| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging optical system which has various aberrations excellently corrected although having a wide angle of view and a small F number, and an optical device with the same.SOLUTION: An imaging optical system comprises a first lens group having negative refracting power, a second lens group having positive refracting power, a third lens group having positive refracting power, a fourth lens group, and a fifth lens group, and has an aperture stop in the second lens group. The first lens group has a first negative lens and a first cemented lens, the second lens group has a second cemented lens and one or a plurality of positive lens elements, and the third lens group has one or a plurality of positive lens elements and a third cemented lens, wherein the first cemented lens has a negative lens on the most reduction side and is concave to a reduction side, the second cemented lens has positive refracting power and is concave to an enlargement side, and the third cemented lens has positive refracting power and has a negative lens on a reduction side.SELECTED DRAWING: Figure 1 |
