PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Contact: Jim Doyle
FOR IMMEDIATE RELEASEFebruary 13, 1996
INFRARED CAMERA HAS VARIETY OF USES
A revolutionary new infrared camera developed by NASA
scientists may soon present new possibilities to doctors, pilots
and environmental scientists and as enable defense forces in the
field to identify various types of rockets by their plumes.
The camera, developed at the Center for Space
Microelectronics Technology at NASA's Jet Propulsion Laboratory
(JPL), Pasadena, CA, in partnership with Amber, a Raytheon
company, uses highly sensitive quantum-well infrared
photodetectors, or QWIPS -- arrays of infrared detectors that
cover longer wavelengths than are possible with previously
The camera is the only one of its kind at present, said the
development team leader Dr. Sarath Gunapala of JPL.
The portable infrared video camera has 65,536 QWIPs arrayed
in a focal plane of 256 by 256. Each QWIP is a pixel. The array
is designed to detect infrared radiation in the 8-to 12-
micrometer (millionths of a meter) wavelength range. This is 20
times longer in wavelength (lower in energy) than visible light.
At these wavelengths room temperature objects naturally glow the
same way red-hot objects glow in the visible.
"Infrared detectors operating in the 8- to 12-micrometer
range have a variety of ground and space-based applications,"
said Gunapala. He said they can be used for early warning
systems, navigation, flight control systems, weather monitoring
The higher sensitivity of long-wavelength QWIPs could allow
doctors to detect tumors using thermographic, or heat, analysis,
allow pilots to make better landings with improved night vision,
and environmental scientists to monitor pollution and weather
Other possible uses include law enforcement, search and
rescue and industrial process control, Gunapala said.
A quantum well, Gunapala said, can be imagined as a very
small well 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.
Then the electrons produce a current which is proportionate
to the amount of infrared photon energy which struck them. By
measuring that current, the photodetector can tell how much
infrared light comes from various sources at the scene being
Photodetectors, such as charged coupled devices (CCDs) in
modern video cameras, "see" when the light has enough energy to
knock electrons loose from the detector, creating an electric
current. the longer the wavelength of light, the less energy the
light has to give to the electrons and the colder the detector
must be to avoid confusion with thermal vibrations. It is very
difficult and expensive to make electronic materials that
naturally have "loose" electrons, what may be called "low band-
Quantum well photodetectors are another approach. In a QWIP
detector, light is "seen" when it has the right energy
(wavelength) to knock an electron out of the quantum well.
Instead of looking for low band-gap alloys that have very "loose"
electrons, quantum wells can be made-to-order for the wavelength
wanted out of easy to manufacture materials.
For infrared light detectors to work, they must be very
cold. The new camera, which weighs less than 10 pounds, contains
a Stirling cooler, a closed-cycle refrigerator about the size of
a fist. The small motor cycles the gas millions of times and
cools the camera from room temperature to very low temperatures,
about -343 degrees Fahrenheit (-208 Celsius), in about 10
The camera can be hooked to batteries to make it more
portable, but the current prototype plugs into a 110-volt wall
socket for power. It is 4.4 inches wide, 10.3 inches deep and 7.2
inches high and the actual weight is 9.9 pounds.
This quantum well infrared photodetector technology has been
developed over the past half decade under contract to NASA's
Office of Space Access and Technology.