JPH04205927A - Objective lens driving mechanism for optical pickup - Google Patents

Abstract

PURPOSE:To allow the execution of focusing and tracking adjustment in a stable state with good weight ballance by constituting a magnetic circuit of a single magnetic circuit and mounting an objective lens on the side opposite from a focusing coil with respect to the centroid of a lens holder. CONSTITUTION:The magnetic circuit of the optical pickup is constituted of the single magnetic circuit and the focusing coil 6 facing the inside of this magnetic circuit is mounted on the side opposite from the objective lens 5 with respect to the centroid G of the lens holder 1. Namely, the objective lens 5 having a relatively large weight and the focusing coil 6 are disposed on the opposite side with the centroid G of the lens holder 1 as a center, by which the weight over the entire part is reduced and the weight balance is obtd. The generation of the inclination of the lens 5 at the time of focusing adjustment and tracking adjustment is prevented in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mechanism for driving an objective lens of an optical pickup used in a CD player or the like while maintaining its posture in the direction of the optical axis and in the direction orthogonal to the optical axis.

(Prior Art) In order to accurately read signals in CD players and the like, it is necessary to make a laser beam incident on the disk in an appropriately focused state and to make the laser beam follow the signal track on the disk.

As a mechanism for this purpose, there is a mechanism in which the lens holder is slidably and rotatably supported on a column erected on the base, or a mechanism in which the lens holder is supported with respect to the base via a wire.

As shown in FIG. 4, which is a plan view, and FIG. 5, which is a side view, the mechanism supported by wires attaches the lens holder 102 to the base 100 using four parallelogram-shaped wires 101. The objective lens 103 is attached to the center of the lens holder 102, and magnets 104 are attached to the left and right sides of the lens holder 102.
A magnetic circuit formed by the magnet 104 (
A focusing coil 106 and a tracking coil 1 are wound around the outer periphery of the lens holder 102 in the magnetic gap).
07, the focusing coil 106 is energized to move the lens holder 102 in the optical axis direction, and the tracking coil 107 is energized to move the lens holder 1
02 in a direction perpendicular to the optical axis for adjustment.

(Problems to be Solved by the Invention) FIG. 6 is a schematic overall view of an optical pickup incorporating the above-described drive mechanism for the lens holder 102, as well as an upright mirror 108, a half mirror 109, a detection lens 110, and a light receiving element 111. As is clear from this figure, the raised mirror 108 can be placed within the same height as the yoke 105, but the height H of the entire optical pickup becomes high and cannot be made thinner.

Furthermore, since two yokes and two magnets are arranged, it is not only disadvantageous in terms of cost but also increases in size and weight.

(Means for Solving the Problems) In order to solve the above problems, the present invention has a single magnetic circuit for an optical pickup, and a focusing coil (driving coil) facing into this magnetic circuit is arranged so that the object is aligned with the center of gravity of the lens holder. I installed it on the opposite side of the lens.

(Function) Since the objective lens and focusing coil, which are relatively heavy, are placed on opposite sides of the center of gravity of the lens holder, the overall weight is reduced and the weight is balanced, making it easier for focusing adjustment and tracking. The lens will not tilt during adjustment. .

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a plan view of the objective lens drive mechanism according to the present invention, and FIG. 2 is a side view of the same drive mechanism. The lens holder 1 has a bifurcated shape such as a U-shape or a 7-shape when viewed from above. , connect the pin 2 protruding outward and the base 3 with a wire 4 such as piano wire.
・The lens holder 1 is supported in a floating manner.

The objective lens 5 is attached to the closed part (left side in FIG. 1) of the bifurcated lens holder 1, and the focusing coil 6 and tracking coil 7 are arranged in the open part, and further below the lens holder 1. A yoke 8 having a U-shape is provided, one rising portion of this yoke 8 faces the window portion 1a formed in the lens holder 1 from below, and a magnet 9 is attached to the inner surface of the other rising portion.
This magnet 9 is positioned within the loop of the focusing coil 6, and the magnet 9 and the yoke 8 are
magnetic gap (magnetic circuit) between one rising part of
A focusing coil 6 and a tracking coil 7 are shown.

By the way, the tracking coil 7 and the focusing coil 6 attached to the focusing coil 6 are
Each coil is arranged so that the boundary line between the two lines coincides with a line passing through the center of gravity G of the lens holder 1, and the pin 2 is provided at a position that is an extension of the line passing through the center of gravity G of the lens holder 1. Therefore, the lens holder 1 has a good weight balance because the objective lens 5 and the focusing coil 6, which are heavy items, are distributed at positions where the weight can be balanced around the center of gravity G, and are supported along an extension line from the center of gravity G. Focusing and tracking adjustments can be made in a stable state.

Although the illustrated example shows a type in which the lens holder is supported by a wire rod, the supporting method is not limited to this.

(Effects) FIG. 3 is a schematic overall view of an optical pickup that incorporates an upright mirror 10, a half mirror 11, a detection lens 12, and a light receiving element 13 in addition to the objective lens drive mechanism according to the present invention. As is clear, according to the present invention, since the magnetic circuit of the optical pickup is made single and drives the center of gravity, it is possible to fit the optical system members such as the yoke and the raising mirror within the same height H. This makes it possible to significantly reduce the thickness of the optical pickup to about 1/2 of that of conventional optical pickups, making it extremely effective as a pickup for portable devices and car stereos.

Furthermore, since the yoke and magnet are single, the weight is light, and the focusing coil and tracking coil can be used in half, which is not only advantageous in terms of cost but also easy to manufacture and assemble.

Furthermore, since the focusing coil facing into the magnetic circuit is mounted on the opposite side of the objective lens with respect to the center of gravity of the lens holder, focusing and tracking adjustments can be made with a small driving force without disrupting the overall weight balance. .

[Brief explanation of the drawing]

FIG. 1 is a plan view of an objective lens drive mechanism according to the present invention, FIG. 2 is a side view of the same drive mechanism, and FIG. 3 is a schematic overall view of an optical pickup to which the objective lens drive mechanism according to the present invention is applied. FIG. 4 is a plan view of a conventional lens driving mechanism, FIG. 5 is a side view of the same lens driving mechanism, and FIG. 6 is a schematic overall view of an optical pickup to which a conventional objective lens driving mechanism is applied. 1... Lens holder, 5... Objective lens, 6...
Focusing coil, 7...Tracking coil,
8... Yoke, 9... Magnet, G... Center of gravity of the lens holder.

Claims (4)

[Claims] (1) A focusing coil and a tracking coil are arranged in the magnetic circuit, and by energizing the focusing coil, the lens holder is moved in the optical axis direction, and by energizing the tracking coil, the lens holder is rotated in a direction perpendicular to the optical axis. In the movable optical pickup, the magnetic circuit is composed of a single single magnetic circuit, and the objective lens is mounted on the opposite side of the focusing coil with respect to the center of gravity of the lens holder. Objective lens drive mechanism for optical pickup. (2) Claim 1, wherein the magnet of the magnetic circuit faces inside a loop surrounded by a focusing coil.
The objective lens drive mechanism of the optical pickup described in . (3) The lens holder has a bifurcated shape such as a U-shape or a V-shape when viewed from the optical axis direction, and the objective lens is attached to the closed part of this lens holder, and the focusing coil is attached to the open part. An objective lens drive mechanism for an optical pickup according to claim 1. (4) The objective lens of the optical pickup according to claim 1, wherein the tracking coil is attached to overlap the focusing coil, and a boundary line between the tracking coil and the focusing coil is on a line passing through the center of gravity of the lens holder. Drive mechanism.