Patent Application
20080198193
1. Field of the Invention
The present invention relates to hand held printers, and, more particularly, to a hand held printer with vertical misalignment correction.
2. Description of the Related Art
A hand held printer, also sometimes referred to as a hand-operated printer, is a printer that mounts a printhead and ink supply, which may be in the form of an ink jet printhead cartridge, wherein the printer itself Is moved relative to the print medium, such as a sheet of paper, to position the printhead relative to the print medium. Thus, unlike a typical desktop printer, the hand held printer does not include a drive mechanism for physically positioning the printhead relative to the print medium, nor does a hand held printer include a media feed system for feeding a sheet of print media.
The hand held printer is typically referred to as a single axis (X-axis) printer. The hand held printer has an optical encoder that is used to provide position data for firing the printhead by sensing the relative motion of the hand held printer relative to the print medium. Thus, such a hand held printer is designed to print a single swath having a height corresponding to the height of the printhead. However, since the vertical spacing between the printhead nozzles of the printhead is relatively small, e.g., 0.04 millimeters, it is difficult for a user to manually maintain the hand held printer along a straight path, and a small shift of the hand held printer in the vertical direction can produce a noticeable detect in the printed image, e.g., in the form of a wavy line of text.
The present invention provides a hand held printer that corrects for vertical misalignment of the hand held printer relative to the print medium.
The terms “first” and “second” preceding an element name, e.g., first buffer nozzle portion, second buffer nozzle portion, etc., are used for identification purposes to distinguish between similar elements, and are not intended to necessarily imply order, nor are the terms “first” and “second” intended to preclude the inclusion of additional similar elements.
Also, as used herein, the terms “horizontal” and “vertical” corresponds to directions within or parallel to the plane of print medium, such as a sheet of paper, unless otherwise specified.
The invention, in one form thereof, is directed to a method for automatically providing vertical misalignment correction in a hand held printer fixedly mounting a printhead having a plurality of ink jetting nozzles arranged in a column. The method includes defining a fixed quantity subset of the plurality of ink jetting nozzles for printing a print swath; defining a reference line corresponding to a desired printing path; assigning print data to the fixed quantity subset of the plurality of ink jetting nozzles for printing the print swath along the desired printing path; determining an amount of vertical deviation of the hand held printer from the reference line as the hand held printer is hand-scanned along the desired printing path; and dynamically shifting a location of the fixed quantity subset within the plurality of ink jetting nozzles to compensate for the amount of vertical deviation as the hand held printer is hand-scanned along the desired printing path.
The invention, in another form thereof, is directed to a method for automatically providing vertical misalignment correction in a hand held printer fixedly mounting a printhead having a plurality of ink jetting nozzles arranged in a column. The method includes segmenting the plurality of ink jetting nozzles to reserve a first buffer nozzle portion and a second buffer nozzle portion that initially are not used in printing a print swath; defining a fixed quantity subset of the plurality of ink jetting nozzles for printing the print swath; defining a reference line corresponding to a desired printing path; assigning print dam to the fixed quantity subset of the plurality of ink jetting nozzles for printing the print swath along the desired printing path; hand-scanning the hand held printer along the desired printing path; determining an amount of vertical deviation of the hand held printer from the reference line as the hand held printer is hand-scanned along the desired printing path; and dynamically shifting a location of the fixed quantity subset into one of the first buffer nozzle portion and the second buffer nozzle portion to compensate for the amount of vertical deviation as the hand held printer is hand-scanned along the desired printing path.
The invention, in another form thereof, is directed to a method for providing vertical misalignment correction in a hand held printer fixedly mounting a printhead having a plurality of ink jetting nozzles arranged in a column. The method includes defining a reference line corresponding to a desired printing path; and displaying an aiming pattern on the display screen to aid a user in keeping the hand held printer on the reference line corresponding to the desired printing path as the hand held printer is hand-scanned along the desired printing path, so as to reduce an amount of vertical deviation of the hand held printer from the reference line as the hand held printer is hand-scanned along the desired printing path.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings and particularly to
Controller 18 includes a processor unit and associated memory, and may be formed as one or more Application Specific Integrated Circuits (ASIC). Controller 18 executes program instructions to perform daw processing and formatting, facilitate device control, and/or facilitate device interaction with respect to a plurality of devices in communication with controller 18. Controller 18 is communicatively coupled to operator panel 20 via communications link 28. Controller 18 is communicatively coupled to I/O device 22 via communications link 30. Controller 18 is communicatively coupled to cartridge receptacle 24 via a communications link 32. Controller 18 is communicatively coupled to position sensor 26 via a communications link 34. As used herein, the term “communications link” generally refers to structure that facilitates electronic communication between components, and may operate using wired or wireless technology.
As shown in
I/O device 22 may be configured in a variety of ways, depending on the source and/or destination of the communicated content. For example, I/O device 22 may be a wired or wireless communication device that provides a communications link to a host computer, or some other intelligent device, that may supply image data for printing by hand held printer 10. Alternatively, I/O device 22 may be a local source of image content, such as for example, a memory card reader and associated memory card.
Cartridge receptacle 24, for example, may be formed in body 12 and configured for receiving and mounting at least one printhead cartridge 42. Cartridge receptacle 24 holds printhead cartridge 42 in a fixed position relative to, i.e., is removably yet fixedly mounted to, hand held printer 10. Printhead cartridge 42 is communicatively coupled to controller 18 via communications link 32. As shown in the example of
Movement of the hand held printer 10 relative to print medium 16 in a travel direction 50, e.g., a horizontal path, results in relative movement of printhead cartridge 42 and printhead 44 with respect to a printing surface of print medium 16. The smooth surface 14 of body 12 contacts print medium 16 to provide the desired spacing between printhead 44 and the printing surface of print medium 16.
In the present embodiment, position sensor 26 is a two-dimensional sensor that collects two-dimensional position data, which, may also sometimes be referred to herein as X-axis data and Y-axis data. Position sensor 26 may be implemented as a charge-coupled device (CCD) of 255×255 pixels having an associated lens 52 positioned on the underside of hand held printer 10, as shown in
Referring now to
As an initial consideration, the print pattern, e.g., print swath height, is shrunk to fit the number of available nozzles in central nozzle portion 56 so that the print pattern does not initially extend into upper nozzle portion 58 or lower nozzle portion 60. Therefore, the optimal number of buffer nozzles may come from usability studies where the size of the print swath height is maximized while handling a majority of vertical alignment errors. In the example having thirty-eight buffer nozzles, leaving 262 nozzles to print the print swath, a shrinkage of the original full pattern (all 300 nozzles) is of only 13 percent. For a fixed number of buffer nozzles, the print patterns may be rescaled and pre-formatted to reflect the number of available nozzles.
Besides setting the amount of buffer nozzles based on usability, the number of buffer nozzles may also either he set by the user or calculated from a specific user's tracking ability. In the first case, there might be a default number of buffer nozzles that can be changed through user preferences. The print pattern would shrink or expand depending on the number of available nozzles. Likewise, controller 18 may monitor the vertical misdirection of hand held printer 10 by the user and reduce the number of buffered nozzles for a next print swath based on better performance by the user.
At step S100, a fixed quantity subset of the plurality of nozzles is defined for printing a print swath.
Referring to
The fixed quantity subset 62 defines a print swath height, i.e., image height, 64, and the region traced by the fixed quantity subset 62 is a print swath, e.g., print swath 66. Continuing the example from above, the fixed quantity subset 62 of the plurality of ink jetting nozzles 48 will contain less than 300 nozzles, such as for example, 262 nozzles. Thus, in this example, as illustrated in
At step S102, a reference line is defined that corresponds to a desired printing path.
Referring to
In orientating reference line 68, it may be assumed that hand held printer 10 is oriented correctly at the onset of initializing printing, e.g., pressing the PRINT button. As an alternative, a reference trajectory based on some finite small distance from the print start position may be used. A further implementation may be to create a reference pattern based on a running average of the direction of travel. Still another alternative may he for the user to dictate the orientation of reference line 68, e.g., as a horizontal reference line, through an initial movement of hand held printer 10.
At step S104, print data, which may be received via I/O device 22, is assigned to the fixed quantity subset 62 of the plurality of ink jetting nozzles 48 for printing the print swath 66 along the desired printing path 70.
At step S106, hand held printer 10 is moved along the desired printing path 70. However, it may be difficult for a user to manually keep printhead 44 in the proper vertical orientation with respect to reference line 68, and in turn the desired printing path 70.
In
At step S108, an amount of vertical deviation 74 of the hand held printer 10 from the reference line 68 is determined as the hand held printer is hand-scanned along the desired printing path 70. The amount of vertical deviation 74 is determined from the Y-axis data supplied to controller 18 from position sensor 26. Sampling of the Y-axis data may occur, for example, at a predefined frequency, e.g., one kilohertz, and may he triggered by horizontal travel in travel direction 50 of a predetermined distance, e.g., 0.5 millimeters.
At step S110, a location of the fixed quantity subset 62 within the plurality of nozzles 48 is dynamically shifted to compensate for the amount of vertical deviation 74 as the hand held printer 10 is hand-scanned along the desired printing path 70. In particular, the fixed quantity subset 62 of said plurality of ink jetting nozzles 48 is shifted from being located entirely in central nozzle portion 56 into one of upper buffer nozzle portion 58 or lower buffer nozzle portion 60 based the vertical direction of vertical deviation 74 of hand held printer 10 from reference line 68.
For example, consider that the region above the reference line 68 is positive (+) and a region below the reference line 68 is negative (−). A positive (+) vertical deviation 74 results in a vertical shift of the fixed quantity subset 62 of the plurality of ink jetting nozzles 48 into lower buffer nozzle portion 60 by an amount of the magnitude of vertical deviation 74, so as to keep print swath 66 being printed by hand held printer 10 horizontally aligned with respect to reference line 68, and in turn, so as to maintain print swath 66 on the desired printing path 70.
Likewise, a negative (−) vertical deviation 74 results in a vertical shift of the fixed quantity subset 62 of the plurality of ink jetting nozzles 48 into upper buffer nozzle portion 58 by an amount of the magnitude of vertical deviation 74, so as to keep print swath 66 being printed by hand held printer 10 horizontally aligned with respect to reference line 68, and in turn, so as to maintain print swath 66 on the desired printing path 70.
Hand held printer 10 has functionality to individually address nozzle firing of each of the plurality of ink jetting nozzles 48, which facilitates controller 18 in being able to shift the fixed quantity subset 62, i.e., the firing nozzles, of the plurality of ink jetting nozzles 48 in real time. Alternatively, the shifting may be effected, for example, by shifting the firing nozzles in the formatter function of controller 18. As another alternative, an external multiplexer component under the control of controller 18 may act as external switcher and shift the fixed quantity subset 62, i.e., the firing nozzles, of the plurality of ink jetting nozzles 48.
There may be eases where the amount of magnitude of vertical deviation 74 becomes greater than the height of upper buffer nozzle portion 58 or the height of lower buffer nozzle portion 60. In this event, one possibility is just to continue printing even though vertical misalignment correction can no longer be achieved. Another possibility is to truncate the image data being printed, so the nozzles continue to shift, but not all the image gets printed. In the case of multi-swath printing, for example, controller 18 of hand held printer 10 may attempt try to quickly load slices of data from a different horizontal row of pixels, and in the extreme case, vertical misalignment correction loads the data for the next horizontal print swath. In other words, the swath of data tries to catch up with the printer's vertical registration, since shifting firing nozzles will no longer work.
Supplemental to the method described above, as shown in the flowchart of
At step S200, an aiming pattern 76 is displayed on display screen 40 to aid a user in keeping hand held printer 10 on reference line 68 corresponding to the desired printing path 70 as hand held printer 10 is hand-scanned along desired printing path 70. Aiming pattern 76 may include, for example, an aiming dot 78 and a representation 80 of reference line 68.
At step S202, a message 82 is displayed on display screen 40 prompting the user to keep the aiming dot 78 in vertical alignment with representation 80 of reference line 68. In the present example, message 82 reads, “FOR BEST RESULTS KEEP DOT ON LINE”.
Aiming dot 78 slides up and down on display screen 40 showing to the user the proper vertical direction of hand held printer 10. Accordingly, the user has some idea how straight hand held printer 10 is moving across the print medium 16. Even though the concept is to correct for vertical misalignment, there is a point that hand held printer 10 runs out of buffered nozzles, e.g., upper buffer nozzle portion 58 or lower buffer nozzle portion 60, and the printed image prints crocked, unless that is the desired effect. The method of
The method of
While this invention has been described with respect to embodiments of the invention, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
