Ejection control using imager

1. A printing system, comprising:

a substrate support to move a substrate in a scan direction;

a printhead assembly positioned facing the substrate support, the printhead assembly comprising:

a plurality of dispensing nozzles extending in an ejection direction towards the substrate support; and

a plurality of fiducial marks; and

an imager, the printhead assembly and imager being relatively movable, and the imager oriented in a direction opposite to the ejection direction for capturing an image including the plurality of fiducial marks indicating positions of the plurality of dispensing nozzles in the printhead assembly,

wherein

the printhead assembly is movable in a cross-scan direction relative to the imager and the substrate support, and positionable in an imaging field of the imager to enable the imager to capture the image while the printhead assembly is passing by the imager, and

the imager is a line scan imager that has a plurality of image sensors in a linear arrangement along the scan direction transverse to the cross-scan direction.

2. The printing system of claim 1 , further comprising:

a controller to

map the positions of the plurality of dispensing nozzles in the printhead assembly to corresponding positions in a frame of reference of the printing system, and

control ejection of print material from the plurality of dispensing nozzles based on the mapped positions of the plurality of dispensing nozzles in the frame of reference of the printing system.

3. The printing system of claim 2 , wherein

the controller

detects, from the image captured by the imager,

the plurality of fiducial marks, and

a dispensing nozzle of the plurality of dispensing nozzles, and

determines the positions of the plurality of dispensing nozzles in the printhead assembly, based on

the detected plurality of fiducial marks, and

the detected dispensing nozzle.

4. The printing system of claim 1 , wherein

the printhead assembly further comprises a plurality of printheads, each printhead having a plurality of printhead marks having predetermined positions relative to the plurality of dispensing nozzles, and

the printing system further comprises a controller to

detect, from the image captured by the imager,

the plurality of fiducial marks, and

the plurality of printhead marks, and

determine the positions of the plurality of dispensing nozzles in the printhead assembly, based on

the detected plurality of fiducial marks,

the detected plurality of printhead marks, and

the predetermined positions of the plurality of printhead marks relative to the plurality of dispensing nozzles.

5. The printing system of claim 1 , wherein

the imager is fixed to be stationary relative to the substrate support.

6. The printing system of claim 5 , wherein

the plurality of dispensing nozzles are arranged in at least one row along the cross-scan direction.

7. The printing system of claim 6 , further comprising:

a controller to control the line scan imager to capture the image to include all of the plurality of dispensing nozzles in a single pass of the printhead assembly in the cross-scan direction by the line scan imager.

8. The printing system of claim 1 , wherein

the imager is movable, in a swing motion, relative to the substrate support.

9. A printing method, comprising:

capturing, by an imager, an image of a plurality of marks of a printhead assembly;

detecting the plurality of marks in the image captured by the imager;

determining positions of a plurality of dispensing nozzles in the printhead assembly, based on the detected plurality of marks; and

ejecting print material from the plurality of dispensing nozzles onto a substrate while moving the substrate relative to the printhead assembly, based on the detected positions of the plurality of dispensing nozzles,

wherein

the printhead assembly comprises:

a housing having the plurality of marks, and

a plurality of printheads removably attached to the housing,

each of the plurality of printheads comprises:

a corresponding set of dispensing nozzles among the plurality of dispensing nozzles in the printhead assembly, and

a printhead mark having a predetermined position relative to the corresponding set of dispensing nozzles,

the method further comprises detecting, from the image captured by the imager, the printhead marks of the plurality of printheads, and

said determining the positions of the plurality of dispensing nozzles in the printhead assembly is performed based on

the detected plurality of marks of the housing,

the detected printhead marks of the plurality of printheads, and

the predetermined positions of each of the printhead marks relative to the corresponding set of dispensing nozzles.

10. The printing method of claim 9 , further comprising:

mapping the determined positions of the plurality of dispensing nozzles in the printhead assembly to corresponding positions in a frame of reference,

wherein said ejecting print material from the plurality of dispensing nozzles is performed based on the mapped positions of the plurality of dispensing nozzles in the frame of reference.

11. The printing method of claim 9 , further comprising:

detecting, from the image captured by the imager, a dispensing nozzle of the plurality of dispensing nozzles,

wherein said determining the positions of the plurality of dispensing nozzles in the printhead assembly is performed based on

the detected plurality of marks, and

the detected dispensing nozzle.

12. The printing method of claim 9 , wherein

said capturing the at least one image is performed while the printhead assembly is moved in a cross-scan direction to pass by the imager.

13. The printing method of claim 12 , wherein

the imager is a line scan imager that has a plurality of image sensors arranged in a single line along a scan direction transverse to the cross-scan direction,

the plurality of dispensing nozzles is arranged in at least one row along the cross-scan direction, and

the image is captured by the line scan imager in a single pass of the printhead assembly by the line scan imager.

14. A printing system, comprising:

a substrate support;

a printhead assembly positioned facing the substrate support, the printhead assembly comprising:

a printhead having a plurality of dispensing nozzles extending in an ejection direction towards the substrate support;

a housing; and

a plurality of fiducial marks on the housing;

an imager movable relative to the printhead assembly and oriented in a direction opposite to the ejection direction for capturing an image including the plurality of fiducial marks indicating positions of the plurality of dispensing nozzles in the printhead assembly; and

a controller to control ejection of print material from the plurality of dispensing nozzles on the substrate, based on the first image,

wherein

the printhead assembly is movable in a cross-scan direction relative to the imager and the substrate support, and positionable in an imaging field of the imager, and

the imager has a plurality of image sensors arranged along a scan direction transverse to the cross-scan direction to enable the imager to image all of the plurality of dispensing nozzles in a single pass of the printhead assembly in the cross-scan direction across the imaging field of the imager.

15. The printing system of claim 14 , wherein the imager is a first imager, the image is a first image, the fiducial marks are first fiducial marks, and the printing system further comprises:

a second imager movable relative to the substrate support and oriented in a direction toward the substrate support for capturing a second image of a substrate on the substrate support,

wherein the controller

detects, from the second image captured by the second imager, a plurality of second fiducial marks indicating a print region of the substrate,

maps positions of the print region as indicated by the detected plurality of second fiducial marks to corresponding positions in a frame of reference of the printing system,

maps the positions of the plurality of dispensing nozzles in the printhead assembly to corresponding positions in the frame of reference of the printing system, and

controls the ejection of print material from the plurality of dispensing nozzles onto a substrate, based on the mapped positions of the plurality of dispensing nozzles and the print region in the frame of reference of the printing system.

16. The printing system of claim 15 , wherein

the plurality of image sensors of the first imager are arranged, along the scan direction, over a whole width of an area in which all of the plurality of dispensing nozzles are arranged, and

the substrate support moves a substrate under the second imager, in the scan direction transverse to the cross-scan direction, to enable the second imager to capture the second image while the substrate is passing under the second imager.

17. The printing system of claim 14 , wherein the controller

detects, from the image captured by the imager,

the plurality of fiducial marks, and

a dispensing nozzle of the plurality of dispensing nozzles, and

determines the positions of the plurality of dispensing nozzles in the printhead assembly, based on

the detected plurality of fiducial marks, and

the detected dispensing nozzle.

18. The printing system of claim 14 , wherein the fiducial marks are first fiducial marks, and

the printhead assembly further comprises a plurality of third fiducial marks having predetermined positions relative to the plurality of dispensing nozzles, and

the controller

detects, from the image captured by the imager,

the plurality of first fiducial marks, and

the plurality of third fiducial marks, and

determines the positions of the plurality of dispensing nozzles in the printhead assembly, based on

the detected plurality of first fiducial marks,

the detected plurality of third fiducial marks, and

the predetermined positions of the plurality of third fiducial marks relative to the plurality of dispensing nozzles.

19. The printing system of claim 14 , wherein

the imager is fixed to be stationary relative to the substrate support.

20. The printing system of claim 14 , wherein the imager is movable, in a swing motion, relative to the substrate support.