US4447774A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Video signal detector
Assignee: International Business Machines Corp
•
Filing: 1981-09-28
•
Granted: 1984-05-08
•
Expires: 2001-09-28
Abstract
Abstract A video detector circuit is disclosed which develops a threshold level from a white or background peak signal in regions of low contrast, and from a combination of both white and black peak levels in regions of high contrast. The circuit is adjustable to compensate for variable affection performance of the detector.
Inventors
- 👤 Nils G. Stalberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 09:50
CPC Classifications
G; G06; G06V; G06V30/00; G06V30/10; G06V30/16; G06V30/162
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
183 words
A video signal detector for converting analog video signals representing optical reflectance from successive small regions on a document into a digital output signal comprising means for producing an analog video signal that varies in magnitude as a function of optical reflection, means responsive to said video signal for developing a white level peak representative voltage signal, means responsive to said video signal for developing a black level peak representative voltage signal, means responsive to said white level peak representative signal and said black level peak representative signal for developing a threshold level voltage signal, comparing means responsive to said video signal and to said threshold level signal for producing a digital output signal, a diode connected between said black level peak signal developing means and said threshold level signal developing means, said diode being oriented to permit conduction in the presence of black level voltage signals, and means supplying back bias to said diode for preventing conduction therethrough in the presence of relatively small black level voltage signals but permitting conduction therethrough in the presence of relatively large black level voltage signals.
Claim 2
Dependent Claim
183 words
A video signal detector for converting analog video signals representing optical reflectance from successive small regions on a document into a digital output signal comprising means for producing an analog video signal that varies in magnitude as a function of optical reflection, means responsive to said video signal for developing a white level peak representative voltage signal, means responsive to said video signal for developing a black level peak representative voltage signal, means responsive to said white level peak representative signal and said black level peak representative signal for developing a threshold level voltage signal, comparing means responsive to said video signal and to said threshold level signal for producing a digital output signal, a diode connected between said black level peak signal developing means and said threshold level signal developing means, said diode being oriented to permit conduction in the presence of black level voltage signals, and means supplying back bias to said diode for preventing conduction therethrough in the presence of relatively small black level voltage signals but permitting conduction therethrough in the presence of relatively large black level voltage signals.
Claim 3
Dependent Claim
43 words
A video signal detector, as defined in claim 1, wherein said video signal producing means comprises signal integrating means having an output connection and time-controlled switch means for periodically resetting said output to a starting value whereby periodic integrated video signals are provided.
Claim 4
Dependent Claim
53 words
A video signal detector, as defined in claim 1, wherein said white level peak representing signal producing means comprises a diode and a condenser that are connected in series with said video signal producing means, and means connecting a point intermediate said diode and said condenser to said threshold level signal developing means.
Claim 5
Dependent Claim
41 words
A video signal detector, as defined in claim 1, wherein said black level peak representing signal producing means comprises a condenser and a diode that are connected in series through a test and hold circuit to said video signal producing means.
Claim 6
Dependent Claim
47 words
A video signal detector, as defined in claim 4, wherein the test and hold circuit is connected through a delay circuit to the output comparator and through a resistor to a point between said condenser and said diode of said black level peak representing signal producing means.
Claim 7
Dependent Claim
37 words
A video signal detector, as defined in claim 1, wherein said threshold level signal developing means comprises adjustable means for controlling the black level peak share and the white level peak share of the threshold level signal.
Claim 8
Dependent Claim
58 words
A video signal detector, as described in claim 1, wherein said comparing means includes an amplifier having a first input for receiving said video signal, a second input for receiving said threshold level signal, an output for delivering a digital output signal, and a feedback connection between said second input and said output to stabilize the output signal.
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) | 1987-05-08 | 1987-11-07 | 1988-05-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-08 | 1991-11-07 | 1992-05-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-08 | 1995-11-07 | 1996-05-08 | $7700.00 | Window Closed / Lapsed |