WO2000030344A1

WO2000030344A1 - Method and apparatus for correcting the image profile

Info

Publication number: WO2000030344A1
Application number: PCT/CN1999/000189
Authority: WO
Inventors: Wenjun Lu
Original assignee: Wenjun Lu
Priority date: 1998-11-15
Filing date: 1999-11-15
Publication date: 2000-05-25
Also published as: CN1215192A; AU1257400A

Abstract

The method and apparatus for eliminating the 'sawtooth' effect of the image profile during the scanning of the picture are disclosed. By using the sub-vertical deflection correcting signal which corresponds to the direction and slope of the image profile, the scanning is made along the edge of the profile. The apparatus consists of the profile detector, generator of sub-vertical deflection correcting signal, driving circuit, sub-vertical deflecting coil and the delay circuit.

Description

Method and device for correcting image contour

The invention relates to a method and a device for correcting the image contour of a scanning imaging system. Background technique

In the scanning imaging system, the following problems exist:

1. The "aliasing" effect will occur when displaying oblique contour images. As shown in Figure 1, Figure 1 (1) is an unscanned original image. After scanning, the image shown in Figure 1 (2) is formed. In some cases, the visible contour is not the original continuous straight line, but the "zigzag" of one tooth per scanning line. The contour is more obvious when the display screen is enlarged (the total number of scanning lines is unchanged). In addition, the contour enhancement technology that is widely used now makes "aliasing" more obvious. In an interlaced scanning system, because a frame image is scanned in two fields, there is a time difference between the front and back fields, so when displaying a moving image The phenomenon of Fig. 1 (3) will occur, that is, a disparity occurs when the front and back fields display the same contour, which causes the amplitude of the "zigzag" of the contour to double, and to some extent it can be said that the definition of the contour is reduced by half.

2. During interlaced scanning, frame rate flicker will occur at the outline of the image. In Figure 2, due to the two-field faint display, in a large area, that is, on the right side of the dotted line in the figure, the field frequency display is visually displayed, and at the outline on the left side of the dotted line, the frame rate flicker occurs.

3. The contour of the image caused by the quality of the video signal is blurred and the sharpness is insufficient. Disclosure of invention

In view of the above problems, an object of the present invention is to provide an image contour correction method and an apparatus thereof, so as to eliminate or reduce the “aliasing” effect of the image contour caused by scanning.

Another object of the present invention is to provide an image contour correction method and device thereof to eliminate or reduce frame rate flicker of an image contour caused by interlaced scanning.

Another object of the present invention is to provide an image contour correction method and device, Enhance the sharpness of the outline of the image to make the outline more prominent.

Another object of the present invention is to provide an image contour detection method and a correction waveform generation method, so that the correction scheme can be smoothly implemented.

In the scanning image contour correction method of the present invention, during the scanning and developing process, when the scanning line scans the image contour, a vertical offset corresponding to the direction and slope of the contour is added to the scanning line, so that the scanning line is at The contour of the image is scanned along the contour, so that the contour of the image is corrected.

The device used in the contour correction method for a scanned image of the present invention is composed of a contour detection circuit, a correction signal generating circuit, a driving circuit, an additional vertical deflection coil and a video delay circuit. The axes of the main and vertical coils are parallel to each other. The direction and slope of the contour detected by the contour detection circuit generate a corresponding correction signal, and the driving circuit amplifies and drives the additional vertical deflection coil to generate the scanning line vertical offset I required for correction. Brief description of the drawings

Figure 1 is a schematic diagram of the "aliasing" effect generation process of a scanned image;

FIG. 2 is a schematic diagram of flicker of contour frame rate generated by interlaced scanning;

Figure 3 is a schematic diagram of the contour correction principle;

FIG. 4 is a schematic diagram of correcting an image to eliminate contour frame rate flicker and contour enhancement; FIG. 5 is a block diagram of a television image contour correction device;

FIG. 6 is a schematic diagram of four contour directions;

7 is a block diagram of a first embodiment of contour detection and correction signal generation; FIG. 8 is a waveform diagram of various signals in FIG. 7;

FIG. 9 is a block diagram of a second embodiment of contour detection and correction signal generation; FIG. 10 is a waveform diagram of various signals in FIG. 9;

Figure 11 is the waveform generating circuit in Figure 9: Differential circuit;

Fig. 12 is a waveform generating circuit in Fig. 9: an integrating circuit. Among them, the drawings are only for illustrative purposes, and the present invention is not limited. In addition, the video signal is set to be positive polarity in the text, which does not limit the present invention. The best way to implement the invention

The method and the device of the present invention are as follows: During the scanning and developing process, when a contour is scanned, a vertical offset corresponding to the contour direction and the slope is added to the scanning line. The scanning line is not the original horizontal line, but is scanned along the contour, so that the contour of the image will not produce "aliasing," or "aliasing," and the amplitude is greatly reduced. This process can be clearly explained from Figure 3. In Fig. 3, (1) is an uncorrected image, (2) is a video signal of a certain line, (3) is a vertical offset added to the scanning line of the line, and (4) is formed after correction. In the image, one of the scanning lines emphasizes the handwriting for easy understanding, and it has no particularity. The additional vertical offset is a triangular pulse wave whose amplitude is the vertical width of a scan line and whose slope is the same as the contour slope. In this case, the best correction can be obtained. Further analysis shows that even if the amplitude, slope, and contour of the additional vertical offset do not exactly match, as long as the direction is correct, the aforementioned "aliasing" effect can be weakened to a large extent.

Figure 4 is a contour corrected image in an interlaced scanning system. In the figure, the shading lines (1) and (2) in different directions respectively indicate the scanning lines of the parity field, and also indicate that the display frequency of each field is the frame frequency, and the display is alternately displayed. It can be seen from the figure that, due to the visual superposition of the human eye at a large area display, the visual display frequency there is a field frequency. At the contour, the part (3) where the shadows overlap in both directions indicates that the parity field is scanned. Therefore, the display frequency here is the field frequency, which is different from the effect produced by visual superposition in a large area. The prime display frequency is actually the field frequency. Compared with the image before correction, the frame rate flicker area at the contour is greatly reduced. If properly corrected, the flicker area can be minimized. On the other hand, the overlapping display of the parity field (3) is obviously stronger, so the brightness is enhanced on the bright side of the outline, and on the dark side, there is a scan line along the outline that is not scanned (actually, the scan line speed). (4), where the brightness is extremely weak, so the contour enhancement is achieved. The present invention is applicable to a scanning imaging system, and an example of its application is a contour correction device for a television image. Fig. 5 is a block diagram of a circuit configuration of the device. (1) in the figure is an image contour detection circuit, and its role is to detect the direction and slope of the image contour. (2) is a correction waveform generating circuit, which generates a corresponding correction signal according to the detection result of the detection circuit (1). In practice, (1) and (2) are generally an integrated functional circuit, and there is no obvious dividing line. . (3) is a correction driving circuit which amplifies the correction signal generated in (2) to drive the correction deflection coil. (4) is the auxiliary vertical deflection coil attached to the picture tube, its axis is parallel to the axis of the main vertical deflection coil of the picture tube, that is, the directions of the deflection magnetic fields generated by the main and auxiliary vertical deflection coils are parallel to each other. (5) is a video delay circuit, and its function is to synchronize the correction signal with the visual signal. The characteristic of this device is to use the auxiliary deflection coil to generate the additional vertical offset of the scanning line.

In the above embodiments, the contour detection circuit and the correction waveform generating circuit are important parts, and this part will be described below.

Contour detection is divided into two parts, one is the direction of the contour, and the other is the slope of the contour. For a system with a fixed number of scan lines, its scan line distance is fixed, so the slope of the contour can be represented by the horizontal distance of this contour on two adjacent scan lines. The directions of the outline are nothing more than four. These four directions are different combinations of bright left or right and left oblique or right oblique. As shown in Figure 6, (1) is right bright and left oblique, and (2) is Left bright right oblique, (3) left bright left oblique, and (4) right bright right oblique. The waveform on the right of each figure indicates the direction of the signal required to correct the contour. Therefore, the detection method can be divided into left and right bright detection and left and right oblique detection. According to the results of different combinations, determine which direction it is. It is relatively simple to detect the left and right bright. After the video signal passes through the differentiation circuit, a pulse is generated at the contour, and it is called a contour pulse. A positive pulse indicates left dark and right bright, and a negative pulse indicates left dark and right dark. The detection of the left and right skew is more complicated. It can delay the video signal by one line and compare the two lines of contour pulses. Another method is to subtract the two lines of signals and generate pulses at the contours, which are called inter-line contour pulses. The direction is determined according to the positive and negative pulses combined with the left and right bright conditions, and the width of the pulse can represent the slope of the contour. Figure 7 is a block diagram of a first embodiment of contour detection and correction signal generation. In the figure, after the video signal enters the detection circuit, it is divided into two channels A and B. B has one more link than A, which is a one-line delay circuit (2), so A and B represent the signals of two adjacent rows, and A is the current signal. Line, B is the previous line, the two signals generate contour pulses after differentiating circuits (3) and (4), and the function of the threshold circuits (5) and (6) is to filter out noise and small signals, that is, the contour should be more Obviously judged to be effective. (7) is a contour direction detection circuit, which judges which direction is based on the positive and negative of the contour pulse and the sequence of the AB pulses. (8) is a slope detection circuit, which is a pulse counter, used to detect the number of pulses between the two contour pulses of AB. The pulses are generated by the clock circuit (11). Obviously, this pulse number can represent the horizontal distance between the two contour points. . The correction waveform generating circuit is composed of a waveform memory (10) and waveform output circuits (9) and (12). A variety of correction waveforms are stored in the memory in advance, a suitable waveform is called according to the detection result of the detection circuit, and a corresponding correction signal is output through the output circuit. The function of the video delay circuit (1) is to synchronize the video signal and the correction signal so that the correction signal and the contour correspond correctly in time.

Figure 8 shows the waveforms of various signals in the above detection and waveform generation process, taking the contours of bright left and right oblique as an example. (1) is the image before correction; (2) is the signal of the previous line, which is the signal of channel B in FIG. 7; (3) is the signal of this line, and is the signal of channel A in FIG. 7; (4), ( 5) are the contour pulses generated by the two types of signals through the differential and threshold circuits; (6) are the pulses generated by the clock circuit; (7) are the pulses counted by the counter; (8) are the correction signals generated by the waveform generation circuit; 9) is the video signal of this line after the delay circuit (1).

FIG. 9 is a block diagram of a second embodiment of contour detection and correction signal generation. Its characteristics are: (1) There are only four correction waveforms, that is, there is only a difference in direction and no difference in slope. Regardless of the contour slope, as long as the directions are the same, the correction signal is the same, which makes the correction circuit much simpler. As long as a more suitable waveform is selected, the correction effect is also very good. (2) Use the result of subtraction of the two lines of signals to determine the left and right skew, so that the circuit is simplified. The principle is explained below. In the figure, the video signal is divided into three channels A, B, (:. Channel A is output for video driving after a delay (1). Channel B enters the left and right slope detection circuit (2) and (3), (2) is a 1-line delay circuit, (3) is an inverting addition circuit, and (3) the output is the result of subtracting two adjacent lines of video signals to generate an inter-line contour pulse at the contour, The positive and negative pulses are used as the basis for judging left and right slopes. The principle can be seen in Figure 10, which will be described later. Channel C enters the differential circuit and generates two types of positive and negative contour pulses, positive means bright on the right, negative means bright on the left, and each enters the pulse generating circuits (6) and (11) after threshold detection. This circuit is a trigger pulse generating circuit. Triggered by a contour pulse produces a width t. And called the correction pulse, t. It is the width of the correction signal. In the case of bright left and dark, the correction signal must be applied before the contour appears, and the correction signal can only be generated after the contour signal is detected. The solution to this problem is: The video signal passes through the delay circuit (1 has The correction signal is applied before the contour arrives. Obviously, the delay amount of (1) should be the same as the width t of the correction signal. In the case of dark and right, the correction signal is applied at the same time when the contour appears, so The correction signal needs to be delayed to synchronize with the delayed video signal. This is the function of the delay circuit (7). It can trigger a falling edge of the pulse generated by (8) to generate a pulse of the same width as the correction pulse. Obviously, this pulse is delayed to and synchronized with the delayed video signal. Another method is to take the contour pulse of the delayed video signal, and then trigger to generate a correction pulse with a width of t, so that the correction pulse and the video signal are The two synchronization pulses pass through the waveform generating circuits (8) and (12), and then pass through the direction control circuits (9) and (13), respectively. (8) is a differential circuit As shown in Figure 11 (12) is an integration circuit. As shown in Figure 12, adjusting the RC value can change the shape of the correction waveform, and selecting an appropriate waveform can make the contours of different slopes better corrected. (9) ) And (13) are directional control circuits, which determine whether the correction signal is a normal phase output or an inverted output according to the output inter-line contour pulses. In this way, there are four different correction waveforms, which correspond to the contours in four different directions. The two kinds of correction signals are turned out by a combining circuit, and the correction coil can be driven after being amplified.

FIG. 10 is an example of a contour of bright right and left oblique. For the waveforms of various signals during the implementation of the foregoing correction method, the signal waveforms of each part and their timing relationship can be clearly seen from the figure. In the figure, (1) is the scanned image; (2) is the signal of the previous line; (3) is the message of the line (4) is the contour pulse generated by the video signal through the differentiation circuit; (5) is the line pulse generated by subtracting the previous line signal from the current line signal, here is a positive pulse, if it is a right-slanted outline, this pulse It will be negative. It can be seen that the width of this pulse reflects the slope of the contour; (6) is a correction pulse of width to generated by the contour pulse trigger; (7) is the delay t ₀ is the correction waveform signal After the direction control circuit is inverted, the final correction signal is formed, and the forward and reverse output is controlled by the inter-line contour pulse; (10) is the video signal of this line after the delay t _Q. It can be seen that the correction signal is synchronized with the video signal. of. Industrial applicability

In the television display system, after using the above-mentioned contour correction device, the jagged contour effect generated by the scanning image is eliminated, the frame rate flicker at the contour is suppressed, and the contour enhancement effect brought by it makes the image sharp. Sharpness and sharpness are greatly improved. The circuit of the aforementioned second calibration method is simple, and some existing devices can be implemented. If the second method can be integrated, the cost will not be high. Today, the high screen quality of large screens is admired, and the present invention is a good way to improve visual effects and image quality.

Claims

Rights request

1. A method for contour correction of scanned images,

It is characterized in that during the scanning and developing process, when the scanning line scans the outline of the image, a vertical offset corresponding to the direction and slope of the outline is added to the scanning line, so that the scanning line runs along the outline of the image Contour scanning, so that the contour of the image is corrected.

2. The device used in the contour correction method of a scanned image according to claim 1, characterized in that it comprises a contour detection circuit, a correction signal generating circuit, a driving circuit, an additional vertical deflection coil and a video delay circuit. The axes of the coils are parallel to each other. The correction signal generating circuit generates a corresponding correction signal according to the direction and slope of the contour detected by the contour detection circuit. The driving circuit amplifies and drives the additional vertical deflection coil to generate the vertical offset of the scanning line required for correction.

The image contour correction device according to claim 2, wherein the contour detection circuit is composed of a one-line delay circuit, a scoring circuit, a direction determination circuit, a pulse generation circuit, and a pulse counting circuit,

It is characterized in that the video signal is divided into two channels, one channel is delayed by one line, and the other channel is not delayed. Therefore, two types of signals representing two adjacent lines each generate a contour pulse at the contour after a differential circuit, and a direction judgment circuit. According to the sequence of the two contour pulses, the direction of the contour is determined, and the pulse counter accumulates the pulse chirp between the two contour pulses to represent the size of the contour slope.

4. The image contour correction device according to claim 2,

It is characterized in that the correction signal generating circuit of the device is composed of a waveform memory and a waveform output device.

5. The image contour correction device according to claim 2,

It is characterized in that the contour detection circuit of the device is composed of a differential circuit, a 1-line delay circuit, and a two-line signal subtraction circuit. The video signal passes through the differential circuit to generate a contour pulse. Direction, subtracting two adjacent line signals to produce a line For the inter-profile pulse, the left-right oblique direction of the profile is determined according to the positive and negative combination of the pulses, and the left and right bright conditions, and the slope of the profile is determined according to the pulse width.

6. An image contour correction device according to claim 2,

It is characterized in that the correction signal generation circuit of the device is composed of a correction pulse generation circuit, a correction waveform generation circuit, and a positive and negative control circuit. The correction pulse generation circuit generates a correction pulse with a certain width corresponding to the contour in time. The waveform generating circuit changes the correction pulse into a desired correction waveform. The forward and reverse control circuit controls the correction waveform in a direction corresponding to the contour.

The image contour correction device according to claim 6,

It is characterized in that the correction waveform generating circuit of the circuit is composed of a differential circuit and an integrating circuit.