Cemented lens and manufacturing method for cemented lens

Abstract

To provide a cemented lens including an aspherical lens and suitably aligned, and a method for manufacturing the cemented lens.SOLUTION: Provided is a cemented lens in which a first joining surface which is one lens surface of a first lens and a second joining surface which is one lens surface of a second lens are jointed together by an adhesive. The second lens has a lens surface of aspherical shape as the other lens surface, and the aspherical axis of the lens surface of aspherical shape of the second lens coincides with the optical axis of the first lens and positionally deviates in the radial direction of the second lens with respect to the paraxial spherical center of the second joining surface. The adhesive between the first and the second joining surfaces differs in thickness in the direction of the positional deviation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a cemented lens and a method for manufacturing the cemented lens.

Background Art

[0002] Patent Document 1 describes a cemented lens in which lenses are bonded together with an adhesive, and the adhesive layer between the bonded lenses is made thicker on the peripheral side of the effective diameter range than on the center side of the effective diameter within the optically effective diameter of the lens, and is thinner than the thickest portion within the effective diameter range outside the effective diameter.

[0003] Patent Document 2 describes a cemented lens composed of a negative-power lens and a positive-power lens, which has a resin adhesive layer that has a positive power and bonds the negative-power lens and the positive-power lens. In this cemented lens, the bonding surface between the negative-power lens and the resin adhesive layer and the bonding surface between the positive-power lens and the resin adhesive layer each have an aspherical shape different from each other.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] One embodiment of the technology according to the present disclosure provides an aspherical lens, a well-aligned cemented lens, and a method for manufacturing this cemented lens.

Means for Solving the Problems

[0006] One aspect of the technology according to the present disclosure is a cemented lens in which a first joint surface, which is one lens surface of a first lens, and a second joint surface, which is one lens surface of a second lens, are joined by an adhesive. The second lens has an aspherical lens surface as the other lens surface. The aspherical axis of the aspherical lens surface of the second lens coincides with the optical axis of the first lens, and there is a displacement in the radial direction of the second lens with respect to the center of the paraxial sphere of the second joint surface. The adhesive between the first joint surface and the second joint surface is a cemented lens having different thicknesses in the direction of the displacement. In the technology of the present disclosure, the second joint surface may be spherical or aspherical. When the second joint surface is spherical, the "center of the paraxial sphere of the second joint surface" is the same as the center of the sphere of the second joint surface.

[0007] The first joint surface and the second joint surface are preferably of the same shape.

[0008] The first joint surface, the other lens surface of the first lens, and the second joint surface may be configured to be spherical.

[0009] When the refractive index of the second lens is Nglass and the refractive index of the adhesive is Nce, the cemented lens of the above aspect preferably satisfies the following conditional expression (1), more preferably satisfies the following conditional expression (1-1), and even more preferably satisfies the following conditional expression (1-2). 0.8×Nglass < Nce < 1.2×Nglass (1) 0.9×Nglass < Nce < 1.1×Nglass (1-1) 0.95×Nglass < Nce < 1.05×Nglass (1-2)

[0010] In the cemented lens according to the above aspect, on a plane perpendicular to the optical axis, the position where the thickness of the adhesive in the direction of the optical axis is maximum is defined as the first position, the position obtained by rotating the first position 90 degrees around the optical axis is defined as the second position, the position obtained by rotating the first position 180 degrees around the optical axis is defined as the third position, and the position obtained by rotating the first position 270 degrees around the optical axis is defined as the fourth position. In this case, it is preferable that the average value of the thicknesses of the adhesive in the direction of the optical axis at the position of the optical axis, the first position, the second position, the third position, and the fourth position is 10 μm or more and 50 μm or less, and more preferably 15 μm or more and 40 μm or less.

[0011] Another aspect according to the technology of the present disclosure is a method for manufacturing a cemented lens that joins a first lens having a first joint surface as one lens surface and a second lens having a second joint surface as one lens surface and an aspherical lens surface as the other lens surface with an adhesive, the method including: a step of filling an adhesive between the first joint surface and the second joint surface; a step of detecting an inclination angle of an aspherical axis of the aspherical lens surface with respect to the optical axis of the first lens and a positional deviation amount in the radial direction of the first lens of the aspherical axis with respect to the optical axis on the aspherical lens surface; a step of adjusting the relative positions of the first lens and the second lens according to the inclination angle and the positional deviation amount; and a step of curing the adhesive in a state where the relative positions are adjusted.

[0012] The method for manufacturing the cemented lens according to the above aspect preferably includes a step of making the optical axis coincide with the aspherical axis by relatively moving the first lens and the second lens in the radial direction of the first lens.

[0013] In the method for manufacturing the cemented lens according to the above aspect, it is preferable to measure the wavefronts of the first lens and the second lens, obtain tilt components and coma components from an interference fringe image obtained by the wavefront measurement, and perform detection based on the tilt components and the coma components.

Advantages of the Invention

[0014] According to the present disclosure, an aspherical lens, a well-aligned cemented lens, and a method for manufacturing the cemented lens can be provided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings referred to in the following description, for ease of viewing, the shapes and ratios of the respective components are appropriately changed and drawn, and do not necessarily show the exact shapes and ratios. Further, in the following description, the unit of length micrometer is described as "μm", the unit of wavelength nanometer is described as "nm", and the unit of angle minute is described as "min".

[0017] <Outline of the Configuration of the Bonding Lens> FIG. 1 is a cross-sectional view for explaining the configuration of a bonding lens 10 according to an embodiment of the present disclosure. The bonding lens 10 includes a first lens 1, a second lens 2, and an adhesive 3. The upper side of FIG. 1 shows the bonding lens 10 in a state before alignment of the first lens 1 and the second lens 2, and the lower side shows the bonding lens 10 in a state after alignment. Here, for convenience of explanation, a lens unit including the first lens 1, the adhesive 3, and the second lens 2 before curing of the adhesive 3 is referred to as the bonding lens 10.

[0018] A first bonding surface 1C, which is one lens surface of the first lens 1, and a second bonding surface 2C, which is one lens surface of the second lens 2, are arranged to face each other. The first lens 1 and the second lens 2 are bonded by an adhesive 3 filled between the first bonding surface 1C and the second bonding surface 2C. A first lens surface 1A, which is the other lens surface of the first lens 1, and a second lens surface 2A, which is the other lens surface of the second lens 2, are air contact surfaces that are not bonded in the example of FIG. 1.

[0019] In the example of FIG. 1, the second lens surface 2A has an aspherical shape, and the second bonding surface 2C, the first bonding surface 1C, and the first lens surface 1A have spherical shapes. In this specification, a lens in which at least one of the two lens surfaces has an aspherical shape is referred to as an "aspherical lens", and a lens in which both of the two lens surfaces have spherical shapes is referred to as a "spherical lens". Therefore, in the example of FIG. 1, the second lens 2 is an aspherical lens, and the first lens 1 is a spherical lens. When the second bonding surface 2C, the first bonding surface 1C, and the first lens surface 1A have spherical shapes, alignment is easier than when at least one of them has an aspherical shape.

[0020] In the example of FIG. 1, the first joint surface 1C and the second joint surface 2C have the same shape. In this specification, the same shape regarding the lens surface means a shape formed based on the same design data. "The same design data" means that in the case of a spherical shape, the radius of curvature is the same, in the case of an aspherical shape, the aspherical formula and the aspherical coefficient are the same, and in the case of a free-form surface shape, the free-form surface formula and the free-form surface coefficient are the same.

[0021] For a sphere, there exists a center of the sphere, that is, a center of curvature, while for an aspherical surface, there exists an aspherical axis. In a spherical lens, an axis passing through two points which are the centers of the spheres of the two lens surfaces, that is, an axis passing through the centers of curvature of the two lens surfaces, can be taken as the optical axis of the lens. In contrast, for an aspherical lens with two aspherical lens surfaces, since there exist aspherical axes for each of the two lens surfaces, in an aspherical lens including component errors, these two aspherical axes do not coincide. Similarly, for an aspherical lens in which one of the two lens surfaces is spherical and the other is aspherical, when including component errors, the center of the sphere of one lens surface is not located on the aspherical axis of the other lens surface. Therefore, in an aspherical lens including component errors, the axes are misaligned between the two lens surfaces. In manufacturing, it is difficult to make the component errors of all aspherical lenses zero.

[0022] The second lens 2 in this example is a lens including the above-mentioned component errors. As shown in FIG. 1, the center 2CO of the sphere 2S of the second joint surface 2C is not located on the aspherical axis 2AX of the second lens surface 2A, and there is a positional deviation of Δfr with respect to the aspherical axis 2AX in the radial direction of the second lens 2. Hereinafter, in order to distinguish it from other positional deviations, the positional deviation between the aspherical axis 2AX and the center 2CO of the sphere 2S of the joint surface 2C in the radial direction of the second lens 2 is called "front-back surface deviation Δfr".

[0023] On the one hand, it is possible to arrange the optical axis 1X of the first lens 1 to coincide with the center 2CO of the spherical surface 2S of the second joint surface 2C, and the upper diagram of FIG. 1 shows the state arranged in this way. However, in the state shown in the upper diagram of FIG. 1, the optical axis 1X of the first lens 1 and the aspherical axis 2AX of the second lens surface 2A do not coincide and are in a displaced state. Generally, the influence on the performance of the cemented lens 10 is greater and the performance degradation is greater when the aspherical axis 2AX is displaced with respect to the optical axis 1X of the first lens 1 than when the aspherical axis 2AX is displaced with respect to the center 2CO.

[0024] Therefore, as shown by the rightward arrow in the lower diagram of FIG. 1, the second lens 2 is moved in the radial direction of the first lens 1 and centered so that the aspherical axis 2AX coincides with the optical axis 1X of the first lens 1. In the lower diagram of FIG. 1, the second lens 2 before movement is shown by a dashed line, and the second lens 2 after movement is shown by a solid line.

[0025] By this centering, the thickness of the adhesive 3 in the direction of the optical axis 1X before centering is almost uniform, whereas the thickness of the adhesive 3 in the direction of the optical axis 1X after centering is different in the direction of the front-back surface displacement Δfr. In the lower diagram of FIG. 1, the thickness tb of the adhesive 3 at a position left of the aspherical axis 2AX is thicker than the thickness ta of the adhesive 3 at a position right of the aspherical axis 2AX. Thus, by providing a thickness distribution of the adhesive 3 in the direction of the front-back surface displacement Δfr, a well-centered cemented lens 10 in which the optical axis 1X of the first lens 1 and the aspherical axis 2AX of the second lens 2 coincide can be obtained, and performance degradation of the cemented lens 10 can be suppressed.

[0026] Next, in order to deepen the understanding of the technology of the present disclosure, a cemented lens using the prior art will be described as Comparative Example 1 and Comparative Example 2. <Comparative Example 1> Referring to FIG. 2, Comparative Example 1 will be described. Comparative Example 1 is an example of joining spherical lenses. The state before centering is shown in the upper part of FIG. 2, and the state after centering is shown in the lower part. The first lens 1 in FIG. 2 is the same as the first lens 1 in FIG. 1, but the second lens 20 in FIG. 2 is different from the second lens 2 in FIG. 1 in that it is a spherical lens.

[0027] The first joint surface 1C, which is one of the lens surfaces of the first lens 1, and the second joint surface 20C, which is one of the lens surfaces of the second lens 20, are arranged to face each other. The first lens 1 and the second lens 20 are joined by an adhesive 3 filled between the first joint surface 1C and the second joint surface 20C. The first lens surface 1A, which is the other lens surface of the first lens 1, and the second lens surface 20A, which is the other lens surface of the second lens 20, are air contact surfaces that are not joined.

[0028] The axis passing through the center 20AO of the spherical surface of the second lens surface 20A and the center 20CO of the spherical surface of the second joint surface 20C is the optical axis 20X of the second lens 20. In the state before alignment shown in the upper diagram of FIG. 2, the center 20CO of the spherical surface of the second joint surface 20C is located on the optical axis 1X of the first lens 1, but the optical axis 20X of the second lens 20 is inclined with respect to the optical axis 1X of the first lens 1.

[0029] During alignment, as shown by the arrow in the lower diagram of FIG. 2, the second lens 20 is swung along a curve with the same curvature as the second joint surface 20C to align the optical axis 20X with the optical axis 1X of the first lens 1. In the lower diagram of FIG. 2, the second lens 20 before swinging is shown by a dashed line, and the second lens 20 after swinging is shown by a solid line.

[0030] In the normal alignment method, it starts from the state where the adhesive 3 is filled between the two lenses to be joined. The thickness of the adhesive 3 in this state is thin, for example, about 20 μm. Also, in the state where the adhesive 3 is filled, the force to swing the lens along the joint surface is smaller than the force to move the lens in the radial direction. Due to the above circumstances, in the conventional alignment method for joined lenses of spherical lenses, the method of swinging the lens along the joint surface is often adopted. Hereinafter, the method of aligning by swinging the lens along the above joint surface is referred to as the "conventional alignment method".

[0031] <Conventional Example 2> Referring to FIG. 3, a second conventional example will be described. The second conventional example is an example in which the above-described conventional centering method is applied to the joining of a spherical lens and an aspherical lens. The state before centering is shown in the upper part of FIG. 3, and the state after centering is shown in the lower part of FIG. 3. The first lens 1 and the second lens 2 of the second conventional example shown in FIG. 3 are the same as the first lens 1 and the second lens 2 of FIG. 1, respectively.

[0032] The state before centering shown in the upper diagram of FIG. 3 is the same as the state before centering shown in the upper diagram of FIG. 1. With respect to the center 2CO of the spherical surface (not shown in FIG. 3) of the second joint surface 2C, the aspherical axis 2AX of the second lens surface 2A has a front-back surface deviation Δfr, and the optical axis 1X of the first lens 1 and the center 2CO of the spherical surface of the second joint surface 2C are in a coincident state.

[0033] During centering, in the same manner as the above-described conventional centering method, as shown by the arrow in the lower diagram of FIG. 3, the second lens 2 is swung along a curve having the same curvature as the second joint surface 2C. In the lower diagram of FIG. 3, the second lens 2 before swinging is shown by a broken line, and the second lens 2 after swinging is shown by a solid line.

[0034] The aspherical axis 2AX after swinging does not coincide with the optical axis 1X of the first lens 1. After swinging, the aspherical axis 2AX is inclined by θ with respect to the optical axis 1X of the first lens 1, and a positional deviation of ΔA occurs on the second lens surface 2A. Hereinafter, the inclination of the aspherical axis 2AX with respect to the optical axis 1X of the first lens 1 will be referred to as "aspherical axis inclination θ", and the positional deviation of the aspherical axis 2AX in the radial direction of the first lens 1 with respect to the optical axis 1X of the first lens 1 on the second lens surface 2A will be referred to as "aspherical axis deviation ΔA".

[0035] When the paraxial radius of curvature of the second lens surface 2A is R2A, the radius of curvature of the second joint surface 2C is R2C, and the center thickness of the second lens 2 is 2t, R2A, R2C, 2t, the front-back surface deviation Δfr, the aspherical axis inclination θ, and the aspherical axis deviation ΔA are in a relationship represented by the following two equations. θ = Δfr / (R2A + 2t - R2C) ΔA = Δfr × R2A / (R2A + 2t - R2C)

[0036] As can be seen from the above two equations, as long as the front-back surface deviation Δfr is not zero, the aspherical axis tilt θ and the aspherical axis deviation ΔA cannot be made zero by the conventional centering method. Also, from the above two equations, the aspherical axis tilt θ and the aspherical axis deviation ΔA are in the relationship expressed by the following equation. As shown by the following equation, in the conventional centering method, the aspherical axis tilt θ and the aspherical axis deviation ΔA are in a proportional relationship. ΔA = R2A×θ

[0037] As can be understood from the above, in the case of a cemented lens including an aspherical lens, in the conventional centering method, the influence of the front-back surface deviation Δfr of the manufacturing error of the aspherical lens appears in the aspherical axis tilt θ and the aspherical axis deviation ΔA, and the influence cannot be removed. That is, in the conventional centering method, for an aspherical lens with a front-back surface deviation Δfr, the aspherical axis 2AX and the optical axis 1X of the first lens 1 cannot be made to coincide. A cemented lens in which the aspherical axis 2AX and the optical axis 1X of the first lens 1 do not coincide causes deterioration of optical performance. On the other hand, according to the cemented lens of the present disclosure in which the thickness of the adhesive 3 is different in the direction of the front-back surface deviation Δfr as shown in FIG. 1, both the aspherical axis tilt θ and the aspherical axis deviation ΔA can be made zero, and the aspherical axis 2AX and the optical axis 1X of the first lens 1 can be made to coincide. Therefore, deterioration of optical performance can be suppressed, and it can contribute to ensuring high optical performance.

[0038] <Preferred Configuration of Cemented Lens> Next, a preferred configuration of the cemented lens according to the present embodiment will be described. In the cemented lens 10 according to the present embodiment, since the adhesive 3 has a thickness distribution to reduce the influence of the front-back surface deviation of the aspherical lens, it is preferable that the refractive index of the second lens 2 and the refractive index of the adhesive 3 are close to each other. Specifically, when the refractive index of the second lens 2 is Nglass and the refractive index of the adhesive 3 is Nce, it is preferable that the cemented lens 10 satisfies the following conditional expression (1). By satisfying the conditional expression (1), deterioration of optical performance due to the adhesive 3 can be suppressed. 0.8×Nglass < Nce < 1.2×Nglass (1)

[0039] In order to ensure higher optical performance, it is more preferable that the cemented lens 10 satisfies the following conditional expression (1-1), and it is even more preferable that it satisfies the following conditional expression (1-2). 0.9×Nglass < Nce < 1.1×Nglass (1-1) 0.95×Nglass < Nce < 1.05×Nglass (1-2)

[0040] Here, Nglass and Nce are refractive indices with respect to the d-line. The wavelength of the d-line is treated as 587.56 nm. The refractive index can be measured, for example, using a Carl Zeiss precision refractometer KPR-3000 (manufactured by Shimadzu Corporation).

[0041] In order to give the thickness of the adhesive 3 a distribution, it is preferable that the average value of the thickness of the adhesive 3 is 10 μm or more. By setting it to 10 μm or more, it becomes easy to give the adhesive 3 a thickness distribution, so it becomes easy to align the aspherical axis 2AX and the optical axis 1X of the first lens 1. More preferably, the average value of the thickness of the adhesive 3 is 15 μm or more. Also, it is preferable that the average value of the thickness of the adhesive 3 is 50 μm or less. By setting it to 50 μm or less, it is possible to suppress a decrease in light transmittance and deterioration of optical performance due to the adhesive 3. More preferably, the average value of the thickness of the adhesive 3 is 40 μm or less.

[0042] The average value of the thickness of the adhesive 3 will be described with reference to FIG. 4. FIG. 4 is a view in a plane perpendicular to the optical axis 1X when the cemented lens 10 is viewed from the first lens 1 side. As shown in FIG. 4, in the plane perpendicular to the optical axis 1X, the position where the thickness of the adhesive 3 in the direction of the optical axis 1X is maximum is defined as the first position 11, the position obtained by rotating the first position 11 90 degrees around the optical axis 1X is defined as the second position 12, the position obtained by rotating the first position 11 180 degrees around the optical axis 1X is defined as the third position 13, and the position obtained by rotating the first position 11 270 degrees around the optical axis 1X is defined as the fourth position 14. The thickness of the adhesive 3 in the direction of the optical axis 1X at a total of five positions, namely the first position 11, the second position 12, the third position 13, the fourth position 14, and the position of the optical axis 1X, is obtained, and the average value of these is taken as the thickness of the adhesive 3.

[0043] When a more detailed average value of the thickness is required, the thickness of the adhesive 3 in the direction of the optical axis 1X at a total of nine positions obtained by adding the following fifth to eighth positions to the above five positions may be determined, and the average value thereof may be used as the thickness of the adhesive 3. Here, as shown in FIG. 4, the position obtained by rotating the first position 11 by 45 degrees around the optical axis 1X is defined as the fifth position 15, the position obtained by rotating the first position 11 by 135 degrees around the optical axis 1X is defined as the sixth position 16, the position obtained by rotating the first position 11 by 225 degrees around the optical axis 1X is defined as the seventh position 17, and the position obtained by rotating the first position 11 by 315 degrees around the optical axis 1X is defined as the eighth position 18.

[0044] The position where the thickness of the adhesive 3 is maximum can be specified, for example, by a wavefront measuring instrument. As the wavefront measuring instrument, for example, a Compact Laser Interferometer F601 (manufactured by Fujifilm Corporation), a Laser Interferometer G102 (manufactured by Fujifilm Corporation), and a Laser Interferometer Verifire (manufactured by Zygo Corporation) can be used. The thickness of the adhesive 3 can be measured, for example, by cutting the bonding lens 10 in a cross section including the direction of the optical axis 1X at each position and using a SEM (Scanning Electron Microscope).

[0045] <Manufacturing method 1 of bonding lens> Next, with reference to FIGS. 5 and 6, an example of a method for manufacturing the bonding lens 10 of FIG. 1 will be described. FIG. 5 is a flowchart showing the operation procedure of the manufacturing method, and FIG. 6 is a diagram schematically showing the steps of the manufacturing method. In this example, centering is performed after filling the adhesive 3.

[0046] In step S100 shown in FIG. 5, the core-chucked first lens 1 and the second lens 2 are prepared. Then, as shown in FIG. 6(a), the first joint surface 1C of the first lens 1 and the second joint surface 2C of the second lens 2 are arranged to face each other. Core-chucking is a process of cutting the outer peripheral side surface of a lens so that the central axis of the lens outer diameter coincides with the optical axis of the lens. That is, for a core-chucked spherical lens, the central axis of the outer shape becomes the optical axis. Note that for the second lens 2, core-chucking may or may not be performed before joining.

[0047] In step S110, as shown in FIG. 6(b), the adhesive 3 is filled between the first joint surface 1C of the first lens 1 and the second joint surface 2C of the second lens 2 from the adhesive injector 30. As an example in this case, an ultraviolet curable adhesive is used as the adhesive 3. As the adhesive 3, for example, various series of Hard Lock OP manufactured by Dencal Co., Ltd., or WORLD ROCK manufactured by Kyoritsu Chemical Industry Co., Ltd. can be used.

[0048] In step S120, as shown in FIG. 6(c), the wavefront measurement of the entire lens assembly composed of the first lens 1, the adhesive 3, and the second lens 2 is performed by the wavefront measuring device 32, and the tilt component and coma component are acquired from the interference fringe image obtained by the wavefront measurement. As the wavefront measuring device 32, for example, a Compact Laser Interferometer F601 (manufactured by Fujifilm Corporation), a Laser Interferometer G102 (manufactured by Fujifilm Corporation), and a Laser Interferometer Verifire (manufactured by Zygo Corporation) can be used.

[0049] In step S130, based on the acquired tilt component and coma component, the angle of the aspherical axis tilt θ and the amount of the aspherical axis deviation ΔA are detected.

[0050] FIG. 7 shows a conceptual diagram of the detection in steps S120 and S130. In wavefront measurement, an interference fringe image 40 in a state where a tilt component and a coma component are mixed is obtained. Using a wavefront measuring device 32 and a computer (not shown), each component is separated, and a tilt component 42 and a coma component 44 are acquired from this interference fringe image 40. From the tilt component 42, the angle of the aspherical axis tilt θ can be detected, and from the coma component 44, the amount of the aspherical axis deviation ΔA can be detected. In this way, by performing wavefront measurement to obtain the tilt component 42 and the coma component 44 and using these tilt component 42 and coma component 44, both the aspherical axis tilt θ and the aspherical axis deviation ΔA can be detected simultaneously with high accuracy. Note that, for the operations in steps S120 and S130, for example, a known technique described in Japanese Patent Application Laid-Open No. 2008-249415 can be used.

[0051] In step S140, according to the detected angle of the aspherical axis tilt θ and the amount of the aspherical axis deviation ΔA, the relative positions of the first lens 1 and the second lens 2 are adjusted so that the optical axis 1X of the first lens 1 and the aspherical axis 2AX of the second lens 2 coincide. The adjustment is mainly performed by relatively moving the first lens 1 and the second lens 2 in the radial direction of the first lens 1. For example, as shown in FIG. 6(d), the first lens 1 may be fixed and the second lens 2 may be gripped by a gripping member 34 and only the second lens 2 may be moved. Alternatively, the second lens 2 may be fixed and only the first lens 1 may be moved, or both the first lens 1 and the second lens 2 may be moved. By relatively moving the first lens 1 and the second lens 2 in the radial direction of the first lens 1, both the aspherical axis tilt θ and the aspherical axis deviation ΔA can be easily adjusted, and it becomes easy to align the optical axis 1X of the first lens 1 and the aspherical axis 2AX of the second lens 2. Note that, if necessary, in addition to the above-described radial movement, the adjustment may be performed by swinging at least one of the first lens 1 and the second lens 2 along a curve having the same curvature as the second joint surface 20C.

[0052] In step S150, it is checked whether the optical axis 1X of the first lens 1 coincides with the aspherical axis 2AX of the second lens 2. Whether the optical axis 1X of the first lens 1 coincides with the aspherical axis 2AX of the second lens 2 can be checked, for example, by performing wavefront measurement using the wavefront measuring device 32 used in step S120.

[0053] Alternatively, instead of wavefront measurement, it may be checked using an ultra-high-precision three-dimensional measuring machine UA3P (manufactured by Panasonic Production Engineering Co., Ltd.). When using the ultra-high-precision three-dimensional measuring machine UA3P, it is performed as follows. The direction of the aspherical axis 2AX of the second lens surface 2A is set as the z direction, and the two directions orthogonal to the z direction are set as the x direction and the y direction, respectively. The aspherical shape of the second lens surface 2A is measured to obtain a plurality of point cloud data. The point cloud data is obtained, for example, at a pitch of 10 μm in the x direction and the y direction. For the point cloud data, using the following aspherical formula and fitting with the coefficients of the aspherical formula as parameters, the aspherical axis tilt θ and the aspherical axis deviation ΔA can be specified. In the following aspherical formula, the curvature is c, the conic coefficient is k, the aspherical coefficient is αi, and the distance from the aspherical axis 2AX to the measurement point is r.

Equation

[0054] If the optical axis 1X of the first lens 1 does not coincide with the aspherical axis 2AX of the second lens 2, the process returns to step S140 to adjust the relative positions of the first lens 1 and the second lens 2.

[0055] When the optical axis 1X of the first lens 1 coincides with the aspherical axis 2AX of the second lens 2, in step S160, as shown in FIG. 6(e), with the relative positions of the first lens 1 and the second lens 2 adjusted, ultraviolet rays are irradiated from the ultraviolet irradiator 36 onto the adhesive 3 to cure the adhesive 3. Note that "curing the adhesive 3 in the adjusted state" includes both "starting to cure the adhesive 3 after the adjustment is completely finished" and "performing the adjustment after starting to cure the adhesive 3 and before the curing is completely finished. That is, it suffices that the state is adjusted at the timing when the curing ends, and at the timing when the curing starts, the adjustment may or may not be finished.

[0056] <Method for manufacturing a cemented lens 2> Next, with reference to FIGS. 8 and 9, another example of the method for manufacturing the cemented lens 10 of FIG. 1 will be described. FIG. 8 is a flowchart showing the operation procedure of the manufacturing method, and FIG. 9 is a diagram schematically showing the steps of the manufacturing method. The manufacturing method 2 is significantly different from the manufacturing method 1 in that the adhesive 3 is filled after centering, and basically only the procedure is different. Therefore, in the following description of the manufacturing method 2, the same reference numerals are given to the same devices and members as those in the manufacturing method 1, and the overlapping description is omitted, and mainly the differences from the manufacturing method 1 will be described.

[0057] In step S200 shown in FIG. 8, the centered first lens 1 and the second lens 2 are prepared. Then, as shown in FIG. 9(a), they are arranged such that the first joint surface 1C of the first lens 1 and the second joint surface 2C of the second lens 2 face each other.

[0058] In step S210, as shown in FIG. 9(b), the wavefront measuring device 32 performs wavefront measurement on the entire lens assembly composed of the first lens 1 and the second lens 2, and obtains the tilt component and the coma component from the interference fringe image obtained by the wavefront measurement.

[0059] In step S220, based on the obtained tilt component and coma component, the angle of the aspherical axis tilt θ and the amount of the aspherical axis deviation ΔA are detected.

[0060] In step S230, according to the detected angle of the aspherical axis tilt θ and the amount of the aspherical axis deviation ΔA, the relative positions of the first lens 1 and the second lens 2 are adjusted so that the optical axis 1X of the first lens 1 coincides with the aspherical axis 2AX of the second lens 2. For example, as shown in FIG. 9(c), the first lens 1 may be fixed and the second lens 2 may be gripped by the gripping member 34 and only the second lens 2 may be moved.

[0061] In step S240, it is confirmed whether the optical axis 1X of the first lens 1 coincides with the aspherical axis 2AX of the second lens 2. If the optical axis 1X of the first lens 1 does not coincide with the aspherical axis 2AX of the second lens 2, the process returns to step S230 to adjust the relative positions of the first lens 1 and the second lens 2.

[0062] If the optical axis 1X of the first lens 1 coincides with the aspherical axis 2AX of the second lens 2, in step S250, as shown in FIG. 9(d), with the relative positions of the first lens 1 and the second lens 2 adjusted, the adhesive 3 is filled between the first joint surface 1C of the first lens 1 and the second joint surface 2C of the second lens 2 from the adhesive injector 30.

[0063] In step S260, with the relative positions of the first lens 1 and the second lens 2 adjusted, ultraviolet rays are irradiated from the ultraviolet irradiator 36 to the adhesive 3 to cure the adhesive 3.

[0064] <Comparison between the Example and the Comparative Example> Next, the comparative data between the example and the comparative example will be described. The examples described below are cemented lenses manufactured using the manufacturing method of the present disclosure, or cemented lenses assumed to be manufactured using the manufacturing method of the present disclosure. The comparative examples described below are cemented lenses manufactured using a conventional centering method, or cemented lenses assumed to be manufactured using a conventional centering method. The design data (that is, the shape, refractive index, and Abbe number of each lens) of the examples and comparative examples described below are the same, and the adhesive used for cementing is also the same.

[0065] <Comparative Data 1> Figure 10 is a diagram showing the aspherical axis tilt θ and the aspherical axis deviation ΔA for an actually manufactured example and an actually manufactured comparative example. In Figure 10, the horizontal axis represents the aspherical axis tilt θ, and the vertical axis represents the aspherical axis deviation ΔA. In Figure 10, the examples are plotted with the symbol "〇", and the comparative examples are plotted with the symbol "□".

[0066] As shown in Figure 10, both the aspherical axis tilt θ and the aspherical axis deviation ΔA of the comparative examples have large values and large variations. In comparison, both the aspherical axis tilt θ and the aspherical axis deviation ΔA of the examples have very small values and small variations.

[0067] <Comparison Data 2> Figure 11 is data showing the resolution when an example or a comparative example is applied to a part of the imaging lens system 100 shown in Figure 12. The resolution in Figure 11 is the value of the MTF (Modulation Transfer Function) obtained by optical simulation. Here, a cemented lens assumed to be manufactured using the manufacturing method of the present disclosure is used as an example, and a cemented lens assumed to be manufactured using a conventional centering method is used as a comparative example.

[0068] The imaging lens system 100 can be used, for example, as an imaging lens for digital camera applications. Figure 12 shows a cross-sectional view of the configuration of the imaging lens system 100. In Figure 12, the left side is the object side, and the right side is the image side. The imaging lens system 100 includes, in order from the object side to the image side along the optical axis Z, lenses L11 to L17, an aperture stop St, lenses L21 to L26, and lenses L31 to L32. Among these, a cemented lens LC in which lens L15 and lens L16 are cemented becomes an example or a comparative example. The cemented lens LC includes an adhesive between lens L15 and lens L16. In addition, in Figure 12, a filter PP, an on-axis light beam K0, and a light beam K1 of the maximum angle of view arranged between the imaging lens system 100 and the image plane Sim are also shown. The detailed data of the imaging lens system 100 will be described later.

[0069] The resolution shown in FIG. 11 is the value of the MTF at the in-focus position with an image height of 0, at a wavelength of 587.56 nm and a frequency of 45 lp / mm (lines pair per millimeter). In the column of "Image height and direction" in FIG. 11, the image height and direction from the optical axis Z are shown. "S" indicates the sagittal direction, and "T" indicates the tangential direction. The values of the front-back surface deviation Δfr, the aspherical axis tilt θ, and the aspherical axis deviation ΔA used in the optical simulation are, for the comparative example, Δfr = 10 μm, θ = 3.5 min, and ΔA = 21 μm, and for the example, Δfr = 10 μm, θ = 0 min, and ΔA = 0 μm.

[0070] As shown in FIG. 11, the resolution of the comparative example has decreased from the design value, indicating that the performance has deteriorated. In contrast, since the difference between the resolution of the example and the design value is zero or almost zero, it can be seen that the performance degradation is well suppressed.

[0071] The detailed data of the imaging lens system 100 are shown below. The basic lens data are shown in Table 1, the specifications and variable surface intervals are shown in Table 2, and the aspherical coefficients are shown in Table 3. Tables 1 to 3 show the rounded numerical values in a predetermined number of digits.

[0072] In Table 1, the column of "Surface number" shows the surface number when the surface closest to the object side is designated as the first surface and the numbers are incremented one by one toward the image side. The column of "Radius of curvature" shows the radius of curvature of each surface. The column of "Surface interval" shows the surface interval on the optical axis between each surface and the surface adjacent to it on the image side. The column of "Refractive index" shows the refractive index of each component with respect to the d-line. The column of "Abbe number" shows the Abbe number of each component based on the d-line. Surfaces 7 to 10 in Table 1 are the cemented lens LC composed of lens L15, the adhesive, and lens L16. The columns of "Refractive index" and "Abbe number" of the eighth surface show the refractive index and Abbe number of the adhesive, respectively. Note that the imaging lens system 100 includes cemented lenses other than the above-mentioned cemented lens LC, but no adhesive data are input for the other cemented lenses.

[0073] In Table 1, the sign of the radius of curvature of the surface facing the object side with a convex shape is positive, and the sign of the radius of curvature of the surface facing the image side with a convex shape is negative. Table 1 also shows the aperture stop St and the filter PP. In the column of the surface number corresponding to the aperture stop St, the surface number and the phrase "(St)" are described. The value in the bottom row of the "Surface Interval" in Table 1 is the distance between the most image-side surface in the table and the image plane Sim.

[0074] Table 2 shows the values of the focal length, the open F-number, the maximum total angle of view 2ω, and the maximum image height. The "[°]" in the column of the maximum total angle of view indicates that the unit is degrees. Table 2 shows the values when focused on an object at infinity with respect to the d-line. When the imaging lens system 100 focuses from an object at infinity to a close object, the lenses L21 to L26 are integrally moved toward the object side for focusing. Note that "integrally moved" means moving simultaneously by the same amount in the same direction.

[0075] In Table 1, an asterisk is attached to the surface number of the aspheric surface, and the numerical value of the paraxial radius of curvature is described in the column of the radius of curvature of the aspheric surface. In Table 3, the column of the surface number shows the surface number of the aspheric surface, and the columns of KA and Am (m = 3, 4, 5, ··· 16) show the numerical values of the aspheric coefficients for each aspheric surface. The "E±n" (n: integer) of the numerical value of the aspheric coefficient in Table 3 means "×10 ±n ". KA and Am are the aspheric coefficients in the aspheric formula represented by the following formula. Zd = C×h 2 / {1+(1 - KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m However, Zd: Aspheric depth (the length of the perpendicular dropped from the point on the aspheric surface with height h to the plane perpendicular to the optical axis Z where the aspheric vertex touches) h: Height (the distance from the optical axis Z to the lens surface) C: Paraxial curvature KA, Am: Aspheric coefficients where Σ in the aspheric formula means the sum with respect to m.

[0076]

Table 1

[0077]

Table 2

[0078]

Table 3

[0079] <Various Modification Examples> In the above embodiment, an example in which the second joint surface 2C has a spherical shape is shown. However, the second joint surface 2C may have an aspherical shape. When the second joint surface 2C has an aspherical shape, the above "center 2CO of the spherical surface of the second joint surface 2C" can be considered in the same way by replacing it with the center of the paraxial spherical surface of the second joint surface 2C.

[0080] In the above embodiment, an example in which the first joint surface 1C and the first lens surface 1A have a spherical shape is shown. However, at least one of the first joint surface 1C and the first lens surface 1A may have an aspherical shape. When only one of the two lens surfaces of the first lens 1 has an aspherical shape, the "optical axis 1X of the first lens 1" is the aspherical axis of the aspherical shape. When both of the two lens surfaces of the first lens 1 have an aspherical shape, the "optical axis 1X of the first lens 1" is the aspherical axis of the lens surface that becomes the air contact surface.

[0081] In the above embodiment, an example in which the first joint surface 1C and the second joint surface 2C have the same shape is shown. However, the first joint surface 1C and the second joint surface 2C may have different shapes. However, it is preferable that the first joint surface 1C and the second joint surface 2C have the same shape. By making these two joint surfaces have the same shape, when aligning the aspherical axis 2AX and the optical axis 1X, the flow of the adhesive tends to be smooth. If they have different shapes, the width of the flow path of the adhesive may increase or decrease, and in that case, there is a risk of hindering the flow of the adhesive.

[0082] In the above-described embodiment, an example of a cemented lens composed of two cemented lenses was shown, but a cemented lens formed by cementing three or more lenses, such as a three-cemented lens, may also be used. That is, at least one of the first lens surface 1A and the second lens surface 2A may be a cemented surface that is cemented to another lens.

[0083] In the above-described embodiment, a cemented lens of a negative lens and a positive lens was illustrated and described, but the sign of the refractive power of the lenses to be cemented is not limited to this. Also, the concavo-convex shape of each lens surface is not limited to the illustrated example and can be arbitrarily selected.

[0084] In this specification, "coincidence" with respect to the axis means coincidence including errors generally acceptable in the technical field of the present disclosure in addition to perfect coincidence. In this specification, "identical" means identical including errors generally acceptable in the technical field of the present disclosure in addition to being completely identical. In this specification, "zero" means zero including errors generally acceptable in the technical field of the present disclosure in addition to being completely zero. In this specification, "maximum" means maximum including errors generally acceptable in the technical field of the present disclosure in addition to being completely maximum. In this specification, "center" means the center including errors generally acceptable in the technical field of the present disclosure in addition to the perfect center. In this specification, "average" means the average including errors generally acceptable in the technical field of the present disclosure in addition to the perfect average. In this specification, "90 degrees" means 90 degrees including errors generally acceptable in the technical field of the present disclosure in addition to being completely 90 degrees. The same applies to "180 degrees", "270 degrees", "45 degrees", "135 degrees", "225 degrees", and "315 degrees" in this specification.

[0085] The above-described description and illustration are detailed descriptions of the part related to the technology of the present disclosure and are merely examples of the technology of the present disclosure. For example, the explanations regarding the above-described configuration, function, operation, and effect are explanations regarding an example of the configuration, function, operation, and effect of the part related to the technology of the present disclosure. Therefore, it goes without saying that within the scope not departing from the gist of the technology of the present disclosure, the above-described description and illustration may be modified by deleting unnecessary parts, adding new elements, or making replacements. Also, in order to avoid complication and facilitate the understanding of the part related to the technology of the present disclosure, the above-described description and illustration omit the explanations regarding common technical knowledge and the like that do not particularly require explanation for implementing the technology of the present disclosure.

[0086] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference.

[0087] The following technology can be understood from the above description. [Appended Claim 1] A cemented lens in which a first joint surface, which is one lens surface of a first lens, and a second joint surface, which is one lens surface of a second lens, are cemented together by an adhesive, wherein the second lens has an aspherical lens surface as the other lens surface, the aspherical axis of the aspherical lens surface of the second lens coincides with the optical axis of the first lens, and there is a positional deviation in the radial direction of the second lens with respect to the center of the paraxial sphere of the second joint surface, and the adhesive between the first joint surface and the second joint surface is a cemented lens having different thicknesses in the direction of the positional deviation. [Appended Claim 2] The cemented lens according to Appended Claim 1, wherein the first joint surface and the second joint surface have the same shape. [Appended Claim 3] The cemented lens according to Appended Claim 1 or Appended Claim 2, wherein the first joint surface, the other lens surface of the first lens, and the second joint surface are spherical. [Supplementary Note 4] When the refractive index of the second lens is Nglass and the refractive index of the adhesive is Nce, 0.8 × Nglass < Nce < 1.2 × Nglass (1) The bonded lens according to any one of Supplementary Notes 1 to 3 that satisfies the conditional expression (1) represented by the above. [Supplementary Note 5] 0.9 × Nglass < Nce < 1.1 × Nglass (1-1) The bonded lens according to Supplementary Note 4 that satisfies the conditional expression (1-1) represented by the above. [Supplementary Note 6] 0.95 × Nglass < Nce < 1.05 × Nglass (1-2) The bonded lens according to Supplementary Note 4 that satisfies the conditional expression (1-2) represented by the above. [Supplementary Note 7] On the plane perpendicular to the optical axis, the position where the thickness of the adhesive in the direction of the optical axis is maximum is the first position, the position obtained by rotating the first position 90 degrees around the optical axis is the second position, the position obtained by rotating the first position 180 degrees around the optical axis is the third position, and the position obtained by rotating the first position 270 degrees around the optical axis is the fourth position. When this is the case, The bonded lens according to any one of Supplementary Notes 1 to 6, wherein the average value of the thicknesses of the adhesives in the direction of the optical axis at the position of the optical axis, the first position, the second position, the third position, and the fourth position is 10 μm or more and 50 μm or less. [Supplementary Note 8] The bonded lens according to Supplementary Note 7, wherein the average value of the thicknesses is 15 μm or more and 40 μm or less. [Supplementary Note 9] A method for manufacturing a bonded lens that bonds a first lens having a first bonding surface as one lens surface and a second lens having a second bonding surface as one lens surface and an aspherical lens surface as the other lens surface with an adhesive, A step of filling an adhesive between the first bonding surface and the second bonding surface, A step of detecting an inclination angle of an aspherical axis of the aspherical lens surface with respect to the optical axis of the first lens and a displacement amount in the radial direction of the first lens of the aspherical axis with respect to the optical axis in the aspherical lens surface; A step of adjusting a relative position between the first lens and the second lens according to the inclination angle and the displacement amount; A method for manufacturing a cemented lens, comprising a step of curing the adhesive in a state where the relative position is adjusted. [Additional Item 10] The method for manufacturing a cemented lens according to Additional Item 9, comprising a step of making the optical axis coincide with the aspherical axis by relatively moving the first lens and the second lens in the radial direction of the first lens. [Additional Item 11] Performing wavefront measurement of the first lens and the second lens, acquiring a tilt component and a coma component from an interference fringe image obtained by the wavefront measurement, and performing the detection based on the tilt component and the coma component. The method for manufacturing a cemented lens according to Additional Item 9 or Additional Item 10.

Explanation of Signs

[0088] 1 First lens 1A First lens surface 1C First joint surface 1X Optical axis 2 Second lens 2A Second lens surface 2AX Aspherical axis 2C Second joint surface 2CO Center 2S Sphere 2t Center thickness 3 Adhesive 10 Cemented lens 11 First position 12 Second position 13 Third position 14 Fourth position 15 Fifth position 16 Sixth position 17 Seventh position 18 Eighth position 20 Second lens 20A Second lens surface 20AO Center 20C Second joint surface 20CO Center 20X Optical axis 30 Adhesive injector 32 Wavefront measurer 34 Gripping member 36 Ultraviolet irradiator 40 Interference fringe image 42 Tilt component 44 Coma component 100 Imaging lens system K0 On-axis light beam K1 Light beam of maximum picture angle L11~L32 Lenses LC Joint lens PP Filter Sim Image plane ta Thickness tb Thickness Z Optical axis ΔA Aspherical axis deviation Δfr Front and back surface deviation θ Aspherical axis tilt

Claims

1. A cemented lens in which a first joint surface, which is one lens surface of a first lens, and a second joint surface, which is one lens surface of a second lens, are cemented together with an adhesive, wherein the second lens has an aspherical lens surface as the other lens surface, the aspherical axis of the aspherical lens surface of the second lens coincides with the optical axis of the first lens, and there is a displacement in the radial direction of the second lens with respect to the center of the paraxial spherical surface of the second joint surface, the adhesive between the first joint surface and the second joint surface is a cemented lens having different thicknesses in the direction of the displacement.

2. The cemented lens according to claim 1, wherein the first joint surface and the second joint surface have the same shape.

3. The cemented lens according to claim 1, wherein the first joint surface, the other lens surface of the first lens, and the second joint surface are spherical surfaces.

4. When the refractive index of the second lens is Nglass and the refractive index of the adhesive is Nce, the cemented lens according to claim 1, which satisfies the conditional expression (1) represented by 0.8 × Nglass < Nce < 1.2 × Nglass (1).

5. The cemented lens according to claim 4, which satisfies the conditional expression (1-1) represented by 0.9 × Nglass < Nce < 1.1 × Nglass (1-1).

6. The cemented lens according to claim 4, which satisfies the conditional expression (1-2) represented by 0.95 × Nglass < Nce < 1.05 × Nglass (1-2).

7. On a plane perpendicular to the optical axis, when the position where the thickness of the adhesive in the direction of the optical axis is maximum is the first position, the position obtained by rotating the first position 90 degrees around the optical axis is the second position, the position obtained by rotating the first position 180 degrees around the optical axis is the third position, and the position obtained by rotating the first position 270 degrees around the optical axis is the fourth position, the cemented lens according to claim 1, wherein the average value of the thicknesses of the adhesive in the direction of the optical axis at the position of the optical axis, the first position, the second position, the third position, and the fourth position is 10 μm or more and 50 μm or less.

8. The cemented lens according to claim 7, wherein the average value of the thickness is 15 μm or more and 40 μm or less.

9. A method for manufacturing a cemented lens, which cements a first lens having a first joint surface as one lens surface and a second lens having a second joint surface as one lens surface and an aspherical lens surface as the other lens surface with an adhesive, ​ ​ ​ A step of filling an adhesive between the first joint surface and the second joint surface; A step of detecting an inclination angle of an aspherical axis of the aspherical lens surface with respect to the optical axis of the first lens and a radial displacement amount of the aspherical axis with respect to the optical axis on the aspherical lens surface of the first lens; A step of adjusting a relative position between the first lens and the second lens according to the inclination angle and the displacement amount; A method for manufacturing a cemented lens, comprising a step of curing the adhesive in a state where the relative position is adjusted.

10. The method for manufacturing a cemented lens according to claim 9, further comprising a step of moving the first lens and the second lens relative to each other in the radial direction of the first lens to align the optical axis and the aspherical axis.

11. The method for manufacturing a cemented lens according to claim 9, wherein wavefront measurement of the first lens and the second lens is performed, a tilt component and a coma component are obtained from an interference fringe image obtained by the wavefront measurement, and the detection is performed based on the tilt component and the coma component.

Images