JPH02220577A - Head controller for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reproduce a noiseless beautiful pattern even at variable speed reproduction by calculating a correction signal to trace a track from the result of time measurement of a detection signal of a number of revolutions of a head and the result of detection of drive speed of a tape. CONSTITUTION:A reproducing signal from a magnetic head 12 is demodulated by a demodulation circuit 3 via an amplifier 1 and a phase locked loop 2. A signal from a loop 2 reflecting a relative speed between a magnetic tape 13 and a magnetic head 12 is inputted to a signal generator 8 and a detection circuit 9 and a reference signal is inputted from a reference signal generator 7. Phase error correction is implemented by a phase detector 11 and a phase correction device 16 so that tracing to the center of a normal track is applied with a synchronizing signal separated from the detector 4 from the signal demodulated by the circuit, 3 and an ID signal from an extraction device 5. Moreover, a signal from the generator 8 and the detector 8 is received to correct the correction with respect to the deviation of a trace angle caused by the speed deviation by an angular error correction device 10. An MPU 17 adds control signals from the correction devices 10, 16 to allow a head 12 to trace the center of the track via a mechanism 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording/reproducing device, and particularly to a head control device suitable for helical scan type variable speed noiseless reproduction V'l'H.

[Background of the invention]

In order to achieve noiseless variable speed, there has been a so-called moving head technology that is mounted on a rotating cylinder and plays back data without traversing the track by deflecting a magnetic head in the width direction of the track. As an example, the technique disclosed in Japanese Patent Publication No. 63-9454 will be explained. When performing syslomorphic or quick playback by making the playback speed different from the recording speed, noise is generated because the head trace locus crosses the track. In order to avoid this, it is necessary to correct the inclination of the trace and to align the center of the trace with the center of the track. The trace slope is particularly corrected by detecting a frequency shift in the horizontal synchronizing signal, and the trace phase shift is corrected by detecting a phase shift in the vertical synchronizing signal. As shown in this conventional example,
Horizontal if you try to correct the slope and phase of the trace only by the signal played from on the tape.

It was common to measure the synchronization of vertical synchronization signals using a constant clock.

[Problem that the invention seeks to solve]

The above conventional technology can achieve noiseless operation when the rotational speed of the rotary head is constant. However, no consideration is given to the case where the rotational speed of the rotary head is changed, and in such a case, there is a problem in that noise is generated on the screen. Furthermore, conventionally, when variable speed playback is performed without noise, playback is performed while keeping the head rotation speed constant, resulting in a tracing time different from that during recording, resulting in the inconvenience that all signals on the track cannot be obtained. If a time code is recorded during the vertical blanking period, a situation will arise in which the recorded code cannot be read.

The purpose of the present invention is to reproduce a beautiful screen without noise even when the rotational speed of the rotary head is changed, regardless of whether it is in a transient state or a steady state. It is possible to realize a magnetic recording/reproducing device with a very simple configuration.

[Means for solving problems]

The above purpose is to generate a correction signal that traces the track without deviating from the rotation detection means that measures the number of rotations of the head, the time measurement result of the rotation detection signal output from the rotation detection means, and the detection result of the tape running speed. This is achieved by adding processing means for calculation.

[Effect]

The processing means for calculating the trace correction signal calculates how much the composite vector of the head trace vector generated from the rotation of the head and the vector generated from the running of the tape deviates from the track, and displaces the rotating head in the track width direction. Since correction is performed by moving the tape, tracing is performed without deviating from the track, and playback is performed without noise. By actively changing the speed of the rotating head, it is possible to pick up all the signals on the tape. .

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. In the figure, 13 is a magnetic tape, and 12 is a magnetic head.

1 is an amplifier, 2 is a phase-locked loop, 5 is a demodulation circuit, 4
5 is a synchronization signal detector, and 5 is an ID signal extractor.

6 is a reproduction circuit, 7 is a reference signal generator, 8 is a beat signal generator, 9 is a traveling direction detector, 10 is an angular error corrector, 1
1 is a phase error detector, 14 is a cylinder motor, 15 is a reproduction speed changer, 16 is a phase error corrector, 17 is a microprocessor, 18 Fi cylinder motor servo circuit, 1
9 is a moving head driver, 2 is a moving mechanism for Qii, 21 is a head rotation speed detector, 50 is a pattern generation port w1, 51 is an adder, and 80 is a head switching signal generator.

First, a signal reproduced from the magnetic tape 13 by the magnetic head 12 is amplified by the amplifier 1, passes through a phase-locked loop 2t-, and is demodulated by the demodulation circuit 6. At this time, the phase-locked loop 2 generates a signal reflecting the relative velocity between the magnetic herad 12 and the magnetic tape 13 and supplies it to the beat signal generator 8 and the running direction detector 9. In addition to this, the beat signal generator 8 and the running direction detector 9 are simultaneously supplied with a signal that serves as a reference during recording from the reference signal generator 7.

This embodiment is basically intended to record signals as digital signals on the magnetic tape 13, and the reference signal generator 7 is used as a clock signal for the digital signals during recording. During reproduction, a clock that is reproduced and phase-locked to the digital signal is required for reading out the digital signal, and the phase-locked loop 2 plays the role of generating this clock.

Now, a trace is performed to the center of the regular track using the synchronization signal demodulated into a video signal or audio signal by the demodulation circuit 5 and separated from the next signal by the synchronization signal detector 4, and the signal output from the ID signal extractor 5. Phase error correction is applied so that the This control is carried out by the phase error detector 11 and the phase error corrector 16. Furthermore, the deviation of the trace angle caused by the speed deviation is detected by the beat signal generator 8 and the running direction detector 9.
The angular error corrector 10 receives the signal from the angular error corrector 10 and performs correction to eliminate the error. Meanwhile, a magnetic head 12 mounted on a cylinder (not shown) and rotating nine times is driven by a cylinder motor 1.
If the number of rotations of 4 is changed, the velocity vector in the track direction changes. Now, assuming that the cylinder, that is, the magnetic head 12, rotates at the same speed as during recording, the reproduction speed changer 15 acts to cause the cylinder motor servo circuit 18 to rotate at the same speed as during recording. 1
7 is the angle error corrector 10 and phase error corrector 16 described above.
The moving head driver 19
In addition, the head moving mechanism 20 is controlled to change in the track width direction so as to always trace the center of the track. Here, the control signals for each element will be described somewhat quantitatively.

Now, set the clock frequency of the reference clock generator 7 to 8M.
Hz, and the rotation speed of the cylinder motor 14 is 90H1. Since the number of images recorded on the tape by the rotation of the cylinder motor 14 is 60 per second, one image is recorded in 3 tracks.
As an example, a so-called segment recording method that composes two images is taken as an example. Each track is recorded with a segment number added to it, and the above-mentioned ID signal extractor 5
Segment numbers are also extracted during signal playback.

The reference clock number for tracing one track during recording is 8x10. 180=44444, and if the head and tape are moved under exactly the same conditions during reproduction as during recording, the number of clocks output from the phase-locked loop 2 will also have the same frequency.

On the other hand, if the tape running speed during playback is double that during recording, the number of output clocks changes. Here, if the running direction of the magnetic tape and the rotating direction of the magnetic head are set to be opposite, and the relative speed increases, the number of phase-locked loop output clocks during double-speed playback will be approximately α5%.
To increase. , this is due to the following circumstances. FIG. 2 is a supplementary diagram for explanation, and in FIG. 1, 30 to 52 are velocity vectors, 33 degrees and 54 are displacements, and 35 is an angle. Now, a velocity vector 30 indicates a trace of the magnetic head 12 during recording, and a vector 51 indicates a velocity error component during reproduction.As a result, the magnetic head 12 changes as shown by a vector 52. Therefore, by displacing the head perpendicularly upward to the vector 32 as shown in Figures 33 and 34, the head can be traced without falling off the track. However, since the track trace is corrected in the direction perpendicular to the direction of movement (rotation) of the head (33.34), the magnitude of the speed remains unchanged υ.Conversely, by detecting this playback speed, It becomes possible to calculate the above-mentioned trace correction amount (for example, the amount of 33.34). Therefore, next, the amount of change in playback speed is determined. If the magnitudes of velocity vectors 30, 31, and 32 are respectively V3oev51 '' 32, then the amount of change in velocity is v52V.tonal.If the angle formed by vectors 30 and 31 is Ass, then from the cosine law.

becomes. A, 5 = 174° V s o = 15 (
L78 (mm)Vs, = 131.7/18
0 X (n-1) e (n: double speed number), the speed change rate ΔV, that is, ΔV '' (Vs 2
Vs. )/v3° is as shown in Table 1.

Table 1 Control for actually correcting the angle by detecting this change in relative speed will be explained in detail below using the third factor. In FIG. 3, 60.61 is a velocity vector, 62.63 is a head displacement, and 65.66 is a head switching signal and a head displacement signal.

In addition, the switch switching signal generator 8 which is an element in the first factor
0, a head switching signal 65 is generated, and the phase is also adjusted so that the heads on the cylinder switch at the appropriate timing. As shown, when the double speed number is different from the standard playback by 2, the trace pattern slopes like a speed vector 61 with respect to the speed vector 60 of the standard speed.

Therefore, in order to correct this angular error, it is sufficient to apply a displacement such as 65.64 to the head, and for this purpose, a voltage that changes as in 66 with respect to the head switching signal 65 is desired. Here, V and -V are voltages required to respectively displace the head one track upward or downward. Now, the conventional standard for generating this is 8MH.
Prepare two counters: a counter for Z and a counter for the output clock from the phase-locked loop 2 described above in synchronization with the reproduced signal, and use the latch pulses of the former to emit at regular intervals to latch the counter value of the latter L1 analog value. However, this method requires 9722 high-speed sets and 1 set of latches. As an alternative method, it is possible to use a logic circuit that outputs the difference between the count values of the two counters described above, but this also requires high-speed operation and requires a large-scale circuit. Therefore, the beat signal generation fund shown in FIG. 4 is used. In FIG. 4, 70 is a multiplier, 71 is an amplifier 72 is a low-pass filter, and 73 is a waveform shaper. First, the multiplier 70, which uses the 8 MHz reference clock and the phase-locked loop output, generates a clock signal that is the difference in the number of clocks between the two. Since this signal has a low level and contains noise components, it is amplified by an amplifier 71, the noise components are removed by a low-pass filter 72, and the signal is shaped into a logic level by a waveform shaper 75. For example, if n==2x speed, 1
While tracing the track, the beat detector outputs a clock of 44444X α5X10 -222. Therefore, if this signal is counted and digital-to-analog converted, the signal 6 in Fig. 3 is obtained.
6 is generated. Of course, at this time, it is necessary to initialize the counter to an appropriate value at the rising or falling edge of the switch changeover signal 65 in FIG. Atta. Compared to 44444 counts per track, only J)222X(n-1) counts are required per track, and high-speed operation is not required and the number of stages may be small.

In the explanation so far, we have assumed that the cylinder rotation speed is always constant even if the playback speed is changed9. However, in this case, when n becomes large, there will be a portion of the signal on the tape that cannot be spread. This situation will be explained using FIG. In FIG. 5, 40 to 42 are velocity vectors, and 45.44 is displacement. When the speed is the same as that during recording (n=)i times, tracing is performed using a velocity vector 40, whereas when n=4, tracing is performed using a velocity vector 41 unless the head is displaced. However, by displacing the head, tracing can be performed without going off track with the velocity vector 42. However, from the table, in this case, since the displacement direction is perpendicular to the trace, a displacement of 45.4444, etc. must be generated near the bottom end of the tape, and especially at displacement 44, there is a situation where the tape is not traced. ing. In this way, when the speed n is different from 1, some parts are not traced. Therefore, in such a case, by slightly changing the number of revolutions of the cylinder motor in accordance with the speed, it becomes possible to reproduce all the signals recorded on the track without leaving anything behind. That is, since increasing the tape speed in the forward direction during playback increases the relative speed with the head, the cylinder is decelerated to keep the relative speed constant and reproduce all the signals on the track.

In this case, the cylinder speed correction amount ΔC is the above-mentioned specific speed correction amount ΔV with the sign reversed, that is, ΔC=−ΔV
becomes. Therefore, the reproduction speed changer 15 outputs a speed change command to the cylinder motor servo circuit 18 to change the cylinder motor.
The rotation speed of 14 acts to produce a difference of -ΔO compared to the time of recording. Then, the velocity component of the head due to the tape speed being different from that during recording is canceled out, and the relative velocity becomes the same as that during recording. At this time, the difference in head trace angle, that is, the angle error cannot be corrected by the angle error corrector. This is because the ninth error component whose relative velocity is equal to that at the time of recording becomes zero. Therefore, at this time, the rotational speed error of the cylinder is detected and the angle error is corrected.

In FIG. 1, the head rotational speed detector 21 detects the rotational speed, and the pattern generator 50 generates a pattern using a frequency component different from that during recording. This is almost the same concept as the beat detection described above. In other words, when the cylinder rotates at 90 Hz and a rotation error of 0% -15% occurs, the number of clocks for one track correction described above is 22.
A head control pattern equivalent to 2 is generated. wife),
When the cylinder rotational speed is changed, the pattern generator 50 generates a waveform corresponding to the fifth factor 66 instead. In FIG. 1, the pattern is generated by detecting the cylinder speed, but it is conceivable to generate the angle correction pattern by directly using the output of the reproduction speed changer 15 as shown in FIG. In this case, the pattern generation circuit 50
' directly receives the speed change command signal (for example, a digital signal of several bits) and changes the slope of the head control signal (No. 51166) based on the bit information, which causes a mechanical delay during transients. In some cases, the transient characteristics deteriorate slightly. Now, a specific example of the configuration of the pattern generator 50 will be explained with reference to FIG. 7th
In the figure, 90 is a period measuring circuit (of the cylinder rotational speed detection signal), 91 is a fixed value generating circuit, and 92 is an accumulator, which is initialized at the rise or fall of the head switching signal 65. The period of the rotational speed detection signal is measured using a standard 8 MHz vc (a different constant clock may be used), and the measurement result is compared with a constant value (period measurement value of the rotational speed detection signal at the time of recording). Then, it is accumulated by an accumulator that is initialized when the head switching signal rises or falls.Next, another configuration of this pattern generator will be shown, and its operation will be explained in detail with reference to waveform diagrams of the main parts.8. Figure 9 shows the main part waveform diagram for the configuration example of the cause.In Figure 8, 1
00 is a counter, 101 is a latch circuit, 102 is a pulse generator, and 103 to 105 are electrical signals. Here, the pulse generator 102 outputs a pulse signal 104 at the rising and falling edges of the head switching signal. After receiving this pulse,
Counter 100 and latch circuit 101 are each initialized.

The counter 100 circulates and counts the reference clock (8MHz), and the pattern of the count value is shown schematically as 1
03, the result will be as shown in FIG. 9, 103a and 105b. FIG. 9 Ca5e (a) shows the cylinder rotation during recording, and (b) shows the case where the cylinder rotation is stopped during reversal. The signal 22 is a cylinder rotation speed detection signal,
As an example, assuming that the frequency at the time of recording is 720 Hz, 11111 counts are counted per cycle during recording.

Therefore, if we assume that the counter returns to zero after counting 11111, then by latching this color/ri count value at the rising edge of signal 22, we will obtain a signal as shown in 105, which schematically shows the latch output, and convert this into an analog quantity. If converted into , it can be used as a head angle correction signal.

Now, as mentioned above, in a system where a time code is recorded near the vertical synchronization signal and can be searched frame by frame,
It is essential that this time code can be detected. However, when the tape running speed becomes many ten times faster than that during recording, it is practically difficult to correct the cylinder rotational speed by many ten times the speed by distributing this time code signal because the change is so large. Therefore, in this case, it is conceivable to deal with this by adjusting the phase of the above-mentioned head switching signal. FIG. 10.11 shows another embodiment of the present invention that takes this point into consideration. In FIG. 10, 150 is a reproduction signal processing circuit, 152 is a moving head control circuit, 155 is a head switching signal generation circuit, and in FIG. 11, 155' is a head switching signal generation circuit, 154 is a time code reproduction circuit, 1
55 is a time code detection circuit. The difference between the tenth factor and the embodiment shown in FIG. 11 is that the embodiment shown in FIG. The time code in the reproduced signal is detected and the head switching phase is changed according to the detected phase. Therefore, the operation will be explained next using the block diagram of FIG. 10 and the explanatory diagram of FIG. 12. In the 12th time, 190° 195 is a velocity vector, 192 is a displacement, 195 is a distance, and 191 is a head switching point during recording. If search playback is now being performed, the head trajectory will follow the velocity vector 190 unless the head is displaced.

If this is displaced as 192 and traced according to the velocity vector 195, a reproduced signal corresponding to the distance 195 cannot be obtained. Therefore, it is decided to advance the switch change signal by a distance of 1930 minutes. Calculate how fast you should go in the following. As shown in Figure 12, the amount of track deviation α that occurs for each track is
Using
Equivalent to 3) 1 - Calculating, the deviation amount is D = (
n-1) α. Assuming that it takes T time to trace the entire length of one track when recording X1,
The timing ΔT for advancing the head changeover switch is as follows.

In the above embodiments of the present invention, for simplicity, the entire hardware configuration including a counter element that counts the reference clock is shown.
These can be inserted into a microprocessor. Furthermore, in this case, the accuracy of measurement can be improved by using the reference clock as a clock for the microprocessor.

〔Effect of the invention〕

According to the present invention, reproduction can be performed without noise even during variable speed reproduction, and since signals near the top and bottom ends of the tape can be reproduced without exception, signals can be reproduced even when a time code or the like is recorded near the vertical synchronization signal. By carefully devising a track trace angle error correction circuit used for head control, a simple circuit with stable operation can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, the second factor, and the third factor.
5 shows the tape pattern on which recording tracks are formed to explain the operation of the embodiment shown in FIG. 1, and the fourth factor shows the components of the embodiment shown in FIG. Block diagram, Figure 9 is a main part waveform diagram of the component block diagram of Figure 8, Figure 6
10 and 11 are block diagrams of other embodiments of the present invention, and FIG. 12 is a tape pattern diagram for explaining the embodiments of FIGS. 10 and 11. Explanation of symbols 2... Phase locked loop, 3... Demodulation circuit, 4... Synchronization signal detector, 7... Reference clock generator, 8. ... Bit signal generator, 10 ... Angle error corrector, 21 ... Cylinder rotation speed detector, 50 ...
...Pattern generator. Figure 8 Ring word n circuit 7-44707 S4 eup go, tA) o, Door λ Kanariinu Soshogaku dai Goro Figure 8 Nu 10 mouth Tsutaguchi Cku 5e ase (b) Figure 1Z Figure 21E ¥1

Claims (1)

[Claims] 1. In a helical scan type magnetic recording and reproducing device in which a movable head is displaced in the width direction of a track, a head rotational speed detection means for detecting the head rotational speed, and a tape running means for detecting the running speed of the tape. speed detection means; head rotation speed error output means for outputting an error from the output during recording according to the output of the head rotation speed detection means; tape running for outputting the output during recording and the error of the output of the tape running speed detection means; A speed error output means, and a head control means for controlling the movable head to be displaced in the width direction based on a calculation output signal of the output of the head rotational speed error output means and the output of the tape running speed error output means. A head control device for a magnetic recording/reproducing device, characterized in that: 2. In a helical scan type magnetic recording/reproducing device in which a movable head is displaced in the width direction of a track, a reference clock generating means for generating a signal that is a clock for a digital signal to be recorded during recording, and a reference clock generating means for generating a signal that is a clock for a digital signal to be recorded during recording, and a reference clock generating means for generating a signal that is a clock for a digital signal recorded during recording, and a a second clock generating means that generates a clock having the same frequency as the reference clock generating means when the relative speed of the tape and the head matches that during recording; and an output of the reference clock generating means; a differential clock generating means for generating a clock having a frequency different from that of the output of the second clock generating means; a counting means for counting the output of the differential clock generating means; 1. A head control device for a magnetic recording/reproducing device, comprising a head control means for controlling displacement in a direction. 3. In a helical scan type magnetic recording and reproducing device in which a movable head is also displaced in the track width direction, a head switching means switches the output of two opposing heads, and reproduction is performed at the same head rotation speed and tape running speed as during recording. head switching signal phase changing means for changing the phase of the reference head switching signal according to the tape playback speed and outputting it as a switching signal for the head switching means; A head control device for a magnetic recording/reproducing device, characterized in that: 4. The above-mentioned tape running speed error output means, rotation speed error output means, and head control means are constituted by a single microprocessor, and its reference clock is the same as the digital signal recording clock. Claim 1
A head control device for the magnetic recording and reproducing device described above. 5. A head control device for a magnetic recording/reproducing apparatus according to claim 2, wherein said differential clock generating means is comprised of a multiplication circuit, a low-pass filter circuit, and an amplification circuit.