Assessment of weak light condition in parallel four-step phase-shifting digital holography.

Minimum optical energy required for four-step parallel phase-shifting digital holography (PPSDH) is evaluated numerically by using photon-counting analysis. PPSDH enables us to develop instantaneous three-dimensional (3D) measurement by single-shot measurement. In fast measurement of dynamic 3D events, detected optical power at an image sensor will be decreased. For biomedical sensing, maximum light intensity exists for preventing the damage of the tissue. In the numerical evaluation, a photon-counting approach is used for the evaluation of minimum detected energy by comparing the reconstructed images. Numerical results indicate that hundreds of photons at each pixel in the image sensor are enough for the reconstruction and total detected energy in a multiplexed hologram is about 1 pJ.