| 摘要 |
PURPOSE:To reduce the weight of a carriage and to shorten accessing time by means of rapid seeking by shielding parallel beams projected obliquely in a seeking direction by a shielding plate fitted to the carriage and detecting a change in the quantity of light by a photodetector. CONSTITUTION:The shielding plate 20 is fitted to the side of the carriage 6 so that parallel beams projected from a light source obliquely to the carriage moving direction can be shielded. The parallel beams 21 shielded and varied by the shielding plate 20 are detected by the photosensor 4 fixed on a device base 3. Since the parallel beams 21 are completely shielded by the shielding plate 20 when the carriage is positioned on the innermost periphery, no light is received by the sensor 4. Since the quantity of receiving light is changed in accordance with the movement of the carriage 6, the position of the carriage can be correctly detected by computing the output of the sensor 4. Thereby, a linear encoder is not required, so that the weight of the carriage can be reduced and rapid seeking can be attained.
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