Development and evaluation of a petal thickness measuring device based on the dual laser triangulation method

Abstract

The growth and health status of plants can be evaluated by their petal or leaf thickness. However, the thickness of these sections is difficult to measure because of the irregular curvature of petal and leaf surfaces and their soft nature. The petal surface is easily damaged when traditional contact mechanical apparatus is used to measure it. In this research, we developed a novel noncontact measuring device that uses dual laser triangulation based on the Scheimpflug principle to measure petal thickness. A cubic spline method is employed to curve fit the multipoints of the petal surface after dual laser triangulation module measurement. The actual petal thickness can be calculated precisely from the normal equations of curvatures of the petal surface. The measuring range and the resolution of the petal thickness measuring device are ±2. mm and 2. μm/pixel, respectively. The total measurement uncertainty (comprising measurement repeatability, different surface slopes, and colors) of the dual laser triangulation system is less than 16. μm. Using Phalaenopsis as a sample case, we make various compensations according to the different surface curvatures of its petal. © 2013 Elsevier B.V.