A security device 10 comprises a substrate 12; a relief structure 20 on a first side 12a of the substrate; and a colour filter 30. The relief structure being a reflective or refractive light-redirecting relief structure configured to redirect light from a light source L to thereby project a caustic image CI. The colour filter is configured to overlap in use at least part of the relief structure and comprises one or more at least semi-transparent materials. At least one of the materials transmitting only a subset of visible light wavelengths corresponding to a respective non-white colour. The caustic image projected by the security device exhibits one or more colour(s) when the security device is illuminated with white light. The security device may be configured such that the caustic image projected by the security device when illuminated with white light exhibits a multi-tonal and/or multi-coloured appearance. The light transmitted by the colour filter varies in colour and/or tone between laterally offset regions of the colour filter.


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    Title :

    Security device and method of manufacture thereof


    Publication date :

    2022-01-19


    Type of media :

    Patent


    Type of material :

    Electronic Resource


    Language :

    English



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