Patent ID: 6910771

Claim:
In a projection-display system for receiving a first light beam embodying a first image from a video device and for enlarging said image to a second image to be embodied in a second light beam adapted for projection onto a screen, said system comprising: a polarized beam splitter (PBS) for separating the first light beam into a reflected spolarized light wave and a transmitted P polarized light wave; delay means for creating a half wavelength delay between the reflected S polarized light wave and the transmitted P polarized light wave; direction-modifying means for changing the direction of the transmitted P polarized light wave in such manner that it becomes parallel to, and travels in the same direction as, the reflected S polarized light wave; and a condenser for condensing the reflected S polarized light wave and the transmitted P polarized light wave; the improvement comprising: an improved PBS-and-delay device (PDD), said PDD comprising an integrally-formed means for separating the first light beam into a reflected S polarized light wave and a transmitted P polarized light wave, and for creating a half wavelength delay between the reflected S polarized light wave and the transmitted P polarized light wave; the integrally-formed PDD comprises a generally planar transparent, dielectric medium having a predetermined thickness, a Brewster Angle characteristic of the medium, an upper surface and a lower surface; the upper surface of the PDD has a thin-film coating adapted for reflecting the S polarized light wave and for transmitting the P polarized light wave from the first light beam, when the PBS receives the first light beam at an angle of incidence equal to the Brewster Angle for said medium, to provide the PBS for the system; and the lower surface of the PDD has a thin-film coating substantially identical to the thin-film coating of the upper surface, whereby any refraction occurring during transmission of the P polarized light wave through the coating on the upper surface is canceled out by transmission of the P polarized light wave through the coating on the lower surface.