Iterative Learning Control for the Active Error Correction of Polygon Mirror Based Laser Scanning

Polygon mirror (PM) based scanners suffer from scan line wobbles caused by facet variant pyramidal errors. The active error correction method uses a fast steering mirror (FSM) to adjust the laser reflection angle actively such that the wobble error can be compensated on the scan surface. This method requires the FSM to follow a fast varying and repetitive reference, which is challenging for the traditional feedback and feedforward control due to limited dynamic bandwidth and model accuracy. This paper proposes to use iterative learning control (ILC) for controlling the FSM, which significantly improves the correction effectiveness and reduces the line wobble for PM scanning systems.