Alphen aan den Rijn, Netherlands
Alphen aan den Rijn, Netherlands

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Ellis J.D.,Technical University of Delft | Ellis J.D.,University of Rochester | Baas M.,Technical University of Delft | Joo K.-N.,Technical University of Delft | And 3 more authors.
Precision Engineering | Year: 2012

Two different measure-and-correct algorithms, the Chu-Ray algorithm and the Eom algorithm, were simulated to estimate their effectiveness for correcting periodic nonlinearity applied a simulated wafer positioning system. Both algorithms, which demonstrated no periodic nonlinearity in some example constant velocity and constant acceleration datasets, and their specific implementations are described in detail. The algorithms were tested for both slit and scan directions using estimated wafer stage trajectories for ramping up to a constant scanning velocity with no velocity in the slit direction. Three different heterodyne frequencies and three different sampling frequencies were simulated to estimate the optical system and data acquisition parameters. The initial phase offset was also considered in the simulations and had a significant effect on both the scan and slit offset errors. The offset error appears to increase for certain initial phase values which manifests from compensating the periodic errors combined with the high stage dynamics. High noise levels and displacement jumps were observed when high velocity changes during a correction period suggesting increasing the minimum velocity threshold and limiting the maximum acceleration can improve the effectiveness of these algorithms. © 2011 Elsevier Inc. All rights reserved.

Tosello G.,Technical University of Denmark | Haitjema H.,Mitutoyo Research Center Europe | Leach R.K.,University of Nottingham | Quagliotti D.,Technical University of Denmark | And 2 more authors.
CIRP Annals - Manufacturing Technology | Year: 2016

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 laboratories worldwide. Results demonstrated that: (i) Agreement among different instruments could be achieved to a limited extent; (ii) standardised guidelines for uncertainty evaluation of areal surface parameters are needed for users; (iii) it is essential that the performance characteristics (and especially the spatial frequency response) of an instrument is understood prior to a measurement. © 2016 CIRP

Hagino T.,Mitutoyo Tsukuba Laboratory | Yokoyama Y.,Mitutoyo Tsukuba Laboratory | Kuriyama Y.,Mitutoyo Tsukuba Laboratory | Haitjema H.,Mitutoyo Research Center Europe
Key Engineering Materials | Year: 2012

A newly developed practical sphericity measurement system by means of stitching interferometry is described in this paper. Spheres are widely used in industry. In particular, spheres with stem are usually used in metrological applications such as reference sphere for Coordinate Measuring Machines. It is common to calibrate form of spheres with tactile roundness measurement, however a comprehensive form measurement is desired for evolving high precision applications. The developed system consists of commercial base Fizeau type interferometer to capture partial surface areas of sphere and five axes stages to handle sphere with stem. Hence the system is very suitable for measurement of such stemmed spheres. This system yields three dimensional form maps of stitched sphere and peak to valley sphericity. Standard deviation of sphericity value yielded using this system is less than 5 nm in 8 times repetition. Finally, an equatorial profile clipped from stitched sphere shows good agreement with a result of tactile roundness measuring method within 10 nm typically. © (2012) Trans Tech Publications, Switzerland.

Joo K.-N.,Technical University of Delft | Joo K.-N.,Mitutoyo Research Center Europe | Ellis J.D.,Technical University of Delft | Spronck J.W.,Technical University of Delft | Schmidt R.H.M.,Technical University of Delft
Precision Engineering | Year: 2011

We describe the combined methods of displacement heterodyne laser interferometry with wavelength tracking based on a Fabry-Perot cavity to correct the instantaneous wavelength in air. The optical frequency of the interferometry source was locked to the resonance peak of an open cavity, directly linking the refractive index changes to frequency changes. Using this method, refractive index changes are compensated by an appropriate change in the laser frequency in real time, eliminating the limitations with environmental parameter measurement bandwidth uncertainties associated with equation-based corrections. In this paper, the principles of the system are explained and experimental results showed a difference of 2 nm compared with traditional equation-based techniques. The measurement uncertainty and practical considerations for implementation are also discussed. © 2010 Elsevier Inc. All rights reserved.

Mitutoyo Research Center Europe BV | Date: 2010-03-10

The invention relates to an instantaneous phase shifting Fizeau interferometer using phase analysis with orthogonally polarized reference and measurement beams. The interferometer comprises a light source, adapted to generate a coherent light beam, a detector adapted to analyze the phase difference of optical light beams, location means for locating an object to be measured, a first optical path from the light source to the object and a second optical path from the object to the detector, wherein the first and the second optical path have a common section adjacent to he object, wherein an optical polarization modulator arranged in the first path switches between two orthogonal polarizations with a modulation frequency fitting the distance between the object plane and the reference plane, such that the two beams reaching the detector have at any time mutual orthogonal polarizations.This avoids the costs and other disadvantages of so called quarter wave plates belonging to prior interferometers of this kind.

Mitutoyo Research Center Europe B.V. | Date: 2011-11-09

The invention concerns an apparatus for calibrating a coordinate measuring machine comprising a sensing probe, the apparatus comprising a test sphere, a base adapted to be fixed to a part of the coordinate measuring machine and a shaft connecting the test sphere with the base, wherein the apparatus comprises a reference element detectable by the coordinate measuring machine and having a fixed spatial relation between the reference element and a defined origin on the surface of the test sphere. This reference element allows to refer the calibration results to the reference element, so that the errors in the calibration may be more accurately defined.

The invention relates to a method and an apparatus for measuring the thickness of a transparent film by broad band interferometry, comprising the steps of preparing a correlogram of the film by an interferometer, applying a Fourier transformation to said correlogram to obtain a Fourier phase function, removing a linear component thereof, applying a second integral transformation to the remaining non-linear component to obtain an integral amplitude function of said non-linear component, identifying the peak location of said integral amplitude function and determining the thickness of the film as the double value of the abscissa at said peak location considering a refractive index of a film which is dependent on wavelength. The last two steps may be replaced by identifying the peak locations of said integral amplitude function and determining the thickness of the films as the double values of the abscissas at the peak locations.

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