Patent ID: 8014080

Claim:
An optical photographing system comprising four lens elements with refractive power, in order from an object side to an image side: a first lens element; a second lens element with positive refractive power, and at least one of the object-side and image-side surfaces thereof being aspheric; a third lens element with negative refractive power having a concave object-side surface and a convex image-side surface, and both of the object-side and image-side surfaces thereof being aspheric; and a fourth lens element with positive refractive power, and both of the object-side and image-side surfaces thereof being aspheric; wherein the optical photographing system further comprises an aperture stop and an electronic sensor positioned on an image plane where an object is imaged, and the aperture stop is positioned between an object and the second lens element; wherein a distance on the optical axis between the object-side surface of the first lens element and the image-side surface of the fourth lens element is Td, half of the diagonal length of the effective pixel area of the electronic sensor is ImgH, an on-axis spacing between the first lens element and the second lens element is T 12 , an on-axis spacing between the third lens element and the fourth lens element is T 34 , an on-axis spacing between the second lens element and the third lens element is T 23 , a radius of curvature of the image-side surface of the second lens element is R 4 , a radius of curvature of the object-side surface of the second lens element is R 3 , a distance on the optical axis between the aperture stop and the image plane is SL, a distance on the optical axis between the object-side surface of the first lens element and the image plane is TTL, and they satisfy the relation: 0.7 <Td/ImgH< 2.0; 1.5<( T 12 +T 34)/ T 23<1.20; 0.0 <|R 4/ R 3|<1.55; and 0.8 <SL/TTL< 1.2.