Direct shape measurement by digital wavefront reconstruction and multiwavelength contouring

We present a direct holographic multiwavelength contouring technique for sh ape measurement of microcomponents with large height steps and/or spatially isolated object areas. The measurement is based on the digital recording a nd reconstruction of wavefronts using a CCD sensor. Absolute phase measurem ent is ensured by multiwavelength contouring. Consequently the whole measur ement procedure delivers a direct and unambiguous approach to the continuou s phase without unwrapping. An algorithm is presented to chose a minimum nu mber of different wavelengths to improve the accuracy of the phase measurem ent. The results are verified by an experimental setup and some practical e xamples. (C) 2000 Society of Photo-Optical instrumentation Engineers. [S009 1-3286(00)00901-6].