Phil,   
   The ouija puck flies in another direction...   
   Just out of curiosity, do you machine and build your prototypes?    
   I have a machine shop with a cnc swiss lathe and a small lathe plus mini-mill.    
   I have been machining various cavities to measure Hb in a thin arteriole model   
   - One approach is to shoot the light directly through transverse. Another is   
   the reflective cavity approach as discussed by M. Johnson. Still a third is a   
   narrow cavity which '   
   supports' an evanescent wave.   
      
   Speaking of reflective, I saw BaSo4 paint at Edmunds. They use a minimum of   
   binder, and I think that's the secret - the Fresnel formula is the square of   
   refractive index index, so just an light-incoherent binder will reduce   
   reflection considerably, even    
   with no interference.    
      
   ButI don't want to pay XXX $ per ounce, so am thinking of "depleting" TiO2   
   paint of its binder.    
      
   JB    
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)