| 摘要 |
<p>A witness plate (12) collects dust or other particulate matter in a controlled environment. The plate is illuminated by a light source (14) so that only the dust appears bright, and causes bright spots to be focussed on a focal plane (25), defined by a CCD array (24). The focal plane is read out on a computer (32) which is programmed to provide sizes and count of the dust particles.</p> |
