2.2 - Optical twist measurement by scatterometry
- Event
- AMA Conferences 2013
2013-05-14 - 2013-05-16
Nürnberg - Band
- Proceedings OPTO 2013
- Chapter
- O2 - Optical Methods for Physical Measurands
- Author(s)
- A. Hertzsch, K. Kröger, M. Großmann - INNOVENT Technology Development, Jena (Germany)
- Pages
- 40 - 45
- DOI
- 10.5162/opto2013/o2.2
- ISBN
- 978-3-9813484-3-9
- Price
- free
Abstract
To ensure that seals do not leak one of the main requirements for the shaft surface is the absence of twist structures. Twist is a periodic, generally thread-shaped microstructure which is superimposed on the roughness of the shaft surface and takes the form of waviness in the axial and circumferential directions. Using an optimized scattering geometry light scattering leads to an intensified mapping of the periodic twist structure of the shaft surface. The optical filtering process reduces the speckle effect from surface roughness and produces a diffraction pattern from the twist structure. We use a rigorous diffraction model to calculate the diffraction efficiencies and to determine the twist parameters twist
depth and twist period length. We introduce an optical scattering apparatus for fast and reliable measurements of the twist structure. A comparison between the experimental results of scatterometry and the experimental results of stylus measurements will be presented for a number of sealing shaft surfaces produced under different machining conditions. We discuss the limitations of the present model and indicate directions of future work.