Exploring Textures of a Nematic Liquid Crystal for Fourier Phase Contrast Microscopy

Phase contrast microscope is used in teaching and research labs to view transparent specimens such as live cell cultures. It enables to study dynamic biological processes. In the past we have developed Fourier phase contrast microscopy technique using photoinduced birefringence in liquid crystals that constitute a fascinating class of matter characterized by the counterintuitive combination of fluidity and long-range order. A low power laser is passed through a commercial inverted microscope to facilitate the Fourier plane at the output of the video port. When the liquid crystal cell is placed at the Fourier plane, low spatial frequencies at the center of the Fourier spectrum are intense to transform the liquid crystal molecules into isotropic phase whereas high spatial frequencies are not intense enough and remain in the anisotropic phase. This results π/2 phase difference between high and low spatial frequencies, a basic requirement for phase contrast imaging. Liquid crystal materials are known for their exceptionally successful applications in displays, smart windows, and biosensing applications. Here we exploit different textures of a nematic liquid crystal 5CB: planar, perpendicular, hybrid and twisted, and investigate their abilities to improve the contrast of phase images.