New quality weight used for phase unwrapping in color fringe reflection method

The fringe -reflection technology has been widely applied in the fields of industrial inspection and measurements. In the present study, three-step phase-shifting is developed using the color fringe-reflection approach to inspect a work-piece surface with rotational symmetry characteristics, and an improved experiment is proposed. In addition, by combining Robert gradient with fringe modulation, a new quality weight, referred to as ‘Modulation-Robert gradient variance’ (MRGV), is proposed for quality-guiding the phase-unwrapping (PU) algorithm. In comparison to the traditional quality weights, MRGV presented higher noise immunity and lower PU error in the root mean square (RMS). In addition, in terms of defect detection, MRGV performed better than the other weights. Finally, after MRGV-guided PU conduction, the proposed experiment method is used in combination with an improved Southwell integration algorithm to realize the 3D reconstruction. The reconstruction error is approximately 3.09% lower than that presented by certain other methods. Furthermore, the results indicated that the combination of the proposed method and the new quality weight could effectively detect the defects and offer an accurate measurement of a rotationally symmetrical surface to a certain extent.