Blog Date: 8/2/2012
Author: Ray Coulombe

Remember the days of the simple photo-electric cell? Using either a transmitter-receiver pair or a single TX/RX with a retro-reflector, the interruption of an IR beam would trigger an alarm, stop a process, or simply act as an input to another process. We have come so far!
Today, using laser technology, a beam can be emitted into free space, reflect off an object, and, upon returning, provide the input to calculate distance of the object based on its flight time. Compound that with the fact that the beam is scanning continuously over a pre-determined arc travelling at 386,000 miles per second and you’ve got something interesting. Some refer to this technology as LIDAR (Light Detection and Ranging), based on the same concept as RADAR, but using laser light instead of radio waves. Because laser light is higher in energy and shorter in wavelength than radio waves, it reflects better from non-metallic objects and provides mapping advantages over RADAR.
Indoor security applications would usually be volumetric, although the laser effectively creates a two-dimensional “slice” of the area. If, for example, the laser was ceiling-mounted, shooting towards a wall, anything breaking the slightly angled plane of the beam would be a candidate to register in the accompanying software. If the laser scanner was mounted to scan parallel to a wall, it could determine if someone were reaching for any object on the wall — making it useful for retail applications, museums, art galleries, etc.
The technology also has applications in people counting and monitoring of restricted or hazardous areas. The advantage of the laser vs. PIR or microwave is the ability to determine the intrusion and its position. The advantage is further enhanced by the accuracy and granularity of the sensor, as well as multiple zones.
Outdoor applications can be volumetric or linear, such as for placement along a perimeter. Because these sensors can be environmentally hardened, they have already found use in applications such as tolling barriers on highways. Based on the positioning of the scanner, they can detect objects or people only above or below a certain height, eliminating ground clutter and small animals. While range is limited, scanners can be complemented by other technologies such as video surveillance.
Link to Complete Article as it appeared in Security Technology Executive Magazine

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