Patent US5608823A successfully refreshed from Google Patents.
US5608823A
Expired / Lapsed
US
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Image reading apparatus for correcting density levels
Assignee: Canon Inc
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Filing: 1994-10-24
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Granted: 1997-03-04
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Expires: 2014-10-24
Abstract
Abstract An image reading apparatus includes an image sensing unit for photoelectrically reading an original image, and outputting an image signal, a converter unit for converting the image signal from the image sensing unit into density data representing density levels of a plurality of steps, a detection unit for detecting frequencies of appearance in units of density levels of the density data from the converter unit, and a correction unit for correcting the density levels expressed by the density data from the converter unit on the basis of the frequencies of appearance detected by the detection unit.
Inventors
- 👤 Kazuo Ohtani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 10:44
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/40; G06T5/90; G06T5/92
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
170 words
An image reading apparatus comprising: reading means for photoelectrically reading an original image, and outputting an image signal; conversion means for converting the image signal from said reading means into density data representing density levels of a plurality of steps; detection means for detecting frequencies of appearance in units of density levels of the density data from said conversion means, said detection means detecting the frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correction means for correcting the density levels expressed by the density data from said conversion means on the basis of the frequencies of appearance detected by said detection means, wherein said correction means detects a minimum density level and a maximum density level among density levels of which frequencies of appearance are higher than a predetermined frequency; and corrects the density levels expressed by the density data on the basis of the detected minimum and maximum density levels.
Claim 2
Dependent Claim
170 words
An image reading apparatus comprising: reading means for photoelectrically reading an original image, and outputting an image signal; conversion means for converting the image signal from said reading means into density data representing density levels of a plurality of steps; detection means for detecting frequencies of appearance in units of density levels of the density data from said conversion means, said detection means detecting the frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correction means for correcting the density levels expressed by the density data from said conversion means on the basis of the frequencies of appearance detected by said detection means, wherein said correction means detects a minimum density level and a maximum density level among density levels of which frequencies of appearance are higher than a predetermined frequency; and corrects the density levels expressed by the density data on the basis of the detected minimum and maximum density levels.
Claim 3
Dependent Claim
24 words
An apparatus according to claim 1, wherein said correction means corrects the density levels so that the density data express all the density levels.
Claim 4
Dependent Claim
20 words
An apparatus according to claim 1, wherein said correction means performs correction of the density data using nonlinear conversion characteristics.
Claim 5
Dependent Claim
35 words
An apparatus according to claim 1, further comprising forming means for forming image data for reproducing a halftone image on the basis of the density data whose density levels are corrected by said correction means.
Claim 6
Dependent Claim
145 words
An image reading method comprising steps of: photoelectrically reading an original image, and outputting an image signal; converting the image signal into density data representing density levels of a plurality of steps; detecting frequencies of appearance in units of density levels of the density data, said detecting step detecting frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correcting the density levels expressed by the density data on the basis of the frequencies of appearance, wherein, in said correcting step, a minimum density level and a maximum density level are detected among density levels of which frequencies of appearance are higher than a predetermined frequency, and the density levels expressed by the density data are corrected on the basis of the detected minimum and maximum density levels.
Claim 7
Dependent Claim
145 words
An image reading method comprising steps of: photoelectrically reading an original image, and outputting an image signal; converting the image signal into density data representing density levels of a plurality of steps; detecting frequencies of appearance in units of density levels of the density data, said detecting step detecting frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correcting the density levels expressed by the density data on the basis of the frequencies of appearance, wherein, in said correcting step, a minimum density level and a maximum density level are detected among density levels of which frequencies of appearance are higher than a predetermined frequency, and the density levels expressed by the density data are corrected on the basis of the detected minimum and maximum density levels.
Claim 8
Dependent Claim
168 words
An image processing apparatus comprising: input means for inputting an image signal representing an original image; conversion means for converting the image signal from said input means into density data representing density levels of a plurality of steps; detection means for detecting frequencies of appearance in units of density levels of the density data from said conversion means, said detection means detecting the frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correction means for correcting the density levels expressed by the density data from said conversion means on the basis of the frequencies of appearance detected by said detection means, wherein said correction means detects a minimum density level and a maximum density level among density levels of which frequencies of appearance are higher than a predetermined frequency, and corrects the density levels expressed by the density data on the basis of the detected minimum and maximum density levels.
Claim 9
Dependent Claim
168 words
An image processing apparatus comprising: input means for inputting an image signal representing an original image; conversion means for converting the image signal from said input means into density data representing density levels of a plurality of steps; detection means for detecting frequencies of appearance in units of density levels of the density data from said conversion means, said detection means detecting the frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correction means for correcting the density levels expressed by the density data from said conversion means on the basis of the frequencies of appearance detected by said detection means, wherein said correction means detects a minimum density level and a maximum density level among density levels of which frequencies of appearance are higher than a predetermined frequency, and corrects the density levels expressed by the density data on the basis of the detected minimum and maximum density levels.
Claim 10
Dependent Claim
24 words
An apparatus according to claim 6, wherein said correction means corrects the density levels so that the density data expresses all the density levels.
Claim 11
Dependent Claim
20 words
An apparatus according to claim 6, wherein said correction means performs correction of the density data using nonlinear conversion characteristics.
Claim 12
Dependent Claim
35 words
An apparatus according to claim 6, further comprising forming means for forming image data for reproducing a halftone image on the basis of the density data whose density levels are corrected by said correction means.
Claim 13
Dependent Claim
23 words
An apparatus according to claim 6, wherein said input means inputs the image signal from reading means which photoelectrically reads the original image.
Claim 14
Dependent Claim
143 words
An image processing method comprising steps of: inputting an image signal representing an original image; converting the image signal into density data representing density levels of a plurality of steps; detecting frequencies of appearance in units of density levels of the density data, said detecting step detecting frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correcting the density levels expressed by the density data on the basis of the frequencies of appearance, wherein, in said correcting step, a minimum density level and a maximum density level are detected among density levels of which frequencies of appearance are higher than a predetermined frequency, and the density levels expressed by the density data are corrected on the basis of the detected minimum and maximum density levels.
Claim 15
Dependent Claim
143 words
An image processing method comprising steps of: inputting an image signal representing an original image; converting the image signal into density data representing density levels of a plurality of steps; detecting frequencies of appearance in units of density levels of the density data, said detecting step detecting frequencies of appearance of density levels in a specific image area which is not an entire original image but a central portion of the original image; and correcting the density levels expressed by the density data on the basis of the frequencies of appearance, wherein, in said correcting step, a minimum density level and a maximum density level are detected among density levels of which frequencies of appearance are higher than a predetermined frequency, and the density levels expressed by the density data are corrected on the basis of the detected minimum and maximum density levels.
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) | 2000-03-03 | 2000-09-02 | 2001-03-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-03-03 | 2004-09-02 | 2005-03-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-03-03 | 2008-09-02 | 2009-03-04 | $7700.00 | Window Closed / Lapsed |