Microscope objective

Tube lens

An <optical microscope> whose <microscope objective>, with the specimen at its designed front <focal plane>, sends out a parallel bundle of <light rays> from each specimen point. Different specimen points generally give different bundle directions. A <tube lens> then forms the finite <intermediate microscope image>; the <microscope eyepiece> views it. This parallel region permits suitable optical accessories to be inserted. Finite-conjugate and infinity-corrected components must be matched to their intended system.<Infinity Optical Systems by Nikon Instruments Inc.>[Infinity Optical Systems, Fig. 2(a–b) and following description of objective, tube lens and eyepieces]{ref}

In the ideal <paraxial approximation>, an object height $h_o$ at objective <focal length> $f_o$ gives bundle slope $-h_o/f_o$. A <tube lens> of <focal length> $f_t$ maps that slope to $h_i=-f_th_o/f_o$, so
$$
m_o=-\frac{f_t}{f_o}.
$$
This is a two-assembly result. Substituting infinity into the single-objective <transverse magnification> $-v_o/u_o$ would not describe the finite recorded image. Infinity correction concerns the region after the objective; relaxed-eye viewing concerns the region after the eyepiece. They are distinct conditions.


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 Incoming links: Infinity-corrected microscope