From: pcdhSpamMeSenseless@electrooptical.net   
      
   On 05/29/2014 03:16 PM, haiticare2011@gmail.com wrote:   
   > Just dashing this off -   
   >   
   > Detecting absorbance changes in a piece of filter paper by diffuse   
   reflectance is   
   > useful in color-change diagnostics.   
   >   
   > I was talking to an engineer at a co. where they have have such a test. He   
   > said measuring the reflection was tricky with a single PD, which was   
   sensitive   
   > to sample position, etc.   
   >   
   > He thought it required an integrating sphere approach.   
   >   
   > Is there a "half baked" approach to getting the benefits of an int. sphere?   
   >   
   > jb   
   >   
      
   If they're using a laser, the issue is speckle size. With a LED source,   
   a normal vertical illuminator geometry should work fine.  The key is to   
   get the LED and the photodiode looking at the same place regardless of   
   distance, i.e. to optically superpose them.   
      
   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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