JPH11134682A - Optical information recording/reproducing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a correct fine moving tracking by providing an opening whose diameter is smaller than that of a laser luminous flux, providing photodetectors at the marginal part of the opening and detecting the peripheral part of the laser luminous flux while passing the main part of the laser luminous flux to control the deflection quantity of the laser luminous flux. SOLUTION: The angle of incidence of the laser luminous flux with respect to the objective optical system provided at the top end of an arm for coarse motion moving in a direction crossing with tracks of a magneto-optical disk having a high surface recording density is finely adjusted by the deflection means of a deflection mirror 26. The neighborhood of the deflection mirror 26 and the principal plane being the front side of the objective lens 10 is made to be roughly a conjugate relation and also a detector 50 having a rectangular opening which is smaller than the diameter of the laser luminous flux is provided in between the deflection mirror 26 and a relay lens 29. Moreover, photodetectors 50A, 50B are provided at the marginal part of the opening to receive the peripheral parts of the laser luminous flux. Thus, the quantity of deflection of the luminous flux is controlled by detecting the turning amount of the deflection mirror 26 correctly while transmitting the laser luminous flux to the relay lens 29.

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 between the deflecting surface of the deflecting means and the relay lens group. An opening having a width smaller in one direction than the diameter of the laser beam, and a photodetector provided with a light receiving portion for receiving a peripheral portion of the laser beam around the opening; Luminous flux through the relay While transmitting the lens group, it is characterized in that to detect the amount of rotation of the deflecting surface of said deflecting means by receiving the peripheral edge.

[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, a configuration of a detector for detecting the amount of rotation of the deflecting mirror 26, which is applicable to the disk drive device 1, will be described with reference to FIGS. FIG. 6 is a diagram showing an optical path from the deflection mirror 26 of the rotating arm 3 of the disk drive device 1 to the optical disk 2. In FIG. 6, the deflecting mirror 26 rotates in a direction parallel to the paper (the paper and the optical disk 2 are parallel).
The light beam incident on the deflecting mirror 26 is
6 has an elliptical shape whose diameter in the rotation axis direction is larger than the diameter in the rotation direction.

As shown in FIG. 6, the deflection mirror 26 and the first
The detector 50 is disposed between the relay lens 29 and the relay lens 29. As shown in FIG. 7, the detector 50 has a rectangular opening 50H in the center. Then, two sets of light receiving areas 50A, 50B, 50 are sandwiched by the opening 50H.
C and 50D are arranged. The light receiving regions 50A and 50B are arranged adjacent to each other along a direction parallel to the rotation direction of the deflecting mirror 26, and the light receiving regions 50C and 50D are opposed to the light receiving regions 50A and 50B with the opening 50H interposed therebetween. They are arranged adjacently.

The length of the opening 50H in the direction parallel to the rotation axis of the deflecting mirror 26 (hereinafter, this length is referred to as the opening 5
0H) is set to be smaller than the major axis (diameter in the rotation axis direction of the deflecting mirror 26) of the light beam having an elliptical cross section incident on the detector 50, and is parallel to the rotating direction of the deflecting mirror 26. (Hereinafter, this length is referred to as the height of the opening 50H) is sufficiently larger than the short diameter (diameter in the rotation direction of the deflecting mirror 26) of the light beam having an elliptical cross section incident on the detector 50. Is set to large.

Further, when the deflecting mirror 26 is at the reference position (for example, the position of the deflecting mirror where the incident angle of the light beam incident on the deflecting mirror 26 is 45 degrees), the center of the incident light beam is substantially equal to the center of the opening 50H. To match, the detector 50
Is arranged. The opening 50H is provided so that the light beam SP1 incident on the detector 50 is turned by the rotation of the deflecting mirror 26.
Is large enough in the direction in which the light beam moves, the incident light beam SP1 has a light-receiving area 50A, 50B, 50
C and 50D are received, and the central part of the light beam SP1 transmits through the opening 50H. Here, the light beam transmitted through the opening 50H has a cross-sectional shape that is not perfectly circular, but the peripheral portion of the ellipse in the major axis direction is shielded by the detector 50, so that the light beam transmitted through the opening 50H has a cross-section. The shape is substantially circular.

When the deflecting mirror 26 is at the reference position, the light receiving areas 50A, 50B, 50C, and 50D respectively receive the peripheral portions of the light beam SP1. Light receiving areas 50A and 50
By detecting the difference between the sum of the amounts of light received by C and the sum of the amounts of light received by the light receiving areas 50B and 50D, the incident light flux SP1 due to the rotation of the deflecting mirror 26 is detected.
The amount of movement on the detector 50 can be known. That is, (the output of the detector 50 corresponding to the amount of received light in the light receiving region 50A + the output of the detector 50 corresponding to the amount of received light in the light receiving region 50C)-(the output of the detector 50 corresponding to the amount of received light in the light receiving region 50B + By determining the output of the detector 50 corresponding to the amount of light received in the light receiving region 50D), the amount of movement of the incident light beam SP1 on the detector 50 can be known. Therefore, the amount of rotation of the deflecting mirror 26 can be known based on the amount of movement.
The luminous flux transmitted through the opening 50H passes through the first and second relay lenses 29 and 30 and the rising mirror 31, and
The light beam SP2 is incident on the objective lens 10 as a substantially circular light beam SP2.
As described above, since the vicinity of the rotation axis of the deflecting mirror 26 and the front main plane (entrance pupil position) of the objective lens 10 have a substantially conjugate relationship, the light beam incident on the objective lens 11 is deflected. The light enters a substantially constant position regardless of the rotation of the mirror 26.

FIGS. 6 and 7 show an example in which the light beam SP incident on the detector 50 is received by the light receiving regions 50A, 50B, 50C and 50D when the incident angle of the light beam incident on the deflection mirror 26 is 45 degrees. . When the deflecting mirror 26 is rotated clockwise in FIG. 6 from this state, as shown in FIGS. 8 and 9, the light beam SP incident on the detector 50 is turned on.
The area ratio of light received by one light receiving region 50A, 50B, 50C, 50D changes. Therefore, the sum of the signals output corresponding to the amounts of received light in the light receiving regions 50A and 50C and the sum of the signals output corresponding to the amounts of received light in the light receiving regions 50B and 50D are determined, and the difference between the two is determined. Thus, the amount of rotation of the deflection mirror 26 can be known.

[0021]

As described above, according to the present invention, for example, the laser beam 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 a device that performs fine movement tracking by finely adjusting the incident angle of the light beam by a deflection means such as a galvo mirror, the amount of movement of the light beam by the deflection means can be accurately known, and accurate fine movement tracking can be realized. it can.

[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 illustrating an arrangement of detectors and a light beam incident on the detector and a light beam transmitted through the detector when the deflection mirror is at a reference position. FIG.

FIG. 7 is a diagram for explaining positions of a detector and an incident light beam.

FIG. 8 is a diagram illustrating a light beam incident on the detector and a light beam transmitted through the detector when the deflection mirror is rotated.

FIG. 9 is a diagram illustrating a position of a light beam incident on a detector when a deflecting 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 Detector 50A, 50B, 50C, 50D Light Receiving Area 50H Opening

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 object 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 an opening having a width smaller than the diameter of the laser beam in one direction between the deflecting surface of the deflecting means and the relay lens group, and a peripheral portion of the laser beam around the opening. A light detector provided with a light receiving unit for receiving the laser beam is transmitted by the light detector to the relay lens group, and the peripheral edge of the light beam is received to reduce the amount of rotation of the deflection surface of the deflection unit. Detect An optical information recording / reproducing head characterized in that: