Optical device and method of manufacture thereof

摘要

An optical device comprising microstructures which comprise microstructures 20A, 20B in at least two sub-arrays whereby the microstructures in each sub-array modify the angle of incident light in different ways to produce two different colours when viewed at different viewing angles. The microstructures modify the angle of incident light due to differences in facet angle, orientation or refractive index. The optical device can be used as a security device. A method for making the optical device is also claimed.