Illumination apparatus using light guide

• US 6,333,779 B1
• Filed: 12/21/1999
• Issued: 12/25/2001
• Est. Priority Date: 12/24/1998
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kawai, Tatsundo, Tabata, Masami
• Primary Examiner(s): Mathews, Alan A.
• Assistant Examiner(s): NGUYEN, HUNG
• Application Number:
  US09/467,982
• Time in Patent Office: 735 Days
• Field of Search: 355/41, 355/55, 355/57, 355/67, 355/70, 355/68, 355/69, 355/71, 250/208.1, 250/235, 250/239, 358/475, 358/471, 358/484
• US Class Current: 355/68
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• 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 1/02835 in combination with a light guide, e.g. optical fibre, glass plate light-guides per se G02B6/00
• CPC Class Codes: H04N 1/0284 in combination with a light integrating, concentrating or diffusing cavity
• CPC Class Codes: H04N 1/02885 Means for compensating spatially uneven illumination, e.g. an aperture arrangement
• CPC Class Codes: H04N 1/0315 using photodetectors and illumination means mounted on separate supports or substrates or mounted in different planes
• CPC Class Codes: H04N 1/0318 Integral pick-up heads, i.e. self-contained heads whose basic elements are a light-source, a lens array and a photodetector array which are supported by a single-piece frame
• CPC Class Codes: H04N 1/1017 the main-scanning components remaining positionally invariant with respect to one another in the sub-scanning direction
• CPC Class Codes: H04N 1/193 using electrically scanned linear arrays , e.g. linear CCD arrays
• CPC Class Codes: H04N 1/484 with sequential colour illumination of the original
• CPC Class Codes: H04N 2201/03112 Light source
• CPC Class Codes: H04N 2201/0312 Reflecting element upstream of the scanned picture elements
• CPC Class Codes: H04N 2201/03125 Light guide upstream of the scanned picture elements
• CPC Class Codes: H04N 2201/03141 Photodetector lens
• CPC Class Codes: H04N 2201/03145 Photodetector
• CPC Class Codes: H04N 2201/0317 Shape
• CPC Class Codes: H04N 2201/03187 Additional optical element
• CPC Class Codes: H04N 2201/03195 Coating, e.g. light adsorbing layer

Abstract

There is disclosed a light guide for guiding light from a light source in a longitudinal direction and radiating the light to illuminate an object to be illuminated, which comprises a diffuser for diffusing the light from the light source along the longitudinal direction of the light guide, and a radiator for radiating the light diffused by the diffuser in a predetermined direction. By arranging the diffuser and the radiator so that a normal line passing through the center of the width of the diffuser is different from the predetermined direction at least in the vicinity of the light source when viewed in the longitudinal direction of the light guide, the illuminance distribution of the longitudinal direction of the light guide is uniformed.

Claims

1. A light guide built in a light guide cover, said light guide cover comprising a light non-transmitting member, and provided with a light transmitting member for guiding light from a light source in a longitudinal direction and radiating the light from a radiating surface of said light guide to illuminate an object to be illuminated,

wherein a light leakage preventing portion for restricting light leakage is arranged in a part of a surface of said light guide, exposed from said light guide cover, other than said radiating surface.

2. The light guide according to claim 1, further comprising a diffuser for diffusing and/or reflecting the light from said light source in the longitudinal direction of said light guide, wherein said radiating surface radiates the light diffused and/or reflected by said diffuser in a predetermined direction.

3. The light guide according to claim 2, wherein said light leakage preventing portion comprises a total reflection surface in which an incidence angle of the light diffused and/or reflected by said diffuser is equal to or more than a total reflection angle.

4. The light guide according to claim 3, wherein said total reflection angle is θ

h=ASN which is a ratio of a refractive index of air and a refractive index of said light guide.

5. The light guide according to claim 3, wherein said total reflection surface is an elliptic curved surface with two points as centers in said diffuser and an illumination position of the object to be illuminated.

6. The light guide according to claim 1, wherein a sectional area of said light guide changes over the longitudinal direction when viewed from the side of an end surface of the longitudinal direction of said light guide.

7. The light guide according to claim 1, wherein said radiating surface comprises a light converging portion for converging the light to be radiated.

8. The light guide according to claim 7, wherein said light converging portion is formed by forming said radiating surface in a lens shape.

9. The light guide according to claim 1, wherein said light leakage preventing portion comprises a reflecting member disposed separately from said light guide.

10. The light guide according to claim 1, wherein said light leakage preventing portion is constituted by roughing the surface of said light guide.

11. The light guide according to claim 1, wherein said light leakage preventing portion is constituted by applying a paint to said light guide.

12. The light guide according to claim 1, wherein said light leakage preventing portion is constituted by processing said light guide in a sawtooth shape.

13. The light guide according to claim 1, wherein said light leakage preventing portion is constituted by depositing a metal to said light guide.