X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
2000-08-11
2001-09-25
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C378S070000, C378S071000
Reexamination Certificate
active
06295335
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the inspection by radiography of an object possessing a crystal lattice.
2. Discussion of the Background
Non-destructive tests (also called non-destructive testing) make it possible to provide information about the condition of a part or a structure without any resulting changes which could prejudice their ulterior use. Thus it is possible to detect internal defects which cannot be revealed during a superficial inspection. Internal defects in a part can vary greatly: shape defects, dimension defects, the presence of inclusions, cracks, etc.
The principle of detecting a defect, according to non-destructive testing, consists of exciting the defect and collecting its response. Thus a part to be inspected can be submitted to a flux of ionising radiation and, by studying the transmitted flux, one can detect an eventual defect thanks to the perturbation of the flux it introduces.
By submitting the part to be inspected to very short wavelength electromagnetic radiation (X or &ggr;), it is possible to collect intensity modulations of the beam transmitted under the form of an image on an appropriate receptor (for example a film). The radiography (X or &ggr;) uses a detector in real time which is an element or an assembly of elements transforming photons (X or &ggr;) into an electric signal which at the outlet delivers either an analogue signal, or digital data. Besides these X and &ggr; radiography procedures, there is also neutrography which uses neutron beams.
According to the radioscopy (X or &ggr;) procedure the radiographic image is captured, by a fluorescent screen for example, and produces an optical image which can be observed directly and in real time.
Contrary to a simple radiography, tomography makes it possible to provide information about the complete morphology of a defect thanks to several exposures taken under different angles.
The field of application of industrial radiography is very vast and concerns parts of all kinds.
However, when an exposure is made under the classic conditions of radiography or radioscopy, if the part being inspected possesses a crystal lattice, this irradiated crystal lattice emits radiations of the same wavelength as the electromagnetic radiation crossing through it. This secondary radiation provokes diffraction according to the Bragg equation. This diffraction causes parasitic radiation, creating confusion between the defects present in the part and the parasitic indications. These parasitic radiations can also mask the indications being looked for.
SUMMARY OF THE INVENTION
The invention has been designed to remedy the inconvenience mentioned above by attenuating the influence of this diffraction.
Thus the aim of the invention is an inspection procedure of an object by radiography, said object possessing a crystal lattice, consisting of submitting said object to electromagnetic radiation in order to obtain a radiographic image of said object on receptor means, characterised in that the radiographic image obtained, corresponding to an exposure, is a composed image resulting from a relative displacement of said object while significantly attenuating the parasitic elements produced by diffraction of the electromagnetic radiation on the crystal lattice of the object.
If the radiographic image is a radioscopy, the relative displacement of the object can be due either to a displacement in the direction of the electromagnetic radiation, or to a displacement of the said object. In this case, the composed image can be an averaged image resulting from the average of several images obtained respectively following several elementary displacements constituting said relative displacement.
If the radiographic image is a single exposure on film, the relative displacement of the object can come either from a change in direction of the electromagnetic radiation, or from a displacement of the film.
If the radiographic image is obtained by tomography and its acquisition carried out by line by line reading, the composed image can be constituted of odd lines corresponding to a first elementary displacement and even lines corresponding to a second elementary displacement.
Advantageously, the first elementary displacement corresponds to a displacement of the object from a first angle defined relative to the direction of the electromagnetic radiation, of the same amplitude as the first defined angle but with inverse sign.
A further aim of the invention is a device for inspection of an object by radiography, said object possessing a crystal lattice, comprising means of emission of electromagnetic radiation able to form a radiographic image, means of support of the object allowing said object to be submitted to said electromagnetic radiation, receptor means of the response of the object to said electromagnetic radiation and supplying a radiographic image of said object, characterised in that means are envisaged for provoking a relative displacement of said object, during the formation of a radiographic image corresponding to an exposure, so as to make it possible to obtain a composed image reproducing to a considerable extent said object while significantly attenuating the parasitic elements produced by diffraction of the electromagnetic radiation on the crystal lattice of the object.
If the device operates in radioscopy, the means provoking the relative displacement of the object can be means of displacement of the direction of electromagnetic radiation or can be constituted by the means of support of the object. The receptor means can then be means making it possible to deliver an averaged image resulting from the average of several images obtained respectively following several elementary displacements constituting said relative displacement.
If the device provides a radiographic image under the form of a single exposure on film, the means provoking the relative displacement of the object can be means for changing the direction of the electromagnetic radiation or means for displacing the film.
If the device operates in tomography, the acquisition of the radiographic image being carried out by line by line reading, the receptor means can include means for constituting said composed image from odd lines corresponding to a first elementary displacement and even lines corresponding to a second elementary displacement. The means provoking the relative displacement of the object can be constituted by the means of support of the object which ensure the first elementary displacement thanks to a displacement of the object by a first angle defined relative to the direction of the electromagnetic radiation, and which ensure the second elementary displacement thanks to a displacement of the object by a second angle defined relative to the direction of the electromagnetic radiation, the first and second elementary displacements being of the same amplitudes but of inverse signs.
REFERENCES:
patent: 5136624 (1992-08-01), Schneider et al.
patent: 5987095 (1999-11-01), Chapman et al.
Kim Robert H.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Societe Nationale d'Etude et de Construction de Moteurs d&a
Song Hoon K.
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