JP2015119355A - Light guide body, illumination device, and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide body capable of efficiently guiding light from a light source to a reading area and to provide an illumination device and an image reader.SOLUTION: The light guide body includes an incident surface on which a luminous flux is made incident, an emission surface from which the luminous flux from the incident surface is emitted toward the reading area, and a side surface which connects the incident surface and the emission surface. Further, the light guide body includes a gap part configured so that a part of the luminous flux made incident on the incident surface and going toward the emission surface, without passing through the side surface is totally reflected and guided to the emission surface.

Description

  The present invention relates to a light guide, and is particularly suitable for an image reading apparatus such as an image scanner, a copying machine, or a facsimile.

  Conventionally, as an illuminating device used in an image reading apparatus that illuminates a document surface and reads an image in a line-sequential manner, a light guide that is long in one direction is used, and the longitudinal direction (main scanning direction) of the light guide is used. A configuration for illuminating a long reading area is known. Patent Document 1 discloses a configuration in which predetermined light emitted outside the optical path of a light guide is totally reflected by a side surface and directed toward a focal point of a cylindrical lens surface as an exit surface. Further, Patent Document 2 discloses a configuration in which the reflectance can be increased by total reflection on the inclined surface of the groove by forming a groove on the exit surface of the light guide used in the liquid crystal display device. Yes.

JP 2011-14301 A JP 2001-42328 A

  However, in patent document 1, since it is necessary to use the peripheral surface of a cylindrical lens surface, the problem that an illuminating device will enlarge will arise. Further, in Patent Document 2, it is only necessary to form a large number of grooves parallel to each other on the exit surface of the light guide, that is, only the number of grooves is considered, and the position of the grooves on the exit surface is not considered. Therefore, this configuration cannot be applied to the lighting device.

  Accordingly, an object of the present invention is to provide a light guide, an illuminating device, and an image reading device that can efficiently guide light from a light source to a reading region.

  In order to achieve the above object, a light guide according to the present invention includes an incident surface on which a light beam is incident, an exit surface from which the light beam from the incident surface exits toward a reading region, the incident surface, and the exit surface. A gap that is incident on the incident surface and totally reflects a part of the light beam that goes to the exit surface without passing through the side surface and guides it to the exit surface. Is provided.

  According to the present invention, light from a light source can be efficiently guided to a document reading area as a reading area.

It is a figure which shows the subscanning cross section of the light guide which concerns on the 1st Embodiment of this invention. It is sectional drawing of the indirect optical path in 1st Embodiment. It is sectional drawing of the direct optical path in 1st Embodiment. It is a graph which shows light quantity distribution of 1st Embodiment. It is a figure which shows the subscanning cross section of the light guide which concerns on 2nd Embodiment. It is sectional drawing of the indirect optical path in 2nd Embodiment. It is sectional drawing of the direct optical path in 2nd Embodiment. It is a graph which shows light quantity distribution of 2nd Embodiment. It is a figure which shows the subscanning cross section of the light guide which concerns on 3rd Embodiment. It is sectional drawing of the indirect optical path in 3rd Embodiment. It is sectional drawing of the direct optical path in 3rd Embodiment. It is a graph which shows light quantity distribution of 3rd Embodiment. It is a sub-scanning sectional view about the principal part of the image reading device carrying a light guide and an illuminating device concerning an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image reading device)
FIG. 13 shows a sub-scanning cross section of the main part of the image reading apparatus equipped with the light guide and the illumination device according to the embodiment of the present invention. Here, in the present specification, “main scanning direction”, “sub-scanning direction”, “main-scanning section”, and “sub-scanning section” are defined as follows. That is, the main scanning direction is the Y direction (first direction) which is the arrangement direction of the point light source groups, the sub-scanning direction is the X direction (second direction), and the main scanning section is the XY section (first section). ), The sub-scanning section is a ZX section (second section) which is a section perpendicular to the arrangement direction of the point light source groups. In the present specification, the main scanning direction is also referred to as the longitudinal direction.

  Illumination light emitted from a tubular light source 101 (point light source group or long light source arranged in the longitudinal direction) extending in the main scanning direction (longitudinal direction) is a light guide 102 extending in the main scanning direction in front of the light source. Is incident on the incident surface.

  The light incident on the incident surface of the light guide 102 propagates through the light guide 102 and is emitted from the exit surface of the light guide 102 to illuminate the document 000 placed on the document table glass 001. The light flux from the reading area on the original surface is connected as a focusing section to the photoelectric conversion element 007 on the photoelectric conversion element 007 as a light receiving section that receives the light flux from the reading area via a plurality of reflecting mirrors 005. An image is formed by the image lens 006. Then, the two-dimensional image of the document is read by the line sequential reading method while the carriage 004 is moved in the sub-scanning direction (X direction) by the sub-scanning driving device 008.

(Light guide)
1) Incident surface, side surface, and exit surface FIG. 1 is a cross-sectional view in the sub-scanning direction of a light guide 102 according to an embodiment of the present invention. An incident surface 103 of the light guide 102 is disposed in the vicinity of the tubular light source 101 extending in the longitudinal direction (Y direction). The light guide 102 includes an entrance surface 103, an exit surface 104 that emits light guided to the document 000, and a side surface 105 that connects the entrance surface 103 and the exit surface 104. The space between the surfaces is filled with an optical medium different from air. In the present embodiment, the light guide 102 is formed by injection molding of acrylic resin.

  The side surface 105 is formed wider than the width of the incident surface 103 in the sub-scan section. The side surface 105 has a condensing function and has a curved surface shape. In the present embodiment, the side surface 105 has an elliptical shape having a positive power. Thus, in the sub-scan section, the position of the midpoint of the incident surface 103 is set as the first focal point of the elliptical surface, and light traveling from the incident surface 103 toward the side surface 105 can be efficiently deflected in the direction of the document 000.

  The exit surface 104 is formed of a refracting surface (convex surface) having positive power (refractive power) as a curved surface on a substantially circular arc that protrudes outward. Of the light that has entered the light guide 102 from the light source 101, the light that reaches the side surface 105 is emitted from the emission surface 104 through total reflection at the side surface 105, and is efficiently guided to the document reading region that is the reading region. (FIG. 2). On the other hand, of the light incident on the light guide 102 from the light source 101, the light that directly reaches the emission surface 104 without passing through the side surface 105 includes a gap described below and a positive refracting surface (convex surface) as the emission surface. ) Can be efficiently guided to the document reading area (FIG. 3).

2) Gap portion A gap portion 106 is provided on the emission surface 104 from the emission surface 104 toward the incidence surface 103 side. The gap 106 is provided at a position where light that does not go to the reading area (document reading area) out of the direct light traveling from the exit surface 104 toward the reading area side reaches the front of the exit surface 104, and the original reading area by total reflection. The angle is set to the light that is directed to Here, the direct light is light from the light source incident from the incident surface 103 and is directed toward the reading region via the emission surface 104 without passing through the side surface 105.

  The gap 106 is formed from the exit surface 104 toward the entrance surface 103 as long as the light beam traveling from the entrance surface 103 toward the side surface 105 is not kicked. Specifically, in the cross section perpendicular to the longitudinal direction (in the sub-scanning cross section), the end of the incident surface 103 farthest from the document reading center is set as the point A, and the end of the nearest exit surface 104 is set as the point B. The gap 106 is formed within a range from the emission surface 104 to a portion intersecting with the straight line AB. More preferably, it is formed up to a portion intersecting with the straight line AB.

  In this way, a portion of the direct light from the exit surface 105 toward the document 000 is not totally reflected by the side surface 105 from the incident surface 103, but is totally reflected by the gap 106, so that a sufficient amount of light is secured in the document 000. In addition, a stable illumination area in the sub-scanning direction can be secured.

  FIG. 4 shows a light amount distribution in the sub-scanning direction in the present embodiment. A solid line indicates the light amount distribution of the present embodiment, and a wavy line indicates the light amount distribution of the conventional embodiment. The amount of light totally reflected by the gap 106 can be increased from the image reading optical axis to the light guide 102 side. In addition, it is possible to strengthen the document floating while securing a desired document reading area of the document 000.

(Effect of this embodiment)
As described above, in the present embodiment, the light emitted from the tubular light source 101 is efficiently guided to the document reading area, and the size of the light guide is made equal to that of the conventional light guide to suppress the increase in the size of the illumination device. be able to.

<< Second Embodiment >>
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. The difference from the first embodiment is that the incident surface is the side end surface of the light guide, a point light source is used as the light source, and the surface facing the emission surface is a diffusion surface.

1) Incident surface, diffusing surface, side surface, exit surface In FIG. 5, a point light source (high-power white LED) 201 at the end in the main scanning direction is incident on the side end surface of the light guide 202 outside the light guide 202. Arranged in the vicinity of the surface 203. The light guide 202 includes an incident surface 203 on which the light beam from the point light source 201 is incident, an output surface 205 from which the light beam guided to the document 000 is emitted, and a light beam from the light source that faces the output surface 205 and passes through the incident surface 203. Has a diffusing surface 204 on which the surface diffuses, and a side surface 206 connecting these surfaces. As in the first embodiment, each surface is filled with an optical medium different from air, and the light guide 202 is formed by injection molding of acrylic resin.

  The side surface 206 has a condensing function and has a curved surface shape. In the present embodiment, an elliptical surface having convex power is used. That is, in the sub-scanning section, by setting the position of the middle point of the diffusing surface 204 as an elliptical reflecting surface having the first focal point of the ellipsoidal surface, the light beam traveling from the diffusing surface 204 toward the side surface 206 is efficiently directed toward the document 000. It can be deflected.

  The exit surface 205 is formed as a positive refracting surface (convex surface) as a curved surface with a substantially arc-shaped cross section protruding outward. Of the light diffused by the diffusion surface 204 from the light incident on the light guide 202 from the light source 201, the light reaching the side surface 206 is emitted from the emission surface 205 through total reflection at the side surface 206 and efficiently It can be led to the document reading area (FIG. 6). On the other hand, the light that has entered the light guide 202 from the light source 201 and is diffused by the diffusing surface 204, the light that directly reaches the exit surface 205 without passing through the side surface 206, the gap described below, and the exit The positive refracting surface (convex surface) of the surface can efficiently lead to the document reading area (FIG. 7).

2) Gap part Here, a gap part 207 is provided on the emission surface 205 from the emission surface 205 toward the diffusion surface 204 side. The gap portion 207 is provided at a position where direct light that goes from the diffusion surface 204 to the document reading region side through the exit surface 205 without passing through the side surface 206 reaches the front of the exit surface 205. It is done. In addition, the gap 207 is set to an angle at which light is directed toward the document reading area by total reflection. In the present embodiment, in the cross section perpendicular to the longitudinal direction where the incident surface is provided, the gap portion 207 is in the same direction as the direction connecting the center position of the incident surface 203 and the center position of the exit surface 205 (other than when parallel). , Including a substantially parallel case).

  The gap portion 207 is formed from the emission surface 205 toward the diffusion surface 204 in a range where the light beam from the diffusion surface 204 toward the side surface 206 is not kicked. Specifically, in the sub-scan section, when the end of the diffusing surface 204 farthest from the document reading center is a point A and the end of the nearest exit surface 104 is a point B, the gap 207 is a straight line from the exit surface 205. It is formed within a range up to a portion intersecting with AB. More preferably, it is formed up to a portion intersecting with the straight line AB.

  In this way, a part of the direct light from the exit surface 205 toward the document 000 is not totally reflected by the side surface 206 from the diffusing surface 204, and is totally reflected by the gap portion 207, thereby ensuring a sufficient amount of light in the document 000. In addition, a stable illumination area in the sub-scanning direction can be secured.

  FIG. 8 shows a light amount distribution in the sub-scanning direction in the present embodiment. A solid line indicates the light amount distribution of this embodiment, and a wavy line indicates the conventional light amount distribution. The amount of light totally reflected by the gap 207 can be increased from the image reading optical axis to the light guide 202 side. In addition, it is possible to strengthen the document floating while securing a desired document reading area of the document 000.

(Effect of this embodiment)
As described above, in the present embodiment, the light emitted from the point light source 201 is efficiently guided to the document reading area, and the size of the light guide is made equal to that of the conventional light guide, thereby suppressing the increase in size of the illumination device. be able to.

<< Third Embodiment >>
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS. The difference from the first embodiment is that the light source is changed from a tubular light source to a surface light source, and the gap is formed in a curved shape at two locations in the sub-scanning cross section.

1) Incident surface, side surface, and exit surface FIG. 9 is a cross-sectional view of the light guide 302 according to the embodiment of the present invention in the sub-scanning direction. An incident surface 303 of the light guide 302 is disposed in the vicinity of the surface light source (organic EL) 301 extending in the longitudinal direction (Y direction). The light guide 302 includes an entrance surface 303, an exit surface 304 that emits light guided to the document 000, and a side surface 305 that connects the entrance surface 303 and the exit surface 304. The space between the surfaces is filled with an optical medium different from air. In this embodiment, the light guide 302 is formed by injection molding of acrylic resin.

  The side surface 305 is formed wider than the width of the incident surface 303 in the sub-scan section. The side surface 305 has a light collecting action and has a curved surface shape. In the present embodiment, the side surface 305 is an elliptical surface having convex power. As a result, in the sub-scan section, the position of the midpoint of the incident surface 303 is the first focal point of the elliptical surface, and light from the incident surface 303 toward the side surface 305 can be efficiently deflected in the direction of the document 000.

  The exit surface 304 is formed as a positive refracting surface (convex surface) as a curved surface with a substantially arc-shaped cross section protruding outward. Of the light incident on the light guide 302 from the surface light source 301, the light reaching the side surface 305 can be emitted from the emission surface 304 via total reflection at the side surface 305 and efficiently guided to the document reading area. (FIG. 10). On the other hand, of the light incident on the light guide 302 from the surface light source 301, the light that directly reaches the exit surface 304 without passing through the side surface 305 includes a gap portion described below and a positive refracting surface (convex surface) of the exit surface. ) Can efficiently lead to the document reading area (FIG. 11).

2) Cavity portion Here, the exit surface 304 is provided with two curved space portions 306 from the exit surface 304 toward the entrance surface 303 side. The gap portion 306 is provided at a position where direct light traveling from the exit surface 304 toward the document reading area reaches the front side of the exit surface 304 and is directed toward the document reading area by total reflection. The angle is set as light. The gap 306 is formed from the exit surface 304 toward the entrance surface 303 within a range in which light rays from the entrance surface 303 toward the side surface 305 are not kicked.

  Here, in the sub-scan section, the end of the incident surface 303 farthest from the document reading center is point A, the end of the nearest exit surface 304 is point B, and the end of the nearest entrance surface 303 is point D, the nearest. The end of the exit surface 304 is point B, and the end of the farthest exit surface 304 is point C. At this time, the gap 306 is formed within a range up to a portion where the straight line AB and the straight line CD intersect. More preferably, it is formed up to a portion where the straight line AB and the straight line CD intersect.

  In this way, a part of the direct light from the exit surface 305 toward the document 000 is totally reflected by the gap portion 306 without being reflected by the side surface 305 from the entrance surface 303. Since the gap 306 has a curved surface shape, the totally reflected light beam is efficiently guided to the document 000, so that a sufficient amount of light can be secured and a stable illumination area in the sub-scanning direction can be secured. .

  FIG. 12 shows a light amount distribution in the sub-scanning direction in the present embodiment. A solid line indicates the light amount distribution of this embodiment, and a wavy line indicates the conventional light amount distribution. The amount of light totally reflected by the gap 306 can be increased from the image reading optical axis to the light guide 302 side. In addition, it is possible to strengthen the document floating while securing a desired document reading area of the document 000.

(Effect of this embodiment)
As described above, in the present embodiment, the light emitted from the surface light source 301 is efficiently guided to the document reading area, and the size of the light guide is made equal to that of the conventional light guide to suppress the increase in the size of the illumination device. be able to.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to this, A various deformation | transformation is possible within the scope of the present invention.

(Modification 1)
In the above-described embodiment, a configuration is adopted in which one light guide is obliquely provided so as to illuminate the original reading area on the original surface from one side. However, the present invention is not limited to this, and a configuration may be adopted in which a plurality of (two) light guides are obliquely arranged with respect to the document reading region so as to illuminate the document reading region on the document surface from both sides. . In this case, the same light guide can be used as a plurality (two) of light guides.

In addition, on the premise of a configuration in which one light guide is provided obliquely, a second light exit surface is formed on this light guide, and a reflective member (mirror, prism, etc.) facing the second light exit surface is provided. It is also possible to adopt a configuration in which the original reading area is illuminated from both sides. in this case,
Similar to the above-described embodiment, the document reading area is illuminated, and the document reading area is illuminated from the opposite side via the second emission surface and the reflecting member.

(Modification 2)
In the first and second embodiments, the gap portion extends in a planar shape, and in the third embodiment, the gap portion extends in a curved shape. On the contrary, in the first and second embodiments, the gap portion is extended. It extends in the shape of a curved surface, and in the third embodiment, the gap portion may extend in a planar shape.

(Modification 3)
In the third embodiment, two gaps are provided. However, in the second embodiment, two gaps can be provided as in the third embodiment. Moreover, such two places can also be made into three or more places.

(Modification 4)
In the above-described embodiment, the side surface of the light guide has an elliptical shape having positive power, but may have a parabolic shape having positive power.

(Modification 5)
In the second embodiment, the diffusion surface is provided opposite to the emission surface. However, the degree of diffusion (diffusivity) in the longitudinal direction (main scanning direction) of the diffusion surface may be changed (for example, The diffusivity is increased on the center side in the longitudinal direction relative to the end side).

102, 202, 302 Light guide, 103, 203, 303... Incident surface, 104, 205, 304... Exit surface, 011, 105, 206, 305 .. side surface, 106, 207, 306.

Claims (15)

A light guide having an incident surface on which a light beam is incident, an exit surface from which the light beam from the incident surface exits toward a reading region, and a side surface connecting the incident surface and the exit surface,
A light guide having an air gap that is incident on the incident surface and totally reflects a part of the light beam directed to the exit surface without passing through the side surface and guides the light to the exit surface.   The light guide according to claim 1, further comprising a diffusing surface for diffusing a light beam incident on the incident surface.   In the cross section perpendicular to the longitudinal direction where the incident surface is provided, the end portion farthest from the center of the reading region on the incident surface is point A, and the end portion closest to the center of the reading region on the exit surface is point B. The light guide according to claim 1 or 2, wherein the gap extends within a range from the emission surface to a portion intersecting with the straight line AB.   The light guide according to claim 3, wherein the gap extends from the exit surface to a portion intersecting with the straight line AB.   The cross section perpendicular to the longitudinal direction in which the incident surface is provided, the gap is provided in the same direction as a direction connecting the center position of the incident surface and the center position of the exit surface. 5. The light guide according to 3 or 4. The gap is provided in two places,
When an end portion closest to the center of the reading area on the incident surface is a point D and an end portion farthest from the center of the reading area on the exit surface is a point C,
The light guide according to claim 3, wherein the gap extends within a range from the emission surface to a portion intersecting with the straight line AB and the straight line CD. A diffusion surface for diffusing the light beam incident on the incident surface;
When the end closest to the center of the reading area on the diffusion surface is point D and the end farthest from the center of the reading area on the exit surface is point C,
The light guide according to claim 4, wherein the gap extends within a range from the emission surface to a portion intersecting with the straight line AB and the straight line CD.   8. The light guide according to claim 6, wherein the two gap portions extend from the emission surface to a portion intersecting with the straight line AB and the straight line CD.   The light guide according to any one of claims 1 to 8, wherein the gap portion extends in a planar shape or a curved shape.   The exit surface is provided along a longitudinal direction, and the exit surface has a curved surface shape having a positive power in a cross section perpendicular to the longitudinal direction. The light guide according to 1.   The light guide according to claim 10, wherein the side surface has a parabolic shape or an elliptical shape having a positive power in a cross section perpendicular to the longitudinal direction.   The light guide according to any one of claims 1 to 11, wherein the light source that causes the light beam to enter the incident surface is a point light source group, a long light source, or a surface light source.   An illumination device comprising: a light source; and the light guide according to claim 1 for guiding a light beam from the light source to the reading region.   The lighting device according to claim 13, wherein two light guides are arranged symmetrically with respect to the reading region.   15. An image comprising: the illumination device according to claim 13; a light receiving unit that receives a light beam from the reading region; and an imaging unit that guides the light beam from the reading region to the light receiving unit. Reader.