| 摘要 |
PURPOSE:To suppress the occurrence of astigmatism and distortion aberration, by dividing the surface of a lens into a long-sight part, an intermediate part and a short-sight part by giving a degree of entry on a main meridian curve, and setting an angle made by a normal on the crossing line with a place being parallel to a place containing the main meridian curve. CONSTITUTION:Curves C1, C2 cross a main meridian curve M in a long-sight center A and a short-sight center B, and the refracted surface of a lens is divided into each area such as a long-sight part 51, an intermediate part 52 and a short-sight part 53. A section curve M1 by the surface being parallel to a place containing the main meridian curve M crosses the curves C1, C2 at points A1, A2, and varies an angle made by a normal of the refracted surface of the lens and the surface containing the main meridian curve M. That is to say, this angle is constant in the area of the long-sight part 51 and the short-sight part 53, and in the intermediate part area 52, it is varied by the same rule as a variation of curvature between the long-sight center A and the short-sight center B on the same main meridian curve M. In this way, astigmatism and distortion aberration are suppressed, and both static vision and dynamic vision are satisfied. |
