Low-power laser reveals high-resolution details from a kilometre away

The new system is said to work by sweeping a low-power infrared laser beam rapidly over an object. It then records the round-trip flight time of the photons in the beam as they bounce off the object and arrive back at the source. The system can resolve depth on the millimetre scale over long distances using a detector that can ‘count’ individual photons.

Although other approaches can have exceptional depth resolution, the ability of the new system to image objects like items of clothing that do not easily reflect laser pulses makes it useful in a wider variety of field situations, said Heriot-Watt University Research Fellow Aongus McCarthy, the first author of a paper on the research published in Optics Express.

‘Our approach gives a low-power route to the depth imaging of ordinary, small targets at very long range,’ McCarthy said in a statement. ‘Whilst it is possible that other depth-ranging techniques will match or out-perform some characteristics of these measurements, this single-photon counting approach gives a unique trade-off between depth resolution, range, data-acquisition time, and laser-power levels.’