GB603381A - Method and apparatus for making lenses and like optical devices - Google Patents

Abstract

603,381. Forming crystal optical devices by solvent action. FARNSWORTH TELEVISION & RADIO CORPORATION. Oct. 19, 1945, No. 27497. Convention date, Oct. 14, 1944. [Class 124] In a method of forming lenses and like optical devices from soluble materials, a protective coating is formed periodically on the surface of a soluble blank which is brought into contact with a mould which is the negative of the device to be formed and which removes the protective covering from the high spots of the blank, the blank and mould are then separated and the exposed portions of the blank are subjected to the action of a solvent. As shown, a sodium chloride crystal blank 5, which may be partly shaped, is supported in a holder 3 attached by a spider 2 to a container 1 for water. A piston 10 supports, above the blank, a mould 19 which may be kept cold by a refrigerating mixture 17A in a container 16 to which the mould is attached, and, below the blank, a quantity of Wood's metal 22 which may be kept molten by an induction coil 24 so that when the piston is raised, e.g. by a cam 14, the Wood's metal mav flow over the surface of the blank. On lowering the piston, a thin layer 6 of metal remains on the surface of the blank so that when the mould 19 is pressed on to the blank the metal is removed from those points where the mould touches and, due to the coldness of the mould, it is solidified. On raising the piston again, water is allowed to flow over the blank and dissolve a small quantity of the exposed sodium chloride. This cycle is continued until the blank assumes the shape of the mould, at which time the downward movement of the mould is limited by the adjustable stops 20A. The mould may have the form of a segment of the device, Fig. 6 (not shown). In a modification, Fig. 5 (not shown), the blank holder may be moved into contact with the mould and then into the solvent. The protective covering may be wax which is melted by a hot air blast, or may be an amalgam, e.g. silver amalgam made molten by the addition of mercury.