Han Haitjema

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Verified

Han verified their affiliation via an institutional email.

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• Prof. dr.
• Emeritus Professor with formal duties at KU Leuven

Fringe projection systems are well established as metrology tools for fast measurements of (large) workpieces. However, as specular surface reflectivity causes camera saturation, the accuracy of fringe projection for (semi-)reflective parts is limited. The use of polarization filters can reduce the effect of this specular reflectivity, but lowers t...

Optical metrology is a driving force in advancing industries ranging from consumer electronics to components for energy and transportation. Despite this progress, there is considerable wasted effort attributable to misleading instrument specifications, inconsistent calibrations, and ambiguous data processing procedures. Confusing statements of accu...

The efficient computation of viewpoints for solving vision tasks comprising multi-features (regions of interest) represents a common challenge that any robot vision system (RVS) using range sensors faces. The characterization of valid and robust viewpoints is even more complex within real applications that require the consideration of various syste...

Keynote Presentation

Determining the roughness of additive manufacturing objects is widely acknowledged as a complex task. This paper therefore presents a practical application of discrete Legendre polynomials in extracting geometrical measurements from Laser sintered material using X-Ray Computed Tomography (XCT). X-Ray Computed Tomography (XCT) is first utilized to e...

Our journal ‘Metrology’ has been up and running for a few years now, with interesting and ground-breaking publications covering the wide field that the concept of ‘metrology’ encompasses. Now, the time has come to contemplate and look back to the publications and consider whether the subjects listed in the scope are still appropriate and up-to-date...

This chapter gives an overview of most commonly used instruments in dimensional metrology

Additive manufactured surfaces, especially metal powder bed fusion surfaces, present unique challenges for measurement because of their complex topographies. To address these measurement challenges, optimisation of the measurement process is required. Using a statistical approach, sensitivity analyses were performed on measurement settings found on...

On-machine optical measurement receives growing attention as a viable quality assurance technique to satisfy the increasingly critical requirements for dimensional accuracy and surface finish upon precision components. It preserves the temporal and spatial consistency between manufacturing and measurement activities, allowing for a substantial prod...

Measurement and instrument noise as proposed in ISO 25178-600 and defined in ISO 25178-700 are assumed to be both stationary and randomly distributed. This paper presents the temporal and lateral Allan deviation as useful tools for deeper noise analysis in surface topography measurements. The temporal Allan deviation may be used to identify and qua...

In the standardized processing of surface topography data, the form removal and filtering operations are clearly separated. This is reflected in the current ISO standards concerning profile surface texture and areal surface texture, the ISO 21920 and the ISO 25178 series respectively. When the scale-limited surface texture is significant compared t...

In order to develop smart laser powder bed fusion (LPBF) devices that autonomously identify a defect and remove it during the process for first-time-right and zero-defect parts, it is important to develop reliable on-machine defect measuring capabilities. As defects in LPBF parts often occur below the layer that is being processed, capturing the in...

The framework of the Geometrical Product Specification defines the nominal geometry of the components and the characteristic tolerances. Various ISO standards describe the nine defined geometrical properties per characteristic of a workpiece. To prove conformance to the task specific tolerances according ISO 14253–1, the uncertainty budget needs to...

This study proposes an algorithm to autonomously generate the scan path for a laser line scanner mounted on a coordinate measuring machine. The scan path is determined based on task-specific measurement uncertainty in order to prove conformance to specified tolerances. The novelty of the algorithm is the integration of measurement uncertainty. This...

To compensate for the straightness error of the slide of a machine tool efficiently and precisely, on-machine self-calibrating measurement of the manufacturing error is critical. The Fourier 3-sensor (F3S) method proposed by Fung is promising in measuring the straightness profile of a workpiece accurately on a machine. However, it still suffers fro...

In-situ monitoring and post-process metrology form a basis to better understand the fundamental physics involved in the Laser Powder Bed Fusion (LPBF) process and ultimately to determine its stability. By utilizing high-speed imaging, various process signatures are produced during single track formation of 316L stainless steel with various combinat...

The presentation describes the background of the standards in the ISO 25178 series and gives their current status and issues it does and does not solve.

This paper takes the broad topic of geometrical surface imperfections on manufactured surfaces and provides an overview of how they affect component functionality and how they may be detected and classified as defects or not. The presented overview considers both human visual inspection and machine vision-based approaches along with their evolving...

In the standardized processing of surface topography data the form-and filter operations are clearly separated. This is reflected in the present ISO standards about profile surface texture and areal surface texture, the ISO 21920 and the ISO 25178 series respectively. When the scale-limited surface texture is significant when compared to the form t...

A metrological characteristic common to all methods for areal surface topography measurement is the topographic spatial resolution (TSR), defined as the ability to distinguish closely-spaced surface features. This ability is limited in mechanical stylus instruments by the stylus tip geometry, while for instruments that rely on optical imaging, infl...

An international comparison of surface topography flatness deviation 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 results demonstrated the following: (i) The flatness varie...

1. Spindle error measurement Ultra-precision spindles have played critical roles in various electro-mechanical systems, such as machining tools, roundness testers, hard drive disks, gyroscope, etc. In these machines, the spindles have error motions of only hundreds or tens of nanometers. To develop such precision spindles and be capable of further...

On-machine surface measurement of micro-scale components after micromachining becomes crucial to satisfy the increasing quality requirements. It implements a seamless measurement activity without interrupting manufacturing actions and hence facilitates the closed-loop quality control inline. Chromatic confocal probe sensing is a promising technique...

Robot CT systems bring great flexibility to X-ray CT based inspection scans. The system geometry needs to be well calibrated in order to avoid serious artifacts in the reconstructed volume. However, conventional calibration methods are normally designed for circular paths, which may be insufficient for a robot CT system. This paper proposes a phant...

Determination of the stylus tip radius and its wear or damage is a classical problem in tactile surface topography measurements. The determination of the stylus geometry may be tedious and inconvenient, therefore we looked for an easily applicable method. This study shows that the Rsk parameter and the difference between the Rv and Rp parameter may...

X-ray computed tomography (X-CT) plays an important role in non-destructive quality inspection and process evaluation in metal additive manufacturing, as several types of defects such as keyhole and lack of fusion pores can be observed in these 3D images as local changes in material density. Segmentation of these defects often relies on threshold m...

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...

It is with sincere pleasure that we welcome you to the inaugural issue of Metrology [...]

Monocrystalline silicon is currently one of the most used materials in the semiconductor industry. However, being hard and brittle, a silicon wafer commonly suffers from machining-induced subsurface damage (SSD). Detecting SSD is important for optimizing the machining process in order to improve the surface integrity of a machined wafer. Among the...

Additive manufacturing techniques such as laser powder bed fusion (LPBF) enable production of components with highly complex geometries. However, their as-built surface quality and geometrical precision remain insufficient for high-end applications, requiring further post-processing. Unlike horizontal surfaces, inclined up-facing surfaces cannot be...

Additive manufactured surfaces, specifically metal powder bed fusion (PBF) surfaces, present unique challenges for measurement due to their complex topographic nature [1]. One of the challenges is to properly separate local surface texture from the form deviations of the specimen. Especially since AM enables manufacturing of intricate forms, it ma...

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...

Considerable surface texture is one of the typical drawbacks of laser powder bed fusion (LPBF). Especially up-facing inclined surfaces suffer from insufficient quality, due to the combination of the staircase effect (also called stair-stepping effect), attached powder particles and elevated edges (edge effect). In this work, the contribution of the...

A surface filtering method based on Legendre polynomials is proposed that can be used to separate form and roughness of surface profiles and areal topographies. The filter has been designed in such a way that it well approaches the properties of a Gaussian filter, especially in the center of the measured region. Theoretical profiles and measurement...

The three-probe method for separating the spindle rotation error and the specimen form error is extensively described in the literature. An attractive feature is its application in in-process measurement. However, the resulting uncertainty is studied far less extensively. In this paper, an evaluation and propagation method for the uncertainty, as w...

This paper presents an algorithm to compensate the systematic error of lasers line scanned data based on the measurement error model of the measurement system. The iterative process of the algorithm is used to determine geometrical features accurately, solely making use of an optical measurement device. The systematic error on the task–specific mea...

In this paper, we will review the development and use of an ISO standardised framework to allow calibration of surface topography measuring instruments. We will draw on previous work to present the state of the art in the field in terms of employed methods for calibration and uncertainty estimation based on a fixed set of metrological characteristi...

Surface topography measurements are vital in industrial quality control. Linear roughness measurements are among the most preferred methods, being quick to perform and easy to interpret. The ISO 16610 standard series prescribes filters that can be used for most cases, but has limitations for restricted measurement lengths. This is because the stand...

Recorded presentation for ASPE Annual Meeting 2020 to support the paper "Comparison of optical and contact surface topography measurement, including uncertainty"

Structuring of mould surfaces is a topic of high interest for both industry and academia. The engineering of mould surface can enable improved functionality and performance. For instance, structured surfaces have been reported to exhibit reduced melt flow resistance, reduced interfacial friction, and better filling of the mould cavity thereby enabl...

Optical measurement and characterization are two of the pillars of metrology. The ability to measure precisely with high dynamic range and accuracy betters our understanding of nature and the universe. In this feature issue, we present a collection of articles that delves into the fundamental techniques used to advance the field.

This paper presents an unambiguous method to obtain the measurement error model of a laser line scanner, comprising both the systematic error and the random error of a measurement with this type of optical probing system. A ring gauge is used as artefact for the acquisition of the data required for determining the measurement error model. The model...

The typical surface topography of parts produced by additive manufacturing differs from those produced by conventional manufacturing. During the powder bed fusion process, spatter particles may eject from the melt pool due to multi-physics phenomena. These spatter particles can have an impact on the part quality as large spatter particles that land...

Surface roughness amplitude parameters tend to be biased towards positive deviations due to the presence of noise in the measurement. This is due to the nature of the roughness parameters themselves, e.g. Sq is essentially the standard deviation of the measurement. Generally this effect is counteracted by averaging the measurement before calculatin...

The typical surface topography of parts produced by additive manufacturing differs from those produced by conventional manufacturing. During the powder bed fusion process, spatter particles may eject from the melt pool due to multi-physics phenomena. These spatter particles can have an impact on the part quality as large spatter particles that land...

Hybrid laser-electrochemical micromachining process involves the simultaneous application of electrochemical machining and laser source in the same machining zone. With this process, a hierarchical cavity structure is observed where the central region is dominantly exposed to laser-ECM interaction and the region towards the edge is mainly exposed t...

This study proposes a polarized laser scattering (PLS) method for detection of the two-dimensional distribution of the grinding-induced subsurface damage (SSD). This study also uses two destructive methods to observe the distribution of SSD in the ground silicon wafers by cross-sectional microscopy and by layer-by-layer microscopy. An experimental...

In dimensional metrology the straightness, flatness or cylindricity of surfaces is commonly measured at a limited number of equidistant points on the surface. This paper describes some opportunities and characteristics of discrete Legendre polynomials to describe and analyze such measurements. The reference surface can be adequately described using...

Multiscale analyses of surfaces are the examination of topographic or tomographic surface coordinates, measured or simulated, over a range that includes several scales.

Displacement measuring sensors play an essential role in all aspects of dimensional metrology. They can be used for direct displacement measurements but more often they are part of a measurement system, such as an atomic force microscope, roughness tester or a coordinate measuring machine (CMM). In order to achieve traceable measurements that can b...

Laser scanner for external diameter measurements are well known: a parallel laser beam scans along a diameter and the diameter is derived from the time interval where there is no signal. If the object is a hollow tube, extra signals are transmitted by internal reflections in the tube. This patent describes how these signals can be used to derive th...

Displacement laser interferometer systems are widely used for the calibration of machine tools and CMMs (Coordinate Measuring Machines). Additionally, they are often the workhorse in dimensional calibration laboratories, where they act as the basic metrological traceability link for many calibrations. This paper gives a review of the calibration of...

Laser powder bed fusion (LPBF) enables producing very complex geometries compared to conventional subtractive manufacturing techniques. However, the geometrical accuracy of LPBF surfaces remains limited and is often insufficient for applications in high-end sectors such as mould making, medical or aircraft industry. The most common imperfections fo...

The talk covered the following: •Review of error separation for absolute flatness •Gradient measurements – extension to small scale •Averaging method for absolute flatness: method, limitations – possibilities for extension using big data and maybe AI •Noise effects, measurement; limitation when ‘aligning’ a reference in contrast to a bit tilting •C...

On-machine and in-process surface metrology are important for quality control in manufacturing of precision surfaces. The definitions, requirements and tasks of on-machine and in-process surface metrology are addressed. The state-of-the-art on-machine and in-process measurement systems and sensor technologies are presented. Error separation algorit...

Many modern products require surfaces with highly complex surface topographies, often involving high slope angles, a mix of random and deterministic texture and freeform underlying geometries (see Fig. 1). In this presentation, we will show a range of recent developments that allow such complex features to be measured and highlight some remaining i...

Textures are abundantly exploited in nature for securing superior functionalities including adhesion, color manipulation, anti-reflection, and drag management. Over millions of years, these advanced properties are endowed to various organisms on the planet to survive and adapt in harsh environmental conditions. Texture characteristics such as featu...

In precision engineering, the demands for close tolerances and accurate dimensions on workpieces are challenging to manufacture but critical for reliable function when assembled into a mechanical system. These dimensions have to be confirmed by measurement, and such measurements always include disturbances that cause the measurement results to devi...

In this chapter the principles of displacement metrology by optical incremental sensors are given. First the basic concepts of displacement interferometer systems as well as their signal processing and error sources are reviewed. Then the concepts of optical encoder systems and some of their design considerations are discussed.

Dimensional metrology is one of the cornerstones of mechanical engineering and is key to manufacturing. Dimensions have to be confirmed by measurement, and such measurements allow tolerances and uncertainties to be calculated. Following on from the metrology basics covered in Chapter 2, this chapter will present the multitude of instruments and tec...

The present invention provides an interference measuring device with an optical system that can receive light reflected from a measurement object of a surface profile that is not perpendicular to an optical axis. An interference measuring device includes a light source for emitting light and an interferometric objective lens. The interferometric ob...

In 2015, an online community of scientists and mathematicians got together to share a love of equations, and, every day that year, a beautiful equation appeared on Facebook. The page has since attracted almost 6000 "likes", showing that lots of other people love equations as much as we do. What do we mean by "beautiful" in the context of equations?...

see patent

Synonyms: Roughness, Surface roughness Definition : Dimensional irregularity of a surface, its deviations from a mathematical flat

Synonyms : Deviation from flatness; Flatness deviation; Planeness Definition: The minimum distance separating two parallel planes between which the surface can be contained.

An international comparison of optical instruments measuring polymer surfaces with arithmetic mean height values in the sub-micrometre range has been carried out. The comparison involved sixteen optical surface texture instruments (focus variation instruments, confocal microscopes and coherent scanning interferometers) from thirteen research labora...

Synonyms: Roughness parameter Definition : Parameter, defined as a number and a unit, that characterizes an averaged dimensional property of a surface.

Synonym: Surface roughness Definition: Dimensional irregularity of a surface, its deviations from a mathematical flat.

Synonyms: Uncertainty of measurement Definition: A nonnegative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used (Source: JCGM 200:2008 2008 (VIM)).

Definition: Collective name for a number of techniques dealing with the measurement and interpretation of the change in the polarization state of a polarized beam of radiation which is reflected from a surface. From this change, optical properties of the reflecting surface can be derived.

The 2.5-dimensional (2.5D) roughness parameters were standardized in 2012. With their increasing use in science and industry, the request for traceability and uncertainty evaluation for these parameters follows logically. This paper gives an overview of the problems and possibilities that appear when uncertainties have to be associated with values...

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 di...

Precision positioning of an object relative to a reference point is a common task in many activities of production engineering. Sensor technologies for single axis measurement, either linear or rotary, which form the fundamentals of measurement technologies for precision positioning, are reviewed. Multi-axis coordinate measurement methods such as t...

Roundness measuring instruments exhibit roundness deviation of the spindle in the 20-30 nm range, and are specified as such. This requires test methods that deliver uncertainties within this range. In order to be feasible such a method must be carried out with a limited amount of measurements within a limited time. In this paper an analysis of the...

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 deri...

Solar cells gained significant interest recently due to the rapid increase in fossil fuel costs and renewed attention to sustainability. The effectiveness of a solar cell in energy harvesting hinges on three key characteristics: efficiency of energy conversion, reliability and life expectancy, and cost. All three attributes are critically influence...

PROBLEM TO BE SOLVED: To improve an interferometer system for generating an interference signal of a sample surface.SOLUTION: An interferometer system for generating an interference signal of a sample surface includes: a broadband illuminator for supplying a broadband illumination beam; a beam splitter for dividing the broadband illumination beam i...

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 d...

Method of determining a property of a sample from a correlogram obtainable by scanning of a surface of the sample through a focal plane of an objective using broad-band interferometry is provided. The correlogram may be displaying interference radiation intensity as a function of the scanning distance from the surface. The correlogram may be correl...