Direct shape measurement by digital wavefront reconstruction and multi-wavelength contouring

We present a direct holographic multiwavelength contouring technique for shape measurement of microcomponents with large height steps and/or spatially isolated object areas. The measurement is based on the digital recording and reconstruction of wavefronts using a CCD sensor. Absolute phase measurement is ensured by multiwavelength contouring. Consequently the whole measurement procedure delivers a direct and unambiguous approach to the continuous phase without unwrapping. An algorithm is presented to chose a minimum number of different wavelengths to improve the accuracy of the phase measurement. The results are verified by an experimental setup and some practical examples.