Abstract:
Printing systems, control systems, and methods are presented for controlling customer image creation in which process control patches are laterally offset from a lateral customer image boundary to mitigate adverse interaction of control patches and customer images and to improve print engine process control.

Description:
BACKGROUND 
       [0001]    The present exemplary embodiment relates to document processing systems and more particularly to improved process control patch measurement methods and print control systems. In the present disclosure, methods and systems are provided for print engine control in a document processing system. Electrophotographic laser printers, xerographic copiers, scanners, facsimile machines and other document processing systems are operable to print images and text onto printable media using imaging components operated according to print data. Electrostatic charge is initially distributed on an outer side surface of a photoreceptor or photographic member, which may be a rotating drum or a belt translated in a process direction in the printing engine. A customer image is optically projected on the charged photoreceptor surface using a raster image scanner leaving a latent image on the photoreceptor surface. The image is developed by the photoreceptor translating past a source of toner such that toner particles are drawn to the latent image via a carrier in order to create a visible image on the photoreceptor surface, and the toner image is then transferred to paper or other printable media and is fused to the media to create a printed document. Following the printing cycle, the photoreceptor is discharged before the photoreceptor is again charged for printing of the next customer image. 
         [0002]    To ensure correct operation of the imaging components of a print engine over time, feedback control techniques are employed using feedback obtained from process control or test patches created on the photoreceptor to adjust the operation of the various imaging components of the printing engine. The control patch is a predefined pattern that is created on the photoreceptor surface between adjacent customer images and is sensed or measured as the photoreceptor moves past a sensor. Different patches may be created for different colors, with each patch including light, dark, and medium areas, where more than one sensor may be used to measure the differently colored control patches created on the photoreceptor. Feedback information obtained from the measured control patch is used to adjust operating parameters of the printing system to maintain image quality, such as toner concentration, the magnitude of the charge on the photoreceptor, the amount of exposure from the scanner, etc. 
         [0003]      FIG. 12  shows a conventional process control patch implementation in which control patches  130  for each developer housing are created in an inter-document zone (IDZ)  122  between successive customer images  120  on a drum or belt type photoreceptor  110   a  that moves along a process direction P. These control patches  130  are sensed with toner patch sensors (not shown) and actuators are adjusted to maintain a three-point tonal response curve (TRC). However, the inventors have appreciated that shortfalls in system performance, such as reload degradation, can cause undesirable interactions between the control patches and the customer images. In this situation, the presence of the customer image may cause distortion in the control patch image, and thereby lead to an error in the measured process control feedback for the print engine. Likewise, the presence of control patches in the IDZ may cause a distortion in the customer image. Thus, there is a need for improved feedback control techniques and systems for print engine control. 
       BRIEF DESCRIPTION 
       [0004]    The present disclosure provides printing systems and control systems therefor, as well as methods for controlling customer image creation, in which process control patches are created on a moving photoreceptor in edge zones that are laterally offset from a lateral customer image boundary. In this manner, image development system deficiencies with respect to customer images are decoupled from the process control or test patch images on the photoreceptor and vice versa, and accordingly the ability to control the print engine in closed loop fashion will not be adversely impacted by system performance degradation. 
         [0005]    One or more aspects of the present disclosure relate to a method for controlling a print engine in a printing system. The method involves creation of images between two lateral edges on a first side of a photoreceptor, where the images are created in predefined customer image areas separated along a process direction by an inter-document zone (IDZ), and where the customer image areas have a lateral boundary inward of the photoreceptor edge. The lateral image area boundary and the IDZ define an edge zone comprising a first portion laterally outside the customer image area between the lateral boundary and the photoreceptor edge alongside the customer image, and a second portion extending laterally outwardly of the lateral boundary through the IDZ. The method includes creating one or more process control patch images within the edge zone of the photoreceptor, sensing the patch image to generate measured control patch feedback information, and controlling the customer image creation in closed-loop fashion at least partially according to the measured control patch feedback information. 
         [0006]    In this manner, and image development system problems introduced by a customer image on the photoreceptor will not affect the control patch image, whereby the feedback control will not be impaired or distorted. Moreover, any image development system effects associated with the presence of the control patch images will not affect the customer images created on the photoreceptor, since the control patch and customer images are laterally offset from one another and do not overlap with respect to the process direction along which the photoreceptor is translated. The control patch(es) may be located in either or both the first and/or second portions of the edge zone, and a given patch image may extend into both portions. Edge zones may be defined along both lateral edges of the photoreceptor with the customer image area therebetween, where control patches can be created in one or both such edge zones. 
         [0007]    Further aspects of the disclosure relate to printing systems and control systems therefor. The printing system includes a photoreceptor having customer image areas separated by inter-document zones along the process direction and having a first lateral boundary defining an edge zone laterally outward from the customer image area, as well as an imaging component, a sensor operative to sense the control patch images created in the edge zone, and a controller that receives feedback information from the sensor and controls the creation images in closed-loop fashion at least partially according to the measured control patch feedback information. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    The present subject matter may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the subject matter. 
           [0009]      FIG. 1  is a schematic system level diagram illustrating an exemplary document processing system with a control system for controlling a print engine using process control patch images in accordance with one or more aspects of the present disclosure; 
           [0010]      FIG. 2  is a simplified partial side elevation schematic diagram illustrating further details of the printing and control components in the document processing system of  FIG. 1 ; 
           [0011]      FIG. 3  is a partial top plan view illustrating a top surface of an exemplary photoreceptor structure in the printing system of  FIGS. 1 and 2  including process control patch images created in second portions of an edge zone laterally outlying customer image areas on the top surface of the photoreceptor in accordance with various aspects of the present disclosure; 
           [0012]      FIG. 4  is an enlarged top plan view illustrating further details of the top photoreceptor surface including a succession of customer image areas to one side of a first lateral boundary and separated from one another along a process direction by an inter-document zone, as well as a first edge zone with a first portion laterally alongside the customer image area and a second portion extending laterally outwardly of the first lateral boundary through the inter-document zone; 
           [0013]      FIG. 5  is a partial top plan view illustrating a top surface of another exemplary photoreceptor structure in the printing system of  FIGS. 1 and 2  including process control patch images created in the first portions of the edge zone outlying the customer image areas; 
           [0014]      FIG. 6  is a partial top plan view illustrating a top surface of another exemplary photoreceptor structure including a plurality of axially aligned different colored process control patch images created in the edge zone outlying the customer image areas; 
           [0015]      FIG. 7  is a partial top plan view illustrating a top surface of another exemplary photoreceptor structure including a plurality of different colored process control patch images created in staggered arrangements in the first portions of the edge zone; 
           [0016]      FIG. 8  is a partial top plan view illustrating a top surface of another exemplary photoreceptor structure including a plurality of different colored process control patch images created in staggered arrangements in the first and second portions of the edge zone; 
           [0017]      FIG. 9  is a partial top plan view illustrating a top surface of another exemplary photoreceptor structure including a plurality of laterally aligned different colored process control patch images created in the second portions of the edge zone; 
           [0018]      FIG. 10  is a partial top plan view illustrating a top surface of another exemplary photoreceptor structure including a plurality of laterally aligned different colored process control patch images created in the first and second portions of the edge zone; 
           [0019]      FIG. 11  is a partial top plan view illustrating a top surface of another exemplary photoreceptor structure including process control patch images created in first and second edge zones laterally outlying the customer image areas; and 
           [0020]      FIG. 12  is a partial top plan view illustrating a top surface of a conventional photoreceptor structure including process control patch images created in an inter-document zone between successive customer image areas. 
       
    
    
     DETAILED DESCRIPTION  
       [0021]      FIGS. 1 and 2  illustrate an exemplary document processing or printing system  10  in accordance with one or more aspects of the present disclosure. The printing system  10  can be any form of commercial printing apparatus, copier, printer, facsimile machine, or other system which may include a scanner or other input device  12  that scans an original document text and/or images to create an image comprising pixel values indicative of the colors and/or brightness of areas of the scanned original, and which has one or more marking engines or print engines  14  by which visual images, graphics, text, etc. are printed on a page or other printable medium, including xerographic, electro photographic, and other types of printing technology, wherein such components are not specifically illustrated in  FIG. 1  to avoid obscuring the various alternate imaging features of the present disclosure. The print engine  14  may be any device or marking apparatus for applying an image from a digital front end (DFE) printer controller  102  to printable media (print media) such as a physical sheet of paper, plastic, or other suitable physical media substrate for images, whether precut or web fed, where the input device  12 , print engine  14 , and controller  102  are interconnected by wired and/or wireless links for transfer of electronic data therebetween, including but not limited to telephone lines, computer cables, ISDN lines, etc. The print engine  14  generally includes hardware and software elements employed in the creation of desired images by electrophotographic processes wherein suitable print engines  14  may also include ink-jet printers, such as solid ink printers, thermal head printers that are used in conjunction with heat sensitive paper, and other devices capable of printing an image on a printable media. 
         [0022]    The image input device  12  may include or be operatively coupled with conversion components for converting the image-bearing documents to image signals or pixels or such function may be assumed by the printing engine  14 . In the illustrated document processor  10 , the printer controller  102  provides the output pixel data from memory to a print engine  14  that is fed with a print media sheets  22  from a feeding source  24  such as a paper feeder which can have one or more print media sources or paper trays  26 ,  28 ,  30 ,  32 , each storing sheets of the same or different types of print media  22  on which the marking engine  14  can print. The exemplary print engine  14  includes an imaging component  44  and an associated fuser  48 , which may be of any suitable form or type, and may include further components which are omitted from the figure so as not to obscure the various aspects of the present disclosure. 
         [0023]    As best shown in  FIG. 2 , the printing engine  14  may include a photoconductive insulating member or photoreceptor  100  ( FIG. 2 ) which is charged to a uniform potential via a corotron  114  and exposed to a light image of an original document to be reproduced via an imaging laser  116  under control of a controller  104  of the DFE  102 . The exposure discharges the photoconductive insulating surface of the photoreceptor  100  in exposed or background areas and creates an electrostatic latent image on the photoreceptor  100  corresponding to image areas of the original document. The electrostatic latent image on the photoreceptor  100  is made visible by developing the image with an imaging material such as a developing powder comprising toner particles via a development unit  118 , and the customer image is then transferred to the print media  22  and permanently affixed thereto in the fusing process. 
         [0024]    In a multicolor electrophotographic process, successive latent images corresponding to different colors can be formed on the photoreceptor  100  and developed with a respective toner of a complementary color, with each color toner image being successively transferred to the paper sheet  22  in superimposed registration with the prior toner image to create a multi-layered toner image on the printed media  22 , and where the superimposed images may be fused contemporaneously, in a single fusing process. The fuser  48  ( FIG. 1 ) receives the imaged print media from the image-forming component and fixes the toner image transferred to the surface of the print media  22 , where the fuser  48  can be of any suitable type, and may include fusers which apply heat or both heat and pressure to an image. Printed media from the printing engine  14  is delivered to a finisher  36  including one or more finishing output destinations  38 ,  40 ,  42  such as trays, stackers, pans, etc. 
         [0025]    The document processing system  10  is operative to perform these scanning and printing tasks in the execution of print jobs, which can include printing selected text, line graphics, images, machine ink character recognition (MICR) notation, etc., on either or both of the front and back sides or pages of one or more media sheets  22 . An original document or image or print job or jobs can be supplied to the printing system  10  in various ways. In one example, the built-in optical scanner  12  may be used to scan an original document such as book pages, a stack of printed pages, or so forth, to create a digital image of the scanned document that is reproduced by printing operations performed by the printing system  10  via the print engine  14 . Alternatively, the print jobs can be electronically delivered to the system controller  102  via a network or other means, for instance, whereby a network user can print a document from word processing software running on a network computer, thereby generating an input print job. 
         [0026]    In the example of  FIG. 1 , a print media transporting system or network or highway  60  of the document processing system  10  links the print media source  24 , the print engine  14  and a finisher  36  via a network of flexible automatically feeding and collecting drive members, such as pairs of rollers  62 , spherical nips, air jets, or the like, along with various motors for the drive members, belts, guide rods, frames, etc. (not shown), which, in combination with the drive members, serve to convey the print media along selected pathways at selected speeds. In the illustrated embodiments, print media  22  is delivered from the source  24  to the print engine  14  via a pathway  64  common to the input trays  26 ,  28 ,  30 ,  32 , and is printed by the imaging component  44  and fused by the fuser  48 , with a pathway  68  from the print engine  14  merging into a pathway  74  which conveys the printed media to the finisher  36 , where the pathways  64 ,  68 ,  74  of the network  60  may include inverters, reverters, interposers, bypass pathways, and the like as known in the art. In addition, the print engine  14  may be configured for duplex or simplex printing and a single sheet of paper  22  may be marked by two or more print engines  14  or may be marked a plurality of times by the same marking engine  14 , for instance, using internal duplex pathways. 
         [0027]    Referring particularly to  FIGS. 2 and 3 , in accordance with various aspects of the present disclosure, the exemplary document processor  10  comprises a control system including a controller  104  and one or more sensors, such as toner patch sensors  110  providing feedback  112  to the controller with respect to process control or test patch images created on the photoreceptor  100 . As best shown in  FIG. 2 , the illustrated photoreceptor is a belt type structure including a top side  100 T and a bottom side  100 B. The DFE controller  104  operates the imaging components  114 ,  116 , and  118  to create customer images on the first or top surface  100 T as the photoreceptor  100  is translated along the process direction P. 
         [0028]    As shown in  FIGS. 3 and 4 , moreover, the first or top side  100 T of the photoreceptor  100  has first and second lateral edges  100   a  and  100   b  generally parallel to the process direction P and includes predefined customer image areas  120  with successive customer image areas  120  separated from one another along the process direction P by inter-document zones (IDZs)  122 . The individual customer image areas  120  have a first lateral boundary  124  laterally inward of the first photoreceptor edge  100   a  that defines a first edge zone  126  with a first edge zone portion  126 P 1  ( FIG. 4 ) laterally outside the customer image area  120  between the first lateral boundary  124  and the first photoreceptor edge  100   a  and a second portion  126 P 2  extending laterally outwardly of the first lateral boundary  124  through the IDZ  122 . 
         [0029]    The controller  104  causes the imaging components  114 ,  116 , and  118  ( FIG. 2 ) to create at least one process control patch image  130  ( FIG. 3 ) within the first edge zone  126  of the photoreceptor top side  100 T, where the example of  FIG. 3  includes process control patch images  130  created in second portions  126 P 2  of the first edge zone  126  laterally outlying (e.g., alongside) the customer image areas  120 . As shown in  FIG. 3 , moreover, the individual patch images  130  include a light portion  131 l, a medium portion  131   m,  and a dark portion  131   d,  where successive patch images  130  may be of different colors, such as cyan (c), magenta (m), yellow (y), and black (k). Other implementations are possible in which individual control patch images  130  only include one portion (e.g., light, medium, or dark). 
         [0030]    In the illustrated implementation, moreover, corresponding toner patch sensors  110   c,    110   m,    110   y,  and  110   k  are located along the edge zone path of the translating photoreceptor  100  so as to allow sensing of the process control patch images  130  as they move along the process direction P. The measurements of the process control patch images  130  are provided from the sensor(s)  130  as feedback  112  signals or data to the controller  104  of the DFE  102  for use in adjusting the operational parameters of the imaging components used in creating customer images in the customer image areas  120  of the photoreceptor  100  in closed loop fashion. 
         [0031]    The inventors have appreciated that system performance shortfalls in the print engine  14  may cause undesirable interaction between the control patches and the customer images where the control patches  130  are located axially between adjacent customer image areas  120  as in the example of  FIG. 12 , leading to distortion in the measured control patch images and/or customer images. Distortion in the measured control patch image feedback would cause errors in the closed loop control of the print engine. By the technique shown in  FIG. 3 , the control patches  130  are moved beyond the lateral extent of the customer image areas  120  so as to decouple image development system deficiencies with respect to customer images from the process control patch images. As a result, the ability to control the print engine in closed loop fashion will not be adversely impacted by system performance degradation since the measured control patch feedback  112  will not be influenced by the presence or absence of customer images in the areas  120 , but will instead be affected only by the performance of the imaging components of the system  10 . Thus, the controller  104  receives the patch sensor feedback  112  and controls the creation of the customer images in closed-loop fashion at least partially according to the measured control patch feedback information  112 . 
         [0032]      FIG. 5  illustrates another example in which the controller  104  causes creation of process control patch images in the first portion  126 P 1  of the first edge zone  126 . In this case, a single test patch image  130  with light, medium, and dark portions  131   l,    131   m,  and  131   d,  respectively, is created in the first portion  126 P 1  alongside each customer image area  120  with successive control patch images being of different colors, such as cyan (patch  130   c ), magenta (patch  130   m ), yellow ( 130   y ), and black (patch  130   k ). Other embodiments are possible in which a control patch  130  is provided alongside every other customer image area  120 , and other spacings may be provided in alternate implementations within the scope of the present disclosure. 
         [0033]      FIG. 6  illustrates yet another exemplary embodiment in which multiple control patch images  130  are created alongside each customer image area  120 , wherein at least two patches  130  are in a given first edge zone portion  126 P 1 . In this embodiment, moreover, different colored process control patch images  130   c,    130   m,    130   y,  and  130   k  are created in the first portions  126 P 1  alongside each customer image area  120 , although not a strict requirement of the broader aspects of the present disclosure. In the embodiment of  FIG. 6 , the differently colored test patches  130  are axially aligned with one another in the first portions  126 P 1  of the first edge zone  126  and the corresponding toner patch sensors  110  are also axially aligned relative to the process direction P although alternate implementations are possible without such axial alignment. 
         [0034]      FIG. 7  illustrates another possible implementation, in which multiple control patch images  130  are again created alongside each customer image area  120  in one or more of the first edge zone portions  126 P 1 , with different colored process control patch images  130   c,    130   m,    130   y,  and  130   k  created in the first portions  126 P 1 . In this embodiment, the different colored process control patch images  130  are created in staggered arrangements in the first portions  126 P 1  of the edge zone  126  with four differently colored patch images  130   c,    130   m,    130   y,  and  130   k  within each of the edge zone first portions. 
         [0035]      FIG. 8  illustrates still another embodiment including a plurality of different colored process control patch images  130   c,    130   m,    130   y,  and  130   k  created in staggered arrangements in the first and second portions of the edge zone. In this regard, different control patch images  130  can be created in the first and second edge zone portions  126 P 1  and  126 P 2  and individual patch images  130  can straddle the two portions  126 P 1  and  126 P 2 , wherein all such variant implementations are possible within the scope of the present disclosure in which at least one patch image  130  is created in the edge zone  126  laterally outlying the boundary  124  of the customer image areas  120 . 
         [0036]      FIG. 9  shows yet another exemplary photoreceptor structure  100  including a plurality of different colored process control patch images  130   c,    130   m,    130   y,  and  130   k  that are laterally aligned with respect to one another in a direction perpendicular to the process direction P, where the patches  130  in this embodiment are created in the second portions  126 P 2  of the edge zone  126  along the first side  100   a  of the photoreceptor  100 . In this example, the control system provides for location of the corresponding toner patch sensors  110   c,    110   m,    110   y,    110   k  at different lateral distances from the edge  100   a  so as to be able to sense the corresponding test patch images  130  as the photoreceptor structure  100  is translated along the process direction P. 
         [0037]    As shown in  FIG. 10 , moreover, the spacing of successive process control patches  130  or groups thereof, need not be the same as the spacing between successive customer image areas  120 . In the implementation of  FIG. 10  a plurality of laterally aligned different colored process control patch images  130  are created in the first and second portions of the edge zone  126 , where the spacing  140  between successive customer image areas  120  is different than the spacing  142  between successive groups of process control patch images  130 . 
         [0038]    In accordance with further aspects of the present disclosure, the customer image areas  120  may have a second lateral boundary  124   a  laterally inward of the second photoreceptor edge  100   b  to thus define a second edge zone  126   a  that itself has a first portion laterally outside the customer image area  120  between the second lateral boundary  124   a  and the second photoreceptor edge  100   b,  as well as a second portion extending laterally outwardly of the second lateral boundary  124   a  through the inter-document zone  122 . 
         [0039]      FIG. 11  illustrates yet another exemplary photoreceptor structure  100  that includes process control patch images  130  created in such first and second edge zones  126  and  126   a,  respectively, each laterally outlying the customer image areas  120 , where the edge zones  126 ,  126   a  may, but need not, be of the same width. Again, this approach essentially decouples any system performance issues with respect to the process control patch images  130  and the images of the customer image areas  120 . In this case, the controller  104  causes the imaging component(s) to create another process control patch image  130  within the second edge zone  126   a  and corresponding sensors are provided along each edge zone  126 ,  126   a  of the photoreceptor structure  100 . In the example of  FIG. 11 , moreover, different colored patches  130  and sensors  110  are provided along each edge zone  126 ,  126   a  for corresponding sensing whereby the feedback control can accommodate laterally varying adjustments. In this embodiment, a first set of cyan, magenta, yellow, and black sensors  110   c   1 ,  110   m   1 ,  110   y b, and  110   k l are provided to sense control patch images  130  of the first edge zone  126 , and a second set of cyan, magenta, yellow, and black sensors  110   c   2 ,  110   m   2 ,  110   y   2 , and  110   k   2  are provided to sense control patch images  130  of the second edge zone  126   a.    
         [0040]    The above examples are merely illustrative of several possible embodiments of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, systems, circuits, and the like), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component, such as hardware, software, or combinations thereof, which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the illustrated implementations of the disclosure. In addition, although a particular feature of the disclosure may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”. It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications, and further that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.