Patent Publication Number: US-2023154351-A1

Title: System and method of adjusting focal distances of images displayed to a user of a simulator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 63/279,566 filed Nov. 15, 2021, which is incorporated herein in its entirety by reference. 
    
    
     FIELD 
     The present disclosure is related generally to adjusting focal distances of images displayed to a user at a designated eye point of a simulator. More particularly, the present disclosure provides systems and methods to adjust a distance between a screen and a mirror of the simulator based on a simulated distance between a designated eye point and an object in an image displayed by the screen and reflected by the mirror. An adjustor is provided to adjust the distance between the screen and the mirror. 
     BACKGROUND 
     An advanced simulator to train a user to operate a vehicle (such as a flight simulator) typically has a primary display to provide an image to the user depicting an environment surrounding the vehicle. Referring to  FIG.  1   , the realism of the image  12  of the primary display  4  is achieved by collimating the light (and thus, the image) to the user  30 , which renders the image at infinity focus. For example, the image may have a focus length of greater than approximately 30 feet. A projector  6  projects the image  12  onto a screen  8  and the image is viewed by the user  30  (such as a pilot) as a reflection in a mirror array  10 . As shown in  FIG.  1   , the image  12  of the primary display  4  is visible to the user as indicated by a first arrow  34  as collimated light rays  14  and seen at a distant focus. The collimated light rays  14  are substantially parallel to each other. 
     Some vehicles, including an aircraft such as a helicopter, may have a window referred to as a “chin” window positioned to provide a downward view from the aircraft as indicated in  FIG.  1    by a second arrow  36 . The chin window may be near the floor of a cabin or cockpit of the aircraft. In some aircraft, the chin window is positioned in front of rudder pedals of the aircraft. A pilot may use the chin window to see a reference point or object (such as the ground) during take-off, landing, and while the aircraft is hovering. 
     Some prior art simulators  2  include a chin display  20  to replicate objects  16 B which would be seen outside the cockpit through a chin window  18 . Known simulators typically use either a real image display system or a wide angle collimated (WAC) display system to display images visible through the chin window. 
     The real image display system  20  uses a monitor or a rear projection screen  22  placed in front of the chin window  18  of the simulator. The pilot or user  30  of the simulator views the image  24  of the real image display system through the chin window  18 . The simulated image  24  created by the real image display system has a view distance of between about 6 feet to about 8 feet. The view distance is equal to the physical distance between the designated eye point  32  of the simulator  2  and the monitor or screen  22  of the real image display system  20 . As will be appreciated by one of skill in the art, the designated eye point  32  represents a preferred or optimal position of an eye of the user  30  when in the simulator. The designated eye point is used when designing components of the simulator to provide an optimal view of images created by the simulator for viewing by the user. 
     The real image display system  20  provides realistic depth cues when the simulator provides a simulation of flying below a simulated height  28  of about 10 feet above the simulated ground  26 . The real image display system also provides a bright and sharp image with a relatively wide field of view (FOV). However, there are several disadvantages with known real image display systems  20 , including that they are not compatible with Night Vision Goggles (NVGs) when those NVGs are focused to be compatible with the near-infinity focus of the primary display  4 . As will be appreciated, this precludes the use of the simulator to provide training for certain activities and for some simulated conditions (such as night flying operations) negatively limiting the training possible with the prior art simulator  2 . 
     Moreover, as generally illustrated in  FIG.  1   , an object  16 B in the image  24  produced by the real image display system  20  for viewing through the chin window  18  will become misaligned with an object  16 A in the collimated image  12  of the primary display  4  when the user&#39;s head moves. This problem is generally illustrated in  FIG.  1    in which an upper portion of a tree  16 A displayed in the image of the primary display  4  is offset horizontally from a lower portion of the same tree  16 B displayed in the image  24  generated by the real image display system  20 . 
     Also, because the real image display system has a fixed focal distance and the primary display is at infinity focus, the user&#39;s eyes must adjust to the different focal lengths as the user looks out the chin window (as indicated by the second arrow  36 ) and then looks out the main window (as shown by the first arrow  34 ). The change in focus negatively impacts the realism of the simulator, causes discomfort to the user, and results in eye fatigue. Known real image display systems also provide unrealistic depth cues when the simulated aircraft has a simulated height  28  of greater than about 10 feet above the simulated ground  26 . 
     A WAC display system used as a chin display provides some benefits compared to a real image display system. For example, an image provided by a WAC display system is at an infinity focus. When viewed through a chin window of a simulator, the image provided by the WAC display system will stay aligned with the image  12  of the primary display  4  even during movement of the user&#39;s head. WAC display systems are compatible with NVGs, and a WAC display system can provide realistic depth cues when the simulated aircraft has a simulated height of greater than about 15 feet above the simulated ground. However, the image provided by the WAC display system will have unrealistic depth cues when the simulated height is less than about 10 feet. Another problem with known WAC display systems is that they have a relatively small FOV of less than about 25° in a horizontal dimension and 15° vertical in a vertical dimension. Other problems of WAC display systems for chin windows are limited brightness and that they are more expensive than real image display systems  20 . 
     A significant disadvantage of both types of prior art chin window displays is that they have a fixed focal distance which can only be optimized for one viewing distance. For example, in a simulation of an aircraft descending from a high hover (such as at a simulated height  28  of approximately 30 feet) to touchdown, a real image display system with a viewing distance of approximately 6 feet to 8 feet is unrealistic for the first 90% of the descent. Similarly, a WAC display system for a chin window is unrealistic for the final portion of the descent from about 30 feet to touchdown. Accordingly, conventional chin displays are inaccurate during significant portions of simulated landing or take-off procedures. The visual errors described for the real image display systems and the WAC display system can result in the user misjudging descent rate and height above terrain using either type of display, resulting in hard landings and difficulty maintaining a hover position. These deficiencies result in significant limitations in the realism and usefulness of prior art simulators. 
     Accordingly, there is a need for systems and methods for adjusting focal distances of images of a simulator in real-time. 
     SUMMARY 
     It is one aspect of the present disclosure to provide a system to adjust focal distances of images displayed to a user at a designated eye point. The system comprises: (1) a screen configured to display an image depicting an object; (2) a mirror configured to reflect the image displayed by the screen to the designated eye point, the mirror spaced from the screen by a distance that is variable; and (3) an adjustor configured to adjust the distance between the screen and the mirror. 
     In some embodiments, the system further comprises a control system in communication with the adjustor, the control system configured to: (a) determine a focal distance for the image based on a simulated distance between the designated eye point and the object in the image; (b) determine a simulated size of the object based on the simulated distance; (c) generate instructions to cause the adjustor to adjust the distance between the screen and the mirror to achieve the focal distance; and (d) adjust a size of the object in the image based on the determined simulated size. 
     The system may include any one or more of the previous embodiments and optionally the control system is further configured to: (1) generate the image; and (2) determine a simulated size of the object. 
     In some embodiments, the screen is at least one of a liquid-crystal display, an organic light-emitting diode display, a liquid crystal on silicon display, a light-emitting diode display, a quantum dot display, and a plasma display. 
     The system may optionally include one or more of the previous embodiments and, in some embodiments, the system may further comprise a projector configured to project the image onto the screen, the screen being one of a front projection screen and a back projection screen. 
     In embodiments in which the screen is a back projection screen, the projector is positioned to project the image onto a rear surface of the screen, and a front surface of the screen is oriented toward the mirror. In this embodiment, the back projection screen may be positioned at least partially between the mirror and the projector. 
     Alternatively, when the screen is a front projection screen, the projector is positioned to project the image onto the front surface of the screen, and the front surface of the screen is oriented toward the mirror. In this embodiment, the projector may be positioned at least partially between the mirror and the front projection screen. 
     In one or more embodiments, the front surface of the screen facing the mirror is convex. 
     Optionally, the front surface of the screen has a shape that includes at least a section of a circle, a sphere, a parabolic, an ellipsoid, a plane, a freeform, and combinations thereof. 
     In some embodiments, the projector is a fixed distance from the screen, and the adjustor is configured to move the screen and the projector. 
     In some embodiments, the adjustor comprises a motor for moving at least one of the screen and the mirror to adjust the distance. 
     In other embodiments, the mirror is stationary. Optionally, the mirror is a fixed distance from the designated eye point. 
     The system may include one or more of the previous embodiments and optionally the screen is interconnected to a platform of the adjustor, the platform being movable. 
     The system may include any one or more of the previous embodiments and optionally the platform is configured to move to adjust the distance between the screen and the mirror. 
     In some embodiments, the adjustor comprises a stop to prevent the screen from contacting the mirror. 
     In some embodiments, the distance from the screen to the mirror correlates to the focal distance. 
     In some embodiments, the screen has a first position at which the screen is a first distance from the mirror and the focal distance is at infinity. 
     Optionally, in the first position, light rays reflected from the mirror are substantially parallel. 
     In a second position the screen is a second distance from the mirror and the focal distance is less than infinity. The first distance is greater than the second distance. 
     In some embodiments, the system includes one or more of the previous features and optionally the mirror has a front surface that is reflective and which is oriented toward the designated eye point and the screen. The front surface of the mirror has a shape configured collimate light from the screen when the screen is a predetermined distance from the mirror. 
     The front surface of the mirror optionally is concave. 
     Optionally, the front surface of the mirror has a shape that is adjustable. 
     Optionally, the front surface of the mirror has a shape that includes at least a section of a circle, a sphere, a parabolic, an ellipsoid, a plane, a freeform, and combinations thereof. 
     The system may include any one or more of the previous embodiments and optionally the system is associated with a simulator, such as a flight simulator. 
     In some embodiments, the simulator is an aircraft simulator and includes a chin window positioned between the designated eye point and the mirror. 
     In at least one embodiment, the image displayed by the screen is visible to the user through the chin window. 
     It is another aspect of the present disclosure to provide a control system for a simulator to adjust focal distances of images displayed to a user at a designated eye point of the simulator. The control system may comprise: (1) a processor; and (2) a memory storing instructions for execution by the processor that, when executed, cause the processor to: (a) generate an image for display by a screen, the screen positioned and oriented such that the image may be reflected by a mirror to the designated eye point; (b) determine a simulated distance from the designated eye point to an object in the image; (c) determine a focal distance for the image based on the simulated distance; (d) determine a simulated size of the object based on the simulated distance; (e) generate instructions to cause an adjustor to adjust a distance between the screen and the mirror to achieve the focal distance; and (f) adjust a size of the object in the image based on the determined simulated size. 
     Optionally, determining the simulated distance comprises one or more of: (1) receiving a position of the designated eye point; (2) determining a simulated position of the object relative to the designated eye point; and (3) determining a distance between the position of the designated eye point and the simulated position of the object. 
     In some embodiments the control system includes one or more of the previous embodiments and the distance from the screen to the mirror correlates to the focal distance. 
     In a first position, the screen is a first distance from the mirror and the focal distance is at infinity. In a second position, the screen is a second distance from the mirror and the focal distance is less than infinity. The first distance is greater than the second distance. 
     The control system may include any one or more of the previous embodiments and optionally the memory includes an instruction to keep the screen at the first position that is the first distance from the mirror when the simulated distance is greater than a predetermined threshold. In some instances, the predetermined threshold is about thirty feet. In other embodiments, the predetermined threshold is greater or less than thirty feet. 
     The control system may include one or more of the previous embodiments and may further comprise an instruction to move the screen to the second position that is the second distance from the mirror when the simulated distance is less than the predetermined threshold. 
     In some embodiments the simulator is configured to simulate an aircraft. The simulator may optionally include a chin window positioned between the designated eye point and the mirror such that the image displayed by the screen is visible to the user through the chin window. 
     It is another aspect of the present disclosure to provide a method for adjusting focal distances of images at a designated eye point, comprising: (1) generating an image for display by a screen, the screen being oriented such that the image is reflected by a mirror of the simulator to the designated eye point; (2) determining a simulated distance between the designated eye point and a simulated position of an object in the image; (3) determining a focal distance for the image based on the simulated distance; (4) determining a simulated size of the object based on the simulated distance; (5) generating an instruction to cause an adjustor to alter a distance between the screen and the mirror to achieve the focal distance; and (6) adjusting a size of the object in the image based on the simulated size. 
     Optionally, the method may further comprise receiving a position of the designated eye point. 
     In some embodiments, the screen and the mirror are associated with a simulator configured to simulate an aircraft. 
     The simulator optionally includes a chin window positioned between the designated eye point and the mirror. 
     In some embodiments, the image displayed by the screen is visible to a user through the chin window. 
     The method may include one or more of the previous embodiments and may further comprise maintaining the screen at a first position that is a first distance from the mirror when the simulated distance is greater than a predetermined threshold. In the first position, light rays reflected from the mirror are substantially parallel such that the focal distance of the image is at infinity. 
     In some instances, the predetermined threshold is about thirty feet. In other embodiments, the predetermined threshold is greater or less than thirty feet. 
     In some embodiments the method further comprises moving the screen to a second position that is a second distance from the mirror when the simulated distance is less than the predetermined threshold. At the second position, light rays reflected from the mirror are not parallel and the image has a fixed focal distance that is less than infinity. 
     The method may comprise any one or more of the previous embodiments and optionally comprises moving the screen away from the mirror to the first position that is the first distance from the mirror when the simulated distance increases from less than the predetermined threshold to greater than the predetermined threshold. 
     Optionally, the method may further comprise moving the screen toward the mirror to the second position when the simulated distance decreases from greater than the predetermined threshold to less than the predetermined threshold. 
     Still another aspect is a flight simulator for training a student to operate an aircraft, comprising: (1) a primary display system to simulate a first view out of a window of the aircraft, comprising: (a) a projector; (b) a first screen, wherein the projector is operable to generate a first image that is displayed on the first screen; and (c) a mirror array to reflect the first image to a designated eye point of the simulator; and (2) a variable collimation display system to simulate a second view outside the aircraft visible through a chin window in a cabin of the simulator, the chin window positioned near a floor of the cabin, the variable collimation display system comprising: (i) a second screen to display a second image; (ii) a mirror to reflect the second image from the second screen through the chin window and to the designated eye point; and (iii) an adjustor configured to move the second screen relative to the mirror. 
     In some embodiments, when the second screen is a first distance from the mirror the second image is at infinity focus. Optionally, when the second screen is spaced the first distance from the mirror, light rays reflected from the mirror are substantially parallel. 
     In at least one embodiment, the front surface of the second screen facing the mirror has a shape that includes at least a section of a circle, a sphere, a parabolic, an ellipsoid, a plane, a freeform, and combinations thereof. 
     Optionally, when the second screen is a second distance from the mirror the second image has a fixed focal distance that is less than infinity, the second distance being less than the first distance. 
     The flight simulator may include one or more of the previous embodiments and optionally, the mirror is a fixed distance from the designated eye point. 
     In some embodiments, the second screen is at least one of a liquid-crystal display, an organic light-emitting diode display, a liquid crystal on silicon display, a light-emitting diode display, a quantum dot display, and a plasma display. 
     The flight simulator may optionally include one or more of the previous embodiments and, in some embodiments, the variable collimation display system may further comprise a second projector configured to project the second image onto the second screen, the second screen being one of a front projection screen and a back projection screen. 
     In embodiments in which the second screen is a back projection screen, the second projector is positioned to project the second image onto a rear surface of the second screen, and a front surface of the second screen is oriented toward the mirror. In this embodiment, the back projection screen is positioned at least partially between the mirror and the second projector. 
     Alternatively, when the second screen is a front projection screen, the second projector is positioned to project the second image onto the front surface of the second screen, and the front surface of the second screen is oriented toward the mirror. In this embodiment, the second projector is positioned at least partially between the mirror and the front projection screen. 
     In some embodiments, the second projector is a fixed distance from the second screen, and the adjustor is configured to move the second screen and the second projector. 
     In some embodiments, the adjustor comprises a motor to move at least one of the second screen and the mirror to adjust the distance between the second screen and the mirror. 
     In other embodiments, the mirror is stationary. 
     The flight simulator may include one or more of the previous embodiments and optionally the second screen is interconnected to a platform of the adjustor, the platform being movable. 
     The flight simulator may include any one or more of the previous embodiments and optionally the platform is configured to move to adjust the distance between the second screen and the mirror. 
     In some embodiments, the adjustor comprises a stop to prevent the second screen from contacting the mirror. 
     In some embodiments, the distance from the second screen to the mirror correlates to the focal distance. 
     In some embodiments, the flight simulator includes one or more of the previous features and optionally the mirror has a front surface that is reflective and which faces the designated eye point and the second screen. The front surface of the mirror has a shape configured collimate light from the second screen when the second screen is a predetermined distance from the mirror. 
     The front surface of the mirror optionally is concave. 
     In some embodiments, the front surface of the mirror has a shape that includes at least a section of a circle, a sphere, a parabolic, an ellipsoid, a plane, a freeform, and combinations thereof. 
     Optionally, the front surface of the mirror has a shape that is adjustable. 
     In some embodiments, the flight simulator includes one or more of the previous embodiments and further comprises a control system in communication with the adjustor. 
     Optionally, the control system is operatable to perform one or more of the following operations: (a) determine a focal distance for the second image based on a simulated distance between the designated eye point and an object in the second image; (b) determine a simulated size of the object based on the simulated distance; (c) generate instructions to cause the adjustor to adjust the distance between the second screen and the mirror to achieve the focal distance; and (d) adjust a size of the object in the second image based on the determined simulated size. 
     Optionally, the control system is further configured to generate the second image. 
     The Summary is neither intended nor should it be construed as being representative of the full extent and scope of the present disclosure. The present disclosure is set forth in various levels of detail in the Summary as well as in the attached drawings and the Detailed Description and no limitation as to the scope of the present disclosure is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary. Additional aspects of the present disclosure will become more clear from the Detailed Description, particularly when taken together with the drawings. 
     The phrases “at least one,” “one or more,” and “and/or,” as used herein, are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions “at least one of A, B and C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “one or more of A, B, or C,” and “A, B, and/or C” means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together. 
     The term “a” or “an” entity, as used herein, refers to one or more of that entity. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. 
     Unless otherwise indicated, all numbers expressing quantities, dimensions, conditions, ratios, ranges, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about” or “approximately”. Accordingly, unless otherwise indicated, all numbers expressing quantities, dimensions, conditions, ratios, ranges, and so forth used in the specification and claims may be increased or decreased by approximately 5% to achieve satisfactory results. Additionally, where the meaning of the terms “about” or “approximately” as used herein would not otherwise be apparent to one of ordinary skill in the art, the terms “about” and “approximately” should be interpreted as meaning within plus or minus 5% of the stated value. 
     All ranges described herein may be reduced to any sub-range or portion of the range, or to any value within the range without deviating from the invention. For example, the range “5 to 55” includes, but is not limited to, the sub-ranges “5 to 20” as well as “17 to 54.” 
     The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Accordingly, the terms “including,” “comprising,” or “having” and variations thereof can be used interchangeably herein. 
     It shall be understood that the term “means” as used herein shall be given its broadest possible interpretation in accordance with 35 U.S.C., Section 112(f). Accordingly, a claim incorporating the term “means” shall cover all structures, materials, or acts set forth herein, and all of the equivalents thereof. Further, the structures, materials, or acts and the equivalents thereof shall include all those described in the Summary, Brief Description of the Drawings, Detailed Description, Abstract, and Claims themselves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosed system and together with the general description of the disclosure given above and the detailed description of the drawings given below, serve to explain the principles of the disclosed system(s) and device(s). 
         FIG.  1    is a schematic side elevation view of a prior art simulator with a real image display system positioned outside of a chin window; 
         FIG.  2    is schematic side elevation view of a simulator with a variable collimation display system of embodiments of the present disclosure; 
         FIG.  3    is an isometric view of portions of the simulator of  FIG.  2   ; 
         FIG.  4 A  is a schematic side elevation view of a variable collimation display system for a simulator according to embodiments of the present disclosure; 
         FIG.  4 B  is a schematic side elevation view of a variable collimation display system for a simulator according to other embodiments of the present disclosure; 
         FIG.  4 C  is a schematic side elevation view of a variable collimation display system for a simulator according to some embodiments of the present disclosure; 
         FIG.  5 A  is a schematic side elevation view of the simulator of  FIG.  2    at a first simulated height above the ground; 
         FIG.  5 B  is another schematic side elevation view of the simulator of  FIG.  2    at a second simulated height above the ground that is less than the first simulated height; 
         FIG.  6    is a schematic diagram of a control system of a system for adjusting a focal distance of an image according to embodiments of the present disclosure; 
         FIG.  7    is a flow chart illustrating a method of adjusting a focal distance of an image according to some embodiments of the present disclosure; and 
         FIG.  8    is another flow chart that generally illustrates a method for determining a simulated distance according to at least one embodiment of the present disclosure. 
     
    
    
     The drawings are not necessarily (but may be) to scale. In certain instances, details that are not necessary for an understanding of the disclosure or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the disclosure is not necessarily limited to the embodiments illustrated herein. As will be appreciated, other embodiments are possible using, alone or in combination, one or more of the features set forth above or described below. For example, it is contemplated that various features and devices shown and/or described with respect to one embodiment may be combined with or substituted for features or devices of other embodiments regardless of whether or not such a combination or substitution is specifically shown or described herein. 
     The following is a listing of components according to various embodiments of the present disclosure, and as shown in the drawings: 
     
       
         
           
               
               
             
               
                   
               
               
                 Number 
                 Component 
               
               
                   
               
             
            
               
                  2 
                 Prior art simulator 
               
               
                  4 
                 Primary display 
               
               
                  6 
                 Projector 
               
               
                  8 
                 Screen 
               
               
                 10 
                 Mirror array 
               
               
                 12 
                 Image of primary display 
               
               
                 14 
                 Collimated light rays 
               
               
                 16 
                 Object in image 
               
               
                 18 
                 Chin window 
               
               
                 20 
                 Real image display system 
               
               
                 22 
                 Monitor or Screen of real image display system 
               
               
                 24 
                 Image of real image display system 
               
               
                 26 
                 Simulated ground 
               
               
                 28 
                 Simulated height above ground 
               
               
                 30 
                 User 
               
               
                 32 
                 Designated eye point 
               
               
                 34 
                 First arrow indicating direct of view at primary display 
               
               
                 36 
                 Second arrow indicating direction of view through chin 
               
               
                   
                 window 
               
               
                 40 
                 Simulator 
               
               
                 42 
                 Cockpit 
               
               
                 44 
                 Window for the primary display 
               
               
                 45 
                 Upper window 
               
               
                 46 
                 Chin Window 
               
               
                 48 
                 Primary display 
               
               
                 50 
                 Projector of primary display 
               
               
                 52 
                 Screen 
               
               
                 54 
                 Mirror array 
               
               
                 56 
                 Image of primary display 
               
               
                 58 
                 Collimated light rays 
               
               
                 60 
                 Object in image 
               
               
                 62 
                 Variable collimation display system (or chin display, or 
               
               
                   
                 variable display) 
               
               
                 64 
                 Image of variable collimation display system 
               
               
                 66 
                 Light Rays of variable collimation display system 
               
               
                 68 
                 Screen of variable collimation display system 
               
               
                   68A-1 
                 Rear or back projection screen 
               
               
                   68A-2 
                 Front projection screen 
               
               
                   68B 
                 Self-illuminating screen 
               
               
                 70 
                 Rear Surface (of the Screen 68) 
               
               
                 72 
                 Front Surface (of the Screen 68) 
               
               
                 74 
                 Mirror of variable collimation display system 
               
               
                 76 
                 Rear Surface (of the Mirror 74) 
               
               
                 78 
                 Front Surface (of the Mirror 74) 
               
               
                 80 
                 Projector of variable collimation display system 
               
               
                 82 
                 Adjustor for variable collimation display system 
               
               
                 84 
                 Platform 
               
               
                 86 
                 Arrow indicating movement of platform 
               
               
                 88 
                 Stand for screen 
               
               
                 90 
                 Mount for projector 
               
               
                 92 
                 Actuator 
               
               
                 94 
                 Stop 
               
               
                 96 
                 Distance between mirror and screen 
               
               
                   96A 
                 First distance 
               
               
                   96B 
                 Second distance 
               
               
                 98 
                 Distance from projector to screen 
               
               
                 100  
                 Perceived (or simulated) distance between designated eye 
               
               
                   
                 point and a simulated object 
               
               
                 102  
                 Height above terrain 
               
               
                 104  
                 Horizontal distance to the object 
               
               
                 106  
                 Simulated size or height of the object 
               
               
                 120  
                 Controller 
               
               
                 122  
                 Control System 
               
               
                 124  
                 Processor 
               
               
                 126  
                 Memory 
               
               
                 128  
                 Communication Interface 
               
               
                 130  
                 User Interface 
               
               
                 132  
                 Focal Distance Model 
               
               
                 134  
                 Size Model 
               
               
                 136  
                 Controller Instructions 
               
               
                 138  
                 Lookup table 
               
               
                 140  
                 Method 
               
               
                 142  
                 Generate image 
               
               
                 144  
                 Determine simulated distance to an object 
               
               
                 146  
                 Determine a focal distance 
               
               
                 148  
                 Determine simulated size of the object 
               
               
                 150  
                 Generate instructions for adjustor 
               
               
                 152  
                 Adjust simulated size of the object 
               
               
                 160  
                 Method 
               
               
                 162  
                 Receive position of the designated eye point 
               
               
                 164  
                 Determine simulated position of an object 
               
               
                 166  
                 Determine simulated distance 
               
               
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION 
     Referring now to  FIGS.  2 - 6   , a simulator  40  with a variable collimation display system  62  according to embodiments of the present disclosure is generally illustrated. The variable collimation display system  62  may be referred to as a variable display or a chin display herein. The variable display  62  is operable to adjust focal distances of images  64  displayed to a user  30  (e.g. a student) at a designated eye point  32  of the simulator  40 . 
     Turning to  FIG.  2   , a simulator  40  with a variable collimation display system  62  according to embodiments of the present disclosure is generally illustrated. The simulator  40  may be an aircraft simulator configured to train the user  30  to operate an aircraft that includes a chin window  46 . The aircraft may be a fixed wing aircraft, a helicopter, a tilt-rotor aircraft, or any other aircraft that has a chin window. However, it will be appreciated that the variable collimation display system  62  can be used with simulators that simulate operation of any type of vehicle. For example, simulators  40  for mobile equipment and vehicles of all sizes and types including cars, trucks, trains, tracked vehicles (such as tanks or construction vehicles), ships, and spacecraft may include a variable collimation display system  62  according to embodiments of the present disclosure. The variable collimation display system may also be used with games or other systems that may need to adjust or alter focal distances of images displayed to a user. 
     The simulator includes a primary display  48  that is configured to operate in coordination with the variable collimation display system  62 . The primary display includes a projector  50  that projects an image  56  onto a screen  52 . The image  56  is viewed by the user  30  as a reflection in a mirror array  54 . The image  56  of the primary display  48  is visible to the user as collimated light rays  58  and seen at a distant focus. The image  56  may include an object  60  with a position simulated to be outside the simulated cockpit and which may be viewed by the user as indicated by a first arrow  34 . In the example of  FIG.  2   , the object  60  is a tree. 
     The image  56  (and the object  60  displayed in the image) may be at an infinity focus, such as with a focal distance of greater than approximately 30 feet. Accordingly, the collimated light rays  58  of the image are substantially parallel to each other. 
     The variable collimation display system  62  is configured to project another image  64  through a chin window  46  of the simulator  40 . The user  30  may view the image  64  by looking through the chin window  46  as generally indicated by a second arrow  36 . 
     The chin window  46  is positioned between the designated eye point  32  where the user  30  will be positioned within the simulator  40  and a mirror  74  of the variable collimation display system  62 . The chin window  46  is generally positioned at or near floor level of the simulator  40  and is typically used by the user  30  during simulations for take-off, landing, and/or hovering of the simulated aircraft. It will be appreciated that the variable collimation display system  62  may also be used during other simulated procedures. 
     The variable collimation system generally includes the mirror  74  and a screen  68 . In some embodiments the variable collimation display system  62  includes a projector  80  such as illustrated in  FIG.  2   . The projector  80  and the screen  68  may have different alignments in other embodiments as described herein such a generally illustrated in  FIG.  4 B . In addition, in some embodiments of the present disclosure (for example, as described in conjunction with  FIG.  4 C ) the screen is self-illuminating such that the variable collimation system  62  does not include a separate projector  80 . In use, the projector  80  (or the screen  68 ) projects the image  64  which is viewed by the user  30  as a reflection in the mirror  74 . 
     In all embodiments of the variable collimation display system  62 , the image  64  will align with the image  56  of the primary display  48 . Accordingly, as generally illustrated in  FIG.  2   , the tree  60  in the images  56 ,  64  of the primary display  48  and the variable collimation display system  62  will stay aligned with each other from the perspective of the user  30  at the designated eye point. Moreover, a control system  122  in communication with the primary display  48  and the variable collimation display system  62  can change the simulated size  106  of the object  60  in the images as the simulated height  102  above the ground  26  of the aircraft changes (as generally illustrated in  FIGS.  5 A,  5 B . 
       FIG.  3    generally illustrates the variable collimation display system  62  according to some embodiments relative to a cockpit  42  of a simulator  40 . The cockpit  42  may include a window  44  associated with the primary display  48 . The variable collimation display system  62  is positioned to display an image  64  through the chin window  46 . Although only one variable collimation display system  62  is illustrated, the simulator  40  may have a second variable collimation display system associated with a second chin window on the other side of the cockpit  42 . 
     In some embodiments, the cockpit  42  may include an upper window  45 . Optionally, the simulator  40  may include a variable collimation display system associated with one or more upper windows  45 . Further, a variable collimation display system could be associated with any window of the cockpit, such as a side window, or a lower side window. 
     Referring now to  FIGS.  4 A- 4 C , embodiments of a simulator  40  with the variable collimation display system  62  of the present disclosure are generally illustrated. In all embodiments, the variable collimation display system is configured and operable to adjust or alter a focal distance of an image  64  displayed to the user  30  based on a simulated or perceived distance  100  (also referred to the “slant distance” or the “line of sight distance”) between the designated eye point  32  of the user and a simulated environment or an object  60  outside of the simulated vehicle. 
     The variable collimation display system  62  comprises a screen  68 , a mirror  74 , and an adjustor  82 . The screen  68  is configured and operable to display an image  64 . The mirror  74  is configured and operable to reflect the image displayed by the screen  68  to the designated eye point  32 . It will be appreciated that although the variable collimation display system is shown in use with a chin window  46 , the variable collimation display system can be used for any display visible through any window of a simulator and in any simulated environment. 
     The focal distance of the variable collimation display system  62  is adjusted by the adjustor  82 . The adjustor  82  is operable to alter a distance  96  between the screen  68  and the mirror  74 . As the focal distance changes, a size or height  106  of the object  60  appearing in the image  64  displayed on the screen may be adjusted by a control system  122  of the simulator, as described herein. The control system  122  is in communication with one or more components of the variable collimation displays system, such as the adjustor  82  and a projector  80 . 
     The mirror  74  has rear surface  76  and a front surface  78  opposite the rear surface. The front surface  78  of the mirror is oriented toward the chin window and toward a front surface  72  of the screen  68  and is adapted to reflect light from the screen to the designated eye point. In this manner, the user  30  views the image  64  in the reflective front surface  78  of the mirror  74 . 
     The mirror  74  and its front surface  78  may be of any shape and size. For example, the mirror  74  may be curved or flat. In some embodiments, the front surface  78  of the mirror has a shape that includes at least a section of a circle, a sphere, a parabolic, an ellipsoid, a plane, a freeform, and combinations thereof. In some embodiments, the front surface  78  may be described as being generally concave. 
     The front surface  78  of the mirror has a shape configured to collimate light from the screen  68  when the screen is a predetermined distance from the mirror  74 . 
     Optionally, the front surface  78  of the mirror is substantially rigid. Additionally, or alternatively, the front surface  78  of the mirror may have a shape that is adjustable. 
     In some embodiments, the mirror  74  may comprise a plurality of mirrors. In such embodiments, the plurality of mirrors may include a combination of curved and/or flat mirrors. 
     In at least one embodiment, the mirror  74  is stationary relative to the chin window  46  and the screen  68  is moveable by the adjustor  82 . In such embodiments, the mirror  74  is at a fixed distance from the designated eye point  32 . 
     The adjustor  82  is configured and operable to alter the distance  96  between the front surface  72  of the screen  68  and the front surface  78  of the mirror. Accordingly, the distance  96  is variable. The adjustor  82  may move the screen  68  in any manner known to one of skill in the art. 
     In some embodiments, the adjustor  82  comprises a platform  84  that is movable relative to the mirror  74 . More specifically, the platform may move toward or away from the mirror  74  as generally indicated by arrow  86 . 
     Optionally, in at least one embodiment, the adjustor  82  is configured to move the screen  68  along an optical centerline (or optical axis) of the mirror  74 . However, in other embodiments, the adjustor  82  can move the screen  68  along a different axis relative to the mirror. 
     The screen  68  may be fixed to the platform  84 . Accordingly, the screen  68  moves with the platform  84  toward or away from the mirror  74  as indicated by arrow  86 . Any suitable means of fixing the screen to the platform known to those of skill in the art may be used with the variable display  62  of the present disclosure. In some embodiments, the screen  68  is fixed to the platform by a mount or a stand  88 . 
     Optionally, the stand  88  is operable to alter the orientation of the screen  68  relative to one or more of the platform  84  and the mirror  74 . In this manner, an orientation of the front surface  72  of the screen  68  may be altered as the platform  84  alters the distance  96  between the screen and the mirror. In some embodiments, the stand  88  can rotate the screen around a vertical axis of the stand. Additionally, or alternatively, the stand may pivot the screen relative to the vertical axis. 
     The adjustor  82  includes an actuator  92  configured to move the platform  84 . The actuator  92  may move the platform  84  toward or away from the mirror in response to a signal from the control system  122 . It will be appreciated that the adjustor  82  may be configured to move any component or any combination of components of the variable collimation display system  62 . 
     The actuator may include any suitable means known to those of skill in the art that is operable to alter the position of the platform  84  relative to the mirror. In some embodiments, the actuator  92  comprises a motor. Additionally, or alternatively, the actuator may comprise a track, a rail, a wheel, a gear, a piston, a servo drive, a worm drive, a belt, a cable and the like. In some embodiments, the adjustor  82  may comprise a track on which the screen  68  is configured to move or slide to adjust the distance  96 . 
     In some embodiments, the adjustor  82  comprises a motor for moving the screen  68 . It will be appreciated that the motor may also be configured to move the mirror  74  and/or the projector  80 . 
     In some embodiments, the adjustor  82  optionally includes a stop  94 . The stop  94  is configured to prevent unintended or inadvertent contact of the screen  68  with the mirror  74 . For example, the stop  94  is configured to maintain a predetermined minimum distance  96  between the screen  68  and the mirror  74 . In this manner, the stop  94  can prevent the screen  68  from contacting the mirror  74 . 
     The stop  94  may be associated with the platform  84 . Alternatively, the stop may be associated with the actuator  92 . Other means of preventing the screen from moving less than a predetermined distance  96  from the mirror may be used with the variable collimation display system  62  of the present disclosure. 
     Referring now to  FIGS.  4 A and  4 B , in some embodiments, the variable collimation display system  62  also includes a projector  80  configured to project the image  64  onto a screen  68 A. In some embodiments, the projector  80  has a lens with a fixed focal length. Alternatively, the projector  80  may include optics, such as one or more lens and/or a mirror, such that the focal length can be adjusted and/or to adjust the size of an object  60  in an image  64 . 
     The projector  80  may be fixed to the platform  84 . Accordingly, the projector  80  may move with the platform  84  as the platform adjusts the position of the screen  68 A relative to the mirror  74 . Any suitable means of fixing the projector to the platform known to those of skill in the art may be used. In some embodiments, the projector  80  is fixed to the platform by a mount  90 . 
     In some embodiments, the projector  80  is positioned a fixed distance  98  from the screen  68 A. Specifically, in some embodiments, the distance  98  between the projector and the screen does not change and is substantially constant. In these embodiments, the adjustor  82  is configured to move both the screens  68 A- 1 ,  68 A- 2  and the projectors  80  substantially simultaneously. 
     Alternatively, in at least one embodiment, the distance  98  between the projectors  80  and the screens  68 A- 1 ,  68 A- 2  may also be altered by the adjustor  82 . 
     The screen  68 A may have any shape. In some embodiments, the screen may be curved or flat. The rear surface  70  of the screen  68 A may be concave and the opposite front surface  72  may be convex. In some embodiments, the screens  68 A- 1 ,  68 A- 2  and  68 B have a shape that includes at least a section of a circle, a sphere, a parabolic, an ellipsoid, a plane, a freeform, and combinations thereof. 
     In embodiments where the variable collimation display system  62  includes the projector  80 , the screen  68 A may be a back projection screen  68 A- 1  (as illustrated in  FIG.  4 A ) or a front projection screen  68 A- 2  (shown in  FIG.  4 B ). 
     As shown in  FIG.  4 A , in embodiments where the screen  68 A- 1  is a back projection screen, the projector  80  is positioned to project an image  64  onto the rear surface  70  of the screen  68 A- 1 . The image  64  is visible on the front surface  72  of the screen  68 A- 1  and is then reflected by the front surface  78  of the mirror. 
     In some embodiments, the screen  68 A- 1  is formed of a clear or substantially transparent material. For example, the screen  68 A- 1  may be an acrylic or may be a glass. Optionally, the screen  68 A- 1  is treated to diffuse light from the projector  80 . In some embodiments the screen  68 A- 1  includes a diffusion coating or film. In some embodiments, a film or coating is applied to the convex front surface  72  to enable the image  64  to be focused onto the screen  68 A- 1 . 
     In embodiments where the screen  68 A- 2  is a front projection screen, as shown in  FIG.  4 B , the projector  80  is positioned to project an image  64  onto the front surface  72  of the screen  68 A- 2 . In some embodiments, the projector  80  may be positioned at least partially between the front surface  72  of the screen  68 A- 2  and the mirror  74 . 
     The image  64  produced by the projector  80  is reflected from the front surface  72  onto the mirror  74 . The screen  68 A- 2  may be formed of an opaque material. In some embodiments, the screen  68 A- 2  is formed of a glass, a plastic, a fiberglass, a metal or similar materials. 
     It will be understood by one skilled in the art that any arrangement of a projector  80 , a screen  68 , and a mirror  74  are within the scope of the present disclosure. In some embodiments, the variable collimation display system  62  can be used with a simulator  40  having screens  68  and mirrors  74  with different configurations and arrangements. For example, a curved screen  68  may be used with a flat mirror  74 , a curved mirror  74  may be used with a flat screen  68 , and/or a curved mirror  74  may be used with a curved screen  68 . In one embodiment, the screen  68  and the mirror  74  are generally concave and curved in two or more dimensions. 
     Referring now to  FIG.  4 C , in other embodiments the variable collimation display system  62  does not include a projector  80 . In these embodiments, the screen  68 B is a self-illuminating screen and may include elements of the projector to project an image  64  from a front surface  72  of the screen  68 B. Accordingly, the screen  68 B projects the image from its front surface  72 . The image  64  is then reflected by the front surface  78  of the mirror  74 . The screen  68 B may be any type of display operable to project an image such as, for example, a self-illuminating curved screen, a set of LED panels, a liquid-crystal display, an organic light-emitting diode display, a liquid crystal on silicon display, a light-emitting diode display, a quantum dot display, or a plasma display. 
     Referring now to  FIGS.  5 A and  5 B , when the variable collimation display system is in use, an image  64  is projected on the screen  68  (whether self-projected or projected by the projector  80 ) and the image is viewed by the user  30  as a reflection in the mirror  74 . The image  64  is visible to the user  30  as light rays  66  with a predetermined focus. The light rays  66  may be collimated (as shown in  FIG.  5 A ) and appear at an infinity focal distance. Alternatively, by altering the position of the screen  68  relative to the mirror with adjustor  82 , the light rays  66  of the image are visible to the user  30  at a fixed focal distance. As the screen  68  is moved closer to the mirror  74  and the distance  96  decreases, the light rays  66  diverge, and focus becomes less than infinity (such as generally illustrated in  FIG.  5 B ). 
     The distance  96  from the screen  68  to the mirror  74  correlates to a focal distance for an image  64  visible to the user  30 . As will be described in further detail, the distance  96  (or the focal distance) is determined based on a simulated distance  100  from the designated eye point  32  to an object  60  depicted in the image  64 . The simulated distance is a perceived viewing distance. In other words, the simulated distance may be a distance between the designated eye point  32  and the object  60  as perceived by a user at the designated eye point if the object was physically present. The simulated distance  100  may also be referred to as the “slant distance”, the “perceived distance” or the “line of sight distance”. 
     When the screen  68  is in a first position (illustrated in  FIG.  5 A ), the mirror  74  is a first distance  96 A from the screen and the focal distance is at infinity. Accordingly, the light rays  66  reflected from the mirror are substantially parallel and the image  64  is collimated. The object  60  in the image  64  is a first distance  100 A from the designated eye point and may be shown with a first simulated size or height  106 A. 
     Referring to  FIG.  5 B , in a second position of the screen  68 , the mirror  74  is a second distance  96 B from the screen  68  and the focal distance is less than infinity. The second distance  96 B is less than the first distance  96 A. In the second position, the light rays  66  are slightly diverging as generally illustrated in  FIG.  5 B . 
       FIG.  5 B  also illustrates a second distance  100 B between the designated eye point  32  and the object  60  in the image  64 , the second distance  100 B being less than the first distance  100 A. Accordingly, because the designated eye point  32  is closer to the object  60  in  FIG.  5 B , the object  60  in the image  64  may be shown with a second simulated size or height  106 B. The second height  106 B is greater than the first height  106 A illustrated in  FIG.  5 A . 
     In some embodiments, the screen  68  remains at the first position (that is, the first distance  96 A) from the mirror  74  when the simulated distance  100  is above a predetermined threshold. In some embodiments, the predetermined threshold is about 30 feet. In other embodiments, the predetermined threshold may be less or greater than 30 feet. 
     The adjustor  82  may move the screen  68  to the second position (that is, the second distance  96 B) from the mirror  74  when the simulated distance  100  meets the predetermined threshold. In at least one example, the predetermined threshold correlates to a height above terrain  102  of a simulated aircraft (such as, for example, a helicopter) in which the focal distance changes from infinity to less than infinity. 
     An example simulated scenario in which the predetermined threshold may be met includes a landing simulation. For example, for a simulated aircraft above the predetermined threshold, the focal distance of an image  64  viewed by the user  30  is infinity. Accordingly, the adjustor  82  may move the screen  68  to the first position at the first distance  96 A from the mirror  74  as generally illustrated in  FIG.  5 A . 
     As the simulated aircraft descends toward a landing surface, the height  102 B decreases and the simulated aircraft will reach the predetermined threshold. The focal distance of the image  64  viewed by the user  30  may be altered to be less than infinity by the adjustor  82  moving the screen  68  from the first position to the second position  96 B and decreasing the first distance to the second distance  96 B as generally illustrated in  FIG.  5 B . As the simulated aircraft continues to descend, the adjustor  82  may move the screen  68  to a third position closer to the mirror  74  to continue adjustment of the focal distance of the image  64 . 
     During a take-off simulation, the opposite will occur. For example, during a take-off simulation, the adjustor  82  adjusts the distance  96  between the first distance  96 A and the second distance  96 B to cause the focal distance of an image  64  viewed by the user  30  to change between infinity and less than infinity or vice versa. 
     In one embodiment, as described with respect to  FIG.  6   , the adjustor  82  may be automatically controlled by a controller  120  to move the screen  68  to adjust the distance  96  between the screen  68  and the mirror  74 . In another embodiment, the adjustor  82  may be manually controlled by the user or an operator via a control system  122 . 
     Referring now to  FIG.  6   , the simulator  40  may include a control system  122  in communication with the variable collimation display system  62 . Suitable control systems  122  are known to those of skill in the art. In some embodiments, the control system  122  is a personal computer, such as, but not limited to, a personal computer running the MS Windows operating system, the Mac OS, Linux or any other known operating system. Optionally, the control system can be a smart phone, a tablet computer, a laptop computer, and similar computing devices. In other embodiments, the control system is a data processing system which includes one or more of, but is not limited to: an input device (e.g. a keyboard, mouse, or touch-screen); an output device (e.g. a display, a speaker); a graphics card; a communication device (e.g. an Ethernet card or wireless communication device); permanent memory (such as a hard drive); temporary memory (for example, random access memory); computer instructions stored in the permanent memory and/or the temporary memory; and a processor. 
     In some embodiments, the control system  122  is integrated or embedded into an image generator associated with the simulator  40 . The control system  122  may also be integrated or embedded in a host computer of the simulator. Additionally, or alternatively, the control system  122  may be a virtual machine running on (or operated by) the computer system of the simulator. In still other embodiments, the control system  122  is associated with a computer system in communication with an image generator or a host computer system of the simulator  40 . 
     The control system  122  according to embodiments of the present disclosure may comprise a processor  124 , a memory  126 , a communication interface  128 , and a user interface  130 . The control system  122  in some embodiments may have more components or fewer components than illustrated in  FIG.  6   . The control system  122  may be any suitable computer known to one of skill in the art. 
     The processor  124  of the control system  122  may be any processor known to one of skill in the art, including a processor described herein or any similar processor. The processor  124  may be configured to execute instructions stored in the memory  126 , which instructions may cause the processor  124  to carry out one or more computing steps utilizing or based on data received from the variable collimation display system  62 . 
     The memory  126  may be or comprise RAM, DRAM, SDRAM, other solid-state memory, any memory described herein, or any other tangible, non-transitory memory for storing computer-readable data and/or instructions. The memory  126  may store information or data useful for completing any operation described herein, including steps or operations of the methods  140  and/or  160  described herein. The memory  126  may store, for example, a focal distance model  132 , a size model  134 , a simulation software, an image engine or image generating software, and/or controller instructions  136 . Such instructions may, in some embodiments, be organized into one or more applications, modules, packages, layers, or engines. The instructions may cause the processor  124  to manipulate data stored in the memory  126  and/or received from the variable collimation display system  62 . 
     In some embodiments, the memory  126  may include a lookup table  138 . Optionally, in at least one embodiment, the lookup table  138  includes predefined distances  96  between the mirror  74  and the screen  68  for a plurality of predefined situations. In some embodiments, the lookup table includes distances  96  based on a simulated height  102  of a simulated aircraft. Additionally, or alternatively, the lookup table may include distances  96  for the screen to be spaced from the mirror based on the slant range or the simulated distance  100  from the designated eye point  32  to an object  60  in an image  64 . 
     For example, the lookup table  138  may indicate that the adjustor  82  should move the screen  68  to a first position with a first distance  96 A (such as generally illustrated in  FIG.  5 A ) when the simulated height  102 A is above a predetermined amount. The lookup table  138  may then include values to decrease the distance  96  when the simulated height  102  is less than the predetermined amount. For example, when the simulated height  102  is 95% of the predetermined amount, the lookup table may include a second distance  96  expressed as a percentage of the first distance, such as 95% of the first distance. Alternatively, the second distance  96  may be expressed as a distance (in inches or centimeters) to be subtracted from the first distance. Continuing this example, as the simulated height  102  continues to decrease, the lookup table may include values to decrease the distance  96  between the screen and the mirror until a minimum distance  96  is reached, such as when the simulated aircraft lands. 
     In some embodiments, the lookup table  138  may define distances  96  between the screen  68  and the mirror  74  based on the simulated distance  100  from the designated eye point  32  to an object  60  in an image  64 . For example, if the simulated distance  100  is greater than a predetermined amount, for example 18 feet, the lookup table may indicate that the screen should be a first distance  96  from the mirror. As the simulated aircraft more closely approaches the object, the lookup table may include values to decrease the distance  96  such that the screen progressively moves closer to the mirror. 
     Including predetermined values for the distances  96  based on one or more of the simulated height  102  and the simulated distance  100  to an object  60  is beneficial to support different flight operations. For example, during a landing or take-off simulation, it may be beneficial to determine the distance  96  between the screen and the mirror based on the simulated height  102  of the aircraft. However, in some simulations, such as a high hover next to an object  60 , the simulated height  102  may be above a predetermined threshold such that the screen  68  would be spaced from the mirror  74  by a distance  96  sufficient that the image  64  of the variable collimation display system would be at infinity focus. But the simulated aircraft may be very close to the object  60  such that the simulated distance  100  is less than the predetermined amount. Accordingly, the screen should be moved toward the mirror to decrease the distance  96  and change the focal length of the object  60  in the image  64 . 
     The control system  122  may also comprise a communication interface  128 . The communication interface  128  may be used for receiving information from an external source (such as the variable collimation display system  62 ), and/or for transmitting instructions, data, or other information to an external system or device (e.g., the adjustor  82 , the projector  80  (or the screen  68 B) and/or variable collimation display system, and the projector  50  of the primary display  48 ). The communication interface  128  may comprise one or more wired interfaces (e.g., a USB port, an ethernet port, a Firewire port) and/or one or more wireless interfaces (configured, for example, to transmit information via one or more wireless communication protocols such as 802.11a/b/g/n, Bluetooth, NFC, ZigBee, and so forth). In some embodiments, the communication interface  128  may be useful for enabling the control system  122  to communicate with one or more other processors  124  or other control systems  122 , whether to reduce the time needed to accomplish a computing-intensive task or for any other reason. 
     The control system  122  may also comprise one or more user interfaces  130 . The user interface  130  may be or comprise a touchpad (for example, of a laptop computer), keyboard, mouse, trackball, monitor, television, touchscreen, joystick, switch, button, and/or any other device for receiving information from a user and/or for providing information to a user. The user interface  130  may be used, for example, to receive a user selection or other user input regarding the focal distance model  132 ; to receive a user selection or other user input regarding a simulation executed by the simulator; to receive user input useful in connection with the controller instructions  136 ; and/or to display the instructions  136 . In some embodiments, the user interface  130  may be useful to allow a user or operator to modify the instructions  136 , the adjustor  82  (such as to change a position of the screen  68 ), or other information displayed, although it will be appreciated that each of the preceding inputs may be generated automatically by the control system  122  (e.g., by the processor  124  or another component of the control system  122 ) or received by the control system  122  from a source external to the control system  122 . In some embodiments, user input such as that described above may be optional or not needed for operation of the systems, devices, and methods described herein. 
     Although the user interface  130  is shown as part of the control system  122 , in some embodiments, the control system  122  may utilize a user interface  130  that is housed separately from one or more remaining components of the control system  122 . In some embodiments, the user interface  130  may be located proximate one or more other components of the control system  122 , while in other embodiments, the user interface  130  may be located remotely from one or more other components of the control system  122 . 
     Optionally, as illustrated in  FIG.  6   , the adjustor  82  may include a controller  120 . The controller  120  is operable to control the adjustor  82  to cause the adjustor  82  to move the screen  68  to alter the distance  96  between the screen  68  and the mirror  74 . In other embodiments, the adjustor does not include the controller  120 . 
     The controller  120  may be an electronic, a mechanical, or an electro-mechanical controller. The controller  120  may comprise or may be any processor described herein. The controller  120  may comprise a memory storing instructions for executing any of the functions or methods described herein as being carried out by the controller  120 . In some embodiments, the controller  120  may be configured to simply convert signals received from the control system  122  (e.g., via a communication interface  128 ) into commands for operating the adjustor  82 . In other embodiments, the controller  120  may be configured to process and/or convert signals received from the adjustor  82 . Further, the controller  120  may receive signals from one or more sources (e.g., the adjustor  82 ) and may output signals to one or more sources. 
     Turning now to  FIG.  7   , a method  140  for adjusting focal distances of images  64  displayed to a user  30  at a designated eye point  32  of a simulator  40  is provided. The method  140  may be performed using, for example, the components described above with respect to  FIGS.  2 - 6   . 
     The method  140  comprises generating an image  64  for display by a screen  68  of the variable collimation display system  62  in operation  142 . The image depicts an environment outside of a simulated vehicle (for example, an aircraft) and may include an object  60 , such as a tree. The image  64  is transmitted to the projector  80  or the screen  68 B of the variable collimation display system. 
     In some embodiments, the projector  80  may project the image  64  on the front surface  72  of the screen  68 A- 2  (for a front projection screen) or on the rear surface  70  of the screen  68 A- 1  (for a back projection screen). In other embodiments where the screen  68 B is a self-illuminating screen, the image may be projected by the screen  68 B itself. 
     The image may be generated by the control system  122 . For example, the image  64  may be generated as part of a simulation software stored in memory  126 . In some embodiments, the image  64  is created by an image generator software stored in the memory  126 . 
     In some embodiments, the image  64  is received by the communication interface  128  from a separate control system, such as a control system that controls the simulator  40  and which is configured to generate the image. 
     The method  140  also comprises operation  144  which includes determining a simulated distance  100  from the designated eye point  32  to the object  60  in the image  64 . The simulated distance may be a perceived viewing distance. In other words, the simulated distance may be a distance between the designated eye point  32  and the object  60  as perceived by a user  30  at the designated eye point if the object was physically present. In some embodiments, the simulated distance may be (or may be related to) a simulated height  102  above terrain of a simulated aircraft, for example. The height above terrain  102  may be a distance between the simulated aircraft and a ground surface  26 . 
     In some embodiments, the simulated distance  100  is determined using the Pythagorean theorem and inputting the height  102  of the simulated aircraft at the designated eye point  32  and the horizontal distance  104  to the object  60 . In some embodiments, the simulated distance may be determined using method  160  described herein. 
     The method  140  also comprises operation  146  which includes determining a focal distance for the image  64  based on the simulated distance  100  between the designated eye point  32  and the object  60  in the image. In some embodiments, determining the focal distance for the image comprises using the focal distance model  132  stored in memory  126  of the control system  122 . In such embodiments, the processor  124  may input the simulated distance  100  to the focal distance model  132 , execute the focal distance model  132 , and receive the focal distance as an output from the focal distance model  132 . In some embodiments, the focal distance model  132  may be trained using, for example, historical distances and/or simulated distances obtained from a simulation. Additionally, or alternatively, operation  146  may comprise retrieving the focal distance from a lookup table  138 . 
     Method  140  may include optional operation  148  which comprises determining a simulated size  106  of the object  60  for display in the image  64 . In some embodiments, the simulator  40  is configured to determine the simulated size  106  of the object. More specifically, the simulator  40  may include a control system which executes instructions to determine the simulated size of the object  60 . The simulator control system may then send a signal to the communication interface  128  with the simulated size. The control system  122  can then send an instruction to the projector  80  (or the self-illuminated screen  68 B) to project the image  64 . 
     In some embodiments, the control system  122  inputs the simulated distance  100  to a size model  134  stored in memory  126 . The size model then outputs the simulated size  106  to the control system  122  and its processor  124 . Optionally, the size model  134  may be trained using, for example, historical distances and/or simulated distances obtained from a simulation. 
     The method  140  may also comprise generating instructions to cause the adjustor  82  to alter the distance  96  between the screen  68  and the mirror  74  to achieve the focal distance in operation  150 . Optionally, operation  150  comprises retrieving the distance  96  from the lookup table  138  based on one or more of the height  102  above terrain, the horizontal distance  104  to an object, and the simulated distance  100  to the object in the image. 
     In some embodiments, the instructions are transmitted to the controller  120  to cause the adjustor  82  to adjust the distance  96 . In embodiments where the adjustor  82  comprises an actuator  92 , the controller  120  may control the actuator to move the screen  68  with respect to the mirror  74  as described herein. 
     The method  140  may also comprise operation  152  in which a size  106  of the object  60  in the image  64  is adjusted. The size of the object  60  in the image  64  may be adjusted based on the simulated size determined in operation  148 . The size  106  of the object is adjusted to accommodate the adjustment to the distance  96  between the screen  68  and the mirror  74 . The size of the object is also adjusted such that the object is visible as it would appear as a physical object at the focal distance. In other words, the size  106  of the object is adjusted to match a perceived view of the object if the object was physically viewable by the user  30 . 
     It will be appreciated that the method  140  may include more or less steps than described above. One or more operations of method  140  may loop or be repeated as necessary such that the focal distance of images  64  displayed to the user  30  and the size  106  of the object  60  visible in the images are continuously updated in real-time. The focal distance as perceived by the user  30  is adjusted to match the perceived distance  100  to the object  60  being displayed in the image  64 . As described herein, this is accomplished by changing the distance  96  between the mirror  74  in which the user  30  views the object  60 , and the screen  68  displaying the image  64  created by the control system  122 . By manipulating the mirror/screen distance  96 , the light rays reflecting from the mirror  74  can be adjusted from collimated (parallel light rays), representing infinity focus or far away objects (as illustrated in  FIG.  5 A ), to gradually more and more diverging rays representing shorter focal distances as the simulated aircraft moves closer to objects and/or the ground (as illustrated in  FIG.  5 B ). By adjusting the focal distance of the images in real-time, the environment as viewed by the user appears to be more accurate, particularly during take-off and/or landing procedures. 
     Turning now to  FIG.  8   , a method  160  for determining the simulated distance  100  is provided. The method  160  may be performed using, for example, the systems and components described above with respect to  FIGS.  2 - 7   . In some embodiments, method  160  is performed before method  140 . Additionally, or alternatively, method  160  may be performed during method  140 . For example, method  160  may be performed prior to operation  146 . Method  140  may be paused for method  160  to be performed, then method  140  may be resumed upon completion of method  160 . 
     Optional operation  162  of method  160  comprises receiving a position of the designated eye point  32 . The position of the designated eye point  32  may be received as an input from a user via the user interface  130  in some embodiments. In other embodiments, the position of the designated eye point  32  may be determined by a sensor positioned near or at the designated eye point  32 . For example, the user may wear a headset having a sensor configured to send sensor data comprising a position of the sensor to the control system  122 . Additionally, or alternatively, the position of the designated eye point  32  may be retrieved from memory  126  of the control system  122 . 
     Method  160  also comprises determining a simulated position of an object  60  depicted in an image  64  relative to the designated eye point  32  in operation  164 . In some embodiments, determining the simulated position of the object may comprise determining a distance between the position of the designated eye point  32  and the mirror  74 . Additionally, or alternatively, a position of the object (or the simulated distance  100  to the object) may be received from the simulator  40 , or as an output of a simulation software or from an image generator creating images for the simulator. 
     The method  160  may also include operation  166  which comprises determining a distance between the position of the designated eye point  32  and the simulated position of the object  60  to yield the simulated distance  100 . The simulated position of the object is received from operation  164 . In some embodiments, determining the distance comprises subtracting the x and/or y coordinate of the designated eye point  32  from the x and/or y coordinate of the simulated position of the object  60 . 
     It will be appreciated that the method  160  may include more or less steps than described above. 
     The methods and systems described herein adjust a focal distance of an image displayed to a user at a designated eye point of a simulator using a mirror, a screen, an adjustor, and a control system to adjust the focal distance in real-time. The methods and systems advantageously adjust the focal distance of the image as the simulator simulates approaching or distancing the designated eye point to the image. Such focal distance adjusting improves the realism of the image to the user, in particular during a landing or a take-off simulation, thereby improving the simulation experience. 
     Another benefit of the methods and systems described herein is that an object  60  displayed in an image  64  of the variable collimation display system  62  will align with (and be of a corresponding size to) an object  60  shown in an image  56  produced by a primary display  48 . This improves realism of simulations run in the simulator. 
     The variable collimation display system  62  of embodiments of the present disclosure provides further benefits in that it is compatible with Night Vision Goggles (NVGs) in situations where NVGs are in-focus in real aircraft. More specifically, as will be appreciated by one of skill in the art, the NVGs used in a simulator  40  are focused at or near infinity to match the focus of the primary “Out the Window” display  48 , as they would be in an actual aircraft which the simulator  40  replicates. This level of realism is important since it means the instrument panel within the simulator cockpit  42  is out of focus in the NVGs, as the instrument panel would be in the real aircraft. To see the instrument panel within the simulator, the pilot  30  must “train like they fly” and learn to pick up instrument cues by glancing below the night vision goggles. 
     A variable collimation display system  62  associated with a chin window  46  of a simulator  40  of the present disclosure can produce near-infinity focus in some simulated flying situations (such as in a high hover). Therefore, when the screen  68  of the variable collimation display system is in the first position a first distance  96 A from the mirror  74  (illustrated in  FIG.  5 A ) to produce near-infinity focus, the image  64  produced by the variable collimation display system  62  will be compatible with NVGs (or will be in focus when viewed through the NVGs). This is similar to a pilot viewing an object through a chin window of a real aircraft (or helicopter) while in a high hover. 
     As a real aircraft descends from high hover, objects will come nearer and become out of focus in the NVGs. A pilot must glance below the NVGs to see objects through a chin window as the aircraft descends. 
     The variable collimation display system  62  can replicate this by moving the screen  68  to a second position that is a second distance  96 B from the mirror  74  (as shown in  FIG.  5 B ) in which the image  64  is at less than infinity focus. The pilot user  30  would then need to look under the night vision goggles to pick up ground cues through the chin window  46  of the simulator (as they would in the real aircraft). In this manner, the variable collimation display system  62  of the present disclosure builds positive habits and improves the realism of the simulator  40 . 
     As may be appreciated based on the foregoing disclosure, the present disclosure encompasses methods with fewer than all of the steps identified in  FIGS.  7  and  8    (and the corresponding description of the methods  140  and  160 ), as well as methods that include additional steps beyond those identified in  FIGS.  7  and  8    (and the corresponding description of the methods  140  and  160 ). While a general order of the methods  140  and  160  are shown in  FIGS.  7 - 8   , it will be understood by one of skill in the art that the steps of the methods can be arranged and performed differently than those shown in  FIGS.  7 - 8   . Further, although the steps of the methods may be described sequentially, many of the steps may in fact be performed in parallel or concurrently. 
     While various embodiments of the system have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. It is to be expressly understood that such modifications and alterations are within the scope and spirit of the present disclosure. Further, it is to be understood that the phraseology and terminology used herein is for the purposes of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof, as well as, additional items. 
     Several variations and modifications of the disclosure can be used. It would be possible to provide for some features of the disclosure without providing others. 
     The features of the various embodiments described herein are not intended to be mutually exclusive. Instead, features and aspects of one embodiment may be combined with features or aspects of another embodiment. Additionally, the description of a specific element with respect to one embodiment may apply to the use of that specific element in another embodiment, regardless of whether the description is repeated in connection with the use of the specific element in the other embodiment. 
     Moreover, though the description of the disclosure has included description of one or more embodiments, configurations, or aspects and certain variations and modifications, other variations, combinations, and modifications are within the scope of the disclosure, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights, which include alternative embodiments, configurations, or aspects to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges, or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges, or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter. 
     One aspect of the disclosure comprises any one or more of the aspects/embodiments as substantially disclosed herein. 
     Another aspect of the disclosure is any one or more of the aspects/embodiments as substantially disclosed herein optionally in combination with any one or more other aspects/embodiments as substantially disclosed herein. 
     It is another aspect of the present disclosure to provide one or more means adapted to perform any one or more of the above aspects/embodiments as substantially disclosed herein. 
     Aspects of the present disclosure may take the form of an embodiment that is entirely hardware, an embodiment that is entirely software (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module,” or “system.” Any combination of one or more computer-readable medium(s) may be utilized. The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. 
     A computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer-readable signal medium may include a propagated data signal with computer-readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A computer-readable signal medium may be any computer-readable medium that is not a computer-readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer-readable medium may be transmitted using any appropriate medium, including, but not limited to, wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
     The terms “determine,” “calculate,” “compute,” and variations thereof, as used herein, are used interchangeably and include any type of methodology, process, mathematical operation or technique. 
     Examples of the processors as described herein may include, but are not limited to, at least one of Qualcomm® Snapdragon® 800 and 801, Qualcomm® Snapdragon® 610 and 615 with 4G LTE Integration and 64-bit computing, Apple® A7 processor with 64-bit architecture, Apple® M7 motion coprocessors, Samsung® Exynos® series, the Intel® Core™ family of processors, the Intel® Xeon® family of processors, the Intel® Atom™ family of processors, the Intel Itanium® family of processors, Intel® Core® i5-4670K and i7-4770K 22 nm Haswell, Intel® Core® i5-3570K 22 nm Ivy Bridge, the AMD® FX™ family of processors, AMD® FX-4300, FX-6300, and FX-8350 32 nm Vishera, AMD® Kaveri processors, Texas Instruments® Jacinto C6000™ automotive infotainment processors, Texas Instruments® OMAP™ automotive-grade mobile processors, ARM® Cortex™-M processors, ARM® Cortex-A and ARM926EJ-S™ processors, other industry-equivalent processors, and may perform computational functions using any known or future-developed standard, instruction set, libraries, and/or architecture. 
     To provide additional background, context, and to further satisfy the written description requirements of 35 U.S.C. § 112, the following references are incorporated by reference herein in their entireties: U.S. Pat. Nos. 9,191,659; 10,942,360; and Canadian Patent Publication No. 3,113,582.