JPS62140250A - Optical disk device - Google Patents

Abstract

PURPOSE:To reduce the influence of the eccentricity of a recording track by storing eccentric state information on tracks based on positional deviation caused by an optical head detection means, prior to recording and reproducing, and using said information for canceling track eccentricity. CONSTITUTION:Prior to actually recording and reproducing information, a motor 2 rotates an optical disk 1, and a focusing action is attained at optional positions on the disk 1. In this state a CPU 33 reads out the output of an A/D converter 29, which converts a tracking deviation signal from a differential amplifier 27 at every sector denoted by a value counted by a sector counter 32, through a data bus 30, and stores it in a RAM 35. Then the information on the eccentricity state of the recording track during one rotation of the disk is built up in the RAM 35, and used for correcting and canceling the eccentricity at the time of recording or reproducing, whereby the influence of the eccentricity of the recording track can be substantially reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical disc device that records or reproduces information by tracking an optical head on a rotating optical disc, and particularly relates to eccentricity correction means for an optical disc. .

[Technical background of the invention and its problems] Generally, this type of optical disc device uses an optical disc having concentric or spiral recording tracks as an information recording medium, and while rotating this optical disc,
By linearly moving the optical head in the radial direction, information is recorded on or reproduced from the recording track of the optical disk.

In such an optical disk device, the optical head must accurately follow the recording track of the rotating optical disk. For this reason, tracking control using a tracking servo system is usually performed.

By the way, in such an optical disc device, when attempting to move the optical head from one recording track to another on a rotating optical disc, tracking is temporarily stopped and the distance from the target recording track is measured.
The optical head is moved and tracking is performed again.

However, in general, the recording track itself of an optical disc is
It is not necessarily a perfect circle with respect to the center of the rotating shaft of the motor that rotationally drives the optical disk, but is often eccentric. For this reason, once tracking is stopped, the relative position between the optical head and the recording track will vary by the amount of eccentricity, and when tracking is performed again after movement, there will be a deviation by that amount, making it difficult to achieve accuracy. , it was difficult to shorten the time required for positioning to the target recording track.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to reduce the effect of eccentricity of recording tracks on an optical disk by 1, and to control the positioning of an optical head with high precision. An object of the present invention is to provide an optical disc device that can perform the following operations.

[Summary of the Invention] In order to achieve the above object, the present invention reads a tracking positional deviation signal output from an optical head before performing an actual recording or reproducing operation, thereby detecting the eccentric shape of a recording track. When the optical head is moved between arbitrary recording tracks for access, a signal is applied as a bias to the tracking control means to cancel the eccentricity of the recording track by the stored data, and the roughness is improved. The moving speed of the optical head is controlled by detecting the moving distance of the optical head.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, 1 is an optical disk, 2 is a motor for rotationally driving the optical disk 1, and 3 is an optical head for recording and reproducing. The optical disc 1 has concentric or spiral recording tracks on its lower surface, and one rotation is defined as, for example, "O~
255'' and 256 sectors. The motor 2 is driven by a motor control circuit 4. As shown in FIG. 2, the optical head 3 is attached to a DC linear motor 5 provided on the underside of the optical disc 1, so that the optical head 3 is moved linearly in the radial direction of the optical disc 1 by the linear motor 5. It has become. That is, the linear motor 5 is composed of a fixed part 6 equipped with a permanent magnet, and a movable part 7 having a drive coil that moves linearly on the permanent magnet of the fixed part 6. 3 is fixed. 8 is an optical scale fixed to the movable part 7; 9
is a detector (transmissive optical sensor) that optically detects the position of the optical scale 8, which detects the position of the movable part 7 (that is, the optical head 3) by a so-called overlapped grating detection method. ing.

The output signal of the detector 9 is connected to the linear motor control means and 10- and is supplied to the near motor control circuit 10.

The linear motor control circuit 10 controls the positioning of the movable part 7, that is, the optical head 3, by driving the linear motor 5 according to a target position signal supplied from a CPU 33 and an output signal from the detector 9, which will be described later. At the same time, the moving distance of the optical head 3 is detected based on the output signal of the detector 9, and the speed of the linear motor 5 is controlled according to the moving distance.

The optical head 3 includes a laser oscillator 11 as a laser beam generating means, a collimator lens 12, a polarizing beam splitter 13, a 1/4 wavelength plate 14, converges the beam onto the optical disc 1, and directs the beam onto the recording track on the optical disc 1. An objective lens 15 for positioning light, a vertical drive coil 16 for moving the objective lens 15 in the vertical direction (optical axis direction), and a vertical drive coil 16 for moving the objective lens 15 in the radial direction of the optical disc 1 (direction perpendicular to the optical axis). A radial drive coil 17, a half prism 18, a condensing lens 19, a knife 20. A two-split photodetector (focus position sensor) 21 that receives reflected light from the optical disc 1 and performs photoelectric conversion, and a condenser lens 22
, a two-split photodetector (tracking position sensor) 23 serving as a detection means for receiving reflected light from the optical disc 1 and performing photoelectric conversion.

That is, the laser oscillator 11 is driven by the drive circuit 24 to perform an oscillation operation and generate a laser beam light. In this case, when recording information on the recording track on the optical disc 1, a laser beam whose light intensity is modulated according to the information to be recorded is generated, and the optical disc 1 is
When reproducing information from the upper recording track, a laser beam having a constant light intensity is generated. The beam light from the laser oscillator 11 is collimated by the collimator lens 12 and then sent to the polarizing beam splitter 1.
3 and is reflected by this polarizing beam splitter 13 toward the optical disk 1 side. This reflected beam light is 1/
The light is guided to the objective lens 15 through the four-wavelength plate 14, and is focused by the objective lens 15, thereby positioning and irradiating the recording track on the optical disc 1 as a spot-like beam of light. The reflected light from the optical disc 1 due to this light irradiation passes through the objective lens 15 and the quarter wavelength plate 14,
Further, the light passes through a polarizing beam splitter 13 and is guided to a half prism 18, where the light is split into two systems in one day. This spectrally reflected light from one side (the defocus detection system) passes through the condenser lens 19 and the knife lens 20, forms an image on the light receiving surface of the photodetector 21, and is photoelectrically converted.

Each output signal of this photodetector 21 is used for focusing control. Further, the reflected light from the other side (tracking positional deviation detection system) separated by the half prism 18 passes through the condensing lens 22 and forms an image on the light receiving surface of the photodetector 23, where it is photoelectrically converted. Each output signal of this photodetector 23 is used for tracking control and reading recorded information.

Each output signal of the photodetector 21 is supplied to a differential amplifier 25, and from the output of this differential amplifier 25, the optical disc 1
A defocus signal of the beam light at the top can be obtained. The defocus signal output from the differential amplifier 25 is supplied to a focusing control circuit 26. The focusing control circuit 26 controls the vertical drive coil 16 according to the input focus shift signal, and controls the vertical drive coil 16 so that the objective lens 1
5 in the vertical direction, focusing control is performed so that the beam of light irradiated onto the optical disc 1 is always in just focus.

Each output signal of the photodetector 23 is supplied to a differential amplifier 27, and a tracking position deviation signal is obtained from the output of the differential amplifier 27. The tracking position shift signal output from the differential amplifier 27 is supplied to a tracking control circuit 28 and an A/D converter 29 as tracking control means, respectively. The tracking control circuit 28 controls the radial drive coil 17 according to the input tracking position shift signal and drives the objective lens 15 in the radial direction of the optical disc 1, so that the beam light is always recorded on the optical disc 1. It is positioned on the track and performs tracking control so that the beam light accurately follows the recording track. In addition, tracking is in progress.

Here, not only the objective lens 15 but also the linear motor control circuit 10 is servoed, and the objective lens 15 and the linear motor 5 are used to position the beam light. A
The /D converter 29 converts the input tracking positional deviation signal into a digital signal and outputs the digital signal to the data bus 30.

Further, each output signal of the photodetector 23 is supplied to a video circuit 31, respectively. The video circuit 31 adds each output signal of the photodetector 23 to produce a reproduction signal of the recorded information, that is, a video signal in which the bits in the recording track are reflected, and binarizes the video signal to obtain read information. It is output to the data bus 30 as .

A drive circuit 24 , a near motor control circuit 10 , and a motor control circuit 4 are connected to the data bus 30 .

The data bus 30 also includes a sector counter 32, a CPLJ (central processing unit) 33 that controls the entire system, and a ROM (read only memory) 34 that stores operating programs for the CPLI 33.
, RAM as a storage means for storing eccentricity correction data
(Random access memory) 35 and a D/A converter 36 as a D/A conversion means are connected.

The sector counter 32 is a counter that operates with 256 sector pulses per rotation of the optical disc 1 generated from the motor control circuit 4 and simply counts from “0 to 255”, and the count value is transmitted to the data bus 30. At the same time as being output, it is also supplied to one input terminal of the selector 37 as an address signal of the RAM 35. The other input terminal of the selector 37 is supplied with an address signal from the CPU 33 . The selector 37 is operated by a hold acknowledge signal supplied from the CPU 33, and its output terminal is connected to the ROM 34 and RA via the address bus 38.
Connected to M35.

When a hold pulse is input from the hold pulse generation circuit 39, the CPU 33 enters a hold state and generates a hold acknowledge signal indicating that it is being held. This hold acknowledge signal is sent to the selector 37,
The signal is supplied to the RAM 35, the D/A converter 36, and the hold pulse generation circuit 39. The D/A converter 36 is a RAM
The data transferred from 35 is converted into an analog signal, and the converted output is supplied to the tracking control circuit 28 and linear motor control circuit 10 as a bias.

The hold pulse generation circuit 39 is connected to the motor control circuit 4.
It is set at the rising edge of the sector pulse generated from C.
This is a latch circuit that is reset by a hold acknowledge signal from the PU 33, and generates a hold pulse that becomes high level and low level depending on the setting and reset.

The operation in such a configuration will be explained. First, in the access operation, position information recorded in advance on the recording track of the optical disc 1 is read, and rough access is performed by moving the optical head 3 with the linear motor 5.
When approaching the target recording track, the beam light can be moved to the target recording track by performing precise access using the objective lens 15. These operations are performed under the control of CPLJ33. Incidentally, since such an access operation is already well known, further explanation will be omitted.

Next, eccentricity correction, which is the most important part of the present invention, will be explained. First, before performing an actual information recording or reproducing operation, the optical disc 1 is rotated by the motor 2, and a focusing operation is performed at an arbitrary position on the optical disc 1. In this state, the CPU 33 converts the output of the A/D converter 29, which A/D converts the tracking position deviation signal obtained from the output of the differential amplifier 27, for each sector indicated by the count value of the sector counter 32. It is read via data bus 30 and stored in RAM 35.

This is performed, for example, for one revolution of the optical disc 1. In this way, the tracking position deviation signal is transferred to the A/D converter 2.
9 performs A/D conversion, reads the data sector by sector,
By storing the data in the RAM 35, data corresponding to the eccentric shape of the recording track for one revolution is stored in the RAM 35, and this data is used as eccentricity correction data.

In this way, when the eccentricity correction data is obtained, the data in the RAM 35 is transferred to the DM during the actual information recording or reproducing operation.
Eccentricity correction is performed by sequentially transferring data to the D/A converter 36 by cycle stealing using the A (direct memory access) method. That is, the start of eccentricity correction is to activate the hold pulse generation circuit 39. The hold pulse generation circuit 39 generates a hold pulse every time a sector is switched, and holds the CPU 33 using the hold pulse.

The CPU 33 generates a hold acknowledge signal every time it is held by a hold pulse, and switches the output of the address bus 38 from the CPIJ 33 to the sector counter 32 by switching the selector 37 using the hold acknowledge signal.

At the same time, the RAM 35 is
and enable the output of the D/A converter 36.
By enabling the input of , data in the RAM 35 is transferred to the D/A converter 36 while the CPU 33 is on hold. This is repeated every time the sector is switched.

The address of the RAM 35 is specified by the sector counter 32, so that sectors and addresses always correspond.

Here, if tracking is in progress, the output of the D/A converter 36 is sent to the tracking control circuit 28 and given as a bias for the drive signal of the radial drive coil 17.

As a result, the apparent eccentricity can be significantly reduced, and even more accurate and stable tracking becomes possible.

On the other hand, when accessing the optical head 3 by turning off the servo system of the tracking control circuit 28 and moving the optical head 3 between arbitrary recording tracks using the linear motor 5, the D/A converter 3
The outputs of the linear motor control circuit 10 and the tracking control circuit 28 are sent to the linear motor control circuit 10 and the tracking control circuit 28 at a constant ratio, and are given as biases for the drive signal of the linear motor 5 and the drive signal of the radial drive coil 17, respectively. or,
The output of the D/A converter 36 is sent only to the tracking control circuit 28 and is given as a bias for the drive signal of the radial drive coil 17. As a result, the apparent eccentricity can be significantly reduced, and the required number of moving tracks is not affected by the eccentricity.

When accessing, the linear motor control circuit 10 detects the moving distance of the optical head 3 based on the output of the detector 9 that detects the optical scale 8 that moves together with the optical head 3, and the linear motor control circuit 10 detects the moving distance of the optical head 3 according to the moving distance. The speed of the linear motor 5 (that is, the moving speed of the optical head 3) is controlled. For example, speed control is performed such that the optical head 3 is at a high speed at the beginning of its movement, and the speed is gradually decreased as it approaches the target recording track.

By performing eccentricity correction and speed control as described above, the influence of eccentricity of the recording i to rack on the optical disk 1 can be minimized, and the positioning of the optical head 3 can be controlled with high precision. .

In the above embodiment, the moving distance of the optical head 3 is detected by the optical scale 8 that moves together with the optical head 3 and the detector 9 that detects the optical scale 8. As shown in the figure, the tracking position deviation signal obtained from the output of the differential amplifier 27 is binarized by the binarization circuit 40 to obtain a signal indicating that the beam light has crossed the recording track. The moving distance of the optical head 3 may be detected by counting with the track counter 41. In this case, the contents of the track counter 41 are sent to the linear motor control circuit 10 via the data bus 30, and the linear motor control circuit 10 controls the speed of the linear motor 5 according to the contents of the track counter 41.

[Effects of the Invention] As detailed above, according to the present invention, an optical disk device is provided which can reduce the effect of eccentricity of recording tracks on an optical disk and can control the positioning of an optical head with high precision. Can be provided.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, and FIG.
This figure is a side view showing a portion of the linear motor in the same embodiment, and FIG. 3 is an overall configuration diagram showing another embodiment of the present invention. 1... Optical disk, 2... Motor, 3
....Optical head, 4..Motor control circuit, 5..Linear motor, 7..Movable part, 8..Optical scale, 9...Detector, 10...Linear motor control circuit, 11...
...Laser oscillator, 15...Objective lens,
17... Radial drive coil, 23...
・Photodetector, 27...Differential amplifier, 28...
...Tracking control circuit, 29...A/D
Converter, 32... Sector counter, 33...
...CPU, 35...RAM, 36...
...D/A converter, 40...Binarization circuit, 41
...Track counter. Applicant's agent Patent attorney Takehiko Suzue Figure 3

Claims (10)

[Claims] (1) A laser beam generating means that moves in the radial direction of a rotating optical disk having concentric or spiral recording tracks and generates a laser beam for at least recording or reproducing information, and this laser beam a tracking means for positioning the laser beam from the light generating means on a recording track of the optical disc; and a detection means for receiving the reflected light from the optical disc to obtain a positional shift signal of the laser beam; an optical head for recording or reproducing information on a recording track of a rotating optical disk; moving distance detecting means for detecting a moving distance of the optical head; moving the optical head in accordance with an output of the moving distance detecting means; control means for controlling the speed; tracking control means for controlling the tracking means according to a positional deviation signal obtained from the detection means for the optical head; detection means for the optical head before performing an actual recording or reproducing operation; storage means for storing data corresponding to the eccentric shape of the recording track by reading a positional deviation signal obtained from the storage means; when the optical head is moved between arbitrary recording tracks for access; An optical disc device comprising eccentricity control means for applying a signal to the tracking control means to cancel the eccentricity of the recording track based on stored data. (2) The moving distance detecting means detects the moving distance of the optical head using an optical scale that moves together with the optical head and a detector that optically detects the optical scale. The optical disc device according to item 1. (3) The movement distance detection means includes a binarization circuit that binarizes the positional deviation signal obtained from the detection means of the optical head, and a counter that counts the output of the binarization circuit to move the optical head. The optical disc device according to claim 1, wherein the optical disc device detects distance. (4) The optical disc device according to claim 1, wherein one revolution of the optical disc is divided into a plurality of sectors. (5) A patent characterized in that the storage means stores data corresponding to the eccentric shape of the recording track of one rotation of the optical disk by reading the positional deviation signal obtained from the detection means of the optical head for each sector. An optical disc device according to claim 4. (6) A linear motor having a movable part having concentric or spiral recording tracks and movable in the radial direction of a rotating optical disk; attached to the movable part of the linear motor, at least recording or reproducing information. a laser beam generating means for generating a laser beam for the purpose of recording, a tracking means for positioning the laser beam from the laser beam generating means on a recording track of the optical disk, and a tracking means for receiving the reflected light from the optical disk. an optical head for recording or reproducing information on a recording track of the rotating optical disk, the optical head comprising: a detection means for obtaining a positional deviation signal of the laser beam; and a movement distance detection device for detecting a movement distance of the optical head. means; linear motor control means for driving the linear motor and controlling the speed of the linear motor according to the output of the moving distance detecting means; a tracking control means for controlling the tracking means; storing data corresponding to the eccentric shape of the recording track by reading a positional deviation signal obtained from the detection means of the optical head before performing an actual recording or reproducing operation; storage means; when the optical head is moved between arbitrary recording tracks for access, the linear motor control means and the tracking control unit send a signal to cancel the eccentricity of the recording track using the data stored in the storage means; 1. An optical disc device comprising: eccentricity control means for controlling eccentricity at a constant ratio to the eccentricity control means. (7) The moving distance detecting means detects the moving distance of the optical head using an optical scale that moves together with the optical head and a detector that optically detects the optical scale. The optical disc device according to item 6. (8) The moving distance detecting means detects the optical head by using a binarizing circuit that binarizes the positional deviation signal obtained from the detecting means of the optical head, and a counter that counts the output of the binarizing circuit. 7. The optical disc device according to claim 6, wherein the optical disc device detects the moving distance of the optical disc device. (9) The optical disc device according to claim 6, wherein one revolution of the optical disc is divided into a plurality of sectors. (10) A patent characterized in that the storage means stores data corresponding to the eccentric shape of the recording track of one rotation of the optical disk by reading a positional deviation signal obtained from the detection means of the optical head for each sector. An optical disc device according to claim 9.