JP2005345889A - Display method of plasma display panel and plasma display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce animation image pseudo-contours, while suppressing the deterioration of gradations and the generation of dither pattern noise. <P>SOLUTION: A first table and a second table varying in the combinations of subfields, with respect to the same luminance, are prepared inside a gradation conversion circuit 5. A γ reverse correction circuit 4 converts an input image into a reference gradation at which the animation image pseudo-contour is less likely to occur. The gradation conversion circuit 5 discriminates, to what position in the dither matrix the image data of a processing object corresponds, Then the circuit compares the image data and a corresponding dither coefficient and performs the dither processing to select either one of the first table and the second table. An output processing circuit 6 causes a cell of a PDP 1 to emit light, only for the period corresponding to the weighting of the selected subfield. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention performs multi-gradation display by dividing one field period of a video signal into a plurality of subfields having different relative luminances and emitting light by appropriately combining the subfields according to the luminance of the pixels of the video signal. The present invention relates to a display method of a plasma display panel and a plasma display device.

  A plasma display device for performing multi-gradation display of a plasma display panel (hereinafter referred to as PDP) in which each pixel is formed in a matrix is configured as shown in FIG. FIG. 1 is a block diagram showing the configuration of a plasma display apparatus according to an embodiment of the present invention. The entire configuration of a conventional plasma display apparatus is the same as that of FIG. A plasma display device will be described.

  The plasma display apparatus of FIG. 1 includes a level adjustment circuit 2 that adjusts the level of an input video signal, an A / D conversion circuit 3 that converts the output of the level adjustment circuit 2 into 8-bit image data by A / D conversion, A γ reverse correction circuit 4 that performs γ reverse correction on the image data output from the A / D conversion circuit 3, and a dither process on the image data that has been subjected to the γ reverse correction, and the dithered image data will be described later. A gradation conversion circuit 5 for converting to pixel drive data, an output processing circuit 6 for controlling light emission of the PDP 1 based on the pixel drive data output from the gradation conversion circuit 5, and a synchronizing signal (vertical) from the input video signal A synchronization separation circuit 7 that separates the synchronization signal and the horizontal synchronization signal), and generation of timing pulses that define the A / D conversion timing of the A / D conversion circuit 3 based on the synchronization signal from the synchronization separation circuit 7 A timing pulse generation circuit 8; a memory control circuit 9 for controlling reading of data from the output processing circuit 6 by inputting the timing pulse; and a display timing of each pixel of the PDP 1 based on the timing pulse. The driving timing generation circuit 10 generates a timing signal.

  When performing display on a display panel using such a PDP 1 or a ferroelectric liquid crystal element, each pixel (discharge cell) has only two states of light emission and non-light emission. The sub-field is divided into a plurality of subfields having different relative ratios of the sustain light emission period (proportional to the light emission luminance) that is the lighting period, and the subfield corresponding to the input video signal is selected to correspond to the weight of the selected subfield. A predetermined gradation display is obtained by causing the corresponding pixel of the PDP 1 to emit light only during the period.

The example of FIG. 23 is an example in which one field display period is composed of eight subfields Sf1 to Sf8, and 256 gradation display is performed by 8 gradation bits. That is, the most significant gradation bit (8th bit) corresponds to the subfield Sf8, the 7th gradation bit is in the subfield Sf7, and the 6th gradation bit is in the subfield Sf6 in the following order. The fifth gradation bit is subfield Sf5, the fourth gradation bit is subfield Sf4, the third gradation bit is subfield Sf3, and the second gradation bit is subfield. Corresponding to Sf2, respectively, the lowest gradation bit (first bit) corresponds to subfield Sf1. In each of the subfields Sf1 to Sf8, the sustain light emission period has the number of gradations (relative ratio of light emission luminance) 1 (= 2 ⁰ ), 2 (= 2 ¹ ), 4 (= 2 ² ), 8 (= 2 ³ ). , 16 (= 2 ⁴ ), 32 (= 2 ⁵ ), 64 (= 2 ⁶ ), 128 (= 2 ⁷ ).

The example of FIG. 23 shows a case where an 8-bit gradation is displayed. Generally, when an n-bit gradation is displayed, the relative ratio of the emission luminance of each subfield is at least 2 ^n−1. : 2 ⁿ⁻² : 2 ⁿ⁻³ ... 2 ² : 2 ¹ : 1 is required to be configured. However, when displaying with such a minimum subfield configuration, no problem occurs in the portion where the image is stationary, but the human eye should not originally exist in the portion where the image is moving. Since luminance is recognized and image quality degradation called a moving image pseudo contour occurs, a configuration of 9 subfields or more is generally used when displaying 8-bit gradation at present. The cause of the occurrence of the moving image pseudo contour is that the human eye recognizes the light emitting part and the non-light emitting part in a certain subfield and the subfields before and after the subfield.

  Furthermore, as a technique for suppressing the moving image pseudo contour, a method has been proposed in which gradations that are difficult to generate moving image pseudo contours are selected and intermediate gradations are displayed by gradation conversion such as dithering or error diffusion processing. (For example, refer to Patent Document 1).

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
JP 2000-276100 A

  Although the plasma display device of Patent Document 1 has a high effect of suppressing the moving image pseudo contour, since the intermediate gradation is displayed by a dither method, an error diffusion process, or the like, light and dark interference such as dither pattern noise and granular noise of the error diffusion process is performed. In some cases, the image quality deteriorates due to the image quality, or when the human line of sight moves in synchronization with the dither pattern in the moving image.

  The present invention has been made to solve the above-described problems. When performing gradation display by a subfield method in a plasma display panel, a moving picture pseudo contour is suppressed while suppressing deterioration of gradation and generation of dither pattern noise. An object of the present invention is to provide a plasma display panel display method and a plasma display device that can be effectively reduced.

  The present invention divides one field period of a plasma display panel into a plurality of subfields each weighted with a light emission period, and controls light emission or non-light emission of each subfield according to the luminance of a pixel of an input image. In a display method of a plasma display panel that performs multi-gradation display, a γ inverse correction procedure for converting an input image into an image having a predetermined number of gradations, and a dither coefficient corresponding to each pixel of the input image in a matrix form The dither matrix arranged in the dither matrix is generated, the pixel data to be processed subjected to the gradation conversion in the γ inverse correction procedure is determined to correspond to the position in the dither matrix, and the pixel data and the corresponding dither are determined. A coefficient for comparing the coefficients and selecting one of the first table and the second table prepared in advance according to the result of the comparison. A pixel representing a subfield corresponding to the pixel data converted by the gradation conversion procedure, and a gradation conversion procedure for converting the pixel data to be processed into pixel data of the display gradation number An acquisition procedure for acquiring drive data from the selected first table or second table, and light emission of the cell of the plasma display panel corresponding to the pixel data to be processed according to the acquired pixel drive data The first table and the second table have different subfield settings.

  Further, in one configuration example of the display method of the plasma display panel of the present invention, the γ reverse correction procedure uses the luminance of the predetermined gradation number in which the movement amount of the light emission center of gravity is small with respect to the luminance change as a reference gradation, and Each pixel data of the input image is converted to this reference gradation, and the first table shows the position of the emission centroid of the reference gradation immediately before the position of the emission centroid for each of the display gradation pixel data. The combination of subfields is set in advance so as to substantially match, and in the second table, the position of the light emission center of gravity for each of the display gradation pixel data is substantially the same as the position of the light emission gravity center of the immediately following reference gradation Thus, the combination of subfields is preset.

  In one configuration example of the display method of the plasma display panel of the present invention, the gradation conversion procedure includes the reference gradation data of the predetermined number of gradations and display gradation data representing the display gradation corresponding thereto. A procedure for obtaining display gradation data corresponding to pixel data to be processed that has been subjected to gradation conversion by the γ reverse correction procedure using a reference gradation table stored in advance, and for each reference gradation of the predetermined number of gradations, A procedure for obtaining luminance difference data corresponding to pixel data to be processed that has been subjected to gradation conversion by the γ reverse correction procedure, by means of a skip gradation table that stores luminance difference data representing a luminance difference from a reference gradation in advance; And a procedure for performing gradation conversion of the pixel data to be processed into pixel data having the number of display gradations based on display gradation data and the luminance difference data.

  Further, the present invention divides one field period of the plasma display panel into a plurality of subfields each weighted with a light emission period, and controls light emission or non-light emission of each subfield according to the luminance of the pixel of the input image. Thus, in the plasma display device that performs multi-gradation display, γ reverse correction means for converting an input image into an image having a predetermined number of gradations, input pixel data, and pixel drive data representing a subfield to be selected A first table stored in association with each other, a second table in which input pixel data and pixel drive data are stored in association with each other, and a combination of subfields represented by the pixel drive data is different from the first table; A dither matrix is generated in which coefficients are arranged in a matrix corresponding to each pixel of the input image, and the γ inverse correction means generates a dither matrix. A determination is made as to which position in the dither matrix the pixel data to be processed corresponding to the tone conversion is performed, and the pixel data to be processed is compared with a dither coefficient at a position corresponding to the pixel data. A dither processing means for selecting one of the first table and the second table, a gradation converting means for converting the pixel data to be processed into pixel data of the number of display gradations, and Acquisition means for acquiring pixel drive data corresponding to the pixel data subjected to gradation conversion by the gradation conversion means from the selected first table or second table; and, depending on the acquired pixel drive data, And a light emission control means for emitting light from the cell of the plasma display panel corresponding to the pixel data to be processed.

  According to the present invention, a reference gradation that hardly generates a moving image pseudo contour is selected in the γ reverse correction procedure, and an intermediate gradation between the reference gradations is displayed by dither processing. At this time, two combinations of subfields to be selected for one luminance, the first table and the second table, are prepared, and two light emission patterns having different light emission centroids are distributed and arranged by dither processing. Since only the light emission center of gravity can be gently changed according to the luminance change without causing a luminance difference between the two light emission patterns, the moving image pseudo contour can be greatly reduced. Further, in the present invention, it is possible to suppress the occurrence of dither pattern noise by setting the two light emission patterns to the same luminance, and it is possible to suppress gradation deterioration by suppressing the dither pattern noise. As a result, according to the present invention, high image quality can be realized in the plasma display device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a plasma display apparatus according to an embodiment of the present invention. The plasma display device of FIG. 1 includes a PDP 1, a level adjustment circuit 2, an A / D conversion circuit 3, a γ inverse correction circuit 4, a gradation conversion circuit 5, an output processing circuit 6, and a synchronization separation circuit 7. , A timing pulse generation circuit 8, a memory control circuit 9, and a drive timing generation circuit 10.

  The gradation conversion circuit 5 constitutes a dither processing means, a gradation conversion means, and an acquisition means, and the output processing circuit 6, the memory control circuit 9, and the drive timing generation circuit 10 constitute a light emission control means.

  The level adjustment circuit 2 performs level adjustment so that the input video signal becomes an appropriate level. The A / D conversion circuit 3 performs A / D conversion on the video signal level-adjusted by the level adjustment circuit 2 and outputs it as 8-bit image data. The γ reverse correction circuit 4 performs γ reverse correction on the 8-bit image data output from the A / D conversion circuit 3 in order to maintain compatibility with the light emission characteristics of the CRT.

  The gradation conversion circuit 5 generates a dither matrix in which dither coefficients are arranged in a matrix corresponding to each pixel of the input image, performs dither processing on the image data subjected to γ inverse correction, and performs dither processing. Data is converted into pixel drive data representing a subfield to be selected.

  The output processing circuit 6 has a field memory (not shown) for storing pixel drive data for one field output from the gradation conversion circuit 5, and each pixel drive data in the field memory is stored in each pixel (discharge) of the PDP 1. Cell) display data is output to the data electrode, thereby causing the discharge cells of PDP 1 to emit light for a period corresponding to the weighting of the subfield selected by the gradation conversion circuit 5.

  The synchronization separation circuit 7 separates a synchronization signal (vertical synchronization signal and horizontal synchronization signal) from the input video signal. The timing pulse generation circuit 8 generates various timing signals to the A / D conversion circuit 3, the memory control circuit 9, and the drive timing generation circuit 10 based on the synchronization signal extracted by the synchronization separation circuit 7.

  The memory control circuit 9 reads out pixel drive data from the field memory of the output processing circuit 6 based on the timing signal of the timing pulse generation circuit 8, and causes the output processing circuit 6 to perform light emission control of the PDP 1 based on this pixel drive data. . The drive timing generation circuit 10 generates subfield timing, pulse signals for driving each scan electrode and sustain electrode of the PDP 1 based on the timing signals from the timing pulse generation circuit 8 and the memory control circuit 9.

  In the plasma display device according to the present embodiment, as shown in FIG. 2, one field period is divided into 12 subfields SF1 to SF12 to enable 256 gradation display. Each of the subfields SF1 to SF12 has a scanning period and a light emission period, and the ratio of the light emission periods of the subfields SF1 to SF12 is 1: 2: 4: 7: 10: 14: 19: 25: 32: 39. : 47:55.

  There are 4096 combinations of subfields SF1 to SF12 with 2 to the 12th power. The conditions for creating the subfield configuration in Fig. 2 are described in the document "" PDP moving image pseudo contour reduction method ", IPSJ Annual Conference 19-10, 1998, p.276. That is, in the subfield configuration created so that the light emission center of gravity during one field period changes gently, the gradation in which the maximum subfield in each gradation changes from OFF to ON, and the second in which the maximum subfield is ON. The gray level at which the largest sub-field changes from OFF to ON, the gray level at which the largest and second largest sub-field changes to ON and the third largest sub-field changes from OFF to ON, etc. ing. However, the gradation that changes from OFF to ON in the sub-fields up to the fourth lower level need not be selected.

  In the present embodiment, a plurality of specific luminances among 256 gradations are referred to as reference gradations. A luminance with a small movement amount of the light emission center of gravity in one field with respect to a luminance change between the reference gradations is selected in advance as a reference gradation.

  In the conventional technique, intermediate gray levels between these selected reference gray levels are expressed by dither processing or error diffusion processing. Error diffusion processing is a method for smooth reproduction of intermediate tones by calculating the error between the color density of each point and white or black, and then distributing the calculated error to the surrounding pixels in order and averaging them. It is. On the other hand, in the dither process, a dither matrix composed of different coefficient values is added to data of a plurality of pixels adjacent to each other vertically and horizontally. At this time, when a plurality of pixels are regarded as one pixel, the apparent number of gradations is increased by the dither processing.

  As an example of the dither matrix, a Bayer matrix shown in FIG. 3 is known. The Bayer matrix in FIG. 3 is a matrix in which dither coefficients of 0 to 15 are arranged in a matrix corresponding to 16 pixels of horizontal 4 pixels × vertical 4 pixels.

  For example, when 107, which is an intermediate gradation between luminance 105 and luminance 111, is expressed by dither processing, 105 × (11/16) + 111 × (5/16) = 106.875≈107, so that the Bayer shown in FIG. Luminance 107 can be expressed by emitting light at a luminance of 111 at positions of coefficients 0 to 4 in the matrix and emitting light at a luminance of 105 at positions of coefficients 5 to 15. The light emission pattern in this case is shown in FIG. 4, and the combinations of the subfields SF1 to SF12 are shown in FIG. By this dither processing, the light emission center of gravity in one field changes gently with the change in luminance, so that the moving image pseudo contour is reduced.

  However, in the conventional technique, pattern noise called dither noise is generated because dither processing is performed at a luminance having a luminance level difference of 105 and 111. In addition, there is a problem that when a dither pattern and the motion of an image are synchronized in a moving image, the gradation is deteriorated and recognized.

  Therefore, in the present embodiment, in order to improve these problems, for example, when displaying the luminance 107, dithering is not performed at the luminances 105 and 111, but as shown in FIG. When the position of the center of gravity is close to the position of the light emission center of gravity in the case of the luminance 105, the position of the Bayer matrix coefficient 5 to 15 is emitted with the luminance 107 (represented as the luminance 107a in FIG. 6) by the subfield configuration selected. The positions of the Bayer matrix coefficients 0 to 4 are emitted with the luminance 107 (represented as the luminance 107b in FIG. 6) by the subfield configuration selected so as to be close to the position of the emission centroid when the position of the emission centroid is luminance 111. .

  FIG. 7 shows combinations of subfields SF1 to SF12 in this case. According to the present embodiment, it is possible to gently change only the light emission center of gravity according to the luminance change without causing a luminance difference between the two light emission patterns.

  Hereinafter, the operation of the main part of the plasma display device of the present embodiment will be described in more detail. As described above, the γ reverse correction circuit 4 performs γ reverse correction on the 8-bit image data output from the A / D conversion circuit 3. At this time, the 256 gradation image data of 0 to 255 is converted to a predetermined gradation. The image data is converted into a number of image data (62 tones in the present embodiment) and output.

  The integer part of the output data of the γ reverse correction circuit 4 represents a reference gradation of 0 to 61, and the decimal part represents an intermediate gradation between the reference gradations. In this way, the gradation conversion processing by the γ reverse correction circuit 4 removes the moving image except for the luminance at which the moving image pseudo contour is likely to be generated, that is, the luminance in which the moving amount of the light emission center of gravity with respect to the luminance change is large. Only the reference gradations that are unlikely to generate pseudo contours are selected.

  FIG. 8 shows the configuration of the gradation conversion circuit 5. The gradation conversion circuit 5 includes a reference gradation table 51, a skip gradation table 52, a dither processing unit 53, a first SFM table 54, a second SFM table 55, and an SFM selector 56. The The dither processing unit 53 constitutes a dither processing unit and a conversion unit of a gradation conversion unit, and the SFM selector 56 constitutes an acquisition unit.

  The reference gradation table 51 stores each reference gradation data of 0 to 61 and display gradation data in association with each other, and displays corresponding to the integer part of the pixel data to be processed input from the γ inverse correction circuit 4. Gradation data is read and output. The configuration of the reference gradation table 51 is shown in FIGS. 9 and 10, γout is a value expressed in decimal notation for the integer part of the output pixel data of the γ inverse correction circuit 4, and refout is a value expressed in decimal notation for the output data of the reference gradation table 51. SF1 to SF12 represent combinations of subfields corresponding to the reference gradation, and “1” represents selection and “0” represents non-selection. According to the reference gradation table 51, for example, the reference gradation 24 corresponds to the luminance 73 when converted into 256 display gradations displayed on the plasma display device.

  The skip gradation table 52 stores a value obtained by converting the luminance difference with the next reference gradation for each reference gradation of 0 to 61 by the display gradation, and the processing target input from the γ reverse correction circuit 4 is stored in the skip gradation table 52. Brightness difference data from the next reference gradation is output for the reference gradation indicated by the pixel data. The configuration of the skip gradation table 52 is shown in FIG. In FIG. 11, “Skipout” is a value representing the output data of the skip gradation table 52 in decimal. According to the skip gradation table 52, for example, it is found that the luminance difference between the reference gradation 24 and the next reference gradation 25 is 6 when converted by the display gradation. This is because the reference gradation 24 corresponds to the luminance 73 when converted to the display gradation, and the reference gradation 25 corresponds to the luminance 79 when converted to the display gradation.

  The first SFM table 54 and the second SFM table 55 store pixel data of 0 to 255 and pixel drive data representing a combination of subfields to be selected in association with each other. 12 to 16 show the configuration of the first SFM table 54, and FIGS. 17 to 21 show the configuration of the second SFM table 55. 12 to 21, input is a value representing 8-bit pixel data in decimal, Aout is a value representing 8-bit pixel drive data in the first SFM table 54 in decimal, and Bout is a second value. This is a value representing 8-bit pixel drive data in the SFM table 55 in decimal. Similar to FIGS. 9 and 10, SF1 to SF12 represent combinations of subfields corresponding to the pixel data input.

  In the first SFM table 54, combinations of subfields are set in advance so that the position of the light emission center of gravity for each of the pixel data inputs 0 to 255 substantially matches the position of the light emission center of gravity of the immediately preceding reference gradation. For example, in the first SFM table 54, when the pixel data input is 74 to 78, the immediately preceding reference gradation is 73 when expressed as a value converted to a display gradation. Therefore, for the pixel data input 74 to 78, the combination of subfields is selected so that the position of the light emission center of gravity substantially coincides with the position of the light emission center of gravity of the reference gradation 73.

  SF1, SF3, SF5 to SF8 are selected in advance as subfields corresponding to the reference gradation 73, and the maximum subfield having the maximum weight is SF8. If the luminance 74 to 78 is expressed by changing the combination of the subfield SF7 and below while the maximum subfield is fixed at SF8, the position of the light emission center of gravity can be made substantially coincident with the reference gradation 73.

  On the other hand, in the second SFM table 55, combinations of subfields are set in advance so that the position of the light emission center of gravity for each of the pixel data inputs 0 to 255 substantially coincides with the position of the light emission center of gravity of the immediately following reference gradation. Yes. For example, in the second SFM table 55, when the pixel data input is 74 to 78, the reference gray level immediately after is 79 in terms of the value converted to the display gray level. Therefore, for the pixel data input 74 to 78, the combination of subfields is selected so that the position of the light emission center of gravity substantially matches the position of the light emission center of gravity of the reference gradation 79.

  SF3, SF5 to SF7, and SF9 are selected in advance as subfields corresponding to the reference gradation 79, and the maximum subfield having the maximum weight is SF9. If the luminance 74 to 78 is expressed by changing the combination of subfield SF8 and lower with the maximum subfield fixed at SF9, the position of the light emission center of gravity can be made substantially coincident with the reference gradation 79.

  Next, the dither processing unit 53 generates a dither matrix in which dither coefficients (threshold values) are arranged in a matrix corresponding to each pixel of the input image, and the pixel to be processed output from the γ inverse correction circuit 4 The position where the data is in the dither matrix is determined for each pixel, the dither coefficient at the determined position is compared with the decimal part of the pixel data to be processed, and the first SFM table 54 and the second SFM are compared. Which of the tables 55 should be selected is determined. At the same time, the dither processing unit 53 outputs the decimal part of the pixel data to be processed output from the γ inverse correction circuit 4, the display gradation data output from the reference gradation table 51, and the skip gradation table 52. The pixel data to be processed is converted into display gradation data of 0 to 255 based on the brightness difference data.

  As the dither matrix, the Bayer matrix shown in FIG. 3 may be repeatedly arranged. The position in the dither matrix corresponding to the pixel data to be processed can be determined based on the vertical synchronization signal, the horizontal synchronization signal, and the pixel clock synchronized with each pixel of the input image. The dither processing unit 53 compares the decimal part of the pixel data to be processed with the corresponding dither coefficient, and if the value of the decimal part of the pixel data is smaller than the dither coefficient, the first SFM table 54 is obtained. Control signal (for example, “0”) is generated, and if the value of the fractional part of the pixel data is greater than or equal to the dither coefficient, a control signal (for example, “1”) for specifying the second SFM table 55 is generated. .

  For example, if the decimal part of the pixel data is 4 in decimal number, the control signal is “1” when the dither coefficient is 4 or less, and the control signal is “0” when the dither coefficient is greater than 4. Become. Therefore, if all the decimal parts of each pixel data of horizontal 4 pixels × vertical 4 pixels corresponding to the dither matrix are all 4, the control signals are arranged corresponding to the dither matrix as shown in FIG.

On the other hand, the dither processing unit 53 receives the display gradation data from the reference gradation table 51, thereby determining the reference gradation (value converted to the display gradation) closest to the luminance of the pixel data to be processed. The luminance difference between the reference gradation and the pixel data to be processed (the value converted into the display gradation) can be determined based on the decimal part of the pixel data and the luminance difference data in the skip gradation table 52. Therefore, the pixel data to be processed can be converted into display gradation data.
The dither processing unit 53 performs the above processing for each pixel, and outputs the generated control signal and gradation-converted pixel data to the SFM selector 56.

  The SFM selector 56 uses the first SFM table 54 or the second SFM table specified by the control signal of the dither processing unit 53 as pixel drive data Aout or Bout corresponding to the pixel data input input from the dither processing unit 53. The acquired pixel drive data is output to the output processing circuit 6.

  When the pixel processing data for selecting, for example, the subfields SF2, SF4, SF5, SF7, and SF8 is output from the SFM selector 56 of the gradation conversion circuit 5, the output processing circuit 6 outputs the subfield SF2 according to the pixel driving data. , SF4, SF5, SF7, and SF8, the corresponding discharge cells of PDP1 are caused to emit light for a period corresponding to the weighting.

  As described above, according to the present embodiment, the reference gray scale in which the moving image pseudo contour is unlikely to be generated is selected by the γ reverse correction circuit 4, and the intermediate gray scale between the reference gray scales is displayed by dither processing. At this time, two combinations of subfields to be selected for one luminance, the first SFM table 54 and the second SFM table 55, are prepared, and two emission patterns having different emission centers of gravity (107a shown in FIG. 6) are prepared. And 107b) are distributed by dither processing, so that only the light emission center of gravity can be gently changed in accordance with the luminance change without causing a luminance difference between the two light emission patterns. Can be suppressed. In the present embodiment, it is possible to suppress the occurrence of dither pattern noise by setting the two light emission patterns to the same luminance, and to suppress the deterioration of gradation by suppressing the occurrence of dither pattern noise. Can do.

  Note that a matrix other than the Bayer matrix may be used in the dither processing of the present embodiment. Further, instead of performing the dither processing, the light emission center of gravity may be dispersed using error diffusion processing, or a gradation conversion technique such as a combination of dither processing and error diffusion processing may be used.

  The present invention can be applied to a plasma display panel that performs gradation display by the subfield method.

It is a block diagram which shows the structure of the plasma display apparatus used as embodiment of this invention. It is a figure which shows the arrangement structure of the subfield in embodiment of this invention. It is a figure which shows one example of a Bayer matrix. It is a figure which shows the dispersion | distribution arrangement | positioning of the light emission pattern by the dither process of the conventional plasma display apparatus. It is a figure which shows the combination of the subfield corresponding to a brightness | luminance in the conventional plasma display apparatus. It is a figure which shows the dispersion | distribution arrangement | positioning of the light emission pattern by the dither process of embodiment of this invention. It is a figure which shows the combination of the subfield corresponding to a brightness | luminance in embodiment of this invention. It is a block diagram which shows the structure of the gradation conversion circuit of the plasma display apparatus of embodiment of this invention. It is a figure which shows the structure of the reference | standard gradation table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the reference | standard gradation table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the skip gradation table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 1st SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 1st SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 1st SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 1st SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 1st SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 2nd SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 2nd SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 2nd SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 2nd SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows the structure of the 2nd SFM table of the gradation conversion circuit in embodiment of this invention. It is a figure which shows an example of the comparison result of the pixel data and dither matrix in embodiment of this invention. It is a figure which shows the arrangement structure of the subfield in the conventional plasma display apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plasma display panel, 2 ... Level adjustment circuit, 3 ... A / D conversion circuit, 4 ... γ reverse correction circuit, 5 ... Gradation conversion circuit, 6 ... Output processing circuit, 7 ... Synchronization separation circuit, 8 ... Timing pulse Generation circuit, 9 ... Memory control circuit, 10 ... Drive timing generation circuit, 51 ... Reference gradation table, 52 ... Skip gradation table, 53 ... Dither processing unit, 54 ... First SFM table, 55 ... Second SFM Table, 56 ... SFM selector.

Claims (6)

By dividing one field period of the plasma display panel into a plurality of subfields each weighted with a light emission period, and controlling the light emission or non-light emission of each subfield according to the luminance of the pixel of the input image In the display method of the plasma display panel that performs display,
Γ reverse correction procedure for converting an input image into an image having a predetermined number of gradations,
A dither matrix in which dither coefficients are arranged in a matrix corresponding to each pixel of the input image is generated, and the pixel data to be processed, which has undergone gradation conversion in the γ inverse correction procedure, corresponds to which position in the dither matrix And comparing the pixel data with a corresponding dither coefficient, and selecting one of a first table and a second table prepared in advance based on the comparison result Processing procedure and
A gradation conversion procedure for converting the pixel data to be processed into pixel data having a display gradation number;
An acquisition procedure for acquiring pixel drive data representing a subfield corresponding to the pixel data converted by the gradation conversion procedure from the selected first table or second table;
A light emission control procedure for causing a cell of the plasma display panel corresponding to the pixel data to be processed to emit light according to the acquired pixel drive data;
The display method of the plasma display panel, wherein the first table and the second table have different subfield settings. The display method of the plasma display panel according to claim 1,
In the γ reverse correction procedure, the luminance of the predetermined gradation number in which the moving amount of the light emission center of gravity is small with respect to the luminance change is set as a reference gradation, and each pixel data of the input image is converted into the reference gradation.
In the first table, combinations of subfields are set in advance so that the position of the light emission center of gravity for each pixel data of the number of display gradations substantially coincides with the position of the light emission center of gravity of the immediately preceding reference gradation,
In the second table, the combination of subfields is set in advance so that the position of the light emission center of gravity for each of the display gradation pixel data substantially matches the position of the light emission center of gravity of the immediately following reference gradation. A display method of a plasma display panel, which is characterized. In the display method of the plasma display panel of Claim 2,
The gradation conversion procedure is:
A pixel to be processed that has been subjected to gradation conversion by the γ reverse correction procedure using a reference gradation table that stores in advance the reference gradation data of the predetermined number of gradations and the display gradation data representing the display gradation corresponding thereto. A procedure for obtaining display gradation data corresponding to the data;
A pixel to be processed that has been subjected to gradation conversion in the γ reverse correction procedure by a skip gradation table that stores in advance luminance difference data representing a luminance difference from the next reference gradation for each reference gradation of the predetermined number of gradations A procedure for obtaining luminance difference data corresponding to the data;
A display method for a plasma display panel, comprising: a step of converting the pixel data to be processed into pixel data having the number of display gradations based on the display gradation data and the luminance difference data. . By dividing one field period of the plasma display panel into a plurality of subfields each weighted with a light emission period, and controlling the light emission or non-light emission of each subfield according to the luminance of the pixel of the input image In a plasma display device that performs display,
Γ reverse correction means for converting an input image into an image having a predetermined number of gradations, and
A first table for storing input pixel data and pixel drive data representing a subfield to be selected in association with each other;
A second table in which input pixel data and pixel drive data are stored in association with each other, and a combination of subfields represented by the pixel drive data is different from the first table;
A dither matrix in which dither coefficients are arranged in a matrix corresponding to each pixel of the input image is generated, and the pixel data to be processed that has undergone gradation conversion by the γ inverse correction means corresponds to which position in the dither matrix The pixel data to be processed is compared with the dither coefficient at the position corresponding to the pixel data to be processed, and one of the first table and the second table is selected based on the comparison result. Dither processing means;
Gradation conversion means for gradation-converting the pixel data to be processed into pixel data of the display gradation number;
Acquisition means for acquiring pixel drive data corresponding to the pixel data subjected to gradation conversion by the gradation conversion means from the selected first table or second table;
A plasma display apparatus comprising: a light emission control unit configured to emit light of the cell of the plasma display panel corresponding to the pixel data to be processed according to the acquired pixel drive data. The plasma display device according to claim 4, wherein
The γ reverse correction means uses the predetermined number of gradations in which the amount of movement of the light emission center of gravity as the luminance change is small as a reference gradation, and converts each pixel data of the input image to this reference gradation.
In the first table, a combination of subfields is set in advance so that the position of the light emission center of gravity for each of the pixel data of the number of display gradations substantially coincides with the position of the light emission center of gravity of the immediately preceding reference gradation,
In the second table, the combination of subfields is set in advance so that the position of the light emission center of gravity for each of the display gradation pixel data substantially matches the position of the light emission gravity center of the immediately following reference gradation. A characteristic plasma display device. The plasma display device according to claim 5, wherein
The gradation converting means includes
The reference gradation data of the predetermined number of gradations and the display gradation data representing the display gradation corresponding to the reference gradation data are stored in advance, and the display corresponding to the pixel data to be processed subjected to gradation conversion by the γ inverse correction circuit A reference gradation table for outputting gradation data;
Luminance difference data representing a luminance difference from the next reference gradation for each reference gradation of the predetermined number of gradations is stored in advance, and the luminance corresponding to the pixel data to be processed subjected to gradation conversion by the γ inverse correction circuit Skip gradation table that outputs difference data,
A plasma display apparatus comprising: a conversion unit configured to perform gradation conversion of the pixel data to be processed into pixel data having the number of display gradations based on the display gradation data and the luminance difference data.

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