US1497356A - Method and system for producing a plurality of images of the same object from the same point of view at the same time - Google Patents

Description

Drasman June 10, 1924.

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D. F. COMSTOCK. IETHOD AND SYSTEM FOR PRODUCIHG A PLURA OBJECT FROM THE SAIE POINT OF VI Filed Feb. 9,

2 Sheets-Sheet 2 uar'mnfvunennnY Patented June l0, 1924.

UNITED STATES PATENT OFFICE.

DANIEL F. COMSTOCK. OF BROOKLINEy MASSACHUSETTS. ASSIGNOR. BY MESNE AS- SIGNMENTS. TO TECHNICOLOR MOTION PICTURE CORPORATION, OF BOSTON, MASSA- CHUSETTS, A CORPORATION OF MAINE.

METHOD AND SYSTEM FOR PRODUCING A PLURALITY OF IMAGES OF THE SAME OBJECT FROM THE SAME POINT OF VIEW AT THE SAME TIME.

Application filed February 9, 1916. Serial No. 77,237.

To all viv/10m t may concern Be it known I. DANIEL F. CoMsTooK, a citizen of the United States, and resident of Brookline. in the county of Norfolk and State of Massachusetts. have invented new and useful Improvements in Methods and Systems for Producing a Plurality of Images of the Same Object from the Same Point of View at the Same Time, of which the following is a specification.

In colored motion-picture projection it has heretofore been the commercial practice to project successively through color-screens Iilm pictures taken successively through color-screens. The results obtained by this method have been open to two serious objections: first, the displacements in successive pictures of the moving objects cause those parts of the moving objects which do not coincide in the successive pictures to appear in the colors of the several color screens rather than in the natural colors which would result from the blending or fusion of the several colors: second, the eye is fatigued by the alternate bombardment of light of different colors. The first difficulty causes what are called fringes and is especially bad when rapidly moving objects are photograplied. The second difficulty causes a feeling of eye strain which is distinctly objectionable.

To overcome this it is desirable to project simultaneously through different colorscreens two or more photographs, taken through color-screens, of the same scene from accurately the same point ofview at the same time. This involves the problem of obtaining on a film or films two or more photographs from accurately the same point of view, of the same scene at the same time.

The problem admits of solution along several distinct lines, according as one or more lenses are used in the camera, and according as the sinmltaneous photographs on the film are similarly arranged. or are symmetrical with relation to a common axis, but inverted or reversed with relation to each other.

In the accompanying drawings, Figs. 1 to l1 inclusive illustrate diagrammatically several possible optical systems for obtaining, in a camera, a plurality of photographs of the. same scene from accurately the same point of view at the same time, disregarding certain refinements which need not be considered in an explanation of the fundamental optical principles involved; and Figs. 12 and 13 illustrate certain symmetrical arrangements on the film of the relatively inverted pictures produced by the system in certain of its forms.

Referring to Fig. 1, O represents the object the scene to be photographed), L represents the lens, and F represents the film. The light beam B from the object passes through the lens and the glass prism P, perpendicular to surface .r of prism P, to the semitransparent reflecting surface fc, which may be made by half-silvering the surface of prism P, or by introducing between P and P a film of some transparent substance of suitable refractive index, or which may be a light dividing grid of transparent material having distributed thereon distinct areas of transmission and of reflection made according to my application, Serial No. 54.270. filed October 5. 1915. Essentially one-half of the light is reflected from surface a: along the path B to the totally reflecting surface .132. and thence along path B to thel film, forming an image on the film F at M. `The remainder of the light passes through vsurface ai and through prisms` P and P to the totally reflecting surface y, paralled to a?, of the prism P', and is thence refiected along the path B2 to the totally reflecting surface y', parallel to :02, of prism P,` and thence along path B22 to the film, and forms a second image on the film F at N. Prism P is separated from prisms P and P by a thin film of air or other substanceofWO sufficiently low refractive index to insure total reflection from surface y. This4 system gives images similarly' arranged, that is, head to foot, since each beam is reflected twice. By the inclusion of prism P" the geometrical lengths of two paths of the divided beam in the same or similar media are the same.

Fig. 3 shows the same principle applied to the formation of three simultaneous pictures similarly arranged (he-ad to foot), and scarcely needs additional explanation. The

beam B enters prism P through surface x2, which is normal to the. beam. Partly transparent reflecting surface .r reflects essentially one-third of the light along path B', to the totally reflecting surface fr and thence along path B to the film F. forming an image at M. The remainder of the light passes t-hrough prism PIv to semi-transparent reflecting surface y, where the beam is again split, substantially half being re` flected along path B2 to the totally reflecting surface y and thence along path B22 to form the image N on the film, while the remainder of the beam passes through prism P, (which furnishes a medium of glass) and prism Pv to totally reflecting surface s. thence along path B3 to totally reflecting surface a', and thence to the film forming an image at O. The surfaces y and s are totally reflecting surfaces, the latter two being rende-red so by films of air between said surfaces and the adjacent prisms. or by applying to the surfaces y and a of prisms Pi" and Pv some medium of suitable refractive indeX such as ordinary balsam, which has a sufficiently low index of refraction to yield total reflection, as in the case of air, and also affords protection against the soiling of the glass surfaces. The prisms P" and Plv-are hollowed out opposite surfaces y and a', and are coated with black balsam as shown at k, c, or other suitable material, to prevent any stray light. from passing between the prisms P" and Pv, and prisms Piv and P". For a in particular it is desirable to use a film of only slightly lower index than the glass. which, without interfering with the total reflection of ray B3, will diminish the loss by reflection of part of the initial beam B when entering the prism P".

Referring now to Fig. 2, which illustrates another form, O represents the object, L the lens, and F the film, as before. The light beam B passes through the lens and the glass prism P2 to the semitransparent reflecting surface whe-nce one-half the light is reflected to the totally reflecting surface m2, and thence out of theprism to the film, forming the image at M. The remainder of the light passes on through the surface and the prism P3 to the totally reflecting surface y2, and thence out of the prism to the film. forming a second image at N, inverted with relation to the image M, (one beam having been reflected twice and the other once), so that the pictures on the' film appear head to head or foot to foot.

It is desirable that prisms P2 and P3 be right-angled and identical, in order that the optical paths to the two images may be equal. It is also desirable, though not essential, that they form in section an equilateral triangle,in other words, that the angles 1, 2, and 3 be each 60, s0 that @he beam enters normally to the surface. If for any reason it is desired to use other angles a thin auxiliary prism may be interposed. presenting one face normally to the incident light, and having the other separated by an airfilm from surface .n2 of prism P2. This avoids the dispersion due to Obliquity: but no advantages are obtained by departing from the form.

The distinctive feature to be observed in the form shown in Fig. 2 is the complete geometrical symmetry of the two beams and images with respect to the semitransparent surface .11 after leaving it. Such surface may thereforeI be termed the symmetrical plane.

It is evident that much space is saved by using the surface r2 of the prism P2 both as a transmitting surface, when the light first enters the prism, and also as a totally reflecting surface for that part of the light reflected back by surface fc.

Instead of placing the symmetrical plane behind the lens, that is, between the lens and film, in which case the beam first passes through the lens and is then split to form two images, it may be placed before two or more lenses, that is, between the object and the lenses` as shown in Fig. 4, in which casethe beam B is first split at the semitransparent surface ,r and then the two parts pass through two lenses L and L2 to the two images M and N on the film. This arrangement makes the point of view of the two lenses the same, and avoids the stereoscopic effect which would result if'the light passed directly from the object to the two lenses in two distinct beams. Since one beam has undergone one more reflection than the other, the images will be relatively inverted.

If it is desired to have the pictures similarly arranged. instead of relatively inverted, this may be accomplished by rotating one of the images by reflection in a rightangled prism, as shown in 'Figs 5 and 6. This arrangement is identical with Fig. 4, with the addition of the plane reflector R and reversing reflector S. The beam passing through lens L2 is reflected up at right angles to the plane of Fig. 5 by the 45 plane totally reflecting mirror or similar reflector R; while the other beam passing through lens L1 is also reflected up at right angles to the plane of the drawing` but is reflected by means of a leaves-of-a-book reflector S comprising two plane reflecting surfaces at right angles to each other, which also reverses the image. or rotates it through 180. The reflectors R and S might obviously be a totally reflecting prism and a right angle prism, but for simplicity and clearness in drawing they are shown as composed of plane mirror surfaces. The resultant images are therefore similarly arranged instead lili of relatively inverted. Fig. 6 shows Fig. 5 viewed from below. This inverting of one image is obviously possible with any symmetrical plane method.

Thus. in order to obtain two pictures from accurately the same point of view at the same time. a symmetrical plane may he used. consisting of a semitransparent surface placed in a position either behind the lens and essentially symmetrical with respect to the two images, or in a position in front of two lenses and essentially symmetrical with respect to them. The arrangement may be varied in several ways. but the essential condition in obtaining relatively inverted images isq the presence of such symmetrical plane.

lVith the use of the .symmetrical plane it is possible to get. in the case of one lens. two paths between the lens and the film. of essentially the same lengths: and in the case of two lenses in the two paths from the symmetrical plane to the film. the two lenses have precisely the same viewpoint regarding the scene to be photographed. In either case the two paths of the split light beyond the symmetrical plane where the light is split. are completely symmetrical to each other and to the symmetrical plane.

With the use of' the' symmetrical plane systems above described. two identical` or inverted and symmetrical images may be ohtained on the film at the same time from precisely the same viewpoint. Such a film with relatively inverted or foot-to-f'oot pictures is illustrated in Fig. 12. wherein F represents a film of usual form, and F and F a pair of foot-to-foot, simultaneously made pictures of the same scene.

Should it be desired to obtain more than two such pictures. sav three or four. this can be accomplished by adding a second symmetrical plane system to the system, illustrated in Fig. 2. in the manner presently to be described. This will produce a. film with four pictures ot' the same scene (or three by merely7 dropping out one picture) taken at the same time, from accurately the same point of view, and arranged symmetrically with relation to two axes. one transverse and one longitudinal of the film. as illustrated in Fig. 13. In this form each picture F on the film F is symmetrically arranged and invertedwith relation to the adjoining picture of the pair. whether considered lengthwise or crosswise of the film: and the four pictures are symmetrical and relatively inverted with relation to two axes.

To produce such a film as that shown in Fig. 13, having four pictures of the same scene from the same point of view taken at the same time, the system illustrated in Figs. 7 and 8 may be used, Fig. 8 being an elevation viewed from the right of Fig. 7 The upper part A represents the same system as Fig. 2. and will produce two images as already explained. ln order to get four pictures in symmetrical positions another similar set of prisms. twice as wide. is placed at B in such position that each ray is split again in a direction at right angles to the former split produced by A. .Each of the two. split beams from A is again split by the semit-ransparent reflecting surface m4, between prisms P and F5 ('Fig. 7) in the same manner as already described with reference toFig. 2. resulting in four symmetrical. relatively inverted images as shown in Fig. 13.

It is further contemplated that the relatively inverted images produced by the symmetrical plane system may be images in register on opposite sides of the same film. An optical system employing for this purpose my symmetrical plane method is shown in Fig. li. The upper part ot' the system, including prisms P2 and P3, is precisely the same as in Fig. 2. The split beams a and a refiected from surfaces .r2 and L1/2 enter the two right angle totally reflecting prisms P6 and P7, respectively, and are by them reflected normally inwardly toward each other along symmetrical paths to opposite sides of the film F, which passes through a narrow space between prisms P5 and P7. The images thus formed on opposite sides of the film will necessarily be in register. since they were made foot-to-foot images by prisms P2 and P3. and the effect of prisms i?6 and PT is to fold the two relatively inverted images upon each other on a central axis. A special film sensitized on both sides. with the sensitive surfaces separated by a film or layer of opaque material, subsequently to be removed. as by dissolution. would be used with this system. Also to make the film of practical use in color projection the two sides of the film and the film itself would be dyed or otherwise colored. Such film, however, will not be further considered as it forms no part of the invention herein claimed: the present application is concerned with the optical system for forming the images rather than with the film.

Figs. 9 and l0 show perspective and plan views. respectively. of another arrangement of prisms for producing a result similar to that of the system shown in Fig. 3, namely, the formation on the same lm of three pictures simultaneously from accurately the same point of view, at equal optic-al paths from the lens. This arrangement involves a longer optical paththan that of Fig. 3, one advantage over the latter being that it involves no angles other than 90 and 45 angles, thus requiring only standard shapes of prisms.

Both Figs. 9 and 10 are diagrammatic or schematic, and the oblique View of the system, shown in Fig. 9 as an aid to visualization. is a view from an angle of approximately 45 to the plane of Fig. 10, from the lower left-hand corner. And in both figures no account is taken of the refraction of light due to entering and leaving the prisms at angles other than right angles: in other words for the sake of clearness and to avoid complication in drawing, diagrams show the paths of the beams as though the prisms wei'e leaves-of-a-hook-mirrors. The beam B is to be divided into three parts, and for clearness is shown in three lines. From the lens L the beam falls upon the partly transparent reflectingsurface c, which may be any suitable form of light-dividing means such as a partly silvered surface. or a light-dividing grid, adapted to transmit substantially twothirds of the light and to reflect substantially one-third of the light, said surface c being arranged at an angle of 4.50 to the path of the beam. The reflected part of the beam passes along path b to the totally reflecting right-angle prism C, whose apex C is in a plane below and parallel to the horizontal plane of the light beam, and in a vertical plane at an angle of 45 to the split beam The beam b strikes the upper face C2 of the prisms and is reflected downward along path b to the lower face C3, and thence along pat-h b2 to the film F, forming an ima e at M. Said lower right-angle prism thus shifts the beam sidewise with relation to the prism, that is, lengthwise of the film, and reverses the image.

The rest of the beam B passes along the path b3 to the semitransparent reflecting surface d, which is a suitable light-dividing means adapted to transmit substantially half of the light and to reflect substantially half of the light, said surface d being arranged at an angle of 450 to the path of the beam. The reflected part of the beam, i. e. substantially half of the beam b3, or onethird of the total beam B, passes along path b* to the totally reflecting right-angle prism D whose apex is in the same horizontal plane as the light beam b4 and at an angle of 45 thereto. This prism D, being centrally located with respect to the horizontal plane of the beam, does not shift the beam but reverses the image and reflects the beam along path b5 and forms an image on the film at N. A plane reflector would accomplish the same purpose as prism D, except that it would not reverse the image, which would then not be arranged similarly to the other two.

The part of the light transmitted by surface d, passes along path be to the upper right-angle totally reflecting prism E, which is similar to prism C but oppositely arranged and has its apex E above the plane of the light beam. The beam 6 strikes theI lower face E2, from which it is reflected along path bl to the upper face E3. This shifts the beam sidewise with relation to the prism, that is, upward and lengthwise of the film, and reverses the image. From surface E3 the beam passes along path bg to the totally reflecting surface r. which is at an angle of 45D to the beam. and thence along path b9 to the film F, forming an image at O.

The three images are similarly arranged. or head-to-foot, since each split beam is once reversed by a right-angle prism, and once reflected. The ent-ire apparatus ma)Y be made in the form of a solid block of glass, of which the prism-surfaces indicated form part of the bounding surface. The incidence is in all cases so oblique as to insure total reflection.

A feature in all of the above arrangements is exact equality between the two or more optical paths from lens to images. This is attained either by complete geometrical symmetry with respect to the surface which splits the beam, or (as in the case of the head-tofoot images) by the exact optical equivalent of such symmetry, in that the lengths of the paths of the split beams in glass and in air are the same. This is highly advantageous as only in this way can the optical corrections for the glass be performed all at once by a single correcting device for the entire beam before the beam is split.

An important problem solved in each of the above devices is to obtain the desired arrangement of images and the necessary equality of paths, without excessive length of path from lens to images. This restriction results from the rigid limitation imposed by practical considerations on the focal length of the lens used,-a limitation which excludes many possible arrangements because of the too great length of path they require.

It follows that, unless metal reflectors are used (which in general is not feasible), in systems involving a single lens, a large part of the path from lens to .images must lie within the glass prisms used to divide and manipulate the light. It is well known in the optical art that this mass of glass (optically equivalent to a single slab in a straight beam) introduces aberrations tending to impair the good definition of the image. Chief among these are curvature of field, chromatic aberration, and spherical aberration. Means for correcting these aberrations as fully as the various conditions allow forms no part of the invention herein claimed, and are therefore not described.

In order to eliminate the problem of making such correction separately for each division of t-he beam, and to permit its correct accomplishment once for al1 at or near the lens, it is highly desirable that the part of every path from lens to image which lies in glass be made equal; that is, that each part of the beam, after division, traverses the same distance in glass. This is an important feature of all the above arrangements.

It is of great importance that the geometrically identical images before referred to should be taken on the same film and not very distant from each other; and in practice the ima-ges of each complemental set should be adjacent, the practical limit of separation being of the order of magnitude of the width of the film. There are several reasons for this, In the first place, any lm, during the mechanical and chemical processes of developing and fixing, undergoes a certain amount of change in form, principally shrinkage, and in general it cannot be assumed that two separate films will shrink to the same degree. Therefore, if the images were taken on two or more different films, they could not be relied upon to remain accurately the same in size through the process of development, printing and projecting upon the screen.

In the second place, the accurate superposition of two or more pictures on the projecting screen depends on the two or more images on the film used in projection, being either positioned to extreme accuracy or out of position by the same small amount. Actual practice proves that lack of register on the screen is more annoying than an irregular displacement of the picture as a whole, that is, of all of the two or more superimposed images to the same degree. It is therefore important that the relative position on the screen of the two or more geometrically identical images should be more accurately constant than the mere positioning of non-attached films by the mechanism of the projector can accomplish. When the two or more images are on the same film and the film is treated uniformly throughout its length, pictures on the projecting screen once in register will remain accurately in register, since the slight irregularities of the mechanism when the pictures are similarly oriented involves similar displacements for all of the superimposed screen images.

From the foregoing description it is evident that the present invention involves among others the following unique features: The various reflecting and semi-reflecting surfaces are so inclined with respect to each other and to the incident beams that the angles subtended by the incident and reflected beams are oblique, i. e., either acute or obtuse, rather than right angles. The surface through which the main beam from the object field enters (0M-wz in Fig. l and m2 in Fig. 2, e. g.) is utilized as a reliecting surface to reflect one of the divided beams. The images are formed in non-super- U-l annum posed relationship and in fiatwise alinement, i. e., in the same plane, and the plane of the images is angularly disposed with respect to the plane of the light-dividing surfaces, i. e., the two planes are not parallel. And the image plane is oblique to the axis of the main beam B.

The images are formed in parallel relationship or with corresponding rectilinear lines in parallelism. For example if a vertical pole or a horizontal cable appears in the scene, the pole or cable in each image of a complemental set is parallel to the corresponding element in each of the other complemental images of the set, although the corresponding elements may be reversed, that is, have their heads or other corresponding sides directed in opposite directions, in respective images of each set. The paths of the main beam and the paths of the divided beams lie in the same plane, for example the plane ofthe paper in Figs. 1 and 2.

Each of these characteristics contributes to the aforesaid objects and results attained by the present invention, particularly to the desired arrangement of images and the necessary equality of paths without excessive lengths of paths, and while all of these characteristics are combined in the illustrated embodiments of my invention they may be utilized independently or in sub-groups within the scope of the appended claims.

I claim: l

l. A system for producing a plurality of images of an object field from the same point of view at the same time on the same side of a film, comprising means including a transmitting-reflecting surface for dividing a. beam of light into a plurality of similar beams and means for reiiecting the divided beams to adjacent picture spaces on the film, the paths of the divided beams being substantially equal in length and said surface being inclined to reflect at an oblique angle.

2. A photographic apparatus for producing from a single point of view two images separated from each other in the same plane comprising a reflecting prism unit having a plane incident beam receiving face and emergent beam faces in a single plane at an angle to the axis of the incident beam, a light dividing refiector at another surface of the unit and certain surfaces of the unit extending across the paths of the divided beams at total reflecting angles to form images separate from one another along the focal plane.

3. A photographic apparatus for producing from a single point of view two images separated from each other in the same plane comprising a reiecting prism unit having a plane incident beam receiving face and emergent beam faces in a single plane at an angle to the plane of the lncident beam receiving face, a light dividing reector at another surface of the unit and certain surfaces of the unit extending across the paths of the divided beams at total reflecting angles to form images separate from one another along the focal plane, said surfaces being so inclined to the respective beams that the angles subtended by the incident and reflected beams are oblique.

4. A photographic apparatus for producing from a single point of view two images separated from each other in the same plane comprising a reflecting prism unit having a plane incident beam receiving face and emergent beam faces in a single plane at an angle to the p-lane of the incident beam receiving face, a light dividing reflector at another surface of the unit and certain surfaces of the unit extending across the paths of the divided beams at total reflecting angles to form images separate from one another along the focal plane, said reflector and said surfaces being so inclined to the respective beams that the angles subtended by the incident and reflected beams are oblique.

5. A photographic apparatus for producing from a single point of view two images separated from each other in the same plane comprising a reflecting prism unit having a plane incident beam receiving face and emergent beam faces in a single plane at an angle to the plane of the incident beam receiving face, a light dividing reflector at another surface of the unit and certain surfaces of the unit extending across the paths of the divided beams, at total reflecting angles to form images separate from one another along the focal plane, said surfaces being so inclined to the respective beams that the angles subtended between the incident and reflected beams are obtuse.

6. A photographic apparatus for producing from a single point of view two images separated from each other in the same plane comprising a reflecting prism unit having a plane incident beam receiving face and emergent beam faces in a single plane at an angle to the plane of the incident beam receiving face, a light dividing reflector at another surface of the unit and certain surfaces of the unit extending across the paths of the divided beams, at total reflecting angles to form images separate from one another along the focal plane, said reflector being so inclined to the respective beams that the angle subtended between the incident and reflected beam is acute and said surfaces being so inclined to the respective beams that the angles subtended between the incident and reflected beams are obtuse.

7. A system for simultaneously producing on the same side of a film a plurality7 of similar images of an object field which comprises a partly transmitting and partly refleeting surface for dividing a beam of light into a plurality of beams and reflecting surfaces for reflecting the divided beams to the film, said first surface being so inclined that the angle subtended between the incident and reflected beams is acute.

8. An optical system for color photography comprising a plurality of reflecting surfaces correlated to direct parts of a beam of light to separate spaces on the same side of the film, one of the surfaces being a partially transmitting and partially reflecting surface in optical alinement with another of the surfaces, both of the surfaces being inclined in the same direction but at diderent angles relatively to the path of the light passing through the first of said surfaces.

9. A system for simultaneously producing on the same side of a film a plurality of similar images of an object field which comprises a partly transmitting and partly refiecting surface for dividing a beam of light into a plurality of beams and reflecting surfaces for reflecting the divided beams to the film, said first surface being so inclined that the angle subtended between the incident and reflected beams is acute and certain of said last surfaces being so inclined that the angles subtended between the incident and reflected beams are obtuse.

l0. In a system for simultaneously producing on the same side of a film complemental images of an object field from the same point of View, the combination of focusing means and prism means, the prism means including a light-dividing surface and surfaces arranged to bend the divided beams in such manner th'at the complemental images produced thereby are angularly but symmetrically disposed with respect to the plane of the light-dividing surface and in parallel relation to each other.

l1. A system for producing complemental images of an object field comprising a lightdividing surface and reflecting surfaces arranged to position the complemental images in spaces in the same plane which are angularly disposed with respect to the plane of the light-dividing surface and which are disposed on opposite sides of said plane equidistantly therefrom with certain of their margins parallel thereto.

l2. A system for producing complemental images of an object field comprising a light-dividing surface and reflecting surfaces arranged to position the complemental images in spaces which are substantially perpendicular to the plane of the light-dividing surfaces and which are equidistant from said plane on opposite sides thereof and which have certa-in of their margins perpendicular thereto.

13. A system for producing complemental images of an object field comprising a lightdividing surface and reflecting surfaces arlli) ranged to position the complemental images in spaces which are substantially perpendicular t0 the plane of the light-dividing surface, and which are substantially in fiatwise alinement and which are equidistant from said plane on opposite sides thereof, and which have juxtaposed margins parallel to said plane.

14. In a system for simultaneously producing on the same side of a film complemental images of an object field from the same point of View, the combination of focusing means and reflecting means correlated to form the compleniental images in uxtaposed picture spaces on one side of the film in reversed and parallel relationship With respect to each other, said reflecting means comprising a partially transmitting and partially reflecting surface disposed at an angle to the plane of said picture spaces.

15. In a system for simultaneously producing on the same side of a film complemental images of an object field from the same point of View, the combination of f0- cusing means and reflecting means comprising a reflector disposed in a plane perpendicular to the film, said means being correlated to form the complemental images on the film equidistantly from said plane, and said reflecting means being arranged to form the images in a plane making an angle to the axis of the focusing means.

16. A system for producing complemental images of an object field comprising a lightdividing surface and reflecting surfaces arranged to position the complemental images in parallelism and substantially in flatwise alinement in spaces which are separated along the length of the film and which are disposed equidistantly from the plane of the light-dividing surface on opposite 'sides thereof.

17. A system for producing complemental images of an object field comprising a light.- dividing surface and reflecting surfaces arranged to position the complemental images in parallelism and equidistantly from the plane of said light-dividing surface in spaces separated from each other along the plane of the film.

18. A system for simultaneously producing a plurality of images of an object field substantially in the same plane comprising means for dividing the main beam of light from the object field into a plurality of similar beams, and means for reflecting the divided beams at such angles as to form the imagesin spaces separated along a plane oblique to the axis of said main beam at equal distances on opposite sides of the plane of the light dividing means.

19. In a system for simultaneously producing complemental images of an object field from the same point of View, the combination of focusing means, light-dividing means in optical alinement with the focusing means for dividing a beam of light into a plurality of parts, the focusing means being adapted to cause the divided parts of the beam to produce images, and reflecting means arranged in the paths of the divided parts of the beam so as to position the images in the same plane with corresponding sides directed in opposite directions.

20. In a system for simultaneously producing complemental images of an object lield from the same point of View, the combination of focusing means, light-dividing means in optical alinement with the focusing means for dividing a beam of light into a plurality of parts, the focusing means being adapted to cause the divided parts of the beam to produce images, and reflecting means arranged in the paths of the divided parts of the beam so as to position the images in the same plane with their heads directed in opposite directions, the geometrical lengths of said paths in similar media being equal.

21. In a system for simultaneously producing on a film complemental images of an object field from the same point of View, the combination of focusing means, and prism means, the prism means including a light-dividing surface and reflecting surfaces, the said means being disposed in optical alinement in such manner that the complemental images produced thereby are symmetrically disposed With respect to the plane of the light-dividing surface in separate spaces along one side of the film with corresponding lines of the images parallel to each other.

22. In a system for simultaneously producing on a film complemental images of an object field from the same point of view, the combination of focusing means, and prism means having a light-dividing surface and reflecting surfaces in optical alinenient with the focusing means, said surfaces being arranged to position the images in separate spaces along the same side of the film, and the reflecting surfaces being symmetrically disposed With respect to the plane of the light-dividing surface.

23. In a system for simultaneously producing on a film complemental images of an object field from the same point of view, the combination of focusing means, and prism means, the prism means having a light-dividing surface and reflecting surfaces in optical alinement with the focusing means, the reflecting surfaces being arranged to position the images transversely of the plane of the light-dividing surface and the light-dividing surface being so disposed With respect to the path of light from the object field that the paths of the divided light are s mmetrically dis osed with respect to sai plane, all of sai paths lying in the same plane, whereby complemental images are symmetrically produced relatively to said plane.

A system for producing on a film a plurality of images of the same object from accurately the same point oi." view at the same time. which comprises means for dividing the light beam into two paths including a plane surface which reflects part' of' the light and transmits part of the light, and means to refiect the divided parts of the beam along paths which are symmetrical with respect to the plane where the light is divided, said means being arranged to position the images on the film in non-superposed relationship with corresponding lilies of the images parallel.

Q5. A system for producing a plurality of images ot' the same object from accurately the same point of view at the same time, comprising a partly transparent reflecting plane adapted to divide the light beam into two parts, and means to project the two parts of the divided beam in distinct paths symmetrical to said plane with said paths and said light beam in the same plane. said means being arranged to position the images on the film in Spaces which are separate from each other along the film.

26. A system for producing a plurality of images of the same object from accurately the same point of view at the same time, comprising two identical juxtaposed prisms in the path of the light beam from the object to the image surface, and a partly transparent reflector between the juxtaposed surfaces of said prisms adapted to reflect part of the light back through the. same prism to the surface through which it entered and to transmit part of the light through the other prism.

27. A. system for producing on a straight film a plurality of images of the same object field from accurately the same point of view at the same time, comprising a lens, and a partly transparent plane between the lens and the film adapted to divide the light into two paths, and reflectors for reflecting the divided light to spaces separate from each other along one side of the film, margins of said spaces being arranged in parallel juxtaposition and said plane being arranged to intersect the film symmetrically between juxtaposed spaces.

28. A. system for producing on a straight film a plurality of images of the same object Jfrom accurately the same point of view at the same time. comprising a lens, a pair of juxtaposed prisms between the lens and film, and a partly transparent reflecting plane between said prisms, adapted to divide the light into two paths, said reflecting plane being angularly but symmetrically arranged with relation to the image spaces,

and said prisms having reflecting surfaces arranged to reflect the light to the film.

2i). .t system for producing on a straight film a plurality of images of the same object from accurately the same point of view at the same time. comprising a lens, a pair of juxtaposed prisms between the lens and film'` and a partly transparent reflecting plane between said prisms and bisecting the angle formed between the outer surfaces of said prisms adapted to divide the light into two paths, said reflecting plane being angularly but symmetrically arranged with relation to the image spaces, and said prisms having refiecting surfaces arranged to reflect the light to the film.

30. A system for producing on a film a plurality of' images of the same object from accurately the same point of view at the same time, comprising a lens, a pair of identical, juxtaposed prisms between the lens and the film, a cross section of each prism forming a right angle triangle and said two triangles together forming an equilateral triangle, a partly transparent reflecting plane between said two prisms adapted to divide the light into two paths, said refleeting plane and the image spaces being symmetrically arranged, and the prism surface through which the light first enters being normal to the light.

3l. A system for producing on a film a plix'ality of images of the same object from accurately the same point of view at the same time, comprising a lens, a pair of juxtaposed prisms between the lens and film, a partly transparent reflecting plane between said prisms, adapted to divide the light into two paths, said reflecting plane being symmetrically arranged with relation to the image spaces, and another pair of similar prisms with a partly transparent reflector between themin the path of one at least of said divided beams, adapted again to divide said divided beam into two paths.

32. A system for producing on a film a plurality of images of the same object from accurately the same point of view at the same time, comprising a lens, a pair of juxtaposed prisms between the lens and film, a partly transparent reflecting plane between said prisms, adapted to divide the light into two paths, said reflecting plane being angularly but symmetrically arranged with relation to the image spaces, and means in the path of one of said divided beams adapted optically to invert the image.

33. In a photographic apparatus in which the incident rays are divided and the divided emergent rays are parallel and separated from each other to simultaneously form two images of the same object displaced from each other in the same plane and adapted to be superposed in congruent relation, an image forming optical train embodying an objective, a light dividing device and reflectors set at angles to direct the divided emergent rays parallel and laterally displaced with relation to each other but with their axes at an obtuse angle to the axis of the incident rays, the light paths of the two divisions being equal in length and having a common focal plane.

34. In a system for simultaneously producing on the same side of a film complemental images of an object field from the same point of View, the combination of focusing means and prism means, the prism means including a light-dividing surface for dividing a main beam into similar divided beams and surfaces arranged to bend the divided beams in such manner that the complemental images produced thereby are angularly but symmetrically disposed with respect to the plane of the light-dividing surface, said surfaces being angularly arranged with respect to the axis of the main bea-m to produce the images in a plane which intersects the axis of the main beam.

35. In a system for simultaneously producing on the same side of a film complemental images of an object field from the marismas same point of View, the combination of focusing means and prism means, the prism means including a light-diyiding surface for dividing a main beam into similar divided beams and surfaces arranged to bend the divided beams in such manner that the complemental images produced thereby are angularly but symmetrically disposed with respect to the plane of the light-dividing surface and in alinement on the iilm with their sides in juxtaposition throughout the Width thereof.

36. In a system for simultaneously producing on a film complemental images of an object field from the same point of view, the combination of focusing means, and prism means having a light-dividing surface and reiiecting surfaces in optical alinement With the focusing means, said surfaces being arranged to position the images in separate spaces along the same side of the film, and the reiiecting surfaces being symmetrically disposed with respect to the plane of the light-dividing surface and having rectilinear elements arallel to said plane.

Signed by me at oston, Massachusetts, this 28th day of January 1916.

DANIEL F. COMSTOCK.

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