There are enormous optical advantages to use a curved image sensor in place of conventional flat focal plane arrays (FPA) because optical systems intrinsically want to focus to a curved focal surface. For this reason, biological imagers such as the human eye have evolved a curved image sensor (i.e. the retina) that enables use of a simple lens to achieve nearly diffraction-limited imaging over a wide FOV – all in a compact package. Today’s digital imagers sample the curved focal surface using a flat FPA resulting in field-curvature aberrations that impose stringent limitations on the imager’s FOV, F/#, resolution and image quality. Here, we introduce techniques to fabricate hemispherical focal plane arrays to enable the development of compact, wide FOV imaging systems. We have developed monolithically integratable flexible interconnects that can be integrated onto the backside of a planar, silicon FPA designed for hemispherical deformation. These interconnects provide: (1) backside signal routing between small regions of the FPA that were designed to be electrically isolated and (2) a flexible handle for the FPA before a through-wafer etch is performed to mechanically separate the electrically isolated regions of the FPA wafer. This process provides a fully interconnected, flexible FPA that can conform to a hemispherical surface for use in visible (all silicon) or infrared (hybrid) imagers.
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