Liquid crystal adaptive lens: High density electrode configuration

The liquid crystal adaptive lens (LCAL) is an electro-optical device. The focal length of the LCAL can be varied by changing voltages applied to the device. The early version of LCAL had 64 electrodes. Because of the discrete nature of the electrodes, it created phase aberrations. The LCAL did not have a diffraction-limited performance due to the phase aberrations. These phase aberrations had been identified as the static phase aberration (which is built-in upon device construction) and the dynamic phase aberration (inaccurate applied voltages). Analysis indicated that the conventional electrode design could not be modified to reduce the static phase aberration. A new electrode architecture called "conductive ladder meshing" (CLM) has been developed which reduces the static phase aberration. To reduce the dynamic phase aberration, a "trial-and-error" voltage dithering technique has been used. A spherical Fresnel LCAL has been built by using the CLM technique. The focusing capability of a spherical LCAL has been demonstrated for a single incoming polarization. Under both monochromatic light and white light illumination, imaging experiments for the spherical Fresnel LCAL have been performed. Images formed by the spherical LCAL were comparable to those formed by a fixed lens in terms of resolution; however, the contrast was three times lower.