| 摘要 |
A device and method are disclosed for the scanning of surfaces, in order to determine the contamination by small particles or defects on or under the surface of a material. Laser beams with different polarisations are directed onto the surface to be scanned, and the light scattered by the contamination by particles or defects on or under the surface is collected and sampled, in order to obtain electrical signals for this. The electrical signals are then processed and form an output signal for the scanned contamination or the scanned defects. In the illustrated and described embodiment, two polarised laser beams, of which one is a laser beam with "P" polarisation and the other is a laser beam with "S" polarisation, are directed separately onto a monitoring region, so that the beams fall on a common point on the surface to be scanned. The scattered light is then collected and divided into two components depending upon whether they have been scattered from the polarised laser beam "P" or from the polarised laser beam "S", each component being separately sampled whereupon the electrical output signals are processed in order to provide the desired indication.
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