'Long shot' Laser 3-D Camera

A 'normal' camera takes flat pictures that have only two dimensions. As children many of us had come across 3D picture viewers that employed two pictures of the same object taken from slightly different angles to 'cheat' the eye into thinking that we are seeing a solid, three-dimensional object.

Now researchers have developed a new laser-driven camera system that creates high-resolution 3-D images of objects from up to a kilometre away. Mimicking radar, a laser beam is swept and bounced off the object, and the time for it to travel back to a detector is measured, from which the contours of the object are computed. The technique, called time-of-flight (ToF), is used in navigation systems for autonomous vehicles, but many current systems have a relatively short range and are virtually useless with objects that do not reflect laser light. The new system, however, has overcome these limitations.

The research team, led by Gerald Buller, professor at Heriot-Watt University in Edinburgh, Scotland, has perfected a ToF imaging system that can gather high-resolution, 3-D information of objects from up to a kilometre away. A low-power infrared laser beam is swept rapidly over an object and the round-trip flight time of the photons in the beam as they bounce off the object and arrive back at the source is recorded. The detector that can count individual photons can resolve depth on the millimetre scale over long distances. Also, 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.

One of the key characteristics of the system is the long wavelength of laser light the researchers chose. The light has a wavelength of 1,560 nanometres, meaning it is longer, or "redder," than visible light. This long-wavelength light travels more easily through the atmosphere, is not drowned out by sunlight, and is safe for eyes at low power. Already the researchers are gunning for extending the range of the 3D 'scanning camera' to 10 kilometres.

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