Patent Publication Number: US-2019196359-A1

Title: System and methods for adjusting toner density in an imaging device

Description:
This application claims priority as a continuation of U.S. patent application Ser. No. 15/795,565, filed Oct. 27, 2017, having the same title. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates generally to toner density calibration methods, and more particularly to, methods for performing toner density calibrations based on duty cycle state changes in an imaging device. 
     2. Description of the Related Art 
     It is common in the imaging space for electrophotographic imaging devices to use a toner density sensor (TDS) to measure an optical reflectance of specific toner patches and to provide feedback to a controller of each imaging device on how to more accurately develop toner at the desired darkness level on a printed media sheet page. In performing a toner density calibration process, particular amounts of toner from the replaceable cartridge supply are developed as patches onto a photoconductive drum (or another intermediate transfer member) and are considered toner waste following the calibration process. Some amounts of toner are thus spent to be able to provide feedback to the controller and properly set an amount of toner on succeeding media sheets to achieve a substantially consistent level of darkness on the printed media. However, waste toners can impact loading capacities of a given toner cartridge, and depending on how the waste toners are stored in the imaging system, waste toners may lower a claimed allowable life of the imaging unit. It is also usual for toner density calibration algorithms to be performed following every power on reset of the imaging device or every predetermined number of pages. 
     Accordingly, it is desired to have more efficient algorithms in performing toner density calibrations such that a minimal amount of toner is being wasted. There also exists a need for methods in triggering said calibrations based on need. 
     SUMMARY 
     An imaging system including an electrophotographic imaging device and methods for adjusting toner density for use in printing in the imaging device are disclosed. 
     One example embodiment for a method of printing in an imaging device includes determining whether a duty cycle state in the imaging device has changed; selecting one of a full toner density calibration and a partial toner density calibration based on the determining; performing the one of the full toner density calibration and the partial toner density calibration; identifying a toner density to be applied during printing as a result of the performing; developing a toned image having a toner density equal to the toner density identified; and printing the toned image on a media sheet. 
     Another example embodiment includes an electrophotographic imaging device performing a method of printing, the method including storing a duty cycle state of a photoconductive member in the imaging device; determining, while processing a print job, whether a current duty cycle state of the photoconductive member is the same as the stored duty cycle state; upon a positive determination, identifying whether a printed page count since last performing a full toner density calibration is within a predetermined threshold; upon a positive identification, performing a partial toner density calibration to identify a new default toner density in printing; and developing a toned image associated with each print page of the print job, wherein the developed image has a toner density equal to the new default toner density. 
     Other embodiments, objects, features and advantages of the disclosure will become apparent to those skilled in the art from the detailed description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of the present disclosure, and the manner of attaining them, will become more apparent and will be better understood by reference to the following description of example embodiments taken in conjunction with the accompanying drawings. Like reference numerals are used to indicate the same element throughout the specification. 
         FIG. 1  is a block diagram of an electrophotographic imaging device, according to one example embodiment. 
         FIG. 2  is a flowchart showing an example method for adjusting toner density in the electrographic imaging device of  FIG. 1 . 
         FIG. 3  is a flowchart including example methods for performing one or more toner density calibrations in the electrographic imaging device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     It is to be understood that the disclosure is not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other example embodiments and of being practiced or of being carried out in various ways. For example, other example embodiments may incorporate structural, chronological, process, and other changes. Examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some example embodiments may be included in or substituted for those of others. The scope of the disclosure encompasses the appended claims and all available equivalents. The following description is therefore, not to be taken in a limited sense, and the scope of the present disclosure is defined by the appended claims. 
     Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use herein of “including”, “comprising”, or “having” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Further, the use of the terms “a” and “an” herein do not denote a limitation of quantity but rather denote the presence of at least one of the referenced item. 
     In addition, it should be understood that example embodiments of the disclosure include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. 
     It will be further understood that each block of the diagrams, and combinations of blocks in the diagrams, respectively, may be implemented by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other data processing apparatus may create means for implementing the functionality of each block or combinations of blocks in the diagrams discussed in detail in the description below. 
     These computer program instructions may also be stored in a non-transitory computer-readable medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium may produce an article of manufacture, including an instruction means that implements the function specified in the block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus implement the functions specified in the block or blocks. 
     Accordingly, blocks of the diagrams support combinations of means for performing the specified functions, combinations of steps for performing the specified functions, and program instruction means for performing the specified functions. It will also be understood that each block of the diagrams, and combinations of blocks in the diagrams, can be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions. 
     Disclosed is an example imaging device and different example methods for adjusting toner density in an imaging device based on duty cycle state changes. For purposes of the present disclosure, the term “duty cycle state” refers to a general state of components in a toner development or imaging unit throughout a period of time the imaging device has been operating. The disclosed methods include an example method for performing one or more toner density calibrations in the imaging device and another example method for adjusting operating parameters applied in performing the toner density calibration(s). 
       FIG. 1  is a block diagram of an electrophotographic imaging device  100 , according to one example embodiment. Imaging device  100  may be a single function printer or a multifunction machine (sometimes referred to as an all-in-one device) capable of printing, scanning, making copies, and/or other functionalities. As shown in  FIG. 1 , imaging device  100  includes a controller  105  having an associated electronic memory  110  and a print engine  120  each communicatively connected to controller  105  as is typical for imaging devices. Print engine  120  includes a laser scanning unit (LSU)  130 , a toner cartridge  135 , an imaging unit  140 , and a fuser  145 . Imaging unit  140  includes a charge roll  150 , a developer roll  155 , a photoconductive (PC) drum or member  160 , and a toner density sensor  165 . Imaging device  100  further includes a media feed system (not shown) including a media input area, a plurality of media feed rolls for forming feed nips and guiding media sheets along a media path within imaging device  100 , and a media output area for receiving a printed media sheet. 
     While not shown, imaging device  100  may be communicatively connected to a client device such as a workstation computer or other mobile devices. Imaging device  100  and the client device may be communicatively connected via a communications link. As used herein, the term “communications link” generally refers to any structure that facilitates electronic communication between multiple components and may operate using wired or wireless technology and may include communications over the Internet. The communications link may be a standard communication protocol, such as, for example, universal serial bus (USB), Ethernet or IEEE    802   .xx. 
     Each client device may include a software program including program instructions that function as an imaging driver, e.g., printer/scanner driver software, for imaging device  100 . The imaging driver facilitates communications between imaging device  100  and the client device. One aspect of the imaging driver may be, for example, to provide formatted print data to imaging device  100  and, more particularly, to print engine  120  for printing an image. In some circumstances, it may be desirable to operate imaging device  100  in a standalone mode, such that all or a portion of an imaging driver in a client device, or a similar driver, may be located in controller  105  of imaging device  100  so as to accommodate printing and/or scanning functionality when operating in the standalone mode. 
     In addition to associated electronic memory  110 , controller  105  includes a processor (not shown). The processor may include one or more integrated circuits in the form of a microprocessor or central processing unit and may be formed as one or more Application-Specific Integrated Circuits (ASICs). Memory  110  may be any volatile or non-volatile memory or combination thereof such as, for example, random access memory (RAM), read only memory (ROM), flash memory and/or non-volatile RAM (NVRAM). Alternatively, memory  110  may be in the form of a separate memory (e.g., RAM, ROM, and/or NVRAM), a hard drive, a CD or DVD drive, or any memory device convenient for use with controller  105 . Controller  105  may be, for example, a combined printer and scanner controller. 
     Toner cartridge  135  and imaging unit  140  may be separately removable from print engine  120 . When imaging unit  140  and toner cartridge  135  are mounted within imaging device  100 , an outlet port on toner cartridge  135  communicates with an inlet port on imaging unit  140  to allow toner transfer. While not shown, toner cartridge  135 , imaging unit  140 , and fuser  145  each includes a processing circuitry and associated electronic memory which may provide authentication functions, safety and operational interlocks, operating parameters and usage information related to toner cartridge  135 , imaging unit  140 , and fuser  145 . Respective processing circuitries of toner cartridge  135 , imaging unit  140 , and fuser  145  may include one or more integrated circuits in the form of a microprocessor or central processing unit and may be formed as one or more Application-specific integrated circuits (ASICs). Each associated electronic memory of toner cartridge  135 , imaging unit  140 , and fuser  145  may be a volatile memory, a non-volatile memory, or a combination thereof or any memory device convenient for use with the corresponding processing circuitry. 
     The electrophotographic printing process is well known in the art and, therefore, is described briefly herein. During a printing operation, charge roll  150  electrically charges an outer surface of PC member  160  to a predetermined voltage. LSU  130  then discharges a selected portion of the outer surface of PC member  160  to create a latent image on an outer surface of PC member  160 . Toner may then be transferred from a toner sump behind developer roll  155  to the latent image on PC member  160  by developer roll  155  (in the case of a single component toner development system) or by a magnetic roll (in the case of a dual component toner development system, not shown) to create a toned image on PC member  160 . The toned image is then transferred to a media sheet received by imaging unit  140  from a media input tray (not shown) for printing. Toner may be transferred directly to the media sheet by PC member  160  or by an intermediate transfer member that receives the toner from PC member  160 . Toner remnants on PC member  160  may be removed by a waste toner removal system (not shown). The toned image is then bonded to the media sheet by fuser  145  and then sent to a media output area (not shown) in imaging device  100  or to one or more finishing options such as a duplexer, a stapler or a hole-punch attached to imaging device  100  (not shown). 
     TDS  165  applies particular amounts of toner (also “toner patches”) onto PC member  160 , calibrates a density thereof along a surface of PC member  160 , and applies this calibrated density in printing toned images in media sheets. It is to be understood that no printing transpires during calibration. When there are changes in the calibrations, the amount of toner applied onto PC member  160  is also changed, adjusting the amount of toner applied from PC member  160  onto a next media sheet. Since a temperature within imaging unit  140  normally increases following a number of times that a toned image is consistently transferred onto a media sheet, printed images may turn relatively darker than when printing images immediately following a power on reset of imaging device  100  or when printing images during a time that imaging device  100  comes right out of standby or idle mode. To regularly adjust the amount of toner applied onto PC member  160  and ensure consistent print quality between media sheets, it is common for TDS  165  to be configured to perform another toner density calibration following every predetermined number of pages, e.g., 500-600 pages. 
     For example, when a toner density calibration is first performed following an initial power on reset (POR) of imaging device  100 , PC member  160  may be in a “cold” duty cycle state. During a time that imaging device  100  has been consistently printing, PC member  160  may be in a “hot” duty cycle state. In the “hot” duty cycle state, an amount of toner applied on the media sheet would have changed from an amount of toner applied when printing immediately after the calibration. In one example, an image on the printed page may be considerably darker. As such, a default toner density set during an initial calibration may no longer guarantee consistent print quality over time, thus requiring a new toner density calibration prior reaching the page count threshold. 
       FIG. 2  is an example method  200  for adjusting toner density in imaging device  100  of  FIG. 1 . Briefly, method  200  is divided into a toner density (TD) calibration process (blocks  205 - 215 ) and a parameter adjustment process (blocks  225 - 240 ). 
     At block  205 , following a POR of imaging device  100 , controller  105  determines whether a duty cycle state (referred to hereinafter and in the drawings as DCS) in imaging device  100  has changed. As discussed above, the term “duty cycle state” is referred to herein as a state of print engine  120  throughout a period of time in which imaging device  100  is being operated and print engine  120  in particular. In one example embodiment and for purposes of the present disclosure, the duty cycle state may refer to a state of PC member  160  following a predetermined period of processing print jobs (i.e., number of revolutions per unit of time). Controller  105  may perform block  205  upon receipt of an instruction to start a TD calibration. The controller counts the number of revolutions of the PC member over a given period of time. 
     The present disclosure categorizes into three states a duty cycle state of the PC member: “hot”, “warm”, and “cold”, where:
         a. “hot”&gt;R1 PC revs in last T minutes,   b. “warm”&gt;=R2 PC revs in last T minutes, &lt;=R1 PC revs in last T minutes,   c. “cold”&lt;R2 PC revs in last T minutes,
           with R1 being a first predetermined high number of revolutions of PC member  160  and R2 being a second predetermined low number of revolutions of PC member  160  lesser than R1.   
               

     Determining whether the DCS has changed may include identifying a current duty cycle state of PC member  160 ; determining whether a DCS of PC member  160  from a previous TD calibration is stored in memory  110 ; and if so, determining whether the current DCS and the stored DCS is the same. In the present disclosure, every time a TD calibration is performed, a DCS of PC member  160  is stored in memory  110  for reference in the next TD calibration. In the context where a TD calibration has never been performed such that no DCS is stored in memory  110 , controller  110  performs a full TD calibration in imaging device  100  and then stores the DCS following the calibration. 
     At block  210 , TDS  165  performs one or more TD calibrations based on whether the DCS has changed. The one or more TD calibrations may include a solid patch TD calibration and/or a pattern patch TD calibration. In some example embodiments, a pattern patch TD calibration may be performed following a solid patch TD calibration. In other example embodiments, TDS  165  may skip a solid patch TD calibration and instead perform only a pattern patch TD calibration. As such, a full TD calibration includes both solid and pattern patch TD calibrations whereas a partial TD calibration includes a pattern patch TD calibration. A page count threshold may also affect whether or not to perform solid patch TD calibration with pattern patch TD calibration, as will be discussed in greater detail below with respect to  FIG. 3 . 
     At block  215 , controller  105  processes then stores data from the one or more TD calibrations performed in block  210 . TD calibration-related data may include a combined voltage index value indicating respective voltages of charge roll  150  and developer roll  155  (referred to hereinafter and in the drawings as CDDI or ChgDevDarknessIndex variable), the DCS when performing the TD calibration, and a reflection ratio of specific toner patches applied onto a surface of PC member  160  as outputted by TDS  165 . 
     At block  220 , controller  105  may process the print job following the TD calibration process from blocks  205 - 215 . In one example embodiment, controller  105  may start processing a print job and print a first page thereof following a first TD calibration. In another example embodiment, controller  105  may continue processing succeeding pages of a print job. 
     At block  225 , controller  105  may detect a DCS change during printing. Similar to block  205 , for every page being processed, controller  105  may determine whether or not there is a change in a current DCS of PC member  160  relative to a stored DCS in memory  110  during the previous TD calibration in block  210 . 
     At block  230 , in response to the DCS change, controller  105  may adjust the set of operating parameters and apply the adjusted parameters in printing succeeding pages. 
     In one example embodiment, controller  105  may adjust the combined voltage index value of charge roll  150  and developer roll  155  or CDDI by adding a predetermined adder value to the CDDI value stored in memory  110 , as obtained in performing the one or more TD calibrations in block  215 . The predetermined adder values may be stored in memory  110 . The adder value to be added on top of the current voltage index value of developer roll  155  may depend on a transition between the stored DCS (in block  215 ) and the current DCS (i.e., from “cold” to “hot”, “warm to cold”, etc.), as will be discussed in greater detail below. 
     In adjusting the CDDI value, an amount of toner retrieved and applied onto PC member  160  is also changed. The adjusted CDDI value will be directly applied in printing succeeding print job pages. In changing the amount of toner desired to be applied by making adjustments to the CDDI value, another TD calibration may be unnecessary. 
     At block  235 , controller  105  may then determine whether a printed page count exceeds a predetermined threshold for performing another TD calibration, and if so, at block  240 , controller  105  triggers another TD calibration. In one example aspect, controller  105  may temporarily suspend printing. In triggering another TD calibration, actions in blocks  205  to  215  are again performed such that new calibration-related data (e.g., CDDI value, stored DCS, reflection ratios) are also obtained and stored for reference in printing the succeeding pages. 
     In the TD calibration process at blocks  205 - 215 , the TD calibration process is optimized by limiting the use of toner during calibration. In particular, since both types of TD calibrations are typically performed together for every calibration cycle, skipping one type of TD calibration based on an absence of change in the DCS saves toner. In the parameter adjustment process at blocks  225 - 240 , operating parameters in printing succeeding pages are dynamically adjusted based on changes in DCS. In doing so, an amount of toner retrieved by developer roll  155  and applied onto PC member  160  is also adjusted in printing incoming pages. Additionally, where in existing art another TD calibration is set following every predetermined number of pages, the present disclosure requires TD calibrations to be made less frequently, as controller  105  depends on both changes in the DCS of PC member  160  and page count thresholds. While blocks  205 - 240  are shown as interconnected in  FIG. 2 , blocks  205 - 215  may be independently performed from blocks  220 - 240  and vice-versa. 
       FIG. 3  is an example method  300  for performing one or more TD calibrations in imaging device  100  of  FIG. 1 . It will be noted that example method  300  is an expanded or a more detailed version of example method  200  in  FIG. 2 . For example, blocks  305  to  330  are covered by or essentially the same as blocks  205  to  215  in  FIG. 2  (TD calibration process) whereas blocks  340  to  395  are covered by or essentially the same as blocks  225  to  240  in  FIG. 2  (adjustment process). Briefly, the disclosed calibration process in blocks  305  to  330  relates to skipping one type of TD calibration based on at least an absence of a DCS change while the disclosed adjustment process in blocks  345  to  395  relates to comparing a current DCS to a stored DCS and maintaining or adjusting the voltage index value of charge roll  150  and developer roll  155  as a result of the comparison. 
     At block  305 , following POR of imaging device  100 , controller  105  may determine whether there is a change in DCS from the last TD calibration. Following a period of time of processing print jobs and having no changes to the DCS of PC member  160 , a darkest possible level of the image on the printed media may be achieved, such that it is unnecessary to perform both solid and pattern patch TD calibrations and to add more toner to the toned image on the media sheet. To get the same level of darkness between toned images, controller  105  may track a count of printed pages since the last TD calibration prior performing again both solid and pattern patch TD calibrations in addition to determining whether there is a DCS change. As such, at block  310 , following a determination that the current DCS remained the same as the stored DCS during the last TD calibration, controller  105  may further determine whether a printed page count since the last TD calibration exceeded a predetermined page count threshold which indicates that the a full TD calibration is to be performed again. 
     At block  315 , upon a determination that the DCS changed since last TD calibration, or in the alternative, upon a determination that the DCS remained the same since last TD calibration and that the printed page count since last TD calibration is greater than the predetermined page count threshold in block  310 , TDS  165  initially performs solid patch TD calibration where a set of solid toner patches are applied onto a surface of PC member  160  to measure toner density, as will be known in the art. At block  320 , controller  105  then stores a new CDDI value along with the DCS determined during the solid patch TD calibration. Additionally, controller  105  may also reset the printed page count for comparison with the threshold at block  310  following performing block  315 . 
     At block  325 , upon a determination that the DCS remained the same since last TD calibration and that the page count since last TD calibration is either less than or equal to the predetermined page count threshold from block  310 , TDS  165  skips solid patch TD calibration and instead performs pattern patch TD calibration, wherein a set of patterned toner patches are applied onto a surface of PC member  160  to measure toner density. At block  330 , controller  105  then stores reflection ratios as identified by TDS  165  along with the DCS during the pattern patch TD calibration. Reflection ratios may include halftone reflection ratio values (for single-function imaging devices) and halftone and stochastic reflection ratio values (for multifunction imaging devices). Additionally, controller  105  may also reset the (pattern patch) page count for comparison with the threshold at block  310 . 
     At block  335 , following performing at least one of the two types of TD calibrations above, controller  105  may then determine whether media sheet pages are available for printing. Upon a determination that no print job is in queue, imaging device  100  may be put on standby or idle mode. At block  340 , upon a determination that there is at least one print job in queue in imaging device  100 , controller  105  may then print a first or a next page of the print job. 
     At block  345 , following start or continuation of the printing process, controller  105  may determine a number of revolutions made by PC member  160  (also “duty cycle count”, referred to in the drawings as DCC) in the last predetermined period, such as, for example, in the last 30 minutes. Generally, determining the number of revolutions made by PC member  160  during the last predetermined period corresponds to determining a DCS of PC member  160 . Controller  105  then compares the determined number of revolutions of PC member  160  to each of the DCS state thresholds discussed above with respect to block  205  ( FIG. 2 ) to determine a current DCS of PC drum  160 . 
     At block  350 , controller  105  may determine whether the DCC from block  345  is greater than the “hot” threshold, and if so, at block  355 , stores the current DCS of PC member  160  as “hot”. Otherwise, controller  105  compares the determined DCC with the warm and cold thresholds in the preceding blocks. 
     At block  360 , upon a determination that the DCC from block  345  does not fall into the “hot” threshold to indicate a “hot” DCS, controller  105  may determine whether the DCC is greater than the “warm” threshold, and if so, stores the current DCS of PC member  160  as “warm” (block  365 ). Otherwise, at block  370 , upon a determination that the DCC from block  345  does not fall into either the “hot” or “warm” thresholds, controller  105  stores the current DCS of PC member  160  as “cold.” 
     At block  375 , controller  105  then determines whether there is a change in DCS. In performing the determination, controller  105  may compare the new DCS identified based on the predetermined DCS thresholds (from any one of blocks  355 ,  365 , and  370 ) with the DCS stored in memory  110  from a last TD calibration (at least one of blocks  315  and  330 . Following a determination of controller  105  that the current DCS and a DCS in the last TD calibration is the same, controller  105  proceeds to block  385 . 
     At block  380 , following a determination that the DCS has changed relative to the DCS stored during last TD calibration, controller  105  modifies the CDDI value for consequently modifying a voltage vector between developer roll  155  and PC member  160  and then proceeds to block  385 . Modifying the CDDI value may include adjusting the current CDDI value to include an adder value in order to achieve the desired voltage for retrieving toner and therefore a desired toner density. The set of adder values are stored in memory  110  of imaging device  100 . Each adder value may be negative or positive in value and may depend on the level of transition between DCSs. A table showing example values to be added to the CDDI value based on the change in DCS is shown below. 
     
       
         
           
               
               
               
             
               
                   
               
               
                 index 
                 duty cycle state change 
                 CDDI adder value 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 0 
                 cold to warm 
                 −3 
               
               
                 1 
                 cold to hot 
                 −3 
               
               
                 2 
                 warm to cold 
                 +3 
               
               
                 3 
                 warm to hot 
                 −3 
               
               
                 4 
                 hot to warm 
                 +3 
               
               
                 5 
                 hot to cold 
                 +15 
               
               
                   
               
            
           
         
       
     
     Blocks  385 ,  390 , and  395  in  FIG. 3  correspond to block  235  in  FIG. 2  where controller  105  keeps track of whether or not to trigger another TD calibration based upon the need after processing a plurality of pages. In the present disclosure, a “soft” page count threshold and a “hard” page count threshold greater in value than the “soft” threshold are predetermined. Both thresholds are set as a basis in triggering another full or partial TD calibration. Broadly, for every page printed, controller  105  determines a printed page count since the last TD calibration; determines whether the page count is still within the soft and hard threshold; and if so, continues printing (block  340 ). 
     In particular, at block  385 , controller  105  may determine whether the page count since the last TD calibration is greater than the “soft” page count threshold. Upon a determination that the page count is less than or equal to the “soft” page count threshold, controller  105  proceeds to block  340  where a next page queued in print engine  120  may be printed. 
     At block  390 , upon a determination that the page count is greater than the “soft” page count threshold, controller  105  may determine whether more pages are queued in print engine  120 . The page(s) may either be page(s) from the same print job or page(s) from another print job. 
     At block  395 , upon a determination that more pages are available for printing, controller  105  may then determine whether the page count since the last TD calibration is greater than the “hard” page count threshold. Upon a determination that the page count since the last TD calibration is greater than the “soft” page count threshold but is less than or equal to the “hard” page count threshold, controller  105  proceeds to block  340  where a next page queued in print engine  120  may be printed. 
     Otherwise, upon either a determination that no more pages are queued in print engine  120  or that the printed page count since the last TD calibration is greater than the “hard” page count threshold, controller  105  may trigger another TD calibration process and again proceed to block  305 . 
     It will be noted that blocks  340  to  395  may be performed as long as a print job is being processed or queued in print engine  120 . Using the disclosed methods above, TD calibration may not only be performed for every predetermined number of pages, but when there is also a change in the DCS. As a result of limiting the frequency of performing TD calibrations based on these two factors, toner is saved and the allowable life of imaging components and supplies of imaging device  100  are more efficiently utilized. Additionally, in skipping solid patch TD calibration when determined to be unnecessary by the present disclosure (i.e., performing block  325  following block  310 ), a darkness level among printed media sheets is made more consistent. 
     It will be appreciated that the actions described and shown in the example flowcharts may be carried out or performed in any suitable order. It will also be appreciated that not all of the actions described in  FIGS. 2 and 3  need to be performed in accordance with the example embodiments and/or additional actions may be performed in accordance with other example embodiments of the disclosure. 
     Many modifications and other embodiments of the disclosure set forth herein will come to mind to one skilled in the art to which these disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.