Uncertainty modeling and analysis of microhole measurement based on grating projection

Grating projection 3D measurement technology is an important optical non-contact measurement technique, which could effectively overcome the limitations of traditional contact measurement methods and show significant advantages in measuring small or complex-shaped holes. However, the measurement results uncertainty tends to be large in the complex measurement process. Achieving an accurate and reliable assessment of measurement uncertainty plays a crucial role in improving the credibility of the results. To assess the uncertainty in grating projection aperture measurement, a model based on the Guide to the Expression of Uncertainty in Measurement (GUM) is proposed. Firstly, the sources of uncertainty are analyzed from both the manufacturing and measurement processes, with particular emphasis on incorporating geometric deformations caused by residual stresses into the uncertainty model. Secondly, the GUM method is used to quantify the uncertainty components and to combine the standard uncertainty. Finally, the Bayesian approach is adopted to optimize the uncertainty model and dynamic update measurement data, achieving real-time optimization of measurement repeatability errors. An example analysis of grating projection aperture uncertainty assessment and optimization is presented to verify the feasibility and effectiveness of the proposed model and optimization method.