JPS59135637A - Driving device for objective lens - Google Patents

Abstract

PURPOSE:To prevent the deviation in tracking owing to focusing by using at least a thin plate spring having arms of such a blanked shape as to have line symmetry with respect to >=2 straight lines running the central part of an elastic support which supports a lens barrel in constituting said elastic support. CONSTITUTION:An elastic support 5a has plural arms 11 which are formed and disposed respectively to have the shape of line symmetry with respect to >=2 straight lines running the central axis, for example, I - I and II-II lines, and are curved to an S shape or the like, and an inside ring 12 and outside ring 13 which are monolithically formed and support both ends of said arms. The ring 12 to be fixed to a lens barrel 3 and the ring 13 to be fixed to a cylindrical housing 8 are formed concentrically. Then, even if the barrel 3 moves from a neutral position by the focusing control by a driving coil 7, the forces in the rotating direction acted by the respective arms 11 on the barrel 3 are offset by each other and therefore the barrel 3 moves in a focusing direction 6 without rotating and the movement of an objective lens 1 in the direction 6 does not affect the tracking operation.

Description

Detailed Description of the Invention Technical Field The present invention relates to an information recording and reproducing device (storage device) etc. that records and reproduces information on a recording medium using optical means.
In particular, the present invention relates to an objective lens driving device suitable for controlling an objective lens to follow an information track when reading information from an information track of a recording medium.

PRIOR ART In the conventional storage device as described above, a disc-shaped optical recording medium (disk) on which information such as video signals is recorded concentrically or spirally is rotated on an iQ, and an optical system consisting of an objective lens etc. A laser beam emitted from a laser light source is focused onto the optical recording medium, and information is read from the reflected reproduction beam. This optical recording medium-1-
The width of the information track recorded on the
It is thin, and the distance between each information track is narrow at 1 to 2 gm, making the information recording density extremely high.

Therefore, when reading information from the information track, it is necessary to drive the objective lens so that the light spot is always focused on the information track. However, in reality, optical recording media have limitations in their manufacturing precision and the precision of their rotational axes, so they rotate with wobbling and eccentricity. Therefore, in order for the objective lens to follow the information track, it is detected whether the reading light spot is focused on the information track, and based on the error detection signal,
The so-called focusing control displaces the objective lens in the optical axis direction (focus direction), detects the deviation of the optical spot from the information track, and moves the objective lens in a direction perpendicular to the information track based on the tracking error detection signal. So-called tracking control is performed to displace it in the (+-racking direction). At that time, a drive mechanism that can move the objective lens independently in each direction (objective (lens drive device) is required.

FIG. 1 shows an example of a conventional objective lens driving device capable of displacing an objective lens in the above-mentioned focusing direction and tracking direction. Here, the objective lens 1 is suspended inside a lens barrel 3 by two parallel objective lens supports 2. This objective lens support 2 is composed of a bimorph element or the like, and can drive the objective lens 1 in the tracking direction shown by an arrow 4. In addition, the mirror layer 3 (with built-in objective lens 1) has two upper and lower disc-shaped 17 placed on the outer periphery of the lens 111, supported by a support 5, and only in the focus direction shown by arrow 8. A movable drive coil 7 fixed to the outer periphery of the lens barrel 3 and a magnetic circuit 8 fixed to the cylindrical body 8.
It is driven by a voice coil composed of. Note that the outer periphery of the elastic support 5 is fixed to a cylindrical body 8.

However, conventionally, as the elastic support 5 supporting the lens barrel 3, a thin plate spring with a spiral hole pattern as shown in FIG. Since the length of each arm of the shaped pattern is constant, when the focusing control is activated and the lens barrel 3 moves from the initial neutral position, the lens barrel 3 rotates around the optical axis as shown by the broken line in FIG. Rotate. As a result, the objective lens 1 built into the lens barrel 3 also rotates in the same way as the lens barrel 3, so the tracking operation direction of the objective lens 1 shifts by the amount of rotation, and the focusing control interferes with the tracking control. There was a serious drawback.

Purpose In view of the above-mentioned points, the present invention provides a thin plate having arms in a punched shape such that the elastic support supporting the lens barrel is line-symmetrical with respect to at least two or more straight lines passing through the central axis of the elastic support. It is an object of the present invention to provide an objective lens drive device that is configured with a spring so that a lens barrel housing the objective lens does not rotate even if the objective lens moves in the optical axis direction for focusing.

Example Hereinafter, the invention will be described in detail with reference to the drawings.

FIG. 4 shows an example of the main structure of the objective lens driving device of the present invention, and other parts are similar to the conventional example shown in FIG. 1, so detailed explanation thereof will be omitted.

In FIG. 4, reference numeral 5a denotes an elastic support body formed of a thin plate spring made of a viscous material such as metal, rubber, or plastic, which replaces the elastic support body 5 shown in FIG.
is supported so that it can be displaced only in the focus direction 6.

As shown in FIG. 4, this elastic support body 5a has two or more straight lines passing through the central axis, such as
A plurality of bent arms 11, such as an S-shape, each formed and arranged so as to have a shape (pattern) symmetrical with respect to a line, and an integrally molded inner ring 12 and outer ring that support both ends of each arm 11. It has a ring 13. Also, an inner ring 12 is fixed to the lens barrel 3, and an outer ring 13 is fixed to the cylindrical inert body 8 (see Fig. 1).
and form two concentric lines.

In this way, since the shape of the elastic support body 5a is line symmetrical with respect to two or more straight lines passing through the central axis, the drive coil 7 (
Even if the lens barrel 3 moves from the neutral position due to focusing control (see Fig. 1), the rotational forces acting on the lens barrel 3 by the arms 11 that make up the line-symmetrical pattern cancel each other out. , the lens barrel 3 moves in the focus direction 6 without rotating. Therefore, movement of the objective lens l in the focus direction 6 by focusing control does not affect the tracking operation.

Further, since the arm 11 of the elastic support 5a is formed into a bent shape such as an S-shape, the spring characteristic can have a wide linear motion range, and can sufficiently accommodate the movable range of the objective lens 1 in the focus direction.

Next, FIG. 5 shows a second embodiment of the apparatus of the present invention. Here, 5b is an elastic support that supports the lens barrel 3 in place of the elastic support 5 shown in FIG. 1, as in the first embodiment shown in FIG. This elastic support 5b has a shape (pattern) that is line symmetrical with respect to the I'-T' and II'-TI' lines.
A plurality of arms 11' that are modified from the S-shape shown in the first embodiment are arranged so that the arms 11' have an integrally molded inner ring 12 and an outer ring 13 that support both ends of each arm 11'. Ori,
There are effects similar to those of the first embodiment.

As explained above, according to the present invention, the elastic support that supports the lens barrel so as to be able to move in the focusing direction is symmetrical to two or more straight lines passing through the central axis of the elastic support. The objective lens is composed of a thin plate spring with multiple arms that form a shape, so when controlling the focusing and tracking of the objective lens, the only option is tracking by focusing, which allows highly accurate objective lens drive control without mutual interference. A lens driving device is obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing an example of the configuration of a conventional device, FIG. 2 is a plan view showing an example of the configuration of the elastic support shown in FIG.
FIG. 4 is a plan view showing an example of the structure of the elastic support according to the present invention, and FIG. 5 is a plan view showing another example of the structure of the elastic support according to the present invention. It is a diagram. DESCRIPTION OF SYMBOLS 1... Objective lens, 2... Objective lens support, 3... Lens barrel, 4... Arrow indicating tracking direction, 5, 5a,
5b... Elastic support body, 6... Arrow indicating focus direction, 7... Drive coil, 8... Cylindrical housing, 9... Magnetic circuit, IN, 11'... Arm, 12...Inner ring, 13...Outer ring.

Claims (1)

[Claims] An objective consisting of a lens barrel with a built-in objective lens, a cylindrical housing having a drive mechanism for moving the lens barrel in the optical axis direction, and an elastic support that holds the lens barrel in the optical axis direction within the cylindrical housing. 1. An objective lens drive device, wherein the elastic support body is formed of a thin plate spring having a punched shape that is symmetrical with respect to two or more straight lines passing through the center axis of the elastic support body.