Resolution investigation for dual-spherical-wave optical scanning holographic microscopy: methods and performance

We present an optical scanning holographic microscopy system that addresses the constraints of recording speed and spatial resolution inherent in conventional implementations. The system adopts a dual-spherical-wave illumination scheme enabled by X-Y galvanometric scanning and an afocal, 4f-like relay. By inserting a scan lens and a tube lens between the galvanometer and the microscope objective, this afocal relay preserves the integrity of the Fresnel zone plate encoded in the scanning beam collected by the microscope objective. In this work, we investigate the effect of spherical-wave curvature adjustment on the achieved resolution. Adjusting the spherical-wave curvatures yields a lateral resolution of 312 nm at 532-nm, surpassing the objective's Rayleigh limit of 432 nm. High-contrast imaging of human red blood cells and submicron transparent plastic particles is demonstrated, indicating the potential of the proposed system for high-speed, high-resolution volumetric imaging of biological and micro-/nanoscale specimens.