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US5953440A
Expired / Lapsed
US
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Method of measuring the focus of close-up images of eyes
Assignee: Sensar Inc
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Filing: 1997-12-02
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Granted: 1999-09-14
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Expires: 2017-12-02
Abstract
Abstract In a method of determining whether an image of an eye is in focus a set of pixels is selected along a line passing through the pupil/iris boundary such that the set contains at least 5 iris portion pixels and at least 5 pupil portion pixels. Statistical values, preferably median values, are computed for all iris pixels in the selected set and for all pupil pixels in the selected set. The step size between the iris pixels and the pupil pixels is computed and absolute gradient values are computed for each pixel. The pixel having a largest absolute gradient value is excluded and an average of the absolute gradient values of the remaining pixels is found. If that average divided by the step size is greater than 0.5 the image is in focus and can be used for identifying a subject whose eye is in the image using iris identification techniques.
Inventors
- 👤 Guang Hua Zhang
- 👤 Marcos Salganicoff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 18:19
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/117; A61B5/1171
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
265 words
A method of determining whether an image of an eye is in focus wherein the image contains an iris portion having a radius r i and a pupil portion having a radius r p and there is an pupil/iris boundary between the iris portion and the pupil portion, the image is formed of pixels and there are at least 5 pixels of the iris portion of the image and at least 5 pixels of the pupil portion of the image on a single line comprised of: a. selecting a set of pixels along a line passing through the pupil/iris boundary the set containing at least 5 iris portion pixels and at least 5 pupil portion pixels: b. computing a statistical value M i of all iris pixels in the selected set; c. computing a statistical value M p of all pupil pixels in the selected set; d. computing a step size H such that H=M i -M p ; e. determining a gradient of pixel values along the line for the selected set of pixels; f. forming a second set of pixels by excluding from the selected set of pixels that pixel having a largest absolute gradient value; g. determining an average S of the absolute gradient values of the pixels in the second set of pixels; h. computing 1/w=S/H; and i. if 1/w is greater than 0.5 using the image for identifying a subject whose eye is in the image using iris identification techniques and if 1/w is less than or equal to 0.5 selecting a new image and repeating steps a through h.
Claim 2
Independent Claim
265 words
A method of determining whether an image of an eye is in focus wherein the image contains an iris portion having a radius r i and a pupil portion having a radius r p and there is an pupil/iris boundary between the iris portion and the pupil portion, the image is formed of pixels and there are at least 5 pixels of the iris portion of the image and at least 5 pixels of the pupil portion of the image on a single line comprised of: a. selecting a set of pixels along a line passing through the pupil/iris boundary the set containing at least 5 iris portion pixels and at least 5 pupil portion pixels: b. computing a statistical value M i of all iris pixels in the selected set; c. computing a statistical value M p of all pupil pixels in the selected set; d. computing a step size H such that H=M i -M p ; e. determining a gradient of pixel values along the line for the selected set of pixels; f. forming a second set of pixels by excluding from the selected set of pixels that pixel having a largest absolute gradient value; g. determining an average S of the absolute gradient values of the pixels in the second set of pixels; h. computing 1/w=S/H; and i. if 1/w is greater than 0.5 using the image for identifying a subject whose eye is in the image using iris identification techniques and if 1/w is less than or equal to 0.5 selecting a new image and repeating steps a through h.
Claim 3
Dependent Claim
22 words
The method of claim 1 wherein the set of pixels is along a radial line extending from a center of the pupil.
Claim 4
Dependent Claim
19 words
The method of claim 1 wherein the set of pixels is along a line extending horizontally across the image.
Claim 5
Dependent Claim
19 words
The method of claim 1 wherein the set of pixels is along a line extending vertically across the image.
Claim 6
Dependent Claim
17 words
The method of claim 1 wherein the statistical values M i and M p are median values.
Claim 7
Dependent Claim
17 words
The method of claim 1 wherein the statistical values M i and M p are mean values.
Claim 8
Independent Claim
241 words
A method of determining whether an image of an eye is in focus wherein the image contains an iris portion having a radius r i and a pupil portion having a radius r p and there is an pupil/iris boundary between the iris portion and the pupil portion, the image is formed of pixels and there are at least 5 pixels of the iris portion of the image and at least 5 pixels of the pupil portion of the image on a single line comprised of: a. selecting a set of pixels along a line passing through the pupil/iris boundary the set containing at least 5 iris portion pixels and at least 5 pupil portion pixels: b. computing a statistical value M i of all iris pixels in the selected set; c. computing a statistical value M p of all pupil pixels in the selected set; d. computing a step size H such that H=M i -M p ; e. determining a gradient of pixel values along the line for the selected set of pixels; f. determining an average S of the absolute gradient values of the pixels in the set of pixels; g. computing 1/w=S/H; and h. if 1/w is greater than 0.5 using the image for identifying a subject whose eye is in the image using iris identification techniques and if 1/w is less than or equal to 0.5 selecting a new image and repeating steps a through g.
Claim 9
Independent Claim
241 words
A method of determining whether an image of an eye is in focus wherein the image contains an iris portion having a radius r i and a pupil portion having a radius r p and there is an pupil/iris boundary between the iris portion and the pupil portion, the image is formed of pixels and there are at least 5 pixels of the iris portion of the image and at least 5 pixels of the pupil portion of the image on a single line comprised of: a. selecting a set of pixels along a line passing through the pupil/iris boundary the set containing at least 5 iris portion pixels and at least 5 pupil portion pixels: b. computing a statistical value M i of all iris pixels in the selected set; c. computing a statistical value M p of all pupil pixels in the selected set; d. computing a step size H such that H=M i -M p ; e. determining a gradient of pixel values along the line for the selected set of pixels; f. determining an average S of the absolute gradient values of the pixels in the set of pixels; g. computing 1/w=S/H; and h. if 1/w is greater than 0.5 using the image for identifying a subject whose eye is in the image using iris identification techniques and if 1/w is less than or equal to 0.5 selecting a new image and repeating steps a through g.
Claim 10
Dependent Claim
22 words
The method of claim 7 wherein the set of pixels is along a radial line extending from a center of the pupil.
Claim 11
Dependent Claim
19 words
The method of claim 7 wherein the set of pixels is along a line extending horizontally across the image.
Claim 12
Dependent Claim
19 words
The method of claim 7 wherein the set of pixels is along a line extending vertically across the image.
Claim 13
Dependent Claim
17 words
The method of claim 7 wherein the statistical values M i and M p are median values.
Claim 14
Dependent Claim
17 words
The method of claim 7 wherein the statistical values M i and M p are mean values.
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) | 2002-09-13 | 2003-03-15 | 2003-09-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-09-13 | 2007-03-15 | 2007-09-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-09-13 | 2011-03-15 | 2011-09-14 | $7700.00 | Window Closed / Lapsed |