Logo of the Physikalisch-Technische Bundesanstalt

Virtual experiments

Working group 8.42


In a virtual experiment a measurement process is modeled mathematically and simulated on a computer. The employed mathematical model of the physical experiment is sought to be as realistic as possible. Virtual experiments allow different scenarios to be easily explored. In this way, measurement processes can be designed and specified with the help of the computer. Virtual experiments can be used to estimate the accuracy that is reached by a real measurement device. Dominant sources of uncertainty can be identified and quantitatively explored by carrying out a sensitivity analysis of the virtual experiment. The results obtained can be used to optimize the considered measurement system. Virtual experiments can help in the development of procedures from data analysis for real experiments, for example to assess and compare different estimation procedures under realistic conditions, or to validate assumptions made about the distribution of measured data.

Simulation of a tilted-wave interferometer (left) and a virtual 3D-measurement of an optical surface (right) using SimOptDevice.


The research of PTB’s Working Group 8.42 focuses on virtual experiments for optical measurement devices and the development of procedures from data analysis for evaluating corresponding measurements. To this end, the simulation environment SimOptDevice has been developed as a software library, which is successfully employed in many applications regarding length-/form- and coordinate measurements, as well as photometry. SimOptDevice is regularly maintained and its functionality improved. It is currently applied to the tilted-wave interferometer, which is suitable for the optical form measurement of aspheres and freeforms. Methods of data analysis in conjunction with virtual experiments are developed and applied to solve the involved inverse problem and to calibrate the measurement process. Other research topics include the evaluation of uncertainties associated with real measurements utilizing the results of the corresponding virtual experiment, or the use of methods from deep learning in connection with virtual experiments. For example, virtual experiments can be used to create a database needed to train a neural network that is designed for analyzing experimental data.


Publication single view


Title: Accuracy evaluation for sub-aperture interferometry measurements of a synchrotron mirror using virtual experiments
Author(s): A. Wiegmann, M. Stavridis, M. Walzel, F. Siewert, T. Zeschke, M. Schulz;C. Elster
Journal: Precision Engineering
Year: 2011
Volume: 35
Issue: 2
Pages: 183--190
DOI: 10.1016/j.precisioneng.2010.08.007
ISSN: 01416359
Web URL: http://www.sciencedirect.com/science/article/pii/S014163591000125X
Keywords: Interferometry,Simulation,Stitching,Virtual experiment,virtual experiment
Tags: 8.42,Form,SimOpt
Abstract: We present a virtual experiment for the accuracy assessment of the sub-aperture interferometric measurement of a synchrotron mirror involving several thousand sub-aperture topographies. The virtual experiment simulates the measurement process and accounts for the influence of positioning device errors, interferometer errors, non-perfect calibration of machine geometry as well as errors in the interferometer reference. Two principles are considered for reconstructing the form of a test specimen from the conducted sub-aperture topographies, a stitching procedure and a direct measurement method. The virtual experiments are applied to the task of absolute form measurement (including its radius of curvature) of a synchrotron mirror with a length of 30cm, a width of 4cm, a maximum curvature of about 44mm−1 and a peak-to-valley of 5mm. As a result, reconstruction accuracies can be expected to be in the range of 100nm when the stitching method is applied, which outperforms the direct measurement method by a factor of about 3.

Back to the list view