JP2003140037A - Cemented lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cemented lens constituted by cementing the bonding surfaces of at least two lenses with a cement and improved so that stress caused on the bonding surfaces of the lenses due to a difference between the linear expansion coefficients of the cemented lenses is absorbed by the elasticity of the cement layer. SOLUTION: As for this cemented lens, the radii of curvature of the bonding surfaces of two lenses are made different from each other so that the gap at the circumferential part of the bonding surface is larger than the gap on the optical axis. The cement layer has flexible elasticity. The cemented lens satisfies a conditional expression (1). (1) |Δα×D/d|<0.03, wherein Δα: the difference between the linear expansion coefficients of the two cemented lenses, D: the diameter of the bonding surface and d: the thickness of the cement layer on the outermost circumference of the bonding surface.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cemented lens used in various optical systems.

[0002]

2. Description of the Related Art A contact type achromatic lens in which at least two lenses, a positive lens and a negative lens, are arranged with a slight air gap, is widely used. Since the contact type achromatic lens gives a strong power to both the positive lens and the negative lens to correct the axial chromatic aberration, both the convex surface and the concave surface facing each other with an air gap have strong surface power. For this reason, when one lens is decentered with respect to the other lens, strong coma and flare occur, and the performance is extremely deteriorated. In order to prevent this performance deterioration, in the conventional contact-type achromatic lens, the lens outer diameter and the lens frame must be processed with high accuracy to suppress the eccentricity of the lens, which results in high cost.

On the other hand, a cemented lens obtained by laminating a pair of properly aligned lenses with an adhesive does not cause eccentricity, so that it is possible to obtain an achromatic lens without performance deterioration due to eccentricity. However, in a cemented lens in which two lenses made of glass materials having different linear expansion coefficients are cemented, when the temperature changes, the two lenses have different expansions (contractions), which causes a difference in lens outer diameter. This difference in lens outer diameter causes radial stress applied to the cemented surface, especially when the temperature changes greatly, the stress applied to the cemented surface becomes large and the lens is distorted or the adhesive layer on the cemented surface cannot withstand the stress. There is a problem that the pasted lens peels off when it disappears.

In particular, the larger the lens outer diameter, the larger the difference in lens outer diameter caused by expansion. Therefore, the above-mentioned problem becomes remarkable in a cemented lens having a large aperture. Further, fluorite and low-dispersion glass are often used for high-performance lenses because of their excellent achromaticity characteristics, but these special glass materials have a coefficient of linear expansion that is at least twice that of general optical glass. Therefore, when the lens made of these special glass materials and the lens made of general optical glass are bonded together, the above problem becomes more remarkable.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a cemented lens in which the cemented surfaces of at least two lenses are bonded together with an adhesive, problems such as distortion and peeling occur. The purpose is to obtain a cemented lens that does not occur. An object of the present invention is to obtain a suitable cemented lens by applying it to a large-diameter cemented lens, or a special glass material such as fluorite or low-dispersion glass and a normal glass lens. Another object of the present invention is to facilitate management of the thickness of the adhesive layer.

[0006]

SUMMARY OF THE INVENTION According to the present invention, in a cemented lens constructed by laminating at least two lenses, the adhesive layer on the cemented surface is provided with an appropriate thickness, while having an appropriate elasticity even after curing. The use of an adhesive that allows the adhesive layer to absorb the stress generated in the cemented surface due to the difference in expansion of the bonded lenses, and the thickness of the adhesive layer should be controlled ( In order to ensure the above), the radius of curvature of the concave surface to be bonded is set to be larger than that of the convex surface to optimize the thickness of the adhesive layer at the outer peripheral portion of the bonding surface.

That is, according to the present invention, in a cemented lens constructed by bonding the cemented surfaces of at least two lenses with an adhesive, the radius of curvature of the cemented surfaces of the two lenses can be calculated as follows: It is characterized in that the intervals are made different from each other so as to be larger than the intervals on the optical axis, the adhesive layer has elastic elasticity and satisfies the following conditional expression (1). (1) | Δα · D / d | <0.03, where Δα: difference in linear expansion coefficient between two lenses to be bonded, D: diameter of the above-mentioned bonding surface, d: maximum bonding surface of the above adhesive layer The thickness at the outer circumference is.

The cemented lens according to the present invention more preferably satisfies the following conditional expression (1 '). (1 ′) | Δα · D / d | <0.01 It is preferable that the following conditional expression (2) is satisfied. (2) d / D <0.002

The present invention is practically applied to an achromatic lens in which two lenses to be bonded are a positive lens and a negative lens. This achromatic lens has the following conditional expression (3).
Alternatively, it is preferable to satisfy (4). (3) | Δν |> 20 (4) | fc ・ (1 / (fp ・ νp) + 1 / (fn ・ νn))
│ <0.02 where fc: focal length of the cemented lens, fp: focal length of the positive lens, fn: focal length of the negative lens, νp: Abbe number of the positive lens, νn: of the negative lens The Abbe number is.

It is preferable that the cemented lens according to the present invention further satisfy at least one of the following conditional expressions (5) to (7). (5) d> 0.015mm (6) d <0.2mm (7) D> 80mm

The cemented lens according to the present invention is preferably applied to a cemented lens made of a combination of glass materials satisfying the following conditional expression (6). (6) | Δα |> 0.0000015

The adhesive is preferably a silicone resin made of an organic silicone compound, and particularly preferably a silicone resin having addition reaction curability. Alternatively, the adhesive may be composed of a silicone resin having an elongation of 100% or more. The elongation is defined by JIS standard and is expressed by the amount of elongation / original length × 100. That is, for example, an elongation of 100% is twice as long, and an elongation of 150% is twice as long.

[0013]

1 shows an embodiment of a cemented lens according to the present invention. In this embodiment, the cemented surface 11 of the first positive lens L1 and the cemented surface 12 of the second negative lens L2 are joined together.
The present invention is applied to a cemented lens in which and are joined by an adhesive layer 13.

The cemented surface 12 (first surface, concave surface) of the second lens L2 has a larger radius of curvature than that of the cemented surface 11 (second surface, convex surface) of the first lens L1. In the vicinity, the second surface of the first lens and the first surface of the second lens are in close contact (the distance between the cemented surfaces 11 and 12 is small), and the adhesive layer becomes thicker as the distance from the optical axis increases (the cemented surfaces 11 and 1).
2 is set larger). The distance between the joint surfaces 11 and 12 in FIG. 1 is exaggerated.

As described above, when the radius of curvature of the joint surfaces 11 and 12 is given a difference such that the distance becomes larger toward the periphery of the joint surfaces, the joint surfaces 11 and 12 come into close contact with each other near the optical axis. The adhesive layer 13 becomes thicker with increasing distance from the axis.
Therefore, the adhesive layer can absorb the shear stress of the joint surface, which increases as the distance from the optical axis increases.

Further, when the radius of curvature of the joint surfaces 11 and 12 is given a difference such that the distance becomes larger toward the periphery of the joint surface, the following adhesive layer is simply and uniformly thicker than the following structure. There are advantages. That is, if the adhesive layer is simply thick, the deviation of the thickness of the adhesive layer induces the misalignment of the lens to deteriorate the optical performance, and if the adhesive is not evenly distributed on the bonding surface, the bonding is performed. There are problems that the stress applied to the surface is not uniform, irregular distortion occurs, and the bonded lens is easily peeled off. On the other hand, according to the present embodiment, since the curvature radii of the lens surfaces to be joined are made different, the thickness of the adhesive layer on the outer periphery of the joining surface is automatically made uniform by the centering process, It is possible to accurately control the thickness of the adhesive layer without requiring any special jig or process.

The centering process is commonly performed when joining lenses. That is, in the bonding step, the adhesive is dropped on the cemented surface of one lens, the other lens is superposed, the air bubbles mixed in the adhesive are removed, and then the centering is performed (the optical axes of both lenses are aligned). Since the procedure is generally to cure the adhesive by a curing process such as UV irradiation and heating, it is not necessary to add a special step.

Each conditional expression of the present invention will be described together with specific examples (examples). Now, the achromatic lens constructed by bonding the cemented lens shown in FIG. 1 in order from the object side with a positive first lens L1 made of OHARA glass material FPL53 and a negative second lens L2 made of NSL36. Let it be a lens. The lens diameter (bonding surface diameter) is 100 mm. Further, the second surface (convex surface) 11 of the first lens L1 which is a cemented surface
The first surface (concave surface) 12 of the second lens L2 is larger than the radius of curvature of
Has a large radius of curvature, the second surface of the first lens L1 and the first surface of the second lens L2 are in close contact with each other in the central portion of the cemented surface (lens central portion), and the thickness of the adhesive layer in the peripheral portion of the cemented surface is large. 0.1 m
It is set to be m. Addition reaction type silicone resin KE109 manufactured by Shin-Etsu Chemical is used for the adhesive.
It was cured at 0 ° C. for 12 hours.

The linear expansion coefficient of FPL53 is 142 × 1.
0 ^-7 , the coefficient of linear expansion of NSL36 is 76 × 10 ^-7 , so the temperature of this cemented lens is from 40 ℃ at the time of joining to 1
When the temperature changes to 0 ° C, the diameter of the first lens L1 is 0.0
Shrink 43 mm, diameter of second lens L2 is 0.023 m
The first lens L1 and the second lens L2 contract 0.
A diameter difference of 02 mm results. This difference in diameter is 0.0 in the radial direction between the outer circumference of the first lens and the outer circumference of the second lens.
It shows that a deviation of 1 mm occurs, and this deviation gives a shear stress in the radial direction to the joint surface. The radial shear stress is small near the optical axis, increases as the distance from the optical axis increases, and becomes maximum at the outer peripheral portion.

It is empirically said that the thickness of the adhesive layer in the conventional cemented lens is about several μ. When the above lenses are pasted together by the conventional technique, the shearing stress cannot be absorbed by the adhesive layer because the displacement of the lens outer peripheral portion due to expansion reaches several times the thickness of the adhesive layer. Therefore, when the adhesive strength of the adhesive is strong, the lens is distorted, and when the adhesive strength is weak, the adhesive cannot withstand the shear stress and the bonded lens is peeled off.

In the above specific example, the deviation of the lens outer peripheral portion is about 1/10 of the thickness of the adhesive layer, and the adhesive KE109 has an elongation of about 150%. The deviation can be easily absorbed by the adhesive layer.

As described above, the deviation of the outer peripheral portion of the cemented lens caused by the expansion of the lens due to the temperature change is determined by the difference in the linear expansion coefficient between the lenses to be laminated, the diameter of the lens and the width of the temperature change. It can be represented by a formula. Δh = Δα · D · ΔT / 2, where Δh: deviation of the outer peripheral portion of the cemented lens caused by expansion of the lens due to temperature change, Δα: difference in linear expansion coefficient between the cemented lenses, D : Diameter of the cemented lens, ΔT: width of temperature change,

Assuming that the adhesive has elasticity and has an elongation of 100%, the thickness of the adhesive layer is equal to the above Δ at the outer peripheral portion.
If it is at least twice as large as h, the shear stress generated in the adhesive layer due to Δh can be sufficiently absorbed by the elasticity of the adhesive layer. That is, when the relationship of the following equation is satisfied, the stress applied to the cemented surface due to the expansion of the lens can be absorbed by the adhesive layer. 2 · | Δh | <d, where d is the thickness of the outer peripheral portion of the adhesive layer on the bonding surface. The following equation is derived from the above equation and the equation. │Δα ・ D / d│ <1 / ΔT

Conditional expression (1) shows the case where the range of temperature change is assumed to be 30 ° C. in the above expression, and by defining the relationship of each numerical value in this way, the expansion of the lens affects the cemented surface. The stress can be absorbed by the adhesive layer. If the upper limit of conditional expression (1) is exceeded, the adhesive layer becomes too thin, and the stress applied to the joint surface cannot be absorbed by the adhesive layer.

Considering the workability of joining, the use environment, the optical characteristics of the adhesive, the cost, etc., it is not always possible to use an adhesive having ideal elasticity. In such a case, it is preferable to define the thickness of the adhesive layer by the conditional expression (1 ′). If the upper limit of conditional expression (1 ′) is exceeded, the adhesive layer becomes too thin, and the stress applied to the joint surface cannot be absorbed by the adhesive layer depending on the elasticity of the adhesive.

When the lenses are bonded together using an elastic adhesive, if the adhesive layer is made too thick, the adhesive layer is elastically deformed due to the weight of the lenses, and the centers of the bonded lenses are misaligned. There is a problem that it occurs. By optimizing the thickness of the adhesive layer according to the conditional expression (2), the misalignment of the lens can be suppressed to be small. If the upper limit of conditional expression (2) is exceeded, the adhesive layer becomes too thick,
Performance is deteriorated due to misalignment of the lens.

As described above, the cemented lens in which the adhesive layer has the minimum necessary thickness and the misalignment of the lens due to the elastic deformation of the adhesive layer is suppressed to a small level is particularly effective in an achromatic lens whose performance is significantly deteriorated due to the misalignment. Has preferred suitability. However, if the difference in Abbe number between the positive lens and the negative lens to be cemented is increased by the conditional expression (3), chromatic aberration can be satisfactorily corrected even if the difference in power between the positive lens and the negative lens is small. Therefore, it is possible to further suppress the performance deterioration due to the misalignment of the negative lens. If the lower limit of conditional expression (3) is exceeded, in order to satisfactorily correct chromatic aberration, it is necessary to increase the difference in power between the positive lens and the negative lens, and the performance will be significantly degraded due to misalignment.

Conditional expression (4) is a condition for the cemented lens to which the present invention is applied to be an achromatic lens whose chromatic aberration is favorably corrected. A cemented lens that exceeds the upper limit of conditional expression (4) and is insufficient in chromatic aberration correction does not require high accuracy, and therefore there is no cost advantage of applying the present invention.

In the present invention, the lower limit of the thickness of the outer peripheral portion of the adhesive layer is defined by the conditional expression (1) or (1 '), but the thickness of the adhesive layer depends on the difference in lens diameter and linear expansion coefficient. In some cases, it may be as thin as a conventional cemented lens. Conditional expression (5) is a condition for defining the lower limit of the thickness of the adhesive layer suitable for applying the present invention. If the lower limit of conditional expression (5) is exceeded, the thickness of the adhesive layer may be as thin as that of a conventional cemented lens, and the cost advantage of applying the present invention is lost.

Further, the upper limit of the thickness of the outer peripheral portion of the adhesive layer is defined by the conditional expression (2), but the thickness of the adhesive layer becomes too thick depending on the lens diameter and the difference in linear expansion coefficient. The core misalignment due to elastic deformation of the adhesive layer may become too large. By defining the upper limit of the thickness of the outer peripheral portion of the adhesive layer by the conditional expression (6), it is possible to obtain a cemented lens with small misalignment due to elastic deformation of the adhesive layer. When the upper limit of conditional expression (6) is exceeded, the thickness of the adhesive layer becomes too thick, and the misalignment due to elastic deformation of the adhesive layer becomes too large.

As described above, in the cemented lens according to the present invention, the thickness of the adhesive layer may be thin depending on the difference in lens diameter and linear expansion coefficient. Conditional expression (7) is a condition for maximizing the effect of the present invention by defining the diameter D of the cemented lens to which the present invention is applied. If the lower limit of conditional expression (7) is exceeded, it becomes unnecessary to increase the thickness of the adhesive layer, and the cost advantage of applying the present invention is lost.

Further, the present invention is particularly suitable for bonding a lens using a glass material having a large linear expansion coefficient such as fluorite or low dispersion glass to a lens using a general glass material,
In particular, it is effective to attach lenses having large differences in linear expansion coefficient as shown in conditional expression (8). When the lenses having a small difference in linear expansion coefficient, which exceeds the lower limit of the conditional expression (8), are attached to each other, it is not necessary to increase the thickness of the adhesive layer, so that there is no cost advantage of applying the present invention. I will end up.

In the specific example of the cemented lens of FIG. 1, a silicon resin made of an organic silicon compound was used as an adhesive. Although there are various types of silicone resins, they have stable chemical properties, and those with a transparent cured product are suitable for use in bonding lenses. In particular, a cured product which is rich in elasticity and whose elasticity does not change even at a low temperature is suitable for use in bonding large-diameter lenses or lenses having large differences in linear expansion coefficient.

The silicone resin is roughly classified into an addition reaction type which is cured by heating and a condensation reaction type which is cured by reacting with moisture in the air, depending on the difference in curing process. When the lenses are stuck together with a condensation reaction type silicone resin, it is difficult to cure since the central part is difficult to be supplied with water. On the other hand, some of the addition reaction type silicone resins are cured at room temperature, which is suitable for application of lenses.

In the present invention, the silicone resin used for the adhesive is preferably highly elastic, and more preferably 100% or more.

According to the present invention, the thickness of the adhesive layer is easily and accurately controlled so that the stress applied to the cemented surface of the bonded lens due to the expansion of the lens can be absorbed by the adhesive layer.
It is not necessarily applied only to the application of a large-diameter lens or a lens with a large difference in linear expansion coefficient.For example, good results can be obtained even when applied to a bonded lens used in an environment with a wide temperature range. To be

Specific numerical examples will be described below with reference to tables and drawings. In the table and drawings, F _{N o.} Is the F-number, F
Is the focal length, W is the incident angle (°), FB is the back focus, R is the radius of curvature of each lens surface, D is the lens thickness or lens spacing, Nd is the d-line refractive index, and ν is the Abbe number. In the various aberration diagrams, SA indicates spherical aberration and SC indicates sine condition. The d-line, the g-line, and the c-line show the chromatic aberration of each wavelength indicated by the spherical aberration.

[Numerical Example 1] FIG. 2 is a lens configuration diagram of Numerical Example 1 of the cemented lens according to the present invention, FIG. 3 is a diagram showing various aberrations thereof, and Table 1 is lens data thereof. In Numerical Data Example 1, as described in the above specific example, the positive first lens L1 made of the glass material FPL53 made by OHARA, and the NSL36.
And the negative second lens L2 made of (3) are attached by an addition reaction type silicone resin KE109 manufactured by Shin-Etsu Chemical Co., Ltd. Concave surface (first surface) 12 of the second lens L2, which is a cemented surface
Is formed to be larger than the radius of curvature of the convex surface (second surface) 11 of the first lens L1, and the thickness of the adhesive layer 13 at the outer peripheral portion of the lens bonding surface is 0.1 mm, and the lens near the optical axis is The bonding surfaces are in close contact with each other, and the thickness d2 of the adhesive layer 13 near the optical axis X is set to be approximately zero. The curing conditions were 40 ° C. and 12 hours. The second surface to the third surface are adhesive layers, and the refractive index and Abbe number of this adhesive layer are measured values. The lens diameter of Numerical Example 1 is 100 mm.

[0039]

[Table 1] F _NO. = 1: 9.0 F = 899.87 W = 1.40 FB = 890.70 Face NO. RD Nd ν 1 514.402 12.00 1.4388 95.0 2 -277.906 0.00 1.356 34.4 3 -283.697 8.00 1.5174 52.4 4 -970.939---

[Numerical Example 2] FIG. 4 is a lens configuration diagram of Numerical Example 2 of the cemented lens according to the present invention, FIG. 5 is a diagram showing various aberrations thereof, and Table 2 is lens data thereof. In Numerical Embodiment 2 in order from the object side, a negative first lens L1 made of a glass material BSL7 made by OHARA and a positive second lens made of FPL53.
The lens L2 and the negative third lens L3 including the NSL 36
It is an achromatic lens constructed by bonding three pieces of the above. The lens diameter in this numerical example is 100 mm. In Numerical Example 2, the first lens and the second lens,
Also, the technique of the cemented lens according to the present invention is applied to the relationship between the second lens and the third lens. The concave surface of the first lens and the convex surface of the second lens, which are cemented surfaces, and the second surface
The convex surface of the lens and the concave surface of the third lens each have a concave surface with a radius of curvature larger than that of the convex surface, and the thickness of the adhesive layer 13 on the outer peripheral portion when the respective cemented surfaces are bonded so as to be in close contact with each other on the optical axis. Is set to 0.1 mm. The adhesive and curing conditions are the same as in Numerical Example 1.

[0041]

[Table 2] F _NO. = 1: 9.0 F = 899.66 W = 1.40 FB = 877.79 Face NO. RD Nd ν 1 362.797 10.00 1.5163 64.1 2 184.898 0.00 1.356 34.4 3 182.269 12.50 1.4388 95.0 4 -773.864 0.00 1.356 34.4 5 -826.356 10.00 1.5174 52.4 6 -2744.353---

[Numerical Example 3] FIG. 6 is a lens configuration diagram of Numerical Example 3 to which the cemented lens according to the present invention is applied, FIG. 7 is a diagram showing various aberrations thereof, and Table 3 is its lens data. The numerical example 3 is a glass material FPL manufactured by OHARA in order from the object side.
A cemented lens constructed by laminating a positive first lens L1 composed of 53 and a negative second lens L2 composed of NSL36, a positive third lens L3 and a negative third lens L3 arranged at a distance. It is composed of four lenses L4, and the technique of the cemented lens according to the present invention is applied to the cementing of the first lens and the second lens. The lens diameter of the first lens and the second lens is 100 mm. In this numerical example,
When the radius of curvature of the concave surface, which is the cemented surface of the first lens L1 and the second lens L2, is made larger than the radius of curvature of the convex surface, and when the cemented surface is bonded so as to be in close contact on the optical axis, the bonding of the outer peripheral portion is performed. The thickness of the agent layer 13 is set to be 0.1 mm. The adhesive and curing conditions are the same as in Numerical Example 1.

[0043]

[Table 3] F _NO. = 1: 6.0 F = 599.84 W = 2.10 FB = 183.60 Face NO. RD Nd ν 1 324.396 12.00 1.4388 95.0 2 -227.303 0.00 1.356 34.4 3 -231.242 8.00 1.5174 52.4 4 -1290.300 419.30--5 85.415 6.00 1.4970 81.6 6 -178.281 12.50--7 -120.133 4.00 1.4875 70.2 8 83.902---

Table 4 shows numerical values corresponding to each conditional expression of each numerical example. Each numerical example satisfies each conditional expression.

[0045]

[Table 4]                Numerical Example 1 Numerical Example 2 Numerical Example 2 Numerical Example 3                              (1st and 2nd lens) (2nd and 3rd lens) ｜ Δα ・ D / d ｜ 0.0066 0.0068 0.0066 0.0066 d / D 0.001 0.001 0.001 0.001 ｜ Δν ｜ 42.6 30.9 42.6 42.6 | fc ・ (1 / (fp ・ νp) ＋ 1 / (fn ・ νn)) |                   0.000902 0.00651 0.00913 0.000447 d 0.10 0.10 0.10 0.10 D 100.0 100.0 100.0 100.0 Δα 0.0000066 0.0000068 0.0000066 0.0000066 αp 0.0000142 0.0000142 0.0000142 0.0000142 αn 0.0000076 0.0000074 0.0000076 0.0000076 νp 95.0 95.0 95.0 95.0 νn 52.4 64.1 52.4 52.4 fc 899.99 636.70 399.63 705.91 fp 413.14 337.58 337.58 306.66 fn -777.72 -744.54 -2289.23 -545.90

[0046]

According to the present invention, even when a cemented lens, especially a large-diameter lens, or a lens made of a special glass material such as fluorite or low-dispersion glass, is bonded to a normal glass lens. It is possible to obtain a cemented lens in which problems such as distortion and peeling do not occur. Further, according to the present invention, it is possible to obtain a cemented lens in which a deterioration in optical performance due to self-weight deformation is small even in an achromatic lens that requires high optical performance.
Further, according to the present invention, since the radius of curvature of the joint surface is made different so that the distance between the peripheral portions is large (the adhesive layer is thick), the thickness of the adhesive layer can be easily controlled with high accuracy. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a cemented lens according to the present invention.

FIG. 2 is a lens configuration diagram of Numerical Example 1 of a cemented lens according to the present invention.

FIG. 3 is a diagram of various types of aberration of the lens in FIG.

FIG. 4 is a lens configuration diagram of Numerical Example 2 of a cemented lens according to the present invention.

FIG. 5 is a diagram of various types of aberration of the lens in FIG.

FIG. 6 is a lens configuration diagram of Numerical Example 3 of the bonded lens according to the present invention.

FIG. 7 is a diagram of various types of aberration of the lens in FIG. L1 first lens L2 second lens L3 Third lens L4 4th lens 13 Adhesive layer

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Claims (13)

[Claims] 1. A cemented lens formed by bonding the cemented surfaces of at least two lenses with an adhesive, wherein the radius of curvature of the cemented surfaces of the two lenses is determined by the distance between the peripheral portions of the cemented surfaces. A bonded lens, wherein the adhesive layer is made different from each other so as to be larger than the distance on the optical axis, and the adhesive layer has elastic properties and satisfies the following conditional expression (1). (1) | Δα · D / d | <0.03, where Δα: difference in linear expansion coefficient between two lenses to be bonded, D: diameter of the above-mentioned bonding surface, d: maximum bonding surface of the above adhesive layer Thickness at the outer circumference. 2. The cemented lens according to claim 1, wherein
A cemented lens that satisfies the following conditional expression (1 '). (1 ′) | Δα · D / d | <0.01 3. The cemented lens according to claim 1, wherein the cemented lens satisfies the following conditional expression (2). (2) d / D <0.002 4. The cemented lens according to claim 1, wherein the cemented lens is cemented through a centering step. 5. The cemented lens according to claim 1, wherein the two lenses are a positive lens and a negative lens, and satisfy the following conditional expression (3). . (3) | Δν |> 20 where Δν: the difference in Abbe number between the positive lens and the negative lens. 6. The cemented lens according to claim 5, wherein:
A cemented lens that satisfies the following conditional expression (4). (4) | fc ・ (1 / (fp ・ νp) + 1 / (fn ・ νn))
│ <0.02 where fc: focal length of the cemented lens, fp: focal length of the positive lens, fn: focal length of the negative lens, νp: Abbe number of the positive lens, νn: of the negative lens Abbe number. 7. The cemented lens according to claim 1, wherein the cemented lens satisfies the following conditional expression (5). (5) d> 0.015mm 8. The cemented lens according to claim 1, wherein the cemented lens satisfies the following conditional expression (6). (6) d <0.2 mm 9. The cemented lens according to claim 1, wherein the cemented lens satisfies the following conditional expression (7). (7) D> 80 mm 10. The cemented lens according to claim 1, wherein the cemented lens satisfies the following conditional expression (8). (8) | Δα |> 0.0000015 11. The cemented lens according to claim 1, wherein the adhesive is made of a silicone resin made of an organic silicon compound. 12. The cemented lens according to claim 11, wherein the silicone resin has an addition reaction curability. 13. The cemented lens according to claim 11, wherein the adhesive is a silicone resin having an elongation of 100% or more.