From: boyd@apt0.sao.arizona.edu   
      
   haiticare2011@gmail.com wrote:   
   > On Friday, January 31, 2014 11:34:24 AM UTC-5, Louis Boyd wrote:   
   >> xxgherold@gmail.com wrote:   
   >>   
   >>> On Friday, January 31, 2014 6:18:23 AM UTC-5, Michael Bzalda wrote:   
   >>   
   >>>> I'd like to use a pattern projector for computer vision tasks. The   
   pattern can be in the NIR range, should not repeat itself but doesn't need to   
   be described exactly, so random noise, speckle etc. should be fine. It would   
   be preferrable, if the    
   pattern can be restricted to a defined field of view instead of being   
   omni-directional and was stable over time. Of course there are several   
   different approaches but I would like to find one which is   
   >>   
   >>>>   
   >>   
   >>>> (a) cheap,   
   >>   
   >>>>   
   >>   
   >>>> (b) robust,   
   >>   
   >>>>   
   >>   
   >>>> (c) efficient (in terms of power consumption),   
   >>   
   >>>>   
   >>   
   >>>> (d) not too complex,   
   >>   
   >>>>   
   >>   
   >>>> (e) has good availability of components and   
   >>   
   >>>>   
   >>   
   >>>> (f) is monochromatic or has small bandwidth.   
   >>   
   >>>>   
   >>   
   >>>>   
   >>   
   >>>>   
   >>   
   >>>> Thanks in advance for any suggestions.   
   >>   
   >>>   
   >>   
   >>> Hmm, what are the different approaches?  I can only think of laser speckle   
   with a moving scattering source.  (So wiggle a ground glass diffusor back and   
   forth.. Well this is going to give a pattern that repeats.)   
   >>   
   >> If the ground glass is left slightly loose in it's holder the chance of   
   >>   
   >> showing  repeatability would be low. The OP didn't mention if the rate   
   >>   
   >> of change of the pattern or direction of pattern motion or the   
   >>   
   >> granularity scale of the pattern matters.  A laser diode can meets all   
   >>   
   >> of the OP's requirements.  A single lens and a field stop can provide a   
   >>   
   >> well defined field of view.   
   >   
   > One way to introduce randomness into the GG is to have, say, 5 led's   
   pointing at the GG screen, and mingle them randomly with a picaxe or similar.   
   You could also glue many of them to an acrylic rod and let the combined light   
   exit out a polished end.    
   The idea is to have their intensities mingle in space and get a lot of   
   randomness that way. This can be done with the pwm output and low pass filter   
   if necessary.   
   >   
   I doubt that LED's would achieve the OP's goal of "monochromatic or has   
   small bandwidth"   
      
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