| 摘要 |
A light source generates a beam of light which is incident on a detector which generates a trigger signal when the beam incident upon it is occluded by a tool. To avoid trigger signals being produced when the beam is temporarily occluded by coolant drips passing through the beam, the detector produces a detection signal each time the beam is occluded, but only produces a trigger signal if a further detection signal is produced in a specified time interval from the generation of an earlier detection signal. Samples of the detection signal are stored in a buffer. When these stored signals indicate a repetitive pattern a trigger signal is issued. <IMAGE> |
