DE102017100594A1 - CT parameters-Machine - Google Patents

Abstract

The invention relates to an arrangement and a method for the automatic or semi-automatic determination of setting parameters for a computed tomography based on at least one model equation for the computed tomographic determination of at least one dimensional measured variable, wherein in the model or model equations at least some of the device parameters of the computer tomograph used for the measurement In this case, default parameters to be observed in the model equation (s) are included, including at least the measurement task parameters describing the one or more measurement tasks, by simulation and / or mathematical calculation based on the one or more model equations and / or computed tomographic test measurements available Parameter space of the setting parameters, the setting parameters are determined for which at least one target parameter is optimized and / or the target parameter undercuts a limit itet or exceeds.

Description

The subject matter of an independent invention is a method for the automatic adjustment of the parameters or measurement parameters used for computed tomography.

For the dimensional measurement of complex geometries (geometric features) different tactile, tactile-optical, optical or computer tomographic sensors (computed tomography or computed tomography sensors) are used. Preferably, these are operated in coordinate measuring machines (CMMs), sometimes also several sensors combined in one device (multi-sensor CMM).

Computed tomography for the dimensional measurement of workpieces is to be understood as meaning that a reconstruction of the volume information (voxel data or voxel amplitudes in the form of gray values) for the volume detected by the detector is performed from the set of two-dimensional radiographic images recorded in a plurality of rotational positions of a workpiece by means of a planar detector , where the voxel data is a measure of the local attenuation coefficients, and measurement points or surface measurement points are generated at material boundaries by surface extraction methods from the voxel data. Measurements on the workpiece or dimensions of features or structures on the workpiece can be determined from these surface measuring points, that is to say dimensional measurements take place. The surface of the workpiece is represented for example by networking the surface points in the so-called STL (Standard Triangulation Language) format.

A computed tomography or a computed tomography (CT) sensor system generally consists of a flat detector, a radiation source, preferably X-ray source, and a mechanical axis of rotation (turntable) for rotating the workpiece to be measured in the beam cone of the detected by the detector part of the radiation source emitted radiation. In kinematic reversal, however, it is also possible to arrange the workpiece firmly and to rotate the detector and radiation source around the workpiece.

The term mechanical axis of rotation serves merely to distinguish it from a mathematical axis of rotation, when a mechanical axis of rotation (also referred to as a turntable) always permits rotation about a mathematical axis of rotation. The use of the term rotational axis therefore refers to the mathematical axis of rotation associated with the mechanical axis of rotation, insofar as the context refers to a direction, and to the mechanical axis of rotation insofar as a device is meant. The term mechanical axis of rotation denotes no restriction on the implemented within the axis of rotation guide principle between fixed and rotatable part of the mechanical axis of rotation. So it means both mechanically stored, as well as air-bearing, or otherwise such as hydraulically mounted, etc., mechanical axes of rotation. The mathematical axis of rotation is also called the physical axis of rotation.

In addition to area-wide detectors, line detectors are also used as detectors. These have only a single detector line. For complete recording of radiographic information of a spatially extended workpiece workpiece and detector must be placed in several along the direction of the axis of rotation (mathematical axis of rotation) shifted positions. The resulting increased expenditure of time is avoided by the use of area detectors. Nevertheless, the present invention or the teachings of the invention can also be implemented for line detectors. Instead of processing radiographic images, ie 2D images, the information recorded with the respective detector line is processed and also referred to as radiographic images for the sake of simplicity.

In the known methods for setting the parameters provided for a computed tomography, the adjustment always takes place in relation to the image quality of one or more previously recorded radiographic images, such as, for example, the EP 2665035 A2 the applicant describes. Here, the measurement parameters are adjusted so that in particular the contrast in the radiographic images is optimized.

The prior art also provides, for example, to optimize the contrast to signal ratio (English: CNR - contrast to noise ratio) or the signal to noise ratio (English: SNR - signal-to-noise ratio).

Although it is possible to optimize the image quality in the radiographic images as the target parameter, it is disadvantageous that it does not directly affect the measurement precision (quantifiable by standard deviation, variance or repetition span), measurement deviation or measurement accuracy, in particular the measurement uncertainty or extended Uncertainty, or the structure resolution can be inferred as a target parameter or this optimized or one or more measurement tasks can be adjusted accordingly.

The measuring precision detects random or stochastic deviations during the measurement. Deviations describe systematic deviations in the measurement. The non-quantifiable concept of measurement accuracy is understood to mean random and systematic deviations, as are taken into account, for example, in the uncertainty of measurement and extended measurement uncertainty.

Measurement precision, measurement accuracy, measurement uncertainty and structure resolution refers to dimensional measurements or dimensional variables such as the position or position of a measurement point in space or measures derived on the basis of measurement points. The measuring points are determined by a surface extraction on volume data. For this purpose, the volume data are determined by reconstruction from a plurality of radiographic images of the workpiece, recorded in a plurality of rotational positions of the workpiece with respect to the X-ray sensor system, at least consisting of X-ray detector and X-ray source. Also, according to the prior art methods, consideration can not be given to such artefact correction methods or other correction methods relating to a correction of the volume data or the surface points determined from the volume data, for example in the STL format, such as those in US Pat WO 2013167616 A2 or the DE 102013107745.5 mentioned.

However, it is desirable for the measurement results of dimensional or geometrical measurements of features by means of computed tomography, in particular 3D positions in space for the dimensional features or measured variables to be linked measuring points, an optimization with respect to the parameters referred to here as target parameters measurement precision, measurement deviation , Measuring accuracy, in particular measurement uncertainty and expanded uncertainty, or structural resolution for one or more measurement tasks, where appropriate, specifying a maximum measurement time, or with respect to the target parameter measurement time for specifying the measurement precision, measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, or structural resolution, here as a default parameter designated to make. In particular, it is desirable for a large number of measurement tasks on a workpiece and taking into account the respectively assigned tolerances, and thus for possibly locally different required measurement uncertainties, to automatically propose suitable measurement parameters which are optionally optimized with respect to the measurement time. The optimization can also affect other target parameters. Thus, for example, under the condition of a given measurement precision, measurement accuracy, measurement deviation, measurement uncertainty, expanded measurement uncertainty or structure resolution and optionally measurement time, the parameters could be calculated which lead to the lowest possible radiation exposure and thus necessary minimum radiation protection measures. This would be beneficial in designing a computed tomography system in terms of the cost and weight of the equipment. But also for the selection of suitable components for a computed tomography system or the selection of a already equipped with fixed components computed tomography system as a target parameter, it is desirable to be able to check in advance, whether or with which components or systems the predetermined measurement precision, measurement accuracy, measurement error, measurement uncertainty, extended measurement uncertainty or structure resolution and, where appropriate, measurement time achievable or best achievable. Here, too, several measurement tasks can be included in the review or optimization, which can also be present on different workpieces to be measured. This makes it possible to perform a device selection or component selection which ensures in advance that all measurement tasks on different workpieces with the desired target and / or default parameters (measurement precision, measurement accuracy, measurement deviation, measurement uncertainty, expanded measurement uncertainty or structure resolution and optionally measurement time) are possible or optimal is possible.

A disadvantage of the prior art is also that initially radiographic images of the real workpiece must be recorded in order to then determine on the basis of the changed measurement parameters, to what extent an optimal image quality is present as a target parameter. This has the disadvantage that the sometimes time-consuming optimization can only be performed when the workpiece to be measured is already arranged in the computer tomograph.

It is therefore an object of the present invention to provide a method in which, for example, at least some of the adjustable parameters (device parameters) and under workpiece-specific boundary conditions (workpiece parameters) and optionally other secondary conditions (generally referred to as default parameters) Setting parameters) are automatically set or set in a computer tomography such that at least either the measurement precision or measurement deviation or accuracy, in particular Uncertainty or extended measurement uncertainty, or structure resolution (target parameter) for one or more measurement tasks (measurement task parameters) on at least one workpiece or the target parameter measurement time is optimized or at least a predetermined limit complies (then counting as a default parameter). The measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, or structure resolution should be related to the position or position of the surface points or to the geometrical or dimensional measurements calculated from surface points and not to the radiographic images.

It is also an object of the present invention to perform the automatic adjustment of at least some of the measurement parameters (adjustment parameters) as optimally as possible, in particular to provide the measurement parameters or at least starting values for the measurement parameters before the actual measurement of the workpiece. This is especially true if the measurement precision is specified as the default parameter.

To solve the invention provides that based on a model equation of computed tomography measurement, a relationship between the measurement parameters to be set (setting parameters), the default parameters and the target parameters is established and the one or more target parameters are optimized by varying the setting parameters.

The invention provides a solution for a method for the automatic or semi-automatic determination of setting parameters for a computed tomography based on at least one model equation for the computed tomographic determination of at least one dimensional measure (measurement task), in particular model equation for determining the measurement precision associated measurement precision or measurement error or measurement uncertainty in the model equation (s), at least some of the device parameters of the computer tomograph used for the measurement are considered to be distinguished by the fact that default parameters to be observed in the model equation (s) are taken into account, at least the measurement task parameters describing the one or more measurement tasks, in particular workpiece parameters count, and that by simulation and / or mathematical calculation based on the one or more model equations and / or computed tomographic test measurement In the available parameter space of the setting parameters, the setting parameters for which at least one target parameter is optimized and / or the target parameter falls below or exceeds a limit value are determined.

In this case, automatic means that after the presence or input of all parameters required for the model equation and calculation or simulation, the setting parameters determined in this case are set and used for computer tomographic measurement. In a semi-automatic procedure, the adjustment parameters are proposed to the operator. The operator can still adjust these manually before the measurement.

Computed tomographic test measurements include the evaluation of the gray values of the radiographic images as well as reconstructed volume data or surface points determined therefrom.

A first alternative according to the invention provides that the measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or expanded measurement uncertainty, or structure resolution is provided as the target parameter, and at least the measurement time as the default parameter. In this case, the measurement parameters are determined which lead to the greatest measurement precision or lowest measurement deviation or greatest measurement accuracy, in particular the lowest measurement uncertainty or lowest expanded measurement uncertainty, or best structural resolution, given measurement time, in particular maximum permissible measurement time. To optimize the measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, a minimum structure resolution is to be taken into account as the default parameter resulting from the measurement task parameters and ensures that the structure to be measured can be detected and measured separately from its environment. When optimizing the structure resolution, in particular the best, ie maximum, structure resolution is sought and, if necessary, a measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, are used as default parameters.

In particular, the invention is characterized in that at least the measurement precision or measurement deviation or Measurement accuracy, in particular measurement uncertainty or extended uncertainty, is considered for the determination of at least the maximum measurement time, and as a default parameter at least the maximum allowable measurement time is taken into account, particularly preferably as a default parameter, a minimum structure resolution is taken into account, which is derived from the one or more metrology parameters ,

Preferably, it is provided that at least the structure resolution for one or more local areas, in particular the environment of the measurement variable relevant to the measurement points, or for the entire workpiece is taken into account, preferably maximum possible structure resolution is taken into account as a target parameter, and that as a default parameter at least the maximum allowable measurement time is taken into account, with a measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or expanded measurement uncertainty, being particularly preferably taken into account as the default parameter.

A second alternative according to the invention provides that the measurement time is provided as the target parameter and at least the measurement precision and / or measurement accuracy, in particular measurement uncertainty or expanded measurement uncertainty, and / or structure resolution as default parameters. Within the scope of the optimization, the measurement parameters are determined which lead to the smallest measurement time for a given measurement precision and / or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, and / or structure resolution. The aforementioned relationship between structure resolution and measurement precision, measurement accuracy, in particular measurement uncertainty and extended measurement uncertainty is to be re-noted.

In particular, the invention is characterized in that at least the measurement time is taken into account as the target parameter, and that at least the measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or expanded measurement uncertainty, is taken into account as the default parameter for the determination of at least one dimensional measured variable, with particular preference as the default parameter a minimum structure resolution is derived, which is derived from the measurement task parameter (s).

In the first two alternatives, the default parameters include in particular the device parameters.

• – zur größten Messpräzision oder geringsten Messabweichung oder größten Messgenauigkeit, insbesondere geringsten Messunsicherheit oder erweiterten Messunsicherheit, oder besten Strukturauflösung, bei gegebenenfalls vorgegebener Messzeit, oder
• – zur geringsten Messzeit bei gegebenenfalls vorgegebener Messpräzision und/oder Messgenauigkeit, insbesondere Messunsicherheit oder erweiterten Messunsicherheit, und/oder Strukturauflösung, oder
• – zur optimalen Kombination aus Messpräzision oder Messgenauigkeit, insbesondere Messunsicherheit oder erweiterten Messunsicherheit, und Messzeit, insbesondere wenn mehrere Messaufgaben und/ oder Werkstücke berücksichtigt werden,

führen. According to a third alternative according to the invention, it is provided that the measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, or structure resolution and / or the measurement time and additionally device parameters are provided as setting parameters as target parameters. The device parameters are thus not fixed but variable in the context of various available for a computer tomograph components (eg, X-ray tubes, X-ray detectors, turntables, etc.) or various available computer tomography. The parameter space of the setting parameters is therefore extended by the device parameters of various components available for a computer tomograph and / or the device parameters of various available computer tomographs, the simulation determining the device components or the device for which the target parameter (s) are optimally respected. In particular, as part of the optimization, the device components or the computed tomography system is determined, the

• - For the greatest precision or least deviation or greatest accuracy, in particular lowest measurement uncertainty or extended measurement uncertainty, or best structure resolution, with possibly predetermined measurement time, or
• At the lowest measuring time with possibly given measuring precision and / or measuring accuracy, in particular measuring uncertainty or extended measuring uncertainty, and / or structural resolution, or
• For the optimum combination of measurement precision or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, and measurement time, in particular if several measurement tasks and / or workpieces are taken into account,

to lead.

• – zur größten Messpräzision oder geringsten Messabweichung oder größten Messgenauigkeit, insbesondere geringsten Messunsicherheit oder erweiterten Messunsicherheit, oder besten Strukturauflösung, bei gegebenenfalls vorgegebenen Vorgabeparametern wie beispielsweise Messzeit,, oder
• – zur geringsten Messzeit bei gegebenenfalls vorgegebener Messpräzision und/oder Messabweichung und/oder Messgenauigkeit, insbesondere Messunsicherheit oder erweiterten Messunsicherheit, und/oder Strukturauflösung, oder
• – zur optimalen Kombination aus Messpräzision oder Messabweichung oder Messgenauigkeit, insbesondere Messunsicherheit oder erweiterten Messunsicherheit, und Messzeit, insbesondere wenn mehrere Messaufgaben und/oder Werkstücke berücksichtigt werden,

führt. Preferably, the invention provides that the parameter space of the setting parameters is additionally extended by the device parameters of various components available for a computer tomograph and / or the device parameters of various available computer tomographs, wherein the simulation or mathematical calculation also determines the device components or the device for which the or the target parameters are optimally respected, in particular the device components or the device is determined that

• - For the greatest precision or least deviation or greatest accuracy, in particular lowest uncertainty or expanded uncertainty, or best structure resolution, with default parameters if necessary, such as measuring time ,, or
• At the lowest measuring time with possibly predetermined measuring precision and / or measuring deviation and / or measuring accuracy, in particular measuring uncertainty or extended measuring uncertainty, and / or structure resolution, or
• For the optimum combination of measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, and measurement time, in particular if several measurement tasks and / or workpieces are taken into account,

leads.

Combination means that different measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, can be required for several workpieces or dimensional measurement tasks. The device parameters are like that select that this can be fulfilled in the maximum allowable measurement time.

In all three alternatives, the default parameters include in particular the workpiece parameters of one or more workpieces, and the measurement task parameters of one or more measurement tasks on one or more workpieces. It is thus also particularly preferably also provided to carry out an optimization of the parameters of a single measurement with respect to a plurality of measurement tasks on a workpiece. In particular, in the selection of components or devices according to the third alternative solution is also provided to perform an optimization of the parameters for measurement tasks on multiple workpieces, the workpieces are measured separately.

As one of the measuring task parameters, it is particularly preferred to take into account the structural resolution which is at least necessary in order to measure the structure to be measured separately from its surroundings.

With regard to the measuring time or the minimum necessary measuring time, it should be noted that this depends on several setting parameters, such as the voltage and the current of the X-ray tube, but also on the magnification and the cone angle. This results from the fact that the length of the necessary exposure time per radiographic image depends on the irradiation of the detector. But not only the exposure time per radiographic image influence the measuring time, but also, if necessary, the number of image averages per rotational position of the workpiece, the number of rotational positions, the travel speed (rotational speed) between the rotational positions, the material properties and the geometry (eg varying thickness depending on the distance to the central beam or depending on the cone angle) of the pre-filter, the image recording mode (image acquisition in the movement, in particular rotational movement, or start-stop operation per rotational position) and possibly present motion cycles of the components turntable, detector and x-ray tube to each other, for example the raster tomography or the local tomography, the relative position of the device components to each other, for example, the focus-detector distance, the focus-object distance and the resulting magnification in the image of the measurement object on the detector. For reasons of computing time, the amount of data generated and processed also has an influence on the measuring time. Among other things, this depends on the local detector resolution (number of pixels), the digitization (bit depth) of the detector, the number of rotation steps and, if applicable, the binning used and the size of the evaluation range, ie the measurement window size (pixels of the detector used) ,

Some of these parameters can also be fixed and then count to the default parameters. In particular, the measuring time itself can be fixed as a default parameter for reasons of economy or a maximum value is below, while the measurement time influencing aforementioned parameters can be at least partially adjustment parameters, or a combination of these is to be found, without the maximum allowable measurement time exceed.

In particular, the number of rotational positions, the exposure time per radiographic image and the number of image averages per rotational position of the workpiece have an influence on the precision and accuracy of the measurement, referred to here as measurement precision or accuracy, the measurement accuracy is in particular the measurement uncertainty or expanded measurement uncertainty, but also on the structure resolution. It is therefore preferably provided according to the invention that these relationships are taken into account in the model equation. It is therefore to be considered that the measurement precision or measurement accuracy, in particular measurement uncertainty or expanded measurement uncertainty, or structural resolution can generally be improved with the measurement time, but not as desired. In general, several parameters influencing the structure resolution are to be taken into account. These are, for example, the measurement parameters such as the focal spot size of the X-ray tube or the present magnification (or magnification), but also device parameters such as the pixel size or the noise behavior of the detector or deviations when rotating the axis of rotation. There are therefore the present in each computer tomography device parameters, in particular the properties of the X-ray tomographic components such as X-ray tube, in particular power or power range and frequency range of the generated X-ray spectrum, and the detector such as pixel size and noise behavior of the pixels and number of pixels in the model equation considered. With regard to the X-ray tube, in particular the power-dependent size of the focal spot influencing the structure resolution is to be taken into account, which depends on the device parameters, for example the target material and the target cooling, and the measuring parameters, in particular the power.

In particular, it is also provided to expand the model equation in a modular fashion in order to accommodate possibly added or additionally to be considered setting parameters or device parameters. These may be, for example, those used for artifact correction or other correction algorithms, such as detector corrections such as distortion correction, shading correction, dark signal correction, light signal corrector, detector tilting, Bad pixel correction, or the like be taken into account (device parameters) or are adjustable (setting parameters).

The one or more target parameters are quantities that are to be optimized, that is to say reach a local or global maximum or minimum in the available parameter space of the setting parameters. The target parameters are preferably the measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, or the measurement time. It is also contemplated that the target parameter is the structure resolution or a collection of available device components or an available device.

The setting parameters are the measuring parameters which can be set automatically by the operator during a computer tomographic measurement and are optionally limited to a parameter space by the present properties of the components of the system (device parameters). The simulation is therefore carried out with different combinations of the values of the different adjustment parameters relative to one another, ie for the available parameter space, in order to determine the target parameters to be optimized. Setting parameters are, for example, the acceleration voltage and the current, in particular target current, the X-ray source used for computer tomography, the exposure time or integration time of the detector, if necessary the number of image averages per radiographic image, possibly also the number of pixels of the detector, which are locally averaged over Binning, the number of rotational positions of the arranged between the X-ray source and the X-ray detector workpiece in which are provided for later reconstruction radiographic images, the position and position (orientation) of the workpiece between the X-ray source and the detector, in particular the magnification present the image of the workpiece on the detector, the position of X-ray detector and X-ray source with respect to the position of the workpiece, in particular position of the turntable used to rotate the workpiece, characterized by the distance between the X-ray source and nd object distance (FOD) and the distance between the X-ray source and the X-ray detector (FDD), the spectrum of emitted X-radiation influenced by the acceleration voltage and possibly to be used mechanical beam filters and possibly other parameters.

• – Eigenschaften der Röntgenquelle, insbesondere Spannung bzw. Beschleunigungsspannung, Strom bzw. Targetstrom, elektrische Leistung und/oder Größe des Röntgenstrahlung abgebenden Brennflecks, und bevorzugt Größe des daraus resultierenden optischen Brennflecks,
• – Filtermaterial und Dicke und vorzugsweise Position des einen Strahlfilters oder Filtermaterial- und -geometrie-Kombination der mehreren Strahlfilter, vorzugsweise Auswahl vorhandenen Strahlfilters oder Kombination vorhandener Strahlfilter, vorzugsweise aus gewünschtem Spektrum der abgegebenen Röntgenstrahlung ergebend,
• – durch zumindest Beschleunigungsspannung, Targetstrom und möglicherweise Strahlfilter beeinflusstes Spektrum der abgegebenen Röntgenstrahlung,
• – Verwendung einer Schlitzblende zur Artefaktverminderung,
• – Eigenschaften des Detektors, insbesondere lokale Detektorauflösung (Anzahl der Pixel) und Lage der das Messfenster bestimmenden Pixel und/oder Integrationszeit bzw. Belichtungszeit bei der Bildaufnahme mit dem Detektor je Durchstrahlungsbild
• – Parameter der digitalen Verarbeitung, insbesondere Bild-Filterung, Binning und/oder Anzahl der Bildmittelungen je Drehstellung und/oder Digitalisierung (Bit-Tiefe) des Detektors und/oder Filter, insbesondere Hochpassfilter, bei der Rekonstruktion,
• – Korrekturverfahren, insbesondere zur Korrektur von Drift (ggf. abhängig zumindest von der Messzeit) und/oder Artefakten (ggf. abhängig von den Werkstückeigenschaften), wie beispielsweise Strahlaufhärtung und/oder Streustrahlung, und/oder Detektorkorrekturen, wie beispielsweise Verzeichnungskorrektur, Shadingkorrektur, Dunkelsignalkorrektur, Hellsignalkorrektor, Detektorverkippung und/oder Bad Pixel-Korrektur
• – Anzahl der Drehstellungen des Drehtischs, in denen Durchstrahlungsbilder des Werkstücks aufgenommen werden,
• – Verfahrgeschwindigkeit (Drehgeschwindigkeit) zwischen den Drehstellungen,
• – Bildaufnahmemodus, insbesondere Bildaufnahme in der Bewegung, insbesondere in der Drehbewegung, oder Start-Stopp-Betrieb je Drehstellung,
• – Werkstückausrichtung, insbesondere Orientierung auf dem Drehtisch
• – Werkstücklage, insbesondere Abbildungsmaßstab bzw. Vergrößerung der Abbildung des Werkstücks auf dem Detektor und/oder durch den Detektor erfasster Kegelwinkel der Röntgenstrahlung, vorzugsweise Distanz zwischen Röntgenquelle und Werkstück (FOD – focus to object distance) und Distanz zwischen Röntgenquelle und Röntgendetektor (FDD – focus to detector distance)
• – Messmodi, insbesondere Mehrfachmessung mit in Richtung der Drehachse des Drehtisches und/oder senkrecht dazu versetzten Positionen des Werkstücks (Raster-Tomografie) und/oder Ausschnitts-Tomografie (Region of interest-Tomografie) und/oder Halbseiten-Tomografie und/oder Tomografie mit eingeschränktem Winkelbereich für die Drehstellungen (180°-Tomografie).

It should also be emphasized that one or more of the following, if and to the extent that they can be set and if not fixed as default parameters, are taken into account as setting parameters

• Properties of the X-ray source, in particular voltage or acceleration voltage, current or target current, electrical power and / or size of the X-ray emitting focal spot, and preferably size of the resulting optical focal spot,
• Filter material and thickness and preferably position of a jet filter or filter material and geometry combination of the plurality of beam filters, preferably selection of existing beam filter or combination of existing beam filters, preferably resulting from desired spectrum of the emitted x-radiation,
• By at least accelerating voltage, target current and possibly beam filter influenced spectrum of the emitted X-radiation,
• Use of a slit aperture for artifact reduction,
• - Characteristics of the detector, in particular local detector resolution (number of pixels) and location of the measuring window determining pixels and / or integration time or exposure time during image acquisition with the detector per radiographic image
• Parameters of digital processing, in particular image filtering, binning and / or number of image averages per rotational position and / or digitization (bit depth) of the detector and / or filter, in particular high-pass filter, during reconstruction,
• - Correction method, in particular for the correction of drift (possibly depending on the measurement time) and / or artifacts (possibly depending on the workpiece properties), such as beam hardening and / or scattered radiation, and / or detector corrections, such as distortion correction, shading correction, dark signal correction , Brightness signal corrector, detector tilt and / or Bad pixel correction
• Number of rotational positions of the turntable in which radiographic images of the workpiece are taken,
• - Traversing speed (rotational speed) between the rotational positions,
• Image recording mode, in particular image recording in the movement, in particular in the rotational movement, or start-stop operation per rotational position,
• - Workpiece alignment, in particular orientation on the turntable
• Workpiece position, in particular image scale or magnification of the image of the workpiece on the detector and / or cone angle of the X-radiation detected by the detector, preferably distance between X-ray source and workpiece (FOD) and distance between X-ray source and X-ray detector (FDD-focus to detector distance)
• - Measuring modes, in particular multiple measurement with in the direction of the axis of rotation of the turntable and / or perpendicular thereto offset positions of the workpiece (raster tomography) and / or excerpt tomography (Region of interest tomography) and / or half-side tomography and / or tomography with limited angular range for the rotational positions (180 ° tomography).

Default parameters are the constraints to be met in computer tomographic measurement, such as the total measurement time (measurement time) for one measurement or for several partial measurements in total, when using advanced measurement modes such as so-called raster tomography or local tomography (region of interest tomography), minimum and maximum radiation power meeting the photodetector (minimum and maximum radiation that can be detected). This measuring time is preferably restricted by the user to an upper limit value (maximum permissible measuring time) in order to ensure economic efficiency. Other simultaneously specified or alternatively specified default parameters are the limits desired by the user for the measurement precision or measurement deviation or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty. This ensures that the one measurement task or the several measurement tasks can be solved preferably taking into account the assigned tolerances. In contrast to the target parameters, the default parameters have to be adhered to precisely or within the limits of a tolerance, or they must only fall below or exceed a limit value, while the target parameters are usually optimized. The measurement task parameters and the workpiece parameters are a subset of the default parameters. Fixed device parameters can also be counted to the default parameters.

• – Messzeit oder maximal zulässige Messzeit, wobei vorzugsweise die Messzeit die maximal zulässige Messzeit unterschreiten darf,
• – Messpräzision und/oder Messabweichung und/oder Messgenauigkeit, insbesondere Messunsicherheit oder erweiterte Messunsicherheit, für die Bestimmung zumindest einer dimensionellen Messgröße, oder Grenzwerte hierfür, vorzugsweise minimale Messpräzision und/oder maximale Messabweichung und/oder minimale Messgenauigeit, insbesondere maximale Messunsicherheit oder maximale erweiterte Messunsicherheit, vorzugsweise aus den Messaufgaben-Parametern abgeleitet,
• – Strukturauflösung oder schlechteste zulässige Strukturauflösung (Mindeststrukturauflösung), vorzugsweise aus den Messaufgaben-Parametern abgeleitet,
• – Messmodus wie Raster-Tomografie, Ausschnitts-Tomografie, Halbseiten-Tomografie oder Tomografie mit eingeschränktem Winkelbereich,
• – Messaufgaben-Parameter,
• – Werkstückparameter,
• – Geräteparameter.

The invention is also distinguished by the fact that one or more of the following, if and to the extent that they can not be set as adjustment parameters, are fixed or within a permissible tolerance or with respect to an extreme value, or are and are taken into account as default parameters

• - measurement time or maximum allowable measurement time, preferably the measurement time may be less than the maximum allowable measurement time,
• Measurement precision and / or measurement deviation and / or measurement accuracy, in particular measurement uncertainty or extended measurement uncertainty, for the determination of at least one dimensional measurement variable, or limit values therefor, preferably minimum measurement precision and / or maximum measurement deviation and / or minimum measurement accuracy, in particular maximum measurement uncertainty or maximum expanded measurement uncertainty , preferably derived from the measurement task parameters,
• - Structure resolution or worst permissible structure resolution (minimum structure resolution), preferably derived from the measurement task parameters,
• Measurement mode such as raster tomography, tomography, half-page tomography or limited-angle tomography,
• - measurement task parameters,
• - workpiece parameters,
• - Device parameters.

Device parameters are properties of a computed tomography system or of the individual components such as X-ray source, X-ray detector and turntable and optionally measuring axis or measuring axes of a computed tomography system and therefore fixed. If a selection of the suitable components or the appropriate computed tomography system is to be made, the parameters are variable within the parameters available and thus belong to the setting parameters.

• – Eigenschaften der Röntgenquelle, insbesondere Dicke (bei Transmissionsröhren) bzw. Winkel (bei Reflexionsröhren) des Targets, Targetmaterial, Targetkühlung, Größe der maximalen Beschleunigungsspannung, Größe des maximalen Targetstroms, Größe der maximal zulässigen elektrischen Leistung, Zusammenhang zwischen elektrischer Leistung und Brennfleckgröße, und/oder notwendige Größe des elektrischen Brennflecks, und bevorzugt Größe des daraus resultierenden optischen Brennflecks,
• – Filtermaterial und Dicke des einen Strahlfilters oder Filtermaterial- und -dicken-Kombination der mehreren Strahlfilter,
• – Eigenschaften des Detektors, insbesondere Rauschverhalten des Detektors bzw. der Detektorpixel, Anzahl der Pixel, Größe der Pixel, minimale Integrationszeit, maximale Integrationszeit, Dicke des Szintillators, Material des Szintillators und/oder Abhängigkeit der Effizienz des Photodetektors von der Wellenlänge des im Szintillator generierten Lichts,
• – Eigenschaften des Drehtisches, insbesondere Abweichungen beim Drehen wie Taumelfehler, Rundlauffehler und/oder Skalenfehler,
• – Korrekturverfahren, insbesondere zur Korrektur von Drift und/oder Artefakten, wie beispielsweise Strahlaufhärtung und/oder Streustrahlung, und/oder Detektorkorrekturen, wie beispielsweise Verzeichnungskorrektur, Shadingkorrektur, Dunkelsignalkorrektur, Hellsignalkorrektor, Detektorverkippung und/oder Bad Pixel-Korrektur.

In particular, the invention is characterized in that as device parameters one or more of the following, if and to the extent not as adjustment parameters adjustable fixed or within an allowable tolerance or with respect to an extreme value are set and are taken into account and taken into account

• X-ray source characteristics, in particular thickness (for transmission tubes) or angles (for reflection tubes) of the target, target material, target cooling, magnitude of the maximum acceleration voltage, size of the maximum target current, size of the maximum permissible electrical power, relationship between electrical power and focal spot size, and or required size of the electric focal spot, and preferably size of the resulting optical focal spot,
• Filter material and thickness of one jet filter or filter material and thickness combination of the plurality of jet filters,
• Characteristics of the detector, in particular noise behavior of the detector or detector pixels, number of pixels, size of the pixels, minimum integration time, maximum integration time, thickness of the scintillator, material of the scintillator and / or dependence of the efficiency of the photodetector on the wavelength of the scintillator generated light
• Properties of the turntable, in particular deviations during turning, such as wobble errors, concentricity errors and / or scale errors,
• Correction method, in particular for correction of drift and / or artifacts, such as beam hardening and / or scattered radiation, and / or detector corrections, such as distortion correction, shading correction, dark-signal correction, bright-signal corrector, detector tilt, and / or Bad pixel correction.

The measuring task parameters are determined by the measuring task and are thus also defined. Measuring task parameters are, for example, the position and type of linking of measuring points on the workpiece for determining the dimensional measured variable, such as distance, diameter, angle, straightness, roundness, flatness, shape deviation, position or position tolerance.

• – Lage und Art der Verknüpfung von Messpunkten am Werkstück zur Bestimmung der dimensionellen Messgröße, wie beispielsweise Abstand, Durchmesser, Winkel, Geradheit, Rundheit, Ebenheit, Formabweichung, Position bzw. Positionstoleranz,
• – Strukturauflösung, die mindestens notwendig ist, um die zu messende Struktur getrennt von ihrer Umgebung zu messen,
• – dem einen oder den mehreren zu bestimmenden dimensionellen Messgrößen zugeordnete Toleranz,
• – Unterscheidung zwischen Messaufgabe – in 2D-Durchstrahlungsbildern, wobei Zielparameter Erkennbarkeit, vorzugsweise SNR (signal to noise ratio) und/oder CNR (contrast to noise ratio), im Durchstrahlungsbild, von beispielsweise Lunkern, Rissen, Montagezuständen, Materialgrenzen bei Multimaterialteilen, ist. – in 3D-Daten, insbesondere 3D-Oberflächendaten
• – Werkstückparameter.

According to one particularly noteworthy proposal, it is provided that as measuring task parameters one or more of the following, if and to the extent that they can not be set as adjustment parameters, are fixed or within a permissible tolerance or with respect to an extreme value, and / or are taken into account and taken into account

• - location and type of linking of measuring points on the workpiece to determine the dimensional measured variable, such as distance, diameter, angle, straightness, roundness, flatness, shape deviation, position or position tolerance,
• - Structure resolution, which is at least necessary to measure the structure to be measured separately from its environment,
• The tolerance associated with the one or more dimensional measures to be determined,
• - Distinction between measuring task - in 2D radiographic images, where target parameter recognizability, preferably SNR (signal to noise ratio) and / or CNR (contrast to noise ratio), in the radiographic image, for example voids, cracks, mounting conditions, material limits in multi-material parts, is. - in 3D data, in particular 3D surface data
• - workpiece parameters.

Thus, according to the invention, measuring tasks or inspection tasks in radiographic images are also provided. Here, the setting parameters for the ideal 2D radiographic examination, such as void detection, crack detection, detection of material boundaries on multi-material parts or detection of mounting conditions are to be optimized. Here, the best recognizability is not necessarily bound to the maximum SNR (Signal to Noise Ratio) or CNR (Contrast to Noise Ratio), but depends on the specific measurement task.

The workpiece parameters result from the workpiece to be measured or the workpieces to be measured and include the geometry and the material or materials of the workpiece. Taking into account the setting parameters position and position (orientation) of the workpiece and optionally further device or setting parameters such as the beam geometry, in particular cone angle emitted by the X-ray source radiation, the maximum transmission length and all transmission lengths and thus the average transmission length. If, in addition to the transmission lengths and the setting parameters or default parameters (if not adjustable), the spectrum of the X-radiation is included, the absorption coefficient and thus the relative attenuation of the X-radiation along a respective beam results as line integral and taking into account the beam power, the beam intensity incident on the X-ray detector. Taking into account the detector efficiency, in particular the energy-dependent scintillator efficiency and the efficiency of the photodetector, the intensity of the detected radiation can be determined from this. The workpiece parameters can also be counted among the measurement task parameters since the measurement task is usually linked to the specific workpiece.

It should be particularly emphasized that the desired data of the workpiece or workpieces, in particular material or material composition, and geometry of the workpiece are taken into account as workpiece parameters.

• – einem CAD-Modell und vorzugsweise bekanntem Material bzw. bekannter Materialzusammensetzung des Werkstücks und/oder
• – Messung von Oberflächenpunkten mit einem Koordinatenmessgerät und/oder
• – Messung des Werkstücks mittels Computertomografie, insbesondere einer Schnell-Tomografie mit verringerter Messzeit, insbesondere mit eingeschränkter Anzahl von Winkelstellungen, in denen Durchstrahlungsbilder aufgenommen werden, und/oder eingeschränkter Detektorauflösung und/oder eingeschränkter Bit-Tiefe des Detektors und/oder vergrößertem Kegelwinkel der ausgenutzten Röntgenstrahlung und/oder verringerter Integrationszeit bei der Bildaufnahme und/oder verringerter Anzahl von Bildmittelungen je Drehstellung.
• – einem oder mehreren Durchstrahlungsbildern, wobei die Durchstrahlungsbilder vorzugsweise vorverarbeitet, insbesondere normiert und/oder logarithmiert und/oder gefiltert, insbesondere Hochpaß gefiltert sind, und wobei aus den dem Linienintegral der Schwächungswerte entlang der Durchstrahlungslinie zwischen jeweiligem Detektorpixel und Brennfleck entsprechenden Grauwerten der Durchstrahlungsbilder die Schwächungswerte entlang der Durchstrahlungslinie ermittelt werden,
• – Vorwissen über die maximale und ggf. mittlere Durchstrahlungslänge und das Material des Werkstücks.

Furthermore, the invention is characterized in that the desired data of the respective workpiece are determined

• A CAD model and preferably known material or known material composition of the workpiece and / or
• - Measurement of surface points with a coordinate measuring machine and / or
• - Measurement of the workpiece by means of computed tomography, in particular a rapid tomography with reduced measurement time, in particular with a limited number of angular positions in which transmission images are taken, and / or limited detector resolution and / or limited bit depth of the detector and / or increased cone angle of the exploited X-radiation and / or reduced integration time during image acquisition and / or reduced number of image averages per rotational position.
• One or more radiographic images, wherein the radiographic images are preferably preprocessed, in particular normalized and / or logarithmized and / or filtered, in particular high-pass filtered, and wherein the line integral of the attenuation values along the transmission line between respective ones Detector pixels and focal spot corresponding gray values of the transmission images the attenuation values along the transmission line are determined
• - Previous knowledge about the maximum and, if necessary, average transmission length and the material of the workpiece.

In particular, the invention is characterized in that by means of the model equation the measurement precision or measurement deviation or measurement uncertainty according to the approach of DIN ENV 13005 (Guide to specifying the uncertainty in measuring) is calculated for the individual points to be linked to the respective dimensional measure, preferably in the connection of the individual points also the approach of DIN ENV 13005 is used.

The following example shows an abstracted model equation. u = f (u ₁ , u ₂ , M)

In this case, M denotes the measurement task parameters (here by way of example for the determination of a distance between two points) and u ₁ or u ₂ the standard deviation, ie a measure of the measurement precision (scattering of the measured values by the expected value), for example two measuring points between them a measure (the distance) is to be determined. In this simple case, the measurement task parameters M result in the standard deviation u for the distance being the square root on the sum of the squares of u ₁ and u ₂ . u ₁ and u ₂ themselves each result from a model equation: u ₁ , u ₂ = f (E, G, V) where E is the setting parameters (eg, tube voltage U _B , target current I _T , number of rotational positions or projections n _P , number of image averages t _I , focus-detector distance FDD, focus-object distance FOD, magnification M as a function of FDD and FOD, filter thickness l _filter , filter material), G are the device parameters (eg tube voltage, scintillator parameters, photodetector parameters, digital processing parameters) and V are the default parameters (eg measuring time, structure resolution).

In the example, the set of adjustment parameters E is sought, which leads to a minimum u (standard deviation for the distance between the two measurement points).

Preferably, it is provided that a plurality of measuring tasks, in particular measuring task parameters describing a plurality of dimensional parameters, are taken into account, wherein at least the maximum permissible measuring time is preferably taken into account as the default parameter.

In particular, the invention is characterized in that the one or more considered measured variables can be measured taking into account the respective associated tolerance, in particular measuring magnitudes or measurement deviations or measurement uncertainties assigned to the measured variables have at least 5 times lower, preferably at least 10 times lower value than the respective tolerance , wherein preferably at least the maximum permissible measuring time is taken into account as a default parameter.

• – Strahlaufhärtung und/oder
• – Kegelstrahlartefakte und/oder
• – Aliasing-Artefakte und/oder
• – Off-Focal-Effekte und/oder
• – Streustrahlung und/oder
• – Bragg-Reflektion und/oder
• – Drift, insbesondere zwischen zumindest zwei der Komponenten Drehtisch, Werkstück, Detektor und Röntgenquelle.

Preferably, the invention provides that the setting parameters are adjusted so that as few and / or low-trained artifacts occur, in particular low-trained

• - beam hardening and / or
• - cone beam artifacts and / or
• - aliasing artifacts and / or
• - off-focal effects and / or
• - scattered radiation and / or
• Bragg reflection and / or
• Drift, in particular between at least two of the components turntable, workpiece, detector and X-ray source.

For this purpose, it is provided, for example, that beam filters are used to influence the spectrum of the X-ray emitted by the X-ray tube, in particular to cut in the selected frequency ranges or at least to weaken them in order to generate narrowband radiation. The position of the beam filter is usually directly at the exit window of the X-ray radiation of the X-ray tube, ie fixed and thus a device parameter. The thickness and material of the beam filter are setting parameters if the computer tomograph used has a filter change. Likewise slit diaphragms are used for the reduction of stray radiation in particular. These are usually arranged between the focal spot and the workpiece. The exact position and whether any slit diaphragm is to be used are adjustment parameters).

Furthermore, the invention is characterized in that in the model equation, the influence of the jig for the workpiece is taken into account, in particular workpiece deformation and / or drift of the workpiece with respect to the turntable and / or detector and / or X-ray source, and / or restriction the measuring range available for the workpiece measurement and / or the available magnification.

In particular, the invention is characterized in that the MTF (modulation transfer function) is used for calculating or approximating and / or optimizing the structure resolution as a function of at least some of the adjustment parameters and at least some of the device parameters, wherein the focal spot size is preferably taken into account in the MTF. preferably the position and position (orientation) of the workpiece, the detector resolution, preferably the pixel aperture, and the pixel size.

The MTF is a further adjustment parameter which can be taken into account according to the invention, since this affects the blurring of the object contrast. The MTF is to be interpreted as intermediate size. It results from the setting and device parameters and has an effect on the parameters to be optimized.

Preferably, it is provided that the model equation is modularly expandable to possibly added or additional adjustment parameters or device parameters such as used for artifact correction or other correction algorithms, such as detector corrections such as distortion correction, shading correction, dark signal correction, Hellsignalkorrektor, detector tilt, Bad pixel correction or similar, which are taken into account (device parameters) or adjustable (setting parameters).

• – für eine Schnelleinstellung der Einstellparameter, wobei die Simulation bevorzugt mit verringerter als der maximal möglichen Genauigkeit durchgeführt wird (Schnell-Simulation) und/oder
• – für eine vereinfachte Simulation unter Verwendung einer eingeschränkten Anzahl von Parametern (Gerätparameter, Einstellparameter, Vorgabeparameter, Messaufgaben-Parameter und/oder Werkstückparameter)
• – durch empirischen Vergleich mit der computertomografischen Messung des Werkstücks, wobei das Modell entsprechend der Abweichungen korrigiert wird, wobei vorzugsweise Skalierungsfaktoren und/oder Korrekturkennlinien anhand von Kalibrierpunkten aus Messungen mit verschiedenen Einstellparametern verwendet werden und/oder wobei das Modell auf weitere Messobjekte ähnlicher Geometrie und Materials übertragen wird und/oder
• – durch Modellanpassung bei Verschleiß der Komponenten des Computertomografen und/oder
• – durch Modell-Interpolation innerhalb des Parameterraums der Einstellparameter und/oder Modell-Extrapolation über den Parameterraum der Einstellparameter hinaus, anhand von Stützstellen und/oder
• – Modell-Extrapolation über den Parameterraum der Werkstückparameter, also Übertragung auf andere Werkstücke, vorzugsweise anhand gemessener Werkstücke und/oder
• – für eine Schnelleinstellung der Einstellparameter, wobei die Simulation bevorzugt mit verringerter als der maximal möglichen Genauigkeit durchgeführt wird (Schnell-Simulation) und/oder
• – für eine vereinfachte Simulation unter Verwendung einer eingeschränkten Anzahl von Parametern (Gerätparameter, Einstellparameter, Vorgabeparameter, Messaufgaben-Parameter und/oder Werkstückparameter).

In particular, the invention is characterized in that the simulation is designed and / or optimized

• For a quick adjustment of the setting parameters, wherein the simulation is preferably carried out with less than the maximum possible accuracy (fast simulation) and / or
• For a simplified simulation using a limited number of parameters (device parameters, setting parameters, default parameters, measuring task parameters and / or workpiece parameters)
• By empirical comparison with the computer tomographic measurement of the workpiece, wherein the model is corrected according to the deviations, wherein preferably scaling factors and / or correction characteristics are used from calibration points from measurements with different setting parameters and / or wherein the model is based on further measurement objects of similar geometry and material is transmitted and / or
• - By model adaptation in case of wear of the components of the computer tomograph and / or
• By model interpolation within the parameter space of the setting parameters and / or model extrapolation beyond the parameter space of the setting parameters, by means of interpolation points and / or
• - Model extrapolation on the parameter space of the workpiece parameters, ie transfer to other workpieces, preferably based on measured workpieces and / or
• For a quick adjustment of the setting parameters, wherein the simulation is preferably carried out with less than the maximum possible accuracy (fast simulation) and / or
• - for a simplified simulation using a limited number of parameters (device parameters, setting parameters, default parameters, measurement task parameters and / or workpiece parameters).

In the simulation, the beam geometry of the X-ray radiation is considered according to the invention. Simplified simulation, for example, takes into account simplified beam geometries based on the central beam.

Likewise, the simulation can also be carried out for a worst-case case (worst possible measurement precision or measurement uncertainty). Instead of the exact workpiece data, the simulation is then carried out with average transmission lengths or maximum transmission lengths and material specifications, which are known, for example, as limited boundary conditions. These boundary conditions may include the existence of a standard model such as sphere, cuboid, pipe or the like.

In particular, it is also envisaged to use an empirical improvement of the automated setting of the setting parameters by a knowledge-based system for improving the model properties. In this case, a correction of the model takes place with and based on changed transfer functions. This affects device and setting parameters that may drift over time. For example, an observation of the X-ray tube wear, the detector wear, whereby the monitoring of the state of wear by evaluating the scaling factor based on the verification of the correction takes place. The check is made for example by comparison with the computer tomographic measurement of the workpiece.

Preferably, the invention provides that the position and / or position (orientation) and / or any shape or dimensions of the workpiece on the turntable is detected (workpiece detection) based on at least two radiographic images in different rotational positions of the turntable or on the basis of a fast tomography and / or by means of an additional camera.

In particular, the invention is characterized in that the position and / or position (orientation) of the workpiece (workpiece alignment) is set automatically or semi-automatically on the turntable in order to achieve or optimize the target parameter, in particular the largest measurement precision and / or smallest measurement error and / or highest accuracy, particularly preferably lowest measurement uncertainty, workpiece recognition and workpiece alignment preferably being carried out iteratively.

The alignment of the measurement object in the beam path during iterative procedure should start at the lowest possible magnification to avoid collisions when turning the turntable. If the workpiece is then roughly recognized, a more accurate detection of the workpiece without collision risk can take place at a higher magnification.

The alignment of the measurement object in the beam path to achieve ideal measurement precision or measurement uncertainty is not necessarily bound to the maximum magnification, as required by the prior art mostly. According to the invention, the magnification is taken into account as an adjustment parameter, if adjustable, but also alternative measurement modes such as raster tomography or excision tomography (region of interest tomography). However, the influence on the measuring time due to the multiple measurement has to be considered.

According to a proposal to be particularly emphasized, it is provided that the model is designed for a linear accelerator, in particular the pairing effect being included in the model equation and the simulation.

Particularly noteworthy is that in the presence of multi-material parts, wherein the detection is preferably carried out by means of rapid tomography, the simulation is optimized for one or more material transitions, in which the measured dimensional variables to be measured are present.

A particularly noteworthy proposal is that the method for the automatic or semi-automatic determination of setting parameters for a computer tomography in a measurement software (software) is performed.

The software for implementing the method for the automatic or semi-automatic determination of setting parameters for a computer tomography is connected to a particularly noteworthy proposal with the control of the computer tomograph, in particular the control of the computer tomograph coordinate measuring machine.

The subject of an independent invention is a method for adjusting the focal spot size of an x-ray tube of a sensor, preferably a computed tomography sensor or radiography sensor or laminography sensor, for inspection and / or measurement, preferably dimensional measurement, of a workpiece.

In the known methods for irradiating workpieces, such as in the present case in computed tomography, laminography or radiography, the achievable structure resolution (detail detectability) is determined at least by the size of the focal spot of the X-ray tube used for imaging, the number of pixels of the radiation images used for the detection , usually matrix-shaped detector in conjunction with the present geometric magnification, and possibly other variables such as the number of rotational steps in which radiographic images are recorded. In this case, the focal spot size only has a limiting effect if a certain minimum size is exceeded. If, therefore, work is always carried out with very small focal spot sizes, although there is no further deterioration of the pattern resolution, on the one hand, only low beam powers can be used and, on the other hand, the wear of the target material of the x-ray tube is higher than necessary.

It is therefore an object of the present invention to set the focal spot in such a way that the wear minimizes, or the power that is available can be maximized, but nevertheless the measuring task is solved and there is no further restriction of the structural resolution.

To solve the invention provides that the present without consideration of the focal spot size structure resolution is determined, in particular in which the cutoff frequency of the modulation transfer function (MTF) of the entire system is determined without regard to the focal spot and then the focal spot is set so large that just no further deterioration the structure resolution is present, so the same cutoff frequency for the modulation transfer function, taking into account the focal spot is present.

The invention provides a method for adjusting the focal spot size of an x-ray tube of a sensor, preferably a computed tomography sensor or radiography sensor or laminography sensor, for inspection and / or measurement, preferably dimensional measurement, of a workpiece, whereby transmission images of the workpiece are set in several orientations, in particular by means of a turntable Rotational positions, between workpiece and sensor with a detector, preferably planar detector, in particular X-ray detector, and wherein from the radiographic images by volume data (voxel volume) of the workpiece are determined, and preferably from the volume data by means of surface extraction measurement points (measured data) generated and used for dimensional measurement, before that is characterized in that the maximum focal spot size is set, which leads to no additional restriction of the structure resolution of the volume data (voxel data) and / or measurement data, taking into account the present without consideration of the focal spot size structure resolution, which is at least from the set voxel size and / or projected into the object plane pixel size of the detector results.

In particular, the invention is characterized in that the focal spot size is set to be smaller than or equal to the projected pixel size in the object plane or less than or equal to the voxel size.

The subject matter of an independent invention is a computer tomography device (computer tomography) with two x-ray tubes and a method for operating the computer tomograph.

When using computer tomography difficult to be irradiated workpieces sometimes several partial measurements with different X-rays are necessary. This applies, for example, to workpieces with widely differing or very large transmission lengths and multi-material workpieces made of materials of very different density, ie with greatly differing absorption behavior with respect to X-ray radiation (eg plastic and steel). In particular, for accurate dimensional measurement otherwise occurring artifacts are disturbing. The different X-ray radiation is made available according to the prior art by changing the setting parameters, in particular the beam power of the X-ray radiation or the used spectrum of X-ray radiation. The resulting partial results are fused on the level of the radiographic images or reconstructed volume data. One possible method of reducing artifacts in multi-material workpieces exemplifies the DE 102012100150 A1 the applicant, in which case only an X-ray tube is used.

However, in the case of particularly difficult to measure workpieces or particularly high accuracy requirements for the dimensional measurement, the necessary differences in the X-ray radiation to be used can no longer be realized by a single X-ray tube. Possible beam spectra and focal spot sizes related to the required beam power are different for the different available x-ray tubes (macro focus, mini focus, micro focus, nano focus, open tubes, closed tubes, tubes with transmission target, tubes with reflection target, .. .) very strong, so that the use of only one tube opens only limited possibilities. Another disadvantage is that when switching the setting parameters of a tube, a stable state (focal spot position, beam power, ...) must be awaited, whereby time losses occur.

Object of the present invention is therefore also to examine complex workpieces with very different transmission lengths or multi-material workpieces from materials of different X-ray absorption accurately and as quickly as possible, in particular to measure dimensionally. This should be done inexpensively and quickly in one device (computer tomograph), if possible without having to re-clamp the workpiece. In this case, it must also be ensured that the measurement data resulting from the partial measurements are spatially exactly assigned to one another, ie present in a common coordinate system, so that the data fusion leads to no or as small as possible measurement deviations. This is particularly important when using the inventively provided several, in particular two x-ray tubes, since they must be moved relative to the workpiece to be examined.

To solve the invention provides that the workpiece is measured automatically with two separate integrated in CT scanners X-ray tubes, which are operated with different setting parameters, ie with different X-rays. It may be identical or different X-ray sources, such as the aforementioned list, act. Both X-ray sources are controlled by a uniform control and the results of the partial measurements are made available to a uniform software and evaluated by them. The evaluation also includes the combination (fusion) of the two partial results, in which radiographic images or volume data are fused.

The invention provides for the solution a method for operating a computer tomograph comprising at least one X-ray detector, preferably planar X-ray detector, a turntable for receiving a workpiece to be measured and a first and a second X-ray source, wherein when using in each case one X-ray source radiographic images of the workpiece in several Rotary positions of the workpiece relative to the X-ray sensor (X-ray source and X-ray detector) are recorded with the X-ray detector, and wherein the radiographic images Volume data (voxel volume) of the workpiece are calculated by reconstruction, and surface points (measuring points) are preferably determined by extraction from the volume data and the measuring points are linked for the purpose of dimensional measurement of the workpiece, characterized in that the workpiece is formed with two in the Computer tomograph integrated and automatically connected to the same control and software X-ray tubes is measured, the two X-ray tubes are operated with different setting parameters, preferably operated with different X-ray spectrums, and combined with both X-ray tubes radiographic images or volume data combined by the controller and / or software and together be evaluated.

In particular, the invention is characterized in that in an automated measurement sequence, the measurement is carried out successively with two X-ray tubes, and the evaluation of the combined radiographic images or volume data takes place, each used X-ray tube, X-ray detector and workpiece relative to each other, particularly preferably X-ray tube or workpiece and detector, be aligned with each other for the measurement of the workpiece with the respective used X-ray source, preferably using measuring axes.

Preferably, it is provided that the transmission images from the measurements are combined with both x-ray tubes into a set of transmission images, preferably transmission images of mutually corresponding rotational positions are fused, and the resulting set of transmission images is reconstructed.

Among the methods of fusion of radiographic images is on the DE 102012100150 A1 referred to, which is incorporated herein by reference.

In particular, the invention is characterized in that the reconstruction already begins parallel to the recording of the radiographic images, preferably begins parallel to the recording of the radiographic images using the second X-ray tube used and the radiographic images are fused.

Preferably, the invention provides that volume data is first reconstructed from the measurements with the two x-ray tubes and these are fused.

To the procedures of the fusion of volume data is likewise on the DE 102012100150 A1 pointed.

It should also be emphasized that transmittance images or volume data which were recorded with different focal spot size and / or different resolution of the X-ray detector and / or different voxel size of the volume data and the resolution and / or voxel size of the merged radiographic images or volume data are not reduced, preferably by the use of interpolation methods and / or extrapolation methods.

The invention is also characterized in that the setting parameters of the two x-ray tubes, in particular the respective x-ray spectrum, are optimized for the respective measuring task, wherein target material of the x-ray tube and / or self-filtering of the x-ray tube and / or mechanical beam filter are selected.

In particular, the invention is characterized in that the focal spot sizes of the two x-ray tubes, in particular by adjusting the focusing of the directed to the emitting X-ray target electron radiation and / or by adjusting the beam power, preferably by adjusting the x-ray voltage and current for the respective measurement task be optimized.

According to one particularly noteworthy proposal, it is provided that the respectively required mechanical beam filter is introduced manually or automatically into the X-ray beam of the respectively used X-ray tube, preferably by controlling separate X-ray tubes associated beam filter change systems.

Particularly noteworthy is that in the measurement with the respective X-ray tube, a region of interest CT and / or a half-side CT and / or a high-speed CT and / or a raster CT is performed.

In the region of interest CT, a workpiece cutout is tomographed in such a high magnification (the workpiece is closer to the X-ray source), so that the workpiece leaves the area covered by the X-ray detector at a certain rotational position perpendicular to the rotational axis of the turntable. The missing radiographic data are taken from a second measurement of a lower magnification or simulation data based on target data of the workpiece.

In the half-side CT, the workpiece, together with the turntable, deliberately becomes rectangular to the original position of the axis of rotation of the turntable (which approximately approximately perpendicularly intersects the central beam between the focal point of the X-ray tube and the center of the detector) so arranged that only one side of the workpiece is imaged on the detector. As a result of the rotation of the workpiece, the regions, which are not initially shown, are sufficiently grasped in the further rotational positions in order to enable a reconstruction.

In the case of the fast CT, it is made use of the fact that rotational positions offset by 180 ° from one another provide, for example, redundant radiographic information (except for deviations in the rotation of the rotary axis, drifting phenomena and the like). Even with this limited set of radiographic images, a reconstruction is possible.

In raster CT, several sections of the workpiece are sequentially tomographed in the same imaging scale. For this purpose, the workpiece is brought in the direction of the axis of rotation and / or perpendicular thereto in a plurality of relative positions to X-ray tube and X-ray detector and recorded in each of the several rotational positions, the radiographic images. If the offset is perpendicular to the axis of rotation, first the radiographic images of the same rotational positions must be assembled before the reconstruction can take place. If the offset is in the direction of the axis of rotation, the same procedure can be used or, alternatively, the reconstruction and then the summarization of the volume data can take place.

To implement the previously described inventive method for examining a workpiece with different adjustment parameters using two x-ray tubes, in particular using different spectra, a suitable device is required.

The devices of the prior art, in which usually two x-ray tubes are integrated in one device, allow the optional operation of the x-ray tubes, depending on the workpiece to be examined. Here are different tasks, which can be solved either with one or the other x-ray tube. High-precision measuring tasks are solved, for example, with micro or so-called nano-focus tubes and inspection tasks usually with macro-focus tubes. A combination of the results of both studies is not provided. This is also not possible, since the investigations would have to be carried out on the same measurement object and the measurement results would have to be spatially aligned with one another. For a correct alignment, however, it is necessary to know exactly the spatial positions of the X-ray tubes, in particular of the X-ray emitting focal spots, in the respective measurement to one another and to the object and the X-ray detector. Required for this exact movement means such as measuring axes and correspondingly suitable controls and software programs are not used in the prior art.

Object of the present invention is therefore to develop a computer tomograph such that the examination of a workpiece with two x-ray tubes, which are operated with different setting parameters, can be done, the measurement results are combined, preferably the radiographic images or the volume data.

To solve the invention provides that a second x-ray tube with different setting parameters is operated in the same device and the results in the investigation of the same workpiece with both x-ray tubes, can be evaluated together by a common control and software is used.

A device according to the invention is formed by a computer tomograph comprising at least one X-ray detector, preferably planar X-ray detector, a turntable for receiving a workpiece to be measured and a first X-ray source, and control and software for recording and evaluating the in several rotational positions of the workpiece relative to the X-ray sensor (X-ray source and X-ray detector), wherein the evaluation comprises at least the reconstruction of the radiographic images to volume data (voxel volume) of the workpiece, and preferably the extraction of surface points (measuring points) from the volume data and linking the measuring points for the purpose of dimensional measurement of the workpiece, thereby characterized in that a second x-ray tube is integrated in the computer tomograph connected to the controller, wherein the controller and the software are designed to provide automated measurement g with both X-ray tubes and the joint evaluation of the same workpiece with both X-ray tubes detected radiographic images and / or volume data to realize, with first and second X-ray tube with different setting parameters are operable, preferably with different X-ray spectrums are operable.

In particular, the invention is characterized in that a plurality of different manually or automatically be introduced into the respective X-ray beam of one or both X-ray tubes mechanical beam filter for influencing the X-ray spectrum are provided, particularly preferably the X-ray tubes are each assigned separate Strahlfilterwechselsysteme, wherein the Beam filter changing systems each have a plurality of beam filters that are either manually or automatically introduced into the X-ray beam of the respective X-ray tube.

It should be emphasized that the control and the software are designed to successively irradiate the workpiece with the X-ray radiation of the respectively used X-ray tubes, wherein the different adjustment parameters are set automatically, and wherein the computer tomograph has moving means such as measuring axes which are formed workpiece, X-ray sources and X-ray detector to move relative to each other such that with the X-ray of each X-ray tube used the workpiece is detected and imaged on the X-ray detector, preferably by workpiece and X-ray detector or by the X-ray sources are moved.

The subject of an independent invention is a method for operating a computer tomograph comprising at least one X-ray source, an X-ray detector, preferably planar X-ray detector, and a rotary unit such as rotary table and / or rotary pivot unit, in particular for the dimensional measurement of a workpiece, wherein radiographic images of the workpiece in several rotational and / or pivot positions of the workpiece relative to the X-ray source and X-ray detector are recorded with the X-ray detector.

Known methods according to the prior art for computer tomographic, in particular X-ray tomographic examination of workpieces based on standard trajectories, such as the rotation of the fixed mounted on the turntable workpiece by 360 ° plus fan angle of the X-ray detected by the detector such as X-ray, or helical tomography characterized by the rotation of the workpiece while moving along the axis of rotation of the turntable, or combined trajectories such as rotating the workpiece by 360 ° plus the fan angle and then moving it along a line parallel to the axis of rotation of the turntable. In this case, the workpiece assumes a fixed position relative to the X-ray sensor system (X-ray source and X-ray detector), in particular in the case of helix tomography, at least with respect to directions deviating from the rotational axis, in particular no pivoting of the workpiece is undertaken.

This results in the disadvantage that due to the arrangement of the workpiece on the turntable under certain circumstances particularly long transmission lengths occur, which could be avoided in a changed position of the workpiece, in particular pivoted position, for at least some areas of the workpiece. This would result in more favorable transmission ratios, in particular shorter maximum transmission lengths occur, which are easier to detect metrologically and are less affected by artifacts. Other areas may be advantageously measurable in another pivot position or lateral position.

In addition, there is the problem that the exposure time of the recorded radiographic images or the number of image averages per rotational position over the entire rotation (at least 360 ° plus the fan angle) is kept constant according to the prior art. This reduces the signal-to-noise ratio for radiographic images with predominantly long transmission lengths, ie predominantly strongly attenuated regions, ie areas of high attenuation, or for the corresponding image areas such as pixels of the radiographic images, in comparison to radiographic images or corresponding areas which are affected by short radiographic lengths ,

Another object of the present invention is therefore to more accurately measure workpieces by having the lowest possible transmission lengths, but also favorable signal-to-noise ratios.

Low transmission lengths are advantageous in order to achieve favorable signal-to-noise ratios in the radiographic images, and thus a particularly accurate, in particular reproducible measurement and / or measurement with low measurement uncertainty.

However, this should also be realized in particular for regions of radiation lengths of different lengths, the reproducibility for which should therefore be constant or nearly constant, for example with respect to a reference value, for example determined by a reference measurement. It is therefore an object of the invention to determine the signal-to-noise ratio for individual pixels or regions of pixels of the transmission images or entire radiographic images and to optimize them by suitable measures also for different transmission lengths, in particular to minimize or equalize them.

To solve the invention, by means of alternative, for example, consisting of several different partial trajectories trajectories, so for example pivoted position or pivoted positions of the workpiece on the turntable and movement of the X-ray sensor (X-ray source and X-ray detector) and the workpiece relative to each other, the maximum transmission lengths and / or the number of To minimize projection images with maximum or generally long or longer transmission lengths, in particular only to produce radiographic images with the shortest possible transmission lengths or to use for evaluation. Thus, taking into account the transmission lengths of the workpiece as a function of a rotary-pivot position to be selected, in particular pivot position, the trajectory is used for the measurement, in which the shortest possible transmission lengths and thus high signal-to-noise ratios occur.

Likewise, it is provided for the solution that automatically increases in the presence of unfavorable values for the attenuation or the transmission length or the signal-to-noise ratio, the exposure time or the number of recorded and averaged in the respective rotational position radiographic images, for example, until a reference value for the weakening or the transmission length or the signal-to-noise ratio is achieved.

The invention provides for the solution a method for operating a computer tomograph comprising at least one X-ray source, an X-ray detector, preferably planar X-ray detector, and a rotary unit such as turntable and / or rotary pivot unit for receiving and adjusting the rotational and / or pivot position of the workpiece to be measured relative to X-ray detector and X-ray source, and preferably measuring axes (translation axes), for adjusting the position of the workpiece and / or the X-ray source and / or the X-ray detector in at least one axis relative to each other, wherein radiographic images of the workpiece in a plurality of rotational and / or pivotal positions of the workpiece relative to the X-ray source and X-ray detector are recorded with the X-ray detector, and wherein from the radiographic images by reconstruction volume data (voxel volume) of the workpiece are calculated, and preferably surface points (measuring points) by extraction au s the volume data are determined and the measuring points are linked for the purpose of dimensional measurement of the workpiece, characterized in that it is characterized in that using different positions of the workpiece and / or the X-ray source and / or the X-ray detector, set by means of the measuring axes (translation axes) , and / or different rotational positions and / or rotational-pivot positions of the workpiece, set using the turntable or the rotary-pivot unit, of the pure rotation of the workpiece about the axis of rotation of the turntable deviating trajectories, ie movement of the workpiece relative to X-ray source and X-ray detector for recording the multiple radiographic images used.

In particular, the invention is characterized in that the trajectories are set such that the maximum transmission lengths in the transmission images are minimized, preferably below a threshold value defined relative to the maximum possible transmission length, and / or that the minimum signal-to-noise ratios of the gray values of the transmission images are maximized be, preferably a predetermined threshold, particularly preferably relative to the lowest possible signal-to-noise ratio fixed threshold, exceed, and / or the number of the maximum transmission lengths and / or minimal signal-to-noise ratios containing transmission images is minimized, preferably based on a model of the workpiece, preferably CAD model, maximum possible transmission length and / or minimum signal-to-noise ratios and transmission lengths and / or signal-to-noise ratios for the various trajectories Rien, in particular different rotary-pivot positions of the workpiece to be simulated.

Preferably, it is provided that by means of the rotary unit and / or rotary-pivot unit and / or by means of the measuring axes (translation axes) workpiece or workpiece together with turntable and / or X-ray source and / or detector are moved to traverse the trajectories.

In particular, the invention is characterized in that by means of measuring axes (translation axes) only turntable with workpiece in the measuring volume for traversing the trajectories is moved and workpiece is rotated by means of turntable.

The measuring volume describes the region between the X-ray source and the X-ray detector, in which the workpiece can be arranged so that at least parts of it are imaged on the X-ray detector.

Preferably, the invention provides that transmission images taken in the respective trajectory are reconstructed into volume data, in particular to a common voxel volume. This requires that the rotational and / or pivotal position and position in the measurement volume (relative to the X-ray source and / or X-ray detector), ie the trajectory, is known for each radiographic image and is taken into account in the reconstruction. So that the positions are known very accurately, measuring axes are preferably used, as they are common in coordinate metrology.

It should also be emphasized that radiographic images are excluded from the reconstruction and / or replaced by interpolated and / or simulated radiographic images which maximum or average attenuation and / or maximum or average transmission length exceed a respectively defined threshold value. For this purpose, the model of the workpiece is preferably used (simulation) or else radiation images (interpolation) recorded in adjacent rotational positions.

The invention also provides a method for the solution, which is characterized in that, in the presence of maximum or average attenuation and / or maximum or average transmission lengths above predetermined threshold values and / or in the presence of minimum or average signal-to-noise ratios below a predetermined threshold, automatically increases the exposure time for the corresponding radiographic image and / or the number of superimposed images (image averaging) is increased in the respective rotational position and / or position on the trajectory until threshold values are preferably undershot and / or previously determined value or value in relation to this is determined, for example, by means of previously performed reference measurement of the workpiece with the computer tomograph or another computer tomograph. This method can be combined with the aforementioned methods or used separately from them.

According to a proposal to be particularly emphasized, it is provided that the workpiece is rotated to receive first radiographic images in an angle range from 0 ° to 180 ° plus the fan angle of the area of the x-ray radiation of the x-ray tube detected by the x-ray detector, the workpiece being rotated in a first rotation Position and / or position relative to the X-ray source and X-ray detector is arranged, preferably irradiation lengths and / or signal-to-noise ratios are optimized for first areas of the workpiece, and the workpiece for receiving second radiographic images in an angular range of 180 ° plus fan angle to 360 ° plus. Double fan angle is rotated, wherein the workpiece is arranged in a second rotary-pivot position and / or position relative to the X-ray source and X-ray detector, preferably irradiation lengths and / or signal-to-noise ratio opt for second areas of the workpiece The second regions particularly preferably correspond to the regions which, when recording the first transmission images, have exceeded predetermined threshold values with respect to transmission lengths or have fallen below in terms of signal-to-noise ratios, and where particularly preferably first and second transmission images are reconstructed into common voxel volumes ,

The subject matter of an independent invention is a method and a device for operating an x-ray tube.

Prior art apparatus and methods for generating x-radiation, in particular for use in computer tomographs, radiographers or laminography sensors, do not provide for quantitative assessment of target wear. Instead, after given cycles, the focal spot, the area of the target from which the X-ray radiation emanates when bombarded with an electron beam, is displaced on the target by mechanically displacing the target relative to the electron beam.

Rotary targets are also known in which the focal spot is parmanently guided on a circular path on the target by the target rotating.

This has the disadvantage that there may be too short or too long intervals between the shifts, and thus either no longer useful ranges of the target are used or measurements with worn target and associated disadvantages, such as fuzzy mapping and associated measurement errors, especially in computed tomography, or the destruction of the target due to excessive heat load occurs. This applies to rotatable targets on the used circular path as well.

The object of the present invention is to provide a method and a device in which the actual target wear can be quantitatively assessed and corresponding intervention limits are defined in which a displacement of the focal spot on the target is to be carried out.

It is also an object of the invention to provide the above-mentioned method and apparatus for permanently rotating targets.

To solve this, the invention provides that the assessment of the target wear is assessed on the basis of the radiation of the X-ray tube detected by an X-ray detector, in particular a surface X-ray detector, in particular the intensity of the present radiation having a reference value of a non-worn region of the target or of an as-new target is compared to the target state as comparable as possible, in particular identical X-ray tube conditions.

Now occur too large deviations of the intensities compared to the reference value, can either a manual or automated intervention is made and the focal spot is displaced on the target either by focusing the electron beam onto another region of the target or by mechanically displacing the target through appropriately provided means. The displacement may, for example, also include a rotation or a translatory movement, or a combination of both movements. It is also envisaged that the rotation or rotation is replaced by a combination of translational movements.

In the case of permanently rotating targets, the aim is to change the circular path by changing the axis of rotation about which the target rotates or about which the focal spot is guided. If the target, together with the rotation device for the target rotation, is displaced perpendicular to the axis of rotation, this also results in a changed radius for the circular path on the target. By combination of rotation and vertical displacement other tracks, such as spiral paths are provided.

The invention provides, as a solution, a method for operating an X-ray tube, preferably an X-ray tube, which is part of a computed tomography sensor or a radiography sensor or laminography sensor, wherein the X-ray tube has an X-ray emitting target, which is exposed to an electron beam, characterized in that for assessing the state of the target, in particular target wear, the point of incidence (focal spot) of the electron beam on the target and the target are shifted relative to each other and the X-ray radiation directed on an X-ray detector is evaluated in each case, in particular change in intensity during or respectively before and / or after the respective displacement of the X-ray radiation determined by the X-ray detector is assessed.

The invention also provides an independent solution or solution which can be combined with a previously described solution in the form of a method for operating an X-ray tube, which is part of a computed tomography sensor or radiography sensor or laminography sensor, wherein the X-ray tube has an X-ray emitting target which is irradiated with an electron beam It is characterized in that the point of impact of the electron beam is displaced onto the target along a circular path by rotating the target about an axis other than the direction of the incident electron beam (rotation axis) or by combining translational displacements of electron beam and target relative to one another to each other in at least two directions perpendicular to the direction of the incident electron beam, the circular path is realized about an axis of rotation, preferably as the displacement according to claim 1, the Verschi is used along the orbit or the shift to a radius and / or position of the axis of rotation changed circular path, preferably for changing the radius, the axis of rotation is moved perpendicular to its present direction, preferably by moving the target perpendicular to the present direction of the axis of rotation together with the rotating device provided for rotation or by correspondingly changed translational displacements of electron beam and target relative to each other.

In particular, the invention is characterized in that the respective present intensity is compared with a reference value, wherein the reference value at the same setting parameters of the X-ray tube, such as X-ray and X-ray current is determined, the reference value is determined when the first time use of the target or the current Time, wherein the focal spot is generated on a hitherto unused area of the target, or wherein the reference value is determined from all the intensities that occur during the one or more shifts, in particular maximum value from all intensities.

It is preferably provided that the target wear, in particular the change in intensity, is evaluated and, when a predetermined value is exceeded, this is either reported to the operator, which manually displaces the focal spot and target relative to each other, in particular by turning and / or lateral shifting, or by automatic turning and / or or lateral displacement of the target relative to the focal spot.

In particular, the invention is characterized in that rotation and / or displacement of the focal spot relative to the target by deflection of the electron beam and / or lateral displacement of the target or the target receiving body as Targetflansches or rotating device relative to the electron beam, in particular relative to the device for deflecting the electron beam having tube body.

As a solution, the invention also provides a device comprising at least one X-ray tube and an X-ray emitting target, which is exposed to an electron beam, and further comprising means for influencing the direction of the X-ray beam and / or means for the mechanical movement of the target and / or Targetflansches and / or provided for rotating the target rotating device relative to the electron beam, in particular perpendicular to the direction of the incident electron beam, or relative to the tube body, such as axes of motion.

The subject matter of an independent invention is a method for correcting the drift occurring during a computer tomographic measurement.

In the known methods for drift correction in the computed tomography (CT) measurements of a component, a simple comparison is made between the radiographic images (projection images) taken in several rotational positions of the component of a rapid tomography (reference tomography) with fewer rotational steps (rotational positions) carried out before or after the actual computer tomographic measurement. and the radiographic images (projection images) recorded during the corresponding rotational steps during the actual tomographic measurement of the component, wherein only the position of the images in the detector plane (projection plane) is compared with one another and the transmission of the radiographic images of the actual computer tomographic measurement is corrected on the basis of the displacement.

However, this does not take into account the changed spatial position of the CT components X-ray tube, X-ray detector and turntable due to the drift to each other and the concomitant change in the CT geometry (position of the CT components to each other), in particular the magnification. Also, a possibly occurring changed orientation such as tilting of the CT components is not taken into account.

A further object of the present invention is therefore to determine the drift occurring during a computed tomographic measurement, in particular displacement of the CT components X-ray tube, X-ray detector and turntable to each other, as well as the associated change in magnification, and in particular the changed orientations due to the drift Correct tilting of the CT components.

To solve this, the invention provides that a corrected volume is reconstructed from the radiographic images of the reference tomography (rapid tomography) and the radiographic images of the actual computed tomographic measurement, in particular corrected projection images or a corrected CT geometry being determined for each projection image, wherein in particular a transformation model is used which takes into account the changed CT geometry, in particular the respectively changed magnification.

As an alternative to rapid tomography as a reference tomography, it is also provided according to the invention to tomostomograph a reference body, such as at least one ball, whose position is fixed with respect to the turntable and fixed or known for all rotational positions, for example by calibration performed before the measurement. By comparing the position and size (in the case of the sphere, diameter) of the image of the reference body in the respective radiographic image during the actual measurement of the object with the previously determined or known position or size, the correction according to the invention, in particular the corrected CT Determine geometry for reconstruction.

The invention provides a method for the correction of the occurring during a computed tomography measurement drift of the computer tomography (CT) CT components used X-ray tube, object to be measured receiving turntable and in several rotational positions of the object to be measured relative to X-ray source and X-ray detector receiving X-ray relative to each other, wherein before and / or after the computed tomography measurement, a rapid tomography (reference tomography) is performed, are taken in the radiographic images in a smaller number of rotational positions with respect to the computed tomography measurement that is characterized in that using the radiographic images of the computed tomography measurement and the radiographic images of the rapid tomography a corrected voxel volume is determined by reconstruction, whereby corrected radiographic images (corrected projection images) are calculated o in that a corrected CT geometry for the reconstruction determined on the basis of the radiographic images of the rapid tomography is assigned to each radiographic image of the computed tomographic measurement, the CT geometry denoting the spatial position of the CT components X-ray tube, X-ray detector and rotary table relative to one another and preferably their orientation such as tilting ,

In particular, the invention is characterized in that, based on a transformation model between actual computed tomography measurement and rapid tomography, a corrected CT geometry is calculated for each radiographic image of the actual computed tomography measurement, which determines the position of the CT components changed by the drift and preferably orientation of the CT. Components considered.

In order to determine the changed by the drift position of the CT components, the invention provides in a particular embodiment additionally, that caused by temperature changes position change, in particular the X-ray tube, determined by using at least one temperature sensor and used for the correction. In the case of the x-ray tube, it is preferable to use at least one temperature sensor contained in the x-ray tube and / or a housing attached to the housing, in particular near the heat sources present within the x-ray tube and / or at the carrier receiving the x-ray tube. The temperature measured values recorded with a plurality of temperature sensors are combined in a particular embodiment preferably linearly to a temperature resulting for the determination of the changed position. It is further envisaged that either the changed position of the X-ray tube is compensated by corresponding opposing positioning of the X-ray tube with corresponding drives such as measuring axes, that the changed CT geometry is taken into account during the reconstruction or the transmission images are corrected.

Preferably, it is provided that a corrected transmission image is calculated for each transmission image of the actual computer tomographic measurement using a transformation model between actual computer tomographic measurement and rapid tomography by changing the gray values (intensities) of the transmission images such that they correspond to the CT geometry resulting from the reference tomography (Reference CT geometry) and reconstructed based on the reference CT geometry.

In particular, the invention is characterized in that the transformation model, depending on all the CT geometry parameters such as translation of the CT components X-ray tube, X-ray detector and turntable to each other and their rotation (tilt) into account, in particular between the fast tomography (reference tomography) and actual computer tomographic measurement is taken into account for each rotational position of changed magnification.

Preferably, the invention provides that in the transformation model of the reference tomography changed magnification of the computer tomographic measurement is taken into account and present after application of the transformation, the respective radiographic image in the magnification of the reference tomography.

It should also be emphasized that the transformation model is determined by comparing the projection images of the reference tomography (reference projection images) with the projection images (radiation images) of the actual computer tomographic measurement (measurement projection images) recorded in the same rotational position and determining the transformation parameters of the transformation model in such a way that, after execution the transformations, the deviations between the image data (gray values) of the reference projection images and the measurement projection images are minimal, for example by minimizing the squares of the intensities (gray values) of the individual pixels of the corresponding radiographic images and / or by correlation methods.

The invention is also distinguished by the fact that the transformation parameters are based on support sites, that is to say based on the rotational positions for which reference projection images and measurement projection images are present, and that the transformation parameters are interpolated for the radiographic images of the actual computer tomographic measurement in the intermediate rotational positions.

In particular, the invention is characterized in that the method is used in a coordinate measuring machine and / or surface measurement points are generated from the reconstructed voxel volume by means of surface extraction, which are particularly preferably used for determining geometric elements and / or dimensions.

The invention relates in particular to a device and the use of this device for a method according to the invention for computer tomography, wherein no already assembled unit consisting of a scintillator and an optical detector is used as the detector for the measuring radiation, as is usually the case in the prior art , but scintillator and optical detector are constructed separately from each other. The scintillator is used to convert the received measurement radiation into optical radiation, which can be received by an optical detector with a plurality of photosensitive elements such as a CCD or CMOS camera. In order to achieve the highest possible resolution scintillators are often provided with ancillary equipment, such as many tubular, the resulting optical radiation-conducting elements. In addition, the achievable resolution is also influenced by the resolution of the optical detector used.

Devices with an optical detector separated from the scintillator have the advantage that an optical system can be used to increase the resolution between the scintillator and the optical detector, as described, for example, in US Pat US 7,400,704 is described. It is disadvantageous, however, that due to the limited aperture of the optics used only small Szintillatorflächen can be detected or the light throughput and thus the Signal-to-noise ratio are very low. Otherwise, very large and expensive optics would be necessary. It is therefore not possible to capture large areas of a scintillator completely in high resolution and image quality. The detected area of the scintillator can not be changed in its size or location. It is likewise disadvantageous in the prior art that, when deflecting mirrors are used, they usually have to have a correspondingly large extent in order to reflect the entire optical radiation emitted by the scintillator.

These problems are solved DE 102013108367.6 Applicant, which is fully incorporated herein by reference, is at least partially implemented by employing a moveable camera and optics unit for piecewise detecting high resolution portions of the scintillator surface. The disadvantage here, however, is that time-consuming successive multiple measurements in several relative positions between the scintillator and camera plus optics for complete detection of Szintillatorfläche are necessary. In addition, the necessary positioning units take up a lot of space. The need for an optic itself is disadvantageous.

Also in the DE 102015110493.8 Applicant, to which reference is also made in its entirety, uses a similar arrangement and method, but using a parabolic mirror, Fresnel lens or glass fiber tapers. With regard to the fiberglass tapers, however, there are no indications of the actual execution. In addition, it is provided to move camera (optical detector) and scintillator relative to each other. The fiber optic taper thus does not completely capture the scintillator and several measurements are time consuming.

The object of the present invention is therefore also to provide an apparatus and a method in order to realize the complete detection of the output of a scintillator optical radiation with high quality, especially high light throughput without the use of classical optics and thus a fast and to ensure accurate measurement of a workpiece by means of, for example, computed tomography. The application to other radiographic methods using X-ray to optical radiation converting scintillators is also contemplated, such as for material inspection or laminography.

To solve the invention provides that between the optical radiation emitting side of the scintillator and a camera one or more fiber bundles, preferably taper, are arranged, which or reflect the optical radiation in the direction of the camera. Preferably, the entire scintillator surface is detected by the one or more fiber bundles.

This results in the advantage that the imaging scale of the scintillator on the camera by the number of fiber bundles used and / or the design of the fiber bundle with respect to the number and packing density of the fibers and thus their diameter can be adjusted. Preferably, the diameter of the individual fibers is smaller than the pixel size of the camera. In an embodiment, an imaging optic is additionally arranged between the camera end of the fiber bundle and the camera. However, this is smaller in size than an optical system that would be necessary for detecting the entire Szintillatorfläche, since the fiber bundle is preferably designed such that the scintillator end facing a larger cross section identifies, as the camera facing the end, the fiber bundle in The direction of the camera is shrunk.

It is also provided according to the invention that each fiber bundle is assigned a separate camera and the images of the individual cameras are combined to form an overall image.

By performing the fiber diameters and optionally using the aforementioned optics, it is possible to achieve very high magnifications, resulting in a small effective pixel size for the detection of the scintillator surface and thus for the tomography.

Particular preference is given to using a directional fiber bundle, also referred to as a taper, which preserves the image. Alternatively, the association of the individual fibers of the bundle with the detected area of the scintillator and the area on which the image is taken on the camera can be measured and the images captured with the camera corrected accordingly.

A device according to the invention for recording a plurality of radiographic images of a measurement object ( 303 ) for performing a computed tomography, wherein radiographic images in a plurality of rotational positions, adjustable by a rotating device such as mechanical axis of rotation ( 305 ), in which the measuring object ( 303 ) and a computed tomography sensor ( 301 . 304 . 308 . 309 . 310 . 311 ) are rotatably arranged relative to each other, preferably the measuring object ( 303 ) is rotatable, are receivable, the computed tomography sensor at least consists of a radiation source such as x-ray tube ( 301 ), at least one extensive scintillator ( 304 ) and at least one planar optical detector ( 310 ), like the camera, wherein the radiographic images of the at least one optical detector ( 310 ) and are reconstructable into a voxel volume from which preferably surface points can be determined at material transitions, wherein the light emitted by the scintillator ( 304 ) emitted optical radiation ( 307 ) at least partially from the at least one optical detector ( 310 ) is detectable, and wherein the computer tomography sensor is preferably integrated in a coordinate measuring machine, is characterized in that between the scintillator ( 304 ) and the optical detector ( 310 ) one or more fiber bundles ( 320 ) are arranged, which the scintillator ( 304 ) associated page ( 321 ) of the fiber bundle (s) from the scintillator ( 304 ) emitted optical radiation ( 307 ) and at the optical detector ( 310 ) facing end ( 322 ) in the direction of the optical detector (s) ( 310 ).

In particular, the invention is characterized in that the diameter of the fibers of the fiber bundle ( 320 ) smaller than the pixel size of the optical detector ( 310 ), in particular <10 μm, preferably <5 μm.

According to a proposal to be emphasized, it is provided that at least one optical system ( 309 ) between the camera side fiber bundle end ( 322 ) and camera ( 310 ) is arranged, which is formed from the camera-side fiber bundle end ( 322 ) exiting optical radiation on the camera ( 310 ).

Particularly noteworthy is that as fiber bundles ( 320 ) a directional fiber bundle (taper) is used, in which the arrangement of the fibers is designed to receive the figure.

Furthermore, the invention is characterized in that, via the fiber bundle or taper selection (number, packing density and diameter), the resolution for the detection of the scintillator surface (FIG. 304 ) is adjustable, wherein preferably the fiber bundle or the or the taper is made interchangeable.

In particular, the invention is characterized in that several taper ( 320 ) with respect to the detected scintillator surface ( 304 ) are juxtaposed so that the entire scintillator surface ( 304 ), the camera-side ends ( 322 ) the taper ( 320 ) of a common camera ( 310 ) or each taper ( 320 ) on a separate camera ( 310 ) is directed, wherein in the case of multiple cameras, the images of the cameras are composable into an overall image that is usable for tomography.

The subject matter of an independent invention is a method for carrying out a computer tomographic measurement with a computer tomograph, wherein the exposure time and the number of radiographic images to be superimposed on a resulting radiographic image are set.

In the known methods for computed tomography of objects or workpieces, a constant exposure or integration time is used for all radiographic images over the entire range of rotation in which the object is rotated, that is to say typically at least by 180 ° or 360 °. To increase the image quality, groups of successively recorded radiographic images which are recorded in the same rotational position during start / stop operation or in a continuous rotary operation within an angular range of equal size are superposed to form a resulting radiographic image, ie the intensities in Form of gray values added up and normalized if necessary. These resulting radiographic images thus also have a constant number of radiographic images over the entire range of rotation of the measurement, from which they are each formed by superposition.

This results in a fixed relationship between the number of rotational positions, number of recorded per rotational position radiographic images, exposure time per radiographic image and the total measurement time. In the case of image acquisition during the rotational movement also results in a constant rotational speed.

However, it is disadvantageous that, especially in the case of objects with a high aspect ratio, the measured intensities, in particular the minimum intensities, vary greatly depending on the component position, ie the maximum irradiated length, whereby the transmission ratios, in particular the utilization of the detector dynamics, are different. This means that, for example, when setting a total integration time so that the darkest areas, ie in the presence of the largest transmission lengths, have a set signal-to-noise ratio or a set minimum intensity, but in rotational positions where significantly lower maximum transmission lengths are present, significantly higher minimum Gray values and thus significantly greater signal-to-noise ratios are present. In other words, significantly higher total exposure times are used in rotational positions with low maximum transmission rates than would be necessary in order to achieve a constant quality, for example signal-to-noise ratios for the darkest regions, over the entire range of rotation. This leads to a high measuring time.

A further object of the present invention is therefore to shorten the overall measuring time for a computer tomographic measurement of a component. As a secondary condition, the quality of the radiographic images or overall radiographic images should meet the minimum requirement, ie, for example, comply with a predetermined minimum signal-to-noise ratio, in particular for the darkest regions present in the respective radiographic image (largest radiographic lengths).

To solve this, the invention provides that the total exposure time assigned to each resulting radiographic image, ie the exposure time of the possibly superimposed radiographic images and the number of radiographic images to be overlaid, is adjusted separately, wherein the setting is made such that a characteristic value assigned to the resulting radiographic image, such as the Minimum signal-to-noise ratio (SNR) of individual pixels or pixel areas remains constant within a predetermined tolerance range. For this purpose, it is necessary to determine the characteristic value to be controlled in the resulting radiographic images and to use this for the determination of the total exposure time of the respectively following radiographic image or resulting radiographic image.

In the sense of a regulation, the characteristic values of a plurality of previous radiographic images or resulting radiographic images are also preferably used.

In order to determine the desired value for the characteristic value (s), the characteristic value is determined from the resulting radiographic image that is recorded in a specific rotational position, preferably in the rotational position at which the maximum transmission length of a component is present. It should be noted here that even for the shortest transmission wavelengths, ie where higher intensities or gray values are present, no over-radiation occurs. Possibly. the characteristic value must be changed accordingly or, instead of increasing the exposure time, it is better to increase the number of radiographic images to be overlaid.

If the radiographic images are recorded during a continuous rotary movement of the rotary table, the exposure time per radiographic image is typically kept constant. In order to maintain the characteristic value, the number of radiographic images to be superimposed is varied. This results in the requirement of how many radiographic images are recorded in a respective angular range and superimposed to form a resulting radiographic image, which in turn results in a specification for the rotational speed of the rotary table. As a result, a slower rotation can be carried out in areas of high maximum radiating distances, and a faster rotary movement can be carried out in areas with lower maximum radiating lengths. This can be a significant time savings. In the case of start / stop operation, the time saved results from shorter total exposure times in the areas having lower maximum transmission lengths, so that the corresponding rotational positions are assumed for shorter periods of time before further rotation to the next rotational position can be carried out.

In addition to setting the exposure time on the basis of the characteristic values determined at the respective previously measured resulting radiographic images, the use of the desired data, in particular of the CAD model of the object, is provided according to the invention. In this case, the maximum transmission length assigned to the respective rotational position can be estimated at least approximately and used to readjust the overall exposure time.

An adaptation of the number of radiographic images to be superposed in order to adhere to the characteristic value can also be carried out in regions in the radiographic images. For this purpose, according to the invention, the radiographic images are segmented into regions of different brightnesses, that is to say intensities or gray values, and the number of radiographic images to be superimposed on the resulting radiographic image is determined separately for the regions. When assembling the resulting radiographic image after the superimposition of the individual areas, normalization to a common overall exposure time must take place.

However, the normalization mentioned above is also fundamentally necessary for implementing the method according to the invention. Before the resulting radiographic images of a reconstruction can be supplied to generate a voxel volume, they must have a uniform illumination level, that is to say be normalized to a uniform overall exposure time.

According to the invention, it is also provided to avoid undesirably high measuring times. For this purpose, the total exposure time of the resulting radiographic images must be limited. This limitation is achieved by calculating the total measuring time on the basis of the transmission ratios in the various rotational positions and in particular the characteristic value to be maintained for the rotational position in which the maximum transmission length is present. With knowledge of the maximum rotational speed of the axis of rotation and the number of transillumination images to be recorded or resulting transmission images, the total measurement time can be estimated and examined with respect to a maximum allowable total measurement time.

The invention provides for a method for performing a computed tomographic measurement with a computer tomograph comprising at least one x-ray tube, the object to be measured receiving and rotating turntable and radiographic images of the object receiving x-ray detector, wherein in several rotational positions of the object and the components of the x-ray tube and x-ray detector relative to each other, in particular in an angular range of at least 360 ° or in an angular range of at least 180 °, radiographic images are taken, wherein the respective recording takes place during a specified exposure or integration time, and wherein a reconstruction of a voxel volume from resulting radiographic images takes place, the resulting radiographic images are the radiographic images themselves or the resulting radiographic images are each a plurality of successively recorded and superposed radiographic images sin d, wherein the total exposure time is assigned to the resulting radiographic images as the sum of the exposure times of the radiographic images used for formation, characterized in that the total exposure time is set separately for each resulting radiographic image, wherein the exposure time and / or the number of radiographic images to be overlaid are set so that at least one of the respective resulting radiographic image associated characteristic value such as minimum signal noise ratio (SNR), minimum intensity or gray value or average intensity or gray value for all resulting radiographic images remains constant or nearly constant, the total exposure time of the respectively received resulting radiographic image is determined from the or the characteristic values, which determined from the one or more respectively directly before received resulting radiographic images were.

In particular, the invention is distinguished by the fact that the characteristics of at least two resulting radiation images taken directly in front of it are used for determining the overall exposure time.

It is preferably provided that the starting or setpoint value for the characteristic value (s) to be kept constant is determined on a transmission image or the resulting radiographic image, preferably on the radiographic image in which the maximum transmission length of the component is present.

In particular, the invention is characterized in that the exposure time and the number of overlapping radiographic images for each resulting radiographic image is set separately, wherein the exposure time for each radiographic image is set in each case so that no over-radiation is present, and to avoid over-radiation, if necessary, the number of is increased to superimposed radiographic images.

Preferably, the invention provides that the transmission images are taken during a continuous rotation of the turntable, wherein preferably the exposure time for the transmission images remains constant, and wherein the rotational speed of the turntable is varied so that for each same angular ranges, in each case a resulting Transmission image is formed, the number of superimposed radiographic images so that the characteristic remains constant.

It should also be emphasized that, based on the desired data, in particular the CAD model of the object, the total exposure time to be set for the respective resulting radiographic image is estimated.

The invention is also characterized in that the adjustment of the total exposure time by adjusting the number of superimposed radiographic images, depending on the respective radiographic length and thus depending on the respective present gray value or intensity in the radiographic image in areas within the radiographic image is set differently, so for the different areas of the characteristic value is set equal or almost, wherein after the superposition of the radiographic images, a normalization of the gray values of the corresponding regions takes place in relation to the number of superimposed radiographic images.

In particular, the invention is characterized in that the gray values of the resulting radiographic images are normalized to a uniform total exposure time before reconstruction.

Preferably, the invention provides that a maximum permissible total exposure time per resulting radiographic image is determined by preferably setting a maximum permissible total measurement time for recording the plurality of resulting radiographic images, wherein preferably at least the maximum rotational speed of the rotational axis and the number of total transillumination images to be taken into account ,

It should also be emphasized that surface measurement points are calculated from the reconstructed voxel volume, which are linked to the dimensional measurement of the object.

The invention is also distinguished by the fact that the position of the component for different trajectories to be executed is adjusted by means of a swivel device and / or rotary swivel device arranged on the rotary table.

• – dem minimalen Signal Rauschverhältnis (SNR) oder
• – der minimalen Intensität bzw. Grauwert oder
• – der mittleren Intensität bzw. Grauwert oder
• – der maximalen Intensität bzw. Grauwert

des Durchstrahlungsbildes oder resultierenden Durchstrahlungsbildes oder logarithmierten normierten Durchstrahlungsbildes bzw. resultierenden logarithmierten normierten Durchstrahlungsbildes. In particular, the invention is characterized in that the characteristic value is formed from

• - the minimum signal to noise ratio (SNR) or
• - the minimum intensity or gray value or
• - the mean intensity or gray value or
• - the maximum intensity or gray value

of the radiographic image or resulting radiographic image or logarithmized normalized radiographic image or resulting logarithmized normalized radiographic image.

The subject matter of an independent invention is a method for correcting temperature-related measurement deviations during measurement, in particular dimensional measurement with a coordinate measuring machine, particularly preferably with a computer tomograph.

In the known methods for correcting temperature-related measurement deviations when using coordinate measuring machines is usually only the extent of the object to be measured and the extent of the scales of the measuring axes, the position of the object relative to the sensors of the coordinate measuring machine, ie the most starting from a quill tactile, optical or tactile-optical sensors. For this purpose, temperature sensors are provided, which are attached to the scale holders or on the object. Optionally, temperature sensors are provided alternatively or additionally, which determine the temperature of the air surrounding the measurement object and use for the correction of the expansion of the measurement object.

The disadvantage here, however, is that temperature-related deviations are detected and corrected only at precisely these two points of the measuring circuit. However, corresponding deviations also occur on the other components and connecting elements of the measuring circuit, in particular due to temperature-related elongation. As a known countermeasure, these assemblies are made of low expansion materials such as Invar or Zerodur. However, these are expensive and difficult to process. In addition, they have inferior thermal conductivity in comparison to the commonly used aluminum alloys, which slows the temperature compensation. The latter leads to difficult to predict elongations and thus measurement errors for the dimensional measurement.

As a measuring circuit, the imaginary connecting line is defined by all the components and connecting elements whose extent has an influence on the measurement result. The respective expansion components are to be differentiated according to the direction of measurement and the sense of direction, ie to observe the sign. The connecting lines to be considered extend in the case of connecting elements between the respective attachment points to the adjacent subassemblies (further connecting elements or components) and, as a rule, only the proportion in the respective measuring direction is used as the length. With more complicated structures and multipoint or even surface bearings, bends and other deformations should also be taken into account. This is possible, for example, based on simulations, but for the practice usually too complex.

Components are, for example, the above-mentioned sensors, recording assemblies for the object to be measured, such as measuring tables and, if necessary, turntables, scales or measuring axes and other functional assemblies, such as X-ray source and X-ray detector in computer tomographs. As connecting elements, the components connecting components are called, which are formed for example as a cuboid, arches or other support structures. As a connecting element is here also understood a base plate or base structure or base support, for example a granite block, which receives the components directly or indirectly via connecting elements.

Therefore, another object of the present invention is to inexpensively correct temperature-related deviations which have a significant influence on the measurement result of the dimensional measurement of the object with the coordinate measuring machine.

To solve the invention, several temperature sensors are arranged along the components and connecting elements along the measuring circuit and the temperature determined therewith is used for the correction, in particular the temperature-related linear expansion. In particular, when using sensors in which the temperature of the air has an influence on the measurement result, for example, in interferometric measuring systems on the temperature, pressure and air humidity-dependent refractive index of the air (according to the Noble formula), this is also Influence by measurement of the air temperature and, if necessary, pressure and humidity corrected.

In a model-based approach to determine the length expansion is usually assumed by locally homogeneous temperature conditions. Alternatively or additionally, experimental approaches are provided, in which the temperature determined with the respective temperature sensor or the elongation determined therefrom is weighted in the correction. The weighting factors can be determined experimentally by regression calculation, for example by determining the dimensional measured values on a known object at different temperatures.

The invention provides for the solution a method for correcting temperature-related measurement deviations during measurement, in particular for dimensional measurement with a coordinate measuring machine, comprising a plurality of components provided for the measurement such as sensors and scales and at least one measuring circuit closing connecting elements, wherein at least one temperature sensor for detecting each current present temperature of a component and / or a connecting element for the correction of the coordinate measuring device determined measuring points and / or dimensions is used, that is characterized in that the temperature measurements of several mounted on the components and / or connecting elements between the components or associated temperature sensors for the correction be used, wherein a model or at least partial models for the temperature-related errors, in particular temperature-induced length expansion of the components and / or Verbindungsele elements themselves and / or each other is used.

In particular, the invention is characterized by the fact that the model provides for linearly connecting the temperature-related linear expansions of at least some of the components and connecting elements forming the measuring circuit, in particular adding them in a signed manner, the coefficient of thermal expansion assigned to the respective component or connecting element and the corresponding respective ones Length along the measuring circle is taken into account or experimentally determined values are used at least for the length to be considered.

The thermal expansion coefficient associated with the respective component or connecting element is usually defined by the material used. When several materials are present along the measuring circle through the respective connecting element or component, partial amounts are calculated from partial models according to the invention. For this purpose, a common or several separate temperature sensors can be provided. It is also provided to determine and use the coefficient of thermal expansion experimentally for one or more materials of one or more connecting elements or components. This can be understood as an effective replacement coefficient and is always useful if there is a reproducible temperature distribution along the measuring circuit through the relevant components, which can be taken into account in particular by means of a temperature sensor. This solution makes it possible to reduce the number of temperature sensors. It is also envisaged to use effective lengths for the lengths, which are determined experimentally, for example. Generalized, it is thus possible to appropriately weight the temperature measurement values of the temperature sensors involved in the correction.

In addition, it is also intended to determine temperatures and to use for the correction, which does not directly measure the temperature of a component or a connecting element, but which are related to the measurement result of the dimensional measurement. According to the invention, provision is made for the determination of the air temperature outside a housing surrounding the coordinate measuring machine, in particular the computer tomograph, the air temperature within this housing near one or more fans which serve for air exchange and thus heat transfer between housing interior and surroundings, in particular fans arranged on the upper side, and Coolant temperature of a provided for cooling the housing or the housing interior coolant system (thermostat). The thermostatic circuit can be used, for example, for optionally additional cooling of the X-ray detector.

• – an einem Grundträger wie Granitblock zur Bestimmung der Lageänderung zwischen den Aufnahmepunkten weiterer Verbindungselemente zu weiteren Komponenten oder Verbindungselementen, wobei die Aufnahmepunkte beispielsweise die Befestigungspunkte der Messachsen oder Maßstabsysteme zur Positionierung von Röntgenröhre, Drehtisch und Röntgendetektor relativ zueinander sind,
• – an den Messachsen oder Maßstabsystemen zur Bestimmung der Lageänderung der durch die Messachsen bewegten Verbindungselemente oder Komponenten relativ zu den Befestigungspunkten am Grundträger,
• – an den Verbindungselementen zwischen dem Grundträger und der Röntgenröhre, insbesondere zwischen den durch die Messachsen bewegten Verbindungselementen und der Röntgenröhre, zur Bestimmung der Lageänderung zwischen Grundträger bzw. durch die Messachsen bewegten Verbindungselementen und der Röntgenröhre,
• – an den Verbindungselementen zwischen dem Grundträger und dem Drehtisch, insbesondere zwischen den durch die Messachsen bewegten Verbindungselementen und dem Drehtisch, zur Bestimmung der Lageänderung zwischen Grundträger bzw. durch die Messachsen bewegten Verbindungselementen und dem Drehtisch,
• – an den Verbindungselementen zwischen dem Grundträger und dem Röntgendetektor, insbesondere zwischen den durch die Messachsen bewegten Verbindungselementen und dem Röntgendetektor, zur Bestimmung der Lageänderung zwischen Grundträger bzw. durch die Messachsen bewegten Verbindungselementen und dem Röntgendetektor
• – an der Röntgenröhre, insbesondere nahe dem die Röntgenstrahlung abgebendem Brennfleck, zur Bestimmung der Lageänderung zwischen Röntgenröhre und Brennfleck der Röntgenröhre,
• – an dem Drehtisch, insbesondere nahe dem das Objekt aufnehmenden drehbaren Teil des Drehtisches, zur Bestimmung der Lageänderung zwischen Drehtisch und drehbarem Teil des Drehtisches, und/oder
• – an dem Röntgendetektor, insbesondere nahe dem das jeweilige Durchstrahlungsbild aufnehmendem Teil des Röntgendetektors wie Detektorfläche, zur Bestimmung der Lageänderung zwischen Röntgendetektor und Durchstrahlungsbild aufnehmendem Teil des Röntgendetektors wie Detektorfläche
• – außerhalb eines den Computertomografen umgebenden Gehäuses zur Bestimmung der Umgebungslufttemperatur,
• – innerhalb eines den Computertomografen umgebenden Gehäuses zur Bestimmung der Lufttemperatur innerhalb des Gehäuses, insbesondere nahe eines oder mehrerer Lüfter, die dem Luftaustausch und damit Wärmetransport zwischen Gehäuseinnerem und Umgebung dienen, insbesondere an der Oberseite des Gehäuses angeordneter Lüfter und/oder
• – im Kühlmittelkreislauf einer zur Kühlung des Gehäuses und/oder des Gehäuseinneren wie beispielsweise Rötgendetektor vorgesehenen Kühlmittelanlage (Thermostat).

Preferably, it is provided that the coordinate measuring machine is a computer tomograph having at least one X-ray tube, the object to be measured receiving and rotating turntable, radiographic images of the object receiving preferably areally extended X-ray detector and connecting components connecting connecting elements, wherein temperature sensors are at least provided:

• On a base support such as granite block for determining the change in position between the receiving points of further connecting elements to further components or connecting elements, wherein the receiving points are, for example, the attachment points of the measuring axes or scale systems for positioning the X-ray tube, turntable and X-ray detector relative to each other,
• On the measuring axes or scale systems for determining the change in position of the connecting elements or components moved by the measuring axes relative to the fastening points on the base carrier,
• On the connecting elements between the base support and the X-ray tube, in particular between the connecting elements moved by the measuring axes and the X-ray tube, for determining the change in position between base support or connecting elements moved through the measuring axes and the X-ray tube,
• On the connecting elements between the base carrier and the turntable, in particular between the connecting elements moved by the measuring axes and the turntable, for determining the change in position between the basic carrier or connecting elements moved through the measuring axes, and the turntable,
• - At the connecting elements between the base support and the X-ray detector, in particular between the moved by the measuring axes connecting elements and the X-ray detector, for determining the change in position between the base support or moving through the measuring axes connecting elements and the X-ray detector
• On the X-ray tube, in particular near the focal spot emitting the X-radiation, for determining the change in position between the X-ray tube and the focal spot of the X-ray tube,
• - On the turntable, in particular near the object receiving the rotatable part of the turntable, for determining the change in position between the turntable and rotatable part of the turntable, and / or
• - At the X-ray detector, in particular near the respective radiographic image receiving part of the X-ray detector such as detector surface, for determining the change in position between the X-ray detector and radiographic image receiving part of the X-ray detector as the detector surface
• Outside a housing surrounding the computer tomograph for determining the ambient air temperature,
• - Within a computer tomography surrounding housing for determining the air temperature within the housing, in particular close to one or more fans, which are used for air exchange and heat transfer between Gehäuseinnerem and environment, in particular arranged on the top of the housing fan and / or
• - In the coolant circuit provided for cooling the housing and / or the housing interior such as Rötgendetektor coolant system (thermostat).

For the movement of components or connecting elements, in each case a plurality of measuring axes can also be provided, for example for different spatial directions. These can be built directly on each other or connected by connecting elements. The plurality of measuring axes or scales are assigned according to the invention separate or common temperature sensors.

With the temperature sensors on the X-ray tube, turntable and X-ray detector, the length expansion between the pickup point of the component on the respective connecting element and the functional element (focal spot, rotatable part or detector surface) is corrected in each case. In this case also occurring in the components Drifterscheinungen be detected by temperature changes and corrected with.

To solve the invention also provides a corresponding to the implementation of the method described above suitable device, which is characterized in that temperature sensors are attached to a plurality of components and / or connecting elements between the components or associated with these.

A device according to the invention for the implementation of the method for the correction of temperature-induced measurement deviations during measuring, in particular dimensional measurement with a coordinate measuring machine is formed by a coordinate measuring machine comprising a plurality of components provided for the measurement such as sensors and scales and at least one connecting circuit closing connecting elements, wherein at least one temperature sensor for detecting the each currently present temperature of a component and / or a connecting element is provided, and wherein a correction device is provided, which is used to correct the measuring points and / or measures determined by the coordinate measuring machine, wherein the correction device is adapted to detect the temperature measured values of the temperature sensors and To calculate the correction, and is characterized in that temperature sensors on several components and / or connecting elements between the components brought or associated with it.

• – an einem Grundträger wie Granitblock, wobei der Grundträger Aufnahmepunkte wie beispielsweise Befestigungspunkte der Messachsen oder Maßstabsysteme zur Positionierung von Röntgenröhre, Drehtisch und Röntgendetektor relativ zueinander, aufweist,
• – an den Messachsen oder Maßstabsystemen,
• – an den Verbindungselementen zwischen dem Grundträger und der Röntgenröhre, insbesondere zwischen den durch die Messachsen bewegten Verbindungselementen und der Röntgenröhre,
• – an den Verbindungselementen zwischen dem Grundträger und dem Drehtisch, insbesondere zwischen den durch die Messachsen bewegten Verbindungselementen und dem Drehtisch,
• – an den Verbindungselementen zwischen dem Grundträger und dem Röntgendetektor, insbesondere zwischen den durch die Messachsen bewegten Verbindungselementen und dem Röntgendetektor,
• – an der Röntgenröhre, insbesondere nahe dem die Röntgenstrahlung abgebendem Brennfleck,
• – an dem Drehtisch, insbesondere nahe dem das Objekt aufnehmenden drehbaren Teil des Drehtisches, und/oder
• – an dem Röntgendetektor, insbesondere nahe dem das jeweilige Durchstrahlungsbild aufnehmendem Teil des Röntgendetektors wie Detektorfläche
• – außerhalb eines den Computertomografen umgebenden Gehäuses zur Bestimmung der Umgebungslufttemperatur,
• – innerhalb eines den Computertomografen umgebenden Gehäuses zur Bestimmung der Lufttemperatur innerhalb des Gehäuses, insbesondere nahe eines oder mehrerer Lüfter, die dem Luftaustausch und damit Wärmetransport zwischen Gehäuseinnerem und Umgebung dienen, insbesondere an der Oberseite des Gehäuses angeordneter Lüfter und/oder
• – im Kühlmittelkreislauf einer zur Kühlung des Gehäuses und/oder des Gehäuseinneren wie beispielsweise Rötgendetektor vorgesehenen Kühlmittelanlage (Thermostat).

In particular, the invention is characterized in that the coordinate measuring machine is a computed tomography, at least comprising an X-ray tube, the object to be measured receiving and rotating turntable, radiographic images of the object receiving preferably areally extended X-ray detector and connecting components connecting connecting elements, wherein temperature sensors are at least provided ,

• On a base support such as a granite block, wherein the base support has receiving points such as attachment points of the measuring axes or scale systems for positioning the X-ray tube, turntable and X-ray detector relative to one another,
• - on the measuring axes or scale systems,
• On the connecting elements between the base support and the X-ray tube, in particular between the connecting elements moved by the measuring axes and the X-ray tube,
• On the connecting elements between the base support and the turntable, in particular between the connecting elements moved by the measuring axes and the turntable,
• At the connecting elements between the base carrier and the X-ray detector, in particular between the connecting elements moved by the measuring axes and the X-ray detector,
• On the X-ray tube, in particular near the focal spot emitting the X-ray,
• - On the turntable, in particular near the object receiving the rotatable part of the turntable, and / or
• - At the X-ray detector, in particular near the respective radiographic image receiving part of the X-ray detector as the detector surface
• Outside a housing surrounding the computer tomograph for determining the ambient air temperature,
• - Within a computer tomography surrounding housing for determining the air temperature within the housing, in particular close to one or more fans, which are used for air exchange and heat transfer between Gehäuseinnerem and environment, in particular arranged on the top of the housing fan and / or
• - In the coolant circuit provided for cooling the housing and / or the housing interior such as Rötgendetektor coolant system (thermostat).

The subject matter of an independent invention is a method and a device for computer tomography of an object, preferably a computer tomographic measurement, the computer tomograph preferably being integrated in a coordinate measuring machine.

In the known methods for computed tomography, the X-ray detector used is aligned with respect to the mean radiation direction of the radiation emitted by an X-ray source so that the perpendicular to the detector plane, hereinafter referred to as detector normal, parallel to this central beam direction. This results in the direction of the average radiation direction, a constant distance of the detector pixels to the X-ray source, and thus a same magnification for all detector pixels. The pixel size to be taken into account for the reconstruction of the recorded radiographic images corresponds to the native pixel size of the pixels of the x-ray detector. The disadvantage here is that the resolution of the measurement is set to the native pixel size of the detector. A corresponding device is for example the WO 2005 119 174 A1 to be taken from the applicant.

Another object of the present invention is therefore to adjust the resolution of the measurement using the same X-ray detector.

To solve the problem, the invention provides an apparatus and a method for operating the apparatus, wherein the apparatus comprises an X-ray detector, which can be tilted in one or in two axes. The two axes are the axis directions perpendicular to the detector normal. The tilting changes the effective pixel size of the pixels of the X-ray detector, which results in projection into the untilted detector plane. The effective pixel size is smaller than the native pixel size of the detector pixels, resulting in improved resolution.

The tilting of the detector results in altered image scales for the individual detector pixels, since the distance to the x-ray source changes depending on the respective tilt angle and the position on the detector. Pixels which occupy a greater distance from the X-ray source are assigned a higher magnification in accordance with the invention. Pixels which are arranged closer to the X-ray source due to the tilt are assigned a lower magnification. The changed image scales must therefore be taken into account in the reconstruction depending on the pixel. For this purpose, the adaptation of the so-called SOUV vectors is provided according to the invention, which include the position of the detector elements with respect to the X-ray source.

According to the invention, it is also provided to combine the changed detector pixel position, detector pixel size and detector pixel shape with a distortion correction of the detector or to take this into account in the distortion correction of the detector.

As explained above, the magnification and thus the resolution for detector pixels, which are arranged closer to the X-ray source after tilting, are reduced. This partially eliminates the improved measurement resolution in the reconstructed voxel volume due to the smaller pixel size. For the detector pixels, which is a larger Taking the distance to the X-ray source after tilting, the increased magnification results in an additional reduction of the voxel size in the voxel volume and thus an additional increase in resolution. The resolution in the voxel volume is thereby locally different, depending on whether the object areas are present on one side or the other of the tilt axis of the detector. Runs the tilting axis perpendicular to the direction of the axis of rotation 9 of the turntable 7 , as in 1 represented, so in the plane of the drawing 1 into, this results in the resolution of the object 8th in voxel volume, for example, for the top and bottom of the object 8th a different value. According to the invention, it is therefore also provided to achieve different resolutions within an object. This makes it possible, for example, to align the object or to align the detector tilt in such a way that details to be measured precisely on an object 8th in higher resolution and inaccurate details to be measured on an object 8th recorded and measured in lower resolution.

The second axis, around which a tilting of the detector can be provided according to the invention, is the vertical direction in the 1 , Because the object 8th around the axis of rotation 9 of the turntable 7 is rotated, thereby all the details of the object 8th depending on the rotational position about the axis of rotation 9 recorded with different magnifications. This is also provided according to the invention, but only leads to the solution of the object according to the invention if the axis of rotation 9 in the direction perpendicular to the plane of the drawing to the mean beam direction of the X-ray source 2 is arranged offset or a virtual axis of rotation is arranged at this point around which the object 8th rotates. This can be present, for example, in a so-called region of interest computed tomography.

The detector normal of the detector 10 runs in the 1 in the horizontal direction.

The invention provides for a device for performing a computed tomography comprising at least one x-ray tube, an x-ray detector, preferably flat X-ray detector, and a turntable receiving and rotating the tomographic object, which is arranged between x-ray tube and x-ray detector, wherein the device is formed, radiographic images of the object in a plurality of rotational positions of the turntable, wherein the radiographic images are preferably reconstructed to a voxel volume by reconstruction, wherein particularly preferably determined from the voxel volume surface points at the material transitions of the object and are particularly preferably used for measuring features or dimensions of the object , wherein the device is particularly preferably integrated in a coordinate measuring machine, before, which is characterized in that the X-ray detector is made tiltable to lower a first axis, which is perpendicular to the detector normal and is preferably designed tiltable about a second axis which is perpendicular to the detector normal and preferably perpendicular to the first axis, wherein the tilt angle about the first and / or second axis manually or electrically, continuously or stepwise adjustable.

The invention also provides for a method using a device mentioned above, which is characterized in that the tilt angle about the first and / or second axis in the range of 0 ° to <+/- 90 °, preferably from 0 ° to + / - <45 °, is set so that the effective pixel size of the pixels of the X-ray detector, which results by projecting the pixels of the tilted X-ray detector in the plane of the untilted X-ray detector, a predetermined pixel size.

According to a proposal which is to be particularly emphasized, it is provided that the effective pixel size and the different first and second tilt angles present in a square deviate from the square of the pixels, and the magnification resulting from the respective tilt angle and the respective position of the pixel on the x-ray detector. Image scale, defined by the ratio of the two distances of the respective detector pixel to the X-ray tube and axis of rotation of the turntable to the X-ray tube, is taken into account in the reconstruction, preferably by adjusting the SOUV vectors, which includes the position of the detector pixels, the rotation axis and the X-ray source to each other.

Subject of an independent invention is a device for computed tomographic examination of an object, having a radiation protection housing.

In the known Strahlenschutzumhausungen for X-ray based computed tomography is provided to use a massive and consisting of a few heavy items radiation protection housing for the assembly and disassembly of a crane or other lifting tool must be provided. The radiation protection housing is usually realized by a complex lead construction or by polymer concrete. In addition to the high weight of the items used for this purpose, the cost of such radiation protection housings are particularly high because either many different parts of different shape and design or elaborately shaped components are used. To have to For example, for maintenance purposes, hatches will be included in the design.

A further object of the present invention is therefore to provide a cost-effective radiation protection housing for a computer tomograph, in particular a computer tomograph integrated in a coordinate measuring machine. Preferably, the radiation protection housing should be easily adaptable to various device sizes and easily be partially or completely dismantled for maintenance purposes.

To solve the invention provides that the radiation protection housing is at least partially formed of a plurality of at least in the form of identical building blocks, forming the layers and in several layers over or next to each other are combined, radiation protection hood is thus at least partially modular.

The individual layers are completed laterally or at the bottom and top by appropriate base plates or cover plates (cover). The base plate or the side plates present on the underside are provided to receive the corresponding components of the computer tomograph, that is to say the x-ray source, the x-ray detector and the rotary table receiving and rotating the measurement object.

The advantage of the layered, modular construction of the radiation protection housing is the possibility to extend the height and width of the enclosure in a particularly simple manner as well as easy disassembly, in pieces or in total. It can therefore be realized a variable height or length of Strahlenschutzumhausung to provide different sized devices (computer tomography) with a radiation protection housing. In addition, the use of identical components results in particularly low individual production costs and thus also low overall production costs. For maintenance purposes, individual components can also be easily disassembled. In the construction, therefore, corresponding maintenance hatches do not necessarily have to be provided.

In order to ensure that a continuous shielding of the X-ray radiation is realized at the transition points between the blocks or the individual layers, the blocks or layers are formed correspondingly in their shape by interlocking such as baffles or heels.

The invention provides for the solution, a device for computed tomography examination of an object, at least comprising an X-ray tube, an X-ray detector, the object to be measured receiving and this rotating turntable and a radiation protection housing, which is characterized in that the radiation protection housing is at least partially formed a variety of building blocks of identical shape.

In particular, the invention is characterized in that the blocks are constructed of a lead layer such as lead plates and this receiving structure, or X-ray shielding cast element.

Preferably, it is provided that the blocks have or form an annular or rectangular shape with a central opening and are assembled one above the other or side by side in several layers, preferably detachably joined together, and preferably on the top and bottom by a single or multi-part base plate and a on or multi-part cover plate, or one or more parts side plates are completed.

In particular, the invention is characterized in that the transitions between the building blocks and / or between the layers of building blocks are formed by interlocking of the building blocks such as baffles or heels.

The subject matter of an independent invention is a method for determining a quality value, measuring precision, measurement uncertainty for surface points determined by means of computed tomography.

Among the known methods for determining the measurement uncertainty of a computed tomography include those in the Guideline VDI / VDE 2630-2.1: 2015 specified procedures using calibrated workpieces. These are procedures based on national and international standards.

An unreturned procedure is used in the DE 10 2014 115851 A1 described. In this case, a quality value is determined from the measured voxel volume data and from this the measurement uncertainty for a surface measuring point.

The methods described in the above-mentioned guideline require the repeated measurement of calibrated workpieces. These have to be very similar to the workpieces for which the measurement uncertainty is to be assigned by means of computer tomography of determined measurement data. Overall, it is a very complicated process.

That in the DE 10 2014 115 851 A1 The method described provides only a very limited solution for the estimation of the measurement uncertainty of computer tomography In particular, measured voxel data must be available and used for an evaluation. This is a time-consuming process.

An object of the present invention therefore also consists in specifying further alternative methods for determining a quality value and / or a measurement precision and / or measurement uncertainty for surface measurement points and dimensions of features determined therefrom, determined by means of computer tomography. The methods should be as easy as possible, in particular be possible without the application of concrete measurement data.

• – Messpräzision und/oder Signal/Rausch-Verhältnis (SNR) des gemessenen Oberflächenpunktes und/oder
• – Messpräzision und/oder Signal/Rausch-Verhältnis (SNR) des simulierten Oberflächenpunktes und/oder
• – Kontrast der simulierten Voxelgrauwerte an den Koordinaten des Oberflächenpunktes und dessen Umgebung und/oder
• – Rauschen der simulierten Voxelgrauwerte an den Koordinaten des Oberflächenpunktes und dessen Umgebung und/oder
• – Kontrast/Rausch-Verhältnis (CNR) der simulierten Voxelgrauwerte an den Koordinaten des Oberflächenpunktes und dessen Umgebung und/oder
• – Intensitäten und/oder Signal/Rausch-Verhältnis (SNR) der Pixel der gemessenen Durchstrahlungsbilder, die durch die Rekonstruktion zu den Voxelgrauwerten beitragen, die an den Koordinaten des Oberflächenpunktes und dessen Umgebung liegen und/oder
• – Intensitäten und/oder Signal/Rausch-Verhältnis (SNR) der Pixel der simulierten Durchstrahlungsbilder, die durch die Rekonstruktion zu den Voxelgrauwerten beitragen, die an den Koordinaten des Oberflächenpunktes und dessen Umgebung liegen.

As a solution, the invention provides that the quality value determined for a surface measurement point by means of computed tomography and the possibly calculable measurement precision or measurement uncertainty result from one of the following options or a combination of several of these:

• Measurement precision and / or signal-to-noise ratio (SNR) of the measured surface point and / or
• Measurement precision and / or signal-to-noise ratio (SNR) of the simulated surface point and / or
• Contrast of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or
• - Noise of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or
• Contrast to noise ratio (CNR) of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or
• Intensities and / or signal-to-noise ratio (SNR) of the pixels of the measured radiographic images contributing through the reconstruction to the voxel gray values located at the coordinates of the surface point and its surroundings; and / or
• Intensities and / or signal-to-noise ratio (SNR) of the pixels of the simulated radiographic images contributing through the reconstruction to the voxel gray levels located at the coordinates of the surface point and its surroundings.

In particular, it is intended to use not only measured voxel volume data but also simulated data. The simulated data may be, in addition to the voxel volume data, also the data on the surface measurement points themselves or the data present in the form of transmission images (e.g., generated by forward projection on target data such as CAD data). As an alternative to using the measured voxel volume data, it is also provided to use the measured radiographic image data or the measured data for the surface measurement points themselves.

To determine the signal-to-noise ratio (SNR) of the measured surface point, the mean value (signal) and the standard deviation or variance (noise) of the surface points can be determined, for example, from several measurements of a single point. The measurement precision of a surface point can be quantified, for example, with the standard deviation or the variance of a measurement point, as in "Krystek, Michael, calculation of measurement uncertainty. Fundamentals and instructions for practical application, 2nd ed. Berlin: Beuth Verlag GmbH, 2015. Beuth Praxis. - ISBN 3410255567 " specified.

For example, to determine the signal-to-noise ratio (SNR) of the simulated surface point, the standard deviation or variance of a surface point can be determined analytically from the voxel gray values used for surface determination and their standard deviation or variance and / or the CNR of the simulated voxel gray values.

The contrast of the simulated voxel gray values is, for example, the differences in the values of the voxels used for surface determination.

The noise of the simulated voxel gray values is, for example, the standard deviation of the values of the voxels used to determine a surface point.

If one compares the two latter quantities, the contrast / noise ratio (CNR) results.

• – Messpräzision und/oder Signal/Rausch-Verhältnis (SNR) des gemessenen Oberflächenpunktes und/oder
• – Messpräzision und/oder Signal/Rausch-Verhältnis (SNR) des simulierten Oberflächenpunktes und/oder
• – Kontrast der simulierten Voxelgrauwerte an den Koordinaten des Oberflächenpunktes und dessen Umgebung und/oder
• – Rauschen der simulierten Voxelgrauwerte an den Koordinaten des Oberflächenpunktes und dessen Umgebung und/oder
• – Kontrast/Rausch-Verhältnis (CNR) der simulierten Voxelgrauwerte an den Koordinaten des Oberflächenpunktes und dessen Umgebung und/oder
• – Intensitäten und/oder Signal/Rausch-Verhältnis (SNR) der Pixel der gemessenen Durchstrahlungsbilder, die durch die Rekonstruktion zu den Voxelgrauwerten beitragen, die an den Koordinaten des Oberflächenpunktes und dessen Umgebung liegen und/oder
• – Intensitäten und/oder Signal/Rausch-Verhältnis (SNR) der Pixel der simulierten Durchstrahlungsbilder, die durch die Rekonstruktion zu den Voxelgrauwerten beitragen, die an den Koordinaten des Oberflächenpunktes und dessen Umgebung liegen.

The invention provides for the solution a method for determining a quality value, which is assigned to a surface measuring point determined by computer tomography, wherein the computer tomography comprises at least the following steps: recording multiple radiographic images of the object to be examined as workpiece in several rotational positions relative to an X-ray source and an X-ray detector , Reconstruction of a voxel volume, which has voxels with assigned voxel gray values, from the transmission images and determination of surface measurement points, characterized in that the quality value is determined from the following data:

• Measurement precision and / or signal-to-noise ratio (SNR) of the measured surface point and / or
• Measurement precision and / or signal-to-noise ratio (SNR) of the simulated surface point and / or
• Contrast of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or
• - Noise of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or
• Contrast to noise ratio (CNR) of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or
• Intensities and / or signal-to-noise ratio (SNR) of the pixels of the measured radiographic images contributing through the reconstruction to the voxel gray values located at the coordinates of the surface point and its surroundings; and / or
• Intensities and / or signal-to-noise ratio (SNR) of the pixels of the simulated radiographic images contributing through the reconstruction to the voxel gray levels located at the coordinates of the surface point and its surroundings.

In particular, the invention is characterized in that, in particular for further processing, the quality value is assigned to the surface measurement point and / or the quality value is used to determine the measurement precision and / or measurement uncertainty and this is assigned to the surface measurement point.

Preferably, it is provided that the respective quality value and / or the respective measurement precision and / or the respective measurement uncertainty is used when using surface measuring points for determining dimensions of features from a plurality of surface measuring points or in a pictorial representation for weighting the respective surface measuring point.

With regard to the weighting of the quality, it is intended to take into account a weighting with factors between 0 and 1. In this case, a continuous weighting proves to be advantageous. In addition, according to the invention, it is also provided to provide a factor of 0 weighting also for the values which distinguish a certain lower limit value, and to provide a factor of 1 weighting for all surface points which exceed a certain upper limit value. In an inventive alternative, it is also envisaged that weights not equal to 0 or 1 should be weighted equally.

The invention additionally comprises a corresponding device with a display device suitable for imaging, such as a screen, in particular a computer tomography device with a corresponding display device, which is preferably integrated in a coordinate measuring machine.

According to a particularly noteworthy proposal, it is provided that the quality value and / or the respective measurement precision and / or the respective measurement uncertainty is recorded and / or displayed, preferably depicted, together with the surface measurement point, for example on a display unit such as a screen, wherein the quality value and / or or the respective measurement precision and / or the respective measurement uncertainty is particularly preferably represented as a line, bar and / or arrow with length and / or color dependent on the quality value and / or on the respective measurement precision and / or on the respective measurement uncertainty and / or as numerical value ,

In particular, the invention is characterized in that secondary information is additionally taken into account for calculating the quality value and / or the measurement precision and / or the measurement uncertainty, such as influences due to systematic deviations and / or uncertainty contributions caused by artifacts such as beam hardening artifacts, cone beam artifacts, scattered radiation artifacts and / or or ring artifacts.

Further details, advantages and features of the invention will become apparent not only from the claims, the features to be taken from them - alone and / or in combination - but also from the following description of the figures.

It shows:

1 a schematic diagram of the device according to the invention, a computer tomograph, with two x-ray sources, in a first position of the measuring axis carrying the x-ray sources and

2 a schematic diagram of the X-ray tube according to the invention,

3 a schematic diagram of the device according to the invention for receiving radiographic images with a fiber bundle,

4 a schematic diagram of the device according to the invention for receiving radiographic images with a plurality of fiber bundles,

5 a schematic diagram of the device according to the invention for the correction of temperature-induced errors in the dimensional measurement with a designed as computer tomography coordinate measuring machine and

6 a schematic diagram of the device according to the invention of a computer tomograph with a modular, constructed of building blocks radiation protection housing.

Based on 1 the device according to the invention is exemplified. The computer tomograph 1 includes the first X-ray tube 2 and the second x-ray tube 3 pointing in the direction of the arrow 4 movable measuring axis 5 go out and with the controller 6 are connected. In the illustrated first position of the measuring axis 5 in the direction of the arrow 4 will that be on the turntable 7 arranged workpiece 8th from the X-ray 11 the first x-ray tube 2 recorded and irradiated and on the X-ray detector 10 displayed. With the x-ray detector 10 be in several rotational positions of the workpiece 8th around the axis of rotation 9 of the turntable 7 the radiographs 13 the first measurement with the first x-ray tube 2 added.

Subsequently, the measuring axis is in the direction of the arrow 4 adjusted so that the X-rays 12 the second x-ray tube 3 the workpiece 8th detected, penetrates and on the X-ray detector 10 images, again in several rotational positions radiographic images 14 recorded in the second measurement. Alternative to the movement of the x-ray tubes 2 . 3 is also provided, X-ray detector 10 and workpiece 7 , along with the turntable 7 , together through the measuring axis 5 in the direction of the arrow 4 to move.

Both sets of radiographs 13 . 14 be to the software 15 passed there and either merged directly or first reconstructed per sentence to volume data and then merged. From the merged data, the measurement results are then 16 calculated. These are, for example, measurement points determined from volume data by surface extraction and linked to dimensions.

Based on 2 a device according to the invention is shown in an exemplary embodiment. The device comprises at least one x-ray tube 100 with an X-ray emitting target 101 , From the X-ray tube body 102 go from at least one electron beam source 103 that has an electron beam 105 give up, means 104 for influencing the direction of the x-ray beam, an optional target flange receiving the target 106 and a turning device 107 , The target 101 or the target flange 106 are with the rotatable part of the rotator 107 connected and thus around the axis of rotation 108 rotatable. This results in the impact of the electron beam 105 on the target 101 in the form of the focal spot 109 along the circular path 110 upon rotation of the target 101 around the axis of rotation 108 ,

Alternatively or additionally, the turning device goes 107 of mechanical movement means such as movement axes 111 and or 112 out, which is a movement along the arrows 111 and or 112 allow, with the moving means 111 respectively. 112 from the X-ray body 102 out. The displacement of the focal spot 109 along the circular path 110 on the target 101 may alternatively to the rotation of the target 101 also by appropriate movement of the moving means 111 and 112 and thus movement of the rotating device 107 together with the target 101 on a circular trajectory 113 respectively. The aforementioned rotation about the rotation axis 108 and the movements along the trajectory 113 can also be combined to any orbits of the focal spot 109 on the target 101 provided.

To change the circular path 110 on the target 101 is also provided, the rotating device 107 at least in the direction of the arrow 112 to move. This results in a changed diameter or radius of the circular path 110 on the target 101 ,

In general, by using the movement means 111 and or 112 a shift and thus changed position of the focal spot 109 on the target 101 will be realized.

3 shows a first schematic diagram of a device according to the invention for computed tomography with a fiber bundle 320 between scintillator 304 and optical detector 310 , The measurement object 303 is between the X-rays 302 emitting X-ray source 301 and the scintillator 304 and on the around the axis of rotation 306 rotatable part of a mechanical axis of rotation 305 arranged. When radiating with the measuring radiation 302 created in the scintillator 304 the optical radiation 307 at the side of the scintillator facing away from the target 304 distributed over the entire surface and distributed over a large angular range (Lambert radiator). As a component, the largest possible part of the optical radiation 307 detected, according to the invention is a fiber bundle 320 intended. The fiber bundle 320 transmits the optical radiation 307 from the end facing the scintillator 321 to the camera 310 facing the end 322 and gives them towards the optical detector like CCD or CMOS camera 310 from. In addition, another optical component, such as a lens or zoom optics 309 to focus on the camera 310 be provided.

One to 3 alternative device, shown in 4 , includes several fiber bundles 321 , Optics 309 and cameras 310 To achieve increased resolution by using the cameras 310 recorded images are combined to form an overall image that is used for the tomography, in particular the necessary reconstruction.

5 shows a schematic diagram of the device according to the invention for the correction of temperature-induced errors in the dimensional measurement with a designed as a computer tomograph coordinate measuring machine. This has the components X-ray tube 401 , object to be measured 403 receiving turntable 405 consisting of fixed part 405b and to the axis of rotation 406 rotatable part 405a , as well as x-ray detector 404 on, also several fasteners 408 . 412 . 419 . 423 and 427 containing the components with the basic carrier 415 connect directly or indirectly.

The x-ray tube 401 shows the X-rays 402 emitting focal spot 401 and one on the x-ray tube 401 attached or integrated in the x-ray tube temperature sensor T1, and is here for example in two directions along the arrows 409 and 417 in relation to the basic carrier 415 adjustable. For this are corresponding measuring axes 410 . 413 provided the scales or scale systems 411 and 414 exhibit. The drives and guides, not shown, of the measuring axes are designed, the connecting element receiving the x-ray tube 408 and the connecting element 412 move accordingly. To determine the temperature of the two connecting elements 408 and 412 the temperature sensors T2 and T4 are provided. To determine the temperature of the scale systems 411 and 414 are provided the temperature sensors T3 and T5, which are arranged on the scale systems directly or near this. The arrangement of the degrees of freedom of movement and the directions of movement is exemplary and not restrictive. It is also intended to make the positioning in one, three or no direction at all.

Analogous to the previously described arrangement and previously described positioning options and temperature sensors of the X-ray tube 401 is also the x-ray detector 404 designed. These are the fasteners 423 . 427 pointing in the direction of the arrows 425 and 426 acting measuring axes 421 . 424 with the scale systems 420 . 422 and the temperature sensors T9, T10, T11, T12, T13. The temperature sensor T13 is preferably as close as possible to the X-ray radiation 402 receiving detector surface 405a of the X-ray detector 405 arranged.

For temperature measurement of the quite large basic carrier 415 a plurality of temperature sensors T6a, T6b and T6c are provided to estimate the temperature profile along the base carrier.

The turntable 405 is over the connecting element 419 with the basic carrier 415 connected and again purely by way of example along the arrow 418 , ie perpendicular to the plane of the drawing, by means of the measuring axis 416 displaceable. The turntable can also be displaceable or fixed in two or three spatial directions. The scale systems and associated temperature sensors are also provided, but not shown here. Furthermore, the temperature sensors T7 for detecting the temperature of the connecting element 419 , and T8 for detecting the temperature of the turntable 405 , in particular the fixed part 405b but as close as possible to the rotatable part 405a intended. The temperature sensor T8 can also be in the rotatable part 405a be arranged.

Further temperature sensors T14 to T17 can be provided on the object to be measured 403 (Temperature sensor T14), outside a housing surrounding the computer tomograph 428 for determining the ambient air temperature (temperature sensor T16) within a housing surrounding the computer tomograph 428 for determining the air temperature within the housing, in particular near one or more fans 429 , which are used for air exchange and thus heat transfer between Gehäuseinnerem and environment (temperature sensor T15), in particular arranged at the top of the housing fan, and in the coolant circuit for cooling the housing 528 and / or the housing interior such as X-ray detector 404 provided coolant system (thermostat) 430 (Temperature sensor T17).

Through the dashed lines 407 the measuring circuit is indicated by way of example, along which the temperature sensors are arranged. The measuring circuit 407 passes through the turntable 405 through into the object to be measured 403 ,

In the 6 is the inventive device for computed tomography of an object 504 as well as this enclosing radiation protection housing or radiation protection hood 500 shown. Exemplary is the radiation protection housing 500 formed by a multipart base plate 500-1 . 500-2 and 500-3 containing several layers 505-1 to 505-12 the building blocks 505 , which are hatched in section, and have corresponding paragraphs, and the cover plate 506 , which is executed by way of example in one piece, but alternatively can also be designed in several parts. From the part 500-1 the base plate goes the x-ray tube 501 from, from the part 500-2 the base plate goes the turntable 503 and the object 504 from and from the part 500-3 the base plate is the X-ray detector 502 out. Alternatively to the structure of the device according to the invention 6 is also provided, the several layers 505 the blocks not in height, but laterally next to each other to arrange. The components 501 . 502 and 503 then go each one laterally from the side panels closing off the layers.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2665035 A2 [0007]
• WO 2013167616 A2 [0011]
• DE 102013107745 [0011]
• DE 102012100150 A1 [0079, 0086, 0089]
• US 7400704 [0155]
• DE 102013108367 [0156]
• DE 102015110493 [0157]
• WO 2005119174 A1 [0214]
• DE 102014115851 A1 [0238, 0240]

Cited non-patent literature

• DIN ENV 13005 [0048]
• DIN ENV 13005 [0048]
• Guideline VDI / VDE 2630-2.1: 2015 [0237]
• "Krystek, Michael, calculation of measurement uncertainty. Fundamentals and instructions for practical application, 2nd ed. Berlin: Beuth Verlag GmbH, 2015. Beuth Praxis. - ISBN 3410255567 " [0244]

Claims (17)

Method for automatic or semi-automatic determination of setting parameters for a computed tomography on the basis of at least one model equation for the computational tomographic determination of at least one dimensional measured variable, in particular model equation for determining the measured precision associated with measurement precision or measurement uncertainty, wherein in the model or model equations at least some of the device parameters of the computer tomograph used for the measurement are taken into consideration, characterized in that default parameters to be observed in the model equation (s) are taken into account, which include at least the measurement task parameters describing the one or more measurement tasks, in particular workpiece parameters, and that by simulation and / or mathematical calculation on the basis of the one or more model equations and / or computer tomographic test measurements in the available parameter space of the setting lparameter parameters are determined for which at least one target parameter is optimized and / or the target parameter falls below or exceeds a threshold. Method for adjusting the focal spot size of an X-ray tube of a sensor, preferably CT or radiography or laminography, for inspection and / or measurement, preferably dimensional measurement of a workpiece, wherein radiographic images of the workpiece in multiple orientations, in particular rotational positions set by a turntable between the workpiece and sensor with a detector, preferably a planar detector, in particular an X-ray detector, and wherein volume data (voxel volume) of the workpiece are determined from the radiographic images, and measurement points (measured data) are preferably generated from the volume data by means of surface extraction and thereby used for dimensional measurement characterized in that the maximum possible focal spot size is set which does not lead to any additional restriction of the structural resolution of the volume data (voxel data) and / or measurement data, taking into account the structural resolution present without taking into account the focal spot size, which results at least from the set voxel size and / or the pixel size of the detector projected into the object plane. Method for operating a computer tomograph, comprising at least one X-ray detector, preferably planar X-ray detector, a turntable for receiving a workpiece to be measured and a first and a second X-ray source, wherein when using each X-ray source radiographic images of the workpiece in several rotational positions of the workpiece relative to the X-ray sensor (X-ray source and X-ray detector) are recorded with the X-ray detector, and wherein by the radiation images by reconstruction volume data (voxel volume) of the workpiece are calculated, and preferably surface points (measuring points) are determined by extraction from the volume data and links the measuring points for the purpose of dimensional measurement of the workpiece be characterized in that the workpiece automatically measured with two integrated in the computer tomograph and connected to the same control and software X-ray tubes The two X-ray tubes are operated with different adjustment parameters, preferably operated with different X-ray spectra, and the radiation images or volume data determined with both X-ray tubes are combined by the control and / or software and evaluated together. Computer tomograph comprising at least one X-ray detector, preferably planar X-ray detector, a turntable for receiving a workpiece to be measured and a first X-ray source, and control and software for recording and evaluating the radiation images recorded in several rotational positions of the workpiece relative to the X-ray sensor (X-ray source and X-ray detector), wherein the Evaluation at least the reconstruction of the radiographic images to volume data (voxel volume) of the workpiece, and preferably the extraction of surface points (measuring points) from the volume data and linking the measuring points for the purpose of dimensional measurement of the workpiece, characterized in that a second x-ray tube integrated in the computer tomograph is connected to the controller, wherein the controller and the software are formed, the automated measurement with both X-ray tubes and the joint evaluation of the same en to realize workpieces with both X-ray tubes determined radiation images and / or volume data, wherein the first and second X-ray tube with different setting parameters are operable, preferably with different X-ray spectrums are operable. Method for operating a computer tomograph, comprising at least one x-ray source, an x-ray detector, preferably a planar x-ray detector, and a rotary unit such as a turntable and / or rotary pivot unit for receiving and adjusting the rotational and / or pivoting position of the workpiece to be measured relative to the x-ray detector and x-ray source, and preferably Measuring axes (translation axes), for adjusting the position of the workpiece and / or the X-ray source and / or the X-ray detector in at least one axis relative to each other, wherein radiographic images of the workpiece in a plurality of rotational and / or pivotal positions of the workpiece relative to the X-ray source and X-ray detector with the X-ray detector in which volume data (voxel volume) of the workpiece are calculated from the transmission images by reconstruction and surface points (measurement points) are preferably determined by extraction from the volume data and the measurement points are linked for the purpose of dimensional measurement of the workpiece, characterized in that using different positions of the workpiece and / or the X-ray source and / or the X-ray detector, adjusted by means of the measuring axes (translation axes), and / or different rotational positions and / or rotational-pivot positions of the workpiece, set using the turntable or the rotational-pivot unit, of the pure rotation of the workpiece about the rotational axis of the turntable deviating trajectories, ie movement of the workpiece relative to the X-ray source and X-ray detector for recording the plurality of radiographic images used. Method according to claim 5, characterized in that in the presence of maximum or average attenuation and / or maximum or average transmission lengths above predetermined threshold values and / or in the presence of minimum or average signal-to-noise ratios below a predetermined threshold value, automatically for the corresponding radiographic image Exposure time is increased and / or the number of superimposed images (image averaging) in the respective rotational position and / or position on the trajectory is increased, preferably to below thresholds and / or previously determined value or value is achieved in this fixed environment the value is determined for example by means of previously performed reference measurement of the workpiece with the computer tomograph or another computer tomograph. Method for operating an x-ray tube, preferably an x-ray tube, which is part of a computed tomography sensor or a radiography sensor or laminography sensor, wherein the x-ray tube has an x-ray emitting target which is exposed to an electron beam, characterized in that for assessing the state of the target, in particular target wear, the impact point (focal spot) of the electron beam are shifted relative to each other and the X-ray radiation directed on an X-ray detector is evaluated, in particular the intensity is changed during or respectively before and / or after the respective displacement of the X-radiation determined by the X-ray detector becomes. Method for operating an x-ray tube, preferably an x-ray tube, which is part of a computed tomography sensor or radiography sensor or laminography sensor, wherein the x-ray tube has an x-ray emitting target, which is exposed to an electron beam, preferably according to claim 7, characterized in that the point of impact of the electron beam on the Target is moved along a circular path by the target is rotated about an axis other than the direction of the incident electron beam (axis of rotation) or by reversing the orbit by combining translational shifts of electron beam and target relative to each other in at least two directions perpendicular to the direction of the incident electron beam a rotation axis is realized, wherein preferably as the displacement according to claim 1, the displacement along the circular path or the displacement to a radius and / or location of Rotationsac The changed orbit is preferably used for changing the radius, the rotation axis being displaced perpendicularly to its present direction, preferably by displacing the target perpendicular to the present direction of the rotation axis together with the rotation means provided for the rotation or by correspondingly changed translatory displacements of electron beam and target relative to each other. Device for implementing the method according to at least one of claims 7 to 8, characterized in that a device comprising at least one x-ray tube ( 100 ) and an X-ray emitting target ( 101 ), which with an electron beam ( 105 ), means ( 104 ) for influencing the direction of the X-ray beam and / or means ( 111 . 112 ) for the mechanical movement of the target ( 101 ) and / or target flange ( 106 ) and / or rotating means provided for the rotation of the target ( 107 ) relative to the electron beam ( 105 ), in particular perpendicular to the direction of the incident electron beam ( 105 ), or relative to the tube body ( 102 ), such as axes of motion ( 111 . 112 ) having. Method for correcting the drift of the CT components used for computed tomography (CT) during a computed tomography measurement X-ray tube, rotary table to be measured and in several rotational positions of the object to be measured relative to X-ray source and X-ray detector receiving X-ray detector relative to each other, wherein prior to and / or after the computed tomography measurement, a rapid tomography (reference tomography) is performed, are absorbed in the transmission images in a smaller number of rotational positions with respect to the computed tomography measurement, characterized in that using the radiographic images of the computer tomographic measurement and the Radiographic images of the rapid tomography a corrected voxel volume is determined by reconstruction, where corrected radiographic images (corrected projection images) are calculated or by assigning each radiograph of the computed tomography measurement on the basis of the radiographic images of the rapid tomography corrected CT geometry for reconstruction, the CT geometry the spatial position of the CT components X-ray tube, X-ray detector and turntable to each other and preferably their orientation as tilted designates. Device for recording a plurality of radiographic images of a measured object ( 303 ) for performing a computed tomography, wherein radiographic images in a plurality of rotational positions, adjustable by a rotating device such as mechanical axis of rotation ( 305 ), in which the measuring object ( 303 ) and a computed tomography sensor ( 301 . 304 . 309 . 310 . 320 ) are rotatably arranged relative to each other, preferably the measuring object ( 303 ) is rotatable, are receivable, the computed tomography sensor at least consists of a radiation source such as x-ray tube ( 301 ), at least one extensive scintillator ( 304 ) and at least one planar optical detector ( 310 ) such as a camera, wherein the transmission images from the at least one optical detector ( 310 ) and are reconstructable into a voxel volume from which preferably surface points can be determined at material transitions, wherein the light emitted by the scintillator ( 304 ) emitted optical radiation ( 307 ) at least partially from the at least one optical detector ( 310 ) is detectable, and wherein the computed tomography sensor is preferably integrated in a coordinate measuring machine, characterized in that between the scintillator ( 304 ) and the optical detector ( 310 ) one or more fiber bundles ( 320 ) are arranged, which the scintillator ( 304 ) associated page ( 321 ) of the fiber bundle (s) from the scintillator ( 304 ) emitted optical radiation ( 307 ) and at the optical detector ( 310 ) facing end ( 322 ) in the direction of the optical detector (s) ( 310 ). Method for carrying out a computer tomographic measurement with a computer tomograph, comprising at least one x-ray tube, the object to be measured receiving and rotating turntable and radiographic images of the object receiving x-ray detector, wherein in several rotational positions of the object and the components of the x-ray tube and x-ray detector relative to each other, in particular in an angular range of at least 360 ° or in an angular range of at least 180 °, radiographic images, wherein the respective recording takes place during a specified exposure or integration time, and wherein a reconstruction of a voxel volume from resulting radiographic images takes place, the resulting radiographic images are the radiographic images themselves or the resulting radiographic images are each a plurality of successively recorded and superimposed radiographic images, the resulting radiographs being gsbildern is assigned as the total exposure time the sum of the exposure times of the radiation images used for the formation, characterized in that for each resulting radiographic image, the total exposure time is set separately, wherein the exposure time and / or the number of each superimposed radiographic images is set so that at least one of the the characteristic value assigned to each resulting transmission image, such as minimum signal noise ratio (SNR), minimum intensity or gray value or average intensity or gray value remains constant or nearly constant for all resulting transmission images, the overall exposure time of the resulting transmission image to be recorded being determined from the characteristic value (s) which were determined from the one or more respective radiographic images respectively taken directly in front of it. Method for correcting temperature-related measurement deviations during measurement, in particular dimensional measurement with a coordinate measuring machine, comprising a plurality of components provided for the measurement, such as sensors and scales and at least one connecting circuit closing connecting elements, wherein at least one temperature sensor for detecting the currently present temperature of a component and / or a Connection element for correcting the measuring points and / or dimensions determined by the coordinate measuring machine, characterized in that the temperature measured values of a plurality of attached to the components and / or connecting elements between the components or associated temperature sensors are used for the correction, wherein a model or at least partial models for the temperature-related measurement deviations, in particular temperature-induced linear expansion of the components and / or connecting elements themselves and / or to each other is used. Apparatus for implementing the method for correcting temperature-related measurement deviations during measurement, in particular dimensional measurement with a coordinate measuring machine according to claim 13, wherein the coordinate measuring machine comprises a plurality of components intended for the measurement ( 401 . 404 . 405 . 411 . 414 . 420 . 422 ) like sensors ( 404 ) and standards ( 411 . 414 . 420 . 422 ) and at least one measuring circuit ( 407 ) closing connecting elements ( 408 . 412 . 415 . 419 . 423 . 427 ), wherein at least one temperature sensor (T1, ..., T17) for detecting the respectively present temperature of a component ( 401 . 404 . 405 . 411 . 414 . 420 . 422 ) and / or a connecting element ( 408 . 412 . 415 . 419 . 423 . 427 ), and wherein a correction device is provided, which is used to correct the measuring points and / or dimensions determined by the coordinate measuring machine, wherein the correction device is designed to detect the temperature measured values of the temperature sensors (T1,..., T17) and the Correction to be calculated, characterized in that temperature sensors (T1, ..., T17) at several components ( 401 . 404 . 405 . 411 . 414 . 420 . 422 ) and / or connecting elements ( 408 . 412 . 415 . 419 . 423 . 427 ) are mounted between or associated with the components. Device for carrying out a computer tomography comprising at least one x-ray tube ( 2 ), an X-ray detector ( 10 ), preferably flat X-ray detector ( 10 ), and an object to be tomographed ( 8th ) receiving and rotating turntable ( 7 ), which between X-ray tube ( 2 ) and X-ray detector ( 10 ), wherein the device is designed to transmit radiographic images of the object ( 8th ) in a plurality of rotational positions of the turntable ( 7 ), wherein the radiographic images can preferably be reconstructed into a voxel volume by means of reconstruction, wherein surface points at the material transitions of the object (particularly preferably from the voxel volume ( 8th ) and particularly preferably for measuring features or dimensions of the object ( 8th ), wherein the device is particularly preferably integrated in a coordinate measuring machine, characterized in that the X-ray detector ( 10 ) is designed to be tiltable, about at least a first axis which is perpendicular to the detector normal and is preferably designed tiltable about a second axis which is perpendicular to the detector normal and preferably perpendicular to the first axis, wherein the tilt angle to the first and / or second axis manually or electrically, continuously or stepwise adjustable. Device for computer tomographic examination of an object, comprising at least one x-ray tube ( 501 ), an X-ray detector ( 502 ), an object to be measured ( 504 ) and this rotating turntable ( 503 ) and a radiation protection housing ( 500 ), characterized in that the radiation protection housing ( 500 ) is at least partially formed from a plurality of building blocks ( 505-1 . 505-2 . 505-3 , ..., 505-12 ) identical shape. Method for determining a quality value, which is assigned to a surface measurement point determined by computer tomography, wherein the computer tomography comprises at least the following steps: recording multiple radiographic images of the object to be examined as workpiece in several rotational positions relative to an X-ray source and an X-ray detector, reconstruction of a voxel volume, which voxels with assigned voxel gray values, from the transmission images and determination of surface measurement points, characterized in that the quality value is determined from the following data: Measurement precision and / or signal-to-noise ratio (SNR) of the measured surface point and / or measurement precision and / or signal / Noise ratio (SNR) of the simulated surface point and / or - contrast of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or - noise of the simulated voxel gray values at d Coordinates of the surface point and its surroundings and / or contrast / noise ratio (CNR) of the simulated voxel gray values at the coordinates of the surface point and its surroundings and / or intensities and / or signal-to-noise ratio (SNR) of the pixels of the measured Radiographic images that contribute to the voxel gray levels that lie at the coordinates of the surface point and its surroundings and / or intensities and / or signal-to-noise ratio (SNR) of the pixels of the simulated radiographic images obtained by the reconstruction to the voxel gray levels contributing to the coordinates of the surface point and its surroundings.

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