Dynamic quantitative phase imaging using calcite crystal-based temporally stable interferometer

This paper describes the development of a common path off-axis quantitative phase microscope (QPM), enabling high-speed quantitative measurements of sub-cellular dynamics in a live cell. The proposed 4f optical system consists of a polarizer, lenses, calcite crystal, pinhole and analyser, attached to the output port of an optical microscope converting it into a temporally stable QPM. The temporal phase stability of this optical configuration is measured to be equal to ∼20 mrad without a vibration isolation table. The utility of the microscope is demonstrated by conducting experiments on a polystyrene sphere (dia. 12 μm) and human red blood cells (RBCs). Furthermore, the developed system is implemented to study temporal membrane fluctuation in human RBCs over ∼30s and mouse embryonic fibroblast cell dynamics over 2 hours. Therefore, the system offers an energy-efficient and simple solution for generating object and reference beams for common-path QPM, making it an attractive alternative to existing approaches.