JP2004326029A - Gradation display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To excellently display both still and moving pictures. <P>SOLUTION: This gradation display device has a means of setting a plurality of gradation value groups consisting of a plurality of gradation values, a means of detecting movement in an image, and a means of switching the plurality of gradation value groups at a moving picture part where the image has the movement at a specified frequency. A plurality of gradation value groups used for the moving picture part have an encoded pattern which does not include subfields of "light non-emission" in a combination of subfields corresponding to a 2nd gradation value of "light emission" in a combination of subfields corresponding to a 1st gradation value, providing that the 1st gradation value and 2nd gradation value in the respective gradation value groups have a relation of (1st gradation value)<(2nd gradation value). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gray scale display device using a subfield, and more particularly to a gray scale display device for reducing disturbance of gray scale display during moving image display, that is, a so-called pseudo outline of a moving image.
[0002]
[Prior art]
Generally, in an image display device such as a display device using a plasma display panel (PDP) that performs gradation display using subfields, noise-like image quality deterioration called a so-called “moving image pseudo contour” is observed in a moving image portion. There was a case. It is known that the moving image pseudo contour is improved by increasing the number of subfields. However, depending on the type of device such as a PDP, it is difficult to secure a light emission time when the number of subfields is increased. Therefore, there was a problem that required luminance could not be obtained.Therefore, the number of subfields was set relatively small, and the combination of subfields with respect to the gradation to be displayed was controlled only in a portion where a pseudo contour of a moving image occurs. Thus, there is an attempt to achieve both moving image quality and luminance assurance (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2003-43979 A
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to provide means for enabling good image display in both still images and moving images.
[0005]
[Means for Solving the Problems]
In order to achieve this object, the gradation display device of the present invention performs gradation display on an input image having a moving image by associating a combination of light emission and non-light emission of a plurality of subfields with a gradation value. A means for setting a plurality of tone value groups composed of a plurality of tone values; a means for detecting image movement; and a method for setting a plurality of tone values in a moving image portion having image movement. Means for switching the group at a predetermined frequency, wherein a plurality of tone value groups used in the moving image portion are (first tone value) <(second tone value) in each tone value group In the first gradation value and the second gradation value satisfying the following relationship, in the combination of the subfields corresponding to the first gradation value, the subfield corresponding to the second gradation value with “light emission” In the combination of Characterized in that the field was nonexistent coding pattern.
[0006]
Further, a coding pattern in which there is no subfield that is “light emitting” in the combination of subfields corresponding to the first gradation value and “non-light emitting” in the combination of subfields corresponding to the second gradation value is present. In the first and second tone values that satisfy the relationship of (first tone value) <(second tone value) in each tone value group, In the combination of the subfields corresponding to the gradation values, the value of the maximum luminance weight among the luminance weights of the subfields that are “light emitting” and “non-light emitting” in the combination of the subfields corresponding to the second gradation value is It is characterized in that an encoding pattern that is equal to or less than a predetermined value is used. Note that “the maximum luminance weight value is equal to or less than a predetermined value” means that the value obtained by dividing by the gradation value is equal to or less than a predetermined threshold value or smaller than a reference value created for each gradation value. Things are also included.
[0007]
Further, the selection of the gradation value group used in the moving image portion is configured such that the gradation value group having a gradation value close to the middle of the gradation values of the already selected gradation value group is sequentially selected. Features.
[0008]
With this configuration, a plurality of encoding methods that are unlikely to generate moving image pseudo-contours are used, and are controlled and combined based on information on the motion or moving part of the image and used for display. It is possible to realize an accurate gradation display.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a gray scale display device according to an embodiment of the present invention will be described with reference to the drawings.
[0010]
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of the gray scale display device according to the first embodiment of the present invention. In FIG. 1, an input image signal is supplied from an input terminal 1 to one input of an adder 2, and a still image encoding circuit as a means for setting a plurality of tone value groups composed of a plurality of tone values 3, the moving picture coding circuit 4 and the moving picture coding circuit 5. Further, the input image signal is simultaneously supplied to a motion detecting circuit 6 which is a means for detecting the motion of the image. The outputs of the two moving picture encoding circuits 4 and 5 are supplied to a selection circuit 7 which is means for switching the plurality of gradation value groups at a predetermined frequency in a moving part of an image. The output of the image encoding circuit 3 and the output of the selection circuit 7 are selected based on the output of the motion detection circuit 6 described above, and are supplied to the plasma display 11 via the subfield control circuit 10.
[0011]
The difference between the output of the selection circuit 9 and the output of the adder 2 is obtained by a subtractor 12 and supplied to the other input of the adder 2 via a feedback circuit 13. The timing signal input 8 inputs a signal for switching the outputs of the two moving picture coding circuits for each pixel.
[0012]
In the first embodiment, a moving image portion of an input image signal is detected, and encoding using different gradation values is performed for a still image portion and a moving image portion. In the moving image portion, two types of encoding methods in which a moving image pseudo-contour is unlikely to occur are alternately checked in pixel units in a checkered manner, thereby eliminating moving image pseudo-contours and achieving gradation.
[0013]
In the configuration of FIG. 1, a still image portion of an input image signal is encoded by a still image encoding circuit 3 so as to display all gradations. The moving image portion, which has been encoded by the moving image encoding circuit 4 and the moving image encoding circuit 5, is switched in, for example, a pixel unit based on the switching signal input of the timing signal input 8 in the selection circuit 7. Are selected by the selection circuit 9 in accordance with the still image and the moving image, and supplied to the plasma display 11 via the subfield control circuit 10 and displayed. In the subfield control circuit 10 and the plasma display 11, gradation is performed using a predetermined number of subfields.
[0014]
FIG. 2 shows an example of an encoding method showing combinations of luminance weights and light emission of subfields when gradation display is performed using ten subfields. As shown in the upper part of FIG. 2, the luminance weight of each subfield is “1,” “2,” “4,” “8,” “16,” “24,” and “24,” respectively, in order from the first subfield. 32 "," 40 "," 56 ", and" 72 ". In the figure, the portion [1] indicates "light emission".
[0015]
As described above, in the moving image portion of the image, as shown in FIG. 2, two types of gradation value groups are encoded as in “moving image mode 1” and “moving image mode 2”, and this is shown in FIG. As described above, encoding is performed by switching to a checkered pattern in pixel units. That is, “moving image mode 1” is a “first gradation value group”, and “moving image mode 2” is a “second gradation value group”.
[0016]
For example, as shown in FIG. 2A, in the “moving image mode 1”, when the gradation value increases from the first gradation value “80” to the second gradation value “120”, the eighth sub Only the field (luminance weight 40) changes from “non-light-emitting” to “light-emitting”, and there is no subfield that changes from “light-emitting” to “non-light-emitting”. As described above, in the encoding of the “moving image mode 1”, all the sub-fields emit light one by one according to the increase of the gradation, and the sub-field which does not emit light when the gradation value increases. Does not exist, and if a display is made using only the encoding pattern of “moving image mode 1”, a so-called moving image false contour does not occur.
[0017]
On the other hand, as shown in FIG. 2B, in the encoding of “moving image mode 2”, the subfield with the luminance weight of “16” remains non-light-emitting, Only the field (luminance weight 32) changes from “non-light emission” to “light emission”, and there is no sub-field from “light emission” to “non-light emission”. That is, all the subfields emit light one by one according to the increase in the gradation, and there is no subfield in which the light emission does not emit when the gradation value increases, and only the encoding pattern of the “movie mode 2” is used. In this case, the pseudo contour of the moving image does not occur.
[0018]
As described above, if the display is performed using only the “movie mode 1” or the “movie mode 2”, the false contour of the movie does not occur. However, since the total number of available gradations is not sufficient, the “movie mode” By switching between "1" and "moving image mode 2," the shortage of the number of gradations can be compensated. At this time, there is a concern that so-called moving image pseudo-contours may occur due to the mixture of “moving image mode 1” and “moving image mode 2”. Since the key transition, for example, a combination of the gradation values “176 to 183” and the gradation values “184 to 191” (C in FIG. 2) is not used, a strong moving image false contour does not occur. In addition, since the two modes are switched at a fine regular period such as “checkered pattern in pixel units” as shown in FIG. 3, floors which may be weakly generated as pseudo contours at the switching portion between the two modes. The turbulence disperses and becomes less noticeable.
[0019]
The gradation value itself is limited and displayed in the moving image portion. However, the difference from the signal before encoding is obtained by the subtractor 12 and added to the original signal via the feedback circuit 13. Therefore, a feedback loop known as error diffusion is formed, and the original tone value can be visually reproduced by approximation. Although not shown, it is known that the feedback loop circuit 13 can be composed of a plurality of delay circuits and coefficient circuits in order to distribute the difference between the input signal and the encoded signal as an error around the pixel of interest.
[0020]
As described above, in the moving image portion of the image, since the gradation value group having the coding pattern in which the moving image pseudo contour is unlikely to be generated is switched and used, it is necessary to secure the gradation while suppressing the moving image pseudo contour. Can be.
[0021]
Regarding the encoding of the subfield, even when the luminance weight of the subfield that does not emit light when the gradation value increases is small, the pseudo contour of the moving image is hardly generated, and the same effect can be obtained. That is, the maximum luminance among the luminance weights of the subfields that are “light emitting” in the combination of subfields corresponding to the first gradation value and “non-light emitting” in the combination of subfields corresponding to the second gradation value A similar effect can be obtained by using an encoding pattern whose weight value is equal to or less than a predetermined value. Here, the small luminance weight of the subfield that does not emit light when the gradation value increases indicates that the value obtained by dividing the luminance weight value by the gradation value to be displayed is equal to or less than a predetermined value. , The values of the luminance weights are not more than the values output by the table created for each gradation value to be displayed.
[0022]
(Embodiment 2)
FIG. 4 is a block diagram showing a configuration of a gradation display device according to the second embodiment of the present invention. In FIG. 4, an input image signal is supplied from an input terminal 1 to one input of an adder 2 and is supplied to a still image encoding circuit 3 and first to seventh moving image encoding circuits 41, 42,. Supplied. The input image signal is simultaneously supplied to the average value detection circuit 50 and the motion detection circuit 61. After the outputs of the seven video encoding circuits 41 to 47 are supplied to the selection circuit 71, the output of the still image encoding circuit 3 and the output of the selection circuit 71 are output from the average value detection circuit 50 by the selection circuit 91. The output is selected based on the output and the timing signal 81, and is supplied to the plasma display 11 via the subfield control circuit 10. The difference between the output of the selection circuit 91 and the output of the adder 2 is obtained by the subtractor 12 and supplied to the other input of the adder 2 via the feedback circuit 13.
[0023]
Next, the operation of the thus configured second embodiment of the present invention will be described with respect to portions that are essentially different from the first embodiment shown in FIG. FIG. 5 is an example of an encoding method showing a combination of luminance weight and light emission of a subfield when gradation display is performed using ten subfields, and is a “still image mode” using all gradation values. And seven “moving image modes” using only discrete gradation values.
[0024]
4 is substantially different from the case of FIG. 1 in that seven systems of moving picture coding circuits are provided, and an average value detecting circuit 50 is provided with means for detecting the average value of the moving picture part, and means for selecting these means. It is a point. The motion of the image is detected by the motion detection circuit 61, and two moving image modes are selected based on the average value of the detected portion. For example, if the average of the gradation values of the moving image portion is “80”, the gradation values of three points (“80”, “64”, and “104”) illustrated by “circle” in FIG. 5 are used. It operates to display "80" equivalently.
[0025]
That is, from FIG. 5A, “moving image mode 1” having the encoding gradation value closest to the gradation value “80” and the gradation value near the gradation value “80” of this “moving image mode 1” The selection circuit 71 operates so as to select “moving image mode 6” having an encoded gradation value that gives a gradation value that best interpolates a jump. The selected “moving image mode 1” and “moving image mode 6” are switched to, for example, a checkerboard in pixel units as in the case of FIG. 1 and supplied to the second selection circuit 91, and are similar to those in FIG. Error diffusion processing is performed, and the error diffusion processing is supplied to the plasma display 11 via the subfield control circuit 10 to perform image display.
[0026]
As described above, in the present embodiment, the moving image portion is not simply coded by the gradation limit based on the fixed gradation value, but is subjected to gradation control according to the average value of the gradation values of the moving image portion. Therefore, it is possible to suppress the false contour of the moving image and to suppress the occurrence of noise due to error diffusion for the gradation recovery processing. If the average value of the gradation values of the moving image portion is, for example, in the vicinity of “136”, encoding is performed using the gradation values surrounded by triangles as shown in FIG. Encoding is performed using “moving image mode 3” and “moving image mode 6”, and the same effect as when the average value of the moving image portion is “80” is obtained.
[0027]
Note that the plurality of encoding groups are not limited to those shown in the figure, and if the increase in the gradation value and the light emitting / non-light emitting pattern of the subfield satisfy the above-described condition that “the video pseudo contour hardly occurs”, The present invention can be modified to a coding pattern having a gradation value that completely equally divides the gradation value of the previously selected code. In addition, when selecting a plurality of encoding groups, the “average value” of the moving image portion was used, but instead, a method of calculating other representative values, such as a median value of the distribution of gradation values of the moving image portion, was used instead. Is also good.
[0028]
(Embodiment 3)
FIG. 6 is a block diagram showing a configuration of the gradation display device according to the third embodiment of the present invention. 6, an input image signal is supplied from an input terminal 1 to one input of an adder 2, and a still image encoding circuit 3, a moving image encoding circuit 4, a moving image encoding circuit 5, a motion direction detecting circuit 62, It is supplied to a motion amount detection circuit 63. After the outputs of the two moving picture coding circuits 4 and 5 are supplied to the selecting circuit 7, the selecting circuit 9 outputs the output of the still picture coding circuit 3 and the output of the selecting circuit 7 to the above-described average value detecting circuit 50. The output is selected based on the output and the timing signal, and is supplied to the plasma display 11 via the subfield control circuit 10. The difference between the output of the selection circuit 9 and the output of the adder 2 is obtained by a subtractor 12 and supplied to the other input of the adder 2 via a feedback circuit 13.
[0029]
Next, the operation of the thus configured third embodiment of the present invention will be described for portions that are essentially different from the first embodiment shown in FIG. The encoding method of the subfield to be used is the same as that in FIG.
[0030]
FIG. 6 is essentially different from FIG. 1 in that a motion direction detection circuit 62 and a motion amount detection circuit 63 are provided, and the outputs of the two moving picture coding circuits are switched based on the detection results. It is. As a result, the method of switching between the two encoding groups in the moving image portion can be a method with less occurrence of gradation disturbance.
[0031]
FIG. 7 shows a relationship between a moving direction of an image and an arrangement method of two encoding groups in a moving image portion. FIG. 7 shows a case where the motion of the image is in the horizontal direction. Since only a single moving image mode exists on the path that takes the horizontal direction of the pixel, the so-called gradation display using the subfield is performed. The resulting gradation disturbance does not occur. In addition, the interval between the pixels to which the two encoding groups belong is also the minimum interval of 1 pixel, and these encodings are visually observed in a merged manner, so that good gradation display can be expected. It is needless to say that the image motion that can be handled is not limited to the horizontal direction shown in the figure, but may be any direction in accordance with the image motion. In particular, by using a method of switching between two coding groups in minimum pixel units in a direction orthogonal to the direction of motion of the image, these two codings are visually merged without generating gradation disturbance. Therefore, good gradation display can be expected.
[0032]
In the embodiments shown in FIGS. 1, 4 and 6, the signal is supplied in parallel to the still picture coding circuit and the plurality of moving picture coding circuits in advance, and the signal is selected at the subsequent stage. However, a method of directly controlling the encoding method using information such as the motion of an image may be used. In addition, it goes without saying that various modifications and simplifications can be made to the subfield encoding method, the number of subfields, the number of encoding modes in the moving image portion, and the like used in the description. Further, for example, all or a part of the above-described embodiments are combined with each other to enhance the effect, such as combining control of an image movement method which is a feature of the third embodiment with the second embodiment. It is also possible.
[0033]
【The invention's effect】
As described above, according to the present invention, in a gradation display device using sub-fields, a plurality of encoding methods in which a pseudo-contour of a moving image is unlikely to occur are used, and the encoding method is performed by using information of image motion and motion parts. By performing the control, it is possible to realize a favorable gradation display while suppressing the false contour of the moving image.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a gradation display device according to Embodiment 1 of the present invention. FIG. 2 is a diagram illustrating a combination of luminance weight and light emission of a subfield in the device. FIG. FIG. 4 is a block diagram illustrating a configuration of a gradation display device according to a second embodiment of the present invention. FIG. 5 is an example of a combination of luminance weight and light emission of a subfield and a coding group in the device. FIG. 6 is a block diagram illustrating a configuration of a gradation display device according to a third embodiment of the present invention. FIG. 7 is a diagram illustrating switching of moving image encoding in the device.
Reference Signs List 1 input terminal 2 adder 3 still picture coding circuit 4, 5, 41, 42, 43, 44, 45, 46, 47 moving picture coding circuit 6, 61 motion detecting circuit 7, 9, 71, 91 selecting circuit 8 timing Signal input 10 Sub-field control circuit 11 Plasma display 12 Subtractor 13 Feedback circuit 50 Average value detection circuit 62 Motion direction detection circuit 63 Motion amount detection circuit

Claims (3)

In a grayscale display device that performs grayscale display on an input image having a moving image by associating a combination of light emission / non-light emission of a plurality of subfields with a grayscale value, a plurality of grayscale values configured with a plurality of grayscale values are used. Means for setting a tone value group, means for detecting motion of an image, and means for switching the plurality of tone value groups at a predetermined frequency in a moving image portion where the image moves, and is used in the moving image portion. The plurality of tone value groups include a first tone value and a second tone value having a relationship of (first tone value) <(second tone value) in each tone value group. An encoding pattern in which there is no subfield that is “light emitting” in a combination of subfields corresponding to the first gradation value and “non-light emitting” in a combination of subfields corresponding to the second gradation value That Gray scale display device according to symptoms. Instead of an encoding pattern in which there is no subfield that is “light emitting” in the combination of subfields corresponding to the first gradation value and “non-light emitting” in the combination of subfields corresponding to the second gradation value, In the first gradation value and the second gradation value in the relation of (first gradation value) <(second gradation value) in each gradation value group, the first gradation value The value of the maximum luminance weight among the luminance weights of the subfields that are “light emitting” in the subfield combination corresponding to the value and “non-light emitting” in the subfield combination corresponding to the second gradation value is a predetermined value. 2. The gradation display device according to claim 1, wherein an encoding pattern having a value equal to or less than a value is used. The selection of the tone value group used in the moving image portion is characterized in that a tone value group having a tone value close to the middle of the tone values of the already selected tone value group is sequentially selected. The gray scale display device according to claim 1 or 2, wherein:

Images