A Comparison of optical measurements in turbid media

Paul Martinsen, V. Andrew McGlone, Biju Cletus, Rainer Künnemeyer, Robert B. Jordan

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

Abstract

Accuracy and precision are typically among the most important factors in the design of an optical measurement system for quantitative assay of natural products. Often the variation expected in the constituent and absorber of interest is small - perhaps less than 20% of the mean as for soluble-solid concentration in Kiwifruit, for example. Most natural products in their raw form are not pure absorbers: they also scatter light. This complicates the measurement problem as scatter can introduce variation far greater than the absorption we are trying to measure. We describe an experimental system, revolving around the measurement of temperature in the liquid phantom Intralipid. Many absorption bands, including those in water, respond to temperature as subtly as they do to concentration in turbid media, yet temperature can be easily controlled and modulated. We have found this useful for quantifying the precision and accuracy of optical measurements in scattering samples. Two methods, intensity-modulated optical spectroscopy and continuous wave coupled with diffusion theory, have been applied to estimate temperature from the absorption coefficient of Intralipid. The precision of these measurements is compared to more conventional near-infrared multi-spectral and partial least-squares calibrations.
Original languageEnglish
Title of host publicationProceedings of American Society of Agricultural and Biological Engineers Annual International Meeting 2010 (ASABE 2010)
Place of PublicationSt. Joseph, Michigan
PublisherAmerican Society of Agricultural and Biological Engineers
Pages98-118
Number of pages21
Volume1
ISBN (Print)9781617388354
DOIs
Publication statusPublished - 2010
Externally publishedYes
EventAmerican Society of Agricultural and Biological Engineers Annual International Meeting - Pittsburgh, Pennsylvania
Duration: 20 Jun 201023 Jun 2010

Conference

ConferenceAmerican Society of Agricultural and Biological Engineers Annual International Meeting
CityPittsburgh, Pennsylvania
Period20/06/1023/06/10

Keywords

  • temperature
  • scattering media
  • absorption coefficient
  • partial least squares
  • multispectral calibration

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