US Patent 11656432 Compact telephoto lens having materials with anomalous relative partial dispersion

A lens for a camera has a longitudinal axis, a focal length, an installation length in the direction of the longitudinal axis of less than 10 mm, a plurality of refractive optical elements and a stop with a maximum diameter. The focal length of the lens can be in the range of 25 mm to 6 mm, and the ratio of focal length to maximum diameter of the stop can be in the range of 1.4 to 8. At least one refractive optical element can be formed of a material with an Abbe number for which the absolute value of the difference between relative partial dispersion of the material and a normal relative partial dispersion at the Abbe number of the material is at least 0.05.