Light-diffracting binary grating structure
US6906861B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 2, 2001 |
| Grant date | Jun 14, 2005 |
| Priority date | — |
| Expiry date | Nov 2, 2021 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S428/916
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
A light-diffractive binary grating structure has a microscopic mesa structure (2) whose plateaux (5) are separated by valleys (4) of substantially rectangular cross-section, wherein the arrangement of the valleys (4) is periodically repeated. Within a period (T) of the mesa structure (2) at least N valleys (4) separate the plateaux (5), N being an integer and greater than 2. The mesa structure (2) is an additive superimposition of N phase-shifted rectangular structures which have the same period (T) of the mesa structure (2). Each of the rectangular structures has a phase shift such that the plateaux (5) of the one rectangular structure fall into the valleys (4) of the N−1 other rectangular structures. In addition the resulting mesa structure (2) has only a single valley between two plateaux (5), which is of a width greater than a seventh of the period (T). The binary grating structures are suitable for use in optically diffractive security elements as the binary grating structures cannot be copied with holographic means.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.