Infrared Camera Helps Spot Perimeter Intruders
Airports and harbors face a common security challenge: Their large areas translate into long perimeters — often many miles long.
Traditional perimeter control has involved a fence, guards and surveillance cameras. However, fences cannot be used with all terrains, such as harbors. Guards are costly, especially when they are patrolling a fence that in all likelihood will not be breached. Cameras can fail during inclement weather or at night. These drawbacks have led the military and security industries to seek better solutions.
The software screen shot shown here displays a 360° (H) × 20° (V) image provided by the sensor head of an infrared camera system. Various alarm settings, adjustable contrast and brightness levels, and the ability to store images for later replay are some of the methods that enable intruder detections. Courtesy of HGH Systèmes Infrarouges.
However, a cooled infrared sensor, such as that in the Vigiscan camera from HGH Systèmes Infrarouges of Igny, France, can spot intruders at night or in fog at distances of several kilometers. The exact distance is determined by the vertical field of view; a narrower field of view produces a longer detection distance.
The camera uses cooled HgCdTe sensors that, depending upon their configuration, detect radiation either in the mid-infrared range at 3.7 to 4.8 μm or in the thermal infrared range at 7.7 to 10.3 μm.
It employs a sensor with a 288 × 4-pixel array that is mounted in a rotating turret, which completes one sweep every second. With a 20° vertical field of view, a complete revolution is 10,000 pixels long. The use of four independent pixels eliminates the long, dark line that would result from a pixel failure. “We measure the average value on those four lines. So even if one pixel is dead, three others are right,” said the company’s Edouard Campana.
The system is portable, but the sensor, when operating, is motionless except for a known rotation. Thus, software can distinguish between fixed points arising from a stationary hot spot and from transitory heat sources resulting from people in motion. As the sensor rotates and captures heat signatures, the data from each scan is compared with the data collected previously. If there is an intruder, one or several of the pixels will have uncharacteristic infrared levels. In that case, the device can transmit an alarm.
According to Campana, there is strong interest from the defense and security community.
“The main applications are protection of industrial-sensitive areas, border and coastal surveillance, airport and harbor monitoring, and military base surveillance,” he said.
Contact: Edouard Campana, HGH Systèmes Infrarouges; e-mail: firstname.lastname@example.org.
- A light-tight box that receives light from an object or scene and focuses it to form an image on a light-sensitive material or a detector. The camera generally contains a lens of variable aperture and a shutter of variable speed to precisely control the exposure. In an electronic imaging system, the camera does not use chemical means to store the image, but takes advantage of the sensitivity of various detectors to different bands of the electromagnetic spectrum. These sensors are transducers...
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