Dual-strategy-guided 2D wavelet transform for single-exposure high dynamic range 3D shape measurement

Fringe projection profilometry (FPP) based on structured light is widely used for three-dimensional (3D) shape measurement due to its non-contact nature and high accuracy. However, in practical measurement scenarios, the surface reflectivity of objects varies significantly, leading to a mix of specular and diffuse reflections. This results in the coexistence of underexposed and overexposed areas, which remains a challenging issue in FPP. To address this problem, a dual-strategy-guided two-dimensional (2D) wavelet transform is proposed for high dynamic range (HDR) 3D shape measurement. The proposed method introduces two natural and intuitive strategies derived from the wavelet function expressions and the spectral intensity (energy) distributions to guide the local rotation of the wavelet spectrum for fringe analysis. Additionally, the measurement system employs one projector (single projection) and one camera (single shot) for phase calculation. Simulations and experiments have been conducted to verify the feasibility of the proposed method. In the experimental evaluation, the standard plane and different HDR scenes were measured for quantitative analysis. A comparison of the results with other methods was also performed. The results demonstrated that the proposed method provides what we believe to be a novel solution for single-exposure HDR 3D shape measurement.