Overhead projector
US5317350A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 19, 1993 |
| Grant date | May 31, 1994 |
| Priority date | — |
| Expiry date | Mar 19, 2013 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S353/04
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An overhead projector has a stage on which original material is placed. The stage has a Fresnel mirror. An electrostatic attracting structure is integral with the Fresnel mirror. The attracting structure includes a conductive membrane of ceramic and a resinous dielectric/protective layer. The conductive membrane consists of a pair of comb-shaped electrodes, which interfinger in coplanar fashion, and are covered by the dielectric/protective layer for insulation and protection. A power supply device applies a high voltage of direct current to the electrodes. The original material is attracted electrostatically by the electrodes, and can be kept flat on the stage. In a preferred embodiment, the power supply device incorporates a self-starting blocking oscillator, which is adapted to boost the voltage sufficiently for electrostatic attraction.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.