JP2570773B2 - Tracking method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tracking system in a recording / reproducing apparatus.

[Conventional technology]

A helical scan type magnetic recording / reproducing apparatus which records or reproduces a video signal on a video track inclined with respect to the longitudinal direction of a magnetic tape by a rotating video head is known. In this type of magnetic recording / reproducing apparatus, a tracking apparatus for accurately scanning a rotating video head on a video track during reproduction is indispensable, and various types are conventionally known. For example, in a method using a pilot signal, at the time of recording a video signal, three or more types of pilot signals are sequentially and cyclically switched every track period and multiplex-recorded together with the video signal on each video track. A reproduced pilot signal from the track
By comparing two types of beat frequency components with a reference pilot signal obtained as crosstalk from tracks adjacent to both sides of the track being reproduced, the direction and amount of tracking deviation are detected, and the video / scan to be scanned is detected. The track is accurately scanned by the rotating video head.

A method of providing a track dedicated for tracking in the longitudinal direction of a magnetic tape has been conventionally known. In this method, at the time of recording, a vertical synchronization signal separated from a video signal to be recorded is recorded as a CTL signal on the tracking-dedicated track by a dedicated head.
A phase difference between the signal and a pulse (30 Hz) related to the rotation phase of the rotary head is detected, and the transport speed of the magnetic tape is controlled so that the difference becomes a predetermined value. This allows the rotating head to scan over the video track to be scanned.

[Problems to be solved by the invention]

Although accurate tracking operation can be realized by the above pilot signal system, it has the following problems. That is, since the video signal and the pilot signal are multiplex-recorded during the video signal recording period, the video signal needs to be an analog signal that can easily realize the multiplex recording. However, in recent years, a digital recording method has been introduced as a recording method of a video signal,
In such a case, the coded video signal occupies a wide frequency band and also has a low-frequency component. Therefore, even if the pilot signal is multiplexed, it is difficult to separate it at the time of reproduction. It is also considered that the reproduced digital signal is adversely affected.

Also, in the method of providing a tracking-only track,
Tracking can be performed regardless of whether the video signal or other signal to be recorded is an analog signal or a digital signal. However, due to the presence of the longitudinal tracks, a fixed head must be prepared, and in configuring the apparatus, it is necessary to arrange the tape path and the like in consideration of the fixed head, which is very disadvantageous. Furthermore, CT
Since the mounting accuracy of the L head directly affects the tracking accuracy, it is not suitable for a high-accuracy tracking device for high-density recording by narrowing the track. Furthermore, it is difficult to maintain the compatibility of the apparatus with the same use, and there is a problem that the cost increases due to the addition of the dedicated head.

Therefore, an object of the present invention is to provide a tracking method which can be applied to recording of coded information of a narrow track and high density, and which can make a head follow an arbitrary track.

[Means for solving the problem]

The tracking method according to the present invention is a device for recording an information signal on a track of a recording medium having a large number of parallel tracks and reproducing recorded information from the track. A tracking signal detection area for tracking error detection and a no-signal recording area sandwiching the area in each track, and the pilot signal recording area between adjacent tracks is arranged in the longitudinal direction of the track. The two types of pilot signals having different frequencies are recorded in the pilot signal recording area so that the frequency differs for each adjacent track, and at the time of reproduction, the levels of the reproduced two types of pilot signals are compared. The level of the two types of pilot signals is determined according to the comparison result. Large and have been detected reproduction level of the first and the other pilot signals at a second timing determined by using the pilot signal, the first and second
The reproduction levels detected at the timing of are compared.
The conversion means is made to follow the target track by controlling so that the comparison result of the reproduction levels detected at the first and second timings is inverted according to the level comparison result of the pilot signal of the type. And

[Action]

Since the pilot signal recording area is shifted in the longitudinal direction of the track, crosstalk of pilot signals from tracks adjacent on both sides is picked up at different timings at the time of reproduction, and the pilot signal of the higher level is picked up. At the first and second timings according to the reproduction timing, the other pilot signal is reproduced as a crosstalk component from an adjacent track. The direction and amount of track deviation can be detected by comparing the reproduction levels. Therefore, auto tracking for an arbitrary track can be realized using the level difference between the crosstalk components. Since only two frequencies are needed as a pilot signal,
The circuit can be constructed simply and inexpensively. Also, narrow tracks,
It can be applied to high-density recording and is not frequency-multiplexed with information signals, so it can be applied to encoded signal recording.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the present invention, pilot signals of different frequencies between adjacent tracks are recorded in a limited tracking-only area. Then, at the time of reproduction, the track deviation of the rotary head is determined by crosstalk from an adjacent track. As the pilot signal, a low frequency with small 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 is minimized. Therefore, in order to record a larger number of waves in the dedicated area, it is preferable to use as high a frequency as possible among low frequencies with low azimuth loss. In the following examples, f ₁ = 300 KHz and f ₂ = 200 KHz were used.

FIG. 7 is a block diagram of a pilot signal recording system according to the present invention.
This is an oscillation circuit that oscillates and outputs various types of frequencies f ₁ and f _2.
Is a changeover switch which is switched by a switching pulse SWP obtained from the rotating head. That is, each time a new track is scanned, the changeover switch 14 is switched so that pilot signals of different frequencies are recorded between adjacent tracks. Reference numeral 16 denotes a gate circuit that closes at a timing corresponding to the tracking-only area, reference numeral 18 denotes a recording amplifier, reference numeral 20 denotes a rotating head, and reference numeral 22 denotes a magnetic tape. As the rotary head 20, a plurality of heads are actually switched and used. It should be noted that the video signal processing and recording circuit portions are omitted.

The gate circuit 16 has a gate pulse GTP formed based on the rise and fall of the switching pulse SWP.
, So that the pilot signal is recorded at a predetermined position on the track at a specified interval. FIG. 5 shows the recording state on the magnetic tape. The In FIG. 5, t ₁ ~t ₄ is a track which is scanned recorded by the rotary head 20, an area of the hatched portion by oblique lines is recorded in the pilot signal, arrow A tape moving direction, arrow B the rotary head
Shows 20 scanning directions. FIG. 6 is an enlarged view of the pilot signal recording area of FIG. The ATF section is a recording area for pilot signals, and pilot signals f ₁ and f ₂ having different frequencies are recorded alternately for each track. The ATF area of each track should partially overlap the ATF area of the adjacent track, and the beginning and end of one ATF area should be the center part of the ATF area of the adjacent track and the opposite adjacent track. Is preferably located at Sixth
The figure shows a preferred example. The IBG area is a non-signal recording area. The presence of the IBG area effectively detects crosstalk of pilot signals from adjacent tracks.

Next, an auto tracking operation during reproduction will be described. FIG. 1 shows the reproduction circuit block, and FIG. 8 shows the waveforms of the respective parts. A pilot signal is recorded on the magnetic tape 22 as shown in FIG. Reference numeral 24 denotes one of the rotating magnetic heads used for reproduction.
More than two heads are switched and used by the head switching pulse SWP. 26 is a reproduction amplifier. The reproduction signal amplified by the reproduction amplifier 26 is sent to a video signal processing circuit (not shown). A pilot signal is time-division multiplexed on the output of the reproducing amplifier 26, and the reproduced pilot signals f ₁ and f ₂ are respectively band-pass filters (BPF) 28, 3
Retrieved at 0. 32 detection circuit of the pilot signal f ₁ is 3
4 is a detection circuit of the pilot signal f _2. Detection circuit 32, 34
Are passed through low-pass filters (LPFs) 36 and 38 to obtain envelope signals c and d corresponding to the respective detection levels.

The peak hold circuits 40 and 42 hold the maximum values of the outputs c and d of the LPFs 36 and 38, respectively. The comparison circuit 44 compares the hold values e and f of the peak hold circuits 40 and 42, and selects whether f ₁ or f ₂ is used for tracking deviation detection or for 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 the monostable multivibrator triggered by the rise of the switching pulse SWP, and is also used for resetting the peak hold circuits 40 and 42.

The large level of the reproduced pilot signal means that
This shows that many parts of the reproducing head are on the track where the 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 and 56,
The envelope signal selected for sampling is supplied to a comparison circuit 58. 47 is a switch for selecting a comparison reference voltage of the sampling envelope signal. The output of the FF 46 switches to the peak hold voltage of the reproduced pilot signal selected for sampling by the switch 50. As the comparison reference voltage, a voltage obtained by dividing the selected peak hold voltage by the resistors 60 and 62 is used. In the illustrated example, 1/2 of the peak hold voltage was used.

The sampling pulse generation circuit 64 generates a narrow sampling pulse in accordance with the rise and fall of the output of the comparison circuit 58. In this embodiment, the pulse width is 20μ.
s. The sampling pulse h generated at the rising edge instantly closes the switch 56, and the sampling pulse i generated at the falling edge instantly 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 crosstalks of pilot signals from the preceding and succeeding adjacent tracks, respectively, and the level difference corresponds to the track shift amount of the rotary head. Auto-tracking of the rotating head is realized by amplifying the voltage of the capacitors 66 and 68 with the differential amplifier 70, supplying the output to the capstan motor drive circuit 72, and applying servo to make the sampling voltage equal. I do.

The switch 52 is a polarity inverting circuit switched by the output of the FF 46, and is set so as to set which of the recorded tracks of the pilot signal frequencies f ₁ and f ₂ the magnetic head 24 controls. is there. In the illustrated embodiment, and such that tracking f ₁ side.

Next, auto-tracking will be described using an actual model as an example. FIG. 2 is a diagram showing the positional relationship between the recording tracks and the rotary head. 24a is a rotary head, whose head width is slightly wider than the recording track width. Head 24a is riding on a large part of the track t _3, but that deviates slightly t ₄ direction from the center of the track. FIG. 3 is a waveform diagram of each part in FIG. 1 when reproduced with the model in FIG. When the rotary head 24a in the state of FIG. 2 scans the track t _3, the pilot burst signals from BPF28,30 (FIG. 3 a, b) is obtained. LPF
The envelope signal c output from 36 is the pilot signal f ₁ of the track t ₃ when the majority of the rotary head scanning. The output d of the LPF 38 is the track t ₂ , t ₄ (pilot signal
f ₂ ) is the crosstalk from the head, the amplitude is small, the head
The crosstalk amount from the adjacent track differs depending on the shift direction of 24a.

The outputs c and d of the LPFs 36 and 38 are held by peak hold circuits 40 and 42, and a comparison circuit 44 compares both peak values. In the illustrated example, since the envelope signal c is always larger than d, the output of the comparison circuit 44 becomes "H", which is latched by the FF 46. By the output of the FF 46, the switch 50 switches the envelope signal d to the switches 54, 5 for detecting the tracking error.
And supplies the envelope signal c to a comparison circuit 58 for sampling. Switch 48 is an envelope signal c
Connected to the output e side of the peak hold circuit 40,
By means of 0 and 62, half of the voltage is supplied to the comparison circuit 58.

The sampling pulse generating circuit 64 generates the sampling pulses h and i (FIG. 3), and thereby the switches 54 and 56
Momentarily closes, and samples the crosstalk voltage from the adjacent tracks t ₂ and t ₄ from the envelope signal d. The sampled voltage is held by the capacitors 66 and 68, and the difference is amplified by the differential amplifier.
It is supplied to the capstan motor drive circuit 72 as V _E. Then, the tape transport speed by the capstan is controlled so that both sampling voltages become equal.

FIG. 4 shows the tracking error characteristic of the present invention.
The horizontal axis position of the rotary head, and the vertical axis represents the tracking error voltage V _E. The arrow indicates the direction in which the auto tracking servo is applied. In this model, the tracking error voltage is in the position of 4a, the rotary head corresponds to the state is shifted to the track t ₄ side. Capstan motor, tracking error voltage V _E to change the magnetic tape feed speed so as to shift from 4a to 4b. This allows
Deviation of the track t ₃ with respect to the rotary head 24a is corrected, the rotary head 24a is accurately scan the track of the pilot signal f _1.

In the above embodiment, the information signal to be recorded / reproduced is a video signal. However, the information signal may be an audio signal or the like. In particular, even if it is an encoded information signal, no restriction is imposed by inserting a pilot signal. Therefore, it can be used for recording and reproducing general information. Further, the recording medium is not limited to a magnetic tape but may be a recording medium such as a magnetic disk. If possible, a plurality of pilot signals may be provided for each track. Then, the tracking accuracy can be improved.

〔The invention's effect〕

As can be easily understood from the above description, according to the present invention, it is possible to realize auto-tracking for an arbitrary track in narrow track and high-density information recording with a simple circuit configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an auto-tracking device according to the present invention, FIG. 2 is an explanatory model of the auto-tracking, and FIG. 3 is a waveform of each part in FIG. 1 when reproduced in the state of FIG. Fig. 4 shows the head position and tracking data.
FIG. 5 is a diagram illustrating a pilot signal recording area of a magnetic tape, FIG. 6 is an enlarged view of the pilot signal recording area of FIG. 5, and FIG. 7 is a diagram of a pilot recording pattern recording system of FIG. FIG. 8 is a block diagram, FIG.
It is a signal waveform diagram of the principal part of a figure. 22 ... Magnetic tape, 24 ... Rotating head, 32,34 ... Detector circuit, 44,58 ... Comparator circuit, 46 ... Flip flop

Claims (1)

(57) [Claims] 1. An apparatus for recording an information signal on a track of a recording medium having a plurality of tracks arranged in parallel and reproducing recorded information from the track, wherein a recording or reproducing conversion means follows the track. A tracking signal detection area for tracking error detection and a no-signal recording area sandwiching the pilot signal recording area on each track, and the pilot signal recording area between adjacent tracks is arranged in the longitudinal direction of the track. The two types of pilot signals having different frequencies are recorded in the corresponding pilot signal recording area so that the frequency is different for each adjacent track, and at the time of reproduction, the levels of the reproduced two types of pilot signals are compared. And the level is determined according to the comparison result in the two types of pilot signals. Detecting the reproduction level of the other pilot signal at the first and second timings determined using the pilot signal determined to be large, comparing the reproduction levels detected at the first and second timings, The conversion means follows the target track by controlling the comparison result of the reproduction levels detected at the first and second timings to be inverted according to the level comparison result of the two types of pilot signals. Tracking method characterized by the following.