Method for compensating a failing nozzle

Patent metadata

Field	Value
Publication number	US-9302469-B2
Application number	US-201514702257-A
Country	US
Kind code	B2
Filing date	May 1, 2015
Priority date	May 2, 2014
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

A method is provided for compensating a failing nozzle in a printhead comprising a series of print elements with nozzles for operation in an inkjet printing process in which a colorant is applied for locally changing an optical density, thereby printing an image. The method comprises at least two compensation mechanisms, each providing a different amount of additional optical density in the environment of a missing dot in the printed image. A nozzle is recorded as a failing nozzle if the associated print element does not apply an ink dot within predetermined specifications. An environment density is determined in an environment of a missing dot associated with said failing nozzle. The environment density is compared with a predetermined threshold, and an appropriate compensation mechanism is selected from the at least two compensation mechanisms. The method is applied in an inkjet printing system for balancing under- and overcompensated optical density.

First claim

What is claimed is:

1. A method for compensating a failing nozzle in a printhead comprising a series of print elements with nozzles for operation in an inkjet printing process in which a colorant is applied to a receiving medium for locally changing an optical density, thereby printing an image, a nozzle being recorded in a list as a failing nozzle if an associated print element is unable to eject an ink drop within predetermined specifications, the method comprising at least two compensation mechanisms, each providing additional optical density in an environment of a missing dot in the printed image associated with a failing nozzle and comprising the steps of:
a) selecting a failing nozzle from the list of failing nozzles;
b) determining an environment density and a density deficit in an environment of a missing dot associated with said failing nozzle;
c) comparing the environment density with a predetermined threshold, and
d) selecting a compensation mechanism from the at least two compensation mechanisms, based on the result of the comparison, each compensation mechanism adding an amount of colorant to compensate the density deficit,
wherein said at least two compensation mechanisms comprise a first mechanism for transferring a density deficit compensation to a neighbouring print element of a failing nozzle and a second mechanism for transferring a density deficit compensation to corresponding nozzle of a different colorant.

2. The method according to claim 1 , wherein the predetermined threshold is dependent on a failing nozzle identifier.

3. The method according to claim 2 , wherein a dependency of the predetermined threshold on a failing nozzle identifier is established by optically capturing a result of a failing nozzle compensation.

4. The method according to claim 1 , wherein the first mechanism comprises the steps of:
a) inspecting an environment of a missing dot associated with the failing nozzle for a vacant dot position in the image;
b) if a vacant dot position is found, transferring said density deficit compensation to a print element associated with the vacant dot position, and
c) if no vacant dot position is found, transferring said density deficit compensation to several print elements in the environment of a missing dot associated with the failing nozzle.

5. The method according to claim 1 , wherein the method further comprises a step of passing a density deficit, which remains after compensating said failing nozzle, to a next position in the image associated with said failing nozzle.

6. The method according to claim 1 , wherein said amount of colorant to compensate the density deficit is corrected for an amount of overlap between ink drops of various print elements in an environment of a failing nozzle.

7. The method according to claim 1 , wherein a print element is configured to eject ink drops of different volumes, each of the drop volumes resulting in a different local change of optical density of the receiving medium.

8. The method according to claim 1 , wherein the environment density is determined by optically capturing an output of the inkjet printing process.

9. An inkjet printing system, comprising control means that are configured to apply a method for compensating a failing nozzle according to claim 1 .

Assignees

• Oce Tech Bv

Inventors

• De Grijs Eduard T H

Classifications

• B41J2/0451 Primary

  for detecting failure, e.g. clogging, malfunctioning actuator · CPC title

• B41J2/2139 Primary

  Compensation for malfunctioning nozzles creating dot place or dot size errors (generating single droplets or particles on demand by pressure, e.g. electromechanical transducers B41J2/045) · CPC title

• B41J2/2146

  for line print heads · CPC title