Patent ID: 11927785
Assignee: SINGAPORE UNIVERSITY OF TECHNOLOGY AND DESIGN
Field: Optics (Instruments)
Classification: CPC G  B | IPC B  G

Claim 19:
20. 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 collectively form a predetermined colour image thereon viewable under a white light illumination, and
wherein the light illuminations associated with the plurality of groups of unit regions of the hologram portion respectively, for producing the respective holographic images are laser illuminations and the respective predetermined wavelengths of the laser illuminations are different from each other.