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 Title: |
US4992963:
Method and apparatus for determining ambient light and surface reflectance
[ Derwent Title ]
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| Country: |
US United States of America
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| Inventor: |
Funt, Brian V.; West Vancouver, Canada
Ho, Jian; Nepean, Canada
Drew, Mark S.; Vancouver, Canada
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| Assignee: |
Simon Fraser University, Burnaby, Canada
other patents from SIMON FRASER UNIVERSITY (514950) (approx. 40)
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| Published / Filed: |
1991-02-12
/ 1988-12-02
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| Application Number: |
US1988000279168
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| IPC Code: |
Advanced:
G01J 1/02;
G01J 1/42;
G01J 3/42;
G01J 3/50;
G01N 21/27;
G01J 3/46;
Core:
G01N 21/25;
more...
IPC-7:
G01J 3/50;
G01N 21/55;
G06F 15/62;
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| ECLA Code: |
G06K9/46L; G01J3/50; S01J3/46K;
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| U.S. Class: |
Current:
382/162;
250/226;
356/402;
Original:
364/526;
250/226;
356/402;
364/521;
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| Field of Search: |
364/581,526,576
250/226
356/402,404-406
358/022,75,81
382/017
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| Priority Number: |
| 1988-12-02 |
US1988000279168 |
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| Abstract: |
An apparatus for dividing light reflected by an illuminated surface into constituent parts of illuminating light and surface spectral reflectance of the surface. The apparatus includes a receiving device for receiving signals representing measured spectral power distribution Im( lambda ) of the light reflected by the illuminated surface. The apparatus generates a weighting coefficient epsilon i for each of M illuminant basis functions EBi( lambda ) for describing the illuminating light. Weighting coefficients sigma j for each of N reflectance basis functions Sbj( lambda ) are generated to describe the reflectance of the surface. The apparatus compares an approximation Ia( lambda ) of the measured spectral power distribution Im( lambda ), Ia( lambda ) being defined by the relation: <IMAGE> where the set of product pairs Ebi( lambda )Sbj( lambda ) is linearly independent. Different weighting coefficients are regenerated until said Ia( lambda ) and said Im( lambda ) are generally equal. Signals representing at least one of the constituent parts of illuminating light and said surface spectral reflectance are generated based on the weighting coefficients sigma i and sigma j which make said Ia( lambda ) generally equal to said Im( lambda ). The apparatus has an output device for outputting the signals.
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| Attorney, Agent or Firm: |
Shlesinger & Myers ;
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| Primary / Asst. Examiners: |
Gruber, Felix D.;
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| Maintenance Status: |
E2 Expired Check current status
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| INPADOC Legal Status: |
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| Family: |
Show 3 known family members
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First Claim:
Show all 27 claims |
What is claimed is:
1. An apparatus for dividing light reflected by an illuminated surface into constituent parts of illuminating light and surface spectral reflectance of the surface, the apparatus comprising:
- (a) means for receiving spectral power distribution signals produced by performing a band-limited spectral analysis of light reflected by said illuminated surface, said spectral power distribution signals representing measured spectral power distribution Im(.lambda.) of the light reflected by the illuminated surface;
- (b) data processing means for:
- generating a weighting coefficient εi for each of M illuminant basis functions Ebi (.lambda.) describing the illuminating light,
- said processing means generating a weighting coefficient .sigma.j for each of N reflectance basis functions Sbj (.lambda.) describing the reflectance of the surface,
said processing means comparing an approximation Ia(.lambda.) of the measured power distribution Im(.lambda.), to the measured spectral power distribution Im(.lambda.), Ia(.lambda.) being defined by the relation: [Figure] the set of product pairs Ebi (.lambda.)Sbj (.lambda.) being forming a linearly independent set,
- said processing means regenerating different weighting coefficients until said Ia(.lambda.) is generally equal to said Im(.lambda.);
- said processing means generating output spectral power distribution signals representing at least one of said constituent parts of illuminating light and said surface spectral reflectance based on said weighting coefficients εi and .sigma.j generated to make said Ia(.lambda.) generally equal to Im(.lambda.),
- said processing means generating said output spectral power distribution signals representing illuminating light according to the equation: [Figure] and said processing means generating said output spectral power distribution signals representing surface spectral reflectance according to the equation: [Figure] where εi and .sigma.j are coefficients for which the approximation Ia(.lambda.) is generally equal to said Im(.lambda.).
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| Background / Summary: |
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| Drawing Descriptions: |
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| Description: |
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| Forward References: |
Show 26 U.S. patent(s) that reference this one
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| Foreign References: |
None
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| Other References: |
Yuille, A. (1987), A Method for Computing Spectral Reflectance Biological Cybernetics, 56, pp. 195-201.
(7 pages)
Brian V. Funt and Mark S. Drew, "Color Constancy Computation in Near-Mondrian Scenes Using a Finite Dimensional Linear Model".
Brian A. Wandell, "The Synthesis and Analysis of Color Images", IEE Transactions on Pattern Analysis and Machine Intelligence, vol. PAMI-9, No. 1, Jan. 1987, pp. 2-13.
(12 pages)
Cited by 3 patents
Laurence T. Maloney and Brian Al Wandell, "Color Constancy: A Method for Recovering Surface Spectral Reflectance", J. Opt. Soc. Am. A/vol. 3, No. 1/Jan. 1986, pp. 29-33.
(5 pages)
Cited by 10 patents
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