September 30, 2002
A revolutionary portable infrared video camera developed by scientists at NASA's Jet Propulsion Laboratory may open new vistas for doctors, pilots, environmental scientists and law enforcement.
The most current version of the camera is the only one of its kind, according to the development team leader at JPL, Dr. Sarath Gunapala. It was developed by JPL's Infrared Focal Plane Array Technology Group in partnership with Indigo Systems Corporation, Goleta, Calif. It uses highly sensitive quantum-well infrared photodetectors, or large format arrays of infrared detectors, that cover longer wavelengths than previous existing detectors.
"Infrared detectors operating in the 8 to 12-micrometer range have a variety of ground and space-based applications," said Gunapala. "They can be used for early warning systems, navigation, security, flight control systems, weather monitoring and astronomy."
The more sensitive longer-wavelength quantum-well infrared photodetectors could allow doctors to detect tumors using thermographic (heat) analysis. The device, with its very high spatial and thermal resolution, suits the medical field well. The camera's abilities and potential uses will be demonstrated in a few weeks during a surgery at San Diego's Children's Hospital.
The technology may help pilots make better landings with improved night vision and help environmental scientists monitor pollution and weather patterns. Other possible uses include law enforcement, search and rescue, and industrial process control, Gunapala noted. The camera's precision allows it to detect a one-hundredths of a Celsius degree temperature difference.
Each detector is the size of a pixel. The camera has 327,680 of them arrayed in a focal plane of 640 by 512. The array is designed to detect infrared radiation in the 8-to-10-micrometer (millionths of a meter) wavelength range. This is 20 times longer in wavelength, which means 20 times lower in energy, than visible light. At these wavelengths room temperature objects glow the same way red-hot objects glow in visible light.
A quantum-well can be imagined as a very small dimple with electrons in it in a state of rest. When they are disturbed by a photon, the smallest energy package in a beam of light, the electrons pop out. The electrons then produce a current proportionate to the amount of infrared photon energy that struck them. By measuring that current, the photodetector can tell how much infrared light comes from various sources at the scene being photographed.
In a quantum-well infrared detector, light is "seen" when it has the right energy (wavelength) to knock an electron out of the quantum-well. The cameras can be made-to-order for the wavelength desired out of easy-to-manufacture materials.
For infrared light detectors to work, they must be very cold. The new camera, which weighs about 3 kilograms (7 pounds), contains a cooler that is about the size of fist. The small motor cycles the helium gas millions of times and cools the camera from room temperature to very low temperatures, approximately minus 343 degrees Fahrenheit (minus 208 Celsius), in about eight minutes.
The camera can be battery-operated to allow transportability, but the current prototype plugs into a 110-volt wall socket for power. It is approximately 4.4 centimeters (1.7 inches) wide, 7.5 centimeters (3 inches) deep and 5.2 centimeters (2 inches) high.
This quantum-well infrared photodetector technology has been developed over the past decade under contract to NASA's Breakthrough Sensors and Instrument Component Technology Program.
Contacts: JPL/Colleen Sharkey (818) 354-0372