JP2004126457A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a picture display device such as a plasma display panel which suppresses a moving picture pseudo outline while sufficient gradation is secured. <P>SOLUTION: The picture display device is provided with a disturbance constant addition circuit 19 generating a plurality of disturbance constants to gradation corresponding to a picture signal, selecting one of the constants and adding it to the picture signal. Disturbance is overlapped with and applied to the respective picture signals. Thus, places where the moving picture pseudo outlines occur are dispersed and they are prevented from being visually recognized. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image display device such as a plasma display panel (PDP) or a digital mirror device (DMD) that divides an image of one field into a plurality of subfield images and performs multi-tone display.
[0002]
[Prior art]
2. Description of the Related Art Image display devices that perform binary control of light emission or non-light emission, such as PDP and DMD, often perform halftone display using a subfield method. In the subfield method, one field is time-divided using a plurality of subfields weighted by the number of times of light emission or the amount of light emission, and binary control of each pixel is performed for each subfield. That is, each subfield has a predetermined luminance weight, and performs a gradation display by the sum of the weights of the subfields that emit light.
[0003]
FIG. 14 shows an example of the configuration of a subfield in a conventional PDP. In this example, one field is divided into eight subfields (SF1, SF2,..., SF8), and each subfield has a luminance of (1, 2, 4, 8, 16, 32, 64, 128). Have weight. Each subfield includes a setup period T1 for performing a preliminary discharge, a writing period T2 for performing data writing of light emission or non-light emission for each pixel, and a sustaining period T3 for simultaneously emitting the pixels to which light emission data has been written. . By emitting light in various combinations of these subfields, 256 levels of gradation from "0" to "255" can be expressed. For example, gradation “7” can be expressed by emitting SF1, SF2, and SF3 having luminance weights 1, 2, and 4, and gradation “21” can be expressed by SF1, SF3 having luminance weights 1, 4, and 16. , SF5 by emitting light.
[0004]
In a display device that performs multi-tone display using such a subfield method, it is known that a pseudo contour (moving image pseudo contour) appears during moving image display and deteriorates image quality. Hereinafter, the pseudo contour of the moving image will be described. Again, it is assumed that one field is divided into eight subfields (SF1 to SF8) weighted as (1, 2, 4, 8, 16, 32, 64, 128). As shown in FIG. 15, consider a case where the image pattern X moves on the screen of the PDP 33 in the horizontal direction. The image pattern X is composed of a region P1 having a gradation of “127” and a region P2 having a gradation of “128”. FIG. 16 is a diagram in which the image pattern X is developed into subfields. The horizontal axis corresponds to the horizontal screen position on the screen of the PDP 33, and the vertical axis corresponds to the time direction. The hatching in FIG. 16 indicates a subfield in which no light is emitted.
[0005]
When the image pattern X is stationary, as shown in FIG. 16, the human viewpoint is also fixed at the screen position A, and thus the original gradations “127” and “128” of the pixel are recognized. However, when the image pattern X moves in the left direction, the viewpoint also moves in the direction of the screen position B-B ', so that the non-light-emitting subfield in the area P2 and the non-light-emitting subfield in the area P1 are seen. , The gradation “0”, that is, the dark line is recognized. Conversely, when the image pattern X moves rightward, the viewpoint also moves to the screen position CC ′, so that the light emitting subfield of the area P1 and the light emitting subfield of the area P2 are viewed, and the gradation “ 255 ", that is, a bright line is recognized. In any case, since these are significantly different from the original gradation (127 or 128), these are recognized as contours. As described above, the pseudo contour occurs at a place where the pattern of the subfield that emits light has a large change even though the change in the gradation is slight. For example, when the above-described weighted subfield is used, when the luminance gradation of adjacent pixels is “63” and “64”, or when the luminance gradation of adjacent pixels is “191” and “192”, it is remarkably observed. . Such a pseudo contour is called pseudo contour noise (see Non-Patent Document 1), and causes image quality to deteriorate.
[0006]
Therefore, as a method of suppressing the moving image pseudo contour, for example, the gradation of the image signal is converted into a “first gradation” and a “middle gradation” in which the moving image pseudo contour is unlikely to occur, and an error generated by the conversion is converted. Interpolation of gradation jumps is performed by diffusing the gradation into peripheral pixels. Next, if the converted gray level is “intermediate gray level”, rounding up or down to the nearest “first gray level” is performed. There has been proposed a method of alternately repeating rounding up and down for each dot, line, and field to express an "intermediate gradation" on average (see Patent Document 1).
[0007]
[Patent Document 1]
JP 2000-276100 A
[Non-patent document 1]
Technical Report of the Institute of Television Engineers of Japan, Vol. 19, no. 2, IDY95-21, pp. 61-66: "Pseudo-contour noise observed in pulse width modulation moving image display"
[0008]
[Problems to be solved by the invention]
However, in such a method, a decrease in the number of gradations near a gradation at which a large moving image false contour occurs is inevitable. That is, if the false contour of the moving image is suppressed, the number of gradations becomes insufficient and the image becomes visually rough. On the contrary, if the number of gradations is secured, the false contour of the moving image occurs.
[0009]
An object of the present invention is to provide an image display device capable of suppressing a false contour of a moving image while securing a sufficient gradation.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, an image display device according to the present invention comprises a disturbance constant generating means for outputting a plurality of disturbance constants for a gradation corresponding to an image signal, and selecting one from a plurality of disturbance constants. Means for selecting a disturbance constant and an adding means for adding the selected disturbance constant and the image signal. It is characterized by being unrecognizable.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
That is, the invention described in claim 1 of the present invention is an image display device that performs multi-gradation display by configuring one field by a plurality of subfields and controlling each subfield to emit light or not to emit light. Disturbance addition means for adding a disturbance constant, wherein the disturbance addition means selects a disturbance constant generating means for outputting a plurality of disturbance constants for a gradation corresponding to an image signal, and one from a plurality of disturbance constants An image display device comprising: a disturbance constant selecting unit that performs the operation; and an adding unit that adds the selected disturbance constant and the image signal.
[0012]
Further, the invention according to claim 2 is an image display device for displaying a multi-gradation by forming one field by a plurality of sub-fields and controlling each sub-field to emit light or not to emit light. The image processing apparatus further includes: a gradation limiting unit that limits the gradation to a difference and generates a display error by error diffusion to peripheral pixels; and a disturbance adding unit that adds a disturbance constant to the image signal limited by the gradation limiting unit. The adding means includes a disturbance constant generating means for outputting a plurality of disturbance constants for the gradation corresponding to the image signal limited by the gradation limiting means, and a disturbance constant selection means for selecting one from the plurality of disturbance constants. An image display device comprising: a unit; and an adding unit that adds a selected disturbance constant and an image signal.
[0013]
The invention according to claim 3 is the image display device according to claim 1 or 2, wherein a total of a plurality of disturbance constants is zero.
[0014]
Hereinafter, embodiments of the present invention will be described with reference to the drawings, together with the operation thereof.
[0015]
(Embodiment 1)
In FIG. 1, an analog-digital (A / D) conversion circuit 11 performs A / D conversion of an RGB signal (image signal). The inverse gamma correction circuit 13 performs inverse gamma correction on the A / D converted image signal. The motion detection circuit 14 detects whether or not the input image is a moving image, for example, based on an inter-field difference. The inclination detection circuit 15 has a part where the gradation has a certain degree of inclination in the screen due to the difference between adjacent pixels and the like, and is continuous over pixels that can be recognized (hereinafter, abbreviated as an inclined gradation area). ) Is detected. The AND circuit 16 detects a moving gradient area by taking the logical product of the outputs of the motion detecting circuit 14 and the tilt detecting circuit 15. The image signal subjected to the inverse gamma correction is sent to a gradation limiting circuit 17 and also sent to a disturbance constant adding circuit 19 as a disturbance constant adding means. The gradation limiting circuit 17 converts the gradation of the sent image signal into a gradation that does not generate a moving image false contour, and increases the number of gradations in a pseudo manner by error diffusion. The gradation limiting circuit 17 and the disturbance constant adding circuit 19 are one of the main parts of the present invention, and will be described later in detail. Based on the output of the AND circuit 16, the selection circuit 23 selects the output of the disturbance constant adding circuit 19 for a moving gradient gradation area, and outputs the output of the gradation limiting circuit 17 for other images. Select This is to make the processing of the disturbance constant adding circuit 19 effective only in a moving gradient gradation area. The image signal-subfield association circuit 25 converts the image signal selected by the selection circuit 23 into field information including a plurality of bits indicating whether or not to emit light in the subfield. The subfield processing circuit 27 determines the number of sustain pulses issued in the sustain period based on the field information. The scanning / sustaining / erasing drive circuit 29 and the data drive circuit 31 control the light emission amount of each pixel based on the output from the subfield processing circuit 27 to display an image of a desired gradation on the PDP 33. The timing pulse generation circuit 35 generates various timing signals based on the horizontal synchronizing signal and the vertical synchronizing signal, and supplies them to various parts in the display device.
[0016]
Next, a description will be given of a gradation used in the embodiment of the present invention, in which a pseudo contour does not occur. In the embodiment of the present invention, as shown in FIGS. 2 to 4, one field is divided into ten subfields (SF1, SF2,..., SF10), and each subfield is (1, 2, 4, 8, 16, 25, 34, 44, 55, 66). 2 to 4, "1" in the column of each subfield indicates that the corresponding subfield emits light.
[0017]
As described above, the dynamic false contour is likely to occur where the pattern of the subfield that emits light is large despite the slight change in gradation between adjacent pixels. For example, there is a case where the gray levels of adjacent pixels are “15” and “16”. At this time, referring to the subfield columns of FIGS. 2 to 4 and arranging SF1 to SF10 in order with the light emitting subfield being 1 and the non-light emitting subfield being 0, the gradation “15” is 111100000 and “16”. Is 00001000000, and it can be seen that the change of the pattern of the emitting subfield is large.
[0018]
Therefore, as a gray scale in which a pseudo contour does not occur,
Condition a: a gradation at which all subfields having a weight smaller than the subfield to emit light emit light.
Can be considered. Specifically, the gradations satisfying this condition are 11 kinds of gradations of (0, 1, 3, 7, 15, 31, 56, 90, 134, 189, 255). These gradations are indicated by “●” in the column of “display gradation a” in FIGS. For example, the gradation “31” satisfies the condition a because all subfields having a weight of SF5 or less emit light and all subfields of SF6 or more do not emit light. In these gradations, the number of subfields to emit light monotonously increases as the gradation value increases. Therefore, when a pixel having a gradation with a close value among the display gradations is adjacent, the sub-light emission is performed. There is no large change in the distribution of the field and the non-light emitting subfield, and no moving image false contour occurs.
[0019]
However, when the display gradations are limited in this way, an image must be displayed using only 11 types of gradations as described above, and the gradation expression ability is greatly reduced. Therefore, in the present embodiment, this condition is relaxed slightly.
Condition b: gray scale in which the subfield that does not emit light is 0 or 1 among all the subfields having a smaller weight than the subfield that emits light
And These gradations are indicated by “●” in the column of “display gradation b” in FIGS. The number of gradations satisfying the condition b is the total number of gradations (2, 5, 6, 11, 13, 14, ..., 251, 253, 254) in addition to the gradations of the condition a. Since there are 56 types, which are far more than the number of gradations that satisfy the condition a, smoother gradation expression is possible. Further, a gradation satisfying the condition b can be used as a gradation in which a pseudo contour is unlikely to be generated since a large change does not occur in the distribution of light emitting / non-light emitting subfields between adjacent pixels.
[0020]
However, when this gradation is used as a display gradation, a large moving image pseudo contour may be observed in an image region having a specific pattern described below. For example, as shown in FIG. 5, consider a case where a pattern Y having a certain degree of gradation and a certain width moves. For example, it is assumed that the pattern Y is represented by six areas of gradations “189”, “200”, “211”, “221”, “230”, and “239” using gradations that satisfy the condition b. FIG. 6 is a diagram in which the image pattern Y is developed into subfields. The horizontal direction corresponds to the horizontal direction on the screen of the PDP 33, and the vertical direction corresponds to the passage of time. The hatching in FIG. 6 represents a non-light emitting subfield. When the image pattern is stationary, the original gradation is recognized because the human line of sight is also fixed at the screen position A. However, when the image pattern Y moves to the left, the line of sight also moves in the direction of the screen position B-B ', so that it follows the middle non-lighted subfield of the six regions, and as a result, it is very much compared to the original image. A dark dark line will be recognized.
[0021]
As described above, when the gradation has a certain degree of gradient in the screen and is continuous over pixels that can be recognized, that is, when the gradient gradation region moves at a speed that can be visually recognized, it is extremely difficult. , A large moving image false contour is recognized. Therefore, in the image display device of the present embodiment, different image processing is performed for the gradient gradation region and the other region (non-gradation gradation region).
[0022]
First, the processing for the non-gradient gradation area will be described. Note that the same processing as that for the non-gradient gradation area is performed for the stationary gradient gradation area.
[0023]
As described above, for the non-tilt gradation area, as the display gradation,
Condition b: gray scale in which the subfield that does not emit light is 0 or 1 among all the subfields having a smaller weight than the subfield that emits light
Is used.
[0024]
FIG. 7A is a circuit block diagram of the gradation limiting circuit 17 according to the embodiment of the present invention. The tone limiting circuit 17 limits the image signal output to a tone that satisfies the condition b using the tone limiting table 53, and performs an error diffusion process using the difference between the input image signal and the tone-limited signal as a display error. Do. In FIG. 7, blocks 65, 67, and 69 denoted by T represent one-pixel delay circuits, and block 63 denoted by HT represents one line minus one pixel delay circuit. As shown in FIG. 7B, it is assumed that attention is paid to a certain pixel P0 and a corresponding image signal is input. At this time, the display errors of the pixels P1, P2, P3 and the immediately preceding pixel P4 one line before the pixel P0 are respectively multiplied by the weighting factors of k3, k2, k1, k0 using the multipliers 77, 75, 73, 71, and added. The signals are added to the input signal of the pixel P0 using the devices 79 and 51. Then, the added signal is compared with the numerical value of the gradation restriction table 53, and the numerical value closest to the added signal is output as an image signal. At the same time, the difference between the added signal and the output signal is obtained using the subtractor 61, and the result is used as a display error for the pixel P5 next to the pixel P0 and the pixels P6, P7, and P8 one line after, respectively. Diffusion is performed by multiplying weight coefficients k0, k1, k2, and k3. Here, each weight coefficient is set to a value that satisfies k0 + k1 + k2 + k3 = 1.
[0025]
By performing this error diffusion process on the entire screen, the amount of gradation to be displayed is preserved, and when the entire screen is viewed, human eyes seem as if the original luminance is being displayed. Therefore, a smooth or smooth image can be displayed.
[0026]
Next, a processing method in the gradation gradient region will be described.
[0027]
As described above, a method of limiting the gradation to a gradation satisfying the condition b cannot be used for a moving gradation gradient region. Instead, even if a moving image false contour is generated, its location is dispersed in the gradation gradient region so that it cannot be visually recognized. That is, a predetermined disturbance is superimposed and applied to each image signal, and as a result, a process of dispersing a moving image false contour occurrence location is performed. This processing is performed in the following procedure. First, as shown in FIG. 8A, a virtual matrix of 2 pixels × 2 lines is considered, and the matrix is spread over the entire screen (FIG. 8B). On the other hand, four disturbance constants d1 to d4 are prepared for each gradation. Then, for each pixel, the disturbance constant specified by the corresponding matrix is selected and added to the image signal. The image display device according to the present embodiment has two types of the above-described matrix, and is used by switching for each field.
[0028]
FIG. 9 is a circuit diagram of the disturbance constant adding circuit 19 that performs these processes according to the embodiment of the present invention. The disturbance constant adding circuit 19 includes a disturbance constant table 100 as a disturbance constant generating means, a disturbance constant selecting circuit 200 as a disturbance constant selecting means, and an adder 300 as an adding means. The disturbance constant table 100 generates disturbance constants d1 to d4 according to the gradation of the input image signal. The disturbance constant selection circuit 200 selects one disturbance constant corresponding to the matrix from the four disturbance constants d1 to d4, and outputs the selected disturbance constant to the adder 300. The adder 300 adds the selected disturbance constant to the image signal.
[0029]
FIG. 10 shows a configuration example of the disturbance constant selection circuit 200 according to the embodiment of the present invention. The two disturbance constant selectors 201 and 202 shown in FIG. 10 switch the four disturbance constants appropriately according to a pixel inversion signal inverted for each pixel and a line inversion signal inverted for each line. At this time, the disturbance constant selector 201 switches the arrangement of the matrix of 2 pixels × 2 lines, for example, to the arrangement shown in FIG. Further, the disturbance constant selector 202 switches the arrangement of the matrix, for example, to the arrangement shown in FIG. Next, the selector 208 alternately selects and outputs the matrix of FIG. 8A or 8C for each field using a field inversion signal that is inverted for each field. As a result, the disturbance constant selection circuit 200 selects the matrix of FIG. 8A in the first field, spreads it over the entire screen as shown in FIG. 8B, and outputs the disturbance constant corresponding to each pixel. In the subsequent fields, the matrix shown in FIG. 8C is selected and spread over the entire screen as shown in FIG. 8D, and the disturbance constant corresponding to each pixel is output.
[0030]
FIG. 11 shows a part of the disturbance constant table used in the first embodiment. Disturbance constants as shown in the columns of disturbance constants d1 to d4 are set for each gradation of the image signal.
[0031]
Next, how to determine the disturbance constant will be described. In this embodiment, since a matrix of 2 pixels × 2 lines is used, it is necessary to determine four disturbance constants d1 to d4 for each gradation. Since the purpose of adding the disturbance constant is to disperse the pseudo contour of the moving image in the inclined gradation area, it is necessary to disperse the non-light emitting subfields in the inclined gradation area. Therefore, the disturbance constant largely depends on the subfield configuration. In the subfield configuration according to the present embodiment, for example, when attention is paid to the gradation 205, the eighth subfield is not lit. At this time, in all of the gradations 201 to 211, the eighth sub-field is not lit. Therefore, in order to disperse the non-light-emitting sub-field, at least one of the four disturbance constants d1 to d4 exceeds 211-205 = 6. And at least one must be set smaller than 201-205 = -4. Further, it is desirable to set the sum of the four disturbance constants d1 to d4 to be 0 in order to match the average value of the gradation after adding the disturbance constant to the original gradation. Here, these disturbance constants were calculated as follows (fractions are rounded off).
[0032]
d4 = (original gradation) × 0.2
d3 = (original gradation) × 0.1
d2 = −d3
d1 = −d4
However, as a matter of course, the disturbance constant can be freely set as long as the above condition is satisfied.
[0033]
As described above, the moving image pseudo contour can be suppressed by spatially dispersing the “intermediate non-lighting subfield” particularly in the inclined gradation area where the moving image pseudo contour is likely to occur. In addition, since the positions of d1 to d4 in the matrix are changed on a field-by-field basis, they are dispersed in time, so that the moving image pseudo contour can be more effectively suppressed. On the other hand, in the non-gradient gradation region, a gradation satisfying the condition b is used as a display gradation, so that sufficient gradation can be maintained. Can be effectively suppressed.
[0034]
(Embodiment 2)
This embodiment is different from the first embodiment in the image signal processing for the gradient gradation area. In the image signal processing for the inclined gradation area in the first embodiment, the processing for adding the disturbance constant to all the gradations without performing the gradation restriction on the image signal is performed. In the image signal processing for the tonal region, a gradation limit and an error diffusion process are once performed in order to disperse the moving image pseudo contour in the inclined gradation region to a wider range, and then a disturbance constant adding process is performed.
[0035]
FIG. 12 is a circuit block diagram of the image display device according to the second embodiment. The A / D conversion circuit 11, the inverse gamma correction circuit 13, the motion detection circuit 14, the inclination detection circuit 15, the AND circuit 16, the gradation limit circuit 17, and the selection circuit 23 are the same as in the first embodiment. In the present embodiment, the image signal subjected to the inverse gamma correction is input to the disturbance constant adding circuit 19 as the disturbance constant adding means via the second gradation limiting circuit 18 as the gradation limiting means. This is a difference from the first embodiment. The image signal-subfield association circuit 25 and the subsequent circuits are the same as those in the first embodiment, and a description thereof will be omitted.
[0036]
FIG. 13 is a diagram showing the gradations restricted by the second gradation restriction circuit 18 and the disturbance constant for each gradation.
[0037]
In the present embodiment, 36 types of gradations obtained by dividing the gradations (1, 3, 7, 15, 31, 31, 56, 90, 134, 189, 255) into four equal parts are used as the limited gradations. , Other gradations may be used. However, if the number of limited gradations is too small, a rough feeling is generated, and if the number is too large, the dispersion range of the pseudo contour of the moving image is narrowed. In addition, since the visibility with respect to a gradation change is large for a dark image, it is desirable to make the gradation interval small in the low gradation part and conversely large in the high gradation part.
[0038]
Next, how to determine the disturbance constant will be described. Since a matrix of 2 pixels × 2 lines is used in the present embodiment, four disturbance constants d1 to d4 are determined for each of the limited gradations. Since the purpose of adding the disturbance constant is to disperse the pseudo contour of the moving image in the gradient gradation area, the disturbance constant needs to be large enough to disperse the non-light emitting subfield in the gradient gradation area. Further, it is desirable to set the sum of the four disturbance constants d1 to d4 to be 0 in order to match the average value of the gradation after adding the disturbance constant to the original gradation.
[0039]
Here, these disturbance constants were calculated as follows.
[0040]
d4 = (two gradations larger than the original gradation among the restricted gradations) − (original gradation)
d3 = (gray level one larger than original gray level among limited gray levels) − (original gray level)
d2 = −d3
d1 = −d4
However, as a matter of course, the disturbance constant can be freely set as long as the above condition is satisfied.
[0041]
In the present embodiment, the gray scale limiting circuit 17 and the second gray scale limiting circuit 18 of FIG. 12 are configured as two independent circuits, but these are shared by one gray scale limiting circuit and AND A configuration in which the content of the gradation table is rewritten by the output of the circuit 16 may be employed. In this case, it is necessary to add control for disabling the disturbance constant adding circuit using the output of the AND circuit 16 for the non-gradient gradation area.
[0042]
As described above, especially in the inclined gradation area where the pseudo contour of the moving image is likely to occur, it is possible to spatially disperse the “intermediate non-lighting subfield” by adding gradation restriction and error diffusion. It is possible to suppress the false contour of the moving image. On the other hand, in the non-gradient gradation region, a gradation satisfying the condition b is used as a display gradation, so that sufficient gradation can be maintained. Can be effectively suppressed.
[0043]
In the first and second embodiments, the size of the matrix is 2 pixels × 2 lines. However, a matrix of an arbitrary size of n pixels × m lines may be used. May be set to n × m disturbance constants.
[0044]
Also, even in a gradient area with motion, if the luminance is low, the pseudo contour of the moving image is difficult to recognize, so that the gradient area with motion and a region with a relatively bright gradation are disturbed. A constant addition process may be performed.
[0045]
【The invention's effect】
As described above, according to the present invention, in the non-graded gradation area, a gradation satisfying the condition b is used as a display gradation, so that sufficient gradation can be maintained. In the inclined gradation region that is easy to perform, since the moving image pseudo contour can be spatially dispersed in a wide range, the moving image pseudo contour can be suppressed while securing the number of gradations. Therefore, it is possible to effectively suppress the false contour of the moving image while keeping the gradation property effective as a whole.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of an image display device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a subfield configuration and display gradations (0 to 119) used in the image display device according to the first and second embodiments of the present invention.
FIG. 3 is a diagram showing a subfield configuration and display gradations (120 to 239) used in the image display device according to the first and second embodiments of the present invention.
FIG. 4 is a diagram showing a subfield configuration and display gradations (240 to 255) used in the image display device according to the first and second embodiments of the present invention.
FIG. 5 is a diagram illustrating a display pattern in which a pseudo contour of a moving image occurs.
FIG. 6 is a view for explaining the cause of generation of a false contour of a moving image.
FIG. 7A is a circuit block diagram of a gradation limiting circuit of the image display device according to the first and second embodiments of the present invention, and FIG. 7B is a circuit block diagram of the image display device according to the first and second embodiments of the present invention. Diagram explaining the operation of the limiting circuit
FIG. 8 is a diagram illustrating an operation of the disturbance constant adding circuit of the image display device according to the first and second embodiments of the present invention.
FIG. 9 is a circuit diagram of a disturbance constant adding circuit of the image display device according to the first and second embodiments of the present invention.
FIG. 10 is a diagram showing a configuration example of a disturbance constant selection circuit of the image display device according to the first and second embodiments of the present invention.
FIG. 11 is a diagram showing a disturbance constant corresponding to each gradation used in the first embodiment of the present invention.
FIG. 12 is a circuit block diagram of an image display device according to a second embodiment of the present invention.
FIG. 13 is a diagram showing a gray scale limited by a second gray scale limiting circuit used in the second embodiment of the present invention and a disturbance constant corresponding to the limited gray scale;
FIG. 14 is a diagram showing an example of a subfield configuration in a conventional PDP.
FIG. 15 is a diagram for explaining a display pattern in which a moving image pseudo contour occurs.
FIG. 16 is a view for explaining a cause of generation of a false contour of a moving image.
[Explanation of symbols]
11 A / D conversion circuit
13 Inverse gamma correction circuit
14. Motion detection circuit
15 Tilt detection circuit
16 AND circuit
17 gradation limiting circuit
18. Second gradation limiting circuit
19 Disturbance constant addition circuit
23 Selection circuit
25 Video signal-subfield association circuit
27 Subfield processing circuit
29 Scan / Maintain / Erase drive circuit
31 Data Drive Circuit
33 Plasma Display Panel (PDP)
35 Timing pulse generation circuit
100 disturbance constant table
200 Disturbance constant selection circuit
201, 202 Disturbance constant selector
208 Selector
300 adder

Claims (3)

What is claimed is: 1. An image display apparatus comprising: a plurality of sub-fields, wherein each sub-field is controlled to emit light or not to emit light;
A disturbance adding means for adding a disturbance constant to the image signal,
The disturbance adding means,
Disturbance constant generating means for outputting a plurality of disturbance constants for the gradation corresponding to the image signal,
A disturbance constant selecting means for selecting one from the plurality of disturbance constants;
Adding means for adding the image signal and the disturbance constant selected by the disturbance constant selection means,
An image display device comprising: What is claimed is: 1. An image display apparatus comprising: a plurality of sub-fields, wherein each sub-field is controlled to emit light or not to emit light;
Tone limiting means for limiting an image signal to a plurality of tones and error-diffusing a difference caused by the limitation to peripheral pixels as a display error;
Disturbance adding means for adding a disturbance constant to the image signal limited by the gradation limiting means,
The disturbance adding means,
Disturbance constant generating means for outputting a plurality of disturbance constants for the gradation corresponding to the image signal restricted by the gradation restriction means,
A disturbance constant selecting means for selecting one from the plurality of disturbance constants;
Adding means for adding the image signal and the disturbance constant selected by the disturbance constant selection means,
An image display device comprising: 3. The image display device according to claim 1, wherein a total of the plurality of disturbance constants is zero.

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