2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/60730We prove that the morphism that maps a rational ruled surface to its singular locus is genericaly injective modulo isomophism and duality. We also calculate the dimension and the degre of its image.In french, 25 pages. Many improvements in the proofs. New results included : the study of GIT properties of the morphism and the study of the singular locus of the image. We prove that the image is rationalAlgebraic Geometry14J26 ; 14F05 ; 14N05text