JPH06292230A - Luminance signal separator circuit - Google Patents

Abstract

PURPOSE:To separate a luminance signal in an excellent way by obtaining a signal of only an edge part of a color in the vertical direction and adding a luminance signal with a color residual component to the color edge so as to cancel the edge. CONSTITUTION:A composite video signal (b) delayed by 1H at a 1H delay circuit 11 is inputted to a delay circuit 32 delaying the signal by a period n/2 of a chrominance subcarrier, the circuit 32 delays further the passing signal (b) by a period n/2 of the chrominance subcarrier to provide a resulting output, which is fed to an adder 33. Furthermore, an output signal (k) of a delay circuit 17 is inputted to the adder 33. The adder 33 adds the signal delayed at the circuit 32 by a predetermined time and the signal (k) delayed by a predetermined time at the circuit 17 to output a sum signal (s). The signal (s) and a signal inverting the passing signal (r) are inputted to an adder 34, in which adds them to output an output signal (t), that is, a luminance (Y) signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a luminance signal separating circuit for effectively separating a luminance signal from a composite video signal in a color television receiver, for example.

[0002]

2. Description of the Related Art In the NTSC system, red, green and blue primary color signals are regenerated into a luminance signal representing the brightness of the screen and a color signal having hue and saturation information and transmitted. In order to reproduce the correct color, the luminance signal has already been sent for the monochrome receiver, so for the color receiver, it is necessary to send the color signal that becomes the primary color signal when added to the luminance signal. .

The relationship between the chrominance subcarrier for carrying the chrominance signal and the luminance signal is selected as shown in FIG. 3 so that interference does not occur between the signals. That is, 0 to 4.2M
Hz luminance signal (Y signal) and the high frequency equivalent part of the luminance signal
A color signal (C signal) having 3.579545 MHz as a subcarrier is inserted. Therefore, in order to reproduce a broadcast signal with a color receiver, it is necessary to separate the luminance signal and the color signal. As a method of separating the luminance signal and the color signal and extracting the luminance signal, the following method is usually used. The first method is a method using a trap. As shown in FIG. 4, the composite video signal input from the input terminal 1 of the composite video signal is passed through the trap circuit 2 of 3.58 MHz to generate a color subcarrier. The neighboring frequency components are removed, that is, the color signal is absorbed and only the luminance signal is extracted. Then, a luminance signal is obtained at the output terminal 3. Although the color signal is not shown, the composite video signal is 3.58 MHz ± 0.5 MHz.
It is taken out by passing through the band filter of.

The second method is a method using a comb filter. The NTSC system utilizes the property that the phase of the color subcarrier is inverted (reverse phase) every horizontal period (1H). FIG. 5 shows the configuration of the comb filter.

In FIG. 5, reference numeral 1 denotes an input terminal of the composite video signal, and the composite video signal input to this terminal 1 is delayed by 1H in the delay circuit 2 for one horizontal period (1H) and added to the adder circuit 3. To be In the adder circuit 3, the signal before delay and 1
Add the H delayed signals. Further, reference numeral 4 is a gain of 1.
It is a water reducer of / 2 and reduces the output signal of the addition circuit 3 to 1/2. Then, a luminance signal is obtained at the output terminal 5.

Further, in recent years, as a third method, for example, a method of separating by utilizing the correlation of color components in a 3-line composite video signal as shown in FIG. 7 has been used.

In FIG. 7, terminal 6 is an input terminal for a composite video signal. Reference numerals 7 and 8 are 1H delay circuits, and reference numerals 9, 10 and 11 are band pass filters (BPF) that pass a 3.58 MHz component. Further, 12 and 15 are intermediate value level detecting circuits, 16 is a polarity inverting circuit, 13, 14 and 1
Reference numeral 7 is an adder circuit. The terminal 18 is a luminance signal output terminal that outputs a luminance signal.

The intermediate value level detection circuits 12 and 15 are circuits for selectively outputting the intermediate level among the levels presented by a plurality of inputs.

The operation of the luminance signal separation circuit having such a configuration will be described.

As shown in FIG. 7, the composite video signal input from the input terminal 6 is supplied to the intermediate value level detection circuit 12 via the filter BPF 9 which passes the 3.58 MHz component. Further, the input composite video signal becomes a signal delayed by the 1H delay circuit for 1H period. The signal delayed for this 1H period is band-limited by the BPF 10, inverted by the polarity inversion circuit 16, and supplied to the intermediate value level detection circuit 12.

On the other hand, the signal delayed by the 1H delay circuit 7 for 1H period is again delayed by the 1H delay circuit 8 for 1H period, that is, a signal delayed by 2H period is generated. The signal delayed for this 2H period is band-limited by the BPF 11 and supplied to the intermediate value level detection circuit 12.

Therefore, the intermediate value level detecting circuit 12
In short, in short, the composite video signal which is the input signal, the signal delayed by 1H period and inverted, and the signal delayed by 2H period are input, and the signals in the vicinity of the respective color subcarriers are compared, that is, the above-mentioned 3 A first intermediate value signal for selectively outputting an intermediate level signal of the two signals is obtained. This first intermediate value signal is supplied to the intermediate value level detection circuit 15.

Further, a signal in which the composite video signal of the input signal is band-limited and a signal in which the composite video signal is delayed by one horizontal period and band-limited and inverted are added by the adder 13 to produce a first addition output. Get the signal. Further, a signal delayed for 2H period and band limited and a signal delayed for 1H period and inverted are added by the adder 14 to obtain a second addition output signal.

Then, the first intermediate value signal and the first intermediate value signal
And the second addition signal are input to the intermediate value level detection circuit 15, and the intermediate level signal of these three signals input here is selectively output, The intermediate value signal of is obtained.

The second intermediate value signal thus obtained is added to the signal delayed by the 1H period by the adder circuit 17 to obtain a luminance signal, and the luminance signal is outputted from the luminance signal output terminal 18. The signal is output.

However, in order to obtain the luminance signal by separating the luminance signal and the chrominance signal from the composite video signal, if the first method by the trap is used, the chrominance signal is removed and at the same time the high frequency component of the luminance signal (specifically However, since the luminance signal (3.58 MHz component) is also removed, there is a drawback that a fine image is blurred and the image quality is deteriorated.

When the second method using the comb filter is used, when there is no correlation around 1H of the composite video signal as shown in FIG. 6, the same video signal as shown in FIG. A portion having a correlation with the 1H-delayed video signal shown in FIG. 7B is added, and then the color is obtained without removing the high frequency component of the luminance signal like the portion A in FIG. The signal can be removed. However, with respect to the portions B and C having no correlation around 1H, the color signal component remains in the luminance signal, and there is a disadvantage that dot interference occurs at the edge portion of the image. In addition, the amplitude of the luminance signal is 1/2 in the B and C parts as compared with the amplitude in the A part, and the reproduced image has a drawback that it becomes an image waiting to spread in the vertical direction.

Further, as shown in FIG. 7, when the third method for detecting and separating the 3-line correlation is used, the high frequency component in the luminance signal is not removed and the dot interference at the edge portion of the image does not occur. Good luminance signal separation is performed. However, since the 1H delay line used in this circuit is expensive and a plurality of 1H delay lines are used, there is a problem that the system is also expensive.

[0019]

As described above, in the circuit for detecting the luminance signal from the composite video signal, in the case of the method using the first band stop filter, not only the chrominance signal but also the high frequency component of the luminance signal is detected. Since it is removed, the signal has a reduced resolution. Also, in the case of the method using the second comb filter, dot interference occurs at the color edge portion in the vertical direction due to the residual component of the color.
Further, when a circuit for detecting and separating three-line correlation is used, good separation is possible, but a plurality of expensive 1H period delay lines are used, so that the system becomes expensive accordingly. There is a point.

Therefore, the present invention has been made in view of the above problems, and even if there is an uncorrelated portion around 1H of the composite video signal, the signal is not degraded in resolution, and the color edge portion in the vertical direction is present. It is an object of the present invention to provide a low-priced luminance signal separation circuit that enables good luminance signal separation without causing dot interference due to the residual component of the color and without using a plurality of 1H period delay lines.

[0021]

A luminance signal separation circuit according to the present invention is supplied with a composite video signal including a luminance signal and a color signal as an input signal, delays this input signal for one horizontal period, and outputs a first delay signal. And a frequency component near the color subcarrier included in the input signal and the first delay signal, and subtracting them from each other to output a first signal mainly composed of a color signal component. First subtracting means, the frequency component near the color subcarrier included in the first delay signal and the output signal of the first subtracting means are subjected to subtraction processing, and before and after the delay by the first delay means. Second subtraction means for outputting a second signal having a color signal component in the signal non-correlation part, and the first signal for n of the color subcarrier.
/ 2 period (n is a positive integer) is delayed by a second delay means for outputting a second delay signal, and the first delay signal,
Third delay means for delaying by the same delay time as the second delay means and outputting a third delay signal, and adding means for adding the second delay signal and the third delay signal, Signal combining means for processing the second signal from the second subtracting means, adding the processed second signal to the output signal of the adding means, and outputting the luminance signal from which the color signal component has been removed. .

[0022]

In the present invention, one 1H delay circuit, delay circuit, band pass filter near 3.58 MHz, minimum value detection circuit, maximum value detection circuit, intermediate value detection circuit, etc. are used.
The color residual component at the vertical color edge is removed by obtaining the signal only at the vertical edge of the color and adding the luminance signal with the residual color component at the color edge to cancel it. It is possible to obtain the brightness signal.

[0023]

EXAMPLES Examples will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a luminance signal separation circuit according to the present invention.

In FIG. 1, a composite video signal is input to the input terminal 10. The composite video signal input to the input terminal 10 is supplied to the band pass filter 12 (hereinafter, referred to as BPF) and the 1H delay circuit 11. The 1H delay circuit 11 delays the composite video signal by 1H and supplies it to the BPF 13 and the delay circuit 32. Each of the BPFs 12 and 13 uses a frequency component (3.58 MHz component) near the color carrier as a pass band, and passes the carrier color signal and the 3.58.MHz band luminance signal of the input composite video signal. In addition, BP
Let the passing signal of F12 be (c), and let the passing signal of the 1H delay circuit 11 (signal delayed by 1H) be (b). BPF
The signal that has passed 13 is input to the polarity reversing circuit 14, which inverts the polarity of the passing signal of the BPF 13 and outputs the passing signal (d).

The passing signals (c) and (d) are added to the adder 1
5 and the adder 15 outputs the passing signal (c),
(D) is added and an addition signal (e) is output. Further, the passing signal (d) and the addition signal (e) are input to a subtractor 16, which subtracts the passing signal (d) and the addition signal (e) to output a subtraction signal (f). . This subtraction signal (f) is the cycle of the color subcarrier n / 2 (n is a positive integer)
It is input to the delay circuit 18 that delays only by. Delay circuit 18
Outputs the passing signal (q) after delaying the subtraction signal (f) for a predetermined time. Further, the passing signal (q) is input to a delay circuit 19 which delays by a cycle n / 2 of the color subcarrier (n is a positive integer), and the delay circuit 19 delays the passing signal (q) by the cycle n of the color subcarrier. The passing signal (g) is output after being delayed by / 2 (n is a positive integer). The passing signal (g) and the subtraction signal (f) are input to the intermediate value level detection circuit 20, and the intermediate value level detection circuit 20 sends the subtraction signal (f) and the passing signal (g) to the AC = 0 signal at the terminal 21. That is, that is, that is, the signal at the intermediate level among the three signals is selectively output to output the passing signal (h). This passing signal (h) is input to the minimum value detection circuit 26 and the maximum value detection circuit 27.
Further, the passing signal (h) is also input to the polarity reversing circuit 25, and the polarity reversing circuit 25 inverts the polarity of the passing signal (h) and further supplies it to the minimum value detection circuit 26 and the maximum value detection circuit 27. The minimum value detection circuit 26 compares the levels of the passing signal (h) and the signal obtained by inverting the polarity of the passing signal (h), selects the minimum level among them, and outputs the passing signal (j). Further, the maximum value detection circuit 24 compares the levels of the passing signal (h) and the signal in which the polarity of the passing signal (h) is inverted, selects the maximum level among them, and outputs the passing signal (i). . The passage signal (j) is input to the maximum value detection circuit 28, and the passage signal (i) is input to the minimum value detection circuit 29.

On the other hand, the output signal (e) of the adder 15 is input to the delay circuit 17 which delays by the cycle n / 2 (n is a positive integer) of the color subcarrier, and this delay circuit 17 passes the passing signal (e). Is delayed by the period n / 2 of the color subcarrier (n is a positive integer) to output the passing signal (k). This passing signal (k) is input to the minimum value detection circuit 23 and the maximum value detection circuit 24. Further, the passing signal (k) has a polarity reversing circuit 22.
Is also input to the polarity reversing circuit 22 and the passing signal (k)
The polarity is inverted and further supplied to the minimum value detection circuit 23 and the maximum value detection circuit 24. The minimum value circuits 23, 2
Reference numerals 6 and 29 are for selectively outputting the minimum level among the levels presented by a plurality of inputs.
Reference numerals 7 and 28 are circuits for selectively outputting the maximum level among the levels presented by a plurality of inputs.

The minimum value detection circuit 23 outputs the passing signal (k).
And the level of the signal of which the polarity of the passing signal (k) is inverted are compared, and the minimum level is selected and the passing signal (m) is output. Further, the maximum value detection circuit 24 compares the levels of the passing signal (k) and the signal in which the polarity of the passing signal (k) is inverted, selects the maximum level among them, and outputs the passing signal (l). . The passing signal (m) is input to the maximum value detection circuit 28, and the passing signal (l) is also input.
Is input to the minimum value detection circuit 29.
The passing signals (m) and (j) are input to the maximum value detecting circuit 28, and the maximum value detecting circuit 28 passes the passing signals (m) and
(J) is compared with the level, and the maximum level is selected and the passing signal (p) is output. The passing signals (l) and (i) are input to the minimum value detecting circuit 29, and the minimum value detecting circuit 29 compares the levels with the passing signals (l) and (i) and selects the minimum level among them. Pass signal (n)
Is output. The passing signals (n) and (p) are input to the intermediate value level detection circuit 30, and further the delay circuit 18 is provided.
The output signal (q) of is also input. The intermediate value level detection circuit 30 compares the passing signal (p) and the passing signal (n) with the output signal (q) of the delay circuit 18, that is, selectively outputs the signal at the intermediate level among the three signals. And outputs a passing signal (r). This passing signal (r) is input to the polarity reversing circuit 31, and the polarity reversing circuit 3
1 reverses the polarity of the passing signal (r) and supplies it to the adder 34.

By the way, the 1H delay circuit 11 sets
The H-delayed composite video signal (b) is input to a delay circuit 32 that delays by a cycle n / 2 (n is a positive integer) of the color subcarrier, and this delay circuit 32 further passes the pass signal (b) to the color. The sub-carrier is delayed by n / 2 (n is a positive integer), output, and supplied to the adder 33. The output signal (k) of the delay circuit 17 is also input to the adder 33. The adder 33 adds the signal delayed by the delay circuit 32 for a predetermined time and the passing signal (k) delayed by the delay circuit 17 for a predetermined time, and outputs an addition signal (s). The signal obtained by inverting the polarities of the addition signal (s) and the passing signal (r) is input to the adder 34, and the adding device 34 adds the addition signal and the signal obtained by inverting the polarity of the passing signal (r). Output signal (t), that is, luminance signal (Y signal)
Is output. The brightness signal is output from the brightness signal output terminal 35.

Next, the operation of the embodiment circuit having such a configuration will be described with reference to FIG.

FIG. 2 is an explanatory diagram for explaining the operation of the luminance signal separation circuit shown in FIG. 1. Waveforms (a) to (t) in FIG. 2 are points (a) to (t) shown in FIG. ) Corresponds to.

First, assume that a composite video signal as shown in FIG. 2A is input to the input terminal 10. Here, the composite video input signal is shown as a set of a Y signal and a C signal for each 1H, and the sync signal is omitted for simplification. This composite video signal has a portion having no correlation and a portion having correlation before and after the 1H section as shown in the figure for the video signal portion. The output of the 1H delay circuit 11 is delayed for a 1H period and becomes a signal as shown in FIG. The input signal (a) is extracted by the band-pass filter 12 only the frequency component (3.58 MHz) near the color subcarrier frequency, and becomes a signal as shown in FIG. 2 (c). Further, the composite video signal (b) delayed by 1H is extracted by the band pass filter 13 only the frequency component (3.58 MHz) near the color subcarrier frequency, and the polarity is inverted by the polarity inverting circuit 14.
The signal is as shown in FIG. Then, the passing signals (c) and (d) are added by the adder 15 to obtain the signal (e). This signal (e) is the result of subtraction of the composite video signal in the 1H period, which is similar to the color signal output of the conventional comb filter. The signal (e) and the signal (d) in the vicinity of the color subcarrier delayed and inverted for 1H period are subtracted by the subtractor 16
Is subtracted to obtain a signal (f). This signal (f) is similar to the signal of the frequency component near the chrominance subcarrier of the luminance signal of the conventional comb filter.

The signal (f) is delayed by the delay circuit 18 by the cycle n / 2 (n is a positive integer) of the color subcarrier to become the signal (q), which is further delayed by the delay circuit 19 in the cycle n of the color subcarrier. The signal (g) is delayed by / 2 (n is a positive integer). The signals (f) and (g) are compared with the AC = 0 signal at the terminal 21 by the intermediate value level detection circuit 20, that is, the signal at the intermediate level among the three signals is selectively output, that is, sporadic. The luminance signal and the signal due to the edge portion of the horizontal eaves are removed to obtain the signal (h).
The signal (h) and the signal obtained by inverting the signal (h) by the polarity inversion circuit 25 are input to the minimum value circuit 26 and the maximum value circuit 27, respectively, and the minimum value detection circuit 26 outputs the signal (h) and the signal (h). Of the signals inverted by the polarity inverting circuit 25 is selected and becomes the signal (j). On the other hand, the maximum level is selected from the maximum value detection circuit 27 and the signal (h) and the signal obtained by inverting the signal (h) by the polarity inversion circuit 25, and becomes the signal (i).

The output signal (e) of the adder 15 is delayed by the delay circuit 17 for a predetermined time in the same manner as the delay circuit 18 to become the signal (k). The signal (k) and the signal obtained by inverting the signal (k) by the polarity inversion circuit 22 are input to the minimum value circuit 23 and the maximum value circuit 24, respectively, and the minimum value detection circuit 23 outputs the signal (k) and the signal (k). Of the signals inverted by the polarity inverting circuit 22 is selected and becomes the signal (m). On the other hand, the maximum value detection circuit 2
4, the signal (k) and the signal (k) are inverted by the polarity inversion circuit 22.
The maximum level of the signals inverted by is selected and becomes the signal (l). Then, as for the output signal (m) of the minimum value detection circuit 23 and the output signal (j) of the minimum value detection circuit 26, the maximum level detection circuit 28 selects the signal of the maximum level among the signal (m) and the signal (j). And becomes a signal (p). Also,
As for the output signal (1) of the maximum value detection circuit 24 and the output signal (i) of the maximum value detection circuit 27, the minimum level signal is selected by the minimum value detection circuit 29 from the signal (l) and the signal (i). (N). That is, the output signal (p) of the maximum value circuit 28 and the output signal (n) of the minimum value circuit 29 are as shown in FIG.
As shown in (n) and (p), only the vertical edge portions of the color are present, and the polarities of the signals are opposite to each other.

Therefore, the intermediate value level detection circuit 30 receives the signals (n) and (p) and the output signal (q) of the delay circuit 18, and outputs the signal only during the period when the signal (n) and the signal (p) exist. (P) is passed and output is performed. That is, the output of the intermediate value circuit 19 becomes a signal (r) having only the edge portion of the color in the vertical direction, as shown in FIG.

The output signal (b) of the 1H period delay circuit 11 is delayed by a predetermined time from the delay circuit 31, and the signal (k) near the color subcarrier is subtracted from this signal (b) before and after the 1H period. A color signal of a conventional comb filter) is added by an adder 33 to obtain a signal (s). This signal (s) is similar to the luminance signal output of the conventional comb filter. That is, dot interference occurs due to the residual color signal at the edge portion of the color in the vertical direction. Therefore,
This signal (s) and the output signal (r) of the maximum value level detection circuit 30 are inverted by the polarity inversion circuit 31 and added by the adder 34, and the output signal (t) as shown in FIG. Becomes That is, the signal (r) is a signal that exists only in the vertical edge portion of the color, and the signal (s) has an element in which the vertical edge portion of the color causes dot interference due to residual color signals, and The inverted signal. That is, by adding these signals (r) and (s), it is possible to cancel the dot interference of the color edge portion existing in the signal (s).

As a result, the output signal (t) of the adder 34 becomes a signal in which dot interference due to the remaining color signal is reduced, that is, the luminance signal (Y signal) is obtained and the luminance signal is output from the luminance signal output terminal 35. Can be output.

Therefore, in the present embodiment, the output characteristic in the case of using the conventional comb filter that inputs the composite video signal, that is, the luminance signal and the color signal at the edge portion in the vertical direction of the color, is close to the color subcarrier. This makes use of the property that the component of (1) remains, so that in the period other than the edge portion of the color in the vertical direction, the signal (color signal) near the color subcarrier subtracted before and after the 1H period is maintained for the 1H period. A luminance signal is obtained by subtracting from the delayed composite video signal. In this case, the luminance signal and the chrominance signal in the vicinity of the color subcarrier rarely exist at the same time, and therefore the luminance signal is output as it is. Also, in the vertical color edge portion, a signal exists in the vicinity of the color subcarrier that is subtracted before and after the 1H period, the subtraction result, and the subtraction result of the video signal near the color subcarrier that is delayed by the 1H period. To do. Therefore, if there are simultaneous signals,
A signal near the color subcarrier obtained by further subtracting the signal subtracted before and after the 1H period from the video signal delayed by the H period,
It is output from the intermediate value detection circuit 30 and added to the luminance signal. Therefore, as described above, the residual color components that interfere with the dots are removed, and it is possible to separate the luminance signal in a good manner even at the color edge portion.

[0038]

As described above, according to the present invention, even if there is an uncorrelated portion around 1H of a composite video signal, it is possible to reduce dot interference due to a residual color component at a color edge portion in the vertical direction. In addition, good luminance signals can be separated without using a plurality of 1H period delay lines. This makes it possible to provide an inexpensive luminance signal separation circuit.

[Brief description of drawings]

1 and 2 show an embodiment of a luminance signal separation circuit according to the present invention, and FIG. 1 is a block diagram.

FIG. 2 is an operation explanatory diagram illustrating an operation of the luminance signal separation circuit shown in FIG.

FIG. 3 is an explanatory diagram illustrating a frequency distribution of an NTSC composite video signal.

FIG. 4 is a block diagram showing an example of a conventional luminance signal separation circuit, in which a trap circuit is used.

FIG. 5 is a block diagram showing an example of a conventional luminance signal separation circuit, in which a comb filter circuit is used.

6 is a waveform diagram showing an output waveform of the luminance signal separation circuit shown in FIG.

FIG. 7 is a block diagram showing an example of a conventional luminance signal separation circuit when using 3-line correlation.

[Explanation of symbols]

 10 ... Input terminal 11 ... 1H delay circuit 12, 13 ... Band pass filter 14, 22, 25, 31 ... Polarity inversion circuit 15, 33, 34 ... Adder 16 ... Subtractor 17, 18, 19, 32 ... Delay circuit 23 , 26, 29 ... Minimum value detection circuit 24, 27, 28 ... Maximum value detection circuit 20, 30 ... Intermediate value level detection circuit 35 ... Output terminal

Claims (1)

[Claims] 1. A first delay means for supplying a composite video signal including a luminance signal and a chrominance signal as an input signal, delaying the input signal for one horizontal period, and outputting a first delay signal, said input signal. And first subtraction means for extracting frequency components near the color subcarrier included in the first delay signal and performing subtraction processing on each other, and outputting a first signal mainly composed of the color signal component, and the first delay. Subtracting the frequency component near the color subcarrier included in the signal and the output signal of the first subtracting means,
Second subtraction means for outputting a second signal having a color signal component in the signal non-correlation part before and after the delay by the first delay means; and the first signal for n / 2 cycles of the color subcarrier ( n is a positive integer) and outputs a second delay signal, and a second delay means for delaying the first delay signal by the same delay time as that of the second delay means. Third delay means for outputting a delay signal, addition means for adding the second delay signal and the third delay signal, and processing the second signal from the second subtraction means to process the second signal. A luminance signal separating circuit comprising: a signal synthesizing unit that adds the output signal of the adding unit and outputs a luminance signal from which a color signal component is removed.