Optical design rules of a camera module with a liquid lens and principle of command for AF and OIS functions

Abstract

We have developed a miniature liquid lens component based on electro-wetting. It is designed to be plugged on a fix focus camera module lens to provide both optical image stabilization (OIS) and auto-focus (AF) functions without any mobile mechanical parts. The OIS/AF liquid lens component features a conical shape supporting the liquid interface in order to maintain a stable optical axis and a multi-electrode design able to induce an average tilt of the liquid interface when a bias voltage is applied to the different electrodes. The miniature size of the OIS/AF liquid lens component is well adapted to imaging applications with ¼ inch, 1/3 inch and possibly 1/2.5 inch sensor formats. We will present general rules for the optical design with an OIS/AF liquid lens. In this context, we will describe a simple calculation, based on the well known Maréchal criterion, to estimate the optical wave front error requirement of an optical component positioned in the aperture stop plane of an imaging lens design to perform images with a pixel resolution quality. We will also present the principle of command of a multi-electrode liquid lens in order to perform AF and OIS functions with an optimal image quality.