| 1. |
- Barup, Kerstin, et al.
(författare)
-
Multi-disciplinary lidar applications
- 2010
-
Ingår i: Laser Applications to Chemical, Security and Environmental Analysis, LACSEA 2010. - 2162-2701. - 9781557528803
-
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.
|
|
| 2. |
- Brydegaard, Mikkel, et al.
(författare)
-
Broad-band multispectral microscope for imaging transmission spectroscopy employing an array of light-emitting diodes
- 2009
-
Ingår i: American Journal of Physics. - : American Association of Physics Teachers (AAPT). - 0002-9505 .- 1943-2909. ; 77:2, s. 104-110
-
Tidskriftsartikel (refereegranskat)abstract
- Optical spectral analysis and multispectral imaging provide powerful means for characterizing samples in a wide variety of applications and on many spatial scales. We present a simple implementation of these techniques in the context of microscopy. A modified commercial microscope equipped with a CMOS imaging detector, combined with an array of light emitting diodes with emission ranging from ultraviolet to near-infrared wavelengths, is described, and examples of information enhancement using multivariate analysis are presented.
|
|
| 3. |
- Brydegaard, Mikkel, et al.
(författare)
-
Feasibility study: fluorescence lidar for remote bird classification
- 2010
-
Ingår i: Applied Optics. - 2155-3165. ; 49:24, s. 4531-4544
-
Tidskriftsartikel (refereegranskat)abstract
- We present a method for remote classification of birds based on eye-safe fluorescence lidar techniques. Mechanisms of quenching are discussed. Plumage reflectance is related to plumage fluorescence. Laboratory measurements on reflectance and fluorescence are presented, as well as test-range measurements. Also we present examples of birds' in-flight lidar returns. The methods are suitable for studies of night migrating species and high-altitude classification with implications for the detailed understanding of bird migration and global virus spread. (C) 2010 Optical Society of America
|
|
| 4. |
- Brydegaard, Mikkel, et al.
(författare)
-
Insect monitoring with fluorescence lidar techniques: feasibility study.
- 2009
-
Ingår i: Applied Optics. - 2155-3165. ; 48:30, s. 5668-5677
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the possibilities of light detection and ranging (lidar) techniques to study migration of the damselfly species Calopteryx splendens and C. virgo. Laboratory and testing-range measurements at a distance of 60 m were performed using dried, mounted damselfly specimens. Laboratory measurements, including color photography in polarized light and spectroscopy of reflectance and induced fluorescence, reveal that damselflies exhibit reflectance and fluorescence properties that are closely tied to the generation of structural color. Lidar studies on C. splendens of both genders show that gender can be remotely determined, especially for specimens that were marked with Coumarin 102 and Rhodamine 6G dyes. The results obtained in this study will be useful for future field experiments, and provide guidelines for studying damselflies in their natural habitat using lidar to survey the air above the river surface. The findings will be applicable for many other insect species and should, therefore, bring new insights into migration and movement patterns of insects in general.
|
|
| 5. |
- Guan, Zuguang, et al.
(författare)
-
Assessment of photon migration in scattering media using heterodyning techniques with a frequency modulated diode laser.
- 2009
-
Ingår i: Optics Express. - 1094-4087. ; 17:18, s. 16291-16299
-
Tidskriftsartikel (refereegranskat)abstract
- A novel technique for studying photon propagation in scattering media is proposed and demonstrated, as is believed, for the first time. Photons propagating through the medium, from a frequency-ramped single-mode diode laser, meet a reference beam from the same source, at a common detector, and beat frequencies corresponding to various temporal delays are observed by heterodyne techniques. Fourier transformation directly yields the temporal dispersion curve. Proof-of-principle experiments on polystyrene foam and a tissue phantom suggest, that the new method, when fully developed, may favorably compete with the more complex time-correlated single-photon counting (TCSPC) and the phase-shift methods, now much employed.
|
|
| 6. |
- Guan, Zuguang, et al.
(författare)
-
Gas analysis within remote porous targets using LIDAR multi-scatter techniques
- 2008
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 93:2-3, s. 657-663
-
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.
|
|
| 7. |
- Guan, Zuguang, et al.
(författare)
-
Insect monitoring with fluorescence lidar techniques: field experiments.
- 2010
-
Ingår i: Applied Optics. - 2155-3165. ; 49:27, s. 5133-5142
-
Tidskriftsartikel (refereegranskat)abstract
- Results from field experiments using a fluorescence lidar system to monitor movements of insects are reported. Measurements over a river surface were made at distances between 100 and 300 m, detecting, in particular, damselflies entering the 355 nm pulsed laser beam. The lidar system recorded the depolarized elastic backscattering and two broad bands of laser-induced fluorescence, with the separation wavelength at 500 nm. Captured species, dusted with characteristic fluorescent dye powders, could be followed spatially and temporally after release. Implications for ecological research are discussed.
|
|
| 8. |
- Guan, Zuguang
(författare)
-
Laser Remote Sensing for Environmental Monitoring
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis studies the techniques of laser remote sensing and their applications in environmental monitoring, as documented in several published papers. The environment where the human being live is degrading with an accelerating speed. Quantitative monitoring characterizes the quality of the environment and offers possibilities to solve environmental problems. Laser remote sensing actively probes physical quantities with advantages of, e.g., large spatial coverage and little environmental influence, and hence becomes a very suitable tool for environmental analysis. Light detection and ranging (LIDAR) measures the backscattered light from remote targets using a short-pulsed laser. Three varieties of LIDAR techniques, based on a vehicle-carried laboratory, have been developed in the work within the thesis. Elastic LIDAR measures the elastic backscattering from the atmospheric aerosols, and has been used to comparatively study their vertical distribution above a Swedish rural area and a Chinese Magacity. Differential absorption LIDAR (DIAL) is able to analyze the distribution of trace pollutants in the atmosphere. Vertical measurements of two serious pollutants, atomic mercury and nitrogen monoxide, have been performed in the same Chinese city. Further, DIAL is also proved to be valid for remote gas analysis in multiple-scattering media. Fluorescence LIDAR can recognize the molecules contained in a remote target, through analyzing the laser-induced fluorescence fingerprint. Such a technique is employed in this thesis mainly for ecological studies, particularly for insect and bird monitoring. Promising performances have been revealed through feasibility tests and field experiments. Tunable diode laser absorption spectroscopy (TDLAS) attracts research attention for its compactness, cost-effectiveness, and high sensitivity. The signal-to-noise ratio of a TDLAS can be conventionally improved by applying modulation; while in the thesis, a different idea is proposed and demonstrated by operating the absorption spectroscopy on a zero light background. Proof-of-principle experiments are performed and considerations regarding real-world applications are discussed. GAs in Scattering Media Absorption Spectroscopy (GASMAS) employs diode lasers for gas analysis as well, and wavelength modulation is frequently applied for sensitivity enhancement. Such an advanced TDLAS tool is applied in the thesis for food package monitoring. Finally, fiber-optic remote sensing realizes the environmental monitoring by employing fiber-optic devices, e.g., fiber Bragg gratings (FBGs). Applications of these sensors are usually limited to temperature and stain monitoring. By using a methane catalyst which transfers the ambient methane into heat, FBG sensors become sensitive to methane. The sensitivity can be improved if the sensing FBG is interrogated by another reference grating having a matched spectrum. The multiplexing of such twin-grating-structure sensors is realized, and thus a distributed sensor network is possible to construct.
|
|
| 9. |
- Guan, Zuguang, et al.
(författare)
-
LIDAR technique for Remote Gas Analysis in Solid Scattering Media
- 2009
-
Ingår i: Asia Optical Fiber Communication & Optoelectronic Exposition & Conference, 2008. AOE 2008.. - 9781557528636
-
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
|
|
| 10. |
- Guan, Zuguang, et al.
(författare)
-
Quasi zero-background tunable diode laser absorption spectroscopy employing a balanced Michelson interferometer.
- 2008
-
Ingår i: Optics Express. - 1094-4087. ; 16:26, s. 21714-21720
-
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.
|
|
