US 3873834 A
A method of tomographic recording wherein a plurality of views of an object are recorded by moving an x-ray source to a number of different locations about a circle, exposing a separate x-ray recording medium corresponding to each position of the x-ray source and superimposing the recorded images on a common viewing plane with incoherent radiation as a superimposed image. Movement of the viewing plane to different positions with relation to the recorded image permits the viewing of different planes of the object tomographically from a single set of exposures.
Description (OCR text may contain errors)
United States Patent Dammann et a].
[ Mar. 25,- 1975 METHOD OF PRODUCING THREE-DIMENSIONAL IMAGES FROM A SERIES OF INDIVIDUAL IMAGES IN DIFFERENT PERSPECTIVES  Inventors: Hans Dammann, Tangstedt;
Manfred Kock, Norderstedt; Ulf Tiemens, Oldenburg, all of Germany  I Assignee: U.S. Philips Corporation, New York, NY.
22 Filed: Jan. 20, 1972 21 Appl. No.: 219,472
 Foreign Application Priority Data Jan. 29, 1971 Germany 2104229  US. Cl. 250/323, 253/320  Int. Cl. G01m 23/02  Field of Search 250/313, 314, 323; 350/130, 320
 References Cited UNITED STATES PATENTS 3,499,146 3/1910 Richards .4 250/323 3,560,740 2/1971 Tripp 3,576,997 5/1971 Slavin 3,614,426 10/ 1 971 Donzelle 3,742,236 6/1973 Richards...
FOREIGN PATENTS OR APPLICATIONS 1,138,617 10/1962 Germany 250/313 856,895 1940 France 250/313 Primary ExaminerArchie R. Borchelt Assistant E.raminerB. C. Anderson Attorney, Agent, or Firm-Frank R. Trifari; Simon L, Cohen [57 ABSTRACT A method of tomographic recording wherein a plurality of views ofan'object are recorded by moving an x-ray source to a number of different locations about a circle, exposing a separate x-ray recording medium corresponding to each position of the x-ray source and superimposing the recorded images on a common viewing plane with incoherent radiation as a superimposed image. Movement of the viewing plane to different positions withdela tion' to tlie recorded image permits the viewing of different planes of the object tomographically from a single set of exposures.
9 Claims, 10 Drawing Figures PJJENTEU HARZS 1975 PATENTEDHARZSIHYS sum 3 o 5 Fig.5b
PATENTEDHAR25I975 3.873.834 sum u If .5
METHOD OF PRODUCING THREE-DIMENSIONAL IMAGES FROM A SERIES OF INDIVIDUAL IMAGES IN DIFFERENT PERSPECTIVES The invention relates to a method of producing a three-dimensional image.
It is known to produce stereoscopic images by holographic methods: Redmann, J. D., Wolton, W. P. and Shuttleworth, E., Nature 2210 (1968), page 58; Kasahara, T., Kimura, Y., I-Iioki, R and Tanaka, S., J. Appl. Phys. 8 (1969) page 124; De Bitetto, D. .I., Applied Optics 8 (1969), page 1740. All these methods have the common feature that a plurality of holograms are made in each of which one of the images recorded with different perspective is stored. When the images are suitably reconstructed the eye of a viewer sees the image in the respective perspective of recording, resulting in a spatial impression.
Further holographic methods have been described by Sun Lu, Prepublished German Patent Application No. 1,952,105, and by G. Groh and M. Kock, Applied Optics 9 1970), page 775. Both methods produce in addition to a stereoscopic virtual image a three-dimensional real image by integration of the individual images.
All. the aforementioned methods use two mutually coherent beams oflight. One beam transilluminates the individual image to be recorded holographically. To enable the entire image information to be stored in one small hologram element the-image is backed with a diffuser screen so that the entire information is evenly distributed over the hologram area. The diffused light interferes with the reference wave and may be recorded, for example photographically. In reconstruction, granulated individual images are obtained the depth of focus of which is limited, because the apertures of the individual holograms must be comparatively large because of the diffraction. A further disadvantage is the small efficiency of diffraction of the holograms. In addition, a substantial amount of experimental work is involved.
It is an object of the invention to produce threedimensional images by means of geometrical optics without the use of holographic effects. This is ensured in that a series of individual images in different perspectives are produced by geometrical/optical means with reproducible recording geometry, and these images are successively or simultaneously placed in their initial positions and are incoherently transilluminated with a ray cone reversed with respect to that used in recording and/or under corresponding recording conditions, so that the initial recording conditions are unambiguously reconstructed and by superimposition of all the images a three-dimensional image is formed or stereoscopic viewing is made possible.
The three-dimensional image is produced by correct superposition of silhouettes. The light may be incoherent in space and in time. The reconstructed object is free of granulation and well-focused throughout.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:
FIG. 1 shows the making of a series of X-ray photographs in different perspectives,
FIG. 2 illustrates a possible method of making bodysection radiographs (tomography),
FIG. 3 shows an embodiment of a system for producing a still, three-dimensional image.
FIG. 4 shows the system of FIG. 3 provided with a diaphragm and an image-forming lens for the suppression of stray light,
FIGS. 5a and 5b show a special system for producing a still three-dimensional image with a stationary construction,
FIG. 50 shows a system of the type shown in FIG. 5b in which, however, the image is formed by means of a ring of lenses,
FIG. 6 shows a system similar to that shown in FIG. 5b combined with the advantageous features of the system shown in FIG. 4, and
FIGS. 7a and 7b show a system in which the radiographs are made and reconstructed in spatially separated relationship.
The method will hereinafter be illustrated with reference to X-ray images. It should be emphasized, however, that this does not mean a restriction. Corresponding images of particle radiation (electrons, protons etc.) and normal optical or electronic images may also be produced by this method.
Referring now to FIG. 1, a source of X-rays is caused to move on a circle 11 in a plane parallel to the plane 4 of a film. At defined positions (for example 12 and 13) radiographs are made of an object 10, so that eventually a series of radiographs made from different perspective viewpoints is obtained. The recording geometry used must be known and reproducible.
The first advantage of the invention consists in the very simple making of body-section radiographs in which the depth of the plane in which the relevant layer lies may be freely chosen. The arrangement is shown diagrammatically in FIG. 2. A point light source 1 in itself a light spot of sufficiently small size is imaged at 4 by a lens 2. When the source 1 is made to move on a circle 3 about the optical axis of the lens 2 the point 4 moves on a circle 8' the diameter of which is equal to that of the circle 11 of FIG. 1. The radiographs made from different perspective viewpoints are successively placed in the plane 14. A radiograph is then transilluminated by a ray cone the orientation and size of which are exactly equal to that of the cone used in making the radiograph. In the region, plane 30, in which the object is formed by image integration an integrating detector for example a film is placed and partially exposed. Then the silhouette is exchanged for a new one in different perspective, 1 is rotated into the correct position so that 4 corresponds to the position which the X-ray source occupied in making this particular image, and a further partial exposure is taken. When this has been done for all the available images and the film is then developed, similarly to tomography the layer of the object in which the film was placed will be sharply defined. Layers situated in front of and behind the said layer are blurred. By changing the. plane 30 and repeating the afore-described procedure another object plane will be obtained so as to be sharply defined.
This method accurately illustrates the fundamental principle of the invention.
FIG. 3 shows an embodiment of an arrangement for producing a still, three-dimensional image of the object 10. The arrangement corresponds to that shown in FIG. 2 except that now a source 1 rotates at an angular velocity w the value of which must be chosen so as to produce a flicker-free image 10. Experiments have shown that a frequency of from 20 to 25 Hertz is sufficient. At
the same frequency to there rotates, for example, a disk 16 on which N radiographs 16' are arranged so that in one revolution each of the N radiographs is once transilluminated by the ray cone 5. This means that the image point 4 and the disk 16 must revolve in synchronism. Because in this arrangement a constribution to the image 10' is to be provided in a given position of the radiograph and of the ray cone, the operation of the source 1 must be pulsed, i.e. the N radiographs are stroboscopically illuminated at a frequency N. to. If N=2O and w=25 Hertz, light flashes must be provided at a frequency of 500 Hertz or an integral multiple thereof. The pulse length depends upon the required resolution and the mean tangential speed of the radiographs on the disk 16. Thus the image 10' is formed behind the disk 16 in the position occupied by the original object when making the radiographs.
If an observer moves his eyes on the circle 11 the stereoscopic impression of the object 10 he receives will be brightest. Discrete planes of the object 10 may be sharply imaged by means of detector surface (plane or curved), whereas layers situated in front of and behind the relevant plane are blurred. Troublesome stray light, which generally is caused by the base of the radiographs, may be eliminated by the arrangement shown in FIG. 4. The rays transmitted by the image at 16 converge in a plane 17 where they produce the image of the light source used. Any stray light broadens the image of the light source, with a consequent reduction in contrast and impairment of the resolution. When therefore a disk diaphragm is so arranged in the plane 17 that only the tips of the light cones for the discrete positions are transmitted and the plane 16 is imaged by a lens 18 in 16 inch, an image of improved contrast is obtained at 10.
The method may also be used for performing conformal transformations of the entire recording geometry. When the radiographs are to be reduced in size by a factor of, say, 2 the dimensions of the arrangement of FIG. 2 must be correspondingly reduced by a factor of 2.
A disadvantage of the aforedescribed arrangement is the required rotation of the image spot 1 (see FIG. 2) and of the disk 16. In addition, stroboscopic illumination is to be provided.
FIGS. a and 5b show an embodiment of an arrangement for producing a three-dimensional image by means of a stationary construction. FIG. 5a shows two ray cones. In a plane 19 in which the cones are separated there is positioned, for example, a photographic plate. The silhouettes projected from 14 may be separately recorded in this plane. This is advantageously effected by means of an imaging lens whilst retaining the geometry so that a quality impairment of the reducedsize radiographs is avoided. FIG. Sb shows schematically the illumination of the resulting ring of images by a suitable ring of point light sources 21 of correct geometry, permitting the object to be formed by integration again. In this arrangement the size of the point light source (21) must be kept small to avoid a loss of resolution. Obviously, as an alternativev the formation of the ring of images 19 may be avoided by using a ring 19' of imaging lenses which each project a small partial image of 19 on to 20. With sufficient depth of focus the object 10 is again produced (see FIG. 5c).
A further possible arrangement is shown diagrammatically in FIG. 6. The advantage of this arrangement as compared with that shown in FIGS. 5a to 5c is: the images in a plane 22 need not be reduced in size in so high a degree and hence the point light sources (I) need not satisfy such stringent requirements. The diaphragm array 17 suppresses any stray light in the manner illustrated in FIG. 4, and this provides an improved image.
If the X-ray source 1' is moved on a circle 3 of a size such as to enable the individual silhouettes to be recorded in spatially separate relationship, the movement of the images and the stroboscopic illumination may be dispensed with. FIG. 7a shows a possible arrangement for producing the individual images of the object 10 in the plane 14, and FIG. 7b shows a possible arrangement for reconstruction in which the ray cones of the arrangement shown in FIG. 7a may be reconstructed by means of a single point light source 34, a suitable diaphragm array 33 and an associated system of mirrors 31, 31, 31", 31" and of lenses 32, 32, 32", 32".
The two-dimensional images from different perspective viewpoints required to produce the threedimensional image may also be formed by means of a computer which calculates the amplitudes and positions of the image points.
What is claimed is:
1. A method for producing a three-dimensional image comprising the steps of separately recording a plurality of views of an object by projecting a first cone of radiation through said object from different perspective viewpoints along a planar circular path on a plurality of planar recording mediums arranged parallel to the plane of the circle, arranging the recordings in the positions they occupied during the recording process and projecting with a further cone of incoherent radiation all the recordings in a superimposed manner on a common area of a viewing plane arranged parallel to the recordings and at selected distances therefrom, said further cone of radiation being the reverse of said first cone of radiation, whereby different planes of said recorded object may be selectively viewed from said plurality of recording mediums.
2. A method as claimed in claim 1, wherein the step of recording comprises recording the internal as well as the external details of the object, and wherein the viewing plane comprises a ground glass plate.
3. A method as claimed in claim 1, wherein the step of projecting each recording comprises the step of stroboscopically and sequentially illuminating each recording in a sequence sufficiently rapid to produce the illusion of a still three-dimensional image.
4. A method as claimed in claim 1, wherein the step of projecting each recording comprises the steps of rotating an incoherent point source oflight about a circular path, rotating a disc containing the recordings about a further circular path, the rotational axes of the two circular paths being parallel, and projecting the radiation from the point source through the recordings with a lens.
5. A method as claimed in claim 1, wherein the step of projecting each recording comprises simultaneously projecting incoherent radiation from a plurality of apparent radiation sources arranged in a circle through the recordings.
6. A method as claimed in claim 5, wherein the step of simultaneously projecting incoherent radiation through the recordings comprises the step of projecting the incoherent radiation through a ring of imaging lenses each optically aligned with a separate recording. 7. A method as claimed in claim 5, wherein the step of projecting illumination from a plurality of point sources further comprises projecting said radiation through a plurality of contrast enhancing diaphragms.
8. A method as claimed in claim 1, wherein the step of projecting each recording on a common area of a viewing plane comprises the step of simultaneously su- 72x 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION March 25, 1975 Patent No. 73,834 Dated Invent f( HANS DAMMANN ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
[- ON THE TITLE PAGE  Foreign Application Priority Data Jan. 29, 1971 Germany .'......2l04229" should read  Foreign Application Priority Data Jan. 29, 1971 Germany .......P.2104229.5-;
Signed and sealed this 10th day of June 1975.
c. MARSHALL DANN RUTH C. MASON Attesting Officer v Commissioner of Patents and Trademarks