| 摘要 |
The present invention relates to an imaging lens with an F-number in the range 2.0 to 4.0, configured from only two lenses, with a short lens optical length, and with sufficiently high image contrast so that sharp images are obtained. The imaging lens is configured by positioning, in order from an object side to an image side, an aperture diaphragm, a first lens, a second diaphragm, and a second lens, satisfying the following conditions. The first lens and second lens are both meniscus-shaped with convex surface facing the object side, and have positive refractive power. <?in-line-formulae description="In-line Formulae" end="lead"?>0.3<f<SUB>1</SUB>/f<SUB>2</SUB><1.0 (1) <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.4<b<SUB>f</SUB>/f<0.5 (2) <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>1.0<d/f<1.3 (3) <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>0.12<D<SUB>2</SUB>/f<0.30 (4) <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>2.0<F<SUB>no</SUB><4.0 (5) <?in-line-formulae description="In-line Formulae" end="tail"?> Here f is the combined focal length of the imaging lens, f<SUB>1 </SUB>is the focal length of the first lens, f<SUB>2 </SUB>is the focal length of the second lens, b<SUB>f </SUB>is the distance (in air) from the image-side surface of the second lens to the image plane, d is the distance (in air) from the object-side surface of the first lens to the image plane, D<SUB>2 </SUB>is the interval between the first lens and the second lens, and F<SUB>no </SUB>is the F-number.
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