US5361769A
Expired / Lapsed
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Method and a system for measuring fluid flow movements by a laser-doppler technique
Assignee: Nobel Coatings AB
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Filing: 1992-08-21
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Granted: 1994-11-08
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Expires: 2012-08-21
Abstract
Abstract The invention relates to a method and to a system for reducing the distance-dependent amplification factor when measuring fluid flow movements with the aid of an image-producing laser-Doppler technique, in particular when measuring blood perfusion through tissue. A laser beam source (1) directs a laser beam (2) onto a measurement object (5), which scatters and reflects the beam (2). The reflected light is received by a detector (9) which senses the broadening in frequency caused by the Doppler effect. One or more lenses (12: 15, 16) are placed in the path of the beam (2) and are intended to maintain constant the number of coherence areas on the detecting surface of the detector and independent of the distance between detector and measurement object.
Inventors
- 👤 Gert Nilsson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:12
CPC Classifications
G; G01; G01P; G01P5/00; G01P5/26; A; A61; A61B; A61B5/00; A61B5/02; A61B5/026; A61B5/0261
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
94 words
A method for measuring fluid flow movements, said method comprising the steps of: directing a laser beam (2) generated by a laser beam source (1) onto a measurement object (5) which scatters and reflects the laser beam (2); receiving and detecting scattered and reflected light from said measurement object (5) in a detector (9) and detecting a broadening in frequency caused by a Doppler effect; maintaining a number of coherence areas on a detector surface of said detector (9) constant and independent of a distance between said detector (9) and said measurement object (5).
Claim 2
Independent Claim
94 words
A method for measuring fluid flow movements, said method comprising the steps of: directing a laser beam (2) generated by a laser beam source (1) onto a measurement object (5) which scatters and reflects the laser beam (2); receiving and detecting scattered and reflected light from said measurement object (5) in a detector (9) and detecting a broadening in frequency caused by a Doppler effect; maintaining a number of coherence areas on a detector surface of said detector (9) constant and independent of a distance between said detector (9) and said measurement object (5).
Claim 3
Dependent Claim
38 words
A method according to claim 1, wherein the number of coherence areas on the detector surface of said detector (9) is kept constant by causing the laser beam (2) to diverge in a direction towards the measurement object.
Claim 4
Dependent Claim
92 words
A method according to claim 2, further comprising the steps of: moving the laser beam (2) over the measurement object (5) in a specific scanning pattern, such that the detector (9) will receive and detect the light reflected from a large number of measurement points (M) along the scanning path; and in each of these measurement points (M) registering and compensating for an angle α between a normal of the detector surface and a line from which the measurement point (M) on the measurement object (5) is seen from the detector (9).
Claim 5
Dependent Claim
33 words
A method according to claim 2, wherein divergence of the light beam (2) is achieved by refraction of the beam through a lens (12) whose focal point coincides with the detector surface plane.
Claim 6
Dependent Claim
92 words
A method according to claim 4, further comprising the steps of: moving the laser beam (2) over the measurement object (5) in a specific scanning pattern, such that the detector (9) will receive and detect the light reflected from a large number of measurement points (M) along the scanning path; and in each of these measurement points (M) registering and compensating for an angle α between a normal of the detector surface and a line from which the measurement point (M) on the measurement object (5) is seen from the detector (9).
Claim 7
Dependent Claim
35 words
A method according to claim 2, wherein divergence of the laser beam (2) is achieved, by refraction of the beam through a plurality of lenses (15, 16) placed at a given distance from one another.
Claim 8
Dependent Claim
92 words
A method according to claim 6, further comprising the steps of: moving the laser beam (2) over the measurement object (5) in a specific scanning pattern, such that the detector (9) will receive and detect the light reflected from a large number of measurement points (M) along the scanning path; and in each of these measurement points (M) registering and compensating for an angle α between a normal of the detector surface and a line from which the measurement point (M) on the measurement object (5) is seen from the detector (9).
Claim 9
Dependent Claim
92 words
A method according to claim 1, further comprising the steps of: moving the laser beam (2) over the measurement object (5) in a specific scanning pattern, such that the detector (9) will receive and detect the light reflected from a large number of measurement points (M) along the scanning path; and, in each of these measurement points (M), registering and compensating for an angle α between a normal of the detector surface and a line from which the measurement point (M) on the measurement object (5) is seen from the detector (9).
Claim 10
Independent Claim
87 words
A system for measuring fluid flow movements, said system comprising: a laser beam source (1) for generating a laser beam (2), means (3, 6) for directing the beam onto a measurement object (5) to be examined, detector means (9) located above the measurement object for receiving light reflected from the measurement object (5) and for detecting a broadening in frequency caused by a Doppler effect, and means (12; 15; 16; 20) for maintaining a constant number of coherence areas on a detecting surface of said detector means.
Claim 11
Independent Claim
87 words
A system for measuring fluid flow movements, said system comprising: a laser beam source (1) for generating a laser beam (2), means (3, 6) for directing the beam onto a measurement object (5) to be examined, detector means (9) located above the measurement object for receiving light reflected from the measurement object (5) and for detecting a broadening in frequency caused by a Doppler effect, and means (12; 15; 16; 20) for maintaining a constant number of coherence areas on a detecting surface of said detector means.
Claim 12
Dependent Claim
40 words
A system according to claim 9, wherein said means for maintaining includes a lens (12) through which said laser beam (2) is caused to pass and refract so as to diverge said beam in a direction towards said measurement object.
Claim 13
Dependent Claim
20 words
A system according to claim 10, wherein a focal point of said lens (12) coincides with the detector surface plane.
Claim 14
Dependent Claim
57 words
A system according to claim 9, wherein said means for maintaining includes two lenses (15, 16) placed at a given distance from one another and so that the laser beam is caused to pass through said lenses (15, 16) and is refracted so as to diverge said beam (2) in a direction towards said measurement object (5).
Claim 15
Dependent Claim
58 words
A system according to claim 9, wherein said means for maintaining includes a shutter means placed at the detector surface and intended to adjustably shutter the detector surface of the detector means (9) contingent on a distance between the detector and the measurement object such as to maintain the number of coherence areas on the detector surface constant.
References Cited (Backward Citations)
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