JPH04307432A - Optical disk device - Google Patents

Abstract

PURPOSE:To provide an actuator control system capable of stably and highly accurately conducting a tracking servo control in an optical disk device provided with the actuator supported by an elastic member, etc. CONSTITUTION:An offset signal generation circuit 15 applies several appropriate offset signals 13, an object lens is shifted to a proper position, a track address is read from the disk, and the respective offset signals 13 and a position signal 10 of the object lens obtained from the track address 8 are stored in a memory 14. At the time of recording and reproducing the signal, the offset value is read out of the memory 14 corresponding to the position of the object lens, and an offset signal 9 is applied from an offset signal generation circuit 13. Thus, the influence of an external force due to the elastic member, etc., can be eliminated and the stable and highly accurate tracking servo control can be realized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device used as an external storage device for a computer.

0002

[Prior Art] Optical discs can record large amounts of information.
Furthermore, it is a recording medium that can be repeatedly erased and reproduced. Optical disc devices use laser light to record and reproduce signals on tracks on a disc.
A high-precision servo mechanism is required to make the laser spot accurately follow the target track on the disk surface. Generally, when performing tracking control, a two-stage servo system is used in which minute movements are performed using a coil actuator or the like, and rough movements are performed using a linear motor or the like.

FIG. 2 is a plan view showing the configuration of an optical head section in a two-stage servo system. An objective lens holder 21, which is a movable part of the optical pickup, is attached with an objective lens 22, a focus coil 23, and a tracking coil 24. This objective lens holder 21 is attached to a fixed part by an elastic member, and is configured to control the tracking control direction and focus. It is movable in the control direction and also has a focus coil 23.
, the effective driving portion of the tracking coil 24 is located in a magnetic circuit formed by a magnet 25, an outer yoke 26, and an inner yoke 27.

When current flows through the focus coil 23, electromagnetic force is generated in the focus control direction, causing the objective lens 22 to move up and down. When a current is applied to the tracking coil 24, an electromagnetic force is generated in the horizontal direction by the magnetic field of the field magnet, and the objective lens 22 moves in the disk radial direction. The radial displacement of the objective lens 22 can be monitored by a sensor. The optical pickup 1 composed of these components is fixed to a carriage 28, and is moved in the radial direction of the disk by a linear motor 29 integrated with the carriage 28.

FIG. 3 is a simple block diagram showing the operation of the two-stage servo system. During the tracking operation, the tracking error signal 32 generated by the optical pickup 30 is input to the tracking control section 33a, and the tracking error signal 32 is input to the tracking control section 33a.
3b controls the position of the objective lens 31 of the optical pickup 30. The displacement of the objective lens 31 at this time is detected by the objective lens displacement sensor 34 fixed to the optical pickup fixing part 37, and the objective lens displacement signal 35 is input to the linear motor 36.
Move so that becomes zero. During the access operation, the access control unit 33b controls the objective lens 3 of the pickup according to the target track signal 38 and the current track position signal 39.
Displace 1. The objective lens displacement signal 35 generated from the objective lens displacement sensor 34 is input to the linear motor 36, and the linear motor 36 moves so that the objective lens displacement signal 35 becomes zero.

[0006] As the diameter of an optical disk becomes smaller, it may be possible to perform both tracking and access using a common actuator from the viewpoint of miniaturization and speeding up. FIG. 4 shows a configuration diagram of a swing arm type optical pickup as an example. An objective lens 41, a focus coil 42, and a tracking coil 43 are attached to the objective lens holder 40, which is a movable part, and this holder can rotate around a support shaft attached to a fixed part and slide in the axial direction. Further, the driving effective portions of the focus coil 42 and the tracking coil 43 are located in a magnetic circuit formed by a magnet 44, an outer yoke 45, and an inner yoke 46. The wiring to the focus coil 42 and tracking coil 43 is connected to the flexible substrate 47.
This is done using When current flows through the focus coil 42, electromagnetic force is generated by the field magnet in the focus control direction, causing the objective lens 41 to move up and down. When a current is applied to the tracking coil 43, an electromagnetic force is generated in the horizontal direction by the magnetic field of the field magnet, and the objective lens 41 rotates around the support shaft. The light beam 48 is transmitted from a fixed optical system 49 to reflective mirrors 50a, 50b, 50.
c and is guided to the disk 51 through the objective lens 41.

According to this method, the configuration of the pickup 30 is simple, and it is possible to realize a reduction in size and weight, and the drive device can be made smaller and faster access can be achieved than in a method in which the optical pickup is mounted on a carriage and driven by a linear motor or the like. very advantageous.

[0008]

However, when tracking control and access control are performed using a single actuator, an actuator with a large stroke length and a wide response frequency band is required. In a moving coil type actuator, wiring to a focus coil and a tracking coil is required for the movable part. As the stroke length of the objective lens increases, the laser beam spot may deviate from the center of the signal recording area of the disk during tracking servo operation due to the effects of stress on the elastic members used for wiring to the focus coil and tracking coil. There are problems in that it is difficult to perform optimal pickup control, such as not being able to control the pickup within an allowable range, or even servo control itself becoming impossible.

An object of the present invention is to solve the problems of the conventional technology, to perform stable and highly accurate tracking control, and to achieve C/
An object of the present invention is to provide an optical disc device that can obtain reproduction signals with a high number of N.

0010

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a track address reading circuit and memory for outputting an objective lens position signal from a reproduced signal of an optical pickup, or a track address reading circuit and a memory for outputting an objective lens position signal from a reproduced signal of an optical pickup. An objective lens position detecting means for directly detecting the position of the objective lens is provided, and an offset signal generating means is provided for outputting an offset signal from the objective lens position signal outputted by the track address reading circuit/memory or the objective lens position detecting means. The output offset signal is input to a tracking servo circuit that drives the optical pickup for feedback control.

[0011]

[Operation] Not only feedback of the tracking error is applied to the tracking servo circuit that performs the tracking operation of the optical pickup, but also a corresponding offset signal is input to the tracking servo circuit from the position signal of the objective lens of the optical pickup to control the objective lens position. went. This prevents tracking offset caused by stress in the elastic member and allows tracking servo control.

0012

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 shows a block diagram of a control circuit of a first embodiment. Immediately after the power of the drive device is turned on, the switch 4 is open by the switch control signal 19 of the CPU section 11, and the tracking servo loop consisting of the phase compensation circuit 3, the tracking servo circuit 5, and the optical pickup 1 is open. At this time, no current flows through the tracking coil of the optical pickup 1. First, the focus servo of the optical pickup 1 is operated, and then the offset signal generation circuit 15 applies an appropriate offset signal 13 to the tracking servo loop according to the offset value 12 which is a command from the CPU section 11, and the tracking coil of the optical pickup 1 is activated. A current is passed through. Switch control signal 19 from CPU section 11 after the objective lens of optical pickup 1 moves
The switch 4 is closed, and the track address reading circuit 7 reads the track address 8 from the reproduction signal 6 from the disk by the optical pickup 1. The memory 9 outputs the objective lens position signal 10 stored in advance according to the track address 8 obtained by the track address reading circuit 7, and the memory 14 generates an offset signal according to a command from the CPU unit 11 in response to the objective lens position signal 10. The circuit 15 stores the offset signal 13 applied to the tracking servo loop. Similarly, CPU section 1
1, the offset signal generation circuit 15 applies several different offset signals 13 to the tracking servo loop, and the track address reading circuit 7 sequentially detects the track address 8.
Objective lens position signal 10 output from memory 9 by
Then, the offset signal 13 corresponding to the offset signal 13 is stored. For offset values for objective lens positions that have not been measured, C
The PU section 11 performs calculation processing, and the offset value 18 approximately obtained by the CPU section 11 is stored in the memory 14. In this manner, offset signals to be corrected for the position of the objective lens are stored in the memory 14 within all movable regions of the objective lens of the optical pickup 1.

When recording, reproducing, and erasing signals, the switch 4 is closed by the switch control signal 19, and the tracking error signal 2 generated by the optical pickup 1 passes through the phase compensation circuit 3 and the tracking servo circuit 5, and its output signal is used as an optical signal. The position of the objective lens of the pickup 1 is controlled. At this time, an offset value 16 previously stored in the memory 14 is input to the offset signal generation circuit 15 in accordance with the objective lens position signal 10, and the offset signal 13 is used for tracking. The signal is applied to a servo loop to control tracking.

FIG. 5 shows a block diagram of the control circuit of the second embodiment. Here, a position sensor 60 is used as the objective lens position detection means. According to this method, the objective lens position signal 10 is directly obtained from the reproduced signal 6 from the optical pickup 1, so the memory 9 used in the first embodiment is no longer necessary. The rest is the same as the first embodiment.

[0015]

According to the present invention, in an optical disk device having an actuator supported by an elastic member or the like, it is possible to eliminate the influence of stress due to the elastic member or the like, and perform tracking servo control more stably and with high precision.
It becomes possible to obtain a reproduced signal with a high C/N.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

[Fig. 2] A plan view showing the configuration of the optical head section in the conventional two-stage servo system.

[Figure 3] Block diagram showing the operation of the conventional two-stage servo system

[Figure 4] Configuration diagram of optical pickup in swing arm method

FIG. 5 is a block diagram of a second embodiment of the present invention.

[Explanation of symbols]

1 Optical pickup 2 Tracking error signal 3 Phase compensation circuit 4 Switch 5 Tracking servo circuit 6 Playback signal 7 Track address reading circuit 8 Track address 9. Memory 10 Objective lens position signal 11 CPU section 12 Offset command value signal 13 Offset signal 14 Memory 15 Offset signal generation circuit 16 Offset value 17 Offset value 18 Approximately determined offset value 19 Switch control signal 21 Objective lens holder 22 Objective lens 23 Focus coil 24 Tracking coil 25 Magnet 26 Outer yoke 27 Inner yoke 28 Carriage 29 Linear motor 30 Optical pickup 31 Objective lens 32 Tracking error signal 33a Tracking control section 33b Access control section 34 Objective lens displacement sensor 35 Objective lens displacement signal 36 Linear motor 37 Optical pickup fixing part 38 Target track signal 39 Current track position signal 40 Objective lens holder 41 Objective lens 42 Focus coil 43 Tracking coil 44 Magnet 45 Outer yoke 46 Inner yoke 47 Flexible board 48 Light beam 49 Fixed optical system 50a Reflection mirror 50b Reflection mirror 50c reflective mirror 51 Disc 60 Position sensor

Claims (2)

[Claims] 1. An optical pickup that performs tracking and access operations on an objective lens using a single coil actuator supported by an elastic member; a tracking servo circuit that performs a tracking servo operation on the coil actuator; A switch that inputs a tracking error signal to the tracking servo circuit by closing the switch to form a feedback control system, a track address reading circuit that outputs a read track address of the disk from a playback signal of the optical pickup, and the track address reading circuit. It consists of a memory that converts the read track address into an objective lens position signal of the optical pickup, and an offset signal generating means that outputs a corresponding offset signal from the objective lens position signal, and the offset signal that the offset signal generating means outputs. An optical disc device characterized in that a signal is input to the tracking servo circuit together with the tracking error signal for feedback control. 2. An optical pickup that performs tracking and access operations on an objective lens using a single coil actuator supported by an elastic member; a tracking servo circuit that performs a tracking servo operation on the coil actuator; A switch that inputs a tracking error signal into the tracking servo circuit by closing the switch to form a feedback control system, an objective lens position detection means for detecting the position of the objective lens, and an objective lens position signal output from the position detection means. The offset signal generating means outputs a corresponding offset signal, and the offset signal generating means outputs a corresponding offset signal from the objective lens position signal, and the offset signal outputted by the offset signal generating means is used as the tracking error signal. An optical disc apparatus characterized in that the tracking servo circuit is inputted to the tracking servo circuit for feedback control.