Image Sensor Displacement Calibration in Large Format Scanners
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Solution Overview
Problem
Large format optical scanners face challenges in calibration due to stress-induced movements and uncertainties in motor operations, leading to artefacts in scanned images, as existing methods have limited ability to compensate for variations between image sensors.
Innovation Solution
A method that correlates two-dimensional images from overlapping and non-overlapping areas of two image sensors to determine displacement, allowing for real-time calibration of large format scanners without manual procedures, using sub-images and correlation algorithms to improve precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manual calibration procedures are used to adjust image sensor positioning, then manufacturing precision can be improved, but device complexity and time consumption increase
Solution Approach 1:
The system performs self-calibration by automatically detecting displacement between image sensors through correlation of overlapping image regions. The calibration process is executed autonomously by the scanner itself during normal operation, eliminating the need for external manual calibration procedures while maintaining high positioning precision.
Solution Approach 2:
The calibration is performed preliminarily during the first scan operation after assembly or transportation. By conducting calibration before actual scanning tasks, the system prepares the image sensor positioning in advance, ensuring accuracy for subsequent scanning operations without requiring separate manual calibration steps.
2Adaptability or versatility
If image sensors are arranged on a movable fixture to scan large objects, then scanning capability is improved, but reliability deteriorates due to stress-induced movements
Solution Approach 1:
The system continuously monitors the relative position of image sensors by correlating overlapping image regions during scanning. This feedback mechanism detects any displacement caused by stress or motor variations and enables real-time compensation, maintaining reliable image sensor positioning despite the movable fixture configuration necessary for large object scanning.
3Speed
If motor-operated rolls are used to move the medium past the fixture, then scanning speed is improved, but measurement precision deteriorates due to motor speed uncertainties
Solution Approach 1:
The correlation-based displacement detection provides continuous feedback on the actual relative positioning of image sensors during motor-driven scanning. This enables the system to compensate for motor speed uncertainties and maintain accurate scan line positioning even at high scanning speeds, as the feedback mechanism detects and corrects positioning deviations in real-time.
Data Source
AI summary
Disclosed is a method of processing image signals from a first and a second image sensor, both of a document scanner unit, where the first image sensor provides a first image, and the second image sensor provides a second image. The first and the second image are two-dimensional images wherein said first and second image are recorded at respective areas of a scanned medium, where a portion of the respective areas is recorded also by the other of the respective image sensors. Thereby image data from overlapping and non-overlapping areas are present in the first and the second image. The method comprises: correlating the first image with the second image, creating a correlation image and processing the correlation image to determine a displacement between the first and the second image. Consequently, a versatile calibration method is provided that can determine a displacement between the first and the second image in two dimensions.