Spectacle lens measuring appts. - has two reference surfaces spaced apart to compensate for distance between lens and eye

摘要

The apparatus has two reference surfaces approximately 12 mm apart. A document may be used, accommodating two datum points, and with a centre line and two marks approximately 60 mm apart, along a line perpendicular to this centre line, and forming the first reference surface. The marks can be temporarily covered by bosses approximately 12 mm thick, and forming the second reference surface. An additional rule can be provided, with two bosses similar to those mentioned above and capable of being temporarily attached to the frame in which the lenses are to be fitted.