Table of contents

The Seventh International Symposium on Measurement Technology and Intelligent Instruments was held on 6–8 September 2005 at the University of Huddersfield, UK.

Although originally held in the People's Republic of China, the popularity and relevance of the Symposium has been such that it has grown into an international event attracting many distinguished participants from around the world. Such is the nature of the Symposium that its programme is allowed to reflect to some degree the particular strengths of the host institute, in this case the Centre for Precision Technologies at Huddersfield University. Although relatively young, the Centre has quickly become a focus in the UK and EU for surface metrology and related subjects under the expert guidance of Professors Jiang and Blunt.

The bulk of the Symposium papers, after peer review, have been published by Institute of Physics Publishing in the Journal of Physics: Conference Series, together with a selected number of posters. However, those papers deemed best to reflect the aims and objectives of the Symposium have been published separately in this special issue of Measurement Science and Technology. Many of the current problems of surface and nanometrology are addressed in this issue. These include the measurement, characterization and instrumentation of the areal (3D) properties of surfaces as well as their standardization, traceability and underpinning mathematics. Also included are some aspects of `free form geometry' and many other related subjects. Traditional sensors and instruments have not been neglected; they ensure the continuity of subjects between this and preceding symposia.

It is hoped that this special issue of Measurement Science and Technology will stimulate more research work in the fascinating and highly relevant subject of Measurement Technology and Intelligent Instruments.

The capability of intelligent sensors to have more intelligence built into them continues to drive their application in areas including automotive, aerospace and defense, industrial, intelligent house and wear, medical and homeland security. In principle it is difficult to overestimate the importance of intelligent (micro) sensors or sensor systems within advanced societies but one characteristic feature is the global market for sensors, which is now about $20 billion annually. Therefore sensors or sensor systems play a dominant role in many fields from the macro sensor in manufacturing industry down to the miniaturized sensor for medical applications. The diversity of sensors precludes a complete description of the state-of-the-art; selected examples will illustrate the current situation. MEMS (microelectromechanical systems) devices are of special interest in the context of micro sensor systems. In past the main requirements of a sensor were in terms of metrological performance. The electrical (or optical) signal produced by the sensor needed to match the measure relatively accurately. Such basic functionality is no longer sufficient. Data processing near the sensor, the extraction of more information than just the direct sensor information by signal analysis, system aspects and multi-sensor information are the new demands. A shifting can be observed away from aiming to design perfect single-function transducers and towards the utilization of system-based sensors as system components. In the ideal case such systems contain sensors, actuators and electronics. They can be realized in monolithic, hybrid or discrete form—which kind is used depends on the application. In this article the state-of-the-art of intelligent sensors or sensor systems is reviewed using selected examples. Future trends are deduced.

It is now fully appreciated that metrology will play an integral role in the successful development and commercialization of micro- and nanotechnology. To this end, the UK Government, through the National Measurement System, funded several groundbreaking projects in its 2002–2005 Programme for Length. This paper will briefly describe the background of the research, concentrating on the technical details of the projects. The Programme for Length normally only funds work into dimensional metrology but this funding cycle also funded work into low force metrology as this area is crucial to most mechanical probing techniques. The projects described include a traceable areal contacting instrument designed to calibrate areal transfer artefacts and hence offer traceability for industrial areal instruments, the production of the areal transfer artefacts, the development of Internet-based softgauges for profile parameters, a primary low force balance with a force resolution of 50 pN and the development of methods for measuring complex micro-scale structures. Amongst others, the projects involved collaboration with PTB, TNO, Taylor Hobson, AWE, Rubert & Co. and the Universities of Warwick, Huddersfield and Eindhoven.

Modern cylinder liner manufacturing processes such as MMC casting, laser honing and laser exposure allow a design of cylinder liner surfaces to meet common development goals like less air pollution and reduced fuel and oil consumption. These goals are reached by aimed insertion of function-relevant structures on the micrometre scale into the surface. Because of these function-relevant structures, the commonly used 2D roughness parameters like Ra and Rz cannot describe the functional behaviour of these surfaces. To describe these surfaces it is necessary to extend the roughness evaluation into the third dimension: z = z(x, y). This paper proposes a 3D roughness evaluation method based on morphological algorithms like the watershed transform to detect and separate the function-relevant structures. Every detected structure is described by a set of structural parameters. Statistical combining of these structural parameters provides a functional characterization of the complete measured surface. The possibilities provided by this flexible method of surface evaluation are shown with a calculation of honing angles.

Some critical aspects of a new kind of on-line measurement technique for micro and nanoscale surface measurements are described. This attempts to use spatial light-wave scanning to replace mechanical stylus scanning, and an optical fibre interferometer to replace optically bulky interferometers for measuring the surfaces. The basic principle is based on measuring the phase shift of a reflected optical signal. Wavelength-division-multiplexing and fibre Bragg grating techniques are used to carry out wavelength-to-field transformation and phase-to-depth detection, allowing a large dynamic measurement ratio (range/resolution) and high signal-to-noise ratio with remote access. In effect the paper consists of two parts: multiplexed fibre interferometry and remote on-machine surface detection sensor (an optical dispersive probe). This paper aims to investigate the metrology properties of a multiplexed fibre interferometer and to verify its feasibility by both theoretical and experimental studies. Two types of optical probes, using a dispersive prism and a blazed grating, respectively, are introduced to realize wavelength-to-spatial scanning.

Ultra-precision freeform surfaces are complex surfaces that possess non-rotational symmetry and are widely used in advanced optics applications. However, there is a lack of a surface characterization method that measures the form accuracy of the ultra-precision freeform surfaces with micrometre to sub-micrometre form accuracy. Due to the high precision requirement of the ultra-precision freeform surfaces, this inevitably involves the outliers in the measured data that would significantly affect the accuracy and the performance of the form characterization method. Although some research work has been found in the development of the form characterization method, most workers have not considered the influence of outliers. It is vital to incorporate robust estimation in the surface characterization method for catering for the influence of outliers. In this paper, a robust form characterization method (RFCM) is presented to characterize the form accuracy of the ultra-precision freeform surfaces. A series of computer simulation and experimental analyses were undertaken to verify the RFCM. The theoretical results agree well with the simulation and experimental results.

This paper presents a nanoindentation instrument for 3D micro/nano-structured surfaces made of soft metals such as LSI circuit patterns. The instrument can carry out indentations with high resolution in both the vertical direction (Z) and lateral directions (XY). An electro-polished tungsten probe with a tip diameter of 100 nm is used as the indenter. The indentation motion along the Z-direction is generated by a PZT actuator. The sample is mounted on the free-end of a steel cantilever. The indentation depth and load can be accurately obtained from the PZT displacement, cantilever spring constant and the cantilever deflection measured by a capacitance-type displacement sensor. Nanoindentation experiments are carried out on an aluminium sample in the vacuum chamber of a scanning electronic microscope. Experimental results demonstrate that the instrument has the ability to perform nanoindentation.

Three optical instruments including an interferometric microscope, a Nipkow disc confocal microscope and a laser scanning confocal microscope and a stylus instrument are used for the measurements of bullet profile signatures of a National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2460 standard bullet. The two-dimensional profile signatures are compared with the virtual bullet standard signature established by the same stylus instrument. The bullet signature differences are quantified by the maximum cross-correlation function CCF_max. If the compared signatures were exactly the same, CCF_max would be 100%. Comparison results show close agreement among the four techniques for bullet profile signature measurements. The average CCF_max values are higher than 90%. This supports the possibility of using surface topography techniques for ballistic identifications as an alternative to the current technology based on image comparisons.

Quality control in the growing field of microsystems technology (MST) demands much higher resolution and accuracy of the testing equipment than conventional products. This is especially challenging in the field of probing. For tactile (i.e., contacting) measurement systems this is equivalent to a demand for miniaturization (in terms of form deviation and size of the contacting element, moving mass, probing force) and hence leads to a top down approach. Another approach is to qualify existing picturing microscopy techniques for three-dimensional measurements such as scanning probe microscopy and various optical microscopy techniques (bottom up approach) emphasizing the improvement of repeatability, linearity and calibration. The challenges and demands of micro systems technology on probing systems and different practical approaches for satisfying them will be presented with their special characteristics, fields and limits of application.

A new type of three-finger micro-tweezers driven by electrostatic force is presented in this paper. The whole system consists of three-finger micro-tweezers and a specially designed high-frequency ac power supply. The three fingers are alternately driven by the power supply with a high-frequency voltage. The direction of the electrostatic forces on the fingers produced by the high-frequency voltage is gyrating between the three fingers quickly, which is equivalent to the invariable forces pointing to the geometrical centre of the micro-tweezers. The tweezers can grasp and manipulate micro objects of size in the range from 30 µm to 100 µm stably.

In this paper, we demonstrate a technique for highly stable atom-tracking control of a scanning tunnelling microscope (STM) tip by referring to an atomic point on a regular crystalline surface. We also demonstrate an atomic encoder using 'atom-by-atom' step control along a crystalline axis. A graphite crystal, whose lattice spacing is approximately 0.25 nm, was utilized as the reference material. To enhance the stability of the atom-tracking control in the presence of external disturbances, a robust controller, consisting of an integrator, a tracer and limiter units, was developed. Experimental results show that the proposed method has high capability for maintaining the atom-tracking control without any jumping of the STM tip to adjoining atoms, even in a noisy environment. This method was also applied to atom-step control of the STM tip by referring to a specific crystalline axis. Atom-stepping control along a crystalline axis over a range of 200 atoms and at a rate of 10 atoms s⁻¹ was performed and demonstrated without missing the atomic array.

Based on silicon on insulator (SOI) technology, a novel high temperature pressure sensor with high frequency response is designed and fabricated, in which a buried silicon dioxide layer in the silicon material is developed by the separation by implantation of oxygen (SIMOX) technology. This layer can isolate leak currents between the top silicon layer for the detecting circuit and body silicon at a temperature of about 200 °C. In addition, the technology of silicon and glass bonding is used to create a package of the sensor without internal strain. A structural model and test data from the sensor are presented. The experimental results showed that this kind of sensor possesses good static performance in a high temperature environment and high frequency dynamic characteristics, which may satisfy the pressure measurement demands of the oil industry, aviation and space, and so on.

A high-precision and low-cost micro-CMM (coordinate measuring machine) is under development. The expected measuring range is 25 × 25 × 10 mm³ and the resolution is 1 nm. In order to enhance the structural accuracy, some new ideas are integrated into the design, such as the arch-shape bridge for better stiffness and thermal accuracy, and the co-planar stage for less Abbe error. The linear diffraction grating interferometer and subdivision technique is proposed for position sensing to nanometre resolution. The focusing probe on the laser interferometer feedback spindle is structured in the Z-axis to guarantee the nanometre stability. In this report, the detailed design principles of the developed micro-CMM are described. The performance evaluation of each module of the prototype micro-CMM is presented. The positioning resolution of each axis to 1 nm can be achieved by combining the coarse and fine motion control on a piezo-ceramic linear motor. The Z-axis measurement can be controlled to within 15 nm repeatability. Parts of the positioning repeatability of the co-planar stage have been achieved to 30 nm. Some problems due to current techniques will be addressed.

Obtaining confidence in a measured value requires a quantitative statement of its quality, which in turn necessitates the evaluation of the uncertainty associated with the value. The basis for the value and the associated uncertainty is traceability of measurement, involving the relationship of relevant quantities to national or international standards through an unbroken chain of measurement comparisons. Each comparison involves calibration of a standard at one level in the chain using a standard at a higher level. Global economy considerations mean that this basis also requires the national measurement institutes to carry out comparative assessment of the degree of equivalence of national standards through their participation in key comparisons. The evaluation of uncertainty of measurement is founded on the use of models of measurement for each stage of the chain and at the highest level to interrelate national standards. Basic aspects of uncertainty evaluation are covered in this paper, and forms for the above types of model considered, with attention given to least squares as a basis for calibration curves (and certain other types of calibration) and also for key comparison data evaluation.

"Geometrical product specifications (GPS)—General Concepts—Part 2: Basic tenets, specifications, operators and uncertainties" (ISO/TS 17450-2:2002) was recently published by ISO TC 213 "Dimensional and geometrical product specifications and verification". This document defines a number of new concepts that provide the underpinnings for a new generation of standards for geometrical product specifications and have the potential of revolutionizing how we think about specification and verification. It enhances the specification language by defining specifications as ordered sets of operations, a much richer language than the simplistic notion of tolerance zones. Additionally, it expands the concept of uncertainty from being something measurement related to being the universal currency for quantifying ambiguity in requirements, specifications and verifications. These new concepts present new opportunities and new challenges both to metrologists and to providers of metrology instrumentation. This paper explores some of these opportunities and challenges.

An approach to establishing rigorous nano- and microdimensional metrology using scanning probe microscopes (SPMs) and metrological profilometers is presented. An overview on calibrations of nanostructures—such as step height, one- and two-dimensional gratings, feature width, nanoroughness and geometry of a nanohardness indenter—and microstructures—such as microgroove, microroughness and geometry of a macrohardness indenter—is given in this paper.

Standard least squares algorithms for finding the best-fit geometric surface to coordinate data implicitly assume that the uncertainties associated with the coordinates are uncorrelated and axis-isotropic, i.e., the uncertainties associated with the x-, y- and z-coordinates are equal (but can vary from point to point). Very few coordinate measuring systems have such uncertainty characteristics but, in the absence of quantitative information about the true uncertainty structure, these assumptions can be justified. However, more effort is now being applied to evaluate the uncertainties associated with coordinate measuring systems and the question arises of how best to use this extra information, for example in surface fitting. This paper describes algorithms for fitting geometric surfaces to coordinate data with general uncertainty structure and shows how these algorithms can be implemented efficiently for a class of uncertainty matrices that arise in many practical systems. The fitting algorithms are illustrated on data simulating laser tracker and coordinate measuring machine measurements.

The paper uses the surface texture parameter RSm as a case study to examine the concepts of unambiguous definitions of measurands and the stability of these definitions. The paper begins by reviewing the current ISO definition of RSm, illustrating the ambiguities and lack of stability in the current ISO definition. The representational theory of measurement, which is the current dominant paradigm for measurement, will be briefly discussed. The representational theory of measurement will be used as a framework to incorporate a generic definition of stable measurand definitions. Here a measurand is considered mathematically stable if a 'small' difference in the value of a measurand implies a 'small' difference in the property it purports to characterize. This is a completely general and very powerful result. A new stable and unambiguous definition of RSm will be presented which uses these results.

This paper presents a NURBS (non-uniform rational B-splines) curves based stereo matching algorithm for which curves replace the edges extracted with a wavelet-based method. Curves in the left images are projected onto the right view and the stereo correspondence problem becomes simply the estimation of the similarity between these projections and the original curves in the right image. The projective invariance characteristic of NURBS curves is effective in reducing false matches due to distortion of the perspective projection and image noise. Experimental results demonstrate that the proposed method is robust and effective in removing abnormal reconstruction data. The obtained 3D reconstruction shape is closer to the real one.

By detecting pressure and flux simultaneously, the leak of an oil-transporting pipe can be found and diagnosed synthetically. The flux of pipes is measured by an ultrasonic flow meter; considering the precision of the flux measured, a method based on the character of intermittent chaos of the Duffing system to detect weak signals under strong noise is introduced. The ultrasonic signals with a certain frequency could be extracted accurately from the complicated strong noise. So the flux of pipes can be computed precisely by an accurate ultrasonic signal. The location of a leak position is mainly determined by the time difference between the negative pressure waves measured by the pressure sensors located at both ends of the oil-transporting pipe. A singular point of a negative pressure wave can be judged accurately by a coefficient feature of the local extreme values of the wavelet transform. So, the precise location of the leak position of the oil-transporting pipe can be found. It can be shown by results of experiments that the precision of the leak location has been improved effectively, which can be about 1%.

Specialized sensing and measurement instruments are under development to aid the controlled culture of cells in bioreactors for the fabrication of biological tissues. Precisely defined physical and chemical conditions are needed for the correct culture of the many cell-tissue types now being studied, including chondrocytes (cartilage), vascular endothelial cells and smooth muscle cells (blood vessels), fibroblasts, hepatocytes (liver) and receptor neurones. Cell and tissue culture processes are dynamic and therefore, optimal control requires monitoring of the key process variables. Chemical and physical sensing is approached in this paper with the aim of enabling automatic optimal control, based on classical cell growth models, to be achieved. Non-invasive sensing is performed via the bioreactor wall, invasive sensing with probes placed inside the cell culture chamber and indirect monitoring using analysis within a shunt or a sampling chamber. Electroanalytical and photonics-based systems are described. Chemical sensing for gases, ions, metabolites, certain hormones and proteins, is under development. Spectroscopic analysis of the culture medium is used for measurement of glucose and for proteins that are markers of cell biosynthetic behaviour. Optical interrogation of cells and tissues is also investigated for structural analysis based on scatter.

Provisional resin materials are widely used in prosthetic dentistry and play an important role in the success of restorative treatment. Therefore, these materials must meet the requirements of preserving surface integrity during the treatment process. This study was done to evaluate surface roughness and microhardness of two provisional resin materials after 37 °C water storage. Two rectangular samples 21 mm × 11 mm × 3 mm, one bis-acrylic (bis-acrylic-Protemp II) and one polyethyl methacrylate (Trim®-PEMA) were fabricated as examples of provisional materials (n = 5 per material). The specimens were stored in 37 °C deionized distilled water for 24 h, 1, 2 and 3 weeks. The control specimens were not stored in water. The surface roughness of the tested materials (n = 10) was measured using a profilometer. Microhardness tests were conducted using a Vickers microscope mounted indenter system (n = 10). At 24 h, the surface roughness was recorded with bis-acrylic-Protemp II as higher than methacrylate materials. No significant differences of microhardness between Trim®-PEMA and bis-acrylic-Protemp II were recognized at 1, 2 and 3 weeks. The microhardness values increased with the increase of surface roughness and vice versa in both Trim®-PEMA and bis-acrylic-Protemp II. Both surface roughness and microhardness are affected by water storage. Bis-acrylic-Protemp II revealed better results in hardness than methacrylate resins, whereas Trim®-PEMA has a better surface roughness.

The metrological characterization of a Fresnel method for measuring the dimensions of objects is investigated. In this method, free space, as an optical element, transforms the input image of the inspected object into its Fresnel image with great accuracy. The major sources of systematic measurement error are estimated analytically including non-uniform illumination of the object, the interference effect of the edge images of the diffracting object, the integration properties of the linear multi-element photodetector, the influence of the extended size of a partially coherent light source and the volumetric properties of a 3D object. It is proposed that algorithms are used to account for any error components; effective algorithms for this are proposed.

Step height and line-width are two key parameters in the metrology of micro-electronic masks. A novel common-path heterodyne interferometric confocal measuring system is presented to measure the step height of masks. It combines both the methods of heterodyne interferometry and confocal microscopy. The resolution is 0.01 nm and the measurement range is around 8 µm. The procedure is direct by the integration of the measurement of intensity and phase, hereby faster than a normal scanning microscope. For the line-width measurement of masks, a polarization heterodyne interferometric confocal microscope is proposed, which combines a polarization interferometer with a confocal microscope. An ideal beam spot is obtained and precise focus is realized by using the confocal technique. The phase shifts of the two orthogonal polarization beams differ from each other when they are reflected at the edge of a sample. The experimental results show that the uncertainty of line-width measurement is 21 nm. Both of the systems satisfy the common-path principle, so as to get high ability of resistance to environment disturbances.

A 3D coherent imaging formula is established for the array confocal microscope system (ACMS) using Kirchhoff's diffraction optic theory to give a high-precision quantitative description of the array confocal imaging process, and then the design of a three-zone amplitude pupil filter is optimized using a 3D super-resolution function derived from the formula established, and consequently, the resolution of ACMS is improved by compressing both transverse and axial half width at half minimax of a detection light path.