Paper-Thin Compound-Eye Camera

The focal length of a lens means that a camera has to have a certain thickness - or so we might think. Insect eyes show that this need not be the case: A camera chip based on the compound-eye principle can be used for person recognition and is as thin as paper.

If p

eople were insects, books on optics would certainly look different. The camera illustrated as the technical equivalent next to a cross-section of the eye with just one lens, one iris and one retina would not be of the conventional type. A compound camera would have many hundreds of individual eyes. Each light-sensitive unit, consisting of a lens and a photocell, would capture a narrow segment of the environment. All the images together form the complete picture. An insect’s compound eye will never achieve a particularly high optical resolution, but the principle according to which it registers images does possess some advantages, and if these were incorporated in a camera it would be very flat and could cover a wide field of view.

It was precisely these advantages which inspired research scientists at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF to develop their ultra-flat camera system. “Our latest prototypes are thinner than 0.4 millimeters,” emphasizes Andreas Bräuer, who is in charge of the Microoptics unit in Jena. “You can gain a real sense of how thin that is by picking up three sheets of carbon paper between your fingers.” Cameras incorporating conventional “human-eye” optics - such as those used in mobile phones - are at best no thinner than seven millimeters.

This development is targeted at all the applications where the advantages of the stick-on sensors really come to the fore. They are already being produced on wafers like microchips, which is a key requirement if they are one day to be manufactured cost-effectively, on an industrial scale. The next stage of the project is to install the camera in series-production units suitable for use in industry. The most important step will be to connect the lens system with receiver arrays, for example with a CMOS chip. The optical and electronic systems will then be so flat that it will be possible to integrate them in a chipcard with a thickness of 0.8 millimeters. If the chipcard “sees” that it is being used by a stranger it could block the money transfer. Just a vision? Interesting applications are also opening up for driver assistance systems in automobiles: Instead of a gawping camera lens, a discrete gray square would blend in with the car interior. From the driver’s line of vision or eye movements, the compound-eye camera could report to the onboard computer that there is a risk of the driver nodding off. Another possibility: Depending on whether a slightly built woman or a heavy man is sitting in the car, the airbag will activate comparatively gently or strongly.

Source: Fraunhofer-Gesellschaft

» Next Article in Physics: Four Innovative Technologies from Argonne Win Research and Development 100 Awards