Position monitoring system using rotating laser beam - has photodetector receiving reflected pulse at measured point within scanning sequence

摘要

The position monitoring system uses a flat laser beam (5) lying in a plane which varies about a reference axis (8). A scanning device (4) subjects the laser beam (5) to a succession of relaxed cycles, each comprising a rotation about the reference axis (8) with initial and final planes (19,20) intersecting at the reference axis (8). A photodetector (13) receives points of light lying in a reception plane intersecting the initial and final planes (19,20) and incorporating a second reference axis (14) parallel to the first. The reception plane is positioned so that its segment of intersection with the laser beam (5) cuts the surface of the moving object during scanning, so that the photodetector (13) receives a reflected pulse. A clock circuit measures the interval between the beginning of the scanning programme and the reception of this pulse from which the object position can be calculated.