Researchers at AIST have developed a device that measures the absolute surface profile of curved optical elements with high precision without touching them.

High-precision curved mirrors are used for light collection and wavefront control in extreme ultraviolet (EUV) lithography systems, synchrotron facilities, astronomical telescopes, gravitational wave detectors and more. The accuracy of their surface profiles significantly affects the performance of these devices.

During manufacturing, it is crucial to determine not only fine-scale surface topography but also the absolute surface profile, including information such as the radius of curvature. These measurements are then used to correct the surface profile. However, measuring the surface profile of curved mirrors with accuracy on the order of a few nanometers without damaging the surface has been difficult.