Calibration of a micro-topographic measurement system based on Talbot fringe projection
نویسنده
چکیده
A calibration method for micro-topographic measuring of a surface is described. Based on fringe projection using a stereo-microscope, an unmagnified Talbot self-image of a Ronchi ruling is imaged on the surface target through one of the microscope oculars. It is well-known that if a linear fringe pattern is projected on a surface object, the fringes are deformed according to its topography. The deformed fringe pattern is observed through the other microscope ocular on which a CCD camera is mounted in order to digitize the deformed fringe pattern. Digital fringe processing based on the Fourier method is carried out in order to have wrapped and unwrapped phase images for mapping to the measured profile. As calibration object, a flat metallic plate mounted on a micrometric translational stage, is used. The certified micrometric calliper and staged with 1 micron resolution is used as traceable measuring instrument. With a Zeiss Stemi 2000-C and achromatic 1.25X, accuracies of 1% laterally and 1-2% axially relative to the volume of the work space are achieved.
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