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.
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.