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Phone-Based Laser Rangefinder Works Outdoors


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The researchers prototyped the sensor using the camera in an ordinary cellphone and a commodity laser emitter that costs about $10.

Researchers in the Massachusetts Institute of Technology Computer Science and Artificial Intelligence Laboratory have developed a new infrared depth-sensing system using a smartphone handset and a $10 laser.

Credit: MIT News

Massachusetts Institute of Technology researchers working in the Computer Science and Artificial Intelligence Laboratory have developed a new infrared depth-sensing system, built from a smartphone with a $10 laser attached to it, that works indoors and outdoors.

The researchers will present the system at the International Conference on Robotics and Automation in May.

The new system performs several measurements, timing them to the emission of low-energy light bursts. The system captures four frames of video, two of which record reflections of laser signals and two of which record only the ambient infrared light. The system then subtracts the ambient light from its other measurements. 

The prototype uses a phone with a 30-frame-per-second camera, so capturing four images imposes a delay of about an eighth of a second. However, a 240-frame-per-second camera, which is already commercially available, would reduce that delay to a 60th of a second.

The system uses a technique called active triangulation, in which a laser mounted at the bottom of the phone emits light in a single plane; the angle of the returning light can thus be measured from where it falls on the camera's two-dimensional sensor. At ranges of three to four meters, the system gauges depth to an accuracy measured in millimeters.

From MIT News
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