Micro-optical sensor system for birefringence characterization of textile-fibers

We report a micro-optical sensor system for the on-line characterization of the textile-fiber birefringence in spinning machines. The measurement set-up is using the method of Senarmont but does not require any moving parts in the optical path. This has been achieved by usage of different micro-optical elements in combination with optical fibers for illumination and signal capturing. One of the key-components is an array of micropolarizers made of subwavelength-period metal-stripe gratings fabricated by e-beam direct writing and ion-beam etching. Having a total height of only 6mm the sensor system is extremely flat and thus applicable also in special spinning equipment.