WO2000055670A1

WO2000055670A1 - An optical sighting device

Info

Publication number: WO2000055670A1
Application number: PCT/IB2000/000288
Authority: WO
Inventors: Daniel Renier Kriek; Tinus Nicolaas Janse Van Rensburg
Original assignee: Vektor A Division Of Denel (Pty.) Ltd.
Priority date: 1999-03-17
Filing date: 2000-03-17
Publication date: 2000-09-21
Also published as: AU3184100A

Abstract

A sighting device comprises an outer housing (12) and a tubular inner housing (14) defining a central axis (16). The tubular housing (14) comprises a round cylindrical aluminium tube. A dichroic mirror lens (22) is mounted to the front end of the tubular housing (14). An elongate optic light collector and guide (36) is positioned and configured primarily to receive overhead light from above the sight via a top window (42) in the outer housing (12). The light is projected from a rear light-emitting end (64) of the optic light collector (36) and is reflected off first and second mirrors (54 and 55). The light follows a path (66) through a reticle (60), with the reticle image being projected onto a concave surface (24) of the dichroic mirror lens (22) at a point which is coincident with the central axis (16) of the tubular housing (14).

Description

AN OPTICAL SIGHTING DEVICE

BACKGROUND OF THE INVENTION

THIS invention relates to an optical sighting device, and in particular to an optical reflex sighting device for day and night use.

A typical sighting device of this type is disclosed in South African patent 96/3824. A light collector assembly provides illumination for a reticle pattern which is projected onto a front dichroic mirror. A fibre optic light collector assembly is located towards the front end of the sighting device, and is defined by a serpentine fibre optic array onto which ambient light is focussed by a similarly configured serpentine lens arrangement which focuses the ambient light radially inwardly into the optical fibre. An artificial light source is included for providing night time illumination of the reticle pattern. The entire assembly is located within an open housing, which is in turn fitted to a base bracket. The base bracket is mounted fast to a firearm, and adjustment of the sight is achieved by adjusting the alignment of the open housing relative to the base plate.

CONFIRMATION COFV SUMMARY OF THE INVENTION

According to the invention there is provided a sighting device for viewing an object along an aiming axis, the sighting device comprising:

a housing defining a central axis, and having a front end for receiving a target to be sighted and a rear viewing end;

a beam splitting means mounted towards the front end of the housing operative for transmitting wavelengths of light over a first wavelength range and reflecting wavelengths of light over a second wavelength range;

an ambient light collector arrangement comprising an elongate optical light collector and guide mounted operatively above the housing and adapted to receive overhead light directed inwardly into the optical collector along a collecting portion thereof and to guide it towards a light-emitting end thereof;

a reticle structure arranged to receive light from the light-emitting end of the optical light collector and guide and to project a reticle pattern onto the beam splitting means to produce a reflected image of the reticle pattern superimposed on the object being viewed; and

light directing means for directing the light from the collecting portion of the optical light collector and guide to the beam splitting means.

Conveniently, the elongate light collector and guide extend in a direction substantially parallel to the central axis of the housing. Typically, the light directing means comprises at least one reflecting surface which is fixed relative to the collecting portion of the light collector and guide.

In a preferred form of the invention, the light collector and guide and the light directing means are integral, with the light directing means comprising at least two angled reflecting surfaces defined at a rear end of the optical light collector and guide for directing light forwardly to the beam splitting means.

Advantageously, the ambient light collector arrangement is formed from a unitary fluorescent polymer.

Preferably, the reflecting surfaces are silvered, and the reticle structure is fixed to an exit surface defined on the light-emitting end of the collector.

Alternatively, the light directing means may comprise at least two reflecting surfaces which are defined by separate mirrors or a separate prism for directing light forwardly to the beam splitting means.

Conveniently, the reticle structure is located between the light directing means and the beam splitting means, with the result that light travels through free space from the reticle structure to the beam splitting means.

Preferably, the light collector arrangement is supported above a top reflecting face of the housing.

In a preferred form of the invention, the housing comprises an inner tubular housing which is mounted movably within an outer housing and the outer housing is formed with an overhead opening for receiving ambient light for collection by the collecting portion of the optical light collector and guide. Typically, sight adjustment means are provided for adjusting the inner tubular housing relative to the outer housing for moving the central axis into alignment with a firing or aiming axis.

Advantageously, the inner tubular housing is connected at a front end to the outer housing by means of a universal connection, with the adjustment means comprising at least a pair of adjusting screws mounted movably within the outer housing towards the rear end thereof, and being arranged to adjust the inner tubular housing in a plane substantially normal to the central axis.

Conveniently, the light emitting end of the light collector and guide is located within a sealed chamber defined by the inner tubular housing.

Alternatively, the housing comprises a tubular housing which is fitted directly to adjustable sighting clamps or an adjustable sighting base.

Conveniently, an artificial light source is mounted adjacent the light directing means for directing artificial light towards the light-emitting end of the collector arrangement.

In one form of the invention, the beam splitting means comprises a dichroic mirror.

Alternatively, a doublet lens arrangement may be used.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a top plan view of a first embodiment of a sighting device of the invention;

Figure 2 shows a cross-section along the line 2-2 of Figure 1 ;

Figure 2A shows a detail of part of the sighting device of Figure 2;

Figure 2B shows a detailed front view of a reticle structure;

Figure 3 shows a rear view of the sighting device of Figure 1 ;

Figure 4 shows a cross-section along the line 4-4 of Figure 3;

Figure 5 shows a cross-sectional side view of a second embodiment of a sighting device of the invention; and

Figure 6 shows a cross-sectional side view of a third embodiment of a sighting device of the invention.

DESCRIPTION OF EMBODIMENTS

The sighting device 10 illustrated in Figures 1 to 4 comprises an outer housing 12 and a tubular inner housing 14 defining a central axis 16. The outer housing 12 comprises a top cowling portion 12.1 and a base 12.2 formed with a lower dovetail-type cavity 18 which forms a sliding fit with a complemental dovetail-type protrusion on a firearm. The top 12.1 and base 12.2 are screwed together by means of screws 19 which extend through threaded apertures 20. The tubular housing 14 is in the form of a round cylindrical aluminium tube, and a dichroic mirror 22 in the form of a lens is mounted to the front end of the tubular housing 14. The lens 22 has an inner concave surface 24 and an outer convex surface 26. The lens is dichroic, in the sense that the inner concave surface 24 is treated with a reflective coating to reflect wavelengths of light in that part of the spectrum which correspond to the predominant wavelengths of the fluorescent light passing through the fluorescent light guide, in this case yellow, and to transmit all other wavelengths of light, in this case light in the blue part of the spectrum, through the outer convex surface 26 of the lens 22. A transparent viewing window 28 treated with an anti-reflex coating is located at the rear end of the tubular housing, and a set block 30 is fitted to the base of the tubular housing at the rear end thereof by means of three threaded mounting screws 32.

The tubular housing 14 is movably mounted to the base of the outer housing 12 by means of a front O-ring 34, which is positioned adjacent the dichroic mirror lens 22. The O-ring 34 allows for universal movement of the housing 14. A more compressible rear O-ring 35 is positioned within a pair of complemental grooves in the respective tubular housing and outer housing adjacent the viewing window 28. The connection arising from the rear O-ring has significantly greater play than the front O-ring connection, with the result that the tubular housing 14 is able to move in a conical locus relative to its central axis 16, with the apex of the cone being located in the region of point 16A. In place of the front O-ring 34, a ball-type joint may also be provided, with the front portion of the tube having a convex rib which is arranged to mate with the complemental concave depression defined within the front portion of the inner walls of the outer housing. A locating pin may extend through the ball joint for preventing rotation thereof. An elongate optical light collector and guide 36 has a front end bonded in position within an aperture 38 extending through a sighting post 39 mounted atop the front end of the tube 16. The mounting post also serves to prevent rotation of the inner tubular housing 14 relative to the outer housing 12, whilst allowing the abovementioned conical movement. The optical light collector 36 is in the form of a fluorescent light guide manufactured from a transparent polymeric such as polystyrene which is doped with a fluorescent dye material to enhance the light transmitting ability. The collector has a diameter of 3mm, with a front end 40 for receiving light from the front of the sight. The light guide 36 is positioned and configured primarily to receive overhead light from above the sight via a top window 42 in the outer housing. In order to increase the amount of light received, the top of the tubular housing 14 is formed with a flat reflective surface 44 which is either whitened or metallized, so that ambient light is reflected back from the surface 44 into the light guide 36.

The light guide 36 passes through a slot 50 in the outer housing and a sealed inner opening 51 formed in a mirror housing 52 surmounted on the inner tubular housing 14. The mirror housing in combination with the inner housing define a sealed chamber 53 and terminates just short of a mirror assembly comprising first and second mirrors 54 and 55 mounted within a mirror block 56 which is in turn supported within the mirror housing 52. A glass reticle 60 is mounted on a reticle bracket 62 carried on the mirror block. The reticle 60 is located at the focal point of the concave surface 24 of the lens 22, and is formed with a suitable aiming pattern, in this case an inverted V 61A and a pair of pointed horizontal aiming lines 61 B, all of which are cut into the surrounding glass, which has a matte black finish. Light is projected from the rear light- emitting end 64 of the optic light collector and is reflected off the first and second mirrors 54 and 55, following a path 66 through the reticle 60, with the reticle image being projected onto the concave surface 24 of the dichroic mirror lens 22 at a point which is coincident with the central axis 16 of the tubular housing 14. As is clear from Figures 3 and 4, a pair of adjusting screws 68 and 70 are provided for facilitating adjustment of the tubular housing 14. The adjusting screws are located in threaded apertures 72, and are formed with chamfered ends 74 which abut against complementally chamfered faces 76 of the set block 30. Clockwise rotation of the screw 68 has the effect of moving the tube diagonally in the direction of arrow 68A, and clockwise rotation of the screw 70 has the effect of moving the screw diagonally in the direction of arrow 70A. Thus, to effect vertical upward adjustment, both screws are rotated to the same degree in a clockwise direction, and to effect vertical downward adjustment both screws are rotated counter-clockwise to the same degree. To effect horizontal adjustment to the right, screw 68 is rotated clockwise and screw 70 counter-clockwise, and to effect horizontal adjustment to the left, screw 68 is rotated counter-clockwise and screw 70 clockwise. A resilient leaf spring 46 formed from sprung steel is located in a cavity between the mirror housing 52 and the outer housing 12, and provides sufficient reaction force against which the screws 68 and 70 may be adjusted. An artificial light source 80 in the form of a pair of tritium lamps is mounted to the mirror housing 52, and is arranged to direct light radially into the light guide 36 adjacent the light-emitting end 64 thereof under low light conditions. The artificial light source may alternatively be electrically powered, or photoluminous.

Referring now to Figure 5, a second embodiment of a sight 82 is shown. In this sight, the optic light guide and collector and the first and second mirrors are replaced by a unitary light collector 84 which is injection moulded or machined from a fluorescent polymeric material. In the particular example, the fluorescent polymeric material includes a LISA® plastics material of the type manufactured by Bayer AC In particular, the material is a polymethyl methacrylate (PMMA) material which is mixed with a Macrolex® fluorescent yellow 10GN coumarin dyestuff in the ratio of 2000:1 , together with titanium dioxide in the ratio of 100:1. The outer surface of the light collector may be coated with a reflective coating having a reflective peak at 580nm, which corresponds to the fluorescing wavelength of the LISA® polymer. As a result, whilst the light collector is able to collect ambient light, in particular in the violet and ultra-violet range, which is then converted into fluorescent yellow light having a wavelength of 580nm, the reflective coating, together with the total internal reflection characteristics of the light guide, serve to ensure that most of the yellow 580nm light is internally reflected. This reduces the external glow of the light guide under low light conditions, thereby decreasing the risk of being spotted by the target by virtue of the fluorescent light guide.

Ambient light enters via the window 42, which may be omitted, and follows a light path indicated by arrow 86, which path is similar to the light path followed in the first sight embodiment. The mirrors 54 and 55 are replaced by similarly angled polished mirrored surfaces 88 and 90 which form an integral part of the light collector 84, as does an exit face 94 through which the light exits just before it passes through a reticle plate 96 which may be bonded to the exit face 94. The angled reflecting faces 88 and 90 may be silvered so as to improve their reflectivity and to prevent the escape of light. The entire light guide 84 is bonded against a top reflective surface 44A of the tubular housing 16A. The reflective surface 44A may be covered by a photo-luminescent coating to retain the specific 580nm (yellow) wavelength of light corresponding to the predominant wavelength of light transmitted through the light guide when under acceptable ambient light conditions, such as just before sunset. Under low light conditions, and in particular at dusk, the recently excited luminescent coating provides an additional artificial light source which serves to supplement, and at least initially dominate the artificial tritium light source to enhance the brightness of the reticle. A variation of the sight 82 shown in Figure 5 is shown in Figure 6 in which similar components have been indicated with similar reference numbers suffixed by an "A".

The sight 98 comprises a fluorescent polymeric unitary light collector 84A formed from a LISA® plastics material of the type manufactured by Bayer AG, and having specifications similar to those of the Figure 5 embodiment. The light collector 84A is positioned and configured to receive ambient light from above the sight via an open top window 42A in the outer housing 12A and a circular aperture 100 formed in the outer housing 12A, as well as light from in front of the sight. Ambient light enters the light collector 84A and follows a light path indicated in chain outline at 86A, which path is similar to the light path followed in the second sight embodiment.

The light collector 84A is bonded to a flat upper surface 101 of the tubular housing 14A. The lower surface 102 of the light collector 84A is formed with a flat metallized reflective surface so that ambient light is reflected back from the surface into the light collector 84A. Alternatively, the lower surface 102 of the light collector 84A may be spray coated with a reflective coating having a reflective peak which is identical to the reflective peak of the lens 22A. As a further alternative, the flat surface 101 of the tubular housing 14A may be coated with a photo-luminescent coating to retain the specific wavelength of light corresponding to the predominant wavelength of light transmitted through the light collector 84A.

A set block 30A is rigidly fitted to the base of the tubular housing 14A by means of a pair of dowel pins 106 and 108 and an epoxy type adhesive. A locating pin 110 is mounted to the base of the outer housing 12A and locates in a corresponding recess 111 formed in the tubular housing 14A. The side faces of the set block 30A are chamfered to enable adjusting screws having conical ends (not shown) to adjust the position of the tubular housing 14A, as is described above with reference to Figures 3 and 4.

The tubular housing 14A is mounted to the base of the outer housing 12A by means of front O-ring 34A. The O-ring 34A is positioned within a pair of complemental grooves formed in the tubular housing 14A and outer housing 12A. The groove in the tubular housing 14A is defined by a pair of curved surfaces 1 12 and 114 which allows the tubular housing 14A to move in a conical locus relative to its central axis 16A. A helical spring 116 is fitted between the tubular housing 14A and the roof of the outer housing 12A and provides sufficient reaction force against which the adjusting screws may be adjusted.

An artificial light source in the form of a pair of gaseous tritium light sources 1 14 is mounted to the angled reflecting face 88A, and is arranged to direct light into the light collector 84A under low light conditions. The gaseous tritium light sources 114 comprise enclosed glass capsules, the inner surfaces of which are coated with a phosphorescent layer. The phosphorescent layer is energised by the low level beta radiation of the tritium gas. A variety of light colours are available, with the present invention typically utilising either blue or white.

The front end of the outer housing 12A includes a threaded aperture for receiving a mounting screw 116 that is used to secure a filter 118 to the outer housing 12A. The filter 118 is made of polymethyl methacrylate (PMMA) and is used to enhance the brightness of the reticle 94A by providing a relatively darker background against which the reticle 94A is viewed.

As the light collector and prism is a unitary structure, it is generally more robust than a structure in which separate mirrors and prisms are provided which may be prone to disalignment. The reticle plate 94, 94A may be glued into position beforehand, in which case the entire reticle plate 94, 94A and collector 84, 84A may simply be dropped into position, or slid into a complemental groove. The structure is also generally more robust than thin optical fibres or separate prisms and mirrors which can be damaged or knocked out of alignment.

By using the above arrangement to convey light to the reticle structure, there is a significant savings in space which results in a relatively low profile sight. The entire tubular housing 14 and mirror housing 52 form a sealed airtight unit into which the optic light collector 84 projects. This makes for a relatively robust sight assembly which requires minimal adjustment after initial adjustment has taken place. As the outer housing is mounted fast to the weapon, and substantially surrounds the inner housing, the outer housing rather than the inner tubular housing is exposed to external impacts and shock, against which the inner tubular housing is substantially protected. Further, the overall length of the light path is minimized to a linear collection path and a linear return path in combination defining a V-shaped path. As the reticle structure 60, 94, 94A is located above the central axis 16, the dichroic mirror lens 22, 22A is tilted slightly downwards at a tilt angle x, with the central axis of the lens 22, 22A being essentially co-linear with the path 66. As a result, light reflected off the front face 26 of the lens will tend to be directed towards the ground, thereby reducing the chances of such reflections being visible from the target.

Claims

1. A sighting device for viewing an object along an aiming axis, the sighting device comprising:

a reticle structure arranged to receive light from the light- emitting end of the optical light collector and guide and to project a reticle pattern onto the beam splitting means to produce a reflected image of the reticle pattern superimposed on the object being viewed; and

2. A sighting device according to claim 1 in which the elongate light collector and guide extend in a direction substantially parallel to the central axis of the housing.

3. A sighting device according to either one of the preceding claims in which the light directing means comprises at least one reflecting surface which is fixed relative to the collecting portion of the light collector and guide.

4. A sighting device according to any one of the preceding claims in which the light collector and guide and the light directing means are integral, with the light directing means comprising at least two angled reflecting surfaces defined at a rear end of the optical light collector and guide for directing light forwardly to the beam splitting means.

5. A sighting device according to claim 4 in which the ambient light collector arrangement is formed from a unitary fluorescent polymer.

6. A sighting device according to either one of claims 4 or 5 in which the reflecting surfaces are silvered, and the reticle structure is fixed to an exit surface defined on the light-emitting end of the collector.

7. A sighting device according to any one of claims 1 to 3 in which the light directing means comprises at least two reflecting surfaces which are defined by separate mirrors or a separate prism for directing light forwardly to the beam splitting means.

8. A sighting device according to any one of the preceding claims in which the reticle structure is located between the light directing means and the beam splitting means, with the result that light travels through free space from the reticle structure to the beam splitting means.

. A sighting device according to any one of the preceding claims in which the light collector arrangement is supported above a top reflecting face of the housing.

10. A sighting device according to any one of the preceding claims in which the housing comprises an inner tubular housing which is mounted movably within an outer housing and the outer housing is formed with an overhead opening for receiving ambient light for collection by the collecting portion of the optical light collector and guide.

1 1. A sighting device according to claim 10 in which sight adjustment means are provided for adjusting the inner tubular housing relative to the outer housing for moving the central axis into alignment with a firing or aiming axis.

12. A sighting device according to claim 11 in which the inner tubular housing is connected at the front end to the outer housing by means of a universal connection, with the adjustment means comprising at least a pair of adjusting screws mounted movably within the outer housing towards the rear end thereof, and being arranged to adjust the inner tubular housing in a plane substantially normal to the central axis.

13. A sighting device according to any one of claims 10 to 12 in which the light emitting end of the light collector and guide is located within a sealed chamber defined by the inner tubular housing.

14. A sighting device according to any one of the preceding claims 1 to 9 in which the housing comprises a tubular housing which is fitted directly to adjustable sighting clamps or an adjustable sighting base.

15. A sighting device according to any one of the preceding claims in which an artificial light source is mounted adjacent the light directing means for directing artificial light towards the light-emitting end of the collector arrangement.

16. A sighting device according to any one of the preceding claims in which the beam splitting means comprises a dichroic mirror.

17. A sighting device according to any one of claims 1 to 15 in which the beam splitting means comprises a doublet lens.