Cover story: Shao J F, Ni Y B, Meng Z Z, et al. Three-dimensional shape measurement of composite surface based on defocused binary display and fringe projection[J]. Opto-Electron Eng, 2024, 51(4): 240024

Optical three-dimensional (3D) topography measurement based on structured light is widely used in production and life because of its advantages of fast, nondestructive and high precision.In the existing technologies, fringe projection technology and fringe reflection technology are widely used in diffuse reflection objects and mirror objects respectively, and also provide research ideas and technical basis for the measurement of composite surface objects. Binary fringe defocusing technology can produce high-quality sinusoidal fringe in defocusing area. It is found that the binary fringe has higher contrast and stronger noise resistance than the traditional sinusoidal fringe at the same defocusing degree.

Professor Zhang's research team put forward a method of measuring the 3D shape of composite surface objects with binary and sinusoidal fringes, aiming at breaking through the limitation of camera depth of field and finally realizing the precise measurement of composite surface objects. The researchers put forward an optimized edge method combined with quadratic fuzzy method to model and quantify the defocus phenomenon, and used checkerboard to demarcate the measurement range of the system. The experimental results show that, compared with the traditional sinusoidal fringe, the measurement accuracy of the mirror surface of the composite step and the joint between the mirror surface and the diffuse reflection surface is improved by 8~14 μm by using the proposed method, which provides a new accurate measurement scheme for obtaining the morphology information of the composite surface.