JPH03185632A - Drive device for optical head - Google Patents

Abstract

PURPOSE:To miniaturize and make light in weight and to improve the rigidity of a movable part by using the yoke of a magnetic circuit of an optical head provided on the fixed side of a drive device as a yoke for a magnetic circuit for tracking and/or a magnetic circuit for focusing. CONSTITUTION:A magnetic circuit formed on both sides of a holder 4 is equipped with magnets 7, 8 on the inner side of a pair of outside yokes 5, 6 and is equipped with inner yokes 9, 10 between the holder 4. Between this pair of magnetic circuit, coils 17-20 are arranged to the magnetic field formed between magnets 13, 14 provided on a carriage 1, and yoke 15, 16 and the inner yokes 9, 10. The holder 4 equipped with a condenser lens 3 is driven in an access direction to the carriage 1, and a light spot from the condenser lens can be moved to a target track. Also, a coil 27 is winded on the outer circumference of the holder 4, and this is arranged on the magnetic field formed between the magnets 13, 14, the yokes 15, 16, and the inner yokes 9, 10, and the light spot from the condenser lens 3 can be focused on the recording surface of an optical disk. Thus, the constitution of the device can be simplified and miniaturized, and the rigidity can be made high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical head driving device used in an optical information recording/reproducing device.

[Conventional technology]

An optical head positions a light beam that has passed through a required optical path from a light source onto an information recording medium on which information is recorded, such as an optical disk, and irradiates a minutely focused light spot to the information recording medium, and then uses the light reflected from the information recording medium to collect the light reflected from the information recording medium. It is used for detection, etc.

The optical head requires an access mechanism to move it to a predetermined position on the information recording medium, and information recording media such as optical disks that rotate at high speed cause vibrations.
Accordingly, a focusing mechanism is required to maintain a constant distance between the condenser lens provided in the optical head and the optical disk. Further, a tracking mechanism is required to follow the optical spot along a spiral or concentric information track on the optical disk.

As described above, since each conventional drive mechanism is provided with a separate drive mechanism, various proposals have been made to simplify the structure and reduce the weight of the entire drive device.

For example, Japanese Patent Laid-Open No. 59-11544 discloses that a magnet device is fixedly arranged to form a magnetic gap over the entire length of the optical head movement locus in the radial direction of the optical disk.
The disclosure discloses that an optical head is driven by a light focusing coil and a tracking coil without moving a heavy magnet device.

[Problem to be solved by the invention]

Nowadays, optical information recording and reproducing devices are required to have higher processing capabilities in order to cope with the increasing density of information on information recording media, and optical heads are required to have faster access speeds. To achieve this, it is necessary to make the optical head smaller and lighter, and to reduce the inertial force during movement.

However, optical heads have many functionally necessary components.
In particular, it is difficult to reduce the size and weight of the magnetic circuit because the size of the magnetic circuit cannot be made too small in order to secure a predetermined driving force. Furthermore, when driving an optical head at high speed, if the rigidity of the movable part is not sufficient, resonance will occur and drive control will not be performed properly.However, as there are many components as mentioned above, the configuration becomes complicated and it is difficult to improve the rigidity. be. Furthermore, it is not easy to assemble the optical head due to the complexity of the structure.

To specifically explain these problems using the conventional example, in the conventional example disclosed in Japanese Patent Application Laid-Open No. 59-11544 shown in FIG. A guide 60 is provided along the magnet device 59. 61 is the moving coil 6
The slider 61 supports a two-dimensional parallel spring support supporting the optical disk 4 so as to be movable along a guide.The slider 61 is provided with an optical system as necessary, and shifts the slider 61 in the radial direction of the optical disk. A coil 62 forming a magnetic circuit and a near motor is attached to the slider 61. 63 is a condensing lens. This conventional example requires a magnetic circuit related to the coil 62 for moving the entire slider 61 and a magnetic circuit related to the movable coil 64 for driving the condensing lens 63, so a large magnetic circuit is required. This makes the equipment larger.
Furthermore, the shape of the movable part cannot be made compact, resulting in low rigidity, and the expensive magnet becomes large, leading to increased costs.

The present invention has been proposed in order to solve the above-mentioned problems, and an object of the present invention is to provide an optical head drive device that makes the optical head smaller and lighter, improves the rigidity of the movable part, and improves production efficiency. It is.

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides an access mechanism for an optical head that moves the optical head and controls the position to a target position, and a condensing lens provided in the optical head. In the drive mechanism for an optical head, the drive mechanism includes a tracking mechanism that controls the position of the light beam by moving the condenser lens, and/or a focusing mechanism that controls the focus of the light beam by moving the condensing lens. The yoke of the access magnetic circuit of the henode is configured to be used as the yoke of the tracking magnetic circuit and/or the yoke of the focusing magnetic circuit.

Since the yoke is shared by each magnetic circuit in this way, the structure of the optical head can be simplified, and the movable part can be made lighter and more rigid due to its miniaturization.

〔Example〕

FIGS. 1A and 1B are a plan view and a sectional view showing a first embodiment of the present invention. This embodiment is a so-called separated optical system in which a movable optical system and a fixed optical system are separated in order to reduce the weight of the movable part. A reflecting mirror 2 is provided at the lower center of the carriage 1, and a holder 4 having a condensing lens 3 on the upper part is movably held in the carriage 1, and the light beam emitted from a fixed optical system (not shown) is reflective mirror 2
It is bent at a substantially right angle, and a light spot is irradiated onto the recording surface of an optical disc (not shown) through a condenser lens 3. A magnetic circuit is formed on both sides of the holder 4 in the access direction, and this magnetic circuit includes magnets 7.8 provided inside the pair of outer yokes 5.6.
．． An inner yoke 9 and an IO are arranged between the inner yoke 8 and the holder 4, respectively.

A coil 11. is fixed to the carriage 1 in a magnetic field formed between the magnet 7.8 and the inner yoke 9.10.
12 is arranged, and by passing a current through it, a force in the access direction is generated to drive the carriage l in the access direction and move it to the vicinity of the target track. Further, between the pair of magnetic circuits, a coil 1 is connected to a magnetic field formed between a magnet 13.14 provided on the carriage 1, a yoke 15.16, and the inner yoke 9.10.
7.18.19.20 is arranged, and by passing a current through it, a force is similarly generated in the access direction, and the holder 4 having the condensing lens 3 is driven in the access direction with respect to the carriage 1, The light spot from the condenser lens 3 can be moved onto the target track. The carriage 1 is provided with a plurality of rollers 21 at its lower part, so that the rollers 21 can smoothly translate in the access direction along two parallel guide shafts 23,24.

Next, the holder 4 is supported by two wires 25 and 26, which are stretched across the fixed part of the carriage l and the side part of the holder.
It is wrapped in . When no current is applied to the coil 27, the holder 4 maintains an intermediate position. The coil 27 has the magnetic eye 3.14, the yoke 15.16 and the inner yoke 9.
The holder 4 is placed in a magnetic field formed between the condenser lens 3 and the condenser lens 10, and by passing a current, a driving force is generated in the holder 4 in the focusing direction, and the light spot from the condenser lens 3 is focused on the recording surface of the optical disk. It is possible to perform focusing to make the image more visible.

FIG. 2 shows a second embodiment of the present invention, in which parts corresponding to those in the first embodiment are given the same reference numerals.

In this embodiment, the magnet 7. is placed below the inner yoke 9.10.
An outer yoke 5.6 having a diameter of 8 is arranged. In addition, the guide shaft 23 is arranged on the outside of the inner yoke 9, 10, etc.
It is made movable in the access direction by two rollers 21 on the other side. The other configurations are essentially the same as those of the first embodiment.

According to each of the above-mentioned embodiments, by forming large magnetic circuits fixed respectively for access and focusing/tracking as in the conventional example shown in FIG. It is possible to avoid problems such as a decrease in the magnet size and an increase in the size of the magnet.

FIG. 3 shows a third embodiment of the invention. In this embodiment, the carriage 1 is slidably supported on the guide shaft 23 by a sliding bearing 30. The coil 12 and the magnetic circuit for driving the carriage 1 are formed of one set of members. The outer yoke 5 and the magnet 8 are provided so as to pass through the inside of the coil 12. A coil 29 is wound around the holder 4 so as to pass through the rotation center 31, and an inner yoke 10 is provided inside the coil 29 so as to pass therethrough. A magnetic field is formed. A yoke 15 having a magnet [3 is provided at a position corresponding to the magnetic circuit with the holder 4 in between, and a magnetic field is formed between the inner yoke 10 and the magnet 13. Therefore, when current is applied to the coil 29, currents in opposite directions flow in both magnetic fields, and forces in opposite directions are generated. Then, the holder 4, which is rotatably supported by two upper and lower wires 28 formed in a V-shape, rotates approximately around the rotation center 31 as each wire 28 deforms, and the holder 4 is assembled. The optical lens 3 can be moved in the tracking direction. The coil 27 is wound in an L-shape and bent into an L-shape, so when a current is applied, a force is generated in the focus direction in the portion parallel to the tracking direction, and the wire 28 is moved in the focus direction. By deforming, the holder 4 having the condensing lens 3 is driven in the focus direction.

In this embodiment, since there is only one set of magnetic circuit and coil for access, the structure can be made simpler and more compact than those of the previous embodiments. Also, the coil 29.2 for driving the holder 4
7 and the access coil 12 are separated in the access direction in the magnetic field, so the length of the magnetic gap formed by the magnet 8 and the inner yoke 10 can be shortened.
Magnetic flux density can be increased. Also four wires 2
8 is disposed symmetrically with respect to the axis in the access direction, and the axial direction of the wire 28 is substantially oriented in the access direction, so that even if the carriage l is driven in the access direction and acceleration is generated in the holder 4, Most of the force acts in the direction of expansion and contraction, which is more rigid than the bending of the wire 28, so the wire 28 is less likely to deform and the position of the holder 4 in the access direction relative to the carriage 1 is less likely to change. The stability of position 3 can be achieved.

[Effects of the Invention] Since the present invention uses the magnetic circuit in common as described above, the structure of the device can be simplified and miniaturized, and the device can have a highly rigid structure. In addition, only one large magnetic circuit is required on the fixed side, and the device can be made smaller, and the movable part can be made lighter and more rigid. Furthermore, since a small piece of magnetite is sufficient, costs can be reduced.

[Brief explanation of drawings]

1 is a plan view and a sectional view showing a first embodiment of the present invention. FIG. 2 is a plan view and a sectional view showing a second embodiment of the invention. FIG. 3 is a plan view and a sectional view showing a second embodiment of the invention. The plan view and sectional view showing the third embodiment, and FIG. 4 show the conventional example. 1... Carriage 3... Condensing lens 5, 6... Outer yoke 7, 8... Magnet 9, 10... Inner yoke 11, 12... Coil 13, 14... Magnet 15・16... Yoke 17, 18, 19, 20... Coil Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. An access mechanism for an optical head that moves the optical head to control the position to a target position; a tracking mechanism that controls the position of a light beam by moving a condensing lens provided in the optical head; and/or Alternatively, in an optical head driving device including a focusing mechanism that moves the condensing lens to control the focus of the light beam, the yoke of the optical head access magnetic circuit provided on the fixed side of the driving device is connected to a tracking magnetic circuit. An optical head driving device characterized in that it is configured to be used as a yoke of a circuit and/or a yoke of a focusing magnetic circuit.