JPH08126026A - Color signal reproducing device - Google Patents

Abstract

PURPOSE: To prevent the distortion in a color image in a practically sufficient range by extracting a signal component at a prescribed band from the output of an oscillation means via a filter means and outputting the signal component to a frequency conversion and phase synchronization means and outputting it to a signal processing means as a reference signal. CONSTITUTION: A band pass filter BPF 35 eliminates undesired frequency components other than a prescibed frequency in a reference chrominance subcarrier inputted from a crystal oscillator 34 and gives the resulting signal to a phase comparator section 20 and a 90 deg. phase shift section 23 and a contour correction section 32 of a reproduction killer section 18. In this case, the phase is synchronized in an APC system color synchronization section 41 by using a reference chrominance subcarrier outputted from the BPF 35 and a color burst signal ouputted from a burst gate section 17. A color image without distortion is displayed by outputting the output signal from the crystal oscillator 34 to the APC system color synchronization section 41 and the contour correction section 32 via a BPF 35 as a common reference signal in this way.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Industrial Application Conventional Technology (FIGS. 2 to 4) Problem to be Solved by the Invention Means for Solving the Problem (FIG. 1) Action (FIG. 1) Example (FIG. 1) Effect of the Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal reproducing device,
For example, it is suitable for application to a color signal reproducing device used in a VTR.

[0003]

2. Description of the Related Art Conventionally, a video tape recorder (VTR)
In the above, the externally input composite video signal is separated into a luminance signal, a color signal, and a synchronization signal, and the color signal is sent to the color signal recording circuit provided inside the VTR for low-frequency conversion, and then the magnetic signal is generated. It is designed to record on tape.

For example, in the case of an NTSC type VTR, FIG.
As shown in, the composite video signal S1 supplied from the outside is input to the band filter (BPF) 2 of the color signal recording circuit 1, the color signal S2 is extracted from the composite video signal S1 in the band filter 2, and then ACC ( Automatic Chroma
Level Control) unit 3 The ACC unit 3 performs gain control so that the signal level of the color signal S2 becomes a constant value, and then sends the gain control signal S3 to the frequency converter 4 and the killer detection unit 6 of the color killer unit 5, respectively.

At this time, the local oscillator 7 to the frequency converter 4
Is the frequency of the gain control signal S3, that is, the color signal S2.
Carrier frequency f _C (≈3.58 [MHz]) and low frequency f _s
Oscillation frequency f _C + f _s which is the sum of (≈629 [KHz])
As a result, the frequency converter 4 outputs the frequency 2f _C + f _s, which is the sum of these frequencies, to the low-pass filter (LP
F) It is designed to be sent to 8. Low-pass filter 8
Removes the carrier frequency f _C from the frequency 2f _C + f _s , extracts only the low frequency band f _s, and sends this to the killer switch 9 of the recording killer unit 5 as the low frequency conversion color signal S4.

In the recording killer unit 5, the killer detection unit 6
Is adapted to send the detection signal S5 obtained by detecting the burst level of the gain control signal S3 to the killer switch 9. Here, the gain control signal S
When 3 is a black and white signal, the burst level is lowered A
Since noise is generated in the CC unit 3, the killer switch 9 removes the noise by blocking the output from the low-pass filter 8 based on the detection signal S5 output from the killer detection unit 6. .

On the other hand, when the gain control signal S3 has a color burst signal, the recording killer unit 5 outputs the low-frequency converted color signal S4 as it is to a video head (not shown) via a recording amplifier (not shown). It is supplied and superimposed on the FM luminance signal and recorded on a magnetic tape (not shown).

In FIG. 3, reference numeral 10 denotes a color signal reproducing circuit, which pre-amplifies the low-frequency converted color signal S4 and FM luminance signal S5 reproduced from the video head of the color signal recording circuit 1 in FIG. After being amplified via, the signal is sent to the low-pass filter 11 of the color signal reproducing circuit 10. The low-pass filter 11 has a low-pass conversion color signal S4 and an FM luminance signal S.
The FM luminance signal S5 out of 5 is removed and sends only the low-band converting chrominance signal S4 composed of low frequency f _s in the ACC unit 12.

The ACC unit 12 performs gain control so that the signal level of the low-frequency converted color signal S4 becomes a constant value, and then the AP
The gain control signal S10 is sent to the frequency converter 14 of the C (Automatic Phase Control) system color synchronizing section 13. The low-frequency converted color signal S4 reproduced at this time often has a jitter (time-axis fluctuation), and in this case, the gain control signal S
10 frequencies, that is, the frequency f _{s of the} low-frequency conversion color signal S4
Is added with the frequency variation Δf due to jitter, and as a result, the frequency converter 14 has a frequency f _s + which is the sum of these.
Δf is sent out.

In the APC system color synchronization section 13, the frequency converter 14 outputs the gain control signal S10 output from the ACC section 12 to the frequency f _s + Δf and the variable voltage controlled oscillator (VCO) 15 outputs the oscillation frequency f _C + f _s. + Δf is injected. As a result, the frequency converter 14 determines that the frequency variation Δ
band filter 1 with carrier frequency f _C where f is canceled
6 is sent.

The band filter 16 has a carrier frequency f _C.
After removing the component other than the predetermined band, it is sent to the killer switch 19 of the burst gate unit 17 and the reproduction killer unit 18 as the carrier color signal S11, and again to the ACC unit 12. There is. The burst gate unit 17 extracts only the color burst signal S12 from the carrier color signal S11 and sends it to the phase comparison unit 20 and the phase comparison unit 21 of the reproduction killer unit 18, respectively.

The phase comparison unit 20 includes a burst gate unit 1
While the color burst signal S12 is input from 7,
Crystal oscillator 22 to 3.58 [MHz] reference color subcarrier S1
3 is input for oscillation. The phase comparison unit 20 compares the phases of the color burst signal S12 and the reference color subcarrier S13 of 3.58 [MHz] and determines the voltage based on the phase difference as VCO1.
By outputting to V5, the oscillation frequency of the VCO 15 is controlled.

Further, the crystal oscillator 22 includes a reproduction killer section 18
The 90 ° phase shifter 23 of the standard color subcarrier S of 3.58 [MHz]
13 oscillates and outputs the 90 ° phase shifter 23.
In (1), after the oscillation output phase of the reference color subcarrier S13 is shifted by 90 °, it is sent to the phase comparison section 21 as a phase shift signal S14.

Therefore, the phase comparison unit 21 of the reproduction killer unit 18
The color burst signal S12 output from the burst gate unit 17 and the phase shift signal S14 output from the 90 ° phase shift unit 23 are input to the. Accordingly, the phase comparison unit 21 compares the phases of the color burst signal S12 and the phase shift signal S14 to determine whether the color burst signal S12 is oscillated in synchronization with the reference color subcarrier S13 of 3.58 [MHz]. Therefore, the phase comparison section 21 sends the comparison result to the killer switch 19 as the comparison output signal S15.

In this way, the VCO 15 can oscillate and output the frequency f _C + f _s + Δf containing the variation Δf of the same frequency as the gain control signal S10 as described above and inject it into the frequency converter 14. As a result, it is possible to obtain the carrier color signal S11 having a stable phase in which the frequency variation Δf is canceled in the frequency converter 14.

Subsequently, when the carrier color signal S11 sent from the APC system color synchronizing section 13 to the killer switch 19 of the reproducing killer section 18 is a black and white signal, the burst level is lowered and noise is generated in the ACC section 12. Therefore, the killer switch 19 cuts off the output from the band filter 16 based on the comparison output signal S15 output from the phase comparison unit 21 to remove the noise.

On the other hand, when the carrier color signal S11 includes a color burst signal, the reproduction killer section 18 sends the carrier color signal S11 as it is to an output amplifier (not shown), and finally a predetermined signal. By performing the processing, for example, a color image based on the primary color signals generated in a color picture tube (not shown) can be reproduced.

In the color signal reproducing circuit 10 having such a structure, a method of providing a decoding / encoding type contour correcting section (not shown) on the output side of the reproducing killer section 18 has been considered. That is, the contour correction unit temporarily decodes the input carrier color signal, and then, for example, reduces the roundness (droop) generated at the rising or falling portion of the signal waveform to 1, for example.
This circuit corrects the edges of the signal waveform by emphasizing the edges of the signal waveform using a delay line having a horizontal period (1H), and then encodes and outputs the color signal.

In this case, the contour correction section uses the carrier signal S11.
Since it is demodulated at a predetermined timing, it is necessary to input the reference color subcarrier to the contour correction unit in order to obtain the predetermined timing. By the way, conventionally, as a method of inputting such a reference color subcarrier, a method of generating the reference color subcarrier based on a color burst signal included in the carrier signal S11 input to the contour correction unit has been considered. There is.

However, according to the above method, a burst gate circuit and a burst gate signal forming circuit for extracting the color burst signal from the carrier signal S11, a circuit for generating a continuous reference color subcarrier from the color burst signal, and the like, It is necessary to newly provide various circuits.
Therefore, there is a problem that the entire apparatus becomes complicated and the adjustment work becomes complicated due to the increase in the number of adjustment points provided associated with these circuits.

As one method for solving this problem, A
Crystal oscillator 22 in the PC system color synchronization unit 13 (FIG. 3)
A method of outputting the oscillating output as the reference color subcarrier to the contour correction unit is considered. As a result, the contour correction unit
It is possible to obtain the reference color subcarrier synchronized with the output signal of the C system color synchronizing section 13, and as a result, the configuration can be simplified as compared with the conventional case, and a relatively large number of adjustment points can be reduced.

That is, in the color signal reproducing circuit 30, as shown in FIG. 4 in which parts corresponding to those in FIG.
In addition to the configuration of FIG. 2, an analog CNR (Chroma Noise Reduction) 31 and a subsequent contour correction unit 32 are provided on the output side of the reproduction killer unit 18, and the contour correction unit 32 and the crystal oscillator 34 in the APC system color synchronization unit 33 are provided. 4.43M BPF
(Bandwidth filter) 35 for connection.

Here, the color signal reproducing circuit 30 is used in a PAL type VTR, and the NTSC type VTR shown in FIG.
The color signal reproducing circuit 10 used for the carrier frequency f _c ≈
Differ in consisting of 4.43 [MHz] and the low frequency f _s ≒ 627 [KHz], the crystal oscillator 34, low pass filter 36 and band filter 37 is different correspondingly.

In the color signal reproduction circuit 30, the carrier color signal S11 output from the APC system color synchronization section 33 is input to the analog CNR 31 via the reproduction killer section 18.
The analog CNR 31 reduces the noise of the carrier color signal S11, and then uses this as the CNR signal S30.
Send to 2.

On the other hand, the crystal oscillator 34 in the APC system color synchronizing section 33 includes a phase comparing section 20 and a reproducing killer section 18.
To the 90 ° phase shifter 23 of 4.43 [MHz] reference color subcarrier S3
1 is also sent to the contour correction unit 32 via the 4.43M BPF 35 to the reference color subcarrier S31 of 4.43 [MHz].
Is sent.

Here, the crystal oscillator 34 and the contour correction unit 3
When the reference carrier wave S31 is transmitted from the crystal oscillator 34 to the contour correction unit 32 without inserting the 4.43M BPF 35 between the two, 4.43 [MHz] of the reference color subcarrier wave S31
Due to the presence of frequency components other than the above, the waveform of the color output signal S33 of 4.43 [MHz] decoded / encoded in the contour correction unit 32 may be distorted.

Therefore, the crystal oscillator 34 and the contour correction unit 3
The 4.43M BPF 35 inserted between the two is a crystal oscillator 34.
4.43 [MHz of the reference color subcarrier S31 output from
After removing unnecessary frequency components other than the above], this is sent to the contour correction unit 32 as the reference color subcarrier S32.

[0028]

However, according to the above method, in the 4.43M BPF 35, the delay between the reference color subcarrier S31 input from the crystal oscillator 34 and the reference color subcarrier S32 output to the contour correction unit 32 is delayed. Since the time increases, the reference color subcarrier S31 and the reference color subcarrier S3
There will be a phase difference with 2. On the other hand, in the APC system color synchronizing section 33, the reference color subcarrier S31 output from the crystal oscillator 34 and the color burst signal S12 output from the burst gate section 17 are synchronized in phase.

As a result, the CNR signal S30 input from the APC system color synchronization section 33 to the contour correction section 32 via the reproduction killer section 18 and the subsequent analog CNR31 is always supplied with the reference color subcarrier S31 output from the crystal oscillator 34. A constant phase relationship is maintained. However, in this case, the reference color subcarrier S31 and the CNR signal S30 are preset so that there is no phase shift between them.

In the 4.43M BPF 35, the phase difference generated between the reference color subcarrier S31 and the reference color subcarrier S32 varies depending on the accuracy of the components constituting the 4.43M BPF 35 and the temperature change. Therefore 4.43M BP
It is necessary to perform adjustment work according to the accuracy of the components that make up the F35, and it is difficult to always maintain the desired adjustment state by performing initial adjustment work based on the temperature characteristics of the 4.43M BPF35. There is a problem.

C input to the contour correction unit 32 in this way
There is a problem that a phase shift occurs between the NR signal S30 and the reference color subcarrier S32 output from the 4.43M BPF 35, and the phase shift also varies.

In this case, in the PAL system, that is, in the system in which the demodulation axis of the CNR signal S30 is switched so as to invert the phase with a difference of ± 45 ° for each 1H with respect to the phase of the CNR signal S30 with reference to the color burst signal. In the contour correction section 32, there is a possibility that the color output signal S33 modulated to 4.43 [MHz] changes in amplitude every 1H and a step is generated. As a result, when the color output signal S33 is finally subjected to predetermined signal processing and reproduced on a color picture tube (not shown), for example, a distorted color image is displayed on the color picture tube. There was a problem.

The present invention has been made in consideration of the above points, and is intended to propose a color signal reproducing apparatus capable of preventing distortion of a color image in a practically sufficient range.

[0034]

In order to solve such a problem, according to the present invention, the low-pass converted color signal is frequency-converted to the same frequency as the output of the oscillating means 34, and the color signal and the phase of the output of the oscillating means are converted. Frequency conversion and phase synchronization means 33 for synchronizing the signals, and signal processing means 3 for performing predetermined signal processing after demodulating the output of the frequency conversion and phase synchronization means 33.
2 and using the output of the oscillation means 34 as a reference signal of a predetermined frequency for demodulating the output of the frequency conversion and phase synchronization means 33 in the signal processing means 32.
0, a filter means 35 for extracting a signal component of a predetermined band from the output of the oscillating means 34 is provided, and the signal component extracted through the filter means 35 is output to the frequency conversion and phase synchronization means 33 and used as a reference signal. The signal is output to the signal processing means 32.

[0035]

After the output of the oscillating means 34 is extracted through the filter means 35 as a signal component in a predetermined band, the signal component is output to the frequency converting and phase synchronizing means 33 and also to the signal processing means 32 as a reference signal. By doing so, it is possible to prevent a phase difference from being generated between the output of the frequency conversion / phase synchronization means 33 and the reference signal input to the signal processing means 32, and thus the distortion of the color image is practically sufficient. Can be prevented.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 4 are designated by the same reference numerals, reference numeral 40 denotes a color signal reproducing circuit as a whole, and unlike the configuration of FIG. 4, the 4.43M BPF 35 has an APC system color synchronizing section 41 inside. Crystal oscillator 34 and phase comparator 2
0. The reference color subcarrier S31 of 4.43 [MHz] output from the crystal oscillator 34 is set to 4.43 MB.
The signals are sent to the phase comparison unit 20, the 90 ° phase shift unit 23 of the reproduction killer unit 18, and the contour correction unit 32 via the PF 35, respectively.

That is, the 4.43M BPF 35 is a 4.43 [MHz] reference color subcarrier S3 input from the crystal oscillator 34.
After removing unnecessary frequency components other than 4.43 [MHz] of No. 1, these are sent to the phase comparison unit 20, the 90 ° phase shift unit 23, and the contour correction unit 32 as the reference color subcarrier S40. In this case, in the APC system color synchronization unit 41, 4.
43M Reference color subcarrier S40 output from BPF 35
And the color burst signal S12 output from the burst gate unit 17 are synchronized in phase.

In the above configuration, the reference color subcarrier S31 output from the crystal oscillator 34 is supplied to the phase comparison unit 20, the 90 ° phase shift unit 23 and the contour correction unit 32 via the 4.43M BPF 35 as a reference having the same signal. Since the color subcarrier S32 is output, the APC color synchronization unit 4
CNR signal S30 input to the contour correction unit 32 from 1 through the reproduction killer unit 18 and the subsequent analog CNR 31.
And the reference color subcarrier S output from the 4.43M BPF 35
No delay time with 40 occurs. However, in this case,
It is set in advance so that there is no phase shift between the reference color subcarrier S40 and the CNR signal S30.

As a result, there is no phase difference between the CNR signal S30 and the reference color subcarrier S40, and a constant phase relationship is always maintained, so that the contour correcting section 32 demodulates the CNR signal S30 and obtains it. In the 4.43 [MHz] color output signal S33, the amplitude does not fluctuate every horizontal period (1H) and a step does not occur.

According to the above configuration, the output signal from the crystal oscillator 34 is output as the common reference signal to the APC system color synchronizing section 41 and the contour correcting section 32 via the 4.43M BPF 35, respectively. The signal demodulated in 32 is not distorted, and thus the predetermined signal processing is finally performed to display a distorted color image on the color picture tube.

In the above embodiment, the case where the 4.43M BPF 35 is used as the filter for extracting the signal component in the band of 4.43 [MHz] from the output signal of the crystal oscillator 34 has been described, but the present invention is not limited to this. No 4.43 (MHz)
The present invention can be applied to a ceramic filter or the like as long as it is a filter for extracting a signal component in the band.

In the above-described embodiment, the crystal oscillator 34 is provided inside the APC system color synchronizing section 41, but the present invention is not limited to this.
May be provided outside the APC system color synchronization section 41.

Further, in the above-described embodiment, the case where the decoding / encoding type contour correction unit 32 is applied has been described, but the present invention is not limited to this, and instead of the contour correction unit 32, a decoding / encoding system is used. If present, the present invention can be applied to various circuits such as a TBC (time base collector) and a noise canceller.

[0045]

EFFECTS OF THE INVENTION After extracting the signal component of a predetermined band from the output of the oscillating means through the filter means, the signal component is output to the frequency converting and phase synchronizing means and also to the signal processing means as a reference signal. By doing so, it is possible to prevent a phase difference between the output of the frequency conversion / phase synchronization means and the reference signal input to the signal processing means, and thus to prevent distortion of the color image in a practically sufficient range.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a color signal reproducing circuit according to the present invention.

FIG. 2 is a block diagram showing a conventional color signal recording circuit.

FIG. 3 is a block diagram showing a conventional color signal reproducing circuit.

FIG. 4 is a block diagram showing a conventional color signal reproducing circuit.

[Explanation of symbols]

11, 36 ... Low-pass filter, 12 ... ACC, 13,
33, 41 ... APC system color synchronization unit, 14 ... Frequency converter, 15 ... VCO, 16, 37 ... Band filter,
17 ... Burst gate part, 18 ... Regeneration killer part, 1
9 ... Killer switch, 20, 21 ... Phase comparator, 2
2, 34 ... Crystal oscillator, 23 ... 90 ° phase shifter, 31 ...
… Analog CNR, 32 …… Outline correction unit, 35 …… 4.43
M BPF.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 9/89

Claims (3)

[Claims] 1. A frequency conversion and phase synchronization means for frequency-converting the low-pass-converted color signal to the same frequency as the output of the oscillating means and for synchronizing the color signal with the output of the oscillating means in phase. Signal processing means for performing predetermined signal processing after demodulating the output of the conversion and phase synchronization means, and for demodulating the output of the oscillation means in the frequency conversion and phase synchronization means of the signal processing means. In the color signal reproducing apparatus using the reference signal of the predetermined frequency as described above, a filter means for extracting a signal component of a predetermined band of the output of the oscillation means is provided, and the signal component extracted through the filter means is subjected to the frequency conversion. And a color signal reproducing device which outputs the reference signal to the signal processing means as well as the phase synchronizing means. 2. The color signal reproducing apparatus according to claim 1, wherein the color signal reproducing apparatus is used in a PAL system video tape recorder. 3. The signal processing means demodulates the output of the frequency conversion and phase synchronization means based on the reference signal, and then emphasizes the contour part of the signal waveform of the output to correct the waveform distortion. The color signal reproducing device according to claim 1, wherein the color signal reproducing device comprises means.