| 摘要 |
<p>A photoelectric device (5) receives radiation passing through the medium and an electrical circuit decodes changes in the irradiation of the photoelectric device. The radiation source (L) is a monochromatic coherent radiator and the radiation follows simultaneously a measuring beam path and a reference beam path, extinction being less in the reference beam path than in the measuring beam path. The radiation from both paths acts on the same photoelectric device and the optical distances of the two paths and the intensity ratio of measuring and reference beams are so set that the two beams are mutually extinguished by interference at the photoelectric device.</p> |
