JP2641264B2 - Tracking control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device for positioning a head on tracks formed in parallel.

2. Description of the Related Art Conventionally, a tracking control mechanism of a rotary head type magnetic recording / reproducing device has been known as one of such tracking control devices.

As a tracking method of a rotary head type magnetic recording / reproducing apparatus, a CTL method, a low frequency pilot signal superimposition method, an area division pilot signal method, and an envelope detection method have been proposed.

[Problems to be Solved by the Invention] However, the first CTL method described above requires a CTL track and a CTL head, so that the sampling rate cannot be increased, and requires adjustment of the CTL head, which is not suitable for auto tracking.

In the second pilot signal superimposition method, the recording level must be kept low in order not to disturb the main signal, and the S / N is poor and a sufficient servo gain cannot be obtained. In particular, when a digital signal is used as a main signal, a signal error is easily induced, which is not suitable.

In the third area division pilot method, a tracking signal is obtained only in the pilot area, and cannot follow a track bend. In particular, in a digital audio tape recorder (DAT), the main signal (audio data) is only 60% of the entire track length, and this is addressed by providing pilot areas before and after the main signal. In the case of high-speed and large-capacity data, more than 90% of the entire length of the track becomes a main signal area, and the pilot area is driven to both ends. Therefore, it is fatal that track narrowing cannot be followed in order to increase the recording density by narrowing the track. Also, since sampling is performed once or twice per track, the sampling rate is not so high.

The fourth envelope detection method is a method used in combination with so-called wobbling or the like when tracking is performed by moving a rotary head using a bimorph element or the like. This results in a complicated and expensive system. In addition, there is a problem that the output always fluctuates even though it is a few percent.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tracking control device capable of performing auto-tracking by following a track bend despite having a simple configuration without adversely affecting main information in view of the above points.

Means for Solving the Problems To achieve the above object, the present invention provides a tracking control device for positioning a head on a track formed in parallel, a signal reproduced from a first area of the track. A first error detecting means for outputting a tracking error signal, a second error detecting means for outputting a phase error signal having a level corresponding to a phase difference between predetermined signals reproduced simultaneously from adjacent tracks, Extracting means for extracting a phase error signal output from the second detecting means in a region or a region close to the first region;
A signal obtained by adding a difference between a phase error signal extracted by the extraction means and a phase error signal output by the second detection means in a region other than the first area, to a tracking error signal output from the first detection means. Control means for performing the tracking control of the head based on the above.

[Operation] According to the present invention, a tracking error signal obtained in a specific area of a track is set to a phase difference between adjacent tracks obtained from the vicinity of the area as a reference phase difference. The tracking operation is performed by generating a tracking control signal by adding an amount related to the deviation.

That is, since the tracking error signal is a signal formed only of a reproduction signal from a specific area (first area) of the track, a tracking error signal cannot be obtained in a portion other than this area. Therefore, the linearity of the track is poor. For example, when the track is bent, there is a possibility that the tracking may deviate in a region other than the above-described region.

On the other hand, when trying to detect a tracking error using the phase error signal, if the recording position of a predetermined signal (for example, a synchronization signal) between adjacent tracks is determined very accurately at a specified position, this signal is output. Although it can be used as it is as a tracking error signal, how accurate the relationship between the recording positions of predetermined signals on adjacent tracks depends on the recording device, and is not always determined accurately.

Therefore, in the present invention, the tracking error in the first area is accurately detected by the tracking error signal, and the phase error of the first area is detected in the other areas so as to compensate for the disadvantages of the above two methods. The change in the tracking error is detected based on the difference between the signal and the phase error signal of the other part, so that the tracking error of the entire track can be accurately detected.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples.

Embodiment 1 FIGS. 1 to 4 show a digital video tape recorder (DVTR) according to a first embodiment of the present invention. Here, FIG. 1 is a block diagram showing a schematic configuration of a DVTR including a tracking control circuit according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a head arrangement of a rotary head drum used in the present embodiment, FIG. 3 is a diagram showing a tape pattern showing each track formed by the rotary head, and FIG. It is a signal waveform diagram shown. In these figures, reference numeral 1 denotes a rotating drum head,
The two heads A +, A-, B +, B- are arranged close to each other in pairs, and each pair is mounted at a position facing 180 °. The magnetic tape 2 is wound around the rotary head drum 1 over a range of 180 ° + α.

By sending a rotary head drum 1 while at a circumferential speed V _H is rotated in the direction shown in the direction of the illustrated tape 2 at a speed V _T, the track pattern as shown in Figure 3 is obtained. On each track formed on the tape, two kinds of pilot signals f ₁ and f ₂ having different frequencies are alternately recorded at a leading portion thereof for a certain period, and thereafter a data area DATA is provided.

Next, the operation of this embodiment will be described with reference to the numbers of the respective blocks shown in FIG.

At the time of recording, first A / D conversion (10) the input signal,
Perform digital signal processing (12) such as data compression, interleaving, and ID addition. Next, 8-10 performs appropriate modulation suitable for magnetic recording such as modulation (14), as well as serial-parallel conversion (16) to the signal two systems, pilot signals (f _1, f _2:
(See FIG. 3) at the beginning of the track to add head A
Record by +, A- or B +, B-.

During reproduction, after amplifying a reproduction signal from each head, waveform equalization is performed by equalizers 18 and 22, a clock component in the signal is detected, and data is reproduced by PLL circuits 26 and 28. After that, it is the reverse of the recording, and after performing serial-to-parallel conversion (32), performs demodulation (34), and then performs digital signal processing (36) such as error correction and deinterleaving to obtain the original digital signal. D / A conversion (38) and output of analog image information.

At the time of this reproduction, tracking control is required for each head to correctly travel on the track on the tape. This tracking control will be described next.

As shown in FIG. 3, the pilot signal f ₁ or f ₂ is recorded at the beginning of each track. First A- obtained from the head reproduced signal filters or square wave or the like device detects the f ₁ signal components by inputting to the (not shown), to obtain a signal waveform of FIG. 4 (a). The Figure 4 by detecting the f ₂ signal component from Similarly A- head reproduced signal (b)
The signal waveform of is obtained. Here, as is apparent from FIG. 3, V ₁ is reproduced from the riding side T2 track, and V ₂ is reproduced from the lower T0 track. S42 is obtained. For this purpose, gate pulses as shown in FIGS. 4 (c) and 4 (d) are formed from the rising and falling edges of the waveform shown in FIG. 4 (a), and the waveform shown in FIG. 4 (b) is sampled. What is necessary is just to comprise so that a level may be compared.

In this manner, the tracking error signal S42 in the pilot signal area is obtained. However, not only the embodiment shown here but also four frequencies used in ordinary DAT may be used. In other words, any device that can obtain a tracking error signal using a predetermined pilot area can be used.

In the present embodiment, in order to perform continuous tracking control, in addition to the above-described tracking control using the pilot area, a tracking error signal S30 is obtained in the entire track area by using a phase difference between channels (described later). Can be. The phase difference between the channels is based on the fact that, as shown in FIG. 5, the tracking error Δ is shifted in the signal phase direction by a distance t = Δ / tan θ depending on the direction of the azimuth θ. In this state, the phase of the signal of the A + head is advanced, and the phase of the A- head is delayed. Since this phase difference and the tracking position are proportional to each other, they can be used as a tracking error signal.However, this signal S30 alone cannot be used to detect the center of the track. I have to do it. In order to obtain this reference phase, the present embodiment uses a differential amplifier 46 and a sample / hold circuit 48 (the operation of which will be described later in detail).

In general, the undulation of the track formed on the tape is gentle, and it is considered that the tracking control performed in the pilot area described above does not significantly change the positional relationship between the head and the track for a while. Therefore, if the reference phase is obtained based on the tracking error signal S42 obtained by referring to the pilot area and the inter-channel phase difference signal S30 at the head of the data area, the timing of the recording signal is adjusted in advance. Auto-tracking is possible without doing so.

In this embodiment, when the A-head passes through the pilot area and enters the data area, the clock is locked to the recording data by the PLL circuit 28 of the detection unit. At this time, since the A + head is already on the data area, the PLL is already locked. Circuit 26 is locked. Therefore, after a lapse of a fixed time from the time when both phases are locked, a sampling / hold timing pulse (see FIG. 4 (f)) is generated. Alternatively, the sample / hold timing pulse shown in FIG. 4 (f) can be obtained from the waveform of FIG. 4 (a) via a delay circuit.

The inter-channel phase difference signal S30 is obtained in the form of a waveform shown in FIG. 4 (g) by comparing the phases of the PLL clocks of the detectors provided for the respective heads. As shown in FIG. 4 (g), the disturbance of the waveform that occurs immediately after the A-head enters the data area is the one during the lock operation of the PLL circuit, and the level becomes stable after the phase lock. the V _4.

The tracking error signal S42 and the phase difference signal S described above
30 is input to the differential amplifier 46, and the difference is sampled / held (see FIG. 4 (e)).

After the sample / hold is performed, the tracking control signal S50 is obtained over the entire track length by obtaining the difference between the inter-channel phase difference signal S30 and the sample / hold signal S48. This signal S50 is used as an interpolation circuit 52
The tracking operation can be performed by adding the control signal to the capstan control circuit 54 and the piezoelectric element control circuit 56 via a (described later). That is, in this embodiment in which the rotary head position is movable by a bimorph element or the like,
The A + and A- heads are simultaneously moved by the tracking control signal S52 so that the track can be followed.

The above-described tracking control signal S50 continues until the A + head or the A- head reaches the trailing end of the track.
Thereafter, a tracking control signal is similarly generated from the outputs of the B + and B- heads. Although a very short time occurs in this switching section, a period occurs in which the tracking control signal cannot be generated. Therefore, during this period, a signal S44B is sent from the timing generation circuit 44 to the interpolation circuit 52 at the timing shown in FIG. 4 (i) from the rotation phase detection signal of the rotary head drum, and interpolation is performed by a previous value hold or the like. .

According to the above-described tracking control of the present embodiment, it is possible to perform tracking to the position indicated by the alternate long and short dash line with only the capstan control for the track bending as shown in FIG. 6A. Further, by using a movable head, the sixth
Tracking like the two-dot chain line shown in FIG. On the other hand, in tracking control using only a pilot signal as in the prior art, tracking is performed as shown in FIG. 6 (b), so that output in the latter half of the track cannot be sufficiently obtained.

Other Embodiments In the embodiment described above, the phase difference signal S3 is determined based on the phase difference of the clock locked by the PLL circuit.
Although 0 is generated, an ID pulse or a PLL clock obtained by dividing the frequency by n may be used. In the above-described embodiment, the digital
Although a VTR has been illustrated, the present invention is also applicable to a DAT or an analog VTR. However, in the case of an analog VTR, the phase difference between the horizontal synchronization signal and the burst signal may be used instead of the PLL clock.

Further, in the above-described embodiment, the case where two channels are reproduced in parallel has been described, but it is also possible to use two or more channels. On the other hand, even when the recorded information is one channel, the present invention can be similarly applied by adding a reverse azimuth reproducing head.

By the way, in the above-mentioned embodiment, the data area is treated as one area. However, as shown in FIG. The present invention can be applied even if it is divided into a plurality of regions before and after P. However, if the area is divided in this way, the longest area (here VIDEO area)
There is preferably a pilot area immediately before If tracking control using only one area (eg, VIDEO area) is not sufficient, for example, AUDIO
In the case where the area is 20% or more of the total track length, or in the case of a multi-channel audio recorder having a plurality of audio areas, the reference phase may be reset at the boundary between the areas. The circuit shown in FIG. 8 shows a configuration example in which a reset circuit for resetting the reference phase at the boundary of each area is added. Here, the same elements as those in FIG. 1 are given the same numbers. The operation of this circuit is as follows.

Immediately before the head passes the boundary of each area, the tracking control signal S52 is supplied to the second sample / hold circuit 8
The signal is held at 2 and input to the differential amplifier 46 via the switch 80. Then, the first sample / hold circuit 48 holds the phase difference from the locked signal S30 after the head has passed through the boundary, and uses this as a reference phase.
That is, tracking control after entering the rear area is performed based on the tracking state in the front area.
If necessary, the tracking control signal can be held at this boundary using the interpolation circuit 52.

With the configuration shown in FIG. 8, it is also possible to perform so-called insert editing in which only a part of a track is rewritten.

[Effects of the Invention] As described above, according to the tracking control device of the present invention, it is possible to easily realize highly compatible auto-tracking control and sufficiently cope with a high recording density due to a narrow track. Becomes possible.

[Brief description of the drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a schematic top view of a rotary head drum, FIG. 3 is a tape pattern diagram, FIG. 4 is a signal waveform diagram, and FIG. FIG. 6 is an explanatory diagram of a phase difference, FIG. 6 is an explanatory diagram of a track bend, FIG. 7 is a diagram showing a recording format according to a second embodiment, and FIG. 8 is a block diagram showing a main part of the second embodiment. . 1 ... Rotating head drum, 2 ... Magnetic tape, 3 ... Capstan, 4 ... Head movable element, 26,28 ... Phase lock circuit, 30 ... Phase comparator, 40 ... Pilot signal detection circuit, 42: Tracking error signal generation circuit, 48: Sample / hold circuit, 46, 50: Differential amplifier, 52: Interpolation (hold) circuit, 54: Capstan control circuit, 56: Piezoelectric element control circuit .

Claims (1)

(57) [Claims] 1. A tracking control device for positioning a head on tracks formed in parallel, using a signal reproduced from a first area of the track.
A first detection unit that outputs a tracking error signal; a second detection unit that outputs a phase error signal having a level corresponding to a phase difference between predetermined signals reproduced simultaneously from adjacent tracks; Extracting means for extracting a phase error signal output from the second detecting means in an area close to one area; and a phase error signal extracted by the extracting means for a tracking error signal output from the first detecting means. A tracking control device, comprising: control means for performing tracking control of the head based on a signal obtained by adding a difference between a signal and a phase error signal output by the second detection means in a region other than the first region.