US3868477A
Expired / Lapsed
US
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Facsimile system contrast enhancement
Assignee: RAPICOM INC A CORP OF DEL
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Filing: 1973-06-20
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Granted: 1975-02-25
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Expires: 1993-06-20
Abstract
Abstract A binary facsimile communication system employing an automatic contrast enhancement method and apparatus wherein a binary output represents either a black level decision or a white level decision, all incoming video signals on one side of a preselected threshold level voltage producing a black level decision and all incoming video signals on the opposite side of the threshold level voltage producing a white level decision, a novel circuit operating when a predetermined change in the video signal input occurs to trigger a change in the binary output from one state to the other state even though the change is not sufficient to cause the video input signal to pass through said preselected threshold level voltage.
Inventors
- 👤 Howard Katzman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 06:30
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/403
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
152 words
Apparatus for producing a binary signal output responsive to an analog signal input, said binary signal output in a first state serving as a black level decision output and in a second state serving as a white level decision output, comprising means for producing a threshold level, means for comparing the level of said analog signal input with said threshold level to produce one of said binary output states when said analog signal level is on one side of said threshold level and produce the other of said binary output states when said analog signal level is on the other side of said threshold level, and means operative when said binary output is in one of said two different states for detecting a preselected change in the level of the analog input and for changing the binary output to the other of said two different states in response to said preselected change.
Claim 2
Dependent Claim
152 words
Apparatus for producing a binary signal output responsive to an analog signal input, said binary signal output in a first state serving as a black level decision output and in a second state serving as a white level decision output, comprising means for producing a threshold level, means for comparing the level of said analog signal input with said threshold level to produce one of said binary output states when said analog signal level is on one side of said threshold level and produce the other of said binary output states when said analog signal level is on the other side of said threshold level, and means operative when said binary output is in one of said two different states for detecting a preselected change in the level of the analog input and for changing the binary output to the other of said two different states in response to said preselected change.
Claim 3
Dependent Claim
47 words
Apparatus as claimed in claim 1 wherein said means for detecting the preselected change operates to change the binary output when said binary output is in said first state serving as a black level decision output, said binary output being changed to a white level decision output.
Claim 4
Dependent Claim
57 words
Apparatus as claimed in claim 1 wherein said means for detecting a preselected change in the level of the analog input comprises means for detecting the peak level of said analog signal, and means for comparing this peak level with a subsequent analog signal input level which varied from said peak level by said preselected level change.
Claim 5
Dependent Claim
47 words
Apparatus as claimed in claim 3 wherein said means for detecting the preselected change operates to change the binary output when said binary output is in said first state serving as a black level decision output, said binary output being changed to a white level decision output.
Claim 6
Dependent Claim
106 words
Apparatus as claimed in claim 1 wherein said means for comparing the level of said analog signal input with said threshold level comprises a first level comparator circuit and a gate coupled to the output thereof, said gate providing said binary signal output, and wherein said means for detecting a preselected change in the level of the analog input comprises means for detecting the peak level of said analog signal, means for comparing this peak level with a subsequent analog signal input level which varied from said peak level by said preselected level change, and means controlled by said latter comparing means for controlling said gate.
Claim 7
Dependent Claim
47 words
Apparatus as claimed in claim 5 wherein said means for detecting the preselected change operates to change the binary output when said binary output is in said first state serving as a black level decision output, said binary output being changed to a white level decision output.
Claim 8
Independent Claim
149 words
The method for producing a binary signal output responsive to an analog signal input, said binary signal output in a first state serving as a black level decision output and in a second state serving as a white level decision output comprising the steps of producing a threshold voltage level, comparing the level of said analog signal input with saiD threshold level to produce one of said binary output states when said analog signal level is on one side of said threshold level and produce the other of said binary output states when said analog signal level is on the other side of said threshold level, detecting a preselected change in the level of the analog input when said binary output is in one of said two different states, and changing the binary output to the other of said two different states responsive to detection of said preselected change.
Claim 9
Independent Claim
149 words
The method for producing a binary signal output responsive to an analog signal input, said binary signal output in a first state serving as a black level decision output and in a second state serving as a white level decision output comprising the steps of producing a threshold voltage level, comparing the level of said analog signal input with saiD threshold level to produce one of said binary output states when said analog signal level is on one side of said threshold level and produce the other of said binary output states when said analog signal level is on the other side of said threshold level, detecting a preselected change in the level of the analog input when said binary output is in one of said two different states, and changing the binary output to the other of said two different states responsive to detection of said preselected change.
Claim 10
Dependent Claim
48 words
The method as claimed in claim 7 wherein the step of detecting the preselected change occurs when said binary output is in said first state serving as a black level decision output to change the binary output to the second state serving as a white level decision output.
Claim 11
Dependent Claim
58 words
The method as claimed in claim 7 wherein said step of detecting a preselected change in the level of the analog input comprises the step of detecting the peak level of said analog signal and thereafter comparing this peak level with a subsequent analog signal input level which varied from said peak level by said preselected level change.
Claim 12
Dependent Claim
48 words
The method as claimed in claim 9 wherein the step of detecting the preselected change occurs when said binary output is in said first state serving as a black level decision output to change the binary output to the second state serving as a white level decision output.
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) | 1978-02-24 | 1978-08-26 | 1979-02-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-24 | 1982-08-26 | 1983-02-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-24 | 1986-08-26 | 1987-02-25 | $7700.00 | Window Closed / Lapsed |