JP4765261B2 - Image display method and image display apparatus - Google Patents

Description

  The present invention relates to an image display method and an image display apparatus, such as a plasma display apparatus, that perform gradation display by dividing and displaying one field of an image into a plurality of subfield images.

  In recent years, a plasma display apparatus using a plasma display panel (PDP) as a thin display device has become widespread. The plasma display device is a matrix-type display device with no defocusing, and has higher responsiveness than a liquid crystal display device, and is accepted as a device suitable as a moving image display. Since the plasma display device performs gradation display digitally, a “subfield method” is used in which gradation display is performed by dividing one field of an image into a plurality of subfield images.

  Here, in the subfield method, depending on the configuration and the control method of the subfield, there is a possibility that a gradation disturbance called a “moving image pseudo contour” may occur in the moving image portion. In order to suppress such a moving image pseudo contour, for example, as shown in a block diagram of a schematic configuration in FIG. There has been a proposal that gradation correction is performed by the gradation correction means 41 in accordance with the degree of movement (see, for example, Patent Document 1). The output from the gradation correction means 41 is converted into an image for each subfield by the subfield conversion means 5 and output to the display panel 6 such as a plasma display device. Although the display panel 6 emits light in pulses, a halftone image in which the moving image pseudo contour is suppressed is displayed as an image reproduced on the retina of the observer by being integrated in the observer's eyes. The Rukoto.

Further, an opportunity to display an image signal subjected to digital compression / decompression processing as a source of an image to be displayed is increasing. In this case, when an image is displayed on the display panel 6 such as a plasma display device, it is necessary to reversely expand or compress the image signal that has been subjected to the digital compression / decompression processing. There may be a problem that noise occurs and becomes noticeable. In order to prevent such a problem, for example, as shown in a block diagram of a schematic configuration in FIG. 5, a block noise detection unit 202 detects a block noise occurrence region, and the low pass filter 30 performs low pass filter processing in that region. The method of applying is proposed (for example, refer patent document 2).
JP-A-11-212517 JP 2000-50275 A

  In the conventional method as described above, the optimum display is not necessarily performed when noise is superimposed on the input signal 1 or when both moving image pseudo contour and block noise may occur. It was not limited.

  For example, with the configuration described with reference to FIG. 4, when tone correction processing is performed in order to display a moving image portion satisfactorily, if noise is superimposed on the original image signal, the tone correction processing described above is performed. In some cases, there is a problem that the noise is emphasized.

  In addition, when performing the process of reducing block noise with the configuration described with reference to FIG. 5, the process of suppressing the moving image pseudo contour is not considered at all, and there is a problem in securing the optimum image quality. was there.

  The present invention has been made in view of the above-described problems, and when the gradation display is performed by dividing and displaying one field of an image into a plurality of subfield images, gradation disturbance called a moving image pseudo contour is performed. An object of the present invention is to realize a good image display method by suppressing the influence of noise included in a signal and block noise.

In order to achieve the above object, the image display method of the present invention is a subfield method image display method that detects a fade-in or fade-out region and a motion with respect to an input signal and interlocks with at least one of the characteristics. A filter operation that controls the above is performed on the input signal, and a gradation correction process is performed in which the characteristics are controlled in conjunction with the detected movement.

In order to achieve the above object, the image display device of the present invention includes a region feature detection unit that detects a region that fades in or out of an input signal, a motion detection unit that detects a motion of the input signal, Filter means for performing a filter operation of characteristics controlled in conjunction with at least one of the output from the region feature detection means and the output from the motion detection means for the input signal, and the output from the filter means A gradation correction unit that performs gradation correction processing with characteristics controlled in conjunction with the output from the motion detection unit; and subfield conversion that divides one field of the output from the gradation correction unit into a plurality of subfields. Means.

  According to the present invention, it is possible to reduce a halftone display disorder called a moving image pseudo contour in contrast to a case where multi-gradation image display is performed by dividing and displaying images of a plurality of subfields. At the same time, it is possible to suppress the influence of noise and block noise contained in the original signal.

That is, according to the first aspect of the present invention, in the image display method based on the subfield method, a filter that detects a fade-in or fade-out region and a motion with respect to an input signal and controls the characteristics in conjunction with at least one of them. An image display method characterized in that a calculation is performed on an input signal, and further, gradation correction processing is performed in which characteristics are controlled in conjunction with detected motion.

According to a second aspect of the present invention, in the first aspect of the present invention, the filter operation switches the pass band to two or more stages according to a combination of the detected fade-in or fade-out region and motion. It is characterized in that it is performed after controlling the characteristics.

The invention of claim 3 is the invention according to claim 1, wherein the filter operation, relatively narrow set its pass band in the region where the fade-in or fade-out is detected, fade in or In a region where the fade-out is not detected, the control is performed after the characteristic is controlled such that the pass band is set relatively wide.

According to a fourth aspect of the present invention, in the invention according to the third aspect , the filter calculation is performed in a region where the amount of motion detected is not more than a predetermined value in a region where no fade-in or fade-out is detected . Is characterized in that the pass band is set to be relatively wide, and in a region larger than a predetermined value, the pass band is set to be relatively narrow.

According to a fifth aspect of the present invention, in the first aspect of the invention, the filter operation is performed on a plurality of pixels adjacent to the target pixel in the pixel direction or the time direction. It is characterized by.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the gradation correction processing includes a plurality of gradation values of the target pixel adjacent to the target pixel in a pixel direction or a time direction. It is characterized by being represented by the average value of the gradation values displayed on the pixels.

According to a seventh aspect of the present invention, in the first aspect of the invention, the gradation correction processing includes surrounding a difference between a gradation value corresponding to the target pixel and a gradation value displayed on the target pixel. In this case, the pixel is sequentially diffused to the other pixels.

According to an eighth aspect of the present invention, an area feature detecting means for detecting a fade-in or fade-out area for an input signal, a motion detecting means for detecting a motion of the input signal, and the input signal, Filter means for performing a filter operation with characteristics controlled in conjunction with at least one of the output from the region feature detection means and the output from the motion detection means, and the output from the filter means from the motion detection means Gradation correction means for performing gradation correction processing with characteristics controlled in conjunction with the output of the output, and subfield conversion means for dividing one field of the output from the gradation correction means into a plurality of subfields. An image display device characterized by the above.

Further, the invention according to claim 9, in the invention described in claim 8, wherein the filtering means, in combination with the output from the output and the motion detector from the region feature detecting means, the passband It is characterized in that the control of the characteristics of switching to two or more stages is performed.

Further, the invention according to claim 10, in the invention described in claim 8, wherein the filter means, by the region character detector, relatively the pass band in the region where the fade-in or fade-out is detected It is characterized in that the characteristic is controlled so that the pass band is set relatively wide in a region where the band is set narrow and no fade-in or fade-out is detected .

According to an eleventh aspect of the present invention, in the invention according to the tenth aspect , the filter means has a predetermined amount of motion of the input signal in an area where the area feature detection means does not detect fade-in or fade-out. In a region that is less than or equal to the value, the pass band is set relatively wide, and in a region that is larger than a predetermined value, the pass band is set relatively narrow.

The invention described in Claim 12 is the invention according to claim 8, wherein the filtering operation by the filter means subjected is performed for a plurality of pixels adjacent to the pixel direction or time direction the pixel of interest It is characterized by being.

The invention described in Claim 13 is the invention according to claim 8, tone correction processing in which the gradation correction means performs is, the tone value of the pixel of interest, the pixel direction or with respect to the pixel of interest It is characterized by being represented by an average value of gradation values displayed on a plurality of pixels adjacent in the time direction.

Further, the invention according to claim 14, in the invention described in claim 8, wherein the gradation correction process gradation correcting means performs is displayed on the pixel of interest and the tone value corresponding to the target pixel gradation It is a means for sequentially diffusing the difference from the value to surrounding pixels.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration of an image display apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is an input signal, 2 is a motion detection means, 3 is a low-pass filter (LPF) as a filter means, 4 is a gradation correction means, 5 is a subfield conversion means, and 6 is a plasma display device, for example. It is a display panel.

  The operation will be described with reference to FIG. In the input signal 1, the motion detection unit 2 detects a region having motion. When the input signal 1 is moving, the gradation display method using the subfield may cause gradation disturbance in the moving image portion, so-called “moving image pseudo contour” depending on the configuration and control method of the subfield. For this reason, in the region where the motion is detected, the tone correction unit 4 performs tone correction in accordance with the degree of motion of the detected image. As a result, the moving image pseudo contour can be suppressed as an image observed by the observer.

  In the actual gradation correction, the gradation value to be displayed before correction is replaced with a combination of a plurality of different gradation values, and the correction is performed. It is necessary to make a comprehensive correction that balances with the above. This correction is configured by a process of expressing a gradation by linking gradation values of a plurality of pixels, such as a combination of gradation replacement, error diffusion, and dither processing. Therefore, for example, if sudden noise or the like is mixed in a pixel unit, this balance is lost, and as a result, the noise may be emphasized.

  Therefore, in order to prevent such a problem, in the present embodiment, the low-pass filter 3 is provided in the preceding stage of the gradation correction unit 4 so that noise does not adversely affect the gradation correction. Note that the gradation correction method and the degree of correction are linked to the movement of the image, so that high frequency components are not cut unnecessarily in areas where gradation correction is unnecessary. .

  Note that the tone-corrected signal from the tone correction unit 4 is converted into an image for each subfield by the subfield conversion unit 5 and output to a display panel 6 such as a plasma display device, as in the prior art. Although the display panel 6 emits light in pulses, a halftone image in which the moving image pseudo contour is suppressed is displayed as an image reproduced on the retina of the observer by being integrated in the observer's eyes. The Rukoto.

  In this way, when gradation display is performed using subfields, gradation correction is performed at a portion where the image moves, and the low-pass filter processing is applied to the gradation correction processing in conjunction with the gradation correction processing. Thus, the moving image and the still image can be satisfactorily displayed by suppressing the influence of the mixed noise while suppressing the moving image pseudo contour.

  In the embodiment of the present invention, the low-pass filter 3 is used for the filter processing performed before the gradation correction unit 4. However, the present invention is not limited to this, and a filter for removing sudden noise and the amplitude value of the high-frequency component are used. Various modifications are possible, such as a non-linear filter that removes noise by processing non-linearly.

(Embodiment 2)
FIG. 2 is a block diagram showing a schematic configuration of an image display apparatus according to Embodiment 2 of the present invention. In FIG. 2, 1 is an input signal, 21 is a region feature detection means, 22 is a motion detection means, 23 is a determination means, 31 is a low pass filter as a filter means, 41 is a gradation correction means, 5 is a subfield conversion means, 6 Is a display panel.

  The operation will be described with reference to FIG. In the input signal 1, a predetermined characteristic area is detected by the area characteristic detection means 21. At the same time, a motion is detected from the image by the motion detection means 22. The determination means 23 determines the characteristics of the filter processing to be performed on the input signal 1 from both the image characteristics and the image motion.

  Here, as the feature detected by the region feature detection means 21, for example, fade-in / fade-out of an image can be mentioned.

  Further, the motion detection means 22 can detect the motion of the image and control the characteristics of the gradation correction means 41 in accordance with the amount of motion of the image, thereby suppressing the pseudo contour in the so-called moving image portion.

  The determination unit 23 controls the characteristics of the low-pass filter 31 using at least one of the image feature amount and the image motion amount. An example of the operation of the determination means 23 is shown in FIG. FIG. 3 shows an example of a pass band of the low-pass filter 31 to be set depending on whether or not a fade-in or fade-out is detected as a feature of an image and whether or not an image motion is detected. In this case, the pass band of the low-pass filter 31 is set to be narrower than when no fade-in or fade-out is detected.

  Also, under the condition where no fade-in or fade-out is detected, if the motion of the image is detected, the pass band of the low-pass filter is set narrower than when the motion of the image is not detected. Yes.

  Further, the operation of the gradation correction means 41 is the same as in the case of FIG. 1 and is performed in accordance with the movement of the image.

  By adopting such a configuration, when there is no image movement and no fade-in or fade-out is detected, the pass band of the low-pass filter is set wide and the information contained in the input signal is displayed as it is. . In addition, when a fade-in or fade-out is detected, for example, there is a high probability that block noise or the like accompanying compression / decompression processing will occur. Therefore, by making the pass band of the low-pass filter 31 narrower, block noise or the like becomes conspicuous. It can prevent becoming easy. Even when no fade-in or fade-out is detected, if a motion of the image is detected, the gradation correction unit 41 corrects the gradation value in order to suppress the occurrence of the moving image pseudo contour. In this case, since the pass band of the low-pass filter is set to be “medium”, it is possible to perform gradation correction while eliminating the influence of noise superimposed on the input signal.

  In the above description, the region feature to be detected is the presence or absence of fade-in or fade-out. However, it may be a means for detecting block noise more directly, or due to lack of gradation due to system characteristics. It may be a means for detecting a pseudo contour region. Further, the control of the characteristics of the low-pass filter 31 with respect to the detected feature amount and the detected image motion amount is not limited to that shown in FIG. 3, and various modifications are possible. Further, in place of the low-pass filter, a non-linear filter for processing the amplitude values of the high-frequency component and the low-frequency component in a non-linear manner, so-called coring processing can be used.

  In the embodiment of the present invention described above, the characteristics of the gradation correction means 4 and 41 have been described as being controlled only by the motion detection means 2 and 22. However, the characteristics of the areas determined to have motion are described. Applications such as controlling the degree of correction in consideration of image characteristics at the same time are also possible.

  As described above, according to the image display method of the present invention, halftone display disturbance called a moving image pseudo contour can be reduced compared to the case where the gradation display of an image is performed by dividing the image into a plurality of subfield images. It is possible to provide an image display method capable of suppressing occurrence of block noise at the same time.

1 is a block diagram showing a schematic configuration of an image display device according to an embodiment of the present invention. 1 is a block diagram showing a schematic configuration of an image display device according to an embodiment of the present invention. The figure for demonstrating the example of operation | movement by the determination means in the image display apparatus by one embodiment of this invention The block diagram which shows schematic structure of the image display apparatus which can reduce the moving image pseudo | simulation outline Block diagram showing a schematic configuration of a conventional image display device capable of reducing block noise

1 Input signal 2 Motion detection means 3, 31 Filter means (LPF, low-pass filter)
4, 41 Gradation correction means 5 Subfield conversion means 6 Display panel

Claims (14)

In the image display method based on the subfield method, a region to be faded in or faded out and a motion are detected with respect to the input signal, and a filter operation whose characteristics are controlled in conjunction with at least one of the input signal is performed on the input signal. An image display method characterized by performing gradation correction processing in which characteristics are controlled in conjunction with detected motion. The filter operation is
2. The image display method according to claim 1 , wherein the control is performed after controlling the characteristic that the pass band is switched to two or more stages according to the combination of the detected fade-in or fade-out area and the movement. The filter operation is
In the region where fade-in or fade-out is detected , the pass band is set relatively narrow, and in the region where fade-in or fade-out is not detected , the pass band is set relatively wide. The image display method according to claim 1 , wherein the image display method is applied. The filter operation is
In areas where fade-in or fade-out is not detected ,
Control of the characteristic that the pass band is set relatively wide in a region where the amount of detected motion is equal to or less than a predetermined value, and the pass band is set relatively narrow in a region larger than the predetermined value. The image display method according to claim 3 , wherein the image display method is performed after performing. The filter operation is
The image display method according to claim 1, wherein the image display method is performed on a plurality of pixels adjacent to the target pixel in a pixel direction or a time direction. The gradation correction process includes
Wherein the gradation value of the pixel of interest, to claim 1, wherein said that the pixel of interest is intended to be represented by an average value of the gradation values to be displayed on the plurality of pixels adjacent to the pixel direction or time direction Image display method. The gradation correction process includes
The image display method according to claim 1, wherein a difference between a gradation value corresponding to a target pixel and a gradation value displayed on the target pixel is sequentially diffused to surrounding pixels. Area feature detection means for detecting an area that fades in or out with respect to an input signal;
Motion detection means for detecting the motion of the input signal;
Filter means for performing a filter operation of characteristics controlled in conjunction with at least one of an output from the region feature detection means and an output from the motion detection means, with respect to the input signal;
Gradation correction means for performing gradation correction processing of characteristics controlled in conjunction with the output from the motion detection means with respect to the output from the filter means;
Subfield converting means for dividing one field of the output from the gradation correcting means into a plurality of subfields;
An image display device comprising: The filter means includes
The combination of the output from the output and the motion detector from the region feature detecting means, an image display according to claim 8, characterized in that the passband control properties that switched in two or more stages are carried out apparatus. The filter means includes
In the region where fade-in or fade-out is detected by the region feature detection means , the pass band is set relatively narrow, and in the region where fade-in or fade-out is not detected , the pass band is set relatively wide. The image display apparatus according to claim 8 , wherein characteristics are controlled. The filter means includes
In a region where no fade-in or fade-out is detected by the region feature detection means,
In a region where the amount of motion of the input signal is equal to or less than a predetermined value, the pass band is set relatively wide, and in a region larger than the predetermined value, the pass band is set relatively narrow. The image display device according to claim 10 . The filter operation performed by the filter means is
The image display device according to claim 8 , wherein the image display device is performed on a plurality of pixels adjacent to the target pixel in the pixel direction or the time direction. The gradation correction processing performed by the gradation correction means is
Wherein the gradation value of the pixel of interest, to claim 8, characterized in that the average value of the gradation values is intended to represent that displays a plurality of pixels adjacent to the pixel direction or time direction with respect to the pixel of interest Image display device. The gradation correction processing performed by the gradation correction means is
9. The image display apparatus according to claim 8 , wherein the image display device is means for sequentially diffusing a difference between a gradation value corresponding to a target pixel and a gradation value displayed on the target pixel to surrounding pixels.

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