Vector Differential Interference Contrast Microscopy Based on a 3-in-1 Phase Mask through a Dynamic Diffractive Optical Element

Abstract

Differential interference contrast (DIC) microscopy is highly desirable in label-free imaging for transparent biological samples. It avoids potential photobleaching and phototoxicity from the contrast agents, such as staining and fluorescence. Commercial DIC microscopes typically use multiple optical elements to construct a phase contrast device and require a further phase shift unit to render quantitative phase imaging. Moreover, conventional DIC microscopes perform the differential operation exclusively along a single direction, constraining their use to differential phase visualization rather than providing the actual phase information for quantitative phase imaging (QPI) applications. Here, a supercompact quantitative DIC microscopy method with a vector differential operation is developed. The featured functions of the vector DIC, namely, vector differential operation, sample imaging, and phase shifting, are integrated into a single diffractive optical element (DOE) device. The DIC microscopy was miniaturized via the off-the-shelf DOE device, converting customary designing paradigm from piling up individual optical elements to the spatial manipulation of the phase, forming the 3-in-1 phase mask. The tube lens, Wollaston/Normasiki prism, and phase shift unit are replaced by a single dynamic 3-in-1 phase mask. Apart from the illumination, the operating element is merely the off-the-shelf DOE device implementing the 3-in-1 phase mask, rendering the vector DIC as an add-on module for the commercial light microscope. The phase maps in orthogonal differential directions are retrieved simultaneously from multiple heterodyne carriers to achieve quantitative phase imaging from the complete phase gradient.