| 摘要 |
PCT No. PCT/FR96/01505 Sec. 371 Date Apr. 7, 1998 Sec. 102(e) Date Apr. 7, 1998 PCT Filed Sep. 26, 1996 PCT Pub. No. WO97/14030 PCT Pub. Date Apr. 17, 1997An apparatus for measuring fallout of particles on a surface of the type using a telltale plate which is exposed for a particular time period to the fallout of the particles. The apparatus illuminates the telltale plate when it is inserted into the measuring apparatus with the illuminating structure being adapted to emit at least one light beam substantially parallel to the upper surface. An opto-electronic device ir, used to detect light diffused by the particles when illuminated and is adapted to measure the intensity of the light diffused in a direction orthogonal to the surface and to deduce therefrom the degree of contamination per unit surface of the telltale plate by the annular structure around the telltale plate and supporting an optical enclosure and the telltale plate illuminating structure comprises at least two monochromatic optical sources fixed to the annular structure and regularly spaced around the telltale plate to illuminate the upper surface of the telltale plate in the same number of separate directions and at a grazing incidence.
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