Infrared Interferometry with a CO(2) Laser Source and Liquid Crystal Detection.

A Mach-Zehnder interferometer illuminated by a CO(2) laser at wavelengths selectable between 9.1 micro and 11.3 micro is described. With a field of view 22 mm in diameter two-dimensional interferograms are recorded. The method uses liquid crystals for ir-optical image conversion. With the small laser used, an exposure time of 1/40 sec is required, while the steady state resolution limit of the detector is a radiation flux of less than 5 mW/cm(2). The interference pattern of an argon plasma jet is shown.