EP1966561A2

EP1966561A2 - Boresighting system and method

Info

Publication number: EP1966561A2
Application number: EP06832263A
Authority: EP
Inventors: Shimon Izraeli
Original assignee: Men At Work
Current assignee: Men At Work
Priority date: 2005-12-29
Filing date: 2006-12-27
Publication date: 2008-09-10
Also published as: WO2007074455A3; WO2007074455A2; IL172905A0; US20090133572A1

Abstract

A boresight device used in an alignment process in which the optical or electro-optical sighting system of a firearm is brought into correlation with the centerline axis of the firearm's muzzle. The boresight device includes a rotating camera and a camera carrier which somprises a tightening arrangement including a lever handle operable by a user between a securing position and a releasing position and coupled mechanically to at least one tightening cam. The camera carrier is connected to a firearm barrel, or removably attachable to the firearm.

Description

BORESIGHTING SYSTEM AND METHOD

FIELD OF THE INVENTION

This invention relates to the field of boresight alignment in flat trajectory firearms.

BACKGROUND OF THE INVENTION

An alignment process in which the optical or electro-optical sighting system of a firearm is brought into correlation with the centerline axis (hereinafter 'boresight') of the firearm's muzzle is termed boresighting.

For an accurate aiming of a weapon's muzzle, it is required that the muzzle's boresight will be accurately correlated with the weapon's sight. Deviating from an optimal correlation between the muzzle's boresight and the sight's line-of-sight will probably result in missing the target by the projectiles thus being shot.

The spatial relationship between weapons muzzle and sight is subjected to often changes resulting from material strains, varying environmental temperature, thermal expansion of the weapon during firing, and other varying factors. Maintenance procedure including boresight alignment and/or verification should thus be carried out either periodically or whenever an inaccuracy in the weapon's actual shooting becomes noticeable.

In a primary stage of boresighting it is required that the imaginary centerline axis of a muzzle's bore will be presented by comparable data indicative of its spatial orientation. Such data may then be compared with respective data indicative of the spatial orientation of the line-of-sight of the weapon's sight, and the required correlation can thus be verified, or otherwise obtained by respective alignment between the sight and the muzzle. A commonly known in the art boresighting method for flat trajectory firearms makes use of a muzzle insert device. The insert device comprises a main body having contact members dimensioned to contact the inner surface of the muzzle in several spaced apart locations, so as to fixate the insert in position along a portion of the muzzle with the muzzle's axis and the insert's axis substantially overlapping or at least extending parallel to one another. The insert further comprises a telescope having an optical reticle (e.g. cross-hair) superimposed into its field of view. The telescope is mounted to the insert adjustably, such that its line-of-sight can be brought into a substantial alignment with the insert's axis. When such alignment exists, both the line- of-sight and the insert's axis will merge with the point indicated by the telescope's crosshair (or other pointing element) on a chosen target. Since the muzzle's centerline axis is parallel to the insert's axis, the indication of the cross hair (or other pointing element) on the chosen target presents (if not exactly at least in an acceptable proximity) the intersection of the muzzle's centerline axis and the target. The hitting point of the muzzle's centerline axis on the target is comparable with the hitting point of the sight's line-of-sight on the same target, and thus, by comparing the two points the boresighting may be completed by an adjusting step.

However, in order to enable a comparison between said two hitting points, cooperation between at least two operators will normally be required. A first operator has to choose a target and to aim the weapon's sight to a predetermined point on the target. A second operator has to position the insert device in the muzzle, to bring the telescope's line-of-view into alignment with the insert's axis in case it deviates, and to communicate with the first operator in order to inform him the coordination of the boresight hitting point with respect to the chosen target. In case the sight and the muzzle have been found out of alignment, the communication between the two operators should be continued until alignment is obtained.

In some cases, e.g. when the boresighting is performed in field conditions, it may happen that none of available targets can unambiguously be agreed on both operators. In such cases, a target in the field should be chosen and be tangibly marked by an appropriate physical sign or pointer, so as to ensure both operators are aiming at the same point. A third operator is therefore needed either for positioning a noticeable target in the field or for physically marking an existing target. In case the weapon undergoing the boresighting is of large dimensions, e.g. a tank canon, the second operator will normally require a ladder for using the boresighting telescope during the alignment.

Although the above described method is held accurate when compared with other known methods and thus preferred by many, it is appreciated that the method still cumbersome, and inconvenient for the operators. This can lead to mistakes and inaccuracies in boresighting due to human errors, especially in case the procedure should be performed under stress conditions, as may often happen during the use of weapons.

WO 02/27259 suggests a method and apparatus for remote boresighting a large caliber gun by electro-optical means, while a single user performs the alignment in close proximity to the sight of a weapons platform carrying the gun. A remote boresight comprised of an imager, which includes a TV camera, is attached either internally or externally to the gun, and used to relay a target image to the single user. The user views the same target through the sight and brings the sight and the gun into alignment. To make sure that an internal boresight (in the context of WO 02/27259 the term boresight relates to a boresighting instrument) is aligned with the gun's muzzle axis, the boresight is rotated inside the muzzle, and a check is made that a crosshair which is normally part of, and visible through the boresight telescope, remains fixed on the same point of a target.

As may be understood from the WO 02/27259 publication, two main alternatives are suggested. A first alternative is to use a fixed TV camera attached to the muzzle externally, for imitating the muzzle's axis. A second alternative is to use a mobile boresighting device having an integral TV camera, to be removably inserted into the muzzle, for imitating the muzzle's axis. According to both alternatives it is necessary to verify from time to time that there is an accurate alignment between the actual axis of the muzzle and between its imitation, that is the line-of-view of the TV camera. This verification will be referred to hereinafter "calibration of boresighting equipment".

As already mentioned, according to WO 02/27259 the calibration of the boresighting equipment includes rotating the boresight inside the muzzle, in order to check whether a crosshair visible through the boresight telescope, indicates the same point of a target, regardless of the rotation.

It is appreciated that the need to rotate the boresighting equipment inside the muzzle and, if needed, the adjustment procedure to follow, are not sufficiently user friendly, and therefore, as indicated by WO 02/27259 the calibration of the boresighting equipment is not to be carried out every time a muzzle's boresighting is performed.

The present invention is therefore aimed at facilitating the calibration procedure of boresighting equipment.

SUMMARY OF THE INVENTION

The accuracy of boresighting equipment much depends on the accurate parallelism between the muzzle's axis and the line-of-view of a boresight imaging device used for imitating the actual muzzle's axis. As suggested by WO 02/27259, the boresight imaging device may include a TV camera as a means for imaging the muzzle's axis.

Unfortunately, TV cameras has the problem that temperature variations, mechanical vibrations, and other factors, factually change along time the respective positioning between the mechanical and optical components of the camera and between a photoelectric substrate aimed at capturing the image. Such changes in the respective positioning between different camera components result in unpredictable often deviations of the camera's line-of-view from some initial position thereof taken as reference.

Therefore, when a TV camera constitutes a means for imitating the muzzle's axis in a boresight imaging device, it is very essential to provide for a real time alignment of the TV camera line-of view.

While WO 02/27259 suggests rotating the boresight inside the muzzle from time to time as a part of calibration procedure, it ignores the above described problem according which the alignment of the camera should be verified on a real time basis, i.e. every time a muzzle's boresighting is to be earned out. Moreover, the verification method suggested by WO 02/27259, i.e. rotating the boresight inside the muzzle, is a manual operation similar to that taken when calibrating boresighting devices having plain optics (with no TV camera) e.g. a telescope, as a means for imaging the actual muzzle's axis.

An innovative calibration system and method, especially useful for boresighting equipment having TV camera as a means for imaging the actual muzzle's axis, has been developed by the inventor of the present invention.

Basically, the invention can be related to as an improvement in boresighting devices having a camera as a means for imitating muzzle's boresight, the improvement is based on a pivotal coupling arrangement between an image-acquiring-unit, e.g. a CCD-camera, and a construction carrying the camera. The latter can be either attached, or removably attachable, to a flat trajectory weapon's barrel. An image-acquiring-unit pivotally coupled to a construction connected to, or removably attachable to a firearm barrel, will be referred to hereinafter also as "rotating camera".

Due to the pivotal coupling arrangement, the rotating camera becomes pivotable not only respective to the construction in which it resides but also respective to the barrel to which the construction is attached. Accordingly, a correlation between a real time line-of-view of the camera and an axis of the construction carrying the camera can easily be achieved by a technique including the following steps: aiming the camera at a remote image origin for acquiring a reference image when the camera is in a first angular position respective to the construction carrying it; rotating the camera to a second angular position for acquiring a comparable image differing from the reference image in an angular orientation of the image; comparing the acquired images and determining a pixel or an array of a few adjacent pixels representing similar portion of the image origin in both acquired images; and marking said pixel or a substantial center of said pixels' array by a reticle, e.g. crosshair, the crosshair (and any other indicator fulfilling a crosshair function, hereinafter will be also referred to a 'crosshair') thus represents the intersection between an image origin constituting a target and between a line-of-view of the boresighting device. Assuming that the boresighting device is properly attached to the weapon's barrel, the thus generated crosshair accurately imitates the intersection between the muzzle's axis and an image origin at which the muzzle is aimed. The crosshair of the boresighting equipment will therefore be referred to as "muzzles crosshair".

After carrying out said steps, a correlation between the muzzle and the weapon's sight can easily be verified by aiming the weapon towards a target, and if necessary aligning the sight until a correlation between its crosshair and the muzzle's crosshair is achieved.

It can be appreciated that a pixel or an array of a few adjacent pixels representing similar portion of the image origin acquired in two angularly spaced camera positions, is inevitably associated with a photosensitive camera region aligned with an axis of rotation of the camera. Said pixel or array of adjacent pixels will thus be referred to also as "central pixel".

An exemplary method for determining the central pixel is by determining XY coordinations of a first point on the reference image representing a reference point on the image origin; rotating the camera 180 degrees about its axis of rotation and, acquiring a comparable image; determining on the comparable image XY coordinations of a second point representing said reference point; and determining the central pixel as a point in substantially the middle between said first and second points.

Said technique, hereinafter "boresighting equipment setup technique" or simply "setup", can be carried out as a preliminary step of a weapon's boresighting process, as a verification step during such process, or whenever an alignment verification of boresighting equipment is desired. Due to the disposal of the needing to rotate the entire boresighting construction, and with the advantage that only the camera should be rotated for the verification of boresighting equipment, it becomes very easy to carry out a successful boresighting process ending with substantially accurate correlation between weapon's sight and muzzle.

Preferably, the pivotal coupling arrangement includes a remote controlled motor configured to rotate the camera. According to some embodiments the motor is responsive to user's rotation commands. According to a best mode of operation, the setup steps are carried out automatically through a computerized process. Such computerized process may be initiated upon user's direct command. Alternatively it can be initiated automatically either upon turning-on the boresighting device or several timed during its operation, e.g. every few seconds.

The computerized process either carried out by a dedicated control unit, or controlled by a weapon's computer, not necessarily requires a rotation of the camera in a substantial angle in order to determining a central pixel. Using appropriate computer algorithms which do not constitute a part of the invention, two images acquired at two angular positions of the rotating camera may be compared for determining a central pixel, i.e. a pixel representing the same point of the image origin in both acquired images, even though the rotation angle of the camera between acquisition of the two images is as small as e.g. about 10 - 20 degrees, or e.g. about 25 - 45 degrees. Accordingly the motor configured for rotating the camera may be controlled for rotating the camera a relatively small angular extent, e.g. about 30 degrees for acquiring angularly spaced images of an image origin. It can be appreciated that such angular rotation is small comparing to a rotation of 180 degrees which is usually performed upon manual setup of some known boresighting equipment. Accordingly, although the motor of the invented boresighting device may be controlled for rotating the camera 180 degree, it is appreciated that a smaller angular rotation may provide for acceptable determination of a central pixel, and thus the time duration needed for completing an automatic setup of the device of the present invention may be very short. The motor for rotating the camera for such small extents can be a relatively small one and may consume very small amounts of energy. Accordingly, it can be battery powered motor, and rechargeable batteries may be used, requiring not very frequent recharging. A controller and a communication unit, as well as the camera itself, may also be powered by the same battery.

The boresighting device of the present invention can thus be provided as a fully wireless and mobile unit.

The invention first relates to a boresighting device including a rotating camera constituting a rotating image-acquiring-unit, and a camera carrier connected to or removably attachable to a firearm barrel. The invention further relates to a boresighting system including a boresighting device having a rotating camera, a camera carrier connected to or removably attachable to a firearm barrel, and a control unit located remotely from the boresighting device.

According to some embodiments the boresighting device includes a mobile muzzle-adapter having a positioning arrangement configured to snugly fit the inside of a firearm's muzzle such that the muzzle-adapter extends along a portion of the muzzle (preferably said portion is of a length not less than three times the diameter of the muzzle) with the longitudinal axis of the muzzle and the longitudinal axis of the muzzle-adapter substantially parallel to one another; at least one image-acquiring-unit having a line-of-view in parallel or close to parallel relationship with the longitudinal axis of the muzzle-adapter; and a communication unit for transmitting a signal indicative of an image acquired by the image acquiring unit, to a remote display unit; the system being characterized in that the image-acquiring-unit is connected to the muzzle-adapter pivotally so as to allow angular motion of the image-acquiring-unit about an axis being, or parallel to, the longitudinal axis of the muzzle-adapter.

It is appreciated that the rotation capabilities of the camera may serve not only for the mere setup of the boresighting equipment, but also for leveling the presentation of an acquired image origin regardless of the current angular orientation of the muzzle- adapter about its own longitudinal axis.

According to some preferred embodiments the boresighting device of the present invention includes an innovative comfortable tightening arrangement facilitating insertion and removal of the muzzle-adapter in and from the muzzle, especially useful but not limited to large caliber weapon. The tightening arrangement includes a lever handle operable by a user between a securing position and a releasing position and coupled mechanically to at least one tightening cam; the tightening cam being moveable by the handle between a tightening position in which the cam protrudes from the muzzle adapter to a first extent, and a releasing position in which the cam is withdrawn into the muzzle-adapter or at least moves to protrude from the muzzle-adapter a second extent smaller from said first extent. This tightening arrangement is advantageous over fitting arrangement currently used in boresighting devices, in that it allows for a considerably tightened fitness of the boresighting device when in position for carrying-out a boresighting process, while providing for ease removal of the boresighting device, with negligible friction with the muzzle's walls, after completing the process.

The invention relates also to a setup method for camera-based boresighting devices, the method includes aiming the boresighting device toward an image origin; activating a camera having a line-of-view for acquiring from the image origin a reference image taken at a first angular position of the camera; rotating the camera about an axis parallel or close to parallel to the line-of-view and acquiring a comparable image from the image origin taken at a second angular position of the camera; comparing the acquired images and determining a pixel or. an array of a few adjacent pixels representing similar portion of the image origin in both acquired images; and marking said pixel or a substantial center of said pixels' array by a crosshair.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of an exemplified boresighting device according to the present invention.

Fig. 2 is a perspective exploded view of a camera module according to an exemplified embodiment.

Fig. 3 is a cross section view through the boresighting device 1 illustrated by Fig. 1.

Fig. 4 is front view of the boresighting device 1 illustrated by Fig. 1.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Fig. l is a perspective view of a mobile boresighting device 1 according to some embodiments of the present invention. The boresighting device 1 has a construction 2 constituting a muzzle-adapter configured to be removably mounted into a weapon's muzzle (not illustrated) with a predetermined imaginary axis 3 of the construction lying substantially parallel and immoveable respective to the centerline axis of the muzzle (i.e. the boresight). A rotating-camera 4, constituting a rotating image-acquiring-unit, in this exemplified embodiment a digital video camera, is accommodated in the construction, inside a pivotal-coupling-arrangement 5 which is shown in more detail in an exploded view in Fig. 2.

The camera focal is configured to infinity thus needing no zoom for covering the range 500 — 1,200 meter, which is the relevant range for boresighting flat trajectory weapons of all types and calibers. Having an improved resolution, the camera requires no external optics. Based on the high resolution of the camera (e.g. between 3 - 8 Mega pixel), an electronic digital-zoom addresses the zooming requirements.

The rotating-camera 4 is configured to generate a machine readable signal indicative of the images it acquires from an image origin. The signal may then be processed and/or used for displaying a picture of the image-origin on a screen (not shown).

The rotating-camera 4 has an image-field-of-view 7 having an axis-of-symmetry 6 (some times referred to in this specification as the "line-of-view"). The pivotal coupling arrangement 5 allows the image-acquiring-unit to pivot about an axis being or lying parallel to the imaginary longitudinal axis 3 of the construction. Pivoting the camera a predetermined angle about the longitudinal axis 3 of the construction will cause a respective angular pivoting of an acquired image of an image-origin about a symmetry point of the picture, such that every acquired point of the image-origin will be represented in the picture with an angular shift from its location in the picture prior the pivoting. In this regard the symmetry point itself is exceptional, since it would not change its original location in the picture in response to pivoting the image acquiring unit about its axis of symmetry.

It is appreciated that when the image acquiring unit 4 is accommodated in the construction with the line-of-view 6 lying parallel to the imaginary axis of the construction 3, and the construction's axis of symmetry 3 lays parallel to the muzzle's centerline axis (not shown), then the line-of-view 6 of the image acquiring unit 4 satisfactory represents the muzzle's boresight. When the image acquired by the image acquiring unit is displayed as a picture on a screen, its symmetry point can be indicated by a virtual reticle (such as a crosshair) superimposed into the picture with an indication point of the reticle merged with the picture's symmetry point.

Assuming now that a weapon's sight is aimed towards a target with a cross-hair of the sight indicating the center of the target, boresighting of the weapon may be approved if the virtual reticle in a picture acquired by the device of the present invention when being mounted in the weapon's muzzle, will also indicate to the same point.

However, as indicated in the summary of the present invention, the line-of-view of a digital camera unpredictably changes through time as a result of different factors. Accordingly, and in order to maintain correlation between the varying line-of-view and the muzzle's boresight, a setup procedure of the boresighting device 1 will be carried out either automatically or upon user's demand, sufficiently often so as to provide for reliability. Since the setup steps are performed automatically, and prolong several seconds and even less, it can be carried out on a real-time basis without any substantial burden. Whenever a deviation of the camera line-of-view 3 from the construction axis 3 is identified during the setup, the crosshair will automatically be re-positioned to merge its indication point with the center of the picture.

The construction 2 may be of any design suitable for snugly fitting inside a muzzle for providing a reference axis imitating the muzzle's boresight. The construction 2 has a positioning arrangement comprising at least six contact areas configured to contact the cylindrical inner wall of a muzzle in at least six remote points so that when the muzzle-adapter 2 is inserted into a muzzle, it will fit into it with the six contact areas in a friction contact with the inside of the muzzle wall. The exemplified construction is an envelope comprising a first portion 9 for accommodating an image-acquiring-unit such as a video camera 4, and for positioning said image-acquiring-unit in appropriate orientation inside the muzzle of a flat trajectory weapon. Two contact members 15 (constituting two of said six contact areas), slightly protrude from the envelop portion 9, and are intended to contact and be pressed to the insides of the muzzle's wall in respective two locations. The envelope further comprises a second portion 10 located remotely from the first portion of the envelope so as to form together with the first envelope's portion an elongated construction 2 having a length of about at least three times the inner diameter of the muzzle. This is in order to minimize inaccuracies resulting from inaccurate positioning of the boresighting device. Additional two contact members 16 (constituting additional two of said six contact areas), slightly protrude from the envelop portion 10, and are intended to contact and be pressed to the insides of the muzzle's wall in respective two locations. The envelope portions 9 and 10 are bridged through a mid portion 11. The wall of the mid portion is perforated by holes 12, thus weighs less than might have been without the perforation, useful for reducing the total weight of the boresighting device. The construction has a flange 13 formed near the end of the envelope portion 9, for restricting slippage of the device to the far depth of the muzzle, and to help in positioning the device properly. A lever handle 14 facilitate insertion and removal of the device to and fro the muzzle, as will be further detailed in the description of Fig. 3. As will be explained, the lever handle 14 controls two cams 30 and 31 (not shown in this Fig.) located at the underbodies of the envelope portions 9 and 10, respectively, said cams constituting the remaining two of the six mentioned contact members.

Fig. 2 is a perspective exploded view of a camera module 18 to be accommodated inside the muzzle-adapter illustrated by Fig. 1. The camera module 18 includes a high resolution infinite focal small CCD camera 4. The camera includes a wireless communication unit 4a and plain optics 4b. The camera is accommodate in a pivotal-coupling arrangement 5 comprising a housing 5a having outer dimensions matching the inner dimensions of the envelope portion 9 of the construction 2 shown in Fig. 1, such that the imaginary axis 19 of the camera module will merge with the longitudinal axis 3 of the construction 2. The camera 4 is coupled to the housing 5a through camera holder 20 which in turn being coupled to the interior of a nose portion 5b of the housing 5a, by means of a pair of ring-shape bearings 21 and 22. The camera holder 20 is geared to an electrical motor 23. Upon rotation of the motor shaft, the camera holder 20 will rotate and so will rotate the camera 4 held by.

Fig. 3 is cross section view through the boresighting device 1 illustrated by Fig. 1. The device comprises a construction 2 having a first and a second envelop portions 9 and 10, respectively, connected through a mid envelop portion 11, perforated by a plurality of holes 12. The first envelop portion 9 accommodates a pivotal-coupling- arrangement 5, coupling between a rotating-camera 4 and the first envelop portion 9. The camera is rotated upon rotation of the shaft of electrical motor 23. A tightening arrangement comprising a lever handle 14 operable by a user between a securing position and a releasing position is also shown. The lever handle 14 is coupled mechanically through force transmission bar 25 and through latching members 26 and 27 to a front and a rear tightening cams 30 and 31, respectively. The tightening cams are moveable by the handle 14 between a tightening position in which the cam protrudes from the muzzle adapter to a first extent as indicated by dotted lines 30a and 31a, and a releasing position in which the cam is withdrawn into the muzzle-adapter (and alternatively at least moves to protrude from the muzzle-adapter a second extent smaller from said first extent).

Fig. 4 illustrates a front view of the embodiment of the boresighting device 1 , illustrated by Fig. 1. The front portion of the camera optics 46 is seen through an opening made in the nose 5b of the pivotal coupling arrangement 5, which is accommodated in the construction 2 which in this Fig. is hidden behind the flange portion 13. The lever handle 14 of a tightening arrangement is seen in a releasing position. After placement of the muzzle-adapter inside a weapon's muzzle the lever-arm is moved upwardly by a user in order to secure the device inside the muzzle by pushing the cams 30 and 31 to protrude out of the envelop so as to contact the interior of the muzzle wall and press the envelop tightly between opposite sides of the circular muzzle's wall.

It should be noted that the same camera module may be useful for any weapon type and caliber, since the same camera module comprising a rotating camera according to the present invention may be coupled to muzzle-adapters of different shapes and sizes. Accordingly, the same system, remote controlling units, and setup algorithms may be used for various weapon types, by only changing the type of muzzle-adapter for addressing the requirements of the specific weapon.

Claims

CLAIMS:

1. A boresighting device, comprising a rotating camera and a camera carrier connected to or removably attachable to a firearm barrel.

2. A boresighting device according to claim 1, further comprising electrical motor coupled to the rotating camera.

3. A boresighting device according to claim 2, wherein the motor being remotely controlled.

4. A boresighting device according to claim 1, further comprising wireless communication unit.

5. A boresighting device according to claim 1, wherein the camera is coupled to a weapon's barrel or to a muzzle-adapter attachable to a weapons barrel, through a ring-shaped bearing.

6. A boresighting device according to anyone of claims 1-5, further comprising a tightening arrangement comprising a lever handle operable by a user between a securing position and a releasing position and coupled mechanically to at least one tightening cam; the tightening cam being moveable by the handle between a tightening position in which the cam protrudes from the muzzle adapter to a first extent, and a releasing position in which the cam is withdrawn into the muzzle-adapter or at least moves to protrude from the muzzle-adapter to a second extent smaller from said first extent.

7. A boresighting device according to anyone of claims 1 - 5, further comprising a control unit located remotely from the boresighting device.

8. In a boresighting device having a camera as a means for imitating muzzle's boresight, the improvement comprising a pivotal coupling arrangement between the camera and a construction carrying the camera.

9. Boresighting system comprising a boresighting device having a rotating camera, a camera carrier connected to or removably attachable to a firearm barrel, and a control unit located remotely from the boresighting device.

10. Setup method for camera-based boresighting devices, the method includes aiming a boresighting device toward an image-origin; activating a camera having a line-of-view for acquiring from the image origin a reference image taken at a first angular position of the camera; rotating the camera about an axis parallel or close to parallel to the line-of-view and acquiring a comparable image from the image origin taken at a second angular position of the camera; comparing the acquired images and determining a pixel or an array of a few adjacent pixels representing similar portion of the image origin in both acquired images; and marking said pixel or a substantial center of said pixels' array by a crosshair.

1 1. Boresighting device having a camera as a means for imitating a muzzle's boresight, the camera being characterized by an invariable zoom and a focal infinity.