Researchers at Fraunhofer Institute for Microelectronic Circuits and Systems (IMS) have developed a diode that can read photons faster than ever before.
In cooperation with the partners of the MiSPiA project consortium the Fraunhofer IMS in Duisburg has advanced the development of CMOS technology and introduced an ultrasensitive image sensor with this technology, based on Single Photon Avalanche Photodiodes (SPAD). Its pixel structure can count individual photons within a few picoseconds, and is therefore a thousand times faster than comparable models. Since each individual photon is recorded, images can be captured with extremely weak light sources.
The new image sensor uses the internal avalanche breakdown effect, a photoelectric amplification effect. The number of avalanche breakdowns corresponds to the number of photons that the pixels hit. In order to count these events, each of the sensor’s pixels comes with very precise digital counters. At the same time, the scientists have applied microlenses to each sensor chip, which focus the incoming beam in each pixel onto the photoactive surface. Another advantage is that processing the digital image signals takes place directly on the microchip, removing the need for analogue signal processing.
‘The image sensor is a major step toward digital image generation and image processing. It allows us to have the capability to use even very weak light sources for photography. The new technology installs the camera directly on the semiconductor, and is capable of turning the information from the light into images at a significantly faster pace,’ stated Dr Daniel Durini, group manager for optical components at the Fraunhofer Institute IMS.
IMS engineered the sensor under the European research project MiSPiA (Microelectronic Single-Photon 3D Imaging Arrays for low-light high-speed Safety and Security Applications). Altogether, seven partners throughout Europe from the fields of research and business are involved in the project. In the next stage, the scientists from Duisburg are working on a process to produce sensors that are back-lighted, and in this regard, even more powerful. At the same time, the new technology is already being utilised in tests for traffic. Chip-based mini-cameras protect vehicles, bicycles and pedestrians from collisions and chip-based accidents, or assist in the reliable functioning of safety belts and airbags.
