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Ling Lin - One of the best experts on this subject based on the ideXlab platform.

  • Improving the quantitative analysis accuracy of bagged liquid components with strong scattering by multi-Pathlength data fusion
    Infrared Physics & Technology, 2019
    Co-Authors: Zhang Mengqiu, Xingwei Hou, Ling Lin
    Abstract:

    Abstract This work proposes the application of VIS-NIR spectroscopy as a potential analytical method to rapid and non-destructive quantitative analysis of bagged liquid products. Rapid and non-destructive quantitative analysis of bagged liquid products with strong scattering properties has been widely demanded in many fields, but due to various interference factors such as differences in packaging bags and strong scattering characteristics of products, the model is unstable and the model is less accurate. In order to improve the measurement accuracy and the robustness of the model, this paper utilized the “multi-Pathlength data fusion” to increase the information of the measured substance carried by the spectrum, which is based on the nonlinear relationship between spectrum and optical Pathlength caused by strong scattering. A non-destructive analysis of hemoglobin (Hb) concentration in blood bags was used to test the effectiveness of the method. The experimental results showed that the data fusion of three optical Pathlengths can make the correlation coefficient of Hb in the prediction set up to 0.9915 and make the RMSEP less than 2 g/L. This results demonstrated that the proposed method could significantly improves the analysis accuracy of Hb in blood bags and reduces the requirements for measurement condition, it also provides ideas for the non- destructive measurement of other bagged liquid products.

  • multi Pathlength method to improve the spectrometric analysis accuracy based on m n theory
    RSC Advances, 2016
    Co-Authors: Yongshun Luo, Ling Lin
    Abstract:

    The Pathlength is a special factor in near-infrared (NIR) spectroscopy analysis. It is a physical variable that is similar to the sample concentration, and is a variable combined with the geometric dimension deviation of the sample pool, installation error of the light source and incident optical fiber. The decrease of accuracy caused by the Pathlength changes is a difficult problem in quantitative spectrometric analysis. The proposed “M + N” theory is a measurement theory in which the quantity impacting the measurement accuracy is classified as M elements and N factors. The theoretical connotation and three application methods of N factors are proposed and analyzed based on the definitions of the theory. “M + N” theory provides a set of guidelines to find a variety of ways to solve the negative impact of N factors on the measurement accuracy. In order to verify the effectiveness of three application methods, an experiment was done to predict the concentration of intra-lipids by single Pathlength and multi-Pathlength modelling. The experimental results showed that the prediction accuracy of the multi-Pathlength was higher than that of the single Pathlength. The experimental results also showed that the distribution of the calibration set should be larger than that of the predication set. In this case, the predication accuracy will be improved significantly. The connotation provides a basis for the measurement, and three methods of N factors can be used to improve the accuracy of quantitative spectrometric analysis. Using the multi-Pathlength method to build a model, the errors caused by the replacement of the sample pool and instrument installation are decreased.

  • Multi-Pathlength method to improve the spectrometric analysis accuracy based on “M + N” theory
    RSC Advances, 2016
    Co-Authors: Luo Yongshun, Li Zeyun, Ling Lin
    Abstract:

    The Pathlength is a special factor in near-infrared (NIR) spectroscopy analysis. It is a physical variable that is similar to the sample concentration, and is a variable combined with the geometric dimension deviation of the sample pool, installation error of the light source and incident optical fiber. The decrease of accuracy caused by the Pathlength changes is a difficult problem in quantitative spectrometric analysis. The proposed “M + N” theory is a measurement theory in which the quantity impacting the measurement accuracy is classified as M elements and N factors. The theoretical connotation and three application methods of N factors are proposed and analyzed based on the definitions of the theory. “M + N” theory provides a set of guidelines to find a variety of ways to solve the negative impact of N factors on the measurement accuracy. In order to verify the effectiveness of three application methods, an experiment was done to predict the concentration of intra-lipids by single Pathlength and multi-Pathlength modelling. The experimental results showed that the prediction accuracy of the multi-Pathlength was higher than that of the single Pathlength. The experimental results also showed that the distribution of the calibration set should be larger than that of the predication set. In this case, the predication accuracy will be improved significantly. The connotation provides a basis for the measurement, and three methods of N factors can be used to improve the accuracy of quantitative spectrometric analysis. Using the multi-Pathlength method to build a model, the errors caused by the replacement of the sample pool and instrument installation are decreased.

Ralph P. Tatam - One of the best experts on this subject based on the ideXlab platform.

  • Ratiometric Pathlength calibration of integrating sphere-based absorption cells
    Optics express, 2020
    Co-Authors: Sarah Bergin, Jane Hodgkinson, Daniel Francis, Ralph P. Tatam
    Abstract:

    Chemical sensors based on optical absorption require accurate knowledge of the optical Pathlength of the sample cell. Integrating spheres offer increased Pathlengths compared to single pass cells combined with tolerance to misalignment, making them attractive for use in challenging environments subject to vibration. However, the equivalent optical Pathlength can be degraded by dirt and / or condensation on the inner surface of the sphere. We present a new scheme for in-situ calibration that uses a ratiometric two-beam approach. Results are presented for an integrating sphere used in the measurement of methane by tunable diode laser spectroscopy (TDLS) at 1651nm. Reduced sphere reflectivity was simulated by applying small areas of black tape on the inner surface. At methane concentrations of 1500ppm and 3125 ppm, for areas of contamination up to 2.3% of the sphere wall, the technique reduced the error from over 50% to within ±4%. At a concentration of 6250 ppm and the most severe fouling corresponding to 2.9% wall coverage, the technique reduced the error from 55-65% to within ±11%.

  • In-situ Pathlength calibration of integrating spheres used in measurement of absorbance
    Optical Sensing and Detection V, 2018
    Co-Authors: Jane Hodgkinson, Sarah Bergin, Daniel Francis, Dackson Masiyano, Nicholas M. Davis, S. E. Staines, Ralph P. Tatam
    Abstract:

    When used as samples cells for optical absorbance measurements, integrating spheres offer increased Pathlengths compared to single pass cells combined with tolerance to misalignment. This makes them attractive during alignment of optical instruments and in challenging environments subject to vibration. However, integrating spheres can suffer problems when used in sensitive and / or accurate absorbance measurement. We present our work to date to address these issues in high resolution laser spectroscopy. Firstly, optical interference effects include both random laser speckle and structured interference fringes created by optical feedback to the laser. Secondly, the sphere’s optical Pathlength is a combination of multiple paths that take an exponential Pathlength distribution. At low values of absorbance, the measured signal is linear with concentration, but at higher absorbances signals follow a nonlinear but predictable function of absorbance. Thirdly, our most recent work concerns calibration of the optical Pathlength, which is a sensitive function of its internal reflectivity. In-situ calibration is needed if the sphere is to be used in dirty environments or with condensing samples. Measurements from multiple independent sources and / or detectors are combined to provide compensation from fouling of the sphere walls and windows. Results are presented for an integrating sphere used in the measurement of methane. The emission from a tunable DFB laser at 1651nm was tuned across the gas absorption line to measure its concentration. Reduced sphere reflectivity was simulated by applying small areas of black tape on the inner surface. Finally, we give an example of one application where our results are being put into practice: use of an integrating sphere with a tunable laser at 3.3μm to measure atmospheric methane, installed on a two seater light aircraft.

  • A method for continuous in-situ Pathlength calibration of integrating sphere based gas cells
    Advanced Environmental Chemical and Biological Sensing Technologies XII, 2015
    Co-Authors: Sarah Bergin, Jane Hodgkinson, Daniel Francis, Ralph P. Tatam
    Abstract:

    We introduce a novel approach to continuous in-situ Pathlength calibration of an integrating sphere based gas cell. Using two light sources and two detectors, a four beam ratiometric scheme is constructed, which compensates for component variation and sample chamber contamination. By applying the scheme to both on and off gas line measurements, changes in Pathlength due to cell wall contamination can be identified and corrected. In this way the gas absorption coefficient can be determined continuously without needing to recalibrate the sphere. Results are presented for detection of methane at 1651nm. This method has the potential for extension to other gases such as CO2, CO, H2S, NOx.

D. T. Delpy - One of the best experts on this subject based on the ideXlab platform.

  • optical Pathlength measurements on adult head calf and forearm and the head of the newborn infant using phase resolved optical spectroscopy
    Physics in Medicine and Biology, 1995
    Co-Authors: A. Duncan, M Cope, J H Meek, M Clemence, Clare E Elwell, L Tyszczuk, D. T. Delpy
    Abstract:

    The authors have used an intensity modulated optical spectrometer, which measures the phase shift across tissue experienced by intensity modulated near-infrared light, to determine the absolute optical Pathlength through tissue. The instrument is portable and takes only 5 s to record Pathlength at four wavelengths (690 nm, 744 nm, 807 nm and 832 nm). The absolute Pathlength divided by the known spacing between the light source and detector on the skin is the differential Pathlength factor (DPF) which previous studies have shown is approximately constant for spacings greater than 2.5 cm. DPF results are presented for measurements on 100 adults and 35 newborn infants to determine the statistical variation on the DPF. All measurements were made at a frequency of 200 MHz with source-detector spacings of >4 cm. Results at 807 nm show a DPF of 4.16(+or-18.8%) for adult arm, 5.51(+or-18%) for adult leg, 6.26(+or-14.1%) for adult head and 4.99(+or-9%) for the head of a newborn infant. A wavelength dependence was obtained for DPF on all tissues and a difference in DPF between male and female was observed for both the adult arm and leg. The results can be used to improve the quantitation of chromophore concentration changes in adults and newborn infants.

  • A Monte Carlo investigation of optical Pathlength in inhomogeneous tissue and its application to near-infrared spectroscopy
    Physics in medicine and biology, 1993
    Co-Authors: Mutsuhisa Hiraoka, Mark Cope, P Van Der Zee, Michael J. Firbank, Matthias Essenpreis, Simon R. Arridge, D. T. Delpy
    Abstract:

    In order to quantify near-infrared spectroscopic (NIRS) data on an inhomogeneous medium, knowledge of the contribution of the various parts of the medium to the total NIRS signal is required. This is particularly true in the monitoring of cerebral oxygenation by NIRS, where the contribution of the overlying tissues must be known. The concept of the time point spread function (TPSF), which is used extensively in NIRS to determine the effective optical Pathlength, is expanded to the more general inhomogeneous case. This is achieved through the introduction of the partial differential Pathlength, which is the effective optical Pathlength in the homogeneous medium, and an analytical proof of the applicability of the modified Beer-Lambert law in an inhomogeneous medium is shown. To demonstrate the use of partial differential Pathlength, a Monte Carlo simulation of a two-concentric-sphere medium representing a simplified structure of the head is presented, and the possible contribution of the overlying medium to the total NIRS signal is discussed.

  • wavelength dependence of the differential Pathlength factor and the log slope in time resolved tissue spectroscopy
    Advances in Experimental Medicine and Biology, 1993
    Co-Authors: Matthias Essenpreis, M Cope, P Van Der Zee, Simon R. Arridge, Clare E Elwell, D. T. Delpy
    Abstract:

    The monitoring of tissue oxygenation by the technique of near infrared spectroscopy (NIRS) was first described by Jobsis in 1977 (Jobsis, 1977). The technique relies upon the relative transparency of tissue to near infrared (NIR) light to enable measurements of changes in optical attenuation across many centimetres of tissue. Early NIRS measurements could only derive qualitative changes in tissue and blood oxygenation from the observed variations in tissue attenuation (Brazy et al., 1985). However, data on the optical Pathlength of light in tissue, measured by time resolved techniques employing picosecond laser pulses, have now permitted a quantitative analysis of attenuation measurements to be made (Delpy et al., 1988; Wyatt et al., 1990a). By incorporating information on the optical Pathlength into a modified Beer-Lambert law it is possible to quantify changes in chromophore concentration from the measured changes in tissue attenuation. The optical Pathlength needed in this calculation, the Differential Pathlength (DP) is defined as the local gradient in a plot of the attenuation measured in a scattering medium versus the absorption coefficient of the medium (Cope et al., 1991a; Cope, 1991b). It has been shown in previous studies (Delpy et al., 1988) that the DP can be approximated by measuring the mean distance that a picosecond light pulse travels across the tissue. Furthermore, a dimensionless multiplying factor, the Differential Pathlength Factor (DPF), can be obtained when the DP is divided by the geometric distance between light source and detector on the tissue surface. This factor has been shown, both theoretically and experimentally, to be approximately constant for any tissue once the optode spacing is larger than about 25 mm (van der Zee et al., 1990; van der Zee et al, in press), enabling clinical NIRS measurements to be made with varying optode geometries.

Robert H Byrne - One of the best experts on this subject based on the ideXlab platform.

Silvia Dalla - One of the best experts on this subject based on the ideXlab platform.

  • from sun to interplanetary space what is the Pathlength of solar energetic particles
    The Astrophysical Journal, 2019
    Co-Authors: T. Laitinen, Silvia Dalla
    Abstract:

    Solar energetic particles (SEPs), accelerated during solar eruptions, propagate in turbulent solar wind before being observed with in situ instruments. In order to interpret their origin through comparison with remote sensing observations of the solar eruption, we thus must deconvolve the transport effects due to the turbulent magnetic fields from the SEP observations. Recent research suggests that the SEP propagation is guided by the turbulent meandering of the magnetic fieldlines across the mean magnetic field. However, the lengthening of the distance the SEPs travel, due to the fieldline meandering, has so far not been included in SEP event analysis. This omission can cause significant errors in estimation of the release times of SEPs at the Sun. We investigate the distance traveled by the SEPs by considering them to propagate along fieldlines that meander around closed magnetic islands that are inherent in turbulent plasma. We introduce a fieldline random walk model which takes into account the physical scales associated to the magnetic islands. Our method remedies the problem of the diffusion equation resulting in unrealistically short Pathlengths, and the fractal dependence of the Pathlength of random walk on the length of the random-walk step. We find that the Pathlength from the Sun to 1au can be below the nominal Parker spiral length for SEP events taking place at solar longitudes 45E to 60W, whereas the western and behind-the-limb particles can experience Pathlengths longer than 2au due to fieldline meandering.