Temporal phase detection of interferograms without frequency carrier

摘要

In our Optical Metrology laboratories, we deal with the problem of demodulating temporal se-quences of interferograms. These sequences of interferograms are obtained by means of opticaltesting of transient events using an Electronic Speckle Pattern Interferometry system (ESPI). It iswell known that using Phase Stepping Interferometry techniques (PSI), one can obtain the mod-ulated interferogram phase with at least three equally temporal phase shifted interferograms. Toobtain these three (or more than three) phase shifted interferograms with a conventional ESPI array,it is necessary to have a static object under test. On the other hand, if the object under test is notstatic, we can make the analysis using dual-pulse subtraction ESPI, introducing a spatial frequencycarrier. However, in our case, we will use a conventional ESPI technique, with a continuous laserand without a frequency carrier. Thus, as we pretend to analyze transient deformations or eventswithout frequency carrier, we can not use the demodulation methods used in dual-pulse subtractionESPI, nor PSI techniques because it results almost impossible to take the least amount of inter-ferograms with the required linear phase shift (or temporal carrier) among them. To accomplishthis, it will be necessary look for alternatives to demodulate temporal sequences of interferogramswithout a frequency carrier and without linear phase-shifting. Here, we present the groundworkaimed at demodulating sequences of interferograms without a frequency carrier, where traditionalPSI techniques are unable to detect the phase correctly.