Image Sensor ADC Offset Compensation Using Unexposed Pixels
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Solution Overview
Problem
Image capture devices face challenges in accurately compensating digital signals from image sensors, leading to suboptimal image quality due to variations in analog-to-digital converter performance and environmental factors.
Innovation Solution
A signal compensating method that involves calculating and applying offset values with higher resolution than the digital signals, using offset calculators and compensators in the image capture device, which are based on reference signals from unexposed image sensor pixels, to adjust the digital signals from exposed pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional digital signal compensation is used, then device complexity is reduced, but measurement precision and reliability deteriorate due to variations in ADC performance and environmental factors
Solution Approach 1:
The patent applies preliminary action by pre-calculating offset values for each ADC channel using unexposed pixels during the image capture process. These offset values are stored in offset registers before being used to compensate exposed pixel signals, eliminating the need for complex real-time calibration systems while maintaining high measurement precision.
Solution Approach 2:
The system uses unexposed pixels (which would otherwise be wasted) to generate reference signals for calculating ADC offset values. This self-service approach allows the image sensor to perform its own calibration without external equipment, improving signal accuracy without increasing device complexity.
2Measurement precision
If offset values with higher resolution than digital signals are used, then measurement precision improves, but loss of information increases due to higher bit number requirements
Solution Approach 1:
The patent applies local quality by using high-resolution offset values (e.g., 18-bit) only where needed for ADC compensation, while maintaining standard resolution for the rest of the image data processing chain. This targeted approach improves measurement precision at the ADC stage without unnecessarily increasing information storage requirements throughout the entire system.
Data Source
AI summary
The signal compensating method includes receiving sensing signals from an image sensor pixel array; converting the sensing signals into digital signals using a plurality of analog-to-digital converters, respectively; and compensating the digital signals using offset values corresponding to the plurality of analog-to-digital converters, respectively.