An absolute encoder based on vision system nanoGPS OxyO was developed by HORIBA France. This encoder provides three types of position information, namely, two inplane co-ordinates and inplane angular orientation. This paper focuses on the characterization of its angular performance. To this aim, the nanoGPS OxyO system was compared with the national angle standard of the National Metrology Institute of Italy (INRIM) that had evaluated accuracy of about 0.1 µrad. The effect of image size and illumination conditions on angular measurements was studied. Precision better than 10 µrad and accuracy better than 63 µrad over 2π rotation were demonstrated. Moreover, the application of nanoGPS OxyO to the characterization of rotation bearing is presented. Small deviations from pure rotational behavior were evidenced that would have not been possible using laser interferometers. As a consequence of its accuracy and versatility, the nanoGPS OxyO encoder is expected to be useful for laboratory experiments and quality-control tasks.

For a long time, investigating the same regions of interest of a sample with different instruments has been recognized as a very useful approach in various scientific fields. This paper presents an original solution for spotting the same points of interest with a high degree of accuracy and simplicity using different microscopes. It is based on small patterned tags fixed to the samples or their substrates. The patterns include an image-based position-sensing technology, for which an image of a small part of the tag can be automatically converted to absolute coordinates and angular orientation. Taking a single snapshot of the tag with an imaging instrument provides a correspondence between the sample and the coordinates of the moving stage. Co-localized observations performed with scanning electron microscopes, optical microscopes, and Raman microscopes are presented. The accuracy is in the range of a few µm up to 20 µm, which is generally sufficient to remove any ambiguity between the observed objects. The different contributions to colocalization errors are investigated experimentally and it is shown that errors related to the tags are negligible and that the main source of error is related to the accuracy of the moving stages integrated into the microscopes. A straightforward estimation of the relocalization error can be performed. It is believed that this solution will save researchers time and facilitate cooperation between laboratories.