Björn Hemming

High-accuracy automatic machine vision based calibration of micrometers

The calibration of simple handheld instruments is often more expensive than the price of a new device. Therefore, the amount of manual labour is kept at a minimum in order to keep the price of calibration at a tolerable level. This also means that only a few points of e.g. a length scale can be checked. By using automatic machine vision based systems, the calibration of measurement instruments can be done faster and more thoroughly. In order to study the possibilities of machine vision automation for volume calibration tasks a set-up for micrometer calibration was constructed at Centre for Metrology and Accreditation (MIKES). With the developed automated machine vision system it is possible to check hundreds of points on the scale of a micrometer, giving new insight into error sources of the micrometer screw. The attained uncertainty is at the same level as calibration with gauge blocks according to ISO 3611.

Calibration of a flatbed scanner for traceable paper area measurement

In this note, we describe a method to calibrate a flatbed scanner to perform traceable paper sample area measurements. Also a detailed uncertainty analysis is presented. The achieved relative uncertainty at the 95% confidence level of the area measurement is under 0.1%. Described calibration procedures can also be used in other applications where dimensional measurements are performed with a flatbed scanner.

MEASUREMENT OF APERTURE AREAS USING AN OPTICAL COORDINATE MEASURING MACHINE

The use of an optical coordinate measuring machine (CMM) for the diameter measurement of optical apertures is described. The traceability and mechanical stability of the aperture areas are of importance for accurate photometric and radiometric measurements. Detailed evaluation of the measurement uncertainty for the aperture diameter is presented. High-accuracy mechanical CMM was used to confirm the validity of the optical CMM results. The difference between the contact and non-contact measurement was 0.1 µm for the mean diameter result. If the required standard uncertainty for the mean diameter is of the order of 1 µm, the optical CMM provides an efficient method for aperture area measurements.

Calibration of dial indicators using machine vision

Using automatic machine vision-based systems, the calibration of measuring instruments can be extended. With machine vision it is possible to check hundreds of points on the scale of a dial indicator, giving new insight into its sources of error. This paper describes a machine vision-based system for the calibration of dial indicators developed at the Centre for Metrology and Accreditation in Finland, with emphasis on the calculation of measurement uncertainty.

A comparison of sensitivity standards in form metrology—final results of the EURAMET project 649

Results of an intercomparison measurement of sensitivity standards are presented. The standards circulated were a flick and two multi-wave standards (MWS). The measurands were form deviation and, for the MWS only, the height of the dominant spectral components. For the flick, influences from mechanical filtering and calibration are discussed. For the MWS several influencing quantities are identified and discussed. Some of these influencing quantities may dominate the result under certain circumstances. It can be shown that standard measurement uncertainties of smaller than 25 nm can be achieved for the amplitude heights of MWS, whereas the form deviation results disagree a little more than expected compared to standard uncertainties of the order of 50 nm.

Design of a calibration machine for optical two-dimensional length standards

Optical measurements with coordinate measurement machines equipped with optical sensors, and video measurement machines, are clearly increasing in industry. Accurately manufactured two-dimensional standards, with a precision typically between 0.05 μm and 5μm, are used to check and calibrate these measuring machines. In order to start a calibration service for two-dimensional standards, a new calibration machine is currently under development at the Centre for Metrology and Accreditation (MIKES). In this paper we describe the mechanical design, properties and present a detailed uncertainty analysis of position measurement. By modeling and compensating mechanical error sources the required standard uncertainty level of 50 nm is achievable.

Calibration of surface roughness standards: Key Comparison EURAMET.L-K8.2013

The key comparison EURAMET.L-K8.2009 on roughness was carried out in the framework of a EURAMET project starting in 2009 and ending in 2011. It involved the participation of 14 National Metrology Institutes from Europe, North America, Central America, South America and Africa representing three regional metrology organisations. Four surface texture standards of different type were circulated and on each of the standards several roughness parameters according to the standard ISO 4287 had to be determined. 27 out of 171 individual results were not consistent with the reference value. After some corrective actions the number of inconsistent results could be reduced to 24, which correspond to about 14% of the total. In addition to the material standards, two soft-gauges were circulated, which allow to test the software of the instruments used in the comparison. The comparison results help to support the calibraton and measurement capabilities (CMCs) of the laboratories involved in the CIPM MRA. == Main text To reach the main text of this paper, click on Final Report [http://www.bipm.org/utils/common/pdf/final_reports/L/K8/EURAMET.L-K8.PDF] . Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/ [http://kcdb.bipm.org/] . The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).