| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom optical system which is superior in object-side telecentricity and invariance in conjugation point and pupil position against variation in focal length and can sufficiently secure a back focus. SOLUTION: The zoom optical system includes a positive 1st lens unit, a negative 2nd lens unit, a positive 3rd lens unit, and a negative 4th lens unit in order from an reduction side to an enlargement side. For power variation, spaces between lens units vary and conjugation points on the enlargement side and reduction side and the position of the pupil between those conjugation points are substantially invariable in the entire power variation area. Then the space between the 1st lens unit and 2nd lens unit at the telephoto end is wider than that at the wide-angle end, the space between the 2nd lens unit and 3rd lens unit at the telephoto end is wider than that at the wide-angle end, and the space between the 3rd lens unit and 4th lens unit at the telephoto end is narrower than that at the wide-angle end. COPYRIGHT: (C)2006,JPO&NCIPI
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