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Measurements of optical inhomogeneity and other properties in substances using propagation modes of light

  • US 6,943,881 B2
  • Filed: 06/03/2004
  • Issued: 09/13/2005
  • Est. Priority Date: 06/04/2003
  • Status: Active Grant
First Claim
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1. A method for optically measuring a sample comprising:

  • directing one beam of guided light in a first propagation mode to a sample;

    directing a first portion of the guided light in the first propagation mode at a location near the sample away from the sample before the first portion reaches the sample while allowing a second portion in the first propagation mode to reach the sample;

    controlling a reflection of the second portion from the sample to be in second propagation mode different from the first propagation mode to produce a reflected second portion;

    directing both the first portion in the first propagation mode and the reflected second portion in the second propagation mode through a common waveguide into a detection module to extract information from the reflected second portion on the sample;

    adjusting a relative phase delay between the reflected first portion and the reflected second portion to a first value to measure a first signal associated with a first layer within the sample;

    adjusting the relative phase delay to a second, different value to measure a second signal associated with a second layer within the sample; and

    obtaining a ratio between the first and the second signals to extract information about a layer of the sample located between the first and the second layers.

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