Lens array

Abstract

A lens array (1a) is provided with two or more lenses (11), an adhesive section (12), a housing (15), and an antireflection film (20). A lens array (1a) is used in a device for inspecting the presence or absence of defects using reflected light from a conveyed object to be inspected. The two or more lenses (11) are arranged in a first direction (y-axis direction), which is a conveying direction of an object to be inspected, and a second direction (x-axis direction), which is perpendicular to the conveying direction. The two or more lenses (11) converge reflected light from the conveyed object to be inspected. The adhesive part (12) fixes the lenses (11) to each other. The housing (15) accommodates the two or more lenses (11) and the adhesive section (12). The antireflection film (20) contains fine particles (21) and a binder (22). The anti-reflection film (20) is disposed in contact with at least one selected from the group consisting of a first surface (11a) of the lens (11) on which reflected light is incident and a second surface (11b) of the lens (11) on which light incident on the first surface (11a) is emitted.

Description

Technical Field

[0001] The present invention relates to lens arrays. Background Art

[0002] Conventionally, a lens array has been used for image reading.

[0003] For example, in patent document 1, a stacked lens array unit for a compound eye optical system is described. The stacked lens array unit is provided with a first lens array, a second lens array and a positioning portion. The first lens array and the second lens array respectively have a quadrilateral profile when observed from the optical axis direction and have more than two lens elements arranged in a two-dimensional manner. The first lens array and the second lens array are stacked in the optical axis direction. The positioning portion is arranged in an enclosed area that surrounds more than two lens elements along the edge of the first lens array and the edge of the second lens array. The positioning portion has a first abutment portion configured on the first lens array side and a second abutment portion configured on the second lens array side and opposite to the first abutment portion, and has a predetermined conical surface. Thus, it is possible to restrict the plane direction required for the lens array and the rotation direction around an axis perpendicular to the plane without applying stress to the lens array. Therefore, it is possible to assemble with high precision while maintaining high optical performance. In addition, it is possible to simplify the structure between adjacent lens elements of the lens array, so that molding can be performed with high precision, and it is easy to ensure the effective area of ​​a wider lens element.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2014 / 192933 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In a device that inspects the presence or absence of defects using reflected light from a transported inspection object, it is not envisioned to use the lens array unit described in Patent Document 1. When a lens array is used in such a device, it is considered advantageous that the lens array can handle various measurement wavelengths depending on the inspection object.

[0009] Therefore, the present invention provides a lens array that is advantageous in terms of the range of measurement wavelengths that can be handled by a device that inspects the presence or absence of defects using reflected light from a transported inspection object.

[0010] Means for solving problems

[0011] The present invention provides a lens array, which is used for a device for inspecting the presence or absence of defects by using reflected light from a transported inspected object, wherein the lens array comprises:

[0012] Two or more lenses, which are arranged in a first direction which is a conveying direction of the inspected object and in a second direction which is perpendicular to the conveying direction, so as to converge the reflected light;

[0013] a bonding portion that fixes the lenses to each other;

[0014] a housing that accommodates the two or more lenses and the bonding portion; and

[0015] Anti-reflective film,

[0016] The anti-reflection film includes particles having a refractive index lower than the refractive index of the lens, and a binder, and is arranged in contact with at least one selected from the group consisting of a first surface of the lens on which the reflected light is incident and a second surface of the lens from which the light incident on the first surface is emitted.

[0017] The binder bonds the fine particles to the first surface or the second surface.

[0018] Effects of the Invention

[0019] The above-mentioned lens array is advantageous from the viewpoint of the range of measurement wavelengths that can be handled by a device that inspects the presence or absence of defects using reflected light from a transported inspection object. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic perspective view showing an example of the lens array of the present invention.

[0021] Figure 2 is a graph showing the refractive index distribution of the lens.

[0022] Figure 3 It is shown Figure 1 A side view of an example of a lens shown.

[0023] Figure 4 It shows that Figure 1 A cross-sectional view of an example of a lens array inspection device shown.

[0024] Figure 5A This is a FE-SEM photograph showing a cross section of the antireflection film of the lens array of Example 1.

[0025] Figure 5B This is a FE-SEM photograph showing a cross section of the antireflection film of the lens array of Example 6.

[0026] Figure 5C This is a FE-SEM photograph showing a cross section of the antireflection film of the lens array of Example 7.

[0027] Figure 6This is a cross-sectional view schematically showing a cross section of an antireflection film of the lens array of Example 8. DETAILED DESCRIPTION

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be noted that the following description relates to an example of the present invention, and the present invention is not limited to the following embodiment.

[0029] like Figure 1 As shown, the lens array 1a has two or more lenses 11, an adhesive portion 12 and a housing 15. The lens array 1a is a device for inspecting the presence or absence of defects using reflected light from a transported object to be inspected. The two or more lenses 11 are arranged in a first direction (y-axis direction) which is the transport direction of the object to be inspected and in a second direction (x-axis direction) perpendicular to the transport direction. The two or more lenses 11 converge the reflected light from the transported object to be inspected. The adhesive portion 12 fixes the lenses 11 to each other. The housing 15 accommodates the two or more lenses 11 and the adhesive portion 12. The lens 11 has a working distance L1 of, for example, more than 5 mm.

[0030] Lens arrays are often used for purposes such as image reading. In this case, if the miniaturization of the device equipped with the lens array is considered, it is advantageous for the lens array to have a small working distance. This is because the distance between the reading object and the lens array can be reduced. On the other hand, when the lens array is used in a device that uses reflected light from the transported inspected object to check for defects, foreign matter from the transported inspected object and the like is likely to adhere to the surface of the lens array. Therefore, in such a device, it may be necessary to perform equipment maintenance regularly or irregularly. In this case, if the distance between the lens array and the inspected object is small, it is difficult to ensure sufficient space for equipment maintenance. According to the lens array 1a, the lens 11 has a working distance of more than 5 mm. Therefore, when the lens array 1a is used in a device that uses reflected light from the transported inspected object to check for defects, the distance between the lens array 1a and the inspected object is likely to become larger, making it easy to ensure sufficient space for equipment maintenance.

[0031] The working distance L1 of the lens 11 is preferably 8 mm or more, more preferably 10 mm or more, further preferably 15 mm or more, particularly preferably 20 mm or more, and particularly preferably 25 mm or more. The working distance L1 is, for example, 60 mm or less, 55 mm or less, or 50 mm or less.

[0032] The lens 11 is, for example, a distributed refractive index lens. Figure 1 In the figure, OP is the object plane, IP is the image plane, TC is the conjugate length, Z is the lens length, X0 is the field of view radius, θ C is the opening angle.

[0033] Figure 1 , L0 is the distance between the image plane IP and the lens 11 when the value of the modulation transfer function (MTF) is maximum. Figure 1 In the figure, the lens array 1a constitutes, for example, a substantially erect equal-magnification imaging system, and the working distance L1 is substantially equal to the distance L0.

[0034] In the lens 11, the conjugate length TC is, for example, 35 mm to 160 mm, preferably 40 mm to 150 mm, and more preferably 48 mm to 100 mm. In the lens 11, the relationship of TC=L1+Z+L0 holds.

[0035] In the lens 11, the aperture angle θ C For example, it is 3° to 22°, preferably 4° to 12°.

[0036] The lens 11 is, for example, a rod lens, and the central axis of the lens 11 extends along the optical axis direction of the lens 11. Figure 2 As shown, the lens 11 has a refractive index distribution in its radial direction. Figure 2 In the formula (1), n0 is the refractive index at the central axis of the lens 11, and r is the distance in the radial direction of the lens 11 from the central axis of the lens 11 [mm]. The refractive index n(r) of the lens 11 at the distance r is expressed by the following formula (1). In the formula (1), g is the refractive index distribution constant of the lens 11 [mm -1 ].

[0037] n(r) 2 =n0 2 {1-(g·r) 2 Formula (1)

[0038] The refractive index distribution constant of the lens 11 is, for example, 0.06 mm -1 ~0.48mm -1 , preferably 0.08mm -1 ~0.26mm -1 .

[0039] The lens 11 may be made of resin or glass. When the lens 11 is made of resin, examples of the resin forming the lens 11 include acrylic resins, polycarbonate resins, polyolefin resins, silicone resins, etc. having light transmittance. On the other hand, when the lens 11 is made of glass, the central portion of the lens 11 may have the following composition, for example. If the central portion of the lens 11 has such a composition, the working distance L1 is likely to become larger, and the working distance L1 is likely to become a desired value. The central portion of the lens 11 is, for example, a portion where the optical axis of the lens 11 is formed.

[0040] The composition expressed in mol% comprises:

[0041] 40%≤SiO2≤65%

[0042] 0%≤TiO2≤10%

[0043] 0.1%≤MgO≤22%

[0044] 0.15%≤ZnO≤15%

[0045] 0.5%≤Li2O≤15%

[0046] 2%≤Na2O≤20%

[0047] 0%≤B2O3≤20%

[0048] 0%≤Al2O3≤10%

[0049] 0%≤K2O≤3%

[0050] 0%≤Cs2O≤3%

[0051] 0%≤Y2O3≤5%

[0052] 0%≤ZrO2≤2%

[0053] 0%≤Nb2O5≤5%

[0054] 0%≤In2O3≤5%

[0055] 0%≤La2O3≤5%

[0056] 0%≤Ta2O5≤5%.

[0057] When the lens 11 is made of glass, the lens 11 can be produced, for example, by a method including the following steps (I) and (II).

[0058] (I) A glass wire material having the above composition is produced.

[0059] (II) The glass wire is immersed in a molten salt containing a second alkali metal element R different from the first alkali metal element Q contained in the above composition, and the first alkali metal element Q in the glass wire is ion-exchanged with the second alkali metal element R in the molten salt, thereby forming a refractive index distribution in the glass wire.

[0060] In step (II), for example, a glass wire is placed in a molten salt in a container, and the glass wire is immersed in the molten salt for a predetermined time. In the molten salt, for example, at least one of potassium nitrate and sodium nitrate is melted. When the glass wire is immersed in the molten salt, cations of a first alkali metal element Q such as Li (lithium) contained in the glass wire are dissolved into the molten salt. On the other hand, cations of a second alkali metal element R such as Na (sodium) in the molten salt enter the glass wire. By adjusting the temperature of the molten salt and the immersion time of the glass wire in the molten salt, the ion exchange of the cations of the first alkali metal element Q and the cations of the second alkali metal element R can be appropriately controlled. A specific concentration distribution of monovalent cations is generated inside the glass wire, and based on the concentration distribution, a cation having Figure 2 The lens 11 has the refractive index distribution shown. It should be noted that since ion exchange hardly occurs in the center of the glass wire, the center of the lens 11 has the original composition of the glass wire. Therefore, the center of the lens 11 has the above composition.

[0061] like Figure 1 As shown, the two or more lenses 11 form, for example, two or more columns in the second direction (x-axis direction). According to such a structure, even when the field of view radius X0 is small, the reflected light from the object to be inspected is easily converged in the entire direction of the second direction in which the two or more lenses 11 are arranged. As a result, the accuracy of inspection for defects in the object to be inspected is easily improved. The number of columns formed by the two or more lenses 11 in the second direction can be two columns, or can be three or more columns. In the columns of the two or more lenses 11 formed in the second direction, the columns of lenses 11 adjacent in the first direction are formed, for example, in such a way that the central axes of the two or more lenses 11 are staggered in the second direction.

[0062] The bonding portion 12 fills the gap between the lenses 11. Thus, two or more lenses 11 are integrated. The bonding portion 12 contains, for example, resin and is colored black.

[0063] The housing 15 is not limited to a specific configuration as long as it can accommodate two or more lenses 11 and the adhesive portion 12. The housing 15 includes, for example, a pair of plates arranged in a first direction and a pair of plates arranged in a second direction, and is formed in the form of a frame formed by these plates. These plates include, for example, fiber reinforced plastic (FRP).

[0064] like Figure 3As shown, the lens array 1a further includes an anti-reflection film 20. The anti-reflection film 20 is, for example, arranged in contact with at least one selected from the group consisting of the first surface 11a and the second surface 11b. The first surface 11a is a surface of the lens 11 on which reflected light from the transported inspection object is incident. The second surface 11b is a surface of the lens 11 from which light incident on the first surface 11a is emitted.

[0065] As described above, the working distance L1 of the lens 11 is more than 5 mm, so the image obtained by the lens 11 is not easy to become bright. In the above-mentioned device, the amount of light incident on the imaging element such as the charge coupled device (CCD) used to check whether there are defects in the inspected object is easy to reduce. Although it also depends on the working distance L1 or the aperture angle of the lens, for example, when a lens with a working distance L1 that is 1.5 times longer is used, the brightness is sometimes reduced by about 30%. Therefore, for example, it is considered to increase the brightness of the light source used to generate reflected light from the inspected object. However, if the brightness of the light source is high, the operating cost of the equipment is likely to increase, and there is also a concern that the inspected object will be affected as the heat generated by the light source increases. On the other hand, if the lens array 1a is equipped with an anti-reflection film 20, the reflected light from the inspected object can be suppressed from being re-reflected on the first surface 11a and the second surface 11b of the lens 11. As a result, even if the brightness of the light source is not increased, it is easy to obtain a bright image through the lens 11, and the amount of light incident on the imaging element is not easy to decrease.

[0066] The antireflection film 20 may be disposed in contact with only the first surface 11 a , may be disposed in contact with only the second surface 11 b , or may be disposed in contact with both the first surface 11 a and the second surface 11 b .

[0067] The anti-reflection film 20 is not limited to a specific form as long as the amount of light emitted from the second surface 11 b can be increased compared to a case where the anti-reflection film 20 is not formed.

[0068] Regarding the antireflection film 20, for example, Figure 3As shown, it has particles 21 and adhesive 22. The particles 21, for example, have a refractive index lower than that of the lens 11. In this case, the refractive index of the lens 11 is the maximum value of the refractive index in the lens 11, for example, the refractive index of the center of the lens 11. The adhesive 22 makes the particles 21 adhere to the first surface 11a or the second surface 11b. With such a structure, the anti-reflection film 20 can easily exert the desired anti-reflection characteristics in a wider wavelength range. Therefore, the lens array 1a can easily cope with various measurement wavelengths. For example, in addition to the case where the measurement wavelength belongs to the visible light region, it is also easy to exert the desired anti-reflection characteristics in the case of belonging to the near-infrared region, and the amount of light emitted from the second surface 11b can be increased. Even if the anti-reflection film 20 is formed in a relatively simple structure such as a single-layer structure, it is easy to exert the desired anti-reflection characteristics. In addition, it is also possible not to perform vacuum processes or high-temperature treatments, etc., which can prevent the influence of such processes or treatments on the lens 11, and the manufacturing cost of the lens array 1a is easy to reduce.

[0069] As a method for forming an anti-reflection film on a lens, a method for forming an optical interference film as a dielectric multilayer film by methods such as vacuum evaporation, sputtering and chemical evaporation (CVD) is also considered. However, in this case, if the design wavelength range is deviated, the reflectivity becomes high sharply, and there is a limit to the anti-reflection effect in a wider wavelength range. In addition, this method requires treatments such as vacuum process or heating at high temperature. For example, the resin contained in the lens array 1a also has the possibility of foaming in the vacuum process. Therefore, it is difficult to say that it is realistic to form a dielectric optical interference film as an anti-reflection film on the lens 11.

[0070] For example, the surface layer of the antireflection film 20 is formed with irregularities by the fine particles 21. Thus, a low refractive index portion 25a having a refractive index lower than that of the lens 11 is formed. With such a configuration, the antireflection film 20 can more easily exhibit desired antireflection characteristics in a wider wavelength range.

[0071] like Figure 3As shown, the anti-reflection film 20 includes a base 25b, for example, between the low refractive index portion 25a and the lens 11 in the thickness direction of the anti-reflection film 20. The adhesive 22 forms a layer between the particles 21 in the base 25b. The low refractive index portion 25a is a portion of the anti-reflection film 20 other than the base 25b. On a mass basis, the content of the adhesive 22 in the base 25b is higher than the content of the adhesive 22 in the low refractive index portion 25a. As a result, the anti-reflection film 20 easily exerts the desired anti-reflection performance, and the anti-reflection film 20 is not easily peeled off from the lens 11. During the maintenance of the above-mentioned equipment, the anti-reflection film 20 may come into contact with other objects. However, since the content of the adhesive 22 in the base 25 is higher than the content of the adhesive 22 in the low refractive index portion 25a, the bonding strength of the anti-reflection film 20 relative to the lens 11 is easily increased.

[0072] The anti-reflection film 20 contains, for example, silicon atoms, and bonds in which silicon atoms participate, such as Si-O-Si bonds, are formed between the anti-reflection film 20 and the lens 11. With such a structure, the bonding strength of the anti-reflection film 20 relative to the lens 11 can be easily increased. In the case where the lens 11 is made of glass, silanol groups will exist on the surface of the lens 11. Therefore, bonds in which silicon atoms participate, such as Si-O-Si bonds, can be formed by the condensation reaction of the silanol groups on the surface of the lens 11 and the silanol groups contained in the anti-reflection film 20. In the case where the lens 11 is made of resin, the surface of the lens 11 can also be primed. As a result, bonds in which silicon atoms participate, such as Si-O-Si bonds, can be formed between the lens 11 and the anti-reflection film 20.

[0073] The components contained in the particles 21 are not limited to specific components. The particles 21 contain silicon dioxide as a main component, for example. In this specification, the main component is the component that contains the most on a mass basis. Bonds involving silicon atoms such as Si-O-Si bonds are formed between the particles 21 and the adhesive 22. With such a structure, the bonding strength of the anti-reflection film 20 relative to the lens 11 is easily increased. The bonding strength between the particles 21 and the adhesive 22 is increased, and the particles 21 are not easily detached from the anti-reflection film 20. As a result, the bonding strength of the anti-reflection film 20 to the lens 11 is easily increased.

[0074] The average particle size of the microparticles 21 is not limited to a specific value. The average particle size of the microparticles 21 is, for example, 80 to 600 nm. As a result, it is easy to adjust the size of the concavo-convex portion 25a formed in the anti-reflection film 20 to the desired range, and the anti-reflection performance of the anti-reflection film 20 is easily improved. The average particle size of the microparticles 21 is obtained, for example, by observing the cross section of the anti-reflection film 20 using a scanning electron microscope (SEM). Specifically, for any 50 particles in which the entire particle can be observed, the maximum diameter and the minimum diameter are measured and the average value is taken as the particle size of each particle, and the average value of the particle sizes of the 50 particles is taken as the "average particle size". The average particle size of the microparticles 21 is preferably 100 nm to 500 nm, more preferably 100 nm to 300 nm, further preferably 100 nm to 200 nm, and particularly preferably greater than 100 nm and less than 150 nm.

[0075] The shape of the microparticle 21 is, for example, a spherical particle. As a result, the concavities and convexities in the low refractive index portion 25a of the anti-reflection film 20 are easily formed uniformly along the first surface 11a or the second surface 11b, and the anti-reflection performance of the anti-reflection film 20 is easily improved. In this specification, "spherical" means a shape in which the ratio (Dl / Ds) of the minimum diameter (Ds) of the microparticle 21 to the maximum diameter (Dl) of the microparticle 21 is less than 1.5 when the microparticle 21 is observed using an SEM.

[0076] When the anti-reflection film 20 is viewed from above, the particles 21 are arranged, for example, in a manner that covers the entire first surface 11a or the second surface 11b. In the anti-reflection film 20, the particles 21 are arranged in a manner that forms a single layer. For example, in a pair of adjacent particles 21, when the center of one particle is located closer to the first surface 11a or the second surface 11b than the outermost portion of the other particle 21 in the thickness direction of the anti-reflection film 20, these particles 21 can be regarded as forming a single layer. The particles 21 can also be arranged in a manner that forms multiple layers. In a pair of adjacent particles 21, when the center of one particle is located closer to the outermost portion of the anti-reflection film 20 than the outermost portion of the other particle 21 in the thickness direction of the anti-reflection film 20, these particles 21 can be regarded as forming multiple layers.

[0077] The microparticles 21 are, for example, solid particles. In this case, the anti-reflection film 20 is likely to have a desired mechanical strength. During maintenance of the above-mentioned equipment, the anti-reflection film 20 may come into contact with other objects, so it is advantageous for the anti-reflection film 20 to have a high mechanical strength in order to suppress the reduction of the anti-reflection performance of the anti-reflection film 20 even during maintenance of the equipment.

[0078] The content of the fine particles 21 in the anti-reflection film 20 is not limited to a specific value. The content is, for example, 35% to 90% by mass. In this case, the fine particles 21 are easily arranged in a desired state in the anti-reflection film 20, and the anti-reflection performance of the anti-reflection film 20 is easily improved. The content of the fine particles 21 in the anti-reflection film 20 is preferably 40% to 90%, and more preferably 45% to 85%.

[0079] The thickness of the anti-reflection film 20 is not limited to a specific value. The thickness of the anti-reflection film 20 is, for example, 80 nm to 800 nm. In this case, the anti-reflection performance of the anti-reflection film 20 tends to be high. The thickness of the anti-reflection film 20 is preferably 100 nm to 500 nm, more preferably greater than 100 nm and less than 150 nm. The thickness of the anti-reflection film 20 can be determined, for example, in the form of the average value of the distance from the first surface 11a or the second surface 11b to the outermost part of the convex part of the surface layer of the anti-reflection film 20 in the thickness direction of the anti-reflection film 20 and the filling rate of the particles 21 in the unit distance. The unit distance is, for example, a distance equivalent to an integer multiple (for example, 10 times) of the average particle size of the particles 21. The filling rate is a value obtained by dividing the number of convex parts contained in the unit distance by an integer multiple of the average particle size of the particles 21 corresponding to the unit distance. The thickness of the anti-reflection film 20 can be determined by observing the cross section of the anti-reflection film 20 using SEM.

[0080] The ratio of the average particle size of the fine particles 21 to the thickness of the antireflection film 20 is not limited to a specific value. The ratio is, for example, 0.3 to 1, preferably 0.5 to 1, and more preferably 0.8 to 1.

[0081] The thickness of the base portion 25b in the anti-reflection film 20 is not limited to a specific value. The thickness of the base portion 25b is, for example, the arithmetic mean of the thickness of the base portion 25b at the location where the thickness of the anti-reflection film 20 is determined. The thickness of the base portion 25b is, for example, 10 nm to 300 nm, preferably 10 nm to 200 nm, and more preferably 10 nm to 70 nm.

[0082] The thickness of the low refractive index portion 25a in the anti-reflection film 20 is not limited to a specific value. The thickness of the low refractive index portion 25a is determined, for example, by subtracting the thickness of the base portion 25b from the thickness of the anti-reflection film 20 determined as described above. The thickness of the low refractive index portion 25a is, for example, 30 nm to 600 nm, preferably 35 nm to 500 nm, more preferably 40 nm to 300 nm, further preferably 40 nm to 200 nm, and particularly preferably 40 nm to 130 nm.

[0083] The ratio of the thickness of the low refractive index portion 25a to the thickness of the base portion 25b is not limited to a specific value. The ratio is, for example, 1 to 8. With such a configuration, the bonding strength of the antireflection film 20 to the lens 11 is easily increased. The ratio is preferably 1 to 7, and more preferably 1 to 6.

[0084] The components contained in the binder 22 are not limited to specific components. The binder 22 contains, for example, silicon dioxide as a main component. The binder 22 may contain only silicon dioxide, may contain a hydrophobic group, or may contain an aluminum compound.

[0085] The content of the binder in the anti-reflection film 20 is not limited to a specific value. The content is, for example, 5% to 64% by mass. In this case, the surface roughness of the anti-reflection film 20 is easily formed in a desired state, and the anti-reflection performance of the anti-reflection film 20 is easily improved. In addition, the base 25b is easily formed throughout the entire anti-reflection film 20, and the bonding strength of the anti-reflection film 20 with respect to the lens 11 is easily increased. The content of the binder in the anti-reflection film 20 is preferably 10% to 60%, and more preferably 15% to 55%.

[0086] For example, when the content of the binder in the antireflection film 20 is 5% to 35%, the antireflection performance of the antireflection film 20 tends to be higher. From the viewpoint of the antireflection performance, the content is preferably 10% to 35%, and more preferably 15% to 35%.

[0087] When the content of the binder in the anti-reflection film 20 is 35% to 64%, the bonding strength of the anti-reflection film 20 with respect to the lens 11 is likely to be higher, and the anti-reflection film 20 is likely to have high durability. For example, the anti-reflection film 20 is likely to have high scratch resistance. From the aspect of scratch resistance, the content is preferably 35% to 60%, more preferably 35% to 50%, and further preferably 35% to 40%. For example, when the anti-reflection film 20 is scratched with a pencil under prescribed conditions, the anti-reflection film 20 has a residual pencil hardness of HB or more. The pencil hardness is preferably H or more, and more preferably 2H or more.

[0088] If the bonding strength of the anti-reflection film 20 relative to the lens 11 is high, the anti-reflection film 20 is likely to have excellent peeling resistance. As described above, the lens array 1a can be used for a device that uses reflected light from the transported object to inspect for defects. Such a device will require space for maintenance. Even if the working distance L1 of the lens is above the specified value as in the lens array 1a, it may not be possible to fully ensure space for equipment maintenance. Therefore, considering the contact between the lens array and other objects during equipment maintenance, it is particularly advantageous to use the anti-reflection film 20 to impart higher damage resistance or peeling resistance to the lens 11.

[0089] The silicon dioxide contained in the binder 22 is derived from, for example, a hydrolyzable silicon compound or a hydrolyzate of a hydrolyzable silicon compound added to the coating solution for forming the anti-reflection film 20. The hydrolyzable silicon compound includes, for example, a compound represented by the following formula (Ia). In the following formula (Ia), X is at least one selected from the group consisting of an alkoxy group, an acetoxy group, an alkenyloxy group, an amino group, and a halogen atom. In this specification, the hydrolyzable silicon compound includes an oligomer of the hydrolyzable silicon compound. The oligomer is formed by condensation of, for example, about 2 to 200 molecules of the same type.

[0090] SiX4(Ia)

[0091] As a supply source of silicon dioxide contained in the binder 22, a hydrolyzable silicon compound represented by silicon alkoxide can be used. Examples of silicon alkoxide include tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane. These hydrolyzable silicon compounds are hydrolyzed and polycondensed by a so-called sol-gel method to form the binder 22.

[0092] The hydrolysis of the hydrolyzable silicon compound can be appropriately implemented, preferably in a solution in which the microparticles 21 are present. This is because the polycondensation reaction of the silanol groups generated by the hydrolysis of the hydrolyzable silicon compounds such as silicon alkoxides on the surface of the microparticles 21 is promoted, and the proportion of the adhesive 22 that helps to improve the binding force of the microparticles 21 is increased. It is preferred to stir the solution containing the microparticles 21 while adding a hydrolysis catalyst and silicon alkoxides in sequence to prepare the coating solution. Silicon alkoxides can be monomers or oligomers. It should be noted that the hydrolysis catalyst can use any of acids and bases, and it is preferred to use acids, especially acids with a high degree of ionization in aqueous solutions. Specifically, it is preferred to use an acid dissociation constant pKa (in the case of a polyacid, it refers to the first acid dissociation constant) of 2.5 or less. As examples of preferred acids, volatile inorganic acids such as hydrochloric acid and nitric acid, organic acids such as trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid and p-toluenesulfonic acid, and polyacids such as maleic acid, phosphoric acid and oxalic acid can be cited. Compared with alkalinity, when it is acidic, the dispersibility of silica particles is good, and the stability of the coating solution is also excellent. In addition, since the chloride ions derived from hydrochloric acid can increase the concentration of chloride ions in the coating solution, when aluminum chloride is added to the coating solution, the effect brought by aluminum chloride can be further promoted.

[0093] When the binder 22 contains a hydrophobic group, the content of the hydrophobic group in the anti-reflection film 20 is not limited to a specific value. The content of the hydrophobic group is, for example, 0 to 10% by mass. With such a configuration, dirt attached to the anti-reflection film 20 can be easily removed. The content of the hydrophobic group contained in the binder 22 in the anti-reflection film 20 is preferably 0.2% to 10%, and more preferably 0.2% to 8%.

[0094] The hydrophobic group contained in the adhesive 22 is preferably derived from a hydrolyzable silicon compound having a hydrophobic group directly bonded to silicon or a hydrolyzate of a hydrolyzable silicon compound added to the coating liquid for forming the anti-reflection film 20. The hydrolyzable silicon compound, for example, includes a compound represented by the following formula (IIa). In the following formula (IIa), Y as a hydrolyzable group is preferably at least one selected from the group consisting of an alkoxy group, an acetoxy group, an alkenyloxy group, an amino group and a halogen atom. In the following formula (IIa), R as a hydrophobic group is preferably a chain or cyclic alkyl group having 1 to 30 carbon atoms in which at least a part of the hydrogen atoms may be substituted by fluorine atoms, more preferably a chain alkyl group, further preferably a chain alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0095] RSiY3(IIa)

[0096] When the binder 22 contains an aluminum compound, the content of the aluminum compound in the anti-reflection film 20 is not limited to a specific value. The aluminum compound is converted into Al2O3, and its content is, for example, 0 to 7% by mass. With such a structure, the chemical durability of the anti-reflection film 20 is likely to be high. Therefore, the anti-reflection film 20 is likely to have the desired chemical resistance, especially the desired alkali resistance. As a result, the objects that can be inspected using the lens array 1a are likely to be widened. The content of the aluminum compound in the anti-reflection film 20 is preferably 2 to 7%, and more preferably 4 to 7%.

[0097] like Figure 4As shown, it is possible to provide a device 2a having a lens array 1a. The device 2a is a device that uses reflected light from a transported inspection object T to inspect the presence or absence of defects. The device 2a includes a reading device 71, an illumination device 72, a controller 73, an output device 74, a conveying device 75, and a conveying control device 76. The lens array 1a is arranged inside the reading device 71. The conveying device 75 is, for example, a belt conveyor. The conveying device 75 may also be a conveying device corresponding to a roll-to-roll method. The conveying device 75 conveys an inspection object T such as a printed substrate, a textile, a film, and paper. The conveying control device 76 is a digital computer for controlling the conveying device 75, and outputs a control signal for adjusting the conveying speed of the conveying device 75 to the conveying device 75. The reading device 71 and the illumination device 72 are, for example, arranged above the conveying device 75, and the inspection object T is passed directly below the reading device 71 by the conveying device 75. The reading device 71 and the lighting device 72 are arranged in such a way that the reflected light generated by the light emitted from the lighting device 72 and reflected by the object to be inspected T converges on the lens array 1a. Thus, the image data of the object to be inspected T is obtained by the reading device 71. The controller 73 is a digital computer for forming the image data of the object to be inspected T. When the object to be inspected T passes directly under the reading device 71, the controller 73 continuously obtains image information from the reading device 71. In addition, the controller 73 obtains the conveying position information of the object to be inspected T from the reading device 71. The controller 73 performs calculation processing based on the image information obtained from the reading device 71 and the conveying position information obtained from the conveying control device 76 to form two-dimensional image information. The formed two-dimensional image information is compared with the information representing defects such as foreign matter, cracks, pinholes, etc. pre-stored in the controller 73. Thus, the controller 73 determines whether there are defects in the object to be inspected T, the number of defects, and the location of the defects. The controller 73 can determine whether the object to be inspected T is good based on the comparison result. The output device 74 is, for example, a monitor, which displays the two-dimensional image information formed by the controller 73.

[0098] Example

[0099] The present invention is described in more detail below by way of examples. It should be noted that the present invention is not limited to the following examples.

[0100] <Reference Example 1>

[0101] Glass raw materials are mixed in a manner to obtain a composition as shown in Table 1, and the mixture is melted to obtain a molten glass (glass composition) of Reference Example 1. The numerical values ​​in Table 1 represent molar %. The molten glass of Reference Example 1 is spun and formed into fibers, and the obtained glass fibers are cut into a specified length and the cut surfaces are polished. Thus, the glass wire of Reference Example 1 is obtained. The diameter (wire diameter) of the glass wire is 1000 μm. Next, each glass wire is immersed in a sodium nitrate molten salt (the sodium nitrate molten salt is heated to near the glass transition temperature of the glass composition constituting each glass wire) and ion exchange treatment is performed. Thus, a refractive index distribution is formed in each glass wire. Then, the glass wire after the ion exchange treatment is cut into a specified length to obtain the lens of Reference Example 1. Table 2 shows the working distance L1, lens length Z, conjugate length TC, field of view radius X0, and opening angle θ of the lens C , refractive index distribution constant g[mm -1 ], the refractive index n0 at the central axis of the lens.

[0102] Between a pair of rectangular FRP flat plates arranged parallel to each other, two or more lenses of Reference Example 1 are arranged in two rows in parallel with each other at intervals of 1 mm along the length direction of the flat plates. In this state, a bonding resin colored black is filled between the flat plates and cured to fix the two or more lenses. In this state, both ends of each lens are cut and both end faces are ground. It should be noted that another pair of FRP substrates are arranged at both ends in the length direction of the flat plates, and two or more lenses and bonding portions obtained by curing the bonding resin are housed in the frame formed by these FRP flat plates. In this way, the lens array of Reference Example 1 is obtained.

[0103] <Example 1>

[0104] 28.3 parts by mass of a silica fine particle dispersion (Quartron PL-7, approximately spherical primary particles with an average particle diameter of 125 nm, solid content concentration of 23% by weight, manufactured by Fuso Chemical Industry Co., Ltd.), 58.6 parts by mass of 1-methoxy-2-propanol (solvent), and 1 part by mass of 1N hydrochloric acid (hydrolysis catalyst) were stirred and mixed, and 12.1 parts by mass of tetraethoxysilane (ethyl orthosilicate, manufactured by Tama Chemical Industry Co., Ltd.) was further added under stirring, and then stirred for 8 hours while keeping warm at 40° C. to hydrolyze tetraethoxysilane to obtain stock solution A. In stock solution A, the mass ratio of the silica fine particles to the mass of the hydrolysis condensation product of the hydrolyzable silicon compound contained in the binder was 65:35.

[0105] The above stock solution A: 16.0 g, propylene glycol (solvent) 5.0 g, 1-methoxy-2-propanol (solvent) 78.5 g, aluminum chloride aqueous solution (prepared by dissolving reagent-grade aluminum chloride hexahydrate (manufactured by Sigma-Aldrich) with a concentration of 47.6% by mass in terms of AlCl3 in deionized water) 0.4 g, and KP-112 (Shin-Etsu Chemical Co., Ltd., polyether-type surface modifier, 1-methoxy-2-propanol solution with a concentration of 50% by mass) 0.1 g were stirred and mixed to obtain a coating solution of Example 1. In this coating solution, the solid content concentration of silicon dioxide (derived from silicon dioxide fine particles and alkoxysilane) converted to SiO2 was 1.6% by mass, and the aluminum compound converted to Al2O3 was 5.0 parts by mass when the silicon oxide converted to SiO2 was 100 parts by mass.

[0106] The coating liquid of Example 1 is applied to both end faces of the lens array prepared in the same manner as Reference Example 1 by dip coating to form a coating film. During the dip coating, the lens array is fixed to the support of the dip coater by a clamp, immersed in the coating liquid of Example 1 that fills the container, and lifted at a speed of 2.6 mm / second to form a coating film. The coating film is heated at 200°C for 1800 seconds to form an anti-reflection film on both end faces of the lens array in the lens length direction. Thus, the lens array of Example 1 is obtained.

[0107] <Example 2>

[0108] The coating solution of Example 2 was obtained in the same manner as in Example 1 except that the aluminum chloride aqueous solution was not added. The lens array of Example 2 was obtained in the same manner as in Example 1 except that the coating solution of Example 2 was used instead of the coating solution of Example 1.

[0109] <Example 3>

[0110] The coating solution of Example 3 was prepared in the same manner as Example 2 except that the addition amount of each raw material was adjusted according to the content of each component as shown in Table 3. It should be noted that the concentration of the solid component in the coating solution of Example 3 was 1.3% by mass. The coating solution of Example 3 was used instead of the coating solution of Example 1, and the lifting speed during the dip coating was adjusted to 2.0 mm / sec. The lens array of Example 3 was obtained in the same manner as Example 1 except that the coating solution of Example 3 was used instead of the coating solution of Example 1.

[0111] <Example 4>

[0112] In addition to tetraethoxysilane, methyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was further added, and the addition amount of each raw material was adjusted according to the content of each component as shown in Table 3. The coating solution of Example 4 was prepared in the same manner as Example 1. As an aluminum compound, aluminum nitrate was used instead of aluminum chloride. It should be noted that the concentration of the solid component in the coating solution of Example 4 was 1.6% by mass. In the solid component of the coating solution, the content of methyl as a hydrophobic group was 2.8% by mass. In addition to using the coating solution of Example 4 instead of the coating solution of Example 1, the lens array of Example 4 was obtained in the same manner as Example 1.

[0113] <Example 5>

[0114] The coating solution of Example 5 was prepared in the same manner as in Example 4, except that methyltriethoxysilane was not added and the addition amount of each raw material was adjusted according to the content of each component as shown in Table 3. The lens array of Example 5 was obtained in the same manner as in Example 1, except that the coating solution of Example 5 was used instead of the coating solution of Example 1.

[0115] <Example 6>

[0116] The lens array of Example 6 was obtained in the same manner as Example 1 except for the following aspects. The amount of each component was adjusted so that the solid content concentration became 2.5 mass %, and the coating liquid of Example 6 was prepared. In the dip coating, the coating liquid of Example 6 was used instead of the coating liquid of Example 1, and the lifting speed in the dip coating was adjusted to 1.0 mm / sec.

[0117] <Example 7>

[0118] The lens array of Example 7 was obtained in the same manner as Example 1 except for the following aspects. The amount of each component was adjusted so that the solid content concentration became 3.5% by mass, and the coating liquid of Example 7 was prepared. In the dip coating, the coating liquid of Example 7 was used instead of the coating liquid of Example 1, and the lifting speed in the dip coating was adjusted to 1.0 mm / sec.

[0119] <Example 8>

[0120] 0.6 g of tetraethoxysilane (TEOS) (manufactured by Tokyo Chemical Industry Co., Ltd.), 1.18 g of methyltriethoxysilane (MTES) (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.82 g of 0.3% by mass formic acid (manufactured by Kishida Chemical Co., Ltd.), 3 g of sol containing hollow silica particles (manufactured by JGC Catalysts & Chemicals Co., Ltd., product name: Thrulya 4110), and 22.4 g of ethanol (manufactured by Kishida Chemical Co., Ltd.) were mixed and reacted at 35°C for 3 hours. The sol containing hollow silica particles used contained a solvent, contained 25% by mass of hollow silica in terms of solid content, and the average particle size of the hollow silica particles in the particle size distribution based on the number of particles was about 50 nm. The thickness of the shell formed by silica of the hollow silica particles was 10 to 20 nm. The maximum size of the internal space of the hollow silica particles was about 10 to 30 nm. The refractive index of the hollow particles was 1.25. Thus, the coating solution of Example 8 was obtained. In the coating solution of Example 8, the content of the solid component derived from TEOS is 0.6% by mass when converted into silica, the content of the solid component derived from MTES, namely methylsilsesquioxane (MeSq), is 1.6% by mass, and the content of the hollow silica particles is 2.6% by mass. In the solid component of the coating solution of Example 8, 13% of silica derived from TEOS, 33% of MeSq derived from MTES, and 54% of hollow silica particles are included on a mass basis. It should be noted that the content of the hollow silica particles is calculated on the assumption that the solid component in the sol containing the hollow silica particles is 25% by mass and the solid component is hollow silica particles. In addition, the ratio of the mass of MTES added in the preparation of the coating solution of Example 8 to the mass of TEOS is 7 / 3. Except for using the coating solution of Example 8 instead of the coating solution of Example 2, the lens array of Example 8 was obtained in the same manner as Example 2. Figure 6 FIG. 1 is a cross-sectional view schematically showing an anti-reflection film in a lens array of Example 8. Figure 6 As shown, the antireflection film 20 is disposed in contact with the longitudinal end surface of the lens 11. The antireflection film 20 includes hollow silica particles 53 and a binder 54. There are gaps 55 inside the antireflection film 20 and at the boundary between the antireflection film 20 and the end surface of the lens 11.

[0121] (Light quantity measurement)

[0122] A flat reflector is arranged on the object plane corresponding to the working distance of the lens of the lens array of each embodiment, and the reflected light generated by reflecting the light from the light source is incident on the lens array, and the amount of light [lx] at the position corresponding to the imaging surface of the lens array is measured. The amount of light at a wavelength of 530nm when using the lens array of Reference Example 1 is set to 100, and the relative value of the amount of light at a wavelength of 530nm when using the lens array of Examples 1 to 7 is calculated. The results are shown in Table 4. For the lens arrays of Examples 1, 3, 4, 6 and 7, the end face of the lens array is rubbed 40 times with a cloth Toraysee (registered trademark) manufactured by Toray Industries, and then the amount of light is evaluated in the same way. The cloth is dried. For the lens arrays of Examples 1, 3, 4, 6 and 7, the end face of the lens array is rubbed 40 times with a cloth soaked with ethanol, and then the amount of light is evaluated in the same way. The results are shown in Table 4.

[0123] (Pencil hardness)

[0124] Using a pencil hardness tester (pencil scratch hardness tester model: 720N, brand: Sheen Instruments-UK) and a pencil (UNI, Mitsubishi pencil, hardness 2B~9H), a pencil hardness test was performed on the anti-reflection film formed in the lens array of Examples 1 to 8 in accordance with Japanese Industrial Standard (JIS) K5600-5-4. In this test, the angle of the pencil relative to the anti-reflection film was 45°, and the pencil was pressed with a load of 750g. The pencil hardness was measured by pressing and moving a pencil lead with several levels of hardness while gradually increasing the hardness. In this measurement, the moving speed of the pencil was 1mm / second, and the moving distance of the pencil was adjusted to be more than 20mm. After the test, the powder of the pencil lead attached to the anti-reflection film was wiped with Bemcot impregnated with ethanol, and the scratches caused by the test in the anti-reflection film were observed under an optical microscope. The hardness that is one level softer than the hardness when a scratch occurs that causes the anti-reflection film to fall off, or the hardness that is one level softer than the hardness when the anti-reflection film is peeled off in a manner that the substrate surface is exposed, is evaluated as the pencil hardness of the anti-reflection film. In other words, the maximum hardness without causing damage to the anti-reflection film or the maximum hardness without causing peeling that exposes the substrate surface is evaluated as the pencil hardness of the anti-reflection film. The results are shown in Table 4.

[0125] (SEM observation)

[0126] A field emission scanning electron microscope (FE-SEM) (manufactured by Hitachi, Ltd., model: S-4500) was used to observe the cross section of the anti-reflection film formed on the lens array of Examples 1 to 7. In the FE-SEM photograph of the cross section of the anti-reflection film obtained from an oblique angle of 10° above, the distance in the thickness direction of the anti-reflection film between the outermost part of each convex part of the concave-convex surface layer of the anti-reflection film appearing at a distance equivalent to 10 times the average particle size of the silica particles (1250nm) and the end face of the lens array in contact with the anti-reflection film was measured, and the arithmetic mean D1 of the distance was calculated. The number of convex parts appearing at this location is then determined. The filling rate f of the silica particles per unit distance is determined by dividing this number by 10. The thickness T1 of the anti-reflection film is determined as the product of the arithmetic mean D1 and the filling rate f. The results are shown in Table 4. In addition, the arithmetic mean T2 of the thickness of the base is calculated at the location of the anti-reflection film used to calculate the arithmetic mean D1. The thickness T3 of the low refractive index portion was determined by subtracting the arithmetic mean T2 of the thickness of the base portion from the thickness T1 of the antireflection film. The results are shown in Table 4. FE-SEM photographs of cross sections of the antireflection films formed by the lens arrays of Examples 1, 6, and 7 are shown in Table 4. Figure 5A , Figure 5B and Figure 5C .

[0127] (Reflectivity measurement A)

[0128] The reflectivity of one end face of the lens array in the lens length direction of the lens array of Reference Example 1 and Examples 1 to 7 was measured using a near-infrared microspectroscopy measuring machine USPM-RU-W manufactured by Olympus Corporation. In this measurement, the wavelength range was set to a range of 380 to 1050 nm, and the diameter of the measurement range was adjusted to 70 μm using an objective lens with a 10-fold magnification. In addition, the measurement position of the reflectivity was adjusted to the center position of the lens of the lens array. The results are shown in Table 4.

[0129] (Reflectivity measurement B)

[0130] Except that a float glass substrate is used instead of a lens array, an anti-reflection film is formed on the surface of the glass plate in the same manner as in Examples 1 and 3. In addition, an optical interference film as a dielectric multilayer film is formed on the surface of the float glass substrate by a physical vapor deposition (PVD) method to obtain the anti-reflection film of Comparative Example 1. The reflectivity of these anti-reflection films formed on the surface of the glass plate was measured using a near-infrared microspectrometer USPM-RU-W manufactured by Olympus Corporation. In addition, the reflectivity of the surface of the glass plate on which the anti-reflection film is not formed was also measured in the same manner. In this measurement, the wavelength range is set to a range of 380 to 1050 nm, and the diameter of the measurement range is adjusted to 70 μm using an objective lens with a magnification of 10 times. The results are shown in Table 5.

[0131] (Salt spray test)

[0132] With reference to JIS C8917:2005, a salt water spray test was performed in which salt water was sprayed onto the end faces of the lens arrays of Examples 1 to 5 in the direction of the lens length. In the salt water spray test, the ambient temperature of the lens array was adjusted to 35°C, and a 5% by mass sodium chloride aqueous solution was used as the salt water. In addition, the salt water spray was performed for 96 hours. The change in transmittance of the lens array before and after the salt water spray test was measured. In the measurement, light in the range of wavelengths of 380 to 850 nm was used to determine the change in the average value of the transmittance in this range. The results are shown in Table 5.

[0133] Since the working distance L1 of the lens of the lens array of each embodiment is 5 mm or more, even in the case of a device for inspecting the presence or absence of defects using reflected light from a transported inspection object, sufficient space for equipment maintenance can be ensured.

[0134] As shown in Table 4, it can be understood from the comparison between the lens array of Reference Example 1 and the lens array of Examples 1 to 8 that by forming an anti-reflection film on the end faces of the lenses of the lens array, the amount of light passing through the lens array can be increased. Therefore, it can be considered that the formation of an anti-reflection film is beneficial from the perspective of suppressing the reduction in the amount of light due to the large working distance L1. In addition, it can be understood that even if the anti-reflection film of the lens array of Examples 1, 3, 4, 6 and 7 is wiped with a specified cloth, the amount of light passing through the lens array can be maintained at a large level. According to the results of reflectivity measurement A, it can be understood that the reflectivity of the end face in the length direction of the lens is reduced by using the anti-reflection film of the lens array of Examples 1 to 7 compared with the lens array of Reference Example 1.

[0135] In particular, it can be understood from Example 3 that the anti-reflection film can exert a high anti-reflection performance and can increase the amount of light passing through the lens array.

[0136] According to Example 4, it was shown that the antireflection film can exhibit the predetermined antireflection performance, and the antireflection film has a high pencil hardness and high scratch resistance.

[0137] As shown in Table 5, the anti-reflection films formed from the coating solutions of Examples 1 and 3 can reduce the reflectance at wavelengths of 530 nm, 700 nm, 900 nm, and 1000 nm, compared to the glass plate on which the anti-reflection films are not formed. In addition, it can be understood that these anti-reflection films can prevent the reflectance from increasing sharply with increasing wavelength as observed in Comparative Example 1, and can also exhibit anti-reflection characteristics at wavelengths in the near-infrared region.

[0138] As shown in Table 4, it can be understood from the comparison between Example 1 and Example 2 that in Example 1, the change in transmittance before and after the salt spray test is small, and compared with the anti-reflection film of the lens array of Example 2, the anti-reflection film of the lens array of Example 1 has high chemical resistance, especially high alkali resistance. It can be understood that from the perspective of improving chemical resistance, especially alkali resistance, it is advantageous to include an aluminum compound in the adhesive of the anti-reflection film. It can be understood from the comparison between Example 4 and Example 5 that in Example 4, the change in transmittance before and after the salt spray test is small, and compared with the anti-reflection film of the lens array of Example 5, the anti-reflection film of the lens array of Example 4 has high chemical resistance, especially high alkali resistance. It can be understood that from the perspective of improving chemical resistance, especially alkali resistance, it is advantageous to include a hydrophobic group such as a methyl group in the adhesive of the anti-reflection film.

[0139] like Figure 5A to Figure 5C As shown, in the surface layer of the anti-reflection film of the lens array formed in Examples 1, 6 and 7, the silica particles are arranged in a manner of forming a single layer or a multilayer to form a low refractive index portion with a concave-convex portion. Considering the refractive index of silica, it can be understood that the refractive index of the low refractive index portion is lower than the refractive index n0 at the central axis of the lens of the lens array. In addition, a base is formed between the concave-convex of the surface layer and the lens array, and an adhesive forms a phase at the base. It is known that a large amount of adhesive is contained in the base of the anti-reflection film, and the content of the adhesive in the base is higher than the content of the adhesive in the low refractive index portion on a mass basis.

[0140] [Table 1]

[0141] Reference Example 1 <![CDATA[SiO2]]> 53 <![CDATA[TiO2]]> 3.5 <![CDATA[B2O3]]> 3 MgO 1 ZnO 9 SrO 6 BaO 6 <![CDATA[Li2O]]> 9.5 <![CDATA[Na2O]]> 9 <![CDATA[K2O]]> 0 <![CDATA[Cs2O]]> 0 <![CDATA[ZrO2]]> 0 <![CDATA[Sb2O3]]> 0

[0142] [Table 2]

[0143] Reference Example 1 <![CDATA[Working distance L1 [mm]]]> 18.1 Lens length Z[mm] 17.8 Conjugate length TC[mm] 54.0 <![CDATA[Visual field radius X0 [mm]]]> 2.9 <![CDATA[Opening angle θ C [°]]]> 9.0 <![CDATA[Refractive index distribution constant g [mm -1 > 0.1964 <![CDATA[Central refractive index n0[-]]]> 1.60

[0144] [Table 3]

[0145]

[0146] [Table 4]

[0147]

[0148] [Table 5]

[0149]

Claims

1. A lens array, which is used for inspecting the presence or absence of defects by using reflected light from a transported object to be inspected, wherein: The lens array has: Two or more lenses, which are arranged in a first direction which is a conveying direction of the inspected object and in a second direction which is perpendicular to the conveying direction, so as to converge the reflected light; a bonding portion that fixes the lenses to each other; A housing that accommodates the two or more lenses and the bonding portion; as well as Anti-reflective film, The anti-reflection film includes particles having a refractive index lower than the refractive index of the lens, and a binder, and is arranged in contact with at least one selected from the group consisting of a first surface of the lens on which the reflected light is incident and a second surface of the lens from which the light incident on the first surface is emitted. The binder bonds the fine particles to the first surface or the second surface.

2. The lens array according to claim 1, wherein: The lens is a distributed refractive index lens.

3. The lens array according to claim 1 or 2, wherein: The antireflection film has a surface layer having projections and depressions formed by the fine particles.

4. The lens array according to claim 3, wherein: The anti-reflection film includes a base portion between the concavoconvex portion and the lens in the thickness direction of the anti-reflection film. The binder forms a layer between the particles in the base.

5. The lens array according to any one of claims 1 to 4, wherein: Bonds involving silicon atoms are formed between the anti-reflection film and the lens.

6. The lens array according to any one of claims 1 to 5, wherein: The fine particles contain silicon dioxide as a main component.

7. The lens array according to claim 6, wherein: Bonds involving silicon atoms are formed between the fine particles and the binder.

8. The lens array according to any one of claims 1 to 7, wherein: The microparticles have an average particle size of 80 nm to 600 nm.

9. The lens array according to any one of claims 1 to 8, wherein: The antireflection film has a film thickness of 80 nm to 800 nm.

10. The lens array according to any one of claims 1 to 9, wherein: The content of the binder in the antireflection film is 5% by mass to 64% by mass. The content of the fine particles in the antireflection film is 35% by mass to 90% by mass.

11. The lens array according to any one of claims 1 to 10, wherein: The binder contains a hydrophobic group.

12. The lens array according to claim 11, wherein: The content of the hydrophobic group in the binder is 10% by mass or less.

13. The lens array according to any one of claims 1 to 12, wherein: The binder includes an aluminum compound.

14. The lens array according to claim 13, wherein: The content of the aluminum compound in the antireflection film is 7% by mass or less when the aluminum compound is converted into Al 2 O 3 .

15. The lens array according to any one of claims 1 to 14, wherein: The lens has a working distance of more than 15 mm.

16. The lens array according to any one of claims 1 to 15, wherein: The lens has a central portion, the central portion comprising, expressed in mol %: 40%≤SiO2≤65% 0%≤TiO2≤10% 0.1%≤MgO≤22% 0.15%≤ZnO≤15% 0.5%≤Li2O≤15% 2%≤Na2O≤20% 0%≤B2O3≤20% 0%≤Al2O3≤10% 0%≤K2O≤3% 0%≤Cs2O≤3% 0%≤Y2O3≤5% 0%≤ZrO2≤2% 0%≤Nb2O5≤5% 0%≤In2O3≤5% 0%≤La2O3≤5% 0%≤Ta2O5≤5%.

17. The lens array according to any one of claims 1 to 16, wherein: The two or more lenses form two or more columns in the second direction.

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