Liquid crystal Fresnel zone lens for dynamic focusing in OCT

An approach to realize dynamic focusing in Optical Coherence Tomography (OCT) is proposed by using liquid crystal Fresnel zone lens. Fresnel zone lens suitable for dynamic focusing in OCT is designed based on optical characteristics of Twisted Nematic Liquid Crystal Spatial light Modulator (TN-LCSLM). Experiments on dynamic focusing control of the TN-LCSLM based on Fresnel zone lens are carried out. Measured focal lengths are in good agreement with the designed ones. Discussion on associated problems with the TN-LCSLM based on Fresnel zone lens for dynamic focusing is carried out as well.