Abstract:
A process to optically align optical systems on a weapon is disclosed. Several different embodiments of the system and method are disclosed. The use of this process/system will ensure a well aligned weapon with mounted optical systems. It can find applications in aligning rifle scopes, aiming lasers, laser range finders, tactical engagement simulation lasers, e.g., MILES, etc.

Description:
GOVERNMENT INTEREST 
       [0001]    The invention described herein may be manufactured, used, sold, imported, and/or licensed by or for the Government of the United States of America. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates in general to optics, and more particularly, to optical alignment of optical weapon systems. 
       BACKGROUND OF THE INVENTION 
       [0003]    The US Armed Forces are adding optical systems onto their weapons with the individual soldier&#39;s weapon (M4, M16, etc.). The optical systems being mounted to the weapon include a variety of optical sights that covers the visible, near-infrared, mid-infrared, and far-infrared spectrum. Also being mounted to the weapon are a variety of laser systems which include, but are not limited to, aiming lasers (visible and near-infrared), laser range finders, and tactical engagement simulation laser transmitters for training (e.g. MILES). An example of a weapon with optical systems mounted is shown in  FIG. 1 . All these optical systems are required to be precisely aligned with the weapon. 
         [0004]    The current process to align optical systems mounted on a weapon to each other and to the weapon is cumbersome, time consuming, prone to error and limited. Users/soldiers deserve a better, simpler and more accurate, means of aligning their optical systems on a weapon to each other and to the weapon. 
         [0005]    The current process of aligning a weapon (e.g., a rifle) with mounted optical systems in the US Armed forces is a two step procedure. 
         [0006]    The first step is to use a borelight and a 10 M (meter) Offset Card  200 . The 10 M Offset Card has marked on it the mechanical offset distances of the mounted optical systems with respect to the rifle bore. The 10 M Offset Card is placed 10 meters from the weapon (e.g., a weapon mounted optical system as exemplified in  FIG. 1 ). The weapon user then aligns his weapon by adjusting the mounted optical systems so that they ‘hit’ the corresponding marks on the 10 M Offset Card, as shown in  FIG. 2 . This alignment procedure is to align all the optical systems together with the weapon. It usually brings the shot group from the weapon onto the 25 M Zeroing Target, but not always! 
         [0007]    This process also depends on how well the ‘laser spots’ look to the user and how well he can place them in that exact spot on the 10 M Offset Card. The least bit of error in location translates to large errors in alignment. This is difficult at best. Bright daylight makes seeing the laser spots 10 meters away very hard. While holding the weapon steady on the 10 M Offset Card while trying to adjust the various optical systems mounted on the weapon can be next to impossible for an individual. 
         [0008]    The second step is to remove the borelight (which is very important since the user needs to fire live rounds). The 25 M Zeroing Target, as shown in  FIG. 3 , is placed 25 meters from the user&#39;s firing position. The user then sights onto the center of mass of the man silhouette on the 25 M Zeroing Target and fires three rounds. He or she will then go to the 25 M Zeroing Target, locate the 3-round shot group, and connect the holes. The center of the holes are used to determine what azimuth and elevation adjustment is needed to align the optical sight with the weapon.  FIG. 3  is an example of a 25 M Zeroing Target. 
       SUMMARY OF THE INVENTION 
       [0009]    A mirror-based optical alignment system is disclosed. Such an alignment system is comprised of a weapon mounted with at least one of a scope, a borelight and a laser range finder, each having a parallel optical path; a mirror optically shaped to have a focal length, the mirror being adjustably disposed at an offset angle to reflect said parallel optical paths at a reflection angle and focus said reflected optical paths on a focal point of a focal plane sufficiently distanced from said parallel optical path; and a target card placed proximately along said focal plane of the mirror such that said reflected parallel optical paths are focused to converge onto said focal point where the target card is placed. 
         [0010]    Further, an optical alignment station is disclosed based on the mirror-based optical alignment system. With such an alignment station a weapon points through its front location towards its rear location where the mirror is adjustably disposed such that said reflected parallel optical paths are focused to converge onto said focal point inside the optical alignment station. 
         [0011]    Further, a process to optically align optical systems to a weapon is disclosed based on the mirror-based optical alignment system. Such a process is comprised of the steps of centering a pattern of mechanical offsets of all the optical systems to be aligned onto the mirror angled as best as possible away from the target card; positioning the weapon borelight onto a borelight marking placed above other optic marking on said target card; and adjusting at least one optical system mounted on the weapon to said other optic marking on the target card, wherein at least one of a reticle and a laser is placed on said other optic marking 
         [0012]    In another aspect, a lens-based optical alignment system is disclosed, Such an alignment system is comprised of a weapon mounted with at least one of a scope, a borelight and a laser range finder, each having a parallel optical path; a refractive lens element, the refractive lens element being adjustably disposed to refract said parallel optical paths incident on one side of said refractive lens element and focus said optical paths on a focal point of a focal plane disposed on an opposite side of said refractive lens element; and a target card placed proximately along said focal plane of the refractive lens element such that said refracted parallel optical paths are focused to converge onto said focal point where the target card is placed. 
         [0013]    Likewise, an optical alignment station based on the lens-based optical alignment system is disclosed. With such an alignment station, a weapon points toward its front location where the lens refractive lens element is adjustably disposed. The target card is placed proximately along said focal plane of the refractive lens element such that said refracted parallel optical paths are focused to converge onto said focal point inside the optical alignment station. 
         [0014]    Finally, a process to optically align optical systems to a weapon based on the lens-based optical alignment system is disclosed. Such a process comprises the steps of centering a pattern of mechanical offsets of all the optical systems to be aligned onto the refractive lens element as best as possible; position the weapon borelight onto a borelight marking placed above other optic marking on said target card; and adjusting at least one optical system mounted on the weapon to said other optic marking on the target card, wherein at least one of a reticle and a laser is placed on said other optic marking 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Additional advantages and features will become apparent as the subject invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
           [0016]      FIG. 1  shows an exemplary weapon mounted optical system. 
           [0017]      FIG. 2  shows exemplary 10 M Offset Card. 
           [0018]      FIG. 3  shows an exemplary 25 M Zeroing Target. 
           [0019]      FIG. 4  shows an exemplary optical alignment station as embodied using a spherical (or parabolic) mirror and target card. 
           [0020]      FIG. 5  shows an exemplary embodiment of a refractive lens element and target card of an optical alignment station. 
           [0021]      FIG. 6  shows an exemplary aligning of a spotting scope and STORM laser range finder using the mirror embodiment. 
           [0022]      FIG. 7  shows an exemplary alignment target card for the M4/M16 weapon where a borelight mark is shown above an optics mark. 
           [0023]      FIG. 8  shows an exemplary embodiment of a system used in the field to optically align an optical system on a weapon. 
           [0024]      FIG. 9  shows an exemplary alternate embodiment having a lens optic disposed on a front location and/or a mirror disposed in a rear location. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    SYSTEM: A system and method is disclosed to optically align an optical system on a weapon. An exemplary system comprises of an optical alignment station that allows the operator to view the optical returns of the various optical systems mounted on the weapon on a simple target card. An exemplary optical alignment station can be made up of an optic (spherical/parabolic mirror or lens) and a target card. See, e.g.,  FIGS. 4 and 5 . 
         [0026]      FIG. 4  shows an exemplary optical alignment station  400  as embodied using a spherical (or parabolic) mirror  410  and a target card  420 . The mirror  410  is shown in  FIG. 4  as being vertically and horizontally adjustable. All incoming parallel rays  430  go to the same position at afocal point  440  where the target card  420  is placed. 
         [0027]      FIG. 5  shows an exemplary embodiment of another optical alignment station  500  based on a refractive lens element  510  and a target card  520 . The refractive lens element  510  is shown in  FIG. 5  as being vertically and horizontally adjustable. All incoming parallel rays  530  go to the same position at a focal point  540  where the target card  530  is placed. 
         [0028]    The optic (e.g., the mirror  410  in  FIG. 4  and the lens element  510  in  FIG. 5 ) is used to ‘translate’ the optical system&#39;s image plane to ‘infinity’ which is the focal plane of the optic. The axes of all the optical systems should converge to a common single point at infinity. 
         [0029]      FIG. 6  shows an exemplary method of aligning of a spotting scope  651  and a small tactical optical rifle mounted (STORM) laser range finder  652  using the mirror embodiment of  FIG. 4 . The key to this process is that the target card  620  is placed at the focal plane of the mirror  610 . The position of the target card  620  is where all parallel lines  630  converge or come to a single point  640 . Therefore, all optical systems  650  mounted on the weapon are overlaid at the same point as shown in  FIG. 6 . 
         [0030]    The borelight is placed at a position slightly higher than the other optical systems due to superelevation that accounts for the bullet drop over distance. The position of the borelight mark is calculated based on the weapon&#39;s bullet drop for a given distance and the focal length of mirror. 
         [0031]    The exemplary embodiment of a method of alignment using the mirror optical alignment station (as exemplified in  FIG. 4 ) is to place the target card  620  on-axis of the curved spherical mirror  610  at the focal plane (note, alternatively, an off-axis parabola may be employed, but it generally costs more). See, e.g.,  FIG. 6 . The placement of the target card  620  may have to be slightly off-axis with respect to the optical axis of the spherical or parabolic mirror  610  (to ‘see’ around the target card  620 ). If necessary, this off-axis placement introduces optical aberrations which would reduce the accuracy of the alignment process, the further off-axis, the less accurate the resulting alignment. The mirror  610  must be sized large enough to encompass the mounted optical systems  650  being aligned. 
         [0032]    The exemplary embodiment of a method of alignment using a lens optical alignment station (as exemplified in  FIG. 5 ) is to place the target card  520  on-axis of the spherical lens  510  at the focal plane  540  of the lens. The lens  510  must be sized large enough to encompass the mounted optical systems being aligned and have an achromatic design to cover the wavelengths used on the weapon system. 
         [0033]    An embodied optical alignment station  910  can be configured in relation to a weapon with mounted optical systems  920  based on any of said exemplary methods of alignment. For example, the front location  911  can be the lens for the lens optical alignment station, or alternatively, the rear location  912  can be the mirror location for the mirror optical alignment station. 
         [0034]    An exemplary Process to Optically Align Optical Systems to a Weapon is disclosed. The steps to such an exemplary process to optically align optical systems to a weapon is as follows: 
         [0035]    STEP 1: ‘Center’ the pattern (mechanical offsets) of all the optical systems to be aligned onto the mirror or lens as best as possible while ‘missing’ the target card. 
         [0036]    STEP 2: Position weapon borelight onto ‘Borelight’ mark on target card. Note, this is usually above the ‘all other optical systems’ mark on the target card due to superelevation that accounts for the bullet drop over distance (a separate target card can be made for different distances).  FIG. 7  is an example of an alignment target card. A trick used to ensure the borelight is centered over the Borelight mark is to put a small hole in the center of the mark, cover the other side of the hole with a translucent tape and then maximize the amount of borelight laser that goes through the hole (brightest spot on tape side). If not firing weapon, as in case of training, skip STEP 2. 
         [0037]    STEP 3: Adjust all optical systems mounted on the weapon to ‘Optics’ marked on the card. All reticles (cross-hairs) and lasers are placed on the same mark. Again, if aligning a visible laser the hole and tape trick works great. If aligning a far-infrared camera (e.g. Thermal Weapon Sight), do not put tape behind the hole but put a heat source (like your hand) behind it to serve as a ‘thermal’ target. 
         [0038]    The user sees the laser beams on the target card much better than on the 10 M Offset Card since it&#39;s only a few feet away. 
         [0039]    An embodiment of a method and system for using a spherical mirror is shown in  FIG. 8 . The use of a spherical mirror has the advantage of being a more compact system but the disadvantage of possibly reflecting a laser back towards the operator. The use of a lens has the advantage of not reflecting laser beams back toward the operator but a disadvantage of being a longer system. 
         [0040]    ADVANTAGES: The various disclosures are directed to improve the quality of the alignment while reducing the time required to perform the alignment for all optical systems mounted on a weapon to each other and to the weapon. The operator can now ‘see’ what he/she is doing while aligning, even in bright daylight. 
         [0041]    APPLICATIONS: The present disclosure may be used in any case where optical systems need to be aligned military or recreational hunting. For example, while aligning the MILES laser with the weapon(s) or when aligning a rifle scope to the bore of a weapon. 
         [0042]    It is obvious that many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as described.