Liquid crystal lens auto-focus extended to optical image stabilization for wafer level camera

Miniaturization and reduction of production cost of optical components in consumer electronics leads to wafer level optics. This miniaturization, associated with the increase of CMOS sensors resolution, generates new needs such as auto-focus (AF) and optical image stabilization (OIS) in order to reduce the blurring caused by hand jitter. In this paper, we propose a wafer scale technology to perform AF and introduce OIS functionality. We managed to create a tunable focal lens by filling with nematic liquid crystal (LC) an assembly of two glass substrates coated with circular hole patterned chromium electrodes and resistive transparent layers of Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS). When a voltage with tunable magnitude and frequency is applied to the electrodes, the resistive layer creates a non-uniform voltage distribution from the edge to the center of the aperture which depends on electrical parameters of PEDOT-PSS and LC. The resultant electric field generates a gradient orientation of the nematic director which allows to focus light polarized along the director. It is also possible to shift the optical axis of the lens by dividing the hole patterned electrodes in several sectors and to apply different voltages on each sectors. The principle of the shifting effect has been demonstrated but its magnitude has to be increased by using more adapted electrode structure to ensure the OIS function. Finally, we characterised the dynamical behaviour of the lens in both focus and shifting modes.