Exemplified by a stitching procedure that is frequently applied in optical surface metrology and that is based on the maximization of the cross-correlation function, the article shows the dependency of the accuracy of a stitching result on many different interdependent influence factors. Furthermore it is shown that the remaining deviations of the regions that are regarded to be the overlapping ones is no generally valid indication for the accuracy of a stitching result. Thus, in the second part of the article, a method to determine the uncertainty of a stitching result based on a Monte Carlo simulation is presented. The input quantities of the stitching procedure, namely the topographic data of the sub-apertures and the position and orientation data of the positioning system are characterized by a probability density function. Afterwards, it is sampled randomly from these probability density functions and the stitching procedure is applied many times. From the obtained distributions, the result of the stitching procedure along with its uncertainty is derived. The obtained results show metrological compatibility to the true values and furthermore enable the recognition of the cases for which the stitching did not improve but impair the accuracy compared to the accuracy of the positioning system.
For providing holistic and complete dataset of sheet bulk metal-formed parts, an optical detection with a fringe projection system is useful. By combining several sensors with varying measuring ranges, the workpiece is captured with adapted spatial resolution depending on the forming zone and geometric requirements. The sensors are registered by a two-dimensional point calibration and registration process. The registration process has already been shown in.1 In this article, the calibration procedure is transferred to the measurement setup with three fringe projection sensors with different measurement resolution. A calibration plate with dot patterns is applied to the positioning unit, which is a high precision hexapod in this set-up. This extended calibration plate allows a continuous control of the registration quality as the sensors are able to capture the calibration plate at any time. For determining the positioning accuracy of the hexapod, a procedure following the DIN EN ISO 10360-3 procedure with three spheres mounted on the hexapod was investigated. Therefore the hexapod was fixed at a coordinate measuring machine Zeiss UPMC 1200 and moved in all 6 degrees of freedom. After each movement, the spheres were measured with a probe, which allows the absolute position precision to be calculated. Comparison of the measurements with the specified translation and rotation movement of the hexapod show a positioning precision of less than 10 µm in the positioning directions x and y.
This article presents the evaluation of the optical performance of a new high-frequency focal-distance-modulated confocal point sensor. While maintaining the known advantages of the confocal measurement principle, the sen- sor represents an innovative combination of a fibre-coupled confocal illumination and detection with a tuneable, acoustically driven gradient-index fluid lens (TAG lens) for the modulation of the focus distance and a novel signal processing utilizing a lock-in amplifier. The new arrangement is able to achieve an approximately linear characteristic curve for the optimised feedback control of nano coordinate measuring systems (CMS) in scanning sample mode. This article emphasises the implementation and use of the sensor in nano CMS (NMM-1) and the advantages of the new signal processing. Measurements on different resolution standards are conducted and compared with the focal-distance-modulated sensor and without focus-distance-modulation as conventional confocal microscope (CCM).
For the requirements of newly developed production processes like sheet bulk metal forming a previously developed measuring method exists for dimensional measurement of these manufactured parts. The presented multi-sensor approach allows the combination of several fringe projection sensors with different measurement resolutions and ranges to meet the requirements of the new production technology. The measurement setup includes a high precision hexapod to position the investigated workpiece inside the measuring volume. The measurement devices utilized are high precision fringe projection systems with 17 µm lateral and 1 µm vertical resolution. An additional overview sensor captures the whole measurement range of the hexapod. This paper presents two approaches that can be used for camera calibration and sensor registration of the fringe projection systems in a global coordinate system. A speckle pattern and a random dot pattern are placed on the hexapod to calculate the intrinsic parameters of the sensor camera and extrinsic parameters of the fringe sensor in one single step. To obtain metric lengths with the calibration process, a defined scale is included additionally on the pattern. The calibration process is executed by an automatic and random movement of the hexapod in the recording area of the sensors. Measurements show a direct transferability from the camera to the sensor coordinate system. This allows the measurement datasets to be directly merged together without the use of a separate registration routine.
Due to recent developments in sheet-bulk metal forming processes, holistic measuring systems are required which provide reliable results for the measurement of all relevant formed part features. The presented multi scale multisensor approach, which combines several fringe projection sensors of different measuring resolutions and ranges, accomplishes the requirements of the new production technology. Calibration of the single measurement systems to a global coordinate system is realized with a specially developed calibration object. A high-precision hexapod positions the calibration object and the workpiece within the measuring range. The result is a holistic dimensional measurement for characteristics whose size exceeds the measuring range of a single sensor. It is also shown that the distance of the measurement sensor to the suface of the measurement object is relevant for the uncertainty of the obtained point cloud. By positioning the workpiece in the focus of camera of the fringe projection system, the standard deviation of the measured point cloud can be significantly reduced.
The nanopositioning and nanomeasuring machines NMM-1 and NPMM-200 were developed at the Technische Universät Ilmenau. These machines realise the Abbe comparator principle and the Bryan principle in all three axes to achieve nanometre accuracy. The length measurements are carried out with fibre-coupled laser interferometers. The length and angle values are used together with the probe system signals for ultra-precision position control during surface and coordinate measurements. This paper presents the metrological concepts, the implemented designs as well as specific aspects of the interferometric measuring systems and the measurement uncertainty estimation.
Due to the development and progress in micro- and nanotechnology the range of measuring tasks is becoming ever more
varied and multifaceted. Decreasing structure widths in combination with large area measurements or complex 3D-micro-
and nanostructures with high aspect ratios not only on flat but also on curved surfaces are some of these
measurement challenges. In order to solve the problems arising within this application spectrum a multi-sensor platform
based on a laser focus probe was developed. This platform is integrated in the Nanopositioning and Nanomeasuring
Machine developed mainly at the Institute of Process Measurement and Sensor Technology at the Ilmenau University of
Technology with a measuring range of 25 mm x 25 mm x 5 mm and subnanometre resolution.
The paper focuses on the utilization of nanopositioning and nanomeasuring machines as a three dimensional coordinate
measuring machine by means of the international harmonized communication protocol Inspection plus plus for
Dimensional Measurement Equipment (abbreviated I++DME). I++DME was designed 1999 to enable the
interoperability of different measuring hardware, like coordinate measuring machines, form tester, camshaft or
crankshaft measuring machines, with a priori unknown third party controlling and analyzing software.
Our recent work was focused on the implementation of a modular, standard conform command interpreter server for the
Inspection plus plus protocol. This communication protocol enables the application of I++DME compliant graphical
controlling software, which is easy to operate and less error prone than the currently used textural programming via
MathWorks MATLab.
The function and architecture of the I++DME command interpreter is discussed and the principle of operation is
demonstrated by means of an example controlling a nanopositioning and nanomeasuring machine with Hexagon
Metrology's controlling and analyzing software QUINDOS 7 via the I++DME command interpreter server.
Dimensional measurements of microstructures with uncertainties below 50nm require both nanopositioning and
nanomeasuring machines (NPMMs) as well as appropriate microprobes. This paper introduces a novel 3-D tactile
microprobe system developed at the Ilmenau University of Technology, Institute of Process Measurement and
Sensor Technology, and contains an analysis of its metrological characteristics.
This microprobe system uses a silicon membrane to induce the measurement force and to operate as the
damping system for the stylus. This damping is entirely brought about by internal friction. An optical detection
system measures the deflection of the membrane and thus of the stylus. The optical detection system uses a
single laser beam, focused on the backside of the silicon membrane. The reflected beam is split, with one part
being used to measure the tilt about the x- and y-axes and the other part being fed back into an interferometer
for deflection measurement in the z-direction. Thus, the deflection of the membrane can be measured with
sub-nanometre resolution.
An NPMM was used to analyse the metrological characteristics of the microprobe system and to calibrate
it. This paper focuses on a detailed analysis of the three-dimensional reproducibility for point measurements
by obtaining and evaluating a directional response pattern. This pattern is then compared to the behaviour of
other microprobe systems. Furthermore, the work shows that the microprobe system can be applied successfully
to scanning measurements and satisfactory results obtained. These results indicate that the microprobe system
is well-suited for universal measurement tasks in dimensional metrology.
This paper presents measurements of calibrated step height and pitch standards using a homodyne interferometer-based
metrological scanning probe microscope (SPM) and a nanopositioning and nanomeasuring machine (NPM machine).
These devices were developed at the Institute of Process Measurement and Sensor Technology of the Technische
Universität Ilmenau. Together these devices are capable of highly exact dimensional and traceable long-range
positioning and measurement with a resolution of 0.1 nm over the positioning and measurement range of
25 mm × 25 mm × 5 mm.
Measurements of different calibrated step height and pitch standards were completed in order to test the
repeatability and accuracy of the metrological SPM. The deviations between the calibrated and measured values were
smaller than the uncertainty values determined by the Physikalisch-Technische Bundesanstalt (PTB) calibration. The
extended uncertainty of the measurement results (step height or mean pitch value) was less than 1 nm.
Precision mechatronics is defined in the paper as the science and engineering of a new generation of high precision systems and machines. Nanomeasuring and nanopositioning engineering represents important fields of precision mechatronics. The nanometrology is described as the today's limit of the precision engineering. The problem, how to design nanopositioning machines with uncertainties as small as possible will be discussed. The integration of several optical and tactile nanoprobes makes the 3D-nanopositioning machine suitable for various tasks, such as long range scanning probe microscopy, mask and wafer inspection, nanotribology, nanoindentation, free form surface measurement as well as measurement of microoptics, precision molds, microgears, ring gauges and small holes.
The paper describes traceable nanometrology based on a nanopositioning machine with integrated nanoprobes. The operation of a high-precision long range three-dimensional nanopositioning and nanomeasuring machine (NPM-Machine) having a resolution of 0,1 nm over the positioning and measuring range of 25 mm x 25 mm x 5 mm is explained. An Abbe offset-free design of three miniature plan mirror interferometers and applying a new concept for compensating systematic errors resulting from mechanical guide systems provide very small uncertainties of measurement. The NPM-Machine has been developed by the Institute of Process Measurement and Sensor Technology of the Technische Universitaet Ilmenau and manufactured by the SIOS Messtechnik GmbH Ilmenau. The machines are operating successfully in several German and foreign research institutes including the Physikalisch-Technische Bundesanstalt (PTB), Germany. The integration of several, optical and tactile probe systems and nanotools makes the NPM-Machine suitable for various tasks, such as large-area scanning probe microscopy, mask and wafer inspection, nanostructuring, biotechnology and genetic engineering as well as measuring mechanical precision workpieces, precision treatment and for engineering new material. Various developed probe systems have been integrated into the NPM-Machine. The measurement results of a focus sensor, metrological AFM, white light sensor, tactile stylus probe and of a 3D-micro-touch-probe are presented. Single beam-, double beam- and triple beam interferometers built in the NPM-Machine for six degrees of freedom measurements are described.
Many scanning probe microscopes (SPMs) are used as image acquisition tools in such industries as microelectronics, micromechanics, lithography and biotechnology. Conventional SPMs use piezoelectric actuators in order to move either the sample or the probe. The voltage across the piezos is taken as a position indicator. However, it is known that piezos suffer from hysteresis, and from time- and temperature-dependent creep. A solution to this problem is provided by accurate, traceable measurement of the cantilever position. An exact dimensional measurement can only take place via direct comparison with a well-known reference. The traceability of the SPM can be achieved using an interferometer, traceable to the 633 nm wavelength of the He-Ne laser. For accurate measurements the position of the cantilever must be measured in addition to the torsion and bending.
This article shows the basic SPM principle as well as the addition of a cantilever position detection system. This system has been realized with a special interferometer with a quadrant diode to detect the cantilever torsion and bending. The measuring beam is focused on the cantilever backside using a lens. The reflected laser beam is split and evaluated; one part of the beam is used for the interferometrical position measurement with the other part focused onto a quadrant diode. Due to the structure of the interferometrical SPM, it can be installed in many different positioning systems with large measuring ranges, including a nanopositioning and nanomeasuring machine (NPM machine), developed at the Institute of Process Measurement and Sensor Technology of the Technische Universitaet Ilmenau.
A new traceable method has been developed and investigated to experimentally determine the total amount of measuring deviations arising through the capture and demodulation of plane-mirror interferometer signals. The basic principle for such an analysis is the precise specification of length variations. However, either a measuring system of excellent accuracy or accurately defined movements within a stable platform are required. A common measuring motion can be achieved through the displacement of a reflecting wedge plate, which creates a constant step-down. The interferometer to be analyzed is used to determine the change in the wedge plate's thickness, which is caused by lateral movements controlled by another interferometer. The wedge's sampled surfaces demand high planarity as the change of thickness acts as the material measure. These conditions can be achieved by using the Nanopositioning and Nanomeasuring Machine in conjunction with a 0.5-degree tilted mirror placed on it. The interferometer to be analyzed is aligned with this mirror. To provide the highest possible linearity for lateral motion, the only measuring points are in nearly error-free lambda/2 steps of the interferometer. The NPM machine's already small deviations in positioning will only affect the evaluation of measuring errors of the reduced interferometer by a factor of about one-hundredth. This is one of the main advantages of the method. The interferometer to be analyzed - like the entire measuring setup - features a compact assembly and high mechanical and thermal stability. The measured deviations in linearity provide excellent verification of the prospected error influences.
Today's technological progress calls for metrologically accurate object measurement, positioning and scanning with nanometre precision and over large measuring ranges. In order to meet that requirement a nanopositioning and nanomeasuring machine (NPM machine) was developed at the Institute of Process Measurement and Sensor Technology of the Technische Universitaet Ilmenau. This device is capable of highly exact long-range positioning and measurement of objects with a resolution of less than 0.1 nm. Due to the structure of the machine many different probe systems can be
installed, including scanning probe microscopes (SPMs). A few SPMs have outstanding metrological characteristics and many commercial microscopes only perform as image acquisition tools. Commercial SPMs use piezoelectric actuators in order to move either the sample or the probe. The position measurement sometimes results from the applied voltage to the piezoelectric actuators or from the strain gauge or capacitive displacement sensor data. This means that they suffer from hysteresis, creep, nonlinear characteristics and Abbe offsets. For an accurate measurement the position of the cantilever must be measured in addition to the torsion and bending. The best solution is a combined detection system with a single laser beam. This system has been realized with a special interferometer system, in which the measuring beam is focused on the cantilever backside using a lens. The reflected beam is split with a part being detected by a quadrant photo-diode and the other part being fed back into the
interferometer for position measurement. The quadrant photo-diode is used to detect the cantilever torsion and bending.
The paper describes the operation of a high-precision long range three-dimensional nanopositioning and nanomeasuring
machine (NPM-Machine). The NPM-Machine has been developed by the Institute of Process Measurement and Sensor
Technology of the Technische Universität Ilmenau. The machine was successfully tested and continually improved in the
last few years. The machines are operating successfully in several German and foreign research institutes including the
Physikalisch-Technische Bundesanstalt (PTB). Three plane mirror miniature interferometers are installed into the NPM-machine
having a resolution of less than 0,1 nm over the entire positioning and measuring range of 25 mm x 25 mm x 5
mm. An Abbe offset-free design of the three miniature plane mirror interferometers and applying a new concept for
compensating systematic errors resulting from mechanical guide systems provide extraordinary accuracy with an
expanded uncertainty of only 5 - 10 nm.
The integration of several, optical and tactile probe systems and nanotools makes the NPM-Machine suitable for various
tasks, such as large-area scanning probe microscopy, mask and wafer inspection, nanostructuring, biotechnology and
genetic engineering as well as measuring mechanical precision workpieces, precision treatment and for engineering new
material. Various developed probe systems have been integrated into the NPM-Machine. The measurement results of a
focus sensor, metrological AFM, white light sensor, tactile stylus probe and of a 3D-micro-touch-probe are presented.
Single beam-, double beam- and triple beam interferometers built in the NPM-Machine for six degrees of freedom
measurements are described.
Driven by increasing precision and accuracy requirements due to miniaturization and performance enhancement, measuring technologies need alternative ways of positioning, probing and measurement strategies. The paper describes the operation of the high-precision wide scale three-dimensional nanopositioning and nanomeasuring machine (NPM-Machine) having a resolution of 0.1 nm over the positioning and measuring range of 25 mm x 25 mm x 5 mm. The NPM-Machine has been developed by the Technische Universitat Ilmenau and manufactured by the SIOS Messtechnik GmbH Ilmenau. Three plane-mirror miniature interferometers and two angular sensors are arranged, to realize in all three coordinates zero Abbe offset measurements. Therefore, this device closes a gap in coordinate-measuring technique regarding resolution, accuracy and measuring range. The machines are operating successfully in several German and foreign research institutes including the Physikalisch-Technische Bundesanstalt (PTB). The integration of several, optical and tactile probe systems and scanning force microscopes makes the NPM-Machine suitable for various tasks, such as large-area scanning probe microscopy, mask and water inspection, circuit testing as well as measuring optical and mechanical precision work pieces such as micro lens arrays, concave lenses, step height standards.
This article deals with a high-precision three-dimensional positioning and measuring machine and its application as a metrological long-range scanning force microscope. At the Institute of Process Measurement and Sensor Technology of the Technische Universitaet Ilmenau an interferometric nanopositioning and nanomeasuring machine has been developed. Which is able to achieve a resolution of less than 0.1 nm over the entire positioning and measurement range of 25 mm x 25 mm x 5 mm and is traceable to the length standard. The Abbe offset-free design in conjunction with a corner mirror as a reference coordinate system provides extraordinary accuracy. The integration of several probe systems and nanotools (AFM, STM, focus sensor, tactile probes) makes the nanopositioning and nanomeasuring machine suitable for various tasks in the micro- and nanotechnologies. Various probe systems have been integrated in the last few years. For example, a commercial piezo tube AFM was integrated and tested. Additionally, interferometeric measurement systems of the nanopositioning and nanomeasuring machine enables the calibration of probe systems. Also in order to achieve the best possible measurement results special probe systems have been developed and tested and are discussed briefly.
The paper describes the design of a high-precision three-dimensional nanopositioning and nanomeasuring machine (NPM-Machine). The NPM-Machine has been developed by the Institute of Process Measurement and Sensor Technology of the Technische Universität Ilmenau and manufactured by the SIOS Meßtechnik GmbH Ilmenau. The machine was successfully tested and continually improved in the last few years. The NPM-Machine has a resolution of less than 0,1 nm over the entire positioning and measuring range of 25 mm x 25 mm x 5 mm. An Abbe offset-free design and the application of a new concept for compensating systematic errors resulting from mechanical bearings provide extraordinary accuracy. An important part of the NPM-Machine is constituted by a mirror corner. The integration of several probe systems and Nanotools makes the NPM-Machine suitable for various tasks, such as large-area scanning probe microscopy, mask and wafer inspection, nanostructuring, biotechnology as well as measuring mechanical precision workpieces a.s.o. Various probe systems have been integrated into the NPM-Machines. The machines are operating successfully in several German and foreign institutes including the Physikalisch-Technische Bundesanstalt (PTB). The article gives basic information on the NPM-Machine and describes the mode of operation and the measurements by means of probe systems.
An initial description of the design and operation of compact miniature interferometers that employ fiberoptic lightguides for all of their optical couplings and are suitable for general-purpose use is followed by a metrological analysis of their mode of operation and examples of their broad applicability, based on several typical instrumental setups.
At the Institute of Process Measurement and Sensor Technology of the TU Ilmenau, a scanning force microscope (measuring range 15 ?m x 75 tm x 15 ?m) having a laser-interferometric 3D-nanomeasuring system free from Abbe errors has been developed in cooperation with the PTB Braunschweig. The extended measuring uncertainty (K =2) is only 0.2 nm and was obtained with a structure standard. To achieve a considerable extension of the measuring range up to 25 mmx 25 mm x 5 mm, a nanopositioning and —measuring machine was developed. The resolution of the measuring axes is 1.24 nm. The laser-interferometric measurement is free from Abbe errors of 1St order in all measuring axes. The deviations of the guides used are compensated by means of a precision mirror corner.
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