Patent ID: 7027231

Claim:
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 image-side surface of the third lens element makes contact with an end surface of an optical fiber bundle, a surface of an image detector, or a cover glass for an image detector; the stop is positioned on or in contact with the object-side surface of the second lens element; and the following conditions are satisfied 2.00<| f 1/ f|< 3.00 2.50<| f 1/ D 2|<7.50 | D 3/ R 4|<1.00 where, f 1 is the focal length of the first lens element, f is the focal length of the endoscope objective lens, D 2 is the on-axis spacing between the first lens element and the second lens element, D 3 is the center thickness of the second lens element, and R 4 is the radius of curvature of the image-side surface of the second lens element.