Measuring Leaf Thickness with 3D Close-Up Laser Scanners: Possible or Not?

Jan Dupuis,Heiner Kuhlmann,Christoph Holst

doi:10.3390/jimaging3020022

Abstract

Measuring the 3D shape of plants for phenotyping purposes using active 3D laser scanning devices has become an important field of research. While the acquisition of stem and root structure is mostly straightforward, extensive and non-invasive measuring of the volumetric shape of leaves, i.e., the leaf thickness, is more challenging. Therefore, the purpose of this paper is to examine whether the leaf thickness is measurable using a high precision industrial laser scanning system. The study comprises a metrological investigation of the accuracy of the laser scanning system with regards to thickness measurements as well as experiments for leaf thickness measurements using several leaves of three different types of crop. The results indicate that although the measuring system is principally able to measure thicknesses of about 74 μ m with statistical certainty, the leaf thickness is not measurable accurately. The reason for this can be attributed to the measurable penetration depth of the laser scanner combined with the variation of the angle of incidence. These effects cause systematic uncertainties and significant variations of the derived leaf thickness.

Highlights

Analyzing the 3D shape of plants to understand the plant’s structural response to its environment has become an important tool for plant phenotyping [1]
Three-dimensional measurements are performed on different scales [2] using active and passive imaging systems resulting in 3D point clouds representing the plant’s surface geometry
This section describes the results of the leaf thickness measurements for the three types of crop

Summary

Introduction

Analyzing the 3D shape of plants to understand the plant’s structural response to its environment has become an important tool for plant phenotyping [1]. Three-dimensional measurements are performed on different scales [2] using active and passive imaging systems resulting in 3D point clouds representing the plant’s surface geometry. From these point clouds, phenotypic parameters such as leaf area [3], leaf area index [4], leaf angle [4], stem height [3] or biomass [5,6,7] are derived. The biomass is estimated indirectly using a function obtained by comparing non-invasive measuring techniques to destructive methods, e.g., biomass compared to pixel area using

Objectives

Methods

Results

Discussion

Conclusion