Objective lens for endoscopes

An objective lens for an endoscope which has an optical lens system including from the object end to the image end first, second and third optical lens elements L.sub.1 -L.sub.3 coaxially arranged at axial distances in a lens barrel and an aperture stop ring member disposed between said second and third optical lens elements for restricting light rays entering said optical system and positioning said second and third optical lens elements at a specified axial distance, said third optical lens element L.sub.3a and L.sub.3b cemented together, and said optical lens system being substantially described as follows:

• TABLE II ______________________________________ Radius of Axial Distance Element Curvature (mm) Between Surfaces N.sub.d .nu..sub.d ______________________________________ r.sub.1 = .infin. L.sub.1 d.sub.1 = 0.40 1.88299 40.9 r.sub.2 = 0.7772 d.sub.2 = 0.23 r.sub.3 = 3.5183 L.sub.2 d.sub.3 = 1.75 1.80517 25.4 r.sub.4 = -1.4831 d.sub.4 = 0.02 r.sub.5 = .infin. L.sub.3a d.sub.5 = 0.40 1.80517 25.4 r.sub.6 = 1.9530 d.sub.6 = 0 r.sub.7 = 1.9530 L.sub.3b d.sub.7 = 1.18 1.69680 55.6 r.sub.8 = -1.7595 ______________________________________
• wherein the lens elements L.sub.1 -L.sub.3b have surface radii r.sub.1 -r.sub.8, the index of refraction is given by N.sub.d, the dispersion is measured by the Abbe number as given by V.sub.d, and the axial distance between adjacent surface is given by d in millimeters (mm).