Patent Application
20130140757
The following U.S. patent applications are assigned to the same assignee hereof, Eastman Kodak Company of Rochester, N.Y., and contain subject matter related, in certain respect, to the subject matter of the present patent application. These patent applications are incorporated herein by reference in their entirety.
U.S. Ser. No. 13/273,263, filed Oct. 14, 2011, entitled “Jam Sensing At Document Feeding Station”;
US patent application filed concurrently herewith, entitled “Combined Ultrasonic-Based Multifeed Detection Method And Sound-Based Damage Detection Method”, and
US patent application filed concurrently herewith, entitled “Combined Ultrasonic-Based Multifeed Detection System And Sound-Based Damage Detection System”.
The present invention is directed to devices and methods of detecting misfeeds in a document handling apparatus. In particular, to devices and methods utilizing only one detector and sonic processing to detect document jams.
Document scanners feed and transport paper documents past one or more imaging subsystems in order to create digital image files representative of the originals. Systems have been described that detect excessive or unique sound energy using audio frequency microphones, the energy created by the document being transported when the document or documents are being damaged, wrinkled, torn or otherwise deformed by the feeding and transport process (referred to herein as a “misfeed”). These sounds are differentiated from the normal sounds of the mechanisms via processing of the audio frequency sounds. The sounds are quantified, compared to a threshold (which may be adjustable), and then used to immediately stop the feeding and/or transport mechanism in order to prevent or substantially limit damage to the documents.
Incorporating multiple devices for receiving audio information (typically in the range of 1 KHz. to 10 KHz.) represents both a cost penalty and a packaging challenge given the position of drive rollers and other sensors within the document transport design.
This invention implements sound-based damage detection based on only one receiving device (in a preferred embodiment, an electret microphone), saving cost and enabling physical placement in paper transport systems where space may be at a premium.
The electret microphone operates over a wide frequency range and is capable of detecting the sound patterns associated with document damage. After buffering the signal with an amplifier, the sound energy is filtered for damage detection. It is important to filter out irrelevant frequencies before it is passed to the damage detection subsystem due to frequency aliasing by the analog-to-digital sampling process. This aliasing results in beat frequencies that can fall into the range of frequencies considered by the damage detection algorithm. After conversion to digital samples, the sound is further filtered to distinguish between sounds associated with a misfeed and the normal sounds of document transport.
Additionally, it has been found that mounting the sound detection device (microphone) in a compliant mount or rubber isolator helps to reduce the conduction of unwanted sounds, noise, and vibrations into the microphone from the scanner mechanisms. The electrical output amplitude of the sound detecting device may require additional amplification of the microphone output.
A preferred embodiment of the present invention comprises a sheet handling apparatus having a transport path, a device adapted to separate a first sheet from a plurality of stacked sheets and to feed the first sheet into the transport path, only one detector positioned near the transport path to detect a misfeed condition indicating that the first sheet is being damaged in the transport path, and a processing system coupled to the detector adapted to receive and process signals from the detector and configured to determine the misfeed in the transport path, and to terminate feeding sheets in response to the determination. The detector comprises a microphone mounted into the apparatus using a compliant noise isolating material. An energy level of the digital audio data is calculated to determine the misfeed.
Another preferred embodiment of the present invention comprises an article processing apparatus having a transport path for the plurality of articles, a feeder device for feeding individual ones of the articles into the transport path, only one audio detector positioned in the transport path to detect a misfeed condition in the transport path, and a processing system coupled to the detector to process signals from the detector and configured to terminate processing in response to the signals from the detector. An energy level of the signals from the detector is calculated to determine if the signals exceed an energy threshold, thereby indicating the misfeed condition. A converter coupled to the detector converts the signals into digital data frames wherein the processing system counts a number of the data frames that indicate the misfeed condition. A termination signal is issued if the number of data frames that exceed the energy threshold exceeds a preselected number.
Another preferred embodiment of the present invention comprises a method for feeding sheets by urging a sheet through a sheet transport path, providing only one audio receiver proximate the transport path, processing audio data detected by the audio receiver and terminating feeding sheets in response to determining a misfeed in the audio data, which includes calculating an energy level of the audio data. The audio receiver is mounted proximate the transport path using a noise isolating compliant material.
Another preferred embodiment of the present invention comprises a method of determining a misfeed in an article processing apparatus by placing only one microphone in the article processing apparatus, feeding an article into the article processing apparatus, generating and collecting digital data frames of sound from the analog sound detected by the microphone, processing the collected data frames to determine the misfeed, including reducing a probability of a false misfeed determination by accumulating a number of data frames collected, and reducing a sensitivity setting if the number of data frames collected exceeds a threshold amount. The number of data frames collected represents a distance that the document has traveled. An energy level of the data frames is calculated and compared to a jam threshold for each data frame. The jam threshold is determined according to the sensitivity setting. A jam count window is opened upon determining that the energy level of a current data frame exceeds its threshold. The jam count window accumulates a jam count, which counts the number of data frames that exceed their threshold. If the jam count reaches a preselected jam count limit while the jam count window is open then a jam signal is issued. The jam count window is closed if the total number of frames that have been processed exceeds a jam count window size and the jam count is reset to zero.
Another preferred embodiment of the present invention comprises a method of processing articles by holding a plurality of the articles to be processed in an input tray, feeding a first one of the articles into an article processing apparatus using a device configured to separate the first one of the articles from the plurality of the articles, collecting sound data using only one microphone, processing the sound data and determining if the sound data indicates a misfeed, and, if so, terminating processing the articles.
It should be noted that in the present patent application preferred embodiments are described in terms of a scanner only for representative preferred embodiments. The present invention is not so limited, and the use of the term “scanner” is hereby intended to refer to any document or paper conveyance machine. These, and other, aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention and numerous specific details thereof, is given by way of illustration and not of limitation. For example, the summary descriptions above are not meant to describe individual separate embodiments whose elements are not interchangeable. In fact, many of the elements described as related to a particular embodiment can be used together with, and possibly interchanged with, elements of other described embodiments. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. The figures below are intended to be drawn neither to any precise scale with respect to relative size, angular relationship, or relative position nor to any combinational relationship with respect to interchangeability, substitution, or representation of an actual implementation.
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The damage detection processor determines when document damage due to misfeeding, wrinkles, staples, adhesion or other factors is occurring and stops the document transport motors and feed mechanisms in a very brief time interval to prevent further damage to the documents. The document damage detection algorithm uses the idea of differentiating between the sound made by a normal document entering a document scanner and the sound of a document being wrinkled due to a jam. For a system to make this distinction, it is important to ignore or in some way isolate the background sounds of the scanner from the sounds coming from the document. The background sounds come from various moving parts of the scanner. The moving parts include, but are not limited to, the transport motors, transport rollers, feeder mechanism and possible cooling fans. These scanner background sounds are typically periodic and have low frequency components relative to that of documents being damaged.
On the other hand, the sounds from a wrinkling or damaging document are a short duration signal in the time domain and have frequency components spread over a wide range in the frequency domain. In addition, the sound of a clean document being scanned typically has frequencies that overlap the frequencies that of a wrinkling document. Therefore, the algorithm can detect a jamming document by computing the energy of the audio signal by looking at a frequency band between F5 and F6 as shown in
With reference to
As the trail-edge of the document enters the document transport and passes over the point of feeding at the contact nip between rollers 105, the trail edge of the document may make a snapping sound that creates a sharp impulse in the audio signal. To reduce the probability of false jam detection on the trail-edge, an additional check 503 needs to be performed to determine where the microphone frame was captured in relation to the lead-edge of the document. This is done by keeping track of how many frames have been processed since the feeder mechanism enable signal was asserted, and if the current frame number has passed the Sensitivity Switch Point (SSP). The Sensitivity Switch Point is dictated by the length of the shortest document that can be safely transported. The trail edge will pass by the point of feeding sooner for short documents and is therefore the limiting case for the need to switch to a lower sensitivity and avoid false jam detections. The number of frames counted to cross the SSP is equivalent to the time to transport the shortest document such that the trail edge passes over the point of feeding.
If the frame count is greater than the Sensitivity Switch Point 505, then the current frame for the microphone is susceptible to this trailing edge false detection and the low sensitivity settings are used 507 in a later stage for determining whether or not a document jam has occurred. If the frame count has not passed the SSP 509, then the high sensitivity settings will be used 511.
Each frame of microphone output data is next processed by sending the digitized data through a band pass filter 513 with lower and upper cutoff frequencies F5 and F6 as previously described in
A 1D median filter 515 is next applied to the frame of data to help distinguish audio characteristics between a document that is merely wrinkled which exhibits intermittent high peak values, as opposed to a document in the process of being damaged which has relatively continuous high values of amplitude. The median filter, energy threshold calculations, and Jam Count window accumulation all combine to distinguish merely wrinkled documents from those being damaged during transport.
After the median filter, the energy of the microphone frame of data is calculated 517. The energy of the frame of data is calculated with the equation below, where N represents the number of data samples within a frame, and micdata is a number correlated to a sound intensity of each individual digitized audio sample.
If the microphone frames are captured immediately after the feeder mechanism is enabled 520 then the algorithm completely ignores these frames of data by forcing the energy level to zero 521. An example number of ignored frames is about thirty. This prevents the algorithm from falsely detecting the feeder mechanism noise as a potential jam. Otherwise 522 the energy calculation from 517 is compared against a sensitivity threshold 523 that is varied depending on whether we are in the low or high sensitivity mode as determined previously in 503. A potential wrinkling document is detected when the energy level of the frame goes above the Energy_Threshold 524. When this occurs, the algorithm initiates a jam count window if one has not been previously initiated and increments the Jam Count variable 525. This window defines a block of frames where the energy level of some minimum number of frames must exceed the Energy_Threshold before an actual jam detection signal is issued. If the Jam Count exceeds the JamCount_Threshold 527, then the jam signal is asserted 529 and the algorithm terminates 541. Otherwise, if the Jam Count is below the JamCount_Threshold 543, then the algorithm waits for next frame of data.
If the energy level of this particular data frame is below the Energy_Threshold 533 then the algorithm increments the current position within the jam count window, assuming a jam had occurred on an earlier frame (jam count >0) and a jam count window was open 535.
If a jam count window was opened by a previous frame exceeding the energy threshold, and the current frame position count reaches the end of the fixed window size 537 before the Jam Count exceeds the JamCount_Threshold, then the window is closed and the Jam Count is reset to zero 539 and the algorithm waits for the next frame of data 551. Otherwise 549 the algorithm waits for the next frame of data 551.
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The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
