JPH0440784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an objective lens driving device that can automatically adjust the focus of a laser beam or the like on a disk in an optical information recording/reproducing device or the like.

[Conventional technology]

Conventionally, there is an objective lens drive device shown in FIG. 1 that can automatically adjust the focus of an objective lens on a disk in an optical information recording and reproducing device that optically reads information from a disk, such as a disk player. .

That is, the objective lens e is placed in a magnetic gap d of a magnetic circuit A formed by a ring-shaped magnet a, a ring-shaped plate b fixed above and below the magnet a, and a yoke c having an L-shaped cross section. A coil h wound around a bobbin g ₁ provided on the outer periphery of a cylindrical body g with a lens barrel f mounted inside is inserted, and elastic supports i ₁ , i ₂ such as leaf springs are inserted. The lens barrel f is elastically supported so as to be able to freely vibrate in the vertical direction of the magnetic circuit A.

When a current is passed through the coil h inserted in the magnetic gap d of the magnetic circuit A, the coil h generates a force in a direction perpendicular to the winding direction of the coil h, that is, in the direction of the optical axis of the objective lens e. Objective lens e
is driven together with the lens barrel f, and can control the position of the objective lens so as to automatically focus on the disk.

[Problem to be solved by the invention]

However, in the conventional device described above, the lens barrel f and the coil h are formed into a complicated double cylindrical shape, making it difficult to manufacture.

Also, the lead wire k from the coil h to the external terminal j
As the distance becomes shorter, the movable part formed by the lens barrel f into which the objective lens e is fitted, the bobbin g ₁ , the coil h, etc. will not move smoothly and will have adverse effects such as stiffness of movement. There is a risk that the lead wire k may break or resonate due to fatigue. Furthermore, when the diameters of the elastic supports i ₁ and i ₂ such as leaf springs are reduced, sufficient axial stroke cannot be obtained, resulting in deterioration of their linearity.

The present invention has been made in view of the above points, and its purpose is to wind a coil around the outer periphery of a bobbin provided in a fixed part so that current flows in opposite directions with a plane perpendicular to the axial direction as a boundary. When the movable part is driven, the lead wire is The objective lens drive device is designed to drive the movable part that has the objective lens attached to the lens barrel smoothly and accurately with good responsiveness by forming the fixed part with a non-magnetic material without being affected by the There is something to offer.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIG.

Reference numeral 1 denotes a movable part that is slidably inserted into a cylindrical cover 2 made of a non-magnetic material. It is formed from a ring-shaped first yoke 6 and a second yoke 7 fixed to the ring. 8 and 9 are wound vertically in columns on both sides of the bobbin 10 fitted in the substantially cylindrical cover 2 with respect to a plane perpendicular to the axial direction, that is, a horizontal plane M perpendicular to the upper and lower midpoint m of the magnet 5. The current flows in the coils 8 and 9 in opposite directions. The bobbin 10 is made of a thin non-magnetic material and has a substantially cylindrical shape, and is fixed inside the cover 2. The lens barrel 3 to which the objective lens 4 is attached
Although shown in the drawing as being attached to the upper surface of the first yoke 6, it can of course also be attached to the lower surface of the second yoke 7. In addition, the ring-shaped magnet 5 is magnetized with different polarities, for example, N on the upper side and S on the lower side, and the magnetic flux jumps out from the outer circumference of the first yoke 6 and flows back to the second yoke 7. The current passes through the coils 8, 9 perpendicularly to the current flowing in opposite directions.

Since the first embodiment of the present invention has the above-described configuration, the magnetic flux from the ring-shaped magnet 5 is
For example, when the upper side of the magnet 5 is magnetized to the north pole and the lower side is magnetized to the south pole, the yoke jumps out from the first yoke 6 fixed to the upper side of the magnet 5 and goes to the second yoke 7 fixed to the lower surface of the magnet 5. It forms a flowing magnetic circuit. The bobbin 10 is wound on both upper and lower sides of a plane perpendicular to the axial direction, that is, a horizontal plane M perpendicular to the upper and lower midpoint m of the magnet 5, so as to face substantially perpendicular to the direction of the magnetic flux flowing through such a magnetic circuit. When a laser beam or the like is irradiated onto the disk through the rotating coils 8 and 9, a focus signal is read by the reflected light, and a current flows in the opposite direction, the current flows from the first yoke 6 to the second yoke 7. The magnetic flux from the magnet 5 that is directed toward the magnet 5 passes through the first and second coils 8 and 9 at right angles, and forces in the same direction are generated in the coils 8 and 9 according to Fleming's left-hand rule. Therefore, a movable part formed by a ring-shaped magnet 5, a first yoke 6, a second yoke 7, a lens barrel 3, and an objective lens 4 mounted in the lens barrel 3 moves inside the hollow cylindrical bobbin 10. 1 is driven in the axial direction of the lens barrel 3, that is, in the optical axis direction, within a fixed part consisting of first and second coils 8, 9, a bobbin 10 made of a non-magnetic material, and a cover 2. At this time, by forming the cover 2 and the bobbin 10, which form the fixed part, from a non-magnetic material, the yokes 6 and 7, which are the movable parts, can be driven without being locally attracted to the fixed part.

Further, when a laser beam or the like is irradiated onto the disk and a focus signal from the reflected light or the like causes a current to flow in the coils 8 and 9 in the opposite direction to the operation described above, the current flows from the first yoke 6 to the second yoke 7. The magnetic flux G from the magnet 5 towards the coils 8 and 9
coils 8 and 9.
According to Fleming's left-hand rule, a force in the same direction will be generated in the opposite direction to the above movement.

By driving the objective lens 4 mounted in the lens barrel 3 in the axial direction in this manner, the focus of the objective lens 4 with respect to an information recording medium such as a disk can be automatically adjusted.

What is shown in FIG. 3 is a second embodiment of the present invention, in which a coil spring 11 is interposed on the lower surface of the second yoke 7 to elastically support the movable part 1. This point differs from the first embodiment in its configuration.

The reason why the coil spring 11 is used is that the elastic support in a conventional device has better linearity than a plate spring, so the stroke can be made larger and the diameter can be made smaller. Further, by interposing the coil spring 11, the center point of vibration of the movable part 1 can be easily selected, so that the movable part 1 is driven stably.

〔Effect of the invention〕

As described above, in the present invention, coils are wound around the outer periphery of the bobbin so that current flows in opposite directions with respect to a plane perpendicular to the longitudinal direction of the bobbin, and each coil is provided above and below a magnet of a magnetic circuit. The objective lens attached to the lens barrel is driven by the passing magnetic flux from the outer periphery of the first and second yokes, and the fixed part consisting of the bobbin and cover is made of non-magnetic material. There is no risk that the yoke will be locally attracted to the fixed part, and the frictional force will locally increase between the sliding parts of the movable part and the fixed part, making it impossible for the movable part to move smoothly. Problems such as deterioration of characteristics, heat generation due to an increase in the amount of current flowing through the coil, and unnecessary servo errors due to fluctuations in the optical axis direction are eliminated, and the focus direction can be controlled with good responsiveness and accuracy.

Furthermore, with the configuration of the present application, the lens barrel to which the objective lens is attached can be supported without using an elastic support member such as a leaf spring, and the size can be particularly reduced in the diametrical direction.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional objective lens driving device, FIG. 2 is a sectional view showing one embodiment of the objective lens driving device of the present invention, and FIG. 3 is another embodiment of the objective lens driving device of the present invention. It is a sectional view showing an example. DESCRIPTION OF SYMBOLS 1... Movable part, 4... Objective lens, 5... Magnet, 6... First yoke, 7... Second yoke, 8, 9... Coil, 10... Bobbin.

Claims (1)

[Claims] 1. A fixed part consisting of a hollow cylindrical bobbin around which a coil is wound so that current flows in opposite directions on both sides of a plane perpendicular to the optical axis direction, and a cover into which the bobbin is fitted is made of non-magnetic material. A ring-shaped magnet is formed and magnetized in the vertical direction,
inserting into the hollow part of the bobbin a movable part having first and second ring-shaped yokes fixed to both poles of the magnet and an objective lens fixed to one of the first and second yokes; An objective lens driving device characterized in that it is movable in an optical axis direction along an inner wall of a bobbin.