The implementation of the basic physical principle of Chromatic Confocal Imaging in the field of Phase stepping interferometry opens new opportunities for the development of an innovative surface metrology system specially dedicated for 3D nanotopography with subnanometric z axis resolution and very large measuring ranges : up to one hundred micrometers. The basic property of optical sectionning observed in Confocal imaging is particularly well adapted to Phase stepping Interferometry since it automatically solves the critical and time consuming problem of phase unwrapping. The axial chromatic extension of the chromatic confocal setup offers a very simple and easy way to determine the height of the different elementary surfaces forming the measured object region by very rapidly spectrally sweeping the extended depth of field. The four phases of the classical method of phase stepping can be successively realized by adequate spectral shifts instead of axial displacements of the reference mirror which then stands in a fixed position. Consequently this chromatic confocal phase stepping interferometer has definitely no moving part, the spectral scanning being done by electrooptical means.
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