Light-beam scanning apparatus comprising divergent or convergent light-shaping means

摘要

An apparatus for light beam scanning corrects a curvature of field which is created in the apparatus and accordingly obtains an excellent drawing quality, without increasing a processing accuracy of a lens surface. A light beam (LB) oscillated by a semiconductor laser (10) is shaped by a collimate lens (20) into divergent light which diverges within a main scanning surface, impinges upon a scanning lens group (40) through a galvanometer mirror (30), and is focused on a surface-to-be-scanned (50). In the scanning lens group (40), center rises r1, r3, r4 and r6 are created in a first surface R1, a third surface R3, a fourth surface R4 and a sixth surface R6, respectively. Since such light beam (LB) which impinges upon the scanning lens group (40) is divergent light which diverges within the main scanning surface, it is possible to correct a curvature of field of an image surface (IS) and obtain an excellent drawing quality. <IMAGE>