Title:
FTHETA LENS SYSTEM IN OPTICAL SCANNER
Document Type and Number:
Japanese Patent JPH0457010
Kind Code:
A
Abstract:
PURPOSE:To satisfactorily correct the curvature of image in the main/sub-scanning directions by constituting the ftheta lens system of the lens surface constitution. CONSTITUTION:A parallel luminous flux from a light source or a light source unit 1 consisting of the light source and a condensing device forms an image as a line image LI being roughly parallel to the deflecting surface in the vicinity of a deflecting/reflecting surface 3a of a rotary polygon mirror by a cylinder lens 2 being a line image forming optical system. The longitudinal direction of this line image LI is the main scan corresponding direction. The luminous flux reflected by the polygon mirror 3 is allowed to form an image like a spot on the surface 6 to be scanned, and scans uniformly the surface 6 to be scanned in accordance with a uniform rotation in the direction as indicated with an arrow of the polygon mirror 3. Even if the deflecting/reflecting surface 3a generates a surface inclination as shown with a code 3a', an image forming position on the surface to be scanned by an ftheta lens system does not move in the sub-scanning direction. Accordingly, the surface inclination is corrected. In this regard, when the polygon mirror 3 rotates, the reflecting surface 3a rotates centering around an axis 3A, therefore, a misalignment DELTAX is generated between an image forming position P of a line image and the reflecting surface 3a in connection with a rotation of the deflecting/reflecting surface, and a position P' of a conjugate image of the line image by the ftheta lens system is shifted by DELTAX' from the surface 6 to be scanned. This shift amount DELTAX' is given by DELTAX'=beta<2>. DELTAX as lateral magnification beta in the sub-scanning direction of the ftheta lens system.
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Inventors:
ITABASHI AKIHISA
Application Number:
JP16926390A
Publication Date:
February 24, 1992
Filing Date:
June 27, 1990
Export Citation:
Assignee:
RICOH KK
International Classes:
G02B26/10; G02B13/00; (IPC1-7): G02B13/00; G02B26/10
Attorney, Agent or Firm:
Toru Kabayama (1 person outside)
Next Patent: JPH0457011