| 摘要 |
PURPOSE:To attain an extremely sharp photodetecting action and to detect a track position with high accuracy by providing a shutter plate turnably at a place near a photoelectric detection means and accelerating the shift of a carriage by the shutter plate. CONSTITUTION:A shutter 28 is supported pivotally turnably by a shaft pin 32 of a photoelectric detection means 26 and energized clockwise by a spring 34 provided at the lower side. The distance between a carriage 18 and a contact part 28b is set small enough compared with the distance between the pin 32 and a notch 28a. As a result, the shift of the notch 28a is satisfactorily accelerated to a photodetecting path 100 when the carriage 18 has a contact with the part 28b and the shutter 28 is turned. Thus even a slight movement of the carriage 18 gives a large movement to the shutter 28 to secure the sharp photodetection. In such a way, a track can be detected accurately at its start position. |
