Modern Optical Features for ID Documents

If you’re overwhelmed by the vast number and types of optical features available to add security to identity documents, you’re not alone. In this paper, a group of experts from the Secure Identity Alliance (SIA) clarifies the options—and when and how to apply them.

By Yit-shun Leung Ki, Christophe Halopé, F. Daniel Françoise, Renaud Laffont-Leenhardt, Serge Wsevolojskoy, Robert Dvorak, Faten Ben Jemaa and Maickel Van Oijen

If you’re overwhelmed by the vast number and types of optical features available to add security to identity documents, you’re not alone. In this paper, a group of experts from the Secure Identity Alliance (SIA) clarifies the options—and when and how to apply them. The paper was first presented by the SIA at the Optical & Digital Document Security (ODDS) 2024 conference in Lisbon, Portugal and published as a series at Keesing.

Sight is our most important sense. The human eye is a complex sensor, backed by the vast processing power of the human brain, accounting for up to 60% of its activity1. Indeed, even for the smartphone-toting primate of the 21st century, seeing is still believing. It is therefore no surprise that optical features play a primordial role in authenticating all manner of things including banknotes, certificates and of course identity documents.

Advances in fabrication technology and, especially, its’ increasingly widespread availability have driven the development of optical features in the past twenty years. Where once holograms and a few specialty inks dominated the optical feature market, now stand a bustle of technologies based on plasmon resonance, liquid crystals, micro-lenses and more; adding to a growing halo of acronyms and confusing terminology.

Starting from the basic principle of Optical Variability, this article aims to cut through the haze and provide an impartial review of the state of the art for informed but non-technical persons involved in ID document specification and design. After a brief overview of the fundamental physical and chemical phenomena which underpin all contemporary optical features, we categorize and describe the different types of optical security elements which can currently be applied to ID documents, whether by print, by overlay, by personalization or during the lamination process. This article focuses exclusively on features that can be authenticated by the naked eye with the occasional assistance of an independent light source (smartphone “white,” UV or IR). In technical terms, our scope is limited to Level 1 and some Level 2 – call them level one-and-a-half – features.

We also briefly address the subject of “perception,” how “good enough is close enough” as far as the counterfeiter is concerned and how a judicious selection of optical features best protects a document.