Digital holography wavefront sensing with a supersonic wind tunnel

The Air Force Research Laboratory (AFRL) Directed Energy Directorate is completing a supersonic wind tunnel to characterize aero-optics effects in high speed flow fields. Optical characterization is accomplished by transmitting a beam of light transverse to the direction of air flow via access windows, thereby illuminating the flow region, a select volume of which is recorded by a suite of sensors. Quantitative measurements of the flow are made using two wave-front sensors (WFS), a Shack-Hartmann (SH) WFS and a digital holography (DH) WFS. Qualitative measurements are made using a traditional Schlieren imaging system. Parenthetically, in addition to characterization of aero-optics effects, we expect to be able to numerically propagate to different planes in the supersonic flow field to characterize boundary layer effects. This paper reviews our wind tunnel system's requirements and, in particular, the design of the DH WFS.