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:
Jan. 26, 1993
Filed:
Oct. 31, 1990
James W Howard, Natick, MA (US);
Digital Equipment Corporation, Maynard, MA (US);
Abstract
A method and apparatus for measuring the focus and tracking of a light beam on a medium in an optical data storage system. A split lens, comprising two halves of a lens separated along the optical axis and displaced from each other along the plane of the cut, is used to focus the light reflected or refracted from the medium onto a quad-cell. The quad cell comprises four light sensors arranged in four quadrants about a center point. According to the invention, the amount of light incident on quadrants of the quad-cell indicates the focus and alignment of the light beam on the medium. In accordance with another aspect of the invention, the above apparatus is used to measure the collimation or distribution of intensity of a light beam. Another aspect of the invention is the manufacture of the split lens. A lens is sawed into two halves and the halves are mounted using a housing displaced from each other along the plane of the cut.