From: oh2hvj@sral.fi   
      
   Hi,   
      
   We're building a device with a light source that has multiple LEDs   
   combined to give suitable wavelength distribution. Earlier I asked   
   here advice for doing this.   
      
   We ended up with a structure where  the LEDs are mounted on a PCB,   
   surrounded with high-reflectivity foil. The LEDs are shining on   
   a semisphere from the same material and the exit fiber is mounted   
   in the middle of the LEDs. Kind of an integrating sphere, the   
   wavelenght distribution, spatial form are excellent and the   
   solution is very stable and easy to manufacture. Also, we've   
   got about 90% of the theoretical coupling maximum, which is   
   surprisingly good for a quick prototype. (The theoretical coupling   
   maximum is nothing to write home about..)   
      
   Ok, now we've got a good working prototype which fulfills the   
   original measurement target.   
      
   The customers product manager has some technical background and keeps on   
   suggesting different solutions which might in his opinion improve the   
   efficiency.  I'm usually very good at explaining complicated technical   
   issues to people of different leve, but in this case I feel completely   
   unarmed!   
      
   So, the question is: how would you explain the idea of optical invariant   
   as simply as possible ?   
      
   --   
   Mikko   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)