An LTP stitching procedure with compensation of instrument errors: Comparison of SOLEIL and ESRF results on strongly curved mirrors

Unknown linearity errors of long trace profilers (LTP) are a troublesome source of measurement errors and discrepancies from instrument to instrument, especially on strongly curved surfaces. This article describes a complete procedure of LTP data acquisition and data processing, which allow to, simultaneously, evaluate the linearity error and reconstruct a corrected slope profile. The method has been tested by performing independent measurements of the same mirrors on SOLEIL and ESRF LTP. Results show that independent measurements using this procedure are in agreement down to 0.2 μrad RMS in slope and 1.6 nm in height.