Polarization separating element having partially polarizing properties for diffracting an ordinary light beam and a process for producing the same

摘要

A polarization separating element 1 is produced by forming a polydiacetylene derivative film 11 on the surface 101 of a glass substrate 10 as an optically isotropic substrate, and selectively irradiating the polydiacetylene derivative film 11 with ultraviolet rays to form a grating 12 which has periodic grooves and two hues and exhibits partially polarizing properties. In a light pickup device containing the polarization separating element 1 having partially polarizing properties, part of the light reflected on an optical disk reaches a receptor without fail even if the optical disk has birefringence, whereby the recorded information can be reproduced with no problem.