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Karl Norris (knnirs)
Junior Member
Username: knnirs

Post Number: 9
Registered: 8-2009
Posted on Monday, September 14, 2009 - 8:21 am:   

Here is what Dr. Tang reported:
"To exam samples including food products, two different components are needed: 1, collect the photons of interest from background noise; 2, detect the photons collected. The technique we developed can solve the second problem. For your application I think we need to develop an efficient way to collect photons from melamine. The way of light-scattering may not be efficient enough."
This is not completely encouraging, but I think this needs to be explored.
Karl
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Howard Mark (hlmark)
Senior Member
Username: hlmark

Post Number: 264
Registered: 9-2001
Posted on Wednesday, September 09, 2009 - 8:14 am:   

Karl - it will certainly be interesting to find that out, but I suspect that if you can make the measurement, you will still be limited by the scattering and other effects that have plagued us since you first developed modern NIR spectroscopy.

I hope you'll report to us what you learn.

\o/
/_\
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Karl Norris (knnirs)
Junior Member
Username: knnirs

Post Number: 8
Registered: 8-2009
Posted on Tuesday, September 08, 2009 - 8:48 pm:   

Ian
I don't agree with Howard. I wish to measure melamine by transmission through a layer of food products where the
log(1/T)will be about 7.0. I'm not sure this technology will work on a scattering sample, but if it can I want a unit.
I will contact Dr. Tang and let you know his response.

Karl
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Howard Mark (hlmark)
Senior Member
Username: hlmark

Post Number: 263
Registered: 9-2001
Posted on Tuesday, September 08, 2009 - 8:17 pm:   

Ian - yes, I'd seen at least one of those writeups. My opinion is that it's not going to have much impact on the routine use of NIR for chemical analysis, because we've never been limited by lack of sensitivity to the amount of light. The S/N ratio for the raw measurement of the light is on the order of 1 part in 10^5 to one part in 10^6, for state-of-the-art instruments. This is comparable to the precision of balances, which is exceeded, as far as I know, only by the measurement of time.

The limitations of our technology lie elsewhere, in the effects of the sample on the readings, in the effects of drift and other instrumental artifacts on the data, and so forth. And by our limited ability to devise rigorous physical theory to explain the effects.

\o/
/_\
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Ian Goodyer (zinir)
Junior Member
Username: zinir

Post Number: 6
Registered: 5-2006
Posted on Tuesday, September 08, 2009 - 3:23 pm:   

There is a story all over the press about the work of Xiao Tang at NIST who seems to have developed single photon detection methods in the NIR and published his work in Optics Express. For example see: http://www.opticsinfobase.org/abstract.cfm?uri=oe-17-16-14395 and http://www.spectroscopynow.com/coi/cda/detail.cda?id=22157&type=Feature&chId=2&page=1.

I would be interested to hear what the group thinks of this research. Will it lead to NIR spectroscopy sensitivity improvements and will this in turn lead to better detection?

Thanks, Ian

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