JPH0520708A - Optical disk device - Google Patents

Abstract

(57) [Abstract] [Purpose] A rotation angle measuring mechanism for galvano mirrors is placed in a small space to reduce the size. [Structure] A beam splitter 22 is arranged on the optical path of a laser light source 21 to divide the optical path into two. A first mirror 26, a galvanometer mirror 23, a second mirror 27, and a light receiving element 29 are sequentially arranged on the optical path of the transmitted light of the beam splitter 22. Part of the light emitted from the laser light source 21 passes through the beam splitter 22, is reflected by the first mirror 26, and reaches the galvanometer mirror 23. Galvano mirror 2
The laser light reflected by 3 travels back and forth a plurality of times between the galvano mirror 23 and the second mirror 27, reaches the light receiving element 29 while amplifying the rotation angle of the galvano mirror 23, and the rotation angle of the galvano mirror 23. Is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separate head type optical disk device using a galvano mirror.

[0002]

2. Description of the Related Art An optical disk head has a separation type head in which an actuator section for holding an objective lens and a laser oscillation section are separated, and only the actuator section moves.
There is an integrated head in which both move integrally. The former separation type head is easy to reduce in weight, and is advantageous for speeding up the tracking operation. Further, in order to further reduce the weight of the separation type head, in consideration of the fact that the tracking operation includes two different frequency regions, tracking in the low frequency region is controlled by the linear motor provided in the head, and tracking in the high frequency region is performed. It is known to use a galvano mirror separate from the head.

In this galvano-mirror type optical disk device, a galvano mirror is installed on the optical path from the laser light source to the optical head, and the optical path of the incident laser light is changed by slightly tilting the galvano mirror to control tracking. There is. The rotation angle at this time is only a few minutes,
The tilt angle of the galvanometer mirror needs to be constantly measured because it is a sufficient amount that it can be displaced under vibration conditions.

As a method of detecting the rotation angle of the galvanometer mirror with high accuracy, a non-contact optical method has been devised as shown in FIG. According to this method, the fixed mirror 2 is arranged at a position facing the galvano mirror 1 obliquely arranged with respect to the optical path L, and the light emitting element 3 provided on the side of the fixed mirror 2 emits a laser beam, By causing the mirror 1 and the fixed mirror 2 to reciprocate a plurality of times, the optical path length and the rotation angle are increased, and the light receiving element 4 detects the light. Since the rotation angle measuring mechanism of such a system is non-contact, it does not burden the driving of the Luvano mirror, and even if the light receiving element 4 has only a resolution of about ten and several μm due to the expansion of the rotation angle and the optical path length, it does not rotate. It has the advantage that corners can be detected sufficiently.

[0005]

However, considering that the rotation angle measuring mechanism is incorporated in a small-sized optical disk device, it is not possible to arrange the light emitting element and the light receiving element in the vicinity of the fixed mirror as in the above-described conventional example. It is quite difficult due to technical restrictions.

An object of the present invention is to provide a compact optical disk device equipped with a rotation angle measuring mechanism for a galvano mirror.

[0007]

In order to achieve the above-mentioned object, an optical disk device according to the present invention divides a laser beam from a laser light source into two by a light dividing member, and divides one of the two divided laser beams into a galvanometer. Light is received by a detector via a mirror, and the rotation angle of the galvano mirror is detected based on the incident position.

[0008]

In the optical disk device having the above-mentioned structure, the laser light emitted from the laser light source is split by the light splitting member, one of which is reflected on the galvano mirror and detected by the detector, and the reflection angle is the galvano mirror. The rotation angle of the galvanometer mirror is detected as a position change on the detector because it changes in proportion to the rotation angle.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a plan view of a main part of a separation type optical disk device. An outer yoke 11, a permanent magnet 12 and an inner yoke 13 are installed in parallel in the radial direction of the optical disk in a laterally symmetrical manner to form a magnetic circuit. The movable optical head is a carriage 1 having a tracking coil 14.
5 and the actuator 17 having the objective lens 16 are lined up in the front and rear direction and are connected by the leaf spring 18, and 2 in the annular structure of the tracking coil 14 and the actuator 17.
The inner yoke 13 of the book is inserted.

The inner surface of the inner yoke 13 and the carriage 15
A V-shaped groove (not shown) is engraved on the outer surface of the ball, and the ball 19 is arranged between them. This allows the carriage 1
Reference numeral 5 is movably supported in the radial direction of the optical disk, that is, along the inner yoke 14, and the actuator 17 is driven forward and backward by a linear motor composed of the tracking coil 14 and a magnetic circuit.

The optical system for sending the laser light to the optical head is arranged behind the magnetic circuit, and the beam splitter 22, on the optical path from the laser light source 21 to the optical head.
The galvanometer mirrors 23 are sequentially arranged. That is,
The transmitted light of the beam splitter 22 is guided to the rotation angle detection mechanism, and the reflected light of the half mirror 22a of the beam splitter 22 is guided to the optical head via the galvanometer mirror 23. Further, the light returning from the optical head is guided to the condenser lens 24 and the sensor 25 via the galvanometer mirror 23 and the beam splitter 22.

The rotation angle detecting mechanism is the first first mirror 26.
And the galvano mirror 23 and the two reflecting surfaces 27a and 27b.
A second mirror 27 having a reflecting surface 27a arranged in parallel with the neutral position of the galvanometer mirror 23, and a light receiving element 29 fixed to a fixed substrate 28 having a fixed elongated hole 28a as shown in FIG. And are arranged in this order on the optical path.

In the above structure, the laser light emitted from the laser light source 21 is reflected by the half mirror 22a of the beam splitter 22 and the galvano mirror 23 rotated by a predetermined angle and reaches the optical head. The laser light incident on the optical head is reflected by a mirror (not shown) and is focused on the optical disk by the objective lens 16. The laser light reflected on the disk returns to the galvanometer mirror 23 through the same path, passes through the half mirror 22a of the beam splitter 22, is condensed by the condenser lens 24, forms an image on the sensor 25, and is detected as a signal. It

The laser light emitted from the laser light source 21 and transmitted through the half mirror 22a is guided to a rotation angle detecting mechanism. That is, the laser light that has entered the galvanometer mirror 23 through the first mirror 26 is reflected multiple times between the second mirror 27 and the galvanometer mirror 23. At this time, as shown in FIG. 3, the rotation angle θ of the galvano mirror 23 is amplified every time reflection is repeated between the two mirrors 23 and 27, and the rotation angle θ is expanded to 8θ in the illustrated example. The laser light having the amplified rotation angle has a sufficient optical path length and is emitted toward the light receiving element 29.
The direction can be largely changed on the other reflecting surface 27b of the. The product of the rotation angle and the optical path length is the lateral displacement, and the rotation angle θ can be detected in the form of the light receiving position of the light receiving element 29.

Since the rotation angle detection mechanism enlarges the rotation angle, the first mirror 26 and the second mirror 2
The mounting error of No. 7 will also be enlarged. For this reason,
As shown in FIG. 3, a fixed elongated hole 28a is provided in a fixed substrate 28 having a light receiving element 29, and when the light receiving element 29 is fixed to the optical disk device main body by a screw 30, the fixing position is adjusted to fix the mirror. Installation error is offset.

[0016]

As described above, in the optical disk device according to the present invention, the laser beam is split into two by the light splitting member, and one of the laser beams is detected as the displacement of the detector through the galvanometer mirror. The rotation angle can be detected in a narrow space, a light emitting element for detecting the rotation angle is not required, and the device can be downsized.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of an optical disc device.

FIG. 2 is an explanatory diagram of a method of mounting a rotation angle detection light receiving element.

FIG. 3 is an explanatory diagram of a process of enlarging the rotation angle of the galvano mirror.

FIG. 4 is a perspective view of a conventional rotation angle detection mechanism.

[Explanation of symbols]

21 Laser light source 22 Beam splitter 22a Half mirror 23 Galvo Mirror 26, 27 mirror 29 Light receiving element

Claims (3)

[Claims] 1. A laser beam from a laser light source is split into two by a light splitting member, and one of the two split laser beams is received by a detector via a galvano mirror, and the galvano mirror of the galvano mirror is detected based on its incident position. An optical disk device characterized by detecting a rotation angle. 2. The optical disk device according to claim 1, wherein the detector detects a laser beam that reciprocates a plurality of times between a mirror arranged at a position facing the galvanometer mirror and the galvanometer mirror. 3. The optical disk device according to claim 1, wherein the detector is positionally adjustable.