<microscopy> When the projected image of the microscope is projected less than 250 mm the objective may be moved enough from its usual position (for visual observation) to degrade the image. It can be restored by adding a lens above the ocular to bring the image into focus on the desired plane but with the objective still in its position of best-corrected image. A similar system requires an ocular in which the same corrections are made. Such lens systems are termed amplifiers.

(05 Aug 1998)