JPH04153922A - Optical device for optical disk - Google Patents

Abstract

PURPOSE:To allow the absorption of the angle errors in the moving direction of an optical head with the mere adjustment of a moving mirror driving part by providing a correcting mechanism for moving a supporting base in a specific direction. CONSTITUTION:An objective lens 3 is provided in the optical head H and a mirror facing the direction of an optical path A direction positioned below this lens is provided. A semiconductor laser 4, pin photodiodes 10a, 10b, beam splitters 6, 8, etc., are provided in a stationary part S. Also the moving mirror 7 and the mirror driving part for driving this mirror are provided. The moving mirror 7 is moved in the direction to incline the reflecting optical path of this mirror and in the direction where the relative facing positions of the moving mirror 7 and the mirror of the optical head H are changed by moving the driving part of the moving mirror 7. The angle errors between the optical path A and the moving direction of the optical head H are corrected simply by changing the position of the driving part of the moving mirror 7 in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc optical device that performs tracking correction on an optical disc using a movable mirror provided in a fixed part, and particularly relates to an optical disc optical device that performs tracking correction on an optical disc using a movable mirror provided in a fixed part. The present invention relates to an optical device for optical discs that can correct errors.

[Prior Art] FIG. 6 is a plan view showing the configuration of an optical device for an optical disk using a movable mirror, and is an optical memory device using, for example, a magneto-optical disk.

The optical disc D is placed on the turntable 1 and driven to rotate. The optical head H moves along the recording surface of the optical disc D in its radial direction. This movement is realized, for example, by a linear motor indicated by reference numeral 2. The optical head is provided with an objective lens 3, a focusing actuator that moves the objective lens 3 in the optical axis direction, and a focusing actuator that moves the objective lens 3 in the optical axis direction.
A mirror facing the optical path A along the moving direction of the optical head H is provided opposite to the lower part of the optical axis of the optical head H. -Fixed blade tXn
C+-1-to1fuL road 1+1. , +J'iJ, <1f and IJa4-+w4qAsaThe emitted laser light is turned into a parallel beam by the collimator lens 5, and is reflected by the beam splitter 6 in the B-axis direction. Further, the fixed part S is provided with a movable mirror 7 and a mirror drive part for operating the movable mirror 7, and the laser beam sent in the B-axis direction is sent to the optical path indicated by A by the movable mirror 7.

The light is then reflected by a mirror provided on the optical head H, and focused onto the recording surface of the optical disc D by the objective lens 3. The movable mirror 7 is swung in the rotational direction by the mirror drive unit approximately around the B axis, and thereby the light sent from the objective lens 3 is swung to scan the tracks on the recording surface of the optical disc D, thereby performing tracking correction. It can be done. In this tracking correction, fine correction is performed by the movable mirror 7, and coarse tracking correction is simultaneously performed by driving the optical head H by the linear motor 2.

The return light from the optical disk D returns from the movable mirror 7 in the B-axis direction and passes through the beam splitter 6.

The light is split by another beam splitter 8, and the condensing lens 9
a and 9b, and are received by bin photodiodes 10a and 10b, respectively.

In this way, by dividing the optical element into the optical head H and the fixed part S, the optical head H becomes smaller and lighter.
The optical head H can now be driven at high speed by the linear motor 2, etc., and random access can be achieved at high speed.

[Problem to be Solved by the Invention j] However, as described above, if the optical elements are separately provided in the optical head H and the fixed part S, the direction of movement of the optical head H and the direction of light reflection by the movable mirror 7 are different. (Optical path A direction) There is a structural problem in which a slight angular deviation occurs.

That is, due to the manufacturing precision of each optical component and the manufacturing precision of the chassis to which the fixed part S and the guide member of the optical head H are attached, the movable mirror 7 is
It is inevitable that an angular error Δθ will occur between the optical path A along which light is sent from the optical head H and the moving direction (direction C) of the optical head H.

If such an angular error Δθ exists, the spot position where the light is received by the bin photodiode will vary depending on whether the objective lens 3 of the optical head H is at the inner circumferential position of the optical disc D or the outer circumferential position. That is, the angle error Δ
According to θ, the optical axis of the laser beam sent to the objective lens 3 is
The objective lens 3 shifts depending on whether it is on the inner periphery or on the outer periphery. Therefore, as shown in FIG. 8(A+) and (B), the light receiving spot on the four-split bin photodiode differs between the inner and outer circumferential positions of the disc, and as shown in FIG. 8(C), a focus error occurs. An offset will occur in the signal.

Conventionally, in order to solve the above problems, the accuracy of each optical element or the mounting of optical parts has been increased, but this method is extremely expensive (and requires a fixed adjustment method). The relative position between the fixed part S and the optical head H is adjusted by changing the position of the entire part S, but with this method, the fixed part and the chassis are separated, resulting in a very complicated structure. This adjustment method also has its limitations.

The present invention solves the above-mentioned conventional problems, and the angular error between the optical path A and the moving direction of the optical head H can be corrected by simply changing the position of the movable mirror drive part, thereby constructing a highly accurate device. It is an object of the present invention to provide an optical device for an optical disc that enables the following.

[Means for Solving the Problems 1] In the optical device for an optical disc according to the present invention, an optical head that moves along the recording surface of the disc is provided with an objective lens and a mirror facing the optical axis of the objective lens, and a fixed part is provided with an optical head that moves along the recording surface of the disc. comprises a light-emitting element, a light-receiving element, a movable mirror located at a position connecting an optical path between the light-emitting element and the light-receiving element, and an optical path reflected by the mirror, and the movable mirror is rotated to emit light irradiated from the objective lens to the optical disk. An optical device for an optical disc is provided with a mirror drive unit that swings in a tracking correction direction, wherein a support base on which the mirror drive unit is supported is connected to a reflecting surface of the movable mirror and a mirror provided on the optical head. The invention is characterized in that it is provided with a correction mechanism that moves in a direction that changes the relative facing position.

[Function] In the above means, the drive unit of the movable mirror provided in the fixed part is moved in the direction of inclining the reflection optical path of the movable mirror and in the direction of changing the relative facing position of the movable mirror and the mirror of the optical head. , thereby absorbing the angular error between the optical path from the movable mirror and the moving direction of the optical head.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

The overall structure of the optical device for optical discs according to the present invention is as follows.
The optical head H, which is basically the same as the one shown in the figure, and which moves along the recording surface of the optical disk D, is provided with an objective lens 3 and a mirror positioned below it and directed toward the optical path A. Furthermore, the fixed part S includes a semiconductor laser 4, a vinyl photodiode 10a, 10b, and a beam splitter 6.
and 8 are provided, and a movable mirror 7 and a mirror drive section for driving the movable mirror 7 are also provided.

1 to 3 show a basic embodiment of the invention.

In the present invention, the adjustment work is performed by moving the mirror drive section that drives the movable mirror 7 within the fixed section S, and the direction of adjustment is shown in each of FIGS. 1 to 3.

In FIG. 1, the movable mirror 7 is rotated by rotating the mirror drive unit.
is rotated around the b axis in the θb force direction. As a result, the direction in which the optical path B extending from the fixed part is reflected, that is, the direction of the optical path A, is changed to the direction of the angle θb, and the direction of the optical path A and the moving direction C of the optical head H are aligned with the direction of the plane of the paper in FIG.

FIG. 2 is a view taken along arrow II of the first section, and as shown in this figure, the mirror drive section is rotated to rotate the movable mirror 7 by θa around the b-axis. As a result, the movable mirror 7
The reflected optical path A and the moving direction C of the optical head H can be made to coincide with the direction of the plane of the paper in FIG. 2 (the direction of the vertical plane in FIG. 1).

Furthermore, as shown in FIG. 3, the movable mirror 7 is moved in parallel in the X direction ((A) in the same figure) or in the Y direction ((B) in the same figure), and the optical path A reflected by the movable mirror 7 is changed from left to right in the figure. move in the direction. As a result, the reflection mirror 7 and the optical head H
The relative facing position with the mirror inside is adjusted. In addition, the third
It is not necessary to adjust both figures (A) and (B) at the same time, and it is sufficient to move the movable mirror 7 in parallel in either the X direction or the Y direction.

By making the adjustments shown in FIGS. 1 to 3 above, even if there is a relative angular error Δθ in the moving direction C of the optical head H as shown in FIG. There is no deviation between the center of the optical path A extending from the movable mirror and the optical axis of the objective lens 3 when it is at the inner circumferential position and when it is at the outer circumferential position, and an error signal as shown in FIG. 8 is generated. offset will no longer occur.

FIG. 4 specifically shows the adjustment mechanism for adjusting the movable mirror 7 in each of the above directions.

In FIG. 4, reference numeral 15 is a mirror drive section. The mirror drive section 15 includes a movable section 16 that supports the movable mirror 7.
A drive coil 17 wound around the movable part 16, a yoke 18 that supports the movable part 16 via an elastic member, and a magnet held by the yoke 18 and opposed to the coil 17 are constructed. The movable part 16 rotates around the axis O-O due to the current applied to the drive coil 17 and the magnetic field of the magnet, and the movable mirror 7 rotates together, so that its reflected optical path A is swung. . Due to this deflection of the optical path A, the spot of the laser beam irradiated from the objective lens 3 is corrected for tracking with respect to the recording surface of the optical disc D.

In the structure shown in FIG. 4, the yoke 18 is fixed to a support base 21. As shown in FIG. The support base 21 has a hole 21a, and the rocking base 22 located below the hole 21a has a bottle 22a protruding therefrom.

The hole 21a is rotatably supported by the bin 22a, so that the support base 21 rotates around the bin 22a. This bin 22a is the b-axis shown in FIG. The position of this b-axis coincides with the center of the surface of the movable mirror 7. The support base 21 has an elongated (or arcuately elongated) 21b, and the swing base 22 has a female threaded hole 22b. A fixing screw 23 is inserted through the long hole 21b and screwed into the female threaded hole 22b. Also, a coil spring 2 is attached to the fixing screw 23 to prevent the support base 21 from lifting up.
4 is exteriorized. Further, a coil spring 25 is placed between the support base 21 and the swing base 22, and thereby the support base 21 is biased clockwise around the bin 22a (b axis). Further, an adjusting screw 27 is screwed into a female screw hole 22c formed in the rocking table 22. This adjustment screw 27 is formed with a tapered surface 27a, and this tapered surface 27a comes into contact with the pressing surface 21c of the support base 21. This pressing surface 21c is the spring 25
It comes into pressure contact with the tapered surface 27a by the urging force of. By adjusting the screwing amount of the adjusting screw 27, the position where the tapered surface 27a and the pressing surface 21c come into contact changes, and the support base 2
1 is pushed clockwise, and as shown in FIG. 1, the movable mirror 7 is adjusted to the left by θb about the b-axis. After the adjustment work is completed, the fixing screw 23 is tightened and, if necessary, the screw is locked with adhesive.

Furthermore, a cylindrical slide surface 2 is provided on the lower surface of the rocking table 22.
2d is formed. On the other hand, a slide surface 28a is also formed on the upper surface of the slide table 28 located below.

As shown in FIG. 5, both sliding surfaces 22d and 28a are
It is a cylindrical surface with the same radius of curvature relative to the axis. By sliding both on this cylindrical surface, the rocking table 22 is rotationally adjusted with respect to the a-axis. As shown in Figure 2, this a-axis is
It is set at a position extending to the center of the reflective surface of the movable mirror 7. A hole 22e is formed in the rocking table 22, and a female threaded hole 28b is formed in the slide table 28, and a holding screw 29 is inserted into the coil spring 31, further inserted into the hole 22e, and screwed into the female threaded hole 28b. . Furthermore, the adjustment screw 32
is inserted into the hole 22f of the rocking table 22 and screwed into the female threaded hole 28c of the slide table 28. As shown in Figure 5,
Since a coil spring 31 is interposed between the head of the push screw 29 and the rocking table 22, by adjusting the screwing amount of the adjusting screw 32, the rocking table 22 can swing around the a-axis. As shown in FIG. 2, the reflected optical path A of the movable mirror 7 is adjusted in the direction of the θa force. After adjustment, the screws can be locked with adhesive if necessary.

Further, the slide base 28 is supported within a groove 33a formed in the chassis 33 of the fixed part S so as to be movable in the X direction. The elongated hole 28d in the slide table 28 connects to the chassis 33.
A female thread 633b is formed in the holder. The fixing screw 34 is inserted through the coil spring 35, passes through the elongated portion 28d, and is screwed onto the female thread 633b. Also, a coil spring 36 is provided between the slide base 28 and the chassis 33.
is applied, and the slide base 28 is pulled in one direction by the biasing force. Further, an adjustment screw 37 is screwed into a female thread 633c formed on the chassis 33. A tapered surface 37a formed on this adjustment screw 37 is in contact with a pressing portion 28e of the slide base 28. This adjustment screw 37
By adjusting the amount of screwing in, the amount of movement of the slide base 28 in the X direction can be adjusted, and the adjustment work shown in FIG. 3 (A+) is performed. After this adjustment is completed,
4 is tightened and screw-locked with adhesive if necessary.

In the adjustment mechanism shown in FIG. 4, the adjustment shown in FIG. 1 is performed by changing the rotation angle of the support base 21 with respect to the b-axis, and the adjustment shown in FIG. The adjustments shown in the figure are made. In addition, by adjusting the amount of movement of the slide table 28 in the X direction,
The adjustment shown in A) is made.

[Effects] As described above, according to the present invention, angular errors in the moving direction of the optical head can be absorbed by only adjusting the movable mirror drive section, and offset of error signals can be prevented.

[Brief explanation of the drawing]

Sections 1 to 3 show basic embodiments of the present invention; FIG. 1 is a plan view, FIG. 2 is a view in the direction of the ■ arrow in FIG. 1,
Figure 3 (A) and FB+ are plan views of individual implementations, Figure 4 is an exploded perspective view showing a specific adjustment mechanism, Figure 5 is a partial sectional view of Figure 4, and Figure 6 is an optical device for optical discs. 7 and 8 (A) and (B) are plan views showing the entire structure of the
, (C) is an explanatory diagram of the problems of the prior art. D... Optical disk, H... Optical head, 3... Objective lens, S... Fixed part, 4... Light emitting element, 7...
Movable mirror, 10a, 10b...light receiving element, 15...
-Mirror drive unit, 21...support stand, 22...swing stand, 28...-slide stand, 33...chassis of fixed part. Figure 1 Figure 2 (A) Figure 3 Figure 8 (A) (B) Disk inner circumference Disk outer circumference error detection signal

Claims (1)

[Claims] 1. An optical head that moves along the recording surface of the disk is provided with an objective lens and a mirror facing the optical axis of the objective lens, and a fixed part includes a light emitting element, a light receiving element, and an optical path between the light emitting element and the light receiving element. and a mirror drive unit that rotates the movable mirror and swings the light irradiated onto the optical disc from the objective lens in a tracking correction direction. In the apparatus, the support base on which the mirror drive unit is supported is moved in a direction in which the degree of inclination of the reflective surface of the movable mirror is changed and in a relative opposing position between the reflective surface of the movable mirror and the mirror provided on the optical head. An optical device for an optical disc, characterized in that it is provided with a correction mechanism that moves in a direction to change the