Patent ID: 6347003
Filing Date: 2002-02-12
Classification: G02B

Abstract:
A multi-beam laser exposure unit, comprising:a plurality of light beam sources each emitting a light beam; pre-deflection optical means for converting said light beams to a convergent light beam in a first direction; deflecting means, having a plurality of reflective surfaces, formed to be rotational about a rotational axis, said first direction parallel to said rotational axis, for deflecting said light beams emitted from said light beam sources in a predetermined direction, wherein said light beams are guided from said pre-deflection optical means to be incident on one of said reflective surfaces at the same time, wherein distances between said light beams on said one of said reflective surfaces are different from each other in a direction parallel to said rotational axis and thereby the light beams are deflected in the predetermined direction at the same time at different pitches; post-deflection optical means having lenses capable of image-forming each of said light beams deflected by said deflecting means to be scanned on a predetermined image surface at a uniform speed, and said lenses capable of correcting influence of variation of an inclination of said one of said reflective surfaces on a position of a light beam on the predetermined image surface, being exerted onto each of the light beams, expressed as deviation of an angle formed between said reflective surface and the rotational axis of the reflective surface; and at least two groups of post-deflection mirror members for separating said respective light beams passed through said post-deflection optical means, a first group of mirror members arranged at different distances from the deflecting means receiving the light beams directly from said post-deflection optical means and a second group of mirror members spaced at a smaller optical-path distance away from the predetermined image surface than the first group of mirror members, wherein at least one of the second group of mirror members receives a light beam reflected from one of the first group of mirror members, and wherein, the first group of mirror members are arranged in such a manner that, of the light beams deflected by the deflecting means, a light beam which forms the shortest distance on said reflective surface from an adjacent beam in a direction parallel to said rotational axis of said deflecting means travels the smallest optical-path distance from a corresponding one of the first group of mirro members to the image surface.