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Howard Mark (hlmark)
Senior Member
Username: hlmark

Post Number: 535
Registered: 9-2001
Posted on Monday, April 08, 2013 - 8:14 am:   

Very good question, Alexey. I don't know that anybody has ever studied it.

I think we all know that we can expect the raw optical signal to decrease as the probe is withdrawn from the sample, giving smaller S/N values, but that's about as far as my knowledge goes. For that reason, most measurements are made with the probe in contact with the sample, or at least with the container. Also that since light will spread out from the probe, more sample surface will be observed thus giving better averaging for a heterogeneous sample. In some cases the larger surface of observation may partially compensate for the decrease in S/N, but I don't know any way to tell when that will happen. This would be particularly pertinent when the data are used for quantitative chemometric analysis.

It will be very interesting to see if anyone knows anything more detailed.

\o/
/_\
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Alexey L. Pomerantsev (alpom)
New member
Username: alpom

Post Number: 5
Registered: 10-2009
Posted on Monday, April 08, 2013 - 7:52 am:   

Dear all,

Could anybody recommend publications regarding the influence of the distance between the fiber probe and solid sample in NIR defuse-reflectance measurements?

Reagrds,
Alexey

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