Revisiting the sample transmittance and camera bit-depth effects on quantitative phase imaging in off-axis digital holographic microscopy

The performance of single-shot off-axis digital holographic microscopy (DHM) is determined by the optimum utilization of the space-bandwidth product and by the contrast of the recorded digital hologram. While the former can be easily achieved through an afocal-telecentric DHM, the finding in nature of samples with non-homogeneous transmittance leads to the recording of digital holograms with contrast ranging from zero to unity. In this work, the effect of the sample transmittance and the bit depth of the digital camera on the performance of quantitative phase imaging in DHM is studied. A theoretical model that links the contrast of the recorded interference fringes, in a transmission-mode DHM, to the bit depth of the digital camera is derived. The model is implemented in an open-source visual script for easy consultation and predicts that, when recorded with a 16-bit-depth camera, digital holograms of samples that have regions with transmittance below 1% can be successfully processed to render reliable phase information. The theoretical and computer-modeled results are validated with experimental results from a complex sample of the mouth of a honeybee and from endothelial cells slide.