Phase contrast imaging using photothermally induced phase transitions in liquid crystals

Phase contrast imaging is performed for live biological species using photothermal induced birefringence in dye doped liquid crystals. Using typical 4-f configuration, when liquid crystal cell is at back focal plane of Fourier lens, low spatial frequencies at center of Fourier spectrum are intense enough to induce local liquid crystal molecules into isotropic phase, whereas high spatial frequencies on the edges are not intense enough and remain in anisotropic phase. This results in pi/2 phase difference between high and low spatial frequencies. This simple, inexpensive, all-optical, user-friendly, self-adaptive phase contrast imaging technique using low-power laser offers several distinct advantages. (c) 2006 American Institute of Physics.