Optical imaging system

Abstract

An optical imaging system includes a first lens having a positive refractive power; a second lens having a concave object-side surface in a paraxial region thereof; a third lens having a positive refractive power; a fourth lens having a negative refractive power; a fifth lens having a refractive power; and a sixth lens having a concave image-side surface in a paraxial region thereof, wherein the first to sixth lenses are sequentially disposed in ascending numerical order along an optical axis of the optical imaging system from an object side of the optical imaging system toward an imaging plane of the optical imaging system, and a conditional expression 0.6 ≦ CT1 / d2 ≦ 1.4 is satisfied, where CT1 is a thickness of the first lens along the optical axis, and d2 is an air gap along the optical axis between the second lens and the third lens.