Lens array unit and image reading device

Abstract

The goal is to achieve good imaging performance at a lower cost compared to conventional methods. [Solution] The device comprises a first lens array and a second lens array, at least one of which has a light-transmitting lens array substrate formed from a material with a linear expansion coefficient smaller than that of the resin forming the lenses, and a resin layer is tightly adhered to at least one of one surface of the lens array substrate that is the light incident side and the other surface opposite to the first surface that is the light exit side, and a plurality of the lenses are formed in the resin layer.

Description

[Technical Field]

[0001] The present invention relates to a lens array unit and an image reading device. [Background technology]

[0002] Conventionally, contact image sensors (CIS) have been used as image reading devices in industrial cameras used for scanners and visual inspection. As a contact image sensor, a system has been proposed in which an erect, 1:1 imaging optical system is formed by a lens array unit composed of multiple resin lens arrays created by injection molding (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-45093 [Overview of the Initiative] [Problem to be solved by the invention]

[0004] However, contact-type image sensors with resin lens arrays have a higher coefficient of thermal expansion than image sensor substrates such as FR-4 (glass epoxy substrate) on which the image sensor is mounted. Therefore, in conventional contact-type image sensors, the position of the lens array and the image sensor can shift significantly during temperature changes, resulting in suboptimal corrections such as shading correction for certain pixels, and potentially degrading imaging performance.

[0005] In contrast, if the lens array is formed from glass, which has a lower coefficient of thermal expansion than resin, the positional shift between the lens array and the image sensor during temperature changes can be suppressed, resulting in better imaging performance compared to when the lens array is formed from resin. However, on the other hand, manufacturing the lens array from glass by cutting or other processes increases costs.

[0006] The present invention has been made in consideration of the above points, and aims to propose a lens array unit and an image reading device that can obtain good imaging performance at low cost. [Means for solving the problem]

[0007] In order to solve this problem, the lens array unit of the present invention comprises: a first lens array having a plurality of lenses, the plurality of lenses being arranged side by side along a first direction perpendicular to the optical axis direction of the lenses; and a second lens array arranged at a distance from the first lens array in the optical axis direction, the plurality of lenses being arranged side by side along the first direction so that their optical axes coincide with those of the lenses of the first lens array; at least one of the first lens array and the second lens array has a light-transmitting lens array substrate formed from a material having a smaller linear expansion coefficient than the resin forming the lenses; and a resin layer is formed in close contact with at least one of one surface of the lens array substrate that is the light incident side and the other surface opposite to the first surface that is the light exit side, and the plurality of lenses are formed in the resin layer.

[0008] The image reading device of the present invention also includes a lens array unit having a lens array in which a plurality of lenses are arranged along a first direction perpendicular to the optical axis direction of the lenses, and an imaging element substrate on which an imaging element that receives light that has passed through the lens array unit is mounted, and the lens array has a light-transmitting lens array substrate formed of a material having a linear expansion coefficient smaller than that of the resin that forms the lenses, and a resin layer is formed in close contact with at least one of one surface of the lens array substrate that is the light incident side and the other surface opposite to the one surface that is the light exit side, and the plurality of lenses are formed in the resin layer.

[0009] In this invention, the lens array is constructed using a lens array substrate made of a material with a lower coefficient of thermal expansion than the resin used to form the lenses, and lenses formed on a resin layer in close contact with the lens array substrate. This reduces the difference in coefficients of thermal expansion between the lens array substrate and the image sensor substrate, thereby suppressing misalignment between the lens array and the image sensor during temperature changes. Furthermore, instead of forming the entire lens array from a material with a lower coefficient of thermal expansion than the resin and thus higher cost, the lens array substrate is formed from the aforementioned material, and the lenses are formed on the lens array substrate using resin, thereby reducing costs. [Effects of the Invention]

[0010] According to the present invention, it is possible to realize a lens array unit and an image reading device that can obtain good imaging performance at a lower cost than conventional ones. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing the configuration of an image inspection device according to a first embodiment. [Figure 2] 1 is a perspective view showing the external configuration of an image reading device according to a first embodiment; [Figure 3] 1 is a cross-sectional view showing the internal configuration of an image reading device according to a first embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a part of FIG. 3. [Figure 5] 4 is a table showing an example of the radius of curvature, conic constant, aspherical coefficient, and distance from the imaging element of each lens according to the first embodiment. [Figure 6] 4 is a table showing an example of the refractive index, Abbe number, and thickness of each lens and each substrate according to the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing the internal configuration of an image reading device according to a second embodiment. [Figure 8] FIG. 8 is an enlarged cross-sectional view of a part of FIG. 7. [Figure 9]10 is a table showing an example of the radius of curvature, conic constant, aspherical coefficient, and distance from the imaging element of each lens according to the second embodiment. [Figure 10] 10 is a table showing an example of the refractive index, Abbe number, and thickness of each lens and each substrate according to the second 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.

[0013] 1. First Embodiment [1-1. Configuration of image inspection device] 1 shows the configuration of an image inspection device 10 according to this embodiment. This image inspection device 10 has a transport system 12 such as a belt conveyor that transports an inspection object 11, an image reading device 101 that reads an image of the inspection object 11 transported by the transport system 12, and a computing device 14 connected to the image reading device 101 via a cable 13.

[0014] The conveying system 12 has a conveying member 12a such as a belt, and is configured to place and convey the inspection objects 11 on this conveying member 12a. Fig. 1 shows an example in which a plurality of inspection objects 11 are placed side by side in the conveying direction of the conveying member 12a, and also placed side by side in the width direction perpendicular to the conveying direction of the conveying member 12a.

[0015] The image reading device 101 is a contact type image sensor disposed above the conveying member 12a, and is a device that reads an image of one line along the width direction of the conveying member 12a (that is, a one-dimensional image).

[0016] In this image inspection device 10, while the inspection object 11 is transported by the transport system 12, the image reading device 101 continuously reads one line of images and sequentially transmits the read images to the calculation device 14 via the cable 13. The calculation device 14 forms a two-dimensional image (i.e., a planar image) by synthesizing the one line of images (i.e., one-dimensional images) continuously transmitted from the image reading device 101, and uses the formed image to detect flaws and inspect the dimensions of each inspection object 11. Note that by mounting an electronic component that performs calculation processing on the image reading device 101, the image reading device 101 may synthesize the read images and transmit the synthesized image to the calculation device 14.

[0017] [1-2. Image reader configuration] Next, the configuration of the image reading device 101 used in the above-mentioned image inspection device 10 and the like will be described in more detail with reference to Figures 2 and 3. Figure 2 is a perspective view showing the external configuration of the image reading device 101, and Figure 3 is a cross-sectional view showing the internal configuration of the image reading device 101. In the following, the optical axis direction of the optical system of the image reading device 101 is defined as the Z direction. The +Z direction is defined as the direction approaching the subject (upward in Figure 2), and the -Z direction is defined as the direction moving away from the subject.

[0018] The image reading device 101 is a contact-type image sensor that is roughly rod-shaped and long in the X direction, which is perpendicular to the Z direction (optical axis direction), and reads an image of a subject such as the above-mentioned inspection object 11 (FIG. 1) as one-dimensional data (one line's worth of data) along the X direction. Also, a two-dimensional image can be obtained by continuously reading images using the image reading device 101 while displacing the subject in the Y direction, which is perpendicular to the Z and X directions, or while displacing the image reading device 101 in the Y direction.

[0019] In this embodiment, the distance from the subject to the lens of image reading device 101 (first lens 110d, described later) is set to 20 mm. The length of image reading device 101 in the X direction is set to approximately 300 mm so that A3 size can be scanned. The length of image reading device 101 in the X direction is defined as the width of image reading device 101.

[0020] As shown in FIG. 3, which is a cross-sectional view of the image reading device 101 taken at a predetermined point in the X direction, the image reading device 101 is composed of an imaging element substrate 102, a lens array unit 103, and a holder 104.

[0021] The holder 104 is a member that holds the imaging element substrate 102 and the lens array unit 103. The holder 104 is a hollow member that is long in the X direction and has a generally convex cross section in which a first portion 104a on the +Z direction side (the side closer to the subject and the upper portion in the drawing) is shorter in the Y direction than a second portion 104b on the -Z direction side (the side farther from the subject and the lower portion in the drawing).

[0022] This holder 104 holds the lens array unit 103 inside a first portion 104a, and holds the image pickup element substrate 102 inside a second portion 104b. The lens array unit 103 and the image pickup element substrate 102 are held in close contact with the inside of the holder 104 by, for example, an adhesive (not shown).

[0023] The holder 104 also has an opening 104c on one surface in the +Z direction (the top surface in the drawing), and the opening 104c is closed by one surface of the lens array unit 103 (i.e., one surface of the lens array unit 103 is exposed through the opening 104c). The holder 104 also has an opening 104d on one surface in the -Z direction (the bottom surface in the drawing), and the image pickup element substrate 102 closes the opening 104d.

[0024] The imaging element substrate 102 is a plate-shaped member, and is equipped with an imaging element 102a that converts an optical image formed by the lens array unit 103 into an image signal, a connector (not shown) for electrically connecting to an external control device (not shown), and various electronic components (not shown) for driving the imaging element 102a. The imaging element substrate 102 is a printed circuit board made of FR-4 (glass epoxy board) or the like, and generally, the linear expansion coefficient of printed circuit boards such as FR-4 is 14×10 -6 / ℃.

[0025] The image sensor 102a is, for example, a CCD (Charge Coupled Device) with a length of about 10 mm in the X direction. On one surface of the image sensor substrate 102 in the +Z direction (the surface facing the lens array unit 103), these image sensors 102a are mounted continuously in the X direction. In this embodiment, 30 image sensors 102a are mounted on one surface of the image sensor substrate 102 in the X direction, and these 30 image sensors 102a constitute a line sensor. The resolution of this line sensor is, for example, 600 dpi (42 μm period).

[0026] The lens array unit 103 is an optical system composed of a first lens array 110 located on the side closer to the subject, a second lens array 111 located on the side further from the subject, and an aperture array 112 located between the first lens array 110 and the second lens array 111. In other words, the lens array unit 103 is an optical system in which the first lens array 110 and the second lens array 111 are spaced apart in the Z direction (optical axis direction), and the aperture array 112 is located between the first lens array 110 and the second lens array 111.

[0027] As shown in the enlarged view in Figure 4, the first lens array 110 consists of a first lens array substrate 110a, which is a plate-shaped glass that is long in the X direction; a first resin layer 110b formed in close contact with one surface of the first lens array substrate 110a in the +Z direction (the surface closer to the subject); and a second resin layer 110c formed in close contact with one surface of the first lens array substrate 110a in the -Z direction (the surface further away from the subject).

[0028] A plurality of first lenses 110d are formed in an array on the first resin layer 110b so as to be in contact with each other in the X direction. A plurality of second lenses 110e are also formed in an array on the second resin layer 110c so as to be in contact with each other in the X direction.

[0029] The first resin layer 110b and the second resin layer 110c are layers of resin that has ultraviolet curing or heat curing properties, and the first lens 110d and the second lens 110e are formed by imprint technology.

[0030] The first lens array 110 is held in the holder 104 so that the first lenses 110d formed on one surface (the surface closer to the subject) of the first lens array substrate 110a in the +Z direction are exposed from the opening 104c of the holder 104.

[0031] As shown in Figure 3, the second lens array 111 has a configuration similar to that of the first lens array 110, and is composed of a second lens array substrate 111a, a third resin layer 111b formed in close contact with one surface of the second lens array substrate 111a in the +Z direction, and a fourth resin layer 111c formed in close contact with the other end surface of the second lens array substrate 111a in the Z direction.

[0032] A plurality of third lenses 111d are formed in an array on the third resin layer 111b so as to be in contact with each other in the X direction. A plurality of fourth lenses 111e are also formed in an array on the fourth resin layer 111c so as to be in contact with each other in the X direction.

[0033] In this embodiment, the first lens 110d, the second lens 110e, the third lens 111d, and the fourth lens 111e are each a circular convex lens with a diameter of 1 mm, and are arranged in an array at a period of 1 mm in the X direction so that their optical axes coincide.

[0034] The radius of curvature r [mm], conic constant k, aspheric coefficient A, and distance [mm] from the image sensor 102a of each lens (first lens 110d, second lens 110e, third lens 111d, and fourth lens 111e) are shown in the table of Fig. 5. The first lens 110d and the third lens 111d are convex lenses that are convex on the +Z direction side (toward the subject), and the second lens 110e and the fourth lens 111e are convex lenses that are convex on the -Z direction side (toward the image sensor 102a).

[0035] Furthermore, the shape of each lens can be expressed by the following equation 1, where z is the displacement from the vertex of the surface in the optical axis direction, r is the radius of curvature, h is the height from the optical axis in a direction perpendicular to the optical axis, k is the conic constant, and A is a fourth-order aspherical coefficient.

[0036]

number

[0037] The lens array unit 103 forms an inverted, reduced image of the subject as an intermediate image using the first lens array 110, and forms an inverted, enlarged image of the intermediate image using the second lens array 111, thereby forming an erect, equal-size image of the subject on the image sensor 102a.

[0038] Note that the radius of curvature r [mm], conic constant k, aspherical coefficient A, and distance [mm] from the image sensor 102a of each lens shown in the table of FIG. 5 are merely examples, and the first lens array 110 and the second lens array 111 may be any optical system that can form an erect, life-size image of the subject on the image sensor 102a.

[0039] Furthermore, the refractive index, Abbe number, and thickness [mm] of each lens (first lens 110d, second lens 110e, third lens 111d, fourth lens 111e) and each substrate (first lens array substrate 110a, second lens array substrate 111a) are shown in the table of FIG. 6. The linear expansion coefficient of the glass forming the first lens array substrate 110a and second lens array substrate 111a is generally 9×10 -6 / °C, and the linear expansion coefficient of the resin forming each resin layer (first resin layer 110b, second resin layer 110c, third resin layer 111b, fourth resin layer 111c) is generally 70×10 -6 It is approximately / ℃.

[0040] Returning to Figures 3 and 4, the aperture array 112 is arranged in an array in the X direction with a period of 1 mm, where apertures 112a are formed by circular holes slightly smaller than each lens of the first lens array 110 and the second lens array 111 penetrating in the Z direction. Each aperture array 112 is positioned such that the optical axes of each lens of the first lens array 110 and the second lens array 111 pass through the center of the circle as viewed from the Z direction.

[0041] In this embodiment, aperture array 112 is formed by cutting stainless steel. The linear expansion coefficient of stainless steel forming aperture array 112 is generally 12×10 -6 / °C. Alternatively, the aperture array 112 may be made of another material such as aluminum. Generally, the linear expansion coefficient of aluminum is 25×10 -6 / ° C. The image reading device 101 has the above-described configuration.

[0042] [1-3. Operation of image reading device] Next, the operation of the image reading device 101 will be briefly explained. The image reading device 101 focuses light from the subject with the first lens array 110 and forms an inverted, reduced intermediate image. Furthermore, the image reading device 101 inverts and enlarges the inverted, reduced intermediate image formed by the first lens array 110 with the second lens array 111, forming an upright, 1:1 image on the image sensor 102a.

[0043] Here, the light emitted from the second lens 110e of the first lens array 110 enters the third lens 111d of the second lens array 111. However, the aperture array 112 prevents the light emitted from the second lens 110e from entering the third lens 111d, which is on a different optical axis than the second lens 110e. In other words, the aperture array 112 ensures that the light emitted from the second lens 110e enters the third lens 111d, which is on the same optical axis as the second lens 110e.

[0044] The image reading device 101 then converts the erect, life-size image formed on the image sensor 102a into an image signal, thereby reading the image of the subject as one-dimensional data (one line's worth of data) along the X direction. The operation of the image reading device 101 is as described above.

[0045] In addition, the image reading device 101 has a linear expansion coefficient of 9×10 for the first lens array substrate 110a and the second lens array substrate 111a. -6 / °C, and the linear expansion coefficient of the imaging element substrate 102 is 14×10 -6 / °C, the difference in the linear expansion coefficient between the first lens array substrate 110a and the second lens array substrate 111a and the imaging element substrate 102 is about 5×10 -6 / ℃.

[0046] For this reason, when the temperature of the image reading device 101 rises from 25 degrees to 50 degrees, for example, if the total length (total width) in the X direction of 300 mm is divided in half at the center in the X direction to 150 mm, the first lens array substrate 110a and the second lens array substrate 111a will be misaligned by approximately 20 μm in the X direction from the image pickup element 102a on the image pickup element substrate 102.

[0047] [1-4. Summary and Effects] As explained above, the image reading device 101 of the first embodiment includes the lens array unit 103 and the imaging element board 102 on which the imaging element 102a that receives light that has passed through the lens array unit 103 is mounted.

[0048] Furthermore, the lens array unit 103 is an optical system that forms an erect, equal-magnification image of a subject on the imaging element 102a using a first lens array 110 and a second lens array 111. The first lens array 110 has a first lens array substrate 110a, which is an example of a lens array substrate that transmits light. A first resin layer 110b is formed in close contact with one surface of the first lens array substrate 110a that is the light incident side (the surface closer to the subject), and a second resin layer 110c is formed in close contact with the other surface opposite to the first surface that is the light exit side. A plurality of first lenses 110d are formed in the first resin layer 110b, and second lenses 110e are formed in the second resin layer 110c.

[0049] On the other hand, the second lens array 111 has a second lens array substrate 111a, and a third resin layer 111b is formed in close contact with one surface (the surface closer to the subject) of the second lens array substrate 111a, and a fourth resin layer 111c is formed in close contact with the other surface opposite to the one surface, and a plurality of third lenses 111d are formed in the third resin layer 111b, and a fourth lens 111e is formed in the fourth resin layer 111c.

[0050] Furthermore, the plurality of first lenses 110d, second lenses 110e, third lenses 111d, and fourth lenses 111e are arranged side by side along the X direction, which is an example of a first direction perpendicular to the optical axis direction, so that their optical axes coincide with each other.

[0051] Furthermore, the first lens array substrate 110a of the first lens array 110 and the second lens array substrate 111a of the second lens array 111 are formed from glass, which is an example of a material having a smaller linear expansion coefficient than the first resin layer 110b, the second resin layer 110c, the third resin layer 111b, and the fourth resin layer 111c (i.e., a material having a smaller linear expansion coefficient than the resin that forms the lenses).

[0052] In this way, in the image reading device 101 of the first embodiment, the lens array (first lens array 110, second lens array 111) is configured by lens array substrates (first lens array substrate 110a, second lens array substrate 111a) formed of glass having a linear expansion coefficient lower than that of the resin forming the lenses, and lenses (first lens 110d, second lens 110e, third lens 111d, fourth lens 111e) formed in resin layers (first resin layer 110b, second resin layer 110c, third resin layer 111b, fourth resin layer 111c) that are in close contact with the lens array substrates.

[0053] By doing this, in the image reading device 101 of the first embodiment, the difference in linear expansion coefficient between the lens array substrate (first lens array substrate 110a, second lens array substrate 111a) and the image sensor substrate 102 is reduced, thereby suppressing misalignment between the lens array (first lens array 110, second lens array 111) and the image sensor 102a when the temperature changes.

[0054] Specifically, for example, when a lens array is formed from resin, the coefficient of thermal expansion of the resin is generally 70 × 10⁻⁶. -6 / °C, and the linear expansion coefficient of the imaging element substrate 102 is 14×10 -6 Since the temperature is approximately / °C, the difference in the coefficient of thermal expansion between the lens array and the image sensor substrate 102 is 56 × 10 -6 / ° C. In this case, for example, if the temperature rises from 25° C. to 50° C., the lens array and the image sensor 102a on the image sensor substrate 102 will be misaligned in the X direction by approximately 210 μm.

[0055] In contrast, in the image reading device 101 according to the first embodiment, the lens array substrates (first lens array substrate 110a, second lens array substrate 111a) are made of glass, so the difference in linear expansion coefficient between the lens array substrates and the image pickup element substrate 102 is 5×10 -6 / ° C. In this case, for example, if the temperature rises from 25° C. to 50° C., the lens array and the image sensor 102a on the image sensor substrate 102 will be misaligned by about 20 μm in the X direction.

[0056] In this way, in the image reading device 101 of the first embodiment, the positional deviation in the X direction between the lens array and the image sensor 102a on the image sensor substrate 102 due to temperature changes can be significantly reduced compared to when the lens array is made of resin.

[0057] Furthermore, in the image reading device 101 of the first embodiment, instead of forming the entire lens array (first lens array 110, second lens array 111) with glass, which has a lower coefficient of thermal expansion and is more expensive than resin, the lens array substrate (first lens array substrate 110a, second lens array substrate 111a) is formed from glass, and the lenses (first lens 110d, second lens 110e, third lens 111d, fourth lens 111e) are formed from resin on the lens array substrate, thereby reducing costs.

[0058] Thus, the image reading device 101 of the first embodiment can provide good imaging performance at low cost.

[0059] Furthermore, the lens array unit 103 of the first embodiment has an aperture array 112 between the first lens array 110 and the second lens array 111, and the aperture array 112 is also made of stainless steel or aluminum, which has a linear expansion coefficient lower than that of the resin that forms the lenses.

[0060] By doing so, in the image reading device 101 of the first embodiment, it is possible to suppress positional deviation in the X direction between the aperture array 112 and the image pickup elements 102a on the image pickup element substrate 102 when the temperature changes.

[0061] [2. Second Embodiment] Next, a second embodiment will be described. In the first embodiment, first lens array 110 and second lens array 111 are configured to have convex lenses on the incident side (side closer to the subject) and the exit side (side farther from the subject). In contrast, in the second embodiment, first lens array 210 corresponding to first lens array 110 is configured to have a convex lens on the incident side (side closer to the subject) and a concave lens on the exit side (side farther from the subject). The other configurations are the same between the first embodiment and the second embodiment.

[0062] [2-1. Configuration of the image reading device] 7, which corresponds to the cross-sectional view of Fig. 3, an image reading device 201 according to the second embodiment is composed of an image pickup element substrate 202, a lens array unit 203, and a holder 204. Here, the image pickup element substrate 202 and the holder 204 are similar to the image pickup element substrate 102 and the holder 104 according to the first embodiment, and therefore a description thereof will be omitted.

[0063] The lens array unit 203 is an optical system configured with a first lens array 210 provided on the side closer to the subject, a second lens array 211 provided on the side farther from the subject, and an aperture array 212 provided between the first lens array 210 and the second lens array 211. Here, the aperture array 212 is the aperture array 112 of the first embodiment lengthened in the Z direction, and therefore a description thereof will be omitted.

[0064] As shown in an enlarged view in Figure 8, the first lens array 210 is composed of a first lens array substrate 210a which is a plate-shaped glass that is long in the X direction, a first resin layer 210b formed in close contact with one surface of the first lens array substrate 210a in the +Z direction (the surface closer to the subject), and a second resin layer 210c formed in close contact with one surface of the first lens array substrate 210a in the -Z direction (the surface farther from the subject).

[0065] A plurality of first lenses 210d are formed in an array on the first resin layer 210b so as to be in contact with each other in the X direction. A plurality of second lenses 210e are also formed in an array on the second resin layer 210c so as to be in contact with each other in the X direction.

[0066] The first resin layer 210b and the second resin layer 210c are layers of resin that has ultraviolet curing or heat curing properties, and the first lens 210d and the second lens 210e are formed by imprint technology.

[0067] The first lens array 210 is held in the holder 204 so that the first lens 210d formed on one surface (the surface closer to the subject) of the first lens array substrate 210a in the +Z direction is exposed from the opening 204c of the holder 204.

[0068] The second lens array 211 has the same configuration as the second lens array 111 of the first embodiment. That is, the second lens array 211 is composed of a second lens array substrate 211a, a third resin layer 211b formed in close contact with one surface of the second lens array substrate 211a in the +Z direction, and a fourth resin layer 211c formed in close contact with the other end surface of the second lens array substrate 211a in the Z direction. A plurality of third lenses 211d are formed in an array on the third resin layer 211b so as to be in contact with each other in the X direction, and a plurality of fourth lenses 211e are also formed in an array on the fourth resin layer 211c so as to be in contact with each other in the X direction.

[0069] In this embodiment, first lens 210d, second lens 210e, third lens 211d, and fourth lens 211e are each a circular lens with a diameter of 1 mm, and are arranged in an array at a period of 1 mm in the X direction so that their optical axes coincide. Furthermore, first lens 210d, third lens 211d, and fourth lens 211e are convex lenses, and second lens 210e is a concave lens.

[0070] Here, the radius of curvature r [mm], cone constant k, aspheric coefficient A, and distance from the image sensor 102a [mm] for each lens (first lens 210d, second lens 210e, third lens 211d, fourth lens 211e) are shown in the table in Figure 9. The first lens 210d and the third lens 211d are convex lenses that are convex in the +Z direction (subject side), the second lens 210e is a concave lens that is concave in the +Z direction, and the fourth lens 211e is a convex lens that is convex in the -Z direction (image sensor 202a side). The shape of each lens can also be expressed by the equation 1 described in the first embodiment.

[0071] The lens array unit 203 forms an inverted, reduced image of the subject as an intermediate image using the first lens array 210, and forms an inverted, enlarged image of the intermediate image using the second lens array 211, thereby forming an erect, equal-size image of the subject on the image sensor 202a.

[0072] Note that the radius of curvature r [mm], conic constant k, aspherical coefficient A, and distance [mm] from the image sensor 102a of each lens shown in the table of FIG. 9 are merely examples, and the first lens array 210 and the second lens array 211 may be any optical system that can form an erect, life-size image of the subject on the image sensor 202a.

[0073] Furthermore, the refractive index, Abbe number, and thickness [mm] of each lens (first lens 210d, second lens 210e, third lens 211d, fourth lens 211e) and each substrate (first lens array substrate 210a, second lens array substrate 211a) are shown in the table of FIG.

[0074] As shown in the tables in Figures 9 and 10, the first lens array 210 of the second embodiment satisfies the conditions for an achromatic lens, as the refractive index of the concave second lens 210e is larger and the Abbe number is smaller than that of the convex first lens 210d. The configuration of the image reading device 101 is as described above. The operation of the image reading device 201 is the same as that of the image reading device 101 of the first embodiment, so a description is omitted.

[0075] [2-2. Summary and Effects] As explained above, the image reading device 201 according to the second embodiment includes the lens array unit 203 having the first lens array 210 and the second lens array 211.

[0076] The first lens array 210 has a first lens array substrate 210a, and a first resin layer 210b is tightly formed on one surface of the first lens array substrate 210a that is the light incident side (the surface closer to the subject), and a second resin layer 210c is tightly formed on the other surface opposite to the first surface that is the light exit side, and a plurality of first lenses 210d are formed on the first resin layer 210b, and second lenses 210e are formed on the second resin layer 210c.

[0077] Furthermore, in the first lens array 210, the first lens 210d is a convex lens and the second lens 210e is a concave lens, and the second lens 210e has a higher refractive index and a smaller Abbe number than the first lens 210d, so that it functions as an achromatic lens.

[0078] In this way, in the image reading device 201 according to the second embodiment, the first lens array 210 is an achromatic lens, so that the first lens array 210 can correct chromatic aberration.

[0079] That is, in the image reading device 201 of the second embodiment, in addition to the same effect as the image reading device 101 of the first embodiment (the effect of being able to significantly suppress misalignment in the X direction between the lens array and the image pickup element 102a on the image pickup element substrate 102), chromatic aberration can be corrected without increasing the number of lens arrays, and therefore better imaging performance can be obtained than in the image reading device 101 of the first embodiment.

[0080] [3. Other Embodiments] [3-1. Other Embodiments 1] In the first embodiment described above, the lens array unit 103 is an optical system configured with the first lens array 110, the second lens array 111, and the aperture array 112, but is not limited to this and may be an optical system having, for example, three or more lens arrays. The same applies to the second embodiment.

[0081] Furthermore, in the first embodiment described above, the image reading device 101 is configured to include a lens array unit 103 of an erect, 1:1 magnification optical system composed of a first lens array 110, a second lens array 111, and an aperture array 112, and an image sensor 102a. However, the image reading device may also be configured to include an optical system having at least one lens array, an image sensor that converts the image from the lens array into an image signal, and an image processing unit that performs image processing on the image signal obtained from the image sensor (for example, image processing that inverts and enlarges an inverted, reduced image from one lens array). The same applies to the second embodiment.

[0082] Furthermore, in the first embodiment described above, the first lens array substrate 110a of the first lens array 110 and the second lens array substrate 111a of the second lens array 111 are made of glass with a lower coefficient of thermal expansion than the resin used to form the lenses. However, the first lens array substrate 110a and the second lens array substrate 111a may be made of other materials (for example, calcium fluoride) with a lower coefficient of thermal expansion than the resin used to form the lenses. In this way, by forming the lens array substrates (first lens array substrate 110a, second lens array substrate 111a) with materials that have a lower coefficient of thermal expansion than the resin, the X-direction misalignment between the lens array and the image sensor 102a on the image sensor substrate 102 can be suppressed compared to the case where the lens arrays (first lens array 110, second lens array 111) are made of resin. The same applies to the second embodiment.

[0083] In the first embodiment described above, the first lens array 110 and the second lens array 111 are configured such that lenses are formed in a resin layer that is in close contact with the lens array substrate, but this is not limiting, and one of the first lens array 110 and the second lens array 111 may be configured such that lenses are formed in a resin layer that is in close contact with the lens array substrate, and the other may have another configuration (for example, a configuration in which the entire lens array is formed from a material (glass, etc.) that has a linear expansion coefficient lower than that of resin). The same applies to the second embodiment.

[0084] Furthermore, in the first embodiment described above, the first lens array 110 is configured such that resin layers are adhered to both one and the other surfaces of the lens array substrate, and lenses are formed in both the resin layer on the one surface and the resin layer on the other surface. However, this is not limiting, and the first lens array 110 may be configured such that a resin layer is adhered to one surface of the lens array substrate, and lenses are formed in the resin layer. The same applies to the second lens array 111; for example, lenses may be formed on both surfaces of the first lens array 110 and lenses may be formed on one surface of the second lens array 111. The same applies to the second embodiment.

[0085] Furthermore, the lenses formed in the resin layer are not limited to being circular, but may be in a racetrack shape, such as a circle with both ends cut off in the diameter direction, or a honeycomb shape, in which regular hexagons are arranged without gaps.

[0086] [3-2. Other embodiment 2] Furthermore, in the second embodiment described above, only the first lens array 210 is an achromatic lens, but this is not limited to this, and both the first lens array 210 and the second lens array 211 may be achromatic lenses, or only the second lens array 211 may be an achromatic lens.

[0087] [3-3. Other embodiment 3] Furthermore, in the first embodiment described above, the present invention is applied to image reading device 101 as a line sensor that reads an image of a subject as one-dimensional data by arranging lenses and image pickup elements side by side in the X direction perpendicular to the optical axis, but is not limited to this. The present invention can also be applied to an image reading device as an area sensor that reads an image of a subject as two-dimensional data by arranging lenses and image pickup elements side by side in the X direction and Y direction perpendicular to the optical axis. In this case, for example, the lenses of first lens array 110 and second lens array 111 and the apertures 112a of aperture array 112 may be arranged side by side in the X direction and the Y direction, respectively.

[0088] Furthermore, in the first embodiment described above, the image reading device 101 equipped with the lens array unit 103 is used in the image inspection device 10, but the present invention is not limited to this, and the image reading device 101 may be used in devices other than the image inspection device 10. For example, the image reading device 101 may be used in devices such as a copy machine or a scanner. The same applies to the second embodiment.

[0089] Furthermore, in the first embodiment described above, the lens array unit 103 is used as the optical system of the image reading device 101, but the present invention is not limited to this, and the lens array unit 103 may be used as the optical system of a device other than the image reading device 101. For example, the lens array unit 103 may be used as the optical system of an exposure device employed in an image forming device such as a printer.

[0090] [3-4. Other embodiment 4] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments, and the scope of application of the present invention extends to embodiments in which the above-described embodiments and other embodiments are combined in part or in whole, or in which only a part of the above-described embodiments is extracted. [Industrial Applicability]

[0091] The present invention can be widely used in, for example, contact type image sensors. [Explanation of symbols]

[0092] 10...Image inspection device, 101, 201...Image reading device, 102, 202...Image pickup element substrate, 102a, 202a...Image pickup element, 103, 203...Lens array unit, 104, 204...Holder, 110, 210...First lens array, 110a, 210a...First lens array substrate, 110b, 210b...First resin layer, 110c, 210c...Second resin layer, 110d, 210d...First lens, 110e, 210e...Second lens, 111, 211...Second lens array, 111a, 211a...Second lens array substrate, 111b, 211b...Third resin layer, 111c, 211c...Fourth resin layer, 111d, 211d...Third lens, 111e, 211e...Fourth lens, 112, 212...Aperture array.

Claims

1. a first lens array having a plurality of lenses arranged side by side along a first direction perpendicular to the optical axis direction of the lenses; a second lens array arranged at an interval in the optical axis direction from the first lens array, the second lens array having a plurality of lenses, the second lens array arranged side by side along the first direction such that the optical axes of the lenses coincide with those of the lenses of the first lens array; Equipped with At least one of the first lens array and the second lens array has a lens array substrate that transmits light and is formed from a material having a linear expansion coefficient smaller than that of a resin that forms the lenses, and a resin layer is formed in close contact with at least one of one surface of the lens array substrate that is a light incident side and another surface opposite to the one surface that is a light exit side, and a plurality of the lenses are formed in the resin layer. A lens array unit characterized by:

2. The optical system including the first lens array and the second lens array is an erect unity magnification optical system.

2. The lens array unit according to claim 1.

3. an aperture array between the first lens array and the second lens array, the aperture array being made of a material having a linear expansion coefficient smaller than that of a resin forming the lenses, the aperture array having a plurality of apertures penetrating the lenses in the optical axis direction and arranged in line along the first direction; 3. The lens array unit according to claim 2.

4. At least one of the first lens array and the second lens array has the resin layer formed in close contact with both the one surface and the other surface of the lens array substrate, and a plurality of the lenses formed in each of the resin layers.

4. The lens array unit according to claim 2 or 3.

5. In at least one of the first lens array and the second lens array, the lenses formed on the resin layer on the incident side are convex lenses, and the lenses formed on the resin layer on the output side are concave lenses.

5. The lens array unit according to claim 4.

6. At least one of the first lens array and the second lens array has a lens formed in the resin layer on the exit side that has a higher refractive index and a smaller Abbe number than the lens formed in the resin layer on the incident side.

6. The lens array unit according to claim 5.

7. a lens array unit including a lens array having a plurality of lenses, the plurality of lenses being arranged side by side along a first direction perpendicular to the optical axis direction of the lenses; an imaging element substrate on which an imaging element that receives light that has passed through the lens array unit is mounted, The lens array is The lens array substrate is made of a material having a linear expansion coefficient smaller than that of the resin forming the lenses, and allows light to pass through. A resin layer is formed in close contact with at least one of one surface of the lens array substrate that is a light incident side and another surface opposite to the one surface that is a light exit side, and a plurality of the lenses are formed in the resin layer. An image reading device characterized by:

8. The imaging element substrate is It is made of a material with a linear expansion coefficient smaller than that of the resin that forms the lens.

8. The image reading device according to claim 7, wherein:

9. The lens array has the resin layer formed in close contact with both the one surface and the other surface of the lens array substrate, and a plurality of lenses formed in each of the resin layers.

9. The image reading device according to claim 8, wherein:

10. In the lens array, the lenses formed on the resin layer on the incident side are convex lenses, and the lenses formed on the resin layer on the output side are concave lenses.

10. The image reading device according to claim 9, wherein:

11. In the lens array, the lenses formed on the resin layer on the exit side have a higher refractive index and a smaller Abbe number than the lenses formed on the resin layer on the incident side.

11. The image reading device according to claim 10.

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