Optical: systems and elements – Lens – Including a nonspherical surface
Reexamination Certificate
1999-06-23
2001-01-30
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
Including a nonspherical surface
C359S383000, C359S665000, C369S013010, C369S014000, C369S112040
Reexamination Certificate
active
06181485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to optical focusing devices, and it particularly relates to a high numerical aperture (NA) optical focusing device. More particularly, the present invention relates to an optical focusing device that generates an evanescent optical field for enabling its use in data storage systems such as optical and magneto-optical (MO) disk drives.
2. Description of Related Art
In a MO storage system, a thin film read/write head includes an optical assembly for directing and focusing an optical beam, such as a laser beam, and an electro-magnetic coil that generates a magnetic field for defining the magnetic domains in a spinning data storage medium or disk. The head is secured to a rotary actuator magnet and a voice coil assembly by a suspension and an actuator arm positioned over a surface of the disk. In operation, a lift force is generated by the aerodynamic interaction between the head and the disk. The lift force is opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the disk.
A significant concern with the design of the MO head is to increase the recording or areal density of the disk. One attempt to achieve objective has been to reduce the spot size of the light beam on the disk. The diameter of the spot size is inversely proportional to the numerical aperture (NA) of an objective lens forming part of the optical assembly, and proportional to the wavelength of the optical beam. As a result, the objective lens is selected to have a large NA. However, the NA in objective lenses cannot be greater than 1 if the focusing spot is located in free space, thus limiting the spot size.
Another attempt to reduce the spot size and to increase the recording areal density has been to use solid immersion lenses (SILs) with near field recording, as exemplified by the following references:
U.S. Pat. No. 5,125,750, titled “Optical Recording System Employing a Solid Immersion Lens”.
U.S. Pat. No. 5,497,359, titled “Optical Disk Data Storage System With Radiation-Transparent Air-Bearing Slider”.
Yet another attempt at improving the recording head performance proposes the use of near-field optics, as illustrated by the following reference:
U.S. Pat. No. 5,689,480, titled “Magneto-Optic Recording System Employing Near Field Optics”.
U.S. Pat. No. 5,881,042, titled “Flying Head with Solid Immersion Lens Partially Mounted on a Slider”.
A catadioptric SIL system is described in the following references, and employs the SIL concept as part of the near-field optics:
Lee, C. W., et al., “Feasibility Study on Near Field Optical Memory Using A Catadioptric Optical System”, Optical Data Storage, Technical Digest Series, Volume 8, pages 137-139, May 10-13, 1998; and
“Parallel Processing”, 42 Optics and Photonics News, pages 42-45, June 1998.
While this catadioptric SIL system can present certain advantages over conventional SILs, it does not appear to capture the entire incident, collimated beam. This represents a waste of valuable energy that could otherwise increase the evanescent optical field.
Other concerns related to the manufacture of MO heads are the extreme difficulty and high costs associated with the mass production of these heads, particularly where optical and electro-magnetic components are assembled to a slider body, and aligned for optimal performance. In addition, the sphericity of the SIL limits the choice of optical material with high index of refraction and could increase the manufacturing cost of the SIL.
SUMMARY OF THE INVENTION
One aspect of the present invention is to satisfy the long felt, and still unsatisfied need for a near-field optical or MO data storage system that uses an optical focusing device for focusing an incident optical beam to a small size focal spot. The focusing device broadens the selectivity of the SIL optical material and can be mass produced at wafer level.
According to one embodiment of the present invention, the optical focusing device includes an objective lens, an optically transparent base plate, and an optically transparent adapter. The adapter is secured to, and disposed intermediate the objective lens and the base plate, and includes an opening that faces the base plate. A fluid fills the adapter opening to form a fluid cell when the adapter is secured to the base plate. The fluid has an index of refraction that substantially matches the index of refraction of the base plate.
REFERENCES:
patent: 4634234 (1987-01-01), Baumann
patent: 5004307 (1991-04-01), Kino et al.
patent: 5039192 (1991-08-01), Basu
patent: 5042928 (1991-08-01), Richards
patent: 5125750 (1992-06-01), Corle et al.
patent: 5497359 (1996-03-01), Mamin et al.
patent: 5689480 (1997-11-01), Kino
patent: 5805346 (1998-09-01), Tonimatsu
patent: 5881042 (1999-03-01), Kinght
patent: 6104687 (2000-08-01), Lee et al.
patent: 758753 A2-A3 (1996-02-01), None
Lee, C.W., et al., “Feasibility Study on Near Field Optical Memory Using A Catadioptric Optical System”, Optical Data Storage, Technical Digest Series, vol. 8, pp. 137-139, May 10-13, 1998.
Mansipur, M. et al. “Parallel Processing”, Scanning Optical Microscopy, Part 2, 42 Optics and Photonics News, pp. 42-45, Jun. 1998.
Epps Georgia
Kassatly Samuel A.
Read-Rite Corporation
Spector David N.
LandOfFree
High numerical aperture optical focusing device for use in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High numerical aperture optical focusing device for use in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High numerical aperture optical focusing device for use in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2472859