New 3D imaging sensors could enable swarms of flying surveillance robots to monitor an area without crashing into each other.
The sensors, developed by researchers in Germany, use short pulses of light to detect objects around them, which its creators say provides more detailed information than radar systems.
The technology is designed to be fitted to aerial drones to allow large groups of them to fly autonomously over events such as football matches, relaying images back to a control centre of outbreaks of violence or criminal activity.
‘The sensor can measure three-dimensional distances very efficiently,’ said Werner Brockherde, head of the development department at the Fraunhofer Institute for Microelectronic Circuits and Systems (IMS) in Duisburg, where the sensor was created.
‘The sensor has a much higher local resolution [than radar]. Given the near-field operating conditions, radar images would be far too coarse.’
Flying robots with the sensor attached would be capable of identifying objects measuring 20cm by 15cm at ranges of up to 7.5m. This distance information is transmitted at a rate of 12 images per second.
The sensors are built with CMOS circuit technology — similar to that found in mobile phone cameras — and use the time-of-flight principle, calculating distance by measuring the time taken for a pulse of light to be emitted by the sensor, reflected off an object and return.
In order to prevent bright ambient light, for example from the sun, from masking the signal, the sensor’s electronic shutter only opens for a few nanoseconds.
The device also takes differential measurements, comparing each signal reading with another captured just before the pulse is sent out in order to calculate the amount of ambient light.
The 3D distance sensors have been built into cameras manufactured by TriDiCam, a spin-off company of Fraunhofer IMS.