US5650610A
Expired / Lapsed
US
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Apparatus and method for remote detection of ice or other birefringent material on a surface
Assignee: National Research Council Canada
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Filing: 1995-03-15
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Granted: 1997-07-22
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Expires: 2015-03-15
Abstract
Abstract An apparatus and method are provided for remotely detecting ice on a polarization preserving surface. A target location on the surface is irradiated with two cross-polarized beams of coherent light. A determination is then made as to whether the speckle patterns from each of the two beams interfere with one another. If interference of the speckle patterns from the two beams is detected, ice or some other birefringent material is said to be present on the surface.
Inventors
- 👤 Robert E. Gagnon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 14:31
CPC Classifications
B; B64; B64D; B64D15/00; B64D15/20
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
128 words
A method of detecting the presence or absence of birefringent material on a polarization-preserving target surface, comprising the steps of: a) irradiating a location on a target surface with at least two beams of coherent, polarized light, the at least two beams being cross polarized with respect to each other; and, b) allowing the at least two beams to reflect off of the irradiated location of the target surface, in the form of a speckle patterns, each beam having an associated speckle pattern; c) determining if the speckle patterns from the at least two beams interfere with each other, wherein the interference of the speckle patterns, other than a small interference due to imperfections in the polarization-preserving surface, indicates the presence of birefringent material on the target surface.
Claim 2
Independent Claim
128 words
A method of detecting the presence or absence of birefringent material on a polarization-preserving target surface, comprising the steps of: a) irradiating a location on a target surface with at least two beams of coherent, polarized light, the at least two beams being cross polarized with respect to each other; and, b) allowing the at least two beams to reflect off of the irradiated location of the target surface, in the form of a speckle patterns, each beam having an associated speckle pattern; c) determining if the speckle patterns from the at least two beams interfere with each other, wherein the interference of the speckle patterns, other than a small interference due to imperfections in the polarization-preserving surface, indicates the presence of birefringent material on the target surface.
Claim 3
Independent Claim
127 words
A method of detecting the presence of ice on a polarization-preserving target surface, comprising the steps of: a) irradiating a location on a target surface with two beams of coherent, polarized light, the two beams being cross polarized with respect to each other and being substantially equal in intensity; and, b) allowing the beams of coherent, polarized light to reflect off of the irradiated location of the target surface, in the form of a speckle patterns, each beam having an associated speckle pattern; c) detecting interference of speckle patterns from the two beams when they interfere with each other, wherein the interference of the speckle patterns, other than a small interference due to imperfections in the polarization-preserving surface, indicates the presence of ice on the target surface.
Claim 4
Independent Claim
127 words
A method of detecting the presence of ice on a polarization-preserving target surface, comprising the steps of: a) irradiating a location on a target surface with two beams of coherent, polarized light, the two beams being cross polarized with respect to each other and being substantially equal in intensity; and, b) allowing the beams of coherent, polarized light to reflect off of the irradiated location of the target surface, in the form of a speckle patterns, each beam having an associated speckle pattern; c) detecting interference of speckle patterns from the two beams when they interfere with each other, wherein the interference of the speckle patterns, other than a small interference due to imperfections in the polarization-preserving surface, indicates the presence of ice on the target surface.
Claim 5
Dependent Claim
35 words
A method of detecting the presence of ice as defined in claim 2, wherein the step of detecting the interference of the speckle patterns is performed by viewing the patterns with a defocused video camera.
Claim 6
Dependent Claim
35 words
A method of detecting the presence of ice as defined in claim 2, including the step of varying a path length of one of the beams in order to cause the interference fringes to move.
Claim 7
Dependent Claim
70 words
A method of detecting the presence of ice as defined in claim 4, including the step of varying a path length of one of the two beams by a small predetermined amount in such a manner as to shorten the path and lengthen the path length of one of the two beams repeatedly for a duration, so that fringes of the interfering speckle patterns observed at a particular location vary.
Claim 8
Dependent Claim
36 words
A method of detecting the presence of ice as defined in claim 5, wherein step (c) of claim 2 includes the step of detecting variation in intensity of the speckle patterns observed at the particular location.
Claim 9
Dependent Claim
63 words
A method of detecting the presence of ice as defined in claim 6, wherein the step of detecting variation in intensity of the overlapping speckle patterns comprises the step of performing said detection in conjunction with applying a threshold of variation, wherein a variation greater than a predetermined minimum variation is said to indicate the presence of ice on the polarization-preserving target surface.
Claim 10
Dependent Claim
53 words
The method of detecting the presence of ice as defined in claim 2 wherein steps (a), (b) and (c) of claim 2 are repeated with two other beams which are cross polarized with respect to each other, said two other beams having a different polarization than the two beams defined in claim 2.
Claim 11
Independent Claim
97 words
A system for detecting the presence of ice on a polarization-preserving target surface, comprising: a) means for irradiating a location on a target surface with two beams of coherent, polarized light, the two beams being cross polarized with respect to each other and being substantially equal in intensity; and, b) means for detecting interference of overlapping speckle patterns from the two coherent polarized beams impinging upon the target surface, wherein the interference of the speckle patterns, other than a small interference due to imperfections in the polarization-preserving surface, indicates the presence of ice on the target surface.
Claim 12
Independent Claim
97 words
A system for detecting the presence of ice on a polarization-preserving target surface, comprising: a) means for irradiating a location on a target surface with two beams of coherent, polarized light, the two beams being cross polarized with respect to each other and being substantially equal in intensity; and, b) means for detecting interference of overlapping speckle patterns from the two coherent polarized beams impinging upon the target surface, wherein the interference of the speckle patterns, other than a small interference due to imperfections in the polarization-preserving surface, indicates the presence of ice on the target surface.
Claim 13
Dependent Claim
30 words
A device as defined in claim 9 wherein the means for detecting the interference includes a defocused video camera for use in detecting the interference of the overlapping speckle patterns.
Claim 14
Dependent Claim
35 words
A device as defined in claim 9 including means for varying a path length of one of the beams in order to cause interference fringes present in the interference of the speckle patterns to move.
Claim 15
Dependent Claim
33 words
A device as defined in claim 11, wherein the means for varying the path length comprises a pair of transparent wedges placed in the path of one of the two beams of light.
Claim 16
Dependent Claim
21 words
A device as defined in claim 11, wherein the means for varying the path length comprises a substantially transparent glass plate.
Claim 17
Dependent Claim
32 words
A device as defined in claim 9 wherein the means for detecting the interference speckle patterns includes means for detecting a variation in intensity at particular location in the overlapping speckle pattern.
Claim 18
Dependent Claim
51 words
A device as defined in claim 9 wherein the means for detecting a variation in intensity at a location in the overlapping speckle patterns includes a thresholding means such that when a predetermined threshold is reached, a signal is generated indicative of the presence of ice on the polarization-preserving target surface.
Claim 19
Dependent Claim
46 words
A device as defined in claim 9, including means for irradiating the location on the target surface with two other beams of coherent, polarized light, the two beams being cross polarized with respect to each other and having a different polarization than the two other beams.
Claim 20
Dependent Claim
45 words
A device as defined in claim 9 wherein the means for detecting the interference of speckle patterns from the two coherent polarized beams of light striking the target includes at least one photodiode for converting a portion of overlapping speckle pattern to an electrical signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-07-21 | 2001-01-20 | 2001-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-07-21 | 2005-01-20 | 2005-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-07-21 | 2009-01-20 | 2009-07-22 | $7700.00 | Window Closed / Lapsed |