JPS60101733A - Focus actuator for optical head - Google Patents

Abstract

PURPOSE:To obtain a thin optical head by arranging a voice coil motor coil which drives a condenser lens so that its focus is set at a specific position and an optical path conversion mirror which changes the optical path of light incident from a light source to a specific optical path in parallel. CONSTITUTION:The voice coil motor (VCM) coil is a flat coil and formed in a U shape. This flat VCM coil 3c is adhered to the internal surface A of a U-shaped fitting member 3. Then folding parts of the coil 3c are inserted into two couples of right and left yokes 6 of magnetic circuits 5 which have permanent magnets in the yokes 6 and are sectioned in a U shape. Further, the mirror 8 as the optical path changing means is provided at the other terminal of the optical path and horizontal optical paths of incidence (perpendicular to paper surface) parallel to the folding parts of the coil are set; and the optical path is bent toward the lens 1 by the optical path changing means.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a mechanical actuator for an optical head used in an optical desk device, and particularly relates to an improvement in the mechanical structure.

(b) Prior Art and Problems In an optical disk device that records information on a recording medium by optical means and reproduces the recorded information, a focus servo system is used to always keep the focus of an objective lens on the recording medium. For this purpose, a focus actuator is usually provided to move the objective lens in a direction perpendicular to the recording medium.

The stroke of this actuator is around one stroke, but since quick response is required, a voice coil motor (hereinafter referred to as VCM) is usually used.

Conventionally, a focus actuator as shown in the sectional view of FIG. 1 has been used, and the mechanical structure of the focus actuator will be explained with reference to the figure.

The recording medium 1 is rotated at high speed by a rotating motor (not shown). The condensing lens 2 condenses light from the light source onto the recording medium 1. The coil bobbin 3 has a VCM coil 3b wound around an excitation bobbin portion 3a. The support mechanism 4 is made of an elastic body such as a leaf spring or rubber, and supports the movable part consisting of the condenser lens 2 and the coil bobbin 3. The magnetic circuit 5 has a U-shaped cross section with a yoke 6 and a permanent magnet 7 connected in series, and a VCM coil 3b is inserted in the 0-shape.

The operation of the focus actuator is such that when a focus position control current input from an external source (not shown) is applied to the VCM coil 3b, the coil moves upward or downward in response to the focus position control current due to interaction with the magnetic flux created by the magnetic path 5. do.

Along with this movement, the condenser lens 2 also moves up and down, condensing the light from the light source onto the recording medium 1.

In the example shown in Figure 1, the light from the light source must enter or exit from the direction of arrow Kl, and the optical system and other components necessary for the optical head must be installed below the focus actuator in Figure 1. . Therefore, there is a drawback that the thickness of the entire optical head becomes thicker. Further, in another conventional example shown in FIG. 2, an optical path converting mirror 8 is provided between the condenser lens 2 and the coil bobbin 3. In this format, the optical system can be installed next to the actuator, making the entire structure thinner than in Figure 1, but it still requires the objective lens 2, optical path conversion mirror 8, and coil bobbin 3 to be arranged in series. The disadvantage is that the overall thickness is determined by

(C1 Purpose of the Invention The present invention was devised in view of the above-mentioned drawbacks of the conventional focus actuator, and its purpose is to improve the mechanical structure of the focus actuator and provide a thinner optical head. be.

+d+ Structure and object of the invention According to the present invention, a flat coil formed in a U-shape is attached to a movable member equipped with a condensing lens, and its bent portion is positioned in a predetermined magnetic field. a focal position adjusting means for adjusting the focal position by controlling the current in the coil and moving the condensing lens; and changing the optical path of the light incident below the coil through the side of the flattened coil toward the condensing lens. This is achieved by a focus actuator for an optical head, which is characterized by being provided with an optical path changing means.

(e) Embodiment of the invention Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. Third
The figure shows a perspective view of the flat coil of the present invention, and FIG. 4 shows a cross-sectional view of the focus actuator of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals.

In the present invention, the VCM coil is a flat coil as shown in FIG. 3, and is bent into a U-shape.

This flat VCM coil 3C is adhered to the inner surface A of the mounting member 3d, which also has a U-shape. In FIG. 4, the bent portion of the U-shaped flat VCM coil 3c shown in FIG. It is inserted into the two pairs of left and right yokes 6 of rotation 1i'85. Further, a mirror 8 as an optical path changing means is provided at the other end of the optical path. This mirror 8 may be a prism. In short, U-shaped flat VC
A horizontal incident optical path (perpendicular to the paper surface) parallel to the bent portion of the M coil 3c is set on the lower surface of the M coil 3c, and the optical path is bent in the direction of the lens 1 by the optical path changing means.

The operation is performed by applying a position control current input from an external device (not shown) to the VCM coil 3c, and moving the VCM coil 3 equipped with the condensing lens 2 with respect to the recording medium 1 to constantly record the focal point of the condensing lens 2. It is connected to a predetermined location on the medium 1 to collect light that is incident from a direction perpendicular to the paper surface of FIG. 4 and whose optical path is changed by the optical path changing mirror 8.

In this way, the incident optical path can be set through one side of the flat VCM coil 3C, and the optical path changing mirror 8 is arranged at approximately the same height as the VCM coil, so it is thinner than the conventional example. An optical head is obtained.

(f) Effects of the Invention As is clear from the above explanation, the present invention is based on a VCM that drives a condenser lens to focus on a predetermined location.
A thin optical head can be obtained by arranging in parallel a coil and an optical path conversion mirror that converts light incident from a light source into a predetermined optical path direction.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional focus actuator, Figure 2 is a cross-sectional view of a conventional focus actuator.
The figure is a cross-sectional view of another conventional focus actuator.
The figure shows a perspective view of the VCM coil 1H4 of the present invention, and FIG. 4 shows a sectional view of the focus actuator of the present invention. In the figure, ■ is a recording medium, 2 is a condensing lens, 3 is a coil bobbin, 3a is an excitation bobbin part, 3b is a VCM coil,
3c is a flat VCM coil, 3d is a coil mounting member, 4 is a support mechanism, 5 is a magnetic circuit, 6 is a yoke, 7 is a permanent magnet, 8
indicates an optical path conversion mirror. 1st Prisoner 2 Leap 3rd Figure 4th Garden 5

Claims (1)

[Claims] A U-shaped flat coil is attached to a movable member equipped with a condensing lens, its bent portion is positioned in a predetermined magnetic field, and the condensing lens is moved by controlling the current of the flat coil. a focal position adjusting means for adjusting the focal position by
A focus actuator for an optical head, comprising an optical path changing means for changing the optical path of light incident below the coil through the side of the flat coil toward the condensing lens.