JPH03198229A - Focus servo actuator - Google Patents

Abstract

PURPOSE:To improve focus servo characteristics by providing a leaf spring with a spring side which extends in one circumferential direction to couple an external and an internal ring part with each other at plural positions of spot symmetry and a spring side which extends in the other circumferential direction. CONSTITUTION:The focus servo actuator 29 consists of a fixed part 21 and a movable part 27 and upper and lower leaf springs 25A and 25B each consist of four leaf spring parts 25c including a spring piece 25d which extends in the counterclockwise circumferential direction viewed from the external ring part 25a and a spring piece 25e which is connected at one end to the cunterclockwise end part of the spring piece 25d and extends in the clockwise direction. Consequently, the movable part 27 is enabled to move only in the optical axis direction of luminous flux which is converted to a 90 deg. upward direction by a raising prism. Consequently, the fine rotary motion of an objective lens 11 can be suppressed within a permissible range and focus servo characteristics can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Description) The present invention relates to a focus servo actuator incorporated in an optical recording/reproducing device used in an optical disk device.

(Prior Art) In recent years, optical disk devices such as magneto-optical disk devices have been used for recording computer data, document files, and the like.

The magneto-optical disk cartridge used in this magneto-optical disk device is a magneto-optical disk for recording/playback that can be freely erased and rewritten, and is made of resin for ease of handling and to make it removable from the recording/playback device. It is housed in a case.

FIG. 2 is an explanatory diagram of recording and reproducing operations of an example of a small magneto-optical disk device incorporating a focus servo actuator according to an embodiment of the present invention and a conventional example, which will be described later.

As shown in the figure, a conventional small magneto-optical disk device 31
In addition to the small magneto-optical disk 2, there is also a base 4 and an electromagnet 5.
, an optical recording/reproducing device 36, and the like.

This conventional small-sized magneto-optical disk 2 has an F for recording and reproducing information using the magneto-optic effect on one surface of a substrate 2a which is a disk made of transparent resin such as polycarbonate.
Magneto-optical film (MO film) 2 made of e, Co, Tb, Gd, etc.
b is formed, a protective film 2C made of ultraviolet curable resin or the like is further formed thereon, and a hub made of a metal plate (not shown) for driving the disk 2 is fixed to the center thereof. It is housed in a resin case (not shown) and becomes a magneto-optical disk cartridge.

In the recording area 3 where information is recorded/reproduced on the magneto-optical film 2b of the disk 2, a spiral or concentric pattern is formed.
A large number of recording tracks are formed at a pitch of 1.5 μm. Each recording track is alternately formed with a management area in which management information is recorded in advance and a data area in which information is recorded/reproduced.

The disk 2 is driven to rotate at CA V 3.60 rpm by a spindle motor (not shown) fixed to a base 4, and the magneto-optical film is rotated by an electromagnet 5 disposed on the protective film 2C side with a gap in between. A perpendicular bias magnetic field is applied to 2b. Further, information is recorded and reproduced from the substrate 2a side onto the magneto-optical film 2b using the laser beam 15 from the optical recording and reproducing device 36.

This optical recording/reproducing device 36 includes a laser diode 7, a collimating lens 8, a beam splitter 9, a raising prism 10, an objective lens 11, a polarizing beam splitter 12,
Condenser lenses 13A and 13B.

It is composed of photodiodes 14A, 14B, etc.

The laser light emitted from the laser diode 7 is made into parallel light by the collimating lens 8, and then
The cross-sectional shape of the beam is shaped into a predetermined shape by a beam shaping prism (not shown), and the beam passes through the beam splitter 9 and enters the rising prism 10 . The laser beam 15 reflected by the raising prism 10 is directed by the objective lens 11 into a small diameter spot 16 on the surface of the magneto-optical film 2b on the recording track of the recording area 3 of the disk 2. is irradiated.

A light spot 16 irradiated onto the surface of this magneto-optical film 2b
has a light intensity suitable for recording when the device 36 is operating in recording mode, and
When operating in the reproduction mode, the laser diode 7 is controlled by an output control device (not shown) so that it has a light intensity suitable for reproduction.

In this recording mode, the perpendicular magnetization direction of the magneto-optical film 2b on the recording track is reversed by the bias magnetic field of the electromagnet 5 only where the optical spot 16 hits, based on a digital signal corresponding to the recording data. This causes the digital signal to be recorded.

In the case of the reproduction mode, the direction of rotation of the polarization plane of the laser beam reflected on the surface of the magneto-optical film 2b changes depending on the perpendicular magnetization direction of the magneto-optical film 2b due to the magneto-optic effect. , the objective lens 11 and the rising prism 10, the light is reflected by the beam splitter 9, and is incident on the polarizing beam splitter 12 via a half-wave plate (not shown). The laser beam transmitted through this polarizing beam splitter 12 is focused by the condensing lens 13A, converted into an electric signal by the photodiode 14A, and output as a detection signal, and is reflected by this polarizing beam splitter 12. The collected laser light is focused by the condenser lens 13B, converted into an electric signal by the photodiode 14B, and output as a detection signal.

At this time, the magnitudes of both detection signals change in opposite directions depending on the rotation direction of the polarization plane as described above due to the action of the polarization beam splitter 13, so the digital signal is reproduced from the difference between these two detection signals. be exposed.

Of the optical recording/reproducing device 36, the fixed unit 6-1 includes the laser diode 7, collimating lens 8, beam splitter 9, polarizing beam splitter 12, condensing lenses 13A, 13B, photodiodes 14A, 14B, etc. A fixed portion of the movable unit 36-2, which is fixed to the base 4 and includes the raising prism 10, objective lens 11, focus servo actuator 40, etc., is fixed to a feed device (not shown).

Note that this base 4 is provided with a vibration-proof mechanism (not shown).
It is configured to be held in the main chassis of the disk device 31 (not shown).

The optical spot 1
The so-called focus servo that automatically tracks the focal point of No. 6 on the surface of the magneto-optical film 2b uses the focus servo actuator 40 to adjust the vertical position of the objective lens 11 based on a focus servo signal based on the detection signal output. It is done by controlling.

In addition, the optical spot 16 is
The so-called tracking servo that automatically tracks the recording track is a tracking servo actuator (not shown) that adjusts the position of the objective lens 11 in the radial direction of the disk 2 based on a tracking servo signal based on a detection signal output from the management area. This is done by controlling the Further, the recording track search is performed by performing a so-called feeding operation in which the optical spot 16 is moved from the outer diameter to the inner diameter of the recording area 3 of the disk 2 by the feed device. The optical spot 16 on the disk 2 due to the tracking servo operation
Since the limit value of the radial movement range of the disc 2 is normally several hundred microns, the radial positioning of the optical spot 16 on the disk 2 is performed by tracking servo operation for precise positioning and feeding operation for coarse positioning. It has become.

The focus servo actuator 4 in FIG.
The configuration of No. 0 is outlined for the purpose of explaining its operation, but the actual configuration is as shown in FIG.

FIG. 3 is a structural diagram showing an example of a conventional focus servo actuator, in which (A) is a side sectional view and (B) is a side sectional view.
FIG. 2 is a plan view of the leaf spring in FIG.

As shown in the figure, the conventional focus servo actuator 40 is composed of a fixed part 41 and a movable part 27, and the fixed part 41 is magnetized in the radial direction, with N poles and A ring-shaped magnet 22 in which a single S-pole magnetic pole is formed, a cylindrical iron back yoke 23 to which the outer periphery of the magnet 22 is fixed to the inner periphery, and the outer periphery of the cylindrical portion is the inner periphery of the magnet 22. A ring-shaped magnetic gap part is formed while maintaining a predetermined distance, and the lower end of this cylindrical part is integrally formed with the inner peripheral part of an annular part whose outer peripheral upper surface is fixed to the lower end surface of the back yoke 23. a ring-shaped upper spacer 26A whose lower end surface is fixed to the upper end surface of the back yoke 23; and a ring-shaped lower spacer 26A whose upper end is fixed to the lower surface of the outer periphery of the annular portion of this yoke 24. Spacer 26B1 An upper plate spring 45A to which a lower surface of an outer ring portion 45A (described later) is fixed to the upper end surface of this upper spacer 26A, and an outer ring portion 4 to the lower end surface of this lower spacer 26B.
It is composed of a lower leaf spring 45B and the like to which the upper surface of 5A is fixed.

The back yoke 23, the annular portion of the yoke 24, the upper and lower spacers 26A, 26B, and the upper and lower leaf springs 45A, 45
The outer diameter dimensions of B are arranged to be the same diameter. The upper and lower leaf springs 45A and 45B have the same shape, and are both formed by pressing thin metal plates such as phosphor bronze and beryllium copper, and are made of ring-shaped rings arranged concentrically. Outer ring part 45a and inner ring part 45
b5 The outer ring part 45a and the inner ring part 45b are connected at four point-symmetric points, respectively.
It is composed of four spring pieces 45c extending in the left rotation direction in the circumferential direction when viewed from 5a, each of which is arranged in parallel, and as described later, the movable part 27 is connected to the fixed part 41.
It is possible to move only in the optical axis direction of the luminous flux converted upward at right angles by the erecting prism 10 without contacting the erecting prism 10.

This movable part 27 includes a cylindrical air-core coil 28 wound in a ring shape, the back yoke 23, the yoke 2
a cylindrical cylindrical part 29a having a height equal to the total height of the annular part 4, upper and lower spacers 26A and 26B;
The outer periphery is fixed to the upper end of the inner periphery of this coil 28, and the annular part 29b whose inner periphery is integrally formed with the upper outer periphery of the cylindrical part 29a is a lens holder formed by integral molding of resin. It is composed of 29 mag.

The vertical center portion of this coil 28 is inserted into the magnetic gap portion, and the cylindrical portion 2 of this lens holder 29
The vertical center portion of 9a is inserted into the center through hole of the cylindrical portion of the yoke 24, and the upper and lower end surfaces of the cylindrical portion 29a are connected to the upper leaf spring 45A and the lower leaf spring 45B.
The fixing unit unit 6- is fixed to the inner ring portion 45b of the cylindrical portion 29a, and the fixing portion unit 6-
The outer periphery of the objective lens 11 is fixed, and the center thereof is located on the optical axis of the light flux from 1, which is converted upward at a right angle by the rising prism 10. Since the upper and lower leaf springs 45A and 45B are arranged perpendicularly to the optical axis direction of the light flux converted upward at right angles, the supporting structure of the objective lens 11 by the leaf springs 45A and 45B is centered This means that it is configured to be movable on this optical axis.

By supplying the focus servo signal to the coil 28, the coil 28 is moved in the vertical direction by the electromagnetic force received by the coil side of the coil 28, which is placed in the magnetic field between the magnet 22 and the cylindrical portion of the yoke 24. Therefore, the optical spot 16 caused by the objective lens 11 is moved in the vertical direction of the disk 2, and the aforementioned focus servo operation is performed.

(Problems to be Solved by the Invention) The conventional focus servo actuator 40 configured as described above has the above-mentioned upper and lower plate springs 45A, 45.
Since B is slightly rotated in the clockwise rotation direction when the lens holder 29 is viewed from above as the lens holder 29 moves up and down, the objective lens 11 is slightly rotated during the focus servo operation described above. There was a problem with rotation. This minute rotational movement of the objective lens 11 causes unnecessary resonance of the movable portion 27. Furthermore, if the center of the objective lens 11 is deviated from the optical axis of the light beam converted upward at right angles by the raising prism 10 due to manufacturing variations of the optical recording/reproducing device 36, this lens 11 If there are variations in the optical characteristics in the circumferential direction, this will cause deterioration of the focus servo characteristics. Also, due to manufacturing variations, etc., the upper and lower leaf springs 45A and 45
If there is a difference in spring characteristics or the like between B, the inclination of the lens holder 29 will fluctuate by a minute amount due to the minute rotational movement, causing deterioration of focus servo characteristics.

The present invention has been made with attention to the above points, and it is possible to reduce minute rotational movements of the objective lens during focus servo operation.
It is an object of the present invention to provide a focus servo actuator that is incorporated into an optical recording/reproducing device used in an optical disk device such as a magneto-optical disk device.

(Means for Solving the Problems) A focus servo actuator of the present invention includes a light-emitting element that emits a laser beam, a light-receiving element that obtains a detection signal from reflected light from an optical disk, and a light beam of the laser beam from the light-emitting element. an upright prism that converts the axis upward at a right angle;
It is incorporated into an optical recording and reproducing apparatus that includes at least an objective lens that is arranged to face the recording area of the optical disk on the optical axis of the light beam converted upward at right angles, and this In a focus servo actuator that moves the objective lens fixed to a movable part in a direction perpendicular to the optical disc to perform a focus servo operation, a leaf spring that supports the movable part so as to be movable in a direction perpendicular to the optical disc has concentric circles. an outer ring part fixed to the fixed part and an inner ring part fixed to the movable part which are arranged in a circumferential direction, and the outer ring part and the inner ring part are respectively connected at a plurality of points symmetrical points; It is configured to have a plurality of leaf spring parts including a spring piece extending in one direction and a spring piece extending in the other direction in the circumferential direction.

(Example) In the focus servo actuator of the present invention, the above-described leaf spring has a spring side extending in one direction in the circumferential direction and a circumferential spring side that connects the outer ring part and the inner ring part at a plurality of point-symmetric points, respectively. The above object is achieved by having a plurality of leaf spring parts including spring sides extending in the other direction.

FIG. 1 is a structural diagram showing an embodiment of the focus servo actuator of the present invention, in which (A) is a side sectional view, and (B) is a plan view of the leaf spring in (A). .

As shown in the figure, the focus servo actuator 20 according to the embodiment of the present invention is composed of a fixed part 21 and the movable part 27, and is different from the conventional focus servo actuator 40 described above. Since only the upper and lower leaf springs 25A and 25B of the portion 21 are different, explanations of the same parts as in the conventional example described above in FIGS. 2 and 3 will be omitted.

The upper and lower leaf springs 25A and 25B each connect a ring-shaped outer ring part 25a and an inner ring part 25b1 arranged concentrically at point-symmetrical 4W points. A spring piece 25d extending in the left rotation direction in the circumferential direction when viewed from the outer ring portion 25a in FIG. 1(B);
It is composed of four leaf spring parts 25c, including a left rotation direction end of this spring side 25d and a spring piece 25e extending in the right rotation direction, one end of which is connected by a folded part. Similarly to the above case, the movable portion 27 is movable only in the optical axis direction of the light beam converted upward at right angles by the rising prism 10. The length and width of these two spring pieces 25d and 25e can be changed within the permissible range of the minute rotational movement of the objective lens 11 described above.

The focus servo actuator 20 according to an embodiment of the present invention having the above-mentioned configuration has the upper and lower leaf springs 2
5A and 25B include the spring pieces 25d extending in the left rotation direction and the spring pieces 25e extending in the right rotation direction, as described above, so that the minute rotational momentum of the objective lens 11 can be kept within the allowable range without increasing costs. This makes it possible to improve the focus servo characteristics in the compact magneto-optical disk device 1 using the optical recording/reproducing device 6 in which the actuator 20 is incorporated in the movable unit 6-2. In addition, since the spring length of the leaf spring portion 25c can be increased, the plate thickness can be increased, which increases horizontal rigidity, reduces secondary resonance caused by the tracking servo operation, and reduces deformation and damage during the manufacturing process. etc. defects are reduced.

(Effects of the Invention) The focus servo actuator of the present invention having the above-described configuration is capable of suppressing the minute rotational momentum of the objective lens within a permissible range. It becomes possible to improve the focus servo characteristics in an optical disk device using the optical disk device, and the function-to-cost ratio of this disk device improves.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a configuration diagram showing an embodiment of the focus servo actuator of the present invention, and FIG.
B) is a plan view of the leaf spring in FIG. 2A, and FIG. 2 is an explanatory diagram of the recording and reproducing operation of an example of a small magneto-optical disk device incorporating an embodiment of the present invention and a conventional focus servo actuator. FIG. 3 is a structural diagram showing an example of a conventional focus servo actuator, in which (A) is a side sectional view, and (B) is a plan view of the leaf spring in (A). 1... Small magneto-optical disk device (optical disk device), 2... Small magneto-optical disk (optical disk), 3...
Recording area, 6... Optical recording and reproducing device, 7... Laser diode (light emitting element), 10... Standing prism, 11... Objective lens, 0... Focus servo actuator... fixed part , 5A, 25B... Leaf spring, 5a... Outer ring part, 25b... Inner ring part, 5c... Leaf spring part, 25d, 25e... Spring piece, 7... Movable part.

Claims (1)

[Claims] a light-receiving element that obtains a detection signal from a light reflected from a light emitting element and an optical disk that emits laser light; a rising prism that converts the optical axis of the beam of laser light from the light-emitting element to a right angle upward direction; The optical disc is incorporated into an optical recording/reproducing device including at least an objective lens disposed opposite to the recording area of the optical disk on the optical axis of the light beam, and is fixed to the movable part by interaction between the fixed part and the movable part. In the focus servo actuator that moves the objective lens in a direction perpendicular to the optical disk to perform a focus servo operation, a plate spring that supports the movable part so as to be movable in the direction perpendicular to the optical disk is arranged concentrically. An outer ring part fixed to the fixed part and an inner ring part fixed to the movable part, each connecting the outer ring part and the inner ring part at a plurality of points symmetrical points, and extending in one direction in the circumferential direction. A focus servo actuator comprising a plurality of leaf spring parts including a spring piece and a spring piece extending in the other circumferential direction.