JP2006195329A - Image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display method in which picture quality can be improved by reducing a false contour generated during moving picture display and also by reducing a flicker. <P>SOLUTION: An image display device which performs multi-gradation display by dividing one field image into a plurality of sub-field images is characterized in that luminance weights of all sub-fields are set to mutually different values, the largest luminance weight is assigned to the final field in one field and the smallest luminance weight is assigned to the sub-field right before it. Thus, the luminance weights are assigned to the respective sub-fields so that the difference in luminance weight between the final sub-field and the sub-field right before it is largest and differences in luminance weight from adjacent sub-fields decrease from subsequent sub-fields to precedent sub-fields. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multi-gradation method by dividing an image of one field into a plurality of subfield images such as a plasma display panel (hereinafter abbreviated as “PDP”) and a digital mirror device (hereinafter abbreviated as “DMD”). The present invention relates to an image display method for performing display.

  In an image display device such as a PDP or DMD that displays an image by binary control of light emission and non-light emission, an image based on a so-called subfield method that performs multi-gradation display by dividing an image of one field into a plurality of subfield images Display is common. In the subfield method, one field period is divided into a plurality of subfields weighted by the number of times of light emission or the amount of light emission, and gradation display is performed by a combination of subfields to emit light.

  FIG. 13 is a diagram illustrating an example of a subfield configuration in a conventional PDP. In the example shown in FIG. 13, one field is divided into eight subfields (SF1, SF2,..., SF8), and (1, 2, 4, 8, 16, 32, 64, 128) a luminance weight. Each subfield includes a setup period (T1) in which preliminary discharge is performed, an address period (T2) in which data is written for each pixel for light emission or non-light emission, and a pixel in which the light emission data is written is maintained at the same time. It consists of a period (T3). By combining these subfields to emit light, 256 gradation levels from “0” to “255” are displayed. For example, when displaying gradation “7”, SF1, SF2, and SF3 having luminance weights “1”, “2”, and “4” are emitted, and when displaying gradation “21”, luminance weights are displayed. SF1, SF3, and SF5 having “1”, “4”, and “16” are caused to emit light.

  In a display method that performs multi-gradation display using such a subfield method, it is known that a phenomenon in which image quality deteriorates and is observed during moving image display occurs. One of the causes is a pseudo contour (moving image pseudo contour). For this moving image pseudo contour, one field is divided into eight subfields (SF1, SF2,..., SF8) having luminance weights of (1, 2, 4, 8, 16, 32, 64, 128). A case will be described as an example.

  FIG. 14 is a diagram illustrating a case where the image pattern 110 moves in the horizontal direction on the screen of the PDP, and FIG. 15 is a diagram in which the image pattern 110 is developed into subfields. As shown in FIG. 14, the image pattern 110 includes a region P1 having a gradation value “127” and a region P2 having a gradation value “128”. In FIG. 15, the horizontal axis represents the screen position in the horizontal direction of the PDP, the vertical axis represents the time direction, and the hatched subfield represents a subfield that does not emit light.

  For example, when the image pattern 110 is stationary and the observer's viewpoint does not move in the horizontal direction and remains fixed at the screen position A as indicated by an arrow AA ′ in FIG. It is possible to observe “127” and “128” which are the original gradation values of the regions P1 and P2. On the other hand, when the image pattern 110 moves to the left and the observer moves the viewpoint in the direction of the arrow BB ′ following the movement of the image pattern 110, the observer moves to the non-light-emitting subfield ( In some cases, SF1 to SF7 in the region P2 and the non-light-emitting subfield (SF8 in the region P1) in the region P1 may be observed. In this case, the observer continuously observes SF1 to SF7 in the region P2 and SF8 in the region P1, and consequently observes the gradation value “0”, that is, a dark line. Conversely, when the image pattern 110 moves to the right and the observer follows the movement of the image pattern 110 and moves the viewpoint in the direction of the arrow CC ′, the observer moves the light emission subfield ( In some cases, SF1 to SF7 in the region P1 and the light emission subfield (SF8 in the region P2) in the region P2 are observed. In this case, the observer continuously observes SF1 to SF7 in the region P1 and SF8 in the region P2, and as a result, observes the gradation value “255”, that is, a bright line. In any case, gradation values significantly different from the original gradation value “127” or “128” are observed, and these are perceived as false contours, that is, pseudo contours.

  As described above, the pseudo contour is generated in a place where the change of the pattern of the subfield to emit light is large although the change of the gradation is slight. For example, when the above-described weighting subfield is used, the pseudo contour is noticeably observed when the luminance gradations of adjacent pixels are “63” and “64”, or “191” and “192”. The As described above, the pseudo contour generated during the moving image display is one of the causes for the deterioration of the image quality.

  As a technique for suppressing the moving image pseudo contour, subfields having a large luminance weight, for example, subfields having luminance weights “128” and “64”, and a plurality of subfields having a smaller luminance weight, for example, luminance weight “32” are used. There has been proposed a display method for performing multi-gradation display by dividing into the above six subfields (see, for example, Patent Document 1). According to this display method, for example, when displaying 256 levels of gradation from “0” to “255”, one field is divided into 12 subfields (SF1, SF2,..., SF12). , Each subfield has a luminance weight of (1, 2, 4, 8, 16, 32, 32, 32, 32, 32, 32, 32). This solves the above-mentioned problem that the pattern change of the subfield that emits light becomes large and the pseudo contour is perceived even though the change in gradation is slight.

Also, a display method has been proposed in which a subfield with a large luminance weight is divided and arranged at the beginning and end of one field when the subfield is divided into a plurality of subfields with a smaller luminance weight (for example, non-patent). Reference 1). According to this display method, for example, when displaying 256 levels of gradation from “0” to “255”, one field is divided into 10 subfields (SF1, SF2,..., SF10). , Each subfield has a luminance weight of (48, 48, 1, 2, 4, 8, 16, 32, 48, 48). In this way, when displaying an image with a large gradation value, subfields with a large gradation value in one field do not emit light continuously, and the pseudo contour can be reduced more effectively. it can.
JP 9-34399 A T. T. et al. Yamaguchi, K .; Toda, S.M. Mikoshiba, A.M. Kohgami, “Improvement in PDP Picture Quality by Three-Dimensional Scattering of Dynamic False Contours”, Proc. SID '96, Digest pp291-294, May (1996).

  However, in the above-described prior art, when images having relatively large gradation values are continuously displayed, subfields having a large luminance weight may emit light continuously. When displaying 256 levels of gradation from “0” to “255”, one field of Patent Document 1 is divided into 12 subfields (SF1, SF2,..., SF12), and each subfield is divided. In the example in which the field has a luminance weight of (1, 2, 4, 8, 16, 32, 32, 32, 32, 32, 32, 32), for example, an image having a gradation value of “224” is continuously displayed. When displaying, the subfields from SF1 to SF5 do not emit light, and the subfields from SF6 to SF12 having a luminance weight of “32” emit light continuously. Alternatively, one field of Non-Patent Document 1 is divided into 10 subfields (SF1, SF2,..., SF10), and (48, 48, 1, 2, 4, 8, 16, In the example of giving luminance weights of 32, 48, and 48), for example, when displaying an image having a gradation value of “192” continuously, the subfields SF3 to SF8 do not emit light, and the luminance weight is “48”. The subfields SF1, SF2, SF9, and SF10 emit light. This is observed as light emission of a continuous subfield of SF9, SF10, SF1, and SF2. In either case, continuous light-emitting subfields and continuous non-light-emitting subfields are alternately generated in units of one field. For example, if the video signal is composed of 60 fields per second, it is observed as a luminance flicker of 60 Hz. If the video signal is composed of 50 fields per second, it may be observed as flickering of 50 Hz luminance. This flickering of luminance is generally called “flicker”, and it is more noticeable as the number of fields or frames per second is smaller, which is one of the causes of image quality degradation.

  As described above, the above-described prior art is effective in reducing the pseudo contour generated during moving image display, but has a problem that flicker is easily perceived.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an image display method in which pseudo contour generated during moving image display is reduced and flicker is reduced to improve image quality.

  In order to achieve such an object, the image display method of the present invention performs multi-grayscale display by configuring one field with a plurality of subfields having different luminance weights and controlling each subfield to emit or not emit light. An image display method, wherein one of the largest luminance weight and the smallest luminance weight is assigned to the last subfield of the plurality of subfields, and the largest luminance weight and the smallest luminance value are assigned to the subfield immediately before the last subfield. By assigning the other of the luminance weights, the luminance weight difference between the last subfield and the immediately preceding subfield is maximized among the luminance weight differences between two different subfields of the plurality of subfields. And in more than one subfield, the later subfield becomes the earlier subfield. Wherein the difference between the luminance weight of the subfield is allocated to luminance weight to each of the plurality of sub-fields to be smaller.

  According to this method, it is possible to improve the image quality by reducing the pseudo contour generated during the moving image display and reducing the flicker.

  In addition, the luminance weight is assigned to one or more subfields in order from the smallest luminance weight in order from the top of the plurality of subfields, and the already assigned luminance weights are assigned to the plurality of subfields excluding the subfield. Except for this, the luminance weight may be assigned to each subfield so that the difference between the luminance weights of the adjacent subfields becomes smaller as the subsequent subfield becomes the previous subfield. According to this method, in addition to the reduction of the pseudo contour during flicker display and the reduction of flicker, in a display device such as a PDP that emits and displays light by discharge, discharge can be generated more stably.

  The image display method according to the present invention is an image display method for performing multi-gradation display by configuring one field with a plurality of subfields having different luminance weights and controlling each subfield to emit or not emit light. Assigning one of the largest luminance weight and the smallest luminance weight to the first subfield, and assigning the other one of the largest luminance weight and the smallest luminance weight to the subfield immediately after the first subfield, Among the differences in luminance weights between two different subfields of the plurality of subfields, the difference in luminance weight between the first subfield and the subfield immediately after is maximized. The brightness of the next subfield increases from the subfield to the next subfield. And assigns luminance weights to each of the plurality of sub-fields as Mino difference becomes smaller.

  Also by this method, it is possible to improve the image quality by reducing the pseudo contour generated during the moving image display and reducing the flicker.

  In addition, the luminance weight is assigned to one or more subfields in order from the smallest luminance weight in order from the top of the plurality of subfields, and the already assigned luminance weights are assigned to the plurality of subfields excluding the subfield. Except for this, the luminance weight may be assigned to each subfield so that the difference in luminance weight with the adjacent subfield becomes smaller as the subfield is changed from the previous subfield. According to this method, in addition to the reduction of the pseudo contour during flicker display and the reduction of flicker, in a display device such as a PDP that emits and displays light by discharge, discharge can be generated more stably.

  In addition, the last sub-part of the first half is so arranged that one field period is substantially equally separated in time into the first half and the second half, and the sum of the luminance weights of the first half and the second half is almost equal. A time interval may be provided between the field and the first subfield in the latter half. According to this method, in addition to the reduction of the pseudo contour during flicker display and the reduction of flicker, in a display device such as a PDP that emits light by discharge, discharge can be generated more stably.

  According to the present invention, in an image display device that performs multi-gradation display by dividing an image of one field into a plurality of subfield images, such as PDP and DMD, the pseudo contour generated during moving image display is reduced and flicker is reduced. An image display method capable of reducing and improving the image quality can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional perspective view showing the structure of a PDP 10 of a plasma display device used for carrying out the image display method of Embodiment 1 of the present invention. On the glass front plate 20 which is the first substrate, a plurality of display electrodes which are paired with a stripe-shaped scan electrode 22 and a stripe-shaped sustain electrode 23 are formed. A dielectric layer 24 is formed so as to cover the scan electrode 22 and the sustain electrode 23, and a protective layer 25 is formed on the dielectric layer 24. A plurality of stripe-shaped data electrodes 32 covered with a dielectric layer 33 are formed on the back plate 30 as the second substrate so as to three-dimensionally intersect the scan electrodes 22 and the sustain electrodes 23. A plurality of barrier ribs 34 are disposed on the dielectric layer 33 in parallel with the data electrodes 32, and a phosphor layer 35 is provided on the dielectric layer 33 between the barrier ribs 34. Further, the data electrode 32 is disposed at a position between the adjacent partition walls 34.

  The front plate 20 and the back plate 30 are opposed to each other with a minute discharge space so that the scanning electrode 22, the sustain electrode 23, and the data electrode 32 are orthogonal to each other, and the outer peripheral portion thereof is made of glass frit or the like. It is sealed with a sealing material. In the discharge space, for example, a mixed gas of neon (Ne) and xenon (Xe) is sealed as a discharge gas. The discharge space is partitioned into a plurality of sections by partition walls 34, and phosphor layers 35 that emit red (R), green (G), and blue (B) light are sequentially disposed in each section. A discharge cell is formed at a portion where the scan electrode 22 and the sustain electrode 23 intersect with the data electrode 32, and one adjacent pixel is formed by three adjacent discharge cells on which the phosphor layers 35 that emit light of each color are formed. The An area where the discharge cells constituting this pixel are formed becomes an image display area, and the periphery of the image display area becomes a non-display area where image display is not performed, such as an area where glass frit is formed.

FIG. 2 is an electrode array diagram of PDP 10 of the plasma display device used for carrying out the image display method according to the first embodiment of the present invention. M columns of data electrodes D _{1 to} D _m (data electrodes 32 in FIG. 1) are arranged in the column direction, and n rows of scan electrodes SC _{1 to} SC _n (scan electrodes 22 in FIG. 1) and n rows of data electrodes are arranged in the row direction. Sustain electrodes SU _{1 to} SU _n (sustain electrodes 23 in FIG. 1) are alternately arranged. A discharge cell C _{i, j} including a pair of scan electrodes SC _i , sustain electrodes SU _i (i = 1 to n) and one data electrode D _j (j = 1 to m) is formed in the discharge space. The total number of discharge cells C is (m × n).

  In the PDP having such a configuration, color display is performed by generating ultraviolet rays by gas discharge and exciting the phosphors of R, G, and B colors with the ultraviolet rays to emit light.

  FIG. 3 is a diagram showing drive voltage waveforms to the respective electrodes of the PDP 10 of the plasma display device used for carrying out the image display method according to the first embodiment of the present invention. As shown in FIG. 3, each subfield has an initialization period, an address period, and a sustain period. Each subfield performs substantially the same operation except that the number of sustain pulses in the sustain period is changed in order to change the weight of the light emission period, and the operation principle in each subfield is also substantially the same. Accordingly, only the operation for one subfield will be described here.

First, in the half of the initializing period, it holds the data electrodes _D 1 to D _m, sustain electrodes _SU 1 to SU _n in each 0 (V), the scan electrodes _SC 1 to SC _n, data electrodes _D 1 to D A ramp waveform voltage that gradually rises from a voltage V _{i1 that is} equal to or lower than the discharge start voltage to a voltage V _i2 that exceeds the discharge start voltage is applied to _m . While this ramp waveform voltage rises, the _first weak initializing discharge occurs between scan electrodes SC _{1 to} SC _n and sustain electrodes SU _{1 to} SU _n and data electrodes D _{1 to} D _m , respectively. Then, the negative wall voltage accumulates on scan electrodes _SC 1 to SC _n top, to the data electrodes _D 1 to D _m and sustain electrodes _SU 1 to SU _n positive wall voltage is accumulated. Here, the wall voltage on the electrode represents a voltage generated by wall charges accumulated on the dielectric layer covering the electrode.

In the second half of the initializing period, maintaining the sustain electrodes _SU 1 to SU _n to a positive voltage Ve, the scan electrodes _SC 1 to SC _n, the voltage _{V i3} which is a discharge start voltage or less with respect to sustain electrodes _SU 1 to SU _{n Is} applied with a ramp waveform voltage that gradually falls toward voltage V _i4 exceeding the discharge start voltage. During this time, the second weak initializing discharge occurs between the scan electrodes SC _{1 to} SC _n and the sustain electrodes SU _{1 to} SU _n and the data electrodes D _{1 to} D _m , respectively. Then, negative wall voltage and sustain electrodes _SU 1 to SU _n positive wall voltage on scan electrodes _SC 1 to SC _n upper are weakened, positive wall voltage on data electrodes _D 1 to D _m upper address operation It is adjusted to a suitable value. This completes the initialization operation.

In the address period, scan electrodes SC _{1 to} SC _n are temporarily held at voltage Vc. Next, in the address operation of the discharge cells C _{p, 1 to} C _{p, m} (p is an integer of ₁ to n), the scan pulse voltage Va is applied to the scan electrode SC _p and the data electrodes D _{1 to} D _m are applied. A positive write pulse voltage Vd is applied to the data electrode D _k (k is an integer of 1 to m) corresponding to the video signal to be displayed in the p-th row. Accordingly, discharge cells corresponding to the intersections of the address pulse voltage to the data electrode D _k of applying a scan electrode SC _P C _p, address discharge in _k is generated. Discharge cells C _p The write _discharge, a positive voltage to the scan electrodes SC _p top of _k is accumulated, and a negative voltage is accumulated on sustain electrode SU _p top, the write operation is completed. Thereafter, the same address operation is performed until the discharge cell C _{n, k} in the _n- th row _, and the address operation is completed.

In the sustain period, scan electrodes SC _{1 to} SC _n are once returned to 0 (V), then positive sustain pulse voltage Vs is applied to scan electrodes SC _{1 to} SC _n , and then sustain electrodes SU _{1 to} SU _n are applied. Return to 0 (V). At this time, the voltage between the upper portion of scan electrode SC _{i and} upper portion of sustain electrode SU _i in discharge cell C _{i, j} in which the address discharge has occurred is in addition to positive sustain pulse voltage Vs, and scan electrode SC _i in the address period. The wall voltage accumulated on the upper part and the upper part of the sustain electrode SU _i is added to become higher than the discharge start voltage, and the first sustain discharge is generated. After the first sustain discharge, the sustain pulse voltage Vs to the sustain electrodes _SU 1 to SU _n is applied, then returned to the scan electrodes _SC 1 to SC _n to 0 (V). At this time, the voltage between the upper portion of scan electrode SC _{i and} upper portion of sustain electrode SU _i in discharge cell C _{i, j} in which the address discharge has occurred is in addition to positive sustain pulse voltage Vs, and scan electrode SC _i in the address period. The wall voltage accumulated in the upper part and the upper part of the sustain electrode SU _i is added to become higher than the discharge start voltage, and a second sustain discharge is generated. Thereafter, in the same manner, by applying sustain pulses alternately to scan electrodes SC _{1 to} SC _n and sustain electrodes SU _{1 to} SUn, the _number of sustain pulses is _equal to the number of sustain pulses for discharge cells C _{i, k} that have caused address discharge. The sustain discharge is continuously performed.

  The above is the electrode arrangement of the PDP 10, the drive voltage waveform for driving the PDP 10, and the timing thereof.

  FIG. 4 is a block diagram showing a configuration of a plasma display device used for carrying out the image display method according to the first embodiment of the present invention. The plasma display device shown in FIG. 4 includes an AD converter 1, a video signal processing circuit 2, a subfield processing circuit 3, a data electrode driving circuit 4, a scanning electrode driving circuit 5, a sustain electrode driving circuit 6, and a PDP 10.

  The AD converter 1 converts the input analog video signal into a digital video signal. The video signal processing circuit 2 emits and displays the input digital video signal on the PDP 10 by a combination of a plurality of subfields having different light emission period weights, and controls each subfield from the video signal of one field. Convert to data.

  The subfield processing circuit 3 generates a data electrode drive circuit control signal, a scan electrode drive circuit control signal, and a sustain electrode drive circuit control signal from the subfield data created by the video signal processing circuit 2, and drives the data electrode Output to the circuit 4, the scan electrode drive circuit 5, and the sustain electrode drive circuit 6, respectively.

As described above, the PDP 10 has m columns of data electrodes D _{1 to} D _m (data electrodes 32 in FIG. 1) arranged in the column direction, and n rows of scan electrodes SC _{1 to} SC _n (scan in FIG. 1). Electrodes 22) and n rows of sustain electrodes SU _{1 to} SU _n (sustain electrodes 23 in FIG. 1) are alternately arranged. A discharge cell C _{i, j} including a pair of scan electrodes SC _i , sustain electrodes SU _i (i = 1 to n) and one data electrode D _j (j = 1 to m) is formed in the discharge space (m Xn) One pixel is formed by three discharge cells that are formed and emit light in red, green, and blue colors.

  The data electrode drive circuit 4 includes a drive circuit that can drive each data electrode 32 independently, and drives each data electrode 32 independently based on a data electrode drive circuit control signal. Sustain electrode drive circuit 6 internally includes a drive circuit that can drive all sustain electrodes 23 of PDP 10 together, and drives sustain electrode 23 based on a control signal for the sustain electrode drive circuit. The scan electrode drive circuit 5 includes a drive circuit that can drive each scan electrode 22 independently, and independently drives each scan electrode 22 based on a scan electrode drive circuit control signal. Each drive is as described in FIG.

  Next, the configuration of the subfield in Embodiment 1 of the present invention will be described.

  In the first embodiment of the present invention, one field has a 13 subfield configuration from SF1 to SF13. The luminance weight of each subfield is (1, 2, 3, 4, 6, 9, 13, 18, 24, 31, 39, 48, 57) from the smaller luminance weight. Therefore, the total luminance weight when all subfields emit light is 255. By configuring the subfields in this way, 256-level gradation display from gradation values “0” to “255” is possible. Do.

  For example, when 256-level gradation display from gradation values “0” to “255” is performed, one field is made up of eight subfields, and luminance weights are (1, 2, 4, 8, 16, 32, 64, 128), the difference in luminance weight between the luminance weights “64” and “128” is 64. As described in the prior art, when there is such a large difference in luminance weight setting, the gradation level of the generated pseudo contour increases and the pseudo contour becomes easy to see. Further, as in the prior art Patent Document 1 and Non-Patent Document 1, the luminance weight between each subfield is formed by replacing the subfield with a large luminance weight with a plurality of subfields obtained by equally dividing the luminance weight. In the configuration in which the difference in brightness is reduced, the gradation level of the pseudo contour is reduced by reducing the difference in luminance weight. On the other hand, the gradation level is reduced by the continuous subfields having the same luminance weight. May show a wide pseudo contour. Therefore, in the first embodiment of the present invention, the luminance weights in each subfield in one field are arranged in order of magnitude so that the sum of all luminance weights is equal to the maximum gradation value. In this case, setting is made so that the difference between the adjacent luminance weights is as small as possible and the luminance weights in all subfields are different from each other, thereby suppressing the occurrence of pseudo contours. By arranging the luminance weight value so that the difference from the adjacent luminance weight gradually increases from the smaller luminance weight to the larger luminance weight when arranged in order of luminance weight, Gradation can be displayed more smoothly.

  In Embodiment 1 of the present invention, luminance weights are not assigned in order from the smallest to the subfields SF1 to SF13, but are assigned in a predetermined order. This luminance weight assignment will be described with reference to the drawings.

  FIG. 5 is a schematic diagram showing the configuration of subfields in Embodiment 1 of the present invention. As shown in FIG. 5 (a), in the first embodiment of the present invention, (13, 9, 18, 6, 24, 4, 31, 3, 39, in order of 13 subfields from SF1 to SF13). 2, 48, 1, 57). FIG. 5B is a schematic diagram showing the configuration of a subfield in which the vertical axis is the luminance weight value in order to make this luminance weight setting easy to understand. As shown in FIG. 5B, in Embodiment 1 of the present invention, the luminance weight “57” having the largest luminance weight is assigned to SF 13 which is the last subfield in one field. The luminance weight “1” having the smallest luminance weight is assigned to SF12 which is a subfield immediately before SF13. Also, the luminance weight “48” having the second largest luminance weight is assigned to SF11 which is the subfield immediately before SF12, and the luminance weight “2” having the second smallest luminance weight is assigned to SF10 which is the subfield immediately preceding SF11. Assigned. In this way, the luminance weight is assigned such that the large luminance weight and the small luminance weight are alternately changed and the difference between the luminance weights of the adjacent subfields becomes smaller as the previous subfield becomes smaller. Thus, in Embodiment 1 of the present invention, the largest luminance weight is assigned to the last subfield in one field, the smallest luminance weight is assigned to the immediately preceding subfield, and the last subfield and the immediately preceding subfield are assigned. In order to maximize the difference in luminance weight with the subfield of the next subfield, the luminance weight of each subfield becomes smaller so that the difference from the subsequent subfield to the previous subfield becomes smaller Assigned.

  With such a configuration, subfields with large luminance weights are not adjacent to each other, and subfields with large luminance weights and subfields with small luminance weights are dispersed, so that the luminance weights in one field are balanced. Since they are dispersed, even if continuous light-emitting subfields and continuous non-light-emitting subfields are alternately generated in units of one field, the perception as flicker can be reduced.

  As described above, according to the first embodiment of the present invention, the luminance weight in each subfield in one field is set so that the sum of all luminance weights is equal to the maximum gradation value and Are arranged so that the difference between the adjacent luminance weights is as small as possible and the luminance weights in all subfields are different from each other. Assign the largest luminance weight to the last subfield, assign the smallest luminance weight to the immediately preceding subfield so that the difference in luminance weight between the last subfield and the immediately preceding subfield is maximized, and Each subfield is set so that the luminance weight difference with the adjacent subfield becomes smaller as the subfield moves forward. It is assigned to the luminance weight to de. By adopting such a subfield configuration, it is possible to improve the image quality by reducing the pseudo contour generated during moving image display and reducing flicker.

  In the first embodiment of the present invention, the configuration of the subfield is not limited to the configuration shown in FIG. 5, but may be configured as shown in FIG. 6 or FIG. 7, for example. FIG. 6 is a schematic diagram showing another example of the configuration of the subfield according to Embodiment 1 of the present invention. As shown in FIG. 6, the smallest luminance weight is assigned to the last subfield, the largest luminance weight is assigned to the subfield immediately before the last subfield, and the next subfield becomes the next subfield. Even if the difference in luminance weight with the subfield is reduced, the same effect as described above can be obtained.

  FIG. 7 is a schematic diagram showing still another example of the configuration of the subfield according to Embodiment 1 of the present invention. In the subfield configuration shown in FIG. 7, from the first subfield (SF1) to the third subfield (SF3) in one field, the smallest luminance weight “1” to the third smallest luminance weight “3” are set. They are assigned in order. In the subfields after SF4, the luminance weights excluding the smallest luminance weight to the third smallest luminance weight are assigned in the order described above.

  When displaying a normal video, it is generally known that the subfield having the highest light emission probability is the subfield having the lowest luminance weight. Further, in a display device that emits light by discharge such as PDP, the first subfield in one field emits light, and the discharge in subsequent subfields is stably generated due to the priming effect by charged particles generated by the discharge. It is known to do. That is, in Embodiment 1 of the present invention, as shown in FIG. 7, the light emission probability of the first subfield is increased by making the first subfield in at least one field the subfield with the smallest luminance weight. In addition to the effects of reducing the pseudo contour and flicker described above, the discharge stability can be further improved.

  In FIG. 7, the smallest luminance weight “1” to the third smallest luminance weight “3” are sequentially assigned to SF1, SF2, and SF3. However, the proportion of luminance weight and the proportion of time in one field are assigned. If there is little influence on the effects such as the reduction of the pseudo contour and the reduction of flicker, it is possible to adopt such a configuration, and in this way, a higher priming effect can be obtained.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment only in the order of assigning the luminance weights in the subfields. The other constituent elements and their operations, and one field from 13 to SF13. The subfield structure is set, and the luminance weight of each subfield is set to (1, 2, 3, 4, 6, 9, 13, 18, 24, 31, 39, 48, 57) from the smaller luminance weight. Etc. are the same as in the first embodiment. Therefore, only the order of assigning the luminance weights in the subfield will be described here.

  FIG. 8 is a schematic diagram showing the configuration of subfields according to Embodiment 2 of the present invention.

  As shown in FIG. 8 (a), in the second embodiment of the present invention, (57, 1, 48, 2, 39, 3, 31, 4, 24, 6, 18, 9, and 13) are assigned luminance weights. FIG. 8B is a schematic diagram showing the configuration of a subfield in which the vertical axis is the luminance weight value in order to make this luminance weight setting easy to understand. As shown in FIG. 8B, in Embodiment 2 of the present invention, the luminance weight “57” having the largest luminance weight is assigned to SF1, which is the first subfield in one field. The luminance weight “1” having the smallest luminance weight is assigned to SF2, which is the next subfield of SF1. Also, the luminance weight “48” having the second largest luminance weight is assigned to SF3 which is the next subfield of SF2, and the luminance weight “2” having the second smallest luminance weight is assigned to SF4 which is the next subfield of SF3. Assigned. In this way, the luminance weights are assigned such that the large luminance weights and the small luminance weights are alternately changed, and the difference between the luminance weights of the adjacent subfields becomes smaller as the subsequent subfields become smaller. Thus, in Embodiment 2 of the present invention, the largest luminance weight is assigned to the first subfield in one field, the smallest luminance weight is assigned to the immediately following subfield, and the first subfield and immediately thereafter are assigned. In order to maximize the difference in luminance weight with the subfield of the next subfield, the luminance weight of each subfield becomes smaller so that the difference from the previous subfield to the subsequent subfield becomes smaller. Assigned.

  With this configuration, subfields with large luminance weights are not adjacent to each other, and subfields with large luminance weights and subfields with small luminance weights are dispersed, so that the luminance weights in one field are balanced. Since they are dispersed, even if continuous light-emitting subfields and continuous non-light-emitting subfields are alternately generated in units of one field, the perception as flicker can be reduced.

  As described above, the largest luminance weight is assigned to the first subfield in one field, the smallest luminance weight is assigned to the immediately following subfield, and the luminance weight between the first subfield and the immediately following subfield is assigned. The luminance weight is assigned to each subfield so that the difference is maximized and the difference in luminance weight with the adjacent subfield becomes smaller as the subfield is shifted from the previous subfield to the subsequent subfield. By adopting such a sub-field configuration, it is possible to improve the image quality by reducing pseudo contours generated during moving image display and reducing flicker as in the first embodiment.

  In Embodiment 2 of the present invention, the configuration of the subfield is not limited to the configuration shown in FIG. 8, and may be configured as shown in FIG. 9 or FIG. 10, for example. FIG. 9 is a schematic diagram showing another example of the configuration of subfields according to Embodiment 2 of the present invention. As shown in FIG. 9, the smallest luminance weight is assigned to the first subfield, the largest luminance weight is assigned to the subfield immediately after the first subfield, and the adjacent subfields become closer to the next subfield from the previous subfield. Even if the difference in luminance weight with the subfield is reduced, the same effect as described above can be obtained.

  FIG. 10 is a schematic diagram showing still another example of the configuration of subfields according to Embodiment 2 of the present invention. In the subfield configuration shown in FIG. 10, the smallest luminance weight “1” to the third smallest luminance weight “3” are sequentially assigned to SF1 to SF3. In the subfields after SF4, the luminance weights excluding the smallest luminance weight to the third smallest luminance weight are assigned in the order described above.

  As shown in FIG. 10, by making the first subfield in at least one field the subfield with the smallest luminance weight, the light emission probability of the first subfield is increased, and the priming effect by the charged particles generated by the discharge, In addition to the effects of reducing the pseudo contour and flicker described so far, the discharge stability can be further improved.

  In FIG. 10, the lowest luminance weight “1” to the third lowest luminance weight “3” are sequentially assigned to SF1, SF2, and SF3. However, the ratio of the luminance weight to one field and the ratio of time If there is little influence on the effects such as the reduction of the pseudo contour and the reduction of flicker, it is possible to adopt such a configuration, and in this way, a higher priming effect can be obtained.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. The third embodiment differs from the first and second embodiments only in the arrangement of subfields in the time axis in one field period, and other components and their operations are the same as in the first embodiment. This is the same as Embodiment 1 and Embodiment 2. Therefore, only the arrangement of the subfields on the time axis in one field period will be described here.

  FIG. 11 is a schematic diagram showing an example of the configuration of subfields in Embodiment 3 of the present invention. The configuration of the subfield shown in FIG. 11 is the same as the configuration example of the subfield shown in FIG. 10 in the second embodiment, and only the arrangement of the subfields on the time axis in one field period is different.

  In the configuration of the subfield shown in FIG. 11, the time between SF7 and SF8 is set longer than the time between other subfields. In this way, the first half of SF1 to SF7 consisting of a combination of a subfield with a large luminance weight and a subfield with a low luminance weight and the second half of SF8 to SF13 consisting of a combination of subfields of luminance weight near the middle. The one field period is separated so as to divide the time period into approximately two minutes. Further, the sum of the luminance weights of the first half from SF1 to SF7 is “121”, and the sum of the luminance weights of the second half from SF8 to SF13 is “134”, which is substantially equal.

  In this way, each subfield is temporally separated into the first half part and the second half part so that one field period is approximately divided into two in time, and the sum of the luminance weights of the first half part and the second half part is For example, if the video signal is 60 fields per second, it can be displayed as if it were a 120 field video signal per second. Further reduction is possible.

  In the third embodiment, the configuration in which one field is divided into the first half and the second half has been described. However, the present invention is not limited to this configuration. For example, the time field is separated into three or more in time. It does not matter as a configuration.

  In addition, the time and luminance weighting of one field in the third embodiment does not mean that the time is divided into two uniformly, and non-uniformity within a range in which the intended effect of the present invention can be obtained. Permissible.

  In the embodiment of the present invention, it is possible to make discharge characteristics more stable by providing a predetermined condition for the combination of light emission in each subfield. FIG. 12 is a diagram showing an example of the conditions of the combination of light emission of each subfield in the embodiment of the present invention. In the conditions shown in FIG. 12, as an example, from the lowest luminance weight in SF1 to SF3 to the third lowest luminance weight shown in FIG. 7 in the first embodiment and FIG. 10 in the second embodiment. The conditions in the subfield configuration in which the stability of discharge is increased by assigning are shown. For example, by setting the conditions shown in FIG. 12 as the conditions for light emission control, in the subfields excluding the subfields arranged with priority in order to enhance the stability of discharge, the subfields that originally emit light first are preceded. Any one of the subfields can emit light, the discharge characteristics can be stabilized, and an image can be displayed more stably.

  Note that the number of subfields and the luminance weights assigned to the respective subfields are merely examples, and are not limited to these values. The number of subfields that can be configured in one field, the configuration of luminance weights, and the like vary depending on various design items such as characteristics of display devices such as PDP and DMD, and gradation values of video signals to be displayed. It is desirable to conduct experiments etc. according to each design condition and to set the optimum value as appropriate.

  In the above-described embodiment, the PDP has been described as an example. However, if the image display method is a subfield method in which an image of one field is divided into a plurality of subfield images to perform multi-gradation display, The invention can be similarly applied, and the same effects as described above can be obtained.

  The image display method according to the present invention can improve the image quality by reducing the pseudo contour generated during the moving image display and reducing the flicker, so that an image of one field such as PDP or DMD can be converted into a plurality of subfield images. It is useful as an image display method for performing multi-gradation display by dividing into two.

Sectional perspective view which shows the structure of PDP of the plasma display apparatus used in order to implement the image display method of Embodiment 1 of this invention PDP electrode arrangement of the plasma display device The figure which shows the drive voltage waveform of each electrode of PDP of the plasma display apparatus Block diagram showing the configuration of the plasma display device Schematic which shows the structure of the subfield in Embodiment 1 of this invention Schematic which shows another example of a structure of the subfield in Embodiment 1 of this invention. Schematic which shows another example of the structure of the subfield in Embodiment 1 of this invention. Schematic which shows the structure of the subfield in Embodiment 2 of this invention. Schematic which shows another example of a structure of the subfield in Embodiment 2 of this invention. Schematic which shows another example of the structure of the subfield in Embodiment 2 of this invention. Schematic which shows the example of a structure of the subfield in Embodiment 3 of this invention. The figure which showed an example of the conditions of the light emission combination of each subfield in embodiment of this invention The figure which showed an example of the structure of the subfield in the conventional PDP The figure which showed the case where an image pattern moves horizontally on the screen of PDP Image pattern expanded into subfields

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AD converter 2 Video signal processing circuit 3 Subfield processing circuit 4 Data electrode drive circuit 5 Scan electrode drive circuit 6 Sustain electrode drive circuit 10 Plasma display panel (PDP)
20 Front plate (made of glass) 22 Scan electrode 23 Sustain electrode 24, 33 Dielectric layer 25 Protective layer 30 Back plate 32 Data electrode 34 Partition 35 Phosphor layer 110 Image pattern

Claims (5)

An image display method in which one field is composed of a plurality of subfields having different luminance weights, and each subfield is controlled to emit or not emit light, thereby performing multi-gradation display.
One of the largest luminance weight and the smallest luminance weight is assigned to the last subfield of the plurality of subfields, and the other of the largest luminance weight and the smallest luminance weight is assigned to the subfield immediately before the last subfield. And the difference in luminance weight between the last subfield and the immediately preceding subfield is maximized among the luminance weight differences between two different subfields of the plurality of subfields, An image in which a luminance weight is assigned to each of the plurality of subfields so that a difference in luminance weight with an adjacent subfield becomes smaller as the subfield from the subsequent subfield to the previous subfield becomes smaller in the plurality of subfields. Display method. The luminance weights are assigned in order from the smallest luminance weight to one or a plurality of subfields in order from the top of the plurality of subfields, and the already assigned luminance weights are assigned to the plurality of subfields excluding the subfield. 2. An image display method according to claim 1, wherein the luminance weight is assigned to each subfield so that the difference between the luminance weights of the adjacent subfields decreases as the subfield from the subsequent subfield to the previous subfield decreases. . An image display method in which one field is composed of a plurality of subfields having different luminance weights, and each subfield is controlled to emit or not emit light, thereby performing multi-gradation display.
One of the largest luminance weight and the smallest luminance weight is assigned to the first subfield of the plurality of subfields, and the other of the largest luminance weight and the smallest luminance weight is assigned to the subfield immediately after the first subfield. And the difference in luminance weight between the first subfield and the subfield immediately thereafter is maximized among the luminance weight differences between two different subfields of the plurality of subfields, An image in which a luminance weight is assigned to each of the plurality of subfields so that a difference in luminance weight with an adjacent subfield becomes smaller as the subfield is shifted from the previous subfield to the subsequent subfield. Display method. The luminance weights are assigned in order from the smallest luminance weight to one or a plurality of subfields in order from the top of the plurality of subfields, and the already assigned luminance weights are assigned to the plurality of subfields excluding the subfield. 4. An image display method according to claim 3, wherein a luminance weight is assigned to each subfield so that a difference in luminance weight with the adjacent subfield becomes smaller as the subfield is shifted from the previous subfield to the subsequent subfield. . The last half of the first half is such that one field period is approximately equally separated in time between the first half and the second half, and the sum of the respective luminance weights of the first half and the second half is substantially equal. 5. The image display method according to claim 1, wherein a time interval is provided between the subfield and the first subfield of the latter half portion.

Images