84b7a5d0   
   XPost: sci.physics, sci.physics.electromag   
   From: gah@ugcs.caltech.edu   
      
   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.   
      
   Traditionally they were done using electron optics, image   
   the input on a photocathode, then through an electron lens onto   
   a phosphor screen, which you then view.   
      
   There are IR to visible light converters that are charged by   
   exposing them to light, then, in the dark they will glow with IR   
   illumination. I believe not efficient enough.   
      
   > I had assumed these devices were regulated, limited to Big   
   > Brother's storm troopers, can't let the peons have access to   
   > dangerous toys!  But then I saw an ad for one at a sporting   
   > goods shop (aimed at hunters) (deer, not man hunters,   
   > presumably).  This is a case where I'm glad to be wrong.   
      
   Maybe the higher quality ones are. They now sell them in   
   toy stores.   
      
   -- glen   
      
   --- SoupGate-Win32 v1.05   
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