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Method and apparatus for performing optical measurements

  • US 5,459,570 A
  • Filed: 03/16/1993
  • Issued: 10/17/1995
  • Est. Priority Date: 04/29/1991
  • Status: Expired due to Term
First Claim
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1. A system for performing selected optical measurements on a sample comprising:

  • a short coherence length optical radiation source at a wavelength λ

    ;

    a reference optical reflector;

    a first optical path leading to said reflector;

    a second optical path leading to said sample;

    means for applying optical radiation from said source through the first optical path to said reflector and through the second optical path to the sample;

    means for altering the relative lengths of said optical paths in accordance with a predetermined velocity profile, said profile providing for continuous alteration in said relative length at an instantaneous velocity V for each point on the profile in at least the region of said profile where said measurements are to be performed;

    means for combining reflections from the reflector received through the first optical path and reflections from the sample received through the second optical path, the resulting combined optical output having interference fringes at length matched points on the two paths and having an instantaneous modulating frequency including a Doppler shift frequency at a frequency fD= 2V/λ

    ;

    means for demodulating said output; and

    means for processing the demodulated output to obtain information concerning said selected measurements.

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