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:
Apr. 11, 1995
Filed:
Jan. 25, 1993
Gordon P Sharp, Newton, MA (US);
Phillip G Ahern, Arlington, MA (US);
Phoenix Controls Corporation, Newton, MA (US);
Abstract
A system is provided for detecting presence and/or motion of a person or other movable entity within a selected space. Detection is accomplished by detecting reflected light or other radiation from the space, presence being signified when detected radiation differs from an established background, either up or down, by an amount exceeding a predetermined threshold. Blending of the entity with the background is avoided by viewing the entity at at least two different angles with different background, for example by use of two spaced detectors, and variations in background are automatically compensated for when a presence indication persists for a selected period of time after the last motion indication is received. The background is updated to the current level when this occurs. With light radiation, the light sources are structured to irradiate substantially the entire space and saturation of a detector by ambient radiation is avoided by providing a bandpass filter which passes only radiation in a narrow overlap wavelength band for the radiation sources and detectors.