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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.

We carried out a systematic study of hexagonal boron nitride/graphene (h-BN/G) heterostructure growth by introducing high incorporation of a carbon (C) source on a heated cobalt (Co) foil substrate followed by boron and nitrogen sources in a molecular beam epitaxy system. With the increase of C incorporation in Co, three distinct regions of h-BN/G heterostructures were observed from region (1) where the C saturation was not attained at the growth temperature (900 °C) and G was grown only by precipitation during the cooling process to form a 'G network' underneath the h-BN film; to region (2) where the Co substrate was just saturated by C atoms at the growth temperature and a part of G growth occurs isothermally to form G islands and another part by precipitation, resulting in a non-uniform h-BN/G film; and to region (3) where a continuous layered G structure was formed at the growth temperature and precipitated C atoms added additional G layers to the system, leading to a uniform h-BN/G film. It is also found that in all three h-BN/G heterostructure growth regions, a 3 h h-BN growth at 900 °C led to h-BN film with a thickness of 1-2 nm, regardless of the underneath G layers' thickness or morphology. Growth time and growth temperature effects have been also studied.