Image reading apparatus

• US 9,277,082 B2
• Filed: 12/17/2014
• Issued: 03/01/2016
• Est. Priority Date: 01/17/2014
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Sugiyama, Takayuki, Ito, Narumasa
• Primary Examiner(s): Worku, Negussie
• Application Number:
  US14/573,179
• Publication Number:
  US 20150207954A1
• Time in Patent Office: 440 Days
• Field of Search: 358/475, 358/474, 358/482, 358/448, 358/483, 362/616, 362/623, 362/217.05, 362/223, 362/235, 250/208.1, 250/227.11, 250/458.1, 250/578.1, 382/275, 399/168, 399/388, 399/45
• US Class Current: 1/1
• CPC Class Codes: H04N 1/0283 in combination with a light deflecting element, e.g. a rotating mirror
• 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 1/02895 Additional elements in the illumination means or cooperating with the illumination means, e.g. filters H04N1/02885 takes precedence; optical elements other than lenses per se G02B5/00
• 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 1/488 using beam-splitters

Abstract

Provided is an image reading apparatus that can inhibit occurrence of a bright spot line image due to microstructures of a light guide. An image reading apparatus satisfies: 45−φ≦θ≦φ−ω/n (0≦ω≦ω_max); and 45−φ≦θ≦φ (−ω_max≦ω≦0), where θ is an angle (deg.) between a surface of original and a reflecting surface of a microstructure reflection surface of a light guide, ω is a half angle of view (deg.) of an imaging forming lens, ω_max (ω_max>0) is a maximum value (deg.) of the half angle of view of the imaging forming lens on an LED light source side with respect to a reading optical axis of the imaging lens, −ω_max is a maximum value (deg.) of the half angle of view of the imaging lens on a side opposite to the LED light source with respect to the reading optical axis, n is a refractive index of the light guide, and φ=sin⁻¹(1/n).

Claims

1. An image reading apparatus, comprising:

an illumination unit comprising a light source and a light guide for guiding a light flux from the light source to a surface of an original, the light guide being elongated in a first direction; and

an imaging unit for collecting a light flux from the surface of the original,

wherein the light guide comprises;

an incident surface provided on an end surface in the first direction, the light flux from the light source entering the incident surface;

an exit surface from which a light flux from the incident surface exits, the exit surface being elongated in the first direction; and

a light guide surface opposed to the exit surface, for guiding the light flux from the incident surface to the exit surface,

wherein the light guide surface comprises a plurality of prisms each having a reflecting surface opposed to the incident surface, and

wherein the following conditions are satisfied;

45−

φ

≦

θ

≦

φ

−

ω

/n (0≦

ω

≦

ω

_max); and

45−

φ

≦

θ

≦

φ

(−

ω

_max≦

ω

≦

0),

where, within a section including the first direction and a directional perpendicular to the surface of the original, θ

is an angle (deg.) between the original surface and the reflecting surface, ω

is a half angle of view (deg.) of the imaging unit, ω

_max (ω

_max>

0) is a maximum value (deg.) of the half angle of view of the imaging unit on the light source side with respect to a reading optical axis of the imaging unit, −

ω

_max is a maximum value (deg.) of the half angle of view of the imaging unit on a side opposite to the light source with respect to the reading optical axis, n is a refractive index of the light guide, and φ

=sin<sup>−

1</sup>(1/n).

2. An image reading apparatus according to claim 1, wherein ω

_max is 20°

or more.

3. An image reading apparatus according to claim 1, wherein the angle θ

changes so as to become smaller as the half angle of view ω

of the imaging unit becomes larger.

4. An image reading apparatus according to claim 1, wherein the plurality of prisms are triangular.

5. An image reading apparatus according to claim 1, wherein the plurality of prisms are trapezoidal.

6. An image reading apparatus according to claim 1, wherein the plurality of prisms comprise polyhedral reflecting surface prisms, wherein the reflecting surface of each is polyhedral.

7. An image reading apparatus according to claim 1, wherein the plurality of prisms comprise curved reflecting surface prisms, wherein the reflecting surface of each is curved.

8. An image reading apparatus according to claim 1, wherein the light guide comprises the incident surface on one end surface in the first direction and an end diffusing surface on another end surface in the first direction.

9. An image reading apparatus according to claim 1, wherein the light guide comprises the incident surface on one end surface in the first direction and an end reflecting surface on another end surface in the first direction.

10. An image reading apparatus according to claim 1, wherein the light guide comprises a transparent member having a refractive index n of 1.4 to 1.9.

11. An image reading apparatus according to claim 10, wherein the light guide is formed of one of polymethyl methacrylate and polycarbonate.

12. An image reading apparatus according to claim 1, wherein the illumination unit comprises two illuminating units arranged on both sides of the reading optical axis of the imaging unit so as to illuminate the surface of the original from both the sides of the reading optical axis.

13. An image reading apparatus, comprising:

an illumination unit comprising a first light source, a second light source and a light guide for guiding a light flux from the first light source and the second light source to a surface of an original, the light guide being elongated in a first direction; and

an imaging unit for collecting a light flux from the surface of the original,

wherein the light guide comprises;

a first incident surface provided on one end surface in the first direction, the light flux from the first light source entering the first incident surface;

a second incident surface that is provided on another end surface in the first direction, the light flux from the second light source entering the second incident surface;

an exit surface from which light fluxes from the first incident surface and the second incident surface exit, the exit surface being elongated in the first direction; and

a light guide surface opposed to the exit surface, for guiding the light fluxes from the first incident surface and the second incident surface to the exit surface,

wherein the light guide surface comprises a plurality of prisms each having a first reflecting surface opposed to the first incident surface and a second reflecting surface opposed to the second incident surface, and

wherein the following conditions are satisfied;

45−

φ

≦

θ

1≦

φ

−

ω

/n (0≦

ω

≦

ω

_max);

45−

φ

≦

θ

1≦

φ

(−

ω

_max≦

ω

≦

0);

45−

φ

≦

θ

2≦

φ

+ω

/n (−

ω

_max≦

ω

≦

0); and

45−

φ

≦

θ

2≦

φ

(0≦

ω

≦

ω

_max),

where, within a section including the first direction and a direction perpendicular to the surface of the original, θ

1 is an angle (deg.) between the surface of the original and the first reflecting surface, θ

2 is an angle (deg.) between the surface of the original and the second reflecting surface, ω

is a half angle of view (deg.) of the imaging unit, ω

_max (ω

_max>

0) is a maximum value (deg.) of the half angle of view of the imaging unit on the first light source side with respect to the reading optical axis of the imaging unit, −

ω

_max is a maximum value (deg.) of the half angle of view of the imaging unit on the side opposite to the first light source with respect to the reading optical axis, n is a refractive index of the light guide, and φ

=sin<sup>−

1</sup>(1/n).

14. An image reading apparatus according to claim 13, wherein the angle θ

1 and the angle θ

2 change so as to become smaller as the half angle of view ω

of the imaging unit becomes larger.