Shifted Excitation Raman Difference Spectroscopy - a potential tool for outdoor measurements in precision agriculture
M. Maiwald1, A. Müller1, J. Selbeck2, J. Käthner2, M. Zude2, D. Fleury3, B. Sumpf1, G. Erbert1, G. Tränkle1
Published in:
Proc. SPIE 9488, Sensing for Agriculture and Food Quality and Safety VII, Baltimore, USA, Apr. 21-22, 94880G (2015).
Abstract:
In this work we present Shifted Excitation Raman Difference Spectroscopy (SERDS) as a potential spectroscopic tool for outdoor measurements in precision agriculture. A dual-wavelength diode laser at 785 nm is used as an excitation light source which provides an optical power up to 100 mW in cw-operation. Both emission lines for SERDS show single mode operation with a spectral width of ≤ 11 pm and a spectral distance of about 10 cm-1 over the whole power range. Raman experiments on apples are carried out and show Raman signals from wax layer and β-carotene. Raman investigations under daylight conditions are performed to simulate outdoor measurements. Here, polystyrene (PS) is used as test sample. A broadband signal together with narrow absorption lines of water vapor and Fraunhofer lines of singly ionized calcium (Ca II) mask the Raman lines of PS. Only the strong Raman signal at 999 cm-1 is visible. SERDS efficiently separates the Raman signals of PS from the background signals and a 14-fold improvement of the signal-to-background noise ratio is achieved.
1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
2 Leibniz Institute for Agricultural Engineering Bornim, Max-Eyth-Allee 100, D-14469 Potsdam-Bornim, Germany
3 Ecole d’Ingenieurs de Changins, Duillier Rd. 50, 1260 Nyon, Switzerland
Keywords:
Raman spectroscopy, shifted excitation Raman difference spectroscopy, SERDS, DBR laser, diode laser, dual-wavelength diode laser, 785 nm, agriculture, food analysis.
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