JPH07222034A - Contour correction circuit - Google Patents

Abstract

PURPOSE:To provide the contour correction circuit capable of displaying an excellent image while suppressing the production of edge business when contour correction is applied to a hatched contour part of a line drawing or a character or the like. CONSTITUTION:This circuit is provided with circuits 2, 12 generating a second derivative signal as a vertical and horizontal enhance signal, enhancement adjustment circuits 10, 20 adjusting the amplitude of the generated vertical and horizontal enhance signals, means (7, 8, 11, 17, 18) for detecting hatched parts of a video image, and control circuits 9, 19 controlling the enhancement adjustment circuits 10. 20 to reduce the enhancement quantity when the slant line component is detected to suppress production of the edge business by decreasing the enhancement quantity in the slant line part where edge business is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction circuit for performing vertical and horizontal contour correction of a video signal in a television receiver or the like.

[0002]

BACKGROUND OF THE INVENTION There is enhancement to enhance an image. Enhance is a process of selectively enhancing or suppressing image information in order to increase the usefulness of the image.
Typical examples include image contrast enhancement, suppression of isolated noise and periodic noise, and geometric distortion correction.

As is well known, in a television receiver, enhancement is performed in order to emphasize image quality, which is realized by a contour correction circuit as shown in FIG.

In the contour correction circuit shown in FIG. 5, the input terminal 3
1, a video signal 201 is supplied, and the video signal 201 is input to a secondary differentiating circuit 32 to input the secondary differential signal 20.
Create 6. This second derivative signal 206 is added to the adder 34
Then, the input signal 201 is combined with the signal 202 delayed by the delay circuit 33 by a predetermined amount, and the combined signal 207 is output terminal 3
5 is derived.

Next, the secondary differentiating circuit 32 in FIG.
Will be described in detail with reference to FIGS. 5 and 6.

The video signal 201 from the input terminal 31 is delayed by a predetermined amount by delay circuits 321 and 322 in order to obtain a second-order differential signal, and delay signals 202 and 203 are created, respectively. The delay amounts of the delay circuits 321 and 322 are equal to the delay amount of the delay circuit 33. Input signal 201
And the delayed signal 203 are added by the adder 323, and the signal 204 is made by multiplying by 1/2 to further adjust the amplitude. The inverted signal 204 and the signal 202 are added by the adder 324 to obtain the signal 205. Further, this is amplified by the amplifier 325 with an appropriate gain to obtain the secondary differential signal 206. The delay signal 202 delayed by a predetermined amount in the delay circuit 33 and the secondary differential signal 206 are combined in an adder 34 to generate a contour-corrected video signal 207, which is output to an output terminal 35.

FIG. 6A shows an input video signal 201 and FIG. 6B.
6 (c) is a video signal 202, 203 created by delaying the input video signal 201 by a predetermined amount, and FIG. 6 (d) is a signal 204 created based on the signal 201, 203. )
And (f) are second-order differential signals 205 and 206 created based on the video signals 202 and 204, and FIG.
2 shows a video signal output whose contour has been corrected by adding a secondary differential signal 206 to.

[0008] By the way, since the television uses disassembly and assembly by scanning lines, there is a phenomenon that a contour portion of a diagonal line such as a line or a character appears or disappears in each field and becomes jagged (called edge business). Occurs. In addition, as described above, the contrast is emphasized to enhance the contrast of the image, so that there is a problem that the edge business is emphasized.

[0009]

As described above, conventionally, when contour correction for enhancing the contrast of an image is performed,
There was a problem that the edge business was emphasized.

In view of the above problems, the present invention provides a contour correction circuit capable of suppressing the occurrence of edge business and obtaining a good image when performing contour correction on the contour portion of a diagonal line. The purpose is to do.

[0011]

According to a first aspect of the present invention, there is provided a contour correction circuit which receives a video signal and generates vertical and horizontal enhance signals for enhancing a contour portion of a video. An enhancement adjustment means for inputting the vertical and horizontal direction enhancement signals, adjusting and outputting the amplitude thereof, and means for detecting a diagonal line portion of an image based on the vertical and horizontal enhancement signals; Means for controlling the enhancement adjusting means so as to reduce the amount of enhancement when a diagonal line portion is detected,
And an adder for combining the enhancement signal from the enhancement adjuster with the video signal.

According to a second aspect of the present invention, there is provided a contour correction circuit which receives a video signal and generates a secondary differential signal in the vertical and horizontal directions, and a secondary differential means from the secondary differential means. Absolute value means for obtaining the absolute value of the secondary differential signal in the horizontal direction, level detection means for detecting the output levels of the absolute value means in the vertical and horizontal directions, and the vertical and horizontal directions detected by the level detection means. Direction signals are compared with each other, and the same signal detecting means for outputting a detection signal in a period in which each signal is at the same level, and the vertical direction of the level detecting means in a period in which the detection signal is detected by the same signal detecting means. Direction and horizontal direction output level control means for outputting a signal for controlling the amount of enhancement, and vertical and horizontal secondary differential signals from the secondary differential means An enhance adjusting means for adjusting and outputting the amplitude of the secondary differential signal by a signal from the enhance amount control means, and a first and a second vertical differential signal for adding the vertical and horizontal secondary differential signals output from the enhance adjusting means. Is added, and the output of the first adding means is used for edge enhancement of the video signal.

[0013]

According to the invention described in claim 1, means for generating vertical and horizontal enhance signals, enhance adjusting means for adjusting the amplitude of the generated enhance signals, and means for detecting a diagonal line portion of an image. , Suppressing the occurrence of edge business by providing means for controlling the enhancement adjustment means so as to reduce the amount of enhancement when a diagonal line portion is detected and reducing the amount of enhancement in the diagonal line portion where edge business occurs You can

According to the second aspect of the invention, vertical and horizontal secondary differential signals of the video signal are used, and each secondary differential signal corresponds to a signal period of the same level, that is, a portion of a diagonal line. The period in which the edge business occurs is detected, and the enhancement adjustment means is controlled during that period to make adjustments to reduce the amount of enhancement in the vertical and horizontal directions. This allows
When performing the contour correction, it is possible to reduce the edge business that stands out in the contour portion of the diagonal line such as a line or a character on the screen.

[0015]

EXAMPLES Examples will be described with reference to the drawings. 1 is a block diagram showing a contour correction circuit according to an embodiment of the present invention, and FIG. 2 is a diagram showing diagonal lines as image information.

First, FIG. 2 will be described.

FIG. 2A shows an example of a diagonal line image in which an edge business is generated. 2 (b) is a vertical signal waveform of the diagonal line portion in FIG. 1, and FIG. 2 (c) is a horizontal signal waveform of the diagonal line portion.

Since the edge business is caused by the fact that the image is created by the scanning lines as described above, the jagged edges are generated every horizontal period (1H) in the vertical direction. Even in the horizontal direction, jaggedness occurs every predetermined period [here, one clock period (1 CLK)].
Therefore, when an enhanced signal (for example, a second derivative signal) that emphasizes the contour portion of the image is generated and the contour of the image is corrected, a means for detecting the portion of the diagonal line in the image is configured, and the portion of the diagonal line is detected. If the control is performed so as to weaken the enhancement upon detection (that is, to reduce the amplitude of the enhancement signal), edge business can be reduced.

Next, the configuration of FIG. 1 will be described.

In FIG. 1, a video signal is input to the input terminal 1. The vertical quadratic differential circuit 2 has the following configuration. Video signal 101 supplied from the input terminal 1
Is delayed by a 1H (H is a horizontal period) delay circuit 3, and this signal 102 is further delayed by 1H by a 1H delay circuit 4 to obtain a signal 10
Get 3. The signal 101 and the signal 103 are added by the adder 5 and multiplied by 1/2 to generate the signal 104. The signal 102 and the inverted signal 104 are added by the adder 6 to obtain the second derivative signal 105. The secondary differential signal 105 is transferred to the absolute value circuit 7
The signal 106 that has been converted into an absolute value by
The signal that exceeds the level value arbitrarily set by is detected.

The horizontal second-order differentiating circuit 12 also has the same signal processing form as in the vertical direction. To make the time axes equal,
The signal 111 delayed by 1H by the 1H delay circuit 3 is sent to 1CLK.
(CLK is a clock period) It is delayed by the delay circuit 13, and the 1CLK delay signal 112 is further delayed by the 1CLK delay circuit 14.
Then, it is delayed by 1 CLK to obtain a signal 113. The signal 111 and the signal 113 are added by the adder 15 and multiplied by 1/2 to create the signal 114. A signal obtained by inverting the signal 112 and the signal 114 is added by the adder 16 to obtain a secondary differential signal 115.

The signal 115 is converted into an absolute value by the absolute value circuit 17, and the level detection circuit 18 detects a signal exceeding a level value arbitrarily set.

The detection signal 107 from the level detection circuit 8 and the detection signal 117 from the level detection circuit 18 are input to the same signal detection circuit 11. The signal detection circuit 11 compares the vertical detection signal 107 and the horizontal detection signal 117, and when the both signals are at the same level, the vertical signal 108 and the horizontal signal 118 indicating that period are shown. Is output.

The absolute value circuits 7 and 17, the level detection circuits 8 and 18, and the signal detection circuit 11 described above constitute a means for detecting a diagonal line portion of an image.

In the vertical direction, during the period in which the signal 108 is output, the enhancement amount control circuit 9 generates the control signal 109 according to the level of the level-detected signal 107. Then, the control signal 109 is used to adjust the amplification degree of the secondary differential signal 105 in the enhancement adjustment circuit 10 to obtain the vertical enhancement signal 110.

Similarly in the horizontal direction, during the period in which the signal 118 is output, according to the level of the detected signal 116,
The enhancement amount control circuit 19 generates a control signal 119. Then, with this control signal 119, the secondary differential signal 1
The amplification degree of 15 is adjusted by the enhancement adjustment circuit 20, and the horizontal enhancement signal 120 is obtained.

The vertical enhance signal 110 and the horizontal enhance signal 120 are added by the adder 21 to obtain the enhance signal 1
21 and adder 2 for this enhanced signal 121
By adding the 1CLK delay signal 112 from the 1CLK delay circuit 13 at 2, the contour-corrected video signal 122 is output from the output terminal 23 with the enhancement weakened during the period when the edge business occurs.

Next, the operation of FIG. 1 will be described with reference to FIGS.

A video signal 101 as shown in FIG. 3A is input to the input terminal 1 and supplied to the vertical quadratic differential circuit 2. The video signal 101 is sequentially delayed by 1H by the 1H delay circuits 3 and 4, and 1H delay signal 102 and 2H delay signal 103 as shown in FIGS. 3B and 3C are generated. Adder 5
Then, the video signal 101 and the 2H delay signal 103 are added and multiplied by 1/2 to obtain a signal 104 as shown in FIG. 3 (d). The signal obtained by inverting the signal 104 and the 1H delay signal 102 are added by the adder 6 to generate a secondary differential signal 105 as shown in FIG. 3 (e). The second-order differential signal 105 is input to the enhancement adjustment circuit 10 capable of adjusting the enhancement amount, and is also input to the absolute value circuit 7. An absolute value signal 106 as shown in FIG. 3 (f) is obtained from the absolute value circuit 7. The absolute value signal 106 is input to the level detection circuit 8, and a signal that exceeds a level value arbitrarily set here (for example, a level with contrast of characters or lines) is detected.

On the other hand, FIG. 4 obtained by the 1H delay circuit 3
The 1H delay signal 111 as shown in (a) is supplied to the horizontal quadratic differential circuit 12. 1H delay signal 111 is 1C
The LK delay circuits 13 and 14 sequentially delay 1 CLK, and the 1 CLK delay signals 112 and 2 as shown in FIGS.
The CLK delay signal 113 is generated. In the adder 15,
The video signal 111 and the 2CLK delay signal 113 are added and 1
It is multiplied by 2 to obtain a signal 114 as shown in FIG.
The signal obtained by inverting the signal 114 and the 1CLK delay signal 112 are added by the adder 16 to generate a secondary differential signal 115 as shown in FIG. 4 (e). The secondary differential signal 115 is input to the enhancement adjusting circuit 20 whose amount of enhancement can be adjusted, and is also input to the absolute value circuit 17. An absolute value signal 116 as shown in FIG. 4 (f) is obtained from the absolute value circuit 17. This absolute value signal 116
Is input to the level detection circuit 18, and a signal that exceeds a level value arbitrarily set here (for example, a level with contrast of characters or lines) is detected.

The vertical signal 107 detected by the level detection circuit 8 is input to one input terminal of the signal detection circuit 11 and is also input to the enhancement amount control circuit 9. The horizontal signal 117 detected by the level detection circuit 18 is input to the other input end of the signal detection circuit 11 and is also input to the enhancement amount control circuit 19.

In the signal detection circuit 11, the vertical signal 107, which is detected by the level detection circuits 8 and 18,
The signals 117 in the horizontal direction are compared, and the detection signals 108 and 118 indicating the periods are provided in a period in which the respective signals have the same level.
Is output. The signal 108 and the signal 118 are the same signal.

The enhancement amount control circuit 9 controls the period (the period of the signal 108) detected by the signal detection circuit 11 as follows.
A control signal 109 for controlling the amount of enhancement is output according to the output level of the level detection circuit 8. Similarly, the enhancement amount control circuit 19 controls the enhancement amount according to the output level of the level detection circuit 18 during the period detected by the signal detection circuit 11 (the period of the signal 118). Is output.

The enhancement adjusting circuit 10 automatically adjusts the amplitude of the secondary differential signal 105 that is input, using the control signal 109 from the enhancement amount control circuit 9 as a gain control signal. Similarly, the enhancement adjustment circuit 20
Is a control signal 11 from the enhancement amount control circuit 19.
9 is used as a gain control signal to automatically adjust the amplitude of the input secondary differential signal 115.

For example, when the level detection circuits 8 and 18 detect a contrasting level of a character or a line and the signal detection circuit 11 detects an oblique portion of a character or a line, the vertical direction, The horizontal enhancement amount control circuits 9 and 19 have control signals 109 and 119 proportional to the signals 107 and 117 from the level detection circuits 8 and 18, respectively.
Is supplied as a gain control signal to the vertical and horizontal enhancement adjustment circuits 10 and 20, and is controlled so as to reduce the amplitude (that is, the amount of enhancement) of the secondary differential signals 105 and 115 in the vertical and horizontal directions.

The enhancement adjustment circuit 10 outputs a vertical enhancement signal 110 as shown in FIG. 3 (h), and the enhancement adjustment circuit 20 outputs a vertical enhancement signal 120 as shown in FIG. 4 (h). The vertical enhance signal 110 and the horizontal enhance signal 120 are added by the adder 21 to form an enhance signal 121, which is supplied to one input end of the adder 22 and is supplied to the other input end of the adder 22. It is added to the 1CLK delay signal 112 and output from the output terminal 23. From the output terminal 23, a video signal whose video contour has been corrected and the contour correction amount (enhancement amount) of the oblique line portion has been reduced (that is, the edge business has been reduced) is output.

In the above embodiment, the control signals 109 and 119 created by the vertical enhancement amount control circuit 9 and the horizontal enhancement amount control circuit 19 are control signals proportional to the magnitudes of the level-detected signals 107 and 117. However,
The present invention is not limited to such a control signal, but can be applied to the signal 10 by changing the gain control method of the enhancement adjustment circuits 10 and 20.
Alternatively, 9 and 119 may be control signals that are inversely proportional to the magnitudes of the signals 107 and 117. Alternatively, the control signals 109 and 119 are level-detected signals 107 and 11 due to the difference in the adjustment amounts of the enhancement adjustment circuits 10 and 20, respectively.
Control signal multiplied by n-order function to the magnitude of 7 or signal 10
It is also possible to use a control signal in which the output becomes zero or becomes maximum at a predetermined value of 7,117.

[0038]

As described above, according to the present invention, it is possible to always supply a good image by eliminating the edge business which is conspicuous in the line on the screen or the oblique line portion of the character.

[Brief description of drawings]

FIG. 1 is a block diagram showing a contour correction circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing diagonal lines as image information input in FIG.

3 is a vertical signal waveform diagram for explaining the operation of FIG. 1. FIG.

FIG. 4 is a horizontal signal waveform diagram for explaining the operation of FIG.

FIG. 5 is a block diagram showing a conventional contour correction circuit.

FIG. 6 is a signal waveform diagram illustrating the operation of FIG.

[Explanation of symbols]

 1 ... Video signal input terminal 2 ... Vertical quadratic differential circuit 7, 17 ... Absolute value circuit 8, 18 ... Level detection circuit 9, 19 ... Enhance amount control circuit 10, 20 ... Enhance adjustment circuit 11 ... Same signal detection circuit 12 ... Horizontal quadratic differential circuit 21, 22 ... Adder 23 ... Video signal output terminal

Claims (2)

[Claims] 1. A means for inputting a video signal to generate vertical and horizontal enhancement signals for emphasizing a contour portion of a video, and inputting the vertical and horizontal enhancement signals,
Based on the enhance signal in the vertical direction and the horizontal direction, an enhancement adjusting unit that adjusts and outputs the amplitude,
Means for detecting a diagonal line portion of the image, means for controlling the enhancement adjusting means so as to reduce the amount of enhancement when the diagonal line portion is detected, and an enhancement signal from the enhancement adjusting means, the video signal A contour correction circuit comprising: 2. A secondary differential means for inputting a video signal to generate vertical and horizontal secondary differential signals, and absolute values of the vertical and horizontal secondary differential signals from the secondary differential means. To obtain the absolute value means, the level detecting means for detecting the vertical and horizontal output levels of the absolute value means, and the vertical and horizontal signals detected by the level detecting means are compared, and the respective signals are compared. The same signal detection means for outputting a detection signal during a period when the same level is detected, and a period in which the detection signal is detected by the same signal detection means, depending on the vertical and horizontal output levels of the level detection means. An enhancement amount control means for outputting a signal for controlling the enhancement amount, and vertical and horizontal secondary differential signals from the secondary differentiation means are input to receive a signal from the enhancement amount control means. And an enhancement adjusting means for adjusting and outputting the amplitude of the secondary differential signal according to, and a first adding means for adding the vertical and horizontal secondary differential signals output from the enhancement adjusting means. A contour correction circuit, wherein the output of the first adding means is used for enhancing the contour of the video signal.