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Title:
OPTICAL PRINTHEAD ALIGNMENT
Document Type and Number:
WIPO Patent Application WO/2021/021144
Kind Code:
A1
Abstract:
An optical printhead alignment system may include an optical alignment platform, a camera, a calibration template, and an adjustment handle. The optical alignment platform may capture an image of an edge of a printhead associated with the alignment of the printhead relative to a pressure roller. The calibration template may facilitate calibration of a camera on the optical alignment platform. The adjustment handle may be selectively rotated to adjust an offset of the printhead relative to the pressure roller until the edge of the printhead captured by the camera is aligned with an alignment reticle on the captured image.

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Inventors:
SHIBATA ALAN (US)
BARRETT SPENCER (US)
GOLOB PHILLIP KEITH (US)
Application Number:
PCT/US2019/044271
Publication Date:
February 04, 2021
Filing Date:
July 31, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HEWLETT PACKARD DEVELOPMENT CO (US)
International Classes:
B41J29/00; B41M5/035
Domestic Patent References:
WO2019071099A12019-04-11
Foreign References:
US6298783B12001-10-09
US20170046603A12017-02-16
US6371591B12002-04-16
EP0978390B12005-09-21
Attorney, Agent or Firm:
FLANAGAN, Justin K. et al. (US)
Download PDF:
Claims:
WHAT IS CLAIMED IS:

1. An optical printhead alignment system, comprising:

an optical alignment platform to secure a printhead of a printer;

a camera to capture an image of an edge of the printhead associated with alignment of the printhead relative to a pressure roller;

a calibration template to calibrate alignment of the camera on the optical alignment platform; and

an adjustment handle to be selectively rotated to adjust an offset of the printhead relative to the pressure roller until the edge of the printhead captured by the camera is aligned with an alignment reticle on the captured image.

2. The alignment system of claim 1 , wherein the optical alignment platform comprises a clamp to:

selectively secure the calibration template for alignment of the camera on the optical alignment platform, and

selectively secure the printhead of the printer for adjustment of the offset of the printhead relative to the pressure roller.

3. The alignment system of claim 2, wherein the optical alignment platform comprises a stowage area to store the calibration template while the clamp is securing the printhead of the printer.

4. The alignment system of claim 1 , further comprising a pressure sensor to measure a pressure signature of the printhead relative to the pressure roller, and wherein the adjustment handle is further selectively rotatable to modify the measured pressure signature to match a target pressure signature.

5. The alignment system of claim 1 , wherein the adjustment handle comprises gearing to provide for fine-tuning of the offset during rotation.

6. The alignment system of claim 1 , wherein the adjustment handle comprises a cam to provide a non-linear adjustment to the offset during rotation.

7. The alignment system of claim 1 , wherein the camera comprises a visible light camera or an infrared camera.

8. The alignment system of claim 1 , wherein the printhead comprises a thermal printhead.

9. The alignment system of claim 1 , wherein the alignment reticle on the captured image comprises a vertical line digitally overlaid on the captured image displayed by an electronic display.

10. A non-transitory computer-readable medium with alignment instructions stored thereon that, when implemented by a processor, cause the processor to:

capture, via a camera, an image of an edge of the printhead associated with alignment of the printhead relative to a pressure roller;

render, for display on an electronic display, the captured image of the edge of the printhead and an alignment reticle; and

indicate a direction for an adjustment tool to be rotated to align the captured edge of the printhead with the alignment reticle.

11. The non-transitory computer-readable medium of claim 10, wherein the alignment instructions, when implemented by the processor, further cause the processor to:

measure, via a pressure sensor, a pressure signature of the printhead relative to the pressure roller, and

indicate an adjustment to be made via the adjustment tool to achieve a target pressure signature.

12. The non-transitory computer-readable medium of claim 10, wherein the alignment instructions, when implemented by the processor, further cause the processor to:

indicate that the printhead would benefit from offset calibration based on an alignment score of a printed media sample.

13. The non-transitory computer-readable medium of claim 10, further comprising calibration instructions that, when implemented by the processor, cause the processor to:

capture, via the camera, an image of an edge of a calibration template secured to the optical alignment platform;

render, for display on an electronic display, the image of the edge of the calibration template relative to a calibration reticle; and

indicate a direction to adjust a position of the camera relative to the optical alignment platform to align the edge of the calibration template with the calibration reticle.

14. A method, comprising:

calibrating, via a calibration template, a calibration alignment of a camera on an optical alignment platform;

securing a printhead to the optical alignment platform;

capturing, via a camera, an image of an edge of the printhead associated with alignment of the printhead relative to a pressure roller; and rotating an adjustment handle to adjust an offset of the printhead relative to the pressure roller until the edge of the printhead, as captured in another image by the camera, is aligned with an alignment reticle.

15. The method of claim 14, further comprising:

rotating the adjustment handle to adjust the offset of the printhead so that a measured pressure signature of the thermal printhead relative to the pressure roller matches a target pressure signature.

Description:
Optical Printhead Alignment

BACKGROUND

[0001] In dye-sublimation printing, an image is created by transferring dye from a ribbon to a medium using heat from a printhead and pressure applied by a pressure roller between the medium and the ribbon. The print quality of the dye sublimation thermal print process corresponds to the alignment accuracy of the thermal printhead and the pressure roller.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Non-limiting and non-exhaustive examples of the disclosure are described with reference to the figures outlined below.

[0003] Figure 1 illustrates a perspective view of an example of an optical alignment platform.

[0004] Figure 2 illustrates a perspective view of an example of a calibration template.

[0005] Figure 3 illustrates an example cross-sectional view of the optical alignment platform.

[0006] Figure 4 illustrates an example adjustment handle of an optical alignment system.

[0007] Figure 5 illustrates an example view of a thermal printhead being aligned with a pressure roller using an optical alignment platform.

[0008] Figure 6 illustrates an example interface of the optical printhead alignment system.

[0009] Figure 7 illustrates an example interface for indicating an adjustment to align a thermal printhead with a pressure roller.

[0010] Figure 8 illustrates an example block diagram of a computing system with various modules to facilitate alignment of a thermal printhead with a pressure roller via an optical alignment system.

[0011] Figure 9 illustrates an example of a flowchart of a method for aligning a thermal printhead. DETAILED DESCRIPTION

[0012] In dye-sublimation thermal printing, an image is created by transferring dye from a ribbon to a medium utilizing heat from a thermal printhead and pressure applied by a pressure roller between the media and the ribbon. The printhead should be appropriately aligned with respect to the pressure roller for the printer to function correctly. A more precise alignment leads to a more precise print.

[0013] An optical alignment system is described herein that facilitates a relatively easy and accurate alignment of a thermal printhead with respect to a pressure roller. The optical alignment system may include an optical alignment platform, a camera, a calibration template, and an adjustment handle. A technician may utilize the calibration template to calibrate the camera on the optical alignment platform. Once the camera on the optical alignment platform is calibrated, an operator may secure a thermal printhead to the optical alignment platform. The optical alignment system may capture an image of an edge of a thermal printhead.

[0014] The edge of the thermal printhead may be displayed on an electronic display along with an alignment reticle. The alignment reticle may be a physical reticle from a lens of the camera that appears on the captured image (e.g., superimposed on the captured image). Alternatively, the alignment reticle may be digitally overlaid onto the captured image of the thermal printhead for display on electronic display. The operator may adjust the location of the thermal printhead relative to the pressure roller by manually moving the thermal printhead (e.g., via an adjustment tool) until a captured image of the edge of the thermal printhead shows the edge aligned with the alignment reticle.

[0015] The examples of the disclosure may be further understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the disclosed examples, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the examples of the systems and methods of the disclosure is not intended to limit the scope of the disclosure, as claimed, but is merely representative of possible examples of the disclosure.

[0016] In some cases, well-known features, structures, or operations are not shown or described in detail. Furthermore, the described features, structures, or operations may be combined in any suitable manner. It is understood that the components of the examples as generally described and illustrated in the figures herein could be arranged and designed in a wide variety of different configurations.

[0017] Figure 1 illustrates a perspective view of an example of an optical alignment platform 100. The optical alignment platform 100 includes a housing 102, a tool nest 104, an alignment pin 106, a clamp 108, and a stowage area 1 10. An operator may use the optical alignment platform 100 to align a printhead with respect to a pressure roller. Alignment of a printhead with respect to a pressure roller may be useful for a wide variety of printer types. For example, a thermal printhead of a thermal printer may be aligned with respect to a pressure roller. A dye-sublimation printhead of a dye-sublimation printer (e.g., a thermal dye-sublimation printhead) may be aligned with respect to a pressure roller. In some example, a pressure roller of a laser printer may be aligned with respect to a laser printhead (e.g., a fuser and/or photoreceptor drum). In other examples, any of a wide variety of pressure rollers for applying pressure to print media may be aligned with respect to any of a wide variety of printheads.

[0018] Prior to aligning a printhead, a technician may utilize a calibration template to calibrate a camera on the optical alignment platform 100. In various examples, the operator aligning the printhead, the technician calibrating the camera, and a user printing with the printer may be a single entity. Alternatively, the technician, the operator, and the user may each be distinct individuals.

[0019] The clamp 108 may selectively secure the calibration template for alignment of the camera on the optical alignment platform 100. The clamp 108 may secure the calibration template and the tool nest 104 to the optical alignment platform 100. Once the camera of the optical alignment system is calibrated, the optical alignment platform 100 may be used to secure a printhead. For example, the tool nest 104 may be utilized to secure the printhead within the housing 102 of the optical alignment platform 100. The alignment pin 106 ensures the printhead is aligned properly within the housing 102. The clamp 108 may further selectively secure the printhead for adjustment of the offset of the printhead relative to a pressure roller. The clamp 108 may secure the printhead and the tool nest 104 to the optical alignment platform 100. The stowage area 1 10 of the optical alignment platform 100 may store the calibration template while the clamp 108 is securing the printhead.

[0020] Figure 2 illustrates a perspective view of an example of a calibration template 200. A technician utilizes the calibration template 200 to calibrate the alignment of the camera on the optical alignment platform. The technician may utilize the calibration template 200 and alignment pins 202a-d to calibrate the camera. The technician may utilize the calibration template 200 to calibrate the camera for alignment of the thermal printhead relative to a pressure roller. The technician may secure the calibration template 200 to the optical alignment platform, and the technician may then press a calibrate button. Pressing the calibration button may cause the camera to capture an image of the edge of the calibration template 200 secured to the optical alignment platform. An electronic display may display the captured image along with an overlaid or superimposed calibration reticle. Based on the image and calibration reticle, the system may indicate to the technician a direction to adjust a position of the camera relative to the optical alignment platform to align the edge of the calibration template 200 with the calibration reticle. In some examples, the calibration reticle may comprise two parallel lines, and calibration is achieved by moving the camera until an edge of the calibration template 200 is between the two parallel lines.

[0021] Figure 3 illustrates a cross-sectional view of an example of an optical alignment platform 300 with an alignment pin 304 on a tool nest 302 to receive a calibration template and/or a printhead. As described herein, a camera may capture an image of the calibration template and/or the printhead. An alignment reticle may be overlaid on the captured image to facilitate the align of the camera during a camera calibration process and/or the printhead with respect to a pressure roller during a printhead calibration process.

[0022] In some examples, the optical alignment platform may further include a pressure sensor to measure a pressure signature of the printhead relative to the pressure roller. An adjustment handle may be selectively rotated to modify the measured pressure signature to match a target pressure signature. In some examples, the pressure sensor may measure the pressure of the printhead relative to the pressure roller multiple times. For example, a pressure sensor may measure the pressure of the printhead relative to the pressure roller while a media sample is printed. In some examples, the target pressure signature is determined based on the score of a printed media sample associated with the pressure of the thermal printhead relative to the pressure roller. The adjustment handle may be selectively rotatable to modify the measured pressure signature to match a target pressure signature.

[0023] Figure 4 illustrates an example adjustment handle 402 paired with a controlling instrument 404 of an optical printhead alignment system 400. The adjustment handle 402 may be paired with a controlling instrument 404, such as a T8 driver, another type of driver, or another mechanism. In some examples, the adjustment handle 402 may include gearing to facilitate fine-tuning of the offset between a printhead and a pressure roller. In some examples, the adjustment handle 402 may include a cam to provide a non-linear adjustment to the offset during rotation. For example, the adjustment handle 402 may be connected to a cam in the shape of an elliptical disk that converts the rotary motion of the adjustment handle into a linear motion that move the printhead relative to the pressure roller. The adjustment handle 402 may be connected to the elliptical disk at an axis of rotation. The distance from the axis of rotation of the elliptical disk to the perimeter of the disk (the radius) may be linear or non-linear with respect to the rotational angle of the elliptical disk. The perimeter of the elliptical disk may contact the printhead itself or a mechanical feature connected to the printhead such that as the elliptical disk is rotated by the adjustment handle 402, the printhead is moved relative to the pressure roller. The offset of the printhead relative to the pressure roller is varied based on which portion of the elliptical disk is in contact with the printhead or mechanical feature connected to the printhead.

[0024] The adjustment handle 402 may be selectively rotated to adjust an offset of the thermal printhead relative to the pressure roller until an edge of the thermal printhead captured by a camera is aligned with an overlaid alignment reticle. The optical alignment system 400 may indicate a direction in which the adjust meant handle 402 should be rotated. For example, an interface may display a right-pointing arrow indicating that an operator should rotate the adjustment handle 402 to the right to align the printhead with the alignment reticle. In some examples, the interface may suggest a number of rotations for the operator to rotate the adjustment handle 402. The operator may rotate the adjustment handle 402 until the printhead is aligned with vertical reticles overlaid on a displayed image of an edge of the printhead.

[0025] Figure 5 illustrates an example view of an optical printhead alignment system 500. The optical printhead alignment system 500 may, in some examples, include a clamp and/or a tool nest 506 to secure a printhead 504, such as a thermal printhead, to the optical alignment platform 502. A camera 514 may capture an image of an edge of the printhead 504 associated with the alignment of the printhead 504 with respect to a pressure roller 508. The camera 514 may, for example, be a visible light camera or an infrared camera.

[0026] In some examples, an electronic display may display the image captured by the camera 514 with the edge of the printhead 504 and an alignment reticle. An interface may indicate to an operator the direction for an adjustment tool to be rotated to align the captured edge of the printhead 504 with the alignment reticle. In some examples, the optical printhead alignment system 500 may measure an offset based on an initial distance between the edge of printhead 504 and the alignment reticle. Based on the measured offset, the optical printhead alignment system 500 may indicate to an operator the direction for an adjustment handle to be rotated to align the captured edge of the printhead 504 with the alignment reticle. Alignment of the printhead 504 with the alignment reticle directly corresponds to the alignment of the printhead 504 with the pressure roller 508. Thus, when the printhead 504 is aligned with the overlaid (or superimposed) alignment reticle, the operator can be confident that the printhead 500 is aligned with respect to the pressure roller 508.

[0027] In some examples, a pressure sensor may be utilized to measure a pressure signature of the printhead 504 relative to the pressure roller 508. The optical printhead alignment system 500 may print multiple media samples to determine a target pressure signature. A printed media sample 512 may receive an alignment score. The alignment score of the printed media sample 512 may be based on the definition, shade, or other defining factors of the content printed on the printed media sample 512. The optical printhead alignment system 500 may indicate to the operator an adjustment to be made via the adjustment handle to achieve the target pressure signature associated with proper alignment of the printhead 504 and the pressure roller 508. [0028] As described herein, a calibration template may be used to calibrate the positioning of the camera 514 on the optical printhead alignment system 500. With a calibration template secured in the optical printhead alignment system 500, the camera 514 may capture an edge of the calibration template. A technician may align the edge of the calibration template captured in the image with an overlaid or superimposed calibration reticle. The calibration reticle may, for example, comprise two parallel lines. In such an example, the positioning of the camera 514 may be adjusted until the captured image of the edge of the calibration template is within the two parallel lines of the calibration reticle. The camera 514 is fully aligned once the edge of the calibration template is aligned with the calibration reticle.

[0029] Figure 6 illustrates an example interface 600 of an optical printhead alignment system. The example interface 600 includes delta 602 and offset 606 displays associated with a left-ribbon side alignment. Additionally, the example interface 600 includes delta 604 and offset displays associated with a right-gear side alignment. Various user interface icons are also available via the example interface 600, including a measure button 610, a pass display 612, a fail display 614, a calibrate button 616, a roller down button 620 a roller up button 622, and an initialize button 618.

[0030] The initialize button 618 may initiate a pressure roller motor home initialization routine. A calibration template may be secured on the optical alignment platform to calibrate a camera. A technician may initiate the calibration process by selecting the calibrate button 616. Once the camera is calibrated, as described herein, an operator may select the measure button 610 to initiate a visual measurement of an alignment offset of a printhead relative to a pressure roller. For instance, the operator may select the measure button 610 to cause the camera to capture an image of and/or measure a distance between an edge of the printhead and an alignment reticle.

[0031] The operator may adjust the offset of the printhead relative to the pressure roller by aligning the edge of the printhead with the alignment reticle. Alignment of the edge of the printhead with the alignment reticle may be associated with a target offset between the thermal printhead and the pressure roller. In some examples, the target offset may be set in a configuration file or specification associated with the particular printhead and/or pressure roller. [0032] The left-ribbon side alignment delta display 602 may display the left-ribbon side distance between the thermal printhead and the alignment reticle. In some examples, if the distance between the thermal printhead and the alignment reticle is not in range of the target offset, the left-ribbon side alignment delta display 602 may display a red color. The right-gear side alignment delta display 604 may display the distance between the thermal printhead and the alignment reticle on the right side of the thermal printhead. In some examples, if the distance between the thermal printhead and the alignment reticle is in range of the target offset, the right-gear side alignment delta display 604 may display a green color. The pass display 612 may display a green color to indicate the printer is within range of the target offset based on the results of the measure button 610. The fail display 614 may display a red color to indicate the printer is outside range of the target offset based on the results of the measure button 610.

[0033] Figure 7 illustrates an example interface 700 for indicating an adjustment to align a printhead with a pressure roller. The interface 700 comprises a right-gear side alignment delta display 702, a direction display 704, a measure button 706, a pass display 708, and a fail display 710. In some examples, the interface 700 may further include a left-ribbon side alignment delta display. An operator may select the measure button 706 to cause an optical printhead alignment system to measure a distance between a printhead and an alignment reticle. The right-gear side alignment delta display 702 may display the difference between the right edge of the printhead and an alignment reticle of the right side of the printhead. In some examples, the left-ribbon side alignment delta display 702 may display the difference between the left edge of the printhead and an alignment reticle of the left side of the printhead.

[0034] In some examples, when the right-gear side alignment delta 702 is within range of a target offset, the pass display 708 may indicate the printhead is aligned. The interface 700 may display the word "PASS,” a green background of the pass display 708, another form of indication, and/or a combination thereof to indicate the printhead is aligned. In some examples, when the right-gear side alignment delta 702 is outside range of a target offset, the interface 700 may display or illuminate the fail display 710 to indicate the printhead is not aligned. For example, the interface 700 may display the word "FAIL," a red background of the fail display 710, another form of indication, and/or a combination thereof to indicate the printhead is not aligned.

[0035] The interface 700 may utilize the direction display 704 to indicate the direction and operator should rotate the adjustment handle to achieve alignment. The optical printhead alignment system may determine the adjustment direction based on the relative locations of the thermal printhead and the pressure roller, as captured in an image by the camera of the optical printhead alignment system.

[0036] Figure 8 illustrates an example block diagram of an example optical printhead alignment system 800 that includes a bus 802 connected to a controller 804 (e.g., microprocessor, Field Programmable Gate Array (FPGA), microcontroller, etc.), a memory 806, a communication interface 808, and a computer-readable storage medium 810. The computer-readable storage medium 810 may include various modules 812-818. In the illustrated example, the modules 812-818 are implemented as instructions to be executed by the controller 804. Flowever, in other examples, the modules 812-818 may be implemented as processor-executable instructions, firmware, hardware, or combinations thereof.

[0037] A location module 814 may determine a location of a printhead relative to a pressure roller. An imaging module 812 may capture, via a camera, an image of an edge of a printhead. The imaging module 812 may instruct the camera to detect the edge of the printhead.

[0038] A visualization module 814 may render the captured image of the edge of the printhead with respect to an alignment reticle. In some instances, the visualization module 814 may digitally overlay alignment reticles on the image of the edge of the printhead. In other examples, the optical path of the camera may include the alignment reticles such that the captured image includes the alignment reticles automatically. For instance, the alignment reticles may be formed on or positioned relative to a lens or a filter of the camera.

[0039] The location module 814 may instruct a camera to detect the location of the printhead. The location module 814 may instruct a camera to capture an image of the printhead. In some examples, the captured image may include an alignment reticle. In some examples, the location module 814 may determine a distance between an edge of the printhead and the alignment reticle.

[0040] The pressure module 816 may determine a pressure signature associated with the printhead and the pressure roller. An operator may adjust an offset of the printhead relative to the pressure roller until a measured pressure signature corresponds to a target pressure signature indicative of proper alignment. An alignment assist module 818 may indicate to an operator a direction for an adjustment tool to be rotated.

[0041] Figure 9 illustrates an example flowchart of a method 900 for aligning a printhead with respect to a pressure roller based on a captured image of the printhead. A technician may utilize a calibration template to calibrate, at 902, a calibration alignment of a camera. Once the camera is calibrated, the technician may remove the calibration template and stow it beneath the optical alignment platform in the stowage area. An operator may secure, at 904, a printhead to the optical alignment platform (e.g., via a clamp). Capture, at 906, an image of an edge of the printhead. The operator may then rotate, at 908, an adjustment handle to adjust the offset of the printhead relative to the pressure roller.

[0042] While specific examples and applications of the disclosure have been illustrated and described, it is understood that the disclosure is not limited to the precise configurations and components disclosed herein. Accordingly, many changes may be made to the details of the above-described examples without departing from the underlying principles of this disclosure consistent with the following claims.