OPTICAL IMAGING SYSTEM

An optical imaging system includes a first lens having a concave object-side surface, a second lens, a third lens having a concave image-side surface, a fourth lens having a concave object-side surface, and a fifth lens. The first to fifth lenses are sequentially disposed from an object side toward an imaging plane. The optical imaging system has a total number of five lenses having a refractive power. A radius of curvature of the image-side surface of the third lens is greater than a radius of curvature of an image-side surface of the second lens. 0≤|n1−n2|≤0.2 and TL/2Y