Improved performance of a refurbished photoelectric autocollimator

An old photoelectric Hilger & Watts autocollimator (AC) has been modified at INRIM to perform accurate angle measurements on two axes in a range of +/- 250 ''. A CMOS camera was placed in the focus of the AC's optical system and a software implemented in LabVIEW processes on-line the image of the reticle projected on the camera. The data acquisition is triggerable at a selectable frequency up to some hertz to allow synchronization in critical applications. The AC's sensitivity was determined through a calibration with respect to the national angle standard. The combined standard uncertainty of the AC calibration results to be equal to 0.035 ''.