Scanning optical apparatus and image-forming apparatus using it

申请公布号：: US6542278(B2)
申请号：: US20010774039
申请日期：: 2001.01.31
申请公布日期：: 2003.04.01
申请人：: CANON KABUSHIKI KAISHA
发明人：: KATO MANABU
分类号：: G02B13/00;B41J2/44;G02B13/18;G02B26/10;G02B26/12;(IPC1-7):G02B26/08
主分类号：: G02B13/00
摘要：: There are provided a compact scanning optical apparatus optimal for high-definition image recording, which is able to uniformize the spot size in the sub-scanning direction in an effective scanning area, and an image-forming apparatus using it. For carrying out scanning by guiding a beam emitted from a light source, through first and second optical elements to a deflecting element and focusing the beam reflectively deflected by the deflecting element on a surface to be scanned, by a third optical element, the third optical element has two or more lenses, radii of curvatures in the sub-scanning direction of a lens surface of at least one lens La out of the two or more lenses continuously change from on the axis toward off the axis in the main scanning direction, a rate of change of the curvatures in the sub-scanning direction within one beam on the lens surface is set to not more than 10%, and the shape of the lens La in the main scanning direction is determined so that F-numbers in the sub-scanning direction of the beam incident to the surface to be scanned are approximately constant in the effective scanning area.