| 摘要 |
A zoom optical system, in order from a reduction side to a magnification side, includes a first lens unit having positive optical power, a second lens unit having the positive optical power, a third lens unit having negative optical power, and a fourth lens unit having the positive optical power, wherein respective intervals between the first, second, third and fourth lens units change during zooming, a conjugate position on the magnification side with respect to a conjugate position on the reduction side, and a position of a pupil of the zoom optical system with respect to the conjugate position on the reduction side, are substantially fixed over an entire zooming range, and during zooming from a wide angle end to a telephoto end, the fourth lens unit moves toward the magnification side, and an interval between the first lens unit and the fourth lens unit increases.
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