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:
Nov. 22, 1988
Filed:
Dec. 18, 1986
Werner E Haas, Webster, NY (US);
John R Andrews, Fairport, NY (US);
Xerox Corporation, Stamford, CT (US);
Abstract
A voltage sensing device having a liquid crystal cell electrically connected to a charged surface and having a light transmissivity varying with applied voltage. A light source is directed through the liquid crystal cell, and a light detector, detects changes in the intensity of light directed through the cell and providing an output indicative of variations in voltage on the charged surface. Polarizers, which polarize light from the light source directed through the liquid crystal cell, and analyze light exiting the cell, convert electro-optically induced phase changes into intensity changes. A saturation level biasing voltage is periodically applied to the liquid crystal cell to set the cell to a reference level, clearing the cell of transient polarization effects. A second reference liquid crystal cell may be provided, electrically coupled to a reference voltage. Signals from the charged surface derived by the liquid crystal cell connected to the surface are compared with reference signals derived by the reference cell prior to output of the signal to eliminate a time-based drift component from the output.