Synthetic image generator for defocusing and astigmatic PIV/PTV

This technical note introduces a synthetic image generator (SIG), referred to as MicroSIG, to be used for particle image/tracking velocimetry (PIV/PTV) analysis involving defocusing or astigmatic particle images. Target applications are experimental setups with volume illumination and small depth of field, in which the defocusing of particles plays a major role. This includes for instance PIV experiments or 3D PTV methods using defocusing or astigmatism to determine the out-of-plane particle position. The software uses an approximated model of spherical lens and conventional ray tracing to create realistic defocused/astigmatic particle images within a reasonable computational time. MicroSIG can be used to compare or optimize different PIV/PTV algorithms using arbitrary flows and different conditions including, non-monodispersed particles, non-uniform illumination, astigmatic optics, non-spherical particles (spheroids). A version of the software, available in Matlab and Python, can be found in the supplementary material and at this link: https://gitlab.com/defocustracking.