Lens holding device, lens assembly, and method for manufacturing elastic body member for lens holding

Abstract

To provide a flexure structure having sufficient flexibility even for a mount for a small-diameter lens.SOLUTION: A lens holding device includes a lens mount member 16 and an elastic body member 18. The elastic body member 18 has an annular shape that includes three or more slots 26 evenly distributed in a circumferential direction. An outer circumferential portion of the elastic body member is fixed to an inner circumferential portion of the lens mount member 16, and an inner circumferential portion of the elastic body member is fixed to an outer circumferential portion of a lens 12. When a dimension of the elastic body member 18 in an optical axis direction is defined as b, and a minimum dimension in a radial direction of a region of the elastic body member 18 on the inner side in the radial direction of the slots 26 is defined as h, the configuration satisfies b≤1 mm, and a ratio (h / b) satisfies 1 / 2≤(h / b)≤1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lens holding device, a lens assembly, and a method for manufacturing an elastic member for holding a lens. [Background technology]

[0002] In semiconductor inspection equipment used to inspect wafers and masks, high-precision objective lenses are used to capture images of defects on an object illuminated with deep ultraviolet light.

[0003] The high-precision objective lenses used in semiconductor inspection equipment have different characteristics from commercially available objective lenses for biological or metallurgical applications. The main differences are as follows:

[0004] First, wavefront aberration must be small. A typical objective lens is considered to be aberration-free if its wavefront aberration in visible light is 0.07 waves rms, but high-precision objective lenses for semiconductor inspection equipment are required to have a wavefront aberration of 0.03 waves rms or less in ultraviolet light. Because the wavelength of ultraviolet light is less than half that of visible light, this standard means that the requirements for high-precision objective lenses are more than four times stricter than those for commercially available objective lenses.

[0005] The second is the performance stability of high-precision objective lenses against the external environment. Objective lenses are exposed to temperature changes and vibrations and shocks during transportation. High-precision objective lenses for semiconductor inspection equipment must not have their performance deteriorated (changed) by these disturbances. Objective lenses are also exposed to temperature changes due to the absorption of illumination light and changes in atmospheric pressure, such as low atmospheric pressure. For this reason, the performance of high-precision objective lenses must not deteriorate even due to such temperature and atmospheric pressure changes.

[0006] Other differences include the following two points: The high-precision objective lens must be resistant to the buildup of outgassing caused by UV irradiation, and the objective lens itself must not have polarization properties, since polarization may be used as a measurement method.

[0007] Thus, high-precision objective lenses in semiconductor inspection equipment are required not only to have smaller aberrations than general objective lenses, but also to have performance stability against various disturbances.

[0008] The elastomer mount structure has long been known as an objective lens holding structure that meets these requirements. In this structure, the lens is bonded to a cell (mount) using an elastomer. Each cell with a lens bonded to it is inserted into a lens barrel or connected to each other to form the objective lens. Silicone potting materials (hereafter referred to as silicone adhesives) are well known as elastomers used to bond lenses. Silicone adhesives can secure the lens without distorting it, and also have the advantage of producing relatively little outgassing.

[0009] Although silicone adhesives have many advantages, their inadequacies have become apparent in recent years. Take high-precision mask defect inspection systems as an example. In these systems, the allowable eccentricity of the objective lens must be kept to a few tens of nanometers or less. Because this type of objective lens has extremely high eccentricity sensitivity and requires strict aberration levels, any residual eccentricity in the lens beyond this level may result in false detection of a false defect. Silicone adhesives are not suitable for fixing lenses used in this type of application. The reasons for this are explained below.

[0010] When temperature changes or vibration shocks are applied to the lens assembly, forces are applied to the individual lenses, causing lens decentering. If the adhesive that secures the lenses has sufficient fixing strength and resilience, the lenses should return to their original positions when the disturbance disappears.

[0011] However, silicone adhesives for fixing lenses have insufficient fixing strength (shear strength of several MPa), are soft (Young's modulus of several MPa), and lack positional recovery. Therefore, when using silicone adhesives for fixing lenses, it is not possible to expect the lens to return to its original position completely after the external disturbance has disappeared.

[0012] To avoid this, a hard elastomer with a Young's modulus of several GPa is useful. An example of a hard elastomer with a Young's modulus of several GPa is epoxy adhesive. Fixing a lens with epoxy adhesive has high linearity with respect to dimensional changes and high adhesive strength. In this case, even if force is applied to the lens due to temperature changes or vibration shock, the lens will return to its original position once the disturbance disappears.

[0013] On the other hand, when a hard adhesive such as an epoxy adhesive is used, another problem arises. Adhesives generally undergo a phenomenon known as cure shrinkage, in which their volume decreases upon hardening. The force applied to the lens due to cure shrinkage is proportional to the Young's modulus. For example, the cure shrinkage stress when an epoxy adhesive is used is nearly 1,000 times that of a silicone adhesive. As a result, wavefront aberration deteriorates due to changes in the lens's surface precision, and polarization characteristics deteriorate due to the lens's photoelastic effect, resulting in degradation of imaging and polarization characteristics.

[0014] Thus, in the conventional elastomer mount structure, there are two conflicting requirements: positional stability and shape stability of the lens.

[0015] One known lens holding structure that addresses this issue is one that provides flexibility to the lens mount (see, for example, Patent Document 1). A flexible structure is called a flexure structure. The difference in the linear expansion coefficient between the lens and the mount due to temperature changes and the cure shrinkage of the adhesive are absorbed by the flexure of the flexure structure itself, minimizing the stress on the lens.

[0016] However, applying a flexure structure to small-diameter objective lenses with a diameter of 30 mm or less, such as those used in semiconductor inspection equipment, is difficult. Flexure structures are formed on the mount by machining such as wire-cut electrical discharge machining. Therefore, the lens mount must be relatively large for machining purposes. Furthermore, in order to increase the flexibility of the flexure structure, it is necessary to provide complex-shaped slots (slits) in addition to the circumferential direction, which also leads to an increase in the size of the mount. While it is possible to increase flexibility by thinning the arm, the limitations of wire-cut electrical discharge machining place restrictions on the diameter and width of the arm.

[0017] Two other structures are known for stably holding lenses: one is a structure that absorbs the difference in linear expansion with a thick elastomer adhesive layer (Non-Patent Document 2), and the other is a structure that absorbs the difference in linear expansion with a resin ring provided between the lens and the mount (Non-Patent Document 3).

[0018] Because the adhesive layer and resin ring can be configured to any size, these lens retention structures are suitable for small-diameter lenses. However, resins are unstable in terms of dimensional change with temperature, so the expected effect may not be achieved. Furthermore, ultraviolet radiation used in semiconductor metrology equipment can chemically damage the mount, potentially compromising dimensional stability and the cleanliness of the lens interior, making these structures unsuitable for advanced semiconductor metrology equipment. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] U.S. Patent No. 4,733,945 [Non-patent literature]

[0020] [Non-Patent Document 1] M. Bayer, Lens barrel optomechanical design principles, Opt. Eng., 1981 [Non-patent document 2] P. Yoder Jr., Mounting Optics in Optical Instruments, second edition Summary of the Invention [Problem to be solved by the invention]

[0021] In view of the above background, an object of the present invention is to provide a lens holding device that realizes a flexure structure with sufficient flexibility to contribute to lens stability even in a mount for a small-diameter lens, and that stably holds a lens. [Means for solving the problem]

[0022] In order to solve the above problem, one aspect of the present invention is a lens holding device (10) for holding a lens (12), comprising a lens mount member (16) and an elastic member (18, 30) provided separately from the lens mount member, the elastic member having an annular shape with three or more equally distributed slots (26, 38) in the circumferential direction, the outer periphery of which is fixed to the inner periphery of the lens mount member and the inner periphery of which is fixed to the outer periphery of the lens, and where b is the optical axis dimension of the elastic member and h is the minimum radial dimension of a region (28, 40) of the elastic member radially inward of the slot, b≦1 mm and the ratio (h / b) satisfies 1 / 2≦(h / b)≦1.

[0023] With this configuration, even in a mount for a small-diameter lens, a flexure structure having sufficient flexibility to contribute to the stability of the lens can be obtained, and the lens can be stably held.

[0024] In the above aspect, each slot may be on an imaginary circle concentric with the elastic member and have an arc shape.

[0025] With this configuration, the lens is held evenly and stably over the entire circumference.

[0026] In the above aspect, the elastic member (30) may have a slot portion (34) that forms part of the slot and may be composed of a plurality of elastic thin plates (32) stacked in the optical axis direction.

[0027] This configuration makes it easy to etch the slots into the individual thin plates that make up the thin elastic plate.

[0028] In the above aspect, the slots of the elastic body thin plates may overlap each other in the optical axis direction.

[0029] With this configuration, even if the elastic member is made up of a plurality of elastic member thin plates, the flexure performance does not differ from that of an elastic member having a single structure.

[0030] In the above aspect, the lens mount member and the elastic member may be made of stainless steel.

[0031] This configuration reduces the thermal stress acting between the lens mount member and the elastic member due to the difference in linear thermal expansion coefficient.

[0032] In order to solve the above problem, one aspect of the present invention is a lens assembly (50) that includes at least one lens holder device according to the above aspect.

[0033] According to this configuration, the lenses are stably held in the lens assembly.

[0034] In order to solve the above-mentioned problems, one aspect of the present invention is a method for manufacturing an elastic member used in the lens holding device according to the above-mentioned aspect, in which the slot is formed by etching.

[0035] According to this manufacturing method, a highly accurate elastic member is manufactured in which there is little residual distortion due to processing stress during the formation of the slots. [Effects of the Invention]

[0036] According to the above aspect, even in a mount for a small-diameter lens, a flexure structure having sufficient flexibility that contributes to the stability of the lens can be obtained, and the lens can be stably held. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is an exploded perspective view showing a lens holding device according to a first embodiment of the present invention; [Figure 2] 1 is a cross-sectional view of a lens holding device according to a first embodiment. [Figure 3] FIG. 1 is a front view of an elastic member used in a lens holding device according to a first embodiment; [Figure 4] FIG. 10 is a front view illustrating a method for manufacturing an elastic member used in the lens holding device of the first embodiment. [Figure 5] FIG. 10 is an exploded perspective view showing a lens holding device according to a second embodiment of the present invention. [Figure 6] 10 is a cross-sectional view of a lens holding device according to a second embodiment. [Figure 7] 1 is a half cross-sectional view of one embodiment of a lens assembly according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0038] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a lens holding device according to the present invention will be described with reference to the drawings.

[0039] (Embodiment 1) 1 to 3 show a lens holding device 10 according to a first embodiment. The lens holding device 10 holds a lens 12 that is circular in front view, and has a lens mount member 16 (cell) including a cylindrical portion 14, and a ring-shaped elastic member 18 (elastic member for holding a lens) that is provided between the lens 12 and the cylindrical portion 14, separate from the lens mount member 16. The lens mount member 16 is made of a metal such as stainless steel. The lens 12 is made of synthetic quartz or the like, and is a small optical lens with an outer diameter of approximately 30 mm or less.

[0040] The elastic member 18 is made of a material having a linear expansion coefficient equivalent to that of the lens mount member 16, for example, the same metal (stainless steel) or the same type of metal as the metal that constitutes the lens mount member 16. The elastic member 18 has a circular ring shape and is made of a circular ring-shaped flat plate (stencil) with a dimension (plate thickness) in the optical axis direction of 1.0 mm or less.

[0041] If the lens mount member 16 and the elastic member 18 are made of the same stainless steel, the thermal stress acting between the lens mount member 16 and the elastic member 18 due to the difference in linear thermal expansion coefficients is reduced.

[0042] The outer diameter of the elastic member 18 is slightly smaller than the inner diameter of the cylindrical portion 14. The inner diameter of the elastic member 18 is slightly larger than the outer diameter of the lens 12. As shown in FIG. 2 , the outer periphery of the elastic member 18 is bonded to the inner periphery of the cylindrical portion 14 by an annular adhesive layer 20 provided between the outer periphery 18A of the elastic member 18 and the inner periphery 14A of the cylindrical portion 14. The inner periphery of the elastic member 18 is bonded to the outer periphery of the lens 12 by an annular adhesive layer 22 provided between the inner periphery 18B of the elastic member 18 and the outer periphery 12A of the lens 12. Suitable adhesives for forming the adhesive layers 20, 22 include epoxy-based adhesives.

[0043] The lens mount member 16 has a ring-shaped flange portion 24 that extends radially inward from the cylindrical portion 14. One end face 24A of the flange portion 24 is in contact with one end face 18C of the elastic member 18. This contact determines the position of the elastic member 18 in the optical axis direction relative to the lens mount member 16.

[0044] The elastic member 18 has three arc-shaped slots 26 that penetrate in the optical axis direction. The slots 26 are formed by etching or the like, and are arranged at equal intervals in the circumferential direction on an imaginary circle that is concentric with the elastic member 18. The slots 26 have the same arc length, and are arranged evenly in the circumferential direction of the elastic member 18.

[0045] The elastic body member 18 forms a flexure beam 28 in a radially inner region of each slot 26. As shown in Fig. 2, each flexure beam 28 has a rectangular cross-sectional shape defined by both end faces 18C, 18D of the elastic body member 18, an inner surface 26A on the radially inner side of the corresponding slot 26, and an inner circumferential surface 18B of the elastic body member 18. When viewed from the front, each flexure beam 28 has an arc shape concentric with the elastic body member 18 and extends in the circumferential direction on an imaginary circle concentric with the elastic body member 18.

[0046] Each flexure beam 28 has a beam structure that can be considered as a doubly supported beam (a beam fixed at both ends) having a flexure beam length L (see FIG. 3) determined by the length measured along the arc of the slot 26, and is a flexure structure that can elastically deform in the radial direction. In the following description, the beam length L may be referred to as the flexure length L.

[0047] An important factor in the flexure performance of the flexure beam 28 is the radial bending rigidity of the flexure beam 28. This rigidity is determined by the Young's modulus E of the flexure beam 28, the cross-sectional shape (rectangle) of the flexure beam 28, which correlates with the second moment of area, and its dimensions.

[0048] The optical axis direction dimension b of the flexure beams 28 is determined by the plate thickness of the elastic member 18 and is 1.0 mm or less. The minimum radial dimension h of each flexure beam 28 is a value in the range from half the optical axis direction dimension b to the optical axis direction dimension b or less. The minimum radial dimension h is the minimum radial dimension of the flexure beam 28 in the region of the elastic member 18 radially inward of the slot 26.

[0049] The ratio (b / h) of the optical axis dimension b of each flexure beam 28 to the minimum radial dimension h (flexure blade thickness) may be such that the following formula (1) is satisfied. 1 / 2≦(b / h)≦1 ...(1)

[0050] If the number of flexure beams 28 is n and the radius of an imaginary circle concentric with the elastic member 18 and connecting the flexure beams 28 to one another is r, the total length n·L of the flexure beams 28 is given by the following equation (2). (2π r)=k(n L) ...(2) where k is a coefficient. The coefficient k may be approximately 0.3 to 0.5, and preferably k = 0.4 The smaller this coefficient k is, the shorter the flexure length L of each flexure beam 28 becomes.

[0051] In the lens holding device 10, the flexure structure is formed on an annular flat plate that constitutes the elastic member 18, separate from the lens mount member 16. The elastic member 18 has flexure beams 28 formed by simply shaped slots 26 that extend in the circumferential direction, so that a flexure structure with sufficient flexibility is realized even for a small-diameter lens mount structure, without the need for slots with complex shapes.

[0052] According to this configuration, the flexure structure is formed on the flat elastic member 18 having a thickness of 1.0 mm or less, separate from the lens mount member 16, so that the rigidity of the flexure beam 28 is sufficiently low even if the flexure length L of the flexure beam 28 is short. This allows for a good flexure structure with sufficient flexibility to be realized in a compact mount for a small-diameter lens.

[0053] This will be explained using a mechanical model in which the flexure structure is regarded as a beam with both ends fixed.

[0054] When a load P [N] is applied to a beam fixed at both ends, the displacement δ [mm] is given by the following equation (3). δ=(PL 3 ) / 192EI ...(3)

[0055] Here, E is the Young's modulus of the flexure beam 28 (unit: MPa), I is the second moment of area of ​​the flexure beam 28 (unit: mm 4 ) Since the flexure beam 28 has a rectangular cross section, the second moment of area I of the flexure beam 28 is given by the following equation (4): I=(bh 3 ) / 12 ...(4)

[0056] Next, when a synthetic quartz lens 12 with a diameter of 20 mm is mounted on a lens mount member made of SUS303, the stress applied to the lens is compared between the example and the comparative example using the above formula.

[0057] Table 1 shows the dimensions of each part of the lens holding device of the embodiment, each specification, and the load (results of stress calculation) acting on the lens when a temperature change of 1° C. occurs.

[0058] [Table 1]

[0059] Table 2 shows the dimensions of each part of the lens holding device of the comparative example that is empirically proven to be effective, the various specifications, and the load acting on the lens when a temperature change of 1°C occurs (results of stress calculations).

[0060] [Table 2]

[0061] In the comparative example, the optical axis dimension b of the flexure beam is larger than that of the example, and the rigidity of the flexure beam is high. Therefore, distortion due to processing stress of the elastic member is small, and the flexure beam is less likely to be distorted even if the minimum radial dimension h of the flexure beam is small. Furthermore, in the comparative example, since slots can be provided in the diameter direction, the flexure length L, which is provided at three equal intervals in the circumferential direction, can be made as large as possible (here, 80% of 1 / 3 of the circumferential length). Therefore, even with a relatively thick flexure beam, the load acting on the lens can be kept sufficiently small.

[0062] On the other hand, if one attempts to miniaturize the elastic member, it is not possible to provide a slot in the diameter direction, and therefore the flexure length L cannot be increased. For example, if the flexure length is half that of Table 2, the load P acting on the lens according to the above formula (3) will be eight times that of Table 2. An effective way to reduce the load P acting on the lens is to reduce the moment of inertia I. One way to achieve this is to form the flexure structure from a thin plate with a thickness of 1.0 mm, thereby reducing the optical axis dimension b.

[0063] The differences between the Examples and Comparative Examples are explained below. The biggest difference between the two is the coefficient k for the flexure length. In the Comparative Example shown in Table 2, k = 0.8, while in the Examples shown in Table 1, k = 0.4. As a result, the rigidity of the flexure structure due to the flexure beams in the Comparative Example is eight times that of the Examples, and therefore the force acting on the lens is also eight times greater. To accommodate this, the optical axis dimension b is set from 10.0 mm in Comparative Example 1 to 0.7 mm in the Examples. Accordingly, the minimum radial dimension h is set from 0.35 mm in the Comparative Example to 0.30 mm in the Examples.

[0064] By setting these parameters, even if the coefficient k changes from 0.8 to 0.4, the load P acting on the lens in the example shown in Table 1 can be reduced to the same extent as that in the comparative example shown in Table 2.

[0065] In the elastic member 18 of the lens holding device 10 of embodiment 1, each slot 26 is located on a virtual circle concentric with the elastic member 18 and has an arc shape, so that the lens 12 is held evenly and stably around its entire circumference.

[0066] Next, one embodiment of a method for manufacturing the elastic member 18 will be described with reference to Fig. 4. In manufacturing the elastic member 18, as shown in Fig. 4(A), first, an outer shape B and an inner shape C are formed coaxially on a metal flat plate A. By forming the outer shape B, an annular member D is manufactured, which has an outer peripheral surface 18A of the elastic member 18, and by forming the inner shape C, an annular member D has an inner peripheral surface 18B of the elastic member 18. The outer shape B and the inner shape C can be formed by any of the following methods: punching, laser machining, electric discharge machining, or etching.

[0067] 4(B), a predetermined number of slots 26 are formed by etching in the annular member D. By forming these slots 26, the elastic member 18 is completed, which has flexure beams 28, which are fixed beams supported at both ends, in the radially inward region of each slot 26.

[0068] In this manufacturing method, the slots 26 are formed by etching rather than by machining such as punching, so that less processing stress remains in the elastic member 18, reducing distortion of the elastic member 18 due to the processing stress. This results in a flexure beam 28 with high shape accuracy, which in turn accurately provides a flexure beam 28 with the required flexure performance, allowing for accurate manufacturing of a high-performance elastic member 18.

[0069] (Embodiment 2) Figures 5 and 6 show a lens holding device 10 of embodiment 2. In Figures 5 and 6, parts corresponding to those in Figures 1 to 3 are given the same reference numerals as those in Figures 1 to 3, and descriptions thereof will be omitted.

[0070] In the second embodiment, the elastic member 30 is formed by a laminate of a plurality of elastic body thin plates 32, four in the illustrated example. Each elastic body thin plate 32 has the same shape, with the same slot portion 34 and flexure beam portion 36. The thickness of each elastic body thin plate 32 is b / 4, so that the total thickness of the four elastic body thin plates 32 achieves a predetermined optical axis dimension b. The slot portions 34 of each elastic body thin plate 32 are formed by stacking the four elastic body thin plates 32 in the optical axis direction to form a slot 38 that is gathered in the optical axis direction. In other words, each slot portion 34 forms a part of the slot 38 in the optical axis direction. The flexure beam portions 36 of each elastic body thin plate 32 are formed by stacking the four elastic body thin plates 32 in the optical axis direction to form a flexure beam 40 that is gathered in the optical axis direction.

[0071] The etching of the slots 34 may be performed individually for each elastic body-constituting thin plate 32. This makes the etching depth for forming the slots 38 smaller than in the first embodiment. This makes it easier to etch the slots 38. As a result, in the second embodiment, it is possible to obtain a flexure portion having a required thickness while keeping the flexure structure thin enough for manufacturing.

[0072] The second embodiment is substantially the same as the first embodiment except for the configuration of the elastic member 30 described above.

[0073] The multiple elastic body thin plates 32 are stacked so that the circumferential positions of the slots 34 and flexure beams 36 are the same. In other words, the multiple elastic body thin plates 32 overlap each other in the optical axis direction with their slots 34 and flexure beams 36 aligned with each other in the circumferential direction.

[0074] As a result, the slot 38 becomes equivalent to the slot 26 of the first embodiment, and the flexure beam 40 becomes equivalent to the flexure beam 28 of the first embodiment. Even if the elastic body member 30 has a laminated structure, a flexure structure with substantially the same characteristics as when the elastic body member 18 has a single-piece structure as in the first embodiment can be obtained. In other words, even if the elastic body member 30 is made up of a plurality of elastic body-constituting thin plates 32, the flexure performance does not differ from that of the elastic body member 18 having a single-piece structure.

[0075] As a result, the lens holding device 10 of the second embodiment functions in the same manner as the lens holding device 10 of the first embodiment, and provides the same effects.

[0076] Next, one embodiment of a lens assembly according to the present invention will be described with reference to FIG.

[0077] 7, lens assembly 50 has a cylindrical lens barrel 52 and a plurality of lenses (seven lenses in the illustrated example) 541-547 arranged in the optical axis direction within lens barrel 52. Lenses 541-547 are fixed to lens barrel 52 by lens holding devices 561-567.

[0078] Each of the lens holding devices 561 to 567 is fitted into the lens barrel 52, and thereby the radial position thereof relative to the lens barrel 52 is determined.

[0079] Lens barrel 52 has an inner flange portion 52A that protrudes radially inward at one end in the optical axis direction. Each of lens holder devices 561-567 is inserted into lens barrel 52 in order from the other end in the optical axis direction of lens barrel 52. A female thread 52B is formed on the radially inner side of the other end of lens barrel 52. An annular setscrew member 58 is threadedly engaged with the female thread 52B. Lens holder devices 561-567 are sandwiched between inner flange portion 52A and setscrew member 58 in the optical axis direction and fixed to lens barrel 52 in the optical axis direction. This determines the optical axis position of each of lens holder devices 561-567 relative to lens barrel 52.

[0080] In this lens assembly 50, the lens holding devices 562 to 566, excluding the lens holding devices 561 and 567 for the lenses 541 and 547 arranged at both ends of the lens barrel 52 in the optical axis direction, each have a structure equivalent to that of the lens holding device 10 having the elastic member 18 of embodiment 1.

[0081] As a result, the lens assembly 50 can effectively obtain the functions and effects of the lens holding device 10 of the first embodiment.

[0082] In another embodiment, the lens holding devices 562 to 566 may have the same structure as the lens holding device 10 having the elastic member 30 of embodiment 2. Furthermore, all of the lens holding devices 561 to 567 may have the same structure as the lens holding device 10 of embodiment 1 or embodiment 2.

[0083] While the present invention has been described above in terms of its preferred embodiments, it is not limited to these embodiments and can be modified as appropriate without departing from the spirit of the present invention. For example, the number of slots 26, 38 and the number of flexure beams 28, 40 associated therewith are not limited to three and may be any number greater than three. The number of elastic body-constituting thin plates 32 in embodiment 2 is not limited to four and may be any other number.

[0084] In addition, some or all of the configurations of the above-described embodiments may be combined with each other. Furthermore, not all of the components shown in the above-described embodiments are necessarily essential, and they may be selected as appropriate without departing from the spirit of the present invention. [Industrial Applicability]

[0085] A small, highly accurate flexure can be constructed from a circular, flat elastic member, and by interposing this between the lens and the mount by bonding, it can be used to stabilize the lens position due to temperature changes without increasing the size of the lens. [Explanation of symbols]

[0086] 10: Lens holding device 12: Lens 16: Lens mount component 18: Elastic member 26: Slot 28: Flexure beam 30: Elastic member 32: Elastic body thin plate 34: Slot section 36: Flexure beam 38: Slot 40: Flexure beam 50: Lens assembly

Claims

1. A lens holding device for holding a lens, a lens mount member and an elastic member provided separately from the lens mount member; the elastic member has an annular shape having three or more slots evenly distributed in a circumferential direction, and the outer periphery is fixed to the inner periphery of the lens mount member, and the inner periphery is fixed to the outer periphery of the lens, A lens holding device in which, when the optical axis dimension of the elastic member is b and the minimum radial dimension of the region of the elastic member radially inward of the slot is h, b≦1 mm and the ratio (h / b) satisfies 1 / 2≦(h / b)≦1.

2. 2. The lens holding device according to claim 1, wherein each slot is on an imaginary circle concentric with said elastic member and has an arc shape.

3. 3. The lens holding device according to claim 1, wherein the elastic member has a slot portion that constitutes a part of the slot, and is made up of a plurality of elastic thin plates stacked in the optical axis direction.

4. 4. The lens holding device according to claim 3, wherein the slots of the elastic body thin plates overlap each other in the optical axis direction.

5. 3. The lens holding device according to claim 1, wherein the lens mount member and the elastic member are made of stainless steel.

6. A lens assembly comprising at least one lens holder device according to any one of claims 1 to 5.

7. 6. A method for manufacturing an elastic member used in the lens holding device according to claim 1, wherein the slot is formed by etching.

Images