Abstract:
A first part has first, second and third inwardly-facing surface portions angularly spaced about an axis, and a second part has outwardly-facing fourth, fifth and sixth surface portions spaced angularly about the axis, a radial distance from the axis to each surface portion decreasing progressively in a given direction along the axis. Each of the fourth, fifth and sixth surface portions faces, is closely adjacent to, and is substantially congruent in shape with a respective one of the first, second and third surface portions. At least one of the first and second parts is an optical component.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to optical systems and, more particularly, to techniques for accurately aligning optical components with respect to each other. 
     BACKGROUND 
     In an optical system, especially a high-performance optical system, it is often necessary for lenses or other optical components to be very precisely aligned with respect to each other. A positional tolerance between the optical axes of two parts may need to be as small as a few microns. 
     As an example, one known configuration involves two lenses, where one lens has a recess that receives the other lens. The recess has a radially-inwardly facing cylindrical surface, and the lens in the recess has a radially-outwardly facing cylindrical surface, the two cylindrical surfaces differing only slightly in diameter, and being closely adjacent each other. Assembling or disassembling the two lenses can be very difficult because, if one lens is tilted even slightly with respect to the other during assembly or disassembly, the cylindrical surfaces bind and resist relative movement of the lenses. 
     To avoid this problem, it is possible to adjust the diameter of at least one of the cylindrical surfaces, in order to increase the space between the lenses. In order to align these two lenses, it is possible to use optical tooling, along with some additional structure that holds the lenses in place after they have been aligned. However, this approach is time consuming, and provides a reduced level of accuracy. 
     While these pre-existing approaches have been generally adequate for their intended purposes, they have not been satisfactory in all respects. No single existing approach provides fast and reliable assembly or disassembly of two optical components, with a high degree of centering accuracy, and without time-consuming alignment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention will be realized from the detailed description that follows, taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  is a diagrammatic sectional side view of an optical apparatus that embodies aspects of the present invention, and that includes first, second and third lenses. 
         FIG. 2  is a diagrammatic bottom view of the first lens in  FIG. 1 . 
         FIG. 3  is a diagrammatic top view of the second lens in  FIG. 1 . 
         FIG. 4  is diagrammatic bottom view of the second lens in  FIG. 1 . 
         FIG. 5  is a diagrammatic top view of the third lens in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a diagrammatic sectional side view of an optical apparatus  10  that embodies aspects of the present invention, and that includes three lenses  12 ,  13  and  14 . The optical apparatus  10  could have any desired orientation.  FIG. 1  shows the apparatus  10  in one possible orientation that has been arbitrarily selected to facilitate a clear and understandable explanation of the apparatus  10 . The depicted orientation, and references to directions in the discussion below, are intended to be exemplary and not limiting. 
     The assembled optical apparatus  10  has an optical axis  18 . The lenses  12 - 14  each have a respective optical axis that is coincident with the optical axis  18 . The lenses  12 ,  13  and  14  are each made from a known optical material that will refract radiation having wavelengths within a range of interest. For example, the lenses may be made of glass where the apparatus  10  is to be used for visible radiation, or may be made of silicon or germanium where the apparatus  10  is to be used for infrared radiation. 
       FIG. 2  is a diagrammatic bottom view of the lens  12 . With reference to  FIGS. 1 and 2 , the lens  12  has a convex surface  21  in the center of an upper side thereof, and has a concave surface  22  in the center of a lower side thereof. An annular, planar, axially-upwardly facing surface  23  extends radially outwardly from an outer peripheral edge of the convex surface  21 , and is perpendicular to and concentric to the optical axis  18 . An annular, planar, axially-downwardly facing surface  24  extends radially outwardly from an outer peripheral edge of the concave surface  22 , and is perpendicular to and concentric to the optical axis  18 . An annular, inwardly-facing surface  26  of frustoconical shape extends downwardly and outwardly from an outer peripheral edge of the annular surface  24 , and is concentric to the optical axis  18 . An annular, planar, axially-downwardly facing surface  27  extends radially outwardly from a lower peripheral edge of the frustoconical surface  26 , and is perpendicular to and concentric to the optical axis  18 . 
     An annular, cylindrical, radially-outwardly facing surface  28  extends axially from an outer peripheral edge of the surface  23  to an outer peripheral edge of the surface  27 , and is concentric to the optical axis  18 . With reference to  FIG. 2 , the frustoconical surface  26  has portions  31 ,  32  and  33  that are designated by broken lines, and that are angularly spaced from each other by intervals of approximately 120°. It will be noted that the radial distance from the axis  18  to the frustoconical surface  26  decreases progressively in an upward direction along the axis  18 , and this is also true for each of the surface portions  31 ,  32  and  33 . 
       FIG. 3  is a diagrammatic top view of the lens  13 , and  FIG. 4  is diagrammatic bottom view of the lens  13 . With reference to  FIGS. 1 ,  3  and  4 , the lens  13  has a convex surface  41  in the center of an upper side thereof, and a concave surface  42  in the center of a lower side thereof. An annular, planar, axially-upwardly facing surface  43  extends radially outwardly from an outer peripheral edge of the convex surface  41 , and is perpendicular to and concentric to the optical axis  18 . An annular, planar, axially-downwardly facing surface  44  extends radially outwardly from an outer peripheral edge of the concave surface  42 , and is perpendicular to and concentric to the optical axis  18 . An annular, inwardly-facing surface  46  of frustoconical shape extends downwardly and outwardly from an outer peripheral edge of the annular surface  44 . The frustoconical surface  46  is concentric to the optical axis  18 . 
     An annular, planar, axially-downwardly facing surface  47  extends radially outwardly from a lower peripheral edge of the frustoconical surface  46 , and is perpendicular to and concentric to the optical axis  18 . An annular, outwardly-facing surface  48  of frustoconical shape extends downwardly and outwardly from an outer peripheral edge of the annular surface  43  to an outer peripheral edge of the annular surface  47 , and is concentric to the axis  18 . With reference to  FIG. 3 , the frustoconical surface  48  has surface portions  51 ,  52  and  53  that are designated by broken lines, and that are angularly spaced from each other by intervals of approximately 120°. The radial distance from the axis  18  to the frustoconical surface  48  decreases progressively in an upward direction along the axis  18 . This is also true for each of the surface portions  31 ,  32  and  33 . 
     With reference to  FIG. 4 , the frustoconical surface  46  has portions  56 ,  57  and  58  that are designated by broken lines, and that are angularly spaced from each other by intervals of approximately 120°. The radial distance from the axis  18  to the frustoconical surface  48  decreases progressively in an upward direction along the axis  18 . This is also true for each of the surface portions  51 ,  52  and  53 . 
     With reference to  FIG. 1 , the annular surface  24  on lens  12  is adjacent and engages the annular surface  43  on lens  13 , thereby preventing upward axial movement of the lens  13  relative to the lens  12 . An air gap is present between the two surfaces  22  and  41 . The frustoconical surface  26  on lens  12  is closely adjacent and may engage the frustoconical surface  48  on lens  13 . In the assembled configuration shown in  FIG. 1 , the radial gap (if any) between frustoconical surfaces  26  and  48  is very small, for example on the order of about one micron. The surface portions  31 ,  32  and  33  of the frustoconical surface  26  are respectively adjacent the surface portions  51 ,  52  and  53  of the frustoconical surface  48 , and each of the surface portions  31 ,  32  and  33  is substantially congruent in size and shape with the corresponding surface portion  51 ,  52  or  56  that is adjacent thereto. The cooperation between the frustoconical surfaces  26  and  48  ensures accurate centering of the lens  13  in relation to the lens  12 , with a very small centering tolerance (for example a centering tolerance on the order of about one micron). When the lenses  12  and  13  are being assembled into or disassembled from the configuration shown in  FIG. 1 , the frustoconical shape of the surfaces  26  and  48  helps to ensure that these surfaces do not bind if one lens happens to tilt slightly in relation to the other lens. 
       FIG. 5  is a diagrammatic top view of the lens  14  of  FIG. 1 . With reference to  FIGS. 1 and 5 , the lens  14  has a convex surface  61  in the center of an upper side thereof, and a concave surface  62  in the center of a lower side thereof. An annular, planar, axially-upwardly facing surface  63  extends radially outwardly from an outer peripheral edge of the convex surface  61 , and is perpendicular to and concentric to the optical axis  18 . An annular, planar, axially-downwardly facing surface  64  extends radially outwardly from an outer peripheral edge of the concave surface  62 , and is perpendicular to and concentric to the optical axis  18 . An annular, outwardly-facing surface  68  of frustoconical shape extends downwardly and outwardly from an outer peripheral edge of the annular surface  63  to an outer peripheral edge of the annular surface  64 , and is concentric to the optical axis  18 . 
     With reference to  FIG. 5 , the frustoconical surface  68  has surface portions  71 ,  72  and  73  that are designated by broken lines, and that are angularly spaced from each other by intervals of approximately 120°. The radial distance from the axis  18  to the frustoconical surface  68  decreases progressively in an upward direction along the axis  18 . This is also true for each of the surface portions  71 ,  72  and  73 . 
     With reference to  FIG. 1 , the annular surface  44  on lens  13  is adjacent and engages the annular surface  63  on lens  14 , thereby preventing upward axial movement of the lens  14  in relation to the lens  13 . An air gap is present between the two surfaces  42  and  61 . The frustoconical surface  68  on lens  14  is closely adjacent and may engage the frustoconical surface  46  on lens  13 . In the assembled configuration shown in  FIG. 1 , the radial gap (if any) between the frustoconical surfaces  46  and  68  is very small, for example on the order of about one micron. The surface portions  56 ,  57  and  58  of the frustoconical surface  46  are respectively adjacent the surface portions  71 ,  72  and  73  of the frustoconical surface  68 , and each of the surface portions  56 ,  57  and  58  is substantially congruent in size and shape with the corresponding surface portion  71 ,  72  or  76  that is adjacent thereto. The cooperation between the frustoconical surfaces  46  and  68  ensures accurate centering of the lens  14  in relation to the lens  13 , with a very small centering tolerance (for example a centering tolerance on the order of about one micron). When the lenses  13  and  14  are being assembled into or disassembled from the configuration shown in  FIG. 1 , the frustoconical shape of the surfaces  46  and  68  helps to ensure that these surfaces do not bind if one lens happens to tilt slightly in relation to the other lens. 
     In  FIG. 1 , the intersections of most surfaces are shown as relatively sharp corners. However, these sharp corners could alternatively be replaced with rounded corners of relatively small radius. 
     In the disclosed embodiment, the surfaces  24 ,  43 ,  26 ,  48 ,  44 ,  63 ,  46  and  68  are all formed using known techniques of single diamond point turning, in order to achieve a high degree of accuracy. Other surfaces on the lenses  12 - 13  could also optionally be formed though the use of diamond point turning. However, the invention is not limited to diamond point turning, and it would be possible to alternatively use any other suitable technique to accurately form surfaces on the lenses. 
     In the disclosed embodiment, the surfaces  26 ,  48 ,  46  and  68  are shown as being frustoconical. Alternatively, however, it would be possible to use some other suitable shape, including but not limited to a shape corresponding to the exterior side surface of any of a variety of frustums. 
     Although the components  12 ,  13  and  14  in the apparatus  10  of  FIG. 1  are all lenses, one or more of them could alternatively be some other type of component. For example, one or more of these components could be an optical mirror. Also, some specific materials have been discussed above for the components  12 - 14 , but they could alternatively be made of any other suitable material. For example, where any of the components  12 - 14  is a lens, it could be made of a suitable plastic material. As another example, where any of the components  12 - 14  is a mirror, it could be made of metal. 
     Although selected embodiments have been illustrated and described in detail, it should be understood that a variety of substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the claims that follow.