U.S. Philips Corporation

Petrus Heller

Jan Haisma

Cornelis J Potters

Udo K Biermann

Nicodemus Hattu

Johannes M Pasmans

Johannes H Angenent

Johan C Wijn

Petrus A Lemmens

A method of manufacturing lens elements, in which a glass preform heated to the softening temperature and an annular metal holder (3) enclosing the glass preform are arranged between the heated moulding dies (7,9) of a mould and are moulded in a pressing step into a lens element comprising a glass lens (21) and a ring (3) enclosing the glass lens and acting as a fitting. During moulding, the ring 3 forms together with the two dies (7,9) a quasi closed moulding cavity having an annular gap (15). During moulding, the ring (3) is expanded radially and a quantity of glass is pressed.

Method of manufacturing lens elements

Providing a transparent layer of an oxide of an element from group IVa of the Periodic Table, notably TiO.sub.2, by providing a substrate with a solution of a compound of the element which upon heating is converted into the relevant oxide, drying the film and heating the dried film so as to form the transparent layer of the oxide. The oxide thus obtained is a form having a comparatively low refractive index. By heating the product, after providing the film, rapidly to a temperature of above 700.degree. C., preferably above 1,000.degree. C., keeping it at this temperature for some time and then rapidly cooling it again, a modification having a higher refractive index (for example, for TiO.sub.2 rutile) is obtained.

Method of manufacturing a layer of an oxide of an element from group IVa

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Eindhoven, Netherlands

Petrus Heller