From: cd@notformail.com   
      
   Gentlemen,   
      
   I have a bunch of red lasers I bought a while ago which perform best   
   at 45mA. So I initially thought I'd knock up a current source for that   
   much to keep them happy. However, I then remembered the temperature   
   issue and wondered how best to compensate for that effect. There was   
   some app note I found on the Mouser site which suggested that by far   
   the best way to operate such laser LEDs is to drop the constant   
   current approach and go for constant power instead, sampling the   
   laser's output with a photodiode and rigging up a feedback loop, so   
   whatever light level I get from 45mA at 20 degrees C can be kept   
   stable regardless of the ambient temp or the device's junction temp.   
   However, the app note didn't go into the practicalities. How is one   
   supposed to sample the light output without interrupting the beam?   
   There's just no appreciable spread within the confines of a housing to   
   get any light from the edge region so how could this be done?   
      
   CD   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)