Comparison among illumination options for SWIR sensors

Feasibility of various illumination sources for a SWIR sensor was explored: Edge Emitting Laser (EEL), Vertical Cavity Surface Emitting Laser (VCSEL), and Light Emitting Diode (LED) were evaluated in terms of level of optical power, optical power variation over temperature and image quality. The highest optical power was measured from the EEL, while the LED showed the best images quality: LED ⪆ VCSEL ⪆ EEL, because of the spatial incoherency of LED as well as the lack of optimization of the EEL diffuser. Emission wavelength variation with temperature requires the use of long pass filtering of the illumination sources. If an application needs a narrow band pass filter, the temperature should be controlled. A combination of numerical, graphical, and actual images will be presented to compare the performance of the devices under study.