Multifocal glass spectacle lenses - with insert for close vision prepd. by welding several glass blanks together

摘要

Multifocal glass spectacle lenses are made, consisting mainly of a base glass, and =1 other part (I) for close vision with different optical properties to glass and a semicircular periphery. A glass blank which will form (I) is joined by melting to a 2nd glass blank which is made of the base glass, to form an insert; the insert is ground and then located in a cavity in the base glass, followed by another grinding operation. Less glass is needed to make the lenses, lower joining temps. can be used, and less furnace space is required for joining, as compared with conventional mfg. methods. At least the base glass can be phototropic.