JPS61265783A - Automatic tracking controller - Google Patents

Abstract

PURPOSE:To prevent a generation of jittering, a variation of a reproduced output and a wear of a recording medium by changing an amplitude of a variable dither signal outputted from a variable dither signal output section proportionally to the amplitude of an error signal outputted from an error signal output section. CONSTITUTION:In proportion to an amplitude of an error signal outputted from an error signal output section 5, an amplitude of a variable dither signal outputted from a variable dither signal output section 6 is changed. A width of an oscillation of the head 1 is changed proportionally to the dislocation in the track. Accordingly, when the dislocation in the track is large, the width of the oscillation of the head 1 is enlarged and when the dislocation in the track is small, the width of the oscillation can be reduced. Thereby, the width of the oscillation of the head 1 is not enlarged above a necessity, and a generation of a jitter, a variation of a reproduced output and a wear of a recording medium or the like can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dither-type automatic tracking control that performs tracking control by vibrating the reproducing head of a reproducing device in the width direction of a recording track formed on a recording medium. Regarding equipment.

[Conventional technology]

Conventionally, playback devices that play back recording media by tracing recording tracks formed on recording media such as tapes and disks using magnetic or optical playback heads, such as tape recorders and electronic still camera playback machines The reproducing apparatus is provided with automatic tracking control devices of various types in order to perform tracking control of the reproducing head during tracing.

By the way, there is an automatic tracking control device that performs tracking control of the reproducing head by vibrating the reproducing head during tracing in the width direction of the recording track, for example, Japanese Patent Laid-Open No. 1983-1999-
Automatic tracking control device described in Publication No. 72021, Japanese Unexamined Patent Publication No. 179988/1988, and Volume 5 "VTR Technology" of "Broadcast Technology Bibook" (published by Japan Broadcasting Publishing Association on October 20, 1982) is known as a dither type automatic tracking control device.

Conventional dither-type automatic tracking control devices vibrate the reproducing head during tracing in the width direction of the recording track using a sine wave or cosine wave dither signal, for example, as described in the above-mentioned "VTR technology". , the reproduction output of the reproduction head is synchronously detected by the dither signal, and an error signal having an amplitude proportional to the direction and amount of track deviation of the reproduction head is extracted.

Furthermore, a head position control signal is formed by superimposing and adding a dither signal to the error signal passed through the integrating circuit, and the DC component included in the head position control signal, that is, the error signal, moves the playback head to the center of the recording track. At the same time, the vibration frequency and amplitude of the playback head are controlled by the frequency and amplitude of the AC component included in the head position control signal, that is, the frequency and amplitude of the dither signal. Tracking control is performed by controlling the position of the reproducing head so that the amplitude of the signal becomes small.

Note that the frequency of the dither signal is based on the above-mentioned Japanese Patent Application Laid-Open No.
As described in Japanese Patent No. 21, in order to prevent the influence of the vibration trace of the reproducing head on the reproducing output, the frequency is set to, for example, an odd multiple of 1/2 of the vertical scanning frequency.

In addition, in order to improve the following characteristics of tracking control,
When integrating and adding the error signal and the dither signal and superimposing the dither signal on the error signal, a specific frequency component included in the error signal, that is, a component that is an integral multiple of the rotational frequency of the head cylinder of the video tape recorder, is combed. This is done by extracting using a filter or the like.

[Problem that the invention seeks to solve]

By the way, the vibration tracing of the reproducing head causes jitter, fluctuations in the reproducing output, wear of the recording medium, etc., so it is desirable to reduce the vibration width of the reproducing head.

On the other hand, let the amount of track deviation of the playback head and the level of the playback output be X and f, and when the amount of track deviation X is 00, the level y becomes the maximum k, and the amount of track deviation If level y becomes 0 when ±h,
In the range -h≦X≦h, the level y changes linearly as shown in FIG.

Note that when x=Q, the reproducing head is controlled to the center of the recording track and is in a proper on-track state.

Since the reproducing head during tracing vibrates in the width direction of the recording track around a certain position, the amount of track deviation
can be regarded as a combination of a direct current component d indicating the position of the center of vibration and an alternating current component b(2)ωt indicating vibration, and the deviation amount X can also be expressed as d − )−b ωt. 8, d and b are constants,
ω is the angular frequency of vibration, and t is time.

Also, the AC component y' of the level y of the reproduction output is X=d-
) - b (2) Based on the formula ω, it becomes as follows.

When 2nπ otsu o otsuta-)-2nZ, y=
−Ding ωtta+2nπ (when t=<tb+2nπ
“=T””tb-1-2nπ(t=j2(n+1)
When π, y=-T-"Furthermore, the dither signal is
When Iω is assumed, the amplitude of the error signal obtained by synchronously detecting the reproduced output with a dither signal becomes the DC component of the AC component y′ and the original dither signal goosω, and in this case, the amplitude of the error signal 2 is as shown below. Note that g is a constant.

・=g(punishment kb,,,(+ten wear/)■)and=gm
When V, h=so%m, and g=lV, b, which indicates the vibration width of the reproducing head, is 6 μm, 471 m,
2 pm, the direct current component d of the track deviation amount X changes as shown by the solid lines 2, 2, and 2 in FIG. 4, respectively, with respect to the amplitude 2 of the error signal. Note that the DC component d indicates the position of the tracking-controlled playback head.

In other words, when the position of the playback head deviates in the positive or negative direction by a larger amount than the vibration width and the playback head goes off-track, the amplitude 2 increases in proportion to the vibration width, but the deviation of the playback head becomes smaller. When the reproducing head approaches the proper on-track position, the relationship between the vibration width and the amplitude 2 is reversed, and the smaller the vibration width is, the larger the amplitude 2 becomes.

And the larger the amplitude 2 of the error signal with respect to the amount of deviation X,
Since the control sensitivity is increased and the position of the playback head is stably and quickly controlled to the center of the recording track, especially when the playback head position approaches the appropriate on-track position, the vibration width of the playback head will be reduced. It is desirable to reduce the

However, if the amplitude of the dither signal is reduced to reduce the vibration amplitude of the playback head, for example, the position of the playback head will be
If the track pitch deviates or the reproducing head goes off-track, it becomes impossible to obtain an error signal from the S/N ratio, etc., and tracking control becomes impossible.

Therefore, the amplitude of the dither signal is set to a relatively large constant amplitude so that an error signal is obtained even when the playback head goes off-track, and in this case, when the playback head approaches the correct on-track position, the The above vibration width will cause vibration, causing negative effects such as occurrence of jitter, fluctuations in playback output, and abrasion of the recording medium, and the amplitude 2 of the error signal will become small, making it impossible to perform stable and quick tracking control. There is a problem.

[Failure to solve the problem]

The present invention is provided in a reproducing apparatus that traces and reproduces a recording track of a recording medium with a reproducing head, vibrates the head during tracing in the width direction of the recording track, and increases the reproduction output of the head due to the vibration. An automatic tracking control device that controls tracking of the head by detecting a track deviation of the head based on a change, the device comprising: a dither signal output section that outputs a dither signal set to a predetermined frequency and a predetermined amplitude; an error signal output section that performs synchronous detection using the dither signal and outputs an error signal with an amplitude proportional to the track deviation; and an error signal output section that varies the amplitude of the dither signal in proportion to the amplitude of the error signal and outputs a variable dither signal. a head position control signal output unit that outputs a head position control signal obtained by superimposing the variable dither signal on the error signal, and variably controls the position of the head in the width direction using the head position control signal. This is an automatic tracking control device characterized by comprising a head drive unit that performs the following operations.

[Function] Therefore, by tracking control, when the position of the playback head approaches the center of the recording track, the amplitude of the variable dither signal becomes smaller, and the vibration width of the playback head becomes smaller.
Conversely, when the position of the playback head moves away from the center of the recording track, the amplitude of the variable dither signal increases and the vibration width of the playback head increases, and the vibration width of the playback head is varied according to the track deviation of the playback head. Ru.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 and 2 showing one embodiment thereof.

In Fig. 1, (1) is a playback head that traces the tracks of the recording medium (2), (3) is a playback processing unit to which the playback output of head (1) is input, and (4) is a predetermined frequency and amplitude. (5) is an error signal output section into which the playback output of the head (1) via the playback processing section (3) and the dither signal are input; The output is synchronously detected (envelope detection) with a dither signal, and an error signal with an amplitude proportional to the direction and amount of track deviation of the head (1) is output.

(6) is a dither amplitude control section to which the dither signal and the error signal are input, which varies the amplitude of the dither signal in proportion to the amplitude of the error signal and outputs a variable dither signal. (7)
is a head position control signal output unit to which the error signal and the variable dither signal are input, and outputs a head position control signal obtained by superimposing and adding the variable dither signal to the error signal. (8) is a head drive unit in which the head position control signal is manually input;
It has a bimorph etc. that changes the position of the head (1),
Drive the bimorph etc. with a head position control signal,
The position of the head (1) in the width direction of the recording track is variably controlled.

Then, the reproduction output of the head (1) is input to the error signal output section (5) via the reproduction processing section (3), and at this time, the dither signal output section (4) outputs the error signal output section (5) and the dither amplitude control section. A sine wave or cosine wave dither signal having a constant frequency, for example, an odd multiple of 172 of the vertical scanning frequency and a constant amplitude is outputted to the section (6).

Further, the error signal output section (5) synchronously detects the playback output of the head (1) with the dither signal from the dither signal output section (4), and the error signal output section (5) then outputs the dither amplitude control section (6) and the dither amplitude control section (6). The head position control signal output section (7) outputs an error signal with an amplitude proportional to the track deviation of the head (1), that is, a direct current component d of the track deviation amount X and the head (1).
An error signal of amplitude 2 in FIG. 4, which is set by the vibration width of , is output.

The dither amplitude control section (6) is configured as shown in FIG. 2, and the dither signal output section (6) is connected to the dither input terminal (Ia).
The dither signal of 4) is inputted, and the error signal of the error signal output section (5) is inputted to the error input terminal (Ib).

Furthermore, the dither signal at the input terminal (Ia) is input to the operational amplifier (
6a) is input to the non-inverting input terminal (G), and the input terminal (
The error signal Ib) is input to the inverting input terminal (→) of the first comparator (6a) via the resistor (Ba), and is input to the non-inverting input terminal (→) of the second comparator (6C) via the resistor (Rh). Input to the input terminal (→).

Moreover, the input terminals (Ic) and (Id) have the first. The second comparison reference signals are respectively input, and the first comparison reference signals of the input terminals (Ic) are passed through the resistors (&) to the first comparators (6b
), and the second comparison reference signal of the input terminal (Id) is input to the inverting input terminal (→) of the second comparator (6C) via the resistor (Rd). Ru.

By the way, in this embodiment, the vibration amplitude of the head (1) is switched stepwise between 4/Im and 2 μm in proportion to the amplitude 2 of the error signal. The amplitude of the second comparison reference signal is set to α and β in FIG. 4, respectively.

Then, the first comparator (6b) compares the amplitude 2 of the error signal with the amplitude α of the first comparison reference signal, and the second
The comparator (6C) compares the amplitude 2 of the error signal with the amplitude β of the second reference signal, and when 2≦β, the first comparator (6C) compares the amplitude 2 of the error signal with the amplitude β of the second reference signal.
The output signal of the second comparator (6b) becomes a low level (hereinafter referred to as "L"), and the output signal of the second comparator (6b) becomes a high level (hereinafter referred to as "'H").

Moreover, when β>Z>α, both comparators (6b) and (60
) output signals are both “L” when p, z, < α,
The output signal of the first comparator (6b) becomes "H" and the output signal of the second comparator (6C) becomes "L".

Furthermore, the output signal of the first comparator (6b) is input to the set terminal (S) and reset terminal (r) of an 88 flip-flop (6d) formed by two fazos (Ga) and (Gb), respectively. At this time, the output terminal (q) of the flip-flop (6d) becomes "H" when the set terminal (S) becomes "H" and the reset terminal (r) becomes "L".
When the set terminal (S) becomes 1'L" and the reset terminal (r) becomes "H", the output terminal (q) becomes "L" and both terminals (r) become 1"L. ``, the output terminal (q) retains its previous state.

Therefore, when the amplitude 2 of the error signal decreases along the curve ■ in Fig. 4, when the amplitude 2 decreases to α, the output terminal (q) is reversed from ``L'' to ``H'', and the error When the amplitude 2 of the signal increases along the curve ■ in Fig. 4, when the amplitude 2 increases to β, the output terminal ((1) becomes 1
It is reversed from "L" to "H".

On the other hand, in the operational amplifier (6a), the inverting input terminal (→ is grounded via a resistor (Re), and the resistors (Rf) and (Rg) are connected in series between the inverting input terminal (→ and the output terminal). has been done.

Further, an analog switch (6e) is provided in parallel with the resistor (head).

And the analog switch (6e) is connected to the output terminal (q)'
When the output terminal (q) is turned on by Y and the output terminal (q) is turned off by 'L'', and the resistance values of the resistors (e), (Rf), and (Rg) are set to R1, R2゜㇠8, the analog switch (
The gain of the amplifier (6a) is (RI+R
2)/By turning off the analog switch (6e), the gain of the amplifier (6a) becomes (RI+R2+Ia)/
Increases to R+.

That is, when the amplification factor of the dither signal by the amplifier (6a) is varied by turning on and off the switch (6e), and the amplitude of the dither signal at the input terminal (ia) is C', the amplitude 2 of the error signal is When it becomes smaller, between 2>α (R1
+R2) is amplified to C/R1, and during zla it is amplified to (R++Z+Ra)C/in.

Furthermore, when the amplitude 2 of the error signal becomes large, it is amplified to (Rt + R2) C'/R1 during zla, and (Rt + R2 + R8) C/R1 during 2>β.
is amplified.

Then, from the output terminal of the amplifier (6a) to the dither output terminal (
0), the amplitude Cx is (Rt
-)-11Lg)C/Suke, (R1+R2+Rs)C/
A variable dither signal variable to R+ is output.

Further, the variable dither signal of the output terminal (0) is input to the head position control signal output section (7), and the variable dither signal is added to the error signal input from the error signal output section (5) by the output section (7). are superimposed and added to form a head position control signal, and at this time, the amplitude of the head position control signal becomes the amplitude obtained by superimposing the amplitude 2 of the error signal with the amplitude Cx of the variable dither signal.

Then, the head position control signal is input to the head drive unit (8), and a drive voltage proportional to the head position control signal is applied to the bimorph etc. of the head drive unit (8).
) moves in the width direction of the recording track formed on the recording medium (1), and at this time, the amplitude of the error signal in the head position control signal increases to 2, and the vibration center position of the head (1) is controlled. The vibration width of the head (1) is set by the amplitude OX of the variable dither signal in the head position control signal.

And the Corote resistance values R1, R2, R11 are the amplitude CX force (
When Rt +R2)C'/R1, the vibration amplitude of the head (1) is 2)tm, and the amplitude Cx is (Rt -1-B
, 2+ Ra )C'/R+, the vibration width of the head (1) is set to be 4 pm.

When the head (1) is off-track and the amplitude 2 of the error signal is larger than β, the amplitude Ox of the variable dither signal is (Rt −1−Rg + Rs)C! '/Rt
Then, the vibration amplitude of the head (1) becomes 4 pm, and at this time, based on the tracking control, the amplitude 2 becomes 4 pm in Fig. 4.
When the amplitude 2 decreases to α and the head (1) approaches the proper on-track position,
The amplitude cx of the variable dither signal is (R1+Rz>c'/Rt
The vibration amplitude of the head (1) is changed to 2 μm9, and at this time, the amplitude 2 increases from α to γ, and
Based on the tracking control, the amplitude 2 changes along the curve (■) in FIG.

When the head (1) is on track and the vibration amplitude of the head (1) becomes Lm2), and the amplitude 2 changes along the curve ■ in Figure 4, the position of the head (1) starts to shift and the amplitude 2 increases to β, the amplitude Cx of the variable dither signal is greatly varied to (R1+R20Rg)σ/h,
The amplitude 2 changes along the curve ▪ in FIG.

When the amount of track deviation X of the head (1) is large, the vibration width of the head (1) becomes 4 μm, and when the amount of track deviation X is small, the vibration width of the head (1) becomes 2 μm. , the vibration width of the head (1) changes depending on the track deviation of the head (1), and the vibration width of the head (1) does not become larger than necessary, causing jitter, fluctuations in reproduction output, and problems with the recording medium. (2) Wear is prevented, and an error signal with a sufficient amplitude Z is always obtained, allowing stable and quick tracking control.

Note that since the amplitude control of the variable dither signal by the dither amplitude control section (6) has hysteresis, tracking control is performed more stably.

By the way, in the above embodiment, the vibration width was varied in two steps of 4 μm and 2 pm in proportion to the amplitude 2 of the error signal.
The vibration amplitude may be varied in three or more stages, or the vibration amplitude may be varied continuously.

〔Effect of the invention〕

As described above, according to the automatic tracking control device of the present invention, the variable dither output unit (6) outputs the variable dither signal in proportion to the amplitude of the error signal output from the error signal output unit (5). By varying the amplitude of the signal and varying the vibration width of the head (1) in proportion to the track deviation,
When the track misalignment is large, the vibration width of the head opening is increased, and when the track misalignment is small, the vibration amplitude of the head (opening) is increased.
1) The vibration width of the head (1) can be made small, so that the vibration width of the head (1) does not become unnecessarily large, resulting in jitter generation and fluctuations in playback output.

This prevents wear of the recording medium and enables stable and quick tracking control.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the automatic tracking control device of the present invention, FIG. 2 is a detailed block diagram of a part of FIG. 1, and FIG. 3 is the relationship between the amount of track deviation and the amplitude of the reproduced output. FIG. 4 is a diagram showing the relationship between the amount of track deviation and the amplitude of the error signal. (1)...Playback head, (2)...Recording medium, (3
)...Reproduction processing section, (4)...Dither signal output section,
(5)...Error signal output section, (6)...Dither amplitude control section, (7)...Head position signal output section, (8)...
...Head drive unit.

Claims (1)

[Claims] (1) Provided in a playback device that traces and plays back a recording track of a recording medium with a playback head, vibrates the head during tracing in the width direction of the recording track, and changes the playback output of the head due to the vibration. In an automatic tracking control device that controls tracking of the head by detecting a tracking deviation of the head from
a dither signal output unit that outputs a dither signal set to a predetermined frequency and a predetermined amplitude; and an error signal output unit that synchronously detects the playback signal of the head with the dither signal and outputs an error signal with an amplitude proportional to the track deviation. a dither amplitude control unit that varies the amplitude of the dither signal in proportion to the amplitude of the error signal and outputs a variable dither signal;
A head position control signal output section that outputs a head position control signal obtained by superimposing the variable dither signal on the error signal, and a head drive section that variably controls the position of the head in the width direction using the head position control signal. An automatic tracking control device characterized by: