Patent ID: 7375901

Claim:
A zoom lens comprising: in order from an object side of the zoom lens, a first lens group having a positive refractive power; a second lens group having a negative refractive power; an aperture diaphragm; a third lens group having a positive refractive power; and a fourth lens group having a positive refractive power, wherein the first lens group and the third lens group are fixed when the zoom lens varies a power thereof and is focused, the second lens group moves along an optical axis thereof when the zoom lens varies the power thereof, and the fourth lens group moves along an optical axis thereof when the zoom lens varies a power thereof and is focused, the first lens group comprises: in order from the object side, a first lens having a negative refractive power; a right-angle prism having an internal reflection face for bending an optical path approximately 90°; a second lens having a positive refractive power; and a third lens having positive refractive power, and the first lens group satisfies Conditions: 1.71<N p <1.80 (1) ν p >30 (2) 1.4<D 2-6 /f w <1.9 (3) wherein N p is a refractive index of the right-angle prism at the d-line, ν p is an Abbe number of the right-angle prism at the d-line, D 2-6 is a distance along the optical axis from an image-side surface of the first lens to an object side surface of the second lens, and f w is a focal length of the zoom lens at wide angle end.