Optical collimating device employing cholesteric liquid crystal and a non-transmissive reflector

  • US 5,408,346 A
  • Filed: 10/20/1993
  • Issued: 04/18/1995
  • Est. Priority Date: 10/20/1993
  • Status: Expired due to Fees
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First Claim
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1. An optical collimating apparatus for focussing an image at infinity or at a desired finite distance as viewed by an observer, the image being formed by an image means to include circular polarized image light having components within a predetermined bandwidth and of a first rotary sense of circular polarization, the apparatus comprising:

  • a cholesteric liquid crystal element of the type reflective to light within the predetermined bandwidth and of a first rotary sense of circular polarization; and

    a non-transmissive optical mirror positioned to receive and reflect the image light to the cholesteric liquid crystal element, reversing the rotary sense of circular polarization in so doing;

    whereby the cholesteric liquid crystal element and the optical mirror are arranged and positioned so that image light from the image means is reflected or transmitted by the cholesteric liquid crystal element then received and reflected by the optical mirror with reversal of the rotary sense of the image light components to the choesteric liquid crystal element and into the line-of-sight of the observer.

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