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Production sequence of Si-spheres and interferometrical determination of the sphere volume

EMPIR-Project TracOptic „Traceable industrial 3D roughness and dimensional measurement using optical 3D microscopy and optical distance sensors“ started


Due to the advantages of areal, fast and non-destructive measurements, optical microscopes and optical distance sensors have become indispensable in manufacturing process fur surface and dimensional measurements and have the possibility to be integrated into the production lines to accelerate the evolution of Industry 4.0.

However, because of the complexity of light-surface interaction and the large variety of surface types and measuring systems, areal surface texture measurements by optical microscopes and dimensional measurements with optical distance sensors are strongly influenced by the measurement principle, the optical instrument’s setup and the feature geometries of the surfaces, i.e. amplitudes, spatial frequencies, slopes, and curvatures. Each of these influence factors is critical to understand if a given instrument can reliably, accurately and traceably measure a certain surface texture and dimension. And end users in industry have little guidance on the selection of a suitable instrument (and the instrument settings) to accurately and traceably measure the test object.

The overall objective of the EMPIR project “Traceable industrial 3D roughness and dimensional measurement using optical 3D microscopy and optical distance sensors” (kurz: TracOptic) is to enable traceable areal roughness and dimensional measurements using optical 3D microscopy and optical distance sensors, with special emphasis on giving guidance for selection of most suitable instrumentation for a particular purpose.

For this purpose, different types of samples, including typical technical surfaces fabricated by classical and new manufacturing methods, solid roughness samples from biology and medicine will be selected and the suitable surface texture parameters will be determined by reference measurements of tactile instruments or AFM.

Metrological characteristics such as maximum measurable slope, measurement noise, topographic spatial resolution / structural resolution and topography fidelity will be investigated using suitable calibration standards to characterize the measurement capability of 3D optical microscopes and optical distance sensors. To characterize the topography fidelity and topographic spatial resolution of optical instruments, a sinusoidal chirp standard has been developed at PTB, having different amplitudes from 50 nm to 10 µm and wavelengths from 2.8 µm to 80 µm and is suitable for the characterization of optical instruments with different magnification and numerical apertures.

In this project analytical and rigorous scattering models will be developed as well to simulate the light-surface interaction. Based on the scattering models virtual instruments will be developed to predict the instrument response for any complex surface geometry and to investigate the measurement uncertainty and systematic deviations and compare the results with real measurements.

Procedures for the selection of appropriate instrumentation for a given measurand will then be developed and validated. The target uncertainties are 5 nm (10 % deviation for 50 nm < Sq < 100 nm) for optical surface texture measurements and 100 nm for optical dimensional measurements. This will include the development of methods for data evaluation and simplified uncertainty estimation. Industrial case studies will be carried out based on the developed good practice guides.

The project TracOptic (20IND07) funded by EMPIR has 24 project partners, is coordinated by PTB and has a duration of 3 years.



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