Light-receiving lens array and optical line sensor, and method for manufacturing a light-receiving lens array

Abstract

Provided is a light-receiving lens array 11 for imaging light from a target object on a reading line extending in a main scanning direction, comprising a plurality of light-receiving lenses 111, and a pair of holding plates 112. The plurality of light-receiving lenses 111 are arranged in the main scanning direction. The pair of holding plates 112 each extend along the main scanning direction, and hold the plurality of light-receiving lenses 111 in a sub-scanning direction. Each of the light-receiving lenses 111 has a first surface and a second surface, which respectively abut each of the pair of the pair of holding plates 112.

Description

Technical Field

[0001] The present invention relates to a light receiving lens array for imaging light from an object on a reading line extending in the main scanning direction, an optical line sensor including the same, and a method for manufacturing the light receiving lens array.

Background Art

[0002] In an image reading apparatus including 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 transmitted through each light receiving lens is received by a plurality of light receiving elements (see, for example, Patent Document 1 below).

[0003] Normally, 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.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] 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.

[0006] This invention has been made in view of the above circumstances, and aims to provide a light-receiving lens array and an optical line sensor with a small number of parts and easy assembly, as well as a method for manufacturing a light-receiving lens array. [Means for solving the problem]

[0007] (1) The light-receiving lens array according to the present invention is a light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, and comprises a plurality of light-receiving lenses and a pair of holding plates. The plurality of light-receiving lenses are arranged in the main scanning direction. The pair of holding plates each extend along the main scanning direction and clamp the plurality of light-receiving lenses in the sub-scanning direction. Each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, respectively.

[0008] With this configuration, multiple light-receiving lenses can be held between a pair of holding plates, with the first and second surfaces of each light-receiving lens in contact with each of the holding plates. Therefore, since there is no need to use a large number of housing components, the number of parts is small and assembly is easy.

[0009] (2) Each light-receiving lens may have its first surface and second surface bonded to the pair of retaining plates, respectively.

[0010] With this configuration, each light-receiving lens can be held by a pair of retaining plates by simply bonding the first and second surfaces of each lens to a pair of retaining plates. Therefore, the number of parts is further reduced, and assembly is easier.

[0011] (3) The plurality of light-receiving lenses may be arranged with space between them so that adjacent light-receiving lenses in the main scanning direction do not come into contact with each other.

[0012] With this configuration, even if each light-receiving lens deforms due to temperature changes, no force acts between the light-receiving lenses, and the relative position of each light-receiving lens can be suppressed.

[0013] (4) The space may be provided with an elastic member having light-shielding and low reflectivity.

[0014] With this configuration, contact between each light-receiving lens can be avoided by the elastic member, and stray light can be suppressed and dust can not be prevented from entering.

[0015] (5) The light-receiving lens array may further include an aperture member through which light transmitted through the light-receiving lens passes. In this case, the width of the aperture member in the sub-scanning direction may coincide with the distance between the first surface and the second surface.

[0016] With this configuration, multiple light-receiving lenses can be held between a pair of retaining plates while both end faces of the aperture member in the sub-scanning direction are in contact with a pair of retaining plates. In this way, by bringing both end faces of each light-receiving lens in the sub-scanning direction, and both end faces of the aperture member in the sub-scanning direction, into contact with a pair of retaining plates, multiple light-receiving lenses can be stably held between a pair of retaining plates.

[0017] (6) The aperture member may have a frustoconical opening.

[0018] With this configuration, light from each light-receiving lens to the aperture member can be guided along a frustoconical opening.

[0019] (7) The aperture member may have an opening and a pinhole into which light passing through the opening is incident, which are separated from each other and facing each other.

[0020] According to such a configuration, light from each light receiving lens can be guided to the aperture member along the aperture and the pinhole.

[0021] (8) The aperture member may be formed with a light shielding portion that blocks a part of the aperture to prevent intrusion of stray light.

[0022] According to such a configuration, the light shielding portion can prevent stray light from entering on the optical path from each light receiving lens to the aperture member.

[0023] (9) The optical axis of the light receiving lens may be displaced in the sub-scanning direction with respect to the reading line.

[0024] According to such a configuration, stray light that is emitted from adjacent light receiving lenses and travels toward the aperture along a direction inclined in the sub-scanning direction with respect to the direction orthogonal to the main scanning direction and the sub-scanning direction can be effectively blocked by the light shielding portion.

[0025] (10) Each light receiving lens may be formed in a trapezoidal shape having the first surface, the second surface whose width in the main scanning direction is smaller than that of the first surface, and a pair of inclined surfaces connecting the first surface and the second surface. In this case, the inclined surfaces of the light receiving lenses adjacent to each other in the main scanning direction may face each other.

[0026] According to such a configuration, each light receiving lens formed in a trapezoidal shape can be efficiently arranged in the main scanning direction.

[0027] (11) The optical axes of the plurality of light receiving lenses may all be on the same plane and parallel to each other.

[0028] According to such a configuration, light from an object can be imaged on the reading line by a plurality of light receiving lenses arranged in a row.

[0029] (12) The optical line sensor according to the present invention includes the light receiving lens array and a plurality of light receiving elements that receive light transmitted through the plurality of light receiving lenses.

[0030] This configuration makes it possible to provide an optical line sensor equipped with a light-receiving lens array that has a small number of parts and is easy to assemble.

[0031] (13) Another optical line sensor according to the present invention comprises a light-receiving lens array and a plurality of light-receiving elements that receive light transmitted through the plurality of light-receiving lenses, wherein the plurality of light-receiving elements constitute a plurality of light-receiving element arrays extending along the main scanning direction. The plurality of light-receiving element arrays are arranged in a staggered pattern on two rows of the reading lines, and the optical axis of each of the plurality of light-receiving lenses is positioned in the middle of the two rows of reading lines.

[0032] With this configuration, by arranging multiple photodetector arrays in a staggered pattern on two reading lines, it is possible to avoid situations where there are no pixels in the main scanning direction between the ends of adjacent photodetector arrays. The ends of each photodetector array may be arranged so as to overlap each other in the sub-scanning direction, or they may be arranged continuously in the main scanning direction within a range where they do not overlap each other. If the ends of each photodetector array are arranged so as to overlap each other in the sub-scanning direction, then by forming each photodetector lens in a trapezoidal shape, each photodetector lens can be efficiently arranged in the main scanning direction in correspondence with each photodetector array.

[0033] (14) A method for manufacturing a light-receiving lens array according to the present invention is a method for manufacturing a light-receiving lens array, comprising a first lens mounting step, a second lens mounting step, and a fixing step. In the first lens mounting step, a portion of the plurality of light-receiving lenses is mounted on one of the pair of retaining plates, spaced apart in the main scanning direction. In the second lens mounting step, the remaining portion of the plurality of light-receiving lenses is mounted on the other of the pair of retaining plates, spaced apart in the main scanning direction. In the fixing step, the pair of retaining plates are brought facing each other such that the plurality of light-receiving lenses mounted on the other of the pair of retaining plates are positioned between the plurality of light-receiving lenses mounted on one of the pair of retaining plates, and each light-receiving lens is clamped and fixed in the sub-scanning direction by the pair of retaining plates.

[0034] With this configuration, only a portion of the multiple light-receiving lenses is attached to one of a pair of retaining plates, the remaining portion of the multiple light-receiving lenses is attached to the other of the pair of retaining plates, and these two pairs of retaining plates are placed facing each other, so that each light-receiving lens is sandwiched between the two plates. This eliminates the need for a large number of housing components, resulting in fewer parts and easier assembly.

[0035] (15) Each light-receiving lens may be formed in a trapezoidal shape having a first surface, a second surface having a width smaller than the first surface in the main scanning direction, and a pair of inclined surfaces connecting the first surface and the second surface. In this case, in the first lens mounting step, the first surface of a portion of the plurality of light-receiving lenses may be attached to one of the pair of retaining plates. In the second lens mounting step, the first surface of the remaining portion of the plurality of light-receiving lenses may be attached to the other of the pair of retaining plates.

[0036] With this configuration, the base side (first surface side) of each trapezoidal light-receiving lens is attached to a pair of retaining plates, and by placing these retaining plates facing each other, the tip side (second surface side) of each light-receiving lens is inserted between the lenses, allowing each light-receiving lens to be clamped between the pair of retaining plates. Therefore, even when using trapezoidal light-receiving lenses, assembly is easy.

[0037] (16) The light-receiving lens array may further include aperture members having openings through which light transmitted via the light-receiving lenses passes. In this case, in the first lens mounting step and the second lens mounting step, the plurality of light-receiving lenses and the aperture members may be attached to the pair of retaining plates using a jig for positioning the plurality of light-receiving lenses and the aperture members in predetermined positions.

[0038] With this configuration, multiple light-receiving lenses and aperture members can be positioned in predetermined locations using a jig, thus simplifying the assembly process. [Effects of the Invention]

[0039] According to the present invention, it is possible to provide a light-receiving lens array and an optical line sensor that have a small number of parts and are easy to assemble, as well as a method for manufacturing a light-receiving lens array. [Brief explanation of the drawing]

[0040] [Figure 1] This is a cross-sectional view showing an example configuration of an optical line sensor according to one embodiment of the present invention. [Figure 2] Figure 1 is an exploded perspective view showing an example of the configuration of the illumination optical system in an optical line sensor. [Figure 3] This figure illustrates a first embodiment of the light-receiving lens array and is a perspective view of the light-receiving lens array according to the first embodiment. [Figure 4]This figure illustrates a first embodiment of the light-receiving lens array and is an exploded perspective view of the light-receiving lens array according to the first embodiment. [Figure 5] This figure illustrates a first embodiment of the light-receiving lens array and is a perspective view of the aperture member according to the first embodiment. [Figure 6] This figure illustrates a second embodiment of the light-receiving lens array and is a perspective view of the light-receiving lens array according to the second embodiment. [Figure 7] This figure illustrates a second embodiment of the light-receiving lens array and is an exploded perspective view of the light-receiving lens array according to the second embodiment. [Figure 8A] This figure illustrates a second embodiment of the light-receiving lens array and is a perspective view of the aperture member according to the second embodiment. [Figure 8B] This is a perspective view showing a modified example of the aperture member according to the second embodiment. [Figure 9] This is a perspective view illustrating the method for manufacturing a light-receiving lens array according to the second embodiment. [Figure 10A] This is a schematic diagram illustrating the positional relationship between the light-receiving lens and the light-receiving element array, and shows the case of a trapezoidal light-receiving lens according to the second embodiment shown in Figures 6 and 7. [Figure 10B] This is a schematic diagram illustrating the positional relationship between the light-receiving lens and the light-receiving element array, and shows a modified example of a light-receiving lens. [Modes for carrying out the invention]

[0041] 1. Overall configuration of the optical line sensor Figure 1 is a cross-sectional view showing an example configuration of an optical line sensor according to one embodiment of the present invention. In Figure 1, a cross-sectional view is shown near the longitudinal center of the optical line sensor. Figure 2 is an exploded perspective view showing an example 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.

[0042] 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 using 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 linear 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 at the opening on the focal plane 20 side of each housing 16.

[0043] 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.

[0044] 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.

[0045] 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 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.

[0046] 2. First embodiment of a light-receiving lens array Figures 3 to 5 are diagrams illustrating a 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.

[0047] 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 straight 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 low coefficient of linear expansion to suppress length changes due to temperature changes. For example, glass epoxy laminate is preferable because it has a low coefficient of linear expansion of about 16 ppm and a low specific gravity, thus keeping the weight down.

[0048] Each light-receiving lens 111 is rectangular in plan view (viewed 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.

[0049] 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 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 retaining plates 112 (retaining plate 112B).

[0050] In this embodiment, the light-receiving lens array 11 includes 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 transmitted through each light-receiving lens 111 passes through the aperture 113A formed in the corresponding aperture member 113 and is guided to the light-receiving element array 12. 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. The position in the Z direction (optical axis direction) of the tapered side of the aperture 113A may be made to coincide with the image-side focal point of the light-receiving lens 111 to form a telecentric optical system. 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 allows for effective reduction of stray light without vignetting of the image formed by the light-receiving lens 111.

[0051] The width of each aperture member 113 in the Y direction corresponds to 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 corresponds to 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.

[0052] 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.

[0053] 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, a convex portion may be formed on a part of the first surface 111A and the second surface 111B of the light-receiving lens 111, and corresponding recesses may be formed on a pair of retaining plates 112. The pair of retaining plates 112 can then be fixed to each other with a fastener while the convex portion is fitted into the recess, thereby clamping each light-receiving lens 111 in the Y direction with the pair of retaining plates 112.

[0054] 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.

[0055] 3. Second embodiment of the light-receiving lens array Figures 6 to 8A illustrate 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.

[0056] 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 straight 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 that 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.

[0057] 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.

[0058] 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.

[0059] As shown in Figure 7, the plurality of light-receiving lenses 111 includes some light-receiving lenses 111 (light-receiving lenses 120) that are attached to one of a pair of retaining plates 112 (retaining plate 112A), and the remaining light-receiving lenses 111 (light-receiving lenses 130) that are attached to the other of the pair of retaining plates 112 (retaining plate 112B). Each light-receiving lens 111 has its first surface 111A attached to each retaining plate 112. That is, the manufacturing method of the light-receiving lens array 11 in this example includes a first lens mounting step in which the first surface 111A of some of the plurality of light-receiving lenses 111 (light-receiving lenses 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 of the plurality of light-receiving lenses 111 (light-receiving lenses 130) is attached to the other of the pair of retaining plates 112 (retaining plate 112B).

[0060] 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.

[0061] 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.

[0062] 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 is in contact with retaining plate 112A, and light-receiving lens 130 is in contact 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 is in contact with retaining plate 112B, and light-receiving lens 130 is in contact with retaining plate 112A).

[0063] In this embodiment, the light-receiving lens array 11 includes 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 transmitted through each light-receiving lens 111 passes through the aperture 113A formed in the corresponding aperture member 113 and is guided to the light-receiving element array 12. 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. The position of the tapered side of the aperture 113A in the Z direction (optical axis direction) may be made to coincide with the image-side focal point of the light-receiving lens 111 to form a telecentric optical system. 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 allows for effective reduction of stray light without vignetting of the image formed by the light-receiving lens 111.

[0064] In this example, as shown in Figure 8A, the aperture member 113 has a light-shielding portion 113B 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 portion 113B has a recess 113C that extends along the optical axis direction. The recess 113C may be semi-cylindrical as shown in Figure 8A.

[0065] The width of each aperture member 113 in the Y direction corresponds to 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 corresponds to 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.

[0066] 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.

[0067] 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, a convex portion may be formed on a part of the first surface 111A and the second surface 111B of the light-receiving lens 111, and corresponding recesses may be formed on a pair of retaining plates 112. The pair of retaining plates 112 can then be fixed to each other with a fastener while the convex portion is fitted into the recess, thereby clamping each light-receiving lens 111 in the Y direction with the pair of retaining plates 112.

[0068] 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.

[0069] Figure 8B is a perspective view showing a modified example of the aperture member 113 according to the second embodiment. In the example in Figure 8A, the aperture member 113 is made up of a rectangular prism-shaped member, and a frustoconical opening 113A is formed so as to penetrate the member. In contrast, in the example in Figure 8B, the aperture member 113 is made up of a rectangular frame, and two openings 113D and 113E are formed in the member so as to face each other.

[0070] 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.

[0071] 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 forms a telecentric optical system. As shown in Figure 8B, the aperture member 113 has a light-shielding portion 113B that blocks a part 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 part 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 portion 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 is incident on it. At this time, it is preferable that the apex angle of the frustoconical shape virtually formed by the apertures 113D and 113E be slightly larger than the aperture angle of the light-receiving lens 111. This allows for effective reduction of stray light without vignetting of the image formed by the light-receiving lens 111.

[0072] 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 portion 113B can effectively shield stray light emitted from adjacent light-receiving lenses 111 that travels 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. Although it is possible to omit the side plates of the aperture member 113 and construct the aperture member 113 with separate top and bottom plates, forming the aperture member 113 into a frame as shown in Figure 8B makes the aperture member 113 a single integrated structure, making it easier to handle.

[0073] Figure 9 is a perspective view illustrating the manufacturing method of a light-receiving lens array 11 according to the 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).

[0074] 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.

[0075] In the first and second lens mounting steps, a pair 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.

[0076] 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 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.

[0077] The optical axis alignment jig 300 is a plate-shaped component 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.

[0078] 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.

[0079] 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.

[0080] Then, with each pair of protrusions 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.

[0081] In this way, the light-receiving lens 111 and aperture member 113 can be attached to the retaining 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 retaining plate 112, skipping one in the X direction.

[0082] 4. Positional relationship between the light-receiving lens and the 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.

[0083] Figures 10A and 10B illustrate 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). Light transmitted through each light-receiving lens 111 is received by 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.

[0084] In Figure 10A, the photodetector arrays 12 are positioned opposite each other at an offset position on 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 as long as 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.

[0085] 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. [Explanation of Symbols]

[0086] 11. Light-receiving lens array 12. Photodetector array 111 Light-receiving lens 112 Retaining plate 113 Aperture Member 113A aperture 113B Light shielding part 114 Elastic members 120 light-receiving lens 130 Light-receiving lens 300 Optical axis alignment jig

Claims

1. A light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, A plurality of light-receiving lenses arranged in the main scanning direction, Each comprises a pair of holding plates that extend along the main scanning direction and sandwich the plurality of light-receiving lenses in the sub-scanning direction, Each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, respectively. Each light-receiving lens is rectangular when viewed from a direction perpendicular to the main scanning direction and the sub-scanning direction, and the first surface, which is one end face in the sub-scanning direction, and the second surface, which is the other end face in the sub-scanning direction, are each composed of flat surfaces, in a light-receiving lens array.

2. The light-receiving lens array according to claim 1, wherein the first surface and the second surface of each light-receiving lens are bonded to the pair of retaining plates, respectively.

3. The light-receiving lens array according to claim 1, wherein the plurality of light-receiving lenses are arranged with space between them so that adjacent light-receiving lenses do not come into contact with each other in the main scanning direction.

4. The light-receiving lens array according to claim 3, wherein an elastic member having light-shielding and low reflectivity is provided in the space.

5. The aperture member further comprises an aperture through which light transmitted through the light-receiving lens passes, The light-receiving lens array according to claim 1, wherein the width of the aperture member in the sub-scanning direction coincides with the distance between the first surface and the second surface.

6. The light-receiving lens array according to claim 5, wherein the aperture member has a frustoconical opening formed therein.

7. The light-receiving lens array according to claim 5, wherein the aperture member has an opening and a pinhole into which light passing through the opening is incident, and these are formed opposite each other with a distance between them.

8. The light-receiving lens array according to claim 6 or 7, wherein the aperture member has a light-shielding portion formed therein that blocks a part of the opening to prevent stray light from entering.

9. The light-receiving lens array according to claim 8, wherein the optical axis of the light-receiving lens is offset in the sub-scanning direction with respect to the reading line.

10. Each light-receiving lens is formed in a trapezoidal shape having a first surface, a second surface having a width smaller than the first surface in the main scanning direction, and a pair of inclined surfaces connecting the first surface and the second surface. The light-receiving lens array according to claim 1, wherein the inclined surfaces of adjacent light-receiving lenses in the main scanning direction face each other.

11. The light-receiving lens array according to claim 1, wherein the optical axes of the plurality of light-receiving lenses are all on the same plane and parallel to each other.

12. The light-receiving lens array according to claim 1, An optical line sensor comprising a plurality of light-receiving elements that receive light transmitted through the plurality of light-receiving lenses.

13. The light-receiving lens array according to claim 11, The system comprises a plurality of light-receiving elements that receive light transmitted through the plurality of light-receiving lenses, The plurality of light-receiving elements constitute a plurality of light-receiving element arrays extending along the main scanning direction. The aforementioned array of multiple light-receiving elements is arranged in a staggered pattern on the two rows of the reading lines. An optical line sensor in which the optical axes of each of the plurality of light-receiving lenses are positioned in the middle of the two rows of reading lines.

14. A method for manufacturing a light-receiving lens array according to claim 1, A first lens mounting step involves attaching a portion of the plurality of light-receiving lenses to one of the pair of retaining plates, spaced apart in the main scanning direction. A second lens mounting step involves mounting the remaining light-receiving lenses to the other of the pair of retaining plates, spaced apart in the main scanning direction. A method for manufacturing a light-receiving lens array, comprising the steps of: positioning a pair of retaining plates facing each other such that a plurality of light-receiving lenses attached to the other of the pair of retaining plates are positioned between a plurality of light-receiving lenses attached to one of the pair of retaining plates, and fixing each light-receiving lens by sandwiching it in the sub-scanning direction with the pair of retaining plates.

15. Each light-receiving lens is formed in a trapezoidal shape having a first surface, a second surface having a width smaller than the first surface in the main scanning direction, and a pair of inclined surfaces connecting the first surface and the second surface. In the first lens mounting step, the first surface of a portion of the plurality of light-receiving lenses is attached to one of the pair of retaining plates. The method for manufacturing a light-receiving lens array according to claim 14, wherein in the second lens mounting step, the first surface of the remaining light-receiving lenses is attached to the other of the pair of retaining plates.

16. The light-receiving lens array further comprises an aperture member having an opening through which light transmitted through the light-receiving lens passes, The method for manufacturing a light-receiving lens array according to claim 14, wherein in the first lens mounting step and the second lens mounting step, the plurality of light-receiving lenses and the aperture members are attached to the pair of holding plates using a jig for positioning the plurality of light-receiving lenses and the aperture members in predetermined positions.

17. A light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, A plurality of light-receiving lenses arranged in the main scanning direction, Each comprises a pair of holding plates that extend along the main scanning direction and sandwich the plurality of light-receiving lenses in the sub-scanning direction, Each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, respectively. The plurality of light-receiving lenses are arranged with space between them so that adjacent light-receiving lenses do not come into contact with each other in the main scanning direction. A light-receiving lens array is provided in the space, in which an elastic member having light-shielding and low reflectivity is provided.

18. A light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, A plurality of light-receiving lenses arranged in the main scanning direction, A pair of holding plates, each extending along the main scanning direction and sandwiching the plurality of light-receiving lenses in the sub-scanning direction, The system comprises an aperture member having an opening through which light transmitted through the light-receiving lens passes, Each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, respectively. The width of the aperture member in the sub-scanning direction is equal to the distance between the first surface and the second surface. The aperture member has a frustoconical opening and a light-shielding portion that blocks a part of the opening to prevent stray light from entering. A light-receiving lens array in which the optical axis of the light-receiving lens is offset in the sub-scanning direction with respect to the reading line.

19. A light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, A plurality of light-receiving lenses arranged in the main scanning direction, A pair of holding plates, each extending along the main scanning direction and sandwiching the plurality of light-receiving lenses in the sub-scanning direction, The system comprises an aperture member having an opening through which light transmitted through the light-receiving lens passes, Each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, respectively. The width of the aperture member in the sub-scanning direction is equal to the distance between the first surface and the second surface. The aperture member is formed with an opening and a pinhole into which light passing through the opening is incident, separated from each other and facing each other, and a light-shielding portion is formed to block a part of the opening and prevent stray light from entering. A light-receiving lens array in which the optical axis of the light-receiving lens is offset in the sub-scanning direction with respect to the reading line.

20. A light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, A plurality of light-receiving lenses arranged in the main scanning direction, Each comprises a pair of holding plates that extend along the main scanning direction and sandwich the plurality of light-receiving lenses in the sub-scanning direction, Each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, respectively. Each light-receiving lens is formed in a trapezoidal shape having a first surface, a second surface having a width smaller than the first surface in the main scanning direction, and a pair of inclined surfaces connecting the first surface and the second surface. A light-receiving lens array in which the inclined surfaces of adjacent light-receiving lenses in the main scanning direction face each other.

21. A light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, comprising: a plurality of light-receiving lenses arranged in the main scanning direction; and a pair of holding plates, each extending along the main scanning direction and sandwiching the plurality of light-receiving lenses in the sub-scanning direction, wherein each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, and the optical axes of the plurality of light-receiving lenses are all on the same plane and parallel to each other, The system comprises a plurality of light-receiving elements that receive light transmitted through the plurality of light-receiving lenses, The plurality of light-receiving elements constitute a plurality of light-receiving element arrays extending along the main scanning direction. The aforementioned array of multiple light-receiving elements is arranged in a staggered pattern on the two rows of the reading lines. An optical line sensor in which the optical axes of each of the plurality of light-receiving lenses are positioned in the middle of the two rows of reading lines.

22. A light-receiving lens array for imaging light from an object onto a reading line extending in the main scanning direction, comprising a plurality of light-receiving lenses arranged in the main scanning direction, and a pair of holding plates each extending along the main scanning direction and sandwiching the plurality of light-receiving lenses in the sub-scanning direction, wherein each light-receiving lens has a first surface and a second surface that contact the pair of holding plates, respectively, a method for manufacturing a light-receiving lens array, A first lens mounting step involves attaching a portion of the plurality of light-receiving lenses to one of the pair of retaining plates, spaced apart in the main scanning direction. A second lens mounting step involves mounting the remaining light-receiving lenses to the other of the pair of retaining plates, spaced apart in the main scanning direction. A method for manufacturing a light-receiving lens array, comprising the steps of: positioning a pair of retaining plates facing each other such that a plurality of light-receiving lenses attached to the other of the pair of retaining plates are positioned between a plurality of light-receiving lenses attached to one of the pair of retaining plates, and fixing each light-receiving lens by sandwiching it in the sub-scanning direction with the pair of retaining plates.

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