JPH0362330A - Focusing and tracking servo actuator - Google Patents

Abstract

PURPOSE:To serve a tracking servo also as feeding operation and to improve the access speed and the reliability by constituting a focusing/tracking servo actuator integrally and expanding the moving range of the actuators. CONSTITUTION:A focusing/tracking servo actuator 20 is constituted by integrating focusing servo (FS)/tracking servo (TS) actuators 21, 32 and the TS and feed operation are served also by the actuator 32. With a TS signal applied to a coil of the actuator 32, the spot is moved in the radial direction of the disk to apply the TS operation. The feeding operation is implemented similarly. Moreover, with an FS signal applied to a coil of the actuator 21, an objective lens 12 is moved on the optical axis, the spot 17 is moved in the broadwise direction on the disk to apply the FS operation. Thus the access speed and the reliability are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a focus and tracking 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. 3 is a configuration diagram showing an example of a conventional small-sized magneto-optical disk used in the devices shown in FIGS. 2, 4, and 5, which will be described later. B) is a partially enlarged sectional view.

As shown in the figure, the conventional small magneto-optical disk 2 has a substrate 2a, which is a disc made of transparent resin such as polycarbonate, on one surface of which is made of Fe, Co, Tb.

A magneto-optical film (MO film) 2b made of Gd or the like is formed, a protective film 2c made of ultraviolet curable resin or the like is further formed thereon, and a hub 4 made of a metal plate for driving the disk 2 is fixed to the center. As described above, this disk 2 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.

FIG. 4 is an explanatory diagram of recording and reproducing operations of an example of a small magneto-optical disk device incorporating a focus and tracking servo actuator of the first conventional example.

As shown in the figure, the first conventional compact magneto-optical disk device 51 includes, in addition to the small magneto-optical disk 2, an electromagnet 6.
, base 55, optical recording/reproducing device 57, feed device 5
It is composed of 9 mag.

The above-mentioned small magneto-optical disk 2 is moved by a spindle motor (not shown) fixed to the base 55 into the CA V 3,
While being rotationally driven at 800 rpm, the protective film 2C
A perpendicular bias magnetic field is applied to the magneto-optical film 2b by an electromagnet 6 placed on the side with a gap in between. Further, information is recorded and reproduced from the substrate 2a side onto the magneto-optical film 2b using the laser beam 16 from the optical recording and reproducing device 57.

This optical recording/reproducing device 57 includes a laser diode 8, a collimating lens 9, a beam splitter 10, a rising prism 11, an objective lens 12, a polarizing beam splitter 13
, condenser lens 14A.

It is composed of 14B1 photodiodes 15A, 15B, etc.

The laser light emitted from this laser diode 8 is made into parallel light by a collimating lens 9, 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 10 and enters the rising prism 11 . The laser beam 16 reflected by the raising prism 11 is directed by the objective lens 12 as a light spot 17 with a minute diameter onto 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 17 irradiated onto the surface of this magneto-optical film 2b
has a light intensity suitable for recording when the device 57 is operating in recording mode, and
When operating in the reproduction mode, the laser diode 8 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 6 only where the optical spot 17 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 12 and the rising prism 11, the light is reflected by the beam splitter 10, and is incident on the polarizing beam splitter 13 via a l/2 wavelength plate (not shown). The laser beam transmitted through the polarizing beam splitter 13 is focused by the condensing lens 14A, converted into an electric signal by the photodiode 15A, and output as a detection signal, and is reflected by the polarizing beam splitter 13. The collected laser light is focused by the condenser lens 14B, converted into an electric signal by the photodiode 15B, 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 57, the laser diode 8, the collimating lens 9, the beam splitter 10. Polarizing beam splitter 13, condensing lenses 14A, 14B, and photodiode 15A.

15B etc. is fixed to the base 55, and a movable unit 57-2 consisting of the raising prism 11, objective lens 12, etc. is attached to the five movable parts 59b of the feed devices. It is installed. In this feed device 59, a movable portion 59b moves in the radial direction of the disk 2 along a guide rail (not shown) via a bearing 59c by the driving force of a linear motor 59a of this device 59 fixed to a base 55. The recording track is searched by moving the optical spot 17 from the outer diameter to the inner diameter of the recording area 3 of the disk 2, a so-called feed operation. The base 55 is configured to be held on the main chassis of the device 51 (not shown) via a vibration isolating mechanism (not shown).

In addition, so-called focus servo, which automatically makes the focus of the optical spot 17 follow the surface of the magneto-optical film 2b in response to surface wobbling of the disk 2, is based on a focus servo signal based on the detection signal output. Based on this, the vertical position of the objective lens 12 is controlled by a focus servo actuator 61 mounted on the movable part 59b of the feed device 59.

Also, due to the eccentricity of the disk 2, the optical spot 17
The so-called tracking servo that automatically tracks the recording track on the recording track is based on a tracking servo signal based on the detection signal output from the management area, and the position of the objective lens 12 in the radial direction of the disk 2 is controlled by the movable part 59b. This is performed by controlling the tracking servo actuator 62 mounted on the vehicle. The movement range of the optical spot 17 in the radial direction of the disk 2 due to this tracking servo operation is normally limited to several hundred μ-. The tracking servo operation and rough positioning are responsible for the feed operation.

FIG. 5 is an explanatory diagram of recording and reproducing operations of an example of a small magneto-optical disk device incorporating a second conventional focus and tracking servo actuator.

As shown in the figure, the second conventional compact magneto-optical disk device 71 is different from the first conventional device 51 described above only in the tracking servo actuator and the feed device. Components similar to those in the conventional example No. 1 are given the same reference numerals, and their explanations will be omitted.

That is, in the second conventional device 71, the tracking servo actuator 62 in the first conventional device 51 is omitted, and the tracking servo operation and the feeding operation are performed by seven feeding devices. It is. The movable unit 77-2 of the optical recording/reproducing device 77 in this second conventional example is the same as the movable unit 57-2 in the first conventional example, except that the tracking servo actuator 62 is removed. It is mounted on seven movable parts 79b. In this feed device 79, a movable portion 79b is fixed to the base 75 or moves in the radial direction of the disk 2 along a guide rail (not shown) via a bearing 79c by the driving force of a near motor 79a, and the above-mentioned feed operation is performed. At the same time, the above-mentioned tracking servo operation is also performed.

(Problems to be Solved by the Invention) First conventional small magneto-optical disk device 5 having the above configuration
1, the movable unit 5 of the optical recording/reproducing device 57 is mounted on the movable unit 59b of the feed device 59.
7-2 has a problem in that its weight is large and the access speed is slow because the tracking servo actuator 62 and five feed devices are switched to perform the search operation. Furthermore, this movable unit 5
7-2 and the feed device 59 have many parts, so
There was a problem that the shape of this part became large. This large size becomes an obstacle when downsizing the device 51. Further, there is a problem that the cost is high due to the large number of parts.

Further, in the second conventional small magneto-optical disk device 71, the feed device 79 has a large static and dynamic frictional resistance of the bearing 79c for moving the movable portion 79b due to its structure. There were problems in that the linearity of feed and tracking servo operations was poor, the frequency characteristics were also poor, and controllability was poor.

Furthermore, this feed device 7 has a problem in that the bearing 79c wears out over time and the frictional resistance changes, resulting in a lack of reliability. Further, since the bearing 79c and the guide rail require machining precision, there is a problem in that the cost is high.

The present invention has been made with attention to the above points, and is an optical disk device such as a magneto-optical disk device that has fast access speed, good controllability, high reliability, and can be miniaturized and cost reduced. The object of the present invention is to provide a focus and tracking servo actuator that is incorporated into an optical recording/reproducing device used in a disk device.

(Means for Solving the Problems) A focus and tracking servo actuator of the present invention includes a fixed unit that includes at least a light emitting element that emits a laser beam and a light receiving element that obtains a detection signal from reflected light from an optical disk; It is equipped with a rising prism that converts the optical axis of the light beam from the fixed part unit upward at a right angle, and an objective lens disposed on the optical axis of the light beam converted upward at a right angle and facing the recording area of the optical disk. The objective lens is moved to perform a focus servo operation, and the objective lens and the raising prism are moved to perform a tracking servo operation or a tracking servo operation and a feed operation. In the focus and tracking servo actuator, the objective lens and the focus servo coil are fixed, and the first movable actuator is supported by a movable end of a first leaf spring that is movable only in the focus direction of the objective lens. and the raising prism and tracking servo coil are fixed,
a second movable part supported by a movable end of a second leaf spring to which a fixed end of the first leaf spring is fixed and movable only in the tracking direction of the objective lens; Field parts for focus servo and tracking servo that form magnetic fields interlinking with the servo coils are respectively fixed, and a fixed part is provided to which the fixed end of the second leaf spring is fixed. It is something.

Further, the focus and tracking servo actuator of the present invention is configured such that the second leaf spring does not interfere with the light flux between the fixed unit and the rising prism. be.

(Embodiment) The focus and tracking servo actuator of the present invention integrally constitutes the focus servo actuator and the tracking servo actuator, and eliminates the five feed devices and 79 in the first and second conventional examples described above. However, by expanding the movement range of the tracking servo actuator, the tracking servo actuator can perform both the tracking servo operation and the feed operation.

FIG. 1 is a structural diagram showing an embodiment of the focus and tracking servo actuator of the present invention, and FIG.
1 is a perspective view with the base removed, FIG. 3B is a top view of FIG. 1A, and FIG. 1C is a side sectional view.

Further, FIG. 2 is an explanatory diagram of recording and reproducing operations of an example of a small magneto-optical disk device incorporating a focus and tracking servo actuator according to an embodiment of the present invention.

As shown in FIG. 2, a small magneto-optical disk device 1 according to an embodiment of the present invention is similar to the device 5 of the first and second conventional examples described above.
1 and 71, only the focus servo actuator, tracking servo actuator, and feed device are different, so the same parts as in the above-mentioned first and second conventional examples are given the same reference numerals, and their explanation will be omitted. do.

A focus and tracking servo actuator 20 according to an embodiment of the present invention incorporated into this device 1 is an integral structure of a focus servo actuator 21 and a tracking servo actuator 32. The five and seven feed devices in the devices 51 and 71 of the second conventional example are omitted, and the tracking servo actuator 32 is used to perform both the tracking servo operation and the feed operation. The fixed parts of the focus servo actuator 21 and the tracking servo actuator 32 incorporated in the movable part unit 7-2 of the optical recording/reproducing device 7 in this apparatus 1 are fixed to the base 5, and the tracking servo actuator 32 is fixed to the base 5. The moving range is configured such that the optical spot 17 can be moved from the outer diameter to the inner diameter of the recording area 3 of the disk 2.

The configuration of the focus and tracking servo actuator 20 in FIG. 2 is schematically shown for explaining its operation, but the actual configuration is as shown in FIG. 1.

As shown in FIG. 1, a focus and tracking servo actuator 20 according to an embodiment of the present invention has a focus servo actuator 21 and a tracking servo actuator 32 integrally constructed as described above.

This tracking servo actuator 32 is composed of a fixed part 33 and a movable part 39.
3 is composed of a rectangular plate-shaped magnet 34 magnetized in the thickness direction, a back yoke 35 made of iron, a prismatic iron yoke 36, spacers 37A and 37B1 angle adjustment parts 38, and the like.

This yoke 36 is arranged so that the magnetized surface of the magnet 34 is
They are fixed at both ends via spacers 37A and 37B so that their surfaces are parallel with a predetermined gap. The surface of the magnet 34 opposite to the surface facing the yoke 36 is fixed to one surface of the back yoke 35, and the back yoke 35 is arranged such that the longitudinal direction of the magnet 34 and the yoke 36 is It is fixed to the lower surface of the base 5 so as to be parallel to the optical axis direction of the light beam from the fixing unit 7-1 of the device 7. Further, the angle adjustment section 38 is fixed to the lower surface of the base 5 so as to be parallel to the back yoke 35 via the movable section 39, the focus servo actuator 21, etc. therebetween.

This movable part 39 includes a rectangular cylindrical air-core coil 40°, a movable part base 41 made of resin, and two left and right leaf springs 42A and 42.
It is composed of B, etc.

This coil 40 is inserted into the yoke 36 with a predetermined gap maintained at the inner periphery of the hollow part, and the surface of the coil side opposite to the coil side facing the magnetized surface of the magnet 34 is It is fixed to the center of the outer surface of the base portion 41a of the movable portion base 41, which is parallel to this magnetized surface. At the lower end of the inner surface of the base portion 41a of the movable portion base 41,
A rising prism holding portion 41b is integrally formed at right angles to the base portion 41a. This rising prism holding part 4
The upright prism 11 is fixed to the tip of the prism 1b so as to correspond to the optical axis of the light beam from the fixing unit 7-1, and converts the tip axis upward at a right angle. Further, one ends of the leaf springs 42A and 42B are fixed at right angles to both ends of the inner surface of the base portion 41a, respectively, and the other ends of the leaf springs 42A and 42B are fixed to both ends of the angle adjustment portion 38. Each is fixed at right angles. The two left and right leaf springs 42A and 42B are connected to the movable portion 3 with the focus servo actuator 21 disposed between them.
The two are movable only in a direction parallel to the optical axis direction of the light beam from the fixed part unit 7-1, and are arranged in parallel at an interval such that they do not come into contact with the focus servo actuator 21 during this movement. There is. This leaf spring 42B
A sunken part 42B-1 is formed in the center of the plate spring 42A so as not to block the light beam from the fixed part unit 7-1.
is formed. In order to improve strength, the barbed portions 42A-1 and 42B-1 of the leaf springs 42A and 42B are made rigid by, for example, increasing the plate thickness.

The focus servo actuator 21 is connected to the fixed part 2
2 and a movable part 26, this movable part 26
is a coil 2 with two air cores in the shape of a rectangular tube with a rectangular cross section.
7A and 27B1 resin objective lens holder 28, two resin coil holders, and two upper and lower leaf springs 30A and 3
It is composed of 0B, etc.

The erecting prism 11 is provided on the inner periphery of the cylindrical lens holder portion protruding from the center of the objective lens holder 28.
The objective lens 12 whose center is located on the optical axis of the luminous flux converted upward at right angles by is fixed. On the left and right sides of the rising prism 11 in the optical axis direction of the light beam from the fixed unit 7-1, the coils 27A 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. Also, this coil 2
The lower end surfaces of 7A and 27B are fixed to the left and right upper surfaces of the two reinforcing coil holders. This objective lens holder 28 and two coils 27A and 27 of the coil holder
These coils 27A and 27B are attached to the part where B is fixed.
A rectangular hole with the same shape as the hollow part is formed in each case. One ends of the leaf springs 30A and 30B are fixed at right angles to the end faces of the objective lens holder 28 and the two coil holders on the base portion 41a side, respectively, and the other ends of the leaf springs 30A and 30B are fixed to the base portion 41a side. Part 41a
are fixed at right angles to the inner surface of each. This top and bottom 2
The two leaf springs 30A and 30B are arranged with a magnet 23B and a back yoke 24B, which will be described later, between them.
The movable part 26 is movable only in the optical axis direction of the luminous flux converted upward at right angles by the rising prism 11, and at an interval such that it does not come into contact with the magnet 23B and the back yoke 24B during this movement. arranged in parallel.

Further, the objective lens 12 is arranged to face the recording area 3 of the disk 2 (not shown) through a hole provided in the base 5.

The fixing part 22 includes a prismatic magnet 23A magnetized in the thickness direction, 2381 iron back yokes 24A and 24B, and rectangular plate-shaped iron yokes 25A and 25.
It is composed of B, etc.

These yokes 25A and 25B are connected to the coil 2, respectively.
They are inserted into the center of the hollow portions 7A and 27B, keeping a predetermined gap from the inner periphery of each coil side, respectively, and their upper end surfaces are fixed to the lower surface of the base 5, respectively. The magnets 23A and 23B have their magnetized surfaces facing the surfaces of the coil sides of the coils 27A and 27B on the side opposite to the raising prism 11, respectively, with a predetermined gap therebetween, and The back yoke 2 has an upper end surface fixed to the lower surface of the base 5, and the surface opposite to the surface facing the coil side is fixed to the lower surface of the base 5.
It is fixed on the surfaces of 4A and 24B.

By sending the tracking servo signal to the coil 40 of the tracking servo actuator 32, this electromagnetic force is applied to the coil side of the coil 40, which is placed in the magnetic field in the gap between the magnet 34 and the yoke 36. The coil 40 moves in the longitudinal direction of the magnet 34 and the yoke 36, so the rising prism 11 moves on the optical axis of the light beam from the fixed unit 7-1, and the light spot 17 formed by the objective lens 12 is moved. By moving the disk 2 in the radial direction, the tracking servo operation described above is performed. Also, the above-mentioned feed operation is also performed by this tracking servo actuator 32.
This is done in the same way.

Further, by sending the focus servo signal to the coils 27A and 27B of the focus servo actuator 21, the coils disposed in the magnetic field in the air gap between the magnet 23A and the yoke 25A and between the magnet 23B and the yoke 25B, respectively. Due to the electromagnetic force that the coil sides of 27A and 27B receive, the coils 27A and 2
7B moves in the vertical direction, so that the objective lens 12
moves on the optical axis of the light beam converted upward at right angles by the raising prism 11, and moves the light spot 17 by the objective lens 12 in the thickness direction of the disk 2, thereby performing the focus servo operation described above. will be held.

Note that the angle adjustment section 38 is connected to the actuator 20.
In the assembly process, the movable parts 26 and 39 of the focus servo actuator 21 and the tracking servo actuator 32 are adjusted and fixed to the bases so that they are in predetermined relative positions with respect to the fixed parts 22 and 33. Ru.

Further, the leaf spring 30A of the focus servo actuator 21 and the tracking servo actuator 32
Rubber damping materials 31A and 31B and 43A and 43B are bonded to 30B, 42A and 42B, respectively, in order to damp harmful vibrations.

In the focus and tracking servo actuator 20 according to the embodiment of the present invention described above, an example has been described in which the tracking servo actuator 32 performs both the tracking servo operation and the feed operation. The servo actuator 32 may be used only for the purpose of expanding the movement range of this tracking servo operation, and this feed operation may be performed by a feed device similar to that in the first and second conventional examples described above.

Further, as described above, the plate springs 42A and 42B of the tracking servo actuator 32 are arranged so that the light beam from the fixed unit 7-1 is not affected by the bent portion 42A-1.
Although we have described an example in which leaf springs 42A and 42B-1 are formed, it is also possible to form a hole for this light beam in the center of each of the leaf springs 42A and 42B, or to form two holes each located above and below this light beam. It can also be divided into leaf springs.

In the focus and tracking servo actuator 20 of the embodiment of the present invention having the above configuration, the movable parts 26 and 39 are composed of only light and heavy parts such as the coils 27A, 27B, 40, etc., and the tracking servo actuator 32 The three movable parts are supported by leaf springs 42A and 42B, and the bearings 59c and 79c and the guide rail are not used as in the first and second conventional examples, so the access speed is low. The process is fast, the controllability is good, and the reliability is high. In addition, since the configuration has a small number of parts, it can be downsized,
Cost reduction becomes possible.

Furthermore, the stubbed portion 42B formed on the leaf spring 42B
-1 makes it possible to bring the light beam between the fixing unit 7-1 and the upright prism 11 close to the lower surface of the base 5, so that the structure can be made thinner.

(Effects of the Invention) The focus and tracking servo actuator of the present invention configured as described above has a fast access speed.
Since the actuator has good controllability and high reliability, the performance and quality of the optical disk device incorporating the actuator of the present invention are improved. Furthermore, since it is possible to make the device smaller and thinner, the usability is improved. Furthermore, since costs can be reduced, the function-to-cost ratio is improved.

[Brief explanation of drawings]

FIG. 1 is a structural diagram showing an embodiment of the focus and tracking servo actuator of the present invention. FIG. 1 (A) is a perspective view with the base removed, and FIG.
A) is a top view, (C) is a side view, FIG. 2 is an explanatory diagram of recording and reproducing operation of an example of a small magneto-optical disk device incorporating the actuator of FIG. 1, FIG. 3 is a diagram of FIG. FIG. 4 is a configuration diagram showing an example of a conventional small magneto-optical disk used in the apparatus shown in FIGS. 4 and 5; FIG.
B) is a partially enlarged sectional view, and FIGS. 4 and 5 are explanatory diagrams of recording and reproducing operations of an example of a small magneto-optical disk device incorporating the focus and tracking servo actuators of the first and second conventional examples. DESCRIPTION OF SYMBOLS 1... Compact magneto-optical disk device, 2... Magneto-optical disk (optical disk), 3... Recording area, 7... Optical recording/reproducing device, 7-1... Fixed unit, 7-2 ...Movable unit, 8...Laser oscillator (light emitting element), 11...Starting prism, 12...Objective lens, 1
5A, 15B... Photodiode (light receiving element), 2
0... Focus and tracking servo actuator, 21... Focus servo actuator, 22...
・Fixed part, 23A, 23B... Magnet (field part), 25A,
25B... Yoke (field part), 26... Movable part (first movable part), 27A, 27B... Coil (focus servo coil), 30A, 30B... Leaf spring (first leaf spring), 32・
... Tracking servo actuator, 33... Fixed part, 34... Magnet (field part), 36... Yoke (field part), 39... Movable part (second movable part), 40 ... Coil (tracking servo coil) 42
A, 42B... Leaf spring (second leaf spring), 42A-1
, 42B-1...Nige part.

Claims (2)

[Claims] (1) A fixed unit including at least a light emitting element that emits a laser beam and a light receiving element that obtains a detection signal from the reflected light from the optical disk; Incorporated into an optical recording and reproducing device comprising a raising prism and a movable unit including an objective lens placed on the optical axis of the light beam converted upward at right angles and facing the recording area of the optical disk,
A focus and tracking servo actuator that moves the objective lens to perform a focus servo operation, and also moves the objective lens and the raising prism to perform a tracking servo operation or a tracking servo operation and a feed operation, wherein the objective lens and A focus servo coil is fixed, a first movable part supported by a movable end of a first leaf spring movable only in the focus direction of the objective lens, and the raising prism and tracking servo coil are fixed. , a second movable part supported by a movable end of a second leaf spring to which a fixed end of the first leaf spring is fixed and movable only in the tracking direction of the objective lens; Field parts for focus servo and tracking servo that form magnetic fields interlinking with tracking servo coils are respectively fixed, and a fixed part is provided to which a fixed end of the second leaf spring is fixed. A focus and tracking servo actuator featuring: (2) The focus and tracking servo actuator according to claim 1, wherein the second leaf spring has a structure that does not obstruct the light flux between the fixed unit and the upright prism.