Spatial coherence profilometry

Pavel Pavlíček; Zhihui Duan; Mitsuo Takeda

doi:10.1117/12.739667

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12 April 2007 Spatial coherence profilometry

Pavel Pavlíček, Zhihui Duan, Mitsuo Takeda

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Proceedings Volume 6609, 15th Czech-Polish-Slovak Conference on Wave and Quantum Aspects of Contemporary Optics; 660916 (2007) https://doi.org/10.1117/12.739667
Event: 15th Czech-Polish-Slovak Conference on Wave and Quantum Aspects of Contemporary Optics, 2006, Liberec, Czech Republic

Abstract

Spatial coherence profilometry is a method for measurement of the geometrical form of objects. In addition to the two lateral coordinates x and y, it measures the longitudinal coordinate z. In this way the complete 3D description of the object's surface is acquired. The main piece of the presented method is a Michelson interferometer illuminated by a monochromatic spatially extended light source. The surface of the object whose geometrical form should be measured is used as one mirror of the Michelson interferometer. By moving of the measured object along the optical axis, the intereference is observable only if the object's surface occurs in the vicinity of the so-called reference plane. The reference plane is given by the position of the object mirror when the Michelson interferometer is balanced. The described effect follows from the form of the spatial coherence function originated by the spatially extended light source. If the intensity at the output of the interferometer is recorded as a function of the position of the measured object, a typical correlogram arises. This correlogram is similar to that known with white-light interferometry. From the maximum of the correlogram, the z coordinate of the object's surface can be determined. Usually a CCD camera is used as the detector at the output of the Michelson interferometer. Then z coordinates of many surface points are parallel measured in the course of one measurement procedure and the 3D description of the object's surface is acquired. The scanning in the lateral direction is not necessary. Thus the described method provides a spatial coherence analogy to white-light interferometry which is based on temporal coherence. Unlike white-light interferometry, the described method does not require a broadband light source, the interferometer is illuminated by a monochromatic light source, usually a laser.

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Pavel Pavlíček, Zhihui Duan, and Mitsuo Takeda "Spatial coherence profilometry", Proc. SPIE 6609, 15th Czech-Polish-Slovak Conference on Wave and Quantum Aspects of Contemporary Optics, 660916 (12 April 2007); https://doi.org/10.1117/12.739667

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