JPH04111237A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To obtain an objective lens driving device miniaturized and with high performance in which the increment of weight of a movable part due to moment balance can be suppressed to a minimum by arranging a focusing coil and a tracking coil at a side opposite to a part where an objective lens is fixed against the neighborhood of the supporting point of a lens holder. CONSTITUTION:The movable part is comprised by fixing the objective lens 21 on the lens holder 22, and fixing the focusing coil 23 and the tracking coil 24 adhered integrally on the hollow part of the lens holder 22. Both terminal of four wires 26 arranged in parallel are soldered on a base substrate 29 fixed on a base 25 and a holder substrate 30 fixed on the lens holder 22, respectively, which support the lens holder in cantilever shape. Thereby, it is possible to prevent the moment of the focusing coil 23 and the tracking coil 24 for the supporting point added as the moment at an objective lens fixing side when the centroid of the movable part is fitted in the supporting point, and a magnet can be miniaturized, and the whole objective lens driving device can be miniatur ized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an objective lens driving device that forms part of an optical pickup that projects a light spot onto a disk to perform recording and reproduction.

BACKGROUND ART FIG. 3 is an exploded perspective view showing the configuration of a conventional objective lens driving device. An objective lens 1 is fixed to a lens holder 2, and a focusing coil 3 and a tracking coil 4, which are bonded and integrated, are fixed to a hollow penetrating portion of the lens holder 2 to constitute a movable part. The four wires 6 arranged in parallel connect to the base board 9 fixed to the base 5.
and a holder substrate 10 fixed to the lens holder 2 at both ends. This allows the lens holder 2 to be supported in a cantilevered manner.

A magnet 8 is fixed to the yoke 7, the base 5 as a fixing member is attached to the yoke 7, and an inner yoke 7a provided on the yoke 7 enters the focus coil 3 with a gap. As a result, part of the focus coil 3 and tracking coil 4 attached to the lens holder 2 can enter the magnetic gap formed between the magnet 8 and the inner yoke 7a. The focus coil 3 is wound so as to be parallel to the central axis or the optical axis of the objective lens 1, and when a current flows through it, the lens holder 2 moves in the direction of the optical axis (Z direction in the figure). Further, the tracking coil 4 is wound as an effective part in the magnetic gear so that a current flows in the direction of the optical axis, and when the current flows, the lens holder 2 moves in a direction perpendicular to the optical axis (
(Y direction in the figure). As described above, the objective lens driving device includes the focus coil 3 and the tracking coil 4.
The objective lens is driven two-dimensionally in the optical axis direction and in the direction perpendicular to the optical axis direction by passing a current through the optical axis.

FIG. 4 is a plan view showing the fixing positions of the focusing coil 3, tracking coil 4, and lens holder 2 in a conventional example. The tracking coil 4 is bonded to the outer peripheral surface of the focus coil 3, and is fixed to the objective lens fixed side near the lens holder support point 2a where the lens holder 2 is supported by the focus coil 3 and the tracking coil 4 by the wire 6. ing.

Problems to be Solved by the Invention Usually, in order to accurately drive an objective lens in the optical axis direction, it is necessary to align the center of gravity of the movable part with the lens holder support point so as not to generate a rotational moment. However, in the above conventional configuration, the objective lens 1, the focus coil 3, and the tracking coil 4 are located in the same direction with respect to the lens holder support point 2a, and in order to balance the moment with these, it is necessary to The shape of the lens holder in the opposite direction must be heavy or must have a sufficient distance from the lens holder support point. This increases the weight of the movable parts, reduces driving ability, and causes unnecessary resonance of the lens holder due to insufficient strength.
Another problem is that the objective lens driving device becomes large.

The present invention has been made to solve the above problems,
It is an object of the present invention to provide a compact, high-performance objective lens drive device that minimizes the weight increase of the movable part due to moment balance and has a small and sufficiently strong movable part.

Means for Solving the Problems In order to solve the above problems, the objective lens drive device of the present invention is arranged in the lens holder by arranging the focusing coil and the tracking coil on the opposite side of the objective lens fixed side with respect to the vicinity of the lens holder support point. It is something that sticks.

Effect When using the above configuration to balance the moment of the movable part so that the center of gravity of the movable part is aligned with the lens holder support point,
Only the difference between the moment of the objective lens with respect to the lens holder support point and the moment of the focusing coil and tracking coil with respect to the lens holder support point needs to be balanced by the lens holder shape, and the weight added by moment balance is significantly reduced compared to the conventional example. At the same time, the lens holder can be made small, and a compact and high-performance objective lens driving device can be achieved.

EXAMPLE Hereinafter, an objective lens driving device of the present invention will be explained with reference to the drawings.

FIG. 1 is an exploded perspective view showing the configuration of an objective lens driving device according to an embodiment of the present invention. The objective lens 21 is fixed to a lens holder 22, and a focusing coil 23 and a tracking coil 24, which are bonded and integrated, are fixed to the hollow part of the lens holder 22 to constitute a movable part. The four parallel wires 26 have both ends soldered to a base substrate 29 fixed to the base 25 and a holder substrate 30 fixed to the lens holder 22, respectively. Thereby, the lens holder 22 is supported in a cantilevered manner. The magnet foot 28 is fixed to the yoke 27, the base 25 as a fixing member is attached to the yoke 27, and the inner yoke 27a provided on the yoke 27 enters the focus coil 23 with a gap. FIG. 2 is a plan view showing the fixing positions of the focusing coil 23, the tracking coil 24, and the lens holder 22 in this embodiment. Tracking coil 24
is adhered to the outer circumferential surface of the focus coil 23, and the focus coil 23 and tracking coil 24 are fixed to the opposite side of the objective lens fixed side near the lens holder support point 22a where the lens holder 22 is supported by the wire 26. ing. The coils for moving both the cast coil 23 and the tracking coil 24 do not exist on the objective lens fixing side with respect to the vicinity of the lens holder support point 22a. By arranging and fixing the focus coil 23 and the tracking coil 24 to the lens holder 22 in this way, the center of gravity of the movable part can be adjusted to the lens holder support point 2.
2a, the tracking coil 24 and focus coil 23 are moved in a direction that further cancels out the moment on the objective lens fixed side with respect to the lens holder support point 22a without increasing it.
The additional weight required to balance the moment of the moving parts can be minimized. This makes it possible to reduce the weight of the movable parts and improve the driving ability, and it also reduces the need to make the shape of the lens and Nalder 22 larger than necessary in order to balance the moment, which causes the problem of unnecessary resonance due to insufficient strength of the lens holder 22. It is possible to avoid this, and at the same time, it is possible to downsize the objective lens driving device.

As described above, according to this embodiment, when the center of gravity of the movable part is aligned with its support point, the moments of the focus coil 23 and the tracking coil 24 relative to the support point are not added as the moment of the objective lens fixed side relative to the support point. Furthermore, since it can be used to counteract this, it is possible to achieve a smaller and lighter moving part without unnecessary increase in the weight of the moving part. As a result, the magnet serving as the driving means can be downsized, and the entire objective lens driving device can also be downsized. Regarding the adjustment of the weight of the focus coil 23 and the tracking coil 24, as long as it is within a range that balances the moment of the objective lens, there will be no needless weight increase of the movable parts, and an efficient design can be achieved and the objective lens can be easily driven with high sensitivity. The effects that can be achieved with this device are enormous.

Effects of the Invention In the present invention, a focusing coil and a tracking coil are arranged near the support point of the lens holder on the opposite side to the objective lens fixing side, and are fixed to the lens holder. It is lightweight, strong against unnecessary resonance, and allows for lightweight moving parts. This allows the magnet to be made smaller and the entire objective lens driving device to be made smaller. Furthermore, regarding the adjustment of the weight of the focus coil and tracking coil, if it is within a range that balances the moment of the objective lens, there will be no unnecessary weight increase in the moving parts, and it will be possible to design the sensitivity of the objective lens drive device more efficiently. This makes it possible to obtain excellent effects and realize a compact and high-performance objective lens driving device.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing the configuration of an objective lens drive device in an embodiment of the present invention, and FIG. 2 is a plan view showing the fixing positions of the lens holder, the tracking coil, and the lens holder in this embodiment. FIG. 3 is an exploded perspective view showing the configuration of a conventional objective lens driving device, and FIG. 4 is a plan view showing the fixing positions of a focusing coil, a tracking coil, and a lens holder in this conventional example. 11...Solder, 21...Objective lens,
22... Lens holder 22a... Lens holder support point, 23... Focus coil, 24... Tracking coil, 25...
...Base, 26...Wire 27...
...Yoke, 28...Magnet, 29...
...Base board, 30...Holder board,
31...Solder. Name of agent: Patent attorney Haruaki Ogata and 2 others 1. seconds. Priα--1il! −F

Claims (1)

[Claims] an objective lens for projecting a light spot onto an optical disk, a lens holder for holding the objective lens, a driving means for driving the objective lens and the lens holder, one end of which is fixed to the lens holder and the other end of which is fixed to the fixing member. a fixed support member; the driving means includes a focusing coil whose central axis is parallel to the optical axis of the objective lens; a tracking coil whose central axis is perpendicular to the optical axis; The focus coil and the tracking coil are located on the opposite side of the objective lens fixed side with respect to the vicinity of the lens holder support point where the lens holder is supported by the support member, and the lens An objective lens drive device, characterized in that it is fixed to a holder.