JPS60171641A - Objective lens driving device of optical pickup - Google Patents

Abstract

PURPOSE:To improve driving characteristic and to improve follow-up capacity of an objective lens by making the position of taking out of a lead wire from a driving coil axial symmetry to the principal axis and canceling rotational moment generated at movable parts. CONSTITUTION:A terminal substrate 101 is attached to opposite side of an objective lens holding member 9 which is a movable part, and both ends of a driving coil 7 are connected. Lead wires 102, 103 to external driving circuit are connected to lead wire pulling out positions 105, 106 of the substrate 101 which is at a position of axial symmery to the principal axis 5. Because of such constitution, when the movable part moves vertically, rotational moment to the movable part due to lead wires 102, 103 goes to nearly zero as those at symmetrical position cancels with each other. Thus, driving characteristic of small friction is obtained even at upper and lower ends and follow-up characteristic of the objective lens 13 can be improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical pickup objective lens driving device using a semiconductor laser.

[Technical background of the invention]

Generally, in an optical pickup using a semiconductor laser, an objective lens is driven in order to read information written on a disk, and the focal depth of the objective lens (usually about 2 μm) is
) Since it is necessary to control the information recording surface of the disk so that it is within the range of 0.001 to 1.00, an objective lens drive device (also called a focus drive device) is used.

This objective lens driving device has conventionally been constructed as shown in FIGS. 1 to 3, and has a main shaft 5 protruding from a substrate (not shown). An inner yoke 1 having a flange 2 is coaxially arranged on the substrate so as to surround the main shaft 5. Furthermore, an annular magnet 3 is disposed coaxially on the flange 2 at a predetermined distance from the inner yoke 1.

A cylindrical outer yoke 4 is coaxially provided on the magnet 3. A magnetic circuit is formed by the inner and outer yokes 1 and 4 and the magnet 3, and a magnetic flux is generated in the gap (referred to as an action area) between the outer surface of the inner yoke 1 and the inner surface of the outer yoke 4. Further, a bearing 6 of an oval plate-shaped objective lens support member 9, which is a movable portion, is rotatably fitted onto the main shaft 5. A coil bibbin 8 is fixed to the back surface of the objective lens support member 9 so as to be located between the inner yoke 1 and the outer yoke 4, and a drive coil 7 is wound around the outer periphery of the coil bibbin 8. Such an objective lens support member 9 has one end connected to a connecting bin 10. It is connected to the flange 2 via a rubber plate 11 and a rubber plate attachment fitting 12, and an objective lens 13 is attached to the other end. Further, the drive coil 7 and the external drive circuit are electrically coupled via a terminal board 14.14 attached to the objective lens support member 9 and a flexible lead wire 15.16. still,
During operation, the objective lens support member 9 moves in the vertical direction and rotational direction around the main shaft 5.

[Problems with background technology]

In the conventional objective lens drive device as described above, the drive characteristic is expressed by the drive current (x) on the horizontal axis and the vertical displacement x'fc of the objective lens 13 on the vertical axis.
Illustrated. From FIG. 4, it can be seen that the hysteresis due to the scratching of the movable part increases in the small and large portions of the displacement X. This is because the pull-out position 17.17 of the lead wire 15.16 is biased towards one end of the movable part, so if it deviates from the neutral point P, the elastic force of the lead wire 15.16 will apply a rotational moment to the movable part. arise, main axis 5
This is because the friction between the This increase in friction at the upper and lower ends means that when driven with the same current, the amount of displacement decreases significantly at the upper and lower ends compared to the neutral point P.
This means that the displacement is not smooth.

When controlling the objective lens 13 using a servo system, this phenomenon not only greatly reduces the tracking performance of the objective lens 13 at the top and bottom ends, but also makes the servo system unstable. This may make control impossible.

[Purpose of the invention]

The purpose of this invention is to make the lead wire extraction position from the drive coil axially symmetrical with respect to the main axis, to improve the drive characteristics by canceling the rotational moment generated in the movable part, and to improve the tracking performance of the objective lens. An object of the present invention is to provide an optical pickup objective lens driving device.

[Summary of the invention]

This invention is capable of driving by acting on a current flowing through a movable part having a bearing or a main shaft, an objective lens, and a drive coil, a main shaft or bearing rotatably fitted to the bearing or main shaft, and the drive coil. In the objective lens driving device for an optical pickup, the objective lens driving device for an optical pickup is provided with at least a fixed part having a magnetic circuit that generates magnetic flux such that the lead wire extraction position of the driving coil is arranged axially symmetrically with respect to the main axis. This is an objective lens drive device for a type pickup.

[Embodiments of the invention]

The objective lens driving device of the present invention is constructed as shown in FIGS. 5 and 6, and the same parts as in the conventional example are given the same reference numerals.

That is, in the present invention, in order to solve the above-mentioned conventional problems, the lead wire connecting the drive coil and the external drive circuit is drawn out at an axially symmetrical position with respect to the main axis. To be more specific, terminal boards 101 and 101 are attached to the center of each opposing side surface of the oval plate-shaped objective lens support member 90, which is a movable part, and both ends of the drive coil 7 are connected to the terminal boards 101 and 101, respectively. Lead wires 102.103 to an external drive circuit are drawn out from this terminal board 101.10J. 10 in the diagram
5, 106 is a lead wire extraction position, which is axially symmetrical with respect to the main shaft 5.

The objective lens driving device of the present invention has the same structure as the conventional example (see FIGS. 1 to 3) except for the above description, so detailed description thereof will be omitted.

〔Effect of the invention〕

According to this invention, the lead wires 102 and 103 connecting the drive coil 7 and the external drive circuit are drawn out at positions 105 and 1.
06 are arranged axially symmetrically with respect to the main axis 5. As a result, even when the movable part moves in the vertical direction, the rotational moment applied to the movable part by the lead wires 102 and 103 is always zero, because those in symmetrical positions cancel each other out. As shown in FIG. 7, drive characteristics with less friction can be obtained even at the upper and lower ends. This is useless, objective lens 1! The tracking performance is also significantly improved.

[Modified example]

FIGS. 8 and 9 show modified examples of this invention,
The same effects as in the above embodiment can be obtained.

That is, in this case, the movable part is equipped with a coil for driving in the tracking direction, and the lead wires 102°, 103, 107,
There are four numerals 108, two of which are drawn out symmetrically with respect to the main axis. In the figure, 109.110 is the lead wire 107
, 108 in the drawer position.

[Brief explanation of drawings]

1 to 3 are a cross-sectional view, a plan view, and a side view showing a conventional objective lens drive device, FIG. 4 is a characteristic curve diagram showing drive characteristics in a conventional objective lens drive device, and FIGS. 6 is a plan view and a side view showing an objective lens drive device according to an embodiment of the present invention, FIG. 7 is a characteristic curve diagram showing drive characteristics of the objective lens drive device of the present invention, and FIGS. 8 and 9 FIG. 2 is a plan view and a side view showing a modification of the present invention. 1... Inner yoke, 2... Flange of inner yoke, 3...
... Magnet, 4... Outer yoke, 5... Main shaft, 6...
・Bearing, 7... Drive coil, 8... Coil bobbin,
9... Objective lens support member, 10... Connection bin, 1
1...Rubber plate, 12...Rubber plate mounting bracket, 13...
・Objective lens, 101... Terminal board, 102,
103... Lead wire, 105, 106... Lead wire pull-out position. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 3 Figure 4 Figure 5 Figure 7

Claims (1)

[Scope of Claims] A movable part having a bearing or a main shaft, an objective lens, and a drive coil, a main shaft or bearing rotatably fitted to the bearing or main shaft, and a movable part that can be driven by acting on a current flowing through the drive coil. In an objective lens drive device for an optical pickup, the lead wire connecting the drive coil and the external drive circuit is drawn out with respect to the main axis. An objective lens drive device for an optical pickup, characterized in that the objective lens drive device is arranged axially symmetrically.