Defect information detection of a spare part by using a dual-frequency line-scan method

The surface defect of a moving spare part is measured by a line-scan system online. The experimental system is combined with a line-scan CCD, a LCD projector, a translation stage, and a personal computer. The deformed fringe patterns of the spare part can be captured and stored in the personal computer. The Fourier transform method is used to extract the fringe deformation. Following the geometric relationship between the fringe deformation and the surface height, the full-field surface 3D information can be obtained. Furthermore, the projection dual-frequency composite grating technique is used to solve 2π phase ambiguity problem because of some bigger surface defect steps. Some experimental results are presented to prove the feasibility of the proposed method and the inspection system.