Illumination device, image reading device, and image forming apparatus

Abstract

To provide an illumination device suitable for use in both fixed original reading and moving original reading in an image reading unit.SOLUTION: An illumination device is used in an image reading device capable of executing a first reading method of reading an object that does not move by reading means that moves in a first direction, and a second reading method of reading the object that moves in the first direction by the reading means that does not move. The illumination device includes: first and second illumination means disposed on one side and the other side in the first direction with respect to a reading position by the reading means, and appropriately sets respective light amounts of light beams emitted from the first and second illumination means at the reading position in the first reading method and respective light amounts of the light beams emitted from the first and second illumination means at the reading position in the second reading method.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a lighting device, an image reading device, and an image forming device.

Background Art

[0002] Conventionally, an image reading device that reads an image line by line forms an image of an illumination area on a document surface illuminated linearly by a lighting device on a reading means such as a line sensor at a predetermined magnification by an imaging optical system, and reads the image.

[0003] In addition, in a lighting device in an image reading device, in order to form an elongated illuminated area in the reading line direction (hereinafter, the main scanning direction), a light emitting diode (hereinafter, LED) is arranged at an end portion in the main scanning direction of a light guide made of a translucent member, and there is an LED end portion arrangement type in which the emitted light beam from the LED is propagated through the light guide. Further, a lighting device using a light guide is known to have a configuration that efficiently guides the light from the LED to the illuminated area on the document surface.

[0004] As means for reading a document, there are a document fixed reading that fixes the document and moves the image reading unit, and a document flowing reading that fixes the image reading unit and conveys the document. Patent Document 1 discloses a technique that uses the shadow of the leading edge of a document to detect the inclination of the document being conveyed in document flowing reading. By using the technique described in Patent Document 1, even when illuminating from both sides on the upstream side and the downstream side in the document conveyance direction with respect to the reading optical axis, a shadow of the leading edge of the document can be generated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, Patent Document 1 does not disclose illumination means suitable for use when an image reading unit is used for both fixed document reading and moving document reading. Further, depending on the configuration of the image reading unit, the light quantity distribution in the sub-scanning direction required for the illuminated area is different, and the relationship between the leading edge shadow of the document and the light quantity distribution in the sub-scanning direction is not disclosed.

[0007] Therefore, an object of the present invention is to provide an illumination device suitable for use when an image reading unit is used for both fixed document reading and moving document reading.

Means for Solving the Problems

[0008] To achieve the above object, the illumination device according to the present invention is an illumination device used in an image reading apparatus capable of executing a first reading method of reading an object that does not move by reading means that moves in a first direction, and a second reading method of reading an object that moves in the first direction by the reading means that does not move, having a first illumination means disposed on one side in the first direction with respect to the reading position by the reading means, and a second illumination means disposed on the other side, when the light quantity at the reading position of the light beam emitted from the first illumination means in the first reading method is Qa, the light quantity at the reading position of the light beam emitted from the second illumination means in the first reading method is Qb, the light quantity at the reading position of the light beam emitted from the first illumination means in the second reading method is Qc, and the light quantity at the reading position of the light beam emitted from the second illumination means in the second reading method is Qd, Qa / Qb≠Qc / Qd 0.90<Qa / Qb<1.11 satisfies the formula, Qa<Qc Qb>Qd and is characterized by satisfying at least one of the formulas.

Effects of the Invention

[0009] According to the present invention, in an image reading unit, it is possible to provide an illumination device capable of improving the contrast of the leading edge shadow of a conveyed document.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] The present invention relates to an illumination device including a light guide, an image reading device having the illumination device, and an image forming device, and is suitable for, for example, image reading devices and image forming devices such as image scanners, copiers, and facsimiles. Conventionally, an image reading device that reads an image line by line forms an image of a reading area on a document surface illuminated linearly by an illumination device on a reading means such as a line sensor at a predetermined magnification by an imaging optical system, and reads the image.

[0012] In addition, as a light source of an illumination device in an image reading device, in recent years, those using a light-emitting diode (hereinafter referred to as LED) are known. In an illumination device using an LED, in order to form an elongated illuminated area in the reading line direction (hereinafter also referred to as the main scanning direction), an LED is arranged at an end portion of a light guide made of a light-transmitting member in the main scanning direction, and there is an LED end portion arrangement type in which the emitted light beam from the LED is propagated through the light guide. Further, an illumination device using a light guide is known as a configuration that efficiently guides the light from the LED to the illuminated area on the document surface.

[0013] As a method of reading a document (object), there are document-fixed reading in which the document is fixed and the image reading unit is moved, and document-flow reading in which the image reading unit is fixed and the document is conveyed. Patent Document 1 discloses a technique of using the shadow of the leading edge of a document to detect the inclination of the conveyed document in document-flow reading, and even when illuminating from both the upstream side and the downstream side in the document conveyance direction across the reading optical axis, the shadow of the leading edge of the document can be clearly generated.

[0014] However, the configuration of Patent Document 1 does not disclose an optimal illumination means when the image reading unit is used for both fixed document reading and flow document reading. Furthermore, the light intensity distribution in the sub-scanning direction (hereinafter referred to as the sub-scanning light intensity distribution) required for the illuminated area differs depending on the configuration of the image reading unit, and the document does not disclose the relationship between the shadow of the leading edge of the document and the sub-scanning light intensity distribution. When a reading method using a reduced optical system with a deep depth of field is adopted, a carriage-integrated scanning method is used in order to simplify the structure of the image reading device, in which a housing integrating a reflecting mirror, imaging lens, line sensor, etc. is moved to scan the document surface and read image information.

[0015] On the other hand, there is also a method that uses a CIS (Contact Image Sensor) method that reads with a 1:1 magnification optical system. The CIS method can shorten the optical path length of the 1:1 magnification optical system compared to a reduction optical system, making it possible to eliminate the need for a reflecting mirror. In the case of an image reading unit that uses a reduction optical system and a reflecting mirror, if the position of the reflecting mirror changes due to factors such as temperature rise, the reading position will shift in the sub-scanning direction. For this reason, the sub-scanning light intensity distribution is generally broadened to minimize changes in light intensity even if the reading position shifts in the sub-scanning direction.

[0016] On the other hand, in the case of an image reading unit using an 1:1 magnification optical system, the change in reading position in the sub-scanning direction due to the influence of temperature rise, etc. is small, so it is common to increase the light amount by sharpening the sub-scanning light amount distribution. However, if the sub-scanning light amount distribution is sharp, there is a problem in that the width of the shadow of the leading edge of the document in the document transport direction (sub-scanning direction, first direction) becomes narrower. Therefore, the present invention aims to provide an illumination device that improves the contrast of the shadow at the leading edge of a transported document in an image reading unit that can perform both fixed document reading and flowing document reading using the CIS method, and is suitable for use in both fixed document reading and flowing document reading.

[0017] First Embodiment Hereinafter, the lighting device and the image reading device according to the present embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings shown below may be drawn at scales different from the actual ones in order to facilitate understanding of the present embodiment. Also, in each drawing, the same members are denoted by the same reference numerals, and redundant explanations are omitted.

[0018] Hereinafter, a light guide, a lighting device, and an image reading device according to the first embodiment of the present invention will be described. FIG. 1 shows a schematic front view of an image forming apparatus 100 including an image reading apparatus 101 according to the present embodiment. Note that the image forming apparatus 100 shown below is merely an example, and a facsimile apparatus, an inkjet printer, a copying machine, etc. including the image reading apparatus 101 also fall under the category of the image forming apparatus including the image reading apparatus according to the present embodiment.

[0019] As shown in FIG. 1, the image forming apparatus 100 includes an image forming apparatus main body 102 (image forming unit) for forming an image on a recording sheet, and a paper feed cassette 103 mounted below the image forming apparatus main body 102 for loading the recording sheet. The image forming apparatus 100 also includes an image reading apparatus 101 mounted above the image forming apparatus main body 102 for reading an image of a document.

[0020] Inside the image forming apparatus main body 102, image forming means (not shown) is disposed substantially at the center, and below it, paper feeding means (not shown) for feeding the recording sheet including the paper feed cassette 103 is disposed. Above the image forming apparatus main body 102, an image reading apparatus 101 including a CCD image sensor or the like as reading means for reading an image of a document is disposed. A space is provided between the image reading apparatus 101 and the image forming apparatus main body 102, and a main body paper discharge portion 104 for loading the recording sheet conveyed and discharged by the image forming apparatus main body 102 is formed.

[0021] In the image forming apparatus main body 102, as an image forming means, a conventionally well-known print engine using an electrophotographic method is provided, and a laser writing unit (not shown), an electrophotographic process unit having a photosensitive surface, a fixing unit, etc. are built therein. Further, as a paper feeding means, a paper feeding roller (not shown) for separating and feeding the recording paper placed on the paper feeding cassette 103 is built therein, and the recording paper is supplied to the image forming means.

[0022] FIGS. 2(a) and (b) respectively show a perspective view and a cross-sectional view of the image reading apparatus 101 according to the present embodiment. As shown in FIGS. 2(a) and (b), the image reading apparatus 101 includes an ADF 201 (Automatic Document Feeder), which is a conveying unit, and a reader 202 provided below the ADF 201 for reading an image of one document surface (front surface, first surface) of the document conveyed by the ADF 201.

[0023] The ADF 201 separates a plurality of documents and feeds them to the reader 202. The ADF 201 includes a document tray 204 for placing a plurality of documents to be fed, and document conveying means 203 for separating and feeding the documents placed on the document tray 204 one by one and conveying them to the reader 202. Further, the ADF 201 includes a paper discharge tray 205 for placing the documents discharged after the image reading by the reader 202.

[0024] As shown in FIG. 2(b), the ADF 201 is provided with a pickup roller 300 and a separation roller pair 301 for separating and feeding a plurality of documents G placed on the document tray 204 as members constituting the document conveying means 203. Further, the ADF 201 is provided with a plurality of roller pairs for conveying the document G separated and fed by the separation roller pair 301, a first platen roller 306, and a second platen roller 308 as members constituting the document conveying means 203. The plurality of roller pairs include a pulling roller pair 302, a conveying roller pair 303, a registration roller pair 304, a lead 1 roller pair 305, a lead 2 roller pair 307, a lead 3 roller pair 309, and a paper discharge roller pair 310.

[0025] Specifically, the document conveying means 203 includes a pair of pulling rollers 302 provided downstream of the pickup roller 300 and the pair of separating rollers 301 for pulling out the document G conveyed from the pair of separating rollers 301. The document conveying means 203 also includes a pair of conveying rollers 303 provided downstream of the pair of pulling rollers 302 and a pair of registration rollers 304 provided downstream of the pair of conveying rollers 303. The pair of conveying rollers 303 conveys the document G conveyed by the pair of pulling rollers 302 to the downstream pair of rollers. The pair of registration rollers 304 corrects the inclination of the document G.

[0026] Furthermore, the document conveying means 203 includes a pair of lead 1 rollers 305, a first platen roller 306 (first conveying member), a pair of lead 2 rollers 307, a second platen roller 308, and a pair of lead 3 rollers 309 provided downstream of the pair of registration rollers 304 for stabilizing the image reading of the document G.

[0027] When the first image reading unit 314 reads the image of one document surface of the document G conveyed, the first platen roller 306 conveys the document G at a predetermined interval with respect to the first platen glass 311 while biasing the document G toward the first platen glass (placement surface) 311 side.

[0028] Also, the document conveying means 203 includes a pair of discharging rollers 310 provided downstream of the pair of lead 3 rollers 309 for discharging the document G after the image is read to the discharge tray 205. A reader 202 is provided below the ADF 201. Inside the reader 202, a first image reading unit 314 for reading the surface image of the document G conveyed onto the first platen glass 311 (first light-transmitting member) by the ADF 201 and the image of the document placed on the first platen glass 311 is provided. The first image reading unit 314 is movable along a sub-scanning direction (first direction) (direction orthogonal to the main scanning direction (second direction)) T on a rail (not shown).

[0029] When the first image reading unit 314 reads the front surface image of the document G conveyed by the ADF 201 in the document feeding reading (second reading method), it stops at the first position P1 below the first platen glass 311 provided on the opposite side (lower side) of the first platen roller 306 and performs image reading. In the document fixed reading (first reading method), the front surface image of the document G is read by the image reading unit that moves an immovable object in the sub-scanning direction T. On the other hand, when reading in the document fixed reading method for reading the image of the document G placed on the platen glass (placement surface) 313, the first image reading unit 314 moves and scans along the sub-scanning direction T from the first position P1 to the second position P2 by driving a motor (not shown) controlled by the control unit 316. In the document feeding reading, the front surface image of the document G is read by the image reading unit that does not move while the object moves in the sub-scanning direction.

[0030] Then, the image data of the document read by the first image reading unit 314 is processed by the control unit 316. Further, inside the ADF 201, a second platen glass 312 is provided on the opposite side of the second platen roller 308 in order to read the image of the other surface of the document G being conveyed (the back surface, the second surface which is the side opposite to the first surface). Also, a second image reading unit 315 is provided at a position C facing the second platen roller 308 with the second platen glass 312 interposed therebetween.

[0031] Thereby, when the document G is conveyed by the ADF 201, the images of both the front and back surfaces of the document G can be read by the first image reading unit 314 and the second image reading unit 315. The first platen glass 311, the second platen glass 312, and the platen glass 313 are made of a material having translucency such as acrylic resin, polyester resin, polycarbonate resin, or glass.

[0032] FIG. 3 shows a schematic diagram of the main part of the document fixing reading image reading unit according to the first embodiment. As shown in FIG. 3(a), in the image reading apparatus 101 according to the present embodiment, the upstream illumination device (first illumination means) 404a and the downstream illumination device (second illumination means) 404b in the first image reading unit 314 illuminate the document G placed on the document table glass 313. The upstream illumination device 404a and the downstream illumination device 404b are symmetrically arranged on the upstream side (one side) and the downstream side (the other side) with the reading optical axis 402 interposed therebetween. With this configuration, it becomes possible to illuminate the illumination area 401 including the reading position 403 of the document G from both sides in the sub-scanning direction. The document G is fixed by pressing the document G against the document table glass 313 by the white plate 317.

[0033] The diffused reflected light from the document G is condensed onto the light receiving unit 405 (image reading sensor) by the imaging optical system 406 (equi-magnification optical system), and the image data of the document G is obtained. The imaging optical system 406 and the light receiving unit 405 constitute image reading means. The light receiving unit 405 consists of an image sensor. As the image sensor, a CCD image sensor, a CMOS image sensor, or the like can be employed. They may be not only line sensors in which a large number of pixels are arranged in a row in the main scanning direction (Y direction), but also sensors in which a large number of RGB pixels are arranged in a row in the main scanning direction, or sensors in which a line sensor of R pixels, a line sensor of G pixels, and a line sensor of B pixels are arranged in parallel in three rows.

[0034] Then, by moving and scanning the first image reading unit 314 along the sub-scanning direction T from the first position P1 to the second position P2, the light receiving unit 405 can read the image information of the entire document surface of the document G in a line sequential manner. The image information read by the light receiving unit 405 is transmitted as an electrical signal to an external device such as an image processing unit (not shown) or a personal computer through an interface.

[0035] Next, with reference to FIGS. 3(b) and 3(c), the shadow generated when the document G is a thick paper (e.g., a business card) will be described. The drive unit 407 moves the first image reading unit 314 in the sub-scanning direction to read the document image.

[0036] Figure 3(b) shows the reading start position of the original document G. Since the original document G is made of cardboard, there is a gap (positional difference in the X direction) corresponding to the thickness of the cardboard between the document table glass 313 and the white plate 317. Therefore, when illuminating the reading start position of the original document with the upstream illumination device 404a and the downstream illumination device 404b, due to the step between the surface of the original document and the white plate 317, a shadow a is generated as a portion that is not illuminated by the illumination light of the downstream illumination device 404b.

[0037] Figure 3(c) shows the reading end position of the original document G. When illuminating the reading end position of the original document with the upstream illumination device 404a and the downstream illumination device 404b, due to the step between the surface of the original document and the white plate 317, a shadow b is generated as a portion that is not illuminated by the illumination light of the upstream illumination device 404a.

[0038] Figure 4 shows an image read by the original document fixed reading according to the first embodiment. In the image read by the original document fixed reading, shadows a and b appear at both ends in the sub-scanning direction (Z direction) of the original document G. If the written shadows a and b have different shadow densities, it will give the user a sense of discomfort with respect to the read image. Therefore, it is desirable to make the densities of shadows a and b equal. Thus, in the original document fixed reading, if the light quantity at the reading position 403 of the illumination area 401 illuminated by the upstream illumination device 404a is Qa and the light quantity at the reading position 403 of the illumination area 401 illuminated by the downstream illumination device 404b is Qb, 0.90 < Qa / Qb < 1.11 ···(1) it is preferable to satisfy the following formula. Here, the reading position 403 corresponds to the intersection line between the plane including the reading optical axis 402 defined by the imaging optical system 406 and the light receiving unit 405 (image reading means) and perpendicular to the sub-scanning direction, and the surface of the document table glass 313 or the surface of the original document side of the first platen glass 311.

[0039] Equation (1) defines the density of the shadows at both ends of the document G in the sub-scanning direction during fixed document reading. By keeping within the range of Equation (1), the density of the shadows (shadow a and shadow b) at both ends of the document G in the sub-scanning direction during fixed document reading can be made equal, without giving the user a sense of discomfort with the read image. When the upper limit value of Equation (1) is 1.11 or more, or the lower limit value is 0.90 or less, the density of the shadows (shadow a and shadow b) at both ends of the document G in the sub-scanning direction during fixed document reading will be different, giving the user a sense of discomfort with the read image. Therefore, it is desirable to satisfy Equation (1).

[0040] It is more preferable that the lighting device of the present invention satisfies the following equation (1a). 0.93 < Qa / Qb < 1.07 ···(1a) It is even more preferable that the lighting device of the present invention satisfies the following equation (1b). 0.96 < Qa / Qb < 1.04 ···(1b) As will be described later, in the present embodiment, the specific value of Qa / Qb is Qa / Qb = 1.00 and it satisfies Equation (1).

[0041] Next, the configuration of the upstream lighting device 404a in the first image reading unit 314 of the image reading apparatus 101 according to the present embodiment and the effects thereof will be described. FIG. 5 shows a schematic diagram (perspective view) of the main part of the upstream lighting device 404a according to the first embodiment. As shown in FIG. 5, in the upstream lighting device 404a according to the present embodiment, a light source (first light source) 414 (white light-emitting diode, LED) is disposed at an end of the light guide (first light guide) 408 in the main scanning direction (Y direction).

[0042] FIG. 16 is an explanatory diagram showing the light distribution characteristics of the light source 414. Since the LED used for the light source 414 is excellent in terms of cost, in particular, without using a resin lens or the like for condensing light, the phosphor is often exposed with a flat surface shape. In the case of such an LED, the light distribution characteristics of the emitted light become the characteristics called Lambert emission as shown in FIG. 16. In FIG. 16, the 0° direction is the main scanning direction (Y direction) (the longitudinal direction of the light guide 408 in FIG. 5). That is, the direction perpendicular to the light emitting surface of the light source 414 (the normal direction) is the 0° direction in FIG. 16, and the direction in which the strongest light is emitted from the light source 414, that is, the direction with high luminance is the 0° direction. And it is widely emitted in the range of ±90° from the normal direction.

[0043] Next, the emission spectrum of the light source 414 will be described. FIG. 17 is an example of the emission spectrum of a general white light emitting diode (LED) used for the light source 414. In FIG. 17, the horizontal axis represents the wavelength of light, and the vertical axis represents the spectral intensity. The white light emitting diode is a blue LED chip that emits light rays with a wavelength of about 450 nm, and by exciting and fluorescing the yellow or orange phosphor filled around it, these lights are mixed to emit a white color. Although a white light emitting diode (LED) is used as the light emitting element, it is not limited to this, and an EL element or the like may be used. Although white light is desirable as the light emitted from the light emitting element, it is not limited to this, and light such as blue, green, or red may be used.

[0044] The first image reading unit 314 includes a light guide 408. The light guide 408 guides the light from the light source 414 through the platen glass 313 to the irradiated surface (original G). As shown in FIG. 5, the light guide 408 has an incident surface 409, an exit surface 410, a scattering surface 411, a first light guide surface 412, and a second light guide surface 413. The light from the light source 414 arranged at the main scanning end enters the incident surface 409. The exit surface 410 emits light toward the irradiated surface perpendicular to the incident surface 409.

[0045] The scattering surface 411 faces the emission surface 410 and diffuses the light from the incident surface 409. The first light guide surface 412 and the second light guide surface 413 connect the emission surface 410 and the scattering surface 411. The scattering surface 411 is formed by performing screen printing of white paint or the like, and is configured such that the density becomes coarser (lower density) to denser (higher density) as it is separated from the incident surface 409. Although white paint is used for the scattering surface 411, it is not limited thereto, and a triangular prism or the like may be used.

[0046] The light emitted from the light source 414 and incident on the incident surface 409 is diffused by the scattering surface 411 while propagating in the main scanning direction while undergoing total internal reflection, and is deflected in the directions of the first light guide surface 412, the second light guide surface 413, and the emission surface 410. The first light guide surface 412 and the second light guide surface 413 have a condensing action and have a curved surface shape. In the present embodiment, the first light guide surface 412 and the second light guide surface 413 are a parabolic surface or an elliptical surface having a convex power.

[0047] This is to set the position of the midpoint of the scattering surface 411 as a parabolic reflecting surface or an elliptical reflecting surface with the focus of the parabolic surface or the elliptical surface in the sub-scanning cross section (XZ cross section, first cross section). Thereby, the light traveling from the scattering surface 411 toward the first light guide surface 412 and the second light guide surface 413 can be efficiently deflected in the direction of the illumination region 401, and a sufficient amount of light can be ensured in the illumination region 401. Then, the light emitted from the emission surface 410 illuminates a linearly long region in the main scanning direction (Y direction) in the illumination region 401 of the document G. Note that the shape is not limited to that shown in the present embodiment as long as the light from the light source 414 can be efficiently guided to the illumination region 401 of the document G.

[0048] As the material of the light guide 408, a light-transmissive inorganic material such as glass or a light-transmissive organic material such as an acrylic resin, a polyester resin, or a polycarbonate resin can be used. Among them, it is preferable to use a synthetic resin material that is easy to mold such as plastic, and in the present embodiment, an acrylic resin (PMMA) is adopted.

[0049] The downstream illumination device 404b has a light source (second light source) (white light-emitting diode, LED) disposed at an end of a light guide body (second light guide body) in the main scanning direction (Y direction), similar to the upstream illumination device 404a. Since the downstream illumination device 404b has the same configuration as the upstream illumination device 404a, detailed description thereof is omitted.

[0050] Here, the problem will be described with reference to FIG. 14. FIG. 14 shows a schematic view of a main part of an image reading unit according to a comparative example. FIG. 14(a) shows the first image reading unit 314 when the reflection optical system 514 is disposed at the designed position. FIG. 14(b) shows the first image reading unit 314 when the posture of the reflection optical system 514 changes due to temperature rise or assembly tolerance.

[0051] The first image reading unit 314 according to the comparative example is different from the first image reading unit 314 according to the first embodiment in the shape of the light guide bodies of the upstream illumination device 504a and the downstream illumination device 504b, including the reflection optical system 514, and that the imaging optical system 506 is a reduction optical system. Otherwise, it has the same configuration as the first image reading unit 314 according to the first embodiment. In the image reading apparatus 101 according to the comparative example, the document G placed on the document table glass 313 is illuminated by the upstream illumination device 504a and the downstream illumination device 504b within the first image reading unit 314.

[0052] Then, the diffused reflected light from the document G is reflected by the reflection optical system 514, and condensed onto the light receiving unit 505 (image reading sensor) by the imaging optical system 506 (reduction optical system), and the image data of the document G is obtained. The imaging optical system 506 and the light receiving unit 505 constitute an image reading means. The reflection optical system 514 includes a first folding mirror 514a, a second folding mirror 514b, a third folding mirror 514c, and a fourth folding mirror 514d.

[0053] When using a reduction optical system, generally the optical path length from the reading position of the document G to the light receiving part becomes long. Therefore, it is common to make the first image reading unit 314 compact by bending the optical path using a folding mirror. When using a folding mirror, the reading optical axis 502 is inclined due to temperature rise or assembly tolerance, and the reading position 503 shifts in the sub-scanning direction. Even if a sub-scanning position shift of the reading position 503 occurs, in order to reduce the change in light amount, the condensing action of the light guide used for the upstream illumination device 504a and the downstream illumination device 504b has convex power only on the emission surface.

[0054] FIG. 15 shows the sub-scanning light amount distribution of the illumination device according to the comparative example. The horizontal axis indicates the sub-scanning direction (Z direction), and the vertical axis indicates the light amount. The light amount distributions of the illumination region 501 by the upstream illumination device 504a and the light amount distribution of the illumination region 501 by the downstream illumination device 504b are combined to obtain the light amount distribution in bilateral illumination. As shown in FIG. 15, the light amount at the reading position 503 when the reflective optical system 514 is designed and arranged is normalized to 100. On the other hand, even if the reading position 503 shifts by 3 mm due to temperature rise or assembly tolerance of the reflective optical system 514, the light amount can be ensured to be 74.

[0055] FIG. 6 shows the sub-scanning light amount distribution of the upstream illumination device according to the first embodiment. The horizontal axis indicates the sub-scanning direction (Z direction), and the vertical axis indicates the light amount (illuminance) on the surface of the first platen glass 311 on the document G side. In the present embodiment using an equal magnification optical system as compared with the comparative example using a reduction optical system, since there is no reflective optical system, the reading position shift in the sub-scanning direction can be reduced. Therefore, the light guide 408 has convex power on three surfaces, namely the emission surface 410, the first light guide surface 412, and the second light guide surface 413, to enhance the condensing action, and the light amount at the reading position 403 is increased by 34% compared with the comparative example.

[0056] FIG. 7 shows the case where the peak value is normalized to 100 with respect to the light quantity distribution in the sub-scanning direction of FIG. 6. When the half-value width at the center position in the main scanning direction of the light guide 408 of the upstream illumination device 404a when normalized by the peak light quantity is defined as E1, in the comparative example, E1 = 6.3 mm, whereas in the present embodiment, by narrowing it to E1 = 3.9 mm, the light quantity at the reading position 403 is increased by 34%.

[0057] FIG. 8 shows a schematic diagram of the main part of the image reading unit in the arrangement during document feeding reading according to the first embodiment. As shown in FIG. 8(a), in document feeding reading, the image on the surface of the document G conveyed by the ADF 201 is read by the first image reading unit 314. The sheet member 318 is a member having a mechanism for conveying the document G along it in order to convey the conveyed document G to the reading position 403 in a state close to being parallel to the first platen glass 311 when conveying the document G to the reading position 403.

[0058] The first platen glass 311 is provided at the reading position 403 of the image on the surface of the conveyed document G. Here, the reading position 403 includes not only the surface of the first platen glass 311 but also the paper surface position of the document G conveyed between the first platen glass 311 and the first platen roller 306. As the document G is conveyed, the light receiving unit 405 can read the image information of the entire document surface of the document G in a line sequential manner.

[0059] Next, with reference to FIG. 8(b), the shadow generated by the conveyed document G will be described. FIG. 8(b) shows the reading start position of the conveyed document G. There is a gap between the first platen glass 311 and the first platen roller 306. Therefore, when illuminating the reading start position of the document with the upstream illumination device 404a and the downstream illumination device 404b, a shadow c is generated by the illumination light of the upstream illumination device 404a due to the step between the document surface and the first platen roller 306.

[0060] Using FIG. 18, the detection of the inclination of the conveyed document will be described. FIG. 18 is an explanatory diagram of the inclination of the document G to be conveyed. The state where the conveyed document G is in the designed state and not inclined is indicated by a dashed line. However, due to manufacturing errors of the ADF 201 or the like, the document may be inclined as indicated by the solid line. By detecting this inclination amount and performing image correction, an image that is not inclined can be provided to the user.

[0061] In order to detect the inclination amount, a shadow c generated at the leading edge of the document is detected. When the position of the shadow c in the sub-scanning direction (Z direction) changes in the main scanning direction, it means that the document is inclined, so the inclination amount is calculated and image correction is performed. If the density of the shadow c relative to the surrounding area of the shadow c is low (the contrast is low), the shadow cannot be detected, leading to misdetection of the inclination amount. Therefore, an improvement in the density of the shadow c relative to the surrounding area of the shadow c (high contrast) is desired.

[0062] Here, using FIG. 9, the description of the shadow in the document feeding reading method according to the first embodiment will be given. Here, for the sake of convenience, the light rays from the downstream side illumination device 404b are omitted, and only the light rays from the upstream side illumination device 404a will be described. The light rays from the upstream side illumination device 404a toward the reading position 403 are composed of a light ray A from the scattering surface 411 toward the emission surface 410, a light ray B from the scattering surface 411 toward the second light guide surface 413, and a light ray C from the scattering surface 411 toward the first light guide surface 412. Assuming that the angle formed by the light ray toward the reading position 403 and the reading optical axis 402 is θ, among the light rays toward the reading position 403, the angle θ1 formed by the light ray C toward the first light guide surface 412 close to the reading position 403 and the reading optical axis 402 is the minimum angle.

[0063] The shadow width W of the shadow c that can be formed on the first platen roller 306 and in the +Z direction (downstream side) from the reading optical axis 402 is composed of the sum of a dark shadow width W1 and a light shadow width W2. The dark shadow width W1 is the width between the position of the light ray C reaching the first platen roller 306 and the reading optical axis 402, and it is the place where the density of the shadow in the shadow c is the darkest (darkest). The light shadow width W2 is the width between the light ray B and the light ray C reaching the first platen roller 306, and the density of the shadow becomes lighter (brighter) as it moves away from the reading optical axis 402.

[0064] When detecting the shadow c generated at the leading edge of the original, it is desirable that the dark shadow width W1 be long. In other words, it is desirable that the angle θ1 be large. On the other hand, when the angle θ1 becomes large, the half-value width spreads, and the amount of light illuminating the illumination area 401 decreases. Therefore, in order to ensure the amount of light with which the upstream illumination device 404a illuminates the illumination area 401, the half-value width E1 in the sub-scanning light amount distribution and the above-described angle θ1 are 3.0 mm < E1 < 5.0 mm ··· (2) 10° < θ1 < 18° ··· (3) It is desirable to satisfy

[0065] Equations (2) and (3) define the amount of light illuminating the illumination area 401. By being within the ranges of Equations (2) and (3), the illumination area 401 can be efficiently illuminated. When the upper limit value of Equation (2) is 5.0 mm or more, or the upper limit value of Equation (3) is 18° or more, the amount of light illuminating the illumination area 401 decreases. When the lower limit value of Equation (2) is 3.0 mm or less, or the lower limit value of Equation (3) is 10° or less, the dark shadow width W1 becomes short, which is disadvantageous for detecting the shadow c. Therefore, it is desirable to satisfy the conditions of Equations (2) and (3).

[0066] It is more preferable that the illumination device of the present invention satisfies the following equations (2a) and (3a). 3.3 mm < E1 < 4.6 mm ··· (2a) 12° < θ1 < 17° ··· (3a) It is even more preferable that the illumination device of the present invention satisfies the following equations (2b) and (3b). 3.6 mm < E1 < 4.2 mm ··· (2b) 14° < θ1 < 16° ··· (3b)

[0067] Regarding the specific numerical values in the comparative example, E1 = 6.3 mm, θ1 = 20°, and regarding the specific numerical values in the present embodiment, E1 = 3.9 mm, θ1 = 15°, and the illumination device of the present embodiment satisfies Equations (2) and (3).

[0068] In order to ensure the amount of light illuminating the illumination area 401, it is desirable that the downstream illumination device 404b also satisfies the following formulas (2′) and (3′) corresponding to the upstream illumination device 404a, similar to the formulas (2) and (3). The half-value width E2 in the sub-scanning light amount distribution and the above angle θ2 are 3.0 mm < E2 < 5.0 mm ··· (2′) 10° < θ2 < 18° ··· (3′) It is desirable to satisfy. Here, E2 is the half-value width at the central position in the main scanning direction of the light guide 408 of the downstream illumination device 404b when the peak light amount is normalized to 100 with respect to the light amount distribution in the sub-scanning direction. θ2 is the angle with the smallest angle formed with the reading optical axis 402 among the light rays from the downstream illumination device 404b toward the reading position 403.

[0069] It is more preferable that the illumination device of the present invention satisfies the following formulas (2a′) and (3a′). 3.3 mm < E2 < 4.6 mm ··· (2a′) 12° < θ2 < 17° ··· (3a′) It is even more preferable that the illumination device of the present invention satisfies the following formulas (2b′) and (3b′). 3.6 mm < E2 < 4.2 mm ··· (2b′) 14° < θ2 < 16° ··· (3b′)

[0070] Next, means for increasing the density of the shadow c generated at the leading edge of the document while ensuring the amount of light illuminating the illumination area 401 will be described. FIG. 10 shows the sub-scanning light amount distribution of the illumination device in the document fixed reading according to the first embodiment. The horizontal axis indicates the position in the sub-scanning direction (Z direction), and the vertical axis indicates the light amount. In order to make the densities of the shadows a and b equal, in the document fixed reading, the light amount Qa of the upstream illumination device 404a and the light amount Qb of the downstream illumination device 404b at the reading position 403 are configured to be symmetric with respect to the reading optical axis.

[0071] FIG. 11 shows the sub-scanning light quantity distribution of the illumination device in the manuscript feeding reading according to the first embodiment. The horizontal axis represents the position in the sub-scanning direction (Z direction), and the vertical axis represents the light quantity. In order to darken the density of the shadow c generated at the leading edge of the manuscript, in the manuscript feeding reading, if the light quantity at the reading position 403 of the illumination area 401 illuminated by the upstream illumination device 404a is Qc, and the light quantity at the reading position 403 of the illumination area 401 illuminated by the downstream illumination device 404b is Qd, then Qa < Qc ··· (4) Qb > Qd ··· (5) at least one of the conditions is satisfied.

[0072] Equations (4) and (5) define the density of the shadow at the leading edge of the manuscript G in the sub-scanning direction in the manuscript feeding reading. By satisfying the conditions of Equations (4) and (5), the density of the shadow (shadow c) at the leading edge of the manuscript G in the sub-scanning direction in the manuscript feeding reading can be darkened, and the false detection of shadow detection can be improved. When the upper limit value of Equation (4) is 1.0 or more, or the lower limit value of Equation (5) is 1.0 or less, the density of the shadow (shadow c) at the leading edge of the manuscript G in the sub-scanning direction in the manuscript feeding reading becomes thin, which is disadvantageous for shadow detection and leads to false detection of the inclination amount of the manuscript.

[0073] Therefore, it is desirable to satisfy at least one of the conditions of Equations (4) and (5). In this embodiment, Qa / Qc = 1.00 Qb / Qd = 1.11 therefore, among Equations (4) and (5), Equation (5) is satisfied.

[0074] The light quantity is adjusted by the current flowing through the light source 414. In the fixed manuscript reading, the currents flowing through the light sources 414 of the upstream illumination device 404a and the downstream illumination device 404b are equal. In the manuscript feeding reading, the current flowing through the light source 414 of the upstream illumination device 404a is the same as that in the fixed manuscript reading, but the current flowing through the light source 414 of the downstream illumination device 404b is 10% less than that in the fixed manuscript reading. Although the current is used for light quantity adjustment, it is not limited to this, and the lighting time, pulse width, etc. may also be used.

[0075] In addition, in the lighting device of the present invention, the value of the ratio of the light quantity (Qa, Qc) of the light beam from the first lighting means to the light quantity (Qb, Qd) of the light beam from the second lighting means at the reading position is different between the value (Qa / Qb) in the fixed original reading and the value (Qc / Qd) in the fixed original reading. That is, Qa / Qb≠Qc / Qd ···(6) It is characterized by satisfying the following formula. The lighting device of the present invention suppresses the difference in the density of the shadows at both ends in the fixed original reading, suppresses the sense of strangeness of the read image given to the user, and improves the false detection of shadows in the moving original reading method. Between the fixed original reading and the fixed original reading, control is performed to change the value of the ratio of the light quantity of the first lighting means to the second lighting means. More specifically, at least one of the first lighting means and the second lighting means is controlled between the fixed original reading and the fixed original reading so as to satisfy at least one of formula (1), formula (4), and formula (5).

[0076] In addition, in the moving original reading, the value of the ratio of the light quantity Qc of the upstream side lighting device 404a to the light quantity Qd of the downstream side lighting device 404b is 1.05<Qc / Qd<1.70···(7) Satisfies the following formula. Formula (7) defines the density of the shadow at the leading end of the original G in the sub-scanning direction (original conveyance direction, moving direction) in the moving original reading. By satisfying formula (7), the density of the shadow (shadow c) at the leading end of the original G in the sub-scanning direction in the moving original reading can be improved, and false detection of the shadow can be suppressed.

[0077] When the upper limit value of formula (7) is 1.70 or more, the current flowing through the light source 414 of the upstream side lighting device 404a increases, and there are concerns about the rated value of the light source 414 and the reduction of the life of the light source or the like, which is not preferable. Or, the current flowing through the light source 414 of the downstream side lighting device 404b decreases, leading to a decrease in the light quantity, which is not preferable.

[0078] When the lower limit value of formula (7) is 1.05 or less, the change in contrast with the periphery of the shadow (shadow c) of the leading edge of the document G in the sub-scanning direction during continuous document feeding reading is small, and the effect of suppressing false detection of the shadow becomes small, which is not preferable. Therefore, it is desirable to satisfy formula (7).

[0079] It is more preferable that the lighting device of the present invention satisfies the following formula (7a). 1.08 < Qc / Qd < 1.50 ··· (7a) It is even more preferable that the lighting device of the present invention satisfies the following formula (7b). 1.08 < Qc / Qd < 1.30 ··· (7b) In the present embodiment, Qc / Qd = 1.11 and it satisfies formula (7).

[0080] As described above, according to the first image reading unit 314 according to the present embodiment, the densities (contrasts with the periphery) of the shadows (shadow a and shadow b) at both ends of the document G in the sub-scanning direction during fixed document reading can be made equal, and the user is not given a sense of discomfort with respect to the read image. And the density of the shadow (shadow c) of the leading edge of the document G in the sub-scanning direction during continuous document feeding reading can be improved (the contrast with the periphery is increased), and false detection of the shadow can be reduced.

[0081] <Second Embodiment> Hereinafter, a second embodiment of the present invention will be described. Since the image reading apparatus according to the present embodiment has the same configuration as the image reading apparatus 101 according to the first embodiment, the description thereof will be omitted. The lighting device of the second embodiment has different currents of the light source 414 of the upstream-side lighting device 404a and the current of the light source 414 of the downstream-side lighting device 404b during continuous document feeding reading with respect to the first image reading unit 314 according to the first embodiment.

[0082] FIG. 12 shows the sub-scanning light quantity distribution of the lighting device in the manuscript feeding reading according to the second embodiment. The horizontal axis represents the sub-scanning direction (Z direction), and the vertical axis represents the light quantity. In order to efficiently illuminate the illumination area 401, by setting E1 = 3.9 mm and θ1 = 15°, equations (2) and (3) are satisfied. In order to make the density (contrast) of the shadows (shadow a and shadow b) at both ends of the manuscript G in the sub-scanning direction in the fixed manuscript reading equal and not give the user a sense of discomfort with respect to the read image, in the fixed manuscript reading, the currents flowing through the light sources 414 of the upstream lighting device 404a and the downstream lighting device 404b are made equal, Qa / Qb = 1.00 so as to satisfy equation (1).

[0083] In order to improve the density (contrast) of the shadow c generated at the leading edge of the manuscript, in the manuscript feeding reading, the current flowing through the light source 414 of the downstream lighting device 404b is the same as that in the fixed manuscript reading, but the current flowing through the light source 414 of the upstream lighting device 404a is increased by 10% with respect to the fixed manuscript reading. Specifically, Qa / Qc = 0.91 Qb / Qd = 1.00 Therefore, among equations (4) and (5), equation (4) is satisfied. The value of the ratio of the light quantity Qc of the upstream lighting device 404a to the light quantity Qd of the downstream lighting device 404b in the manuscript feeding reading is Qc / Qd = 1.10 Therefore, equation (7) is satisfied. Also, equation (6) is satisfied.

[0084] As described above, according to the first image reading unit 314 according to the present embodiment, the densities of the shadows (shadow a and shadow b) at both ends of the manuscript G in the sub-scanning direction in the fixed manuscript reading can be made equal, and the user is not given a sense of discomfort with respect to the read manuscript. And the density (contrast with respect to the surroundings) of the shadow (shadow c) at the leading edge of the manuscript G in the sub-scanning direction in the manuscript feeding reading can be improved, and false detection of the shadow can be reduced.

[0085] <Third Embodiment> Hereinafter, a third embodiment of the present invention will be described. Since the image reading apparatus according to this embodiment has the same configuration as the image reading apparatus 101 according to the first embodiment, the description thereof will be omitted. The difference from the first image reading unit 314 according to the first embodiment lies in the current of the light source 414 of the upstream illumination device 404a and the current of the light source 414 of the downstream illumination device 404b in the document feeding reading.

[0086] FIG. 13 shows the sub-scanning light quantity distribution of the illumination device in the document feeding reading according to the third embodiment. The horizontal axis represents the sub-scanning direction (Z direction), and the vertical axis represents the light quantity. In order to efficiently illuminate the illumination area 401, by setting E1 = 3.9 mm and θ1 = 15°, the equations (2) and (3) are satisfied. In order to make the densities of the shadows (shadow a and shadow b) at both ends of the document G in the sub-scanning direction in the document stationary reading equal and not give the user a sense of discomfort with respect to the read image, in the document stationary reading, the currents flowing through the light sources 414 of the upstream illumination device 404a and the downstream illumination device 404b are made equal, Qa / Qb = 1.00 so that the equation (1) is satisfied.

[0087] In order to improve the density (contrast) of the shadow c generated at the leading edge of the document, in the document feeding reading, the current flowing through the light source 414 of the upstream illumination device 404a is increased by 20% compared to the document stationary reading, and the current flowing through the light source 414 of the downstream illumination device 404b is decreased by 20% compared to the document stationary reading. Specifically, Qa / Qc = 0.83 Qb / Qd = 1.25 Therefore, both the equations (4) and (5) are satisfied. In the document feeding reading, the value of the ratio of the light quantity Qc of the upstream illumination device 404a to the light quantity Qd of the downstream illumination device 404b is Qc / Qd = 1.50 Therefore, the equation (7) is satisfied. Also, the equation (6) is satisfied.

[0088] As described above, according to the first image reading unit 314 according to this embodiment, it is possible to equalize the densities of the shadows (shadow a and shadow b) at both ends in the sub-scanning direction of the document G in fixed document reading, and it does not give the user a sense of discomfort with respect to the read image. Further, it is possible to improve the density (contrast with the surroundings) of the shadow (shadow c) at the leading edge of the document G in the sub-scanning direction in continuous document reading, and it is possible to reduce false detection of the shadow.

[0089] Note that, in the embodiment, a configuration for improving the density of the shadow at the leading edge of the document G in the sub-scanning direction in continuous document reading and reducing false detection of the shadow is exemplified. As a result, in continuous document reading, when recognizing the inclination of the read image and outputting the image read by an image forming apparatus or the like, it is possible to correct and output the position based on the acquired inclination. Note that, in continuous document reading, instead of the leading edge of the document G in the sub-scanning direction, a configuration may be adopted in which the density of the shadow at the trailing edge of the document is improved to reduce false detection in shadow detection. In that case, Qa>Qc ···(8) Qb<Qd ···(9) it may be configured to satisfy at least one of the conditions. Also in this case, similar to the first to third embodiments, in continuous document reading, it is possible to improve the density of the shadow at the trailing edge of the document G in the sub-scanning direction and reduce false detection of the shadow at the trailing edge of the document.

[0090] As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

[0091] The disclosure of this embodiment includes the following configurations. (Configuration 1) An illumination device used in an image reading apparatus capable of executing a first reading method of reading an object that does not move by a reading unit that moves in a first direction, and a second reading method of reading an object that moves in the first direction by the reading unit that does not move, A first illumination means disposed on one side in the first direction with respect to the reading position by the reading means, and a second illumination means disposed on the other side. In the first reading method, the light quantity at the reading position of the light beam emitted from the first illumination means is Qa, the light quantity at the reading position of the light beam emitted from the second illumination means in the first reading method is Qb, the light quantity at the reading position of the light beam emitted from the first illumination means in the second reading method is Qc, and the light quantity at the reading position of the light beam emitted from the second illumination means in the second reading method is Qd. Qa / Qb ≠ Qc / Qd 0.90 < Qa / Qb < 1.11 Satisfies the formula: Qa < Qc Qb > Qd An illumination device, characterized by satisfying at least one of the formulas. (Configuration 2) 1.05 < Qc / Qd < 1.70 The illumination device according to claim 1, characterized by satisfying this condition. (Configuration 3) The reading position is a region having a longitudinal direction in a second direction perpendicular to the first direction. The first illumination means includes a first light source and a first light guide having a longitudinal direction in the second direction for guiding the light from the first light source to the reading position. In the light quantity distribution of the first illumination means in the first direction, when the half-value width at the central position in the second direction of the first light guide is E1. 3.0 mm < E1 < 5.0 mm The illumination device according to Configuration 1 or 2, characterized by satisfying the formula. (Configuration 4) The reading position is a region having a longitudinal direction in a second direction perpendicular to the first direction. The second illumination means includes a second light source and a second light guide having a longitudinal direction in the second direction for guiding the light from the second light source to the reading position. In the light quantity distribution of the second lighting means in the first direction, when normalized by the peak light quantity, if the half-value width at the center position in the second direction of the second light guide is E2, 3.0 mm < E2 < 5.0 mm The lighting device according to any one of Configurations 1 to 3, characterized by satisfying the formula. (Configuration 5) The lighting device according to any one of Configurations 1 to 4, characterized in that one side is the upstream side in the moving direction of the object in the second reading method, and the other side is the downstream side in the moving direction of the object in the second reading method. (Configuration 6) In a first cross section parallel to the first direction and perpendicular to the placement surface, among the angles formed by the light rays from the first lighting means toward the reading position and the reading optical axis of the reading means, if the minimum angle is θ1, 10° < θ1 < 18° The lighting device according to any one of Configurations 1 to 5, characterized by satisfying the formula. (Configuration 7) The lighting device according to any one of Configurations 1 to 6, characterized in that the light quantity in the first reading method and the second reading method is switched by changing the current to at least one light source of the first lighting means and the second lighting means. (Configuration 8) The lighting device according to any one of Configurations 1 to 6, characterized in that the first lighting means and the second lighting means are arranged symmetrically with respect to each other across the reading optical axis of the reading means in the first direction. (Configuration 9) An image reading device, comprising: the lighting device according to any one of Configurations 1 to 8; a light receiving unit that receives light from the lighting area illuminated by the lighting device; and an imaging optical system that guides the light from the lighting area to the light receiving unit. (Configuration 10) The image reading device according to Configuration 9, characterized in that the imaging optical system is an equi-magnification optical system. (Configuration 11) The image reading apparatus according to configuration 9 or 10, characterized by having a conveying means for conveying the object toward the reading position. (Configuration 12) An image forming apparatus, comprising: the image reading apparatus according to any one of configurations 9 to 11; and an image forming unit configured to form an image on a photosensitive surface based on the image of the object obtained by the image reading apparatus.

Explanation of Signs

[0092] 101 Image reading apparatus 311 First platen glass (placement surface) 313 Document table glass (placement surface) 401, 501 Illumination area 403, 503 Reading position 404a, 504a Upstream side illumination device (first illumination means) 404b, 504b Downstream side illumination device (second illumination means)

Claims

1. An illumination device used in an image reading apparatus capable of executing a first reading method of reading an object that does not move by a reading means moving in a first direction, and a second reading method of reading an object moving in the first direction by the reading means that does not move, comprising a first illumination means disposed on one side in the first direction with respect to a reading position by the reading means, and a second illumination means disposed on the other side, wherein, in the first reading method, the light quantity at the reading position of the light beam emitted from the first illumination means is Qa, the light quantity at the reading position of the light beam emitted from the second illumination means in the first reading method is Qb, the light quantity at the reading position of the light beam emitted from the first illumination means in the second reading method is Qc, and the light quantity at the reading position of the light beam emitted from the second illumination means in the second reading method is Qd, Qa / Qb ≠ Qc / Qd 0.90 < Qa / Qb < 1.11 satisfies the formula, Qa < Qc Qb > Qd and satisfies at least one of the formulas. An illumination device characterized by this.

2. 1.05 < Qc / Qd < 1.70 The illumination device according to claim 1, characterized by satisfying the formula.

3. The reading position is a region having a longitudinal direction in a second direction perpendicular to the first direction, the first illumination means includes a first light source and a first light guide having a longitudinal direction in the second direction for guiding light from the first light source to the reading position, in the light quantity distribution in the first direction of the first illumination means, when the half-value width at the central position in the second direction of the first light guide is E1, 3.0 mm < E1 < 5.0 mm The illumination device according to claim 1, characterized by satisfying the formula.

4. The reading position is a region having a longitudinal direction in a second direction perpendicular to the first direction, the second illumination means includes a second light source and a second light guide having a longitudinal direction in the second direction for guiding light from the second light source to the reading position, in the light quantity distribution in the first direction of the second illumination means, when normalized by the peak light quantity, when the half-value width at the central position in the second direction of the second light guide is E2, 3.0 mm < E2 < 5.0 mm The illumination device according to claim 1, characterized by satisfying the formula.

5. The one side is the upstream side in the moving direction of the object in the second reading method, and the other side is the downstream side in the moving direction of the object in the second reading method. The lighting device according to claim 1 is characterized by this.

6. In a first cross section parallel to the first direction and perpendicular to the placement surface, among the angles formed by the light ray from the first lighting means toward the reading position and the reading optical axis of the reading means, when the minimum angle is θ1, 10° < θ1 < 18° The lighting device according to claim 1 is characterized by satisfying the formula.

7. The lighting device according to claim 1 is characterized by switching the amount of light in the first reading method and the second reading method by changing the current to at least one of the light sources of the first lighting means and the second lighting means.

8. The lighting device according to claim 1 is characterized in that the first lighting means and the second lighting means are arranged symmetrically with respect to each other across the reading optical axis of the reading means in the first direction.

9. An image reading device, comprising: the lighting device according to any one of claims 1 to 8; a light receiving part that receives light from the lighting area illuminated by the lighting device; and an imaging optical system that guides the light from the lighting area to the light receiving part.

10. The image reading device according to claim 9 is characterized in that the imaging optical system is an equal magnification optical system.

11. The image reading device according to claim 9 is characterized by having a conveying means for conveying the object toward the reading position.

12. An image forming device, comprising: the image reading device according to claim 9; and an image forming part that forms an image on a photosensitive surface based on the image of the object obtained by the image reading device.

Images