Enhanced limited field of view simulator
BACKGROUND OF THE INVENTION 
     Various methods have been employed to provide visual imagery to produce the sensation of flying for pilot training simulators. Some have used video generated systems while others have used computer generated imaging (CGI) to project visual imagery onto a screen, producing a normal field of view. Limited Field of View (LFOV) systems are those in which the field of view is less than a full 360×360 degree continuous visual image. A typical LFOV system would be a fully reproduced continuous visual image of 160 degrees (horizontal)×60 degrees (vertical). 
     In a LFOV system, problems result when a primary object of interest, such as an enemy fighter, target, runway, etc. migrates outside of the field of view. Once outside of this field of view, the pilot no longer has visual contact with the primary object but must track it using only his instruments. The optimum solution is to produce a fully reproduced 360×360 degree continuous visual image such that the primary object or objects could be visually tracked at all times. However, the computer memory and cost involved (approximately in the order of magnitude of ten times) currently prohibits such a system. Therefore, what is required in the art is a method for visually tracking a primary object at all times without substantially increasing the overall system cost. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention, which is an advancement in the art of aircraft simulators, provides for increasing the visual tracking of a primary object or target without substantially increasing the cost and/or complexity of the simulator. A primary obJect, while within the limited field of view, is fully reproduced and displayed on the screen. However, once the primary object migrates outside of this area, or if an additional primary object is located outside of this area, it is not fully reproduced but is represented by a light spot. The pilot then is visually able to continuously track a primary object. The relative distance between a primary object tracking outside the LFOV and the manned simulated cockpit is illustrated by varying the magnitude of the light spot. Once a primary object passes within the limited field of view, the light spot will be extinguished and replaced by the fully reproduced primary object. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following is a brief description of the drawings: 
     FIG. 1 is a diagrammatic representation of the preferred arrangement of the enhanced limited field of view simulator. 
     FIG. 2 is a diagrammatic representation of the preferred embodiment of the enhanced projecting means. 
     FIG. 3 is a block diagram of the computer means control logic. 
    
    
     DESCRIPTION OF THE INVENTION 
     FIG. 1 of the drawings illustrates a diagrammatic representation of an enhanced limited field of view aircraft simulator with the improvement incorporated therein. The aircraft simulator is comprised of a screen 10, a visual projecting means 11, a manned simulated cockpit 12, a computer means 13, and an enhanced projecting means generally indicated by reference number 14. 
     The visual projecting means 11 receives electronic signals, indicated by line 32, from the computer means 13 and projects imagery onto the screen 10 producing a limited field of view 16. The screen 10 is usually at least partly spherical in shape with the preferred embodiment resulting in a domed structure. The limited field of view system is typically less than the screen area and may be approximately 160 degrees (horizontal) by 60 degrees (vertical). The limited field of view 16 includes background imagery 17 and at least one a primary object 18 such as a target, aircraft, runway, etc., in imagery form. 
     A primary obJect 18 is fully reproduced while within the limited field of view 16. As it starts to migrate outside of this limited field of view 16, it becomes only partially reproduced, as indicated by reference number 18A, and upon totally migrating outside the field 16, the primary object is represented by a light spot 19. Furthermore, if another primary object approaches the manned simulated cockpit from outside the limited field of view and the original primary object is still within the field, then the other primary object will be tracked as a light spot until it too enters the field of view. As long as a primary object is outside of the limited field of view, its position will be tracked as a light spot. 
     Distance information is illustrated by varying the magnitude of the light spot 19. As the relative distance between the primary object increases, the magnitude of the light spot will decrease as illustrated by reference number 19A and as the relative distance decreases, the magnitude of the light spot will increase as illustrated by reference number 19B. 
     The manned simulated aircraft cockpit 12 transmits electronic input signals, indicated by line 33, to the computer means 13. The computer means generates electronic output signals, indicated by line 34, which are transmitted to the enhanced projecting means 14. The enhanced projecting means responds to these signals such that it projects a light spot 19 onto the screen for tracking the primary object 18 outside of the normal field of view. The enhanced projecting means is comprised of a light spot projector, generally referred to by numeral 20, a shutter 21 and a light source 22. The enhanced projecting means is located outside of the pilot&#39;s line of sight. A typical location would be between the screen 10 and in front of the manned simulated aircraft 12. 
     Now, referring to FIG. 2, the light source 22, which may be a laser light source, generates and transmits rays of light 35 to a shutter 21. The shutter 21 is positioned such that in its full closed position the transmission of light is effectively blocked, while in its full open position the rays of light are substantially transmitted through the shutter 21. Between these two positions the rays of light are proportionally transmitted. The opening and closing of the shutter 21 is controlled electronically by output signals, indicated by line 34A, from the computer means 13. 
     The rays of light 35 transmitted through the shutter are received along the &#34;C&#34; axis 36 and redirected by the light spot projector along axes &#34;A&#34; and &#34;B&#34; (37, 38) and finally projected out of the light spot projector 20 as indicated by line 39. The light spot projector 20 may be, but not necessarily, a two part construction including a first and second assembly (23, 24). If the rays of light 35 received from the shutter 21 along the &#34;C&#34; axis 36 do not coincide with the &#34;A&#34; axis 37, then a third mirror 25 located within the second assembly 24 may be used to bend the rays of light along the the &#34;A&#34; axis 37. The first assembly 23 rotates about the &#34;A&#34; axis and is driven by a first servo-motor 26 through a first geared assembly 27. The first servo-motor 26 may be mounted to the second assembly 24. The rays of light received along the &#34;A&#34; axis by the first assembly 23 are bent along an orthogonal axis &#34;B&#34; 38 by a first mirror 28 attached to the first assembly 23. The light transmitted along the &#34;B&#34; axis is bent and redirected out of the light spot projector 20 by a second mirror 29. The second mirror 29 is attached to the first assembly 23, rotated about the &#34;A&#34; axis 37 with the first assembly 23, and also rotates independently about the &#34;B&#34; axis through a second geared assembly 30 driven by a second servo-motor 31. The second servo-motor 31 is also attached to the first assembly 23. The rotation positioning by the first and second servo-motors (26, 31) are controlled electronically by output signals 34B and 34C from the computer means 13, 
     Referring to FIG. 3, the computer means receives input signals from the manned simulated aircraft cockpit as indicated by Block A. Once this information has been received, the coordinates and attitude of the simulated aircraft cockpit are calculated as indicated by Block B. The primary object&#39;s coordinates are received from the main program, these coordinates and the simulated aircraft coordinates are used to calculate the slant range between the simulated aircraft and the primary obJect as indicated by Block C. The result of this calculation is fed into Blocks D and F. In Block D the information is used to calculate the axal rotations necessary to rotate the light spot projector to track the primary object. As a result, output signals are transmitted to the first and second servo-motors for the appropriate degree of rotation as indicated by Block E. Simultaneously in Block F it is determined if the primary object is within the normal field of view. If it is, output signals are transmitted to the shutter to close, thereby blocking the transmission of light as indicated by Block G. If the primary object is not within the normal field of view, then the shutter&#39;s opening position is calculated and resulting output signals are transmitted to the shutter as indicated by Blocks H and J. 
     The programming of the computer means corresponding to the above steps, described generally in Blocks A through J, is within the capacity of those skilled in the art. 
     These descriptions and details have been shown for the purpose of illustrating this invention and that it will become apparent to those skilled in the art that various changes and/or modifications may be made without departing from the original spirit and scope of the invention.