Patent ID: 8289437

Claim:
An image pickup optical system consisted of five lenses, comprising in order from an object side: an aperture stop; a first lens having a positive refracting power; a second lens having a negative refracting power; a third lens; a fourth lens having a positive refracting power; and a fifth lens having a negative refracting power, wherein at least one of surfaces of the fifth lens has an inflection point, and the image pickup optical system satisfies the following conditional expression âˆ’1.27< r 8/ f<âˆ’ 0.25â€ƒâ€ƒ(1) 0.36< f 4/ f< 0.98â€ƒâ€ƒ(2) where, f denotes a focal length of the overall image pickup optical system, f 4 denotes a focal length of the fourth lens, and r 8 denotes a paraxial radius of curvature of an object side surface of the fourth lens.