JPS6320732A - Optical pickup for disk - Google Patents

Abstract

PURPOSE:To obtain a disk-use optical pickup provided with small moment of inertia and capable of easy accessing at a high speed by distributing separately the component parts like an objective lens, a light source, a photodetector, etc. at a rotary tip part and a rotary center part of a swing member. CONSTITUTION:A semiconductor laser 8 having a comparatively large weight, a collimator lens 9, a beam splitter 10, a critical angle prism 11, a photodetector 12 and access tracking coils 18a and 18b are equipped to a main head part 2 of a swing member 1 which is attached rotatably to a fixed shaft 6a via a bearing 5a. A subhead part 4 set via parallel springs 3a and 3b contains a reflecting mirror 14 which has a comparatively small weight and projects the light of a light source to a disk 7 after focusing it, an objective lens 15 and focusing coils 16a and 16b. A rotary tip part has a means smaller than that of a rotary center part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a swing arm type optical pickup for recording and reproducing information on and from a disk such as an optical disk or a magneto-optical disk.

(Prior Art) As a conventional swing arm type optical pickup, one has been proposed in which a light source, a light receiver, an optical system, and an actuator are attached to the rotating tip of the swing arm, and these are rotated together. ing.

[Problem that the invention seeks to solve]

However, in the conventional optical pickup mentioned above, all of its components are attached to the rotating tip of the swing arm, which increases the weight of that part, which increases the moment of inertia and makes high-speed access difficult. The problem is that it becomes difficult.

One possible way to solve this problem is to shorten the distance between the tip of the swing arm and the center of rotation. As the objective lens moves in an arc, the relative position of the objective lens in the tangential direction of the track on its center deviates greatly, and the imaging width of the tracking error signal changes greatly depending on the playback position, making it difficult to accurately control tracking. The problem is that it cannot be done.

This invention was made by focusing on such conventional problems, and it is possible to reduce the moment of inertia without shortening the distance between the pivoting tip of the swing member to which the objective lens is mounted and the pivot center. It is an object of the present invention to provide an optical pickup for a disk that is appropriately configured so that r can be reduced and high-speed access can be easily performed.

(c) Means and operation for solving the problem] In order to achieve the above object, in this invention, the above-mentioned method is adopted so that the mass of the rotatable tip of the rotatable swing member is smaller than the mass near the center of rotation. At least an objective lens is attached to the rotating tip.
At least a light source and a light receiver are mounted near the center of rotation, and light from the light source is guided to the disk via the objective lens, and light reflected from the disk is guided to the light receiver via the objective lens. Configure.

[Embodiment] FIGS. 1 and 2 are a plan view and a sectional view showing a first embodiment of the present invention. The swing member 1 includes an arc-shaped main head portion 2, two parallel plate springs 3a and 3b, and a sub-head portion 4. The main head section 2 is rotatably attached to fixed shafts 5a, 5b via bearings 5a, 5b, and parallel leaf springs 3a, 3 are attached to the main head section 2.
The sub-head section 4 is mounted so as to be displaceable in the normal direction of the disk 7 via the sub-head section b. In this example, the parallel plate springs 3a and 3b are formed into a trapezoidal shape whose width increases from the sub-head portion 4 toward the main head portion 2.

The main head section 2 is equipped with a relatively heavy semiconductor laser 8, a collimator lens 9, a beam splitter 10, a critical angle prism 116, and a photodetector 12 having a light receiving area divided into four parts, and a holder 13 is attached to the sub-head section 4. A relatively light reflecting mirror 14 and an objective lens 15 are attached to this holder 13, and the light from the semiconductor laser 8 is guided to the beam splitter 10 through the collimator lens 9, and the light beam transmitted through the beam splitter 10 is The light is guided and reflected by the reflection mirror 14 of the sub-head section 11 through the parallel plate springs 3a and 3b, and the reflected light is converged by the objective lens 15 and projected onto the disk 7. Further, the reflected light from the disk 7 is reflected by the objective lens 15, the reflection mirror 14, and the parallel leaf springs 3a, 3.
The beam is guided to the beam splitter 10 of the main head section 2 through the beam splitter 10 of the main head section 2, and the light beam reflected here is made to enter the photodetector 12 via the critical angle prism 11, and an information signal is generated based on the output of the photodetector 12 divided into four light receiving areas. , a focus error signal and a tracking error signal.

In addition, in order to focus the objective lens 15 using the focus error signal, a pair of focus coils 16a and 16b are attached to the holder 13, and the focus coil 1 is moved by rotating the swing member 1.
A permanent magnet 11 is arranged on a fixed member (not shown) opposite to the rotation locus of the focus coil 16a and 16b.
, 16b @ generates a transverse magnetic flux.

Furthermore, the objective lens 15 is
Tracking coil: In order to access the objective lens 15 to a desired position on the disk 7, a pair of access/tracking coils la is attached to the main head section 2.
a, 18b, and these coils 18a.
, 18b are connected to each other so as to sandwich the outer yoke 19.
a, 19b and inner yokes 20a, 20b are arranged, and a coil 18a is placed on the outer yokes 19a, 19b.

Permanent magnets 21a, 21 such that the magnetic flux crosses 18b
Attach b. Note that the inner yokes 20a and 20b are
The main head portion 2 is disposed so as to pass through arc-shaped openings 22a and 22b formed around the fixed N16a.

As described above, in this embodiment, the main head section 2 is provided at the center of rotation of the swing member 1, the sub-head section 4 is provided at the tip of the rotation, and the main head section 2 is provided with a relatively heavy semiconductor laser 8. , a collimator lens 9, a beam splitter 10, a critical angle prism 11, a photodetector 12, and Ackles tracking coils laa, tab, and a relatively light reflecting mirror 14 in the sub-head part 4.
, objective lens 15 and focus coil 16a,
Since +6b is installed, the amount of 11 at the tip of the rotation can be made smaller than the amount of 1 at the center of rotation. Therefore, the moment of inertia (-) can be reduced without shortening the distance between the rotation tip and the rotation center, making it possible to easily perform high-speed access.

Furthermore, since the lengths of the parallel leaf springs 3a and 3b are sufficiently long with respect to the amount of displacement in the focus direction of the sub-head part 4, the thickness can be increased, and the width of the parallel leaf springs 3a and 3b can be increased with respect to the rotation center. Since it has a wide trapezoidal shape, sufficient strength can be obtained. Therefore, vibration of the parallel leaf springs 3ay3b during high-speed access can be effectively suppressed, and stable operation can be achieved.

Furthermore, since the swing member 1 is rotated by attaching the access tracking coils 18a and 18b to the main head portion 2, the rotational force acting on the access tracking coils 18a and 18b is applied from the point of application to the center of rotation. By increasing the ratio of the distance between the center of rotation and the distance from the rotation center to the objective lens 15, the main head section 2
The amount of displacement of the objective lens 15 due to the rotation can be amplified.

3 and 4 are a plan view and a sectional view showing a second practical example of the present invention. In this embodiment, access and tracking coils 18a and 18b are attached to the holder 13 of the sub-head section 4 to perform access and tracking control, which is the first practical f+! ! This is different from the example, and the other configurations are similar to the first practical example and IQi. According to this embodiment, the outer yoke 19a in the first embodiment
, 19b, inner yoke 20a.

Since the permanent magnets 21a, 21b, etc. 20b1 are not required, there is an advantage that the structure is simpler and can be made cheaper.

In addition, since the access drive is performed at the rotating tip, the first
Another advantage is that the access speed can be made even faster than in the embodiment.

Note that this invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, in the first embodiment, a tracking coil may be provided in the sub-head portion, so that access control and tracking control may be performed separately. Further, in the above embodiment, focus detection is performed using a critical angle prism, but other focus detection methods such as an astigmatism method using a cylindrical lens may also be applied.

〔Effect of the invention〕

As described above, according to the present invention, components of an optical pickup such as an objective lens, a semiconductor laser, and a photoreceiver are arranged so that the mass of the rotating tip of the swing member is smaller than the mass of the rotating center. Since the rotating tip portion and the rotating center portion are mounted separately, the moment of inertia can be reduced without shortening the distance between them.

Therefore, high-speed access can be easily performed without any adverse effect on tracking control.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a first embodiment of this invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, FIG. 3 is a plan view showing a second embodiment of this invention, and FIG. is a sectional view taken along the line IV-IV in FIG. 3; 1... Swing member 2... Main head part 3
a, 3b...Parallel leaf spring 4...Sub head portion 5a, 5b...Bearing 6a, 6b...
Fixed ring 7...Disk 8...Semiconductor laser 9...Collimator lens 10...Beam splitter 11...Critical angle prism 12...Photodetector 13...Holder 14...Reflection mirror 15. ...Objective lenses 16a, 16b...Focus coil 17...
permanent magnet

Claims (1)

[Claims] 1. At least an objective lens is provided at the rotating tip, and at least a light source and a light receiver are placed near the rotating center so that the mass of the rotating tip of the rotatable swing member is smaller than the mass near the rotation center. A light for a disk, characterized in that the light source is equipped with a device to guide light from the light source to the disk via the objective lens, and to guide light reflected by the disk to the light receiver via the objective lens. pick up.