| 摘要 |
PURPOSE:To obtain a stable length measuring device having good accuracy, by providing a tape like body having a large number of marks at a constant pitch and a plurality of light receivers arranged at positions shifted to each other. CONSTITUTION:A floodlight projector 13 capable of projecting light to the through-holes 7 provided to a measuring tape 5 by drilling emits light to a plurality of light receivers 14 provided under the tape 5 and is composed of lead and provided directly above the intermediate position in the arrangement direction of the group of the light receives. The light receivers 14 are composed of photodiodes and arranged at positions shifted to each other along the longitudinal direction of the tape 5. By this constitution, when the light from the floodlight projector 13 is received by the light receivers 14 through the through-holes 7, a cyclic analogue signal having the phase difference corresponding to the arranging interval of the light receivers 14 is outputted to be amplifier by an amplifier 15 and converted to digital quantity by an A/D converter 16 and the draw-out quantity of the tape 5 is operated on the basis of said digital quantity in a CPU 8 according to a predetermined program.
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