Method and apparatus for detection of multiple documents in a document scanner using multiple ultrasonic sensors
View Patent ↗An apparatus ( 10 ) for detection of multiple documents ( 42 ) in a document transport system comprises a first transmitter ( 13 ) emitting a first signal at a first interval through a document feed path ( 40 ). A first sensor ( 14 ) detects the first signal from the first transmitter ( 13 ). A second transmitter ( 15 ) emits a second signal at a second interval through the document feed path ( 40 ). A second sensor ( 16 ) detects the second signal from the second transmitter ( 15 ).
1. An apparatus for detection of multiple documents in a document transport system comprising:
a first transmitter emitting a first signal for a first interval through a document feed path;
a first sensor for detecting said first signal from said first transmitter;
a second transmitter for emitting a second signal for a second interval through said document feed path;
a second sensor for detecting said second signal from said second transmitter; and
wherein said first signal is an ultrasonic signal.
2. An apparatus as in claim 1 wherein said first interval does not overlap said second interval.
3. An apparatus as in claim 1 wherein said first transmitter and said second transmitter are separated by at least one-half a width of said feed path.
4. An apparatus as in claim 1 wherein said first and second signal are at a common frequency.
5. An apparatus for detection of multiple documents in a document transport system comprising:
a first transmitter emitting a first signal for a first interval through a document feed path;
a first sensor for detecting said first signal from said first transmitter;
a second transmitter for emitting a second signal for a second interval through said document feed path;
a second sensor for detecting said second signal from said second transmitter;
a third transmitter for a emitting a third signal for a third interval through said document feed path; and
a third sensor for detecting said third signal from said third transmitter.
6. An apparatus as in claim 5 wherein said first, second, and third signals are ultrasonic signals.
7. An apparatus as in claim 5 wherein said first, second, and third intervals do not overlap.
8. An apparatus for detection of multiple documents in a document transport system comprising:
a first transmitter emitting a first signal for a first interval through a document feed path;
a first sensor for detecting said first signal from said first transmitter;
a second transmitter for emitting a second signal for a second interval through said document feed path;
a second sensor for detecting said second signal from said second transmitter;
a third transmitter for a emitting a third signal for a third interval through said document feed path;
a third sensor for detecting said third signal from said third transmitter; and
wherein said first, second, and third transmitters are equally spaced across said feed path.
9. An apparatus for detection of multiple documents in a document transport system comprising:
a first transmitter emitting a first signal at a first frequency through a document feed path;
a first sensor for detecting said first signal from said first transmitter;
a second transmitter for emitting a second signal at a second frequency through said document feed path; and
a second sensor for detecting said second signal from said second transmitter.
10. An apparatus as in claim 9 wherein said first signal is an ultrasonic signal.
11. An apparatus as in claim 9 wherein said first frequency is at least five kHz greater than said second frequency.
12. An apparatus as in claim 9 wherein said first frequency is approximately 40 kHz.
13. An apparatus as in claim 9 wherein said first transmitter and said second transmitter are separated by at least one-half a width of said feed path.
14. An apparatus as in claim 9 comprising:
a third transmitter for a emitting a third signal at a third frequency through said document feed path; and
a third sensor for detecting said third signal from said third transmitter.
15. An apparatus as in claim 14 wherein said first, second, and third signals are ultrasonic signals.
16. An apparatus as in claim 14 wherein said first, second, and third frequencies do not overlap.
17. An apparatus as in claim 14 wherein each of said frequencies is less than two MHz.
18. An apparatus as in claim 14 wherein said first, second, and third transmitters are equally spaced across said feed path.
19. A method for detection of multiple documents in a document transport system comprising the steps of:
emitting a first signal for a first interval through a document feed path;
detecting said first signal;
emitting a second signal for a second interval through said document feed path;
detecting said second signal; and
wherein said first signal is an ultrasonic signal.
20. The method of claim 19 wherein said first interval does not overlap said second interval.
21. The method of claim 19 wherein a first transmitter and a second transmitter for emitting said first signal and said second signal are separated by at least one-half a width of said feed path.
22. A method for detection of multiple documents in a document transport system comprising the steps of:
emitting a first signal for a first interval through a document feed path;
detecting said first signal;
emitting a second signal for a second interval through said document feed path;
detecting said second signal;
comprising the further step of:
emitting a third signal for a third interval through said document feed path; and
detecting said third signal from said third transmitter.
23. The method of claim 22 wherein said first, second, and third signals are ultrasonic signals.
24. The method of claim 22 wherein said first, second, and third intervals do not overlap.