JPS60113314A - Reproducing device - Google Patents

Abstract

PURPOSE:To correct exactly a track shift of a magnetic head without being influenced by expansion and contraction, etc. of a tape, and to improve a scanning property by detecting a break of a pilot signal whose frequency has been converted, and switching a frequency of a track selecting signal from a variable frequency oscillator basing on said detection. CONSTITUTION:A low-pass filter (LPF)8 is connected to each magnetic head 7a, 7b through the second changeover switch, and separates pilot signals f1, f2, f3 and f4 contained in a reproducing RG signal, and a video signal. A mixer 9 receives outputs of the LPF8 and a variable frequency oscillator 10, and outputs them to BPFs 1a, 1b after converting the frequency. A controlling circuit 11 receives an output of an FF12 and executes a switching control of a track selecting signal of the variable frequency oscillator 10. Comparators 13a, 13b constitute a means for detecting a fact that outputs of detectors 2a, 2b have been varied by a break of outputs of the BPFs 1a, 1b.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for recording parallel inclined tracks arranged adjacent to each other on a magnetic tape together with a tracking pilot signal that changes in a predetermined repetition order. The present invention relates to a reproducing apparatus that includes a rotating magnetic head that scans these tracks in order to reproduce information signals, and that corrects track deviation of the magnetic head based on the pilot signal.

[Prior art]

FIG. 1 shows an example of a recording pattern on a magnetic tape applied to this type of reproducing apparatus, where TD indicates the running direction of the magnetic tape T and HD indicates the head scanning direction. This pattern is formed on the magnetic tape T based on so-called diagonal scanning. The tracks form a certain inclination angle with respect to the length direction of the magnetic tape T. For this purpose,
For example, the magnetic tape T is spirally passed over the peripheral surface of a head drum (not shown) having two rotating magnetic heads (not shown), and the rotating magnetic heads are caused to scan. The rotating magnetic head moves in the direction of arrow HD in the figure and continuously tracks T1 #T! #TS e T4 m 'r1
Scan...

The magnetic tape T is 1 for the head drum of the above type.
Tracks are generally formed by winding over 80°, and each track has overlap portions 11 and 12 at each end thereof.

The part F sandwiched between the overlap part 12 and 180' of the head drum is a section corresponding to a corner.

In the case of a two-head type video tape recorder, this F section corresponds to exactly one field of the video signal.

Furthermore, each track has a frequency f1 as shown in FIG.
．． Pilot signals f, , f3 and f4 are recorded sequentially. During recording, each of these pilot signals f1 to f4 is generated in accordance with a switching timing pulse created based on a position pulse from a position detector (not shown) that detects the rotational position of the head drum with respect to the magnetic tape T.
For each field of the video signal, the frequency is fl, fl,
f, , f4 and are sequentially recorded. These frequencies are 1flfsl=
lfn-f41=fAsI fs-f41-I f2-
f31=fa, and the switching point of these frequencies is the above F
It is assumed that one field of video signal is recorded during the period of the F section. Here, during recording, the start and end of section F are recording points at the same times as the end of section F of the previous track and the start of section F of the next track, respectively. For example, in the case of a two-head video tape recorder, the first head is the track T.
1 and TS, and when the second head forms tracks T2 and T4, respectively, the first head forms tracks T! At the same time as reaching the end of section F of track h, the second head has reached the beginning of section F of track h.

Next, the second bottom is Truck T! At the same time as the first head reaches the end of the F portion of the track T3, the first head reaches the start of the track T3.

The overlap portion 11x, To is a period in which the two heads are in contact with the tape T at the same time, and the same video signal as that near the end of the F section of the previous track is recorded in one overlap ls. In the overlap 12, the same video signal as that immediately after the starting end of the F section of the next track is simultaneously recorded. The pilot signal may be recorded only in the F part, or in order to simplify the pilot signal recording circuit and the pilot switching timing pulse circuit, the pilot signal may be recorded in the overlap part, lls, I; In the same way as recording, the pilot signal may also be recorded at the same time near the lower end near the end or immediately after the start end. In this case, the frequencies of the pilot signals recorded in each overlap IIs and II are as shown in FIG.

As described above, the video signal and the pilot signal are sequentially recorded on the valley tracks, but since each track is formed by diagonal scanning, the starting point of each track is shifted by αH from the adjacent track.

This deviation αH is usually expressed in units of intervals H between horizontal synchronizing signals, for example, αH=IH. Corresponding to this shift, the start and end ends of the F section are also shifted by αH=IH with respect to the start and end ends of the F section of the adjacent track.

Next, in a device for reproducing signals from such a magnetic tape T, in the reproduction mode, a variable frequency oscillator (not shown) continuously generates a track selection signal every time the rotating magnetic head scans the magnetic tape T. The crosstalk generated by the track selection signal and the magnetic head (
(crosstalk of pilot signals of adjacent tracks),
Obtain tracking signal. The tracking signal causes the servo system to operate so that the magnetic head scans the track defined by the track selection signal generated by the variable frequency oscillator.

When obtaining a tracking signal, it is necessary to switch the track selection signal at the switching point of the pilot signal as described in FIG. However, conventionally, this switching is performed based on the above-mentioned position pulse using a monostable multivibrator and a flip-flop (hereinafter referred to as FF). The position of the switching timing pulse will be out of order due to misalignment between devices, and further due to timing misalignment due to temperature changes or aging of the monostable multivibrator.

As a result, the tracking signal obtained in the vicinity of the switching point of the pilot signal will not be adversely affected, such as a dog interruption. This drawback is due to the fact that the pilot signal is switched during reproduction not based on information from the recording pattern on the tape, but indirectly based on the position information of the rotary head.

[Summary of the invention]

The present invention is configured to detect discontinuities in the frequency-converted pilot signal and switch the track selection signal based on this detection output, thereby preventing the tracking signal from being adversely affected by tape expansion and contraction. It is an object of the present invention to provide a reproducing apparatus which can improve the scanning performance of a magnetic head.

[Embodiments of the invention]

FIG. 2 shows an example of a reproducing apparatus according to the present invention.

In the figure, (xa) and (lb) are band pass filters (hereinafter referred to as BPF) and (2a).

(2b) is a detector connected to each BPF (la) and (lb), and (3) is a transverse transducer (2a) and (2b).
) K-connected differential amplifier outputs a tracking error signal; (4) is an inverting amplifier.

(5a) and (5b) are bimorph drivers connected to the differential amplifier (3) and the output of the differential amplifier (4) via a first changeover switch (described later); (6a) and (6b);
are bimorphs driven by bimorph drivers (5a) and (5b), respectively, and each has a magnetic head (7).
a) and (7b) are installed. (8) #'i A low-pass filter (hereinafter referred to as
(referred to as LPF), and the pilot signals f, , f, , f8 . f, and the video signal. (9) is the above L P F
(8) and a mixer that receives the output of the variable frequency oscillator (101), converts the frequency, and outputs the BPF (1a) and (lb)K.

(11) is a control circuit that receives the output of FFa2 and controls the switching of the track selection signal of the variable frequency oscillator (10). ), (lb) constitutes a means for detecting a change in the outputs of the detectors (2a), (2b) due to an interruption in the outputs. (14a), (14b)
are delay circuits that delay the outputs of the comparators (13a) and (13b) for a certain period of time, and are respectively F'F(
It is connected to the set terminal S and reset terminal R of 121, and together with FF'f12) constitutes switching timing pulse generating means.

(The first changeover switch is for supplying a racking error signal whose polarity is inverted for each track to the bimorph drivers (5a) and (5b).

<161 is a second changeover switch for guiding the reproduced RF signal to L P F (8).

Next, the operation of the above configuration will be explained.

The RP multiplied signal consisting of the video signal reproduced by the magnetic head (7a) and the pilot signal is guided to the video signal processing circuit aη via the second changeover switch mark a, while the LPF (
8). The pilot signal f, f, f3 or f4 included in the reproduced RF signal is the above LP
It is separated from the video signal by F(8)K and input to the mixer (9). As the other input of the mixer (9), a rack selection signal from the variable frequency oscillator (10) is inputted.

Assuming that the magnetic head (7a) is scanning the track defined by the track selection signal, the pilot signal of the reproduced track and the track selection signal have the same frequency. The pilot signal reproduced from the magnetic head (7a) consists of the pilot signal of the track being scanned and the pilot signals obtained as crosstalk from the tracks on both sides adjacent to the track. These pilot signals are frequency-converted by a mixer (9) and separated into fA frequency components and fB frequency components at BPFs (la) and (lb).

For example, since the frequency of the track selection signal when the magnetic head (7&) is scanning the F section of track T1 in FIG. 1 is fl, fA-1f1-fA l and f
a=lfl fA1. These are the detectors (
2a) and (2b), the signal is envelope-detected and applied to the non-inverting input and the inverting input of the differential amplifier (3).

A tracking error signal corresponding to the track deviation is output from the differential amplifier (3). When the track selection signal is f above, the output of the differential amplifier (3) is the inverting amplifier (
4) and the first changeover switch (151) to the bimorph driver (5a). The tracking error signal is applied to the bimorph driver (5a) according to the above-mentioned tracking error signal. (6a) to shift the magnetic head (7a) in a direction perpendicular to the track.This corrects the tracking and performs correct scanning.

Since the polarity of the tracking error signal in the direction of track deviation is reversed depending on the track, the output of the differential amplifier (3) is reversed when, for example, tracks TI and T3 in Fig. 1 are reproduced by the magnetic head (7a). Amplifier (4)
Through it, another truck T! and T4 to the magnetic head (7b
), the tracking error signal is directly guided to the first changeover switch (15) without being inverted. When reproducing with the magnetic head (7b), the same operation as described above is performed and tracking correction is performed.

The magnetic heads (7a) and (7b) perform servo control to correct track deviation based on the tracking error signal so as to scan the corresponding track using a track selection signal frequently generated by the variable frequency oscillator 00). receive. The track selection signal is transmitted by the magnetic head (7a) or (7b) to one of each track T1 to T4 shown in FIG.
It is necessary to switch each time the F part corresponding to the field is scanned, and the reproduced RF signal from each track is
(8) The second changeover switch (10) for reversing the polarity of the tracking error signal for each track and the first changeover switch (the fence must be changed in the same way. This will be explained using the waveform diagram in FIG.

Now, when the track selection signal generated by the variable frequency oscillator α0) has a frequency f, the magnetic head (7a) is scanning the track T1 in FIG. 1 due to the above servo control, and the BPF (la) and the output of BPF (lb) have frequencies of -1f, -fl1 and 1B=lf, respectively, as shown by Tl in Figure 3 (A) and CB).
A signal of t fA1 is obtained. When the magnetic head (7a) reaches the distance αH from the end of the F portion of the track Tl, the pilot signal from the track T2 is interrupted. Therefore, the output of BPF(la) is also interrupted as shown in FIG. 3(5). Therefore, the output of the detection a (2a) falls to zero level. This change causes the comparator (13
The output of a) changes from L (low level) to H (high level) as shown in ) of FIG. This output is the delay circuit (1
4a) and generates the pulse shown in FIG. 3 (Q) with a certain time delay. This pulse is applied to the set terminal S of FFQ21 and sets the output terminal Q of FFQ121 to H.

The timing at which the output of the FF scream is reversed is determined by the magnetic head (7a
The delay time of the delay circuit (14a) is set so that the delay time of the delay circuit (14a) almost coincides with the time when the signal (14a) reaches the end of the F section. This delay time corresponds to αH.

On the other hand, the pilot signal from truck T4 is
, the magnetic head (7a) continues to record until the end of the F section of the track T, and therefore the BPF (lb)
The output is also not interrupted as shown in FIG. 3 0.

When F'FQ21 is inverted at the end of the F section, the control circuit Ql) receives the output of F F (121) and changes the track selection signal of the variable frequency oscillator from frequency f1 to 2 in frequency.
Switch to control. Also, FF (first and second changeover switch f15 according to the signal of output terminal Q of 13),
The contact piece (16) is reversed from the state shown in FIG. At this time, the magnetic head (7b) has reached the starting end of section F of track T3.

Track selection signal and changeover switch (15), [16
) is switched as described above, the magnetic head (7b)
The same servo control as described above is performed for this.

At this time, the pilot signal recorded on the track Ta exists from υαH before the start of the F section of the track T2, so the output of BPF (lb) is as follows at the start of the F section:
It continues without interruption as shown in FIG. 30. On the other hand, since the pilot signal recorded on track T is generated from the distance αH behind the starting end of section F of track T2,
The output of BPF (la) has an interruption period of 2αH as shown in FIG. At the end of the F section, if we consider the same as described regarding the scanning of the magnetic head (7a),
This time, there is an interruption in the output of BPF (lb), and the output of BPF (lb) is interrupted.
The output of la) is uninterrupted. Due to the interruption of BPF (lb), the output of the comparator (13b) changes from L to H as shown in FIG. 3 (g).

This output is delayed by the delay circuit (14b) in the same manner as described above and is output as a pulse shown in FIG. This pulse is applied to the reset terminal R of FF (121), and sets the output terminal Q of FF (121 to L. The control circuit O
B receives the output from the FF (121) and changes the track selection signal of the variable frequency oscillator aO1 from frequency f2 to frequency f,
Controls IC switching. In addition, the changeover switches (151 and (16)) are also inverted by the output of F F (IZ), and the contact pieces are in the state shown in FIG. 2. From this point on, the frequency of the track selection signal is changed to f4. f.

, f, , f3, etc. are repeated, and the state of each signal becomes as shown in FIG.

As described above, the track selection signal is switched at approximately the same point as the pilot signal switching point at the time of recording. Moreover, since this switching is performed based on the pilot signals f, -f4 themselves recorded on the tracks T1-T4, the drawbacks of the conventional indirect method can be eliminated.

Regarding the amount of delay caused by the delay circuits (14a) and (14b), in the past, a monostable multivibrator was used to provide a large amount of delay, in order to provide sufficient margin for mechanical variations in the mounting position of the position detector. For example, the delay time is about 1 m8, but in the above configuration, the delay amount can be as small as αH1, for example, IH=63.5μ8, and therefore, there is an advantage that errors that occur can be suppressed as much as possible.

Note that the above explanation was for the case where the pilot signals shown in parentheses in FIG. 1 were not recorded in the overlaps ls and llz;
.

Further, in the above embodiment, BPF(la) and BPF(l
The track selection signal was switched using both outputs of b), but
For example, the output of only the BPF (la) is used to guide a signal to the set terminal S of the FF (121) via the comparator (13a) and the delay circuit (14a), while the output of the comparator (13a) or It may be configured such that the output of the delay circuit (14a) is applied to a counter, a delay pulse is created by a counting method using clock pulses, and this is applied to the reset terminal R of the FF (13).

〔Effect of the invention〕

As described above, the present invention is configured to detect discontinuity in the frequency-converted pilot signal and switch the frequency of the track selection signal from the variable frequency oscillator based on the discontinuity. Therefore, it is possible to provide a reproducing apparatus that can appropriately correct the track deviation of the magnetic head.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a recording pattern on a magnetic tape.
FIG. 2 is a block diagram showing an example of a reproducing apparatus according to the present invention, and FIG. 3 is a signal waveform diagram for explaining the operation of the apparatus according to the present invention. (1a), (1b)... Bandpass filter, (2a, ), (2b)... Detector, (7
a), (7b)...magnetic head, (9)...mixer, aα...variable frequency oscillator, α1)...control circuit,
■...Flip-flop, (13a), (13b)
...Comparator, (14a), (14b)...Delay circuit, f1-f4...Pilot signal, T...Magnetic tape, T1-T4...Track. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Proceedings Amendr (voluntary) Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent Application No. 58-221116 is 2, Device for reproducing the name of the invention 3, Part of the representative of the person making the amendment + 1 + Part 8 of the person making the amendment To ', 15. "Detailed Description of the Invention" column of the specification subject to amendment and drawings. 6 Contents of amendment A, specification: (1) Page 5, line 14; “Lower part” will be amended to read “Part F.” (2) Page 13, line 12; "r(A), (B)" is replaced by r(A). We will correct it to "(D)." (3) Page 13, line 13, 1; “T1” has been corrected to “tl”. Drawing 89: (]) Since there was a defect in Figure 2, we will submit a corrected drawing of the same figure as attached. I"2

Claims (1)

[Claims] (1) A tracking pilot signal located in a predetermined section of each track for each inclined track arranged adjacent to each other on a magnetic tape and having a frequency that changes in a predetermined repetition order is recorded on the track. a rotating magnetic head that scans said track to reproduce an information signal; and a track selection signal whose frequency changes in the same repeating order as said pilot signal in response to a switching timing pulse generated during said magnetic head's scanning. comprising a variable frequency oscillator that continuously generates a variable frequency oscillator, and a frequency converter for converting the frequency of a pilot signal including crosstalk of both adjacent tracks reproduced by a magnetic head during scanning and a track selection signal from the variable frequency oscillator, In a playback device that corrects track deviation of a magnetic head based on a pilot signal frequency-converted by the mixer, the discontinuation of the frequency-converted pilot signal is detected at the beginning or end of the predetermined section on the track. A reproducing device comprising a detecting means and a control circuit that receives a signal based on the detection signal detected by the detecting means and switches a track selection signal.