JPH0644220Y2 - Luminance / Chromaticity separation circuit - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a luminance / chromaticity separation circuit suitable for use in a VTR recording system or the like.

[Outline of device]

The present invention supplies a color video signal to a luminance / chromaticity separator, separates it into a luminance signal and a carrier color signal, and supplies the separated luminance signal to a carrier color signal component extraction circuit to convey a carrier color signal component. In the luminance / chromaticity separation circuit configured to output the luminance signal from which the carrier color signal component is removed by extracting the carrier color signal component from the luminance signal.
A detector for detecting the carrier color signal from the luminance / chromaticity separator, and when the carrier color signal is not detected by this detector, the carrier color signal component is supplied from the carrier color signal component extraction circuit to the subtractor. When the carrier color signal is output from the luminance / chromaticity separator, the carrier color signal component of the luminance signal output from this luminance / chromaticity separator is ensured by providing a blocking circuit for blocking In addition, the high frequency component of the luminance signal is not lost when the carrier color signal is not output.

[Conventional technology]

The conventional luminance / chromaticity separation circuit will be described below with reference to FIG. Color video signal a to the input terminal (1)
(See FIG. 3A). In this color video signal (here, NTSC color video signal) a, α
Indicates a signal portion (having a high-level portion and a low-level portion) having no luminance signal and only a luminance signal, and β
Indicates a signal portion having a carrier color signal. This color video signal a is supplied to the luminance / chromaticity separator (4).

The luminance / chromaticity separator (4) is composed of a vertical correlator (comb filter). In the luminance / chromaticity separator (4), (5) and (7) are delay devices each having a delay time of one horizontal period (1H), and (6) and (8) are subtractors.

Then, the color video signal a is supplied to the subtractive comb filter constituted by the delay device (5) and the subtractor (6), and the carrier color signal b (see FIG. 3B) is separated therefrom. Is output to the output terminal (2).

In addition, the color video signal a is supplied to the delay device (7) and delayed, and is formed at the same timing as the carrier color signal b.
The subtractor (8) subtracts the carrier color signal b from the delayed color video signal to obtain the luminance signal d.
(See FIG. 3D) are separated. The luminance signal d includes the carrier color signal component γ.

An adder is provided instead of the subtractor (8), and the color video signal from the input terminal (1) and the delayed color video signal from the delay device (7) are added by the adder. Therefore, the luminance signal may be separated.

Then, the luminance signal d is supplied to a horizontal correlator (9) as a carrier color signal component extraction circuit to extract the carrier color signal component e (see FIG. 3E). In the subtracter (11), the luminance signal d is delayed by the delay device (10), and the carrier color signal component e is subtracted from the delayed luminance signal d '(D in FIG. 3) to output the output terminal (3). In addition, the luminance signal g ′ (see FIG. 3G) from which the carrier color signal e (γ) is removed is obtained.

The delay time of this delay device (10) is the period T _{SC of the} carrier color signal.
1/2 of that. As will be apparent from what will be described later, the carrier color signal component e obtained from the horizontal correlator (9) is delayed with respect to the luminance signal d by half the period T _SC of the carrier color signal. The luminance signal d is delayed by this delay device (10) so that it has the same timing as the carrier color signal component e obtained from the horizontal correlator (9).

Next, a concrete configuration example of the horizontal correlator (9) (Japanese Patent Application No. 58-18).
No. 8851) will be described.

In FIG. 4, the carrier color signal S _C supplied to the input terminal (21) is supplied to the first minimum value detector (22) and the first maximum value detector (24). This carrier color signal S _C is further supplied to a delay element (27) composed of a delay line or the like,
A carrier color signal delayed by a time corresponding to the period T _SC is output, which is the minimum value and maximum value detector (22), respectively.
Supplied to (24). In addition, the carrier color signal delayed by the time corresponding to T _SC / 2 minutes is output from the intermediate tap (27a) of the delay element (27), and this is output via the inverter (28) to the minimum and maximum value detectors, respectively. It is supplied to (22) and (24).

The first minimum value detector (22) detects the carrier color signal of the minimum level among the three input carrier color signals thus shifted by the time T _SC / 2, and this is the first minimum value signal. S _N1
Is output as. Similarly, the first maximum value detector (24) similarly detects the maximum level of the carrier color signal among the three input carrier color signals and outputs it as the first maximum value signal S _X1 .

The first minimum value signal S _N1 is supplied to a second maximum value detector (25) having a non-signal level as a reference level for level comparison with the reference level, and the signal with the larger one is The maximum value signal S _X2 of ₂ is output. Further, the first maximum value signal S _X1 is also supplied to the second minimum value detector (23) whose reference level is the non-signal level, and the signal having the smaller input level of the input signals is the second signal. It is output as the minimum value signal S _N2 .

These signals S _X2 and S _N2 are added by an adder (29), and a carrier color signal S _C ′ in which an asynchronous signal is suppressed is obtained from a terminal (30).

Next, the operation of this horizontal correlator will be described with reference to FIG. First, the signal obtained from the intermediate tap (27a) of the delay element (27) is S _O , and the time point at this time is τ ₀ , from which T
The signal at time point τ ₁ advanced by _SC / 2 is S ₁ , T _SC / 2 time point τ _-1
Let S _-1 be the signal of.

As shown in FIG. 5A, a periodic signal, that is, a carrier color signal S_CThat
Describes the case when something is input to the input terminal (21).
It Each of the first minimum value detectors (22) shown in FIG.
T_SCThree carrier color signals S with a time difference of / 2₁， S_-1And ▲
Since ▼ is input at the same time, at this time each level
Are the same, so now τ₁Transport color based on
Signal S₁Is the first minimum signal S_N1Is output as.

On the other hand, the level is the same in the first maximum value detector (24).
3 carrier color signals S₁， S_-1And ▲ ▼ is supplied at the same time
Therefore, the carrier color signal S₁Is the first maximum
Signal S_X1Is output as.

In this example, the first minimum value signal S _N1 (that is, the carrier color signal S ₁ ) has a positive level, so when compared with the no signal level, that is, the zero level, the second maximum value detector (25 ) _Shows that the first minimum signal S _N1 itself is the second maximum signal S _X2
Is output as.

Similarly, in this example, the first maximum value signal S _X1 is at a positive level, and as a result of being compared with the no signal level, that is, the zero level, the zero level itself from the second minimum value signal (23). Is output as the second minimum value signal S _N2 . As a result, the second maximum value signal S _X2 is output from the terminal (30).

Thus, in the case of a periodic signal, the periodic signal itself is output.

On the other hand, when an aperiodic signal as shown in FIG. 5B, for example, the high frequency component ΔY of the luminance signal is input to the terminal (21), the following operation is performed. In this example. For the sake of convenience, the pulse width of the high-frequency luminance component ΔY is substantially equal to 1/2 of the carrier color signal period T _SC as shown in the figure.

If the time point τ ₁ of the signal is set as shown in FIG. 9B, either the signal S ₁ or S ₋₁ from the first minimum value detector (20),
Since based on the time tau ₁ in this example signal S ₁ is the first
Is output as the minimum value signal S _N1 , and the first maximum value detector (24) outputs the signal S ₁ , that is, the high-frequency luminance component ▲ ▼ as the first maximum value signal S _X1 . Therefore the second
Since the minimum value signal S _{N2 of} is zero, the output level of the terminal (30) is zero.

The pulse width of the high frequency luminance component ΔY is the period T of the carrier color signal._SCYo
If it is sufficiently long, it is supplied to the detectors (22) and (24).
Signal S₁▲ ▼, S_-1Is either positive or negative
In this case, the second maximum
Large signal S_X2Or the second minimum signal S_N2Is not zero
Obtained with a fixed level. For this reason, the terminals (30)
An aperiodic signal suppressed to a constant level is obtained.

[Problems to be solved by the invention]

According to such a conventional luminance / chromaticity separation circuit, it is possible to obtain a luminance signal in which the carrier color signal component is surely removed.
However, the luminance signal obtained from the luminance / chromaticity separator (4) does not include the carrier color signal indicated by α in FIG. 3A,
When the signal portion including the luminance signal only includes a portion (a rising edge and a falling edge) whose level changes abruptly, the portion includes a high frequency component corresponding to the frequency of the carrier color signal. Therefore, this high frequency component is extracted from the horizontal correlator (9). This extracted signal part δ
(See FIG. 3E) is subtracted from the portion where the level of the signal portion α of the luminance signal d from the luminance / chromaticity separator (4) changes abruptly, so that it becomes the frequency of the carrier color signal of the luminance signal. The corresponding high-frequency component is lost (see FIG. 3G), resulting in a decrease in sharpness.

In view of this point, the present invention can reliably remove the carrier color signal component of the luminance signal output from the luminance / chromaticity separator when the carrier color signal is output from the luminance / chromaticity separator. The present invention intends to propose a luminance / chromaticity separation circuit in which the high frequency component of the luminance signal is not lost when the carrier color signal is not output.

[Means for Solving Problems] The present invention provides a luminance / chromaticity separator (4) to which a color video signal is supplied and a luminance signal obtained from the luminance / chromaticity separator (4). Carrier Color Signal Component Extraction Circuit (9)
And a subtractor (1 that subtracts the carrier color signal component from the luminance signal
1) and a luminance signal from which a carrier color signal component is removed from the subtractor (11) and a carrier color signal is output from the luminance / chromaticity separator (4). A detector (13) for detecting the carrier color signal from the luminance / chromaticity separator (4) in the chromaticity separation circuit, and this detector (13)
When the carrier color signal is not detected by the, a cutoff circuit (12) for cutting off the supply of the carrier color signal component from the carrier color signal component extraction circuit (9) to the subtractor (11) is provided. .

[Action]

According to the present invention, the detector (13) allows the brightness /
When it is detected that the carrier color signal is output from the chromaticity separator (4), the cutoff circuit (12) is disabled and
A subtractor (11) subtracts the carrier color signal component from the carrier color signal component extraction circuit (9) from the brightness signal from the luminance / chromaticity separator (4) to obtain a brightness / chromaticity separator (4). If it is not detected that the carrier color signal was output from,
The cutoff circuit (12) is activated and the luminance signal from the luminance / chromaticity separator (4) is output as it is.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to FIG. 1, but in FIG. 1, parts corresponding to those in FIG. The luminance / chromaticity separation circuit of FIG. 1 differs from the luminance / chromaticity separation circuit of FIG. 2 in the following points.

That is, in the luminance / chromaticity separation circuit of FIG. 1, the carrier color signal component e (see FIG. 3E) obtained from the horizontal correlator (9) as the carrier color signal component extraction circuit is converted into a mute amplifier. It supplies to the subtractor (11) through (12),
A detector (13) for detecting the carrier color signal from the luminance / chromaticity separator (4) is provided, and the mute amplifier (12) is controlled by the detection signal c (see FIG. 3C) from the detector (13). I am trying to do it.

Then, when the carrier color signal is detected by the detector (13) (when the detection signal becomes high level), the mute amplifier (12) is controlled to the non-mute state (amplification state), and the carrier color signal is not detected. Then (when the detection signal becomes low level), the mute amplifier (12) is controlled to the mute state. Other configurations are the same as those in FIG.

The detector (13) is composed of, for example, an amplitude detector and a comparator that compares the detected output with a reference level. When the detection output level of the amplitude detector is equal to or higher than the reference level, the carrier color is detected. A high level detection output indicating that there is a signal is generated, and when the level of the detection output is less than the reference level, a low level detection output indicating that there is no carrier color signal is generated.

According to the luminance / chromaticity separation circuit of FIG. 1, the luminance signal obtained from the luminance / chromaticity separator (4) is represented by α in FIG. 3A.
, Which does not include the carrier chrominance signal, but includes a portion whose level changes abruptly, such as a signal portion of only the luminance signal, that portion has a high frequency component corresponding to the frequency of the carrier chrominance signal. Since this is included, this high frequency component is extracted from the horizontal correlator (9). However, since the detector (13) detects that the carrier color signal is not output from the luminance / chromaticity separator (4), the mute amplifier (12)
Is muted and the extracted signal portion δ
(See FIG. 3E) is not output, and the output f of the mute amplifier (12) is only the carrier color signal component γ as shown in FIG. 3H, and thus is output from the subtractor (11). As shown in FIG. 3F, the luminance signal g does not lose the high frequency component corresponding to the frequency of the carrier color signal of the luminance signal.
Therefore, when the color video signal is reproduced on the monitor receiver, it is possible to avoid a decrease in the sharpness of the reproduced image having no color or a light image.

When the detector (13) detects that the carrier color signal b (β) is output from the luminance / chromaticity separator (4), the mute amplifier (12) is in an amplification state. In the subtractor (11), the carrier color signal component f obtained by the horizontal correlator (9) is calculated from the luminance signal d '(see FIG. 3D).
(Γ) (see FIG. 3H) is subtracted, and the carrier color signal component γ contained in the luminance signal d ′ is surely removed.

In the above-described embodiment, the luminance / chromaticity separator (4) is composed of a vertical correlator (comb filter), but it can be used as a low-pass filter for luminance signal separation and a pan-pass filter for carrier color signal separation. It can also be configured.

Further, in the above-mentioned embodiment, the carrier color signal component extraction circuit is constituted by the horizontal correlator (9), but it may be constituted by a band pass filter for carrier color signal component separation. However, using the horizontal correlator (9) is better than using the pan-pass filter.
The carrier color signal component of the luminance signal can be removed more reliably.

[Effect of device]

According to the present invention described above, when the carrier color signal is output from the luminance / chromaticity separator, the carrier color signal component of the luminance signal output from the luminance / chromaticity separator can be reliably removed, and When the carrier color signal is not output, it is possible to obtain a luminance / chromaticity separation circuit in which the high frequency component of the luminance signal is not lost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional example, FIG. 3 is a waveform diagram for explaining the embodiment and the conventional example, and FIG. 4 is a horizontal correlator. FIG. 5 is a block diagram showing an example, and FIG. 5 is a waveform diagram for explaining the horizontal correlator. (4) is a luminance / chromaticity separator, (9) is a horizontal correlator, and (1
1) is a subtractor, (12) is a mute amplifier, and (13) is a detector.

Claims (1)

[Scope of utility model registration request] 1. A luminance / chromaticity separator to which a color video signal is supplied, a carrier color signal component extraction circuit to which a luminance signal obtained from the luminance / chromaticity separator is supplied, and the luminance signal to the above A subtractor for subtracting the carrier color signal component, and the subtractor outputs the luminance signal from which the carrier color signal component is removed, and the luminance / chromaticity separator outputs the carrier color signal. In the luminance / chromaticity separation circuit, a detector for detecting the carrier color signal from the luminance / chromaticity separator, and when the carrier color signal is not detected by the detector, the carrier color signal component extraction circuit A luminance / chromaticity separation circuit provided with a cutoff circuit for cutting off the supply of the carrier color signal component to the subtractor.