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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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