PARFOCAL

Adjective

parfocal (not comparable)

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

Source: Wiktionary

Par*fo"cal, a. [Pari- + focal.] (Opt.)

Definition: 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.

Source: Webster’s Unabridged Dictionary 1913 Edition