Patent ID: 8488255

Claim:
An image pickup optical system, comprising five lens elements with refractive power arranged sequentially from an object side to an image side: a first lens element with positive refractive power, having a convex object-side surface; a second lens element with negative refractive power, having a concave object-side surface and a convex image-side surface; a third lens element with refractive power; a fourth lens element with refractive power, having a concave image-side surface, and at least one of an object-side surface and the image-side surface being aspheric; a fifth lens element with refractive power, having a concave image-side surface, and at least one of an object-side surface and the image-side surface being aspheric, and at least one of the object-side and image-side surfaces including at least one inflection point; and the image pickup optical system further comprising a stop; wherein R 3 is a curvature radius of the object-side surface of the second lens element, R 4 is a curvature radius of the image-side surface of the second lens element, D R1S is an axial distance from the object-side surface of the first lens element to the stop, D R1R4 is an axial distance from the object-side surface of the first lens element to the image-side surface of the second lens element; and the following relations are satisfied: −4.5<( R 3 +R 4 )/( R 3 −R 4 )<−1.0; 0.25 <D R1S /D R1R4 <1.20.