Quality assessment of autofocusing criteria on noisy holograms in off-axis digital holography

Digital holography (DH) is becoming more and more popular as a 3D visualization and measurement technique in various fields. Particularly in the field of fluid mechanics where it is widely used in the detection and tracking of tracer particles, this technic is commonly called DHPIV (Digital Holographic Particle Image Velocimetry). The characterization is achieved numerically where the reconstructing distance is an important parameter which has to be determined accurately. In context of DH, several autofocusing criteria have been proposed to obtain the best reconstruction distance. Here, we are interested in the evaluation of various autofocus operators belonging to different families: edge detection, sparsity measure, statistical texture image feature, spectral decomposition (Fourier, cosine, Welsh- Hadamard) and others on real holograms and in the presence of increased noise, i.e., by simulating on a real hologram the various noises involved in the recording process by the CCD sensors. The analysis and comparison results of these criteria are performed on ideal holograms (without the addition of noise) and on noisy holograms by considering the off-axis configuration. The experimental results show that some criteria are very challenging in presence of noise to determine the location of these particles. Finally, the most robust and reliable criterion for the best autofocusing criteria is proposed.