JPH11134685A - Optical information recording/reproducing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly enable fine adjustable tracking by using a device for finely adjusting the incident angle of a laser beam on the objective optical system of a magnetooptical disk by means of a deflecting means such as a galvano-mirror. SOLUTION: In this optical information recording/reproducing head, a light beam transmitted from a laser beam source is made to be a parallel beam, thereafter, it is made incident on an objective optical system through a deflecting means 26 and converged on an optical disk. An afocal relay optical system composed of a relay lens group and an imaging lens group is arranged between the deflecting means and the objective optical system, the vicinity of the deflection plane of the deflecting means and the principal plane position of the objective optical system are made to be almost a conjugate relation, a transmissive coating for a parallel light beam is performed in a first area of the incident plane 261 of a wedge-like prism 260 consisting a deflection member, a reflection coating for a transmissive light beam is performed on the wedge plane of the wedge-like prism through it, an antireflection coating, transmitting a reflected light beam by the reflection coating from a second area being not overlapped on the first area of the incident plane, is performed on the second area, the transmitted laser beam from the second area is detected by a photodetector 50 and the turning amount of the incident being the deflection plane of the deflecting means is detected.

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 and then deflect the light. 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 the deflecting member of the deflecting means is formed of a wedge-shaped prism.
A transmission coat that transmits a part of the parallel light flux is applied to a first area of the incident surface of the wedge prism, and a reflection coat that reflects the light flux transmitted through the transmission coat is applied to the wedge surface of the wedge prism. An anti-reflection coat is applied to the second area to emit a light beam reflected by the reflection coat from a second area of the incident surface that does not overlap the first area, and a laser light beam emitted from the second area Is detected by a photodetector to detect the amount of rotation of the incident surface, which is the deflecting surface of the deflecting means.

[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, referring to FIGS. 6 to 11, the present invention can be applied to the disk drive device 1 configured as described above.
A configuration for detecting the amount of rotation of the deflection surface of the deflection mirror will be described. In this modification, a deflection mirror prism 260 is used instead of the above-described deflection mirror 26.

FIG. 6 is an optical layout diagram showing the configuration of an optical system in which a detection device is incorporated. 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. The vertical direction in FIG. 6 and the direction perpendicular to the paper surface in FIG. 7 are the tracking directions.

The parallel light beam emitted from the light source module 7 is applied to a deflecting mirror prism 26 and is deflected in its traveling direction. As will be described in detail later, the deflecting mirror prism 260 has a transmission film / semi-transmission film region formed on the surface, reflects a part of the incident light beam on the surface, transmits a part of the surface, and transmits the inside of the deflecting mirror prism 26. To reflect light. Similarly to the above-described deflecting mirror 26, the deflecting mirror prism 260 has a structure that can slightly rotate about the rotation axis O1 as a rotation center. This rotating operation is performed by a galvano motor (not shown), and the deflecting mirror prism 260 forms a so-called galvano mirror.

The parallel light beam B2 reflected by the deflecting mirror prism 260 enters the first relay lens 29 and becomes convergent light. The first relay lens 29 and the second relay lens 30 are arranged so that their focal positions coincide with each other, and the center of rotation of the deflecting mirror prism 260 (the rotation axis O
The relay lens system is configured such that the relationship between 1) and the main plane (entrance pupil position) of the objective lens 10 is a so-called conjugate relationship. Therefore, even if the deflecting mirror prism 260 rotates and the reflected parallel light flux B2 is tilted with respect to the optical axis at the center of the design, the parallel light flux incident on the objective lens 10 does not shift only by changing the incident angle, and the objective light is not shifted. The configuration is such that vignetting of light incident on the lens 10 can be prevented. As shown in FIG. 7, the light flux returned to the parallel light flux by the second relay lens 30 is reflected by the rising mirror 31 and enters the objective lens 10. The hemispherical solid immersion lens (SI
L) 11 is disposed integrally with the objective lens 10,
The light beam converged by the objective lens 10 is applied to the optical disc 2 as a finer evanescent light beam.

In the optical system having the above configuration, the configuration of the detection device will be described with reference to FIGS. As shown in FIG. 9, the deflecting mirror prism 260 has a wedge shape,
The front surface 261 and the back surface 262 are non-parallel. The surface 261 of the deflecting mirror prism 260 has a semi-transmissive film region 26
0a and a permeable membrane region 260b are formed. The back surface 262 is provided with a reflective coat.

A part of the parallel light beam B1 incident on the deflecting mirror prism 260 is reflected by the semi-transmissive film area 260a and is incident on the first relay lens 29 as a light beam B2. Further, a part of the parallel light flux B1 is partially
Through the back surface 262 of the deflecting mirror prism 260.
Thus, the light is reflected toward the transmission film region 260b of the surface 261. The transmitted light beam B4 reflected by the back surface 262 and transmitted through the transmissive film region 260b is refracted by the front surface 261 and becomes light detector 50
Irradiation. As shown in FIG. 8, the photodetector 50 includes a light receiving element 5 having an area divided into two in the direction in which the transmitted light beam B4 moves by the rotation of the deflecting mirror prism 260.
0a, 50b are formed, and the light receiving elements 50a, 50b
The position of the transmitted light beam irradiated on the photodetector 50 can be detected by the differential output of the electric signal output from the terminal b.

The returning light flux reflected from the optical disk 2 and returned is deflected by the deflecting mirror prism 26 in the same manner as the forward light.
The light enters the semi-transmissive region 260a of the surface 261 of the zero. The only light beam required here is the reflected light beam reflected by the semi-transmissive film region 260a,
The transmitted light flux transmitted through the semi-transmissive film area 260a after being reflected at 61 and emitted from the deflecting mirror prism 260 is unnecessary light. Therefore, the unnecessary light is emitted as an unnecessary light flux B5 in a direction that does not affect the detection optical system (not shown).

FIGS. 10 and 11 are diagrams showing changes in the light flux when the deflecting mirror prism 260 is rotated by θ. When the deflecting mirror prism 260 rotates by a rotation angle θ with respect to the reference optical axis, the amount of change in the reflection angle of the parallel light flux B2 reflected by the semi-transmissive area 260a becomes 2θ and is obliquely incident on the first relay lens 29. . Therefore, the light flux of the relay lens system formed by the first relay lens 29 and the second relay lens 30 moves in a direction parallel to the paper surface. At this time, the transmitted light flux B4 transmitted through the semi-transmissive film region 260a on the front surface 261 of the deflecting mirror prism 260, reflected on the back surface 262, and further emitted from the transmissive film region 260b on the front surface 261 is also rotated by the rotation of the deflecting mirror prism 260. The light beam B4 moves in a direction parallel to the paper surface of FIG. 10, and the position of the light beam B4 irradiated on the photodetector 50 changes (see FIG. 11).

The photodetector 50 is a two-divided element having light receiving elements 50a and 50b. If the transmitted light beam B4 is set at the reference position shown in FIG. 6 so as to be located at an intermediate position between the light receiving elements 50a and 50b (FIG. 8). 6), the electric signal output of the light receiving elements 50a and 50b is different due to the movement of the transmitted light beam B4.
It is possible to know the change in the position of the light beam from the reference optical axis shown in (1), and to detect the rotation angle of the deflecting mirror prism 260 in proportion thereto.

[0026]

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 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 with a simple configuration, and accurate fine movement tracking can be performed. 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 deflecting mirror prism and a photodetector.

FIG. 7 is a diagram illustrating an optical path until a light beam emitted from a relay lens system enters an optical disk.

FIG. 8 is a diagram showing the position of a beam irradiated on the photodetector in the state of FIG.

FIG. 9 is a diagram showing a structure of a deflecting mirror prism and an optical path of an incident light beam.

FIG. 10 is a diagram for explaining a change in the position of a light beam incident on the photodetector when the deflection mirror prism is rotated.

FIG. 11 is a diagram showing the position of a beam irradiated on the photodetector in the state of FIG.

[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 Light Detector 50a, 50b Light Receiving Element 260 Deflection Mirror Prism 260a Semi-Transmissive Film Area 260b Permeable membrane area 261 Front 262 Back

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 deflecting member of the deflecting means is constituted by a wedge-shaped prism, and a first area of the incident surface of the wedge-shaped prism is provided with a transmission coat for transmitting a part of the parallel light flux, and the transmission coat is applied through the transmission coat. A reflection coat for reflecting the transmitted light beam is applied to the wedge surface of the wedge-shaped prism, and the light beam reflected by the reflection coat is emitted from a second area of the incident surface that does not overlap the first area. An anti-reflection coating is applied to the second region, and a laser beam emitted from the second region is detected by a photodetector to detect the amount of rotation of the incident surface, which is the deflecting surface of the deflecting means. An optical information recording / reproducing head characterized in that: