JPH03222122A - Objective lens driver - Google Patents

Abstract

PURPOSE:To ensure the irradiation of laser light to a recording surface by making the shape of a tracking coil which is installed together with a focusing coil at a movable part to constitute an objective lens driving device nearly triangular, and in addition, making one side of a part intersecting the central part of its magnetic field perpendicular to a tracking direction. CONSTITUTION:The focusing coil 5 is wound around the outer circumference of a bobbin 7 surrounding the objective lens 2, and the tracking coil 1 is installed at the part of its surface positioned in the tracking direction, and at that time, the coil 1 is made flat, and in addition, its shape is made nearly triangular. Namely, in order to make the difference of electromagnetic force due to the difference of the distribution of intensity of magnetic field in a focus ing direction small, the central part where the intensity of magnetic field is large is used as driving force in the tracking direction. Besides, unnecessary electromagnetic force acting in the focusing direction makes one side of the coil situated at a position where the difference of the distribution of the mag netic field in the focusing direction is small. Thus, track tracing correct to the recording surface can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an objective lens drive device for irradiating a recording medium with laser light in an optical information recording device, and particularly to a drive mechanism for driving an objective lens in a track direction.

[Conventional technology]

To optically record and read from media, laser light must be precisely focused onto the recording surface. That is, a support mechanism and a driving device are required that allow the objective lens to be moved in the focus direction, which is perpendicular to the recording surface, and in the track direction, which is the radial direction of the recording medium. These methods include methods that utilize electromagnetic forces obtained by spring support mechanisms, magnets, and coils. for example,
As shown in FIG. 3, which is a side view of the main part of the movable body, the objective lens 2 is held by a bobbin 7, and a focus coil 5 and a track coil 11 to which current is applied are connected to the bobbin 7.
is fixed to. Here, the arrow of the track coil 11 indicates a unidirectional example of the current direction. The focus coil 5 and the track coil 11 are arranged in a magnetic circuit that generates a magnetic field perpendicular to the drawing, and the objective lens 2 and the bobbin 7 are driven in the focus direction and the track direction by electromagnetic action with the current flowing through the coil. .

[Problem to be solved by the invention]

In the above-described configuration, the driving direction and driving force are determined by the magnetic field direction and current direction in the track coil 11, so it is necessary to consider the balance of the driving force in order to accurately drive the bobbin 7 in the track direction. There is. In particular, when the bobbin 7 is moved in the focus direction, a difference occurs in the number of interlinked magnetic fluxes of the track coil 11 in the focus direction, which appears as a difference in driving force. That is, due to the strength distribution of the magnetic field and the shape of the track coil, a rotational moment is generated that causes the objective lens to tilt in the track direction, causing a resonance phenomenon in the rolling direction of the support spring, making it impossible to accurately trace the track on the recording surface. The drawback is that it disappears.

[Means to solve the problem]

The objective lens drive device of the present invention holds an objective lens that irradiates a recording medium with a laser beam, and also includes a movable member having a flat coil, and a plurality of springs that support the movable member movably in a track direction and a focus direction. and a magnetic circuit that generates a driving force by electromagnetic action, the flat coil has a substantially triangular shape, and a portion interlinking with the center of the magnetic field is perpendicular to the track direction. The configuration is such that one side of the triangle is arranged so that

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) is a plan view showing one embodiment of the present invention.

FIG. 1(b) is a side view of FIG. 1(a). The objective lens driving device of the present invention includes a track coil 1, an objective lens 2,
．． Magnet 3. Spring 4. Focus coil5. Base 6
．． It consists of a bobbin 7 and a yoke 8, and the bobbin 7 is connected to the base 6.
It is supported by a spring 4 and is movable in the focus direction and the track direction. Further, a magnet 3 is fixed to the base 6 so as to face a yoke 8, and a focus coil 5 and a track coil 1 are arranged in a gap. Then, the focus coil 5 and the track coil 1 are energized, and as a driving force of electromagnetic action,
The fixed bobbin 7 and objective lens 2 are driven in the track direction and the focus direction.

FIG. 2 is a plan view showing a track coil of a movable body which is a main part of an embodiment of the present invention. The track coil 1 of the present invention has a substantially triangular shape, and one side of the triangle is arranged such that the portion interlinking with the center of the magnetic field is perpendicular to the track direction.

Here, the track coil 1 uses the center part where the strength of the magnetic field is large as a driving force in the track direction in order to reduce the difference in electromagnetic force due to the difference in the distribution of magnetic field strength in the focus direction. The unnecessary electromagnetic force acting on the magnetic field is eliminated by arranging the coil at a position where the difference in the distribution of the magnetic field in the focus direction is small. That is, even if the objective lens is moved up and down in the focus direction, the difference in driving force of the track fill in the focus direction due to the difference in magnetic field strength can be reduced.

〔Effect of the invention〕

As explained above, by using the objective lens driving device of the present invention, unnecessary driving force in directions other than the track direction becomes extremely small, and the objective lens can be accurately driven in the track direction. That is, the laser beam can be reliably irradiated onto the recording surface, and accurate track racing against the recording surface can be performed.

[Brief explanation of drawings]

FIG. 1(a) is a plan view showing an embodiment of the present invention, FIG. 1(b) is a side view of FIG. 1(a), and FIG. 2 is a side view of essential parts showing an embodiment of the present invention. FIG. 3 is a side view of main parts showing a conventional example. 1.11...Track coil, 2...Objective lens,
3...Magnet, 4...Spring~5...Focus coil 6...Base, 7...Bobbin, 8...Yoke.

Claims (1)

[Claims] A movable member that holds an objective lens that irradiates a recording medium with a laser beam and has a flat coil, a plurality of springs that support the movable member so as to be movable in the track direction and the focus direction, and generates a driving force by electromagnetic action. In the objective lens driving device, the flat coil has a substantially triangular shape, and one side of the triangle is arranged so that a portion interlinking with the center of the magnetic field is perpendicular to the track direction. An objective lens driving device characterized by: