The invention relates to a miniaturised instrument for simulating simultaneous vision by generating masks with a single image forming optical channel. The instrument comprises: a mask generating element (EGM) which generates at least two complementary masks with a temporal frequency of alternation such that when one partially blocks the incident light the other allows the incident light to partially pass and vice versa an adjustable lens (LA) of variable optical power which generates with said frequency of alternation at least two different optical powers corresponding to at least two observation distances. The EGM and the LA are located in a single optical channel via which the incident light circulates such that each mask of the EGM is temporally synchronised with a power of the LA. The combination of all the masks and optical powers produces a pupil pattern via high speed temporal fusion in which pattern at least two optical powers corresponding to at least two observation distances are combined.
