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Measuring arrangement for examining a subject with visible, NIR or IR light

  • US 5,309,907 A
  • Filed: 08/26/1992
  • Issued: 05/10/1994
  • Est. Priority Date: 09/04/1991
  • Status: Expired due to Term
First Claim
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1. An apparatus for optically analyzing tissue in vivo comprising:

  • means for directing a measuring chirp signal at a tissue-containing subject, said measuring chirp signal being a coherent optical signal of light selected from the group consisting of visible, NIR and IR light, a part of said measuring chirp signal emerging from said subject after interacting therein with tissue to be analyzed and forming an emerging signal;

    means for generating a reference chirp signal having a defined phase relationship to said measuring chirp signal;

    means for superimposing said emerging signal with said reference chirp signal to form a superposition signal having sets of beats, each set of beats having a respective beat frequency;

    filter means, for receiving said superposition signal and having a transmission range with an upper limit frequency, for generating from said superposition signal a filtered signal having at least one beat frequency within said transmission range; and

    means for dimensioning parameters including the transit time of said measuring chirp signal outside said subject, the transit time of said reference chirp signal, and said upper limit frequency of said filter means for causing said filtered signal to represent substantially only parts of said emerging signal which have traversed an optical path length in said subject which does not exceed a defined maximum optical path length.

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