An on-line phase measuring profilometry for objects moving with straight-line motion

Abstract

An on-line phase measuring profilometry for objects moving with straight-line motion is proposed. While a sinusoidal grating is projected onto the moving object, by controlling the phase-shifting direction independent of the object׳s moving direction and shifting the grating for N steps at the same phase of 2π/N, N frames of deformed patterns caused by the object at different positions can be captured by a Charge-coupled Device (CCD) in real time. By pixel matching and information extraction, N frames of equivalent phase-shifting deformed patterns in the region of interest can be cut out. Then the three-dimensional (3D) profile of the moving object can be reconstructed from the equivalent phase-shifting deformed patterns by the unwrapping and the height mapping. The experimental results show the feasibility of the proposed methods. The measured absolute error is less than 0.071mm and its root of mean square error is less than 0.076mm in the measured region of 1–10mm. It is suitable for on-line 3D inspection in automatic assembly lines.