JPH0614342A - Magnetic recorder - Google Patents

Abstract

PURPOSE:To provide a magnetic recorder capable of suppressing the deterioration of picture quality at the time of recording/reproducing a chroma signal. CONSTITUTION:In the case of recording a chroma signal, the whole chroma signal is non-linearly emphasized by a chroma dynamic emphasis circuit 38 and then a burst signal is emphasized by a burst emphasizing circuit 8. At the time of reproducing the chroma signal, the burst signal is deemphasized by a burst deemphasizing circuit 26 and then the chroma signal is non-linearly deemphasized by a chroma dynamic deemphasizing circuit 39. Since the chroma signal is emphasized/deemphasized, the interference of crosstalking is suppressed, and because the burst signal is also emphasized/deemphasized, spurious interference due to a comb filter can also be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and more particularly, to a good reproducing image quality in a color video signal recording / reproducing apparatus for recording / reproducing an FM-modulated luminance signal and a carrier color signal whose frequency is converted into a low frequency band. And a magnetic recording / reproducing apparatus for providing the same.

[0002]

2. Description of the Related Art As a conventional technique for improving chroma image quality in a color video signal processing circuit, Japanese Patent Publication No. 51-43.
As described in Japanese Patent No. 331, 331, there is one that emphasizes the amplitude of a burst signal in a chroma signal at the time of recording and suppresses it at the time of reproduction.

This conventional technique has the following problems.

(1) Increased crosstalk interference from adjacent video tracks.

(2) Increase in spurious interference of the comb filter provided in the reproduction color video signal processing circuit.

(3) Generation of phase distortion due to emphasis and suppression of burst signal amplitude.

[0007]

FIG. 1 shows an embodiment of a conventional color video signal processing circuit in a magnetic recording device.

First, the operation of the signal processing circuit of the recording system from the input terminal 1 to the recording head 13 will be described with reference to FIG. The recording color video signal supplied to the input terminal 1 is supplied to the LPF (low pass filter) 2 and the BPF.
(Band pass filter) 6 is introduced. The LPF 2 and the BPF 6 separate the color video signal into a luminance signal and a color signal, and the luminance signal is output to the LPF 2 as a luminance signal.
Color signals are introduced to the outputs of the BPF 6, respectively. The luminance signal separated by the LPF 2 passes through the AGC circuit (automatic gain control circuit) 3 for level adjustment, and is FM-modulated by the FM modulator 4. The FM signal after modulation has a band of about 1.2 MHz to 1.5
Passing through an HPF (high-pass filter) 5 above MHz,
It is led to the mixer 6. On the other hand, the color signal separated by the BPF 6 passes through the ACC circuit (automatic color level control circuit) 7 for level adjustment, and is guided to the burst emphasis circuit 8.
The burst signal portion of the color signal is emphasized by about 6 dB. (Hereinafter, referred to as burst emphasis.) The color signal subjected to the burst emphasis is guided to the frequency converter 9 and low-frequency converted to about 0.2 MHz to 1.2 MHz. This low-pass converted color signal is guided to the mixer 6 through the LPF having a band of about 1.2 MHz. The FM signal and the low-frequency conversion color signal guided to the mixer 6 as described above pass through the recording amplifier 12 and the recording head 13 to the video tape 1.
Recorded in 4.

Next, the operation of the signal processing circuit of the reproducing system from the reproducing head 15 to the output terminal 28 will be described. The signal reproduced from the video tape 14 by the reproducing head 15 passes through the preamplifier 16 and the HPF 17 and LPF.
21. The HPF 17 and the LPF 21 separate the reproduction signal into an FM signal and a low frequency conversion color signal,
The FM signal is output to the output of the HPF 17, and the low-frequency conversion color signal is output to the output of the LPF 21.

The FM signal separated by the HPF 17 passes through a limiter circuit 18, and is demodulated into a luminance signal by an FM demodulator 19. The demodulated luminance signal passes through the LPF 20 and is guided to the mixer 27. On the other hand, the low-pass conversion color signal separated by the LPF 21 passes through the ACC circuit 22, is guided to the frequency converter 23, and is converted into a color signal of the original subcarrier band of about 3,58 MHz ± 500 KHz. This color signal is BP
A comb filter 25 for suppressing the crosstalk component of the color signal from the adjacent video track that passes through F24.
Be led to. The color signal in which the crosstalk component is suppressed is guided to the burst de-emphasis circuit 26, the burst signal portion is suppressed by about 6 dB, and is guided to the mixer 27 (hereinafter referred to as burst de-emphasis). The luminance signal and the color signal guided to the mixer 27 as described above are guided to the output terminal 28 as a reproduced color video signal.

In the color signal processing circuit of the above-mentioned conventional example, the S / N of the reproduced burst signal is improved by performing burst emphasis during recording, and although not shown, the reproduced APC is used.
It is characterized in that the phase error of the circuit (automatic phase control circuit) is suppressed and the residual phase jitter in the reproduced color signal component is improved.

On the other hand, the conventional example shown in FIG. 1 has the following problems in the burst emphasis and the de-emphasis.

First, there is an increase in crosstalk of burst signal components from adjacent video tracks. FIG. 2 shows an example of a recorded video track pattern in the case where the number of deviations H of H from an adjacent video track is αH = 1H. In particular, as shown in FIG. 2, when 2αH ≠ (n + 1) (where n is an integer),
The positions of the horizontal sync signals with the adjacent video tracks are not adjacent to each other, the so-called H arrangement is deviated, and the crosstalk component of the burst signal from the adjacent video tracks is superimposed on the chroma signal, so that it appears in the playback screen and the image quality is remarkably improved. to degrade.

Secondly, there is deterioration of reproduced image quality due to spurious components of the delay line used in the reproduction comb filter 25. As the comb filter 25, 1H in the NTSC system
The delay line (where H represents one horizontal period) is PA
In the L system, a 2H delay line is used.
Spurious components such as secondary reflection and tertiary reflection are superimposed on the output signal of the comb filter 25. Therefore, guiding the burst-emphasized color signal to the comb filter 25 as shown in FIG. 1 increases the level of the spurious component of the burst signal and deteriorates the reproduced image quality.

Third, there is a phase distortion of the burst signal due to burst emphasis and de-emphasis. That is, by emphasizing and suppressing only the burst signal component of the color signal by about 6 dB, the relative phase between the burst signal and the chroma signal changes, and a hue change occurs in the reproduced image quality.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording apparatus capable of suppressing deterioration of image quality due to burst emphasis and de-emphasis in the above-mentioned conventional example and improving residual phase jitter in reproduced color signal components.

[0017]

In order to achieve the above object, a chroma dynamic emphasis which emphasizes a low level chroma signal at the time of recording and a low level chroma signal at the time of reproduction are suppressed so as to be complementary to that at the time of recording. When it has a characteristic chroma dynamic de-emphasis, the chroma dynamic de-emphasis is provided after the reproduction chroma comb filter.

Further, burst de-emphasis in the reproducing system is performed before the comb filter.

[0019]

According to the present invention, since the chroma signal at the time of recording is emphasized to a low level, the crosstalk interference from the adjacent video track is reduced.

Also, de-emphasis of the burst signal before the comb filter does not increase the spurious interference of the comb filter.

[0021]

FIG. 3 shows an embodiment of the present invention. The circuit configuration of FIG. 3 is almost the same as that of FIG. 1, except that the chroma dynamic emphasis circuit 38 that emphasizes a low-level chroma signal nonlinearly depending on the level and a low-level chroma signal with a characteristic complementary thereto. The chroma dynamic de-emphasis circuit 39 that suppresses the non-linearity depending on the level is provided, and in the conventional example of FIG. 1, the burst emphasis circuit 8 at the time of recording is input to the input side of the frequency converter 9 and burst at the time of reproducing. While the de-emphasis circuits 26 are provided on the output sides of the frequency converters 23, respectively, conversely, in the present invention, the burst emphasis circuit 8 is provided.
Is provided on the output side of the frequency converter 9 and the burst de-emphasis circuit 26 is provided on the input side of the frequency converter 23.

Hereinafter, it will be described that the one embodiment reduces crosstalk interference of the burst signal from the adjacent video track and suppresses image quality deterioration.

As is known, the crosstalk component of the chrominance signals from adjacent video tracks is reproduced comb filter 25.
Is suppressed by. When an ultrasonic delay line is used for the reproduction comb filter 25, the average D of 15 dB or more in the band is obtained.
/ U ratio (however, D is the required signal and U is the unnecessary signal)
Is obtained. Further, even if the reproduction level of the color signal from the adjacent video track to the main video track due to mistracking of the reproduction head is set to about -6 dB, the crosstalk component of the burst signal is -20 dB of the main signal.
It becomes the following small amplitude components. Therefore, the chroma dynamic de-emphasis circuit 39 provided after the reproduction comb filter suppresses the crosstalk component of the burst signal, which is a small amplitude component, and reduces crosstalk interference. For example, when the suppression level when the input level of the dynamic de-emphasis circuit 39 is -20 dB is selected to be about 6 dB, the crosstalk component of the burst signal when the burst emphasis amount is about 6 dB is set to the same level as in the case where the burst emphasis is not performed. can do. That is, by using the one embodiment, it is possible to secure the same image quality as the image quality deterioration due to the burst interference from the adjacent video track when the burst emphasis is not performed.

As described above, in order to suppress the crosstalk of the burst signals from the adjacent video tracks, the chroma dynamic de-emphasis circuit 39 must be provided at the subsequent stage of the reproduction comb filter 25. Therefore, the chroma dynamic de-emphasis circuit 39 is provided after the burst de-emphasis, so that the chroma dynamic emphasis circuit 38 has a characteristic complementary to that of the de-emphasis circuit 39.
Must be provided before the burst emphasis circuit 8.

Next, it will be explained that the second problem is that the deterioration of the image quality due to the spurious component of the delay line used in the reproduction comb filter 25 is suppressed.

An ultrasonic wave delay line is generally used for the reproduction comb filter 25, and in order to secure the band of this ultrasonic wave delay line, the low frequency conversion color signal cannot be used as an input signal. Therefore, the reproduction comb filter 25 is provided on the output side of the frequency converter 23, and as an input signal,
Color signals in the subcarrier band are used. Therefore, by performing the burst de-emphasis in front of the comb filter as in the present invention, the comb filter 25 receives the color signal which has been frequency-converted into the original sub-carrier band by the frequency converter 23 and which has been burst de-emphasized. Be guided. Therefore, the level of the spurious component of the burst signal generated in the comb filter 25 is reduced. For example, when the burst emphasis amount and the de-emphasis amount are about 6 dB, the spurious component of the burst signal is reduced by about 6 dB as compared with the conventional example of FIG.

Although the image quality deterioration due to the spurious component of the burst signal becomes remarkable when the chroma signal level is small, the image quality deterioration can be greatly suppressed by using the present invention.

Further, it will be explained that the third embodiment suppresses the hue change of the reproduced image quality due to the relative phase change between the burst signal and the chroma signal, which is the third problem of the conventional example of FIG.

Generally, in a circuit for switching the gain of a small signal like the burst emphasis circuit 8 or the de-emphasis circuit 26, the delay difference of the circuit at each gain becomes the phase difference. Therefore, as the frequency of the small signal is lower, the phase difference can be suppressed more. That is,
In the conventional example as shown in FIG. 1, the burst emphasis and the de-emphasis are performed by the color signal in the subcarrier band of about 3.58 MHz ± 500 KHz, whereas in the present invention, the frequency converter 9 is used at the time of recording as described above. Burst emphasis is performed on the color signal that has been converted to a low frequency range of about 0.2 MHz to 1.2 MHz, and the frequency converter 26 is used during reproduction.
Since the burst de-emphasis is performed by the low-frequency conversion color signal on the input side of, the change in the relative phase between the burst signal and the chroma signal due to the burst emphasis and de-emphasis is suppressed, and the hue change in the reproduced image quality can be reduced.

Further, in the embodiment of the present invention shown in FIG. 3, not only the above-mentioned image quality improvement but also the S / N improvement of the reproduction chroma signal and the recorded FM signal and other frequency components (for example, pilot signal) are It is also possible to reduce color moire, cross color interference, and the like caused by leaking to the low-frequency conversion color signal during reproduction.

Furthermore, by using the present invention, FIG.
It is possible to reduce the damage of switching that occurs when the gains of the burst signal and the chroma signal are switched at the time of burst de-emphasis, which has occurred in the conventional example. That is, as shown in FIG. 2, the burst de-emphasis circuit 2 is used in the present invention.
Since the frequency converter 23 and the BPF 24 are provided on the output side of 6, the above-mentioned switching flaw, which is an impulse or a DC offset, is in a wide band, and is guided to the BPF 24 through the frequency converter 23 to cause this switching. The energy component of the wound is greatly reduced. This also reduces the phase distortion of the burst signal that is caused by switching flaws and suppresses the hue change of the reproduced image quality.

FIG. 4 is a color signal processing circuit showing an embodiment of the present invention in which the ACC circuits 7 and 22 of the recording and reproducing system and the frequency converters 9 and 23 are shared in the example of FIG. .

In FIG. 4, reference numeral 29 is an input terminal for a color signal separated from a recorded color video signal, 30 is an input terminal for a low frequency conversion color signal separated from a reproduction signal, 31, 34 are switch circuits, and 32 is an ACC. Circuit, 34 is a frequency converter,
Reference numeral 35 is an output terminal for a recording low frequency conversion color signal, 36 is an output terminal for a reproduction color signal, and others are the same as in FIGS. 1 and 3.

In the one embodiment, the switch circuits 31 and 33 are connected as shown in the drawing during recording, and are connected in reverse to the one shown in the drawing during reproduction. The circuit operation is similar to that shown in FIG. 3 and can be easily inferred, so the description thereof is omitted here. However, although not shown, A for controlling the ACC circuit 32
As the CC detection signal, the burst signal in the preceding stage of the frequency converter 33 is used for recording, and the comb filter 25 is used for reproduction.
The burst signal in the latter stage is suitable. That is, ACC
Since both of the detection signals are in the sub-carrier band and are not subjected to burst emphasis, the reproduction color signal level from the output terminal 36 can be made constant, and the input level of the frequency converter 34 can be made almost constant for recording and reproduction. You can choose the optimum range.

Further, when the present invention of FIG. 4 is used as described above, the ACC circuit 32 and the frequency converter 34 can be used for both recording and reproduction, and the number of constituent circuits can be reduced and the dynamic range of the circuit can be optimized. It can be a circuit suitable for being integrated into an IC.

Next, specific circuit configurations of the chroma dynamic emphasis circuit 38 and the de-emphasis circuit 39 used in the present invention as described above will be described.

FIG. 5 shows a concrete embodiment of the chroma dynamic emphasis circuit 38, and FIG. 6 shows a concrete embodiment of the chroma dynamic de-emphasis circuit 39.

5 and 6, 40 and 44 are input terminals of the respective circuits, 41 is a limiter circuit, 42 is an adder, and 4
3, 46 are output terminals of the respective circuits, and 45 is an adder. In the embodiment of FIG. 5, the limiter circuit 41 limits the amplitude of the large-amplitude signal and does not limit the amplitude of the small-amplitude signal.
As a result, there is a dynamic characteristic in which the amount of emphasis increases when the signal has a small amplitude. FIG. 6 is an inverse circuit of FIG. 5, and by constructing with a negative feedback type, complementary characteristics can be obtained respectively.

7 and 8 show another specific embodiment of the chroma dynamic emphasis circuit 38 and the de-emphasis circuit 39, respectively.

In FIGS. 7 and 8, 47 is an inverse bell filter, which is different from FIGS. 5 and 6. 7 and 8, by providing the inverse bell filter 47,
Frequency characteristics are added to chroma dynamic emphasis and de-emphasis.

9 and 10 show another specific embodiment of the chroma dynamic emphasis circuit 38 and the de-emphasis circuit 39, respectively.

In FIGS. 9 and 10, reference numeral 48 denotes a trap circuit, which does not have the dynamic characteristic at the center of the band of the chrominance signal but gives the both side bands with the dynamic characteristic.

[0043]

As described above, by providing chroma dynamic emphasis and de-emphasis,
Burst interference from adjacent video tracks is reduced,
Good color reproduction image quality can be obtained.

Further, by further using the present invention,
It is possible to improve the hue change of the reproduced image quality caused by the burst emphasis and the de-emphasis and the deterioration of the image quality due to the spurious of the burst signal in the reproduced comb filter.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a conventional magnetic recording / reproducing apparatus.

FIG. 2 is a tape pattern diagram.

FIG. 3 is a block diagram showing an embodiment of the present invention.

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is a block diagram showing an example of a dynamic emphasis circuit.

FIG. 6 is a block diagram showing an example of a dynamic de-emphasis circuit.

FIG. 7 is a block diagram showing an example of a dynamic emphasis circuit.

FIG. 8 is a block diagram showing an example of a dynamic de-emphasis circuit.

FIG. 9 is a block diagram showing an example of a dynamic emphasis circuit.

FIG. 10 is a block diagram showing an example of a dynamic de-emphasis circuit.

[Explanation of symbols]

 6, 24 ... BPF, 7, 32 ... ACC circuit, 8 ... Burst emphasis circuit, 9, 23, 34 ... Frequency converter, 10, 21 ... LPF, 25 ... Regenerative comb filter, 26 ... Burst de-emphasis circuit, 31 , 33 ... Switch circuit, 38 ... Chroma dynamic emphasis circuit, 39 ... Chroma dynamic de-emphasis circuit.

Claims (2)

[Claims] 1. An ACC circuit for controlling a signal level of a chroma signal to a predetermined level, a conversion circuit for frequency-converting a chroma signal whose level is controlled by the ACC circuit to a low frequency side of a frequency-modulated luminance signal, and a frequency-converted circuit. In the chroma signal recording system including the recording means for recording the low-frequency conversion chroma signal on the recording medium, the level-controlled chroma signal is output so that the emphasis amount of the low level signal becomes larger than that of the high level signal. A non-linear emphasis means for emphasis according to the level, a burst emphasis means for emphasising a burst signal in the non-linearly emphasized chroma signal by a predetermined amount, and a non-linear emphasis means are provided between the ACC circuit and the recording means. Magnetic recording device. 2. An ACC circuit for controlling a signal level of a chroma signal to a predetermined level, a conversion circuit for frequency-converting a chroma signal whose level is controlled by the ACC circuit to a low frequency side of a frequency-modulated luminance signal, and a frequency-converted circuit. The recording means for recording the low-frequency converted chroma signal on the recording medium, and the chroma signal whose level is controlled, which is provided between the ACC circuit and the recording means, responds to the signal level so that the lower the level, the greater the emphasis amount becomes. Provided between the non-linear emphasis means for nonlinearly emphasising a burst signal in the non-linearly emphasized chroma signal by a predetermined amount, and the non-linear emphasis means and the recording means,
A recording system having a burst emphasis means for emphasising a burst signal in a non-linearly emphasized chroma signal by a predetermined amount, a burst de-emphasis means for de-emphasis of a burst signal in a reproduction signal from a recording medium, and the burst described above. A comb filter that removes crosstalk components from the output signal of the de-emphasis means, and a non-linear de-emphasis means that de-emphasis the output signal from the comb filter with characteristics that are the reverse of the emphasis characteristics of the non-linear emphasis means. A magnetic recording / reproducing apparatus comprising a reproducing system having the same.