Patent US3873843A successfully refreshed from Google Patents.
US3873843A
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Document detection apparatus
Assignee: DECISION DATA Inc A CORP OF
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Filing: 1973-11-29
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Granted: 1975-03-25
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Expires: 1993-11-29
Abstract
Abstract Document detection apparatus especially adapted for the detection of double document conditions occurring in character recognition apparatus. The object detection apparatus includes a light source and a light detector positioned on opposite sides of the document feed path. The detector output signal amplitude is a function of the opacity of the document being passed between the light source and detector. When a doubles condition (two or more documents) exists, the detector output signal amplitude changes considerably more than for a single document so as to cause an alarm signal to be generated. An automatic opacity measuring and adjusting network is also provided to be responsive to the feed of a first document so as to set the detector output signal to a level corresponding to the capacity of thickness of such first document.
Inventors
- 👤 Clifford E Martin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 22:42
CPC Classifications
G; G06; G06V; G06V10/00; G06V10/10
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
147 words
In document detection apparatus in which a source of radiant energy and a radiant energy responsive detector are positioned on opposite sides of a document detection station, said apparatus including a circuit for producing an alarm signal whenever the detector output signal amplitude exceeds by a predetermined amount a threshold value corresponding to the opacity of a single document; the improvement which comprises: means responsive to the feed of the first document of a group of documents to measure the opacity of such first document; said detector being a phototransistor; collector resistance means coupling the phototransistor collector to a bias voltage source. a bank of resistors, and switching means responsive to the measured opacity to couple selected ones to said resistors in shunt with at least a portion of the collector resistance to adjust the phototransistor collector current to a senstivity level commensurate with the measurEd opacity.
Claim 2
Dependent Claim
147 words
In document detection apparatus in which a source of radiant energy and a radiant energy responsive detector are positioned on opposite sides of a document detection station, said apparatus including a circuit for producing an alarm signal whenever the detector output signal amplitude exceeds by a predetermined amount a threshold value corresponding to the opacity of a single document; the improvement which comprises: means responsive to the feed of the first document of a group of documents to measure the opacity of such first document; said detector being a phototransistor; collector resistance means coupling the phototransistor collector to a bias voltage source. a bank of resistors, and switching means responsive to the measured opacity to couple selected ones to said resistors in shunt with at least a portion of the collector resistance to adjust the phototransistor collector current to a senstivity level commensurate with the measurEd opacity.
Claim 3
Dependent Claim
128 words
Document detection apparatus as set forth in cliam 1 and further including: means responsive to the feed of the first document to produce a first document feed signal; wherein said measuring means includes: means responsive to the first document feed signal (1) to lower the reference signal value and (2) to generate clock pulses in time sequence, means responsive to said clock pulses to operate the switching means to couple said resistors one at a time in shunt with the collector resistance until the collector voltage rises above the lowered reference value sufficiently to cause the comparator to produce a change in its output signal level, and means for coupling the comparator output signal to said clock pulse generating means to stop the generation of further clock pulses.
Claim 4
Dependent Claim
128 words
Document detection apparatus as set forth in cliam 1 and further including: means responsive to the feed of the first document to produce a first document feed signal; wherein said measuring means includes: means responsive to the first document feed signal (1) to lower the reference signal value and (2) to generate clock pulses in time sequence, means responsive to said clock pulses to operate the switching means to couple said resistors one at a time in shunt with the collector resistance until the collector voltage rises above the lowered reference value sufficiently to cause the comparator to produce a change in its output signal level, and means for coupling the comparator output signal to said clock pulse generating means to stop the generation of further clock pulses.
Claim 5
Dependent Claim
39 words
Document detection apparatus as set forth in claim 2 wherein said switch operating means is a shift register with an input circuit containing a predetermined bit pattern which is shifted into the register in response to said clock pulses.
Claim 6
Dependent Claim
55 words
Document detection apparatus as set forth in claim 3 wherein the shift register is cleared to the all 0''s condition in response to the first document feed signal; and wherein the bit pattern is all 1''s so that each clock pulse causes one of the resistors to be coupled in shunt with the collector resistance.
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) | 1978-03-24 | 1978-09-23 | 1979-03-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-24 | 1982-09-23 | 1983-03-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-24 | 1986-09-23 | 1987-03-25 | $7700.00 | Window Closed / Lapsed |