Optimized coherence parameters for high-resolution holographic microscopy

A holographic in-line microscope setup with a glass sample carrier commonly uses a coherent laser light source, with the disadvantage of an incomplete suppression of disturbing interferences and coherence induced noise. We use temporally partially coherent and spatially partially coherent illumination in the micrometer range of 5 to 100 µm generated by spectrally and spatially filtered light emitting diodes (LEDs) and tungsten filament lamps. It is shown how errors in reconstructed holograms are decreased by a factor of more than two and the spatial resolution reaches the limit as determined by the numerical aperture. A straightforward model is developed to investigate the effects of partial coherence. The optimization of the coherence parameters improves the imaging quality up to the limit of a conventional microscope.