Grating-based common-path quantitative phase microscopy in low photon budget regime

Abstract

Quantitative phase microscopy (QPM) is making waves in live cell imaging owing to label-free time-lapse investigation capabilities. Common-path straightforward configurations are advantageous because of their robustness and stability. Diffraction grating based quantitative phase microscope is a good example of such systems. Grating is employed to decouple conjugate object beams, and their total shear interference is recorded by the camera as a self-referenced hologram (object replica interferes with the object-free background replica; optical path difference between +1 and -1 orders is 0). This allows for the possibility of altering the temporal coherence and suppressing coherent noise (speckle) and artifacts. Generally, in QPM, laser light is used to generate a hologram with encoded sample phase information, and live cells can be impaired by elongated interactions with radiation. To limit the possible photo-damage and photostimulation and examine live unimpaired cells in their natural photo-stress-free environment, a low dose of radiation is deployed. In such a low photon budget regime, the signal-to-noise ratio of the recorded hologram can be drastically reduced, which leads to a strong shot-noise presence in demodulated phase maps and deteriorated the quantitative characterization and diagnosis capabilities. In this contribution, we investigate how a low photon budget affects the quantitative examination of phase objects in grating-based common-path QPM. We explore numerical methods to reduce phase noise via additional holograms and phase map filtering.