Fast MTF and Aberrations Analysis of MWIR and LWIR Imaging Systems using Quadri Wave Interferometry

We present the application of Quadri-Wave Lateral Shearing Interferometry (QWLSI), a wave front sensing technique, to characterize optical beams at infrared wavelengths from 2 to 16 mu m with a single instrument. We apply this technique to qualify optical systems dedicated to MWIR (lambda within 3 and 5 mu m) and LWIR (lambda within 8 and 14 mu m) wavelength ranges. The QWLSI offers the crucial advantage that it yields an analyzed wave front without the use of a reference arm and consequent time consuming alignment. The qualification of an optical system with QWLSI gives a complete diagnostic, from the aberration cartography to the PSF and MTF curves for every direction in one single measurement. In this paper, we first present the QWLSI technology and its main features, we also detail an experimental comparison between our MTF measurement and the results given by a classical MTF test bench. We finally show the experimental analysis of an infrared lens at two different wavelengths, one in the MWIR range (lambda = 3.39 mu m) and the other in the LWIR range (lambda = 10.6 mu m).