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Polarization based optical sensor utilizing total internal reflection

  • US 5,483,346 A
  • Filed: 04/11/1994
  • Issued: 01/09/1996
  • Est. Priority Date: 04/11/1994
  • Status: Expired due to Fees
First Claim
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1. A polarization based optical sensor utilizing total internal reflection for detecting substances and changes in said substances on a transparent material comprising at least one polarized-light source that generates a polarized light, at least one polarized-light detector that is sensitive to a particular polarization of light, and said transparent material that is transparent to said polarized light;

  • said polarized-light source oriented so that said polarized light produced thereby enters said transparent material, undergoes a number of substantially-total-internal reflections within said transparent material by striking a boundary of said transparent material at an angle of incidence greater than both a critical angle for a surrounding medium and a critical angle for said substances, exits said transparent material, and strikes said polarized-light detector;

    said polarized-light source also oriented so that said polarized light produced thereby has an original-electric field consisting of a parallel-electric field parallel to a plane of incidence of said substantially-total-internal reflections and a perpendicular-electric field perpendicular to said plane of incidence of said substantially-total-internal reflections;

    said polarized light having a phase shift between said parallel-electric field and said perpendicular-electric field;

    said phase shift dependent upon an index of refraction of said substances and said surrounding medium at said substantially-total-internal reflections, a change in said substances causing a corresponding change in said index of refraction, in turn causing a resulting change in said phase shift;

    said resulting change in said phase shift causing a transfer of energy between said original-electric field and an electric field perpendicular to said original-electric field;

    said polarized-light detector oriented so that said transfer of energy causes a measurable change in an output of said polarized-light detector;

    whereby said substances and changes in said substances are detected.

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