Technology: Bump in the Night

Krista D. Zanolli, krista.zanolli@laurin.com

On a moonless night when the sky seems at its darkest, a perpetual atmospheric short-wave infrared (SWIR) light source is present, but typically goes undetected. About 90 km (approximately 56 miles) high in the Earth’s atmosphere, solar energy is agitating the band of hydroxyl ions, causing them to release energy in the form of light. It is with this natural phenomenon that new specialized image sensors can see in the darkest of conditions.

On a moonless night, NoblePeak Vision’s TriWave image sensors achieve revolutionary night vision. Photo courtesy of NoblePeak Vision Corp.

The latest achievement in night vision is the single-chip TriWave, a complementary metal oxide semiconductor (CMOS) image sensors from NoblePeak Vision Corp. of Wakefield, Mass., that can detect this atmospheric SWIR light. The TriWave significantly enhances the wavelength response of a standard CMOS image sensor through the addition of germanium.

Because of its smaller band gap properties, a photodiode made from germanium has longer wavelength sensitivities, enabling it to detect naturally occurring light from the Earth’s atomosphere emitted in the SWIR band of the electromagnetic spectrum with wavelengths of 1200 to 1800 nm (visible light is in the 400- to 700-nm range).

SWIR light cannot be seen by the human eye and cannot be detected by millions of security cameras installed around the world because of their silicon-based CMOS or CCD image sensors.

According to Phil Davies, vice president of sales and marketing at NoblePeak, previous image sensors that could sense in the SWIR were manufactured with a hybrid chip-to-chip assembly, consisting of a sensor array made from complex semiconductor materials, interfaced to a CMOS-based electronic signal readout chip. This made them more complex, expensive and less attractive to commercial security camera OEMs.

“Security and surveillance cameras that are TriWave-enabled can sense this short-wave infrared band and have significant advantages over cameras that use visible and near-infrared (NIR) wavelengths for night imaging,” Davies said.

“Our TriWave image sensor technology enables security and surveillance video cameras to see in zero visible light conditions, while allowing high-resolution imagers with smaller optics, reducing the camera system size, weight and cost. With the ability to see SWIR light, maybe we can finally find out what exactly goes bump in the night,” he said.