Abstract
The demand for bendable sensors increases constantly in the challenging field of soft and micro-scale robotics. We present here, in more detail, the flexible, functional, insect-inspired curved artificial compound eye (CurvACE) that was previously introduced in the Proceedings of the National Academy of Sciences (PNAS, 2013). This cylindrically-bent sensor with a large panoramic field-of-view of 180° × 60° composed of 630 artificial ommatidia weighs only 1.75 g, is extremely compact and power-lean (0.9 W), while it achieves unique visual motion sensing performance (1950 frames per second) in a five-decade range of illuminance. In particular, this paper details the innovative Very Large Scale Integration (VLSI) sensing layout, the accurate assembly fabrication process, the innovative, new fast read-out interface, as well as the auto-adaptive dynamic response of the CurvACE sensor. Starting from photodetectors and microoptics on wafer substrates and flexible printed circuit board, the complete assembly of CurvACE was performed in a planar configuration, ensuring high alignment accuracy and compatibility with state-of-the art assembling processes. The characteristics of the photodetector of one artificial ommatidium have been assessed in terms of their dynamic response to light steps. We also characterized the local auto-adaptability of CurvACE photodetectors in response to large illuminance changes: this feature will certainly be of great interest for future applications in real indoor and outdoor environments.
Highlights
The compound eyes of insects and crustaceans, which show an extraordinarily wide range of designs, a remarkable optical layout, high sensitivity in dim light, even at night, and polarized light sensitivity, provide an endless source of inspiration for designing the curved, flexible visual sensors of the future
630 photodetectors grouped in 42 identical columns of 15 photodetectors which are placed on a thin flexible printed circuit board (PCB) wrapped around the cylindrical scaffold
It is based on a MOSFET feedback (MFB) transistor operating in the sub-threshold region where the current-to-voltage characteristic shows logarithmic variations in a large dynamic range of up to several decades
Summary
The compound eyes of insects and crustaceans, which show an extraordinarily wide range of designs (see [1] for a review), a remarkable optical layout, high sensitivity in dim light, even at night, and polarized light sensitivity, provide an endless source of inspiration for designing the curved, flexible visual sensors of the future. Song et al [23] succeeded in bending a stretchable planar compound eye to obtain a spherical compound eye composed of 180 ommatidia with an overall field-of-view of 160◦ × 160◦ This remarkable design is based on cutting-edge technologies, such as flexible micro-lens arrays and micro-electronics (photodiode), encapsulated within a flexible polyimide support. This new principle was associated with non-uniform visual sampling, and because of the very coarse resolution of the eye (the interommatidial angle ranged from 8◦ to 11◦ ), large computational resources were required to put (“stitch”) together the various subimages acquired by the ommatidia.
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