JPS5880979A - Tracking device - Google Patents

Abstract

PURPOSE:To detect and correct a track skip by measuring time intervals of a vertical synchronizing signal in a reproduced video signal. CONSTITUTION:A reproduced video signal from a demodulator 11 is inputted to a vertical synchronizing signal separating circuit 22. A vertical synchronizing signal separated therein is inputted to one input terminal of a time-voltage converting circuit 23, and a heat switching signal from a pulse processing circuit 9 is inputted to the other input terminal. When a magnetic tape running speed is 2N times as fast as that during recording, a peak value of a waveform corresponding to whether a track skip is caused or not, or the number of skipped tracks is obtained at the output terminal of the circuit 23. This peak value is held by a holding circuit 24, and then compared with the peak values of adjacent fields by a level comparing circuit 25 to discriminate the direction of the track skip. Information on this track skip is supplied to a track skip correcting circuit 26 through a switch SW. According to the output of the circuit 26, the position of a video head 2 is moved to correct the skip.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking device for a video tesso recorder or the like.

In order to accurately scan the recorded trunk during playback, so-called auto-tracking devices are beginning to be introduced.

This auto-tracking device can provide a reproduced image free of noise bands in special mode reproduction such as slow playback and still playback in which the tape is played back at a running speed different from the tape running speed at the time of recording. Such auto-tracking devices usually have a video head for reproducing video signals attached to an electro-mechanical conversion element, and
A DITHKR signal, which is a drive signal, is applied to the mechanical transducer, and the position of the video head with respect to the recording track is determined from the MTHICR signal and the playback envelope of the video head, and a control loop is configured so as to be on-track. ing.

When a plurality of video heads are used in a tracking device of this type, each video head is controlled as described above based on its playback envelope. There was a problem in that it could not be determined whether the image was being scanned, and so-called "track jumping" occurred.

The present invention determines whether a video head is scanning a desired trunk or an adjacent track by measuring the synchronization signal period in a reproduced video signal, for example, the time interval of a vertical synchronization signal. This is designed to solve the problems of the conventional example. Hereinafter, the present invention will be explained, and in order to facilitate understanding of the structure, operation, and effects of the present invention, the explanation will be sequentially made in comparison with a conventional example.

FIG. 1 is a block diagram of a main part of a conventional example of an auto-tracking device using a DITHRR signal, and FIG. 2 is a block diagram of a main part of an example of an auto-tracking device according to the present invention. It should be noted that the same numbers are given to the same components in FIG. 1 and FIG. 2. In FIG. 1, reference numerals 1 and 2 are video heads having the same azimuth angle (for example, 6°), and these are free of electro-mechanical transducers 18 and 19, such as bimorph piezoelectric elements. It is attached to the tip which is the end (movable end). The other end of the electro-mechanical transducer 18, 19 is attached to the rotating disk 4. 3 is a magnet for detecting the rotational phase of the video heads 1 and 2, which is also attached to the rotating disk 4. A rotational phase detector 6 is installed on the fixed part side corresponding to the magnet 3. The rotating disk 4 is rotationally driven by a DC motor (not shown) via a rotating shaft 6, and rotates at high speed at a period of about 30H2. Since the phase control of the rotating disk 4 is well known, the explanation here will be omitted. The magnetic tape (shown in Figure 3) is attached to a rotating disk 4.
It is wound over approximately 1,800 times or more, and is driven at a constant speed by a capstan and a vi/tir roller. Since such a magnetic tape drive system is also well known, illustration thereof is omitted here.

Output signals from the video heads 1 and 2 are supplied to a fixed-side preamplifier 8 via a rotating shaft 6 and a rotating transformer 7. The output signal of the preamplifier 8 is transmitted to the rotational phase detector 6.
The RF multiplied signals from video heads 1 and 2 are alternately switched by a signal processed by a pulse processing circuit 9 (hereinafter referred to as a head switching signal), and are supplied to an envelope detector 10 and a demodulator 11. Ru. The envelope detector 1o detects amplitude fluctuations of the RF multiplied signal reproduced by the video heads 1 and 2.

The output signal of the envelope detector 10 is supplied to one input terminal of the synchronous detector 13. Further, the output signal of the DITHER signal generator 14 is supplied to the other input terminal of the synchronous detector 13. The output signal of the synchronous detector 13 is added to the output signal of the DITHICR signal generator 14 in an adder 16 and supplied to DC amplifiers 16 and 17. This signal is transmitted to the electro-mechanical conversion elements 18 and 19.
is applied to electro-mechanical transducers 18 and 19 via ring 21 sufficiently to drive .

Note that the slip ring 21 is attached to the rotating shaft 6. On the other hand, the output signal of the demodulator 11 is supplied to the output terminal 12.

Next, parts of the configuration shown in FIG. 2 that are different from those shown in FIG. 1 will be explained. The other output signal of the demodulator 11 is input to the time-voltage conversion circuit 23 via the vertical synchronization signal separation circuit 22. The output signal of the time-voltage conversion circuit 23 is supplied to a hold circuit 24 and a level comparison circuit 26. The output signal of the hold circuit 24 is sent to the adder 1 via a level comparison circuit 26, a switch circuit 8W, and a track jump determination circuit 26.
6.

Next, the operations of the conventional example and the present embodiment will be described. FIG. 3 illustrates a recording track pattern recorded on the magnetic tape 27. In Figure 3, MUQ + BQ +
M + l Bl s M 2 indicates video tracks each recorded using one field of a video signal as a predetermined unit, and M 0 . M4. "01 B+" is recorded with a video head (not shown) having the same azimuth angle (+6° in this example), and "01B+" is recorded with a video head (not shown) having a different azimuth angle (-50 in this example). (not shown).

Note that the shaded portion in each track indicates the recording position of the horizontal synchronizing signal, and the matte-grained portion indicates the recording position of the vertical synchronizing signal.

Also, there is a V written on the satin-like part. s v1+ v2 indicates a vertical synchronizing signal recorded on a track of + e O azimuth. In the case of this embodiment, the so-called H alignment is 1.6H, as shown in FIG. 3. Trackum with the same azimuth. The combination of H between and Tranocum 1 is 3H, and the 0 or 1 field is 262.5H, assuming the case of an NTSG signal.

(In the case of a PAL signal, one field is 312.5 H.) On the other hand, Tc is a control track in which a control signal indicating the recording position of the video signal is recorded. In the control trunk Tc, 30.31 is a control signal recorded once per frame,
Mu when recording. Assume that the track start point and the control signal 3o are recorded at the same timing (7), and the M1 trunk start point and the control signal 31 are recorded at the same timing.

First, the rotational phases of the video heads 1 and 2 are detected by a combination of a magnet 3 and a rotational phase detector 6. The pulse processing circuit 9 uses, for example, three stages of mono-multivibrator circuits to obtain a head switching signal as shown in FIG. 4(D).

It is assumed that the rising edge coincides with the timing at which the video head 1 starts scanning the track, and the falling edge coincides with the timing at which the video head 2 starts scanning the track. Therefore, the reproduction signals reproduced by the video heads 1 and 2 are alternately selected by the preamplifier 8 using the head switching signal from the pulse processing circuit 9, converted into continuous signals, and sent to the envelope detector 10 and the demodulator. is supplied to the container 11. A reproduced signal as shown in FIG. 4(m) is input to the envelope detector 10. The envelope detector 1° is constituted by an ordinary diode detection circuit, and a signal indicating an envelope as shown in FIG. 4 is outputted at its output terminal.

The synchronous detector 13 is supplied with the envelope signal and the X terminal output signal of the ITHER signal generator 14 as shown in FIG.

As a result, when the video head 1 is scanning the current video track as a desired track during still playback, if the video head 1 shifts upward, the synchronous detector 13 outputs a negative signal as a scanning position correction signal. If the voltage shifts downward, a positive voltage is output. Note that when on-track, the output is zero. Such a scanning position correction signal is added to the Y terminal output signal (same phase as the X terminal output) of the DITHICR signal generator 14 in the adder 16, and the DC amplifiers 16 and 17 and the conductive brush 2o
, the electro-mechanical conversion element 18 via the slip ring 21
and 19. Therefore, the scanning positions of the video heads 1 and 2 are corrected to be on-track, and a loop is established.

In addition, the RF multiplied signal shown in Fig. 4, video head 1
and 2 are both upwardly shifted relative to the video track.

However, during still playback, video head 1 scans the video track, and video head 2 scans the video track. Even if both are scanned and shifted upward, an RF multiplied signal similar to that shown in FIG. 4 is obtained, and a control loop is established.

That is, in the conventional configuration shown in FIG. ” is occurring.

On the other hand, in FIG. 2 which is an embodiment of the present invention, for example, when "track jump" occurs in still playback, the demodulator 11 is shown in FIG. 6(b) separated from the signal as described above. The synchronizing signal is input to one input terminal of the time-voltage conversion circuit 23, and the input terminal of the pulse processing circuit 9 is input to the other input terminal as shown in FIG. 5(c).

A mode switching signal is also input.

An example of the configuration of the time-voltage conversion circuit 23 is shown in FIG.

In the figure, the vertical synchronizing signal shown in FIG. 6('b) is input to the vs input terminal, and the head switching signal shown in FIG. 6(0) is input to the Hs input terminal. The vertical synchronization signal shown in FIG. 6(b) input to the VS input terminal is
Two human-powered NAND gate circuits 28 and 2 which are logic circuits
9 is input to each one input terminal.

The head switching signal shown in FIG. 6(0) input to the H8 input terminal is similarly transmitted to the NAND gate circuit 2 via the other input terminal of the NAND gate circuit 28 and the inverter 27.
9 is input to the other input terminal.

Therefore, vertical synchronizing signals as shown in FIG. 6(d) and (6) are obtained at the output terminals of HAND gate circuits 28 and 29, respectively. These signals are input to each set input terminal S and reset input terminal H of the RS flip-flop circuit constituted by NmND gate circuits 3o, 81 and 32.33, respectively. At the output terminal, signals as shown in FIGS. 6(f) and (g) are obtained which are alternately set and reset by the tune synchronization signals shown in FIGS. 5(d) and (6). In the signals shown in FIGS. 6(f) and (g5), for example, the H level period indicates one field time of the video signal.

Next, resistors R1 and R2, capacitors C1 and 02. Operational amplifiers 36 and 36. During the H level period of the signals shown in FIGS. 6(f) and (h), the respective capacitors C1 and C2 are charged by an integrating circuit composed of switches 34 and 36, and the voltages shown in FIGS. 5(g) and (i) are charged. ) is obtained. Therefore, measuring the peak value of the voltage waveform shown in Figure 5 (i) means measuring the time for each field of the reproduced video signal, that is, the time between one vertical synchronizing signal and the next vertical synchronizing signal. This is true. Figure 5 (g)
, There is a difference N in the peak value of the voltage waveform shown in (i), but this is due to the "track jump" described above. Since the tape 27 is played back by video heads 1 and 2 with the same azimuth, in the case of still playback without "track jumping", the vertical synchronization signal interval between each field is 264H (however, H is the horizontal synchronization signal interval). Therefore, no difference appears between fields. but,
As mentioned above, in still playback, video head 1
scans the video track 1, and the video head 2 scans the video track 1. If a "track jump" occurs during scanning, as shown in FIG. The interval between them is 267H. Also, the vertical synchronization signal V reproduced by the video head 2. The interval between this and the vertical synchronization signal v1 reproduced next by video head 1 is 261H.
become. This is the difference between the peak values of the voltage waveforms in FIGS. 6(g) and (i).

As mentioned above, in still playback, if "f track jump" does not occur, 1 field = 264H.
The reason for this is that the so-called H combination is 1.6H, and
The electro-mechanical conversion element 18 for on-tracking
．． 19, the video heads 1 and 2 are driven approximately at right angles to the video track.

The explanation so far is about track jump detection in still playback, but if the magnetic tape running speed during playback is 2N (however, H is any integer including zero) times the magnetic tape running speed during recording, also shows that it is possible to detect track jumps with a similar configuration. Also,
Although the detection of track jumping has been described by taking the video track automatic tracking method using the DITHER signal as an example, other methods may be used as the video track automatic tracking method itself. For example, by multiplexing a pilot signal for automatic tracking onto a signal recorded on a video track,
During playback, this pilot signal is used to automatically track the video track, or the above-mentioned DITH
The "mountain climbing method", which is considered a modification of the KR method, may also be used. The above-mentioned "Yamabo 9 method" is a method in which the positions of the video heads 1 and 2 are moved a predetermined distance perpendicular to the video track, the level change of the envelope of the reproduced RF signal from the video head is detected, and the result is detected. , which is then used to determine the direction when moving the video heads 1 and 2 to form a control loop. Alternatively, in an open loop, for example, by generating a signal waveform (equivalent to a scanning position correction signal in the control loop) that satisfies the on-track conditions during variable speed playback based on the running information of the magnetic tape 270, and applying it to the DC amplifiers 16 and 17. Zero-travel information that may establish on-track is obtained from the control signal and the rotation angle of the rotating body that rotates as the magnetic tape 27 advances.

Figure 7 shows that the running speed of the magnetic tape is the inverse twice the running speed of the magnetic tape during recording (N'=-2) I still (N:O)
, twice (N=2), the scanning trajectory of the video head 1 is shown when no signal is applied to the electro-mechanical conversion element 18 and when the above-mentioned scanning position correction signal is applied. Note that the track pattern is the same as that shown in FIG. 3, and shows the track pattern at the time of recording. In FIG. 7, a trajectory 100 is a trajectory that satisfies the on-trunk condition. That is, at each speed, a zero trajectory 101 indicates the scanning trajectory of the video head 1 when a scanning position correction signal is added.
is the scanning locus of the video head 1 at reverse double speed when no signal is applied to the electro-mechanical conversion element 18. Similarly, the scanning trajectory of the video head 1 during still playback when the trajectory 102 indicates that no signal is applied to the electro-mechanical conversion element 18, and the scanning trajectory of the video head 1 during double-speed playback when the trajectory 103 indicates that no signal is applied to the electro-mechanical conversion element 18. This is a scanning locus of the head 1. The time length of one field (vertical synchronization signal interval) at these speeds is as follows when no "track jump" occurs.

Reverse double speed...267H (H is horizontal scanning time) Still playback...264H Double speed playback...261H In other words, in 2N double speed playback, 2N double speed playback... ...(264-31) becomes H.

Here, if a "track jump" of 2M pitch (where M is any integer not including zero) occurs, the first field... ((264-sN) ± 3M
)H second field...((26'4-3N
)乎3M)H (The signs are in the same order, and the field played by video head 1 is the first field, and the field played by video head 2 is the second field.)
Always (csM)H in the first and second fields.
Alternatively, a difference of (-eM)H occurs.

This difference is detected by the detection circuit described above.

Note that the sign of the difference is that video head 2 is tracked by video head 1. It shows whether you are jumping in the direction or in the direction of the truck. Further, the absolute value of the difference indicates the number of jumping tracks.

With this configuration, the time-voltage changing circuit 2
At the output end of No. 3, a peak value of a waveform corresponding to whether or not "track jumping" occurs and the number of jumping tracks is obtained. This peak value is held in the hold circuit 24, and the peak value in the second field is compared with the peak value in the first field to the next level comparison circuit 2.
6, video head 2 is tracked compared to video head 1. It is determined whether the robot is jumping in one direction or in two directions. Such a hold circuit 24 is usually configured to include an operational amplifier, a hold capacitor, and an analog switch for discharging the charge of the capacitor.Furthermore, the level comparison circuit 26 is usually configured by a comparator. By configuring the level comparison circuit 25 with a plurality of window comparators, it is possible to detect the absolute value of the above-mentioned difference and whether the difference is zero, that is, "no track jump". As a result, video head 2 is tracked with respect to video head 1. Whether it is jumping in the direction of the track or in the track direction, and the number of tracks that are jumping (number of track pitches)
It is possible to detect how many pieces there are. In this way, the detected track jump information is supplied to the track jump correction circuit 26 via the switch SW. Switch SW is 2N
It is a closed circuit near double speed. The track jump correction circuit 26 supplies a voltage according to the track jump information to the adder 16 for each field, and an example thereof will be shown below. The video head 1, ie, the first field, is used as a reference, and all jump correction is performed in the video head 2, ie, the second field. That is, during the second field, a voltage corresponding to the above-described difference is output to the adder 16, and during the first field, zero voltage is output. Here, the position of the video head 2 is adjusted to 2M by the output voltage of the trunk jump correction circuit 26.
The pitch is moved and jump correction is performed. As a result, the time length of the first field and the time length of the second field match, and the level comparison circuit 25 outputs the information "no track jump".

This information causes the switch SW to become an open circuit.

Track jump correction is achieved by maintaining the trunk jump correction circuit 26 in the state when the switch SW is closed.

As described above, the method using the video head 1, that is, the first field, as a reference has the advantage of a simple circuit configuration, but there is a possibility that an extra voltage is applied to the electro-mechanical conversion elements 18 and 19. In order to improve the problem, the track jump correction circuit 26 may operate as shown below. It is assumed that the track jump correction circuit 26 also receives the above-mentioned track jump information and voltage information applied to the electro-mechanical conversion elements 18 and 19. Here, as a result of comparing the above voltage information and executing track jump correction, the above voltage information is compared.
Track jump correction is distributed to the first field and the second field so that the voltage applied to the mechanical transducer elements 18 and 19 is minimized. As a result, the electro-mechanical conversion element 18
．． Track jump correction is performed without applying any extra voltage to 19. Note that the track jump correction circuit 26 is
It consists of a hold circuit that holds track jump information, and a voltage source that supplies a predetermined voltage to a predetermined field according to the information.

However, the switch SW described above is also considered to be open circuit in the following cases.

(1) The field in which the level of the reproduced RF signal of the video head 1 or 2 drops to the extreme i, and the immediately following first and second field periods. This is to prevent the vertical synchronization signal separation circuit 22 from malfunctioning due to so-called dropout, and as a result, the track jump correction circuit 26 from malfunctioning.

(II) The first and second field periods immediately following the field in which track updating was performed during slow playback or reverse slow playback. Here, track updating will be explained using W double speed as an example. Dedicated speed means trackum,
is played over 4 fields, and then track 2 is played over 4 fields.
Trunk update refers to the timing at which track 2 is played back after track 2 is played back. Here, when playing the same track, the conditions are the same as still playback, so by measuring the time length of the field.

It is possible to detect all "truck jumps".

However, since the time length of one field is different before and after the track is updated even if no track jump occurs, the level comparison circuit 26 malfunctions. To avoid this, switch SW is opened. Similarly, it is possible to detect "trunk jump" even at around 2N times the speed. In this case, if the number of tracks being scanned is every 2N in each field, the switch SW is set as a closed circuit. In addition, in every 2N fields out of order, the switch SW is kept open during the field including this field and the immediately following first and second fields. As a result, if the tape speed during playback is around 2N double speed, "track jump" can be detected and corrected.

With this configuration, the two-head helical scan V
This solves the problem of "track jumping," which is a major problem when using an auto-tracking device in a TR.

Oh, the configuration described above can be explained using an analog circuit. In particular, digital circuits are effective for the hold circuit 24, level ratio circuit 25, and track jump correction circuit 26. In addition, the above explanation has been made regarding the case where a magnetic tape recorded on an azimuth type two-head helical scan VTR is played back on a two-head helical scan VTR with the same azimuth.
A similar configuration can be used when playing back on a head helical scan type VTR. Moreover, in this case, since the +6° azimuth track mode also plays back the 6° azimuth track, at tape speeds around N times
Detection and correction of "truck jump" becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts of a conventional auto-tracking device, FIG. 2 is a block diagram of main parts of an embodiment of the present invention, and FIG. 3 is a diagram showing an example of a video trunk pattern used to explain the present invention. , Fig. 4 (mu), (B), ((j).
d), (e), (f), (g), (h
). 4 (1) is a signal waveform diagram of each part in FIG. 2, FIG. 6 is a circuit diagram showing a configuration example of a time-voltage conversion circuit in an embodiment of the present invention, and FIG. 7 is a video track in an embodiment of the present invention. FIG. 3 is a diagram showing a rotation locus of a video head with respect to a pattern. 1. Hiteo head for 2, 10... Envelope detector, 11... Demodulator, 13...
... Synchronous detector, 14 ... DITHIER signal generator, 16 ... Adder, 18.19 ...
...Electro-mechanical conversion element, 22... Vertical synchronization signal separation circuit, 23... Time-voltage conversion circuit, 2
4...Hold circuit, 26...Level comparison circuit, 26...Track jump correction circuit, S
W...Switch. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 2127 Figure 4 Ca2 =----1 (t) ---1- (p)- Figure 5 (4°) Figure 6, 7, J4 Figure 7

Claims (1)

[Claims] (1) When a video signal of a predetermined unit length is recorded as a video trunk having a predetermined inclination with respect to the longitudinal direction of the magnetic tape, a video head scans and reproduces the video signal from a magnetic tape. A tracking device for a video signal reproducing device or a video signal recording and reproducing device, in which a target position is moved in a direction substantially perpendicular to the video track using an electro-mechanical conversion element, and the tracking device is a tracking device for a video signal recording and reproducing device, the video signal being played back by the video head. The period of the perpendicular 1aJ signal included in the reproduced video signal that is
provided that N is any integer including zero), the video head is measured when the speed is at or around double speed, and the position of the video head is moved so that the predetermined cycle is reached when the cycle is other than the predetermined cycle. tracking device. (2) The tracking device according to claim (1), wherein the moving distance of the video head is an integral multiple of the video track distance.