| 摘要 |
A projection optical system which sufficiently corrects variations in aberrations during focusing irrespective of a distance at which an object is located, i.e. whether the object is located at a point of infinity or at a short distance, while maintaining advantages of a rear focus retrofocus type optical system, is disclosed. This projection optical system has, in order from the enlarging side, a first lens unit having negative optical power, and a second lens unit having positive optical power and moves in a direction of an optical axis for focusing. The following condition is satisfied: 0<=|F/T1|<0.2 where reference character t1 denotes a distance from the reducing-side conjugate plane to a pupil and reference character f denotes a focal length of the entire system.
|
