| 摘要 |
PURPOSE:To produce small sized, light weight microfresnel lens in large amt. and at low cost by forming in a parent glass material ring zones causing variation of refractive index or quality of material by the MCVD process (modified chemical vapor deposition process) with desired ratios of radii of the ring zone, stretching the glass parent material by heating, then cutting the stretched glass parent material in round slices at a prescribed dimension. CONSTITUTION:A rod 10 of a glass parent material having ring zones A1-A4 corresponding to a zone pattern of a Fresnel lens is formed utilizing the MCVD process. After stretching the rod 10 to a desired diameter d by heating, it is cut in round slices with a specified thickness to prepare thus microfresnel lenses. Since the thickness of a dopant to be deposited internally by the vapor deposition in the stage of production of an optical fiber parent material by the MCVD process can be regulated with high precision and to an extremely fine thickness, the amt. of the dopant is controlled exactly and ring zones having optional refractive index depending on the material are formed exactly. By this process, Fresnel lenses having small size and high NA value are produced in large amt. |
