| 摘要 |
PROBLEM TO BE SOLVED: To realize a high-performance lens system made bright and having a wide viewing angle while realizing the reduction of cost and the shortening of entire length with the reduced number of lenses. SOLUTION: The lens system is constituted by disposing a 1st meniscus lens G1 turning its concave surface to an object side, having an aspherical surface at least as one surface and made of plastic material, a 2nd lens G2 turning its convex surface to the object side and made of glass material, and a 3rd meniscus lens G3 turning its concave surface to the object side, having an aspherical surface at least as one surface and made of plastic material in order from the object side, and satisfies following conditional expressions (1) to (3).Δνshows a difference between the Abbe number of the 1st lens G1 and that of the 3rd lens G3, N2 shows the refractive index of the 2nd lens G2, andν2 shows the Abbe number of the 2nd lens G2. (1) ¾Δν¾>23, (2) N2>1.6 and (3)ν2>50. COPYRIGHT: (C)2005,JPO&NCIPI
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