Blank for eyeglass lenses having ellipse-like edge curves and means and method for selecting

US4630906A · kind A · utility

Assignee

• Carl Zeiss Stiftung · DE

Inventors

• Hubert Bammert · Aalen, DE
• Hans Lahres · Aalen, DE
• Egon Mosch · Oberkochen, DE

Key dates

• Filing date: May 11, 1983
• Grant date: Dec 23, 1986
• Expiry date: May 11, 2003

Classification

• Technology area (CPC G): Physics
• CPC primary: G02C13/005
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

In eyeglass lenses which have a center thickness greater than the edge thickness in at least one cross section and different dioptric powers in different sections, round-blanks lead to ground eyeglass lenses which are of relatively high weight. The weight of such an eyeglass lens, and thus its center and edge thickness, is reduced if the blank is imparted a substantially elliptical edge curve. In order to reduce cost and expense, the dioptric range of the series of eyeglass lenses is divided into a predetermined number of ranges and a given type of edge curve is associated with each range. Within each range there are a number of centrally similar edge curves of different height and width for such type of edge curve. All edge curves are so selected that the eyeglass lens blanks provided with them have an edge thickness over the elliptical portion of their periphery which varies by less than 1.5 mm. An easily operated device is provided in order to select the optimal blank for mounting in an eyeglass frame.