| 摘要 |
The arrangement comprises a tracking sensor with a light source, an optical means and a receiver with two photosensitive detectors, as well as a measuring apparatus with a computing unit. The optical means focuses light to provide a beam which falls on a moving web of foil. The tracking sensor may, for example, be installed in a re-winding installation, and during re-winding of the web, senses by means of the beam a marking track which is embossed in the web in the longitudinal direction of the web and which is composed of two different diffraction grating tracks. Each diffraction grating track projects the light diffracted therefrom in a predetermined direction of incidence to a respective detector. The sensed signals supplied by the receiver are converted into a difference signal by the measuring apparatus, and processed to provide correction signals which are supplied to a control means of the re-winding installation in order to compensate for lateral deviation of the moving web of foil.
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