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July 9; 1946. S. M. MacNEILLE " 2,403,732 f RA'NGE FINDER ‘ Filed March 11, I944 HGJ. 1 ' V ' | >2? STEPHEN M.MACNEILLE 75/ v\ / ‘ . 75%24 \ /65‘ 64 INVENTOR BY‘WMW I ATT’Y & AG’T ‘July 9, 1946. i s. M. MacNElLLrEi » 2,403,132 _ RANGE FINDER Filed March» 11', 1944 _ >FIG.4. ' s Shéets-Sheet 2 FIG.5. STEPHENMJMCNEILLE - INVENTOR ‘ BY myéw/ ATTY¢§ AG'T July. 9, 1946. s. M. MaQNIEILLE > 2,403,732; RANGE FINDER 3 Sheets-Sheet 3 _ FiledMarch 11, 1944 FIG. 10‘. oa/nu w f /./ mm.” .. M \A. 1 |0 M w 2 w a 7.. 3 cc:2,hc:s: m, m w m . S .T v. W W mM MM M“ m .G i Patented July 9, 1946 , r 2,403,132 UNITED STATES PATENT OFFICE 2,403,732 I RANGE FINDER ,. 7 Stephen M. MacNeille, Oak Ridge, Tenn, assign or to Eastman Kodak Company, Rochester,v N. 11, a corporation of New Jersey Application March 11, 1944, Serial No. 526,020 ' 12 Claims. This invention relates to range ?nders. This (c1. 88-_-2.'7) 2 I posite directions. ' If, due to the presence of suit applicationis a continuation in ‘part of one entitled “Range ?nders,” 'case P, Serial No. able objectives, an image is formed at or near the combining re?ector, it. is obvious that the rota 505,016, ?led October 5, 1943, and in the series it replaces that application and becomes case P. The object of the present invention is to pro effect. However, the effect is the same where ever the images are formed and the prism unit tion of the beams gives the required invert ?eld vide an accurate range ?nder of the invert split ?eld type primarily for an ortho-pseudo-stereo ?nder but also usefulin those of the coincidence used can actually be anywhere in the beams with respect to these images; in fact, the light may be I - colllmated as it travels through the prism unit. One embodiment of the invention has the prism 10 type. . in the converging beam optically following a pair Most ortho-pseudo-stereo range ?nders in the of relay lenses which ‘form images in the focal past have had independent means for forming planes of the eyepieces. This embodiment re; the right and left eye ?elds, or as in-case K, Serial quires the ?eld separating means to be located No. 479,101, ?led March 13, 1943, Mihalyi and at the primary images, i. e. to have the primary‘ MacNeille, have had two ?elds with a relay lens 15 images opaque over one-half of their. total area system to image each ?eld adjacent to the other. and requires the dividing line'to be. carefully It is an object of thepresent invention to pro adjusted. A second embodiment has the images vide a system for producing both the right and formed at or near a beam combiner, with an left eye ?elds in a single plane. It is a primary additional set of relay lenses for relayingv these object to do this in a symmetrical manner, 20 images to‘the eye pieces. Since the images are thereby eliminating many of the errors which in the same prismunit and since the opaquing arise in unsymmetrical range ?nder systems. of half of each ?eld'is accordingly provided by It is an object of the preferred embodiment masks on this prism unit, the dividing line can be of the invention to provide such an arrangement carefully adjusted once and for all when the which is as simple and as compact as possible and 25 [prism assembly is made and will remain ac which may be made up from a number of identi curate probably for the whole life of the instru cal prisms. One preferred embodiment of the ment. invention re-employs a polarizing beam splitter If the ?nder is to be used as a coincidence type, such as described in copending application Serial the pair. of images are viewed from one side of No. 481,391, ?led by me on April 1,1943, or such 30 the combining re?ector, whereas if the instru as a Nicol prism arranged to allow both the ordi ment is to be used as a stereo range ?nder, means nary and extraordinary rays to emerge. The beam splitter described in my copending a-ppli- ' are provided for viewing both beams from one side of the re?ector with one eye and both beams cation is the preferred one because of the pos the other side of the re?ector with the sibility of selecting any desired angle ‘of in 35 from other eye. , Preferably, a similar pair of re?ec It consists of .cidence within a wide range. tors is included optically to follow the beam alternate layers of materials of high and‘ low combining re?ector, to receive the light from, indices of refraction with thicknesses approxi each side thereof and to send two beams out in mating that e?ectively equal to one quarter of opposite directions along a second optical axis 40 the wave length of light so that by optical inter parallel to the original one. > > ference, the composite multilayer material selec The actual orientation of the two re?ecting sur tively re?ects and transmits light of opposite ‘ faces which receive the light beams from the polarizations. viewing points andsend them to the combining According to the present invention the range ?nder is made up with two viewing points and 45 re?ector depends on the angle at which the beams strike this re?ector. If the angle between each some means such as pentaprisms for directing of the light beams and the re?ector is A, then, in the light beams, received from the target being each beam, the pair of re?ecting surfaces should ranged, directly toward each other along an form a dihedral angle whose cosine is equal to optical axis. To one side of this axis and co planar therewith, there is located a semi-trans parent, semi-re?ecting‘ mirror to act as a beam combiner. In line with each beam are two re ?ectors such .as prisms oriented to re?ect the beams to the combining re?ector from opposite sides and to rotate the beams through 90° in op 55 i/% sin% 3 2,403,732 I have found in practice that the angle whose cosine equals 4 may be used for this purpose including double re +/% sin 42 lay systems. By means of prism units 25 and 26, light from the right and left viewing point image planes is directed respectively to opposite sides is quite satisfactory. For convenience and to per of a beam-combining re?ector 24 which is located co-planar with the axis 55 and to one side thereof. mit the eXit system to be symmetrical with the The path of the light is perhaps bestseen in Fig. entrance system, I preferably arranged the angle 3. As the beams strike the beam-combining re between the incident beam and the combining re ?ector 24 they are both in a plane which is orthog ?ector to be 45°. In this case the dihedral angle 10 onal to the axis I5 and, in this plane, they strike between each pair of re?ecting surfaces in the the re?ector 24 at an angle A. Each beam is split entrance system should be 62°19’, ‘78°58’, 101°D2’ by the combining re?ector 24 so that through or 117°31'.v In the most preferred form of the in prism 21 parts of each beam pass to the right eye vention I arrange the prisms so that the angle of and through prism 28 parts of each beam pass to incidence at each of the two re?ections are equal. the left eye. Additional prisms 3Z8, rhombs 3i In this case the prisms which constitute the re and eyepleces 32 have been provided to permit ?eeting surfaces can all be made identical to each stereo viewing of these images. other, although their shape is somewhat unusual The actual ?elds of views 35 and 3% are shown when they are out to be, as compact as possible for in Fig. 2. The image 28 from the primary plane i2 any given aperture. _ 20 is split by the semi-re?ector 24, so that the right The prism unit for combining these light beams eye sees the image .20 by reflection and the left eye is useful in any‘ system where two beams ap~ sees it (marked 29' in Fig. 2) by transmission. proach each other and are to be combined sym Similarly, the left eye sees the image 21 by re?ec metrically. ‘ tion and the right eye sees it (marked M’) by The invention will be fully understood from the‘ 25 transmission. In the prism unit 25 the light from following description of the preferred embodi the image I2 is re?ected twice before it strikes the ment thereof when read in connection with the beam-combiner 24, the two re?ecting surfaces be accompanying drawings, in which ing oriented to rotate the beam through 90°. From Fig. 1 is a plan view of an optical system for an the symmetry of the arrangement, it will be seen ortho-pseudo-stereo range ?nder incorporating that the beams are rotated in opposite directions a simple embodiment of the invention, Figs. 1A so that‘, the images are inverted one with respect and 1B showing the ?elds in the primary image to the other and do not overlap because of the planes thereof. masking of the lower half'of each of the primary image planes. Fig. 2 shows a binocular field of view through the instrument shown in Fig. 1. ’ In addition to all of the advantages of ortho Fig. 3 shows diagrammatically an end View of pseudo-stereo range ?nders combined with the the prism unit shown in Fig. 1. advantages of invert ?eld range ?nders, the Figs. 4 and 5 are perspective views shaded to present system has the advantage of symmetry, show the structure of the prism unit and vcorre namely, constancy of image size, uniformity of sponding respectively to the views shown in Figs. 40 illumination and balancing out of various errors 1 and 3. and aberrations. Each eye sees an invert ?eld Figs. 6A to 6F are various views of the indi which may be separately used for simple coinci~ vidual prism units, eight of which are combined dence type of ranging. with the simple unit shown in Fig. 7 to form the In Figs. 1 to 3, the actual angleA is not speci total unit shown in Figs. 4 or 5. ?ed and the re?ections in the prism units may Fig. 7 shows a prism unit in the cemented sur be at different angles of incidence. However, if face of which is included a semi-transparent, for the sake of symmetry, one further speci?es beam-combining re?ector. that the angles of incidence at each re?ection Figs. 8 and 9 show an alternative embodiment be equal, and the angle A be 45°, then the simplest using simple mirrors in place of prisms and illus form of prism unit which can be made up from trating the rotation of the beams. eight identical prisms and a pair of right angle Fig. 10 is similar to Fig. 1 and illustrates a'pre prisms having the beam combiner cemented and ferred embodiment of the invention. hypotenuse surfaces is shown in Figs. 4-7. Light Fig. 11 is similar ‘to Fig. 5 but corresponds to the embodiment shown in Fig. 10. Fig. 12 is a perspective view corresponding to Figs. 4 and 5 (or to Fig.’ 11). In Fig. 1 light from a target being ranged is received at spaced viewing points, by optical squares l0 and directed through objectives ll into focus in right and. left ?elds l2 and 13 re spectively, adjacent to which are located ?eld lenses. The deviation of one beam relative to the other is provided in the usual way by a light de viator I4. It will be noted that the two beams are directed exactly toward each other along optical axis l5 and are not offset in any way. Figs. 1A from the left viewing point is re?ected by prisms 4t and 4! through prism M to the beam-combin ing re?ector 24 and similarly light from the right viewing point is re?ected by prisms 42 and 43 through prism 45 to the other side of the beam combiner 24. An identical exit system is made up of prisms Alt, 4?, 48 and 49. The details are shown in Figs. 6 and 7. Each prism unit is essen tially a simple one with entrance and exit faces 50 and 52 and a single internal re?ecting surface 5!. To permit assembly of the prisms in the minimum space, corners of each prism not used for transmitting light are cut away. Further more, to permit the eight re?ecting prisms to be identical, certain additional facets are cut un necessarily on the outer prisms, 4i} and 132, say, but which correspond to necessary facets on prisms 4i and 43 to permit assembly; Similarly, certain and 1B show the two ?elds l2 and 13 with images 20 and 2! of the target respectively in each ?eld. The lower half of each ?eld is masked off so that when the two ?elds are brought together in in: verted relation, there will be nooverlapping of the images. Relay lenses 22 and 23 are employed facets which are necessary .on the outer prisms to re-image the light beams in the focal plane of appear on the inner .prisms'but are unnecessary the eyepieces, but various other optical systems 75 here. 2,403,732; 6 bly in the form of a biconcave or plane-concave. ~-lnfFigs.i 8- and Qasimpli?ed form of ‘them airspace if this is desired. vIn any case the lenses vention is shown in whichrthe light beams from image's-'80 and T0 traveling towardv eachother' 82,- 83 and '85 should be’ of su?icient diameter to ‘utilize substantially 'all'of the entrant and exit faces- of the prism assembly, along axis 15 strike mirrors '81 and »'H,-respe'c 'tively, the orientation of the beams at this sur In' Fig. 10 the whole lens system between‘ the. face being shown by arrows 62 and ‘I2. 1 The re flected beams then strike mirrors~83 and ‘I3 re-v spectively, the orientation being shown by ar rows 64 and ‘I4 and travel thence to the beam combining re?ectorv 24 to strike opposite sides viewing points‘ [0 and the ‘prism unit, can be considered as one for forming ‘the vimage near the beamcombining re?ector. That- is, the pri mary images themselves’ may be formed in- the .prism~84\by~ a single lens in place of the lenses thereof-with the beams 65 and 15 inverted rela " " tive to‘ one another. If the lower half of ‘each ' 'll,80'and82.1 ' When the beam combining re?e'ctoris oflthe of the images 60 and ‘I0 is masked off as in Fig. polarizing’ type, the adjacent'image plane may 1, the resulting beams at the beam-combiner-24, 15 be in the position shown with masks 81 and 88 or wherever the actual images are formed, are of for cutting off complementary halves or alter the split-?eld invert-type. -~ ' I natively may be anywhere in the‘ unit includ ‘In a preferred embodiment of the invention, the ing- planes optically following the beam com beam-combiner 24 is made of- an optical inter bining re?ector. For example if the; images ference multilayer ?lm to re?ect and transmit light of opposite polarization.’ The focal planes 20_ I2 and I3 may then be optically after the prism unit and separation of they ?eld is then provided by two polarizing ?lters, respectively, over each are formed on the exit faces of the prisms 84 in stead of on the entrant faces, the masks 8'lland 88 should ' be omitted. The complementary masking is then done‘by polarizing ?ltersvover the exit faces as'shown'by broken lines. I These half of each ?eld with their vibration axes mutu 25 broken-lines are drawn partly with long sections , ally at right angles. It will be noted that no and partly with short sections= to ‘represent polarizing ?lter or other selecting‘ ?lter is neces schematically the orientation of the vibration: sary in‘ embodiments of the invention wherein the » axis of the ?lters. The sections labelled 108 focal planes I2 and 13 are ahead of ‘the prism - will serve to illustrate the function of the polariz unit and are masked over half of their ?eld. ' In Fig. 10 ‘the primary images are formed on ?eld lenses 8!] and’ 8| which differ from Fig. 1 by the fact that there is no opaque mask cover ing half ‘of the images at these points. These 80 ing ?lter in this embodiment; Primarily-the polarizing ?lters must have exaetly'the vsame action as the opaque masks 81 and 88.» That is the ray 94 must be transmitted by the “filter I00, both the part re?ected and the part trans images are relayed by lenses 82 and 83, which 35 mitted at the beamwcombirling re?ector 86. -_The are of shorter focal length thanthe correspond part re?ected at the surface 86 due to the polar ing lenses of Fig. 1, so that in the presentcase izing action of this surface has its vibration'axis perpendicular to the plane of the paper and is the images are formed on the optical front sur hence transmitted by the ?lter I00. Similarly faces of prisms 84 (corresponding to 44 and 45 of Fig. 5). These images are then relayed by 40 the part of the ray 94 which is transmitted by _ the surface 86 has its vibration axis parallel to additional relay lenses 85 to form images in the the plane of the paper and accordingly is transj focal planes of the‘ eyepiece 32. To permit the mitted by the ?lter I00 as shown. Onjthe other lenses 85 to be located; in the positions shown hand the ray 9| which in this embodiment is not longer rhombs 19 are used to replace. the rhombs 3| in Fig. 1. At these secondary images on the 45 v‘masked by any mask 88 is divided or split by the-"surface 86 but is-polarized therebyso that surfaces of the prisms 84, masks ‘81 and 88 are both the transmittedportionand the re?ected located opaqing one-half of each image (see portion are stopped by the polarizing ?lters 100. Fig. 11). This is indicated by the stoppage of The other two parts of the polarizing ?lters are the light represented by arrows 9| and 92, where as, the light represented by arrows 93 and 94 50 similarly arranged as shown to transmit both parts of the ray 93 but to stop both- parts of the passes through in each case to be split at the ray 92. Obviously such an arrangement of semi-transparent mirror surface. The position polarizing ?lters can be used at the image planes of the mask 81 is unique, but except for the slight wherever they are located, providing of course out of focus edge,.the mask 88 could be replaced by one located by positions shown by broken 55 that the operation of the polarizing beam split ter is not adversely affected. 1 > line 96. A mask in the position 88 is preferable Fig. 12 is added merely for clarity in demon however. The edges 89 and 90 of the masks must strating the path of the two beams through. the‘ correspond optically to one another since they. prism. As shown the two beams are combined represent and produce the dividing line in the and emerge only toward one eyepiece, the other ultimate ?eld. This is one of the chief advan 60 emerging beam being omitted from the drawing tages of this embodiment of, the invention since since it would tend to confuse the picture. This the edges 89 andi9ll will stay in adjustment, once they are ?xed whereas in Fig. l, the masks pro ’ ducing the dividing line are located on elements. I2. and I3 separated from each other so that they are liable to get out of adjustment. The advan tages of having a clean, accurate dividing line without any overlapping and without any sepa ration, is well known to any one who has ‘used 70 a split ?eld range ?nder. - The double relay system in this embodiment shown in Fig. 10 has the additional advantage of optical e?iciency. If desireda ?eld lens could be included near the center of the prism assem Fig. 12 corresponds either to Figs. 4 and 5or to Fig. 11. . Having thus described the preferred embodi mentsof my invention, I wish to point out that it is not limited to these structures but is of the scope of‘the appended claims. . I claim: ‘ - 1. A range ?nder comprising means at spaced viewing points for receiving light beams from the target being ranged'and for directing them toward each other along an optical axis, a beam combining re?ector lying coplanar with the axis 78 and to one side thereof, a plurality of re?ecting 2,403,732,: 7 ' surfaces in each beam oriented to direct the beams to opposite sides .of said re?ector :andto rotate .them through 90° in opposite directions, lens means for focusing each beam to form images which, due to the rotation of the beams, are inverted relative to one another andmeans 8 ing light of opposite polarizations lying coplanar with the axis and to one‘ side- thereof, a pair of re?ecting surfaces in each target beam oriented to direct the beams to opposite sides of said re 1 ?ector and to rotate them through 90° in oppo site directions, lens means for. forming right and for viewing the images from Eat least one side of left viewing point images superimposed in invert the combining re?ector. , ed relation in right and left eye image planes op _ 2. A range ?nder comprising meansat spaced viewing points for receiving light beams from the target; being ranged andrfor directing them to—. ward each other along an optical axis, a beam combininggre?ectorylying coplanar with the axis and to one side thereof, a pair of re?ecting sur faces‘in each beam oriented to direct the beams to opposite sides of said re?ector and to rotate thenrthrough 90° "in opposite directions, lens means for focusing each beamto form images which, due to the rotation of the beams,’ are in tically after the said beam-combining re?ector, a pair of polarizing ?lters with their vibration axis mutually at right anglesat and dividing each of the said image planes and means for stereo viewing the images. 9. A range ?nder comprising means at spaced viewing points for receiving light beams from the target being ranged and for directing them to ward each other along an optical axis, an objec tive in each beam for forming images in primary image planes, right and left eye eyepieces and a verted relative to one another and means for 20 relay system for relaying both images to. each viewing the images from at least one side of the. eyepiece," said relay system including a beam combining re?ector. combining re?ector lying coplanar with said op ,3. A range ?nder according to claim 1 in tical axis and to one side thereof, a pair of re which the viewing means is binocular with right ?ecting surfaces in each beam oriented to direct and left eye eyepieces for receiving respectively 25 the beams to opposite sides of said re?ector and light from opposite sides of the combining re to rotate them through 90° in opposite directions, ?ector whereby ortho-pseudo-stereo ?elds are. a relay lens in each beam for relaying the pri presented. , . mary image to form a secondary image near the 4. A range ?nder according to claim 2 in re?ector, masking means at each of the‘second cluding a similar pair of re?ecting surfaces in 30 ary image planes for masking o? complementary each of the beams from opposite sides of the combining re?ector. 5. A. prism unit for combining light beams halves of the images and secondary relay lens means for relaying the transmitted parts of both secondary images to each eyepiece. which are approaching each other along an axis 10. A range ?nder according 'to claim 9 in comprising a beam-combining re?ector coplanar 35 which the secondary images are optically ahead with the axis and to one side thereof, two en of the beam-combining re?ector vand the mask trance faces on the unit orthogonal to the axis ing means are opaque over one-half of each and in line therewith to receive the beams, and image. re?ecting surfaces on the unit for totally in v11. A range ?nder according to claim 9 in ternallyre?ecting each beam twice, oriented to. 40 which the beam combining re?ector is'a polariz direct the beams to opposite sides of the combin 111g beam splitter for transmitting and re?ecting ing reflector and to rotate the beams through light of opposite polarizations, the secondary 90‘? in opposite directions. images are formed optically after the re?ector 6. A prism unit including the combining unit and the masking means at each image plane according» to claim 5 and an identical unit fol-' consists of a polarizing ?lter with adjacent halves lowing, the re?ector for sending parts of both oriented with their vibration axis at right angles beams. in each direction out along .a second axis to selectively mask the two images. parallel. vto the ‘original axis. 7. A, range ?nder comprising means at’ spaced 12. A range ?nder comprising means at spaced viewing points for receiving light beams from the 50' viewing points for receiving light beams-from the target being ranged and for directing'them to target being ranged and for directing them to» ward each other ‘along an optical axis, right and ward each other along an optical axis, an objec left eye eyepieces and means for directing both tive in each beam for forminggimages in primary beams to each eyepiece including a beam com image planes, .right and left "eye eyepieces and a relay system for relaying both images to each . bining re?ector lying coplanar with said optical axis and to one‘ side thereof, a pair of re?ecting eyepiece, said relay, system including a beam surfaces in each beam oriented to direct the combining. re?ector lyingcoplanar with said op~ beams to opposite sides of said re?ector and to tical-axis and to one side thereof, a pair of re rotate them through 90° in opposite directions, ?eeting surfaces in each beam oriented to direct lens means in each beam optically between the the beams to opposite sides of said re?ector and viewing point and the re?ecting surfaces for to ‘rotate them through 90° in opposite-directions and ‘relaylens means in each beam, correspond forming near the beam combining re?ector an ing halves of each of the primary image planes image of the target, the two ‘images being opti being masked off. cally inverted relative to one another, masking _ .8. .A range .?nder comprising means at spaced 65 means at each of the image planes for masking off complementary halvesof the image and relay viewing points-for receiving light beams from the target being ranged and for directing them to lens means for relaying the unmasked parts of ward each other along an optical axis, a beam both images to each eyepiece. combining re?ector for transmitting and re?ect STEPHEN M. MAcNElLLE.