Objective lens for an endoscope

1. An objective lens for an endoscope comprises an object-side lens element including a plane-convex rod lens and an image-side lens element including a single biconvex lens arranged at an image-side end of the objective lens, wherein, as viewed from an object side of the objective lens,

the object-side lens element further includes a single plane-convex first lens and a single biconcave second lens which form a front lens arranged in this order on an object side of the plane-convex rod lens which forms a third lens, and

the image-side lens element further includes a single biconvex fourth lens, a single concave-plane fifth lens and a single biconcave sixth lens arranged in this order on an object side of the single biconvex lens that is arranged at the image-side end of the objective lens and which forms a seventh lens.

2. The objective lens according to claim 1 , characterized in that the single plane-convex first lens and the single biconcave second lens and the single plane-convex third lens of the object-side lens element are cemented to each other.

3. The objective lens according to claim 1 , characterized in that the single biconvex fourth lens, the single concave-plane fifth lens, the single biconcave sixth lens and/or the single biconvex seventh lens of the image-side lens element are cemented to each other.

4. The objective lens according to one of the claim 1 , characterized in that the plane-convex third lens is formed by a single plane-convex rod lens and a single glass rod which are cemented to each other.

5. The objective lens according to claim 4 , characterized in that the single glass rod is made of flint glass and/or has an antireflection coating.

6. The objective lens according claim 1 , characterized in that the optical axis of the front lens is angled with respect to a longitudinal axis of an endoscope shaft of the endoscope, that between the single biconcave second lens and the single plane-convex third lens a prism is arranged such that it causes a beam deflection from the optical axis of the front lens to the longitudinal axis of the endoscope shaft of the endoscope, and that the prism is cemented to the plane-convex third lens.

7. The objective lens according to claim 6 , characterized in that between the single biconcave second lens and the prism a plane-parallel glass plate is arranged and cemented thereto.

8. The objective lens according to claim 6 , characterized in that the prism has a high-reflection coating.

9. The objective lens according to claim 1 , characterized in that the single plane-convex first lens, the single biconcave second lens, the plane-convex third lens, the single biconvex fourth lens, the single concave-plane fifth lens, at least one of the single biconcave sixth lens or the single biconvex seventh lens is made of flint glass.

10. The objective lens according to claim 1 , characterized in that at least one of the single plane-convex first lens, the single biconcave second lens, the plane-convex third lens, the single biconvex fourth lens, the single concave-plane fifth lens, the single biconcave sixth lens or the single biconvex seventh lens has an antireflection coating.

11. The objective lens according to claim 1 , characterized in that the single plane-convex first lens and the single biconcave second lens are radially surrounded by a material such that the diameter of the front lens and the diameter of the plane-convex third lens are matched.

12. The objective lens according to claim 1 , characterized in that a sapphire glass window is arranged on the object side of the single plane-convex first lens.

13. The objective lens according to claim 1 , wherein between the object-side lens element and the image-side lens element a mechanical separation point for exchanging the object-side lens element is arranged.

14. A stereoscopic objective lens comprising two objective lenses, each objective lens having an object-side lens element including a plane-convex rod lens and an image-side lens element including a single biconvex lens arranged at an image-side end of the objective lens,

wherein, as viewed from the object side of the objective lens,

each object-side lens element includes a single plane-convex first lens and a single biconcave second lens which form a front lens arranged in this order on an object side of the plane-convex rod lens which forms a third lens, and

the image-side lens element includes a single biconvex fourth lens, a single concave-plane fifth lens and a single biconcave sixth lens arranged in this order on an object side of the biconvex lens that is arranged at the image-side end of the objective lens and which forms a seventh lens.

15. An endoscope comprising at least one objective lens having an object-side lens element including a plane-convex rod lens and an image-side lens element including a single biconvex lens arranged at an image-side end of the objective lens,

wherein, as viewed from the object side of the objective lens,

the object-side lens element includes a single plane-convex first lens and a single biconcave second lens which form a front lens arranged in this order on an object side of the plane-convex rod lens which forms a third lens, and

the image-side lens element includes a single biconvex fourth lens, a single concave-plane fifth lens, and a single biconcave sixth lens arranged in this order on an object side of the biconvex lens that is arranged at the image-side end of the objective lens and which forms a seventh lens.