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Eagle Eyes from a 3D Printer

Would you like to have the incredibly sharp eyes of an eagle? It’s now all possible by simply pressing the key combination control + P. Scientists have produced a sensor system with a surface area of only a few square millimeters – a type of mini digital camera that captures razor-sharp images with four lens elements. These optics come from a 3D printer.

Soaring majestically at dizzy heights, an eagle can easily spot its lunch on a field but, despite focusing its beady eyes on its future meal, it can also see a fellow raptor, a contender for the little field mouse below, approaching threatingly from the side.

Imagine if an autonomous car could use the breathtaking precision of these eagle eyes to capture slow-flowing traffic, the vehicle coming up behind it and the two kids playing ball at the side of the street. To ensure that it doesn’t need a rotating roof camera, like the Google street car, for example, or a large number of other cameras to perform this task, scientists at the University of Stuttgart in Germany have copied the eagle’s biology and printed the structure of its eye on a microchip.

Biology as the role model

Thanks to the large number of photoreceptor cells on their central fovea, eagles can see even tiny details from a great distance. This is all made possible by a depression in the center of the yellow spot, the area of sharpest vision on the retina. Eagles additionally have a second fovea at the edge of their eyes which also gives them sharp peripheral vision.

The plan of the research scientists working on Professor Harald Giessen’s team was to implement a sensor featuring an adjustable focal length and visual field that would make it possible to zoom into objects. To ensure that individual pixels would not become visible due to an overly high zoom, which is the case with a digital zoom (test the zoom of your smartphone and see for yourself), the scientists turned their attention to the “good, old days”: an optical zoom directly on the lens can be used to adjust the focal length to obtain a wider or narrower visual field.

However, a mechanically adjustable zoom on a mini lens element is practically impossible. Therefore, the researchers printed several lens elements with different focal lengths on a chip.

Comparison of imaging performance for the foveated (left) and the non-foveated case (right). Image: University of Stuttgart, PI4

Comparison of imaging performance for the foveated (left) and the non-foveated case (right)

Image: University of Stuttgart, PI4

CMOS sensor with different lenses in groups of four. Image: University of Stuttgart, PI4

CMOS sensor with different lenses in groups of four

Image: University of Stuttgart, PI4

The optical method behind this technology: Foveated Imaging

Using 3D printers for 3D micro printing from the Karlsruhe-based company Nanoscribe, the scientists can print a set of micro-lenses on a high-resolution CMOS chip.

The smallest of the four lens elements has a focal length corresponding to that of a wide-angle lens, the largest element displays the focal length of a typical tele lens, and the two other lenses capture the central field of view. The images generated by the lens elements on the chip are read out simultaneously and processed electronically. A small computer program composes the images so that the image of the tele lens is shown in the center and the image of the wide-angle lens on the outside. This technology can be used for autonomous cars, for example. They could also be a very welcome new feature for smartphone users with a tele lens function. They could be integrated into 4-centimeter small mini drones or help robots not only to grasp small objects in front of them, but also to dodge a second robot approaching from the side.

3D printing in the nano range

3D printers are capable of printing individual points with a diameter of 200 nanometers (a human hair has a diameter of 50,000 nanometers). The printing process is done with a special laser light in a photoresist. “The material hardens in areas where the laser is particularly strongly focused,” explains Andreas Frölich, a physicist at Nanoscribe. “This means you can draw in three dimensions like with the tip of a pencil.” The hardened structures are made of a plastic material – a polymer. The technique is similar to a standard photochemical process. In a standard photoresist alight particle (photon) also triggers a polymerization process. However, this is not sufficient for nano 3D printing: to harden the photoresists, two light particles must strike a molecule simultaneously to have any effect. Therefore, this process is also called 2-photon polymerization. Under normal conditions two photons never act simultaneously. To generate these, a femtosecond laser is used. It generates pulses that last for one hundred thousand billionth of a second.

3D printing process directly onto the CMOS chip

Image: University of Stuttgart, PI4

High-tech startup straight out of a picture book: Nanoscribe GmbH

Nanoscribe is a spin-off from the Karlsruhe Institute for Technology and was founded more than ten years ago by Prof. Dr. Georg von Freymann, Martin Hermatschweiler, Dr. Michael Thiel and Prof. Dr. Martin Wegener. The researchers gradually made inroads into the science market through “door-knocking”: by making presentations at exhibitions, taking part in congresses and publishing articles in trade magazines. As scientists are very receptive to innovations, they were greeted with open arms almost without exception. ZEISS also supported the startup with technology and advice right from day one and participated financially in the new company by acquiring shares in it in September 2008. 40 people currently work for Nanoscribe. Its high-precision systems can now be found in 100 renowned research institutes in 25 countries around the globe. A single printer costs as much as a McLaren 675LT – the grand total of 400,000 euros.

Photonic Professional GT: 3D printer for the fabrication of micro-optics

Image: Nanoscribe

Elite universities put their trust in the innovative technology

Harvard University, the California Institute of Technology, the University of Oxford and the ETH in Zurich – they all put their trust in the high-precision 3D printers from the German company Nanoscribe. This leading-edge technology allows the production of optical and mechanical components which could not be produced before due to technical restrictions. With a resolution of far below one micrometer and structure sizes of below 150 nanometers, the systems are simply miles ahead of anything previously on the market. The printers are also suitable for maskless lithography, therefore eliminating the need for customers to purchase a second system. What Giessen himself most values are the reliable and stable production conditions of the systems from Karlsruhe.

Therefore, further exciting ideas for the use of the 3D printers are eagerly awaited from the research institutes. Just something to whet your appetite beforehand: this technology may one day be used to cure gynecological cancer. But that is still a long way off.

Further information

Further information

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