Patent US5237431A successfully refreshed from Google Patents.
US5237431A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Image reading apparatus for producing high quality images based on tone correction
Assignee: Fujifilm Business Innovation Corp
•
Filing: 1991-06-18
•
Granted: 1993-08-17
•
Expires: 2011-06-18
Abstract
Abstract An image reading apparatus including an A/D converter for converting an analog detection signal read by an image reading sensor to a digital signal, a logarithmic converter, in which density levels to be converted are divided into a plurality of regions, for converting an output of the A/D converter to a logarithmic value, a decoder for judging a density region of the logarithmic converter based on the output of the A/D converter, and a bit shifter for converting an output of the logarithmic converter to a density signal in accordance with a judgment made by the decoder. The image reading apparatus as constructed above can maintain the tone level of an 8-bit signal, thereby producing high-quality images. Further, 10-bit signals can be subjected to shading correction while using an inexpensive 8-bit memory.
Inventors
- 👤 Yoshiya Imoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:32
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/407
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
156 words
An image reading apparatus comprising: A/D conversion means for converting an analog detection signal read by an image reading sensor to a digital value, the digital value being in one of a plurality of value ranges and consisting of n+Δn bits, wherein n and Δn are whole numbers; logarithmic conversion means for converting the digital value from said A/D conversion means to a logarithmic value according to predetermined conversion characteristics, the logarithmic value being in one of a plurality of density regions and consisting of n bits, the predetermined conversion characteristics being different for each value range; identification means for identifying the density region of the logarithmic value of said logarithmic conversion means based on the digital value of said A/D conversion means; and bit conversion means for converting the logarithmic value of said logarithmic conversion means to a density signal consisting of n+Δn bits in accordance with the density region identified by said identification means.
Claim 2
Dependent Claim
156 words
An image reading apparatus comprising: A/D conversion means for converting an analog detection signal read by an image reading sensor to a digital value, the digital value being in one of a plurality of value ranges and consisting of n+Δn bits, wherein n and Δn are whole numbers; logarithmic conversion means for converting the digital value from said A/D conversion means to a logarithmic value according to predetermined conversion characteristics, the logarithmic value being in one of a plurality of density regions and consisting of n bits, the predetermined conversion characteristics being different for each value range; identification means for identifying the density region of the logarithmic value of said logarithmic conversion means based on the digital value of said A/D conversion means; and bit conversion means for converting the logarithmic value of said logarithmic conversion means to a density signal consisting of n+Δn bits in accordance with the density region identified by said identification means.
Claim 3
Dependent Claim
19 words
An image reading apparatus according to claim 1, wherein said logarithmic conversion means is formed of a look-up table.
Claim 4
Dependent Claim
26 words
An image reading apparatus according to claim 1, wherein said density regions comprise a low density region, an intermediate density region, and a high density region.
Claim 5
Dependent Claim
14 words
An image reading apparatus according to claim 1, wherein said value n is 8.
Claim 6
Dependent Claim
38 words
An image reading apparatus according to claim 1, further comprising: means for storing n-bit reference density data; and means for subtracting the reference density data stored in said storage means from an output of said bit conversion means.
Claim 7
Dependent Claim
30 words
An image reading apparatus according to claim 5, wherein said storage means is formed of a random access memory and stores white reference data converted by said logarithmic conversion means.
Claim 8
Dependent Claim
54 words
An image reading apparatus according to claim 1, wherein said A/D conversion means includes: means for dividing an input signal into two intensity proportions; two n-bit A/D converters for converting said divided input signals respectively; and means for synthesizing respective outputs of said n-bit A/D converters into a digital value consisting of n+Δn bits.
Claim 9
Dependent Claim
14 words
An image reading apparatus according to claim 1, wherein said value Δn is 2.
Claim 10
Dependent Claim
181 words
An image reading apparatus comprising: A/D conversion means for converting an analog detection signal read by an image reading sensor to a digital value, the digital value being in one of a plurality of value ranges and consisting of n+Δn bits, wherein n and Δn are whole numbers; logarithmic conversion means for converting the digital value from said A/D conversion means to a logarithmic value according to predetermined conversion characteristics, the logarithmic value being in one of a plurality of density regions and consisting of n bits, the predetermined conversion characteristics being different for each value range; identification means for identifying the density region of the logarithmic value of said logarithmic conversion means based on the digital value of said A/D conversion means; and bit conversion means for converting the logarithmic value of said logarithmic conversion means to a density signal consisting of n+Δn bits in accordance with the density region identified by said identification means, wherein said identification means is formed of a decoder for identifying a density region from upper bits in an output of said A/D conversion means.
Claim 11
Dependent Claim
181 words
An image reading apparatus comprising: A/D conversion means for converting an analog detection signal read by an image reading sensor to a digital value, the digital value being in one of a plurality of value ranges and consisting of n+Δn bits, wherein n and Δn are whole numbers; logarithmic conversion means for converting the digital value from said A/D conversion means to a logarithmic value according to predetermined conversion characteristics, the logarithmic value being in one of a plurality of density regions and consisting of n bits, the predetermined conversion characteristics being different for each value range; identification means for identifying the density region of the logarithmic value of said logarithmic conversion means based on the digital value of said A/D conversion means; and bit conversion means for converting the logarithmic value of said logarithmic conversion means to a density signal consisting of n+Δn bits in accordance with the density region identified by said identification means, wherein said identification means is formed of a decoder for identifying a density region from upper bits in an output of said A/D conversion means.
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) | 1996-08-16 | 1997-02-15 | 1997-08-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-08-16 | 2001-02-15 | 2001-08-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-08-16 | 2005-02-15 | 2005-08-17 | $7700.00 | Window Closed / Lapsed |