Patent Publication Number: US-2004042797-A1

Title: Low profile FSO transceiver and apparatus for mounting same to a window

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention generally relates to free-space optical (FSO) communications systems, and, more specifically, to a low-profile FSO transceiver and an apparatus for mounting the transceiver to a window.  
       [0003] 2. Background Information  
       [0004] With the increasing popularity of wide area networks (WANs), such as the Internet and/or the World Wide Web, network growth and traffic has exploded in recent years. Network users continue to demand faster networks and more access for both businesses and consumers. As network demands continue to increase, existing network infrastructures and technologies are reaching their limits.  
       [0005] An alternative to present day hardwired or fiber network solutions is the use of wireless optical communications. Wireless optical communications utilize point-to-point communications through free-space and therefore do not require the routing of cables or fibers between locations. Thus, wireless optical communications are also known as free-space or atmospheric optical communications. For instance, in a free-space optical communication system, a beam of light is directed through free-space from a transmitter at a first location to a receiver at a second location. Data or information is encoded into the beam of light, and therefore, the information is transmitted through free-space from the first location to the second location.  
       [0006] A conventional free-space optical system is shown in FIGS. 1A and 1B. The free-space optical system includes a pair of terminals (i.e., transceivers)  10  that are typically located on or in separate buildings or towers, such as depicted by buildings  11  and  12 . Each terminal  10  includes a primary collector  13  to which a secondary mirror  14  is coupled via a plurality of rigid struts  16 . The terminals further include a transmitted signal lens  18  mounted within secondary mirror  14 , and a set of transmitter/receiver optics and electronics  20 . All of components  13 ,  14 ,  16 ,  18 , and  20  are operatively coupled to a yoke that is connected to a base  22  via a gimbal assembly, such that these components are all moved in response to a gimbaled movement of the yoke relative to a static surface on which the base  22  is placed.  
       [0007] With reference to FIG. 1B, data is transmitted from a terminal  10 T to a terminal  10 R in the following manner. An optical signal  24  is generated by transmitter/receiver optics and electronics  20 T of terminal  10 T and directed through an opening  26 T defined in primary collector  13 T towards transmitted signal lens  18 T, which produces a collimated signal  28 . As collimated signal  28  moves toward terminal  10 R, the width of the signal diverges very gradually. As will be recognized by those skilled in the art, the divergence of the various optical signals depicted in the Figures contained herein are exaggerated for clarity. Upon reaching terminal  10 R, the outer portions of collimated signal  28  impinge upon primary collector  13 R, which comprises a concave mirrored surface that redirects those portions of the signal that impinge upon it toward secondary mirror  14 R. Collimated signal  28  is then reflected by secondary mirror  14 R towards the secondary mirror&#39;s focal point  30 , where it is received by transmitter/receiver optics and electronics  20 R.  
       [0008] The conventional terminal mounting technique that employs the base and gimbaled assembly discussed above has several drawbacks. One drawback is that since the base is typically mounted on a floor, the terminal is susceptible to floor motion, such as vibrations caused by people and/or equipment in offices or rooms in which the terminal is located. The conventional terminal is also somewhat obtrusive, occupying a significant amount of office space. Furthermore, the conventional mounting technique enables users to potentially cause damage to a terminal and interfere with received or transmitted signals. Accordingly, it would be advantageous to provide FSO transceivers and mounting equipment that enables FSO equipment to be deployed in an office such that the equipment has minimal impact on the office environment, and the activity of office personnel are unlikely to cause adverse effects to the FSO equipment.  
       SUMMARY OF THE INVENTION  
       [0009] A free-space optical (FSO) transceiver head and mounting assembly to enable the FSO transceiver head to be mounted to a window. The FSO transceiver head has a binocular configuration including respective sets of transmit and receive optics configured to facilitate transmission and reception of optical signals. The mounting assembly provides a pair of adjustable axes to enable the FSO transceiver head to be rotated and tilted relative to an axis that is normal to the window. The mounting assembly also provides adjustable feet for fine-pointing. Upon assembly, the entire apparatus has a depth of approximately 3½ inches, enabling it to be deployed in a standard-sized window frame behind a window blind. Generally, the apparatus may be deployed on any type of window, including but not limited to office windows, vehicle windows and outbuilding windows. A breakaway feature is also provided such that the apparatus will break free from a window to which it is mounted rather than having the window break when a sufficient force is applied to the mounting assembly and/or transceiver head.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
     [0011]FIG. 1A is an illustration of a conventional free-space optical communications system that uses on-axis primary and secondary reflectors and provides transmitting and receiving capabilities at a pair of transceiver stations disposed at remote locations within respective buildings;  
     [0012]FIG. 1B shows how an optical communications signal is transmitted by a first transceiver station and received by a second transceiver station;  
     [0013]FIG. 2 is an exploded view of an FSO transceiver head and mounting assembly in accordance with one embodiment of the invention;  
     [0014]FIG. 3 is an assembled view of the apparatus of FIG. 2;  
     [0015]FIG. 4 is an isometric view of the apparatus of FIG. 2 viewed from outside of a window to which the apparatus is mounted, wherein the front plate has been removed for to more clearly illustrate the components disposed behind it;  
     [0016]FIG. 5 is an isometric view of the apparatus of FIG. 3, wherein the transceiver head is rotated 45 degrees about a pivotal X axis.  
     [0017]FIG. 6 is a partially-exploded view of the apparatus of FIG. 3 showing further details of the adjustable feet employed by the invention to enable fine pointing of the transceiver head;  
     [0018]FIG. 7 is an exploded view illustrating further details of the FSO transceiver head of FIG. 2;  
     [0019]FIG. 8 is a frontal elevation view of the FSO transceiver head;  
     [0020]FIG. 9 is an exploded view of a fiber positioner assembly used to position the end of optical fibers used for receiving and transmitting optical signals;  
     [0021]FIG. 10 is an isometric view of a positioning fixture used to align the fiber positioner assemblies within the primary optics of the transceiver heads;  
     [0022]FIG. 11 is a cross-section view corresponding to section cut  11 - 11  of FIG. 3;  
     [0023]FIG. 12 is an isometric view of the apparatus of FIG. 2 further including a cover used to protect the apparatus from access by unauthorized personnel;  
     [0024]FIGS. 13A, 13B, and  13 C show various views of one embodiment of a detachable foot mount assembly, wherein FIG. 13A shows an exploded isometric view, FIG. 13B shows a plan view, and FIG. 13C shows an elevation sectional view corresponding to the section cut  13 C- 13 C or FIG. 13B; and  
     [0025]FIG. 14A shows an isometric view of an apparatus installation employing a window-frame mounting assembly that is mounted to a window frame.  
    
    
     DETAILED DESCRIPTION  
     [0026] Embodiments of a free-space optical (FSO) transceiver head and mounting assembly to enable the FSO transceiver head to be mounted to a window are described herein. In the following description, numerous specific details are disclosed to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.  
     [0027] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.  
     [0028] In one example embodiment of the present invention, point-to-point free-space optical communications are provided from a transmitter to a receiver. The transmitter and receiver may be located at the same location or at different locations such as on different buildings within a line of sight of each other. It is appreciated that the transmitter and the receiver may be parts of transceivers, or transmitter-receiver combinations, at their respective locations, such that bi-directional communications are provided. In the example embodiment, the transmitter includes an optical source that generates an optical communications beam, such as a laser beam or the like, on which data or information is modulated. The optical communications beam is not limited to being monochromatic or to any particular wavelength or color and may include the visible light as well as ultra violet or infra-red portions of the spectrum.  
     [0029] Exploded and assembled isometric views of an apparatus  100  comprising a low-profile binocular FSO transceiver and associated window mounting assembly in accordance with one embodiment of the invention are respectively shown in FIGS. 2 and 3. Primary components and subassemblies of apparatus  100  include a base plate  102 , a coarse pointing ring  104 , and an FSO transceiver head  106 . As further shown in FIG. 4, upon deployment, base plate  102  is mounted to a window  108  via a plurality of adjustable feet  110 . Coarse pointing ring  104  is rotatably-coupled to base plate  102  via a “slip ring” interface, thereby enabling the coarse pointing ring and transceiver head  106  to be rotated about a Z axis that is normal to the window to form a first axis of rotation.  
     [0030] Transceiver head  106  is pivotally mounted to coarse pointing ring  104  via a pair of trunnion mounts, each including a plain bearing  114  and a shaft  116 , thereby enabling transceiver head  106  to be pivoted about an X axis to form a second axis of rotation. In one embodiment, the configuration of the mounting assembly and transceiver head  106  is such that the transceiver has a field of regard of plus or minus 45 degrees. For example, in the embodiment, transceiver head  106  may be rotated approximately plus 45 degrees about the X axis; as shown in FIG. 5; to get the minus 45 degrees, the coarse pointing ring is rotated 180 degrees about the Z axis. The position of the transceiver head about the X-axis is secured via a clamping mechanism that includes a coarse pointing fin  118  and a locking screw  120 . Upon assembly, the shaft of locking screw  120  is disposed within both a slot  122  defined in the coarse mounting fin and a slot  124  defined in an upright member  126  extending upward from coarse pointing ring  104 . The upright member further includes a slot  128  that is configured to slidingly engage the sides of coarse pointing fin  118 . Once a desired position of transceiver head  106  about the X-axis is reached, locking screw  120  is tightened (through threading into a nut  130 ), thereby locking the position in place. If desired, an optional washer  132  may also be employed.  
     [0031] In one embodiment, the “slip ring” interface between base plate  102  and coarse mounting ring  104  is configured in the following manner. A groove  134  is formed in the internal periphery of base plate  102 . In general, a tongue will be formed around an external periphery of coarse pointing ring  104  to mate with the groove formed in base plate  102 , thereby forming a tongue and groove interface. In the illustrated embodiment, a groove  136  is formed in the periphery of coarse pointing ring  104  so as to define a pair of flanges  138  and  140 , wherein flange  138  functions as the tongue. In the illustrated embodiment, the rotation position of the coarse pointing ring about the Z-axis is secured via one or more screws  142  that are threaded into respective threaded holes  144 , causing the end of the screws to engage an opposing portion  146  on the top of the base plate.  
     [0032] With further reference to FIG. 6, in one embodiment each of adjustable feet  110  comprise a base  150 , a threaded shaft  152 , a helical spring  154 , and an internally threaded cap  156 . Upon assembly, a ball-end  158  of threaded shaft  152  is captured by a socket  160  defined within a slotted boss  162  formed in the base. The threaded end of thread shaft  152  passes through a hole  164  defined in a lobe  166  extended outward from base plate  102 , and the lobe is captured by threading internally-threaded cap  156  onto threaded shaft  152 . In one embodiment, base  150  is secured to the window using a double-sided adhesive  168 . Optionally, other common means may be used to secure bases  150  to the window.  
     [0033] Typically, three adjustable feet  110  will be employed, enabling the base plate to be pivoted in a tripod-like manner. In this instance, the adjustable feet may be disposed approximately 120 degrees apart, as is common for a typical tripod, or may be disposed with uneven angular separations, such as depicted in the Figures herein. The adjustable feet enable the distance between each lobe  166  and window  108  to be independently adjusted by turning threaded caps  156  so as to increase or decrease the height of helical springs  154 . Generally, these “fine pointing” adjustments will be made after coarse positioning adjustments (i.e., coarse rotational positioning about the Z and X axes) have been performed. As a result, a pointing direction P of the transceiver head can be finely positioned along any direction within a “cone of pivotation”  170 .  
     [0034] With reference to FIG. 7, in one embodiment transceiver head  106  includes an optically-transparent front plate  180 , a pair of secondary optics  182 , a chassis  184 , a pair of primary optics  186 , and a pair of fiber positioner assemblies  188 . As defined herein, optically-transparent means that the component is made of a material through which an FSO optical signal may pass with minimal attenuation. It is noted that since FSO optical signals may comprise infra-red light, which is not visible to the human eye, an optically-transparent component does not need to appear transparent to the human eye. In one embodiment, front plate  180  is made of a clear acrylic (which is visibly clear).  
     [0035] Upon assembly, secondary optics  182  are disposed within respective recesses  190  defined in the backside of front plate  180 . Each secondary optic may be secured within its corresponding recess using one of many conventional mounting techniques, such as adhesives, fasteners, and the like. In one embodiment, a plurality of slots  192  are defined on the periphery of recesses  190  to hold liquid adhesive, whereby the secondary optic is secured when the adhesive cures. Likewise, front plate  180  may be secured to chassis  54  using a conventional mounting technique. In one embodiment, an adhesive is used to bond the front plate to the chassis. Front plate  50  also includes a pair of horizontally-disposed cutouts  194  and vertically-disposed cutouts  196  and  198  to assist in securing the front plate to chassis  184 , further details of which are in shown FIG. 8.  
     [0036] In the illustrated embodiment, chassis  184  comprises a pair of wedge-cut tubes  200  that define respective chambers  202 . The wedge-cut tubes are connected by an upper web  204  and a lower web  206 . In one embodiment, a bridge  208  is also connected between the tubes. As explained in further detail below, bridge  208  is used to facilitate mounting of an alignment scope  210  to the transceiver head.  
     [0037] Upon assembly, primary optics  186  are secured within respective chambers  202 . In one embodiment, this is enabled by means of a plurality of tabs  212  extending toward the back of each wedge-cut tubes  200  and a plurality of ledges  214  defined within respective chambers  202 , whereby the primary optics are encapsulated between a frontside  216  of the tabs and a backside of the ledges.  
     [0038] Once the front plate, secondary optics chassis and primary optics are assembled, fiber positioner assemblies  188  are secured to the backside of the primary optics. Upon assembly, a cylindrical portion  218  of a fiber positioner body  220  (see FIG. 9) is disposed with an aperture  222  defined through the center of each primary optic. The diameter of aperture  222  is slightly larger than the diameter of cylindrical portion  218 , thereby enabling the fiber positioner assembles to be positioned along the X and Y axis. In one embodiment, a positioning fixture  224  is used to position the fiber positioner assembles within the respective holes during an alignment process in which a test signal T is directed toward the transceiver head, as shown in FIG. 10. During the positioning process, a pair of alignment pins engage a pair of respective alignment holes  226  defined in each fiber positioner assembly. The position of each fiber positioner assembly is adjusted in the X and Y directions, as appropriate, via X and Y stages of the positioning fixture until a desired XY alignment of an end  228  of an optical fiber  230  is obtained, further details of which are shown in FIG. 11. An adhesive  232  is then injected into the gap between cylindrical portion  218  and aperture  222  and allowed to cure to secure each fiber positioner assembly to its respective primary optic (optionally, the adhesive may be applied to cylindrical portion  218  prior to inserting the positioner body into aperture  222 ).  
     [0039] As further shown in FIG. 9, each fiber positioner assembly  188  includes a Z-axis fiber positioner block  234  having a cylindrical extension  236  that slidingly engages the surface of a bore  238  defined in fiber positioner body  220  to enable the end  228  of optical fiber  230  to be positioned along the Z axis. Positioning along the Z axis is further enabled by a pair of springs  240  having first ends that are captured within respective holes  242  defined in Z-axis fiber positioner block  234  and opposing ends that are defined within corresponding holes (not shown) defined in fiber positioner body  220 . Z-axis fiber positioner block  234  further includes a hole from which a fiber alignment tube  244  extends, wherein the fiber alignment tube is used to fixedly position the end  228  of optical fiber  230  relative to the positioner block. Upon assembly, a shoulder screw  246  having a threaded shaft that engages a threaded hole defined in fiber positioner body  220  (not shown) is used to adjust the Z-axis position of the end of the optical fiber. The shaft and head of the shoulder screw are disposed within a counterbore  248  defined in Z-axis fiber positioner block  234  (See, e.g., FIG. 5). An optional dust cover  250  may be provided to prevent dust and other particulars from obscuring the end of the optical fiber.  
     [0040] A pair of apparatus&#39;  10  are installed in respective offices to provide a FSO link between network nodes to which the transceivers are attached. In order to establish the FSO link, the two transceivers first must be aligned. The alignment process is facilitated by the pivotal transceiver head positioning adjustments about the X and Z axes, and the tripod-like positional adjustment that is provided by adjustable feet  110 . Initially, coarse adjustments will be made to align the transceivers. This is further facilitated by alignment scope  210  and a beacon  252 .  
     [0041] During the foregoing fiber positioner assembly alignment process, alignment scope  210  is also aligned with the optics of transceiver head  106 . In one embodiment, alignment scope  210  is coupled to a mounting plate  254  made of a magnetic material, such as steel, as shown in FIG. 5. In one configuration, three magnets (not shown) are mounted to the backside of three mounting pads  256  radially-spaced 120 degrees apart, as shown in FIG. 8. Upon assembly, mounting plate  254  is drawn toward these magnets. At the same time, three screws (not shown) are threaded into threaded holes  258  defined in chassis  184  so as to engage the underside of mounting plate  254 , enabling the alignment scope to be positioned in a tripod-like manner.  
     [0042] The use of the foregoing magnetic attachment scheme enables the alignment scope to be easily removed after the FSO transceiver heads have been properly aligned. Furthermore, the scheme enables the alignment scope to be reattached for further alignment, if necessary, whereby the alignment scope will still be properly aligned with the FSO optics.  
     [0043] Returning to FIG. 11, a plurality of ray traces corresponding to a received optical signal  260  and a transmitted optical signal  270  are shown. As depicted, the transceiver head includes a receive sub-assembly comprising the left half of the cross-section, and a transmit sub-assembly comprising the right half of the cross-section. In the illustrated embodiment, components that make up receive and transmit sub-assemblies are substantially identical. Optionally, the components of the two sub-assemblies may have different configurations.  
     [0044] The receive optical signal  260 , which is transmitted by another FSO transceiver disposed in a remote location (e.g., in another building), is collected by a primary receive optic  186 R. The primary receive optic comprises a parabolic mirror that is configured to redirect the light rays toward a secondary receive optic  182 R. The light rays are then reflected toward the end of a receive optical fiber  230 R, which receives the incoming receive optic signal. The receive optic signal passes through the receive optical fiber and is processed using circuitry designed for such purposes. In one embodiment, a portion of the circuitry may be located proximate to the transceiver head, e.g., within an enclosure covering the apparatus, is shown in FIG. 12. In another embodiment, the circuitry is located in a remote chassis that is linked to the transceiver head using appropriate fiber-based cabling.  
     [0045] The light paths illustrated by the ray traces for the transmitted optical signal  270  are substantially identical to the received optical signal, except in the reverse direction. Accordingly, the transmitted optical signal begins as a modulated optical beam that is emitted out of the end  228  of a transmit optical fiber  230 T. As the modulated optical beam exits the optical fiber, it impinges on various portions of a secondary transmit optic  182 T. The light rays are then directed toward a primary transmit optic  186 T, which redirects the light rays outward to be received by a remote FSO transceiver. As with the receive subassembly, the transmit subassembly may further include circuitry for generating the modulated optical beam that may be disposed proximate to the transceiver head, or in a remote chassis connected to the transceiver head using appropriate fiber-based cabling.  
     [0046] As further depicted in FIG. 12, the apparatus may be configured such that it occupies an envelope of space having a depth D of approximately 3½ inches. Accordingly, the apparatus may be installed within a standard window frame. In fact, depending on the particular installation, the apparatus may be installed on a window behind a window blind, whereby the occupants of the office in which the apparatus is installed may not even be aware of its presence.  
     [0047] Breakaway Feature  
     [0048] In accordance with one aspect of the invention, the mounting assembly is configured to break away from it mounting surface (e.g., a window) when a sufficient force (e.g., a moment, horizontal, or vertical force) is applied to the mounting assembly and/or the FSO transceiver head. This breakaway feature provides enhanced safety in the event the apparatus is grabbed or otherwise disturbed by someone proximate to the window. For example, in one embodiment described below, the apparatus will become detached from its feet rather than possibly causing the window to break.  
     [0049] Returning to FIG. 6, upon assembly, ball-end  158  of threaded shaft  152  is captured by socket  160  defined in slotted boss  162 , as discussed above. The slots in the boss enable the socket to expand to receive the ball-end of the shaft when a sufficient force is applied to the threaded shaft toward the socket. This mechanism works similarly in reverse. Upon sufficient force being applied to the threaded shaft away from the socket, the top portion of the ball end engages the inner lip of the socket, causing the socket to expand, thereby enabling the shaft to be detached. Since the base  150  of each of the adjustable feet is affixed to the window via double-sided adhesive  168 , and threaded shafts  152  are operatively coupled to coarse pointing ring  102  (and thus the mounting assembly), the remainder of the apparatus (i.e., mounting assembly and FSO transceiver head) will become detached from the window when sufficient force is applied to either the transceiver head or the mounting assembly, thus preventing the window from being broken.  
     [0050] Various views corresponding to a second embodiment of a detachable foot assembly  300  is shown in FIGS.  13 A- 13 C. Assembly  300  includes a cap  302 , a fine pointing adjustment screw  304 , a washer  306 , a helical compression spring  308 , a steel leg  310 , a magnet  312 , a foot  314 , and an adhesive pad  316 . Generally, the head of fine pointing adjustment screw  304  will be secured within a recess in cap  302 , such as via a press fit or adhesive. Optionally, the combination of the cap and screw may be purchased as a single component.  
     [0051] Upon assembly, the upper portion of the shaft of fine pointing adjustment screw  304  is disposed within hole  164  of lobe  166 , as depicted in FIG. 13C. The lower threaded portion of shaft is threaded into mating threads formed in a bore  318  of steel leg  310 . The helical compression spring  308  is captured around the minor diameter potion of steel leg  310 , and is compressed via opposing surfaces comprising the underside of lobe  166  and a shoulder  319  formed in steel leg  310 , whereby a gap  320  between the base of lobe  166  and the top of steel leg  310  may be adjusted by turning the fine pointing adjustment screw via cap  302 .  
     [0052] Magnet  312  is disposed within a bore  322  passing though foot  314  and secured within the bore via a press fit or adhesive. In one embodiment, foot  314  is made of aluminum. Foot  314  may be made of other common materials as wells, such as plastics and various metals. Preferable, foot  314  will be made of a nonferromagnetic material, but this isn&#39;t a strict requirement. The head of magnet  312  is positioned such that the base of steel leg  310  is coupled to it via magnetic attraction. Furthermore, the base of the steel leg is disposed with a chamfered recess  324  formed in foot  314  and includes a mating chamfer  326  (having a large diameter). The chamfered edges improve side load release and ease assembly.  
     [0053] Upon assembly of an apparatus (e.g., apparatus  100 ) employing detachable foot assembly  300 , feet  314  are secured to a window via adhesive pads  316 . In one embodiment, detachable foot assembly  300  will be pre-assembled prior to securing the apparatus to the window so as to properly position feet  314 . In an optional embodiment, a template may be used to position the feet on the window.  
     [0054] In the event of an undesirable load is applied to FSO transceiver head  106  and/or the mounting apparatus, steel legs  310 , the magnetic force securing the base of steel legs  310  to feet  314  will be exceeded, causing the mounting apparatus and FSO transceiver head to be detached from the window. The amount of force necessary to produce this result may be tuned via magnet sizing, coupling surface dimensions, and magnetic strength. Thus, damage to the window can be prevented, enhancing safety. Reattachment of the mounting apparatus may be performed by simply reseating the steel legs  310  within chamfered recesses  324 .  
     [0055] In the illustrated embodiments described above, the apparatus is generally mounted to a window, such as an office window. This is not meant to be limiting, as the apparatus may be mounted to any type of window, including vehicle windows (e.g., automobiles, boats, aircraft, etc.) and windows for outside installations, such as outdoor cabinets and out-buildings.  
     [0056] In some instances, it may be desired to mount the FSO transceiver head/mounting apparatus to a window frame, rather than the window itself. For instance, the window might be fragile or have other problems. As illustrate in FIG. 14, this may be accomplished via a window-frame mount adaptor  400 . Generally, the window frame-mount adapter will have an open-box configuration, preferably having at least two sides  402  and a base  404 . The base of the adapter and the side configuration may be adapted to fit the contours or overall outline of the apparatus mounted to it, as shown in FIG. 14. In one assembly embodiment, appropriate sides  402  of the window-frame mount adapter are secured to corresponding window frame members  406  and  408 . Apparatus  100  is then mounted to base  404  in the same manner it would be mounted to a window described above. In another assembly embodiment, apparatus  100  is first mounted to base  404  of the window-frame mount adapter, and then the adapter is secured to the window frame. Preferably, at least the base  404  of the window-frame mount adapter should be made of a material that is optically transparent, comprising one of various plastics or reinforced glasses. The adapter may be formed from a single piece of material, or may comprise an assembled configuration made of one or more materials. Generally, casting and heat/pressure forming operations may be used to manufacture the adapter.  
     [0057] In the foregoing detailed description, the method and apparatus of the present invention have been described with reference to specific exemplary 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 present invention. The present specification and Figures are accordingly to be regarded as illustrative rather than restrictive. Furthermore, it is not intended that the scope of the invention in any way be limited by the above description, but instead be determined entirely by reference to the claims that follow.