| 摘要 |
PURPOSE:To enable easy detection of the coordinates of an optional obstacle located within a tablet frame by operating the time of interception of beams scanning within the tablet frame. CONSTITUTION:A laser beam L1 strikes upon an obstacle 7 located on an optional point with the counterclockwise rotation of a rotary multiface mirror 2. Next, a laser beam L2 strikes thereupon through the intermediary of a mirror 5x29. Thus, out of the laser beams emitted from a laser oscillator 1 and reflected by the rotary multiface mirror 2, L1, L2, L3 and L4 do not fall on a photodetector 4 because of the presence of the obstacle 7. In this way, on cndition that the rotary multiface mirror 2 rotates at an equal angular speed and that the laser beams are reflected in proportion to the rotation, the time of the interception of the laser beams are reflected in proportion to the rotation, the time of the interception of the laser beams caused by the obstacle 7 within the tablet frame 3 can be found. That is, the time of interception of beams is operated by a processing device 14 based on the data of logic circuits 12 and 13 and the result of the operation is indicated in a coordinates-in- dicating device 15. |
