JPH0830986A - Optical disk recording/reproducing device - Google Patents

Abstract

PURPOSE:To always attain stable servo control regardless of a regular speed time or an N-fold speed time by switching a gain and a phase of a focusing servo and/or a tracking servo set at every speed. CONSTITUTION:Switches 7, 8 are controlled by an operation support signal from a microcomputer 11 according to mode switching between a regular speed and a double speed, and are switched so that a focus phase compensation circuit 5a, a tracking phase compensation circuit 5b and the tracking phase compensation circuit 6a are selected at the regular speed time, and the focus phase compensation circuit 5b and the tracking phase compensation circuit 6b are selected at the double speed time. A focus control circuit 9 controls stably a focus actuator of a pickup 3 based on a switched focus error signal in either one between the regular speed time and the double speed time, and a tracking control circuit 10 controls stably the tracking actuator and the pickup feed mechanism of the pickup 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk recording / reproducing apparatus, and more particularly to an optical disk recording / reproducing apparatus which enables stable focus and tracking control.

[0002]

2. Description of the Related Art A conventional optical disk recording / reproducing apparatus is shown in FIG.
The configuration is as shown in. That is, the optical disc 1 is rotationally driven by the disc motor 2. The matrix circuit 4 amplifies the electric signal obtained by the optical pickup 3.
Generates a tracking error signal TE and a focus error signal FE. Focus error signal FE generated
Is the focus phase compensating circuit 5, and the tracking error signal TE has the optimum gain and phase set by the tracking phase compensating circuit 6, and the focus control circuit 9 causes the focus phase compensating circuit 5 to operate in response to an operation instruction from the microcomputer 11. The focus actuator of the pickup 3 is controlled based on the focus error signal that has passed through. The tracking control circuit 10 also controls the tracking actuator and the pickup feed mechanism of the pickup 3 based on the tracking signal that has passed through the tracking phase compensation circuit 6. Reference numeral 12 denotes a constant linear velocity rotation of the optical disc 1 from the normal velocity to the N-fold velocity (N is a positive real number) so that the recording / reproduction of the optical disc 1 can be performed at the normal velocity or the N-fold velocity (N is a positive real number). It is a rotation control circuit for rotating at variable speed. This rotation control circuit 12
The FG signal from the disk motor 2 and the error signal of the reference clock signal are controlled so that the motor rotation speed at start-up rises to a predetermined rotation speed, and then the wobble signal and the reference clock signal of the pregroove of the optical disk 1 are detected. A motor servo system for controlling the CLV of the disk motor 2 based on the error signal is configured. By switching the reference clock signal frequency in accordance with the normal speed mode and the Nx speed mode, the disk motor 2 can be operated corresponding to each mode. It is a speed change rotation control.

The above-mentioned conventional optical disc recording / reproducing apparatus is
In both the focus servo system and the tracking servo system, each servo system is controlled by using a circuit having the same phase compensation and the same gain characteristic at the normal speed recording / reproducing and at the N-times speed replay. By the way, in the optical disc standard, the vertical and track radial direction limit displacements are defined as follows. (1) Compact disc (CD) standards a) Vertical displacement limit of the information recording layer with respect to the reference plane 500 Hz or less component ・ Vertical displacement 12 cm disc: ±
0.5mm ・ Acceleration: 10m / s2 or less b) Track radial displacement limit component of 500Hz or less ・ Track radial deflection: ± 70
μm or less ・ Radial acceleration: 0.4m / s2 or less

Therefore, in the focus and tracking servo, it is necessary to suppress the above standard value to the target value, and from this, the limit value that each servo system must cover can be obtained. Generally, at N times speed, the frequency band of the limit value characteristic is wider than that at the normal speed. For example, as will be described later in detail, at the 2 times speed, the frequency band of the limit value characteristic is twice that at the normal speed. Becomes

As an example, let us calculate the frequency deviation standard of surface runout and eccentricity according to the above standard at normal speed and at double speed. Generally, the displacement x (t) and the acceleration x ″ (t) are expressed as follows.

[Equation 1]

[Equation 2]

(Equation 3) Here, A is amplitude, ω is angular velocity, and t is time.

When the cutoff frequency f at the maximum displacement and the maximum acceleration is obtained by the above equations (2) and (3), the case of surface wobbling (focus) is as follows.

[Equation 4]

(Equation 5)

(Equation 6)

In the case of double speed, the acceleration becomes four times.
It looks like this:

(Equation 7)

(Equation 8)

On the other hand, the case of eccentricity (tracking) is as follows.

[Equation 9]

[Equation 10]

[Equation 11]

In the case of the double speed, it is as follows.

(Equation 12)

(Equation 13)

The target value to be suppressed by the focus servo is 1μ
If m, the DC gain is as follows.

[Equation 14]

When the target value to be suppressed by the tracking servo is 0.1 μm, the DC gain is as follows.

(Equation 15)

From the above calculation results, the frequency characteristic standards of focus and tracking at normal speed and at double speed are shown in FIGS. 3 and 4, respectively.

[0013]

However, in the conventional optical disk recording / reproducing apparatus described above, the normal speed and N
Since the circuit of the same phase compensation and the same gain characteristic is used at the double speed (for example, at the double speed), the limit value characteristic cannot be satisfied at the N-fold speed, and the recording / reproducing performance is deteriorated as compared with the normal speed. There was a problem to do. This problem is double speed N
Becomes worse as the value increases. An object of the present invention is to provide an optical disk recording / reproducing apparatus which does not deteriorate recording / reproducing performance even at N times speed (N is a positive real number).

[0014]

An optical disk recording / reproducing apparatus according to the present invention comprises a focus servo circuit for focusing a laser beam spot on an optical disk and a tracking servo circuit for following a laser beam to a guide groove or a recorded pit of the optical disk. An optical disc recording / reproducing apparatus having a circuit and a rotation control circuit for rotating a constant linear velocity rotation of an optical disc from a normal speed to a N-fold speed (N is a positive real number) at a variable speed, based on a double speed number N of the rotation control circuit. A control means for adjusting and controlling loop gain and phase compensation of at least one of the servo circuit and the tracking servo circuit is provided.

[0015]

The gain and phase of the focus servo and / or the tracking servo set for each speed can be switched depending on the difference between the normal speed recording / reproduction and the Nx speed recording / reproduction. Since the optimum phase margin and gain margin are obtained for each speed, stable servo control is always performed during recording / reproduction regardless of the normal speed or the N times speed.

[0016]

1 is a block diagram showing an embodiment of an optical disk recording / reproducing apparatus according to the present invention. In FIG.
The optical disc 1 is rotationally driven by a disc motor 2.
The matrix circuit 4 amplifies the electric signal obtained by the optical pickup 3 to generate and output a tracking error signal TE and a focus error signal FE. The generated focus error signal FE is input to the focus phase compensation circuits 5a and 5b, and the tracking error signal TE is input to the tracking phase compensation circuits 6a and 6b, respectively.
Is input to Here, the focus phase compensation circuit 5a and the tracking phase compensation circuit 6a are the matrix circuit 4
Are set so as to give optimum gain and phase to the focus error signal FE and the tracking error signal TE at normal speed, and the focus phase compensating circuit 5b and the tracking phase compensating circuit 6b similarly set the optimum gain at double speed. And a phase are set.
The switches 7 and 8 are controlled by an operation instruction signal from the microcomputer 11 that accompanies mode switching between the normal speed and the double speed, select the focus phase compensation circuit 5a and the tracking phase compensation circuit 6a at the normal speed, and focus at the double speed. It is switched to select the phase compensation circuit 5b and the tracking phase compensation circuit 6b.

The focus control circuit 9 stably controls the focus actuator of the pickup 3 based on the switched focus error signal at both the normal speed and the double speed. Similarly, the tracking control circuit 10 stably controls the tracking actuator and the pickup feed mechanism of the pickup 3 at both the normal speed and the double speed based on the switched tracking signal.

As described above, the normal speed and double speed modes have been described as an example. However, by adding a focus phase compensation circuit and a tracking phase compensation circuit that give optimum gains and phases according to the double speed number N to be switched. Thus, an optical disk recording / reproducing device capable of supporting the normal speed and the N times speed mode can be obtained.

[0019]

According to the present invention, the oscillation of the servo system can be surely suppressed and stable servo control can be performed in any mode of recording / reproducing at the normal speed and recording / reproducing at the N-fold speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical disc recording / reproducing apparatus according to the present invention.

FIG. 2 is a block diagram showing a conventional optical disc recording / reproducing apparatus.

FIG. 3 is a frequency characteristic diagram of a focus standard of an optical disc at normal speed and at double speed.

FIG. 4 is a frequency characteristic diagram of a tracking standard of an optical disc at normal speed and at double speed.

[Explanation of reference numerals] 1 optical disk 2 disk motor 3 optical pickup 4 matrix circuit 5, 5a, 5b focus phase compensation circuit 6, 6a, 6b tracking phase compensation circuit 7, 8 switch 9 focus control circuit 10 tracking control circuit 11 microcomputer 12 Rotation control circuit

Claims (1)

[Claims] 1. A focus servo circuit for focusing a laser beam spot on an optical disc, a tracking servo circuit for following the laser beam to a guide groove or a recorded pit of the optical disc, and a constant linear velocity rotation of the optical disc from normal velocity to N. In an optical disc recording / reproducing apparatus having a rotation control circuit for changing speed to a double speed (N is a positive real number), a loop gain and / or a loop gain of at least one of the focus servo circuit and the tracking servo circuit is determined based on the double speed number N of the rotation control circuit. An optical disk recording / reproducing apparatus comprising a control means for adjusting and controlling phase compensation.