Optical scanning device and image forming apparatus
AssigneeRicoh Company, Ltd.
InventorShigeaki Imai
Life of this patent
Estimating the term…
Abstract
At least one of a coupling lens and a cylindrical lens has a diffraction lens surface having a ring-band structure with a height h between adjacent ring-bands. The diffraction lens surface has an area A having a shape similar to that of the ring-band structure with a height h′, where h≠h′. The ring-band structure has a function of correcting a fluctuation in focal position of the scanning beam on the scanning surface, and the area A has a function of expanding a focal depth of a light spot on the scanning surface.
Claims16
An optical scanning device comprising:
- a laser light source that emits a light beam;
- an optical unit that guides the light beam to a deflecting unit from the laser light source, wherein the deflecting unit has a deflecting reflection surface and deflects the light beam focused near the deflecting reflection surface by a cylindrical lens;
- and
- a scanning lens that focuses the light beam deflected by the deflecting unit into a scanning beam on a scanning surface, wherein
- at least one optical element of the optical unit has a diffraction lens surface having a ring-band structure with a height h between adjacent ring-bands,
- the diffraction lens surface has an area A having a shape similar to that of the ring-band structure with a height h′, where h′ is different from h.
An image forming apparatus that forms an electrostatic latent image on a photosensitive element, the image forming apparatus comprising:
- an optical scanning device that scans a surface of the photosensitive element with a light beam, the optical scanning device including:
- a laser light source that emits the light beam,
- an optical unit that guides the light beam to a deflecting unit from the laser light source, wherein the deflecting unit has a deflecting reflection surface and deflects the light beam focused near the deflecting reflection surface by a cylindrical lends;
- and
- a scanning lens that focuses the light beam deflected by the deflecting unit into a scanning beam on a scanning surface, wherein
- at least one optical element of the optical unit has a diffraction lens surface having a ring-band structure with a height h between adjacent ring-bands,
- the diffraction lens surface has an area A having a shape similar to that of the ring-band structure with a height h′, where h′ is different from h.
Dependencies are inferred from the claim text.