Confocal Scanning Imaging System for Surface Characterization in Additive Manufacturing System


Yujie Yang

Date of Award


Degree Name

M.S. in Electro-Optics


Department of Electro-Optics


Advisor: Thomas Weyrauch


In this theses we describe the development and evaluation of the prototype for a confocal imaging system with a fiber transceiver that could be incorporated into a powder bed system for laser additive manufacturing to provide information about surface roughness and surface structure to a process controller. The transceiver fiber is mounted to a piezoelectric bimorph actuator which allows for modulation of the fiber tip along a single axis and by reimaging onto the sample surface scans the surface along a line. After evaluating different options for the confocal imaging optical system, a benchtop prototype of the imaging system was built. Two-dimensional scans of sample areas were enabled using a motorized translation stage moving the target orthogonal to the scanning axis. The confocal imaging system prototype was analyzed and calibrated using a standard resolution target, before assessing the system using different samples with rough surfaces.Evaluation of the images obtained from a microfinish comparator with several areas of calibrated surface roughness demonstrated that the approach provides sufficient information to distinguish despite the challenge of needing a large distance between optics and samples in a laser additive manufacturing environment. It was further demonstrated that signal-to-noise ratio in the experimental system was sufficient to image the surface of strongly scattering powder surfaces. Images of different surfaces of test samples made by laser additive manufacturing clearly showed surface features and the dependence of the acquired images on the surface texture and roughness.


Optics, confocal imaging system, surface characterization, fiber scanner

Rights Statement

Copyright 2019, author