Print Resolution Error Detection Using Iterative 1D Hough Transform

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Solution Overview

Problem

Variations in substrate movement speed through a print device cause inconsistencies in document resolution, leading to image quality degradation and errors in edge detection and fiducial marking recognition.

Innovation Solution

Implementing an iterative one-dimensional Hough transform to analyze images with targets at known locations, measuring differences between expected and actual resolution, and using affine transformations to correct errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If iterative 1D Hough transform is used to detect targets and measure resolution, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improveresolution measurement precisionVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the complex 2D Hough transform into multiple simpler 1D Hough transforms. Specifically, it performs 1D Hough transforms along horizontal lines and vertical lines separately to detect target centers, rather than using a single complex 2D transform. This segmentation reduces computational complexity while maintaining measurement precision for resolving print resolution errors.

Inventive Principle:

Principle #1Segmentation

2Productivity

If traditional edge detection methods are used, then processing speed is improved, but measurement precision deteriorates due to resolution variations

Engineering Contradiction:

Improveprocessing speedVSAvoidedge detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from edge-based methods to target-center-based methods using Hough transform. Instead of detecting edges which are sensitive to resolution variations, the system detects the centers of printed targets through iterative 1D Hough transforms. This parameter change makes the measurement more robust to resolution variations while maintaining processing efficiency.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If high resolution scanning is performed to detect fiducial markings, then measurement precision is improved, but use of energy increases

Engineering Contradiction:

Improvefiducial detection accuracyVSAvoidscanning energy consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent performs preliminary resolution measurement and correction using targets printed at known locations before attempting fiducial marking detection. By first measuring the actual print resolution through target analysis and correcting for any deviations, the system enables accurate fiducial detection at the expected resolution rather than requiring high-resolution scanning to compensate for potential errors.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12531951B1Method for resolution error detection in print device using iterative transform

Publication Date: 2026.01.20 XEROX CORP

AI summary

Methods of identifying and measuring resolution error in a print device are disclosed. The methods include processing a scan of a document on which targets are printed at known reference locations. The system identifies and performs a 1D Hough transform process on each of the targets. In the process, the system measures differences between an identified location for each target and an expected location for each target. The system then uses the difference to measure the document's image resolution and estimate resolution error, if any, in the document.