JPH0362331A - Focusing servo actuator - Google Patents

Abstract

PURPOSE:To make the profile of a focusing servo actuator thin by bisecting a focus servo coil to the left and right and arranging a raising prism between the coils. CONSTITUTION:A focusing lens 11 is fixed to the center of a luminous flux axis converted upward in the perpendicular direction with a raising prism 10 at the inner circumference of a cylindrical holder in the center of a lens holder 28. Air-core coils 27A, 27B are arranged to the left and right sides of the prism 10 respectively. A stator 21 is constituted of prism-shaped magnets 22A, 22B magnetized in the thickness direction, iron-made back yokes 23A, 23B, iron made rectangular yokes 24A, 24B and a stator base 25. Through the constitution above,the focus actuator with a small height is obtained and when a focusing servo signal flows to the coils 27A, 27B, the coils 27A, 27B moves in the vertical direction to move the spot by an objective lens 11 in the thickness direction of a disk thereby implementing the focusing servo.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) 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.

As shown in the figure, a conventional small magneto-optical disk device 41
In addition to the small magneto-optical disk 2, there is also a base 4 and an electromagnet 5.
, an optical recording/reproducing device 46, and the like.

The small magneto-optical disk 2 of this conventional example has a substrate 2a, which is a disc made of a transparent resin such as polycarbonate, on the surface thereof.
Fe for recording and reproducing information using magneto-optic effect
, Co, Tb, Gd, etc. magneto-optical film (MO film) 2b
A protective film 2c made of ultraviolet curing resin or the like is formed on the protective film 2c, and a hub made of a metal plate (not shown) for driving the disk 2 is fixed to the center of the disk 2, as described above. , which 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, there are 1
．． A large number of recording tracks are formed at a pitch of 5 μm.

Each recording track is alternately formed with a data area where information is recorded/reproduced and a management area where management information is recorded in advance.

The disk 2 is rotated by a spindle motor (not shown) fixed to the base 4 at a speed of 3.80 rpm, 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 46.

This optical recording/reproducing device 46 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 light 15 reflected by the raising prism 10 is formed by the objective lens 11 as a light spot 16 with a minute diameter on the magneto-optical film 2b on the recording track of the recording area 3 of the disk 2. irradiated onto the surface of

A light spot 16 irradiated onto the surface of this magneto-optical film 2b
has a light intensity suitable for recording when the device 46 is operating in the 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 beam is reflected by the beam splitter, and is incident on the polarizing beam splitter 12 via a 172 wavelength 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 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 12, so the digital signal is reproduced from the difference between these two detection signals. be exposed.

Of the optical recording/reproducing device 46, a fixed unit 6 includes the laser diode 7, collimating lens 8, beam splitter 9, polarizing beam splitter 12, condensing lenses 13A, 13B, photodiode 14A14B, etc.
-1 is fixed to the base 4, and the fixed part of the movable unit 46-2 consisting of the raising prism 10, objective lens 11, focus servo actuator 50, etc. 7 is similarly fixed to the base 4. There is.

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 device 41 (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 is based on a focus servo signal based on the detection signal output, and the vertical position of the objective lens 11 is controlled by the focus servo actuator 50. 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, a 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 using a feed device (not shown). The movement range of the optical spot 16 in the radial direction of the disk 2 due to the tracking servo operation is normally limited to several hundred μm, so the positioning of the optical spot 16 in the radial direction of the disk 2 is performed by precision positioning. The servo operation and rough positioning are responsible for the feed operation.

The focus servo actuator 5 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 perspective view with the base removed, FIG. 3 (B) is a top view of FIG. Figure (C) is a side sectional view.

As shown in the figure, the conventional focus servo actuator 50 is composed of a fixed part 51 and a movable part 56. The lens is comprised of a coil 57, an objective lens holder 58 made of resin, and the like.

The fixing unit 6-
The objective lens 11 is fixed, the center of which is located on the optical axis of the light flux from 1, which is converted upward at right angles by the rising prism 10 supported by the fixing part 51, which will be described later. . The coil 57 is wound around a rectangular tube-shaped winding frame formed on the outer periphery of the objective lens holder 58, surrounding the winding frame. On the upper surface of the objective lens holder 58 that connects the upper end surface of the winding frame and the lower end surface of the lens holder, on the left and right sides of the optical axis direction of the light beam from the fixing unit 6-1 of the lens holder. Rectangular holes are formed along the inner periphery of the winding frame. The plate springs 30 are attached to the upper and lower end surfaces of the fixed part base 55 of the objective lens holder 58 on the side of the movable part holding part 55a, which will be described later.
One ends of A and 30B are each fixed at right angles,
The other ends of the leaf springs 30A and 30B are each fixed at right angles to the inner surface of the movable part holding portion 55H. These upper and lower two leaf springs 30A and 30B move the movable part 56 to the upright prism 1 with a magnet 22B and a back yoke 23B, which will be described later, arranged between them.
It is possible to move only in the optical axis direction of the luminous flux converted upward at right angles by 0, and during this movement, this magnet 22
B and the back yoke 23B at an interval that does not contact the
arranged in parallel.

Further, the objective lens 11 is arranged to face the recording area 3 of the disk 2 (not shown) through a hole provided in the base 4.

The fixed part 51 includes a prismatic magnet 22A magnetized in the thickness direction, back yokes 23A and 23B made of 2281 iron, and rectangular plate-shaped iron yokes 24A and 24.
B1 consists of the fixing part base 55 and the like.

The yokes 24A and 24B are respectively disposed through holes in the objective lens holder 58 so that their outer surfaces face the center of the inner surface of the winding frame portion with a predetermined gap therebetween, and their upper end surfaces are They are respectively fixed to the lower surface of the base 4.

The magnets 22A and 22B are attached to this yoke 24A.
and 24B, so that a magnetic field is formed between them.
The magnetized surfaces thereof are respectively arranged to face the surface of the coil side of the coil 57 with a predetermined gap, and the surfaces opposite to the surfaces facing the coil side are respectively arranged on the base 4. The upper end surfaces of the back yokes 23A and 23B are fixed to the inner surfaces of the back yokes 23A and 23B, respectively.

The fixed part base 55 has magnets 22A and 22B.
The movable part holding part 55a is parallel to the magnetized surface of the movable part holding part 55a, and the rising prism holding part 55b is integrally formed at right angles to the lower end of the inner surface of the movable part holding part 55a. At the tip of the rising prism holding section 55b, the fixed section unit 6-1 is located below the objective lens holder 58.
The upright prism 10 is fixed to correspond to the optical axis of the light beam from the base, and the upright prism 10 converts the axis upward at a right angle. It is fixed to the bottom surface of 4. Since the coil 57 is wound around the outer periphery of the objective lens holder 58, the position of the above-mentioned light beam is below the coil 57 and the objective lens holder 58, so the position of the rising prism 10 is also in this position. etc. is below.

Then, by sending the focus servo signal to the coil 57, the magnet 22A and the yoke 24A are connected to each other.
The coil 57 moves vertically due to the electromagnetic force received by the coil sides of the coil 57 placed in the magnetic field in the air gap between the magnet 22B and the yoke 24B, and therefore the objective lens 11 is vertically moved. Raised prism 1
Move on the optical axis of the luminous flux converted upward at right angles by 0,
By moving the optical spot 16 by the objective lens 11 in the thickness direction of the disk 2, the aforementioned focus servo operation is performed.

In order to damp harmful vibrations during the focus servo operation, rubber damping materials 31A and 31B are bonded to the leaf springs 30A and 30B, respectively.

(Problems to be Solved by the Invention) The conventional focus servo actuator 50 having the above configuration has a structure in which the raising prism 10 is disposed below the coil 57 and the objective lens holder 58, so the height dimension The problem was that it became large. This large height dimension becomes an obstacle when making the compact magneto-optical disk device 41 thinner.

The present invention has been made with attention to the above points, and an object of the present invention is to provide a focus servo actuator that is small in height and is incorporated in an optical recording/reproducing device used in an optical disk device such as a magneto-optical disk device. That is.

(Means for Solving the Problems) A focus servo actuator of the present invention includes at least a light emitting element that emits laser light, a light receiving element that obtains a detection signal from reflected light from an optical disk, and a light receiving element that obtains a detection signal from reflected light from the light emitting element. incorporated into an optical recording and reproducing device comprising a rising prism for converting an optical axis upward at a right angle, and an objective lens disposed opposite to a recording area of the optical disk on the optical axis of the light beam converted upward at a right angle, The focus servo actuator moves the objective lens and performs a focus servo operation, and is configured such that air-core coils are respectively disposed on the left and right sides of the objective lens.

(Embodiment) The focus servo actuator of the present invention is made thinner by dividing the focus servo coil into left and right halves and arranging the raising prism between the two coils.

As shown in FIG. 2 described above, a small magneto-optical disk device 1 incorporating a focus servo actuator 20 according to an embodiment of the present invention is incorporated into a movable unit 6-2 of an optical recording/reproducing device 6. Only this focus servo actuator 20 is different from the device 41 of the conventional example described above, so the same parts as in the conventional example are given the same reference numerals and the explanation thereof will be omitted.

This focus servo actuator 2 in Fig. 2
Although the configuration of No. 0 is outlined for the purpose of explaining its operation, the actual configuration is as shown in FIG.

Fig. 1 is a structural diagram showing an embodiment of the focus servo actuator of the present invention, in which (A) is a perspective view with the base removed, and (B) is a top view of Fig. 1 (A). , the same figure (C) is a side sectional view.

As shown in the figure, a focus servo actuator 20 according to an embodiment of the present invention is composed of a fixed part 21 and a movable part 26. Air-core coils 27A and 27B1 Resin objective lens holder 28, Resin coil holder 29
, two upper and lower leaf springs 30A and 30B, etc.

The fixing unit 6-
The objective lens 11 is fixed, and the center thereof is located on the optical axis of the light beam that is converted upward at right angles by the raising prism 10 supported by the fixing part 21, which will be described later. . On the left and right sides of the rising prism 11 with respect to the optical axis direction of the light beam from the fixed part unit 6-1, air cores are wound so that the winding direction of the long side coil side is parallel to the front axis direction. The coil 27A of
and 27B are arranged, and the upper end surfaces of the coils 27A and 27B are fixed to the left and right lower surfaces of the lens holder portion of the objective lens holder 28. The lower end surfaces of the coils 27A and 27B are fixed to the left and right upper surfaces of the reinforcing coil holder 29. This objective lens holder 28
The coils 27A and 27B are attached to the portions of the coil holder 29 where the coils 27A and 27B are fixed, respectively.
A rectangular hole with the same shape as the hollow part is formed in each case. One end of the leaf springs 30A and 30B is fixed at a right angle to the end face of the fixed part base 25 of the objective lens holder 28 and the two coil holders, which will be described later, on the movable part holding part 25a side. The other ends of the springs 30A and 30B are fixed at right angles to the inner surface of the movable part holding section 25a, respectively. These two upper and lower leaf springs 30A and 30B move the movable portion 26 with a magnet 22B and a back yoke 23B, which will be described later, arranged between them.
They are movable only in the optical axis direction of the luminous flux converted upward at right angles by the raising prism 10, and are arranged in parallel at such intervals that they do not come into contact with the magnet 22B and the back yoke 23B during this movement. .

Further, the objective lens 11 is arranged to face the recording area 3 of the disk 2 (not shown) through a hole provided in the base 4.

The fixed part 21 includes a prismatic magnet 22A magnetized in the thickness direction, back yokes 23A and 23B made of 2281 iron, and rectangular plate-shaped iron yokes 24A and 24.
B1 consists of the fixed part base 25 and the like.

The yokes 24A and 24B are inserted into the center of the hollow portion of the coils 27A and 27B, respectively, while maintaining a predetermined gap from the inner periphery of each coil side.
Their upper end surfaces are fixed to the lower surface of the base 4, respectively. The magnets 22A and 22B have their magnetized surfaces aligned with the coils 27A and 27, respectively, so that a magnetic field is formed between them and the yokes 24A and 24B, respectively.
B are arranged opposite to the surface of the coil side opposite to the raising prism 10 with a predetermined gap, and are opposite to the surface facing the coil side. are fixed to the inner surfaces of the back yokes 23A and 23B, respectively, whose upper end surfaces are fixed to the lower surface of the base 4.

The fixed part base 25 includes magnets 22A and 22B.
The movable part holding part 25a is parallel to the magnetized surface of the movable part holding part 25a, and the rising prism holding part 25b is integrally formed at right angles to the lower end of the inner surface of the movable part holding part 25a. At the tip of the rising prism holding portion 25b, a tip is located between the two left and right coils 27A and 27B, and the tip axis is oriented perpendicularly upward in correspondence with the optical axis of the light beam from the fixing unit 6-1. The rising prism 10 to be converted is fixed, and the upper end surface of the movable part holding portion 25a is fixed to the lower surface of the base 4.

By sending the focus servo signal to the coils 27A and 27B, the coil 27A is placed in the magnetic field in the gap between the magnet 22A and the yoke 22A and between the magnet 22B and the yoke 24B.
The coils 27A and 27B move in the vertical direction due to the electromagnetic force received by the coil sides of the coils 27A and 27B, and therefore the objective lens 11 moves on the optical axis of the luminous flux converted upward at right angles by the raising prism 10. By moving the light spot 16 by the objective lens 11 in the thickness direction of the disk 2, the aforementioned focus servo operation is performed.

In this case, if the movable part 26 is supported by a cantilevered spring as in this embodiment, there is a risk that the movable part 26 will be slightly tilted due to the above-mentioned vertical movement, but the two coils 27
This inclination can be corrected by adjusting both types of flow values of the focus servo signals sent to A and 27B, respectively.

In order to damp harmful vibrations during the focus servo operation, rubber damping materials 31A and 31B are bonded to the leaf springs 30A and 30B, respectively.

The focus servo actuator 20 according to an embodiment of the present invention having the above configuration has two coils 27A on the left and right.
and 27B, the height dimension is smaller than that of the conventional example described above.

(Effects of the Invention) Since the focus servo actuator of the present invention having the above configuration has a small height dimension, it is possible to reduce the thickness of an optical disk device using an optical recording/reproducing device incorporating this actuator. The usability of this device is improved.

[Brief explanation of drawings]

FIG. 1 is a structural diagram showing an embodiment of the focus servo actuator of the present invention, in which (A) is a perspective view showing the state with the base removed, and (B) is a top view of FIG. Figure 2 (C) is a side sectional view, Figure 2 is an explanatory diagram of the recording and reproducing operation of an example of a small magneto-optical disk device incorporating the actuators shown in Figures 1 and 3, and Figure 3 is a conventional focus These are structural diagrams showing an example of a servo actuator, where (A) is a perspective view with the base removed, and (A) is a perspective view with the base removed.
B) is a top view of the same figure (A), and the same figure (C) is a side sectional view. 1... Small magneto-optical disk device, 2... Small magneto-optical disk (optical disk), 3...
Recording area, 6... Optical recording/reproducing device, 7... Laser diode (light emitting element), 10... Standing prism, 11... Objective lens, 14A, 14B
... Photodiode (light receiving element), 15 ... Laser light, 20 ... Focus servo actuator, 21 ...
・Fixed part, 22A, 22B... Magnet (field part), 24A,
24B... Yoke (field part), 25... Fixed part base, 26... Movable part, 27A, 27B... Coil, 28... Objective lens holder,

Claims (1)

[Claims] at least a light emitting element that emits laser light and a light receiving element that obtains a detection signal from reflected light from the optical disk; 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; A focus servo actuator that is incorporated in an optical recording and reproducing device that includes an objective lens that is arranged to face a recording area of the optical disk on the optical axis of the converted light beam, and that moves the objective lens to perform a focus servo operation, A focus servo actuator characterized in that air-core coils are arranged on the left and right sides of the objective lens.