Lighting device, image-reading device, color-document reading apparatus, image-forming apparatus, projection apparatus

• US 7,438,443 B2
• Filed: 09/17/2004
• Issued: 10/21/2008
• Est. Priority Date: 09/19/2003
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Tatsuno, Hibiki, Nishina, Kiichiro
• Primary Examiner(s): Sember; Thomas M
• Application Number:
  US10/942,908
• Publication Number:
  US 20050111115A1
• Time in Patent Office: 1,495 Days
• Field of Search: 362296-305
• US Class Current: 362/297
• CPC Class Codes: H04N 1/02815 Means for illuminating the original, not specific to a particular type of pick-up head
• CPC Class Codes: H04N 1/02825 in combination with at least one reflector which is fixed in relation to the light source H04N1/02835 and H04N1/0284 take precedence
• CPC Class Codes: H04N 1/0284 in combination with a light integrating, concentrating or diffusing cavity

Abstract

A lighting device includes an illumination face having a length and a width; a light-emitting element having a light-ray-releasing face the maximum length of which is equal to or less than the width of the illumination face; and a light-source unit that has an optical element which changes the direction of light rays released from the light-emitting element to be directed to the illumination face. The optical element has a concave-face reflecting unit having a cross section that is shaped into a quadratic curve or a pseudo quadratic curve, which is placed at least on one portion thereof, and a luminance distribution on the illumination face has a flat portion that is equal to or not less than a predetermined width.

Claims

1. A lighting device comprising:

an illumination face that reflects and/or absorbs light and including a length and a width;

a light-emitting element including a light emitting diode and a light-ray-releasing face, a maximum length of which light-ray-releasing face is equal to or less than the width of the illumination face; and

a light-source unit that has an optical element which changes the direction of light rays released from the light-emitting element to be directed to the illumination face, wherein

the optical element has a concave-face reflecting unit including a cross section that is shaped into a quadratic curve or a pseudo quadratic curve (hereinafter, “

a quadratic curve”

), which is placed at least on one portion thereof, and a luminance distribution on the illumination face has a flat portion that is substantially equal to the width of the illumination face, the concave-face reflecting unit being constituted by a curve that is located on one side when viewed from the vicinity of an apex of the quadratic curve and a symmetric axis of the quadratic curve.

2. The lighting device according to claim 1, wherein

the optical element includes at least one of a transparent glass and a synthetic resin, and has a light-ray incident face facing the light-emitting element and a light-ray releasing face that is virtually orthogonal to the light-ray incident face, and faces the illumination face, with the two faces being connected by the concave-face reflecting unit.

3. The lighting device according to claim 2, wherein

the light-ray releasing face of the light-emitting element is parallel to the symmetric axis of the quadratic curve.

4. The lighting device according to claim 2, wherein

the light-ray releasing face of the light-emitting element is tilted by a predetermined angle with respect to the symmetric axis of the quadratic curve.

5. The lighting device according to claim 4, wherein

the predetermined angle corresponds to an angle at which the maximum quantity of light is made incident on an effective reflection area of the concave-face reflecting unit.

6. The lighting device according to claim 1, wherein

the illumination face is tilted by a predetermined angle with respect to the symmetric axis of the quadratic curve.

7. The lighting device according to claim 1, wherein

the light-emitting element has a center that is placed at a focal point of the quadratic curve, or placed at a distance within the length of the light-ray releasing face of the light-emitting element from the focal point.

8. The lighting device according to claim 1, wherein the quadratic curve is an ellipse.

9. The lighting device according to claim 1, wherein the quadratic curve is a parabolic line.

10. The lighting device according to claim 1, wherein the quadratic curve is a hyperbolic line.

11. The lighting device according to claim 1, wherein

the pseudo quadratic curve corresponds to a curve that is approximated to a quadratic curve by connecting partial straight lines.

12. The lighting device according to claim 1, wherein the light-emitting element is packaged on a circuit substrate.

13. The lighting device according to claim 12, wherein the circuit substrate is coupled to the optical element.

14. The lighting device according to claim 1, wherein the light-emitting diode is of a reflection type.

15. The lighting device according to claim 1, wherein the light-emitting diode is a 1-chip-type white light-emitting diode including a fluorescent material.

16. The lighting device according to claim 1, wherein

the light-emitting diode is a white light-emitting diode including at least two or more chips including respectively different light-emitting colors so that white light is emitted based on a mixing of the different light-emitting colors.

17. The lighting device according to claim 1, wherein

a plurality of light-emitting elements are arranged along the length of the illumination face.

18. The lighting device according to claim 17, wherein

a distance separating the light-emitting elements is greater than the length of the illumination face.

19. The lighting device according to claim 17, wherein a distance separating the light-emitting elements from each other is equal for each of the light-emitting elements.

20. The lighting device according to claim 17, wherein

an interval between the light-emitting elements closest to the center is P0 and an interval from any light-emitting element to a light-emitting element closest to the end is Pn with n ≧

1, and a layout interval of the light-emitting elements simultaneously satisfies the following inequalities;

Pn−

1≧

Pn

0.2≧

Pn/PO≧

1.

21. The lighting device according to claim 1, further comprising:

two light-source units installed, respectively, on opposite sides of a normal to the illumination face.

22. The lighting device according to claim 21, wherein the two light-source units are light-source units having the same basic specifications.

23. The lighting device according to claim 22, wherein

the two light-source units are light-source units having mutually different specifications.

24. The lighting device according to claim 1, wherein

the light-ray releasing face is tilted with respect to the symmetric axis of the quadratic curve by a predetermined angle corresponding to an angle at which light rays within a half-value angle in a luminous intensity distribution of the light-emitting element are made incident on an effective reflection area of the concave-face reflecting unit.

25. The lighting device according to claim 1, wherein

a plurality of light-emitting elements are arranged in a direction coincident with the symmetric axis direction of the quadratic curve.

26. The lighting device according to claim 25, wherein

the plurality of light-emitting elements are packaged on a same circuit substrate.

27. The lighting device according to claim 25, wherein

the plurality of light-emitting elements includes a plurality of light-emitting elements arranged in the length direction of the illumination face so that light-emitting element rows that are adjacent to each other in the length direction have a staggered pattern.

28. The lighting device according to claim 1, further comprising:

a lens, which exerts different refracting powers in two directions that are orthogonal to each other, the lens being placed near the light-ray releasing face of the light-emitting element.

29. The lighting device according to claim 1, further comprising:

a lens, which exerts different refracting powers in two directions that are orthogonal to each other, the lens being located between the light-ray releasing opening and the illumination face.

30. A lighting device, comprising:

an illumination face that reflects and/or absorbs light, and has-a predetermined length and width, the lighting device configured to apply light onto the illumination face to utilize reflected light from the illumination face; and

a light-source unit including a light-emitting element having a light emitting diode; and

an optical element that has a light-ray incident opening near a light-ray releasing face of the light-emitting element and a concave-face reflecting unit that has a partially cylindrical shape having a light-ray releasing opening that faces the illumination face, with a cross sectional shape of the concave-face reflecting unit including a quadratic curve or a pseudo quadratic curve (hereinafter, “

a quadratic curve”

), wherein

an illumination area derived from light applied from the light-emitting element has a luminance distribution area having a flat portion, with the-flat portion being virtually coincident with the illumination face, the concave-face reflecting unit being constituted by a curve that is located on one side when viewed from the vicinity of an apex of the quadratic curve and a symmetric axis of the quadratic curve.

31. The lighting device according to claim 30, wherein

the optical element includes at least one of a transparent glass and a synthetic resin, the light-ray incident opening is a light-ray incident face made of a flat face and the light-ray releasing opening is a light-ray releasing face made of a flat face that is virtually orthogonal to the light-ray incident face, with the two flat faces being connected by the concave-face reflecting unit so that light rays are inner-face-reflected by the concave-face reflecting unit.

32. The lighting device according to claim 30, wherein

the illumination face is tilted by a predetermined angle with respect to the symmetric axis of the quadratic curve.

33. The lighting device according to claim 30, wherein

the light-emitting element has a center that is placed at a focal point of the quadratic curve, or placed at a distance within the length of the light-ray releasing face of the light-emitting element from the focal point.

34. The lighting device according to claim 30, wherein the quadratic curve is an ellipse.

35. The lighting device according to claim 30, wherein the quadratic curve is a parabolic line.

36. The lighting device according to claim 30, wherein the quadratic curve is a hyperbolic line.

37. The lighting device according to claim 30, wherein

the light-ray releasing face of the light-emitting element is parallel to the symmetric axis of the quadratic curve.

38. The lighting device according to claim 30, wherein

the light-ray releasing face of the light-emitting element is tilted by a predetermined angle with respect to the symmetric axis of the quadratic curve.

39. The lighting device according to claim 38, wherein

the predetermined angle corresponds to an angle at which a maximum quantity of light is made incident on an effective reflection area of the concave-face reflecting unit.

40. The lighting device according to claim 30, wherein

the pseudo quadratic curve corresponds to a curve that approximates a quadratic curve by connecting partial straight lines.

41. The lighting device according to claim 30, wherein the light-emitting element is packaged on a circuit substrate.

42. The lighting device according to claim 41, wherein the circuit substrate is coupled to the optical element.

43. The lighting device according to claim 30, wherein the light-emitting diode is of a reflection type.

44. The lighting device according to claim 30, wherein the light-emitting diode is a 1-chip-type white light-emitting diode that includes a fluorescent material.

45. The lighting device according to claim 30, wherein

the light-emitting diode is a white light-emitting diode including at least two chips having respectively different light-emitting colors so that white light is emitted based on a mixing of the different light-emitting colors.

46. The lighting device according to claim 30, wherein

a plurality of light-emitting elements are arranged along the length of the illumination face.

47. The lighting device according to claim 46, wherein

a distance separating the light-emitting elements is greater than the length of the illumination face.

48. The lighting device according to claim 46, wherein a distance separating the light-emitting elements from each other is equal for each of the light-emitting elements.

49. The lighting device according to claim 46, wherein

an interval between the light-emitting elements closest to the center is P0 and an interval from any light-emitting element to a light-emitting element closest to the end is Pn with n ≧

1, and a layout interval of the light-emitting elements simultaneously satisfies the following inequalities;

Pn−

1≧

Pn

0.2≧

Pn/PO≧

1.

50. The lighting device according to claim 30, further comprising:

two light-source units installed, respectively, on opposite sides of a normal to the illumination face.

51. The lighting device according to claim 50, wherein the two light-source units are light-source units having the same basic specifications.

52. The lighting device according to claim 51, wherein

the two light-source units are light-source units having mutually different specifications.

53. The lighting device according to claim 30, wherein

the light-ray releasing face is tilted with respect to the symmetric axis of the quadratic curve by a predetermined angle corresponding to an angle at which light rays within a half-value angle in a luminous intensity distribution of the light-emitting element are made incident on an effective reflection area of the concave-face reflecting unit.

54. The lighting device according to claim 30, wherein

a plurality of light-emitting elements are arranged in a direction coincident with the symmetric axis direction of the quadratic curve.

55. The lighting device according to claim 54, wherein

the plurality of light-emitting elements are packaged on a same circuit substrate.

56. The lighting device according to claim 54, wherein

the plurality of light-emitting elements includes a plurality of light-emitting elements arranged in the length direction of the illumination face so that light-emitting element rows that are adjacent to each other in the length direction have a staggered pattern.

57. The lighting device according to claim 30, further comprising:

a lens, which exerts different refracting powers in two directions that are orthogonal to each other, the lens being placed near the light-ray releasing face of the light-emitting element.

58. The lighting device according to claim 30, further comprising:

a lens, which exerts different refracting powers in two directions that are orthogonal to each other, the lens being located between the light-ray releasing opening and the illumination face.