Digital twins of measurement systems are used to estimate their measurement uncertainty. In the p... more Digital twins of measurement systems are used to estimate their measurement uncertainty. In the past, virtual coordinate measuring machines have been extensively researched. Research on digital twins of optical systems is still lacking due to the high number of error contributors. A method to describe a digital twin of an optical measurement system is presented in this article. The discussed optical system is a laser line scanner mounted on a coordinate measuring machine. Each component of the measurement system is mathematically described. The coordinate measuring machine focuses on the hardware errors and the laser line scanner determines the measurement error based on the scan depth, in-plane angle and out-of-plane angle. The digital twin assumes stable measurement conditions and uniform surface characteristics. Based on the Monte Carlo principle, virtual measurements can be used to determine the measurement uncertainty. This is demonstrated by validating the digital twin on a se...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
The Utrecht facility for accelerator mass spectrometry is described. The setup with an EN tandem ... more The Utrecht facility for accelerator mass spectrometry is described. The setup with an EN tandem accelerator is designed for measurements of a broad range of long-lived radionuclides and of stable trace elements. In particular, dating measurements with "Be and r4C can be performed with high precision by rapid switching between the measurements of the isotopes. Optimal beam transmission through the accelerator is achieved with a new injection system in conjunction with the installation of axially symmetric acceleration tubes with spirally inclined electrodes. The first 14C/"C measurement with this setup is reported.
This paper describes a system that enables a traceable dynamic calibration of probes of roughness... more This paper describes a system that enables a traceable dynamic calibration of probes of roughness testers and roundness testers, for example. The system is based on a digital piezo translator (DPT). For the calibration of the DPT itself, an interferometric technique was used. After calibration by laser interferometry, the DPT is used as a transfer standard that can be driven by signals of various, but exactly known, form. This time-displacement form can range from square to sinusoidal or quasi-random with a maximum displacement of 15 pm and a maximum frequency of about 300 Hz. From a practical calibration of a roughness tester, it is shown that, depending upon the profile, roughness parameters can be measured with an uncertainty ranging from a few nm to 1%.
With use of an ellipsometric measurement the polarization state of several optical components use... more With use of an ellipsometric measurement the polarization state of several optical components used in interferometry was measured. A model of a heterodyne laser interferometer was developed, enabling to predict the non-linearities resulting from non-ideal polarization optics.
ABSTRACT In this paper, the calibration and verification infrastructure to support areal surface ... more ABSTRACT In this paper, the calibration and verification infrastructure to support areal surface texture measurement and characterisation will be reviewed. A short historical overview of the subject will be given, along with a discussion of the most common instruments and directions of current international standards. Traceability and uncertainty will be discussed, followed by a presentation of the latest developments in software and material measurement standards. The concept and current infrastructure for determining the metrological characteristics of instruments will be highlighted and future research requirements will be presented.
Surface Topography: Metrology and Properties, 2015
With the definition and further standardisation of 2.5-D roughness measuring methods and paramete... more With the definition and further standardisation of 2.5-D roughness measuring methods and parameters, the demand of traceability and uncertainty estimation for measurements and parameters automatically becomes eminent. This paper gives an overview of the problems and possibilities that appear when uncertainties have to be put to values that are derived from a measured surface topography such as: the Ra-value of a periodic specimen, the RSm-value of a typeD standard, the Sa-value of a single cutoff length of a type D standard. It is shown that straightforward implementation of the methods described in the GUM leads to impossible and impracticable equations because of the correlations between some millions of measurement points. A practical solution is found in taking the main aspects of uncertainty, as these are given in the recent ISO 25178 standards series and apply these to a measured surface topography as a whole.
A relatively low cost pre-prototype measurement machine for measuring the geometry of double side... more A relatively low cost pre-prototype measurement machine for measuring the geometry of double side polished wafers has been developed. The measurement principle is based on a scanning double side Fizeau interferometer with which the front side flatness and the back side flatness of a wafer is measured simultaneously. Both flatness maps are used to calculate the wafer thickness variation. The influence of lens aberrations, alignment errors and flatness errors of reference flats is compensated for by self-calibrating software compensation techniques.
This document is the result of interlaboratory comparisons of surface plates that were held in th... more This document is the result of interlaboratory comparisons of surface plates that were held in the past in the context of RvA accreditation of calibration laboratories. This document provides simulated measurement data of imaginary surface plates which are suitable for software testing. The software is tested for consistency, calculating the correct reference plane and the effect of type A uncertainty ("noise") on the end result. For a few geometries, the measurements given that should give that geometry as a result. The test is suitable for the processing of measurements of both electronic levels and angle measurements with eg, an autocollimator, laser interferometer with angular optics, etc. Both a square / rectangular grid, and the "Union Jack" method can be tested. From this test conclusions about the uncertainty of a measurement can be drawn in addition to temperature effects that are mentioned in document TCGM-03 "Temperature and moisture effects on su...
Fundamental Principles of Engineering Nanometrology, 2014
ABSTRACT This chapter presents the field of static length measurement. Some basic optics are intr... more ABSTRACT This chapter presents the field of static length measurement. Some basic optics are introduced to lead up to the field of interferometry – length measurement using light. Different configurations of interferometer are presented including the Michelson, Twyman-Green, Fizeau, Jamin, Mach-Zehnder and Fabry-Pérot. Gauge blocks as length standards are discussed in detail along with gauge block interferometry. The various sources of error in gauge block interferometry are presented and the chapter finishes with some alternative methods for gauge block measurement, such as double-sided interferometry.
Digital twins of measurement systems are used to estimate their measurement uncertainty. In the p... more Digital twins of measurement systems are used to estimate their measurement uncertainty. In the past, virtual coordinate measuring machines have been extensively researched. Research on digital twins of optical systems is still lacking due to the high number of error contributors. A method to describe a digital twin of an optical measurement system is presented in this article. The discussed optical system is a laser line scanner mounted on a coordinate measuring machine. Each component of the measurement system is mathematically described. The coordinate measuring machine focuses on the hardware errors and the laser line scanner determines the measurement error based on the scan depth, in-plane angle and out-of-plane angle. The digital twin assumes stable measurement conditions and uniform surface characteristics. Based on the Monte Carlo principle, virtual measurements can be used to determine the measurement uncertainty. This is demonstrated by validating the digital twin on a se...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
The Utrecht facility for accelerator mass spectrometry is described. The setup with an EN tandem ... more The Utrecht facility for accelerator mass spectrometry is described. The setup with an EN tandem accelerator is designed for measurements of a broad range of long-lived radionuclides and of stable trace elements. In particular, dating measurements with "Be and r4C can be performed with high precision by rapid switching between the measurements of the isotopes. Optimal beam transmission through the accelerator is achieved with a new injection system in conjunction with the installation of axially symmetric acceleration tubes with spirally inclined electrodes. The first 14C/"C measurement with this setup is reported.
This paper describes a system that enables a traceable dynamic calibration of probes of roughness... more This paper describes a system that enables a traceable dynamic calibration of probes of roughness testers and roundness testers, for example. The system is based on a digital piezo translator (DPT). For the calibration of the DPT itself, an interferometric technique was used. After calibration by laser interferometry, the DPT is used as a transfer standard that can be driven by signals of various, but exactly known, form. This time-displacement form can range from square to sinusoidal or quasi-random with a maximum displacement of 15 pm and a maximum frequency of about 300 Hz. From a practical calibration of a roughness tester, it is shown that, depending upon the profile, roughness parameters can be measured with an uncertainty ranging from a few nm to 1%.
With use of an ellipsometric measurement the polarization state of several optical components use... more With use of an ellipsometric measurement the polarization state of several optical components used in interferometry was measured. A model of a heterodyne laser interferometer was developed, enabling to predict the non-linearities resulting from non-ideal polarization optics.
ABSTRACT In this paper, the calibration and verification infrastructure to support areal surface ... more ABSTRACT In this paper, the calibration and verification infrastructure to support areal surface texture measurement and characterisation will be reviewed. A short historical overview of the subject will be given, along with a discussion of the most common instruments and directions of current international standards. Traceability and uncertainty will be discussed, followed by a presentation of the latest developments in software and material measurement standards. The concept and current infrastructure for determining the metrological characteristics of instruments will be highlighted and future research requirements will be presented.
Surface Topography: Metrology and Properties, 2015
With the definition and further standardisation of 2.5-D roughness measuring methods and paramete... more With the definition and further standardisation of 2.5-D roughness measuring methods and parameters, the demand of traceability and uncertainty estimation for measurements and parameters automatically becomes eminent. This paper gives an overview of the problems and possibilities that appear when uncertainties have to be put to values that are derived from a measured surface topography such as: the Ra-value of a periodic specimen, the RSm-value of a typeD standard, the Sa-value of a single cutoff length of a type D standard. It is shown that straightforward implementation of the methods described in the GUM leads to impossible and impracticable equations because of the correlations between some millions of measurement points. A practical solution is found in taking the main aspects of uncertainty, as these are given in the recent ISO 25178 standards series and apply these to a measured surface topography as a whole.
A relatively low cost pre-prototype measurement machine for measuring the geometry of double side... more A relatively low cost pre-prototype measurement machine for measuring the geometry of double side polished wafers has been developed. The measurement principle is based on a scanning double side Fizeau interferometer with which the front side flatness and the back side flatness of a wafer is measured simultaneously. Both flatness maps are used to calculate the wafer thickness variation. The influence of lens aberrations, alignment errors and flatness errors of reference flats is compensated for by self-calibrating software compensation techniques.
This document is the result of interlaboratory comparisons of surface plates that were held in th... more This document is the result of interlaboratory comparisons of surface plates that were held in the past in the context of RvA accreditation of calibration laboratories. This document provides simulated measurement data of imaginary surface plates which are suitable for software testing. The software is tested for consistency, calculating the correct reference plane and the effect of type A uncertainty ("noise") on the end result. For a few geometries, the measurements given that should give that geometry as a result. The test is suitable for the processing of measurements of both electronic levels and angle measurements with eg, an autocollimator, laser interferometer with angular optics, etc. Both a square / rectangular grid, and the "Union Jack" method can be tested. From this test conclusions about the uncertainty of a measurement can be drawn in addition to temperature effects that are mentioned in document TCGM-03 "Temperature and moisture effects on su...
Fundamental Principles of Engineering Nanometrology, 2014
ABSTRACT This chapter presents the field of static length measurement. Some basic optics are intr... more ABSTRACT This chapter presents the field of static length measurement. Some basic optics are introduced to lead up to the field of interferometry – length measurement using light. Different configurations of interferometer are presented including the Michelson, Twyman-Green, Fizeau, Jamin, Mach-Zehnder and Fabry-Pérot. Gauge blocks as length standards are discussed in detail along with gauge block interferometry. The various sources of error in gauge block interferometry are presented and the chapter finishes with some alternative methods for gauge block measurement, such as double-sided interferometry.
An international comparison of surface topography measurement noise was carried out. The comparis... more An international comparison of surface topography measurement noise was carried out. The comparison involved twelve optical surface topography instruments (focus variation instruments, confocal microscopes and coherence scanning interferometers) from six European research laboratories. The purpose of this comparison was to perform a practical test of the ISO definition and procedures for determining measurement noise on a variety of instruments, and to provide good practice guidance to the user community for quantifying, specifying and interpreting measurement noise. Despite taking steps to enable an optimal comparison by supplying a variety of specimens, where the 'best' could be selected and the measurement area was clearly defined, an appropriate comparison of the measurement noise beyond the actual measurement conditions was complex, as the measurement time, speed and lateral resolution were difficult to establish for most of the instruments. The results that could be obtained were: (i) the measurment noise N M can be reliably estimated from two measurements, (ii) noise may vary considerably between instruments, even when they have the same measurement principle, (iii) the noise in a practical measurement may be considerably higher than the noise with a levelled flat, and (iv) the 'rms repeatability' has little correlation to the noise determined according to the ISO specification standard, and may lead to values that are more than a hundred times smaller.
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