| 摘要 |
The light emitted by light source is picked up by the optical fibres of a cable (1) grouped in three flat beams (2a, 2b and 2c) of which the alignments of the beginning of the fibres face, through a space (3), the alignments of the beginning of the fibres of three other flat beams (4a, 4b, 4c) from three cables (5a, 5b, 5c), a photoelectric cell being arranged at the end of each of these cables. The propagation of light may be allowed or interrupted in the space (3) by a screen (6) which may be moved under the influence of a mechanical means, for example a membrane manometer. The response of the cells may be used to act on adjusting means; thereby, the pressure in a closure may be kept constant. The device allows to avoid optical systems composed of lenses.
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