Image reading apparatus

Abstract

The present disclosure relates to an image reading apparatus having a configuration with high accuracy, which easily enlarges a depth of field (improves a depth of field) without necessarily changing the basic characteristics of a lens body. The image reading apparatus is characterized by having an overlap preventing portion (5) disposed between a lens body array (1) and a sensor element array (3) to prevent the overlapping of images of the lens bodies (2) with each other, the overlap preventing portion (5) having a plurality of slit plates (7) that divide a space extending in a sub-scanning direction and are arranged in a main scanning direction, the slit plates (7) being fixed to a fixed plate (13).

Description

Technical Field

[0001] This disclosure relates to an image reading device that uses an array of lenses configured in an array shape to focus transmitted and reflected light from a reading object (the object being illuminated) and read the light through an array of sensor elements. Background Technology

[0002] In conventional image reading devices (line image sensors for image reading and image input devices using the same line image sensor), light is shone onto the object to be read, and the transmitted and reflected light from the object is focused using rod-shaped lenses arranged in an array. The light is then read by an array of light sensors arranged in a line (see, for example, Patent Document 1). Such image reading devices are used in image reading devices such as copiers and scanners that electronically display images, text, patterns, etc., on the object to be read.

[0003] For lens arrays in image reading devices, examples include rod lens arrays and microlens arrays in upright, equal-magnification optical systems. Such lens arrays are used in devices such as copiers and scanners for digitizing information such as images, text, and patterns printed on paper media. Patent Document 1 discloses an image reading device (line image sensor) that uses a rod lens array in which rod-shaped lenses are arranged in an array according to the reading width. Reading is performed by imagering reflected and transmitted light, including information about the object being read illuminated by a linear light source, onto a light sensor array arranged on opposite sides of the lens array.

[0004] In addition, the rod-shaped lens array disclosed in Patent Document 1 is formed from inorganic materials such as glass and resin, and its refractive index is distributed radially in a manner with a specified aperture angle, conjugate length and in an upright equal-multiplication system. By arranging the rod-shaped lenses in an array, it is possible to obtain an uninterrupted linear image.

[0005] In addition to input units such as fax machines, rod lens arrays have recently been used as back-end reading line image sensors in ADF (Automatic Document Feeder) built into document scanners and copiers. Furthermore, their applications have expanded to production lines for print inspection and film inspection in commercial printing lines. This is because, although rod lenses have fixed focal points, by shortening the conjugate length of the lens (the distance between focal points), a more compact image input system can be formed than conventional optical systems that reduce the image size and image it onto a small sensor surface.

[0006] Thus, with the expansion of application specifications, research was conducted to further expand the application scope of image sensors, addressing the issue of short conjugate lengths that contribute to miniaturization. To further expand application scope, it is necessary to improve the tolerance (depth of field) for the positional relationship between the focal point and the object being read (shallow depth of field). Especially in the case of online inspection of paper or film printing for image inspection applications, there are situations where the object being read is transported at speeds exceeding 200 m / min; therefore, it is necessary to improve the resolution variation of the read image caused by object jitter.

[0007] Against this backdrop, various studies have been conducted on increasing the depth of field in line image sensors. For example, there are cases where overlapping of images caused by multiple lens elements is limited by forming overlap limiting members between the lens elements of a lens element body, thereby controlling the imaging diameter of each lens element and increasing the depth of field (improving the depth of field) (e.g., Patent Document 1).

[0008] In addition, there are cases where the resolution is not reduced due to image overlap between the rod lenses by making the peripheral portion of the rod lens nontransparent and a light-absorbing layer, and the depth of field is increased (improved) as a whole as the rod lens array by making the depth of field characteristics of the rod lens array close to those of the individual rod lenses (for example, Patent Document 2).

[0009] Furthermore, there are cases where the peripheral portion of the rod lens is made nontransparent and a light-absorbing layer, thereby ensuring the uniformity of the characteristics of the rod lens array by setting gaps between the lenses when arranging the rod lenses, and improving the light quantity and resolution deviation between the lenses caused by the structure disclosed in Patent Document 2, further expanding the depth of field (improving the depth of field) (for example, Patent Document 3).

[0010] Patent Document 1: Japanese Patent Application Publication No. 6-342131

[0011] Patent Document 2: Japanese Patent Application Publication No. 2000-35519

[0012] Patent Document 3: WO2013 / 146873

[0013] In line image sensors using rod lens arrays, there are challenges in ensuring depth of field. To date, various studies have been conducted to improve depth of field to achieve the performance of individual lenses. In the technology shown in Patent Document 1, there is a problem of not being able to restrict light incident on the limiting component at a low angle of incidence.

[0014] In the technology shown in Patent Document 1, a general-purpose product is used for the lens array, and a light-shielding component with a spacing matching the fixed lens spacing is prepared in advance. The depth of field is often improved by limiting the light path emitted from the lens. However, it is envisioned that a light-shielding assembly is formed by using a single component or by combining light-shielding assemblies. An optical system is constructed by combining the lens array 1, which originally only manages the arrangement of rod lenses on the flat plate without managing the position of each rod lens, with the light-shielding component.

[0015] Therefore, in the technology shown in Patent Document 1, there is a problem that it is difficult to accurately position the light-shielding component in a bar lens array with a diameter of 0.3 to 1.0 mm to match the dimensional variations in the bar lens array, such as the thickness deviation of each bar lens and the deviation of the arrangement spacing.

[0016] Furthermore, considering the dimensional changes caused by thermal expansion and contraction of the lens array due to temperature and humidity variations during image capture in the sensor system using the lens structure shown in Patent Document 1, the light-shielding component is constructed as a separate part. Therefore, it is difficult to maintain a constant positional relationship between the light-shielding component and the rod lens. Additionally, it is difficult to prevent significant image quality degradation caused by overlapping images and varying image density due to changes in the positions of the individual lenses in the lens array and the light-shielding component. Summary of the Invention

[0017] This disclosure is made to solve the problems mentioned above, and relates to an image reading device with a high-precision structure that easily expands the depth of field (improves the depth of field) even without having to change the basic characteristics of the lens body.

[0018] The image reading apparatus disclosed herein is characterized by having: a lens array, which is formed by arranging lens bodies in an array along the main scanning direction between two fixed plates extending along the main scanning direction; a sensor element array, which is formed by arranging sensor elements that receive light focused by the lens bodies in an array along the main scanning direction; and an anti-overlap portion disposed between the lens array and the sensor element array to prevent the images of the lens bodies from overlapping, wherein the slit portion serving as the anti-overlap portion has a plurality of slit plates extending along the sub-scanning direction to divide space and arranged along the main scanning direction, the slit plates being fixed to the fixed plates.

[0019] As described above, according to this disclosure, by utilizing a structure with high-precision positioning and by limiting the optical path, light (specific light) incident at a low angle of incidence is prevented from directly incident on the sensor element 4, thereby enabling an image reading device that suppresses the decrease in light intensity and expands the depth of field (improves the depth of field). Attached Figure Description

[0020] Figure 1 This is a structural diagram of the image reading device according to Embodiment 1.

[0021] Figure 2 It is a diagram representing the overlap of images from an image reading device.

[0022] Figure 3 It is a diagram representing the overlap of images from an image reading device.

[0023] Figure 4 This is a structural diagram illustrating the anti-overlapping part (optical path limiting component) of the image reading device according to Embodiment 1.

[0024] Figure 5 This is a structural diagram showing the lens array, anti-overlap portion, and sensor element array of the image reading device according to Embodiment 1.

[0025] Figure 6 This is a structural diagram showing the lens array and anti-overlap portion of the image reading device according to Embodiment 1.

[0026] Figure 7 This is a structural diagram showing the anti-overlap portion of the image reading device according to Embodiment 1.

[0027] Figure 8 This is a structural diagram showing the anti-overlap portion of the image reading device according to Embodiment 1.

[0028] Figure 9 This is a diagram showing the depth-of-field characteristics of the image reading device of Embodiment 1 and the image reading device of the comparative example.

[0029] Figure 10 This is a structural diagram showing the anti-overlap portion of the image reading device according to Embodiment 1.

[0030] Figure 11 This is a structural diagram showing the anti-overlap portion of the image reading device according to Embodiment 1.

[0031] Figure 12 This is a structural diagram showing the anti-overlap portion (slit plate and specific light blocking component) of the image reading device according to Embodiment 1.

[0032] Figure 13 This is a structural diagram showing the anti-overlap portion (slit plate and specific light blocking component) of the image reading device in Embodiment 2.

[0033] Figure 14 This is a structural diagram showing the lens array of the image reading device in Embodiment 3.

[0034] Figure 15This is a structural diagram showing the lens array and anti-overlap portion of the image reading device in Embodiment 3.

[0035] Figure 16 This is a structural diagram showing the lens array and anti-overlap portion of the image reading device in Embodiment 3.

[0036] Figure 17 This is a structural diagram showing the lens array of the image reading device in Embodiment 3.

[0037] Figure 18 This is a structural diagram showing the lens array and anti-overlap portion of the image reading device in Embodiment 3.

[0038] Figure 19 This is a structural diagram showing the lens array of the image reading device in Embodiment 3.

[0039] Figure 20 This is a structural diagram showing the lens array and anti-overlap portion of the image reading device in Embodiment 3.

[0040] Figure 21 It is a diagram showing the positional offset of the image reading device.

[0041] Figure 22 It is a diagram showing the positional offset of the image reading device.

[0042] Figure 23 It is a diagram showing the positional offset of the image reading device.

[0043] Figure 24 It is a graph representing the data related to the depth of field of the image reading device in Embodiment 3.

[0044] Figure 25 This is a structural diagram showing the lens array of the image reading device in Embodiment 3.

[0045] Figure 26 This is a structural diagram showing the lens array and anti-overlap portion of the image reading device in Embodiment 3. Detailed Implementation

[0046] In Embodiments 1 and 2, a basic description of the slit portion and a specific light-blocking component applicable to the image reading device of Embodiment 3 are provided. In Embodiment 3, the fixing of the slit portion is described.

[0047] Implementation method 1.

[0048] The following uses Figures 1 to 12 Embodiment 1 will be described. In the figures, the same reference numerals denote the same or equivalent parts and detailed descriptions of them are omitted. Figure 1(a) is a cross-sectional view along the sub-scanning direction (transfer direction) of the image reading device. Figure 1 (b) is a partial perspective view of the image reading device. Figure 3 (a) is a diagram of a single lens (rod lens) in an image representing an image reading device. Figure 3 (b) is a diagram showing the lens array (bar lens array) in the overlapping diagram of the images of the image reading device.

[0049] exist Figures 1 to 12 In this embodiment, the lens array 1 is formed by arranging lens bodies 2 in an array along the main scanning direction of the image reading device. The main scanning direction intersects the sub-scanning direction (transfer direction), and is preferably orthogonal. The main scanning direction and the sub-scanning direction (transfer direction) are orthogonal to the focal depth direction (depth of field direction). In this application, the optical axis direction of the lens array 1 (lens body 2) is shown as being orthogonal to both the main scanning direction and the sub-scanning direction (transfer direction). Furthermore, although the lens body 2 is shown as a rod lens 2, i.e., the lens array 1 is a rod lens array 1, the lens array 1 can also be a microlens array 1, etc. The lens body 2 is preferably a lens body in an upright, equal-magnification optical system, such as a rod lens 2 or a microlens 2. In more detail, in the lens array 1, the lens bodies 2 are arranged in an array along the main scanning direction, sandwiched between two fixing plates extending along the main scanning direction. The lens bodies 2 are sandwiched between the two fixing plates and have sealing resin (fixing resin) filling the gaps between them. Therefore, in order to simplify the representation of the fixing plate and the sealing resin (fixing resin) in the figure, the fixing plate and the sealing resin (fixing resin) are sometimes represented as a single unit.

[0050] exist Figures 1 to 12In this configuration, the sensor element array 3 consists of sensor elements 4 (sensor IC4) that receive light focused by the lens body 2, arranged in an array along the main scanning direction. A slit portion 5 is positioned between the lens body array 1 and the sensor element array 3 to prevent the images of the lens bodies 2 from overlapping. The slit portion 5 includes multiple slit plates 7 extending in the sub-scanning direction to divide space and arranged along the main scanning direction. Multiple spaces are arranged in an array along the main scanning direction, corresponding one-to-one with the lens bodies 2. That is, the slit portions of the slit portion 5 are arranged according to each optical axis of the lens body 2. Of course, it is not necessary to arrange slit portions of the slit portion 5 with the same number of slit portions as the lens bodies 2. For example, one slit portion of the slit portion 5 can be arranged for every 1.5 lens bodies 2. That is, multiple spaces can be formed in an array along the main scanning direction, corresponding to the lens bodies 2 in a 1-to-1.5 pair. The slit portion 5 includes a sidewall plate 6, the aforementioned slit plates 7, and a specific light-blocking component 8. The slit portion of the slit 5 is the part surrounded by the side wall plate 6 and the slit plate 7. The slit portion 5 can be described as an anti-overlapping part 5 used as a component for limiting the optical path. Figure 8 (a) and Figure 11 (a) is a cross-sectional view of the plane along the sub-scanning direction (transfer direction) of the slit section 5. Figure 8 (b) and Figure 11 (b) is a cross-sectional view of the surface along the main scanning direction of the slit section 5.

[0051] exist Figures 1 to 12 In this process, the object to be read 9 (the illuminated object 9) is a sheet-like object, including documents, banknotes, securities, etc., or an electronically informational object such as a substrate, mesh (fabric, cloth, etc.) containing images, text, patterns, etc., on its surface. The object to be read 9 is conveyed in the sub-scanning direction (transfer direction). The light source 10 illuminates the object to be read 9. In addition, the lens array 1 (lens 2) focuses the reflected or transmitted light from the object to be read 9. In this application, the light source 10 is exemplified as an LED array, which focuses the reflected light from the object to be read 9 emanating from the light source 10. The light is focused. The sensor substrate 11 is a substrate on which the sensor element array 3 (sensor element 4) is formed. The housing 12 is a housing that holds or houses the lens array 1 (lens 2), the sensor substrate 11 (sensor element array 3 (sensor element 4)), the slit 5, and the image reading device of the light source 10. The light source 10 and the sensor substrate 11 may also be outside the image reading device (housing 12). The transfer of the object to be read 9 in the sub-scanning direction (transfer direction) may transfer the object to be read 9 itself or the image reading device (housing 12).

[0052] That is, the image reading device of Embodiment 1 can be described as a row image sensor having a light source 10 and a sensor element array 3, wherein the light source 10 illuminates the object 9 to be read at the reading center of the bar-shaped lens array 1 with the bar-shaped lens array 1 as the center, and the sensor element array 3 converts the medium image formed by the bar-shaped lens array 1 into an electrical signal. Here, the necessity of the slit portion 5 in the image reading device (row image sensor) of Embodiment 1 and the basic function of the slit portion 5 will be explained in detail.

[0053] First, the necessity of the slit 5 will be explained in detail. As explained in the research paper, the area where the line image sensor using the rod lens array 1 should be improved is ensuring the depth of field. The overall image formed by the imaging engineering system (lens) is not formed solely by the individual rod lenses 2. Figure 2 as well as Figure 3 As shown, the images of multiple rod-shaped lenses 2 overlap to form a unified image.

[0054] like Figure 2 as well as Figure 3 As shown, the main reason for the decrease in depth of field is not the performance of individual lenses, but rather the fact that when lenses are arrayed, the images formed by the adjacent lenses of a specified overlap degree m do not overlap in the correct positions. The overlap degree m is half the value obtained by dividing the diameter of the area where the image is transferred by a rod lens 2 at the conjugate point by the diameter of the rod lens 2. This lack of overlap in the correct positions causes image blurring. Furthermore, the overlap degree m is a parameter representing the repetition of the image caused by adjacent rod lenses 2, indicating the number of lenses that repeat the image from the optical axis center of the rod lens 2 of interest towards one side of the lens.

[0055] By placing the rod-shaped lens 2 on the array, at the conjugate point, such as Figure 2 As shown, the region where an image is formed by a rod lens, as indicated by the overlap, is a region m units away from the center of the lens, equivalent to the distance from a single lens. This is because light passing through 2×m rod lenses 2 is used to form an image at a single point, and to ensure resolution at the conjugate point, all lens characteristics must be identical, and the lens configuration must be error-free to image the image at the same point. However, in reality, due to differences in the optical characteristics of each rod lens 2 and assembly errors, the image transferred from the rod lens 2 contains a slight positional shift, and the optical characteristics of the resolution at the conjugate point are also lower than those of a single rod lens 2.

[0056] In addition, such as Figure 3 As shown on the left of (a), when the positional relationship between the object being read 9 and the sensor element array 3 is at a conjugate point, the rod lens 2 forms an upright, equal-magnification image. However, as... Figure 3As shown to the right of (a), when the position of the object 9 being read moves away from the conjugate point (in this case, the focal point), the image on the sensor element array 3 shrinks. In this case, the images of each rod lens 2 are shrunk on the sensor element array 3, and as the rod lens array 1, the image formed on the sensor element array 3 is slightly offset on each rod lens 2. Therefore, as... Figure 3 As shown to the right of (b), with Figure 3 Compared to the case shown on the left of (b), the blurriness increases and the resolution decreases.

[0057] Thus, the performance of the individual rod lens 2 is not the primary reason for the decrease in depth of field caused by the reduction in resolution due to the object 9 being far from the conjugate point (focal position). The primary reason is that by setting the rod lens 2 as a rod lens array 1, the characteristic differences of adjacent rod lenses 2 as specified by the aforementioned overlap m, optical axis offset caused by assembly errors, and image magnification / reduction caused by the object 9 shifting from the focal position will result in the images formed by each rod lens 2 not overlapping at their proper positions on the sensor element array 3, but rather forming images with positional offset, thus causing image blurring. Therefore, as Figure 4 As shown, a slit section 5 is required to avoid a decrease in depth of field.

[0058] Next, use Figures 5 to 9 The basic functions of the slit portion 5 of the image reading device in Embodiment 1 will be explained in detail. As... Figure 5 as well as Figure 6 The rod-shaped lens 2, simplified in representation, uses the SLA (trade name) SLA9A-1 series manufactured by Nippon Sheet Glass, with an aperture angle of 9°, a conjugate length of approximately 80 mm, a lens diameter Φ of approximately 1.0 mm, and an overlap m of 4.2. The rod-shaped lens array 1 is configured with slits 5 as follows: Figure 5 as well as Figure 6 The state shown. Figure 7 as well as Figure 8 The slit portion 5 shown has a length of L in the main scanning direction, a length of W in the sub-scanning direction, and a length (height) in the optical axis direction of H. The length of the sidewall plate 6 in the main scanning direction is equivalent to L. The length (height) of the slit plate 7 in the optical axis direction is equivalent to H. The pitch e in the main scanning direction of the slit plate 7 is approximately 2.0 mm, the thickness T of the slit plate 7 is 0.2 mm, and the height H is 20 mm. Furthermore, in embodiment 3 described later, the pitch e in the main scanning direction of the slit plate 7 is approximately 1.0 mm, the thickness T of the slit plate 7 is 0.2 mm, and the height H is 10 mm.

[0059] Figures 5 to 8The wall surface of the slit portion 5 shown is made of black velvet to minimize light reflection and to block all light incident on the surface of the slit portion 5, including reflected and scattered light. That is, the surfaces of the slit plate 7 and the specific light-blocking component 8 are preferably black. Furthermore, the side wall plate 6 is preferably black at least for the surface continuous with the slit plate 7. And the black surface is preferably a black velvet surface. The black velvet surface is a black, pear-skin-like surface.

[0060] The slit section 5 is fixed with sidewall plates 6 to maintain each slit plate 7 at a certain distance. Specifically, two sidewall plates 6 are used to fix each slit plate 7. Therefore, the sidewall plates 6 can also be called spacers 6. That is, the sidewall plates 6 (spacers 6) are two sidewall plates that extend in the main scanning direction and are opposite each other in the sub-scanning direction, which intersects the main scanning direction. Furthermore, multiple slit plates 7 are arranged between the two sidewall plates 6 along the sub-scanning direction, dividing the space between the two sidewall plates 6, and forming the slit portion of the slit section 5. Figures 6 to 8 As shown, the sidewall plate 6 can also limit the light incident on the slit portion 5 by bending the rod-shaped lens array 1 laterally and partially covering the end of the slit plate 7 in the sub-scanning direction. In this case, the cross-section of the sidewall plate 6 along the sub-scanning direction becomes an L-shaped plate.

[0061] The mechanical dimensions of the slit portion 5 are preferably determined for the following reasons. When the overlap (m: half the value obtained by dividing the diameter of the area where the image is transferred by the conjugate point of one rod lens 2 by the lens diameter Φ) and aperture angle (θ) of the rod lens 2 are set, the following applies: The adjacent spacing e of the plurality of formed slit plates 7 is less than or equal to the overlap m and the lens diameter Φ multiplied by 0.6. The length of the slit portion 5 (slit plate 7) in the optical path is greater than or equal to the value obtained by dividing the spacing e by the tangent θ when the aperture angle of the rod lens 2 is set to θ. That is, based on the relationship that the spacing e of the slit plates 7 is “e≤0.6×m×Φ” and the height H of the slit plate 7 is “H≥e / tan(θ)”, the spacing e is set to approximately 2.0 mm (0.5×m×1 mm). Considering the relative margin of the lens aperture angle, a constraint is imposed to limit it to 6°, and the height of the slit plate 7 (slit portion 5) is set to 2.0 / tan(6°)≈20 mm. Furthermore, the height of the slit plate 7 (slit portion 5) is the height along the optical axis (reading optical axis direction). Using... Figure 9 One solid line represents the depth-of-field characteristics under that condition. The other solid line represents the depth-of-field characteristics of the image reading device being compared.

[0062] Furthermore, in Embodiment 3 described later, the adjacent spacing e of the plurality of formed slit plates 7 is equal to the lens diameter Φ, and the length of the slit portion 5 (slit plate 7) in the optical path is greater than or equal to the value obtained by dividing the spacing e by the tangent θ when the aperture angle of the rod lens 2 is set to θ. That is, based on the relationship that the height H of the slit plate 7 is "H≥e / tan(θ)", the spacing e is set to 1 mm, and the lens aperture angle is constrained to be 9°, so the height of the slit plate 7 (slit portion 5) is set to 1.0 / tan(9°)≈10 mm.

[0063] Figure 9 The depth-of-field characteristics of the image reading device are shown, relative to a resolution of 5.681 lp / mm (line pairs / mm). Figure 9 In the diagram, the black diamond (with slit) represents the depth-of-field characteristics of the image reading device of Embodiment 1. Similarly, the black circle (Normal) represents the depth-of-field characteristics of the image reading device of the comparative example. Specifically, the image reading device of Embodiment 1 has an anti-overlap portion 5, i.e., a slit portion 5 (with slit). On the other hand, the image reading device of the comparative example does not have an anti-overlap portion 5 (Normal). Furthermore, Figure 9 The vertical axis represents the MTF (Modulation Transfer Function), expressed as a percentage. Figure 9 The horizontal axis represents the distance from the focal point (Focus plane) of the object being read (object 9), in mm.

[0064] according to Figure 9 As can be seen from the solid line within, in the image reading device with the slit portion 5, although the peak resolution at the focal position is slightly reduced, it significantly improves the positional variation of the reading object portion 9 in the direction of the reading optical axis (depth of field). Figure 9 (As can be seen from the portion surrounded by the dashed line on the left, referring to the portion surrounded by the dashed line on the right). The depth of field can be obtained over an area approximately three times larger. However, when the reflectivity of the black velvet surface of the slit plate 7 (slit portion 5) is high, a thinner folded image is produced due to the effect of this reflection, therefore it is necessary to manage the state of the black velvet surface (the surface of the slit portion 5). As described above, the black velvet surface comprises a black and pear-skin-like surface.

[0065] In the image reading device of Embodiment 1, in order to obtain a more stable light-blocking state, the slit portion 5 described so far is preferably […]. Figures 10 to 12The slit portion 5, as shown, further forms a specific light blocking member 8. The specific light blocking member 8 protrudes from the slit plate 7 in the main scanning direction to prevent specific light incident at an angle less than the aperture angle of the rod lens 2 from entering the sensor element 4. Specifically, the specific light blocking member 8 mechanically prevents light (specific light) incident at a low angle of incidence onto the surface (wall) of the slit portion 5 from directly entering the sensor element 4. The specific light blocking member 8 is a beam-shaped member 8 spanning between one sidewall plate 6 and the other sidewall plate 6. The beam-shaped member 8 (specific light blocking member 8) may also be discontinuous with the sidewall plate 6. Preferably, the specific light blocking member 8 is a member in which the portion on the rod lens 2 side protrudes more than the portion on the sensor element 4 side; this will be explained in detail in Embodiment 2.

[0066] For example, Figures 10 to 12 Multiple light-blocking components 8 are formed on the slit plate 7 along the optical axis of the rod lens 2. Specifically, the slit plate 7, which has been surface-treated in black, has black beams (light-blocking components 8) arranged at equal intervals along the reading optical axis (the direction perpendicular to the reading optical axis). This structure reflects low-angle light incident on the light-blocking components 8 (the beam portions) back towards the rod lens 2, preventing it from incident towards the sensor element 4. By providing a certain number of light-blocking components 8 (beam-shaped components), light with an exit angle of 9° or less emitted from the rod lens 2 (approximately 1 mm in diameter) can be controlled to block light.

[0067] like Figure 12 As shown, the thickness d (length d in the optical axis direction) of the specific light-blocking component 8 (beam-shaped component) is 0.1 mm, the height a (length a in the main scanning direction, or the height a protruding in the main scanning direction) is 0.1 mm, and the pitch f (pitch f) is 0.55 mm. The thickness T of the slit plate 7 is 0.2 mm. The height a (length a in the main scanning direction, or the height a protruding in the main scanning direction) and the pitch f of the specific light-blocking component 8 (beam-shaped component) depend on the aperture angle θ of the rod lens 2. That is, preferably, the height a and the pitch f satisfy the relationship "a / f ≥ tan(θ)".

[0068] By using the specific light-blocking component 8 (beam-shaped component), the influence of the surface (wall) state of the slit portion 5 is less likely to occur, resulting in stable characteristics. Even with the specific light-blocking component 8 (beam-shaped component) installed, the peak resolution at the focal position is slightly reduced, but the positional variation of the reading object portion 9 in the direction of the reading optical axis is greatly improved. The depth of field can be obtained over an area approximately three times larger.

[0069] Implementation method 2.

[0070] use Figure 13 Embodiment 2 will be described. Sometimes, descriptions of parts common to Embodiment 1 are omitted. Additionally, in the figures, the same reference numerals denote the same or equivalent parts, and detailed descriptions of them are omitted. For example... Figure 13 As shown, in Embodiment 2, the image reading device is such that the specific light blocking member 8 is a member (beam-shaped member) in which the portion on the side of the rod-shaped lens 2 protrudes more than the portion on the side of the sensor element 4. In other words, it can be said that the sensor element 4 side is lower than the rod-shaped lens 2 side in terms of the height a (length a in the main scanning direction, or the height a protruding in the main scanning direction) of the specific light blocking member 8 (beam-shaped member). Preferably, the shape of the specific light blocking member 8 in the imaginary cross-section where the main scanning direction intersects the optical axis is a right-angled triangle. The hypotenuse of this right-angled triangle may not be a straight line in the strict sense, but may be an arc. Furthermore, in the specific light blocking member 8 of the image reading device of Embodiment 1, the shape of the specific light blocking member 8 in the imaginary cross-section where the main scanning direction intersects the optical axis is rectangular.

[0071] By using the specific light-blocking component 8 of the image reading device of Embodiment 2, the hypotenuse of the specific light-blocking component 8, i.e., the right triangle, is tilted relative to the optical axis, thus further suppressing the reflection of light towards the sensor element 4 caused by the specific light-blocking component 8. Therefore, when the thickness d (length d in the optical axis direction), pitch f (pitch f), length t of the entire main scanning direction of the slit plate 7 including the specific light-blocking component 8 (beam-shaped component) in the image reading device of Embodiment 2 are set to be the same as those in the image reading device of Embodiment 1, since the height a of the specific light-blocking component 8 (beam-shaped component) is shorter on the sensor element 4 side, an image reading device with more stable depth-of-field improvement and stable image quality can be obtained. Furthermore, in the image reading device of Embodiment 2, it is also preferable to satisfy the relationship "a / f ≥ tan(θ)".

[0072] As described above, the image reading apparatus according to embodiments 1 and 2 prevents light (specific light) incident at a low angle of incidence from directly incident on the sensor element 4 by limiting the optical path, thereby suppressing the decrease in light intensity and increasing the depth of field (improving the depth of field).

[0073] On the other hand, the improvement in depth of field of the rod-shaped lens unit shown in Patent Document 2 still has the following problems. As indicated by Patent Document 3, it is difficult to ensure uniformity of resolution and brightness when the depth position of the object being read changes. Furthermore, in Patent Document 2, when a long linear sensor is formed, changes in the environment (especially the relative position of the lens and sensor array due to thermal expansion differences caused by temperature variations) cause changes in brightness distribution, regardless of the brightness correction performed. This unevenness in illuminance and sensitivity degrades image quality. Additionally, in improving the depth of field of the rod-shaped lens unit, the area where the lens functions must be reduced to ensure lens independence, resulting in a decrease in the amount of light contributing to image formation and a darker image. This necessitates preparing illumination of a higher degree than required, making it difficult to construct a faster reading system.

[0074] The technology shown in Patent Document 3 ensures uniformity of resolution and brightness despite changes in the medium's position as shown in Patent Document 2. However, compared to Patent Document 2, the technology shown in Patent Document 3 requires further reduction in the area where the lens functions, leading to a decrease in the amount of light contributing to image formation and a darker image, or the need for more than the required brightness of illumination, making it difficult to construct a higher-speed reading system. Furthermore, the technologies shown in Patent Documents 2 and 3 require changes to the fundamental characteristics of the lens, making it difficult to handle various operating distances (distances from the lens end to the reading medium) required for applications such as inspection.

[0075] The image reading devices of embodiments 1 and 2 differ from those of patent documents 1, 2 and 3, and relate to an image reading device that can easily increase the depth of field (improve the depth of field) even without having to change the basic characteristics of the lens body.

[0076] Implementation method 3.

[0077] use Figures 14 to 26 Embodiment 3 will be described. Although the illustrations of the side wall plate 6 (spacer 6) and the specific light blocking member 8 described in the image reading devices of Embodiments 1 and 2 are omitted, the image reading device of Embodiment 3 can be applied. Apart from the side wall plate 6 (spacer 6) and the specific light blocking member 8, the basic structure of the image reading device in Embodiment 3 is the same as that in the image reading devices of Embodiments 1 and 2, so the description is omitted.

[0078] In the image reading device of embodiment 3 Figure 14 , Figure 15 , Figure 16 The structure shown Figure 17 as well as Figure 18 The structure shown Figure 19 as well as Figure 20 The structure shown is a positioning configuration where a light-shielding wall (slit plate 7) is set between the lens bodies 2, and the two side plates, i.e., the fixing plates 13, that form the lens body array 1 are positioned one-to-one with the lens bodies 2. These are high-precision positioning structures, and by limiting the optical path, light (specific light) incident at a low incident angle is prevented from directly incident on the sensor element 4 side, thereby suppressing the decrease in light amount and increasing the depth of field (improving the depth of field).

[0079] exist Figures 14 to 20 In this embodiment, the fixing plate 13 clamps the lens body 2 between two fixing plates extending along the main scanning direction, and arranges the lens bodies 2 in an array along the main scanning direction to form a lens body array 1. As described in Embodiment 1, a sealing resin (fixing resin) is filled between the lens body 2 and the fixing plate 13. The slit portion 5, which serves as a slit portion to prevent overlap, has a plurality of slit plates 7 extending in the sub-scanning direction to divide space and arranged along the main scanning direction. The slit plates 7 are fixed to the fixing plate 13. The illustration shows that the plurality of slit plates 7 extend in the sub-scanning direction to divide space and are arranged along the main scanning direction. A plurality of spaces are formed in an array along the main scanning direction, corresponding one-to-one with the lens body 2. The slit portion 5 has a fixing leg 14 extending toward the lens body array 1 side, and the fixing leg 14 contacts the fixing plate 13. The fixing plate 13 has a fitting portion 15 that engages with the fixing leg 14.

[0080] like Figure 14 , Figure 15 , Figure 16 As shown, the fitting portion 15 consists of multiple grooves 16 formed along the optical axis of the lens array 1 (the optical axis direction is consistent with the cylindrical direction or the focal depth direction (depth of field direction)). Alternatively, as... Figure 17 as well as Figure 18 As shown, the fitting portion 15 consists of multiple holes 17 through which the fixing legs 14 are inserted along the optical axis of the lens array 1. Furthermore, as... Figure 19 as well as Figure 20 As shown, the two fixing plates 13 can also be linearly symmetrical in the main scanning direction and extend in a serrated shape along the main scanning direction, with grooves 18 shorter than other parts in the sub-scanning direction serving as fitting portions 15. In this case, as shown, the two fixing plates 13 fix the lens body 2 between the grooves 18. The fitting portions 15 can be said to have a plurality of structures formed along the main scanning direction. Figure 19 as well as Figure 20 The material of the fixing plate 13 shown will be described later.

[0081] Figure 14 (A) is a diagram of the lens array 1 as viewed from the optical axis direction. Figure 14 (B) is a diagram of the lens array 1 viewed from the sub-scanning direction. Figure 14The lens array 1 is shown before the slit plate 7 is installed. The dimensions are in mm. Figure 15 Is Figure 14 The diagram shows the state in which multiple slit plates 7 are fixed on the lens array 1. Figure 16 (A) is a diagram showing the lens array 1 and the slit plate 7 viewed from the optical axis direction. Figure 16 (B) is a diagram showing the lens array 1 and the slit plate 7 as viewed from the sub-scanning direction.

[0082] Figure 14 , Figure 15 , Figure 16 The structure shown serves as a positioning structure for the lens array 1. A groove 16 is provided on the side plate, i.e., the fixing plate 13, which is used to clamp and hold the lens array 1. The groove 16 has a center on the truncated extension of the adjacent lens 2 and is parallel to the cylindrical direction (optical axis direction) of the lens 2. By engaging with the fixing leg 14, the positioning and uprightness of the slit portion 5 (slit plate 7) are ensured.

[0083] Figure 17 (A) is a diagram of the lens array 1 as viewed from the optical axis direction. Figure 17 (B) is a diagram of the lens array 1 viewed from the sub-scanning direction. Figure 17 (B) Hole 17 (fitting part 15) is indicated by dashed lines for perspective purposes. Figure 17 The lens array 1 is shown before the slit plate 7 is installed. Figure 18 In order to be in Figure 17 The diagram shows a lens array 1 with multiple slit plates 7 fixed in place, and the fixing leg 14 is to be inserted (fitted) into the hole 17 (fitting part 15).

[0084] Figure 17 as well as Figure 18 The structure shown serves as a positioning structure for the lens array 1. A hole 17 is provided in the side plate, i.e., the fixing plate 13, used to clamp and hold the lens array 1. This hole 17 has a center on the truncated extension of the adjacent lens body 2 and a depth in the cylindrical direction (optical axis direction) of the lens body 2. By engaging with the fixing leg 14, the positioning and uprightness of the slit portion 5 (slit plate 7) are ensured. The fixing leg 14 is shaped to be inserted into the hole 17.

[0085] Figure 19 (A) is a diagram of the lens array 1 as viewed from the optical axis direction. Figure 19 (B) is a diagram of the lens array 1 viewed from the sub-scanning direction. Figure 19 The lens array 1 is shown before the slit plate 7 is installed. Figure 20 In order to be in Figure 19The diagram shows a lens array 1 with multiple slit plates 7 fixed in place, and the fixing leg 14 is to be inserted into the slot 18 (fitting part 15) (fitting).

[0086] Figure 19 as well as Figure 20 The structure shown serves as a positioning configuration for the lens array 1. A groove 18 is provided on the side plates, i.e., the fixing plates 13, used to clamp and hold the lens array 1. This groove 18 has a center on the truncated extension of the adjacent lens body 2 and is parallel to the cylindrical direction (optical axis direction) of the lens body 2. The groove 18 is the portion of the two side plates, i.e., the fixing plates 13, that is, linearly symmetrical in the main scanning direction and extends in a serrated shape along the main scanning direction, with a shorter distance than the other portions in the sub-scanning direction. Thus, the positioning and uprightness of the slit portion 5 (slit plate 7) are ensured by the engagement of the groove 18 with the fixing leg 14.

[0087] This concludes the explanation of the case where the fixing leg 14 is formed on the slit plate 7. However, the fixing leg 14 can also be formed on the side wall plate 6 (spacer 6) described in embodiments 1 and 2. When the fixing leg 14 is formed on the side wall plate 6, the slit plate 7 is fixed to the fixing plate 13 via the side wall plate 6. Of course, the fixing leg 14 can also be formed on both the slit plate 7 and the side wall plate 6. That is, the fixing leg 14 only needs to be formed on at least one of the slit plate 7 or the side wall plate 6. In addition, since the fixing leg 14 is also part of the slit portion 5, its surface can also be black. In particular, at least the surface of the fixing leg 14 that is continuous with the slit plate is black. For example, the black surface is a black velvet surface.

[0088] The image reading device in Implementation Method 3 is Figure 14 , Figure 15 , Figure 16 The structure shown Figure 17 as well as Figure 18 The structure shown Figure 19 as well as Figure 20 As shown in the structure, by fixing the fixing leg 14 formed in the slit portion 5 (at least one of the slit plate 7 or the side wall plate 6) to the fixing plate 13, the slit plate 7 of the slit portion 5 can be positioned with improved positional accuracy.

[0089] Figure 21 , Figure 22 , Figure 23 This is a graph representing the positional offset of the image reading device. In Figure 21 In the diagram, the horizontal axis represents the distance between lens bodies 2, and the vertical axis represents the frequency. Figure 22 This is a diagram of lens array 1 viewed from the optical axis. Dimensions are in mm. Figure 23 This is a diagram showing the lens array 1 and the slit plate 7 viewed from the optical axis. In the lens array 1, the spacing deviation of the lens bodies 2 is as follows... Figure 21 , Figure 22 As shown, the distribution of the average value between two individual lens bodies is approximately ±5 μm. Even within the same lens body array 1, the distribution of the spacing between lens bodies 2 is approximately ±10 μm. In the 7 groups of slit plates formed with a single spacing, due to the cumulative spacing offset, as... Figure 23 As shown, this can result in parts where the optical path separation between the individual lens bodies 2 cannot be performed correctly, which sometimes makes it impossible to obtain a uniform image over the entire length of the sensor element array 3.

[0090] To prevent the inability to obtain a uniform image along the entire length of the sensor element array 3, during the processing of the side plate (fixed plate 13) of the lens array 1, the number and size of the lenses 2 in the total reading length are measured, the average spacing is calculated, and the influence of the lens spacing deviation between the individual lenses 2 in the lens array 1 is removed. Furthermore, after determining the starting point, sets of fitting portions 15 (slots 16, holes 17, grooves 18) are formed at equal intervals according to the average spacing of the lens array 2. In this way, by forming sets of fitting portions 15, it is possible to prevent the center position of the slit plate 7 from deviating from the arrangement of the lenses 2 by more than a certain amount.

[0091] By preventing misalignment of the lens body 2, the fitting portion 15 (groove 16, hole 17, slot 18) can be formed with a maximum offset of ±0.03mm relative to the ideal configuration of 0.1mm thickness (the slit plate 7 overlaps with each of the two lens bodies 2 by 0.05mm). When higher precision is required, the fitting portion 15 (groove 16, hole 17, slot 18) can be aligned by an image device such as a camera recognizing the position of the lens body 2 during its formation.

[0092] Furthermore, in the image reading device of Embodiment 3, the slit plate 7 is thinned while ensuring strength. To increase the aperture ratio of the lens body 2, a 0.1mm thick stainless steel plate is formed into a fitting shape with a width of 4.0mm, a height of 10mm (height in the optical axis direction) of slit plate 7, and a length of 5mm for the fitting portion 15. Both sides of the slit plate are treated with the aforementioned black finish, i.e., blackening and low-reflection treatment. Specifically, since the material is stainless steel, the stainless steel surface is sandblasted to achieve a pear-skin finish, and then a low-reflection black electroplating process is performed on it. Furthermore, the slit plate 7 is formed in the lens array 1 by applying an adhesive to the fitting portion (fitting portion) and fixing the slit plate 7 to the hole and side groove of the lens array 1, i.e., the fitting portion 15.

[0093] Therefore, in the image reading device of Embodiment 3, the volume occupied by the slit plate 7 can be reduced (the width dimension of the slit plate 7 can be reduced), and assembly can be performed without significantly changing the conventional sensor module structure. In addition, even without the connecting part between the slit plates 7 (the holding part of the slit plate 7 in the main scanning direction of the lens array 2), i.e., the side wall plate 6 (spacer 6), the slit plate 7 can stand upright, thus easily eliminating the influence of proximity reflection of the emitted light.

[0094] Figure 24 This is a graph representing the depth-of-field data related to the image reading device of Embodiment 3. The horizontal axis represents the focal position, and the vertical axis represents the resolution (MTF). The dashed line represents the data of the lens array 1 without the slit plate 7, and the solid line represents the data of the lens array 1 with the slit plate 7, i.e., the data of the image reading device of Embodiment 3. Three samples are plotted separately. In detail, Figure 24 The three solid lines represent the depth of field in the structure of the image reading device of Embodiment 3. (The last part, "relative to...", seems to be a fragment and doesn't translate directly.) Figure 24 The three dashed lines represent the depth of field of the previous lens body 2. The resolution is slightly reduced at the peak, but it can be seen that the positional variation of the reading medium in the direction of the reading optical axis is greatly improved, and the depth of field is about three times larger.

[0095] Therefore, although the width of the slit plate 7 is set to approximately 4.0 mm, which is roughly the same as the width of the lens array 1, the width of the slit plate 7 can be any width where the light-blocking portion is the same as the diameter of the lens 2. Even with variations to match the assembly mechanism, the same effect can be achieved. While stainless steel can be used as the base material for the slit plate 7 to ensure strength, a resin that is easy to process and shape can also be used to perform a low-reflection treatment on the surface of the slit plate 7. Furthermore, although the thickness of the slit plate 7 is set to 0.1 mm for material availability, the thinner the slit plate 7, the less restricted the area of ​​light emitted from the lens array 1, thereby mitigating the reduction in brightness of the optical system.

[0096] like Figure 17 as well as Figure 18 As shown, in the case where the fitting part 15 of the image reading device in Embodiment 3 is a hole 17, rows of holes 17 with a predetermined diameter are formed on both sides of the side plate of the lens array 1 and at the tangential position between adjacent lens bodies 2. By inserting a group of slit plates 7 with blackened surfaces and low-reflection treatment into these rows of holes 17, a group of slit plates 7 with a one-to-one positional relationship with the lens body 2 is formed. Since the lens body array 1 is arranged perpendicularly to the lens surface, the rows of holes 17 formed on the side plate (fixed plate 13) of the lens array 1 can be formed in the vertical direction relative to the lens surface.

[0097] In this embodiment, 17 rows of holes with a diameter of 0.2 mm and a depth of 5 mm are formed on both side plates on the light-emitting surface side of the lens, relative to the thickness of the slit plate 7 (0.2 mm). These holes are aligned and fixed between adjacent lens bodies 2, thereby positioning the lens body 2 and the slit plate 7 in a one-to-one manner. At this point, the diameter of the holes 17 used to fix the slit plate 7 only needs to retain a thickness sufficient to maintain strength relative to the thickness of the side plate (fixed plate 13) of the lens array 1. For example, a diameter of 0.2 mmΦ is set relative to the thickness of the side plate (fixed plate 13) (approximately 1.9 mm). This can be increased to approximately half or less of the thickness of the side plate (fixed plate 13) of the lens array 1.

[0098] Thus, the fitting part 15 of the image reading device in Embodiment 3 is constructed by processing the side plate, i.e., the fixing plate 13, of the lens array 1, thereby enabling the positioning and setting of the slit part 5 (slit plate group 7). These structures do not increase the cross-sectional area occupied by the lens system itself, and the mechanism for improving depth of field can be set without significantly changing the mechanism of conventional image reading devices.

[0099] Furthermore, in the lens array 1, the lens bodies 2 are arranged in an array along the main scanning direction, and the lens bodies 2 are sandwiched between two fixing plates 13 extending along the main scanning direction. The fixing plates 13 may not be components of the lens array 1, but may be formed outside the lens array 1. However, it goes without saying that even with this configuration, the lens bodies 2 can be sandwiched between the two fixing plates 13. That is, the lens array 1 can be integrated with the fixing plates 13, or it can be separate (individual components).

[0100] When the lens array 1 and the fixing plate 13 are integrated, the lens array 1 needs to be machined to accommodate the fitting part 15. This requires significant time and precision in the machining process, potentially increasing manufacturing costs. Therefore, considering a configuration where the lens array 1 and the fixing plate 13 are separate components, the positioning and installation of the slit part 5 (7 sets of slit plates) in the following structure were investigated. Figure 25 as well as Figure 26 Explanation will be provided. In Figure 25 as well as Figure 26 In this configuration, the fixing plate 13 is a rubber plate 13 separate from the lens array 1. A groove 16 is formed on the rubber plate 13 (fixing plate 13) along the optical axis of the lens array 1 (the optical axis direction is consistent with the cylindrical direction or the focal depth direction). The adhesive layer 19 is a layer of adhesive such as double-sided tape.

[0101] Figure 25 (A) is a diagram of the lens array 1 as viewed from the optical axis direction. Figure 25 (B) is a diagram of the lens array 1 viewed from the sub-scanning direction. Figure 25 The lens array 1 is shown before the slit plate 7 is installed. The dimensions are in mm. Figure 26 In order to be in Figure 25 The diagram shows the lens array 1 with multiple slit plates 7 fixed in place, and the fixing leg 14 to be inserted (fitted) into the slot 16 (fitting part 15). Figure 26 In order to make it easier to understand the positional relationship, for the fixing plate 13 (rubber plate 13), adhesive layer 19, and side plate of lens body 2, it is hypothetically shown that the ends are separated from each other by adhesive layer 19 before the fixing plate 13 (rubber plate 13) and the side plate of lens body 2 are bonded.

[0102] Figure 25 as well as Figure 26 The fitting part 15 of the image reading device of Embodiment 3 shown is formed on a rubber plate 13, i.e., a fixing plate 13, which is separate from the lens array 1. The assembly method will be described. First, unlike the lens array 1, a thin rubber plate 13 is formed by molding. The rubber plate 13 has a required number of slots 16 with the same width as the slit plate 7 arranged side by side at a spacing that is the statistical minimum of the arrangement spacing of the lens bodies 2. Next, it is bonded by an adhesive layer 19. The opposite side of the lens array 1 is also treated in the same way, so that the slots 16 of the rubber plate 13 are located between adjacent lens bodies 2.

[0103] By making the spacing of the grooves 16 in the rubber plate 13 smaller than the spacing between the lens bodies 2, the lens body array 1 and the rubber plate 13 are fixed by aligning the position of the grooves 16 at one end of the lens body array 1. Then, when the lens body array 1 and the rubber plate 13 are bonded, the rubber plate 13 is stretched and fitted so that the position of the grooves 16 matches the position of the lens bodies 2, thereby adjusting the position of the lens bodies 2 and the position of the grooves 16 along the entire length of the lens body array 1. This process is performed on the opposite side as well, so that the slit plate 7 is positioned and fixed at a predetermined position between the lens bodies 2. Of course, as long as the thickness of the rubber plate 13 can be appropriately selected, it is also possible to form a slit plate 13 with a slit plate 13 with a slit plate 13. Figure 17 as well as Figure 18 The hole 17 shown can replace the groove 16. Alternatively, two rubber plates 13 can be linearly symmetrical in the main scanning direction and extend in a serrated shape along the main scanning direction. The groove 18, which is shorter than the other part in the sub-scanning direction, can be used as the fitting part 15.

[0104] The slit plate 7 can be positioned and held by inserting the slit portion 5 (slit plate 7 or sidewall plate 6) into the fitting portion 15 formed on these rubber plates 13. At this time, the rubber plate 13 after the groove is processed can be processed by rubber molding. As long as the length change of about 5% over the whole length can be ensured as the stretchability after molding, the position of the lens body 2 and the position of the fitting portion 15 can be aligned. Moreover, it can be produced as a separate part, thus resulting in a cost advantage.

[0105] This concludes the description of the preferred structure for mounting the slit portion 5 (slit plate 7) on the lens array 1 during post-processing; however, the image reading device of Embodiment 3 is not limited to this. Further explanation will be given regarding the positioning of different slit portions 5 (slit plates 7). The lens array 1 is manufactured by placing lens bodies 2 parallel to each other on an FRP (Fiber Reinforced Plastics) plate, clamping them together with two FRP plates, and bonding them together. When a fixing plate 13 is integrally formed with the lens array 1, the FRP plate functions as the fixing plate 13. Because lens system deviations, rod deformations, tilting, etc., occur during arrangement, and the lens arrangement reference is only the two ends of the lens array arrangement, it is difficult to determine the position of each lens body 2 in subsequent processes.

[0106] Therefore, a structure for arranging the lens body 2 is pre-formed on the side plate of the lens body 2, and then an FRP plate with a structure indicating the position between paired lenses is used on the opposite surface, thereby forming a structure indicating the position between lens bodies 2 in the lens body array 1 itself. Preferably, Figure 19 as well as Figure 20 The two fixing plates 13 (FRP plates) shown are linearly symmetrical in the main scanning direction and extend in a serrated shape along the main scanning direction. The groove 18, which is shorter than the other parts in the sub-scanning direction, is the fitting part 15. The lens body 2 is fixed between the grooves 18.

[0107] Specifically, a structure is formed by connecting the lens body 2 fixing side of the FRP plate to both sides of the lens body with a triangular cross-section at a spacing matching the generatrix diameter of the lens body 2, thereby creating a retaining row of protrusions. On the opposite side of the FRP plate, a structure (e.g., a triangular concave shape) indicating the arrangement position of the lens bodies 2 is provided at a position offset by 1 / 2 of the distance from the lens fixing protrusions. A lens array 1 is formed by two such side plates. Thus, as... Figure 19 As shown, regardless of the lens diameter or arrangement distortion, the position of the lens body 2 can be determined relative to the side plate solely by the shape of the outer surface of the lens body array 1. Figure 20 The location of the light-shielding wall (slit plate 7) shown is determined and set.

[0108] Formed from FRP board Figure 19 as well as Figure 20 In the case of the fixing plate 13 shown, it can be formed together with the FRP sheet during molding, or it can be formed in a way that is later installed relative to the parent FRP sheet, or it can be bonded as a separate component. By setting the fixing plate 13 in this way, the positional accuracy of the lens can be improved, and by setting and fixing the light shield in the recessed part of the side plate, both optical characteristics and workability can be improved.

[0109] Thus, it can be said that the image reading device of Embodiment 3 has a structure in which the lens array 1 is provided with a side plate (fixed plate 13) for holding the lens 2 to position the lens 2, and a positioning structure corresponding to the positioning structure of the lens 2 is formed on the opposite side of the side plate. In addition, it can be said that in the lens array 1 having a structure in which two side plates (fixed plates 13) are used to fix the lens 2 arranged in a row, there is a fixing structure that has a height of less than 1 / 3 of the lens diameter for fixing the lens position on the lens fixing surface of the side plate (fixed plate 13) and is arranged at the lens spacing in a manner that contacts the side of the lens 2. A slit plate 7 is disposed on the outer surface of the side plate (fixed plate 13) to fix the lens 2 between the lens 2, and the lens 2 is bonded to the side plate.

[0110] Furthermore, the image reading device of Embodiment 3 includes a slit plate 7 group as a lens array 1. This slit plate 7 group uses a thin plate having a structure on one side for positioning and holding the slit plate 7 as a light-shielding component to clamp and bond the lens bodies 2 arranged in an array, and is positioned relative to the lens body 2 group at a predetermined position. Additionally, the thin plate (fixing plate 13) having the structure for positioning and holding the slit plate 7 as a light-shielding component can also be made of a stretchable material. The portions for positioning and holding the slit plate 7 can also be arranged at a spacing less than or equal to the minimum lens pitch of the lens array 2.

[0111] Furthermore, in the image reading device of Embodiment 3, as a method for forming the lens array 1, a stretchable thin plate (rubber plate 13) having a structure group (fitting part 15 group) for holding the slit plate 7 can be fixed after being aligned at the end of the lens array 1 or at the center of the fitting part 15 which serves as the setting structure for the lens body 2 and the slit plate 7, and the other parts can be pasted sequentially while the thin plate is stretched, so as to ensure the positional accuracy of the lens and light-shielding member setting structure along the entire length.

[0112] The image reading devices of embodiments 1 to 3, by fitting (inserting) the fixing leg 14 into the fitting portion 15 formed on the fixing plate 13, can easily perform high-precision alignment of the slit portion 5 (slit body 7), thus enabling a stable image reading device with improved depth of field and stable image quality.

[0113] Furthermore, the image reading devices in embodiments 1 to 3 restrict the optical path by using the slit portion 5 or the fixing plate 13 to prevent light (specific light) incident at a low angle of incidence from directly incident on the sensor element 4 side. Therefore, even without changing the basic characteristics of the lens body, it is possible to obtain an image reading device with stable depth-of-field improvement and stable image quality.

[0114] Explanation of reference numerals in the attached figures

[0115] 1... Lens array (bar lens array); 2... Lens body (bar lens); 3... Sensor element array; 4... Sensor element (sensor IC); 5... Slit (anti-overlap part); 6... Side wall plate (spacer); 7... Slit plate; 8... Specific light blocking component (beam-shaped component); 9... Reading object (illuminated object); 10... Light source; 11... Sensor substrate; 12... Housing; 13... Fixing plate (rubber plate); 14... Fixing leg; 15... Fitting part; 16... Groove; 17... Hole; 18... Groove; 19... Adhesive layer.

Claims

1. An image reading device, characterized in that, have: A lens array is formed by arranging lenses in an array along the main scanning direction between two fixed plates that extend along the main scanning direction. A sensor element array, which consists of sensor elements that receive light focused by the lens body, arranged in an array along the main scanning direction; and An anti-overlap portion is disposed between the lens array and the sensor element array to prevent the images of the lenses from overlapping. The slit portion serving as the anti-overlapping portion includes: a plurality of slit plates that extend along a sub-scanning direction intersecting the main scanning direction to divide space and are arranged along the main scanning direction. The slit portion has a fixing leg extending toward the lens array side, the fixing leg contacting and being fixed to the fixing plate.

2. The image reading device according to claim 1, characterized in that, The plurality of slit plates extend along the sub-scanning direction to divide the space and are arranged along the main scanning direction. Multiple such spaces are arranged in an array along the main scanning direction, forming a one-to-one correspondence with the lens body.

3. The image reading device according to claim 1 or 2, characterized in that, The fixing plate has a fitting portion that engages with the fixing leg.

4. The image reading device according to claim 3, characterized in that, The fitting portion is either a plurality of grooves formed along the optical axis of the lens array, or a plurality of holes along the optical axis of the lens array for the insertion of the fixing leg.

5. The image reading device according to claim 3, characterized in that, The two fixing plates are linearly symmetrical in shape and extend in a serrated pattern along the main scanning direction.

6. The image reading device according to any one of claims 1, 2, 4, and 5, characterized in that, The fixing plate is a rubber plate that is separate from the lens array.

7. An image reading device, characterized in that, have: A lens array is formed by arranging lenses in an array along the main scanning direction between two fixed plates that extend along the main scanning direction. A sensor element array, which consists of sensor elements that receive light focused by the lens body, arranged in an array along the main scanning direction; and An anti-overlap portion is disposed between the lens array and the sensor element array to prevent the images of the lenses from overlapping. The slit portion serving as the anti-overlapping portion includes: a plurality of slit plates that extend along a sub-scanning direction intersecting the main scanning direction to divide space and are arranged along the main scanning direction. The slit plate is fixed to the fixing plate. The fixing plate is a rubber plate that is separate from the lens array.

8. The image reading device according to any one of claims 1, 2, 4, 5, and 7, characterized in that, The slit portion has a specific light-blocking component that is formed protruding from the slit plate in the main scanning direction to prevent specific light incident at an angle below the aperture angle of the lens from incident on the sensor element.

9. The image reading device according to claim 8, characterized in that, The slit portion also has two sidewall plates that extend along the main scanning direction and are opposite each other in the sub-scanning direction. The specific light-blocking component is a beam-shaped component disposed between one sidewall panel and the other sidewall panel.

10. An image reading device, characterized in that, have: A lens array is formed by arranging lenses in an array along the main scanning direction between two fixed plates that extend along the main scanning direction. A sensor element array, which consists of sensor elements that receive light focused by the lens body, arranged in an array along the main scanning direction; and An anti-overlap portion is disposed between the lens array and the sensor element array to prevent the images of the lenses from overlapping. The slit portion serving as the anti-overlapping portion includes: two sidewall plates extending along the main scanning direction and facing each other in a sub-scanning direction intersecting the main scanning direction; and a plurality of slit plates extending along the sub-scanning direction to divide space and arranged along the main scanning direction. The slit plate is fixed to the fixing plate. The slit portion has a specific light-blocking component, which is a beam-shaped component formed protruding from the slit plate in the main scanning direction to prevent specific light incident at an angle below the aperture angle of the lens body from incident on the sensor element, and is disposed between one side wall plate and the other side wall plate.

11. The image reading device according to claim 9 or 10, characterized in that, At least one of the slit plate or the sidewall plate has a fixing leg extending toward the lens array side.

12. The image reading device according to claim 9 or 10, characterized in that, The plurality of slit plates are arranged between the two sidewall plates along the sub-scanning direction, thereby dividing the space between the two sidewall plates.

13. The image reading device according to claim 9 or 10, characterized in that, The specific light-blocking component is a component whose portion on the lens body side protrudes more than the portion on the sensor element side.

14. An image reading device, characterized in that, have: A lens array is formed by arranging lenses in an array along the main scanning direction between two fixed plates that extend along the main scanning direction. A sensor element array, which consists of sensor elements that receive light focused by the lens body, arranged in an array along the main scanning direction; and An anti-overlap portion is disposed between the lens array and the sensor element array to prevent the images of the lenses from overlapping. The slit portion serving as the anti-overlapping portion includes: a plurality of slit plates that extend along a sub-scanning direction intersecting the main scanning direction to divide space and are arranged along the main scanning direction. The slit plate is fixed to the fixing plate. The slit portion has a specific light-blocking component, which is formed on the slit plate protruding in the main scanning direction to prevent specific light incident at an angle below the aperture angle of the lens body from incident on the sensor element, and the portion on the lens body side protrudes more than the portion on the sensor element side.

15. The image reading device according to any one of claims 9, 10, and 14, characterized in that, The specific light-blocking components are formed in multiples along the optical axis of the lens array in the slit plate.

16. The image reading device according to claim 15, characterized in that, The adjacent spacing e of the multiple slit plates formed is less than or equal to the value obtained by multiplying the overlap m by 0.6 and the lens diameter Φ of the lens body, i.e., e ≤ 0.6 × m × Φ.

17. An image reading device, characterized in that, have: A lens array is formed by arranging lenses in an array along the main scanning direction between two fixed plates that extend along the main scanning direction. A sensor element array, which consists of sensor elements that receive light focused by the lens body, arranged in an array along the main scanning direction; and An anti-overlap portion is disposed between the lens array and the sensor element array to prevent the images of the lenses from overlapping. The slit portion serving as the anti-overlapping portion includes: a plurality of slit plates that extend along a sub-scanning direction intersecting the main scanning direction to divide space and are arranged along the main scanning direction. The slit plate is fixed to the fixing plate. The slit portion has a specific light-blocking component, which is formed protruding from the slit plate in the main scanning direction to prevent specific light incident at an angle below the aperture angle of the lens body from entering the sensor element. Multiple such specific light-blocking components are formed in the slit plate along the optical axis of the lens array. The adjacent spacing e of the multiple slit plates formed is less than or equal to the value obtained by multiplying the overlap m by 0.6 and the lens diameter Φ of the lens body, i.e., e ≤ 0.6 × m × Φ.

18. The image reading device according to claim 16 or 17, characterized in that, The length of the slit in the optical path is greater than or equal to the value obtained by dividing the interval e by the tangent θ when the aperture angle is set to θ.

19. The image reading device according to any one of claims 9, 10, 14, 16, and 17, characterized in that, The surfaces of the slit plate and the specific light-blocking component are black.

20. The image reading device according to claim 9 or 10, characterized in that, At least one side of the sidewall panel that is continuous with the slot plate is black.

21. The image reading device according to claim 19, characterized in that, The black surface is a black velvety surface.

22. An image reading device, characterized in that, have: A lens array is formed by arranging lenses in an array along the main scanning direction between two fixed plates that extend along the main scanning direction. A sensor element array, which consists of sensor elements that receive light focused by the lens body, arranged in an array along the main scanning direction; and An anti-overlap portion is disposed between the lens array and the sensor element array to prevent the images of the lenses from overlapping. The slit portion serving as the anti-overlapping portion includes: a plurality of slit plates that extend along a sub-scanning direction intersecting the main scanning direction to divide space and are arranged along the main scanning direction. The slit plate is fixed to the fixing plate, and the slit portion has a specific light-blocking component. This specific light-blocking component is formed on the slit plate protruding in the main scanning direction to prevent specific light incident at an angle below the aperture angle of the lens from incident on the sensor element. The surfaces of the slit plate and the specific light-blocking component are black. The black surface is a black velvety surface.

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