KR0141128B1 - Apparatus for separating chroma signal - Google Patents

Abstract

A separation device for separating color signals included in a video signal is disclosed. A vertical correlator having a first delay for delaying the video signal, an inverter for inverting the output from the first delay, a second delay for delaying the output from the first delay and a zero level signal generator. do.

Description

Color signal separator

1 is a view showing a color signal separation apparatus using a conventional three-line comb filter.

2A to 2D are views showing images in various cases.

3A to 3H are views showing the position of the horizontal scan line on the screen when the image shown in FIGS. 2A to 2D is input.

4A to 4H are diagrams showing angular waveforms in FIG. 1 when the image shown in FIGS. 2A to 2D is input.

5 is a view showing a color signal separation apparatus using a three-line comb filter of the present invention.

6A to 6H are diagrams showing respective waveforms in FIG. 5 when the image shown in FIGS. 2A to 2D is input.

7 is a view showing another embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1, 2: Delayer 3: Inverter

4, 5, 6: Bandpass filter 7, 8, 12: Low voltage detector

9, 10, 11: high voltage detector 13: adder

14: zero level signal generator 16: delay

17: Subtractor

The present invention relates to a color signal processing apparatus of a color image signal reproducing apparatus, and more particularly, to an apparatus for removing a cross-color included in a carrier color signal in an image having a vertical noncorrelation portion or a high luminance gradient line. will be.

Nowadays, color television systems use composite video signals in which color signals (carrier color signals) balanced by color carriers are frequency superimposed on luminance signals. For this reason, a luminance / color signal separation device is required on the receiving side. Early luminance / color signal separation devices used low pass filters and band pass filters. However, the low pass filter and the band pass filter cannot completely separate the luminance signal and the color signal, causing problems such as cross color (color signal component generated by the luminance signal component) and color bleeding. Since then, a two-line comb filter (comb filter) has been developed, which greatly improves the luminance / color signal separation performance. The two-line type comb filter uses the same phase of the luminance signal and inverts the phase of the color signal in two adjacent horizontal scan lines, delaying one horizontal scan line for one horizontal scanning period, and subtracting it from the next horizontal scan line. A color signal from which the luminance signal is canceled is obtained and used again to separate the luminance signal. However, since the two-line type comb filter adds or subtracts color signals of two horizontal scan lines, color smearing in the vertical direction cannot be avoided. To solve this problem, a method of adding or subtracting color signals of three horizontal scan lines, that is, a three-line comb filter, has been proposed. In a three-line comb filter, the color signal at a horizontal scan line is determined by the correlation between the horizontal scan line and the signals adjacent to the front and rear thereof. Therefore, the vertical resolution is increased and the horizontal DOT interference and cross-color are hardened. However, in the conventional three-line comb filter, there is a problem in that cross-color removal in the vertical non-correlated portion (the portion not correlated between adjacent horizontal scan lines) is insufficient and cross collar removal in the high-brightness inclined line portion is impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved color signal separation device capable of efficiently removing cross collars in vertical uncorrelated portions and in high luminance oblique line portions.

A color signal separation apparatus of the present invention for achieving the above object is in the device for separating the color signal from the video signal including the color signal modulated by the color carrier,

A first delayer for delaying and outputting the video signal for a predetermined period;

A second delayer which outputs the output of the first delayer and delays the output by the same period as the first delayer;

An inverter for introducing an output of the first delay unit and outputting the phase inverted;

A first low voltage detector configured to input the output of the video signal and the inverter and to select and output a signal having a low voltage level among them;

A second low voltage detector for introducing an output of the inverter and an output of the second delay unit, and selecting and outputting a signal having a low voltage level among them;

A first high voltage detector configured to input the output of the video signal and the inverter and to select and output a signal having a high voltage level among them;

A second high voltage detector configured to input an output of the inverter and an output of the second delay unit, and select and output a signal having a high voltage level among them;

A zero level signal generator for generating a color signal modulated by a zero level chroma signal;

A third high voltage detector configured to input an output of the first low voltage detector, an output of the second low voltage detector, and an output of the zero level signal generator, and select and output a signal having a high voltage level among them;

A third low voltage detector configured to input an output of the first high voltage detector, an output of the second high voltage detector, and an output of the zero level signal generator, and select and output a signal having a low voltage level among them; And

And an adder for introducing the output of the third high voltage detector and the output of the third low voltage detector and adding them to output a color signal separated from the image signal. Hereinafter, the color signal separation apparatus of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a three-line comb filter as disclosed in US Pat. No. 4,930,005. The three-line comb filter shown in FIG. 1 includes first and second delayers 1, 2, an inverter 3, and a vertical correlator 15. The vertical correlator 15 includes first, second, and third high voltage detection circuits (hereinafter referred to as MAX circuits) 9, 10, 11, first, second, and third circuits. Lower Voltage Detecting Circuits (hereinafter referred to as MIN circuits) 7, 8, 1, and an adder 13. Here, the delay characteristic of the retarders 1, 2 is 1H in-between syringe 1H for NTSC.

The operation of the luminance / color signal separation device according to the configuration will be described with reference to FIGS. 2A to 2C and 3A to 3C. The color signal from a bandpass filter (not shown) having a frequency characteristic in which the frequency of the color carrier is a pass frequency (3.58 MHz in the case of NTSC) is obtained by using the first delay unit (1), the first MIN circuit (7), and the first MAX. Supplied to the circuit 9.

The delayed signal b output from the first delay unit 1 is supplied to the inverter 3 and the second delay unit 2.

The inverted signal d from the inverter 3 is supplied to the first MIN circuit 7, the second MIN circuit 8, the first MAX circuit 9, and the second MAX circuit 10. The delayed signal c output from the second delay unit is supplied to the second MIN circuit 8 and the second MAX circuit 10.

In the first MIN circuit 7, the first low voltage signal h between the carrier color signal a and the inverted signal d is obtained, the first low voltage signal h is obtained, and the first low voltage signal h is the third MAX circuit 11. Is supplied. In the second MIN circuit 8, a second voltage signal i between the inverted signal d and the signal c delayed by the second delay unit 2 is obtained, and this second low voltage signal, i is the third MAX circuit 11 Is supplied. In the third MAX circuit 11, the third high voltage signal m between the first low voltage signal h and the second low voltage signal i is obtained, and the third high voltage signal m is supplied to the adder 13. In the first MAX circuit 9, the first high voltage signal h between the carrier color signal a and the inverted signal d is obtained, and the first high voltage signal i is supplied to the third MIN circuit 12. In the second MAX circuit 10, a second high voltage signal h is obtained between the inverted signal d and the signal c delayed by the second delay unit 2, and the second high voltage signal h is obtained by the third MIN circuit 12. Supplied to. In the third MIN circuit 12, the third low voltage signal n between the first high voltage signal j and the second high voltage signal k is obtained, and the third low voltage signal n is supplied to the adder 13. In the adder 13, a signal o obtained by adding the third high voltage signal m and the third low voltage signal n is obtained, and the added o is output as an output signal of the three-line comb filter.

The operation of the three-line comb filter for removing color blur from the color signal will be described. It is assumed that a color signal having an original image as shown in FIG. 2A is applied to the three-line comb filter of FIG. The image is composed of an uncolored part (A) at the top, a part (C) with a color of the middle, and an uncolored part (E) at the bottom. The symbol V represents the first line of the middle colored portion C, and the symbol D represents the first line of the lower colored portion.

When the signal corresponding to the portion B is output from the first delay unit 1, the sequential horizontal scan line signals a ', b', and c 'are displayed as shown in FIG. 3A. In this case the respective signals a, b, c, d, h, i, j, k, m, n and o without crosstalk are shown in Figure 4A.

When the signal corresponding to the portion D is output from the first delay unit 1, the horizontal scan line signals a ', b', and c 'are displayed on the screen as shown in FIG. 3B. In this case the respective signals a, b, c, d, h, i, j, k, m, n and o are shown in Figure 4B. In the signal o, it can be seen that no color signal is output.

If the sequential signals a ', b', and c 'have the same color, all signals a, b, c, d, h, i, j, k, m, n, and have the same color o is as shown in Fig. 4C. In the case where all signals do not have color, a signal o without color is obtained.

The color signal separation operation in the vertical uncorrelated portion (the portion where there is no correlation between the horizontal scan lines) will be described. It is assumed that a color signal having an original image as shown in FIG. 2B is applied to a three-line comb filter. In this image, a portion with a color signal and a portion without a color signal are repeated at intervals corresponding to the width of one horizontal scanning line in the center portion. The symbol F is denoted to indicate any part with a color signal and G is used to denote any part without a color signal. In this case, when the signal corresponding to the portion F is output from the first delay unit 1, the sequential horizontal scanning line signals a ', b' and c 'on the screen are displayed as shown in FIG. 3D. In this case the respective signals a, b, c, d, h, i, j, k, m, n and the signal o with color are shown in FIG. 4D.

When a signal corresponding to the portion G is output from the first delay unit 1, sequential horizontal scan line signals a ', b' and c 'are displayed as shown in FIG. 3E. In this case the respective signals a, b, c, d, h, i, j, k, m, n and a signal o with color are shown in FIG. 4E. Therefore, it can be seen that the color is attached to the part without color.

An operation of removing the luminance signal of the component corresponding to the frequency of the color carrier is described. It is assumed that a carrier color signal having an original image as shown in FIG. 2C is applied to a three-line comb filter. In this image, vertical lines arranged at intervals corresponding to one-half of the wavelengths of the color carriers are arranged in the upper portion H of the screen, and the lower portion I is assumed to have a flat surface with no change in luminance. The symbol J represents any horizontal scan line in the upper part H and the symbol K represents the last horizontal scan line in the upper part K. When the signal corresponding to the J portion is output from the first delay unit 1, the horizontal scan line signals a ', b' and c 'are displayed as shown in FIG. 3F on the screen. In this case, the respective signals a, b, c, d, h, i, k, m, n and the signal o from which the cross color is removed are shown in FIG. 4F. When the signal corresponding to the portion K is output from the first delay unit 1, the horizontal scan line signals a ', b' and c 'are displayed as shown in FIG. 3G on the screen. In this case, the respective signals a, b, c, d, h, i, j, m, n and a signal o having an inverse luminance signal are shown in FIG. 4G.

The operation in the case of having a high brightness oblique line will be described. It is assumed that a signal having an original image as shown in FIG. 2D is input to a three-line comb filter. The image of FIG. 2G has a high luminance line in an oblique direction on the screen. It is assumed that the horizontal distance between adjacent high-level inclination lines and the adjacent horizontal scan lines is 1/2 of the wavelength of the color carrier. The symbol L is shown to represent the scanning line at any position on the screen. When the signal corresponding to the L portion is output from the first delay unit 1, the sequential horizontal scan line signals a ', b' and c 'are displayed as shown in FIG. 3H. In this case, the signals o having respective signals a, b, c, d, h, i, j, k, m, n and a half wavelength luminance signal are shown in FIG. 4H.

As described above, in the conventional three-line comb filter, color signal separation in the vertical uncorrelated portion (Fig. 4E), cross color removal by the luminance signal (Fig. 4G) having the frequency of the color carrier, and high luminance gradient line ( It can be seen that the cross-color removal in FIG. 4H) is insufficient.

5 is a view showing a color signal separation device of the present invention. The color signal separation device of the present invention shown in FIG. 5 is similar to the conventional color signal separation device shown in FIG. 1 except for the zero level signal generator 14. The same reference numerals as those of FIG. 1 perform the same operations as those of FIG. 1, and a description thereof will be omitted.

The color signal separation device of the present invention shown in FIG. 5 includes first and second delayers (1, 3), inverter (3), first and second band pass filters (4, 5, 6), and A vertical correlator 15.

The delay characteristic of the retarders 1 and 2 is one horizontal syringe stem 1H for NTSC. The first, second and third band pass filters 4, 5 and 6 have the frequency of the color carrier (3.58 MHz in the case of NTSC) as the pass frequency. The vertical correlator 15 includes a low voltage detection circuit 7, 8, 12, a high voltage detection circuit 9, 10, 11, an adder 13, and a zero level signal generator 14.

The zero level signal generator 14 of the present invention generates a signal without a color signal. A signal without a color signal is, for example, the same signal as o in FIG. 3C. In the current color television system, the color signal (carrier color signal) modulated by the color carrier is superimposed on the luminance signal and separated from the received color signal through a band pass filter having a band pass frequency corresponding to the frequency of the color carrier. The color signal superimposed on the luminance signal changes its center value according to the potential change of the luminance signal, but the carrier color signal through the bandpass filter becomes a sine wave oscillating up and down with a constant center. In other words, when a color signal is present, it has a sinusoidal wave shape that vibrates with a certain phase and wave height, and maintains a constant potential when there is no color signal. In a normal case, this constant potential becomes the ground power source OV. The zero level signal generator of the present invention preferably includes a constant voltage power supply, but may be grounded directly or through a resistor or the like. The zero level signal 1 from the zero level signal generator 11 is supplied to the third high voltage detection circuit 9 and the third low voltage detection circuit 10.

The operation of the color signal separation device of the present invention shown in FIG. 5 will be described with reference to FIGS. 2A-2D, 3A-3H and 6A-6H.

The color signal separation operation in the vertical correlation portion will be described. When a signal corresponding to part B of FIG. 2A is output from the first delay unit 1, the sequential horizontal scan line signals a ', b' and c 'on the screen are displayed as shown in FIG. 3A. In this case the respective signals a, b, c, d, h, i, j, k, m, n and o without cross talk are shown in FIG. 6A.

When the signal corresponding to the portion D of FIG. 2 is output from the first delay unit 1, the horizontal scan line signals a ', b' and c 'on the screen are displayed as shown in FIG. 3B. In this case the respective signals a, b, c, d, h, i, j, k, l, m, n and o are shown in Figure 6B. In the signal o, it can be seen that no color signal is output.

When the sequential signals a ', b' and c 'have the same color, all the signals a, b, c, d, h, i, j, k, l, m, n and the same color o is as shown in FIG. 6C. In the case where all signals do not have color, a signal o without color is obtained.

When the signal corresponding to the portion F of FIG. 2B is output from the first delay unit 1, the sequential horizontal scan line signals a ', b' and c 'are displayed on the screen as shown in FIG. 3D. In this case the respective signals a, b, c, d, h, i, k, l, m, n and the signal o with color are shown in FIG. 6D. When a signal corresponding to the portion G is output from the first delay unit 1, sequential horizontal scan line signals a ', b' and c 'are displayed as shown in FIG. 3E. In this case each of the signals a, b, c, d, h, i, j, k, l, m, n and a signal o without color are shown in FIG. 6E.

An operation of removing the luminance signal of the component corresponding to the frequency of the color carrier is described. When a signal corresponding to the portion J of FIG. 2C is output from the first delay unit 1, the horizontal scan line signals a ', b' and c 'on the screen are displayed as shown in FIG. 3F. In this case, the respective signals a, b, c, d, h, i, j, k, l, m, n and the signal o from which the cross color is removed are shown in FIG. 6F. When the signal corresponding to the portion K is output from the first delay unit 1, the sequential horizontal scan line signals a ', b' and c 'are displayed as shown in FIG. 3G. In this case, the respective signals a, b, c, d, h, i, j, k, l, m, n and a signal o having no luminance signal are shown in FIG. 6G.

The operation in the case of having a high brightness oblique line will be described. When the corresponding signal of the L portion of FIG. 2D is output from the first delay unit 1, the sequential horizontal scan line signals a ', b' and c 'on the screen are displayed as shown in FIG. 3H. In this case, the respective signals a, b, c, d, h, i, j, k, l, m, n and a signal o having no luminance signal are shown in FIG. 6H.

As described above, it can be seen that the color signal separation device of the present invention removes the cross color in the vertical uncorrelated portion and the portion having the high brightness oblique line, thereby achieving improved color signal separation compared to the conventional color signal separation apparatus.

Those skilled in the video signal processing will be well aware of the separation of the luminance signal using the color signal obtained through the color signal separation apparatus of the present invention. Such a luminance signal separation device generally includes a delayer and an adder for correcting a transmission delay error with a color signal processed through a vertical correlator.

7 is a view showing an example of such a luminance / color signal separation device. In FIG. 7, the signal b delayed by the first delay unit 1 is adjusted so that the phase with the color signal o separated by the third delay unit 16 for correction is appropriately placed and input to the subtracted means of the subtractor 17. do. The color signal o is supplied from the subtractor of the subtractor 17. In the output terminal of the subtractor 17, the separated luminance signal p can be obtained.

The apparatuses of the present invention can be commonly applied to NTSC and PAL. For example, the delayers shown in FIGS. 5 and 7 delay by one horizontal syringe stem 1H. This is because in the NTSC system, the phase of the color carrier is opposite between adjacent horizontal scan lines.

Since the phase of the color carrier is 90 ° between adjacent horizontal scan lines in the PAL method, the delay characteristics of the retarders may be changed to 2H to be applied to the PAL method. In addition, the pass frequency of the band pass filter is also 4.3 MHz in the PAL method.

Accordingly, it is apparent that the objects and spirit of the present invention should not be limited to the embodiments shown but should be determined by the appended claims.

Claims (5)

An apparatus for separating a color signal from an image signal including a color signal modulated by a color carrier, A first delay unit (1) for delaying and outputting the video signal for a predetermined period; A second delayer (2) which inputs the output of the first delayer (1) and delays the output by the same period as the first delayer (1); An inverter (3) for introducing an output of the first delay unit (1), and inverting the output of the first delay unit (1); A first low voltage detector (7) for introducing the video signal and the output of the inverter (3) and selecting and outputting a signal having a low voltage level among them; A second low voltage detector (8) for inputting an output of the inverter (3) and an output of the second delay unit (2), and selecting and outputting a signal having a low voltage level among them; A first high voltage detector (9) for introducing the video signal and the output of the inverter (3) and selecting and outputting a signal having a high voltage level among them; A second high voltage detector (10) for introducing an output of the inverter (3) and an output of the second delay unit (2), and selecting and outputting a signal having a high voltage level among them; A zero level signal generator 14 for generating a signal modulated by a zero level chroma signal; The output of the first low voltage detector 7, the output of the second low voltage detector 8, and the output of the zero level signal generator 14 flow in and select and output a signal having a high voltage level among them. A third high voltage detector 11; An output 9 of the first high voltage detector, an output 10 of the second high voltage detector, and an output of the zero level signal generator 14 to select and output a signal having a low voltage level among them; 3 low voltage detector; And And an adder (13) for introducing the output of the third high voltage detector (11) and the output of the third low voltage detector (12) and adding them to output a color signal separated from the image signal. The color signal separation device according to claim 1, wherein the first delay unit (1) and the second delay unit (2) are 1H delay units which delay by one horizontal scanning period (1H) according to the NTSC method. The color signal separation device according to claim 1, wherein the first delay unit (1) and the second delay unit (2) are 2H delay units for delaying by 2H between two horizontal syringes according to the PAL method. 2. The color signal separation method according to claim 1, wherein the zero level signal generator (14) generates a signal having a ground potential. A first video signal including a color signal modulated by a color carrier, a second video signal obtained by delaying the first video signal by one horizontal scanning period (NTSC) or two horizontal scanning periods (PAL) and inverting a phase; and In a vertical correlator for injecting a third video signal obtained by delaying the first video signal by two horizontal scanning periods (NTSC) or four horizontal scanning periods (PAL), and separating the color signal by the vertical correlation of the video signal, A first low voltage detector (7) which inputs the first video signal and the second video signal and selects and outputs a signal having a low voltage level among them; A second low voltage detector (8) which receives the second video signal and the third video signal and selects and outputs a signal having a low voltage level among them; A first high voltage detector (9) which inputs the first video signal and the second video signal and selects and outputs a signal having a high voltage level among them; A second high voltage detector 10 which inputs the second video signal and the third video signal and selects and outputs a signal having a high voltage level among them; A zero level signal generator 14 for generating a color signal modulated by a zero level chroma signal; A first input of an output of the first low voltage detector 7, an output of the second low voltage detector 8, and an output of the zero level signal generator 14 to select and output a signal having a high voltage level among them; 3 high voltage detector 11; An output of the output of the first high voltage detector 9, the output of the second high voltage detector 10, and an output of the zero level signal generator 14 to select and output a signal having a low voltage level among them; 3 low voltage detector 13; And And an adder (13) for adding the output of the third high voltage detector (11) and the output of the third low voltage detector (12) to output a color signal separated from the image signal.