| 摘要 |
PURPOSE:To obtain the titled mold readily that can produce a multifocal Fresnel lens whose pitch is short, by heat-shrinking a Fresnel lens surface formed on a synthetic resin plate that is biaxially stretched with the draw ratios in the longitudinal and lateral directions being different, and using the resulting Fresnel lens surface as a matrix. CONSTITUTION:First, for example, an riginal plate 1A of a thermoplastic synthetic resin is stretched under heating to produce a stretched plate 1B whose draw ratios in the longitudinal and lateral directions are different, and a Fresnel lens surface is formed on the stretched plate 1B to obtain a Fresnel lens 1C. The Fresnel lens 1C is heat-treated to shrink the Fresnel lens surface of the stretched part to obtain a multifocal Fresnel lens plate 1D. Finally, using the multifocal Fresnel lens plate 1D as a matrix, the multifocal Fresnel lens surface is transferred by electroforming or the like to obtain the aimed mold M. |
