JP2006268961A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive which can make high precision tilt control by detecting a warped disk without using a specific detector, such as a tilt sensor. <P>SOLUTION: This drive creates a tilt drive value table by calculating optimum inclinations of the objective lens at various radial positions in the tilt correction controller 20 by using the disk tilt value at various radial positions obtained by calculating the focus drive values from the inner periphery side focusing coil 91 and the magnet 8 and from the outer periphery side focusing coil 92 and the magnet 8, and the objective lens inclination obtained for desirable reproduction characteristics in a specific radial position, then feeds it back to the inner focusing coil 91 and/or the outer focusing coil 92. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that records and reproduces information by irradiating an optical disc with a light beam, and more particularly to a technique for performing good recording in response to warping of the optical disc.

  In recent years, an optical disk apparatus is required as a means for recording / reproducing a large amount of data. In order to realize high-density recording, it is necessary to control the inclination (tilt amount) of the recording surface of the optical disc with respect to the optical axis of the light beam to an optimum angle. When the tilt (tilt amount) of the recording surface of the optical disk with respect to the optical axis of the light beam cannot be maintained at an optimum angle, the light spot when the light beam is focused on the optical disk has aberration and is recorded with high density. It is difficult to read data accurately and record high-quality signals at high density.

  However, since the substrate of an optical disk is generally formed by molding a resin material, warping often occurs due to distortion during storage or storage conditions. Furthermore, the amount of warpage gradually changes during recording due to temperature changes inside the device or due to temperature differences between the storage environment of the disc and the temperature inside the device, and the amount of change varies depending on the radial position. There is. In particular, when the amount of change is large, it becomes difficult to continue the recording operation. Conventionally, several methods have been proposed as a method for controlling the tilt (tilt amount) of the optical axis of a light beam with respect to the recording surface of an optical disc having such a warp.

For example, as in Patent Document 1, Patent Document 2, Patent Document 3, and the like, a so-called tilt sensor composed of a light emitting element and a light receiving element divided into two parts is provided on the optical head. A device that detects the relative tilt of the recording surface and controls the tilt of the recording surface of the optical disc with respect to the optical axis of the light beam while tilting the entire optical head by a drive mechanism based on the detection signal of the tilt sensor.
Japanese Utility Model Publication 2-72414 JP 7-272300 A Japanese Patent Laid-Open No. 10-308023

  However, in the conventional configuration, in order to detect the inclination of the recording surface of the optical disc with respect to the optical axis of the light beam, a dedicated tilt sensor is used. Therefore, a space for arranging the tilt sensor is required, and the cost is increased in addition to the driving circuit and the detection circuit as well as the sensor alone. In addition, since the tilt sensor does not detect the relative tilt between the optical axis of the light beam and the recording surface of the optical disc, the optical axis adjustment residual of the light beam or the optical axis shift of the light emitting element with respect to the mounting surface of the tilt sensor. In order to correct this, an adjustment operation is required to match the detection origin angle of the tilt sensor with the inclination of the optical axis of the light beam. Further, since it is difficult to arrange the position where the tilt sensor detects the tilt and the position of the light spot due to the size of the tilt sensor, the tilt of the recording surface of the optical disc at the position of the light spot is difficult. Cannot be detected. In other words, the detected inclination of the recording surface of the optical disc is an inclination at a radial position different from the position where recording / reproduction is actually performed, and a detection error constantly occurs. In particular, when the amount of warpage greatly changes due to the temperature change of the disk during recording, the detection error becomes large, the tilt shift increases, and the recording quality cannot be maintained.

  The present invention has been made in view of the above problems, and can accurately detect the tilt of the recording surface of the optical disc with respect to the optical axis of the light beam without providing a special detection device such as a tilt sensor, and tilt the objective lens. An object of the present invention is to provide an optical disc apparatus capable of controlling the angle of the optical disc to an optimum angle corresponding to the inclination of the recording surface of the optical disc.

  An optical disc apparatus according to the present invention includes a light source for irradiating a light beam onto an optical disc having a spiral or concentric track, a condensing unit for condensing the light beam on a recording surface of the optical disc, and the condensing A focus direction moving means for moving the means in the direction of the optical axis of the light beam, an optical head having a photodetector for receiving reflected light from the recording surface, and detecting a defocus of the light beam with respect to the recording surface A focus error detecting means for driving the focus direction moving means based on an output of the focus error detecting means so that the light beam is focused on the information surface; and A tracking direction moving means for moving in a radial direction; a rotating means for rotating the optical disc; Disc tilt detecting means for detecting a disc tilt value, which is the tilt of the recording surface, based on an average value of output values of the focus control means at a plurality of different positions in the radial direction of the disc, and the inclination of the light collecting means is variable. Tilt driving means for driving, tilt driving means for driving the tilt varying means, and tilt driving for calculating an input value to the tilt driving means as a tilt driving value based on the disc tilt value obtained by the disc tilt detecting means. Storing a tilt driving value calculated based on the disc tilt value at a plurality of different positions in the radial direction of the optical disc, and calculating the radial position and the tilt from the tilt driving value at each radial position. A calculation formula that approximates the relationship between drive values is derived, and a tilt drive value table is generated and recorded at predetermined intervals in the radial direction. A tilt driving value table generating means, a reproducing signal measuring means for measuring a reproducing signal based on the output of the photodetector, and an inclination of the light collecting means by changing an input value to the tilt driving means. A reference tilt driving value calculating means for obtaining an output value of the reproduction signal measuring means and calculating an input value to the tilt driving means at which the output value of the reproduction signal measuring means becomes a target value as a tilt driving reference value; And calculating both the tilt drive reference value and the tilt drive value at at least one substantially the same radial position, and adding the difference as an offset to the tilt drive value obtained at a plurality of radial positions, the offset The tilt drive value table is updated based on the tilt drive value corrected in accordance with the above, and at a desired radial position during the recording operation or the reproduction operation. The tilt driving value at the corresponding radial position is obtained from the tilt driving value table updated in order to set the inclination of the light collecting means to an optimum value corresponding to the relative inclination of the recording surface of the optical disc and the light beam. The tilt driving means is then input to drive the tilt variable means.

  The optical disc apparatus according to the present invention has a disc tilt amount obtained at a plurality of radial positions using a focus drive value and an inclination of the objective lens at which a reproduction characteristic obtained at a specific radial position has a good reproduction characteristic. Since the tilt drive value table for obtaining the optimum tilt is generated, the tilt of the objective lens is always recorded on the optical disc regardless of the amount of warp of the optical disc without providing a special detection device such as a tilt sensor. It is possible to set an optimum value according to the relative inclination of the surface and the light beam. Therefore, it is possible to realize a small, thin and highly reliable optical disc apparatus.

(Embodiment)
Hereinafter, an embodiment of 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 optical disk apparatus of the present embodiment, and FIG. 2 is a diagram showing the configuration of the optical system of the optical head 3 of the optical disk apparatus of the present embodiment. In FIG. 1, an optical disk 1 is driven to rotate by a spindle motor 2, and the rotation frequency of the spindle motor 2 is controlled by a spindle control circuit 5. The optical head 3 focuses the light beam 39 on the recording surface of the optical disc 1 to record or reproduce data. A binary signal to be recorded is converted into a recording signal by a recording signal processing circuit (not shown) and sent to the optical head 3, and a reproduction signal read from the optical disk 1 is converted into a binary signal by the reproduction signal processing circuit 19. It is processed. The objective lens 4 of the optical head 3 is driven in the optical axis direction (focus direction) of the light beam by a focus actuator 7 including a magnet 8, a first focus drive coil 91, and a first focus drive coil 92. The The focus control circuit 6 controls the voltage applied to the focus drive coils 91 and 92 to focus the light beam 39 emitted from the optical pickup 3 on the recording surface of the optical disc 1, and the focal position of the objective lens 4. Control. Similarly, the objective lens 4 is driven in the radial direction (tracking direction) of the optical disc 3 by a tracking actuator 12 including a magnet 8 and a tracking drive coil 11. The tracking control circuit 12 controls the optical axis position of the objective lens 4 by controlling the voltage applied to the tracking drive coil 10 so that the light beam emitted from the optical pickup 3 follows the track formed on the recording surface. To do. A focus error signal indicating a shift in the focal position of the light beam 39 and a tracking error signal indicating a shift in the track direction are generated by the reproduction signal processing circuit 19 based on the reproduction signal from the optical pickup 3. It is sent to the tracking control circuit 12.

  The optical head moving means 13 for moving the optical head 3 to different radial positions includes a traverse motor 14, a lead screw 15, a rack 16, and a guide shaft 17, and the lead screw 15 formed on the rotating shaft of the traverse motor 14 is The optical head 3 is engaged with a rack 16 fixed to the optical head 3, and the optical head 3 is supported by a guide shaft 17 so as to be able to advance straight. The optical head 3 is moved in the radial direction of the optical disc 1 by the rotational torque of the traverse motor 14 transmitted through the lead screw 15 and the rack 16.

  The configuration of the optical system of the optical head 3 will be described in more detail with reference to FIG. The optical head 3 includes an objective lens 4, a laser light source 31, a coupling lens 32, a polarizing beam splitter 33, a quarter wavelength plate 34, a reflection mirror 35, a detection lens 36, a cylindrical lens 37, and a photodetector 38. The light beam 39 generated from the laser light source 31 is converted into parallel light by the lens 32, passes through the polarization beam splitter 33 and the ¼ wavelength plate 34, is bent by the reflection mirror 35, and is optical disc by the objective lens 4. 1 is focused and irradiated on the recording surface.

  The return light reflected by the data surface of the optical disc 1 passes through the objective lens 4, is bent by the reflection mirror 35, passes through the quarter-wave plate 34, etc., and is focused and irradiated on the photodetector 38. The photodetector 38 is formed of a light receiving element divided into four as shown in FIG.

  Next, the photodetector 34 and the reproduction signal processing circuit 19 provided in the optical head 3 will be described with reference to FIGS. FIG. 3 shows the relationship between the configuration of the photodetector 38 and the reflected light from the optical disc 1. The photodetector 38 includes four divided light receiving elements A, B, C, and D, and outputs a, b, c, and d are output to the reproduction signal processing circuit 19, respectively. FIG. 4 shows a reproduction signal processing circuit 19, which detects tracking error (TE) signal = (a + d) − (b + c), focus from outputs a, b, c, d of the photodetector 38. An error (FE) signal = (a + c) − (b + d) and an RF signal = (a + b + c + d) are generated.

  This TE signal is sent to the tracking servo circuit 12 and used for tracking servo for causing the light spot to follow the track of the optical disk. The FE signal is sent to the focus servo circuit 6 and is used for focus servo for controlling the focal position of the objective lens 4 in order to focus the light spot on the recording surface of the optical disc 1.

  Next, a more detailed configuration of the tilt actuator for tilting the objective lens 4 will be described with reference to FIG. The tilt actuator includes a magnet 8, an inner periphery side focus drive coil 91, and an outer periphery side focus drive coil 92. When a voltage having the same phase is applied to the inner periphery side focus drive coil 91 and the outer periphery side focus coil 92, the objective lens 4 is driven in the focus direction (vertical direction). Further, when voltages having opposite phases are applied to the inner peripheral focus drive coil 91 and the outer peripheral focus coil 92, the objective lens 4 tilts, and the tilt angle of the objective lens 4 is controlled by controlling the voltage input to these coils. Can be controlled.

The configuration of the tilt correction control unit 20 will be described with reference to FIG. The tilt correction control unit 20 includes a disc tilt detection unit 24, a tilt drive value calculation unit 25, a tilt drive value table generation unit 26, and a reference tilt drive value calculation unit 27. The output value of the focus control circuit, that is, the average value of the focus drive value is measured at a plurality of different positions in the radial direction, and the disc tilt value, which is the tilt of the recording surface, is detected based on this value. As shown in FIG. 7, when the optical disc 1 is warped, a difference ΔH is generated in the height in the focus direction of the recording surface of the optical disc 1 at two points separated by a radial distance ΔR. The disc tilt θ at this time is (Equation 1)
θ = tan ⁻¹ (ΔH / ΔR) (Formula 1)
It is represented by

  At this time, since the objective lens 4 is controlled by the focus control circuit 12 so as to be focused on the recording surface, the distance from the recording surface of the optical disc 1 is maintained at the focal length WD, and the objective lens is equal to ΔH. The height of 4 also changes. When the coefficient of the moving amount in the focus direction with respect to the focus drive value (voltage) is Kf, the disc tilt θ is expressed as (Equation 2).

  Therefore, the disc tilt θ can be detected by measuring the difference ΔV between the focus drive values at two points separated by a predetermined distance ΔR in the radial direction. In order to optimize the tilt of the objective lens 4 based on the disc tilt value obtained in this way, the tilt drive value calculation unit 25 moves to the inner periphery side focus drive coil 91 and the outer periphery side focus coil 92 constituting the tilt actuator 29. The tilt drive value that determines the applied voltage is calculated. In order to measure the disc tilt value at a plurality of points in the radial direction, the tilt correction controller 28 sends an instruction to move to the measurement position to the traverse control circuit 18, and also sends the measurement position information to the disc tilt detection unit 24 and the tilt drive value table. The data is sent to the generation unit 26. Further, the tilt correction controller 28 removes the influence of fluctuations in the focus drive value due to the surface shake of the optical disc 1, and the FG signal obtained from the spindle motor control circuit 5 so that averaging can be performed in a period that is an integral multiple of one rotation. Is used to send a measurement timing signal to the disc tilt detector 24. The tilt drive value table generation unit 26 stores the tilt drive value at each measurement position obtained from the tilt drive value calculation unit 25, and approximates the relationship between the radial position and the tilt drive value from the tilt drive value at each measurement position. A tilt driving value table storing tilt driving values at predetermined intervals in the radial direction is generated and stored. For example, as shown in FIG. 8, a linear approximation is made between the five points based on the tilt drive values of R1, R2, R3, R4, and R5 where the disc tilt value is measured, and the distance ΔX is calculated from the linear approximation formula. A tilt drive value table for each interval is generated and stored.

  Next, the reference tilt drive value calculation unit 27 acquires the jitter value from the reproduction jitter measurement circuit 21 while forcibly changing the tilt of the objective lens 4 by changing the tilt drive value in a predetermined step. A tilt drive value that minimizes the value is obtained. The purpose is to remove the influence of the tilt of the light beam 93 of the objective lens 4 on the optical axis. As shown in FIG. 9, the inclination ΔθL of the light beam 93 of the objective lens 4 with respect to the optical axis when the tilt drive value is zero is mainly caused by an adjustment error during manufacturing and an offset between channels of the driver IC. In either case, it is impossible to completely zero. Since the method of obtaining the tilt drive value from the focus drive value of the present embodiment is to substantially measure the disc tilt value itself of the optical disc 1, the amount of change in the radial direction of the disc tilt value can be obtained without error. it can. Therefore, if the difference between the tilt drive value obtained from the focus drive value and the jitter drive value at which at least one radial position is minimized, the difference corresponds to the tilt error of the objective lens 4, If only the difference is corrected, tilt correction can be accurately performed at all radial positions. As shown in FIG. 10, when the jitter value is measured while changing the tilt drive value in the plus and minus directions with zero as a reference, and the result is approximated to a quadratic expression using the least square method, the jitter value is obtained. The minimum tilt drive value can be obtained. Then, a value obtained by multiplying the difference ΔVt between the tilt drive value obtained from the focus drive value and the tilt drive value that minimizes the jitter value by the tilt drive sensitivity Kt (tilt angle / tilt drive value of the objective lens 4) is This corresponds to a deviation angle ΔθL of the objective lens 4 with respect to the optical axis. More specifically, as shown in FIG. 11, a reference tilt drive value that minimizes the jitter value is obtained at the position of R1 where the disc tilt value is measured, and the difference from the tilt drive value obtained in R1 is tilt driven. The tilt drive value table is updated in addition to the tilt drive values R1 to R5 recorded by the value table generation unit as an offset.

  In this way, by generating a tilt drive value table storing the optimum tilt drive value at an arbitrary radial position, the tilt drive value at the corresponding radial position is recorded from the tilt drive value table during the recording operation or the reproduction operation. Thus, by driving the tilt actuator 29, the inclination of the objective lens 4 can be set to an optimum value according to the relative inclination between the recording surface of the optical disc 1 and the light beam. As described above, according to the configuration of the present embodiment, the disc tilt amount obtained based on the focus drive value is corrected by the reproduction signal so as to obtain the optimum tilt of the objective lens. Provided is an optical disc apparatus capable of stable recording and reproduction even when the amount of warping of the optical disc is large without providing a tilt drive mechanism such as a device or a tilt motor.

  As described above, the optical disc apparatus of the present invention can detect the optimum tilt amount reliably even when the amount of warp of the optical disc is large without providing a special detection device such as a tilt sensor. A highly reliable tilt correction can be realized. Therefore, the configuration of the optical disk apparatus of the present invention is an optical disk recording that performs both recording and reproduction of a DVD-R apparatus, DVD-RAM apparatus, DVD-RW apparatus, CD-R apparatus, CD-RW apparatus, magneto-optical recording apparatus, and the like. It is suitable for any one of the reproducing apparatus and the optical disk reproducing apparatus such as a reproduction-only DVD-ROM apparatus, a CD-ROM apparatus or a reproduction-only MD apparatus, and an optical disk recording apparatus that performs only recording. Needless to say, the same effect can be obtained.

  The disk apparatus of the present invention can be applied to an optical disk apparatus that records and reproduces information by irradiating an optical disk with a light beam.

1 is a block diagram showing a configuration of an optical disc apparatus according to an embodiment of the present invention. Explanatory drawing which showed the structure of the optical head in the embodiment Explanatory drawing which showed the structure of the optical detection recorder of the optical head in the embodiment Explanatory drawing of the reproduction signal processing circuit of the optical disc apparatus in the same embodiment Explanatory drawing of the tilt actuator of the optical disk device in the same embodiment Block diagram of a tilt correction control unit of the optical disc apparatus in the same embodiment Explanatory drawing of the disc tilt measurement of the optical disc apparatus in the same embodiment Explanatory drawing of the tilt drive value table of the optical disk apparatus in the same embodiment Explanatory drawing of the shift | offset | difference of the objective lens and optical axis of the optical disk apparatus in the same embodiment Relationship diagram between tilt drive value and jitter value of optical disc apparatus in same embodiment Explanatory drawing of the tilt drive value table update of the optical disk device in the same embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Spindle motor 3 Optical head 4 Objective lens 20 Tilt control part

Claims (1)

A light source for irradiating a light beam onto an optical disk having a spiral or concentric track, a condensing means for condensing the light beam on a recording surface of the optical disk, and a light condensing means for the light of the light beam An optical head having a focus direction moving means for moving in the axial direction and a photodetector for receiving reflected light from the recording surface;
A focus error detecting means for detecting a defocus of the light beam with respect to the recording surface;
Focus control means for driving the focus direction moving means based on the output of the focus error detecting means so as to focus the light beam on the information surface;
Tracking direction moving means for moving the light beam in a radial direction of the optical disc;
Rotating means for rotating the optical disc;
Based on the average value of the output values of the focus control means at a plurality of different positions in the radial direction of the optical disk, the inclinations of the disk tilt detection means for detecting the disk tilt value, which is the inclination of the recording surface, and the condensing means are determined. Variable tilting means;
A tilt driving means for driving the tilt varying means;
Tilt drive value calculation means for calculating an input value to the tilt drive means as a tilt drive value based on the disk tilt value obtained by the disk tilt detection means, and the disc at a plurality of different positions in the radial direction of the optical disc The tilt drive value calculated based on the tilt value is stored, and a calculation formula that approximates the relationship between the radial position and the tilt drive value is derived from the tilt drive value at each radial position, and a predetermined interval in the radial direction is derived. A tilt drive value table generating means for generating and storing a tilt drive value table for each, and a reproduction signal measuring means for measuring a reproduction signal based on the output of the photodetector;
By changing the input value to the tilt driving means, the output value of the reproduction signal measuring means is acquired while changing the inclination of the light converging means, and the output value of the reproduction signal measuring means becomes the target value. Reference tilt drive value calculation means for calculating an input value to the means as a tilt drive reference value,
Obtain both the tilt drive reference value and the tilt drive value at at least one substantially the same radial position, add the difference between them as an offset to the tilt drive value obtained at a plurality of radial positions, and correct by the offset The tilt driving value table is updated based on the tilt driving value, and the inclination of the light collecting means at a desired radial position during the recording operation or the reproducing operation is determined as the relative inclination between the recording surface of the optical disc and the light beam. The tilt drive value at the corresponding radial position is obtained from the tilt drive value table updated to set the optimum value according to the value, and is input to the tilt drive means to drive the tilt variable means. An optical disc apparatus characterized by comprising:

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