Optical exposer unit

• US 5,774,249 A
• Filed: 03/29/1996
• Issued: 06/30/1998
• Est. Priority Date: 03/31/1995
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Yamaguchi, Masao, Shiraishi, Takashi
• Primary Examiner(s): Phan, James
• Application Number:
  US08/625,552
• Time in Patent Office: 823 Days
• Field of Search: 359/204-207, 359/212-219, 359/662, 359/708, 359/710-711, 359/717-718, 347/256-261, 347/225, 347/232-235, 347/241-244, 250/234-236
• US Class Current: 359/205.1
• CPC Class Codes: G02B 26/124 Details of the optical system between the light source and the polygonal mirror G02B26/123, G02B26/127 take precedence
• 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: H04N 1/506 Reproducing the colour component signals picture-sequentially, e.g. with reproducing heads spaced apart from one another in the subscanning direction

Abstract

The present invention provides an image forming apparatus, which can provide a color image having no color shift with low manufacturing cost, and an optical exposer unit applied to the image forming apparatus. Thereby, the image forming apparatus comprises a finite focus lens for providing a predetermined optical characteristic to the laser beam sent from a plurality of light sources, a cylinder lens, a laser synthesizing mirror unit for synthesizing the laser beams passed through the lenses into one flux of beams, a deflector for deflecting the synthesized beam, first and second image forming lenses for shaping aberration characteristics provided on the image-formed position of the deflected beam, and one or three mirrors for emitting the beam passed through the respective image forming lenses at a predetermined position, thereby a color image having no color shift can be provided.

Claims

1. An optical exposer unit comprising:

at least one or more light sources having a sum total of numbers N₁ to N_M (M=one or more integral number), for respectively emitting light beams;

first lens means for converting each of said light beams emitted from each of said light sources to either a convergent light beam or a parallel light beam, said first lens means including one of a finite lens and a collimate lens of the sum total of numbers N₁ to N_M ;

second lens means for providing lens power of a first direction so as to converge a light beam emitted from each of said first lens means to only the first direction, said second lens means provided to be M pairs;

deflecting means for deflecting the light beams emitted from said second lens means to a second direction perpendicular to said first direction, said deflecting means including a reflection surface formed to be rotatable around a rotation axis extended to be parallel to said first direction; and

image forming means, including at least one lens, for image-forming each of said light beams deflected at an equal speed by said deflecting means at a predetermined position, said image forming means for correcting a shift of the image formed position against said predetermined position generated by a tilt of said reflection surface of said deflecting means, a curvature of at least one surface of said lens in said first direction changing along the first direction and a curvature of said second direction chancing along the second direction in said image forming means.

2. The optical exposer unit according to claim 1, wherein said image forming means includes an optical axis perpendicular to each of said first and second directions, and a shape of a line, defined when at least one lens surface of the lens in said image forming means crosses the surface extended to said second direction, is asymmetrical to said optical axis.

3. The optical exposer unit according to claim 2, wherein the shape of the lens surface of said image forming means does not depend on a rotation symmetrical axis when the lens surface is formed.

4. The optical exposer unit according to claim 1, wherein a curvature of said first direction said image forming means changes in the entire area of said second direction.

5. The optical exposer unit according to claim 4, wherein a sign of the curvature of said first direction of at least one of the lens surfaces of the lens in said image forming means is reversed to correspond to a position of said second direction.

6. The optical exposer unit according to claim 1, wherein at least one of lens surfaces of said lens in said image forming means includes an optical axis, and two extreme values as a result of a primary differential value by showing a line, defined to cross the surface extended to the second direction, along the second direction on a coordinate defined along said optical axis.

7. The optical exposer unit according to claim 6, wherein the shape of lens surface of said image forming means does not depend on the rotation symmetrical axis when the lens surface is formed.

8. The optical exposer unit according to claim 1, wherein lens power of the second direction of at least one of the lens surfaces of said lens in said image forming means changes in the entire area of said second direction.

9. The optical exposer unit according to claim 8, wherein a sign of the power of said second direction of at least one of the lens surfaces of the lens in said image forming means is reversed to correspond to a position of said second direction.

10. The optical exposer unit according to claim 1, further comprising synthesizing means, provided at the side of a light source rather than said deflecting means, for synthesizing the light beams of the sum total of numbers N₁ to N_M into one flux of beams.

11. An optical exposer unit comprising:

light sources having a sum total of numbers N₁ to N_M (M=two or more integral number), for respectively emitting light beams, wherein at least one of N₁ to N_M is two or more;

first lens means for converting each of said light beams emitted from each of said light sources to either a convergent light beam or a parallel light beam, said first lens means including one of a finite lens and a collimate lens of the sum total of numbers N₁ to N_M ;

second lens means for providing lens power of a first direction so as to converge a light beam emitted from each of said first lens means to only a first direction, said second lens means provided to be M pairs;

deflecting means for deflecting the light beams emitted from said second lens means to a second direction perpendicular to said first direction, said deflecting means including a reflection surface formed to be rotatable around a rotation axis extended to be parallel to said first direction; and

image forming means, including at least one lens, for image-forming each of said light beams deflected at an equal speed by said deflecting means at a predetermined position, said image forming means for correcting a shift of the image formed position against said predetermined position generated by a tilt of said reflection surface of said deflecting means.

12. The optical exposer unit according to claim 11, wherein said image forming means includes an optical axis perpendicular to each of said first and second directions, and a shape of a line, defined when at least one lens surface of the lens in said image forming means crosses the surface extended to said second direction, is asymmetrical to said optical axis.

13. The optical exposer unit according to claim 12, wherein the shape of the lens surface of said image forming means does not depend on a rotation symmetrical axis when the lens surface is formed.

14. The optical exposer unit according to claim 11, wherein a curvature of said first direction of at least one of lens surfaces of the lens in said image forming means changes in the entire area of said second direction.

15. The optical exposer unit according to claim 14, wherein a sign of the curvature of said first direction of at least one of the lens surfaces of the lens in said image forming means is reversed to correspond to a position of said second direction.

16. The optical exposer unit according to claim 11, wherein at least one of lens surfaces of said lens in said image forming means includes an optical axis, and two extreme values as a result of a primary differential value by showing a line, defined to cross the surface extended to the second direction, along the second direction on a coordinate defined along said optical axis.

17. The optical exposer unit according to claim 16, wherein the shape of a lens surface of said image forming means does not depend on the rotation symmetrical axis when the lens surface is formed.

18. The optical exposer unit according to claim 11, wherein lens power of the second direction of at least one of the lens surfaces of said lens in said image forming means changes in the entire area of said second direction.

19. The optical exposer unit according to claim 18, wherein a sign of the power of said second direction of at least one of the lens surfaces of the lens in said image forming means is reversed to correspond to a position of said second direction.

20. The optical exposer unit according to claim 11, further comprising synthesizing means, provided at the side of a light source rather than said deflecting means, for synthesizing the light beams of the sum total of numbers N₁ to N_M into one flux of beams.

21. The optical exposer unit according to claim 20, wherein each of said beams synthesized by said synthesizing means is crossed between a lens surface closest to said deflecting means and an image plane.

22. The optical exposer unit according to claim 21, further comprising detecting means, provided on an image plane, for detecting each of the light beams passed through said image forming means.

23. The optical exposer unit according to claim 22, wherein said detecting means includes a position sensor.

24. The optical exposer unit according to claim 11, further comprising:

resolution changing means for providing a light beam emitted with a predetermined value of GP where a latent image corresponding to one pixel satisfies the following equation;

space="preserve" listing-type="equation">GP=AMP×

LGP×

{1-(DPI/DPIo}/(Pi-1)

wherein AMP;

a constant ranging from 1.2 to 1.6, LGP;

line distance at the time of writing the image by a signal laser beam, DPIo;

first resolution of an image forming apparatus, DPI;

second resolution smaller than said first resolution, and Pi;

number of light beams, Pi is two or more in number.

25. An optical exposer unit comprising:

light sources having a sum total of numbers N₁ to N_M (M=two or more integral number), for respectively emitting light beams;

first lens means for converting each of said light beams emitted from each of said light sources to either a convergent light beam or a parallel light beam, said first lens means including one of a finite lens and a collimate lens of the sum total of numbers N₁ to N_M ;

second lens means for providing lens power of a first direction so as to converge a light beam emitted from each of said first lens means to only the first direction, said second lens means provided to be M pairs;

deflecting means for deflecting the light beams emitted from said second lens means to a second direction perpendicular to said first direction, said deflecting means including a reflection surface formed to be rotatable around a rotation axis extended to be parallel to said first direction; and

image forming means, including at least one lens, for image-forming each of said light beams deflected at an equal speed by said deflecting means at a predetermined position, said image forming means for correcting a shift of the image formed position against said predetermined position generated by a tilt of said reflection surface of said deflecting means,

wherein at least one of the N₁ to N_M of said light sources is different from the others.

26. The optical exposer unit according to claim 25, wherein said image forming means includes an optical axis perpendicular to each of said first and second directions, and a shape of a line, defined when at least one lens surface of the lens in said image forming means crosses the surface extended to said second direction, is asymmetrical to said optical axis.

27. The optical exposer unit according to claim 26, wherein the shape of the lens surface of said image forming means does not depend on a rotation symmetrical axis when the lens surface is formed.

28. The optical exposer unit according to claim 25, wherein a curvature of said first direction of at least one of lens surfaces of the lens in said image forming means changes in the entire area of said second direction.

29. The optical exposer unit according to claim 28, wherein a sign of the curvature of said first direction of at least one of the lens surfaces of the lens in said image forming means is reversed to correspond to a position of said second direction.

30. The optical exposer unit according to claim 25, wherein at least one of lens surfaces of said lens in said image forming includes an optical axis, and two extreme values as a result of a primary differential value by showing a line, defined to cross the surface extended to the second direction, along the second direction on a coordinate defined along said optical axis.

31. The optical exposer unit according to claim 30, wherein the shape of a lens surface of said image forming means does not depend on the rotation symmetrical axis when the lens surface is formed.

32. The optical exposer unit according to claim 25, wherein lens power of the second direction of at least one of the lens surfaces of said lens in said image forming means changes in the entire area of said second direction.

33. The optical exposer unit according to claim 32, wherein a sign of the power of said second direction of at least one of the lens surfaces of the lens in said image forming means is reversed to correspond to a position of said second direction.

34. The optical exposer unit according to claim 25, further comprising synthesizing means, provided at the side of a light source rather than said deflecting means, for synthesizing the light beams of the sum total of numbers N₁ to N_M into one flux of beams.

35. An optical exposer unit comprising:

at least one or more light sources having a sum total of numbers N₁ to N_M (M=one or more integral number), for respectively emitting light beams, wherein at least one of N₁ to N_M is two or more;

first lens means for converting each of said light beams emitted from each of said light sources to either a convergent light beam or a parallel light beam, said first lens means including one of a finite lens and a collimate lens of the sum total of numbers N₁ to N_M ;

second lens means for providing lens power of a first direction so as to converge a light beam emitted from each of said first lens means to only a first direction, said second lens means provided to be M pairs;

deflecting means for deflecting the light beams emitted from said second lens means to a second direction perpendicular to said first direction, said deflecting means including a reflection surface formed to be rotatable around a rotation axis extended to be parallel to said first direction; and

image forming means, including at least one lens, for image-forming each of said light beams deflected at an equal speed by said deflecting means at a predetermined position, said image forming means for correcting a shift of the image formed position against said predetermined position generated by a tilt of said reflection surface of said deflecting means, a curvature of at least one surface of said lens in said first direction changing along the first direction and a curvature of said second direction changing along the second direction in said image forming means.

36. An optical exposer unit comprising:

light sources having a sum total of numbers N₁ to N_M (M=two or more integral number), for respectively emitting light beams, wherein at least one of N₁ to N_M is two or more;

first lens means for converting each of said light beams emitted from each of said light sources to either a convergent light beam or a parallel light beam, said first lens means including one of a finite lens and a collimate lens of the sum total of numbers N₁ to N_M ;

second lens means for providing lens power of a first direction so as to converge a light beam emitted from each of said first lens means to only the first direction, said second lens means provided to be M pairs;

deflecting means for deflecting the light beams emitted from said second lens means to a second direction perpendicular to said first direction, said deflecting means including a reflection surface formed to be rotatable around a rotation axis extended to be parallel to said first direction;

image forming means, including at least one lens, for image-forming each of said light beams deflected at an equal speed by said deflecting means at a predetermined position, said image forming means for correcting a shift of the image formed position against said predetermined position generated by a tilt of said reflection surface of said deflecting means, wherein each of said beams is crossed between a lens surface closet to said deflecting means and an image plane; and

detecting means, provided on an image plane, for detecting each of the light beams passed through said image forming means, wherein said detecting means includes a position sensor.

37. The optical exposer unit according to claim 36, further comprising resolution changing means for changing a position corresponding to the first direction of at least one light emission element of said light sources.

38. An optical exposer unit comprising:

light sources having a sum total of numbers N₁ to N_M (M=one or more integral number), for respectively emitting light beams, wherein at least one of N₁ to N_M is two or more;

first lens means for converting each of said light beams emitted from each of said light sources to either a convergent light beam or a parallel light beam, said first lens, means including one of a finite lens and a collimate lens of the sum total of numbers N₁ to N_M ;

second lens means for providing lens power of a first direction so as to converge a light beam emitted from each of said first lens means to only a first direction, said second lens means provided to be M pairs;

deflecting means for deflecting the light beams emitted from said second lens means to a second direction perpendicular to said first direction, said deflecting means including a reflection surface formed to be rotatable around a rotation axis extended to be parallel to said first direction;

image forming means, including at least one lens, for image-forming each of said light beams deflected at an equal speed by said deflecting means at a predetermined position, said image forming means for correcting a shift of the image formed position against said predetermined position generated by a tilt of said reflection surface of said deflecting means; and

resolution changing means for providing a light beam emitted with a predetermined value of GP where a latent image corresponding to one pixel satisfies the following equation;

space="preserve" listing-type="equation">GP=AMP×

LGP×

{1-(DPI/DPIo}/(Pi-1)

wherein AMP;

a constant ranging from 1.2 to 1.6, LGP;

line distance at the time of writing the image by a signal laser beam, DPIo;

first resolution of an image forming apparatus, DPI;

second resolution smaller than said first resolution, and Pi;

number of light beams, Pi is two or more in number.

39. The optical exposer unit according to claim 38, wherein said resolution changing means changes a position corresponding to the first direction of at least one light emission element of said light sources.

40. The optical exposer unit according to claim 38, wherein said image forming means includes at least one lens, and each of said beams is crossed between a lens surface closest to said deflecting means and an image plane.

41. The optical exposer unit according to claim 40, further comprising detecting means, provided on an image plane, for detecting each of the light beams passed through said image forming means.

42. The optical exposer unit according to claim 41, wherein said detecting means includes a position sensor.

43. The optical exposer unit according to claim 38, further comprising resolution changing means for changing a position corresponding to the first direction of at least one light emission element of said light sources.

44. An optical exposer unit comprising:

at least one or more light sources having a sum total of numbers N₁ to N_M (M=one or more integral number), for respectively emitting light beams;

deflecting means for deflecting a light beam, said deflecting means including a reflection surface formed to be rotatable around a rotation axis extended to be parallel to a first direction, said deflecting means deflecting light beams to a second direction perpendicular to said first direction; and

image forming means, including at least one lens, for image-forming each light beam deflected at an equal speed by said deflecting means at a predetermined position, said image forming means for correcting a shift of the image formed position against said predetermined position generated by a tilt of said reflection surface of said deflecting means, a curvature of at least one surface of said lens in said first direction changing along the first direction and a curvature of said second dirction changing along the second direction in said image forming means.