JPH02149070A - Contour improvement circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a contour improving circuit for improving the contour of a signal whose band has deteriorated, such as a reproduced color signal of a VTR.

Conventional technology The conventional method for improving the contour of a signal with degraded bandwidth is as follows:
For example, it is shown in Buttokai Publication No. 59-89077. This conventional example will be explained using the block diagram of FIG. 4 and the waveform diagram of FIG. 6.

A color difference signal a with degraded band is inputted from a terminal 20 1,
The signal is differentiated by the differentiating circuit 21 to obtain a signal, and the full-wave rectifier circuit 22
The signal is full-wave rectified to obtain a signal C, and the waveform is shaped by a waveform shaping circuit 23 to obtain a signal d. The input signal a is sampled and held by the sample and hold circuit 24 using this signal d, and an output e is obtained. Looking at this, it can be seen that although the outline of the signal in the output e is emphasized, the time of the edge portion is shifted by t.

On the other hand, when the input signal is the signal a1 with little change, the output of the differential signal C1 is small, so the control signal d1 is not generated and the input signal is output as is.

In other words, the edge shift amount depends on the waveform.

The period t2 during which the input signal is sampled and held changes depending on the magnitude of the change in the input signal, and a waveform that changes greatly is delayed, while a waveform that changes small is not delayed, and appears to be relatively advanced. When viewed on a TV screen, the colors of small change areas appear to bleed to the left, causing color shift and making the image difficult to see.

Therefore, in recent years, a method as shown in FIG. 6 has been proposed, which further improves the above circuit and samples and holds up to the center of the contour regardless of the magnitude of signal change.

This conventional example will be explained below using the block diagram of FIG. 6 and the waveform diagram of FIG. 7. Here, a in Figures 6 and 7
-k correspond to each other.

An image consists of a luminance signal (Y signal) and a color difference signal (e.g. R-Y,
Since the correlation between the B and Y signals is extremely strong, it can be considered that the luminance signal also changes in the portion where the color difference signal changes. Therefore, in the conventional example shown in FIG. 6, the control signal f is obtained from the luminance signal.

The luminance signal a that has entered the terminal 1 is input to the control signal generation circuit 3. In the control signal generation circuit 3, a low-pass filter (LPF) e limits the band and generates a signal, a first differentiation circuit 7 differentiates the signal C, and a full-wave rectifier circuit 8 converts the signal C into a full-wave signal. The rectified signal d is used as the second differentiator circuit 9.
The signal d is differentiated into a signal e, and the waveform shaping circuit 1o detects the positive pulse portion of the signal e to obtain a control signal f.

In other words, this control signal amount indicates the range from the start point of the edge portion of the signal line (point A in the figure) to the center of the edge (point B in the figure).

Terminal 2 is connected to a color difference signal q (for example, R-Y or B-Y
signal) is inputted to the waveform adjustment circuit 4.

In the waveform adjustment circuit 4, the signal q is passed through a delay circuit 1 having an appropriate delay time corresponding to the processing time in the control signal generation circuit 3.
1 and also to the differentiating circuit 12.

The output of the differentiating circuit 12 is sliced at a very small level by the slicing circuit 13 to remove the noise component of the waveform center potential to obtain signal 1, which is added to the output of the delay circuit 11 by the adder 14 to obtain signal j. .

This signal j is sampled and held in a sample and hold circuit 6 using a control signal f to obtain a signal k, which is output to a terminal 16. Input signal q and signal j are also shown superimposed in the waveform diagram of the output signal, and as can be seen, the contours are significantly improved compared to input signal q, and the time shift of the edges is It turns out that there are few.

Problems to be Solved by the Invention However, in the above configuration, since the edge portion of the color difference signal is improved using the change in the first luminance signal, when the change in the edge portion of the luminance signal is large, , when the sample-hold pulse width is wide, the degree of improvement of the edges of the color difference signal becomes large; conversely, when the change in the edge part of the luminance signal is small, the sample-hold pulse width becomes narrow, and the degree of improvement of the edges of the color difference signal becomes small. I had a problem (2).

That is, when the change in the edge portion of the luminance signal is large (in the case of the solid line waveform in Figure 7), the sample and hold pulse also becomes wider (see the solid line waveform in Figure 7 f). As shown in Figure 7, the contour is greatly improved, but when the change in the edge part of the luminance signal is small (in the case of the broken line waveform in Figure 7), the amplitude of the signal d obtained by full-wave rectification of the differential waveform also becomes small. , the amplitude of the signal e obtained by differentiating the signal d is also the seventh
As a result, the width of the sample-and-hold pulse becomes narrower (see the broken line waveform in Figure 7 f), and the edge portion of the two-color difference signal is
This had the problem that the improvement in contour was small. In addition, as can be seen by comparing the waveforms k and ' in the same figure, even if the color difference signal is the same, the time shift at the edge of Δ can also change depending on whether the change in the luminance signal is large or small. There were also issues that could arise.

Means for Solving the Problems In order to solve the above problems, the contour improvement circuit of the present invention inputs a first input signal to a control signal generation circuit including a circuit that performs differentiation operations at least twice, The input signal is input to a waveform adjustment circuit including a delay circuit, and the output signal of the waveform adjustment circuit is sampled and held in a sample hold circuit using a control signal output from the control signal generation circuit, and the output signal of the sample hold circuit is is characterized in that the control signal generation circuit includes a first differentiating circuit, a full-wave rectifier circuit that unifies the polarity of the output signal of the first differentiating circuit in one direction, and a full-wave rectifying circuit that unifies the polarity of the output signal of the first differentiating circuit in one direction; a clip circuit that removes a predetermined amplitude or more of the output waveform of the rectifier circuit; a second differentiator circuit that differentiates the output of the clip circuit;
The waveform shaping circuit detects a signal level above or below a predetermined level of the output of the differentiating circuit and shapes the waveform.

Operation The present invention generates a sample-and-hold pulse with a constant time width without depending on the magnitude of change in the edge portion of the luminance signal with the above-described configuration, thereby making it possible to improve contours with less color blurring.

Embodiment Hereinafter, a contour improving circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 shows waveforms of various parts in FIG. 1. Here, a- in FIG. 1 and FIG. 2 are opposite to each other. Figure 3 is a characteristic diagram showing the features of the present invention.

Since the correlation between the luminance signal and the color difference signal in an image is extremely strong, it can be considered that the luminance signal is also changing in a portion where the color difference signal changes. Therefore, in the embodiment, a case will be shown in which the control signal f is obtained from a luminance signal.

First, the luminance signal a input to the terminal 1 is input to the control signal generation circuit 3. The control signal generation circuit 3 limits the entire band with a low pass filter (LPF) e and generates a signal.
A first differentiating circuit 7 differentiates the signal S to obtain a signal C, a full-wave rectifier circuit 8 full-wave rectifies the signal C to obtain a signal d1, a clip circuit 16 clips the signal d1 to a clip level to obtain a signal d2, A second differentiating circuit 9 differentiates the signal d2 to obtain a signal e, and a waveform shaping circuit 10 detects a positive pulse portion of the signal e that is equal to or higher than the threshold level to obtain a control signal (sample hold pulse) f.

In other words, this control signal f indicates the beginning of the edge part of the signal line up to the center of the edge, and when the change in the edge part of the luminance signal a is small as shown by the broken line in Fig. 2 a-e, However, the full-wave rectified signal d1 is clipped by the clip circuit 9.
Since the signal d2 is obtained by clipping the upper part of the waveform, the pulse width of the control signal amount does not change.

FIG. 3 shows that the pulse width T of the control signal f changes depending on the amount of change H in the edge portion of the input luminance signal depending on the presence or absence of the clip circuit 9.
Show how things are changing.

In the same figure, the straight line marked A is for the case where the clip circuit 9 is provided, and the straight line marked for B is for the case where the output signal d1 of the full-wave rectifier circuit 9 is input directly to the second differentiating circuit 9 without the clip circuit 9. It is. As can be seen from this, in the absence of the clipping circuit 9, as the amount of change H in the edge portion of the input luminance signal increases, the pulse width T of the control signal f also increases;
When the clip circuit 9 is provided, the pulse width T of the control signal f is maintained at a constant value even if the amount of change H in the edge portion of the input luminance signal increases, and the pulse width remains almost constant regardless of the input luminance signal. A control signal f is obtained.

Next, terminal 2 receives a color difference signal q (for example, RY.

or B-Y signal) is inputted to the waveform adjustment circuit 4.

In the waveform adjustment circuit 4, the signal q is passed through a delay circuit 1 having an appropriate delay time corresponding to the processing time in the control signal generation circuit 3.
1 and also to the differentiating circuit 12.

The output of the differentiating circuit 12 is sliced to a very small level in a slicing circuit 13 to remove noise in the waveform center potential to obtain a signal 1, which is added to the output of the delay circuit 11 in an adder 14 to obtain a signal j. This signal j is sampled and held in a sample and hold circuit 6 using a control signal f to obtain a signal k, which is output to a terminal 16.

As described above, according to this embodiment, the edge portion of the first input signal (for example, a luminance signal) is detected by the first differentiating circuit and the full-wave rectifier circuit, and the output waveform of the full-wave rectifier circuit is a clipping circuit that cuts out an amplitude value or more; a second differentiation circuit that differentiates the output of the clipping circuit; and a waveform adjustment circuit that detects a signal level of the output of the second differentiation circuit that is a predetermined level or higher and shapes the waveform. By providing , the first
A control signal (sample and hold pulse) having a predetermined pulse width is obtained regardless of the amount of change in the edge portion of the input signal, and this control signal is used to sample and hold the second input signal (for example, a color difference signal). By sample-holding in the circuit, it is possible to improve the contour of the edge portion of the second input signal.

In this embodiment, to simplify the explanation, the differentiating circuit 11 is explained as a first-order differential type differentiating circuit, but by using a second-order differential type differentiating circuit using a transversal filter, open The effect will be greater if the configuration is configured so that it can be added to both mutes.

In addition, the pulse width T of the output signal (sample hold pulse) f of the waveform shaping circuit 10 should be approximately 300μ to SOOμS in order to improve the contour of the consumer VTR reproduced chroma signal (bandwidth 500KHz or less). and
Any circuit other than the waveform adjustment circuit 10 described in this embodiment may be used as long as the circuit is capable of generating such pulses.

Furthermore, LPFe in the control signal generation circuit 3 may be omitted.

Furthermore, the processing described in the present invention can be actually reduced by digital processing after A/D conversion of the video signal.

Effects of the Invention As described above, the present invention inputs a first input signal to a control signal generation circuit including a circuit that performs differentiation operations at least twice, and inputs a second input signal to a control signal generation circuit that includes a delay circuit that performs waveform adjustment. The output signal of the first input signal is input to the circuit, the output signal of the waveform adjustment circuit is sampled and held in a sample and hold circuit, and the output of the sample and hold circuit is used as the output signal. Regardless of the magnitude of the change, sample and hold is performed up to the center position of the contour of the second input signal, and the contour can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the contour improvement circuit of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, and FIG.
4 and 6 are block diagrams showing a conventional contour improvement circuit. FIG. 7 is a waveform diagram of each part of the circuit. 3... Control signal generation circuit, 4... Waveform adjustment circuit, 6... Sample hold circuit, 6...
...Low pass filter, 7, 9, 12...
・・・Differential circuit, 8...Full wave rectifier circuit, 10...
... Waveform shaping circuit, 13 ... Slicer,
14... Addition circuit, 16... Clip circuit. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 1 Figure d. /, : 3 figures included A) Knee bond conversion IH (77IV'Pp) Figure

Claims (2)

[Claims] (1) A first input signal is input to a control signal generation circuit including a circuit that performs differentiation operations at least twice, a second input signal is input to a waveform adjustment circuit including a delay circuit, and the control signal is generated. A contour improvement circuit that samples and holds an output signal of the waveform adjustment circuit in a sample and hold circuit according to a control signal that is an output of the circuit, and uses the output of the sample and hold circuit as an output signal, the control signal generation circuit comprising: a first differentiating circuit, a full-wave rectifier circuit that unifies the polarity of the output signal of the first differentiator circuit in one direction, and a clip circuit that cuts out a predetermined amplitude value or more of the output waveform of the full-wave rectifier circuit; It is characterized by comprising a second differentiating circuit that differentiates the output of the clipping circuit, and a waveform shaping circuit that detects a signal level of the output of the second differentiating circuit that is above or below a predetermined level and shapes the waveform. Contour improvement circuit. (2) The waveform adjustment circuit includes a delay circuit that delays an input signal by a predetermined amount, a differentiation circuit that differentiates the input signal, a slice circuit that slices a predetermined level from the center potential of the output of the differentiation circuit, and the slice circuit 2. The contour improving circuit according to claim 1, further comprising an adder that adds the output of the delay circuit and the output of the delay circuit.