COLLIMATING MARK DEVICE

Abstract: A collimating mark device is provided with an infrared collimating mark intended to be observed through a sight. The infrared collimating mark is designed such that it comprises at least two essentially V-shaped intensity distributions. The points of the V-shapes face each other. Despite a relatively blurred image after conversion into a visible collimating mark that blurred visible collimating mark can be brought in a reproducible and reliable manner into coincidence with a fixed alignment mark.

Description: T le: Coll imat iπg Mar Device The invention relates to a collimatiπg mark device provided with an infrared collimatiπg mark intended to be observed through a sight. It is known that the firing direction of a gun, that is to say the direction of the end of the firing barrel of the gun, and the viewing direction of a viewing sight are brought into coincidence with each other by reflecting an externally generated light image (collimat¬ iπg mark), for example a dot or a cross, via a mirror placed on the end of the firing barrel into the sight and bringing the image thus obtained in the site into coin¬ cidence with a fixed alignment mark. Such a technique can be used in other situations in which the centre lines of two elements have to be adjusted to be parallel to or in line with each other. As an example, mention may be made of the alignment of the centres of a long lathe. In order to bring the image of the collimating mark in the sight into coincidence with a f ed align- meπt mark, the position of the sight is adjustable. In this manner, the alignment of the sight with respect to the firing direction can be checked at any desired instant and corrected if necessary, and compensa¬ tion may be made for mechanical and thermal effects which may cause both the firing direction and the viewing direction of the sight to vary. This is of considerable ' importance because even a small deviation from the ideal position leads to a large difference between the actual point of impact and the desired point of impact of a projectile which has been fired. By carrying out the check at various elevations of the firing barrel, it is also possible for the track¬ ing of the viewing direction of the sight and the barrel to be adjusted. The know.n systems are quite satisfactory provided visible light .is employed. If infrared sights which com¬ prise an infrared camera and a collimating mark formed " with infrared light are used, problems arise, however, " because it is not readily possible to form an image of an infrared collimating mark sharply in the sight. As a consequence of this, it is also not readily possible to bring the blurred image of the collimatiπg mark after conversion to visible form accurately into coincidence with the fixed alignment mark. There are several reasons for the loss of defini¬ tion of a collimatiπg mark formed with infrared light, a visible image of which is formed in the sight. A first reason is the fact that infrared light has a rela- tively large wavelength, as a result of which defractioπ phenomena are more likely to play a role than in the case of visible light. " These defraction phenomena play a greater role, the smaller tire o ' t cal elements are which are used in the infrared light path. In the case of a field adjustment device, the mirror or collimator placed on the firing barrel should always have small dimens ons, in the order of Z to 3 cm diameter, in order to keep the mass inertia forces encountered on the mirror or colli¬ mator during the sometimes violent movements of the firing barrel as small as possible. A further reason for the loss of definition of a collimating mark formed with infrared light after it has been converted into a visible collimatiπg mark is that this conversion is usually carried out in the iπfra- red cameras normally used in I.R. aiming systems by scan¬ ning the infrared image .presented with discrete detectors which scan the image presented in accordance with a pre¬ determined pattern. The width of the image lines of the image which is built up in this manner is not negligible with respect to the lines of the collimatiπg mark. As a consequence of the two reasons ' mentioned above, a blurred visible collimatiπg mark is produced which is difficult to bring accurately into coincidence with the fixed alignment mark. The result is that different people usually adjust the sight and the firing direction in different positions with respect to each other,. al though only one position is correct. This problem s further intensified if the fixed alignment mark is self obtained by generating a signal electronically in predetermined positions of the scanning infrared detectors. After all, the fixed alignment mark cannot in that case be any sharper than accords with the dimensions of the detectors. In that case, for the alignment, a relatively blurred collimating mark has to be brought accurately into coincidence with a relatively blurred fixed alignment mark, which makes an accurate alignment very difficult. The object of the invention is to eliminate the drawbacks outlined and to make available an infrared collimatiπg mark which, despite a relatively blurred image after conversion into a visible collimating mark, can nevertheless be brought in a reproducible and reliable manner into coincidence with a fixed alignment mark. According to the invention, a collimatiπg mark device is provided, for this purpose, with an infrared collimating mark which is characterized in that the collimating mark device is designed in a manner such that the infrared collimatiπg mark comprises at least two essentially V-shaped intensity dis ributions, the points of the V shapes facing each other. Attention is drawn to the fact that the collima¬ tiπg mark device according to the invention can be used in all the situations in which an infrared camera has to be aligned or adjusted by means of a collimatiπg mark. As an example, mention may be made of the use of a collimatiπg mark according to the invention in a device for adjusting the tracking in a vertical plane of an (infrared) sighting device and a swivelable element of the type as described in the Dutch Patent Application 8,402,659. The collimatiπg mark according to the invention may, in addition, be used with advantage in a field adjustment device which is suitable for infrared light. The invention will be explained in more detail below with reference to the accompanying • drawing. Figure 1 shows di agrammati cal ly the relative positions of the f ring barrel of a gun of a combat tank and of the aiming camera of the combat tank; Figure 2 illustrates diagrammati cally a sharp and a blurred image of a linear collimatiπg mark and the associated intensity distributions; Figure 3 illustrates diagrammatically a blurred i age of a cross-shaped collimatiπg mark; Figure 4 shows diagrammatically a front view of a first exemplary embodiment of a collimatiπg mark according to the invention; Figure 5 shows the colli atiπg mark of Figure 4 in side view; Figure 6, Figure 7, Figure 8 and Figure 9 show, diagrammat cally, modified exemplary embodiments of a coll ma ng mark according to the invention; Figures 10 to 12 iπcl. illustrate a few more exemplary embodiments of a collimating mark according to the invention; and Figure 13 shows yet another exemplary embodiment., Figure 1 shows diagrammatically in plan view a turret 1 of a combat tank, not shown in more detail, which is provided with a gun, the firing barrel 2 of which can be seen. In addition, an infrared aiming camera 3 is shown diagrammatically and this extends partially through the turret in the usual manner so that the surroundings can be observed and imaged on a screen situ¬ ated inside the turret. In order to be able to aim the firing barrel of the gun accurately, a fixed relationship which is deter- mined as accurately as possible should exist between the position of the aiming camera and that of the firing barrel, or between the viewing direction of the aiming camera and the firing direction. In Figure 1 the v ewing direction is diagrammatically indicated by a centre line 4, while the firing direction is indicated by a centre line 5. Usually the adjustment of the aiming camera is chosen so that both centre lines are parallel, but it is also possible to choose a point at a certain distance where the centre lines intersect each other. Since the centre lines 4 and 5 are only abstract lines, to determine the viewing direction of the aiming camera use is made of an alignment mark which usually consists of two lines which intersect each other, the intersection point of which indicates the aiming point. As in the case of sights for visible light, the alignment mark can be provided on the screen, for example by etching, drawing or engraving, but it may also be genera- ted electronically as already described above. To bring the viewing direction into coincidence with the firing direction, use is made of a collimating mark which may likewise consist, for example, of two lines which inter¬ sect each other and which is projected from the mouth of the firing barrel onto the entrance window of the aiming camera as indicated by an arrow 6. For this purpose, the collimating mark may itself be placed on the mouth of the firing barrel and projected onto the aiming camera via a collimator. Often the collimating mark is also placed on or near the beginning of the firing barrel as indicated at 7 in Figure 1 and is reflected via a mirror 8 (autocolli- mator) on the mouth of the firing barrel into the aiming camera. If the alignment mark and the collimatiπg mark then coincide with each other in a predetermined manner on the viewing screen of the aiming camera, for example, in the event that the alignment mark and the collimating mark each consist of two lines which intersect each other, by the intersects of said lines coinciding, the aiming camera is precisely aligned. After an initial alignment of the aiming camera, the alignment should be repeatedly checked during use because the position of the aiming camera with respect to the iring barrel and, in particular, the mouth of the firing barrel, which determines the firing direction, may vary during operation as a result of mechanical and thermal effects. The alignment technique described above, usually referred to by the term "field adjustment" is per se already used with good result for aiming systems operat¬ ing with visible light. As already pointed out, this known technique cannot readily be used with equally good results if an infrared aiming camera is used. This is a consequence of the greater wavelength of infrared light, as a result of which the sharpness of the image is more likely to be affected by defraεtion phenomena, and in addition, of the fact that, in the aiming camera, the infrared image r-e- . ceived has to be converted into a visible image. This last operation is usually performed by scanning in accord¬ ance with a raster pattern by means of discrete infrared detectors which, as it were, sample the image presented, as a result of which additional loss of definition (sampling noise) is introduced. All this is illustrated in more detail in Figures 2 and 3 0 Figure 2.a shows a line 10, drawn thickly for the sake of clarity, which may, for example, be a line of a collimatiπg mark. Figure 2b shows the associated light ntensity distribution along the line 11 in Figure 2a, it being assumed that the line 10 is lighter than the surroundings. Figure 2c shows the image 10* of the line 10 as it is rendered visible on the viewing screen of the infrared camera, while figure 2d again shows the associated intensity distribu on. It is clear that the image 10 1 is less sharp than the image 10 presented. Figure 3a shows two lines 12, 13 which intersect each other and Figure 3b shows the associated image " on the viewing screen of the infrared camera. From the image shown in Figure 3b, the exact position at which the inter¬ sect of the lines 12 and 13 is situated can no longer be accurately inferred, whereas, if lines which intersect each other are used as collimating mark, the position of the intersect, in particular, is of considerable impor¬ tance for an accurate adjustment of the aiming camera. As a result of the phenomena described above and illustrated in Figures 2 and 3, it is not readily possible to adjust the aiming camera accurately if an infrared aiming camera is used, at least, not by means of the same techniques as are used in the case of aiming systems designed for visible light. From investigations and experiments by the Applicant it has emerged, however, that the disadvantageous effects of. a blurred image of an infrared collimatiπg mark on the viewing screen of an infrared aiming camera may essentially be eliminated if the infrared collimating mark is presented in the form of a special spatial intensity distribution. Figure 4 shows a front view of a first embodi¬ ment of a collimating mark device according to the iπven- tion, as well as the intensity distribution obtained there¬ with, and Figure 5 shows the collimating mark device of Figure 4 in side iew. The collimating mark device depic¬ ted comprises a plate 15 which is p in this case rectangular and which is heated during operation to pro ide an image which can be observed with an infrared camera. The plate 15 can be heated by passing an electric current through the plate, which should then be manufactured from conduc¬ ting material, or, as depicted in Figure 5, by heating the plate by means of a more or less diagrammatically indicated source of heat 16 which may be placed, for example, in a house 17 which also serves as mounting for the plate. Two approximately triangular -flat shielding ele¬ ments 18, 19 are placed essentially parallel to the plate 15 at some distance from the plate 15 on the side of the plate 15 facing the aiming camera during operation. The bases of the two triangular elements are situated level with the two opposite sides of the plate 15, while the angles or points 20, 21, situated opposite the bases, of the shielding elements face each other and are situated near the centre of the plate, but lie at low distance from each other. Two intensity distributions along the lines -p-q and r-s which are produced if the plate 15 is heated are shown on the right in Figure 4. It has emerged that, although the intensity distributions do not contain sharp junctions, the human eye nevertheless constructs two sharp lines with a well defined intersect, and does so in a reproducible manner, from the two-dimensional intensity distribution thus obtained which does not contain any sharp lines or points even after conversion into visible light on the viewing screen of the infrared aiming camera of the sight. These lines observed by the human eye are iπdi- cated in Figure 4 by 23 and 24, while the intersect is indicated by 25. The lines observed by the human eye run parallel to the sides of the triangular shielding elements at some distance therefrom, and the intersect - is situated between the two points 20, 21 of the tri- angular shielding elements. This intersect can therefore be brought in a sufficiently accurate manner into coin¬ cidence with the fixed alignment mark in order to adjust the aiming camera. The sharpness of the lines 23, 24 and, in particular of the intersect 25 can be adjusted by making the distance between the points 20, 21 of the triangular elements adjustable. For this purpose, the triangular elements, may be mounted so as to slide, as indicated by arrows 26, 27, in the collimating mark device. The sharpness of the intersect 25 may, in addition, be adjusted by means of the brightness and contrast con¬ trol system of the infrared camera. Attention is drawn to the fact that the sides which interact at the points of the triangular elements do not necessarily have to be straight but could also be somewhat curved. It is only important that two approx mately V-shaped intensity distributions are obtained which, with a correct adjustment, blend with each other in a manner such that the human eye observes two lines, optionally curved, which intersect each other and have a sharp intersect. Figures 6 and 7 show alternative ' embodiments of the triangular elements having convex and concave sides respect vely. The intersects are indicated by 30 and 31 respect ively. The apex angles of the triangular elements are preferably 90°, but other values are possible. If desired, the size of the apex angle can be matched to the resolution of the infrared camera if, for example, the hor zontal resolution is not equal to the vertical reso¬ lution. It is also not strictly necessary for the tri- angular elements to be symmetrical with respect to a perpendicular dropped from the apex angle to the base, that is to say, in the case of Figure 4, that the tri¬ angular elements are not isosceles, but a symmetrical shape is preferred. Another possible embodiment is shown in Figure 8. In this embodiment, the triangular elements are construc¬ ted as wide V-shaped plates 32 and 33. This embodiment can also be used n principle but, as the result of the lack of shielding material at the bases of the elements, it results in an image which is less pleasant to observe. In addition, it is possible to use, instead of two triangular elements, four such elements as shown in Figure 9 in which two additional elements 34 and 35 are shown so that only two strips along the diagonals of the plate 15 are not covered. This embodiment, however, offers virtually no improvement with respect to the embodi¬ ment having two triangular elements but requires, on the other hand, a very accurate adjustment of the two additional elements 34, 35 with respect to the other two elements 18, 19. An embodiment having two covering elements is therefore preferred. It is pointed out that, in the foregoing, the assumption has always been made of a heated plate 15 which is partially shielded by cooler covering elements. The desired effect can, however, also be obtained by heating just the triangular elements. The plate 15 then remains cooler, optionally by providing special cooling means for the plate 15, so that two essential V-shaped intensity distribu ions are again obta ned. The plate 15 could in that case in principle even be omitted entirely. The essentially triangular elements, optionally having curved sides, may be manufactured in a suitable manner from thin metal sheet, for example a thin steel sheet. In a test arrangement, triangular platelets cut from scissors were used successfully. As indicated in the foregoing, it is essential for the invention that such a two-dimensional intensity distribution is generated that the human eye can con¬ struct therefrom two sharp lines which intersect each other and have a sharp intersect, after conversion into a visible image. According to the exemplary embodiment described in the foregoing, for this purpose, at least two essentially triangular elements are used which have their points facing each other and which extend in a plane which is essentially transverse to the direction of observation, that is to say transverse to the imaginary connecting line indicated by 36 in Figure 5 between the centre of the collimatiπg mark and the centre of the entrance window of the aiming camera or of the mirror or collimator on the barrel. In this manner, the desired two-dimensional intensity distribution extending in the same plane is automa cally obtained. It is, however, also possible to generate a suitable two-dimensional intensity distri¬ bution extending in a transverse plane situated trans¬ versely to the connecting line 36 by means of elements which are not situated in the transverse plane. For this purpose, use may, for example, be made of an electrical conductor which passes an electric current during operation and which lies essentially in a plane containing the connecting line 36 and intersects the connecting line essent ally perpendicularly. In order to obtain an X-shaped intensity distribution in this manner, the conductor should have a coldest point from which the temperature increases towards both ends. This can be achieved by constructing the conductor in a manner such that the resistance thereof is highest at the ends and decreases gradually to a minimum value in the direction of a point situated bet een the two ends. The principle is shown in Figure 10. A conductor 40 passes an electric current I during operation. The variation in resistance of the conductor over the length thereof is indicated next to the conductor. The resistance R is highest at the ends 41, 42 of the conductor and lowest in the centre of the conductor at point 43. The amount of heat generated in the conductor therefore decreases from the ends 41, 42 towards the point 43 so that, as a consequence of the small numerical aperture of the infrared optics used, the conductor produces an hour glass-shaped spatial heat distribution which provides a similar intensity distribution in a plane through the conductor as was obtained in the embodiments described above . Such a conductor may be formed by means of a flat metal plate which is cut out in a manner such that the cross-sectional area thereof is small at the ends and is large in the . central region. An example is shown in Figure 11. Figure 11 shows a plate-type conductor 44 having a diamond shape which lies in a plane containing the connecting line 36. One of the diagonals (45) extends transversely to the line 36, and the other diagonal coincides with the line 36. An electrical energy source is connected between the ends of the diagonal 45. The plate-type conductor may also have curved sides such as are shown by the broken lines in Figure 11. In addition, he plate could be constructed not only more widely, but also, at least in part, more thickly in the vicinity of the line 36 than at the ends. As an alternative, two separate conductors of approximately triangular shape,. which leave the region in the vicinity of the line 36 free, may be used. Such an embodiment is shown in Figure 12. Figure 12 shows a first approximately triangular conductor 50 which passes a current I during operation and a second matching con¬ ductor 51 which likewise passes a current I during opera¬ tion. Both conductors lie in one and the same plane w ich also contains the connect ng line 36 and are placed symmetrically with respect to the connecting line 36, a gap being present between the two conductors. In Figure 12, one of the sides of the two con¬ ductors is curved. The other sides could likewise be of curved cons ruction. The edges of the two conductors wh ch face the other conductor may also include a mutual angle, as can the edges drawn in line with each other in Figure 12. In addition, the conductors may again be thicker at the level of the ends facing each other than in the vicinity of the apex angles situated opposite. Figure 13 shows a simple embodiment in which no external heat source is necessary. . On a plate 60 of a first material, a pattern of two triangles 61 and 62 is provided with a second material. The materials are chosen in such a manner that they have different visibility in the infrared. The difference in visibility is obtained, for example, by manufacturing the plate 60 from germanium on which the triangles 61 and 62 are provided in a manner known per se as reflective coatings of alternating layers of ZnS and Ge so that a reflection of approximately 97% is achieved in the infrared region concerned. In the same manner known per se, the remaining triangles 63 and 64 are provided with an antireflection coating of alternating layers of ZnS and Ge so that a transm.issioπ of approxi- mately 98% is achieved. As a result of the difference in visibility in the infrared, the pattern is visible without there being any question of a difference in tem¬ perature between the two materials. This embodiment has particular advantages in those cases n which an external heat source s undesirable or impossible. By way. of example, it may be mentioned that an infrared detector contains a number of detector elements on a carrier. The dimensions on the carrier are approxi¬ mately 10 mm diam. On the carrier connec ing points are provided to the outside. Each connecting point is conn¬ ected to one or more detector elements. Such a detector can be used in an infrared detection system in order to cause, by means of autocoll ima ion, the viewing direction of the infrared sight to coincide with the firing direc¬ tion of a gun as already described above. The viewing screen on the aiming camera then shows the mirror image of the detector on which the detector elements and connec¬ ting points are visible. The viewing and firing directions coincide if one specific point of the image of the detector shown coincides with a specific point of the alignment mark. However, such detectors consist, in general, of a matrix of iden ical, indistinguishable elements. Which part of the detector is visible cannot be inferred from the image of the detector when adjusting the viewing direction and/or the firing direction. Although another part of the detector will become visible as a result of displacement, the observer of the image on the viewing screen is not capable of distinguishing the new image from the old image. In this situation it is particularly advantageous if a s ngle marking symbol is provided on the detector which has to be brought pre- cisely into coincidence with a specific point of the alignment mark. For this purpose, for example, a colli¬ mating mark is provided on the carrier of the detector as described above and consists of a pattern of two triangles vapour-deposited using gold and having dimen- sioπs in the order of 0.1 mm. As a result of the diff¬ erence in emission coefficient of gold and carrier, the pattern will be visible for the infrared detection system despite the fact that no temperature difference is present. Attention is drawn to the fact that, after the foregoing, various modifications of the embodiments described are obvious to those skilled in the art. Thus, in the configuration of Figure 10, use could also be made of two conductors which cross each other but are identical" in other respects. In an analogous manner, two diamond- shaped conductors as shown in Figure 11 could be used w ich are placed behind each other in planes w ch inter¬ sect each other perpendicularly. Equally, four triangular conductors as shown in Figure 12 may be used. Such modifications are considered to fall within -the scope of the invention.

Claims: CLAIMS 1.. Colli ating mark device provided ith an infra¬ red collimating mark intended to be observed through a sight, characterized in that the collimating mark device is designed in a manner such that the infrared colli- mating mark comprises at least two essentially V-shaped intensity distributions, the points of the V shapes facing each other. 2. Collimating mark device according to Claim 1, characterized in that the essentially V-shaped intensity distributions are obtained by means of at least two essentially triangular plate-type elements, the apex angles of which face each other and which lie in a plane extending transversely to the optical connecting line between the sight and the collimating mark device. 3. Collimating mark device according to Claim 2, character zed in that triangular elements a r e shielding elements which are placed in front of a heated plate. 4. Collimating mark device according to Claim 3, characterized in that the apex angles, which face each other, of the triangular elements are at some distance from each other. 5„ Collimating mark device according to Claim 2, characterized in that the triangular elements are heated elements . 6. Collimating mark device according to one of Claims 2 to 5 incl., characterized in that at least the sides of the triangular elements which come together at the apex angles are curved. 7. Collimatiπg mark device according to one of the Claims 2 to 6 incl., characterized in that the triangular elements are each provided with a cut-out in the side situated opposite the apex angle. 8. Collimating mark device according to one of the Claims 2 to 7 incl., characterized in that the collimatiπg mark device comprises four essentially triangular elements situated in one plane with the apex angles facing each other in pairs. 9. Collimating mark device according to Claim 1, characterized in that the essentially V-shaped intensity distribut ons are obtained by means of at least one electrical conductor which extends essentially transverse- 5 ly to the optical connecting line between the sight and the collimating mark device in a plane containing the optical connecting ' line and which passes an electric current during operation, the resistance of the conductor decreasing from the ends of the conductor in the direction 0 of a point situated between the ends. 10. Collimating mark evice according to claim 9, characterized in that the electrical conductor extends in a plane containing the optical connecting line and, has the shape of a diamond-shaped plate, the first d.iag- 5 onal of the diamond shape being parallel to the optical connecting line or coinciding therewith, while the second diagonal exte.πds transversely to the optical connecting line, and the electrical connections of the conductor being situated at the two ends of the second 0 diagonalo 11o Collimating mark device according to Claim 10, character zed in that the sides of the diamond shape are curved. 12. Collimating mark dev ce according to Claim 10 or 5 11, charac erized by a second diamond-shaped conductor which is situated in a plane perpendicular to the plane of the first conductor and the first diagonal of which is in line with the first diagonal of the first conductor. 13. Collimatiπg mark device according to Claim 9, ° characterized in that the at least one conductor consists of two conductors situated in line with each other, some gap being present between the ends of the conductors which face each other and both conductors each passing an electric current during operation, the resistance of each 5 conductor decreasing in the direction of the end facing the other conductor. 14. Collimating mark device according to Claim 13, character zed in that both conductors essentially have the shape of a triangular, plate and are situated in one plane, the ends facing each other being formed in each case by one side of the triangular shape and each being provided with- an electrical connection, while the other electrical connec ion of each conductor is situated at the apex angles situated opposite .the sides which face each other, of the tr i angular shapes . 15. Collima- iπg mark device according to Claim 14, characterized in that at least one of the sides of the two triangular conductors is curved. 16. Colli atiπg mark device according to Claims 13 to 15 incl., characterized in that two sets of conductors situated in line i h each other are used, the one set being situated in a plane which intersects the plane of the αthe.r set essentially perpendicularly and the inter¬ section line of the two planes being parallel to the optical connecting line or coinciding therewith. 17. Collimating mark device according to one of the Claims 10 to 13 incl., characterized in that the diamoπd- shaped plate is at least in part thicker at the level of the second diagonal than at the level of the electrical connec ions . 18. Collimating mark device according to one of the Claims 14 to 16 incl., characterized in that at least one of the triangular plates is at least in part thicker at the level of the side facing another- triangular plate than at the level of the . apex angle facing away from the other triangular plate. 19. Collimatiπg mark device according to Claim 1 or 2, characterized by a plate-type carrier on which a pattern of two triangles with the apices directed towards each other is provided, the carrier having a surface which strongly absorbs infrared radiation, while the triangles have a surface which strongly reflects infrared radiation. 20. Collimating mark device according to Claim 19, characterized in that the carrier is manufactured from germanium and, outside the areas of the triangles, is provided with an anti reflection coating for infrared radiation, while an infrared radiation reflecting coating is provided at the position of the triangles. 21. - Collimating mark device according to Claim 19, characterized in that the triangles are formed by vapour deposition of gold. 22. Adjustment device for aligning the line of direc¬ tion of an infrared sight and the firing direction of a gun, the adjustment device comprising a coll matiπg mark device which generates an infrared collimatiπg mark representing the firing direction of the gun during oper¬ at on, as well as means for imaging the collimatiπg mark in the sight in visible form and means for adjusting the sight in a manner such that the image of the collimatiπg mark coincides with a fixed alignment mark in the sight, chara terized by a coll matiπg mark device according to one or more of the preceding claims.

Inventors: ELSHOUD NICOLAAS PETER, ELSHOUD, NICOLAAS, PETER
Applicants: OPTISCHE IND DE OUDE DELFT NV, B.V. OPTISCHE INDUSTRIE "DE OUDE DELFT"
Application year: 1988
Main classification: F41G3
IPC codes: F41G3