This article is a short introduction to mechanical tube length. For a simple monocular microscope, the mechanical tube length is the distance between the flange of the objective lens (also known as the shoulder of the objective) and the seating surface on which the eyepiece rests (e.g. 170 mm). For most research microscopes, the effect of the tube lens (or tube lenses) must be taken into account when measuring the effective, mechanical tube length. For instance, using an objective turret for transmitted light microscopy, the mechanical tube length of the Leitz Ortholux is 223 mm. A special tube lens consisting of a concave lens element adjusts this 223 mm tube length into the effective 170 mm mechanical tube length. This leads to an unwanted extra magnification factor that commonly plagues microscopes designed for the finite mechanical tube length.

The Mechanical Tube Length – A Short Introduction
1st Edition of November 2015
by Gregor Overney
(pdf format, size 854 kbytes)

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