Optical system

Abstract

This optical system includes a compound lens having a first lens and a second lens. The first lens is formed from a resin, and the second lens is formed from glass. The optical system satisfies conditional formulae (1) and (2) where the maximum value of the thickness of the first lens is A (mm) and the minimum value of the thickness of the first lens is B (mm):　Conditional formula (1): A / B≤10. Conditional formula (2): A≤3 mm. The resin satisfies conditional formula (3) where x (µm) is a plastic deformation amount if an indenter is pressed in at a loading rate of 200 mN / 10 sec at an environmental temperature of 25°C.　Conditional formula (3): 1.0 µm≤x≤4.0 µm.

Description

optical system

[0001] The techniques of this disclosure relate to optical systems that include compound lenses.

[0002] Japanese Patent No. 6824424 discloses an apparatus for manufacturing a compound lens having a substrate lens and a resin layer having an optical surface shape that covers the optical surface of the substrate lens.

[0003] Japanese Patent Laid-Open Publication No. 07-68568 discloses a molding method for a composite optical element, in which an energy-curable resin placed on a substrate of the optical element is pressed with a mold having a molding surface with a desired optical shape to form a resin layer, and the resin layer is cured by irradiating it with energy.

[0004] Japanese Patent Laid-Open Publication No. 07-112491 discloses a composite optical element having aspherical resin layers made of thermally polymerized resin on both sides of a glass substrate.

[0005] Japanese Patent Laid-Open Publication No. 08-258172 discloses a method for producing a plastic lens, which comprises a first step in which a specific plastic lens composition is partially polymerized with active energy rays to make it imfluid, and a second step in which the polymerization is completed by a subsequent heat treatment.

[0006] WO 2022 / 039143 discloses a compound capable of obtaining a cured product that achieves a sufficiently low Abbe number and excellent transmittance, a curable resin composition containing this compound, a cured product obtained from this curable resin composition, and an optical element and a lens that include this cured product.

[0007] Japanese Patent Application Laid-Open Publication No. 2009-248483 discloses a method for manufacturing a composite optical element, which includes a first discharging step of discharging a first resin onto an optical element substrate or a mold, a first irradiation step of irradiating the first resin with curing energy to cure it, a second discharging step of further discharging a second resin onto the surface of the cured first resin, a stretching step of bringing the optical element substrate or the mold close to the second resin to spread the second resin, and a second irradiation step of irradiating the spread second resin with curing energy to cure it.

[0008] Japanese Patent Application Laid-Open No. 2003-262708 discloses a composite optical element including an element substrate and a resin layer fixed to the surface of the element substrate.

[0009] Japanese Patent No. 3071277 discloses a method for manufacturing a lens in which a glass member consisting of a substantially disk-shaped main body and a body attached portion connected to the outer periphery of the main body so as to surround the outer periphery is used as a base material, and a resin layer having a predetermined surface shape is formed by molding on an optically functional surface formed on the surface of the main body and having an outer diameter smaller than that of the main body, thereby forming a lens in which glass material and resin material are integrated.

[0010] Japanese Patent No. 4632942 discloses a resin-bonded optical element having an optical element substrate and a resin layer bonded to the optical element substrate.

[0011] Japanese Patent Application Laid-Open No. 2011-186440 discloses a composite optical element having a first optical functional surface facing one side in the optical axis direction and a second optical functional surface facing the other side in the optical axis direction, and including a glass substrate having an outer peripheral surface provided around the first optical functional surface, and a resin layer bonded to the second optical functional surface of the glass substrate.

[0012] Japanese Patent Laid-Open Publication No. 05-323104 discloses a composite aspherical lens in which an aspherical synthetic resin layer is attached to the surface of a glass lens.

[0013] Japanese Patent Application Laid-Open No. 2005-060696 discloses a resin composition for a hybrid lens, which contains a radical polymerizable monomer and a silane coupling agent and is used to form a resin layer of a hybrid lens formed by bonding a resin layer to a glass lens base material.

[0014] Japanese Patent Application Laid-Open No. 2003-191260 discloses an apparatus for bonding a transparent resin film to one surface of a glass lens, the surface being used as a resin film bonding surface, in order to give the lens predetermined properties.

[0015] Japanese Patent Application Laid-Open No. 2018-151420 discloses a lens structure having a first resin layer on a support, the first resin layer having an indentation modulus of elasticity at room temperature of greater than 0 MPa and not greater than 3000 MPa, and a second resin layer on the first resin layer, and the amount of warping of the support is 0 μm to 50 μm.

[0016] Japanese Patent Application Laid-Open No. 2015-219422 discloses an optical element made of a substrate and resin, which satisfies a specific formula when the resin thickness of the thinnest part of a main component pattern made of resin is RTmin and the resin thickness of the thickest part is RTmax.

[0017] One embodiment of the technique of the present disclosure provides an optical system that can ensure the quality of the first lens.

[0018] A first aspect of the disclosed technique is an optical system including a compound lens having a first lens and a second lens, wherein the first lens is formed of resin and the second lens is formed of glass, and the optical system satisfies conditional expressions (1) and (2) expressed by: A / B≦10 (1) A≦3 mm (2) where A [mm] is the maximum thickness of the first lens and B [mm] is the minimum thickness of the first lens, and the resin satisfies conditional expression (3) expressed by: 1.0 μm≦x≦4.0 μm (3) where x [μm] is the amount of plastic deformation when an indenter is pressed into the resin at a loading rate of 200 mN / 10 sec at an ambient temperature of 25° C.

[0019] A second aspect of the technique of the present disclosure is the optical system according to the first aspect, which satisfies conditional expressions (5) and (6) expressed as: A≧0.1 mm (5) B≧0.02 mm (6).

[0020] A third aspect of the technique of the present disclosure is the optical system according to the first or second aspect, wherein the hardness of the resin at 25° C. is 186 MPa or more and 196 MPa or less.

[0021] A fourth aspect of the technique of the present disclosure is an optical system according to any one of the first to third aspects, wherein the hardness of the resin at 75°C is 149 MPa or more and 164 MPa or less.

[0022] A fifth aspect of the technology of the present disclosure is an optical system according to any one of the first to fourth aspects, in which the elastic recovery rate of the resin at 75°C is 59% or more and 63% or less.

[0023] A sixth aspect of the technology of the present disclosure is an optical system according to any one of the first to fifth aspects, wherein the indentation modulus of the resin at 25°C is 3.5 GPa or more and 3.6 GPa or less.

[0024] A seventh aspect of the technique of the present disclosure is an optical system according to any one of the first to sixth aspects, wherein the indentation modulus of the resin at 75°C is 2.4 GPa or less.

[0025] An eighth aspect according to the technique of the present disclosure is an optical system according to any one of the first to seventh aspects, wherein the resin has photocuring and thermosetting properties.

[0026] A ninth aspect according to the technique of the present disclosure is an optical system according to any one of the first to eighth aspects, wherein the first lens has positive refractive power and is made of resin, and satisfies conditional expression (7) expressed as follows: 0<d×(1 / Rf−1 / Rr)<0.05 (7) where d is the center thickness of the first lens, Rf is the radius of curvature of the object-side surface of the first lens, and Rr is the radius of curvature of the image-side surface of the first lens.

[0027] A tenth aspect according to the technique of the present disclosure is an optical system according to any one of the first to ninth aspects, comprising a front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group being arranged in this order from the object side to the image side, the rear group having positive refractive power and including at least one Lp lens formed of resin, the first lens being the Lp lens, and satisfying conditional expression (8) expressed as follows: 0.1<TL / fp<1.2 (8) where TL is the sum of the distance on the optical axis from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image side and the air equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane when focused on an object at infinity, and fp is the focal length of the Lp lens.

[0028] An eleventh aspect according to the technique of the present disclosure is an optical system according to any one of the first to tenth aspects, the optical system including a front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group being arranged in this order from the object side to the image side, the rear group having positive refractive power and including at least one Lp lens formed of resin, the first lens being the Lp lens, and satisfying conditional expression (9) expressed as 0.2<Hpp / Hpm<1.1 (9) where Hpp is the height from the optical axis of a chief ray of a maximum half angle of view at the object side surface of the Lp lens in a state focused on an object at infinity, and Hpm is the height from the optical axis of an on-axis marginal ray at the object side surface of the Lp lens in a state focused on an object at infinity.

[0029] A twelfth aspect of the technique of the present disclosure is an optical system according to any one of the first to eleventh aspects, the optical system including a front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group being arranged in this order from the object side to the image side, the rear group having positive refractive power and including at least one Lp lens made of resin, the first lens being the Lp lens, the radius of curvature of the image side surface of the Lp lens being Rr, and when focused on an object at infinity, In this optical system, when a point at the position of the aperture stop on the optical axis is defined as an object point, the distance on the optical axis from the image-side surface of the Lp lens to an image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop to the image-side surface of the Lp lens is defined as De, and De is calculated assuming that the medium on the image side of the Lp lens is air, and the sign of De is negative if the image point is closer to the object side than the image-side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image side than the image-side surface of the Lp lens on the optical axis.

[0030] A thirteenth aspect of the technique of the present disclosure is an optical system according to any one of the first to twelfth aspects, which includes a front group, an aperture stop, and a rear group, and the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the rear group has positive refractive power and includes at least one Lp lens formed of resin, the first lens is the Lp lens, and the optical system satisfies conditional expression (11) expressed by 0.04<ffoc / fp<0.36 (11), where ffoc is the focal length of the focus group that moves along the optical axis in the case of focusing, and fp is the focal length of the Lp lens.

[0031] A fourteenth aspect of the technique of the present disclosure is an optical system according to any one of the first to thirteenth aspects, comprising a front group, an aperture stop, and a rear group, the front group, aperture stop, and rear group being arranged in this order from the object side to the image side, the first lens being an Lp lens having positive refractive power and formed of resin, the rear group including an Lp lens if conditional expression (12) expressed by ωm≧45° (12) is satisfied when the maximum angle of view in a state focused on an object at infinity is ωm, and the optical system includes an Lp lens if conditional expression (13) expressed by ωm<45° (13) is satisfied.

[0032] A fifteenth aspect according to the technique of the present disclosure is an optical system according to any one of the first to fourteenth aspects, the optical system including a front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group being arranged in this order from the object side to the image side, the rear group having positive refractive power and including at least one Lp lens formed of resin, the first lens being the Lp lens, wherein A denotes a central thickness of the Lp lens, B denotes a thickness of the compound lens on both sides of the Lp lens in the optical axis direction at the maximum effective diameter height, Y denotes a maximum image height, θgF denotes a partial dispersion ratio between the g-line and the F-line of the Lp lens, and νd denotes an Abbe number of the Lp lens based on the d-line, and ΔθgF is expressed by conditional formula (15): ΔθgF=θgF−(0.6438−0.001682×νd) (14) The optical system satisfies the conditional expression (16) expressed as follows: 0.004<(|A−B|ΔθgF) / Y<0.020 (15).

[0033] A sixteenth aspect of the technique of the present disclosure is an optical system according to any one of the first to fifteenth aspects, which includes a front group, an aperture stop, and a rear group, and the front group, aperture stop, and rear group are arranged in this order from the object side to the image side, the composite lens is included in the front group, and the second lens is arranged on the object side relative to the first lens.

[0034] A seventeenth aspect of the technique of the present disclosure is an optical system according to any one of the first to fifteenth aspects, which includes a front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group being arranged in this order from the object side to the image side, the composite lens being included in the rear group, and the second lens being arranged on the image side relative to the first lens.

[0035] An eighteenth aspect of the technique of the present disclosure is an optical system including a compound lens having a first lens and a second lens, wherein the first lens has a convex surface and a first surface that protrudes radially outward from the outer circumferential edge of the convex surface of the compound lens, and the second lens has a concave surface bonded to the convex surface and a second surface that protrudes radially outward from the outer circumferential edge of the concave surface and is bonded to the first surface, and wherein the optical system satisfies conditional expressions (16) and (17) expressed by a<b (16) 5μm≦a / Ra (17), where a length of the first surface along the radial direction is a [μm], b length of the second surface along the radial direction is b [μm], and Ra surface roughness is Ra [μm].

[0036] FIG. 1 is a longitudinal sectional view showing an example of a compound lens. FIG. 2 is a longitudinal sectional view showing an example of the dimensional relationship of a compound lens. FIG. 3 is an explanatory diagram showing an example of a manufacturing method for a compound lens. FIG. 4 is a longitudinal sectional view explaining an example of a problem with a compound lens. FIG. 5 is a graph showing an example of a load-displacement curve in a microhardness test. FIG. 6 is a longitudinal sectional view showing an example of an imaging lens. FIG. 7 is a longitudinal sectional view showing an example of a distance De in an imaging lens. FIG. 8 is a longitudinal sectional view showing an example of a height Hpp and a height Hpm in an imaging lens. FIG. 9 is a longitudinal sectional view showing an example of an imaging lens according to Example 1. FIG. 10 is an explanatory diagram showing each aberration of the imaging lens according to Example 1. FIG. 11 is a longitudinal sectional view showing an example of an imaging lens according to Example 2. FIG. 12 is an explanatory diagram showing each aberration of the imaging lens according to Example 2.

[0037] Hereinafter, an example of an embodiment of an optical system according to the technique of the present disclosure will be described with reference to the accompanying drawings.

[0038] In the description of this specification, "orthogonal" refers to orthogonal in the sense of including, in addition to perfect orthogonal, an error that is generally acceptable in the technical field to which the technology of the present disclosure belongs and that does not contradict the spirit of the technology of the present disclosure. In the description of this specification, "parallel" refers to parallel in the sense of including, in addition to perfect parallel, an error that is generally acceptable in the technical field to which the technology of the present disclosure belongs and that does not contradict the spirit of the technology of the present disclosure. In the description of this specification, "plane" refers to a plane in the sense of including, in addition to perfect plane, an error that is generally acceptable in the technical field to which the technology of the present disclosure belongs and that does not contradict the spirit of the technology of the present disclosure.

[0039] (Configuration of Compound Lens) First, an example of the configuration of the compound lens 10 will be described. As an example, as shown in Fig. 1 , the compound lens 10 has a first lens 12 and a second lens 14. The first lens 12 and the second lens 14 are both formed in a circular shape when viewed in the optical axis direction of the compound lens 10. The first lens 12 is formed from resin, and the second lens 14 is formed from glass.

[0040] As an example, the first lens 12 is a concave meniscus lens, and has a convex surface 16 and a concave surface 18. The convex surface 16 is formed in a convex shape, and the concave surface 18 is formed in a concave shape. The concave surface 18 is a surface located on the opposite side to the convex surface 16 in the optical axis direction of the compound lens 10. The convex surface 16 and the concave surface 18 are formed on a lens body 20 of the first lens 12. The lens body 20 is a portion that defines the effective diameter of the first lens 12.

[0041] The first lens 12 also has a flange 22. The flange 22 protrudes from the outer peripheral edge of the lens body 20 radially outward of the compound lens 10. The flange 22 is formed in an annular shape along the outer peripheral edge of the lens body 20. The flange 22 has a first flange surface 24 and a second flange surface 26. The first flange surface 24 protrudes from the outer peripheral edge of the convex surface 16 radially outward of the compound lens 10, and the second flange surface 26 protrudes from the outer peripheral edge of the concave surface 18 radially outward of the compound lens 10. As an example, the first flange surface 24 and the second flange surface 26 both extend in a direction perpendicular to the optical axis direction of the compound lens 10. The concave surface 18 and the second flange surface 26 form a molded surface 28 that is molded by a mold 56 (see FIG. 3 ), which will be described later.

[0042] As an example, the second lens 14 is a plano-concave lens and has a flat surface 30 and a concave surface 32. The flat surface 30 is formed in a flat shape, and the concave surface 32 is formed in a concave shape. The concave surface 32 is a surface located opposite the flat surface 30 in the optical axis direction of the compound lens 10. The convex surface 16 of the first lens 12 is bonded to the concave surface 32. The second lens 14 also has a polished surface 34. The polished surface 34 is formed by a rough surface with concaves and convexes. The polished surface 34 protrudes from the outer peripheral edge of the concave surface 32 radially outward of the compound lens 10. As an example, the polished surface 34 extends in a direction perpendicular to the optical axis direction of the compound lens 10. A ridge line 36 is formed between the concave surface 32 and the polished surface 34. The ridge line 36 is formed in an annular shape along the outer peripheral edge of the concave surface 32.

[0043] The first flange surface 24 is bonded to the sliding surface 34. As an example, the first flange surface 24 is bonded to a first region 34A of the sliding surface 34 on the concave surface 32 side. A second region 34B of the sliding surface 34 excluding the first region 34A is used, for example, as a gripping margin when the compound lens 10 is gripped by a gripping device (not shown). In other words, the portion of the compound lens 10 including the second region 34B is a gripped portion 38 that is gripped by the gripping device.

[0044] 1, a plano-concave lens is given as an example of the second lens 14, but the second lens 14 may be a biconcave lens having a concave surface instead of the flat surface 30. The second lens 14 may also be a concave meniscus lens having a convex surface instead of the flat surface 30.

[0045] The compound lens 10 is an example of a "compound lens" according to the technology of the present disclosure. The first lens 12 is an example of a "first lens" according to the technology of the present disclosure. The second lens 14 is an example of a "second lens" according to the technology of the present disclosure. The convex surface 16 is an example of a "convex surface" according to the technology of the present disclosure. The concave surface 18 is an example of a "concave surface" according to the technology of the present disclosure. The first flange surface 24 is an example of a "first surface" according to the technology of the present disclosure. The sliding surface 34 is an example of a "second surface" according to the technology of the present disclosure. The second flange surface 26 is an example of a "third surface" according to the technology of the present disclosure.

[0046] (Dimensional Relationship of the Compound Lens) Next, the dimensional relationship of the compound lens 10 will be described. As an example, as shown in FIG. 2 , in the following description, the length of the first flange surface 24 along the radial direction of the compound lens 10 will be referred to as "length a", and the length of the sliding surface 34 along the radial direction of the compound lens 10 will be referred to as "length b". Furthermore, the length from the first flange surface 24 to the second flange surface 26 along the optical axis direction of the compound lens 10 will be referred to as "length c", and the surface roughness of the sliding surface 34 will be referred to as "surface roughness Ra". The units of length a, length b, length c, and surface roughness Ra are all "μm (micrometer)".

[0047] Furthermore, the maximum value of the thickness of the first lens 12 is referred to as the "maximum thickness A," and the minimum value of the thickness of the first lens 12 is referred to as the "minimum thickness B." The units of the maximum thickness A and the minimum thickness are both "mm (millimeters)." The thickness of the first lens 12 is defined by the length from the convex surface 16 to the concave surface 18 along the optical axis direction of the compound lens 10. As an example, the maximum thickness A corresponds to the thickness of the first lens 12 at the center of the first lens 12. As another example, the minimum thickness B corresponds to the thickness of the end of the lens body 20 on the flange 22 side.

[0048] (Dimensions Applied to the Compound Lens) Next, an example of dimensions applied to the compound lens 10 will be described. The difference between the thickness of the first lens 12 at the center of the convex surface 16 and the thickness of the first lens 12 at the first flange surface 24 (i.e., the thickness of the flange 22) is 0.01 mm or more and 1 mm or less. The effective diameter of the convex surface 16 is 3 mm or more and 50 mm or less. The outer diameter of the second lens 14 is 4 mm or more and 110 mm or less. The thickness of the second lens 14 at the center of the concave surface 32 is 0.5 mm or more and 10 mm or less. The effective diameter of the concave surface 32 is 3 mm or more and 50 mm or less. The radius of curvature of the concave surface 32 is 5 mm or more and 300 mm or less. The radius of curvature of the convex surface 16 is the same as the radius of curvature of the concave surface 32. Note that the above dimensions are merely an example, and the dimensions of the compound lens 10 may be other than those described above.

[0049] (Materials Applied to First Lens and Second Lens) Next, an example of a material applied to the first lens 12 and the second lens 14 will be described. As an example, the first lens 12 is formed from a photothermosetting resin that has photocuring properties and thermosetting properties. Specifically, the first lens 12 is formed from a mixed resin of a photocuring resin that has photocuring properties and a thermosetting resin that has thermosetting properties. Examples of the photothermosetting resin that forms the first lens 12 include the curable resins described in WO 2022 / 039143.

[0050] For example, the linear expansion coefficient of the first lens 12 is 6×10 －５ / °C, and the elastic modulus of the first lens 12 is 2.5×10 ９ Pa. Examples of glass that forms the second lens 14 include S-FPL5 manufactured by OHARA Corporation. For example, the linear expansion coefficient of the second lens 14 is 0.77×10 －５ / °C, and the elastic modulus of the second lens 14 is 106.7×10 ９ It is Pa.

[0051] (Method of Manufacturing Compound Lens) Next, an example of a method of manufacturing compound lens 10 will be described. In the example shown in FIG. 3 , resin 50 is used as the resin for forming first lens 12. Resin 50 is a photothermosetting resin. In the method of manufacturing compound lens 10, first, uncured resin 50 is supplied to concave surface 32 by supply device 52. Next, with second lens 14 held by jig 54, resin 50 is pressed toward second lens 14 from the side opposite second lens 14 by mold 56. Mold 56 has a molding surface 58 formed in a shape that is an inverted version of molded surface 28. Molded surface 28 is formed in resin 50 by molding surface 58.

[0052] Next, light 62 is output from a light source 60 arranged on the opposite side of the resin 50 and the mold 56. The light 62 is light in a wavelength band that hardens the resin 50. The light 62 output from the light source 60 passes through the second lens 14 and is irradiated onto the resin 50. When the resin 50 is irradiated with the light 62, the photocurable resin contained in the resin 50 undergoes a hardening reaction, and the resin 50 becomes semi-hardened. Next, the mold 56 is heated by a heating device 64. The heat from the mold 56 heated by the heating device 64 is transferred to the resin 50, heating the resin 50. Then, the thermosetting resin contained in the resin 50 undergoes a hardening reaction, and the resin 50 becomes hardened. When the resin 50 hardens, the first lens 12 integrated with the second lens 14 is formed. In this manner, the compound lens 10 having the first lens 12 and the second lens 14 is manufactured.

[0053] (Issues with the Compound Lens) Next, the issues with the compound lens 10 will be described. As an example, as shown in FIG. 4, an uneven shape is formed on the sliding surface 34. The uneven shape formed on the sliding surface 34 meshes with the uneven shape formed on the first flange surface 24. The diameter φ of the recesses 40 included in the uneven shape formed on the sliding surface 34 is approximately 50 μm. In FIG. 4, the size of the uneven shape is exaggerated to make it easier to understand.

[0054] The sliding surface 34 is formed by polishing, for example. A region of the sliding surface 34 on the boundary side with the concave surface 32 (hereinafter referred to as the "boundary region 34C") generates a plurality of microcracks 42 as a result of the polishing process. The microcracks 42 are generated by stress concentration in the boundary region 34C when the sliding surface 34 is polished. Stress is concentrated in the boundary region 34C because the boundary region 34C is in contact with the ridge line 36. The region adjacent to the boundary region 34C (hereinafter referred to as the "adjacent region 34D") does not include microcracks 42 because the region is separated from the ridge line 36, thereby alleviating stress.

[0055] In the example shown in Fig. 4, the first flange surface 24 is bonded to the sliding surface 34 only at the boundary region 34C. That is, the first flange surface 24 is included within the range of the length of the boundary region 34C. In the example shown in Fig. 4, if the first lens 12 is deformed radially inward of the compound lens 10 (i.e., toward the arrow IN) due to cure shrinkage and / or thermal shrinkage, etc., the sliding surface 34 will be pulled by the first flange surface 24, and cracks 44 may occur starting from the microcracks 42 and extending from the sliding surface 34 toward the inside of the second lens 14. If the number and / or size of the cracks 44 exceed the allowable range, the second lens 14 may be destroyed by physical forces generated by the deformation of the first lens 12.

[0056] Here, it is conceivable to reduce the value of the surface roughness Ra in order to suppress the force with which the sliding surface 34 is pulled by the first flange surface 24. However, if the value of the surface roughness Ra is reduced, there is a risk that optical defects will occur in the compound lens 10 due to light reflection at the sliding surface 34.

[0057] Therefore, the compound lens 10 is required to be able to prevent optical defects caused by reflection of light at the sliding surface 34 and to prevent the second lens 14 from being destroyed by physical forces caused by deformation of the first lens 12. In addition, the first lens 12 formed from resin is required to be able to ensure quality in terms of optical performance.

[0058] (Examples and Comparative Examples of Compound Lenses) Next, examples of examples and comparative examples of compound lenses 10 with different lengths a, c, and surface roughness Ra will be described with reference to Table 1. As an example, the evaluation items for the examples and comparative examples include "crack occurrence," "optical properties," and "graspability."

[0059] Regarding "crack occurrence," the occurrence of cracks 44 originating from microcracks 42 present in the boundary region 34C of the sliding surface 34 is evaluated as "excellent," "good," or "poor." A rating of "excellent" for "crack occurrence" indicates that cracks 44 do not occur and that destruction of the second lens 14 can be prevented. A rating of "good" for "crack occurrence" indicates that cracks 44 occur, but the number and / or size of the cracks 44 are within an acceptable range and destruction of the second lens 14 can be prevented. A rating of "poor" for "crack occurrence" indicates that the number and / or size of the cracks 44 are outside the acceptable range and that destruction of the second lens 14 will occur.

[0060] Regarding "optical characteristics," the optical characteristics of the compound lens 10 are evaluated as "excellent," "good," or "poor." The closer the sliding surface 34 is to a flat surface, the greater the intensity of light reflected by the sliding surface 34, which affects the optical characteristics of the compound lens 10. "Optical characteristics" of "excellent" indicate that the optical characteristics of the compound lens 10 are not affected and optical defects in the compound lens 10 can be prevented. "Optical characteristics" of "good" indicate that the optical characteristics of the compound lens 10 are affected, but the intensity of light reflected by the sliding surface 34 is within an acceptable range and optical defects in the compound lens 10 can be prevented. "Optical characteristics" of "poor" indicate that the intensity of light reflected by the sliding surface 34 is outside the acceptable range and optical defects in the compound lens 10 can be prevented.

[0061] Regarding "graspability," the workability when the gripped portion 38 is gripped by a gripping device is evaluated as "excellent," "good," or "poor." As described above, the compound lens 10 has the gripped portion 38, and transportation and assembly operations are performed with the gripped portion 38 gripped by the gripping device. "Grappleability" being "excellent" indicates that the length of the gripped portion 38 is longer than the minimum length required for the gripped portion 38 to be gripped by the gripping device, thereby ensuring the stability of the compound lens 10 when the gripped portion 38 is gripped by the gripping device. "Grappleability" being "good" indicates that the length of the gripped portion 38 is set to the minimum length required for the gripped portion 38 to be gripped by the gripping device, thereby ensuring the stability of the compound lens 10 when the gripped portion 38 is gripped by the gripping device. A "graspability" of "impossible" indicates that the length of the graspable portion 38 is shorter than the minimum length required for the graspable portion 38 to be grasped by the grasping device, and therefore the graspable portion 38 cannot be grasped by the grasping device.

[0062]

[0063] From the examples and comparative examples shown in Table 1, it is preferable that the compound lens 10 satisfies the following conditional expressions (1), (2), and (3): a<b (1) 100 μm≦a (2) 0.5 μm≦Ra≦20 μm (3)

[0064] When the length a is less than 100 μm in conditional expression (2), cracks 44 will occur, destroying the second lens 14. When the length a is 100 μm or greater in conditional expression (2), the occurrence of cracks 44 is suppressed, thereby preventing the second lens 14 from being destroyed. When the length a is 100 μm or greater, the occurrence of cracks 44 originating from microcracks 42 present in the boundary region 34C of the sliding surface 34 is suppressed. It is presumed that this is because the first flange surface 24 is bonded not only to the boundary region 34C containing the microcracks 42, but also to the adjacent region 34D adjacent to the boundary region 34C (i.e., the region not containing the microcracks 42).

[0065] When the surface roughness Ra is less than 0.5 μm in conditional expression (3), light reflected by the polished surface 34 affects the optical properties of the compound lens 10, thereby causing optical defects in the compound lens 10. When the surface roughness Ra is 0.5 μm or more in conditional expression (3), the light reflected by the polished surface 34 is prevented from affecting the optical properties of the compound lens 10, thereby preventing optical defects in the compound lens 10. When the surface roughness Ra is more than 20 μm in conditional expression (3), cracks 44 are generated starting from microcracks 42 present in the boundary region 34C of the polished surface 34, thereby destroying the second lens 14. When the surface roughness Ra is 20 μm or less in conditional expression (3), the cracks 44 are prevented from being generated starting from microcracks 42 present in the boundary region 34C of the polished surface 34, thereby preventing damage to the second lens 14. When the surface roughness Ra is 20 μm or less, it is presumed that the reason why cracks 44 are prevented from occurring starting from microcracks 42 present in the boundary region 34C of the sliding surface 34 is that the force of the interlocking between the uneven shape of the sliding surface 34 and the uneven shape of the first flange surface 24 is suppressed, thereby suppressing the physical force generated in the boundary region 34C of the sliding surface 34 due to deformation of the first lens 12.

[0066] The difference in the linear expansion coefficient between glass and resin has a smaller effect than the elastic modulus of the resin on breaking of the second lens 14. Furthermore, the lower the elastic modulus of the resin, the less likely cracks 44 will occur. However, as a result of extensive research by the inventors, it has been experimentally revealed that the effects of length a, length c, and surface roughness Ra are greater than the effect of the elastic modulus of the resin.

[0067] Furthermore, from the examples and comparative examples shown in Table 1, it is preferable that the compound lens 10 satisfies the following conditional expression (4): b - a ≥ 700 μm (4)

[0068] In the examples and comparative examples of the compound lens 10, the length b is set to 1700 μm, and in Table 1, a corresponding value of 700 μm or more in conditional formula (4) corresponds to a length a of 1000 μm or less. If the corresponding value of conditional formula (4) is less than 700 μm, the gripping device interferes with the flange 22, making it impossible for the gripping device to grip the gripped portion 38, and making it difficult to assemble the compound lens 10 to the imaging lens. If the corresponding value of conditional formula (4) is 700 μm or more, when the gripping device grips the gripped portion 38, interference between the gripping device and the flange 22 is avoided, and the stability of the compound lens 10 is ensured. This ensures ease of assembly of the compound lens 10 to the imaging lens.

[0069] It is more preferable that the compound lens 10 satisfies the following conditional expression (5): 5≦a / Ra (5)

[0070] When the corresponding value of conditional expression (5) is 5 or greater, it is possible to more effectively prevent optical defects caused by reflection of light at the second surface and damage to the second lens 14 due to physical forces generated by deformation of the first lens 12.

[0071] It is more preferable that the compound lens 10 satisfies the following conditional expression (6): 10 μm≦c≦300 μm (6)

[0072] If the length c is less than 10 μm in conditional expression (6), when the resin 50 is supplied to the concave surface 32 by the supply device 52, variations in the amount of resin 50 cannot be tolerated, and the length a is unstable. If the length c is 10 μm or greater in conditional expression (6), when the resin 50 is supplied to the concave surface 32 by the supply device 52, variations in the amount of resin 50 can be tolerated, and the length a is stable. Furthermore, if the length c is greater than 300 μm in conditional expression (6), cracks 44 will occur, destroying the second lens 14. If the length c is 300 μm or less in conditional expression (6), the occurrence of cracks 44 is suppressed, and destruction of the second lens 14 can be prevented.

[0073] It is more preferable that the compound lens 10 satisfies the following conditional expression (7): 100 μm≦c≦300 μm (7)

[0074] When the length c is 100 μm or more in the conditional expression (7), the effect obtained when the length c is 10 μm or more is enhanced. Furthermore, when the length c is 100 μm or more in the conditional expression (7), the first lens 12 is easier to manufacture than when the length c is less than 100 μm.

[0075] It is more preferable that the compound lens 10 satisfies the following conditional expression (8): 1 μm≦Ra≦4 μm (8)

[0076] When the surface roughness Ra is 1 μm or more in the conditional expression (8), the effect obtained when the surface roughness Ra is 0.5 μm or more is enhanced.When the surface roughness Ra is 4 μm or more in the conditional expression (8), the effect obtained when the surface roughness Ra is 20 μm or less is enhanced.

[0077] Next, with reference to Table 2, an example in which the maximum thickness A and the minimum thickness B of the first lens 12 are made different will be described for the examples and comparative examples. In addition to the maximum thickness A and the minimum thickness B, Table 2 lists, as parameters, the thickness deviation ratio A / B, which indicates the ratio of the maximum thickness A to the minimum thickness B. As an example, "quality of the first lens" is listed as an evaluation item for the examples and comparative examples.

[0078] The "quality of the first lens" is evaluated, by way of example, with respect to the quality of the molded surface 28 formed by the mold 56, as "excellent," "good," or "poor." A "quality of the first lens" of "excellent" indicates that the occurrence of air bubbles and transfer defects on the molded surface 28 is prevented when the resin 50 is molded using the mold 56, thereby ensuring the quality of the optical performance of the first lens 12. Transfer defects occur due to insufficient pressing force from the mold 56 on the portion of the first lens 12 corresponding to the maximum thickness A (hereinafter referred to as the "maximum thickness portion"). A "quality of the first lens" of "good" indicates that air bubbles and / or transfer defects occur on the molded surface 28, but the number and / or size of the areas where the air bubbles and / or transfer defects occur are within an acceptable range, thereby ensuring the quality of the optical performance of the first lens 12. A "quality of the first lens" of "poor" indicates that the number of areas where the air bubbles and / or transfer defects occur is outside the acceptable range, thereby resulting in insufficient quality of the optical performance of the first lens 12.

[0079]

[0080] From the examples and comparative examples shown in Table 2, it is preferable that the first lens 12 satisfy the following conditional expressions (9) and (10): A / B≦10 (9) A≦3 mm (10)

[0081] When the thickness deviation ratio A / B is greater than 10 in conditional expression (9), air bubbles are generated on the molded surface 28, resulting in a lack of quality in terms of optical performance of the first lens 12. When the thickness deviation ratio A / B is 10 or less in conditional expression (9), air bubbles and transfer defects are prevented from being generated on the molded surface 28, thereby ensuring quality in terms of optical performance of the first lens 12. When the maximum thickness A is greater than 3 mm in conditional expression (10), air bubbles are generated on the molded surface 28, resulting in a lack of quality in terms of optical performance of the first lens 12. When the maximum thickness A is 3 mm or less in conditional expression (10), air bubbles and transfer defects are prevented from being generated on the molded surface 28, thereby ensuring quality in terms of optical performance of the first lens 12.

[0082] Furthermore, from the examples and comparative examples shown in Table 2, it is preferable that the first lens 12 satisfy the following conditional expressions (11) and (12): A≧0.1 mm (11) B≧0.02 mm (12)

[0083] If the maximum thickness A is less than 0.1 mm in conditional expression (11), transfer defects occur on the molded surface 28, resulting in a lack of quality in terms of optical performance of the first lens 12. If the maximum thickness A is 0.1 mm or greater in conditional expression (11), the occurrence of air bubbles and transfer defects on the molded surface 28 is suppressed, thereby ensuring quality in terms of optical performance of the first lens 12. If the minimum thickness B is less than 0.02 mm in conditional expression (12), air bubbles occur on the molded surface 28, resulting in a lack of quality in terms of optical performance of the first lens 12. If the minimum thickness B is 0.02 mm or greater in conditional expression (12), the occurrence of air bubbles and transfer defects on the molded surface 28 is suppressed, thereby ensuring quality in terms of optical performance of the first lens 12.

[0084] (Microhardness Test on Resin) Next, an example of a microhardness test performed on a resin used in the first lens 12 will be described. For the microhardness test, for example, a dynamic ultra-microhardness tester DUH-211S manufactured by Shimadzu Corporation is used. A Berkovich type indenter is used as the indenter. Note that other measuring devices similar to the dynamic ultra-microhardness tester DUH-211S manufactured by Shimadzu Corporation may also be used for the microhardness test.

[0085] In the microhardness test, a flat test piece having a diameter of 7.4 mm and a thickness of 1.3 mm is used as an example of a test piece of a cured resin. The thickness of the test piece is generally set to approximately 10 times the amount of plastic deformation x (see Figure 5), which will be described later. Therefore, the thickness of the resin does not need to be 1.3 mm. For example, if the amount of plastic deformation is 5 μm, the thickness of the resin may be 50 μm, 100 μm, or 200 μm. Furthermore, as long as the thickness requirement is met, the resin used in the microhardness test does not need to be flat. The test piece is placed in an environment where the environmental temperature is set to 25°C. As an example, the test piece is placed on a hot plate set to 25°C. 25°C is a temperature simulating room temperature. Instead of a hot plate, a thermostatic bath may be used, and the temperature of the thermostatic bath may be set to 25°C. The test piece is pressed by an indenter at a load rate of 200 mN / 10 sec under an ambient temperature of 25°C.

[0086] As an example, Fig. 5 shows a load-displacement curve when an indenter is pressed into a test piece in a microhardness test. In the microhardness test, the test piece is subjected to creep by holding the maximum load and the unloaded state for 5 seconds each.

[0087] Table 3 shows the relationship between the amount of plastic deformation x obtained by the microhardness test and the evaluation items for the composite lens 10. The unit of the amount of plastic deformation x is "μm (micrometer)." In the microhardness test, the amount of plastic deformation x is measured when different resin materials are used. The amount of plastic deformation x is defined as the amount of deformation remaining after the test piece creeps by holding the unloaded state for 5 seconds. Ten tests were conducted for each material, and the amount of plastic deformation x was calculated as the average value of the values ​​obtained in each test. As an example, the evaluation items for the composite lens 10 include "coating quality," "environmental resistance," and "adsorption resistance."

[0088] Regarding "coating quality," the quality of the coating on the first lens 12 when the first lens 12 is coated with an AR (Anti-Reflection) coating is evaluated as "excellent," "good," or "poor." The AR coating refers to a multilayer anti-reflection film applied to the concave surface 18 of the first lens 12. The AR coating is formed, for example, by vapor deposition. A "coating quality" of "excellent" indicates that the AR-coated concave surface 18 does not deform, ensuring coating quality. A "coating quality" of "good" indicates that the concave surface 18 deforms, but the amount of deformation of the concave surface 18 is within an acceptable range, ensuring coating quality. A "coating quality" of "poor" indicates that the amount of deformation of the concave surface 18 is outside an acceptable range, resulting in insufficient coating quality.

[0089] Regarding "environmental resistance," the durability of the composite lens 10 when placed in a low-temperature environment is evaluated as "excellent," "good," or "poor." "Excellent" "environmental resistance" indicates that even when the composite lens 10 is placed in a low-temperature environment, cracks 44 do not occur and the second lens 14 can be prevented from being destroyed. "Good" "environmental resistance" indicates that when the composite lens 10 is placed in a low-temperature environment, cracks 44 occur, but the number and / or size of the cracks 44 are within an acceptable range, and the second lens 14 can be prevented from being destroyed. "Poor" "environmental resistance" indicates that when the composite lens 10 is placed in a low-temperature environment, the number and / or size of the cracks 44 that occur are outside of an acceptable range, and the second lens 14 will be destroyed.

[0090] Regarding "stiction resistance," scratches that occur on the concave surface 18 of the first lens 12 when the concave surface 18 is suctioned with a suction pad or the like to transport the compound lens 10 are evaluated as "excellent," "good," or "poor." "Stiction resistance" of "excellent" indicates that the concave surface 18 of the first lens 12 does not deform even when the concave surface 18 is suctioned with a suction pad or the like, and the quality of the first lens 12 can be ensured. "Stiction resistance" of "good" indicates that the concave surface 18 of the first lens 12 deforms when the concave surface 18 is suctioned with a suction pad or the like, but the amount of deformation of the concave surface 18 is within an acceptable range, and the quality of the first lens 12 can be ensured. "Stiction resistance" of "poor" indicates that the amount of deformation of the concave surface 18 when the concave surface 18 of the first lens 12 is suctioned with a suction pad or the like is outside the acceptable range, and the quality of the first lens 12 is insufficient.

[0091]

[0092] From the results of the microhardness test shown in Table 3, it is preferable that the resin satisfy the following conditional expression (13): 1.0 μm≦x≦4.0 μm (13)

[0093] If the amount of plastic deformation x is less than 1.0 μm in conditional expression (13), cracks 44 will occur, causing the second lens 14 to break. If the amount of plastic deformation x is 1.0 μm or greater in conditional expression (13), the occurrence of cracks 44 will be suppressed, and the second lens 14 will be prevented from breaking. If the amount of plastic deformation x is greater than 4.0 μm in conditional expression (13), when the concave surface 18 of the first lens 12 is sucked by a suction pad or the like, the concave surface 18 will deform, causing the quality of the first lens 12 to be insufficient. If the amount of plastic deformation x is 4.5 μm or greater in conditional expression (13), when the first lens 12 is coated with an AR coating, the concave surface 18 will deform, causing the quality of the first lens 12 to be insufficient. When the amount of plastic deformation x is 4.0 μm or less in conditional expression (13), deformation of concave surface 18 of first lens 12 is prevented even when the concave surface 18 of first lens 12 is suctioned with a suction pad or the like, and deformation of concave surface 18 is also prevented even when an AR coating is applied to first lens 12. This ensures the quality of the first lens.

[0094] The hardness of the resin at 25°C is preferably 186 MPa or more and 196 MPa or less. If the hardness of the resin at 25°C is less than 186 MPa, scratches will occur on the concave surface 18 of the first lens 12 when the concave surface 18 is adsorbed with a suction pad or the like. If the hardness of the resin at 25°C is 186 MPa or more, scratches on the concave surface 18 can be prevented even when the concave surface 18 of the first lens 12 is adsorbed with a suction pad or the like. If the hardness of the resin at 25°C is more than 196 MPa, the second lens 14 will be destroyed by physical forces generated by deformation of the first lens 12 in low-temperature environments, etc. If the hardness of the resin at 25°C is 196 MPa or less, damage to the second lens 14 can be prevented even in low-temperature environments, etc.

[0095] Furthermore, the hardness of the resin at 75°C is preferably 149 MPa or more and 164 MPa or less. 75°C is a temperature assuming that an AR coating or the like is applied to the concave surface 18 of the first lens 12. If the hardness of the resin at 75°C is less than 149 MPa, the concave surface 18 will deform when the AR coating is applied to the first lens 12. If the hardness of the resin at 75°C is 149 MPa or more, deformation of the concave surface 18 can be prevented even when the AR coating is applied to the first lens 12. If the hardness of the resin at 75°C is more than 164 MPa, the second lens 14 will be destroyed by a physical force generated by deformation of the first lens 12 when the AR coating or the like is applied to the concave surface 18 of the first lens 12. If the hardness of the resin at 75°C is 164 MPa or less, even if an AR coating or the like is applied to the concave surface 18 of the first lens 12, the second lens 14 can be prevented from being destroyed by the physical force generated by deformation of the first lens 12.

[0096] Furthermore, the elastic recovery rate of the resin at 75°C is preferably 59% or more and 63% or less. If the elastic recovery rate of the resin at 75°C is less than 59%, scratches will occur on the concave surface 18 of the first lens 12 when the concave surface 18 is adsorbed with a suction pad or the like. If the elastic recovery rate of the resin at 75°C is 59% or more, scratches on the concave surface 18 can be prevented even when the concave surface 18 of the first lens 12 is adsorbed with a suction pad or the like. If the elastic recovery rate of the resin at 75°C is more than 63%, cracks 44 will occur, destroying the second lens 14. If the elastic recovery rate of the resin at 75°C is 63% or less, cracks 44 will be suppressed, preventing damage to the second lens 14.

[0097] Furthermore, the indentation elastic modulus of the resin at 25°C is preferably 3.5 GPa or more and 3.6 GPa or less. If the indentation elastic modulus of the resin at 25°C is less than 3.5 GPa, the concave surface 18 will deform when the first lens 12 is coated with an AR coating. If the indentation elastic modulus of the resin at 25°C is 3.5 GPa or more, deformation of the concave surface 18 can be prevented even when the first lens 12 is coated with an AR coating. If the indentation elastic modulus of the resin at 25°C is more than 3.6 GPa, the second lens 14 will be destroyed by physical forces generated by deformation of the first lens 12 in low-temperature environments, etc. If the indentation elastic modulus of the resin at 25°C is 3.6 GPa or less, destruction of the second lens 14 can be prevented even in low-temperature environments, etc.

[0098] Furthermore, the indentation modulus of the resin at 75° C. is preferably 2.2 GPa or more and 2.4 GPa or less. If the indentation modulus of the resin at 75° C. exceeds 2.4 GPa, the second lens 14 will be destroyed by the physical force generated by deformation of the first lens 12 due to thermal expansion. If the indentation modulus of the resin at 75° C. is 2.4 GPa or less, destruction of the second lens 14 can be prevented even if the first lens 12 is deformed due to thermal expansion.

[0099] (Configuration of imaging lens including compound lens 10) Next, an example of an imaging lens including the compound lens 10 will be described. As an example, FIG. 6 shows a state in which an imaging lens according to an embodiment of the present disclosure is focused on an object at infinity. The imaging lens is an example of an "optical system" according to the technology of the present disclosure. Note that in this specification, an object at a distance of infinity is referred to as an infinite object, and an object at a close distance is referred to as a close object. In the example shown in FIG. 6, the left side is the object side, and the right side is the image side.

[0100] As an example, Fig. 6 shows an example in which a parallel-plate-shaped optical member PP is arranged between the imaging lens and the image plane Sim, assuming that the imaging lens is applied to an imaging device. The optical member PP is a member that is assumed to include various filters and / or cover glass, etc. The various filters are low-pass filters, infrared cut filters, and / or filters that cut off specific wavelength ranges, etc. The optical member PP is a member that does not have refractive power. It is also possible to configure the imaging lens without the optical member PP.

[0101] The imaging lens has a front group GF, an aperture stop St, and a rear group GR, which are arranged in this order from the object side to the image side along the optical axis Z. This configuration is advantageous for suppressing various aberrations while maintaining a compact and lightweight design.

[0102] As an example, the front group GF and rear group GR of the imaging lens are configured as follows: The front group GF has a first lens group G1. The first lens group G1 has, in order from the object side to the image side, nine lenses, L11 to L19. The rear group GR has, in order from the object side to the image side, a second lens group G2 and a third lens group G3. The second lens group G2 has eight lenses, L21 to L28. The third lens group G3 has one lens, lens L31.

[0103] In the example shown in Figure 6, when focusing, the first lens group G1 and the third lens group G3 are fixed with respect to the image plane Sim, and the entire second lens group moves integrally along the optical axis Z. Here, "moving integrally" means moving simultaneously in the same direction by the same amount. In this specification, the group that moves along the optical axis Z when focusing is referred to as the focus group. Focusing is achieved by the movement of the focus group. The left-pointing arrow below the second lens group G2 in Figure 6 indicates that the second lens group G2 is the focus group that moves toward the object when focusing from an object at infinity to a close object.

[0104] In this specification, a "lens group" is a component of an imaging lens that includes at least one lens separated by an air gap that changes when focusing. When focusing, each lens group is moved or fixed, and the mutual spacing between lenses within each lens group does not change. In other words, in this specification, a group in which the spacing between adjacent groups changes when focusing, but the total spacing between adjacent lenses within itself does not change, is defined as one lens group.

[0105] The rear group GR of the imaging lens includes at least one Lp lens Lp made of resin and having positive refractive power, cemented to a lens. By arranging the above-mentioned Lp lens Lp made of resin in the rear group GR, it becomes easy to correct axial chromatic aberration and lateral chromatic aberration in a well-balanced manner while achieving weight reduction. In the example shown in FIG. 6, lens L24 corresponds to the Lp lens Lp. In the example shown in FIG. 6, lens L24 is cemented with lenses L23 and L25. The image-side surface of the Lp lens corresponds to a convex surface, and the object-side surface of the Lp lens corresponds to a concave surface.

[0106] It is preferable that the Lp lens Lp satisfy the following conditional expression (14). Here, d denotes the central thickness of the Lp lens Lp, Rf denotes the radius of curvature of the object-side surface of the Lp lens Lp, and Rr denotes the radius of curvature of the image-side surface of the Lp lens Lp. As an example, FIG. 7 shows an enlarged view of a portion of the imaging lens shown in FIG. 6 that includes the Lp lens Lp. The Lp lens Lp that satisfies conditional expression (14) has a small value of d and a shape in which Rf and Rr are close to each other. By ensuring that the corresponding value of conditional expression (14) is not equal to or less than the lower limit, the refractive power of the Lp lens Lp can be strengthened, thereby achieving a higher chromatic aberration correction effect. By ensuring that the corresponding value of conditional expression (14) is not equal to or greater than the upper limit, the refractive power and thickness of the Lp lens Lp can be appropriately set, thereby making it easier to suppress aberration fluctuations when the refractive index of the Lp lens Lp fluctuates due to environmental changes such as temperature. In order to obtain better characteristics, it is more preferable that the Lp lens Lp satisfies the following conditional formula (14-1), it is even more preferable that the Lp lens Lp satisfies the following conditional formula (14-2), and it is even more preferable that the Lp lens Lp satisfies the following conditional formula (14-3): 0<d×(1 / Rf−1 / Rr)<0.05 (14) 0.0001<d×(1 / Rf−1 / Rr)<0.025 (14-1) 0.0005<d×(1 / Rf−1 / Rr)<0.015 (14-2) 0.0013<d×(1 / Rf−1 / Rr)<0.009 (14-3)

[0107] It is preferable that the imaging lens satisfy the following conditional expression (15). Here, when focused on an object at infinity, TL is the sum of the on-optical axial distance from the lens surface of the front group GF closest to the object to the lens surface of the rear group GR closest to the image, and the on-optical axial air-equivalent distance from the lens surface of the rear group GR closest to the image to the image plane Sim, and fp is the focal length of the Lp lens Lp. Note that fp is calculated assuming that the medium on the object side and the image side of the Lp lens Lp is air. By ensuring that the corresponding value of conditional expression (15) is not equal to or less than the lower limit, the chromatic aberration correction effect of the Lp lens Lp can be enhanced. By ensuring that the corresponding value of conditional expression (15) is not equal to or greater than the upper limit, it is possible to suppress aberration fluctuations when the refractive index of the Lp lens Lp fluctuates due to environmental changes such as temperature. In order to obtain better characteristics, it is more preferable that the imaging lens satisfy the following conditional expression (15-1), and it is even more preferable that the imaging lens satisfy the following conditional expression (15-2). 0.1<TL / fp<1.2 (15) 0.15<TL / fp<0.95 (15-1) 0.25<TL / fp<0.61 (15-2)

[0108] It is preferable that the imaging lens satisfy the following conditional expression (16). Here, Hpp is the height from the optical axis Z of the chief ray 3p at the maximum half angle of view ωm on the object-side surface of the Lp lens Lp when focused on an object at infinity. Also, Hpm is the height from the optical axis Z of the axial marginal ray 2m on the object-side surface of the Lp lens Lp when focused on an object at infinity. As an example, FIG. 8 shows the heights Hpp and Hpm of the imaging lens shown in FIG. 6. FIG. 8 also shows an enlarged view from the lens L24 corresponding to the Lp lens Lp to the image plane Sim along with each ray. Making sure that the corresponding value of conditional expression (16) is not equal to or less than the lower limit is advantageous for correcting lateral chromatic aberration. Making sure that the corresponding value of conditional expression (16) is not equal to or greater than the upper limit is advantageous for correcting axial chromatic aberration. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional formula (16-1), and it is even more preferable that the imaging lens satisfies the following conditional formula (16-2): 0.2<Hpp / Hpm<1.1 (16) 0.31<Hpp / Hpm<0.9 (16-1) 0.5<Hpp / Hpm<0.72 (16-2)

[0109] It is preferable that the imaging lens satisfy the following conditional expression (17). Here, when an object at infinity is focused, and a point on the optical axis at the position of the aperture stop St is defined as an object point, De is the distance on the optical axis from the image-side surface of the Lp lens Lp to an image point formed by the optical system from the lens surface adjacent to the image side of the aperture stop St to the image-side surface of the Lp lens Lp. As an example, FIG. 7 shows the distance De for the imaging lens shown in FIG. 6. Here, De is calculated assuming that the medium on the image side of the Lp lens Lp is air, and the sign of De is negative if the image point is closer to the object than the image-side surface of the Lp lens Lp on the optical axis, and positive if the image point is closer to the image than the image-side surface of the Lp lens Lp. Making sure that the corresponding value of conditional expression (17) is not equal to or less than the lower limit is advantageous for correcting chromatic aberration of magnification. Making sure that the corresponding value of conditional expression (17) is not equal to or greater than the upper limit is advantageous for compactness. To obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional formula (17-1), and it is even more preferable that the imaging lens satisfies the following conditional formula (17-2): −0.9<(De−Rr) / (De+Rr)<0.9 (17) −0.7<(De−Rr) / (De+Rr)<0.5 (17-1) −0.56<(De−Rr) / (De+Rr)<0.16 (17-2)

[0110] When the focal length of the focus group that moves along the optical axis Z when focusing is defined as ffoc, the imaging lens preferably satisfies the following conditional expression (18). By ensuring that the corresponding value of conditional expression (18) is not equal to or less than the lower limit, it is advantageous to suppress fluctuations in chromatic aberration when focusing. By ensuring that the corresponding value of conditional expression (18) is not equal to or greater than the upper limit, it is possible to suppress fluctuations in aberration when the refractive index of the Lp lens Lp fluctuates due to environmental changes such as temperature. In order to obtain better characteristics, it is more preferable that the imaging lens satisfies the following conditional expressions (18-1), and it is even more preferable that the imaging lens satisfies the following conditional expressions (18-2). 0.04<ffoc / fp<0.36 (18) 0.065<ffoc / fp<0.28 (18-1) 0.094<ffoc / fp<0.22 (18-2)

[0111] When the maximum angle of view when focused on an object at infinity is ωm, if the imaging lens satisfies the following conditional expression (19), it is preferable that the rear group GR includes an Lp lens Lp. The unit of ωm for the maximum angle of view is "° (degrees)." By ensuring that the corresponding value of conditional expression (19) does not fall below the lower limit, good optical performance can be obtained. ωm≧45° (19)

[0112] On the other hand, when the imaging lens satisfies the following conditional expression (20), it is preferable that the front group GF includes an Lp lens Lp. Good optical performance can also be obtained by ensuring that the corresponding value of conditional expression (20) is not equal to or greater than the lower limit: ωm<45° (20)

[0113] When the central thickness of the Lp lens Lp is A, the thickness of the compound lens Lp in the optical axis direction at the maximum effective diameter height on both sides of the Lp lens Lp is B, the maximum image height is Y, the partial dispersion ratio of the Lp lens between the g-line and the F-line is θgF, and the Abbe number of the Lp lens based on the d-line is νd, and ΔθgF is expressed by conditional expression (21), it is preferable that the imaging lens satisfies conditional expression (22). By ensuring that the corresponding value of conditional expression (22) is not equal to or less than the lower limit, a higher chromatic aberration correction effect can be obtained. By ensuring that the corresponding value of conditional expression (22) is not equal to or greater than the upper limit, the difference in deformation between the central and peripheral portions of the Lp lens Lp can be suppressed even when the temperature changes. ΔθgF=θgF-(0.6438-0.001682×νd) (21) 0.004<(|A-B|ΔθgF) / Y<0.020 (22) It is more preferable that (|A-B|ΔθgF) / Y is greater than 0.006 and smaller than 0.014. It is further preferable that (|A-B|ΔθgF) / Y is greater than 0.008 and smaller than 0.012.

[0114] In the imaging lens, the compound lens 10 may be included in the front group GF, and the second lens 14 may be arranged on the object side relative to the first lens 12. Alternatively, in the imaging lens, the compound lens 10 may be included in the rear group GR, and the second lens 14 may be arranged on the image side relative to the first lens 12.

[0115] Next, examples of the imaging lens of the present disclosure will be described with reference to the drawings. The reference symbols assigned to the lenses in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanation and the drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the configuration is the same.

[0116] Example 1 Fig. 9 shows a cross-sectional view of the configuration of an imaging lens according to Example 1. The imaging lens according to Example 1 includes, in order from the object side to the image side, a first lens group having positive refractive power, an aperture stop St, a second lens group having positive refractive power, and a third lens group having positive refractive power. The front group GF includes the first lens group. The rear group GR includes the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0117] The Lp lens Lp is included in the second lens component from the object side of the second lens group. This lens component is a cemented lens formed by cementing, in order from the object side, the Lp lens Lp and a negative lens.

[0118] For the imaging lens of Example 1, basic lens data is shown in Table 4, specifications and variable surface spacing are shown in Table 5, and aspherical coefficients are shown in Table 6. The table of basic lens data is written as follows: The Sn column shows the surface numbers, with the surface closest to the object as surface 1 and the numbers increasing by one toward the image side. The R column shows the radius of curvature of each surface. The D column shows the surface spacing on the optical axis between each surface and its adjacent surface on the image side. The Nd column shows the refractive index of each component with respect to the d-line. The νd column shows the Abbe number of each component with respect to the d-line. In the θgF column, the column for the lens corresponding to the Lp lens Lp shows the partial dispersion ratio between the g-line and F-line of that lens. Surfaces 23 and 24 in Table 4 correspond to the Lp lens Lp.

[0119] In the table of basic lens data, the sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative. The surface number and the phrase (St) are entered in the column for the surface number corresponding to the aperture stop St. The value in the bottom column of the surface spacing column in the table is the spacing between the surface closest to the image side in the table and the image plane Sim. The symbol DD[ ] is used for the variable surface spacing during focusing, and the surface number on the object side of this spacing is entered in the brackets [ ] in the surface spacing column.

[0120] In the data in each table, the angle unit is "° (degrees)" and the length unit is "mm (millimeters)", but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table shown below, the values ​​are rounded to a predetermined number of decimal points.

[0121]

[0122]

[0123]

[0124] [Example 2] Fig. 11 shows a cross-sectional view of the configuration of an imaging lens of Example 2. The imaging lens of Example 2 has, in order from the object side to the image side, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having negative refractive power. The second lens group includes an aperture stop St. The front group GF has the first lens group and a part of the second lens group facing the object side. The rear group GR has the other part of the second lens group and the third lens group. When focusing from an object at infinity to a close object, the first lens group and the third lens group are fixed with respect to the image plane Sim, and the second lens group moves toward the object side.

[0125] The Lp lens Lp is included in the second lens component from the object side of the second lens group. This lens component is a cemented lens formed by cementing, in order from the object side, the Lp lens Lp and a negative lens.

[0126] For the imaging lens of Example 2, basic lens data is shown in Table 7, specifications and variable surface spacing are shown in Table 8, aspherical coefficients are shown in Table 9, and aberration diagrams are shown in Fig. 12. Surfaces 12 and 13 in Table 7 correspond to the Lp lens element Lp.

[0127]

[0128]

[0129]

[0130] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and can take other values.

[0131] All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

[0132] The following additional notes are provided regarding the above-described embodiments.

[0133] (Supplementary Note 1) In the optical system according to the first aspect, the first lens is formed of a resin having photocurability and thermosetting properties. (Supplementary Note 2) The linear expansion coefficient of the first lens is 6×10 －５ / °C, and the elastic modulus of the first lens is 2.5×10 ９ Pa, and the linear expansion coefficient of the second lens is 0.77×10 －５ / °C, and the elastic modulus of the second lens is 106.7×10 ９The optical system according to the first aspect, wherein the difference between the thickness of the first lens at the center of the convex surface and the thickness of the first lens at the first surface is 0.01 mm or more and 1 mm or less, the effective diameter of the convex surface is 3 mm or more and 50 mm or less, the outer diameter of the second lens is 4 mm or more and 110 mm or less, the thickness of the second lens at the center of the concave surface is 0.5 mm or more and 10 mm or less, the effective diameter of the concave surface is 3 mm or more and 50 mm or less, and the radius of curvature of the concave surface is 5 mm or more and 300 mm or less. (Supplementary Note 3) The optical system according to the first aspect, wherein the difference between the thickness of the first lens at the center of the convex surface and the thickness of the first lens at the first surface is 0.01 mm or more and 1 mm or less, the effective diameter of the concave surface is 3 mm or more and 50 mm or less,

Claims

1. An optical system including a compound lens having a first lens and a second lens, the first lens is made of resin, the second lens is made of glass; The maximum thickness of the first lens is A [mm], When the minimum thickness of the first lens is B [mm], A / B≦10 (1) A≦3 mm (2) The conditional expressions (1) and (2) are satisfied. When the resin is pressed with an indenter at a loading rate of 200 mN / 10 sec at an environmental temperature of 25° C., the amount of plastic deformation is expressed as x [μm]. 1.0μm≦x≦4.0μm (3) Satisfying conditional expression (3) expressed by optical system.

2. A≧0.1mm (5) B≧0.02mm (6) The conditional expressions (5) and (6) are satisfied. The optical system of claim 1 .

3. The hardness of the resin at 25° C. is 186 MPa or more and 196 MPa or less. The optical system of claim 1 .

4. The hardness of the resin at 75° C. is 149 MPa or more and 164 MPa or less. The optical system of claim 1 .

5. The elastic recovery rate of the resin at 75° C. is 59% or more and 63% or less. The optical system of claim 1 .

6. The indentation elastic modulus of the resin at 25° C. is 3.5 GPa or more and 3.6 GPa or less. The optical system of claim 1 .

7. The indentation modulus of the resin at 75° C. is 2.4 GPa or less. The optical system of claim 1 .

8. The resin has photocuring and thermosetting properties. The optical system of claim 1 .

9. the first lens is a lens having a positive refractive power and made of resin, The center thickness of the first lens is d, The radius of curvature of the object-side surface of the first lens is Rf, When the radius of curvature of the image side surface of the first lens is Rr, 0<d×(1 / Rf-1 / Rr)<0.05 (7) Satisfying conditional expression (7) expressed as The optical system of claim 1 .

10. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the rear group includes at least one Lp lens having positive refractive power and made of resin, the first lens is the Lp lens, TL is the sum of the distance on the optical axis from the lens surface of the front group closest to the object side to the lens surface of the rear group closest to the image side and the air-equivalent distance on the optical axis from the lens surface of the rear group closest to the image side to the image plane when the lens surface is focused on an object at infinity, When the focal length of the Lp lens is fp, 0.1<TL / fp<1.2 (8) Satisfying conditional expression (8) expressed by The optical system of claim 1 .

11. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the rear group includes at least one Lp lens having positive refractive power and made of resin, the first lens is the Lp lens, The height from the optical axis of the principal ray of the maximum half angle of view on the object side surface of the Lp lens when focused on an object at infinity is Hpp, When the height of the axial marginal ray from the optical axis on the object side surface of the Lp lens in a state where the lens is focused on an object at infinity is Hpm, 0.2<Hpp / Hpm<1.1 (9) Satisfying conditional expression (9) expressed as The optical system of claim 1 .

12. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the rear group includes at least one Lp lens having positive refractive power and made of resin, the first lens is the Lp lens, The radius of curvature of the image-side surface of the Lp lens is Rr, In a state where an object at infinity is focused, a point at the position of the aperture stop on the optical axis is defined as an object point, the distance on the optical axis from the image side surface of the Lp lens to an image point formed by the optical system from a lens surface adjacent to the image side of the aperture stop to the image side surface of the Lp lens is defined as De, De is calculated assuming that the medium on the image side of the image side surface of the Lp lens is air, and the sign of De is negative if the image point is closer to the object side than the image side surface of the Lp lens on the optical axis, and positive if the image point is closer to the image side than the image side surface of the Lp lens. -0.9<(De-Rr) / (De+Rr)<0.9 (10) Satisfying conditional expression (10) expressed by The optical system of claim 1 .

13. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the rear group includes at least one Lp lens having positive refractive power and made of resin, the first lens is the Lp lens, Let ffoc be the focal length of the focus group moving along the optical axis when focusing, When the focal length of the Lp lens is fp, 0.04<ffoc / fp<0.36 (11) Satisfying conditional expression (11) expressed by The optical system of claim 1 .

14. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the first lens is an Lp lens having a positive refractive power and made of resin, When the maximum angle of view when focused on an object at infinity is ωm, ωm≧45° (12) the rear group includes the Lp lens, ωm<45° (13) When the conditional expression (13) expressed by the following formula is satisfied, the front group includes the Lp lens. The optical system of claim 1 .

15. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the rear group includes at least one Lp lens having positive refractive power and made of resin, the first lens is the Lp lens, The central thickness of the Lp lens is A, The thickness of the compound lens in the optical axis direction at the maximum effective diameter height on both sides of the Lp lens is B, The maximum image height is Y, The partial dispersion ratio between the g-line and the F-line of the Lp lens is θgF, The Abbe number of the Lp lens based on the d line is defined as νd, When ΔθgF is expressed by conditional expression (14), ΔθgF=θgF-(0.6438-0.001682×νd) (14) 0.004<(|AB|ΔθgF) / Y<0.020 (15) Satisfying conditional expression (15) expressed by The optical system of claim 1 .

16. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the compound lens is included in the front group, The second lens is disposed on the object side with respect to the first lens. The optical system of claim 1 .

17. A front group, an aperture stop, and a rear group, the front group, the aperture stop, and the rear group are arranged in this order from the object side to the image side, the compound lens is included in the rear group, The second lens is disposed on the image side of the first lens. The optical system of claim 1 .

18. 1. An optical system including a compound lens having a first lens and a second lens, the first lens has a convex surface and a first surface extending from an outer circumferential edge of the convex surface toward a radially outer side of the compound lens; the second lens has a concave surface bonded to the convex surface, and a second surface that protrudes outward in the radial direction from an outer circumferential edge of the concave surface and is bonded to the first surface, When the length of the first surface along the radial direction is a [μm], the length of the second surface along the radial direction is b [μm], and the surface roughness of the second surface is Ra [μm], a < b (16) 5μm≦a / Ra (17) The conditional expressions (16) and (17) are satisfied. optical system.

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