Conjugate optical plane
= Conjugate optical plane
Two <conjugate optical planes> are object and image planes related by an imaging system: points in one are imaged onto corresponding points in the other in the <paraxial approximation>. For a converging <thin lens> forming a <real image> in air, their distances $u,v>0$ obey $1/u+1/v=1/f$. Exchanging $u$ and $v$ preserves this relation; this symmetry gives the two settings of the <Bessel lens displacement method>.