Abstract: Optical projectors of the kind which supply a beam of radiation whose total ngular field 2.rho.' is determined in at least one reference plane, the angular field containing all the radiant flux, the projector also incorporating a source of radiation associated with a reflecting optical collector system, a conoid or pyramidoid mirror which has at least the reference plane as a plane of symmetry and the minor base of which in conjunction with the reflecting optical collector system, entirely contains optically the source of radiation. The mirror is made to conform to the following dimensional relationships which apply to each cross-section of the mirror through a plane of symmetry: ##EQU1## WHERE D and d are respectively the cross-sectional lengths of the major and minor bases of the mirror in the cross-sectional plane in question, .gamma. is half the mean apex angle of the mirror in the cross-sectional plane in question, and .theta.