Optical assembly as well as devices and methods for aligning components of optical assembly

Abstract

To align components of an optical assembly.SOLUTION: An alignment device for aligning components of an optical assembly includes: a chuck that is configured to support the optical assembly; and an adjustable flexure assembly that is disposed around the chuck. The adjustable flexure assembly includes a plurality of flexures. The plurality of flexures are positioned relative to the chuck such that each of the plurality of flexures contacts with the optical assembly when the optical assembly is positioned on the chuck. By adjusting positions of one or more flexures of the plurality of flexures when the optical assembly is positioned on the chuck, aligning an optical axis of an optical component of the optical assembly is adjusted. The alignment device is configured to, with the optical axis of the optical component aligned with an angle of deviation less than about 1,000 μrad, provide an extinction ratio within the optical assembly equal to or greater than 1000:1.SELECTED DRAWING: Figure 1A

Description

Related Applications

[0001] This application claims the benefit of priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 62 / 891,055, filed August 23, 2019, and U.S. Provisional Patent Application No. 62 / 902,667, filed September 19, 2019, the contents of which are relied upon and incorporated by reference in their entireties herein. [Technical field]

[0002] The present specification relates generally to optical assemblies and apparatus and methods for aligning components of optical assemblies, and more particularly to apparatus and methods for aligning the optical axes of lenses in optical assemblies. [Background technology]

[0003] An optical assembly, such as a "doublet" or "triplet," may include two or more lenses bonded together with an optical adhesive between adjacent optical surfaces. Such devices can be used in a range of applications, such as, but not limited to, ultraviolet and visible wavelength imaging objectives in semiconductor inspection, microscope imaging, visible light cameras, etc.

[0004] During the manufacture of optical assemblies, it is desirable to properly align the optical axes of the individual lenses, which may prove difficult depending on the desired alignment tolerances. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, a need exists for alternative apparatus and methods for aligning components of an optical assembly for improved optical performance. [Means for solving the problem]

[0006] In a first aspect, an alignment device for aligning components of an optical assembly comprises a chuck configured to support the optical assembly and a flexure assembly disposed about the chuck. The adjustable flexure comprises a plurality of flexures. The plurality of flexures is positioned relative to the chuck such that each of the plurality of flexures contacts the optical assembly when the optical assembly is positioned on the chuck. Adjustment of the position of one or more of the plurality of flexures adjusts alignment of optical axes of optical components of the optical assembly when the optical assembly is positioned on the chuck, and the alignment device is configured to align the optical axes of the optical components to a deviation angle of less than about 1,000 μrad to provide an extinction ratio in the optical assembly of 1000:1 or greater.

[0007] In a second aspect related to the first aspect, the adjustable flexure assembly is rotatable about the reference axis.

[0008] In a third aspect related to the second aspect, the chuck is rotatable about the reference axis.

[0009] In a fourth aspect relating to any one of the first to third aspects, the chuck comprises a vacuum passage, and the optical assembly is supported on the chuck by vacuum pressure provided through the vacuum passage.

[0010] In a fifth aspect related to any one of the first through fourth aspects, the adjustable flexure assembly further comprises a tip tilt assembly disposed about the chuck, the tip tilt assembly comprising a base plate defining a support surface, an adjustable plate adjustably coupled to the base plate and supporting the multiple flexures, and one or more adjustment actuators configured to adjust a position of the adjustable plate relative to the support surface of the base plate.

[0011] In a sixth aspect relating to the fifth aspect, the present invention further comprises a column supporting the chuck, the adjustable flexure assembly being disposed about the column and slidable along the column so as to be adjustably positioned along the length of the column.

[0012] In a seventh aspect related to the fifth or sixth aspects, the base plate defines a base plate opening and the adjustable plate defines an adjustable plate opening aligned with the base plate opening, and the base plate opening and the adjustable plate opening are dimensioned to allow the chuck to pass therethrough.

[0013] In an eighth aspect relating to any one of the fifth to seventh aspects, the one or more adjustment actuators are configured to adjust an inclination of the adjustable plate relative to a support surface of the base plate.

[0014] In a ninth aspect relating to any one of the fifth through eighth aspects, the device further comprises a plurality of flexure clamps coupled to the adjustable plate.

[0015] In a tenth aspect related to the ninth aspect, each flexure clamp is coupled to the adjustable plate. Each flexure clamp comprises a fixed portion fixedly coupled to the adjustable plate, a sliding portion to which a predetermined flexure of the plurality of flexures is coupled, and a flexible webbing coupling the fixed portion to the sliding portion. The adjustable flexure assembly further comprises a slide actuator associated with each flexure clamp, the slide actuator configured to contact the sliding portion of the flexure clamp to displace the sliding portion relative to the adjustable plate, thereby deflecting the flexible webbing to adjust a position of the flexure coupled to the flexure clamp relative to the adjustable plate and the chuck.

[0016] In an eleventh aspect relating to the tenth aspect, the device further includes a plurality of stops coupled to the adjustable plate proximate the sliding portion of the flexure clamp, each stop limiting the sliding of the sliding portion of the flexure clamp.

[0017] In a twelfth aspect relating to any one of the first to eleventh aspects, the optical assembly further comprises a decentering measurement device configured to measure an optical axis alignment of one or more components of the optical assembly.

[0018] In a thirteenth aspect according to any one of the first to twelfth aspects, a force / displacement ratio applied to the optical component by the plurality of flexures is about 1.0×10 -6 N / mm~approx. 2×10 -6 N / mm.

[0019] In a fourteenth aspect relating to any one of the first to thirteenth aspects, each flexure of the plurality of flexures comprises a length to diameter ratio of about 80:1 to about 160:1.

[0020] In a fifteenth aspect, a method for aligning components of an optical assembly includes the steps of placing a first lens including a first lens optical axis on a chuck of an alignment device for aligning components of an optical assembly; applying a liquid to a bonding surface of the first lens; placing a second lens including a second lens optical axis on the bonding surface of the first lens such that the liquid is disposed between the first lens and the second lens; contacting an edge of the second lens with a plurality of flexures; and adjusting a position of one or more flexures of the plurality of flexures contacting the second lens, thereby aligning a second lens optical axis of the second lens with a first lens optical axis of the first lens.

[0021] A sixteenth aspect relating to the fifteenth aspect further includes the step of rotating the alignment device about the reference axis.

[0022] A 17th aspect relating to the 15th or 16th aspect further includes a step of measuring the optical axis alignment between the first lens and the second lens with an eccentricity measurement device, and a step of evaporating the liquid when the optical axis alignment between the first lens and the second lens is within a predetermined alignment range.

[0023] In an 18th aspect relating to any one of the 15th to 17th aspects, the first lens has a convex bonding surface, the second lens has a concave bonding surface, and the concave bonding surface of the second lens is in liquid contact with the convex bonding surface of the first lens.

[0024] In a nineteenth aspect, an optical assembly comprises a first lens, a second lens, and an optical adhesive bonding the first lens and the second lens. The first lens comprises a first lens optical axis, and the second lens comprises a second lens optical axis. The first lens optical axis is aligned with the second lens optical axis such that a deviation angle between the first lens optical axis and the second lens optical axis is less than about 1,000 μrad. During alignment of the first lens optical axis and the second lens optical axis, a liquid is disposed between the first lens and the second lens to reduce stress distribution within the optical assembly, and an extinction ratio of the optical assembly is 1000:1 or greater.

[0025] In a twentieth aspect relating to the nineteenth aspect, the first lens has a concave bonding surface, the second lens has a convex bonding surface, and the concave bonding surface of the first lens is bonded to the convex bonding surface of the second lens.

[0026] In a twenty-first aspect relating to the nineteenth or twentieth aspects, the original liquid comprises a viscosity of less than about 500 cps (about 500 mPa·s).

[0027] In a twenty-second aspect relating to any one of the nineteenth to twenty-first aspects, the original liquid has a viscosity of about 10 cps (about 10 mPa·s) to 500 cps (500 mPa·s).

[0028] In a twenty-third aspect relating to any one of the nineteenth to twenty-second aspects, a deviation angle between the first lens optical axis and the second lens optical axis is less than about 10 μrad.

[0029] In a twenty-fourth aspect relating to any one of the nineteenth to twenty-third aspects, a deviation angle between the first lens optical axis and the second lens optical axis is less than about 1 μrad.

[0030] In a twenty-fifth aspect relating to any one of the nineteenth to twenty-fourth aspects, the first lens is molecularly bonded to the second lens.

[0031] In a twenty-sixth aspect, a method for aligning a component of an optical assembly includes positioning a first lens including a first lens optical axis on an alignment device for aligning a component of the optical assembly. The alignment device includes a chuck configured to support the optical assembly and on which the first lens is positioned, and an adjustable flexure assembly disposed about the chuck and including a plurality of flexures. The plurality of flexures are positioned relative to the chuck such that each of the plurality of flexures contacts the optical assembly when the optical assembly is positioned on the chuck. Adjustment of a position of one or more of the plurality of flexures adjusts alignment of the optical axes of the optical components of the optical assembly when the optical assembly is positioned on the chuck. The method further includes the steps of applying a liquid to the bonding surface of the first lens; placing a second lens including a second lens optical axis on the bonding surface of the first lens such that the liquid is disposed between the first lens and the second lens; contacting an edge of the second lens with a plurality of flexures; adjusting a position of one or more of the plurality of flexures in contact with the second lens; and aligning the second lens optical axis of the second lens with the first lens optical axis of the first lens such that a deviation angle between the first lens optical axis and the second lens optical axis is less than about 1,000 μrad and an extinction ratio of the optical assembly is 1000:1 or greater.

[0032] A 27th aspect relating to the 26th aspect further includes a step of measuring the optical axis alignment between the first lens and the second lens with an eccentricity measurement device, and a step of evaporating the liquid when the optical axis alignment between the first lens and the second lens is within a predetermined alignment range.

[0033] In a 28th aspect relating to the 26th or 27th aspects, the first lens has a convex bonding surface, the second lens has a concave bonding surface, and the concave bonding surface of the second lens is in liquid contact with the convex bonding surface of the first lens.

[0034] In a 29th aspect relating to the 26th or 28th aspect, the liquid is an optical adhesive.

[0035] In a 30th aspect relating to the 29th aspect, the method further includes a step of curing the optical adhesive when the optical axis alignment between the first lens and the second lens is within a predetermined alignment range.

[0036] In a thirty-first aspect relating to any one of the twenty-sixth to thirtieth aspects, the adjustable flexure assembly is rotatable about a reference axis.

[0037] In a thirty-second aspect relating to the thirty-first aspect, the chuck is rotatable about a reference axis.

[0038] In a thirty-third aspect relating to any one of the twenty-sixth to thirty-second aspects, the chuck comprises a vacuum passage, and the optical assembly is supported on the chuck by vacuum pressure provided through the vacuum passage.

[0039] In a thirty-fourth aspect relating to any one of the twenty-sixth to thirty-third aspects, the adjustable flexure assembly further comprises a tip tilt assembly disposed about the chuck, the tip tilt assembly comprising a base plate defining a support surface, an adjustable plate adjustably coupled to the base plate and supporting the multiple flexures, and one or more adjustment actuators configured to adjust a position of the adjustable plate relative to the support surface of the base plate.

[0040] In a thirty-fifth aspect relating to the thirty-fourth aspect, the alignment device further includes a column supporting the chuck, the adjustable flexure assembly being disposed about the column and slidable along the column so as to be adjustably positioned along a length of the column.

[0041] In a thirty-sixth aspect relating to the thirty-fourth or thirty-fifth aspects, the base plate defines a base plate opening and the adjustable plate defines an adjustable plate opening aligned with the base plate opening, and the base plate opening and the adjustable plate opening are dimensioned to allow the chuck to pass therethrough.

[0042] In a thirty-seventh aspect relating to any one of the thirty-fourth to thirty-sixth aspects, the one or more adjustment actuators are configured to adjust an inclination of the adjustable plate relative to a support surface of the base plate.

[0043] In a thirty-eighth aspect relating to any one of the thirty-fourth to thirty-seventh aspects, the adjustable flexure assembly further comprises a plurality of flexure clamps coupled to the adjustable plate.

[0044] In a thirty-ninth aspect relating to the thirty-eighth aspect, each flexure clamp is coupled to the adjustable plate and comprises a fixed portion fixedly coupled to the adjustable plate, a sliding portion to which a predetermined flexure of the plurality of flexures is coupled, and a flexible webbing coupling the fixed portion to the sliding portion, and the adjustable flexure assembly further comprises a sliding actuator associated with each flexure clamp, the sliding actuator being configured to contact the sliding portion of the flexure clamp to displace the sliding portion relative to the adjustable plate, thereby bending the flexible webbing to adjust a position of the flexure coupled to the flexure clamp relative to the adjustable plate and the chuck.

[0045] In a fortieth aspect relating to the thirty-ninth aspect, the adjustable flexure assembly further includes a plurality of stops coupled to the adjustable plate proximate the sliding portion of the flexure clamp, each stop limiting sliding of the sliding portion of the flexure clamp.

[0046] In a forty-first aspect relating to any one of the twenty-sixth to fortieth aspects, the alignment device further comprises an eccentricity measurement device configured to measure optical axis alignment of one or more components of the optical assembly.

[0047] These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description taken in conjunction with the drawings. [Brief description of the drawings]

[0048] The embodiments described in the drawings are illustrative and exemplary in nature and are not intended to limit the subject matter defined by the claims. The following detailed description of illustrative embodiments can be understood when read in conjunction with the following drawings, in which like structure is indicated with like reference numerals and in which: [Figure 1A] 1 illustrates a pre-aligned orientation of components of an optical assembly according to one or more embodiments shown and described herein. [Figure 1B] 1B illustrates the optical assembly of FIG. 1A after alignment according to one or more embodiments shown and described herein. [Figure 2A] 1 illustrates an alignment device for aligning components of an optical assembly according to one or more embodiments shown and described herein. [Figure 2B] 2B illustrates a cross-section of the alignment device of FIG. 2A according to one or more embodiments shown and described herein. [Figure 2C] 2B illustrates a partial cross-section of the alignment device of FIG. 2A showing a tilted configuration in accordance with one or more embodiments shown and described herein. [Diagram 3] 1 illustrates a flowchart of a method for aligning components of an optical assembly according to one or more embodiments shown and described herein. [Figure 4A] 1 illustrates a first lens positioned on a chuck of an alignment apparatus according to one or more embodiments shown and described herein. [Figure 4B] 4B illustrates a second lens positioned over the first lens of FIG. 4A according to one or more embodiments shown and described herein. [Figure 4C] 1 illustrates an alignment of a first optical axis of a first lens with a second optical axis of a second lens according to one or more embodiments shown and described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] The embodiments described herein are directed to an apparatus and method for aligning components of an optical assembly. For example, an alignment apparatus for aligning components of an optical assembly can include a chuck configured to support the optical assembly and an adjustable flexure assembly. The adjustable flexure assembly can be disposed around the chuck and can include a plurality of flexures. The plurality of flexures is configured to contact the optical assembly, e.g., an edge of the optical assembly. Adjustment of the position of one or more of the plurality of flexures adjusts the optical axis alignment of one or more components (e.g., lenses) of the optical assembly. Thus, alignment of the optical axes of various components of the optical assembly can be achieved. The flexures can provide a slight contact force to displace the components of the optical assembly in alignment. Such a slight contact force can improve the quality and optical properties of the optical assembly by reducing force disturbances and stresses in the optical adhesive disposed between the optical components. Various embodiments of the alignment apparatus and method as well as the optical assembly shall be described in more detail herein.

[0050] Ranges can be expressed herein as from "about" one particular value and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by using the antecedent "about," it will be understood that the particular value forms another embodiment. The endpoints of each of the ranges are both significant in relation to the other endpoint and independent of the other endpoint.

[0051] Directional terms used herein, e.g., up, down, right, left, front, back, upper, bottom, top, lower, refer only to the drawings depicted and are not intended to imply absolute orientation.

[0052] Unless otherwise specified, it is never intended that any method described herein be construed as requiring that its steps be performed in a particular order, or that any apparatus require a particular orientation. Thus, where a method claim does not actually recite an order that its steps should be followed, or where any apparatus claim does not actually recite an order or orientation for individual components, or where the claims or description do not specifically state in any way that the steps are to be limited to a particular order, or where a particular order or orientation for the components of the apparatus is not recited, no order or orientation is ever intended to be inferred in any respect. This applies to any possible implicit basis for interpretation, including matters of logic regarding the arrangement of steps, operational flow, component order or component orientation, plain meaning derived from grammatical organization or punctuation, and the number or type of embodiments described herein.

[0053] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an "a" component includes aspects having two or more such components, unless the context clearly dictates otherwise.

[0054] 1A and 1B, an optical assembly 10 is generally depicted. As used herein, an "optical assembly" is an arrangement of optical components (e.g., lenses, mirrors, etc.) that direct the transmission of light. The optical assembly 10 can include various components, each of which includes an optical axis. As used herein, an optical axis is an imaginary line or line segment that passes through the center of curvature of the surface of a lens. In particular, the optical assembly 10 can include a first lens 20 that includes a first lens optical axis 21 and a second lens 30 that includes a second lens optical axis 31.

[0055] During conventional manufacturing of optical assemblies (e.g., doublets, triplets, etc.), precise alignment of the first lens optical axis 21 and the second lens optical axis 31 is desired. Alignment can be a tedious and difficult process, especially when dealing with lenses of various sizes, mating curvatures, and curvature orientations. For example, it can be difficult to stabilize the upper lens in a preferred orientation relative to the lower lens such that the optical axes 21, 31 are aligned. This can be especially true for small lenses with small radii of curvature (e.g., having diameters of 10 mm or less).

[0056] The embodiments described herein are directed to apparatus and methods for stabilizing upper and lower lenses to provide a desired alignment. Additionally, the embodiments provided herein can be used to align micro-optical components (e.g., lenses having edge thicknesses of 2-3 mm or less and diameters less than 8 mm). Additionally, the embodiments provided herein can provide low contact forces that do not stress the optical elements or connecting adhesive layers to the same extent as traditional assembly techniques (i.e., adhesives are at least partially cured during alignment). Additionally, the embodiments can provide fine adjustment for sub-micrometer and / or micrometer radian level alignment.

[0057] 1A and 1B, in Fig. 1A, the optical assembly 10 is misaligned. That is, the first lens optical axis 21 is misaligned with the second lens optical axis 31. For example, in this misaligned state, the deviation angle α between the first lens optical axis 21 and the second lens optical axis 31 is greater than a predetermined alignment range (e.g., greater than about 1,000 μrad, greater than about 500 μrad, greater than about 100 μrad, greater than about 10 μrad, greater than about 1 μrad, etc.) depending on the particular application or type of optical assembly.

[0058] 1B shows the first lens optical axis 21 aligned with the second lens optical axis 31. Although the first lens optical axis 21 is shown coincident with the second lens optical axis 31, the optical assembly 10 may be considered aligned if the deviation angle α between the first lens optical axis 21 and the second lens optical axis 31 is within a predetermined alignment range. For example, alignment may be achieved when the deviation angle α is less than about 1,000 μrad, less than about 500 μrad, less than about 100 μrad, less than about 10 μrad, less than about 1 μrad, etc. The predetermined threshold value for the deviation angle α may be determined by the particular constraints or end use of the optical assembly 10.

[0059] In the embodiments described herein, the first lens 20 can be a convex lens (e.g., biconvex, equiconvex, plano-convex, convex-concave, meniscus, etc.) such that at least one surface of the first lens 20 through which the first lens optical axis 21 extends is convex. For example, the first lens 20 can include a first lens first surface 22 and a first lens bonding surface 24 opposite the first lens first surface 22. In particular, the first lens bonding surface 24 can be a convex bonding surface.

[0060] It is noted that although the opposing surfaces of first lens 20 (i.e., first lens first surface 22 and first lens bonding surface 24) are shown as being convex, in embodiments, only one surface of first lens 20 can be convex, while the opposing surface is flat or concave. In embodiments where the opposing surfaces of first lens 20 are both convex, the radii of curvature can be the same or different.

[0061] The second lens 30 can be a concave lens (e.g., biconcave, equiconcave, plano-concave, meniscus, convex-concave, etc.) such that at least one surface of the second lens 30 through which the second lens optical axis 31 extends is concave. For example, the second lens 30 can include a second lens first surface 34 and a second lens bonding surface 32 opposite the second lens first surface 34. In particular, the second lens bonding surface 32 can be a concave bonding surface.

[0062] It is noted that although the opposing surfaces of the second lens 30 (i.e., the first surface 34 of the second lens and the bonding surface 32 of the second lens) are shown as being concave, in embodiments, only one surface can be concave, while the opposing surface is flat or convex. In embodiments where the opposing surfaces of the second lens 30 are both concave, the radii of curvature can be the same or different.

[0063] 1A and 1B , the concave bonding surface 32 of the second lens 30 may be adhered to the convex bonding surface 24 of the first lens 20 by an optical adhesive 40. In an embodiment, the concave bonding surface 32 and the convex bonding surface 24 may have similar radii such that the convex bonding surface 24 of the first lens 20 nests within the concave bonding surface 32 of the second lens 30.

[0064] When the optical assembly 10 includes only the first lens 20 and the second lens 30, as shown in FIG. 1A and FIG. 1B, the optical assembly 10 can be referred to as a doublet. However, it is noted that additional lenses can be added to the optical assembly 10. For example, a third lens can be bonded to a free surface of the optical assembly 10 (e.g., the third lens can be bonded to the first surface 22 of the first lens or the first surface 34 of the second lens). The third lens can be convex, concave, or flat to mate with the surface of the first lens 20 or the second lens 30. An optical assembly 10 having three lenses can be referred to as a triplet. The third lens can be bonded to the optical assembly 10 using the same or a different optical adhesive as that used to bond the first lens 20 to the second lens 30. It is noted that a larger number of lenses can be bonded together to form an optical assembly.

[0065] As described above, the optical adhesive 40 is provided to bond the first lens 20 to the second lens 30. The properties (e.g., refractive index, thickness, coefficient of thermal expansion, etc.) of the optical adhesive 40 used to bond the lenses of the optical assembly 10 may affect the optical performance. In particular, the optical adhesive may be selected to enhance salient properties of the final optical assembly. The optical adhesive may also be selected based on adhesive properties, such as cure time, cure temperature, shrinkage, etc., that may affect the manufacturability of the optical assembly 10. Thus, any commercially available optical adhesive may be used depending on the particular application. In an embodiment, the optical adhesive may be provided as a liquid. The optical adhesive 40 may be applied between the lenses and then cured (e.g., by UV curing, IR curing, thermal curing, timed curing, etc.) once the desired alignment between the lenses is achieved. In embodiments, optical adhesive 40 can have a pre-cured or uncured viscosity of less than about 500 cps or between about 10 cps and 500 cps, although it should be understood that other viscosities for optical adhesive 40 are contemplated and possible. In some embodiments, optical adhesive 40 can be applied in a layer that is between about 10 μm and about 15 μm thick.

[0066] As mentioned above, manufacturing an optical assembly having two or more lenses can be tedious. In particular, it can be difficult to properly align the optical axes of the various lenses. In addition, curing the optical adhesive 40 during alignment can affect the optical properties of the optical assembly 10. Traditionally, one technique for providing stable positioning of the lenses during assembly is to use a viscous adhesive, which can allow for reduced positioning drift (e.g., slipping off) of a lens relative to another lens. However, such a viscous adhesive can have inferior optical properties compared to a low viscosity adhesive. Another technique can be to partially cure the optical adhesive 40, which can increase the viscosity of the optical adhesive 40 and improve the response of the lenses to forces during alignment. However, the optical properties of the optical adhesive 40 can be adversely affected by the introduction of shear stress or compression during the partially cured stage, which can result in stress birefringence in the optical assembly 10. The introduction of stress and the resulting stress birefringence degrades the optical quality of the optical assembly 10. For example, stress birefringence may induce a change in the polarization state of transmitted light. The embodiments provided herein may include aligning the optical axes of various components of the optical element with the optical adhesive 40 in a liquid, uncured state to reduce or substantially eliminate the introduction of stress during the alignment step. Thus, a reduced stress distribution within the optical assembly 10 may be achieved, as opposed to optical assemblies in which alignment is performed while the optical adhesive 40 is at least partially cured.

[0067] For example, the optical adhesive 40 can be provided as a liquid adhesive that is coated or otherwise applied to the bonding surface 24 of the first lens, the bonding surface 32 of the second lens, or a combination thereof. While the optical adhesive 40 is in an uncured liquid state, the optical axis 21 of the first lens and the optical axis 31 of the second lens can be aligned using an apparatus and method as described in more detail herein. Once aligned to a predetermined alignment threshold, the optical adhesive 40 can be cured to securely fix the first lens 20 to the second lens 30. Because the optical adhesive 40 is provided in a liquid uncured state, the optical adhesive 40 can function as a liquid bearing that supports the movement of the first lens 20 and / or the second lens 30 to align their respective optical axes 21, 31. Thus, excessive stresses and corresponding stress birefringence introduced into the optical assembly 10 can be avoided.

[0068] 2A and 2B, an embodiment of an alignment apparatus 100 for aligning the optical axes of two or more components of the optical assembly 10 is depicted in schematic form. The alignment apparatus 100 generally includes a chuck 112 and an adjustable flexure assembly 120. As used herein, a "chuck" is any device that holds a workpiece (e.g., a lens) in place. The chuck 112 and the adjustable flexure assembly 120 may be mounted to a rotation mechanism (e.g., a rotating platform, a rotating bearing, etc.) that defines a reference axis 102. As used herein, a "reference axis" is an axis to which geometric and / or dimensional tolerances are referenced. The chuck 112 and the adjustable flexure assembly 120 may be mounted to the rotation mechanism to rotate on a common axis of rotation that corresponds to the reference axis 102 for aligning the components of the optical assembly 10. The chuck 112 and the adjustable flexure assembly 120 may rotate about the reference axis 102 in synchronization with one another. For example, but not by way of limitation, the column 104 supporting both the chuck 112 and the adjustable flexure assembly 120 may be coupled to a motor (not shown) that may be controlled (e.g., by an electronic controller) to rotate the chuck 112 and the adjustable flexure assembly 120. In an embodiment, the chuck 112 and the adjustable flexure assembly 120 may be freely rotatable (e.g., via bearings) by manual actuation (e.g., a turntable, etc.). In an embodiment, the alignment apparatus 100 may be aligned with the reference axis 102 without rotating about the reference axis 102, or the reference axis 102 may be defined in some manner.

[0069] The column 104 can include a top surface 106 to which the chuck 112 can be attached. In embodiments, the column 104 and the chuck 112 can be integral with one another. In embodiments, the column 104 and the chuck 112 can be separate components that can mate with one another to securely couple the chuck 112 to the column 104. For example, with reference to FIG. 2B, the column 104 can define a chuck receiving opening 108 configured to receive a mating portion 114 of the chuck 112 therein. For example, the mating portion 114 can nest within the chuck receiving opening 108 of the column 104. In embodiments, a retention tab 115 can engage the chuck receiving opening 108 to prevent withdrawal of the chuck 112 in the +Z direction of the illustrated coordinate axis. Other engagement mechanisms (e.g., fasteners, welding, brazing, etc.) can be used to attach the chuck 112 to the column 104.

[0070] The chuck 112 is configured to support the optical assembly 10 thereon. For example, the chuck 112 can include a support 118 configured to engage and hold the optical assembly 10. For example, the support 118 can be a tubular wall extending from the body 117 of the chuck 112. The tubular wall can be configured to contact only a portion of the surface of the optical assembly 10 (e.g., the surface of the first lens 20). The tubular shape of the wall allows for avoidance of contact with quality regions of the first lens 20 (e.g., regions toward the center of curvature of the first lens 20), thus preserving the surface quality and optical performance of the first lens 20. It is noted that the tubular wall can have any cross-section (e.g., circular, elliptical, rectangular, or other regular or irregular polygonal) without departing from the scope of the present disclosure.

[0071] In an embodiment, the optical assembly 10 is secured to the chuck 112 via one or more securing means. Such securing means may include, but are not limited to, for example, temporary adhesives, vacuum pressure, and the like. If vacuum pressure is used, the chuck 112 may be plumbed to a vacuum pressure source (not shown) such that vacuum pressure may be achieved through the support 118 of the chuck 112 to hold the optical assembly 10 to the chuck 112. In some embodiments, a vacuum passage 119 may extend from the support 118 of the chuck 112 through the column 104 to provide fluid communication between the vacuum pressure source (not shown) and the support 118 of the chuck 112.

[0072] Referring again to FIG. 2A, the adjustable flexure assembly 120 may be disposed about the chuck 112 and may include a plurality of flexures (e.g., flexures 150a, 150b, 150c) configured to contact components (e.g., lenses) of the optical assembly 10 positioned on the chuck 112. As used herein, a "flexure" is a flexible element that is elastically displaceable and recoverable in at least one plane. For example, the plurality of flexures 150a, 150b, 150c may be elastically displaceable and recoverable in a plane parallel to at least a portion of each of the plurality of flexures 150a, 150b, 150c. For example, FIG. 2A illustrates each of the flexures 150a, 150b, 150c extending parallel to the XY plane of the illustrated coordinate axes. The flexures 150a, 150b, 150c are elastically displaceable and recoverable in the XY plane to contact edges of the optical assembly 10 to adjust the alignment of the optical assembly 10. In further embodiments, the multiple flexures 150a, 150b, 150c can be elastically displaceable and recoverable through other or multiple planes (e.g., the XZ plane, the YZ plane, and / or any plane angled relative to the XY, XZ, and / or YZ planes).

[0073] Each flexure 150a, 150b, 150c may be coupled to and cantilevered from a corresponding flexure clamp 162 (described in more detail herein). For example, with reference to flexure 150a, a first end 152 of flexure 150a may be held securely by a dedicated flexure clamp 162, and a second end 153 of flexure 150a may extend beyond the support 118 of the chuck 112 so as to be cantilevered from the end of the flexure clamp 162. The length that flexures 150a, 150b, 150c extend from their corresponding flexure clamp 162 may depend on the size of the optical assembly 10 being aligned. For example, each flexure 150a, 150b, 150c may extend to tangentially contact an edge of the optical assembly 10 or a subcomponent thereof (e.g., second lens 30) when the optical assembly 10 is placed in the chuck 112. In some embodiments, it is contemplated that one or more of the flexures 150a, 150b and / or 150c may be oriented toward the edge of the optical assembly 10 in a direction perpendicular to the edge of the optical assembly 10. In some embodiments, multiple flexures 150a, 150b, 150c may be positioned to be oriented perpendicular to a vertical axis (e.g., the Z axis of the illustrated coordinate system) and radially contact the edge of the optical assembly 10.

[0074] Each of the flexures 150a, 150b, 150c can be made of a resilient material configured to apply a force to one or more components of the optical assembly 10. For example, each of the flexures 150a, 150b, 150c can be a wire made of steel, plastic, or the like. Each of the flexures can have a circular, square, rectangular, or any other cross-section. Additionally, while each of the flexures is shown as a straight wire, in various embodiments, the flexures can have various contour shapes (e.g., curved, hooked, S-shaped, O-shaped, etc.). Contact of the multiple flexures 150a, 150b and / or 150c with the optical assembly 10 may cause one or more of the flexures to bend. Because the flexures 150a, 150b, 150c are resilient, they resist bending and therefore apply a radial adjustment force to the components of the optical assembly 10 with which the flexures 150a, 150b, 150c are in contact. It is contemplated that the plurality of flexures 150a, 150b, and / or 150c may distort when contacted by the optical assembly 10, although such distortion may be on a small scale. For example, the distortion or bending may be on the scale of tens of nanometers (e.g., less than about 10 mm, less than about 8 mm, less than about 6 mm, about 1 nm to about 10 mm, e.g., about 1 nm to about 8 mm, about 1 nm to about 6 mm, etc.) relative to the initial position of the flexures 150a, 150b, 150c. The amount of distortion or bending is measured at the free end of the flexures 150b, 150c (i.e., the end of the flexure proximate the optical assembly 10) and is the difference in the position of the flexures 150a, 150b, 150c before bending (i.e., the initial position) and after bending (i.e., the final position). A subcomponent of the optical assembly 10 (e.g., the second lens 30) is initially misaligned (e.g., the optical axis is not aligned within an acceptable range) so that the force imbalance provided by the multiple flexures 150a, 150b, 150c guides the optical component into the desired alignment.

[0075] Each flexure 150a, 150b, 150c can have a flexure stiffness (or elasticity) that can be selected based on the size of the lens and / or the viscosity of the optical adhesive 40 used to bond the components of the optical assembly 10. For example, larger lenses may benefit from stiffer flexures to affect adjustment, while smaller lenses may require more flexible flexures to provide fine adjustment. Additionally, optical adhesives 40 with higher viscosity may benefit from flexures with higher flexure stiffness to overcome the damping forces of the optical adhesive 40.

[0076] The adjustable flexure assembly 120 facilitates adjustment of the position of one or more of the flexures 150a, 150b, 150c relative to the support 118 of the chuck 112 to adjust the alignment of the optical axes of one or more components of the optical assembly 10 supported on the support 118 of the chuck 112. For example, to facilitate adjustment of the position of the multiple flexures 150a, 150b, 150c, the adjustable flexure assembly 120 may include a tip tilt assembly 122. The tip tilt assembly 122 may include a base plate 124, an adjustable plate 130, and one or more adjustment actuators 136 (shown in FIG. 2B). As described in more detail herein, the adjustable plate 130 may be tilted relative to the base plate 124 to adjust the position of the multiple flexures (150a, 150b, 150c) coupled thereto.

[0077] The base plate 124 can include a base plate opening 126 for slidably receiving the column 104 and chuck 112. For example, the base plate 124 can be positionable in the + / -Z direction of the indicated coordinate axes along the column 104. For example, the base plate 124 can be slid along the column 104 to a desired position and then secured thereto by a securing structure 121 (e.g., a bracket, collar, clamp, etc.).

[0078] The base plate 124 can define a support surface 128 on which the adjustable plate 130 can be positioned. While the base plate 124 is shown as circular, it is noted that the base plate 124 can be any shape (e.g., oval, rectangular, or any regular or irregular polygon) without departing from the scope of the present disclosure. As shown, the base plate opening 126 is sized to allow the column 104 and chuck 112 to pass therethrough, allowing height adjustment of the base plate 124 in the + / -Z direction of the coordinate axes shown relative to the column 104. By positioning the base plate 124 relative to the column 104, the entire tip tilt assembly 122 can be moved relative to the support 118 of the chuck 112. Thus, optical assemblies of different dimensions can be aligned using the alignment apparatus 100. That is, as an additional lens is added to the optical assembly 10 positioned on the support 118 of the chuck 112, the base plate 124 can move the column 104 upward in the +Z direction of the indicated coordinate axis to allow for adjustment of the added lens.

[0079] Additionally, to facilitate adjustment of the entire tip tilt assembly 122 relative to the column 104, the adjustable plate 130 can define an adjustable plate opening 132 that aligns with the base plate opening 126 of the base plate 124 such that a continuous opening extends through the base plate 124 and the adjustable plate 130. It is noted that although the base plate opening 126 and the adjustable plate opening 132 are shown as having substantially equal diameters, in embodiments the base plate opening 126 and the adjustable plate opening 132 can have different diameters.

[0080] The adjustable plate 130 may be coupled to the base plate 124 via one or more adjustment actuators 136. As used herein, an adjustment actuator includes any device configured or capable of adjusting in any manner a position (e.g., tilt or position) of the adjustable plate 130 relative to the support surface 128 of the base plate 124. The one or more adjustment actuators 136 may include any actuator capable of tilting or otherwise adjusting the position of the adjustable plate 130 relative to the support surface 128 of the base plate 124. In an embodiment, the one or more adjustment actuators 136 may include multiple adjustment actuators. In an embodiment, the number of adjustment actuators may correspond to the number of flexures disposed on the adjustable plate 130. For example, if there are three flexures 150a, 150b, 150c, there will be three adjustment actuators corresponding to the positions of the three flexures 150a, 150b, 150c, allowing fine adjustment of the position of each of the flexures 150a, 150b, 150c.

[0081] 2B illustrates a specific example of an actuator for the one or more adjustment actuators 136. In such an embodiment, the one or more adjustment actuators 136 may include a push bar 138 (e.g., a fine pitch screw) that extends through the thickness T of the base plate 124 to contact the underside 134 of the adjustable plate 130. The push bar 138 may include a first end 140 and a second end 141. The first end 140 of the push bar 138 may be coupled to an adjuster 142 (e.g., a crank, knob, rotary actuator, etc.) configured to adjust the length of the push bar 138 that extends through the support surface 128 of the base plate 124 by rotating the push bar 138.

[0082] A second end 141 of the push bar 138 may extend through the support surface 128 of the base plate 124 and contact the underside 134 of the adjustable plate 130. In embodiments, the second end 141 of the push bar 138 may be coupled (e.g., pivotally coupled) to the underside 134 of the adjustable plate 130 to allow the adjustable plate 130 to tilt about the second end 141 of the push bar 138 without coming off thereof.

[0083] In embodiments, the push bar 138 can be threaded along its length between the first end 140 and the second end 141. The threads can engage with a threaded passageway 144 extending through the base plate 124. In such embodiments, twisting motion of the push bar 138 can enable the push bar 138 to traverse the threaded passageway 144 and extend through the support surface 128 of the base plate 124, pushing the adjustable plate 130 out of contact with the base plate 124. Thus, the adjustable plate 130 can be tilted at a tilt angle β relative to the support surface 128 of the base plate 124, as shown in FIG. 2C. When in contact with a lens, tilting the adjustable plate 130 can cause the multiple flexures 150a, 150b and / or 150c to push or tilt the position of the lens they are in contact with so as to urge the lens into a position that aligns the optical axis of the lens they are in contact with (e.g., the second lens 30) with the optical axis of the first lens 20.

[0084] 2A, each flexure (150a, 150b, 150c) of the plurality of flexures can be part of a flexure assembly (e.g., flexure assembly 161a, 161b, or 161c) coupled to the upper surface 135 of the adjustable plate 130. In the illustrated embodiment, a first flexure assembly 161a, a second flexure assembly 161b, and a third flexure assembly 161c are provided. However, there may be a fewer or greater number of flexure assemblies without departing from the scope of the present disclosure. Each of the flexure assemblies 161a, 161b, and 161c can include a flexure clamp 162, a sliding actuator 164, and a stop 166. That is, the alignment device 100 can include a plurality of flexure clamps, a plurality of sliding actuators, and a plurality of stops. It is noted that each of the flexure assemblies 161 a , 161 b , 161 c may be substantially identical to one another and may be circumferentially spaced apart about the chuck 112 .

[0085] As used herein, a "flexure clamp" may include any device capable of attaching a flexure (e.g., flexures 150a, 150b, and / or 150c) to adjustable plate 130. Flexure clamp 162 may include a fixed portion 163 fixedly coupled to upper surface 135 of adjustable plate 130, and a sliding portion 165 configured to slidably move across upper surface 135 of adjustable plate 130 in response to application of a force to sliding portion 165. To facilitate such sliding movement, sliding portion 165 may be coupled to fixed portion 163 via flexible webbing 177. As used herein, the term "flexure webbing" is a portion of flexure clamp 162 that has a small cross-section relative to fixed portion 163 of flexure clamp 162. The small cross-section allows flexible webbing 177 to be elastically displaceable and recoverable in at least one plane. In an embodiment, the flexible webbing 177 can be integral with the sliding portion 165 and the fixed portion 163 or can be a separate item coupled to the sliding portion 165 and the fixed portion 163 by any coupling technique (adhesive, welding, fasteners, etc.). For example, the flexure clamp 162 can be machined or otherwise formed from the same block of material (e.g., plastic, metal, etc.) such that the fixed portion 163, the sliding portion 165 and the flexible webbing 177 are integrally formed. The flexible webbing 177 can have a thickness of about 3 mm or less (e.g., about 2 mm or less, about 1 mm or less, etc.). As discussed above, the flexible webbing 177 is elastically displaceable and recoverable in at least one plane. In particular, the flexible webbing 177 can be elastically displaceable and recoverable in a plane parallel to the top surface 135 of the adjustable plate 130. That is, the flexible webbing 177 can have a flexural stiffness that provides some resistance to bending and a tendency to return to its previous shape before bending. Such flexural stiffness may allow fine (nanometer-scale) adjustments to the portion of the slider 165 across the top surface 135 of the adjustable plate 130.

[0086] The fixed portion 163 of the flexure clamp 162 may be fixedly coupled to the adjustable plate 130, for example, by bolts 176 or other coupling devices or methods (e.g., fastening, gluing, brazing, welding, etc.). The slide 165 may define a flexure support surface 172 for supporting a flexure (e.g., flexure 150a). The slide 165 may include a clamping device 174 configured to fix the position of the flexure 150a to the flexure support surface 172. Thus, the clamping device 174 may include any device configured to rigidly hold a portion of the flexure 150a to the slide 165. For example, one or more bolts may be coupled to the slide 165 to clamp the flexure 150a to the slide 165 with flanges (or washers) of the one or more bolts.

[0087] During adjustment, the slider 165 is configured to slide across the upper surface 135 of the adjustable plate 130 when a force is applied thereto. This force introduces a bending moment into the flexible webbing 177. This may allow positioning of the flexures 150a relative to the optical assembly 10 supported on the chuck 112 to facilitate alignment of different sized optical assemblies (e.g., optical assemblies having larger or smaller diameters (e.g., less than 8 mm)).

[0088] A sliding actuator 164 can be coupled to the top surface 135 of the adjustable plate 130. As used herein, a "sliding actuator" can include any device that can slide or displace the sliding portion 165 of the flexure clamp 162 to a desired position relative to the adjustable plate 130. For example, the sliding actuator 164 can be positioned on one side of the sliding portion 165 of the flexure clamp 162. The sliding actuator 164 can include a plunger 180 (e.g., a fine pitch screw) that can be extended or retracted (e.g., manually using a handle, crank, or similar device or using an electronic actuator). The plunger 180 can contact and push against the sliding portion 165 of the flexure clamp 162, thereby introducing a bending moment into the flexible webbing 177. This bending moment displaces the sliding portion 165 to a desired position. In some embodiments, the plunger 180 may be coupled to the sliding portion 165 of the flexure clamp 162 to facilitate sliding the sliding portion 165 in a clockwise and / or counterclockwise direction about the fixed portion 163 across the top surface 135 of the adjustable plate 130. In other embodiments, the plunger 180 may not be coupled to the sliding portion 165 of the flexure clamp 162. For example, the plunger 180 may move the sliding portion 165 of the flexure clamp 162 across the top surface 135 of the adjustable plate 130 simply by contacting the sliding portion 165 of the flexure clamp 162 and then move out of contact with the sliding portion 165 of the flexure clamp 162 such that the sliding portion 165 is biased back to its original position by the flexible webbing 177. The plunger 180 may be controllably positioned by an electronic, pneumatic or hydraulic actuator using an electronic controller or may be advanced and / or retracted manually.

[0089] A stop 166 can be coupled to the adjustable plate 130 proximate the slide 165 and on the opposite side of the slide 165 of the flexure clamp 162 from the slide actuator 164. The stop 166 can be positioned, for example, to limit further displacement of the slide 165 of the flexure clamp 162 in a clockwise direction about the fixed portion 163. The stop 166 can include a stop member 167 (e.g., a bolt, set screw, spring, etc.) or similar structure that can be advanced into contact with the slide 165 of the flexure clamp 162 to firmly hold the slide 165 of the flexure clamp 162 in a desired position between the slide actuator 164 and the stop 166. Similar to the plunger 180, the stop member 167 can be controllably positioned by an electronic, pneumatic, or hydraulic actuator using an electronic controller, or can be advanced and / or retracted manually.

[0090] During use, the slide 165 of the flexure clamp 162 can be moved by one or more slide actuators 164 to bring the plurality of flexures 150a, 150b, 150c into contact with a top lens (e.g., second lens 30) of the optical assembly 10. Such contact can introduce a bending moment into one or more of the flexures 150a, 150b and / or 150c of the plurality of flexures 150a, 150b, 150c. This bending moment biases the top lens into a desired alignment. To mitigate the induction of stresses in the components of the optical assembly 10 or the optical adhesive 40 during alignment, the force applied by the plurality of flexures 150a, 150b, 150c to the optical assembly 10 can be relatively low. For example, the force / displacement ratio of each of the plurality of flexures 150a, 150b, 150c is approximately 1.0×10 -6 N / mm~approx. 2×10 -6The bending of a flexure may be equal to N / mm. The bending of a flexure is proportional to the cube of the length of the flexure and inversely proportional to the fourth power of the diameter of the flexure. For example, a steel flexure having a diameter of 0.25 to 0.5 mm and a length of about 20 to about 40 mm provides a length to diameter ratio of about 80:1 to about 160:1, and when displacing a lens having a mass of less than 10 grams, the force / displacement ratio can be approximated using conventional beam bending calculations. As noted above, such a force / displacement ratio is approximately 1.0×10 -6 N / mm~approx. 2×10 -6 The flexure may be equal to 100 N / mm and may provide sufficient force for fine (e.g., micrometer radian or sub-micrometer level) adjustment and sufficient friction to maintain contact with the optical assembly 10. It is noted that the more the flexure of the flexure, the less force it applies to the components of the optical assembly 10. Conversely, too little flexure may not allow for fine adjustments to align the optical axis of the optical assembly 10.

[0091] It is noted that the plurality of flexures 150a, 150b, and 150c can be moved into contact with a component of the optical assembly 10 such that only one of the plurality of flexures 150a, 150b, and 150c bends, thereby providing an increased force on the optical assembly 10 at that flexure. Meanwhile, the total resultant force acting on the optical assembly 10 does not change significantly because the balance of the two opposing flexures (e.g., non-bending flexures) increases the force of the one bending flexure. This imbalance causes the component of the optical assembly 10 to contact the plurality of flexures 150a, 150b, and 150c and move into alignment while maintaining a low stress state within the optical assembly 10.

[0092] 4A-4C, the alignment device 100 may further include a centering measurement device 400, e.g., an alignment telescope, a displacement measurement sensor, or other metrology device, configured to measure the optical axis alignment of one or more components of the optical assembly. For example, the commercially available Trioptics OpticCentric® measurement device uses an optical signal directed at the optical article to determine the position of the optical axis of the top lens and provide feedback regarding the alignment. The centering measurement device 400 may detect or in some manner measure the position of the optical axis of the top lens relative to the reference axis 102 and provide position feedback to a user, an electronic controller, or a combination thereof. Based on this information, the user or electronic controller may adjust the position of one or more flexures 150a, 150b, and / or 150c (e.g., by one or more adjustment actuators 136 and / or one or more sliding actuators 164) to align the optical axes 21, 31, as desired. As shown in FIGS. 4A-4C, an eccentricity measurement device 400 can be positioned on the support 118 of the chuck 112 to measure the optical alignment of the optical assembly 10 positioned thereon.

[0093] 3 illustrates a flow chart of a method 200 for aligning components of the optical assembly 10. Although the method 200 illustrates several steps in a particular order, it is noted that more or fewer steps may be performed without departing from the scope of the present disclosure. Additionally, such steps may be performed in an order different from that illustrated without departing from the scope of the present disclosure.

[0094] In a first step 202, the first lens 20 of the optical assembly 10 can be positioned on the support 118 of the chuck 112 as described above. The first lens 20 can be held in place using, for example, vacuum pressure as described herein. The first lens optical axis 21 can be aligned with the reference axis 102 of the assembly. For example, the decentering measurement device 400 can be used to determine and position the alignment of the first lens optical axis 21 of the first lens 20 to be aligned with the Z-axis of the illustrated coordinate system. In the illustrated embodiment, the first lens 20 is a biconvex lens. It is noted that placing the convex side of the first lens 20 in contact with the chuck 112 allows the chuck 112 to better seal against the lens. It is also noted that the first lens 20 can be any other type of lens described herein.

[0095] Once aligned with and attached to the chuck 112, the first lens bonding surface 24 of the first lens 20 can be coated with an optical adhesive 40 as described herein in step 204. The optical adhesive 40 can be applied in a liquid state. In step 206, the second lens 30 can be placed on the first lens 20. The second lens bonding surface 32 of the second lens 30 can also be coated with the liquid optical adhesive 40. The second lens 30 can be a concave lens to mate with the convex surface of the first lens 20. The multiple flexures (150a, 150b, 150c) can be positioned so as not to contact any portion of the optical assembly 10 during initial engagement of the first lens 20 and the second lens 30. Once the second lens 30 is positioned over the first lens 20, as shown in FIG. 4B, the operator may move the multiple flexures (150a, 150b, 150c) in step 210 to contact the edge 36 of the second lens 30. As described above, the multiple flexures (150a, 150b, 150c) may be brought into contact with the top surface of the lens (e.g., if the top lens has a convex top surface and a very small edge surface) by applying a force to the slider 165 of one or more flexure clamps 162 via one or more slide actuators 164 to introduce a bending moment into the flexible webbing 177 and allow the slider 165 to slide across the top surface 135 of the adjustable plate 130. It is noted that while the sliding portion 165 can slide across the top surface 135 of the adjustable plate 130, the sliding portion 165 need not be in contact with the top surface 135 of the adjustable plate 130. For example, as shown in FIG. 2B, in some embodiments, the sliding portion 165 and flexible webbing 177 can be spaced apart from the adjustable plate 130 in the Z direction of the illustrated coordinate axis such that a gap 173 separates the sliding portion 165 and the top surface 135 of the adjustable plate 130. Thus, friction between the sliding portion 165 and the adjustable plate 130 can be avoided.When sliding the slider 165, the flexible webbing 177 can deflect a small amount (e.g., less than about 1 mm, less than 10 μm, less than 100 nm, etc.) to position the multiple flexures 150a, 150c, 150b. Additionally, the tip tilt assembly 122 can adjust the tilt of the adjustable plate 130 relative to the base plate 124 for proper positioning of one or more flexures 150a, 150b, 150c to contact non-quality areas of the lens. Avoiding contact with quality areas of the lens (e.g., away from the optical axis) can prevent undesired damage to the quality areas of the lens.

[0096] The decentering measurement device 400 can measure the optical axis alignment of the second lens optical axis 31 relative to the reference axis 102 with which the first lens optical axis 21 is aligned. Based on feedback that can be provided to the operator via a user interface, e.g., a display, the operator or electronic controller can, in step 212, adjust one or more of the multiple flexures (e.g., flexures 150a, 150b and / or 150c), e.g., by one or more adjustment actuators 136 and / or one or more sliding actuators 164, to gently move the second lens optical axis 31 of the second lens 30 into alignment with the first lens optical axis 21 of the first lens 20 within an acceptable range. As described herein, the second lens 30 can be moved into the aligned position while the optical adhesive 40 is in a liquid and uncured state, such that the optical adhesive 40 acts as a liquid bearing to reduce the introduction of stresses into the layer of optical adhesive 40, such as may occur when the optical adhesive 40 is partially cured. Throughout the measurement and alignment, the alignment device 100 can be rotated (e.g., at about 100 RPM) about the reference axis 102. Once alignment is achieved within a desired tolerance (which may take less than 15 minutes or about 5-15 minutes), the optical adhesive 40 can be cured (e.g., by IR curing, time, UV curing, or a combination thereof) in step 214. After curing, the process can be repeated with additional lenses added to the optical assembly 10. As noted above, the height of the adjustable flexure assembly 120 can be adjusted along the column 104 to facilitate adding additional lenses to the optical assembly 10.

[0097] In some embodiments, the optical adhesive 40 can be replaced with a temporary liquid that acts as a liquid bearing to aid in alignment. Examples of temporary liquids include, but are not limited to, water, alcohol, hydroxide solutions, any combination thereof, and the like. Such temporary liquids can be evaporated to initiate very intimate contact of the surfaces of the first and second lenses and / or allow atomic level chemical bonding between the surfaces. For example, once proper alignment is achieved, the liquid can be evaporated such that the two opposing surfaces of the first lens 20 and the second lens 30 remain aligned and in contact with each other, as described above. An atomic or molecular level bond (e.g., by diffusion bonding, optical contact bonding, chemically activated bonding, and the like) can then be achieved between the first lens 20 and the second lens 30 to provide an adhesive-free bond. That is, the embodiments described herein can perform alignment using adhesive 40 or other low viscosity liquids (e.g., less than about 500 cps or between about 10 cps and 500 cps). Thus, any discussion provided above regarding alignment using an optical adhesive is equally applicable to alignment using a temporary liquid that is subsequently evaporated.

[0098] Alignment using the alignment apparatus 100 described herein can reduce stress in the optical assembly 10. As described above, stress can cause birefringence. Birefringence induces a change in the polarization state of the transmitted light through the optical assembly 10. Alignment using the described methods and apparatus allows the polarization state of the light transmission through the assembly or system to be maintained to maximize the transmitted intensity or transmitted intensity uniformity of the system. This characteristic can be quantified using conventional optical polarization measurement equipment (e.g., including but not limited to a polarized light source, one or more wave plates, an analyzing polarizer and / or detector) and the article or system under test to determine the polarization transmission efficiency ratio or, conversely, the extinction ratio for a particular polarization state. For example, polarization performance measurements can be made with a polarizer for the appropriate wavelength and a commercially available polarimeter instrument from, for example, Hinds Instruments™ (e.g., Stokes Polarimeters) or Ilis (e.g., Strain Scope®) to perform intensity detector or optical retardation measurements. For example, articles with little birefringence can be quantified by very high extinction ratios (e.g., 10,000:1 or more) when evaluated by a linear polarizer measurement device. Optical assemblies with significant birefringence may exhibit extinction ratios on the scale of 100:1 or 200:1. Optical assemblies subjected to the alignment methods and apparatus described herein exhibit extinction ratios of more than 1000:1 (e.g., more than 1200:1, more than 1400:1, more than 1600:1, etc.). On the other hand, optical assemblies manufactured using partially cured adhesives often have extinction ratios of less than 1000:1 or even less than 600:1. Thus, the embodiments described herein provide reduced stress during alignment compared to optical assemblies aligned using partially cured adhesives.

[0099] It should be understood that the embodiments provided herein are directed to an apparatus and method for aligning components of an optical assembly. For example, an alignment apparatus for aligning components of an optical assembly can include a chuck configured to support the optical assembly and an adjustable flexure assembly. The adjustable flexure assembly can be disposed around the chuck and can include a plurality of flexures. The plurality of flexures can be configured to contact edges of the optical assembly. Adjustment of the position of one or more of the plurality of flexures adjusts the optical axis alignment of one or more components of the optical assembly. Thus, alignment of the optical axes of the various components of the optical assembly can be achieved. The flexures can provide a slight force to move the components of the optical assembly to facilitate alignment. Such slight contact can reduce force disturbances in the adhesive disposed between the optical components to provide a better quality optical assembly.

[0100] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications can be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.

[0101] Preferred embodiments of the present invention will be described below in detail.

[0102] EMBODIMENT 1 1. An alignment apparatus for aligning components of an optical assembly, comprising: a chuck configured to support the optical assembly; an adjustable flexure assembly disposed about said chuck and comprising a plurality of flexures; Equipped with the plurality of flexures are positioned relative to the chuck such that each of the plurality of flexures contacts the optical assembly when the optical assembly is positioned on the chuck; adjusting the position of one or more of the plurality of flexures adjusts alignment of optical axes of optical components of the optical assembly when the optical assembly is positioned on the chuck, and the alignment device is configured to align the optical axes of the optical components to a deviation angle of less than about 1,000 μrad to provide an extinction ratio in the optical assembly of 1000:1 or greater. Alignment device.

[0103] EMBODIMENT 2 2. The alignment device of embodiment 1, wherein the adjustable flexure assembly is rotatable about a reference axis.

[0104] EMBODIMENT 3 3. The alignment apparatus of embodiment 2, wherein the chuck is rotatable about the reference axis.

[0105] EMBODIMENT 4 the chuck includes a vacuum passage; the optical assembly is supported on the chuck by vacuum pressure provided through the vacuum passage; An alignment device according to any one of embodiments 1 to 3.

[0106] EMBODIMENT 5 The adjustable flexure assembly further comprises a tip tilt assembly disposed about the chuck, the tip tilt assembly comprising: a base plate defining a support surface; an adjustable plate adjustably coupled to the base plate and supporting the plurality of flexures; one or more adjustment actuators configured to adjust the position of the adjustable plate relative to the support surface of the base plate; Equipped with An alignment device according to any one of embodiments 1 to 4.

[0107] EMBODIMENT 6 6. The alignment device of embodiment 5, further comprising a column supporting the chuck, the adjustable flexure assembly being disposed about the column and slidable along the column so as to be adjustably positioned along a length of the column.

[0108] EMBODIMENT 7 the base plate defines a base plate opening; the adjustable plate defines an adjustable plate aperture aligned with the base plate aperture; the base plate opening and the adjustable plate opening are sized to allow the chuck to pass therethrough; An alignment device as described in embodiment 5.

[0109] EMBODIMENT 8 6. The alignment device of embodiment 5, wherein the one or more adjustment actuators are configured to adjust the inclination of the adjustable plate relative to the support surface of the base plate.

[0110] EMBODIMENT 9 6. The alignment device of embodiment 5, further comprising a plurality of flexure clamps coupled to the adjustable plate.

[0111] EMBODIMENT 10 Each flexure clamp is coupled to the adjustable plate; a stationary portion fixedly coupled to the adjustable plate; a sliding portion to which a predetermined one of the plurality of flexible bodies is coupled; a flexible webbing connecting the fixed portion to the sliding portion; the adjustable flexure assembly further comprising a slide actuator associated with each flexure clamp, the slide actuator configured to contact the slide of the flexure clamp to displace the slide relative to the adjustable plate, thereby deflecting the flexible webbing to adjust a position of the flexure coupled to the flexure clamp relative to the adjustable plate and the chuck. An alignment device as described in embodiment 9.

[0112] EMBODIMENT 11 11. The alignment device of embodiment 10, further comprising a plurality of stops coupled to the adjustable plate proximate the sliding portion of the flexure clamp, each stop limiting sliding of the sliding portion of the flexure clamp.

[0113] EMBODIMENT 12 An alignment device according to any one of embodiments 1 to 11, further comprising an eccentricity measurement device configured to measure optical axis alignment of one or more components of the optical assembly.

[0114] EMBODIMENT 13 a force / displacement ratio applied to the optical component by the plurality of flexures is about 1.0×10 -6 N / mm~approx. 2×10 -6 13. The optical assembly according to any one of the preceding embodiments, wherein the axial length of the optical assembly is 1.2 N / mm.

[0115] EMBODIMENT 14 14. The optical assembly of any one of embodiments 1 to 13, wherein each of the plurality of flexures comprises a length to diameter ratio of about 80:1 to about 160:1.

[0116] EMBODIMENT 15 1. A method for aligning components of an optical assembly, comprising: placing a first lens including a first lens optical axis on a chuck of an alignment device for aligning components of the optical assembly; applying a liquid to a bonding surface of the first lens; placing a second lens including a second lens optical axis on the bonding surface of the first lens such that the liquid is disposed between the first lens and the second lens; contacting an edge of the second lens with a plurality of flexures; adjusting a position of one or more of the plurality of flexures in contact with the second lens, thereby aligning the second lens optical axis of the second lens with the first lens optical axis of the first lens. A method comprising:

[0117] EMBODIMENT 16 16. The method of embodiment 15, further comprising rotating the alignment device about a reference axis.

[0118] EMBODIMENT 17 measuring optical axis alignment between the first lens and the second lens by an eccentricity measuring device; evaporating the liquid when an optical axis alignment between the first lens and the second lens is within a predetermined alignment range. 17. The method of embodiment 15 or 16, further comprising:

[0119] EMBODIMENT 18 18. The method of any one of embodiments 15 to 17, wherein the first lens has a convex bonding surface and the second lens has a concave bonding surface, and the concave bonding surface of the second lens contacts the convex bonding surface of the first lens by the liquid.

[0120] EMBODIMENT 19 1. An optical assembly comprising: a first lens including a first lens optical axis; a second lens including a second lens optical axis; Equipped with the first lens optical axis is aligned with the second lens optical axis such that a deviation angle between the first lens optical axis and the second lens optical axis is less than about 1,000 μrad; a liquid is disposed between the first lens and the second lens to reduce a stress distribution in the optical assembly during alignment of the first lens optical axis and the second lens optical axis, and an extinction ratio of the optical assembly is 1000:1 or greater. Optical assembly.

[0121] EMBODIMENT 20 the first lens having a concave bonding surface; the second lens having a convex coupling surface; the concave bonding surface of the first lens is bonded to the convex bonding surface of the second lens; 20. The optical assembly of embodiment 19.

[0122] EMBODIMENT 21 21. The optical assembly of claim 19 or 20, wherein the original liquid has a viscosity of less than about 500 cps (about 500 mPa·s).

[0123] EMBODIMENT 22 22. The optical assembly according to any one of embodiments 19 to 21, wherein the original liquid has a viscosity of about 10 cps (about 10 mPa·s) to 500 cps (500 mPa·s).

[0124] EMBODIMENT 23 23. The optical assembly of any one of embodiments 19 to 22, wherein the deviation angle between the first lens optical axis and the second lens optical axis is less than about 10 μrad.

[0125] EMBODIMENT 24 24. The optical assembly of embodiment 23, wherein the deviation angle between the first lens optical axis and the second lens optical axis is less than about 1 μrad.

[0126] EMBODIMENT 25 25. The optical assembly of any one of claims 19 to 24, wherein the first lens is molecularly bonded to the second lens.

[0127] EMBODIMENT 26 1. A method for aligning components of an optical assembly, comprising: an alignment device for aligning components of the optical assembly, comprising: a chuck configured to support the optical assembly and in which the first lens is positioned; an adjustable flexure assembly disposed about said chuck and comprising a plurality of flexures; Equipped with the plurality of flexures are positioned relative to the chuck such that each of the plurality of flexures contacts the optical assembly when the optical assembly is positioned on the chuck; adjusting the position of one or more of the plurality of flexures adjusts alignment of optical axes of optical components of the optical assembly when the optical assembly is positioned on the chuck. placing a first lens including a first lens optical axis on the alignment device; applying a liquid to a bonding surface of the first lens; placing a second lens including a second lens optical axis on the bonding surface of the first lens such that the liquid is disposed between the first lens and the second lens; contacting an edge of the second lens with the plurality of flexures; adjusting a position of one or more of the plurality of flexures in contact with the second lens; aligning the second lens optical axis of the second lens with the first lens optical axis of the first lens such that a deviation angle between the first lens optical axis and the second lens optical axis is less than about 1,000 μrad and an extinction ratio of the optical assembly is 1000:1 or greater. A method comprising:

[0128] EMBODIMENT 27 measuring optical axis alignment between the first lens and the second lens by an eccentricity measuring device; evaporating the liquid when the optical axis alignment of the first lens and the second lens is within a predetermined alignment range. 27. The method of embodiment 26, further comprising:

[0129] EMBODIMENT 28 28. The method of embodiment 26 or 27, wherein the first lens has a convex bonding surface and the second lens has a concave bonding surface, and the concave bonding surface of the second lens contacts the convex bonding surface of the first lens by the liquid.

[0130] EMBODIMENT 29 29. The method of any one of embodiments 26 to 28, wherein the liquid is an optical adhesive.

[0131] EMBODIMENT 30 30. The method of embodiment 29, further comprising a step of curing the optical adhesive when an optical axis alignment of the first lens and the second lens is within a predetermined alignment range.

[0132] EMBODIMENT 31 31. The method of any one of embodiments 26 to 30, wherein the adjustable flexure assembly is rotatable about a reference axis.

[0133] EMBODIMENT 32 32. The method of embodiment 31, wherein the chuck is rotatable about the reference axis.

[0134] EMBODIMENT 33 the chuck includes a vacuum passage; 33. The method of any one of embodiments 26 to 32, wherein the optical assembly is supported on the chuck by vacuum pressure provided through the vacuum passage.

[0135] EMBODIMENT 34 The adjustable flexure assembly further comprises a tip tilt assembly disposed about the chuck, the tip tilt assembly comprising: a base plate defining a support surface; an adjustable plate adjustably coupled to the base plate and supporting the plurality of flexures; one or more adjustment actuators configured to adjust the position of the adjustable plate relative to the support surface of the base plate; Equipped with The method of any one of embodiments 26 to 33.

[0136] EMBODIMENT 35 35. The method of embodiment 34, wherein the alignment device further comprises a column supporting the chuck, the adjustable flexure assembly being disposed about the column and slidable along the column so as to be adjustably positioned along the length of the column.

[0137] EMBODIMENT 36 the base plate defines a base plate opening; the adjustable plate defines an adjustable plate aperture aligned with the base plate aperture; the base plate opening and the adjustable plate opening are sized to allow the chuck to pass therethrough; The method of embodiment 34.

[0138] EMBODIMENT 37 35. The method of embodiment 34, wherein the one or more adjustment actuators are configured to adjust the inclination of the adjustable plate relative to the support surface of the base plate.

[0139] EMBODIMENT 38 35. The method of embodiment 34, wherein the adjustable flexure assembly further comprises a plurality of flexure clamps coupled to the adjustable plate.

[0140] EMBODIMENT 39 Each flexure clamp is coupled to the adjustable plate; a stationary portion fixedly coupled to the adjustable plate; a sliding portion to which a predetermined one of the plurality of flexible bodies is coupled; a flexible webbing connecting the fixed portion to the sliding portion; the adjustable flexure assembly further comprising a slide actuator associated with each flexure clamp, the slide actuator configured to contact the slide of the flexure clamp to displace the slide relative to the adjustable plate, thereby deflecting the flexible webbing to adjust a position of the flexure coupled to the flexure clamp relative to the adjustable plate and the chuck. The method of embodiment 38.

[0141] EMBODIMENT 40 40. The method of embodiment 39, wherein the adjustable flexure assembly further comprises a plurality of stops coupled to the adjustable plate proximate the sliding portion of the flexure clamp, each stop limiting the sliding of the sliding portion of the flexure clamp.

[0142] EMBODIMENT 41 A method described in any one of embodiments 26 to 40, wherein the alignment device further comprises an eccentricity measurement device configured to measure optical axis alignment of one or more components of the optical assembly.

Claims

1. 1. An optical assembly comprising: a first lens including a first lens optical axis; a second lens including a second lens optical axis; Equipped with the first lens optical axis is aligned with the second lens optical axis such that a deviation angle between the first lens optical axis and the second lens optical axis is less than about 1,000 μrad; a liquid is disposed between the first lens and the second lens to reduce a stress distribution in the optical assembly during alignment of the first lens optical axis and the second lens optical axis, and an extinction ratio of the optical assembly is 1000:1 or greater. Optical assembly.

2. the first lens having a concave bonding surface; the second lens having a convex coupling surface; the concave bonding surface of the first lens is bonded to the convex bonding surface of the second lens; The optical assembly of claim 1 .

3. The optical assembly of claim 1 , wherein the deviation angle between the first lens optical axis and the second lens optical axis is less than about 10 μrad.

4. The optical assembly of claim 3 , wherein the deviation angle between the first lens optical axis and the second lens optical axis is less than about 1 μrad.

5. The optical assembly of claim 1 , wherein the first lens is molecularly bonded to the second lens.

6. The optical assembly according to claim 1 , wherein the liquid is an optical adhesive.

7. The optical assembly of claim 6 , wherein the optical adhesive is in an uncured state.

8. The optical assembly of claim 6 , wherein the optical adhesive is in a cured state.

9. The optical assembly of claim 1 , wherein the liquid comprises an uncured viscosity of less than about 500 cps (about 500 mPa·s).

10. The optical assembly of claim 9 , wherein the liquid comprises an uncured viscosity of about 10 cps to about 500 cps.

Images