Two-step carrier-wave stitching method for aspheric and freeform surface measurement with a standard spherical...

Area of Science:

• Optics and Photonics
• Metrology
• Surface Science

Background:

• Measuring aspheric and freeform surfaces is difficult due to their complex shapes, large apertures, and significant deviations from spherical forms.
• Traditional interferometry methods struggle with large deviations and require specialized equipment or phase-shifting mechanisms.

Purpose of the Study:

• To propose and demonstrate a novel two-step carrier-wave stitching method for digital Moiré interferometry.
• To enable accurate measurement of aspheric and freeform surfaces using standard spherical interferometers.
• To overcome the limitations of existing methods for complex surface metrology.

Main Methods:

• A two-step carrier-wave stitching technique was developed to expand the measurement bandwidth of digital Moiré interferometry.
• Aspheric and freeform surfaces were measured using a standard spherical interferometer without a phase-shifting mechanism.
• Experimental validation and simulation of residual wavefronts were performed to assess accuracy and repeatability.

Main Results:

• The proposed method demonstrated high consistency with UA3P contact measurement results.
• Experimental results achieved a root-mean-square repeatability better than 1/200λ.
• Simulation results confirmed measurement accuracies of peak-to-valley value of 10^-3λ for various residual wavefronts.

Conclusions:

• The two-step carrier-wave stitching method is effective for measuring surfaces with large residual wavefronts.
• This technique offers a flexible and accurate approach for the metrology of aspheric and freeform optical components.
• The method has significant potential for advancing the manufacturing and quality control of complex optical surfaces.