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Beam-splitting optical system

  • US 4,288,148 A
  • Filed: 08/29/1979
  • Issued: 09/08/1981
  • Est. Priority Date: 08/29/1979
  • Status: Expired due to Term
First Claim
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1. A unit power optical system for insertion into projection apparatus to permit viewing an image projected on an image plane without affecting its quality, size or position comprising:

  • a beam splitting element disposed in the optical path of the converging light before the image plane so that said beam splitting element will transmit the radiation to the image plane and reflect a portion of the radiation reflected from the image plane in a direction which permits viewing;

    means disposed in said optical path to correct for image displacement and aberrations caused by said beam splitting element; and

    said optical system being afocal so that said system will remain at unit power when it is shifted longitudinally and the image position is insensitive to longitudinal displacement.

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