XPost: sci.physics, sci.physics.electromag   
   From: r.peter.webbbbb@gmail.com   
      
   "glen herrmannsfeldt"  wrote in message   
   news:jh26nn$ngj$1@speranza.aioe.org...   
   > In sci.physics.electromag RichD  wrote:   
   >> How do IR, night vision gogglles work?  I'll guess, much like digital   
   >> cameras - lenses, sensor, viewscreen, amplifiers and necessary   
   >> electronics.  My question is, could a unit be designed to operate   
   >> completely passively, just lenses and filters, i.e. no battery   
   >> required, like hand held binoculars?   
   >   
   > They also do amplification, so, no, they can't be passive.   
   >   
      
   Sure they can. You just need a lens or a mirror larger than the human pupil   
   at the front end, and you will get gain. If you don't believe me, try   
   looking at the moon through a large astronomical telescope at low   
   magnification. Unfortunately you generally also get magnification, which   
   depending on the application may be a bad thing. But passive devices can   
   definitely amplify the light that you see.   
      
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