Recent developments in nanoradian-angle metrology

An angle metrology project (SIB58 Angles) addressing the challenging issues related to performance of autocollimators in slope measuring profilers run for three years and was completed recently with cooperation of a wide range of partners. Outcomes of the project which are for interest to the X-ray optics community are presented; new aperture centring device (ACenD) for the accurate centring of a beam-limiting aperture in front of an autocollimator (with a positional accuracy of +/- 0.1 mm), performance of autocollimators with varying distances to reflector at small apertures, developed guides for calibration of autocollimators and reference angle encoders, first 2D calibration of autocollimators, new devices and novel methods for traceable generation and measurement of angles at nanoradian precision.