Optical gun sight

Abstract: An optical gun sight (10) having a central axis (112) for a hand gun, shot gun and/or rifle having a firing axis and with the gun sight (10) having an image erector system (100) located generally at the focal plane (98) of the gun sight (10) and with the gun sight (10) including adjustment means (136) operative on the image erector system (100) for selectively moving the image erector system (100) in two transverse directions which are in turn transverse to the central axis (112) to provide calibration of the position of the image of the target relative to the firing axis of the hand gun, shot gun or rifle whereby compensation can be provided for the trajectory of the bullet to the target.

Description: SUMMARY BACKGROUND OF THE INVENTION The present invention relates to optical gun sights for hand guns, shot guns or rifles and more particularly to an optical gun sight having internal adjustment means for providing sight and firing calibration and alignment. Optical gun sights are commonly telescopic in nature, i.e. producing a magnified image of the target, and are provided with a reticle pattern which can be crosshairs, dots or other indicia which facilitates aiming of a rifle improving the accuracy of firing. These optical gun sights, however, are mounted on a rifle, usually above the barrel, and for this and other reasons required adjustment or calibration to provide alignment between the target sighted on the reticle pattern and the trajectory of the bullet to provide accuracy in firing. Often the adjustment is provided by an external adjustment mechanism located between the optical gun sight itself and the mounting structure of the rifle. This adjustment mechanism permits movement of the optical gun sight vertically and horizontally to provide the desired movement of the reticle pattern and/or target relative to the central axis of the optical gun sight and hence relative to the axis of the barrel for calibration. The result is a relatively heavy and bulky construction. Other constructions in the past have provided for an internal adjustment effective with the sighting reticle pattern and/or image of the target via a spherical bearing but, because of the location of the components, have resulted in a lengthy, heavy construction. In some instances, optical gun sights are mounted on a handle-like structure at the top of the rifle; this is provided to facilitate carrying the rifle by manually gripping the rifle by the handle and optical gun sight. However, the noted heavy, bulky and/or lengthy constructions tend to inhibit the ease of manual gripping at the handle and add to the overall weight of the rifle. With the present invention, an internal adjustment is provided for calibration and alignment via, in the preferred form, a spherical bearing assembly which operates both on an image erector system having a prism structure and on a reticle projecting structure for defining the reticle pattern, i.e. sighting crosshairs, dots, etc. The result is a relatively lightweight, compact structure. The optical gun sight can be adapted to be mounted on an external handle on a rifle and, because of its lightweight and compact size, facilitates manual gripping and carrying. It is an object of the present invention to provide a new and unique optical gun sight for a rifle (shotgun and/or handgun) which has a novel internal adjustment for sight and firing calibration and alignment. It is also an object of the preferred form of the present invention to provide such an optical gun sight where the internal adjustment is accomplished by a spherical bearing assembly operatively associated with an image erector system. US-A-4 200 355 discloses an optical gun sight in accordance with the prior art portion of claim 1. With this prior gun sight, the erector means comprises a single lens which is mounted in a housing, the position of which is adjustable, to adjust the path of light from the objective and thus to change the aim of the gun sight. This is typical of prior heavy and elongated gun sights in that the whole device needs to be elongated in order to obtain the image via the erector lens on a reticle for subsequent viewing through an ocular lens system. Thus, with this prior construction, two focal planes are provided, one betyween the objective and the erector lens and the other at a reticle, giving a substantial length to the gun sight. The present invention, as defined in claim 1, provides for a prismatic erector system which enables the gun sight to be shortened, made lighter, and to have a single focal plane intermediate the ends of the erector prism arrangement with it being possible to have the reticle also at the same location, permitting the provision of a very compact but easily adjustable system. In the preferred construction, the reticle can be provided on a surface of the prism to be directed at a plane which is coincident with the focal plane of the sight whereby the reticle and the erector prism system can be simultaneously adjustable to provide good, clear sighting, substantially regardless of the degree of adjustment. While prism arrangements are known, for example as shown in DE-A-2 501 178, these do not provide any appreciation of the possibility of including the prism arrangement in an adjustable manner, such that the focal plane of an objective lens operated with such prism system can be provided within the extent of the prism system so as to be adjustable in position by a simple tilting action enabling, as specified in the preferred construction of the present invention, a reticle to be located in the image plane for simultaneous movement with the prism system. With the embodiment as later described, the internal adjustment is accomplished by manipulation of the image erector system and a reticle projecting structure for defining the reticle pattern for sighting, the image erector system having a reticle projecting structure formed therewith and internal adjustment for sighting calibration being provided by simultaneous manipulation of the image erector system and reticle projecting system. The optical gun sight as later described has means for day and night illumination of the reticle projecting structure for defining the reticle pattern and is of a construction facilitating such illumination. Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, in which: Figure 1 is a pictorial partially fragmentary view depicting an optical gun sight of the present invention mounted upon a handle of a rifle with the rifle only partially shown; Figure 2 is a side, partially sectional view, to enlarged scale, of the optical gun sight of Figure 1 taken generally along the lines 2-2 in Figure 1; Figure 2A is a fragmentary sectional view taken generally along the lines 2A-2A in Figure 2; Figure 3 is a top elevational view of the optical gun sight of Figures 1 and 2 with some parts shown broken away and others shown in section; Figure 3A is a sectional view of the day illumination structure of the optical gun sight of Figures 1-3 taken generally along the lines 3A-3A in Figure 3; Figure 4 is a top elevational view to increased scale of a prism housing of the optical gun sight of Figures 1, 2 and 3; Figure 5 is a pictorial view of the prism housing of the optical gun sight of Figure 4 taken generally in the direction of the Arrow 5 in Figure 4; Figure 6 is a fragmentary, sectional view to enlarged scale of the adjustment assembly of the optical gun sight of Figures 1, 2 and 3 taken generally along the lines 6-6 in Figure 2; Figure 7 is fragmentary view to enlarged scale of the reticle pattern provided by the reticle projecting structure of the optical gun sight of Figures 1, 2 and 3; Figure 8 is a pictorial view of the prism assembly of the optical gun sight of Figures 1, 2 and 3 and generally depicting the light path through the prism assembly; and Figure 9 is a depiction of the light path through the prism assembly of Figures 1, 2 and 3 with the prism assembly shown in a developed, unfolded representation. Looking now to Figures 1-3, an optical gun sight 10 is shown mounted on a handle 12 of a rifle 14 (partially shown) and includes a housing assembly having a forwardly located main housing 16 and a rearwardly located eyepiece housing 18. The main housing 16 is tubular having an enlarged counterbore 20 at its forward end tapering rearwardly via a tapered bore 21 to a reduced diameter bore 22 which terminates in a generally transversely elliptical or oblong bore portion 24 at its inner end (see Figures 2 and 3). An external mounting flange 26 is located at the inner, terminal end of the main housing 16. The eyepiece housing 18 is also tubular and defined by a generally straight cylindrical bore 28 at its rearward end which terminates at its forward end in a bore portion 30 which is generally transversely elliptical or oblong similarly to bore portion 24. The eyepiece housing 18 also has an external mounting flange 32 which is contoured similarly to main housing flange 26. The body portion 34 of the main housing 16 in the area of the tapered bore 21 is also generally externally tapered or conical in shape. The eyepiece housing 18, except for the flange 32 and oblong bore portion 30, is generally of a straight cylindrical construction. An axially extending truncated portion 36 at the forward end of the main housing 16 defines a sun shade. The main housing 16 has a longitudinally extending mounting base 38 at its bottom side. The mounting base 38 is narrow and adapted to be received in a slot 40 in the handle 12 at the upper portion of the rifle 14 and is removably secured to the handle 12 by a pair of threaded bolts 42. In order to minimize the overall weight of the optical gun sight 10, the mounting base 38 is constructed with a width W no greater than around one third of the nominal outside diameter D of eyepiece housing 18 at its straight cylindrical portion. In addition, a bore 44 extends longitudinally through the base 38 to provide an opening through which the iron sights 45 and 47 at the rear and front of the barrel 49 of the rifle 14 can be viewed (see Figure 1). Thus the iron sights 45 and 47 can be readily used in lieu of the lens system of the optical gun sight 10 without the need for removal of the optical gun sight 10 from the rifle 14. In addition the bore 44 acts as a lightening hole to further decrease the overall weight of the optical gun sight 10. Thus it can be seen that the main housing 16 and eyepiece housing 18 define a compact relatively streamlined contour of minimum size and weight. An objective lens system 46 is located in the counterbore 20 at the forward end of the main housing 16 and includes a doublet lens 48 which comprises a generally double-convex lens 50 and a generally concave-convex lens 52 secured together by a suitable adhesive. The doublet objective lens 48 can be of a generally known construction the details of which do not constitute a part of the present invention and hence such details have been omitted for purposes of simplicity. The doublet objective lens 48 is partially surrounded and held in an annular support ring 54 which is threadably mounted in a rear threaded portion 56 of counterbore 20. An annular seal 58 extends around the forward periphery of the doublet objective lens 48 and engages a smooth bore portion 60 of the counterbore 20 to provide a seal therewith; a retaining ring 62 is threaded into a forward threaded portion 64 of the counterbore 20 and clamps the doublet objective lens 48 in place. An ocular lens system 64 is located at the opposite end of the optical gun sight 10 and is assembled in the eyepiece housing 18 from its enlarged, flanged end. Thus the ocular lens system 64 includes an eyepiece singlet or generally double-convex lens 66 which is located against an annular radially inwardly directed lip 68 at the small diameter end of the eyepiece housing 18. An annular seal 70 in an annular groove 72 adjacent the lip 68 provides a seal around the periphery of the eyepiece lens 66. A doublet ocular lens 74 is located a selected axial distance from the singlet eyepiece lens 66 by an annular spacer ring 76. The doublet ocular lens 74 comprises a generally double-convex lens 77 and a generally double-concave lens 79 secured together by a suitable adhesive. The doublet ocular lens 74 can be of a generally known construction the details of which do not constitute a part of the present invention and hence such details have been omitted for purposes of simplicity. A retaining ring 82 is threadably secured in a threaded bore portion 84 and clamps the eyepiece lens 66, spacer 76 and doublet ocular lens 74 together generally in a fixed location. On the other hand the objective lens system 46 can be selectively axially moved to provide adjustment to position the focal plane of the image of the sighted target at the desired location relative to the image erection system to be described. Of course, the axial position of the ocular lens system 64 can be varied for individual needs simply by utilizing a selectively variable adjustment for changing the axial position of the lenses in that system. As can be seen from the drawings, the main housing 16 and eyepiece housing 18 are secured together at their respective flanges 26 and 32 by a plurality of threaded fasteners 86. An annular seal 88 is located in a groove 90 and provides for a seal between the mating flange surfaces. The oblong portions 24 and 30 are formed with generally diametrically opposite circular, cylindrical portions 92 and 94, respectively. Spherically contoured seat portions 95 and 97′ are formed in these opposite cylindrical portions 92 and 94 and together define a spherical seat 96 at the juncture of the main housing 16 and eyepiece housing 18; the center X of the radius R for the spherical contour of the seat 96 is in a transverse plane 97 defined by that juncture; as will be seen the transverse plane 97 is generally coincident with the effective focal plane 98 of the objective lens system 46 of the optical gun sight 10. In order to present the viewed or final image of the sighted target to the eye with proper right to left and up and down orientation, an image erector system 100 is provided between the objective and ocular lens systems 46 and 64, respectively. As will be seen, the image erector system 100 also cooperates with the objective lens system 46 to optically locate the effective focal plane 98 with the properly oriented image of the sighted target at the desired position. The image erector system 100 is rotatably mounted within the spherical seat 96 and to this end is supported by a prism housing 102 (see Figures 4 and 5). The prism housing 102 is generally tubular and has a rearwardly extending radially open portion 104 formed with a generally spherically shaped bearing portion 106 adapted to be matably supported in the spherical seat 96 for rotational, adjustable movement about a horizontal axis 108 (Figure 3) and a vertical axis 110 (Figure 2) both extending transversely to the axis 112 of the objective and ocular lens systems 46 and 64, respectively. Note that both the horizontal axis 108 and vertical axis 110 are generally located in the effective focal plane 98. The image erector system 100 includes a prism assembly 114 which is secured within the open portion 104 of the prism housing 102. A web or rib 116 extends diagonally from the closed side of the open portion 104 to the open side at the diametrically and axially opposite end of the open portion 104. The rib 116 is provided with a generally U-shaped opening 118 at its forward end for a purpose to be seen. The prism assembly 114 is preferably generally of a Schmidt or Pechan Z type and includes a roof prism 120 and a helper prism 122. The roof prism 120 and helper prism 122 are separated by a narrow air gap defined by the U-shaped opening 118 and hence are located in spaced relationship on opposite sides of the web 116. The prism assembly 114 has a generally elongated contour having its longitudinal dimension located in the major diameter areas of oblong bore portions 24 and 30 and hence the longitudinal dimension is generally horizontally oriented. The prism assembly 114 in cooperation with the objective lens system 46 determines the location of the effective focal plane 98 and is selected to locate it substantially in coincidence with the transverse plane 97 at which the center X of the radius R for the spherical seat 96 is located; hence the prism assembly 114 receives the image from the objective lens system 46 and through a series of reflections provides an erected, properly oriented focused image which in turn provides the final image to the eye of the viewer through the ocular lens system 64. The focused image can be considered to be generally at the effective focal plane 98. Thus, as will be seen, in calibrating the optical gun sight 10, the prism assembly 114 is rotated about two axes within the effective focal plane 98 whereby the image and reticle pattern are moved to provide the desired adjustment. With binoculars or scopes using a Pechan type prism assembly, it is conventional practice to have the roof prism 120 and helper prism 122 arranged in a reverse order, i.e. the helper prism 122 is located closest to the objective lens system 46. With the present invention, however, the preferred orientation as shown locates the effective focal plane 98 within the confines of the prism assembly 114. Thus this preferred orientation facilitates calibration via an internal adjustment operating on the image erector system 100 and/or the prism assembly 114 and also facilitates in the design of an efficient ocular lens system permitting a compact structure. The various reflections between the roof prism 120 and helper prism 122 are shown in Figures 3, 8 and 9. Thus the image I on axis 112 impinges surface "a" of roof prism 120 and being normal to the surface "a" passes through without reflection along line a-b until it hits surface "b". Here the image I is reflected along a direction b-c against surface "c" of the 'roof' segment 121 of prism 120. The surface "c" is actually the peak 123 of the 'roof' segment 121. Other rays of the image I along the axis 112 are at slight angles and/or displacements to this representation, but the surfaces of the 'roof' segment 121 coact with each other to reflect from one roof surface to the other and behave in effect as though reflecting at the peak 123. Image I is then reflected from the 'roof' segment of prism 120 in a direction c-d against surface "a". The image I is then reflected along the line d-e in a direction generally normal to surface "b" across air gap 118 in direction e-f and against and generally normal to surface "f" of helper prism 122. In this regard, the opening 118 of the rib 116 is made sufficiently large to permit transmission of generally the full image as received from the objective lens system 46 by the roof prism 120 to the helper prism 122. Image I then travels in a direction f-g against helper prism surface "g" which is a mirrored surface having a silver coating. The reticle pattern 130 of Figure 7 is formed on the surface "g" by etching the pattern through the silver coating. The roof prism 120 and helper prism 122 are constructed and located in conjunction with the objective lens system 46 such that the image I is substantially focused at mirrored surface "g" and has superimposed thereon the reticle pattern 130. Now the focused image I with the reticle pattern 130 superimposed thereon is reflected in a direction g-h against helper prism surface "f". From here the image I and reticle pattern are reflected in a direction h-i through helper prism surface "i" to determine the final image as viewed by the eye through the ocular lens system 64. It can be seen that, by moving the prism assembly 114 with the prism housing 102 via the associated spherical bearing, the received image I of the target at the effective focal plane and the superimposed reticle pattern can be moved together to provide the desired calibration. As noted the image I is substantially in focus at the mirrored surface "g" and hence in a sense the mirrored surface "g" is at the focal length of the objective lens system 46 and can be considered to define a "prism focal plane". However, an unfolded analysis of the prism assembly 114 shows that the effective or 'air equivalent' focal plane 98 will be generally located at the plane 97. Generally the focal plane of the objective lens system 46 will be at the focal length of the objective lens system which is routinely determined considering the light to be traveling solely through air, i.e. no travel through glass as with prism assembly 114. The use of reflective prism surfaces, however, permits the optical gun sight to be considerably shortened while still providing the equivalent length or focal length for locating the focal plane. But since air and glass have different densities and indexes of refraction compensation must be made for the prism glass. An analysis of the compensation for the travel of light in the prism assembly 114 of a sample of the present invention can be seen in Figure 9. As noted the image I was focused at mirrored surface "g"; however, the location of the effective focal plane 98 can be determined by analysis of the light path through the prism assembly 114 in its unfolded or developed representations. Thus, in Figure 9, the roof prism 120 and helper prism 122 are shown in a developed or unfolded view with the light image I shown traveling in a straight line through the glass and narrow air gap e-f of the prism assembly 114. The distances a-b, b-c, c-d, d-e, f-g, g-h and h-i represent the distances traveled in glass by the light beam of image I. The distance e-f is the distance traveled in air across the air gap 118. The prism material for the helper prism 122 was Schott BaK 4 with a refractive index of 1.57. The prism material for the roof prism 120 was Schott BK7 with a refractive index of 1.52. The sum of the distances (g-h + h-i) from the mirrored surface "g" to the prism exit surface "i" was divided by the index of refraction for the glass and the equivalent distance B in air was determined to locate point X′ which is the point at which the focused image I would be effectively located relative to the exit surface "i" and hence provides for a theoretical determination of the location of the effective focal plane 98 within the optical gun sight 10. The noted distances for one example of the present invention are shown in the scale in Figure 9; with the noted distances being in millimeters, the distance B was 14.6 millimeters. When the distance B from surface "i" is applied to the actual prism assembly 114 (see Figures 3 and 9), the point A is located in coincidence with point X on the plane 97 which is the theoretical or effective focal plane 98 for the objective lens system 46. Note, however, that the mirrored surface "g", with the focused image and projected reticle pattern 130 thereon, is also located proximate to the plane 97 and to the effective focal plane 98. Thus the mirrored surface "g" with the focused image thereon and the effective focal plane 98 are located within the confines of the image erector system 100 and within the confines of the prism assembly 114. The roof prism 120 and helper prism 122 are initially held in place on the prism housing 102 by set screws 124. After initial assembly, the roof prism 120 and helper prism 122 are permanently fixed to the prism housing 102 via a suitable adhesive applied at openings 126 in prism housing 102 (see Figure 4). Note that the operative portions of reflective and transmitting surfaces of roof prism 120 and helper prism 122 are spaced from and are not engaged by their adjacent, confronting surfaces and similarly the operative portions of reflective and transmitting surfaces of roof prism 120 and helper prism 122 are spaced from and not engaged by the adjacent, confronting surfaces of the prism housing 102. As noted the prism assembly 114 is integrally connected with a reticle projecting structure 128 and also as noted the surface "g" of the helper prism 124 is silver coated to provide a mirror surface. A portion of the silver coat is etched away to define the reticle pattern 130, i.e. crosshairs, dots, etc. During daylight sighting the reticle pattern 130 can be naturally illuminated as black lines, dots or other indicia to the viewer. For night sighting a source of illumination 132 is provided behind the surface "g". In one form, a radioactive red tritium lamp having a half life of 12.7 years was used to provide the reticle pattern 130 in red for night sighting; other radioactive materials could be used, i.e. green carbon fourteen. Alternatively a battery operated light source could be employed. For day lighting of the reticle pattern 130 a light transmitting optic system 131 can be utilized. Thus a thin molded rod 134 has its forward end 135 located at the forward end of main housing 16 proximate to the sunshade 36. The rod 134 can be made of translucent red acrylic light collecting and transmitting material such as Rohm and Haas #577 and will generally collect light along its entire exposed length; thus the rod 134 extends outside of the housing assembly for generally the full length of the main housing 16, i.e. greater than around 50% of the housing length and preferably between around 70% to 90% of that length. The transmitting end 137 of the rod 134 extends through a boss 133 in the main housing 16 with a seal 139 sealing its entry therein. The extended length of rod 134 exposed to daylight improves the efficiency of the daylight illumination. A flexible polymer fiber optic 141 communicates the light at the transmitting end 137 to the location of the source of night illumination 132. The rod 134 is located in and protected by a clear polycarbonate shield 143 which overlays the rod 134 and is located at its forward end in a notched channel 145 at the tip of the sunshade 36 (see Figure 3A). Note that both the tritium lamp and the transmitting end of the fiber optic 141 are located behind the reticle pattern 130 etched on the back of mirror surface "g" to direct the reticle pattern 130 along the line g-h, the line of reflected image I, toward helper prism surface "f". In this way, day and night illumination can be provided to the reticle pattern 130. The reticle pattern 130 is shown to include a series of crossed lines and dots which are etched in the silver coating on the back of prism surface "g" (Figure 7). Note that with routine use of the rifle 14, the plane of mirrored prism surface "g" is substantially vertical and hence reticle pattern 130 will be substantially vertical with point A′ being generally at point A in the effective focal plane 98. Thus in the pattern 130 the line V will extend vertically while the line H will extend horizontally on the prism surface "g". Note that since the mirror surface "g" and hence the horizontal line H is skewed relative to the axis 112 there can be some parallax and difference in clarity of the focus between the extreme positions H1 and H2 of the image of the target at the mirror surface "g". This can be partially compensated by generally locating the ocular lens system 64 to be slightly, but generally imperceptibly, out of focus relative to point A whereby the image at points H1 and H2 will be generally viewed with the same clarity. Importantly, however, the vertical sighting line V will substantially not suffer from parallax. This permits the use of gradation lines V1-V4. These gradation lines can be used by the operator to compensate the vertical position of the sighting axis 112 for distances other than the distance of calibration for point A. If a significant vertical parallax condition existed such gradation lines would be of diminished value. In order to calibrate a rifle for use with an optical gun sight some means must be provided to vary the position of the final image of the sighted target and/or reticle pattern relative to the axis of the barrel of the rifle to compensate for the trajectory of the bullet. As noted, frequently this is accomplished by an external mechanism which permits horizontal and vertical movement of the entire housing and lens system relative to the line or firing axis of the rifle barrel. Other constructions have used internal adjustment means in the scope whereby the received image can be moved relative to the final image viewed by the eye. In both cases, however, the results have been bulky and/or lengthy, heavy constructions. In the present invention, the calibrating movement is provided by moving the image erector system which is generally located at the focal plane of the telescope via a pair of axes located at the theoretical or effective focal plane. The result as has been shown is a compact, lightweight structure. Thus the image erector system 100 is supported by the prism housing 102 with its spherical bearing portion 106 which in combination with the spherical seat 96 defines a spherical bearing by which the image erector system 100 can be articulated vertically and/or horizontally to provide the desired calibration for alignment purposes. The calibration and alignment are facilitated by a pair of adjustment assemblies 136 located in quadrature with each other for providing separate vertical and horizontal adjustments. The general construction and operation of adjustment assemblies, such as adjustment assembly 136, are known in the art. Looking now to Figures 2, 3 and 6, the main housing 16 has a pair of internally threaded bosses 138 adapted to receive the adjustment assemblies 136. The adjustment assembly 136 includes a hollow adaptor 140 which is externally threaded at its inner end 142 to be threadably received within the threaded bos 138. A plug 144 has a threaded, small diameter portion 146 which is threadably received within a reduced diameter threaded bore 148 at the inner end 142 of the adapter 140. The plug 144 has an enlarged head portion 150 generally located within an enlarged bore 152 at the outer end 154 of the adapter 140. A detent assembly 156 is located in a radial cross bore 158 through the head portion 150 of plug 144. The detent assembly 156 includes an adjustment screw 160 threadably movable within a threaded portion 162 of cross bore 158 and a bias spring 164 which is operative on a detent pin 166. The enlarged bore 152 is provided with a plurality of axially extending grooves 168 which are circumferentially located at preselected, equally spaced intervals. The bias on spring 164 urges the detent pin 166 outwardly from the cross bore 158 into engagement with the side wall of the enlarged bore 152 such that upon threadably advancing or retracting the plug 144 discernible physical and/or audible 'clicks' can be sensed by the operator as the detent pin 166 moves into an adjacent groove 168 to facilitate calibration. The plug 144 is provided with an engaging pin 170 at its inner most end which pin 170 is adapted to engage a raised cylindrical portion 172 at the forward end of the prism housing 102. To this end the prism housing 102 is provided with four raised, generally cylindrical portions 172 located in quadrature with each other such that two of the raised portions will be in line with the adjustment assemblies 136. Diametrically opposite each of the adjustment assemblies 136 are bias assemblies 174 which operate against associated ones of the raised portions 172 to continually bias the opposite ones of the raised portions 172 against the engaging pins 170. The bias assists in maintaining the desired vertical and horizontal orientation of the prism housing 102 and hence of the prism assembly 114. In this regard while the upper surfaces of the cylindrical portions 172 are curved in the longitudinal or axial direction of the axis 112 they are generally straight and have no curvature across their width W1 extending transversely to the central axis 112. The bias assemblies 174 are located in bores 176 in the main housing 16 and include a spring member 178 and a spring cap 180 which is adapted to engage the associated raised portion 172 in response to the bias on the spring member 178. Thus the vertical and horizontal positions of the prism housing 102 can be selectively adjusted by threading the plug 144 inwardly or outwardly with the calibration being facilitated by the discernible 'clicks' provided by the detent assemblies 156. Note that the bias of the detent assemblies 156 in the grooves 168 also helps to maintain the selected vertical and horizontal adjustment by resisting self turning of the plug 144. The plug 144 is provided with a cross slot 182 in its enlarged head portion 150 to facilitate adjustment with a screw driver like element. In order to seal the main housing 16, the adjustment assembly 136 is provided with a cap 184 which is threadably engageable with an externally threaded outer end 186 of adapter 140 (see Figure 6). An annular seal 188 is located on a smooth, intermediate portion 190 on adapter 140 and provides the desired seal for the adjustment assembly 136 and the main housing 16. The seals 58, 70, 88 and 188 can be of a design and type selected by those skilled in the art; however, in a preferred form, standard, industrial sized seals of 1.78 millimeters of minimum diameter were used. The seals were in accordance with Military Specification MIL-R-25988, Type 1, Class 1, Grade 70 according to AMS3304. Silicone rubber was selected for operation in the extreme hot and cold temperatures. Thus it can be seen that calibration can be readily provided by simply rotating the image erector system 100 via the spherical bearing assembly as noted. In addition since the reticle projecting structure 128 is integrally connected with the prism assembly 114 movement of the prism assembly 114 and prism housing 102 will result in a similar movement of the reticle projecting structure 128 and its associated illumination source 132. In this regard it should be noted that calibration is effected by moving the image relative to firing axis 169 of the rifle 14 with the reticle pattern 130 remaining in the same position relative to the scope axis 112, i.e. traditionally in the center of the image viewed by the operator through the ocular lens system 64. Note that location of the received image at the theoretical or effective focal plane 98 in the plane 97 of the center of rotation X for the spherical bearing about the two axes 108 and 110 enhances the accuracy of the calibration. Likewise location of the plane of the mirrored surface "g", which receives the focused image and generates the reticle pattern 130, at or proximate to the plane 97 of the center of rotation X of the spherical bearing assembly enhances the accuracy of calibration. Thus accurate calibration will result from the selective, adjustment movement of the final image and reticle pattern 130 as observed through the ocular lens system 64. It should be noted that for convenience the calibration adjustment has been referred to as being in vertical and horizontal directions; more generally, the calibration is provided in two transverse directions which in turn are transverse to the central axis 112 of the housing assembly, i.e. housings 16 and 18, to permit adjustment of the position of the image of the target and reticle pattern 130 relative to the firing axis 169 of the barrel 49 (partially shown) of the rifle 14 whereby compensation can be provided for the trajectory of the bullet to the target. In one form of the invention the objective lens system 46 and ocular lens system 64 were selected to provide a telescopic effect with a magnification ratio of four to one; however, it should be noted that the principles of the present invention are readily applicable to optical gun sights of different magnification ratios including one to one.

Claims: An optical gun sight (10) for attachment to a manually portable gun (14) having a firing axis (169), comprising: a tubular housing (16,18) having a generally elongated and hollow housing section (16) for sighting a target at its forward end whereby an image of such target is viewable at its rearward end, said tubular housing means (16,18) having a securing section (38) for securement of said gun sight (10) to a gun (14), an objective lens (46) located at the forward end of said hollow housing section (16) arranged to provide a substantially focused image of the target at a preselected plane (98) at a predetermined location within said hollow housing section (16), an ocular lens (64) located at said rearward end of said hollow housing section (16) through which an image of such target is viewable, an image erector assembly (100) located within said hollow housing section (16) intermediate said objective (46) and ocular lens (64) to provide a properly oriented image of the target to the viewer through said ocular lens (64), and internal adjustment means (136) operative on said image erector assembly (100) and selectively operable for moving said image erector assembly (100) in two transverse directions which are in turn transverse to the central axis (112) of said tubular housing (16,18) to calibrate the position of the image of the target relative to the firing axis (169) of the gun (14) whereby compensation can be provided for the trajectory of the bullet to the target, said optical gun sight being characterised in that said image erector assembly comprises a prism assembly (114) having a plurality of light transmitting and reflective surfaces (a,b,f,g,h,i), said image erector assembly (100) being operatively associated with said objective lens (46) to receive the image of the target from said objective lens (46) and to provide and locate the image of the target at said preselected plane (98) at said predetermined location within said axially extending length of said image erector assembly (100) to provide a properly oriented image of the target for viewing through said ocular lens (64). An optical gun sight according to claim 1, wherein said plurality of light transmitting and reflective surfaces (a,b,f,g,h,i) include a first (a) and a second (i) of said surfaces axially spaced along said central axis (112) and defining the axially extending length of said image erector assembly (100), said prism assembly (114) and said light transmitting and reflective surfaces including said first (a) and second (i) of said surfaces being connected together in a prism housing to provide said image erector assembly (100). An optical gun sight according to claim 1 or 2, further comprising reticle projecting means (128) providing a reticle pattern with the image of the target from said objective lens (46), said reticle projecting means (128) being supported for movement with said image erector assembly (100) and being located within said axially extending length of said image erector assembly (100). An optical gun sight according to claim 3, further comprising illumination means (132) for illuminating said reticle pattern and connected with said reticle projecting means (128) for movement with said image erector assembly (100). An optical gun sight according to claim 3 or 4, wherein said prism assembly (114) comprises a roof prism (120) and a helper prism (122), said light transmitting and reflective surfaces (a,b,f,g,h,i) are defined by surfaces on said roof prism (120) and said helper prism (122), said reticle projecting means (128) comprise a mirror surface (g) on one of said prism surfaces on said helper prism (122), and said prisms (120,122) provide a substantially focused image of the sighted target on said mirror surface (g) of said reticle projecting means (128). An optical gun sight according to claim 5, when appendant to claim 4, wherein said illumination means (132) comprises day illumination means (131) including a light collecting and transmitting rod (134) located at a forward portion of said hollow housing section (116) and extending into said hollow housing section (116) at a position proximate to the back of said mirror surface (g) and includes a flexible fibre optic (141) connected to said collecting rod (134) and communicating the collected light to a preselected position behind said reticle pattern. An optical gun sight according to any preceding claim, wherein said internal adjustment means (136) comprises support housing means (92,94) supporting said image erector assembly (100) and a spherical bearing structure (96,106) connecting said support housing means (92,94) with said tubular housing means (16,18) for selective movement of said erector assembly (100) in said two transverse directions, first (a) and second (i) of said surfaces of said image erector assembly (100) being generally axially located within the confines of said spherical bearing structure (96,106). An optical gun sight according to claim 7, wherein said tubular housing means (16,18) comprises a forward housing member (16) having a forward connecting portion (26) and a rearward housing member having a rearward connecting portion (32), and connecting means connecting said forward (16) and rearward (18) housing members together at said forward (26) and rearward (32) connecting portions, said forward and rearward housing members (16,18) having generally spherically contoured internal surfaces (95,97') located generally at said forward and rearward connecting portions (26,32) to define a spherically contoured bearing seat (96), said image erector assembly including a prism housing (102) having a generally spherically contoured external surface matably received within said spherical bearing seat (96) to define therewith a spherical bearing, the image erector assembly being movable in said spherical bearing by said internal adjustment means (136). An optical gun sight according to claim 8, wherein said prism assembly (114) includes a roof prism (120) and a helper prism (122), said prism housing (102) being generally tubular in construction and having a rearward portion having a circumferential opening with a web (116) extending longitudinally, diagonally across said circumferential opening, and said roof prism (120) and said helper prism (122) being supported in spaced relationship on opposite sides of said web (116). An optical gun sight according to claim 8 or 9, wherein said prism housing (102) includes a plurality of engaging surfaces (172) located in quadrature with each other, and said internal adjustment means (136) further includes adjustment assemblies (140,144) supported in said forward housing member (16) and including radially movable adjustment members (144) engageable with said engaging surfaces (172) for providing selective movement of said prism housing (102) and hence of said prism assembly (114) and of said preselected plane (98) in said two transverse directions.

Inventors: BINDON GLYN AUBREY JOHN, BINDON, GLYN AUBREY JOHN
Applicants: TRIJICON INC, TRIJICON, INC.
Application year: 1988
Main classification: F41G1
IPC codes: G02B27, F41G1, G02B23