From: etaloncn@gmail.com   
      
   Dear all,   
   Thanks for your kindly suggestions!   
      
   The doublets were returned to supplier side. The first feedback is on UV   
   curing process. Too strong point source was used in pre-curing. That may bring   
   some effect in cementing layer itself. I try to get some splitted lenses to   
   confirm lenses' surface.   
      
   Thank you all very much!   
      
   Best regards   
   Jeff   
      
   On Tuesday, December 11, 2012 1:59:46 AM UTC+8, anorton wrote:   
   > "Jeff"  wrote in message news:d2d2d724-407   
   -440d-88eb-06300261ef31@googlegroups.com... > Dear Samlon and Anorton, >   
   Thanks for your kindly reply! > > Here I am in a inspection room of an OEM and   
   have not many options and >    
   accessories, even a retro sphere. > > I understand Anorton's suggestion that   
   weak refractive index gap > contribute less on final wavefront. But as OEM,   
   measuring is the top > priority. I will try Anorton's configuration on flat   
   mirror, which should >    
   bring less astigmatism than my own. > > The thinking to decrease aperture of   
   measuring beam comes from below > points. 1, The small aperture bring much   
   less Spherica aberration, which > may bring much less overlapping effect. 2,   
   The IRR happens in    
   central > area. > > The IRR fringe is so like a discontinuous function. I just   
   can not imagine > it caused by polishing process. Maybe it comes from uneven   
   UV curing. I doubt The issue is due to index inhomogeneity of the cement. The   
   cement is very thin    
   so index inhomogeneity has a small effect. You did not say how many fringes   
   was the discontinuity, but lets say it is 1/2 fringe. Lets also assume a   
   generous cement gap of 10 microns. This would require an inhogeneity in the   
   cement index of 0.047 -- a    
   very large amount. If the gap is smaller, or the irregularity larger, it would   
   require even more inhomogeneity to explain the irregularity. Perhaps you are   
   looking at stress-induced birefringence in one of the glass elements caused by   
   the cementing    
   process. This might explain the the odd "overlap" pattern (although I am not   
   sure exactly what you mean by that) you mentioned in the zygo interferogram.   
   Try looking at it between crossed polarizers. You can also use an LCD computer   
   monitor as a    
   polarized light source and polarized sunglasses as an analyzer if you have   
   nothing else. -- Adam Norton Norton Engineered Optics www.nortonoptics.com   
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