding to the n second half subframes.

[0078] The minimum luminance level here is 0, and the maximum luminance level is 1. That is, as shown in FIG. 12, regardless of the values ​​of the first-half subframe coefficient Pf and the second-half subframe coefficient Ps, in all of graphs 41 to 43 and 51 to 53, the minimum input luminance level "0" corresponds to the minimum output luminance level "0", and the maximum input Brightness level "1" is maximum output 19 corresponds to the luminance level "1". Therefore, regardless of the value of the first half subframe coefficient Pf, if the luminance level of the pixel of the nth frame is 0, the first half subframe luminance determination unit 16 determines 0 as the luminance level of the pixel of the nth first half subframe. Furthermore, if the luminance level of the pixel of the nth frame is 1, the first half subframe luminance determination unit 16 determines 1 as the luminance level of the pixel of the nth first half subframe. Similarly, regardless of the value of the second half subframe coefficient Ps, if the luminance level of the pixel of the nth frame is 0, the second half subframe luminance determination unit 18 determines 0 as the luminance level of the pixel of the nth second half subframe. Furthermore, if the luminance level of the pixel of the nth frame is 1, the second half subframe luminance determination unit 18 determines 1 as the luminance level of the pixel of the nth second half subframe. The same applies to the other frames. Therefore, the luminance levels of the pixels in all the first half subframes and the second half subframes shown in FIG. 19 are the same as the luminance level of the corresponding pixel in the corresponding frame. As a result, the display device 1 displays an image identical to the image of the nth frame on the OLED panel 22, for example, in the nth first half subframe and the nth second half subframe, respectively.

[0079] Fig. 20 is a diagram showing the distribution of luminance levels of each pixel in L rows of the nth first half subframe and the distribution of luminance levels of each pixel in L rows of the nth latter half subframe. In Fig. 20, graph 81 shows the distribution of luminance levels of each pixel in L rows of the nth first half subframe shown in Fig. 19. Graph 82 shows the distribution of luminance levels of each pixel in L rows of the nth latter half subframe shown in Fig. 19. In Fig. 20, the horizontal axis shows the position of each pixel in L rows, and the vertical axis shows the output luminance level after conversion.

[0080] As shown in Fig. 20, the luminance level of each pixel in the n-th first subframe is the same as the luminance level of the same pixel in the n-th second subframe for any pixel. Therefore, when an image is displayed by driving it at double speed as shown in Fig. 19, no flicker occurs in the entire image. In this way, the display device 1 can prevent the display quality of a moving image from deteriorating when a moving image having an edge between the minimum and maximum luminance levels is displayed by driving it at double speed.

[0081] Fig. 21 is a diagram showing a moving image blur waveform visually recognized by a user. Graph 91 is a graph showing the distribution of luminance levels actually visually recognized by a user when a moving image is displayed at 60 Hz as shown in Fig. 18. Graph 92 is a graph showing the distribution of luminance levels actually visually recognized by a user when a moving image is displayed at double speed driving of 120 Hz as shown in Fig. 19. In Fig. 21, the horizontal axis indicates the position of each pixel in row L of an image, and the vertical axis indicates the luminance level actually visually recognized by a user.

[0082] Graph 91 corresponds to the waveform of the blurred moving image when the moving image is displayed at 60 Hz, and graph 92 corresponds to the waveform of the blurred moving image when the moving image is displayed at double speed, 120 Hz. 219, the width of the edge of the luminance level included in graph 92 is the same as the width of the edge of the luminance level included in graph 91. In this way, when a moving image having an edge between the minimum and maximum luminance levels is displayed at 120 Hz, the display device 1 can prevent the degree of moving image blurring occurring at the edge from worsening.

[0083] (Modification) In the display device 1, the conversion data for determining the luminance level for the first half subframe and the conversion data for determining the luminance level for the second half subframe may be interchanged. In this modification, when the input luminance level is In and the output luminance level is Fn, the conversion data for the n-th first half subframe is defined as follows: Fn=In×Pf+In (when In is 0.5 or less) Fn=(1-In)×Pf+In (when In is greater than 0.5).

[0084] Furthermore, if the input luminance level is In and the output luminance level is Sn, the conversion data for the n-th latter subframe is defined as follows: Sn = (-1 × In) × Ps + In (when In is 0.5 or less) Sn=(In-1)×Ps+In (when In is greater than 0.5).

[0085] In this example, graphs 51 to 53 shown in Fig. 12 show the correspondence relationship between the input luminance level and the output luminance level in the conversion data for determining the luminance level of the first half subframe. Graphs 41 to 43 shown in Fig. 12 show the correspondence relationship between the input luminance level and the output luminance level in the conversion data for determining the luminance level of the second half subframe.

[0086] In this example, the difference between the output luminance level corresponding to the input luminance level in the conversion data for the n first half subframe and the output luminance level corresponding to the same input luminance level in the second conversion data for the n second half subframe remains the same as in the previous example, but in the range where the input luminance level is greater than 0 and less than 1, the output luminance level corresponding to the input luminance level in the conversion data for the n first half subframe is greater than the output luminance level corresponding to the same input luminance level in the conversion data for the n second half subframe.

[0087] Fig. 22 is a diagram showing the actual luminance levels of pixels in six subframe images constituting converted display data in a modified example of the present invention, and the luminance levels of each pixel as viewed by a user when the image is displayed at double speed. Image data conversion unit 2 converts the luminance levels of each pixel shown in Fig. 6 into the images of each subframe shown in Fig. 22 by the method of this modified example. At this time, the values ​​of the first half subframe coefficient Pf and second half subframe coefficient Ps of each pixel determined during the process are the same as those shown in Fig. 7.

[0088] FIG. 23 is a diagram showing the distribution of luminance levels of each pixel in L rows in the nth first half subframe and the distribution of luminance levels of each pixel in L rows in the nth latter half subframe. 23 22. Graph 101 shows the distribution of luminance levels of pixels in L rows in the nth first half subframe shown in FIG. 22. Graph 102 shows the distribution of luminance levels of pixels in L rows in the nth second half subframe shown in FIG. 23 , the horizontal axis indicates the position of each pixel in row L, and the vertical axis indicates the output luminance level after conversion.

[0089] As shown in graph 101 of Fig. 22 and Fig. 23, the luminance levels F12(n) to F15(n) of the pixels X12 to X15 in the nth first half subframe are all 0.5 or more. first halfIn the subframe image, the luminance level of the edge position near pixel X12 is emphasized. Furthermore, as shown in graph 102 in Figures 22 and 23, the luminance levels S8(n) to S11(n) of pixels X8 to X11 in the nth latter subframe are all 0. That is, in the image of the nth latter subframe, black is inserted at the edge position near pixel X12.

[0090] As shown in graphs 101 and 102 of Fig. 22 and Fig. 23, in an area away from an edge, the luminance level of the nth first subframe and the luminance level of the nth latter subframe at the same pixel position are the same value. For example, in an area to the left of an edge, the luminance level is 0.25 in both the nth first subframe and the nth latter subframe. Also, in an area to the right of an edge, the luminance level is 0.5 in both the nth first subframe and the nth latter subframe. In this way, the position where black display is inserted in the nth latter subframe is limited to the position where an edge exists.

[0091] Therefore, in this example, the display device 1 can also display edges more sharply by inserting black display, thereby improving the display quality of moving images. Furthermore, because black display is inserted only near edges, even if flicker occurs in moving images displayed at 120 Hz, the position where the flicker occurs is limited to the edge vicinity where black display is inserted. This makes it possible to keep the position where flicker occurs in moving images to a minimum range, thereby preventing a decrease in the display quality of moving images in areas other than edges.

[0092] 24 is a diagram showing a moving image blur waveform visually recognized by a user. Graph 111 is a graph showing the distribution of luminance levels actually visually recognized by a user when a moving image is displayed at 60 Hz as shown in FIG. 112is a graph showing the distribution of luminance levels actually perceived by a user when a moving image is displayed at double speed of 120 Hz as shown in Fig. 23. In Fig. 24, the horizontal axis shows the position of each pixel in row L of the image, and the vertical axis shows the luminance level actually perceived by the user.

[0093] Graph 111 corresponds to the moving image blur waveform when moving images are displayed at 60 Hz, and graph 112 corresponds to the moving image blur waveform when moving images are displayed at double speed at 120 Hz. As shown in FIG. 24, the width of the edge of the luminance level included in graph 112 is narrower than the width of the edge of the luminance level included in graph 111. In this way, in this example as well, the display device 1 can suppress the degree of moving image blur that occurs at the edges when moving images are displayed at 120 Hz, thereby improving the display quality of the moving images. quality can be improved.

[0094] (Other variations) In the present embodiment, for the sake of convenience, an example has been described in which only pixels arranged around the pixel of interest in the same row as the pixel of interest are specified as the surrounding pixels. However, the present invention is not limited to this, and the display device 1 may also specify pixels arranged around the pixel of interest in the vertical and diagonal directions as the surrounding pixels. Specifically, when the pixel of interest is superimposed on the center A55 of the filter 31 in the L row of the image of the nth frame, the frame memory controller 14 may specify all of the 80 pixels in total that are superimposed on each filter value other than A55 in the filter 31 as the surrounding pixels. This allows the frame memory controller 14 to specify the pixels arranged around the pixel of interest in the horizontal, vertical, and diagonal directions as the surrounding pixels. Furthermore, when the pixel of interest is superimposed on the center B33 of the filter 32 in the L row of the image of the nth frame, the line memory controller 13 may specify all of the 24 pixels in total that are superimposed on each filter value other than B33 in the filter 32 as the surrounding pixels. This allows the line memory controller 13 to specify pixels disposed around the pixel of interest in the horizontal direction, vertical direction, and diagonal direction as surrounding pixels.

[0095] The shape of the filters 31 and 32 may be any planar shape other than a square. Specifically, the filters 31 and 32 may be any planar shape in which a plurality of filter values ​​are arranged in a plane. Examples of such shapes include a rectangle, a circle, and an ellipse.

[0096] The size of filter 31 may be any size other than 9 rows and 9 columns. Each filter value included in filter 31 may be any value other than the filter values ​​shown in Fig. 8. The size of filter 32 may be any size other than 5 rows and 5 columns. Each filter value included in filter 32 may be any value other than the filter values ​​shown in Fig. 9.

[0097] The gradation / luminance converter 11 and the luminance / luminance converter 6 are not necessarily required for the display device 1. That is, the image data converter 2 converts the luminance / luminance into the gradation level of each pixel of the nth frame of the image .... The grayscale level of each pixel of the image of the n-th first half subframe and the grayscale level of each pixel of the image of the n-th latter half subframe may be determined. In this example, the conversion data for the n-th first half subframe and the conversion data for the n-th latter half subframe need to be implemented as a conversion table that defines the correspondence between the input grayscale level and the output grayscale level in consideration of the gamma characteristics of the OLED panel 22.

[0098] The display device 1 may include any display panel other than the OLED panel 22 capable of high-speed response. For example, the display device 1 may include a display panel having a slower response speed than the OLED panel 22. In this case, it is desirable to appropriately adjust the correspondence between the input luminance level and the output luminance level in the conversion data shown in FIG. 12 according to the response speed of the display panel included in the display device 1.

[0099] 〔summary〕 A display device according to a first aspect of the present invention is a display device that divides one frame into a first sub-frame and a second sub-frame, and displays an image in each of the first sub-frame and the second sub-frame, and includes: a pixel of interest identifying unit that identifies one of a plurality of pixels constituting the image of the one frame as a pixel of interest; a first peripheral pixel identifying unit that identifies a plurality of first peripheral pixels arranged around the pixel of interest in the image; a first difference coefficient determination unit that determines a plurality of first difference coefficients based on differences between pixel values ​​of the pixel of interest and the plurality of first peripheral pixels in the image of the one frame, and a pixel value of the pixel of interest in the image of the one frame; a first coefficient determination unit that determines a first coefficient by performing an operation using a first filter on each of the plurality of first difference coefficients; and a filter that defines a relationship between an input pixel value, the first coefficient, and an output pixel value. a second peripheral pixel specifying unit that specifies a plurality of second peripheral pixels arranged around the pixel of interest in the image; a second difference coefficient determination unit that determines a plurality of second difference coefficients based on differences between pixel values ​​of the pixel of interest and the plurality of second peripheral pixels in an image of a frame following the one frame and pixel values ​​of the pixel of interest and the plurality of second peripheral pixels in the image of the one frame; a second coefficient determination unit that determines a second coefficient by performing an operation using a second filter on each of the plurality of second difference coefficients; and a second pixel value determination unit that determines a pixel value of the pixel of interest in the image of the latter subframe based on second conversion data that specifies an input pixel value and a relationship between the second coefficient and an output pixel value, Before The larger the first and second coefficients are, the larger the difference between the output pixel value corresponding to the input pixel value in the first transformed data and the output pixel value corresponding to the same input pixel value in the second transformed data.

[0100] A display device according to aspect 2 of the present invention may be configured in such a way that, in the above-mentioned aspect 1, the first filter has a plurality of first filter values ​​arranged two-dimensionally, and the first surrounding pixel identification unit identifies, when a first filter value located at the center of the first filter is superimposed on the pixel of interest, a plurality of pixels that are superimposed on each of the first filter values ​​around the center of the first filter as the first surrounding pixels, and the second filter has a plurality of second filter values ​​arranged two-dimensionally, and the second surrounding pixel identification unit identifies, when a second filter value located at the center of the second filter is superimposed on the pixel of interest, a plurality of pixels that are superimposed on each of the second filter values ​​around the center of the second filter as the second surrounding pixels.

[0101] A display device according to a third aspect of the present invention may be configured in the second aspect above, wherein the first filter is larger than the second filter.

[0102] A display device according to aspect 4 of the present invention may be configured in such a way that, in aspect 1 above, regardless of the values ​​of the first coefficient and the second coefficient, the output pixel value corresponding to the smallest input pixel value in the first conversion data is identical to the output pixel value corresponding to the smallest input pixel value in the second conversion data, and the output pixel value corresponding to the largest input pixel value in the first conversion data is identical to the output pixel value corresponding to the largest input pixel value in the second conversion data.

[0103] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included in the technical scope of the present invention. New technical features can also be formed by combining the technical means disclosed in each embodiment. [Explanation of symbols]

[0104] 1 Display device 2 Image data conversion section 3 Line Memory 4 Frame Memory 5 Data Selector 6 Luminance gradation conversion section 7 Image display section 11 Gradation brightness conversion section 12 Timing Controller 13 Line Memory Controller 14 Frame Memory Controller 15 First half subframe coefficient determination section 16 First half subframe luminance determination section 17 Second half subframe coefficient determination section 18 Second half subframe luminance determination section 21 Panel drive unit 22 OLED Panel 31, 32 Filter

Claims

1. A display device that divides one frame into a first half sub-frame and a second half sub-frame, and displays an image in each of the first half sub-frame and the second half sub-frame, a pixel of interest specification unit that specifies one of a plurality of pixels constituting an image of one frame as a pixel of interest; a first surrounding pixel specifying unit that specifies a plurality of first surrounding pixels arranged around the pixel of interest in the image; a first difference coefficient determination unit that determines a plurality of first difference coefficients based on differences between pixel values ​​of the pixel of interest and the plurality of first peripheral pixels in the image of the one frame and a pixel value of the pixel of interest in the image of the one frame; a first coefficient determination unit that determines a first coefficient by performing an operation using a first filter on each of the plurality of first difference coefficients; a first pixel value determination unit that determines a pixel value of the pixel of interest in an image of the first half subframe based on first conversion data that defines a correspondence relationship between an input pixel value, the first coefficient, and an output pixel value; a second surrounding pixel specifying unit that specifies a plurality of second surrounding pixels arranged around the pixel of interest in the image; a second difference coefficient determination unit that determines a plurality of second difference coefficients based on differences between pixel values ​​of the pixel of interest and the plurality of second peripheral pixels in an image of a frame immediately following the one frame and pixel values ​​of the pixel of interest and the plurality of second peripheral pixels in the image of the one frame; a second coefficient determination unit that determines a second coefficient by performing an operation using a second filter on each of the plurality of second difference coefficients; a second pixel value determination unit that determines a pixel value of the pixel of interest in an image of the latter subframe based on an input pixel value and second conversion data that defines a correspondence relationship between the second coefficient and an output pixel value, A display device characterized in that the larger the first coefficient and the second coefficient that are identical to each other, the larger the difference between the output pixel value corresponding to the input pixel value in the first conversion data and the output pixel value corresponding to the same input pixel value in the second conversion data.

2. the first filter has a plurality of first filter values ​​arranged two-dimensionally; the first surrounding pixel identification unit identifies, when a first filter value located at a center of the first filter is superimposed on the target pixel, a plurality of pixels that are superimposed on each of the first filter values ​​around the center of the first filter as the first surrounding pixels; the second filter has a plurality of second filter values ​​arranged two-dimensionally; The display device according to claim 1, characterized in that, when a second filter value located at the center of the second filter is superimposed on the target pixel, the second surrounding pixel identification unit identifies a plurality of pixels that are superimposed on each second filter value around the center of the second filter as the second surrounding pixels.

3. The display device according to claim 2 , wherein the first filter is larger in size than the second filter.

4. A display device according to any one of claims 1 to 3, characterized in that the output pixel value corresponding to the input pixel value in the second conversion data is greater than the output pixel value corresponding to the same input pixel value in the first conversion data.

5. The display device according to any one of claims 1 to 4, characterized in that, regardless of the values ​​of the first coefficient and the second coefficient, the output pixel value corresponding to the smallest input pixel value in the first conversion data is identical to the output pixel value corresponding to the smallest input pixel value in the second conversion data, and the output pixel value corresponding to the largest input pixel value in the first conversion data is identical to the output pixel value corresponding to the largest input pixel value in the second conversion data.

Images