title: Remote nocturnal bird classification by spectroscopy in extended wavelength ranges.
abstract: We present optical methods at a wide range of wavelengths for remote classification of birds. The proposed methods include eye-safe fluorescence and depolarization lidar techniques, passive scattering spectroscopy, and infrared (IR) spectroscopy. In this paper we refine our previously presented method of remotely classifying birds with the help of laser-induced β-keratin fluorescence. Phenomena of excitation quenching are studied in the laboratory and are theoretically discussed in detail. It is shown how the ordered microstructures in bird feathers induce structural "colors" in the IR region with wavelengths of around 3-6 μm. We show that transmittance in this region depends on the angle of incidence of the transmitted light in a species-specific way and that the transmittance exhibits a close correlation to the spatial periodicity in the arrangement of the feather barbules. We present a method by which the microstructure of feathers can be monitored in a remote fashion by utilization of thermal radiation and the wing beating of the bird.
authors: Atomic Physics Division, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden. patrik.lundin@fysik.lth.se
authors: Patrik
authors: P
authors: Lundin
authors: Per
authors: P
authors: Samuelsson
authors: Sune
authors: S
authors: Svanberg
authors: Anna
authors: A
authors: Runemark
authors: Susanne
authors: S
authors: Åkesson
authors: Mikkel
authors: M
authors: Brydegaard
mesh_terms: D000818:Animals; D001717:Birds; D003116:Color; D004867:Equipment Design; D005241:Feathers / Q000502:physiology*; D005843:Geography; D007834:Lasers; D008027:Light; D055095:Optics and Photonics; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence / Q000379:methods; D013057:Spectrum Analysis / Q000379:methods*; D013548:Sweden; D053800:beta-Keratins / Q000378:metabolism*
chemical_list: D053800:beta-Keratins