Pixel Circuit Switching and Capacitor Layout for HDR Image Sensors
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Solution Overview
Problem
Current active-pixel sensors (APS) in image sensors, such as CMOS image sensors, face challenges in capturing high dynamic range images effectively, particularly in varying illumination conditions, which limits their ability to capture detailed information across a wide range of light intensities.
Innovation Solution
The implementation of a pixel structure with capacitors and switches that operate in different modes to accumulate and transfer charges, allowing for the generation of transfer and auxiliary voltages, enabling the storage of additional light information in capacitors during integration periods and efficient readout operations, thereby enhancing the dynamic range of captured images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional active-pixel sensor structures are used, then the device complexity is low, but the dynamic range capability is limited
Solution Approach 1:
The pixel circuit is divided into multiple operational modes (first mode and second mode) with different charge accumulation paths. In the first mode, charges are accumulated in a first capacitor through a first switch, while in the second mode, charges are accumulated in a second capacitor through a second switch. This segmentation allows the sensor to capture both bright and dark regions effectively, expanding the dynamic range without requiring a completely new sensor architecture.
Solution Approach 2:
The patent implements dynamic switching between different charge accumulation modes based on illumination conditions. The circuit can adaptively select which capacitor to charge and which switch to activate, allowing the sensor to dynamically adjust its response to varying light intensities. This dynamic operation enables the sensor to handle both low and high illumination conditions within the same pixel structure.
2Adaptability or versatility
If multiple capacitors and switches are added to enhance dynamic range, then the dynamic range capability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent designs the pixel circuit with multi-functional components that serve different purposes in different operational modes. The first and second capacitors, along with the first and second switches, are integrated into a unified circuit structure that can operate in multiple modes. This universal design approach allows the same physical components to fulfill different functional roles, reducing the need for additional specialized structures and thereby lowering manufacturing precision requirements.
Solution Approach 2:
The patent combines multiple charge accumulation functions into a single pixel circuit structure. Instead of using separate dedicated circuits for different dynamic range modes, the invention merges the charge accumulation, transfer, and readout functions into an integrated circuit that can switch between different operational states. This merging reduces the overall component count and simplifies the fabrication process while maintaining enhanced dynamic range capability.
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 allows for the capture of high dynamic range images by effectively managing charge accumulation and readout, improving the sensor's ability to handle both low and high illumination conditions, resulting in enhanced image quality and increased detectable distance in time-of-flight applications.
Implementation Method 1
each pixel containing a photodetector and an active amplifier
Data Source
AI summary
A circuit is provided and includes first to second switching units, a sensing unit, and first to second capacitive units. The first switching unit and the second switching unit are alternately turned on in response to, respectively, a first control signal and a second control signal that have different voltage levels. First terminals of the first and second switching units are coupled to each other. A sensing unit generates a sensing voltage, in response to light, at the first terminals of the first and second switching units. The first capacitive unit generates a first voltage, in response to the sensing voltage, at a second terminal of the first switching unit. The second capacitive unit generates a second voltage, in response to the generating the sensing voltage, at a second terminal of the second switching unit.