DIMENSIONAL MEASUREMENT METHOD USING A PROJECTIONAL IMAGE ACQUIRED BY AN X-RAYSTIC CT DEVICE

Abstract

Dimensional measurement method in which a projection image obtained from an X-ray CT device is used, wherein the dimensional measurement method comprises measuring a dimension of an object to be measured made from a single material: Taking multiple radiographic images of the object to be measured using the X-ray CT device and subsequently generating the respective projection images; Achieving a synchronization of the projection images with the CAD data used in the design of the object to be measured; Calculating the dimensions of the object to be measured using a relationship between the superimposed CAD data and the projection images; Selection of a representative group of projection images to match the superimposed CAD data; Determination of combinations of all projection values ​​of the representative projection image group with transmission lengths estimated from the CAD data; and Calculation of the dimensions of the object to be measured using a relationship between the determined projection values ​​and the estimated transmission lengths.

Description

CROSS-REFERENCE TO RELATED REGISTRATION

[0001] The disclosure of Japanese patent application No. 2018-127917, including description, drawings and claims, filed on July 4, 2018, is incorporated herein in its entirety by reference. Technical area

[0002] The present invention relates to a dimensional measurement method using a projection image acquired by an X-ray CT scanner. In particular, the present invention relates to a dimensional measurement method in which a projection image obtained from an X-ray CT scanner is used and by which, using several dozen projection images and design information, a highly precise dimensional measurement of an object to be measured made of a single material can be achieved without performing a CT reconstruction. Technical background

[0003] Medical X-ray CT scanners have been in practical use since the 1970s. Based on these techniques, industrial X-ray CT scanners emerged in the early 1980s. Since then, industrial X-ray CT scanners have been used to monitor and inspect castings for cavities, welds for defective welding, and circuit diagrams of electronic components for defects that are difficult to detect visually. With the widespread use of 3D printers in recent years, the need has increased not only for monitoring and inspecting the interior of 3D-printed items, but also for 3D dimensioning of internal structures and for higher precision.

[0004] Due to the aforementioned technical developments, the use of X-ray CT measuring devices is becoming increasingly widespread, particularly in Germany (see the published Japanese patent applications No. 2002-071345 and No. 2004-012407). Such an X-ray CT measuring device performs X-ray irradiation while simultaneously rotating an object to be measured which is positioned in the center of a rotary table.

[0005] Publication US 2008 / 0212734A1 describes a method for the online correction of nonlinearities in the imaging system during data acquisition in industrial computed tomography. It describes a method for providing corrected projection data as improved CT reconstruction, in which measurement beams are emitted from a radiation source passing through the sample, and their intensity is recorded by a detector.The following steps are planned: an initial initialization, in which the initial orientation of the sample is only roughly determined with a first rapid acquisition; an acquisition in which the position of the sample is determined more precisely, in particular by feature point pairs; a movement, in which, after successful acquisition of several projections, the position of the sample is calculated for at least one further projection; a simulation, in which a virtual CT is performed using the results from the previous step; providing input data for an adjusting correction procedure for the CT reconstruction; performing a correction, in which parameters are determined from the correction data during data acquisition by the detector and then a correction is performed; and the reconstruction, in which the projection data corrected during the acquisition process are provided as a CT reconstruction during the period at the end.

[0006] The publication JP H09-5262A describes an X-ray tube. The X-ray tube emits a fan-shaped beam of X-rays onto a specimen on a sample stage, and the transmitted X-rays pass through a collimator and a detector shield into a detector. Occasionally, the incidence from all directions is achieved by rotating the stage, i.e., the specimen, to obtain a fan-shaped projection image of the specimen. A projection image of the specimen under test is obtained in the same manner, and the respective positions of the centers of gravity of these images at each projection angle, as well as the moments of inertia about the axes of these centers of gravity, are extracted as feature values.

[0007] German patent application DE 10 2010 000 473 A1 describes a method for correcting radiographic images or projection data for CT reconstruction, wherein, during a measurement, a workpiece to be measured is positioned between an X-ray source emitting X-rays and an X-ray detector receiving the X-rays. The document further describes a method for determining parameters for computed tomography with images on a detector based on previously acquired radiographic images, as well as an arrangement for determining the structures and / or geometry of an object using a measuring system, preferably a computed tomography measuring system, consisting of at least one radiation source, at least one radiation detector, and at least one axis of rotation.

[0008] The claimed invention is defined by the subject matter of the independent claims. Further embodiments constitute the subject matter of the dependent claims.

[0009] Fig. Figure 1 shows a configuration of a typical X-ray CT scanner 1 used for measurements. An X-ray source 12, an X-ray detector 14, a rotary table 16, and an XYZ motion mechanism 18 are housed within an X-ray shielding cover 10. The X-ray source 12 emits an X-ray beam 13. The X-ray detector 14 detects the X-rays 13. An object W to be measured (for example, a workpiece) is positioned on the rotary table 16, and the rotary table 16 rotates the workpiece W for CT imaging. The XYZ motion mechanism 18 is used to adjust the position and magnify the workpiece W projected onto the X-ray detector 14. The X-ray CT scanner 1 also includes a controller 20, which controls these devices, and a control PC 22, which sends instructions to the controller 20 according to operating procedures.

[0010] In addition to controlling the devices, the control PC 22 has the function of displaying a projection image of the workpiece W projected onto the X-ray detector 14 and the function of reconstructing a tomographic image based on several projection images of the workpiece W.

[0011] As in Fig. As shown in Figure 2, the X-rays 13 emitted by the X-ray source 12 penetrate the workpiece W on the rotary table 16 and reach the X-ray detector 14. The workpiece W is rotated from all directions by the X-ray detector 14 to obtain transmission images (projection images) of the workpiece W. To generate a tomographic image of the workpiece W, a reconstruction is performed using a CT reconstruction algorithm such as a back-projection algorithm and an iterative reconstruction algorithm.

[0012] The position of the workpiece W can be moved by controlling the X, Y, and Z axes of the XYZ motion mechanism 18 and a θ axis of the rotary table 16. The imaging area (position and magnification) and the imaging angle of the workpiece W can thus be adjusted.

[0013] To obtain a tomographic image or volume data (a stereoscopic image or a set of tomographic images in the direction of the Z-axis) of the workpiece W, which is the ultimate task of the X-ray CT device 1, a CT scan is performed on the workpiece W.

[0014] The CT scan comprises two processes: the acquisition of projection images of the workpiece W and CT reconstruction. During the projection image acquisition process, the rotary table 16, on which the workpiece W is positioned, is rotated during X-ray irradiation, either continuously at a constant speed or intermittently at a constant step size. This results in the acquisition of projection images of the workpiece W in all circumferential directions at regular intervals. The projection images obtained in all circumferential directions at regular intervals are then subjected to CT reconstruction using a CT reconstruction algorithm, such as a back-projection algorithm or an iterative reconstruction algorithm. As described in Fig. 3, this results in a tomographic image or volume data of the workpiece (according to Fig. 3 mast balls).

[0015] The obtained volume data can be used to perform various measurements such as dimensional measurement and defect analysis. SUMMARY OF THE INVENTION Technical Problem

[0016] As described above, an X-ray CT-based internal and external measurement of an object involves generating volumetric data (a three-dimensional image) by CT reconstruction of a large number of projection images acquired by an X-ray CT scanner and performing a measurement on this volumetric data. Generating volumetric data with the resolution required for the measurement typically requires several hundred to several thousand projection images. When the duration of the CT reconstruction is also taken into account, the measurement process becomes very time-consuming.

[0017] The present invention was developed to solve the problem described above in conventional technology, and one of its objectives is to achieve a highly precise dimensional measurement of an object to be measured made of a single material using several dozen projection images and construction information without performing a CT reconstruction. Solution to the problem

[0018] The present invention solves the aforementioned problem of measuring the dimension of an object to be measured made of a single material by: taking several radiographic images of the object to be measured using an X-ray CT device and subsequently generating respective projection images; achieving a superposition of the projection images with CAD data used in the design of the object to be measured and calculating the dimension of the object to be measured using a relationship between the superimposed CAD data and the projection images.

[0019] Here, a representative projection image group can be selected for the superimposed CAD data. Combinations of all projection values ​​from the representative projection image group with transmission lengths estimated from the CAD data can be determined. The dimensions of the object to be measured can be calculated using a relationship between the determined projection values ​​and the estimated transmission lengths.

[0020] The attenuation coefficient of an X-ray beam can be determined using superimposed CAD data, thus reducing the difference between a calculated intensity at a measurement point with a known intensity and a design value. The dimensions of the object to be measured can then be calculated using this attenuation coefficient.

[0021] The projection images and the CAD data can be aligned by: determining barycentric positions of the object to be measured in the respective projection images; calculating a three-dimensional barycentric position of the object to be measured using the determined barycentric positions of the object to be measured in the respective projection images; determining a barycentric position of the object to be measured in the CAD data; aligning the barycentric positions of the object to be measured, determined from the respective projection images, with the barycentric positions of the object to be measured in the CAD data, and rotating the CAD data so that the orientation of the object to be measured on one of the projection images matches that of the object to be measured in the CAD data.

[0022] The barycentric position of the object to be measured in the CAD data can be determined by assuming a set of triangular pyramids with a given point as the apex and the respective triangles as the basis for all net triangles, and by determining a weighted mean of the volumes and barycenters of the respective triangular pyramids.

[0023] Alternatively, the barycentric position of the object to be measured can be determined in the CAD data using 3D solid model CAD software.

[0024] Orientation by rotating the CAD data can be achieved by determining the orientation about axes of the projection image by comparing the moment of inertia when rotating the CAD data about the axes.

[0025] The axes can be a horizontal axis and a vertical axis.

[0026] Orientation alignment by rotating the CAD data can be performed by rotating the CAD data in such a way that the contours coincide.

[0027] Orientation by rotating the CAD data can be achieved by initially determining the orientation around the horizontal and vertical axes of the projection image by comparing the moment of inertia when rotating the CAD data around the horizontal and vertical axes, and then rotating the CAD data in a plane of the projection image in such a way that the contours coincide.

[0028] The coverage of the contours can be determined based on a ratio R of an overlap area Sa to a total area Sb, i.e., R = Sa / Sb. Advantageous results of the invention

[0029] According to the present invention, no CT reconstruction is required. This significantly reduces the time required for measurement and allows internal and external measurements to be obtained without being affected by form errors resulting from a CT reconstruction algorithm.

[0030] These and other novel features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The preferred embodiments are described with reference to the drawings, in which corresponding elements in all figures are designated by the same reference numerals, wherein Fig. 1 is a sectional view showing an overall configuration of a typical X-ray CT scanner used for measurements; Fig. 2 is a perspective view that shows an arrangement of essential parts of the same; Fig. 3 is a diagram that shows an overview of a CT reconstruction through this; Fig. 4 is a diagram showing an overview of a calculation procedure according to an embodiment of the present invention; Fig. 5 is a diagram showing an overview of a strength measurement according to the embodiment; Fig. 6 is a flowchart showing a processing procedure according to the embodiment of the present invention; Fig. 7 a perspective view to describe a method for calculating the barycentric position of a projection image according to the embodiment; Fig. 8 is a top view showing the calculation of a three-dimensional barycentric position according to the embodiment; Fig. 9 is a flowchart showing a procedure for comparing CAD data according to the embodiment; Fig. 10 a diagram describing a method for calculating the barycentric position of a CAD model according to the embodiment; Fig. 11 is a diagram showing how projection images obtained from the CAD data are compared with an actual projection image according to the embodiment; Fig. 12 is a diagram showing a state in which contours are compared according to the embodiment; Fig. 13 is a diagram showing a state in which a strength is measured using a projection image according to the embodiment; Fig. 14 is a perspective view showing examples of measurement points according to the embodiment; Fig. 15 is a sectional view showing an example of a relationship between the strength of the object to be measured and that of the CAD data according to the embodiment; and Fig. 16 is a diagram showing a test result according to the embodiment. Description of the embodiments

[0032] An embodiment of the present invention is described in detail below with reference to the drawings. It should be noted that the present invention is not limited to the description of the following embodiment or the examples. The constituent features of the embodiment and the examples described below include what is readily apparent to those skilled in the art, what is essentially identical, and what falls within the so-called range of equivalence. The components disclosed in connection with the following embodiment and the examples can be suitably combined or suitably selected and used.

[0033] Fig. Figure 4 shows an overview of a calculation procedure according to the embodiment of the present invention.

[0034] According to the present embodiment, (A) a barycenter is determined, and then (B) CAD data is rotated around the x, y, and z axes of a simulator to generate virtual projection images, followed by alignment. Next, (C) a thickness measurement point is selected, and (D) the thickness is measured using the aligned CAD data and a captured image.

[0035] For a strength measurement, initially, as in Fig. 5 shown, (A) by fitting, for example, using a projection image and the entered CAD data, a CAD transmission length L = f(p) (p is an actual measured projection value) is determined based on the method of least squares using the following equation: [Eq. 1] L=f(p)=w1p+w2p2+w3p3

[0036] Next, using unit vectors n and a and the transmission length L estimated from the projection value p, a strength T is determined in (B): [Eq. 2] T=L(a→⋅n→)

[0037] Fig. Figure 6 shows details of the processing procedure according to the present embodiment.

[0038] According to the present embodiment, projection images and CAD data are initially superimposed. Then, using the projection images and the design information from the CAD data, the attenuation coefficient of an object to be measured is estimated, and the strength of a measurement point is measured.

[0039] More details will be provided in step 100 according to Fig. 6 using an X-ray CT device 1 such as the one described in Fig. The projection images shown in section 1 depict an object W to be measured. More precisely, as shown in section 1, the following are taken: Fig. Figure 2 shows the object W to be measured arranged on a rotary table 16. Radiographs are acquired while the angle of the object W is changed. The angle is changed in approximately 10 to 50 steps. The angular intervals do not need to be constant. The number of steps can theoretically be two. After retrieving the radiographs, they are logarithmically converted into corresponding projection images. In contrast, 800 to 2000 projection images are conventionally required.

[0040] The processing continues with step 110. In step 110, the barycentric positions of the respective projection images are calculated. A projection value p of a projection image is the integral of the magnitudes of a linear attenuation when the object W to be measured is irradiated with the X-ray beam 13. If the object W to be measured is made of a single material, its pixel value therefore corresponds to its mass.

[0041] As in Fig. As shown in Figure 7, an x-axis and a y-axis are set for a projection image. A three-dimensional vector from an X-ray source 12 to a pixel on an X-ray detector 14 is denoted by q(x, y). A three-dimensional vector v(θ) from the X-ray source 12 to the barycenter of the projection image can be determined by calculating a weighted average of the three-dimensional vectors q(x, y) and the projection values ​​Pθ(x, y) using the following equation: [Eq. 3] v(θ)=∫Pθ(x,y)q(x,y)dxdy∫Pθ(x,y)dxdy

[0042] Deviations of the X-ray source 12 and errors in the projection image due to the beam cone can thus be taken into account.

[0043] The processing continues with step 120. In step 120, a three-dimensional barycentric position is calculated using the barycentric positions of the respective projection images. It is assumed that the object W to be measured is fixed and that the X-ray source 12 and the X-ray detector 14 are rotated. As in Fig. As shown in Figure 8, straight line segments connecting the X-ray source 12 with the barycenters of the respective projection images (the calculation results of step 110) intersect at a point whose position is the three-dimensional barycentric position of the object W to be measured. Although the straight line segments theoretically intersect at a single point, it is possible that the actual calculations will not. In such a case, a nearest point calculated using the least squares method can be used.

[0044] The processing continues with step 130. In step 130, the alignment with the CAD data is achieved. More details will be provided at the beginning of step 140, as described in... Fig. Figure 9 shows a barycentric position of the CAD data.

[0045] As in Fig. As shown in Figure 10, for all net triangles a set of triangular pyramids is assumed with an arbitrary point O as the apex and the respective triangles as the base.

[0046] A nominal volume V i The barycenter G of each triangular pyramid is determined using the following equation (4). i The triangular pyramid is also determined: [Eq. 4] Vi=(a→×b→)⋅c→6 Gobject→=∑iViGι→∑iVi

[0047] After calculating the volume V i and the barycenters G i For all triangles, a weighted average of the volumes V is calculated. i and the barycenters G idetermined as expressed by Eq. (5). The resulting weighted mean is assumed to be the barycenter of the CAD model. The reason is that the barycenter would vary depending on the mesh size if the mean of the vertex coordinates were simply calculated. Such a technique is then used taking the volume into account.

[0048] The barycenter can be determined, for example, using a solid model (not a surface model) 3D CAD software, if the reliability of the barycenter calculation by the software is high.

[0049] Next, in step 150, the barycentric position in the CAD data and the barycentric positions of the actual projection images are aligned so that with each rotation of the CAD data, a projection image of the CAD data (a CAD projection image) can be calculated.

[0050] More precisely, how in Fig. Figure 11 shows that an arbitrary representative projection image is selected from the actual projection images. The CAD data is rotated around the barycenter so that the orientation of the actual projection image matches that of the CAD projection image. In Fig. 11 represent θ, Φ and Ψ, respectively, the angles around the x-, y- and z-axes.

[0051] A procedure for rotating the CAD data is described. As in step 160 according to Fig. As shown in Figure 9, the orientation around the two, the horizontal and the vertical rotation axes is initially determined, for example, by comparing the moment of inertia when rotating the CAD data around the horizontal and the vertical axis of the actual projection image.

[0052] More precisely, when the CAD data is rotated around the horizontal (y-) and vertical (z-) axes (according to Fig. 11 Φ and Ψ) the moment of inertia I at each angle of rotation is calculated using the following equation: [Eq. 5] I=∫Pθ(x,y)(x2+y2)dxdy

[0053] The value is compared to the moment of inertia of the actual projected image.

[0054] The values ​​of the moment of inertia are consistent if the orientation of the CAD data around the horizontal and vertical axes matches that of the actual projection image.

[0055] Once the orientation of the CAD data in relation to the representative actual projection image has been determined, the orientation of the CAD data in relation to further actual projection images can be calculated using angle information when retrieving the representative actual projection image.

[0056] Next, in step 170, the contours are compared when the CAD data is rotated in the plane of the projection image, as shown in Fig. Figure 12 shows that during contour calculation, the orientation of the actual projection image and that of the CAD projection image are aligned by calculating a degree of contour coverage R, which indicates the degree of overlap, using the following equation: [Eq. 6] R=Sa / Sb where S a an overlapping surface and S b a total area.

[0057] The higher the degree of contour coverage R, the better the match. Using the degree of contour coverage R, the orientation can therefore be calculated with a high probability of shape matching with minimal computational effort.

[0058] The captured images and the CAD data are aligned as described above. The alignment can be precisely adjusted by performing orientation alignment using a combination of the method that uses the moment of inertia and the method that uses contours, as described above. Orientation alignment can be performed using either method.

[0059] Next, the processing continues with step 200 according to Fig. 6 continued. In step 200, the thickness of the object W to be measured, which is made of a single material, is precisely measured using a projection image.

[0060] The object W to be measured and the CAD data were aligned through processing up to step 130. If the effect of beam hardening by the X-rays is ignored, as in Fig. As shown in Figure 13, the strength T at a measurement point can be expressed using the projection value p at the measurement point, an attenuation coefficient µ (unknown), and the normal vector n and the X-ray direction vector a to the surface at the measurement point as follows: [Eq. 7] T=pμ|n→⋅a→|=L|n→⋅a→| where L is the length of the transmission L = p / µ (referred to as the transmission length).

[0061] The strength T can therefore be calculated using Eq. (8) if the attenuation coefficient µ can be determined.

[0062] As in Fig. As shown in 14, several measuring points S1, ..., S i (according to Fig. 14 applies i = 6) with the same known strength T, set arbitrarily. The attenuation coefficient µ is determined such that differences between calculated strengths at the measuring points and a design value T0 are reduced.

[0063] More details will be provided in step 200 according to Fig. 6, as in Fig. 15 shown, strengths T1, T2, ..., T i Measured at several points with the same thickness T0 in the CAD data. The thicknesses include the unknown µ.

[0064] In step 210, the attenuation coefficient µ is estimated, for example, using the least squares method, as follows, so that the differences to the strengths in the CAD data decrease: [Eq. 8] E=∑i(T0−Ti)2→min E=∑i(T0−piμ|n→⋅a→|)2=∑i(T0−api|n→⋅a→|)2 (a=1μ) ∂E∂α=−∑i2pi(T0−αpi|n→⋅a→|)=0 α=T0∑ipi∑ipi2|n→⋅a→| μ=1α=∑ipi2|n→⋅a→|T0∑ipi

[0065] In step 220, the strength measurement T can be calculated using the estimated attenuation coefficient µ: [Eq. 9] T=average(T1,T2,⋯Ti)

[0066] Based on this estimate of the attenuation coefficient µ, the strength T at a given measuring point can be determined.

[0067] The actual attenuation coefficient µ fluctuates due to the effect of beam hardening. The greater the transmission length L, the lower the attenuation coefficient µ. Therefore, the previously stated linearity between L and µ is not maintained, and the pixel value becomes lower than that for the transmission length.

[0068] The transmission lengths L are then expressed by a function f of p. More precisely, several elements of the projection image data (a representative projection image group) are selected for the superimposed CAD data, and the combinations of all projection values ​​in the representative projection image group with the transmission lengths estimated from the CAD data are determined. The relationship between the obtained projection values ​​and the group of data elements to the transmission lengths is approximated using the function f.

[0069] The function f can be expressed, for example, by the following polynomial: [Eq. 10] L=f(p)=w1∗p+w2∗p2+w3∗p3⋯wn∗pn=∑(wn∗pn)

[0070] Here, the unknown constants w can be used. n for example, using the least squares method.

[0071] Several known measuring points S1, ..., S i The parameters are set arbitrarily, and the function f is determined such that the differences between the calculated thicknesses at the measurement points and the design value T0 decrease. More precisely, the function f is determined, for example, using the method of least squares, as follows, so that differences from the thickness in the CAD data decrease: [Eq. 11] E=∑(T0i−Ti)2→min Ti=L∗|n→⋅a→|=f(p)∗|n→⋅a→|

[0072] The function f is not restricted to a polynomial.

[0073] Fig. Figure 16 shows a test result. The relationship between the projection value and the transmission length determined by the above procedure was: [Eq. 12] L=f(p)=13.086914p+2.244019p2+0.321014p3

[0074] Applying the formula to five measuring points with a thickness of 20.05 to 20.07 mm yielded a mean value of 21.36 mm, with the measured values ​​at the five measuring points being 21.386114 mm, 21.242886 mm, 21.446529 mm, 21.360237 mm and 21.367506 mm.

[0075] In the foregoing embodiment, the present invention is applied to the measurement of a workpiece. However, the object to be measured is not limited to a workpiece.

[0076] It should be obvious to those skilled in the art that the embodiments described above serve only for illustration and represent the application of the principles of the present invention. Numerous modified arrangements can easily be developed by those skilled in the art without deviating from the basic idea and scope of the invention.

Claims

[1] Dimensional measurement method in which a projection image obtained from an X-ray CT device is used, wherein the dimensional measurement method comprises measuring a dimension of an object to be measured made of a single material: Taking multiple radiographic images of the object to be measured using the X-ray CT device and subsequently generating the respective projection images; Achieving a synchronization of the projection images with the CAD data used in the design of the object to be measured; Calculating the dimensions of the object to be measured using a relationship between the superimposed CAD data and the projection images; Selection of a representative group of projection images to match the superimposed CAD data; Determination of combinations of all projection values ​​of the representative projection image group with transmission lengths estimated from the CAD data; and Calculation of the dimensions of the object to be measured using a relationship between the determined projection values ​​and the estimated transmission lengths. [2] Dimensional measurement method according to claim 1, further comprising: such a determination of an attenuation coefficient of the X-rays using the superimposed CAD data, such that a difference between a calculated strength at a measurement point with a known strength and a design value decreases; and Calculation of the dimensions of the object to be measured using the attenuation coefficient. [3] Dimensional measurement method according to claim 1, wherein the projection images and the CAD data are aligned by: Determining the barycentric positions of the object to be measured in the respective projection images; Calculating a three-dimensional barycentric position of the object to be measured using the determined barycentric positions of the object to be measured in the respective projection images; Determining a barycentric position of the object to be measured in the CAD data; Achieving a match between the barycentric positions of the object to be measured, determined from the respective projection images, and the barycentric position of the object to be measured in the CAD data; and Rotating the CAD data in such a way that the orientation of the object to be measured on one of the projection images matches that of the object to be measured in the CAD data. [4] Dimensional measurement method in which a projection image obtained from an X-ray CT device is used, wherein the dimensional measurement method comprises measuring a dimension of an object to be measured made of a single material: Taking multiple radiographic images of the object to be measured using the X-ray CT device and subsequently generating the respective projection images; Achieving a synchronization of the projection images with the CAD data used in the design of the object to be measured; Calculating the dimensions of the object to be measured using a relationship between the superimposed CAD data and the projection images; where the projection images and the CAD data are brought into alignment by: Determining the barycentric positions of the object to be measured in the respective projection images; Calculating a three-dimensional barycentric position of the object to be measured using the determined barycentric positions of the object to be measured in the respective projection images; Determining a barycentric position of the object to be measured in the CAD data; Achieving a match between the barycentric positions of the object to be measured, determined from the respective projection images, and the barycentric position of the object to be measured in the CAD data; and Rotating the CAD data in such a way that the orientation of the object to be measured on one of the projection images matches that of the object to be measured in the CAD data; and wherein the barycentric position of the object to be measured in the CAD data is determined by assuming a set of triangular pyramids with a given point as the apex and the respective triangles as the basis for all net triangles and determining a weighted mean of the volumes and the barycenters of the respective triangular pyramids. [5] Dimensional measurement method according to claim 3, wherein the barycentric position of the object to be measured in the CAD data is determined using a volume model 3D CAD software. [6] Dimensional measurement method according to claim 3, wherein the orientation alignment is carried out by rotating the CAD data by determining the orientation about axes of the projection image by comparing the moment of inertia when rotating the CAD data about the axes. [7] Dimensional measuring method according to claim 6, wherein the axes are a horizontal axis and a vertical axis. [8] Dimensional measurement method in which a projection image obtained from an X-ray CT device is used, wherein the dimensional measurement method comprises the following when measuring a dimension of an object to be measured made of a single material: Taking multiple radiographic images of the object to be measured using the X-ray CT device and subsequently generating the respective projection images; Achieving a synchronization of the projection images with the CAD data used in the design of the object to be measured; Calculating the dimensions of the object to be measured using a relationship between the superimposed CAD data and the projection images; where the projection images and the CAD data are brought into alignment by: Determining the barycentric positions of the object to be measured in the respective projection images; Calculating a three-dimensional barycentric position of the object to be measured using the determined barycentric positions of the object to be measured in the respective projection images; Determining a barycentric position of the object to be measured in the CAD data; Achieving a match between the barycentric positions of the object to be measured, determined from the respective projection images, and the barycentric position of the object to be measured in the CAD data; and Rotating the CAD data in such a way that the orientation of the object to be measured on one of the projection images matches that of the object to be measured in the CAD data; and where the orientation alignment is carried out by rotating the CAD data in such a way that the contours coincide. [9] Dimensional measurement method according to claim 8, wherein the coverage of the contours is determined based on R = Sa / Sb, a ratio R of an overlap area Sa to a total area Sb. [10] Dimensional measurement method in which a projection image obtained from an X-ray CT device is used, wherein the dimensional measurement method comprises the following when measuring a dimension of an object to be measured made of a single material: Taking multiple radiographic images of the object to be measured using the X-ray CT device and subsequently generating the respective projection images; Achieving a synchronization of the projection images with the CAD data used in the design of the object to be measured; Calculating the dimensions of the object to be measured using a relationship between the superimposed CAD data and the projection images; where the projection images and the CAD data are brought into alignment by: Determining the barycentric positions of the object to be measured in the respective projection images; Calculating a three-dimensional barycentric position of the object to be measured using the determined barycentric positions of the object to be measured in the respective projection images; Determining a barycentric position of the object to be measured in the CAD data; Achieving a match between the barycentric positions of the object to be measured, determined from the respective projection images, and the barycentric position of the object to be measured in the CAD data; and Rotating the CAD data in such a way that the orientation of the object to be measured on one of the projection images matches that of the object to be measured in the CAD data; and where The orientation alignment is performed by rotating the CAD data through: Initial determination of the orientation around the horizontal and vertical axes of the projection image by comparing the moment of inertia when rotating the CAD data around the horizontal and vertical axes, and subsequent rotation of the CAD data in a plane of the projection image such that the contours coincide. [11] Dimensional measurement method according to claim 10, wherein the coverage of the contours is determined based on R = Sa / Sb, a ratio R of an overlap area Sa to a total area Sb.

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