US5901243A
Expired / Lapsed
US
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Dynamic exposure control in single-scan digital input devices
Assignee: Hewlett Packard Development Co LP
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Filing: 1996-09-30
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Granted: 1999-05-04
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Expires: 2016-09-30
Abstract
Abstract In the present invention statistical methods are used to estimate the reflectance of the paper and align the tone gamut to the dynamic range of a digital input device such as a scanner during a single scan. The estimate is refined during the scan. This refinement increases the robustness with respect to unfavorable originals (e.g., originals with a dark border) and at the same time also can take into account such phenomena as the change of the response of the sensor due to thermal effect during slow scans. In the present invention no spatial information on the image is collected. Instead a histogram of the occurrence of each tone level is accumulated during the scan. The background color of the image, i.e., the tone value of the paper is estimated by analyzing the histogram. When this value is known, the parameters for a tone reproduction curve (TRC) can be calculated. The shape of the TRC is not altered by these parameters, i.e., the exposure can be controlled independently of the tone reproduction. This process is repeated from time to time during the scan to assure robustness and to compensate for drifts in the sensitivity of the sensor.
Inventors
- 👤 Giordano B. Beretta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 10:18
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/407; H04N1/4072; H04N1/4074
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
141 words
An exposure control method for a digital input device, comprising the steps of: collecting a histogram for a scanned line on a medium; updating a cumulative histogram based upon the histogram collected for the scanned line; and using the histogram collected for the scanned line to estimate the reflectance of the medium; wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the step of estimating the reflectance of the medium includes determining an average tone value within the cumulative histogram and determining an average tone deviation value within the cumulative histogram.
Claim 2
Dependent Claim
141 words
An exposure control method for a digital input device, comprising the steps of: collecting a histogram for a scanned line on a medium; updating a cumulative histogram based upon the histogram collected for the scanned line; and using the histogram collected for the scanned line to estimate the reflectance of the medium; wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the step of estimating the reflectance of the medium includes determining an average tone value within the cumulative histogram and determining an average tone deviation value within the cumulative histogram.
Claim 3
Independent Claim
23 words
The method as set forth in 1, wherein the step of estimating the reflectance of the medium is performed for predetermined scanned lines.
Claim 4
Independent Claim
23 words
The method as set forth in 1, wherein the step of estimating the reflectance of the medium is performed for predetermined scanned lines.
Claim 5
Independent Claim
24 words
The method as set forth in 1, wherein the step of estimating the reflectance of the medium is performed for randomly determined scanned lines.
Claim 6
Independent Claim
24 words
The method as set forth in 1, wherein the step of estimating the reflectance of the medium is performed for randomly determined scanned lines.
Claim 7
Dependent Claim
135 words
An exposure control method for a digital input device, comprising the steps of: collecting a histogram for a scanned line on a medium; updating a cumulative histogram based upon the histogram collected for the scanned line; using the histogram collected for the scanned line to estimate the reflectance of the medium; and wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the step of estimating the reflectance of the medium includes determining an average tone value for a particular color channel within the cumulative histogram.
Claim 8
Dependent Claim
135 words
An exposure control method for a digital input device, comprising the steps of: collecting a histogram for a scanned line on a medium; updating a cumulative histogram based upon the histogram collected for the scanned line; using the histogram collected for the scanned line to estimate the reflectance of the medium; and wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the step of estimating the reflectance of the medium includes determining an average tone value for a particular color channel within the cumulative histogram.
Claim 9
Independent Claim
33 words
The method as set forth in 4, wherein the step of estimating the reflectance of the medium includes determining an average tone deviation value for a particular color channel within the cumulative histogram.
Claim 10
Independent Claim
33 words
The method as set forth in 4, wherein the step of estimating the reflectance of the medium includes determining an average tone deviation value for a particular color channel within the cumulative histogram.
Claim 11
Independent Claim
13 words
The method as set forth in 4, wherein the particular color is red.
Claim 12
Independent Claim
13 words
The method as set forth in 4, wherein the particular color is red.
Claim 13
Independent Claim
23 words
The method as set forth in 4, wherein the step of estimating the reflectance of the medium is performed for predetermined scanned lines.
Claim 14
Independent Claim
23 words
The method as set forth in 4, wherein the step of estimating the reflectance of the medium is performed for predetermined scanned lines.
Claim 15
Independent Claim
24 words
The method as set forth in 4, wherein the step of estimating the reflectance of the medium is performed for randomly determined scanned lines.
Claim 16
Independent Claim
24 words
The method as set forth in 4, wherein the step of estimating the reflectance of the medium is performed for randomly determined scanned lines.
Claim 17
Dependent Claim
145 words
An exposure control apparatus for a digital input device, the apparatus comprising: means for collecting a histogram for a scanned line on a medium; means for updating a cumulative histogram based upon the histogram collected for the scanned line; and means for using the histogram collected for the scanned line to estimate the reflectance of the medium; wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the estimation of the reflectance of the medium includes determining an average tone value within the cumulative histogram and determining an average tone deviation value within the cumulative histogram.
Claim 18
Dependent Claim
145 words
An exposure control apparatus for a digital input device, the apparatus comprising: means for collecting a histogram for a scanned line on a medium; means for updating a cumulative histogram based upon the histogram collected for the scanned line; and means for using the histogram collected for the scanned line to estimate the reflectance of the medium; wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the estimation of the reflectance of the medium includes determining an average tone value within the cumulative histogram and determining an average tone deviation value within the cumulative histogram.
Claim 19
Independent Claim
22 words
The apparatus as set forth in 9, wherein the estimation of the reflectance of the medium is performed for predetermined scanned lines.
Claim 20
Independent Claim
22 words
The apparatus as set forth in 9, wherein the estimation of the reflectance of the medium is performed for predetermined scanned lines.
Claim 21
Independent Claim
23 words
The apparatus as set forth in 9, wherein the estimation of the reflectance of the medium is performed for randomly determined scanned lines.
Claim 22
Independent Claim
23 words
The apparatus as set forth in 9, wherein the estimation of the reflectance of the medium is performed for randomly determined scanned lines.
Claim 23
Dependent Claim
139 words
An exposure control apparatus for a digital input device, the apparatus comprising: means for collecting a histogram for a scanned line on a medium; means for updating a cumulative histogram based upon the histogram collected for the scanned line; and means for using the histogram collected for the scanned line to estimate the reflectance of the medium; wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the estimation of the reflectance of the medium includes determining an average tone value for a particular color channel within the cumulative histogram.
Claim 24
Dependent Claim
139 words
An exposure control apparatus for a digital input device, the apparatus comprising: means for collecting a histogram for a scanned line on a medium; means for updating a cumulative histogram based upon the histogram collected for the scanned line; and means for using the histogram collected for the scanned line to estimate the reflectance of the medium; wherein the histogram collected for the scanned line is used to estimate the reflectance of the medium indirectly by revising an estimation based upon the updated cumulative histogram and thereby align an estimated tone gamut of the medium to the dynamic range of the digital input device to generate a tone response curve during a single scan; and wherein the estimation of the reflectance of the medium includes determining an average tone value for a particular color channel within the cumulative histogram.
Claim 25
Independent Claim
22 words
The apparatus as set forth in 12, wherein the estimation of the reflectance of the medium is performed for predetermined scanned lines.
Claim 26
Independent Claim
22 words
The apparatus as set forth in 12, wherein the estimation of the reflectance of the medium is performed for predetermined scanned lines.
Claim 27
Independent Claim
23 words
The apparatus as set forth in 12, wherein the estimation of the reflectance of the medium is performed for randomly determined scanned lines.
Claim 28
Independent Claim
23 words
The apparatus as set forth in 12, wherein the estimation of the reflectance of the medium is performed for randomly determined scanned lines.
Claim 29
Independent Claim
32 words
The apparatus as set forth in 12, wherein the estimation of the reflectance of the medium includes determining an average tone deviation value for a particular color channel within the cumulative histogram.
Claim 30
Independent Claim
32 words
The apparatus as set forth in 12, wherein the estimation of the reflectance of the medium includes determining an average tone deviation value for a particular color channel within the cumulative histogram.
Claim 31
Independent Claim
13 words
The apparatus as set forth in 12, wherein the particular color is red.
Claim 32
Independent Claim
13 words
The apparatus as set forth in 12, wherein the particular color is red.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2002-05-03 | 2002-11-02 | 2003-05-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-05-03 | 2006-11-02 | 2007-05-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-05-03 | 2010-11-02 | 2011-05-04 | $7700.00 | Window Closed / Lapsed |