Lens unit, light receiving device and reading device

Abstract

Maintain reading quality. [Solution] The reading head (6) has a substrate (14) on which a plurality of image pickup elements (33) are mounted in the X direction, a lens unit (20) that receives light from the object (4) to be inspected and passes it toward the image pickup elements (33) to converge it, 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 so that their optical axes coincide with those of the first lenses (22L) and that converges the light incident from the first lens array (22), and an aperture array (25) in which a plurality of apertures (25A) are arranged in the X direction between the first lens array (22) and the second lens array (30L) so that their optical axes coincide with those of the first lenses (22L) and the second lenses (30L).

Description

[Technical Field]

[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. [Background technology]

[0002] Conventionally, contact image sensors (CIS) have been used as light receiving devices in scanners and industrial cameras used in 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 according to the pitch of the lenses in the pair of lens arrays, may be disposed midway through the optical system of the lens unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-45093 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[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.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 lens and the second lens.

[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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a perspective view showing the configuration of an inspection device. [Figure 2] FIG. 1 is a perspective view showing the configuration (1) of a read head. [Figure 3] FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, showing the configuration (2) of the reading head. [Figure 4] 1A and 1B show the configuration (1) of a lens unit according to a first embodiment, in which (A) is an exploded cross-sectional view, (B) is a partially enlarged view of a first lens array, and (C) is a partially enlarged view of a second lens array. [Figure 5] 4 is a diagram showing the configuration of the first lens array as viewed from the Z direction. FIG. [Figure 6] FIG. 10 is a view showing the configuration of the aperture array as viewed from the Z direction. [Figure 7] FIG. 10 is a view showing the configuration of the aperture array as viewed from the Z direction. [Figure 8] FIG. 2 is a vertical cross-sectional view showing the configuration (2) of the lens unit according to the first embodiment. [Figure 9] 10 is a table showing the shape of each lens surface. [Figure 10] FIG. 10 is a vertical cross-sectional view showing the configuration of a lens unit according to a second embodiment. [Figure 11] 10A and 10B are longitudinal cross-sectional views of lens units showing a comparison of how light is reflected. [Figure 12] FIG. 10 is a perspective view showing the configuration of a lens unit according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[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 the inspection device] As shown in FIG. 1, the inspection device 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 for flaws, dimensions, and other defects. 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 device 1 acquires an image of the inspection object 4, which is the subject, as one-dimensional data along the X direction, and reads a two-dimensional image of the inspection object 4 by continuously reading the image of the inspection object 4 displacing in the Y direction. In this embodiment, the distance from the subject of inspection 4 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. A 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), drives 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] [1-2. Read head configuration] 2 and 3, the reading head 6 is formed as a rectangular parallelepiped elongated in the X direction as a whole, and the lens unit 20, substrate 14, etc. are attached to the holder 12 so that they are stacked. 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 and Z directions 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 by, for example, 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." The holder 12 holds the lens unit 20, substrate 14, and other components. The lens unit 20 and substrate 14 are adhered to the holder 12 with an adhesive (not shown). The holder 12 is centered around a bottom portion 12B that is elongated in the X direction and thin in the Z direction. Two plate-like side portions 12W, elongated in the X direction and thin in the Y direction, extend from both Y-direction edges of the bottom portion 12B toward the -Z direction. A holder opening 12A is formed at the end of the -Z direction. A slit-shaped hole 12L, elongated in the X direction and thin in the Y direction, is drilled at approximately the center of the bottom portion 12B in the Y direction, penetrating the Z direction.

[0016] [1-2-2. Lens unit configuration] 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 inserted into the hole 12L. As shown in Fig. 4, 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. 4 and 5 , the first lens array 22 is fabricated by resin injection molding or the like, and the glass material of the resin is APL5514 manufactured by 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 first lens array 22 in the Y direction, multiple first lenses 22L are arranged at equal intervals of, for example, 0.5 mm, in a substantially linear line along the X direction (the arrangement direction) with their optical axes aligned in the Z direction. The positions of adjacent first lenses 22L in the X direction are aligned with each other in the Y direction. When viewed from the Z direction, the first lenses 22L have a shape such that both ends of a circle 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 the first lenses 22L, is located at the center of the first lenses 22L. Here, the lens surface of each first lens 22L on the +Z direction side (toward the subject) is referred to as lens surface 22LSo, and the lens surface of each first lens 22L on the −Z direction side (toward the imaging element) is referred to as lens surface 22LSi.

[0018] [1-2-2-2. Configuration of the second lens array] As shown in FIG. 4 , 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 similar 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, in a substantially linear line along the X direction (the arrangement 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 a circle centered on the center of the second lens 30L 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 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] Lens unit 20 forms an inverted, reduced image of the subject as an intermediate image using first lens array 22, and then forms an inverted, enlarged image of the intermediate image using second lens array 30, thereby forming an erect, life-size image of the subject on image sensor 33 (FIG. 3). In this way, 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 vertex of the surface, can be calculated by the following equation (1).

[0022]

number

[0023] [1-2-2-3. Aperture array configuration] As shown in FIGS. 4 and 7 , the aperture array 26 is generally a plate-like member that is elongated in the X direction and thin in the Z direction. In the center 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 row along the arrangement direction (X direction) with their central axes aligned in the Z direction. The holes 26A adjacent to each other 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, hole 26A is positioned in the Z direction so that the focal length position on the −Z direction side (image pickup element side) of first lens 22L is located at the center in the Z direction of hole 26A. Aperture array 26 blocks so-called stray light and flare light other than light rays that form an image of lens unit 20.

[0024] [1-2-2-4. Configuration of the subject-side aperture array group] As shown in Figures 4, 6 and 8, the subject-side aperture array group 24 is arranged between the first lens array 22 and the aperture array 26, and is composed of, for example, 11 aperture arrays 25 bonded together so as to be 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 first lenses 22L adjacent 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 linearly aligned in the Z direction from the +Z direction end to the -Z direction end. Therefore, the outer wall surfaces of the wall portions 25W (described later) are linearly aligned 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. Furthermore, 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 the center of the opening 25A coincides with the center of the first lens 22L (FIG. 5).

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

[0027] [1-2-2-5. Configuration of the image sensor side aperture array group] 4 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 object-side aperture array group 24.

[0028] As described above, a plurality (11) of 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 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. Circuit board configuration] As shown in FIG. 3 , the substrate 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 substrate 14 is made of a so-called glass epoxy substrate and is formed as a plate that is elongated in the X direction and thin in the Z direction. Multiple wiring layers, each with a predetermined wiring pattern, are stacked in the Z direction. On the surface of the +Z direction side of the substrate 14, a line sensor 32 is mounted in a linear array along the longitudinal direction of the substrate 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 an image of a subject, such as the inspection target 4, formed by the lens unit 20 (i.e., an optical image formed by the optical system) into an electrical signal. Since the line sensor 32 is linearly arranged along the X direction, it generates a one-dimensional image. In this embodiment, for example, the reading width of the line sensor 32 in the X direction is 250 mm, and 25 image sensors 33 are mounted. In addition, the board 14 is mounted with a connector (not shown) to which the cable 8 (Figure 1) is connected and which electrically connects the board 14 to an external control device, and various electronic components (not shown) that drive the imaging element 33.

[0031] [1-3. Actions and Effects] 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 to form an inverted, reduced intermediate image. At this time, the light La from the subject is stopped down by the holes 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 approximately the optical axis. In this way, in the lens unit 20, the chief ray is 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 lens 22L of the first lens array 22 from being incident on any lens surface 30LSo of the second lens 30L of the second lens array 30 other than the lens surface 30LSo through which the optical axis of each lens surface 22LSi passes. 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. As a result, 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 wall portions 25W of a plurality of aperture arrays 25 that are closely adjacent to 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 disposed 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 the 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 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 conceivable to produce aperture array 25 by injection molding of resin. However, when producing aperture array 25 by injection molding, it is difficult to process the mold, and therefore it is difficult to process apertures 25A into a shape other than circular to match the lens shapes of first lenses 22L of first lens array 22 and second lenses 30L of second lens array 30, which are shapes other than circular. Furthermore, when producing aperture array 25 by injection molding, from the viewpoint of resin fluidity, the wall thickness between adjacent apertures 25A in the X direction (i.e., the thickness of wall portion 25W in the X direction) needs to be at least about 0.3 mm, which makes it impossible to arrange apertures 25A of aperture array 25 at narrow intervals in the X direction (i.e., the pitch of apertures 25A cannot be narrowed). For this reason, 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, machining 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 so that an aperture array 25 having a plurality of apertures 25A, which is a high-definition aperture pattern, is fabricated by etching a silicon wafer or the like. As a result, the inspection device 1 can arrange the apertures 25A of the aperture array 25 at narrow intervals in the X direction (i.e., the apertures 25A can be narrowly spaced). 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 narrowly spaced apertures 25A. This enables the inspection device 1 to extend 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 lenses are arranged between the first lens array 22 and the second lens array 30 so that they are 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 element 33 and converges the light, and a holder 12 that supports the substrate 14 and the lens unit 20. The lens unit 20 includes 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 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 axes extend, and in which a plurality of openings 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.

[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] 2. Second Embodiment [2-1. Configuration of inspection device and reading head] 1 and 2, the inspection device 101 according to the second embodiment differs from the inspection device 1 according to the first embodiment in that it has a reading head 106 instead of the reading head 6, but is otherwise configured similarly. As shown in FIGS. 2 and 3, the reading head 106 according to the second embodiment differs from the reading 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] [2-2. Lens unit configuration] As shown in FIG. 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 has 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 subject-side aperture array group] The object-side aperture array group 124 according to the second embodiment differs from the object-side aperture array group 24 according to the first embodiment in that a plurality of aperture arrays 125 is provided instead of the plurality of aperture arrays 25, but is otherwise configured similarly. The aperture array 125 according to the second embodiment differs from the aperture array 25 according to the first embodiment in that apertures 125A are provided instead of apertures 25A, and wall portions 125W are provided instead of wall portions 25W, but is otherwise configured similarly.

[0045] Compared to opening 25A, the inner wall surface of opening 125A is linearly inclined in 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 in 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 in the Z direction toward the central axis of opening 125A as they move from the +Z end to the -Z end. Such a shape of opening 125A is created by controlling the etching process.

[0046] [2-2-2. Configuration of the image sensor side aperture array group] The aperture arrays 125 of the image sensor side aperture array group 128 are configured similarly to the aperture arrays 125 of the object side aperture array group 124 .

[0047] [2-3. Actions and Effects] A comparison between lens unit 20 according to the first embodiment and lens unit 120 according to the second embodiment is shown in Fig. 11. In the case of lens unit 20 shown in Fig. 11(A), opening 25A has a generally cylindrical shape overall, and therefore its inner wall surface is linearly aligned in the Z direction from its end on the +Z direction side to its end on the -Z direction side. Therefore, when light L2 from first lens 22L of first lens array 22 enters opening 25A of aperture array 25 of lens unit 20, light L2 is reflected by the inner wall surface of opening 25A, enters second lens array 30, and then enters image sensor 33 as stray light, which is an unintended light component, potentially degrading imaging performance.

[0048] In contrast, in the case of the lens unit 120 shown in FIG. 11(B), the inner wall surface of the opening 125A is linearly inclined with respect 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, repeating this process. Therefore, in the case of the lens unit 120, the 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 is 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 apertures 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 linear row along the X direction, and having a reading head 6 in which line sensors 32 are mounted in a linear row along the X direction corresponding to the lens unit 20.

[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 the optical axis of each second lens 54L aligned with the first lens 50L. The multi-row aperture array 52 has a plurality of apertures 52A arranged two-dimensionally along the X and Y directions with the optical axis of each first lens 50L and second lens 54L aligned with the optical axis of each second lens 54L. The shape of the apertures 52A is created by controlling the etching process. Between adjacent openings 52A, wall portions 52W are formed from the side surface on the +Z direction side to the side surface on the -Z direction side of multi-row opening array 52. ​​Although 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 first lens 50L, second lens 54L, and openings 52A.

[0052] In the first embodiment described above, the reading head 6 forms an erect, life-size image of the subject on the imaging element 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 imaging element 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 in 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 imaging element 33. The same applies to the second embodiment.

[0053] Furthermore, in the above-described first embodiment, 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 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 reading head 6 has been described as having the outer shape of the openings 25A of the aperture array 25 similar to that of the first lens 22L. However, the present invention is not limited to this, and the reading head 6 may have the outer shape of the openings 25A of the aperture array 25 in 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 reading 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 reading 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 reading head 6 has been described as arranging the first lenses 22L of the first lens array 22 in a single, substantially linear row along the X direction. However, the present invention is not limited to this. The reading head 6 may alternatively arrange the first lenses 22L of the first lens array 22, for example, in two parallel, substantially linear rows along the X direction, alternately, i.e., in a zigzag pattern. In this case, the apertures 25A in the aperture array 25 of the object-side aperture array group 24, the holes 26A in the diaphragm array 26, and the apertures 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 for performing 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 in the Z direction toward the central axis of the aperture 125A as it moves from the +Z end to the −Z 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 toward the central axis of the aperture 125A as it moves from the +Z end to the −Z end. Alternatively, the read head 106 may form an inflection point along the way rather than linearly in the inner wall surface of the aperture array 125 from the +Z end to the −Z 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 side) than on the subject side (+Z 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 of the aperture arrays 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 as image forming devices that 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 any of 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 used as part of the configuration of any of the above-described embodiments and other embodiments, or 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, a lens unit, and a holding member having various other configurations, and the lens unit may have the first lens array, the second lens array, and the aperture array having various other configurations, and a reading device may be configured having this light receiving device. [Industrial Applicability]

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

[0067] 1, 101... Inspection device, 2... Transport 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...wall in the optical axis direction, 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 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 axes of the second lenses coincide with those of the first lenses; an aperture array 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 the optical axes of the first lens and the second lens coincide with each other; A lens unit having:

2. Wall portions are formed between the openings adjacent to each other in the first direction, and the plurality of opening arrays stacked in the optical axis direction form optical axis direction walls in which the wall portions extend continuously in the optical axis direction. The lens unit according to claim 1 .

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

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

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

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

7. The aperture array is formed from silicon. The lens unit according to claim 1 .

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

9. The opening is With respect to the width in the first direction at a predetermined location in the optical axis direction, there is a portion where the width in the first direction is narrower on the second lens array side than on the predetermined location in the optical axis direction. The lens unit according to claim 1 .

10. 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 entrance side. The lens unit according to claim 9.

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

12. The aperture array comprises: The aperture array is disposed on the first lens array side and the second lens array side. The lens unit according to claim 11.

13. The optical system formed by at least two lenses including the first lens and the second lens is an erect unity magnification optical system.

13. The lens unit according to claim 1.

14. a substrate on which a plurality of light receiving elements are mounted in a first direction; a lens unit that passes and converges light from a light source toward the light receiving element; a support member that supports the substrate and the lens unit; and The lens unit comprises: a first lens array on which the light is incident, the first lens array including a plurality of first lenses arranged in the first direction; a second lens array in which a plurality of second lenses are arranged in the first direction so that the optical axes of the second lenses coincide with those of the first lenses, and which converges the light incident from the first lens array; an aperture array 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 the optical axes of the first lens and the second lens coincide with each other; have Light receiving device.

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

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