DOE for the formation of the effect of switching between two images when an element is turned by 180 degrees

Abstract

An optical security element forming different 2D images when it is turned by 180 degrees is developed and manufactured for the first time. A synthesis technology is developed that incorporates the computation of the beam pattern in elementary hogels with sizes smaller than 100 microns, computation of the phase function of the diffractive optical element (DOE), and formation of the microrelief of the DOE using electron-beam technology. The DOE employed is a multilevel kinoform with an asymmetrical microrelief shaped with a precision of 10 nm. The resulting security feature is easy to control visually, and the DOE is securely protected against counterfeiting. These DOEs are easy to replicate using standard technologies in the manufacturing of embossed holograms and can be used to protect bank notes, securities, and documents against counterfeiting.