Single lens, wide field-of-view camera inspired by aquatic animals

Abstract

The intriguing optical properties arise from the unique structural and functional features of the aquatic eye that consists of i) a protruding monocentric lens, ii) a hemispherical retina, iii) an iris, and iv) retractor/protractor muscles (Fig. 1a) [1]. The protruding monocentric lens with the spherical and symmetric shape forms a hemispherical focal plane, enabling the wide FoV. In addition, the parabolic refractive index (RI) profile of the monocentric lens (Fig. 1a left inset) minimizes optical aberrations. The retina contains elongated rod cells (Fig. 1a right inset), which elongate the light path for better light absorption. The tailored monocentric lens (Fig. 1b), inspired by the protruding monocentric lens in aquatic eyes, has a spherical symmetric shape and is composed of the half-ball lens (BK7) and the shell lens (SF16). Such a core-shell structure is inspired by the parabolic profile of refractive index in the protruding monocentric lens of aquatic eyes. An imaging system inspired by the aquatic vision can be developed by integration of a tailored monocentric lens and hemispherical Si photodiode array (h-Si-PDA) (Fig. 1c). Inspired by the hemispherical retina with elongated rod cells in aquatic eyes, we developed h-Si-PDA, 23-by-23 hexagonal mesh-shape array of silicon photodiodes with light-trapping structure. The h-Si-PDA is connected to the external electronics via the anisotropic conductive film, and the photocurrent is measured using a customized data acquisition system. The aquatic-vision-inspired camera successfully performs wide FoV imaging without optical aberrations (Fig. 1d).