| 摘要 |
PURPOSE:To enhance performance of a Fresnel lens by forming an optical glass into a Fresnel mold, and when needed, subjecting the surface to transmittance raising treatment. CONSTITUTION:Molten optical glass is poured into the mold of the Fresnel lens, and molded by cooling, or heat softened optical glass is molded with said mold to prepare a Fresnel lens 1. The Fresnel lens thus formed, when needed, is coated with vacuum evaporation deposition, or the like to raise transmittance. Since the optical glass is formed by molding, a glass material high in refractive index can be used and an inclination angle alpha can be made smaller than that of a plastic molded lens, formation using a mold can be made easy. The use of glass materials having various Abbe numbers facilitates the correction of color aberration, too, thus permitting enhancement of Fresnel lens performance. |
