Optical system and apparatus including optical system

Abstract

An optical system includes six or less lenses, wherein the six or less lenses include a plurality of positive lenses, and a final lens having negative refractive power and disposed closest to an image, and wherein, where a total optical length obtained by addition of a back focus to a distance from a lens surface closest to an object in the optical system to a final lens surface is TL, a half angle of view is ω[°], a focal length of a whole system is f, and an average value of a refractive index of a lens having a highest refractive index and a refractive index of a lens having a second highest refractive index among the plurality of positive lenses is np12ave, following conditions are satisfied: 0.50<TL/(f×tan ω)<1.90, and 1.80<np12ave<2.20.

Dependencies are inferred from the claim text.