DUAL-HOLOGRAM SHEARING INTERFEROMETRY WITH REGULATED SENSITIVITY

A novel optical diagnostic technique, namely, dual-hologram shearing i nterferometry with regulated sensitivity, is proposed for visualizatio n and measuring of the density gradients of compressible flows in wind tunnels. It is superior to conventional shearing interferometry in bo th accuracy and sensitivity. The method is especially useful for stron g turbulent or unsteady regions of the flows, including shock flows. T he interferometer has proved to be insensitive to mechanical vibration s and has allowed us to record holograms during the noisy wind-tunnel run. The proposed approach is demonstrated by application to a superso nic flow over spherically blunted and sharp nose-cone-cylinder models. We believe that the technique will become an effective tool for recei ving optical data in many flow facilities. (C) 1998 Optical Society of America.