http://www.medicalnewstoday.com/medicalnews.php?newsid=28496
"A new sensor being patented by Ohio State University could be used to detect concealed weapons or help pilots see better through rain and fog. Unlike X-ray machines or radar instruments, the sensor doesn't have to generate a signal to detect objects - it spots them based on how brightly they reflect the natural radiation that is all around us every day. "
