Improved depth of field of the composite micro-lens arrays by electrically tunable focal lengths in the light field imaging system

Abstract

Conventional micro-lens arrays (MLAs) for a light field imaging system can capture 3D images, which can be optically reconstructed. However, the sensed images frequently suffer from a fixed or limited depth of field (DOF) of MLAs. In this work, we propose composite micro-lens arrays (CMLAs), which are composed of electrically tunable liquid crystal MLAs (LC MLAs) and ultraviolet-curing MLAs (UVC MLAs). Moreover, we experimentally confirmed that the proposed CMLAs possess a tunable and improved DOF by electrically controlling the operating voltages applied to the LC MLAs in the light field imaging system. In the single LC MLA, the focal length changes from 1.62 mm to 2.53 mm, and the DOF is transferred from 0.83 mm to 23.85 mm under the influence of the operating voltage. The focal length of the CMLAs is tunable from 2.02 mm to 3.68 mm compared with LC MLAs, and the corresponding DOF could vary from 1.19 to 43.38 mm, which is much higher than that of the single LC MLAs. Furthermore, the CMLAs can capture clear images at large depth positions under lower operating voltages. Therefore, the CMLAs with the improved and adjustable DOF exhibit potential application for the light field imaging system and can be extended to the industrial and medical microscopy applications.