Adaptive double refraction interference microscopy for label-free imaging of living cells

The benefits of label-free microscope observations are undeniable. However, the majority of current microbiology observations are made by using either labelled (altered) samples or equipment that many research laboratories can't afford. In this work, a new method of visualization of unlabeled low-contrast isotropic (phase) objects is developed by combining electrically variable double refraction with polarization interference. Small optical path differences, generated by phase objects, are transformed into intensity modulation when the object is in focus and without using additional optical components. The proposed technique is studied experimentally and compared with other microscopy techniques (bright field, phase contrast, etc.). The demonstrated method will enable large-scale deployment of label-free observation tools and will promote scientific education and research in many fields of biomedicine and beyond.