Patent ID: 9638917
Date: 2017-05-02
CPC Classifications: G02B,G03B

Claim:
1. A zoom lens comprising in order from an object side to an image 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, a fourth lens unit having a positive refractive power, wherein the first lens unit includes in order from the object side, a negative meniscus lens having a object side surface which is convex surface directed toward the object side, a negative lens having an image side surface which is concave surface directed toward the image side, and a positive lens having a object side surface which is convex surface directed toward the object side, the second lens unit includes in order from the object side, a positive lens having a object side surface which is convex surface directed toward the object side, a negative lens having an image side surface which is concave surface directed toward the image side, and a biconvex positive lens, in the second lens unit, the positive lens has an aspheric surface and the biconvex positive lens is cemented to the negative lens, the third lens unit includes a biconcave negative lens and the biconcave negative lens has an aspheric surface, the fourth lens unit includes a biconvex positive lens, the total number of lenses included in the zoom lens is eight, an aperture stop is disposed between an image side surface of the first lens unit and an image side surface of the second lens unit, at a time of zooming from a wide angle end to a telephoto end, the first lens unit, after moving toward the image side, moves toward the object side, the first lens unit positions at the image side, at the telephoto end than at the wide angle end, the second lens unit moves so as to position at the object side, at the telephoto end than at the wide angle end, a distance between the second lens unit and the third lens unit, and a distance between the third lens unit and the fourth lens unit change at the telephoto end with respect to the wide angle end, a position of the fourth lens unit is fixed at the time of zooming from the wide angle end to the telephoto end, at a time of focusing, the third lens unit moves, and the following conditional expressions (11) and (19) are satisfied: where, LTL the overall length is a distance on an optical axis from a refracting surface of the zoom lens nearest to the object side and a refracting surface of the zoom lens nearest to the image side, fb LTL fb