Fitzpatrick, Cella, Harper & Scinto
Process for thin film formation by sputtering
 A process is provided for forming a thin film having refractive index thereof varying continuously or stepwise in a thickness direction. The process comprises sputtering in a vacuum chamber by introducing, during film formation, at least two kinds of gases selected from a nitrogen-containing gas, an oxygen-containing gas, and a fluorine-containing gas with the flow rate ratio of the gases varied continuously or stepwise. This process enables variation of the refractive index in the thickness direction, simply without difficulty. 
Canon Kabushiki Kaisha
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inventional inventional inventional
Kenji Hidehiro Ryuji Minoru Yasuyuki
Ando Kanazawa Biro Otani Suzuki