On Wednesday, May 3, 2017 at 5:28:39 PM UTC-4, lalou...@gmail.com wrote:   
   > Hi all,   
   >    
   > In most of the optical layout I can see for photodetection, light arrives as   
   a focused beam onto the photodetector. I'm wondering if it would equally work   
   with a collimated beam (parallel) onto the detector (without any focusing lens   
   in front of    
   detector). For large area photodetectors, like the photocathode of a PMT, it   
   seems to me that a collimated beam would generate a more repeatable response   
   compared to a beam focused onto one single point, notably in case of   
   photocathode response non-   
   uniformity.   
   > Of course, for imaging detectors, it's clear to me that detector plane must   
   be optically conjugated to sample plane. However, for photometric   
   measurements, where image is not needed, I don't really understand the   
   interest of optical conjugation between    
   sample and detector.   
   >    
   > Thanks,   
      
   For laser sources I rarely use a lens.  Just send the beam onto    
   a photodiode, align from maximum signal.     
      
   George H.   
      
   --- SoupGate-Win32 v1.05   
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