JP3365229B2 - Image display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to one of input image signals.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for improving display of grayscale irregularity in halftone display that occurs during moving image display, in a display device that performs multitone display by dividing a field portion into a plurality of subfield images for display. It is a thing.

[0002]

2. Description of the Related Art Conventionally, gradation display is performed by using a display device, such as a plasma display device, for displaying one field of an input image signal by dividing it into a plurality of subfield images and displaying the divided image. In this case, it is known that so-called pseudo contour-like gradation disturbance occurs in moving image display. Hereinafter, the gradation disorder associated with the moving image display will be referred to as "moving image pseudo contour". The generation of the moving image pseudo contour will be described with reference to FIG.

FIG. 10 shows a state of light emission by a subfield when an image having an adjacent pattern of two levels of level 15 and level 16 (an example is shown in FIG. 11) is displayed, and the pattern is translated. It shows how it is observed when following the image. In a display device that performs gradation display by dividing one field of an input image signal into a plurality of subfields, when a still image is displayed,
The average brightness of one field of the observed image is A in FIG.
It is expressed by the integral of the light emission between −A ′, and the gradation display is correctly performed.

On the other hand, when a moving image is displayed, depending on the direction of the movement of the line of sight, the retinal area between BB 'and C- in FIG.
The integral of the emission between C'is observed. The value obtained by combining the respective bits between BB 'is approximately 0, and the total of the respective bits between CC' is approximately 31. Thus, level 1
When observing a portion where two levels 5 and 16 are adjacent to each other, the luminance level observed in the level changing portion as shown in FIG. 10 is significantly disturbed by the amount of movement of the image or the amount of movement of the line of sight. 10B-B 'and FIG. 10C-
As is clear from the comparison of C ′, the degree of this disturbance and the sign of the disturbance vary depending on the movement of the line of sight, the amount of movement of the line of sight, or the amount of movement of the image or the direction of movement of the image.

It should be noted that, in FIG. 10, it is illustrated that light emission is continuously performed in each subfield with a predetermined width. However, in an actual plasma display, each subfield corresponds to each luminance weighting. Although it consists of a set of pulsed light emission a certain number of times, the moving image pseudo contour is generated by the same principle. In this way, since halftones are expressed by integrating the luminance of each subfield in the time direction, when the line of sight moves in a moving image, etc., the image at a position different from the original pixel position will be displayed over time. Since the weight of each bit is integrated, the halftone display is greatly disturbed.

Therefore, in the conventional image display device, an attempt has been made to reduce the disturbance of halftone display in moving image display by dividing the upper bits and disposing them in a distributed manner to form subfields. There is. FIG. 12 shows a subfield structure in the moving image pseudo contour reducing method according to the conventional method, which is intended to display 8-bit gradation, that is, 256 gradations by using 10 subfields. The luminance weighting of each subfield is 48, 48, 1, 2, 4, 8, 16, 32, 4 in order.
It is 8 and 48. The luminance weights of the upper 2 bits 64 and 128 of the original input image signal are divided into 4 and distributed at both ends of the subfield, and the weight of the most significant bit is reduced to suppress the occurrence of halftone disturbance as much as possible. At the same time, by arranging the subfields with large weights at the beginning and the end of the subfields in a distributed manner, blurring occurs in the image observed when the moving image is displayed,
It is intended to make the dynamic image pseudo contour inconspicuous.

[0007]

[Problems to be Solved by the Invention] As shown in FIG.
In a conventional image display device, a subfield having a large luminance weighting is divided to reduce the maximum value of a moving image pseudo contour generated. For this reason, if the subfields are divided while the number of displayable gray scales is secured, the total number of subfields inevitably increases, and this is achieved using a display device having a limited drive pulse width and the like. It was difficult. Moreover, when the number of subfields cannot be increased significantly, the subfield division is limited to bits, and the effect of improving the moving image pseudo contour is insufficient.

[0008]

In order to solve the above-mentioned problems, an image display apparatus of the present invention divides one field of an image signal into a plurality of sub-fields having a predetermined luminance weighting to display multi-gradation. In the image display device for performing the above, a signal obtained by performing a predetermined calculation on a part or all of the image signal is displayed while being held at substantially the same value for a plurality of fields. .

Further, the image display device of the present invention is an image display device which divides one field of an image signal into a plurality of sub-fields having a predetermined luminance weighting to perform multi-gradation display, and at least the image signal is provided. The image storage means for storing one field, the image calculation means for performing a predetermined calculation on a part or all of the output of the image storage means, and the output of the image calculation means are held at substantially the same value for a plurality of fields. An image display device characterized by comprising display means for displaying.

According to the present invention, in an image display device for performing multi-gradation display by dividing one field of an image signal into a plurality of sub-fields having a predetermined luminance weighting, a part or all of the image signal is Since it is displayed while being held at a substantially constant value during the subsequent multiple fields, the relative amount of movement between the image and the line of sight is intentionally set when the line of sight follows the moving part when displaying a moving image. Can be controlled to suppress the occurrence of video false contour,
It becomes possible to visually cancel.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The image display device according to the first and second aspects of the present invention divides one field of an input image signal into a plurality of subfields having a predetermined luminance weighting for multi-gradation display. An image display device for performing a predetermined calculation on the input image signal, and then displaying a part or all of the signal while maintaining a substantially constant value during a plurality of subsequent fields. ing. Therefore, for example, only a specific field of the input image signal can be sampled and displayed, and can be stored in the memory and repeatedly displayed in the next field. In this case, after the same image is displayed for a certain number of fields, the next field is displayed at a position corresponding to a larger amount of movement than the original movement per field.

On the other hand, the movement of the line of sight following a moving object is
Generally, since the response speed is not so fast, it is a speed obtained by averaging the movements of images in a plurality of fields, which is the same as the movement of the original image. Therefore, based on the movement of the line of sight, two images that move alternately are formed on the retina on the retina, for example, a display image on the left side in one field and a display image on the right side in another field. . On the other hand, when it is considered that a moving image pseudo contour generated in a plasma display or the like is noise added to an image, the amplitude of this noise is known to be reversed depending on the direction of the movement of the line of sight. Therefore, since the pseudo contours formed on the retina and added to the two images that are moving alternately are in the directions canceling each other, the degree of the recognized moving picture pseudo contours can be reduced.

In the image display device according to the third aspect of the present invention, the input image signal is sampled at a sampling interval of 2 fields or more, and then held at a substantially constant value for 2 fields or more and displayed. I am trying. For this reason, after the same image is displayed for two or more fields, the image position is moved and displayed in the next field by an amount twice or more than the original amount of movement per field.

On the other hand, since the movement of the line of sight following the moving object is generally not so fast in response speed, the movement of images in a plurality of fields is averaged, which is the same as the movement of the original image. It's speed. Therefore, based on the movement of the line of sight, two images that move alternately are formed on the retina on the retina, for example, a display image on the left side in one field and a display image on the right side in another field. .

On the other hand, a moving image pseudo contour generated in a plasma display or the like is considered as noise added to an image,
It has been found that the amplitude of this noise is reversed depending on the direction of eye movement. Therefore, since the pseudo contours formed on the retina and added to the two images that are moving alternately are in the directions canceling each other, the degree of the recognized moving picture pseudo contours can be reduced.

The image display device according to a fourth aspect of the present invention is for displaying an input image signal by applying a low-pass filter in the time direction and then sampling at sampling intervals of two fields or more. Since the change in the image in the time direction is suppressed by the low-pass filter in the time direction, even if the interval at which the image to be displayed is updated is twice or more the conventional interval, there is no aliasing distortion in the time axis direction. The moving image part can be displayed without any discomfort.

The image display device according to a fifth aspect of the present invention is obtained by performing a predetermined calculation on a portion where the ratio of each component of red, green or blue constituting the input image signal is within a predetermined range. The obtained signal is displayed while being held at substantially the same value for a plurality of fields. Therefore, only the image of the flesh-colored portion where the moving image pseudo contour is particularly likely to be recognized is held and displayed at a substantially same value for a plurality of fields to suppress the generation of the moving image pseudo contour and to prevent the moving image pseudo contour from being generated much. The inconspicuous part can be displayed by updating the display value for each original field to ensure the smoothness of the moving image display.

Further, in the image display device according to claim 6 of the present invention, when a plurality of continuous fields of the input image signal are signals having substantially the same image information, the image signal is continuously output. Each field is sampled and displayed, and when the image signal is a signal that does not continue to have substantially the same image information over a plurality of consecutive fields, the image signal is intermittently sampled and displayed. There is.

For this reason, for example, when the input image signal is an image signal in which a movie program of 24 frames per second is converted by signal processing and the number of fields per second is 60,
It is possible to distinguish between displaying a signal in which a continuous plurality of fields are signals having substantially the same image information and displaying a normal camera signal, and in either case, Good image display can be performed by suppressing the occurrence of moving image pseudo contours.

According to a seventh aspect of the present invention, in the image display device, an image signal obtained by sampling an odd field signal of the input image signal is held for a predetermined plurality of fields, and an even field of the input image signal. The image obtained by sampling the signal of (1) and the signal held for a plurality of predetermined fields are switched and displayed for each predetermined pixel unit. For this reason, a signal obtained by sampling the odd field signal of the input image signal and a signal obtained by sampling the even field signal of the input image signal can be mixed in the same field screen, and an image with vigorous movement can be displayed. In this case, it is possible to prevent the image from jumping discontinuously and to be displayed, and it is possible to suppress the occurrence of a moving image pseudo contour and perform a smooth image display.

[0021]

[0022]

(Embodiment 1) Embodiments of the invention described in claims 1 to 4 of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is an input image signal, 21 and 22 are field memories that delay the input image signal by one field, 31 is a time low-pass filter that smoothes the signal in the time axis direction, and 32 is an input signal.
A resampling circuit for sampling and outputting for each field, 5 is a subfield control circuit, and 6 is a plasma display.

In FIG. 1, the temporal low-pass filter 31
Suppresses a change in the time direction by using signals obtained by delaying the input signal 1. The resampling circuit 32 performs sampling at a cycle twice the field cycle of the input image signal. The sub-field control circuit 5 divides the output of the resampling control circuit 32 into a plurality of sub-fields for one field of the input image signal and performs gradation display. Therefore, from the plasma display 6, the image is updated and displayed every two fields. In this case, the update rate of the image is reduced to once in every two fields, but since the low-pass filter processing in the time direction is performed before the resampling, the aliasing distortion due to the sampling is generated even if the image moves. It does not occur, and the moving image can be displayed without discomfort. At this time, the relationship between the movement of the image and the movement of the line of sight is illustrated in FIG.

In FIG. 2, since the image is sampled for each field and displayed every field, the motion of the image on the screen is also every two fields, but the motion of the line of sight following the motion image is the average motion of the image. It shows that it becomes a thing. As can be seen from FIG. 2, the image remains stationary from time t1 to time t2, but the movement of the line of sight is m per field. Also, from time t2 to time t3
However, the movement of the image is 2 m, but the movement of the line of sight is still m per field.

Therefore, the relative movement between the image and the line of sight is
Between time t1 and time t2 and between time t2 and time t3, the magnitudes are the same and the directions are opposite. That is,
The relative moving speed between the display image and the line of sight is shown in FIG. 3, and the relative speed between the image on the screen and the line of sight is inverted for each field. Therefore, the moving image pseudo contours generated at this time are in the direction of canceling each other, and the amount recognized as the moving image pseudo contours can be greatly reduced by the integration effect of the temporal response characteristics of the visual characteristics.

(Embodiment 2) An embodiment of the invention described in claim 5 of the present invention will be described below with reference to FIG. 4 is different from FIG. 1 in that
The point is that the flesh color detection circuit 4 and the image switching circuit 35 are provided. Only operations different from those of FIG. 1 in the embodiment of FIG. 4 will be described.

The skin color detection circuit 34 detects only the skin color portion of the input image signal. The image switching circuit 35, on the basis of the result of the flesh color detection circuit described above, displays an image subjected to low-pass filtering in the time axis direction for the flesh color portion of the image, and for the other color portions in the time axis direction of the input image signal The signal which is not subjected to the low-pass filter processing of is selected and output. As a result, the image is updated and displayed every two fields for the portion where the moving image pseudo contour is prominent, such as a human face, and the other portions are updated with the field cycle of the original image unchanged.

Therefore, the moving picture pseudo contours that are likely to occur in the skin-colored portion such as a person's face can be canceled as in the first embodiment described above, and the portion where the generation of the moving picture pseudo contours is not so noticeable is the original field. Since the display value is updated and displayed every time, by holding the response in the time direction in the moving image portion, it is possible to suppress the occurrence of blurring in the moving image and improve the overall image quality.

(Embodiment 3) An embodiment of the invention described in claim 6 of the present invention will be described below with reference to FIG. In FIG. 5, a switching control circuit 40 is provided in the part that is essentially different from the case of FIG.
The image switching circuit 36 is configured to be controlled based on the output of. Differences between the embodiment of FIG. 5 and those of FIGS. 1 and 4 will be described.

The switching control circuit 40 is composed of a continuous field detection circuit 41, a flip-flop 42 for generating a field alternating signal, and an AND circuit 43. The continuous field detection circuit 41 detects whether or not the image signals of the input image signals are substantially the same over a continuous field. This operation will be described with reference to FIG. That is, in the period in which the input signal is the moving image of the camera signal, the continuous field detection circuit 41 outputs the output “1” because the input image has a high frequency of changing to each field. Therefore, the output of the flip-flop 42 is supplied as it is as the switching operation signal of the image switching circuit 36, and the input a or b of 36 is alternately selected by the signal s alternating with each field. As a result, the displayed image is a signal of only the odd field or even field of the input signal.
Therefore, the moving image pseudo contours generated at this time can be set to cancel each other for each field.

When a signal in which the image signals are substantially the same over continuous fields is input, the continuous field detection circuit 41 becomes "0" and the image switching circuit 36 switches regardless of the output of the flip-flop 42. The operation signal s is always “0”, and the image signal for each field is supplied to the subfield control circuit 5.

At this time, since the input image signal is originally a signal in which the image signals are substantially the same over consecutive fields, the moving image pseudo contours should be canceled and displayed for the same reason as described in the first embodiment. You can

In an image obtained by converting a movie program of 24 frames per second into a television signal, since the number of fields per second is converted from 24 to 60, at least the same image is repeatedly displayed for two fields. Will be. If such an image is sampled and displayed every two fields, the movement may become unnatural about once every several fields. Therefore,
When a continuous signal is a signal in which continuous multiple fields have almost the same image information, it is displayed as it is.On the other hand, continuous multiple fields are not always displayed, such as a moving image obtained from a normal TV camera signal. In any case where the signals do not have substantially the same image information, the input image is updated every two fields, and the substantially same image signals are displayed in a plurality of consecutive fields so that the moving image can be displayed regardless of the type of the input signal. It is possible to suppress the occurrence of pseudo contours and display an image obtained by converting a movie program into a television signal while suppressing the unnaturalness of the moving image display.

(Embodiment 4) Hereinafter, an embodiment of the invention described in claim 7 of the present invention will be described with reference to FIGS.
Will be explained. In FIG. 7, a part that is essentially different from the case of FIG. 1 is provided with a switching control circuit 50 that generates a control signal for switching an image based on a signal that changes in pixel units, line units, and field units. The image switching circuit 37 is controlled based on the output of the circuit 50.

In FIG. 7, HSYNC is a horizontal synchronizing signal, VSYNC is a vertical synchronizing signal, 51 is a PLL circuit for generating a dot clock DCK that is an integral multiple of the horizontal synchronizing signal,
Reference numerals 52 to 54 are flip-flop circuits, and 55 to 56 are exclusive OR circuits. The outline of each waveform of FIGS. 7A to 7E is as shown in FIG. 8, and the signal (e) for controlling the image switching circuit 37 is, as shown in the drawing, a horizontal pixel unit, a line unit, and a field. The signals are inverted in units.

On the other hand, if the pixels of the display device are classified into two types of P or Q according to the pixel position as shown in FIG. 9A, the signals displayed at the pixel positions of P and Q are shown in FIG.
It shall be shown by (b). That is, when the field number in the input image signal is “2”, FIG.
As is clear from "1 field" of the input image signal
A signal in which the eyes and the “second field” are arranged in a grid pattern is displayed. Similarly, when the field number in the input image signal is “3”, as is clear from FIG.
A signal in which the "2nd field" and the "3rd field" of the input image signal are arranged in a grid pattern is displayed.

Here, as is clear from comparison between FIG. 9C and FIG. 9D, half of the whole pixels are held for two fields to display the same value. become.
In this example, the “second field” and “third field” of the input image signal are
In any of the "fields", the signal of the "second field" of the input signal is repeatedly displayed. Therefore, with respect to the signal of the "second field", the same value is displayed during two consecutive fields, and as described in the first embodiment, the moving image pseudo contour generated at this time is the "second field". And the “third field” cancel each other, and the amount recognized as a moving image pseudo contour can be significantly reduced.

As for the signal of the "third field", the pseudo contours of the moving image can be canceled out between the "third field" and the "fourth field". On the other hand, the pseudo contour of the moving image can be significantly suppressed. Further, according to the present embodiment, the half of the image is updated for each field,
Even in the case of displaying an image with a large amount of motion, it is possible to obtain a practically great effect that a smooth moving image can be displayed while suppressing the occurrence of a pseudo contour of a moving image.

The present invention is not limited to the first to fourth embodiments described above, and various applications can be made by combining these.

[0041]

As described above, according to the image display device of the present invention, the following effects can be obtained.

According to the image display device according to the first aspect, the second aspect, and the third aspect of the present invention, the pseudo contours of the moving image formed on the retina can be made to cancel each other in the time direction. Therefore, it is possible to reduce the degree of the recognized moving image pseudo contour.

Further, according to the image display device of the fourth aspect of the present invention, since the change in the time direction of the image is suppressed by the low-pass filter in the time direction, the interval at which the displayed image is updated is conventionally. Even if it is twice or more, it is possible to suppress the aliasing distortion in the time axis direction, suppress the generation of the dynamic false contour, and realize good image display.

According to the image display device of the fifth aspect of the present invention, the generation of the moving image pseudo contour is suppressed and the generation of the moving image pseudo contour is conspicuous while suppressing the generation of the moving image pseudo contour in the flesh color portion where the moving image pseudo contour is particularly easily recognized. The non-existing portion can be displayed by updating the display value for each original field to ensure the smoothness of the moving image display.

According to the image display device of the sixth aspect of the present invention, the unnaturalness of the moving image display is suppressed for both the moving image shot by the camera and the image obtained by converting the movie program into the television signal. Thus, it becomes possible to display an image while suppressing the generation of a moving image pseudo contour.

According to the image display device of the seventh aspect of the present invention, it is possible to display a smooth moving image while suppressing the occurrence of a pseudo contour of a moving image even when an image with a large amount of motion is displayed. A great effect can be obtained in practical use.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between movement of an image and movement of a line of sight according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relative moving speed of a display image and a line of sight according to the first embodiment of the present invention.

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

FIG. 5 is a configuration diagram of an image display device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing an operation of a switching control circuit according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram of an image display device according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing an operation of a switching control circuit according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between pixels and signals of a display device in Embodiment 4 of the present invention.

FIG. 10 is a diagram showing generation of a moving image pseudo contour in a conventional image display device.

FIG. 11 is a diagram showing an example of a display image pattern in a conventional image display device.

FIG. 12 is a diagram showing an example of on / off control of each subfield in a conventional image display device.

[Explanation of symbols]

5 Subfield control circuit 6 Plasma display 21,22 field memory 31-hour low-pass filter 32 resampling circuit 35, 36, 37 image switching circuit 40, 50 switching control circuit 41 Continuous field detection circuit 42 flip-flops 43 AND circuit 51 PLL circuit 53,54 flip-flop 55,56 Exclusive OR circuit

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Claims (7)

(57) [Claims] The method according to claim 1 input image signal of one screen, one field
An image display apparatus for performing divided and multi-tone display into a plurality of subfields having a predetermined luminance weighting for each cycle, a signal obtained by performing predetermined processing on a portion or the whole of the input image signal, pre after displaying and mahogany <br/> lifting of a plurality of fields which defines, in the next field, display the original field the signal
Apply the specified processing to some or all of the input image signals shown
An image display device characterized by updating and displaying the obtained signal . 2. A method input image signal of one screen, one field
In an image display device for performing multi-gradation display by dividing into a plurality of sub-fields having a predetermined luminance weighting for each cycle, an image storage means for storing the input image signal for at least one field, and an output of the image storage means. Image processing means for performing a predetermined process on a part or all of the above, and an output of the image processing means of a plurality of predetermined fields.
After displaying and mahogany lifting, the next field, the image
The output of the processing means is displayed on the screen that displays the original field.
An image display device comprising display means for updating and displaying the output of the image processing means . Wherein the predetermined processing, the image display apparatus according to claim 1, wherein it is a process of sampling the input image signal in two fields or more sampling intervals. Wherein said predetermined process, said after performing a low-pass filter the input image signal in a time direction, according to claim 1 or 2, wherein it is a process of sampling in two fields or more sampling intervals Image display device. 5. A skin color for detecting a skin color portion of an input image signal.
A signal obtained by further performing a predetermined process on a flesh-colored portion in which a ratio of red, green, or blue components forming an input image signal for each pixel is within a predetermined range, further including a detection circuit. The compound
Holds and displays for a few fields, then the next field
In the original field the signal table Shimesuru input image
Signal obtained by subjecting part or all of the signal to prescribed processing
The information is updated and displayed on the screen.
The image display device described. Wherein said predetermined process, when the state more successive fields of the input image signal is a signal having a same image information is a signal to continue to every field sampling the input image signal processing And the input image signal is spread over a plurality of consecutive fields.
Te when the state having the same image information is a signal not to continue the image display apparatus according to claim 1, wherein it is a process for sampling every plural fields that defines the input image signal in advance . 7. The predetermined processing is a first signal in which an image signal obtained by sampling an odd field signal after performing low-pass filtering in the time direction on the input image signal is held for two fields, and the input signal After the image signal is low-pass filtered in the time direction, the image signal obtained by sampling the even field signal is divided into the second signal held for two fields,
The image display apparatus according to claim 1 or 2, wherein the said first and second signals is a process of horizontal pixels and for each switch for each vertical pixels in the same field.