Cost-effective infrared lenses produced

A new fabrication process that its creators compare with making waffles lowers the cost of infrared lenses for thermal cameras by 70 percent – an accomplishment that could bring luxury-class vehicle features such as night vision within reach of the average car owner.

Infrared lenses are usually made of expensive crystalline materials such as germanium, zinc selenide or zinc sulfide, which can be processed only mechanically. Laborious and expensive processes such as grinding, polishing or diamond-turning are required to shape them correctly.

Because of this, current thermal imagers cost about $2500 and are used mostly in luxury-class vehicles to warn drivers of danger ahead, such as an animal crossing the road.

(Top) Thermal image, taken with pressed lenses in a test camera. (Bottom) Pressed lenses made of chalcogenide glass.

Researchers at Fraunhofer Institute for Mechanics of Materials turned to amorphous chalcogenide glass to make their microbolometer infrared lenses.

“Its softening temperature – that is, the temperature at which it can be formed – is low,” said Dr. Helen Müller, a scientist at Fraunhofer IWM. “We can form it using nonisothermic hot stamping.”

The two pressing tools used to form the glass resemble a waffle iron. In contrast with conventional processed optics, no further refining is needed, and the lenses exhibit the same optical imaging quality as those that were polished.

Once the process is refined enough to make mass production cost-effective, the microbolometers could become practical for applications such as production process monitoring, warning systems and energy audits, the researchers say.