High-precision profile measurement method for axisymmetric aspheric mirror (invited)

In order to achieve the goal of high-precision and traceable aspheric surface profile measurement, a mathematical model of the measurement trajectory is established for the surface profile measurement of axisymmetric aspheric mirrors, and a non-contact coordinate scanning measurement method with independent metrology loop is proposed. The method applies a separated metrology frame, which effectively reduces the influence of each motion module on the measurement accuracy of the system during the measurement process; the probe adopts a four-quadrant interferometry system with integrated array waveplates, which improves the dynamic performance of the probe and is more conducive to the measurement of complex aspheric surface shapes; the motion module with a common reference between the scanning actuator and the multiplexed laser interferometry system is designed to track the position information of the scanning motion mechanism in real time, which improves the accuracy of the scanning motion and enables the measurement of the surface shape. The scanning actuator is designed to track the position information of the scanning motion mechanism in real time to improve the accuracy of the probe motion and make its measurement value traceable to the definition of "meter". The measurement device is built and the surface profile of the standard sphere and aspheric mirror are measured separately. The test results show that the measurement error is less than 0.2 μm and the repeatability accuracy was 70 nm, and the system measurement accuracy reaches submicron level.