Measurement of Radial Runout and Wobble

This application note presents the PICOSCALE Interferometer's role in measuring radial run-out and wobble of rotating objects, such as spindles or synchrotron sample holders. These measurements are crucial for applications that demand precise rotational alignment, particularly in high-precision engineering and synchrotron-based tomography, where sample positioning must be exact to ensure data accuracy.

Problem: In precision applications like synchrotron end-stations, radial run-out and wobble in rotating systems impact measurement and imaging quality, potentially introducing errors into crystal tomography or other high-resolution techniques. Minimizing these rotational inaccuracies is vital for ensuring high-quality outcomes in tasks such as sample positioning and material examination.

Solution: The PICOSCALE Interferometer, equipped with specialized sensor heads, was utilized to measure both radial run-out and wobble in a cylindrical target. By using line-focused sensor heads, the setup captures precise radial displacements and angular deviations, enabling real-time measurement and correction of wobble and run-out in rotating systems. This approach leverages PICOSCALE's sub-nanometer accuracy and adaptability to varied cylindrical surfaces.

Implementation: A test setup featured a polished steel cylinder mounted on a SmarAct XY-stage and a rotary stage. The XY-stage allowed for controlled eccentric adjustments to simulate or correct large run-outs. Two line-focused sensor heads were positioned orthogonally to capture eccentricity, while a third sensor tracked wobble. Using incremental rotation and recording displacement for each angle, the system calculated run-out and applied necessary adjustments to maintain the sample's rotational precision.

Results: The PICOSCALE Interferometer successfully tracked run-outs up to 1 mm and detected wobble within ±1.5 µm, effectively demonstrating its capability for high-precision applications. The system accurately captured large displacements and maintained stability across different cylinder diameters, confirming its versatility in various cylindrical configurations. This method is suitable for ensuring precision in tasks that demand strict control over rotational movement, reinforcing PICOSCALE’s utility in high-precision engineering and synchrotron applications.