# US 2014/0196623 A1 · Reducing print quality defects

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- Number: US 2014/0196623 A1
- Document ID: US20140196623A1
- Status: Published application
- Kind: A1
- Application number: 13/741,861
- Filed: 2013-01-15
- Published: 2014-07-17
- Earliest claimed: 2013-01-15
- Assignees: Hewlett-Packard Development Company, L.P.
- Applicants: Hewlett-Packard Development Company, L.P.
- Inventors: Matthew G. Lopez; Roya S. Akhanvalin; James M. Pingel; David F. Chiu
- Web page: https://patentgrep.com/patent/US20140196623A1

## CPC

- B41J 19/147: {Colour shift prevention}
- B41F 31/02: Ducts, containers, supply or metering devices
- G03G 15/10: using a liquid developer
- G03G 15/11: Removing excess liquid developer, e.g. by heat
- H04N 19/00: Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- G03G 2215/00569: Calibration, test runs, test prints
- B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41F: PRINTING MACHINES OR PRESSES (manifolding devices or office printing machines B41L)
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Reducing print quality defects can include printing a pattern with an offset printing device having a binary ink developer roller, determining a variation for a hue shift of the printed pattern; and varying gain in a feedback loop of a servo motor coupled to the binary ink developer roller to reduce the variation.

## Claims

### Claim 1

A method for reducing print quality defects comprising:
printing a pattern with an offset printing device having a binary ink developer roller;
determining a variation for a hue shift of the printed pattern; and
varying gain in a feedback loop of a servo motor coupled to the binary ink developer roller to reduce the variation.

### Claim 2 (depends on 1)

The method of claim 1, wherein varying gain in the feedback loop of the servo motor includes reducing gain in the feedback loop of the servo motor.

### Claim 3 (depends on 1)

The method of claim 1, wherein varying gain in the feedback loop of the servo motor includes increasing gain in the feedback loop of the servo motor.

### Claim 4 (depends on 1)

The method of claim 1, wherein determining the variation for the hue shift includes determining a standard variation for the hue shift of the printed pattern.

### Claim 5 (depends on 1)

The method of claim 1, including determining a variation for a density shift of the printed pattern.

### Claim 6 (depends on 5)

The method of claim 5, wherein determining the variation for the density shift includes determining a standard deviation for a density shift of the printed pattern.

### Claim 7

A non-transitory computer-readable medium storing a set of instructions executable by a processor to cause a computer to
print a pattern with an offset printing device having a binary ink developer roller;
determine a standard deviation for a density shift of the printed pattern; and
vary gain in a feedback loop of a servo motor coupled to the binary ink developer roller to reduce the standard deviation.

### Claim 8 (depends on 7)

The medium of claim 7, wherein the instructions executable by a processor include instructions to scan the printed pattern with the offset printing device.

### Claim 9 (depends on 7)

The medium of claim 7, wherein the standard deviation for a density shift is associated with black ink.

### Claim 10 (depends on 7)

The medium of claim 7, wherein the instructions executable by the processor include instructions to vary proportional gain in the feedback loop of the servo motor coupled to the binary ink developer roller to reduce the standard deviation.

### Claim 11 (depends on 7)

The medium of claim 7, wherein the instructions executable by the processor include instructions to vary integral gain in the feedback loop of the servo motor coupled to the binary ink developer roller to reduce the standard deviation.

### Claim 12 (depends on 7)

The medium of claim 7, wherein the instructions executable by the processor include instructions to vary proportional gain and integral gain in the feedback loop of the servo motor coupled to the binary ink developer roller to reduce the standard deviation.

### Claim 13

A system for reducing print quality defects, the system comprising a processing resource in communication with a memory resource, wherein the memory resource includes a set of instructions and wherein the processing resource is designed to carry out the set of instructions to:
print a pattern with an offset printing device having a plurality of binary ink developer rollers;
determine a standard deviation for a hue shift of the printed pattern;
determine a standard deviation for a density shift of the printed pattern;
vary gain in a feedback loop of a servo motor coupled to a first of the plurality of binary ink developer rollers to reduce the standard deviation for the hue shift; and
vary gain in a feedback loop of a servo motor coupled to a second of the plurality of binary ink developer rollers to reduce the standard deviation for the density shift.

### Claim 14 (depends on 13)

The system of claim 13, wherein the processing resource is designed to vary a variable of integration in the feedback loop of the servo motor coupled to the first of the plurality of binary ink developer rollers to reduce the standard deviation for the hue shift

### Claim 15 (depends on 13)

The system of claim 13, wherein the processing resource is designed to vary a variable of integration in a feedback loop of a servo motor coupled to the second of the plurality of binary ink developer rollers to reduce the standard deviation for the density shift.