Projection type lensmeter
US4564291A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 10, 1980 |
| Grant date | Jan 14, 1986 |
| Priority date | — |
| Expiry date | Dec 10, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01M11/0228
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A projection type lensmeter in which the target image for measuring the refractive power of a lens is projected on a screen and the projected image is magnified and observed through a magnifying observation optical system including a collimator lens having a focal length f.sub.1 adapted to collimate light projected from the target image, and a projection lens having a focal length f.sub.2 adapted to project light from the target image to the screen. The magnifying observation optical system has an effective diameter .phi. and a magnification m.sub.2. The focal lengths f.sub.1 and f.sub.2, the effective diameter .phi., and the magnification m.sub.2 satisfy the following relations: EQU 25 mm.ltoreq.f.sub.1 .ltoreq.30 mm EQU 409 mm.ltoreq.f.sub.2 .ltoreq.600 mm EQU 60 mm.ltoreq..phi..ltoreq.70 mm EQU 1.25.ltoreq.m.sub.2 .ltoreq.1.83. The overall magnification of the lensmeter is 30 or greater.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.