Patent ID: 9122043
Filing Date: 2015-09-01
Classification: G02B,G03B

Abstract:
1. A projection zoom lens substantially consisting of two lens groups which are a first lens group having negative refractive power and a second lens group having positive refractive power, arranged in this order from the magnification side, the first lens group substantially consists of one lens which is a first lens composed of a negative meniscus lens with a convex surface toward the magnification side; the second lens group substantially consists of four lenses which are a second lens that is a positive lens, a third lens which is a positive meniscus lens with a convex surface toward the magnification side, a fourth lens which is a negative lens, and a fifth lens which is a positive lens, arranged in this order from the magnification side; the first lens group and the second lens group are moved in the direction of the optical axis while changing magnification; at least one of the positive lenses in the two lens groups has an Abbe number and a refractive index that each falls within a range that satisfies the condition wherein the refractive index is lower than that of a straight line which passes through two points which are (νd,Nd)=(55,1.65) and (νd,Nd)=(34,1.75) in an orthogonal coordinate system having Abbe numbers νd with respect to the d-line as the horizontal axis and refractive indices Nd with respect to the d-line as the vertical axis; and conditional expressions (1) through (3) below are satisfied: where