Adaptive ADC Readout Circuitry for Image Sensor Noise Mitigation
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Solution Overview
Problem
Conventional image sensors face challenges in mitigating column fixed pattern noise (CFPN) without the use of column gain amplifier circuitry, which is costly and inefficient, especially in miniaturized and low-power image sensing applications.
Innovation Solution
The implementation of adaptive analog-to-digital converter (ADC) readout circuitry that includes a differential amplifier and feedback path, capable of accommodating varying gain levels based on detected lighting conditions, allowing for image sensor data processing independent of column gain amplification, and utilizing a ramp signal and control signal to configure loop gains for effective noise mitigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If column gain amplifier circuitry is used to mitigate CFPN, then noise reduction effectiveness is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the column gain amplifier from the signal path by implementing ADC circuitry that performs analog-to-digital conversion directly at the pixel level, removing the need for subsequent column-level gain amplification while maintaining CFPN mitigation capability
Solution Approach 2:
The patent uses multiple copies of the same ADC circuitry distributed across different columns, where each ADC independently converts its column's signal, replacing the need for a centralized column gain amplifier with distributed conversion units
2Measurement precision
If column gain amplifier circuitry is used to mitigate CFPN, then noise reduction effectiveness is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive column gain amplifier circuitry with simpler, cheaper ADC circuitry that can be manufactured using standard CMOS processes, reducing manufacturing cost while achieving the same CFPN mitigation function
Solution Approach 2:
The ADC circuitry performs multiple functions including signal conversion, gain control, and CFPN mitigation in a single integrated unit, eliminating the need for separate column gain amplifier components and reducing overall manufacturing complexity
3Measurement precision
If column gain amplifier circuitry is used to mitigate CFPN, then noise reduction effectiveness is improved, but power consumption increases
Solution Approach 1:
The patent performs analog-to-digital conversion at the earliest possible stage in the signal chain, before signals are amplified and processed further, thereby eliminating the need for high-power column gain amplifiers that would otherwise be required to compensate for earlier conversion losses
Data Source
AI summary
Techniques and mechanisms to mitigate fixed pattern noise in image sensor data. In an embodiment, readout circuitry includes an adaptive analog-to-digital converter (ADC) comprising a differential amplifier and a feedback path coupled across the differential amplifier, where the ADC is to receive a ramp signal, a control signal associated with a transition rate of the ramp signal, and an analog signal generated by one or more pixels. In another embodiment, the feedback path and/or one or more other circuit elements coupled to the differential amplifier are configured, based on the control signal, to provide one of multiple loop gains with the differential amplifier. The ADC provides a digital output to determine a comparison based on the ramp signal and the analog signal.