Abstract:
A system and method of detecting the presence of metallic objects in media to be conveyed in a medium transport system is disclosed. One or more metal detectors are included in the medium transport system to detect the presence of metal in the medium being transported. Signals from the metal detectors are sent to a system processor, which analyzes the signals, and produces proximity, duration, and/or intensity values therefrom. One or more microphones may also be included which detect the sound created as the medium is being transported. The processor computes sound values from the microphone signals, and analyzes the computed sound values along with the proximity, duration, and/or intensity values in order determine if the conveyance of the medium along the transport path should be stopped due to the presence of metal in the media or a jam occurring within the medium transport path.

Description:
FIELD OF THE INVENTION 
     This invention pertains to the field of indicating medium jams in a medium transport system, and in particular to a method and system to prevent a medium jam by detecting documents with sheets stapled or paper clipped together. 
     BACKGROUND OF THE INVENTION 
     In document scanners, and other media transport systems, hardcopy media may sometimes jam as the hardcopy media moves along the media transport path. Objects like staples and paper clips are commonly used to hold hardcopy media containing several sheets together. Before transporting these hardcopy media through the media transport path of document scanners and other imaging devices, the operator typically removes these staples and paper clips. However, sometimes the operator fails to remove these staples and paper clips, or fails to notice them on the media, before the media are transported through the document scanner. These staples and paper clips often cause damage to the hardcopy media, the transport media path, or the document scanners itself. In addition, if two or more hardcopy media attached by a staple or paperclip are transported through the media transport path then information can be lost due to hardcopy media not be imaged properly. 
     While others have implemented systems to check for staples before documents go from an input tray into a scanner device, these systems are limited in the scope of detection and may miss staples, paper clips, or other objects included in media transported into the system, and thus jams may still occur. In addition, these systems do not provide a way to locate the position of a jam within the media transport system. For example, U.S. Pat. No. 5,087,027 includes a document handler system with a staple detector to detect the presence of staples in documents loaded into an input tray. However, this system only looks for staples in predetermined areas of the document, and only looks for 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, this system may miss staples in documents where staples are present, but are not in a preselected position on the document that the staple detector is monitoring. 
     There remains a need for a simple, fast and robust technique to monitor hardcopy media input to a media transport system for staples, paper clips, or other metal objects, and to indicate the location of hardcopy media jams along a hardcopy media transport path should a jam occur. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method and system of detecting hardcopy media that contain staples, paper clips or other metallic binding clips before the hardcopy media is transported along a medium transport path in a document scanner, or other imaging or media transport device. Document scanners typically include one or more rollers, driven by a motor, for use in conveying the medium along the medium transport path. One or more metal detectors are included in the scanner to detect the presence of metal in the medium being transported. The metal detectors produce signals representing the presence of metal in the proximity of the sensor, which are sent to a processor. The processor analyzes the signals, and produces proximity, duration, and/or intensity values therefrom. One or more microphones are also included in the scanner, and detect the sound created as the medium is being transported. The microphones produce signals representing the sound, which are sent to the processor. The processor computes sound values from the signals, and analyzes the computed sound values along with the proximity, duration, and/or intensity values in order determine if the conveyance of the medium along the transport path should be stopped due to the presence of metal in the media or a jam occurring within the medium transport path. 
     The processor may be included in a computer system that is part of, or in communication with, the scanner system, including the microphones and metal detectors therein. The processor may execute computer program instructions stored on a non-transitory computer-readable medium which cause the processor to acquire signals from the metal detectors as well as sound signals from the plurality of microphones responsive to the sound generated by a medium being transported along a medium transport in the scanner. The computer-readable medium includes further instructions enabling the processor to determine whether metal is present in the media being transported, and whether a jam has occurred based on the sound signal values according to a detection method, as described in detail below. 
     Based on the proximity, duration, and/or intensity values and the sound signals received, the processor may change the detection method based upon sensed characteristics of the media. For example, if the proximity, duration, and/or intensity values indicate the presence of metal, the loudness thresholds for indicating a jam may be lowered. 
     The one or more microphones can detect the sound of a medium jamming over a larger physical area than optical or mechanic methods, which are localized in nature. As a result, one microphone can replace the need for several optical or mechanic sensors. By using multiple microphones, a larger area can be monitored and signals from the multiple microphones can be compared against each other to determine the location of the sound source better than one microphone could. Determining the location of the noise source may be helpful in determining the location of the jam as it is typical for the jam to cause the detected noise, and thus the noise source is often the jam location. However, detecting a jam using only signals from the microphones relies on the noise generated by the hardcopy media wrinkling. When the hardcopy media is bound tightly together with staples, paper clips or other metallic binding clips, the hardcopy media does not always generate sufficient loudness for the processor to stop the hardcopy media transport path based on an analysis of the signals received. In addition, a single hardcopy media with a staple or paper clips or other metallic binding clips may not make any additional noise. By including a metal detector, the conveyance of a medium along the transport path can be stopped before hardcopy media that contain staples, paperclips, or other metallic binding clips are transported too far into the medium transport path, thus lessening the chance of a jam occurring. In addition, by adjusting the sound thresholds when media containing staples, paperclips, or other metallic objects are detected within the system, the medium transport system may be able to better determine when a jam is occurring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a high-level diagram showing the components of medium transport system in the form of an imaging scanner. 
         FIG. 2  is a high-level diagram showing the components of a medium transport system. 
         FIG. 3  is a high-level diagram showing a flattened view of the components of a medium transport system. 
         FIG. 4  is an example of a block diagram which shows the general configuration of a medium transport system. 
         FIGS. 5A-C  are illustrations showing different examples of metal attached to hardcopy media. 
         FIGS. 6A-C  are examples of the waveforms produced from examples in  FIGS. 5A-C . 
         FIG. 7  is a diagram illustrating a process for detecting metallic objects. 
         FIG. 8  is an illustration showing the relationship between sound profile and metallic detection. 
         FIG. 9  is a diagram illustrating a processing for detecting sound jams combined with metal detection processing output. 
         FIG. 10  is a diagram illustrating an alternative location of metallic detector. 
         FIG. 11  is a diagram illustrating a metallic patch code and corresponding waveform. 
         FIG. 12  is an example of the waveforms produced from examples in  FIG. 11 . 
         FIG. 13  is a diagram illustrating an alternative embodiment using a segmented induction detector. 
         FIG. 14  is a diagram illustrating an alternative embodiment using a multiple induction detectors to find location of metallic objects. 
         FIG. 15  is an illustration showing the relationship between metallic objects location and induction detector layout in  FIG. 14 . 
         FIG. 16  is a diagram illustrating an alternative embodiment of in  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to a media transport system, and in particular to a system and method for detecting staples, paper clips, and other metallic objects attached to hardcopy media within the media transport system. In addition to detecting metallic objects, the system also includes microphones to detect sound profiles of documents being transported through the media transport system, and analyzes these sound profiles to determine the occurrence and location of jams. The method may be carried out using a process stored as instructions on a computer program product. The computer program product can include one or more non-transitory, tangible, computer readable storage medium, for example; magnetic storage media such as magnetic disk (such as a floppy disk) or magnetic tape; optical storage media such as optical disk, optical tape, or machine readable bar code; 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 a computer program having instructions for controlling one or more computers to practice the method according to the present invention. 
       FIG. 1  shows a medium transport system  10  that includes a scanner base  100 , a scanner pod  180 , an input tray  110 , an output tray  190 , and an operation control panel  122 . The scanner pod  180  covers the top surface of the medium transport system  10  and connects to the scanner base  100  with hinges. The hinges allow the document scanner to be opened and closed when there is a media jam within the scanner or when the scanner needs to be cleaned. 
     The input tray  110  is connected to the scanner base  100  with hinges, allowing the input tray  110  to be opened and closed as illustrated by an arrow A 3 . The input tray  110  may be opened at times of scanning and closed when the medium transport system  10  is not in use. When the input tray  110  is closed the footprint of the medium transport system  10  can be reduced. Hardcopy media  115  to be scanned is placed into the input tray  110 . Examples of the hardcopy media are paper documents, photographic film, and magnetic recording media. The top hardcopy medium  117  is the medium at the top of a stack of hardcopy media  115 , and is the next hardcopy medium to be pulled into the scanner by the 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 hardcopy media  115 . By positioning the side guides  130   a  and  130   b  to match with the width of the hardcopy media  115 , it is possible to limit the movement of the hardcopy media  115  in the input tray  110  as well as set the position (left, right or center justified) of the top hardcopy medium  117  within the media transport path. The input side guides  130   a  and  130   b  may be referred to collectively as the input side guides  130 . The input tray  110  may be attached to a motor (not shown) that causes the input tray  110  to raise top hardcopy medium  117  to the urging roller  120  for scanning or to lower the input tray  110  to allow additional hardcopy media  115  to be added to the input tray  110 . 
     The output tray  190  is connected to the scanner pod  180  by hinges, allowing the 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 hardcopy media  115 , that is, to the left and right directions from the transport direction of the hardcopy media  115 . By positioning the output side guides  160   a  and  160   b  to match with the width of the hardcopy media  115 , it is possible to limit the movement of the output hardcopy media  150  in the output tray  190 . The output side guides  160   a  and  160   b  may be referred to collectively as the output side guides  160 . An output tray stop  170  is provided to stop the top hardcopy medium  117  after being ejected from the output transport roller  140 . When the output tray  190  is in the up state as shown in  FIG. 1 , the ejected hardcopy media is trail-edge aligned. In the down state, the ejected hardcopy 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 the operator. An operation 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 operation input  125  may be one or more buttons, switches, portions of a touch-sensitive panel, selectable icons on a visual display  128 , or any other selectable input mechanism. The override command may allow the operator to temporarily disable multi-feed detection, jam detection, or other features of the scanner 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  could include selectable icons relating to commands and operations of the media transport device. The operator control panel  122  may also contain speakers and LEDs (not shown) to provide additional feedback to the operator. 
       FIG. 2  illustrates the transport path inside of the medium transport system  10 . The transport path inside of the medium transport system  10  has multiple rollers, including urging rollers  120 , feed rollers  223 , separator rollers  220 , take-away rollers  260 , transport rollers  265 , and an output transport roller  140 . The urging rollers  120  and feed roller  223  may be referred to collectively as the feed module  225 . Microphones  200   a ,  200   b ,  200   c , a first media sensor  205 , a second media sensor  210 , an ultrasonic transmitter  282 , and an ultrasonic receiver  284  are positioned along the media transport path  290  to sense media and conditions within the media transport path  290  as the top hardcopy medium  117  is transported through the system. A pod image acquisition unit  230  and a base image acquisition unit  234  are included to capture images of the 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 and upper media guide  292  of the media transport path  290 . A delta wing  185  may be provided which helps to guide the media from the input tray into the media transport path  290 . As shown in  FIG. 2 , the delta wing may be a removable section of the upper media guide  292 , transitioning from the upper media guide  292  to the scanner cabinetry of the pod  180 . The delta wing may 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 hardcopy 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  may be mounted within the input tray  110 , and detects if hardcopy media  115  is placed on the input tray  110 . The first media detector  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 by the top hardcopy 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 rollers  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 the top hardcopy medium  117  during transport of the 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 . The microphones  200   a  and  200   b  may be 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  may be mounted in the upper media guide  292  using a vibration reducing gasket. As an example, the microphones may 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 hardcopy media 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 hardcopy 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. 
     An induction sensor  215  is arranged near the near the entry of point of media from the input tray into the document transport path. In particular, the induction sensor  215  may be arranged at a downstream side of the feed roller  223  and the separator roller  220 , and at an upstream side of the second media detector  210 . The induction sensor  215  detects if there is any metallic material, including, but not limited to, paper clips or staples, attached to the hardcopy media. The induction sensor  215  generates and outputs a metal detection signal which changes in signal value depending on whether metallic material is present. The induction sensor  215  can be of any form known to those skilled in the art including, but not limited to, inductive sensors or proximity sensors. 
     An ultrasonic transmitter  282  and an ultrasonic receiver  284 , together forming an ultrasonic sensor  280 , are arranged near the media transport path  290  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 hardcopy medium  117  and is detected by the ultrasonic receiver  284 . The ultrasonic receiver then generates and outputs a signal, which may be an electrical or digital signal, corresponding to the detected ultrasonic wave. 
     A plurality of ultrasonic transmitters  282  and ultrasonic receivers  284  may 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 . 
     A pod image acquisition unit  230  is included that has an image sensor, such as a CIS (contact image sensor) or CCD (charged coupled device). Similarly, a base image acquisition unit  234  is included that has an image sensor, such as a CIS or CCD. 
     As the top hardcopy medium  117  travels through 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 hardcopy 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 hardcopy 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 hardcopy medium  117  is imaged. 
     The top hardcopy 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 hardcopy medium  117  between the drive roller and normal force roller. In the medium transport system  10 , the initial drive and normal force rollers that grab the top hardcopy medium  117  within 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 may be driven by a single motor where all the rollers start and stop together. Alternatively the rollers may 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 medium transport system  10  may have an output transport roller  140 . The output transport roller  140  is connected to a separate drive motor that either speeds-up the top hardcopy medium  117  or slows down the top hardcopy medium  117  for modifying the way the output hardcopy media  150  is placed into the output tray  190 , as described in detail in U.S. Pat. No. 7,828,279, incorporated herein by reference. 
     Hardcopy 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 hardcopy 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 hardcopy media  115  placed on it, only the top hardcopy 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 hardcopy media  115  below the top hardcopy medium  117  is restricted by the separator roller  220  to prevent feeding more than one medium at a time, which is referred to as a multi-feed. 
     The top hardcopy 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 guide  292 . The top hardcopy medium  117  is sent past the pod image acquisition unit  230  and the base image acquisition unit  234  for imaging. The top hardcopy medium  117  is then ejected into the output tray  190  by the output transport roller  140 . In addition to microphones  200   a ,  200   b , and  200   c , a microphone  297  may be provided near the exit of the transport path. This microphone  297  detects the sounds of the hardcopy media towards the end of the transport path, and as the media is output into the output tray. These detected sounds may be used to detect jams occurring in the output tray or as documents are exiting the media transport device. A system processing unit  270  monitors the state of the medium transport system  10  and controls the operation of the medium transport system  10  as described in more detail below. 
     Although  FIG. 2  shows the urging roller  120  above the stack of hardcopy media  115  to select the top hardcopy media  117 , in a feeding configuration often referred to as a top feeding mechanism, other configurations may 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 hardcopy media at the bottom of the hardcopy media stack  115 . In this configuration, microphone  200   a  and  200   b  may be moved into the scanner base  100 . 
     In addition, a hardcopy media preparing station may be provided that allows an operator to check hardcopy media for metallic objects before conveying the hardcopy media into the medium transport system. The hardcopy media preparing system may be part of the input tray, or could be a separate preparation area. The hardcopy media preparation station may include one or more induction sensors located within a tray on the preparation station or within a sensing arm. When located in a sensing arm, the operator may move the sensing arm around media on the preparation station, with the induction sensors in the arm providing signals to generate an alert when a metallic object within the media is found. Once metallic objects have been detected and located, they can be removed manually by the operator or through an automated process. 
       FIG. 3  is a block diagram of the medium transport system  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 rollers  223  along the delta wing  185 . The second microphone  200   b  is provided to the right of the urging roller  120  and feed rollers  223  along the delta wing. The placement of microphones  200   a  and  200   b  capture sound from the top hardcopy 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 rollers  223 . The placement of microphone  200   c  captures sound from the top hardcopy medium  117  as it passes the feed roller  223  and before reaching the take-away rollers  260 . The induction sensor  215  may be mounted in the lower transport guide  294  at the entrance of the media transport path  290  to detect metallic objects as early as possible. One more induction sensors  215  may also be included at various other positions along the transport path. Since there are various metal components within the scanner base  100  and scanner pod  180 , the area of detection of the induction sensor  215  is selected to be small to avoid picking up the metal components. Thus, the induction sensor  215  may be placed along the back side of the separator roller  220  where the top hardcopy media  117  position is controlled by the feed roller  223  and separator roll  220  such that hardcopy media  117  is within the field of the induction sensor  215 . 
       FIG. 4  is a block diagram which shows the schematic illustration of a medium transport system  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 element using CMOS (complementary metal oxide semiconductors) which are arranged in a line in the main scan direction. As noted above, instead of a CIS, it is also possible to utilize 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 element using CMOS&#39;s (complementary metal oxide semiconductors) which are arranged in a line in the main scan direction. As noted above, instead of a CIS, it is also possible to utilize an image capturing sensor of a reduced magnification optical system type using CCD&#39;s (charge coupled devices). The base imaging A/D converter  412  converts an analog image signal which is 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. 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 medium transport system  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 medium transport system  10  by supplying various types of information required for operation of the medium transport system  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 which is 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  may comprise discrete devices or may 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 which is output from the second microphone  200   b  by a 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 which is 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  outputs will be referred to as the “right sound signal.” The second sound acquisition unit  420   b  may comprise discrete devices or may 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 which is output from the third microphone  200   c  by a 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 which is 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  outputs will be referred to as the “center sound signal.” The third sound acquisition unit  420   c  may comprise discrete devices or may be integrated into a single device such as a digital output MEMS microphone. 
     Below, the first sound acquisition unit  420   a , second sound acquisition unit  420   b  and the third sound acquisition unit  420   c  may be referred to overall as the sound acquisition unit  420 . 
     A field detection unit  432  includes the induction sensor  215 , field signal processing  434 , and a field A/D Converter  436 , and generates a signal responsive to the electromagnetic field picked up by the induction sensor  215 . The field signal processing  434  filters and removes noise from the signal which is output from the induction sensor  215  by passing the signal through a filter to shape or smooth the signal. The field signal processing  434  also amplifies the signal and outputs it to the field A/D Converter  436 . The field A/D Converter  436  converts the analog signal which is output from the field signal processing  434  to a digital metallic detection 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. 
     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 hardcopy medium  117  through 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 functions of the medium transport system  10 . Furthermore, the system memory  455  may 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  may be a single programmable processor or may 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 operation input  125 , the operator display  128 , first media sensor  205 , second media sensor  210 , ultrasonic sensor  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 , image processing unit  485 , image buffer memory  475 , network interface  445 , system memory  455 , transport driver unit  465 . 
     The system processing unit  270  further controls the transport driver unit  465 , and the pod image acquisition unit  230  and base image acquisition unit  234  to acquire captured images. 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 , and a multi-feed detector  470 . These units are functional modules which are 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, may 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 rollers  120  and the feed rollers  223  to feed the top hardcopy 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 hardcopy 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 that a jam has occurred if the lead-edge and trail-edge detection signal are not obtained 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  may 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 hardcopy 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 hardcopy media entered the media transport path  290  may 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 hardcopy media contains metallic material. Situations in which the metal detector  495  determines that the hardcopy media entered the media transport path  290  contains metallic material may be referred to as a metal 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, 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 user of media jam using the operator control panel  122 . Alternatively, the machine controller may display an abnormality condition on the operator display  128  or issue an abnormality condition notice over the network interface, 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 hardcopy medium  117  to acquire a captured image. The pod imaging acquisition unit  230  images the top hardcopy 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 hardcopy medium  117  via the base image device  410 , base image A/D converter  412 , and base pixel correction  414 . 
       FIG. 5A ,  FIG. 5B  and  FIG. 5C  are views illustrating various metallic objects attached to a hardcopy medium. In  FIG. 5A , hardcopy medium  500  contains staple  510  that is attached vertically to the hardcopy medium  500 .  FIG. 5B  illustrates a hardcopy medium  520  that contains staple  530  attached horizontally to the hardcopy medium  520 . The width of the staple is defined as the distance between the two legs that punch through the hardcopy medium and is sometimes referred to as the crown. The gauge of the staple is referred as the diameter of the metal the staple is made from.  FIG. 5C  illustrates a hardcopy medium  540  with metallic foil  550  attached to it. The edge that is parallel to the lead-edge of the hardcopy medium is referred to as the width of the foil, while the edge that is perpendicular to the lead-edge is referred to as the height. 
       FIG. 6A ,  FIG. 6B  and  FIG. 6C  illustrate example waveforms from the field detection unit  432  acquired from hardcopy media containing various metallic objects as shown in  FIG. 5A-C . The graph  600 , which is shown in  FIG. 6A , illustrates the output waveform  610  from the field detection unit  432  when hardcopy medium  500  is transported past the induction sensor  215 . In this configuration, staple  510  is positioned parallel to the transport direction as indicted by arrow A 4 . At time T 1 , the disturbance in the magnetic field caused by staple  510  has been detected and the output of the field detection unit  432  changes state indicating the presence of a metallic object. At time T 2 , the staple  510  passes through the magnetic field and the output of the field detection unit  432  changes its state back it normal state. Time  0  corresponds to the machine controller  430  activating the transport driver unit  465  to activate the urging roller  120  to pull the top hardcopy medium  117  towards the feed roller  223  and the separator roller  220 . Timer unit  480  can be used to determine time delay TD 1 , which represents the time from activating the transport driver unit  465  to the change in the output of the field detection unit  432  indicating the presence of a metallic object. In addition, Timer unit  480  can be used to determine the duration the metal object is within the field, as represented in  FIG. 6A  as TD 2 . Since the staple  510  is positioned parallel to the transport direction as indicted by arrow A 4 , the width of staple  510  is represented by the duration of TD 2 . 
     The time delays can be converted to distances using the speed the transport driver unit  465  drives the motors by the formula shown below.
 
distance=TimeDelay*TransportSpeed
 
Using the speed the transport driver unit  465  drives the motors, the location of the staple from the lead-edge of the hardcopy medium can be calculated from TD 1 , and the physical width of the staple can be calculated from TD 2 . The thickness or diameter of the staple  510  will be related to the intensity.
 
     The graph  620 , which is shown in  FIG. 6B , illustrates the output waveform  630  from the field detection unit  432  when hardcopy medium  520  is transported past the induction sensor  215 . In this configuration, staple  530  is positioned perpendicular to the transport direction as indicted by arrow A 4 . At time T 3 , the disturbance in the magnetic field caused by staple  530  has been detected and the output of the field detection unit  432  changes state indicating the presence of a metallic object. At time T 4 , the staple  530  passes through the magnetic field and the output of the field detection unit  432  changes its state back it normal state. Time  0  corresponds to the machine controller  430  activating the transport driver unit  465  to activate the urging roller  120  to pull the top hardcopy medium  117  towards the feed roller  223  and the separator roller  220 . Timer unit  480  can be used to determine time delay TD 3 , which represents the time from activating the transport driver unit  465  to the change in the output of the field detection unit  432  indicating the presence of a metallic object. In addition, Timer unit  480  can be used to determine the duration the metal object is within the field as represented in  FIG. 6B  as TD 4 . Since the staple  530  was positioned perpendicular to the transport direction as indicted by arrow A 4 , the pulse width TD 4  is much narrower than the width TD 2 . Based on the narrow pulse we know the object passed through the field quickly. The width of the staple  530  is related to the intensity. In this case the staple  530  was perpendicular to the transport direction so the full width of the staple was in the field at the same time. The wider staple  530  is, the larger the intensity. Using the speed the transport driver unit  465  drives the motors, the location of the staple from the lead-edge is calculated from TD 3  using the formula below, and the thickness or diameter of the staple  530  will be related to the intensity. 
     The graph  640 , which is shown in  FIG. 6C , illustrates the output waveform  650  from the field detection unit  432  when hardcopy medium  540  is transported past the induction sensor  215 . In this configuration, hardcopy medium  540  contains metallic foil  550 . At time T 5 , the disturbance in the magnetic field caused by metallic foil  550  has been detected and the output of the field detection unit  432  changes state indicating the presence of a metallic object. At time T 6 , the metallic foil  550  passes through the magnetic field and the output of the field detection unit  432  changes its state back it normal state. Since the metallic foil  550  is a uniform size and consistency, the lead-edge and trail-edge will produce similar levels of intensity at the output of the field detection unit  432 . Time  0  corresponds to the machine controller  430  activating the transport driver unit  465  to activate the urging roller  120  to pull the top hardcopy medium  117  towards the feed roller  223  and the separator roller  220 . 
     Timer unit  480  is used to determine time delay TD 5 , which represents the time from activating the transport driver unit  465  to the change in state of the output of the field detection unit  432  indicating the presence of a metallic object. In addition, Timer unit  480  is used to determine the duration the metallic foil  550  was within the field, as represented in  FIG. 6C  as TD 6 . The length of metallic foil  550  is represented by the duration of TD 6 . Using the speed the transport driver unit  465  drives the motors, the location of the metallic foil  550  is calculated from TD 5 , and the physical length of the metallic foil  550  is calculated from TD 6 . The width of the metallic foil  550  is related to the intensity. The larger the intensity, the wider the metallic foil. 
     As seen in  FIG. 6A , the longer the metallic object stays with the field, the longer the field will be disrupted. Waveform  620  illustrates the metallic object passing through the field quickly as represented by a narrow pulse, but the intensity of disruption to the field is considerably more than waveform  600 . The intensity of the field disruption is directly related to the amount of the metal object under the induction sensor  215 , while the duration of the field disruption is directly related to the amount of time the metal object stays in the field. 
       FIG. 7  is an example of a flowchart of the process used to determine the presence of metallic objects in the hardcopy media. The induction signal  700  from induction  215  is processed in block  710 , where the waveform for the induction signal  700  is extracted. Blocks  720 ,  730 ,  740  and  750  test the extracted waveform to determine if a metallic object is present. 
     Block  720  compares the maximum intensity of the detected waveforms to an intensity threshold T I1 . If the maximum intensity is greater than the intensity threshold T I1 , then processing continues to Block  760  where a metal detection exception is indicated. If the maximum intensity is not greater than the intensity threshold T I1 , then the testing moves to block  730  which compares the maximum pulse width to a pulse width threshold T P1 . 
     Block  730  compares the maximum pulse width to the pulse width T P1 . If the maximum pulse width is greater than the pulse width threshold T P1 , then processing continues to Block  760  where a metal detection exception is indicated. If the maximum pulse width is not greater than the pulse width threshold T P1 , then the testing moves to block  740  which compares the maximum intensity to the intensity threshold T P2 . 
     Block  740  compares the maximum intensity to an intensity threshold T I2 . If the maximum intensity is less than the intensity threshold T I2 , then processing moves to block  770  to continue. If the maximum intensity is greater than the intensity threshold T I2 , then processing continues to Block  750 , where block  750  compares the maximum pulse width to a pulse width threshold T P2 . If the maximum pulse width is greater than the pulse width threshold T P2 , then processing continues to Block  760  where a metal detection exception is indicated. If the maximum pulse width is not greater than the pulse width threshold T P2 , then process moves to block  770  to continue. 
       FIG. 8  shows the relationship between an audio profile  800  captured at one of the microphones and the induction signal  810  captured by the induction sensor  215 . By combining the induction signal  810  with the audio signal  800  captured at one or more of microphones  200   a ,  200   b  and  200   c , false jams resulting from hardcopy media with embedded metallic material can be avoided. Since most hardcopy media jams are the result of multiple hardcopy media attached with a staple or paper clip, lower loudness threshold can be used in the sound jam detection processing executed by the sound jam detector  450  when the audio profile  800  is combined with the induction signal  810  output from the field detection unit  432 . Since the induction sensor  215  is mounted at upstream of microphone  200   c , it will start to detect metallic objects before the top hardcopy media starts to wrinkle when it is attached to the hardcopy media below it. If the metal detector indicates that a metal object is present, but the audio processing does not detect a jam, the medium may be allowed to continue along the transport path. 
     At time T 9  in  FIG. 8  the induction signal  810  starts to change state in response the detection of a metallic object by the induction sensor  215 . At T 9  the sound jam detection processing switches to lower thresholds to allow sound jam detection processing to detect hardcopy media jam with a lower maximum loudness. As noted above, lower thresholds may be necessary as multiple sheets of media transported through the device may generate lower sound profiles as compared to single sheets. Thus, when multiple sheets are attached with a staple, paper clip, or other metallic object, the sound thresholds can automatically be adjusted in response to the signal from the induction sensor to account for this. 
     If sound jam detection processing detects a sound jam when metallic detection processing detects the presence of a metallic object, then abnormality condition is issued. On the other hand, if the sound jam detection processing does not detect a sound jam when metallic detection processing detects the presence of a metallic object, then the top hardcopy media  117  might have an embedded magnetic strip or label. By combining the metallic detection processing with sound jam detection processing, false abnormality conditions can be avoided. 
     Alternatively, the induction signal  810  could be combined with the ultrasonic detection signal acquired from the ultrasonic detector  280 . Since most hardcopy media multi-feeds are the result of multiple hardcopy media attached with a staple or paper clip, the thresholds used in multi-feed detection processing executed by the multi-feed detector  470  can be adjusted so as to change the sensitivity of multi-feed detection. Different sensitivities may be necessary for multi-feed detection processing, as multiple sheets of media transported past ultrasonic detector  280  may generate different ultrasonic detection signal profiles as compared to single sheets. Thus, when multiple sheets are attached with a staple, paper clip, or other metallic object, the multi-feed sensitivity can automatically be adjusted in response to the signal from the induction sensor to account for this. 
     Since the induction sensor  215  is mounted upstream of the ultrasonic detector  280 , the induction sensor  215  will start to detect metallic objects before the top hardcopy media reaches the ultrasonic detector  280 . By combining the induction signal  810  with the output of the ultrasonic detector  280 , missed multi-feeds can be reduced by changing the sensitivity of multi-feed detection. In addition, if the metal detector indicates that a metal object is present, but the multi-feed detection processing does not detect a multi-feed, then the top hardcopy media  117  might have an embedded magnetic strip or label, and the medium may be allowed to continue along the transport path. If the metal detector does not indicate that a metal object is present, but the multi-feed detection processing does detect a multi-feed, then the top hardcopy media  117  might have a non-magnetic strip or label, and the medium may be allowed to continue along the transport path. In both cases false multi-feeds can be reduced by combining the induction signal  810  with the output of the ultrasonic detector  280 . In addition, the signal from the induction sensor, microphone sensors, and ultrasonic detector may all be combined in the processing. 
       FIG. 9  is flowchart illustrating additional processing that may be performed. Block  940  performs the sound detecting processing on the audio output from the sound acquisition unit  420  to produce a loudness  950  for signals from microphones  200   a ,  200   b  and  200   c . Concurrently, an induction signal  900  from the induction sensor  215  is processed in block  910 , where the waveform of the induction signal  900  is extracted. Block  920  tests the extracted waveform to determine if a metallic object is present. If the extract waveform from block  910  exceeds a predefined intensity threshold or duration threshold, then a YES condition is produced and processing moves to block  960  where the loudness  950  at microphones  200   a ,  200   b  and  200   c  can be checked. Block  960  tracks the loudness  950  over time to determine if the overall loudness is increasing or decreasing. If the overall loudness  950  is increasing, then the waveform extracted from  910  represents a hardcopy media with metal attached to it and processing moves to block  970  where a jam is issued. If the overall loudness  950  is not increasing then the waveform extracted from  910  may represent foil that is embedded into a hardcopy media and processing continues with block  930 . Hardcopy media with metallic material, such as foil, can be of any form including, but not limited to, checks, credit or debit cards, smartcards, or other hardcopy media were data is embedded in magnetic strip or integrated circuit. 
       FIG. 10  shows the system with an induction sensor being mounted in the input tray. As seen in  FIG. 10 , the induction sensor  1000  may be mounted in the input tray  110 . By mounting the induction sensor  1000  in the input tray  110 , a larger induction sensor  1000  and field can be used to check all the hardcopy media  115  in the input tray  110  at once. The operator may be notified that that a problem exists with the hardcopy media  115  in the input tray  110  by displaying a message in the operator display  128  on the operator control panel  122 . This allows the operator to take action before the documents are transported into the device, thus avoiding jams and potential damage the hardcopy media or media transport device itself. This induction sensor in the input tray may be used in addition to the induction sensor mounted within the media transport system, as described above, or may be used instead of the induction sensor mounted within the media transport system. 
     As shown in  FIG. 11 , barcodes present on hardcopy media can be detected. Metallic material is used to create barcode  1100  in any form, including, but not limited to, foil or metallic ink. In barcode  1100 , the thick black lines  1110 ,  1120  and  1130  are created from thick metallic material spaced apart with nonmetallic gaps. Thin line  1140  is created using a thin metallic material. The barcode may include unified spacing between the thick lines  1110 ,  1120  and  1130  and thin line  1140 . Other barcode patterns may also be used, including codes with varying thicknesses or spacing between lines. 
       FIG. 12  shows the output of the field detection unit  432  represented as a binary signal waveform  1210  when a barcode, such as that shown in  FIG. 11  is present. This waveform  1210  is used by the metallic detection processing for barcode detection. At time T 1 , the start of line  1110  is detected. At time T 2  the end of line  1110  is detected. At time T 3 , the start of line  1120  is detected. At time T 4  the end of line  1120  is detected. At time T 5 , the start of line  1130  is detected. At time T 6  the end of line  1130  is detected. At time T 7 , the start of line  1140  is detected. At time T 8  the end of line  1140  is detected. Timer unit determines time delay TD 1 , which represents the time from activating the transport driver unit  465  to the change in state of the output of the field detection unit  432  indicating the presence of a metallic object. In addition, Timer unit  480  is used to determine the thickness of the metal object barcode lines where TD 2 , TD 4 , TD 6  and TD 8  represent the thickness of the black lines  1110 ,  1120 ,  1130  and  1140 . The spacing between the lines is represented by TD 3 , TD 5  and TD 7 . Having the ability to detect barcodes generates many different options for what can be done with the hardcopy media. The barcode could tell the system processing unit  270  where the hardcopy should go in applications where sorting the hardcopy media to multiple output trays is desired. The barcodes could also determine the image processing performed by the image controller  440 , and where the network controller  490  sends final images. 
       FIG. 13  illustrates the system with multiple induction sensors  1310 A-F positioned across the width of the media transport path  290 . Induction sensors  1310 A-F allow more flexibility for detection of metallic material with the ability to have detection “zones” that can be individually turned on and off. Monitoring different detection zones may provide a detection location within the media transport system indicating where a metallic object is presently located. In addition, having multiple zones allow some induction sensors  1310 A-F to be allocated for detection of barcodes while others are used for staple detection. As an example,  FIG. 13  shows a staple  1320  located in the upper left corner of top hardcopy medium  117  and a barcode pattern  1130  using metallic material on the right side of top hardcopy medium  117 . Induction sensors  1310 A-C could be configured for staple detection while induction sensors  1301 D-F could be configured for barcode detection. 
       FIG. 14  illustrates a configuration of the system where the location of the metallic object can be determined. In  FIG. 14  induction sensors  1400 ,  1410 ,  1420 , and  1430  are positioned across the width of the media transport path  290 . Induction sensors  1400  and  1410  are arranged to form an angle θ 1  and induction sensors  1420  and  1430  are arranged to form an angle θ 2 . When the transport driver unit  465  enables the urging rollers  120  and the feed rollers  223  to feed the top hardcopy medium  117 , a top hardcopy medium  117  containing staple  1440  is pulled into the media transport path  290 . Staple  1440  will pass induction sensor  1400  at location A after time delay TDT 1  and then pass metal detector  1410  at location B after a delay TDT 2 . 
     Timer unit  480  is used to determine time delay TDT 1 , which represents the time from activating the transport driver unit  465  to enable the feed module  225  to feed the top hardcopy medium  117  to when staple  1440  crosses induction sensor  1400 . Timer unit  480  is also used to determine time delay TDT 2 . Using the speed the transport driver unit  465  drives the motors, the location of the staple  1240  from the lead-edge of top hardcopy medium  117  is calculated from TDT 1  and the distance between points A and B is calculated from TDT 2 . 
       FIG. 15  shows the right triangle formed when staple  1440  crosses induction sensors  1400  and  1410 . The length of the segment AB, labeled Y is the distance between points A and B calculated from TDT 2 . The angle θ 1  formed by induction sensors  1400  and  1410 , as seen in  FIG. 14 , is represented by θ in  FIG. 15 . The value X represents the location of the staple  1440  on the top hardcopy media  117  relative to the center of the media transport path  290 . Using the formula below, the length of X can be calculated. 
     
       
         
           
             X 
             = 
             
               Y 
               
                 
                   tan 
                   
                     - 
                     1 
                   
                 
                 ⁡ 
                 
                   ( 
                   θ 
                   ) 
                 
               
             
           
         
       
     
     Sometimes, the lead-edge of top hardcopy media  117  might be pre-staged under the urging roller  120 , or the urging roller  120  may spin on the top hardcopy media  117  before the top hardcopy media  117  begins to move. These two conditions would add error to the above calculations of the location of staple  1440 . As seen in  FIG. 16 , media sensor  1600  may be added between induction sensors  1400  and  1420  and feed roller  223 . Media sensor  1600  may provide more accurate location of the lead-edge by eliminating any error introduced by pre-staging or urging roller  120  spinning from the calculation to determine the location of staple  1440 . In  FIG. 16 , the time delay TD 1  is now measured from media sensor  1600  to when staple  1440  crosses induction sensor  1400 . 
     Induction sensors  1420  and  1430  would function the same as induction sensors  1400  and  1410  if staple  1440  was located on the left side of the top hardcopy media  117 . In addition, the exact positions of the induction sensors are not critical to locating staple  1440  as long as the induction sensors  1400  and  1420  are perpendicular to transport direction as shown by A 4  and induction sensors  1410  and  1430  form a fixed angle in relation to induction sensors  1400  and  1420 .