Open frame sight viewfinder
US4891658A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 30, 1989 |
| Grant date | Jan 2, 1990 |
| Priority date | — |
| Expiry date | Jan 30, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B13/04
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An open frame sight viewfinder for a photographic camera comprises an aiming or target ring positioned forward of a correspondingly shaped viewing aperture. The aiming ring is encircled by a relatively narrow annular zone of light rays, including the extreme rays, which pass through the viewing aperture, and it has an outer diameter which is greater than the viewing diameter of the viewing aperture. Consequently, when the camera is correctly aimed at the subject, the aiming ring appears to be concentrically located within the viewing aperture although separated from the periphery of the viewing aperture by a narrow band of ambient light. However, when the camera is incorrectly tilted relative to the subject, the aiming ring appears distorted within the viewing aperture and quickly eclipses a section of the narrow light band.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.