April 6, 2010: U.S. Army soldiers move to an over watch position in Sabari, Khowst province, Afghanistan.U.S. Army/Sgt. Jeffrey Alexander
Jan. 4, 2010: Capt. David Snodgrass checks his night vision goggles before a mission at Bagram Airfield, Afghanistan.U.S. Air Force / Tech. Sgt. Jeromy K. Cross
Breakthroughs in flexible semiconductors may lead to better and easier night vision for the military and law enforcement, thanks to the University of Wisconsin.
To build goggles with more accurate night vision for pilots and soldiers, the DOD and USAF Office of Scientific Research worked with University of Wisconsin-Madison electrical and computer engineer professor Zhenqiang "Jack" Ma.
The Air Force Office of Scientific Research gave the school $750,000 in funding to support the first project: a new curved surface for night-vision goggles.
A curved surface can improve the field of view, making it wider, for night-vision goggles. But building a curved surface is tricky, and requires not just highly photosensitive materials but also a pliable material.
'They are looking for the highest resolution they can get. Something that can take one picture with everything in it.'
- University of Wisconsin professor Zhenqiang "Jack" Ma
Silicon used in many image sensors is simply not good enough; Ma’s solution was to use flexible germanium nanomembranes instead -- that’s the obscure element germanium from the periodic table, not geranium as in potted plants on the porch.
High “dark current” has made this flexible semiconductor material difficult to use in imagers. Dark current is background electrical current that flows through photosensitive materials whether or not the material is subjected to light.
Germanium-based imagers have an elevated dark current and this causes noisier images.
Ma solved the problem by reducing the dark current with new tech that makes this critical flexible material practical to use.
IR and visible image in one picture
In a second imaging project, Ma focused on the search for one picture combining IR and visible images in the highest possible resolution.
The DOD gave him a second $750,000 in funding to develop a military surveillance imager that can span multiple spectra and combines infrared and visible light into a single image.
Currently, the traditional approach uses one sensor for visible light, another for IR images and then the two versions of the image are combined.
"They are looking for the highest resolution they can get," Ma said. "Something that can take one picture with everything in it."
IR can penetrate obscurants like dust and smoke that visible light might find difficult.
While visible light imagers can be made with relatively cheap silicon, IR imagers are made of materials that are not compatible with silicon.
Ma solved the incompatibility problem by using a heterogeneous semiconductor nanomembrane and by layering the two incompatible materials in each pixel on top of each other.
“Simultaneous visible and IR imaging allows [the military] to see everything," he said.
Ballet dancer turned defense specialist Allison Barrie has traveled around the world covering the military, terrorism, weapons advancements and life on the front line. You can reach her at firstname.lastname@example.org or follow her on Twitter @Allison_Barrie.