JPS6051380A - Magnetic reproducing device - Google Patents

Abstract

PURPOSE:To compensate the drop part of a reproducing output signal level of a main rotary head by an auxiliary rotary head and also to eliminate a skew generated at that time by using a delay time control means. CONSTITUTION:Main rotary heads M1, M2 and auxiliary rotary heads S1, S2 are spaced by a distance corresponding to the two horizontal synchronizing signal period of a video signal, and installed on the same rotary plane of a rotary disk 3. In this state, the drop part of a reproducing output of the main rotary heads M1, M2 in case of reproducing at a high speed is eliminated by replacing it with the reproducing output signal of the auxiliary rotary heads S1, S2. Also the skew generated in case of switching a main rotary head reproducing signal and an auxiliary rotary head reproducing signal is eliminated by making a reproducing video signal pass through a variable delay line, varying its delay time and correcting the variation of an interval of a horizontal synchronizing signal by a skew correcting circuit 25.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic reproducing apparatus capable of special (variable speed) reproduction, such as a two-rotation head type azimuth recording type video tape recorder.

Conventional configurations and their problems In recent years, in video signal magnetic recording and reproducing devices using magnetic tape such as video tape recorders, there has been a growing demand for a special (variable speed) playback function that plays back at a tape speed different from that during recording. 1 is there. Regarding still playback or slow motion playback.

A method has been proposed to control the running of the magnetic tape so that the portion where the playback head output decreases becomes the vertical retrace period.
Still playback or slow motion playback in which the noise bar hardly appears on the playback screen has been put into practical use.

However, no device has been proposed that realizes high-speed playback or reverse high-speed playback, which is one of the special (variable speed) playback functions, without noise bars.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a magnetic reproducing device that does not generate noise bars or skews not only during still playback and slow motion playback, but also during high speed playback and reverse high speed playback.

Structure of the Invention The present invention uses an auxiliary rotary head mounted close to the main rotary head to compensate for the drop in the playback output signal level of the main rotary head by switching to the reproduction output signal of the auxiliary rotary head. ′-: The skew that occurs at that time is detected by a variable delay line, a detection means for detecting the amount of skew from the reproduced output signal that has passed through the variable delay line, and a delay time of the variable delay line according to the output of the detection means. It is configured to eliminate this by using a delay time control means.

Description of examples Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a diagram showing the main part of an embodiment of the present invention, and FIG. 2 shows an example of a track pattern of a magnetic tape in which azimuthal recording is performed. In FIG. 1, Ml is a main rotating head with an azimuth angle of +6°, and Sl is an auxiliary rotating head with an azimuth angle of -6°. M2 is -6°
S2 is another main rotating head with an azimuth angle of +6, and S2 is another auxiliary rotating head with an azimuth angle of +6.

The main rotating heads M1 and M2 are 180° apart from each other.

The auxiliary rotary heads S1 and S2 are also 1800 apart from each other. The main rotary head and the auxiliary rotary head are separated by a distance corresponding to, for example, 6·-' for two horizontal synchronizing signal periods of the video signal, and are connected to a rotary disk (screw or drum) 3 as shown in FIG. are mounted on the same rotation plane. The rotating disk 3 is rotated by a motor 6 via a rotating shaft 4 in the direction of an arrow 9 at a rotation speed of 1800 r, p, m. The rotational phase of the rotating disk 3 is
It is detected by the magnet) 13, 15 and the detection head 14. The magnetic tape 6 is guided by guide posts 7 and 8 and is wound around the rotating disk 3 over 1000 times or more, and is wound around the pinch roller 1 in the direction of the arrow 10.
1 and capstan 12.

A schematic track pattern of the magnetic tape 6 is shown in FIG. In Figure 2, the track 99°101.1o
3, 105, 107 and 109 were recorded with an r5J rotating head with an azimuth angle of +6°, tracks 100+
102r j O4y 106+108 and 110
is a track recorded with a rotating head having an azimuth angle of -6°.

The diagonal lines in each track in FIG. 2 indicate horizontal synchronizing signal recording positions, and the inclination angle thereof indicates the azimuth angle. (Half of the magnetic tape 6 in the width direction is omitted with diagonal lines.) -! , and the deviation of the diagonal lines in adjacent tracks indicates that the recorded horizontal synchronization signal is deviated due to cylinder jitter. In addition, the second
The figure shows a track pattern when the magnetic tape 6 is running at 1x speed (same as the tape speed during recording). Therefore, if the main rotary head M1 scans the start point of track 101 at the field start point during 1x speed playback, then at the end of the field, track 101
Scan the end point of. As an example of high-speed playback, as shown by the broken line in FIG.
1 is the field start point, and the start point of track 101 is scanned.

At the end of the field, the end point of track 109 is scanned. The auxiliary head S1 has the same rotation plane as the rotary head M1, and is mounted close to the main rotary head M1 (in this embodiment, separated by a distance corresponding to two horizontal synchronization signal periods of the video signal). Therefore, the main rotating head M
1. Perform almost the same scan as 1. During such nine times speed reproduction, the main rotary head M1 has an unmass angle of +6, so that a head output signal as shown in FIG. 3(A) is obtained.

Further, since the auxiliary rotary head S1 has an azimuth angle of -6°, a head output signal as shown in ) in FIG. 3 is obtained. Typically, these head output signals consist of an FM-modulated luminance signal with a carrier frequency of about 3.9 ratio and a carrier color signal with a color subcarrier frequency down-converted to about e29 kHz. . Figure 3 (g) shows the time scale. Here, to indicates the field start time, and t5 indicates the field end time. During high-speed reproduction as shown in FIG. 3(A), several noise bars (portions where the head output signal is zero) occur within the field.

This allows the level drop portion of the reproduced output signal of the main rotary head M1 to be transferred to the auxiliary rotary head S1 as shown in FIG. 3(B).
It can be removed by replacing it with the reproduced output signal. However, when switching between the main rotary head reproduction signal and the auxiliary rotary head reproduction signal as described above, the deviation of the recorded horizontal synchronization signal causes a change in the interval of the reproduced horizontal synchronization signal. Skew appears on the screen.

The present invention passes a reproduced video signal through a variable delay line.

By changing the delay time, the above-mentioned change in the interval of the horizontal synchronizing signal is corrected and skew is removed.

Main rotating head M1. Switching between M2 and the auxiliary rotary heads S1 and S2 is performed as follows, for example, in the case of 9x speed.

In FIG. 4, the movable pieces of switches 21 and 22 are connected, for example, to the X side when the head switch signal [FIG. 3 (D)) is at H level, and to the Y side when it is at L level. Here, the head switch signal is sent to the detection head 14 from two magnets 113.15VC separated by 18o0 as shown in FIG.
This is a signal obtained by processing the output signal obtained in
return. This is shown in FIG. 3(D). FIG. 3 shows the field signal when the head switch signal is at H level. The magnets 13, 15 have different polarities 101-', and the cylinder phase can be detected every 1800 degrees, so that fields can be distinguished.

In FIG. 4, the movable pieces of switches 21 and 22 are connected, for example, to the X side when the head switch signal is at H level, and to the Y side when it is at L level. Now, if the head switch signal is at H level, the main rotating head M1. From the auxiliary rotary head S1, reproduction outputs as shown in FIGS. 3A and 3B, for example, are obtained. Similarly, when the head switch signal is at L level, main rotating head M2. Signals as shown in FIG. 3 (A) and (B) are obtained from the auxiliary rotary head S2.

These are input to the switch 23.

The movable piece of the switch 23 is connected to the Y side when the signal applied to the terminal 65, that is, the output signal of the switching timing control means 66 is at the H level, and to the X side when the signal is at the L level. If switching is performed by applying the main and auxiliary rotary head switching signal shown in α) in the figure, the reproduced output signal shown in FIG. 3(C) is obtained at the output end of the switch 23. Here, one embodiment of the switching timing control means will be described with reference to FIG. 5, 111-. Connect terminals 18 and 1 as previously described.
The reproduced output signals of the main rotary head and the auxiliary rotary head obtained in step 9 are passed through envelope detectors 8o and 81, respectively, to detect the envelope of the reproduced output signals. The level comparator 82 compares the level of each obtained envelope signal.
For example, if we take FIG. 3 as an example, the level of the reproduction output signal of the main rotary head, that is, the signal shown in FIG.
Level comparator 8 when the level is lower than the level of the signal shown in B).
If the output is set to the Camobi level of 2, or the L level in the opposite case, the main/auxiliary head switching signal shown in Figure 3 can be obtained.

As can be seen from Figures 3 (A) and (B), changes in the playback output signal level during high-speed playback have periodicity, so it is possible to know the level of the playback output signal by knowing the rotational phase of the rotary head. You can do it. Therefore, the main/auxiliary rotary head switching signal shown in FIG. 3 (dog) can also be generated from the rotational phase of the rotary head.

When the reproduced output signal obtained at the output terminal of the switch 23 as described above is input to the video signal demodulation circuit 24 shown in FIG. 4, a 9x reproduced video signal without noise bars is obtained from the output. However, when this reproduction signal is reproduced on the screen, as described above, the main rotary head M1. This is because skew occurs when switching between M2 and the auxiliary rotating head S1°S2.

The reproduced signal is passed through a fourth skew correction circuit 25 to correct the skew.

Next, a skew correction method will be explained.

As mentioned above, skew is caused by changes in the interval of horizontal synchronization signals, so by passing the reproduced output signal through a delay line,
This can be removed by switching the delay time and correcting the interval. To do this, it is necessary to detect the change in the interval and obtain an error signal. The error signal is obtained as follows from a closed loop circuit consisting of a phase comparator, a low-pass filter, and a voltage controlled oscillator (hereinafter abbreviated as VCO).

The output obtained from the video signal demodulation circuit 24 in FIG.
The signal obtained by switching the taps with the switch 31 through the tapped delay line 30 shown in the figure is passed through the 137°-mi horizontal synchronizing signal separation circuit 37 shown in FIG. input. The phase of the horizontal synchronizing signal input to the phase comparator 47 is compared with the output of the VCO 42. The phase difference becomes an error signal voltage and is sent to the phase comparator 4.
Appears on the output terminal of 7.

This output passes through a low-pass filter 43 and controls the oscillation frequency of the VCO 42. Therefore, the error voltage has a waveform as shown in FIG. 7(A), for example, and error information appears at its peak value.

The error signal voltage obtained in this way is input to an arithmetic circuit 6o composed of sample and hold circuits 5Q and 51,
Obtain the signal that activates the comparator. The operation of the arithmetic circuit 60 will be described below.

The tapped delay line 3o is connected to the main rotary head M1. M2 and auxiliary rotating head S1. Depending on the error signal voltage obtained from the phase comparator 47 when S2 is switched, the delay time at that time is switched to increase or decrease.

Therefore, the arithmetic circuit 6o adds the peak value of the error signal voltage to the output value of the arithmetic circuit 6o immediately before the error signal voltage appears,
It is necessary to perform an operation 4t-7 to make this a new output value. The actual operation is performed as follows. The error signal voltage obtained at the output of the phase comparator 47 is added to the output of the sample and hold circuit 51, and the sample pulse output from the timing signal generation circuit 39 is used to generate the sample and hold circuit. 50. At this time, no sample pulse is input to the sample hold circuit 51,
Output value does not change. Next, the timing signal generation circuit 39
The sample pulse is sent to the sample hold circuit 51, stored in the sample hold circuit 61, and its value is output. In this way, the error signal voltages are integrated one after another and appear at the output of the sample and hold circuit 51. Further, the two sample and hold circuits 50 and 51 input a vertical synchronizing signal to the input terminal 52 to perform reset, thereby preventing the circuit from being saturated due to accumulation of error signal voltages.

The output of the arithmetic circuit 6o obtained as described above is compared with the reference voltage generated from the reference power supply 36 by the comparator 36, and the output voltage is switched depending on the output voltage using the switch 31, for example, 7. Adjust the horizontal synchronization interval of the reproduced video signal by switching the two taps.

In this way, it is possible to obtain a playback screen without noise bars during high-speed playback and without skew when switching between the main rotating head and the auxiliary rotating head. Head 31. The scanning locus of S2 on the magnetic tape 6 is different from the above explanation, but the output signals of the main rotary heads M1 and M2 and the output signals of the auxiliary rotary heads S1 and S82 as shown in FIGS. 3(A) and (B) equivalent to (
That is, since the time at the point indicating the maximum output level and the time at the point indicating the minimum output level almost match, the circuit configuration shown in FIG. 4 can provide the same effect as during high-speed reproduction.

Here, the timing signal generation circuit 39 is configured by, for example, a monostable multipipe rake.

The head switch signal 65 and horizontal synchronization signal are input to the timing circuit 39, and sample pulses and
Creates a main/auxiliary head switching signal.

Here, a method of switching tapped delay lines was used as a means of varying the delay time, and discrete skew correction was performed, but a charge-coupled device (CAN) delay line was used instead of the tapped delay line. If the output of vCO, which is controlled by the output of the arithmetic circuit 60, is used as the clock, the delay time can be changed continuously, so skew correction can be performed continuously, and discrete It is possible to perform more accurate correction than in the conventional method. 8th
The figure shows an example of the circuit. In the figure, 70 is VCO171
is a COD delay line, and the other parts are the same as those shown in FIG. 5, so corresponding parts are given the same reference numerals.

Effects of the Invention As is clear from the above explanation, the present invention has advantages in still playback,
With a simple configuration, it is possible to realize a magnetic reproducing device that does not generate noise bars or skews not only in slow-motion reproduction but also in high-speed reproduction or reverse high-speed reproduction. Furthermore, as mentioned above, since the horizontal synchronizing signal for error detection is obtained from the reproduced output signal after passing through the tapped delay line, skew correction is performed by the feedback loop configuration. That is, the correction continues until the horizontal synchronization interval of the reproduced output signal obtained at the output of the changeover switch 31 becomes constant. Therefore, the phase comparator 47. Voltage controlled oscillator 42
．． Even if the detection means consisting of the low-pass filter 43 and the arithmetic circuit co contain non-linear elements, it has an excellent feature that it is possible to correct the horizontal synchronization interval to be constant, and its practical use is ” The value of the second one is very strong.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the main part of an embodiment of the present invention, FIG. 2 is a diagram showing an example of a track pattern of a magnetic tape recorded azimuthally, and FIG. 3 is a time chart of signals in an embodiment of the present invention. , FIG. 4 is a block diagram of an embodiment of the present invention, FIG. 5 is a block diagram of an example of a switching timing control circuit that can be used in the present invention, and FIG. 6 is a block diagram of an example of a switching timing control circuit that can be used in the present invention. "A block diagram of one example of a correction circuit, FIG. 7 is a waveform diagram showing an example of input and output signals of the arithmetic circuit in FIG. 6, and FIG. 8 is a block diagram of another skew correction circuit that can be used in the present invention. FIG. 2 is an example block diagram. Ml, M2... Main rotating head, Sl, S2...
...Auxiliary rotating head, 6...Magnetic tape,
21.22+23...Switch circuit, 42...
... Voltage limited oscillator, 43 ... Low pass filter, 47 ... Phase comparator, 30 ...
...Tapped delay line, 70...Voltage controlled oscillator, 71...Charge coupled device (CAN) delay line. Name of agent: Patent attorney Toshio Nakao and 1 other person ^
αko pirate ＼ −

Claims (5)

[Claims] (1) a set of two main rotating heads with different azimuth angles, and a set of two auxiliary rotating heads with different mounting positions from the main rotating heads and different azimuth angles;
a switching timing control means for controlling switching timing of reproduction output signals of the main rotary head and the auxiliary rotary head when running the magnetic tape at a running speed different from the tape speed during recording; and a switching timing auxiliary means. switch means for replacing the reproduction output signal of the main rotary head with the reproduction output signal of the auxiliary rotary head according to an output signal; and reproduction obtained by replacing the reproduction output signal of the main rotary head with the reproduction output signal of the auxiliary rotary head. a detection means for passing an output signal through a variable delay line and detecting a skew amount generated at the time of replacement from a change in the period of a horizontal synchronization signal of a reproduced output signal that has passed through the variable delay line; and an output of the detection means. The delay time of the variable delay line is changed according to. A magnetic reproducing device comprising a delay time control means for removing the skew. (2) The detection means includes a feedback loop circuit including a phase comparator, a voltage-side legged oscillator, and a low-pass filter, and a reproduced horizontal synchronization signal is input to the phase comparator,
The magnetic reproducing device according to claim 1, wherein the magnetic reproducing device is configured to detect the output signal of the phase comparator as a skew amount. (3) The switching timing control means includes a level detector that detects the level of the reproduction output signal of each of the main rotary head and the auxiliary rotary head, and switches between the main rotary head and the auxiliary rotary head according to the output of the level detector. The magnetic reproducing device according to claim 1 or 2, wherein the magnetic reproducing device is configured to control timing. (4) The switching timing control means is the main rotation head 31
-- The invention is characterized in that the switching timing between the main rotary head and the auxiliary rotary head is controlled according to the rotation angle of the main rotary head or the auxiliary rotary head. The magnetic reproducing device described in (2). (5) The delay time system means is configured to set the delay time of the variable delay line to a value at the midpoint of the variable delay time range of the variable delay line for each vertical synchronization period. A magnetic reproducing device according to claim (1) or (2).