Abstract: A method and apparatus for making cylindrical glass preforms with convex, optical quality convex end surfaces is taught. A glass ball preform is placed on a heated lower platen. The temperature of the glass ball preform is raised to a temperature above the glass transition temperature of the glass ball preform. The glass ball preform is engaged with an upper platen. At least one of the upper platen and the lower platen is moved vertically to cause the gap between the upper platen and the lower platen to narrow to a predetermined dimension. Simultaneously, at least one of the upper platen and the lower platen is moved horizontally relative to the other platen to cause the glass ball preform to roll between the upper platen and the lower platen and form a cylindrical preform having a predetermined diameter, the cylindrical preform having convex, optical quality end surfaces.

Abstract: A method and apparatus for making cylindrical glass preforms with convex, optical quality convex end surfaces is taught. A glass ball preform is placed on a heated lower platen. The temperature of the glass ball preform is raised to a temperature above the glass transition temperature of the glass ball preform. The glass ball preform is engaged with an upper platen. At least one of the upper platen and the lower platen is moved vertically to cause the gap between the upper platen and the lower platen to narrow to a predetermined dimension. Simultaneously, at least one of the upper platen and the lower platen is moved horizontally relative to the other platen to cause the glass ball preform to roll between the upper platen and the lower platen and form a cylindrical preform having a predetermined diameter, the cylindrical preform having convex, optical quality end surfaces.

Abstract: A method for fabricating a mold tool for molding optical elements is taught which comprises heating a mold tool blank made from a vitreous material to a temperature above the glass transition temperature of the vitreous material; generating an axial viscosity gradient in the mold tool blank; pressing a punch into an optical quality mold surface of the mold tool blank, the punch including a pressing surface with a predetermined geometry for forming an optical feature; cooling the mold tool blank to a temperature below the glass transition temperature of the material; and removing the punch from the mold tool blank thereby creating the optical feature in the optical quality mold surface. The axial viscosity gradient is achieved by creating an axial thermal gradient.

Abstract: A method for making working mold tools for use in a compression molding process for molding optical glass elements from high temperature glasses having Tg's in the range of from about 400° C. to about 850° C. An yttria aluminosilicate glass is fabricated by traditional melting and casting processes to thereby make an amorphous base material having a minimum apparent viscosity of 1015 poise at the temperature at which the optical glass elements are to be molded. A mold preform is made from the base material. A first surface figure for the optical element to be molded with the working mold tool is defined. A second surface figure for a master mold tool and a third surface figure for the working mold tool are computed based upon the first surface figure and the coefficients of thermal expansion of the optical element, the master mold tool, and the working mold tool, the temperature at which the working mold tool is molded, and the temperature at which the optical element is to be molded.

Abstract: A process for perforating a urethane anti-static filled coating of a metallic drum core with clean holes of substantially uniform size and shape. The process includes placing an electrically conducting absorbing tape between the urethane coating and the metallic core to absorb the urethane melt generated by the laser cutting process. The coated core after being placed in a fixture, is subjected to a laser beam generated by a pulsed CO2 gas laser that passes through a set of rotary optics capable of spinning the beam in circles as it passes through a gas jet/nozzle assembly before beam impact with the coating. Through the use of conductive tape a good ground may be maintained between the anti-static filled coating and the metallic core to prevent static build up on the outer surface of the drum.