JPS6319945Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an optical system drive device in an optical information reading device.

In an optical information reading device, an information recording medium such as a video disc or a digital audio disc records the information signal by forming minute pits (indentations) in the form of spiral tracks in accordance with the information signal on its surface. It is to be recorded. When reproducing such a disk, the disk is rotated at a predetermined number of revolutions while a spot light is irradiated onto the track, and changes in the intensity of the reflected light or transmitted light are converted into electrical signals, which are then used as the original information signals. It is something to be regenerated.

When playing back this disc, the irradiated light must be accurately focused on the recording surface of the disc, so it is necessary to control the position of the optical system in the direction perpendicular to the recording surface, that is, in the focus direction (focus servo). Furthermore, since the irradiation light must always accurately track the recording track, it is necessary to control the irradiation light in the radial direction of the disk, that is, in the tracking direction (tracking servo).

For this purpose, an optical system driving device is used that drives an optical system that irradiates the recording surface of the disk with spot light for reading information in accordance with a focus error signal and a tracking error signal.

Such an optical system drive device is provided with a support mechanism that supports the optical system so as to be movable in the focusing direction and the tracking direction.

Various support mechanisms have been proposed in the past, and the first
Examples are shown in Figures 3 to 3.

In the first example of the support mechanism shown in FIGS. 1a and 1b, the optical system 1 is fitted into approximately the center of circular leaf springs 2 and 3 whose peripheral edges are fixed, and the circular leaf spring 2 and 3 are supported so as to be movable within a predetermined range in the optical axis direction of the optical system 1, that is, in the focus direction, as indicated by an arrow Z. Also, a fixing member (hatching part) that fixes the circular leaf springs 2 and 3.
The entire body including this is supported by another support means (not shown) so as to be movable within a predetermined range in the tracking direction (arrow x direction). Note that 4 is an objective lens fitted into the optical system 1, and 5 and 6 are a lens barrel portion and a driving coil of the optical system 1, respectively.

In this type of support mechanism, the movement stroke in the focus direction cannot be made large, and support means for movably supporting the optical system in the focus direction and the tracking direction are each provided separately, so the overall external The drawback was that the diameter was large. Therefore, it is difficult to reproduce information recorded near the center of the disk due to the need for a spindle motor that rotationally drives the disk, and in order to reproduce information, it is necessary to make the outer diameter of the spindle motor extremely small.

Furthermore, since the movement stroke in the focus direction cannot be made large, discs with a large amount of wobbling on the recording surface cannot be reproduced, and there are other inconveniences such as the need for precise adjustment in the focus direction, that is, the optical axis direction. .

In the second example of the support mechanism shown in FIGS. 2a and 2b, a pair of leaf springs 7 and 8 are disposed parallel to the disk recording surface (not shown) and have one end fixed. An optical system 1 is fixed and supported by leaf springs 7 and 8 so as to be movable in the focus direction (arrow Z direction). Further, the entire body including the fixing members (hatching portions) for fixing the leaf springs 7 and 8 is supported by another support means (not shown) so as to be movable in the tracking direction (not shown). Note that the same reference numerals are used for members having the same configuration as those of the support mechanism of the first example, and the same applies hereinafter.

This support mechanism does not have the disadvantage of the movement stroke in the focus direction as in the support mechanism of the first example. However, for the same reason as the support mechanism of the first example, there is a drawback that the overall outer diameter becomes large.

Further, as shown in FIG. 2a, when the optical system 1 moves in the focus direction, a tensile force or a compressive force acts on the leaf springs 7 and 8, so the optical system 1 is tilted with respect to the focus direction. There is a drawback that (see Figure 2b). Furthermore, there is a drawback that parasitic resonance is likely to occur during information reproduction due to the action of the tensile force and compressive force.

In another example of the support mechanism shown in FIG. 3, the optical system 1 has one end fixed to a lever 10 fixed via an elastic body 9, and the other end of the optical system 1 is fixed in the focus direction by the lever 10. and is supported movably in the tracking direction.

This support mechanism has the same drawback as the support mechanism of the second example, in that when the optical system 1 moves in the focus direction, the optical system 1 tilts with respect to the focus direction.

The present invention was developed in view of the above-mentioned points, and is small and lightweight, has a large movement stroke in the focusing direction and tracking direction, and when the optical system moves in both directions, the optical system moves in the focusing direction. It is an object of the present invention to provide an optical system driving device that does not tilt relative to the optical system.

An optical system drive device according to the present invention includes an optical system for irradiating a recording surface of a recording medium with spot light, and a drive for driving the optical system in an optical axis direction of the optical system and in a direction perpendicular to the optical axis direction. and a support mechanism that supports the optical system so that the optical system is movable in the optical axis direction and in the perpendicular direction and that the optical axis is perpendicular to the recording surface. , the support mechanism includes a substantially cantilever-shaped flexible member that is flexible in the optical axis direction, and one end of which is fixed to the free end of the flexible member and which is oriented toward the fixed end of the flexible member. and a support member that extends from the free end to support the optical system at the other end so as to be movable only in the perpendicular direction, and the length of the support member is from the free end in the optical axis direction and in the perpendicular direction. The distance to the center of gravity of the optical system is 1/2 of the distance from the fixed end to the free end.
It is characterized by being made so that.

Hereinafter, an optical system driving device according to the present invention will be explained with reference to the drawings.

As shown in FIGS. 4 to 6, the optical system 1
A driving coil 13 for driving in the focus direction Z is wound in the circumferential direction around the outer periphery of the bobbin portion 12 provided in the bobbin portion 12 . A pair of substantially rectangular bobbin parts 15 and 16 are provided on the lens barrel part 14 of the optical system 11 so as to protrude in the tracking direction x, and each of the bobbin parts 15 and 16 is provided with a driving coil in the tracking direction x. 17 and 18 are wound. Further, 19 is an objective lens fitted into the lens barrel portion 14.

The focusing leaf spring 20 is arranged to be flexible in the focusing direction Z, and has a fixed end 21 fixed to a base 22 by a fixing member 23, a pair of bolts 24, and a spring washer 25.

A tracking leaf spring 27 is disposed approximately at the center of the free end 26 of the focusing leaf spring 20 and extends from the free end 26 toward the fixed end 21 and is flexible only in the tracking direction x. One end 28 of is fixed. One end 28 is fixed to the free end 26 by a fitting groove 29 provided on both ends.
and 30 are fitted together.

The optical system 11 has its center of gravity fixed to the other end 31 of the tracking leaf spring 27, and the bobbin part 12 is fixed to the magnetic circuit part 3 fixed to the base 22.
The magnetic gap 36 of the pair of magnetic circuit parts 34 and 35, in which the bobbin parts 15 and 16 are fixed to the base 22, is located in the magnetic gap 33 of the second magnetic circuit part 2.
and 37, respectively.

In addition, magnets 38 and 3 which are fitted into the magnetic circuit parts 34 and 35 and constitute a part of the magnetic circuit parts
9 are each magnetized as shown in FIG. 6b.

On the other hand, as shown in FIG.
1, the inclination angle i ₁ at the free end 41 when the downward force W in the figure is applied is obtained by the following equation.

i ₁ = Wl ² /2EI However, E: Young's modulus of cantilever beam 40 I: Passes through the neutral axis of cantilever beam 40 and cantilever beam 4
The second moment of inertia of the cantilever beam 40 with respect to the longitudinal direction of 0 and the axis perpendicular to the vertical direction in the figure.
The inclination angle i ₂ when a moment M in the counterclockwise direction in _the figure acts on the free end 4 is as shown in FIG.
Considering the case where the above force W and moment M are applied simultaneously to 1, calculate the magnitude of moment M when the inclination angle i ₁ due to W and the inclination angle i ₂ due to moment M cancel each other out, that is, the sum of both inclination angles becomes 0. demand. That is,
From equations (1) and (2), Wl ₂ /2EI−Ml/EI=0, so M=Wl/2 is obtained.

This means that, as shown in FIG. 7d, one end 43 of a rigid body 42 with length l/2 and negligible weight is attached to the free end 41 of the cantilever beam 40. is fixed so as to extend toward the fixed end 44, and when a force W is applied to the other end 45, the free end 4
The inclination angle at 1 is always 0 regardless of the size of W.
This shows that it is possible to

Based on the above principle, the length of the tracking leaf spring 27 is such that the distance from the free end 26 of the focusing leaf spring 20 to the center of gravity of the optical system 11 is 1/2 of the distance from the fixed end 21 to the free end 26. It is made to be.

In another embodiment of the invention shown in FIG. 8, two pairs of focusing leaf springs 48 and 49 are provided.
are arranged parallel to the focus direction Z and in a direction perpendicular to the tracking direction x and flexible in the focus direction Z. Each pair of focusing plate springs 48 and 49 are arranged facing each other with a predetermined gap in the focusing direction Z, and have one end (fixed end) 50 and 51, respectively.
is fixed.

Further, a rectangular plate 54 is fixed to the free ends 52 and 53 of the focusing leaf springs 48 and 49. At approximately the center of both ends of the rectangular plate 54 in the tracking direction x, a pair of plates are arranged to extend from the free ends 52 and 53 toward the fixed ends 50 and 51 and to be flexible in the tracking direction x. One end 56 of the tracking leaf spring 55 is fixed. An optical system (not shown) is fixed to the other end 57 of the tracking leaf spring 55.

The length of the tracking leaf spring 57 is the same as that of the focusing leaf springs 48 and 4 in the direction perpendicular to the focusing direction Z and the tracking direction x.
9 from the free ends 52 and 53 of the optical system (not shown)
The distance from the center of gravity to the center of gravity is 1/2 of the distance from the fixed ends 50 and 51 to the free ends 52 and 53.

Further, the focusing plate springs 48, 49, the rectangular plate 54, and the tracking plate spring 55 can also be manufactured by integral forming processing.

Note that the examples are not limited to the above examples, and for example, a pair of focusing leaf springs and a tracking leaf spring, a pair of focusing leaf springs and a tracking leaf spring, or a pair of focusing leaf springs and a tracking leaf spring. Various modifications are conceivable regarding the number of focusing leaf springs and tracking leaf springs, such as one leaf spring.

As detailed above, the optical system drive device of the present invention has a support mechanism that supports the optical system so that it can move in the focusing direction and the tracking direction, and so that the optical axis is always perpendicular to the disk recording surface. Therefore, stable recording and playback is possible.

Further, in the optical system drive device of the present invention, the supporting means that has a substantially cantilever-like structure and supports the optical system movably in two directions, the focusing direction and the tracking direction, are integrated into one. The movement stroke of the optical system is large, and the entire device can be made smaller.

Therefore, the space below the turntable is widened, and restrictions on the size or arrangement of the spindle motor for driving the disk are alleviated.

[Brief explanation of the drawing]

1A and 1B are diagrams showing a first example of a conventional support mechanism; FIGS. 2A, 2B, and 3 are diagrams each showing a second and third example of a conventional support mechanism; FIG. are perspective views of the support mechanism according to the present invention, FIGS. 5 and 6 a
are side sectional views and plan views of the support mechanism, FIG. 6b is a diagram showing the magnetic circuit section, FIGS. 7a, b, c, and d are diagrams showing the principle of the support mechanism, and FIG. It is a figure which shows the 2nd Example based on an invention. Explanation of symbols of main parts, 11...Optical system, 1
2, 15, 16...Bobbin part, 13, 17, 18
... Coil, 14 ... Lens barrel section, 19 ... Objective lens, 20 ... Focusing plate spring, 22 ...
Base, 27...Tracking leaf spring, 32,
34, 35...Magnetic circuit section, 33, 36, 37...
...magnetic gap.

Claims (1)

[Scope of utility model registration request] an optical system for irradiating a recording surface of a recording medium with spot light; a driving means for driving the optical system in the optical axis direction of the optical system and in a direction perpendicular to the optical axis direction; an optical system drive device that includes a support mechanism that supports the optical system movably in an axial direction and in the perpendicular direction and that supports the optical axis so that the optical axis is perpendicular to the recording surface; a generally cantilever-like flexible member flexible in the direction; one end fixed to the free end of the flexible member and extending toward the fixed end of the flexible member, and the optical member fixed at the other end; a support member that supports the system movably only in the perpendicular direction, and the length of the support member is such that the distance from the free end to the center of gravity of the optical system in the optical axis direction and the perpendicular direction is An optical system drive device in an optical information reading device, characterized in that the distance from the fixed end to the free end is 1/2.