Optical disc and optical system for reproducing the optical disc

摘要

An optical disc has a recording film with information recorded thereon, and a photochromic material film provided adjacent the recording film. The photochromic material film is made of a photochromic material. The photochromic material has a first state irradiated with reading light having a first wavelength. In the first state, the transmittance of the material is increased so as to enable reading of the recorded information. The photochromic material further has a second state irradiated with auxiliary light having a second wavelength, where the transmittance becomes low so as to disable the reading of the recorded information.