Bidirectional Print Alignment via Vernier Test Patterns

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Solution Overview

Problem

Bidirectional scanning print systems face misalignment issues due to variables like substrate thickness and scanning speed, leading to inaccurate ink dot placement and image artifacts.

Innovation Solution

A print alignment test pattern using a Vernier scale is printed in both directions, allowing for the calculation of misalignment and subsequent calibration of the printhead to ensure accurate ink dot placement by shifting print data in the scanning directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If bidirectional scanning is used to increase printing productivity, then printing speed and efficiency are improved, but misalignment between swathes printed in opposite directions occurs due to variables like substrate thickness and scanning speed

Engineering Contradiction:

Improveprinting speedVSAvoiddot placement accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The system performs preliminary calibration by printing test patterns in both scanning directions before actual printing. The calibration data obtained from these test patterns is stored and used to pre-correct positioning errors, allowing the system to compensate for misalignment issues during high-speed bidirectional scanning without sacrificing productivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements a feedback mechanism where test patterns are printed, their alignment is measured and analyzed, and the results are used to adjust and optimize the printing parameters. This closed-loop feedback enables continuous improvement of dot placement accuracy while maintaining high printing speeds through bidirectional scanning.

Inventive Principle:

Principle #23Feedback

2Device complexity

If calibration procedures are simplified to reduce device complexity, then ease of operation is improved, but additional test procedures and calibration steps may be required to ensure alignment accuracy

Engineering Contradiction:

Improvecalibration procedure complexityVSAvoidcalibration time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The system merges the calibration functionality into the main printing operation by using the same print mechanism and media path. The test patterns are printed using the bidirectional scanning print mechanism itself, combining the calibration function with the existing printing infrastructure, which reduces overall system complexity while maintaining calibration effectiveness.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The print mechanism serves multiple functions: it performs both regular printing operations and calibration test pattern printing. The same printhead, scanning system, and media transport mechanism are used for both productive printing and alignment verification, eliminating the need for separate dedicated calibration hardware and reducing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9533513B1Print alignment in a bidirectional scanning print system

Publication Date: 2017.01.03 HEWLETT PACKARD DEVELOPMENT COMPANY LP

AI summary

A system, method and non-transitory computer readable medium for testing the alignment of a bidirectional scanning print system are described. A first swathe is printed in first direction, and a second swathe is printed after the first in a second direction along a print axis. Each swathe comprises a plurality of printed blocks aligned along the print axis, separated by unprinted bars. Misalignment in the print system can be identified from the print output.