Multilayered optical security device

A multilayered optical security device for displaying an image and one or more patterns, the device comprising:

• an aperture arranged to face an observer such that the one or more patterns are viewable to the observer through the aperture, the aperture defining a top side of the device;
• an under layer below the top side for generating the image upon the under layer being illuminated;
• and
• a resonant waveguide grating (RWG) layer located between the top side and the under layer, the RWG layer comprising a plurality of RWGs configured to generate the one or more patterns upon illuminated with an incident light beam received through the aperture, an individual RWG comprising a waveguide and first and second diffraction gratings both attached to the waveguide, an individual diffraction grating having a grating period, wherein:
• the grating period is selected such that a first light beam having a preselected wavelength and a preselected propagation direction resonates with the individual RWG under the selected grating period, causing the first light beam to couple in or out of the individual RWG while avoiding interference to a second light beam that is out of resonance with the individual RWG during the second light beam propagating through the individual RWG, thereby avoiding the RWG layer to interfere the image during transmission from the under layer to the aperture;
• and
• the individual diffraction grating comprises one or two periodic arrangements of scattering elements, an individual scattering element having a curved shape to thereby enhance an angular tolerance in observing the one or more patterns by the observer.