JPH04205821A - Objective lens drive device - Google Patents

Abstract

PURPOSE:To achieve overwriting and enable recording and reproduction speed of information to be improved by mounting a plurality of objective lenses to a same bobbin, placing each objective lens in the same track circumferential direction of a recording medium, and driving in focus direction and track direc tion independently. CONSTITUTION:Detection beams 3a and 3b which are emitted from a fixed optical system 2 are sent to a coarse actuator 4 which runs in radial direction of a recording medium 1, are guided to an objective lens drive device 5a which is mounted to the coarse actuator 4, and are collected onto a target track on a recording medium 1 by objective lenses 6a and 6b, thus enabling information to be recorded and reproduced. At this time, the objective lens is controlled independently by an objective lens drive device 5a using two objective lenses at the same bobbin 12, thus achieving overwriting and at the same time improving recording and reproduction speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an objective lens driving device that forms a light spot on a recording medium for recording and reproducing information.

[Conventional technology]

Conventionally, in optical disk devices that use a recording material for recording and reproducing information, information is erased in one rotation of the recording medium and written in the second rotation, so the recording process is performed twice to record new information. Because the medium was rotated, it took time to rewrite the data, and the information transfer speed was slow.

On the other hand, for example, the objective lens active device described in ``Development of twin actuator magneto-optical head for override'' at the Spring National Conference of the Institute of Electronics, Information and Communication Engineers (1989) and in Japanese Patent Application Laid-Open No. 2-49224, An attempt has been made to solve the above problem by using an independent objective lens driving device for the purpose of writing information immediately after erasing it.

In this method, the interval between the objective lenses provided in each objective lens driving device, that is, the interval in the circumferential direction of the recording medium between the beam spot of the focused beam emitted from each objective lens on the recording medium is independent. Due to the configuration of the two objective lens driving devices, there are 36 II [l] on the outer peripheral side of the recording medium, and 18 ends on the inner peripheral side.

[Problem to be solved by the invention]

In the prior art, the interval between the objective lenses provided in each objective lens recording device, that is, the interval in the circumferential direction of the recording medium between the beam spot of the condensed beam emitted from the objective lens on the recording medium. However, on the outer circumferential side of the recording medium, it is 36 mm.
, and there are 18 strokes on the inner circumferential side. By reducing this interval, it is possible to further shorten the rewriting time, but due to the structure of the two independent objective lens drive devices, it is difficult to reduce the interval to less than this.

SUMMARY OF THE INVENTION An object of the present invention is to construct an optical disc device that allows overwriting of recording media for recording and reproduction and has a high information transfer rate, and to reduce the size and cost of an objective lens driving device.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an optical disc device using a recording medium for recording and reproducing information, in which a plurality of objective lenses are attached to the same bobbin, and each of the objective lenses is attached to the same track circle of the recording medium. The objective lenses are arranged adjacent to each other in the circumferential direction, and each objective lens has a means for independently moving in the focus direction and the track direction.

[Effect]

In the present invention, by attaching the objective lenses of the objective lens driving device to the same bobbin, the interval between the objective lenses, that is, the recording of the beam spot of the condensed beam emitted from the objective lens on the recording medium. The circumferential spacing between the media can be reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 10. FIG. 1 shows a perspective view of the vicinity of an access mechanism of an optical disc device equipped with an objective lens drive device according to an embodiment of the present invention.

A detection beam 3a emitted from the fixed optical system 2.

3b is sent to the course actuator 4 traveling in the radial direction of the recording medium 1, guided to the objective lens drive device 5a mounted on the course actuator 4, and then driven by the objective lenses 6a and 6b included in the objective lens drive device. , focuses the light onto a target track on the recording medium 1, and records and reproduces information. The present invention is an objective lens driving device using two objective lenses on the same bobbin as shown in the figure, and by independently controlling the objective lenses, it is possible to override and improve the recording and playback speed. . The objective lens driving device will be explained in detail later.

FIG. 2 is a perspective view of the vicinity of an access mechanism of a conventional optical disc device. One objective lens 6 is attached to the objective lens driving device 5, and information is recorded onto and reproduced from the recording medium 1 using only the objective lens 6.

FIG. 3 is a perspective view of the vicinity of an access mechanism of an optical disk device equipped with a recently proposed objective lens drive device. This has a configuration that uses two conventional objective lens drive devices. The objective lens moving device will be explained in detail with reference to FIG.

Detection beam 3a from fixed optical system 2 in FIG.

3b is sent to each independent objective lens driving device by the raising prism 11 attached to the coarse actuator 4. For example, one objective lens driving device is used for erasing information, and the other is for writing information, so that writing can be performed immediately after erasing. Therefore, it is possible to increase the recording and reproducing speed. But recorded as mentioned above.

In order to increase the playback speed, the distance between the objective lenses 6a and 6b provided in the objective lens active device, that is, the distance between the beam spot on the recording medium 1 of the condensed beam emitted from the objective lens and the distance on the recording medium 1 is determined. The problem is how to reduce the distance in the circumferential direction (the current diameter of the lens is about 51 mm)
1I11, approximately 10Wn is considered to be the limit) In this configuration, a magnetic circuit (drive coils 10a, 10b, magnet 8a,
A yoke 7a) is arranged, and due to the structure, it is not possible to reduce this interval to the above-mentioned limit.

Furthermore, since two objective lens drive devices are used, the device itself becomes large and has a large number of parts, making it impossible to reduce costs.

FIG. 5 is a perspective view of the objective lens driving device 5a shown in FIG. 1, which is provided in an optical disc device according to an embodiment of the present invention. The bobbin 12 includes an objective lens 6a that focuses the detection beam 3a emitted from the fixed optical system 2 onto the recording medium 1, and an objective lens 6b that focuses the detection beam 3b onto the recording medium 1.
A focusing magnet 8c, a yoke 7c, a driving coil 10C1, and a tracking magnet 8d are attached as magnetic circuits for controlling the respective objective lenses 6a and 6b in the focusing direction and the tracking direction.

A yoke 7d and a drive coil 10d are provided.

FIG. 6 shows the driving direction of the objective lens and the support method of the bobbin 12. As shown in the figure, the opening direction is the focus direction and the track direction as the translation direction, and the rotation direction is the four directions of rotation about the disk radial direction and the disk normal direction. A movable support system must be used in these four directions, and a highly rigid support system must be used in all directions other than the four directions to minimize unnecessary displacement. Therefore, the support system was a combination of two Versuspensions 9C and two leaf springs. The versatility 9c has high rigidity in the longitudinal direction, that is, the track direction, and low rigidity in other directions, so it can be displaced in the focus direction but cannot be moved in the track direction. Therefore, the two Versuspensions 9C are supported by two leaf springs 9b in a direction perpendicular to the longitudinal direction of the Versuspension 9C via the intermediate holder part 13, and the other end is fixed to the support part 14. And so.

Since the two leaf springs 9b have low rigidity in the track direction (direction around the axis in the focus direction in the figure),
In combination with c, displacement in the track direction is possible.

FIG. 7 shows a plan view of an objective lens prompting device according to another embodiment as viewed from the recording medium 1 side, and FIG. 8 shows a perspective view of FIG. 7. The magnetic circuit includes a drive coil 1 in the focus direction.
With 0c as the upper part, yoke 7c.

The magnet 8c is configured in a loop shape, thereby making it a magnet.

The gap magnetic flux density and distribution between the yokes can be used effectively to increase thrust and sensitivity. Also,
Similar effects can be obtained by using a track magnetic circuit for the magnetic circuit configuration.

Conditions for independently controlling the objective lens in the focus direction and the track direction in the objective lens driving device described above will be explained using FIG. 9.

In the figure, F□, F2 are the driving forces applied to each optical head, G is the center of gravity of the movable part, γ is the distance between the center of the movable part and the lens, and Ω is the distance between the center of the movable part and the driving force TF2 (noted). The position is the thrust center position of the drive coil) X, x2 is the amount of lens movement due to the driving force F, F2.

Also, the natural frequency ωnP in the translational direction and the natural frequency ω in the rotational direction. , then...(1)...(2).

If this relationship is expressed in a matrix, it will be as follows (4). Here, matrix B is added to achieve stable control.

...(5) In the above, let the determinant be. The condition is that when one lens is controlled, the other does not move, that is, A, 2 = O A2 □ = O A1 □ = A2 □ Therefore, A1 □ = C □ 1 B work, + C1 □ *B2□A1□=C2
□Wood B□, +C2□C12□A21= c,, *B
12 + C work 2*B2□A2□=C2□*B□2+C
Must be 2□*B2□. Therefore, each term B00 of matrix B. The mutual relationship between B engineering m + 13zx + BZ□ must satisfy (8), (9), and (10). In equations (8) to (10) above, the value of B-factor 2 is a proportional constant, so the gain is
It can be adjusted depending on the size of B work 2.

FIG. 10 shows the flow of the aforementioned control.

The amount of movement of each lens is becomes.

By driving two-dimensional actuators mounted on the same bobbin for both lenses through a matrix circuit including matrix BIJ that satisfies the above conditions, the two objective lenses can be controlled by independent command signals F1.

〔Effect of the invention〕

According to the present invention, it becomes possible to override in an optical disk device, improve the recording and reproducing speed of information, increase the processing speed of information, and make it possible to respond to continuous data such as image information in real time. . Furthermore, the present invention can be applied to fields where high data transfer speed is required, such as optical disks and computer memories of magneto-optical disk devices.

Further, the objective lens driving device can be made smaller, and the number of parts can be reduced, thereby reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the peripheral part of the objective lens drive device of the optical disc device of the present invention, and FIG. FIG. 3 is a perspective view of the peripheral area of a conventional objective lens drive device;
FIG. 4 is a perspective view of a conventional objective lens drive device, FIG. 5 is a perspective view of an objective lens drive device of the present invention, and FIG. 6 is a control method and support system for the objective lens drive device of the present invention. A perspective view, FIGS. 7 and 8 are a plan view and a perspective view of another embodiment of the objective lens drive device, FIG. 9 is an explanatory diagram of the relationship between drive and displacement, and FIG. 10 is a control block. It is a diagram. DESCRIPTION OF SYMBOLS 1: Recording medium, 2: Fixed optical system, 3: Detection beam, 4: Coarse actuator, 5a: Objective lens drive device of the present invention, 5b: Conventional objective lens drive device,
6...Guide rail, 7.Yoke, 8.Magnet, 9.
・Supporting member, 10... Drive coil, 11... Standing prism, 12... Bobbin, 13 Intermediate holder, Figure 1, Figure 2! 4th 0L 50th 7m

Claims (1)

[Claims] 1. In an optical disc device, a plurality of objective lenses are attached to the same bobbin, the objective lenses are arranged adjacent to each other in the circumferential direction of the same track of a recording medium, and the objective lenses are independently directed in the focusing direction and in the track direction. An objective lens driving device characterized by being provided with driving means.