JP2010033098A - Plasma display and display method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma display for selecting a gradation number suitable to the number of sustaining pulses changed in response to a display load rate. <P>SOLUTION: The plasma display for displaying input signals in gradation by having a plurality of sub-fields weighing brightness by each field and controlling lighting of each sub-field includes: a number of sustaining pulses modification controlling part (116) for modifying and controlling the total number of sustaining pulses of each field; a gradation number conversion processing part (104) for converting input signals into display signals of selected gradation numbers by selecting the gradation number expressed by the plasma display in response to the total number of sustaining pulses; and an error diffusion processing part (106) for spatially diffusing values corresponding to decimals when gradation values of the display signals in the selected gradation number have the value corresponding to the decimals. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma display device and a display method thereof.

  Since the plasma display device performs constant power control, the number of sustain pulses that can be emitted is determined according to the display load factor. Further, the actual number of gradations of the plasma display device is determined by the sum of the weights of all subfields, and this does not depend on the display load factor. Therefore, since the total number of sustain pulses is increased in an image with a small display load factor, that is, a dark image, the number of light emission sustain pulses per gradation is increased. On the other hand, since the total number of sustain pulses decreases in an image with a large display load factor, that is, a bright image, the number of light emission sustain pulses per gradation is small. In particular, since the sub-field with the minimum weight is used for the error diffusion processing bit, the luminance of the error diffusion bit changes depending on the video scene, so that it is recognized as flicker. Further, in a dark image with a small display load factor, the expressive power of the low gradation value portion is insufficient. This is because the luminance difference between the gradation values is larger in the darker video as compared with the brighter video.

  In Patent Document 1 below, the peak luminance of one field is changed according to the average luminance level (APL) of video data. However, it controls the amount of power input, controls the number of sustain pulses according to the display load factor of each subfield to improve peak luminance, and keeps the heat of plasma display panels and circuit parts below a certain temperature. If control or the like is performed to reduce the number of sustain pulses in order to maintain, the APL and the number of sustain pulses do not necessarily match. For this reason, a non-negligible difference may occur between the number of gradations and the number of sustain pulses that can be input. For example, if the number of sustain pulses is too large for the number of gradations, the number of sustain pulses assigned to the minimum subfield does not become a constant value. Therefore, diffusion errors and flicker (the luminance of the minimum subfield fluctuates in the low gradation value part). Occurs). For example, when the number of gradations is 256, if the number of sustain pulses that can be input is 1000, the number of sustain pulses assigned to the minimum subfield is 4, and if the number of sustain pulses that can be input is 768, the minimum subfield is assigned. The number of sustain pulses is three. The number of sustain pulses that can be input varies depending on the image, and accordingly, the number of sustain pulses assigned to the minimum subfield also varies. Conversely, when the number of sustain pulses is too small relative to the number of gradations, the ratio of the number of sustain pulses assigned to each subfield is different from the luminance ratio indicated by the subfield arrangement, resulting in an image with insufficient gradation. In particular, it occurs in a subfield with a small weight, and contour noise occurs in a low gradation value portion of an image.

JP 2003-29704 A

  An object of the present invention is to provide a plasma display apparatus and a display method thereof capable of selecting the number of gradations suitable for the number of sustain pulses that changes in accordance with the display load factor.

  The plasma display apparatus according to the present invention is a plasma display apparatus in which one field has a plurality of subfields whose luminance is weighted, and the input signal is expressed in gradation by controlling lighting of each subfield. A sustain pulse number change control unit for changing and controlling the total number of sustain pulses, and selecting the number of gradations to be expressed by the plasma display device according to the total number of sustain pulses, and selecting the input signal as the selected number of gradations A gradation number conversion processing unit for converting the display signal into a display signal, and when the gradation value of the display signal at the selected gradation number has a value corresponding to the decimal, the value corresponding to the decimal is spatially diffused And an error diffusion processing unit.

  Further, the display method of the plasma display device of the present invention is a plasma display device in which one field has a plurality of subfields weighted with luminance, and the input signal is expressed in gradation by controlling lighting of each subfield. In the display method, the total number of sustain pulses in one field is calculated, the number of gradations expressed by the plasma display device is selected according to the total number of sustain pulses, and the input signal is selected from the selected number of gradations. When the gradation value of the display signal in the selected number of gradations has a value corresponding to a decimal, the value corresponding to the decimal is spatially diffused.

  An appropriate total number of sustain pulses can be determined according to the display load factor, and an appropriate number of gradations can be selected according to the total number of sustain pulses. Flicker when the display load factor is large can be prevented, and lack of expressive power of the low gradation value portion when the display load factor is small can be prevented. Further, flicker can be prevented when the total number of sustain pulses is too large with respect to the number of gradations, and noise due to insufficient gradation when the total number of sustain pulses is too small with respect to the number of gradations can be prevented.

It is a figure which shows the structural example of the plasma display apparatus by the 1st Embodiment of this invention. 2A to 2C are diagrams showing an example of a cross-sectional configuration of the display cell. It is a figure which shows the structural example of 1 field of an image | video. It is a figure which shows the weighting of each subfield of six gradation numbers. It is a figure which shows the relationship between the selection pattern of a subfield of 512 gradations, and an output gradation value. It is a figure which shows the relationship between the selection pattern of a subfield of 448 gradations, and an output gradation value. It is a figure which shows the relationship between the selection pattern of a 384 gradation subfield, and an output gradation value. It is a figure which shows the relationship between the selection pattern of a 320 gradation subfield, and an output gradation value. It is a figure which shows the relationship between the selection pattern of 256 sub-fields, and an output gradation value. It is a figure which shows the relationship between the selection pattern of a 192 gradation subfield, and an output gradation value. It is a graph which shows the relationship between a display load factor and the total number of sustain pulses. It is a graph for demonstrating the process of a non-linear gain control process part. It is a figure which shows the structural example of a nonlinear gain control process part and an error diffusion process part. It is a figure which shows the example which an error diffusion process part produces | generates a gradation value by error diffusion. It is a figure which shows the structural example of the plasma display apparatus by the 2nd Embodiment of this invention.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of a plasma display device according to a first embodiment of the present invention. The address controller 121 supplies a predetermined voltage to the address electrodes A1, A2,. Hereinafter, each of the address electrodes A1, A2,... Or their generic name is referred to as an address electrode Aj, where j means a subscript.

  The Y electrode control unit 123 supplies a predetermined voltage to the Y electrodes Y1, Y2,. Hereinafter, each of the Y electrodes Y1, Y2,... Or their generic name is referred to as a Y electrode Yi, and i means a subscript.

  The X electrode control unit 122 supplies a predetermined voltage to the X electrodes X1, X2,. Hereinafter, each of the X electrodes X1, X2,... Or their generic name is referred to as an X electrode Xi, and i means a subscript.

  In the display region 124, the Y electrode Yi and the X electrode Xi form a row extending in parallel in the horizontal direction, and the address electrode Aj forms a column extending in the vertical direction. The Y electrodes Yi and the X electrodes Xi are alternately arranged in the vertical direction.

  The Y electrode Yi and the address electrode Aj form a two-dimensional matrix with i rows and j columns. The display cell Cij is formed by the intersection of the Y electrode Yi and the address electrode Aj and the X electrode Xi adjacent thereto corresponding thereto. The display cell Cij corresponds to a pixel, and the display area 124 can display a two-dimensional image. The X electrode Xi and the Y electrode Yi in the display cell Cij have a space between them and constitute a capacitive load.

  FIG. 2A is a diagram illustrating a cross-sectional configuration example of the display cell Cij in FIG. The X electrode Xi and the Y electrode Yi are formed on the front glass substrate 211. A dielectric layer 212 for insulating the discharge space 217 is deposited thereon, and an MgO (magnesium oxide) protective film 213 is further deposited thereon.

  On the other hand, the address electrode Aj is formed on a rear glass substrate 214 disposed opposite to the front glass substrate 211, and a dielectric layer 215 is deposited thereon, and further a phosphor is deposited thereon. ing. Ne + Xe Penning gas or the like is sealed in the discharge space 217 between the MgO protective film 213 and the dielectric layer 215.

  FIG. 2B is a diagram for explaining the panel capacitance Cp of the AC drive type plasma display. The capacity Ca is the capacity of the discharge space 217 between the X electrode Xi and the Y electrode Yi. The capacitance Cb is the capacitance of the dielectric layer 212 between the X electrode Xi and the Y electrode Yi. The capacitance Cc is the capacitance of the front glass substrate 211 between the X electrode Xi and the Y electrode Yi. The total of these capacitors Ca, Cb, and Cc determines the panel capacitance Cp between the electrodes Xi and Yi.

  FIG. 2C is a diagram for explaining light emission of the AC drive type plasma display. On the inner surface of the rib 216, phosphors 218 of red, blue, and green are arranged and applied in stripes for each color, and the phosphor 218 is excited by a discharge between the X electrode Xi and the Y electrode Yi. Light 221 is generated.

  FIG. 3 is a diagram illustrating a configuration example of one field FD of a video. The video is formed at 60 fields / second, for example. One field FD is formed by a first subfield SF1, a second subfield SF2,..., An nth subfield SFn. This n is, for example, 10, and corresponds to the number of gradation bits. Each of the subfields SF1, SF2, etc. or their generic name is hereinafter referred to as a subfield SF.

  Each subfield SF includes a reset period Tr, an address period Ta, and a sustain (sustain discharge) period Ts. In the reset period Tr, the display cell is initialized. In the address period Ta, light emission or non-light emission of each display cell can be selected by address discharge between the address electrode Aj and the Y electrode Yi. In the sustain period Ts, a sustain discharge is performed between the X electrode Xi and the Y electrode Yi of the selected display cell to emit light. In each subfield SF, the number of times of light emission by the sustain pulse between the X electrode Xi and the Y electrode Yi (the length of the sustain period Ts) is different. Thereby, the gradation value can be determined.

  FIG. 4 is a diagram showing the weighting of each of the subfields SF1 to SF10 having six gradations. In the present embodiment, one gradation number is selected from among the six gradation numbers in accordance with the total number of sustain pulses in one field. The number of gradations that can be selected is not limited to six, but a case of six will be described as an example. One field consists of, for example, 10 subfields. Each subfield SF1 to SF10 has a weighted number of sustain pulses. The number of these six gradations is, for example, 512 gradations, 448 gradations, 384 gradations, 320 gradations, 256 gradations, and 192 gradations. The subfields SF1 to SF10 have different weights.

  By selecting each of the subfields SF1 to SF10, the image can be expressed in gradation. For example, if the subfield SF1 is selectively displayed, the gradation value is 1, the gradation value is 2 if the subfield SF2 is selectively displayed, and the gradation value is 3 if the subfields SF1 and SF2 are selectively displayed. Become.

  The sum of the weights of all subfields SF1 to SF10 is the number of gradations. Of the six selectable gray levels, the subfield SF1 (and subfields SF2 to SF4) having the smallest weight for each grayscale number is subfield SF1 (and subfield SF2 to subfield SF2 having the smallest weight for the other gray levels). SF4) has the same weight, and subfield SF10 (and subfields SF9 to SF7) having the largest weight in each gradation number is subfield SF10 (and subfields SF9 to SF7) having the largest weight in the other gradation numbers. And the weight is different.

  FIG. 5 shows the relationship between the selection pattern of the 512 gradation subfields SF1 to SF10 (subfield numbers 1 to 10) and the output gradation value, and FIG. 6 shows the selection pattern of the 448 gradation subfields SF1 to SF10. FIG. 7 shows the relationship between the output gradation values and the selection pattern of the 384 gradation subfields SF1 to SF10, and FIG. 8 shows the selection of the 320 gradation subfields SF1 to SF10. 9 shows the relationship between the pattern and the output gradation value, FIG. 9 shows the relationship between the selection pattern of the 256 gradation subfields SF1 to SF10 and the output gradation value, and FIG. 10 shows the 192 gradation subfields SF1 to SF10. The relationship between the selected pattern and the output gradation value is shown.

  5 to 10 all include the same selection pattern CM. As the selection pattern CM, output gradation values 43, 44, 45, 46, and 47 with 192 gradations, output gradation values 49, 50, 51, 56, and 57 with 256 gradations, and output gradation with 320 gradations Values 57, 58, 59, 66, 67, 384 tone output tone values 61, 62, 63, 74, 75, 448 tone output tone values 61, 62, 63, 78, 79, Output gradation values 61, 62, 63, 80, and 81 of 512 gradations are the same selection pattern.

  In other words, the selection pattern of the subfield for expressing each gradation value of 192 gradations, which is the smallest gradation number among the six selectable gradation numbers, is all other gradation numbers (512 gradations). 448 gradations, 384 gradations, 320 gradations, and 256 gradations) are included in the subfield selection pattern for expressing each gradation value.

  In this example, when the number of gradations increases from 192 gradations, another selection pattern is inserted between the selection pattern “000011111” and the selection pattern “000101110”. The inserted selection patterns are all patterns in which the seventh subfield SF7 is selected.

  That is, when the gradation values of the 192 gradations that are the smallest gradation number are arranged in ascending order, the gradation value selected for the first time in a specific subfield (for example, the subfield SF7) and the previous gradation value In order to express each gradation value of other gradation numbers (512 gradations, 448 gradations, 384 gradations, 320 gradations, and 256 gradations) by inserting a selection pattern of another subfield between them. Subfield selection patterns are configured.

  It is not necessary to store all the subfield selection patterns in the memory for every six gradation levels shown in FIGS. The subfield selection pattern of 512 gradations that is the maximum gradation number includes all subfield selection patterns of 448 gradations, 384 gradations, 320 gradations, 256 gradations, and 192 gradations that are other gradation numbers. . Accordingly, the memory stores a subfield selection pattern of 512 gradations that is the maximum number of gradations, and other subfield selection patterns that are not used among the subfield selection patterns of the maximum number of gradations. What is necessary is just to memorize. Thereby, the capacity to be stored in the memory can be reduced.

  The configuration of FIG. 1 will be described. The inverse gamma conversion processing unit 101 receives a digital video signal and performs inverse gamma conversion. The one vertical scanning period (1V) delay unit 102 delays the inverse gamma converted video signal by one vertical scanning period. The gain control unit 103 performs gain control on the output signal of the 1V delay unit 102 and outputs it to the gradation step conversion processing unit 104.

  The sustain pulse number prediction unit 110 includes a gain control unit 111, an error diffusion processing unit 112, a subfield conversion processing unit 113, a display load factor measurement unit 114 for each subfield, and a first sustain pulse number calculation processing unit 115. Predict the number of sustain pulses.

  The gain control unit 111 performs gain control on the output signal of the inverse γ conversion processing unit 101 and outputs it to the error diffusion processing unit 112. The error diffusion processing unit 112 performs error diffusion processing so that the video signal has the minimum number of gradations (192 gradations) among the above six gradations. That is, when an error of the decimal part occurs when the number of gradations of the input video signal is converted to the minimum number of gradations, the error of the decimal part is diffused to spatially adjacent pixels. The subfield conversion processing unit 113 performs subfield conversion according to the selection pattern of the minimum number of gradations (192 gradations) in FIG. 10 and determines the selection pattern of each subfield.

  The display load factor measurement unit 114 for each subfield calculates the display load factor for each subfield. The display load factor is detected based on the number of pixels that emit light and the gradation value of the pixels that emit light. For example, when all the pixels of one field image are displayed with the maximum gradation value, the display load factor is 100%. When all the pixels of one field image are displayed with 1/2 of the maximum gradation value, the display rate is 50%. The display rate is also 50% when only half (50%) pixels of one field image are displayed with the maximum gradation value.

  The first sustain pulse number calculation processing unit 115 calculates the total number of sustain pulses in one field by the constant power control and load correction processing according to the display load factor. In the constant power control, as shown in FIG. 11, the total number of sustain pulses in one field is controlled in accordance with the display load factor in one field. Regardless of the display load factor, if the total number of sustain pulses in one field is made constant, the larger the display load factor, the larger the electric power and the greater the amount of heat. Therefore, when the display load factor of one field is large, calculation is performed so as to reduce the total number of sustain pulses in one field, and constant power control is performed.

  The load correction process will be described. The effective display brightness of each sub-field is determined by the brightness by the sustain discharge and the number of sustain pulses (sustain discharge period). The number of sustain pulses in each subfield is a ratio of a predetermined weight. If the display load factor of each subfield is the same, the luminance due to the sustain discharge is also the same, and the display brightness is the same ratio as the ratio of the number of sustain pulses. Become. However, when the display load factor of each subfield is different, the luminance due to the sustain discharge is different for each subfield, and the display brightness of each subfield does not become a predetermined ratio. When this occurs, the gradation value displayed by combining the subfields is not displayed accurately. In a serious case, there is a problem that the brightness is reversed between the gradation values. In order to solve this, the number of sustain pulses in each subfield is corrected according to the display load factor of each subfield. The first sustain pulse number calculation processing unit 115 calculates the total number of sustain pulses in one field after the correction.

  The gradation number selection unit 116 selects the number of gradations that is the sum of the weights of all subfields according to the total number of sustain pulses calculated by the first sustain pulse number calculation processing unit 115. For example, one optimal one is selected from the above six gradation numbers. As the total number of sustain pulses is larger, a larger number of gradations is selected. A gradation step is obtained by dividing the total number of sustain pulses by the number of gradations, and the gradation step is preferably a constant value.

  The number-of-gradations selection unit 116, when the number of gradations, which is a value obtained by dividing the calculated total number of sustain pulses by a predetermined number of gradation steps, is between a plurality of selectable gradation numbers, Any selectable number of gradations before and after the number of gradations is selected. At that time, of the selectable number of gradations before and after the above, the one with the lower number of sustain pulses in the subfield having a smaller weight than the previously selected number of gradations is selected.

  The gradation step conversion processing unit 104 converts the video signal output from the gain control unit 103 into the selected number of gradations. Specifically, the dynamic range of the input video signal is divided into equal steps by the selected number of gradations to convert the number of gradations. For example, when converting a signal of 256 gradations to 512 gradations, a calculation of 256 ÷ 512 is performed. In this case, since 256 ÷ 512 = 0.5, the video signal is output to the subsequent nonlinear gain control processing unit 105 with a step width of 0.5 gradation.

  Similar to the gain control unit 111 and the error diffusion processing unit 112 described above, the nonlinear gain control processing unit 105 and the error diffusion processing unit 106 spatially diffuse the decimal part error caused by the gradation number conversion and Contour prevention processing is performed. The subfield selection pattern having a specific gradation value, together with the subfield pattern of adjacent pixels, appears to the human eye as if there is a pseudo contour having a large gradation value during moving images. This phenomenon is a moving image pseudo contour. In order to prevent this moving image pseudo contour, the specific gradation value is replaced with another gradation value so that the specific gradation value is not used, and error diffusion processing is performed.

  The non-linear gain control processing unit 105 performs gain processing suitable for the selected number of gradations, maintains the linearity of the input video signal and the output signal, and at the same time, performs error diffusion on gradation values that are likely to generate moving image pseudo contours. Non-linear gain processing is performed to generate new gradation values by processing. The error diffusion processing unit 106 can reduce the moving image pseudo contour by performing error diffusion processing on the output signal of the nonlinear gain control processing unit 105. Details of the nonlinear gain control processing unit 105 and the error diffusion processing unit 106 will be described later with reference to FIGS.

  The linearity compensation processing unit 107 converts the gradation value into a subfield selection pattern according to the selection pattern of the subfield corresponding to the selected number of gradations. The subfield conversion processing unit 108 performs subfield conversion processing on the output signal of the linearity compensation processing unit 107 and converts it into subfield data. The address controller 121 generates a voltage of the address electrode Aj for selecting a subfield to be lit for each pixel according to the subfield data.

  The second sustain pulse number calculation processing unit 117 corrects the total sustain pulse number calculated by the first sustain pulse number calculation processing unit 115 as necessary, and outputs the total sustain pulse number. The correction is a correction that reduces the total number of sustain pulses in order to keep heat below a certain temperature or to reduce power by an external operation.

  The sustain pulse signal generation unit 118 divides the total number of sustain pulses so that the weight ratio of the subfields corresponding to the selected number of gradations is generated, and generates a sustain pulse signal for display. The X electrode control unit 122 and the Y electrode control unit 123 generate voltages for the X electrode Xi and the Y electrode Yi in accordance with the sustain pulse signal. The display cell selected by the address electrode Aj emits light by sustain discharge between the X electrode Xi and the Y electrode Yi.

  FIG. 13 is a diagram illustrating a configuration example of the nonlinear gain control processing unit 105 and the error diffusion processing unit 106. The non-linear gain control processing unit 105 includes a look-up table, and performs non-linear gain control shown in FIG. 12 to prevent moving image pseudo contour. In the characteristic 1201 before nonlinear gain control, the input signal G1 displays the luminance L1 by the subfield selection pattern (hereinafter referred to as selection pattern) P1, the input signal G2 displays the luminance L2 by the selection pattern P2, and the input signal G3 is The luminance L3 is displayed by the selection pattern P3, and the input signal G4 displays the luminance L4 by the lighting pattern P4. At this time, if the selection patterns P1 and P2 are selection patterns that greatly change the light emission center of gravity, a moving image pseudo contour is generated. In order to reduce the moving image pseudo contour, a diffusion process may be performed between the selection patterns for generating the moving image pseudo contour. Therefore, the luminances L2 and L3 are displayed by diffusion of the luminances L1 and L4 without using the selection patterns P2 and P3 in consideration of the magnitude of the movement. In order to realize this, as shown by the characteristic 1202, the nonlinear gain control processing unit 105 converts the input signal G1 into the selection pattern P1, the input signal G2 is P1 + α, the input signal G3 is P1 + β, and the input signal G4 is P4. Convert to Here, 0 <α <β <1.

  The error diffusion processing unit 106 includes a diffusion filter 1301 and an addition unit 1302. The adding unit 1302 adds the output signal of the nonlinear gain control processing unit 105 and the output signal of the diffusion filter 1301 and outputs the result. The output has an integer part S1311 and a decimal part S1312. The integer part S1311 is output to the linearity compensation processing unit 107. The diffusion filter 1301 can spatially diffuse the error of the decimal part by filtering the decimal part S1312. As a result, the selection pattern P1 displays the luminance L1, the selection pattern P1 + α displays the luminance L2, the selection pattern P1 + β displays the luminance L3, and the selection pattern P4 displays the luminance L4.

  FIG. 14 is a diagram illustrating an example in which the error diffusion processing unit 106 generates gradation values by error diffusion. For example, at 512 gradations, the selection pattern of FIG. 14 is corrected based on the selection pattern of FIG. In a subfield selection pattern having a large number of gradations, such as 512 gradations, an example in which gradation values before and after a gradation value at which a larger subfield (for example, the seventh subfield SF7) is lit for the first time are expressed by diffusion processing. Indicates. In contrast to the selection pattern of gradation value 63, the selection pattern of gradation value 70 is lit with the heavy subfield SF7 that has not been lit up until now, so that a moving image pseudo contour is likely to occur. Therefore, six gradation values AR of gradation values 64, 65, 66, 67, 68 and 69 are inserted between the two gradation values, and these gradation values are selected as the gradation value 63. Error diffusion processing is performed with the pattern and the selected pattern of gradation value 70, and the result is displayed. That is, the gradation values 64 to 69 are replaced with the gradation values 63 or 70, and the difference is spatially diffused.

  The error diffusion processing unit 106 performs error diffusion processing by replacing the specific gradation value with another gradation value so that the specific gradation value is not used in the gradation value after the gradation number conversion. The specific gradation value is a gradation value (for example, gradation value 64 in FIG. 5) in which a specific subfield (for example, the seventh subfield SF7) is selected for the first time when the gradation values are arranged in ascending order. Including. Also, the higher the gradation value side is, the more the specific gradation value is, and the lower gradation value side is the absence of the specific gradation value or the specific gradation value is small.

(Second Embodiment)
FIG. 15 is a diagram illustrating a configuration example of a plasma display device according to the second embodiment of the present invention. FIG. 15 differs from FIG. 1 in that the second sustain pulse number calculation processing unit 117 outputs the minimum gradation number selection signal S1501 to the gradation number selection unit 116 in accordance with the calculation result. The gradation number selection unit 116 selects the minimum gradation number when receiving the minimum gradation number selection signal S1501. The second sustain pulse number calculation processing unit 117 performs sustain pulse control such as control for reducing the number of sustain pulses in order to keep the heat of the plasma display panel, circuit components, etc. below a certain temperature, and power reduction by external operation. Processing to change the number may be performed. In this case, the number of sustain pulses predicted by the sustain pulse number prediction unit 110 may be greatly different, which affects the image quality. In order to prevent this, the second sustain pulse number calculation processing unit 117 prevents image quality deterioration by switching the number of gradations to the minimum number of gradations in the current or next field when the number of sustain pulses is greatly changed. .

  As described above, according to the first and second embodiments, the first feature is to measure the display load factor of one field period of the input signal using the smallest number of gradations and perform a predetermined calculation. The number of gradations is selected using the result of calculating the total number of sustain pulses. As a result, an appropriate total number of sustain pulses can be determined according to the display load factor, and an appropriate number of gradations can be selected according to the total number of sustain pulses. Flicker when the display load factor is large can be prevented, and lack of expressive power of the low gradation value portion when the display load factor is small can be prevented. Further, flicker can be prevented when the total number of sustain pulses is too large with respect to the number of gradations, and noise due to insufficient gradation when the total number of sustain pulses is too small with respect to the number of gradations can be prevented.

  The second feature is that the subfield selection pattern corresponding to the smallest number of gradations is included in the subfield selection pattern of other gradations, and the memory for storing the subfield selection pattern is not increased as much as possible. is there. In the case of a method having a lookup table of a selection pattern for each average luminance level (APL), a large increase in memory is caused. However, in this embodiment, the lookup table stored in the memory is only the selection patterns for the maximum number of gradations, and only the selection patterns that are not used in the lookup table are stored in the memory when the number of gradations is switched. That's it.

  The third feature is that when the subfield selection patterns are arranged so that the gradation values are in ascending order, the subfield selection pattern having the other gradation number different from the selection pattern having the smallest gradation number has the smallest gradation. Among sub-field selection patterns, a large weight sub-field is between the first selected gradation value after successive non-selection and the previous gradation value. In addition to eliminating the luminance step due to the increase in the difference, the generation of the moving image pseudo contour is reduced as much as possible.

  The fourth feature is that, in a selection pattern having a large number of gradations, the gradation values before and after the gradation value for which the sub-field with the greater weight is selected for the first time are expressed by diffusion processing. This further reduces the moving image pseudo contour that cannot be reduced by the third feature.

  The fifth feature is that the gradation value expressed by the diffusion process is increased on the higher gradation value side, and the diffusion process is not performed on the low gradation value side or the gradation value to be diffused is decreased. The purpose of increasing the gradation value expressed by the diffusion process toward the higher gradation value side is to reduce the moving image pseudo contour as described in the fourth feature above, and the low gradation value side is not subjected to the diffusion process. Alternatively, the purpose of reducing the gradation value to be diffused is to display the low gradation value portion with high-density lighting pixels. In order to reduce the moving image pseudo contour with all gradation values, the gradation value to be diffused is allowed even on the low gradation value side. For this reason, the weighting of the lower side subfield is not necessarily a binary number.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  The embodiment of the present invention can be applied in various ways as follows, for example.

(Appendix 1)
A plasma display apparatus that includes a plurality of subfields each having a weighted number of sustain pulses in one field, and that represents a gray scale image by selecting each subfield,
A sustain pulse number calculation unit for calculating a display load factor of the input video signal and calculating a total sustain pulse number of one field according to the display load factor;
A plasma display apparatus comprising: a gradation number selection unit that selects a gradation number that is a sum of weights of all subfields according to the calculated total number of sustain pulses.
(Appendix 2)
The plasma display apparatus according to claim 1, further comprising a gradation number conversion unit that divides the dynamic range of the input video signal into equal steps by the selected gradation number and converts the gradation number.
(Appendix 3)
Furthermore, the plasma display apparatus of Claim 2 which has an error diffusion process part which performs an error diffusion process, when the gradation value after the said gradation number conversion has a fraction part.
(Appendix 4)
The plasma display apparatus according to claim 1, wherein the sustain pulse number calculation unit calculates the display load factor by using the smallest number of gradations among a plurality of selectable gradation numbers.
(Appendix 5)
The plasma display apparatus according to appendix 1, wherein the plurality of gradation numbers that can be selected by the gradation number selection unit have the same number of subfields and different weights for each subfield.
(Appendix 6)
In the plurality of gradation numbers that can be selected by the gradation number selection unit, the subfield with the smallest weight for each gradation number has the same weight as the subfield with the smallest weight for the other gradation numbers, and each gradation number The plasma display apparatus according to appendix 5, wherein the subfield with the largest weight is different in weight from the subfield with the largest weight of the other number of gradations.
(Appendix 7)
The selection pattern of the subfield for expressing each gradation value having the smallest number of gradations among the plurality of gradation numbers selectable by the gradation number selection unit is all the gradation values having other gradation numbers. 2. The plasma display device according to appendix 1, which is included in a subfield selection pattern for expression.
(Appendix 8)
When the gradation values having the smallest number of gradations are arranged in ascending order, a selection pattern of another subfield is inserted between the gradation value at which a specific subfield is selected for the first time and the previous gradation value. The plasma display apparatus according to appendix 7, wherein a subfield selection pattern for expressing each gradation value of the other gradation number is configured.
(Appendix 9)
Further, an error diffusion processing unit that performs error diffusion processing by replacing the specific gradation value with another gradation value so that the specific gradation value is not used in the gradation value after the gradation number conversion is performed. The plasma display device as set forth in appendix 1, wherein:
(Appendix 10)
The plasma display apparatus according to claim 9, wherein the specific gradation value includes a gradation value at which a specific subfield is selected for the first time when the gradation values are arranged in ascending order.
(Appendix 11)
The plasma display device according to appendix 9, wherein the higher the gradation value side, the more the specific gradation value is, and the lower gradation value side there is no specific gradation value or the specific gradation value is small.
(Appendix 12)
The plasma display apparatus according to claim 1, wherein the sustain pulse number calculation unit calculates a display load factor of one field and calculates a total sustain pulse number of one field according to the display load factor of one field.
(Appendix 13)
13. The plasma display device according to appendix 12, wherein the sustain pulse number calculation unit calculates so as to reduce the total number of sustain pulses in one field when the display load factor in one field is large.
(Appendix 14)
The plasma display apparatus according to claim 1, wherein the sustain pulse number calculation unit calculates a display load factor of each subfield, and calculates a total sustain pulse number of one field according to the display load factor of each subfield.
(Appendix 15)
The number-of-gradations selection unit, when the number of gradations, which is a value obtained by dividing the calculated total number of sustain pulses by a predetermined number of gradation steps, is between a plurality of selectable gradation numbers, 2. The plasma display device according to appendix 1, wherein a selectable number of gradations before and after the number of gradations is selected.
(Appendix 16)
The gradation number selection unit selects one of the selectable gradation numbers before and after the one that has a smaller number of sustain pulses in a subfield having a smaller weight than the previously selected gradation number. 15. The plasma display device according to 15.
(Appendix 17)
Further, the calculated total number of sustain pulses is corrected as necessary, and the total number of sustain pulses is divided so that the weight ratio of the sub-fields of the selected number of gradations is obtained. 2. The plasma display device according to appendix 1, further comprising a signal generation unit that generates the signal.
(Appendix 18)
The plasma display apparatus according to claim 17, wherein the signal generator performs correction to reduce the total number of sustain pulses in order to keep the heat below a certain temperature or to reduce power by an external operation.
(Appendix 19)
The plasma display apparatus according to appendix 18, wherein the gradation number selection unit selects the smallest number of gradations according to a correction result of the signal generation unit.
(Appendix 20)
A control method of a plasma display device, wherein a field is composed of a plurality of subfields having a weighted number of sustain pulses, and gradation is expressed by selecting each subfield,
A sustain pulse number calculating step of calculating a display load factor of the input video signal and calculating a total sustain pulse number of one field according to the display load factor;
A method of controlling a plasma display apparatus, comprising: a gradation number selection step of selecting a gradation number that is a sum of weights of all subfields according to the calculated total number of sustain pulses.

101 Inverse Gamma Conversion Processing Unit 102 1V Delay Unit 103 Gain Control Unit 104 Tone Step Conversion Processing Unit 105 Nonlinear Gain Control Processing Unit 106 Error Diffusion Processing Unit 107 Linearity Compensation Processing Unit 108 Subfield Conversion Processing Unit 110 Sustain Pulse Number Prediction Unit 111 gain control unit 112 error diffusion processing unit 113 subfield conversion processing unit 114 display load factor measurement unit for each subfield 115 first sustain pulse number calculation processing unit 116 gradation number selection unit 117 second sustain pulse number calculation processing unit 118 Sustain pulse signal generator 121 Address controller 122 X electrode controller 123 Y electrode controller 124 Display area

Claims (10)

A plasma display apparatus in which one field has a plurality of luminance-weighted subfields, and represents an input signal by gradation by controlling lighting of each subfield,
A sustain pulse number change control unit for changing and controlling the total number of sustain pulses in one field;
A gradation number conversion processing unit that selects the number of gradations expressed by the plasma display device according to the total number of sustain pulses, and converts the input signal into a display signal of the selected gradation number;
And an error diffusion processing unit that spatially diffuses the value corresponding to the decimal when the gradation value of the display signal at the selected gradation number has a value corresponding to the decimal. Display device.   The gradation number conversion processing unit is configured to generate the gradation based on a ratio between a luminance weight of the lowest subfield having the smallest luminance weight among the plurality of subfields and a luminance weight corresponding to the total number of sustain pulses. 2. The plasma display device according to claim 1, wherein a number is selected.   The plasma display apparatus according to claim 1, wherein the luminance weight of the lowest subfield having the smallest luminance weight among the plurality of subfields is constant even if the number of gradations of the display signal changes. .   The plasma display apparatus as claimed in claim 2, wherein the luminance weight of the lowest subfield is constant even when the number of gradations of the display signal changes.   5. The plasma display apparatus according to claim 3, wherein the number of the plurality of subfields constituting the one field is constant even when the total number of sustain pulses is changed. A display method of a plasma display apparatus, wherein one field has a plurality of luminance-weighted subfields, and the input signal is expressed by gradation by controlling lighting of each subfield,
Calculate the total number of sustain pulses in one field,
Select the number of gradations to be expressed by the plasma display device according to the total number of sustain pulses, convert the input signal to a display signal of the selected number of gradations,
A display method for a plasma display device, wherein when a gradation value of the display signal in the selected gradation number has a value corresponding to a decimal, the value corresponding to the decimal is spatially diffused.   The number of gradations is selected based on a ratio between a luminance weight of the lowest subfield having the smallest luminance weight among the plurality of subfields and a luminance weight corresponding to the total number of sustain pulses. The display method of the plasma display apparatus of Claim 6.   7. The plasma display apparatus according to claim 6, wherein the luminance weight of the lowest subfield having the smallest luminance weight among the plurality of subfields is constant even if the number of gradations of the display signal changes. How to display.   8. The display method of the plasma display apparatus according to claim 7, wherein the luminance weight of the lowest subfield is constant even when the number of gradations of the display signal changes.   10. The display method of the plasma display device according to claim 8, wherein the number of the plurality of subfields constituting the one field is constant even when the total number of sustain pulses is changed.

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