Patent ID: 7710665

Claim:
An imaging optical system comprising: an aperture stop; a first lens disposed at an image side of the aperture stop, the first lens having a positive refractive power and the front surface of the first lens having a convex object-side surface; a second lens disposed at an image side surface of the first lens, the front surface of the second lens having a concave object-side surface; a third lens disposed at an image side surface of the second lens, the rear surface of the third lens having a concave image-side surface; a fourth lens disposed at an image side surface of the third lens, the fourth lens having a positive refractive power and the rear surface of the fourth lens having a convex image-side surface; and a fifth lens having a negative refractive power and the rear surface of the fifth lens having a concave image-side surface, wherein a combined refractive power of the second and third lenses is negative.