parfocal

With the lower focal points all in the same plane: said of interchangeable eyepieces, for microscopes or telescopes, so mounted that whichever one is used the focus remains the same. See eyepiece.

With the lower focal points all in the same plane; — said of sets of eyepieces so mounted that they may be interchanged without varying the focus of the instrument (as a microscope or telescope) with which they are used.

Having multiple lenses that have corresponding focal points in the same plane