JPH11134683A - Optical information recording / reproducing head - Google Patents

Abstract

(57) [Summary] (Problem corrected) [PROBLEMS] To determine the angle of incidence of a laser beam on an objective optical system provided at the tip of a coarse movement arm that moves in a direction intersecting a track of a magneto-optical disk having a high surface recording density. A fine movement tracking device that makes fine adjustments by a deflecting means such as a mirror enables accurate fine movement tracking. SOLUTION: An optical information recording / reproducing head which converts a light beam emitted from a laser light source into a parallel light beam, enters an objective optical system via a deflecting device 26, and condenses it on an optical disk. An afocal relay optical system consisting of a relay lens group and an imaging lens group is arranged so that the vicinity of the deflecting surface of the deflecting means and the main plane position of the objective optical system have a substantially conjugate relationship. The one-dimensional optical position detector 50 receives the laser beam separated by the light beam separating means 60 for separating the laser beam near the convergence point of the laser beam between the lens groups, and detects the amount of rotation of the deflecting surface of the deflecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing head, and more particularly to a technique for detecting a deflection amount of a head for performing fine movement tracking of an optical disk by deflecting a laser beam.

[0002]

Recently, the areal recording density is 1
Magneto-optical disk devices exceeding 0 Gbit / (inch) ² are being developed. In this apparatus, the angle of incidence of a laser beam on an objective optical system provided at the tip of a coarse movement arm that rotates, for example, in a direction intersecting the track of the magneto-optical disk is finely adjusted by a deflecting means such as a galvo mirror, and the fine movement is performed. It is considered that tracking is accurately performed at a narrow track pitch level of, for example, 0.34 μm. In this case, in order to realize fine movement tracking, it is necessary to detect the mirror rotation amount of the galvo mirror.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and a first aspect of the present invention is to convert a light beam emitted from a laser light source into a parallel light beam, An optical information recording / reproducing head for causing the light to enter an objective optical system via an optical disk and condensing the light on an optical disk, wherein an afocal relay comprising a relay lens group and an imaging lens group is provided between the deflecting means and the objective optical system. An optical system is arranged so that the vicinity of the deflecting surface of the deflecting means and the main plane position of the objective optical system have a substantially conjugate relationship, and a laser beam between the relay lens group and the imaging lens group. Is provided near the convergence point of the laser beam, and the laser beam separated by the beam separating means is received by a one-dimensional optical position detector to thereby adjust the deflection of the deflecting means. Characterized in that to detect the amount of rotation of the surface.

[0004]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, near-field recording (NFR: near) has been proposed in response to a demand for an external storage device accompanying the recent advances in hardware and software related to a computer, particularly a demand for a large storage capacity. field recor
An outline of a magneto-optical disk recording / reproducing apparatus using a recording / reproducing method called a technique will be described with reference to FIGS.

FIG. 1 is an overall schematic diagram of the optical disk device. An optical disk 2 is mounted on a rotating shaft of a spindle motor (not shown) in the disk drive device 1. On the other hand, a rotating (coarse movement) arm 3 for reproducing or recording information on the optical disk 2 is mounted so as to be parallel to the recording surface of the optical disk 2. This rotating arm 3
Is rotatable about a rotation shaft 5 by a voice coil motor 4. A floating optical head 6 having an optical element mounted thereon is mounted on a tip of the rotating arm 3 facing the optical disk 2. In addition, the rotating arm 3
A light source module 7 having a light source unit and a light receiving unit is disposed in the vicinity of the rotation shaft 5 and is configured to be driven integrally with the rotating arm 3.

FIGS. 2 and 3 illustrate the distal end portion of the rotating arm 3, and particularly illustrate the floating optical head 6 in detail. The floating optical unit 6 is attached to the flexure beam 8 and is arranged to face the optical disc 2. The flexure beam 8 is fixed to the rotating arm 3 at the other end, and presses the floating optical unit 6 at the distal end portion in a direction in which the floating optical unit 6 comes into contact with the optical disc 2 by the elastic force of the flexure beam 8.

The floating optical unit 6 includes a floating slider 9, an objective lens 10, and a solid immersion lens (S
IL) 11 and a magnetic coil 12, and functions to converge a parallel laser beam 13 emitted from the light source module 7 onto the optical disc 2. A rising mirror 31 is fixed to the tip of the rotating arm 3 to guide the laser beam 13 to the floating optical unit 6. Objective lens 1 by rising mirror 31
The laser light flux 13 incident on 0 is converged by the refraction of the objective lens 10. A solid immersion lens (SIL) 11 is disposed near the light-collecting point.
The convergent light is applied to the optical disc 2 as finer evanescent light 15.

A magnetic coil 12 for recording in a magneto-optical recording system is formed around a solid immersion lens (SIL) 11 facing the optical disk 2. It can be applied on the surface. This evanescent light 1
5 and the magnetic coil 12 enable high-density recording and reproduction on the optical disk 2. The floating optical unit 6 floats by a very small amount due to the airflow generated by the rotation of the optical disk 2 and follows the surface runout of the optical disk 2. For this reason, focus control (focus servo) of the objective lens, which is required in the conventional optical disk device, is not required.

The light source module 7 mounted on the rotating arm 3 and the light beam guided to the floating optical unit 6 will be described in detail below with reference to FIGS. The rotating arm 3 has a floating type optical unit 6 mounted at the tip and a driving coil 1 for driving a voice coil motor 4 at the other end.
6 is fixed. The drive coil 16 is a flat coil, and is inserted and arranged in a magnetic circuit (not shown) with a gap. The rotating shaft 5 and the rotating arm 3 are provided with a bearing 17,
When the current is applied to the drive coil, the rotation arm 3 can be rotated about the rotation shaft 5 by the electromagnetic action with the magnetic circuit.

The light source module 7 mounted on the rotating arm 3 has a semiconductor laser 18, a laser drive circuit 19,
Collimating lens 20, composite prism assay 21, laser power monitor sensor 22, reflection prism 2
3, a data detection sensor 24 and a tracking detection sensor 25 are arranged. The laser beam in a divergent beam state emitted from the semiconductor laser 18 is converted into a parallel beam by the collimating lens 20. The cross-sectional shape of the parallel light beam is an elliptical shape due to the characteristics of the semiconductor laser 18, and it is inconvenient to narrow the light beam onto the optical disk 2 minutely. Therefore, the cross-sectional shape of the parallel light beam is shaped by making the parallel light beam having an elliptical cross section emitted from the collimating lens 20 enter the composite prism assay 21.

The entrance surface 21a of the composite prism assay 21
Has a predetermined slope with respect to the incident optical axis. By refracting the incident light, the cross-sectional shape of the parallel light beam can be shaped from an oval shape to a substantially circular shape. The shaped laser beam travels through the complex prism assay 21 and enters the first half mirror surface 21b. The first half mirror surface 21b transmits information obtained from the optical disk 2 to the data detection sensor 24 and the tracking detection sensor 25.
However, on the outward path, it serves to separate the light beam to the laser power monitor sensor 22 for detecting the output power of the laser emitted from the semiconductor laser 18.

Since the laser power monitor sensor 22 outputs a current proportional to the intensity of the received light, the output of the semiconductor laser 18 can be stabilized by feeding back this output to a laser power control circuit (not shown). . The laser beam 13 having a substantially circular cross-sectional shape and emitted from the composite prism assay 21 is applied to the deflecting mirror 26, and the traveling direction of the laser beam 13 is changed. The deflecting mirror 26 is attached to a galvano motor 27 having a rotation center about an axis perpendicular to the plane of the paper, and can deflect the laser beam 13 by a small angle in a direction parallel to the plane of the paper.

The galvano motor 27 is provided with a deflection mirror position detection sensor 28 for detecting the rotation angle of the deflection mirror 26. The laser beam 13 reflected by the deflecting mirror 26 is transmitted to the first relay lens 29 and the second relay lens 29.
After passing through a relay lens (imaging lens) 30, the light is reflected by a rising mirror 31 and reaches the floating optical unit 6. The first relay lens 29 and the second relay lens 30 make the relationship between the reflection surface of the deflecting mirror 26 and the pupil surface (principal plane) of the objective lens 10 arranged in the floating optical unit 6 into a conjugate relationship. That is, a relay lens optical system is formed. That is, when the condensed beam on the optical disk 2 is slightly deviated from a predetermined track, the deflecting mirror 26 is slightly rotated to tilt the laser beam 13 incident on the objective lens 10 to move the focal point on the optical disk 2. Correction. However, when performing focus correction with this method,
If the optical distance between the deflecting mirror 26 and the objective lens 10 is long, the amount of movement of the laser beam 13 incident on the objective lens 10 increases, and it may not be possible to enter the objective lens 10.

In order to avoid such a phenomenon, the first relay lens 29 and the second relay lens 30
The relationship between the reflection surface of the deflecting mirror 26 and the pupil surface of the objective lens 10 is set to be a conjugate relationship, and even if the deflecting mirror 26 rotates, the laser beam 13 incident on the objective lens 10 does not move, Tracking control is made possible. The access operation over the inner circumference / outer circumference of the optical disk 2 is performed by rotating the rotating arm 3 by the voice coil motor 4, and only minute tracking control is performed by rotating the deflection mirror 26.

The return laser beam 13 reflected from the optical disk 2 and returning returns to the deflecting mirror 2 in a direction opposite to the forward path.
The reflected light is incident on the composite prism assay 21.
Thereafter, the light is reflected by the first half mirror surface 21b and travels to the second half mirror surface 21c. The second half mirror surface 21c generates transmitted light directed to the tracking detection sensor 25 and reflected light directed to the data detection sensor 24, and separates the laser beam on the return path. The laser beam transmitted through the second half mirror surface 21c is applied to the tracking detection sensor 25, and outputs a tracking error signal.

On the other hand, the laser beam reflected by the second half mirror surface 21c is polarized and separated by the Wollaston prism 32, converted into convergent light by the condensing lens 33, and then reflected by the reflecting prism 23 to be detected by the data detection sensor. 24. The data detection sensor 24 has two light receiving areas, and receives two polarized beams polarized and separated by the Wollaston prism 32 to read data information recorded on the optical disk 2 and output a data signal. To be precise, the tracking error signal and the data signal are generated by a head amplifier circuit (not shown) and sent to a control circuit or an information processing circuit.

Next, with reference to FIG. 6 to FIG. 9, a description will be given of a detection device for detecting the amount of rotation of the deflection surface of the deflection mirror 26, which is applicable to the disk drive device 1 configured as described above. FIG. 6 is an optical arrangement diagram showing the arrangement of the detection device. FIG. 6 is a diagram when the light beam is on the optical axis at the center of design. FIG. 7 is a diagram of the detection device viewed from the direction of arrow A in FIG. In FIG. 6, the vertical direction,
In FIG. 7, the direction perpendicular to the paper is the tracking direction.

The parallel light beam applied to the deflecting mirror 26 is
The traveling direction is deflected by the reflection coat applied to the surface of the deflection mirror 26. As described above, the deflecting mirror 26 has a structure capable of slightly rotating about the rotation axis O1. This rotating operation is performed by a galvano motor (not shown), and the deflecting mirror 26 has a so-called galvano mirror configuration.

The parallel light beam reflected by the deflecting mirror 26 enters the first relay lens 29 and becomes convergent light. First
The relay lens 29 and the second relay lens 30 of
The focal positions are coincident, and the relay lens system is set such that the relationship between the rotation center (rotation axis O1) of the deflecting mirror 26 and the main plane (entrance pupil position) of the objective lens 10 is a so-called conjugate relationship. ing. Therefore, even if the parallel light flux reflected by rotation of the deflecting mirror 26 is tilted with respect to the optical axis at the center of design, the parallel light flux incident on the objective lens 10 does not shift but only changes the incident angle. This configuration can prevent vignetting of incident light. As shown in FIG. 7, the light beam that has exited the second relay lens 30 and has been returned to the parallel light beam is reflected by the rising mirror 31 and enters the objective lens 10. A hemispherical solid immersion lens (SIL) 11 is disposed integrally with the objective lens 10 near the converging point of the objective lens 10.
The light flux converged by the light is irradiated on the optical disc 2 as a finer evanescent light flux.

In the optical system having the above configuration, the detection device has the following configuration. The first relay lens 29 and the second
Near the convergence point of the laser beam between the first relay lens 29 and the second relay lens 30.
When the focal lengths of the two lenses 29 and 30 are substantially equal to each other, the separation prism 6 having the semi-transmissive film 60A at
0 is arranged, a part of the light beam on the outward path is separated and irradiated on the photodetector 50. The photodetector 50 has a non-divided light receiving element 50S for detecting the position of one-dimensional light in the direction in which the light beam SP moves by the rotation of the deflection mirror 26. The position of the light beam SP applied to the light detector 50 can be detected based on the electric output of the light receiving element 50S. Therefore, the amount of rotation of the deflection mirror 26 can be detected. Note that the light flux transmitted through the semi-transmissive film 60A of the separation prism 60 is, as described above, the second relay lens 30, the rising mirror 31, the objective lens 10,
The optical disk 2 is irradiated via the solid immersion lens 11.

FIG. 8 is a diagram showing a change in a light beam when the deflection mirror 26 is rotated by an angle θ as compared with FIG. FIG. 9 shows the photodetector 5 when the deflecting mirror is rotated.
FIG. 9 is a diagram for explaining a position of a light beam incident on 0, as viewed from an arrow B in FIG. 8. The amount of change in the reflection angle of the parallel light beam with respect to the rotation angle θ of the deflecting mirror 26 is 2θ,
The parallel light flux is obliquely incident on the first relay lens 29. Therefore, the first relay lens 29 and the second relay lens 3
The convergence point of the laser beam between zero and zero moves in a direction parallel to the paper surface. At this time, the light beam reflected by the semi-transmissive film 60A of the separation prism 60 placed between the first relay lens 29 and the second relay lens 30 also moves, and the irradiation beam SP on the light receiving element 50S is moved. The position changes (see FIG. 9). Since the light receiving element 50S can detect the position of the one-dimensional light, the change in the position of the light beam with respect to the design center optical axis due to the rotation of the deflecting mirror 26 can be detected. Can be detected.

[0022]

As described above, according to the present invention, for example, the laser for the objective optical system provided at the tip of the coarse movement arm which moves in the direction intersecting the track of the magneto-optical disk having extremely high areal recording density. In an apparatus that performs fine movement tracking by finely adjusting the incident angle of a light beam by a deflecting means such as a galvo mirror, the deflecting means (deflection mirror 26)
, The amount of movement of the light beam can be accurately known, and accurate fine movement tracking can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic configuration of a magneto-optical disk device according to an embodiment.

FIG. 2 is a diagram showing a distal end portion of a rotating arm.

FIG. 3 is a cross-sectional view showing a floating optical unit.

FIG. 4 is a plan view showing a deflection mirror and a floating optical unit.

FIG. 5 is a side sectional view of a rotating arm.

FIG. 6 is a diagram showing an arrangement of a separation prism and a photodetector.

FIG. 7 is a diagram for explaining a position of a light beam incident on a photodetector.

FIG. 8 is a diagram showing a path of a light beam when a deflecting mirror is rotated.

FIG. 9 is a diagram for explaining a position of a light beam incident on a photodetector when a deflection mirror is rotated.

[Explanation of symbols]

2 Optical Disk 3 Rotating Arm 6 Floating Optical Unit 8 Flexure 26 Deflection Mirror 29 First Relay Lens 30 Second Relay Lens (Imaging Lens) 50 Photodetector 60 Separating Prism 60A Semi-Transmissive Film

Claims (1)

[Claims] 1. An optical information recording / reproducing head for converting a light beam emitted from a laser light source into a parallel light beam, then entering the objective optical system via a deflecting device, and condensing the light beam on an optical disk. An afocal relay optical system composed of a relay lens group and an imaging lens group is arranged between the objective optical system, and the vicinity of the deflecting surface of the deflecting unit and the main plane position of the objective optical system have a substantially conjugate relationship. And a light beam separating means for separating the laser light beam near the convergence point of the laser light beam between the relay lens group and the imaging lens group. An optical information recording / reproducing head, wherein the amount of rotation of the deflecting surface of the deflecting means is detected by receiving light with the optical position detector.