JPH0514771A - Outline correcting device - Google Patents

Abstract

PURPOSE:To operate the outline correction of a video signal without any preshoot or over shoot, and to make the width of the black and white parts of a longitudinal line the same with that before the correction when viewed on a screen by providing a delay circuit, subtracting circuit, and adding circuit. CONSTITUTION:A primary differentiation signal (e) whose width is narrow, is obtained from an input video signal (a) by a delay circuit 1, subtracting circuit 2, delay circuit 3, and minimum value circuit 4. Moreover, a secondary differentiation signal (g) is obtained by a delay circuit 5, and a subtracting circuit 6, a little direct current value is superimposed on the signal (g) by an adding circuit 11, the minimum value of the obtained signal (1) and a primary differentiation signal (h) is obtained by a minimum value circuit 8, and defined as a correction signal (i). The correction amounts of the black side of the outline part of the obtained correction signal (i) are a little large. Then, the correction signal (i) is subtracted from an input video signal (j) passing through a delay circuit 9, and a video signal (h) to which a required outline correction is operated can be obtained.

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 for making a rising or falling edge of a contour portion of a video signal of a television receiver, a video tape recorder or a video projector steeper. is there.

[0002]

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

The applicant has previously applied 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, which obtains the 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. Three
Is a delay circuit, which obtains a delayed primary differential signal d from the primary differential signal c. A minimum value circuit 4 takes out the minimum value of the primary differential signal c and the delayed primary differential signal d to obtain the minimum primary differential signal e. Delay circuits 5 and 7 have a minimum value of 1
From the second derivative signal e, the first delay minimum value first derivative signal f or the second delay minimum value first derivative signal h is obtained. Reference numeral 6 denotes a subtraction circuit, which subtracts the first delay minimum value first-order differential signal f from the minimum value first-order differential signal e to obtain a second-order differential signal g. A minimum value circuit 8 takes out the minimum value of the secondary differential signal g and the second delay minimum value primary differential signal h to obtain a correction signal i. Reference numeral 9 denotes a delay circuit, which 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 the output video signal k.
To get

The operation of the contour correction device configured as described above will be described below (FIG. 6). First, the input video signal a is delayed by the delay circuit 1 to obtain the 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 the primary differential signal c. . Next, the delay circuit 3 causes the primary differential signal c
After obtaining the delayed primary differential signal d delayed by the same time as the delay circuit 1, the minimum value circuit 4 selects the smaller absolute value of the primary differential signal c and the delayed primary differential signal d, The minimum value first derivative signal e is obtained. However, if the signs are different, zero is output. Minimum value first derivative signal e thus obtained
Always has the same width as the rising or falling time of the contour portion of the input video signal a. Next, the delay circuit 5,
7, the minimum first-order differential signal e is delayed to
Delay minimum value first derivative signal f and second delay minimum value 1
The second derivative signal h is obtained. At this time, the delay time of the delay circuit 7 is 1/2 of the delay time of the delay circuit 5. Next, the subtraction circuit 6 subtracts the first delay minimum value first-order differential signal f from the minimum value first-order differential signal e to obtain a second-order differential signal g, and the minimum-value circuit 8 outputs the second-order differential signal. g and the smaller absolute value of the second delay minimum value first-order differential signal h are selected to obtain the correction signal i. However, the same sign as the second derivative signal g is used. Next, the subtraction circuit 10 subtracts the correction signal i from the signal j obtained by delaying the input video signal a by the time required for the above arithmetic processing to obtain the output video signal k. Since this signal k always has the same width as the rising or falling time of the contour portion of the input video signal a,
Contour correction can be performed without preshoot and overshoot.

[0005]

In the contour correction apparatus described above, since the correction signal having the same time width as the rising or falling time of the contour portion is generated from the inclination of the contour portion of the input video signal, the input image signal is corrected. The contour of the image can be corrected finely and sharply without preshooting or overshooting according to the inclination of the contour portion. However, because of the physical properties of the cathode ray tube, the brightness of the screen does not change linearly even if the signal amplitude changes linearly, and the amount of change in brightness becomes smaller as it gets darker. Exists. For this reason, even though the waveform was corrected symmetrically in the vertical direction as a signal, when an image whose contour was actually corrected was viewed on a CRT, the white line became thick and the black line became thin in the image with vertical lines of white and black. An unnatural phenomenon such as

In view of the above problems, the present invention provides a contour correction device capable of making the inclination of a contour portion of an input video signal steep without unnaturally changing the impression of a white portion or a black portion when viewed on a cathode ray tube. To do.

[0007]

In order to achieve this object, the contour correction device of the present invention comprises: (1) a first delay circuit for delaying an input video signal, and a signal obtained thereby. A first subtraction circuit for subtracting from an input video signal, a second delay circuit for delaying an output signal of the first subtraction circuit, a signal obtained thereby, and a first subtraction circuit Of the output of the first minimum value circuit, a third delay circuit for delaying the output signal of the first minimum value circuit, and a signal obtained by the third delay circuit. Second subtraction circuit for subtracting from the output signal of the second subtraction circuit, an addition circuit for adding a certain DC voltage to the output signal of the second subtraction circuit, and a delay of the output signal of the first minimum value circuit. Absolute value of the fourth delay circuit and the output signal of the adder circuit and the output signal of the fourth delay circuit Of the second minimum value circuit, the fifth delay circuit for delaying the input video signal, and the output signal of the second minimum value circuit from the output signal of the fifth delay circuit. Third to add
This is a configuration including a subtraction circuit of. (2) A first delay circuit that delays an input video signal, a first subtraction circuit that subtracts a signal obtained thereby from an input video signal, and a first subtraction circuit A second delay circuit that delays the output signal, a first minimum value circuit that outputs the smaller of the signal obtained by this and the output of the first subtraction circuit, and the first minimum value circuit A third delay circuit for delaying the output signal, a second subtraction circuit for subtracting the signal thus obtained from the output signal of the first minimum value circuit, and an output signal of the first minimum value circuit A fourth delay circuit for delaying; a second minimum value circuit for outputting the smaller absolute value of the output signal of the second adding circuit and the output signal of the fourth delay circuit; and a second minimum value circuit Only the signal in the positive direction is taken out of the output of the A fifth delay circuit for delaying a video signal, a third configuration with subtraction circuit for subtracting the output signal of the limiting circuit from the output signal of the fifth delay circuit.

[0008]

With this configuration, the present invention (1) subtracts a signal obtained by delaying an input video signal by a delay circuit from the input video signal, and then, minimizes this signal and a signal obtained by delaying this signal by the delay circuit. The value is taken to obtain a differential signal having the same width as the contour portion. Next, a signal obtained by delaying this differential signal by a delay circuit is subtracted from the original differential signal, and then a preset constant DC voltage is added. The smaller absolute value of this signal and the differential signal is taken, and the polarity of the former signal is used as the correction signal. By subtracting this correction signal from the input video signal delayed by the time required for the above calculation processing, no preshoot or overshoot occurs even if the input signal has any inclination, and the vertical black line , The inclination of the contour portion is made steep without changing 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 taken to obtain the same width as the contour portion. Obtain the differentiated signal. Next, the signal obtained by delaying this differential signal by the delay circuit is subtracted from the original differential signal. After taking the smaller absolute value of this signal and the differential signal,
If the polarity of the former signal is positive, output the signal as it is,
If it is 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 calculation processing, no preshoot or overshoot occurs even if the input signal has any inclination, and the vertical black line , The inclination of the contour portion is made steep without changing the width direction of the white line.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A contour correcting apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram of an embodiment of the contour correcting apparatus according to the first aspect. In (Fig. 1)
Reference numeral 1 denotes a delay circuit which obtains 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 taken out to obtain the minimum value primary differential signal e. Denoted at 5 and 7 are delay circuits, which calculate the first delay minimum value 1 from the minimum first-order differential signal e.
The secondary differential signal f and the second delay minimum value primary differential signal h are respectively obtained. 6 is a subtraction circuit, which is the minimum value first-order differential signal e
From the first delay minimum value primary differential signal f to obtain a secondary differential signal g. An adder circuit 11 adds a constant value to the secondary differential signal g.

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

The operation of the contour correction device having the above-described structure will be described below with reference to FIG. First, the input video signal a is delayed by the delay circuit 1 to obtain the 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 the primary differential signal c. . Next, the delay circuit 3 delays the first-order differential signal c by the same time as the delay circuit 1 to obtain a delayed first-order differential signal d.
To get Then, the minimum value circuit 4 selects the smaller absolute value of the primary differential signal c and the delayed primary differential signal d to obtain the minimum primary differential signal e. However, if the signs are different, zero is output. Minimum value first derivative signal e thus obtained
Always has the same width as the rising or falling time of the contour portion of the input video signal a. Next, the delay circuit 5,
7, the minimum first-order differential signal e is delayed to
Delay minimum value first derivative signal f and second delay minimum value 1
The second derivative signal h is obtained. At this time, the delay time of the delay circuit 7 is 1/2 of the delay time of the delay circuit 5.

Next, in the subtraction circuit 6, the minimum value first-order differential signal e
From the first delay minimum value primary differential signal f to obtain a secondary differential signal g. Next, the addition 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 absolute value of the corrected secondary differential signal 1 and the second delay minimum value primary differential signal h to obtain the corrected signal i. However, the same sign as the second derivative signal g is used. Next, the subtraction circuit 10 subtracts the correction signal i from the signal j obtained by delaying the input video signal a by the time taken for the above processing to obtain the output video signal k. This signal k is always the one in which the contour correction is performed in proportion to the steepness of the rising or falling of the contour portion of the input video signal a, and the time of the portion rising from the input video signal a is before correction. It will be slightly shorter than the signal. This makes it possible to perform contour correction without adding preshoot and overshoot, and without actually changing the widths of the black portion and the white portion on the screen.

FIG. 3 shows a block diagram of an embodiment of the contour correcting apparatus according to the present invention. Of the respective constituent elements of (FIG. 3), those denoted by the same reference numerals as those of (FIG. 1) are the same as those of (FIG. 1), and detailed description thereof will be omitted. The minimum value circuit 8 extracts the minimum value of the secondary differential signal g and the second delay minimum value primary differential signal h to obtain the correction signal i. Reference numeral 12 is a limiting circuit, which is a minimum value circuit 8
With respect to the correction signal i which is the output of the above, if it has a positive polarity, it is output as it is, and if it has a negative polarity, its output is made zero. 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 correction device configured as described above will be described below with reference to FIG. The process of obtaining the secondary differential signal g from the input video signal a is the same as the description using (FIG. 2) described above. Following this, the minimum value circuit 8 selects the smaller absolute value of the secondary differential signal g and the second delay minimum value primary differential signal h to obtain the correction signal i. However, the same sign as the second derivative signal g is used. Next, the limiting circuit 12 causes the correction signal i
A signal m in which the signal of the negative sign portion of is zero is obtained. Next, the subtraction circuit 10 subtracts this signal m from the signal j obtained by delaying the input video signal a by the time taken to generate the correction signal to obtain the output video signal k. This signal k
Shows that only the black edge of the contour portion of the input video signal a is steep. This makes it possible to perform contour correction without adding preshoot and overshoot, and without actually changing the widths of the black portion and the white portion on the screen.

As described above, according to this embodiment, the steep difference between the rising edge and the falling edge 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 is actually seen on the screen. A sharper and narrower contour correction can be performed without changing the width and without preshooting or overshooting.

[0017]

As described above, according to the present invention, the delay circuit, the subtraction circuit, the addition circuit, the minimum value circuit, and the limiting circuit are used to change the rising edge of the contour portion from the inclination of the contour portion of the input video signal. A correction signal with the same time width as the fall time is created, and in consideration of the characteristics of the cathode ray tube, there is no preshoot or overshoot without changing the width of the black and white parts in the contour part when viewed on the screen. In addition, the image quality can be improved by correcting the contour of the image finely and sharply, and its practical effect is great.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram for explaining the operation of the embodiment of claim 1.

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 diagram 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 adder circuit 12 Limiting circuit

Claims (2)

[Claims] 1. A first delay circuit for delaying an input video signal; a first subtraction circuit for subtracting a signal obtained from the first delay circuit from the input video signal; A second delay circuit for delaying the output signal of the first subtraction circuit;
First minimum value circuit for outputting the smaller of the signal obtained by the delay circuit and the output signal of the first subtraction circuit, and a third delay circuit for delaying the output signal of the first minimum value circuit And a second subtraction circuit for subtracting the signal obtained by the third delay circuit from the output signal of the first minimum value circuit, and a constant DC voltage in the output signal of the second subtraction circuit. An adder circuit for adding and a fourth delay circuit for delaying the output signal of the first minimum value circuit
Delay circuit, a second minimum value circuit for outputting the smaller absolute value of the output signal of the adder circuit and the output signal of the fourth delay circuit, and a fifth delay circuit for delaying the input video signal. And a third 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 an input video signal, a first subtraction circuit for subtracting a signal obtained from the first delay circuit from the input video signal, A second delay circuit for delaying the output signal of the first subtraction circuit;
A first minimum value circuit for outputting the smaller of the signal obtained from the delay circuit and the output signal of the first subtraction circuit;
A third delay circuit for delaying the output signal of the minimum value circuit of
A second subtraction circuit that subtracts the signal obtained from the third delay circuit from the output signal of the first minimum value circuit; and a fourth delay circuit that delays the output signal of the first minimum value circuit. , A second minimum value circuit that outputs the smaller absolute value of the output signal of the second adder circuit and the output signal of the fourth delay circuit, and the output signal of the second minimum value circuit are input. If the polarity of the signal is in the positive direction, it will pass through as it is, and if it is in the negative direction, it will be passed through as it is, and the output will be zero, a fifth delay circuit for delaying the input video signal, and the output of the fifth delay circuit. A contour correction device comprising a third subtraction circuit for subtracting the output signal of the limiting circuit from the signal.