Fresnel lens is a kind of lenses, which include dark and bright rings. By adding electrically variable focal length feature to Fresnel lens, a new kind of lens has been introduced. The methyl red dye was doped to nematic liquid crystal with 1% w/w. By illumination of cell with 532 nm laser using a Fresnel lens shaped mask and according to guest host effect, the IR spectroscopy results show that the dye molecules near the cell surface make a hydrogen bond with PVA layer on cell, which make them remains in contact with surface on illuminated parts. Therefore, according to guest-host effect, this kind of dye can make new specifications on liquid crystal cell so, pattern can be print on the surface of cell. This new configuration lead to change the reorientation of LC molecules in the ring shape illuminated parts of cell and the According to experiments, the focal length of developed lens can change from 29 cm to 44 cm.
Keywords: Liquid Crystal, Diffraction, Lens, Fresnel, Azo Dye