X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1999-03-19
2001-03-06
Bruce, David V. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S062000
Reexamination Certificate
active
06198795
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 198 12 055.9 filed Mar. 19, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to a method for processing images to recognize materials by means of X-rays in which the X-rays, emitted by a radiation source, have different energy spectra. The X-rays which penetrate an article, such as a piece of luggage containing the materials to be examined, are received by a detector, converted into signals and evaluated by a computer system.
The X-rays transilluminate the articles, such as pieces of luggage, for classifying the materials carried therein to prevent luggage holding prohibited items, for example, explosives, from clearing the safety checkpoints.
An apparatus for transilluminating luggage with X-rays is disclosed, for example, in German Offenlegungsschrift 31 42 759. The luggage is subdivided visually into local, narrow strips which are transilluminated with X-rays emanating from two X-ray sources. The weakening of the X-rays is measured at least by one line or strip-like bank of detectors and applied to an image memory. In order to obtain an overall image of the examined luggage, the separately stored measuring values obtained from the rays of the different X-ray sources are recombined by means of an electronic image processing system into a single image after the passage of the luggage.
A method for detecting luggage containing prohibited items is disclosed, for example, in German Patent No. 44 06 956. According to the method described therein, the luggage is examined in a multi-stage detector arrangement in which in a lower process stage a subdivision of the luggage into at least a two-dimensional coordinate system is effected and in a higher process stage exclusively a local examination of those luggage zones takes place which have not been unequivocally cleared.
It has been found in practice, however, that the above-outlined methods are time-consuming because the results are available only after a complete passage of the luggage and thus only after the construction of the overall image.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved method of the above-outlined type with which results, particularly as concerns the materials enclosed in an article, may be obtained as early as during the introduction of the article into the path of the X-rays.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the image processing method for recognizing a material contained in an article includes the following steps: transilluminating the article with X-rays having different energy spectra; generating, by an X-ray detector, signals representing the X-rays passing through the article; applying the signals to a computer system as continuous image data; subdividing the image data into defined zone-wise image strips; briefly storing the image strips in an image data memory; and determining the material from the image strips before completing the transillumination of the article.
The invention is based on the principle that the image data detected during a transillumination of an article are subdivided into image strips or lines and such image lines are, for a short period of time, temporarily stored in a memory as image strips to access the necessary information line by line. For this purpose, detectors supply continuous image lines which are inputted in the image memory, stored and thus stripwise evaluated or processed. In case of an on-line evaluation between the material determined from the image lines and the characteristics of the material stored in the memory, even before the construction of the image, that is, as early as during a partial transillumination of the article, a determination can be made whether the material is a prohibited substance.
The above-outlined image processing method according to the invention provides for the possibility of automatically distinguishing from one another and identifying several juxtapositioned and/or superpositioned materials. For this purpose, during the transillumination of the article, the continuously inputted image data (image dots) are combined into short image pieces and, for example, stored sequentially in a memory. With the aid of the different energy ranges the first material is determined. Such a step, as known, is performed by utilizing the weakened X-rays since the material and the material thickness affect the absorption of the X-ray radiation. If in such an image piece a further unknown material is present, then the already-determined material is filtered out of the image piece so that for the image processing there remains the determination of the second, unknown material. This means that from originally four unknown magnitudes for determining the materials two are already known and thus, the determination of the second material needs to be concentrated only to two unknown quantities. The determination of these two unknown quantities is effected in a known manner. If in the selected image piece a further material is present, then the already-determined materials are computed out or filtered out from the now necessary determination. To prevent the image processing from containing not well-determined (“watered down”) regions which may be present, since typically image processing functions cannot work correctly up to the edge of the image, the image strips are used in an overlapping fashion so that no image data are influenced by the edge effects to thus be lost during the evaluation.
REFERENCES:
patent: 4856404 (1989-08-01), Geluk
patent: 5974111 (1999-10-01), Krug et al.
patent: 31 42 759 (1983-05-01), None
patent: 44 06 956 (1997-01-01), None
patent: 0 825 457 (1998-02-01), None
patent: 92/02892 (1992-02-01), None
Beneke Knut
Henkel Rainer
Naumann Dirk
Bruce David V.
Heimann Systems GmbH
Kelemen Gabor J.
Venable
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