Monocular depth estimation method using a focus tunable lens

We propose a method for the passive-type estimation of depth using a focus tunable lens. The proposed method utilizes a lens group and a focus tunable lens and charge coupled device. The target object is imaged by the group of lenses and measured by changing the focal length of the focus tunable lens. The method aims to measure depth information in the image domain and not in the object domain. An autofocusing algorithm finds the best focus position of the target object through the focus value calculated by the Sobel operator. We believe that the proposed method is applicable to depth measurement systems because it offers a simple configuration without any active light source and can operate in real time. The experiment, performed for comparison with theoretical calculations, confirms the feasibility of the proposed method.