Image Sensor ADC Reference Amplification for Gain-Uncertain Signals
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Solution Overview
Problem
Conventional image sensors face inaccuracies in analog-to-digital conversion due to uncertain or inconsistent amplifier gains, which affect the conversion of amplified signals into digital signals.
Innovation Solution
The solution involves an analog-to-digital converter configuration where the reference voltage is amplified by the same amplifier that amplifies the input signal, allowing the converter to accurately determine the input signal value regardless of the amplifier gain, by using switches to select between the input signal and a correction voltage as the amplifier input, and directing the amplified output to either the comparator or the digital-to-analog converter as a reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional amplifiers are used for signal amplification prior to analog-to-digital conversion, then signal amplification is achieved, but amplifier gain uncertainties cause conversion inaccuracies
Solution Approach 1:
The patent implements a feedback mechanism where the amplifier output is fed back to the analog-to-digital converter, allowing the converter to automatically adjust for amplifier gain variations. The ADC receives both the amplified signal and feedback from the amplifier output, enabling real-time compensation for gain uncertainties without requiring external calibration.
Solution Approach 2:
The patent introduces an intermediary compensation signal that mediates between the amplifier and ADC. This compensation signal is generated based on the amplifier output and is used to correct the amplified signal before conversion, effectively decoupling the conversion accuracy from amplifier gain uncertainties.
2Measurement precision
If calibration procedures are implemented to correct amplifier gain uncertainties, then conversion accuracy is improved, but calibration time is increased
Solution Approach 1:
The system performs self-calibration by using its own internal signals and feedback mechanisms. The analog-to-digital converter automatically compensates for amplifier gain variations using feedback from the amplifier output, eliminating the need for external calibration equipment and procedures. This self-service approach maintains high conversion accuracy without requiring time-consuming calibration steps.
3Power
If multiple amplifier stages are used to maintain signal levels, then signal strength is maintained, but gain uncertainty errors accumulate
Solution Approach 1:
The patent extends the feedback mechanism to cover multiple amplifier stages by taking the final output of the amplifier chain as feedback to the ADC. This allows the converter to compensate for the cumulative gain of all amplifier stages simultaneously, preventing error accumulation even when multiple stages are used to maintain signal strength.
Data Source
AI summary
An image sensor may contain an array of imaging pixels arranged in rows and columns. Each column of imaging pixels may be coupled to a column line which is used to read out imaging signals from the pixels. The column line may be coupled to an analog-to-digital converter for converting analog imaging signals from the pixels to digital signals. An amplifier may be included to amplify the analog imaging signals before being converted by the analog-to-digital converter. However, amplifier gain uncertainties may lead to errors in the result of the analog-to-digital conversion when the analog imaging signals are amplified by an amplifier. To mitigate these types of errors, the reference voltage for a digital-to-analog converter in the analog-to-digital converter may also be amplified by the amplifier. By multiplying the reference voltage by the same amplifier gain as the imaging signals, uncertainties in the amplifier gain will not affect the results of the analog-to-digital conversion.