Characterizing the impact of optically induced blurring of a high-resolution phase-shift 3D scanner

A model to predict and characterize the impact of out-of-focus blurring on the range uncertainty associated with the measurement by a phase-shift 3D scanner is presented. First, the reduction of the sine wave magnitude introduced by the projector lenses and the camera lenses is considered. Then, the noise reduction effects related to the camera image blurring introduced by the camera lenses are also included in the model. The main results of this study indicate that the uncertainty for a high-resolution system varies and exhibits a slanted “W” shape, which significantly differs from the inverse square of the range expected from the triangulation equation or the slanted “U” shape, which may be intuitively expected when combining blurring caused by a limited depth of field and the triangulation equation. We provide a comprehensive experimental characterization of a purposely constructed 3D scanner designed to isolate the performance degradation caused by out-of-focus projection and acquisition lenses. This scanner is designed to mimic the characteristics of a high-resolution scanner that can be employed for demanding quality control applications. In the tested configurations, the predicted depth-of-fields were within 16.3% of the corresponding measured values. This concordance between the theoretical results and experimental results suggests that the proposed model can be used to assist the design of phase-shift scanners.