JP2012185333A - Display device and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize an error as the whole image and further improve an image quality while addressing the plural rows at the same time.SOLUTION: A data conversion table 12 consisting of original image data X, bit values d1,d2,d3(or d5),d4(or d6), image data Y for display of which the difference with the original image data X is minimized, and error δ, is preset. A data determination part 3 of a display device 1, by using the data conversion table 12, extracts image data Y1-Y4 for display and its errors δ1-δ4 about all combinations of original image data X1-X4 and d1-d6 for every four rows of a predetermined number of rows, calculates 64 kinds of Δ=δ1+δ2+δ3+δ4(k=0-63), and specifies the image data Y1-Y4 for display, of which Δis smallest, as image data for display having the smallest error for the whole original image data X1-X4.

Description

  The present invention relates to a matrix display device such as a plasma display panel (PDP) and a display method, and in particular, a field for displaying image data is divided into a plurality of subfields, and the plurality of subfields are added to produce a gradation. It relates to display technology.

  2. Description of the Related Art Conventionally, there is known a matrix type display device that selects a plurality of pixels arranged in a horizontal direction (row direction) and a vertical direction (column direction) to emit light by applying a voltage to electrodes arranged in a matrix. Yes. In this display device, a field for displaying image data is temporally divided into a plurality of subfields, the display times of the divided subfields are weighted, and these subfields are added together (by time integration). ) Display an image. As a result, gradation display can be realized by temporal integration of an image reflected in the human eye.

  For example, in Patent Document 1, in order to display an image of 256 gradations on a display panel, one field is divided into eight subfields and weights of 1, 2, 4, 8, 16, 32, 64, and 128 are given. In each of the subfields, a display device that displays an image by adding these subfields is described.

  In this display device, when displaying 8-bit image data per pixel on a display panel in 256 gradations, 8-bit image data is divided into 8 types of 2 from subfield 1 (SF1) to subfield 8 (SF8). Convert to value image data. Then, according to the converted binary image data, the processing of SF1 to SF8 is performed to display an image with 256 gradations. Specifically, the image display is performed by simultaneously addressing one row for SF1 to SF8 and writing one row of data in one address period.

  However, in the display device disclosed in Patent Document 1, when the number of scanning lines increases and the number of rows increases or the number of bits to be displayed increases, the number of addresses increases, the address time becomes longer, and sufficient address pulses are generated. It becomes impossible to take the width. In addition to the problem that the luminance is reduced and the frame rate is lowered, there is a problem that the number of SF cannot be increased and the power of the address electrode pulse is increased.

  In order to solve such a problem, Patent Document 2 describes a display device that displays an image by simultaneously addressing a plurality of rows of SF1 to SF8 and writing a plurality of rows of data in one address period. Yes. In this display device, in a divided SF, a plurality of rows adjacent in the vertical direction are set to the same value, and a multi-run simultaneous scanning drive is performed to simultaneously address the plurality of rows.

  FIG. 10 is a diagram for explaining image data for each SF in the prior art of Patent Document 2. In FIG. The conventional display device sets the binary image data of SF in a plurality of predetermined rows to be the same with respect to the original image data in accordance with a preset rule, and the image data of the field in that row The remaining SF binary image data is set so that the error between the original image data and the original image data is minimized. The image data of the field set in this way becomes image data after conversion with respect to the original image data.

  As shown in FIG. 10, a predetermined rule for determining (converting) image data in a conventional display device is that the image data of SF1 in 4m to 4m + 3 rows is determined to be the same image data D1, and 4m to 4m The image data of SF2 in the 4m + 3 row is determined as the same image data D2, the image data of SF3 in the 4m, 4m + 1 row is determined as the same image data D3, and the image data of SF4 in the 4m, 4m + 1 row is the same image data. The image data of SF3 in 4m + 2, 4m + 3 rows is determined to be the same image data D13, and the image data of SF4 in 4m + 2, 4m + 3 rows is determined to be the same image data D14. Specifically, the image data D1 of SF1 in 4m rows is used as a reference, and the image data of SF1 in 4m + 1 to 4m + 3 rows is copied. Similarly, SF2 image data D2 in 4m rows is SF2 image data in 4m + 1 to 4m + 3 rows, SF3 image data D3 in 4m rows is SF3 image data in 4m + 1 rows, and SF4 image data D4 is in 4m rows. The SF4 image data in the 4m + 1 row, the SF3 image data D13 in the 4m + 2 row, the SF3 image data in the 4m + 3 row, and the SF4 image data D14 in the 4m + 2 row are copied to the SF4 image data in the 4m + 3 row, respectively.

  The conventional display device inputs, for example, image data of SF1 to SF8 (“D1, D2, D3, D4, D5, D6, D7, D8” / original image data) in pixels of 4 m rows, and this image data. Is output as is. Then, SF1 to SF8 image data ("d11, d12, d13, d14, d15, d16, d17, d18" / original image data) in the pixels of the 4m + 1 row are processed according to the rules shown in FIG. The image data of SF4 is determined to be the same as the image data D1 to D4 of SF1 to SF4 in the 4m row image. That is, “D1” is set (copied) instead of “d11”, and “D2, D3, D4” is set instead of “d12, d13, d14”. And for 4m + 1 rows, between the image data “D1, D2, D3, D4, *, *, *, *” and the original image data “d11, d12, d13, d14, d15, d16, d17, d18”. “*, *, *, *” = “D9, D10, D11, D12” is calculated and set to “*, *, *, *” so that the error of the error is minimized. An image obtained by converting such image data “D1, D2, D3, D4, D9, D10, D11, D12” into the original image data “d11, d12, d13, d14, d15, d16, d17, d18”. Determine as data.

  Further, the conventional display device inputs the image data of SF1 to SF8 (“d21, d22, d23, d24, d25, d26, d27, d28” / original image data) in the pixels of 4m + 2 rows, and FIG. According to the rule shown, the image data of SF1 and SF2 are set to be the same as the image data D1 and D2 of SF1 and SF2 in the 4m-column image. That is, “D1” is set instead of “d21”, and “D2” is set instead of “d22”. The error between the image data “D1, D2, *, *, *, *, *, *” and the original image data “d21, d22, d23, d24, d25, d26, d27, d28” is minimized. "*, *, *, *, *, *" = "D13, D14, D15, D16, D17, D18" is calculated and changed to "*, *, *, *, *, *" Set. Such image data “D1, D2, D13, D14, D15, D16, D17, D18” is converted into the original image data “d21, d22, d23, d24, d25, d26, d27, d28”. Determine as data. Similarly, the conventional display device uses the image data “D1, D2, D13, D14, D19, D20, D21, D22” for the image data of SF1 to SF8 in the pixels of 4m + 3 rows and the original image data “ It is determined as image data after conversion for “d31, d32, d33, d34, d35, d36, d37, d38”.

  According to this conventional display device, the image data of SF1 and SF2 is the same for 4 pixels of 4m to 4m + 3 rows, and SF3 is used for 2 pixels of 4m, 4m + 1 rows and 2 pixels of 4m + 2, 4m + 3 rows. Since the image data of SF4 is the same, it is possible to display an image by simultaneously addressing a plurality of rows and writing the same data in a plurality of rows in one address period. As a result, the power of the address electrode pulse can be reduced, and the error of the image data can be minimized within the row as shown in FIG.

Japanese Patent No. 3259253 JP 2010-175687 A

  As described above, the conventional display device described in Patent Document 2 uses binary image data with respect to SF of a bit having a small weight for a plurality of predetermined rows according to a preset rule with respect to original image data. Are set to be the same, and binary image data is set for the remaining SF so that the error between the field image data and the original image data in the row is minimized. Thereby, the error of the image data in the row is minimized. However, this conventional display device has a problem that the error of the entire image is not minimized, and the image quality of the entire image is deteriorated.

  Accordingly, the present invention has been made to solve the above-described problems, and the object thereof is to minimize errors in the entire image and to further improve image quality while simultaneously addressing a plurality of rows. And a display method are provided.

  In order to achieve the above object, the display device according to the present invention, when displaying a plurality of pixels arranged in a row direction and a column direction in gray scale, converts the original image data of the pixels into a subfield indicating a bit position. Converting to display image data consisting of each bit value and selecting the pixel; and a display period for causing the selected pixel to emit light based on the bit value for a time corresponding to the weight of the bit position; In the display device that performs the gradation display according to the display image data by the processing of the subfield consisting of: the original image data, a plurality of display image data for the original image data, and the original image data And a data conversion table storing an error between the display image data and a plurality of data in a predetermined number of rows using the data conversion table. For each image data, an error between the plurality of original image data and the plurality of display image data is minimized, and a predetermined subfield includes a plurality of consecutive rows within the predetermined number of rows. The original image data is converted into the display image data so that the bit values are the same, and a data determination unit that determines the display image data, and the continuous sub-field in the address period of the predetermined subfield And a driver unit that simultaneously scans pixels in a plurality of rows.

  In the display device according to the present invention, the data conversion table includes a predetermined one of the original image data, a plurality of display image data for the original image data, and all subfields constituting the display image data. The bit values in the subfields and the error between the original image data and the display image data are stored correspondingly.

  Further, in the display device according to the present invention, the data determination unit corresponds to the bit value in a predetermined subfield stored in the data conversion table for each original image data in the predetermined number of rows. Extracting the display image data and the error that are the same, summing the extracted errors, and specifying the bit value and the display data in the predetermined subfield when the summed error is the minimum, It is characterized by that.

  In the display device according to the present invention, when the data determining unit uses the data conversion table to determine display image data so that bit values of a plurality of consecutive rows in a predetermined subfield are the same. In addition, for the first subfield of the predetermined subfield, if the number of consecutive rows having the same bit value is the maximum value, the bit is set for the second subfield of the predetermined subfield. The number of consecutive lines having the same value is a divisor of the maximum value.

  In the display device according to the present invention, when the data determining unit uses the data conversion table to determine display image data so that bit values of a plurality of consecutive rows in a predetermined subfield are the same. In addition, the number of consecutive rows is increased as the subfield has a smaller bit weight.

  Furthermore, in the display method according to the present invention, when a plurality of pixels arranged in the row direction and the column direction are displayed in grayscale, the original image data for the pixels is composed of bit values for each subfield indicating a bit position. Processing of a subfield comprising an address period for converting to display image data and selecting the pixel, and a display period for causing the selected pixel to emit light based on the bit value for a time corresponding to the weight of the bit position In the method of performing the gradation display according to the display image data, the original image data, a plurality of display image data for the original image data, and the original image data and the display image data For each of a plurality of image data in a predetermined number of rows, a plurality of the original image data and a plurality of the original image data The original image data so that the error between the display image data is minimized and the bit values of a plurality of consecutive rows within the predetermined number of rows are the same for a predetermined subfield. Respectively converting the display image data into the display image data and determining the display image data; and simultaneously scanning the pixels in the plurality of consecutive rows in the address period of the predetermined subfield. It is characterized by.

  As described above, according to the present invention, it is possible to minimize the error of the entire image while simultaneously addressing a plurality of rows, and it is possible to further improve the image quality.

It is a block diagram which shows the structure of the display apparatus by embodiment of this invention. It is a figure explaining a drive timing. It is a figure explaining an address period. It is a figure explaining the image data for a display for every SF determined by the data determination part. It is a figure which shows the structure of a data conversion table. It is a figure explaining the outline | summary of the algorithm of a data determination part. It is a flowchart which shows the process of a data determination part. It is a figure explaining the specific example of the algorithm of a data determination part. It is a figure explaining an image quality evaluation result. It is a figure explaining the image data for every SF in a prior art.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
[Outline of the Invention]
In a display device according to an embodiment of the present invention, in a matrix type display device that selects pixels by orthogonal row / column electrodes such as PDP, the original image data is converted into bit-by-bit data to form data for each SF. The grayscale display of the image data is performed by temporally superimposing (integrating) the SF processing by a cycle comprising an address period for selecting and a display period for causing the selected pixel to emit light for a time corresponding to the bit weight. I do. In order to shorten the address period, the image data of a predetermined SF is set to the same value in a plurality of consecutive rows, and the plurality of rows are addressed simultaneously. Further, in order to suppress deterioration in image quality, a predetermined number of rows of images are used by using a predetermined data conversion table set in advance so that an error between the original image data and the display image data is reduced. For each data, the original image data is converted into display image data.

  In this data conversion table, the error between the original image data and the display image data is calculated in advance for all combinations between the original image data and the SF bit values for simultaneous scanning of a plurality of rows. , A table storing data of all combinations thereof. When determining the display image data, the display device instantly derives an error between the original image data and the display image data by referring to the preset data conversion table, Compare errors. Then, the combination having the smallest error is specified, and the display image data in the combination is specified.

[Configuration of display device]
First, the configuration of the display device according to the embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a display device according to an embodiment of the present invention. The display device 1 is a matrix display device such as a PDP having pixels arranged in M rows × N columns, and includes a subfield conversion unit 2, a data determination unit 3, a frame memory 4, a timing pulse generation unit 5, a display A panel 6, a data driver 7, a sustain driver 8, an address electrode 9, a scan electrode 10, a sustain electrode 11, and a data conversion table 12 are provided. In FIG. 1, the scan electrode 10 and the sustain electrode 11 are different electrodes, but are shown as the same electrode for convenience in order to simplify the description.

The subfield conversion unit 2 inputs image data of 8 bits per pixel for each pixel, and displays it on the display panel 6 with 2 ⁸ = 256 gradations, from the least significant bit to the most significant bit, The image data is converted into eight types of binary image data (bit values) including only each bit, and binary image data for each SF in SF1 to SF8 is output to the data determination unit 3. The conversion process by the subfield conversion unit 2 is performed based on the timing signal generated by the timing pulse generation unit 5.

  The data determination unit 3 inputs binary image data for each SF in SF1 to SF8 as one-pixel image data (original image data) from the subfield conversion unit 2. Then, the data determining unit 3 uses the data conversion table 12 for each predetermined number of lines of image data, and uses the data conversion table 12 to display the original image data (original image data as a whole in a predetermined number of lines) and display image data. So that the error between the (predetermined number of rows of image data for display as a whole) is small and the bit values of adjacent rows are the same for a given SF of the same weight. The image data is converted into display image data, that is, the original image data of 8 bits is distributed to the display image data from SF1 to SF8, thereby determining the display image data. Are stored in the frame memory 4 as binary image data for each SF in SF1 to SF8. For example, when the image data is converted, the data determination unit 3 uses the same bit values d1 and SF2 for SF1 and SF2 in which the weight of the image data for display is small in rows 4m to 4m + 3 as shown in FIG. Set to be d2, and SF3 and 4 are set so that the bit values are the same d3 and d4 in the 4m and 4m + 1 rows, so that the bit values are the same d5 and d6 in the 4m + 2 and 4m + 3 rows, respectively. . The determination process by the data determination unit 3 is performed based on the timing signal generated by the timing pulse generation unit 5. Details of processing of the data determination unit 3 that converts the original image data into display image data by referring to the data conversion table 12 will be described later.

  The frame memory 4 stores binary image data (display image data / image data for one pixel) for each SF in SF1 to SF8 by the data determination unit 3, and is composed of M rows × N columns of pixels. Image data is stored in units of frames of one screen. In the frame memory 4, binary image data for each subfield in SF1 to SF8 is read by the data driver 7 for each frame. The processing by the frame memory 4 is performed based on the timing signal generated by the timing pulse generator 5.

  The timing pulse generation unit 5 inputs 8-bit image data per pixel, and the subfield conversion unit 2, the data determination unit 3, the frame memory 4, the data driver 7, and the sustain driver 8 perform respective processes according to the input timing. A timing signal for performing the above is generated.

  The display panel 6 includes two glass plates, an address electrode 9, a scanning electrode 10, a sustain electrode 11, and the like, and discharge cells in a space partitioned by the two glass plates and the partition walls are arranged in a horizontal direction (row direction). ) And a plurality of pixels arranged in the vertical direction (column direction). A rare gas is sealed in the discharge cell. In the address period of SF, when a voltage is applied to the address electrode 9 by the data driver 7 and a voltage is applied to the scan electrode 10 by the sustain driver 8, discharge occurs and ultraviolet rays are generated. A phosphor is applied to the partition walls, and the phosphor is excited by ultraviolet rays, so that the pixels emit light. Further, when a voltage is alternately applied to the scan electrode 10 and the sustain electrode 11 by the sustain driver 8 during the display period, the discharge and the charge are repeated, and the light emission of the pixel continues for the display period. Note that the emission colors of the phosphors are colored red, green, and blue for each discharge cell, and the pixel of the discharge cell is selected according to the image data to perform color display.

  The data driver 7 reads from the frame memory 4 binary image data for each SF in SF1 to SF8 for one frame. In the address period constituting the SF, a drive pulse (address electrode pulse) is applied to the address electrode 9 for each row and for each SF according to binary image data for each SF. Specifically, the data driver 7 applies each address electrode pulse to the address electrode 9 according to the image data of the first row / each column of SF1 in the address period of SF1. The same processing is sequentially performed for the second to Mth rows of SF1. In the address period of SF2 to SF8, the same processing is sequentially performed for the first to Mth rows. A pixel to emit light is selected by applying the address electrode pulse.

  In the embodiment of the present invention, the data driver 7 applies address electrode pulses of the same timing to the address electrodes 9 for a plurality of rows in the SF in which the same binary image data is set by the data determination unit 3. Accordingly, since a plurality of rows are scanned simultaneously, the number of address electrode pulses applied to the address electrodes 9 can be reduced. That is, the number of address scans can be reduced, the address period can be shortened, and the power of the address electrode pulses can be reduced.

  The sustain driver 8 applies a drive pulse (scan electrode pulse) to the scan electrode 10 for each row at a preset timing in the address period constituting the subfield. Thereby, when the address electrode pulse from the data driver 7 is applied at the same time, the pixel to emit light is selected. The sustain driver 8 applies a different number of scan electrode pulses to the scan electrode 10 for each SF in the display period constituting the SF, and generates a drive pulse (sustain electrode pulse) paired with the scan electrode pulse. 11 is applied. Scan electrode pulses and sustain electrode pulses are alternately applied repeatedly, and the smaller the bit weight, the smaller the number of repetitions and the shorter the display period.

  In the embodiment of the present invention, the sustain driver 8 applies each scan electrode pulse to the scan electrode 10 at the same timing for a plurality of rows in the SF in which the same binary image data is set by the data determination unit 3. Thereby, since a plurality of rows are scanned simultaneously, the number of address scans can be reduced, and the address period can be shortened.

  When the address electrode pulse applied by the data driver 7 and the scan electrode pulse applied by the sustain driver 8 are simultaneously applied to the discharge cell, a discharge occurs, the phosphor is excited, and the pixel emits light. Thereby, an address period is executed. In the display period, when the scan electrode pulse and the sustain electrode pulse applied by the sustain driver 8 are alternately applied to the discharge cell, the discharge and the charge are repeated, and the light emission of the pixel is continued. Thereby, the display period is executed. In this way, the address period is executed according to the binary image data of SF, and the pixel selected by executing the address period emits light by executing a display period of a time length corresponding to the SF weight. Then, by executing SF from SF1 to SF8, it is possible to display 256 gradations according to the image data.

[Drive timing]
Next, drive timing will be described. FIG. 2 is a diagram for explaining drive timings in the display device 1 shown in FIG. 1, and FIG. 3 is a diagram for explaining an address period constituting the SF shown in FIG. As shown in FIG. 4 which will be described later, the display device 1 has 8-bit gradation weights of 1, 2, 4, 8, 16, 32, 64, and 128 when displaying 8-bit image data. When displaying with SF1 to SF8, the image data of 4 adjacent rows (4m to 4m + 3rd row) of SF1 and SF2 having weights 1 and 2 are set to the same value, and addresses are simultaneously assigned to the adjacent 4 rows. Set the image data of the adjacent two rows (4m, 4m + 1, and 4m + 2, 4m + 3) of SF3 and SF4 having the weights of 4 and 8 to the same value, and simultaneously address the adjacent two rows . The display apparatus 1 addresses SF5 to SF8 having weights of 16, 32, 64, and 128 for each row as in the past.

  Referring to FIG. 2, one field is divided into eight SFs of SF1 to SF8, and each SF is composed of address periods a1 to a8 and display periods b1 to b8. The address periods a1 to a8 are not all the same time length, the time length of a5 to a8 is the longest, the time length of a3 and a4 is 1/2 of the time length of a5 to a8, and the time length of a1 and a2 Is 1/4 of the time length of a5 to a8. In the display periods b1 to b8, the display period b1 has the shortest time length, and the display period b8 has the longest time length.

  The address period will be described in detail with reference to FIG. The abscissa indicates the elapsed time, and the ordinate indicates the address electrode pulses and the scan electrode pulses 4m to 4m + 3 with respect to the elapsed time, and these pulses are applied to the respective electrodes. In the address period a1 of SF1, address electrode pulses of n columns are applied to the address electrodes 9 at the same timing every four consecutive rows, and scan electrode pulses are also applied to the scan electrodes 10 at the same timing every four consecutive rows. . The same applies to the address period a2 of SF2. Specifically, the n-column address electrode pulses and four consecutive rows of scan electrode pulses 4m to 4m + 3 are simultaneously applied to the respective electrodes. As a result, the time length of the address periods a1 and a2 can be shortened to ¼ the time length t of the address periods a5 and a6.

  In the address period a3 of SF3, the address electrode pulse of n columns is applied to the address electrode 9 every two consecutive rows at the same timing, and the scan electrode pulse is also applied to the scan electrode 10 at the same timing every two consecutive rows. Is done. The same applies to the address period a4 of SF4. Specifically, the scanning electrode pulses 4m and 4m + 1 for two rows that are continuous with the first address electrode pulse in the n column are applied to the respective electrodes at the same time, and are continuous with the second address electrode pulse in the n column. Two rows of scan electrode pulses 4m + 2 and 4m + 3 are simultaneously applied to the respective electrodes. As a result, the time length of the address periods a3 and a4 can be shortened to ½ of the time length t of the address periods a5 and a6.

  Further, in the address period a5 of SF5, address electrode pulses of n columns are applied to the address electrodes 9 for each row, and scan electrode pulses are also applied to the scan electrodes 10 for each row. The same applies to the address periods a6 to a8 of SF6 to SF8. Specifically, the address electrode pulse and the scan electrode pulse 4m are simultaneously applied to the electrodes, and then the address electrode pulse and the scan electrode pulse 4m + 1 are simultaneously applied. The same applies to scan electrode pulses 4m + 2 and 4m + 3. The time length of these address periods a5 to a8 is the time length t.

  In this way, the data driver 7 applies the address electrode pulse to the address electrode 9 for every four adjacent rows according to the same image data for SF1 and SF2 by the data determination unit 3. In addition, the sustain driver 8 applies the scan electrode pulse to the scan electrode 10 at the same timing for every four adjacent rows for SF1 and SF2. As a result, the number of address electrode pulses applied to the address electrode 9 can be reduced to ¼, and the address period can be shortened to ¼.

  Similarly, the data driver 7 applies the address electrode pulse to the address electrode 9 every two adjacent rows according to the same image data for SF3 and SF4 by the data determination unit 3. Further, the sustain driver 8 applies the scan electrode pulse to the scan electrode 10 at the same timing for every two adjacent rows for SF3 and SF4. Thereby, the number of address electrode pulses applied to the address electrode 9 can be reduced to ½, and the address period can be shortened to ½.

[Data decision part]
Next, the data determination unit 3 of the display device 1 shown in FIG. 1 will be described. As described above, the data determination unit 3 uses the data conversion table 12 for each image data of a predetermined number of rows, and displays the original image data (original image data as a whole in a predetermined number of rows) and the display data. So that the error between the image data (the image data for display as a whole in a predetermined number of rows) is small and the bit values of adjacent rows are the same for a given SF of the same weight. The original image data is converted into display image data, and display image data is determined.

  FIG. 4 is a diagram for explaining the display image data for each SF, which is determined by the data determination unit 3. As shown in FIG. 4, image data of four adjacent rows (4m to 4m + 3rd row) is treated as one unit, and the same processing is performed on all pixels every four rows. For the four lines of image data that are the conversion units, the original image data is X1 to X4, and the converted image data is display image data Y1 to Y4, and between Xi and Yi (i = 1 to 4). Is a square error of δi.

  The image data of SF1 to SF8 in the display image data Y1 to Y4 is set so that the error between the original image data and the display image data is minimized for each conversion unit (four rows). Is done. In this case, the display image data Y1 to Y4 are set so that the bit values are the same d1 and d2 for SF1 and SF2 having a small weight for each conversion unit (four rows). In the two rows, the bit values are set to be the same d3 and d4, and in the next two rows, the bit values are set to be the same d5 and d6. That is, the SF is set so that the number of rows with the same bit value increases as the SF of the bit weight is smaller. Even if the SF image data with a small bit weight is changed, the influence on the image quality is not so great, so that the image quality deterioration can be suppressed.

  FIG. 5 is a diagram illustrating a configuration of the data conversion table 12 used when the data determination unit 3 performs data conversion. The data conversion table 12 is created in advance before the display device 1 actually operates. The data conversion table 12 includes original image data X, d1 indicating the bit value of SF1, d2 indicating the bit value of SF2, d3 and d5 indicating the bit value of SF3, d4 and d6 indicating the bit value of SF4, for display Image data Y and error δ. The original image data X and the display image data Y are values from 0 to 255, d1 to d6 are bit values of 0 or 1, and the error δ is the original image data X and the display image data Y. Is the square error between. By making the error δ a square error, the error between the original image data X and the display image data Y can be adapted to the visual characteristics of the person viewing the image. The image quality can be improved by specifying the image data.

A combination between the original image data X and the bit values of d1, d2, d3 (or d5), d4 (or d6) is, for example, d1, d2, d3 ( Or there are 2 ⁴ = 16 combinations of bit values d5) and d4 (or d6), and there are 16 combinations of original image data X = 1. Therefore, when the original image data X is 8 bits and the data range is 0 to 255, there are 256 × 16 = 4096 patterns. That is, in the data conversion table 12 of FIG. 5, there are 4096 combinations of d1, d2, d3 (or d5), and d4 (or d6) for the original image data X.

The display image data Y includes original image data X, image data including bit values d1, d2, d3 (or d5), d4 (or d6) of SF1 to SF4 and bit values of SF5 to SF8. Data that minimizes the difference between is set. For example, if the original image data X = 0, d1, d2, d3 (or d5), d4 (or d6) = (1100) at the location (1) in FIG. Data with the smallest difference from the original image data X = 0, that is, image data when SF5 to SF8 = 0 = (11000000). That is, the display image data Y = 3, and the error δ = (0−3) ² = 9. Further, at the location (2) in FIG. 5, when the original image data X = 255, d1, d2, d3 (or d5), d4 (or d6) = (1011), the display image data Y is Data with the smallest difference from the original image data X = 255, that is, image data when SF5 to SF8 = 1111 = (10111111). That is, the display image data Y = 253, and the error δ = (255−253) ² = 4.

  In this way, the original image data X, the bit values d1, d2, d3 (or d5), d4 (or d6) of the SF1 to SF4, the bit values d1, d2, d3 of the original image data X and SF1 to SF4 ( Alternatively, the data conversion table 12 including the display image data Y and the error δ that minimize the difference between the image data including the bit values of d5), d4 (or d6) and SF5 to SF8 is preset.

  FIG. 6 is a diagram for explaining the outline of the algorithm of the data determination unit 3, and FIG. 7 is a flowchart showing the processing of the data determination unit 3. FIG. 8 is a diagram for explaining a specific example of the algorithm of the data determination unit 3. First, the data determination unit 3 inputs the image data X1 to X4 for every predetermined four rows from the subfield conversion unit 2 (step S701), and sets the parameter k = 0 (step S702). Here, k is a numerical value considering the weight of each bit value of d1 to d6. For example, k = 0 indicates d1 to d6 = (000000), k = 1 indicates d1 to d6 = (100,000), similarly, k = 62 indicates d1 to d6 = (011111), and k = 63 Indicates d1 to d6 = (111111). In the specific example of FIG. 8, the data determination unit 3 inputs image data X1 = 47, X2 = 60, X3 = 44, and X4 = 47.

Returning to FIG. 6 and FIG. 7, the data determination unit 3 displays the original image data X = X1, k = 0 (ie, d1 to d6 = (000000)) from the data conversion table 12 shown in FIG. Image data Y = Y1 and error δ = δ1 are extracted. Similarly, display image data Y = Y2 to Y4 and errors δ = δ2 to δ4 in the original image data X = X2 to X4 and k = 0. Is extracted (step S703). Then, the data determination unit 3 calculates an error Δ _k = δ1 + δ2 + δ3 + δ4 (step S704), calculates k = k + 1, and resets d1 to d6 (step S705).

  The data determination unit 3 determines whether k is larger than 63 (whether k> 63) (step S706), and k is larger than 63 (k> 63), that is, k = 64. If it is determined that there is any (step S706: Y), the process proceeds to step S707. On the other hand, if it is determined in step S706 that k is not larger than 63 (k> 63 is not satisfied) (step S706: N), the data determining unit 3 proceeds to step S703 and performs processing for a new k. .

In the specific example of FIG. 8, when k = 0, that is, when d1 to d6 = (000000), the data determination unit 3 reads the display image data Y1 = 48, Y2 = 64, Y3 from the data conversion table 12. = 48, Y4 = 48, and errors δ1 = 1, δ2 = 16, δ3 = 16, δ4 = 1 are extracted, and the error Δ ₀ = 1 + 16 + 16 + 1 = 34 is calculated. Similarly, the data determination unit 3 extracts display image data Y1 to Y4 and errors δ1 to δ4 when k = _{1 to 63,} and calculates errors Δ1 to Δ63.

Returning to FIG. 6 and FIG. 7, the data determining unit 3 shifts from step S706, the out of all the error delta _k at k = 0 to 63, the error delta _k becomes minimum k = k _min; (d1 , D2,..., D6) are specified (step S707), and display image data Y1 to Y4 at k = _kmin are specified (step S708). Then, the data determination unit 3 outputs Y1 to Y4 specified in step S708 to the frame memory 4 as display image data Y1 to Y4 having a minimum error with respect to the entire original image data X1 to X4 ( Step S709).

In the specific example of FIG. 8, the data determination unit 3 determines the minimum error Δ ₆₁ = 10 among the errors Δ _{0 to} Δ ₆₃ , that is, k = k _min = 61; d 1 that minimizes the error Δ _k. -D6 = (101111) is specified, and display image data Y1 = 45, Y2 = 61, Y3 = 45, Y4 = 45 when k = _kmin = 61 is specified and output to the frame memory 4.

  The data determination unit 3 repeatedly performs the processing shown in FIGS. 6 and 7 for all the pixels constituting the image, thereby converting all the image data for display constituting the image into the frame memory 4. Output to.

〔Experimental result〕
Next, experimental results (results of computer simulation) will be described. FIG. 9 is a diagram for explaining the image quality evaluation result. In FIG. 9, (1) shows PSNR (Peak Signal to Noise Ratio) of the image quality evaluation result when using a display device according to the prior art (the display device of Patent Document 2), and (2) is shown in FIG. The PSNR of the image quality evaluation result when the display device 1 according to the illustrated embodiment of the present invention is used is shown. In addition, “kisya”, “drama”, and “night” on the horizontal axis indicate respective images, and the vertical axis indicates PSNR [dB]. From FIG. 9, it can be seen that in all the images, the image quality of about 2 dB is improved in the embodiment of the present invention in (2) than in the prior art in (1). PSNR was calculated by the following equation.

As described above, according to the display device 1 according to the embodiment of the present invention, the original image data X, the bit values d1, d2, d3 (or d5), d4 (or d6) of SF1 to SF4, the original image data. Display image data Y that minimizes a difference between X and image data composed of bit values d1, d2, d3 (or d5), d4 (or d6) of SF1 to SF4 and SF5 to SF8. A data conversion table 12 composed of the error δ is set in advance, and the data determination unit 3 uses the data conversion table 12 to store the original image data X1 to X4 and d1 to d6 for every four rows, which is a predetermined number of rows. for all combinations of extracts image data Y1~Y4 and error δ1~δ4 for display, to calculate the 64 kinds _{Δ k = δ1 + δ2 + δ3} + δ4 (k = 0~63), Δ k is smallest Image data Y1~Y4 of 示用, was to identify the image data for display having the smallest error with respect to the entire original image data X1 to X4.

  As a result, the display image data Y has the same bit value for adjacent rows of SF of a predetermined weight, so the data driver 7 addresses a plurality of rows simultaneously according to the value of the display image data Y. be able to. In the prior art, the display image data Y that minimizes the error relative to the original image data X is specified in the row, whereas in the display device 1 according to the embodiment of the present invention, a predetermined row is specified. Since a plurality of display image data Y for which the error is minimized with respect to the entire plurality of original image data X is specified in several units, the error is minimized for the entire image. In addition, since the display device 1 uses the data conversion table 12 including the display image data Y specified in the conventional technique when specifying the display image data Y, as a result, the display apparatus 1 has an error that is lower than that in the conventional technique. Small display image data Y can be specified, and the image quality can be improved. That is, the image quality can be further improved by minimizing the error of the entire image while simultaneously addressing a plurality of lines.

  Further, according to the display device 1 according to the embodiment of the present invention, the data determining unit 3 specifies the display image data Y1 to Y4 using the data conversion table 12 including error information. Thereby, it is not necessary to calculate the error for specifying the display image data Y1 to Y4 each time, and the processing load and the processing time can be reduced.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea thereof. For example, in the embodiment, the data determination unit 3 of the display device 1 uses the data conversion table 12 that defines the square error between the original image data X and the display image data Y. Instead of the error, a data conversion table 12 that defines the difference between the original image data X and the display image data Y may be used.

  Further, the present invention does not limit the number of gradations of image data to 8 bits, and does not limit SFs for distributing bits to set the same bit value to SF1 to SF4. For example, SFs that set the same bit value may be SF1 to SF3, or SF1 to SF5. Further, which SF is the target of the simultaneous address of a plurality of rows and what is the data conversion table 12 are not limited to the above embodiment. In the present invention, the unit for performing data conversion by the data determination unit 3 is four lines, but may be eight lines, for example.

  In addition, in the display image data Y1 to Y4 for each SF shown in FIG. 4, SF1 and SF2 having small weights are set to have the same bit values d1 and d2 for each conversion unit (four rows). SF3 and SF3 are set so that the bit values are the same d3 and d4 in the first two rows, and the bit values are also the same d5 and d6 in the next two rows. That is, in SF1 and SF2, the number of rows in which the same bit value continues is 4, which is the maximum value. On the other hand, in SF3 and SF4, the number of rows in which the same bit value continues is 2, which is a divisor of the maximum value 4. In the present invention, for a predetermined first SF (SF1 and SF2 in the example of FIG. 4), when the number of consecutive rows having the same bit value is the maximum value (maximum value 4 in the example of FIG. 4), For a second SF different from the first SF (SF3 and SF4 in the example of FIG. 4), the number of consecutive rows having the same bit value is a divisor of the maximum value (example of FIG. 4). Then, the number of rows of SF3 and SF4 is 2), and the image data Y for each display may be determined.

DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Subfield conversion part 3 Data determination part 4 Frame memory 5 Timing pulse generation part 6 Display panel 7 Data driver 8 Sustain driver 9 Address electrode 10 Scan electrode 11 Sustain electrode 12 Data conversion table

Claims (6)

When gradation-displaying a plurality of pixels arranged in a row direction and a column direction, the original image data for the pixels is converted into display image data composed of bit values for each subfield indicating a bit position, and In accordance with the display image data, processing is performed in a subfield including an address period for selecting a pixel and a display period for causing the selected pixel to emit light based on the bit value for a time corresponding to the weight of the bit position. In a display device that performs gradation display,
A data conversion table in which the original image data, a plurality of display image data for the original image data, and an error between the original image data and the display image data are stored;
Using the data conversion table, for each of a plurality of image data in a predetermined number of rows, an error between the plurality of original image data and the plurality of display image data is minimized, and a predetermined sub Data determination for converting the original image data into the display image data and determining the display image data so that the bit values of a plurality of consecutive rows within the predetermined number of rows are the same for the field And
A driver unit configured to simultaneously scan the pixels in the plurality of consecutive rows in the address period of the predetermined subfield;
A display device comprising: The display device according to claim 1,
The data conversion table is:
The original image data, a plurality of display image data for the original image data, a bit value in a predetermined subfield of all the subfields constituting the display image data, and the original image data A display device, wherein an error with respect to the display image data is stored correspondingly. The display device according to claim 2,
The data determination unit
For each of the original image data in the predetermined number of rows, the display image data and the error corresponding to the bit values in the predetermined subfield stored in the data conversion table and having the same bit value are extracted. The display apparatus characterized in that the extracted errors are summed, and the bit value and the display data in the predetermined subfield when the summed error is minimum are specified. The display device according to claim 3,
When the image data for display is determined by the data determination unit using the data conversion table so that the bit values of a plurality of consecutive rows for the predetermined subfield are the same, If the maximum number of consecutive rows having the same bit value for the first subfield of the second subfield, the number of consecutive rows having the same bit value for the second subfield of the predetermined subfields Is a divisor of the maximum value. The display device according to claim 3,
When display data is determined by the data determination unit using the data conversion table so that the bit values of a plurality of consecutive rows in a predetermined subfield are the same, the subweight having a small bit weight is used. A display device characterized in that the number of consecutive rows is increased as the field is increased. When gradation-displaying a plurality of pixels arranged in a row direction and a column direction, the original image data for the pixels is converted into display image data composed of bit values for each subfield indicating a bit position, and In accordance with the display image data, processing is performed in a subfield including an address period for selecting a pixel and a display period for causing the selected pixel to emit light based on the bit value for a time corresponding to the weight of the bit position. In the method of performing gradation display,
Using the original image data, a plurality of display image data for the original image data, and a data conversion table storing errors between the original image data and the display image data, For each of a plurality of image data in the number of rows, an error between the plurality of original image data and the plurality of display image data is minimized, and a predetermined subfield is within the predetermined number of rows. Converting the original image data into the display image data so that the bit values of a plurality of consecutive rows are the same, and determining the display image data;
Simultaneously scanning the plurality of rows of pixels in the address period of the predetermined subfield;
A display method characterized by comprising:

Images