| 摘要 |
PROBLEM TO BE SOLVED: To obtain an inexpensive super wide angle lens which is constituted of a small number of lenses and has a wide angle of view and where aberration other than distortion aberration is excellently compensated by arranging a 2nd lens having negative meniscus shape as an aberration compensating lens between a 1st lens being a divergent lens and a 3rd lens being an image- formation lens. SOLUTION: The thick negative meniscus lens whose convex surface is turned to an object side is inserted between the 1st lens L1 and the 3rd lens L3 as the 2nd lens L2, and constituted so that the dispersion of the 2nd lens L2 may be larger than the dispersion of the 1st lens L1 and that of the 3rd lens L3. Then, a condition, that is, an expression 0.5<ν2r3/(ν1r2)<0.8 is satisfied. In the expression, r2 shows the radius of curvature of the surface of the 1st lens L1 on an image side and r3 shows the radius of curvature of the surface of the 2nd lens L2 on the object side.ν1 shows the Abbe number of the 1st lens L1 andν2 shows the Abbe number of the 2nd lens L2. Thus, the inexpensive super wide angel lens is realized by the constitution of only three lenses.
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