| 1. |
- Barup, Kerstin, et al.
(författare)
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Multi-disciplinary lidar applications
- 2010
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Ingår i: Laser Applications to Chemical, Security and Environmental Analysis, LACSEA 2010. - 2162-2701. - 9781557528803
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Konferensbidrag (refereegranskat)abstract
- Lidar is a powerful technique normally associated with atmospheric monitoring. However, lidar techniques, also of the laser-induced fluorescence and laser-induced breakdown spectroscopy varieties, provide many new possibilities in unconventional fields including cultural heritage and ecological applications.
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| 2. |
- Guan, Zuguang, et al.
(författare)
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Gas analysis within remote porous targets using LIDAR multi-scatter techniques
- 2008
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 93:2-3, s. 657-663
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Tidskriftsartikel (refereegranskat)abstract
- Light detection and ranging (LIDAR) experiments are normally pursued for range resolved atmospheric gas measurements or for analysis of solid target surfaces using fluorescence of laser-induced breakdown spectroscopy. In contrast, we now demonstrate the monitoring of free gas enclosed in pores of materials, subject to impinging laser radiation, employing the photons emerging back to the surface laterally of the injection point after penetrating the medium in heavy multiple scattering processes. The directly reflected light is blocked by a beam stop. The technique presented is a remote version of the newly introduced gas in scattering media absorption spectroscopy (GASMAS) technique, which so far was pursued with the injection optics and the detector in close contact with the sample. Feasibility measurements of LIDAR-GASMAS on oxygen in polystyrene foam were performed at a distance of 6 m. Multiple-scattering induced delays of the order of 50 ns, which corresponds to 15 m optical path length, were observed. First extensions to a range of 60 m are discussed. Remote observation of gas composition anomalies in snow using differential absorption LIDAR (DIAL) may find application in avalanche victim localization or for leak detection in snow-covered natural gas pipelines. Further, the techniques may be even more useful for short-range, non-intrusive GASMAS measurements, e.g., on packed food products.
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| 3. |
- Guan, Zuguang, et al.
(författare)
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LIDAR technique for Remote Gas Analysis in Solid Scattering Media
- 2009
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Ingår i: Asia Optical Fiber Communication & Optoelectronic Exposition & Conference, 2008. AOE 2008.. - 9781557528636
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Konferensbidrag (refereegranskat)abstract
- LIDAR techniques are used to measure gases in solid scattering media remotely, by analyzing the differential absorption observed in the multiple scattering light. The gas exchange (O-2/N-2) in polystyrene foam is monitored. (C)2008 Optical Society of America
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| 4. |
- Guan, Zuguang, et al.
(författare)
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Quasi zero-background tunable diode laser absorption spectroscopy employing a balanced Michelson interferometer.
- 2008
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Ingår i: Optics Express. - 1094-4087. ; 16:26, s. 21714-21720
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Tidskriftsartikel (refereegranskat)abstract
- Tunable diode laser spectroscopy (TDLS) normally observes small fractional absorptive reductions in the light flux. We show, that instead a signal increase on a zero background can be obtained. A Michelson interferometer, which is initially balanced out in destructive interference, is perturbed by gas absorption in one of its arms. Both theoretical analysis and experimental demonstration show that the proposed zero-background TDLS can improve the achievable signal-to-noise ratio.
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| 5. |
- Larsson, Jim, et al.
(författare)
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A 3-D printed phantom for optical techniques in medicine
- 2017
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Ingår i: CLEO: Applications and Technology, CLEO_AT 2017. - 9781943580279 ; Part F43-CLEO_AT 2017
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Konferensbidrag (refereegranskat)abstract
- Development of optical techniques in medical applications can be difficult due to limited access to realistic phantoms. Here a 3-D printed model based on CT-images of the thorax of an infant is developed and tested.
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| 6. |
- Larsson, Jim, et al.
(författare)
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Comparison of dermal vs internal light administration in human lungs using the TDLAS-GASMAS technique—Phantom studies
- 2019
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Ingår i: Journal of Biophotonics. - : Wiley. - 1864-063X .- 1864-0648. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen and water vapor content, in the lungs of a 3D-printed phantom model based on CT-images of a preterm infant, is evaluated using Tunable Diode Laser Absorption Spectroscopy (TDLAS) in Gas in Scattering Media Absorption Spectroscopy (GASMAS), that is, the TDLAS-GASMAS technique. Oxygen gas is detected through an absorption line near 764 nm and water vapor through an absorption line near 820 nm. A model with a lung containing interior structure is compared to a model with a hollow lung. Compared to the model with the hollow lung, both the mean absorption path length and the transmitted intensity are found to be lower for the model with the structured lung. A new approach, where laser light is delivered internally into the model through an optical fiber, is compared to dermal light administration, that is, illumination onto the skin, for the model with structure inside the lung. The internal light administration generally resulted in larger gas absorption, and higher signal-to-noise ratios, compared to the dermal light administration. The results from the phantom measurements show great promise for the internal illumination approach and a natural next step would be to investigate it further in clinical studies.
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| 7. |
- Larsson, Jim, et al.
(författare)
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Development of a 3-dimensional tissue lung phantom of a preterm infant for optical measurements of oxygen—Laser-detector position considerations
- 2018
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Ingår i: Journal of Biophotonics. - : Wiley. - 1864-063X. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- There is a need to further improve the clinical care of our most vulnerable patients—preterm infants. Novel diagnostic and treatment tools facilitate such advances. Here, we evaluate a potential percutaneous optical monitoring tool to assess the oxygen and water vapor content in the lungs of preterm babies. The aim is to prepare for further clinical studies by gaining a detailed understanding of how the measured light intensity and gas absorption signal behave for different possible geometries of light delivery and receiver. Such an experimental evaluation is conducted for the first time utilizing a specially developed 3-dimensional-printed optical phantom based on a geometry model obtained from computer tomography images of the thorax (chest) of a 1700-g premature infant. The measurements yield reliable signals for source–detector distances up to about 50 mm, with stronger gas absorption signals at long separations and positions related to the lower part of the lung, consistent with a larger relative volume of this. The limitations of this study include the omission of scattering tissue within the lungs and that similar optical properties are used for the wavelengths employed for the 2 gases, yielding no indication on the optimal wavelength pair to use.
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| 8. |
- Lewander, Märta, et al.
(författare)
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Clinical system for non-invasive in situ monitoring of gases in the human paranasal sinuses
- 2009
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Ingår i: Optics Express. - 1094-4087. ; 17:13, s. 10849-10863
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Tidskriftsartikel (refereegranskat)abstract
- We present a portable system for non-invasive, simultaneous sensing of molecular oxygen (O-2) and water vapor (H2O) in the human paranasal cavities. The system is based on high-resolution tunable diode laser spectroscopy (TDLAS) and digital wavelength modulation spectroscopy (dWMS). Since optical interference and non-ideal tuning of the diode lasers render signal processing complex, we focus on Fourier analysis of dWMS signals and procedures for removal of background signals. Clinical data are presented, and exhibit a significant improvement in signal-to-noise with respect to earlier work. The in situ detection limit, in terms of absorption fraction, is about 5 x 10(-5) for oxygen and 5 x 10(-4) for water vapor, but varies between patients due to differences in light attenuation. In addition, we discuss the use of water vapor as a reference in quantification of in situ oxygen concentration in detail. In particular, light propagation aspects are investigated by employing photon time-of-flight spectroscopy. (C) 2009 Optical Society of America
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| 9. |
- Lewander, Märta, et al.
(författare)
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Food monitoring based on diode laser gas spectroscopy
- 2008
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 93, s. 619-625
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Food is frequently packed in a controlled environment of gas, in order to extend shelf life. It is of great importance to be able to monitor the status of the packed food to ensure quality. We demonstrate a technique to monitor the gas inside packages non-intrusively by using a laser spectroscopicmethod in scattering solid materials. The technique named GASMAS (GAs in Scattering Media Absorption Spectroscopy) is based on tunable diode laser absorption spectroscopy and relies on the fact that free gas inside solid materials absorbs much sharper spectrally than the bulk material. Results from time dependent measurements of molecular oxygen and water vapour in packages of minced meat, bake-off bread, and the headspace of a milk carton are presented. We show that the technique allows gas measurements inside the food through the package, and assessment of the integrity of the package.
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| 10. |
- Lewander, Märta, et al.
(författare)
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Gas Analysis in Food Packages Using Tunable Diode Laser Spectroscopy
- 2009
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Ingår i: Asia Optical Fiber Communication & Optoelectronic Exposition & Conference, 2008. AOE 2008.. - 9781557528636
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Konferensbidrag (refereegranskat)abstract
- Gas inside packed food is monitored by a technique named GASMAS, GAs in Scattering Media Absorption Spectroscopy. The sharp gas absorption line in contrast to the broadband bulk absorption enables gas detection in situ. (C)2008 Optical Society of America
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