Lens unit, light receiving device, and reading device

Abstract

[Problem] To maintain reading quality. [Solution] A reading head 6 is provided with a substrate 14 on which a plurality of imaging elements 33 are installed in an X direction, a lens unit 20 on which light from an inspection object 4 is incident and which transmits and converges the light toward the imaging elements 33, and a holder 12 that supports the substrate 14 and the lens unit 20. The lens unit 20 has a first lens array 22 in which a plurality of first lenses 22L are arranged in the X direction and on which light is incident, a second lens array 30 in which a plurality of second lenses 30L are arranged in the X direction such that the respective optical axes thereof match those of the first lenses 22L, and which converges the light that is incident thereon from the first lens array 22, and a plurality of opening arrays 25 which are positioned between the first lens array 22 and the second lens array 30 so as to be layered in a Z direction in which the optical axes extend, and in each of which a plurality of openings 25A are arranged in the X direction such that the respective optical axes thereof match those of the first lenses 22L and the second lenses 30L.

Description

Lens unit, light receiving device and reading device

[0001] The present invention relates to a lens unit, a light receiving device, and a reading device, and is suitable for application to a light receiving device in an industrial camera used for, for example, a scanner or visual inspection.

[0002] Conventionally, contact image sensors (CISs) have been used as light receiving devices in scanners and industrial cameras used for visual inspection. These contact image sensors have a shallow depth of field, which can make it difficult to read images of subjects at different heights. In response to this, a lens unit has been proposed that forms a telecentric erect, life-size image using a pair of lens arrays, thereby improving the depth of field of the contact image sensor (see, for example, Patent Document 1). In a light receiving device having such a lens unit, an aperture array, in which apertures are formed to match the pitch of the lenses in the pair of lens arrays, may be disposed midway through the optical system of the lens unit.

[0003] JP 2013-45093 A

[0004] In such a light receiving device, it is desirable to maintain reading quality by preventing unintended light images (stray light) that are generated when light from lenses with different optical axes enters the lens array.

[0005] The present invention has been made in consideration of the above points, and aims to propose a lens unit, a light receiving device, and a reading device that can maintain reading quality.

[0006] In order to solve this problem, the lens unit of the present invention includes a first lens array in which a plurality of first lenses are arranged in a first direction, a second lens array in which a plurality of second lenses are arranged in the first direction so that their optical axes coincide with those of the first lenses, and an aperture array in which a plurality of lenses are arranged between the first lens array and the second lens array so that they are stacked in the optical axis direction in which the optical axes extend, and in which a plurality of apertures are arranged in the first direction so that their optical axes coincide with those of the first lens and the second lens.

[0007] In addition, the light-receiving device of the present invention includes a substrate on which a plurality of light-receiving elements are mounted in a first direction, a lens unit that passes light from a light source toward the light-receiving elements and converges it, and a support member that supports the substrate and the lens unit, and the lens unit includes a first lens array in which a plurality of first lenses are arranged in the first direction and light is incident, a second lens array in which a plurality of second lenses are arranged in the first direction so that their optical axes coincide with those of the first lenses and converge the light incident from the first lens array, and an aperture array in which a plurality of lenses are arranged between the first lens array and the second lens array so that they are stacked in the optical axis direction in which the optical axes extend, and in which a plurality of apertures are arranged in the first direction so that their optical axes coincide with those of the first lenses and the second lenses.

[0008] Furthermore, the reading device of the present invention is provided with the above-mentioned light receiving device.

[0009] According to the present invention, the apertures of the aperture array can block light emitted from a first lens from entering a second lens having an optical axis different from that of the first lens.

[0010] According to the present invention, the apertures in the aperture array can block light emitted from a first lens from entering a second lens having an optical axis different from that of the first lens, thereby realizing a lens unit, a light receiving device, and a reading device that can maintain reading quality.

[0011] 1 is a perspective view showing the configuration of an inspection device. FIG. 1 is a perspective view showing the configuration (1) of a reading head. FIG. 2 is a cross-sectional view of the configuration (2) of a reading head taken along the line A-A in FIG. 2. FIG. 1 is an exploded cross-sectional view showing the configuration (1) of a lens unit according to a first embodiment. FIG. 2 is a partial enlarged view of a first lens array. FIG. 3 is a partial enlarged view of a second lens array. FIG. 4 is a view from the Z direction showing the configuration of the first lens array. FIG. 5 is a view from the Z direction showing the configuration of the aperture array. FIG. 6 is a vertical cross-sectional view showing the configuration (2) of a lens unit according to the first embodiment. FIG. 7 is a table showing the shape of each lens surface. FIG. 8 is a vertical cross-sectional view showing the configuration of a lens unit according to a second embodiment. FIG. 9 is a vertical cross-sectional view of a lens unit showing a comparison of how light is reflected. FIG. 10 is a vertical cross-sectional view of a lens unit showing a comparison of how light is reflected. FIG. 11 is a perspective view showing the configuration of a lens unit according to another embodiment.

[0012] Hereinafter, modes for carrying out the invention (hereinafter referred to as "embodiments") will be described with reference to the drawings. [1. First Embodiment] [1-1. Configuration of Inspection Apparatus] As shown in FIG. 1 , the inspection apparatus 1 mainly includes a conveying system 2, a reading head 6, a cable 8, and a computing device 10, and inspects the appearance of an inspection object 4, such as scratches and dimensions. The conveying system 2 is, for example, a belt conveyor, and conveys the inspection object 4 placed on the upper surface of the endless belt in the +Y direction, which is the conveying direction, at a constant speed. The reading head 6 is supported by a support member (not shown) above the inspection object 4 on the upper surface of the endless belt so as to extend along the X direction, which is the conveying width direction perpendicular to the conveying direction. The reading head 6 forms an erect, life-size image of the inspection object 4 on an image sensor 33 ( FIG. 3 ), and converts the optical image of the inspection object 4 into an image signal. The inspection apparatus 1 acquires an image of the inspection object 4, which is the subject, as one-dimensional data along the X direction, and continuously reads the image of the inspection object 4 displacing in the Y direction, thereby reading a two-dimensional image of the inspection object 4. In this embodiment, the distance from the inspection object 4, which is the subject, to the lens of the reading head 6 (specifically, the lens surface 22LSo of the first lens 22L of the first lens array 22 (details will be described later)) is set to 20 mm. The cable 8 is connected to the reading head 6 and the arithmetic unit 10, and relays the image signal generated by the reading head 6 when the image signal is transmitted to the arithmetic unit 10. The arithmetic unit 10 acquires the image signal transmitted from the reading head 6 via the cable 8, performs synthesis processing of the image signal, and uses the generated image to detect flaws on the inspection object 4, inspect dimensions, etc.

[0013] In this configuration, the inspection device 1 illuminates the inspection object 4 with a lighting device (not shown) while driving the conveying system 2 to convey the inspection object 4 at a constant speed, converts the optical image of the inspection object 4 into an image signal with the reading head 6, and performs detection of scratches on the inspection object 4 and inspection of dimensions, etc. with the calculation device 10.

[0014] 2 and 3, the reading head 6 is formed as a rectangular parallelepiped elongated in the X direction as a whole, with the lens unit 20, substrate 14, etc. attached to the holder 12 in a stacked manner. Hereinafter, the -Z direction will also be referred to as the imaging element direction, and the +Z direction will also be referred to as the subject direction. Also, below, the X direction, which is the arrangement direction of the line sensors 32, will also be referred to as the longitudinal direction (arrangement direction, main scanning direction), the Y direction perpendicular to the X direction and Z direction will also be referred to as the sub-scanning direction, and the Z direction will also be referred to as the optical axis direction of the lens unit 20.

[0015] [1-2-1. Holder Configuration] The holder 12 is fabricated, for example, by cutting metal, sheet metal, or resin injection molding. Its overall shape resembles a hollow rectangular prism formed along the X direction with the -Z direction side removed. Its cross section resembles the capital letter "U." It holds the lens unit 20, substrate 14, and other components inside. The lens unit 20 and substrate 14 are adhered to and held in the holder 12 by an adhesive (not shown). The holder 12 is centered around a plate-like bottom 12B that is elongated in the X direction and thin in the Z direction. Two plate-like side portions 12W that are elongated in the X direction and thin in the Y direction extend from both Y-direction edges of the bottom 12B toward the -Z direction. A holder opening 12A is formed at the -Z direction end. A slit-shaped hole 12L that is elongated in the X direction and penetrates the bottom 12B in the Z direction is drilled approximately at the center of the bottom 12B in the Y direction.

[0016] [1-2-2. Configuration of Lens Unit] The lens unit 20 is attached to the holder 12 with its longitudinal direction aligned along the X direction and the vicinity of the end on the +Z direction side fitting into the hole 12L. As shown in Fig. 4A , the lens unit 20 is configured such that a first lens array 22, an object-side aperture array group 24, an aperture array 26, an image sensor-side aperture array group 28, and a second lens array 30 are stacked in this order along the Z direction from the +Z direction side (the object side) to the -Z direction side (the image sensor side).

[0017] [1-2-2-1. Configuration of the First Lens Array] As shown in FIGS. 4A, 4B, and 5, the first lens array 22 is fabricated by injection molding or the like using APL5514 resin glass material from Mitsui Chemicals, Inc. The first lens array 22 is a plate-like member elongated in the X direction and thin in the Z direction. In the center of the Y direction, multiple first lenses 22L are arranged at equal intervals of, for example, 0.5 mm, so as to be aligned in a substantially linear line along the X direction (the arrangement direction) with their optical axes aligned in the Z direction. Adjacent first lenses 22L in the X direction are aligned in the Y direction. When viewed from the Z direction, the first lenses 22L have a shape such that both ends of a circle centered on the center of the first lens 22L in the X direction are linearly cut off along the Y direction. The first lenses 22L are formed from a material that transmits light incident on the image sensor 33. The lens optical axis, which is the optical axis of light passing through this first lens 22L, is located at the center of the first lens 22L. Here, the lens surface of each first lens 22L facing in the +Z direction (toward the subject) is referred to as lens surface 22LSo, and the lens surface of each first lens 22L facing in the −Z direction (toward the image sensor) is referred to as lens surface 22LSi.

[0018] [1-2-2-2. Configuration of the Second Lens Array] As shown in FIGS. 4A, 4B, and 4C, the second lens array 30, like the first lens array 22, is manufactured by resin injection molding or the like, and the glass material of the resin is APL5514 manufactured by Mitsui Chemicals, Inc. This second lens array 30 is configured similarly to the first lens array 22 except for the inclusion of second lenses 30L instead of the first lenses 22L. In the center of the second lens array 30 in the Y direction, multiple second lenses 30L are arranged at equal intervals of, for example, 0.5 mm so as to be aligned in a substantially linear line along the arrangement direction, which is the X direction, with their optical axes aligned in the Z direction. The positions of adjacent second lenses 30L in the X direction are aligned with each other in the Y direction. When viewed from the Z direction, the second lenses 30L have a shape such that both ends of the X direction of a circle with the center of the second lens 30L as the axis are linearly cut off along the Y direction. Here, the lens surface of each second lens 30L on the +Z direction side (toward the subject) is referred to as lens surface 30LSo, and the lens surface of each second lens 30L on the −Z direction side (toward the image sensor) is referred to as lens surface 30LSi.

[0019] The second lens 30L has lens surfaces 30LSo and 30LSi whose shapes are different from those of the lens surfaces 22LSo and 22LSi of the first lens 22L. The first lens array 22 and the second lens array 30 are arranged so that the lens optical axis of the first lens 22L and the lens optical axis of the second lens 30L coincide with each other.

[0020] The lens unit 20 forms an inverted, reduced image of the subject as an intermediate image using the first lens array 22, and then forms an inverted, enlarged image of the intermediate image using the second lens array 30, thereby forming an erect, life-size image of the subject on the image sensor 33 (FIG. 3). In this way, the lens unit 20 is an erect, life-size optical system.

[0021] 9 shows the radius, radius of curvature r, conic constant k, fourth-order aspherical coefficient A, and distance of each lens surface in the Z direction from the image sensor 33, which represent the shape of each lens surface of the first lens 22L of the first lens array 22 and the second lens 30L of the second lens array 30. Furthermore, when h is the height from the optical axis, z, which is the depth from the tangent plane to the surface vertex, can be calculated by the following equation (1):

[0022]

[0023] [1-2-2-3. Configuration of the Aperture Array] As shown in FIGS. 4A and 7 , the aperture array 26 is a plate-like member that is elongated in the X direction and thin in the Z direction. In the center of the aperture array 26 in the Y direction, a plurality of substantially cylindrical holes 26A are arranged at equal intervals of, for example, 0.5 mm, similar to the first lens 22L and the second lens 30L, so that they are aligned in a substantially linear line along the arrangement direction, which is the X direction, with their central axes aligned in the Z direction. Adjacent holes 26A in the X direction are aligned in the Y direction. The holes 26A penetrate the aperture array 26 from the side surface facing the +Z direction to the side surface facing the −Z direction. The holes 26A are arranged so that the optical axis of light passes through the center of the holes 26A. In this embodiment, the opening diameter of the holes 26A is 0.26 mm, and the thickness of the holes 26A in the Z direction (i.e., the thickness of the aperture array 26 in the Z direction) is 0.3 mm or less. Furthermore, the hole 26A is positioned in the Z direction so that the focal length position on the −Z direction side (the side toward the image sensor) of the first lens 22L is located at the center in the Z direction of the hole 26A. The aperture array 26 blocks so-called stray light and flare light other than the light rays that form the image of the lens unit 20.

[0024] 4A, 6, and 8, the object-side aperture array group 24 is disposed between the first lens array 22 and the aperture array 26, and is configured by, for example, adhering 11 aperture arrays 25 so that they are stacked in the Z direction.

[0025] The aperture array 25 is fabricated by etching a silicon wafer or the like. The aperture array 25 is generally a plate-like member elongated in the X direction and thin in the Z direction. In the center of the Y direction, a plurality of approximately cylindrical apertures 25A are arranged at equal intervals of, for example, 0.5 mm, similar to the first lenses 22L and second lenses 30L, so that they are aligned in a substantially linear line along the X direction, with their central axes aligned in the Z direction. The positions of adjacent first lenses 22L in the X direction are aligned in the Y direction. The apertures 25A penetrate the aperture array 25 from the +Z direction side surface to the -Z direction side surface. Because the apertures 25A are generally cylindrical, their inner wall surfaces are aligned linearly in the Z direction from the +Z direction end to the -Z direction end. Therefore, the outer wall surface of the wall portion 25W (described later) is aligned linearly in the Z direction from the +Z direction end to the -Z direction end. This opening 25A is positioned so that the optical axis of light passes through the center of the opening 25A. The opening 25A has an outer shape similar to that of the first lens 22L (FIG. 5) but is smaller than the first lens 22L (FIG. 5), and its center coincides with that of the first lens 22L (FIG. 5).

[0026] Furthermore, the apertures 25A are arranged in the X direction at equal intervals similar to those of the first lens 22L and the second lens 30L, with their centers coinciding with the centers of the first lens 22L (FIG. 5), and therefore, linear wall portions 25W extending along the Y direction are formed between apertures 25A adjacent to each other in the X direction, extending from the side surface on the +Z direction to the side surface on the −Z direction of the aperture array 25. In this embodiment, the thickness of the wall portions 25W in the X direction is 0.1 mm, and the thickness of one aperture array 25 in the Z direction is 0.3 mm.

[0027] 4A and 6, the image sensor-side aperture array group 28 is disposed between the diaphragm array 26 and the second lens array 30, and is configured by, for example, bonding nine aperture arrays 25 together so that they are stacked in the Z direction. The aperture arrays 25 of the image sensor-side aperture array group 28 are configured in the same manner as the aperture arrays 25 of the subject-side aperture array group 24.

[0028] As described above, a plurality (11) of the aperture arrays 25 of the subject-side aperture array group 24 are bonded together so as to be stacked in the Z direction, and a plurality (9) of the aperture arrays 25 of the image sensor-side aperture array group 28 are bonded together so as to be stacked in the Z direction. For this reason, as shown in Fig. 8, between the first lens array 22 and the aperture array 26, and between the aperture array 26 and the second lens array 30, the wall portions 25W of the plurality of aperture arrays 25 that are in close contact with each other in the Z direction and adjacent to each other are connected without any gaps, thereby forming optical axis direction wall portions 40 that are thin walls extending in the Z direction.

[0029] Therefore, the reading head 6 (Figure 3) can prevent light that passes through the lens surface 22LSi of the first lens 22L of the first lens array 22 and then through the aperture array 26 from being incident as stray light on the second lens array 30, whose optical axis does not coincide with that of the first lens 22L, thereby maintaining reading quality.

[0030] [1-2-3. Board Configuration] As shown in FIG. 3 , the board 14 is attached to the holder 12 on the −Z-direction side of the lens unit 20, with its longitudinal direction aligned with the X-direction. The board 14 is made of a so-called glass epoxy board, elongated in the X-direction and thin in the Z-direction, and is configured with multiple wiring layers with predetermined wiring patterns laminated in the Z-direction. On the +Z-direction surface of the board 14, a line sensor 32 is mounted in a linear array along the longitudinal direction of the board 14, approximately at the center in the Y-direction, facing the lens unit 20. The line sensor 32 includes multiple image sensors 33, each approximately 10 mm long in the X-direction, arranged linearly at predetermined intervals. The line sensor 32 converts the image of a subject, such as the inspection object 4, formed by the lens unit 20 (i.e., the optical image formed by the optical system) into an electrical signal. Furthermore, since the line sensor 32 is arranged linearly along the X-direction, it generates a one-dimensional image. In this embodiment, for example, the reading width in the X direction of the line sensor 32 is 250 mm, and 25 image pickup elements 33 are mounted. Also mounted on the board 14 are a connector (not shown) to which the cable 8 (FIG. 1) is connected and which electrically connects the board 14 with an external control device, and various electronic components (not shown) that drive the image pickup elements 33.

[0031] [1-3. Operation and Effects, etc.] In this configuration, when light La from a subject enters the first lens array 22 ( FIG. 8 ) of the lens unit 20, the first lens array 22 condenses the light La and forms an inverted, reduced intermediate image. At this time, the light La from the subject is stopped down by the apertures 26A of the aperture array 26 at a focal length position on the −Z direction side (toward the image sensor) of the first lens 22L, so the aperture array 26 cuts off light that enters the second lens array 30 along directions other than the direction of the optical axis. In this way, the lens unit 20 has a chief ray parallel to the optical axis only on the +Z direction side (toward the subject) of the lens surface 22LSi of the first lens array 22. This makes the lens unit 20 an object-side telecentric optical system.

[0032] The stacked aperture arrays 25 also prevent light emitted from each lens surface 22LSi of the first lenses 22L of the first lens array 22 from being incident on lens surfaces 30LSo of the second lenses 30L of the second lens array 30 other than the lens surfaces 30LSo through which the optical axes of the lens surfaces 22LSi pass. Next, the second lens array 30 inverts and enlarges the inverted, reduced intermediate image of the subject, and forms an erect, life-size image on the image sensor 33.

[0033] Furthermore, the reading head 6 is configured so that a plurality of aperture arrays 25 are stacked in the Z direction between the first lens array 22 and the aperture array 26, and between the aperture array 26 and the second lens array 30. Therefore, the reading head 6 can form optical axis direction wall portions 40, which are thin walls extending in the Z direction, between the first lens array 22 and the aperture array 26, and between the aperture array 26 and the second lens array 30, in which the wall portions 25W of the plurality of aperture arrays 25 that are in close contact with each other in the Z direction are connected without any gaps.

[0034] Furthermore, the reading head 6 is configured so that the optical axis direction wall portion 40 is located on a straight line L1 connecting a predetermined first lens 22L and a second lens 30L whose optical axis does not coincide with that of the first lens 22L. This prevents light that passes through the lens surface 22LSi of the first lens 22L of the first lens array 22 and then passes through the diaphragm array 26 from being incident as stray light on the second lens array 30 whose optical axis does not coincide with that of the first lens 22L, thereby maintaining reading quality.

[0035] Here, due to the complexity of the shape and manufacturing costs, it is also possible to fabricate the aperture array 25 by injection molding of resin. However, when fabricating the aperture array 25 by injection molding, it is difficult to process the mold, making it difficult to process the apertures 25A into a shape other than circular to match the lens shapes of the first lenses 22L of the first lens array 22 and the second lenses 30L of the second lens array 30, which are shapes other than circular. Furthermore, when fabricating the aperture array 25 by injection molding, from the perspective of resin fluidity, the wall thickness between adjacent apertures 25A in the X direction (i.e., the X-direction thickness of the wall portion 25W) needs to be at least approximately 0.3 mm, which makes it impossible to arrange the apertures 25A of the aperture array 25 at narrow intervals in the X direction (i.e., the apertures 25A cannot be arranged at a narrow pitch). Therefore, the first lenses 22L of the first lens array 22 and the second lenses 30L of the second lens array 30 must be matched to the pitch of the openings 25A of the opening array 25, and therefore the pitch between the first lenses 22L and the second lenses 30L cannot be made narrower.

[0036] On the other hand, it is conceivable that the apertures 25A of the aperture array 25 are fabricated at a narrow pitch by, for example, mechanical processing or laser processing to match the lens shapes of the first lens 22L and the second lens 30L. However, in this case, mass production is poor and mass production is not realistic.

[0037] In contrast, the inspection device 1 is configured such that a silicon wafer or the like is etched to create an aperture array 25 having a plurality of apertures 25A that are a high-definition aperture pattern. This allows the inspection device 1 to arrange the apertures 25A of the aperture array 25 at narrow intervals in the X direction (i.e., the apertures 25A can be spaced at narrow pitches). Therefore, the inspection device 1 can narrow the pitch between the first lenses 22L of the first lens array 22 and the second lenses 30L of the second lens array 30 to match the narrow-pitch apertures 25A. This allows the inspection device 1 to expand the depth of field and reduce uneven brightness.

[0038] Furthermore, the outer shape of the opening 25A (FIG. 6) of the reading head 6 is similar to and smaller than the first lens 22L (FIG. 5) and the second lens 30L. Therefore, by arranging the openings 25A at a narrow pitch and matching the shape of the openings 25A with the first lens 22L and the second lens 30L, the reading head 6 can expand the depth of field and reduce uneven brightness.

[0039] According to the above configuration, the lens unit 20 of the inspection device 1 includes a first lens array 22 in which first lenses 22L as a plurality of first lenses are arranged in the X direction as a first direction, a second lens array 30 in which second lenses 30L as a plurality of second lenses are arranged in the X direction so that their optical axes coincide with those of the first lenses 22L, and an aperture array 25 in which a plurality of apertures 25A are arranged between the first lens array 22 and the second lens array 30 so as to be stacked in the Z direction as the optical axis direction in which the optical axes extend, and in which a plurality of apertures 25A are arranged in the X direction so that their optical axes coincide with those of the first lenses 22L and the second lenses 30L.

[0040] Furthermore, according to the above configuration, the reading head 6 of the inspection device 1 includes a substrate 14 on which a plurality of image pickup elements 33 serving as light receiving elements are mounted in the X direction as a longitudinal direction, a lens unit 20 that passes light from the inspection object 4 as a light source toward the image pickup elements 33 and converges it, and a holder 12 that supports the substrate 14 and the lens unit 20. The lens unit 20 includes a first lens array 22 on which a plurality of first lenses 22L are arranged in the X direction and on which light is incident, a second lens array 30 on which a plurality of second lenses 30L are arranged in the X direction so that their optical axes coincide with those of the first lenses 22L and which converges the light incident from the first lens array 22, and an aperture array 25 arranged in plurality between the first lens array 22 and the second lens array 30 so as to be stacked in the Z direction as the optical axis direction in which the optical axis extends, and a plurality of apertures 25A arranged in the X direction so that their optical axes coincide with those of the first lenses 22L and the second lenses 30L.

[0041] As a result, the reading head 6 can use the aperture 25A of the aperture array 25 to block light emitted from the first lens 22L from entering the second lens 30L, which has an optical axis different from that of the first lens 22L.

[0042] 1 and 2, an inspection device 101 according to the second embodiment differs from the inspection device 1 according to the first embodiment in that it has a read head 106 instead of the read head 6, but is otherwise configured similarly. As shown in FIGS. 2 and 3, the read head 106 according to the second embodiment differs from the read head 6 according to the first embodiment in that it has a lens unit 120 instead of the lens unit 20, but is otherwise configured similarly.

[0043] 10, in which the same reference numerals are used for components corresponding to those in FIG. 8, lens unit 120 according to the second embodiment differs from lens unit 20 according to the first embodiment in that it is provided with an object-side aperture array group 124 in place of object-side aperture array group 24 and an image sensor-side aperture array group 128 in place of image sensor-side aperture array group 28, but is otherwise configured similarly.

[0044] [2-2-1. Configuration of the Object-Side Aperture Array Group] The object-side aperture array group 124 according to the second embodiment is configured similarly to the object-side aperture array group 24 according to the first embodiment, except that it has a plurality of aperture arrays 125 instead of the plurality of aperture arrays 25. The aperture array 125 according to the second embodiment is configured similarly to the aperture array 25 according to the first embodiment, except that it has apertures 125A instead of apertures 25A and walls 125W instead of wall portions 25W.

[0045] Compared to opening 25A, the inner wall surface of opening 125A is linearly inclined relative to the Z direction toward the central axis of opening 125A as it moves from the +Z direction end to the -Z direction end. Therefore, the maximum width of opening 125A in the X direction at the end on the light exit side (-Z direction) is narrower than the maximum width in the X direction at the end on the light incident side (+Z direction). Therefore, the outer wall surfaces of both ends of wall 125W in the X direction are linearly inclined relative to the Z direction toward the central axis of opening 125A as they move from the +Z direction end to the -Z direction end. Furthermore, the maximum width of opening 125A in the Y direction at the end on the light exit side (-Z direction) is narrower than the maximum width in the Y direction at the end on the light incident side (+Z direction). Therefore, the outer wall surfaces of both ends of wall portion 125W in the Y direction are linearly inclined with respect to the Z direction toward the central axis of opening 125A as they move from the +Z direction end to the -Z direction end. Such a shape of opening 125A is produced by controlling the etching process.

[0046] [2-2-2. Configuration of Image Sensor Side Aperture Array Group] The aperture arrays 125 of the image sensor side aperture array group 128 are configured in the same manner as the aperture arrays 125 of the subject side aperture array group 124 .

[0047] 11A and 11B show a comparison between the lens unit 20 according to the first embodiment and the lens unit 120 according to the second embodiment. In the case of the lens unit 20 shown in FIG. 11A, the opening 25A has a generally cylindrical shape overall, and therefore its inner wall surface is linearly aligned in the Z direction from its end in the +Z direction to its end in the −Z direction. Therefore, when light L2 from the first lens 22L of the first lens array 22 enters the opening 25A of the opening array 25 of the lens unit 20, the light L2 is reflected by the inner wall surface of the opening 25A, enters the second lens array 30, and then enters the image sensor 33 as stray light, which is an unintended light component, potentially reducing imaging performance.

[0048] In contrast, in the case of the lens unit 120 shown in FIG. 11B , the inner wall surface of the opening 125A is linearly inclined relative to the Z direction toward the central axis of the opening 125A as it moves from the +Z direction end to the -Z direction end, so that the width of the end on the light L3 exit side is narrower than the width of the end on the light L3 entrance side. Therefore, when light L3 enters the opening 125A of the aperture array 125 of the lens unit 120 from the first lens 22L of the first lens array 22 and reaches the inner wall surface of the opening 125A, the light L3 is reflected more toward the +Z direction than the opening 25A, and then reaches the inner wall surface of the opening 125A on the opposite side in the X direction, for example, and is reflected again, repeatedly. Therefore, in the case of the lens unit 120, light L3 reflected by the opening 125A is less likely to enter the second lens array 30 than in the lens unit 20. This allows the lens unit 120 to suppress stray light more effectively than the lens unit 20.

[0049] In addition, the inspection device 101 according to the second embodiment can achieve substantially the same effects as the inspection device 1 according to the first embodiment.

[0050] [3. Other Embodiments] In the above-described first embodiment, the present invention has been described as being applied to an inspection device 1 having a lens unit 20 in which the first lenses 22L of the first lens array 22, the openings 25A of the aperture array 25, the holes 26A of the diaphragm array 26, and the second lenses 30L of the second lens array 30 are mounted in a single linear row along the X direction, and having a reading head 6 in which line sensors 32 corresponding to the lens unit 20 are mounted in a single linear row along the X direction.

[0051] The present invention is not limited to this, and may also be applied to an inspection device having a lens unit 220 for an area sensor shown in FIG. 12 . The lens unit 220 is configured such that a first multi-row lens array 50, a plurality of multi-row aperture arrays 52, and a second multi-row lens array 54 are stacked in order along the Z direction from the +Z direction (toward the subject) to the −Z direction (toward the image sensor). The first multi-row lens array 50 has a plurality of first lenses 50L arranged two-dimensionally along the X and Y directions. The second multi-row lens array 54 has a plurality of second lenses 54L arranged two-dimensionally along the X and Y directions with their optical axes aligned with the first lenses 50L. The multi-row aperture array 52 has a plurality of apertures 52A arranged two-dimensionally along the X and Y directions with their optical axes aligned with the first lenses 50L and the second lenses 54L. The shape of the apertures 52A is created by controlling the etching process. Between adjacent openings 52A, a wall portion 52W is formed extending from the +Z direction side surface to the −Z direction side surface of the multi-row opening array 52. ​​Although the lens unit 220 does not include an aperture array, it may include an aperture array in which holes are formed with the optical axes aligned with the first lens 50L, the second lens 54L, and the openings 52A.

[0052] In the first embodiment described above, the reading head 6 forms an erect, life-size image of the subject on the image sensor 33 using the lens unit 20. The present invention is not limited to this, and the reading head 6 may form, for example, various other images of the subject on the image sensor 33 using the lens unit 20. The same applies to the second embodiment. Furthermore, the reading head 6 may have a numerical relationship other than that shown in FIG. 9 and equation (1) as long as it is an optical system that forms an inverted, reduced image of the subject as an intermediate image within the optical system and then forms an inverted, enlarged image of the intermediate image to form an erect, life-size image of the subject on the image sensor 33. The same applies to the second embodiment.

[0053] Furthermore, in the first embodiment described above, the reading head 6 has been described as having the object-side aperture array group 24 disposed between the first lens array 22 and the aperture array 26, and the image sensor-side aperture array group 28 disposed between the aperture array 26 and the second lens array 30. However, the present invention is not limited to this, and the reading head 6 may omit either the object-side aperture array group 24 or the image sensor-side aperture array group 28, provided that light that passes through the lens surface 22LSi of the first lens 22L of the first lens array 22 and then passes through the aperture array 26 does not enter the second lens array 30, whose optical axis does not coincide with that of the first lens 22L, as stray light. The same applies to the second embodiment.

[0054] Furthermore, in the first embodiment described above, the outer shape of the openings 25A of the aperture array 25 of the read head 6 is similar to that of the first lens 22L. However, the present invention is not limited to this, and the outer shape of the openings 25A of the aperture array 25 of the read head 6 may be various shapes other than a shape similar to that of the first lens 22L. The same applies to the second embodiment.

[0055] Furthermore, in the first embodiment described above, the aperture array 25 of the read head 6 is fabricated by etching a silicon wafer or the like. However, the present invention is not limited to this, and the aperture array 25 of the read head 6 may be fabricated by etching various other materials that can be etched. The same applies to the second embodiment.

[0056] Furthermore, in the first embodiment described above, the first lens array 22 and the second lens array 30 of the read head 6 are manufactured by injection molding of resin or the like. However, the present invention is not limited to this, and the first lens array 22 and the second lens array 30 of the read head 6 may be manufactured by various other methods, such as molding glass or cutting glass. The same applies to the second embodiment.

[0057] Furthermore, in the first embodiment described above, the reading head 6 has been described as having two lens arrays, the first lens array 22 and the second lens array 30, in the lens unit 20. However, the present invention is not limited to this, and the reading head 6 may have any number of lens arrays, three or more, in the lens unit 20. The same applies to the second embodiment.

[0058] Furthermore, in the first embodiment described above, the read head 6 has been described as arranging the first lenses 22L of the first lens array 22 in a substantially linear row along the X direction. However, the present invention is not limited to this. The read head 6 may also arrange the first lenses 22L of the first lens array 22, for example, in two parallel, substantially linear rows along the X direction, alternating, i.e., in a zigzag pattern. In this case, the openings 25A in the aperture array 25 of the object-side aperture array group 24, the holes 26A in the diaphragm array 26, and the openings 25A in the aperture array 25 of the image sensor-side aperture array group 28 may be formed to match the arrangement of the first lenses 22L of the first lens array 22. This is also true in the second embodiment.

[0059] Furthermore, in the first embodiment described above, the inspection device 1 has been described as performing synthesis processing of image signals obtained by converting an image of the inspection object 4 in the image sensor 33 in the calculation device 10. However, the present invention is not limited to this, and the inspection device 1 may have electronic components that perform arithmetic processing mounted on the reading head 6, perform synthesis processing of image signals obtained by converting an image of the inspection object 4 in the image sensor 33 in the reading head 6, transmit the synthesized image signals to the calculation device 10, and perform detection of scratches on the inspection object 4, inspection of dimensions, etc. in the calculation device 10. The same applies to the second embodiment.

[0060] Furthermore, in the second embodiment described above, the read head 106 linearly inclines the inner wall surface of the aperture array 125 relative to the Z direction toward the central axis of the aperture 125A as it moves from the +Z direction end to the −Z direction end. The present invention is not limited to this. For example, the read head 106 may linearly incline the inner wall surface of only one end of the aperture array 125 in the X direction relative to the Z direction toward the central axis of the aperture 125A as it moves from the +Z direction end to the −Z direction end. Alternatively, the read head 106 may form an inflection point along the way rather than linearly inclining the inner wall surface of the aperture array 125 from the +Z direction end to the −Z direction end. Essentially, the read head 106 may form a space in the aperture 125A such that the distance in the X direction is narrower on the image sensor 33 side (−Z direction side) than on the subject side (+Z direction side).

[0061] Furthermore, in the second embodiment described above, the reading head 106 has been described as having the openings 125A in all of the aperture arrays 125 in the subject-side aperture array group 124 and the openings 125A in all of the aperture arrays 125 in the image sensor-side aperture array group 128 shaped like the above-mentioned aperture 125A. The present invention is not limited to this, and it is sufficient that the reading head 106 has the openings 125A in at least one aperture array 125 in the subject-side aperture array group 124 or the image sensor-side aperture array group 128 shaped like the above-mentioned aperture 125A.

[0062] Furthermore, in the first embodiment described above, the reading head 6 is described as having one aperture array 26 in the lens unit 20. However, the present invention is not limited to this, and the reading head 6 may have any number of aperture arrays 26, two or more, in the lens unit 20. Furthermore, the reading head 6 may not have an aperture array 26 in the lens unit 20, and may omit it. The same applies to the second embodiment.

[0063] Furthermore, in the first embodiment described above, the present invention has been described as being applied to the inspection device 1. However, the present invention is not limited to this, and may also be applied to devices such as printers, facsimiles, MFPs (multifunction printers), and copiers that serve as image forming devices and have an LED head as an exposure device instead of the reading head 6. The present invention may also be applied to scanners that convert optical signals into electrical signals, sensors and switches, input / output devices that use these, biometric authentication devices, communication devices, dimension measuring instruments, and the like.

[0064] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments. That is, the scope of application of the present invention also extends to embodiments in which the above-described embodiments are combined in part or in whole with the above-described other embodiments. The scope of application of the present invention also extends to embodiments in which part of the configuration described in any of the above-described embodiments and other embodiments is extracted and replaced or diverted with part of the configuration of any of the above-described embodiments and other embodiments, or embodiments in which part of the extracted configuration is added to any of the above-described embodiments.

[0065] Furthermore, in the first embodiment described above, the reading head 6 as a light receiving device is configured by the substrate 14 as a substrate, the lens unit 20 as a lens unit, and the holder 12 as a support member, and the lens unit has the first lens array 22 as a first lens array, the second lens array 30 as a second lens array, and the aperture array 25 as an aperture array, and the inspection device 1 as a reading device having this light receiving device is described. The present invention is not limited to this, and the light receiving device may be configured by a substrate, lens unit, and holding member having various other configurations, and the lens unit may have the first lens array, second lens array, and aperture array having various other configurations, and a reading device may be configured having this light receiving device.

[0066] The present invention can be used, for example, in a read head mounted in a scanner.

[0067] 1, 101... Inspection device, 2... Conveyance system, 4... Inspection object, 6, 106... Reading head, 8... Cable, 10... Calculation device, 12... Holder, 12B... Bottom, 12W... Side, 12A... Holder opening, 12L... Hole, 14... Substrate, 20, 120, 220... Lens unit, 22... First lens array, 22L... First lens, 22LSo, 22LSi... Lens surface, 24, 124... Object-side aperture array group, 25, 125... Aperture array, 2 5A, 125A...aperture, 25W, 125W...wall, 26...aperture array, 26A...hole, 28, 128...image sensor side aperture array group, 30...second lens array, 30L...second lens, 30LSo, 30LSi...lens surface, 32...line sensor, 33...image sensor, 40...optical axis direction wall, 50...first multi-row lens array, 50L...first lens, 52...multi-row aperture array, 52A...aperture, 54...second multi-row lens array, 54L...second lens.

Claims

1. A lens unit comprising: a first lens array in which a plurality of first lenses are arranged in a first direction; a second lens array in which a plurality of second lenses are arranged in the first direction so that the optical axis of each of the second lenses coincides with that of the first lens; and an aperture array in which a plurality of lenses are arranged between the first lens array and the second lens array so that they are stacked in the optical axis direction in which the optical axis extends, and in which a plurality of apertures are arranged in the first direction so that the optical axis of each of the apertures coincides with that of the first lens and the second lens.

2. A lens unit as described in claim 1, wherein a wall portion is formed between adjacent openings in the first direction, and a plurality of opening arrays stacked in the optical axis direction form an optical axis direction wall portion in which the wall portion extends continuously in the optical axis direction.

3. The lens unit according to claim 2, wherein the optical axis direction wall portion is arranged on a straight line connecting a predetermined first lens and a second lens whose optical axis does not coincide with that of the first lens.

4. The lens unit according to claim 2, wherein the wall portion extends linearly in a direction perpendicular to the first direction and the optical axis direction.

5. The lens unit according to claim 2, wherein the thickness of the wall portion in the first direction is 0.3 mm or less.

6. The lens unit according to claim 1, wherein the opening has a shape substantially similar to that of the first lens.

7. The lens unit according to claim 1, wherein said aperture array is made of silicon.

8. The lens unit according to claim 1, wherein the aperture array is fabricated by etching.

9. A lens unit as described in claim 1, wherein the opening has a portion whose width in the first direction is narrower on the second lens array side than on the predetermined location in the optical axis direction, compared to the width in the first direction at the predetermined location in the optical axis direction.

10. A lens unit as described in claim 9, wherein the maximum width in the first direction of the end of the opening on the light exit side is narrower than the maximum width in the first direction of the end of the opening on the light incident side.

11. The lens unit of claim 1, further comprising an aperture array between the first lens array and the second lens array, the aperture array having a plurality of apertures arranged in the first direction so that the optical axes of the apertures are aligned with the first lens and the second lens.

12. The lens unit according to claim 11, wherein the aperture arrays are arranged on the first lens array side and the second lens array side relative to the diaphragm array.

13. The lens unit according to claim 1, wherein the optical system formed by at least two lenses including the first lens and the second lens is an erect unity magnification optical system.

14. A light-receiving device comprising: a substrate on which a plurality of light-receiving elements are mounted in a first direction; a lens unit that passes light from a light source toward the light-receiving elements and converges the light; and a support member that supports the substrate and the lens unit, wherein the lens unit comprises: a first lens array in which a plurality of first lenses are arranged in the first direction and on which the light is incident; a second lens array in which a plurality of second lenses are arranged in the first direction so that each of the second lenses has an optical axis coinciding with that of the first lens and converges the light incident from the first lens array; and an aperture array in which a plurality of apertures are arranged between the first lens array and the second lens array so as to be stacked in the optical axis direction in which the optical axis extends, and in which a plurality of apertures are arranged in the first direction so that each of the optical axes of the apertures coincides with that of the first lens and the second lens.

15. A reading device having the light receiving device of claim 14.

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