Mirau-Based CSI with Oscillating Reference Mirror for Vibration Compensation in In-Process Applications

We present a Mirau-type coherence scanning interferometer (CSI) with an oscillating reference mirror and an integrated interferometric distance sensor (IDS) sharing the optical path with the CSI. The IDS works simultaneously with the CSI and measures the distance changes during the depth scanning process with high temporal resolution. The additional information acquired by the IDS is used to correct the CSI data disturbed by unwanted distance changes due to environmental vibrations subsequent to the measurement. Due to the fixed reference mirror in commercial Mirau objectives, a Mirau attachment (MA) comprising an oscillating reference mirror is designed and built. Compared to our previous systems based on the Michelson and the Linnik interferometer, the MA represents a novel solution that completes the range of possible applications. Due to its advantages, the Mirau setup is the preferred and most frequently used interferometer type in industry. Therefore, the industrial use is ensured by this development. We investigate the functioning of the system and the capability of the vibration compensation by several measurements on various surface topographies.

Analysis of the tribological interaction of a polytetrafluoroethylene-lined radial lip oil seal, shaft and lubricant sample

To investigate the tribological interaction and wear mechanisms of polytetrafluoroethylene-lined radial lip oil seals in service, a sleeve, seal and lubricant sample taken off a rotating rig are studied. The test was terminated at 72 h, after severe leakage in the final 15 h of the test. All three components are studied using a coherence scanning interferometer and environmental scanning electron microscopy to investigate wear after testing. Results show a wear band on the aerospace grade case-hardened sleeve, appearing as a ‘polished in’ area by the seal. A study of the filler content of the polytetrafluoroethylene coating uncover glass fibres, calcium carbonate, carbon and graphite layers present, assumed responsible for the wear to the sleeve. The polytetrafluoroethylene coating is a 300 μm coating, distinct from the bulk elastomer. This finding is confirmed after observing this layer on both, the tested and new seal lip. Wear of the seal lip is measured and facilitated by comparison to the identical new seal. Lastly, debris from the seal and sleeve wear are found in the lubricant sample.