Researchers Print Sensors With An Eagle's Eye

Physicists from the University of Stuttgart have produced sensors that are supposed to copy the properties of an eagle's eye. The sensors come from the 3D printer and are primarily intended for autonomous driving, where a clear all-round view is required. The scientific journal Science Advances reports on the sensors in its current edition.

An eagle eye for the self-driving car

The advantages of the eagle's eye are the sharp view from a distance, so that you can spot a mouse from a height of 3 km, and the wide field of view so that the birds can see hostile animals. The reason for the proverbial eagle look are extremely many visual cells in the central fovea, a depression in the center of the yellow spot, the area of ​​the sharpest vision. In addition, eagles have a second fovea on the edge of the eye, which ensures a clear view to the sides.

Such an all-round view would be worth a lot for self-driving vehicles: In front, his camera should see particularly clearly, recognize obstacles and assess the distance to the vehicle in front, but still keep an eye on everything to the side. So far, a whole series of cameras and sensors around the vehicle or a rotating camera on the roof have been used.

3D printer prints lenses on a CMOS chip

Simon Thiele from the Institute for Technical Optics and his colleagues around Harald Giessen from the 4th Physics Institute at the University of Stuttgart have developed a sensor that is supposed to replicate this eagle eye in a small area. The Stuttgart researchers printed a whole set of micro-objective lenses with different focal lengths and fields of view directly on a high-resolution CMOS chip. The smallest lens has a focal length that corresponds to a wide-angle lens, followed by two lenses with a rather medium field of view, and the largest lens has a very long focal length and a small field of view - like a typical telephoto lens.

The 3D printer uses the so-called two-photon polymerization to produce the lenses precisely on the CMOS chip. In this process, two photons from a red femtosecond laser pulse are absorbed in the photoresist and act like a blue photon that starts the crosslinking process in the liquid photoresist. With the help of a scanner, layer by layer of the free-form lens structure is written.

According to the researchers, all four images that the lenses generate on the chip are electronically read out and processed at the same time. A small computer program composes the image so that the high-resolution image of the telephoto lens is shown in the center and the image of the wide-angle lens on the outside. The researchers tested the camera on various test objects and, according to their own statements, were able to demonstrate the improvement in resolution at the center of this so-called “foveated imaging” system.

Lenses also conceivable for mini drones

Since the entire sensor system is a few square millimeters in size - the lenses have diameters in the range of a hundred to a few hundred micrometers - the researchers also have other possible applications in view. So the lenses could also be used in mini drones. The sensors are connected to a small mini computer that has its own IP address and that can be addressed and read out via the smartphone. The system is therefore already suitable for Industry 4.0 applications.

The work was supported by the Baden-Württemberg Foundation and the Federal Ministry of Education and Research. The research was carried out under the roof of the Scope research center at the University of Stuttgart and could be carried out thanks to the latest 3D printing technology from the Karlsruhe company Nanoscribe.