Reminders of instrumental optics
Optical observation and measurement instruments

A centered optical system is a set of lenses (and/or mirrors) with their axes of symmetry coinciding, which refract (and/or reflect) light [1] . In such a system, a number of characteristic cardinal elements are defined (figure 1 ).

The transverse magnification g _t (ratio of the length of an image A′B′ to the length of the conjugate object AB) is : $g_{\text{t}}=\frac{{\text{A}}^{\prime }{\text{B}}^{\prime }}{\text{AB}}$