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:
Sep. 01, 1998
Filed:
May. 05, 1997
Richard A Riedel, Carmel, IN (US);
UMM Electronics Inc., Indianapolis, IN (US);
Abstract
A method and apparatus for eliminating the effects of varying sample distance on optical measurements. In a first embodiment, a light source and a detector are both positioned in front of a measurement sample. A light source lens assembly focuses the light such that its focal point is behind the measurement sample, while a detector lens assembly focuses the light reflected from the measurement sample such that its focal point is in front of the measurement sample. Any movement of the measurement sample away from its nominal position does not affect the detector output because the effects of the source lens assembly and the detector lens assembly cancel each other. In a second embodiment, a light source and two detectors are positioned on one side off a measurement sample. The first detector is placed at a small angle relative to the sample normal, while the second detector is placed at a relatively large angle relative to the sample normal. A system output, which does not vary if the measurement sample is moved from its nominal position, comprises the weighted summation of the first and second detector outputs and a correction signal. The correction signal comprises a weighted difference of the first and second detector outputs.