| 摘要 |
A retro focus lens having three lens groups arranged, in order from the longer conjugate length side of the lens, as follows: a negative first lens group G1, a positive second lens group G2, and a positive third lens group G3. The first group G1 includes, in order from the longer conjugate length side of the lens, a first lens element L1 of small positive refractive power and made of plastic with an aspherical surface, a second lens element L2 of negative refractive power that is made of glass and has a concave surface facing the shorter conjugate length side of the lens, and a third lens element L3 of negative refractive power with a concave surface facing the shorter conjugate length side of the lens, there being no additional lens elements between the first lens element L1 and the third lens element L3. By satisfying preferred conditions, favorable chromatic aberrations and distortion are attained while achieving a high resolution and a sufficiently large back focus to allow the lens to be used as a projection lens for liquid crystal color projectors.
|
