Structured light, using either laser lines or projected patterns, have gained wide use in the profiling parts from extruded parts of complex assemblies. A line of light is projected from one angle and viewed from another angle to provide a view of the profile of the surface using the principles of triangulation. There can be many sources of noise in these systems such as speckle or surface texture which have been addressed by numerous methods. One of the more difficult challenges often encountered with structured light systems is the presence of reflection of the line of light that are not as expected or wanted. These outlier reflections may be due to multiple reflections from one surface to another or in the case of transparent surfaces, from other surfaces behind the surface being contoured. This paper will discuss these challenges and the commonly used assumptions that may not be sufficient to sort out the right light profile, then present several new methods that allow the separation of the desired profile data from the noise.

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Kevin Harding, "Methods for addressing multiple reflections in a structured light profiler," Proc. SPIE 10991, Dimensional Optical Metrology and Inspection for Practical Applications VIII, 109910L (Presented at SPIE Defense + Commercial Sensing: April 17, 2019; Published: 13 May 2019); https://doi.org/10.1117/12.2518261.