The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 11, 2001
Filed:
Apr. 08, 1999
Walter Daschner, Half Moon Bay, CA (US);
Barry Block, Los Altos, CA (US);
Arnold Thornton, San Jose, CA (US);
Bernard Kress, Neubourg, FR;
Aerial Imaging Corporation, Milpitas, CA (US);
Abstract
A magneto optic or optical disk drive comprises a laser source for providing laser beam, and a lens or compound lens for focussing the laser onto a currently inserted recording disk with specific overcoat thickness. In one embodiment, the lens is a compound lens that can focus aberration-free spots on different types of disk media having recording layers located under overcoats of different thicknesses. When a specific disk is inserted, only one spot in focussed onto the current recording layer. Furthermore, if the disk spins rapidly, it can wobble. The lens or compound lens comprises different regions where the focal length may vary slightly and continuously or discretely. Because of this, as the disk wobbles, the lens can nonetheless continue to focus laser light onto a small spot on the recording media, providing increased depth of focus in the vicinity of the currently inserted recording media. Furthermore, the increased depth of focus will also remedy problems related to the change in focal length of the lens with changes in wavelength of the laser source. Because some of these changes in wavelength occur abruptly, this is also a case in which the limited performance of the auto-focus tracking system would be overly burdened.