JP2940229B2 - Contour correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correcting device which can be used when the rise or fall of a contour portion of a video signal of a television receiver, a video tape recorder or a video projector is made steeper. is there.

[0002]

2. Description of the Related Art In recent years, the trend toward higher image quality of television receivers has been strengthened, and an outline correction device has been regarded as important in order to make the outline portion of an image look sharper.

[0003] The applicant has previously filed an application for a contour correction device as described below. FIG. 5 shows a block diagram thereof. In FIG. 5, reference numeral 1 denotes a delay circuit for obtaining a delayed input video signal b from an input video signal a. A subtraction circuit 2 subtracts the delayed input video signal b from the input video signal a to obtain a primary differential signal c. 3
Is a delay circuit, and obtains a delayed primary differential signal d from the primary differential signal c. Reference numeral 4 denotes a minimum value circuit which extracts a minimum value of the primary differential signal c and the delayed primary differential signal d to obtain a minimum primary differential signal e. Reference numerals 5 and 7 denote delay circuits having a minimum value of 1.
A first delay minimum value primary differential signal f or a second delay minimum value primary differential signal h is obtained from the secondary differential signal e. A subtraction circuit 6 subtracts the first delayed minimum primary differential signal f from the minimum primary differential signal e to obtain a secondary differential signal g. Reference numeral 8 denotes a minimum value circuit, which extracts a minimum value of the secondary differential signal g and the second delay minimum primary differential signal h to obtain a correction signal i. Reference numeral 9 denotes a delay circuit that obtains a delayed input video signal j from the input video signal a. Reference numeral 10 denotes a subtraction circuit which subtracts the correction signal i from the delayed input video signal j to output an output video signal k.
Get.

[0004] The operation of the contour correction device configured as described above will be described below with reference to FIG. First, the input video signal a is delayed by the delay circuit 1 to obtain a delayed video input signal b, and the delayed video input signal b is subtracted from the input video signal a by the subtraction circuit 2 to obtain a primary differential signal c. . Next, the primary differential signal c
Is obtained by delaying the first-order differential signal d by the same time as the delay circuit 1, and the minimum value circuit 4 selects the smaller one of the absolute values of the first-order differential signal c and the delayed first-order differential signal d, A minimum primary differential signal e is obtained. However, if the signs are different, zero is output. The minimum primary differential signal e thus obtained
Has the same width as the rise or fall time of the contour portion of the input video signal a. Next, the delay circuit 5,
7, the first-order differential signal e is delayed by the first
Delay first-order differential signal f and second delay minimum 1
The next differential signal h is obtained. At this time, the delay time of the delay circuit 7 is １ ／ of the delay time of the delay circuit 5. Next, the subtraction circuit 6 subtracts the first delay minimum value primary differential signal f from the minimum value primary differential signal e to obtain a secondary differential signal g. The smaller of the absolute values of g and the second minimum delay value primary differential signal h is selected to obtain a correction signal i. However, the same sign as that of the secondary differential signal g is used. Next, an output video signal k is obtained by subtracting the correction signal i from the signal j obtained by delaying the input video signal a by the time required for the above-described arithmetic processing by the subtraction circuit 10. Since this signal k always has the same width as the rise or fall time of the contour portion of the input video signal a,
Contour correction can be performed without preshoot and overshoot.

[0005]

In the above-described contour correction device, a correction signal having the same time width as the rise or fall time of the contour portion is generated from the inclination of the contour portion of the input video signal. In accordance with the inclination of the outline portion, the outline of the image can be corrected sharply and steeply without preshoot and overshoot. However, because of the physical properties of cathode ray tubes, even if the signal amplitude changes linearly, the luminance of the screen does not change linearly, and the amount of change in luminance decreases as the area becomes darker. Exists. For this reason, even though the waveform was corrected vertically and symmetrically as a signal, when the image whose contour was actually corrected was viewed with a cathode ray tube, in an image with vertical black and white lines, the white lines became thicker and the black lines became thinner. Such an unnatural phenomenon occurs.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a contour correction device capable of steepening the slope of a contour portion of an input video signal without unnaturally changing the impression of a white portion or a black portion viewed on a CRT. Is what you do.

[0007]

Means for Solving the Problems In order to achieve this object, the contour correction apparatus of the present invention, (1) a first delay circuit for delaying the input video signal, from the first delay circuit a first subtraction circuit for subtracting the signal obtained from the input video signal, the first
A second delay circuit for delaying the output signal of the subtraction circuit, before
Delaying a first minimum value circuit for outputting the smaller the serial second the obtained signal by the delay circuit of the first output signal of the subtraction circuit, the output signal of the first minimum value circuit the subtracted from the third delay circuit and the output signal of the third the first minimum value circuit and the resulting signal by the delay circuit of 2
Of the subtraction circuit, and an adding circuit for adding a constant DC voltage on the output signal of the second subtraction circuit, and a fourth delay circuit for delaying the output signal of the first minimum value circuit, said fifth delay for delaying the second minimum value circuit for outputting a smaller absolute value of the output signal of the output signal and the fourth delay circuit adder circuit, said <br/> input video signal circuit and the <br/> a third configuration with subtraction circuit for subtracting the output signal of the second minimum value circuit from the output signal of the fifth delay circuit. (2) a first delay circuit for delaying the input video signal, a first subtraction circuit to subtract from the video signal a signal obtained from said first delay circuit is the input, wherein the 1
A second delay circuit for delaying the output signal of the subtraction circuit, before
Delaying a first minimum value circuit for outputting the smaller the serial second the obtained signal by the delay circuit of the first output signal of the subtraction circuit, the output signal of the first minimum value circuit the subtracted from the third delay circuit and the output signal of the third the first minimum value circuit and the resulting signal by the delay circuit of 2
Of the subtraction circuit, the fourth delay circuit for delaying the output signal of the first minimum value circuit, the absolute value of the output signal of the output signal and the fourth delay circuit of the second subtraction circuit better second minimum value circuit for outputting a small, the output signal of the second minimum value circuit is input, as it passes if polarity is the positive direction of the signal, its output if the negative direction a limiting circuit for zero, fifth delaying said input video signal
A delay circuit, a third configuration with subtraction circuit for delaying the output signal of the <br/> limiting circuit from the output signal of the fifth delay circuit.

[0008]

With this configuration, the present invention provides: (1) a signal obtained by subtracting a signal obtained by delaying an input video signal by a delay circuit from an input video signal, Take a value to obtain a differentiated signal with the same width as the contour part. Next, a signal obtained by delaying the differentiated signal by the delay circuit is subtracted from the original differentiated signal, and a predetermined constant DC voltage is added. The smaller value of the absolute value of this signal and the differential signal is taken, and the polarity is adopted as the correction signal by adopting the former signal polarity. By subtracting this correction signal from the input video signal delayed by the time required for the above arithmetic processing, no preshoot or overshoot occurs even if the input signal has any inclination, and the vertical black line The steepness of the outline portion is made steep without causing a change in the width direction of the white line. (2) A signal obtained by delaying the input video signal by the delay circuit is subtracted from the input video signal, and the minimum value of this signal and the signal obtained by delaying this signal by the delay circuit is obtained. Obtain differentiated signal. Next, a signal obtained by delaying the differentiated signal by the delay circuit is subtracted from the original differentiated signal. After taking the smaller of the absolute value of this signal and the derivative signal,
If the polarity of the former signal is positive, the signal is output as it is,
If negative, the output is set to zero and this is used as a correction signal. By subtracting this correction signal from the input video signal delayed by the time required for the above arithmetic processing, no preshoot or overshoot occurs even if the input signal has any inclination, and the vertical black line The steepness of the outline portion is made steep without causing a change in the width direction of the white line.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a contour correcting apparatus according to an embodiment of the present invention; FIG.

FIG. 1 is a block diagram showing an embodiment of the contour correcting apparatus according to the present invention. (FIG. 1)
Reference numeral 1 denotes a delay circuit for obtaining a delayed input video signal b from the input video signal a. A subtraction circuit 2 subtracts the delayed input video signal b from the input video signal a to obtain a primary differential signal c. A delay circuit 3 obtains a delayed primary differential signal d from the primary differential signal c. 4 is a minimum value circuit,
The minimum value of the primary differential signal c and the delayed primary differential signal d is extracted to obtain the minimum primary differential signal e. Reference numerals 5 and 7 denote delay circuits, which determine the first delay minimum value 1 from the minimum value primary differential signal e.
A second derivative signal f and a second minimum delay value first derivative signal h are obtained. Reference numeral 6 denotes a subtraction circuit, which is a minimum value primary differential signal e.
Is subtracted from the first differential minimum signal f to obtain a secondary differential signal g. Reference numeral 11 denotes an addition circuit which adds a constant value to the secondary differential signal g.

Reference numeral 8 denotes a minimum value circuit which extracts a minimum value of a signal 1 obtained by adding a constant value to the secondary differential signal g and a second delayed minimum primary differential signal h to obtain a correction signal i. Reference numeral 9 denotes a delay circuit that obtains a delayed input video signal j from the input video signal a. Reference numeral 10 denotes a subtraction circuit, which is a delayed input video signal j.
The output video signal k is obtained by subtracting the correction signal i from.

The operation of the contour correcting apparatus having the above-described configuration will be described below with reference to FIG. First, the input video signal a is delayed by the delay circuit 1 to obtain a delayed video input signal b, and the subtraction circuit 2 subtracts the delayed video input signal b from the input video signal a to obtain a primary differential signal c. . Next, a delayed primary differential signal d obtained by delaying the primary differential signal c by the same time as the delay circuit 1 by the delay circuit 3
Get. Thereafter, the minimum value circuit 4 selects the smaller one of the absolute values of the primary differential signal c and the delayed primary differential signal d, and obtains the minimum primary differential signal e. However, if the signs are different, zero is output. The minimum primary differential signal e thus obtained
Has the same width as the rise or fall time of the contour portion of the input video signal a. Next, the delay circuit 5,
7, the first-order differential signal e is delayed by the first
Delay first-order differential signal f and second delay minimum 1
The next differential signal h is obtained. At this time, the delay time of the delay circuit 7 is １ ／ of the delay time of the delay circuit 5.

Next, the subtraction circuit 6 outputs the minimum primary differential signal e.
Is subtracted from the first differential minimum signal f to obtain a secondary differential signal g. Next, the adder circuit 11 adds a certain value to the secondary differential signal g to obtain a corrected secondary differential signal l. Next, the minimum value circuit 8 selects the smaller one of the absolute values of the corrected secondary differential signal 1 and the second delayed minimum primary differential signal h to obtain a correction signal i. However, the same sign as that of the secondary differential signal g is used. Next, an output video signal k is obtained by subtracting the correction signal i from the signal j obtained by delaying the input video signal a by the time required for the above processing by the subtraction circuit 10. The signal k always has the contour corrected in proportion to the steepness of the rise or fall of the contour part of the input video signal a, and the time of the part rising from the input video signal a is the time before the correction. It will be slightly shorter than the signal. As a result, the contour can be corrected without adding a preshoot or an overshoot and without actually changing the width of the black portion and the white portion as viewed on the screen.

FIG. 3 is a block diagram showing an embodiment of the contour correcting apparatus according to the second aspect. Components of FIG. 3 which have the same reference numerals as those in FIG. 1 are the same as those in FIG. 1 and will not be described in detail. The minimum value circuit 8 extracts the minimum value of the secondary differential signal g and the second delayed minimum primary differential signal h to obtain a correction signal i. 12 is a limiting circuit, and a minimum value circuit 8
Is output as it is if it has a positive polarity, and its output is made zero if it has a negative polarity. The subtraction circuit 10 outputs a signal obtained by subtracting the output of the limiting circuit 12 from the output signal of the delay circuit 9 as an output video signal k.

The operation of the contour correcting apparatus having the above-described configuration will be described below with reference to FIG. The process until the secondary differential signal g is obtained from the input video signal a is the same as that described with reference to FIG. Subsequently, the minimum value circuit 8 selects the smaller of the absolute values of the secondary differential signal g and the second delayed minimum primary differential signal h to obtain a correction signal i. However, the same sign as that of the secondary differential signal g is used. Next, the correction signal i
To obtain a signal m in which the signal of the negative sign part of is zero. Next, an output video signal k is obtained by subtracting the signal m from the signal j obtained by delaying the input video signal a by the time required for generating the correction signal by the subtraction circuit 10. This signal k
Is such that only the black side edge of the contour portion of the input video signal a is sharp. As a result, the contour can be corrected without adding a preshoot or an overshoot and without actually changing the width of the black portion and the white portion as viewed on the screen.

As described above, according to the present embodiment, the sharp difference between the rise and fall of the contour portion of the input signal is maintained even after the contour correction, and the black-and-white portion in the horizontal direction as viewed on the actual screen is maintained. Steeper and narrower contour correction can be performed without changing the width and without preshoot and overshoot.

[0017]

As described above, according to the present invention, by using a delay circuit, a subtraction circuit, an addition circuit, a minimum value circuit, and a limiting circuit, the rise of the contour portion or the rise of the contour portion of the input video signal can be obtained. A correction signal with the same time width as the fall time is created, taking into account the characteristics of the cathode ray tube, without changing the width of the black and white parts in the outline viewed on the screen, and without preshoot and overshoot. In addition, the image quality can be improved by sharply and sharply correcting the outline of an image, and its practical effect is large.

[Brief description of the drawings]

FIG. 1 is a block diagram of a contour correction device according to a first embodiment of the present invention;

FIG. 2 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 3 is a block diagram of a contour correction device according to a second embodiment of the present invention;

FIG. 4 is a waveform chart for explaining the operation of the embodiment of claim 2;

FIG. 5 is a block diagram of a conventional contour correction device.

FIG. 6 is a waveform chart for explaining the operation of the conventional example.

[Explanation of symbols]

 1, 3, 5, 7, 9 delay circuit 2, 6, 10 subtraction circuit 4, 8 minimum value circuit 11 addition circuit 12 limiting circuit

Claims (2)

(57) [Claims] 1. A first argument to be subtracted from the first delay circuit and a video signal the signal obtained from said first delay circuit is the <br/> input for delaying the input video signal Arithmetic circuit and before
A second delay circuit for delaying the output signal of the serial first subtraction circuit, the signal obtained by the second delay circuit and the first
Resulting in the first minimum value circuit for outputting a smaller one of the output signal of the subtraction circuit, a third delay circuit for delaying the output signal of the first minimum value circuit, by the third delay circuit a second subtraction circuit for subtracting the resulting signal from the output signal of the first minimum value circuit, and an adding circuit for adding a constant DC voltage on the output signal of the second subtraction circuit, the a fourth delay circuit for delaying the output signal of the first minimum value circuit, before
Serial and second minimum value circuit for outputting a smaller absolute value of the output signal of the output signal and the fourth delay circuit adder circuit, a fifth delay circuit for delaying the video signal the input, It said fifth third subtracting the output signal of the second minimum value circuit from an output signal of the delay circuit of the contour correction apparatus provided with a subtraction circuit. 2. A first delay circuit for delaying the input video signal, a first subtraction circuit to subtract from the video signal a signal obtained from said first delay circuit is the input, Previous
A second delay circuit for delaying the output signal of the serial first subtraction circuit, the signal obtained by the second delay circuit and the first
Resulting in the first minimum value circuit for outputting a smaller one of the output signal of the subtraction circuit, a third delay circuit for delaying the output signal of the first minimum value circuit, by the third delay circuit a second subtraction circuit for subtracting the resulting signal from the output signal of the first minimum value circuit, and a fourth delay circuit for delaying the output signal of the first minimum value circuit, the second a second minimum value circuit for outputting a smaller absolute value of the output signal of the output signal and the fourth delay circuit subtraction circuit, the output signal of the second minimum value circuit are input, the signal polarity passes directly if positive, a limiting circuit to the output zero if negative direction, a fifth delay circuit for delaying the input video signal, said fifth delay circuit contour with a third subtraction circuit for delaying the output signal of the limiting circuit from the output signal correction instrumentation .