Patent ID: 7212351
Filing Date: 2007-05-01
Classification: G02B

Abstract:
1. An image taking optical system comprising, in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power, wherein the second lens unit moves toward the object side so that a space between the first lens unit and the second lens unit decreases, and the third lens unit moves so that a space between the second lens unit and the third lens unit changes, in a case where zooming is performed from a wide-angle end to a telephoto end, the first lens unit includes at least one lens, among which there exists only one lens that has a negative refractive power, and the second lens unit includes at least one positive lens and at least one negative lens, the image taking optical system satisfying the following conditions: wherein W_L denotes the whole length of the image taking optical system in the wide-angle end, ω denotes a half field angle of the image taking optical system at a time when the image taking optical system is in an arbitrary state, FL denotes a focal length of the image taking optical system in the arbitrary state, ΔD12 denotes a change amount of the space between the first lens unit and the second lens unit during the zooming from the wide-angle end to the telephoto end, and PAVd denotes the Abbe number of the positive lens of the second lens unit.