Automatic focus adjustment device for telescope system of levelling instrument

摘要

The focus adjustment device uses an optical beam splitter (18a,18b) for dividing the light between an objective lens system and a focussing plane containing a focus detection device (21), for controlling a focussing lens group within the objective lens system. The beam splitter and the focus detection device are incorporated in a separate unit which is releasably secured to the telescope, together with an optical horizontal compensation system (13).