A magnetic shield has a multiple-layered lid and a multiple-layered base, wherein each layer of the lid is aligned with the corresponding layer of the base. The magnetic shield also includes an alignment mechanism to maintain the alignment of the corresponding layers of the lid and the base of the s...http://www.google.com.hk/patents/US6627810?utm_source=gb-gplus-share專利 US6627810 - Magnetic shield for optical gyroscopes
