Extrawide-angle retrofocus type of objective

Claim 1

An extrawide-angle retrofocus objective having four lens element sections the first of which is situated at the front of the objective nearest to the object to be photographed and has a divergent effect, said first lens element section consisting of four elements arranged with air gaps respectively situated therebetween and the first, second and fourth of said elements of said first section, considered in the direction from the front toward the rear, being negative meniscus lenses respectively having convex surfaces directed forwardly toward the object, while the third of said four elements is a positive lens element, the second of said four lens element sections being situated behind the first, having an extremely weak refractive power in its entirety and including at least two but not more than three lens elements the first of which is nearest to the object and has a concave surface which is directed forward toward the object, the third of said lens element sections being situated behind the second and forming a positive lens system including at least one but not more than two lens elements, and the fourth of said lens element sections being situated behind the third and including from the front toward the rear a negative biconcave lens element, a positive lens having a convex surface of large curvature directed toward the object, a positive meniscus lens having a convex surface directed rearwardly toward the image plane, and a positive rear lens, the first and second lens elements of said fourth lens element section being cemented to each other at a forwardly directed convex surface of the second lens element of said fourth lens element section, and the remaining elements of said fourth lens element section being separated by air gaps.