Patent Number: 
Section: description

FIG. 1 illustrates a measurement path in an X-ray (testing) machine, not shown in detail. In a known manner, an X-ray source 1 generates X-ray radiation FX and radiates it onto an object 2 to be X-rayed, the object 2 being located on a transport device 3. A collimator or aperture arrangement 4a, 4b generates a primary beam FX1 preferably as a pencil beam. As dictated by the crystal-lattice structure of the material of the object 2 to be X-rayed, the primary beam FX1 is diffracted in a known way at a plurality of lattice points G (only one is shown here). As a result of the diffraction at the lattice points, at least part of the primary beam FX1 is deflected as the radiation FX1xe2x80x2 with a specific beam energy at an angle "THgr"M that is a function of the material. In a known manner, this condition is utilized to determine the material in the beam on the basis of the physical effect of X-ray diffraction (Bragg""s interference pattern). Through the predetermined of a specific angle "THgr"M, different energies are measured (in accordance with Bragg) and compared to known values. FIG. 2 illustrates a collimator 6, which can be used to determine the material or type of material of the object X-rayed with the primary beam FX1 (FIG. 1). The collimator 6 is a round-slot collimator with a crystal detector 11 disposed behind it. Both the collimator 6 and the detector 11 are used for a measurement employing X-ray diffraction. A blind-bore-like opening 7 that is integrated into the center of the collimator 6 acts as a central collimator. At a radial distance from the central opening 7, the collimator 6 has a conically-expanding round slot 10, which determines an angular path of the predetermined angle "THgr"M. Disposed inside the opening 7 are a first detection device 8 and, behind it at a defined distance, a second detection device 9. The surface of the crystal detector 11 is large enough to permit the scattering-cone beams (radiation FX1xe2x80x2) exiting through round slot 10 to be recorded. The crystal 11 has a preferably circular, X-ray-sensitive surface 12 that faces the collimator 6. The X-ray source is indicated by 1 in FIGS. 1-3. FIG. 3 depicts a further collimator 26, which has a first detection device 28 in a central, blind-bore-like opening 27, and a second detection device 29 at a defined distance from the first detection device, preferably at the rear end of the passage 27. The first detection device 28 is embodied as a detector for relatively lower X-ray energies, while the second detection device 29 is embodied as a detector for relatively higher X-ray energies. This collimator/detection device is used, for example, for conventional material detection. FIG. 4 schematically shows the inside structure of the collimator 6, 26 with the electrical connections for signal evaluation, which are necessary for adjustment. Apertured-diaphragm arrangements 13a, 13b and 14a, 14b, are disposed, respectively, in front of the detection device 8, 28 or the detection device 9, 29. These arrangements adapt the detection surface of the detection device 8, 28 or the detection device 9, 29 to the diameter of the primary beam FX1. Elements 15 and 17 represent signal-amplifier stages, which are necessary for amplifying the signals picked up at the respective detection devices 8, 28 and 9, 29. These amplifier stages 15 and 17 are connected to display units 16 and 18, respectively, and are also connected to a microprocessor (computer) 23. The additionally-illustrated crystal detector 11 is omitted if a simple collimator 26 is to be adjusted instead of a ring-slot collimator 6. A further embodiment according to FIG. 5 employs detection devices 8, 28, 9, 29, which permit the determination of the center of gravity of the intensity distribution of the X-ray or primary beam FX1 impacting them. The detectors can be numerous individual detectors, detector arrays, four-quadrant detectors or position sensitive detectors having multiple-segmented diodes. Amplifier stages that operate in parallel are disposed downstream of these detection devices 8, 28, 9, 29; for the sake of a clear overview, the stages are only indicated by a respective reference numeral 19 or 21. An amplifier of the respective amplifier stage 19, 21 is associated with each individual detector, each detector in the array and each diode in the detection devices 8, 28, 9, 29. A display unit 20 or 22 is disposed downstream of these amplifier stages 19, 21. The amplifier stages 19, 21 are also electrically connected to the microprocessor 23. The first collimator arrangement 13a, 13b and the second collimator arrangement 14a, 14b, or only the second collimator arrangement 14a, 14b from FIG. 4, can be omitted if the orientation is effected in a pencil beam (point beam) FX1. Regardless of the embodiment, the adjustment process is performed as follows: As shown in FIG. 6, the X-ray radiation emitted as a primary beam FX1 and observed inside the passage 7 prior to the adjustment may be located outside of the center of the first and second detection devices 8, 28 and 9, 29. A first point P1 that is predetermined for the adjustment and a second point P2 on the primary beam do not coincide with the respective center point (center) of the detection device 8, 28 or 9, 29. Consequently, the collimator 6, 26 must be oriented spatially, that is, in three planes, to reach its optimum spatial position without having any tilt relative to the primary beam FX1. In a first step of the adjustment, the collimator 6, 26 is moved, for example in a plane perpendicular or approximately perpendicular to the propagation direction of primary beam, until the generated signal is maximal in the first detection device 8, 28. The primary beam FX1 lies in the point P2, further outside of the center of the second detection device 9, 29. The signals generated in the detection devices 8, 28 and 9, 29 are displayed on the display unit 16 and 20, respectively. For the optimum orientation of the collimator 6, 26, it is necessary to orient the collimator toward the second point P2 in a second step. For the orientation toward this point, the collimator 6, 26 is rotated or adjusted in two independent planes about an imaginary point P3, which is preferably located near the center of the first detection device 8, 28, until the signal from the second detection device 9, 29 is also at its maximum. This rotational plane encompasses a pointed conical region (see arrows) originating from the point P3. After this second step, the maximum of the first rotational plane is established, effecting a first local pre-orientation of the collimator 6, 26. After the intensity maximum in the first plane has been determined, the rotation in the second rotational plane is initiated for the further spatial orientation. A point near the center of the first detection device 8, 28 is also selected for this orientation; the point P3 can serve as a reference. Also in this case, the collimator 6, 26 is rotated inside the pointed conical region such that the intensity maximum is established at the respective detection devices 8, 28 or 9, 29. This procedure is also to be performed in the third rotational plane, so the primary beam FX1 then impacts the centers of the first and second detection devices 8, 28, 9, 29 at a right angle. The order of the collimator moving and rotating steps may be varied depending, for example, on the initial alignment condition and alignment reproducibility. In an embodiment comprising a plurality of position-sensitive detectors, the amplitudes of the individual signals of the detection devices 8, 28 and 9, 29 are first analyzed step-wise in the microprocessor (computer) 23 and further processed. The current position of the beam center of the primary beam FX1 is determined from the individual signals and compared to the center of the respective detection device 8, 28 or 9, 29. The detection centers are readjusted to the beam center of the primary beam FX1 until the generated signal values are at their maximum. In this way, an offset between the respective detection center and the center of the primary beam can be more clearly identified and corrected in one step with the aid of a one-time calibration. In an embodiment comprising a four-quadrant detector in the detection device 8, 28 or 9, 29, the signals generated quadrant-wise are evaluated, with the detection center being established when the primary beam FX1 impacts the common intersection of the quadrants and generates signals of identical magnitude in each quadrant. Thus, simplified means are used to effect an optimum orientation of the collimator 6, 26 along a primary beam FX1. The collimator position in an X-ray testing machine (not shown in detail here) is sequentially varied with the aid of a regulating device (not shown in detail here) until both of the detection devices 8, 28 and 9, 29 are impacted maximally by the primary beam FX1. The collimator 6, 26 is rotated stepwise in the individual planes by mechanical elements installed in the X-ray machine, which are automatically controlled and regulated with a program controlled by the microprocessor (computer) 23. The intensity maxima determined in the first adjustment can be stored for future use. In the use of a calibrated collimator 6, 26 with a plurality of location-sensitive detectors, a one-time measurement can immediately reveal the offset between the primary-beam maximum and the detection center, and the method can correct the offset. It is further possible to use a plurality of detection devices that are disposed one behind the other inside the passage 7, but it is not necessary for the adjustment process itself, because this feature renders the method more costly. The invention now being fully described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.