JPH03137831A - Optical disk device - Google Patents

Abstract

PURPOSE:To compensate the adverse influence of aberrations due to the inclination of the optical axis of a beam to the surface of a disk fast by controlling a voice coil actuator which detects an error in the angle of the optical axis of the beam emitted from the condenser lens of an optical head and slanting a condenser lens holding part. CONSTITUTION:The irradiation light from a light source 38 which is passed through the parallel detection lens 40 of a tilt error detector 36 is passed through the mirror 34 of a lens holder 16 and reflected by the disk 44 to strike on a photodetector 41, and the angle error of the optical axis of the light beam which is emitted through the condenser lens 14 of an optical head main body 12 is detected. Its detection output is supplied to voice coils 22 and 24 of a voice coil actuator motor to control the optical axis of the beam light irradiating the disk 44 and the adverse influence of the aberrations due to the inclination of the beam optical axis to the disk surface is compensated fast.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a CD (compact disc) player,
The present invention relates to a disc playback device such as an Lv (laser vision disc) player or an optical disc device such as an optical disc recording device, and is capable of quickly correcting the inclination of the beam optical axis with respect to the disc surface.

[Conventional technology]

In disc playback devices such as CD players and LV players, if the optical axis of the signal playback beam is tilted with respect to the disc surface, optical aberrations may occur, increasing crosstalk and causing pit reading errors. Furthermore, in an optical disc recording device, if the optical axis of the signal recording beam is tilted with respect to the disc surface, mistakes may occur in pit formation.

In conventional LV players, etc., the average amount of warpage of the disc in the radial direction is detected, and
A tilt servo device was provided that controls the beam optical axis by tilting the entire optical head using a tilt motor (DC motor).

[Problem to be solved by the invention]

The amount of curvature of the disk surface changes during one rotation, but the conventional tilt servo device described above tilts the entire optical head and uses a normal motor for driving, so the response is poor. However, it has been impossible to accurately follow such changes in the amount of warpage during one rotation of the disk.

By the way, for high-density recording and reproduction, it is necessary to use a beam focusing lens with a high NA (numerical aperture) (that is, a large diameter) to increase the resolution. The degree of comatic aberration associated with the inclination of the beam optical axis increases in proportion to (NA)3, and the change in the amount of warpage during one revolution of the disk becomes an extremely serious problem and is attracting attention. The above-mentioned conventional tilt servo device cannot compensate for this with average correction control over one round, and therefore the aperture of the beam focusing lens cannot be made very large, which is the limit of high-density recording and reproduction. .

In addition, although the disk surface tilts not only in the radial direction but also in the circumferential direction (for example, creating a wavy shape in the circumferential direction), conventional tilt servo devices have no ability to deal with such circumferential tilt. It wasn't taken into account.

SUMMARY OF THE INVENTION The present invention aims to solve the problems in the conventional techniques and provide an optical disc device that can quickly compensate for the adverse effects of aberrations caused by the inclination of the beam optical axis with respect to the disc surface.

[Means to solve the problem]

This invention first includes a beam angle error detection means for detecting an angular error of a beam optical axis emitted from a focusing lens of an optical head with respect to a direction perpendicular to a disk surface; Based on the detection output of the focusing lens support mechanism that tiltably supports the head body, the voice coil actuator that tilts the focusing lens support/hakama part, and the beam angle error detection means,
and control means for driving and controlling the voice coil actuator to tilt the focusing lens parallel to the disk surface.

In addition, the present invention secondly includes a focus error detection means for detecting a focus error of a beam optical axis emitted from a focusing lens of an optical head with respect to a disk recording surface, and a focus error detection means for detecting an angular error of the beam optical axis with respect to a direction perpendicular to the disk surface. a beam angle error detection means for detecting a beam angle error; a focusing lens support mechanism that supports a focusing lens holder holding the focusing lens so as to be movable and tiltable in the optical axis direction with respect to the optical head body; placed opposite each other,
A plurality of voice coil actuators are individually drivable and each generates a predetermined driving force in the optical axis direction with respect to the focusing lens holding portion, and the plurality of voice coil actuators are equally actuated based on the focus error. The focusing lens holder is moved in the optical axis direction so as to make the focus error zero by driving, and the plurality of voice coil actuator drive means are unevenly driven based on the angular error. and control means for tilting the focusing lens holder so that it becomes parallel to the surface of the focusing lens disc.

[For production]

According to the first solution of the present invention, the voice coil actuator is driven based on the detection output of the beam angle detection means, the focusing lens holder is tilted with respect to the optical head body, and the focusing lens is parallel to the disk surface. - Fixed all the time.

As a result, the aberration generating element changes from a lens optical axis error with respect to the disk surface to a beam incident angle error with respect to the focusing lens, and coma aberration is reduced as a result. As a result, crosstalk due to beam tilt errors can be reduced, or it is possible to use a focusing lens with as large an NA as possible. Since a voice coil actuator is used for driving the disc, a high-speed response can be achieved, and high-quality signal recording or reproduction can be performed by following changes in the inclination during one revolution of the disc.

Further, according to the second solution of the present invention, focus control is performed by uniformly driving a plurality of voice coil actuators arranged at positions facing each other with the focusing lens holder in between, based on the focus error. Since the converging lens is controlled to be parallel to the disk surface by non-uniform driving based on the angular error, both controls can be realized using a common voice coil actuator, and the configuration can be simplified.

〔Example〕

Examples of this invention will be described below.

(Embodiment 1) The embodiment shown in FIG. 1 is designed to deal with the case where the beam light from the optical head is tilted in the radial direction of the disk with respect to the disk surface. The optical head 10 is an optical head main body 1
2, a lens holder 16 fixedly holding a focusing lens 14 therein;
It accommodates. Disc circumferential direction of lens holder 16 -
A support portion 2 is formed on the optical head body 12 via a spring suspension 18 arranged in the circumferential direction of the disk on the side surface.
0, and is tiltable in the disk radial direction as shown by arrow A, and the focusing lens 1 is supported as shown by arrow B.
It is movable in the direction of the optical axis of No. 4, and further in the radial direction of the disk as shown by arrow C.

Voice coils 22 and 24 are attached to both sides of the lens holder 16 in the disk radial direction.

And, in the space inside these voice coils 22 and 24, U
One end of the yoke 26, 28 is inserted respectively. The U-shaped yokes 26 and 28 are fixed to the optical head body 12. Further, magnets 30 and 32 are attached to the other ends to form magnetic flux orthogonal to the voice coils 22 and 24, thereby forming voice coil motors 31 and 33.

A tilt error detection mirror 34 is attached at an angle to the other side of the lens holder 16 in the disk circumferential direction.

Further, a tilt error detector 36 is attached to the optical head body 12 and disposed near the mirror 34 in the disk circumferential direction.

The tilt error detector 36 includes a light source (laser diode, LED, etc.) 38 and a parallel detection lens 40, as shown in FIG.
It also has a built-in photodetector 41.

The tilt error detection beam 42 emitted from the light source 34 is made into almost parallel light by the parallel detection lens 4o, reflected by the mirror 34 of the lens holder 16, and then reflected by the recording surface of the disk 44. This reflected light is made to approximately converge on a photodetector 41 via a parallel detection lens 40.

When the mirror 34 and the recording surface of the disk 44 are at a predetermined angle (the angle when no tilt error occurs),
The angle of the returned light that re-enters the parallel detection lens 4o is kept constant, and images are formed on substantially the same point on the photodetector 41.

When the mirror 34 and the recording surface of the disk 44 deviate from a predetermined angle, the angle of the returning light to the parallel detection lens 4o changes, and the position where the image is formed on the photodetector 41 changes.

The photodetector 41 is composed of, for example, a four-split light receiving element, and when the optical axis of the focusing lens and the recording surface of the disk 44 are perpendicular to each other, the returned light is approximately equal to the four-split light receiving element, as shown in FIG. It is installed so that an image is formed at the center and the image moves as shown by the arrow when a tilt error occurs in the disk radial direction. Note that the photodetector 41 can also have a two-part structure in which elements 1 and 2 and elements 3 and 4 are integrated.

An example of a tilt control circuit is shown in FIG. This control circuit 5
0 also serves as a focus control circuit.

The detection outputs of elements 1 and 2 and elements 3 and 4 of the 4-split photodetector 41 are added together and input to a subtracter 52, where a tilt error is detected. This tilt error detection signal PE is synthesized by an adder 54 and a subtracter 56 with a focus error signal FE generated based on a return light detection signal of a recording or reproducing laser beam separately irradiated from a focusing lens 14. That is, the input signal is inputted to the adder 54 and the subtracter 56 in the same phase as the focus error signal FE, and the tilt error signal PE is inputted in the opposite phase. Output F of adder 54
The voice coil 22 is driven by E+PE, and the subtracter 5
The voice coil 24 is driven by the output FE-PE of 6.

Since the focus error signal FE is applied to the voice coils 22 and 24 in the same phase, the lens holder 16 is moved in parallel in the direction B (FIG. 1) along the optical axis, thereby realizing focus control. Since the tilt error signals PE are applied to the voice coils 22 and 24 in opposite phases, the lens holder 16 is tilted in the direction A, thereby tilting the focusing lens f so that it is approximately parallel to the disk surface. Note that when the focusing lens is parallel to the disk surface, it means that the axial direction of the lens is perpendicular to the disk surface direction. Note that even if the focusing lens becomes parallel to the disk surface, the beam itself remains unchanged throughout the optical head, so it is irradiated in the same direction as before. However, this significantly changes the factors that cause optical coma aberration and astigmatism. Namely. When the beam direction has an error angle with respect to the disk surface, comatic aberration is more dominant than astigmatism, but according to the beam incidence angle error on the lens, astigmatism becomes more dominant than comatic aberration. , and the amount of astigmatism is a value that poses no problem in practice.

In addition, the problem when increasing the NA was serious because the increase in coma aberration caused by the beam angle error with respect to the disk surface was effective in the form of the cube of the NA. There is almost no problem with the incident beam angle error of the lens.

Although not shown in FIG. 1, a tracking actuator using a voice coil motor is separately provided in the optical head 10, and drives the lens holder 16 in the direction of arrow C to perform tracking control.

(Example 2) Another example of the present invention is shown in FIG. This is to deal with the problem of the inclination of the Radbeam in both the disk radial direction and the disk circumferential direction.

The optical head 16 accommodates a lens holder 66 in which a focusing lens 64 is fixedly held within an optical head main body 62. A spring suspension 68 is disposed in the disk circumferential direction on the side surface of the lens holder 66 in the disk radial direction.
It is supported by a support portion 74 formed on the optical head main body 62 via a spring suspension 72 provided, and is tiltable in the disk radial direction as shown by arrow A, and in the disk circumferential direction as shown by arrow E. It is also movable in the direction of the optical axis of the focusing lens 64 as shown by arrow B, and in the radial direction of the disk as shown by arrow C.

Voice coils 82 and 84 are attached to both sides of the lens holder 66 in the disk radial direction.

And, in the space inside these voice coils 82 and 84, U
One end of the letter-shaped yokes 86 and 88 are inserted, respectively. U-shaped yokes 86 and 88 are fixed to the optical head body 62. Further, a magnet 90.92 is attached to the other end to form a magnetic flux perpendicular to the voice coil 82.84, thereby forming a voice coil motor 94.95.

Voice coils 98 and 100 are attached to both sides of the lens holder 66 in the disk circumferential direction.

One end portions of U-shaped yokes 99 and 101 are inserted into the spaces within these voice coils 98 and 100, respectively. The U-shaped yokes 99 and 101 are the optical head main body 62
Fixed. In addition, a magnet 103 is provided at the other end.
105 is attached to form a magnetic flux perpendicular to the voice coils 103, 105, and the voice coil motors 96, 9
7.

A tilt error detector 102 as shown in FIG. 6, for example, is accommodated in the lens holder 66. This tilt error detector 102 uses a light source (laser diode, LE
D etc.) 104, photodetector 106 and half mirror 10
It has 8.

Tilt error detection beam 10 emitted from light source 104
9 is bent by a half mirror 108 to form a focusing lens 6
4, the light is made almost parallel and irradiated onto the recording surface of the disk 44. The reflected light from the recording surface of the disk 44 enters the focusing lens 64 again, is bent by the half mirror 108, and is imaged on the photodetector 106.

A signal recording or reproducing laser beam 110 enters the lens holder 66 from below, passes through the half mirror 108 and the focusing lens 64, and is irradiated onto the recording surface of the disk 44 to read signal pits. The reflected light passes through a focusing lens 64 and a half mirror 108 and forms an image on a photodetector (not shown), and an RF multiplied signal focus error signal is created from the received light signal.

The photodetector 100 is composed of, for example, a four-part light-receiving element, and when the optical axis of the focusing lens and the recording surface of the disk 44 are perpendicular to each other, the returned light passes through the four-part light-receiving element as shown in FIG. The image is formed approximately at the center, and when a tilt error occurs in the disk radial direction, the image moves as shown by the arrow, and when a tilt error occurs in the disk circumferential direction, the image moves as shown by the arrow E. Set it up like this.

An example of the tilt control circuit is shown in FIG. This control circuit 1
12 also serves as a focus control circuit.

The detection outputs of elements 1 and 2 and elements 3 and 4 of the 4-split photodetector 106 are added together and input to a subtracter 114, where a disk radial tilt error is detected. This tilt error detection signal PE is combined with a focus error signal FE generated based on a return light detection signal of a recording or reproducing laser beam 110 (FIG. 6) separately irradiated from a focusing lens 14, an adder 116, and a subtracter. 118.

That is, the focus error signal FE is in the same phase as the adder 1.
16 and a subtracter 118, and the tilt error signal PE is input in reverse phase. Output FE+P of adder 116
The voice coil 82 is driven by E, and the voice coil 84 is driven by the output FE-PE of the subtracter 118.

Also, elements 2 and 3 and elements 1 and 4 of the 4-split photodetector 106
The detection outputs are added together and input to the subtracter 120, and a disk circumferential tilt error is detected. This tilt error detection signal PE' is a focus error signal F.
It is combined with E by an adder 122 and a subtracter 124. That is, the focus error signal FE is in the same phase as the adder 12.
2 and the subtracter 124, and the tilt error signal P
E' is input in reverse phase. Output FE+ of adder 122
The voice coil 98 is driven by PE', and the subtracter 1
The voice coil 100 is driven by the output FE-PE' of 24.

Focus error signal FE is voice coil 8284.9
8 and 100 in the same phase, the lens holder 66 is moved in parallel in direction B (FIG. 5) along the optical axis, thereby realizing focus control. Tilt error signal P
Since E is applied to the voice coils 82 and 84 in mutually opposite phases, the lens holder 66 is tilted in the A direction, thereby tilting the focusing lens in the disk radial direction almost parallel to the disk surface, thereby achieving the above-mentioned coma aberration reduction effect. play.

Further, the tilt error signal PE' is output from the voice coil 98.
100 in opposite phases to each other, the lens holder 66 is tilted in the A direction, thereby tilting the focusing lens in the disk circumferential direction substantially parallel to the disk surface, which also contributes to the reduction of coma aberration described above. As a result, the focusing lens 64
The recording or reproducing laser beam 110 emitted from the recording or reproducing laser beam 110 is irradiated onto the recording surface of the disk 44 in a state where the degree of occurrence of coma aberration that inhibits an increase in NA is small.

Although not shown in FIG. 5, a tracking actuator using a voice coil motor is separately provided in the optical head 16, and drives the lens holder 66 in the direction of arrow C to perform tracking control.

〔Effect of the invention〕

As explained above, according to the first solution of the present invention, the inclination is corrected by tilting only the focusing lens holder instead of the entire optical head, and a voice coil actuator is used to drive it. A high-speed response can be realized, the occurrence of coma can be reduced by following changes in the tilt during one rotation of the disk, and high-quality signal recording or reproduction can be performed.

Further, according to the second solution of the present invention, focus control is performed by uniformly driving a plurality of voice coil actuators arranged at positions facing each other with the focusing lens holder in between, based on the focus error, Since parallel control of the focusing lens is performed by non-uniformly driving based on the angular error, both types of control can be realized using a common voice coil actuator, and the configuration can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention, showing the internal structure of an optical head. FIG. 2 is a longitudinal sectional view showing the internal structure of the tilt error detector 36 of FIG. 1. FIG. 3 is a diagram showing image formation on the photodetector 41 of FIG. 2. FIG. 4 is a block diagram showing a configuration example of a tilt control circuit using the output of the photodetector 41 of FIG. 2. FIG. 5 is a perspective view showing another embodiment of the present invention, showing the internal structure of the optical head. FIG. 6 is a longitudinal sectional view showing the configuration of a tilt error detector provided in the lens holder 66 of FIG. 5. FIG. FIG. 7 is a diagram showing image formation on the photodetector 106 of FIG. 6. FIG. 8 is a block diagram showing a configuration example of a tilt control circuit using the output of the photodetector 106 of FIG. 6. 10.60... Optical head, 12.62... Optical head body, 14.64... Focusing lens, 16.66...
Lens holder (focusing lens holding part), 18.6872・
...Spring suspension (focusing lens support mechanism), 31
,33,94,95.96.97...Voice coil motor (voice coil actuator),50.122
...Tilt control circuit, 52°114.120...Subtractor (beam angle error detection means).

Claims (2)

[Claims] (1) Beam angle error detection means for detecting an angular error of the optical axis of the beam emitted from the focusing lens of the optical head with respect to a direction perpendicular to the disk surface; and a focusing lens holder holding the focusing lens relative to the optical head body. a focusing lens support mechanism that tiltably supports the focusing lens; a voice coil actuator that tilts the focusing lens holding section; An optical disc device comprising: control means for driving and controlling the voice coil actuator to tilt the voice coil actuator. (2) a focus error detection means for detecting a focus error of a beam optical axis emitted from a focusing lens of an optical head with respect to a disk recording surface; and a beam angle error detection means for detecting an angular error of the beam optical axis with respect to a direction perpendicular to the disk surface. means, a focusing lens support mechanism for movably and tiltably supporting a focusing lens holder holding the focusing lens in the optical axis direction with respect to the optical head body, and facing each other with the focusing lens holder in between. a plurality of voice coil actuators that are arranged at positions and can be driven individually, and each generate a predetermined driving force in the optical axis direction with respect to the focusing lens holder; The focusing lens holder is moved in the optical axis direction so as to reduce the focus error to zero by driving the voice coil actuators uniformly, and the plurality of voice coil actuator driving means are moved unevenly based on the angular error. and control means for tilting the focusing lens holder so that the focusing lens becomes parallel to the disk surface by driving the optical disc device.