3D Imaging with Double-Helix Point Spread Function and Dynamic Aberration Correction Using a Deformable Mirror

Abstract

Imaging-based measurements through fluctuating phase boundaries such as free water surfaces or droplets have usually a higher uncertainty due to the changing refraction of light at the boundary. In this paper, a novel measurement system is presented for both 3D imaging with only one camera and aberration correction of light propagation through one boundary. 3D imaging is achieved by introducing a Double-Helix Point Spread Function (DH-PSF). The dynamically introduced aberrations of the phase boundary are measured with a Fresnel Guide Star (FGS) and are corrected with a deformable mirror in a closed-loop system with low latency. The measurement system and the adaptive optics image correction were characterized by means of a linear actuator and a demonstration measurement through an oscillating droplet. For the latter, the uncertainty of a reference flow could be lowered by 58 % using adaptive optics. The technique has the potential to measure complex three-dimensional flows that are optically difficult to access without modification of the experimental setup. Possible applications are optimizations of fuel cells for reducing the consumption of fossil energy.