Patent ID: 8054558

Claim:
A multiple magnification optical system for viewing a specimen, comprising: a single objective lens; the objective lens having a focal length equal to F 0 ; the objective lens having a principal plane; the objective lens located inside the vacuum chamber of an instrument; a gradient-index lens; the gradient-index lens positioned to receive light passing through the objective lens; the gradient-index lens having first and second ends; a beam splitter; the beam splitter creating first and second optical axes; the beam splitter located outside the vacuum chamber and positioned to receive light passing through the gradient-index lens; the first end of the gradient-index lens located inside the vacuum chamber adjacent to the objective lens; the second end of the gradient-index lens located outside the vacuum chamber adjacent to the beam splitter; a first camera aligned in the first optical axis; a first lens in the first optical axis; the first lens having a focal length equal to F 1 ; the first lens situated a distance F 1 from the first camera; a second camera aligned in the second optical axis; the second camera situated a distance from the principal plane of the objective lens equal to 2F 0 ; so that a first magnification of the specimen at the first camera is obtained where the working distance of the objective lens from a specimen is equal to F 0 , and a second magnification of the specimen at the second camera is obtained where the working distance of the objective lens from the specimen is equal to 2F 0 .