A powerful scanning methodology for 3D measurements of small parts with complex surfaces and sub millimeter-sized features, based on close range photogrammetry

A powerful and cost effective photogrammetric scanning methodology, suitable for reconstructing a full 3D digital model of parts with complex surfaces and sub millimeter-sized features, is described. The scanner employed for this purpose is composed of a computerized system that drives and control the movements of a rotary table, and a digital SLR camera for the images acquisition. The object is positioned on the rotary table that rotates at fixed angles, while the digital camera, mounted on the stator through a rigid frame, captures the images. The scanning process has been optimized with the aim to minimize the number of shots and thus, the time needed to obtain a complete 3D digital model, which is not dependent from the dimensions of the object. With the aim to demonstrate the effectiveness of the proposed scanning methodology, four benchmarks have been realized to provide complex examples. The 3D digital models were compared with those obtained with an Optimet™ Conoscan 4000 which uses a conoscopic holographic sensor.