초록 ▼

An objective lens system for an endoscope includes first to fifth lens elements L1 to L5 arranged in this order from the front to the rear. An aperture stop is disposed between the second and third lens elements L2 and L3. The first lens element L1 is a negative lens concave to the rear, the second

An objective lens system for an endoscope includes first to fifth lens elements L1 to L5 arranged in this order from the front to the rear. An aperture stop is disposed between the second and third lens elements L2 and L3. The first lens element L1 is a negative lens concave to the rear, the second lens element L2 is a positive lens having a flat surface facing rearward, the third lens element L3 is a positive lens having a flat surface facing forward, the fourth lens element L4 is a positive lens having a flat surface facing forward and the fifth lens element L5 is a negative meniscus lens. The fourth and fifth lens elements L4 and L5 are cemented together to form a cemented lens having a positive refracting power. The following formulae (1) to (3) are satisfied, 0.75f1×Bf/f2│1) Dii│(2) u23) wherein f1 represents the focal length of the first lens element L1, Bf represents the back focal length of the overall objective lens system, f represents the combined focal length of the overall objective lens system, Di represents the central thickness of an lens element Li having a convex face, Ri represents the radius of curvature of the convex face of an lens element Li having a convex face and u2 represents the Abbe\s number of the second lens element L2.

대표청구항 ▼

An objective lens system for an endoscope comprising first to fifth lens elements L1 to L5 arranged in this order from the front to the rear and an aperture stop disposed between the second and third lens elements L2 and L3, the first lens element L1 being a negative lens concave to the rear, the se

An objective lens system for an endoscope comprising first to fifth lens elements L1 to L5 arranged in this order from the front to the rear and an aperture stop disposed between the second and third lens elements L2 and L3, the first lens element L1 being a negative lens concave to the rear, the second lens element L2 being a positive lens having a flat surface facing rearward, the third lens element L3 being a positive lens having a flat surface facing forward, the fourth lens element L4 being a positive lens having a flat surface facing forward, the fifth lens element L5 being a negative meniscus lens, the fourth and fifth lens elements L4 and L5 being cemented together to form a cemented lens having a positive refracting power wherein the following formulae (1) to (3) are satisfied, 0.751×Bf/f2│1) Dii(2) u23) wherein f1 represents the focal length of the first lens element L1, Bf represents the back focal length of the overall objective lens system, f represents the combined focal length of the overall objective lens system, Di represents the central thickness of an lens element Li having a convex face, Ri represents the radius of curvature of the convex face of an lens element Li having a convex face and u2 represents the Abbe\s number of the second lens element L2.