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Limits of Active Laser Triangulation as an Instrument for High Precision Plant Imaging
Institute of Geodesy and Geoinformation, Chair of Geodesy, University of Bonn, Nußallee 17, Bonn 53115, Germany
Institute of Crop Science and Resource Conservation, Division Plant Nutrition, University of Bonn, Karlrobert-Kreiten-Str. 13, Bonn 53115, Germany
* Author to whom correspondence should be addressed.
Received: 27 December 2013; in revised form: 26 January 2014 / Accepted: 30 January 2014 / Published: 5 February 2014
Abstract: Laser scanning is a non-invasive method for collecting and parameterizing 3D data of well reflecting objects. These systems have been used for 3D imaging of plant growth and structure analysis. A prerequisite is that the recorded signals originate from the true plant surface. In this paper we studied the effects of species, leaf chlorophyll content and sensor settings on the suitability and accuracy of a commercial 660 nm active laser triangulation scanning device. We found that surface images of Ficus benjamina leaves were inaccurate at low chlorophyll concentrations and a long sensor exposure time. Imaging of the rough waxy leaf surface of leek (Allium porrum) was possible using very low exposure times, whereas at higher exposure times penetration and multiple refraction prevented the correct imaging of the surface. A comparison of scans with varying exposure time enabled the target-oriented analysis to identify chlorotic, necrotic and healthy leaf areas or mildew infestations. We found plant properties and sensor settings to have a strong influence on the accuracy of measurements. These interactions have to be further elucidated before laser imaging of plants is possible with the high accuracy required for e.g., the observation of plant growth or reactions to water stress.
Keywords: high resolution 3D laser scanning; plant leaves; chlorophyll; optical properties of leaf surfaces
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MDPI and ACS Style
Paulus, S.; Eichert, T.; Goldbach, H.E.; Kuhlmann, H. Limits of Active Laser Triangulation as an Instrument for High Precision Plant Imaging. Sensors 2014, 14, 2489-2509.
Paulus S, Eichert T, Goldbach HE, Kuhlmann H. Limits of Active Laser Triangulation as an Instrument for High Precision Plant Imaging. Sensors. 2014; 14(2):2489-2509.
Paulus, Stefan; Eichert, Thomas; Goldbach, Heiner E.; Kuhlmann, Heiner. 2014. "Limits of Active Laser Triangulation as an Instrument for High Precision Plant Imaging." Sensors 14, no. 2: 2489-2509.