A time-multiplexed stereoscopic 3d projection system for projecting a randomly polarized incident image-beam generated by a single-lens projector onto a polarization-preserving projection-screen , the system comprising: a beam-splitting element operable to split the randomly polarized incident image-beam generated by the single-lens projector into one primary image-beam , having a primary image-beam path, possessing a first state of linear polarization and two secondary image-beams , each having respective secondary image-beam paths, both possessing a second state of linear polarization, said first and second states of linear polarization being mutually orthogonal and said secondary image-beam paths for said secondary image-beams both being diverted by reflecting-surfaces such that said primary and secondary image-beams partially overlap and mutually recombine to form a complete image on the surface of the polarization-preserving projection-screen ; three polarization modulators , a respective one of said modulators being disposed in each of the primary image-beam path and the two secondary image-beam paths, configured to modulate said first and second states of linear polarization between a left and right circular polarization state in synchronization with the images generated by said projector; at least one contrast enhancement film disposed within the optical-path of at least one of said primary and secondary image-beams and positioned between the an associated one of the polarization modulators and the projection-screen ; wherein said at least one contrast enhancement film comprises a stack of at least three separate uniaxially stretched retardation-films configured to improve the degree of circular polarization of the at least one of said primary and secondary image-beams exiting the associated one of the polarization modulators ; and wherein said uniaxially stretched retardation-films each individually possess an in-plane retardation value being equal to one of 140nm, 270nm, or 540nm. a beam-splitting element operable to split the randomly polarized incident image-beam generated by the single-lens projector into one primary image-beam , having a primary image-beam path, possessing a first state of linear polarization and two secondary image-beams , each having respective secondary image-beam paths, both possessing a second state of linear polarization, said first and second states of linear polarization being mutually orthogonal and said secondary image-beam paths for said secondary image-beams both being diverted by reflecting-surfaces such that said primary and secondary image-beams partially overlap and mutually recombine to form a complete image on the surface of the polarization-preserving projection-screen ; three polarization modulators , a respective one of said modulators being disposed in each of the primary image-beam path and the two secondary image-beam paths, configured to modulate said first and second states of linear polarization between a left and right circular polarization state in synchronization with the images generated by said projector; at least one contrast enhancement film disposed within the optical-path of at least one of said primary and secondary image-beams and positioned between the an associated one of the polarization modulators and the projection-screen ; wherein said at least one contrast enhancement film comprises a stack of at least three separate uniaxially stretched retardation-films configured to improve the degree of circular polarization of the at least one of said primary and secondary image-beams exiting the associated one of the polarization modulators ; and wherein said uniaxially stretched retardation-films each individually possess an in-plane retardation value being equal to one of 140nm, 270nm, or 540nm. <EOS>