Scanner Streak Compensation via Dual Calibration Targets
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Solution Overview
Problem
Traditional image scanning methods fail to effectively compensate for streaks caused by contamination on the scanner lens, leading to degraded scan quality due to the inability to measure weaker light signals from contaminants during Photo-Response Non-Uniformity (PRNU) compensation using a white calibration target.
Innovation Solution
The implementation of a scanning system that generates a first calibration target data set and a second calibration target data set, where the second calibration target scan represents detected streaks, allowing for recalibration of the scanning device to compensate for streaks by determining pixel values and adding them to the first calibration target data set.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PRNU compensation is performed using a white calibration target, then photoresponse uniformity is improved, but streaks caused by lens contamination remain uncompensated
Solution Approach 1:
The patent divides the calibration process into two separate calibration targets: a white calibration target for PRNU compensation and a second calibration target (with gray levels or black regions) for detecting and compensating lens contamination streaks. This segmentation allows each calibration target to address specific issues without interference, resolving the contradiction between photoresponse uniformity and scan quality.
Solution Approach 2:
The patent performs PRNU compensation using the white calibration target before scanning the second calibration target to detect streaks. By establishing the photoresponse uniformity first, the system creates a baseline that allows subsequent streak detection to focus specifically on contamination artifacts, enabling both compensation goals to be achieved sequentially.
2Device complexity
If a single calibration target is used for PRNU compensation, then the calibration process is simple, but streaks from lens contamination cannot be detected
Solution Approach 1:
The patent segments the calibration function into two distinct calibration targets with different purposes: the first white calibration target handles PRNU compensation, while the second calibration target (containing gray levels or black regions) is specifically designed for streak detection. This segmentation enables streak detection without significantly increasing overall system complexity.
Solution Approach 2:
The second calibration target incorporates specific local features (gray level regions or black regions with known reflectance properties) that are optimized for detecting streaks caused by lens contamination. These localized features provide the necessary contrast and measurement capability for streak detection without requiring complete redesign of the entire calibration system.
3Loss of time
If the white calibration target is used for both PRNU and streak compensation, then the calibration time is reduced, but streak compensation accuracy deteriorates
Solution Approach 1:
The patent segments the calibration functionality across two targets, allowing the white calibration target to be optimized purely for PRNU compensation while the second target is optimized for streak detection. This segmentation prevents the compromise that would occur if a single target had to serve both functions, maintaining high accuracy in both compensation areas.
Solution Approach 2:
The patent performs PRNU compensation as a preliminary step using the white calibration target, then proceeds to streak detection using the second calibration target. This sequential approach ensures that each measurement is performed under optimal conditions without time pressure, maintaining high accuracy while completing both calibration tasks.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances scan quality by accurately compensating for streaks caused by contamination, improving the accuracy of scanned images by recalibrating the scanning device using both calibration target data sets.
Implementation Method 1
light reflected from a printed image is focused through an optics system onto arrays of photosensitive devices
Data Source
AI summary
Example implementations relate to streak compensation. Some examples may calibrate an initial gain for data from an optical element based on a scan of a first calibration target, obtain an image of a second calibration target from the optical element using the calibrated initial gain, and detect at least one streak in the image of the second calibration target. Some examples may also record data representing the at least one detected streak and may calibrate a final gain for the optical element based on the initial gain and the data representing the at least one detected streak.