JPH10319903A - Multi-level picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a picture while suppressing occurrence of flicker in picture display for still picture mainly and to display the picture while reducing halftone display disturbance called as dynamic picture pseudo contour and picture blurring in the picture display for dynamic picture mainly. SOLUTION: When a still picture is mainly displayed, plural sub-fields having large luminance weight are arranged with sub-fields having small luminance weight between, main light emission are performed two or more times per one field. When dynamic picture is mainly displayed, occurrence of dynamic picture pseudo contour can be suppressed, and picture reduced in the blurring of dynamic picture can be displayed by arranging sub-fields having comparatively large luminance weight concentrically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, such as a plasma display device, which divides one field of an image into a plurality of sub-field images and displays the resulting image, thereby displaying a still image and a moving image. The present invention relates to a multi-tone image display device capable of favorably displaying images.

[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.

[0005] The generation of a pseudo contour when displaying a moving image will be described with reference to FIG. FIG. 9 shows level 15 and level 16
With two adjacent patterns (see FIG. 10)
FIG. 5 shows an example of the display when the adjacent pattern follows a parallel-moved pattern.

In a display device that divides one field of an input image into a plurality of subfields and performs gradation display, when a still image is displayed, the average luminance of one field of the observed image is AA in FIG. This is represented by the integral of the light emission during the period, and the gradation is correctly displayed.

On the other hand, when a moving image is displayed, on the retina, depending on the direction of movement of the line of sight, between BB ′ in FIG.
The emission integral during C 'is observed. Between BB ', the combined value of each bit is almost 0, and the sum of each bit between CC' is almost 31.

Thus, level 15 and level 16
When observing a portion where the two levels are adjacent to each other, in the level change portion, the observed luminance level is significantly disturbed by the motion of the image as shown in FIG.

Although FIG. 9 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 or the like, a position different from the original pixel position with the lapse of time. Will be integrated, and the halftone display will be greatly disturbed.

Since the halftone disturbance is recognized so that a false contour appears in the image, it is hereinafter referred to as a moving image pseudo contour.

[0010] As an attempt to reduce the false contour of a moving image,
In a conventional multi-tone image display device, an attempt is made to reduce the halftone display disturbance in a moving image display by dividing the luminance weight of a subfield corresponding to a plurality of higher-order bits and further distributing and arranging them. Has been made.

FIG. 11 shows a subfield structure in the moving image pseudo contour reducing method according to the conventional method.
An 8-bit gray scale, that is, 256 gray scales is to be displayed by using a subfield.

The luminance weighting of each subfield is 48, 48, 1, 2, 4, 8, 16, 32, 48,
48. Upper 2 bits 6 of original input image signal
The luminance weights of the sub-fields 4 and 128 are divided into four parts and distributed at both ends of the sub-field. The weight of the most significant bit is reduced so as to suppress the occurrence of halftone disturbance as much as possible. By distributing subfields having large weights at the beginning and end, blur is generated in an image observed when a moving image is displayed, and the pseudo contour of the moving image is made inconspicuous.

[0013]

As shown in FIG.
In the conventional multi-tone image display device, the subfields having the highest luminance weight are distributed and arranged in the first half and the second half of one field. For this reason, the four sub-fields 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, the main information on the brightness of the image is repeatedly displayed in the first half and the second half of one field, separated in time. Therefore, when the 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. Further, when a still image is displayed, especially in an image having a large-area high-luminance portion, light emission using the latter two luminance weights of 48 in one field is equivalent to the two luminance weights of the first half of the next field. Since the light is emitted in time close to the light emission of = 48, there is a problem that the flicker is easily perceived as one flicker in one field in the high luminance portion.

As described above, in the display device having the conventional subfield structure, it is difficult to reduce the false contour of the moving image and achieve the blurring of the moving image at the same time, and there is a problem that flicker is easily perceived in the still image display.

[0016]

In order to solve the above-mentioned problems, a multi-tone image display device of the present invention divides one field of an input signal into a plurality of sub-fields having a predetermined luminance weight, In an image display device that performs multi-tone display by a combination of on-control or off-control of each of the sub-fields, the display of the input signal corresponds to a case where a display mainly includes a moving image and a case where a display mainly includes a still image. And controlling the luminance weight of each of the subfields and the order of each of the subfields for display.

Further, in the multi-tone image display device according to the present invention, the luminance weight of each sub-field and the order of each sub-field may be such that when the display of an input signal is mainly a still image, Of these, subfields having a relatively large luminance weight are arranged before and after one field, and subfields having a relatively small luminance weight are assigned to one field.
It is characterized in that it is controlled to be arranged at the center of the field.

In the multi-tone image display device according to the present invention, when the display of the input signal is mainly composed of a still image, one of the sub-fields having a relatively large luminance weight is assigned to one of the sub-fields. Are divided into two groups, a front field and a rear field, and the two groups are arranged so that the sum of the luminance weights of the subfields is substantially equal.

Further, in the multi-tone image display device according to the present invention, when each of the sub-fields is mainly composed of a still image, the sub-field having the largest luminance weight among the sub-fields may be used. Two fields are arranged at a predetermined position of one field with a period of approximately one half of one field period, and on / off control of the two subfields is performed in unison. .

Further, in the multi-tone image display device of the present invention, when the display of the input signal is mainly a still image, the sub-fields having a relatively large luminance weight among the sub-fields may be the same. Are arranged at substantially equal intervals at predetermined positions within one field period.

Further, in the multi-tone image display device according to the present invention, when the display of the input signal is mainly a still image, one of the sub-fields having a relatively large luminance weight among one of the sub-fields may be used. , Are arranged in a distributed manner in front, in the center, and in the rear, and are arranged such that a subfield having a relatively small luminance weight is interposed between the subfields having a relatively large luminance weight.

Further, in the multi-tone image display device of the present invention, the control of the luminance weight of each of the sub-fields and the order of each of the sub-fields may be performed when the display of the input signal is mainly a moving image. The control is characterized in that the subfields of which luminance weight is relatively large among the subfields are arranged in a concentrated manner.

According to the present invention, the luminance weight of each of the sub-fields and the order of each of the sub-fields depend on the case where the display of the input signal is mainly composed of a moving image and the case where the display is mainly composed of a still image. In the image display mainly composed of still images, flickering is suppressed and displayed, and in the image display mainly composed of moving images, it is called a moving image pseudo contour. Halftone display disturbance and image blur can be reduced and displayed.

Further, according to the present invention, when the display of the input signal is mainly a still image, the sub-fields of which luminance weight is relatively large among the respective sub-fields are arranged before and after one field. However, since the control is performed such that the subfield having a relatively small luminance weight is arranged at the center of one field, in a still image display, the first half and the second half of one field are used in an image portion having a relatively large luminance. Most of the light is emitted in two separate shots. For this reason,
The main light emission in one field becomes twice, and it is possible to avoid being perceived as flicker.

According to the present invention, the control of the luminance weight of each sub-field and the order of each sub-field is performed when the display of the input signal is mainly a still image. The sub-fields having relatively large weights are dispersedly arranged in front, center, and rear of one field, and the sub-fields having relatively small luminance weights are arranged so as to be sandwiched between the sub-fields having relatively large luminance weights. Therefore, in the image portion where the luminance is relatively large, most of the light emission is performed in a plurality of times in the first half, the center portion, and the second half of one field. For this reason, the main light emission in one field becomes two or more times,
Perception as flicker can be avoided.

According to the present invention, the control of the luminance weight of each sub-field and the order of each sub-field is performed when the display of the input signal is mainly a moving image.
Since the sub-fields having relatively large luminance weights among the respective sub-fields are arranged in a concentrated manner, most of the total luminance weights are temporally concentrated, and the gaze follows the moving image. Even in this case, the occurrence of image blurring is small, so that fine moving characters can be read.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-tone image display device according to the present invention (claim 1) divides one field of an input signal into a plurality of sub-fields having a predetermined luminance weighting. In an image display device that performs multi-tone display by a combination of on-control and off-control, the sub-signals are displayed in accordance with the case where the display of the input signal mainly includes a moving image and the case where the display mainly includes a still image. The luminance weight of the field and the order of the subfields are controlled and displayed.

For this reason, for example, in displaying an image mainly composed of a still image, such as when displaying a computer image, one image is displayed.
By using a subfield configuration in which the number of main light emissions in a field is displayed in a dispersed manner, display can be performed using a subfield configuration in which flicker is suppressed.

On the other hand, when displaying an image mainly composed of a moving image, such as when displaying a television image, a subfield structure in which a display is emphasized with an emphasis on the elimination of halftone display disturbance called a pseudo-contour of a moving image rather than suppression of flicker. To provide a multi-gradation display device capable of performing control such as display using a sub-field configuration that reduces blurring of a moving image, and capable of favorably displaying various signal sources. Can be.

In the multi-tone image display device according to the present invention (claims 2 to 4), the control of the luminance weight of each sub-field and the order of each sub-field is mainly performed by displaying a still image on the input signal. In this case, among the subfields, a subfield having a relatively large luminance weight is arranged in front and rear of one field, and a subfield having a relatively small luminance weight is arranged in the center of one field. Control.

For this reason, in the still image display, most of the light is emitted in the first half and the second half of one field in the image portion where the luminance is relatively large. In the center of one field, a subfield having a relatively small luminance weight is arranged. Even in a subfield having a small luminance weight, light emission data is written to the panel and initialized for a certain period, and light emission is stopped during this period.

Therefore, the main light emission in one field is divided into the first half and the second half, and the number of light emission per field is doubled, so that the light emission is prevented from being perceived as flicker. effective. A computer image has a relatively large number of still image portions and flickers are conspicuous, and it is extremely effective to display the computer image while avoiding the flicker.

Further, in the multi-tone image display device according to the present invention (claims 5 and 6), the control of the luminance weight of each of the sub-fields and the order of each of the sub-fields is such that the display of the input signal is a still image. In the case where the main field is the main field, the sub-fields whose luminance weights are relatively large among the respective sub-fields are dispersedly arranged at the front, center, and rear of one field, and the sub-fields whose luminance weights are relatively small are assigned to the luminance fields. It is arranged so as to be sandwiched between subfields having relatively large weights.

For this reason, the main light emission in one field is divided into three or more times in the first half, the central part, and the second half, and the number of light emission per field becomes three times or more, and is perceived as flicker. This has the effect of avoiding being performed.

A computer image has a relatively large number of still image portions, and flickers are conspicuous. It is extremely effective to display the computer image while avoiding the flicker.

Further, in the multi-tone image display device according to the present invention (claim 7), the control of the luminance weight of each of the sub-fields and the order of each of the sub-fields is mainly performed by displaying the input signal mainly on a moving image. In such a case, since the subfields of which luminance weights are relatively large among the subfields are concentratedly arranged, most of the total luminance weights are temporally concentrated, and Even when the line of sight follows the image, the occurrence of image blur is small.
The moving small characters can also be read.

Further, since most of the total luminance weights are temporally concentrated, even when the level of the input signal slightly changes, the main part of the light emission changes little with time. It also has the effect of reducing the occurrence of moving image false contours.

(Embodiment 1) Embodiments of the present invention (claims 1 to 4) will be described below with reference to the drawings.
In FIG. 2, 1 is an 8-bit digital 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 12 read-only memories corresponding to a digital signal represented by 12 bits. This is a subfield control circuit that controls on or off of the subfield. Reference numeral 4 denotes a plasma display device capable of expressing gradation by a plurality of subfields.

In FIG. 2, the order of the subfields and the luminance weighting of each subfield have a relationship as shown in FIGS. 1 and 3, which is determined by the contents of the read-only memory 2.

In the image display device configured as described above, as can be seen from FIGS. 1 and 3, the upper 4 bits of the 8-bit digital signal are divided into two, converted into a 12-bit signal, and based on this, A subfield is configured. That is, if the MSB of the input image signal is ON, both the subfield 7a and the subfield 7b are ON, and light emission is performed 64 times according to 64 luminance weights.

Similarly, subfield numbers 6a to 4a and 6b in accordance with signals of the upper 4 bits of the input image.
To 4b are controlled. On the other hand, as the lower 4 bits, the lower 4 bits of the input image signal are used as they are. In FIG. 3, the numerical value “1” indicates “ON” or “H” of the digital signal.

In the multi-tone image display device of the present embodiment thus configured, the light emission pattern of the upper 4 bits is dispersed at a time Tm as shown in FIGS. 1 (a) and 1 (b). ing. Tm is approximately 2 of the field period T1.
Light emission by each subfield is performed via (c). Since the light emission luminance due to (c) is relatively small, light emission due to the upper bits is mainly (a).
And (b) emit light separately.

Therefore, light emission within one field is twice light emission within the range of all values of the input image signal. When the field period T1 is 1/60 second, the flicker component is 120.
Hz, which can be generally prevented from being perceived as flicker, and can provide an extremely effective means for displaying a still image.

(Embodiment 2) Embodiments of the present invention (claims 5 and 6) will be described below with reference to the drawings.
In FIG. 4, 1 is an 8-bit digital input image signal, 21 is a read-only memory for converting an 8-bit input image signal into a 9-bit signal, and 31 is a 9-bit digital signal corresponding to a 9-bit digital signal. This is a subfield control circuit that controls on or off of the subfield.

In FIG. 4, the order of the subfields and the luminance weighting of each subfield have a relationship as shown in FIG. 5, which is determined by the contents of the read-only memory 21.

In the image display device configured as described above, as can be seen from FIG. 5, the MSB of the 8-bit digital signal is divided into two and converted into a 9-bit signal, and a subfield is formed based on this. Is done. That is,
If the MSB of the input image signal is ON, both the subfield 7a and the subfield 7b are turned ON, and light emission is performed 64 times according to 64 luminance weights. On the other hand, the lower 7 bits use the lower 7 bits of the input image signal as they are. By setting the order of the subfields and the luminance weight to appropriate values, Ta, T
The values of b and Tc are set to be substantially equal.

In the multi-tone image display device of the present embodiment configured as described above, the light emission pattern based on the upper bits has the time (Ta + T) as shown in FIGS. 5A and 5B.
b). Light emission by the second MSB is located in the middle of light emission by the MSB. For this reason, in a relatively bright image portion where the input signal level is 128 or more, the light emission is 3a of 7a, 6 and 7b.
Since light is emitted in one or more subfields, the flicker frequency can be approximately three times the field frequency, and the flicker can be prevented from being perceived.

(Embodiment 3) Hereinafter, an embodiment of the present invention (claim 7) will be described with reference to the drawings. FIG.
2 is different from the case of FIG.
In that a moving image detection circuit 51 is provided instead of the sub-field and the order and luminance weight of the subfields are different.

As can be seen from FIGS. 7 and 8, of the consecutively arranged subfields of "luminance weight = 32", the subfield that is turned on is determined by the approximate value of the input image signal. 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 when the input image signal level is 32 or more and 63 or less, the leading “luminance Only the first subfield of “luminance weight = 32” is turned on among the subfields of “weight = 32”.

Thereafter, each time the input image signal level increases by 32, the "luminance weight = 32" subfield, which is sequentially turned on from the beginning, extends backward, and the "luminance weight = 32"
ON / OFF of the subfield 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 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 which are sequentially turned on in accordance with the increase of the input image signal extend rearward. Is controlled in a way that goes
Increase of signal level of input image signal and "luminance weight = 32"
Is guaranteed to be monotonous, and the generation level of the false contour of the moving image is suppressed even when the image moves.

Further, according to the present embodiment, since subfields having a large luminance weight are arranged consecutively, most of the total luminance weight is temporally concentrated. When the line of sight follows, the occurrence of image blurring is small, and therefore, there is an effect that fine moving characters can be read.

[0053]

As described above, according to the present invention, the following effects can be obtained.

According to the multi-tone image display device according to the present invention (claim 1), the display of the input signal mainly depends on a moving image and a case where the input signal is mainly displayed on a still image. Since the luminance weight of each sub-field and the order of the sub-fields are controlled and displayed, in the image display mainly using a still image, the flicker is suppressed and displayed, and the moving image is mainly displayed. In the image display described above, it is possible to reduce the halftone display disturbance called image pseudo contour and image blurring and display the image.

According to the multi-tone image display device according to the present invention (claims 2 to 4), in the still image display, the main light emission in one field is performed by being divided into the first half and the second half. The number of times of light emission per field is 2
This has the effect of avoiding flicker. A computer image or the like has a relatively large number of still image portions, and if there is a flicker component, it is easy to stand out.

According to the multi-tone image display device according to the present invention (claims 5 and 6), in the still image display, the main light emission in one field is divided into the first half, the center, and the second half or more. In this case, the number of times of light emission per field is substantially tripled, and there is an effect that flicker is avoided. A computer image or the like has a relatively large number of still image portions, and if there is a flicker component, it is more noticeable. However, it can be displayed by avoiding the flicker component, and a good image display can be realized.

According to the multi-tone image display device according to the present invention (claim 7), when the input image is mainly a moving image display, of the plurality of sub-fields provided for performing the tone display, The input image signal is roughly displayed in gradation using a predetermined number of subfields arranged at consecutive positions, and when the signal level of the input image signal is gradually increased, adjacent subfields are sequentially displayed. The light-emitting position can be turned on, so that there is no extreme movement of the light-emitting position due to a subfield having a large luminance weight with respect to a smooth increase in the signal level of the input image signal, and it is possible to suppress the occurrence of a moving image false contour.

Further, since the subfields with large luminance weights are arranged consecutively, most of the total luminance weights are temporally concentrated, and 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 diagram showing subfield numbers and luminance weighting of each subfield in Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram of a multi-tone image display device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a value of an input image signal and a subfield to be turned on in Embodiment 1 of the present invention;

FIG. 4 is a configuration diagram of a multi-tone image display device according to a second embodiment of the present invention.

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

FIG. 6 is a configuration diagram of a multi-tone image display device according to a third embodiment of the present invention.

FIG. 7 is a diagram showing subfield numbers and luminance weighting of each subfield in Embodiment 3 of the present invention.

FIG. 8 is a diagram illustrating a relationship between a value of an input image signal and a subfield to be turned on in Embodiment 3 of the present invention.

FIG. 9 is a diagram for explaining generation of a moving image false contour in a conventional image display device.

FIG. 10 is a diagram showing an example of an image having a pattern in which two levels are adjacent to each other;

FIG. 11 is a diagram showing an example of a subfield configuration in a conventional moving image false contour reduction method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input image signal 2 Read-only memory 3 Subfield control circuit 4 Plasma display 5, 51 Still image detection circuit 6 Moving image detection circuit

Claims (7)

[Claims] 1. An image display apparatus which divides one field of an input signal into a plurality of subfields having a predetermined luminance weighting and performs multi-tone display by a combination of ON control or OFF control of each of the subfields. The sub-fields whose luminance weights are relatively large may be dispersed or concentrated according to the case where the display of the input signal is mainly composed of a moving image and the case where the display is mainly composed of a still image. A multi-tone image display device characterized by controlling and displaying. 2. The method according to claim 1, wherein when the display of the input signal is mainly a still image, each of the sub-fields includes a sub-field of which luminance weight is relatively large among the sub-fields before and after one field. 2. The multi-tone image display device according to claim 1, wherein the sub-fields are arranged in a distributed manner, and a sub-field having a relatively small luminance weight is arranged in the middle of one field. 3. When each of the subfields is mainly composed of a still image, the subfields include subfields having relatively large luminance weights in front and rear of one field. 2. The multi-tone image display device according to claim 1, wherein the image data is divided into two groups and arranged so that the sum of the luminance weights of the subfields of the two groups becomes substantially equal. 4. When each of the sub-fields is mainly composed of a still image, the sub-field having the maximum luminance weight among the respective sub-fields is substantially one at a predetermined position of one field. 2. The multi-tone image display device according to claim 1, wherein two of the two sub-fields are arranged so as to be separated from each other by a half period of the field period, and on / off control of the two sub-fields is performed in unison. . 5. Each of the sub-fields has the same luminance weight among the sub-fields having a relatively large luminance weight among the sub-fields when the display of the input signal is mainly a still image. Subfield 1
2. A multi-tone image display device according to claim 1, wherein said multi-tone image display device is arranged at a predetermined position in a field period at substantially equal intervals. 6. The control of each of the sub-fields, wherein when the display of the input signal is mainly a still image, a sub-field having a relatively large luminance weight among the sub-fields, 2. The multi-gradation according to claim 1, wherein the control is performed in such a manner that the sub-fields having a relatively small luminance weight are sandwiched between the sub-fields having a relatively large luminance weight. Image display device. 7. The control of the luminance weight of each of the subfields and the order of each of the subfields is such that when the display of the input signal is mainly a moving image, the luminance weight of each of the subfields is relatively large. 2. The multi-tone image display device according to claim 1, wherein the control is such that the subfields are arranged in a concentrated manner.