Image Sensor Pixel Architecture for High Dynamic Range and Global Shutter
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Solution Overview
Problem
Existing image sensor technologies face limitations in simultaneously achieving high dynamic range and global shutter modes, as well as variable sensitivity, due to constraints in charge handling capacity and operational modes.
Innovation Solution
A pixel architecture with multiple capacitance nodes and independent readout paths allows for selective connection and disconnection of additional capacitance to the photosensor, enabling variable sensitivity and high dynamic range modes, while also supporting global shutter operation by synchronizing the integration and readout phases across all pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an extra capacitor is added in parallel to increase charge handling capacity, then the dynamic range is improved, but the device complexity increases
Solution Approach 1:
The patent combines the integration capacitor and storage capacitor into a single physical capacitor structure that can function as both integration and storage capacitor through selective connection via transistors. This merging approach increases charge handling capacity without proportionally increasing device complexity, as the same hardware component serves multiple functions depending on its connection state.
2Adaptability or versatility
If a select transistor is added to enable variable sensitivity mode, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The select transistor M5304 serves multiple functions: it enables variable sensitivity mode by connecting or disconnecting the storage capacitor, and also enables global shutter mode by controlling the timing of charge transfer. This multi-functionality approach increases adaptability without proportionally increasing device complexity, as a single transistor component handles multiple operational requirements.
3Measurement precision
If the readout time is increased to read the sensor plane, then the measurement precision is improved, but motion distortion increases
Solution Approach 1:
The global shutter mechanism uses a storage capacitor to preliminarily store the integrated charge from all pixels simultaneously at the end of the integration period. This preliminary storage action freezes the image data before readout begins, allowing the subsequent readout process to take place without affecting the captured image data, thus eliminating motion distortion during the extended readout period.
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 architecture enhances charge handling capacity, allows for multiple operating modes, and reduces motion distortion by enabling simultaneous high sensitivity and high full well operations, along with global shutter functionality, thereby improving image quality and handling various illumination conditions effectively.
Implementation Method 1
a photodiode PD 101 converts received radiation into a charge
Data Source
AI summary
The present invention concerns an image sensor having a plurality of pixels each including a photosensor, a first node having a first capacitance connected to the photosensor, a second node having a second capacitance and selectively connected to the photosensor, and reading circuitry operable to read independently a first voltage value stored at the first node and a second voltage value stored at the second node.