ZOOM OPTICAL SYSTEM AND IMAGE PROJECTION APPARATUS HAVING THE SAME

摘要

A zoom optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first optical group, and a second optical group having a zoom function. The second optical group includes, in order from the enlargement conjugate side to the reduction conjugate side, a lens unit B21 with positive refractive power, a lens unit B22 with positive refractive power, and a lens unit B23 with positive refractive power. The lens units B21 and B22 move with a distance therebetween changed at the time of zooming. A predetermined relationship between a focal length fR of the second optical group in a wide-angle end and a focal length fB22 of the lens unit B22 is satisfied.

主权项

1. A zoom optical system comprising, in order from an enlargement conjugate side to a reduction conjugate side:
a first optical system; and a second optical group having a zoom function, wherein the zoom optical group has an optical action to conjugate an enlargement conjugation point on the enlargement conjugate side with an intermediate imaging position between the first optical group and the second optical group, and to conjugate the intermediate imaging position with a reduction conjugation point on the reduction conjugate side, wherein the second optical group includes, in order from the enlargement conjugate side to the reduction conjugate side, a lens unit B21 with positive refractive power, a lens unit B22 with positive refractive power, and a lens unit B23 with positive refractive power, and wherein the lens unit B21 and the lens unit B22 move with a distance therebetween changed at the time of zooming, and a condition
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