Colour-corrected scanning lens

摘要

A colour-corrected scanning lens is described. The lens has five lens groups, of which three have a positive refractive power and two a negative refractive power. It was realised according to the invention that it is advantageous for the correction of image errors when the refractive power D2 of the second lens group satisfies the inequality <IMAGE> in the case of a normalised total focal length, and the radius of curvature R of the surface, foremost in the direction of the scanning beam, of the second of the two negative lens groups satisfies the inequality <IMAGE> Furthermore, the fifth lens group has a positive refractive power and a convex air/glass surface of small radius of curvature compared with the other surfaces; the centre of this surface coincides approximately with the image point. Correction of the image errors is further facilitated through the observance of further conditions.