JPH01102425A - Galvanomirror - Google Patents

Abstract

PURPOSE:To obtain a galvanomirror prevented from generating disconnection or the like of a feeder at the time of high-speed operation by sing a permanent magnet formed by a prescribed production process to obtain the galvanomirror with structure omitting power supply to the movable part. CONSTITUTION:Alloy consisting of Nd, Fe and B as basic components is converted into a mixed state of crystal and amorphous by melt spunning method and ground to form magnetic powder and the magnetic powder is cylindrically molded by hot compacting processing and magnetized with multipoles divided at least into 4 poles in the radial direction to obtain the movable permanent magnet 102. A back york consisting of a soft magnetic material such as Fe is engaged with the inner peripheral part of the magnet 102 and a reflection mirror 101 is fixed on the back yoke 103 at 45 deg. angle from the cylindrical shaft of the movable part. The movable part is supported by two or more ball bearings 105 and its outer wheel is fixed on the movable part through a movable sleeve 104. A neutral holding permanent magnet 104 and a holding magnet 203 are arranged on the outside of the magnet 102 and one or more electromagnets each of them consists of magnetic poles 204, 206 or the like for generating a magnetic field controlling the rotational motion of the movable part is arranged on the outside of the magnet 102.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a galvanometer mirror used for tracking control of a laser beam of an optical memory &1H.

[Conventional technology]

Conventionally, many lens actuators used in optical heads of optical memory devices have a coil as a movable part, as shown in Japanese Patent Laid-Open No. 57-210456.

[Problem that the invention seeks to solve]

However, with conventional technology, depending on the power feeding method to the moving coil, the power feeding line may interfere with high-speed operation.
This causes problems such as disconnection of the power supply line and deterioration of the adhesive due to overheating of the coil, such as coil deformation. In addition, in order to find the optimum specifications for the coil (number of turns, linearity, etc.), cut-and-try operations are often repeated (and changing the coil specifications leads to a change in the mass of the moving part, making it difficult to convert into KIF).

The present invention is intended to solve these problems, and its purpose is to provide a tracking actuator for the movable part when the optical head has a separate structure in order to increase the speed of the optical memory device. The goal is to use permanent magnets to construct a galvanometer mirror that has a highly rigid structure and does not require power supply to moving parts, thereby realizing high-speed optical memory devices.

[Means for solving problems]

(1) The galvanomirror of the present invention is a galvanomirror having a structure in which a permanent magnet is a part of a movable part as a tracking control means for a laser beam of an optical memory device.(a) An alloy whose basic composition is Nd1Fes and B, By using the melt span method, the magnetic powder obtained by mixing crystals and amorphous amorphous is softened and pulverized is placed in a mold, subjected to hot consolidation treatment, made into a cylindrical shape, and multi-polarized with at least four divisions or more in the radial direction. a movable permanent magnet (b); a back yoke made of a soft magnetic material such as iron that is engaged with the inner circumferential portion of the movable permanent magnet; 45
(d) A reflecting mirror (d) fixed at an angle of 0.degree.;
A support mechanism (e) having a structure in which the outer rings of two or more ball bearings are engaged with a sleeve made of the same material as the support shaft that is engaged with the inner ring of the ball bearing, and the movable part is fixed to the sleeve. A neutral holding permanent magnet and a holding magnetic pole (f) provided outside the movable permanent magnet as means for maintaining the neutral position of the movable part.A magnetic field for controlling the rotational movement of the movable part provided outside the movable permanent magnet. It is characterized by consisting of one or more electromagnets provided as means for generating.

〔Example〕

The present invention will be explained in detail below based on one embodiment.

FIG. 1 is a plan cross-sectional view of a galvanometer mirror of the present invention, in which a reflecting mirror 101 is a movable permanent magnet 10 of Nd-Fe-B system.
2. The ball bearings 106, 1 are integrated with the back yoke 103 and the movable sleeve 104 and are rotatable.
The outer ring of 08 is glued to the movable sleeve. The back yoke and the movable sleeve are a close fit, and the mirror holder 107 is bonded to the back yoke and the movable sleeve. The support shaft 108 is engaged with the inner ring of the ball bearing, tightened in the thrust direction by a fixing nut 109, and preloaded in the thrust direction by a preload collar 110. According to the structure of this embodiment, even if the support shaft expands and contracts due to thermal expansion, the movable sleeve is made of the same material as the support shaft, so that the reflecting mirror does not fall. For example, in the case of an application example as shown in FIG. 4 (described in detail later), even a small displacement of the reflecting mirror in the direction of the support shaft has little effect, but tilting of the reflecting mirror has an extremely large effect.

FIG. 2 is a sectional view of the movable mechanism of the galvanometer mirror of the present invention, in which a permanent magnet 2 for neutralization is used as a means for neutralization of the movable part.
01, holding & i-poles 202, 203 are provided. By moving the neutral holding permanent magnet and holding magnetic pole left and right (as shown in Figure 2), alignment during assembly becomes easier and more effective than when neutral holding is done by means such as springs. It is. The electromagnet has a magnetic pole 204 and a coil 205
, a magnetic pole 20B, and a coil 207, and by controlling the current flowing through the coils 205 and 207, the rotation angle of the movable part can be controlled. The movable permanent magnet 102 is magnetized into eight poles as shown in the figure. The number of magnetized poles is considered to be 2°4.8.8tJi, but it is difficult to realize two poles, and when using the neutral holding mechanism of this embodiment, six or eight poles are easiest to make.
In this embodiment, the back yoke has eight poles, which can reduce the weight of the back yoke.

FIG. 3 shows the manufacturing process of the movable permanent magnet 102. N
A ribbon with a mixed state of crystal and amorphous is created using an alloy with the composition of d*5 Feas, tBa, and s using the melt-spun method, and the ribbon is crushed and the resulting magnetic powder is placed in a circular mold and hot consolidated. processed. The maximum energy product of the permanent magnet (BH) m a X s coercive force t Hc s residual magnetic flux density Br is (BH) max = 13 [: MGO
e]iHc =8.5 [kOel Br ==7.9 [kG] were obtained. With the permanent magnet obtained in this way,
By driving the galvano mirror, the moving parts can be made smaller and
The weight is reduced, the high-speed response is improved, and the cost is also reduced.

FIGS. 4(a) and 4(b) are schematic diagrams of the optical system of an optical measurement device using the galvanometer mirror of the present invention. The laser beam is then swung to a laser beam B, and the direction of the laser beam is further changed using a fixed mirror 403 fixed to a linear motor 402 to perform a tracking operation on the disk 404. Focusing is performed by moving the objective lens 406 up and down by a lens focusing actuator 405 mounted on a linear motor.

(Effects of the Invention) As explained above, according to the present invention, by using permanent magnets in the movable part, it is possible to realize a galvanomirror with a structure that does not require power supply to the movable part, and during high-speed operation. There is no need to worry about llr # of the power supply line, etc., and it is possible to avoid the coil deforming due to heat generation and coming into contact with the magnetic circuit.
Even if the coil specifications are changed, the mass of the moving part does not change, so design changes can be made easily. Further, by using an Nd-re-B electromagnet as the cylindrical movable permanent magnet, the movable part can be made smaller and lighter. In this way, it is possible to obtain a galvanometer mirror with excellent high-speed response and high reliability. Furthermore, since a permanent magnet is used as the neutral holding means for the movable part, adjustment after assembly is easier and more accurate than with the conventional method using springs. Furthermore,
In the optical system having the configuration shown in FIG. 4, since the cross-sectional shapes of the laser beams A and B do not change, the tracking range can be widened by using the galvanometer mirror of the present invention. Since the parts that engage with the ring are made of the same material, the reflective mirror hardly falls due to thermal expansion of the parts.

[Brief explanation of the drawing]

FIG. 1 is a plan cross-sectional view of the galvano mirror of the present invention. FIG. 2 is a front cross-sectional view of the galvano mirror of the present invention. (b) is a schematic diagram of the optical system of the optical memory 1IW1 when the galvanometer mirror of the present invention is used. Applicant: Seiko Epson Corporation Figure 3 (^) #J, 2! Figure 4

Claims (1)

[Claims] (1) In a galvanometer mirror having a structure in which a permanent magnet is a part of the movable part as a tracking control means for a laser beam of an optical memory device, (a) neodymium (Nd), iron (Fe), and boron (
B) The alloy having the basic composition is made into a mixed state of crystals and amorphous by using the melt-span method, and the resulting magnetic powder is placed in a mold and hot-consolidated to form a cylinder, and the magnetic powder is pulverized into a cylindrical shape with at least four cylindrical shapes in the radial direction. (b) A back yoke made of a soft magnetic material such as iron that is engaged with the inner circumference of the movable permanent magnet. (c) The back yoke and the movable permanent magnet. (d) a reflecting mirror fixed at an angle of 45° with respect to the cylindrical axis of the movable part; (d) at least two mirrors that rotatably support the movable part consisting of the reflecting mirror, the back yoke, and the movable permanent magnet;
(e) A support mechanism having a structure in which a sleeve made of the same material as the support shaft, which engages with the inner ring of the ball bearing, is engaged with the outer ring of one or more ball bearings, and the movable part is fixed to the sleeve. A neutral holding permanent magnet and a holding magnetic pole (f) provided outside the movable permanent magnet as a means for holding the neutral position of the movable part; 1. A galvanometer mirror comprising at least one electromagnet provided as a means for causing the galvanometer to move.