JPS6319938B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an objective lens driving device in an optical disc player or the like.

<Prior Art> An optical disc playback device, such as a compact disc player, focuses light emitted from a light source onto a row of pits on a recording disc, and causes a light spot to accurately follow this row of pits. , to read and reproduce information by converting changes in the amount of light reflected from the disk surface into electrical signals.

In this way, the objective lens is driven in a direction perpendicular to the disk surface as a means of focus control to always focus light on a minute spot on the disk pit row and tracking control to make this spot accurately follow the pit row. In addition, there are methods in which a galvanometer mirror is placed in the optical path between the light source and the objective lens and tracking is controlled by rotating it, and a method in which the objective lens is driven two-dimensionally to control the focus and tracking. Methods for controlling both types are known.

However, in the first method using a galvano mirror, the optical axis in the objective lens is tilted, so the aperture diameter of the lens needs to be large, and each has an independent control mechanism, so it becomes large. There are drawbacks such as being easy to use. On the other hand, several methods of driving the objective lens in the second example two-dimensionally are already known, but they can be broadly divided into methods in which separate coils and magnetic circuits are provided for focus control and tracking control. It is conceivable that a coil for focus control and a coil for tracking control are disposed in an intersecting manner in a gap in one magnetic circuit. When comparing both of the second examples, the latter is easier to downsize.

By the way, when the coil for focus control and the coil for tracking control are arranged intersectingly in one air gap as described above, it is inconvenient if magnetic flux passes through the return path of the coil for tracking control. Approximately half of the coil is passed through an area with no magnetic flux.

For example, as shown in FIG. 1, the objective lens holder 2 is configured to be rotatable around the support shaft 1 and slidable in the axial direction of the support shaft 1, and the objective lens holder 2 is spaced apart from the support shaft 1. A coil 4 for focus control and coils 5, 5, . ) is proposed in which the magnetic circuit is placed in the air gap of one magnetic circuit. but,
As is clear from the figure, in order to prevent magnetic flux from being applied to the return path of the tracking control coils 5, 5, ..., cutouts 7, 7 are provided in the yoke 6 inside and outside the objective lens holder 2, and the focus control coils 4 is wound around the entire circumference of the objective lens holder 2, the coil action of the notches 7, 7 is wasted.

<Object of the Invention> The present invention was made in order to eliminate the above-mentioned drawbacks, taking into consideration the miniaturization so that it can be used in compact disc players. A focus control coil provided on the outer periphery is placed in the gap of the magnetic circuit,
As a rotational drive mechanism, a tracking coil is provided inside the focus control coil in a substantially perpendicular direction, and the forward path of the tracking control coil is placed in the same gap of the magnetic circuit, and the return path is placed outside the gap, and a notch in the yoke is used. There is only a small L-shaped notch for the movement space of the tracking control coil and to simplify assembly, and a hole for light to pass through, so it is very wasteful.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a longitudinal sectional view showing one embodiment, and FIG. 3 is an exploded perspective view of the same.

At the center of the objective lens holder 11 is a thin support shaft 12.
is attached, and this support shaft 12 is coated with a low-friction material to make it slippery. Further, a hole is provided in the objective lens holder 11 at a position slightly away from the axis, and the objective lens 13 is inserted into this hole and fixed. Furthermore, a coil 14 for focal direction control is wound circularly around the outer periphery of the objective lens holder 11, and rectangular coils 15, 15 for tracking direction control are attached inside the coil 14 in a substantially perpendicular direction.

On the other hand, the magnetic circuit consists of a yoke plate 16, a magnet 17, and a cylindrical yoke 18 with a flange.As shown in FIG. A hole 18b is formed for this purpose.

The bearing stand 19 is the support shaft 12 of the objective lens holder 11.
The light hole 21 has a bearing portion 20 corresponding to the light hole 18b of the cylindrical yoke 18. The cylindrical yoke 18, magnet 17, and yoke plate 16 are stacked on this bearing stand 19,
When fixing these magnetic circuit components to the bearing stand 19, the optical hole 18b of the cylindrical yoke 18 and the bearing stand 1
The nine light holes 21 are arranged so as to coincide with each other.

The support shaft 12 of the objective lens holder 11 is connected to the bearing stand 1
9, the tracking direction control coils 15, 15 are inserted into the bearing portion 20 of the cylindrical yoke 18 so that the upper end openings of the L-shaped notches 18a, 18a and the tracking direction control coils 15, 15 are aligned, and then twisted slightly to a predetermined position. . As a result, a portion of the cylindrical yoke 18 left by the notch is inserted into the tracking direction control coils 15, 15. and,
When the objective lens 13 and the optical holes 18a and 21 are aligned, insert the damping elastic body 22 made of rubber or the like from the back side of the bearing pedestal 19, and insert the outer peripheral part of the elastic body 22 into the bearing pedestal 19. The inner peripheral portions are respectively fixed to the support shafts 12 of the objective lens holder 11. The retaining ring 23 and retaining pin 24 further reinforce these fixations.

Note that the damping elastic body 22 also has a light hole 18.
A hole 22a is provided that corresponds to 21, and a dummy hole 22b is also provided here to make the shape symmetrical with respect to the support shaft 12.

According to this structure, the focal direction control coil 14 and the tracking direction control coils 15 and 1 are provided in the magnetic gap between the yoke plate 16 and the cylindrical yoke 18.
The outward paths of the tracking direction control coils 15, 15 are arranged outside the gap, and the notches 18a, 18a of the inner cylindrical yoke 18 are also used for tracking direction control. A small L-shaped one is used for the movable space of the coils 15, 15 and for easy assembly, and there is little waste. Furthermore, the number of parts is small, making assembly easier.

FIG. 4 is an exploded perspective view showing another embodiment.

In this case, the relationship between the support shaft and the bearing part is reversed, and a bearing part 25 is provided in the center of the objective lens holder 11 instead of the support shaft, and it is assembled by fitting into the support shaft 27 of the support shaft holder 26. This is how it was done. in this case,
The damping elastic body 22 is located on the front side of the spindle base 26, and its outer circumferential portion is attached to a fixed body such as the cylindrical yoke 18, and its inner circumferential portion is attached to the bearing portion 25 of the objective lens holder 11.
It will be fixed at Other parts are shown with the same reference numerals as those in FIGS. 2 and 3,
Constructed and assembled in the same way.

In this embodiment as well, the outgoing paths of the focal direction control coil 14 and the tracking direction control coil 15 are arranged in a magnetic gap between the yoke plate 16 and the cylindrical yoke 18, so that they intersect with each other.
The return path of the tracking direction control coil 15 is outside the gap, and is located at the notches 18a, 1 of the cylindrical yoke 18.
8a may also be a small L-shaped one for the movable space of the tracking direction control coil 15 and to simplify assembly, thereby reducing waste.

<Effects of the Invention> As described above, the present invention can provide a useful objective lens driving device that is compact and efficient in generating magnetic flux.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a conventional example, Fig. 2 is a longitudinal sectional view showing an embodiment of the present invention, Fig. 3 is an exploded perspective view of the same, and Fig. 4 is an exploded perspective view showing another embodiment. be. 11... Objective lens holder, 12... Support shaft, 1
3... Objective lens, 14... Coil for focal direction control, 15.15... Coil for tracking direction control, 16... Yoke plate, 17... Magnet, 18... Cylindrical yoke, 18a, 18a... L
letter-shaped notch, 19... bearing stand, 20... bearing part, 25... bearing part, 26... spindle stand, 27...
Spindle.

Claims (1)

[Scope of Claims] 1. An objective lens holder is provided with an objective lens spaced apart from a center line, and focus control is performed by driving the objective lens in the direction of the center line of the objective lens holder, In a device that performs tracking control by rotationally driving an objective lens about a line, a focal direction control coil provided on the outer periphery of the objective lens holder is disposed in a gap in a magnetic circuit, and the focal direction control A tracking direction control coil is provided inside the tracking direction control coil in a direction substantially perpendicular to the tracking direction control coil. An objective lens driving device characterized in that an outward path is arranged in the same gap of the magnetic circuit, and a return path is arranged outside the gap.