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:
May. 21, 1991
Filed:
May. 16, 1989
Harry J Mamin, Palo Alto, CA (US);
Daniel Rugar, Palo Alto, CA (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A highly sensitive apparatus for sensing the position of a movable member comprises an optical directional coupler providing four external ports. Light from a short coherence length diode laser is injected into the first port. The coupler serves as a beam splitter to direct one portion of the injected light to the member via the second port and a single mode optical fiber. Part of this one portion is reflected concurrently from the member and from the adjacent polished coating at the end face of said fiber back into said fiber and optically coupled via the third port to a photodetector to provide a signal whose amplitude is indicative of the position of the member, based upon the relative phase of said concurrent reflections. The other portion of the injected light is optically coupled to and via the fourth port to another photodetector for providing, as a reference, a signal proportional to the intensity of the injected light. These two signals are supplied to a subtractive circuit for providing an output in which power fluctuations of the laser are minimized.