5. Conclusion

Six academic laboratories have set up a comparative metrology working group within the optics and photonics network of the CNRS mission for cross-disciplinary and interdisciplinary initiatives, to share their interferometric measurement methods.

3 mirrors (2 planar and 1 spherical) and 2 roughness standard substrates were exchanged in order to compare different know-how through visits to each of the laboratories.

The results show very good agreement on surface reconstruction for the majority of laboratories. The results show that the measurement procedures used in each laboratory are well mastered. They also highlight the influence of the reference mirror, which cannot be completely eliminated by the "rotation" method. It therefore remains difficult to obtain good measurement results on a mirror whose shape deviations are less than those...