JPH113530A - Objective lens drive - Google Patents

Abstract

(57) [Problem] To improve the acceleration sensitivity by reducing the weight of a movable part to realize a high-speed operation. SOLUTION: A lens holder 1 for holding an objective lens 11, a support mechanism for supporting the lens holder 1 with metal wires 15a to 15d, and magnets 19a, 19ab and yoke bases 20b, 20c held by the lens holder 1. And a focusing coil 2 and tracking coils 13a to 13d disposed between the lens holder 1 and the focusing coil 2 as an air-core type and held on two opposite sides of the lens holder 1 to reduce the size and weight of the lens holder 1. It is possible to achieve a high thrust by reducing the weight of the movable part, thereby realizing a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device used in an optical disk device for optically writing or reading information on a disk-shaped recording medium such as a compact disk and an optical disk.

[0002]

2. Description of the Related Art When optically recording or reproducing data on or from a disk-shaped recording medium such as a compact disk or an optical disk, an optical disk device performs tracking due to vertical movement due to warpage of the disk-shaped recording medium or eccentricity. In order to correct the deviation, the objective lens is moved in an optical axis direction perpendicular to the surface of the recording medium (hereinafter referred to as focus direction) F and in a radial direction parallel to the surface of the recording medium (hereinafter referred to as tracking direction). ) Driving to two axes of T. Such optical pickups are required to be more compact and, in particular, thinner, in addition to being reduced in price, as portable disc players and the like have recently become portable. Hereinafter, an example of a conventional objective lens driving device for an optical pickup will be described with reference to the drawings.

FIG. 4 is a partially exploded perspective view of a conventional objective lens driving device, FIG. 5 is a plan view of the objective lens driving device, and FIG.
FIG. 6 is a sectional view taken along line BB of FIG. 5. In these figures,
Reference numeral 11 denotes an objective lens, and reference numeral 12 denotes a rectangular lens holder, which holds the objective lens 11 at a substantially central portion thereof. Reference numerals 13a to 13d denote tracking coils, which are attached to side surfaces of the lens holder 12 in a direction perpendicular to the tracking direction T. Reference numeral 14 denotes a focus coil wound around the outer peripheral surface of the lens holder 12. Fifteen
Reference numerals a to 15d denote metal wires that support the lens holder 12 in a cantilevered state, and the base ends of the metal wires support the suspension holder 16a.
, And is supported by a support substrate 18, and the tip is supported on the same vertical line on both sides of the lens holder 12 in the tracking direction T via the substrates 17 a and 17 b. 19
Reference numerals a and 19b denote magnets, which are fixed to the inner side surfaces of the outer rising pieces 20a and 20d of the yoke base 20, and the yoke base 20 has holes 12a and 12b provided with the inner rising pieces 20b and 20c provided in the lens holder 12. It is fixed to the base plate 21 so as to penetrate. 22
Is a reflection mirror, which is fixed to the base plate 21 so that its reflection surface 22a faces in a direction S perpendicular to the tracking direction T in the same horizontal plane. 23 is an optical disk.

The operation of the objective lens driving device having the above-described configuration when the objective lens 11 is driven in two axes, ie, the focus direction F and the tracking direction T, will be described. Lens holder 1 with objective lens 11 attached
2 are four metal wires 15a to 15 arranged in parallel with each other.
The suspension holder 16 is supported on the yoke base 20 via a support substrate 18 by the support 5d. Light emitted from a semiconductor laser (not shown) is reflected by a reflection surface 22 of a reflection mirror 22.
a from the objective lens 11 to the optical disc 2
The recording surface of No. 3 is irradiated. The light reflected from the recording surface of the optical disc 23 enters the objective lens 11 again, enters a photodetector (not shown), and reads the recorded information and detects the amount of deviation in the focus direction F and the tracking direction T. A current flows from a control circuit (not shown) to the focus coil 14 and the tracking coils 13a to 13d in accordance with the detected shift amount. The focus coil 14 and the tracking coils 13a to 13d are
9a, 19b and inner rising piece 2 of yoke base 20
0b and 20c, the lens holder 12 is moved in the focusing direction F and the tracking direction T by the action of the electromagnetic force when a current flows through each coil, and the displacement amount is reduced. Will be corrected. As shown in FIG. 5, the entire objective lens driving device is driven by a motor (not shown) in the same access direction Ac as the tracking direction F.

[0005]

In the above-mentioned objective lens driving device, with the recent increase in the speed of the optical disk device, high thrust by high efficiency is required. The acceleration sensitivity α representing the generated acceleration per drive current is an item representing the generated thrust performance of the objective lens driving device.
There is. The acceleration sensitivity α can be expressed by the following equation. α = BL / m where B is the generated magnetic flux density, L is the effective magnetic field length of the coil, m
Is the weight of the movable part. In order to achieve high thrust,
It is an essential condition that the sensitivity of the acceleration α be increased and the drive current be increased.

However, with the recent trend of miniaturization and thinning of optical pickups, it is difficult to increase the generated magnetic flux density B and the effective magnetic field length L of the coil for increasing the acceleration sensitivity α. In addition, when the drive current is increased, the heat generation of the focus coil and the tracking coil due to the increase of the current is increased, and the deformation of the objective lens, which is the weakest thermally, is likely to be caused to cause deterioration in performance. For this reason, there is a problem that there is a limit in increasing the thrust in the objective lens driving device.

SUMMARY OF THE INVENTION The present invention solves such a conventional problem. An objective lens driving device capable of improving acceleration sensitivity by reducing the weight of a movable portion and realizing higher speed is provided. The purpose is to provide.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a lens holder having a small size and light weight, and a movable portion having a reduced weight to achieve a high thrust and a high speed. It was done.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided a focus coil which supports a lens holder for holding an objective lens with a metal wire and is disposed in a magnetic circuit while being held by the lens holder. And an objective lens driving device for driving the objective lens in a focusing direction and a tracking direction by using a tracking coil, wherein the focusing coil is held as an air-core type on two opposite sides of a lens holder. Since the focus coil is not wound around the outer peripheral surface of the lens holder as in the related art but is held on two opposite sides, the size and weight of the lens holder can be reduced, and the weight of the movable portion can be reduced. This has the effect of achieving high thrust and realizing high speed.

According to a second aspect of the present invention, a width of a portion of the lens holder for holding the focus coil is substantially smaller than a width of a portion of the lens holder for holding the objective lens. The objective lens driving device according to claim 1, wherein the weight of the lens holder can be further reduced and the heat generated by the focus coil can be suppressed from being transmitted to the objective lens, so that a higher thrust and a higher speed can be realized. It has the action of:

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of an objective lens driving device according to Embodiment 1 of the present invention, and FIG.
FIG. 4 is a sectional view taken along line AA of FIG. 5, and reference numerals used in the description of the conventional example are used for similar members. 1 and 2, reference numeral 1 denotes a rectangular lens holder which is long in the tracking direction T, and an objective lens 11 is held substantially at the center thereof. Reference numeral 2 denotes an air-core type, here a focus coil wound in a rectangular ring shape, and its two sides in the tracking direction T are held by the lens holder 1. 13a-
Reference numeral 13d denotes a tracking coil, two of which are mounted on each of two sides on both sides in a direction perpendicular to the tracking direction T of the focus coil 2. Reference numerals 15a to 15d denote metal wires that support the lens holder 1 in a cantilevered state. The base ends of the metal wires penetrate through the suspension holder 16 and are supported by the support substrate 18, and the front ends of the metal wires are in the tracking direction T of the lens holder 1. Substrates 17a, 1 on the same vertical line on both sides
7b. Reference numerals 19a and 19b denote magnets, which are outer rising pieces 20a and 2a of the yoke base 20.
The yoke base 20 is fixed to the base plate 21 such that its inner rising pieces 20b and 20c are located inside the lens holder 1. Reference numeral 22 denotes a reflection mirror, which is fixed to the base plate 21 so that its reflection surface 22a faces in a direction S perpendicular to the tracking direction T in the same horizontal plane. 23
Is an optical disk.

The operation of the objective lens driving device having the above-described configuration when the objective lens 11 is driven in two axes, ie, the focus direction F and the tracking direction T, will be described. Lens holder 1 with objective lens 11 attached
Are four metal wires 15a to 15 arranged in parallel with each other.
The suspension holder 16 is supported by the suspension holder 16 by d, and is attached to the yoke base 20 via the support substrate 18. Light emitted from a semiconductor laser (not shown) is reflected by a reflection surface 22 a of the reflection mirror 22.
Reflected by the objective lens 11 and the optical disc 23
The recording surface is irradiated. The light reflected from the recording surface of the optical disk 23 enters the objective lens 11 again, enters a photodetector (not shown), and reads the recorded information and detects the amount of deviation in the focus direction F and the tracking direction T.
A current flows from a control circuit (not shown) to the focus coil 2 and the tracking coils 13a to 13d according to the detected shift amount. The focus coil 2 and the tracking coils 13a to 13d are
a, 19b and the inner rising piece 20 of the yoke base 20
b and 20c, the lens holder 1 is moved in the focus direction F and the tracking direction T by the action of an electromagnetic force when a current flows through each coil, and the amount of displacement is reduced. Will be corrected. The entire objective lens driving device is driven by a motor (not shown) in the same access direction Ac as the tracking direction F.

As described above, according to the first embodiment,
Since the focus coil 2 is held on two opposing sides of the lens holder 1, the lens holder 1 can be reduced in size and weight, and a high thrust can be achieved by reducing the weight of the movable part, thereby realizing high speed. be able to.

(Embodiment 2) FIG. 3 is a plan view of an objective lens driving device according to Embodiment 2 of the present invention. The difference from Embodiment 1 is that the lens holder 1A for holding the focus coil 2 is different. A bifurcated notch is formed in the portion, and the width of the portion is changed to the objective lens 1 of the lens holder 1A.
That is, the contact area with the focus coil 2 is reduced by making the width substantially smaller than the width of the portion holding the focus coil 1. By doing so, the weight of the lens holder 1A can be further reduced, and the heat transfer to the objective lens 11 which is thermally weakest against the heat generated by the focus coil 2 can be suppressed, and the drive current can be further increased to further increase the drive current. High thrust and high speed can be realized.

[0015]

According to the present invention, as is apparent from the above embodiment, the focus coil is of the air-core type and is held on two opposite sides of the lens holder, and the acceleration sensitivity is reduced by reducing the weight of the movable part. By improving, the speed of the objective lens driving device can be further increased.

[Brief description of the drawings]

FIG. 1 is a plan view of an objective lens driving device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is a plan view of an objective lens driving device according to a second embodiment of the present invention.

FIG. 4 is a partially exploded perspective view of a conventional objective lens driving device.

FIG. 5 is a plan view of a conventional objective lens driving device.

FIG. 6 is a sectional view taken along line BB of FIG. 5;

[Explanation of symbols]

 1, 1A Lens holder 2 Focus coil 11 Objective lens 12 Lens holder 13a, 13b, 13c, 13d Tracking coil 14 Focus coil 15a, 15b, 15c, 15d Metal wire 16 Suspension holder 17a, 17b Substrate 18 Support substrate 19a, 19b Magnet 20 Yoke base 21 Base plate 22 Reflection mirror 23 Optical disk

Claims (2)

[Claims] 1. A lens holder for holding an objective lens is supported by a metal wire, and the objective lens is held in the lens holder and arranged in a magnetic circuit to move the objective lens in a focus direction and a tracking direction. 2. The objective lens driving device according to claim 1, wherein said focus coil is of an air-core type and held on two opposite sides of a lens holder. 2. The objective lens driving device according to claim 1, wherein a width of a portion of the lens holder for holding the focus coil is substantially smaller than a width of a portion of the lens holder for holding the objective lens. .