| 摘要 |
PURPOSE:To obtain a high-precision optical glass element free from surface defect on optical surface, by feeding glass gob to a molding bottom mold through a conduit set in a slant or curved state based on a pair of molding molds and press moldings. CONSTITUTION:Temperature of molten glass 2 in a crucible 4 and temperature of discharged glass from a nozzle 14 are precisely controlled by heaters 3 and 5. On the other hand, temperature of a molding bottom mold 9 receiving optical surface 13 and nonoptical surface 12 is precisely controlled. Then a given amount of discharged glass is cut 6, glass gob 8 having a cutting trace 15 on the top is prepared, introduced through a conduit 7 set in a slant state from the nozzle 4 to the bottom mold 9 to the position of the bottom mold 9 and sent to the optical surface 13 of the bottom mold 9. In the operation, the cutting trace 15 of the gob 8 is transferred to the end part in the direction of the horizontal plane. Then, in the above state, the gob 8 is immediately press molded by a molding top mold 11 and the bottom mold 9 and annealed to give a high- precision optical glass element having the trace 15 in the nonoptical surface and the optical surfaces to which the shapes of the molds 11 and 9 are accurately transferred, having neither cutting trace nor orange mark.
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