Armstrong, Westerman, Hattori, McLeland & Naughton
Process for producing rod glass having refractive index distribution
 A process for producing a rod glass having a refractive index distribution, which includes pressing a glass at a temperature below the glass transition temperature to form a glass having a density increased towards the surface layer thereof, or alternatively includes heating a glass at a temperature around the transition temperature at the lowest to prepare glass having a uniformly enhanced density and heating the treated glass under a pressure lower than the applied pressure at a temperature below the glass transition temperature of the glass to prepare a glass having a density increased towards the central portion. 
Agency of Industrial Science and Technology
C C C
C03B C03B C03B
inventional inventional inventional
Jun Saburo Kenichi Naoyuki Kohei Hiroshi Makoto Isao
Matsuoka Kose Kinugawa Kitamura Fukumi Yamashita Kinoshita Kondoh