JPH1173673A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device capable of improving detection accuracy by lessening the deterioration of the wave front aberration of a laser beam. SOLUTION: This optical disk device has a beam shaping prism 29 for magnifying and shaping the laser beam emitted from a semiconductor laser 27 in a prescribed direction, a galvanomirror 23 for deflecting the laser beam shaped by the beam shaping prism 29 in a radial direction of the optical disk 21 and an objective lens 26 for converging the deflected laser beam to the information recording surface 21a of the optical disk 21. The device described above aligns the beam magnifying direction of the beam shaping prism 29 and the deflection direction of the galvanomirror 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises shaping means for shaping a laser beam emitted from a laser light source, and deflecting means for deflecting the laser beam shaped by the shaping means in the radial direction of the optical disk. The present invention relates to an optical disk device.

[0002]

2. Description of the Related Art In recent years, magneto-optical disk devices having a surface recording density exceeding 10 Gbit / (inch) ² have been developed. In such a magneto-optical disk device, for example, the.
The beam spot is positioned on the track by performing fine movement tracking on a track formed with a narrow pitch of 34 μm. When the beam spot is positioned on the track by fine movement tracking, the angle of incidence of the beam incident on the objective optical system is changed.

[0003]

However, in such a configuration, the optical characteristics of the spot light emitted from the objective optical system and formed on the optical disk are significantly deteriorated in accordance with the angle of incidence on the objective optical system. There was a problem.

The present invention has been made in view of the above circumstances, and has as its object to provide an optical disk apparatus capable of keeping the quality of a beam incident on an optical disk constant regardless of the angle of incidence on an objective optical system. It is in.

[0005]

In order to achieve the above object, a first aspect of the present invention is a shaping means for enlarging and shaping a laser beam emitted from a laser light source in a direction of a minor axis of a cross section of the laser beam. An optical disc device comprising: a deflecting means for deflecting the laser beam shaped by the shaping means in a radial direction of the optical disc; and an objective lens for converging the deflected laser beam to an information recording surface of the optical disc. The beam expanding direction of the shaping unit and the deflecting direction of the deflecting unit are matched.

According to a second aspect of the present invention, an image forming lens is provided between the objective lens and the deflecting means so that the center of rotation of the deflecting means and the principal point of the objective lens are in a conjugate relationship. And

According to a third aspect of the present invention, in the image forming lens, the image forming optical system includes a pair of relay lenses, and the parallel light beam deflected by the deflecting means is transmitted to the objective lens via the relay lens. It is characterized by being incident as a parallel light beam.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk device according to the present invention will be described below with reference to the drawings.

In FIG. 1A, 20 is an optical system support member, 21 is a rotating optical disk, 21a is its information recording surface, and the optical disk 21 is a magneto-optical disk here. The optical system support member 20 includes a laser light source 22, a galvano mirror 23 as a rotatable deflection unit, and a light receiving unit 2.
4, carrying a reflection mirror 25 and an objective lens 26;
The laser light source 22 is roughly composed of a semiconductor laser 27, a collimator lens 28, a beam shaping prism 29, and a beam splitter 30.

The laser beam R1 emitted from the semiconductor laser 27 has a radiation angle different between the vertical direction and the horizontal direction with respect to the bonding surface of the semiconductor constituting the laser diode. Therefore, as shown in FIG. 28
As a result, the cross section of the laser beam R2, which has been converted into a parallel light beam, in a plane perpendicular to the beam traveling direction becomes elliptical.

The laser beam R 2 is expanded by a beam shaping prism (shaping means) 29 in the elliptical minor axis direction, shaped into a circular parallel light beam, and guided to the galvanomirror 23. A laser beam R3 which is the shaped parallel light beam
Is reflected by the galvanometer mirror 23 toward the reflection mirror 25 side. The direction of deflection by the galvanomirror 23 and the direction of enlargement of the beam shaping prism 29 match. The galvanomirror 23 serves to move the parallel light beam R3 in the tracking direction T of the optical disk 21.

The optical system support member 20 is provided with a wing member (not shown) in the vicinity of the front end portion for supporting the objective lens 26, and utilizes the flow of air based on the rotation of the optical disk 21 to make the front end of the optical system support member 20 more convenient. Float the portion 20a for a predetermined distance,
When the distance between the objective lens 26 and the information recording surface 21a is maintained at a predetermined distance L '(see FIG. 1B), the objective lens 26 is brought close to the information recording surface 21a, and the information recording is performed. It is reciprocated in the radial direction D (tracking direction T) while maintaining a predetermined distance L 'with respect to the surface 21a.

The objective lens 26 has a front principal point S1 and a rear principal point S2, and converges the laser beam R3 reflected by the galvanometer mirror 23 on the information recording surface 21a.
It plays a role of forming a spot light on the information recording surface 21a. The distance L from the objective lens 26 to the galvanometer mirror 23 is constant, that is, the distance L from the rotation center O1 of the galvanometer mirror 23 to the front principal point S1 of the objective lens 26.
Is assumed to be constant.

The optical system support member 20 is provided with a pair of relay lenses 36 and 37 as an image forming optical system between the rotation center O1 of the galvanometer mirror 23 and the objective lens 26. The relay lenses 36 and 37 have focuses F1 and F2
Image lens is used. The relay lens 36 is disposed at a position where one focal point F1 coincides with the rotation center O1 of the galvanometer mirror 23. The relay lens 37 has its focal point F2 coincident with the focal point F1 on the other side of the relay lens 36 and the front principal point S1 of the objective lens 26, respectively. The principal points of the relay lenses 36 and 37 are one for convenience of explanation. The principal points of the relay lenses 36 and 37 are denoted by symbols S3 and S4.

The center of rotation O1 and the front principal point S1 are conjugated by the relay lenses 36 and 37. The relay lenses 36 and 37 are connected to the galvanometer mirror 23.
Is formed on the front principal plane S1 'including the front principal point S1.

The laser beam R 3 incident on the galvanometer mirror 23 is reflected by the galvanometer mirror 23 and guided to the relay lens 36. In FIG. 1, a solid line indicates an optical path when the galvanomirror 23 is at the reference position, and a broken line indicates an optical path when the galvanomirror 23 is rotated by an angle θ from the reference position. When the galvanomirror 23 is at the reference position, the principal point S of the relay lens 36 is
The laser beam R3 is incident on the relay lens 36 in a state where 3 and the center where the light intensity distribution of the laser beam R3 has the maximum and are parallel to the optical axis O3 of the relay lens 36, and the relay lens 36 forms an imaging position E1. After convergence, the light diverges and enters the relay lens 37. Since the image forming position E1 coincides with the focal point F2 of the relay lens 37, the light beam incident on the relay lens 37 is again emitted as a parallel light beam by the relay lens 37 and guided to the reflection mirror 25.

When the galvanomirror 23 is rotated from the reference position by a predetermined angle θ, the principal point S3 of the relay lens 36 does not coincide with the center of the light intensity distribution of the laser beam R3 on the principal plane of the relay lens 36. The laser beam R3 (see the broken line) is incident on the optical axis O3 of the relay lens 36 at an angle. The laser beam R3 is once converged to the position E2 by the relay lens 36 and then diverges to the relay lens 37.
Incident on. Since the relay lens 37 and the relay lens 37 are arranged so that their focal points coincide with each other, the light beam emitted from the relay lens 37 becomes a parallel light beam again, and the central position where the light intensity distribution of the parallel light beam becomes maximum. Is incident on the objective lens 26 in such a manner as to be at the front principal point S1 of the objective lens 26.

That is, regardless of the rotation angle of the galvanometer mirror 23, the center where the intensity distribution of the laser beam R3 becomes maximum always passes through the principal point of the objective lens 26, so that the coupling efficiency of the objective lens 26 is not reduced. In addition, a spot light can be formed on the information recording surface 21a without causing a bias in the light intensity distribution.

As described above, since the rotation center O1 of the galvanometer mirror 23 and the front principal point S1 of the objective lens 26 are substantially conjugate, the light quantity distribution Q of the laser beam R3 reflected by the galvanometer mirror 23 Of the objective lens 26 with respect to the optical axis O2 of the center G1 can be eliminated (see FIG. 3). In other words, the movable range of the galvanomirror 23 can be expanded.

Further, since the laser beam R2 converted into a parallel light beam by the collimating lens 28 has an elliptical shape as shown in FIG. 2, in the short axis direction of the laser beam R2,
The influence of aberration by the collimator lens 28 is smaller than in the long axis direction. The beam shaping prism 29
Since the laser beam R2 is enlarged and shaped so that the beam diameter in the short axis direction becomes the dimension in the long axis direction and the laser beam R2 is circular, the wavefront aberration in the short axis direction is flattened and improved compared to the long axis direction. ing. In the present embodiment, since the direction of deflection by the galvanometer mirror 23 and the direction of enlargement of the beam shaping prism 29 are made to coincide with each other, even if the laser beam R3 is obliquely incident on the objective lens 26 and the wavefront aberration deteriorates, Deterioration is minimized.

That is, the deterioration of the wavefront aberration of the spot light formed on the information recording surface 21a is minimized. In other words, since the direction in which the wavefront aberration is good corresponds to the direction that greatly affects the deterioration of the wavefront aberration, the deterioration of the wavefront aberration of the spot light is two-dimensionally dispersed in the radial direction and the tangential direction of the disk, and The deterioration of wavefront aberration is minimized. That is, the optical disk 2
The quality of the beam incident on 1 is constant irrespective of the angle of incidence on the objective lens 26. in short,
According to the above-described configuration, the galvanomirror 23 can achieve both expansion of the movable range and stabilization of the optical characteristics of the spot light.

The light reflected by the spot light on the information recording surface 21a is condensed by the objective lens 26, reflected by the reflection mirror 25 toward the galvano mirror 23, and traces the original optical path again to the beam splitter. 30
And is directed toward the light receiving section 24 by the reflection surface 30 a of the beam splitter 30.

The light receiving section 24 is roughly composed of an imaging lens 32, a beam splitter 33, and detection sensors 34 and 35. Light reflected from the optical disk 21 is guided to the beam splitter 33 via the imaging lens 32, Part of the light is reflected by the reflection surface 33a of the splitter 33 and is guided to the detection sensor 34, and part of the light is transmitted through the reflection surface 33a and guided to the detection sensor 35.
5 is formed. The received light output of the detection sensor 34 is used as a detection signal of information data recorded on the information recording surface 21a, and the received light output of the detection sensor 35 is used as a detection signal of a tracking error, thereby recording on the information recording surface 21a. When the information is detected and the shift of the objective lens 26 in the tracking direction T is detected, and the parallel light flux P3 is shifted with respect to the tracking direction T, the rotation angle of the galvanometer mirror 23 is adjusted to reduce the tracking shift. Servo control is performed so as not to occur.

As described above, the light reflected by the spot where the deterioration of the wavefront aberration is minimized is detected by the detection sensors 34 and 3.
5, the detection accuracy is improved.

[0025]

As described above, according to the present invention, since the beam expanding direction of the shaping unit and the deflecting direction of the deflecting unit are matched, the wavefront aberration of the laser beam on the information recording surface is obtained. Degradation can be reduced. That is, the quality of the beam incident on the optical disc can be made constant regardless of the angle of incidence on the objective optical system, and the detection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of an optical system of an optical disk device according to the present invention, in which (a) is a schematic diagram showing the entirety, and (b) is a schematic diagram of a main part thereof.

FIG. 2 is an explanatory diagram showing a relationship between a collimating lens and a laser beam.

FIG. 3 is a light amount distribution diagram of a laser beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Optical disk 21a Information recording surface 23 Galvano mirror (deflection means) 26 Objective lens 27 Semiconductor laser (laser light source) 29 Beam shaping prism (shaping means)

Claims (3)

[Claims] 1. A shaping means for enlarging and shaping a laser beam emitted from a laser light source in a minor axis direction of a cross section of the laser beam, and deflecting the laser beam shaped by the shaping means in a radial direction of an optical disk. An optical disk apparatus comprising: a deflecting unit for causing the laser beam to converge on the information recording surface of the optical disk; and a beam expanding direction of the shaping unit and a deflecting direction of the deflecting unit. An optical disc device characterized by the above-mentioned. 2. An imaging lens arranged between the objective lens and the deflecting means so as to make a center of rotation of the deflecting means and a principal point of the objective lens have a conjugate relationship. Optical disk device. 3. The image forming lens, wherein the image forming optical system includes a pair of relay lenses, and a parallel light beam deflected by the deflecting means is incident on the objective lens as a parallel light beam through the relay lens. 3. The optical disk device according to claim 2, wherein: