Abstract:
Sheet media jams are detected along a media transport path by one or more vibration sensors that capture mechanical movements of components along the path that interact with the sheet media for driving or guiding the sheet media along the transport path. The detected vibrations during the advancing of the sheets are analyzed for distinguishing between detected vibrations associated with normal handling of the sheets and detected vibrations associated with abnormal handling of the sheets. An error condition can be signaled to a control system in response to distinguishing the detected vibrations associated with the abnormal handling of the sheets.

Description:
TECHNICAL FIELD 
     The invention relates to media handling systems, including systems transporting sheet media for such processing purposes as printing, imaging, copying, sorting, arranging and binding, and more particularly to methods and apparatus for sensing medium handling problems during the separation, feeding, and transport of the sheet media for processing. 
     BACKGROUND OF THE INVENTION 
     Media processing apparatus, such as document scanners, copiers, printers, fax machines, and other media processing systems that obtains data from, or imprint images and text onto sheet media, include media transport systems to move the sheet media along a transport path. These media transport systems can sometimes jam as the sheet media moves along the media transport path due to problems or abnormalities in either the media processing apparatus or the sheet media itself. Before loading sheet media into the media transport path of a media processing apparatus, an operator typically removes staples, paper clips, or other fasteners used to hold sheet media containing two or more sheets together. However, sometimes the operator fails to remove or even notice these fasteners. Advancing the sheet media along the media transport path without removing the fasteners can cause significant damage to the sheet media, and can also damage the media transport path, imaging or printing system, or other information transfer system located along the media transport path. In addition, removal of the fasteners, particularly staples, can damage the sheet media before the media is loaded, such that two or more sheets remain attached as they are fed into the transport path. If two or more sheets remain attached together with a fastener or as a result of residual damage caused by the removal of the fastener, then the intended processing of the sheet media can be compromised. For example, a failure to independently image the individual sheets in a document scanner can lead to a loss of information. 
     While systems have been implemented to check for staples, paper clips, or other fasteners binding sheet media together before the sheet media are transported from an input tray into a scanner device, their scope of detection can be limited and they sometimes fail to detect the fasteners binding sheet media transported into the scanner device. In these situations, jams still occur. In addition, these systems often fail to locate the position of a jam within the media transport system. 
     Some document handler systems detect the presence of staples in documents loaded into an input tray. However, such systems generally only look for staples in predetermined areas of the documents, and are only capable of detecting staples while the documents are in the input tray. Some documents do not fit into the input tray, and thus no staples in these documents would be detected before they are passed into the scanner. Additionally, many types of documents, including those of varying sizes, do not have a “preselected” area for a staple. Thus, the prior systems can miss staples in documents where staples are present but not in the preselected areas that are monitored. 
     In addition to the problems caused by fasteners, media processing apparatus are particularly prone to problems during the separation of the queued media in the input tray which can also be caused by poor document preparation or stacking, folds or wrinkles in the fed media sheets, different media weights and thicknesses, and other media-related problems, as well as problems with the media transport components themselves, caused by wear, dust and dirt, and other factors. These problems can be particularly acute with high-speed media processing apparatus or with media processing apparatus that handle fragile media. Failure to detect a problem with the handling of the media in time can damage the original media, causing loss of data, require special handling to correct the problem, and reduce equipment efficiency due to down time. 
     Various approaches have been used for monitoring the transport of sheet media in a media processing apparatus. Automatic media processing systems have used a range of different approaches of mechanical, optical, and audio sensors for the purpose of preventing damage to media being processed. 
     In one approach, the sound sheet media makes as it moves along media transport path can be used to diagnose the condition of the sheet media. Quiet or uniform sounds can indicate a normal or problem-free passage of the sheet media along the media transport path. Loud, unexpected, or non-uniform sounds can indicate a disruption in the passage of the sheet media such as a stoppage due to jamming or tearing, or physical damage of the sheet media. 
     Other known methods of detecting jams include using optical or mechanical sensors to monitor the times at which the sheet media passes through various locations along the media transport path. If the sheet media does not arrive at a given location in a given amount of time after the start of transport, a sheet media jam is inferred. These sensors tend to have a limited range of detection, and several sensors are typically required along the media transport path to produce useful results. 
     Commonly assigned U.S. Pat. No. 8,857,815 describes placing a microphone near the beginning of a sheet media feed path in order to detect the sound of a sheet media jam in progress. The microphone signal is processed by counting the number of sound samples above a given threshold within a sampling window. If the count is sufficiently large, a sheet media jam is signaled. However, information is not provided about the location of the sheet media as it moves along the media transport path. Thus, although sound can be used to detect a jam in progress, information regarding the location of the jam is unavailable. 
     A need remains for a simple, fast and robust technique to monitor sheet media advanced by media transport systems for various abnormalities. These abnormalities may be caused, for example, by the presence or residual effects of binding objects, or by problems attributable to the presentation or condition of the media itself. There further exists a need for a simple, fast and robust technique to prevent damage to the media, the media transport systems, and the media processing apparatus, to avoid losses of information, and to reduce downtime. In addition, there remains a need for a fast and robust technique to indicate sheet media jams that also accurately identifies the location of the jams along the media transport path. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a method and system of detecting abnormalities along the media transport path of document scanners and other media processing apparatus, such as the abnormalities caused by the presence or residual effects of binding objects, or by defects in the presentation or condition of the media itself. Preferably, such abnormalities are detected before the sheet media encounter any imaging systems, printing systems, or other information transfer systems located along the media transport path. 
     Appropriately positioned and mounted vibration detectors along the media transport path produce continuous signals, which may be communicated to a processor to detect various types of abnormalities detrimental to the intended functioning of media processing apparatus. Signal processing within the processor can distinguish vibrations indicative of abnormalities in the transport of media from vibrations accompanying the normal movements of media along the media transport path. Vibrations indicative of normal operations may be obtained by sensing vibrations at a time when the media transport system is known to be operating under normal conditions, and these sensed normal signals may be stored in a memory. Alternatively, the signals indicative of normal condition for implementing the comparison may be pre-stored in a memory accessible by the process, included in a program executed by the processor, other accessible from a server in communication with the processor. The vibrations which may be indicative of abnormalities can be monitored in a number of ways including sensing variations in the position, acceleration, or stress of components along the media transport path. Multiple vibration detectors may be positioned along the media transport path, particularly in association with different stages of media transport such as feeding media into the media handling system, advancing the media within the media transport, ejecting the sheet media into an output tray, or sorting the media into different output trays or positions. The signals from the detectors can be analyzed individually or collectively, to ascertain or even anticipate sources of malfunction or performance concerns. 
     The detection and characterization of the abnormalities provides information that may be used to optimize operation of the media processing apparatus, including halting the further transport of the media if there is a suspected jam, undue stress, or risk to components of the media processing apparatus. Automated interventions can be implemented to identify, protect, or even bypass media responsible for the detected abnormality. Warnings or alerts can be issued or logged to identify the media or information contained thereon that may have been compromised, or the components that may have been subject to wear, stress, misalignment, or damage. For example, if the document jams in the transport, the scanned image may not be readable. As another example, if the speed of the document moving through the transport changes, the scanned image may be incomplete or compromised. 
     The method and system described herein may also include sensor systems of different types, such as sensor systems for detecting both sounds&#39; transmitted through the air and vibrations propagating in supporting structures. 
     Damage to sheet media during transport though a media processing apparatus may be avoided by advancing the sheets with a transport apparatus from a queue mechanism through one or more media processing stages to an ejection mechanism. Rollers, which are rotatably supported in support structures of the transport apparatus, engage the sheets for driving or guiding the sheets. Vibrations propagating in one of the support structures may be detected with one or more sensors mounted on the support structure, or nearby the support structure. Data from the sensors is provided to a processing system, which analyzes the detected vibrations during the advancing of the sheets for distinguishing between detected vibrations associated with normal handling of the sheets and detected vibrations associated with abnormal handling of the sheets. Based on this analysis, damage to the sheet media can be avoided by signaling an error condition to a control system in response to distinguishing the detected vibration associated with the abnormal handling of the sheets. 
     The media processing apparatus may also include one or more media processing stages and a transport apparatus for advancing the sheets from a queue mechanism through the one or more media processing stages to an ejection mechanism. The transport apparatus includes rollers for engaging the sheets and support structures for rotatably supporting the rollers. Sensors mounted on one or more of the support structures detect vibrations propagating in the support structures. A processing system analyzes the detected vibrations during the advancing of the sheets, and distinguishes between detected vibration associated with normal handling of the sheets and detected vibration associated with abnormal handling of the sheets. A control unit receives an error condition signal from the processing system in response to the analysis associating the detected vibration with the abnormal handling of the sheets. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a diagram showing the components of a media processing apparatus in the form of a document scanner. 
         FIG. 2  is a diagram showing components of a media transport system of the media processing apparatus of  FIG. 1 . 
         FIG. 3  is a diagram showing a flattened view of the components of the document scanner. 
         FIGS. 4A and 4B  are a block diagram showing signal and information transfers of the document scanner.  FIG. 4B  is a continuation of the view of the block diagram from  FIG. 4A , as indicated on the drawings. 
         FIG. 5  is a diagram of the operation of a system processing unit for information input from a vibration detection unit. 
         FIG. 6  is a plot of vibration values collected along three orthogonal axes during the initial advance of a sheet medium along the media transport system. 
         FIG. 7  is a flow chart showing the processing of vibration values for detecting a vibration exception. 
         FIG. 8  is a flow chart showing a logic structure of an exception test block of  FIG. 7 . 
         FIG. 9  is an illustration showing a calibration procedure that may be performed. 
         FIG. 10  is a diagram showing components of an alternative media transport system for the media processing apparatus of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to systems and methods for the detection of abnormalities involving media transported through a media transport system. Vibration detectors detect vibration profiles associated with media, typically documents, being transported through the media transport system. A processor analyzes these vibration profiles to determine the occurrence and location of potential malfunctions, such as paper jams, or other performance concerns. The processing can be carried out using an instruction set implemented within a programmable computer that can include one or more non-transitory, tangible, computer readable storage media. For example, the programmable computer may include magnetic or optical storage media, solid-state electronic storage devices such as random access memory (RAM), or read-only memory (ROM), or any other physical device or media employed to store the instructions for carrying out the desired processing. In addition, the instructions may be embedded in a machine readable bar code, which is read by an imaging device and processed by the programmable computer. 
     The system and method may be implemented with document handling equipment for imaging apparatus including document scanners, and equipment of other types, such as copiers, fax machines, printers, binding devices, and other systems. A document feed tray, or other member for receiving a document as a stack of serial-fed sheets, can include single-sheet feed, top feed, bottom feed, or other serial feed configurations. 
     A media processing apparatus is depicted in  FIG. 1  as a document imaging scanner  10  includes a scanner base  100 , a scanner pod  180 , an input tray  110 , an output tray  190 , and an operator control panel  122 . The scanner pod  180  covers a top surface of the document scanner  10  and connects to the scanner base  100  with hinges. The hinges allow the document scanner  10  to be opened and closed when there is a media jam within the document scanner  10  or when the document scanner  10  needs to be cleaned. 
     The input tray  110  can be opened at times of scanning and closed when the document scanner  10  is not in use, as illustrated by arrow A 3 . When the input tray  110  is closed, the footprint of the document scanner  10  can be reduced. Sheet media  115  to be scanned can be placed into the input tray  110 . Examples of such sheet media  115  include paper documents, photographic film, and magnetic recording media. Top sheet medium  117  is the medium at the top of a stack of sheet media  115 , and is the next sheet medium to be pulled into the document scanner  10  by an urging roller  120 . The input tray  110  is provided with input side guides  130   a  and  130   b , which can be moved in a direction perpendicular to a transport direction of the sheet media  115 . By positioning the side guides  130   a  and  130   b  to match the width of the sheet media  115 , movement of the sheet media  115  in the input tray  110  is reduced and the position of the sheet media  115  (e.g., left, right or center justified) for initiating automated transport is set. The input side guides  130   a  and  130   b  can be referred to collectively as the input side guides  130 . The input tray  110  can be attached to a motor (not shown) that causes the input tray  110  to raise the top sheet medium  117  into engagement with the urging roller  120  for initiating automated transport or to lower the input tray  110  to allow additional sheet media  115  to be added to the input tray  110 . 
     The output tray  190  is connected to the scanner pod  180  by hinges, allowing an angle of the output tray  190  to be adjusted as shown by the arrow marked A 1 . The output tray  190  is provided with output side guides  160   a  and  160   b  which can be moved in a direction perpendicular to a transport direction of the sheet media  115 , that is, to the left and right directions from the transport direction of the sheet media  115 . By positioning the output side guides  160   a  and  160   b  to match with the width of the sheet media  115 , it is possible to limit the movement of output sheet media  150  in the output tray  190 . The output side guides  160   a  and  160   b  can be referred to collectively as the output side guides  160 . An output tray stop  170  is provided to stop the top sheet medium  117  after being ejected by the output transport rollers  140 . When the output tray  190  is in the up state as shown in  FIG. 1 , the ejected sheet media is trail-edge aligned. In the down state, the ejected sheet media is lead-edge aligned against the output tray stop  170 . 
     The operator control panel  122  is attached to the scanner base  100  or scanner pod  180 , and can be tilted as shown by the arrow marked A 2  to allow optimal positioning for an operator. An operator input  125  is arranged on the surface of the operator control panel  122 , allowing the operator to input commands such as start, stop, and override. The operator input  125  can include one or more buttons, switches, portions of a touch-sensitive panel, selectable icons on an operator display  128 , or other selectable input mechanism. The override command can allow the operator to temporarily disable multi-feed detection, jam detection, or other features of the document scanner  10  while scanning. The operator control panel  122  also includes an operator display  128  that allows information and images to be presented to the operator. As noted above, the operator display  128  can include selectable icons relating to commands and operations of the document scanner  10 . The operator control panel  122  can also contain speakers and LEDs (not shown) to provide additional feedback to the operator. 
       FIG. 2  illustrates a media transport path  290  inside of the document scanner  10 . A plurality of rollers are positioned along the media transport path  290 , including an urging roller  120 , a feed roller  223 , a separator roller  220 , take-away rollers  260 , transport rollers  265 , and output transport rollers  140 . The urging roller  120  and feed roller  223  can be referred to collectively as a feed module  225 . A vibration sensor  255 , microphones  200   a ,  200   b ,  200   c , a first media sensor  205 , a second media sensor  210 , an induction sensor  215 , an ultrasonic transmitter  282 , and an ultrasonic receiver  284  are positioned along the media transport path  290  to sense sheet media within the media transport path  290 , for example as the top sheet medium  117  is transported along the media transport path  290 . A pod image acquisition unit  230  and a base image acquisition unit  234  are included to capture images of the sheet media. 
     The top surface of the scanner base  100  forms a lower media guide  294  of the media transport path  290 , while the bottom surface of the scanner pod  180  forms an upper media guide  292  of the media transport path  290 . A delta wing  185  can be provided which helps to guide the sheet media from the input tray  110  into the media transport path  290 . As shown in  FIG. 2 , the delta wing  185  can be arranged as a removable section of the upper media guide  292 , transitioning from the upper media guide  292  to the scanner cabinetry of the scanner pod  180 . The delta wing  185  can be angled to allow microphones  200  A, B to point into the input tray  110 , thereby improving signal pickup. 
     In  FIG. 2 , the arrow A 4  shows the transport direction that the sheet media travels within the media transport path  290 . As used herein, the term “upstream” refers to a position relative to the transport direction A 4  that is closer to the input tray  110 , while “downstream” refers to a position relative to the transport direction A 4  that is closer to the output tray  190 . The first media sensor  205  has a detection sensor which is arranged at an upstream side of the urging roller  120 . The first media sensor  205  can be mounted within the input tray  110 , and detects if sheet media  115  is placed on the input tray  110 . The first media sensor  205  can be of any form known to those skilled in the art including, but not limited to, contact sensors and optical sensors. The first media sensor  205  generates and outputs a first media detection signal which changes in signal value depending on whether or not media is placed on the input tray  110 . 
     The first microphone  200   a , second microphone  200   b , and third microphone  200   c  are examples of sound detectors that detect the sound generated for example by the top sheet medium  117  during transport through the media transport path  290 . The microphones generate and output analog signals representative of the detected sound. The microphones  200   a  and  200   b  are arranged to the left and right of the urging roller  120  while fastened to the delta wing  185  at the front of the scanner pod  180 . The microphones  200   a  and  200   b  are mounted so as to point down towards the input tray  110 . To enable the sound generated by for example the top sheet medium  117  during transport of the sheet media to be more accurately detected by the first microphone  200   a  and the second microphone  200   b , a hole is provided in the delta wing  185  facing the input tray  110  in order to improve the ability of first microphone  200   a  and second microphone  200   b  to detect sound. The microphones  200   a  and  200   b  are mounted to the delta wing  185  using a vibration reducing gasket. The third microphone  200   c  is at the downstream side of the feed roller  223  and the separator roller  220  while fastened to the upper media guide  292 . A hole for the third microphone  200   c  is provided in the upper media guide  292  facing media transport path  290 . The microphone  200   c  is mounted in the upper media guide  292  using a vibration reducing gasket. As an example, the microphones can be MEMS microphones mounted flush to a baffle with isolator material to reduce vibration transferring from the baffle to the MEMS. By mounting the MEMS flush, the amount of internal machine noise behind the microphone that can be detected by the microphone is reduced. 
     The second media detector  210  is arranged at a downstream side of the feed roller  223  and the separator roller  220  and at an upstream side of the take-away rollers  260 . The second media detector  210  detects if there is a sheet medium present at that position. The second media detector  210  generates and outputs a second media detection signal which changes in signal value depending on whether sheet media is present at that position. The second media detector  210  can be of any form known to those skilled in the art including, but not limited to, contact sensors, motion sensor, and optical sensors. 
     One or more vibration sensors  255  are located within the media transport apparatus. A vibration sensor  255 , which may be mounted on the upper media guide  292 , is arranged proximate the feed module  225  on a common mount with the urging roller  120  and the feed roller  223 . The vibration sensor  255  may be accelerometers, gyroscopes, or external foil strain gauges. A vibration sensor  255  is preferably mounted on a common platform with adjacent rollers  120 ,  223  of the feed module  225  so that disturbances associated with operative engagements between the sheet media and the feed roller  223  can be detected. A vibration sensor  255  may also be located in structural, solid-to-solid, connection to one or more guide surfaces that are subject to disturbances associated with the transport of the sheet media along the media transport path  290 . For example, a vibration sensor  255  could be mounted on the delta wing  185 , which helps to guide the sheet media from the input tray  110  into the media transport path  290 . A vibration sensor  255  may also be located upstream of the take-away rollers  260  to provide localized detection of disturbances associated with the entry of the sheet media into the media transport path  290  so that problems with the sheet media or its transport can be detected before the sheet media engages more sensitive structures within the document scanner  10  or can interfere with the transport of succeeding sheet media. 
     The induction sensor  215 , which is mounted on the lower media guide  294 , is positioned downstream of the feed roller  223  and the separator roller  220  while upstream of take-away rollers  260  to further monitor the entry of the sheet media into the media transport path  290 . The induction sensor  215  detects metal components, such as from staples or other fasteners, which might bind sheet media together or otherwise interfere with the intended further movement of the sheet media along the media transport path  290 . The induction sensor  215  is also preferably located upstream of the take-away rollers  260  to provide detection of potentially disruptive metal components upon the initial entry of the sheet media into the media transport path  290   
     The ultrasonic transmitter  282  and the ultrasonic receiver  284 , together forming an ultrasonic detector  280 , are arranged near the media transport path  290  of the top sheet medium  117  so as to face each other across the media transport path  290 . The ultrasonic transmitter  282  transmits an ultrasonic wave that passes through the top sheet medium  117  and is detected by the ultrasonic receiver  284 . The ultrasonic receiver then generates and outputs a signal, which can be an electrical signal, corresponding to the detected ultrasonic wave. 
     A plurality of ultrasonic transmitters  282  and ultrasonic receivers  284  can be used. In this situation, the ultrasonic transmitters  282  are positioned across the lower media guide  294  perpendicular to the transport direction as marked by arrow A 4  while ultrasonic receivers  284  are positioned across the upper media guide  292  perpendicular to the transport direction as marked by arrow A 4 . 
     The pod image acquisition unit  230  has an image sensor, such as a CIS (contact image sensor) or CCD (charged coupled device). Similarly, the base image acquisition unit  234  has an image sensor, such as a CIS or CCD. 
     As the top sheet medium  117  travels along the media transport path  290 , it passes the pod imaging aperture  232  and the base imaging aperture  236 . The pod imaging aperture  232  is a slot in the upper media guide  292  while the base imaging aperture  236  is a slot in the lower media guide  294 . The pod image acquisition unit  230  images the top surface of the top sheet medium  117  as it passes the pod imaging aperture  232  and outputs an image signal. The base image acquisition unit  234  images the bottom surface of the top sheet medium  117  as it passes the base imaging aperture  236  and outputs an image signal. It is also possible to configure the pod image acquisition unit  230  and the base image acquisition unit  234  such that only one surface of the top sheet medium  117  is imaged. 
     The top sheet medium  117  is moved along a media transport path  290  by sets of rollers. The sets of rollers are composed of a drive roller and normal force roller. The drive roller is driven by a motor which provides the driving force to the roller. The normal force roller is a freewheeling roller that provides pressure to capture the top sheet medium  117  between the drive roller and normal force roller. In the document scanner  10 , the initial drive and normal force rollers that grab the top sheet medium  117  for transport along the media transport path  290  are referred to as take-away rollers  260 . The additional drive and normal force roller pairs along the media transport path  290  are referred to as transport rollers  265 . The rollers can be driven by a single motor, where all the rollers start and stop together. Alternatively, the rollers can be grouped together, where each group is driven by its own motor. This allows different motor groups to be started and stopped at different times or run at different speeds. 
     The document scanner  10  can have output transport rollers  140 . The output transport rollers  140  are connected to a separate drive motor that either speeds-up the top sheet medium  117  or slows down the top sheet medium  117  for modifying the way the output sheet media  150  is placed into the output tray  190 , as described in detail, for example, in U.S. Pat. No. 7,828,279, which is hereby incorporated by reference. 
     Sheet media  115  placed on the input tray  110  is transported between the lower media guide  294  and the upper media guide  292  in the transport direction shown by arrow A 4  by rotation of the urging roller  120 . The urging roller  120  pulls the top sheet medium  117  out of the input tray  110  and pushes it into the feed roller  223 . The separator roller  220  resists the rotation of the feed roller  223  such that when the input tray  110  has a plurality of sheet media  115  placed on it, only the top sheet medium  117  which is in contact with the feed roller  223  is selected for feeding into the media transport path  290 . The transport of the sheet media  115  below the top sheet medium  117  is restricted by the separator roller  220  to prevent feeding more than one sheet medium at a time, which is referred to as a “multi-feed.” 
     The top sheet medium  117  is fed between the take-away rollers  260  and is transported through the transport rollers  265  while being guided by the lower media guide  294  and the upper media guide  292 . The top sheet medium  117  is sent past the pod image acquisition unit  230  and the base image acquisition unit  234  for imaging. The top sheet medium  117  is then ejected into the output tray  190  by the output transport rollers  140 . In addition to microphones  200   a ,  200   b , and  200   c , a microphone  297  can be provided near the exit of the media transport path  290 . This microphone  297  detects the sounds of the sheet media towards the end of the transport path, and as the sheet media is output into the output tray  190 . These detected sounds can be used to detect jams occurring in the output tray  190  or as sheet media are exiting the media transport path  290 . A system processing unit  270  monitors the state of the document scanner  10  and controls the operation of the document scanner  10  as described in more detail below. 
     Although  FIG. 2  shows the urging roller  120  above the stack of sheet media  115  to select the top sheet media  117 , in a feeding configuration often referred to as a “top feeding mechanism,” other configurations can be used. For example, the urging roller  120 , feed roller  223  and separator roller  220  can be inverted such that the urging roller selects the sheet medium at the bottom of the sheet media stack  115 . In this configuration, microphones  200   a  and  200   b  can be moved into the scanner base  100 . The vibration sensor  255  can also be mounted on the lower media guide  294 . 
       FIG. 3  is a block diagram of document scanner  10  as seen from the viewpoint shown by the direction arrow A 5  in  FIG. 2 . As shown in  FIG. 3 , the first microphone  200   a  is provided to the left of the urging roller  120  and feed roller  223  along the delta wing  185 . The second microphone  200   b  is provided to the right of the urging roller  120  and feed roller  223  along the delta wing  185 . The placement of microphones  200   a  and  200   b  capture sound from the top sheet medium  117  as it is being urged into the feed roller  223  by the urging roller  120 . The third microphone  200   c  is preferably located slightly behind and downstream of the feed roller  223 . The placement of microphone  200   c  captures sound from the top sheet medium  117  as it passes the feed roller  223  and before reaching the take-away rollers  260 . 
     The vibration sensor  255  is depicted in  FIG. 3  downstream of the feed roller  223  but upstream of the third microphone  200   c . Although mounted on the lower media guide  294  beneath the third microphone  200   c , the induction sensor  215  is shown in  FIG. 3  in a layout position between the vibration sensor  255  and the third microphone  200   c . The induction sensor  215  preferably spans the full width of the sheet media to detect metal components that might be located in any area of the sheet media. The ultrasonic detector  280  is located downstream of the take-away rollers  260  and the upstream of the transport rollers  265 . Additional sets of the transport rollers  265  straddle both the pod imaging aperture  232  and the base imaging aperture  236 , which also preferably span the full width of the sheet media to capture graphical, text, or other types of information carried anywhere on the front or back sides of the sheet media. 
       FIGS. 4A and 4B  illustrate a block diagram of signal and information transfers within the document scanner  10 . The pod image acquisition unit  230  is further composed of a pod image device  400 , pod image A/D converter  402 , and pod pixel correction  404 . As noted above, the pod image device  400  has a CIS (contact image sensor) of an equal magnification optical system type, which is provided with an image capture device using CMOS (complementary metal oxide semiconductors). The elements of the image capture device are arranged in a line in a main scan direction, which is perpendicular to the media transport path  290  as shown by arrow A 4 . As noted above, instead of a CIS, it is also possible to use an image capturing sensor of a reduced magnification optical system type using CCD&#39;s (charge coupled devices). The pod imaging A/D converter  402  converts an analog image signal which is output from the pod image device  400  to generate digital image data, which is then output to the pod pixel correction  404 . The pod pixel correction  404  corrects for any pixel or magnification abnormalities. The pod pixel correction  404  outputs the digital image data to the image controller  440  within the system processing unit  270 . The base image acquisition unit  234  is further composed of a base image device  410 , base image A/D converter  412 , and base pixel correction  414 . The base image device  410  has a CIS (contact image sensor) of an equal magnification optical system type, which is provided with an image capture device using CMOS&#39;s (complementary metal oxide semiconductors), the elements of which are arranged in a line in the main scan direction. As noted above, instead of a CIS, it is also possible to use an image capturing sensor of a reduced magnification optical system type using CCD&#39;s (charge coupled devices). The base image A/D converter  412  converts an analog image signal output from the base image device  410  to generate digital image data, which is then output to the base pixel correction  414 . The base pixel correction  414  corrects for any pixel or magnification abnormalities. The base pixel correction  414  outputs the digital image data to the image controller  440  within the system processing unit  270 . Digital image data from the pod image acquisition unit  230  and the base image acquisition unit  234  will be referred to as “captured images.” 
     The operator configures the image controller  440  to perform the required image processing on the captured images either through the operator control panel  122  or network interface  445 . As the image controller  440  receives the captured images, it sends the captured images to the image processing unit  485  along with a job specification that defines the image processing that should be performed on the captured images. The image processing unit  485  performs the requested image processing on the captured images and outputs processed images. It will be understood that the functions of image processing unit  485  can be provided using a single programmable processor or by using multiple programmable processors, including one or more digital signal processor (DSP) devices. Alternatively, the image processing unit  485  can be provided by custom circuitry (e.g., by one or more custom integrated circuits (ICs) designed specifically for use in digital document scanners), or by a combination of programmable processor(s) and custom circuits. 
     The image controller  440  manages image buffer memory  475  to hold the processed images until the network controller  490  is ready to send the processed images to the network interface  445 . The image buffer memory  475  can be internal or external memory of any form known to those skilled in the art including, but not limited to, SRAM, DRAM, or Flash memory. The network interface  445  can be of any form known to those skilled in the art including, but not limited to, Ethernet, USB, Wi-Fi or other data network interface circuit. The network interface  445  connects the document scanner  10  with a computer or network (not shown) to send and receive the captured image. The network interface  445  also provides a means to remotely control the document scanner  10  by supplying various types of information required for operation of the document scanner  10 . The network controller  490  manages the network interface  445  and directs network communications to either the image controller  440  or a machine controller  430 . 
     A first sound acquisition unit  420   a  includes the first microphone  200   a , a first sound analog processing  422   a , and a first sound A/D converter  424   a , and generates a sound signal responsive to the sound picked up by the first microphone  200   a . The first sound analog processing  422   a  filters the signal output from the first microphone  200   a  by passing the signal through a low-pass or band-pass filter to select the frequency band of the interest. The first sound analog processing  422   a  also amplifies the signal and outputs it to the first sound A/D converter  424   a . The first sound A/D converter  424   a  converts the analog signal which is output from the first sound analog processing  422   a  to a digital first source signal and outputs it to the system processing unit  270 . As described herein, outputs of the first sound acquisition unit  420   a  are referred to as the “left sound signal.” The first sound acquisition unit  420   a  can comprise discrete devices or can be integrated into a single device such as a digital output MEMS microphone. 
     A second sound acquisition unit  420   b  includes the second microphone  200   b , a second sound analog processing  422   b , and a second sound A/D Converter  424   b , and generates a sound signal responsive to the sound picked up by the second microphone  200   b . The second sound analog processing  422   b  filters the signal output from the second microphone  200   b  by passing the signal through a low-pass or band-pass filter to select the frequency band of the interest. The second sound analog processing  422   b  also amplifies the signal and outputs it to the second sound A/D converter  424   b . The second sound A/D converter  424   b  converts the analog signal output from the second sound analog processing  422   b  to a digital second source signal and outputs it to the system processing unit  270 . As described herein, outputs of the second sound acquisition unit  420   b  will be referred to as the “right sound signal.” The second sound acquisition unit  420   b  can comprise discrete devices or can be integrated into a single device such as a digital output MEMS microphone. 
     A third sound acquisition unit  420   c  includes the third microphone  200   c , a third sound analog processing  422   c , and a third sound A/D Converter  424   c , and generates a sound signal responsive to the sound picked up by the third microphone  200   c . The third sound analog processing  422   c  filters the signal output from the third microphone  200   c  by passing the signal through a low-pass or band-pass filter to select the frequency band of the interest. The third sound analog processing  422   c  also amplifies the signal and outputs it to the third sound A/D converter  424   c . The third sound A/D converter  424   c  converts the analog signal output from the third sound analog processing  422   c  to a digital third source signal and outputs it to the system processing unit  270 . As described herein, outputs of the third sound acquisition unit  420   c  will be referred to as the “center sound signal.” The third sound acquisition unit  420   c  can comprise discrete devices or can be integrated into a single device such as a digital output MEMS microphone. 
     Below, the first sound acquisition unit  420   a , the second sound acquisition unit  420   b , and the third sound acquisition unit  420   c  can be referred to overall as the “sound acquisition unit  420 .” 
     A field detection unit  432  includes the induction sensor  215 , a field signal processing  434 , and a field A/D Converter  436 , and generates a field signal responsive to the presence of metal components picked up by the induction sensor  215 . Field signal processing  434  amplifies desired aspects of the signal output from induction sensor  215  and outputs it to the field A/D converter  436 . The A/D converter  436  converts the analog signal output from the field signal processing  434  to a digital first source signal and outputs it to the system processing unit  270 . The field detection unit  432  may comprise discrete devices or may be integrated into a single device such as a digital output module or ASIC device. 
     A vibration detection unit  442  includes the one or more vibration sensors  255  a vibration signal processing  444 , and a vibration A/D converter  446 . The vibration detection unit  442  generates a vibration signal responsive to the vibration picked up by the vibration sensor  255 . Vibration signal processing  444  filters the signal output from vibration sensor  255  by passing the signal through a low-pass or band-pass filter to select the frequency band of the interest. The vibration signal processing  444  also amplifies the signal and outputs it to the vibration A/D converter  446 . The A/D converter  446  converts the analog signal output from the vibration signal processing  444  to a digital first source signal and outputs it to the system processing unit  270 . The vibration detection unit  442  may comprise discrete devices or may be integrated into a single device such as a digital output module or ASIC device. 
     The transport driver unit  465  includes one or more motors and control logic required to enable the motors to rotate the urging roller  120 , the feed roller  223 , the take-away rollers  260 , and the transport rollers  265  to transport the top sheet medium  117  along the media transport path  290 . 
     The system memory  455  has a RAM (random access memory), ROM (read only memory), or other memory device, a hard disk or other fixed disk device, or flexible disk, optical disk, or other portable storage device. Further, the system memory  455  stores a computer program, database, and tables, which are used in various control function of the document scanner  10 . Furthermore, the system memory  455  can also be used to store the captured images or processed images. 
     The system processing unit  270  is provided with a CPU (central processing unit) and operates based on a program which is stored in the system memory  455 . The system processing unit  270  can be a single programmable processor or can be comprised of multiple programmable processors, a DSP (digital signal processor), LSI (large scale integrated circuit), ASIC (application specific integrated circuit), and/or FPGA (field-programming gate array). The system processing unit  270  is connected to the operator input  125 , the operator display  128 , first media sensor  205 , second media sensor  210 , ultrasonic detector  280 , pod image acquisition unit  230 , base image acquisition unit  234 , first sound acquisition unit  420   a , second sound acquisition unit  420   b , third sound acquisition unit  420   c , field detection unit  432 , vibration detection unit  442 , image processing unit  485 , image buffer memory  475 , network interface  445 , system memory  455 , transport driver unit  465 . 
     The system processing unit  270  controls the transport driver unit  465 , the pod image acquisition unit  230 , and base image acquisition unit  234  to acquire a captured image. Further, the system processing unit  270  has a machine controller  430 , an image controller  440 , a sound jam detector  450 , a position jam detector  460 , a metal detector  495 , a vibration detector  498  and a multi-feed detector  470 . These units are functional modules may be realized by software operating on a processor. These units may also be implemented on independent integrated circuits, a microprocessor, DSP or FPGA. 
     The sound jam detector  450  executes the sound jam detection processing. In the sound jam detection processing, the sound jam detector  450  determines whether a jam has occurred based on a first sound signal acquired from the first sound acquisition unit  420   a , a second sound signal acquired from the second sound acquisition unit  420   b , and/or a third sound signal acquired from the third sound acquisition unit  420   c . Situations in which the sound jam detector  450  determines that a media jam has occurred based on each signal, or a combination of signals, can be referred to as a “sound jam.” 
     The position jam detector  460  executes the position jam detection processing. The position jam detector  460  uses second media detection signals acquired from the second media sensor  210 , an ultrasonic detection signal acquired from the ultrasonic detector  280 , and a timer unit  480 , started when the transport driver unit  465  enables the urging roller  120  and the feed roller  223  to feed the top sheet medium  117 , to determine whether a jam has occurred. The position jam detector  460  can also use pod image acquisition unit  230  and base image acquisition unit  234  to detect the lead-edge and trail-edge of the top sheet media  117 . In this case, the image controller  440  outputs a lead-edge and trail-edge detection signal, which is combined with the timer unit  480 , to determine whether a jam has occurred if the lead-edge and trail-edge detection signal are not asserted within a predefined amount of time. Situations in which the position jam detector  460  determines that a media jam has occurred based on the second media detection signal, the ultrasonic detection signal, pod image acquisition unit  230 , or base image acquisition unit  234  can be referred to as a “position jam.” 
     The multi-feed detector  470  executes multi-feed detection processing. In the multi-feed detection processing, the multi-feed detector  470  determines whether the feed module  225  has allowed multiple sheet media to enter the media transport path  290  based on an ultrasound signal acquired from the ultrasonic detector  280 . Situations in which the multi-feed detector  470  determines that multiple sheet media entered the media transport path  290  can be referred to as a “multi-feed.” 
     The metal detector  495  executes the metallic detection processing. The metal detector  495  uses metallic detection signals acquired from the field detection unit  432 , to determine whether the sheet media contains metallic material. Situations in which the metal detector  495  determines that the sheet media entered the media transport path  290  contains metallic material may be referred to as a “metal detect exception”. 
     The vibration detector  498  executes the vibration detection processing. The vibration detector  498  uses the vibration detection signals acquired from the vibration detection unit  442 , to determine whether any vibration is detected by the vibration sensor  442 . Situations in which the vibration detector  498  determines that the sheet media entered the media transport path  290  caused vibration may be referred to as a “vibration detect exception”. 
     The machine controller  430  determines whether an abnormality condition, such as a medium jam, has occurred along a media transport path  290 . The machine controller  430  determines that an abnormality has occurred when there is at least one of a sound jam, a position jam, metal detect exception, vibration detect exception, and/or a multi-feed condition. When an abnormality is detected, the machine controller  430  takes action based on the operators predefined configuration for abnormality conditions. One example of a predefined configuration would be for the machine controller  430  to inform the transport driver unit  465  to disable the motors. At the same time, the machine controller  430  notifies the operator of media jam using the operator control panel  122 . Alternatively, the machine controller  430  may display an abnormality condition on the operator display  128  or issue an abnormality condition notice over the network interface  445 , allowing the operator to manually take action to resolve the condition. 
     When a medium jam along a media transport path  290  has not occurred, the image controller  440  causes the pod imaging acquisition unit  230  and the base imaging acquisition unit  234  to image the top sheet medium  117  to acquire a captured image. The pod imaging acquisition unit  230  images the top sheet medium  117  via the pod image device  400 , pod image A/D Converter  402 , and pod pixel correction  404  while the base imaging acquisition unit  234  images the top sheet medium  117  via the base image device  410 , base image A/D converter  412 , and base pixel correction  414 . 
       FIG. 5  is a block diagram of the processing for a preferred embodiment of the present invention. One or more vibration sensors  255  detect vibrations associated with the rotational motions and deflections of the urging roller  120  and the feed roller  223  transmitted through the feed module  225 , particularly as produced by the pulling of the top sheet medium  117  into the media transport path  290 . The signal output from the vibration sensor  255 , which may be an accelerometer or gyroscope, includes three signal components recording changes in speed, direction, or orientation along or about three orthogonal axes. These signals are shown in  FIG. 5  as signal X  510 , signal Y  520  and signal Z  530 . System processing unit  270  produces X-axis vibration values  550 , Y-axis vibration values  560 , and Z-axis vibration values  570 . The system processing unit  270  accounts for spurious influences including the effects of gravity. The effects of gravity are lessened, or removed, by normalizing all three axes to zero. This normalization may be done by computing a cumulative average of the data points from the channels. If the effects of gravity are not accounted, the large values due to gravity would skew channels, adding a bias to the information received. Normalizing also provides for smaller changes in vibrations to be detected. 
     A vibration is created when the sheet media moves through the media transport path  290  and suddenly stops due to a jam. Vibrations propagating in the feed module  225  can be detected by the vibration sensor  255  and used to determine a vibration detect exception. In this regard, one or more vibration sensors  255  are preferably mounted on the upper or lower transport guides  292 ,  294  or the upstream of the take-away rollers  260 . This provides for the detection of sheet media jamming as the top sheet medium  117  enters the media transport path  290 . Additional vibration sensors could be mounted elsewhere along the transport media path  290  to detect the location of vibrations by comparing the strength of vibration detected between multiple sensors. 
       FIG. 6  represents a set of vibration values produced by a normal passage of the top sheet medium  117  along the media transport path  290  as detected by vibration sensor  255 . Collectively the X-axis vibration values  550  represent the vibration profile  630 , the Y-axis vibration values  560  represent the vibration profile  640 , and the Z-axis vibration values  570  represent the vibration profile  650 , all over a common span of time at the position of the vibration sensor  255 . 
     Detection of the vibration associated with the transport of the top sheet medium  117  begins at points  600 ,  610  and  620  for the respective recorded vibration values  550 ,  560 , and  570  taken along the orthogonal X, Y, and Z axes. Points  600 ,  610  and  620  mark the start of Region A corresponding to the machine controller  430  activating the transport driver unit  465  to engage the urging roller  120  to pull the top sheet medium  117  towards the feed roller  223  and the separator roller  220 . Region A represents the vibration values captured in a delay between the machine controller  430  activating the transport driver unit  465  and the urging roller  120  actually rotating. Region B in  FIG. 6  corresponds to the urging roller  120  starting to rotate and the pulling the top sheet medium  117  into the feed roller  223  and the separator roller  220 . The duration of region B extends until the roller vibration noise, caused by the sudden change in velocity urging roller  120 , and feed roller  223 , dissipates into the background of the vibration noise from the top sheet medium  117 . Region C corresponds to the top sheet medium  117  being selected and pushed towards the take-away rollers  260 . At the end of region C, the top sheet medium  117  has reached the ultrasonic detector  280 . Region D corresponds to the top sheet medium  117  after it passes the take-away rollers  260  and ends when the transport driver unit  465  de-activates the feed module  225  to prevent additional sheet media  115  from entering the media transport path  290 . The separator roller  220  resists the feeding of addition sheet media  115 , if present, and the next of the sheet media  115  to come to the top of the media stack in the input tray  110  is pre-staged at the separator roller  220 . Region E in  FIG. 6  corresponds to the top sheet medium  117  in the media transport path  290  after the feed module  225  is de-activated. Additional regions could be created by using additional sensors such as the second media sensor  210  to determine the location of the top sheet medium  117  within the media transport path  290 . 
     A vibration exception detection region is used to define the region(s) of vibration values in vibration profiles shown in  FIG. 6  where the vibration detector  498  executes the vibration detection processing on the vibration values looking for a vibration exception.  FIG. 7  is a flowchart of vibration exception detection processing. A compute maximum vibration block  700  computes a maximum X-axis vibration  730  from the X-axis vibration values  550 . A compute maximum vibration block  710  computes a maximum Y-axis vibration  740  from the Y-axis vibration values  560 . A compute maximum vibration block  720  computes a maximum Z-axis vibration  750  from the Z-axis vibration values  570 . An exception test block  760  tests the maximum X-axis vibration  730 , the maximum Y-axis vibration  740 , and the maximum Z-axis vibration  750  against respective thresholds. These thresholds may be a predetermined calibration value, as discussed in more detail below. A YES result from the test indicates a medium exception  770  has been detected. A NO result from the test indicates a medium jam has not been detected. The medium transport system continues operation through block  780  if a medium jam is not detected. Examples of a medium jam include stoppages of medium movement along the media transport path  290 , multiple sheet media  115  being simultaneously fed into a media transport path  290  designed to convey only single medium of sheet media  115  at one time, and wrinkling, tearing, or other physical damage to the sheet media  115 . 
     In  FIG. 7 , the compute maximum vibration block  700  computes the maximum X-axis vibration  730 , which represents how much vibration was produced or the intensity of vibration produced from the X-axis vibration values  550 . The maximum X-axis vibration  730  can be computed by a high amplitude count from the X-axis vibration values  550 , as described, for example, in U.S. Patent Publication No. US2014/0251016, which is hereby incorporated by reference. The maximum X-axis vibration  730  can be represented by, for example, the maximum peak-to-peak amplitude or peak amplitude of the X-axis vibration values  550 . The maximum X-axis vibration  730  can also be represented by any other comparison of characteristics or qualities of the X-axis vibration values  550 . A moving window can be used to partition the X-axis vibration values  550  into frames that are collectively used together in the compute maximum vibration block  700 . The moving window computes the maximum X-axis vibration  730  from the most recent N 1  X-axis vibration values  550  within the vibration detection region for the vibration profile  630 , where N 1  is typically 1024. The compute maximum vibration block  700  begins at  600  and continues until a vibration exception is detected or the end of the X-axis vibration values  550  has been reached or the end of the vibration detection window is reached. When the urging roller  120  and the feed roller  223  initially start rotating, they produce a spike or burst of vibration noise, as shown in region B of the vibration profile  630 . This spike is referred to as mechanical noise and is due to the mechanical parts of the urging roller  120  and the feed roller  223  going from stationary to a rotating motion. The compute maximum vibration block  700  ignores the X-axis vibration values  550  within region A or region B of the vibration profile  630  to avoid producing a false vibration exception based on the mechanical noise. Alternatively the compute maximum vibration block  700  can weight the X-axis vibration values  550  within region A or region B of the vibration profile  630  to reduce the chance of producing a false vibration exception. 
     The compute maximum vibration block  710  computes the maximum Y-axis vibration  740 , which represents how much vibration was produced or the intensity of vibration produced from the Y-axis vibration values  560 . The maximum Y-axis vibration  740  can be computed by a high amplitude count from the Y-axis vibration values  560 , as described, for example, in U.S. Patent Publication No. US2014/0251016. The maximum Y-axis vibration  740  can be represented by, for example, the maximum peak-to-peak amplitude or peak amplitude of the Y-axis vibration values  560 . The maximum Y-axis vibration  740  can also be represented by any other comparison of characteristics or qualities of the Y-axis vibration values  560 . A moving window can be used to partition the Y-axis vibration values  560  into frames that are collectively used together in the compute maximum vibration block  710 . The moving window computes the maximum Y-axis vibration  740  from the most recent N 2  the Y-axis vibration values  560  within the vibration detection region for the vibration profile  640 , where N 2  is typically 1024. The compute maximum vibration block  710  begins at  610  and continues until a vibration exception is detected or the end of the Y-axis vibration values  560  has been reached or the end of the vibration detection window is reached. When the urging roller  120  and the feed roller  223  initially start rotating, they produce a spike or burst of vibration noise, as shown in region B of the vibration profile  640 . This spike is referred to as mechanical noise and is due to the mechanical parts of the urging roller  120  and the feed roller  223  going from stationary to a rotating motion. The compute maximum vibration block  710  ignores the Y-axis vibration values  560  within region A or region B of the vibration profile  640  to avoid producing a false vibration exception based on the mechanical noise. Alternatively the compute maximum vibration block  710  can weight the Y-axis vibration values  560  within region A or region B of the vibration profile  640  to reduce the chance of producing a false vibration exception. 
     The compute maximum vibration block  720  computes the maximum Z-axis vibration  750 , which represents how much vibration was produced or the intensity of vibration produced from the Z-axis vibration values  570 . The maximum Z-axis vibration  750  can be computed by a high amplitude count from the Z-axis vibration values  570 , as described, for example, in U.S. Patent Publication No. US2014/0251016. The maximum Z-axis vibration  750  can be represented by, for example, the maximum peak-to-peak amplitude or peak amplitude of the Z-axis vibration values  570 . The maximum Z-axis vibration  750  can also be represented by any other comparison of characteristics or qualities of the Z-axis vibration values  570 . A moving window can be used to partition the Z-axis vibration values  570  into frames that are collectively used together in the compute maximum vibration block  720 . The moving window computes the maximum Z-axis vibration  750  from the most recent N 3  Z-axis vibration values  570  within the vibration detection region for the vibration profile  650 , where N 3  is typically 1024. The compute maximum vibration block  720  begins at  620  and continues until a vibration exception is detected or the end of the Z-axis vibration values  570  has been reached or the end of the vibration detection window is reached. When the urging roller  120  and the feed roller  223  initially start rotating, they produce a spike or burst of vibration noise, as shown in region B of the vibration profile  650 . This spike is referred to as mechanical noise and is due to the mechanical parts of the urging roller  120  and the feed roller  223  going from stationary to a rotating motion. The compute maximum vibration block  720  ignores the Z-axis vibration values  570  within region A or region B of the vibration profile  650  to avoid producing a false vibration exception based on the mechanical noise. Alternatively the compute maximum vibration block  720  can weight the Z-axis vibration values  570  within region A or region B of the vibration profile  650  to reduce the chance of producing a false vibration exception. 
     It should be noted that compute maximum vibration blocks  700 ,  710 , and  720  do not have to use the same method to compute the maximum vibration of vibration values  550 ,  560  and  570 . A different method can be used for each axis, including high amplitude count, peak-to-peak amplitude count, peak amplitude, average amplitude, and/or frequency. 
       FIG. 8  is a detailed diagram of the exception test block  760 . Block  800  compares the maximum X-axis vibration  730  to vibration threshold T A1 . If the maximum X-axis vibration  730  is greater than the vibration threshold T A1 , an exception  770  is indicated. If the maximum X-axis vibration  730  is not greater than the threshold TAI, then the jam test moves to block  810 , which compares the maximum Y-axis vibration  740  to vibration threshold T B1 . 
     If the maximum Y-axis vibration  740  is greater than the vibration threshold T B1 , an exception  770  is indicated. If the maximum Y-axis vibration  740  is not greater than the vibration threshold T B1  then the jam test moves to block  820  which compares the maximum Z-axis vibration  750  to vibration threshold T C1 . 
     If the maximum Z-axis vibration  750  is greater than the vibration threshold T C1 , an exception  770  is indicated. If the maximum Z-axis vibration  750  is not greater than the vibration threshold T C1  then the jam test moves to block  830 , which compares the maximum X-axis vibration  730  to vibration threshold T A21  and compares the maximum Y-axis vibration  740  to vibration threshold T B21 . 
     If the maximum X-axis vibration  730  is greater than the vibration threshold T A21  and the maximum Y-axis vibration  740  is greater than vibration threshold T B21 , an exception  770  is indicated. If the maximum X-axis vibration  730  is not greater than the vibration threshold T A21 , or the maximum Y-axis vibration  740  is not greater than the vibration threshold T B21 , then the jam test moves to block  840  which compares the maximum X-axis vibration  730  to vibration threshold T A22  and compares the maximum Z-axis vibration  750  to vibration threshold T C22 . 
     If the maximum X-axis vibration  730  is greater than the vibration threshold T A22  and the maximum Z-axis vibration  750  is greater than vibration threshold T C22 , an exception  770  is indicated. If the maximum X-axis vibration  730  is not greater than the vibration threshold T A22 , or the maximum Z-axis vibration  750  is not greater than the vibration threshold T C22 , then the jam test moves to block  850 , which compares the maximum Y-axis vibration  740  to vibration threshold T B23  and compares the maximum Z-axis vibration  750  to vibration threshold T C23 . 
     If the maximum Y-axis vibration  740  is greater than the vibration threshold T B23  and the maximum Z-axis vibration  750  is greater than vibration threshold T C23 , an exception  770  is indicated. If the maximum Y-axis vibration  740  is not greater than the vibration threshold T B23  or the maximum Z-axis vibration  750  is not greater than the vibration threshold T C23 , then the jam test moves to block  860 , which compares the maximum X-axis vibration  730  to vibration threshold T A3 , compares the maximum Y-axiS vibration  740  to vibration threshold T B3 , and compares the maximum Z-axis vibration  750  to vibration threshold T C3 . 
     If the maximum X-axis vibration  730  is greater than the vibration threshold T A3  and the maximum Y-axis vibration  740  is greater than vibration threshold T B3  and the maximum Z-axis vibration  750  is greater than vibration threshold T C3 , an exception  770  is indicated. If the maximum X-axis vibration  730  is not greater than the vibration threshold T A3  or the maximum Y-axis vibration  740  is not greater than the vibration threshold T B3  or the maximum Z-axis vibration  750  is not greater than the vibration threshold T C3 , then the jam test moves to continue  780 . 
     In media processing apparatus such as the document scanner  10 , many jams are often the result of poor preparation where the operator does not ensure that the multiple sheet media  115  are not attached together before they are placed into the input tray  110 . The sheet media  115  can be attached together with, for example, staples, paper clips or adhesive. 
     A sheet media jam is most likely to occur when the top sheet medium  117  is being selected from the stack of sheet media  115  in the input tray  110  by the feed module  225  and is being fed into the media transport path  290  by the feed roller  223 . The one or more vibration sensors  255  together with the third microphone  200 C are ideally positioned for detecting a media jam in the area of the feed roller  223 . Once the lead-edge of the top sheet medium  117  passes the take-away rollers  260 , the probability of a media jam is reduced. As the trail-edge of the top sheet medium  117  approaches urging roller  120 , the chance of a trail-edge jam begins increasing. During this time, the one or more vibration sensors  255  together with the first microphone  200   a  and the second microphone  200   b  are ideally positioned for detecting a media jam along the trail-edge of the top sheet medium  117 . 
     For example, as the sheet media moves through the media transport path  290 , the lead-edge of the top sheet medium  117  is pinched in the nip between the drive roller and normal force roller. When the lead edge of sheet media enters the nip, the lead-edge hits the drive roller and normal force roller, a spike or burst of audio noise and vibration is produced that can be detected within the audio and vibration profiles produced by the microphones  200  and the one or more vibration sensors  255 . By combining information from the sound acquisition units  420  with information from the vibration detection unit  442 , the sound jam processing can weight the digital source signal from the sound acquisition units  420  differently to reduce the possibility of false sound jam that result from the noise as the lead-edge of the top sheet medium  117  enters the nips. 
     Over time, the vibration profiles  630 ,  640 ,  650  as shown in  FIG. 6  change as the mechanical components of the media transport path  290  wear. For example, the vibration profiles may become amplified as the parts wear and generate more vibration. When this occurs, the system can provide an audible or visual alert to the operator that maintenance or replacement of parts may be required. To detect or compensate for additional vibration introduced by mechanical components, a calibration procedure can be implemented within the document scanner  10 . In region A of vibration profiles  630 ,  640 ,  650 , the urging roller  120  has not started to urge the top sheet medium  117  into the feed roller  223 . The X-axis vibration values  550 , the Y-axis vibration values  560 , and the Z-axis vibration values  570  within region A of  FIG. 6  are used to detect any changes in the mechanical components of the media transport path  290  as well as changes in the vibration sensor pickup. In an alternative implementation, the gap between two consecutive top sheet media  117  could be used. In this case, the X-axis vibration values  550 , the Y-axis vibration values  560 , and the Z-axis vibration values  570  can be used after the trail-edge of the top sheet medium  117  has passed the first media sensor  205  as indicted by the first media detection signal. 
       FIG. 9  is an example of a flowchart for a calibration process in the preferred embodiment for a single vibration sensor  255 . The calibration process may be applied to each axes (X, Y and Z) of the vibration sensor individually, or may be applied to groups of vibration sensors. A compute maximum vibration on calibration region block  905  produces calibration vibration  910  from the vibration values  900  that represent the vibration values from region A of the vibration profiles shown in  FIG. 6  for the vibration sensor  255 . The size of region A of  FIG. 6  may contain a limited number of samples to perform an effective calibration so the multiple vibration profiles can be concatenated together before being fed into the calibration process. Block  945  determines if the calibration vibration  910  is within an acceptable tolerance range. The acceptable range is typically ±50 ADC steps from the default calibration value stored in system memory  455 , or a certain percentage of the full scale of the ADC. Note that each axis X, Y and Z can have a different default calibration value stored in system memory  455 . If the calibration vibration is within an acceptable range then processing continues to block  960  where no calibration is needed. If the calibration vibration  910  is not with the acceptable range then processing continues to block  950  which determines if the calibration vibration  910  is greater than the default calibration value T C  stored in system memory  455 . If the calibration vibration  910  is not greater than the default calibration value T C  then the vibration sensor is picking up less vibration than previously used in the vibration detection processing. To compensate for the reduction in the calibration vibration  910 , the threshold values used by the vibration detection processing for that vibration sensor axis are decreased in block  955  to the increase the sensitivity of vibration detector  498 . If the calibration vibration  910  is greater than the default calibration value then the medium transport system  10  is producing more vibration. This could be the result of a mechanical part becoming worn and is in need of replacement or there is a change in the sensitivity of the vibration sensor. The operator is notified in block  965  and has the option to accept the change in calibration vibration  910  in block  970 . If the operator does not accept the change in calibration vibration  910  then the medium transport system  10  requires servicing as shown in block  980 . If the operator accepts the increase in calibration vibration  910  then the vibration sensor is picking up more vibration than previous. To compensate for the increase in the calibration vibration  910 , the threshold values used by the vibration detection processing for that vibration sensor are increased in block  975  to the decrease the sensitivity of vibration detector  498 . 
     The initial thresholds T A1 , T B1 , T C1 , T A21 , T B21 , T A22 , T C22 , T B23 , T C23 , T A3 , T B3  and T C3  can be computed through a training process. The vibration profiles  630 ,  640  and  650  of the vibration sensor  255  are captured from the normal passage of sheet media  115  along the media transport path  290  to create a library of vibration profiles. The library consists of a collection of vibration profiles  630 ,  640  and  650  for N 4  sheet media  115  where N 4  is typically 250. The training process then analyzes the vibration profile  630 ,  640  and  650  for each sheet media  115  in the library and computes the maximum X-axis vibration  730 , the maximum Y-axis vibration  740 , and the maximum Z-axis vibration  750  over the library of vibration profiles. To find the thresholds used for multiple threshold tests  830 - 860 , the vibration profiles are compared to each other to find the vibration values that produce the maximum vibrations along all three orthogonal axes X, Y, and Z. 
     The process is repeated while all but one of the vibration axis value is held constant. While holding one vibration value constant, the other vibration profiles are searched for vibration values that produce a vibration that is greater than the previous vibration found. If a greater vibration is found then that vibration value for the axis replaces the current vibration for that axis. The process continues searching the vibration profiles of each axis while holding the other vibration axis value constant. 
     These maximum vibration values are then used to set the thresholds T A1 , T B1 , T C1 , T A21 , T B21 , T A22 , T C22 , T B23 , T C23 , T A3 , T B3  and T C3 . Since a library of vibration profiles was created using the normal passage of sheet media  115  through the media transport path  290 , an exception  770  would be indicted anytime the X-axis vibration values  550 , the Y-axis vibration values  560 , and the Z-axis vibration values  570  produce a maximum X-axis vibration  730 , a maximum Y-axis vibration  740 , and a maximum Z-axis vibration  750  that exceeded the threshold tests as described in  FIG. 8 . 
     The operator can put the media transport path  290  into a training mode to allow for optimization of thresholds to match the type of sheet media  115  being loaded into the input tray  110 . The thresholds T A1 , T B1 , T C1 , T A21 , T B21 , T A22 , T C22 , T B23 , T C23 , T A3 , T B3  and T C3  can be generic thresholds meaning that the thresholds will work for wide range of types of sheet media  115 . They can also be custom thresholds meaning that thresholds T A1 , T B1 , T C1 , T A21 , T B21 , T A22 , T C22 , T B23 , T C23 , T A3 , T B3  and T C3  are defined for a specific type of sheet media  115 . For example, a media transport path  290  could be processing only 110# card stock media. In this case, the training would be done using only 110# card stock media in order to optimize the thresholds for this type of media. Whenever a media transport path  290  restricts its use to a particular set of types of media, the training can be done using only those media types to optimize the thresholds. Alternatively each of the thresholds can be set as a mixture of generic and custom thresholds across the entire vibration profile thereby allowing the vibration detection processing to use custom thresholds specific to a type sheet media in specific regions of the vibration profiles  630 ,  640  and  650 . 
     In addition, the thresholds can be set specifically for each media transport path  290 . In this case, each different media processing apparatus can produce a vibration profile for sheet media  115  that is unique to that system. Alternatively, the thresholds T A1 , T B1 , T C1 , T A21 , T B21 , T A22 , T C22 , T B23 , T C23 , T A3 , T B3  and T C3  can be global thresholds meaning that the thresholds will be applied across the entire vibration profile. They can also be local thresholds meaning that thresholds T A1 , T B1 , T C1 , T A21 , T B21 , T A22 , T C22 , T B23 , T C23 , T A3 , T B3  and T C3  are defined for a specific region A-E, thereby handling unique characteristics of the various sections of the media transport path  290 . Unique characteristics of the media transport path  290  can be of any form known to those skilled in the art including, but not limited to, change in roller material, rollers speed, bends or curves within the media transport path  290 . 
       FIG. 10  illustrates additions to the media transport path  290  between the output transport rollers  140  and the output tray stop  170 . An output guide flap  1020  deflects individual sheet media into the output tray  190 . The output guide flap  1020  is attached at the end of the media transport path  290  in such a way as to control the sheet media placed into the output tray  190 . 
     A vibration sensor  1010  may be mounted on the output guide flap  1020  to monitor the output of sheet media from the media transport path  290  into the output tray  190 . By placing the vibration sensor  1010  on the output guide flap  1020 , the output of the sheet media into the output tray  190  can be confirmed. The output of the vibration sensor can also be monitored to count the number of sheets or otherwise detect the fullness state of the output tray  190 . For example, as the output tray  190  becomes full, the inclination of the vibration sensor  1010  on the output guide flap  1020  changes. In addition, the vibration sensor  1010  can monitor unexpected changes to the deflection or orientation of the output guide flap  1020  to detect instances in which the sheet media exiting the media transport path  290  rolls over or does not stack properly in the output tray  190 . For example, the vibration sensor  1010  can detect if the guide flap  1020  does not return to its expected position as an indication of a problem in the loading of the output tray  190 . A warning can be generated at the start of a new batch of sheet media  115  added to the input tray  110  if the output guide flap  1020  is not in a position indicating the output tray  190  is empty. This prevents the feeding of a new batch of sheet media into the media transport path  290  before the previous batch of sheet media has been removed from the output tray  190 . 
     The vibration sensor  1010  is preferably an accelerometer to monitor impacts of the individual sheet media ejected from the media transport path  290 , although other types of vibration sensors may be used. Vibrational values from the vibration sensor, which operates via a vibration detection unit similar to the vibration detection unit  442 , can be monitored for abnormalities indicating problems associated with the ejection of the sheet media from the media transport path  290  or the stacking of the output sheet media  150  in the output tray  190 . 
     Alternatively, the vibration sensor  1010  or another vibration sensor could be mounted in or on the output tray  190  or any of it various components including the output tray stop  170 . The timing of expected vibration peaks monitored by the vibration sensor  1010  can be compared to the timing of expected vibration peaks monitored by vibration sensor  255  to identify timing errors indicative of problems in the media transport path  290  between the input and output of the individual sheet media. 
     Vibration sensors could also be added in other locations along the media transport path  290  to monitor for abnormal vibrations, particularly in the form of vibrations that vary from an expected amplitude, pattern, or timing between events. For example, vibrations sensors can be located in a variety of positions along the media transport path  290 , including in various positions on the upper media guide  292  and the lower media guide  294 , particularly in positions in mechanical communication with the components of the media transport path that contribute to the movement of the sheet media or respond to movement of the sheet media. Vibration sensors can also be mounted in positions at or near the entrance and exit of the media transport path  290  including positions in mechanical engagements with the components of the input tray  110  and output tray  190 . 
     Vibration values monitored by the vibration detection unit  442  can be interpreted by the system processing unit  270  together with sound values monitored by the sound acquisition units  420  to more accurately detect jams along the media transport path  290 . For example, when the urging roller  120  and feed roller  223  initially start rotating, they produce a spike or burst of audio noise accompanying the vibration profile as shown in region B of  FIG. 6 . This audio noise spike is referred to as mechanical noise and is due to the mechanical parts of the urging roller  120  and feed roller  223  going from stationary to a rotating motion. The location and duration of this mechanical noise is difficult to predict. However, vibration sensor  255  can detect the vibration from the mechanical parts. By combining information from the vibration detector  498  with information with the audio profiles from the sound acquisition units  420 , the sound jam detector  450  can weight the digital source signal from the sound acquisition units  420  differently to reduce a false sound jam resulting from the spike or burst of audio noise from the urging roller  120  and feed roller  223 . 
     Output of the vibration detection unit  442  can also be monitored to detect physical abuse of the document scanner  10  such as by monitoring for extreme shocks or motions beyond the range for which the scanner  10  is designed to accommodate. The system processing unit  270  can respond in a number of ways including creating a log of such events, provide a warning that such an event has taken place, or perform a system check to determine if damage has been sustained.