Patent ID: 8497931
Filing Date: 2013-07-30
Classification: G02B

Abstract:
1. An image taking optical system comprising, in order from the object side, a stop, a first lens having a biconvex shape and having a positive refractive power, a second lens having a concave surface facing the image side and having a negative refractive power, a third lens having a convex surface facing the image side and having a positive refractive power, and a fourth lens having a negative refractive power, wherein the largest air distance is provided between the second lens and the third lens from a first lens disposed closest to the object to a last lens, the image taking optical system satisfies the following conditional expression (1) and conditional expression (2′): where d5 is the air distance between the second lens and the third lens on the optical axis, d6 is the thickness of the third lens, r6 is the paraxial radius of curvature of the object side surface of the third lens, and r7 is the paraxial radius of curvature of the image side surface of the third lens.