Fast modulation measurement profilometry based on phase-shifting and modulation ratio

The modulation measurement profilometry technique is characterized by vertical measurement, effectively mitigating issues related to shadows and occlusions during the measurement process. This paper proposes a fast modulation measurement profilometry based on phase-shifting and modulation ratio, and establishes a corresponding measurement system. The measurement system comprises a high-speed camera and a high-speed projector, integrated with a beam splitter to form a coaxial optical measurement system. A cylindrical lens is installed in front of the projector lens to separate the vertical and horizontal grating image planes along the measuring depth direction, thereby forming the measurement area. Vertical and horizontal binary sinusoidal gratings with three-step phase shifts are respectively and cyclically projected onto the surface of a moving object, responsively capturing the modulation information of the fringes in both vertical and horizontal directions, and then calculating the modulation ratio. By utilizing a pre-established mapping relationship between height and modulation ratio, the three-dimensional surface profile of the measured object is successfully and rapidly reconstructed. Experimental results demonstrate the feasibility of the proposed method.