Patent Publication Number: US-10766253-B2

Title: Sideband signal for fluid ejection

Description:
BACKGROUND 
     Print systems are used to print on various types of media or substrates. Some media and substrates have large widths. Print systems can include fluid ejection devices that span a width of the media that can print across the large widths of some media. The fluid ejection devices can eject fluid onto the media or substrate to print an image. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an example system of the present disclosure; 
         FIG. 2  is a block diagram of an example fluid ejection system of the present disclosure; 
         FIG. 3  is a block diagram of example fluid ejection devices of the present disclosure; 
         FIG. 4  is a block diagram of an example timing system of the present disclosure; 
         FIG. 5  is a block diagram of an example configuration of the fluid ejection devices of the present disclosure; 
         FIG. 6  is a block diagram of another example configuration of the fluid ejection devices of the present disclosure; and 
         FIG. 7  is a flow diagram of an example method for distributing sideband signals in the fluid ejection system. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure discloses methods and apparatuses for distributing a plurality of real-time sideband signals in a distributed print system. Many print systems utilize sideband signals. Sideband signals are signals other than the image data to be printed that are used to control and synchronize the printing of the image data. These sideband signals may include speed or position of the media relative to the fluid ejection devices, or timing information for an event such as top-of-form. 
     As discussed above, some print systems may be capable of printing across a large width of a media. For example, some print systems may print across a media that is 110 inches wide. The sideband signals may be used to synchronize the printing of the image data across these large widths that use a plurality of fluid ejection devices. 
     To handle such large widths, multiple sub systems can be wired together to work together to print across the large widths of media. The sub systems can be wired together to allow each sub system to receive the sideband signals for accurate printing. 
     However, some wiring methods can have signal integrity challenges and physical cable routing issues. These wiring methods do not scale well when additional sub systems are added as the distributed print system is used to print on wider and wider media. 
     The present disclosure uses concepts of time division multiplexing within the distributed print system to ensure that the real-time sideband signals are properly delayed for each sub system. As a result, each sub system may receive the real-time sideband signal at the correct time to accurately eject fluid onto a media. 
     In addition, the present disclosure provides a method that is easily scalable as additional sub systems are added to the distributed print system. Using the methods of the present disclosure, adding large amounts of additional physical wiring and hardware when sub systems are added may be avoided. 
       FIG. 1  illustrates a block diagram of an example system  100  of the present disclosure. In one example, the system  100  may include a fluid ejection system  102  and an inspection system  104 . The fluid ejection system  102  may dispense fluid or ink to thereby deposit fluid onto a media  106  such that an image may be formed on the media  106 . The media  106  may be paper, plastic or any other substrate that may receive the fluid or ink from the fluid ejection system  102 . As will be appreciated, the fluid ejection system  102 , as described herein, may selectively eject droplets of fluid such that the droplets of fluid may be deposited on the media  106 . The patterning of such deposited droplets of fluid on the media  106  may cause an image to be formed on the media  106 . Such formation of an image may be referred to as printing. In other examples, the patterning of such deposited droplets of fluid on the media  106  may be performed in a layer-wise additive manufacturing process, where the formation of the image may correspond to formation of a cross-sectional portion of a three-dimensional object. 
     In one implementation, the inspection system  104  may be used to analyze the image that is printed onto the media  106 . The results of the analysis may be fed back to the fluid ejection system  102  to allow one or more adjustments to be made by the fluid ejection system  102  when printing subsequent lines of the image onto the media  106 . 
       FIG. 2  illustrates a block diagram of one example of the fluid ejection system  102 . In one implementation, the fluid ejection system  102  may include a plurality of fluid ejection devices  202   1  to  202   n  (hereinafter referred to individually as fluid ejection device  202  or collectively as fluid ejection devices  202 ). In one example, the fluid ejection devices  202  may be controlled to print each line of an image onto the media  106 . 
     In some implementations, the fluid ejection devices  202  may be controlled by real-time sideband signals that instruct each one of the fluid ejection devices  202  when to print. The real-time sideband signals may be generated by a controller or a processor (not shown) of the fluid ejection system  102  based on a print job that is received. 
     In some examples, the media  106  may be wide. For example, the media  106  may be up to 110 inches wide or even greater that uses more than one fluid ejection device  202  to print each line. If the real-time sideband signals are not received with a correct timing by the fluid ejection devices  202 , each line of the image may be printed incorrectly. In other words, if some of the fluid ejection devices  202  receive the real-time sideband signals at incorrect times, then there may be a visible offset between pixels printed by different fluid ejection devices  202 . 
     In some examples, the multiple sub systems use the sideband signals that arrive at each sub system at the exact same time. This may be the case when different sub systems control fluid ejection devices  202  that are arranged next to each other across the width of the media  106 . The sub systems receive the sideband signals at the same time to ensure that the pixels are printed at the same down-web locations (e.g., a direction of the media transport) on the media  106 . 
     In other examples, the multiple sub systems may receive the sideband signals at different, but related times. This may be the case when the different sub systems control the fluid ejection devices  202  that are arranged upstream and downstream from each other along a length of the media  106 . The sub system may receive the sideband signals, with the appropriate delays to ensure that the pixels are printed at the same down-web locations on the media  106 . 
     In one example, the fluid ejection system  102  may include a sensor  204  and feedback system  206 . The sensor  204  and the feedback system  206  may be part of the inspections system  104  that is part of the fluid ejection system  102  or a component that is separate from the fluid ejection system  102 . 
     In one example, the sensor  204  may be an optical sensor that analyzes each line that is printed by the fluid ejection devices  202 . The sensor  204  may analyze each line to detect or collect information regarding a location of each pixel that is printed by two different fluid ejection devices  202 . The feedback system  206  may determine how much offset exists between two different pixels based on the location information collected by the sensor  204 . 
     The feedback system  206  may use the amount of offset to calculate an amount of time delay for each fluid ejection device  202  to receive the real-time sideband signals. For example, using the amount offset that is determined by the sensor  204  and knowing the speed at which the media  106  is moving, or the speed at which the plurality of fluid dejection devices  202  are moving, the feedback system  206  can calculate the amount of time delay for each fluid ejection device  202 . 
     The amount of time delay may be defined as a difference in the amount of time that each fluid ejection device  202  takes to receive a respective real-time sideband signal relative to a reference fluid ejection device  202 . For example, the reference fluid ejection device  202  may be the fluid ejection device  202  that receives the real-time sideband signal first. 
     The respective amount of time delay calculated for each one of the fluid ejection devices  202  may be inserted into the real-time sideband signals. As a result, each one of the fluid ejection devices  202  may receive the real-time sideband signals at the correct time to ensure that the pixels printed by the fluid ejection devices  202  are aligned properly such that each line of the image is printed accurately. In other words, the amount of time delay may allow each one of the fluid ejection devices  202  to receive the real-time sideband signal at a correct time that correctly aligns the fluid ejection devices  202  when printing. Said another way, the amount of time delay that is inserted into the real-time sideband signals may synchronize the fluid ejection devices  202 . For example, a first fluid ejection device  202  may be at a different location than a second fluid ejection device  202  along the width of the media  106 . The amount of time delay that is inserted into the real-time sideband signal may synchronize the first fluid ejection device  202  and the second fluid ejection device  202  such that fluid that is dispensed by the first fluid ejection device  202  and the second fluid ejection device  202  may hit the same location on the media  106 . Notably, if the real-time sideband signal is not received at a correct time by the second fluid ejection device  202 , then the fluid dispensed by the second fluid ejection device  202  may not be at the same location as the fluid dispensed by the first fluid ejection device  202  causing an offset or a misalignment of the pixels during printing. 
     In contrast, some systems use a complicated system of physical cabling to ensure that each fluid ejection device  202  receives the real-time sideband signals. For example, each fluid ejection device  202  is physically connected to a source of the real-time sideband signals using wide parallel cables. However, the number of physical connections for each fluid ejection system  102  may be limited and as printing widths grow and additional fluid ejection devices  202  are added, physical cabling may grow more complicated and consume more space in the fluid ejection system  102 . In addition, physical cabling may suffer from skew, signal loss and degradation over time. 
     With the fluid ejection system  102  of the present disclosure, a single optical connection may be used for each fluid ejection device  202 . In addition, any signal loss or degradation can be compensated for based on the amount of time delay that is calculated by the inspection system  104  or the feedback system  206 . 
       FIG. 3  illustrates one example of the fluid ejection devices  202  and how the fluid ejection devices are connected. In one example, a first fluid ejection device  202   1  may include a timing system  302   1 , a print system  304   1 , a signal delay  306   1 , a local parallel bus  308   1 , a serializer/deserializer (SERDES)  310   1  and an optical/wired connection  312   1 . In one example, a second fluid ejection device  202   2  may include a timing system  302   2 , a print system  304   2 , a local parallel bus  308   2 , a SERDES  310   2  and an optical/wired connection  312   2 . Although two fluid ejection devices  202   1  and  202   2  are illustrated in  FIG. 3 , it should be noted that any number of fluid ejection devices may be deployed. 
     In one implementation, the timing system  302   1  may receive the amount of time delay for each fluid ejection device  202  (e.g., fluid ejection device  202   2  in the present example) that is calculated by the feedback system  206 . The timing system  302   1  may perform the insertion and transmission of the amount of time delay into the real-time sideband signals that are transmitted to the other fluid ejection devices  202 . 
     In one example, the amount of time delay may be inserted using a delay module. In one example, the delay module may be a programmable delay module such as the signal delay module  306   1 . In another example, the delay module may be a non-programmable delay module such as the local parallel bus  308   1 . 
     The timing system  302   1  may insert the amount of time delay into the real-time sideband signal via one or more of the delay modules and then transmit the real-time sideband signals with the amount of time delay inserted. For example, the print system  304   1  may receive one of the real-time sideband signals with the respective amount of time delay to eject the fluid or ink onto the media  106 . The inserted amount of time delay may allow the fluid ejection device  202   1  to operate based on the real-time sideband signal at the same time that the fluid ejection device  202   2  operates based on the real-time based sideband signal. 
     The timing system  302   1  may also transmit the other real-time sideband signals through the SERDES  310   1  and the optical/wired connection  312   1 . The SERDES  310   1  may serialize a plurality of real-time sideband signals into a serial signal that can be transmitted to other fluid ejection devices via the optical/wired connection  312   1 . For example, if there were two additional fluid ejection devices  202 , then the SERDES  310   1  may serialize the two real-time sideband signals addressed to the two additional fluid ejection devices  202 . The optical/wired connection  312   1  allows the real-time sideband signals to be transmitted faster than using other types of physical cabling. 
     The real-time sideband signal with the amount of time delay inserted may be received by the optical/wired connection  312   2  and deserialized (if necessary) by the SERDES  310   2 . The timing system  302   2  may receive the respective real-time sideband signal with the amount time delay and transmit the real-time sideband signal to the print system  304   2  of the fluid ejection device  202   2 . As a result, the print system  304   1  and the print system  304   2  may receive the real-time sideband signals at the correct time to print on the media  106  with a correct alignment. For example, if there is a respective amount of time delay associated with the fluid ejection device  202   2 , then the print system  304   2  may receive the real-time sideband signal with the respective amount of time delay that is inserted. 
       FIG. 4  illustrates an example block diagram of the timing system  302 . In one implementation, the timing system  302  may include a bus  402 , a plurality of computation printer circuit assemblies (PCA)  404   1 - 404   n  (hereinafter referred to individually as computation PCA  404  or collectively as computation PCAs  404 ) and a plurality of rear transition modules (RTMs)  406   1 - 406   n  (hereinafter referred to individually as RTM  406  or collectively as RTMs  406 ). 
     In one example, each computation PCA  404  may be responsible for calculating the print parameters and generating a sideband signal to print on a predetermined width of an image associated with a respective computation PCA  404 . For example, each computation PCA  404  may be responsible for printing on a different predetermined width of the media  106 . Thus, if a width of the media  106  is wider than a total width capability of the number of computation PCAs  404  within a fluid ejection device  202 , then additional fluid ejection devices  202  may be added to add additional computation PCAs  404 . The real-time sideband signals for each portion of the image may be generated by the computation PCAs  404   1  to  404   n . The real-time sideband signals may then be transmitted by the respective RTMs  406   1  to  406   n . 
     In one example, each computation PCA  404  may also be responsible for calculating the print parameters and generating a sideband signal to print in a down-web direction as well. For example, each computation PCA  404  may control a different printbar or color, which print at the same part of the width, but one is upstream relative to the other. 
     As noted above, previously, the RTMs  406  were all connected by a daisy chain of physical wires and cabling. As additional PCAs  404  are deployed with additional fluid ejection devices  202 , large parallel buses were added to daisy chain all of the RTMs  406 . However, with the design of the fluid ejection system  102  of the present disclosure, a single optical connection can be used to connect all of the RTMs  406  using a SERDES  310 . 
     In addition, the delay associated with serializing the signals can be compensated for by calculating a respective amount of time delay for each fluid ejection device  202  to receive the real-time sideband signal. The respective amount of time delay can be inserted into the real-time sideband signal that is transmitted to the fluid ejection devices  202 . 
       FIG. 5  illustrates a block diagram of an example configuration  500  of the fluid ejection devices  202  of the present disclosure. In one example, the fluid ejection device  202   1  may also include a link protocol module  314   11  and  314   12  and a time division multiplexing (TDM) module  316   11  and  316   12 . The link protocol module  314   11  and  314   12  and the TDM module  316   11  and  316   12  may be added when more real-time sideband signals are generated or used than the hardware of a fluid ejection device can handle. For example, if a fluid ejection device  202   1  can handle 8 signals, but printing a particular image uses 16 signals, then the additional 8 signals may be time division multiplexed and the link protocol modules  314   11  and  314   12  may switch between the link protocols. 
     In one example, the configuration  500  may be deployed to determine an initial estimate for an amount of time delay. The configuration  500  may include a feedback channel or loopback physical channel  502  that includes an addition optical/wired connection  312   12 , SERDES  310   12 , link protocol module  314   12  and TDM  316   12 . The loopback physical channel  502  may simulate a transmission of the real-time sideband signal to a respective fluid ejection device  202 . For example, if a third fluid ejection device  202  were deployed, the loopback physical channel  502  may include a third stack. 
     The loopback physical channel  502  may provide an estimated time delay to the timing system  302   1  that can be used as the initial time delay to add to the real-time sideband signal for the fluid ejection device  202   2 . The configuration  500  of  FIG. 5  may use additional hardware in adding additional stacks of the loopback physical channel  502 , but may provide faster processing. 
       FIG. 6  illustrates a block diagram of an example configuration  600  of the fluid ejection devices  202  of the present disclosure. In one implementation, the fluid ejection devices  202  are connected such that the real-time sideband signal is forwarded to a last fluid ejection device  202   n . For example, the real-time sideband signal may be forwarded by the middle fluid ejection devices  202  (e.g., the fluid ejection device  202   2 ) via a feed forward timing signal  602  in the link protocol module  314   2 . In another implementation, the feed forward timing signal  602  may be performed at the TDM  316   2  as well. 
     The amount of time delay associated with the last fluid ejection device  202   n  may be forwarded back to the first fluid ejection device  202   1 . The amount of time delay seen by the last fluid ejection device  202   n  may be used as an initial amount of time delay for all of the fluid ejection devices  202   1  to  202   n . 
     In one example, after the initial amount of time delay is used, the amount of time delay may be adjusted based on an analysis by the sensor  204  and the calculations performed by the feedback system  206 . In one example, the amount of time delay may be continuously calculated and inserted into the real-time sideband signals as each line is printed by the fluid ejection system  102  and the fluid ejection devices  202 . 
     As a result, the examples of the present disclosure minimize the number of physical connections in the fluid ejection system  102 . Reducing the number of physical connections can lead to higher system reliability. In addition, the reduction of the number of physical connections allows the design of the present disclosure to scale easily when a larger number of fluid ejection devices  202  are added for wider and wider media  106 . 
       FIG. 7  illustrates a flow diagram of an example method  700  for distributing sideband signals in a fluid ejection system. In one example, the blocks of the method  700  may be performed by the system  100  or the fluid ejection system  102 . 
     At block  702 , the method  700  begins. At block  704 , the method  700  prints a line of an image on a media via a plurality of fluid ejection devices of a fluid ejection system. For example, a plurality of real-time sideband signals may be generated to print each line of an image. The plurality of real-time sideband signals may be used to control each one of the plurality of fluid ejection devices to print each pixel of each line of the image across a width of a media. 
     At block  706 , the method  700  determines a respective amount of time delay for each one of the plurality of fluid ejection devices based on an analysis of the line of the image on the media such that each one of the plurality of fluid ejection devices is correctly aligned when a sideband signal is received. In one example, an optical sensor may be used to determine an amount of offset between pixels printed by two different fluid ejection devices. The optical sensor may measure the amount of offset for each pair of fluid ejection devices. For example, if there are three fluid ejection devices deployed, the optical sensor may measure the amount of offset between the first and second fluid ejection devices and the amount of offset between the second and third fluid ejection devices. 
     The amount of offset may be used by a feedback system to calculate the respective amount of time delay for each one of the plurality of fluid ejection devices. For example, the feedback system may know a speed of the media moving below the fluid ejection devices or a speed of the fluid ejection devices moving over the media. Based on the speed and the amount of offset that is determined by the optical sensor, the feedback system may determine the respective amount of time delay of the sideband signal to reach each fluid ejection device. 
     At block  708 , the method  700  inserts the respective amount of time delay for the each one of the plurality of fluid ejection devices that is determined into the sideband signal for printing a subsequent line of the image on the media. In one example, the feedback system may forward the respective amount of time delay for each fluid ejection device that is calculated to a first timing system. In one example, the first timing system may be associated with a first fluid ejection device (e.g., as illustrated in  FIG. 3 ). The first timing system may then insert the respective amount of time delay into the sideband signals via a delay module and transmit the time delayed sideband signals to the remaining time systems associated with the remaining fluid ejection devices. The delay module may be a programmable delay module and/or a non-programmable delay module. 
     At block  710 , the method  700  transmits the sideband signal to the plurality of fluid ejection devices with the respective amount of time delay. In one implementation, the sideband signal may include a plurality of sideband signals that are serialized and transmitted over a single optical wired connection. The remaining fluid ejection devices may have a respective SERDES that deserializes the sideband signals and uses the respective sideband signal with the respective amount of time delay. The remaining sideband signals may be serialized and forwarded to the next fluid ejection device, and so forth. 
     At block  712 , the method  700  prints the subsequent line of the image on the media via the plurality of fluid ejection devices using the sideband signal with the respective amount of time delay. For example, the subsequent line of the image may be printed with a correct alignment of the fluid ejection devices using the sideband signal with the respective amount of time delay. 
     In one example, the method  700  may use an initial amount of time delay that is estimated. For example, the configuration  500  illustrated in  FIG. 5  or the configuration  600  illustrated in  FIG. 6  may be used to estimate the initial amount of time delay. 
     In one example, the method  700  may be repeated for each subsequent line of the image that is printed until printing of the image is completed on the media. For example, the method  700  may analyze the subsequent line that is printed, determine a respective time delay and print the next line with the respective amount of time delay inserted into the sideband signals, and so forth. At block  714 , the method  700  ends. 
     It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. 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.