Optical scanning apparatus and image forming apparatus using the same including relationship between interval between deflector and scanned surface and a natural convergent point

Filing Information

• Patent Number: US7557974
• Application Number: US12243124
• Filing date: 10/01/2008
• Issue date: 07/07/2009
• Prior Publication Data:
  • US20090022518 - 01/22/2009
• Predicted expiration date: 02/09/2027

• U.S. Classifications: 359/205.1  · 347/259  · 359/212.1  ·
• International Classifications: G02B2608 ·
• Related U.S. Application Data:
  CROSS-REFERENCE TO RELATED APPLICATIONS
  This application is a divisional of application Ser. No. 11/672,996, filed Feb. 9, 2007, now U.S. Pat. No. 7,450,284, the entire disclosure of which is hereby incorporated by reference.
• Foreign Priority: JP2006059541 - 03/06/2006 ·
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Patent Family

Abstract

A compact optical scanning apparatus capable of desirably correcting an f characteristic, a field curvature, and other aberrations, and an image forming apparatus using the same, which includes an incident optical system (LA) for guiding a beam from a light source (1) to a deflector (4) and an imaging optical system (LB) for guiding the beam to a scanning surface (7), wherein a scanning field angle region where 1<3 and 2<3 are satisfied exists within effective scanning field angle region, where in a main scanning cross section and for a scanning field angle 1, 2 represents an angle between a principal ray of beam incident on an optical element included in the imaging optical system and located closest to the scanning surface and an optical axis of the imaging optical system and 3 an angle between a principal ray of a beam from the optical element and the optical axis.

Independent Claims | See all claims (10)

1. 1. An optical scanning apparatus, comprising: a light source unit; an incident optical system for guiding a light beam emitted from the light source unit to a deflecting unit; and an imaging optical system for imaging the light beam deflected by the deflecting unit onto a surface to be scanned, wherein the following conditions are satisfied, 0.85≦W/2L, and 0.4|θ3| and |θ2|>|θ3| are satisfied as an absolute value of the scanning field angle (|θ1|) increases, where in a main scanning cross section and for a finite scanning field angle θ1 (deg.) (|θ1|>0), θ2 (deg.) represents an angle formed between a principal ray of a light beam incident on the imaging optical element LR and an optical axis of the imaging optical system and θ3 (deg.) represents an angle formed between a principal ray of a light beam emitted from the imaging optical element LR and the optical axis of the imaging optical system.
2. 6. An optical scanning apparatus, comprising: a light source unit; an incident optical system for guiding a light beam emitted from the light source unit to a deflecting unit; and an imaging optical system for imaging the light beam deflected by the deflecting unit onto a surface to be scanned, wherein the following conditions are satisfied, 0.85≦W/2L, and 0.4|K×θ| (when |θa|<|θ|≦|θmax|).