Optiks™

Type

Diffractive — super-wide windowed security thread incorporating a thin-film interference filter structure, fully embedded in banknote paper but exposed through a clear see-through window. Recipient of the 2013 Queen's Award for Enterprise: Innovation for the thread and its associated paper-making process.

Overview

Optiks™ was a super-wide (typically 18 mm) security thread for paper banknotes, developed by De La Rue and introduced commercially in the late 2000s. Its defining innovation was the combination of an unusually wide thread with a fully transparent see-through window in the banknote substrate, achieved via a proprietary paper-making process developed alongside the thread itself. When held up to the light, the embedded thread became fully visible through the transparent window, displaying repeating images and microtext that delivered a striking and intuitive Level 1 authentication cue. The technology won De La Rue the Queen's Award for Enterprise: Innovation in 2013, recognising both the thread itself and the associated papermaking process. The technical lineage traces back to thin-film interference filter research by the National Research Council of Canada in the 1970s and to subsequent Bank of England work proposing dichroic-filter security threads viewed through superposed windows. As reported in Currency News (February 2026), Optiks has now been discontinued as a security feature; existing deployments remain in circulation, and De La Rue is migrating issuers using Optiks to alternative holographic stripe solutions incorporating its FILIGREE™, DEPTH™ and PUREIMAGE™ features.

Technology & Effects

The Optiks thread combined a wide carrier (18 mm in commercial deployments, much wider than conventional 1.5–4 mm windowed threads) with a thin-film optical structure descended from the dichroic-filter principle. Earlier dichroic-filter security threads were built on three-layer metal/dielectric constructions producing a colour in reflection and a complementary colour in transmission. Optiks extended this architecture to a much wider format and combined it with repeating image and text elements visible across the full width of the thread when the banknote was held against the light. The breakthrough that made commercial Optiks possible was not the thread alone but the paper-making process developed in parallel — a method that allowed the thread to be embedded within the full body of the paper while leaving a fully transparent window region above it, rather than the partial windowing characteristic of conventional embedded threads. Effect type: Diffractive (acknowledging the thin-film interference origin); the feature is most accurately classified as an interference-filter windowed thread rather than a holographic or micro-optic one.

Form Factors & Application

Optiks was supplied as a wide windowed security thread for paper banknotes, embedded during the paper-making stage at De La Rue's paper mills (Portals De La Rue from 2018 onwards). The 18 mm thread width is a defining commercial parameter — significantly wider than conventional security threads — and the associated transparent-window paper-making process was an essential complementary technology. Optiks was a paper-substrate feature; it was not offered for SAFEGUARD® polymer banknotes, which have other transparent-window technologies available natively from the substrate construction. Specific implementations could vary the thread width, image content and text within the supplier-controlled construction limits.

Security Levels

• Level 1 (public): A wide, distinctive thread visible in reflection across the front of the banknote, with repeating images and denomination text fully visible when the banknote was held up to the light through the transparent window. The unusually wide format and the see-through window made the feature instantly recognisable to the public.
• Level 2 (cash handler): The thin-film interference structure produced different colour responses in reflected and transmitted light. The combination of wide-thread embedding and the associated paper-making process for the transparent window represented a significant industrial barrier to counterfeiting — neither component was reproducible without specialist equipment.

Notable Deployments

• Iceland — 10,000 króna banknote (Central Bank of Iceland, issued 31 October 2013): high-value note dedicated to the Icelandic poet, scholar and naturalist Jónas Hallgrímsson. The 18 mm Optiks thread carried repeating flower images and the text "10000 KRÓNUR" visible through the see-through window.
• Solomon Islands — $50 banknote (Central Bank of Solomon Islands, issued September 2013): first issuing authority to deploy Optiks in the 2013 calendar year.
• Solomon Islands — $100 banknote (Central Bank of Solomon Islands, issued 10 April 2015): second denomination in the new banknote family; same Optiks super-wide windowed thread.
• Seychelles — 500 rupee banknote (Central Bank of Seychelles, 2016 issue): Optiks thread laid over a transparent oval window displaying the Seychelles vinegar fly. Replaced in the 2026 update with a holographic stripe combining FILIGREE™, DEPTH™ and PUREIMAGE™, depicting a Hawksbill turtle.
• De La Rue "Lighthouse 200" promotional/house note (2007): early showcase of the Optiks thread outside circulating issues.