Radiant energy – Invisible radiant energy responsive electric signalling – Including a radiant energy responsive gas discharge device
Reexamination Certificate
1999-04-26
2001-07-10
Allen, Stephone B. (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Including a radiant energy responsive gas discharge device
C356S370000
Reexamination Certificate
active
06259100
ABSTRACT:
BACKGROUND
Description of Related Art
Contemporary document handling systems have an ongoing need to detect when documents are present in one or more document-handling tracks associated with such handling systems. Typically, it is important to detect the presence of a document as a precursor to some further activity, such printing on the document, scanning the document, or performing some other function on the document.
Some document handling systems use light emitter/detector pairs to detect when a document is present. Such emitter-detector pairs have been arranged in at least two configurations. First, the emitter and detector can be mounted on opposing sides of the document path, so that the emitter transmits a light beam across the document path directly to the detector. Second, the emitter and detector can be mounted on the same side of the document path, with a mirror or other reflector mounted on the opposite side of the path to optically couple the emitter and the detector. In either case, the light beam as emitted, reflected, and detected provides a normally-closed light “circuit”, which is broken or opened by an opaque document, thereby indicating the presence of the document.
Electronic circuitry is connected to the detector to determine when light is reaching the detector. When a document passes along the track between the emitter and detector, the document breaks the beam and opens the normally-closed light “circuit,” thereby alerting the electronic circuitry that a document is present and is ready for whatever processing is necessary.
One design issue with such handling systems is how best to detect documents having variable dimensions. If all the documents that will be handled by the system are substantially the same size, then one standard arrangement of the emitter, detector, and reflector will suffice for all the documents. However, more typical document handling systems may have to detect documents having various dimensions. In this case, the “one size fits all” arrangement described above may not detect certain smaller documents. Specifically, if the emitter-detector pair is located in the center of the width of the document path, then smaller documents may pass on either side of the pair and escape detection.
One solution to this problem is to increase the resolution of the detector circuit by providing additional emitter-detector pairs that monitor the document path at certain intervals. However, this approach, while perhaps effective at detecting smaller documents, introduces substantial additional cost into the design and manufacture of the document handling system. Specifically, this additional cost includes the cost of the added emitters and detectors themselves, along with the cost of the circuitry necessary to interface these additional emitters and detectors to the rest of the system. Further, these additional emitters, detectors, and interface circuitry take up more physical space, further complicating the design and manufacture of the entire system.
Accordingly, there is a need in the art for an optical sensor capable of detecting variably sized documents without the added expense of more emitter-detector pairs or interface circuitry.
SUMMARY
The present invention addresses the above need in the art by providing an optical sensor for detecting a document moving along a document path. The invention provides at least two light paths across the document path, so that the document breaks at least one of the light paths as it moves along the document path, and this broken light path indicates the presence of the document. In an exemplary embodiment, the optical sensor comprises a photo-emitter that emits light across the document path to provide the first light path. A first reflector is optically coupled to the photo-emitter, and receives and reflects the light emitted by the photo-emitter. At least a second reflector is optically coupled to the first reflector to receive the light from the first reflector and to reflect that light across the document path to provide the second data path. A photo-detector is disposed across the light path from the second reflector and is optically coupled to the second reflector. The photo-detector is operable to detect the presence of the document by detecting when the document has broken at least one of the light paths.
Additional features and advantages of the present invention will become evident hereinafter.
REFERENCES:
patent: 5260564 (1993-11-01), Bruggeling et al.
patent: 5585645 (1996-12-01), Goto
Allen Stephone B.
Starr Mark T.
Unisys Corporation
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