A three-degree-of-freedom measurement system for the acquisition of the straightness and roll errors of a moving linear
stage is described. The horizontal (Δx) and vertical (Δy) straightness errors are obtained by measuring the lateral displacement
of a triple prism with a laser beam and position sensitive detectors. From two simultaneously performed vertical
straightness measurements the roll angle (Θz) can be calculated. The system consists of a cable-free reflector head
and a detector head. The position sensitive detectors have been calibrated using a precision x,y-stage equipped with two
plane mirror interferometers. Different position sensitive detectors are compared with regard to position sensitivity, linearity,
null-shift stability and sensitivity to the intensity profile of the detected laser beam. In combination with an already
known triple-beam plane mirror interferometer, additional information about the linear position (Δz) and the pitch (Θx)
and yaw (Θy) angle can be obtained from three parallel linear measurements. Thus all six-degree-of-freedom geometric
errors can be measured simultaneously.
Systematic errors of the three-degree-of-freedom measurement due to misalignment of the laser beams and geometric
errors of the triple reflectors are discussed. An approach for correction of those errors caused by the triple reflectors is
shown. The method is based on determination of the reflector geometry and calculation using the additional information
(Δz) acquired by the interferometer. Furthermore the metrological properties of the proposed system for the measurement
of straightness and roll are compared to other measurement principles. Experimental results demonstrate the
measurement capabilities of the system.
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.
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.
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.
Laser interferometers are important instruments for the measurement of length in today's mechanical engineering and manufacturing technology. The principle on which interferometers have operated to date is that of interference between beams with the same direction of propagation. However, optical beams can interfere with each other not only in the same direction of propagation but also in opposing directions. The name given to this type of interference is the standing wave. A beam of light strikes a plane mirror at 90° to it, is reflected and interferes with the beam currently being reflected at the mirror. The outcome of the interference is a standing wave in front of the plane mirror. The only way of detecting the maxima and minima of the intensity of a standing wave photoelectrically is to use a photoelectric detector which is partially transparent. The photoelectric detector is placed in path of the standing wave, which propagates through it. Phase-shifted signals can be received if two photoelectric detectors with a phase shift between them are positioned in the standing wave. These enable sin and cos signals to be registered so that bi-directional fringe counting can take place. The authors have named this assembly an optical Standing-Wave Interferometer. The form taken by the partially transparent photoelectric detectors is that of photodiodes based on amorphous silicon, in a TCO-pin-TCO structure. Phase-shifted signals are received by two components with a TCO1-(pin)1-TCO2-(pin)2-TCO3 composition, integrated at the engineering stage, which are called by the authors transparent phase selective photodiodes (TPS). The TPS have been used to carry out measurement of length in a technological setting in such a way that the standing-wave interferometer could be compared with a plane mirror interferometer.
A novel interferometer based on sampling the maxima and minima of intensity of an optical standing wave has been developed. The photoelectric detection of the standing wave is performed by using a partially transparent thin-film photodiode. The automatic bidirectional fringe counting is provided by a partially transparent and phase-sensitive detector which is realized by the integration of two stacked transparent photodiodes along the optical axis of the standing wave. To obtain the ideal sine and cosine signals, the transparent phase-sensitive detector has to be optimized by adjusting the thickness of the single layers. Some features of optimization will be presented and explained. Length measurements have been demonstrated by displacing the plane mirror and bidirectional fringe counting within the standing wave.
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.
A novel interferometer concept will be presented which is based on an optical standing wave. This standing wave is scanned by a novel, partially transparent photodetector, which is designed as nip-photodiode and contacted with transparent conductive oxide (TCO). Two transparent photodiodes are integrated to a transparent phase-sensitive sensor. The photodiodes are longitudinally arranged on the optical axis of the standing wave and generate a sine and a cosine signal for the up- and down-counting of the intensity maxima and minima of the standing wave. The layer thickness of the transparent photodiodes has been designed so as to take appropriate coating into account. These measures are demonstrated by a number of experimental results. An incorrect phase relation between the photodiodes will be corrected using the Heydemann algorithm. The non-linearity of the interferometer at a length of <λ/2 will be discussed.
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.
A commercial scanning force microscope (SFM) has been equipped with an additional 3D position measurement system consisting of three miniature laser interferometers. This modification serves to further improve its metrological performance and calibration. This SFM is applied to topographical measurements including several types of calibration. In order to avoid the influence of Abbe errors two new interferometers have been implemented in the SFM. From this results a reduction of the measurement uncertainty. Furthermore, we report on a combination of the SFM including incorporated laser interferometers with a sophisticated detection system of another commercial scanning probe microscope. This enables to analyze further interactions between probe and specimen.
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