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US4868671A
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Method of and apparatus for noise reduction in multi-gradation image signal in halftone image reader
Assignee: Dainippon Screen Manufacturing Co Ltd
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Filing: 1987-12-21
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Granted: 1989-09-19
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Expires: 2007-12-21
Abstract
Abstract A multi-gradation image signal obtained by multi-gradationization of a signal obtained by reading through a CCD an original having a half tone is supplied to an unsharp signal producing part, which in turn outputs an unsharp signal produced from the multi-gradation image signal and the multi-gradation image signal itself. A comparator discriminates a shadow portion of the original by comparing the multi-gradation image signal with a reference value. As a result, a signal which is unsharp in the shadow portion of the original is produced from the multi-gradation image signal and the unsharp signal.
Inventors
- 👤 Shigeo Murakami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 13:59
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/409; H04N25/00; H04N25/60; H04N25/67; H04N25/671; H04N25/672
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
100 words
A method for reducing noise in a multi-gradation image signal obtained by making multi-gradationed a signal obtained by reading with a solid-state image sensing element an original having a half tone, said method comprising the steps of: producing an unsharp signal from said multi-gradation image signal; comparing said multi-gradation image signal with at least one prescribed reference value to discriminate whether a portion of said original is a shadow portion and producing a signal that is unsharp from at least one of said multi-gradation image signal and said unsharp signal when said portion is discriminated to be a shadow portion.
Claim 2
Independent Claim
100 words
A method for reducing noise in a multi-gradation image signal obtained by making multi-gradationed a signal obtained by reading with a solid-state image sensing element an original having a half tone, said method comprising the steps of: producing an unsharp signal from said multi-gradation image signal; comparing said multi-gradation image signal with at least one prescribed reference value to discriminate whether a portion of said original is a shadow portion and producing a signal that is unsharp from at least one of said multi-gradation image signal and said unsharp signal when said portion is discriminated to be a shadow portion.
Claim 3
Dependent Claim
47 words
A method in accordance with claim 1, wherein said at least one prescribed reference value is a single reference value, and said step of producing said signal that is unsharp is performed by selecting said unsharp signal when said portion is discriminated to be a shadow portion.
Claim 4
Dependent Claim
61 words
A method in accordance with claim 1, wherein said at least one prescribed reference value is a plurality of reference values, and said step of producing said signal that is unsharp is performed by mixing said multi-gradation image signal and said unsharp signal in one of a plurality of prescribed ratios when said portion is discriminated to be a shadow portion.
Claim 5
Dependent Claim
73 words
A method in accordance with claim 1, further including the steps of: producing a contrast signal by taking the difference between said multi-gradation image signal and said unsharp signal ; and comparing said contrast signal with at least one prescribed reference value to discriminate whether said portion of said original is a low-contrast portion; wherein said signal that is unsharp is produced when said portion is discriminated to be a low-contrast shadow portion.
Claim 6
Dependent Claim
30 words
A method in accordance with claim 1, wherein said step of producing the unsharp signal is performed by averaging said multi-gradation image signal over a prescribed area of said original.
Claim 7
Dependent Claim
39 words
A method in accordance with claim 5, wherein said at least one prescribed reference value is a plurality of reference values, and said prescribed area is changed in size when said portion is discriminated to be a shadow portion.
Claim 8
Independent Claim
118 words
An apparatus for reducing noise in a multi-gradation image signal obtained by making multi-gradationed a signal obtained by reading with a solid-state image sensing element an original having a halftone, said apparatus comprising: unsharp signal producing means for producing an unsharp signal from said multi-gradation image signal; first comparing means for comparing said multi-gradation image signal with at least one prescribed reference value to discriminate whether a portion of said original is a shadow portion ; and signal producing means for producing a signal that is unsharp from at least one of said multi-gradation image signal and said unsharp signal in response to said first comparing means indicating that said portion is discriminated to be a shadow portion.
Claim 9
Independent Claim
118 words
An apparatus for reducing noise in a multi-gradation image signal obtained by making multi-gradationed a signal obtained by reading with a solid-state image sensing element an original having a halftone, said apparatus comprising: unsharp signal producing means for producing an unsharp signal from said multi-gradation image signal; first comparing means for comparing said multi-gradation image signal with at least one prescribed reference value to discriminate whether a portion of said original is a shadow portion ; and signal producing means for producing a signal that is unsharp from at least one of said multi-gradation image signal and said unsharp signal in response to said first comparing means indicating that said portion is discriminated to be a shadow portion.
Claim 10
Dependent Claim
62 words
An apparatus in accordance with claim 7, wherein said at least one prescribed reference value is a single reference value, and said first comparing means includes means for comparing said multi-gradation image signal with said single reference value, and said signal producing means includes means for selecting said unsharp signal in response to a shadow portion discriminated by said first comparing means.
Claim 11
Dependent Claim
77 words
An apparatus is accordance with claim 7, wherein said at least one prescribed reference value is a plurality of reference values, and said first comparing means includes means for comparing said multi-gradation image signal with said plurality of reference values, and said signal producing means includes means for mixing said multi-gradation image signal and said unsharp signal in one of a plurality of prescribed ratios in response to a shadow portion discriminated by said first comparing means.
Claim 12
Dependent Claim
90 words
An apparatus in accordance with claim 7, further including: means for producing a contrast signal in accordance with the difference between said multi-gradation image signal and said unsharp signal; and second comparing means for comparing said contrast signal with at least one prescribed reference value to discriminate whether said portion of said original is a low contrast portion; said signal producing means including means for producing a signal that is unsharp when said portion is discriminated by said first and second comparing means to be a low contrast shadow portion.
Claim 13
Dependent Claim
38 words
An apparatus in accordance with claim 7, wherein said unsharp signal producing means includes means for producing an unsharp signal for a prescribed area of said original by averaging said multi-gradation image signal over said prescribed area of
Claim 14
Dependent Claim
49 words
An apparatus in accordance with claim 11, wherein said at least one prescribed reference value is a plurality of reference values, and said unsharp signal producing means includes means for changing a size of said prescribed area in response to a shadow portion discriminated by said first comparing means.
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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) | 1992-09-18 | 1993-03-20 | 1993-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-09-18 | 1997-03-20 | 1997-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-09-18 | 2001-03-20 | 2001-09-19 | $7700.00 | Window Closed / Lapsed |