High speed digital wavefront sensing for aero-optics and flow diagnostics

Abstract

This paper describes digital, photonic, two-dimensional, dynamic-wavefront sensing methods for flow diagnostics. A system described herein employs a 532 nm diode pumped solid state laser to produce quantitative, fully reduced phase maps at virtually real time acquisition rates to evaluate flows in wind tunnel facilities. This is done using instantaneous electronic phase shifting interferometry methods. Because measurements are instantaneous and not compared to a stored reference data point, the instrument is not vulnerable to vibrations and other environmental effects found in test facilities. A flow field can be analyzed quantitatively by measuring its effect on a traversing optical wavefront if the wavefront sensor can respond as fast as the field changes. Conversely, the effect of flow fields on optical imaging gives rise to the field of aero-optics, and the wavefront distortion and correction are of principal interest. Developments in aero-optics, electro-optics and image processing in general have led to more advanced variations and applications of interferometry improving speed, sensitivity, automation, and robustness. Video recording and new methods for performing high-speed interferometric wavefront and flow diagnostics electronically to speed up the process are described.