| 摘要 |
PURPOSE:A glass cylinder in which its refractive index changes from the center toward the periphery is heated in a mold at elevated temperature and simultaneously pressed downward to make it possible to produce a flat plate lens or a lens built in with a flat plate lens. CONSTITUTION:A cylindrical glass 1 whose refractive index changes larger or smaller from the center toward the periphery is placed in a mold 6 made of graphite, alumina or molybdenum and heated at about 1,800 deg.C in the furnace 8 in an inert gas atmosphere and simultaneously it is pressed with the plate 7 at a pressure P. The cylinder becomes half-melted and formed into a flat plate lens in the mold. Further, the resultant flat lens 3 is placed between 2 half-circular rods of quartz glass 9 to prepare a basic material for conjugate lens 10, which is heated at 2,000 deg.C in an electric furnace 11 and drawn downward to give a lens of small diameter. |
