Boots – shoes – and leggings
Patent
1981-01-21
1983-09-13
Smith, Jerry
Boots, shoes, and leggings
364728, 364822, G06F 15336, A61B 602
Patent
active
044046316
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of coding and decoding an image of an object by means of radiation which is emitted by point sources and which irradiates the object in different directions in order to form shadow images of the object which are superposed on a recording medium, the coded image thus formed being decoded by convolution of the superposed shadow images with a function which is determined by the point source distribution used for irradiating the object.
The invention furthermore relates to a device for coding and decoding an image of an object by means of penetrating radiation, said device comprising for the coding of an image of an object a two-dimensional distribution of point sources and a two-dimensional image recording medium which are situated in two parallel planes at a distance from each other in order to form superposition images of the object, said device comprising for the decoding of the superposition images means for convoluting the recorded superposition images with at least a part of an image point function which is defined by the point source distribution, and means for summing the convoluted superposition images.
It is known that objects can be coded by irradiating the object from different positions by means of X-rays or other incoherent radiation and by recording the shadow images on a recording medium. Thus, a superposition image is obtained in which the information concerning the object is not directly accessible. The object or a layer object can be made visible again only during a second phase, i.e. the decoding of the superposition image. A method and a device of the described kind are known from German Patent Application No. P 25.35.408.9 (U.S. Pat. No. 4,118,099).
The decoding by means of the known specific arrays of the recording sources using incoherent or also coherent point distributions produces artefacts which prevent the signal-to-noise ratio from exceeding a given threshold.
The invention has for its object to provide a method of and a device for the coding and decoding of images of the described kind in which the object is decoded without disturbing artefacts.
To this end, a method in accordance with the invention is characterized in that the point sources are arranged according to a regular matrix, at least three different groups of point sources being used to form a corresponding number of superposition images in succession, a combination of groups forming a first source distribution function and a further combination of groups forming a second source distribution function, the sum of the autocorrelation functions of said source distribution functions having the value zero except in one point (origin), after which the different superposition images, or combinations with the negatives thereof, are convoluted with image point functions of the groups of sources in order to obtain convoluted images which are summed in order to obtain a decoded image. The combinations of groups which produce a first and a second source distribution function having the said property (the sum of the autocorrelation functions is zero with the exception of a value in one point (the origin)) are referred to as complementary combinations or complementary source distribution functions.
In the case of self-radiating objects, the array of radiation sources is effectively replaced by a corresponding array of diaphragms with holes wherethrough the radiation emitted by the object passes and is incident on a recording medium. The method can be used for two-dimensional as well as three-dimensional objects. In the case of three-dimensional objects, the reconstruction of the individual layers can be continuously performed by changing the scale of all superposition images on the recording means.
The artefact-free decoding of a layer may be understood to mean that the radiation sources are subdivided into groups of each time positive sources (recording on a positive film) and negative sources (recording on a negative film), so that the sum of the autocorrelation of the distributions in the origin
REFERENCES:
patent: 4149259 (1979-04-01), Kowalski
patent: 4212062 (1980-07-01), Kohno et al.
patent: 4241404 (1980-12-01), Lux
patent: 4326252 (1982-04-01), Kohno et al.
Pasedach Klaus
Weiss Hermann
Haken Jack E.
Smith Jerry
U.S. Philips Corporation
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