JPH0649024Y2 - Video signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a video signal processing circuit, and in particular, by removing a frequency band component in which a color signal is interpolated from a luminance signal, the luminance signal and the color signal A color television signal capable of preventing interference is obtained.

(Prior Art) Generally, in the low frequency conversion VTR, the reproduced luminance signal is not subjected to any correction processing, only the color signal is subjected to the time base correction, and these are combined to generate a composite signal. However, since the band of the luminance signal was about 0 to 2.6 MHz, it was lower than 3.58 MHz ± 700 KHz, which is the band of the carrier color signal, and there was no interference between them. In addition, low frequency conversion color signal and FM
The cross-modulation distortion that occurs when recording and reproducing by frequency division multiplexing with the luminance signal causes the carrier frequency of the carrier color signal to be 40Fh.
By selecting (Fh is the horizontal synchronization frequency), it was made inconspicuous on the playback screen.

(Problems to be solved by the invention) However, when the band of the luminance signal is expanded, there is no problem with the intermodulation distortion, but the following problem occurs due to the overlapping of the band of the luminance signal and the band of the carrier color signal. Occurred.

As described above, since the time base correction is performed only for the color signals, the reproduction luminance signal and the reproduction carrier color signal have no interleave relationship with each other, and the two interfere with each other. Also, when recording YC
If the degree of separation is not sufficient in the separation, interference between the two similarly occurs.

If the frequency component in which the carrier color signal is interpolated is simply removed from the reproduction luminance signal using a comb filter, there is no line phase in the reproduction luminance signal, which causes a problem that the vertical resolution deteriorates.

Therefore, an object of the present invention is to obtain a color television signal without interference by removing the color signal frequency component remaining in the band of the reproduction luminance signal without deteriorating the vertical resolution.

(Means for Solving Problems) The present invention provides the following configurations in order to solve the above problems. That is, it is used in a device for reproducing a color television signal by separating it into a luminance signal and a chrominance signal, and synthesizing a reproduction luminance signal and a reproduction color signal which have undergone the reproduction processing into a color television signal. A color signal comb-shaped filter circuit for extracting a comb-shaped frequency band component including a frequency band component in which the reproduced color signal is interpolated from the reproduced luminance signal; and an output signal of the color signal comb-shaped filter circuit. Filter for limiting the frequency band component of the reproduced color signal to the frequency band component occupied by the reproduction color signal, an amplitude limiting circuit for limiting the amplitude level of the output signal of the band filter within a predetermined range, and an output signal of the amplitude limiting circuit A subtraction unit for subtracting from the reproduction luminance signal, and a combining unit that combines the output signal of the subtractor and the reproduction color signal to obtain a color television signal. That there is provided a video signal processing circuit.

(Operation) In the video signal processing circuit configured as described above, a frequency band component having a small amplitude level that interferes with a color signal or is mixed into the color signal band as noise is extracted using the amplitude limiting circuit 4, By removing the band component from the luminance signal a and synthesizing it with the color signal g, interference between the luminance signal a and the color signal g and mixing of noise can be eliminated, and it occurs when the luminance signal a has no line correlation. It is possible to reduce deterioration in vertical resolution.

(Embodiment) A preferred embodiment according to the present invention will be described in detail below with reference to FIGS. 1 to 10.

FIG. 1 is a block diagram showing the configuration of a first embodiment of a video signal processing circuit according to the present invention. In this circuit, a magnetically recorded and reproduced luminance signal a is input to an input terminal 1, and the luminance signal a is inputted. a is supplied to the color signal comb filter circuit 2.

The color signal comb filter circuit 2 is composed of a 1H delay circuit 11 and a mix circuit 12 as shown in FIG. 2 when it is based on the NTSC system, and is shown in FIG. 3 when it is based on the PAL system. As described above, the frequency characteristics of the filter circuit 2 having the 2H delay circuit 14 and the mix circuit 12 are shown in FIGS. 4 and 5, respectively.
It is as shown in the figure.

The color signal comb filter circuit 2 generates the signal i delayed by the 1H delay circuit 11 or the 2H delay circuit 14, and the mix circuit 12 subtracts the signal i from the luminance signal a. Then, the signal b having the frequency characteristic as shown in FIG. 4 or 5 is output.

This signal b is centered on the color subcarrier in the bandpass filter 3 (3.58 [MH in the case of NTSC color television signal).
z], 4.43 [MH for PAL color television signals
z]) and the frequency is limited to a bandwidth of about 700 [kHz] and output as a signal c.

Then, this signal c is supplied to the limiter circuit 4, which is the amplitude limiting circuit in the present embodiment, where the amplitude level is limited (in this embodiment, it is set to about 1/5),
A signal d consisting of only the frequency band component of the small amplitude level is supplied to the subtractor 6.

Here, the signal d composed only of the frequency band component of such a small amplitude level causes interference with the color signal g or mixes into the color signal band as a nozzle.

On the other hand, the luminance signal a is delayed by the delay circuit 5 having the same delay time as the bandpass filter 3, and the delayed signal e is supplied to the subtractor 6.

The subtracter 6 subtracts the signal d from the signal e, that is, the delayed luminance signal a, and outputs the signal f.

Here, the signal f is obtained by removing the unnecessary signal d from the luminance signal a as described above, and the signal f is combined with the color signal g supplied through the input terminal 8 in the adder 7. And output as a color television signal h from the output terminal 9.

The signal f has the frequency characteristic and the amplitude characteristic shown in FIG. 6 (in the case of NTSC system color television signal) or FIG. 7 (in the case of PAL system color television signal), and is magnetically recorded and reproduced. When the color signal g comes from the terminal 8 and is added in the adder 7, it interferes with the color signal g, or frequency band components that interfere with the mixing of nozzles in the color signal band (these components). The amplitude level is generally small) is removed, and the removal processing is limited for signals with large amplitude levels that are easily perceived due to deterioration of vertical resolution, which causes interference with color signals. It is possible to obtain a color television signal h that is free from deterioration and has little deterioration in vertical resolution.

FIG. 8 is an actual circuit example for realizing FIG. 1. The same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

The luminance signal a input from the input terminal 1 is composed of a CCD delay line or a glass delay line.
A signal i is generated by being delayed through the 1H delay circuit 11 or the 2H delay circuit 14.

The signal i is output in advance polarity is inverted, the resistance R ₁₀
In-phase amplification with NPN transistor Q ₂ and resistors R ₈ and R ₇ that form a base-grounded amplifier that is added to the signal a that has passed through resistor R ₉ and is subtracted because the polarity is actually inverted Then, the output signal b of the color signal comb filter circuit 2 is generated.

The resistor R ₁₀ is for adjusting the amount of addition of the signal a and the signal i, and the resistors R ₅ , R ₆ and the capacitor C ₁ are the body voltage sources necessary for operating the base-grounded amplifier. Are configured.

Then, the signal b is subjected to band limitation by the band filter 3 and then subjected to amplitude limitation by the limiter circuit 4 including the capacitor C ₂ and the diodes D ₁ and D ₂ .

The NPN transistor Q ₃ is a switching circuit for turning the limiter circuit 4 on and off, and operates the limiter circuit 4 only when a high-level control signal is input to the terminal 15.

On the other hand, the signal c output from the bandpass filter 3 is a resistance
Resistor R whose level is adjusted by R ₁₁ and which constitutes the phase adjustment circuit
_The phase is adjusted by the resistor R _{14 with 12} , R ₁₃ , R ₁₄ , the capacitor C ₃ , and the NPN transistor Q ₄ , and the NPN transistor Q ₅ ,
It is output to the collector of the transistor Q ₅ by the inverting amplifier circuit composed of the resistor R ₁₅ .

The luminance signal a passes through the resistor R ₁ and is converted into a signal e by the delay circuit 5, and further passes through the resistor R ₂ and is in-phase amplified by the NPN transistor Q ₁ and resistors R ₃ and R ₄ which form a base-grounded amplifier. Is output to the collector of the transistor Q ₁ .

Then, the signal e is added to the signal d by the transistor Q ₅ to be a signal f and output from the output terminal 16 (actually, since the signal d side is an inverting amplifier circuit, a subtraction process is performed).

In this way, the signal f having the characteristics shown in FIG. 6 or 7 is generated, and this signal f is supplied from the terminal 16 to the transistor
It is supplied to the adder 7 with the color signal composed of Q ₁₀ , Q ₁₁ , resistors R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ and the amplifier 21, and here, the color supplied via the input terminal 8. It is combined with the signal g and output from the output terminal 9 as a television signal h.

In the circuit shown in FIG. 8, the amplitude limiting operation can be turned on / off by inputting a control signal to the terminal 15, so that a color television signal is input to the input terminal 1 at the time of recording. When it comes, it can be used as a separation circuit for the luminance signal and the color signal.
It also has the advantage that the input of a low-level control signal to 15 can be used as a circuit that outputs a luminance signal to terminal 16 and a color signal to terminal 17.

Next, FIG. 9 shows a block diagram of a second embodiment according to the present invention. In the figure, those parts which are the same as those corresponding parts in FIG. 1 are designated by the same reference numerals, and a description thereof will be omitted.

In FIG. 9, a luminance signal a input from an input terminal 1 is processed by a color signal comb filter circuit 2 and a bandpass filter 3 to generate a processed signal c. This signal c is subjected to subtraction processing with the signal e that has passed through the delay circuit 5 in the mix circuit 19 to form a luminance signal comb type filter circuit, and its output signal j is the dotted line shown in FIG. 6 or 7. It has frequency characteristics.

On the other hand, the signal c has its small amplitude level (about 1/5 or less) removed by the slice circuit 18 which is the amplitude limiting circuit in the present embodiment, and is added to the signal j in the mix circuit 20 to generate the signal f. To do.

As a result, a signal of a large amplitude level which is not removed by the slice circuit 18 has the frequency characteristic of the solid line shown in FIG. 6 or 7, and an effect equivalent to that of the first embodiment shown in FIG. 1 is obtained. be able to.

Next, FIG. 10 shows a specific example of a circuit which constitutes FIG.
10, those parts which are the same as those corresponding parts in FIGS. 8 and 9 are designated by the same reference numerals, and a description thereof will be omitted.

In FIG. 10, the signal d passed through the color signal comb type filter circuit 2 and the bandpass filter 3 is the NPN transistor Q7 and the resistor R.
_An emitter-follower composed of ₁₆ capacitors C ₄ ,
It is sent to the slicing circuit 18 consisting of diodes D ₃ and D ₄ and resistors R ₁₇ and R ₁₈ , where the small amplitude level signal is removed, and then the emitter follower consisting of transistor Q ₈ and resistor R ₁₉ The output signal j of the luminance signal comb filter circuit sent out by the emitter follower composed of the transistor Q ₆ and the resistor R ₂₂ sent out is resistance-added by the resistors R ₂₀ , R ₂₁ to obtain the output signal f.

This output signal f is output via the output terminal 16 to the transistors Q ₁₀ , Q ₁₁ , resistors R ₂₅ , R ₂₆ , R ₂₇ , R ₂₈ and the amplifier 21.
Is supplied to the adder circuit 7, which is combined with the color signal g supplied through the input terminal 8 and is output from the output terminal 9 as the television signal h.

And this circuit is also transistor Q ₃ , capacitor C ₅
By inputting a control signal to the terminal 15 by the ON / OFF circuit of the slice circuit 18 configured by, the addition of the slice circuit output k can be turned ON / OFF and the terminal 15 can be controlled at a low level. By inputting a signal, it can be used also as a separation circuit for the precision signal a and the color signal g at the time of recording.

(Effect) As described above, according to the configuration of the present invention, the color signal frequency component remaining in the band of the reproduction luminance signal can be removed, so that the image quality of the wide band color television signal can be improved. effective.

Further, according to the configuration of the present invention, in particular, since the band filter for limiting the frequency band component of the output signal of the color signal comb filter circuit to the frequency band component occupied by the reproduced color signal is provided, Since the luminance signal frequency component is not removed in areas other than the occupied frequency band, the vertical resolution of the reproduced luminance signal is not unnecessarily degraded, and an amplitude limiting circuit that limits the amplitude level of the output signal of the bandpass filter within a predetermined range is provided. Since it is provided, since the reproduction luminance signal frequency component having no vertical correlation is not removed even within the frequency band occupied by the reproduction color signal, it is possible to prevent deterioration of the vertical resolution of the reproduction luminance signal.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment according to the present invention, FIGS. 2 and 3 are block diagrams of a color signal comb type filter circuit for NTSC and PAL color television signals, respectively, and FIGS. Are frequency characteristic diagrams of the circuits shown in FIGS. 2 and 3, and FIGS. 6 and 7 are outputs of NTSC and PAL color television signals of luminance signals processed by the circuit of the present invention. FIG. 8 is a diagram showing each frequency characteristic and amplitude characteristic of a signal, FIG. 8 is a concrete circuit diagram of the block diagram shown in FIG. 1, and FIG. 9 is a second circuit diagram according to the present invention.
FIG. 10 is a block diagram of the embodiment, and FIG. 10 is a concrete circuit diagram of the block diagram shown in FIG. 2 ... Color signal comb filter circuit, 4 ... Amplitude limiting circuit (limiter circuit), 6 ... Subtractor, 7 ... Adder, 18 ... Amplitude limiting circuit (slice circuit).

Claims (1)

[Scope of utility model registration request] 1. A color television signal which is used in an apparatus for reproducing a color television signal by separating it into a luminance signal and a color signal, and synthesizing a reproduced luminance signal and a reproduced color signal which have been subjected to a reproduction process into a color television signal. A video signal processing circuit, which extracts a comb-shaped frequency band component including a frequency band component in which the reproduced color signal is interpolated from the reproduced luminance signal, and the color signal comb-shaped filter circuit Bandpass filter for limiting the frequency band component of the output signal of the above to the frequency band component occupied by the reproduction color signal, an amplitude limiting circuit for limiting the amplitude level of the output signal of the bandpass filter within a predetermined range, and the amplitude limiting circuit A subtractor for subtracting the output signal of the above from the reproduced luminance signal, and a combining means for combining the output signal of the subtractor and the reproduced color signal to obtain a color television signal. A video signal processing circuit according to claim.