Pixels smaller than the photons they detect
21 April 2013
A US high-tech company has demonstrated a long-wave infrared camera that uses pixels just five microns across - about half the size of the photons it detects.
Long-wave infrared (LWIR) cameras are used in military applications as thermal imagers to detect humans at night. These cameras are usually mounted on vehicles as they are too large and too expensive to be carried by a single combatant. Now, DARPA researchers have demonstrated a new five-micron pixel LWIR camera that could make this class of camera smaller and less expensive.
Engineers at DRS Technologies, Inc., working on the DARPA Advanced Wide FOV Architectures for Image Reconstruction and Exploitation (AWARE) programme, have demonstrated the first LWIR camera that uses pixels only five microns across.
This is the first IR camera with pixels about half the size of the photons it detects - about one-sixth the area of the current state-of-the-art. The pixels are configured in a 1280x720 focal plane array (FPA) — a relatively high resolution for an IR camera.
The benefits of developing smaller pixels for LWIR cameras are similar to those in sisible spectrum cameras, such as those found in mobile phones. Smaller pixels mean smaller optical components and packaging without forfeiting sensitivity, resolution or field of view.
A higher density of pixels over a given area makes it easier to capture the photons from, and thus image, a target. The cumulative result is a smaller, lighter and more portable LWIR camera.
These new LWIR cameras may also be less expensive than current sensors because the cost of FPAs is proportional to chip area. FPAs are processed on a given wafer size. The more FPAs that can be printed on a single wafer, the lower the cost per FPA. Smaller pixels will therefore reduce the size, weight, power and cost.
DARPA hopes that with appropriate optical adjustments, the advantages of smaller pixel FPAs will find a home in a multitude of next generation applications.