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Endoscope objective lens

  • US 20040160682A1
  • Filed: 02/10/2004
  • Published: 08/19/2004
  • Est. Priority Date: 02/14/2003
  • Status: Active Grant
First Claim
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1. An endoscope objective lens having a three-group, three-lens element construction, comprising, in order from the object side:

  • a first lens element of negative refractive power and either a meniscus or a plano-concave shape with its concave surface on the image side;

    a stop;

    a second lens element of positive refractive power and a plano-convex shape with its convex surface on the image side;

    a third lens element of positive refractive power and a plano-convex shape with its convex surface on the object side;

    wherein the stop positioned on or in contact with the object-side surface of the second lens element; and

    the following conditions are satisfied 2.00<

    |f1/f|<

    3.00 2.50<

    |f1/D2|<

    7.50 |D3/R4|<

    1.00 where, f1 is the focal length of the first lens element, f is the focal length of the endoscope objective lens, D2 is the on-axis spacing between the first lens element and the second lens element, D3 is the center thickness of the second lens element, and R4 is the radius of curvature of the image-side surface of the second lens element.

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