Single wavelength measurements of absorption coefficients based on iso-pathlength point

Feder, Idit; Duadi, Hamootal; Fixler, Dror

doi:10.1364/boe.401591

Cited by 8 publications

(23 citation statements)

References 38 publications

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“…The sample's extinction coefficient, µ, i.e., the sum of the absorption coefficient, µ a , and the scattering coefficient, µ s , can be a priori known via an independent experimental method such as absorption spectroscopy or collimated transmittance spectroscopy. This type of independent extinction coefficient measurement has been reported earlier for pure water [21], various emulsions [22], bioliquids [23], oils [24] and semiconductors [25]; typically, the relative error, σ µ = δµ/µ, in the measurement of the extinction coefficient is of 0.1% to 10% [26][27][28][29][30].…”

Section: Main Conceptsupporting

confidence: 72%

Critical Angle Refractometry for Lossy Media with a Priori Known Extinction Coefficient

Koutsoumpos

Giannios

Moutzouris

2021

Physics

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Critical angle refractometry is an established technique for determining the refractive index of liquids and solids. For transparent samples, the critical angle refractometry precision is limited by incidence angle resolution. For lossy samples, the precision is also affected by reflectance measurement error. In the present study, it is demonstarted that reflectance error can be practically eliminated, provided that the sample’s extinction coefficient is a priori known with sufficient accuracy (typically, better than 5%) through an independent measurement. Then, critical angle refractometry can be as precise with lossy media as with transparent ones.

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Section: Main Conceptsupporting

confidence: 72%

Critical Angle Refractometry for Lossy Media with a Priori Known Extinction Coefficient

Koutsoumpos

Giannios

Moutzouris

2021

Physics

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“…11,16 In a previous study, it was possible to isolate the absorption coefficient from the light intensity even when the scattering was unknown. 15 This was due to the correction for the Beer−Lambert law with the IPL separation of the scattering from the absorption. According to the modified Beer−Lambert law:…”

Section: Introductionmentioning

confidence: 99%

“…When the absorption coefficient is changed but the scattering is unchanged, the IPL point will not appear . This implies that the IPL point allows for the separation of scattering and absorption; changes in absorption do not affect the position of the IPL point, only attenuating its intensity. , Therefore, in order to accurately determine the position of the IPL point, the absorption coefficient must be kept constant, requiring careful sample preparation . It is also important to know the sample diameter because the position of the IPL point is proportional to the optical depth, which is accounted for both by the sample diameter and the distance between the detector and the sample. , In a previous study, it was possible to isolate the absorption coefficient from the light intensity even when the scattering was unknown .…”

Section: Introductionmentioning

confidence: 99%

Detecting Contaminants in Water Based on Full Scattering Profiles within the Single Scattering Regime

Tzroya,

Erblich,

Duadi

et al. 2023

ACS Omega

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Clean water is essential for maintaining human health. To ensure clean water, it is important to use sensitive detection methods that can identify contaminants in real time. Most techniques do not rely on optical properties and require calibrating the system for each level of contamination. Therefore, we suggest a new technique to measure water contamination using the full scattering profile, which is the angular intensity distribution. From this, we extracted the iso-pathlength (IPL) point which minimizes the effects of scattering. The IPL point is an angle where the intensity values remain constant for different scattering coefficients while the absorption coefficient is set. The absorption coefficient does not affect the IPL point but only attenuates its intensity. In this paper, we show the appearance of the IPL in single scattering regimes for small concentrations of Intralipid. We extracted a unique point for each sample diameter wherein light intensity remained constant. The results describe a linear dependency between the angular position of the IPL point and the sample diameter. In addition, we show that the IPL point separates the absorption from the scattering, which allows the absorption coefficient to be extracted. Eventually, we present how we used the IPL point to detect the contamination levels of Intralipid and India ink in concentrations of 30–46 and 0–4 ppm, respectively. These findings suggest that the IPL point is an intrinsic parameter of a system that can be used as an absolute calibration point. This method provides a new and efficient way of measuring and differentiating between various types of contaminants in water.

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“…Furthermore, absorption does not change the position of this point; it only attenuates the intensity [24]. It is therefore the optimal point for absorption measurements since it minimizes changes in optical pathlength [25]. Despite the fact that theoretical and numerical simulations are highly agreed, a consistent difference exists over experimental results [19].…”

Section: Introductionmentioning

confidence: 95%

Influence of Detector Size and Positioning on Near-Infrared Measurements and Iso-pathlength Point of Turbid Materials

2021

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Measuring physical phenomena in an experimental system is commonly limited by the detector. When dealing with spatially defined behaviors, the critical parameter is the detector size. In this work, we examine near-infrared (NIR) measurements of turbid media using different size detectors at different positions. We examine cylindrical and semi-infinite scattering samples and measure their intensity distribution. An apparent crossing point between samples with different scatterings was previously discovered and named the iso-pathlength point (IPL). Monte Carlo simulations show the expected changes due to an increase in detector size or similarly as the detector’s location is distanced from the turbid element. First, the simulations show that the intensity profile changes, as well as the apparent IPL. Next, we show the average optical pathlength, and as a result, the differential pathlength factor, are mostly influenced by the detector size in the range close to the source. Experimental measurements using different size detectors at different locations validate the influence of these parameters on the intensity profiles and apparent IPL point. These findings must be considered when assessing optical parameters based on multiple scattering models. In cases such as NIR assessment of tissue oxygenation, size and location may cause false results for absorption or optical path.

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Single wavelength measurements of absorption coefficients based on iso-pathlength point

Cited by 8 publications

References 38 publications

Critical Angle Refractometry for Lossy Media with a Priori Known Extinction Coefficient

Critical Angle Refractometry for Lossy Media with a Priori Known Extinction Coefficient

Detecting Contaminants in Water Based on Full Scattering Profiles within the Single Scattering Regime

Influence of Detector Size and Positioning on Near-Infrared Measurements and Iso-pathlength Point of Turbid Materials

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