Compensation for nonlinear properties in a liquid crystal lens with variable focal length

A liquid crystal lens has a unique feature in that its focal length can continuously be varied between the values for the ordinary ray and the extraordinary ray by varying the applied voltage. However, the focal length begins to increase at the threshold voltage and saturates gradually as the applied voltage increases. In this paper, attempts are made to compensate or linearize the nonlinear properties of the liquid crystal lens. That is, transmission properties of a guest-host cell or properties of the capacitance of a homogeneously aligned liquid crystal cell are used. Then the compensation is made by using their inverse functional signals as a driving voltage since these liquid crystal cells have properties similar to those of the liquid crystal lens. The driving voltage for the compensation can be produced by using a simple system with the liquid crystal cell in an electric circuit. Then the nonlinear properties of the lens can be improved. The temperature dependence of the compensation properties of this system and that of the liquid crystal lens show that the compensation is also effective for the temperature dependence. This is because the output voltage from the driving circuit varies to compensate the temperature dependence of the liquid crystal lens.