From: pcdhSpamMeSenseless@electrooptical.net   
      
   On 03/27/2014 08:44 AM, sgpopticsguru@gmail.com wrote:   
   > Hi,   
   > I have a quick question. I searched but couldn't find any data on the   
   internet. The CFLs and LED lights usually run at a 100 Hz through their   
   ballast. If you take a high frame rate camera you can easily see the   
   flickering on the screen. My question is    
   during this 100Hz operation, does the CFL or Led lights change their spectrum   
   output? (I mean during their 1msec period).   
   >   
   > In other words, is the spectrum different at the peak and at the lowest   
   point of the AC current? I have a spectrometer but not fast enough to observe   
   any change. Inputs appreciated?   
   >   
      
   Yup.  The emission lines respond faster than the phosphor.  Near the   
   ends of the tube, electronic ballast tubes have emission lines modulated   
   by up to the ~50th harmonic of the 40 kHz drive frequency.   
      
   Makes high-bandwidth IR links much harder to do nowadays.   
      
   Cheers   
      
   Phil Hobbs   
      
   --   
   Dr Philip C D Hobbs   
   Principal Consultant   
   ElectroOptical Innovations LLC   
   Optics, Electro-optics, Photonics, Analog Electronics   
      
   160 North State Road #203   
   Briarcliff Manor NY 10510   
      
   hobbs at electrooptical dot net   
   http://electrooptical.net   
      
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