Two-wavelength contouring in difference holographic interferometry and DISCO

Abstract

The first two-wavelength contouring method of difference holographic interferometry (DiffHI) has been developed - as a more sensitive and more user-friendly alternative to the already existing two-refractive-index contouring method of DiffHI. It is built on "compensation-friendly" two-wavelength contouring method and on its tilt compensation version, developed specially for this purpose. Experimental verification is presented for the numerically correct functioning of the two-wavelength contouring method of DiffHI - although it is limited temporarily to mirror objects, only, because of intensity problems of the available laser. However, we hope to get the same results on diffuse objects, too - just in the near future. Two ideas seem to be applicable in the digital holographic version of the two-wavelength contouring method of DiffHI and subsequently in the Distant Shape Control project (DISCO), too. The first one is the application of the extra adjustment-monitoring mirror surface to control alignment accuracies in holographic illuminations and in remote duplication of the optical arrangement. The second one is the tilt compensation process which can correct the previous inaccuracies. The first one, on the other hand, can be used for the control of the accuracy of the calculated reference direction change, as well - at contouring with non-holographic illumination, too.