A precise aperture centring device (ACenD) for autocollimator-based surface measuring profilers

A new Aperture Centring Device (ACenD) for precisely positioning small apertures with respect to the autocollimator's optics has been developed. With the new device, differences in the angle response of autocollimators between the calibration at a laboratory and their subsequent application in the slope measuring profilers are significantly minimized. Evaluation of the device with a circular aperture size of d=2.5 mm was carried out in different laboratories. It was verified that the ACenD is capable of achieving a reproducible aperture alignment < 0.1 mm. The device is a substantial aid for the operation of slope measuring profilometers and enables the measurable, documentable, and transferable positioning of apertures that did not exist before.