Spiral phase mask 3D-imaging with adaptive optical image correction

3-dimensional imaging often requires substantial effort in order to get depth information along the optical z-axis. For micro- and nano-fluidic applications, fluidic mixing processes and environmental interaction on a microscopic scale are of particular importance for pharmaceutical applications and often demand for 3D information. For the observation of turbulent mixing in 3 dimensions a scan-free wide-field approach along the optical axis is required. Here we present a 3D spiral phase mask imaging technique based on fluorescent tracer particles. A double-helix point spread function (DH-PSF) is generated by a spatial light modulator for light emerging from the observed focal plane. Each particle appears as a double-image on the camera. Within the orientation of the double-image, depth information along the optical axis is encoded. By using a deformable mirror, the technique is combined with wide-field aberration correction. Image distortions are iteratively compensated with a deformable mirror by applying different orders of Zernike polynomials. The measurement uncertainty resulting from aberrations can be significantly reduced, thus allowing reliable 3D flow field measurements.