Adaptive information retrieval in automated fringe based full-field optical metrology

Abstract

Optical metrology provides very attractive means for noninvasive and highly accurate evaluation of different features of various objects. Information is acquired and processed over whole sensor area using so-called full-field methods. In coherent light techniques the measurand is stored in the complex amplitude of the optical field. Due to physical limitations the recorded intensity distribution is generally captured in a form of a fringe pattern with information encoded in phase and/or amplitude modulation distributions, hence the importance of their demodulation techniques. In this contribution several recently developed adaptive techniques for information retrieval in automated fringe based full-field optical metrology will be presented. Adaptivity constitutes advantage enabling robustness and versatility – presented methods adapt their performance according to characteristics of analyzed fringe patterns providing efficient means to successfully retrieve information obtained by various optical techniques, i.e., interferometry (classical two-beam, multi-beam, timeaveraged, speckle, grating), moire and structured illumination. Developed fringe pattern demodulation techniques are based on the concept of single-frame processing using advanced image pre-filtering techniques, i.e., empirical mode decomposition and variational image decomposition. The phase/amplitude demodulation is conducted utilizing the 2D Hilbert transform and complex analytic signal paradigm. Applications of these specially tailored methods include but are not limited to: coherent phase microscopy for stationary and live biological objects (e.g., prostate cancer cells, red blood cells, semen cells etc.), vibration amplitude studies of technical microobjects, wavefront sensing, optical testing etc.