JPS58137140A - Optical system driving device of optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To decrease the number of parts and to realize a simplified, small- sized structure, by providing the 1st driving means for driving an optical system in its optical-axis direction and the 2nd driving means for driving the optical system nearly at right angles to the optical-axis direction. CONSTITUTION:A magnetic circuit part 4 consists of a pole yoke 7, permanent magnet 8, and plate 9 for forming a magnetic gap between the magnet and tip of the pole yoke 7 and a magnetic field is produced in the magnetic gap in a radius direction. Then, a coil 2 is positioned at this magnetic gap and the coil 2 and magnetic circuit 4 constitute the 1st driving means. An electromagnet 10 constitute the 2nd driving means for driving an objective lens 1 nearly at right angles to its optical axis by utilizing leakage magnetic flux generated at the magnetic circuit part. Thus, the number of parts is decreased and the structure is simplified and small-sized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical system drive device in an optical information recording/reproducing device.

In an optical information recording and reproducing device, the information recording medium, such as a video disk, records the video signal by forming minute bits (indentations) in the form of a spiral track on its surface in accordance with the video signal. It is something to do. When playing such a video disc, the disc is rotated at a predetermined number of revolutions while a spot light is irradiated onto the video track, and changes in the intensity of the reflected light or transmitted light are converted into electric signals, and the video signal is generated. It is to be reproduced as a.

When playing this video disc, the irradiation light must always accurately track the recording track, so it is necessary to control the irradiation light in the radial direction of the disc, that is, in the tracking direction (tracking servo). In order to accurately converge the irradiated light onto the recording surface, it is also necessary to position the optical system in a direction perpendicular to the recording surface, that is, in the direction of the A-cush (focus servo). For this purpose, an optical system driving device is used that drives an optical system for irradiating the recording surface of the disk with a spot light in at least two directions according to a tracking error signal, a focus error signal, and the like.

Various types of optical system drive devices have been proposed in the past, but in general, those configured using separate coils and permanent magnets for each drive direction are often used. However, in such a configuration,
Due to mutual interference between each permanent magnet, the operating sensitivity is low.
This results in disadvantages such as deterioration of linearity and deterioration of linearity. Furthermore, since there are many parts, the structure is complicated and large, and assembly is troublesome.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide an optical system drive device in an optical information recording/reproducing device that has a simple structure, is easy to assemble, and can be downsized.

In the optical system driving device according to the present invention, the first and second driving means for driving the optical system in the direction of its optical axis and in the direction substantially orthogonal to the optical axis, respectively, have at least one permanent t
The structure is such that ab and b are used and magnetic fields generated by the permanent magnets at different positions are utilized.

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 and 2 are a plan view and a sectional view showing a first embodiment of the present invention. In the figure, 1 is an objective lens constituting an optical system, and a bobbin 3 around which a coil 2 is wound is attached to the objective lens 1. ] An external magnetic circuit section 4 is provided in order to generate a magnetic field in the coil, and the objective lens 1 is supported movably in the front axis direction by elastic supports 5 and 6 relative to the magnetic circuit section 4. has been done. The magnetic circuit section 4 is connected to the ball yoke 7 by 1! in the thickness direction. It consists of an annular permanent magnet 8 magnetized and placed on the pole yoke 7, and a plate 9 placed on this permanent magnet 8 and forming a magnetic gap between it and the tip of the ball yoke 7. , so that a magnetic field is generated in the radial direction in the magnetic field. The aforementioned coil 2 is located in this magnetic gap. The coil 2 and the magnetic circuit section 4 constitute a first driving means for driving the objective lens 1 in its forward axis direction. That is, moving coil 2
By applying a current according to the focus error signal to A, the objective lens 1 can be driven in the direction of the optical axis A, and thus focus servo can be performed.

The electromagnet 10 is connected to the plate 9 and the pole yoke to constitute a second driving means that drives the objective lens 1 in a direction substantially perpendicular to its optical axis direction by utilizing leakage magnetic flux generated at the outer circumference of the magnetic circuit section 4. 7 and are arranged opposite to each other at a predetermined interval. In the magnetic circuit section 4, for example, the plate 9
If the side is the south pole, the magnetic field is created so that the pole yoke 7 side is the north pole, the end of the electromagnet 10 facing the plate 9 is the north pole, and the end facing the ball yoke 7 is the south pole. When a current is applied to the coil 10, the focus drive system including the objective lens 1 receives an attractive force, and conversely, the focus drive system including the objective lens 1 receives an attractive force.
If a current is passed through the end facing the ball yoke 7 so that the polarity is opposite to these magnetic poles, the focus drive system receives a repulsive force. Then, tracking servo can be performed by making the driving direction correspond to, for example, the tracking direction and passing an appropriate current through the electromagnet 10 in accordance with the tracking error signal. Note that the focus drive system is movably supported by a damper 11 on a support (not shown) in a direction substantially orthogonal to the optical axis of the objective lens 1.

3 and 4 are a plan view and a sectional view showing a second embodiment of the present invention, in which parts equivalent to those in FIGS. 1 and 2 are designated by the same reference numerals. In this embodiment, part of the outer periphery of the ball yoke 7 and plate 9 of the magnetic circuit section 4 protrudes outward to form a magnetic gap between the tips of both, and the magnetic flux generated in this magnetic gap is perpendicularly crossed. By providing a coil 13 wound around a bobbin 12,
A second driving means for driving a focus driving system including the objective lens 1 in a direction substantially perpendicular to the optical axis of the objective lens 1 is configured. Therefore, if the driving direction is made to correspond to, for example, the tracking direction and a current corresponding to the tracking error signal is caused to flow through the coil 13, tracking revolution can be performed by interaction with the magnetic field generated in the magnetic gap. The first driving means, that is, the focus driving system has the same structure as the first embodiment.

In addition, in the first and second embodiments described above, driving is shown in one direction (tracking direction) within a plane that receives the optical axis of the objective lens 1, but the same driving means is also driven in a direction perpendicular to the plane of the paper. By providing this direction and making this direction correspond to the tangential direction, it becomes possible to drive in three directions: focusing, tracking, and tangential. In addition, when driving in one direction (travel, pulling direction, or tangential direction), another driving means is provided on the opposite side, and a current is supplied so that the generated force is in the same direction. It is also possible to do this.

FIG. 5 is a front view showing a third embodiment of the present invention. In this embodiment, the first driving means is composed of a permanent magnet 614 wound around the objective lens 1 and a fixed coil 15 wound around the optical axis below the objective lens 1. When a current is passed through the fixed coil 15, the objective lens 1 is driven in the focus direction due to interaction with the magnetic field of the permanent magnet 14, and focus servo can be performed. -b1 An electromagnet 16A is provided on the side of the objective lens 1 at a certain distance from the permanent magnet 14.

16B constitutes a second driving means, which applies current to each coil of the electromagnets 16A and 16B to generate a repulsive force and an attractive force in the same direction with the permanent magnet 14, thereby moving the objective lens 1 to the light. It can be moved within the city approximately perpendicular to the axis.

Incidentally, only one electromagnet 16A, 16B may be used, and by providing the same driving means in the direction perpendicular to the plane of the paper, it is possible to drive in two directions perpendicular to the optical axis of the objective lens 1, which is approximately perpendicular to the optical axis of the city. Therefore, focusing, tracking, and tangential navigation can be performed.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but may be configured such that the drive system corresponding to each drive direction also uses at least one permanent magnet and utilizes the magnetic field generated by the permanent magnet 6 at different positions. If it's something, I'll eat it.

As detailed above, in the present invention, the drive system corresponding to each drive direction has a structure in which at least one permanent magnet also serves and the magnetic field from the one permanent magnet at different positions is utilized. As a result, the number of parts is small, the structure is simple, it is easy to assemble, and it is possible to downsize.
Since the portion that becomes an ineffective magnetic field in the moving direction is used for driving in the other right direction, the efficiency of magnetic flux utilization is increased.

[Brief explanation of the drawing]

1 and 2 are a plan view and a sectional view showing a first embodiment of the present invention, and FIGS. 3 and 4 are a plan view and a sectional view showing a second embodiment of the invention, and FIG. FIG. 5 is a front view showing a third embodiment of the present invention. Explanation of symbols of main parts 1... Objective lens 2.13.15... Coil 4... Magnetic circuit section 8.14... Permanent magnet

Claims (2)

[Claims] (1) An optical system driving device for driving an optical system for irradiating a recording surface of a recording medium with a spot light, comprising: a first driving means for driving the optical system in the optical axis direction (a); a second driving means for driving the optical system in a direction substantially perpendicular to the front axis of the optical system; the first and second driving means also serve as at least one permanent magnet, and An optical system drive device in an optical information recording/reproducing device characterized by utilizing a magnetic field generated by a magnet. (2) The optical information recording/reproducing device according to claim 1, wherein the second driving means is configured to drive the optical system in the 2h direction orthogonal to the 2h direction. Optical system drive device.