Chromatic confocal sensor-based sub-aperture scanning and stitching for the measurement of microstructured optical surfaces

The noncontact optical probe-based surface scanning is promising for the measurement of complex-shaped optical surfaces. In this study, by combining a chromatic confocal sensor and a planar nano-positioning stage, a sub-aperture scanning and stitching method is developed for the noncontact measurement of the microstructured optical surfaces, with the measured form accuracy being irrespective of the accuracy of the global scanning stage. After the scanning, the Gaussian process-based denoising is employed to remove the measurement noises, and a hybrid registration algorithm is proposed to achieve a 6-DOF alignment of any neighbored sub-apertures. For the registration, the differential evolution-based minimization is implemented to find a coarse transformation which then serves as the initial value for the iterative closest point-based fine registration. The hybrid method is beneficial in finding an optimal registration with a greatly reduced computation burden. Finally, the effectiveness of the developed measurement system, as well as the stitching algorithm, is comprehensively demonstrated through practically measuring a sinusoidal micro-grid surface. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

This study develops a sub-aperture scanning and stitching method for the noncontact measurement of microstructured optical surfaces by combining a chromatic confocal sensor and a planar nano-positioning stage. After scanning, denoising is employed to remove measurement noises, and a hybrid registration algorithm is proposed for 6-DOF alignment of sub-apertures with greatly reduced computation burden.