3D measuring in the field of endoscopy

Anton Schick; Frank Forster; Michael Stockmann

doi:10.1117/12.889167

26 May 2011 3D measuring in the field of endoscopy

Anton Schick, Frank Forster, Michael Stockmann

Proceedings Volume 8082, Optical Measurement Systems for Industrial Inspection VII; 808216 (2011) https://doi.org/10.1117/12.889167
Event: SPIE Optical Metrology, 2011, Munich, Germany

Abstract

Industrial optical 3D-measurement techniques are well established to achieve quality targets in production and manufacturing. However measurements inside of objects, especially small ones, are still a challenge since there is no easy access for measurement tools. Inspection tools like endoscopes, which provide a 2D-view or a stereoscopic view of inner surfaces, are commercially available and widely used. Nevertheless, there is no technique for precisely measuring the inner surface geometry of a small hollow object. Especially medical applications would greatly benefit from "dimensional" measuring. Thus a novel approach and a corresponding prototype of a miniaturized endoscopic 3D-scanner are presented. To be suited even for very narrow objects, the prototype has a maximum diameter of 3.6 mm, its flexible design allows for access to bent tubes or canals. The 3D scanning approach is based on the principle of active triangulation, which means that a coded light pattern is projected and then viewed under a different angle. It is usually difficult to realize triangulation setups in a small embodiment. Therefore an optical tandem of a miniaturized pattern projector and a small camera with a resolution of 400 x 400 pixel is presented as a practical solution. The projector projects a pattern of 15 rings of distinct colors into a cylindrical measurement space where the color sequence constitutes a code. The camera uses a catadioptric setup with a spherical mirror to enhance its field of view. It detects the projected rings and is then able to unambiguously reconstruct the 3D-shape of a surface using ray-cone intersection. This so called color coding approach provides several advantages. For example, only a static projection pattern is needed, which greatly reduces complexity and size of the projector compared to phase shifting technologies. Experimental 3D-scans of arbitrarily shaped tubes demonstrate good performance and an accuracy of about 0.1mm.

Citation Download Citation

Anton Schick, Frank Forster, and Michael Stockmann "3D measuring in the field of endoscopy", Proc. SPIE 8082, Optical Measurement Systems for Industrial Inspection VII, 808216 (26 May 2011); https://doi.org/10.1117/12.889167

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