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:
Aug. 29, 1995
Filed:
Nov. 06, 1992
Timothy S Gardner, Tucson, AZ (US);
Ronald P Stahl, Tucson, AZ (US);
Syed T Shafaat, Langley, WA (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
This invention provides an equal path length lateral shearing interferometer and its implementation in focus detection devices, particularly for optical data storage devices. The interferometer comprises a beamsplitter and two abutting roof prisms. Shifting the placement of a roof prism along an axis orthogonal to the direction of light propagation and to the peak of the roof creates a lateral shear between the two output beams. Rotation a roof prism about this axis produces a tilt between the two output beams. This creates an interference pattern with a rotational orientation which is a function of the focus of the beam impinging on the optical storage medium. A pattern sensor is provided to adjust the focus of the beam in an accurate and dynamic manner.