WO2015031602A1

WO2015031602A1 - Optical alignment interface

Info

Publication number: WO2015031602A1
Application number: PCT/US2014/053139
Authority: WO
Inventors: Ryan MURDICK
Original assignee: Rhk Technology, Inc.
Priority date: 2013-08-29
Filing date: 2014-08-28
Publication date: 2015-03-05

Abstract

An optical alignment system that includes a mount and an alignment cradle. The mount is located on a first optic, and the alignment cradle is couplable to the mount. The cradle has at least one spherical locator or at least one pilot cavity for receiving at least one spherical locator.

Description

OPTICAL ALIGNMENT INTERFACE

This application claims the benefit of U.S. Provisional Application No. 61/871,591, filed August 29, 2013. The content of the above application is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates generally to optical alignment and, more particularly, to optical systems for testing purposes. BACKGROUND

Scanning probe microscopy (SPM) is a technique that scientists use to analyze a sample material by monitoring interaction between a probe and the material. WO2012/116168 discloses an SPM microscope having a peripheral optic.

BRIEF SUMMARY One illustrative embodiment includes an optical alignment system that includes a mount and an alignment cradle. The mount is located on a first optic, and the alignment cradle is couplable to the mount. The cradle may have at least one spherical locator or at least one pilot cavity for receiving the spherical locator(s).

Another embodiment includes a method of assembling an optical calibration apparatus for a concave optic. The steps of the method include: movably carrying a first optic in a cradle; mounting the cradle to the concave optic so that the first optic is positioned at least partially within an interior region of the optic; moving the first optic to an alignment position; and immobilizing the first optic with respect to the cradle in the alignment position. Another embodiment includes a method of aligning a first optic to a second optic. The steps of the method include: providing the second optic having a mounting surface; positioning a cradle having a complementary mounting surface with respect to the second optic such that the mounting surface of the second optic and the complementary mounting surface of the cradle pair; positioning the first optic carried by the cradle with respect to a focal point of the second optic; receiving directed light through a third optic and into the second optic resulting in: incident light onto the first optic, and reflected light off the first optic; adjusting the position of at least one of the first, second, or third optics until the incident light and reflected light overlap; and fixing the position of the first optic with respect to the cradle.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of one or more of the disclosed embodiments of this disclosure will be apparent to those of ordinary skill in the art from the following detailed description of illustrative embodiments and the claims, with reference to the accompanying drawings in which:

FIG. 1 is a schematic view of an illustrative embodiment of an optical alignment system that may be used in an illustrative embodiment of an alignment process; FIG. 2 is an image in perspective of an alignment cradle of the optical alignment system of FIG. 1 ;

FIG. 3 is a schematic view of a mounting surface of an optic of the optical alignment system along section lines 3-3 of FIG. 1; and

FIG. 4 is an image in perspective of a portion of the mounting surface of FIG. 3.

DETAILED DESCRIPTION

The use of optical microscopy hardware (e.g., SPM, Raman spectroscopy, TERS, etc.) typically involves alignment of the hardware with the subject matter or specimen to be examined. This alignment process can be both time consuming and require the assistance of a technician or specialist to perform the alignment for each specimen to be examined. The following description generally describes an optical alignment system 8 having an optical alignment or calibration interface 10 and methods of manufacturing and aligning the interface 10. Following an initial alignment, the interface 10 may be used to rapidly examine different specimens without the assistance of a specialist. The description provides one or more illustrative embodiments. While the example embodiments are described with reference to the optical alignment system 8, it will be appreciated as the description proceeds that the inventions are useful regardless of the particular system or apparatus and may be implemented in many embodiments.

As shown generally in the schematic view of FIG. 1, the alignment interface 10 includes the coupling or adjoining of an optic (e.g., optic A) and a cradle 12 for carrying another optic (e.g., optic B). The alignment interface 10 (between the cradle 12 and optic A) may be decoupled and recoupled such that the alignment of optic A and optic B is repeatable within a predetermined and acceptable margin of error. For purposes of illustration, FIG. 1 illustrates optic B as a retroreflector carried by the alignment cradle 12 which has a mounting surface 14 and optic A as an elliptical mirror (or concave optic) having a mount or mounting surface 16 for coupling or mating to mounting surface 14. The cradle 12 and optic A, together with their respective mounting surfaces 14, 16, are described more fully below.

The alignment cradle 12 is depicted in FIGS. 1 and 2 as a generally annular-shaped member having multiple spherical locators 20 and one or more magnets 22 on mounting surface 14. In FIG. 2, there are three circumferentially, evenly spaced spherical locators 20 and three circumferentially, evenly spaced magnets 22 interposed between the spherical locators 20. For example, the spherical locators 20 are circumferentially spaced approximately 120 degrees from one another with respect to a center axis L of the cradle 12; similarly, the magnets 22 are shown approximately 120 degrees from one another as well. The locators 20 and magnets 22 may be provided in any other suitable spacing and configuration.

The spherical locators 20 may include any locating device having at least a partially- spherical shape, and need not be complete spheres. In FIG. 2, the spherical locators 20 have diameters (Ds) that extend approximately a full-hemisphere from the mounting surface 14 of the cradle 12; however, other implementations are possible. For example, the spherical locators 20 may be a pin or post coupled to the mounting surface 14 and having a partially-hemispherical region extending from the pin (e.g., on the end thereof). Also, each of the spherical locators 20 may be full or partial spheres located within recesses 30 of the mounting surface 14. Or the locators 20 may be spheres surface-coupled to mounting surface 14 (i.e., without recesses 30). These of course are merely examples and other implementations will be apparent to those having ordinary skill in the art.

The illustrated magnets 22 are shown as cylindrical members each longitudinally oriented parallel to the center axis L and each having an end 32 facing outwardly from the mounting surface 14. Here, each magnet 22 is located within recesses 34 of the mounting surface 14. However, the shape of the magnets 22 and their relative location at the mounting surface 14 may vary. For example, while these magnets 22 have ends 32 generally co-planar to the mounting surface 14, this is not necessary. For example, the magnets 22 may be surface-mounted to the cradle 12 instead or partially extend outwardly from the mounting surface 14 from the recesses 34. Other implementations are possible. Both the spherical locators 20 and the magnets 22 may be coupled to the mounting surface 14 and/or recesses 30, 34 in any of various ways known to those of ordinary skill in the art (e.g., use of solder, fasteners, adhesives, welding, etc.).

FIGS. 1 and 2 illustrate the cradle 12 having an outer radius (Ro) and an inner radius (Ri). Between the inner and outer radii Ri, Ro is a shoulder 36 and a wall 38. The cradle 12 may have a counterbore 40 at least partially defined by the wall 38 and a counterbore surface 42; i.e., the depth of the counterbore 40 is defined by the wall 38, and the diameter of the counterbore 40 is defined by the inner radius Ri and the span (Rc) of the counterbore surface 42 (i.e., diameter = 2*[Ri + Rc]).

Now turning to optic A and mounting surface 16, optic A is illustrated in FIGS. 1 and 3 as having a cylindrical body 50 and an ellipsoidal passage 52 extending longitudinally therethrough along axis L; more specifically, the passage 52 extends from an opening 54 at a first end 56 of the body 50 to another opening 58 at the opposing or second end 60 having the mounting surface 16 located thereat. The opening 54 at the first end 56 is shown as wider than the opening 58 at the second end 60. The illustrated passage 52 has a reflective or mirror-like surface 62. The body 50 of optic A may be composed of any suitable material and the passage surface 62 may or may not be a coating. For example, in some embodiments, the body 50 may be composed of a ferrous material and the surface 62 may be of the same material and polished to a suitable reflectance. Or for example, the body 50 may be non-metallic and the surface 62 may be a coating having a suitable reflectance. Or the passage 62 may have a reflective insert. Of course, these are merely examples and other implementations are also possible.

The mounting surface 16 of optic A may complement the mounting surface 14 of the alignment cradle 12. For example, as best shown in the schematic view of FIG. 3, the mounting surface 16 may have multiple pockets or pilot cavities 70 for receiving or cooperating with the spherical locators 20 and one or more magnetically responsive regions 72 for magnetically cooperating or coupling with the magnets 22. The regions 72 may include ferrous material, magnetic material, or the like. The pockets 70 and magnetically responsive regions 72 may be circumferentially spaced around the second opening 58. For example, in FIG. 3, there are three circumferentially, evenly spaced pockets 70 and three circumferentially, evenly spaced magnetically responsive regions 72 interposed between the pockets 70. More specifically, in the illustrated implementation, the pockets 70 are circumferentially spaced approximately 120 degrees from one another with respect to the axis L; similarly, the magnetically responsive regions 72 are shown approximately 120 degrees from one another as well. This spacing and arrangement is merely one example however. The regions 72 and/or the pockets 70 may be at a common radial distance from center L.

The pockets 70 may be of any suitable shape; in FIG. 3 they are illustrated as rectangular. Each pocket 70 may have one or more fiducial surfaces therein. In one illustrative implementation, the fiducial surfaces are the exterior surfaces of one or more locators76. The locators 76 may include cylinders, as illustrated, and/or may include elements of any other suitable shape(s) and size(s). The locators 76 may be arranged and/or oriented in various ways. For example, the longitudinal axes Mi, M2 of the locators 76 may lie in a plane parallel to the mounting surface 16. Further, while the axes Mi, M2 in FIG. 3 are shown generally parallel to one another, this is not necessary. For example, the locator axes Mi, M2 may be positioned radially inwardly or traverse to the center axis L. In some embodiments, the diameter (Dc) of the locators 76 may vary; and in some embodiments, the locators 76 may protrude from the pocket 70 outwardly beyond the mounting surface 16, and in other embodiments, they may not. In one implementation, the ratio of the diameter of the spherical locator 20 (Ds) to the locator 76 diameter (D_c) may be between 1.5 and 4 (e.g., 1.5 < D_s / D_c < 4). The locators 76 may be soldered, welded, adhered, fastened, or coupled in any other suitable manner to the pockets 70.

The magnetically responsive regions 72 may comprise the body 50 of the optic A itself (e.g., where the body is machined or cast from a ferrous material). In other implementations, the regions 72 may be inserts of ferrous material or any other material responsive to a magnetic field. Still further, the regions 72 may be one or more surface-mounted plates or even a plating composed of a magnetically responsive material coupled to the second end 60 of the optic A. The regions 72 may or may not extend outwardly from the mounting surface 16. In the illustrated embodiment of FIG. 1, the regions 72 are generally flush with the second end 60, and the body 50 of the optic A itself is composed of aluminum.

Both the pockets 70 and the magnetically responsive regions 72 may be positioned on optic A to complement the respective locations of the spherical locators 20 and magnets 22 of the cradle 12 - thus, enabling the mounting surfaces 14, 16 to pair. Further, the pairing of the spherical locators 20 with the pockets 70 may bring the spherical locators 20 into contact with each of the locators 76 within the pockets 70 (e.g., three spherical locators 20 may be in contact with six locators 76).

In operation or use, the two mounting surfaces 14, 16 may be coupled and decoupled from one another. For example, when the alignment cradle 12 is brought into proximity with the second end 60 of optic A, the spherical locators 20 of mounting surface 14 may align with the pockets 70 of mounting surface 16. The spherical locators 20 may seat or locate at least partially between the locators 76 in the respective pockets 70. Furthermore, the spherical locators 20 (or at least the portion extending beyond the mounting surface 14) may be at least partially located within the depth of the pockets 70 further bringing the magnets 22 into closer proximity with the magnetically responsive regions 72. In the illustrated embodiment, when assembled, the magnets 22 of the alignment cradle 12 may be flush with the mounting surface 16 of optic A (i.e., the magnets 22 also contact the regions 72).

After pairing or coupling the two mounting surfaces 14, 16 together, they may be decoupled and recoupled at any future point in time. The location of the alignment cradle 12 with respect to the optic A will be relocated in substantially the same position and orientation as it was previously. A maximum deviation from its original position (or repeatability) may be predetermined based on a number of factors, including: manufacturing tolerances (e.g., of the spherical locators 20, locators 76, the body 50 of optic A, the cradle 12, etc.); thermal stability and deformation characteristics of the materials of the cradle 12, optic A, and their various components; and various system conditions and environmental conditions and characteristics known to those of ordinary skill in the art (e.g., ambient temperature, dust, scratches, etc.). The deviation may be a predetermined value based on these known characteristics and conditions. In at least one implementation, the predetermined value may be less than 0.05 microns (micrometers (μιη)); i.e., the position and orientation of the alignment cradle 12 with respect to optic A is repeatable with an error less than 0.05 microns.

As previously described, the alignment cradle 12 may be used to carry another optic - optic B and, as will be described below, where optic B is fixed to the alignment cradle 12, the position and orientation of optic A with respect to optic B may be repeatable within the predetermined value described above (i.e., 0.05 microns).

As shown in illustrated example of FIG.1, optic B (the spherical retroreflector) includes a sphere 78 and a hub 80 having a reflective cavity 82; however, optic B may be any suitable reflective device or apparatus having reflective properties. For example, optic B may be a flat or curved mirror. Further, retroreflectors also vary - e.g., while a spherical retroreflector is shown, other embodiments are also possible (e.g., a corner retroreflector).

The hub 80 may be any suitable device for carrying a mirror or reflector. In one implementation, the hub 80 has a disk-shaped body 84 with the reflective cavity 82 on one side 88. The reflective cavity 82 is illustrated as semi-spherical; however, other implementations are possible. The diameter (DH) of the hub body 84 may be greater than the inner diameter of the alignment cradle 12 (i.e., 2*¾) and less than the diameter of the counterbore 40 (i.e., 2*[¾ + Rc]). A second side 90 of the body 84 (i.e., opposite of the reflective cavity 82) may have a surface shaped and prepared to receive the counterbore surface 42 of the cradle 12. For example, in at least one implementation, both the second side 90 and counterbore surface 42 are generally flat.

FIG. 1 further illustrates a positioning stage 96 carried by a test stand or bench 98 and suitably coupled to the second side 90 of the hub body 84 for carrying optic B. The positioning stage 96 may have up to six degrees of freedom (e.g., translation in the x-, y-, and z-directions as well as pitch, roll, and yaw). Adjustment of the positioning stage 96 may be incremental - e.g., having coarse and fine adjustment knobs (not shown); further the stage 96 may be motorized or manually operated. In addition, the stage 96 may include one or more nano-positioning devices, which may include piezo-electric elements. Positioning stages are known to artisans of ordinary skill in the art.

Also shown in FIG. 1 is a third optic (optic C). Optic C may be any optic for conveying or transmitting light into optic A. For example, optic C may be an active device (e.g., a laser) or a passive device (e.g., a prism or one or more lenses). In the illustrated implementation, optic C is an objective lens receiving light from a source (not shown) and redirecting that light into optic A.

A method of aligning optics A and B is described below, according to one illustrative embodiment. Optic B may be initially aligned with optic A, and thereafter optic B may be fixedly assembled to the cradle 12 so that when the cradle 12/optic B are displaced from optic A, they may thereafter be re-located proximate to one another without re- performing alignment. When the cradle 12/optic B are displaced, the spherical locators 20 are decoupled from the pockets 70 and the magnets 22 are decoupled from the magnetically responsive regions 72. And when the cradle 12/optic B are re-located, the spherical locators 20 are recoupled to the pockets 70 and the magnets 22 are recoupled to the magnetically responsive regions 72 - and the precision of the alignment is within a predetermined value (e.g., 0.05 microns).

The method includes placing a bonding agent 100 on the counterbore surface 42 of the cradle 12, and then locating optic B (e.g., the spherical retroreflector) within the alignment cradle 12; more specifically, by locating the hub 80 within the counterbore 40 such that the second surface 90 of the hub 80 is in contact with the bonding agent 100 and the counterbore surface 42. This may require coarse adjustment of the positioning stage 96 (or may simply be performed manually). Thus, prior to the bonding agent 100 setting, optic B may be movably carried by the cradle 12. Since the body 84 of the hub 80 is smaller than the counterbore 40 of the cradle 12, the hub 80 will be movable having some play or leeway. The amount of play will at least partially depend on the diameter (DH) of the hub body 84 and the diameter of the counterbore 40 (2*[Ri + Rc]). In at least one embodiment there will be only lateral play not exceeding 5 millimeters (mm). Alternatively, the bonding agent 100 may be located near the periphery of the second side 90 of the hub body 84.

After optic B is carried by the cradle 12, the cradle 12 may be mounted or located proximate to optic A using the alignment interface 10 (i.e., the spherical locators 20, pockets 70, magnets 22, and magnetically responsive regions 72). This may locate the sphere 78 and/or the reflective cavity 82 at least partially within the interior of the optic A's passage 52. More specifically, the sphere 78 may be generally proximate to a focal point ( ) of optic A (e.g., the focal point of the elliptical mirror).

After optic A and the cradle 12 are coupled to one another, optic B may be further aligned to an alignment position by moving the hub 80 carrying the sphere 78 and the reflective cavity 82 with respect to the cradle 12. More specifically, in the illustrated example, the hub 80 may be moved until the center of the sphere 78 is located coincident with the focal point ( ) of optic A. This movement may be facilitated using the fine adjustments of the positioning stage 96. Achieving a co-location of the center of the sphere 78 and the focal point ( ) of optic A may include moving the hub 80 until incident light received from optic C (e.g., the objective lens) onto optic B is coincident with or overlaps with the light reflected from optic B (e.g., light entering the sphere 78 overlaps light exiting the glass sphere 78). Once the incident light overlaps the reflected light, initial alignment is complete.

Thereafter, the bonding agent 100 may be permitted to set and/or cure. For example, where the bonding agent 100 is an adhesive, the aforementioned initial alignment may be performed while the adhesive is unset or during its working time. The working time of adhesives will vary; in at least one implementation, the adhesive may have a working time up to 60 minutes. One commercially available adhesive having such working time is Loctite™ 907 Hysol. Other suitable adhesives will be apparent to those having ordinary skill in the art. Of course, other bonding agents are also possible (e.g., soldering, welding, fastening, etc.).

After the bonding agent cures, the cradle 12 fixedly carries optic B, and the realignment of optics A and B is simplified by merely recoupling the mounting surface 14 of the cradle 12 to mounting surface 16 of optic A. This process of decoupling and recoupling may be repeated as often as necessary. Further, the alignment of optics A and B will be within 0.05 microns.

The scope of this disclosure includes other embodiments of the alignment interface 10. For example, either of the spherical locators 20 or the pockets 70 may be located on optic A, optic B, or both. Likewise, either of the magnets 22 or magnetically responsive regions 72 may be located on optic A, optic B, or both. Thus, in at least one example, either optic A or optic B substantially could be composed of a ferrous material. Or in another example, one spherical locator 20 may be located on the cradle 12 while two spherical locators 20 may be located on the mounting surface 16 of optic A. Or for example, one magnet 22 may be located on the cradle 12 while two magnets 22 may be located on the mounting surface 16 of optic A. In addition, any combination or other suitable variation of these embodiments are possible.

The alignment interface 10 further is not limited to three spherical locators 20, three pockets 70, three magnets 22, and three magnetically responsive regions 72. The alignment interface 10 may have any suitable number of any of these features. Furthermore, other suitable features may be included with one or more spherical locators 20 (and pockets 70) and/or one or more magnets 22 (and regions 72). Additionally, in at least one implementation, the alignment interface 10 does not have magnets 22 and/or magnetically responsive regions 72.

In another implementation, each pocket 70 may have different locator 76 arrangements. For example, as illustrated in FIG. 4, the shape of the pocket may differ having a main bore 102 and having two lobes 104 each carrying a locator 76 extending from both sides of the main bore 102. Or in another example (not shown), each pocket 70 may have three or four locator located therein. Or the pockets 70 may have other fiducial surfaces or members located therein.

Also, in FIGS. 1, 2, and 3, the optic A, optic B, and cradle 12 are all shown having the same center or longitudinal axis L; however, this is not required either. For example, the alignment process described above may be successfully achieved where the cradle 12 is not coaxial with optic A.

Other embodiments of the alignment process also exist. For example, in aligning optic A to optic B, optic A and/or optic C may be moved rather than only optic B. Thus, to perform the alignment process described above, one or more of the optics A, B, or C may be moved or adjusted until the incident light at optic B and reflected light from optic B overlap.

Thus, there has been described both an optical alignment system 8 and various methods of using the system 8 to perform an initial alignment that enables simplified future re- alignment within a predetermined value.

It is to be understood that the foregoing is a description of one or more embodiments of the disclosure. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

As used in this specification and claims, the terms "e.g.," "for example," "for instance," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

1. An optical alignment system, comprising:

a mount located on a first optic; and

an alignment cradle couplable to the mount and having at least one spherical locator or at least one pilot cavity for receiving the at least one spherical locator.

2. The optical alignment system of claim 1, wherein the mount has at least one spherical locator or at least one pilot cavity for receiving the at least one spherical locator.

3. The optical alignment system of claim 2, wherein the at least one pilot cavity of the mount or alignment cradle carries two cylinders spaced for receiving the spherical locators.

4. The optical alignment system of claim 2, wherein the mount and the alignment cradle each have at least one of: at least one magnet, or at least one magnetically responsive region.

5. The optical alignment system of claim 4, wherein the mount has at least three pilot cavities and at least three magnetically responsive regions interposed between the three pilot cavities, wherein the alignment cradle has at least three spherical locators and at least three magnets interposed between the three spherical locators.

6. The optical alignment system of claim 1, wherein the alignment cradle carries a second optic.

7. The optical alignment system of claim 6, wherein the second optic is a spherical retroreflector.

8. The optical alignment system of claim 6, wherein the second optic includes a sphere and a hub for carrying the sphere, wherein the hub is fixably couplable to the alignment cradle using an adhesive.

9. The optical alignment system of claim 8, wherein a positioning stage carries the hub.

10. The optical alignment system of claim 1, wherein the first optic includes a concave passage for receiving light having a first opening at a first end and a second opening at a second end, wherein the second end is adapted to receive the alignment cradle using the at least one spherical locator or the at least one pilot cavity.

11. A method of assembling an optical calibration apparatus for a concave optic, comprising the steps of:

movably carrying a first optic in a cradle;

mounting the cradle to the concave optic so that the first optic is positioned at least partially within an interior region of the optic;

moving the first optic to an alignment position; and

immobilizing the first optic with respect to the cradle in the alignment position.

12. The method of claim 1 1, wherein the first optic is a retroreflector.

13. A method of aligning a first optic to a second optic, comprising the steps of:

providing the second optic having a mounting surface;

positioning a cradle having a complementary mounting surface with respect to the second optic such that the mounting surface of the second optic and the complementary mounting surface of the cradle pair;

positioning the first optic carried by the cradle with respect to a focal point of the second optic;

receiving directed light through a third optic and into the second optic resulting in:

incident light onto the first optic,

and reflected light off the first optic; adjusting the position of at least one of the first, second, or third optics until the incident light and reflected light overlap; and

fixing the position of the first optic with respect to the cradle.

14. The method of claim 13, wherein the first optic is a retroreflector having a center positioned coincident with the focal point of the second optic, wherein the second optic is an elliptical mirror.

15. A retroreflector-affixed cradle produced by the method of claim 14.

16. An elliptical mirror having coupled thereto a retroreflector-affixed cradle produced by the method of claim 14.

17. The method of claim 13, wherein at least one of the cradle or second optic mounting surfaces include a plurality of pockets and at least one of the cradle or second optic mounting surfaces include a plurality of spherical locators for cooperation in the pockets, and at least one of the cradle or second optic mounting surfaces include one or more magnets and at least one of the cradle or second optic mounting surfaces include ferrous material for cooperation with the one or more magnets to couple the cradle to the second optic.

18. The method of claim 17, wherein the cradle is decouplable and recouplable with the mounting surface of the second optic using the plurality of spherical locators and the plurality of pockets, wherein when the cradle is decoupled and recoupled to the mounting surface, the relative new position of the first optic with respect to the second and third optics is within a predetermined value of its relative original position prior to decoupling.

19. The method of claim 13, wherein the first optic includes a hub and a sphere coupled to the hub, wherein the fixing step further comprises fixing the hub to the cradle.

20. The method of claim 13, further comprising the step of coupling a cradle to the second optic, wherein the cradle supports the first optic with respect to the second optic, and wherein the fixing step includes fixing the first optic to the cradle.