JPH05135373A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To miniaturize it, to lighten it and to accelerate access by holding a carrier of an optical head movably and rotatably on a plane along the radius direction of an optical recording medium and along a perpendicular direction to a recording surface. CONSTITUTION:The carrier (bobbin 3) of the square cylinder shape of the optical head holding an objective lens 4 and a refracting mirror 5, is held movably in the radius direction of the recording medium D along a guide rail 2. Further, the bobbin 3 is held rotatably on the common plane in the seeking direction and in a focusing direction perpendicular to the recording surface of the medium D. Further, the quantity of inclination of a lens 4 is detected by a inclination sensor 11 and a focusing error by the lens 4 is detected by a servo sensor. From these both results, the rotation and the linear movement of the bobbin 3 is controlled by a controlling means through coils 6, 7A, and 7B. Thus, the carrier is miniaturized, is lightened and the access is accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an optical or magneto-optical recording / reproducing apparatus for irradiating an optical recording medium with a laser beam to optically record or erase information. The present invention relates to an objective lens driving device.

[0002]

2. Description of the Related Art An objective lens driving device of this type, for example, when recording / reproducing information on / from a rotating optical disc, a recording / reproducing section on the optical disc surface is read through the objective lens.
The light is for focusing the light.
The light is controlled to move in the radial direction and the focusing direction of the disc. A conventional recording / reproducing apparatus is movably equipped with an optical head including the objective lens driving device.
In particular, in order to improve the access speed, the laser light emitting part and the sensor part are separated from the objective lens driving part and fixedly installed on the device frame side, and the optical parts of the moving parts are reduced. , Has also been made lighter.

[0003]

However, the above-mentioned optical head movable part (carrier) uses the objective lens driving device provided on the carrier to perform focus operation of the objective lens (direction perpendicular to the disc surface) and In order to perform tracking operation (a minute range in the radial direction of the disk), a magnetic circuit including a magnet is configured on the carrier, and an actuator equipped with a coil corresponding to the tracking and focusing operation is provided. A seek operation (movement over the entire recording / reproducing range in the radial direction of the disk) is performed by an electromagnetic force generated by a magnetic circuit provided and a coil provided on the carrier. Therefore, the structure of the entire carrier including the objective lens driving device for focusing and tracking becomes complicated,
It is difficult to reduce the size and it is difficult to move the objective lens at high speed.

Therefore, the applicant has already been
Equipped with only an electromagnetic coil for focusing and tracking of the objective lens, an optical component, an optical component support, and an electromagnetic coil for moving the carrier in the seek direction. By providing a circuit on the side of the device frame, the movable part of the optical head is sufficiently miniaturized to propose an objective lens driving device that can realize high-speed access.

[0005]

SUMMARY OF THE INVENTION The present invention achieves the above object of realizing high-speed access by sufficiently miniaturizing the movable portion of an optical head, and at the same time, mechanical structure of an actuator for an objective lens. It is intended to provide an objective lens driving device which can be made highly accurate by simplifying the lens so that it can be moved in a single plane.

[0006]

Therefore, according to the present invention,
The objective lens of the optical head is held on the carrier together with the refraction mirror, and the carrier is equipped with seek driving and tracking driving coils and focusing driving coils, and a disk-shaped optical recording medium A magnetic circuit composed of a magnet and a magnetic material is arranged along the radial direction, and the objective lens is moved in the seek direction, the tracking direction, and the focusing direction by controlling the magnetic flux of the magnetic circuit and the current to the coil. In the objective lens driving device for controlling the movement of the optical recording medium, there is provided a holding means for holding the carrier so that the carrier can be moved and swung on a plane along the radial direction of the optical recording medium and the direction perpendicular to the recording surface.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. Here, the laser emission part and the sensor
An optical head of a so-called separation optical system, which is equipped on the apparatus frame side as the fixed optical unit 1, is shown. The movable part (carrier) of the optical head is a prism-shaped bobbin 3 (aluminum material) which is moved along guide rails 2 and 2 extending in the seek direction, an objective lens 4 and a refraction mirror 5. The laser beam from the fixed optical unit 1 is introduced to the objective lens 4 via the mirror 5 and the objective lens 4 is held.
Collects the light on a disk-shaped optical recording medium D by
The reflected light is returned to the fixed optical unit 1 via the objective lens 4 and the mirror 5.

The bobbin 3 is provided with two seek driving and tracking driving coils 6, 6 located in front of and behind the objective lens 4, respectively. , 6 are located on the left and right, and there are two focusing coils 7A, 7A and 7 respectively.
B and 7B are attached. And these coils are
It faces a pair of magnets 8, 8 arranged in parallel outside the guide rails 2, 2. The magnets 8, 8 together with the magnetic bodies 9, 9 provided along the back surface thereof constitute a magnetic circuit commonly used for driving in the seek, tracking and focusing directions. 6, 6 and 7 ... Cut off the magnetic flux of the magnetic circuit. Since the guide rails 2 and 2 form a closed magnetic circuit as a part of the magnetic circuit so as to increase the magnetic flux density in the vicinity of each coil, they are preferably made of a magnetic material.

Further, the bobbin 3 is provided with the guide rail.
The bobbin 3 can rotate on a plane common to the seek direction and the direction perpendicular to the recording surface of the recording medium D (focusing direction) between the bollbin 2 and the bobbin (see FIG. 4). ), Suitable holding means are provided. The holding means is, for example, the ceiling inner wall portion 3 of the bobbin 3.
A, and the tops of the guide rails 2 and 2 are in sliding contact therewith. In this case, the guide rails 2, so that the bobbin 3 does not tilt left and right.
Both side surfaces of 2 are in contact with the inner wall surface of the bobbin 3. At the time of actual assembly, the clearance between the bobbin 3 and the side surfaces of the guide rails 2 and 2 is
It is preferable that the length be maintained at about 5 μm over the entire length in the seek direction. Furthermore, it is preferable that the inner peripheral surface of the bobbin 3 is coated with a Teflon-based lubricant to improve the sliding of the guide rails 2 and 2.

The guide rails 2 and 2 may be formed in a circular cross section as shown in FIG. 5 so that the sliding contact surface is reduced and the sliding is improved. Further, a plurality of balls 10 as shown in FIG. 6 may be rotatably supported on the inner wall surface of the bobbin, and the side surfaces of the guide rails 2 and 2 may be slid on this.

Further, inside the bobbin 3, tilt sensors 11, 11 which are located at the edge of the optical path from the mirror 5 to the objective lens 4 and are composed of photoelectric elements are provided. As shown in FIG. 4, when the bobbin 3 is rotated on a plane common to the seek direction and the direction perpendicular to the recording surface of the recording medium D (focusing direction), the inclination of the bobbin 3 can be measured. I am doing it. Then, based on the detection signals of the sensors 11 and 11, the phase / gain compensator 12A of the control means 12 shown in FIG. 7 is driven. The phase / gain compensator 12A is, for example,
It may be composed of an amplifier and a filter.

In addition to the phase / gain compensator 12A, the control means 12 is based on an optical signal provided from the optical recording medium D to the fixed optical unit 1 via the objective lens 4 and the mirror 5. It is equipped with a phase / gain compensator 12B that is driven by the motor. The signals from the phase / gain compensators 12A and 12B are given to the coils 7A, 7A and 7B, 7B functioning as focus servos via the adder 13A and the subtractor 13B. ing.

In such a structure, when the carrier (bobbin 3) is sought to the desired track of the recording medium D, a current for generating a magnetic field is passed through the coils 6, 6. As a result, the carrier is moved along the guide rails 2, 2. On the other hand, in the fixed optical unit 1, an error in the distance between the recording surface of the recording medium D and the focal point of the objective lens 4 is detected by a servo sensor (not shown),
At the same time, the tilt sensors 11, 11 detect the tilt amount of the objective lens 4. As a result, the control means 1 as described above
At 2, the coils 7A, 7A and 7B, 7B can be energized to apply the focus servo. In this case, the coils 7A and 7A have a phase / gain compensator 12
The two signals from A and 12B are added and the two signals are given to the coils 7B and 7B by subtracting the two signals. This is because it is necessary to give the bobbin 3 a rotational movement for tilt correction. For example, in FIG. 4, it is necessary that the upward driving force acts on the coil 7A and the downward driving force acts on the coil 7B.

For track tracking, an error in the distance between the required track and the focused spot position is read by a servo sensor (not shown) on the fixed optical unit 1 side, and the coils 6 and 6 are read according to the amount. Supply current to 6. This achieves fine adjustment in the tracking direction.

Although the tilt sensor detects the light emitted from the fixed optical unit 1 in the above embodiment, another light source may be prepared to detect the light from the light source. Of course good things. Further, in the above embodiment, the tilt sensor detects the tilt of the objective lens with respect to the linear motor, but it may detect the tilt of the objective lens with respect to the disk-shaped recording medium.

Further, in this embodiment, the drive coil for giving the turning motion to the bobbin by the detection signal of the tilt sensor also serves as the coil for correcting the focus error. Needless to say, the bobbin may be separately equipped with a coil for focusing driving.

[0017]

Since the present invention is constructed as described in detail above, it does not have a magnetic circuit on the movable part (carrier) of the optical head, so it can be made compact and lightweight, and is convenient for high speed access. Further, since the magnetic circuit is also used for tracking, focusing, and seeking functions, the overall structure is simplified. Also, the actuator for the objective lens
High precision can be achieved by simplifying the mechanical structure of the computer so that it can be moved in one plane. Furthermore, since the leakage of the magnetic flux generated from the magnetic circuit has almost no component perpendicular to the optical disk surface, there is an effect such that there is no adverse effect of the magnetic field on the recording film when recording / reproducing information on / from the disk.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional side view of the above embodiment.

FIG. 3 is a schematic vertical sectional end view of the embodiment.

FIG. 4 is a schematic vertical sectional side view showing a mode of use of the above embodiment.

FIG. 5 is a schematic vertical sectional end view showing an example of a holding means in the above-mentioned embodiment.

FIG. 6 is a schematic vertical sectional end view showing another example of the holding means in the above-mentioned embodiment.

FIG. 7 is a circuit configuration diagram showing an example of control means in the above embodiment.

[Explanation of symbols]

 1 Fixed Optical Unit 2 Guide Rail 3 Bobbin 4 Objective Lens 5 Refraction Mirror 6, 7A, 7B Coil 8 Magnet 9 Magnetic Material 10 Ball 11 Tilt Sensor 12 Control Means 12A, 12B Phase / Gain Compensator

Claims (5)

[Claims] 1. A refraction mirror for an objective lens of an optical head.
Along with being held on a carrier, the carrier is equipped with a coil for seek driving and a coil for tracking driving and a coil for focusing driving, and a magnet and a magnetic material are provided along the radial direction of the disk-shaped optical recording medium. In an objective lens driving device for arranging a constructed magnetic circuit, and controlling the movement of the objective lens in the seek direction, the tracking direction and the focusing direction by controlling the magnetic flux of the magnetic circuit and the current to the coil, An objective lens driving device comprising a holding means for holding the carrier so as to be movable and rotatable on a plane along a radial direction of the optical recording medium and a direction perpendicular to a recording surface. 2. A tilt sensor for detecting a tilt of an objective lens according to rotation of a carrier on the plane is provided, and an operation of the holding means is controlled by a detection signal of the tilt sensor. The objective lens driving device according to item 1. 3. A tilt sensor for detecting a tilt between a disk surface of the optical recording medium and an objective lens is provided, and the operation of the holding means is controlled by a detection signal of the tilt sensor. The described objective lens drive device. 4. A control means for controlling current supply to a coil for driving the carrier to rotate by a detection signal of the tilt sensor is provided.
The objective lens driving device according to item 1. 5. The objective lens drive device according to claim 4, wherein the coil for driving the carrier to rotate is also used as the focusing drive coil.