| 摘要 |
A scanning device is described which comprises a rotationally symmetrical rotating reflecting facet disc (3) in which a scanning beam (2, 2') is focussed on a face (5, 6) of the facet elements (4). The sensitivity of the device to surface defects or dust particles on the faces of the facet elements can be reduced by means of a first astigmatic element (20) which widens the beam (2') issuing from the detector (10) at the location of the facet disc in a direction transverse to the scanning direction (18), while a second astigmatic element (21) cancels the astigmatism of the first element.
|
