Abstract:
A structure for visibly boresighting an invisible MILES-type laser beam emitted by a small arms transmitter to sights of a weapon intermittently projects a visible light beam that is parallel to the beam emitted by the MILES-type laser. Adjusting the visible beam to impinge on that portion of a target in the sights of the weapon also boresights the MILES-type laser to the weapon&#39;s sights.

Description:
FIELD 
       [0001]    The invention pertains to combat simulation systems. More particularly, the invention pertains to structure and methods of boresighting an infrared laser to sights of a weapon. 
       BACKGROUND 
       [0002]    In known MILES-type combat simulation systems involving individual combatants, MILES-type small arms transmitters (SAT) are affixed to combatants&#39; rifles, for example, or other similar small arms for purposes of the simulation. The MILES-type lasers emit an infrared beam which is intentionally not visible to the human eye. While this configuration is desirable for simulation purposes, it does present problems for boresighting the beam to the sights of the weapon. Various solutions had been implemented to solve this problem. 
         [0003]    In a known implementation, a fixture can be used for purposes of boresighting the MILES beam to the sights of the weapon. While effective, the use of fixtures is costly, at times inconvenient, especially during times when the combatants are in the field preparing to or conducting a simulation, require logistics support, and have limited accuracy. 
         [0004]    There continues to be a need for small arms transmitters which conveniently incorporate an intermittently usable visible laser beam for boresighting purposes. Preferably the source of the visible laser beam could be incorporated into the SAT without a need for substantial or expensive changes thereto. It is also necessary and preferable that the resultant multimode transmitter be easily adjustable for boresighting purposes and robust so as to retain boresight adjustment during firing exercises as well as during rough handling of the weapon. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a block diagram of a small arms transmitter in accordance with the invention mounted on the barrel of a weapon; 
           [0006]      FIG. 2  is a schematic diagram illustrating optical characteristics of the small arms transmitter of  FIG. 1 ; 
           [0007]      FIG. 3  is a view, partially in section, illustrating additional aspects of the small arms transmitter of  FIG. 1 ; and 
           [0008]      FIG. 4  is a sectional view illustrating an alternate embodiment of the small arms transmitter of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    While embodiments of this invention can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention, as well as the best mode of practicing same, and is not intended to limit the invention to the specific embodiment illustrated. 
         [0010]    In a disclosed embodiment, a visible laser beam, co-aligned with a MILES-type laser beam, is built into a small arms transmitter (SAT) so that a user can effectively see where the MILES-type beam is incident. The visible laser can be a laser diode emitting in the red region of the visible spectrum. Other-color laser diodes may be used instead of red, but red laser diodes are adequately visible for this application. 
         [0011]    The user aims his/her weapon, using his/her normal sights, at a point on an easily-visible stationary target sufficiently distant so that the parallax introduced by the fact that the laser beams are not laterally co-located with the gun sight axis, is not significant. At 100 meters the parallax error is a few tenths of an mrad, which is smaller than the error in most boresighting operations. 
         [0012]    One of the common retro-reflective, self-adhesive tapes can be attached to the target to enhance the visible-laser visibility. The SAT is then adjusted until the visible laser beam strikes the same point. The MILES laser beam, emitted by the SAT, which was previously co-aligned with the visible laser beam, is therefore boresighted to the weapon&#39;s sights. 
         [0013]    In another aspect of the invention, the two laser diodes, along with their collimating lenses, are mounted in a SAT optics sub-assembly. At the time of manufacture the sub assembly frame is mounted on a precision fixture that simulates the angular orientation of the sub assembly when mounted in the SAT, with respect to the weapon-barrel angular orientation. The MILES laser diode is positioned so that the beam characteristics and angular direction are correct, and then cemented in place. The visible-laser diode is similarly positioned and adjusted so that its beam is collinear with the MILES laser beam. It is then also cemented in place. At this point in the procedure the two laser beams are aligned permanently parallel to one another and therefore boresighted to each other. 
         [0014]    In yet another aspect of the invention, the optics sub-assembly is next installed into the SAT. In a disclosed embodiment, the sub-assembly is attached to the frame of the SAT by a ball joint, which will allow rotation in the two orthogonal directions while not allowing translation. 
         [0015]    The sub assembly can be rotated about two orthogonal axes perpendicular to the optical axis of the MILES laser beam by two adjustment screws. In this way the two co-aligned laser beams are angularly moved with respect to the barrel of the weapon for boresighting to the angular orientation of the barrel. 
         [0016]    In known SATs the boresight angular adjustment range is about +/−8 mrad, which has proven adequate. Collimating lenses having a focal length on the order of 15 mm can be included. Hence, the overall length of the SAT optics sub-assembly can be about 20 mm. A +/−8 mrad adjustment range translates into about 6 mils of translation at the location of manually operable adjustment screws. 
         [0017]    The adjustment screws can have TEFLON plastic or other low-friction elements either on the end of the screw or on a pad that the screw contacts. Another approach is to include a flexible joint in each linkage between the adjustment screws and the laser assembly. Something of this nature is preferred because of the slight motion of the SAT optics sub-assembly transverse to one screw symmetry axis when the orthogonal screw is adjusted. The fine-thread adjustment screws can be configured to work against stiff springs to eliminate backlash, and to retain the boresight adjustment during blank firing and rough handling of the gun. Linear adjustments could be used as an alternate. 
         [0018]    A protective window can be incorporated in the SAT. It provides an environmental seal because the SAT optics sub-assembly will move during the boresight adjustment. 
         [0019]    In yet another aspect of the invention, it would be desirable if the beams for the MILES laser and the visible, boresighting laser passed through common SAT optics. For example and without limitation, a beam splitter could be used to fold the visible beam into coincidence with the MILES beam. Both beams could then be directed through a common collimating lens prior to exiting the SAT transmitter. The beams can be adjusted by laterally displacing the collimating lens using a simple two dimensional positioning device. 
         [0020]      FIG. 1  illustrates a block diagram view of a small arms transmitter  12  in accordance with the invention. As illustrated in  FIG. 1 , the SAT  12  can be coupled to the barrel of a weapon B, for example the barrel of a rifle, by a removable mounting bracket  16 . Those of skill in the art will understand that a variety of mounting brackets could be used without departing from the spirit and scope of the present invention. 
         [0021]    SAT  12  emits an infrared MILES beam, invisible to the human eye,  20  and a visible boresighting beam  24 . Both beams  20 ,  24  exit the SAT  12  displaced and parallel to one another. 
         [0022]    It will be understood that the SAT  12  includes a housing or a frame  26  which incorporates the sources of the beams  20 ,  24  as well as any other appropriate optics. As described subsequently, the beams  20 ,  24  can be adjusted in unison for boresighting purposes. 
         [0023]      FIG. 2  illustrates a schematic view of an optics sub-assembly  30  which can be carried within a frame or housing  26  which defines an interior region. The assembly  26  incorporates a source  20 - 1 , for example a laser diode, of the invisible MILES laser beam  20 . The assembly  30  also incorporates a second source  24 - 1  of the visible laser beam  24  which could emit monochromatic light of a wavelength visible to the human eye of any desirable color. 
         [0024]    Each of the sources  20 - 1 ,  24 - 1  is located at a focal point of a respective collimating lens  20 - 2  and  24 - 2 . Radiant energy which passes through the respective collimating lens  20 - 2 ,  24 - 2  is emitted from the frame or housing  26  as a respective beam  20 ,  24 . 
         [0025]      FIG. 3  illustrates additional details of the SAT  12 . The sub-assembly  30  is carried within an interior region  26 - 1  of the housing or frame  26 . It is preferably supported therein by a ball joint  34 . It will be understood that other means of support could be used without departing from the spirit and scope of the present invention. 
         [0026]    The housing  26  also carries a protective optically transparent window  36  to protect the sub-assembly  30  from external environmental conditions. Those of skill will understand that the window  36  could be formed of selected glass or plastic. 
         [0027]    As illustrated in  FIG. 3 , the transmitter  12  incorporates an elevation adjustment screw  38 - 1  and an azimuth adjustment screw  38 - 2 . In use, the simulation participant, under appropriate conditions, can energize the source  24 - 1  of the visible boresighting beam  24 . 
         [0028]    Using the adjustment elements  38 - 1 ,  38 - 2  the user can then aim the weapon using its normal sights at a point on an easily-visible stationary target. The target is selected such that it is sufficiently distant that any parallax introduced by the fact that the two beams  20 ,  24  are not laterally co-located with the sights of the weapon is insignificant. 
         [0029]    The sub-assembly  30  can then be adjusted using adjusting elements  38 - 1 ,  38 - 2  so that the visible beam  24  is incident on the same point at which the weapon is being aimed using its normal sights. The MILES beam  20  emitted by source  20 - 1  was previously co-aligned with the visible beam  24 . It is as a result boresighted to the weapon&#39;s sights. 
         [0030]    For purposes of providing a stable orientation and adjustment of the sub-assembly  30 , a spring  40 , or other friction inducing element, can be associated with each of the adjustment elements  38 - 1 ,  38 - 2 . Those of skill will understand that the housing or frame  26  of the SAT can be formed of metal, plastic or the like all without limitation. 
         [0031]      FIG. 4  illustrates an alternate embodiment of a SAT  50 . The SAT  50  incorporates a source, such as the source  20 - 1  of an infrared MILES laser beam and a source  24 - 1  of a beam of visible laser light. The beam emitted by the visible laser light, such as beam  24 - 2  is folded by a prism  52  and deflected by a beam splitter  54  so as to be coextensive with the beam  20 - 2  emitted by the MILES source  20 - 1 . The composite beam passes through a collimating lens  56  and exits the SAT  50  via an environmental seal window  60 . The collinear beams from the respective sources  20 - 1 ,  24 - 1  extend parallel to a common axis A and coextensive with one another. 
         [0032]    An adjusting element such as element  62  can be used to laterally deflect the lens  56 . An orthogonal adjustment screw, not shown, can be used to laterally deflect the lens in the orthogonal direction so that these two lens deflection directions will steer the two coincident beams to align them to the weapon sight axis. It will be understood that other adjusting elements and configurations to achieve the desired coextensive emission of the beams could be used without departing from the spirit and scope of the present invention. 
         [0033]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.