JPH09153222A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the seek time of an optical disk device which conducts a seeking by driving a pulse motor and an actuator. SOLUTION: The device recognizes the information related to the position of an optical head 1 at the start of a seek, the information relative to the position of an objective lens 4 and the information relative to the position of a target and computes the positions of the head 1 and the lens 4 at the target position reaching point based on the information above so that the relative position of the lens with respect to the head 1 does not exceed a prescribed range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc device.

[0002]

2. Description of the Related Art In recent years, as optical disk devices, optical disk devices such as CD players and magneto-optical disk devices such as MD have been commercialized, and are still being actively developed.

In this type of device, for example, Japanese Patent Publication No. 59-3
As disclosed in Japanese Patent No. 1129, an optical head (pickup) is moved by a DC motor or a linear motor in the radial direction of the optical disk.

By the way, DC motors and linear motors are
Although it has the advantage of shortening the seek time, it not only requires a complicated control system such as various filter circuits, gain control circuits, phase compensation circuits, etc., but is also vulnerable to shocks and external disturbances applied to the device, and in some cases runaway. Then, there is a drawback that the optical head is damaged.

In consideration of this point, there is a method of using a pulse motor as a moving means of the optical head. The pulse motor is a preferable motor for moving the optical head, because the control system circuit can be simply constructed, and there is no risk of runaway as long as normal excitation is performed.

However, since the pulse motor has a structure in which the optical head is moved with a predetermined distance as one step, the smaller the step interval, the closer the operation can be made to the linear motor. Has the drawback of becoming long.

Therefore, the interval of one step of the pulse motor is usually set to about several tens of times the track pitch of the optical disk, and in order to move the light beam on each track between steps, the tracking is required. The objective lens had to be moved to the target track only by the actuator.

[0008]

In the above prior art,
When the target track is distant, there is a problem that the seek time becomes long because the tracking actuator is accessed after the pulse motor is driven to move the entire optical head.

[0009]

In order to solve the above-mentioned problems, an optical disk device of the present invention comprises an optical head for focusing a light beam on a track of an optical disk via an objective lens, and the optical head. Moving means for moving in the radial direction, tracking control means for controlling the tracking state of the light beam by moving the objective lens in the radial direction of the optical disk according to the amount of deviation between the track and the light beam, and seek start A current position recognizing means for recognizing information on the position of the optical head at a time, an objective lens position detecting means for recognizing information on the position of the objective lens, and a target position recognizing means for recognizing information on a target position, The position of the optical head and the position of the objective lens at the time when the target position is reached are calculated based on the information from the respective recognizing means. A that calculating means, said calculating means calculates the position of the objective lens the optical head relative positions so as not to exceed the predetermined range of relative to the optical head.

Further, the predetermined range is ½ of the minimum moving distance of the moving means.

Further, the calculation means includes a storage means, and the storage means stores a range in which the objective lens can be displaced for each position of the optical head.

According to the optical disk device of the present invention, the relative position of the objective lens with respect to the optical head controlled by the tracking control means can be prevented from exceeding a predetermined range.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An optical disk device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the main part of the present invention. 1 is an optical head, a semiconductor laser 2,
The half mirror 3, the objective lens 4, the actuator 5, and the photodetector 6 are integrally formed. The laser light emitted from the semiconductor laser 2 is reflected by the half mirror 3 and focused on the optical disk 10 by the objective lens 4. The converged laser light is reflected by the optical disk 10 and again passes through the objective lens 4 toward the half mirror 3. The reflected light transmitted through the half mirror 3 is converged on the photodetector 6, and the signal recorded on the optical disk 10 is read by this output. Further, the output of the photodetector 6 is also used as a signal for focus control and tracking control.

The pulse motor 8 is driven on the basis of a signal from the control section 7, and thereby moves the optical head 1 in the radial direction (AA ') of the optical disk 10.
At that time, the position of the optical head 1 is counted by the head address counter 9. The actuator 5 is driven on the basis of a signal from the control unit 7, whereby the objective lens 4 is moved in the radial direction (A-
A ') and the optical disc 10 are moved in the direction perpendicular to the information recording surface (BB'). Generally, the AA 'direction is called the tracking direction and the BB' direction is called the focus direction. The structure and operation of the actuator 5 will be described with reference to FIG.

Reference numeral 11 is a lens holder on which the objective lens 4 is arranged, 12 is a tracking coil wound around the lens holder 11, 13 is a focusing coil wound around the lens holder 11, and 14 is the first to the second lens holders. The frame is held by the fourth conductive wires 17 to 20. The first to fourth conductive wires 17
Nos. 2 to 20 have one end penetrating the hole of the frame 14 and fixed to the printed circuit board 16 by soldering, and the other end penetrating a damper member (not shown) filled in the hole of the frame 14 with the hole member 2
1, and the central portion is adhesively fixed to the lens holder 11. As a result, the lens holder 11 is attached to the frame 1
4 is supported so as to be displaceable. Furthermore, the first
And the second conductive wires 17 and 18 are connected to the tracking coil 12, and the third and fourth conductive wires 19 and 20 are connected to the focusing coil 13.

In order to perform tracking control of the objective lens 4 with the above configuration, the first and second support wires 17 and 1 are provided.
When a tracking control signal is applied to 8, a current flows through the tracking coil 12 and the lens holder 11 moves in the tracking direction (A-
Move to A '). At this time, the moving direction of the lens holder 11 is determined according to the polarity of the applied control signal, and the moving distance is determined according to the magnitude of the control signal.

On the other hand, in order to perform focus control, the third
When a focus signal is applied to the fourth support wires 19 and 20, a current flows through the focusing coil 14 and the lens holder 11 moves in the focus direction (BB '). At that time, similarly to the tracking control, the moving direction of the lens holder 11 is determined according to the polarity of the applied control signal, and the moving distance is determined according to the magnitude of the control signal.

Next, in the above configuration, the pulse motor 8
The optical head 1 having an interval of 1 step of 50 μm, the control range of the actuator 5 in the tracking direction being −50 μm to +50 μm centering on the reference position of the objective lens 4 was used, and the compact disc was used as the optical disc 10. The operation in this case will be described below.

The reference position referred to here means the position of the objective lens 4 when the current value of the drive current applied to the tracking coil 12 of the actuator 5 is zero, but is not limited to this. The actuator 5 can set an arbitrary position within a range in which the objective lens 4 can be moved in the tracking direction.

When the optical disc 10 is inserted into the device,
The controller 7 drives the pulse motor 8 to move the optical head 1 to the innermost position. The detection of the innermost peripheral position of the optical head 1 is performed by a mechanical or optical detection switch (not shown) attached to the innermost peripheral position, and the pulse motor 8 is driven according to the detection by this switch. To stop. At the same time, the control unit 7 sets the value N of the head address counter 9 to N = 0. The position of the light spot at that time is shown in FIG.

After that, when the pulse motor 8 is driven to move the optical head 1 in the radial direction of the optical disk, the value N of the head address counter 9 is increased or decreased according to the movement. Therefore, the control unit 7 reads the value N of the head address counter 9 to read the optical head 1
Can be recognized.

Then, the optical disk 10 is rotated by driving a spindle motor (not shown), and the optical head 1 is moved to a predetermined position while increasing the value N of the head address counter 9. Control part 7
Turns on the semiconductor laser 2 and drives the actuator 5 to operate the tracking servo and the focus servo. As a result, the control unit 7
Can recognize the position where the optical spot is currently following based on the subcode signal read from the optical disk 10 via the optical head 1.

After that, the light spot is moved to a desired position by driving the pulse motor 8 and the actuator 5 in the tracking direction based on the control signal from the control section 7.

Therefore, as shown in FIG. 3B, the track number nx (the value of the head address counter 9 at this time is N1) from the state where the light spot follows the track number n1 (at this time). The operation of seeking the value of the head address counter 9 (Nx) will be described with reference to FIG.

When the seek from the position of the track number n1 to the track number nx is instructed, the drive amount ΔNx of the pulse motor 8 for moving the optical head 1 to seek the target track is calculated according to the flowchart shown in FIG. It

Based on the seek instruction to the target track nx, the control section 7 divides the product of the target track number nx and the track pitch of the compact disk of 1.6 μm by the step distance 50 μm of the pulse motor 8 and the remainder R. Is calculated (steps S1 and S2). The remainder R is 2
If it is 4 or less, R is adopted as the value Nx of the head address counter 9 at the target track number nx, and R is 2
If it exceeds 4, R + 1 is adopted as Nx (steps S3, S4, S5).

In FIG. 3, since the remainder R is 24 or less, that is, the target track number nx is on the Nx side from the intermediate position Ty between Nx and Ny, the value Nx of the head address counter 9 at the target position is set. R is adopted. Furthermore,
Drive amount Δ in the tracking direction of the actuator 5
The remainder R corresponds to nx, and the polarity and magnitude of the drive current are determined based on this value.

Next, the drive amount ΔNx of the pulse motor 8 is obtained by taking the difference between the value Nx of the head address counter 9 at the target position and the value N1 of the head address counter 9 at the current position (step S6). ).

Here, the control unit 7 drives the pulse motor 8 based on the drive amount ΔN of the pulse motor 8 obtained in accordance with the above-described procedure, so that the optical head 1 has the value of the head address counter 9 set to Nx. Move to the position.

Next, the objective lens 4 is moved based on the polarity and magnitude of the drive current of the actuator 5 in the tracking direction, which is determined based on the drive amount Δrx of the actuator 5 in the tracking direction. As a result, the light spot can follow the position of the track number nx as shown in FIG.

Further, as shown in FIGS. 4 (b) and 4 (c),
Track number n1 (head address counter 9 at this time
The operation of seeking from the track number ny (the value of the head address counter 9 at this time is Ny) from the value of N1) is described.

When the seek from the position of the track number n1 to the track number ny is instructed, the pulse motor 8 is operated in the same manner as in the case of FIG. 3 according to the flowchart shown in FIG.
Drive amount ΔNy is calculated.

In FIG. 4, the remainder R exceeds 24, that is, the target track number nx is on the Ny side of the intermediate position Ty between Nx and Ny. Therefore, the head address counter 9 at the target position is R + 1 is adopted as the value Ny. Further, a value R ′ obtained by subtracting 50 from R corresponds to the drive amount Δry of the actuator 5 in the tracking direction, and the polarity and magnitude of the drive current are determined based on this value.

Then, the pulse motor 8 is driven based on the drive amount ΔNy of the pulse motor 8 to move the optical head 1 to a position where the value of the head address counter 9 becomes Ny, and then in the tracking direction of the actuator 5. The objective lens 4 is moved based on the driving amount Δry in the above. As a result, the light spot can follow the position of the track number ny as shown in FIG.

After that, the signal read from each track is
The objective lens 4, which is performed through the tracking-controlled and focus-controlled objective lens 4, is detected based on the current value of the drive current flowing to the tracking coil 12.
When the position of reaches the intermediate position of each step interval (50 μm), that is, when the amount of deviation of the objective lens 4 from the reference position reaches +25 μm, the pulse motor 8 is driven by one step to drive the optical head. 1 is sent in the radial direction of the optical disk 10. At that time, at the same time when the pulse motor 8 is driven by one step, the objective lens 4 is displaced by -25 from the reference position.
It is moved to a position of μm, whereby signals are continuously read from the track.

Therefore, the control range of the actuator 5 in the tracking direction is from -50 μm to +50 μm.
m is used, but the control is actually -2.
It is performed in the range of 5 μm to +25 μm.

In each of the above examples, the calculation is performed based on the track number of the designated target position,
Although the value of the head address counter 9 at the target position is obtained, the range of the control track of the actuator 5 corresponding to all the values that the head address counter 9 can take is RO.
It can be obtained by storing it in M. One example thereof will be described with reference to FIG.

For example, the control section 7 is further provided with a ROM, and the range of the control track of the actuator 5 corresponding to all possible values of the head address counter 9 is previously stored in the ROM. In addition, the value Nx of the head address counter 9 is associated with track numbers Tx to T'x, and Ny is associated with Ty to T'y.

When a seek from the track number n1 to the target track nx is instructed, the control section 7 refers to the data of the ROM, and the value Nx of the head address counter to which the target track nx belongs is A. By recognizing this, and taking the difference between that value and the current value N1 of the head address counter, the drive amount ΔNx of the pulse motor 8 is obtained.

Further, in each of the above examples, the step driving of the pulse motor 8 is based on the normal excitation method, but by dividing the excitation current of each phase by N, 1 / N of the normal step is obtained. It is clear that the same control can be performed also for a so-called micro-step type pulse motor that performs step by step.

Further, as the method of detecting the position of the objective lens 4, the method of detecting the current value of the drive current flowing to the tracking coil 12 for driving the actuator 5 by the control section 7 was used. LED having a light-shielding portion in the center of the lens holder 11
It is also possible to obtain the amount of light by detecting the amount of light with a two-division photosensor attached to the frame.

[0043]

As described above, according to the optical disk device of the present invention, the relative position of the objective lens with respect to the optical head controlled by the tracking control means is within a predetermined range, for example, one half of the minimum moving distance of the optical head. Since it is possible not to exceed the range, the control range of the objective lens in the tracking direction of the actuator 5 is narrowed and the seek time is shortened.

Further, by providing storage means for storing the displacement range of the objective lens, it is possible to reduce the load on the CPU serving as the calculation means.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of an optical disk device of the present invention.

FIG. 2 is a perspective view illustrating an example of an actuator.

FIG. 3 is a diagram for explaining the operation of the present invention.

FIG. 4 is a diagram for explaining the operation of the present invention.

FIG. 5 is a flowchart showing a calculation method of the present invention.

[Explanation of symbols]

 1: Optical Head 2: Semiconductor Laser 3: Half Mirror 4: Objective Lens 5: Actuator 6: Photo Detector 7: Control Section 8: Pulse Motor 9: Head Address Counter 10: Optical Disk

Claims (4)

[Claims] 1. An optical head for focusing a light beam on a track of an optical disk via an objective lens, a moving means for moving the optical head in a radial direction, and a shift amount between the track and the light beam in accordance with the shift amount. Tracking control means for controlling the tracking state of the light beam by moving the objective lens in the radial direction of the optical disc; current position recognition means for recognizing information on the position of the optical head at the start of seek; Objective lens position detecting means for recognizing information on the position of the lens, target position recognizing means for recognizing information on the target position, and the optical head at the time when the target position is reached based on the information from the recognizing means. Of the objective lens and the position of the objective lens, the arithmetic means including the objective lens with respect to the optical head. The optical disk device is characterized in that the position of the optical head is calculated so that the relative position thereof does not exceed a predetermined range. 2. The optical disk device according to claim 1, wherein the predetermined range is one half of the minimum moving distance of the moving means. 3. The optical disk device according to claim 1, wherein the moving means is a pulse motor. 4. The optical disk according to claim 1, wherein the arithmetic means includes storage means, and the storage means stores a range in which the objective lens can be displaced for each position of the optical head. apparatus.