KR100446760B1 - Method and appatatus for gray scale display - Google Patents

Abstract

The present invention relates to a gradation display method and a display device thereof. To this end, the present invention divides each subfield from subfields SF1 to SF4 having a high luminance ratio into two, and displays the frame in order of increasing luminance ratio of each divided subfield. The subfields are alternately arranged at the head and the end, and the non-divided subfields are arranged at the center of the flame, and the adjacent images are driven in symmetric emission patterns, respectively, so that video signals are displayed using plural subfields. In this case, there is an effect of reducing image quality deterioration, which is called a moving picture false contour.

Description

Gradient display method and display device {METHOD AND APPATATUS FOR GRAY SCALE DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation display method and a display device such as a plasma display panel, and more particularly, to a gradation display method for reducing image quality deterioration called moving picture fake contours generated when gradation display of an image signal using a plurality of subfields; It relates to a display device.

FIG. 1 is a diagram showing the arrangement of subfields used in a conventional PDP apparatus. As shown in FIG. 1, in a display panel using a plasma display panel (hereinafter referred to as PDP) or a ferroelectric liquid crystal element, one frame period is It consists of a plurality of subfields SF1 to SF8 having different relative ratios of lighting periods (sustaining discharge period; proportional to light emission luminance), and the conventional gradation display method according to such a configuration converts the input analog video signal by A / D conversion. The digital signal is converted into a digital signal of the number of bits corresponding to the number of subfields, and the corresponding pixel is lit by an appropriate subfield based on this bit data to display a predetermined grayscale image.

Fig. 1 shows an example in which gradation display is performed by eight gradation bits. The most gradation bit (eighth bit) corresponds to SF1, and in the following order, the gradation bit (seventh bit) is in SF2 and the gradation bit (6). Bit) in SF3, gradation bit (5th bit) in SF4, gradation bit (4th bit) in SF5, gradation bit (3rd bit) in SF6, and gradation bit (second bit) in SF7. Corresponding to each, the lowest gradation bit (the first bit) corresponds to SF8.

Each of the subfields SF1 to SF8 is provided with sustain discharge periods of, for example, the number of gradations (relative ratio of luminescence brightness) 128, 64, 32, 16, 8, 4, 2 and 1, respectively, as shown in FIG. Arrangement in order is considered to be the most efficient. However, when the subfields are simply arranged in luminance ratio order for display, a deterioration of image quality called a fairy tale fake outline (a phenomenon in which gradation is disturbed in a portion where gradation changes gradually, such as a human cheek, for example) occurs. . In order to prevent the deterioration of image quality as described above, a method of changing the arrangement of each subfield or changing the relative ratio of luminance of each subfield has been performed.

That is, in order to eliminate the deterioration of image quality called a moving picture fake outline in a conventional display panel which performs gradation display as described above, for example, Japanese Patent Laid-Open No. 10-124001 discloses a high-brightness subfield in the center of the frame. Although it is described in the above, if it is arranged in the center part of the frame having a large relative luminance ratio among the subfields divided as in the publication, the moving picture false contour can be reduced in the middle gradation (display of a medium gradation with relative luminance ratio). There was no problem.

Also, in order to eliminate the false fake contour, a subfield having a large relative luminance ratio is placed in the center of one frame, and at the same time, the subfields corresponding to the subbits such as subfields SF7 or SF8 in odd and even frames are replaced. In some cases, there is a problem in that, however, the fairy tales cannot be sufficiently reduced.

Accordingly, an object of the present invention is to provide a gradation display method and a display device for reducing image quality deterioration called a moving image fake outline in a display panel that performs gradation display using a plurality of subfields. There is this.

In order to achieve the above object, the present invention converts an input video signal of one frame into a digital value and at the same time has a luminance corresponding to the digital value among a plurality of subfields constituting one frame with different luminance ratios. In a display device for selecting a ratio subfield and performing gradation display on the display unit based on the luminance ratio of the selected subfield, at least one subfield having a large luminance ratio is selected to be two subfields having the same luminance ratio. The first step of dividing, the second step of arranging the non-divided subfield in the center of the frame, and the divided one and the other divided subfield are alternately selected in the order of the highest luminance ratio, respectively, to the head and the end of the flame. The third step of alternately arranging on the secondary side, and the same luminance ratio at the head and the end of the flame centered on the undivided subfield arranged at the center of the flame. Luminance ratios of the respective divided subfields are generated as a first light emission pattern having a first luminance ratio and a second luminance ratio in a first mode, respectively, and in the second mode, the luminance ratios of the divided subfields respectively have the second luminance ratio and the first luminance ratio. A fourth step of generating a second light emission pattern and a fifth step of driving unit display portions adjacent to each other in the display unit by different light emission patterns are performed.

Here, in the first step, as shown in FIG. 3A, a sixth step of sequentially dividing the subfields having the highest luminance ratio from the plurality of subfields into the largest luminance ratio is performed, and the third step is divided. A seventh step is performed in which the divided subfields of the one and the other are alternately selected in the order of the highest luminance ratio, and arranged in the direction from the head to the center of the flame and from the end of the flame to the center. In addition, in the third step, the divided subfields of one side and the other divided as shown in FIG. 3B are alternately selected in order of increasing luminance ratio, respectively, from the head of the flame to the center portion and the flame from the center portion to the tail portion. Perform the eighth step of arranging.

In the first step, as shown in FIG. 4, the ninth step of dividing the subfields from the subfield except the largest luminance ratio into the two subfields in the order of the highest luminance ratio is performed. The subfields are arranged as the first subfield at the center position of the frame, and one divided subfield and the other divided subfield are alternately selected in the order of the highest luminance ratio, respectively, based on the processing of the third step. As a result of the arrangement, when the one divided subfield is arranged to the arrangement position of the first subfield, a tenth step of disposing the remaining non-divided subfield between the other subfield and the first subfield is performed. As shown in Figs. 4A and 4B, the frame is made up of an odd frame and an even frame adjacent to the odd frame. In the case of one of the odd and even frames, an eleventh step of arranging the remaining undivided subfields in the order of the highest luminance ratio, and the other frame performs the eleventh step of arranging the remaining undivided subfields in the order of the lowest luminance ratio. do.

1 is a configuration diagram showing an arrangement of subfields used in a conventional PDP apparatus.

2 is a block diagram showing the configuration of a PDP apparatus to which the present invention is applied.

3 is a configuration diagram showing an arrangement of subfields applied to a PDP apparatus;

4 is a configuration diagram showing another arrangement of subfields.

5 is an exemplary diagram showing an example of a light emission pattern generated by a light emission pattern control unit in the PDP apparatus.

* Description of the symbols for the main parts of the drawings *

1: A / D converter 2: flame memory

3: Sync separation unit 4: Subfield configuration unit

5: system clock generator 6: driver

7: PDP 8: light emission pattern control unit

a: Video signal

SF1, SF1-1, SF1-2, SF2-1, SF2-2, SF3-1, SF3-2, SF4-1, SF4-2, SF5, SF6, SF7, SF8: Subfield

Hereinafter, the present invention will be described in detail with reference to the drawings.

Fig. 2 is a block diagram showing the structure of a plasma display panel (PDP) device to which the present invention is applied. The A / D converter 1 converts an analog video signal a into a digital signal, and A frame memory 2 to be accumulated, a synchronous separator 3 for separating a synchronous signal from an analog video signal a, a subfield constitution unit 4 for generating each subfield described later, and a subfield A system clock generator 5 for generating a clock signal for generating a light, a light emission pattern controller 8 for generating a light emission pattern based on the output of the subfield configuration unit 4, a PDP 7, and a flame memory ( The digital signal of 2), the light emission pattern from the light emission pattern control unit 8, and the drive unit 6 for driving the PDP 7 on the basis of the output of the subfield constitution unit 4 are comprised.

Here, the subfield configuration section 4 uses the clock generated by the system clock generation section 5 on the basis of the vertical synchronization signal separated by the synchronization separation section 3 to have a relative ratio of luminance of 2 ^n-1 : 2. ^n-2 :… The first subfield SF1 to the nth subfield SF ⁿ are formed to be 2: 2: 1. In addition, the A / D converter 1 converts the analog video signal a into digital video data having a bit number corresponding to the number of subfields. In other words, when the number of subfields is n, the data is converted into n bits of digital video data. The frame memory 2 also stores digital video data of one frame converted by the A / D converter 1. In addition, the driving unit 6 is based on the digital image data read out from the flame memory 2, the timing control signal from the subfield constitution unit 4, and the light emission pattern from the light emission pattern control unit 8 as described above. Thus, the operation of sequentially driving light emission of the PDP 7 is repeated from the first subfield having a high relative luminance to the nth subfield having a low relative luminance.

According to the configuration of the present invention as described above, a method of operating the gradation display of the PDP 7 will be described with reference to Figs.

One frame period of the display data is usually about 1/60 second (16.7 msec), and one frame period is divided into eight subfields SF1 to SF8 as described above. In addition, each of the subfields SF1 to SF8 has a period between syringes and a sustain discharge period.

Between the syringes of the subfield SF1, the driving unit 6 reads by applying a scanning pulse to each pixel constituting all the display panels of the PDP 7 based on the image data of the most significant gradation bit (the eighth bit). After the reading of all the display panels of (7) is completed, the driving unit 6 applies a sustain pulse to the read pixels in the sustain discharge period to cause light emission display. Next, between the syringes of the subfield SF2, the driving unit 6 reads each pixel similarly on the basis of the image data of the gradation bit (seventh bit) of the next highest gradation bit, and similarly in the sustain discharge period. A sustain pulse is applied to the read pixel. Hereinafter, each subfield SF3, SF4, SF5, SF6, SF7, SF8 corresponding to each gradation bit (6th bit, 5th bit, 4th bit, 3rd bit, 2nd bit, 1st bit) of the video data. In the same manner, each driving process is similarly performed between the syringes and the sustain discharge period. When the processing of one frame period ends, the driving unit 6 starts the driving process between the syringes of the subfield SF1 of the next flame. Here, the light emission luminance of the PDP 7 is ensured with sufficient luminance, and the relative ratio of the luminance of each sustain discharge period of each subfield SF1 to SF8 is 2 ^n-1 : 2 ^n-2 :... For example, the drive unit 6 is 128 times in the subfield SF1, 64 times in the subfield SF2, 32, 16, 8 in the subfields SF3, SF4, SF5, SF6, SF7, and SF8 so as to be 2: 2: 1. , 4, 2 or 1 sustain pulses are applied to the pixel to emit light.

(First embodiment)

3 is a configuration diagram showing an arrangement of subfields applied to the PDP apparatus, and FIG. 3A shows a first embodiment showing an arrangement of subfields according to the present invention.

The first embodiment divides each subfield from subfield SF1 to subfield SF4 having a large light emission luminance ratio (hereinafter referred to as light emission luminance ratio) in two and subfields SF1-1, SF1-2, SF2-1, SF2-2, SF3-1, SF3-2, SF4-1, SF4-2, and each of the subfields SF5, SF6, SF7, SF8 having a small light emission luminance ratio is undivided. Here, the light emission luminance ratios of the divided subfields SF1-1 and SF1-2 are almost the same, and the light emission luminance ratios are substantially the same in the subfields SF2-1 and SF2-2, and the subfields SF3-1 and SF3-2. The emission luminance ratio is almost the same also in the subfields SF4-1 and SF4-2. Then, the divided subfields are arranged in an alternating manner in the direction from the head side to the end side of the flame and the direction from the end side to the head side of the flame, in order from the largest light emission luminance ratio. That is, as shown in Fig. 3A, when one side (SF1-1) of the divided subfield SF1 having the largest luminous intensity ratio is disposed at the leading position of the flame, the other side of the divided subfield SF1 is positioned at the end of the flame. (SF1-2) is placed. Next to the divided subfield SF1-1, one side SF2-1 of the divided subfield SF2 having the next highest light emission luminance ratio is disposed, and the other sub SF2-2 of the divided subfield SF2 is divided. It is disposed after the field SF1-2.

In this manner, one and the other of the divided subfields are arranged in order from the position of the head of the flame to the center of the flame and from the position of the end of the flame to the center of the flame. Accordingly, SF1-1, SF2-1, SF3-1, SF4-1 are arranged in order from the head position of the flame to the center portion, and the subfields SF1-2, SF2 are sequentially placed from the end position of the flame to the center portion. After -2, SF3-2, SF4-2 are arranged, each subfield SF5, SF6, SF7, SF8 of undivided light emission luminance ratio is arranged in the center of the flame. When the non-divided subfields SF5 to SF8 are arranged, in the embodiment according to the present invention, following the two-divided subfield SF4-1, as shown in FIG. 3A, the non-divided subfields SF6 → SF5 → SF7 → SF8 Arrange them in order. That is, each non-divided subfield is first arranged in descending order of its emission luminance ratio (i.e., the direction from the subfield with the large emission luminance ratio to the subfield with the small emission luminance) to SF5 → SF6 → SF7 → SF8. The non-divided subfield SF5 having the largest luminous luminance ratio and the next non-divided subfield SF6 having the largest luminance luminance ratio are replaced. Such subfields are generated and arranged by the subfield constructing unit 4 of FIG.

Here, when the driving unit 6 performs light emission driving of the PDP 7 in accordance with the subfields generated and arranged by the subfield constructing unit 4, the light emitting pattern control unit 8 performs the The light emission pattern as shown in Fig. 5 is generated based on the output (subfield array output). The driver 6 drives the PDP 7 by emitting light by selecting the light emission pattern from the light emission pattern control unit 8 as a pattern of mode A or mode B alternately for each line or pixel. Therefore, the center shift of the light emission pattern generated at the time of increasing the number of gradations (i.e., when changing from field SF2-2 to SF1-2, etc.) is reversed with each other or for each pixel, and disappears (clears). As a result, fairy tales can be suppressed.

FIG. 5 is an exemplary view showing an example of a light emission pattern generated by the light emission pattern control unit 8 in the PDP apparatus, and shows a light emission pattern selected corresponding to the number of gray levels of the input subfield SF. The light emission pattern of FIG. 5 corresponds to the arrangement pattern of the subfields shown in FIG. 3A. For example, if mode A is a selection pattern for pixel A, mode B is a selection pattern of pixel B adjacent to pixel A. That is, as shown in FIG. 3A, the sub-fields SF1-1, SF2-1, SF3-1, SF4-1 with gray levels of 64, 32, 16, 8, 4, 8, 2, 1, 8, 16, 32, and 64 When the adjacent pixels A and B are driven to emit light by SF6, SF5, SF7, SF8, SF4-2, SF3-2, SF2-2 and SF1-2, the non-divided subfields SF6, SF5, SF7, SF8 The luminance ratio patterns (i.e., the light emission patterns) of the divided subfields having the same emission luminance ratio (the same number of gradations) are the symmetrical patterns in the mode A and the mode B. Here, the black circled display in FIG. 5 represents a pattern that is necessarily selected, and the white circled display represents a pattern selected in correspondence with the gradation.

In this way, the subfield having a large emission luminance ratio is divided into two, and each divided subfield is alternately arranged at the head side and the end side of the flame, and a different light emission pattern is alternately selected for each line or for each pixel, so that the PDP 7 By driving, the center shift caused by the sudden fluctuation of the light emission pattern generated when the number of gradation bits of the light emission luminance ratio is raised can be suppressed to the minimum, so that the moving picture false contour can be reduced.

In addition, since the non-divided subfields SF5 to SF8 are arranged at the center of the frame and the arrays are arranged in the order of subfields SF6 to SF5 to SF7 to SF8 as shown in Fig. 3A, the non-divided subfields are arranged. Compared to the case of simply arranged in descending or ascending order (i.e., the direction from the subfield with the smallest luminance ratio to the subfield with the highest luminance), the center shift in the gray scale with the small luminance ratio can be suppressed. At small gradations, the image quality of the moving picture is reduced and the image quality is improved.

In the first embodiment, the non-divided subfields SF5 to SF8 are arranged in the center of one frame in the order of subfields SF6 to SF5 to SF7 to SF8, as shown in Fig. 3A. (I.e., SF8 → SF7 → SF6 → SF5), the non-divided subfield SF5 having the largest emission luminance ratio and the next undivided subfield SF6 having the largest luminance luminance ratio are replaced and arranged (i.e., SF8 → SF7 → SF5 → SF6).

In the first embodiment, although each subfield from subfields SF1 to SF4 having a large light emission luminance ratio is divided into two, the number of subfields to be divided into two may be increased or decreased differently. That is, for example, each subfield from subfields SF1 to SF3 may be divided into two, or each subfield from subfields SF1 to SF6 may be divided into two. If the number of subfields divided into two is increased, the moving picture false contour is further reduced and the image quality is further improved.

(Second embodiment)

Fig. 3B is a second embodiment showing the arrangement of the subfields according to the present invention. The non-divided subfields SF5 to SF8 are arranged in the center of the frame, and the arrangement is shown in Fig. 3B. Arrange in the order of → SF5 → SF6 → SF8. Then, each subfield SF1 to SF4 is divided, and the divided subfields SF1-1, SF2-1, SF3-1, SF4-1 are arranged in order from the position of the head of the flame to the light emission luminance ratio. Subsequently, the subfields SF1-2, SF2-2, SF3-2, and SF4-2 are arranged in the order of increasing luminance luminance ratio in the end direction after the non-divided subfield SF8 in the center portion. In other words, the divided subfields are arranged so as to arrange the divided subfields in the order from the largest emission luminance ratio before and after the non-divided subfield having the small emission luminance ratio so as to be arranged almost evenly in the frame. Further, the divided subfields may be arranged in order from the smallest light emission luminance ratio.

Here, in the second embodiment, as in the first embodiment, the moving picture is displayed when the number of gradation bits of the gradation bit having a large luminous luminance ratio is increased as the light emission pattern from the light emission pattern control unit 8 performs light emission for each line or pixel. The outline can be reduced, and the moving picture outline in the gray level of the subfield having a small light emission luminance ratio can be reduced.

(Third Embodiment)

Fig. 4 is a third embodiment showing another arrangement of subfields according to the present invention. As shown therein, the subfield SF1 having the largest emission luminance ratio is made non-distributed, and the next subfield SF2 having the largest emission luminance ratio is shown. To subfield SF4 by dividing into subfields SF2-1, SF2-2, SF3-1, SF3-2, SF4-1, SF4-2, and each of the remaining subfields SF5 through which the emission luminance ratio is small. Non-segmented arrangement of SF8.

As shown in Figs. 4A and 4B, the non-divided subfield SF1 having the largest luminous intensity ratio is arranged at a position substantially in the center of the frame, and one of the two divided subfields SF2-1, SF3-1, SF4- One SF4-1 of the divided subfield is adjacent to the subfield SF1 by arranging 1 in descending order from the head of the frame to the center (ie, in the order of SF2-1 → SF3-1 → SF4-1). In addition, for the other SF2-2, SF3-2, SF4-2 of the divided subfield, descending from the end of the flame toward the center portion (that is, the subfields SF2-2 → SF3-2 → SF4-). 2) in order.

Here, the non-divided subfields SF5 to SF8 are arranged between the non-divided subfield SF1 and the other SF4-2 of the subdivided subfield.

In this case, in the embodiment according to the present invention, the odd frames and the even frames are divided into non-divided subfields SF5 to SF8 in the odd frames as shown in FIG. 4A (that is, in the order of SF5 → SF6 → SF7 → SF8). ) Further, in even frames, they are arranged in ascending order (i.e., in the order of SF8 → SF7 → SF6 → SF5) as shown in Fig. 4B.

The subfields of this arrangement are generated and arranged by the subfield constructing section 4. Then, the driver 6 drives light emission of the PDP 7 in accordance with the subfields, and realizes gradation display of the PDP 7.

Therefore, by arranging each of the non-divided subfields SF5 to SF8 between the odd frames and the even frames adjacent thereto, the moving picture false contour can be eliminated in the gradation of the subfields having the small luminance luminance ratio.

Herein, in the third embodiment, as in the first embodiment, the light emission pattern from the light emission pattern controller 8 performs light emission for each line or pixel, so that moving pictures appear when the number of gradation bits having a large light emission luminance ratio is increased. The contour can be reduced. In addition, by arranging the non-divided subfield in the center of the frame, adverse effects on image quality such as flickering can be prevented.

As described in detail above, according to the present invention, a luminance corresponding to the digital value is converted from among a plurality of subfields constituting one frame with different luminance ratios while converting an input video signal of one frame into a digital value. In a display device for selecting a ratio subfield and performing gradation display on the display unit based on the luminance ratio of the selected subfield, at least one subfield having a large luminance ratio is selected to be two subfields having the same luminance ratio. The subdividing subfields are arranged in the center of the frame, and the divided subfields of the divided one and the other are alternately selected in the order of the highest luminance ratio, and arranged alternately at the head side and the end side of the flame. In addition, the first and second light emission patterns may be generated to drive unit display parts such as pixels adjacent to each other in the display unit by using different light emission patterns. Since, there is an effect that can be reduced moving image pseudo contour generated in the luminance ratio is changed is greater gradation can be reduced deterioration of picture quality, called moving image pseudo contour and at the same time, the luminance ratio of a gradation generated in turn.

Claims (10)

While converting the input video signal of one frame into a digital value, a subfield having a luminance ratio corresponding to the digital value is selected from a plurality of subfields each having a different luminance ratio and constituting one frame. A display device for performing gradation display of a display unit on the basis of a luminance ratio of A first step of sequentially selecting from the subfields having the largest luminance ratio among the plurality of subfields in the order of the highest luminance ratio, and dividing into two subfields having the same luminance ratio; Disposing a non-divided subfield at the center of the frame; A third step of alternately selecting the divided one and the other divided subfields from the order of increasing luminance ratio, and arranging them alternately at the head side and the end side of the flame; In the first mode, the luminance ratio of each divided subfield having the same luminance ratio at the head side and the end side of the frame centered on the non-divided subfield arranged at the center of the frame, respectively, the first luminance ratio and the second luminance ratio are respectively determined. A fourth step of generating as a first light emission pattern having a second light emission pattern having a second brightness ratio and a first brightness ratio in a second mode; The gray scale display method according to claim 5, wherein unit display portions adjacent to each other in the display unit are driven by different light emission patterns. The method of claim 1, The third step is a sixth step of alternately selecting the divided one and the other divided sub-fields in the order of the highest luminance ratio and arranged in the direction from the head of the flame to the center portion and from the end of the flame to the center portion Gradation display method characterized in that performed. The method of claim 1, The third step is a seventh step of arranging the divided one and the other divided sub-field in the order of the highest luminance ratio, and arranged in the direction from the head of the flame to the center portion and the direction of the flame from the center portion of the flame Gradation display method characterized in that performed. The method of claim 1, The first step is to perform the eighth step of dividing into two subfields in the order of the highest luminance ratio from the subfield except the subfield having the largest luminance ratio, In the second step, the non-divided subfield having the largest luminance ratio is arranged as the first subfield at the position of the center portion of the flame, and at the same time, one division subfield and the other division are based on the processing of the third step. As a result of the subfields being selected and arranged alternately in the order of the highest luminance ratio, when the one divided subfield is arranged up to the arrangement position of the first subfield, the remaining non-division between the other subfield and the first subfield And a ninth step of arranging subfields. The method of claim 4, wherein The frame consists of an odd frame and an even frame adjacent to the odd frame, In the ninth step, when the remaining non-divided subfield is disposed between the other subfield and the first subfield, the remaining non-divided subfields are arranged in the order of increasing luminance ratio in one of odd and even frames. And at the same time, the other frame performs the tenth step of arranging the remaining undivided subfields in order of decreasing luminance ratio. Converting the input video signal of one frame into a digital value and simultaneously selecting a subfield having a luminance ratio corresponding to the digital value from among a plurality of subfields each having a different luminance ratio and constituting one frame, the selected subfield A display device for sequentially performing gradation display on a display unit based on a luminance ratio of Dividing means for sequentially selecting from the subfields having the largest luminance ratio among the plurality of subfields in order of increasing luminance ratio, and dividing into two subfields having the same luminance ratio; Arranging means for arranging an undivided subfield in the center of said flame; Arranging means for alternately selecting one divided subfield and the other divided subfield in an order of increasing luminance ratio, and arranging the divided subfields to the head side and the end side of the flame; The luminance ratio of each divided subfield having the same luminance ratio at the head side and the end side of the frame centering on the undivided subfield arranged at the center of the flame, in the first mode, respectively, is the first luminance ratio and the second luminance. A light emission pattern control unit generating as a first light emission pattern having a ratio, and generating as a second light emission pattern having a second luminance ratio and a first luminance ratio in a second mode; A driver for driving unit display portions adjacent to each other in the display portion by different light emission patterns; Gray display device, characterized in that consisting of. The method of claim 6, And the arranging means is configured to alternately select the divided one and the other divided subfields in the order of the highest luminance ratio, and arrange them in order from the head of the flame to the center portion and from the end of the flame to the center portion. Gradient display device. The method of claim 6, And the arranging means is configured to alternately select the divided one and the other divided subfields in the order of the highest luminance ratio, and arrange them in the order from the head of the flame to the center portion and from the center of the flame to the tail portion. A gradation display device characterized by the above-mentioned. The method of claim 6, The dividing means divides the subfields into two subfields in the order of the highest luminance ratio from the subfields except the largest one. The arranging means arranges the undivided subfield having the largest luminance ratio as the first subfield at the position of the flame center portion, and at the same time, the one or more divided subfields have the same brightness ratio by the arranging means. As a result of being alternately selected and arranged in a large order, when the one divided subfield is arranged up to the arrangement position of the first subfield, the remaining non-divided subfield is arranged between the other subfield and the first subfield. Gradient display device characterized in that. The method of claim 9, The frame consists of an odd frame and an even frame adjacent to the odd frame, When the arranging means arranges the remaining undivided subfields between the other subfield and the first subfield, in one of odd and even frames, the remaining undivided subfields are arranged in order of increasing luminance ratio. And in the other frame, the remaining undivided subfields are arranged in order of decreasing luminance ratio.