Comparison of Red versus Blue Laser Light for Accurate 3D Measurement of Highly Specular Surfaces in Ambient Lighting Conditions

Inspection or Quality Control is an essential stage of the production line. For some products, their accurate three-dimensional (3D) reconstructions are necessary for inspection [1]. The type of surface of the product plays a critical part in choosing a suitable 3D reconstruction method. The inspection of highly specular surfaces is still a limitation of most of the state-of-art 3D measurement techniques. Most of the available commercial solutions cannot inspect specular surfaces in ambient lighting conditions. This research paper focuses on a simple and accurate 3D measurement technique using laser and stereo cameras for the inspection of reflective surface objects. In this technique, a single laser line is projected onto the surface, and its stereo images are captured and processed for 3D reconstruction. The method overcomes the limitation of traditional methods and works robustly in ambient lighting conditions. As our experiments are performed in ambient lighting conditions, it is essential to project the right type of laser light on the object. Two different colours (Red and Blue) of laser lights are considered. Here, we reconstructed 3D profiles of three different shapes and estimated sizes of these objects using these two lights. This research article compares the output 3D profiles obtained using red laser light with which achieved using blue laser light. The results are quantitatively evaluated in terms of accuracy with the ground truth 3D model of the acquitted objects for accuracy evaluation. We also discuss the dependency on the specularity of the surface.