JP2760257B2 - Contour correction circuit - 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 correction circuit for enhancing a contour component of a video signal or the like and obtaining a sharp image.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional contour correction circuit, which is a well-known delay line type contour correction circuit. Its configuration and operation will be described with reference to a waveform diagram shown in FIG. The waveforms (a) to (g) shown in FIG. 6 correspond to the signals a to g in FIG. In FIG. 5, FIG.
Is input to the delay line 1 and is delayed by a time τ to become a signal b shown in FIG. This signal b is input to the delay line 2 and is further delayed by time τ.
The signal c shown in FIG.

An input signal a and a signal b are input to a subtractor 3, and the subtracter 3 outputs a signal d shown in FIG. 6D by subtracting the input signal a from the signal b. Similarly, the signal b and the signal c are input to the subtractor 4, and the subtractor 4
Outputs the signal e shown in FIG. 6E by subtracting the signal c from the signal b. The signal d and the signal e are input to the adder 5, and the adder 5 adds the signal d and the signal e, thereby extracting a contour signal f which is a contour component shown in FIG. Become. This contour signal f is added to the adder 1
6 is input. The signal b output from the delay line 1 is also input to the adder 16, and the adder 16 outputs the signal b and the contour signal f.
Are added, and the contour is corrected to output a signal g having a sharp feeling. Generally, the contour signal f is added to the signal b after the gain is controlled by the gain control circuit, so that arbitrary contour correction is possible.

[0004]

Now, let us consider a case where a signal including a noise component as shown in FIG. 7 is input to the above-described conventional contour correction circuit. When the noise component shown in FIG. 7A is input as the input signal a, the signal b
7g have waveforms shown in FIGS. 7B to 7G by the above-described operation. The noise component g output via the contour correction circuit shown in FIG. 5 has three times the amplitude of the input noise component a. Therefore, in the conventional contour correction circuit,
This has the effect of sharpening the contour of a dull signal, while at the same time emphasizing a noise component. In particular, when a video signal is projected on a screen of a television receiver or the like, an image having sharpness is obtained by passing through a contour correction circuit, but noise is also emphasized at the same time, which has been a problem.

The present invention has been made in view of such a problem, and has as its object to provide a contour correction circuit that does not correct noise components.

[0006]

According to the present invention, in order to solve the above-mentioned problems of the prior art, a first signal (A) is delayed by delaying an input first signal (A). 1 delay means (1), second delay means (2) for delaying the second signal to generate a third signal (c), and converting the first signal from the second signal. A first subtraction means (3) for subtracting to generate a fourth signal (d); and a second subtracting means for subtracting the third signal from the second signal to generate a fifth signal (e). Subtraction means (4), first addition means (5) for adding the fourth signal and the fifth signal to generate a sixth signal (f), Means for generating a seventh signal (q) by taking the minimum value of the maximum value of the fifth signal and the value obtained by inverting the minimum value of the fourth signal and the fifth signal. 9) Means (10-12) for taking an absolute value of the absolute value of the fourth signal and the absolute value of the fifth signal to generate an eighth signal (k); Means for adding an eighth signal, multiplying the added output by the sixth signal to generate a ninth signal (s), and adding the ninth signal and the second signal. To obtain a tenth signal (S) which is an output signal whose contour has been corrected.
And a summing means (16).

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A contour correction circuit according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of the contour correction circuit of the present invention, and FIGS. 2 to 4 are waveform diagrams for explaining the operation of the contour correction circuit of the present invention. In FIG. 1, the same portions as those in FIG. 5 are denoted by the same reference numerals.

First, the configuration and operation of an embodiment of the contour correction circuit according to the present invention shown in FIG. 1 will be described with reference to the waveform diagram shown in FIG. The waveforms shown in FIG.
(S) corresponds to the signals A to S in FIG. In FIG. 1, an input signal A shown by a solid line in FIG. 2A is input to a delay line 1 and is delayed by a time τ to become a signal A shown by a broken line in FIG. This signal A is input to the delay line 2 and further delayed by time τ to become a signal C shown by a broken line in FIG.

An input signal A and a signal A are input to the subtracter 3, and the subtracter 3 subtracts the input signal A from the signal A to output a signal D shown by a solid line in FIG.
Similarly, the signal A and the signal C are input to the subtractor 4, and the subtractor 4 subtracts the signal C from the signal A by
A signal (o) indicated by a broken line is output to (e). The signal D and the signal O are input to the adder 5, and the adder 5 adds the signal D and the signal O, thereby extracting a contour signal F which is a contour component shown in FIG. Become.

The signal D and the signal O are connected to a maximum value detection circuit 6.
The maximum value detection circuit 6 detects the maximum value of the input signal and outputs a signal indicated by a broken line in FIG. The minimum value detection circuit 7 detects the minimum value of the input signal, and outputs the signal of the minimum value to the inversion circuit 8.
, And becomes a signal indicated by a broken line in FIG. These signals are input to the minimum value detection circuit 9, which detects the minimum value of the input signal and outputs the minimum value detection signal indicated by the solid line in FIG. I do.

On the other hand, the signal d is also input to the absolute value circuit 10 and its absolute value is taken.
1 and its absolute value is taken. Absolute value circuit 1
The absolute values of the signals D and E output from 0 and 11 are input to the minimum value detection circuit 12, and the minimum value detection circuit 12 detects the minimum values of these signals and is shown by a solid line in FIG. A minimum value detection signal is output. These minimum value detection signals 及 び and 入 力 are input to an adder 13 (a + b) / 2 (a and b are input signals), and the adder 13 adds the minimum value detection signals コ and コ (in this embodiment, ( Fig. 2 (A)
Is output.

The contour signal output from the adder 5 as described above is subjected to limiter amplification by the amplifier 14 and
The signal shown in FIG. Further, the signal input and the signal input are input to the multiplier 15, and the multiplier 15 multiplies these to obtain an outline correction signal S shown in FIG. Then, the contour correction signal is input to the adder 16. The signal A output from the delay line 1 is also input to the adder 16, and the adder 16 adds the signal A and the contour correction signal S, corrects the contour, and shows a sharp feeling in FIG. Outputs a signal. In this case, too, by inserting a gain control circuit between the multiplier 15 and the adder 16, the contour correction signal is controlled to obtain a signal whose contour is arbitrarily corrected as shown in FIG. Can be.

According to the contour correction circuit of the present invention described above, compared with the conventional example having a delay line of the same delay amount,
The width of overshoot and preshoot is halved,
Further, it can be seen that the edge changes sharply. Therefore, in the case of a video signal, it is possible to obtain a sharp video with an increased sharpness as compared with the related art.

Next, consider a case where a signal containing a noise component as shown in FIG. 3 is input to the contour correction circuit of the present invention shown in FIG. When a noise component indicated by a solid line in FIG. 2A is input as an input signal A, the signals I to C have the waveforms shown in FIGS. Here, the difference between FIG. 2 and FIG. 3 is that the signal output from the minimum value detection circuit 9 and the signal output from the minimum value detection circuit 12 have opposite polarities, as can be seen from FIG.
That is, the output signal of the adder 13 becomes 0, and the contour correction signal is not output. Therefore, no contour correction signal is added to the input noise component, and only the original signal component is contour-enhanced. In particular, when the contour correction circuit of the present invention is mounted in the case of a video signal, the sharpness of the projected image is improved but the noise component does not change, so that a clear and easy-to-view image can be obtained.

[0015]

As described above in detail, the contour correction circuit of the present invention has the above configuration, and the width of the overshoot and the width of the preshoot are smaller than those of the conventional example having a delay line having the same delay amount. It becomes half and the edge changes sharply. At the same time, the configuration is such that no contour correction signal is added to the input noise component, and there is an excellent feature that the noise is not enhanced and only the original signal component is enhanced. In particular, when the contour correction circuit of the present invention is mounted in the case of a video signal, the sharpness of the projected image is improved, but the noise component is not emphasized, so that a clear and easy-to-view image can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the present invention.

FIG. 3 is a waveform chart for explaining the operation of the present invention.

FIG. 4 is a waveform chart for explaining the operation of the present invention.

FIG. 5 is a block diagram showing a conventional example.

FIG. 6 is a waveform chart for explaining a conventional example.

FIG. 7 is a waveform diagram for explaining a conventional example.

[Explanation of symbols]

 1, 2 delay line 3, 4 subtractor 5, 13, 13, 16 adder 6 maximum value detection circuit 7, 9, 12 minimum value detection circuit 8 inversion circuit 10, 11 absolute value circuit 14 amplification circuit 15 multiplier

Claims (1)

(57) [Claims] 1. A first delay means for delaying an input first signal to generate a second signal, and a second delay for delaying the second signal to generate a third signal. Means, first subtraction means for subtracting the first signal from the second signal to generate a fourth signal, and subtracting the third signal from the second signal to obtain a fifth signal A second subtraction unit that generates a signal; a first addition unit that adds the fourth signal and the fifth signal to generate a sixth signal; a fourth signal and the fifth signal; Means for generating a seventh signal by taking the minimum value of the maximum value of the signal and the value obtained by inverting the minimum value of the fourth signal and the fifth signal; Means for generating an eighth signal by taking the minimum value of the value and the absolute value of the fifth signal; adding the seventh signal and the eighth signal; Means for generating a ninth signal by multiplying the calculated power by the sixth signal; and a tenth signal which is an output signal whose contour has been corrected by adding the ninth signal and the second signal. And a second adding means for obtaining the following.