Patent ID: 8687293

Claim:
An optical imaging system comprising, in order from an object side to an image side: a first lens element with a positive refractive power; a second lens element; a third lens element; a fourth lens element with a positive refractive power having a convex image-side surface, wherein at least one of the object-side and the image-side surfaces of the fourth lens element is aspheric; and a fifth lens element with a negative refractive power having a convex object-side surface in a paraxial region and a concave image-side surface, wherein at least one of the object-side and the image-side surfaces of the fifth lens element is aspheric, wherein there is a spacing between each lens element on an optical axis; wherein on the optical axis, the sum of the thicknesses of all the lens elements with refractive power is (Î£CT), a distance from the object-side surface of the first lens element to the image-side surface of the fifth lens element is Td, and the following condition is satisfied: 0.81<(Î£CT)/Td<0.93.