| 摘要 |
A laser generating tube and associated optical system is mounted on a laser support which is mounted to pivot relative to a cradle about a first axis. The cradle is mounted to pivot about a second axis (transverse to the first) relative to a frame. First and second levelling motors control the angle of the support relative to the cradle and of the cradle relative to the frame. Thus the slope of the laser beam emitted from the optical system is controlled in two planes. Fixed to the laser support is a grade control device consisting of a base and a grade plate which is tripod mounted relative to the base, two of the three support points being on screws which are driven by first and second grade motors so that the slope of the grade plate relative to the base (and then to the laser support) may be adjusted in two planes. First and second potentiometers are arranged to adjust as the screws are turned. Fixed to the grade plate are two level-sensitive transducer vials which are parallel to the first and second axes and give out an electrical signal proportional to slope. Switches, manually or otherwise controlled, are set at the desired slopes and through the potentiometers servo-control the grade motors to adjust the grade plate (and thus the vials) relative to the base. The vials then servo-control the levelling motors until the vials are horizontal and thus the laser and optical system are at the slope set by the switches.
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