Fourier phase contrast multimodal optical microscopy for real time display of phase and fluorescence at the same time

Microorganisms, cells and thin tissue sections are transparent and not visible to view in ordinary microscope. Techniques such as phase contrast and Normarski/Differential interference contrast microscopy transform the phase variation information into intensity distribution to reveal the details of internal structures. Similarly fluorescence microscope uses intrinsic or extrinsic chromophores to reveal specific and hidden details. Advances achieved in recent years have greatly improved the versatility of microscopes to obtain more insightful information about different physiological functions that occur at cellular level. Understanding the cell response, involving both structural and functional changes within the cell, dictates ability to image cell structure and function at the same time. We report a novel optical Fourier phase contrast multimodal optical microscopy technique for real time display of phase and fluorescence features of biological specimens at the same time. It combines the principles of (a) Fourier phase contrast microscopy which exploits monochromaticity, intensity and phase coherence of the laser beam via optical Fourier transform and photoinduced birefringence of dye doped liquid crystal for phase contrast imaging, and (b) common-path multimodal optical microscopy for co-registered imaging of phase and fluorescence features of biological specimens in real time using a single optical path, single light source, and single camera with no requirement of image registration. Further the instrument also enables co-registered imaging of fluorescence and spatial filtering facilitating simultaneous display of structural and functional information. This comprehensive microscope has the capability of simultaneously providing both structural and functional information in a streamlined simplified design and may find applications in highthroughput screening and automated microscopy.