Patent ID: 8724238

Claim:
A monofocal optical lens system comprising, in order 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; a third lens element with refractive power, wherein at least one of an object-side surface and an image-side surface of the third lens element is aspheric; a fourth lens element with negative refractive power made of plastic material, and having a concave object-side surface and a convex image-side surface, wherein the object-side surface and the image-side surface of the fourth lens element are aspheric; and a fifth lens element with refractive power made of plastic material, and having a concave object-side surface, wherein the object-side surface and an image-side surface of the fifth lens element are aspheric, the image-side surface of the fifth lens element is convex or planar at a paraxial region and is convex at a peripheral region; wherein the monofocal optical lens system further comprises a stop, an axial distance between the object-side surface of the first lens element and the stop is Dr 1 s, an axial distance between the object-side surface of the first lens element and an image-side surface of the second lens element is Dr 1 r 4 , a curvature radius of the object-side surface of the fifth lens element is R 9 , a curvature radius of the image-side surface of the fifth lens element is R 10 , and the following relationships are satisfied: −0.2 <Dr 1 s/Dr 1 r 4<0.9; and 0 ≦R 9 /R 10<0.30.