An alignment, on a first projector, of a second projector, including: activating the projectors to project respective circles; transmitting projected image data from pictures of the projections to an analysis device that identifies respective centers of the projected circles and transmits adjustment commands the second projector to make the projected circle centers coincide. The analysis device: identifies at least one first and one second pair of projected-image zones, each zone of a pair including an arc of a circle, and the zones, pairwise, being spaced a maximum distance apart; identifies luminous intensity extrema in respective profiles of spatial distribution of luminous intensity; deduces spatial co-ordinates of points corresponding to said intensity extrema; defines spatial co-ordinates of the medium between the two points of the first pair and of the medium between the two points of the second pair, to deduce therefrom spatial co-ordinates of the center of the circle.