Tilted illumination in-line holographic velocimetry: Improvements in the axial spatial resolution

Abstract Two are the main limitations of in-line holography: the twin image problem and the poor spatial resolution in the optical axis direction. The twin image problem can be solved with the introduction of an imaging lens and a knife-edge aperture located at its focal plane. In this work, a theoretical analysis of the axial resolution with and without aperture is provided from the perspective of the Optical Diffraction Tomography. Theoretical analysis and controlled experiments with the different recording options, demonstrate that a small tilt of the illumination beam, together with a centered rectangular aperture, is a key parameter as it improves the spatial resolution along the optical axis during the location and tracking of a particle field.