| 摘要 |
PROBLEM TO BE SOLVED: To provide a projection optical system capable of drastically switching picture size with simple constitution and equipped with adequate optical performance, and a projector using the projection optical system. SOLUTION: The projection optical system 13 for projecting light can be switched to a first system and a second system having a different focal length from the first system. The first system and the second system are switched by replacing a first lens group that is a first optical element group constituting the first system with a second lens group that is a second optical element group constituting the second system. COPYRIGHT: (C)2008,JPO&INPIT
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