Recording and reproducing device having a stabilizing board and vertically-oscillating slider Number:6,826,769 from the United States Patent and Trademark Office (PTO) owispatent

Title: Recording and reproducing device having a stabilizing board and vertically-oscillating slider

Abstract: A recording and reproducing device of the present invention is provided to achieve the object of realizing stable and desirable recording and reproducing of information by suppressing fluttering of an optical disk by way of suppressing pressure fluctuation which is caused, for example, when an objective lens or an optical pickup with the objective lens is moved. The object is attained by a transparent stabilizer, provided between a disk and an optical pickup, which is moved with the optical pickup, and a slider which is provided to face the transparent stabilizer with the disk in between. The slider is supported to oscillate, and the surface of the slider facing the disk is flat. During rotation of the disk, the slider moves to balance the air pressure between the transparent stabilizer and the disk with that between the slider and the disk.

Patent Number: 6,826,769 Issued on 11/30/2004 to Hirokane,   et al.

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Inventors:	Hirokane; Junji (Nara, JP); Iwata; Noboru (Tenri, JP)
Assignee:	Sharp Kabushiki Kaisha (Osaka, JP)
Appl. No.:	034865
Filed:	December 27, 2001

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Foreign Application Priority Data

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Dec 27, 2000 [JP]			2000-399587
Dec 27, 2000 [JP]			2000-399589
Mar 13, 2001 [JP]			2001-070486
Mar 23, 2001 [JP]			2001-085305
Oct 18, 2001 [JP]			2001-321147
Oct 18, 2001 [JP]			2001-321162

Current U.S. Class:	720/688
Current International Class:	G11B 5/60 (20060101)
Field of Search:	720/688,658,659,663,672,681,682,686 369/13.13,53.28,13.32,13.23,13.2,13.11,13.02

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References Cited [Referenced By]

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U.S. Patent Documents

	4334302		June 1982		Peppers
	4530082		July 1985		Howe et al.
	5125750		June 1992		Corle et al.
	5189574		February 1993		Imamura et al.
	5247503		September 1993		Nomiyama et al.
	5497359		March 1996		Mamin et al.
	6108292		August 2000		Zijp
	6292453		September 2001		Ichimura et al.
	6404705		June 2002		Watanabe et al.

Foreign Patent Documents

	05-067362		Mar., 1993		JP
	10-308059		Nov., 1998		JP
	11-120551		Apr., 1999		JP
	1998-0643+94		Oct., 1998		KR

Other References

Yamamoto et al., "0.8 Numerical Aperture Two Element Objective Lens for the Optical Disc", Jpn. J. Appl. Phys. vol. 36 (1997) Pt. 1, No. 1B, pp. 456-459.* . German Patent and Trademark Office Communication dated Feb. 5, 2003 (5 pp.) and English translation (5 pp.). . Korean Intellectual Property Office Communication dated Nov. 26, 2003 (2 pp.) and English translation (5 pp.)..

Primary Examiner: Watko; Julie Anne
Attorney, Agent or Firm: Edwards & Angell, LLP Conlin; David G. Hartnell, III; George W.

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Claims

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What is claimed is:

1. A recording and reproducing device, which includes a light source, focusing means for converging and projecting a laser beam, which was emitted from the light source on a disk, and rotation driving means for rotating the disk, said recording and reproducing device comprising: a stabilizing board, provided on a first side of the disk between the disk and the focusing means, which is moved with the focusing means; and a vertically-oscillating slider, which is disposed on an opposite side of the disk and is facing the stabilizing board, to balance air pressures between the stabilizing board and the disk and between the slider and the disk.

2. The recording and reproducing device as set forth in claim 1, wherein said stabilizing board is transparent.

3. The recording and reproducing device as set forth in claim 1, wherein the stabilizing board is supported to oscillate.

4. The recording and reproducing device as set forth in claim 1, wherein the slider has a flat surface facing the disk.

5. The recording and reproducing device as set forth in claim 1, wherein the stabilizing board is fixed to the focusing means via an elastic member having elasticity.

6. The recording and reproducing device as set forth in claim 1, wherein the focusing means is a complex lens which is composed of at least two lenses.

7. The recording and reproducing device as set forth in claim 1, wherein the slider includes a magnetic field generating element for generating a magnetic field.

8. The recording and reproducing device as set forth in claim 1, wherein a surface of the stabilizing board facing the disk is flat and is parallel to a surface of the disk.

9. The recording and reproducing device as set forth in claim 8, wherein a surface of the vertically-oscillating slider is flat and is parallel to a surface of the disk.

10. The recording and reproducing device as set forth in claim 9, wherein the focusing means is disposed such that an optical axis of the focusing means passes through the stabilizing board in a direction of thickness at substantially a center of a surface of the stabilizing board facing the disk.

11. The recording and reproducing device as set forth in claim 8, wherein the focusing means is disposed such that an optical axis of the focusing means passes through the stabilizing board in a direction of thickness at substantially a center of a surface of the stabilizing board facing the disk.

12. The recording and reproducing device as set forth in claim 1, wherein a surface of the vertically-oscillating slider facing the disk is flat and is parallel to a surface of the disk.

13. The recording and reproducing device as set forth in claim 12, wherein the focusing means is disposed such that an optical axis of the focusing means passes through the stabilizing board in a direction of thickness at substantially a center of a surface of the stabilizing board facing the disk.

14. The recording and reproducing device as set forth in claim 1, wherein the focusing means is disposed such that an optical axis of the focusing means passes through the stabilizing board in a direction of thickness at substantially a center of a surface of the stabilizing board facing the disk.

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Description

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FIELD OF THE INVENTION

The present invention relates to a recording and reproducing device, disk cartridge, and optical disk device, which can be used to record and reproduce information in high density, and in particular to a recording and reproducing device, disk cartridge, and optical disk for recording and/or reproducing a data signal with respect to a flexible optical disk.

BACKGROUND OF THE INVENTION

Optical disks, such as a magneto-optical disk, have been widely used conventionally to record and reproduce information using a laser. In recent years, recording density of optical disks has been increasing to accommodate recording of more information. Along with this, optical disks have adopted smaller recording pits.

In order to read out information from such a high-density optical disk, the optical pickup needs to focus a light beam in such a way that the beam spot falls on a small domain of the optical disk where information is recorded. This makes it possible to read out information recorded in such a small domain. The smaller spot size enables recording of more information.

The spot size is proportional to wavelength .lambda. of the light source used, and is inversely proportional to numerical aperture NA of the objective lens. Thus, the spot size of a light beam can be reduced by either reducing the wavelength .lambda. of light from the light source, or by increasing the numerical aperture NA of the objective lens.

However, reducing the spot size by either of these methods causes large comatic aberration on the light beam when the optical disk tilts. The result of this is that the light beam cannot be accurately focused on the optical disk.

One conventional approach to solve this problem is to reduce thickness of the optical disk, and in turn length of optical path in the optical disk, so as to provide a larger margin of error for a tilt of the optical disk substrate.

For example, a CD-ROM has a numerical aperture NA=0.45, wavelength .lambda.=780 nm, and thickness of the optical disk substrate 1.2 mm. In contrast, a DVD-ROM has a numerical aperture NA=0.6, wavelength .lambda.=655 nm, and thickness of the optical disk substrate 0.6 mm. The DVD-ROM thus employs a light source which emits light of a shorter wavelength .lambda., an objective lens with larger numerical aperture NA, and a thinner optical disk substrate, so as to increase recording capacity and a margin of error for a tilt of the optical disk substrate.

However, rigidity of the optical disk substrate weakens when the thickness of the optical disk substrate is further reduced to provide more margin of error for a tilt of the optical disk substrate. In fact, this only worsens the tilt of the optical disk substrate because weaker rigidity of the optical disk substrate causes the optical disk substrate to flutter. Therefore, there is a limit in reducing wavelength .lambda. of light of the light source and increasing numerical aperture NA of the objective lens.

In light of this problem, Japanese Unexamined Patent Publication No. 308059/1998 (Tokukaihei 10-308059) (published date: Nov. 17, 1998) teaches a recording and reproducing device which stabilizes rotation of an optical disk to allow for use of a thinner optical disk, an objective lens with larger numerical aperture NA, and light of a shorter wavelength .lambda.. FIG. 52 shows a structure of this recording and reproducing device.

As shown in FIG. 52, the recording and reproducing device is adapted to record and reproduce information with respect to an optical disk 401, by including a spindle 405 for rotating the optical disk 401, an optical pickup 403 for projecting and focusing a light beam on the optical disk 401, and an stabilizer 402 for stabilizing rotation of the optical disk 401. The optical disk 401 is very thin and flexible.

The optical disk 401 has a magnetic center hub 404 which fixes the optical disk 401 on the spindle 405 by magnetic coupling. The optical pickup 403 has focusing means such as a complex objective lens. The stabilizer 402 and the optical pickup 403 are disposed face to face on the both sides of the optical disk 401.

To record or reproduce information with respect to the optical disk 401, the optical disk 401 is rotated in the vicinity of the stabilizer 402. Here, a space of reduced pressure is created between the optical disk 401 and the stabilizer 402. Thus, the optical disk 401, being flexible, is drawn toward the stabilizer 402, and rotates at a constant distance from the stabilizer 402. As a result, fluttering of the optical disk 401 is suppressed, thereby recording and reproducing information in the recording and reproducing device with the optical pickup 103 having a wavelength of light not more than 650 nm and numerical aperture NA of the complex objective lens not less than 0.7.

Further, the foregoing publication also teaches a recording and reproducing device which uses a disk cartridge 406 integrally provided with the stabilizer 402, as shown in FIG. 53. In this case, the optical pickup 403 is inserted into the disk cartridge 406 through an opening (not shown) of the disk cartridge 406. The provision of the stabilizer 402 with the disk cartridge 406 suppresses fluttering of the optical disk 401 as in the recording and reproducing device of FIG. 52, thus realizing recording and reproducing of information with the thin optical disk 401, the objective lens with large numerical aperture NA, and light of short wavelength .lambda..

Further, the foregoing publication discloses a structure in which a light beam is focused using a dual objective lens. For example, in a reproducing device shown in FIG. 54, a flexible optical disk 501, fixed on a center hub 503, is rotated by a spindle 504, so that the optical disk 501 is drawn toward the stabilizer 502 to stably rotate at a constant distance from the stabilizer 502.

A light beam 510 from a light source in a light emitting and detecting unit 505 is reflected at a mirror 506 and focused through the dual objective lens composed of a first objective lens 507 and a second objective lens 508 before it strikes the optical disk 501. The reflected light from the optical disk 501 is detected by a photodetector provided in the light emitting and detecting unit 505, so as to record or reproduce information with respect to the optical disk 501.

The dual lens is driven by a biaxial actuator 509 to carry out tracking and focusing. With such a reproducing device, a wavelength of light not more than 650 nm and numerical aperture NA of the dual lens not less than 0.7 can be realized.

However, the foregoing arrangement has the following problems.

Generally, recording and reproducing of information with respect to the optical disk employ a focus control whereby a constant distance is maintained between the optical disk and focusing means to maintain the laser beam in focus, so that the surface of the optical disk carrying the information is always within the depth of focus of the focusing means such as the objective lens.

In this manner, a focus control is carried out to record or reproduce information with respect to the optical disk 401. The optical pickup 403 approaches the optical disk 401. In this instance, in the arrangement of the foregoing publication, regardless of whether it is the recording and reproducing device of FIG. 52 or the recording and reproducing device using the disk cartridge 406 as shown in FIG. 53, the surface of the optical pickup 403 provided with the focusing means such as the objective lens is the surface facing the optical disk 401, which surface has relatively large irregularities. Thus, pressure fluctuates around the focusing means, or around the optical pickup 403, every time the focusing means is moved during a focus control, which causes fluctuation of air pressure between the optical pickup 403 and the optical disk 401. That is, the movement of the focusing means causes the optical disk 401 to flutter, which prevents stable focus control.

Further, in the reproducing device of FIG. 54, the flexible optical disk 501 fixed on the spindle 504 is rotated by the spindle 504 so that a space of reduced pressure is created between the flexible optical disk 501 and the stabilizer 502. The reduced pressure draws the optical disk 501 toward the stabilizer 502 so that the optical disk 501 stably rotates at a constant distance from the stabilizer 502. As a result, fluttering of the optical disk 501 is suppressed, thereby desirably recording or reproducing information.

However, because the dual objective lens which is disposed opposite the stabilizer 502 approaches the flexible optical disk 501 to reproduce information, the pressure between the dual objective lens and the optical disk 501 fluctuates. This causes the optical disk 501 to flutter (shudder) and thus prevent desirable recording and reproducing of information. Similarly, in the arrangement in which the disk cartridge is integrally provided with the stabilizer 502, desirable reproducing of information becomes difficult because the dual objective lens approaches the flexible optical disk 501.

Thus, one conventional problem is fluttering of the optical disk which is caused by pressure fluctuation around the optical disk, for example, due to movement of the focusing means of the optical pickup during a focus control. This means instable focus control, and therefore it was difficult to record and reproduce information desirably.

Another problem is that fluttering of the disk becomes more serious as the disk is rotated at higher speed, irrespective of whether the disk is flexible or not. It was therefore difficult to record and reproduce information stably.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a recording and reproducing device, a disk cartridge, and an optical disk device, which can be used to record and reproduce information both stably and desirably with less fluttering, even at a high rotational speed, by suppressing fluttering of an optical disk by way of suppressing pressure fluctuation which is caused, for example, when an objective lens is moved.

In order to achieve this object, a recording and reproducing device of the present invention, in a recording and reproducing device which records and reproduces information by projecting a laser beam on a disk being rotated, comprises: a stabilizing slider which is disposed to face the disk and is supported to oscillate, a surface of the stabilizing slider facing the disk being flat.

According to this arrangement, rotation of the disk induces an air flow between the disk and the stabilizing slider, and air bearing is created between the stabilizing slider and the disk because the surface of the stabilizing slider facing the disk is flat. Further, since the stabilizing slider is supported to oscillate, the stabilizing slider can be moved in such a way that a constant distance is always maintained from the disk during rotation of the disk.

Thus, the disk rotates at a constant distance from the stabilizing slider. That is, fluttering of the disk is prevented even when the disk is rotating at high speed, thus stably recording and reproducing information.

Further, in order to achieve the foregoing object, in a disk cartridge of the present invention which contains a disk in a cartridge used in the recording and reproducing device, the disk being exposed when recording and reproducing information, the cartridge has inner wall surfaces which define a stabilizing board for creating a space of reduced pressure between the disk and the inner wall surfaces.

According to this arrangement, the stabilizing board defined by the both inner wall surfaces of the disk cartridge suppresses fluttering of the disk more effectively, thus realizing more stable and desirable recording and reproducing.

Further, in order to achieve the foregoing object, an optical disk device of the present invention, in an optical disk device which records and reproduces information with respect to an optical disk, comprises: rotation driving means for rotating an optical disk; a focusing unit for focusing light from a light source on the optical disk; a support member for supporting the focusing unit; and a rotation stabilizing board, fixed to the support member so as to be disposed between the focusing unit with the support member and the optical disk, for stabilizing rotation of the optical disk.

According to this arrangement, the rotation stabilizing board for stabilizing rotation of the flexible optical disk is provided on the focusing unit and the support member of the focusing unit. This prevents fluttering of the optical disk which may be caused when the focusing unit and the support member of the focusing unit are positioned in the vicinity of the optical disk. As a result, desirable recording and reproducing can be realized.

For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a structure of relevant part of a recording and reproducing device according to one embodiment of the present invention.

FIG. 2 is an enlarged cross sectional view showing the structure of relevant part of the recording and reproducing device of FIG. 1.

FIG. 3 is an enlarged cross sectional view showing the structure of relevant part of the recording and reproducing device of FIG. 1 when a magneto-optical disk is used.

FIG. 4 is an enlarged cross sectional view showing the structure of relevant part of the recording and reproducing device of FIG. 1 when a dual lens is used.

FIG. 5 is an enlarged cross sectional view showing the structure of relevant part of the recording and reproducing device of FIG. 1 when a transparent stabilizer is fixed on an optical pickup via a spring.

FIG. 6 is a cross sectional view showing a structure of relevant part of a recording and reproducing device according to another embodiment of the present invention.

FIG. 7 is a plan view of a stabilizer.

FIG. 8 is a cross sectional view showing the structure of relevant part of the recording and reproducing device of another embodiment of the present invention when both inner walls of the cartridge define the stabilizer.

FIG. 9 is a plan view of the cartridge.

FIG. 10 is a cross sectional view showing another structure of the recording and reproducing device of FIG. 8 when a space inside a disk cartridge is restricted.

FIG. 11 is a cross sectional view showing a structure of relevant part of a recording and reproducing device according to yet another embodiment of the present invention.

FIG. 12 is a perspective view of a first stabilizer.

FIG. 13 is an enlarged cross sectional view showing the structure of relevant part of the recording and reproducing device of FIG. 11 when a magneto-optical disk is used.

FIG. 14 is an enlarged cross sectional view showing the structure of relevant part of the recording and reproducing device of FIG. 11 when a dual lens is used.

FIG. 15 is an enlarged cross sectional view showing the structure of relevant part of the recording and reproducing device of FIG. 11 when a first stabilizer is fixed on an optical pickup via a spring.

FIG. 16 is a cross sectional view showing a structure of relevant part of a recording and reproducing device according to still another embodiment of the present invention.

FIG. 17 is a plan view of a second stabilizer.

FIG. 18 is a cross sectional view showing the structure of relevant part of the recording and reproducing device of another embodiment of the present invention when both inner walls of the cartridge define the second stabilizer.

FIG. 19 is a plan view of the cartridge.

FIG. 20 is a cross sectional view showing another structure of the recording and reproducing device of FIG. 18 when a space inside a disk cartridge is restricted.

FIG. 21 is a cross sectional view schematically showing yet another embodiment of the optical disk device of the present invention.

FIG. 22 is a plan view of an optical disk cartridge of the optical disk device of FIG. 21.

FIG. 23 is an enlarged cross sectional view showing a structure of relevant part of the optical disk device of FIG. 21.

FIG. 24 is a cross sectional view schematically showing another structure of the optical disk device.

FIG. 25 is a cross sectional view schematically showing still another structure of the optical disk device.

FIG. 26 is a cross sectional view schematically showing yet another structure of the optical disk device.

FIG. 27 is a cross sectional view schematically showing still another structure of the optical disk device.

FIG. 28 is a cross sectional view schematically showing yet another structure of the optical disk device.

FIG. 29 is a cross sectional view showing a structure of relevant part of a recording and reproducing device of still another embodiment of the present invention.

FIG. 30 is a cross sectional view showing a structure of relevant part of the recording and reproducing device of FIG. 29.

FIG. 31 is a plan view showing a structure of relevant part of the recording and reproducing device of FIG. 30.

FIG. 32 is a cross sectional view schematically showing a structure of the recording and reproducing device of FIG. 29 when light is projected from the side of a disk substrate of the disk.

FIG. 33 is a cross sectional view schematically showing a structure of relevant part of the recording and reproducing device of FIG. 29 when light is projected from the side of a protective film of the disk.

FIG. 34 is a cross sectional view schematically showing a structure of relevant part of the recording and reproducing device of FIG. 29 when light is projected from the side of a protective film of the disk.

FIG. 35 is a cross sectional view showing a structure of relevant part of the recording device of FIG. 29 when focusing control is carried out differently from FIG. 29.

FIG. 36 is a cross sectional view showing a structure of relevant part of a recording and reproducing device according to still another embodiment of the present invention when both inner walls of a cartridge define a stabilizer.

FIG. 37 is a plan view of the cartridge.

FIG. 38 is, a cross sectional view showing a structure of relevant part of the recording and reproducing device of FIG. 29 when a magneto-optical disk is used.

FIG. 39 is a cross sectional view showing a structure of relevant part of the recording and reproducing device of FIG. 29 when a magneto-optical disk is used.

FIG. 40 is a cross sectional view showing a structure of relevant part of the recording and reproducing device of FIG. 29 when a magneto-optical disk is used.

FIG. 41 is a cross sectional view schematically showing one embodiment of an optical disk device of the present invention.

FIG. 42 is an enlarged cross sectional view showing relevant part of FIG. 41.

FIG. 43 is a cross sectional view showing a structure of relevant part of another embodiment of the optical disk device of the present invention.

FIG. 44 is a cross sectional view showing a structure of relevant part of yet another embodiment of the optical disk device of the present invention.

FIG. 45 is a cross sectional view showing a structure of relevant part of still another embodiment of the optical disk device of the present invention.

FIG. 46 is a cross sectional view of the optical disk device and an entire rotation stabilizer of the present invention.

FIG. 47 is a plan view of the entire rotation stabilizer of FIG. 46.

FIG. 48 is a cross sectional view of the optical disk device and an optical disk cartridge of the present invention.

FIG. 49 is a plan view of the optical disk cartridge of FIG. 48.

FIG. 50 is a cross sectional view of the optical disk device and an optical disk cartridge of the present invention.

FIG. 51 is a plan view of the optical disk cartridge of FIG. 50.

FIG. 52 is a cross sectional view showing a structure of relevant part of a conventional recording and reproducing device.

FIG. 53 is a cross sectional view showing a structure of relevant part of a recording and reproducing device using a conventional cartridge.

FIG. 54 is a cross sectional view showing how light is projected in the recording and reproducing device of FIG. 52.

DESCRIPTION OF THE EMBODIMENTS

[First Embodiment]

The following will explain one embodiment of the present invention. Note that, the following embodiments will describe the case where the present invention is applied to a flexible disk, but the present invention is also applicable to inflexible disks as well.

FIG. 1 is a cross sectional view showing a relevant part of a recording and reproducing device. As shown in FIG. 1, the recording and reproducing device according to the present embodiment includes a spindle (rotation driving means) 3, an optical pickup 4, a transparent stabilizing board (first stabilizing board) 5, a support section 6, a slider 7, and a suspension 8, which are incorporated to record and reproduce information with respect to a disk 1.

The transparent stabilizing board 5 is integrally fixed on an upper portion of the optical pickup 4. The optical pickup 4 with the transparent stabilizing board 5 is provided at a predetermined distance from one surface of the disk 1, and the slider 7 is disposed above the other surface of the disk 1 on the opposite side of the transparent stabilizing board 5 and the optical pickup 4. The optical pickup 4 and the slider 7 are integrally provided via the support section 6 and the suspension 8 which together make up a support member.

The disk 1 is a thin flexible disk made of transparent resin. Further, the disk 1 has a magnetic center hub 2, whereby the disk 1 is chucked to the spindle 3 by magnetic coupling. The disk 1 is rotated by driving the spindle 3 by a motor (not shown). Information is recorded and reproduced as the disk 1 rotates.

Note that, the type of disk 1 is not particularly limited as long as it is a flexible optical disk. For example, the disk 1 may be a ROM (Read-Only Memory) disk with a series of pits, which are recessions on a surface of the disk substrate; or a write once disk which incorporates an organic pigment material as the recording medium; or a rewritable optical disk which incorporates a phase change material as the recording medium.

Here, it is assumed that the disk 1 is a write once disk or a rewritable optical disk. As shown in FIG. 2, the disk 1 includes a disk substrate 1a with guiding grooves which are recessed and raised portions on a surface of the disk, a recording medium 1b which is formed on the surface of the recessed and raised guiding grooves; and a protecting layer 1c for protecting the recording medium 1b.

As shown in FIG. 2, the optical pickup 4 includes an optical pickup casing 15. In the optical pickup casing 15 are provided an light emitting and detecting optical system (light source) 10, a biaxial actuator 14, a lens holder 13, and an objective lens (focusing means) 12.

The light emitting and detecting optical system 10 includes a light emitting element which makes up a light source to emit a laser beam 11 in a direction toward the disk 1. The biaxial actuator 14 is provided on the optical pickup casing 15 to support the lens holder 13. The lens holder 13 is provided to hold the objective lens 12 between the light emitting and detecting optical system 10 and the transparent stabilizing board 5 which is provided on the optical pickup 4.

The electromagnetic force generated by coils provided in the biaxial actuator 14 drives the objective lens 12 in such a way that the objective lens 12 is freely displaced in focusing directions (vertical direction with respect to the disk 1) and in tracking directions (directions indicated by arrows in FIG. 1) with respect to the guiding grooves of the disk 1, thereby enabling the objective lens 12 to accommodate fluttering of the disk 1 or eccentricity of the tracks formed on the disk 1, in case where the recording and reproducing device is disturbed, for example, by oscillation.

The laser beam 11 emitted by the light emitting and detecting optical system 10 is focused through the objective lens 12 to irradiate the disk 1. The laser beam 11 on the disk 1 is reflected at the recording medium 1b of the disk 1. The light reflected at the recording medium 1b travels back to the light emitting and detecting optical system 10 through the objective lens 12. The light in the light emitting and detecting optical system 10 is detected by a photoreceptor element (not shown) therein, thereby recording or reproducing information.

The transparent stabilizing board 5 is provided on the optical pickup 4, i.e., on the surface of the optical pickup 4 on the side of the disk 1, at a predetermined distance from the disk 1. The optical pickup 4 and the transparent stabilizing board 5 are linked to each other. The transparent stabilizing board 5 is made of a transparent material to allow transmission of the laser beam 11 which is emitted by the optical pickup 4 to irradiate the disk 1.

The support section 6 is fixed to the optical pickup 4 at one end, and on the other end to the suspension 8 which leads to the slider 7 toward the tip. The support section 6 is driven by a linear motor (not shown) to guide the optical pickup 4 and the slider 7 to a predetermined position of the disk 1. This brings about integral movement of the transparent stabilizing board 5 and the slider 7 which are linked to the optical pickup 4.

The slider 7, supported by the suspension 8 and provided opposite the transparent stabilizing board 5 via the disk 1, can oscillate relative to the support section 6 in a vertical direction with respect to the surface of the disk 1. The surface of the slider 7 facing the transparent stabilizing board 5 is flat. When recording or reproducing information with respect to the disk 1, i.e., during rotation of the disk 1, the rotation of the disk 1 induces an air flow between the disk 1 and the slider 7, with the result that the air pressure between the slider 7 and the disk 1 is increased because the surface of the slider 7 facing the disk 1 is flat. That is, pressure is created between the slider 7 and the disk 1. In the same manner, rotation of the disk 1 also induces an air flow between the disk 1 and the transparent stabilizing board 5 to create pressure therebetween. In addition, the slider 7 is supported to oscillate. Thus, the slider 7 can be moved to balance out the air pressure between the disk 1 and the transparent stabilizing board 5 with that between the slider 7 and the disk 1.

By this pressure-induced state and balancing of it between (1) the slider 7 and the disk 1 and (2) the transparent stabilizing board 5 and the disk 1, the disk 1 rotates at a predetermined distance from the slider 7 and the transparent stabilizing board 5. This suppresses fluttering of the disk 1 when it is rotating, thereby stabilizing rotation of the disk 1.

Note that, when the surface of the slider 7 facing the transparent stabilizing board 5 is flat as in the foregoing case, the rotation of the disk 1 induces an air flow between the disk 1 and the slider 7 to create pressure therebetween. However, the pressure between the slider 7 and the disk 1 is reduced when the surface of the slider 7 facing the transparent stabilizing board 5 has a groove which acts to drain the air out of the gap between the slider 7 and the disk 1 when the disk is rotating.

Generally, recording and reproducing of information with respect to the disk 1 employ a focus control which keeps the laser beam 11 in focus by maintaining a constant distance between the disk 1 and the objective lens 12, so that the recording medium 1b of the disk 1 is always within a depth of focus of the objective lens 12.

Here, as shown in FIG. 52, when a disk 401 and an optical pickup 403 are directly face to face with nothing in between, the surface of the optical pickup 403 facing the disk 401 makes up a surface with focusing means such as an objective lens, for example. Such a surface has relatively large irregularities, which cause the pressure to fluctuate around the focusing means every time the focusing means is moved during the focus control. Thus, the air pressure between the focusing means and the disk 401 easily fluctuates with the result that the disk 401 flutters in response to the movement of the focusing means.

However, according to the arrangement as shown in FIG. 1, since the transparent stabilizing board 5 is placed between the disk 1 and the objective lens 12, the surface of the optical pickup 4 facing the disk 1 becomes flat by the flat surface of the transparent stabilizing board 5. As a result, the air pressure between the flat surface of the transparent stabilizing board 5 and the disk 1 becomes evenly distributed. This suppresses fluctuation of air pressure between the transparent stabilizing board 5 and the disk 1 even when, for example, the objective lens 12 is moved to carry out the focus control, thus suppressing fluttering of the disk 1.

Further, because the slider 7 is supported in such a way that it can oscillate in a vertical direction with respect to the disk 1, fluctuation of air pressure between the disk 1 and the transparent stabilizing board 5, which may be caused, for example, when the optical pickup 4 with the objective lens 12 is moved during the focus control, can be compensated for by varying the air pressure between the disk 1 and the slider 7 in such a manner that it is balanced with the air pressure between the disk 1 and the transparent stabilizing board 5.

Thus, even in cases where the objective lens 12 is moved relative to the disk 1, or the transparent stabilizing board 5 is moved with the optical pickup 4, the slider 7 accommodates this movement to follow the disk 1, so as to balance air pressure between the disk 1 and the transparent stabilizing board 5 with that between the disk 1 and the slider 7. Further, since the surface of the slider 7 facing the disk 1 is flat, the air pressure between the slider 7 and the disk 1 can be balanced easily and stably. As a result, it is possible to suppress displacement of the disk 1 in a vertical direction due to pressure fluctuation around the disk 1, i.e., fluttering of the disk 1 can be suppressed. This makes it possible to stably and easily carry out a focus control, or tracking of the disk 1 with the laser beam 11 in the track direction, even when the biaxial actuator 14 employing the conventional servo technique is used.

As a result, rotation of the disk 1 can be stabilized even when the objective lens 12 or the optical pickup 4 is moved, thus providing a recording and reproducing device which is capable of recording and reproducing information stably and desirably even when the disk 1 is a thin disk. Further, with a thin disk, the optical path length in the disk 1 can be made shorter, which increases a margin or error for a tilt of the disk 1. As a result, recording density of the disk 1 can be increased.

Note that, not limiting to the optical disk, the disk 1 may be, for example, a magneto-optical disk which uses a magneto-optical recording medium as the recording medium 1b.

Referring to FIG. 3, the following describes an example of a recording and reproducing device which uses a magneto-optical disk as the disk 1 to record and reproduce information. Recording of information on a magneto-optical disk requires a recording magnetic field. A recording magnetic field needs to be applied to an area where the laser beam 11 is focused. To this end, a magnetic head (magnetic field generating element) 30 is embedded in the slider 7. The structure of the recording and reproducing device other than the slider 7 which is integrally provided with the magnetic head 30 is as already described with reference to FIG. 2.

When recording information in the disk 1, the laser beam 11 projected on the disk 1 raises temperature of the recording medium 1b which is provided on the disk substrate 1a, thereby reducing coercive force of the recording medium 1b. Here, the magnetic field generated by the magnetic head 30 is applied to the disk 1.

The laser beam 11 emitted from the light emitting and detecting optical system 10 is converged by the objective lens 12 in the optical pickup 4 to irradiate the disk 1. The coercive force of the disk 1 is reduced in the foregoing manner, and the magnetic field generated by the magnetic head 30 changes the magnetization direction of the disk 1. Here, the magnetic head 30 and the optical pickup 4 are driven integrally. Information is recorded in the disk 1 in this manner.

In this way, the provision of the magnetic head 30 in the slider 7 can realize a recording and reproducing device which can record and reproduce information using a magneto-optical disk with a recording medium which requires a magnetic field for recording.

As in the structure of FIG. 2, the structure shown in FIG. 3 also includes the transparent stabilizing board 5, as well as the slider 7 which is provided opposite the transparent stabilizing board 5 via the disk 1. Thus, pressure fluctuation around the disk 1 and the optical pickup 4 can be suppressed even when the objective lens 12 or the optical pickup 4 provided with the objective lens 12 is moved. This stabilizes rotation of the disk 1 and thus provides a recording and reproducing device which can stably and desirably record and reproduce information even when the disk 1 is a thin disk.

Further, the objective lens 12 is not just limited to a simple lens as shown in FIG. 2, and it may be a dual lens which incorporates at least two lenses. For example, FIG. 4 shows an exemplary structure of the recording and reproducing device of FIG. 1, in which a dual lens composed of two lenses is used as the objective lens 12.

The dual lens as the objective lens 12 includes a lens 40 and a lens 41. This increases numerical aperture NA of the objective lens 12. Specifically, with the use of the dual lens, the numerical aperture NA of the objective lens 12 can be increased to 0.7 or greater, preferably 0.8 to 0.95. This makes it possible to reduce the spot size of the laser beam 11 projected on the disk 1, which in turn increases the recording capacity of the disk 1, and thus density of the disk 1. As a result, the recording and reproducing device which is suitable for high density recording and reproducing can be provided.

The numerical aperture NA of the objective lens 12 can also be increased using a simple lens. However, the use of the dual lens allows the objective lens 12 to be manufactured with large numerical aperture NA. Thus, the dual lens is preferable for the objective lens 12 when the numerical aperture NA is to be increased to 0.7 or greater as in the present embodiment.

Note that, the structure of FIG. 4 includes the magnetic head 30 and uses a magneto-optical disk as the disk 1. However, an optical disk may be used as well. In this case, the magnetic head 30 is not required.

Further, as shown in FIG. 5, the transparent stabilizing board 5 may be fixed to the optical pickup 4 via a board spring 50 (elastic member). FIG. 5 shows the structure of the recording and reproducing device of FIG. 3, with the additional member board spring 50 between the transparent stabilizing board 5 and the optical pickup 4.

As shown in FIG. 5, the transparent stabilizing board 5 is fixed on the optical pickup casing 15 via the board spring 50. According to the structure of FIG. 5, even when the slider 7 oscillates in response to external force and the disk 1 oscillates by the pressure created between the disk 1 and the slider 7 in response to this oscillation of the slider 7, the transparent stabilizing board 5 can follow the oscillation of the disk 1 by the stretch and compression of the board spring 50 to balance out the air pressure between the disk 1 and the transparent stabilizing board 5 with that between the disk 1 and the slider 7.

Thus, it is possible to prevent damage to the disk 1 which may be caused by a collision between the disk 1 and the transparent stabilizing board 5 due to external oscillation.

Note that, the board spring 50 is not just limited to a spring as long as it is elastic. For example, materials such as rubber or foamed resin may be used instead. Here, as the term is used, "spring" may be any elastic body. The spring is preferable because it has a large stroke in response to a load.

[Second Embodiment]

The following will describe another embodiment of the present invention. Note that, constituting elements having the same functions as those described in the First Embodiment are given the same reference numerals and explanations thereof are omitted here.

FIG. 6 is a cross sectional view showing a relevant portion of a recording and reproducing device according to the present embodiment, in which a stabilizing board (second stabilizing board) 60 is added to the structure of FIG. 1. FIG. 7 is a plan view of the stabilizing board 60. Note that, the cross section of FIG. 6 showing a relevant portion of the recording and reproducing device is taken along the central line in the radial direction of the stabilizing board 60 at a second opening 62.

The stabilizing board 60 is larger than the transparent stabilizing board 5, and, for example, in the form of a circle slightly larger than the disk 1, as shown in FIG. 7. Further, the stabilizing board 60 has a first opening 61 for chucking a center hub 2 of the disk 1 to a spindle 3, and the second opening 62 which is used to position an optical pickup 4 with a transparent stabilizing board 5 in the vicinity of the disk 1. Further, the stabilizing board 60 in the recording and reproducing device is fixed at such a position that it is opposite the disk 1 and can create a space of reduced pressure between the disk 1 and the stabilizing board 60 when the disk 1 rotates.

By thus providing the stabilizing board 60 larger than and separately from the slider 7 or the transparent stabilizing board 5 at a position opposite and in the vicinity of the disk 1, air flows out from the outer periphery of the stabilizing board 60 when the disk 1 is rotating, which reduces air pressure between the stabilizing board 60 and the disk 1. Here, the disk 1, by being flexible, is drawn to the stabilizing board 60 and rotates at a constant distance from the stabilizing board 60.

Thus, the addition of the stabilizing board 60 can further stabilize rotation of the disk 1, compared with the case where rotation of the disk 1 is stabilized by providing only the transparent stabilizing board 5 and the slider 7, which are smaller than the stabilizing board 60 and are provided within the domain of the second opening 62 to balance the pressure which is created by the air flowing into the space between the transparent stabilizing board 5 and the disk 1 and between the slider 7 and the disk 1 when the disk 1 rotates. Thus, it is possible to more effectively suppress fluttering of the disk 1 when the disk 1 is rotating, and to stabilize rotation of the disk 1 at a position distanced from the slider 7 and the transparent stabilizing board 5, which are moved, for example, during the focus control.

Thus, in the focus control, because the rotation of the disk 1 is stabilized even at a distant position from the transparent stabilizing board 5 and the slider 7, the disk 1 is less influenced by the pressure fluctuation which may be caused, for example, when the transparent stabilizing board 5 and the slider 7 are moved with the optical pickup 4 to balance the air pressure between the disk 1 and the transparent stabilizing board 5 with that between the disk 1 and the slider 7. As a result, fluttering of the disk 1 is suppressed more effectively. This brings stable and easy focus control or tracking even when the biaxial actuator 14 using the conventional servo technique is used, thus providing the recording and reproducing device which can record and reproduce information more stably and more desirably.

Note that, in order to create a space of reduced pressure between the disk 1 and the stabilizing board 60 to attain stable rotation of the disk 1, the distance between the disk 1 and the stabilizing board 60 is preferably not less than 10 .mu.m and not more than 200 .mu.m.

Further, the optical pickup 4 with the transparent stabilizing board 5 provided below the disk 1 and the slider 7 provided above the disk 1 may be switched in their positions with respect to the disk 1. In the case where the slider 7 is below the disk 1 (on the side of the stabilizing board 60 of the disk 1), the second opening 62 of the stabilizing board 60 makes up an opening which is used to position the slider 7 in the vicinity of the disk 1.

Further, as shown in FIG. 8, the stabilizing board 60 may be defined by an inner wall surface of a cartridge 80 which contains the disk 1.

FIG. 8 is a cross sectional view showing a structure of relevant part of the recording and reproducing device of FIG. 1, when it is operated to record and reproduce information with respect to the disk 1 contained in a disk cartridge 85. Here, the disk cartridge 85 refers to the cartridge 80 containing the disk 1 therein. As shown in FIG. 8, the lower surface of the cartridge 80 (the surface of the cartridge 80 facing the disk 1 on the side of the optical pickup 4) makes up a stabilizing section 80a which is provided as the stabilizing board 60. That is, the lower surface of the cartridge 80 serves as the stabilizing board 60. Note that, the cross section of relevant part of the recording and reproducing device shown in FIG. 8 is taken along the central line in the radial direction of the disk 1 at a second opening 82 as shown in FIG. 9.

The stabilizing section 80a has a first opening section 81 for chucking the center hub 2 of the disk 1 to the spindle 3, and the second opening 82 which is used to position the optical pickup 4 with the transparent stabilizing board 5 in the vicinity of the disk 1. Further, the upper surface of the cartridge 80 (the surface of the cartridge 80 facing the disk 1 on the side of the slider 7) has a third opening 83 which is used to position the slider 7 in the vicinity of the disk 1 at a position opposite the second opening 82.

Further, FIG. 9 is a plan view showing the cartridge 80 as viewed from the side of the optical pickup 4, i.e., from below the cartridge 80. As shown in FIG. 9, the cartridge 80 further includes a slide shutter 84 which can be opened or closed in the directions of arrows, capable of covering the first opening 81 and the second opening 82. The slide shutter 84 is open when the first opening 81 and the second opening 82 are used during rotation of the disk 1, whereas it is closed when the cartridge 80 containing the disk 1 is taken out of the recording reproducing device.

Further, on the upper face of the cartridge 80 is provided a slide shutter (not shown) for covering the third opening 83. This slide shutter is also open when the third opening 83 is used, whereas it is closed when the cartridge 80 containing the disk 1 is taken out of the recording and reproducing device. This is to protect the disk 1 from dusts.

The lower face of the cartridge 80 makes up the stabilizing section 80a which serves as the stabilizing board 60. That is, one of inner wall surfaces of the cartridge 80 makes up the stabilizing board 60. Thus, a space of reduced pressure is created between the disk 1 and the stabilizing section 80a when the disk 1 is rotating. The disk 1, being flexible, is drawn to the stabilizing section 80a and rotates at a constant distance from the stabilizing section 80a. This suppresses fluttering of the disk 1 further effectively when the disk 1 is rotating, and rotation of the disk 1 can be stabilized at a distant position from the slider 7 and the transparent stabilizing board 5.

Thus, in the focus control, because the rotation of the disk 1 is stabilized even at a distant position from the transparent stabilizing board 5 and the slider 7, the disk 1 is less influenced by the pressure fluctuation which may be caused, for example, when the transparent stabilizing board 5 and the slider 7 are moved with the optical pickup 4 to balance the air pressure between the disk 1 and the transparent stabilizing board 5 with that between the disk 1 and the slider 7. As a result, fluttering of the disk 1 is suppressed more effectively, thus providing the recording and reproducing device which can record and reproduce information more stably and more desirably.

Further, since the lower face of the cartridge 80 makes up the stabilizing section 80a to serve as the stabilizing board 60, rotation of the disk 1 can be stabilized without adding a new member as the stabilizing board 60.

Note that, as in the foregoing example, the optical pickup 4 with the transparent stabilizing board 5 provided below the disk 1 and the slider 7 provided above the disk 1 may be switched in their positions with respect to the disk 1. When the slider 7 is below the disk 1 (on the side of he stabilizing board 80a), the second opening 82 of the cartridge 80 becomes an opening which is used to position the slider 7 in the vicinity of the disk 1, and the third opening 83 becomes an opening which is used to position the optical pickup 4 with the transparent stabilizing board 5 in the vicinity of the disk 1.

Referring to FIG. 10, the following will describe a recording and reproducing device in which the stabilizing board 60 is defined by the both inner wall surfaces of a cartridge 90 containing the disk 1.

The recording and reproducing device shown in FIG. 10 has the same structure as that of FIG. 8 except for a disk cartridge 91, which is provided instead of the disk cartridge 85 to contain the disk 1.

As with the cartridge 80, the lower face of the cartridge 90 has the stabilizing section 80a as shown in FIG. 9, as well as the first opening 81, the second opening 82, the third opening 83, and the slide shutter 84. Further, as with the cartridge 80, the upper face of the cartridge 90 has a slide shutter (not shown) covering the third opening 83. This protects the disk 1 from dusts.

Further, the cartridge 90 differs from the cartridge 80 of FIG. 8 in that the width of the cartridge 90 across the surface of the cartridge 90 facing the disk 1 on the side of the slider 7 (hereinafter referred to as upper surface of the cartridge 90) and the surface of the cartridge 90 facing the disk 1 on the side of the optical pickup 4 (hereinafter referred to as lower surface of the cartridge 90), i.e., a distance between the inner wall surfaces of the cartridge 90 centered by the disk 1, is restricted within such a range which enables the cartridge 90 to serve as the stabilizing board 60.

That is, in order for the upper and lower surfaces of the cartridge 90 respectively facing the disk 1 to serve as the stabilizing board 60, the upper and lower surfaces of the cartridge 90 need to be positioned in such a manner that a space of reduced pressure is created above and below the disk 1 between the upper and lower surfaces of the cartridge 90.

Specifically, it is preferable that the distance between the disk 1 and the upper surface of the cartridge 90 and the distance between the disk 1 and the lower surface of the cartridge 90 are each not less than 10 .mu.m and not more than 200 .mu.m.

A distance of not less than 10 .mu.m between the disk 1 and each surface of the cartridge 90 facing the disk 1 prevents a collision between the disk 1 and the cartridge 90, which may be caused by external influence such as oscillation, and thus prevents the disk 1 from being scratched.

Further, a distance of not more than 200 .mu.m between the disk 1 and each surface of the cartridge 90 facing the disk 1 makes the disk 1 less susceptible to external influence such as oscillation. That is, because the space inside the cartridge 90 is restricted, the influence of external oscillation on the state of reduced pressure between the disk 1 and the upper and lower surfaces of the cartridge 90 becomes less. Thus, it is possible to suppress fluttering of the disk 1 in the cartridge 90, which is caused when rotation of the disk 1 in the cartridge 90 becomes instable in response to external force, for example, by oscillation. As a result, rotation of the disk 1 can be stabilized.

The foregoing restriction of the space within the cartridge 90 enables the upper and lower surfaces of the cartridge 90 respectively facing the disk 1 to function as the stabilizing board 60. That is, the state of reduced pressure between the disk 1 and the cartridge 90 is stabilized, and the disk 1 becomes less susceptible to external influence such as oscillation. This prevents fluttering of the disk 1 in the cartridge 90, thus stably rotating the disk 1. Further, the disk 1 is prevented from colliding with the upper or lower surface of the cartridge 90, thus preventing a scratch on a surface of the disk 1.

Thus, the recording and reproducing device provided with the cartridge 90 can stabilize rotation of the disk 1 at a distant position from the slider 7 and the transparent stabilizing board 5, when, for example, the transparent stabilizing board 5 and the slider 7 are moved with the optical pickup 4. As a result, recording and reproducing can be carried out more stably and more desirably.

Further, since the stabilizing board 60 is defined by the upper and lower surfaces of the cartridge 90, rotation of the disk 1 can be stabilized more effectively without introducing a new member as the second stabilizing board 60.

Further, the stable rotation of the disk 1 allows the use of a thinner disk for the disk 1. Here, in order for the disk 1 to be effectively flexible, the thickness of the disk 1 is preferably not less than 30 .mu.m and not more than 400 .mu.m. Since the disk 1 is flexible, a thickness less than 30 .mu.m makes it difficult to maintain sufficient strength for the disk 1 to withstand rotation. On the other hand, a thickness of the disk 1 exceeding 400 .mu.m makes the disk 1 less flexible, which prevents the disk 1 from being drawn to the stabilizing section 80a even with the presence of a space of reduced pressure between the disk 1 and the stabilizing section 80a. As a result, the effect of suppressing fluttering of the disk 1 becomes less effective.

According to the foregoing First and Second Embodiments, a recording and reproducing device of the present invention includes a light source, focusing means for converging and projecting a laser beam which was emitted from the light source on a disk, and rotation driving means for rotating the disk, the recording and reproducing device comprising: a first stabilizing board, provided between the disk and the focusing means, which is moved with the focusing means, for example, such as an objective lens; and a slider which is disposed to face the first stabilizing board via the disk and supported to oscillate, a surface of the slider facing the disk being flat.

According to this arrangement, when recording or reproducing information with respect to the disk, i.e., when rotating the disk, the rotation of the disk causes air to flow into the space between the disk and the slider, which increases the air pressure between the disk and the slider because the surface of the slider facing the disk is flat. That is, pressure is created between the disk and the slider. In the same manner, the rotation of the disk causes air to flow into the space between the disk and the first stabilizing board, which creates pressure between the disk and the first stabilizing board. Further, the slider is supported to oscillate. This enables the slider to move to such a position that the air pressure between the disk and the first stabilizing board and that between the slider and the disk balance out.

Balancing the pressure between the slider and the disk with that between the first stabilizing board and the disk in this manner enables the disk to rotate at a constant distance from the slider and the first stabilizing board. As a result, fluttering of the rotating disk can be suppressed, thus stabilizing rotation of the disk.

If it is assumed here that the first stabilizing board is not provided and the disk and the focusing means are disposed face to face with nothing in between, the focusing means, when it is driven on the optical pickup for example, makes up the surface of the optical pickup facing the disk. Therefore, this surface of the optical pickup has re