Development of a non-contact coordinate measuring machine for 2-dimensinally curved hard x-ray focusing mirrors

We manufacture ultra-precise X-ray mirrors, known as “Osaka Mirror,” with sub-nanometer accuracy for synchrotron radiation and free-electron laser facilities worldwide. Our advanced metrology and polishing techniques, including RADSI, MSI, and elastic emission machining, enable the production of these high-precision mirrors. Two-dimensionally curved focusing mirrors, such as Wolter, ellipsoid, and parabolic mirrors, have gained attention due to their advantages, including fewer required mirrors, easier alignment, and larger apertures. However, measuring these mirrors with sub-nanometer accuracy using RADSI and MSI is challenging. To address this, we have developed a coordinate measuring machine (CMM) specifically for two-dimensional curved mirrors. The CMM features two-axis air-bearing stages for scanning, a non-contact probe with 0.03 nm resolution, and error correction via heterodyne interferometers. By suppressing lateral displacement, we have improved measurement accuracy and reliability.