Method for dimensional x-ray measurement, in particular by computed tomography, and x-ray computed tomography scanner

1. A method for dimensional X-ray measurement, comprising:

(a) irradiating a test object with non-monochromatic X-ray radiation from a virtually punctiform X-ray source,

(b) measuring an intensity of the X-ray radiation in a radiation path behind the test object by a flat detector which has a plurality of pixels to obtain pixel-dependent intensity data, and

(c) calculating at least one dimension of the test object using the pixel-dependent intensity data,

(d) correcting the pixel-dependent intensity data based on

an effective penetration depth change on the flat detector due to beam hardening and/or

a displacement of an effective source location change on a target of the X-ray source due to beam hardening.

2. The method according to claim 1 wherein the X-ray radiation is generated by irradiating a source point of a target with electrons,

(i) calculation of dimensions of the test object is executed using an enlargement factor, which depends on

a distance of the source point from the detector and

a distance of the source point from the test object, and that

(ii) the enlargement factor is corrected based on an X-ray emission spectrum that changes due to a changing electron penetration depth into the target.

3. The method according to claim 1 wherein

the X-ray radiation is generated by irradiating a source point of a target with electrons such that raw radiation occurs, and

further comprising filtering of the raw radiation by a filter, said filter filtering out a maximum of 75% of a total intensity of the raw radiation.

4. An X-ray computed tomography scanner, comprising:

(a) an X-ray source for generating X-ray radiation,

(b) a detector, which features a plurality of pixels, for measuring pixel-dependent intensity data of the X-ray radiation,

(c) a movement device for moving a test object relative to the X-ray source and the detector, and

(d) an evaluation unit for calculating a three-dimensional image of the test object using the pixel-dependent intensity data,

wherein the evaluation unit is designed to automatically execute a method according to claim 1 .

5. The X-ray computed tomography scanner according to claim 4 , wherein the evaluation unit is designed to automatically execute a method containing the steps:

correcting pixel-dependent intensity data based on a penetration depth on the detector and/or a displacement of the effective source location on a target of the X-ray source, such that corrected pixel-dependent intensity data is obtained, and

calculating the three-dimensional image using the corrected pixel-dependent intensity data.

6. The X-ray computed tomography scanner of claim 4 wherein the movement device is a rotation device.

7. A method for dimensional X-ray measurement, comprising:

(a) irradiating a test object with non-monochromatic X-ray radiation from a virtually punctiform X-ray source,

(b) measuring an intensity of the X-ray radiation in a radiation path behind the test object by a flat detector which has a plurality of pixels to obtain pixel-dependent intensity data, and

(c) calculating at least one dimension of the test object using the pixel-dependent intensity data,

(d) correcting the pixel-dependent intensity data based on an effective penetration depth on the flat detector and/or a displacement of an effective source location on a target of the X-ray source wherein

the pixel-dependent intensity data is corrected by a change in the effective penetration depth on the detector, said change being caused by beam hardening.

8. A method for dimensional X-ray measurement, comprising:

(a) irradiating a test object with non-monochromatic X-ray radiation from a virtually punctiform X-ray source,

(b) measuring an intensity of the X-ray radiation in a radiation path behind the test object by a flat detector which has a plurality of pixels to obtain pixel-dependent intensity data, and

(c) calculating at least one dimension of the test object using the pixel-dependent intensity data,

(d) correcting the pixel-dependent intensity data based on an effective penetration depth on the flat detector and/or a displacement of an effective source location on a target of the X-ray source, wherein

the pixel-dependent intensity data is corrected by a displacement of the effective source location on the target of the X-ray source, said change being caused by beam hardening.

9. A method for dimensional X-ray measurement, comprising:

(a) irradiating a test object with non-monochromatic X-ray radiation from a virtually punctiform X-ray source,

(b) measuring an intensity of the X-ray radiation in a radiation path behind the test object by a detector which has a plurality of pixels to obtain pixel-dependent intensity data, and

(c) calculating at least one dimension of the test object using the pixel-dependent intensity data,

(d) correcting the pixel-dependent intensity data based on an effective penetration depth on the detector and/or a displacement of an effective source location on a target of the X-ray source, wherein

the correction by a change in the effective penetration depth comprises the following steps:

for at least a majority of the pixels

(i) identifying a zero point distance of a pixel from an optical axis,

(ii) identifying an intensity of the X-ray radiation measured by the pixel,

(iii) allocating a corrected position depending on the zero point distance and the intensity for the pixel, and

(iv) calculating corrected pixel-dependent intensity data from all corrected positions and the corresponding intensities.

10. The method according to claim 9 , wherein

a corrected position and a zero point distance of an original position lie on one line.

11. The method according to claim 9 wherein

a differential distance between the zero point distance of a corrected position and a zero point distance of an original position is calculated from a term which contains a product of a function of the intensity, an intensity correction parameter and a constant.

12. The method according to claim 11 , comprising:

measuring a test object in the form of a calibration body,

changing a filter strength of a filter, and

calculating an intensity correction parameter from a displacement of a shadow image of the test object on the detector, depending on the intensity of the X-ray radiation.