Fabrication and characterization of aspherical lens manipulated by electrostatic field

An aspherical lens is fabricated from an ultraviolet (UV) curable polymer and is characterized by measuring its focal spot. Electrostatic force is employed to manipulate the shape of the liquid polymer lens. Experiment results show that a liquid lens in a strong electrostatic field can be distorted from initial spherical shape to parabolic to even near cone shape. With in situ measurement of the surface profile and focal spot, an aspherical liquid lens with good performance can be cured to a solid aspherical lens by UV light. A probe scanning microscope is employed to accurately measure the focal spot of the aspherical lens, and the modulation transfer function (MTF) of the aspherical lens is calculated to characterize it. A focal spot of 1.825 microm diameter, an MTF of 800 line pairs/mm cutoff spatial frequency, and a Strehl ratio of 0.742 are achieved. These demonstrate the feasibility of fabricating an aspherical lens with small aberrations by using this method.