JPS6141283A - Control method for tape feed of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To control the feed phase of a magnetic tape by dividing a pulse signal having a frequency double as much as that of the output signal of a switch circuit into the specific value in a cue or review action modes of N-fold speed as high as a record mode and using a phase error signal obtained between said divided signal and the revolving phase of a rotary head. CONSTITUTION:A dividing circuit 39 divides an artificial control signal down to 1/N-1 in an N-fold speed cue action mode and then down to 1/N+1 in a review action mode respectively. The control signal supplied from a terminal 40 is supplied also to a speed control circuit 32. The circuit 32 functions to set the tape feed speed of an N-fold speed mode at a level about N times as high as the speed of a record mode. A phase comparator 41 compares the phase of the pulse signal divided in a field cycle by the circuit 39 with that of the head switching signal which is supplied from a terminal 42 and delivers a phase error signal corresponding to the phase difference of both signals. This error signal is supplied to the circuit 32 via a switch 33 for control of the tape feed phase.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a magnetic recording and reproducing device (hereinafter simply referred to as a VTR).
The present invention relates to a method for controlling the phase of tape feed during special playback of tapes, particularly during cue and review times in VTRs that perform tracking control using pilot signals recorded on the same recording track along with video signals. This relates to transmission phase control.

Conventional Structure and Problems In a conventional VTR, tracking control during reproduction is performed using a control signal (hereinafter referred to as a CTL signal). That is, during recording, a signal synchronized with the rotational phase of the rotary head is recorded on the control track, and during playback, a CTL signal is reproduced from the control track.
This is a method of controlling the tape feeding speed so that the phase with the rotational phase of the rotating head is constant.

In such a VTR, even during cue review operation in which the tape is transported at a tape speed different from that during recording to produce a reproduced image, the phase control of tape transport is such that the frequency of the CTL signal is six times the value of normal playback. Therefore, this CTL signal is
The tape feeding phase is controlled so that the phase of the signal frequency-divided by 5 and the signal synchronized with the rotational phase of the rotary head is constant. By performing such phase control, the position of the noise bar on the screen can be fixed on the screen, and an easy-to-see reproduced image can be provided.

However, in recent years, new tracking control methods that do not use CTL signals have been proposed. The details of this method will be described later, but during recording, a pilot signal for tracking control (hereinafter simply referred to as the pilot signal) is superimposed on the video signal and recorded by a rotating head, and during playback, the pilot signal is reproduced from the rotating head. This is a method of controlling the phase of tape feeding using The new tracking control method using pilot signals does not require CTL signals. Therefore, since the conventional method using a CTL signal cannot be applied to phase control of tape feeding during cue and review, it is necessary to consider a new method.

Before explaining the present invention in detail, a method for creating a tracking error signal using a pilot signal will be explained first.

FIG. 1 shows recorded magnetization trajectories in which four types of pilot signals are recorded, and FIG. 2 is a block diagram of a reproducing circuit for obtaining a tracking error signal.

In FIG. 1, A1. B1. A2. ...is A
Each recording track is recorded on a magnetic tape at an angle in the longitudinal direction of the tape by a rotary head and a B rotary head. Arrow 1 indicates the scanning direction of the rotary head. In each recording track, pilot signals indicated by f1 to f4 are sequentially recorded for each field together with the video signal. The recording order of the pilot signals is the order shown in FIG. 1, and one type of pilot signal is continuously recorded within one field period.

The frequency of the pilot signal is set to a value shown in Table 1, for example.

Table 1 In Table 1, fH indicates the frequency of the horizontal synchronization signal, and 6.6fH indicates a frequency that is 6.6 times the frequency of the horizontal synchronization signal.

The frequency difference of the pilot signal between each recording track is the first
As shown in the figure, the frequency is approximately fH or 3fH. Then, the head is Ai (i=1.

2.3. (...) When scanning a track, the frequency difference between the pilot signal of the scanning track and the pilot signal recorded on the adjacent track on the right on the paper is always fH, and that on the left is always 3fH. It is. When the head scans the Bi) rack, the above relationship is reversed; the frequency difference between the pilot signals between the scanning track and the adjacent track on the right is always 3 fH, and that on the left is always fH.

Since the pilot signal is a relatively low frequency signal around 100 KHz, the pilot signal recorded on the adjacent track can be reproduced as a crosstalk signal without the head scanning the adjacent track. .

For example, the pilot signal obtained when the head on-tracks the A2 track and performs reproduction scanning is f2 ' f3
” 4 composite signals, f3 has the highest level, and then f2 and f4 are reproduced at the same level. When the head slightly shifts from track A2 to track B2 and scans for reproduction, the gain is obtained. The level of the reproduced pilot signal obtained decreases in the order of f3° f4.f2. Conversely, when the head shifts to the track B1 side and scans, the level of the obtained pilot signal decreases in the order of f3, ' 2 # f 4.

Therefore, by separating and extracting the difference signals fH and 3fH between the pilot signal on the main scanning track and each pilot signal recorded on both adjacent tracks, and comparing the reproduction levels of both signals, the difference signals fH and 3fH can be extracted from the main scanning track. The amount and direction of head displacement can be determined.

FIG. 2 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In FIG. 2, a reproduced RF signal in which a video signal and a pilot signal are combined is input from a terminal 2. Circuit 3 is a low-pass filter, and the reproduction R
Separate and extract only the pilot signal from the F signal. The pilot signal obtained at this time is a composite signal of the main scanning track and the pilot signals recorded on both adjacent tracks. Circuit 4 is a balanced modulation circuit, which multiplies the aforementioned composite signal by the reference signal supplied from terminal 6.

The reference signal supplied from the terminal 6 is a pilot signal having the same frequency as the pilot signal recorded on the main scanning track.

For example, in FIG. 1, when the head reproduces and scans the track A2, the input signal to the balanced modulation circuit 4 is f 2 s
fs m f4, and the reference signal supplied from terminal 6 is f3. Therefore, the output signal of the balanced modulation circuit 4 is f2tf3. The sum and difference signals of each signal of f4 and the signal of f3 are output. The circuit 6 is a tuned amplifier circuit tuned to the fH signal, and the circuit 7 is a tuned amplifier circuit of sfH. Circuits 8 and 9 are detection rectifier circuits, and circuit 1o is a level comparison circuit.

Therefore, each pilot signal taken out as a crosstalk signal from both adjacent tracks is separated and taken out as a difference signal from the pilot signal recorded on the main scanning track, and then the level comparison circuit 10 A signal corresponding to the level difference is taken out to the terminal 11. As for the signal obtained at the terminal 11, when the reproduction level of fH is higher than the reproduction level of sfH, a potential of ■ corresponding to the level difference is taken out, and in the opposite case, a potential of O is taken out. The signal output to the terminal 11 can be used as a tracking error signal containing information on the amount and direction of the head's track deviation. However, a tracking error signal that is actually suitable for practical use requires further processing. This is because, as is clear from Figure 1,
This is because the relationship between the direction of head displacement and the beat signal (fH or 3fH) obtained at that time is opposite to that of the A track and the B track.

In FIG. 2, the circuit 12 is an analog inversion circuit;
The circuit 13 is an electronic switch that switches according to the level of the head switching signal supplied from the terminal 14. Therefore, for example, when the head is reproducing and scanning the A track, the signal obtained at the terminal 11 is directly outputted to the terminal 16, and when the head is reproducing and scanning the B trunk, the signal obtained from the terminal 11 is output as is.
The signal obtained in 1 is inverted in an analog manner and output.
Therefore, the signal obtained at the terminal 16 is A, B) Regardless of the rack, when the head deviates to the right from the track to be scanned, the potential ■ is always output, and when the head deviates to the left, the potential θ is always output. Therefore, if the tracking error signal obtained at the terminal 16 is supplied to, for example, a capstan motor as a phase error signal to control the tape feeding phase, the head will always scan on-track on the main scanning track. .

The above is an overview of the method for obtaining a tracking error signal using four types of pilot signals.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a new method for controlling tape transport phase during cue and review operations using pilot signals for tracking control.

Structure of the Invention The present invention provides a second
A pulse (pseudo control pulse) is created at the zero-crossing point of the error signal obtained from the terminal shown in Figure 16, and the nine tape feeding phases are controlled so that this pulse and the rotational phase of the rotary head have a constant relationship. . Specifically, the pseudo control pulse obtained during cue operation is expressed as (N-1
), and during review operation, the tape feed phase is controlled so that the phase of the pulse frequency-divided to the resulting pseudo control pulse (Ne1) and the head switching signal is constant. , Fig. 2 terminal 6
The switching order of the reference signals supplied to the data is the same as the order at the time of recording, which is fl-f2-+f3->f4.

Description of examples The present invention will be explained in detail below.

FIG. 3 is a diagram showing the recording magnetization locus, the cue, and the scanning locus of the head at the time of review. In FIG. 3, A1.
B1. . . . indicates each recording magnetization locus on the magnetic tape, arrow 16 indicates the tape transport direction, arrow 17 indicates the scanning direction of the rotary head, and f1 to f4 indicate pilot signals for tracking control. .

That is, it shows that the pilot signal f1 is recorded on track A.

The tape speed at the time of cue and review used in the explanation of the present invention is hereinafter explained as a tape speed six times the tape speed at the time of recording, unless otherwise specified.

In FIG. 3, arrows 18 to 2o indicate the scanning locus of the head during the cue operation. When the tape is transported at a tape speed five times the tape speed during recording, the rotary head scans from the beginning of track A1 (lower end on the paper) to the end of track A3. In other words, the trajectory shown by the arrow 18 is taken. In a two-head helical scan type VTR, when the A head is located at the end of track A3, the B head is located at the beginning of track B3. Therefore, the B head follows the scanning trajectory shown by arrow 19.

The scanning trajectory of the head during review operation at 5x speed is shown by arrow 2.
1. Take the trajectory shown in 22. The reason for this is the same principle as the cue operation, and it is also well known.
Detailed explanation will be omitted.

Next, a tracking error signal obtained during cue and review operations will be explained.

Figure 4 shows the recording track and the reference signal of the balanced modulation circuit.
ls... indicates the level of the tracking error signal obtained when fixed to each mf4.

Aj j B, jA2 #・・・・・・shown in Figure 4a
indicates each recording track, and each frequency of the pilot signal is recorded corresponding to each track shown in the figure. The vertical axis of each signal shown in b to e in the figure indicates the level of the tracking error signal obtained at the terminal 11 of the circuit shown in Fig. 2, and the horizontal axis corresponds to the track position of the recording track shown in Fig. 4 a. are doing. The waveform shown in FIG. 4 is a tracking error signal obtained when the frequency of the reference signal input to the balanced modulation circuit is fixed at f. head or track B1
When the trunk B2 is located at the center of the width direction, the fH tuning signal level is the highest, and when the trunk B2 is located at the widthwise center, the 3fH tuning signal level is the highest.

Therefore, when the reference signal is fixed at f, the tracking error signal obtained at the terminal 11 shown in FIG. 2 becomes the signal shown in FIG. 4. It is clear that when the reference signal is fixed at f2sf3*f4, the tracking error signals shown in FIG. 4c, d, and e can be obtained using the same concept.

FIG. 5 is a diagram showing a tracking error signal obtained during a cue operation, and FIG. 6 is a diagram showing a tracking error signal obtained during a review operation. In addition,
It has already been mentioned that the order of the reference signals supplied to the balanced modulation circuit during the cue and review operations is in the same direction as the order during recording. FIG. 6a shows each recording track A1. B1. ... shows the song and the pilot signal recorded on the valley track. Arrows 23 to 25 indicate the scanning locus 18 shown in FIG.
It corresponds to ~2°. That is, the rotary head scans from tracks A1 to A3 within one field period, and then from tracks B3 to B6. FIG. 5 shows a tracking error signal, and the error signal indicated by a solid line is a tracking error signal obtained at the terminal 11 shown in FIG. The error signal indicated by the broken line is connected to terminal 1 shown in FIG.
This is the tracking error signal obtained in Figure 5. That is, the error signal outputted to the terminal 11 is a tracking error signal that is inverted and extracted only when, for example, the B head scans the magnetic tape. FIG. 6C shows the frequency of the reference signal supplied to the balanced modulation circuit. arrow 2
During the first scan, indicated at 3, the reference signal is fl. The tracking error signals obtained at this time are signals from tracks A1 to A3 shown in FIG. arrow 24
During the second scan indicated by , the reference signal is f2. Therefore, the tracking error signal before inversion obtained at this time is the signal from B to B3 shown in FIG. 4O. Below, the tracking error signal during each scan can be considered using the same concept. Note that the flow of time during the cueing operation is in the direction shown by the arrow 26.

Next, the tracking error signal during the review operation will be explained. FIG. 6a shows the recording track and pilot signal frequency, b shows the tracking error signal, and C shows the reference signal. Regarding the tracking error signal, the solid line indicates the signal before inversion, and the broken line indicates the signal after inversion.

Arrows 27, 28, and 29 indicate head scanning within one field period, and correspond to scanning trajectories 21 and 22 in FIG. 3. Note that the flow of time in FIG. 6 is in the direction indicated by an arrow 30. The reference signal during the scanning period indicated by the arrow 27 is f, and the tracking error signal obtained at this time is the fourth
These are the signals from tracks A4 to A of the signals shown in the figure. The reference signal for the scanning period indicated by arrow 28 is f2;
The tracking error signal obtained at this time before inversion is
Tracks B3 to A of the signal shown in FIG. 4C.

(Although not shown, this is the track to the left of track A1 on the paper, and f4 is recorded). A tracking error signal for each scan can be devised using the same concept below.

7 and 8 depict the tracking error signals explained in FIGS. 6 and 6 in correspondence with the head switching signal (hereinafter referred to as a, SW signal). The tracking error signal at this time is the signal output to the terminal 16 shown in FIG. 2, that is, the error signal in which only the signal of one channel is inverted.

FIG. 7a and FIG. 8a show H and SW multiplied signals. Figure 7 is a temporally continuous representation of Figure 6. In FIG. 5, the end of arrow 23, ie, the time of track A3, and the start of arrow 24, ie, the time of track B3, are the same time. Therefore, if the signal shown in FIG. 6 is plotted continuously over time, the waveform shown in FIG. 7 will be obtained. The signals shown in FIG. 8 are also temporally continuous representations of the signals shown in FIG. 6 based on the same concept. 7C and 8C are pulse signals created by detecting the zero cross levels of the signals b and b. As is clear from FIGS. 7C and 8C, four pulses are obtained within one frame during the 6x cue operation, and six pulses are obtained during the review operation. In general, it is known that the number of pulses within 17 frames obtained by the above-mentioned method is (N-1) during a cue operation at N times the speed, and (N+1) during a review operation. Therefore, during the N-times speed queue operation, the signal (Fig. 7C) is divided into (N-1), and during the review operation, the signal (Fig. 8C) is divided into (N+).
1) If the tape feeding phase is controlled so that the frequency-divided signal and the 8·S'W signal have a constant phase relationship, H-
5W signal and signal (Figure 7b) or signal (Figure 8b)
It is possible to maintain a constant phase relationship with This means that
This means that the position of the noise on the screen can be fixed on the screen. This is because if the A head scans during the scanning period indicated by the arrow 23 in FIG. 6, the video signal can be reproduced when scanning on the A track, but the video signal cannot be reproduced when scanning on the B track. Unable to play. In other words, it becomes a noise signal. These noise positions correspond to the maximum and minimum level positions of the signal (FIG. 6b). Therefore, if the phases of the triangular wave signal and the H-5W signal shown in FIG. 7 can be kept in a constant relationship, the position of the noise on the screen can be fixed.

In addition, in the explanation so far, the scanning start point of the head has been explained as starting from the center of one of the tracks, but the scanning start point of the head can start from any position on the track as shown in FIG. And a continuous triangular wave signal as shown in FIG. 8b can be obtained.

Furthermore, if the reference signal supplied to the balanced modulation circuit at the time of cue and review is also in the same order as the recording order of the pilot signals during recording, the scanning period 23 shown in FIG. 6, for example, is not necessarily the reference signal of fl. There's no need.

FIG. 9 is a block diagram showing a specific embodiment of the present invention.

In the figure, 27 is a magnetic tape, and 29 is a capstan motor. Although not shown, a normal VTR
As shown in , magnetic tape is transported by being wound around a rotating cylinder or various tape guide posts. arrow 28
indicates the direction in which the magnetic tape is transported. 3o is a frequency generator (hereinafter referred to as FG) fixed to the capstan motor 29
17.31 is a detection head for detecting a signal of a frequency corresponding to the rotation speed of the capstan motor 29 from the FG 30. 32 is a well-known speed control circuit using an FG multiplied signal. The speed control circuit 32 controls the feeding phase of the magnetic tape.
This can be accomplished by supplying a phase error signal from the switch 33.

The circuit 36 is a phase control circuit during normal recording and reproduction;
During recording, a signal corresponding to a phase error between a signal obtained by dividing the signal obtained from the capstan FG into one field period and an h-sw multiplied signal synchronized with the rotational phase of the rotary head is output. During normal playback, the tracking error signal already described, that is, the signal taken out from the terminal 16 in FIG. 2 is output.

The switch 33 is connected to the terminal 34 during normal recording and playback, and is connected to the terminal 35 during cue and review.

Next, a circuit for generating a phase error signal at the time of cue and review will be explained.

A signal output to the terminal 16 shown in FIG. 2 is supplied to the terminal 37 shown in FIG. 9. However, the order of the reference signals supplied to the balanced modulation circuit 4 at this time is the same as that during recording. The circuit 38 is a pseudo CTL signal generating circuit for obtaining the pseudo CTL signals shown in FIGS. 7C and 8C, and its details will be described later. Circuit 39 is a frequency divider circuit, which divides the frequency into N and (N+1) during review operation.
This is a circuit that divides the frequency into Cue and review control signals are supplied from a terminal 40. The control signal supplied from the terminal 4o is also supplied to the speed control circuit 32. At the time of N times speed, the speed control circuit 32 operates so that the tape feeding speed becomes approximately N times that during recording. The circuit 41 is a phase comparator circuit, which receives the pulse signal frequency-divided into one field period by the frequency divider circuit 39 and the H- signal supplied from the terminal 42.
The phase is compared with the SW multiplied signal or a signal whose phase is synchronized with the 8.SW signal, and a phase error signal corresponding to the phase of both signals is output. The phase error signal is supplied via switch 33 to speed control circuit 32, resulting in control of the tape advance phase.

Next, a pseudo CTL signal generation circuit indicated by circuit 38 will be explained.

FIG. 10 shows a block diagram of the pseudo CTL signal generating circuit, and a to f in FIG. 11 show waveforms at various parts in FIG.

d and b in FIG. 11 correspond to a and b in FIG.
Figure 1a shows the H-SW signal, and b shows the tracking error signal during cue operation. From terminal 43 in FIG.
The signal shown in the figure is input. The circuit 44 is a Schmitt circuit with a hysteresis characteristic of ±ΔV. The output signal C of this Schmitt circuit 44 becomes a high potential when the triangular waveform signal shown in a becomes higher than the zero cross level by +ΔV, and then becomes a low potential when it becomes lower by −ΔV. . The circuit 45 is a trapezoidal wave generating circuit, which generates a trapezoidal wave signal (FIG. 11d) having a constant slope in synchronization with the rise or fall of the signal (FIG. 11C). circuit 4
6 is a rectangular wave signal generation circuit, which becomes High when the trapezoidal wave signal (Fig. 11 d) is at a pH level higher than a certain threshold voltage.
When the gh potential is at a low level, a rectangular wave signal (FIG. 11e) which becomes a low potential is output. Circuit 47 is E
It is an X-OR circuit whose input is the signal t (Figure 11C)
and the signal (FIG. 11e) are rectangular wave signals. The signal (FIG. 11e) is a signal with a constant phase lag with respect to the signal (FIG. 11C). The EX-OR circuit outputs a high potential only when the potentials of each input signal are different.

Therefore, the output of the EX-OR circuit is the signal (Fig. 11C)
This results in a pulse signal (FIG. 11f) having a width corresponding to the phase lag between the signal (FIG. 11e) and the signal (FIG. 11e). The signal outputted to the terminal 48 (FIG. 11f) is a pseudo CTL signal.

Effects of the Invention As is clear from the above explanation, according to the present invention, even in a tracking control method that does not use a CTL signal, the obtained tracking error signal is processed by the above-mentioned and processing steps to generate equidistant pseudo CTL signals. and this pseudo CTL
The signals can be used to control tape advance phase during cue and review operations.

[Brief explanation of drawings]

Figure 1 is a diagram showing magnetization trajectories recorded with four types of pilot signals, Figure 2 is a block diagram of how to process four types of pyro signals to obtain a tracking error signal, and Figure 3 is a diagram showing recorded magnetization trajectories. And cue. Figure 4 shows the scanning locus of the head during review operation. Figure 4 shows the tracking error signal waveform obtained when the reference signal supplied to the balanced modulation circuit is fixed. Figures 6 and 6 show the cue and review. A diagram for explaining a tracking error signal waveform obtained during operation, FIGS. 7 and 8 are diagrams showing a tracking error signal and a pseudo CTL signal during cue and review operations, and FIG. 9 is a specific embodiment of the present invention. A block diagram showing the pseudo (!I CT
FIG. 11 is a diagram showing an example of the L signal generation circuit, and FIG. 11 is a waveform diagram of each part of FIG. 10. fH...Horizontal synchronization signal frequency, 4...
Balanced modulation circuit, 6.7... Tuning circuit, 8,9.
...Detection rectifier circuit, 12...Analog inverting circuit, 32...Speed control circuit, 38...
... Pseudo CTL signal generation circuit, 41 ... Phase comparison circuit, 44 ... Schmitt circuit, 45 ...
. . . Trapezoidal wave signal generation circuit, 46 . . . Waveform shaping circuit, voice-X-OR circuit. Figure 1 Figure 2 Figure 4 (2u Ward - q - CI
CJ5. ++ \-7 Figure 8 Figure cI Figure 9 2I Figure 10 Figure 11

Claims (1)

[Claims] A rotating head sequentially records video signals as a group of recording trajectories inclined with respect to the longitudinal direction of the magnetic tape, and
Four types of pilot signals with different frequencies for tracking control are superimposed on the video signal and sequentially switched cyclically and recorded, and during reproduction, the sum and difference signals of the reproduced pilot signal and the reference signal are recorded. a multiplier circuit for obtaining a signal, a tuning circuit for separating the output of the multiplier circuit into first and second frequency components, a comparison circuit for comparing the levels of each output signal of the tuning circuit, and an output of the comparison circuit. In a magnetic recording/reproducing apparatus equipped with a switch circuit for alternately inverting and non-inverting and retrieving the reference signal, the reference signal is The switching order is the same as the switching order during recording, and a pulse signal with twice the number of cycles of the output signal of the switch circuit obtained at this time is created, and this pulse signal is 1/(N
-1), during review operation, the frequency is divided by 1/(N+1), and the magnetic A method for controlling a tape feed phase of a magnetic recording/reproducing device, the method comprising controlling the tape feed phase.