JPH043332A - Actuator for optical pickup - Google Patents

Abstract

PURPOSE:To miniaturize an actuator and to improve the response performance by holding a mobile body in the floating state by repulsion between floating magnets and linearly moving it in the state free from slide friction. CONSTITUTION:When a spot reaches a target track or its vicinity, the current for access to a coil 10 is cut off, and the current for fine tracking flows again to start the tracking operation, and the spot is formed on the target track. At this time, a mobile body 1 is in the floating state by the repulsion between floating magnets 14 and 15, and consequently, it can be linearly moved in the state free from slide friction. Since the floating magnet 15 and a second yoke 13 are arranged to pierce the coil 10 and partially share a space, the actuator is miniaturized and the response performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] This invention relates to a method for maintaining the posture of an actuator of an optical pickup, particularly an actuator that moves linearly in the radial direction of an information recording disk (hereinafter referred to as "disk") for track access. This invention relates to improvements in means and driving means.

Drive means for linearly moving the optical pickup or actuator in the radial direction of the disk for track access include a torsional feed system for low-speed movement and a linear motor type for high-speed movement. In either method, the conventional attitude holding means has been a method of sliding along a sliding shaft or a method of rolling using a roller bearing. Therefore, there has been a drawback that it is difficult to meet the increasing demands for smaller size and lighter weight and to improve the response characteristics of track access.

[Structure of the Invention] In this invention, a non-contact structure is adopted in which posture maintenance for linear movement of the actuator is performed using the repulsive force of a magnet, and a driving coil and a magnet that constitute a driving means for track access operation are used. The mounting structure of the yoke that holds the yoke has been downsized. This improved the linear movement response characteristics of the actuator.

Examples of the present invention will be described below. A movable body 1 of the optical pickup includes a cylindrical body 2 and holds an objective lens 3 that bundles several light beams from a light source (not shown) onto a disk. The cylindrical body 2 is placed in the space 1a of the movable body 1 in an upper and lower direction.
It is elastically fixed via a leaf spring 4, and is movable up and down for focus control. Focus control is performed by a focus drive coil 5 disposed at the lower end of the cylinder 2, a yoke 6 fixed to the bottom of the movable body 1, and a focus drive magnet 7 fixed to the yoke 6. It will be done. 8 is a through hole for guiding the light beam from the light source into the interior of the movable body 1, and 9 is a prism for guiding the light beam to the objective lens. Prism 9 is fixed inside movable body 1 by a known method. Further, there are provided posture holding means for holding the movable body 1 in a movable state, and electromagnetic driving means for driving the movable body 1 in the horizontal direction along the disk surface for track access.

First, the electromagnetic drive means for track access operation will be explained. A coil 10 is installed in the center of the side wall of the movable body 1.
is fixed with adhesive, and a U-shaped first yoke 11 is arranged adjacent to this coil 10.
A magnet 12 extending in the longitudinal direction of the movable body 1 is fixed to the inner wall portion facing the coil 10 . And “ko”
A second yoke 13 passing through the coil 10 is fixed to the open end of the letter-shaped yoke. The electromagnetic drive means having such a configuration are arranged side by side on both sides of the movable body 1. The magnets 12 and the second yoke 13 of both electromagnetic drive means are arranged parallel to each other, and will be described in detail below. The movable body 1 held by the posture holding means is connected to the prism 9
The light beam incident on the optical axis 100 is guided along the optical axis 100 of the optical beam. Note that the first yokes 11 are each fixed to a case (not shown) of an optical pickup.

The attitude holding means is constituted by plate-shaped magnets arranged on both opposing side walls of the movable body 1 and on the second yoke 13, respectively. Approximately "U"-shaped recesses 1b are formed in both side walls of the movable body 1, and two recesses 1b are formed in each of the upper and lower upright parts 1c of the recess 111b, that is, two recesses are provided on the left and right sides of the coil 1o in the vicinity of the coil 1o. A total of four floating magnets 14, 2Il on the upper and lower sides, are fixed. On the other hand, two plate-shaped floating magnets 15 are juxtaposed on the second yoke 13, which is arranged parallel to the wall of the recess of the movable body 1. jI Nyoku 1
3 has a trapezoidal new surface as shown in the figure, and the two floating magnets 15 are placed on the upper and lower oblique sides of the movable body 1, which are opposite to the upper and lower two rows of floating magnets 14 on the movable body 1, respectively. The floating magnets 14 are fixedly facing each other. This floating magnet 15 has a constant length depending on the moving distance of the movable body 1. As shown in FIG. 3, the polarity of each floating magnet 14, 15 fixed on the movable body 1 and the second yoke 13 is such that the same poles face each other so as to repel each other, and the lines of force of each pair of upper and lower magnets are intersect to maintain the posture of the movable body 1.

In this embodiment, the floating magnets 14 are separate upper and lower plate-shaped magnets, but it is also possible to use integrally molded approximately "C"-shaped magnets with similar polarity at the upper and lower ends. It's possible.

The same applies to the opposing floating magnet 15.

[Operations and Effects of the Invention] Next, the operation will be explained. Parallel light from a light source enters a prism 9 along an optical axis 100, is reflected, and enters a lens 3. Several beams of light are bundled by the lens 3 and reach the recording surface of the disk to form a spot. Concentric or spiral tracks are formed on the recording surface. The track is formed by a series of unevenness or a series of bits. The light reflected from the recording surface passes through lens 3 again.
The light returns to the light source side, following the reverse direction of incidence. On the way to the light source, the light reaches a light receiving element by a separating optical system constituted by means such as a known half prism, and the intensity of the reflected light from the disk is converted into an electrical signal. The light receiving element is configured to be able to read the recorded signal as well as the degree of focus of the lens and the degree of deviation from the track using a generally known method.

The focus shift signal is amplified by a known focus fade pack circuit and serves to drive a focus drive coil to keep the lens 3 within a constant depth of focus from the disk. The spot deviation signal from the track is
It is amplified by a known trunk feedback circuit and applied to coil 10. The coil 1o is placed in the magnetic flux generated in the gap between the magnet 12 and the facing surface of the yoke 13,
The movable body 1 is driven in the direction of the arrow of the optical axis 100 or in the opposite direction depending on the direction in which the current is applied. The arrow direction of the optical axis 100 is set in the radial direction of the disk, that is, in the direction in which the spot crosses the track as the movable body 1 moves. Therefore, a current is applied to the coil 10 in response to the deviation of the spot from the track, thereby achieving fine tracking, that is, preventing the spot from deviation from the track.

Next, the actions to quickly reach the target truck,
That is, the access operation will be explained.

The address of the track currently being tracked is recognized by a known address reading circuit.

To quickly reach the target truck from there.

It is necessary to move the movable body 1 so that the spot crosses the track. Therefore, the fine tracking operation is interrupted immediately before movement. Then, in order to move the spot in the direction of the target track, an access current is applied to the coil 1o to drive and accelerate the movable body 1. When approaching the target truck, the direction of the current is changed to decelerate the vehicle in order to stop it. The m dynamic current is normally changed in accordance with the moving distance from the current location to the target truck, but it can also be a constant value. When the spot reaches the target track or its vicinity, the current for accessing the coil 10 is cut off, the current for fine tracking is supplied again, the tracking operation is started, and the spot is placed on the target track. is formed. The operation of the embodiment has been described above. At this time, the movable body 1 is in a floating state due to the mutual repulsive force of the floating magnets 14 and 15, and therefore can move in a straight line without any sliding friction.

In conventional structures for linear movement using this type of coil, the coil and yoke, which are the sources of driving force, and the structure for maintaining posture, that is, the movement structure using slide shafts and ball bearings, are separate. This has hindered miniaturization of the entire actuator. According to the present invention, the floating magnet 15 and the second yoke 13 are arranged in a structure that both penetrate the coil 10, and share a part of the space. This helps reduce the size of the actuator and improve response performance.

This embodiment has a structure in which the light source is located in a non-moving part. That is, an example has been described in which a light source and a light receiving element are not held inside the movable body 1 of the actuator.

It is also possible to adopt a structure in which these light sources and light receiving elements are incorporated inside the movable body 1.

As described above, according to the optical pink-up actuator according to the present invention, response characteristics are improved due to the non-contact linear movement structure, and as a result, fine tracking and access can be achieved with one actuator, thereby simplifying the tracking system. At the same time, by being smaller and lighter, there is an advantage that access speed can be increased.

Furthermore, since it is a non-contact floating structure, it has the effect of blocking the transmission of external vibrations to the movable body and stabilizing control.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a perspective view showing the inside of the movable body, and FIG. 113 is a sectional view showing the polarity of the magnet. 1... Movable body, ・Objective lens, 10... Coil, ・Magnet.・Second yoke, 14°15 ・・Floating magnet

Claims (1)

[Scope of Claims] 1. A movable body that holds an objective lens for recording or reproducing information by irradiating light onto an information recording disc and moves in the radial direction of the information recording disc, a side wall of the movable body; an electromagnetic drive means comprising a coil fixed to a portion of the movable body and a magnet disposed near the coil to cooperate with the coil to drive the movable body; a pair of yokes provided on both sides of the movable body; and each of the yokes. A movable body consisting of a magnet having two rows of upper and lower working pole surfaces fixed to the magnet, and magnets fixed to both sides of the movable body each having a working pole surface of the same polarity as the upper and lower two rows of working pole surfaces of the magnet. What is claimed is: 1. An actuator for an optical pickup comprising a posture holding means, wherein directions of lines of force of working pole surfaces of opposing magnets in two rows of upper and lower rows of the movable body posture holding means intersect with each other. 2. The actuator for an optical pickup according to claim 1, wherein the yoke is provided to penetrate the coil.