Digitally Enhanced, Polarization-Based Microscopy: Reality and Dreams

Abstract Polarized light microscopy is used to identify and image optically anisotropic regions of the specimen; to determine their optical character; and to explore the arrangement of the molecules, fine structure, or atomic lattices that are responsible for the anisotropy. These studies can be carried out non-destructively in real time, and reveal events or structures that lie far below the resolution limit of the light microscope, or indeed at times even the electron microscope. In biology, to study the dynamically changing, minute and weakly anisotropic domains within living cells, the polarizing microscope must be able to detect and measure birefringence retardances to a fraction of a nm, record the image with high microscopic resolution at nearvideo rate, and do so while the cell remains active. Over the years, the extinction property and imaging capability of the basic polarizing microscope have been substantially improved by advances in optical design. More recently, video and CCD imaging and digital electronic processing have further enhanced the quality of the polarizing microscope image and our ability to rapidly detect and measure weak anisotropy.