Rapid depth estimation based on a key electrowetting liquid-lens with electrically adjusted imaging focus.

Abstract

An effective method for rapidly performing depth estimation using a type of electrowetting liquid-lens is proposed. The liquid-lens is architectured by directly coupling a cylindrical copper sidewall electrode and a top ITO electrode, leading to a dual-mode lens adjusted electrically, including a beam diverging mode and a beam converging mode, and also an intermedium phase retard state. By increasing the applied signal voltage from 0 to 120 V, the focus of the liquid-lens presents a wide dynamic range of (-∞, -128.6 mm) ∪ (45.6 mm, +∞). The key performances of the liquid-lens, such as the focus tunable electrically and an element response duration of less than 5 ms, are evaluated experimentally. By sweeping the signal voltage applied over the liquid-lens coupled with an arrayed CMOS sensor to form an imaging setup, a sequence of images leading to a focal stack is acquired. Considering the dual-mode character of the liquid-lens, the depth of field of the imaging equipment mainly based on the liquid-lens can be remarkably extended by further utilizing the phase retard effect in the transition region between the positive and negative focus. A rapid algorithm for aligning the focal stack and then eliminating the scene parallax is also achieved.