Patent ID: 8432620

Claim:
A lens optical system comprising first to fourth lenses that are sequentially arranged from an object, and which are between the object and an image sensor on which an image of the object is formed, wherein the first lens has a positive (+) refractive power and is convex toward the object, the second lens has a negative (−) refractive power and is biconcave, the third lens has a positive (+) refractive power and is convex toward the image sensor, and the fourth lens has a negative (−) refractive power and at least one of an incident surface and an exit surface of the fourth lens is an aspherical surface, wherein an aperture is arranged between the first and second lenses and the following mathematical expressions are satisfied: 0.5 <f 1 /f 3 <1.5 Mathematical Expression 1 2 <|r 4 /r 5 |<7, Mathematical Expression 2 wherein, in Mathematical Expression 1, f 1 and f 3 are respectively focal lengths of the first and third lenses and in Mathematical Expression 2, r 4 and r 5 are respectively a radius of curvature of an incident surface of the second lens and a radius of curvature of an exit surface of the second lens.