JPH10247326A - Optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select an objective lens by smoothly turning a lens holder whereon plural objective lenses are mounted, with a small electric power. SOLUTION: On the lens holder 1 provided so as turnable around a supporting shaft 8 and slidable along this supporting shaft 8, the objective lens 2 for CD and the objective lens for DVD(digital versatile disk) are mounted. Magnets 4, 4' are fixed on the lens holder 1, and tracking coils 6, 6' and focus coils 7, 7' having the fixed relation with the supported shaft 8 are arranged at the positions confronted with the magnets 4, 4'. Yokes 5, 5' guiding the magnetic flux generated from the magnets 4, 4' to the directions of coils 7, 7' are arranged almost all around the lens holder 1. The objective lens is selected by turning the lens holder 1 by 180 deg. with a current supplied to the coils 6, 6', in accordance with the kind of optical disks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recording a signal on an optical information recording medium (hereinafter, also referred to as an optical disk) such as a CD (compact disk), LD (laser disk), DVD (digital versatile disk), or The present invention relates to an optical head device for reproducing a signal.

[0002]

2. Description of the Related Art Conventionally, as an optical head device of this type, one disclosed in Japanese Patent Application Laid-Open No. Hei 8-7306 is known. This is described by borrowing the drawings of the publication,
As shown in FIGS. 6A and 6B, the objective lens 12 is fixed to a lens holder 11, and the lens holder 11 is rotatable about a support shaft 14 positioned parallel to the optical axis of the objective lens 12. And slidably provided along the support shaft 14. Also, the lens holder 11
A rod-shaped magnet 13 is fixed to the central portion of. Further, a tracking coil 5a and a focusing coil 5b which are fixed to the support shaft 14 are disposed outside the lens holder 11.
By passing a current through 5b, the magnet 13 fixed to the lens holder 11 is driven by receiving a force.
Inside the coils 5a and 5b, there is provided a yoke made of a magnetic material for efficiently guiding the magnetic flux generated by the magnet 13 toward the coils 5a and 5b.

In the above-described arrangement, the lens holder 11 is rotated or slid about the support shaft 14 to finely adjust the position of the objective lens 12, thereby reliably reading and writing data from / to the optical disk. Playback / recording). In addition, in the publication, as shown in FIGS. 6C and 6D, the objective lens 22 is
Some of the lens holders 21 have arc-shaped magnets 23 fixed thereto. This FIG. 6 (c)
In FIG. 6D, the same reference numerals as those in FIGS. 6A and 6B denote the same components, and a detailed description thereof will be omitted.

[0004]

A high-density optical recording / reproducing apparatus using the DVD, which has been actively developed in recent years, needs to be compatible with the CD. However, CDs and DVDs have differences in the wavelength of the laser used, differences in disk thickness, differences in the size of recording pits on recording media, and the like. Therefore, these C
Recording and reproducing two different types of discs such as D and DVD are performed by using an optical head device using one objective lens,
For example, it is difficult with the conventional optical head device shown in FIG.

In order to provide compatibility as described above, 2
There is also known one in which two objective lenses are mounted on a lens holder (see JP-A-8-221779 or JP-A-8-321206). In such a device, the operation of switching (selecting) the objective lens is required. However, in the above-mentioned publications, the power for excitation supplied to the coil is increased to switch the objective lens. There was a problem that it became difficult. In view of the above, it is an object of the present invention to provide an optical head device that can smoothly rotate a lens holder on which at least two objective lenses are mounted with low power and can perform the lens switching. is there.

[0006]

An optical head device according to the present invention, which solves the above-mentioned problems and achieves the above object, comprises:
A lens holder is provided that is rotatable about an axis and is slidable along the axis.In this lens holder, a magnet and a plurality of objective lenses are fixed,
A focus / tracking coil having a fixed relationship with the axis is arranged at a position facing the magnet, and the objective lens is selected by rotating the lens holder according to the type of the optical information recording medium. In the optical head device described above, the yoke for efficiently guiding the magnetic flux generated by the magnet in the direction of the coil is disposed substantially along the entire locus of the magnet drawn by the rotation of the lens holder. It is characterized by the following. In the lens holder, two different objective lenses are arranged symmetrically with respect to the axis, and the objective lens is selected by rotating the lens holder by 180 degrees along the yoke. You may. The lens holder is moved from a predetermined stable position of the lens holder where the objective lens is located at the center of the light source.
An inner diameter portion of the yoke corresponding to the magnet position when rotated by 0 degrees may be scraped off.

[0007]

According to the optical head device of the present invention constructed as described above, the yoke is disposed inside and around the tracking and focus coils so as to be closed in an arc shape or in a straight line, and the position with respect to the magnet is adjusted. Since the relationship is kept constant, the lens holder is always attracted to the yoke so that the optical pickup lens holder equipped with at least two or more objective lenses can be rotated with low power and smoothly. To change the lens.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is an assembly view of an optical head device, FIG. 2 is a lens holder of the device, FIG. 3 is a yoke of the device, FIG. 4 is a tracking coil of the device, and FIG. 5 is a focusing coil of the device. It is. As shown in FIG. 1, C
An objective lens 2 for D and an objective lens 3 for DVD are arranged, and the lens holder 1 is mounted on a support shaft 8 so as to be rotatable about the support shaft 8 and slidable along the support shaft 8. . The support shaft 8 is provided along the optical axis direction of the objective lenses 2 and 3. A driving magnet 4 is provided on a side surface of the lens holder 1.
The magnetic flux generated by the magnets 4 and 4 'is concentrated on yokes 5 and 5' made of a magnetic material, and the tracking coils 6, 6 'and the focus fixed to the yokes 5, 5' are fixed. By driving a current through the coils 7, 7 ', the driving force of the lens holder 1 is obtained by the generated Lorentz force.

A light source for reading an optical disk is shown in FIG.
The tracking coil 6 is disposed only below the VD objective lens 3 to reproduce a CD recording disk.
The lens holder 1 is turned by 180 degrees for switching by passing a pulse current in a certain direction in 6 '. At this time, the magnet 4 attached to the lens holder 1,
4 'rotates while being sucked along the yokes 5, 5'. The arc portions of the yokes 5, 5 'are magnets 4, 4'
In order to maintain a certain distance, the yoke 5,
The change in the attraction force generated between 5 ′ and the magnets 4 and 4 ′ is small. Therefore, the switching operation of the lens can be performed with a small current. However, the yokes 5, 5 'and the magnet 4,
If the suction force does not change too much between the magnets 4 and 4 ', the magnets 4 and 4' are rotated by the magnets 4 and 4 'when the lens holder 1 shown in FIG. '
Therefore, there is a fear that this rotation may be stopped in the vicinity. Therefore, the distance between the magnets 4, 4 'and the yokes 5, 5' is increased by intentionally shaving off the portions 11, 11'12, 12 'so as to avoid the stop of the rotation as described above. Good.

Although the conventional optical head device having no arc portion of the yoke as shown in FIG. 6 can switch the lens, the current value required for the rotation is smaller than that of the optical head device of the present invention. In addition, at locations where the yoke is interrupted, the attractive force generated in the lens holder and the magnet decreases rapidly, so that the rotation of the lens holder stops at a position where the rotation of the objective lens is not completed. There is fear.

In the optical head device of the present invention, it is necessary to position the objective lenses 2 and 3 of the lens holder 1 at the center of the light source in a stable state. As a countermeasure, the center of the yokes 5 and 5 'shown in FIG. Drill holes 10 and 10 'in the vicinity,
In the hole, a magnetic piece (not shown) is arranged on the inner peripheral side of the arc of the yokes 5, 5 'so that the magnets 4, 4' are restrained to some extent. This allows the objective lens 2,
Reference numeral 3 enables stable positioning at the center position of the light source.

In the above embodiment, the arc-shaped (semicircular) yokes 5, 5 'are arranged over the entire circumference of the lens holder 1, but short straight lines are joined at a predetermined angle. A yoke having a shape may be used, and the yoke may be arranged in a polygonal shape over the entire circumference as described above. Further, in the above-described embodiment, the case where two objective lenses are used has been described. However, the present invention can be implemented by mounting more objective lenses on the lens holder.

[0013]

As described above, since the optical head device of the present invention is configured as described above, two or more objective lenses can be switched stably and with a small current.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a main part of the device shown in FIG.

FIG. 3 is a perspective view showing another main part of FIG. 1;

FIG. 4 is a perspective view showing another main part of FIG.

FIG. 5 is a perspective view showing another main part of FIG.

6 (a) is a plan view of a first conventional example, FIG. 6 (b) is a partial longitudinal front view thereof, FIG. 6 (c) is a plan view of a second conventional example, (D) is a partial longitudinal front view thereof.

FIG. 7 is a perspective view showing a modification of the one shown in FIG. 3;

[Explanation of symbols]

 Reference Signs List 1 lens holder 2 CD objective lens 3 DVD objective lens 4, 4 'magnet 5, 5' yoke 6, 6 'tracking coil 7, 7' focus coil 8 support shaft 10, 10 'hole

Claims (3)

[Claims] A lens holder provided rotatably about an axis and slidable along the axis, wherein a magnet and a plurality of objective lenses are fixed to the lens holder; Focus / fixed relationship with axis
In an optical head device, a tracking coil is disposed at a position facing the magnet, and the objective lens is selected by rotating the lens holder according to the type of the optical information recording medium. An optical head device, wherein a yoke for efficiently guiding a generated magnetic flux in the direction of the coil is disposed substantially along the entire locus of the magnet drawn by the rotation of the lens holder. 2. The optical head device according to claim 1, wherein two different objective lenses are symmetrically arranged on the lens holder with respect to the axis, and the lens holder is rotated by 180 degrees along the yoke. An optical head device wherein an objective lens is selected by rotating. 3. The optical head device according to claim 2, wherein the objective lens corresponds to the magnet position when the lens holder is rotated 90 degrees from a predetermined stable position of the lens holder located at the center of the light source. An optical head device, wherein an inner diameter portion of the yoke is cut off.