Inventors:
Mao Wang - Sunnyvale CA
John C. Tsai - Saratoga CA
Assignee:
Excel Precision Corp. - Santa Clara CA
International Classification:
G01C 308
Abstract:
A measurement apparatus (10, 110) and methods to perform positional types of measurement with normalization respective to either or both of light beam (16, 116) intensity and measurement target (12, 112) reflectivity. A light source, such as a laser diode (14, 114), produces a light beam (16, 116) which is directed at the measurement target (12, 112). One or more beamsplitters (28, 120, 124) in the path of the light beam (16, 116) direct sample portions into one or more photodetectors (32, 36, 122, 128) to obtain either or both of illumination and reflectivity sample values. A portion of the light beam (16, 116) which is reflected by the measurement target (12, 112) is passed through and restricted by an aperture (26, 132) and then detected by a position sensitive detector (38, 134) to obtain a position value. The position value may then be normalized based on either or both of the illumination and reflectivity sample values.