EP4278149A1 - Appareil et procédé de tomodensimétrie - Google Patents

Appareil et procédé de tomodensimétrie

Info

Publication number
EP4278149A1
EP4278149A1 EP22706610.7A EP22706610A EP4278149A1 EP 4278149 A1 EP4278149 A1 EP 4278149A1 EP 22706610 A EP22706610 A EP 22706610A EP 4278149 A1 EP4278149 A1 EP 4278149A1
Authority
EP
European Patent Office
Prior art keywords
data
measurement
sim
simulation
vol
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22706610.7A
Other languages
German (de)
English (en)
Inventor
Ralf Christoph
Raoul CHRISTOPH
Michael Hammer
Manfred Voss
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Werth Messtechnik GmbH
Original Assignee
Werth Messtechnik GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Werth Messtechnik GmbH filed Critical Werth Messtechnik GmbH
Publication of EP4278149A1 publication Critical patent/EP4278149A1/fr
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
    • G01B15/04—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring contours or curvatures
    • G01B15/045—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring contours or curvatures by measuring absorption
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computed tomography [CT]
    • A61B6/032—Transmission computed tomography [CT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5205—Devices using data or image processing specially adapted for radiation diagnosis involving processing of raw data to produce diagnostic data
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5258—Devices using data or image processing specially adapted for radiation diagnosis involving detection or reduction of artifacts or noise
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/54—Control of apparatus or devices for radiation diagnosis
    • A61B6/547—Control of apparatus or devices for radiation diagnosis involving tracking of position of the device or parts of the device
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/58—Testing, adjusting or calibrating thereof
    • A61B6/582—Calibration
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/58—Testing, adjusting or calibrating thereof
    • A61B6/582—Calibration
    • A61B6/583—Calibration using calibration phantoms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/58—Testing, adjusting or calibrating thereof
    • A61B6/586—Detection of faults or malfunction of the device
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
    • G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
    • G01B21/045—Correction of measurements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
    • G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
    • G01B21/047—Accessories, e.g. for positioning, for tool-setting, for measuring probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/046—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T12/00—Tomographic reconstruction from projections
    • G06T12/10—Image preprocessing, e.g. calibration, positioning of sources or scatter correction
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00—Image enhancement or restoration
    • G06T5/50—Image enhancement or restoration using two or more images, e.g. averaging or subtraction
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G06T7/0004—Industrial image inspection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/40—Imaging
    • G01N2223/419—Imaging computed tomograph
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/40—Imaging
    • G01N2223/426—Imaging image comparing, unknown with known substance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/646—Specific applications or type of materials flaws, defects
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10072—Tomographic images
    • G06T2207/10081—Computed x-ray tomography [CT]
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/20—Special algorithmic details
    • G06T2207/20212—Image combination
    • G06T2207/20221—Image fusion; Image merging

Definitions

  • the present invention relates to a method for operating a coordinate measuring system such as a coordinate measuring machine with a computed tomography sensor, for creating a measurement and/or evaluation program for a computed tomography sensor, and a device for executing the method or the program.
  • a coordinate measuring system such as a coordinate measuring machine with a computed tomography sensor, for creating a measurement and/or evaluation program for a computed tomography sensor, and a device for executing the method or the program.
  • the workpiece to be examined is placed between a radiation source, usually an X-ray source, and a radiation detector, so that radiographic images can be recorded with the detector in different rotational positions of the workpiece in relation to the source and detector and can be reconstructed into a volume data set (voxel volume).
  • a radiation source usually an X-ray source
  • a radiation detector so that radiographic images can be recorded with the detector in different rotational positions of the workpiece in relation to the source and detector and can be reconstructed into a volume data set (voxel volume).
  • the workpiece is arranged on a turntable in order to realize the different rotary positions by turning about a rotary axis.
  • the workpiece is stationary and the source and detector rotate about the workpiece about an axis of rotation.
  • the unit consisting of the source, detector and turntable is referred to as a computed tomography sensor.
  • the detector used to capture the 2D radiographs is mostly flat, i.e.
  • a 2D detector designed as a 2D detector, and consists of a scintillator layer, in which the X-rays are converted into light, tubular light channels located behind it in the direction of radiation, which reduce crosstalk between different detector areas, and one directly behind it, a fixed pixel matrix, i.e. a flat matrix camera, such as a CCD or CMOS camera.
  • a fixed pixel matrix i.e. a flat matrix camera, such as a CCD or CMOS camera.
  • line detectors with one or a few lines are also known. In order to record large measuring ranges, however, the workpiece has to be shifted across the line direction, which is time-consuming, and irradiated several times. Here, individual layers are also reconstructed separately.
  • the invention is therefore advantageously based on flat detectors or detectors with a flat detection surface such as a flat scintillator layer.
  • boundary surface points or surface (measuring) points are generated from the volume data, for example in STL format (STL—Standard Triangulation Language) and linked to geometric properties and dimensions.
  • STL Standard Triangulation Language
  • the computer tomograph or computer tomography sensor is then designed as a coordinate measuring device or coordinate measuring system.
  • programs for simulating a measurement with a computer tomography sensor are known, e.g. the Artist program from BAM Berlin, programs for numerical measurement uncertainty determination of measurements with computer tomography sensors, simulations for correcting artifact correction methods (for example in the present document and the documents cited therein by Applicant), and programs for optimizing setting parameters of computed tomography sensors (for example the Applicant's TomoAssist measurement software).
  • the disadvantage is that there are separate software packages for operating a coordinate measuring device (or generally a coordinate measuring system) with a computed tomography sensor and for simulating computed tomography.
  • the simulation of radiographic images is carried out with the Artist software, the reconstruction with another software tool (e.g. the freely available Astra reconstruction) and the evaluation of dimensional features of workpiece geometries with a third software.
  • Controlling the coordinate measuring machine with the computed tomography sensor requires additional software, which often already includes the last-mentioned step of dimensional evaluation (e.g. the applicant's WinWerth measuring software), which is why it is generally referred to here as measuring software.
  • the prior art lacks the possibility of completely offline learning of computed tomography measurements and the evaluation of the measurement data determined, possibly taking into account effects which lead to systematic and/or result in random measurement deviations, and/or possibly taking into account the calibration status of the device or sensor to be simulated (computed tomography sensor).
  • the object of the present invention is therefore also to specify a method, measurement software and a device that is suitable for realizing continuous, joint operation of computed tomography simulation software and control of a coordinate measuring machine with computed tomography sensor within one piece of software (measuring software).
  • This should also be used to operate a coordinate measuring system such as a coordinate measuring machine with at least one computed tomography sensor and/or to create a program for controlling the computed tomography sensor and/or to create a program for evaluating data determined with a computed tomography sensor.
  • the invention provides that the measurement software has a function for simulating (simulation function) at least one step of a computed tomography measurement, preferably at least the step of recording the intensity image.
  • the simulation function is fully integrated into the measuring software of a coordinate measuring machine with a computed tomography sensor and in particular that the following functions are implemented: i) virtual equipping of the device (also multiple measurements, including equipping of a workpiece holder, positioning of the workpiece holder on the manipulators) ii) setting parameters such as projection geometry , voltage, power, pre-filter, integration time, set image averaging number iii) Simulate intensity image acquisition iv) Perform reconstruction of the simulated intensity images v) Calculate interface points from the reconstructed volume vi) Calculate regular geometry elements vii) Calculate geometric properties viii) Carry out inspection tasks and thus learn the entire measurement process offline allows.
  • the invention also sees the duplication of a model at n positions, preferably at positions defined by CAD elements, as a special, independent solution positions and/or at calculated positions and/or at manually defined positions.
  • Focal spot distribution preferably focal spot size depending on the set parameters and the properties of the components of the X-ray tube
  • Tube parameters such as voltage, power
  • Detector parameters such as integration time, image averaging number
  • the attenuation coefficients are preferably read out from values of empirically determined attenuation coefficients stored in tables as a function of the
  • Target geometry is a measured or calculated model such as a target point cloud
  • Target geometry is a constructed model such as a CAD model
  • the present invention also relates to a computed tomography method in which physical effects such as artefacts when passing through a workpiece are corrected using simulation methods.
  • Correction methods known from the prior art for measured data from computed tomography, which work by means of simulation, are named in the applicant's WO2013167616 and DE102013107745.
  • the correction data are determined by forming the difference between a simulation that takes the artifacts into account and a simulation that does not take artifacts into account (generally referred to as effects, mostly physical properties during transmission).
  • Data representing the shape or dimensions of the workpiece are required as input data for the forward projection within the framework of the simulation of radiographic image data.
  • the nominal data of the workpiece such as CAD data or STL data (i.e. surface point data in STL format, Standard Triangulation Language) from an already performed measurement of the workpiece (master part measurement) are used for this purpose.
  • the calculation and application of the correction takes place selectively or mixed in the radiographic image data, the volume data reconstructed therefrom or the surface point data determined from the volume data. This means that the differences of the simulations are formed, for example, in the transmission image data and are then also applied directly to the transmission image data of the real measurement.
  • the differences in the transmission image data can first be reconstructed and then subtracted from the volume data of the measurement.
  • the nominal data or STL data do not match the actual dimensions of the workpiece (real workpiece shape) sufficiently to allow an exact simulation of the artifacts and thus an exact correction guarantee.
  • Another problem is that at particular strong artefact-laden measurement data STL data, i.e.
  • a first solution is offered by the subsequently published invention DE 102020130442.0, going back to the applicant's DE102019135686.5. All contents of these writings are explicitly included here.
  • the applicant's DE102020130442.0 also proposes using nominal data of the workpiece as input data for the simulations, ie surface data, preferably in the form of CAD data, or STL data of a master part measurement of the workpiece.
  • nominal data of the workpiece ie surface data, preferably in the form of CAD data, or STL data of a master part measurement of the workpiece.
  • This data may not or not yet be available in the data processing or already have discrepancies that are undesirable.
  • a further object of the present invention is therefore to avoid or at least reduce deviations that occur when determining a correction for measurement data from computed tomography by simulating effects, mostly physical effects such as artifacts (caused by any influences on the CT measurement, such as e.g. geometric or partial volume effects) can occur, in particular those occurring when determining the correction by forming the difference between a simulation taking account of the artefacts and a simulation without taking these artefacts into account, even without nominal data such as CAD data or STL data of a measurement of the workpiece being mandatory for which simulations must be used. Deviations to be expected in the simulation due to deviations in the input data from the workpiece shape that is actually present should be reduced or avoided.
  • volume data can now also be used as input data for the simulations, for example volume data of a master part measurement of the Workpiece or otherwise generated volume data, for example volume data determined from CAD data.
  • a master piece measurement is a calibrated measurement according to a different method, for example with a different measuring device, or a computed tomography method, for example with higher accuracy, is provided.
  • the solution also provides for the well-known correction, referred to here as a preliminary correction (Sim-Artifacts), which usually results from the difference between a simulation with (Sim-Vol) and a simulation without (Ideal-Vol) taking into account the effects to be corrected physical effects such as artefacts, by applying a transformation rule (distortion M AP) to a final correction (real artefact) for the measurement data (real volume) is adjusted.
  • a preliminary correction Sim-Artifacts
  • disortion M AP transformation rule
  • the transformation rule is the mapping of the simulation data, taking into account the physical effects (Sim-Vol) onto the measurement data (Real-Vol).
  • the part of the deviations of the simulation data taking into account the artifacts, from the actually measured artifact-prone measurement data, which results from the deviation of the input data for the simulations from the real workpiece shape, is recorded and used to calculate the simulation data (Sim-Vol) and (Ideal - Vol) or the provisional correction from the difference between the two simulation data (Sim-Vol) and (Ideal-Vol) or in the case of the shortened procedure only the simulation data (Ideal-Vol) to be adjusted accordingly.
  • the correction is particularly preferably carried out on the basis of the volume data.
  • measurement data are also present in the form of volume data if they are affected by artifacts in such a way that surface data (STL data) cannot be calculated, or if they show large deviations from the actual workpiece shape.
  • the invention also provides fundamentally, the correction based on To realize transmission image data or the surface point data or mixed, as previously explained to the applicant's writings from the prior art.
  • the correction is applied in the same way as described above or below.
  • the application is readily possible since radiographic image data is already before the
  • volume data always available.
  • a prerequisite for the application of the method according to the invention based on the surface data is that these can be formed from the volume data.
  • the following explanations are given by way of example for the case of determining and applying the correction from or to the volume data.
  • the simulation taking into account artefacts (referred to below as Sim-Vol), is initially based on input data in the form of nominal data such as CAD data of the workpiece. If available, surface data (STL data) from a measurement of the corresponding workpiece can also be used. Another alternative is to use existing volume data for the simulation. These can be obtained during the workpiece measurement or from the CAD model. The simulation is then also carried out on the identical input data without taking the artefacts into account.
  • the simulations each take the form of a so-called forward projection, with simulated radiographic image data being calculated and reconstructed into simulated volume data.
  • the transformation rule is determined, which maps the artifact-afflicted simulation data in volume data format (Sim-Vol) to the measured volume data (Real-Vol) reconstructed from the measured radiographic image data.
  • the transformation specification works on the basis of the gray values of the voxels of the volume data (or on the basis of the gray values of the radiographic images, if this is to be corrected) and reassigns the gray values in such a way that, by means of affine and/or non-affine transformations, the differences between the simulation data and the measurement data in relation to the position shift between the gray value transitions. These gray value transitions are later representative of the surface data to be determined. In this way, the dimensional deviations between the simulation data and the actually measured data in the area of the volume data are recorded in order to subsequently use this information to calculate a more precise To enable correction of the measured volume data. If the surface data is corrected, the positions of the surface points are transformed accordingly instead of the gray values.
  • a sim artifact is an artifact volume that is formed by calculation, in particular difference formation from the simulation with and the simulation without considering the artifacts.
  • this artefact volume is adapted to the actual workpiece shape by applying the transformation rule, or the simulation volume data without (ideal volume) taking into account the artefacts and possibly also the
  • Simulation volume data with (Sim-Vol) consideration of the artifacts themselves are adjusted to the correct workpiece geometry (to Ideal-Vol-K or Sim-Vol-K) by applying the transformation rule, which means that the simulation data corrected with the transformation rule (Ideal-Vol-K) directly to the corrected measurement volume data (Corr-Vol) or the difference between (Sim-Vol-K)
  • the transformation rule results, so to speak, in a scaling, rotation, translation, shearing and thus shifting of the gray values in the artifact volume (Sim-Artifact) or the simulation volume data (Ideal-Vol) and possibly (Sim-Vol) in such a way that the deviations in the edge locations ( Gray value transitions) between simulation data and measured data are corrected or generally simulation data and measured data are adjusted.
  • the mentioned reassignment of the gray values is not necessarily source-free, especially in the case of scaling operations, i.e. the sum of the gray values of a volume can be changed by the transformation rule.
  • the final correction data for correcting the volume data of the real measurement (Real - Vol) applied, preferably by subtraction or addition of the gray values of the final correction data (real artifact).
  • the surface data i.e Determines surface measuring points, which are preferably used to determine dimensional dimensions on the workpiece.
  • the finally corrected volume data can also be used to determine internal features such as inclusions or blowholes of the workpiece.
  • the invention provides a method for calculating and applying a correction (real artifact) for measurement data (real-vol) determined by means of computed tomography, the measurement data preferably being those of the workpiece to be measured in several rotational positions when irradiated by a radiation source (source).
  • X-ray source measurement radiation emitted, radiographic image data recorded by means of a detector, preferably a 2D X-ray detector, and/or volume data reconstructed from the radiographic image data and/or surface point data determined from the volume data, with simulation data initially being used for the correction, taking into account the physical effects to be corrected, such as artifacts computed tomography (Sim-Vol) and simulation data without these effects (Ideal-Vol) are calculated using as input data
  • Sim-Vol artifacts computed tomography
  • Ideal-Vol simulation data without these effects
  • CAD/STL/volume nominal data of the workpiece in the form of surface data, preferably CAD data, or STL data of a master part measurement of the workpiece, or volume data of the workpiece, for example a master part measurement or generated from the CAD data, are used for the simulations, characterized by the following steps:
  • a transformation rule that maps the simulation data to the measurement data (Real-Vol) taking into account the effects, such as physical effects (Sim-Vol), and -
  • Simulation data without these effects (Ideal-Vol), or o on the simulation data taking into account the effects to be corrected, such as physical effects (Sim-Vol) for determining corrected simulation data (Sim-Vol-K) and on the simulation data without these effects (Ideal-Vol) to determine corrected simulation data (Ideal-Vol-K), and determination of the final correction data (real artifact) by taking the difference between (Sim-Vol-K) and (Ideal-Vol-K ), and application of the final correction data (Real Artifact) to the measurement data (Real-Vol) to determine the corrected measurement data (Corr-Vol) or
  • the invention is characterized in that all the steps listed below are performed on the respective radiographic image data or the respective volume data or the respective surface point data:
  • the transformation rule corresponds to the gray values of the volume data of the simulation with artifacts (Sim-Vol), gray values of the volume data of the Assigns measurement data (Real-Vol) depending on the location and preferably changes it, for example in the form of an affine mapping and/or non-affine mapping and/or a look-up table (LUT), with the transformation rule preferably shifting the surface transitions by rearranging the gray values associated gray value gradients.
  • Sim-Vol gray values of the volume data of the simulation with artifacts
  • Real-Vol gray values of the volume data of the Assigns measurement data
  • LUT look-up table
  • the invention is characterized in that the transformation rule is determined by optimizing a cost function, this cost function consisting of a number of individual terms, such as equality metrics and/or functions thereof and/or restricting boundary conditions.
  • the invention is also characterized in that the finally corrected measurement data from computed tomography (Korr-Vol) are used to determine features inside the workpiece, such as inclusions or cavities, by evaluating the finally corrected volume data and/or for determining dimensional measurements of the workpiece are used by evaluating the surface point data.
  • Korr-Vol computed tomography
  • the method is used in a computer tomograph designed as a coordinate measuring machine, which is designed to determine dimensions on workpieces from the surface point data, ie to link surface points to dimensions.
  • the method will be applied iteratively. This means that the corrected measurement data (Corr-Vol) is used as input data for a simulation and the correction procedure described above is repeated to perform an improved correction.
  • Corr-Vol measurement corr (measurement data without artefact)
  • Sim-Vol Sim-uncorr (simulation data with artefacts)
  • Ideal-Vol Sim-unkorr-T (simulation data transformed with artifacts)
  • Sim-Vol-K Sim-korr (simulation data without artifact)
  • Ideal-Vol-K Sim-korr-T (simulation data transformed without artefacts)
  • Real artefact Sim-artefact-T (transformed simulated artefact)
  • Measurement-uncorr-T -1 measured data with artefacts inversely transformed
  • the invention provides a method for calculating a correction (measurement artifact) for measurement data determined by means of computed tomography (measurement inaccurate), the measurement data being of the workpiece from a number of different viewing angles when irradiated by a radiation source (source), preferably an X-ray source, emitted measurement radiation, radiographic image data recorded by means of a detector, preferably a 2D X-ray detector, and/or volume data reconstructed from the radiographic image data and/or surface point data determined from the volume data, with simulation data taking into account the physical effects to be corrected, such as artefacts in computed tomography ( Sim-uncorr) and simulation data without these effects (Sim-corr) are calculated and/or used, with simulation data in the form of radiographic images taken from different perspectives and/or volume data and/or sizes surface points are used the input data for
  • a radiation source preferably an X-ray source, emitted measurement radiation
  • radiographic image data recorded by means of a detector preferably a 2D
  • X-ray image data preferably X-ray length images, and/or volume data of the workpiece, for example a master part measurement or generated from the CAD data, and/or surface data, preferably CAD data, or STL data of a master part measurement of the workpiece are used, which are reflected in the following steps awards,
  • Transformation-Sim-Real which the simulation data with and/or without taking into account the disturbing effects, such as physical effects (Sim-uncorr and/or Sim-corr), and/or the simulated artefacts (Sim- artifact) onto the measurement data (measuring uncorr) and/or calculation of an inverse transformation rule (transformation-real-sim) that maps the measurement data (measurement uncorr) onto the simulation data (sim-uncorr and/or sim-corr and /or Sim Artifact), and
  • the invention is characterized in that the correction data (measurement artifact) is applied to the measurement data (measurement uncorr) to determine the corrected measurement data (measurement corr). It is preferably provided that the calculation of the provisional correction data (sim artifact) from simulation data taking into account the disturbing effects (sim uncorr) and simulation data without the disturbing effects (sim corr), preferably by subtraction, and the calculation of the correction data (meas -Artifact) by application the transformation rule (Transformation-Sim-Real) to the provisional correction data (Sim artifact).
  • the invention is also distinguished by the fact that the corrected measurement data (measurement corr) is calculated by transforming the simulation data without taking into account the disruptive effects (sim corr) using the transformation rule (transformation sim real).
  • the calculation of the corrected measurement data can also be carried out using a combination of inverse transformation (Transformation-Real-Sim) of the measurement data (Mess-unkorr), subsequent correction of the measurement data, preferably using the provisional correction data (Sim -Artifact), and transformation (Transformation-Sim-Real) of this inversely transformed corrected measurement data (Messkorr-T -1 ) can be obtained.
  • the invention is characterized in that the transformation rule the gray values of the volume data of the simulation, preferably with artifacts (sim uncorr) and / or without artifacts (sim corr) and / or the preliminary correction data (sim artifact), gray values of assigns the volume data of the measurement data (measuring uncorr) location-dependent, or the inverse transformation rule assigns the gray values of the volume data of the measurement data (measurement uncorr) to those of the simulation (sim-uncorr and/or sim-corr and/or sim-artefact) depending on the location, and preferably changed, for example in the form of an affine mapping and/or non-affine mapping and/or a look-up table (LUT) and/or a vector field,
  • LUT look-up table
  • the transformation rule can be achieved by optimizing a cost function, with this cost function consisting of several Individual terms such as equality metrics and/or functions thereof and/or restricting boundary conditions and/or is determined by applying an empirical and/or analytical rule.
  • the invention is characterized in that the finally corrected measurement data from computed tomography (measurement correction) are used to determine features inside the workpiece, such as inclusions or cavities, by evaluating the finally corrected volume data and/or to determine dimensional parts dimensions of the workpiece are used by evaluating the surface point data.
  • the invention is also characterized in that the method is used in a computer tomograph designed as a coordinate measuring machine, which is designed to determine dimensions on workpieces from the surface point data, ie to link surface points to dimensions.
  • Fig. 1 is a schematic representation of the process of an inventive
  • flight 3 shows a schematic representation of the sequence of an alternative, shortened correction method according to the invention for artifacts in computed tomography.
  • FIG. 1 shows an exemplary basic representation of the sequence of a correction method according to the invention for artifacts in computed tomography.
  • the nominal data in the form of CAD data or surface data in STL format of the workpiece from, for example, a master part measurement or volume data of the workpiece are used for simulations 501, 502 of the computed tomographic measurement of a workpiece.
  • the simulation 501 takes place without taking artifacts 503 into account and supplies the simulation data Ideal-Vol.
  • the simulation 502 takes place taking into account selected artifacts 503 and supplies the simulation data Sim-Vol.
  • the simulation involves the calculation of transmission image data of the workpiece by means of forward projection, with the parameters of the respective computer tomograph such as focal spot size, spectrum and power of the measurement radiation emitted by the radiation source, size, pixel size, number of pixels, pixel spacing of the detector and position of the components of the radiation source, Detector and workpiece, as well as the position of the axis of rotation of the rotary table for rotating the workpiece, are taken into account in relation to one another.
  • the simulated radiographic image data are each first reconstructed into volume data, so that volume data are denoted here by Ideal-Vol and Sim-Vol.
  • the Real-Vol volume data reconstructed from the radiographs taken are also available from the real measurement of the workpiece with the computer tomograph.
  • the transformation rule (distortion MAP) 505 that maps Sim-Vol to Real-Vol is determined from Real-Vol and the volume data Sim-Vol from the simulation 502, taking into account the artifacts 503.
  • the transformation rule 505 is then applied to the artifact volume sim artifact 504 (preliminary correction data) in order to form the final correction data real artifact 506 .
  • the final correction data Real Artifact 506 are subtracted from the volume data of the Real-Vol measurement, that is to say the respective gray values of the associated voxels are subtracted in order to determine the corrected volume data Corr-Vol.
  • This corrected measurement data is evaluated in the volume range in order to determine features inside the workpiece, such as inclusions or cavities.
  • surface point data are determined from the corrected volume data Corr-Vol using surface extraction methods or segmentation, from which dimensional dimensions of the workpiece are determined.
  • FIG. 2 shows an alternative procedure to FIG. 1, with the simulated
  • volume data Ideal-Vol and Sim-Vol are converted into the corrected volume data Ideal-Vol-K and Sim-Vol-K by applying the transformation rule 505 , the difference between which is formed in order to form the final correction data Real Artifact 506 .
  • the application of the transformation rule 505 to the simulated volume data Sim-Vol results in the corrected simulated volume data Sim-Vol-K matching the measurement data Real-Vol.
  • the final correction data Real-Artifact 506 therefore correspond to the difference between the measurement data Real-Vol and the corrected simulated volume data Sim-Vol-K, which means that the corrected volume data of the measurement Korr-Vol exactly match the corrected volume data Sim-Vol -K match.
  • the application of the transformation rule 505 to the simulated volume data Sim-Vol can therefore be omitted and the corrected volume data of the measurement Korr-Vol are obtained directly by applying the transformation rule 505 to the simulated volume data Ideal-Vol, as shown in FIG.

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Abstract

L'invention concerne un procédé pour faire fonctionner une machine à mesurer tridimensionnelle comprenant au moins un capteur de tomodensitométrie et pour créer un programme destiné à commander le capteur de tomodensitométrie et/ou pour créer un programme pour évaluer des données déterminées au moyen du capteur de tomodensitométrie avec un logiciel de mesure qui présente une fonction de simulation d'au moins une étape d'une mesure de tomodensitométrie.
EP22706610.7A 2021-02-26 2022-02-18 Appareil et procédé de tomodensimétrie Pending EP4278149A1 (fr)

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PCT/EP2022/054084 WO2022179947A1 (fr) 2021-02-26 2022-02-18 Appareil et procédé de tomodensimétrie

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