The sensor can be implemented using a random domain film or a stripe domain film to create a phase grating diffraction pattern.

The optical diffraction pattern defining layer (3) is formed by a polymeric layer permanently bonded to the transparent carrier layer (2) which, when heated, causes the diffraction pattern to undergo an irreversible change.

A polarizerless optic sensor is provided that uses a random domain magneto-optic film and a modulated normal magnetic field to vary or modulate the energy distribution in a diffraction pattern.

A tamper resistant security seal comprises a laminate having a transparent carrier layer (2); an optical, diffraction pattern defining layer (3, 4); and an adhesive layer (6) for adhering the tape to a substrate.

Methods for enhancing the visibility of and imparting a metallic luster to holographic and diffraction pattern surface embossments on transparent media such as plastic films (12) are disclosed.