Optical device
First Claim
1. An optical device comprising a holographic diffractive structure comprising at least two discrete linear regions arranged to replay in response to white light illumination a visual holographic optically variable image comprising a plurality of visually discernable linear graphical elements corresponding to the at least two discrete linear regions, wherein the graphical elements are located at or near the physical plane containing the holographic diffractive structure, and arranged to replay in response to coherent light illumination a plurality of secondary covert images corresponding to the at least two discrete linear regions wherein the secondary covert images are visible to an observer when imaged at a separate image plane away from the physical plane containing the holographic diffractive structure, the plurality of secondary covert images being arranged to be non-visible under white light illumination, and wherein the secondary covert images are reconstructed at different positions at their image plane.
1 Assignment
0 Petitions
Accused Products
Abstract
An optical device for security and anti-counterfeit applications comprises a holographic diffractive structure (8) that generates a holographic optically variable image by diffraction that consists of at least two separate substantially co-located linear regions that generate in response to white light illumination a visually observable holographic image consisting of at least two defined graphical elements and which generates in response to coherent illumination (1) at least two covert images (5, 6, 7) focussed at a separate image plane a distance away from the real physical plane of the device, each covert image (5, 6, 7) corresponding to the replay from one of the linear regions, each covert image (5, 6, 7) being separated on its image plane from the adjacent covert image (5, 6, 7) by at least its own dimensions.
51 Citations
29 Claims
- 1. An optical device comprising a holographic diffractive structure comprising at least two discrete linear regions arranged to replay in response to white light illumination a visual holographic optically variable image comprising a plurality of visually discernable linear graphical elements corresponding to the at least two discrete linear regions, wherein the graphical elements are located at or near the physical plane containing the holographic diffractive structure, and arranged to replay in response to coherent light illumination a plurality of secondary covert images corresponding to the at least two discrete linear regions wherein the secondary covert images are visible to an observer when imaged at a separate image plane away from the physical plane containing the holographic diffractive structure, the plurality of secondary covert images being arranged to be non-visible under white light illumination, and wherein the secondary covert images are reconstructed at different positions at their image plane.
Specification