| 摘要 |
<p>The invention relates to a position indicating system employing an alignment laser beam. The object of the invention is to provide such a system with a means of detecting and correcting any error in the x-axis direction additional to detecting and correcting any error in the y-axis direction, which objective is met by a system in which a beam splitter is located in the path of the laser beam to provide a primary beam for the purpose of establishing a datum line and to create a secondary beam for projection on to a target. Thus, with the primary beam set in its required direction, the target is located such that the secondary beam is at its centre, and when any deviation of the primary beam direction is automatically signalled by movement of the secondary beam from the centre of its target.</p> |
