JP2014187444A - Light source device for document reading - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device capable of satisfying an optical characteristic for making an irradiation light conducive to document reading excellent without reducing the efficiency of light utilization, and capable of irradiating the document to be read with light having high illuminance and even illuminance distribution while suppressing costs.SOLUTION: By having integrally branch parts 21, 21 having a pair of branch paths 21a, 21b disposed facing each other at longitudinal opposite end parts and branched in two transverse paths toward the opposed end part and a pair of light guide parts 22a, 22b extending in parallel between the facing branch paths 21a, 21b and communicating the branch paths 21a, 21b with each other, a ring-shaped light guide body 2 having a longitudinally long opening 2a has a light-outgoing surface 23 for linking the top ends of the light guide parts 22a, 22b together, at least one end face thereof being a light-incoming surface 24, and an LED light source 3 is disposed by directing the luminous surface of a light-emitting element thereto.

Description

  The present invention relates to a document reading light source device used as a light source in a document reading device such as a scanner.

  Conventionally, reading of a document in a document reading apparatus such as a reduction optical system and a contact optical system scanner is performed in the following procedure. In other words, scanning is performed with linear light having a predetermined width on a surface to be read of a document to be read placed on a contact glass, and the reflected light or transmitted light is an optical element composed of an optical element such as a mirror or a lens. Through a system, an image is formed on a linear solid-state imaging device (line CCD (charge-coupled device) or the like). Then, by performing predetermined signal processing on the imaging signal output from the linear solid-state imaging device, the reading target surface is read as a document image.

At this time, when the document image is a color image, in order to read the color document image with high definition, linear light having a high illuminance and a uniform illuminance distribution is applied to the reading target surface of the document to be read. Therefore, there is a demand for a technique (that is, a light source device capable of emitting such linear light).
In addition, in recent years, LED (Light Emitting Diode), which can reduce power consumption and heat generation compared to tube lamps such as xenon lamps and cold-cathode fluorescent lamps (CCFLs), has excellent durability. : Light-emitting diodes) as a light source has been increasingly demanded and has become widespread.

As an example of a document reading light source device that can irradiate linear light that satisfies such a requirement (hereinafter referred to as a light source device as appropriate), for example, as shown in FIG. A so-called array type device having LED light sources 80 arranged in a line in the scanning direction is known (see, for example, Patent Document 1).
In this light source device, linear light emitted from a small area of each LED of the LED light source 80 is reflected by a first mirror 81 as a reflector, and the reflected light is placed on a contact glass 82 to be read. The irradiated portion 84 of the document 83 is irradiated. Then, the reflected light (reflected light including the original image) reflected by the reading target surface of the original 83 to be read is reflected by the second mirror 85, and the original image is reduced on the imaging surface of the line sensor 86 which is a photoelectric conversion element. It is formed as an image.

  As a document reading light source device of a system different from the array system, for example, a so-called LGL (Light-Guide-Lens) system including a light guide as an optical element instead of the LED light source 80 is used. is there. This LGL-type light source device includes a light guide that is long in the main scanning direction, like the LED light source 80, and LEDs that are arranged at one or both ends in the main scanning direction (longitudinal direction) of the light guide. The light which LED light-emits is comprised, and it is irradiated through a light guide. That is, the light guide enters the light emitted from the LEDs arranged at one end or both ends, and faces the contact glass 82 side while guiding the light to the other end or one end opposite to the other using total reflection. The linear light emitted from the side surface in the main scanning direction is reflected by the first mirror 81, and the reflected light is irradiated to the irradiated portion 84 of the read original 83 placed on the contact glass 82. is there.

  However, in the document reading light source device having the above-described configuration, the light emitted from the LED light source 80 or the light guide is not directly irradiated on the irradiated portion 84 but is irradiated on the irradiated portion 84. The optical element (first mirror 81) is disposed in the optical path up to the point. For this reason, the optical path length in the meantime becomes long, and the optical loss in the said optical path will become large. As a result, the utilization efficiency of the light emitted from the LED light source 80 is reduced, the amount of irradiation light contributing to the reading of the original is reduced, and a clear original image may not be formed on the imaging surface of the line sensor 86. there were.

  Therefore, as an ideal configuration for preventing the above-described reduction in light use efficiency and the reduction in the amount of irradiation light contributing to the reading of the original document, the two-row arrangement of the LED light sources 80 by the array method, the LGL method, and the like. The two arrangements of the light guides according to the above. However, these have two LED light sources 80 and two light guides, both of which tend to be worried because the number of parts is doubled and the cost of materials increases, resulting in increased manufacturing costs. It was.

  Therefore, as a document reading light source device that prevents a decrease in light utilization efficiency as described above and a reduction in the amount of irradiation light that contributes to document reading without causing an increase in manufacturing cost, Patent Document 2 The thing of patent document 3 is proposed. The former light source device employs an array method, and the latter light source device employs an LGL method. These light source devices are configured in substantially the same manner except that the light source system is different. When schematically described with reference to FIG. 20 described above, the first mirror 81 is perpendicular to the center of the document 83 to be read. The LED light source 80 or the light guide (not shown) is disposed at a position that is substantially symmetrical with respect to the virtual plane. Then, a part of the light emitted from the LED light source 80 (light guide) is reflected by the first mirror 81, so that the LED light sources 80 (light guides) are arranged in two rows (two). It is possible to make it function. For this reason, linear light directly emitted from the LED light source 80 (light guide) and the first mirror 81 are reflected on the irradiated portion 84 of the read original 83 placed on the contact glass 82. The on-line light is radiated face-to-face.

  In these document reading light source devices, the linear light directly emitted from the LED light source 80 (light guide) and the first mirror 81 on the surface to be read of the document 83 to be read placed on the contact glass 82. The on-line light reflected by the light is irradiated in a face-to-face manner from a symmetrical position with respect to a virtual plane perpendicular to the center of the document 83 to be read. Thereby, for example, even when the document to be read is a booklet and the surface to be read is lifted, a dark portion due to the lift is obtained by irradiating linear light to the floating portion of the surface to be read. Will not be generated. Therefore, it is possible to improve the illuminance distribution of the irradiation light that contributes to the reading of the document without reducing the light use efficiency as described above.

JP 2008-304860 A Japanese Patent No. 4659698 Japanese Patent No. 4793288

  By the way, in the document reading light source device using this type of LED, in order to read a document image with high definition, linear light having a high illuminance and a uniform illuminance distribution is applied to the reading target surface of the document to be read. In order to achieve this, it is necessary to improve the illuminance distribution of the irradiation light that contributes to the reading of the document without reducing the light use efficiency. Therefore, it is required to satisfy the following optical characteristics. That is, such optical characteristics include absolute illuminance value, main scanning light distribution, sub-scanning light distribution, illumination depth indicating the amount of light necessary to accurately read the surface to be read of the original, and floating on the original to be read. In other words, a facing irradiation ratio for preventing a dark portion from being generated on the surface to be read in the case of occurrence of a brightness, a luminance ripple that thresholds a dark portion condition between adjacent LEDs when a plurality of LEDs are arranged, and the like.

In these document reading light source devices of Patent Document 2 and Patent Document 3, by arranging the LED light source 80 (light guide) and the first mirror 81 symmetrically below the contact glass 82, in terms of performance, It can be achieved that the face-to-face irradiation ratio (light distribution ratio with respect to the reading target surface) is 5: 5 (that is, substantially uniform).
However, in order to make this facing irradiation ratio uniform, the optical axis of the main light emitted from the LED light source 80 (light guide) must be tilted toward the first mirror 81, and thereby the reading target Performance surface (ie absolute illuminance value, main scanning light distribution, sub-scanning light distribution, illumination depth, luminance ripple, etc.) other than the face-to-face ratio, such as the illuminance of the main light irradiated to the surface is reduced Any one of them was sacrificed, and it was difficult to efficiently satisfy these performance aspects.

  Accordingly, the present invention has been made in view of the above-described circumstances, and in an original reading light source device used as a light source for an original reading device, irradiation light that contributes to reading of an original is reduced without reducing light use efficiency. An object of the present invention is to make it possible to satisfy the optical characteristics for achieving good quality, and to irradiate light with a high illuminance and a uniform illuminance distribution on a document to be read while suppressing costs.

In order to solve the above problem, the invention according to claim 1 of the present invention provides:
An original that contributes to reading of an original in the original reading apparatus by irradiating a reading target surface of an original to be read placed on the contact glass of the original reading apparatus with light having a predetermined width from below the contact glass. In the reading light source device,
A short shape that has a ring shape with a long opening along the longitudinal direction, is disposed opposite to both ends in the longitudinal direction, and is perpendicular to the longitudinal direction horizontally toward the opposite ends. A branch section having a pair of branch paths branched in two directions and a branch path facing these branch sections are respectively extended in parallel along the longitudinal direction and communicated with each other. A light guide body that has a pair of light guide portions integrally, and has a light exit surface as a virtual surface formed by connecting upper ends of the light guide portions facing each other in the lateral direction;
A semiconductor light source disposed with a light-emitting surface of a light-emitting element facing a light-incident surface formed on an end surface of at least one of the end portions in the longitudinal direction of the light guide;
The light guide body and the semiconductor light source are accommodated, and the portion corresponding to the light output surface of the light guide body is long in the longitudinal direction for irradiating the light opened upward toward the contact glass. A housing having a light emission part,
Each of the light guides includes
The contact positioned appropriately above while guiding the light incident through the light incident surface and the branched portion continuous from the light incident surface by light emission of the semiconductor light source to the opposite end side. The light guide irradiation reflecting portion for emitting light toward the glass extends along the longitudinal direction at a position that is obliquely below the contact glass on the outer peripheral side of each light guide portion. ,
Inside the housing,
Located inside the opening of the light guide, disposed opposite the inner peripheral side of the branching portion on the end side where the semiconductor light source is disposed, and is incident from the semiconductor light source through the light incident surface A spectroscopic reflector that totally reflects the light thus split along each branch path of the branch section;
Each of the branches on the outer peripheral side of each of the light guide portions arranged along the outer peripheral side of each of the branch paths in the branch section on the end side where the semiconductor light source is disposed and communicated with each of the branch paths Stray light that is arranged along the vicinity of the connecting portion with the path and has a direction other than the direction of total reflection by the spectroscopic reflector is guided to each light guide section that communicates along each branch path. A plurality of light guiding reflectors for providing,
Light emitted from the semiconductor light source and incident on the light guide through the light incident surface is guided to the light guides via the branch paths while being dispersed in the branch parts. The contact glasses are respectively guided from the portions corresponding to both of the light guide portions on the light exit surface while being guided to the end portions facing each other along the longitudinal direction in both of the light guide portions. The light is emitted through the light exiting portion toward the reading target surface of the document to be read, which is the upper light receiving surface, and the light receiving surface is irradiated face-to-face.

According to a second aspect of the present invention, in the document reading light source device according to the first aspect,
Each of the lights emitted from portions corresponding to both of the light guide portions on the light exit surface of the light guide and irradiated to the light receiving surface on the contact glass crosses the light receiving surface. It is characterized by that.

Further, the invention described in claim 3 is the light source device for reading a document according to claim 1 or 2,
The spectroscopic reflector has a triangular prism shape, and among the three surfaces erected in the vertical direction, two surfaces are arranged to face the inner peripheral surface of each branch path of the branch portion, respectively. Each of the two surfaces is a specular reflection surface.

Furthermore, the invention described in claim 4 is the document reading light source device according to any one of claims 1 to 3,
The width of the light incident surface of the light guide is set to be equal to or larger than the width of the light emitting surface of the semiconductor light source in the range of 0.5 mm to 1 mm. To do.

Further, the invention according to claim 5 is the light source device for reading a document according to any one of claims 1 to 4,
The light guide is made of a transparent resin material, and each branch path in the branch portion is inclined by 45 ° with respect to the longitudinal central axis connecting the centers of the opposite ends of the light guide. It is arranged to have an angle.

According to the present invention, in the document reading light source device used as a light source in the document reading device, the light guide is disposed to face both ends in the longitudinal direction, and toward the ends facing each other in the longitudinal direction. A branch part having a pair of branch paths branched in two in the lateral direction perpendicular to the horizontal direction, and a branch section extending in parallel along the longitudinal direction between the branch paths facing each of the branch sections. By integrally having a pair of light guide portions that communicate with each other, a ring shape having a long opening along the longitudinal direction is formed, and the pair of light guide portions are opposed to each other in the short direction. A virtual surface formed by connecting the upper ends is used as a light emitting surface. In addition, a semiconductor light source is disposed with a light-emitting surface of the light-emitting element facing a light-incident surface formed of a mirror-like flat surface formed on an end surface of at least one of the both ends in the longitudinal direction of the light guide. . Furthermore, the light guide and the semiconductor light source are long in the longitudinal direction for irradiating the portion corresponding to the light exit surface of the light guide with the light that opens toward the contact glass of the document reading device located above. It is housed in a housing having a light emitting part.
Then, light emitted from the semiconductor light source and incident into the light guide through the light incident surface is guided to each light guide through each branch path while being dispersed in the branch. While being guided to the opposite end side along the longitudinal direction in both of the light parts, from the portion corresponding to both of the light guide parts on the light exit surface, to be read each serving as a light receiving surface on the contact glass The light is emitted toward the reading target surface of the document through the light output unit, and the light receiving surface is irradiated face-to-face.

As a result, in the original reading light source device of the present invention, an optical element is not arranged in the optical path connecting the light exit surface and the light receiving surface, so that the optical path length is prevented from becoming long, and light loss in the optical path is reduced. Therefore, it is possible to improve the irradiation light that contributes to the reading of the original without reducing the utilization efficiency of the light emitted from the semiconductor light source.
That is, in a ring-shaped light guide having an elongated opening in the longitudinal direction, which is disposed below the contact glass, the light emitted from the semiconductor light source is split by the branching portion, and both the split light beams are symmetrical. By emitting each light from the light exit surface composed of a pair of light guides arranged, the facing irradiation ratio with respect to the light receiving surface (read target surface of the document to be read) can be improved. In addition, for example, each branch path in the branch portion is disposed with an inclination angle of 45 ° with respect to the central axis in the longitudinal direction connecting the centers of opposite ends of the light guide. The face-to-face irradiation ratio of the read original to the surface to be read can be made substantially uniform.
At this time, since it is different from the conventional configuration using a reflector, the number of parts can be reduced and the cost can be reduced, and the main light emitted from the semiconductor light source is split into a pair of light guides and read. Since irradiation is performed on the target surface, it is not necessary to incline the light output angle of the light source or the light guide toward the reflector side in order to improve the in-plane irradiation ratio. Therefore, it is possible to prevent the illuminance of the main light irradiated on the reading target surface from decreasing. Furthermore, since the main light emitted from the semiconductor light source is split into a pair of light guides and irradiated onto the surface to be read, the absolute illuminance value, main scanning light distribution, sub-scanning light distribution, illumination depth, There is no sacrifice in performance in terms of optical characteristics such as luminance ripple. Therefore, these optical characteristics can be satisfied efficiently.

  Thus, in a document reading light source device used as a light source in the document reading device, it is possible to satisfy the optical characteristics for improving the irradiation light contributing to the document reading without reducing the light use efficiency. Thus, it is possible to irradiate light to be read with high illuminance and uniform illuminance distribution while suppressing cost.

1 is a schematic perspective view showing a document reading light source device according to an embodiment of the present invention. FIG. 2 is a schematic plan view showing a light guide in the document reading light source device of FIG. 1. It is a side view which shows the side surface of the longitudinal direction in the light guide of FIG. It is the schematic which shows one edge part of the transversal direction in the light guide of FIG. It is a fragmentary sectional view which shows the AA cross section in the light guide of FIG. It is an enlarged view which expands and shows a part of light guide of FIG. It is an enlarged view which expands and shows the principal part of the light guide of FIG. It is the schematic which shows the other edge part of the transversal direction in the light guide of FIG. FIG. 2 is an explanatory diagram of an optical path related to the original reading light source device of FIG. 1. It is an optical path explanatory view in a manuscript reading device using a manuscript reading light source device of the present invention. It is an optical path explanatory drawing concerning a light guide. Similarly, it is an optical path explanatory drawing concerning a light guide. Similarly, it is an optical path explanatory drawing concerning a light guide. Similarly, it is an optical path explanatory drawing concerning a light guide. It is a graph which compares and shows the light distribution of the light quantity of the main scanning direction in the light guide of FIG. 2, and the conventional light guide. It is a graph which compares and shows the light distribution of the light quantity of the subscanning direction in the light guide of FIG. 2, and the conventional light guide. It is a graph which compares and shows the light distribution ratio from the light source in the light guide of FIG. 2, and the conventional light guide. It is a graph which compares and shows the illumination depth with respect to the light-receiving surface in the light guide of FIG. 2 and the conventional light guide. It is a graph which compares and shows the luminance ripple in the light guide of FIG. 2, and the conventional light guide. It is explanatory drawing of the original reading apparatus using the conventional light source device for original reading.

Hereinafter, an embodiment of a light source device for reading a document according to the present invention will be described in detail with reference to the drawings. The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise described, the present invention is not limited to these embodiments.
In the following description, as a document reading light source device according to the present invention, a reading target of a document to be read which is a light receiving surface placed on a contact glass of a document reading device (not shown) (for example, an OA device such as a scanner). A case will be described in which the surface is irradiated with light having a predetermined width from below the contact glass and applied to a document that contributes to reading of a document in the document reading apparatus.

  FIG. 1 is a perspective view schematically showing a schematic structure of a document reading light source device 1 according to this embodiment, and FIG. 2 is a plan view schematically showing a light guide 2 in the document reading light source device 1. FIG. FIG. 3 is a side view showing a side surface in the longitudinal direction of the light guide 2, and FIG. 4 is a schematic view showing one end portion in the short direction of the light guide 2.

  In the case of the present embodiment, as shown in FIG. 1, the document reading light source device 1 includes a light guide 2, an LED light source 3 as a semiconductor light source, and a so-called lamp that houses the light guide 2 and the LED light source 3. And a housing 4 as a house. The light guide 2 has a ring shape having a long opening 2a along the longitudinal direction, and the LED light source 3 is disposed on the end surface of at least one of the both ends in the longitudinal direction. Yes. The housing 4 has a substantially rectangular box shape and houses the light guide 2 and the LED light sources 3 and 3. Further, the housing 4 is preferably made of a highly light-shielding material, and is positioned above the light source device 1 for reading the document at a portion corresponding to a light output surface 23 (see FIG. 2) described later of the light guide 2 to be accommodated. A light emitting portion 4a elongated in the longitudinal direction for emitting light from the LED light source 3 opened toward the contact glass 50 (see FIGS. 9 and 10 described later).

  Specifically, the light guide 2 is made of a transparent resin material such as acrylic, and as shown in FIG. 2, has a pair of branch portions 21 and 21 disposed to face both ends in the longitudinal direction. Moreover, these branch parts 21 and 21 have a pair of branch path 21a, 21b branched into the two directions of the transversal direction orthogonal to a longitudinal direction toward the mutually opposing edge part. That is, each of the branch portions 21 and 21 has branch paths 21a and 21b that branch in a short direction from the end portion on its own side toward the end portion on the other side, and the prismatic acrylic is substantially Y in plan view. It is formed in a letter shape.

  The light guide 2 is extended in parallel along the longitudinal direction between the opposing branch paths 21a, 21a and 21b, 21b of the branch sections 21, 21, respectively, and each of the branch paths 21a, 21a and 21b. , 21b and a pair of cylindrical light guide portions 22a, 22b communicating with each other. And the light guide 2 has comprised the branch parts 21 and 21 and each light guide part 22a, 22b integrally, and has comprised the ring shape which has the elongate opening 2a in a longitudinal direction. At this time, in the light guide 2, a virtual surface area formed by connecting upper ends of the light guide portions 22 a and 22 b facing each other in the short direction is used as a light exit surface 23, and a central portion of the light guide body 22 is used as an effective illumination region 23 a. Yes. Here, the effective illumination area 23a is emitted from the light exit surface 23 toward a document reading device (not shown) positioned above, and irradiates the light receiving surface 51 (see FIG. 10 described later) of the document reading device. The irradiation light L3a and L3b (refer FIG. 10) to be irradiated means the area | region which can be irradiated best.

  In addition, a light incident surface 24 composed of a mirror-surface flat surface is formed on an end surface of at least one of the both end portions in the longitudinal direction of the light guide 2. The LED light source 3 is arranged with the light emitting surface (both not shown) facing (see FIG. 1 and FIG. 9 described later). In the case of the present embodiment, light incident surfaces 24 and 24 are formed on both end surfaces of the light guide 2, respectively, and the LED light sources 3 and 3 are described above on the light incident surfaces 24 and 24, respectively. It is arranged in a state. In addition, the mirror surface flat surface which comprises the light-incidence surfaces 24 and 24 shows a shape, and all are processing the shape of transparent resin material (in this case acrylic). That is, a reflective film or the like is not formed as a mirror surface, but has a function of total reflection due to a difference in refractive index between resin and air.

  Further, as shown in FIG. 3 and FIG. 4, the light guides 22 a and 22 b of the light guide 2 are positioned above the light source device 1 for reading the document on the outer peripheral side of the light guides 22 a and 22 b. The light guide irradiation reflecting portion 25 is extended along the longitudinal direction at a position obliquely below the contact glass 50 (see FIGS. 9 and 10). The light guide irradiation reflecting portion 25 passes through the light incident surfaces 24 and 24 and branch portions 21 and 21 continuous from the light incident surfaces 24 and 24 by light emission of the LED light sources 3 and 3 (see FIGS. 1 and 9). The incident light is guided toward the opposite end side, and is appropriately emitted toward the contact glass 50 positioned above. Specifically, the light guide irradiation reflecting portion 25 has a general configuration as an existing light guide technology, and includes a pattern surface 25a formed in the obliquely lower position of each light guide 22a, 22b, and the pattern surface. And a reflection sheet 25b disposed along 25a. Specifically, as shown in FIG. 5 showing the AA cross section of FIG. 4 and FIG. 6 in which the main part K2 of FIG. 5 is enlarged, the pattern surface 25a is composed of dots (including white printing), knurls, etc. In this case, knurling is adopted as the pattern shape. At this time, the knurled pattern is determined by selecting the pitch P1, the height P2, and the angle θ. In addition, as a normal pattern, it is preferable that the scale and the angle of 1/1000 to 1/100 are determined in the range of about 95 ± 10 ° with respect to the thickness.

Here, the shape definition of the light guide 2 will be described with reference to FIGS. 7 and 8 in which the main part K1 of FIG. 2 is enlarged. Here, for convenience, the branching portion 21 at the end portion on one side of the light guide 2 will be described in an enlarged manner, but the branching portion 21 at the end portion on the other side is similarly configured.
As shown in FIG. 7 and FIG. 8, as the entire layout of the light guide 2, the outermost shape (full length and full width) has a length X1 (see FIG. 2) in the longitudinal direction (main scanning direction) and a short direction. When determined by the width Y1 in the (sub-scanning direction), the shapes of the branch portion 21 and the light guide portions 22a and 22b are determined as follows.

  That is, in the present embodiment, the LED light source 3 is used as the light source, and the light emitting element is an LED that is a point light source. Therefore, the width Y <b> 2 of the light incident surface 24 is a width having a tolerance margin with respect to the light emitting surface width of the LED light source 3. In this case, the tolerance is preferably 0.5 mm to 1.0 mm. Thereby, the light L1 emitted from the LED light source 3 (see FIG. 9 described later) can be efficiently taken into the light guide 2 through the light incident surface 24.

  Next, in the branching portion 21, the R shape R1 of the light guide portions 22a and 22b in the main scanning direction after branching is in a range of R1> c / 2, where c is the diameter of the light guide portions 22a and 22b. Set as follows. That is, the R shape R1 of the light guide portions 22a and 22b is set to be larger than ½ of the diameter c. Incidentally, in the present embodiment, the diameter c of the light guide portions 22a and 22b is equal to the width Y2 of the light incident surface 24, and the light incident surface 24 is formed in a square shape.

  Next, the light incident path length X2 from the light incident surface 24 in the main scanning direction is equal to or less than ½ of the width Y2 of the light incident surface 24, but the outermost shape is the length X1 in the main scanning direction (see FIG. 2). For example, when the dimension cannot be increased in the main scanning direction due to the restriction of the width Y1 in the sub-scanning direction, X2 = 0 may be set.

  Subsequently, the width Y3 (that is, the length from the center of the light incident surface 24 to each edge of the light guide portions 22a and 22b) as a half length of the width Y1 in the sub-scanning direction is the effective illumination. The width is set to be greater than the width Y4 of the region 23a (see FIG. 2) plus the width Y2 of the light incident surface 24 that is the width of the branched light guide 2a or 2b. In other words, it is set so that Y3> Y4 + 2Y2. At this time, the length X3 from the light incident surface 24 to the communicating portion between the branch path 21a or 21b in the main scanning direction and the light guide portion 22a or 22b is equal to the half width Y3 of the light guide 2 Set to

Further, the length X4 from the light incident surface 24 to the portion where the branch paths 21a and 21b start to branch is set to a length equivalent to the light incident surface width Y2. Then, by determining the half width Y3 of the light guide 2, the branch angle α of the branch paths 21a and 21b is obtained from the length X3 and the width Y3.
Here, a case where the branching angle α and the branching angle α ′ facing the branching angle α are set to the same angle in order to uniformly split the light from the light incident surface in each branching path 21a, 21b is described as an example. However, the present invention is not limited to this, and each may be set at a different desired angle according to the user's request.
These branch angles α and α ′ are obtained by α = α ′ = ArcTan (Y3 / X3), and thereby, near the point light source (that is, from the light incident surface 24 on which the LED light source 3 is disposed, the light guide portions 22a and 22b. The incident light shape is determined. Incidentally, in the case of this embodiment, these branch angles α and α ′ are set to 45 °, respectively.

  Furthermore, the inclination angle (that is, the light output angle) β of the pattern surface 25a in the light guide portions 22a and 22b is the thickness t of the contact glass 50 positioned above (hereinafter referred to as the glass thickness t), It depends on the refractive index of the contact glass 50, the vertical distance V from the light guide 2 to the bottom surface of the contact glass 50, and the horizontal distance H to the center of the CCD in the document reading device (not shown). Strictly speaking, it is desirable to set the angle to be an intersection that coincides with the center of the CCD. However, in consideration of the illumination depth, it is preferable that the light output axes intersect at a position slightly higher than the CCD center. By this method, the central axis D extending vertically from the center of the light guide 2 without considering the refractive index of the contact glass 50 and the light output axes La and Lb in the respective light guide portions 22a and 22b are connected. The light emission angle β on the pattern surface 25a can be determined.

  Further, the width of the pattern surface 25a varies depending on the required specifications of the main scanning light distribution in the optical characteristics described above. For example, the light output axes La and Lb in the light guide portions 22a and 22b correspond to the light guide portions. It is preferable to form a width of about ± 1 mm as the width of the pattern surface 25a from a point orthogonal to the bottom surface of the pattern surface 25a of 22a and 22b. Then, by extending such a pattern surface 25a in the main scanning direction, distances X5 and X6 (see FIG. 3) from the light incident surfaces 24 and 24 at each end are determined, and the length is long in the longitudinal direction. The shape of the light guide 2 having a ring shape is determined.

Next, in the document reading light source device 1 having the light guide 2 whose shape is determined as described above, the light emitted from the LED light sources 3 and 3 is emitted from the document reading light source device 1 to the outside. The optical path formation until this time will be described with reference to FIGS.
FIG. 9 is an explanatory diagram of an optical path related to the document reading light source device 1, and FIG. 10 is an optical path to the light receiving surface located on the contact glass 50 of the document reading device (not shown) using the document reading light source device 1. It is explanatory drawing. 9 and 10, for convenience, the inner side of the housing 4 is illustrated, and the housing 4 is not illustrated.

  In the document reading light source device 1, as shown in FIG. 9, the housing 4 is located inside the opening 2 a of the light guide 2, and on the end side where the LED light sources 3 and 3 are disposed ( In this case, the light beams that are arranged to face the inner peripheral side of the branch portions 21 and 21 at both ends) and that are incident from the LED light sources 3 and 3 through the light incident surfaces 24 and 24 are used as the branch portions 21 and 21. Spectral reflectors 41 and 41 are provided for total reflection so that the light is split along the branch paths 21a and 21b. In addition, stray light having a direction other than the direction of total reflection by the spectroscopic reflectors 41 and 41 is transmitted to the light guide portions 22a and 22b that communicate along the branch paths 21a and 21b. A plurality of light guiding reflectors 42 for guiding light are provided. The light guide reflectors 42 are arranged along the outer peripheral sides of the branch paths 21a and 21b in the branch parts 21 and 21 on the end side where the LED light sources 3 and 3 are arranged, and the branches. It arrange | positions along the connection part vicinity with each branch path 21a, 21b in the outer peripheral side of each light guide part 22a, 22b connected to the path 21a, 21b, respectively. The spectroscopic reflectors 41 and 41 and the light guide reflectors 42 have specular reflection surfaces (not shown) at positions facing the branch paths 21a and 21b and the light guide portions 22a and 22b, respectively. ing. The specular reflection surface is formed of a reflective metal film such as silver (Ag) or the like, or the resin film is made of silver (Ag) or the like. It is formed by providing a reflective metal film.

  Here, regarding the relationship between the light guide 2 and the spectroscopic reflectors 41 and 41 and the light guide reflectors 42..., FIGS. I will explain. 11 to 14, for the sake of convenience, only one end side of the light guide 2 is illustrated, but it goes without saying that the same phenomenon occurs when the LED light source 3 is arranged also on the other end side. Yes. Further, the detailed description of the individual portions in the light guide 2 is omitted because it overlaps.

  As shown in FIGS. 11 to 14, in the light guide 2, the light emitted from the LED light source 3 (in the case where the spectroscopic reflector 41 and the light guide reflector 42. The utilization efficiency (shown by a solid line in the figure) is completely different. That is, when the spectroscopic reflector 41 and the light guide reflectors 42 are not arranged, stray light having a direction other than the light distribution by total reflection does not exist in the spectroscopic reflector 41 and the light guide reflectors 42. It leaks from the site to the outside (see FIGS. 11 to 13).

  On the other hand, when the spectroscopic reflector 41 and the light guide reflectors 42 are appropriately disposed, the stray light can be appropriately guided, and the light L1 emitted from the LED light source 3 is effectively utilized. It is understood that the utilization efficiency of the light L1 can be improved. Therefore, in this embodiment, as described above, the spectroscopic reflector 41 and the light guide reflectors 42 are appropriately arranged. The spectroscopic reflector 41 also serves to shield direct light (light L1) from the LED light source 3 from being reflected on the CCD (both not shown) of the document reader.

  In the original reading light source device 1 configured as described above, as shown in FIG. 9, first, the lights L1 and L1 emitted from the LED light sources 3 and 3 are transmitted through the light incident surfaces 24 and 24, respectively. The light enters the light guide 2. These light beams L1 and L1 are reflected by the inner walls of the respective branch paths 21a and 21b at the branch sections 21 and 21 at the respective end portions, and light guide paths 22a and 22b communicating with the respective branch paths 21a and 21b. To the light L1a and L1b. In addition, the other part is transmitted through the inner walls of the respective branch paths 21a and 21b, but is reflected by the spectroscopic reflectors 41 and 41 and the light guide reflectors 42 arranged on the outer periphery, and the respective branch paths 21a and 21b. The light is guided as light L1a and L1b to the light guide paths 22a and 22b communicating with the branch paths 21a and 21b. In other words, the spectroscopic reflector 41, which is a total reflection member, causes the LED light sources L1 and L1 emitted from the LED light source 3 to enter the LED light sources at the opposing branch portions 21 and 21 when they enter the light incident surfaces 24 and 24. The light is reflected so as to be branched into the branch paths 21a and 21b without being transmitted along the optical axes 3 and 3 to the inner peripheral side of the opening 2a. The lights L1 and L1 incident on the light guide 2 through the light incident surfaces 24 and 24 are split into the light L1a and the light L1b at the branch parts 21 and 21, respectively. Light is guided to the light guide portions 22a and 22b via 21b. At this time, the branching angles α and α ′ of the branching portions 21 and 21 are set to 45 °, respectively, so that the lights L1 and L1 can be uniformly dispersed.

  Next, the light beams L1a and L1b split at the branch portions 21 and 21 are guided to the light guide portions 22a and 22b through the branch passages 21a and 21b, and in both the light guide paths 22a and 22b. While being reflected by the light guide irradiation reflecting portion 25 (specifically, by the pattern surface 25a), the light is guided toward the opposite end portions as the light L2a and L2b. At this time, when the light L2a and L2b exceed the critical angle on the upper end side that becomes the light exit surface 23 of each light guide portion 22a and 22b, the light exits from the light exit surface 23 without being emitted as described above in the light guide paths 22a and 22b. The light is guided to the ends facing each other along the longitudinal direction while repeating reflection.

  If the light exit surface 23 does not exceed the critical angle, it is refracted in the light guide longitudinal direction (main scanning direction), and as shown in FIG. 10, the light exit surface 23 (the upper end side of the light guide portions 22a and 22b). To emit light as L3a and L3b. That is, the lights L3a and L3b are emitted from the portions corresponding to both the light guide portions 22a and 22b on the light exit surface 23 toward the contact glass 50 through the light exit portion 4a (see FIG. 1). Then, the lights L3a and L3b are transmitted through the contact glass 50 and are radiated face-to-face on a reading target surface of a document to be read (not shown) which becomes the light receiving surface 51 on the contact glass 50. At this time, it is preferable that the light beams L <b> 3 a and L <b> 3 b irradiated on the light receiving surface 51 face each other at the light receiving surface 51. Thereby, the utilization efficiency of these light L3a, L3b (namely, light L1 emitted from LED light source 3) can be improved. Further, the light L3a and L3b that are transmitted through the contact glass 50 and irradiated to the light receiving surface 51 are vertically reflected to a CCD (not shown) by the light receiving surface 51 and read as an image by the CCD.

In the document reading light source device 1 configured as described above, the optical characteristics described above, specifically, the main scanning light distribution, the sub-scanning light distribution, and the center connecting both ends of the light guide 2 in the longitudinal direction. Light distribution ratio in the light guide paths 22a and 22b arranged on the left and right with respect to the axis (that is, the facing irradiation ratio for preventing a dark portion from being generated on the surface to be read when the document to be read is lifted), illumination As shown in the graphs of FIGS. 15 to 19, the depth and the luminance ripple are remarkably improved as compared with the conventional case.
15, 16, and 19, the original reading light source device 1 of the present embodiment is indicated by a solid line, and the conventional original reading light source device is indicated by a broken line. In FIG. 17, in the light guide of the document reading light source device 1 of the present embodiment, one light guide 22 a is a solid line, and the other light guide 22 b is a one-dot chain line. The light source side in the apparatus is indicated by a broken line, and the reflector side is indicated by a two-dot chain line. Further, in FIG. 18, the original reading light source device 1 of the present embodiment has a depth of 0 mm as a solid line, a depth of 2 mm as a dashed line, a conventional original reading light source device of a depth of 0 mm as a broken line, and a depth of 2 mm. Is shown by a two-dot chain line.

  As described above, according to the document reading light source device 1 of the present embodiment that is used as a light source in the document reading device, the light guides 2 are disposed to face both ends in the longitudinal direction and face each other. Bifurcation portions 21 and 21 having a pair of bifurcation paths 21a and 21b bifurcated in a short direction perpendicular to the longitudinal direction toward the end portion, and the bifurcations facing these bifurcation portions 21 and 21 A pair of light guide portions 22a and 22b that extend in parallel along the longitudinal direction between the paths 21a and 21b and communicate with each other of the branch paths 21a and 21b are integrated into the longitudinal direction. A virtual surface formed by connecting the upper ends of the pair of light guide portions 22a and 22b facing each other in the short direction is used as a light exit surface 23. In addition, among the both ends in the longitudinal direction of the light guide 2, the LED light sources 3, 3 with the light emitting surface of the light emitting element facing the light incident surface 24 formed of a mirror-like flat surface formed on the end surface of at least one end. Is arranged. Furthermore, the light guide 2 and the LED light sources 3 and 3 irradiate the light corresponding to the light exit surface 23 of the light guide 2 with light that is opened toward the contact glass 50 of the document reading device located above. Are housed in a housing 4 having a light output portion 4a that is long in the longitudinal direction.

  The light L1 emitted from the LED light sources 3 and 3 and incident on the light guide 2 through the light incident surfaces 24 and 24 is split into the light L1a and the light L1b at the branching portions 21 and 21. Light is guided to the respective light guide portions 22a and 22b via the respective branch paths 21a and 21b, and the light L2a and the light L2a to both ends of the respective light guide portions 22a and 22b that face each other along the longitudinal direction. While being guided as L2b, the light output portion 4a from the portion corresponding to both of the light guide portions 22a and 22b on the light output surface 23 toward the reading target surface of the document to be read that becomes the light receiving surface 51 on the contact glass 50, respectively. The light is emitted as light L3a and L3b via the light, and is incident on the light receiving surface 51.

As a result, in the document reading light source device 1 of the present invention, the optical path length can be avoided without increasing the length of the optical path without arranging an optical element in the optical path connecting the light exit surface 23 and the light receiving surface 51. Since the loss can be reduced, the irradiation light (lights L3a and L3b) contributing to the reading of the document can be improved without reducing the utilization efficiency of the light L1 emitted from the LED light source 3.
That is, in the ring-shaped light guide 2 having an opening 2a elongated in the longitudinal direction and disposed below the contact glass 50, the light L1 emitted from the LED light source 3 is split into the light L1a and the light by the branch portions 21 and 21. The light receiving surface 51 is divided into L1b and emitted from the light output surface 23 as light L3a and L3b through a pair of light guides 22a and 22b arranged symmetrically. The facing irradiation ratio with respect to the (read target surface of the document to be read) can be improved.

  At this time, since it is different from the conventional configuration in which a reflector is used together, the number of parts can be reduced and the cost can be suppressed, and the main light L1 emitted from the LED light sources 3 and 3 is a pair of light guide portions 22a. , 22b is split and irradiated to the reading target surface (light receiving surface 51), so that the light emission angle of the light source or the light guide is tilted toward the reflector side in order to improve the ratio of facing irradiation as in the prior art. There is no need. Therefore, it is possible to prevent the illuminance of the main light L1 irradiated on the reading target surface from decreasing. Further, the main light L1 emitted from the LED light sources 3 and 3 is split toward the pair of light guides 22a and 22b and irradiated onto the reading target surface (light receiving surface 51). There is no sacrifice in performance in terms of optical characteristics such as scanning light distribution, sub-scanning light distribution, illumination depth, and luminance ripple. Therefore, these optical characteristics can be satisfied efficiently.

  Thus, in the document reading light source device 1 used as a light source in the document reading device, the optical characteristics for making the irradiation light contributing to the reading of the document good can be satisfied without reducing the light use efficiency. In addition, it is possible to irradiate light to be read with high illuminance and uniform illuminance distribution while suppressing cost.

  In addition, the document reading light source device 1 of the present embodiment has a simple structure for irradiating linear light with high illuminance and uniform illuminance distribution, and thus can be reduced in size and cost. As a result, it is possible to contribute to the reduction in size and cost of an original reading apparatus such as a scanner incorporating the original reading light source device 1 of the present invention.

  In addition, it is preferable that the light beams L3a and L3b irradiated to the light receiving surface 51 on the contact glass 50 intersect at the light receiving surface 51. Thereby, the utilization efficiency of these light L3a, L3b (namely, light L1 emitted from the LED light source 3) can be improved.

Further, the spectroscopic reflector 41 has a triangular prism shape, and two of the three surfaces erected in the vertical direction are respectively connected to the inner peripheral surfaces of the branch paths 21a and 21b of the branch portions 21 and 21. It is preferable that the two surfaces are arranged to face each other, and each of the two surfaces is a specular reflection surface. As a result, stray light having a direction other than the light distribution due to total reflection can be prevented from leaking from a portion where the spectroscopic reflector 41 does not exist to the outside, and the stray light can be appropriately guided. can do. For this reason, it becomes possible to utilize effectively the light L1 emitted from the LED light source 3, and the utilization efficiency of the said light L1 can be improved.
In addition, the spectral reflector 41 can shield the direct light (light L1) from the LED light source 3 so that it is not reflected on the CCD (both not shown) of the document reader.

  Further, the width Y2 of the light incident surface 24 in the light guide 2 is set to be equal to or larger than the width of the light emitting surface in the LED light source 3 in the range of 0.5 mm to 1 mm. desirable. Thereby, the light L1 emitted from the LED light source 3 can be efficiently taken into the light guide 2 via the light incident surface 24.

  Further, the light guide 2 is made of a transparent resin material such as acrylic, and the branch paths 21a and 21b in the branch portions 21 and 21 are on the central axis in the longitudinal direction connecting the centers of the opposite ends of the light guide 2 with each other. On the other hand, it is preferable that they are arranged with an inclination angle of 45 °. Thereby, the facing irradiation ratio with respect to the reading target surface (light receiving surface 51) of the document to be read can be made substantially uniform.

  The present invention is not limited to the above-described embodiments, and various improvements and design changes can be made as appropriate without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the case where the LED light sources 3 and 3 are applied as the semiconductor light source using the light emitting element has been described. However, the embodiment is not limited to this example, and various other light emission such as an organic EL can be used. The device can be widely applied.

DESCRIPTION OF SYMBOLS 1 ... Light source apparatus for document reading 2 ... Light guide 2a ... Opening 21 ... Branch part 21a, 21b ... Branch path 22a, 22b ... Light guide part 23 ... Light exit surface 23a ... Effective illumination area 24 ... Light entrance surface 25 ... Light guide Reflection part 25a ... Pattern surface 25b ... Reflective sheet 3 ... LED light source (semiconductor light source)
4 ... Case (lamp house)
4a ... Light emitting part 50 ... Contact glass 51 ... Light receiving surface

Claims (5)

An original that contributes to reading of an original in the original reading apparatus by irradiating a reading target surface of an original to be read placed on the contact glass of the original reading apparatus with light having a predetermined width from below the contact glass. In the reading light source device,
A short shape that has a ring shape with a long opening along the longitudinal direction, is disposed opposite to both ends in the longitudinal direction, and is perpendicular to the longitudinal direction horizontally toward the opposite ends. A branch section having a pair of branch paths branched in two directions and a branch path facing these branch sections are respectively extended in parallel along the longitudinal direction and communicated with each other. A light guide body that has a pair of light guide portions integrally, and has a light exit surface as a virtual surface formed by connecting upper ends of the light guide portions facing each other in the lateral direction;
A semiconductor light source disposed with a light-emitting surface of a light-emitting element facing a light-incident surface formed on an end surface of at least one of the end portions in the longitudinal direction of the light guide;
The light guide body and the semiconductor light source are accommodated, and the portion corresponding to the light output surface of the light guide body is long in the longitudinal direction for irradiating the light opened upward toward the contact glass. A housing having a light emission part,
Each of the light guides includes
The contact positioned appropriately above while guiding the light incident through the light incident surface and the branched portion continuous from the light incident surface by light emission of the semiconductor light source to the opposite end side. The light guide irradiation reflecting portion for emitting light toward the glass extends along the longitudinal direction at a position that is obliquely below the contact glass on the outer peripheral side of each light guide portion. ,
Inside the housing,
Located inside the opening of the light guide, disposed opposite the inner peripheral side of the branching portion on the end side where the semiconductor light source is disposed, and is incident from the semiconductor light source through the light incident surface A spectroscopic reflector that totally reflects the light thus split along each branch path of the branch section;
Each of the branches on the outer peripheral side of each of the light guide portions arranged along the outer peripheral side of each of the branch paths in the branch section on the end side where the semiconductor light source is disposed and communicated with each of the branch paths Stray light that is arranged along the vicinity of the connecting portion with the path and has a direction other than the direction of total reflection by the spectroscopic reflector is guided to each light guide section that communicates along each branch path. A plurality of light guiding reflectors for providing,
Light emitted from the semiconductor light source and incident on the light guide through the light incident surface is guided to the light guides via the branch paths while being dispersed in the branch parts. The contact glasses are respectively guided from the portions corresponding to both of the light guide portions on the light exit surface while being guided to the end portions facing each other along the longitudinal direction in both of the light guide portions. An original reading light source device, which is emitted through the light emitting unit toward a reading target surface of the read original document serving as an upper light receiving surface, and is radiated facing the light receiving surface.   Each of the lights emitted from portions corresponding to both of the light guide portions on the light exit surface of the light guide and irradiated to the light receiving surface on the contact glass crosses the light receiving surface. The document reading light source device according to claim 1.   The spectroscopic reflector has a triangular prism shape, and among the three surfaces erected in the vertical direction, two surfaces are arranged to face the inner peripheral surface of each branch path of the branch portion, respectively. The document reading light source device according to claim 1, wherein each of the two surfaces is a specular reflection surface.   The width of the light incident surface of the light guide is set to be equal to or larger than the width of the light emitting surface of the semiconductor light source in the range of 0.5 mm to 1 mm. The document reading light source device according to claim 1.   The light guide is made of a transparent resin material, and each branch path in the branch portion is inclined by 45 ° with respect to the longitudinal central axis connecting the centers of the opposite ends of the light guide. The document reading light source device according to any one of claims 1 to 4, wherein the light source device is arranged with an angle.

Images