JPH05219519A - Vertical contour correcting device - Google Patents

Abstract

PURPOSE:To obtain a sharp picture by reducing dot disturbance without deteriorating the vertical resolution of a luminance signal. CONSTITUTION:A contour component resulting from a subtraction processing between an input signal and a signal after being delayed by 11 horizontal scanning periods passes through a filter 6 in the vertical contour correction device in which one delay element 1 is employed to add simultaneously overshoot and preshoot to the vertical contour for one horizontal period. Then the output of the filter 6 is inputted to a coring level control voltage detection circuit 8. When a chroma component is not sufficiently eliminated in the output of the filter 6, the mixing of the chroma component to the luminance signal is prevented and dot disturbance is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical contour correction device in an image processing device used in a TV or VTR,
In particular, the present invention relates to a vertical contour correction device that reduces dot interference due to leakage of chroma components.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a vertical contour correcting device used in a conventional TV or VTR. This vertical contour correction device has a comb-shaped filter characteristic, is capable of separating a luminance signal and a carrier color signal, and uses only one horizontal scanning period delay element to form a vertical contour. A preshoot and an overshoot are added at the same time.

A video signal input terminal 1 is connected to adders 2, 4 and a subtractor 5. The output of the adder 2 is input to the delay element 3 for one horizontal scanning period, and the output of the delay element 3 is input to the adder 4 and the subtractor 5. The output of the subtractor 5 is output to the color signal output terminal 12. The output of the adder 4 is given to the adder 13, and the output of the adder 13 is output to the luminance signal output terminal 14. A cutoff frequency of 1.6M is provided between the color signal output terminal 12 and the input terminal of the adder 2.
A low-pass filter (LPF) 6 of about HZ, a coring processing circuit 9, and an inverting amplifier 10 are connected in series in this order, and the output end of the coring processing circuit 9 and the adder 13 are connected.
The inverting amplifier 11 is connected between the input terminal of the
An inverting amplifier 7 is connected between the output end of 6 and the input end of the adder 13.

Next, the operation of this conventional vertical contour correcting device will be described.

A video signal of reference numeral 15 shown in FIG. 2 is input to the input terminal 1 shown in FIG. For the sake of convenience, the video signal 15 is shown by omitting the sync signal and the burst signal.
On the screen is a window waveform of a white window in a black screen. The horizontal axis represents V rate. This signal 15 is delayed by one horizontal scanning period delay element 3 for one horizontal scanning period, and the signal waveform 16 of FIG. 2 is obtained. The signal 15 and the signal 16 are input to the subtractor 5, respectively.
The subtractor 5 has a brightness of a comb-shaped filter characteristic that utilizes the characteristic of the NISC signal that the phase of the color signal is inverted before and after one horizontal scanning period and the signals before and after one horizontal scanning period are similar. It is for color signal output calculation for separating the signal and the color signal, and a signal in which only the edge portion uncorrelated with the color signal component remains is obtained at the output. This subtractor 5
, The correlated luminance signals before and after one horizontal scanning period are not output because they have the same phase. The signal output from the subtractor 5 is passed through the low-pass filter 6 in order to remove the uncorrelated edge signal 17 and the unnecessary color signal of the color signals. This low pass filter 6
It has a trap with a cutoff frequency of about 1.5 MHZ, and the color signal is removed here. The output of the low pass filter 6 is input to the adder 13 via the inverting amplifier 7.

An input signal 15 and a signal 16 delayed by one horizontal scanning period are input to the adder 4, and a signal 18 having a blunt edge waveform is obtained at the output. A signal that has passed through the inverting amplifier 7 in the output waveform 18 of the adder 4 is calculated by the adder 13, and as a result, a signal 19 in which the edge portion is corrected can be obtained.

The output of the low-pass filter 6 is also input to the coring processing circuit 9. The coring processing circuit 9 removes noise contained in the output of the low-pass filter 6, and then the inverting amplifiers 10 and 11 receive the noise. Is entered. The signal that has passed through the inverting amplifier 10 is input to the adder 2. Since the adder 2 performs the arithmetic processing of the input video signal and the output signal of the inverting amplifier 10, it is possible to obtain a signal waveform with overshoot added at the output at the rising and falling portions in the vertical direction. .. The signal that has passed through the inverting amplifier 11 is input to the adder 13.
As a result, the output of the adder 13 is simultaneously provided with the preshoot together with the overshoot provided by the adder 2, and the output waveform 20 to which the vertical contour component is added can be obtained.

[0008]

Generally, the spectrum of the carrier chrominance signal in the video signal is characterized by frequency interleaving that appears in the valleys of the spectrum of the luminance signal at intervals of the horizontal scanning frequency centered on the chrominance subcarrier. , That band is ± 500K centered on 3.58MHz
Hz.

The low-pass filter 6 has a cutoff frequency of about 1.5 MHz and has a trap at 3.58 MHz. Therefore, when a color signal is passed through the low-pass filter 6, the upper side band of 3.58 MHz is generated. Although the color signal component of the component can be removed, since the cutoff frequencies are relatively close to 1.6 MHz and 3.58 MHz, 3.
The sideband component below 58 MHz is difficult to remove.

The output of the low-pass filter 6 is the inverting amplifier 7
When the coring level is large, the correlation is small before and after one horizontal scanning period because the coring level is set by the external fixed bias in the coring processing circuit 9. , The contour component is buried in the coring level, and preshoot and overshoot cannot be added. If the coring level is set low, the lower sideband component of the color signal that has not been removed by the low-pass filter 6 will be added to the luminance signal that has been arithmetically processed by the adder 13 via the inverting amplifier 11, resulting in a result. Since the color signal is mixed with the luminance signal, dot interference increases, and there is a problem that a clear image cannot be obtained.

In order to avoid the problem due to the dot interference without making the coring level variable, the cutoff frequency of the low-pass filter 6 is further lowered below 1.5 MHz to remove the sideband component below 3.58 MHz. Although such a method may be considered, it also attenuates the vertical component of the luminance signal and deteriorates the vertical resolution of the luminance signal, which is not an appropriate means.

The present invention has been made in view of the above problems, and it is possible to reduce dot interference without deteriorating the vertical resolution of a luminance signal and to obtain a vertical contour correction capable of obtaining a clear image. The purpose is to provide a device.

[0013]

A vertical contour correction apparatus according to the present invention uses an input signal of 1 by a horizontal scanning period delay element.
An adder and a subtractor for adding and subtracting a signal delayed in the horizontal scanning period and an input signal to have a comb-shaped filter characteristic and separating a luminance signal and a chrominance signal, and an output signal of the subtractor are input. 2. A low-pass filter with a trap at 0.58 MHz and the output of this low-pass filter are input.
A coring level control voltage detection circuit that outputs a voltage for controlling the coring level according to the level of the lower sideband component of the 58 MHz color signal, and a coring whose level is adjusted by the output of this coring level control voltage detection circuit. A processing circuit, a feedback circuit network that supplies the output of the coring processing circuit to an addition process with an input signal through an inverting amplifier, and an adder that corrects a vertical edge by a signal obtained by amplifying the output of the low-pass filter by the inverting amplifier. And an adder for simultaneously adding overshoot and preshoot.

[0014]

In the vertical contour correction device according to the present invention, the coring level control voltage detection circuit inputs the output signal of the low pass filter and detects the level of the color signal not removed by the low pass filter. Based on the above, the coring level of the coring processing circuit is changed. In this way, by controlling the coring level by the output of the coring level control voltage detection circuit, it is possible to prevent mixing of the color signal into the luminance signal.

[0015]

Embodiments of the present invention will now be specifically described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a vertical contour correcting device according to an embodiment of the present invention, in which a luminance signal and a chrominance signal are separated by a comb filter.

A video signal is input to the input terminal 1, and the adder 2 adds and calculates the input signal and the contour signal. The input signal is also input to the delay element 3 for one horizontal scanning period, and the signal delayed for one horizontal scanning period is output from this delay element 3. The adder 4 performs an addition operation on the input signal and the signal delayed by one horizontal scanning period, and the subtracter 5 adds the input signal to the 1
A subtraction calculation process is performed on the signal delayed in the horizontal scanning period. The low-pass filter 6 includes a color signal and a delay element 3 for one horizontal scanning period.
It is a low-pass filter that removes the clock component of the CCD used in the above, and has a characteristic that the cutoff frequency is 1.5 MHZ and the trap is at 3.58 MHZ. The output of the low-pass filter 6 is input to the inverting amplifier 7, the coring level control voltage detection circuit 8 and the coring processing circuit 9. The output of the coring processing circuit 9 is input to the adders 2 and 13 via the inverting amplifiers 10 and 11, respectively. The adder 13 arithmetically processes the output of the adder 4 having a blunt edge and the contour signal component. The output of the adder 13 is given to the luminance signal output terminal 14, and the output of the subtractor 5 is given to the color signal output terminal 12.

Next, the operation of the vertical contour correcting device of the present embodiment constructed as described above will be explained.

The video signal 15 shown in FIG. 2 is input to the input terminal 1, and this video signal 15 is delayed by one horizontal scanning period by the one horizontal scanning period delay element 3, and the signal waveform 16 shown in FIG. can get. Both the signal 15 and the signal 16 are input to the adder 4 and the subtractor 5. In this case, the adder 4 and the subtractor 5 are used for a comb filter that separates an input signal into a luminance signal and a chrominance signal by using a commonly used one horizontal scanning period delay element 3. The luminance signals added by the adder 4 remain in the same phase before and after one horizontal scanning period and remain as they are, and the chrominance signals have opposite phases, which cancel each other and are not output. On the contrary, in the subtractor 5, the in-phase and correlated luminance signals cancel each other out, and the color signal is output as it is. Accordingly, the edge signal (contour signal) and the color signal of the non-correlation part having no correlation before and after one horizontal scanning period are output to the output of the subtractor 5.

Next, the output of the subtractor 5 passes through a low-pass filter 6 to remove unnecessary color signals as contour signals. The low-pass filter 6 has a cutoff frequency of 1.5 MHz and a trap of 3.58 MHz, so that the color signal component of 3.58 MHz is
It is removed by this low pass filter 6.

The output of the low-pass filter 6 is 3.58M
The color signal having a spectrum in the lower side band of Hz and the edge signal of the non-correlation part are output and input to the inverting amplifier 7, the coring level voltage detection circuit 8 and the coring processing circuit 9, respectively.

As described above, the coring level voltage detection circuit uses the output of the low pass filter 6 at 3.58 MHz.
When the color signal component of the lower side band of 3 to 3.58 MHz is large, a control voltage for increasing the coring level is output, and when the level is small, the coring level is decreased. Output a proper control voltage.

The coring level is controlled by the coring level control voltage detection circuit 8, and the coring processing circuit 9 is operated.
Noise is removed from the signal that has passed through the inverting amplifiers 10, 1
Input to 1. The signal passed through the inverting amplifier 10 is added to the input signal by the adder 2. As a result, at the output of the adder 2, it is possible to obtain a signal waveform with an overshoot added at the rising and falling portions in the vertical direction. The signal passing through the inverting amplifier 11 is input to the adder 13 as a signal forming a preshoot, and the signal passing through the inverting amplifier 7 is input as a vertical contour correction signal. As a result, the output of the adder 13 has a luminance signal output waveform in which the vertical edge portion is corrected and the contour component is added. On the other hand, the color signal is obtained by the output of the subtractor 5.

As described above, the output of the low-pass filter 6 is input to the coring level control voltage detection circuit 8 and is not removed by the output of the low-pass filter 6 at 3.58 MH.
By controlling the coring level of the coring processing circuit 9 according to the level of the color signal having the lower sideband component of z, the coring level is increased when the lower sideband component of 3.58 MHz is large. Increase
It is possible to prevent color signals from being mixed in the adder 13 without lowering the cutoff frequency of the low-pass filter 6. Further, when the lower sideband component of 3.58MHZ is small, the coring level can be reduced and the contour component can be prevented from being buried in the coring level. Therefore, it is possible to reduce dot interference without deteriorating the vertical resolution of the luminance signal and obtain a clear image.

[0025]

As described above, according to the present invention, the output of the low pass filter is input to the coring level control voltage detection circuit, and the lower side band component of 3.58 MHZ which is not removed by the output of the low pass filter is included. By controlling the coring level of the coring processing circuit according to the level of the color signal, the coring level is increased when the lower sideband component of 3.58 MHz is large, and the cutoff frequency of the low-pass filter is increased. It is possible to prevent the color signal from being mixed in the adder without lowering the frequency, and to reduce the coring level when the lower sideband component of 3.58 MHz is small, so that the contour component is equal to the coring level. Since it can be prevented from being buried inside, dot interference can be reduced without degrading the vertical resolution of the luminance signal. It is possible to obtain a clear image.

[Brief description of drawings]

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

FIG. 2 is a signal waveform diagram of each part.

FIG. 3 is a block diagram showing a conventional vertical contour correction control device.

[Explanation of symbols]

 1; Input terminals 2, 4, 13; Adder 5; Subtractor 7, 10, 11; Inversion amplifier 12; Color signal output terminal 14; Luminance signal output terminal

Claims (1)

[Claims] 1. An addition for adding and subtracting a signal obtained by delaying an input signal by one horizontal scanning period delay element by one horizontal scanning period and an input signal to separate a luminance signal and a chrominance signal with a comb filter characteristic. And a subtractor, a low-pass filter to which the output signal of this subtractor is input and having a trap at 3.58 MHz, and the output of this low-pass filter is input to A coring level control voltage detection circuit that outputs a voltage for controlling the coring level, a coring processing circuit whose level is adjusted by the output of the coring level control voltage detection circuit, and an inverting amplifier that outputs the coring processing circuit. A feedback network that supplies the input signal via the feedback circuit and a signal obtained by amplifying the output of the low-pass filter with an inverting amplifier. A vertical contour correction device having an adder for correcting vertical edges and an adder for simultaneously adding overshoot and preshoot.