U.S. patent application number 09/785178 was filed with the patent office on 2001-08-23 for image reading apparatus and light guide member used therefor.
Invention is credited to Fujimoto, Hisayoshi, Torama, Minori.
Application Number | 20010015892 09/785178 |
Document ID | / |
Family ID | 18568505 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015892 |
Kind Code |
A1 |
Fujimoto, Hisayoshi ; et
al. |
August 23, 2001 |
Image reading apparatus and light guide member used therefor
Abstract
An image reading apparatus includes a light source, an elongate
light guide member for guiding light emitted from the light source
toward an image read line, and a plurality of light receiving
elements for receiving light reflected at the image read line. The
light guide member includes a first portion, a second portion, and
a connecting portion for connecting the first portion and the
second portion. The first portion includes a light incidence
surface facing the light source for entry of light emitted from the
light source, and the light incidence surface is convexly curved
widthwise of the light guide member. The second portion includes a
light exit surface oriented toward the image read line for emitting
light toward the image read line. The connecting portion is
narrower than the first portion and the second portion.
Inventors: |
Fujimoto, Hisayoshi; (Kyoto,
JP) ; Torama, Minori; (Kyoto, JP) |
Correspondence
Address: |
Michael D. Bednarek
SHAW PITTMAN
1650 Tysons Boulevard
McLean
VA
22102-4859
US
|
Family ID: |
18568505 |
Appl. No.: |
09/785178 |
Filed: |
February 20, 2001 |
Current U.S.
Class: |
362/602 |
Current CPC
Class: |
H04N 2201/03125
20130101; H04N 1/0318 20130101; H04N 2201/0317 20130101; H04N
2201/03116 20130101; H04N 2201/03145 20130101; H04N 1/0314
20130101; H04N 2201/03141 20130101; H04N 1/0312 20130101; H04N
2201/03112 20130101 |
Class at
Publication: |
362/31 |
International
Class: |
F21V 007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2000 |
JP |
2000-046012 |
Claims
1. An image reading apparatus comprising: at least one light
source; an elongate light guide member for guiding light emitted
from the light source toward an image read line; and a plurality of
light receiving elements for receiving light reflected at the image
read line; wherein the light guide member includes a first portion,
a second portion, and a connecting portion for connecting the first
portion and the second portion; wherein the first portion includes
a light incidence surface facing the light source for entry of
light emitted from the light source, the light incidence surface
being convexly curved widthwise of the light guide member; wherein
the second portion includes a light exit surface oriented toward
the image read line for emitting light toward the image read line;
and wherein the connecting portion is narrower than the first
portion and the second portion.
2. The image reading apparatus according to claim 1, wherein the
first portion of the light guide member further includes additional
light exit surfaces each of which is convexly curved, the second
portion of the light guide member further including an additional
light incidence surface facing each light exit surface of the first
portion.
3. The image reading apparatus according to claim 1, wherein the
first portion, the second portion and the connecting portion are
formed of transparent resin as one piece.
4. The image reading apparatus according to claim 1, wherein the
connecting portion is located on a widthwise center axis of the
first portion.
5. The image reading apparatus according to claim 4, wherein the
widthwise center axis of the first portion is located directly
above the light source.
6. The image reading apparatus according to claim 1, wherein the
light exit surface of the second portion is convexly curved at
least partially.
7. The image reading apparatus according to claim 1, wherein the
light exit surface of the second portion is offset widthwise toward
the image read line relative to the light incidence surface of the
first portion.
8. An image reading apparatus comprising: at least one light
source; an elongate light guide member for guiding light emitted
from the light source toward an image read line; and a plurality of
light receiving elements for receiving light reflected at the image
read line; wherein the light guide member includes a first portion,
a second portion, and a connecting portion for connecting the first
portion and the second portion; wherein the first portion includes
a first light incidence surface facing the light source for entry
of light emitted from the light source, and at least one first
light exit surface facing the second portion, the first light exit
surface being convexly curved; wherein the second portion includes
at least one second light incidence surface facing the first light
exit surface of the first portion for reentry of light, and a
second light exit surface oriented toward the image read line for
emitting light toward the image read line; and wherein the
connecting portion is narrower than the first portion and the
second portion.
9. An elongate light guide member comprising: a first portion; a
second portion; and a connecting portion connecting the first
portion and the second portion; wherein the first portion includes
a light incidence surface oriented away from the second portion for
entry of light, the light incidence surface being convexly curved
widthwise of the light guide member; wherein the second portion
includes a light exit surface oriented away from the first portion
for emitting light; and wherein the connecting portion is narrower
than the first portion and the second portion.
10. The light guide member according to claim 9, wherein the first
portion of the light guide member further includes additional light
exit surfaces each of which is convexly curved, the second portion
of the light guide member further including an additional light
incidence surface facing each light exit surface of the first
portion.
11. The light guide member according to claim 9, wherein the first
portion, the second portion and the connecting portion are formed
of transparent resin as one piece.
12. The light guide member according to claim 9, wherein the
connecting portion is located on a widthwise center axis of the
first portion.
13. The light guide member according to claim 9, wherein the light
exit surface of the second portion is convexly curved at least
partially.
14. The light guide member according to claim 9, wherein the second
portion includes a pair of side surfaces which are inclined with
respect to a widthwise center axis of the first portion.
15. An elongate light guide member comprising: a first portion; a
second portion; and a connecting portion connecting the first
portion and the second portion; wherein the first portion includes
a first light incidence surface oriented away from the second
portion for entry of light, and at least one first light exit
surface facing the second portion, the first light exit surface
being convexly curved; wherein the second portion includes at least
one second light incidence surface facing the first light exit
surface of the first portion for reentry of light, and a second
light exit surface oriented away from the first portion for
emitting light; and wherein the connecting portion is narrower than
the first portion and the second portion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image reading apparatus.
It also relates to a light guide member used for an image reading
apparatus.
[0003] 2. Description of the Related Art
[0004] As is well known, a typical image reading apparatus
incorporating a linear image sensor is designed to illuminate an
image read line of a document with light emitted from a light
source. The light reflected at the image read line is received by a
plurality of light receiving elements. Each of the light receiving
elements outputs signals corresponding to the received amount of
light.
[0005] With such an image reading apparatus, if the image read line
is not illuminated sufficiently, the image reading quality may be
deteriorated. Therefore, light emitted from the light source needs
to be effectively directed to the image read line. For this
purpose, JP-A-9-307696 for example discloses an image reading
apparatus in which a light guide member (prism) is arranged in
facing relationship to a light source for guiding light emitted
from the light source toward an image read line. In this image
reading apparatus, light from the light source can be directed
toward the image read line even if the light source is not disposed
in facing relationship to the image read line.
[0006] In the above-described image reading apparatus, the light
guide member has a flat light incidence surface. Light entering the
light guide member through the light incidence surface is emitted
through a light exit surface toward the image read line. However,
the light guide member with the flat light incidence surface has
the following problems.
[0007] Generally, light emitted from the light source has a
tendency to diverge as it travels. Since the light incidence
surface of the prior art light guide member is flat, the light
entering the light guide member through the light incidence surface
continues to diverge within the light guide member. Therefore, the
amount of light directed toward the light exit surface is reduced.
Specifically, most of the light entering the light guide member
travels toward the light exit surface while being totally reflected
by the surfaces of the light guide member. However, since light
disperses in various directions within the light guide member, a
large amount of light impinges on the surfaces of the light guide
member at an angle smaller than the total reflection critical
angle, thereby passing through the light guide member. As a result,
the amount of light guided toward the light exit surface is
reduced, resulting in deterioration of the image reading
quality.
[0008] Moreover, even if a large amount of light is guided toward
the light exit surface, it is difficult to efficiently illuminate
the image read line because the light is not converged.
[0009] Thus, the prior art image reading apparatus needs to be
improved to enhance efficiency in illuminating the image read
line.
SUMMARY OF THE INVENTION
[0010] It is therefore an object of the present invention to
provide an image reading apparatus which is capable of effectively
illuminating an image read line of a document.
[0011] An object of the present invention to provide a light guide
member which may be advantageously incorporated in such an image
reading apparatus.
[0012] In accordance with a first aspect of the present invention,
an image reading apparatus comprises at least one light source, an
elongate light guide member for guiding light emitted from the
light source toward an image read line, and a plurality of light
receiving elements for receiving light reflected at the image read
line. The light guide member includes a first portion, a second
portion, and a connecting portion for connecting the first portion
and the second portion. The first portion includes a light
incidence surface facing the light source for entry of light
emitted from the light source, and the light incidence surface is
convexly curved widthwise of the light guide member. The second
portion includes a light exit surface oriented toward the image
read line for emitting light toward the image read line. The
connecting portion is narrower than the first portion and the
second portion.
[0013] Preferably, the first portion of the light guide member
further may include additional light exit surfaces each of which is
convexly curved, whereas the second portion of the light guide
member may further include an additional light incidence surface
facing each light exit surface of the first portion.
[0014] Preferably, the first portion, the second portion and the
connecting portion may be formed of transparent resin as one
piece.
[0015] Preferably, the connecting portion may be located on a
widthwise center axis of the first portion, and the widthwise
center axis of the first portion may be located directly above the
light source.
[0016] Preferably, the light exit surface of the second portion may
be convexly curved at least partially.
[0017] Preferably, the light exit surface of the second portion may
be offset widthwise toward the image read line relative to the
light incidence surface of the first portion.
[0018] According to a second aspect of the present invention, there
is provided an image reading apparatus which comprises at least one
light source, an elongate light guide member for guiding light
emitted from the light source toward an image read line, and a
plurality of light receiving elements for receiving light reflected
at the image read line. The light guide member includes a first
portion, a second portion, and a connecting portion for connecting
the first portion and the second portion. The first portion
includes a first light incidence surface facing the light source
for entry of light emitted from the light source, and at least one
first light exit surface facing the second portion and convexly
curved. The second portion includes at least one second light
incidence surface facing the first light exit surface of the first
portion for reentry of light, and a second light exit surface
oriented toward the image read line for emitting light toward the
image read line. The connecting portion is narrower than the first
portion and the second portion.
[0019] According to a third aspect of the present invention, there
is provided an elongate light guide member which comprises a first
portion, a second portion, and a connecting portion connecting the
first portion and the second portion. The first portion includes a
light incidence surface oriented away from the second portion for
entry of light and convexly curved widthwise of the light guide
member. The second portion includes a light exit surface oriented
away from the first portion for emitting light. The connecting
portion is narrower than the first portion and the second
portion.
[0020] Preferably, the first portion of the light guide member may
further include additional light exit surfaces each of which is
convexly curved, and the second portion of the light guide member
may further include an additional light incidence surface facing
each light exit surface of the first portion.
[0021] Preferably, the first portion, the second portion and the
connecting portion may be formed of transparent resin as one
piece.
[0022] Preferably, the connecting portion may be located on a
widthwise center axis of the first portion.
[0023] Preferably, the light exit surface of the second portion may
be convexly curved at least partially.
[0024] Preferably, the second portion includes a pair of side
surfaces which are inclined with respect to a widthwise center axis
of the first portion.
[0025] According to a fourth aspect of the present invention, there
is provided an elongate light guide member which comprises a first
portion, a second portion, and a connecting portion connecting the
first portion and the second portion. The first portion includes a
first light incidence surface oriented away from the second portion
for entry of light, and at least one first light exit surface
facing the second portion and convexly curved. The second portion
includes at least one second light incidence surface facing the
first light exit surface of the first portion for reentry of light,
and a second light exit surface oriented away from the first
portion for emitting light. The connecting portion is narrower than
the first portion and the second portion.
[0026] Other features and advantages of the present invention will
become clearer from the detailed description given below with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a sectional view showing an image reading
apparatus embodying the present invention.
[0028] FIG. 2 is a sectional view taken along lines II-II in FIG.
1.
[0029] FIG. 3a is a plan view of a light guide member incorporated
in the image reading apparatus shown in FIG. 1.
[0030] FIG. 3b is a front view of the same light guide member.
[0031] FIG. 3c is a left side view of the same light guide
member.
[0032] FIG. 3d is a sectional view taken along lines III-III in
FIG. 3b.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Preferred embodiments of the present invention will be
described below in detail with reference to the accompanying
drawings.
[0034] FIGS. 1 and 2 illustrate an example of image reading
apparatus in accordance with the present invention. FIG. 3
illustrates an example of light guide member in accordance with the
present invention. In this embodiment, the present invention is
applied for a so-called flat bed type image reading apparatus for
reading an image of a document disposed on a transparent document
supporting panel.
[0035] The illustrated image reading apparatus A is elongate in a
primary scanning direction indicated by an arrow Na in FIG. 2. The
image reading apparatus A generally comprises a plurality of light
sources 2, a light guide member 3, a lens array 4, a row of light
receiving elements 5, a substrate 6, a housing 1 for accommodating
these components, and a document supporting panel 7.
[0036] The housing 1 is made of a synthetic resin. The housing 1 is
supported by a non-illustrated movable member below the document
supporting panel 7 for movement in a secondary scanning direction
indicated by an arrow Nb in FIG. 1. The substrate 6 is mounted at
the bottom of the housing 1.
[0037] The lens array 4 comprises a row of image forming lenses 40
extending in the primary scanning direction, and a holder 41 made
of a synthetic resin for holding the lenses 40. Each of the lenses
40 may be a selfoc lens (self focusing lens) capable of forming an
actual size erect image of a document D. Alternatively, use may be
made of other lenses such as a convex lens. On the document
supporting panel 7, an image read line S extending in the primary
scanning direction is defined in alignment with the row of lenses
40.
[0038] The row of light receiving elements 5 for photoelectric
conversion is disposed directly below the lens array 4 on the
substrate 6 in alignment with the lens array 4. When each of the
light receiving elements 5 receives light reflected on the image
read line S and collected by the lens array 4, the light receiving
element 5 outputs signals corresponding to the received amount of
light.
[0039] The light sources 2 are arranged on the substrate 6 at a
predetermined pitch in a row extending in the primary scanning
direction. Each of the light sources 2 may comprise an LED for
example.
[0040] The light guide member 3 may be formed by molding a
transparent resin such as PMMA (polymethyl methacrylate
(methacrylate resin)) or polycarbonate. The light guide member 3,
which is elongate in the primary scanning direction, generally
comprises a body 30c having a uniform cross section, and a pair of
engaging portions 30a, 30b provided at longitudinally opposite ends
of the body 30c. All surfaces of the light guide member 3 are
mirror-finished. Therefore, when light traveling within the light
guide member 3 impinges on the mirror surfaces of the light guide
member 3 at an angle larger than the total reflection critical
angle (which is determined depending on the material of the light
guide member), it is totally reflected. On the other hand, light
impinging on the mirror surfaces of the light guide member 3 at an
angle smaller than the critical angle passes therethrough. The
surfaces of the light guide member 3 need not necessarily be
polished to serve as mirror surfaces. In the present invention,
mirror surfaces may be provided by resin-molding the light guide
member 3 to have smooth surfaces.
[0041] As clearly shown in FIGS. 1 and 3d, the body 30c of the
light guide member 3 comprises a first or lower portion 31, a
second or upper portion 32 and a connecting neck portion 33.
[0042] The lower portion 31 has a first light incidence surface 35
which is downwardly convex, and a pair of first light exit surfaces
37a each of which is laterally and upwardly convex.
[0043] The connecting neck portion 33 connects the lower portion 31
and the upper portion 32. The provision of the connecting neck
portion 33 allows the lower portion 31 and the upper portion 33 to
be integrally formed. In this embodiment, the light guide member 3
as a whole is formed as one piece. The connecting neck portion 33
is arranged so that a widthwise center of the connecting neck
portion 33 coincides with a widthwise center axis C1 of the lower
portion 31. The connecting neck portion 33 has a smaller width s1
than the lower and the upper portions 31, 32. As a result, a pair
of recesses 36 opposed widthwise of the light guide member 3 are
formed between the lower portion 31 and the upper portion 32.
[0044] The upper portion 32 comprises a second light exit surface
38, a pair of side surfaces 39a, 39b, and a pair of second light
incidence surfaces 37b. The second light incidence surfaces 37b
face the first light exit surfaces 37a of the lower portion 31,
respectively. Each second light incidence surface 37b is flat in
this embodiment but may be convex. The side surface 39a is inclined
so that light entering the upper portion 32 from the lower portion
31 is totally reflected at the side surface 39a toward the second
light exit surface 38. The second light exit surface 38 emits the
light reflected by the side surface 39a to the outside. The second
light exit surface 38 is made entirely or generally entirely convex
laterally upward.
[0045] As clearly shown in FIG. 1, the light guide member 3 is
arranged in the housing 1 with the widthwise center axis C1 of the
lower portion 31 positioned directly above the light sources 2 so
that the first light incidence surface 35 faces the light sources
2. The second light exit surface 38 is oriented toward a reverse
surface of the document supporting panel 7. As clearly shown in
FIG. 3, each of the engaging portions 30a, 30b is formed with a
projection 34a which fits into a non-illustrated recess of the
housing 1, thereby positioning the light guide member 3 relative to
the housing 1. Further, the side surface 39b of the upper portion
32 is formed with a plurality of projections 34 each of which fits
into a corresponding recess 19a formed in a partition member 19 of
the housing 1. As a result, the light guide member 3 is positively
positioned relative to the housing 1.
[0046] The image reading apparatus A having the above-described
structure operates as follows.
[0047] Referring to FIG. 1, when the light sources 2 are turned on,
light emitted from the light sources 2 enters the lower portion 31
through the first light incidence surface 35. At this time, since
the first light incidence surface 35 is convexly curved, it works
to refract the light substantially in the same way as a convex
lens. As a result, the light diverging from the light sources 2
converges widthwise in entering the lower portion 31.
[0048] After the light enters the lower portion 31, a portion of
light traveling at or near the widthwise center axis C1 of the
lower portion 31 directly enters the upper portion 32 through the
connecting neck portion 33. On the other hand, a portion of light
traveling away from the widthwise center axis C1 exits the lower
portion 31 through the first light exit surfaces 37a, passing
through the recesses 36 and the reentry surfaces 37b before
entering the upper portion 32. At this time, since each of the
first light exit surfaces 37a is convexly curved, the diverging
portion of light impinging on the first light exit surface 37a is
again refracted inwardly widthwise. In this way, the widthwise
light is twice refracted inwardly. As a result, the light emitted
from the light sources 2 can be reliably guided into the upper
portion 2 generally along the widthwise center axis C1 of the lower
portion 1.
[0049] The light entering the upper portion 32 reaches the side
surface 39a. At this time, since the light travels in parallel or
generally parallel with the center axis C1, the entire or almost
entire portion of light is totally reflected by the side surface
39a. Thus, a large amount of light can be directed toward the light
exit surface 38, and hence to the image read line S. As a result,
it is possible to effectively illuminate the image read line S,
thereby enhancing the image reading quality.
[0050] By contrast, light emitted from the light sources 2 diverges
longitudinally of the light guide member 3. However, light is not
converged in this direction so that the image read line S can be
effectively illuminated over its entire length.
[0051] The specific structure of the image reading apparatus and
the light guide member of the present invention is not limited to
the embodiment described above but may be modified in various
ways.
[0052] For example, the connecting neck portion may be a
transitional portion indistinguishable from the lower portion and
the upper portion. In other words, the lower and the upper portion
may be connected directly. In this case, the portion at which the
lower and the upper portions are connected may be regarded as a
connecting neck portion.
[0053] In the embodiment described above, the present invention is
applied to a flat bed type image reading apparatus. However, the
present invention is applicable to other type of image reading
apparatus such as a sheet feed type image reading apparatus in
which image reading is performed with the document transferred in
the secondary scanning direction by a platen roller, or an image
reading apparatus for reading images on an electronic white board
to make a copy of the image thereon.
[0054] Further, a cold cathode tube may be employed as a light
source instead of LEDs.
* * * * *