PHASE-SHIFTING TWYMAN-GREEN INTERFEROMETER UTILIZING NEMATIC AND CHOLESTERIC LIQUID-CRYSTAL CELLS

We show a phase shifting Twyman-Green interferometer utilizing a nematic liquid crystal (NLC) cell and a cholesteric liquid crystal (CLC) cell. NLC cell is used as a phase shifter (PS) and CLC cell is used as an intensity stabilizer. The NLC PS is designed to induce a phase shift of 2 pi rad for He-Ne laser beam (lambda=632.8 nm) with the applied voltage of about 10 V, and a CLC cell which is designed to exhibit its selective reflection peak at 632.8 nm, is used to remove the fluctuation of the intensity of the interferogram. The interferometer system is evaluated by testing a concave mirror surface and the result is discussed.