Patent ID: 6111703
Filing Date: 2000-08-29
Classification: G02B

Abstract:
An image pickup optical system comprising, in order from an object side:a first lens component which comprises a meniscus lens element having a convex surface on an object side thereof and a positive refractive power;a second lens component which comprises a negative lens element;a third lens component which comprises a cemented lens component consisting of a negative meniscus lens element having a convex surface on an object side thereof and a biconvex lens element; anda fourth lens component which comprises a negative meniscus lens element having a convex surface on an image side,wherein said optical system comprises a stop which is disposed on the object side of said third lens component, andwherein said optical system satisfies the following conditions (1) and (2):1.2<R.sub.3 /.DELTA.N.sub.3 .multidot.f<3.0 (1)0.1<.DELTA.N.sub.3 <0.25 (2)wherein the reference symbol R.sub.3 represents a radius of curvature on a cemented surface of the third lens component, the reference symbol .DELTA.N.sub.3 designates a difference between a refractive index of the biconvex lens element of the third lens component for the d-line and a refractive index of the negative meniscus lens element for the d-line, and the reference symbol f denotes a focal length of the optical system as a whole.