JPH0676312A - Tracking servo circuit - Google Patents

Abstract

PURPOSE:To obtain a tracking servo circuit which can perform optimum tracking control in accordance with an optical information recording medium by measuring eccentric amount of the optical information recording medium and setting servo gain in accordance with measured eccentric amount, when the optical information recording medium is reproduced. CONSTITUTION:Eccentric amount of an optical disk is measured by counting the number of tracks crossing per an unit hour in a traverse signal counting circuit 15. A microcomputer 18 sets optimum servo gain in accordance with eccentric amount of the optical disk to a gain setting switching circuit 14 according to a program stored in a memory not illustrated based on a measured value by the traverse signal counting circuit 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo circuit for an optical information recording medium.

[0002]

2. Description of the Related Art In recent years, by collecting a light beam and irradiating it onto an optical information recording medium (hereinafter referred to as an optical disk), a pit row or the like is formed on the optical disk to optically record information, Various optical information recording / reproducing devices (hereinafter, referred to as optical disk devices) capable of receiving the returning light from the recorded pit row and reproducing recorded information have been proposed.

In the above-mentioned optical disk device, a great number of tracks on which information is recorded are provided on the optical disk in order to record information at a high density. Therefore, in order to record or reproduce information, tracking servo for causing the light beam to follow the track is performed.

A tracking servo circuit used for a tracking servo of an optical disk device generally has a predetermined gain (for example, 1K) when a predetermined optical disk is reproduced.
Hz; 0 dB).

Incidentally, for example, various types of optical discs to be reproduced by an optical disc device, such as a disc with a very large eccentricity amount, a disc with scratches or dirt, etc., are conceivable, but as is generally well known. For example, when reproducing a disc with a large eccentricity, it is advantageous that the servo gain is high, and conversely, when reproducing a disc with scratches or dirt, a low servo gain is advantageous. Further, the servo noise radiated to the outside decreases as the servo gain decreases.

[0006]

However, since the conventional tracking servo circuit sets the servo gain to a predetermined gain in advance as described above, for example, the predetermined gain to be adjusted in advance is set to a high value. If the disc is scratched or dirty, the track will be out of place, and skipping will occur easily.On the contrary, if the predetermined gain that is adjusted in advance is set low, However, it becomes stronger for a disc with scratches and dirt, and the servo noise is reduced, but there is a risk that a disc with large eccentricity cannot be reproduced.

The present invention has been made in view of the above circumstances. When reproducing an optical information recording medium, the eccentric amount of the optical information recording medium is measured, and the servo gain corresponding to the measured eccentric amount is measured. It is an object of the present invention to provide a tracking servo circuit capable of performing optimum tracking control according to an optical information recording medium by making settings.

[0008]

In the tracking servo circuit of the present invention, a disc-shaped optical information recording medium having a plurality of tracks is rotated around a central axis to return a light beam applied to the optical information recording medium. An eccentricity amount that detects the eccentricity amount of the optical information recording medium before the tracking servo pull-in in the tracking servo circuit that controls the light beam to follow the track based on the tracking error signal obtained by receiving the light. It is characterized in that it is provided with detecting means and gain setting means for setting the gain of the tracking error signal based on the eccentricity amount of the optical information recording medium detected by the eccentricity amount detecting means.

[0009]

In the tracking servo circuit having the above structure, the gain setting means sets the gain of the tracking servo signal based on the eccentricity amount of the optical information recording medium detected by the eccentricity amount detecting means, so that the optimum servo is achieved. Performs tracking servo by gain.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 relate to an embodiment of the present invention. FIG. 1 is a block diagram showing the structure of a tracking servo circuit, and FIG. 2 is a structure showing the structure of an optical information reproducing apparatus using the tracking servo circuit. FIG. 3 is an explanatory diagram for explaining the traverse signal, and FIG. 4 is a flowchart showing a control flow of the optical information reproducing apparatus using the tracking servo circuit.

As shown in FIG. 2, in the optical information reproducing apparatus 1 using the tracking servo circuit of this embodiment, an optical pickup 4 is arranged so as to face an optical disk 3 which is rotationally driven by a spindle motor 2. ing.
The optical pickup 4 is attached to a carriage 5 and can be moved by a moving means such as a carriage motor 6 in a radial direction of the optical disc 3, that is, in a direction T traversing a concentric circular or spiral track of the optical disc 3.

A laser diode 7 is housed in the optical pickup 4 as a means for generating a light beam, and the light beam generated by the laser diode 7 is condensed through an objective lens 8 and irradiated onto the optical disc 3 as a beam spot. To be done. The objective lens 8 can be moved in the direction T traversing the track of the optical disc 3 and in the direction perpendicular to the surface of the optical disc 3 by applying a drive current to the lens actuator 9 via the control circuit 10.

For example, by supplying a drive current to the tracking actuator which constitutes the lens actuator 9, the objective lens 8 (light spot) can be moved in the track crossing direction T of the optical disk 3. Further, by activating the tracking servo system using the tracking error signal generated by receiving the return light from the optical disc 3, the current track can be tracked to the light spot.

On the other hand, the focusing actuator constituting the lens actuator 9 is operated with a focus servo system using a focus error signal, so that the distance between the objective lens 8 and the optical disk 3 is maintained at a distance at which the objective lens 8 is brought into a focused state. You can

As shown in FIG. 1, the tracking servo circuit for realizing the above tracking servo system passes the tracking error signal supplied from the tracking error signal terminal 11 through a low pass filter (LPF) 12 and a phase compensation circuit 13. By this, a tracking servo signal is generated. The tracking servo signal is set to an appropriate servo gain described later by the gain setting switching circuit 14 and supplied to the drive amplifier 17 via the switch 16.

The drive amplifier 17 is connected to a tracking coil 19 of a tracking actuator which constitutes a lens actuator 9 provided in the optical pickup 4, and supplies a drive current to the tracking coil 19 to cross the track of the optical disk 3. Direction T
Move the light spot to and activate the tracking servo system.

The switch 16 is a switch for performing on / off control of the tracking servo system, and is turned on / off by the microcomputer 18. The tracking servo signal when the switch 16 is turned off and the tracking servo is not applied becomes a traverse signal generated when the light beam emitted from the optical pickup 4 crosses a track on the optical disc, as shown in FIG. It has a nice waveform.

Since the frequency of the traverse signal obtained by rotating the optical disc 3 and stopping the optical pickup 4 changes depending on the amount of eccentricity of the optical disc, this traverse signal is output to the traverse signal count circuit 15. The eccentricity amount of the optical disc 3 is measured by counting the number of tracks traversing per unit time.

The microcomputer 18 gains an optimum servo gain according to the eccentricity amount of the optical disk 3 based on the number of tracks traversed per unit time measured by the traverse signal counting circuit 15 according to a program stored in a memory (not shown). The setting switching circuit 14 is set.

The operation of the tracking servo circuit thus constructed will be described.

When the optical disc 3 is mounted on the optical information reproducing device 1, the optical information reproducing device 1 performs control as shown in FIG. That is, starting from step S1, the rotation of the optical disk 3 is controlled by the spindle motor 2 in step S2. Next, in step S3, while turning on the laser diode 7 of the optical pickup 4,
The objective lens 8 is moved by the focusing actuator that constitutes the lens actuator 9 to start the focus servo pull-in operation, and the focus servo is performed so that the recording surface of the optical disk 3 is always within the depth of focus of the objective lens 8. At this time, the switch 16 is off,
The tracking servo is not operating.

Then, in step S4, the traverse signal counting circuit 15 counts the traverse signals. The frequency of the traverse signal at this time changes according to the magnitude of the eccentricity of the optical disc, as described above. Based on the number of tracks traversed per unit time measured by the traverse signal count circuit 15, the microcomputer 18 follows a program stored in a memory (not shown).
The optimum servo gain according to the amount of eccentricity of the optical disk is set in the gain setting switching circuit 14. In step S5, the switch 16 is turned on to start the tracking servo pull-in operation, the tracking servo is performed with the optimum servo gain set in step S4, and the process proceeds to step S6 to end the startup control.

As described above, according to the tracking servo circuit of this embodiment, the eccentric amount of the mounted optical disk is measured before the tracking servo is pulled in.
Since the servo gain is set low for optical discs with large eccentricity and set high for optical discs with relatively small eccentricity, tracking is performed with the optimum servo gain according to the eccentricity of the optical disc. Servo can be performed.

The eccentricity amount is measured by the traverse signal based on the tracking error signal, but the invention is not limited to this. For example, the eccentricity amount of the optical disk is determined by a signal (RF signal) based on the information reproduction signal. You may make it measure.

[0026]

As described above, according to the tracking servo circuit of the present invention, when reproducing the optical information recording medium, the eccentricity amount of the optical information recording medium is measured, and the eccentricity amount is measured according to the measured eccentricity amount. Since the servo gain setting is performed, there is an effect that optimum tracking control can be performed according to the optical information recording medium.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a tracking servo circuit according to an embodiment.

FIG. 2 is a configuration diagram showing a configuration of an optical information reproducing device using a tracking servo circuit according to an embodiment.

FIG. 3 is an explanatory diagram illustrating a traverse signal according to an example.

FIG. 4 is a flowchart showing a control flow of the optical information reproducing apparatus using the tracking servo circuit according to the embodiment.

[Explanation of symbols]

 12 LPF 13 Phase compensation circuit 14 Gain setting switching circuit 15 Traverse signal count circuit 16 Switch 17 Drive amplifier 18 Microcomputer

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[Procedure amendment]

[Submission date] November 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

As described above, according to the tracking servo circuit of the present embodiment, by measuring the eccentricity amount of the mounted optical disc before the tracking servo pull-in, the servo gain is increased for the optical disc with a large eccentricity amount. Since the servo gain is set to a low value for an optical disc having a relatively small eccentricity, tracking servo can be performed with an optimum servo gain according to the eccentricity of the optical disc.

Claims (3)

[Claims] 1. A tracking error signal obtained by rotating a disc-shaped optical information recording medium having a plurality of tracks around a central axis and receiving return light of a light beam applied to the optical information recording medium. In a tracking servo circuit for controlling the light beam to follow the track based on, an eccentricity amount detecting means for detecting the eccentricity amount of the optical information recording medium before the tracking servo pull-in, and the eccentricity amount detection means. A tracking servo circuit, comprising: gain setting means for setting the gain of the tracking error signal based on the amount of eccentricity of the optical information recording medium detected by the means. 2. The eccentricity amount detecting means detects the eccentricity amount of the optical information recording medium by measuring the number of the tracks crossed by the light beam within a predetermined time before the tracking servo pull-in. The tracking servo circuit according to claim 1, wherein: 3. The eccentricity amount detecting means detects the eccentricity amount of the optical information recording medium after the focus servo pull-in and before the tracking servo pull-in. Tracking servo circuit.