Transparent sheets containing directional images and method for forming the same
US4691993A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 13, 1985 |
| Grant date | Sep 8, 1987 |
| Priority date | — |
| Expiry date | May 13, 2005 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K19/14
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A directional image is created in transparent sheeting comprising a monolayer of microlenses by forming deformations in at least some of the microlenses by irradiation with a laser beam which has a short pulse duration. The directional images may be formed in transparent sheeting which has been applied to a document as an overlay. When viewed under diffuse lighting conditions, the deformations appear as a dark image. The deformations may be formed so that when viewed under retroreflective conditions within a conical field the image is darker than the surrounding background, and when viewed under retroreflective conditions outside the conical field the image is brighter than the surrounding background.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.