Diffraction grating and method of manufacture
US5428479A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 12, 1994 |
| Grant date | Jun 27, 1995 |
| Priority date | — |
| Expiry date | Jul 12, 2014 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB42D2035/34
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
A diffraction grating providing an optically variable image includes a pixellated diffraction grating in which each pixel is an individual optical diffraction grating so that the pixellated diffraction grating when illuminated generates an optically variable image. In another aspect the grating in some or all of the pixels of a diffracting grating formed by a regular matrix of pixels is arranged such that a reproduction of the grating by reflection contact printing generates a zero-order pattern which is grossly flawed by Moire or Talbot fringe effects. A method of forming the diffraction grating includes producing a counterpart pixellated diffraction grating of a substantially optically invariable image wherein each pixel of the optically invariable image is maped to a respective pixel of the pixellated diffraction grating. Each grating pixel is an individual optical diffraction grating of the associated pixel in the optically invariable image, so that the pixellated diffraction grating when illuminated generates an optically variable reproduction of the optically invariable image.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.