Wide-Band Imaging for enhanced Day and Night Vision

Visible-band cameras using silicon imagers provide excellent video under daylight conditions, but become blind at night. The night sky provides illumination from 1-2 μm which cannot be detected with a silicon sensor. Adding short-wave infrared detectors to a CMOS imager would enable a camera which can be used day or night. A germanium-enhanced CMOS imager (TriWave®) has been developed with broadband sensitivity from 0.4 μm to 1.6 μm. A 744 x 576 format imager with 10 μm pixel pitch provides a large field of view without incurring a size and weight penalty in the optics. The small pixel size is achieved by integrating a germanium photodetector into a mainstream CMOS process. A sensitive analog signal chain provides a noise floor of 5 electrons. The imagers are hermetically packaged with a thermo-electric cooler in a windowed metal package 5 cm 3 in volume. A compact ( 3 ) camera core has been designed around the imager. Camera functions implemented include correlated double sampling, dark frame subtraction and non-uniformity corrections. In field tests, videos recorded with different filters in daylight show useful fog and haze penetration over long distances. Under clear moonless conditions, short-wave infrared (SWIR) images recorded with TriWave make visible individuals that cannot be seen in videos recorded simultaneously using an EMCCD. Band-filtered videos confirm that the night-sky illumination is dominated by wavelengths above 1200 nm.