Laser beam deflection polygon scanner using HTS bearings

A light scanning device with a rotating mirror up to 3 kHz rotational frequency for directing and aiming a radiation beam at a surface was developed and tested. Conventional fluid and air bearing systems because of friction are unable to accelerate up to 60 mm rotors above 2 kHz frequency. The rationale for the selection of the magnetic bearing configuration using YBCO, the control of the bearing and low power motor concepts are discussed. Radial centering and axial stabilization of the rotor are affected by means of two superconducting radial bearings with oppositely magnetized PM rings. The rim speed of the polygon is close to 600 m/s, giving rise to appreciable centrifugal forces and necessitates high quality material selection. The extreme optical sensitivity requires a soft suspension of the rotor coupled with a high damping efficiency. Low consumption LN/sub 2/ cooling gives stable cryogenic conditions in case of power failure. Features and limitations of this novel scanning system are discussed, especially those related to a higher line deflection frequency.