| 摘要 |
PURPOSE:To enable the accurate measurement of the length of an object to be measured, by measuring the length in the vicinity of the centers of the opposite end faces of the object and also by detecting and correcting the attitude in conveyance of the object. CONSTITUTION:A light from a projector 5a to receiver 5b is set so that it is positioned at the height determined to be at the center of the thickness of a tread 1 substantially and that it is vertical to the tread. When the tread 1 passes along a conveyance route, accordingly, a length in the vicinity of the center thereof can be measured, and thus an error caused when an edge part tending to be changed in a shape is detected does not occur. In the case when the tread 1 is conveyed in inclination, a counter 11 conducts counting during a period when a sensor 5 detects the tread 1 from the fore end to the rear end thereof, and so the number of pulses, i.e. the counts equivalent to the length of the tread 1, is outputted to an arithmetic circuit 13. Besides, an output of an image sensor 8 in a line sensor camera 7 is inputted to a numerical coding circuit 12, which determines distances x1 and x2 from a reference line to a picture element obtained by detecting the corner parts of the tread 1 and outputs the same to the circuit 13. The circuit 13 corrects the length of the tread 1 delivered from the counter 11, on the basis of the distances x1 and x2 outputted from the circuit 12.
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