JPH0438077A - Contour correcting circuit - Google Patents

Abstract

PURPOSE:To improve the sharpness of a video signal without generating the deterioration of picture quality even when the adding quantity of a contour compensating signal by thinning the preshooting and overshooting of the outline compensating signal. CONSTITUTION:A differential signal (h) is obtained from video signals (a), (c) by the subtracting processing of a subtracting circuit 9 and rectified by a full wave rectifier circuit 10 to obtain a control signal (i), and when an outline compensating signal (f) is amplified by a variable gain amplifier 11, the gain of the circuit 11 is controlled by the signal (i). Since the gain of the circuit 11 is controlled by the control signal (i) obtained by shaping the waveform of a differential signal, a shoot to be added to a synthetic video signal (k) can be furthermore thinned and the required synthetic video signal (k) can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video signal processing circuit of a television receiver or the like, and in particular, to improving the sharpness of the video signal (i.e., improving the sharpness of the video signal The present invention relates to a contour correction circuit suitable for making the contours of an image stand out.

[Conventional technology]

A typical contour correction circuit uses a delay line aperture control method, and examples of conventional contour correction circuits using a delay line aperture control method include those described in Television Technical Book October 1989 Extra Edition [Electronic Technology] Publishing Co., Ltd. 2
It is introduced on page 1 as ``Principle of Delay Line Abacon'' and on page 82 as method 2 of r-double DL contour correction.

The circuit configuration of such a conventional contour correction circuit is shown in FIG. 7, and the waveforms of the main signals in FIG. 7 are shown in FIG. 8, respectively.

In FIG. 7, 1 is an input terminal, 2 and 3 are delay lines each having a delay time τ, 4 and 5 are each a subtraction circuit,
6 and 7 are adder circuits, and 8 is an output terminal. Note that the symbols of each signal in FIG. 7 correspond to the symbols of the waveforms in FIG. 8.

The operation of the circuit shown in FIG. 7 will be described below with reference to FIG.

Video signal a input from input terminal 1: Well, it passes through delay line 2 to become a video signal, and further passes through delay line 3 to become video signal C.

Then, a subtraction circuit 4 obtains a preshoot signal d from the video signals a and b, and a subtraction circuit 5 obtains a preshoot signal d from the video signals a and b.
An overshoot signal e is obtained from c, and further, an adder circuit 6 synthesizes the preshoot signal d and the overshoot signal e to obtain a contour compensation signal [.

Then, in the adder circuit 7, the contour compensation signal f is added to the video signal S to obtain a composite video signal g, which is output from the output terminal 8.

(Problems to be Solved by the Invention) However, the above-described conventional contour correction circuit has the following problems.

That is, as shown in FIG. 8, the temporal width β of the preshoot/overshoot portion of the contour compensation signal is wider than the temporal width α of the contour portion of the video signal, If the contour compensation signal f is added to the signal, a thick chute will be added to the composite video signal g.Moreover, in order to improve the sharpness of the video signal, the amount of addition of the contour compensation signal f should be increased (i.e., If the amplitude of the contour compensation signal f is increased and added), there is a problem in that the image quality is significantly degraded.

In addition, by shortening the delay time of the delay line 2.3, it is possible to reduce the amount of signal attached to the composite video signal g, but the band of the video signal is limited, and the loop 73 Since the frequency component of can't be higher than 5, no matter how short the delay time of delay line 2.3 is, the shoot attached to the composite video signal g will never become thinner than the value. , even if it is the thinnest, the temporal width γ of the changing part of the composite video signal g (equal to the temporal width β of the preshoot/overshoot part of the contour compensation signal f) is the time width of the contour part of the video signal Be narrower than the target width α: No.

As described above, the conventional contour correction circuit C has a problem in that an attempt to improve the sharpness of the video signal causes a significant deterioration of the image quality.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a contour correction circuit that can solve the problems of the prior art described above and improve the sharpness of a video signal without causing deterioration of image quality.

(Means for Solving the Problems) In order to achieve the above-mentioned objects, the present invention provides: a differentiating means for differentiating a video signal to obtain a differential signal; A waveform shaping means for shaping a waveform, and a control means for controlling the signal amplitude of the contour compensation signal according to the differential signal waveform-shaped by the waveform shaping means, the control means controlling the signal amplitude. 5V>
The hi m signal is added to the video signal.

[Effect]

In the present invention, the amplitude of the contour compensation signal is controlled in accordance with the differential signal obtained by differentiating the video signal and shaping the waveform.

As a result, the gain for the contour compensation signal becomes maximum at the switching point from preshoot to overshoot (or from overshoot to preshoot) in the contour compensation signal, and as a result, the contour compensation signal obtained by controlling , that '7'' IJ shoot, as the peak of the overshoot becomes closer to the switching point,
Its preshoot overshoot becomes thinner.

Therefore, even if the addition amount of the contour compensation signal is increased, the sharpness of the video signal can be improved without deteriorating the image quality.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a waveform diagram showing the waveforms of the main signals in FIG. 1.

In FIG. 1, the same parts as in FIG. 7 are designated by the same reference numerals. In addition, 9 is a subtraction circuit, 101 is a full-wave rectifier circuit, and 11 is a variable gain amplifier.

Note that the symbols of each signal in FIG. 1 correspond to the symbols of the waveforms in FIG. 2.

Hereinafter, the operation of the circuit shown in FIG. 1 will be explained using FIG. 2.

A video signal a input from an input terminal 1 passes through a delay line 2 to become a video signal, and further passes through a delay line 3 to become a video signal C.

Then, a subtraction circuit 4 obtains a preshoot signal d from the video signals a and b, and a subtraction circuit 5 obtains a preshoot signal d from the video signals a and b.
An overshoot signal e is obtained from c, and an adder circuit 6 synthesizes the preshoot signal d and overshoot signal e to obtain a contour compensation signal r, and then this contour compensation signal f is set to have a variable gain. It is amplified by an amplifier 11.

On the other hand, by performing subtraction processing in the subtraction circuit 9, a differential signal h (a signal approximated to the signal obtained by differentiating the video signal) is obtained from the video signals a and c, and furthermore, this differential signal is converted into a full-wavelength signal h. The rectifier circuit 10 rectifies the signal to obtain a control signal 1. Then, at the variable gain amplifier 114, the contour compensation signal f
When amplifying the variable gain amplifier 11, the gain of the variable gain amplifier 11 is controlled by the control signal i.
Control with. As a result, the contour compensation signal f is reshaped by the variable gain amplifier 114 to become the contour compensation signal j.

Then, in the adder circuit 7, the contour compensation signal j is added to the video signal S to obtain a composite video signal k, which is output from the output terminal 8.

In this way, by controlling the gain of the variable gain amplifier 11 using the control signal 1 obtained by shaping the differential signal, the preshoot in the contour compensation signal [2] is obtained as shown in FIG. At a switching point A (corresponding to the center point of the contour of the video signal) from overshoot to shoot (or from overshoot to preshoot), the gain of the variable gain amplifier 11 becomes maximum. Therefore, when the contour compensation signal r is amplified by such a variable gain amplifier 11, the peak of the preshoot overheard signal j will be closer to the switching point A, and as a result, the composite image The chute attached to the signal k can be made thinner, and a desired composite video signal k can be obtained.

Next, FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG. 4 is a waveform diagram showing waveforms of main signals in FIG. 3.

In FIG. 3, the same parts as in FIG. 1 or FIG. 7 are given the same reference numerals. Additionally, 12 is an amplifier, and 13 is a slice circuit. Note that the symbols of each signal in FIG. 3 correspond to the symbols of the waveforms in FIG. 4.

Hereinafter, the operation of the circuit shown in FIG. 3 will be explained using FIG. 4.

In this embodiment, the differential signal obtained by the subtraction circuit 9 is amplified by the amplifier 12 to obtain the differential signal! Then, this differential signal r is sliced by a slicing circuit 13 to obtain a signal m, and the signal m is further waveform-shaped by a full-wave rectifier circuit 10 to obtain a control signal n. When the variable gain amplifier 11 amplifies the contour compensation signal f, the gain of the variable gain amplifier 11 is controlled by the control signal n.

As a result, the contour compensation signal f is reshaped by the variable gain amplifier 11 and becomes the contour compensation signal O.

Then, in the adder circuit 7, the contour compensation signal 0 is added to the video signal p to obtain a composite video signal p, which is output from the output terminal 8.

By controlling the gain of the variable gain amplifier 11 using the signal n obtained by slicing the differential signal and shaping the waveform, the chute attached to the composite video signal p can be made extremely thin, as shown in FIG. , a desired composite video signal P can be obtained.

Furthermore, since the slice circuit 13 removes small amplitude signals, there is also the effect of noise reduction on the contour compensation signal.

Next, FIG. 5 is a block diagram showing a third embodiment of the present invention.

In FIG. 5, the same parts as in FIG. 1 or FIG. 7 are given the same reference numerals. Others, 1415.16.17
are each day line.

In this example, four Dayley Lights are used.
By shaping the waveform of the difference signal between the input and output of the two inner delay lines 15 and 16 and using it as the control signal 6L, a waveform equivalent to that of the embodiment shown in FIG. 3 is obtained as a composite video signal without a slice circuit. be able to.

Next, FIG. 6 is a block diagram showing a fourth embodiment of the present invention.

In FIG. 6, the same parts as in FIG. 1 and FIG. 7 are given the same reference numerals. In addition, 18 is a delay line.

In this embodiment, three delay lines are used, and the difference signal between the input and output of delay line 2 is delayed and waveform-shaped.
By using it as a control signal, it is possible to obtain a waveform equivalent to that of the embodiment shown in FIG. 3 as a composite video signal without using a slice circuit.

As explained above, according to each of the embodiments, it is possible to make the preshoot of the contour compensation signal thinner and the shoot attached to the composite video signal thinner than in the past, thereby reducing the deterioration of image quality. It is possible to make the sharp layer of the video signal as described above without causing the problem.

[Effects of the Invention] Conventionally, in an attempt to improve the sharp layer of a video signal, the addition amount of the contour compensation signal was increased (which caused deterioration of image quality), but according to the present invention, the addition amount of the contour compensation signal was increased. Since the preshoot and overshoot can be made thinner, the sharp layer of the video signal can be improved without deteriorating the image quality even if the addition amount of the contour compensation signal is made thicker.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a waveform diagram showing the waveforms of the main signals in Figure 1, and the waveform diagram shown in Figure 3.
FIG. 1 is a block diagram showing a second embodiment of the present invention, FIG. 4 is a waveform diagram showing waveforms of main signals in FIG. 3, and FIG. 5 is a block diagram showing a third embodiment of the present invention. , FIG. 6 is a block diagram showing a fourth embodiment of the present invention, FIG. 7 is a block diagram showing a conventional contour correction circuit, and FIG. 8 is a waveform diagram showing waveforms of main signals in FIG. be. Explanation of symbols l...Input terminal, 2.3,1415 17.18...Delay line, 4,59 circuit, 6.
7...addition circuit, output terminal, full wave rectifier circuit, 1
1... variable gain amplifier, single width amplifier, 13... slice circuit. ...Subtraction 10... 2...Increase agent Patent attorney Akio Namiki lfl Figure U 5E2 υ 5th @] [ M Wa Figure 3 Medical 114 Figure Maki 7 Figure 8

Claims (1)

[Claims] 1. Extracting means for extracting high-frequency components in a portion of a video signal where the signal amplitude changes (hereinafter referred to as a contour portion) to obtain a preshoot signal and an overshoot signal; and the extraction means combining means for synthesizing the preshoot signal and overshoot signal obtained by the above to obtain a contour compensation signal, and adding the contour compensation signal obtained by the synthesis means to the video signal to generate a contour portion of the video signal. an addition means for correcting the image signal; a differentiating means for differentiating the video signal to obtain a differential signal; a waveform shaping means for shaping the waveform of the differential signal obtained by the differentiating means; control means for controlling the signal amplitude of the contour compensation signal obtained by the synthesis means according to the differential signal whose waveform has been shaped by the shaping means; A contour correction circuit characterized in that, instead of the contour compensation signal, a contour compensation signal whose signal amplitude is controlled by the control means is added to the video signal. 2. In the contour correction circuit according to claim 1, the differentiating means obtains, as the differential signal, a differential signal whose temporal width is narrower than that of the contour compensation signal obtained by the synthesizing means. A contour correction circuit characterized by: 3. In the contour correction circuit according to claim 1 or 2,
The differentiating means includes a delay means for delaying the video signal;
A contour correction circuit comprising: subtraction means for subtracting the video signal and the video signal delayed by the delay means. 4. The contour correction circuit according to claim 1, 2 or 3, wherein each signal is a digital signal.