Abstract:
A system and method for focusing electromagnetic radiation is presented. A lens has an outside perimeter. A curved lens surface is located inside the outside perimeter. The curved lens surface is to bend at least one wavelength of electromagnetic energy passing through the curved surface. One (or more) mounting surface(s) are located between the outer perimeter and the curved lens surface. The mounting surface has at least one flat surface.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. Provisional Application Ser. No. 61/886,703, filed Oct. 4, 2013; the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The current invention relates generally to apparatus, systems and methods for optical systems. More particularly, the apparatus, systems and methods relate to mounting optical components. Specifically, the apparatus, systems and methods provide for creating mechanical features on optical components such as lenses, for example. 
         [0004]    2. Description of Related Art 
         [0005]    The field of optical fabrication covers the manufacture of optical elements, typically from glass, but also from other materials. Glass is used for nearly all optical elements because it is highly stable and transparent for light in the visible range of wavelengths. Glass optics are economically manufactured to high quality in large quantities. Glass also can be processed to give a nearly perfect surface, which transmits light with minimal wave front degradation or scattering. 
         [0006]    Additional materials besides glass are also used for optics. Plastic optics have become increasingly common for small lenses (&lt;25 mm) and for irregular optics with reduced accuracy requirements. Metal mirrors are used for applications with stringent dynamic requirements or thermal loading. Optics made from crystals are used for special purpose lenses and prisms. 
         [0007]    The optical engineer who is specifying the optical elements needs to understand how the size and quantity affect the manufacturing process, quality, and cost. Special tooling is required for large and difficult parts, which drives the cost up. However, special tooling can also lead to an efficient process, reducing the per-item cost for parts made in large quantities. Like any industrial process, optical fabrication has significant economies of scale, meaning that items can be mass-produced more efficiently than they can be made one at a time. There is always a tradeoff between improved efficiency and tooling costs. (“Tooling” refers to any special equipment used for manufacturing an item. Tooling is not used up in the process, so it can be used repeatedly). If only a few elements are needed, it does not make sense to spend more on tooling than it would cost to make the parts by a less efficient method. 
         [0008]    The most difficult aspect for many optical components comes from the tight tolerances specified for optics. The optical system engineer must assign specifications that balance performance with fabrication costs. The tolerances must be tight enough to assure acceptable system performance, yet not so tight that the parts cannot be made economically. For a particular project, the fabrication process is usually selected to achieve the specified tolerances. Parts with tighter requirements are nearly always more expensive and take longer. 
         [0009]    As the trend to minimize size, weight, and power in military imaging systems continues, designs must meet performance requirements with fewer lens elements. Conventional machining uses lens spacers that can often make control of the airspace difficult on steep surfaces and may not allow for easy control of lens tilt. What is needed is a better optical system. 
       SUMMARY 
       [0010]    One aspect of an embodiment of the invention may include a system and method for focusing electromagnetic radiation. A lens has an outside perimeter. A curved lens surface is located inside the outside perimeter. The curved lens surface is to bend at least one wavelength of electromagnetic energy passing through the curved surface. One (or more) mounting surface(s) are located between the outside perimeter and the curved lens surface. The mounting surface has at least one flat surface. 
         [0011]    In one aspect the invention, another embodiment may provide for an optical system that includes a first lens with a first flat surface as well as a second lens with a second flat surface. The optical system can further include a spacer with a first flat surface and a second flat surface. The first flat surface of the first lens presses against the first flat surface of the spacer and the second flat surface of the second lens presses against the second flat surface of the spacer. 
         [0012]    Another aspect of the invention can be a method of building an optical device that includes a physical mounting structure and an optical surface on the same piece of material. The method begins by fabricating an optical surface on a material. The optical surface is to later bend at least one electromagnetic waveform passing through the optical surface. A physical mounting structure with at least one flat surface is also fabricating on the material. The physical mounting structure allows the material to be mounted in an optical system using the flat surface(s). 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    One or more preferred embodiments that illustrate the best mode(s) are set forth in the drawings and in the following description. The appended claims particularly and distinctly point out and set forth the invention. 
           [0014]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example methods, and other example embodiments of various aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale. 
           [0015]      FIG. 1  illustrates how prior art lenses were mounted in an optical system. 
           [0016]      FIG. 2  illustrates a preferred embodiment of a novel way to produce physical mounting features in two lenses and mount them together. 
           [0017]      FIG. 3  illustrates details of the example mounting features of  FIG. 2 . 
           [0018]      FIG. 4A  illustrates an example side view of a diamond cutting system that can be used to cut novel mechanical mounting features in a lens. 
           [0019]      FIG. 4B  illustrates an example top view of a lens on the a diamond cutting system that can be used to cut novel mechanical mounting features in a lens. 
           [0020]      FIG. 5  illustrates an example embodiment of a method for mounting lenses with mechanical features built into them. Similar numbers refer to similar parts throughout the drawings. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  illustrates a prior art lens system  1 . It includes two lenses  3 A-B separated by two spacers  5 A-B. Alternatively, the spacers  5 A-B could be a single cylindrical spacer; however, for ease of explanation, two spacers  5 A-B will be discussed. Lens  3 A has a flat upper surface  10  and a curved lower surface  11  while lens  3 B has a curved upper surface  12  as well as a curved lower surface  14 . Because the spacers  5 A-B must be placed between the lower curved surface  11  of lens  3 A and the upper curved surface  12  of lens  3 B, they are difficult to fabricate with tight physical tolerances. This is because it is hard to create curved surfaces on the spacers  5 A-B in exactly the same shape as the corresponding curved surfaces of the lenses  3 A-B. 
         [0022]    Very simple optical designs can provide excellent nominal performance, but can make definition of a good tolerance budget very difficult. Very high sensitivities require very tight tolerances to maintain good performance for the as-built hardware. However, as discussed above with reference to  FIG. 1 , it is very challenging to create highly accurate spacers  5 A-B with very tight tolerances because of their curved top  7 A-B and curved bottom  9 A-B surfaces. Understanding that diamond turning equipment is, for example, essentially an extreme precision CNC lathe, it can be envisioned how tolerances that would be extremely challenging to hold in a conventional machine shop are able to be held in a diamond turning process. By diamond turning novel features into the lens itself, a spacer with square edges can be used. 
         [0023]    As illustrated in  FIG. 2 , by fabricating lens  13 A-B with mechanical features in them, it is possible to easily manufacture very simple spacers  15 A-B to be used to separate the lenses  13 A-B. While two spacers are discussed, a single simple cylindrical spacer could be used to replace them. Spacers  15 A-B are easier to manufacture and measure making control of airspaces between lenses  13 A-B easier. Additionally, the lens shoulder is machined at the same time as the optical surfaces, thereby providing for surfaces that are extremely perpendicular and centered relative to an optical axis  37 . 
         [0024]    The optical system  16  of  FIG. 2  has two lenses  13 A-B and two spacers  15 A-B, similar to those of  FIG. 1 . The first lens  13 A has spaced apart flat and curved surfaces  27 ,  28  while the second lens  13 B has two spaced apart curved surfaces  29 ,  30 . In general, air  8  fills the space between the lenses  13 A-B but in other configurations, other materials may fill the space between them. In the preferred embodiment, the lenses  13 A-B are formed out of glass, plastic or crystals but in other embodiments they can be formed with other materials. 
         [0025]    One novel aspect of the preferred embodiment is the mechanical features  19 ,  21  (e.g., physical mounting features) are built into the lenses  13 A-B. As best seen in  FIG. 3 , the lens  13 A and mechanical features  19 ,  21  have been formed with a flat surface  50  that is parallel to the flat surface  27  until it reaches curved surface  28 . Somewhat similarly, lens  13 B is formed with flat surfaces  51 ,  52  that are both parallel to surfaces  27  and  50  of lens  13 A. Lens  13 A is formed with a side surface  53  that is perpendicular and  90  degrees with respect to surfaces  27  and  50 . Similarly, Lens  13 B is formed with a side surface  54  that is perpendicular and  90  degrees with respect to surfaces  51  and  52 . Even though  FIG. 3  illustrates spacer  15 A, spacer  15 B can also have similar features. 
         [0026]    As illustrated, the lens surfaces  28 ,  29  can be curved until they reach the spacers  15 A-B. The mechanical features  19 ,  21  formed on the lenses  13 A-B, the spacer(s)  15 A-B used to separate them have flat top surfaces  23 A-B and flat bottom surfaces  25 A-B. These flat surfaces provide for the spacers separating to take advantage of these flat surfaces. Because the spacers  15 A-B have flat top surfaces  23 A-B, flat bottom surfaces  25 A-B, flat outside surfaces  33 A-B, and flat inside surfaces  34 A-B, they are much easier to produce than the curved prior art spacers of  FIG. 1 . Notice that the top surface  23 A of the spacer  15 A, the bottom surface  25 A, the outside surface  33 A and the inside surface  34 A form a cross-section that is rectangular in shape. Similarly, spacer  15 B has a top surface  23 B, a bottom surface  25 B, an outside surface  33 B and an inside surface  34 B that form a cross-section that is also rectangular in shape. Spacers that have a rectangular cross-section are much easier to manufacture and allow for tighter tolerances than prior art spacers that had cross-sections with curved surfaces because mechanical features were not machined into the lenses they were mounted to. 
         [0027]      FIGS. 4A-B  illustrated an example diamond cutting system  70  that is used to cut a material into an optical component  71  that includes a lens and that also includes mechanical/mounting features cut into that same material. While these figures illustrate an example diamond cutting system  70 , those of ordinary skill in the art will appreciate that any high precision cutting system could be used. The material to become the optical component is mounted to a lens mount  73  that rotates/spins in the direction of arrow A. The lens mount  73  is designed to spin with essential no wobble or only a few millionths of an inch of wobble. 
         [0028]    This example diamond cutting tool has a cutting shank  75  positioned above the optical component  71 . The cutting shank  75  is positioned in a shank control mechanism  77  that moves the shank  75  up and down in the directions of arrows B and C. A diamond cutting device  79  is attached to the lower end of the cutting shank  75 . The diamond cutting device  79  cuts the optical component  71  into a convex lens  81  that will includes mechanical features  83  while it is spun by the lens mount  73  spins the optical component. In this illustration, the mechanical feature is a flat cylindrical mounting surface  85  that can later be used with a simple cylindrical spacer to mount this lens  81  in an optical system with a high degree of precision. 
         [0029]    Example methods may be better appreciated with reference to flow diagrams. While for purposes of simplicity of explanation, the illustrated methodologies are shown and described as a series of blocks, it is to be appreciated that the methodologies are not limited by the order of the blocks, as some blocks can occur in different orders and/or concurrently with other blocks from that shown and described. Moreover, less than all the illustrated blocks may be required to implement an example methodology. Blocks may be combined or separated into multiple components. Furthermore, additional and/or alternative methodologies can employ additional, not illustrated blocks. 
         [0030]      FIG. 5  illustrates a method  500  of producing an optical device. The method begins, at  502 , by fabricating an optical surface on a material. The optical surface is to later bend at least one electromagnetic waveform passing through the optical surface. For example, the optical surface can be a convex surface and can be cut into the material using a diamond cutting tool as discussed above. A physical mounting structure that includes a flat surface is fabricating on the material, at  504 . Unlike prior art lenses, this mounting structure is fabricated with the optical surface and flat surface of the physical mounting structure on the same piece of material. In some configurations, physical mounting structure can be fabricated on an outer perimeter of the material. 
         [0031]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. Therefore, the invention is not limited to the specific details, the representative embodiments, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. 
         [0032]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described. References to “the preferred embodiment”, “an embodiment”, “one example”, “an example”, and so on, indicate that the embodiment(s) or example(s) so described may include a particular feature, structure, characteristic, property, element, or limitation, but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element or limitation. Furthermore, repeated use of the phrase “in the preferred embodiment” does not necessarily refer to the same embodiment, though it may.