Patent Publication Number: US-11041695-B2

Title: Aiming device and method

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electronic aiming device and an aiming method using such a device. The device of the invention is particularly suited to the firing of munitions having a parabolic trajectory (i.e. having a substantial difference between the aiming angle and the sighting angle). 
     BACKGROUND 
     All aiming systems require knowledge of the distance. This is particularly true for projectiles having a highly curved (parabolic) trajectory, since in this case the aiming line and the sight line may be very different. 
     According to the prior art, this distance may be entered either automatically (communication between the aiming system and a rangefinder) or manually. In the first case, the system in question is more complex since it involves an aiming system and a rangefinder, which may or may not be combined. Here, the case of a standalone aiming system without communication with another electronic system is considered. Consequently, in order to use the aiming system, the firer must be kept updated as to the distance from the target either by a partner or by estimation. With the exception of the case of aiming systems having a complete (mechanical, holographic, etc.) grid sight, and hence lower resolution, this distance must then be entered manually into the aiming system so that it positions the aiming means at the desired angle. It should also be emphasized that aiming systems having a complete (mechanical or electronic) grid sight generally have lower resolution and do not allow multiple ballistics charts to be taken into account. 
     An example of an aiming system for parabolic firing is described in the patent document EP 1 818 645. In this document, a movable red dot is placed at an adequate sighting angle, according to the predetermined distance, such that superposition of the red dot over the target provides a correct range for the munition. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an aiming system for a firearm comprising:
         a clinometer measuring at least the angle of elevation of the firearm;   a computer comprising a memory of an initial angle of elevation;   a ballistics chart included in the computer, which matches a firing distance with an angle of elevation (α) relative to the initial angle of elevation;   a first display device which, when in use, displays for the user the firing distance as a function of the initial angle of elevation and the instantaneous angle of elevation.       

     According to preferred embodiments of the invention, the aiming system of the invention comprises one, or a suitable combination, of at least two of the following features:
         the aiming system comprises a second display device indicating the vertical bore axis;   the system comprises movable designation means, the computer being arranged to move, when in use, said designation means along a vertical axis so as to keep said designation means at the initial angle of elevation;   the movable designation means are selected from the group consisting of a red dot, a reticle and a pointer;   the system comprises a low-pass frequency filter between the clinometer and the computer, so as to stabilize the inclination measurement;   the system comprises means for laterally moving the display of the vertical axis of the firearm or the movable designation means, so as to apply an azimuthal correction for the Magnus effect and/or for the cant angle;   the system comprises a second clinometer that is connected to the computer, measuring the cant angle of the firearm, the display means indicating to the user when the cant angle compensates for the Magnus effect for the displayed distance;   the system comprises optical magnification means, and tracking means that are arranged to keep, when in use, the area of magnification at the initial angle of elevation;   the system comprises a semitransparent surface superposing over the target an image at infinity of a screen displaying the distance.       

     A second aspect of the invention relates to an aiming method for a firearm using the aiming system of the invention, comprising the following steps:
         determining the distance from a target;   marking the angle of elevation of the target;   increasing the angle of elevation of the firearm until the distance from the target is displayed, adequate aim being achieved when the displayed distance corresponds to the displayed distance.       

    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  schematically shows the general parameters of a parabolic trajectory. 
         FIG. 2  schematically shows the general algorithm for a firing system using the aiming system of the invention. 
         FIG. 3  schematically shows one example of the display of the parameters superposed over the environment, as perceived by the user. (a) when locking onto the target, (b), when firing. 
         FIG. 4  schematically shows another example of the display of the parameters superposed over the environment, as perceived by the user. (a) when locking onto the target, (b), when firing. 
         FIG. 5  schematically shows one example of a device for displaying the range according to the invention, in the position for locking onto the target. 
         FIG. 6  schematically shows another example of a device for displaying a range according to the invention, in firing position. 
         FIG. 7  schematically shows another example of a device for displaying the range according to the invention, in the position for locking onto the target. 
         FIG. 8  schematically shows another example of a device for displaying a range according to the invention, in firing position. 
         FIG. 9  schematically shows one example of a device for displaying a range according to the invention comprising optical magnification means, in the position for locking onto the target. 
         FIG. 10  schematically shows another example of a device for displaying the range according to the invention comprising optical magnification means, in firing position, this device having both a movable reticle and a device for designating/illuminating the target. 
         FIG. 11  schematically shows another example of a device for displaying the range according to the invention comprising optical magnification means, in the position for locking onto the target. 
         FIG. 12  schematically shows the device for displaying the range from  FIG. 11  in firing position. 
     
    
    
     KEY 
     
         
         
           
               1 . User 
               2 . Target 
               3 . Distance from the target (range) 
               4 . Sight axis 
               5 . Firearm 
               6 . Trajectory 
               7 . Aiming device 
               8 . Movable red dot or reticle 
               9 . Display of the lock state (in the non-locked state) 
               10 . Initial digital display of the distance 
               11 . Digital display of the range 
               12 . Display of the lock state (in the locked state) 
               13 . Bore axis 
               14 . Second display device 
               15 . First display device 
               16 . Computer 
               17 . Memory 
               18 . Clinometer 
               19 . Second clinometer 
               20 . Fixed vertical reticle 
               21 . Initial display of the distance 
               22 . Display of the range 
               28 . Fixed red dot or reticle 
               30 . Display screen 
               31 . Lens 
               32 . Fixed mirror for redirecting the image from the display 
               34 . Semireflective plate 
               41 . Off-center red dot for movement of the movable red dot or reticle 
               50 . Movable mirror 
               51 . Axis of rotation of the movable mirror 
               60 . Tracking mirror 
               61 . Objective lens 
               62 . Semitransparent redirecting mirror 
               63 . Eyepiece lens 
               65 . Light source for designation or illumination (in the focal plane of the objective lens) 
               70 . Reflective tracking prism 
               71 ,  72 ,  74 . Redirecting mirrors 
               73 . Semireflective mirror 
               75 . Axis of rotation of the prism  70 . 
           
         
       
    
     DETAILED DESCRIPTION 
     The principle of the invention is to display the range of a munition as a function of the angle α formed between the sight axis  4  and the bore axis  13  to a user in real time. These basic firing parameters are shown in  FIG. 1 . According to the invention, the aiming device comprises a clinometer and a computer comprising the ballistics chart for the munition in question. To determine the firing conditions, the user  1  first determines the sight line  4 . In the case in which the sight line  4  is not horizontal, the firer must mark (or lock) this sight line  4 . It may be marked in various ways, such as by pressing a button, by holding this sight line for a given time, or by any other means (voice command, blinking an eye, etc.) allowing the system to decide that it does indeed signify the designation of a target. 
     The elevation of this sight line is then memorized by the computer. A display  10 ,  21  then initially indicates a range of zero to the user. During the marking operation, an indicator light may advantageously switch from an off state  9  signifying that the sight line has not been locked to an on state  12  indicating that the sight line has been locked. 
     Once this sight line has been locked, the firer simply has to increase the angle of elevation of the firearm until the displayed distance  11 ,  22  corresponds to the distance from the target. The general principle of this firing mode is shown in  FIG. 2 . 
     During this vertical movement, a change in the azimuthal direction of the firearm  5  by the firer should be avoided. The simplest way to achieve this is to use a point of reference such as a vertical reticle projected to infinity by a suitable device and superposed visually over the target, such as shown in  FIG. 3 . 
       FIG. 3  shows the simplest mode of implementation of the invention, having the advantage of using no moving parts. In  FIG. 3 a   , the user designates the target by means of a fixed reticle  28  and marks the target. The indicated distance  10  is then 0 and the indicator light  9  is initially off. Next, as shown in  FIG. 3 b   , the user locks the sight line and raises the firearm while keeping the target in the vertical fixed reticle  20  until the predetermined distance is displayed. 
     The display from  FIG. 3  may for example be provided by the device from  FIG. 5 . In this figure, a display screen  30  is placed at the focal point of a lens  31 , and the image of the display screen  30  at infinity is redirected via a fixed redirecting mirror  32  to a semireflective device  34  allowing the image of the screen to be superposed over the image of the target in the sight of the user  1 . The semireflective device may for example comprise a simple semireflective plate, a prism, or a cube formed of two prisms and comprising a semireflective diagonal. 
     In this embodiment, the visual field over which the display is superposed must be large enough to keep the display of the distance  11  and the vertical reticle  20  visible and superposed over the target  2  regardless of the elevation. 
     The display screen  30  may for example comprise a simple LED display such as shown in  FIG. 3 , a vertical linear LED for visually representing the vertical reticle  20  and a horizontal LED forming, with the vertical LED, the reticle  28 . Alternatively, the display screen  30  comprises a small, high-resolution matrix display in order to limit the bulk of the device. Such a system affords the display greater flexibility, but generally has the drawback of increased energy consumption. The computer must also, in this case, comprise more sophisticated graphics means (GPU). 
     According to a more sophisticated embodiment of the invention as shown in  FIG. 4 , when raising the firearm after lock, the designation reticle  8  tracks the aiming line by means of a tracking device, the computer moving the reticle  8  vertically in real time so as to track the target on the sight line. The display of the distance may (as in  FIG. 4 b   ) or may not track an equivalent movement in the visual field. In this case, once in firing position, the firer aligns the reticle with the target until the displayed distance is suitable for the firer. In practice, the position of the reticle is controlled and stabilized by means of a PID controller, for example, so that it is kept aligned with the firing line defined by the firer at the start. 
     In this case, the tracking may also be provided by the device from  FIG. 5 . It is then sufficient to move the representation of the reticle  41  over the display device  30 . For example, it may be moved simply by moving the image of the reticle over the high-resolution matrix display such as described above. This movement is shown in  FIG. 6 . 
     Preferably, the tracking device, such as shown in  FIGS. 7 and 8 , comprises a movable redirecting mirror  50  rotating about a horizontal axis  51  allowing the sighting angle of the display to be adjusted. 
     Regardless of whether the redirecting mirror is fixed or movable, the semitransparent device allowing the reticle and the display to be superposed over the target may advantageously comprise a splitter cube  52  comprising two prisms separated by a splitter plate  53 . This type of cube is used both to improve the robustness of the superposing plate and to decrease the bulk of the system. Specifically, refractions of the projected image of the screen at the entrance and at the exit of the prism have the effect of decreasing the movement of the corresponding light beams over the splitter plate  53 , thus decreasing the required length of the splitter plate  53 . The second prism, on the target side, allows the chromatic distortions of the image of the target caused by refraction to be removed. 
     Advantageously, the device of the invention may be incorporated within a target magnification device such as shown in  FIGS. 9 and 10 . In this case, the system advantageously comprises a tracking mirror  60  that is able to rotate about a horizontal axis, redirecting the sight axis  4  onto the optical axis  64  of an objective lens  61 , the computer comprising means for controlling the rotation of the tracking mirror  60  that are arranged to keep, once the elevation has been locked, the aiming axis  4  redirected onto the optical axis  64  of the objective lens  61 . 
     In this case, the display device may advantageously be placed behind a semitransparent plate  62  that redirects the optical axis  64  from the objective lens  61  onto an eyepiece lens  63 , the display screen  30  being placed in a conjugate plane of the focal plane of the eyepiece lens  63  so as to project the image of the display screen  30  to infinity. 
     Advantageously, as shown in  FIG. 10 , an illuminator/pointer  65  may be placed in the extension of the optical axis  64  of the objective lens  61 , and at the focal point thereof so as to illuminate the target  2 . 
     Conventionally, the eyepiece lens  63  is a divergent lens, forming what is termed a Galilean scope geometry with the objective lens, allowing an upright image to be formed. Of course, the term “eyepiece lens” is understood to mean a simple divergent lens, or an assembly of achromatic lenses such as an achromatic doublet or triplet, well known to those skilled in the art. 
     Alternatively, the eyepiece  63  may be a convergent lens forming what is termed a Keplerian geometry with the objective lens. In this case, a device for rectifying the image is generally used. This type of geometry makes it possible to place a fixed (passive) reticule at the focal point of the objective lens and a passive LCD digital display, thereby allowing the consumption of the device to be decreased. 
     When magnification is used, it may be desirable to keep the gaze of the user on the axis of the sight line  4  rather than along the aiming axis  13 . In this case, two additional redirecting mirrors are used, the mirror redirecting to the user being movable and slaved to the tracking mirror  60 , these two mirrors being arranged to keep an angle of 90° between them. 
     An exemplary embodiment of such a device is shown in  FIG. 11 . In this device, the abovementioned slaving of the mirror redirecting to the user to the tracking mirror is provided by using two faces of one and the same reflective prism  70 . When the device is locked onto the elevation of the sight line, the angle of elevation is tracked by rotating the prism  70  on its axis  75 . When the angle of elevation increases by a value a, the prism rotates by α/2. The image of the target is next reflected toward the objective lens  61  and then successively redirected by the mirrors  71 ,  72 ,  73 ,  74 , one of these being semitransparent so as to superpose the display of the display screen  30  located in a conjugate plane of the focal plane of the eyepiece lens  63 . The advantage of the geometry presented in  FIG. 11  is that it provides minimal bulk. 
     Advantageously, the device of the invention comprises a low-pass frequency filter allowing the noise caused by involuntary small movements of the firer (parasitic vibrations) to be decreased so that they do not affect the readability of the displayed distance. 
     One advantage of the invention is that it makes it possible not to have to manually enter the distance into the aiming system. It also makes it possible to benefit from the possibility of using different ballistics charts according to the projectile being used without modifying hardware, unlike in mechanical aiming systems. 
     Advantageously, the device of the invention also comprises means for applying an azimuthal correction for the Magnus effect. For example, the movable reticle or the vertical reticle may be moved laterally according to the calculated distance. 
     Alternatively, the Magnus effect may be corrected for by modifying the cant angle. In this case, the device of the invention comprises a clinometer measuring the cant angle, the computer determining, as a function of the displayed range, the ideal cant angle (i.e. that correcting for the Magnus effect). The display then comprises an indicator indicating to the firer whether or not the tilt is adequate. For example, the display comprises two indicator lights indicating in which direction the user should increase the cant angle, these indicator lights turning off to indicate an adequate angle.