Theodolite having object-viewing telescope with auto-focussing, for construction industry

摘要

The theodolite has an automatic focussing system for a telescope having two objective lenses, each producing an image, two line sensors (21) each having a number of light sensitive elements on which the object image is formed. A focussing lens group (12) with a drive to move it in the direction of the optical axis of the telescope controlled by data provided by the line sensors. A pulse recorder (46) detects the position of the focussing lens group whilst a CPU (47) selects the number of light sensitive elements of every line sensor to be used when focussing, the latter number depending on the position of the focussing lens groups. A control system (45,47) controls the drive (43,44) according to the data provided by the light sensitive elements selected.