It’s not just televisions and smartphones that are looking forward to a curved future. Astronomers are now looking to put curved camera sensors into spacecraft exploring the depths of the Universe – since they promise to provide better imaging performance in a more compact package – and recent tests by researchers in the US and France show that prototype curved devices are more than up to the task.
In the study, Simona Lombardo of the Laboratoire d’Astrophysique de Marseille and her colleagues tested five CMOS chips that they curved into both concave and convex shapes, and with different radii of curvature. Using commercially available flat CMOS devices, the team first thinned the sensors to increase their mechanical flexibility and then glued them onto a curved substrate to create a spherical shape.
The researchers found that in almost all cases the characteristics of the curved sensors matched those of a flat CMOS chip – confirming that there was no degradation in performance as a result of the curving process. But they also found that the curved detectors generated a much lower dark current – one of the main sources of noise in image sensors – than the flat version.
“The dark current is due to intrinsic movement of electrons in the pixels of the sensor, even when not exposed to light,” explains Lombardo. “These electrons are then collected in the pixels and become indistinguishable from the electrons generated by the incoming light (from a star or a nice landscape).”
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