Image Sensor Pixels with Lateral Overflow Storage
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Solution Overview
Problem
Low-light image sensors face challenges in achieving high dynamic range and high frame rates due to increased noise levels and limited full-well capacity, which affects image quality and frame rate, especially in photon-limited conditions.
Innovation Solution
The implementation of a multi-stage lateral overflow integrating capacitor with additional in-pixel readout transistors and a spatial noise canceling methodology using gate-induced source leakage measurement and subtraction, allowing for sub-e-read noise and high dynamic range without slowing down frame rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If compensation methods are applied to low-light image sensors, then image quality is improved, but noise level increases significantly
Solution Approach 1:
The pixel is segmented into multiple independent photodetectors (first photodetector and second photodetector) within a single pixel unit. Each photodetector independently captures light signals, allowing the sensor to combine multiple low-light measurements to improve image quality while managing noise through spatial diversity rather than temporal stacking.
2Measurement precision
If increased exposure times are used to compensate for low light, then image quality is improved, but frame rate is reduced
Solution Approach 1:
By segmenting the pixel into multiple photodetectors that can operate simultaneously, the system captures multiple signals in parallel during the same exposure time. This allows for improved image quality through signal combination without extending the exposure duration, thereby maintaining high frame rates.
3Measurement precision
If sensor gain is increased to compensate for low light, then image quality is improved, but noise level increases significantly
Solution Approach 1:
The pixel is divided into multiple photodetectors that independently capture light signals. By combining signals from multiple photodetectors spatially, the system achieves signal averaging that improves image quality without requiring high sensor gain, thereby avoiding the noise amplification that would result from excessive gain application.
4Device complexity
If full-well capacity is limited in conventional pixels, then device complexity is reduced, but dynamic range is reduced
Solution Approach 1:
The pixel is segmented into multiple photodetectors within a single pixel unit. This segmentation effectively increases the full-well capacity of the pixel by distributing charge storage across multiple photodetectors, thereby extending the dynamic range without requiring complex multi-capacitor structures or additional overflow pathways.
5Adaptability or versatility
If multi-stage lateral overflow capacitors are implemented, then dynamic range is improved, but device complexity increases
Solution Approach 1:
Instead of implementing complex multi-stage lateral overflow capacitors, the patent segments the pixel into multiple photodetectors. This simpler segmentation approach achieves similar dynamic range extension by distributing charge storage capacity across multiple photodetectors, avoiding the need for complex capacitor networks and associated control circuitry.
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 enables low read noise and high dynamic range imaging while maintaining high frame rates, effectively addressing the limitations of current technologies by increasing full-well capacity and reducing spatial noise.
Implementation Method 1
a photodetector in electrical communication with a floating diffusion capacitor via a transfer gate
Data Source
AI summary
An image sensor includes sensing pixels, each comprising a photodetector in electrical communication with a floating diffusion capacitor via a transfer gate, and a lateral overflow storage capacitor coupled to the floating diffusion capacitor via a lateral overflow control gate. A first readout circuit circuitry located between the transfer gate and the lateral overflow control gate comprises a first amplifier. A second readout circuitry, located opposite the lateral overflow control gate from the first readout circuitry, comprises a second amplifier. Following image integration, charge stored on the floating diffusion capacitor is readout using the first readout circuitry and charge stored on the lateral overflow storage capacitor is readout using the second readout circuitry. In a second readout, charge stored on the photodetector is readout using the first readout circuitry with a first amplification applied and charge stored on the photodetector is readout with a second, different amplification applied.