They are characterised by 1/R = 0. The formulas become :
A dioptric plane is perfectly stigmatic for any object point to infinity.
The parallel plate is composed of two distant dioptric planes of e, n is the medium index. An object point A has, as an image, a point A' situated on the perpendicular led from A to the plates sides.
We show that :
This is true for any point A in space, real or virtual. For a given object this displacement is independent from the plate positionning.