Patent Publication Number: US-2022219450-A1

Title: Accurate detection of a print start location

Description:
BACKGROUND 
     Printing devices may apply a print substance to a print media. In some examples, a printing device may apply ink to a paper media. In other examples, the printing device may apply a fluid other than ink to the print media. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various examples will be described below by referring to the following figures. 
         FIG. 1  is a plan view of an example of a printing device and a print guide; 
         FIG. 2  is a cross section elevation view of an example of a printing device and a print guide; 
         FIG. 3  is a plan view of an example of a print guide; 
         FIG. 4  illustrates examples of signals generated by the printing device; 
         FIG. 5  is an example of multi-line sequence printing on a print media; and 
         FIG. 6  is a flow diagram illustrating an example of a method for accurate detection of a print start location. 
     
    
    
     Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations in accordance with the description; however, the description is not limited to the examples and/or implementations provided in the drawings. 
     DETAILED DESCRIPTION 
     A printing device may apply a print substance to a print media. Examples of printing devices include printers, copiers, fax machines, multifunction devices including additional scanning, copying, and finishing functions, all-in-one devices, pad printers to print images on three dimensional objects, and three-dimensional printers (additive manufacturing devices). 
     In some examples, the print substance may include printing agents or colorants. The printing device may apply the print substance to a substrate. A substrate is a superset of print media, such as plain paper, and can include any suitable object or materials to which a print substance from a printing device is applied including materials, such as powdered build materials, for forming three-dimensional articles. In addition, in some examples, a printing device may print on various media such as inanimate objects, skin, books, wood, plastic, metal, concrete, wallpaper, or other materials. Print substances, including printing agents and colorants, are a superset of inks and can include toner, liquid inks, or other suitable marking material that may or may not be mixed with fusing agents, detailing agents, or other materials and can be applied to the substrate. 
     In other examples, the printing device may be a fluid ejection device. For example, the printing device may be used in life-science applications (e.g., lab-on-chip fluidic designs), bio-printing, printed manufacturing features and sensors for additive manufacturing applications. These applications may use a print substance other than ink or toner. 
     Examples of methods to improve image placement by a printing device are described herein. In some examples, the printing device may be a handheld printer. The printing device may include a sensor to detect device movement. In some examples, the printing device may use the sensor to detect a print start marker indicative of the position of the device within a print guide. The sensor may trigger a signal as the printing device advances within the print guide. A distance measurement sensor of the printing device may provide an accurate measure of distance traveled. 
     In some examples, the print guide may include a reference marker to provide a very accurate representation of a print start location to a user. The location of the reference marker may be configured as a known distance from the print start marker sensed by the sensor. The sensor and reference marker may enable edge alignment of print media. The edge alignment may further enable accurate multi-line sequence printing (e.g., stitching) when the user manually sequences multiple print swaths on the print media. 
       FIG. 1  is a plan view of an example of a printing device  102  and a print guide  104 . The printing device  102  may apply a print substance to a print media. 
     In some examples, the printing device  102  may be a handheld printing device. For example, a user may manually move the printing device  102  over a print media. The printing device  102  may measure its movement and may apply a print substance as the user moves the printing device  102 . 
     The print guide  104  may be used to facilitate accurate printing. The print guide  104  may be used to align the printing device  102  to the print media. In some examples, the print guide  104  may constrain movement of the printing device  102  in one direction while allowing movement of the printing device  102  in another direction. In this example, the print guide  104  allows movement of the printing device  102  along an X-axis  120  over a certain distance. The print guide  104  limits movement of the printing device  102  along a Y-axis  122 . 
     In some examples, the printing device  102  may be easily removable from the print guide  104 . For instance, a user may place the printing device  102  within the print guide  104  to print. The user may then lift the printing device  102  out of the print guide  104  after printing. In some examples, the printing device  102  may not be physically attached to the print guide  104 . 
     In some examples, the print guide  104  may include a base  124  upon which the printing device  102  moves. The base  124  of the print guide  104  may have an opening  118  through which the printing device  102  prints on the print media. Therefore, the print guide  104  may be positioned between the printing device  102  and the print media. In some examples, the base  124  may be fabricated from a transparent material to facilitate placement of the print guide  104  on the print media. 
     The printing device  102  may include a marker sensor  106  to detect a print start marker  110  on the print guide  104  as the printing device  102  moves on the print guide  104 . The print start marker  110  may be located on the print guide  104  at a distance before a print start location  112 . As used herein, the print start location  112  is the beginning of a region in which printing may take place. For example, the printing device  102  may print on the print media starting at the print start location  112 . Therefore, the print start location  112  is the starting boundary for printable area. The print start location  112  may also be referred to as a print boundary. 
     It should be noted that the printing device  102  may or may not start printing at the print start location  112 . Rather, the print start location  112  is the place along the X-axis  120  where printing may begin. For example, if the printing device  102  is to print an image, in some cases, the image may start at the print start location  112 . In these cases, the printing device  102  may begin printing at the print start location  112 . In other cases, the image may begin after the print start location  112 . In these cases, the printing device  102  may begin printing after the print start location  112 . As used herein the term “starts printing” includes the printing device  102  beginning to apply a print substance to the print media or the printing device  102  entering a region in which printing could occur based on the content of the print job. 
     The distance traveled by the printing device  102  after sensing the print start marker  110  and before the printing device  102  starts printing is referred to as the print offset distance  116 . The print offset distance  116  may be a configured distance traveled by the printing device  102 . The print offset distance  116  may be a certain distance that the printing device  102  travels in the X-axis  120  before the printing device  102  starts printing. In some examples, the print offset distance  116  may be equal to zero. In other words, in this case, the printing device  102  may start printing immediately upon sensing the print start marker  110 . 
     In some examples, the print offset distance  116  may be related to the position of the marker sensor  106  and a printhead  109  on the printing device  102 . Therefore, the print offset distance  116  may be the distance that the printhead  109  moves after the marker sensor  106  senses the print start marker  110 . For example, if the marker sensor  106  and the printhead  109  are located in different locations along the X-axis  120 , then the print offset distance  116  may be different than a marker offset distance  115 . As used herein, the distance between the print start marker  110  and the print start location  112  may be referred to as a marker offset distance  115 . The marker offset distance  115  may have a configured relationship with the print offset distance  116 . If the marker sensor  106  and the printhead  109  are co-located on the X-axis  120 , then the print offset distance  116  may equal the marker offset distance  115 . 
     In some examples, the print offset distance  116  and/or the print start location  112  may be configurable by a user. For instance, the print offset distance  116  and/or the print start location  112  may be configurable through a user interface. In some approaches, the user interface to configure the print offset distance  116  and/or the print start location  112  may be located on the printing device  102 . In other approaches, the user interface to configure the print offset distance  116  and/or the print start location  112  may be implemented on a remote device (e.g., on an application of a remote computing device). Therefore, the print offset distance  116  and/or the print start location  112  may be adjustable (e.g., may be increased or decreased) by a user through the user interface. 
     In some examples, the marker sensor  106  may be an optical sensor to detect an optical pattern of the print start marker  110 . In these examples, the print start marker  110  may be a visible object or feature on the print guide  104 . For example, the print start marker  110  may be a dark bar, mirror, hole or other feature on the print guide  104  that is detectable by marker sensor  106 . 
     In some examples, the optical marker sensor  106  may be implemented with a light-sensing component (e.g., photoresistor, photodiode, etc.). In some examples, the optical marker sensor  106  may also include a light-emitting component (e.g., light-emitting diode (LED)) to facilitate optical sensing of the print start marker  110 . Other implementations of the optical marker sensor  106  may include an infrared sensor. In other implementations, the optical marker sensor  106  may be an optical through-beam. In yet other implementations, the optical marker sensor  106  may include a camera sensor to capture digital images. 
     The optical marker sensor  106  may detect the print start marker  110  based on changes in the optical signal measured by the marker sensor  106 . For example, the marker sensor  106  may detect light regions of the print guide base  124  as not the print start marker  110 . When the marker sensor  106  detects a dark region on the base  124 , this may be interpreted by the printing device  102  as sensing the print start marker  110 . Therefore, upon sensing a change in optical pattern (e.g., from light to dark or dark to light), the marker sensor  106  may trigger the detection of the print start marker  110 . 
     In other examples, the marker sensor  106  may be a mechanical switch. In this implementation, the print start marker  110  may be a physical structure that actuates the mechanical switch. For example, the print start marker  110  may project from the print guide  104 . As the printing device  102  moves over the print guide  104 , the mechanical switch of the marker sensor  106  may contact the print start marker  110 . This contact may be sensed by the marker sensor  106  to indicate a detection of the print start marker  110 . 
     It should be noted that in the example illustrated in  FIG. 1 , the print start marker  110  is located on the base  124  of the print guide  104 . In other examples, the print start marker  110  may be located on other regions of the print guide  104 . For instance, the print start marker  110  may be located on side walls of the print guide  104 . In this case, the marker sensor  106  may be located on a corresponding side of the printing device  102 . For example, the marker sensor  106  may be located on a vertical side of the printing device  102  to detect a print start marker  110  positioned on the side of the print guide  104 . 
     In some examples, the printing device  102  may include a distance measurement sensor  108  to measure distance traveled by the printing device  102 . The distance measurement sensor  108  may measure the distance traveled by the printing device  102  upon detecting the print start marker  110 . Once the marker sensor  106  senses the print start marker  110 , the distance measurement sensor  108  may trigger a start of printing at the print start location  112 . For example, the distance measurement sensor  108  may trigger a start of printing in response to determining that the printing device has traveled the configured print offset distance  116 . 
     In an example, the printing device  102  may be placed on the print guide  104  such that the marker sensor  106  is positioned before the print start marker  110 . In the example of  FIG. 1 , the printing device  102  may be placed on the left side of the print guide  104 . As the printing device  102  is moved to the right, the marker sensor  106  may sense the print start marker  110 . A signal may be communicated to the distance measurement sensor  108  to measure the distance moved by the printing device  102  when the marker sensor  106  detects the print start marker  110 . When the distance measurement sensor  108  determines that the printing device  102  has moved the configured print offset distance  116 , the distance measurement sensor  108  may trigger the printing device  102  to start printing. 
     In some examples, the distance measurement sensor  108  may be implemented as an encoder. For example, the encoder may be coupled to a wheel or axle of the printing device  102 . In this implementation, the distance measurement sensor  108  may be coupled to a wheel that rotates as the printing device  102  moves. The distance measurement sensor  108  may be calibrated to determine distance based on the rotation of the wheel or axle of the wheel. In other examples, the distance measurement sensor  108  may measure distance using mechanisms other than an encoder. For instance, the distance measurement sensor  108  may be an optical distance measurement sensor that measures distance based on sensed optical signals. In some examples, the marker sensor  106  may also act as the distance measurement sensor  108 . For instance, an optical marker sensor  106  may detect the print start marker  110  and may measure the distance moved by the printing device  102 . 
     The print guide  104  may also include a reference marker  114 . In some examples, the reference marker  114  may be located in relation to the print start location  112  to provide an accurate indication of the print start location  112  to a user. The reference marker  114  may be used to align the print guide  104  on the print media. For example, an edge or location (e.g., center) of the print media may be aligned with the reference marker  114 . 
     In the example of  FIG. 1 , the reference marker  114  is located at the print start location  112 . In other examples, the reference marker  114  may be offset from the print start location  112 . For instance, the reference marker  114  may be offset from the print start location  112  to ensure an unprinted border on the print media. In another example, the reference marker  114  may be located in the center of the print media. In this example, the width of the print media may be used to determine the print start location  112  in relation to the print start marker  110 . In other words, the print offset distance  116  may be configured based on the width of the print media. 
     The reference marker  114  may be painted, machined or formed on the print guide  104 . For example, in one approach, the reference marker  114  may be painted on the print guide  104 . In another approach, the reference marker  114  may be cut or etched into the print guide  104 . In yet another approach, the reference marker  114  may be formed on the print guide  104  during fabrication of the print guide  104 . In this approach, the reference marker  114  may be a recessed channel or raised projection. 
     In some examples, the reference marker  114  may be a line located on the print guide  104 . In this approach, the reference marker  114  may be a line marked on the base  124  to align the print media with the print start location  112 . In other examples, other shapes or patterns may be used for the reference marker  114 . 
     In some examples, the print start marker  110  may be moveable to configure the print start location  112  in relation to the print start marker  110 . For example, the print start marker  110  may be a moveable (e.g., slidable) structure that can be positioned in different locations on the print guide  104 . In this approach, the print offset distance  116  may be reconfigured. In some implementations, the print start marker  110  may be a movable plastic flag that may slide to adjust the print start location  112 . 
     In some examples, the reference marker  114  may be moveable on the print guide  104 . In this approach, the reference marker  114  may be positioned based on print media size and/or print alignment (e.g., left, center, right, etc.). 
     The reference marker  114  may provide the user a very accurate representation of the start of the print. The use of the print start marker  110  in combination with the reference marker  114  improves image placement while using the print guide  104 . 
       FIG. 2  is a cross section elevation view of an example of a printing device  202  and a print guide  204 . The printing device  202  and print guide  204  may be implemented in accordance with the printing device  102  and the print guide  104  described in  FIG. 1 . 
     In this example, the printing device  202  has a maker sensor  206  to detect the print start marker  210  located on the base  224  of the print guide  204 . The maker sensor  206  is oriented on the base of the printing device  202  to sense the print start marker  210 . The print start marker  210  may be located on the print guide  204  at a marker offset distance  215  from the print start location  212 . 
     The printing device  202  may print on the print media (not shown) positioned under the print guide  204 . The printing device  202  may print through the opening  218  of the print guide  204 . 
     In this example, the printing device  202  includes a distance measurement sensor  208  implemented as an encoder wheel. The distance measurement sensor  208  measures the distance traveled by the printing device  202  along the X-axis  220 . Upon sensing the print start marker  210  by the maker sensor  206 , the distance measurement sensor  208  may measure the distance moved by the printing device  202 . The distance measurement sensor  208  may trigger the start of printing at the print start location  212  once the distance measurement sensor  208  determines that the printing device  202  has moved the print offset distance  216 . In this example, the print offset distance  216  is configured as the distance between the printhead  209  and the print start location  212  when the marker sensor  206  detects the print start marker  210 . 
     In some examples, the print guide  204  may also include a reference marker  214 . In some examples, the reference marker  114  may be located in relation to the print start location  212  to provide an accurate indication of the print start location  212  to a user. 
       FIG. 3  is a plan view of an example of a print guide  304 . The print guide  304  may be implemented in accordance with the print guide  104  described in  FIG. 1 . 
     In some examples, the print guide  304  may have a rectangular shape. For instance, the sides of the print guide  304  oriented along the X-axis  320  may be longer than the sides oriented along the Y-axis  322 . 
     In some examples, the print guide  304  may also have a transparent base  324 . For example, the base  324  of the print guide  304  may be fabricated from a transparent material (e.g., plastic, glass, etc.). The transparent base  324  may include an opening  318  to facilitate printing on a print media. The opening  318  may also be rectangular. 
     In some examples, the print guide  304  may have walls  326  surrounding the perimeter of the print guide  304 . For example, the walls  326  may project up from the base  324  of the print guide  304 . In some examples, the walls  326  may be sized and positioned to constrain movement of the printing device  102  in the Y-axis  322  while permitting movement of the printing device  102  in the X-axis  320 . 
     A print start marker  310  may be located on the transparent base  324 . The print start marker  310  may be detectable by a marker sensor  106  of the printing device  102  (not shown) as the printing device  102  moves on the print guide  304 . The print start marker  310  may be used to trigger a start of printing by the printing device  102  at the print start location  312 . 
     The print start marker  310  may be positioned a certain distance  330  from a side wall  326 . For example, the distance  330  to the print start marker  310  may be sufficient to allow placement of a marker sensor  106  of the printing device  102  before the print start marker  310 . In some examples, the print start marker  310  may have a configured marker width  332 . 
     The marker offset distance  315  may be the distance from the print start marker  310  to the print start location  312 . The marker offset distance  315  may be related to the print offset distance  116  used by the printing device  102  to trigger printing. The print start location  312  is the start of the printable area  334  where the printing device  102  may print on the print media. 
     In this example, the marker offset distance  315  starts at the end of the marker width  332 . In other words, the printing device  102  may begin measuring the print offset distance  116  after sensing the end of the print start marker  310 . In other examples, the print offset distance  116  may start at the beginning of the print start marker  310 . 
     The print guide  304  may also include a reference marker  314 . The reference marker  314  may be located in relation to the print start location  312  to provide an accurate indication of the print start location  312  to a user. In some examples, the reference marker  314  may be a line that spans the opening  318 . The reference marker  314  may be used to align the print guide  304  on the print media. In some examples, the reference marker  314  may be offset from the print start location by a reference offset  336 . The reference marker  314  may be oriented on either side of the print start location  312 . For example, the reference marker  314  may be positioned on the print guide  304  based on the print alignment (e.g., left, center, right) of the print media. 
     In some examples, the print guide  304  may also include a print stop marker  327 . The print stop marker  327  may be detectable by the printing device  102  to determine a print stop location  329 . For example, the marker sensor  106  may detect the print stop marker  327 . The print stop marker  327  may be used for an accurate detection of the print stop location  329 . In some examples, the print stop location  329  may be a location where the printing device  102  stops printing. For example, upon detecting the print stop marker  327 , the printing device  102  may continue to print for a certain distance before stopping printing at the print stop location  329 . Therefore, in some examples, the print guide  304  may have two print markers. The print start marker  310  may be used to start the print and the print stop marker  327  may be used to stop the print. 
     Having an accurate print stop location  329  may be helpful for a repeating image with no set end position. For example, without a known print stop location  329 , the user may have to stop the printing device  102  and lift it up. In this scenario, an inaccurate rainbow affect may occur at the end of the print due to the die spacing between cyan, yellow, and magenta. Using the print stop marker  327  to sense an accurate print stop location  329  will allow the printing device  102  to finish the print cleanly before the user lifts the printing device  102 . This would also ensure that the printing device  102  stops printing and does not accidentally print onto the print guide  304 . 
       FIG. 4  illustrates examples of signals generated by the printing device  102 . In this example, the signals are generated as the printing device  102  moves along the print guide  104 . Therefore, the signals correspond to the printing device location  440  on the print guide  104 . 
     When the printing device  102  begins moving, the marker sensor  106  of the printing device  102  does not detect the print start marker  110 . Therefore, the marker sensor signal  442  may be low at the start of printing device movement. The low marker sensor signal  442  indicates that the marker sensor  106  does not detect the print start marker  110 . 
     When the printing device  102  reaches the start  448  of the print start marker  110 , the marker sensor signal  442  goes high. The marker sensor signal  442  may remain high until the end  450  of the print start marker  110 . 
     When the marker sensor signal  442  transitions from high to low, this triggers the distance measurement sensor  108  to begin measuring the distance traveled by the printing device  102 . Therefore, distance measurement activity  444  transitions from low (i.e., OFF) to high (i.e., ON) in response to the sensor signal transition. In this approach, the distance measurement sensor  108  is triggered on the high-to-low transition of the marker sensor signal  442 . In other approaches, the distance measurement sensor  108  may be triggered on the low-to-high transition of the marker sensor signal  442 . 
     When the distance measurement sensor  108  measures that the printing device  102  has moved the print offset distance  416 , the distance measurement sensor  108  determines that the printing device  102  has reached the print start location  412 . The distance measurement sensor  108  may then trigger the printing activity  446  to begin printing. In this example, a high signal for the printing activity  446  indicates that printing by the printing device  102  may occur. 
       FIG. 5  is an example of multi-line sequence printing on a print media  552 . A printing device  502  and print guide  504  may be implemented in accordance with the printing device  102  and print guide  104  described in  FIG. 1 . For example, the printing device  502  may include a marker sensor  506  to detect the print start marker  510  of the print guide  504 . 
     In this example, the print guide  504  includes a first reference marker  514   a  and a second reference marker  514   b  located on both sides of an opening  518 . The reference markers  514   a - b  are implemented as lines. An edge  555  of the print media  552  may be aligned with the reference markers  514   a - b  to achieve an accurate alignment of the start of printing. 
     In this example, multiple sequences of printing may be performed on the same print media  552  to create an image that is larger than a single pass of the printing device  502 . This technique may be referred to as print swaths or stitching. A number of print swaths  554   a - e  may be printed on the print media  552  to create a single image. 
     In this example, the top of the print media  552  may be positioned under the print guide  504  to print the first print swath  554   a . The print media  552  or the print guide  504  (or both) may then be moved to print the second print swath  554   b . This process may be repeated until all of the print swaths  554   a - e  have been printed. The print media  552  may be aligned with the reference markers  514   a - b  for each print swath  554   a . The edges  556  of the print swaths  554   a - e  are depicted as a dash-dot line in  FIG. 5 . 
     The addition of the accurate reference markers  514   a - b  indicating the start of print on the print guide  504  improves the ability of the user to align the edge  555  of the print media  552  while manually sequencing the print swaths  554   a - e.    
       FIG. 6  is a flow diagram illustrating an example of a method  600  for accurate detection of a print start location. The method  600  may be implemented by a printing device  102 . In some examples, the printing device  102  may be a handheld device. The printing device  102  may be positioned on a print guide  104 . The print guide  104  may be physically separate from a print media. 
     The printing device  102  may detect  602  a print start marker  110  on a print guide  104  as the printing device  102  moves on the print guide  104 . For example, the printing device  102  may include a marker sensor  106  to detect  602  the print start marker  110 . The print start marker  110  may be located on the print guide  104  at a distance  116  before a print start location  112 . The print guide  104  may have a reference marker  114  located in relation to the print start location  112  to provide an accurate indication of the print start location  112  to a user. 
     The printing device  102  may measure  604  distance traveled by the printing device  102  after detecting the print start marker  110 . For example, the printing device  102  may include a distance measurement sensor  108  to measure how far the printing device  102  has moved in response to sensing the print start marker  110 . 
     The printing device  102  may trigger  606  a start of printing at the print start location  112 . For example, the printing device  102  may determine that the printing device  102  has travelled a configured print offset distance  116  from the print start marker  110 . The start of printing may be triggered  606  in response to determining that the printing device  102  has travelled the configured print offset distance  116 . In some examples, the print offset distance  116  that the printing device  102  travels after detecting the print start marker  110  and before the start of printing may be configured.