Microscope objectives

An introduction to 'infinity' corrected microscope objectives.

Contents

Working distance

The working distance (w.d.) is the range over which an objective can be moved towards the infinity corrected image plane before it mechanically collides with the sample (Pawley 2006). So importantly it is the maximum depth of standard focus (where the objective is moved towards the sample or vice versa). For a typical air objective this can simply be the distance from the front surface of the objective to the image plane:

working_distance.png
(.odp sketch)

For a coverslip corrected objective it is the distance to the coverslip when the image plane is immediately above the coverslip:

working_distance_coverslip.png
(.odp sketch)