SENSITIVITY CORRECTION COEFFICIENT CALCULATING SYSTEM AND X-RAY ANALYZER

Abstract

The invention provides a sensitivity correction coefficient calculating system for an X-ray detector with which the sensitivity correction coefficient can be calculated using a multipurpose X-ray source instead of a specific X-ray source. In the sensitivity correction coefficient calculating system for an X-ray detector having a detection surface where detection elements for detection the X-ray intensity are aligned one-dimensionally or two-dimensionally, fitting is carried out on the measured X-ray intensity detected by a detection element using an approximation function so as to calculate the sensitivity correction coefficient using the calculated X-ray intensity calculated from the approximation function and the measured X-ray intensity.

Claims

1. A sensitivity correction coefficient calculating system for an X-ray detector having a detection surface where detection elements for detecting an X-ray intensity are aligned one-dimensionally or two-dimensionally, characterized in that an X-ray source, where fitting of the X-ray intensity distribution is possible with an approximation function for the X-rays with which said detection surface is irradiated, is used to carry out function fitting on the measured X-ray intensity detected for each detection element, and the sensitivity correction coefficient for each detection element is found from the ratio of the calculated X-ray intensity calculated from the fitted approximation function to the measured X-ray intensity.

2. The sensitivity correction coefficient calculating system according to claim 1, characterized in that said approximation function is a polynomial function.

3. The sensitivity correction coefficient calculating system according to claim 1, characterized in that said approximation function is a sum of a polynomial function and a Gaussian function.

4. An X-ray analyzer, comprising: an X-ray source for emitting characteristic X-rays to a sample; an X-ray detector having a detection surface where detection elements for detecting the intensity of the X-rays emitted from said sample are aligned one-dimensionally or two-dimensionally; a correction coefficient storage unit for storing the sensitivity correction coefficient for each detection element; and an X-ray intensity distribution image forming unit for forming a corrected X-ray intensity distribution image by carrying out correction operations on the measured X-ray intensities detected by said detection elements using said sensitivity correction coefficients, characterized by further comprising: a control unit for carrying out function fitting on the measured X-ray intensity distribution gained by measuring an already-known sample and allowing the correction coefficient storage unit to store the ratio of the calculated X-ray intensity calculated by the fitting function to the measured X-ray intensity as the sensitivity correction coefficient for each detection element.

5. The X-ray analyzer according to claim 4, characterized in that said control unit uses said fitting function as a polynomial function and uses a background region where there are no peaks when measuring said already-known sample.

6. The X-ray analyzer according to claim 4, characterized in that said control unit uses the sum of a polynomial function and a Gaussian function as said fitting function and carries out fitting so that the Gaussian function is added to the location of a peak in the measured X-ray intensity distribution of said already-known sample.

Description

DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is a schematic diagram showing the configuration of an example of the X-ray diffraction analyzer according to one embodiment of the present invention;

[0029] FIG. 2 is a flow chart showing the method for using the X-ray diffraction analyzer according to the present invention;

[0030] FIG. 3 is a graph showing the measured X-ray intensity distribution of a reference sample detected by a line sensor;

[0031] FIG. 4 is a graph showing the overlapping of the measured X-ray intensities I.sub.n for the respective detection elements and the calculated X-ray intensity i.sub.n;

[0032] FIG. 5 is a graph showing the sensitivity correction coefficients for the respective detection elements;

[0033] FIG. 6 is a graph showing the measured X-ray intensity distribution of a powder sample detected by a line sensor;

[0034] FIG. 7 is a graph showing a corrected X-ray intensity distribution image; and

[0035] FIG. 8 is a schematic diagram showing the configuration of an example of a conventional X-ray diffraction analyzer.

DETAILED DESCRIPTION OF EMBODIMENTS

[0036] In the following, the embodiments of the present invention are described in reference to the drawings. The present invention is not limited to the below-described embodiments, but needless to say, includes various modifications as long as the gist of the present invention is not deviated from.

[0037] FIG. 1 is a schematic diagram showing the configuration of one example of the X-ray diffraction analyzer according to one embodiment of the present invention. Here, the same symbols are attached to the corresponding components as in the X-ray diffraction analyzer 101.

[0038] An X-ray diffraction analyzer 1 is provided with an X-ray source unit 10, a detection unit 20, a goniometer 30 and a computer 40 for controlling the entirety of the X-ray diffraction analyzer 1.

[0039] The detection unit 20 is provided with a line sensor (X-ray detector) 21 having a detection surface where N (1280, for example) detection elements (semiconductor elements) are aligned one-dimensionally. Thus, the measured X-ray intensity (read out data) I.sub.n (detection element number n=1, 2 . . . , N) can be outputted to the computer (control unit) 40 from each detection element.

[0040] In addition, the detection unit 20 is mounted along the 2θ axis of the goniometer 30, and at the same time, the sample S to be measured is mounted along the θ axis of the goniometer 30. The detection unit 20 and the sample S are rotated around the center axis of the goniometer 30 in accordance with the θ-2θ interlocking drive method.

[0041] The computer 40 is provided with a CPU 41, an input unit 42, a display unit 43 and a memory 44. The functions processed by the CPU 41 are described in the boxes, which include an X-ray source control unit 41a for allowing the X-ray tube 11 to emit characteristic X-rays, an acquisition unit 41b for acquiring the N measured X-ray intensities In from the line sensor 21, an X-ray intensity distribution image forming unit 41c for forming a corrected X-ray intensity distribution image, a corrected coefficient calculating unit 41d for calculating the N sensitivity correction coefficients α.sub.n, and an operation control unit 41e for driving and rotating the goniometer 30.

[0042] In addition, the memory 44 has a corrected coefficient storage unit 44a for storing the N sensitivity correction coefficients α.sub.n.

[0043] When the sample analyzing mode is turned on due to the input signal from the input unit 42, the X-ray intensity distribution image forming unit 41c substitutes the sensitivity correction coefficient α.sub.n stored in the corrected coefficient storage unit 44a and the measured X-ray intensity I.sub.n acquired by the acquisition unit 41b into the formula (1) so as to calculate the corrected X-ray intensity I.sub.n′, and forms a corrected X-ray intensity distribution image that shows the relationship between the corrected X-ray intensity I.sub.n′ and the detection element number n so as to display the resulting image on the display unit 43 in accordance with the control.

[0044] When the user turns on the sample analysis mode, the sample S to be measured is mounted at the center of the goniometer 30 along the θ axis, and a powder sample that is formed in a square plate shape having sides of approximately 20 mm by means of a sample holder can be cited as an example of the sample S to be measured.

[0045] When the sample analyzing mode is turned off due to the input signal from the input unit 42, that is to say, when the system is set to the correction coefficient calculating mode, the correction coefficient calculating unit 41d finds an approximation cubic function (4′) by carrying out fitting on the measured X-ray intensity In acquired by the acquisition unit 41b using the cubic function (4) for each detection element and substitutes the calculated X-ray intensity in calculated from the approximation cubic function (4′) and the measured X-ray intensity In into the formula (3) so as to calculate the sensitivity correction coefficient α.sub.n, and thus allows the correction coefficient storage unit 44a to store the resulting sensitivity correction coefficient α.sub.n in accordance with the control.

I=an.sup.3+bn.sup.2+cn+d  (4)

I=−1.sup.−0.6n.sup.3−0.0024n.sup.2+0.384n+31744  (4′)

[0046] When the user or a service person sets the system to the correction coefficient calculating mode, a reference sample (already-known sample) S′ that emits X-rays having a region without a steep difference in the intensity is mounted at the center of the goniometer 30 along the θ axis, and a square copper plate having sides of approximately 20 mm can be cited as an example of the reference sample S′. When the acquisition unit 41b acquires the measured X-ray intensity In from the reference sample S′ which is a copper plate that emits X-rays having a region (background region) where there are no diffraction peaks, the operation control unit 41e may automatically drive and rotate the goniometer 30 so that the detection surface of the line sensor 21 can be irradiated with the diffracted X-rays from the region where there are no diffraction peaks.

[0047] Next, an example of a method for using the X-ray diffraction analyzer 1 is described. FIG. 2 is a flow chart showing the method for use.

[0048] First, in the process in step S101, the CPU 41 determines whether or not the sample analyzing mode has been turned off.

[0049] When it is determined that the sample analyzing mode has been turned off, that is to say, the system has been set to the correction coefficient calculating mode, the procedure moves to the process in step S102.

[0050] In the process in step S102, the user places a reference sample S′ at the center of the goniometer 30 along the θ axis.

[0051] Next, in the process in step S103, the surface of the reference sample S′ is irradiated with the characteristic X-rays emitted from the X-ray tube 11 via the emanation slit 12, and the line sensor 21 that is mounted along the 2θ axis, detects the diffracted X-rays emitted from the reference sample S′. FIG. 3 is a graph showing the intensity distribution of the measured X-rays from the reference sample S′ that are detected by the line sensor 21.

[0052] Next, in the process in step S104, the correction coefficient calculating unit 41d carries out fitting on the measured X-ray intensity I.sub.n acquired by the acquisition unit 41b with the cubic function (4) using a publicly-known operation, and thus prepares an approximation cubic function (4′).

[0053] Furthermore, in the process in step S105, the approximation cubic function (4′) is used to calculate the calculated X-ray intensity i.sub.n for each detection element using the approximation cubic function (4′). FIG. 4 is a graph showing the overlapping of the measured X-ray intensities I.sub.n for the respective detection elements and the calculated X-ray intensity i.sub.n.

[0054] Next, in the process in step S106, the correction coefficient calculating unit 41d substitutes the measured X-ray intensity I.sub.n for each detection element and the calculated X-ray intensity i.sub.n into the formula (3) so as to calculate the sensitivity correction coefficient α.sub.n for each detection element, and stores the resulting sensitivity correction coefficient α.sub.n the correction coefficient storage unit 44a. FIG. 5 is a graph showing the sensitivity correction coefficients α.sub.n for the respective detection elements. Then, the procedure returns to the process in step S101 after the completion of the process in step S106. That is to say, when the correction coefficient calculating mode is set, the processes in steps S102 through S106 are carried out so that the N sensitivity correction coefficients α.sub.n stored in the correction coefficient storage unit 44a are updated to N new values.

[0055] Meanwhile, when it is determined that the sample analyzing mode has been turned on in the process in step S101, the user places a sample S to be measured at the center of the goniometer 30 along the θ axis in the process in step S107.

[0056] Next, in the process in step S108, the surface of the sample S to be measured is irradiated with the characteristic X-rays emitted from the X-ray tube 11 via the emanation slit 12, and the line sensor 21 that is mounted along the 2θ axis detects the diffracted X-rays emitted from the sample S to be measured. FIG. 6 is a graph showing the intensity distribution of the measured X-rays from the sample S to be measured detected by the line sensor 21.

[0057] Next, in the process in step S109, the X-ray intensity distribution image forming unit 41c substitutes the sensitivity correction coefficient α.sub.n stored in the correction coefficient storage unit 44a and the measured X-ray intensity I.sub.n acquired by the acquisition unit 41b into the formula (1) so as to calculate the corrected X-ray intensity I.sub.n′.

[0058] Next, in the process in step S110, the X-ray intensity distribution image forming unit 41c forms a corrected X-ray intensity distribution image showing the relationship between the corrected X-ray intensity I.sub.n′ and the detection element number n and displays the resulting image on the display unit 43. FIG. 7 is a graph showing the corrected X-ray intensity distribution image.

[0059] Next, in the process in step S111, it is determined whether or not a new sample S to be measured is to be analyzed. When it is determined that a new sample S to be measured is to be analyzed, the procedure returns to the process instep S101. When it is determined that a new sample S to be measured is not to be analyzed, the present flow chart is complete.

[0060] As described above, in the X-ray diffraction analyzer 1 according to the present invention, the simple operations of setting the correction coefficient calculating mode at an appropriate time after shipping to the user and placing a reference sample S′ can allow the sensitivity correction coefficient α.sub.n to be calculated.

Other Embodiments

[0061] (1) Though the X-ray diffraction analyzer 1 has such a structure where a line sensor 21 having a detection surface where N detection elements are aligned one-dimensionally is provided and a one-dimensional approximation function (curve) is used as described above, the structure may be provided with an X-ray detector having a detection surface where N×M detection elements are aligned two-dimensionally where a two-dimensional approximation function (curved surface) is used.

[0062] (2) Though the X-ray diffraction analyzer 1 has such a structure where a cubic function (4) is used as an approximation function as described above, the structure may use a linear function or a quadratic function as an approximation function depending on the type of reference sample S′. Alternatively, the structure may use a combination of a cubic function and a Gaussian function as an approximation function. That is to say, the characteristics of the intensity distribution of the X-rays with which the detection surface is irradiated may be taken into consideration so that a function that is appropriate for these can be used.

[0063] (3) Though the above-described embodiment provides the structure of the X-ray diffraction analyzer 1, a structure of an X-ray fluorescence analyzer or an X-ray absorption spectroscope may be provided instead of the X-ray diffraction analyzer.

[0064] Though the sensitivity correction coefficient α.sub.n is calculated when the X-ray detector is in the form of the X-ray diffraction analyzer 1, the sensitivity correction coefficient may be calculated by using a multipurpose X-ray source when the X-ray detector is in the form of a line sensor in a line sensor production factory, for example.

INDUSTRIAL APPLICABILITY

[0065] The present invention can be applied to X-ray analyzers that are used as X-ray diffraction analyzers, X-ray fluorescence analyzers and X-ray absorption spectroscopes.

EXPLANATION OF SYMBOLS

[0066] 1 X-ray diffraction analyzer

[0067] 21 Line sensor (X-ray detector)