Image projection system with a polarizing beam splitter

  • US 6,234,634 B1
  • Filed: 07/28/1999
  • Issued: 05/22/2001
  • Est. Priority Date: 07/28/1999
  • Status: Expired due to Term
First Claim
Patent Images

1. An image projection system for providing a bright and clear image, the system comprising:

  • a light source producing a visible light beam;

    a polarizing beam splitter located near the light source in the light beam and oriented at an angle with respect to the light beam, the beam splitter comprising a transparent substrate having a first surface located in the light beam with the light beam striking the first surface at an angle, and a generally parallel arrangement of thin, elongated elements supported by the substrate, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

    a reflective array located near the polarizing beam splitter in either the reflected or transmitted beam, the array modulating the polarization of the beam by selectively altering the polarization of the beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back towards the polarizing beam splitter;

    the beam splitter further being located in the modulated beam and oriented at an angle with respect to the modulated beam, and the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam, to separate out the unaltered polarization from the modulated beam;

    a screen located in either the second reflected beam or the second transmitted beam for displaying the encoded image information.

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