there is provided a subminiature imaging optical system installed in a mobile telecommunication terminal or a pda , or used in a surveillance camera or a digital camera . the subminiature imaging optical system including : first , second , third and fourth lenses sequentially positioned from an object side to an image side , the first lens having positive refractive power , the second lens having negative refractive power , the third lens having negative refractive power , and the fourth lens having positive refractive power , wherein each of the third and fourth lenses has at least one aspherical surface . the subminiature imaging optical system corrects chromatic aberration superbly to reduce color fringing significantly , thereby achieving high resolution and compactness as well .