Image Sensor Dual-Sampling Circuit for Wide Dynamic Range
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Solution Overview
Problem
Current image sensors face challenges in achieving a wide dynamic range, particularly in varying illumination conditions, which affects their ability to capture high-quality images with both high and low light levels effectively.
Innovation Solution
The image sensor employs a dual-sampling operation using multiple sampling capacitors and transistors controlled by specific gate signals, allowing for dual-conversion gain and adaptive sampling based on illumination levels, enabling efficient charge transfer and voltage generation across different lighting conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single sampling capacitor is used in conventional image sensors, then the device complexity is low, but the dynamic range is limited and cannot capture both high and low illumination levels effectively
Solution Approach 1:
The patent divides the single sampling capacitor into multiple sampling capacitors (first sampling capacitor and second sampling capacitor), each optimized for different illumination conditions. This segmentation allows the system to handle both high and low illumination levels effectively, expanding the dynamic range while managing complexity through specialized sub-components.
Solution Approach 2:
The patent implements dynamic switching between different sampling capacitors based on illumination levels. The control circuit dynamically selects which sampling capacitor to use, allowing the system to adapt its behavior to varying light conditions. This dynamic approach enables wide dynamic range performance without requiring a completely complex redesign for each illumination scenario.
2Adaptability or versatility
If multiple sampling capacitors are introduced to achieve wide dynamic range, then the illumination adaptability improves, but the transistor count and circuit complexity increase
Solution Approach 1:
The patent designs the pixel circuit with multi-functional transistors that serve multiple purposes. For example, certain transistors are involved in both charge transfer and sampling operations, and the same circuit structure handles both high and low illumination modes. This universality reduces the overall transistor count despite the presence of multiple sampling capacitors, mitigating the complexity increase.
Solution Approach 2:
The patent merges several functions into integrated circuit blocks. The multiple sampling capacitors are combined with shared control logic and readout circuits, creating a unified structure that handles both illumination conditions. This merging approach consolidates the complexity rather than distributing it across separate independent circuits.
3Measurement precision
If dual-sampling operation is implemented for different illumination levels, then image quality in varying light conditions improves, but the sampling time and processing complexity increase
Solution Approach 1:
The patent employs periodic switching between different sampling modes based on illumination conditions. Rather than continuously operating in both modes, the system periodically selects the appropriate sampling capacitor based on current light levels. This periodic action reduces the effective sampling time required while maintaining image quality across varying illumination conditions.
Solution Approach 2:
The patent performs preliminary determination of illumination levels to pre-select the appropriate sampling capacitor before actual sampling occurs. This preliminary action allows the system to quickly configure the optimal sampling path, avoiding time-consuming switching during the critical sampling phase and thereby reducing overall sampling time while maintaining precision.
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 solution enables the image sensor to achieve a high dynamic range, ensuring improved image quality by accurately capturing details in both high and low illumination scenarios, thereby enhancing the overall performance of the imaging device.
Implementation Method 1
a first transistor connected between a photodiode and a floating diffusion node
Data Source
AI summary
An operating method of an image sensor, including performing a first sampling operation corresponding to first illumination in at least one pixel; performing a second sampling operation corresponding to second illumination in the at least one pixel; and outputting a first pixel voltage corresponding to the first sampling operation, or outputting a second pixel voltage corresponding to the second sampling operation, in the at least one pixel.