JPH0517618B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an objective lens driving device, particularly to a reproduction device that controls track deviation and defocus of a light spot focused on an information recording surface of an optical disk. The present invention relates to an objective lens driving device for a device or a recording/reproducing device.

[Prior Art] FIGS. 7 to 10 show a conventional objective lens drive device. In the figures, 1 is an objective lens, 2 is a counterweight, and 3 is a cylindrical bearing 3.
4 is a support shaft on which the bearing 3a of the lens holder 3 is fitted so as to be slidable in the axial direction of arrow A in FIG. 8 and rotatable in the direction of arrow B in FIG. 9; support rubber that holds the lens holder 3;
6a, 6b are permanent magnets, 7a, 7b are yokes, 8
9 is a yoke that also serves as a holding base for the support shaft 4 and permanent magnets 6a and 6b, 9 is a fixing base for the support rubber 5, 10 is a focus control coil, 11a, 11b, 11c, and 11d are track control coils, 12a, 12b 1 is a fixing screw for attaching the support rubber 5 to the fixing base 9, 13 is a cover, and 14 is a coil holder.

Next, the operation will be explained. By applying a desired current to the focus control coil 10, the lens holder 3 slides in the direction of arrow A to perform focus control. In addition, track control coils 11a, 11
By applying a desired current to b, 11c, and 11d, the lens holder 3 rotates in the direction of arrow B.
Track control is performed by rotating the objective lens 1, which is fixed at a position on the lens holder 3 that is a certain distance away from the support shaft 4.

[Problems to be Solved by the Invention] Since the conventional objective lens drive device is configured as described above, the focus control coil 10, the track control coils 11a, 11b, 11c, 11d
are permanent magnets 6a, 6b and yokes 7a, 7
Since the same magnetic circuit formed by magnets 6a and 8 is used, the permanent magnets 6a and 6b cannot be arranged around the entire circumference, and a portion thereof must be cut out. this is,
Truck control coils 11a, 11b, 11c,
Since 11d is rectangular, the focus control coil 1
If you try to use the same magnetic circuit as 0, the track control coils 11a, 11b, 11c, 11d
This is because only a part of the magnetic field can be placed in the magnetic path.

For this reason, the entire circumference of the focus control coil 10 cannot be used, resulting in poor usage efficiency. or,
Since the track control coils 11a, 11b, 11c, and 11d are attached above the focus control coil 10, the gap in the magnetic circuit needs to be large. That is, as shown in FIG. 10, since the gap H of the magnetic circuit is determined by the coil holder 14, the focus control coil 10, and the track control coil 11a, it is necessary to increase the gap of the magnetic circuit. Therefore, in order to obtain the necessary magnetic flux density, it is necessary to increase the volume of the permanent magnet, which increases the cost and makes it difficult to downsize.

Furthermore, the structure in which the track control coils 11a, 11b, 11c, and 11d are pasted on the focus control coil 10 has problems such as precision and difficulty in assembling because the gap is to be made as small as possible. It was hot.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain an objective lens driving device with good driving efficiency.

[Means for Solving the Problems] The objective lens driving device according to the present invention corrects the track deviation of a light spot with respect to the information track of a disk on which information is recorded and the focal deviation of the light spot with respect to the information recording surface of the disk. and controlling the position of a lens that forms the light spot according to the detected amounts of the track deviation and defocus, and optically extracts information from the information track by the light spot irradiated from the controlled lens. In a disk reading device that reads
A lens holder rotatable around a predetermined axis and movable along the axis, and supported at a position eccentric from the axis of the lens holder so that its optical axis is substantially parallel to the axis. a lens, a track control coil provided on the lens holder and wound in an annular shape so that its magnetic flux is orthogonal to the axis; and a focus control coil wound in a cylindrical shape with one end fixed to the lens holder. a coil for
It consists of a permanent magnet and a yoke arranged opposite to both the control coils, and controls the rotation of the lens holder and the movement along the axis by flowing a desired current to both the control coils. a drive device that performs track shift control and focus shift control, and another part of the focus control coil is inserted between a magnetic gap formed by the permanent magnet and the yoke. .

[Function] According to the objective lens drive device according to the present invention having the above-described configuration, the only factor that determines the gap in the magnetic circuit is the focus control coil, and the magnetic flux density is greatly improved. drive efficiency is improved.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing an objective lens driving device according to an embodiment of the present invention, and FIG.
3 is an exploded perspective view of the main parts, FIG. 4 is a partial sectional view showing the relationship between the gap of the magnetic circuit and the focus control coil, and FIG. 5 is a cross-sectional view of the lens holder and the focus control coil. Exploded perspective view showing assembly, No. 6
The figure is a partial perspective view showing a lens holder and a focus control coil, and the same parts as in FIGS. 7 to 10 are given the same reference numerals.

In FIGS. 1 to 3, a lens holder 3 with an objective lens 1 and a counterweight 2 attached thereto
is supported by a support rubber fixing pin 15 via a support rubber 5, and this support rubber fixing pin 15 is attached to the fixing base 1.
It is held at 6.

Further, the lens holder 3 is provided with a cylindrical portion 3b concentric with the cylindrical bearing 3a. Cylindrical part 3b
One end of a focus control coil 10 wound into a cylindrical shape is attached to the cylindrical end surface of the lens holder 3, and track control coils 11a and 11b are attached to the left and right side surfaces of the lens holder 3 apart from the end. The focus control coil 10 is arranged in a magnetic path formed by a focus control permanent magnet 17 provided on the fixed side and a focus control yoke 18, and the track control coils 11a and 11b are Permanent magnets 19a, 1 for track control provided on the fixed side
9b, and is arranged in a magnetic path formed by the track control yokes 20a and 20b.

By applying a desired current to the focus control coil 10, the lens holder 3 slides in the direction of arrow A, and the focal length of the objective lens 1 is adjusted. Also,
By applying a desired current to the track control coils 11a and 11b, the lens holder 3 is rotated in the direction of arrow B, and the objective lens 1 is rotated to perform track control.

The focal point control permanent magnet 17 and the track control permanent magnets 19a and 19b are each composed of a ring magnet magnetized in the radial direction and a left and right bipolar magnet. Therefore, as shown in FIG. 4, the focus control coil 10 is the only factor that determines the gap H' of the magnetic circuit, making it possible to minimize the gap of the magnetic circuit.

Further, as shown in FIG. 5, a notch is also provided in the lens holder 3b to ensure a space for drawing out the focus control coil wire 10 and for applying adhesive.

Further, when the lens holder 3b is made of plastic material, the focus control coil 10 is formed by integral molding.

[Effects of the Invention] As described above, according to the present invention, the focus control coil is wound in a cylindrical shape and one end is fixed to the lens holder, so that the gap in the magnetic circuit is eliminated only by the focus control coil. Since the size of the objective lens driving device is determined, it can be made extremely small, the magnetic flux density can be significantly improved, and the objective lens driving device can be made smaller and its cost can be reduced.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an objective lens driving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line shown in FIG. 1, FIG. 3 is an exploded perspective view of main parts, and FIG.
The figure is a partial cross-sectional view showing the relationship between the gap of the magnetic circuit and the focus control coil, Figure 5 is an exploded perspective view showing the assembly of the lens holder and focus control coil, and Figure 6 is the assembly of the lens holder and focus control coil. FIG. 7 is an exploded perspective view of a conventional objective lens drive device, FIG. 8 is a cross-sectional view of its assembled state, FIG. 9 is a partially exploded perspective view of it, and FIG. 10 is a partial perspective view showing integrated molding. is a partial sectional view showing the relationship between the gap and the coil of the magnetic circuit. In the figure, 1 is an objective lens, 3 is a lens holder, 4 is a support shaft, 10 is a focus control coil, 11
a, 11b are track control coils, 17, 18
is a focus control magnetic circuit (permanent magnet, yoke), 1
9a, 19b, 20a, 20b are magnetic circuits for track control (permanent magnet, yoke). In addition, in the drawings, the same reference numerals indicate the same or equivalent members.

Claims (1)

[Scope of Claims] 1. Track deviation of a light spot with respect to an information track of a disk on which information is recorded and a focal deviation of the light spot with respect to an information recording surface of the disk are detected, and the position of a lens forming the light spot is determined. A disk reading device that optically reads information from the information track using the light spot irradiated from the controlled lens by controlling according to the detected amount of the track deviation and defocus, a lens holder having a cylindrical end face that is rotatable at the same time and movable along the axis; and the lens holder is supported at a position eccentric from the axis so that its optical axis is substantially parallel to the axis. a track control coil provided on the lens holder and wound in an annular shape so that its magnetic flux is perpendicular to the axis; a fixed focus control coil; at least one notch formed in a fixed portion of the lens holder to the focus control coil; a permanent magnet and a yoke disposed opposite to both the control coils; a drive device that controls the rotation of the lens holder and the movement along the axis by flowing a desired current to both the control coils, thereby controlling the track shift and the focus shift; An objective lens driving device characterized in that another part of the focus control coil is inserted between a magnetic gap formed by the permanent magnet and the yoke.