| 摘要 |
Disclosed is a method for optically generating a scatter pattern of a biaxially stretched foil web at at least two positions of the foil web in the longitudinal and/or transverse direction. The scatter pattern is, in particular, rotated by transverse stretching in relation to a principal orientation direction. This rotation causes a change of the optical anisotropy condition of the foil web. The magnitude of the rotation is measured and utilized for the regulation of the temperature of a temperature field for the thermal fixing of the foil web, the orientation condition of the molecule chains in the foil web being made uniform as a result of the regulation of the temperature field. In order to generate the scatter pattern, a light source and at least one polarizer are disposed on one side of the foil web and an analyzer is disposed on the other side of the foil web. The light beam from the light source is polarized by the polarizer and oscillates in a specific plane of oscillation. The scatter pattern is produced by scattering at the molecule chains of the foil web. Behind the analyzer is situated a light-sensitive element, for example, a photocell or a video camera, which is connected to a computer for the evaluation of the contrast values of the scatter pattern.
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