| 摘要 |
PURPOSE:To manufacture easily a small-sized lens having high resolution by joining in one body a meniscus lens made of plastic and a positive lens made of glass, and specifying numerical relation between a radius of curvature and a refractive index of glass. CONSTITUTION:A meniscus lens L1 made of plastic and a positive lens L2 made of glass are joined in one body by a joining agent. The opposite side of a joint surface to the positive lens L2 of the meniscus lens L1 is made to form an aspherical surface of a radius of curvature r1, and a radius of curvature of the joint surface of the lens L1 and L2, a radius of curvature of an image point side of the lens L2, and a refractive index of the lens L2 are denoted as r2, r3 and n2, respectively, so that conditions of expressions I -III are satisfied among these numerical values. In such a way, a lens which is small in size and has a high resolution is manufactured easily and its price is reduced. It is suitable for reading out a CD, etc. |
