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Proceedings Paper

White-light moire phase-measuring interferometry
Author(s): H. Philip Stahl
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Paper Abstract

Moire is a common technique for contouring large scale features on diffuse surfaces. Typically, this is accomplished by projecting a high-frequency line grating onto the object and viewing its image through another high-frequency line grating. The resultant pattern, produced by aliasing between the two gratings, shows lines of surface contour. The surface height between these contour lines is determined by triangulation between the illumination and observation beams. Although moire is really a geometric ray technique, it is typically referred to as interferometry because its contour patterns resemble interferograms; Moire contouring can be classified as either shadow or projection moire. Shadow moire uses the same grating for both illumination and observation, while projection moire uses separated gratings. Another surface contouring technique is projected fringe. This approach is similar to moire in that it projects a line grating and uses triangulation to measure surface height, however, there is no second grating or aliasing. Rather, the projected pattern is.viewed directly. Although it is not really moire (because it does not use aliasing with a second grating), projected fringe is typically considered a moire technique. This paper has four parts. First, it reviews the theory behind moire contouring. Second, it outlines how to phase modulate a moire 'interferogram'. Third, it discusses practical considerations associated with performing moire contouring such as projection and observation geometry, imaging, and illumination. And fourth, it presents two examples of objects that were contoured using a white-light moire phase-measuring interferometer.

Paper Details

Date Published: 1 January 1991
PDF: 11 pages
Proc. SPIE 1332, Optical Testing and Metrology III: Recent Advances in Industrial Optical Inspection, (1 January 1991); doi: 10.1117/12.51122
Show Author Affiliations
H. Philip Stahl, Stahl Optical Systems and Rose-Hulman Institute of Technolog (United States)

Published in SPIE Proceedings Vol. 1332:
Optical Testing and Metrology III: Recent Advances in Industrial Optical Inspection
Chander Prakash Grover, Editor(s)

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