JPH0697536B2 - Tracking servo auxiliary device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tracking servo assisting device for improving a tracking servo required when reproducing a disk-shaped recording medium.

[Outline of Invention]

According to the present invention, in a reproducing apparatus in which a disc mounted on a turntable is rotated to read recorded information from a circular-centric or spiral recording track, an RF output from a disc set to a reproducing state is used. The eccentric direction of the disk is detected from the signal and the tracking error signal, and the signal indicating the eccentric direction is used to drive the actuating portion that moves the disk in the radial direction to bring about almost no eccentric error of the disk. Therefore, it is possible to improve the response characteristics of the normal tracking servo that operates during reproduction.

[Conventional technology]

For example, in an optical recording / reproducing apparatus for recording / reproducing information on / from an optical disc, a tracking servo is inevitable in order to accurately track a recording track having an extremely narrow width.

In this case, the cause of the tracking error signal is the vibration applied from the outside or the nonuniformity of the recording track groove of the disc, but the eccentricity error when the disc is mounted on the turntable is the largest value, This eccentricity error hinders the improvement of the tracking servo function.

Therefore, an eccentricity correction device capable of reducing this eccentricity error has been proposed, for example, as disclosed in Japanese Patent Application Laid-Open No. 51-73317.

Videos 1 to this conventional device shown in FIG. 5
A mark detecting element for detecting a concentric circle mark 6 formed, for example, on the innermost circumference of the signal groove 2 after the disk is mounted on a special disk support 5 fixed to the rotation shaft of the motor 3.
The eccentric amount of the disc is detected by 7 and the bimetal or the like provided in the disc support 5 is operated by a signal indicating the eccentric amount, and the mounted video disc 1
The eccentricity of is removed.

[Problems to be solved by the invention]

However, according to such an eccentricity correction device, the mark detecting element 7 for detecting the amount of eccentricity and the magnetic piece 11 for detecting the rotational position of the disk, the rotational phase detecting element 1
2 and an X synchronous detector for forming an eccentricity correction signal
9 , Y sync detector 10 , X, Y displacement correction circuits 14 , 15 are required, and there is a problem that the structure of the disk support 5 becomes complicated.

The present invention has been made in view of the above problems, and forms a signal for indicating the eccentric direction of a disc and a signal for removing the eccentricity from a normal reproduction RF signal output from a pickup and a tracking error signal. The present invention provides a tracking servo assist device in which eccentricity of a disk is removed by a simple device.

[Means for solving problems]

FIG. 1 (a) is a block diagram showing the outline of the tracking servo assisting device of the present invention. 10 is an optical disk on which a video signal is recorded, 11 is a turntable clamper directly connected to a spindle motor, and 12 is The pickups 13a and 13b are two actuating portions provided on the outer circumference of the optical disc 10, and are plunger type contact pieces 14a which are configured to project toward the disc side by the magnetic field of the current flowing in the electromagnetic coil L, for example. , 14b are provided.

Reference numeral 15 is a signal reproduction circuit outputting a reproduction RF signal output from the pickup 12 and a tracking error signal, and 16 is a relative movement between the optical disk 10 and the pickup 12 by processing an output signal of the signal reproduction circuit 15. An eccentricity direction detection circuit that detects the direction and outputs a drive pulse having a polarity corresponding to the movement direction, and 17 is a drive circuit that drives the actuating units 13a and 13b.

[Action]

When the optical disk 10 is set on the turntable in a semi-fixed state and rotated at a slightly reduced speed, and the pickup 12 with the focus servo is stopped, the tracking error signal due to the eccentricity of the optical disk 10 and detracking are caused. The RF signal reproduced in the state is obtained. Since the phase relationship between the tracking error signal and the RF signal differs depending on the relative moving directions of the pickup 12 and the optical disc 10 as described later, as shown in the waveform ID of FIG. An "H" level signal is obtained when the optical disk 10 moves in the A direction due to eccentricity, and an "L" level signal is obtained when the optical disk 10 moves in the B direction. Then, in response to such a signal, the positive drive pulse P ⁺ and the negative drive pulse P ⁻ are formed as shown by the waveform PD. Therefore, a positive drive pulse P ⁺ is supplied to the actuating portion 13a to contact the contact piece 1a.
When 4a is urged, the optical disc 10 is pressed in the B direction.
Further, a negative driving pulse P ^- contact pieces 1 by supplying the operating portion 13b
When the 4b is urged, the optical disk 10 is pressed in the A direction.

Since the optical disk 10 is mounted on the turntable in a semi-fixed state, the optical disk 10 is applied by such a pressing force.
Is controlled so that the eccentricity is gradually eliminated.

When the amount of eccentricity falls below a predetermined range, the optical disc 10 is fixed and switched to the normal tracking servo state.

〔Example〕

FIG. 2 is a block diagram showing an embodiment of the tracking servo assisting device of the present invention. T ₁ is a terminal to which a reproduced RF signal is input, T ₂ is a terminal to which a tracking error signal is input, and 21 is RF. Envelope forming circuit for detecting signal envelope, 22 0 cross comparator, 23 tracking error signal 0 cross comparator, 24 D flip-flop (D-F / F), 25 pulse generating circuit, 26 polarity reversing circuit , 27 are drive circuits.

Reference numeral 28 denotes an operating portion that moves the position of the optical disk 10 in the radial direction, and magnetizes one end of the two drive rods 28a and 28b pivotally supported at a point P to both ends of the electromagnetic coil L. The other end is arranged with a gap so as not to contact the outer circumference of the optical disc 10. Therefore, when the positive polarity pulse is supplied, for example, the drive rod 28a is driven in the direction away from the disc 10, and the drive rod 28b is driven in the direction to press the disc. When a negative pulse is supplied, the drive rod 28a is pressed toward the disc, and the drive rod 28b is driven in a direction away from the disc.

The operation of this embodiment will be described below with reference to the waveform chart of FIG.

As described above, the optical disc 10 on which the information is recorded is set on the turntable in a semi-fixed state, and the reproduction mode is set. At this time, when the pickup 12 is stopped, the eccentricity of the optical disk 10 for one rotation causes the pickup 12 to move to several tens of degrees.
Since the recording tracks of up to several hundreds are traversed, the tracking error signal S _TE and the RF signal S _{RF in the} detrack state are obtained as shown in FIG.

In this figure, t ₀ , t ₁ , t ₃ , ... t ₂ n are picked up by eccentricity.
12 shows the time when 12 passes over the recording tracks C ₀ , C ₁ , C ₂ , ... Cn, and the RF signal S _RF reproduced at this time t ₀ , t ₁ , ... t ₂ n is the maximum value. Becomes

The recording track that is most displaced in the radial direction due to the eccentricity of the optical disc 10 is Cn, and from this point, the time to return to the first recording track C ₀ is indicated by tn ₊₁ → tn ₊₂ .

Therefore, it means that the optical disk 10 has rotated half a turn from t _{0 to} t ₂ n, and a similar signal can be obtained in the other half rotation.

The RF signal S _RF thus obtained is envelope-detected and then compared at the level (0 level) indicated by the alternate long and short dash line, and is output as the signal D _RF from the 0-cross comparator 22. Similarly, the tracking error signal S _{TE Is} also output as a signal D _TE from the 0-cross comparator 23.

As can be understood from the signal waveforms (D _TE , D _RF ) of both of them, the time t ₀ to when the track deviation increases in one direction.
During tn, the maximum value of the RF signal S _RF occurs after the − polarity of the tracking error signal _TE , whereas in the period of time tn → t ₂ n when the track deviation increases in the other direction, The maximum value of RF signal S _RF is + of tracking error signal S _TE .
It can be seen that it occurs after the polarity.

Accordingly, a signal D _TE connected to the D terminal of the D-F / F 24, as shown by a signal ID detects the level at the falling point of the signal D _RF, relative movement with respect to the radial direction of the pickup 12 and the optical disc 10 The direction can be detected.

Therefore, the pulse of the pulse generation circuit 25 composed of a monostable multivibrator or the like triggered by the falling edge or falling edge of the signal D _TE is inverted at the “L” level of the signal ID to drive as described above. When inputting to the polarity reversing circuit 26 that forms the pulses P ⁺ and P ⁻ and supplying the output to the drive circuit 27 that drives the operating portion 28, when the drive pulse P ⁺ is output, for example, the drive rod 28a is The outer periphery of the optical disc 10 is tapped from one side, and when the drive pulse P ^- is output, the drive rod 28b is urged to strike the outer periphery of the optical disc 10 from the opposite direction, so that the optical disc 10 is rotated for several revolutions. Eccentricity gradually decreases, tracking error signal
Pitch S _TE is below about 1 or 2 in one revolution, the eccentric error becomes less than several [mu] m. In this case, drive pulse
Since P ⁺ and P ^- also decrease, switching to the normal tracking servo operation when this point is detected makes the tracking error signal a very small value, so stable tracking servo can be realized even when rotating at high speed. .

FIG. 4 shows an example of the structure when an optical disk is clamped on a turntable, 30 is a spindle motor, 31 is a turntable fixed to the shaft of the motor,
Reference numeral 32 is a ring-shaped magnet having a slip stopper 33 such as felt attached to the lower surface thereof, and 34 is a chucking member around which an electromagnetic coil 35 is wound.

The central convex portion of the turntable 31 is set to have a size slightly smaller than the position regulating hole formed in the center of the optical disk 10.

With such a structure, when the optical disk 10 is mounted on the turntable 31, and the ring-shaped magnet 32 is set on the upper surface of the optical disk 10 by a mechanism (not shown), the magnetized ring-shaped magnet 32 is turned on. The optical disk 10 is held in a semi-fixed state on the turntable 31 by the force of being attracted to the turntable 31. Also, at this time,
Since a slight gap G is generated in the radial direction between the turntable 31 and the optical disk 10, as described above, the operating portion 28
When a force is applied from the outer peripheral wall of the optical disc 10 by (13a, 13b), the optical disc 10 can be slightly moved by the force, and can be set at the position where the eccentricity is minimized as described above. Then, when a current is applied to the electromagnetic coil 35 in this state, the ring-shaped magnet 32 is repulsed by the electromagnetic force, and the optical disk 10 is in a fixed state in which it is strongly pressed against the turntable 31 side.

The chucking structure for changing from the semi-fixed state to the fixed state is one example, and a mechanism using another spring material may be adopted.

In addition, in order to move the position of the optical disk, the operating unit 28 (13a,
13b) can also be structured to operate on the inner peripheral side of the optical disc 10.

〔The invention's effect〕

As described above, the tracking servo auxiliary device of the present invention detects the eccentric direction of the disk from the tracking error signal and the RF signal output from the pickup, and the eccentric amount of the disk is detected based on the signal indicating the eccentric direction. There is an advantage that the device can be simplified because the operating portion that is reduced in number is operated. When the normal tracking servo is driven when the amount of eccentricity is close to 0, the control range of the servo mechanism is reduced, stable tracking servo can be performed, and high-speed rotation is possible even when the disk processing accuracy is poor. There is an effect that it is possible to realize a tracking servo with good responsiveness that can be followed by.

[Brief description of drawings]

1 (a) and 1 (b) are schematic diagrams of a tracking servo auxiliary device showing the outline of the present invention, and waveform diagrams for explaining the operation thereof.
FIG. 2 is a block diagram showing an embodiment for detecting the relative movement direction of the pickup and the disc to reduce the amount of eccentricity, FIG. 3 is the main waveform diagram of FIG. 2, and FIG. 4 is the disc. Sectional view showing an example of the chucking mechanism of FIG.
FIG. 1 is a schematic view showing a conventional eccentricity correction device for a rotating body. In the figure, 10 is an optical disk, 11 is a clamper, 12 is a pickup, 13a and 13b are operating parts for driving the contact pieces 14a and 14b,
Reference numeral 15 is a signal reproducing circuit, and 16 is an eccentric direction detection circuit.

Claims (1)

[Claims] 1. A signal reproducing circuit for outputting a tracking error signal and an RF signal of a disk semi-fixed on a turntable, and a pickup arranged to face the disk traverses a recording track due to the eccentricity of the disk. Output from the eccentric direction detection circuit, which detects the relative movement direction of the pickup with respect to the recording track of the disc, based on the phase information of the tracking error signal and the RF signal detected when A pulse generation circuit that generates a drive pulse corresponding to the polarity of the signal, and by supplying the drive pulse, the peripheral portion of the semi-fixed disk is pressed by the drive pulse to eliminate the eccentricity of the disk. And a moving part for displacing the disk as described above. Servo assist device.