JP2005085323A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tilt feature of an objective lens for irradiating a recording surface with a laser beam from an optical pickup always vertically even the optical disk has curvature, and an optical disk device with this feature. <P>SOLUTION: The optical disk device 10 comprises: an optical pickup 12 which irradiates an optical disk D with a laser beam L and reads reflected light from the optical disk; an objective lens 14 which converges the laser beam emitted from the optical pickup; an actuator 16 for changing the angle of the objective lens against the reference plane for irradiating the optical disk with the laser beam; and an actuator control means 20 of controlling operation of the actuator. The device also comprises: a shape calculating means 20a of calculating an approximate expression showing an altitudinal location of the optical disk D from the reference plane; a location calculating means 20b of grasping the current location of the optical pickup 12; and a tilt angle calculating means 20c of calculating a tilt angle K of the optical disk D against the reference plane in the current location of the optical pickup 12, based on the altitudinal location of the optical disk D from the reference plane between two points separated at a predetermined interval from the current location of the optical pickup calculated by the approximate expression, and the horizontal interval between the two points. The actuator control means 20 controls the actuator 16 which tilts the objective lens 14 to a tilt angle K calculated by the tilt angle calculating means 20e against the reference plane. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus, and more particularly to an optical disc apparatus having an objective lens tilt mechanism capable of always irradiating a laser beam applied to an optical disc at a right angle to a recording surface.

Conventionally, various optical disks such as CDs and DVDs are designed on the assumption that laser light emitted from an optical pickup is emitted perpendicularly to the recording surface of the optical disk.
However, since the above-mentioned various optical disks are formed by pressing two disk-shaped bodies formed of a resin such as polycarbonate with the recording layer and the reflective layer sandwiched therebetween, the optical disk may have warpage. Many. As described above, in an optical disk that is actually used, since the laser beam is not irradiated perpendicularly to the recording surface, it may not be possible to obtain reading quality and recording quality as designed.

Therefore, a tilt mechanism for making the laser light emitted from the optical pickup perpendicular to the optical disc has been proposed.
For example, in Patent Document 1, the first and second tilt detectors detect the tilt of the recording surface of the optical disc from the reference surface, and the first tilts the objective lens based on the detection result of the first tilt detector. After the objective lens is tilted to a predetermined angle, the optical pickup is tilted at a predetermined angle by the second driving means based on the detection result of the second tilt detecting means. Thus, there is disclosed a tilt control device that controls to always irradiate a laser beam perpendicularly to a recording surface of an optical disc.
JP 2001-126284 A

  According to the optical disk device using the tilt mechanism according to Patent Document 1, since laser light is irradiated perpendicularly to the recording surface of the optical disk, high-quality recording / reproduction is possible, which is useful. In addition, the driving means for controlling the tilt of the objective lens and the driving means for controlling the tilt of the optical pickup are each provided as a single unit, so that the short-term laser light irradiation angle control and the long-term laser light irradiation angle control are performed. When the laser beam irradiation angle is stable, it is advantageous to maintain the laser beam irradiation angle.

  However, since the tilt mechanism of Patent Document 1 requires a plurality of tilt detection means and drive means, and the number of parts is greatly increased, there is a problem that the manufacturing cost of the optical disk apparatus increases.

  The present invention obtains an approximate expression that approximates the positional relationship between the recording surface of the optical disk and the reference surface, and tilts the objective lens with respect to the inclination of the optical disk calculated based on the approximate expression, whereby laser light is applied to the recording surface. An object of the present invention is to provide an optical disk apparatus having a tilt mechanism of an objective lens that can always irradiate vertically.

In order to achieve the above object, the present invention comprises the following arrangement.
That is, an optical pickup that irradiates an optical disc with laser light and reads reflected light from the optical disc, an objective lens that converges the laser light emitted from the optical pickup, and the objective with respect to a reference plane that irradiates the optical disc with laser light. An optical disk device comprising an actuator for changing the angle of the lens and an actuator control means for controlling the driving of the actuator, and in a state where the optical disk is mounted on the optical disk device, a recording surface of the optical disk in advance Optical disk shape calculating means for measuring the distance to the objective lens at a plurality of radial positions and calculating an approximate expression for determining the distance of the optical disk with respect to the reference surface at a desired position of the optical disk based on the measured distance And the optical disc Storage means for storing the approximate expression obtained by the shape calculating means, optical pickup position calculating means for calculating the current position of the optical pickup in the radial direction of the optical disc, and the light calculated by the optical pickup position calculating means The distance from the current position of the pickup to the reference plane of the optical disc at two locations spaced apart from each other by a predetermined distance in the radial direction of the optical disc is calculated by an approximate expression stored in the storage means, and the horizontal distance between the two points and the Optical disc tilt angle calculation means for calculating an inclination angle of the optical disc with respect to the reference surface at the current optical pickup position based on a difference in distance from the reference surface of the optical disc, and the actuator control means includes the objective The lens is tilted with respect to the reference plane. An optical disk apparatus characterized by controlling the actuator so as to tilt the tilt angle calculated by the means.

  Further, the two locations separated by a predetermined distance for calculating the distance from the reference surface of the optical disc by the approximate expression are positions separated by a predetermined distance from the current position of the optical pickup in the outer shape and the inner diameter direction of the optical disc. It is characterized by.

  The optical disk shape calculating means measures the distance from the objective lens to the recording surface of the optical disk a plurality of times at a plurality of positions provided at required intervals in the radial direction of the optical disk, and then averages the respective measurement positions. And an approximate expression for calculating the distance from the reference surface of the optical disc based on the average value at a plurality of positions of the optical disc. As a result, the accuracy of the calculated approximate expression is improved, the tilt angle of the optical disk can be accurately obtained, and more accurate data reading and writing can be performed.

  Furthermore, the optical disc shape calculating means operates at the time of initialization performed when the optical disc is mounted on the optical disc apparatus. Thereby, since it is not necessary to measure the inclination with respect to the reference plane of the optical disk each time data is accessed to the optical disk, the objective lens can be quickly inclined.

  If the optical disk device having the objective lens tilt mechanism according to the present invention is employed, even if the optical disk is warped, an approximate expression representing the shape is calculated for each optical disk, and the optical pickup is based on the calculated approximate expression. The inclination angle with respect to the reference plane of the optical disk at the current position can be obtained, and the objective lens can be inclined with respect to the obtained inclination of the optical disk. Thereby, it becomes possible to always irradiate the laser beam perpendicularly to the recording surface of the optical disc, and it is possible to provide an optical disc apparatus with high reproduction recording quality. In addition, since the number of components constituting the tilt mechanism is reduced, it is possible to provide an optical disc apparatus that is less expensive to manufacture than before.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an optical disc apparatus according to the present embodiment.
The optical disk apparatus 10 is a turntable T on which the optical disk D is placed, a spindle motor M that rotates the optical disk D via the turntable T, and a laser beam L is irradiated onto the optical disk D and the reflected light from the optical disk D is read. The optical pickup 12, the objective lens 14 that converges the laser light L, the actuator 16 that tilts the objective lens 14 with respect to the horizontal plane, and the control means 20 that controls various operations of the optical disc apparatus 10 are outlined. .
The control means 20 (hereinafter also referred to as actuator control means 20) is constituted by a CPU, a memory, and the like, and operates based on a control program stored in advance in a memory (not shown).

As the optical disk D, known optical disks such as various CDs and DVDs are used. The optical disc D has a recording surface on which pits indicating data are formed. The optical disc apparatus 10 reads data from the optical disc D by irradiating the recording surface with the laser light L perpendicularly from the optical pickup 12 and observing the reflected light from the recording surface of the laser light L. On the other hand, data is written onto the optical disc D by the laser light L irradiated perpendicularly to the recording surface from the optical pickup 12 on the recording surface of the optical disc D to form pits on the recording surface.
A wobble groove in which address information of the optical disk D is recorded is formed on the recording surface in the optical disk D, and the reflected light from the optical disk D includes a component of address information by the wobble groove. The optical disk D is fixed to the turntable T of the optical disk apparatus 10 and is rotated by the spindle motor M via the turntable T.

  The optical pickup 12 includes an objective lens 14 for irradiating and condensing the optical disc D with laser light L, and a photodiode (not shown) for extracting various signals included in the reflected light observed by the objective lens 14. And an actuator 16 for holding the objective lens 14 and adjusting the optical axis of the objective lens 14 with respect to the horizontal plane. The objective lens 14 in the optical pickup 12 is arranged so that its optical axis is perpendicular to the horizontal plane on the premise that the optical disk D is fixed horizontally to the turntable T.

The actuator 16 is for changing the holding state of the objective lens 14 with respect to the recording surface of the optical disc D. Specifically, the actuator 16 adjusts the distance between the objective lens 14 and the optical disc D and the irradiation angle of the laser light L applied to the optical disc D, that is, the optical axis of the objective lens 14.
Specifically, the actuator 16 is an electromagnetic coil disposed so as to sandwich the objective lens 14 in the vicinity of the objective lens 14 and supplies a focus drive-out signal (hereinafter referred to as an FDO signal) to this coil. Thus, the holding state of the objective lens 14 is changed.

The optical pickup 12 is placed on the carrier 18. The carrier 18 moves in the radial direction of the optical disk D in a horizontal plane at a position away from the recording surface of the optical disk D within the optical disk device 10.
The optical pickup 12 configured as described above reads the reflected light of the laser beam L irradiated onto the recording surface of the optical disc D, acquires address information of the optical disc D, and reads and writes data.

Next, the operation of the objective lens tilt mechanism of the optical disc apparatus 10 in the present embodiment will be described. FIG. 2 is a schematic diagram showing a state in which the warpage of the optical disk is detected in the optical disk apparatus according to the present embodiment. FIG. 3 is an explanatory diagram showing an example of a method for calculating the tilt angle of the optical disc at the current position of the optical pickup.
The outline of the tilt mechanism of the objective lens 14 in the present invention is that the recording surface of the optical disk D having warpage or deformation is always irradiated perpendicularly with the laser light L from the objective lens 14, so that the position of the recording surface of the optical disk D is actually set. An inclination angle with respect to the reference surface of the optical disk D at the current position of the optical pickup 12 is obtained based on the approximate expression representing the deformation of the optical disk D calculated by the measurement, and the actuator control means 20 operates the actuator based on the obtained inclination angle. 16, the holding state of the objective lens 14 is adjusted, and the optical axis of the laser light L is controlled.

First, the operation at the time of initialization will be described.
When the optical disc D is loaded in the optical disc apparatus 10, initialization for reading track information and the like is performed. At the time of initialization, the carrier 18 is moved from the innermost peripheral portion to the outermost peripheral portion of the optical disc D while being kept horizontal by driving means (not shown). The carrier 18 pauses at required intervals in the radial direction of the optical disc D, and the optical pickup 12 irradiates the recording surface of the optical disc D with the laser light L at each paused position and observes the reflected light. . In the present embodiment, the radial direction of the recordable portion of the recording surface of the optical disc D is paused at 12 locations every 3 mm, and the laser beam L is irradiated 32 times per location where the pause is performed, and the reflection to each is performed. Light is observed and the average of the observation results is taken as the observed value at that position. The reflected light includes a component related to address information, a component related to a focus error signal (hereinafter referred to as FE signal), and the like, and each signal component can be extracted from the reflected light using a photodiode (not shown).

  The FE signal extracted from the reflected light is input from the optical pickup 12 to the control means 20. The FDO signal generation unit 20a in the control unit 20 generates an FDO signal from the FE signal using a unique conversion coefficient that is different for each optical disc apparatus 10. The FDO signal is output from the control means 20 to the actuator 16, and the actuator 16 is driven to adjust the height position of the objective lens.

Thus, since the FDO signal is a signal for moving the objective lens 14 toward and away from the optical disc D, it has a signal level proportional to the distance between the objective lens 14 and the recording surface of the optical disc D. Therefore, the distance calculation means 20b in the control means 20 calculates the distance between the objective lens 14 and the recording surface of the optical disc D based on the signal level of the FDO signal.
The distance between the objective lens 14 calculated as described above and the recording surface of the optical disc D is stored in the storage unit 22 together with the address information of the optical disc D (the radial position of the optical disc D).

  Based on the address information stored in the storage means 22 and the distance between the optical disk D and the objective lens 14, the optical disk shape calculation means 20c of the control means 20 calculates an approximate expression representing the shape of the optical disk D. That is, the state in which the signal level of the FDO signal is 0 (the holding state of the objective lens 14 is the initial state) is the reference plane, the distance y from the reference plane to the recording surface of the optical disc D is the vertical axis, and data recording on the optical disc D is performed. The approximate expression here is the expression of the shape of the optical disc D as (x, y) when the radial distance x in the portion is represented by the x-y coordinate with the horizontal axis. Therefore, when the radial position in the data recording portion of the optical disc D is input to the approximate expression, the distance from the reference surface to the recording surface of the optical disc D at that position can be obtained.

In the present embodiment, the cubic function of x in the xy coordinate plane is used as an approximation formula, but the present invention is not limited to only the cubic function of x in the xy coordinate plane. An approximate expression based on an average method or an approximate expression based on a spline curve can also be adopted.
The approximate expression obtained as described above is stored in the storage means 22.

Next, the operation of the optical disc apparatus 10 when reading / writing actual data after the initialization is completed will be described.
When actually reading and writing data recorded on the recording surface of the optical disc D, the carrier 18 on which the optical pickup 12 is mounted moves gradually in the radial direction of the optical disc D in the same manner as in a normal optical disc apparatus. This is performed by irradiating the recording surface of the optical disc D with the laser light L and observing the reflected light from the recording surface.
Further, the optical pickup position calculating means 20d of the control means 20 extracts the wobble signal included in the reflected light from the optical disk D, and to which position of the optical disk the optical pickup 12 is currently irradiating the laser light. Is calculated.

  After the current position of the optical pickup 12 is calculated by the optical pickup position calculating means 20d, the optical disk tilt angle calculating means 20e uses the approximate expression stored in the storage means 22 from the current position of the optical pickup 12 to the inner circumference of the optical disk D. The distance from the reference surface on the recording surface of each optical disc D is calculated from the approximate expression at two points at the required distance in the direction and the outer peripheral direction, and the horizontal distance between these two points and the height relative to the reference surface of the optical disc D The tilt angle of the optical disk D is calculated from the difference in position. In the present embodiment, as shown in FIG. 4, a position r 1 that is 0.5 mm away from the current position r 0 of the optical pickup 12 in the radial inner circumference (minus) direction and outer circumference (plus) direction, respectively. At r2, the height positions h1 and h2 of the recording surface of the optical disc D with respect to the reference surface are calculated, and light is obtained using a trigonometric function from the horizontal distance 1 mm between these two points and the height difference (difference ΔH between h2 and h1). The tilt angle K of the optical disk D at the current position r0 of the pickup 12 is calculated.

The FDO signal generation unit 20a generates an FDO signal based on the FE signal at the current position of the optical pickup 12 calculated by the optical pickup position calculation unit 20d.
The tilt offset signal generating unit 20f generates a tilt offset signal at the current position of the optical pickup 12 based on the tilt angle K calculated by the optical disc tilt angle calculating unit 20e.

  Both the FDO signal and the tilt offset signal generated as described above are input from the actuator control means 20 to the actuator 16. Based on these signals, the actuator 16 makes the height position of the objective lens 14 constant with the optical disc D, and tilts the optical axis of the objective lens 14 in the same direction as the tilt angle K. Let

By adjusting the height position and optical axis of the objective lens 14 by the objective lens tilt mechanism described above, the distance between the objective lens 14 and the optical disc D is maintained constant, and the light is irradiated from the optical pickup 12. As shown in FIG. 5, since the laser beam L is always perpendicular to the recording surface of the optical disc D, the reading quality and the writing quality are the same as those obtained when reading and writing data from the optical disc D under ideal conditions. Can be done to the extent.
In addition, since the data is read and written after the deformation state of the optical disk D is grasped in advance, the adjustment of the irradiation angle of the laser light L to the optical disk D can be quickly performed without a time lag.

  In the present embodiment, when calculating the shape of the optical disc D, the objective lens 14 and the recording surface of the optical disc D are each 32 times at 12 points provided at intervals of 3 mm in the radial direction of the optical disc D. The distance is measured, and the average of these observation distances is used to calculate the distance between the objective lens 14 and the recording surface of the optical disk D at that position. Of course, it is not limited to these numerical values and can be appropriately changed.

  Further, as shown in FIG. 4, the method of calculating the tilt angle K with respect to the reference surface of the optical disk D at the current position r0 of the optical pickup 12 is as follows. The height positions h1 and h2 of the recording surface of the optical disc D with respect to the reference surface are calculated at positions r1 and r2 that are 1 mm apart in the direction, respectively, and the horizontal distance 2 mm between these two points and the height difference (difference between h2 and h1: ΔH) is calculated by using a trigonometric function, but the present invention is not limited to this method. For example, as shown in FIG. 6, the distance between the recording surface and the reference surface actually measured at the current position r0 of the optical pickup 12 or The distance h0 calculated by the approximate expression and the approximation at the position r1 that is a predetermined distance away from the optical pickup 12 in the outer peripheral direction or the inner peripheral direction of the optical disc D It may be a method of calculating the inclination angle K with respect to the reference surface of the optical disc D by a trigonometric function based on the distance h1 between the recording surface and the reference surface calculated by.

  Further, as shown in FIG. 7, the measured distance between the recording surface and the reference surface at the current position r0 of the optical pickup 12 or the distance h0 calculated by an approximate expression and the current position of the optical pickup 12 in the inner circumferential direction of the optical disk D. A point in the inner circumferential direction with respect to the reference surface of the optical disc D calculated using a trigonometric function based on the distance h1 between the recording surface and the reference surface calculated by the approximate expression at the point r1 separated by a predetermined distance and the horizontal distance between these two points. And the distance calculated by the approximate expression or the actual distance between the recording surface and the reference surface at the current position r0 of the optical pickup 12 and the current position of the optical pickup 12 away from the current position of the optical pickup D by a predetermined distance. It is a trigonometric function based on the distance h2 between the recording surface and the reference surface calculated by the approximate expression at the point r2 and the horizontal distance between these two points. The calculated tilt angle K2 calculated from the outer peripheral direction with respect to the reference surface of the optical disc D is calculated, and the average value of the tilt angle K1 calculated from the inner peripheral direction and the tilt angle K2 calculated from the outer peripheral direction is the current position of the optical pickup 12. It is also possible to adopt a method of setting the tilt angle with respect to the reference plane of the optical disc D in

1 is a schematic configuration diagram of an optical disc device according to an embodiment. It is a schematic diagram which shows the state which detects the curvature of the optical disk in the optical disk apparatus of this Embodiment. It is explanatory drawing which shows an example of the method of calculating the inclination angle of the optical disk in the present position of an optical pick-up. It is explanatory drawing which shows the calculation method of the inclination angle with respect to the reference plane of the optical disk in the present position of the optical pick-up in this Embodiment. It is a schematic diagram which shows the irradiation state of the laser beam with respect to the optical disk in this Embodiment. It is explanatory drawing which shows the method of calculating the inclination angle with respect to the reference plane of the optical disk at the current position of the optical pickup from the measured distance of the current position and the approximate value of one point on the outer peripheral side. It is explanatory drawing which shows an example of the other calculation method of the inclination angle with respect to the reference plane of the optical disk in the present position of an optical pick-up.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical disk apparatus 12 Optical pick-up 14 Objective lens 16 Actuator 18 Carrier 20 Control means (actuator control means)
20a FDO signal calculation means 20b distance calculation means 20c optical disk shape calculation means 20d optical pickup position calculation means 20e optical disk tilt angle calculation means 20f tilt offset signal generation means 22 storage means D optical disk K tilt angle L laser light M spindle motor T turntable

Claims (4)

An optical pickup that irradiates an optical disc with laser light and reads reflected light from the optical disc;
An objective lens for converging the laser light emitted from the optical pickup;
An actuator for changing an angle of the objective lens with respect to a reference plane for irradiating the optical disc with laser light;
An actuator control means for controlling the drive of the actuator;
In a state where the optical disc is mounted on the optical disc apparatus, the distance between the recording surface of the optical disc and the objective lens is measured in advance at a plurality of radial positions, and based on the measured distance, the optical disc at the desired position of the optical disc is measured. An optical disc shape calculating means for calculating an approximate expression for obtaining a distance of the optical disc with respect to the reference plane;
Storage means for storing the approximate expression obtained by the optical disk shape calculating means;
An optical pickup position calculating means for calculating a current position of the optical pickup in the radial direction of the optical disc;
Calculated by the approximate expression stored in the storage means at two locations that are separated from the current position of the optical pickup calculated by the optical pickup position calculating means by a predetermined distance in the radial direction of the optical disk with respect to the reference surface of the optical disk. And an optical disk inclination angle calculating means for calculating an inclination angle of the optical disk with respect to the reference surface at a current optical pickup position based on a difference between a horizontal distance between the two points and a distance of the optical disk with respect to the reference surface; Have
The optical disk apparatus, wherein the actuator control means controls the actuator so that the objective lens is inclined with respect to the reference plane at an inclination angle calculated by the optical disk inclination angle calculation means. The two locations separated by a predetermined distance for calculating the distance of the optical disc with respect to the reference surface by the approximate expression are positions separated by a predetermined distance from the current position of the optical pickup in the outer shape and the inner diameter direction of the optical disc. The optical disc apparatus according to claim 1. The optical disc shape calculating means measures the distance between the objective lens and the recording surface of the optical disc a plurality of times at a plurality of positions provided at required intervals in the radial direction of the optical disc, and then calculates an average value of each measurement position. The optical disk apparatus according to claim 1, wherein an approximate expression for calculating a distance from the reference surface of the optical disk is calculated based on the average value at a plurality of positions of the optical disk. The optical disc apparatus according to any one of claims 1 to 3, wherein the optical disc shape calculating unit operates at initialization performed when the optical disc is mounted on the optical disc apparatus.

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