Split-Gate Conditional-Reset Image Sensor Pixel Architecture
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Solution Overview
Problem
Current image sensors face challenges in efficiently converting pixel signals to digital data while minimizing noise and maintaining dynamic range, particularly in low-light conditions, due to limitations in sampling thresholds and reset mechanisms.
Innovation Solution
The implementation of a multi-bit sampling architecture with conditional reset and progressive read-out pixels, which allows for non-destructive sampling and correlated double sampling, enabling efficient conversion of pixel signals to digital data by dissociating reset thresholds from sample generation and using shared floating diffusion structures for decimation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional single-bit sampling architecture is used, then the device complexity is low, but the signal-to-noise ratio is insufficient and dynamic range is limited
Solution Approach 1:
The sampling architecture is segmented into multiple bits, where each bit represents a different threshold level. This multi-bit segmentation allows for more precise measurement of the pixel signal while maintaining a relatively simple overall structure through systematic organization of the sampling components.
2Adaptability or versatility
If a reset mechanism with fixed threshold is used, then the device operation is simple, but the adaptability to different lighting conditions is poor
Solution Approach 1:
The reset threshold is made dynamic rather than fixed. The threshold can be adjusted based on the actual lighting conditions and signal levels, allowing the sensor to adapt to different environments. This is achieved through control circuitry that modifies the reset threshold voltage according to the detected signal characteristics.
3Measurement precision
If correlated double sampling is implemented, then the noise reduction is improved, but the sampling time and power consumption increase
Solution Approach 1:
The correlated double sampling process is implemented through periodic alternating phases: a first sampling phase captures the reset level, and a second sampling phase captures the signal level. By periodically switching between these two sampling modes and subtracting the reset sample from the signal sample, noise is reduced while the total sampling time is managed through efficient phase alternation.
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 enhances signal-to-noise ratio, reduces power consumption, and allows for flexible resolution modes, improving the overall performance of image sensors in various lighting conditions.
Implementation Method 1
a photodetector configured to convert photons incident upon the photodetector into electric charge
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
In a pixel array within an integrated-circuit image sensor, a pixel (870) includes a photodetector (260) and floating diffusion (262) formed within a substrate. First (881) and second (883) gate elements are disposed adjacent one another over a region (885) of the substrate between the photodetector and the floating diffusion and coupled respectively to a row line (TGr) that extends in a row direction within the pixel array and a column line (TGc) that extends in a column direction within the pixel array.