| 摘要 |
A projection optical system comprises a first lens group with positive power, a second lens group with negative power, a third lens group with positive power, a fourth lens group with negative power, and a fifth lens group with positive power. At least one of the first, second, and third lens group has an aspherical surface. A lens arrangement of one embodiment has a plurality of waists of lenses, with aspherical surface before and after a first waist.
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