Composite electromagnetic lens with variable focal distance
US5038045A · kind A · utility
5Cited by
1References
3Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Mar 7, 1990 |
| Grant date | Aug 6, 1991 |
| Priority date | — |
| Expiry date | Mar 7, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/141
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The lens is formed by the association of two electromagnetic lenses sharing one and the same magnetic circuit crossed by one and the same central channel. The first lens is a shielded lens and has an annular gap at one of its ends. This annular gap cuts the central channel along a direction the plane of which is perpendicular to the optical axis. The second lens is a single-pole lens surrounding the annular gap of the first lens. It has an annular gap demarcated by two lips, the walls of which have shapes generated by revolution around the optical axis. Induction coils enable the magnetic flux of the gaps to be made to vary.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.