On Thursday, January 16, 2014 11:43:54 AM UTC-5, gghe...@gmail.com wrote:   
   > On Thursday, January 16, 2014 11:19:18 AM UTC-5, haitic...@gmail.com wrote:   
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   > > On Wednesday, January 15, 2014 6:57:24 PM UTC-5, gghe...@gmail.com wrote:   
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   > > Hi George,   
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   > > My mispent youth - doing TF work. Thanks for your understanding. I am just   
   doing quantitative work, covering a Si Photodiode with a filter that may not   
   preserve an image, just most of the light. So the BP34 (which Phil Hobbs   
   kindly told me about), is    
   about 2.5 mm square, as I recall.    
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   > > The bandpass filters in Edmunds optics cost over $100 for the 12-25 mm dia   
   sizes. But these filters are for the "satin underwear" crowd who don't mind   
   paying high prices for filters that maintain coherence over every square mm of   
   their aperture, a    
   luxury unnecessary in quantitative measurements.   
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   > > The thickness of the bandpass designs I don't know - I'm going to make a   
   wild guess - It's 10 layers X 400 angstroms (40 nm). So that's a thickness of   
   .4 micron, if my math OK. Probably low by 2-3X.   
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   > > The whole thing is a thought experiment, at least to me, to just see what   
   is the minimum required for quantitative measurements in narrow bandwidth   
   filters. Depositing directly onto a Si surface another way to go.   
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   > > JB   
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   > No problem,  I don't even bother looking at optics from Edmunds anymore.     
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   > (too expensive) Thor labs has 12mm IF's for ~$50.   
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   > We buy some unmounted ones from optometrics for ~$28.  (but that price is   
   from an old PO so...)   
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   > George H.   
      
   Thank you George. I'll look into them. Edmunds IS pricey - I note their BaSO4   
   paint >200$. I'm betting its got a minimal binder.   
      
   --- SoupGate-Win32 v1.05   
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