Improvements in the accuracy and the repeatability of long trace profiler measurements

摘要

Modifications of the long trace profiler at the Advanced Photon Source at Argonne National Laboratory have significantly improved its accuracy mad repeatability for measuring the figure of large fiat and long-radius mirrors. Use ora Dove prism in the reference beam path corrects phasing problems between mechanical errors and thermally induced system errors. A single reference correction now completely removes both of these error signals from the measured surface profile. The addition of a precision air conditioner keeps the temperature in the metrology enclosure constant to within ±0.1 ℃ over a 24-h period and has significantly improved the stability and the repeatability of the measurements. Longradius surface curvatures can now be measured absolutely with a high degree of confidence. These improved capabilities are illustrated with a series of measurements of a 500-mm-long mirror with a 5-kin radius of curvature. The standard deviation in the average often slope profile scans is 0.3 μrad, and the corresponding standard deviation in the height error is 4.6 nm.