| 摘要 |
PURPOSE:To obtain excellent measuring accuracy regardless of the kind of long materials, by repeatedly moving a plurality of running marking bodies at an approximately constant interval, and providing a plurality of detectors on a running path at a specified distance. CONSTITUTION:A mark 1 on each marking body 2, which is coupled to a moving body running on a loop rail by a coupling means, is repeatedly moved at a speed equal to the running speed of a long material. By utilizing the clock frequency of an image sensor 5, which projects a mark image, a distance DELTAlx from a detecting reference point C of each detector 4 to the mark 1 in a detecting region is computed. From a reference length l between the detectors 4 and 4, a length lx between the marks 1 and 1 is obtained. At this time, lx is computed by the expression in the Figure, where (m) is a magnification of a lens, DELTAn (bits) is the deviation of an image at the projecting point of the image sensor, Ls is the width of 1 bit of the image sensor, and lo is the width of the mark 1. |
