It comprises a first prism (10, 10a, 10b), with triangular base, on which is arranged at least one second transparent prism (2, 11) the combination defining a prismatic body which is arranged on the stereoscopic pair so that, when the user's eyes (13, 14) are positioned in front of the upper face of the prismatic body, each eye visualises the corresponding stereogram (3, 4) via the upper face of the prismatic body, reproducing the three-dimensional vision effect. In an embodiment of the invention the second prism (2, 11) is triangular and provision has been made for a third prism (12, 15) of identical configuration to the above, in which case the stereoscopic photographs/images (3, 4) are divided into halves A, B, C, D which are duly arranged for achieving three-dimensional visualisation. It comprises illumination equipment (5), some lenses (8, 8a) and a directional filter (9).