Patent ID: 7990621

Claim:
A projection lens comprising: a first lens group having a negative refractive power; and a second lens group having a positive refractive power, wherein the first and second lens groups are arranged in this order from a magnification side, a lens unit arranged closest to a reduction side in the first lens group is moved along an optical axis to adjust focus, and at least two lenses are made of a material satisfying the following conditional expression: 0.018<θ−(−0.00164 ·νd+ 0.6427)<0.06 (1) where θ=(n g −n F )/(n F −n C ), νd=(n d −1)/(n F −n C ), n g indicates a refractive index with respect to the g-line of 435.84 nm in wavelength, n F indicates a refractive index with respect to the F-line of 486.13 nm in wavelength, n d indicates a refractive index with respect to the d-line of 587.56 nm in wavelength, and n C indicates a refractive index with respect to the C-line of 656.28 nm in wavelength, wherein in the second lens group, a magnification-side lens unit includes a negative meniscus lens having a concave surface facing the reduction side and a positive lens having a convex surface facing the reduction side arranged in this order from the magnification side, the negative meniscus lens of the second lens group consists of a single lens, and the positive lens of the second lens group consists of another single lens.