Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1991-03-08
1992-08-04
Rosenberger, Richard A.
Optics: measuring and testing
By polarized light examination
With light attenuation
250237G, G01B 900
Patent
active
051353091
ABSTRACT:
Several bar patterns are projected in sequence on the object (O) to be measured by time-division multiplexing, and images of the bar patterns are recorded by a camera (K). The phases of each bar pattern, as distorted by the object, are calculated for preselected image points by a computer connected with the camera. For each image point, the calculated phases for one of said bar patterns are compared to the phases calculated for at least one other of said bar patterns, thereby producing a beat frequency which can be used to determine height measurements in the direction of the camera axis (z). In order to increase the range of the height measurements, at least two beat frequencies of quite different effective wavelengths are generated and evaluated. Different systems are disclosed for generating the different beat frequencies. In one embodiment, the bar patterns are projected by three different projectors (P.sub.1, P.sub.2, P.sub.3) which are inclined at different angles relative to each other (.alpha..sub.1, .alpha..sub.2). In a second embodiment, only two projectors are used, but each projector has two gratings, the respective periods of which differ from each other only slightly.
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"Interferometric Phase Measurement Using Spatial Synchronous Detection" by K. H. Womack, Optical Engineering, vol. 23, No. 4, Jul./Aug. 1984, pp. 391-395.
Hof Albrecht
Kuchel Michael
Carl-Zeiss-Stiftung
Rosenberger Richard A.
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