Patent ID: 7869141

Claim:
A fisheye objective lens having a series of lens elements aligned coaxially into a front group and a rear group and spaced on an optical axis to focus the image of an object on an image plane, each lens element surface being characterized as an object surface if facing the object, or characterized as a image surface if facing the image plane, the front group comprising: a first lens element, being the first most object side lens element of the front group, with a convex object surface and a concave image surface, a second lens element, being the second most object side lens element of the front group, with a concave object surface and a concave image surface, and a third lens element, being the third most object side lens element of the front group, the compact fisheye objective lens having a total track length “TT” and an effective focal length f, the elements in the front and rear groups being spaced along the optical axis to obtain a ratio of the distance “TT” to the effective focal length “f” of the fisheye objective lens as being greater than eight and less than nineteen, and wherein the rear group further comprises: a fourth lens element, being the first most object side lens element of the rear group, having a convex object surface and a convex image surface, a fifth lens element, being the second most object side lens element of the rear group, having a convex object surface and a convex image surface, and a sixth lens element, being the third most object side lens element of the rear group, having a concave object surface and a convex image surface and wherein, the sixth lens element has an Abbe number less than 30.