Stereoscopic 3D system using linear polarization

A polarization conversion system comprising:

• a polarization beam-splitting element configured to separate a randomly polarized incident image-beam emitted by a projector into:
• a transmitted image-beam possessing a first state of linear polarization, and
• at least one reflected image-beam possessing a second state of linear polarization wherein said first and second states of linear polarization are substantially mutually orthogonal;
• a reflective surface configured to deflect the optical-path for at least one of said transmitted or reflected image-beams towards a projection surface, said transmitted and reflected image-beams being arranged to at least partially overlap on said projection surface;
• and
• at least a first and second polarization modulator, respectively located within the optical-paths for each of said transmitted and reflected image-beams and arranged to modulate the polarization states of said transmitted and reflected image-beams between a first and second output linear polarization state in synchronization with the image-beam emitted by said projector, wherein the first and second output linear polarization states are substantially mutually orthogonal, each of said polarization modulators further comprising:
• at least a first and second pi-cell liquid crystal element aligned in a mutually crossed orientation wherein the surface molecular alignment directors for said first pi-cell liquid crystal element are aligned substantially perpendicular to the surface molecular alignment directors for said second pi-cell liquid crystal element, each of said pi-cell liquid crystal elements being switched between at least a first and second optical-state, at least one of said optical-states having an in-plane optical retardation value corresponding to a quarter-wave plate (QWP) for at least a portion of the visible wavelength spectrum, and
• there being provided a quarter-wave plate located in close proximity to at least one of said pi-cell liquid crystal elements, wherein the optical axis for the in-plane optical retardation for at least one of said pi-cell liquid crystal elements when switched to at least one of said optical-states is aligned substantially perpendicular to the optical axis for said quarter-wave plate.