US 3712199 A
A color stereoscopic of three-dimensional picture system which is fully compatible with unaided two-dimensional viewing. A filter divides the lens aperture stop into left and right halves, and lets mutually exclusive portions of the spectrum pass through each half, preferably red left, and blue-green right. When viewed with glasses consisting of identical filters over the corresponding eye, psychophysiological illusion of 3-D is created.
Description (OCR text may contain errors)
United States Patent [1 1 Songer, Jr.
154] THREE-DIMENSIONAL COLOR PHOTOGRAPHIC PROCESS, APPARATUS AND PRODUCT [75) Inventor: Jimmie D. Songer, Jr., Los Angeles,
 Assignee: Video West, Inc, Santa Monica,
 Filed: Sept. 23, 1970  App1.No.: 74,762
 US. Cl ..95/18 R, 352/60, 350/132  Int. Cl. ..G03b 35/08  Field of Search ...,....95/1 8; 352/57, 60; 350/132  References Cited UNITED STATES PATENTS 7/1919 Quick ..352/57 2,568,327 9/1951 Dudley ..95/18 R 2,360,322 10/1944 Harrison.... ....352/6O X 2,596,129 5/1956 Cristiani.... ..352/60 1,372,645 3/1921 Cooper ..95/18 2,672,799 3/1954 Terwilliger 95/18 X 1 Jan. 23, 1973 2,751,826 6/1956 Harrison ..95/18 FOREIGN PATENTS OR APPLICATIONS 1,135,752 8/1962 Germany ..95/18 872,923 3/1942 France ..95/18 360,977 11/1931 Great Britain ..95/18 Primary Examiner-John M. Horan Assistant ExaminerAlan A. Mathews Att0rneyF1ehr, Hohbach, Test, Albritton & Herbert  ABSTRACT A color stereoscopic of three-dimensional picture system which is fully compatible with unaided twodimensional viewing. A filter divides the lens aperture stop into left and right halves, and lets mutually exclusive portions of the spectrum pass through each half, preferably red left, and blue-green right. When viewed with glasses consisting of identical filters over the corresponding eye, psychophysiological illusion of 3-D is created.
7 Claims, 10 Drawing Figures PATENTEDJAH23|973 3,712,199
SHEET 2 [IF 3 BLUE GREEN YELLOW R EE SOF/VE A5 COALESCED IN Ml/VD 0F V/EWEP I NVENTOR. J/MM/E D. 50N618 MyM 1 THREE-DIMENSIONAL COLOR PHOTOGRAPHIC PROCESS, APPARATUS AND PRODUCT BACKGROUND OF THE INVENTION This invention relates to full color stereoscopic three-dimensional photography including still and motion pictures and to methods and camera apparatus for their production. More particularly, the invention relates to a three-dimensional photographic system which 1 produces a compatible three-dimensional picture capable of being alternatively viewed with appropriate glasses for full color three-dimensional effect or viewed without glasses as a two-dimensional photograph.
Three-dimensional photography using full color has been heretofore available in a form insufficiently compatible with ordinary viewing. Reference is made to U. S. Pat. No. 2,751,826 dated June 26, 1956 for Color Stereo System and Attachment to W. H. Harrison and to U.S. Pat. No. 2,360,322 dated Oct. 17, 1944 and entitled Apparatus for Producing Stereoscopic Pictures in Color to W. H. Harrison In general, these patents propose that the color spectrum be divided into two distinct image spaces having a separation proportional to the binocular disparity produced in a two aperture photographic system. Pictures produced by the method of the Harrison patents suffered from various distortions resulting from the use of distinct image spaces and two apertures. Where distinctly resolved double images were formed at the focal plane, they could not be compatibly viewed, without special glasses. And even when focal plane images nearly coincided, Harrison pictures weresubject to peripheral keystone distortion due to lack of registry of separately derived image spaces, focal length distortion from differing paths of the separate image formation apertures and axes mechanically caused distortions resulting from operator error, and error in machining tolerances of Harrisons apparatus. Furthermore, where Harrisons double image space is used to produce distinctly resolved and focused double foreground and background images, viewer discomfort and fatigue results because of the non-correspondence with normal vision in which outof-focus foreground and background is blurred. And, any convergence error is made even more noticeable by sharp images. This disadvantage could probably not be eliminated since -l-larrisons disclosure appears to require large depth of field to obtain optimum results. Also, a separate, bulky attachment of Harrison was hard to handle and difficult and costly to manufacture. Further, such an attachment made it difficult to produce a truly compatible stereo picture reliably and conveniently since the mechanical tolerances required to obtain pictures having exact registry at the focal point was generally at the limit of the state of the art of mechanical devices. Moreover, a separate aperture mirror system such as Harrison's requires exact vertical registry as well in order to prevent vertical and diagonal convergence error. There is therefore a need for a new and improved three-dimensional photographic system including product, method for producing the product, and optical apparatus for carrying out the method.
SUMMARY OF THE INVENTION AND OBJECTS provide a three-dimensional stereo system includingmethod, apparatus, and product which will overcome the above-named limitations and disadvantages in a single image space, one aperture, single lens system.
A further object of the invention is to provide a three-dimensional photographic system of the above character in which the resulting photograph is optically sharp at the focal plane, i.e., zero binocular disparity, and in which the binocular disparity is directly related to the distance from the focus distance of the lens, and
0 in some applications the disparity can also be made proportional to the defocus blur normally associated with an unfocused image, i.e., the stereo information is carried in the blur normally associated with out-offocus region of operation of the lens.
Another object of the invention is to provide a threedimensional photographic system of the above character which is free of keystone effects and which utilizes a multiple path technique having identical path lengths so that distortion produced by pathlength differences is eliminat-d and therefore is particularly adapted for use in micro and macro photographic applications.
Another object of the invention is to provide a threedimensional photographic system of the above character which is capable of producing a photograph which resembles the same view of object space as would be seen by a person having two eyes focused on the focal point of the same scene and is therefore'free of distinct double images.
Another object of the invention is to provide a three dimensional photographic system of the above character and particularly method and apparatus for producing stereo pictures which is particularly convenient and practical to carry out as a modification to existing lenses and which involves essentially no auxiliary equipment or attachments in most embodiments.
Another object of the invention is to provide threedimensional photographic system and camera apparatus which requires no external camera attachments and requires no mechanical adjustments to achieve stereo photography, and further, which is automatically adjusted simultaneously in the act of adjusting focal distance of the camera lens.
Another object of the invention is to provide a threedimensional photographic system of the above character in which the resulting photographs are particularly comfortable to view either utilizing special glasses for stereo effect or without viewing aids as compatible two-dimensional photographs or motion pictures.
In general, the foregoing objects are achieved by providing a three-dimensional photographic system which utilizes a split filter positioned at the aperture stop of a standard photographic objective or taking lens. The filter includes right and left halves which pass approximately equal energy portions of the spectrum such that light travelling through the right half of the aperture stop is reduced by one portion of the spectrum while light travelling through the left half of the aperture stop is reduced by the complimentary portion of the spectrum. The lens still continues to produce a single image space corresponding element for element to object space. In the usual way, images formed at the image focal plane, i.e., the photosensitive surface, are coalesced into registry by the lens to yield an exposure of the photosensitive surface containing one set of focused and converged images which correspond to the plane of interest in object space. Images which are located before or after the focal plane in image space due to correspondence to foreground or background planes in object space will be converged into single images either in front of or behind the photosensitive surface and as a result would normally appear as blurred images as they pass the focal plane. However, by passing the light rays through the filter, such images are characterized by being formed of left and righthand ray bundles which expose the photosensitive surface as an image having left and right edge colored fringes, the amount of fringence or the width of the fringes edge corresponding directly and proportionally to the binocular disparity caused by the remoteness of the object from the object plane of interest in object space. Furthermore, the orientation of each image fringe system with respect to another will be found to reverse according to whether the image originated in the foreground or background of object space and also in accordance with whether the image is of a bright or dark object. Accordingly, a completely resolvable set data is presented and photographedwhich can subsequently be viewed by left-eye and right-eye filters corresponding to those used in the taking lens, and, when so viewed, there occurs a natural tendency for the viewer to converge or diverge his eyes slightly to bring these'image edges into registry. This results in coalescence of colors and image clarification in the viewers mind and the eye movement in do soing producespsychophysiological 3-D because of the associated convergence or divergence.
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows a simplified diagram of a camera and lens modified in accordance with the present invention.
FIG. 2 shows an enlarged schematic diagram of the camera lens and film exposure frame of the camera of FIG. 1.
FIG. 3 is a graph showing curves of filter band pass characteristics-for filters constructed and employed in accordance with the present invention.
FIG. 4 is a plan view illustrating the geometry of viewing a stereo picture in accordance with the present invention.
FIG. 5 is similar to that of FIG. 2 and illustrates the operation of the camera lens and film plane when dark objects are photographed.
FIG. 6 is an enlarged elevation of the film plane of FIG. 5., V
FIG. 7 is a plan view illustrating a second analysis of the operation of the present invention utilizing the arrangement of FIG. 1. a
FIGS. 8, 9 and 10 illustrate alternate forms of filters for use in the present invention.
DETAILED DESCRIPTION OF EPREEERRED EMBODIMENTS Referring more particularly to FIGS. 1 and 2 there is shown a camera 10 which has been modified in accordance with the present invention. The camera consists of a camera body 12 which provides a light tight chamber for holding and advancing photographic sensitive materials such as roll film 14, past an exposure frame 16. As will become'more apparent camera body 12 may be of any type as for example a movie camera or a still camera. A lens 18 is mounted to the body and so positioned to form an image at its plane of focus which coincides with the photosensitive material at the exposure frame 16. No loss in generality will result if theplane of focus is assumed to lie precisely at the particular plane of the photosensitivematerial at the exposure frame since for any practical lens some plane of focus will be so located,'And, in the present application, we shall define this plane in correspondence to its counterpart in object space as the object and image planes of interest. Obviously, the photosensitive material may be of any common varietu such as 35mm roll film, movie film, or plate glass having a suitable photosensitive surface. The only requirement is that the photosensitive surface be spectrally sensitive so that color information can be recorded thereon throughout the visible spectrum. 1
As apractical matter, the present invention has been reduced to practice utilizing a Bessler Topcon Camera using a 58mm f/1.4 Topcor Automatic Lens. This lens is only schematically shown in the drawings and is generally of the double meniscus anastigmat type having twonegative meniscus inner doublets 20,22 and outer positive elements 24, 26 the last of which has been compounded asa doublet. This lens has an aperture stop which is located between the inner meniscus elements 20,22. As will become more clear, the existence of the aperture stop is assumed in the present invention and it will be found that every lens which might be the subject of a modification in accordance with this invention will be found to have at least one aperturestop. Accordingly, the disclosure of a particular modified lens herein is for the purpose of illustration and is not to be taken in any sense as a limitation on the present invention. For, it will be found that the present invention is adapted for use with all types of photographic objectives including the meniscus anastigmats, airspaced triplets, and so on. Additionally, any of the various telephoto and other lenses can also be modified in accordance with this invention. It is a general characteristic of a lens system that there exists a plane, physically associated with reference to the lens, which possesses characteristics termed the aperture stop plane. Thisaperture stop limits the size of the axial cone of energy which is accepted from object space and transferred to image space. It is a property of the aperture stop that all light eminating from an point in 3- dimensional object space and accepted by the lens generally fills the aperture stop, that is to say, the resultant image 'in image space within the camera is made up of approximately even distribution of rays which have travelled equally throughout the entire area of the aperture stop. As a corollary, itis observed that division of the aperture stop into right and left halves, one of which is shielded, results in loss of approximately one half of the light energy being transferred by the lens from object to image space. As is known, an iris 28 is positioned immediately adjacent or in the vicinity of the aperture stop so that the amount of light from object space can be easily controlled by merely shutting down orclosing off the outer periphery of the aperture stop to therebydecrease the amount of light passed by the lens. 1
In accordance with the present invention, a special filter 30 is positioned at approximately the aperture stop of the lens and may proceed or succeed the iris. Generally, the filter includes at least mutually exclusive left and right half filter elements 32, 34. Generally, the filter elements are positioned contiguous to each other in a common plane located at or immediately adjacent the aperture stop and serve to divide the stop into left and right halves. One filter element is designed to pass a predetermined portion of the visible spectrum and the other filter is selected to pass only a complementary portion of the visible spectrum. Preferably, the portions of the spectrum are approximately of equal visual energy content as will be hereinafter described. The lens is not otherwise modified except as may be necessary to compensate slightly for the presence of the thickness of the filter. However, it has been found that the lenses modified in accordance with the present invention to date have not required additional compensation of the elements in order to obtain satisfactory results.
The filter 30 is constructed to provide equal brightness transmission of mutually exclusive portions of the spectrum so that when the resulting photograph is viewed with similar viewing filters to be describe, approximately equal brightness sensation will be produced in the view's eyes. This will avoid any discomfort which might be caused by the pupils of each eye being required to respond to different brightness levels. While many possible divisions of the spectrum are possible, one particular division is preferred and is illustrated in FIG. 3 which shows transmission of each filter element as a function of wavelength. Curve 36a illustrates the transmission response of the blue-green filter 34 while curve 38a illustrates the preferred transmission response of the red filter 32. These filters possess a band pass transmission characteristic which is quite high throughout the range over which they are transmissive but reduces to a negligible value outside of this range. Such filters can take any of various forms, dichroic reflectors made by coating transparent substrates being one particularly efiicient type. An additional set of curves, 36b, 38b illustrates filters of the gelatin type Kodak types 26 for red, 44a for bluegreen) which can be used but which generally have such high losses as to render them less preferable than the more efficient dichroic types. The curves as shown, illustrate an important requirement of the filters in that there is extremely low cross-talk between them, that is to say, their overlapping coverage at 39 of transmission is made as negligible as economically feasible. This results in less eye fatigue and confusion to the viewer.
The filters are preferably arranged so that, when oriented toward object space, the red filter covers the left half of the aperture stop and incoming bundle 40a of rays while the blue-green filter covers the right half of the stop-and incoming bundle of rays 40b. In the usual case, and in that shown for illustrative purposes in FIGS. 1 and 2, this coincides with positioning of the red filter over the left half of the aperture stop and the blue-green filter overthe right half. It should be understood however, that when using image erection systems or image relay systems that reference should be had to left and right half ray bundles as propagated from object spacerather a particular arbitrary aperture stop (or image ofstop) within the lens system in order to correctly orient the filters. Preferably, the filters are positioned exactly at the aperture stop, are exactly in the plane of the stop throughout, and laterally bifurcate the stop into equal halves along a line precisely vertical and intersecting the axis of the lens. Mispositioning of the filter as by imperfections of lateral placement, axial displacement from the plane of the stop and vertical misalignment or skew are found to be reasonably noncritical, the more detailed effects of which will be more fully discussed hereinafter.
CAMERA OPERATION With reference particularly to FIGS. 1 and 2, assume a particular plane of interest in object space 42 is imaged on the focal plane of the photosensitive surface in image space 44 and further assume that there exists a plurality of foreground and background planes in object space which areimaged into background and foreground planes respectively in image space. This assumption is entirely reasonable from the known principles of the operation oflenses. It should again be noted that every ray of energy eminating from an object in object space and capable of passing through the lens represents a single point in the plane of the aperture stop and that all light received from the object completely fills the aperture stop (this assumption neglects directed ray energy, i.e., light sources having a directed output, but this lack of generality is so minor as to be negligible). By positioning the filters at the aperture stop, therefore, its plane is divided into equal halves and each element of permissible image space 44 (taken in the 3-dimensional sense) is illuminated by a first group of rays which have passed through the red transmission side of the stop and a second group of rays which have passed through the blue-green transmission side of the stop. At each image location in 3-dimensional image space these groups converge into a composite image having balanced color composition derived from the addition together of the two groupd of ray bundles. (The apparent notch in the yellow will not be noticeable since subjective yellow is also derived from the combination of red and blue-green.) Each of these two bundles however, have a binocular separation or disparity relative to the aperture stop of approximately one-halfits horizontal diametral dimension.
The geometry of the situation is set forth in FIGS. 1 and 2 with reference to three posts 50, 52, 54 positioned in different planes of object space and their corresponding images 60, 62, 64 in image space. FIG. 2 also shows how each image in image space is constructed of the converge bundles eminating from opposite sides of the aperture stop and having differing spectral content which adds up to an approximately equal energy distribution in the resulting images.
Assume the lens is adjusted to bring a particular plane of interest in 3-dimensional object space into focus on the plane of the photosensitive surface within the exposure frame. In general, this requires nothing more than adjusting the distance of the lens or other appropriate geometry from the photosensitive surface in such a manner that those images from the plane of interest in object space and formed into images in 3- dimensional image space fall into registry with the photosensitive surface. It is immediately recognized that images formed in fromt of or behind this imagplane of interest will not be in exact focus registry with the plane. Referring now to the thrpe posts 50, 52 and 54 in object space, post 50 being in the plane of interest, post 52 being in the foreground, and post 54 being in the background: first, the post 50 will be converged and appear as a coalesced and sharp image 60 at the photosensitive surface. It accordingly will expose that surface as though no filtering action had taken place.
However, the foreground post 52 will become an image 62 lying in the background of image space and accordingly the separate ray bundles 62a, 62b will be converging as they intersect the plane of the photosensitive surface. This results in slight lateral displacement or fringing of the exposure of the photosensitive surface in correspondence to the distance of the image 62 away from the plane of the photosensitive surface in image space. This in trun is obviously directly and proportionally related to the counterpart distance of post 52 from the plane of interest in object space.
And, the post 54 in the background of the object space is imaged in front of or in the foreground ofimage space by image 64 formed by ray bundles 64a, 64b so that the exposure of the film at the photosensitive surface is accompanied by lateral displacement of the diverging ray bundles 64a, b, eminating from image 64. And, the amount of displacement is directly proportional to the displacement of post 54 in background object space and its corresponding displacement of image 64 toward the foreground of image space.
The resulting transparency or picture formed from exposure in the plane of interest is characterized by a number of properties which distinguish it from previous 3-D pictures. First it should be noted that the image space in which the exposure frame is located is singular, i.e., image space contains only one set of images formed by ray bundles travelling equal length symmetric paths from object space through a single aperture. As a result there is no path length difference in the image space to which. the picture is exposed and no resulting path length difference distortion and no keystone. Keystone results from viewing object space from spaced apart apertures and causes the resultant picture to lose detail at the periphery, particularly the corners, due to distortion in which an originally square pattern is reproduced larger at one side than at the other side.
In addition, the resulting product can be adjusted to contain no sharp double images by adjustment of the iris for limited depth of field so that all stereo information is automatically carried in the defocus blur ofa single set of image space data. This renders the resultant product particularly acceptable since defocus blur of the present product corresponds with subjective human vision, i.e., the double blurred mental image of human vision and that produced in the present invention are very similar. Accordingly, an appreciable improvement is obtained in reducing discomfort of viewing stereo pictures compared with stereo pictures containing sharp double images. For, sharp double images in peripheral vision are annoying to most viewers and do not correspond to what we actually see in normal vi sion. We now set forth an analysis of how the picture of the present invention is viewed with stereoscopic effect and how each element thereof is believed to be created.
It will be convenient to assume for the present 7 discussion, although without loss of generality to variant application of the invention as in color television, that a color positive transparency is exposed by the camera of FIG. l,'developed, and now is to be viewed.
Such a transparency is illustrated in FIG. 4 in relation to a viewer. As is known, the transparency must be viewed in relation to its orientation in the camera in a directionfacing towards object space and upside down, unless anerecting lens system is used. It is also assumed that the resultant transparency is viewed in correct orientation and rotated l80for the convenience of the viewer. It will then appear as shown in FIG. 4. Without any viewing aids the converged image of the plane of interest will appear perfectly sharp and focused and will have balanced color rendition in accordance with the additive properties of the converged color components from each of the filters.
In contrast, the foreground image 72a will appear with blue-green fringe 72b shifted from a red fringe 72a, in proportion to the distance of the foreground image 62 from the plane of interest. Likewise, the background image will appear with a red shifted left fringe 74a and a blue-green shifted right fringe 74b separated from each other in proportion to the distance of the background image from the plane of focus in image space. Without viewing aids these images will generally merge into a relatively blurred image having indistinct colored fringes at their borders. It will be appreciated however, that the degree of blur and the amount of fringing can be controlled by iris 28 and the resulting depth of field so that this does not become highly noticeable, particularly where the suggestion of 3-dimensional effect is desired and a maximum of compatibility with 2-dimensional viewing is also desired.
.Now assume the viewer wears a pair of filtering spectacles 76 in which the left lens 77 is'red transmissive and the right lens 78 is blue-green transmissive as attached hereto as a model (FIG. 14). These lenses 77, 78 may for example, correspond identically'with the filter specifications previously set forth and with the sole restriction that the amount of cross transmission of the lenses must be kept to an absolute minimum in order to avoid confusing the viewer. With the lenses in front of the viewer the converged image in the plane of interest in image space will not be affected except as to the amount of light available to the viewers eye, that is to say, the illumination of the object will be decreased by at least a theoretical factor of one-half since onehalf of the light to each eye is blocked. But the color rendition will not be materially changed. If the viewer is assumed to focus initially upon the plane of interest he finds there a converged sharp exposure image. Now consider the left side exposure image which was produced from the foreground object 52 in object space. This image has a blue-green left fringe 72b and a red right fringe 72a which induces the viewer to converge his eyes in such a manner as to bring these images into registry. When doing so, the relative effect is to induce in' the viewers mind psychophysiolo gical 3-D since this corresponds to a requirement of the same type of convergence as is normally associated in viewing any object in real life referenced from a plane behind a given object.
Likewise, the exposure image associated with the background image 54 of object space is shown at 74 with a left-shifted red fringe 74a and a blue-green shifted right fringe 74!) which induces the viewer to diverge his eyes so as to bring these images into registry. When so doing, their color rendition is again balanced and the viewer is induced into a psychophysiological illustion that the fused image is behind the plane of image in the transparency being viewed. Furthermore, the amount of light in the resultant fused images derived from convergence or the divergence of the viewer's wyes results in a significant increase in the irradiance produced so that the image actually seems to stand out more clearly and more brightly when the viewer fuses the exposure images by convergence or divergence.
The above discussion has analyzed illuminated, light colored objects in foreground, background or the plane of interest of object space and, in general, such light objects will present a positive reflection of light towards the camera. It is also found that dark objects are also separated into blue-green and red fringed images the fringes of which are reversed from light images and therefore which would ordinarily be thought of as leading to reversed convergence across the plane of focus. However, this is not found to be the case. Such dark objects really represent an absence of color or illumination at their position while the background or foreground to such objects, as for example the surrounding terrain, represents a positive illumination or highlight.
For bright objects, that is to say, for objects which give a positive illumination in light forces, such as white, the foreground objects give red shift or fringe to the right and a blue-green shift or fringe to the left, as has been explained.
Referring to FIGS. and 6 for dark foreground objects which give little or no illumination, such as black, a non-red image is shifted to the right of the image and a non-blue-green image is shifted to the left, and this results in the image possessing fringes which are the reverse of those of the previous discussion, i.e., a bluegreen fringe 172a and a red fringe l72b as shown in FIG. 6. This statement is geometrical: i.e., those rays coming through the red filter 32 are shifted to the right, and if no rays come through, one can consider the result as non-red. This results in a right shifted bluegreen fringe corresponding to the absence of red, and a left shifted red fringe corresponding to the absence of blue-green.
Byway of further explanation, reference is made to FlG. 7 which illustrates in plan view an object plane 42 in front of which is a foreground black post 80. A camera lens 82 including a filter 84a, b is positioned to view the object plane 86 on which focus will be assumed. Now, let 86a, b 88a, b be rays which pass, through each filter. As the rays sweep the scene from right to left it is observed that a point 90 is reached whereat the right and left rays 86a, 88a both focus on the object plane. Beyond this point the left, red, ray 86a is cut off by the foreground black object so that bluegreen ray 88b only continues to exist and it too is cut off after a short distance. At this point the exposure goes black in correspondence with the object but is given a right blue-green fringe l72b which consists of background detail seen through the right filter 84b.
As the background is further traversed, the left ray 86c clears the left side of the back object first to see details through filter 84a. Shortly thereafter both rays 86d, 88d clear the edge of the object to bring out restoration of color balance. In this way object is seen at the exposure frame as a dark object having a left red fringe and a right blue-green fringe. When viewed with the glasses 76 the right eye sees a left shifted dark image resulting from the absence of blue-green in the red image fringe, and, the left eye sees a right shifted dark image resulting from an absence of red in the blue-green right image fringe. These shifts force convergence in the viewer in order to fuse the fringes and put the resultant image into the foreground in correspondence with the object.
Where background objects are black, they are found by the same type of analysis to have right shifted red fringes and left shifted blue-green fringes since the associated rays diverge as they enter the image focal plane. And, when viewed with glasses 76, divergence will bring the resultant fringes into registry so that the image will fuse in the background in correspondence with the associated object.
The entirety of image space as developed by the present invention is characterized in that it consists of a single set of images which fused into balanced correct color at the location of each image whether or not that image is at the focal plane. That is to say, object space plane of interest objects appear as images at the image plane 44b of interest focused, and color balanced, being made up of left and right complementary portions of the spectrum that have passed through the filter. Likewise foreground and background objects become background and foreground images similarly complete and in focus in the respective background and foreground plane 44c, 44a. No second set of images, exists. These foreground and background images, of course, are formed by diverging or converging rays with respect to the ray intersection with the plane of interest 44b which contains the film. Accordingly, the film is exposed with fringing as herein set forth. However, it is not possible to obtain a film having distinct double images since image space consists of only a single set and whatever fringing takes place upon the film in recording the depth information in accordance with the present method occurs because geometrical considerations related to lens focus and not because of the double imaging system. This inherent feature of the present invention precludes the obtaining of results wherein background or foreground double imaging occurs and eliminates the unpleasant sensation which results from viewing distinct double images. Furthermore, the product of the present invention conforms very closely to that which is experienced by the binocular human vision in that we ourselves see blurred, out-of-focus images when we defocus our eyes from, for example a foreground object, and fix upon a background object. It is realized of course that human vision is a two aperture system. In the present invention a divided single aperture system is used and results in the single set of images just explained. When the resulting product is used it tends to pull the viewers attention to the plane of interest very strongly since the viewer cannot easily concentrate on fixing his attention to any double image system. And, the only way the blurred images in foreground and background can be 11 clarified is by convergence or divergence which necessitates that the viewers vision follow the stereoscopic effect built-in to the structure of the picture.
It can be shown that the resultant product or image to be viewed is invariant to being produced through lens relay systems and the like in which multiple images are utilized. First it is clear that handedness of the image can only be correct if viewed from the background of image space, i.e., the final product whether transparency or print must be viewed from the direction in whichtheoriginal was taken. Now as is known, the first image will be inverted and can only be correctly viewed when rotated 180. If erected (or rotated) by a suitable lens, this image will not only be rotated l80but foreground and background image space will be exchanged. This causes all information contained in the colored fringes of the product to also be interchanged through the reference image plane so that optical rotation of the reference image through 180is accompanied by interchange of the stereo information as well. This appears to be inherent in any optical system since continuing by the same reasoningan additional rotation would also produce such an interchange. This result means that the present invention is invariant with respect to background, foreground interchange caused by a more complex lens system provided that handedness is preserved. Of course, as with ordinary transparencies handedness may be inadvertently exchanged in handling transparencies in which case the product of the present invention will lose its 3- dimensional character and for some persons may even become reverse S-dimensional.
An additional property of the present invention is its relative freedom from critical dimensional factors. As previously mentioned, certain misorientations and alignment are not critical with the present invention, for example, angular misorientation due to rotation of the filter about the optic axis of the lens is not critical and neither is horizontal displacement. It will be found that a hue-shift occurs at the left and right margins of the resultant transparencies as a function of axial movement of the filter along the axis of the lens. Even this shift is tolerable when viewed with glasses but can be easily be eliminated by trial and error positioning of the filter. In this connection, it should be pointed out that in general, the iris of the lens and the filter will be olcated at the aperture stop. However, this is not always convenient and irises and other elements may indeed conflict with lenses elements themselves which necessitates positioning of such elements slightlyaway from the theoretical position of the aperture stop. In
' addition, it should be pointed out that unlike many previous S-dimensional stereo systems, the present is particularly free of distortion as a function of the angular orientation of the viewers head. Very often viewers will desire, for the sake of comfort, to angularly orient' their heads with a slight cant. In prior systems this often resulted in immediate loss of 3-D and double image distortion. ln the present system, such angular misorientation is not critical. It eventually leads to loss of 3-D but not until rather appreciable angle from the vertical is reached.
The resultant product is particularly pleasing to view since it corresponds so closely with the physics of unaided vision. For example, the fusing of double images by the convergence angle of the viewer cor? responds directly to double image convergence in unaided vision and as a consequence the viewer is subjected to a minimum of discomfort since he is already quite used to the same physical manipulation of the eyes in order to view the present invention as he has become used to ordinary vision. Another similarity is results from subjective impression of increase contrast of the image upon fusing of fringes by the viewer. This leads to confirmation of correct viewing in the viewers mind and enhancement of the 3-dimensional effect. It should also be pointed out that this too corresponds exactly to that which is experienced in unaided vision of object space; for, the total brightness impression from an object is seen much reduced when only focused upon by one eye. T
In this connection a large improvement in the foreground and background image quality is achieved on convergence by the viewer, for, as the left and right edge fringes of objects are brought into registry the entire detail of the object is considerably improved and sharpened. However, the upper and lower edges can contain defocus blur and are not improved since the viewer can only supply horizontal convergence and not vertical convergence. FIGS. 8, 9, and 10 all lined for color and viewed from object space show filters of construction so that definition in upper and lower edges of images is rendered comparable to that which can be achievedby horizontal convergence of lateral edges by the viewer. In general, these filter specifications are the same as those discussed in connection with the embodiment of FIGS. 1 and 3 and each incorporates a suitable left side red filter 132 and a right side blue-green filter 134. However, the filter is masked or blanked out at its upper and lower portions so that it resembles something similarto a butterfly shape where transmissive. Virtually, any shape in which the rays travelling predominately along vertically displacedpaths through the lens are selectively eliminated compared to those travelling on more horizontally displaced paths would achieve this purpose. FIGS. 8, 9 and 10 illustrate various designforms which would be suitable. More particularly FIG. 8 shows a filter design in which upper and lower circular quadrants or wedges of the aperture stop are blanked out and when developed further results in the configuration of FIG. 8 in whichupper and lower quadrants are removed. This leaves right and left half filter elements defining a preference for passing predominantly left and right rays laterally displaced from the lens axis. FlG. l0 shows a' filter utilizing two disc filter elements positioned approximately mid position on each side of the lens at the aperture stop blocked by opaque material on all sides.
These geometrical configurations "are generally characterized by emphasis on providing selectively larger number of raysv travelling through laterally displaced or horizontally displaced portions of the lens while discriminating or blanking out those rays which contain little stereo information and which pass through the upper and lower extremes or quadrants of the lens. Each suitable blocking means is also characterized by being symmetrically disposed both vertically and horizontally about the center of the aperture stop and lens. By direct analogy to the analysis previously presented in connection with the horizontally displaced rays, one can immediately see that the fringing of the upper and lower edge of objects is a direct result of exposure of the film to rays which have travelled to upper and lower edges of the aperture stop of the lens. When these rays are selectively eliminated as by the filter stops of FIGS. 8, 9 and 10 proposed, the upper and lower edges of objects become distinctly sharper.
To those skilled in the art to which this invention relates many other modifications and adaptations thereof will suggest themselves. By way of example, the present single invention is immediately applicable to macroscopic and microscopic photographic systems. it is readily seen that such objectives can be modified to include filters of the type disclosed herein incorporated at the lens aperture stop. The degree of smallness to which the present invention is adapted for use does not appear to be limited except by way of limitations which would also apply to an optical system.
Furthermore, the system disclosed in the present invention can also be applied to color television. With four channel NTSC color, a system currently used in the United States, a slight modification should be incorporated. For, there is a luminance signal which is derived from the color signals in order to provide compatibility with black and white sets. It will be found that by rolling off the upper edge of the red signal, that is to say, electronically rolling off the red shelf in the yellow region will permit satisfactory results to be obtained, since the luminance is thereafter derived solely from the blue-green signal. If this is not done, color convergence by the viewer will be confusing and less effective due to the underlying presence of the luminance signal.
Accordingly, although the present invention has been disclosed in certain preferred forms, it is not intended thereby to limit the invention except as defined in the following claims.
1. In a stereo color picture, a carrier sheet having photographically recorded thereon a composite image having a balanced, single, sharply focused, a-curate color image of objects from an object plane of interest and laterally displayed stereoscopically related color images of objects corresponding to fforeground and background planes, said stereoscopically related color images being of mutually exclusive but complementary colors.
2. Apparatus for making stereo pictures, comprising:
a lens having an aperture stop, filter, and image receiving medium disposed to receive a focused image of a particular plane of interest from an object space, means dividing the plane of the aperture stop into mutually exclusive left and right segments, including a filter disposed over the left segment at the aperture stop plane to eliminate a first predetermined portion of the spectrum, and a second filter positioned in the right segment of the aperture stop plane to eliminate a second predetermined portion of the spectrum, said portions of the spectrum selected to be mutually exclusive and further selected to contain equal spectral content having approximately equal brightness on the human eye so that rays from an object in the plane of interest and object space are divided into two groups at said aperture stop plane and conver ed into coincidence and focused in the plane of e Image receiving medium to form a composite image having a balanced, single, sharply focused, accurate color image of objects from said plane of interest and laterally displaced, stereoscopically related color images of objects in all other planes from said object space.
3. Apparatus as in claim 2 including means for blocking out a significant percentage of the rays passing through the upper and lower extremes of the aperture stop thereby reduce upper and lower edgewise blur whereby lateral image edges fused in the mind of the viewer yield an impression of overall sharpness of image since lateral fusion can take place in the viewers mind and upper and lower blur is eliminated by the blocking means.
4. Apparatus as in claim 3 in which said blocking means comprises an opaque stop having portions throughout regions consisting of upper and lower wedges symmetrically disposed about vertical and horizontal lines interesting the center of said aperture stop.
5. Apparatus as in claim 3 in which said blocking means is opaque over the uppermost and lowermost areas of the aperture stop.
6. Apparatus as in claim 3 wherein said blocking means blocks all areas of said stop except for horizontally spaced apart and symmetrically disposed openings on which said filters are disposed.
7. Apparatus as in claim 5 wherein said openings are circular and have center to center spacing of about ,Qthe diametral dimension of said aperture stop.