| 摘要 |
PROBLEM TO BE SOLVED: To provide a long-focus zooming projection optical system which is made relatively compact as a whole and has high performance, while suppressing an increase in size of lenses on a screen side, i.e., an enlarging side.SOLUTION: A projection lens 40 is a zoom lens and comprises first to N-th groups arranged in order from the enlarging side (i.e., the screen side), where N is 6 or 7. The first group G1 comprises, in order from the enlarging side, a first A group G1-1 and a first B group G1-2. The first A group G1-1 comprises two positive lenses, and the first B group G1-2 comprises a cemented lens of a positive lens and a negative lens. A second group G2 has at least two negative lenses. When varying power, at least the first group and N-th group are fixed and at least the third to (N-1)th groups are moved along an optical axis. When focusing, the first A group G1-1 on the enlarging side in the first group G1 is moved independently along an optical axis OA. |
