This paper presents a new optical system to measure internal cylindrical surfaces combining photogrammetry and fringe projection. The device uses two identical cameras, equipped with spherical and conical lenses, facing each other and aligned with the optical axis. A 360° helical fringe projector is used to project a sequence of phase shifted helical fringe pattern in the inner surface to be measured. The phase patterns are used to identify corresponding points and to reconstruct the surface in a regular cylindrical mesh using an alternative approach. A prototype was built, calibrated and tested. The paper presents the results of an application where two welded joints were measured in a 150 mm (6") diameter pipe. The goal was to inspect for defects in the internal part of the welding seams and to measure the transversal misalignment between the jointed parts.

Date Published: 17 June 2009
PDF: 12 pages
Proc. SPIE 7389, Optical Measurement Systems for Industrial Inspection VI, 73891W (17 June 2009); doi: 10.1117/12.827544

Published in SPIE Proceedings Vol. 7389:
Optical Measurement Systems for Industrial Inspection VI
Peter H. Lehmann, Editor(s)