Abstract:
A method for aligning and assembling two lens pieces, and a machine to accomplish this task are provided. In one example of the method, the method includes holding an upper lens above a lower lens, holding the lower lens in a horizontal position, lowering the upper lens into a contact position with the lower lens, and allowing the upper lens to self-align to a top surface of the lower lens.

Description:
RELATED APPLICATIONS 
     This Patent Application claims priority under 35 U.S.C. 119(e) of the U.S. Provisional Pat. App. No. 60/703,539, filed Jul. 29, 2005, entitled “Method for Aligning the Upper and Lower Centering Bells of a Lens Doublet Assembly Machine”, which is hereby incorporated by reference. The Patent Application is related to concurrently filed U.S. patent application Ser. No. 11/495,330, now U.S. Pat. No. 7,508,606 B2, entitled “Method for Aligning the Upper and Lower Centering Bells of a Lens Doublet Assembly Machine”, which is herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to lens doublets for cameras. More particularly, the present invention relates to techniques and machines for aligning lens doublets for cameras. 
     BACKGROUND OF THE INVENTION 
     Correctional Lens Doublets consist of two lenses generally made of different optical materials attached to each other to derive better optical performance over wavelengths of interest. Currently, the most popular methods of achieving micron level centration of the two pieces of lens doublets involve active alignment or other methods. Unfortunately, these methods are slow, high in cost and not amenable to volume production. The problem of centration is even more difficult for very small lens pieces such as used in handheld cameras or cell phone cameras. 
     Active alignment involves passing an optical beam through the lenses or lens assemblies. Controlled movement of the lenses is executed using the location of the projected beam image for feedback. The Laser Alignment and Assembly Station™ of Opto-Alignment Technology, Inc. is an example of a apparatus that utilizes active alignment. A rotating air bearing stage has X-Y-theta-phi adjustments to set the lens barrel or other optic holder to run true to serve as a reference. Then a reflection from a laser imaged on a CCD camera is used to center multiple optical elements. 
     There are several ways in which the lens can be centered on the bell-shaped centering bell. Many of these methods are discussed with figures in “Fabrication Methods for Precision Optics,” by Hank H. Karow. Brief descriptions are provided here. 
     An older transfer spindle method is still used for prototype and low-volume production and for centering lenses made from soft and sensitive materials. According to Karow, the lens is mounted on a precise centering bell which is fastened on a thread to a precision spindle. This centering bell is nearly always made of brass, although steel bells are sometimes used as well. The lens is mechanically or optically aligned on the centering bell so that the optical and mechanical axes of the lens are coincident. The spindle with the centered lens is then mounted in a centering machine, which is used to grind the diameter of the lens concentric to the axis of rotation. 
     In one centering method, the lens and the centering bell are heated sufficiently so that a small amount of a specially formulated centering wax can be applied to the edge of the centering bell. The heated lens is then positioned on the centering bell by mechanical means or by an optical alignment method. For the mechanical method, the edge thickness variations must be nulled out or at least reduced to a minimum while the lens rotates. The run-out is monitored by means of a digital indicator. 
     Another centering method is an optical method that relies on light reflected off the outer surface of the lens. The lens is mounted on a centering bell, which rotates the lens. The centering bell is mounted to the spindle. 
     Yet another centering method is an optical method that relies on the rotation of a target image that is projected through the lens. A lamp, a collimating lens and mirrors form the target image and project the target image through the lens. The lens is mounted on the centering bell, which rotates the lens. 
     A laser beam alignment method is used for more critical centration requirements. It is quite similar to the target image projection method. Both of these optical centration methods are only useful for lenses made from visually transparent materials. Projection methods are not possible for infrared materials and metal optics because they are not transparent in the visible region of the spectrum. 
     Another centering method is bell chuck centering for small lenses. Using two coaxial bell chucks to align a single lens to the chuck axis. The lens is typically arranged horizontally. Bell chuck centering is a method in which a suitably curved lens is self-centering when clamped between identical and precision aligned brass centering bell or bell chucks. Bell chuck centering is a purely mechanical method that relies on the fact that the lens will slide along the edge of the bell chuck until it seats itself at the zone of equal edge thickness. In this alignment the optical axis of the lens and the mechanical axis of the spindle become colinear. When the edges of the centering chucks are well rounded and polished, the lens surface will not be damaged, even at high chuck pressures. The bell chuck centering method with a horizontal spindle can be used for lenses with diameters as small as 3 mm and as large as 150 mm. 
     Still another centering method is bell chuck centering for larger lenses. Lenses up to 250 mm in diameter can be centered with this bell chucking method using vertically aligned spindles. For larger lenses, a vacuum assist method is necessary to reduce the otherwise required high clamping loads on the lens surfaces that can lead to damage. 
     Regarding centerability limitations, for the centering method known as transfer spindle, there is no theoretical optical limit on centerability, although some practical limits do exist. Even lenses with very weak optical power can be centered with this method as long as the centration error can be optically or mechanically detected. There is a well-defined centerability limit, however for the bell-chucking method. When the lens radii become too long, even strong forces will not prevent the lens from being displaced by the appreciable side pressures exerted by a side wheel typically formed of diamond. Before a lens production run is committed to a bell-chucking machine, it must first be determined if the lens can be safely, accurately and reproducibly centered this way. 
     The limit of centerability with the bell-chucking method is a function of the slide angle of the lens relative to the chuck edge and the coefficient of friction between lens and chuck. The motion component which can be derived from chuck pressure causes the lens to move between the bell chuck edges. This motion component must be large enough so that it can overcome the friction between the bell chuck edges and the lens surfaces. Since the value of this component depends on the shape of the lens, it is possible for it to become smaller than the friction component. The lens will then no longer slide between the bell chuck edges, and it can no longer be centered this way. The limit of centerability can be calculated from the lens diameter, the lens radii, and the coefficient of friction. 
     Doublet alignment is yet another prior art method based on aligning the doublet to equal lens edge thickness. The doublet includes a convex and a concave lense joined together. The two lenses of a cemented or joined doublet have a common optical axis. 
     For noncritical doublets it is sufficient to align the lenses by their common diameter. The doublet is put into a V-jig for this purpose. The cemented doublet is then centered as accurately as individual lenses. The centering tolerances can be additive, however. 
     A somewhat more accurate centering method for doublets uses a fixture in which the doublet is held in a lens holder. Mounted above the doublet is a centering bell on the same axis as the lens holder. This centering bell is lowered until it contacts the doublet, which will then automatically align the lense to an equal edge thickness. Alignment to equal edge thickness is also the principle on which an older instrument was based. 
     Doublets for high quality objectives are optically aligned. A transmitted light method is well known for which the setup is equipped with a collimator and a telescope. Systems are also used in which the light from an autocollimator passes through a doublet and is reflected back by a plane mirror. 
     Doublets can also be cemented and aligned to their common optical axis on a laser centering test unit. The cement is applied and evenly distributed. This method works best with UV cement. The lens pair is then placed on the centering chuck of the instrument where it is held by light vacuum pressure. The lower, typically concave, lens is pushed against a laterally attached V-stop which has been previously adjusted with a centered lens and locked into position. 
     The laser passes through a focusing apparatus that compensates for the refractive powers of the doublet. A plane mirror redirects the beam from there through the doublet, which then passes through the hollow spindle and impinges as a light spot on a detector plate. The detector is electronically coupled to an image screen that displays the light spot as a bright dot. A change in position of the light spot on the detector plane is seen magnified many times on the image screen. The upper lens is then shifted in such a way that the dot on the screen remains stationary as the spindle is rotated. The centered doublet is now irradiated with UV light The cement sufficiently precures in a few seconds, so then the cemented doublet can be removed from the centering chuck and fully cured later in a ultra violet light oven. 
     The Laser Alignment and Assembly Station™ by Opto-Alignment Technology, Inc., is an instrument to improve quality of assembly and inspection of precision and ultra-precision multi-element lens assemblies. The Laser Alignment and Assembly Station™ operates by reflecting a laser beam from any surface of an object being aligned or measured. A centering and tilt stage is mounted on an air bearing to bring the mechanical axis of a lens housing into collinear alignment with the incident test beam. The optical module provides a focused laser test beam which, when reflected from the surface under test, falls on a charge-coupled device (CCD) detector. If the surface is accurately centered, the reflection produces a stationary bright spot in the center of the video monitor. A misaligned surface will reflect the laser beam at an angle and displace the bright spot away from the center of the CCD. Rotation of the air bearing causes the decentered spot to orbit around the center of the CCD. The radius of the orbit viewed on a monitor is proportional to the tilt of the surface under test and is independent of its radius of curvature. A frame-grabber can be used to import the image to a computer and software can automate the measurements and store the data on the individual lenses and the entire lens assembly. 
     Voice coil linear actuators with flexural bearings are also part of prior art. The LFA-10 Linear Focus Actuator™ of Equipment Solutions Inc. is a positioning apparatus using such voice coil linear actuators. It was specifically developed for optical applications requiring both high precision and high-speed positioning over a short to medium stroke. The LFA-10 Linear Focus Actuator™ is well suited for optical focusing and other micropositioning applications such as scanning interferometry, surface structure analysis, disk drive testing, autofocus systems, confocal microscopy, biotechnology and semiconductor test equipment. The LFA-10 Linear Focus Actuator™ is guided along a single axis by a flexure design. The use of flexures within the design produces a compact and light package with zero stiction/friction, ultra-high resolution and exceptional guiding precision. This stage architecture allows it to be oriented in either a vertical or horizontal position. The LFA-10 Linear Focus Actuato™ uses a high force low mass moving voice coil architecture. The LFA-10 Linear Focus Actuator™ includes a sub-micron resolution linear displacement sensor. 
     All of the aforementioned methods are too slow to justify their capital cost of equipment and operator labor. Note that executing a lens alignment method using automated pick and place machines is possible. However, such a method is not accurate enough due to imperfections in lens outlines and poor correlation between the outline of the lens and its optical axis. 
     SUMMARY OF THE INVENTION 
     What is needed is an improved apparatus having features for addressing the problems mentioned above and new features not yet discussed. Broadly speaking, the present invention fills these needs by providing a method of aligning and assembling two lens pieces, and a machine to accomplish this task. It should be appreciated that the present invention can be implemented in numerous ways, including as a method, a process, an apparatus, a system or a device. Inventive embodiments of the present invention are summarized below. 
     In one embodiment, a method of lens doublet aligning is provided. The method comprises holding an upper lens above a lower lens, holding the lower lens in a horizontal position. The upper lens is then lowered into a contact position with the lower lens, the upper lens to self-aligns to a top surface of the lower lens. 
     In another embodiment, a method of lens doublet aligning is provided. The method comprises holding the upper lens above the lower lens. The lower lens is held in a horizontal position. The upper lens and the lower lens are brought into contact preferably by lowering the upper lens. The upper lens is aligned with respect to edge datums of the lower lens. 
     In still another embodiment, an apparatus for lens doublet aligning is provided. The apparatus comprises an upper bell chuck; an upper bell shaft having the upper chuck attached at a lower end of the upper bell shaft; one or more flexural bearings, wherein the one or more flexural bearings support the upper bell shaft in an upright position, wherein the upper bell shaft traverses through a center of the one or more flexural bearings; a flexural bearing housing attached to outer radial edges of the flexural bearings, wherein the flexural bearing housing supports the one or more flexural bearings within the flexural bearing housing; a lower bell chuck; and a base plate supporting the lower bell chuck and the flexural bearing housing on an upper portion of the base plate. 
     The invention encompasses other embodiments are configured as set forth above and with other features and alternatives. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. 
         FIG. 1  shows an aligning method in which an upper lens is aligned with respect to the top surface of a lower lens, in accordance with an embodiment of the present invention; 
         FIG. 2  shows an aligning method in which an upper lens is aligned with respect to edge datums shared by the lower lens and a lower chuck, in accordance with an embodiment of the present invention; 
         FIG. 3  is a perspective view of a lens aligning apparatus, in accordance with an embodiment of the present invention; 
         FIG. 4  is a cut-away perspective view of the lens aligning apparatus of  FIG. 3 , in accordance with an embodiment of the present invention; 
         FIG. 5  is close-up view of the flexural bearing of the lens aligning apparatus, in accordance with an embodiment of the present invention; 
         FIG. 6  shows the lens aligning apparatus during a lens aligning of the upper lens with respect to the upper bell chuck and the lower chuck, in accordance with an embodiment of the present invention; 
         FIG. 7  shows the lens aligning apparatus during a lens raising of the upper lens in preparation for placement of the lower lens, in accordance with an embodiment of the present invention; 
         FIG. 8  shows the lens aligning apparatus during a lens placement of the lower lens, in accordance with an embodiment of the present invention; 
         FIG. 9  shows the lens aligning apparatus during a lens aligning of the upper lens with respect to the lower lens, in accordance with an embodiment of the present invention; 
         FIG. 10  is an isometric cross-sectional view of the lens aligning apparatus during a bell alignment process of the upper bell chuck, in accordance with an embodiment of the present invention; 
         FIG. 11  shows the lens aligning apparatus during a bell aligning of the lower chuck with respect to the upper bell chuck, in accordance with an embodiment of the present invention; and 
         FIG. 12  is a close-up view of the lens aligning apparatus during the bell aligning of  FIG. 11 , in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An invention for a method of aligning the upper and lower centering bells of a lens doublet assembly machine is disclosed. Numerous specific details are set forth to provide a thorough understanding of the present invention. It will be understood, however, to one skilled in the art, that the present invention can be practiced with other specific details. Two different methods of lens doublet aligning are disclosed depending on the centration requirements as shown in the diagrams below. 
     Overview of Lens Doublet Aligning 
       FIG. 1  shows an aligning apparatus  101  in which an upper lens L 1  is aligned with respect to the top surface of a lower lens L 2 , in accordance with an embodiment of the present invention. The lower lens L 2  is preferably precisely held to be horizontal via edge datums  110  shared between the lower lens L 2  and a lockable lower chuck  104 . The chamfer  112  is a groove formed in the lockable lower chuck  104  by precisely cutting the lockable lower chuck  104  such that the lockable lower chuck  104  meets the lower lens L 2  at edge datums  110 . Edge datums  110  are precise edges shared between the lower lens L 2  and the lockable lower chuck  104 . 
     The lockable lower chuck  104  is allowed to translate radially in any direction to allow the upper lens L 1  to be seated in proper alignment  106  on a raised ring  114  of the lower lens L 2 . The raised ring  114  is molded as a part of the lower lens L 2 . The raised ring  114  has a thickness of between about 10 μm and about 15 μm. The raised ring  114  allows the lower lens L 2  to behave as a lower bell. Accordingly, the raised ring  114  serves as a lower bell contact and as a spacer to maintain a correct adhesive gap between the upper lens L 1  and the lower lens L 2 . The raised ring  114  allows the upper lens L 1  to self-align to the lower lens L 2 . Supporting precision balls  102  allow such radial and horizontal translation of the lockable lower chuck  104  in any direction. There are at least three supporting balls  102  to support the lockable lower chuck  104 . The precision balls  102  are surrounded by a thin layer of grease to hold the precision balls  102  in place during assembly and to reduce wear during use. The upper bell chuck  108  precisely guides the upper lens L 1  into the proper position with respect to the top surface of the lower lens L 2 . 
       FIG. 2  shows an aligning apparatus  201  in which an upper lens L 1  is aligned with respect to the edge datums  110  shared by the lower lens L 2  and the lockable lower chuck  104 , in accordance with an embodiment of the present invention. The lockable lower chuck  104  (or bottom fixture) is held fixed after alignment with respect to the upper bell chuck  108 . Such an arrangement allows alignment  202  of the upper lens L 1  with respect to the edge datums  110 . 
     The choice of techniques, between the apparatus of  FIG. 1  and  FIG. 2 , depends on the desired optical characteristics of the doublet and the tolerances of various features on the lower lens L 2 . Note that lack of symmetry between the lenses is exaggerated in  FIG. 1  and  FIG. 2  to highlight the differences in the two methods. 
     An important aspect of the present invention is the use of supporting precision balls  102  to align the upper lens L 1  with respect to the lower lens L 2 . There are at least three supporting balls  102  to support the lockable lower chuck  104 . In the apparatus of  FIG. 1 , the lenses are self-aligned by contact of their shared optical interfaces. This self-aligning is enabled by the radial freedom of the lockable lower chuck  104 . Another important aspect of the present invention is the use of supporting precision balls  102  to align the upper bell chuck  108  with respect to the lockable lower chuck  104 . The bell chuck aligning occurs in an earlier step before the lens aligning. During the bell chuck aligning, the lockable lower chuck  104  is free to move radially with respect to each other until locked in alignment by meltable wax or any alternative method of attachment such as epoxy adhesive. However, before the lens aligning apparatus can be utilized to align the upper lens L 1  with respect to the lower lens L 2 , the upper bell chuck  108  needs to be calibrated or aligned with respect to the lockable lower chuck  104 . 
     Details of Bell Chuck Aligning 
       FIG. 10  is an isometric cross-sectional view of the lens aligning apparatus during a perpendicularity aligning process  1001  of the upper bell chuck  108 , in accordance with an embodiment of the present invention. The lens aligning apparatus is fitted with an alignment tool  1003  for perpendicularity. The alignment tool  1003  ensures perpendicularity of the upper bell chuck  108  with respect to the base plate  304 . A base plate bore  1007  positions the alignment tool  1003  with respect to the base plate  304 . The alignment tool  1003  includes a threaded hole  1005  for clamping the alignment tool  1003  with respect to the base plate  304 . A sleeve  1009  positions the upper bell shaft  406  with respect to the alignment tool  1003  by contacting an outer radial edge of the upper bell shaft  406 . The sleeve  1009  shares a coaxial center with the alignment tool  1003  and is supported in the alignment tool  1003 . After the upper bell shaft  406  is positioned into alignment by the alignment tool  1003 , the flexural bearings  308  are tightened around the outer radial edge of the upper bell shaft  406  using flexural clamps  302 . The flexural bearings  308  hold the upper bell shaft  406  such that the upper bell shaft  406  passes through a center axis of the flexural bearing housing  310  and the flexural bearings  308 . The flexural bearings  308  preferably precisely hold the upper bell shaft  406  into perpendicular alignment and a centered position in the lens alignment apparatus. The upper bell chuck  108  is part of a lower end of the upper bell shaft  406 . The upper bell chuck  108  and the upper bell shaft  406  share a coaxial axis. Accordingly, positioning the upper bell shaft  406  automatically positions the upper bell chuck  108 . 
     The alignment tool  1003  is bolted to the base plate  304  with a screw through the base plate bore  1007 . The alignment tool  1003  comprises low coefficient of thermal expansion (CTE) material, preferably 6061-T6 aluminum. The sleeve  1009  is comprises a higher CTE material, preferably acetal. The upper bell shaft  406  is preferably 303 stainless steel. The alignment tool  1003 , the sleeve  1009 , the base plate  304  and the upper bell chuck  108 , including the upper bell shaft  406 , are cooled in a refrigerator, preferably to approximately −20° C. The parts are then removed from the refrigerator. Before significant warming can occur, the alignment tool  1003  with attached base plate  304  is mated to the upper bell chuck  108  by inserting the upper bell chuck  108  into the alignment tool  1003  to a depth that will result in the flexural bearings  308  remaining planar during a subsequent step. 
     The combination alignment tool  1003  with base plate  304  is then allowed to warm to room temperature after which the remaining parts from the lens aligning apparatus are fitted to the combination. The flexural bearings  308  are then clamped into alignment at their inner and outer surfaces by tightening a top nut  314  at the top of the upper bell shaft  406  and the flexural clamp nuts  312  fastening the flexural clamps  302 . 
     The entire lens aligning apparatus as shown in  FIG. 10  is returned to the refrigerator and cooled, preferably to approximately −20° C. The lens aligning apparatus is then removed from the refrigerator. The alignment tool  1003  is removed by unscrewing the screw holding the alignment tool  1003  to the base plate  304 , detaching the base plate  304  from the flexural bearing housing  310 , and slipping the alignment tool  1003  off the upper bell chuck  108 . These steps, after removing the lens aligning apparatus from the refrigerator, are preferably carried out quickly while the cooled components are still cold. 
     Substantially all the parts shown in  FIG. 10  are then allowed to warm to room temperature before the base plate  304 , without the alignment tool  1003 , is fastened to the flexure housing  310  with screws (not shown). The screws are set to a torque that matches that used during the room temperature flexure alignment, described above, to replicate any part distortions that may have resulted from the attachment forces. 
     The axis of the upper bell chuck  108  is now perpendicular to the top surface of the base plate  304 . The perpendicularity is defined by the outside shaft diameter  1017 , or outer radial edge, of the upper bell shaft  406  with respect to a top surface of the base plate  304 . The sleeve  1009  is preferably machined with dimensions such that at room temperature the sleeve  1009  has a tight interference fit with the alignment tool  1003  and the upper bell shaft  406 . However, the machining should allow the sleeve  1009  to maintain an interference fit with the alignment tool  1003  at approximately −20° C., but with a movable fit between the sleeve  1009  and the upper bell shaft  406 , thereby allowing insertion and removal of the alignment tool  1003 . Such thermal properties of the components allows the upper bell chuck  108  to be held rigidly in perpendicular alignment with the base plate at the operating temperature, in other words, room temperature. The base plate bore  1007  with a stub (not shown) on the alignment tool  1003  ensures that all screw hole patterns will be in sufficient alignment to allow the flexure bearings  308  to align to the upper bell shaft  406 . The perpendicularity aligning process  1001  is then complete. 
       FIG. 11  shows the lens aligning apparatus during a coaxial aligning process  1101  of the lockable lower chuck  104  with respect to the upper bell chuck  108 , in accordance with an embodiment of the present invention. The upper bell is aligned to the lower bell by clamping a bell alignment ball  1103  between the upper bell chuck  108  and lockable lower chuck  104  while allowing the lockable lower chuck  104  to translate radially. The lockable lower chuck  104  is initially free to translate radially. The lockable lower chuck  104  translates radially by rolling on its supporting precision balls  102  positioned between the lockable lower chuck  104  and the base plate  304 . There are preferably three supporting precision balls  102  preferably evenly positioned at approximately 120 degree spacing near the periphery of the lockable lower chuck  104  to allow radial translation. The clamping force is applied to the voice coil actuator  306  of  FIG. 3 , thereby moving the upper bell chuck  108  downward. The lockable lower chuck  104  is preferably locked into the aligned position by a curing epoxy  602 . The curing epoxy  602  is already pre-applied between the underside of the lockable lower chuck  104  and the pedestal just underneath the underside of the lockable lower chuck  104 . The curing epoxy  602  is also pre-applied to the supporting precision balls  102 . After the epoxy has cured, the clamping force and bell alignment ball  1103  are removed to complete the alignment process of the upper lens L 1  and lower lens L 2 . 
       FIG. 12  is a close-up view  1201  of the lens aligning apparatus during the bell aligning  1101  of  FIG. 11 , in accordance with an embodiment of the present invention. The lockable lower chuck  104  is directly aligned with the bell alignment ball  1103 . The top of the surface of the lockable lower chuck  104  includes a chamfer  112 . The lower surfaces of the lower lens L 2  are the adjacent counterbore bottom and wall of the chamfer  112  of the lockable lower chuck  104 . Accordingly, it is important that the chamfer of the lockable lower chuck  104  is accurately machined relative to the counterbore surfaces of the lower lens L 2 . The coaxial aligning process  1101  is then complete. 
     More Details of Lens Doublet Aligning 
       FIG. 3  is a perspective view  301  of a lens aligning apparatus, in accordance with an embodiment of the present invention. The lens aligning apparatus includes, among other things, a base plate  304 , an actuator  306 , a flexural clamp  302 , a flexural bearing  308 , a flexure housing  310 , flexural clamp nuts  312 , a top nut  314  and a floating lower chuck  316 . The flexural clamp  302  secures the flexural bearing  308  into place. 
       FIG. 4  is a cut-away perspective view  401  of the lens aligning apparatus of  FIG. 3 , in accordance with an embodiment of the present invention. The lens aligning apparatus further includes, among other things, the upper bell chuck  108 , an upper bell shaft  406  and a vacuum passage  408 . The upper bell chuck  108  is attached at a lower end of the upper bell shaft  406 . One or more flexural bearings  308  support the upper bell shaft  406  in an upright position. The upper bell shaft  406  traverses through a center of the one or more flexural bearings  308 . The flexural bearing housing  310  is attached to outer radial edges of the flexural bearings  308 . The flexural bearing housing  310  supports the one or more flexural bearings  308  within the flexural bearing housing. The base plate  304  supports the lockable lower chuck  104  and the flexural bearing housing on an upper portion of the base plate  304 . A floating lower chuck  316  is positioned to float above the lockable lower chuck  104  and the base plate  304 . The vacuum passage  408  passes traverses though a center axis of the upper bell chuck  108 . The base plate  304  supports the mechanical insert  404 , or heater  404 , in a center portion of the base plate  304 . The heater  404  includes a drilled hole  402  for reducing heat conduction occurring from heat coils to the base plate  304 . 
       FIG. 5  is a close-up view of the flexural bearing  308  of the lens aligning apparatus, in accordance with an embodiment of the present invention. Flexural bearings ensure highly repeatable linear translation of the upper bell chuck  108  with respect to lockable lower chuck  104 . Additionally, stacks of flexural bearings  308  can be free to move to allow initial setup alignment and clamped to lock in the alignment. 
       FIG. 6  shows the lens aligning apparatus during an operation of lens aligning  601  of the upper lens L 1  with respect to the upper bell chuck  108  and the lockable lower chuck  104 , in accordance with an embodiment of the present invention. The upper lens L 1  is placed in the lockable lower chuck  104  by hand after the upper bell chuck  108  is preferably raised approximately one quarter of inch (¼ in.) by a pneumatic cylinder of the upper bell chuck  108 . Then, the upper bell chuck  108  is lowered first by the pneumatic cylinder and then by the voice coil  306 . The upper lens L 1  is seated between the upper bell chuck  108  and the lockable lower chuck  104  by the force of the voice coil  306 , and is thereby aligned with the bell chucks. A vacuum passage  408  is used for subsequent handling of the upper lens L 1 . The floating lower chuck  316 , discussed above with reference to  FIG. 4 , is optional. There are at least three supporting balls  102  (two shown) to support the floating lower chuck  316  above the base plate  304 . As discussed above with reference to  FIG. 1 , there are at least three supporting balls  102  (two shown) to support the lockable lower chuck  104  above the base plate  304 . 
       FIG. 7  shows the lens aligning apparatus during a lens raising  701  of the upper lens L 1  in preparation for placement of the lower lens L 2 , in accordance with an embodiment of the present invention. The vacuum passage  408  applies suction to the upper lens L 1 . Accordingly, the upper lens L 1  is raised first by the voice coil  306 , then by the pneumatic cylinder as the upper bell chuck  108  is raised. 
       FIG. 8  shows the lens aligning apparatus during a lens placing  801  of the lower lens L 2 , in accordance with an embodiment of the present invention. The lower lens L 2  is precisely held to be horizontal via edge datums  110  between the lower lens L 2  and the lockable lower chuck  104 . 
       FIG. 9  shows the lens aligning apparatus during a lens aligning  901  of the upper lens L 1  with respect to the lower lens L 2 , in accordance with an embodiment of the present invention. The upper lens L 1  is lowered onto the lower lens L 2 . 
     In the method of lens aligning according to  FIG. 1 , the lockable lower chuck  104  is free to translate radially. Such radial freedom enhances alignment of the upper lens L 1  with respect to the lower lens L 2 , as discussed with reference to  FIG. 1 . The natural alignment of the optical surfaces of the upper lens L 1  and the lower lens L 2  is assured by a natural mating of the optical surfaces. When the ring on L 2  is of diameter larger than a critical value to allow bell centering based on the critical angle for friction. The natural mating of the optical surfaces occurs because the lockable lower chuck  104  is free to translate radially. Accordingly, to some extent, the lens aligning apparatus relies on the ability of the lower lens L 2  to self-align with the upper lens L 1  via the radial freedom of the lockable lower chuck  104 . This self-alignment of the lenses uses the upper surface of the lockable lower chuck  104  while perpendicular to the upper bell chuck  108 . This perpendicularity is accomplished during a previous perpendicularity aligning process  1001  of the upper bell chuck  108 . This perpendicular aligning process  1001  is discussed above with reference to  FIG. 10 . 
     On the other hand, in the method of lens aligning according to  FIG. 2 , the lockable lower chuck  104  is fixed with respect to the upper bell chuck  108 . In this embodiment, the upper bell chucks undergoes a previous coaxial aligning process  1101  and is fixed into coaxial alignment. This coaxial aligning process  1101  is discussed above with reference to  FIG. 11 . 
     Once the lenses are aligned, the lenses are ultra-violet (UV) cured into a doublet assembly. The upper bell chuck  108  is raised using the pneumatic cylinder. Then, the doublet assembly is removed by hand from the lens aligning apparatus. 
     Advantageously, the present invention is much lower in cost than conventional methods when considering capital and operator labor. A reason for this costs savings is due to the passive aligning of the lower lens L 2  to the upper lens L 1 . This passive aligning is enabled by a previous aligning of the upper bell chuck  108  and the lockable lower chuck  104 . The upper bell chuck  108  undergoes perpendicular bell aligning with respect to the lockable lower chuck  104 , as discussed with reference to  FIG. 10 . The lockable lower chuck  104  undergoes coaxial bell aligning with respect to the upper bell chuck  108 , as discussed with reference to  FIG. 11 . The bell aligning utilizes, among other things, an alignment ball  1103 , supporting precision balls  102  and curing epoxy  602  to affix the lockable lower chuck  104  after aligning the lockable lower chuck  104 . 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.