article_Adv.Imging_305 - Solutions for the Electronic...

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W W W . A D V A N C E D I M A G I N G P R O . C O M Solutions for the Electronic Imaging Professional March 2005 A Cygnus Publication
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A Little Night Vision InGaAs shortwave infrared emerges as key complement to IR for military imaging By Martin H. Ettenberg The camouflage pattern on the Humvee blends into the environ- ment in the visible (photo above). In the SWIR band, the pattern in camouflage is very reflective and actually becomes less effective (photo right). A lthough thermal imaging has been well estab- lished for military night vision, indium gallium arsenide (InGaAs)-based shortwave infrared im- aging (SWIR) is quietly earning a growing place as a vital complement to that technology. It is poised to make night vision capabilities even better than they are today. Jeff Paul, program manager for the Defense Ad- vanced Research Project Agency (DARPA), says: “The shortwave region contains F ve to seven times more energy from starlight and the glow of the night sky — even without moonlight — than any other spectral waveband. A variety of very interesting applications starts to come to mind once you have an imager that provides good, passive imagery in the SWIR spectral region. We are very interested in this technology.” The reasons are simple. SWIR detectors and cameras can intrinsically see things that thermal detectors can- not, and they can see them through glass. They can transmit digital information more readily than current image-intensiF er tubes and with greater sensitivity than intensiF ed imagers attached to CCDs (I 2 CCDs). Also, unlike SWIR cameras based on mercury cadmium telluride (HgCdTe) or indium antimony (InSb) detec- tors, InGaAs SWIR cameras operate at 20C, require no cooling or mechanical shutters and never need F eld Non Uniformity Corrections (NUCs). InGaAs is a prov- en material, that has been used in high volumes by the telecommunication industry for more than 20 years. As a result, InGaAs SWIR cameras are as compact, versatile and simple to use as a commercial digital video camcorder. They provide analog video to stan- dard TV or any commercial frame grabber card. Be- cause they deliver simultaneous analog and digital outputs, advanced InGaAs SWIR cameras enable such easy transmission of information that Command and Control can see exactly what the soldier in the F eld sees as he sees it. They are also small and light. An InGaAs SWIR cam- era about the size of a 9-volt battery went into F eld test- ing last year on unmanned aerial vehicles, including the Special ±orces Pointer made by Aeroenvironment Inc. (Simi Valley, CA) EYE-SAFE Also, there is the eye-safe beneF t. It so happens that the “hot” part of the InGaAs detector’s response characteristic is large and peaks in the eye-safe (greater than 1400 nanometers) laser range. This makes In- GaAs the suitable platform for imaging universal eye- safe laser-target illuminators. Lasers and LEDs at 1550 nanometers, moreover, are invisible to the enemy eyes
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article_Adv.Imging_305 - Solutions for the Electronic...

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