Optical scanning lens, optical scanning device and image forming apparatus

• US 6,400,391 B1
• Filed: 06/06/2000
• Issued: 06/04/2002
• Est. Priority Date: 06/09/1999
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Suhara, Hiroyuki, Yamaguchi, Takao, Ito, Tatsuya, Ueda, Takeshi, Suzuki, Seizo, Hayashi, Yoshinori, Itoh, Satoru, Kouchiwa, Taira, Aoki, Magane, Takanashi, Kenichi, Hirakura, Koji
• Primary Examiner(s): PHAM, HAI CHI
• Application Number:
  US09/588,342
• Time in Patent Office: 728 Days
• Field of Search: 347/241, 347/244, 347/243, 347/258, 347/259, 359/206, 359/215, 359/226, 359/205, 359/654
• US Class Current: 347/244
• CPC Class Codes: B41J 2/471 using dot sequential main scanning by means of a light deflector, e.g. a rotating polygonal mirror
• CPC Class Codes: G02B 13/0005 having F-Theta characteristic scanning systems employing movable or deformable optical elements G02B26/10
• CPC Class Codes: G02B 26/125 Details of the optical system between the polygonal mirror and the image plane G02B26/123, G02B26/127 take precedence; F-Theta lenses G02B13/0005
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: Y10S 359/90 Methods

Abstract

An optical scanning lens is used in a scanning and image forming optical system which gathers a light flux deflected by a light deflector in the vicinity of a surface to be scanned. The lens is formed by plastic molding of polyolefin resin, and the following condition is satisfied: 0<|Δn(x)−min[Δn(x)]|<34×10⁻⁵, where Δn(x) denotes a refractive-index distribution existing inside the lens, in a range which the light flux passes through, in the lens, and min[Δn(x)] denotes the minimum value of the Δn(x).

Claims

1. An optical scanning lens which is used in a scanning and image forming optical system which gathers a light flux deflected by a light deflector in the vicinity of a surface to be scanned, wherein:

said lens is formed by plastic molding of polyolefin resin; and

the following condition is satisfied

2. The optical scanning lens as claimed in claim 1, wherein the following condition is satisfied

3. An optical scanning device which deflects a light flux from a light source, gathers the deflected light flux on a surface to be scanned by a scanning and image forming optical system as a beam spot, and performs optical scanning of said surface to be scanned,

wherein the optical scanning lens as claimed in claim 2 is mounted as an optical scanning lens used in said scanning and image forming optical system.

4. The optical scanning device as claimed in claim 3 comprising a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

5. The optical scanning device as claimed in claim 4 wherein an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

6. An image forming apparatus which performs optical scanning of a photosensitive surface of an image carrying body and thereby forms a latent image thereon, develops the latent image and thereby visualizes it,

wherein the optical scanning device as claimed in claim 3 is mounted as an optical scanning device which performs the optical scanning of the photosensitive surface of said image carrying body as the surface to be scanned.

7. The image forming apparatus as claimed in claim 6, wherein said optical scanning device comprises a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

8. The image forming apparatus as claimed in claim 7 wherein, in said optical scanning device, an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

9. The image forming apparatus as claimed in claim 6, wherein said image carrying body is a photoconductive photosensitive body,

after the photosensitive surface being charged uniformly, an electrostatic latent image being formed thereon by the optical scanning,

the thus-formed electrostatic latent image being developed so that a toner image is obtained, and

the thus-obtained toner image being transferred and fixed onto a sheet-like recording medium.

10. An optical scanning device which deflects a light flux from a light source, gathers the deflected light flux on a surface to be scanned by a scanning and image forming optical system as a beam spot, and performs optical scanning of said surface to be scanned,

wherein the optical scanning lens as claimed in claim 1 is mounted as an optical scanning lens used in said scanning and image forming optical system.

11. The optical scanning device as claimed in claim 10 comprising a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

12. The optical scanning device as claimed in claim 11 wherein an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

13. An image forming apparatus which performs optical scanning of a photosensitive surface of an image carrying body and thereby forms a latent image thereon, develops the latent image and thereby visualizes it,

wherein the optical scanning device as claimed in claim 10 is mounted as an optical scanning device which performs the optical scanning of the photosensitive surface of said image carrying body as the surface to be scanned.

14. The image forming apparatus as claimed in claim 13, wherein said optical scanning device comprises a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

15. The image forming apparatus as claimed in claim 14 wherein, in said optical scanning device, an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

16. The image forming apparatus as claimed in claim 13, wherein said image carrying body is a photoconductive photosensitive body,

after the photosensitive surface being charged uniformly, an electrostatic latent image being formed thereon by the optical scanning,

the thus-formed electrostatic latent image being developed so that a toner image is obtained, and

the thus-obtained toner image being transferred and fixed onto a sheet-like recording medium.

17. An optical scanning lens which is used in a scanning and image forming optical system which gathers a light flux deflected by a light deflector in the vicinity of a surface to be scanned, wherein:

said lens is formed by plastic molding of polyolefin resin; and

the following condition is satisfied

18. An optical scanning device which deflects a light flux from a light source, gathers the deflected light flux on a surface to be scanned by a scanning and image forming optical system as a beam spot, and performs optical scanning of said surface to be scanned,

wherein the optical scanning lens as claimed in claim 17 is mounted as an optical scanning lens used in said scanning and image forming optical system.

19. The optical scanning device as claimed in claim 18 comprising a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

20. The optical scanning device as claimed in claim 19 wherein an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

21. An image forming apparatus which performs optical scanning of a photosensitive surface of an image carrying body and thereby forms a latent image thereon, develops the latent image and thereby visualizes it,

wherein the optical scanning device as claimed in claim 18 is mounted as an optical scanning device which performs the optical scanning of the photosensitive surface of said image carrying body as the surface to be scanned.

22. The image forming apparatus as claimed in claim 21, wherein said optical scanning device comprises a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

23. The image forming apparatus as claimed in claim 22 wherein, in said optical scanning device, an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

24. The image forming apparatus as claimed in claim 21, wherein said image carrying body is a photoconductive photosensitive body,

after the photosensitive surface being charged uniformly, an electrostatic latent image being formed thereon by the optical scanning,

the thus-formed electrostatic latent image being developed so that a toner image is obtained, and

the thus-obtained toner image being transferred and fixed onto a sheet-like recording medium.

25. An optical scanning lens which is used in a scanning and image forming optical system which gathers a light flux deflected by a light deflector in the vicinity of a surface to be scanned, wherein:

said lens is formed by plastic molding of polyolefin resin; and

the following condition is satisfied

26. The optical scanning lens as claimed in claim 25, wherein the following condition is satisfied

27. An optical scanning device which deflects a light flux from a light source, gathers the deflected light flux on a surface to be scanned by a scanning and image forming optical system as a beam spot, and performs optical scanning of said surface to be scanned,

wherein the optical scanning lens as claimed in claim 26 is mounted as an optical scanning lens used in said scanning and image forming optical system.

28. The optical scanning device as claimed in claim 27 comprising a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

29. The optical scanning device as claimed in claim 28 wherein an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

30. An image forming apparatus which performs optical scanning of a photosensitive surface of an image carrying body and thereby forms a latent image thereon, develops the latent image and thereby visualizes it,

wherein the optical scanning device as claimed in claim 27 is mounted as an optical scanning device which performs the optical scanning of the photosensitive surface of said image carrying body as the surface to be scanned.

31. The image forming apparatus as claimed in claim 30, wherein said optical scanning device comprises a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

32. The image forming apparatus as claimed in claim 31 wherein, in said optical scanning device, an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

33. The image forming apparatus as claimed in claim 30, wherein said image carrying body is a photoconductive photosensitive body,

after the photosensitive surface being charged uniformly, an electrostatic latent image being formed thereon by the optical scanning,

the thus-formed electrostatic latent image being developed so that a toner image is obtained, and

the thus-obtained toner image being transferred and fixed onto a sheet-like recording medium.

34. An optical scanning device which deflects a light flux from a light source, gathers the deflected light flux on a surface to be scanned by a scanning and image forming optical system as a beam spot, and performs optical scanning of said surface to be scanned,

wherein the optical scanning lens as claimed in claim 25 is mounted as an optical scanning lens used in said scanning and image forming optical system.

35. The optical scanning device as claimed in claim 34 comprising a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

36. The optical scanning device as claimed in claim 35 wherein an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

37. An image forming apparatus which performs optical scanning of a photosensitive surface of an image carrying body and thereby forms a latent image thereon, develops the latent image and thereby visualizes it,

wherein the optical scanning device as claimed in claim 34 is mounted as an optical scanning device which performs the optical scanning of the photosensitive surface of said image carrying body as the surface to be scanned.

38. The image forming apparatus as claimed in claim 37, wherein said optical scanning device comprises a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

39. The image forming apparatus as claimed in claim 38 wherein, in said optical scanning device, an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

40. The image forming apparatus as claimed in claim 37, wherein said image carrying body is a photoconductive photosensitive body,

after the photosensitive surface being charged uniformly, an electrostatic latent image being formed thereon by the optical scanning,

the thus-formed electrostatic latent image being developed so that a toner image is obtained, and

the thus-obtained toner image being transferred and fixed onto a sheet-like recording medium.

41. An optical scanning lens which is used in a scanning and image forming optical system which gathers a light flux deflected by a light deflector in the vicinity of a surface to be scanned, wherein:

said lens is formed by plastic molding of polyolefin resin; and

the following condition is satisfied

42. An optical scanning device which deflects a light flux from a light source, gathers the deflected light flux on a surface to be scanned by a scanning and image forming optical system as a beam spot, and performs optical scanning of said surface to be scanned,

wherein the optical scanning lens as claimed in claim 41 is mounted as an optical scanning lens used in said scanning and image forming optical system.

43. The optical scanning device as claimed in claim 42 comprising a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

44. The optical scanning device as claimed in claim 43 wherein an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

45. An image forming apparatus which performs optical scanning of a photosensitive surface of an image carrying body and thereby forms a latent image thereon, develops the latent image and thereby visualizes it,

wherein the optical scanning device as claimed in claim 42 is mounted as an optical scanning device which performs the optical scanning of the photosensitive surface of said image carrying body as the surface to be scanned.

46. The image forming apparatus as claimed in claim 45, wherein said optical scanning device comprises a light deflector which deflects the light flux from the light source, wherein:

said light deflector has a deflection reflecting surface and deflects the light flux at a uniform angular velocity; and

said optical scanning lens has a function of causing the scanning of said surface to be scanned to be performed at a uniform velocity.

47. The image forming apparatus as claimed in claim 46 wherein, in said optical scanning device, an image is formed from the light flux from the light source in the vicinity of the deflection reflecting surface of said light deflector, said image being approximately a line long in main scanning direction.

48. The image forming apparatus as claimed in claim 45, wherein said image carrying body is a photoconductive photosensitive body,

after the photosensitive surface being charged uniformly, an electrostatic latent image being formed thereon by the optical scanning,

the thus-formed electrostatic latent image being developed so that a toner image is obtained, and

the thus-obtained toner image being transferred and fixed onto a sheet-like recording medium.