The human eye is a remarkable imaging device, with many attractive design features1,2. Prominent among these is a hemispherical detector geometry, similar to that found in many other biological systems, that enables a wide field of view and low aberrations with simple, few-component imaging optics3,4,5. This type of configuration is extremely difficult to achieve using established optoelectronics technologies, owing to the intrinsically planar nature of the patterning, deposition, etching, materials growth and doping methods that exist for fabricating such systems. Here we report strategies that avoid these limitations, and implement them to yield high-performance, hemispherical electronic eye cameras based on single-crystalline silicon. The approach uses wafer-scale optoelectronics formed in unusual, two-dimensionally compressible configurations and elastomeric transfer elements capable of transforming the planar layouts in which the systems are initially fabricated into hemispherical geometries for their final implementation. In a general sense, these methods, taken together with our theoretical analyses of their associated mechanics, provide practical routes for integrating well-developed planar device technologies onto the surfaces of complex curvilinear objects, suitable for diverse applications that cannot be addressed by conventional means.
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We thank T. Banks, K. Colravy, and J. A. N. T. Soares for help using facilities at the Frederick Seitz Materials Research Laboratory. The materials and optics aspects were developed in work supported by the US Department of Energy, Division of Materials Sciences under Award No. DE-FG02-07ER46471, through the Materials Research Laboratory and Center for Microanalysis of Materials (DE-FG02-07ER46453) at the University of Illinois at Urbana-Champaign. The processing approaches and the mechanics were developed in work supported by the National Science Foundation under grant DMI-0328162. C.-J.Y. acknowledges financial support from the Korea Research Foundation (grant KRF-2005-214-D00329) funded by the Korean Government (MOEHRD). J.B.G. acknowledges support from a Beckman postdoctoral fellowship.
Author Contributions H.C.K., M.P.S., V.M. and J.A.R. designed the experiments. H.C.K., M.P.S., J.S., V.M., W.M.C, C.-J.Y., J.B.G., J.X., S.W., Y.H. and J.A.R. performed the experiments and analysis. H.C.K., M.P.S., J.S., Y.H. and J.A.R. wrote the paper.
The text and Supplementary Figures S1-S29 provide detailed fabrication methods, a electrical response characterization of the hemispherical cameras, and a discussion of the optical testing procedures. Mechanics models to describe the planar to hemispherical transformation process and the strains in the hemispherical focal plane arrays are presented. (PDF 5886 kb)
This movie shows the data acquisition process using a hemispherical camera. A series of photographs or movie is captured, using the computer interface shown on the left, as the image text "E-EYE" is slowly translated across the objective. The movie is shown in real time. (QT 7188 kb)
This movie shows a hemispherical camera being used to collect a high resolution image. The camera scans over the entire "E" image using a series of small eucentric rotations, in this case scanning from -20 to 20° in both the θ and ϕ directions in 5° increments. (QT 5569 kb)
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Ko, H., Stoykovich, M., Song, J. et al. A hemispherical electronic eye camera based on compressible silicon optoelectronics. Nature 454, 748–753 (2008). https://doi.org/10.1038/nature07113
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