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Single focus lens

  • US 7,408,725 B2
  • Filed: 09/28/2006
  • Issued: 08/05/2008
  • Est. Priority Date: 09/29/2005
  • Status: Active Grant
First Claim
Patent Images

1. A single focus lens comprising:

  • in order from an object side of the single focus lens,a first lens having positive power and having a convex surface on the object side;

    a second lens of a negative meniscus lens and having a concave surface of the object side on its paraxial axis; and

    a third lens of an aspherical lens having a convex surface on the object side on its paraxial axis,wherein the single focus lens satisfies conditions (1) to (7);


    0.6<

    f
    1/f<

    1.5 



    (1)
    69<

    ν

    dA




    (2)
    24<

    ν

    dB
    <

    32 



    (3)
    NdA<

    1.55 



    (4)
    1.48<

    NdB
    <

    1.65 



    (5)
    L/D<

    1.8 



    (6)
    0.30<

    RA/f
    <

    0.40 



    (7)whereinf represents a focal length of the single focus lens;

    f1 represents a focal length of the first lens;

    ν

    dA represents Abbe number of the first lens;

    ν

    dB represents Abbe number of the second lens;

    NdA represents a refractive index at the d-line of the first lens;

    NdB represents a refractive index at the d-line of the second lens;

    RA represents a paraxial radius of curvature of an object-side surface of the first lens;

    L represents a distance along an optical axis between the object-side surface of the first lens and an image-forming position; and

    D represents a maximum image height.

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