Digital focimeter and method

US4370058A · kind A · utility

Assignee

• Carl Zeiss Stiftung · DE

Inventors

• Otto Trotscher · Aalen, DE
• Horst Stacklies · Greding, DE
• Meinrad Machler · Oakville, CA

Key dates

• Filing date: Jul 29, 1980
• Grant date: Jan 25, 1983
• Expiry date: Jul 29, 2000

Classification

• Technology area (CPC G): Physics
• CPC primary: G01M11/0228
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The invention contemplates a method and apparatus for automatically performing digital measurement of vertex dioptric powers in the principal planes of toric spectacle lenses. A spectacle lens is transilluminated by a parallel-ray bundle of monochromatic light which, after passage through the spectacle lens, is limited by an annular stop in the immediate vicinity of the vertex of the spectacle lens. A beamsplitter divides the light which passes through the spectacle lens into two individual light beams. As a result, an elliptical figure is projected to two planes, in each of which is located at least one self-scanning diode line. Diode-line scanning develops intercepts of the projected elliptical figure, and from the positional locations of these intercepts (in relation to the local intercept of the optical axis) a computer performs a selected one of a plurality of evaluation procedures (a) to develop projected-figure reorientation or displacement as necessary to permit it then (b) to perform a desired measurement evaluation. Provision is made for automatic detection of whether a given spectacle lens is or is not within the currently set range of measurement capability and, if dete…