Short coherence length, doppler velocimetry system
First Claim
1. Apparatus for measuring a profile of speed of blood, wherein the speed is parallel or antiparallel to the direction of a sample beam, the profile being across a blood vessel in a biological sample, in particular, in a retinal blood vessel, which apparatus comprises:
- a source of a beam of radiation having a principal wavelength, which beam of radiation is substantially spatially coherent and has a temporal coherence length which is less than 1 picosecond;
means for splitting the beam into the sample beam and a reference beam;
means for reflecting the reference beam;
means for altering an optical path length of the reference beam from the splitting means to a detector means at an alteration velocity;
means for directing the sample beam within the biological sample to pass through the blood vessel;
wherein the detector means comprises means;
(a) for detecting interferences between reflections of the sample beam from matter in the sample including matter situated across the blood vessel and reflections of the reference beam from the reflecting means and (b) for generating an interference signal;
analyzer means for analyzing the interference signal to determine the profile of the speed of the blood from an analysis of frequency spectra of time segments of the interference signal, the alteration velocity in the time segments, and the principal wavelength.
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Accused Products
Abstract
Apparatus for measuring the speed of blood in blood vessels in biological samples, for example, in retinal blood vessels, which apparatus includes: (a) a source of a beam of radiation having a principal wavelength, which radiation is substantially spatially coherent and has a temporal coherence length which is less than 1 picosecond; (b) a beam splitter for splitting the beam into a sample beam and reference beam; (c) optical apparatus for directing the sample beam to an area within the biological sample; (d) a reflector for reflecting the reference beam; (e) a detector for detecting an interference between the sample beam reflected from the area and the reflected reference beam and for generating an interference signal; (f) apparatus for altering an optical path length of the reference beam from the beam splitter to the detector at an alteration velocity; and (g) an analyzer for analyzing the interference signal to determine the speed of the blood in the area from a shift of a central frequency of a frequency spectrum of the interference signal from a frequency determined from the alteration velocity and the principal wavelength.
112 Citations
19 Claims
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1. Apparatus for measuring a profile of speed of blood, wherein the speed is parallel or antiparallel to the direction of a sample beam, the profile being across a blood vessel in a biological sample, in particular, in a retinal blood vessel, which apparatus comprises:
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a source of a beam of radiation having a principal wavelength, which beam of radiation is substantially spatially coherent and has a temporal coherence length which is less than 1 picosecond; means for splitting the beam into the sample beam and a reference beam; means for reflecting the reference beam; means for altering an optical path length of the reference beam from the splitting means to a detector means at an alteration velocity; means for directing the sample beam within the biological sample to pass through the blood vessel; wherein the detector means comprises means;
(a) for detecting interferences between reflections of the sample beam from matter in the sample including matter situated across the blood vessel and reflections of the reference beam from the reflecting means and (b) for generating an interference signal;analyzer means for analyzing the interference signal to determine the profile of the speed of the blood from an analysis of frequency spectra of time segments of the interference signal, the alteration velocity in the time segments, and the principal wavelength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. Method for measuring a profile of absolute value of velocity of blood across a blood vessel in a biological sample, in particular, in a retinal blood vessel, which method comprises the steps of:
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generating a sample beam having a principal wavelength from a short coherence length Michelson interferometer having a reference beam whose reference beam path is varied at an alteration velocity; aiming the sample beam at a wall of the blood vessel; scanning the sample beam over the blood vessel in a first direction by varying the reference beam path at the alteration velocity and detecting an interference signal produced by an interference between reflections of the sample beam and the reference beam; determining a first position of a first wall and a first position of a second wall from the interference signal; determining components of velocity of the blood parallel or antiparallel to a direction of the sample beam from the interference signal by analyzing frequency spectra of time segments of the interference signal; scanning the sample beam in a second direction to determine a second position of the second wall; determining an angle of the first direction with respect to a direction of the blood vessel from the positions; and determining the absolute velocity profile of the blood from the components of velocity and the angle.
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19. Method for measuring a profile of absolute value of velocity of blood across a blood vessel in a biological sample, in particular, in a retinal blood vessel, which method comprises the steps of:
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generating a sample beam having a principal wavelength from a short coherence length Michelson interferometer having a reference beam whose reference beam path is varied at an alteration velocity; aiming the sample beam at a wall of the blood vessel; scanning the sample beam over the blood vessel in a first direction by varying the reference beam path at the alteration velocity and detecting an interference signal produced by an interference between reflections of the sample beam and the reference beam; determining a first position of a first wall from the interference signal; determining components of velocity of the blood parallel or antiparallel to a direction of the sample beam and a first position of a maximum of velocity from the interference signal by analyzing frequency spectra of time segments of the interference signal; scanning the sample beam in a second direction to determine a second position of a maximum of velocity; determining an angle of the first direction with respect to a direction of the blood vessel from the first position and the second position; and determining the absolute velocity profile of the blood from the components of velocity and the angle.
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Specification