JPH01107355A - Tracking system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking method in a recording/reproducing apparatus.

[Conventional technology]

2. Description of the Related Art A helical scan type magnetic recording/reproducing apparatus is known in which a rotating video head records or reproduces a video signal on a video track inclined with respect to the longitudinal direction of a magnetic tape. This type of magnetic recording/reproducing apparatus requires a tracking device for accurately scanning a rotating video head over a video track during reproduction, and various types of tracking devices are known. For example, in a method using a viroft signal, when recording a video signal, three or more types of pilot signals are sequentially and cyclically switched every track period and multiplexed with the video signal on each video track. The direction and amount of tracking deviation can be determined by comparing two types of beat frequency components: the reproduced pilot signal from the track being played back and the reference pilot signal obtained as crosstalk from tracks adjacent on both sides of the track being played back. The rotating video head is sensed and scanned to precisely follow the video track to be scanned.

[Problem that the invention seeks to solve]

Although this biloft signal method can achieve accurate tracking operation, it has the following problems.

That is, since the video signal and the pilot signal are multiplexed and recorded during the video signal recording period, the video signal needs to be an analog signal that can easily realize multiplex recording. However, in recent years,
Digital recording methods are being introduced as video signal recording methods, and in that case the encoded video signal occupies a wide frequency band and also has low frequency components, so it can be reproduced even if the pilot signal is multiplexed. Sometimes difficult to separate. Furthermore, it is possible that the reproduced digital signal may be adversely affected.

SUMMARY OF THE INVENTION An object of the present invention is to improve the pilot signal system and provide a tracking system suitable for narrow track, high-density coded information recording.

[Means for solving problems]

The tracking method according to the present invention records information signals while sequentially forming a large number of tracks inclined with respect to the longitudinal direction of a tape-shaped recording medium, and reproduces the information signals from the tracks with a rotating head. A tracking method for causing the head to follow the track concerned, wherein when recording the information signal, first and second tracking areas are provided in each track for recording a pilot signal for detecting a tracking error, and when recording the information signal. When reproducing, a pilot signal in a signal obtained by mixing the reproduction signal of the rotary head tracing the first tracking area and the reproduction signal of the rotary head tracing the second tracking area is used. The rotary head is made to follow the target track.

[Effect]

By mixing the reproduced pilot signals from the first and second tracking areas during reproduction,
Even when the linearity of the track is poor, it is possible to make the rotary head follow the ideal tracing position. Also, since the pilot signal is not frequency multiplexed with the information signal,
Applicable to coded signal recording.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

In the present invention, pilot signals of different frequencies between adjacent tracks are recorded in a limited tracking area. During playback, track misalignment of the rotating head is determined based on crosstalk from adjacent tracks. As the pilot signal, a low frequency with little azimuth loss is used in both rotating heads having different azimuth angles. In order to increase the information recording density, it is preferable that the area dedicated to tracking be kept to a minimum. Therefore, in order to be able to record a large number of waves in the dedicated area, it is preferable to use a frequency that is as high as possible among low frequencies with less azimuth loss. In the following example, f r = 300 KHz, fz = 2
00 KHz was used.

FIG. 2 is a block diagram of the pilot signal recording system,
10.12 is an oscillation circuit that oscillates and outputs two different frequencies ft and fz used for pilot signals, and 14
is the switching pulse swp obtained from the rotating head
(See FIG. 3(a)). That is, each time scanning of a new track is started, the changeover switch 14 is switched so that pilot signals of different frequencies are recorded between adjacent tracks. 15. 16A and 16B are gate pulses GTPI (Fig. 3 (bl)) and GTP 2 (Fig.
C)) is a gate circuit that is opened and closed by GTP 3 (FIG. 3(d)). Although not shown, the gate circuits 16A and 16B are supplied with not only the pilot signal from the gate circuit 15 (but also encoded information signals such as video signals to be recorded). 18A and 18B are recording amplifiers;
OA, 20B is a rotating magnetic head, and 22 is a magnetic tape. The rotating magnetic heads 20A and 20B are mounted on a rotating drum facing each other by 180°.

FIG. 4 shows the recording state of the magnetic tape 22-F.

jl+j3 is a track scanned for recording by the rotary magnetic head 20A, and h+t4 is a track scanned for recording by the rotary magnetic head 20B. Arrow A indicates the tape moving direction, and arrow B indicates the scanning direction of the rotating rods 20A and 20B. The part marked L and fz is the pilot signal fi f
This is the ATF area where t is recorded, and the AT of each track is
The F area should partially touch the ATF area of the adjacent track at a head scanning force of 1 ilB, and if possible, the start and end of the ATF area should be in the center of the ATF area of the adjacent track and the opposite side of the ATF area of the adjacent track. Preferably, the IBG area is a no-signal recording area. This IBG area effectively detects pilot signal crosstalk from adjacent trunks. The hatched portion with diagonal lines is the recording area of the video signal. The magnetic tape 22 is wound around a rotating head drum over 180 degrees, and the ATF areas at the beginning and end of each track are spaced 180 degrees apart.

Next, the auto-tracking operation during playback will be explained.

The reproduction circuit block is shown in FIG. 1, and the waveforms of each part are shown in FIG. A pilot signal is recorded on the magnetic tape 22 as shown in FIG. 24A and 24B are rotary magnetic heads used for reproduction, and in the case of dual use for recording and reproduction, they are also used as heads 20A and 20B. 25A and 25B are reproduction amplifiers, 26A and 26B are the above GTP2 (Figure 3 (CI)
, GTP3 (FIG. 3(d)).

Pilot signals are time-division multiplexed on the reproduced signals that have passed through the gate circuits 26A and 26B, and the reproduced pilot signals f, ft are respectively extracted by band pass filters (BPF) 28 and 30. Gate circuit 26
The passing signals A and 26B are also sent to a video signal processing circuit (not shown), but since that circuit is not related to the present invention, its explanation will be omitted.

32 is a detection circuit for the pilot signal f, and 34 is a detection circuit for the biloft signal f. The outputs of the detection circuits 32 and 34 are passed through low-pass filters (LPF) 36 and 38 to obtain envelope signals c and d corresponding to each detection level. Peak hold circuit 40.42 is LPF36,38
The maximum values of the outputs c and d are held. Comparison circuit 4
4 is the hold value e of each peak hold circuit 40.42
, f are compared, and a selection is made as to whether to use the pilot signals f,, ft for tracking deviation detection or sampling. The output of the comparison circuit 44 is supplied to a flip-flop (FF) 46 and latched and held in phase with the reset pulse REP. This reset pulse REP is a pulse formed by monostable multi-vibration using the rising edge of the switching pulse SWP as a trigger, and is also used to reset the peak hold circuits 40 and 42.

A high level of the reproduction pilot signal indicates that a large portion of the reproduction head is on the track where that pilot frequency is recorded.

The switch 50 is a switch for switching the envelope signals c and d from the LPFs 36 and 38 for tracking deviation detection and sampling.

The envelope signal selected for tracking is applied to gate switches 54,56, and the envelope signal selected for sampling is provided to a comparator circuit 58. Reference numeral 48 denotes a switch for selecting a reference voltage for comparison of the envelope signal for sampling, and is switched to the peak hold voltage of the reproduced pilot signal selected for sampling by the switch 50 in accordance with the output of the FF 46. As the comparison reference voltage, a voltage obtained by dividing the selected peak hold voltage by a resistor 60.62 is used.

In the illustrated example, 1/2 of the peak hold voltage is used.

The sampling pulse generation circuit 64 generates narrow sampling pulses in response to the rise and fall of the output of the comparison circuit 58. A sampling pulse h occurring at the rising edge instantaneously closes the switch 56, and a sampling pulse i occurring at the falling edge instantaneously closes the switch 54. As a result, the envelope signal voltage for tracking deviation detection is sampled and held by the capacitors 66 and 68 via the switch 52.

The voltages sampled by the sampling pulses h and i are the crosstalk of the pilot signals from the front and rear adjacent tracks, respectively, and the level difference is the
This corresponds to the average value of the track deviation amounts of 0A and 20B. Auto-tracking of the rotating head is realized by amplifying the voltage of the capacitors 66 and 68 with a differential amplifier 70, supplying its output to the capstan motor drive circuit 72, and applying a servo so that the sampling voltages are equal. do.

The switch 52 is a polarity reversal circuit that is switched by the output of the FF 46, and is set so that the magnetic head 24A converges on either the track jli F or the track tz or t4. 24A is track 1. , 1. I started tracking. Note that the switch 52 is fixed when azimuth recording is being performed by the heads 20A and 20B.

Next, we will explain Auto Tiger 7 King using an actual model as an example. FIG. 5 shows the positional correspondence between the recording track and the rotary head. The head width of the rotating heads 24A and 24B is slightly wider than the recording track width. Heads 24B and 24A are on track 1. , 1. , but it is slightly shifted to the right from the center of the track in the head scanning direction B.

FIG. 6 is a waveform diagram of each part of FIG. 1 when reproduced using the model of FIG. 5. Rotating heads 24B, 24 in the state shown in FIG.
When A scans on track tz, t+, BPF28
．． 30 to pilot burst signal (Figure 3 a, b)
is obtained. The envelope signal C output from the LPF 36 is a pilot signal f1 that occupies most of the scanning of the rotating head, and has a larger amplitude than the component of the pilot signal f2. The output d of the LPF 38 is the pilot signal f,
, the amplitude is small, and the head 24B,
The amount of crosstalk from adjacent tracks differs depending on the direction of shift of 24A. Corresponding to the positional relationship shown in FIG. 5, the crosstalk from the right direction is larger than the crosstalk from the left direction.

The outputs c and d of the LPF 36.38 are held by a peak hold circuit 40.42, and a comparison circuit 44 compares both peak values. In the illustrated example, since the envelope signal C is always larger than the envelope signal d, the output of the comparison circuit 44 becomes "H", which is launched into the FF 46. Based on the output of the FF 46, the switch 50 supplies the envelope signal d to the switches 54 and 56 for tracking deviation detection, and supplies the envelope signal C to the comparison circuit 58 for sampling. The switch 48 is connected to the peak hold circuit 40 output e side of the envelope signal C, and half the voltage is supplied to the comparator circuit 58 through the resistors 60 and 62.

Sampling pulse generator circuit 64 generates sampling pulses h, i (FIG. 6) which momentarily close switches 54,56 to sample the crosstalk voltage from envelope signal d. Pulse h samples the crosstalk voltage from the left track and pulse i from the right track. The sampled voltages are held by capacitors 66 and 68, and the difference between them is amplified by a differential amplifier and supplied to the capstan motor drive circuit 72 as a sampling error voltage V.

Then, the tape transport speed by the capstan is controlled so that both sampling voltages are equal.

FIG. 7 shows the tracking error characteristics of the present invention. The horizontal axis shows the position of the rotary head 24A, and the vertical axis shows the tracking error voltage V. The arrow indicates the direction in which the auto tracking servo is applied.

In this model, the tracking error voltage is at position 4a, which corresponds to the state in which the rotary head 24A is shifted to the 4 side on the track. The capstan motor is
Tracking error voltage■.

The magnetic tape feeding speed is changed so that the number shifts from 4a to 4b. This causes the rotor to rotate 24A.

The deviation of 24B with respect to track j:l+t2 is corrected and the rotary heads 24A, 24B precisely scan track 13.12.

In the above embodiments, the information signal to be recorded and reproduced is a video signal, but it may also be an audio signal, and in particular, even if it is a coded information signal, no restrictions are imposed by inserting a pilot signal. Therefore, it can be used for recording and reproducing information related to boat fishing.

Furthermore, since the outputs of both the head nozzles 24A and 24B are used at the same time, for example, if the linearity of the track is poor and the tracking state of the head 24A for track t is different from the tracking state of the head 24B for track t2, Also, the heads 24A and 24B can be controlled to their optimum tracing positions. In other words, it is controlled so as to precisely trace the information signal partial tetra track in the center of the track.

〔Effect of the invention〕

As can be easily understood from the above explanation, according to the present invention, automatic tracking can be realized with a simple circuit configuration, and even if the track is curved, the playback head can be positioned at the optimal tracing position. can be controlled.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of an auto-tracking device according to the present invention, FIG. 2 is a block diagram of a viroft signal recording circuit, and FIG.
Timing chart of pulse GTPI ~ 3, Figure 4 is an example of a magnetic tape recording pattern, Figure 5 is an explanatory model of auto tracking, Figure 6 is a diagram of Figure 1 when played back in the condition shown in Figure 5. FIG. 7 is a diagram showing the relationship between the head position and the tracking error voltage.

Claims (1)

[Claims] In an apparatus for recording an information signal while sequentially forming a large number of tracks inclined with respect to the longitudinal direction of a tape-shaped recording medium, and reproducing the information signal from the track with a rotating head,
A tracking method for causing the rotary head to follow the track, which includes providing first and second tracking areas for recording a pilot signal for tracking error detection on each track when recording the information signal; When reproducing an information signal, a pilot signal in a signal obtained by mixing the reproduced signal of the rotary head tracing the first tracking area and the reproduced signal of the rotary head tracing the second tracking area. A tracking method characterized by causing the rotary head to follow a target track using the following.