| 摘要 |
PURPOSE: To provide an imaging lens in which various aberrations are satisfactorily corrected, which can be manufactured at a low cost and which has an optical length of 10 mm or less. CONSTITUTION: The pickup lens is constituted by arranging, in order from an object side, a first lens L1 having a meniscus shape with a concave surface turned to the object side and having negative refractive power, an aperture diaphragm S, a second lens L2 having convex surfaces turned to both sides and having positive refractive power, a third lens L3 having concave surfaces turned to both sides and having negative refractive power and a fourth lens L4 having convex surfaces turned to both sides and having positive refractive power. Further the image pickup lens satisfies the following conditions: (1) +5.0<(r2+r1)/(r2-r1)<+7.0 (2) 0.15f<d1<0.3f wherein r1 is radius of curvature near an optical axis of an object side face of the first lens(radius of curvature on the axis), r2 is radius of curvature near an optical axis of an image side face of the first lens(radius of curvature on the axis), d1 is wall thickness of the first lens and f is a focal distance of a whole system.
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