JP3379359B2 - Image display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for displaying one field of an image by dividing it into a plurality of subfield images for multi-gradation display, and displaying a halftone at the time of displaying a moving image. The present invention relates to an image display device that improves and displays the irregular gradation.

[0002]

2. Description of the Related Art Conventionally, when one field of an image is divided into images of a plurality of sub-fields and displayed to perform multi-gradation display, for example, when performing gradation display using a plasma display device, It is known that so-called pseudo contour-like gradation disturbance occurs in moving image display.
Generation of the pseudo contour at the time of displaying the moving image will be described with reference to FIG.

FIG. 6 shows two levels, level 15 and level 16.
It shows a case where an image (an example of which is shown in FIG. 7) having adjacent patterns of two levels is displayed and how this adjacent pattern is observed when following a translated pattern. 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 represented by the integral of light emission, and the gradation display is performed correctly.

On the other hand, when a moving image is displayed, depending on the direction of the movement of the line of sight, the retinal area may be taken between BB 'and CC' in FIG.
The integral of the emission between is observed. The value obtained by combining the respective bits between BB 'is approximately 0, and the total of the respective bits between CC' is approximately 31. Thus, when observing a portion where two levels of level 15 and level 16 are adjacent to each other, the luminance level observed in the level changing portion as shown in FIG. 6 is significantly disturbed by the movement of the image.

Although FIG. 6 shows that light emission is continuously performed in each subfield with a predetermined width, in an actual plasma display, each subfield corresponds to each luminance weighting. Although it is composed of a set of pulsed light emission a certain number of times, the gradation disorder during display of a moving image is essentially the same. In this way, since halftones are expressed by integrating the luminance of each subfield in the time direction, when the line of sight moves in a moving image, etc., the image at a position different from the original pixel position will be displayed over time. Since the weight of each bit is integrated, the halftone display is greatly disturbed.

Therefore, in the conventional image display device, an attempt has been made to reduce the disturbance of halftone display in moving image display by dividing the upper bits and disposing them in a distributed manner to form subfields. There is. FIG. 8 shows a subfield structure in the moving image pseudo contour reducing method according to the conventional method, which is intended to display 8-bit gradation, that is, 256 gradations by using 10 subfields. The luminance weighting of each subfield is 48, 48, 1, 2, 4, 8, 16, 32, in order.
It is 48, 48. The luminance weights of the upper 2 bits 64 and 128 of the original input image signal are divided into 4 and distributed at both ends of the subfield, and the weight of the most significant bit is reduced to suppress the occurrence of halftone disturbance as much as possible. By allocating the subfields with large weights at the beginning and the end of the subfields,
This is intended to make a moving image pseudo contour inconspicuous by causing blurring in an image observed when the moving image is displayed.

[0007]

As shown in FIG. 8, in a conventional image display device, subfields having the highest luminance weighting are dispersedly arranged 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 the input image signal level. For example, as the signal level of the input image signal increases from 143 to 144, the number of “brightness weighting = 48” subfields that are turned on becomes 2 to 3.

At this time, even though the level of the input image signal is slightly increased by 1, the subfield having the largest luminance weighting is turned on at a position distant in time.

Therefore, when the same phenomenon as in FIG. 5 is observed, that is, when the moving image is observed while the line of sight is observed,
As shown in (a) and FIG. 9 (b), strong gradation disturbances that differ depending on the direction of the line of sight have occurred, and the suppression of moving image pseudo contours was insufficient. Further, the four subfields of “brightness weight = 48” arranged apart from each other form a total of 192 brightness weights, and occupy most of the total brightness weights. Therefore, when a moving image is displayed and the line of sight is followed, the observed image is a combination of image components that are temporally distant from each other, and as a result, image blurring occurs in the moving image portion. For this reason, there is a problem in that the moving fine characters are duplicated to make them unreadable and thus the image quality is deteriorated.

[0011]

In order to solve the above-mentioned problems, the image display device of the present invention divides one field of an input image signal into a plurality of sub-fields having a predetermined luminance weighting, and each sub-field is divided into a plurality of sub-fields. In an image display device that performs multi-gradation display by field on control or off control, among the plurality of subfields, a plurality of subfields arranged at consecutive positions have continuous signal levels of the input image signal. In this case, the ON control is sequentially performed according to the order of the continuous arrangement.

Further, the image display device is characterized in that each of the plurality of sub-fields arranged in the continuous position has substantially equal brightness weighting values.

According to the present invention, of the plurality of subfields provided for gradation display, a predetermined number of subfields arranged at consecutive positions are used to display the input image signal in a rough gradation. Therefore, when the signal level of the input image signal is gradually increased, the adjacent subfields can be sequentially turned on. Therefore, the brightness weighting is applied to the smooth increase of the signal level of the input image signal. Since there is no extreme movement of the light emitting position due to a large subfield, the generation of a moving image pseudo contour can be suppressed to a low level.

Further, according to the present invention, since the sub-fields having a large luminance weighting are continuously arranged,
Most of the total brightness weights are concentrated in terms of time, and even when the line of sight follows the moving image, there is little image blurring. Therefore, it is possible to read moving small characters. It has the effect that

[0015]

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 predetermined luminance weighting, and performs on-control of each of the subfields. In an image display device that performs 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 order 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. Therefore, the brightness weighting is applied to the smooth increase of the signal level of the input image signal. Since there is no extreme movement of the light emitting position due to a large subfield, the generation of a moving image pseudo contour can be suppressed to a low level.

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

For this reason, by sequentially turning on a plurality of sub-fields having substantially equal brightness weightings arranged at the continuous positions successively and stepwise, the approximate value of the brightness of the image is expressed stepwise. can do. At this time, since the plurality of sub-fields having the brightness weighting of substantially the same value are arranged at consecutive positions and are controlled so as to be continuously turned on, the smooth increase of the signal level of the input image signal Thus, there is no extreme movement of the light emitting position due to the subfield having a large luminance weight, and the generation of the pseudo contour of the moving image can be suppressed to a low level.

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

(First Embodiment) A first embodiment of the present invention will be described below 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, and 3 is 1
It is a subfield control circuit for controlling ON / OFF of 12 subfields corresponding to a digital signal represented by 2 bits. In FIG. 1, the subfield number and the luminance weighting of each subfield have a relationship 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 subfields of "luminance weight = 32", the subfield that is turned on is the input image signal. It is determined by the approximate value of. That is, when the input image signal level is 31 or less, the subfield that is turned on is “0” among the “brightness weight = 32” subfields, and the input image signal level is 32.
In the case of 63 or more, the first sub-field of "luminance weight = 32" among the top sub-fields of "luminance weight = 32" is turned on. After that, each time the input image signal level increases by 32, the brightness is sequentially turned on from the beginning "luminance weight =
The on / off of the subfield of "luminance weight = 32" is controlled so that the subfield of "32" extends rearward.

On the other hand, the five subfields of subfield number 1 to subfield number 5 are on / off controlled according to the value of the lower 5 bits of the input image signal, and are responsible for the detailed expression of gradation display. As described above, the subfields of “luminance weight = 32” that represent the approximate value of the input image signal are arranged continuously, and the subfields that are sequentially turned on as the input image signal increases extend backward. It is guaranteed that the increase in the signal level of the input image signal and the positional relationship of the "brightness weight = 32" subfield have a monotonous relationship, even when there is an image motion. , The generation level of the moving image pseudo contour is suppressed.

Further, according to the present embodiment, since the sub-fields having a large luminance weighting are continuously arranged, most of the total luminance weighting is temporally concentrated, and the moving image Even when the line of sight follows, there is little image blurring, and therefore, it is possible to make small moving characters legible.

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

In the present embodiment, the total number of gradation representations is 256, which is a sufficient value, so that the so-called full-color display capability is maintained, image blurring is suppressed, and moving image pseudo contours are displayed. It is possible to provide an extremely effective means capable of suppressing the occurrence and displaying a high quality image.

(Second Embodiment) A second embodiment of the present invention will be described below 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 weights =
Of the "24" subfields, the subfields to be turned on are determined by the approximate value of the value of the input image signal.

That is, when the input image signal level is 23 or less, 0 of the "brightness weight = 24" subfields are turned on, and when the input image signal level is 24 or more and 47 or less, "Luminance weight = 24" at the beginning
Only the first sub-field of “luminance weight = 24” is turned on.

Thereafter, each time the input image signal level increases by 24, the "brightness weight = 24" subfield, which is turned on sequentially from the beginning, extends rearward so that "brightness weight = 24".
ON / OFF of the subfield of is controlled.

On the other hand, the five subfields of subfield number 1 to subfield number 5 are on / off controlled according to the value of the remainder of the input image signal divided by 24, and carry out detailed representation of gradation display.

As described above, the subfields of "luminance weight = 24" which are sequentially turned on in accordance with the increase of the input image signal are controlled so as to extend rearward. Compared with the case of the first embodiment. The luminance weights of subfields that are sequentially turned on and extending rearward are small, and the number of expressible gray scales is reduced to 192, but it is possible to set a smaller value for the occurrence of a moving image pseudo contour. Become.

In addition, in FIG. 3, the subfields 1 to 5 located in the front are controlled as shown in FIG. Therefore, it is possible to suppress the generation of the moving image pseudo contour in a wide range of the signal level of the input image signal.

[0032]

As described above, according to the image display device of the present invention, of a plurality of subfields provided for performing gradation display, a predetermined number of subfields arranged at consecutive positions are used. When the signal level of the input image signal is gradually increased, the adjacent subfields can be sequentially turned on. Therefore, the signal level of the input image signal can be changed. With respect to a smooth increase, 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 pseudo contour can be suppressed to a low level.

Further, since subfields having a large luminance weighting are arranged consecutively, most of the total luminance weighting is concentrated in time, and even when the line of sight follows a moving image. As a result, there is little image blurring, and therefore, it is possible to make small moving characters legible.

[Brief description of 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 according to the first embodiment of the present invention.

FIG. 3 is a diagram showing reduction of a false 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 according to the second embodiment of the present invention.

FIG. 5 is a diagram showing luminance weighting of subfield numbers 1 to 5 according to the second embodiment of the present invention.

FIG. 6 is a diagram showing generation of a moving image pseudo 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 subfield configuration diagram 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]

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

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Claims (4)

(57) [Claims] 1. A dividing one field of the input image signal into subfield several, have rows multi-gradation display by ON control or OFF control of the plurality of sub-fields, the largest luminance weight in the one field Have a continuous
The plurality of subfields arranged and the maximum brightness in the one field from the input image signal level.
The brightness weights of multiple subfields with
With the detailed part which is controlled on / off according to the value of the remainder
In the image display device that constitutes the one field, in the detailed portion, the brightness weighting is performed in ascending order.
A number of sub-fields are placed, among the details
Only the subfield with the highest intensity weighting is
Image display device characterized by being arranged in succession
Place 2. The detailed portion is subfield number 1
The image display device according to claim 1, wherein the image display device comprises five subfields of subfield number 5. 3. The image display according to claim 2, wherein the sub-dield having the maximum luminance weight in the detailed portion is continuously arranged in sub-field number 4 and sub-field number 5. apparatus. Wherein said maximum luminance weighting luminance weight 2
4. The image display device according to claim 1, wherein the image display device is 4.