| 摘要 |
A description is given of a reader for microfilms, in which the distance between the imaging object and the glass sheet or plastic film covering the sheet/flat film is held constant in all the positions of the film gate/trap by virtue of the fact that in principle the lens, which can be displaced in the direction of its optical axis, or a support element joined to it in a fixed manner rests on the sheet or film covering the flat film. Direct contact between the lens or support element, on the one hand, and the covering glass sheet or plastic film, on the other hand, is avoided, however, by arranging for compressed air to be blown between these elements from a nozzle so that the lens or the support element floats on an air cushion of low thickness. As a result, scratches are avoided on the sheet or film, and the ease with which the film gate can be displaced is increased.
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