US3600506A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Background sensing and black level setting circuit
Assignee: Philips North America LLC
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Filing: 1969-03-03
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Granted: 1971-08-17
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Expires: 1989-03-03
Abstract
Abstract A background sensing and black level setting circuit for a facsimile transmission system is disclosed which linearly ''''stretches'''' the particular gray scale input of a document to yield an output having complete black to white gray scale characteristics. The circuit decreases its own gain rapidly when the lightest part of a document (exceeding some threshold) is scanned but increases its gain much more slowly when scanning darker areas so as to maintain its output for a document background as white. The circuit also serves to fix the darkest area of the document scanned as being black.
Inventors
- 👤 William E Richeson Jr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 01:36
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/407; H04N1/4072
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
164 words
In a facsimile system variable gain amplifier having maximum and minimum voltage output levels which represent the signal magnitude necessary for reproducing black and white on a copy and having input voltage levels which are representative of the lightest and darkest areas of a scanned document and which may be less than the magnitude necessary for reproducing said maximum and minimum output voltage levels, an improved black and white level setting circuit comprising: amplifier means for initially amplifying the input signal at a first gain level to produce an output signal with a dynamic range which is less than the minimum and maximum voltage levels necessary for reproducing black and white on a copy; and gain control means responsive to the amplifier output signal for subsequently increasing the gain of said amplifier means to produce an output signal with a dynamic range which corresponds to the minimum and maximum voltage output levels of said amplifier necessary for reproducing black and white on a copy.
Claim 2
Dependent Claim
164 words
In a facsimile system variable gain amplifier having maximum and minimum voltage output levels which represent the signal magnitude necessary for reproducing black and white on a copy and having input voltage levels which are representative of the lightest and darkest areas of a scanned document and which may be less than the magnitude necessary for reproducing said maximum and minimum output voltage levels, an improved black and white level setting circuit comprising: amplifier means for initially amplifying the input signal at a first gain level to produce an output signal with a dynamic range which is less than the minimum and maximum voltage levels necessary for reproducing black and white on a copy; and gain control means responsive to the amplifier output signal for subsequently increasing the gain of said amplifier means to produce an output signal with a dynamic range which corresponds to the minimum and maximum voltage output levels of said amplifier necessary for reproducing black and white on a copy.
Claim 3
Dependent Claim
175 words
In a facsimile system variable gain amplifier having maximum and minimum voltage output levels which represent the signal magnitude necessary for reproducing black and white on a copy and having input voltage levels which are representative of the lightest and darkest areas of a scanned document and which may be less than the magnitude necessary for reproducing said maximum and minimum output voltage levels, an improved black and white level setting circuit comprising: amplifier means for initially amplifying the input signal at a first gain level to produce an output signal which is less than the maximum voltage level; means for shifting said amplifier output so that the maximum output signal values correspond to said maximum voltage level; gain control means responsive to the amplifier output signal for subsequently increasing the gain of said amplifier means to produce an output signal the minimum values of which correspond to the minimum output level of said amplifier; and said minimum and maximum voltage levels are of the amplitude necessary to reproduce black and white on a copy.
Claim 4
Dependent Claim
175 words
In a facsimile system variable gain amplifier having maximum and minimum voltage output levels which represent the signal magnitude necessary for reproducing black and white on a copy and having input voltage levels which are representative of the lightest and darkest areas of a scanned document and which may be less than the magnitude necessary for reproducing said maximum and minimum output voltage levels, an improved black and white level setting circuit comprising: amplifier means for initially amplifying the input signal at a first gain level to produce an output signal which is less than the maximum voltage level; means for shifting said amplifier output so that the maximum output signal values correspond to said maximum voltage level; gain control means responsive to the amplifier output signal for subsequently increasing the gain of said amplifier means to produce an output signal the minimum values of which correspond to the minimum output level of said amplifier; and said minimum and maximum voltage levels are of the amplitude necessary to reproduce black and white on a copy.
Claim 5
Dependent Claim
15 words
The improvement of claim 1 wherein said gain control means comprises a nonlinear feedback circuit.
Claim 6
Dependent Claim
15 words
The improvement of claim 2 wherein said gain control means comprises a nonlinear feedback circuit.
Claim 7
Dependent Claim
18 words
The improvement of claim 2 wherein said means for shifting and said gain control means are effective contemporaneously.
Claim 8
Dependent Claim
37 words
The improvement of claim 5 wherein the time required to shift said amplifier output to attain said maximum voltage level is T1 and the time required to attain said minimum voltage output level is T2 and T2>T1.
Claim 9
Dependent Claim
25 words
The improvement of claim 1 wherein portions intermediate said darkest and lightest portions of said scanned document are printed proportionately intermediate to black and white.
Claim 10
Dependent Claim
25 words
The improvement of claim 2 wherein portions intermediate said darkest and lightest portions of said scanned document are printed proportionately intermediate to black and white.
Claim 11
Dependent Claim
32 words
The improvement of claim 1 wherein the maximum voltage output level corresponds to black and wherein the relative maximum voltage input level corresponds to the relatively lightest area of the scanned document.
Claim 12
Dependent Claim
32 words
The improvement of claim 2 wherein the maximum voltage output level corresponds to black and wherein the relative maximum voltage input level corresponds to the rElatively lightest area of the scanned document.
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) | 1974-08-16 | 1975-02-15 | 1975-08-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-08-16 | 1979-02-15 | 1979-08-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-08-16 | 1983-02-15 | 1983-08-17 | $7700.00 | Window Closed / Lapsed |