Line Sensor Image Correction for Skew and Misalignment
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Solution Overview
Problem
Image reading apparatuses using multiple line image sensors face errors in connecting processed data due to mechanical misalignment and varying document conveyance speeds, leading to inaccuracies in image alignment and skew during document conveyance.
Innovation Solution
An image reading apparatus with a conveyance unit, calculation unit, and adjusting unit that calculates and adjusts correction values based on read data from a chart with dot patterns to correct deviations in line image sensor alignment and document conveyance, ensuring accurate image connection regardless of skew during conveyance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multiple line image sensors are used to reduce cost, then manufacturing cost is reduced, but connecting accuracy deteriorates due to mechanical misalignment
Solution Approach 1:
The patent replaces mechanical alignment methods with image processing techniques. By capturing images of a specific pattern (such as a grid or calibration target) and using software algorithms to calculate and correct positional deviations, the system achieves high connecting accuracy without requiring precise mechanical assembly of multiple line image sensors. This substitution of mechanical precision with computational correction resolves the contradiction between cost-effective multi-sensor design and accurate image connection.
2Productivity
If document conveyance speed is increased to improve productivity, then reading speed is improved, but connecting accuracy deteriorates due to speed variations
Solution Approach 1:
The patent employs feedback mechanisms where the system continuously monitors the actual conveyance speed and position of the document during scanning. By comparing the expected position (based on commanded speed) with the actual position (detected via markers or reference patterns), the system calculates speed variations and applies real-time corrections to the image data. This feedback loop enables high-speed document conveyance while maintaining accurate connecting processing between multiple line image sensors.
3Manufacturing precision
If calibration is performed to correct misalignment, then connecting accuracy is improved, but processing time is increased
Solution Approach 1:
The patent performs calibration by capturing images of a specific pattern (such as a grid or calibration target) and calculating correction values in advance. These correction values are stored and applied during normal operation, allowing the system to achieve high connecting accuracy without performing time-consuming calibration calculations during each scanning task. The preliminary calibration action separates the accuracy-critical computation from the time-critical scanning operation.
4Manufacturing precision
If document conveyance position is detected to correct speed variations, then connecting accuracy is improved, but device complexity is increased
Solution Approach 1:
The patent introduces an intermediary element (such as a calibration target with specific patterns or markers on the document) that facilitates position and speed detection. Instead of requiring complex direct measurement systems, the intermediary pattern serves as a reference that simplifies the detection process. The system captures images of this intermediary and uses its known geometry to calculate conveyance position and speed variations, thereby achieving accurate correction with reduced system complexity.
Data Source
AI summary
An object of the present disclosure is to implement highly accurate image connecting processing between line sensors. One embodiment of the present invention is an image reading apparatus having: a plurality of line image sensors arrayed in a first direction; a conveyance unit configured to convey a document in a second direction intersecting with the first direction; a calculation unit configured to calculate a correction value for correcting a deviation at the time of connecting image data obtained by each of the plurality of line image sensors based on read data obtained by reading a chart with the plurality of line image sensors, on which a plurality of dot patterns is printed and which is conveyed by the conveyance unit; a measurement unit configured to measure an amount of conveyance in the first direction in a case where the document is conveyed in the second direction by the conveyance unit.