Slip rings

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Schleifring has developed a range of slip rings for use in computed tomography systems. The development of this optical slip ring enables the transmission range to be extended as far as 10GBit/s and upwards. GigaFOS (Gigabit Fiber Optical Slip ring) has been developed in cooperation with the University of Applied Sciences in Nuremberg, under the direction of Professor Dr Hans Poisel. The university researched various mechatronical approaches. Besides varying optical implementation, different approaches regarding the mounting of components were also tested and evaluated. Schleifring coordinated each step, and simulation methods for optics, cybernetics and air-flow were employed to discover critical parameters and to define optimal determining factors already at the prototype stage.

The method applied transfers light waves along the inside of a curvature by means of reflection, known as ‘whispering gallery effect’. A reflective coating is applied to the inside of a torus (mirrored groove). Light waves are launched tangentially by an optical fibre and led alongside the barrier by reflection until a ‘pick-up’ reads the light signals. The light waves are guided very close to the barrier. This demands an optimal geometry of the mirror groove and a sufficiently large diameter to guarantee transmission of the original signals with minimal loss.

The ‘pick-up’ consists of a prismatic polished optical fibre, being led over the mirror surface with a clearance of only 20 to 30µm. A specially-developed air-pressure system, keeps the ‘pick-up’ in position. Sliding on an air cushion, the ‘pick-up’ follows the surface structure ideally even at small mechanical inconsistencies. The optical thumbing unit is tracking all radial and axial movements on an air bearing. This optical system requires a dust cover, protecting the mirror groove from pollution.