Abstract:
An optic assembly is provided, that assembly comprising: a bullet collection lens; a plurality of fiber optic fiber bundles; and those fiber optic bundles being parallel to a central channel.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/321893, filed Apr. 8, 2010. This application is herein incorporated by reference in their entirety for all purposes. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to apparatus and methods for uniform angle resolution over the entire FOV. 
       BACKGROUND OF THE INVENTION 
       [0003]    The known collection optic assembly illustrated in  FIGS. 1 and 2 , consists of a barrel spherical collection lens  9  and seven bundles of fiber optic strands  11 , each bundle  11  dedicated to a specific photon sensing detector (not shown). Each fiber bundle  11  contains over 1000 fiber optic strands. One fiber optic bundle  13  is located in the center of the six surrounding bundles  15 . All seven fiber optic bundles  11  are pre-cast and end polished to precision diameters prior to assembly. This center bundle  13  is aligned to the system boresight axis. In the such a configuration, these six surrounding bundles are spaced at 60° with respect to each other and inclined at 14° with respect to the center bundle. They are also sized and positions to be in tangential contact to the center bundle and to each other. These bundles are epoxied into a ferrule (not shown) having precision sized gap and precision angled holes. Precision ferrules, fixtures and skilled technicians are required to properly fabricate and assemble the collection optic assembly. As illustrated in  FIG. 2 , significant space is left in the ferrule between the bundles  13 , 15  to allow for the correct orientation with respect to the barrel lens  9 . In this previous configuration, it was necessary to maintain a precision air gap  17  between the polished ends of the seven fiber bundle to the rear surface of the collection lens within +/−0.001 inches or less. 
         [0004]    The previous design yielded poor gain curve performance in the center of the field of view (FOV), thereby resulting in poor angle resolution. This was a key system performance parameter of seekers since most weapon systems typically track in the center of the FOV at the termination range. 
         [0005]    Expensive component costs and fixture costs. Difficult assembly requiring skilled technicians. High number of assembly process steps. 
         [0006]    What is needed, therefore, are techniques to optimize the seeker gain curves to generate a uniform angle performance over the 14 degree linear field of view (FOV). 
       SUMMARY OF THE INVENTION 
       [0007]    One embodiment of the present invention provides an optic assembly, the assembly comprising, a bullet collection lens, a plurality of fiber optic fiber bundles, and the fiber optic bundles being parallel to a central channel and abutting a flat side of the bullet collection lens. 
         [0008]    Another embodiment of the present invention provides such an optic assembly further comprising thin wall shrink sleeving disposed around each fiber optic bundles in the plurality of fiber optic bundles. 
         [0009]    A further embodiment of the present invention provides such an optic assembly further comprising a collar disposed around the plurality of fiber optic bundles. 
         [0010]    Yet another embodiment of the present invention provides such an optical assembly wherein the collar is disposed proximate to an end of the plurality of fiber optic bundles, and the end of the plurality is polished and flush with the collar. 
         [0011]    A yet further embodiment of the present invention provides such an optical assembly wherein the bullet lens is configured to optimize a spot size being ported to fibers within the plurality of fiber optic fiber bundles. 
         [0012]    Still another embodiment of the present invention provides such an optical assembly wherein each fiber optic bundle comprises a plurality of fiber optic fibers surrounded by a conformable sleeve. 
         [0013]    A still further embodiment of the present invention provides such an optical assembly wherein the plurality of fiber optic bundle comprises seven fiber optic bundles. 
         [0014]    One embodiment of the present invention provides a method for the manufacturing of an optical assembly; the method comprising: assembling a plurality of fiber optic bundles within a collar; aligning ends of bundles within the plurality of fiber optic bundles with each other such that the ends of bundles are substantially coplanar; polishing the ends of bundles flush to the collar; applying the ends to a flat surface of a bullet collection lens. 
         [0015]    Another embodiment of the present invention provides such a method further comprising inspecting the plurality of fiber optic bundles after the assembling a plurality of fiber optic bundles. 
         [0016]    A further embodiment of the present invention provides such a method, the method further comprising inspecting aligned ends of the bundles. 
         [0017]    Yet another embodiment of the present invention provides such a method, the method further comprising inspecting the ends once polished flush with the collar. 
         [0018]    A yet further embodiment of the present invention provides such a method further comprising inspecting the optical assembly once completed. 
         [0019]    The features and advantages described herein are not all-inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and not to limit the scope of the inventive subject matter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a diagram illustrating a prior art optic assembly. 
           [0021]      FIG. 2  is a diagram illustrating a plan view of a prior art optic assembly. 
           [0022]      FIG. 3  is a elevation view illustrating an optic assembly configured in accordance with one embodiment of the present invention. 
           [0023]      FIG. 4  is a plan view illustrating a cross section of an optic assembly configured in accordance with one embodiment of the present invention. 
           [0024]      FIG. 5  is a flowchart of a method for manufacturing an optical assembly configured according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    One embodiment of the present invention, illustrated in  FIG. 3  provides a bullet collection lens  12  having a curved end  14  and a flat end  16 . A plurality of fiber optic bundles  18  are collected into a collar  20 . Bundles  18  are formed by many optical fibers  22  surrounded by a conformable sheath or sleeving  24 . The collar  20  compresses the bundles  18  together, deforming the rounded bundles  18  into a “flower” shaped cross section illustrated in  FIG. 4 . The fiber bundles  18 , are aligned such that they have a flat end. The end of the now assembled plurality of fiber bundles is polished flush to the collar  20  allowing for a smooth joint to the flat surface of the bullet collection lens  12 . The fiber optical bundles  18  are abutted to the flat surface  16  of the bullet lens at their polished end flush with the collar  20 . The bundles  18  may be secured to the collar  20  and to the ends of the fiber bundles  18 . The bundles  18  are thus in contact with the lens  12  in a way that is substantially free of gaps. 
         [0026]    The previous design rejected energy in the surrounding bundles (the energy exceeded the NA limits of the fibers), resulting in flat gain curves at the center of the FOV. In contrast to the previous design, bullet lens, by collecting all the energy, provides a uniform transform between amplitude and angle space, thus excellent angle response over the FOV of the seeker. 
         [0027]    By altering the lens design from the spherical lens to the bullet lens, and by making the surrounding bundles parallel to the center channel, the numerical aperture (NA) of the fibers are now matched with the bullet lens performance. 
         [0028]    As illustrated in  FIG. 5 , the system is produced by a method comprising several steps. The optical fiber bundles are assembled with a conformable sleeve  32 . The bundles thus formed are aligned within the collar such that the end of the bundle is flush with the surface of the collar  34 . The ends are polished  36  and the polished ends of the assembly are coupled to the bullet lens  38 . After each step in the process, inspection  40 ,  42 ,  44  may occur allowing for improved quality control. 
         [0029]    An additional benefit of the bullet lens design was: it simplified the fabrication of the fiber bundles and the assembly of the system. The fiber bundles are constructed as a grouping rather as separate bundles, reducing the fabrication time. The assembly process of the fiber bundles to the lens requires multiple fabrication steps to set the lens spacing and the orientation of the fibers to the lens. The bullet lens design simple allows the fibers to be ganged together and butted to the base of the bullet lens. 
         [0030]    The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.