Feb. 5, 1952‘ R. TOUSEY 2,584,171 GUN SIGHT HAVING A PLURALITY OF ILLUMINATED RETICLES Filed Feb. 25, 1943 2 SHEETS-SHEET 1

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RICHARD TOUSEY Feb.5, 1952 R. TOUSEY 2,584,! 7.1 GUN SIGHT HAVING A PLURALITY OF ILLUMINATED RETICLES Filed Feb. 25, 1943 2 SHEETS—-SHEET 2

QWWM ? RICHARD TOUSEY / 131E 3%, WI?Q/é WW Patented Feb. 5, 1952 2,584,171

UNITED STATES TENT oFFicE ‘2,584,171 GUN SIGHT HAVING A PLURALITYOF ILLUMINATED .RETICLES Richard Tousey, Forest Heights, lMd. Application February 25, 1943, Serial No. ‘477,030 3 Claims. (01. 88-23) .(Granted under the act of March 3, <1.883,:as amended April 30, 1928,; .370 0. G. 757) 2 This invention relates to an optical ‘device and ‘are received as such by the eyes of ‘the capable of projecting a virtual image at an in? observer. nite distance, and it is particularly concerned Brie?y, the invention comprises va system of with anew type of alignment device or gun sight identical, aligned pictures (by which ‘is meant any which permits greater freedom of movement of kind of two-dimensional representation, includ the observer than conventional types. ing real images formed by lenses) and an array For certain types of guns the old style sights of convex lenses all of substantially the same focal placed in the path of vision ‘have long since been length and lying in the same plane. Each lens is discarded. in favor of optical systems which pro axially aligned with one picture and ‘the system ject a luminous reticle on the target in the form of pictures ‘is positioned so that each individual of a virtual image. An inherent advantage of picture lies at the focal distance from its ‘lens. such a system is its freedom from visual obstrucn The pictures may be illuminated in any conven— tion, that is, the gunner has a‘ clear ?eld of View tional way so that they may be ‘visible through at all times. ‘By design of ‘very large lenses and‘ the lens array, and where the device is to be used complicated lens systems it has ‘been possible to - as a gun sight, one or more partially re?ecting project the virtual image of the reticle in such surfaces are employed to project the virtual image a manner that the gunner need not ‘keep his eye of the picture at a substantially in?nite distance in one exact position, but he may move his ‘head, against the vbackground or target observed by perhaps two or three inches, away from dead vision through the partially re?ecting surface. center and still see the image of the reticle super- ' In order that the invention may ‘be clearly imposed on his target. However, the'best of these understood its theory of operation and construc sights heretofore designed requires complex lens ticn are described ‘in detail with reference to the systems of wide aperture, with consequent cost accompanying drawing, vinwhich: liness of production, and even then does not pe - '1 is a schematic diagram illustrating the mit ‘the gunner to move his head very far from optics of the lens array; center without losing the image of the reticle. Fig. 2 is a schematic diagram illustrating the This restriction is often very annoying to gunners, optics of multiple partially re?ecting surfaces particularly where they are located on fast mov and the e?’ect of lens placement on image ing craft, because they either must concentrate illumination ; in maintaining a certain relative body position a Fig. 3 is a diagram illustrating the placement or lose the gun sight, either of which often results of a picture or reticle in the focal surface of a in poor aim. lens, and This invention provides an ‘optical device which ‘Fig. 4 ‘is a drawing in perspective of a complete is capable of projecting a ‘virtual image at an gun sight made in accordance with the invention. in?nite distance in such a manner that it ‘may Referring to Fig. 1, a simple lens array In is be seen by the observer, ‘not only from a centered shown in section and parallel to a system of pic position, ‘but from any position to one side or tures or images H (shown as small arrows). The another (which includes backward or forward) individual lenses in the array I!) all have the same from the center, with as far a displacement as is focal length. Each picture or arrow in the sys desired. The appartus is particularly adapted as 40 tem ii is axially in alignment with an individual a gun sight inasmuch as changes in the gunner’s lens and is spaced a distance equal to the focal position do not introduce parallax, or throw the length (I) away from the ‘lens. Also all arrows image of the reticle o? of the target, and a par are ‘orientated in the same direction. According ticularly valuable feature resulting from this fact to the optics of convex lenses it is seen that, with is that the gunner may employ both eyes in nor 45 the arrangement described, all rays of light com-i mal manner in training the gun. Other advan ing from corresponding points of all pictures and tages include its small height, fewer lens surfaces passing through the lenses ‘will leave the lens per reticle and consequent more brilliant, trouble array parallel to one another. This ‘is shown free image. The apparatus of this invention may schematically for points at the ends and center be employed for many kinds of alignment prob 50 of each arrow, solid lines representing rays from lems, of which training a gun is only one. the center points, dotted lines representing rays By the term “in?nite distance” it is meant that from the heads of the arrows and dot-dash lines rays of light emanating from a single point of indicating rays from the tails of the arrows. If the picture or real image being ‘projected emerge any of these parallel rays now enter an observer’s from the apparatus in substantially parallel rays eye, say at a position 12, the observer will view 2,584,171 3 4 parts of several arrows so aligned that a single plane, since the reticle may be ruled or photo virtual image l3 appears, and the image l3 always graphed on a plastic ?lm especially shaped to remains directly in front of the observer no lie in the focal surfaces of the lens array. Such matter where the observer may move from the an arrangement is illustrated for a single lens position l2, until he has moved so far that the and reticle in Fig. 3, in which a transparent sup parallel rays no longer enter his eye. Since the port 30 has a curved depressed portion 3| on rays from corresponding points on the arrows are which the reticle (or other picture) is printed, parallel the image I 3 will appear to be at an in? engraved, or otherwise placed. The portion 3! nite distance from the observer, that is, super lies at the focal surface of a lens 32. If desired, imposed on a distant object, and because the 10 the entire system of reticles may be stamped from image l3 does not shift across the distant object a metal sheet, with the reticles cut through the as the observer moves, the observer (e. g. a gun depressed parts which ?t in the focal surfaces of ner) is free to move any distance within the limits the lenses. of the lens array without encountering parallax In Fig. 4, a complete gun sight is shown in or losing his “bead” on the distant object. 15 perspective, certain obvious supports having been From theoretical considerations it is obvious omitted and other parts broken away for the that the image 13 does move across the distant sake of clearness. A lens array 40 is shown in object with respect to the lens array, and this a square pattern although the hexagonal array displacement is actually equal to the movement 26 of Fig. 2 could equally well be used. The in of the observer. However, for observer’s move 20 dividual lenses of the array 40 are shown with ments of a foot or so the angular shift of the out support to simplify the drawing, but they image !3 is negligible when superimposed on may be mounted, for example, by cementing them objects at an appreciable distance, and for gun to a plane sheet of glass (the cement or pitch nery from moving vehicles an error of a foot at being placed in the voids between adjacent lenses) , a distance, say, of a thousand yards is less than or the entire array may be molded from a sheet the unavoidable errors in aim. of clear plastic, the lenses then being integral Where circular lenses are used to build up an with the sheet. array there are unavoidable spaces or voids be Below the array 40 is a system of reticles 4i tween the lenses, which preferably should be ren positioned with respect to the lenses as described _ dered opaque to avoid stray light from interfer 30 with reference to Fig. 1 or Fig. 3. The system :35 ing with observation of the image. These voids may be a photographic reproduction or an em will not in any way disturb the single virtual im graving or any other preparation which is trans~ age seen by the observer, unless they are at least >lucent or transparent and will permit illumina~ as large as the lenses themselves in aperture, and tion of the reticles by transmitted light. Any this will not be encountered if the lenses are CA! Ur translucent support, such as glass or various placed adjacent each other. The voids will, how plastics may be used, and a sheet of molded plas-i ever, have some effect on the brightness of the tic, or stamped metal with the reticles cut virtual image, but, their effect can be minimized through, is preferred where the reticles are to or even eliminated from the practical standpoint be curved as described with reference to Fig. 3. by observing the image by means of a plurality Below the system 4| is a source of illumination of parallel partially re?ecting surfaces, as is comprising lamps 42, a re?ector 43 and a diffuser shown in Fig. 2. The voids can be eliminated by 44, of conventional design to furnish substan cutting the lenses in a square or hexagonal shape. tially uniform illumination of the system of reti~ In Fig. 2 a lens array 20 is shown in simpli cles 4|. ?ed form below a pair of reflecting surfaces 2| Above the lens array 40 is a plate 45 of glass and 22 which may be the surfaces of a sheet or clear plastic having plane-parallel surfaces of glass 23. Arrows indicate the paths of center and rigidly mounted with respect to the array 48 rays, part of which are re?ected from the sur and system 4'. When this device is placed so face 2! and part from the surface 22. To an that the ?eld of view or target is observed through observer the lens array appears overlapped, as the plate 45, say from the position 46, a luminous shown by images 24 and 25. If the lens array reticle image 4'!’ appears superimposed on the 25 is in the closest spaced form (i. e., triangular distant target. Lines drawn from the position 451' or hexagonal pattern) the overlapping caused by to the plate 45 and thence through ?ve adjacent the re?ection from the surfaces 2| and 22 prac lenses to corresponding reticles indicate the for tically eliminates noticeable variation in virtual mation of the image (see also Fig. 1) . image brightness, whereas a “square” array re Due to the closeness of the reticles it is ofteri quires more reflecting surfaces (e. g. two parallel possible to see them through lenses other than sheets of glass, giving four re?ecting surfaces) the axially aligned ones, and this causes the ap to reduce the effects of the voids to the same ex pearance of spurious images displaced laterally tent. The effect of the two re?ecting surfaces 2 IV from the true one. The spurious images are and 22 on hexagonal and square arrays 26 and easily obviated by enclosing the space between 2'! is shown in corresponding double images 28 the lens array 40 and the system of reticles M and 29, respectively, the voids in each case being with a set of shields or partitions arranged in ?lled in for easy identi?cation. It is obvious that a “honeycomb" so that only rays from the proper the amount of overlap of the reflections depends reticle can pass through each lens. Such a hon on the spacing between the parallel re?ecting eycomb shield is shown as a shield 48, partly surfaces, and an optimum spacing (or thickness broken away to simplify the drawing. of the re?ecting glass) is easily found for a given In the lens array 40 the individual lenses lens array and angle of re?ection. may be of the simplest type, but for the most For extreme accuracy, such as is required of 70 accurate gun sight the lenses should be of the certain types of gun sights, it is generally more achromatic type and also corrected for spherical convenient and economical to design the reticles aberration. A satisfactory compound lens of‘ so that they will lie in curved focal surfaces of this type has been found to be the typical ob the lens array, rather than to design a complex jective lens of any good grade of ?eld glasses, lens system whose focal surfaces approach a 75 these being generally two or three componentv 2,584,171 5 6 cemented systems. Compound lenses also ma)r ole-lens system, all of said lenses being arranged be molded from two or more plastic sheets of ' to lie in the same plane and all of said reticles different densities, and the sheets cemented to- v being arranged to lie in a plane parallel to said gether to form the complete array. lens plane, the elements of the system combin For use, the gun sight is rigidly mounted on ing light from an object viewed through the re the gun carriage (or other support whose posi- ‘ ?ector with light from-the reticles to give a tion follows that of the gun) and the partly re virtual image of a single reticle superimposed ?eeting plate 45 (or the whole instrument) is on the object viewed. adjusted until the reticle image appears exactly 2. A gun sight comprising a plane transpar on the target, for whatever range is desired. ent re?ector placed to be used as a viewer, a Then the plate 45 (or entire instrument) is plurality of substantially identical small lenses rigidly clamped in place. arranged in a plane which determines an angle The means selected for illuminating the reticle with the viewer, a plurality of small reticles cor system will depend on what is the most con responding in size to said lenses to form a plu venient under the circumstances. A simple ': rality of substantially identical reticle-lens pairs, means is shown in Fig. 4, but any other means arranged in a plane parallel to said lens plane of obtaining fairly uniform illumination may be ' each reticle being centered with respect to the used, such as a single lamp and full parabolic axis of a corresponding lens, shields separating re?ector, individual lamps for each of they the lens-reticle pairs from each other, and an reticles, or the sky itself may be employed. In'{ I20 illumination system beneath said reticle plane, the latter case the gun sight is mounted in an said reticles, lenses, and viewer cooperating to inverted position without the lamps 42, the re combine light from an object viewed with light ?ector 43 and the diffuser 44 so that sky light from said illumination system to give a virtual or sunlight may fall directly on the reticle sys image of a single reticle superimposed thereon tem. Alternatively, mirrors may be used to di when viewed through any portion of the viewer. rect the light against the reticle system, and a .. 3. A gun sight comprising a plane transpar fairly constant degree of contrast between image ent reflector placed at an angle to the line of and target may be obtained by re?ecting light sight, a plurality of small convex lenses having from the target area itself onto the reticle sys the same focal length and the same diameter ar tem. In such an arrangement (as well as 34% ranged to lie in a plane parallel to the line of others) it is desirable to increase the re?ec sight, a plurality of small reticles corresponding tivity of the surface 45 so that the image can in size to the said lenses arranged to lie in the be seen with a minimum of reticle illumination. focal plane of said lenses each reticle center be The surface 45 may be partially silvered, but a ing aligned with the center of a corresponding more e?icient combination of re?ection and " lens, said arrangement of reticles, lenses and re transmission is obtained by depositing a highly ?ector cooperating to combine light from an re?ecting ?lm on the surface 45, such as tita object viewed through said re?ector with light nium dioxide or zinc sul?de (or other high from said reticles to give a virtual image of a density, transparent substance). single reticle superimposed on said object. If the gun sight is to be used in aircraft of ~10 RICHARD TOUSEY. the ?ghter type, where the guns are ?xed in the direction of ?ight, the pilot’s windshield itself REFERENCES CITED may serve the function of the partially reflect; ' The following references are of record in the ing surface 45. However, the device is not as file of this patent: ?exible in operation if the windshield is used 45 to direct the virtual reticle image because against UNITED STATES PATENTS a brilliant background, such as sunlit clouds, it’ Number Name Date \ may be so di?icult to distinguish the reticlev Re. 19,070 Chretien ______- Feb. 6, 1934 image that it is necessary to reduce the back; 533,324 Stevens ______Jan. 29, 1895 ground brilliancy by means of tinted glass or ' 50 683,203 Grubb ______-_ Sept. 24, 1901 other optical ?lters, and it is seldom desirable 922,938 Mustin __"______May 25, 1909 to tint the windshield permanently. On the, 1,610,532 Russell et al. ______Dec. 14, 1926 other hand a separate re?ecting surface 45 may 2,071,676 Williams ______Feb. 23, 1937 be tinted to reduce background glare without 2,190,569 Macgill ______Feb. 13, 1940 53 dimming the reticle image and can be substié 2,198,714 Williams ______Apr'. 30, 1940 tuted by clear material (or a ?lter removed) 2,251,984 Cleaver et al. ______Aug. 12, 1941 whenever the background illumination is low. " 2,281,474 Cartwright et al. ____ Apr. 28, 1942 Many variations will be apparent to those, 2,313,204 Morelle ______Mar. 9, 1943 skilled in the art, and the invention should not’ be limited other than as de?ned by the ap; 60 FOREIGN PATENTS pended claims. Number Country Date The invention described herein may be manu 21,456 Great Britain ______Sept. 20, 1909 factured and used by or for the Government of 15,708 Great Britain ____ .. Nov. 6, 1915 the United States of America for governmental 437,444 Great Britain ______Oct. 28, 1935 purposes without the payment of any royalties 65 147,613 Austria ______Nov. 10, 1936 thereon or therefor. 828,107 France ______Feb. 7, 1938 I claim: 1 1. An optical alignment apparatus comprising OTHER REFERENCES a source of illumination, a plurality of substan-__ Pfund in J. O. S. A., vol. 24, April 1934, pages tially identical reticle-lens pairs in which the 99, 100. Photostatic copy in 88/1. reticle is positioned axially with respect to its Cartwright et al. in Bulletin Am. Phy. Soc., associated lens, and a plane transparent re?eef vol. 14 #2 April 1939, page 24, article 92. (Pho tor arranged at an angle to the axis of the reti-, tostatic copy in 88-1.)