| 摘要 |
The sensor is located at a section of the paper band (10) which is running essentially flat. The course of the band is not affected by the lower section (14). Preferred features: The lower section has a streamlined form, controlling pressure against the band. The shape is such that the lower section experiences a driving force along the band. It can be constructed to pull a reduced pressure against the band. A relieved region follows the area of contact. A step (not shown) follows it in a variant, or a bump may be included. In a further variation, a free running roller forms the lower section. The roller is small in radius, compared with the length of the flat section of material. The lower section is a transverse cylindrical smoothing iron with similar aspect ratio. The lower section is pressed against the band by a spring- or spring-loaded arm (28) at an angle to it. Suction is applied from the lower surface. An upper section of the apparatus (12) is supported above the band using an air cushion. An optical system conducting e.g. triangulation is used for measurement. Size of a light spot is on the surface is measured. Transit time of electromagnetic waves especially, is measured.
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