Optical line sensor

Abstract

Provided is an optical line sensor capable of effectively preventing stray light from entering each of a plurality of light receiving element arrays. A plurality of light receiving lenses 111 are disposed in a line along a main scanning direction and transmit light from an illuminated object. A plurality of openings 113E through which the light transmitted through each of the plurality of light receiving lenses 111 passes are formed in an aperture member 113. A plurality of light receiving elements constitute a plurality of light receiving element arrays 12 that correspond respectively to the plurality of openings 113E and that extend along the main scanning direction. The plurality of light receiving element arrays 12 are arranged in a staggered manner on two rows of reading lines L. A light shielding block 114 is provided between the aperture member 113 and the plurality of light receiving element arrays 12 to prevent light that has passed through an opening 113E adjacent to the opening 113E corresponding to each light receiving element array 12 from entering the light receiving element array 12.

Description

Optical line sensor

[0001] The present invention relates to an optical line sensor that reads an object relatively moved along a sub-scanning direction with a reading line extending in a main scanning direction.

[0002] In an image reading apparatus provided with an optical line sensor, light is irradiated from a light source toward an object, and reflected light or transmitted light from the object is imaged on a reading line by a light receiving lens, and thus is received by a light receiving element on the reading line. A plurality of light receiving lenses are arranged, and light passing through each light receiving lens is received by a plurality of light receiving elements (see, for example, Patent Document 1 below).

[0003] Usually, a plurality of light receiving lenses are integrally held by a housing. In the example of Patent Document 1, the housing is composed of a number of housing components, and a light receiving lens is held by each housing component. A clearance is provided between each housing component to prevent a shift in relative position due to a temperature change.

[0004] However, in the conventional configuration as described above, a large number of housing components are required, and the shape of each housing component is complicated, so there is a problem that the manufacturing cost of the components becomes high. In addition, there is also a problem that the assembly work becomes complicated due to the large number of components.

[0005] Therefore, the applicant of the present application has proposed an optical line sensor including a pair of holding plates that sandwich a plurality of light receiving lenses in a sub-scanning direction as an optical line sensor with a small number of components and easy assembly work (see Patent Document 2 below).

[0006] International Publication No. 2021 / 049177 International Publication No. 2024 / 106058

[0007] In the configuration disclosed in Patent Document 2, an aperture member having an aperture through which light passing through the light receiving lens passes is provided, and a light shielding portion that blocks a part of the aperture to prevent stray light from entering the light receiving element array is formed on the aperture member. By this light shielding portion, it is possible to effectively prevent the entry of stray light toward the aperture along a direction inclined in the sub-scanning direction with respect to the optical axis direction into the light receiving element array.

[0008] However, in the configuration disclosed in Patent Document 2, it was sometimes not possible to prevent stray light from entering the photodetector array in a direction inclined in the main scanning direction with respect to the optical axis. Specifically, light that passed through an aperture adjacent to the aperture corresponding to each photodetector array in the main scanning direction, rather than the aperture corresponding to that aperture, sometimes entered each photodetector array as stray light.

[0009] This invention has been made in view of the above circumstances, and aims to provide an optical line sensor that can effectively prevent stray light from entering each light-receiving element array.

[0010] (1) The optical line sensor according to the present invention is an optical line sensor that reads an object that is moved relative to it along the sub-scanning direction with a reading line extending in the main scanning direction, and comprises a plurality of light-receiving lenses, an aperture member, and a plurality of light-receiving elements. The plurality of light-receiving lenses are arranged in a line along the main scanning direction and transmit light from the illuminated object. The aperture member has a plurality of openings through which the light that has been transmitted through the plurality of light-receiving lenses passes. The plurality of light-receiving elements are arranged in a line along the main scanning direction and receive light that has passed through the plurality of openings. The plurality of light-receiving elements constitute a plurality of light-receiving element arrays that each extends along the main scanning direction in correspondence with the plurality of openings. The plurality of light-receiving element arrays are arranged in a staggered pattern on the two rows of the reading line. Between the aperture member and the plurality of light-receiving element arrays, a first light-shielding portion is provided to prevent light that has passed through an opening adjacent to the opening corresponding to each light-receiving element array from entering each light-receiving element array.

[0011] With this configuration, the first light-shielding portion provided between the aperture member and the array of light-receiving elements prevents light passing through an adjacent aperture from entering each light-receiving element array. Therefore, stray light can be effectively prevented from entering each light-receiving element array.

[0012] (2) Multiple first light-shielding portions may be provided in correspondence with the plurality of openings. In this case, light passing through an opening adjacent to the opening corresponding to each light-receiving element array may be blocked by the first light-shielding portion provided in correspondence with the adjacent opening.

[0013] With this configuration, the multiple first light-shielding sections associated with each aperture can prevent stray light from entering each photodetector array. In particular, stray light that passes through an aperture adjacent to an aperture corresponding to each photodetector array, and that is directed in a direction inclined with respect to the optical axis direction towards the main scanning direction, is effectively blocked by the first light-shielding section provided in conjunction with the adjacent aperture.

[0014] (3) The multiple first light-shielding portions may be arranged in a staggered pattern on the two rows of reading lines.

[0015] With this configuration, multiple first light-shielding sections can be arranged in a staggered pattern on two reading lines, corresponding to multiple staggered arrays of photodetectors. In this case, if each first light-shielding section corresponding to each photodetector array is positioned offset in the sub-scanning direction relative to each photodetector array, then stray light passing through an aperture adjacent to the aperture corresponding to each photodetector array, which is inclined in the main scanning direction and the sub-scanning direction with respect to the optical axis, is effectively blocked by the first light-shielding section provided in correspondence to the adjacent aperture.

[0016] (4) The width of the first light-shielding portion in the main scanning direction may be greater than or equal to the field of view width at the installation position of the first light-shielding portion in the adjacent aperture to which the first light-shielding portion is attached, and less than or equal to the width of the light-receiving element array.

[0017] With this configuration, the first light-shielding portion can effectively block stray light that passes through adjacent apertures to which it is attached, and which is directed beyond the field of view of those adjacent apertures in the main scanning direction.

[0018] (5) The first light-shielding portion may have through holes that extend along the optical path of light passing through the opening and entering the light-receiving element array corresponding to the opening.

[0019] With this configuration, light passing through the opening and heading toward the photodetector array corresponding to the opening is reliably guided to the photodetector array along the through-hole, and stray light can be reliably blocked by the first light-shielding portion that constitutes the inner circumferential surface of the through-hole.

[0020] (6) The plurality of openings may be located between the two rows of reading lines when viewed from a direction perpendicular to the main scanning direction and the sub-scanning direction. In this case, the through holes may be formed in a tapered shape that is inclined in the sub-scanning direction with respect to the direction perpendicular to the main scanning direction and the sub-scanning direction.

[0021] With this configuration, even if the photodetector array corresponding to the aperture is positioned offset in the sub-scanning direction relative to the aperture, light passing through the aperture and heading towards the corresponding photodetector array is reliably guided to the photodetector array along a tapered through-hole that is inclined in the sub-scanning direction.

[0022] (7) The through hole may extend in a stepped manner along the direction in which the through hole is inclined.

[0023] With this configuration, light passing through the aperture and heading towards the corresponding photodetector array is reliably guided to the photodetector array along the stepped through-holes.

[0024] (8) Each of the plurality of light-receiving lenses constitutes a telecentric optical system, and the width of each light-receiving lens in the sub-scanning direction may be smaller than the width in the main scanning direction.

[0025] With this configuration, a telecentric optical system can be used to realize an optical line sensor with a deep depth of field. Furthermore, because the width of the light-receiving lens in the sub-scanning direction is smaller than its width in the main scanning direction, the light-receiving lens can be positioned closer to the sub-scanning direction, resulting in a more compact optical line sensor.

[0026] (9) The plurality of openings may be formed in the shape of a frustocone.

[0027] With this configuration, light from each light-receiving lens to the aperture member can be guided along a frustoconical opening.

[0028] (10) The aperture member may have a plurality of pinholes formed in it, into which light that has passed through the plurality of openings is incident, with each opening separated from the others and facing each other.

[0029] With this configuration, light from each light-receiving lens to the aperture member can be guided along the aperture and pinhole.

[0030] (11) The aperture member may have a second light-shielding portion that blocks a part of the opening to prevent stray light from entering.

[0031] With this configuration, the second light-shielding section can prevent stray light from entering the optical path from each light-receiving lens to the aperture member.

[0032] (12) The aperture member may consist of a plurality of aperture members, each having an opening formed thereon. In this case, the optical line sensor may further include a pair of retaining plates and a pair of sensor holders. The pair of retaining plates sandwich at least two of the plurality of light-receiving lenses and at least one of the plurality of aperture members in the sub-scanning direction. The pair of sensor holders sandwich a plurality of light-receiving lens arrays arranged in the main scanning direction in the sub-scanning direction, with the pair of retaining plates and the at least two light-receiving lenses and the at least one aperture member sandwiched between them forming a single light-receiving lens array. Alternatively, one of the pair of retaining plates may be positioned on one of the pair of sensor holders by a first positioning member, and the other of the pair of retaining plates may be positioned on the other of the pair of sensor holders by a second positioning member, so that the pair of sensor holders are connected to each other, thereby positioning the pair of retaining plates facing each other in the sub-scanning direction.

[0033] With this configuration, by sandwiching multiple light-receiving lens arrays in the sub-scanning direction with a pair of sensor holders, at least two light-receiving lenses and at least one aperture member included in each light-receiving lens array can be fixed between the pair of sensor holders. Therefore, even if some of the light-receiving lenses in one of the light-receiving lens arrays are defective, only that light-receiving lens array needs to be replaced, thus minimizing waste of parts.

[0034] Furthermore, since one of the pair of retaining plates is positioned on one of the pair of sensor holders by a first positioning member, and the other of the pair of retaining plates is positioned on the other of the pair of sensor holders by a second positioning member, assembly is easy, and each light-receiving lens array can be accurately positioned and fixed between the pair of sensor holders. This makes it possible to easily and accurately position multiple light-receiving lenses and multiple aperture members.

[0035] (13) Each of the pair of retaining plates may have a fixing screw hole. In this case, each of the pair of sensor holders may have a through hole at a position opposite to the fixing screw hole. Alternatively, one of the pair of retaining plates may be fixed to one of the pair of sensor holders by inserting a first fixing screw through the through hole formed in one of the pair of sensor holders and screwing it into the fixing screw hole formed in one of the pair of retaining plates, and the other of the pair of retaining plates may be fixed to the other of the pair of sensor holders by inserting a second fixing screw through the through hole formed in the other of the pair of sensor holders and screwing it into the fixing screw hole formed in the other of the pair of retaining plates.

[0036] With this configuration, for each light-receiving lens array, one of a pair of retaining plates is fixed to one of a pair of sensor holders with a first fixing screw, and the other of the pair of retaining plates is fixed to the other of a pair of sensor holders with a second fixing screw. By connecting the pairs of sensor holders to each other, multiple light-receiving lens arrays can be sandwiched in the sub-scanning direction by a pair of sensor holders. This allows for even more precise positioning of multiple light-receiving lenses and multiple aperture members.

[0037] (14) The optical line sensor may further include a spacer. The spacer is positioned between the pair of sensor holders and is used to maintain a constant distance between the pair of sensor holders when the plurality of light-receiving lens arrays are sandwiched between the pair of sensor holders in the sub-scanning direction.

[0038] With this configuration, when connecting a pair of sensor holders to each other, the distance between the pair of sensor holders can be kept constant by the spacers, allowing for more precise positioning of multiple light-receiving lenses and multiple aperture members.

[0039] (15) The optical line sensor may further include a light-receiving substrate on which the plurality of light-receiving elements are mounted. In this case, each of the pair of sensor holders may be formed in an L-shape having a first plate portion facing the plurality of light-receiving lens arrays and a second plate portion extending from one end of the first plate portion toward the side opposite to the plurality of light-receiving lens arrays. The light-receiving substrate may also be mounted so as to straddle the pair of sensor holders on the side of the second plate portion.

[0040] With this configuration, multiple light-receiving lenses and multiple aperture members can be positioned between the first plate portions of a pair of sensor holders, and then a light-receiving substrate can be attached on the second plate portion side so as to straddle the pair of sensor holders. Therefore, the multiple light-receiving lenses and multiple aperture members and the multiple light-receiving elements mounted on the light-receiving substrate can be precisely positioned relative to each other.

[0041] (16) The optical axes of the plurality of light receiving lenses may be located on the center line between the two rows of the reading lines.

[0042] According to such a configuration, in the configuration where the optical axes of the respective light receiving lenses are located on the center line between the two rows of reading lines, the plurality of light receiving lenses, the plurality of aperture members, and the plurality of light receiving element arrays can be accurately positioned with respect to each other.

[0043] (17) A plurality of pairs of sensor holders may be arranged side by side in the main scanning direction.

[0044] According to such a configuration, by arranging a plurality of pairs of sensor holders side by side in the main scanning direction, the reading range in the main scanning direction can be expanded.

[0045] (18) The optical line sensor may further include a third light shielding portion that covers a gap between adjacent ones of the aperture members.

[0046] According to such a configuration, stray light that enters from the gap between adjacent aperture members can be blocked by the third light shielding portion, so that the incidence of stray light on each light receiving element array can be effectively prevented.

[0047] (19) The optical line sensor may further include a cover member provided so as to straddle end faces on the light incident side of the pair of holding plates.

[0048] According to such a configuration, the entry of foreign matter between the pair of holding plates can be blocked by the cover member.

[0049] (20) At least one injection hole may be formed in the pair of holding plates at positions facing the light receiving lenses. In this case, the pair of holding plates and the at least two light receiving lenses may be fixed by an adhesive injected into the at least one injection hole.

[0050] According to such a configuration, by injecting an adhesive into at least one injection hole formed in the pair of holding plates, each light receiving lens can be reliably fixed to the pair of holding plates.

[0051] (21) The pair of retaining plates may have at least one first adjustment screw hole at a position facing the light-receiving lens. In this case, the angle of the light-receiving lens relative to the pair of retaining plates may be adjusted by a first adjustment screw that is screwed into the at least one first adjustment screw hole and whose tip contacts the light-receiving lens.

[0052] With this configuration, the angle of the light-receiving lens relative to the pair of retaining plates can be finely adjusted using the first adjustment screw, making it easy and accurate to adjust the optical axis of the light-receiving lens.

[0053] (22) The pair of sensor holders may have at least one second adjustment screw hole at a position facing the retaining plate. In this case, the angle of the retaining plate relative to the pair of sensor holders may be adjusted by a second adjustment screw that is screwed into the at least one second adjustment screw hole and whose tip abuts against the retaining plate.

[0054] With this configuration, the angle of the retaining plate relative to a pair of sensor holders can be finely adjusted using a second adjustment screw. This allows for easy and accurate adjustment of the optical axis of the light-receiving lenses even after fixing each light-receiving lens array between the pair of sensor holders.

[0055] (23) The pair of retaining plates may have fitting portions for fitting together and connecting the pair of retaining plates.

[0056] With this configuration, a pair of retaining plates are securely connected by a fitting portion, allowing for more precise positioning of multiple light-receiving lenses and multiple aperture members.

[0057] According to the present invention, it is possible to effectively prevent stray light from entering each light-receiving element array.

[0058] This is a cross-sectional view showing an example configuration of an optical line sensor according to one embodiment of the present invention. This is an exploded perspective view showing an example configuration of the illumination optical system in the optical line sensor of Figure 1. This is a perspective view of a light-receiving lens array according to the first embodiment. This is an exploded perspective view of a light-receiving lens array according to the first embodiment. This is a perspective view of an aperture member according to the first embodiment. This is a perspective view of a light-receiving lens array according to the second embodiment. This is an exploded perspective view of a light-receiving lens array according to the second embodiment. This is a perspective view of an aperture member according to the second embodiment. This is a perspective view for explaining a method for manufacturing a light-receiving lens array according to the second embodiment. This is a schematic diagram for explaining the positional relationship between the light-receiving lens and the light-receiving element array, showing the case of a trapezoidal light-receiving lens according to the second embodiment shown in Figures 6 and 7. This is a schematic diagram for explaining the positional relationship between the light-receiving lens and the light-receiving element array, showing the case of a light-receiving lens according to a modified example. This is a diagram showing the case when normal light (light that is not stray light) that passes through the light-receiving lens, enters the aperture member, and exits from the aperture is received by the light-receiving element array. This is a diagram for explaining a specific example of stray light that enters the light-receiving element array in a direction tilted in the X direction with respect to the Z direction. This figure illustrates a specific example of stray light incident on a photodetector array in a direction inclined in the X direction with respect to the Z direction. This figure illustrates a specific example of stray light incident on a photodetector array in a direction inclined in the X direction with respect to the Z direction. This is a cross-sectional view of an optical line sensor equipped with a light-shielding block along the XY plane. This is a cross-sectional view of an optical line sensor equipped with a light-shielding block along the XZ plane. This is a cross-sectional view of an optical line sensor equipped with a light-shielding block along the YZ plane, showing the cross section at the installation position of the light-receiving lens. This is a cross-sectional view of an optical line sensor equipped with a light-shielding block along the YZ plane, showing the cross section at the installation position of the light-receiving lens. This is a view of one retaining plate along the Y direction, from the light-receiving lens side. This is a view of the other retaining plate along the Y direction, from the opposite side from the light-receiving lens side. This is a cross-sectional view of an optical line sensor along the YZ plane, showing the cross section cut at the position of the positioning hole. This is a cross-sectional view of an optical line sensor along the YZ plane, showing the cross section cut at the position of the fixing screw hole.This is a cross-sectional view of an optical line sensor along the YZ plane, showing a cross-section at one end in the X direction of a pair of sensor holders. This is a schematic plan view showing an example of an elongated optical line sensor. This figure shows the case where stray light entering the light-receiving element array is prevented, corresponding to Figure 11B. This is a cross-sectional view of the installation position of the light-receiving lens in Figure 17A, along the YZ plane, showing the case where stray light toward the light-receiving element array is blocked by a light-shielding block. This is a cross-sectional view of the installation position of the light-receiving lens in Figure 17A, along the YZ plane, showing the case where normal light is incident on the light-receiving element array. This figure shows the case where stray light entering the light-receiving element array is prevented, corresponding to Figure 11C. This is a cross-sectional view of the installation position of the light-receiving lens in Figure 18A, along the YZ plane, showing the case where stray light toward the light-receiving element array is blocked by a light-shielding block. This is a cross-sectional view of the installation position of the light-receiving lens in Figure 18A, along the YZ plane, showing the case where normal light is incident on the light-receiving element array. This figure shows the case where stray light entering the light-receiving element array is prevented, corresponding to Figure 11D. Figure 19A is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens, showing the case where stray light directed toward the light-receiving element array is blocked by the light-shielding block. Figure 19A is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens, showing the case where normal light is incident on the light-receiving element array. This figure is for explaining a modified example of the light-shielding block. Figure 20A is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens, showing the case where normal light is incident on the light-receiving element array. Figure 20A is a cross-sectional view along the YZ plane at the installation position of a light-receiving lens adjacent to the light-receiving lens, showing the case where normal light is incident on the light-receiving element array. Figure 20B is for explaining a modified example of the through-hole of the light-shielding block shown. Figure 20C is for explaining a modified example of the through-hole of the light-shielding block shown. This figure is for explaining a further modified example of the light-shielding block. Figure 21A is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens, showing the case where normal light is incident on the light-receiving element array. Figure 21A is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens adjacent to the light-receiving lens, showing the case when normal light is incident on the light-receiving element array.

[0059] 1. Figure 1, an overall diagram of the optical line sensor, is a cross-sectional view showing an example of the configuration of an optical line sensor according to one embodiment of the present invention. Figure 1 shows a cross-sectional view of the optical line sensor near the longitudinal center. Figure 2 is an exploded perspective view showing an example of the configuration of the illumination optical system in the optical line sensor of Figure 1. In Figure 2, the X direction is the main scanning direction, and the Y direction is the sub-scanning direction. The Z direction is orthogonal to the X and Y directions.

[0060] This optical line sensor is a contact image sensor (CIS) that primarily illuminates thin objects such as printed materials or films with light, and receives the reflected or transmitted light from the object with a light-receiving element. In the optical line sensor shown in Figure 1, two housings 16 are arranged opposite each other with a focal plane 20 in between. Each housing 16 is provided with a line-shaped light source unit 10 for illuminating an object on the focal plane 20. One of the housings 16 is provided with a light-receiving lens array 11 and a light-receiving element array 12, and the light from the illuminated object is guided to the light-receiving element array 12 by the light-receiving lens array 11. The light-receiving lens array 11 images the light from the object onto the light-receiving element array 12 on a reading line extending in the X direction. In the optical line sensor shown in Figure 1, with respect to the focal plane 20, one of the two light source units 10 is positioned on the side of the light-receiving element array 12, and the other is positioned on the opposite side from the light-receiving element array 12. Furthermore, protective glass 14 is installed in the opening on the focal plane 20 side of each housing 16.

[0061] The light-receiving element array 12 is mounted on a substrate 13 fixed to one of the housings 16. Light that has passed through the light-receiving lens array 11 is received by the light-receiving surface 12A of the light-receiving element array 12, and a signal corresponding to the amount of light received is output from the light-receiving element array 12. As the object is transported in the Y direction along the focal plane 20, light from the object is continuously received by the light-receiving element array 12, and an image of the object is obtained based on the output signal from the light-receiving element array 12. In this way, the object being transported in the Y direction is read by the light-receiving element array 12 extending in the X direction, using a reading line formed by the light-receiving surface 12A of the light-receiving element array 12. However, the configuration is not limited to one in which the object is transported; it may also be a configuration in which the object moves relative to a stationary object by moving the optical line sensor.

[0062] A UV-cut filter 15 may be provided at any position between the focal plane 20 and the photodetector array 12 to prevent ultraviolet light from entering the photodetector array 12. Furthermore, a color filter 18 that allows visible light in a specific wavelength range to pass through may be provided between the photodetector array 12 and the UV-cut filter 15.

[0063] In the example shown in Figures 1 and 2, the light source unit 10 comprises a transparent light guide 101 extending along the longitudinal direction (X direction), a light source 103 provided near one end face in the longitudinal direction, and a cover member 102 for holding each side surface of the light guide 101. Light emitted from the light source 103 enters the light guide 101, propagates through the light guide 101, is appropriately reflected by the light diffusion pattern P, and is emitted from the light emission surface in the direction of the arrow, becoming a line of illumination light that illuminates the object.

[0064] 2. First Embodiment of the Light-Receiving Lens Array Figures 3 to 5 are diagrams illustrating the first embodiment of the light-receiving lens array 11. Figure 3 is a perspective view of the light-receiving lens array 11 according to the first embodiment. Figure 4 is an exploded perspective view of the light-receiving lens array 11 according to the first embodiment. Figure 5 is a perspective view of the aperture member 113 according to the first embodiment.

[0065] The light-receiving lens array 11 comprises a plurality of light-receiving lenses 111 and a pair of retaining plates 112. The plurality of light-receiving lenses 111 are arranged in a line along the X direction. More specifically, the optical axes of the plurality of light-receiving lenses 111 are all on the same plane and parallel to each other. The pair of retaining plates 112 are each thin rectangular plate members and extend parallel to each other along the X direction. The plurality of light-receiving lenses 111 are sandwiched in the Y direction between the pair of retaining plates 112. If it is desired to increase the X-direction dimension of the retaining plates 112, it is advisable to select a material with a small coefficient of linear expansion to suppress length changes due to temperature changes. For example, glass epoxy laminate is preferable because it has a small coefficient of linear expansion of about 16 ppm and a low specific gravity, thus keeping the weight down.

[0066] Each light-receiving lens 111 is rectangular in plan view (view in the Z direction), and one end face in the Y direction (first surface 111A) and the other end face (second surface 111B) are each composed of flat surfaces. The incident surface (the surface on the focal plane 20 side) and the exit surface (the surface opposite the incident surface) of each light-receiving lens 111 are, for example, composed of convex curved surfaces, and play the role of forming an image of the light incident on each light-receiving lens 111 onto the light-receiving surface 12A.

[0067] The width in the Y direction (the distance between the first surface 111A and the second surface 111B) of each light-receiving lens 111 is the same. Therefore, by integrally clamping multiple light-receiving lenses 111 with a pair of retaining plates 112, the first surface 111A of each light-receiving lens 111 can be brought into contact with one of the pair of retaining plates 112 (retaining plate 112A), and the second surface 111B of each light-receiving lens 111 can be brought into contact with the other of the pair of retaining plates 112 (retaining plate 112B).

[0068] In this embodiment, the light-receiving lens array 11 comprises a plurality of aperture members 113. Each aperture member 113 is associated one-to-one with each light-receiving lens 111 and is spaced apart from each light-receiving lens 111 in the optical axis direction. Light from the illuminated object passes through each light-receiving lens 111, then passes through the opening 113A formed in the corresponding aperture member 113 and is guided to the light-receiving element array 12. However, instead of providing a plurality of aperture members 113, each with an opening 113A, a configuration in which a plurality of openings 113A are formed in a single aperture member 113 is also possible.

[0069] As shown in Figure 5, the aperture 113A formed in the aperture member 113 penetrates the aperture member 113 in the optical axis direction and is formed in a frustoconical shape that tapers from the light-receiving lens 111 side toward the light-receiving element array 12 side. By aligning the position of the tapered side of the aperture 113A in the Z direction (optical axis direction) with the image-side focal point of the light-receiving lens 111, the aperture member 113 may constitute a telecentric optical system together with multiple light-receiving lenses 111. In this case, it is preferable that the apex angle of the frustoconical aperture 113A be slightly larger than the aperture angle of the light-receiving lens 111. This effectively reduces stray light without vignetting the image formed by the light-receiving lens 111.

[0070] The width of each aperture member 113 in the Y direction coincides with the distance between the first surface 111A and the second surface 111B of each light-receiving lens 111. In other words, the width of each aperture member 113 in the Y direction coincides with the width of each light-receiving lens 111 in the Y direction. Therefore, when multiple light-receiving lenses 111 are integrally clamped by a pair of retaining plates 112, both Y-direction end faces of each aperture member 113 come into contact with the pair of retaining plates 112.

[0071] In this embodiment, each light-receiving lens 111 has its first surface 111A bonded to one retaining plate 112A and its second surface 111B bonded to the other retaining plate 112B. Similarly, each aperture member 113 has one surface in the Y direction bonded to one retaining plate 112A and the other surface in the Y direction bonded to the other retaining plate 112B. Bonding between the members can be done using general-purpose adhesives or double-sided tape. However, each aperture member 113 is not a separate member from the pair of retaining plates 112, but may be integrally formed with either of the retaining plates 112.

[0072] Each light-receiving lens 111 does not need to be glued to a pair of retaining plates 112, as long as it is in contact with the respective plate. For example, protrusions may be formed on parts of the first surface 111A and the second surface 111B of the light-receiving lens 111, corresponding recesses may be formed on the pair of retaining plates 112, and the pair of retaining plates 112 may be fixed to each other with a fastener while the protrusions are fitted into the recesses, thereby clamping each light-receiving lens 111 in the Y direction with the pair of retaining plates 112.

[0073] It is preferable that each light-receiving lens 111 is arranged so as not to come into contact with one another. That is, multiple light-receiving lenses 111 may be arranged with space between them so that adjacent light-receiving lenses 111 in the X direction do not come into contact with each other. In this case, it is preferable that an elastic member having light-shielding and low reflectivity is provided in the space. Examples of elastic members include urethane, but are not limited to this, and an elastic member may be formed between each light-receiving lens 111 by filling with an elastic adhesive or the like.

[0074] 3. Second Embodiment of the Light-Receiving Lens Array Figures 6 to 8A are diagrams illustrating a second embodiment of the light-receiving lens array 11. Figure 6 is a perspective view of the light-receiving lens array 11 according to the second embodiment. Figure 7 is an exploded perspective view of the light-receiving lens array 11 according to the second embodiment. Figure 8A is a perspective view of the aperture member 113 according to the second embodiment.

[0075] The light-receiving lens array 11 comprises a plurality of light-receiving lenses 111 and a pair of retaining plates 112. The plurality of light-receiving lenses 111 are arranged in a line along the X direction. More specifically, the optical axes of the plurality of light-receiving lenses 111 are all on the same plane and parallel to each other. The pair of retaining plates 112 are each thin rectangular plate members and extend parallel to each other along the X direction. The plurality of light-receiving lenses 111 are sandwiched in the Y direction between the pair of retaining plates 112.

[0076] Each light-receiving lens 111 is trapezoidal in plan view (view in the Z direction), and one end face in the Y direction (first surface 111A) and the other end face (second surface 111B) are each composed of flat surfaces. The second surface 111B has a smaller width in the X direction than the first surface 111A, and the second surface 111B faces the center of the first surface 111A in the X direction. The first surface 111A and the second surface 111B are connected by a pair of inclined surfaces 111C. That is, one end of the first surface 111A in the X direction and one end of the second surface 111B in the X direction are connected by one inclined surface 111C, and the other end of the first surface 111A in the X direction and the other end of the second surface 111B in the X direction are connected by the other inclined surface 111C.

[0077] The incident surface (the surface facing the focal plane 20) and the exit surface (the surface facing the incident surface) of each light-receiving lens 111 are, for example, made of a convex curved surface, and play the role of forming an image of the light incident on each light-receiving lens 111 onto the light-receiving surface 12A. In this example, each light-receiving lens 111 is made up of two trapezoidal lenses (a biconvex lens and a meniscus lens) aligned on the optical axis along the Z direction, but the configuration is not limited to this, and each light-receiving lens 111 may be made up of one trapezoidal lens, or it may be made up of three or more trapezoidal lenses.

[0078] As shown in Figure 7, the plurality of light-receiving lenses 111 includes a portion of the light-receiving lenses 111 (light-receiving lens 120) attached to one of the pair of retaining plates 112 (retaining plate 112A), and the remaining light-receiving lenses 111 (light-receiving lens 130) attached to the other of the pair of retaining plates 112 (retaining plate 112B). Each light-receiving lens 111 has a first surface 111A attached to each retaining plate 112. That is, the method for manufacturing the light-receiving lens array 11 in this example includes a first lens mounting step in which the first surface 111A of a portion of the plurality of light-receiving lenses 111 (light-receiving lens 120) is attached to one of the pair of retaining plates 112 (retaining plate 112A), and a second lens mounting step in which the first surface 111A of the remaining light-receiving lenses 111 (light-receiving lens 130) is attached to the other of the pair of retaining plates 112 (retaining plate 112B).

[0079] In the first lens mounting step, half of the multiple light-receiving lenses 111 (light-receiving lenses 120) are attached to one of the pair of retaining plates 112 (retaining plate 112A), skipping one lens in the X direction. In the second lens mounting step, the remaining half of the multiple light-receiving lenses 111 (light-receiving lenses 130) are attached to the other of the pair of retaining plates 112 (retaining plate 112B), skipping one lens in the X direction. Since the first and second lens mounting steps are essentially the same operation, work efficiency can be improved and the number of assembly jigs can be reduced.

[0080] After multiple light-receiving lenses 111 are attached to each of a pair of retaining plates 112 in the manner described above, the pair of retaining plates 112 are brought facing each other, and each light-receiving lens 111 is sandwiched between the pair of retaining plates 112 in the Y direction, thereby fixing each light-receiving lens 111 between the pair of retaining plates 112 (fixing step). In this fixing step, as shown in Figures 6 and 7, multiple light-receiving lenses (light-receiving lenses 130) attached to the other of the pair of retaining plates 112 (retaining plate 112B) are inserted between multiple light-receiving lenses (light-receiving lenses 120) attached to one of the pair of retaining plates 112 (retaining plate 112A). In this state, the inclined surfaces 111C of adjacent light-receiving lenses 111 (light-receiving lenses 120 and light-receiving lenses 130) in the X direction face each other.

[0081] The width in the Y direction (the distance between the first surface 111A and the second surface 11B) of each light-receiving lens 111 is the same. Therefore, by integrally clamping multiple light-receiving lenses 111 with a pair of retaining plates 112, the first surface 111A of each light-receiving lens 111 can be brought into contact with one of the pair of retaining plates 112 (light-receiving lens 120 with retaining plate 112A, and light-receiving lens 130 with retaining plate 112B), and the second surface 111B of each light-receiving lens 111 can be brought into contact with the other of the pair of retaining plates 112 (light-receiving lens 120 with retaining plate 112B, and light-receiving lens 130 with retaining plate 112A).

[0082] In this embodiment, the light-receiving lens array 11 comprises a plurality of aperture members 113. Each aperture member 113 is associated one-to-one with each light-receiving lens 111 and is spaced apart from each light-receiving lens 111 in the optical axis direction. Light from the illuminated object passes through each light-receiving lens 111, then passes through the opening 113A formed in the corresponding aperture member 113, and is guided to the light-receiving element array 12.

[0083] As shown in Figure 8A, the aperture 113A formed in the aperture member 113 penetrates the aperture member 113 in the optical axis direction and is formed in a frustoconical shape that tapers from the light-receiving lens 111 side toward the light-receiving element array 12 side. By aligning the position of the tapered side of the aperture 113A in the Z direction (optical axis direction) with the image-side focal point of the light-receiving lens 111, the aperture member 113 may constitute a telecentric optical system together with a plurality of light-receiving lenses 111. In this case, it is preferable that the apex angle of the frustoconical aperture 113A be slightly larger than the aperture angle of the light-receiving lens 111. This effectively reduces stray light without vignetting the image formed by the light-receiving lens 111.

[0084] In this example, as shown in Figure 8A, the aperture member 113 has a light-shielding wall (second light-shielding portion) 113B formed thereon that blocks a part of the opening 113A to prevent stray light from entering. In this example, by blocking one half of the frustoconical opening 113A in the Y direction (the portion through which stray light passes), a semi-frustoconical opening 113A having a semi-circular surface and a flat surface is formed. The flat surface constituting the light-shielding wall 113B has a recess 113C that extends along the optical axis direction. The recess 113C may be semi-cylindrical as shown in Figure 8A.

[0085] The width of each aperture member 113 in the Y direction coincides with the distance between the first surface 111A and the second surface 111B of each light-receiving lens 111. In other words, the width of each aperture member 113 in the Y direction coincides with the width of each light-receiving lens 111 in the Y direction. Therefore, when multiple light-receiving lenses 111 are integrally clamped by a pair of retaining plates 112, both Y-direction end faces of each aperture member 113 come into contact with the pair of retaining plates 112.

[0086] In this embodiment, the light-receiving lens 120 has its first surface 111A bonded to the retaining plate 112A and its second surface 111B bonded to the retaining plate 112B. Similarly, the light-receiving lens 130 has its first surface 111A bonded to the retaining plate 112B and its second surface 111B bonded to the retaining plate 112A. Likewise, each aperture member 113 has one surface in the Y direction bonded to one retaining plate 112A and the other surface in the Y direction bonded to the other retaining plate 112B. Bonding between each member can be done using general-purpose adhesive or double-sided tape. However, each aperture member 113 is not a separate member from the pair of retaining plates 112, but may be integrally formed with either of the retaining plates 112.

[0087] Each light-receiving lens 111 does not need to be glued to a pair of retaining plates 112, as long as it is in contact with the respective plate. For example, protrusions may be formed on parts of the first surface 111A and the second surface 111B of the light-receiving lens 111, corresponding recesses may be formed on the pair of retaining plates 112, and the pair of retaining plates 112 may be fixed to each other with a fastener while the protrusions are fitted into the recesses, thereby clamping each light-receiving lens 111 in the Y direction with the pair of retaining plates 112.

[0088] It is preferable that each light-receiving lens 111 is arranged so as not to come into contact with one another. That is, multiple light-receiving lenses 111 may be arranged with space between them so that the inclined surfaces 111C of adjacent light-receiving lenses 111 in the X direction do not come into contact with each other. In this case, it is preferable that an elastic member having light-shielding and low reflectivity is provided in the space. Examples of elastic members include urethane, but are not limited to this, and an elastic member may be formed between each light-receiving lens 111 by filling with an elastic adhesive or the like.

[0089] Figure 8B is a perspective view showing a modified example of the aperture member 113 according to the second embodiment. In the example of Figure 8A, the aperture member 113 is made of a rectangular prism-shaped member, and a frustoconical opening 113A is formed so as to penetrate the member. In contrast, in the example of Figure 8B, the aperture member 113 is made of a rectangular frame, and two openings 113D and 113E are formed in the member so as to face each other. That is, the aperture member 113 in Figure 8B is a hollow member, and light incident from opening 113D passes through the internal space within the aperture member 113 and exits from opening 113E.

[0090] Specifically, the aperture member 113 in Figure 8B has an upper plate and a lower plate extending horizontally so as to face each other in the vertical direction, and a pair of side plates extending vertically so as to connect the ends of the upper plate and the lower plate, and has a rectangular frame shape when viewed horizontally. The upper plate and the lower plate are arranged parallel to each other with a gap between them, and an opening 113D is formed in the upper plate and an opening 113E is formed in the lower plate. As a result, the openings 113D and 113E are formed to face each other with a gap between them.

[0091] The aperture 113E is positioned such that its position in the Z direction (along the optical axis) coincides with the image-side focal point of the light-receiving lens 111. This allows the aperture member 113 to form a telecentric optical system together with the multiple light-receiving lenses 111. As shown in Figure 8B, the aperture member 113 has a light-shielding wall (second light-shielding portion) 113B that blocks a portion of the aperture 113D to prevent stray light from entering. In this example, by blocking one half of the circular aperture in the Y direction (the portion through which stray light passes), a semicircular aperture 113D having a semicircular surface and a flat surface is formed. The flat surface constituting the light-shielding wall 113B may have a semicircular recess extending along the optical axis, similar to the example in Figure 8A. The aperture 113E is a smaller circular pinhole than the aperture 113D, and light that has passed through the aperture 113D enters it. In this case, it is preferable that the apex angle of the frustoconical shape virtually formed by apertures 113D and 113E be slightly larger than the aperture angle of the light-receiving lens 111. This effectively reduces stray light without vignetting the image formed by the light-receiving lens 111.

[0092] As shown in the example in Figure 10A or Figure 10B described later, if the optical axis of each light-receiving lens 111 is offset in the Y direction with respect to the light-receiving element array 12 (reading line L), the light-shielding wall 113B can effectively shield stray light emitted from adjacent light-receiving lenses 111 and directed toward the aperture 113E along a direction inclined in the Y direction with respect to the Z direction (directions perpendicular to the X and Y directions). In this case, it is not necessary to provide a partition plate between adjacent light-receiving lenses 111 and aperture members 113. It is also possible to omit the side plates of the aperture member 113 and construct the aperture member 113 with separate top and bottom plates, but if the aperture member 113 is formed into a frame as shown in Figure 8B, the aperture member 113 becomes an integrated structure, making it easier to handle.

[0093] Figure 9 is a perspective view illustrating a method for manufacturing a light-receiving lens array 11 according to a second embodiment. When manufacturing this light-receiving lens array 11, the holding plate 112 is placed on the mounting base 200, and each light-receiving lens 111 and each aperture member 113 are attached to the holding plate 112 (first lens mounting step and second lens mounting step).

[0094] The mounting base 200 is equipped with a first positioning section 201 and a pressing mechanism 202. The first positioning section 201 is composed of a plurality of protrusions, and the retaining plate 112 can be positioned by bringing the side edge of the retaining plate 112 into contact with the side surface of the first positioning section 201. With the retaining plate 112 positioned, the retaining plate 112 is pressed by the pressing mechanism 202, thereby fixing the retaining plate 112 to the mounting base 200. In this example, a pair of pressing mechanisms 202 are provided, which can press both ends of the retaining plate 112 in the longitudinal direction. However, the first positioning section 201 is not limited to being composed of protrusions, but may also be composed of recesses, for example.

[0095] In the first and second lens mounting steps, a plurality of light-receiving lenses 111 and aperture members 113 are attached to a pair of retaining plates 112 using an optical axis alignment jig 300. The optical axis alignment jig 300 is a jig for positioning the light-receiving lenses 111 and aperture members 113 in predetermined positions and aligning their optical axes.

[0096] The mounting base 200 has a second positioning section 203 for positioning the optical axis alignment jig 300. The second positioning section 203 is composed of multiple protrusions. Specifically, multiple pairs of protrusions, each corresponding to a pair of light-receiving lenses 111 and aperture members 113, are arranged in a row along the X direction. The spacing (pitch) in the X direction between the multiple pairs of protrusions matches the spacing (pitch) in the X direction when each light-receiving lens 111 and each aperture member 113 is attached to the retaining plate 112. However, the second positioning section 203 is not limited to being composed of protrusions; for example, it may be composed of recesses.

[0097] The optical axis alignment jig 300 is a plate-shaped member and is used while placed on a retaining plate 112 attached to a mounting base 200. The optical axis alignment jig 300 has a first through hole 301, a second through hole 302, and a third through hole 303 formed therein.

[0098] The first through-hole 301 is a hole for inserting the light-receiving lens 111 and has a shape that abuts against the positioning portion of the light-receiving lens 111 for positioning. The second through-hole 302 is a hole for inserting the aperture member 113 and has a shape that abuts against the positioning portion of the aperture member 113 for positioning. The third through-hole 303 has a shape that corresponds to a pair of protrusions that constitute the second positioning portion 203, and a pair of third through-holes 303 are formed that are spaced at the same interval as the pair of protrusions.

[0099] When manufacturing the light-receiving lens array 11, the optical axis alignment jig 300 is placed on the retaining plate 112 while the retaining plate 112 is fixed to the mounting base 200 by the pressing mechanism 202. At this time, the multiple pairs of protrusions constituting the second positioning section 203 are sequentially inserted, one pair at a time, into the pair of third through holes 303 of the optical axis alignment jig 300.

[0100] Then, with each pair of projections inserted into a pair of third through-holes 303 of the optical axis alignment jig 300, the light-receiving lens 111 is inserted and positioned in the first through-hole 301 and attached to the retaining plate 112, and the aperture member 113 is inserted and positioned in the second through-hole 302 and attached to the retaining plate 112. At this time, the light-receiving lens 111 is inserted into the first through-hole 301 with adhesive applied to the contact surface with the retaining plate 112. Similarly, the aperture member 113 is inserted into the second through-hole 302 with adhesive applied to the contact surface with the retaining plate 112. Alternatively, if a retaining plate 112 is prepared with adhesive or double-sided tape already applied to one side, the work of applying adhesive to the light-receiving lens 111 and aperture member 113 can be omitted.

[0101] In this way, the light-receiving lenses 111 and aperture members 113 can be attached to the holding plate 112 at positions corresponding to each pair of protrusions constituting the second positioning section 203. As a result, as shown in Figure 7, multiple light-receiving lenses 111 and multiple aperture members 113 are attached to each holding plate 112, skipping one in the X direction.

[0102] 4. Positional Relationship between Light-Receiving Lens and Light-Receiving Element Array Figures 10A and 10B are schematic diagrams illustrating the positional relationship between the light-receiving lens 111 and the light-receiving element array 12. Figure 10A shows the case of a trapezoidal light-receiving lens 111 according to the second embodiment shown in Figures 6 and 7. On the other hand, Figure 10B shows the case of a modified light-receiving lens 111.

[0103] Figures 10A and 10B describe a layout in which multiple light-receiving lenses 111 are arranged in a single row along the X direction, and light-receiving element arrays 12 are arranged in a staggered pattern in two rows. That is, in Figures 10A and 10B, multiple light-receiving element arrays 12 extending along the X direction are arranged in a staggered pattern on two rows of reading lines L. Each light-receiving element array 12 is equipped with multiple light-receiving elements arranged in a line along its longitudinal direction (X direction). The multiple light-receiving elements constitute multiple light-receiving element arrays 12 that extend along the main scanning direction, corresponding to the multiple openings of the aperture member 113. Light that passes through each light-receiving lens 111 and through the openings of the aperture member 113 is received by the multiple light-receiving elements provided in the light-receiving element array 12 corresponding to each light-receiving lens 111. The optical axis of each light-receiving lens 111 is positioned midway between the two rows of reading lines L. In other words, the optical axis of each light-receiving lens 111 is located on the center line between the two rows of reading lines L.

[0104] In Figure 10A, the photodetector arrays 12 are positioned opposite each other at a location offset to the upper base side (shorter side) of each trapezoidal photodetector lens 111. The ends of each photodetector array 12 in the X direction overlap each other in the Y direction. However, the configuration is not limited to the ends of each photodetector array 12 overlapping in the Y direction; the photodetector arrays 12 may be arranged in a staggered pattern within a range where they do not overlap in the Y direction. Each photodetector lens 111 has a shape in which the width W1 in the Y direction is smaller than the width W2 in the X direction.

[0105] In Figure 10B, each light-receiving lens 111, which has a rectangular convex or concave portion formed at both ends in the X direction, is arranged in a single row along the X direction. Each light-receiving lens 111 is arranged so that the convex or concave portions of adjacent light-receiving lenses 111 interlock with each other. Each light-receiving lens 111 has a shape in which the width W1 in the Y direction is smaller than the width W2 in the X direction.

[0106] 5. Specific Examples of Stray Light Below, specific examples of stray light incident on the photodetector array 12 in a direction inclined in the X direction with respect to the Z direction will be explained using Figures 11A to 11D. Here, we will explain the case in which light that has passed through the aperture 113E of the aperture member 113 shown in Figure 8B is incident on the photodetector array 12. However, even when using an aperture member 113 with a different configuration than that shown in Figure 8B, stray light may similarly be incident on the photodetector array 12.

[0107] Figure 11A shows the case where normal light (light that is not stray light) that passes through the light-receiving lens 111, enters the aperture member 113, and is emitted from the opening 113E is received by the light-receiving element array 12. Figures 11B to 11D show the case where stray light that passes through the light-receiving lens 111, enters the aperture member 113, and is emitted from the opening 113E is received by the light-receiving element array 12.

[0108] In the example shown in Figure 11A, we will focus on the light-receiving lens 1111 located at the end, and the aperture member 1131 and light-receiving element array 121 facing the light-receiving lens 1111 in the Z direction. Light transmitted through the light-receiving lens 1111 passes through the aperture member 1131 and is emitted from the opening 113E. At this time, the normal light spreads out at a predetermined field of view angle and heads toward the light-receiving element array 121, where it is received only by the light-receiving element array 121. That is, the normal light emitted from the opening 113E is not received by another light-receiving element array 12 adjacent to the light-receiving element array 121.

[0109] In the example shown in Figure 11B, light transmitted through the light-receiving lens 1111 is reflected by the inner wall of the aperture member 1131 and exits from the opening 113E, resulting in stray light being emitted at a different angle from the normal light received by the light-receiving element array 121. This stray light is received by the light-receiving element array 122, which is adjacent to the light-receiving element array 121 in the X direction. The intrusion of such stray light into the light-receiving element array 122 becomes noise and therefore needs to be prevented.

[0110] In the example shown in Figure 11C, light transmitted through the light-receiving lens 1111 passes through an aperture member 1132 adjacent to the aperture member 1131 facing the light-receiving lens 1111 in the X direction and exits from the opening 113E, resulting in stray light being emitted at a different angle from the normal light received by the light-receiving element array 122. This stray light is received by a light-receiving element array 123 adjacent to the light-receiving element array 122 in the X direction. The intrusion of such stray light into the light-receiving element array 123 becomes noise and therefore needs to be prevented.

[0111] In the example shown in Figure 11D, light incident on the light-receiving lens 1111 passes through the adjacent light-receiving lens 1112 in the X direction, is reflected within the light-receiving lens 1112, and then exits through the aperture member 1133 adjacent to the aperture member 1132 facing the light-receiving lens 1112 in the X direction, exiting from the opening 113E. As a result, it is emitted as stray light at a different angle from the normal light received by the light-receiving element array 123. This stray light is received by the light-receiving element array 124 adjacent to the light-receiving element array 123 in the X direction. The intrusion of such stray light into the light-receiving element array 124 becomes noise and therefore needs to be prevented.

[0112] 6. Example of Light-Blocking Block In this embodiment, in order to prevent stray light as illustrated in Figures 11B to 11D, in addition to the above-described configuration, a light-blocking block (first light-blocking portion) 114 is provided between the aperture member 113 and the light-receiving element array 12. The light-blocking block 114 may be made of a material having light-blocking and low reflectivity. Preferably, at least the surface of the light-blocking block 114 that forms the optical path through which light passes is made of a light-absorbing material.

[0113] Figure 12A is a cross-sectional view of the optical line sensor equipped with the light-shielding block 114 along the XY plane. Figure 12B is a cross-sectional view of the optical line sensor equipped with the light-shielding block 114 along the XZ plane. Figure 12C is a cross-sectional view of the optical line sensor equipped with the light-shielding block 114 along the YZ plane, showing the cross-section at the installation position of the light-receiving lens 1111. Figure 12D is a cross-sectional view of the optical line sensor equipped with the light-shielding block 114 along the YZ plane, showing the cross-section at the installation position of the light-receiving lens 1112.

[0114] As shown in Figures 12A to 12D, multiple light-shielding blocks 114 are provided in correspondence with each aperture member 113 (each opening 113E), and are arranged in a staggered pattern on the two rows of reading lines L. Specifically, each light-shielding block 114 corresponding to each light-receiving element array 12 is positioned offset in the Y direction relative to each light-receiving element array 12. As a result, as shown in Figure 12A, the staggered arrangement of each light-receiving element array 12 and the staggered arrangement of each light-shielding block 114 are arranged symmetrically with respect to the center line C between the two rows of reading lines L. That is, with respect to the center line C between the two rows of reading lines L, the positions where each light-receiving element array 12 is arranged in a staggered pattern and the positions where each light-shielding block 114 is arranged in a staggered pattern are reversed.

[0115] As shown in Figure 12B, a light-shielding film 113F is provided between adjacent aperture members 113. Each light-shielding film 113F constitutes a third light-shielding portion that covers the gap between adjacent aperture members 113. Each light-shielding film 113F may extend in the Y direction from one retaining plate 112A to the other retaining plate 112B between adjacent aperture members 113. This prevents stray light from entering through the gap between adjacent aperture members 113, thereby effectively preventing stray light from entering each light-receiving element array 12. However, the third light-shielding portion is not limited to a film-like light-shielding film 113F, but can be any member that can cover the gap between adjacent aperture members 113.

[0116] As shown in Figure 12C, the light-receiving element array 121 facing the light-receiving lens 1111 and aperture member 1131 is located on one side with respect to the center line C between the two rows of reading lines L, and the light-shielding block 1141 is located on the other side with respect to the center line C between the two rows of reading lines L. Also, as shown in Figure 12D, the light-shielding block 1142 facing the light-receiving lens 1112 and aperture member 1132 is located on one side with respect to the center line C between the two rows of reading lines L, and the light-receiving element array 122 is located on the other side with respect to the center line C between the two rows of reading lines L.

[0117] As shown in Figures 12C and 12D, the light-receiving lens array 11 is held by a pair of sensor holders 115. Specifically, of the pair of plate-shaped sensor holders 115, one sensor holder 115 abuts against one of the holding plates 112 of the light-receiving lens array 11, and the other sensor holder 115 abuts against the other holding plate 112 of the light-receiving lens array 11. The light-shielding block 1141 is attached to one of the sensor holders 115, and the light-shielding block 1142 is attached to the other sensor holder 115. Alternatively, the light-shielding blocks 1141 and 1142 may be fixed in contact with only one of the sensor holders 115.

[0118] Thus, a plurality of light-shielding blocks 114 located on one side of the center line C between the two rows of reading lines L may be attached to one sensor holder 115, and a plurality of light-shielding blocks 114 located on the other side of the center line C between the two rows of reading lines L may be attached to the other sensor holder 115. However, the configuration is not limited to a configuration in which the plurality of light-shielding blocks 114 are provided separately, but may also be a configuration in which the plurality of light-shielding blocks 114 are provided integrally as a single light-shielding block (first light-shielding part).

[0119] The openings 113E formed in each aperture member 113 are located between the two rows of reading lines L when viewed from the Z direction. More specifically, the openings 113E formed in each aperture member 113 are arranged in a line along the center line C between the two rows of reading lines L.

[0120] 7.1 Example of a pair of retaining plates and a pair of sensor holders In the example shown in Figures 12A to 12D, multiple light-receiving lens arrays 11 are sandwiched between a pair of sensor holders 115. That is, rather than just one light-receiving lens array 11 being sandwiched between a pair of sensor holders 115, multiple light-receiving lens arrays 11 aligned in the X direction are sandwiched in the Y direction. Note that in Figure 12A, only one light-receiving lens array 11 and a portion of another light-receiving lens array 11 adjacent to that light-receiving lens array 11 are shown, but three or more light-receiving lens arrays 11 may be sandwiched between a pair of sensor holders 115.

[0121] In each light-receiving lens array 11, at least two light-receiving lenses 111 and at least one aperture member 113 are sandwiched in the Y direction between a pair of retaining plates 112. In the example shown in Figures 12A to 12D, three light-receiving lenses 111 and three aperture members 113 are attached to one retaining plate 112, and three light-receiving lenses 111 and three aperture members 113 are also attached to the other retaining plate 112, so that six light-receiving lenses 111 and six aperture members 113 are sandwiched between a pair of retaining plates 112.

[0122] However, the number of light-receiving lenses 111 sandwiched between a pair of retaining plates 112 is not limited to six; it may be two to five or seven or more. Similarly, the number of aperture members 113 sandwiched between a pair of retaining plates 112 is not limited to six; it may be two to five or seven or more. Furthermore, if the aperture member 113 is not individually provided for each of the multiple openings 113E, but rather multiple openings 113E are formed in a single aperture member 113, then there may be only one aperture member 113 sandwiched between a pair of retaining plates 112.

[0123] In this way, a pair of retaining plates 112, at least two light-receiving lenses 111 sandwiched between the pair of retaining plates 112, and at least one aperture member 113 constitute a single light-receiving lens array 11. By sandwiching multiple light-receiving lens arrays 11 in the Y direction with a pair of sensor holders 115, even if some of the light-receiving lenses 111 in any of the light-receiving lens arrays 11 are defective, only that light-receiving lens array 11 needs to be replaced, thus minimizing waste of parts.

[0124] Furthermore, a pair of retaining plates 112 may have a fitting portion (not shown) for connecting the pair of retaining plates 112 by fitting them together. Any fitting portion can be adopted, such as a snap-fit ​​structure in which a claw portion and a receiving portion are fitted together, or a press-fit structure in which a shaft portion is fitted into a hole.

[0125] As shown in Figures 12C and 12D, each of the pair of sensor holders 115 is formed in an L-shape, having a first plate portion 1151 facing the plurality of light-receiving lens arrays 11, and a second plate portion 1152 extending from one end of the first plate portion 1151 toward the side opposite to the plurality of light-receiving lens arrays 11. The second plate portion 1152 is formed to protrude in the Y direction from the end of the first plate portion 1151 opposite to the side on which light is incident.

[0126] However, the second plate portion 1152 may extend from one end of the first plate portion 1151 not only on the side opposite to the multiple light-receiving lens arrays 11, but also towards the multiple light-receiving lens arrays 11. In this case, the amount of protrusion of the second plate portion 1152 toward the multiple light-receiving lens arrays 11 is smaller than the amount of protrusion of the second plate portion 1152 toward the opposite side in the Y direction, and is included in the concept of "L-shape".

[0127] The light-receiving element array 12 is mounted on a light-receiving substrate 12B having an electrical circuit. Signals output from the multiple light-receiving elements included in the light-receiving element array 12 are processed in the electrical circuit of the light-receiving substrate 12B on which these light-receiving elements are mounted. The number of light-receiving substrates 12B is not limited; one light-receiving substrate 12B may be provided for a pair of sensor holders 115, or one light-receiving substrate 12B may be provided for a pair of retaining plates 112.

[0128] The light-receiving substrate 12B is mounted so as to straddle a pair of sensor holders 115 on the second plate portion 1152 side. That is, on the side opposite to the light incident side of the pair of sensor holders 115, one end of the light-receiving substrate 12B in the Y direction is attached to one sensor holder 115, and the other end is attached to the other sensor holder 115. This allows the multiple light-receiving lenses 111 and multiple aperture members 113 to be positioned between the first plate portions 1151 of the pair of sensor holders 115, and then the light-receiving substrate 12B to straddle the pair of sensor holders 115 on the second plate portion 1152 side. Therefore, the multiple light-receiving lenses 111 and multiple aperture members 113 and the multiple light-receiving elements mounted on the light-receiving substrate 12B can be accurately positioned relative to each other.

[0129] Each light-receiving lens array 11 is provided with a cover member 11A to prevent foreign matter from entering from the light-incident side. The cover member 11A is provided so as to straddle the end faces of the light-incident side of a pair of retaining plates 112. That is, on the light-incident side of the pair of retaining plates 112, one end of the cover member 11A in the Y direction is attached to the end face of one retaining plate 112 (retaining plate 112A), and the other end is attached to the end face of the other retaining plate 112 (retaining plate 112B).

[0130] The cover member 11A is preferably made of a transparent material, such as a transparent film, so as not to obstruct the incidence of light to the light-receiving lens 111. The cover member 11A is not limited to being provided for each light-receiving lens array 11, but a common cover member 11A may be provided for multiple light-receiving lens arrays 11. In this case, one cover member 11A may be provided for a pair of sensor holders 115.

[0131] Figure 13A shows one of the retaining plates 112A as viewed from the light-receiving lens 111 side along the Y direction. Figure 13B shows the other retaining plate 112B as viewed from the opposite side of the light-receiving lens 111 side along the Y direction. Each retaining plate 112A and 112B is a rectangular plate with an elongated shape along the X direction, and in this example, the lengths in the X and Y directions are the same.

[0132] Each retaining plate 112A, 112B has a plurality of positioning holes 1121 formed therein. Each positioning hole 1121 is a through hole formed by a cylindrical inner surface with a smooth surface. In this example, positioning holes 1121 are formed at both ends in the X direction of each retaining plate 112A, 112B. However, there may be three or more positioning holes 1121.

[0133] Furthermore, each retaining plate 112A, 112B has multiple fixing screw holes 1122 formed therein. Each fixing screw hole 1122 is a through hole with a screw groove formed on its cylindrical inner surface. In this example, the fixing screw holes 1122 are formed at both ends in the X direction of each retaining plate 112A, 112B, near the positioning holes 1121. However, there may be three or more fixing screw holes 1122.

[0134] Figure 14A is a cross-sectional view of the optical line sensor along the YZ plane, showing a cross-section cut at the positioning hole 1121. In Figure 14A, the light-shielding block 114 is omitted. As shown in Figure 14A, a pair of sensor holders 115 have positioning pins 1153 formed at positions corresponding to the positioning holes 1121 formed in a pair of retaining plates 112. Therefore, by inserting each positioning pin 1153 into each positioning hole 1121, the pair of retaining plates 112 can be positioned on the pair of sensor holders 115.

[0135] Each positioning pin 1153 is an example of a positioning member for positioning a pair of retaining plates 112 onto a pair of sensor holders 115. Specifically, one of the pair of retaining plates 112 (retaining plate 112A) is positioned onto one of the pair of sensor holders 115 (sensor holder 115A) by the positioning pin 1153, which acts as a first positioning member. The other of the pair of retaining plates 112 (retaining plate 112B) is positioned onto the other of the pair of sensor holders 115 (sensor holder 115B) by the positioning pin 1153, which acts as a second positioning member.

[0136] After the holding plates 112A and 112B are positioned on the sensor holders 115A and 115B as described above, the sensor holders 115A and 115B are connected to each other, so that the holding plates 112A and 112B are positioned facing each other in the Y direction, as shown in Figure 14A. By using the positioning pins 1153 for positioning, assembly work is made easy, and each light-receiving lens array 11 can be accurately positioned and fixed between the pair of sensor holders 115. This makes it possible to easily and accurately position multiple light-receiving lenses 111 and multiple aperture members 113.

[0137] However, the first positioning member and the second positioning member are not limited to positioning pins 1153 formed on a pair of sensor holders 115. For example, positioning pins may be formed on a pair of retaining plates 112, and these positioning pins may be inserted into positioning holes formed on a pair of sensor holders 115. Alternatively, the pair of retaining plates 112 may be positioned on the pair of sensor holders 115 by members other than positioning pins.

[0138] Figure 14B is a cross-sectional view of the optical line sensor along the YZ plane, showing a cross-section cut at the position of the fixing screw hole 1122. In Figure 14B, the light-shielding block 114 is omitted. As shown in Figure 14B, each of the pair of sensor holders 115 has through holes 1154 formed at positions corresponding to the fixing screw holes 1122 formed in the pair of retaining plates 112. The inner diameter of each through hole 1154 is larger than the inner diameter of the fixing screw hole 1122. A fixing screw 1155 is inserted into each through hole 1154 from the side opposite to the fixing screw hole 1122, and the tip of the fixing screw 1155 that has passed through each through hole 1154 is screwed into the fixing screw hole 1122.

[0139] Each fixing screw 1155 is a component for fixing a pair of retaining plates 112 to a pair of sensor holders 115. Specifically, a fixing screw 1155, which is a first fixing screw, is inserted through a through hole 1154 formed in one of the pair of sensor holders 115 (sensor holder 115A) and screwed into a fixing screw hole 1122 formed in one of the pair of retaining plates 112 (retaining plate 112A), thereby fixing one of the pair of retaining plates 112 (retaining plate 112A) to one of the pair of sensor holders 115 (sensor holder 115A). Furthermore, a fixing screw 1155, which serves as a second fixing screw, is inserted through a through hole 1154 formed in the other of the pair of sensor holders 115 (sensor holder 115B), and screwed into a fixing screw hole 1122 formed in the other of the pair of retaining plates 112 (retaining plate 112B), thereby fixing the other of the pair of retaining plates 112 (retaining plate 112B) to the other of the pair of sensor holders 115 (sensor holder 115B).

[0140] Next, referring again to Figures 13A and 13B, the method for fixing and adjusting the light-receiving lenses 111 will be described. Each light-receiving lens 111 is fixed to each retaining plate 112A, 112B using adhesive, and each retaining plate 112A, 112B has a plurality of injection holes 1123 for injecting the adhesive. At least one injection hole 1123 is formed for each light-receiving lens 111 at a position facing each light-receiving lens 111 on the retaining plate 112A, 112B to which each light-receiving lens 111 is attached.

[0141] In the examples shown in Figures 13A and 13B, four injection holes 1123 are formed for each light-receiving lens 111 at positions opposite to each light-receiving lens 111 on the retaining plates 112A and 112B to which each light-receiving lens 111 is attached. Specifically, two injection holes 1123 are formed at positions opposite to both ends of each light-receiving lens 111 in the X direction, so as to be symmetrical in the X direction with respect to the center of each light-receiving lens 111 in the X direction. The four injection holes 1123 are arranged in the X direction. However, the configuration may be one injection hole 1123 formed for each light-receiving lens 111, or two, three, or five or more injection holes 1123 may be formed.

[0142] Adhesive is injected into each injection hole 1123 formed in each retaining plate 112A and 112B. The adhesive injected into each injection hole 1123 hardens with a portion of it in contact with each light-receiving lens 111. The adhesive force of this adhesive fixes each retaining plate 112A and 112B to each light-receiving lens 111. The material of the adhesive is not particularly limited, but an adhesive mainly composed of synthetic resin such as epoxy resin can be used.

[0143] In addition to the injection holes 1123, at least one first adjustment screw hole 1124 is formed in the holding plates 112A and 112B to which each light-receiving lens 111 is attached, at a position facing each light-receiving lens 111. In the example shown in Figures 13A and 13B, two first adjustment screw holes 1124 are formed for each light-receiving lens 111. Specifically, one first adjustment screw hole 1124 is formed at each of the positions facing both ends of each light-receiving lens 111 in the Z direction. The two first adjustment screw holes 1124 are formed to be aligned in the Z direction. However, the configuration may be one first adjustment screw hole 1124 formed for each light-receiving lens 111, or three or more may be formed.

[0144] A first adjustment screw 1125 is screwed into each first adjustment screw hole 1124 from the opposite side of each light-receiving lens 111 (the back side of the paper in Figure 13A, and the front side of the paper in Figure 13B) relative to each retaining plate 112A, 112B. The tip of each first adjustment screw 1125 abuts against each light-receiving lens 111, but is not screwed into each light-receiving lens 111. Therefore, by adjusting the amount of protrusion of each first adjustment screw 1125 from each retaining plate 112A, 112B, the tip of each first adjustment screw 1125 presses against each light-receiving lens 111, and the angle of each light-receiving lens 111 relative to each retaining plate 112A, 112B can be adjusted.

[0145] If multiple first adjustment screws 1125 are provided for a single light-receiving lens 111, the angle of each light-receiving lens 111 can be finely adjusted using each first adjustment screw 1125. For example, as shown in the examples in Figures 13A and 13B, if two first adjustment screws 1125 are provided for a single light-receiving lens 111 so as to be aligned in the Z direction, the angle of each light-receiving lens 111 in the Y direction relative to the Z direction can be finely adjusted by adjusting the amount of protrusion of each first adjustment screw 1125 relative to each retaining plate 112A, 112B.

[0146] Figure 15 is a cross-sectional view of the optical line sensor along the YZ plane, showing a cross-section of one end of a pair of sensor holders 115 in the X direction. As shown in Figure 15, a spacer 116 is provided at one end of the pair of sensor holders 115 in the X direction. The spacer 116 is a member whose end faces in the Y direction extend parallel to the X and Z directions, and the width of the spacer 116 in the Y direction matches the width of the light-receiving lens array 11 in the Y direction.

[0147] One end face of the spacer 116 in the Y direction abuts against the first plate portion 1151 of one sensor holder 115A, and the other end face of the spacer 116 in the Y direction abuts against the first plate portion 1151 of the other sensor holder 115B. A through hole 1156 extending in the Y direction is formed in the first plate portion 1151 of each sensor holder 115A and 115B at a position opposite to the spacer 116 in the Y direction. In the example of Figure 15, two through holes 1156 are formed at one end in the X direction of each sensor holder 115A and 115B. The two through holes 1156 are formed at both ends in the Z direction of the first plate portion 1151 of each sensor holder 115A and 115B.

[0148] Furthermore, the spacer 116 has fixing screw holes 1161 formed at positions opposite to each through hole 1156. Fixing screws 1157 are inserted through each through hole 1156 of each sensor holder 115A, 115B from the opposite side of the spacer 116, and the tips of the fixing screws 1157 are screwed into the fixing screw holes 1161 of the spacer 116 that are opposite to each through hole 1156. As a result, the spacer 116 is placed between a pair of sensor holders 115, and the multiple light-receiving lens arrays 11 are fixed in a state where they are sandwiched in the Y direction by the pair of sensor holders 115. In this state, the distance between the pair of sensor holders 115 is kept constant by the spacer 116, so that the multiple light-receiving lenses 111 and the multiple aperture members 113 can be positioned even more accurately.

[0149] Figure 15 only describes the structure of one end of a pair of sensor holders 115 in the X direction, but the other end in the X direction has a similar structure, and a spacer 116 is provided between the pair of sensor holders 115. However, the number of fixing screws 1157 connecting each sensor holder 115A, 115B and the spacer 116 is not limited to the number of fixing screws 1157 shown in Figure 15. In addition, each sensor holder 115A, 115B and the spacer 116 may be connected by fixing members other than the fixing screws 1157.

[0150] As shown in Figure 15, each sensor holder 115A, 115B has at least one second adjustment screw hole 1158 formed in the first plate portion 1151 at a position facing the pair of retaining plates 112 of each light-receiving lens array 11. In the example of Figure 15, two second adjustment screw holes 1158 are formed at a position facing one retaining plate 112A of each light-receiving lens array 11, and two second adjustment screw holes 1158 are formed at a position facing the other retaining plate 112B of each light-receiving lens array 11.

[0151] Two second adjustment screw holes 1158 facing one retaining plate 112A of each light-receiving lens array 11 are positioned opposite both ends of the retaining plate 112A in the Z direction and are aligned in the Z direction. Similarly, two second adjustment screw holes 1158 facing the other retaining plate 112B of each light-receiving lens array 11 are positioned opposite both ends of the retaining plate 112B in the Z direction and are aligned in the Z direction. However, the configuration may be one second adjustment screw hole 1158 per retaining plate 112, or three or more second adjustment screw holes 1158 may be formed.

[0152] A second adjustment screw 1159 is screwed into each second adjustment screw hole 1158 from the opposite side of the light-receiving lens array 11 to the first plate portion 1151 of each sensor holder 115A, 115B. The tip of each second adjustment screw 1159 abuts against each retaining plate 112A, 112B, but is not screwed into each retaining plate 112A, 112B. Therefore, by adjusting the amount of protrusion of each second adjustment screw 1159 from the first plate portion 1151 of each sensor holder 115A, 115B, the tip of each second adjustment screw 1159 presses against each retaining plate 112A, 112B, and the angle of each retaining plate 112A, 112B relative to each sensor holder 115A, 115B can be adjusted.

[0153] If multiple second adjustment screws 1159 are provided for a single retaining plate 112, the angle of each retaining plate 112A, 112B can be finely adjusted using each second adjustment screw 1159. For example, as shown in the example in Figure 15, if two second adjustment screws 1159 are provided for a single retaining plate 112 so as to be aligned in the Z direction, the angle of each retaining plate 112A, 112B in the Y direction relative to the Z direction can be finely adjusted by adjusting the amount of protrusion of each second adjustment screw 1159 relative to the first plate portion 1151 of each sensor holder 115A, 115B. This makes it possible to easily and accurately adjust the optical axis of the light-receiving lens 111 even after fixing each light-receiving lens array 11 between a pair of sensor holders 115.

[0154] 8. Extending the Optical Line Sensor Figure 16 is a schematic plan view showing an example of an extended optical line sensor. In this example, multiple pairs of sensor holders 115 are arranged in a line in the X direction. That is, multiple pairs of sensor holders 115, which sandwich multiple light-receiving lens arrays 11 in the Y direction, are arranged in a straight line along the X direction. This allows for an expansion of the reading range in the X direction.

[0155] In the example shown in Figure 16, spacers 116 are provided at both ends of each sensor holder 115 in the X direction. However, the configuration is not limited to this, and a configuration in which spacers 116 are not placed between adjacent light-receiving lens arrays 11 may be made by omitting the spacers 116 between adjacent sensor holders 115 in the X direction. In this case, adjacent sensor holders 115 in the X direction may be connected by members other than spacers 116.

[0156] 9. Specific Examples of Preventing Stray Light Intrusion Below, specific examples of preventing stray light from entering areas other than the photodetector array 121 using the light-shielding block 114 will be described. Here, we will describe the case where stray light entering areas other than the photodetector array 121, corresponding to Figures 11B to 11D, is prevented, but stray light directed toward the photodetector array 121 can also be prevented by the light-shielding block 114 in other ways.

[0157] Figure 17A shows the case where stray light entering the light-receiving element array 122 is prevented, corresponding to Figure 11B. Figure 17B is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1111 in Figure 17A, showing the case where stray light directed toward the light-receiving element array 122 is blocked by the light-shielding block 1141. Figure 17C is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1111 in Figure 17A, showing the case where normal light is incident on the light-receiving element array 121.

[0158] As shown in Figures 17A and 17B, when light transmitted through the light-receiving lens 1111 is reflected by the inner wall of the aperture member 1131 and emitted from the opening 113E, the stray light that heads toward the light-receiving element array 122 travels along directions that are inclined in the X and Y directions with respect to the Z direction. At this time, since the light-shielding block 1141 is located on the straight line connecting the opening 113E of the aperture member 1131 and the light-receiving element array 122, the stray light is blocked by the light-shielding block 1141.

[0159] In this way, light passing through the opening 113E of an aperture member 1131 adjacent to the opening 113E of an aperture member 1132 corresponding to the light-receiving element array 122 is blocked by a light-shielding block 1141 provided in correspondence with the opening 113E of the adjacent aperture member 1131. As a result, the intrusion of light that has passed through the opening 113E of the adjacent aperture member 1131 into the light-receiving element array 122 is prevented.

[0160] On the other hand, as shown in Figure 17C, the normal light that passes through the light-receiving lens 1111 and enters the aperture member 1131 and exits from the opening 113E travels along a direction that is inclined in the Y direction with respect to the Z direction. At this time, since the light-shielding block 1141 is positioned offset in the Y direction relative to the light-receiving element array 121, the normal light is received by the light-receiving element array 121 without being blocked by the light-shielding block 1141.

[0161] Figure 18A shows the case where stray light corresponding to Figure 11C is prevented from entering the light-receiving element array 123. Figure 18B is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1112 in Figure 18A, showing the case where stray light directed toward the light-receiving element array 123 is blocked by the light-shielding block 1142. Figure 18C is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1112 in Figure 18A, showing the case where normal light is incident on the light-receiving element array 122.

[0162] As shown in Figures 18A and 18B, light transmitted through the light-receiving lens 1111 passes through the aperture member 1132 adjacent to the aperture member 1131 facing the light-receiving lens 1111 in the X direction and exits from the opening 113E. As a result, stray light heading towards the light-receiving element array 123 travels along directions that are inclined in the X and Y directions with respect to the Z direction. At this time, since the light-shielding block 1142 is located on the straight line connecting the opening 113E of the aperture member 1132 and the light-receiving element array 123, the stray light is blocked by the light-shielding block 1142.

[0163] In this way, light passing through the opening 113E of an aperture member 1132 adjacent to the opening 113E of an aperture member 1133 corresponding to the light-receiving element array 123 is blocked by a light-shielding block 1142 provided in correspondence with the opening 113E of the adjacent aperture member 1132. As a result, the intrusion of light passing through the opening 113E of the adjacent aperture member 1132 into the light-receiving element array 123 is prevented.

[0164] On the other hand, as shown in Figure 18C, the normal light that passes through the light-receiving lens 1112 and enters the aperture member 1132 and exits from the opening 113E travels along a direction that is inclined in the Y direction with respect to the Z direction. At this time, since the light-shielding block 1142 is positioned offset in the Y direction relative to the light-receiving element array 122, the normal light is received by the light-receiving element array 122 without being blocked by the light-shielding block 1142.

[0165] Figure 19A shows the case where stray light corresponding to Figure 11D is prevented from entering the light-receiving element array 124. Figure 19B is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1113 in Figure 19A, showing the case where stray light directed toward the light-receiving element array 124 is blocked by the light-shielding block 1143. Figure 19C is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1113 in Figure 19A, showing the case where normal light is incident on the light-receiving element array 123.

[0166] As shown in Figures 19A and 19B, light incident on the light-receiving lens 1111 passes through the adjacent light-receiving lens 1112 in the X direction, is reflected within the light-receiving lens 1112, and then exits through the aperture member 1133 adjacent in the X direction to the aperture member 1132 facing the light-receiving lens 1112, exiting from the opening 113E. As a result, stray light heading towards the light-receiving element array 124 travels along directions that are inclined in the X and Y directions with respect to the Z direction. At this time, since the light-shielding block 1143 is located on the straight line connecting the opening 113E of the aperture member 1133 and the light-receiving element array 124, the stray light is blocked by the light-shielding block 1143.

[0167] In this way, light passing through the opening 113E of an aperture member 1133 adjacent to the opening 113E of an aperture member 1134 corresponding to the light-receiving element array 124 is blocked by a light-shielding block 1143 provided in correspondence with the opening 113E of the adjacent aperture member 1133. As a result, the intrusion of light passing through the opening 113E of the adjacent aperture member 1133 into the light-receiving element array 124 is prevented.

[0168] On the other hand, as shown in Figure 19C, the normal light that passes through the light-receiving lens 1113 and enters the aperture member 1133 and exits from the opening 113E travels along a direction that is inclined in the Y direction with respect to the Z direction. At this time, since the light-shielding block 1143 is positioned offset in the Y direction relative to the light-receiving element array 123, the normal light is received by the light-receiving element array 123 without being blocked by the light-shielding block 1143.

[0169] 10. Modified Examples of the Light-Blocking Block Figure 20A is a diagram illustrating a modified example of the light-blocking block 114. Figure 20B is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1111 in Figure 20A, showing the case where normal light is incident on the light-receiving element array 121. Figure 20C is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1112 adjacent to the light-receiving lens 1111 in Figure 20A, showing the case where normal light is incident on the light-receiving element array 122.

[0170] As shown in Figure 20A, the width of the light-shielding block 114 in the X direction is less than or equal to the width W3 of the light-receiving element array 12. Also, the width of the light-shielding block 114 in the Z direction is less than or equal to the distance D between the aperture members 113 and the light-receiving element array 12 that are facing each other in the Z direction. It is preferable that the light-shielding block 114 does not come into contact with the aperture members 113 and the light-receiving element array 12.

[0171] The light-shielding block 114 has a through-hole 114A that extends along the optical path of light that passes through the opening 113E of the aperture member 113 and enters the light-receiving element array 12 corresponding to the opening 113E. As shown in Figure 20B, normal light passing through the opening 113E of the aperture member 1131 enters the light-receiving element array 121 through the through-hole 114A formed in the light-shielding block 1141. At this time, stray light emitted from the opening 113E of the aperture member 1131 is emitted in a direction different from the direction in which the through-hole 114A extends, and is therefore absorbed when it hits the light-shielding block 1141 (the inner surface of the through-hole 114A).

[0172] Furthermore, as shown in Figure 20C, the normal light passing through the opening 113E of the aperture member 1132 enters the light-receiving element array 122 through the through hole 114A formed in the light-shielding block 1142. At this time, the stray light emitted from the opening 113E of the aperture member 1132 is emitted in a direction different from the direction in which the through hole 114A extends, and is therefore absorbed upon contact with the light-shielding block 1142 (the inner circumferential surface of the through hole 114A).

[0173] Thus, each through-hole 114A is formed in a tapered shape that is inclined in the Y direction with respect to the Z direction. Although only the configurations of the light-shielding blocks 1141 and 1142 have been described in Figures 20B and 20C, for the other light-shielding blocks 114, it is sufficient if light-shielding blocks 114 having the same configuration as in Figure 20B and light-shielding blocks 114 having the same configuration as in Figure 20C are arranged alternately along the X direction.

[0174] Figures 20D and 20E illustrate a modified example of the through-hole 114A of the light-shielding block 114 shown in Figures 20B and 20C. In this example, the through-hole 114B formed in each light-shielding block 114 extends in a stepped manner along the direction in which the through-hole 114B is inclined (the direction in which the through-hole 114B extends). That is, each through-hole 114B alternately has a portion extending in the Z direction (vertical portion) and a portion extending in the X direction (horizontal portion), and the connection between the vertical portion and the horizontal portion is a stepped surface.

[0175] As shown in Figure 20D, normal light passing through the opening 113E of the aperture member 1131 enters the light-receiving element array 121 through the through hole 114B formed in the light-shielding block 1141. At this time, stray light emitted from the opening 113E of the aperture member 1131 is emitted in a direction different from the direction in which the through hole 114B extends, and is therefore absorbed upon contact with the light-shielding block 1141 (the inner circumferential surface of the through hole 114B).

[0176] Furthermore, as shown in Figure 20E, normal light passing through the opening 113E of the aperture member 1132 enters the light-receiving element array 122 through the through hole 114B formed in the light-shielding block 1142. At this time, stray light emitted from the opening 113E of the aperture member 1132 is emitted in a direction different from the direction in which the through hole 114B extends, and is therefore absorbed upon contact with the light-shielding block 1142 (the inner circumferential surface of the through hole 114B).

[0177] Although Figures 20D and 20E only describe the configurations of light-shielding blocks 1141 and 1142, for the other light-shielding blocks 114, it is sufficient if light-shielding blocks 114 having the same configuration as in Figure 20D and light-shielding blocks 114 having the same configuration as in Figure 20E are arranged alternately along the X direction.

[0178] Figure 21A is a diagram illustrating further modifications of the light-shielding block 114. Figure 21B is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1111 in Figure 21A, showing the case when normal light is incident on the light-receiving element array 121. Figure 21C is a cross-sectional view along the YZ plane at the installation position of the light-receiving lens 1112 adjacent to the light-receiving lens 1111 in Figure 21A, showing the case when normal light is incident on the light-receiving element array 122.

[0179] As shown in Figure 21A, the width of the light-shielding block 114 in the X direction is greater than or equal to the field of view width W4 at the installation position of the light-shielding block 114 in the opening 113E of the aperture member 113 to which the light-shielding block 114 is attached. That is, it is preferable that the width of the light-shielding block 114 in the X direction is greater than or equal to the field of view width W4 at the installation position of the light-shielding block 114 in the opening 113E of the aperture member 113 to which the light-shielding block 114 is attached (see Figure 21A), and less than or equal to the width W3 of the light-receiving element array 12 (see Figure 20A).

[0180] As shown in Figure 21B, the normal light passing through the opening 113E of the aperture member 1131 is received by the light-receiving element array 121 without being blocked by the light-shielding block 1141. Also, as shown in Figure 21C, the normal light passing through the opening 113E of the aperture member 1132 is received by the light-receiving element array 122 without being blocked by the light-shielding block 1142.

[0181] Although Figures 21B and 21C only describe the configurations of light-shielding blocks 1141 and 1142, for the other light-shielding blocks 114, it is sufficient if light-shielding blocks 114 having the same configuration as in Figure 21B and light-shielding blocks 114 having the same configuration as in Figure 21C are arranged alternately along the X direction.

[0182] 10 Light source unit 11 Light-receiving lens array 11A Cover member 12 Light-receiving element array 12B Light-receiving substrate 111 Light-receiving lens 112 Holding plate 113 Aperture member 113B Light-shielding wall 113E Opening 113F Light-shielding film 114 Light-shielding block 114A Through hole 114B Through hole 115 Sensor holder 116 Spacer 1121 Positioning hole 1122 Fixing screw hole 1123 Injection hole 1124 First adjustment screw hole 1125 First adjustment screw 1151 First plate part 1152 Second plate part 1153 Positioning pin 1154 Through hole 1155 Fixing screw 1156 Through hole 1158 Second adjustment screw hole 1159 Second adjustment screw 1161 screw holes for fixing

Claims

1. An optical line sensor for reading an object that is moved relative to it along a sub-scanning direction using a reading line extending in the main scanning direction, comprising: a plurality of light-receiving lenses arranged in a line along the main scanning direction and transmitting light from an illuminated object; an aperture member having a plurality of openings through which the light transmitted by the plurality of light-receiving lenses passes; and a plurality of light-receiving elements arranged in a line along the main scanning direction and receiving the light that has passed through the plurality of openings, wherein the plurality of light-receiving elements constitute a plurality of light-receiving element arrays that each extends along the main scanning direction corresponding to the plurality of openings, the plurality of light-receiving element arrays are arranged in a staggered pattern on two rows of the reading line, and a first light-shielding portion is provided between the aperture member and the plurality of light-receiving element arrays to prevent light that has passed through an opening adjacent to the opening corresponding to each light-receiving element array from entering each light-receiving element array.

2. The optical line sensor according to claim 1, wherein the first light-shielding portions are provided in multiple locations corresponding to the plurality of apertures, and light passing through an aperture adjacent to an aperture corresponding to each light-receiving element array is blocked by the first light-shielding portion provided in relation to the adjacent aperture.

3. The optical line sensor according to claim 2, wherein the plurality of first light-shielding portions are arranged in a staggered pattern on two rows of reading lines.

4. The optical line sensor according to claim 2, wherein the width of the first light-shielding portion in the main scanning direction is greater than or equal to the field of view width at the installation position of the first light-shielding portion in the adjacent aperture to which the first light-shielding portion is associated, and less than or equal to the width of the light-receiving element array.

5. The optical line sensor according to claim 1, wherein the first light-shielding portion has a through-hole that extends along the optical path of light passing through the opening and incident on the light-receiving element array corresponding to the opening.

6. The optical line sensor according to claim 5, wherein the plurality of openings are located between two rows of reading lines when viewed from a direction perpendicular to the main scanning direction and the sub-scanning direction, and the through holes are formed in a tapered shape that is inclined in the sub-scanning direction with respect to the direction perpendicular to the main scanning direction and the sub-scanning direction.

7. The optical line sensor according to claim 6, wherein the through hole extends in a stepped manner along the direction of inclination of the through hole.

8. The optical line sensor according to claim 1, wherein each of the plurality of light-receiving lenses constitutes a telecentric optical system, and the width of each light-receiving lens in the sub-scanning direction is smaller than the width in the main scanning direction.

9. The optical line sensor according to claim 1, wherein the plurality of apertures are formed in a frustoconical shape.

10. The optical line sensor according to claim 1, wherein the aperture member has a plurality of pinholes into which light passing through the plurality of openings is incident, and these pinholes are formed opposite each other at intervals from each opening.

11. The optical line sensor according to claim 9 or 10, wherein the aperture member has a second light-shielding portion formed therein that blocks a part of the opening to prevent stray light from entering.

12. The optical line sensor according to claim 1, wherein the aperture member comprises a plurality of aperture members, each having an opening formed thereon, and further comprises: at least two light-receiving lenses from the plurality of light-receiving lenses and a pair of holding plates that sandwich at least one aperture member from the plurality of aperture members in the sub-scanning direction; and a pair of sensor holders that sandwich a plurality of light-receiving lens arrays arranged in the main scanning direction in the sub-scanning direction, with the at least two light-receiving lenses and the at least one aperture member sandwiched between the pair of holding plates forming a single light-receiving lens array, and one of the pair of holding plates being positioned on one of the pair of sensor holders by a first positioning member, and the other of the pair of holding plates being positioned on the other of the pair of sensor holders by a second positioning member, and the pair of sensor holders being connected to each other so that the pair of holding plates are positioned facing each other in the sub-scanning direction.

13. The optical line sensor according to claim 12, wherein each of the pair of retaining plates has a fixing screw hole, each of the pair of sensor holders has a through hole formed opposite to the fixing screw hole, and one of the pair of retaining plates is fixed to one of the pair of sensor holders by screwing a first fixing screw, which is inserted through the through hole formed in one of the pair of sensor holders, into the fixing screw hole formed in one of the pair of retaining plates, and the other of the pair of retaining plates is fixed to the other of the pair of sensor holders by screwing a second fixing screw, which is inserted through the through hole formed in the other of the pair of sensor holders, into the fixing screw hole formed in the other of the pair of retaining plates.

14. The optical line sensor according to claim 12, further comprising a spacer disposed between the pair of sensor holders for maintaining a constant distance between the pair of sensor holders when the plurality of light-receiving lens arrays are sandwiched between the pair of sensor holders in the sub-scanning direction.

15. The optical line sensor according to claim 12, further comprising a light-receiving substrate on which the plurality of light-receiving elements are mounted, wherein each of the pair of sensor holders is formed in an L-shape having a first plate portion facing the plurality of light-receiving lens arrays and a second plate portion extending from one end of the first plate portion toward the side opposite to the plurality of light-receiving lens arrays, and the light-receiving substrate is mounted so as to straddle the pair of sensor holders on the side of the second plate portion.

16. The optical line sensor according to claim 12, wherein the optical axes of the plurality of light-receiving lenses are located on the center line between the two rows of reading lines.

17. The optical line sensor according to claim 12, wherein a plurality of the pair of sensor holders are arranged in a row in the main scanning direction.

18. The optical line sensor according to claim 12, further comprising a third light-shielding portion that covers the gap between adjacent aperture members.

19. The optical line sensor according to claim 12, further comprising a cover member provided so as to straddle the end faces on the light incidence side of the pair of holding plates.

20. The optical line sensor according to claim 12, wherein the pair of retaining plates has at least one injection hole formed in it at a position facing the light-receiving lens, and the pair of retaining plates and the at least two light-receiving lenses are fixed by an adhesive injected into the at least one injection hole.

21. The optical line sensor according to claim 12, wherein the pair of retaining plates has at least one first adjustment screw hole formed in it at a position facing the light-receiving lens, and the angle of the light-receiving lens relative to the pair of retaining plates can be adjusted by a first adjustment screw that is screwed into the at least one first adjustment screw hole and whose tip contacts the light-receiving lens.

22. The optical line sensor according to claim 12, wherein the pair of sensor holders have at least one second adjustment screw hole formed at a position opposite to the retaining plate, and the angle of the retaining plate relative to the pair of sensor holders can be adjusted by a second adjustment screw that is screwed into the at least one second adjustment screw hole and whose tip abuts against the retaining plate.

23. The optical line sensor according to claim 12, wherein the pair of retaining plates have a fitting portion for fitting together and connecting the pair of retaining plates.

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