Abstract:
A system including binoculars augmented with a computer-generated virtual display of navigation information (hereinafter referred to as “nav glasses”) and marine navigation systems employing such binoculars. The computer-generated display is superimposed on the real world image available to the user. Nav glasses also have the components needed to link them to a navigation system computer which is utilized to generate the see-through display of the navigation information. They are preferably equipped with sensors compass and an inclinometer for acquiring azimuth and inclination information needed by the navigation computer and a sensor for measuring any magnification of the field of view. The nav glasses can be employed to lock onto a moving target, which can then be tracked by onboard radar. The navigation system in which the nav glasses are incorporated also accept inputs from other sources such as a shipboard compass, a GPS, and other navigation aids; and a route planning system. The field of view of the nav glasses is calculated from information obtained from the nav glasses and navigation sensors, and a display manager generates a pre-fetch display of navigation information from the route planning and radar inputs. This pre-fetch display or image extends well beyond the nav glass field of view. Consequently, as the glasses are shifted from side-to-side or up or down, all that may be required to match the virtual display to the real world image is to align a different segment of the pre-fetch image with the actual field of view. Once the alignment of the virtual display of navigation information and the actual field of view is completed, the virtual overlay is transmitted in coded form to a video output component of the navigation computer and forwarded to the nav glasses where the virtual display is constructed and superimposed on the real world view.

Description:
RELATED APPLICATION 
     This application is based on prior copending provisional application Ser. No. 60/015,954, filed Apr. 24, 1996, the benefit of the filing date of which is hereby claimed under 35 U.S.C. §§ 119(e) and 120. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to novel, improved navigation aids and, more specifically, to marine binoculars augmented with a visual display of navigation information and to marine navigation systems employing such binoculars. 
     BACKGROUND OF THE INVENTION 
     Ships and boats at sea need a variety of information in order to navigate safely. This information includes: the vessel&#39;s position relative to its planned course; the vessel&#39;s position relative to visible navigation hazards such as land masses and other ships; and the vessel&#39;s position relative to hidden hazards such as submerged rocks, channel boundaries, shipping lane separation zones, and restricted areas. The mariner acquires this information in a number of ways. 
     The first is by visual reference. By monitoring the vessel&#39;s position relative to known points of land, often with the aid of a compass, the navigator can triangulate the ship&#39;s position relative to its intended course. By monitoring other vessels, the navigator calculates whether a course change will be required to avoid a collision. And, by monitoring the ship&#39;s position relative to buoys, lights, and other visual aids to navigation, the mariner can also avoid some of the unseen hazards to navigation. 
     This same information is commonly augmented by radar which also displays the ship&#39;s position relative to visible hazards such as land masses and other vessels. In addition, the radar, with input from the ship&#39;s gyro or magnetic compass, can more accurately calculate range and bearing and perform collision avoidance calculations. 
     To best avoid unseen navigation hazards such as submerged rocks, the navigator needs to continuously calculate the absolute geographic position of the vessel and plot that position against a nautical chart on which the hidden hazards to navigation are indicated. This process is greatly facilitated by use of a Global Positioning Systems (GPS) receiver and an Electronic Chart System (ECS). The ECS displays a digital representation of a conventional paper nautical chart. On this chart, the ECS overlays the position of the ship based on input from the GPS. The ECS usually consists of a navigation computer containing an electronic nautical chart (ENC) database, interfaces to navigation sensors such as those identified below, and a fairly high resolution computer display screen. 
     While the ECS represents a vast improvement over manually plotting the ship&#39;s position against a paper chart, it has a number of drawbacks and limitations. The first is that it is often difficult to relate: (a) the information in the electronic chart display (usually oriented course-up) with (b) the real world as seen from the navigator&#39;s field of view (often a completely different direction). A second significant limitation is that the ECS requires a color, fairly high resolution (therefore fairly large size) display to be most effective. Many mariners, however, navigate from an open cockpit or a flying bridge conning station. There, the lack of space, glare from direct sunlight, and exposure to the elements limit the utility of an ECS display. 
     Others have attempted to improve marine navigation by augmenting marine binoculars with information pertinent to navigation. Heretofore, these attempts have been limited to adding only bearing and, in a few cases, distance information. This information is at best of limited utility in identifying hidden obstacles and other unseen hazards to navigation. Furthermore, these products usually split the field of view between the real world image and an image of a compass, using mirrors and normal lens optics. This is awkward and can actually distract from instead of enhance the real world image available to the mariner. 
     From the foregoing, it will be apparent to the reader that there is a present and continuing need for better aids to marine navigation. 
     SUMMARY OF THE INVENTION 
     The need for improved navigation aids has now to a significant extent been satisfied by instruments which embody the principles of the present invention and are referred to hereinafter as “nav glasses.” 
     Nav glasses are, generally speaking, marine binoculars augmented with a see-through, computer-generated overlay or display of navigation information. The computer-generated display is superimposed on the real world image available to the user. 
     Nav glasses also have the components needed to link them to the navigation computer which is utilized to generate the see-through display of navigation information. Also, they typically are equipped with instruments such as a fluxgate compass and an inclinometer for acquiring azimuth and inclination information needed by the navigation computer. In appropriately configured navigation systems, the nav glasses can be employed to lock onto a moving target, which can then be tracked by onboard radar. 
     The navigation systems in which the nav glasses are incorporated also accept inputs from other sources such as a compass, a GPS, and other navigation aids; a route planning system; and onboard radar. The field of view of the nav glasses is calculated from information obtained from the nav glasses and navigation sensors, and a display manager generates a pre-fetch display of navigation information from the route planning and radar inputs. This pre-fetch display or image extends well beyond the nav glass field of view. Consequently, as the glasses are shifted from side-to-side or up or down, all that is required to match the virtual display to the real world image is to align a different segment of the pre-fetch image with the actual field of view. This is an important feature of the present invention inasmuch as the just-described approach is much faster then generating a new virtual image each time the nav glasses are shifted. If the field of view lies beyond the boundaries of the current pre-fetch image or overlay, a flag is raised; and a new pre-fetch overlay is generated and aligned with the current field of view. 
     Once the alignment of the virtual display of navigation information and actual field of view is completed, the virtual overlay is transmitted in digital form to a video output component of the navigation computer and forwarded to the nav glasses where the virtual display is constructed and superimposed on the real world field of view. Also important is a navigation system feature which allows additional, textual information to be added to the virtual display at the option of the user of the nav glasses. The user also has the option of canceling the display of the additional information at any time. 
     The advantages, features, and objects of the present invention will be apparent to the reader from the foregoing and the appended claims and as the detailed description and discussion of the invention proceeds in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a marine navigation system which includes nav glasses embodying the principles of the present invention; 
     FIG. 2 is a top view of the nav glasses depicted in FIG. 1; 
     FIG. 3 is a bottom view of the nav glasses; 
     FIG. 4 is an end view of the nav glasses; 
     FIG. 5 is a block diagram showing the components of the FIG. 1 nav glasses; 
     FIG. 6 is a fragment of a conventional marine navigation chart; 
     FIGS. 7 and 8 are companion representations of the real world image and virtual overlay available to the user of nav glasses embodying the principles of the present invention; 
     FIG. 9 is a fragment of a second marine navigation chart; 
     FIGS. 10 and 11 are companion representations of a real world view and virtual display of navigation information available to the user of the nav glasses; in this instance, the virtual display involves a three-dimensional projection of navigation data; and 
     FIGS. 12A AND 12B, taken together, constitute a flow diagram depicting the operation of the FIG. 1 navigation system. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawing, FIG. 1 depicts an onboard navigation system  20  which includes a computer  22 , a transceiver  24 , and nav glasses  26  which embody, and are constructed in accord with, the principles of the present invention. Nav glasses  26  provide the mariner or other user looking in the direction of arrow  28  with a real world, magnified image of the scene encompassed by the nav glasses field of view. Superimposed on this image is a virtual, see-through display or overlay of navigation information. This information may include, but is not necessarily limited to: 
     1) azimuth (true) 
     2) text labels of strategic geographical features on the horizon 
     3) highlighted symbols indicating positions of navigation aids such as buoys and lights 
     4) the intended course line and planned cross-track deviation limits 
     5) safety depth contour lines 
     6) a “point-and-click” bullseye target finder 
     7) highlighted symbols indicating positions of ARPA (Automatic Radar Plotting Aid) targets 
     8) course, speed, closest point of approach and time to closest point of approach for tracked ARPA targets 
     9) an instrument gauge displaying critical own-ship navigation information such as: heading, speed, bearing to waypoint, cross-track deviation, depth, and rudder angle 
     Nav glasses  26  have conventional binocular optics, and the real world image is formed by those optics in a conventional manner. The virtual display of navigation information is generated by navigation computer  22  and is transmitted to the nav glasses by either the wireless transceiver shown in FIG. 1 or by a conventional data cable  30  (see FIGS. 3 and 5) supplied in lieu of or in addition to transceiver  24 . 
     Referring now to FIGS. 3-5, nav glasses  26  include a casing  32  which houses the optics that form a real world image of the scene viewed by the user. The optics of nav glasses  26  are collectively identified in FIG. 5 by reference character  33 . They include left and right objective lens  34 L and  34 R (see FIGS. 2 and 3) and corresponding eyepieces  36 L and  36 R (see FIG.  4 ). Rings  38  and  40  allow the user of nav glasses  26  to bring the image formed by optics  33  into sharp focus and to change the magnification offered by nav glasses  26 . 
     Also housed in the casing  32  of nav glasses  26 , as best shown in FIG. 5, are: (a) a microprocessor  42  which controls the flow of data to and from navigation computer  22 ; (b) a virtual display head  44  which employs micro LCD&#39;s and a beam splitter virtual retinal display techniques, or an appropriate alternative to superimpose the see-through display of navigation information on the real world image generated by binocular optics  33 ; (c) a fluxgate compass and inclinometer  46 / 48  or equivalent tracking mechanism; (d) a wireless modem  50 ; (e) a connector  52  for data cable  30 ; and (f) a set of controls collectively identified by reference character  54 . The controls include push buttons  56  and  58  with programmable functions and a thumb-operated track ball  60 . The track ball is employed to position a movable cursor  61  (FIG. 7) on a target selected by the user of nav glass  26 . Push button  58  is then clicked, locking the cursor on the designated target. That enables onboard radar to track the target, making available on the virtual display information such as: the course of the target and its speed, the target&#39;s closest point of approach, and the time to the closest point of approach. 
     Nav glasses  26  have two data channels served by the wireless or cable-type data link. These are: (1) a control channel which sends azimuth and inclination information and the current magnification of the real world image to navigation computer  22 ; and (2) a display channel which receives the computer generated see-through overlay from the navigation computer, typically as a standard VGA-type video signal. 
     Referring now to FIG. 1, navigation computer  22  includes the following elements: 
     1) a PC architecture (CPU and system RAM) 
     2) serial interface ports for receiving navigation information from the GPS and other navigation sensors 
     3) a control data interface port for receiving azimuth, inclination, magnification, cursor position, and push button status information from the nav glasses 
     4) a video display controller capable of generating and sending a standard VGA video signal to the nav glasses 
     5) a hard disk or other long-term storage device for ENC storage and retrieval 
     6) a removable media drive (e.g., floppy, S-RAM, or CD) used for loading and updating the ENC database 
     7) software to: (a) process the navigation sensor inputs, (b) process the azimuth and other control signals from the nav glasses, (c) calculate the angle subtended by the current field of view, (d) use the resulting spatial information to retrieve from the ENC navigation information which should be included in the field of view, and (e) generate the see-through display overlay 
     8) optionally, an available radar interface board which enables the above-discussed target tracking mode of nav glasses  26 . 
     Other sensors may advantageously be interfaced with digital computer  22  to provide to the computer such useful information as rudder angle, engine RPM, propeller pitch, thruster status, and wind force and speed. By interfacing navigation computer  22  both to the GPS and other sensors such as those just described, the see-through display available to the user of nav glasses  26  may also be generated to include a dashboard type of representation with digital emulations of analog gauges, for example an emulation of a tachometer. 
     The details of the several elements of navigation computer  22  are not relevant to an understanding of the present invention, and they will accordingly not be discussed herein. Thus, the serial interface ports of the navigation computer are shown only schematically and collectively identified by reference  62 . These ports input to the computer RAM and/or CPU information supplied by, for example: the Global Positioning System, an onboard compass or gyro compass, a speed log, an echo sounder, ARPA radar, an autopilot, etc. The ENC data storage device is identified by reference character  64  and the drive for the removable data storage device is identified by reference character  66 . I/O interface ports between navigation computer  22  and transceiver  24  (or a data cable such as that bearing reference character  30 ) are identified by reference characters  68  and  70 . 
     Referring still to the drawing, FIG. 6 is a fragment  72  of a marine navigation chart covering the Valdez Narrows. FIG. 7 is a pictorial representation  74  of: (a) the real world image  76 , and (b) a superimposed, see-through, virtual display  78  seen by a user of nav glasses  26  located at the position identified by reference character  80  in FIG. 6 with the nav glasses trained in the direction indicated by reference character  82 . As would be expected, geographical features are readily visible in the real world image as are the manmade structures collectively identified by reference character  83 . 
     In this representative example, information on: (a) the position  80  of the mariner&#39;s vessel  84  from the GPS, and (b) azimuth and magnification information from nav glasses  26  is inputted to navigation computer  22 ; and the ENC database is accessed. Also, if the azimuth is derived from a shaft sensor and is therefore relative, the heading of the vessel, obtained from a magnetic or gyro compass, is inputted to the navigation computer. 
     Navigation computer  22  then calculates the direction and angle subtended by the field of view of nav glasses  26  ;extracts from the ENC database pertinent navigation information included within the estimated field of view using available and proven algorithms; and generates a VGA, see-through image displaying the selected ENC text or labels making up see-through display  78 . 
     The VGA image is transmitted from navigation computer  22  via transceiver  24  to the antenna  86  of modem  50 , thence to VGA overlay display head  44 , which causes see-through virtual display  78  to be superimposed on the real world image  76  generated by binocular optics  33  and seen by the mariner. 
     A perhaps more sophisticated application of navigation system  20  is presented in FIGS. 8 and 9. FIG. 8 is a fragmentary navigation chart  88 . FIG. 9 pictorially depicts the real world image  90  and virtual image  92  seen by a mariner at position  96  (FIG. 8) with his nav glasses  26  trained in the direction indicated by arrow  98 . Natural and manmade geographical features are clearly visible. Also appearing in the mariner&#39;s field of view in the form of a see-through display are: the contour line  100  for a water depth of ten meters needed for vessel  94  to proceed in safety, the course  102  to be followed by the vessel to the berth  104  at the end of pier  106 , and the allowable limits of cross-track deviation from the course identified by reference characters  108  and  110 . In this representative example, therefore, there is a display of navigation data with vectors in all three dimensions to aid in the navigation of vessel  94 . 
     Generation of a see-through virtual display with three-dimensional data as just discussed requires accurate information on azimuth, inclination, and magnification. The requirement for accurate inclination information can be relaxed by providing a tick mark (identified by reference character  112  in FIG. 9) at a vertical edge  114  of see-through virtual display  92 . The mariner aligns real world image  90  and virtual display  92  by registering tick mark  112  with horizon  116 . This eliminates the inclination information needed for computer  22  to align the real world and virtual images. 
     Referring still to the drawings, the operation of navigation system  20  can perhaps best be appreciated by referring to the logic diagram of FIGS. 12A and 12B in which the depicted boxes represent components, states, or functions, the arrows with solid tails represent the flow of control, and the arrows with outline tails represent the flow of data. 
     Available from navigation glasses  26 , as discussed above and shown by box  118  in FIG. 12A, are parameters which describe the orientation of nav glasses  26 . These are the inclination of the glasses provided by inclinometer  48 , the heading of the glasses from fluxgate compass  46 , and the magnification factor determined by the setting of ring  40 . This data is transmitted to navigation computer  22  along with ship heading and position data obtained from navigation sensors such as a gyro compass and a global positioning system (GPS) receiver (box  120 ), route planning information including way points and the intended track of vessel  80  or  96  (box  122 ); the range, bearing, speed, course, closest point of approach, and/or time of closest point of approach of targets being tracked by radar (box  124 ), and inputs from the target-selecting cursor  61  which is employed when more information is wanted on a vessel, obstacle, etc. to which the cursor is locked. Referring now to both FIG.  12 A and FIG. 12B, the nav glass sensor inputs are continuously monitored (routine  125   a ); and the inclination, azimuth, and magnification are computed. The navigation sensors are also continuously monitored (routine  125   b ), and the ship heading and position are computed from the data supplied by those sensors. From the parameters just discussed—inclination, azimuth, magnification, ship heading, and ship position—the field of view of the nav glasses is continuously calculated (routine  126   a ). 
     Concurrently, the virtual overlay or image of navigational information available to the user of nav glasses  26  is generated. Specifically, stored chart information is read from the database  127  in storage device  66  and transmitted to a display manager  127   a . Typically, this information will provide the locations of charted objects such as buoys and lighthouses, the contours of coastlines, and depth contours. The virtual overlay generating process also takes information from a route planning system (box  127   b ) and provides the relevant information to the display manager  127   a  in computer  22 . The information includes the intended track of the vessel, the actual track—which may or may not duplicate the intended track—, and a series of way point positions. The actual route of the vessel is monitored by routine  127   c.    
     At the same time, the data relevant to radar tracked targets is monitored (routine  127   d ) and transmitted to the display manager. As shown in FIG. 12A, this data may include: the position, heading, and speed of the target as well as the closest point of approach to the target and the time to the closest point of approach. 
     The information supplied to the display manager extends over a pre-fetched range which encompasses the unmagnified field of view of nav glasses  26  but extends well beyond that field in all four directions—left, right, up, and down. This formation of the pre-fetch field is an important feature of the present invention because it minimizes the time required to provide a new virtual display when the user of the nav glasses  26  slews the glasses to a new direction. With the pre-fetch image having already been constructed, all that is required to provide the corresponding virtual image when a new field of view appears in nav glasses  26  is to select the appropriate segment from the existing pre-fetch image. This is a much faster process than building a new image from the information discussed above for the new field of view. 
     Another function of computer  22 , shown in FIG. 12A, is to monitor the controls of nav glass  26 ; viz. , the position of cursor  61  and the status of programmable push buttons  56  and  58  (routine  127   e ). 
     Referring now most particularly to FIG. 12B, reference character  128  identifies a routine in which computer  22  determines whether the pre-fetch image encompasses the current field of view of nav glasses  26 . If this question is answered in the affirmative, a further determination is made as to whether a new segment of the pre-fetch image is needed to align the virtual display with the current field of view of nav glasses  26 . If computer  22  finds that the virtual image and field of view are aligned, the comparison process continues. If alignment is required to match the virtual image to the field of view of nav glasses  26 , the pre-fetch image is panned to align the appropriate segment of that image with the actual field of view of the nav glasses as indicated in the block identified by reference character  132 . It was pointed out above that this is a much simpler and correspondingly faster process of matching the virtual display to the actual field of view than is the building a new virtual image from the input data discussed above. 
     In conjunction with the foregoing, the field of view of nav glasses  26  changes when the user of nav glasses  26  adjusts the magnification of nav glasses  26  with magnification ring  40 . Computer  22  treats a new field of view attributable to a change in magnification in the same manner as any other new field of view—i. e. , one resulting from stewing or changing the inclination of nav glasses  26 . 
     When the comparison routine shown in block  128  determines that a current field of view lies beyond the boundaries of the available pre-fetch image, the boundaries for a new pre-fetch image are calculated (see block  134 ); and a flag is raised, indicating that a pre-fetch image with new boundaries is needed. The new pre-fetch overlay is created with the routine identified by reference  136 . Specifically the new boundaries are transmitted to display manager  126   b . The display manager responds by supplying to routine  136  the current data from the sources identified in blocks  118 ,  120 ,  122 , and  124  and the information from database  127  needed to create the new pre-fetch overlay. 
     The new pre-fetch image is supplied to the comparison routine (block  128 ). Because the new pre-fetch image extends beyond the current field of view to the left and right of and above and below the current field of view, routine  128  finds that the current field of view is within the boundaries of the new pre-fetch overlay and passes that information to routine  132  to align the new pre-fetch image with a current field of view. 
     Once the actual field of view is aligned with the virtual image, the virtual image in coded form is routed to video output  138  of computer  22 . The signal from the video output is transferred as by data cable  30  to nav glasses  26 . There, the virtual image is formed as an overlay to the real world image by virtual display head  44  under the control of microprocessor  42 . 
     Referring still to FIG. 12B, there are circumstances in which additional information on a virtually displayed object can be beneficial. For example, in a typical scenario involving a navigation light, it may be advantageous to know that the light is red, flashes on a two second cycle, lies eight miles from the vessel equipped with system  22 , and locates the entrance to a strait. This information can be provided to a window in the virtual display seen by the user of the nav glasses  26  by invoking the routine identified by reference character  140  as can information on vessels being tracked by radar and other useful navigational information. 
     In applications of the invention involving the supply of additional object information, one of the nav glasses pushbuttons (for example, pushbutton  58 ) is programmed as discussed above to function as a query button and the second pushbutton  26  is employed to lock cursor  61  onto a selected object or target. 
     A routine  141  (see FIG. 12A) continuously monitors the position of cursor  61 , the status of cursor lock button  56 , and the status of query button  58  and reports to interface manager  142  on the status of the pushbuttons and the position of the cursor. If the interface manager finds that the query button has been activated, it raises a flag indicating that this has been done and provides the position of the cursor. Routine  140  then interrogates display manager  127   a , retrieving the additional information on the object to which the cursor is locked by the activation of pushbutton  56 . With information on that object available from display manager  127   a , routine  140  builds an information panel and supplies the data constituting that panel to video output  138 . From there the data is routed as by data cable  30  to nav glasses  26 . Microprocessor  42  and virtual display head  44  construct the virtual panel identified by reference character  144  in FIG. 8 from the transmitted data and add this panel to the virtual overlay shown in that figure. 
     The subsequent opening of query switch  58  invokes the routine identified in FIG. 12B by reference character  146 . This routine cancels the transmission of the data from which panel  144  is constructed, and video output  138  routes to nav glasses  26   a  signal which causes panel  144  to disappear from the virtual display seen by the user of nav glasses  26 . 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.