JPS61260430A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To make a circuit part, which drives an objective lens reverse to a receding position, unnecessary by attaching a magnetic piece to a movable holding member to place the objective lens in the position most distant from the recording face of a rotating disc in the initial state. CONSTITUTION:A ring-shaped magnetic piece 13 is attached to the upper face of a bobbin 12 concentrically to an objective lens 6. Since a leaked magnetic field 15 attracts the magnetic piece 13, no only the weight of a moving part itself (a bobbin 12, a driving coil 10, the objective lens 6, the magnetic piece 13, etc.) supported by a suspension 11 but also an electromagnetic force F act upon this moving pat. Thus, the suspension 11 is deformed downward, and the objective lens 6 is always placed as low as possible. That is, a convergent spot 3 is always placed under a disc recording face S, and therefore, the objective lens 6 is driven only upward for leading-in of focus servo to bring it to the optimum focus position.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an objective lens driving device in an optical information reading device such as an optical video disc player, and more specifically, the field of application of the invention relates to an objective lens driving device in an optical information reading device such as an optical video disc player. ) The present invention relates to such an objective lens drive device with a structure that is conducive to good retraction of the direction servo.

[Background of the invention]

FIG. 4 is a perspective view showing an example of the configuration of a general pickup unit for reading information from a disc in a video disc player (optical information reading device).

In the figure, 1 is an information (disc) recording surface, 2 is a pickup section, 3 is a convergence spot, 4 is a laser beam, 5 is an objective lens drive device, 6 is an objective lens, 7 is a laser diode, and 8 is a photodetector. , 2Ati collimating lens, 2
B is a diffraction grating, 2C is a prism beam splitter, 2D
, 2E are mirrors, 2F is a 7-wave plate, 2G, 2H
are lenses, and 2I is a cylindrical lens.

As is well known, the operation of this pickup unit is such that the luminous flux 4 emitted from the laser diode 7 is 2B.

The objective lens 6 passes through various optical components such as 2C, 2D, and 2F.
The reflected light flux that connects the convergent spot 3 on the recording surface 1 and thereby obtains the recorded information on the recording surface 1 and the position information of the spot 3 is again 6.2F, 2D, 2C, 2H, 2
It can be said that the present invention relates to an improvement of the objective lens driving device 5 in such a pickup section.

FIG. 5 is a sectional view showing details of a conventional objective lens driving device. In the figure, the objective lens 6 is attached to a bobbin 12 having a focus direction drive coil 10. The bobbin is suspended by a suspension 11 in a magnetic circuit consisting of a magnet (9t)*yokes (9-2) and (9-3). 16 is a fixed frame.

Now, when trying to play back a disc 1 that has been deformed downward for some reason using the objective lens drive device described above, the objective lens 6 will only move down a distance of W/ due to its own weight (here K
(W is the spring constant of the suspension for all movable parts including the objective lens, bobbin, etc.) Therefore, as shown in the figure, the convergence spot 3 must originally be located below the disk recording surface S. In some cases, the recording surface S may be located so that it penetrates above the recording surface S.

When the convergence spot 3 is initially located below the recording surface S, the objective lens 6 is gradually driven upward, and when the spot 3 reaches the recording surface S, a focus error signal is generated.
Then, a means not shown starts pulling in the focus servo of the objective lens.

However, if the convergent spot 3 penetrates the recording surface S and is above it from the beginning, when trying to position the spot 3 on the recording surface 3, a current is first applied to the drive coil 10 and the objective lens 6 is pushed down once. , it is necessary to gradually push up the objective lens 6 again.

While the objective lens 6 is being pushed up in this manner, a focus error signal appears on the photodetector 8 near the optimal focus position (the position where the spot 3 reaches the recording surface S), and the servo is turned on.

For this reason, in the conventional technology, when trying to reproduce a disk that is deformed downward, where the convergence spot 3 penetrates the recording surface S and is located above it, the focus pull-in circuit becomes complicated and an expensive servo circuit is required. there was.

Incidentally, as a conventional document that touches on this problem, Japanese Patent Application Laid-open No. 128707/1983 can be mentioned.

[Purpose of the invention]

The purpose of the present invention is to prevent the deformation from occurring without requiring complicated operations such as pushing down the objective lens and then gradually lifting it up, even when attempting to play a disc that has been significantly deformed downward for some reason. To provide an objective lens drive device for an optical information reading device, which allows the objective lens to be easily drawn into a focus servo by gradually driving the objective lens upward from the beginning, as in the case of trying to reproduce a normal disk that is not properly read. It is in.

[Summary of the invention]

In order to achieve the above object, the present invention provides a magnetic piece on the top surface of a lens holding bobbin of an objective lens driving device, and constantly moves the objective lens to a further level by the attraction effect that acts between the magnetic piece and the leakage magnetic field of the magnetic circuit. Even if the disc is pulled down to a low position (far away from the recording surface) and deformed downward, the convergence spot will never penetrate the recording surface and will always remain below the recording surface (far away from the recording surface). direction).

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of the present invention.

In this figure, the same parts as in FIG. 5 are given the same reference numerals. In addition, 13 indicates a ring-shaped magnetic piece (for example, a molded product of light ferrite and plastic), and 14 indicates electromagnetic force.

The difference between the conventional structure shown in FIG. 1 and the conventional structure shown in FIG. It is a point that is attached concentrically.

FIG. 2 is a perspective view of the main parts in FIG. 1.

By referring to the figure, it will be easily understood that the ring-shaped magnetic piece 13 is attached to the top plate of the pobbin 12 concentrically with the objective lens 6.

Figure 3 shows the magnetic circuit ("Magnets") (9) in Figure 1.
-1), yoke (9-2), and (9-kl)) is an explanatory diagram showing a situation where a leakage magnetic field 15 is generated.

Referring again to FIG. In FIG. 1, the movable parts (bobbin 12,
drive coil 10, objective lens 6, magnetic piece 13, etc.),
In addition to its own weight, an electromagnetic force F (14 shown in FIG. 1) acts on it. Therefore, the suspension 11 is largely deformed downward, and the objective lens 6 is always located at the lowest possible point.

That is, as shown in FIG. 1, the convergence spot 6 is always located below the disk recording surface S, so when the focus servo is pulled in, the objective lens 6 is driven only upward to bring it to the optimum focal position. I can go.

It should be noted that the present invention has been described with reference to a case where the objective lens driving device is a stationary device arranged in a direction perpendicular to the horizontal direction, and a case where the movable part is supported by a suspension is taken as an example.
It goes without saying that the present invention can also be applied to an objective lens drive device having a structure in which the objective lens drive device is installed horizontally and the suspension supporting the movable part is not provided.

〔Effect of the invention〕

According to the present invention, in an objective lens driving device for an optical information reading device, a circuit section for driving the objective lens in the reverse direction to the retracted position is unnecessary by simply mounting a lightweight magnetic piece on the bobbin. . Therefore, it is possible to significantly reduce costs and reduce the number of parts.

It is clear that the same effect can be obtained even if a small magnet is provided instead of the lightweight magnetic piece.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
FIG. 3 is an explanatory diagram showing a situation where a leakage magnetic field is generated from the magnetic circuit in FIG. 1. FIG. 4 is an example of the configuration of a general pickup section in an optical information reading device. FIG. 5 is a sectional view showing details of a conventional objective lens driving device. Symbol explanation 1...disk, 2...pickup, 3...convergence spot, 4...laser beam, 5...objective lens drive Device, 6...
...Objective lens, 7...Laser diode,
8...Photodetector, 9-1...Magnet, 9-2.9-3...Yoke, 10...
... Drive coil, 11... Suspension /, 1
2...Bobbin, 13...Magnetic piece, 14
・・・・・・Electromagnetic force, 15・・・△ ・・・Leakage magnetic flux, 2A to 2 engineering・・・・Optical parts, 1
6... Suspension fixed frame agent Patent attorney Akio Namiki Fig. 1 Tomi 2 TyJ kl Surirenmata @ 3 WJ Fig. 5 Parking I + 7 coil 舊 4 Fig. 9L * See you tomorrow 1ζ

Claims (1)

[Claims] 1) A coil is placed on a movable holding member that holds the objective lens and placed in a magnetic field, and the interaction between the current flowing through the coil and the magnetic field causes the objective lens to be moved to the recording surface of the rotating disk. In an objective lens driving device for an optical information reading device that is driven to move toward or away from the coil, a magnetic piece is attached to the movable holding member, and in an initial state in which no current is flowing through the coil, the magnetic piece An objective lens driving device characterized in that the objective lens is positioned at a position farthest from a recording surface of a rotating disk by interaction between the magnetic field and the magnetic field.