JPH06121333A - Yc separator provided with vertical outline correction - Google Patents

Abstract

PURPOSE:To obtain a clear picture by reducing a dot disturbance even when a chroma signal component is mixed with an outline signal component, at the time of a vertical outline correction. CONSTITUTION:At the time of the vertical outline correction, an overshoot and a pre-shoot are simultaneously added by using only one 1H delay element 2. And also, at the time of supplying the output of a core ring processing circuit 8 through an inversion amplifier 10 to an adder 12, a switch 11 is provided. The switch 11 is controlled by a switch control detecting circuit 7 which inputs a signal obtained by allowing the outline component obtained by the subtraction processing of an input signal and a 1H delayed signal to pass through a low pass filter 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image device used in TVs, VTRs, etc., and more particularly to a YC separation device with vertical contour correction for reducing dot interference due to leakage of chroma components.

[0002]

2. Description of the Related Art A conventional YC separation device with vertical contour correction used in TVs, VTRs and the like has a comb filter characteristic and is capable of separating a luminance signal and a carrier color signal. Moreover, the preshoot and the bober shoot are simultaneously added to the vertical contour by using only one horizontal scanning period delay element.

FIG. 3 is a block diagram of a YC separation device with vertical contour correction having a comb-shaped filter characteristic showing such a conventional example. As shown in FIG. 3, the conventional YC separator with vertical contour correction has an adder 1 for adding a feedback signal to a video signal from an input terminal IN, and a horizontal scanning period delay for delaying the output of the adder 1. The element 2, the adder 3 and the subtracter 4 for adding and subtracting the video input signal and the output of the one horizontal scanning period delay element 2, respectively, and the subtractor 4 having a characteristic of a cutoff frequency of about 1.6 MHZ. A low-pass filter 5 for performing a filtering process on the output of the, and an inverting amplifier 6 for inverting and amplifying the output of the low-pass filter 5,
Similarly, the output of the low-pass filter 5 is input, the coring processing circuit 8, the inverting amplifiers 9 and 10 for inverting and amplifying the output of the coring processing circuit 8, the output of the adder 3 and the output of the inverting amplifiers 6 and 10, respectively. And an adder 12 for adding. The output of the inverting amplifier 9 is the adder 1
The output of the adder 12 is output from the luminance signal output terminal OUT1 as a luminance signal, and the output of the subtractor 4 is output from the color signal output terminal OUT2 as a color signal.

First, a video signal is input to the input terminal IN. Although this video signal omits the sync signal and the burst signal for convenience, it is a window window waveform in a black screen on the screen, and the horizontal axis is V rate display. Next, this video signal is input to the delay element 2 for one horizontal scanning period via the adder 1. As a result, the video delay signal is obtained by being delayed by one horizontal scanning period. These video signal and video delay signal are both input to the subtractor 4. The phase of the color signal in the subtractor 4 is inverted before and after one horizontal scanning period. This is because the color signal strength calculation is performed to separate the luminance signal and the color signal of the Kumi filter characteristic, which makes use of the characteristic of the NTSC signal that the signals before and after one horizontal scanning period are similar. Therefore, at the output of the subtracter 4, a signal in which only the non-correlated edge portion remains before and after one horizontal scanning period with the color signal component is obtained. The subtractor 4 does not output the luminance signals having a correlation before and after one horizontal scanning period because they have the same phase.

Next, the signal is passed through the low-pass filter 5 for the purpose of removing a color signal which is an unnecessary signal among the color signal and the uncorrelated edge signal output from the subtractor 4. This low-pass filter 5 has a cutoff frequency of about 1.5 MHz.
It has a trap in the order of 3.58 MHZ and the color signal is removed here. Moreover, one output of the low-pass filter 5 is input to the adder 12 via the inverting amplifier 6.

On the other hand, the adder 3 inputs an input signal and a signal delayed by one horizontal scanning period, and outputs a signal having a blunt edge waveform. The output waveform of the adder 3 is added to the inverting amplifier 6
The signal passed through is calculated by the adder 12, and as a result, the edge-corrected signal is obtained.

The other output of the low-pass filter 5 is input to the coring processing circuit 8, and the low-pass filter 5 removes noise contained in the output, and the inverting amplifier 9
And 10 are input. Since the signal that has passed through the inverting amplifier 9 is input to the adder 1 as a feedback signal, the adder 1 performs arithmetic processing of the input video signal and the output of the inverting amplifier 9.
As a result, at the output of the adder 1, it is possible to obtain a signal waveform with overshoot added at the rising and falling portions in the vertical direction. Further, the signal passed through the inverting amplifier 10 is input to the adder 12. As a result, the adder 12
In addition to the overshoot added by the adder 3, the preshoot is simultaneously added to the output of 1 and the output waveform in which the vertical contour component is added can be obtained.

FIGS. 4A and 4B are energy characteristic diagrams of the luminance signal and the color signal in FIG. 3, respectively. As shown in FIG. 4A, 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 centering on the chrominance subcarrier. The band is ± 500 KHZ centered on 3.58 MHZ. However, the low-pass filter 5 has a cutoff frequency of 1.
Since it is about 5 MHZ and has a trap at 3.58 MHZ, when a color signal is passed through this low-pass filter 5, the color signal component of the upper side band component of 3.58 MHZ can be removed. However, since the cutoff frequencies are relatively close to 1.5 MHZ and 3.58 MHZ, it is difficult to remove the sideband component below 3.58 MHZ. This state is shown in FIG.

As shown in FIG. 4B, in the signal passing through the low-pass filter 5 and the coring processing circuit 8,
When a color signal component that cannot be removed by the low-pass filter 5 and the coring processing circuit 8 is mixed, as a result, the color signal is mixed in the luminance signal. This causes an increase in dot interference. In order to avoid this effect, a circuit may be considered in which the cutoff frequency of the low-pass filter 5 is further lowered below 1.5 MHZ to remove the lower side band component of 3.58 MHZ. Since the vertical component is attenuated, the vertical resolution of the luminance signal is deteriorated.

[0010]

SUMMARY OF THE INVENTION In the conventional YC separation device with vertical contour correction described above, a color signal is mixed with a luminance signal,
Since dot interference increases, there is a drawback that a clear image cannot be obtained on the screen. Further, even if the cut-off frequency of the low-pass filter for avoiding this effect is further lowered, the vertical component of the luminance signal is attenuated, so that the vertical resolution of the luminance signal is deteriorated.

An object of the present invention is to provide a YC separation device with vertical contour correction capable of preventing a color signal from mixing in such a luminance signal and obtaining a clear image without lowering the cutoff frequency of a low pass filter. To provide.

[0012]

A YC separation device with vertical contour correction according to the present invention is a switch control voltage detection circuit for receiving the output of a low pass filter and detecting the level of a chroma signal which has not been removed by the low pass filter. And a switch for turning on and off the input to the adder that is driven by the output of the switch control voltage detection circuit and outputs a luminance signal.

[0013]

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

FIG. 1 is a block diagram of a YC separation apparatus with vertical contour correction showing an embodiment of the present invention. As shown in FIG. 1, this embodiment separates a luminance signal and a chrominance signal by a comb filter. Also in this embodiment, the adder 1 for adding the video signal and the contour signal input from the input terminal IN, the one horizontal scanning period delay element 2 for delaying the output of the adder 1, the input signal and the one horizontal scanning period delay An adder 3 and a subtracter 4 for computing the processed signals, a CCD having a cutoff frequency of 1.6 MHZ and a trap at 3.58 MHZ, and a color signal and a CCD used for one horizontal scanning period delay element 2. Of the low pass filter 5, an inverting amplifier 6 that outputs and inverts and amplifies the low pass filter 5, a coring processing circuit 8, inverting amplification circuits 9 and 10, and a blunt edge portion. 1 for calculating the output of the adder 3 and the contour component
2 and these are the same as the conventional example described above. The difference from the present embodiment is that a switch control voltage detection circuit 7 for detecting a switch control voltage based on the output of the low pass filter 5 and a switch 11 controlled by the detection circuit 7 are provided. Also, the luminance signal output terminal OUT1
And the color signal output terminal OUT2 are the same. In particular, switch 11 passes or blocks the output of inverting amplifier 10 to adder 12.

FIG. 2 is a waveform diagram of signals at respective parts in FIG. As shown in FIG. 2, the video input signal a is input terminal IN.
Is input from the delay element 2 for one horizontal scanning period.
It is delayed by the horizontal scanning period to obtain the video delay signal b. The video signal a and the video delay signal b are both input to the adder 3 and the subtractor 4. The adder 3 and the subtractor 4 here are used for a Kumi filter that separates a luminance signal and a chrominance signal by using a generally used one horizontal scanning period element 2. In particular, the luminance signal added by the adder 3 is 1
Since they are in phase before and after the horizontal scanning period, they remain as they are, and since the color signals are in opposite phase, they do not cancel each other out. On the contrary, in the subtracter 4, the in-phase and correlated luminance signals do not cancel each other out, but the chrominance signal remains as it is. Therefore, the edge signal C of the non-correlation part and the color signal are output to the output of the subtractor 4.

Next, of the output of the subtractor 4, a low pass filter 5 is passed in order to remove a color signal unnecessary as a contour signal. The low-pass filter 5 has a cutoff frequency of 1.6 MHZ and a trap of 3.58 MHZ, so that the color signal component of 3.58 MHZ is removed. The output of the low-pass filter 5 is 3.
A color signal having a spectrum in the lower side band of 58 MHZ, that is, a level of 3 MHZ to 3.58 MHZ is detected by the switch control voltage detection circuit 7, and the switch 11 is controlled according to the level. Furthermore, the output of the low-pass filter 5 is input to the core-limb processing circuit 8 and the inverting amplifier 6 as in the conventional example. The switch control voltage detection circuit 7 is provided with the low-pass filter 5 as described above.
Is the lower sideband of 3.58MHZ8 at the output of 3
When the level of the color signal component of up to 3.58 MHZ is high, the control voltage is output so as to turn off the switch 11. Conversely, when the level is low, the switch 11 is turned on.
The control voltage is output so that

On the other hand, the signal passed through the inverting amplifier 6 is added by the adder 1
Noise is removed from the output signal of the low-pass filter 5 supplied to No. 2 and inputted to the coring processing circuit 8 and inputted to the inverting amplifiers 9 and 10, respectively. The signal passing through the inverting amplifier 9 is fed back to the adder 1 and added to the input signal a.

As a result, it is possible to obtain a signal in which overshoot is added to the output of the adder 1 at the rising and falling portions in the vertical direction. The signal that has passed through the inverting amplifier 10 is input to the adder 12 via the switch 11 that is controlled by the output of the switch control voltage detection circuit 7. Therefore, in the adder 12, the signal d whose waveform at the edge portion is the output of the adder 3 and the signal e which has passed through the inverting amplifier 6 and serves as a signal for edge portion correction, the coring processing circuit 8, the inverting amplifier 10, The signal forming the preshoot that has passed through the switch 11 is arithmetically processed, and as a result, the luminance signal output f to which the vertical contour component is added can be obtained. The color signal is obtained from the output of the subtractor 4.

[0019]

As described above, the YC separation device with vertical contour correction of the present invention is provided with the switch control voltage detection circuit for inputting the output of the low pass filter and the switch controlled by the circuit, and is removed by the low pass filter. By controlling the switch depending on the level of the color signal having the spectrum of the lower sideband component of 3.58MHZ, which is not present, the adder of the output stage even when the lower sideband component of 3.58MHZ is large It is possible to prevent a color signal from being mixed in, and reduce dot interference without lowering the cutoff of the low-pass filter and without deteriorating the vertical resolution of Y, and obtain a clear image. The effect is that you can do it.

[Brief description of drawings]

FIG. 1 is a block diagram of a YC separation device with vertical contour correction showing an embodiment of the present invention.

FIG. 2 is a waveform diagram of signals of respective parts in FIG.

FIG. 3 is a block diagram of a conventional YC separation device with vertical contour correction showing an example.

4 is an energy characteristic diagram of a luminance signal and a color signal in FIG.

[Explanation of symbols]

 1,3,12 Adder 2 1 Horizontal scan period delay element 4 Subtractor 5 Low pass filter 6,9,10 Inversion amplifier 7 Switch control voltage detection circuit 8 Coring processing circuit 11 Switch IN Video signal input terminal OUT1 Luminance signal output terminal OUT2 Color signal output terminal

Claims (2)

[Claims] 1. A switch control voltage detection circuit that receives the output of a low pass filter and detects the level of a chroma signal that has not been removed by the low pass filter, and a luminance signal driven by the output of the switch control voltage detection circuit. YC with vertical contour correction, characterized in that it has a switch for turning on and off an input to an adder for outputting.
Separation device. 2. A first for adding an input signal and a feedback signal
Adder, one horizontal scanning period delay element for delaying one horizontal scanning period with respect to the output of the first adder, and a second addition for adding the input signal and the output of the one horizontal scanning period delay element. And a subtractor for performing subtraction between the input signal and the output of the one horizontal scanning period delay element, a low-pass filter having the trap of 3.58 MHZ as an input, and an output of the low-pass filter To a coring processing circuit for performing coring processing, a first inverting amplifier for inverting amplification, second and third inverting amplifiers for respectively inverting and amplifying outputs of the coring processing circuit, and the third inverting amplifier. The switch connected to the output side of the inverting amplifier and the output of the low-pass filter detect the level of the lower sideband component of the 3.58 MHZ color signal, and A switch control voltage detection circuit for controlling the switch, a feedback circuit for supplying the output of the second inverting amplifier to the addition processing with the input signal, the second adder, the first inverting amplifier, and A YC separation device with vertical contour correction, comprising: a third adder for adding signals from the switches to disable overshoot and premute at the same time.