Document Feeder Image Mapping to Correct Scan Distortion

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Solution Overview

Problem

Scanners with document feeders experience image distortion due to changes in document transportation state during scanning, such as slippage and rotation, which existing techniques fail to adequately correct.

Innovation Solution

An image forming apparatus with a controller that generates and corrects document images by specifying a mapping function correlating document and image coordinates, transforming the image to account for changes in transportation state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a document is transported by a document feeder during scanning, then scanning efficiency is improved, but image distortion occurs due to slippage and changes in transportation state

Engineering Contradiction:

Improvescanning efficiencyVSAvoidimage accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces mechanical correction methods with a computational approach. Instead of using complex mechanical systems to physically correct document position during scanning, the invention uses image processing algorithms to detect document boundaries and apply geometric transformations (affine transformations) to correct distortion in the scanned image, thereby maintaining scanning efficiency while improving image accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the parameters of the scanned image through affine transformation based on detected document boundary parameters. By calculating transformation parameters from the detected quadrangle vertices and applying these parameters to correct the image geometry, the system maintains high scanning speed while achieving accurate document reproduction

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If existing distortion correction techniques are applied to scanned images, then some distortion is reduced, but original content areas are lost due to aggressive transformation

Engineering Contradiction:

Improvedistortion correctionVSAvoidoriginal content

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent applies partial correction by focusing only on the essential affine transformation needed to correct document skew and perspective distortion, rather than applying excessive correction that would crop or distort content areas. The method transforms the image based on detected boundary parameters while preserving the original content within the transformed boundaries

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent creates an accurate copy of the original document by detecting its boundary and applying transformation only to restore the correct geometry. The method preserves the original content by mapping it to the correct position in the output image, ensuring that no content is lost during the correction process

Inventive Principle:

Principle #26Copying

Data Source

PatentUS20250247485A1Image forming apparatus and method for controlling image forming apparatus

Publication Date: 2025.07.31 SHARP KK

AI summary

An image forming apparatus includes one or more controllers; an image inputter that optically reads a document; and a document transporter that transports the document, wherein the one or more controllers generate a document image obtained by creating an image of the document after the image inputter reads the document while the document transporter transports the document, specify a mapping function correlating each coordinate of the document with each coordinate of the generated document image, and correct a distortion of the document image by transforming the document image for the mapping function.