A scanning device using a first optical system with a first focal length and a second optical system with a second focal length

摘要

A scanning device which optically scans a surface along a scan line (14, fig. 1b). The scanning device comprises: a radiation source 2 such as a laser to illumination a scanning surface 6; a detection system 8 to detect radiation from the scanning surface and a deflection element 4 which has a scanning centre to scan radiation beam 12. A first optical system 5 with a first focal length f1 converges the radiation from deflection element to a scanning spot 13 and a second optical system 3 such as a parabolic mirror with a second focal length f2 converges radiation from the surface onto the detection system 8. The system is characterised in that the combination of the first optical system and the second optical system images the scanning centre onto the detection system. The combination of the first optical system and the second optical system may form a telescopic system. The detection system may comprise a plurality of detectors (17a-17d, fig. 2) which take radiation from the surface at different angles.