JPH10153980A - Picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of moving image pseudo-contours to a lower level and to read fine characters even though they are moving by successively on control plural subfields arranged at continuous locations in accordance with the order, which is continuously arranged, when the signal level of input picture signals is continuously increased. SOLUTION: A reading dedicated memory 2 converts input picture signals 1, which are 8 bit signals for example, to 12 bit signals. A subfield control circuit 3 performs on or off control of twelve subfields corresponding to the digital signals expressed in 12 bits. Plural subfields arranged in continuous locations among plural subfields are successively on controlled in accordance with the order arranged in a continuous manner when the signal level of the signals 1 is continuously increased. Thus, the extreme movement of the light emitting position by the subfields having a large luminance weight is eliminated, when the signal level of the signals 1 is gradually increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device which displays a multi-gradation display by dividing one field of an image into a plurality of sub-field images and displaying the image. The present invention relates to an image display device for displaying images with improved gradation disturbance.

[0002]

2. Description of the Related Art Conventionally, when a gray scale display is performed using a display device, such as a plasma display device, which divides and displays one field of an image into a plurality of sub-field images and displays the image, for example, a plasma display device. It is known that so-called pseudo-contour-like gradation disturbance occurs in moving image display.
With reference to FIG. 6, the generation of the pseudo contour at the time of displaying a moving image will be described.

[0003] FIG. 6 is a block diagram of level 15 and level 16.
7 shows a state in which an image having a pattern in which two levels are adjacent to each other (an example is shown in FIG. 7) is displayed, and a state in which the adjacent pattern follows a pattern that has been translated. In a display device that performs gradation display by dividing one field of an input image into a plurality of subfields, when a still image is displayed, the average luminance of one field of the observed image is between AA ′ in FIG. It is expressed by integration of light emission, and a correct gradation display is performed.

On the other hand, when a moving image is displayed, the retina is placed on the retina between BB 'and CC' in FIG.
The integration of the emission between is observed. Between BB ', the combined value of each bit is approximately 0, and the sum of each bit between CC' is approximately 31. As described above, when a portion where two levels 15 and 16 are adjacent to each other is observed, in the level change portion, the luminance level observed as shown in FIG. 6 is significantly disturbed by the motion of the image.

Although FIG. 6 shows that light emission is continuously performed with a predetermined width for each subfield, in an actual plasma display, each subfield is assigned a luminance weight. Although it is composed of a set of pulsed light emission of the number of times, the gradation disturbance at the time of displaying a moving image is essentially the same. As described above, since an attempt is made to express a halftone by integrating the luminance of each subfield in the time direction, if the line of sight moves in a moving image, the image at a position different from the original pixel position over time elapses. Since the weight of each bit is integrated, the halftone display is greatly disturbed.

For this reason, in the conventional image display apparatus, an attempt has been made to reduce halftone display disturbance in moving image display by dividing a plurality of upper bits and distributing them to form subfields. I have. FIG. 8 shows a subfield configuration in a method of reducing a pseudo contour of a moving image according to the conventional method, in which an 8-bit gray scale, that is, 256 gray scales is displayed by using 10 subfields. The luminance weighting of each subfield is 48, 48, 1, 2, 4, 8, 16, 32,
48, 48. The luminance weights of the upper two bits 64 and 128 of the original input image signal are divided into four and distributed at both ends of the subfield, and the weight of the most significant bit is reduced to minimize the occurrence of halftone disturbance. By distributing large subfields at the beginning and end of the subfield in a distributed manner,
Blur is generated in an image observed when a moving image is displayed, so that a pseudo outline of the moving image is made inconspicuous.

[0007]

As shown in FIG. 8, in a conventional image display device, subfields having the largest luminance weight are distributed in the first half and the second half of one field.

FIG. 8 shows an example of on / off control of each subfield with respect to an input image signal level. For example, as the signal level of the input image signal increases from 143 to 144, the number of “luminance weighting = 48” subfields that are turned on decreases from two to three.

At this time, although the level of the input image signal is slightly increased by one, the subfield having the largest luminance weight is turned on at a position temporally separated.

For this reason, when the same phenomenon as that of FIG. 5 is observed, that is, when a moving image is observed with the sight line of sight, FIG.
As shown in (a) and FIG. 9 (b), strong grayscale disturbances differing depending on the direction of the line of sight occurred, and the suppression of the moving image false contour was insufficient. Further, four subfields of “luminance weight = 48” arranged at both ends apart form a total of 192 luminance weights, and occupy most of the total luminance weights. Therefore, when the moving image is displayed and the line of sight follows, the observed image is a combination of temporally separated image components, and as a result, the moving image portion is blurred. For this reason, there is a problem that the image quality is deteriorated such that the moving fine characters are duplicated and cannot be read.

[0011]

In order to solve the above-mentioned problems, an image display device according to the present invention divides one field of an input image signal into a plurality of sub-fields having a predetermined luminance weight, and In an image display apparatus that performs multi-tone display by on-control or off-control of a field, among the plurality of subfields, a plurality of subfields arranged at consecutive positions have a continuous signal level of the input image signal. When the number is increased, the on-control is sequentially performed in accordance with the order of the continuous arrangement.

Further, the image display device is characterized in that the respective luminance weights of the plurality of subfields arranged at the continuous positions have substantially the same value.

According to the present invention, of the plurality of subfields provided for performing grayscale display, the input image signal is roughly grayscale displayed using a predetermined number of subfields arranged at consecutive positions. Therefore, when the signal level of the input image signal is gradually increased, the adjacent subfields can be sequentially turned on, so that the luminance weight is set for the smooth increase of the signal level of the input image signal. There is no extreme movement of the light emission position due to the subfield having a large value, and the occurrence of the false contour of the moving image can be suppressed low.

Further, according to the present invention, since the subfields having a large luminance weight are continuously arranged,
Most of the total luminance weights are concentrated in time, so that even when the gaze follows a moving image, there is little occurrence of image blur, and therefore, moving small characters should be legible. It has the effect that it can be done.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image display apparatus according to the present invention (claim 1) divides one field of an input image signal into a plurality of subfields having a predetermined luminance weight, and controls ON or OFF of each subfield. In the image display device performing multi-gradation display by off control, among the plurality of subfields, a plurality of subfields arranged at consecutive positions are provided when the signal level of the input image signal continuously increases. It is characterized in that the on-control is sequentially performed in accordance with the sequence of the continuous arrangement.

For this reason, when the signal level of the input image signal is gradually increased, the adjacent subfields can be sequentially turned on. There is no extreme movement of the light emission position due to the subfield having a large value, and the occurrence of the false contour of the moving image can be suppressed low.

Further, in the image display device according to the present invention (claim 2), the luminance weights of the plurality of subfields arranged at the continuous positions are equal to or substantially equal to each other. Features.

For this reason, the approximate value of the luminance of the image is expressed stepwise by successively and successively turning on a plurality of sub-fields having luminance weights of substantially equal values arranged at the consecutive positions. can do. At this time, the plurality of subfields having the luminance weights of substantially the same value are arranged at continuous positions and are controlled to be continuously turned on, so that a smooth increase in the signal level of the input image signal As a result, there is no extreme movement of the light emitting position due to the subfield having a large luminance weight, and the occurrence of a moving image false contour can be suppressed to a low level.

Further, according to the embodiment of the present invention, since the subfields having a large luminance weight are successively arranged, most of the total luminance weight is temporally concentrated. Even when the line of sight follows the image,
The occurrence of image blurring is small, and therefore, moving small characters can be read.

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In FIG. 1, 1 is an input image signal, 2 is a read-only memory for converting an 8-bit input image signal into a 12-bit signal, 3 is 1
This is a subfield control circuit that controls on / off of 12 subfields corresponding to a digital signal represented by 2 bits. In FIG. 1, the relationship between the subfield number and the luminance weight of each subfield is as shown in FIG. 2, which is determined by the contents of the read-only memory.

In the image display device configured as described above, as can be seen from FIG. 2, of the consecutively arranged sub-fields of "brightness weight = 32", the sub-field which is turned on is the input image signal. Is determined by the approximate value of. That is, when the input image signal level is 31 or less, among the subfields of “luminance weight = 32”, the subfield to be turned on is 0, and the input image signal level is 32.
If the value is 63 or less, only the first sub-field of “brightness weight = 32” of the first sub-field of “brightness weight = 32” is turned on. Thereafter, each time the input image signal level increases by 32, the luminance signal is turned on sequentially from the top.
On / off of the subfield of “luminance weight = 32” is controlled in such a manner that the subfield of “32” extends backward.

On the other hand, the five sub-fields of sub-field number 1 to sub-field number 5 are on / off controlled according to the value of the lower 5 bits of the input image signal, and bear detailed expression of gradation display. As described above, the subfields of “brightness weight = 32” representing the approximate value of the input image signal are arranged continuously, and the subfields that are sequentially turned on in accordance with the increase of the input image signal extend rearward. It is guaranteed that the increase in the signal level of the input image signal and the positional relationship between the subfields of “brightness weight = 32” are monotonous, and even when there is image movement. In addition, the generation level of the false contour of the moving image is suppressed.

Further, according to the present embodiment, since the subfields with large luminance weights are arranged consecutively, most of the total luminance weights are temporally concentrated, and Is less likely to occur even when the user's line of sight follows, so that there is an effect that moving small characters can be read.

FIG. 3 illustrates the on / off control of the subfield according to the present embodiment and the effect of improving the pseudo contour of a moving image with respect to the conventional example shown in FIG. 3 and 9, a comparison between (a) and (b) and (c)
From the comparison between (d) and (d), the degree of occurrence of the false contour of the moving image can be roughly compared. As is clear from FIGS. 3 and 9, when the subfield control according to the present embodiment is used, the occurrence of a moving image false contour is reduced as compared with the conventional subfield control.

In this embodiment, the total number of gradation representations is 256, which is a sufficient value, and the blur of an image can be suppressed while maintaining the so-called full-color display capability and the pseudo contour of a moving image can be suppressed. Generation can be suppressed, and extremely effective means for enabling high-quality image display can be provided.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the contents of the read-only memory 2, which is different from the case of FIG. As can be seen from FIG. 3, “luminance weight =
Among the subfields of "24", the subfield turned on is determined by the approximate value of the input image signal.

That is, when the input image signal level is 23 or less, of the subfields of “luminance weight = 24”, 0 subfields are turned on. When the input image signal level is 24 or more and 47 or less, First “luminance weight = 24”
, Only the first subfield of “luminance weight = 24” is turned on.

Thereafter, every time the input image signal level increases by 24, the "luminance weight = 24" subfield, which is sequentially turned on from the top, extends backward to form "luminance weight = 24".
ON / OFF of the subfield is controlled.

On the other hand, the five sub-fields of sub-field number 1 to sub-field number 5 are on / off controlled in accordance with a value obtained by dividing the input image signal by 24, and bear detailed expression of gradation display.

As described above, the subfield of “luminance weight = 24”, which is sequentially turned on in accordance with the increase of the input image signal, is controlled to extend backward, and is compared with the case of the first embodiment. The luminance weight of the subfields which are sequentially turned on and extend rearward is reduced, and the number of expressible gradations is reduced to 192, but it is possible to set a smaller value for the generation of a moving image false contour. Become.

In FIG. 3, the sub-fields 1 to 5 located in front of the moving image are controlled as shown in FIG. It is possible to suppress the occurrence of a moving image false contour in a wide range of the signal level of the input image signal.

[0032]

As described above, according to the image display apparatus of the present invention, a predetermined number of subfields arranged at consecutive positions among a plurality of subfields provided for performing gradation display are used. In this case, the input image signal is displayed in approximately gray scale, and when the signal level of the input image signal is gradually increased, adjacent sub-fields can be sequentially turned on. There is no extreme movement of the light emission position due to the subfield having a large luminance weight with respect to the smooth increase, and it is possible to suppress the generation of the false contour of the moving image.

Further, since the subfields with large luminance weights are arranged consecutively, most of the total luminance weights are temporally concentrated, so that even when the visual line follows the moving image, This has the effect that the occurrence of image blurring is small, and therefore, fine characters that move can be read.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing subfield numbers and luminance weighting of each subfield in Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating reduction of a pseudo contour of a moving image according to the first embodiment of the present invention.

FIG. 4 is a diagram showing subfield numbers and luminance weighting of each subfield in Embodiment 2 of the present invention.

FIG. 5 is a diagram showing luminance weighting of subfield numbers 1 to 5 in Embodiment 2 of the present invention.

FIG. 6 is a diagram showing generation of a moving image false contour in a conventional plasma display device.

FIG. 7 is a diagram showing an example of an image having a pattern in which two levels are adjacent to each other;

FIG. 8 is a diagram illustrating a subfield configuration for reducing a false contour of a moving image in a conventional image display device.

FIG. 9 is a diagram showing an example of on / off control of each subfield in a conventional image display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input image signal 2 Read-only memory 3 Subfield control circuit 4 Plasma display

Claims (2)

[Claims] An image display apparatus for dividing one field of an input image signal into a plurality of subfields having a predetermined luminance weighting and performing multi-tone display by on / off control of each of said subfields. The plurality of subfields arranged at consecutive positions among the plurality of subfields are sequentially turned on in accordance with the order in which the subfields are consecutively arranged when the signal level of the input image signal continuously increases. An image display device characterized in that the image is displayed. 2. The image display device according to claim 1, wherein each of the plurality of subfields arranged at the continuous positions has an equal or substantially equal luminance weight.