Double Sided Interferometer, Profiling Measurement Simultaneously Yields Thickness and Form

Thickness measurements have been a basis for metrology since its inception and represent a fundamental technique for calibration of reference artifacts used world-wide, such as gage blocks. However, as materials and their applications have become more exotic, traditional contact based measurement techniques have become less applicable. In addition, quantification of from deviation between two surfaces has become more critical and usually requires a large point density to describe in detail. Optical probing or imaging techniques offer an alternative where there is little or no interaction with the part and can provide fast, accurate data for a large number of materials, but can be limited by reflectivity, acceptance angle seen by sensor and optical depth. A modular optical system adaptable to commercially available white light profilometers and optical coordinate measuring machines (CMMs) has been developed to measure absolute thickness and form.