Patent ID: 9535237
Date: 2017-01-03
CPC Classifications: G02B,H04N

Claim:
1. A zoom lens, comprising, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power; and a fourth lens unit having a positive refractive power, the second lens unit and the third lens unit being configured to move along loci different from each other during zooming so that an interval between adjacent lens units is changed, wherein at least one lens unit of the first lens unit, the second lens unit, the third lens unit, or the fourth lens unit comprises a positive lens and a negative lens that are arranged adjacent to each other, and wherein materials for the positive lens and the negative lens satisfy the following conditional expression: where, when a refractive index of a lens material at a wavelength of 400 nm is N400, a refractive index of a lens material at a wavelength of 1,050 nm is N1050, a refractive index of a lens material at a wavelength of 1,700 nm is N1700, and an Abbe number νIR and a partial dispersion ratio θIR of a lens material are νIR−(N1050−1)/(N400−N1700) and θIR=(N400−N1050)/(N400−N1700), respectively, νIRP and θIRP represent an Abbe number and a partial dispersion ratio of the material for the positive lens, respectively, and νIRN and θIRN represent an Abbe number and a partial dispersion ratio of the material for the negative lens, respectively.