Quantitative phase imaging based on Fresnel diffraction from a phase plate

The structural complexity and instability of many interference phase microscopy methods are the major obstacles toward high-precision phase measurement. In this vein, improving more efficient configurations as well as proposing new methods are the subjects of growing interest. Here we introduce Fresnel diffraction from a phase step to the realm of quantitative phase imaging. By employing Fresnel diffraction of a divergent (or convergent) beam of light from a plane-parallel phase plate, we provide a viable, simple and compact platform for three-dimensional imaging of micron-sized specimens. The recorded diffraction pattern of the outgoing light from an imaging system in the vicinity of the plate edge can be served as a hologram, which would be analyzed via Fourier transform method to measure the sample phase information. The period of diffraction fringes is adjustable simply by rotating the plate without the reduction of both field of view and fringe contrast. The noticeable fringe contrast as well as high stability of the presented method are affirmatively confirmed through comparison the results with those of conventional Mach-Zehnder based digital holographic method. Quantitative phase measurements on silica microspheres and red blood cells ensures the validity of the method and its ability for monitoring nanometer-scale fluctuations of living cells, particularly in real-time.