| 摘要 |
PURPOSE:To vary magnification from a low value to a high value by constituting an object lens with a lens group A having a positive reflecting power and a lens group B having a negative refracting power and fixing an eyepiece lens and moving the lens group B to the side of the eyepiece lens on the optical axis and moving the lens group A on the optical axis to compensate the diopter varied by movement of the lens group B. CONSTITUTION:The moving course of the lens group A is dependent upon a paraxial lateral magnification beta of the lens group B when the lens group B is moved linearly, and the paraxial lateral magnification beta is -a/b. Conse quently, the paraxial lateral magnification beta is always a negative value. When the lens group B is moved linearly, the moving direction of the lens group A is changed with beta=-1 as the boundary. That is, when the magnification is varied from a low value to a high value, the lens group A is moved to the side of an object on the optical axis in case of beta>-1 and is moved to the side of the eyepiece lens in case of beta2<-1, thereby compensating the variance of diopter accompanied with magnification varying of the lens group B.
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