Amplifier Gain Calibration for White Level Accuracy
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Solution Overview
Problem
Existing image scanning devices face challenges in quickly and accurately calibrating the white level without negatively impacting black level calibration, requiring a method that converges rapidly to target levels while being compatible with black level calibration techniques.
Innovation Solution
A method and circuit that determines a high white level for pixel data output, applies gain adjustments to the amplifier to correct errors between the target and high white levels, using iterative and proportional corrections to ensure accurate and rapid convergence, while being compatible with black level calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a white reference region is scanned to determine white level codes and calibrate the white level, then the white level calibration accuracy is improved, but the calibration time increases because only a few scan lines can be collected
Solution Approach 1:
The patent applies partial correction by adjusting the amplifier gain by only a portion of the calculated difference between measured and target white level codes. This prevents overcorrection and allows stable convergence within a limited number of scan lines, thereby achieving accurate calibration without requiring excessive calibration time
Solution Approach 2:
The patent implements feedback by continuously measuring the white level codes from scanned reference regions, comparing them to target values, and iteratively adjusting the amplifier gain based on the error signal. This closed-loop feedback mechanism enables accurate calibration to be achieved rapidly through progressive convergence
2Measurement precision
If the amplifier gain is adjusted to calibrate the white level, then the white level calibration is improved, but the black level calibration may be negatively impacted
Solution Approach 1:
The patent applies partial correction by adjusting the amplifier gain by only a portion of the calculated difference between measured and target white level codes. This conservative adjustment prevents overcorrection that could destabilize the black level calibration, allowing both white and black level calibrations to coexist stably
Solution Approach 2:
The patent changes the amplifier gain parameter iteratively based on white level measurement errors. By controlling the magnitude of gain changes and applying them progressively across multiple scan lines, the system maintains stability in the black level calibration while achieving accurate white level calibration
Data Source
AI summary
Calibrating a white level in an image scanning device. A target white level is accessed. A high white level is determined for pixel data output by an amplifier. A gain adjustment to the amplifier is determined to correct a portion of an error between the target white level and the high white level. The gain adjustment is applied to the amplifier.