Transmission light from a detection lens is directed to a polarization element as incident light. The polarization element is rotated, and the light is received and detected by an array-state light-receiving element, and the birefringence of the detection lens is calculated. The distance between a lens...http://www.google.com/patents/US6266141?utm_source=gb-gplus-sharePatent US6266141 - Birefringence measuring apparatus and method of measuring birefringence
