JPH0249255A - Tracking controller - Google Patents

Abstract

PURPOSE:To eliminate an (alpha) component in an error signal by performing the division of the difference and the sum of the components of a pilot signal on a reproducing track. CONSTITUTION:Division output Vo is outputted by adding the output of a sample and hold circuit 44 on that of an envelope detection circuit 43 at an adder circuit 1 and inputting the output V1 of an adder circuit 45 and the output V2 of the circuit 1 to a division circuit 2, and it is sampled and held at a circuit 47 by a sampling signal phi2 from a control circuit 46, and a held value is sent to a capstan servo circuit as the error signal. A rotary head H traces a track, and the circuit 44 is sampled and held by a sampling signal phi1, and the output becomes the level value of the pilot signal on an adjacent track, and the output of the circuit 43 at the time of outputting the signal phi2 becomes the level value of the pilot signal on the adjacent track. Those level values are supplied to the circuits 45 and 1, and the output Vo of the circuit 2 becomes a value not depending on a proportional constant (alpha) by the output V1 and V2 of the circuits 45 and 1, respectively, and is outputted from the circuit 47 as a tracking error signal, thereby, the (alpha) component can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking control device suitable for use in a rotary head type digital audio tape recorder or the like.

[Prior art and its problems]

In a rotary head type magnetic recording/reproducing device, it is necessary for the rotary head to accurately track the track formed during recording during reproducing, and various tracking control methods have been considered for this purpose.

A common control method is one that uses control signals found in 1/2-inch VTRs (video tape recorders). In this system, a control signal recorded on one end of the magnetic tape in the width direction is reproduced by a fixed head, and the rotation phase of the rotary head is controlled by this reproduction control signal. However, since this method requires a separate fixed head, a new control method that does not use a fixed head has been adopted for 8 mm VTRs. this is,
In this method, four pilot signals having different frequencies are circulated for each track and recorded in a frequency multiplexed manner, and tracking control is performed so that the levels of the pilot signals obtained as crosstalk components from both adjacent tracks are equal during playback.

Further, recently, the development of rotary head type digital audio tape recorders has been progressing, and the following tracking control methods are being considered for use therein.

That is, as shown in FIG. 2, recording tracks are formed diagonally on the magnetic tape in the order of A, B, C, and D by a rotating head without creating a guard band. A PCM audio signal is recorded on each track A to D, and two blocks of tracking pilot signal fP and one block of synchronization signal fs are recorded in an area different from the recording area of this PCM audio signal. Ru. The pilot signal fP and the synchronization signal fs are fixed frequency signals that differ from each other, and are recorded between three consecutive tracks as shown in Fig. 2 so that they do not overlap when viewed from the direction orthogonal to the head scanning direction. be done. During reproduction, as shown in FIG. 3, a rotary head H having a gap width wider than the width of the recording track traces the track and reproduces one recording signal.

FIG. 4 shows a circuit that performs tracking control using the pilot signal fp. A reproduction signal from the rotary head H is amplified by a reproduction amplifier 41 and then applied to a bandpass filter 42. This bandpass filter 42 passes only the frequency component of the pilot signal fP, and its output is applied to a sample hold circuit 44 and an adder circuit 45 after the envelope component is detected by an envelope detection circuit 43. On the other hand, the output of the reproducing amplifier 41 is given to the control circuit 46.

This control circuit 46 detects the synchronization signal fs in the reproduced signal, and outputs the sampling signal φ1 at the time of detection, and outputs the sampling signal φ2 after a time period of, for example, two blocks has elapsed from the detection time. The sampling signal φl is applied to a sample hold circuit 44, and the sampling signal φ2 is applied to a sample hold circuit 47. Said addition circuit 45
is for detecting the level difference between the output of the sample and hold circuit 44 and the output of the envelope detection circuit 43, and its output is given to the sample and hold circuit 47.

Now, suppose that the rotary head H is tracing the track B shown in FIG. 2. Since the width of the rotary head H is wider than the track width, the recording signals of the adjacent tracks A and C are also recorded along with the recording signal of the track B. It will be played. When the rotary head H begins to trace the recording area of the synchronization signal fs, the control circuit 46 outputs the sampling signal φ at that point. At this time, since the pilot signal fP of the adjacent track C is being reproduced as a crosstalk component, the sample and hold circuit 44 samples and holds the level of the pilot signal fP of the adjacent track C. Then, when the rotary head H starts reproducing the pilot signal fp of the adjacent track A as a crosstalk component, the control circuit 46 outputs the laser sampling signal φ2.
A sample hold circuit 47 samples and holds the output of the adder circuit 45. At the time of this φ2 output, the output of the envelope detection circuit 43 is the reproduction level value of the pilot signal fP of the adjacent track A, and the adder circuit 45 has already set the level value of the pilot signal fP of the adjacent track A to the sample hold circuit 44. The difference between the level value of the pilot signal fP of the adjacent track C held by the sample and hold circuit 47 is output.
The sample is held. Therefore, the output of this sample and hold circuit 47 has a value corresponding to the track deviation of the rotary head H, and this output is sent as a tracking error signal to a capstan servo circuit (not shown), so that the tape is adjusted so that the level difference becomes zero. By controlling the amount of transport, the rotating Rad H can accurately trace the track.

Here, as shown in Fig. 3, the width of the rotating head H is 1.5T.
,) Let T be the rack width, and let the level of the pilot signal fP of the reproduced tracks A and C be A
Assuming that the level of the reproduced signal is proportional to the overlap between the head and the track as t CP, 8P+CP can be expressed as follows.

Ap=α(+-x) ・・・・・・(1) CP=α(+
+x)...(2) m above, formula (2) is T=l,
x is the case where the track C side is positive, -1≦X≦1, and α is a proportionality constant. Therefore, the level difference between CP and AP is cp-AP=2αx (3).

2αX shown in equation (3) above is given to the servo circuit as an error signal, and this proportionality constant α can be thought of as the product of the value α1 related to the recording level of the tape and the value α2 related to the playback device. Of these, α2 can be considered a known quantity, but αl is considered an unknown quantity because it changes depending on the recording current level and tape sensitivity of the recording device, and the servo loop gain varies depending on the individual playback tape. As a result, there was a risk that upper racking could not be performed accurately.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is a tracking error signal that outputs an amount that does not depend on the absolute level of the reproduction signal but only depends on the relative position of the reproduction head with respect to the recording track as a tracking error signal; The purpose is to provide a control device.

[Summary of the invention]

That is, the above-mentioned α component is removed by creating a difference signal and a sum signal between CP and A, feeding both signals to a division circuit, and using the output as an error signal.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 shows a tracking control circuit to which the present invention is applied, in which the same components as in FIG. 4 are denoted by the same reference numerals, and their explanation will be omitted.

Therefore, the circuit of FIG. 1 has a configuration in which an adder circuit 1 and a divider circuit 2 are added to the circuit of FIG. The outputs are added, and the division circuit 2 inputs the output v1 of the addition circuit 45 and the output v2 of the addition circuit 1, and outputs the division output vo. This #calculated output vo is as follows, assuming that the applied reference potential is vr.

This divided output (2o) is sampled and held in a sample and hold circuit 47 by a sampling signal φ2 from a control circuit 46, and this held value is sent to a capstan servo circuit (not shown) as an error signal.

Here, if the rotary head H is tracing on the track B shown in FIG. The level value CP of the signal fP becomes the level value CP, and the output of the envelope detection circuit 43 at the time of outputting φ2 becomes the level value AP of the pilot signal fP to the adjacent track. This CP
+AP is given to the adder circuit 45.1, and the respective outputs v
1+"2 is the above (11, (0 V which can be expressed as follows from formula 21, = Cp - Ap ==2 (1x ・Old" (5) V
2 = Cp + A p = -”・161 Therefore, the output vO of the division circuit 2 at the time of outputting φ2 is the above (4
), (5), and (6), the proportionality constant α
It is a value that does not depend on , that is, a value that depends only on the positional deviation fix between the track center and the head center shown in FIG. 3,
This Vo is output from the sample hold circuit 47 as a tracking error signal.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to remove the α component from the error signal. Therefore, even when reproducing a tape recorded with a different recording device, an error signal that is not affected by large or small recording currents can be obtained, and is not affected by tape sensitivity. This allows stable tracking control.

Note that the present invention is not limited to the recording pattern shown in FIG. 2; for example, the synchronizing signal f8 may be set to 2Ta and differ between adjacent tracks, or a recording pattern in which both ends of the recording area of the pilot signal fP are in the head scanning direction. It is also applicable to recording patterns that slightly overlap when viewed from the orthogonal direction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a pilot signal recording pattern of a magnetic tape,
Figure 3 is a diagram showing the relationship between the head and the recording track, wJ4
The figure shows a conventional tracking control circuit. 41...Reproduction amplifier 42...Band pass filter 43...Envelope detection circuit 44.47...
...Sample hold circuit 1.45...Addition circuit 2...Divide circuit 46...Control circuit

Claims (1)

[Claims] (1) A recording signal is recorded without a guard band on a diagonal track by a rotating head, and a pilot signal for tracking is recorded on a part of the track, and most of the recording positions of this pilot signal are on three consecutive tracks. In a tracking control device for reproducing a magnetic tape recorded in such a way that the tracks do not overlap each other when viewed from the direction perpendicular to the head scanning direction, using a rotary head having a gap width wider than the recording track width, A pilot signal detection means for detecting the pilot signal component from the reproduced signal, an envelope detection means for detecting an envelope component of the output of the pilot signal detection means, and a first sample and hold means for sampling and holding the output of the envelope detection means. and a division means for dividing the difference signal between the output of the first sample and hold means and the output of the envelope detection means and a sum signal, and a second sample and hold means for sample-holding the output of the division means. When the rotary head reaches a pilot signal recording position on one track adjacent to the predetermined track while reproducing the predetermined track, the first sample hold means is operated, and the pilot signal is recorded on the other adjacent track. A tracking control device comprising: control means for controlling the second sample and hold means to operate when the second sample and hold means reaches a position, and performs tracking control based on the output of the second sample and hold means.