Teaching or amusement apparatus
US4627819A · kind A · utility
72Cited by
2References
8Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Oct 31, 1985 |
| Grant date | Dec 9, 1986 |
| Priority date | — |
| Expiry date | Oct 31, 2005 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S283/901
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A printed substrate has areas printed in a screen of carbon black ink dots and other areas printed in a corresponding screen of infrared transparent ink dots, whereby, the presence of the carbon black ink dots is made visually undetectable but can readily be detected by an infrared emitter and detector.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.