Real-time measurements in optical metrology

Methods as well as recording materials for real-time measurements were discussed. Electrooptical crystals can be used for nearly realtime contactless measuring techniques. The BSO was found appropriate for real-time holographic interferometry, contour line display and for deformation, displacement and vibration analysis. Furthermore, for real-time speckle photography the BSO was found to be very useful. For noise and vibration analysis of oscillating objects such as rotating car tyres, gearing boxes, turbines blades, a vibrometer based on Doppler shift measuring principles was found to be useful, leading to an amplitude and frequency analysis. For the analyse of rotating objects an image derotator is frequently used for compensation of the rotation. In optical metrology real-time methods will be useful for the engineer in future

Doppelheterodyn-Interferometrie für hochgenaue Vermessung im Nahbereich

In diesem Aufsatz wurde ein Meßsystem vorgestellt, welches sich aus der Kombination der Zweiwellenlängen-Interferometrie mit dem intensitätsunabhängigen Heterodyn-Verfahren zusammensetzt. Die resultierende Doppelheterodyn-Interferometrie vereinigt die Vorteile der beiden Verfahren. Ein großer Eindeutigkeitsbereich entsprechend der effektiven Wellenlänge A entsteht, darüberhinaus sind optisch rauhe Oberflächen als Meßobjekte zulässig; reduzierte Empfindlichkeit gegenüber Vibrationen und Umwelteinflüssen, hohe Auflösung infolge elektronischer Phasenbestimmung sowie hochgenaue Abstandsmessung in Echtzeit sind weitere Vorteile. Das Doppelheterodyn-Interferometer wird in Zukunft zu einem effektiven und dynamischen Meßinstrument zur hochgenauen Entfernungsmessung im Mikrometerbereich bis hin zu Meßdistanzen von 100 m entwickelt werden, für das sich schon jetzt zahlreiche Einsatzmöglichkeiten abzeichnen

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta