Holographic optical element and method of forming thereof

A method of forming a holographic optical element, the method comprising:

• forming a hologram portion comprising a plurality of groups of unit regions, each group of unit regions of the hologram portion being configured to produce a respective holographic image under a respective light illumination having a respective predetermined wavelength;
• and
• forming a colour filter portion on the hologram portion, the colour filter portion comprising a plurality of groups of unit regions, each group of unit regions of the colour filter portion being arranged on a corresponding group of the plurality of groups of unit regions of the hologram portion,
• wherein said forming the colour filter portion comprises spatially arranging the plurality of groups of unit regions of the colour filter portion to form a predetermined colour image.

An article having optical security incorporated therein, the article comprising:

• a substrate;
• and
• one or more holographic optical elements formed on the substrate for providing the optical security, each of the one or more holographic optical elements comprising:
• a hologram portion comprising a plurality of groups of unit regions, each group of unit regions of the hologram portion being configured to produce a respective holographic image under a respective light illumination having a respective predetermined wavelength;
• and
• a colour filter portion formed on the hologram portion, the colour filter portion comprising a plurality of groups of unit regions, each group of unit regions of the colour filter portion being arranged on a corresponding group of the plurality of groups of unit regions of the hologram portion,
• wherein the plurality of groups of unit regions of the colour filter portion is spatially arranged to form a predetermined colour image.