Patent ID: 8358473

Claim:
An optical lens for image pickup, sequentially arranged from an object side to an image side, comprising: a first lens element with positive refractive power, having a convex object-side surface; a second lens element with negative refractive power, having a convex object-side surface and a concave image-side surface; a plastic third lens element with positive refractive power, having a concave object-side surface and a convex image-side surface, and both object-side surface and image-side surface thereof being aspheric; and a plastic fourth lens element with positive refractive power, having a convex object-side surface and a concave image-side surface, and both object-side surface and image-side surface thereof being aspheric; 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, R 5 is a curvature radius of the object-side surface of the third lens element, R 6 is a curvature radius of the image-side surface of the third lens element, f is a focal length of the optical lens for image pickup, and the following relations are satisfied: 0.20<( R 3 −R 4 )/( R 3 +R 4 )<0.70; |( R 5 −R 6 )/( R 5 +R 6 )|<0.21; and 0.1 <R 4 /f< 0.5.