Refocusing capabilities in a miniaturized multi-channel multi-resolution imaging system using a tunable lens

Abstract

Inspired by nature, many application domains might gain from combining the multi-channel design of the compound eyes of insects and the refocusing capability of the human eye in one compact configuration. Multi-channel refocusing imaging systems are nowadays only commercially available in bulky and expensive designs since classical refocusing mechanisms cannot be integrated in a miniaturized configuration. We designed a wafer-level multi-resolution two-channel imaging system with refocusing capabilities using a voltage tunable liquid lens. One channel is able to capture a wide field-of-view image (2x40°) of a surrounding with a low angular resolution (0.078°), whereas a detailed image of a small region of interest (2x7.57°) can be obtained with the high angular resolution channel (0.0098°). The latter high angular resolution channel contains the tunable lens and therefore also the refocusing capabilities. In this paper, we first discuss the working principle, tunability and optical quality of a voltage tunable liquid lens. Based on optical characterization measurements with a Mach-Zehnder interferometer, we designed a tunable lens model. The designed tunable lens model and its validation in an imaging setup show a diffraction-limited image quality. Following, we discuss the performance of the designed two-channel imaging system. Both the wide field-of-view and high angular resolution optical channels show a diffraction-limited performance, ensuring a good image quality. Moreover, we obtained an improved depth-of-field, from 0.254m until infinity, in comparison with the current state-of-the art published wafer-level multi-channel imaging systems, which show a depth-of-field from 9m until infinity.