Design and fabrication of silicon-tessellated structures for monocentric imagers

US researchers have developed a curved photodetector array that could lead to miniature monocentric imagers. Silicon imagers in cell-phone cameras are planar grids of photodetectors, requiring flat imaging planes and complex lens designs to correct for aberrations. The curved imager would allow a simple, compact, and wide field-of-view spherical lens to be used instead of conventional lens stacks. Roger Howe and co-workers from Stanford University, California, have created a tessellated thin silicon array of optoelectronic devices that can conform to a 10-mm-diameter ball lens. The team constructed the photodetectors on a silicon-on-insulator substrate. The 20-μ-thick device layer was etched into gore segments consisting of arrays of spring-connected hexagons. These interconnected, compliant segments were released from the substrate and assembled onto the hemispherical mounting surface for the ball lens.