The modelling of caustics to produce a projection image

1Note Issue Department, Reserve Bank of Australia 2Disney Research, Zurich 3Dartmouth College

In Optical Security Documents Conference, 2018

Silica master (left) containing four PBI lens arrays and the projected images from a Samsung smartphone flash. The lens array, applied to polymer substrate is illuminated by an iPhone 6s flash (middle) and by the sun (right). The projected image can be clearly resolved.


The Projection-Based Image is a new banknote security feature that projects a desired image when an array of microlenses embossed into the banknote substrate is exposed to a light source. The feature is designed computationally to make the projected image difficult to discern by inspection of the lens structures, and to accommodate a range of light sources, allowing wide accessibility to users with a simple mobile phone flash. The projected image is formed from a collection of Gaussian-shaped caustic profiles, each arising due to light refracting through a single microlens.



Luke Maguire, Marios Papas, Wojciech Jarosz, Phillip Fox, Greg Dicinoski, Maria Olivares. The modelling of caustics to produce a projection image. Optical Security Documents Conference, January 2018.
    author    = {Maguire, Luke and Papas, Marios and Jarosz, Wojciech and Fox, Phillip and Dicinoski, Greg and
                 Olivares, Maria},
    title     = {The modelling of caustics to produce a projection image},
    booktitle = {Optical Security Documents Conference},
    year      = {2018},
    month     = jan