Effect of Wavefront Properties on Numerical Aperture of Fresnel Hologram in Incoherent Holographic Microscopy

Fresnel incoherent correlation holographic (FINCH) microscopy is a recently developed new technique, which employs a spatial light modulator (SLM) as the beam splitter. Light originating from the same object point is split into two beams by the wavefront-division phase mask displayed on SLM, and a Fresnel-zone plate-like hologram is formed by the interference of the two beams. The numerical aperture NA_H of the recorded Fresnel hologram is introduced as a comprehensive parameter for evaluating the imaging characteristics in the FINCH scheme. The effect of wavefront properties on NA_H of the hologram is investigated theoretically in the sense of optimizing imaging resolution. The variation trends of NA_H are described and an optimal NA_H is achieved by implementing an appropriate phase mask for a given recording distance between SLM and CCD; thus optimized imaging resolution and signal-to-noise ratio are demonstrated experimentally.