| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve optical properties of optical instruments with variable magnification, such as zoom binoculars, to reduce the weight thereof, and to enable a user to quickly change magnifications. Ž<P>SOLUTION: The optical instrument with a focal length-varying lens 4 disposed on the optical axis between an objective lens 7 and an eyepiece 3 movably along the optical axis further includes an adjusting lens 5 for adjusting optical properties when the focal length-varying lens is in an area to provide high magnification. The adjusting lens is supported so that it moves between a location on the optical axis and a location off the path. In conjunction with a magnification-varying mechanism that controls the position of the focal length-varying lens, the adjusting lens is moved to the on-the-axis location when the focal length-varying lens is in an area to provide high magnification, and to the off-the-axis location when it is in an area to provide low magnification. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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