Underwater plenoptic cameras optimized for water refraction

Abstract

By inserting a microlens array (MLA) between the main lens and imaging sensor, plenoptic cameras can capture 3D information of objects via single-shot imaging. However, for an underwater plenoptic camera, a waterproof spherical shell is needed to isolate the inner camera from the water, thus the performance of the overall imaging system will change due to the refractive effects of the waterproof and water medium. Accordingly, imaging properties like image clarity and field of view (FOV) will change. To address this issue, this paper proposes an optimized underwater plenoptic camera that compensates for the changes in image clarity and FOV. Based on the geometry simplification and the ray propagation analysis, the equivalent imaging process of each portion of an underwater plenoptic camera is modeled. To mitigate the impact of the FOV of the spherical shell and the water medium on image clarity, as well as to ensure successful assembly, an optimization model for physical parameters is derived after calibrating the minimum distance between the spherical shell and the main lens. The simulation results before and after underwater optimization are compared, which confirm the correctness of the proposed method. Additionally, a practical underwater focused plenoptic camera is designed, further demonstrating the effectiveness of the proposed model in real underwater scenarios.

Calculation and Analysis of Key Parameters of Underwater Optical Imaging System

“…Figure 10b-d present specific data on the front working distance obtained through both methods, corresponding to different models. The data obtained by both methods are consistent, affirming the reliability of the work distance calculation method and the accuracy of Equation (15). The findings depicted in Figure 10 indicate a substantial increase in the system's front working distance, expanding multiple times from 0.1 m when transitioning from air to seawater, attributable to water's negative lensing effect on the imaging system.…”

“…F. Menna et al also tested a commercial underwater camera in a pool and used photogrammetric techniques to describe the optical phenomena of flat windows and dome windows [ 14 ], but they lacked precise calculations. G. Jiang et al modeled and analyzed the imaging process of an underwater plenoptic camera and proposed an optimization method for an underwater plenoptic camera [ 15 ]. However, this method is not generalizable and is only relevant to plenoptic cameras using microlens arrays.…”