1 April 2002
Moose detector saves windshelds
By Nicholas Sheble
NASA regularly pushes the technology it develops at taxpayers’ expense to the private sector for commercial gain.
The Insurance Corporation of British Columbia (ICBC) is very interested in a NASA Jet Propulsion Laboratory (JPL)–developed sensor that originally came about to work in the Star Wars missile defense system. ICBC wants the technology for a moose warning system.
The quantum-well infrared photodetector (QWIP) can see at 8.5-micron wavelength.
The human eye can see only a small slice—blue to red—of the light spectrum. Only objects hot enough to glow at these colors and those that reflect visible light appear visible to the eye.
Most objects, however, are too cold to glow visibly, making them invisible at night. But their finite temperature does give them an infrared glow. It is this glow, or its reflection, that night-vision infrared cameras strive to see. Recent developments at JPL have culminated in one of the most sensitive yet affordable handheld, long-wavelength, infrared cameras.
Objects at room temperature glow brightest in the wavelength range of 8–10 microns. Cameras that can see 8.5-micron light find uses in areas such as security and surveillance, navigation and flight control, and early warning systems.
Scan several road miles
Early warning is what Canadian drivers need, Wired magazine reported. A company called InTransTech is using infrared photo sensors to detect animals on British Columbia’s mountain roads in hopes it will cut back on the number of accidents caused by motorists slamming into deer, moose, and other wildlife.
InTransTech in Edmonton, Alberta, is a spin-off company of QWIP Technologies, the incubator used to commercialize the JPL’s technology. It sees the sensors as a viable solution to the moose mashings and deer damage that take place with disturbing regularity on the province’s highways.
Last year, British Columbia drivers reported more than 10,000 accidents involving wildlife, resulting in about $20 million (Canadian) worth of insurance claims. Deer are the leading cause of crashes because they’re common throughout the province.
However, the more catastrophic collisions come from moose. Moose are particularly dangerous because of their long legs. When a car plows into one of the ungainly mammals, it is likely to come up over the hood and right through the vehicle’s windshield.
The infrared sensors can scan several miles of road and relay warnings to 4- by 8-foot digital signs posted along the highway. The signs will identify what species of animal is on the road and warn drivers to slow down.
The animal detectors are slated to field test in British Columbia’s rugged Kootney Mountain region this month, with production and installation scheduled for 2003.
Housed in trailers, the cameras scan the area for heat signatures. They are sensitive enough to detect heat sources from one pixel to the next of 0.01°C.
InTransTech’s standard sensors contain some 81,900 pixels and can work through darkness, smoke, snow, fog, and rain, although precipitation will reduce the system’s visibility.
A single camera system that monitors several miles of road costs $50,000 (Canadian). In contrast, it costs $40,000 to $80,000 to fence about 1 mile of highway and far more for tunnels for the animals to get past fenced areas.
Photon strikes square well
QWIP consists of a stack of quantum wells designed to detect infrared light. An elegant candidate for QWIP is the square quantum well of basic quantum mechanics. When the quantum well is sufficiently deep and narrow, its energy states quantize (become discrete).
The potential depth and width of the well can adjust so it holds only two energy states: a ground state near the well bottom and a first excited state near the well top. A photon striking the well excites an electron in the ground state to the first excited state, and then an externally applied voltage sweeps the photoexcited electron out, producing a photocurrent.
Only photons that have energies corresponding to the energy separation between the two states are absorbed, resulting in a detector with a sharp absorption spectrum. Designing a quantum well to detect light of a particular wavelength becomes a simple matter of tailoring the potential depth and width of the well to produce two states separated by the desired photon energy.
QWIP might have remained a textbook curiosity, had it not been for the spectacular advances in the past 20 years in the crystal growth and processing techniques of large band gap compound semiconductors such as gallium arsenide and aluminum gallium arsenide with different aluminum compositions.IT
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