Multipurpose Photodetector Circuit for Wide-Dynamic-Range Imaging
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Solution Overview
Problem
Image capture devices are optimized for specific modes of operation (low ambient light, bright ambient light, or high amplification), leading to competing requirements that limit their utility in varying conditions, as they are designed for unique operational modes, restricting their application range.
Innovation Solution
A system with a unit cell incorporating a Capacitor TransImpedance Amplifier (CTIA) subcircuit, Source Follower per Detector (SFD) subcircuit, and Direct Injection (DI) subcircuit, controlled by a column amplifier, allowing operation in multiple modes based on a control signal, enabling the same image sensor to perform various capture, read, and reset operations using the same components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If image capture devices are optimized for low ambient light scenes with low noise and low capacitance components, then sensitivity is improved, but the device cannot handle bright ambient light scenes requiring higher capacitance
Solution Approach 1:
The unit cell is designed to perform multiple functions by integrating three different subcircuits (CTIA, SFD, and DI) that can be selectively activated. Each subcircuit is optimized for different operating conditions, allowing the same physical unit cell to adapt to low ambient light, bright ambient light, and high amplification scenarios without requiring separate dedicated hardware for each mode.
Solution Approach 2:
The system dynamically switches between different operational modes (CTIA, SFD, DI) based on controlling signals that respond to scene conditions. This dynamic reconfiguration allows the unit cell to adjust its characteristics in real-time, transitioning from low noise/low capacitance configuration to high capacitance configuration as needed, rather than being fixed in a single optimized state.
2Quantity of substance
If image capture devices are optimized for bright ambient light scenes with higher capacitance, then charge storage capability is improved, but sensitivity for low ambient light scenes deteriorates
Solution Approach 1:
The unit cell integrates multiple subcircuits including both high capacitance configurations (suitable for bright light) and low capacitance configurations (suitable for low light), allowing it to serve multiple functions. The same physical structure can store large charges when needed for bright scenes while maintaining low noise characteristics for sensitive low-light detection.
Solution Approach 2:
The system changes operational parameters (capacitance values, noise characteristics) by switching between different subcircuit configurations. When transitioning from bright light to low light scenarios, the unit cell reconfigures its electrical parameters through controlling signals, effectively adapting its charge storage capability and noise characteristics to match the current lighting conditions.
3Power
If image capture devices are optimized for high amplification, then signal amplification capability is improved, but performance in other modes deteriorates
Solution Approach 1:
The unit cell is designed as a universal structure that incorporates high amplification capability as one of its modes (through the appropriate subcircuit configuration) while also maintaining capability for standard amplification and direct injection modes. This allows the device to provide high amplification when needed without sacrificing operational flexibility for other scenarios.
Solution Approach 2:
The system dynamically selects the appropriate amplification level and mode based on scene requirements. The controlling signals enable real-time switching between high amplification mode and other operational modes, allowing the device to adapt its amplification capability rather than being permanently fixed in a high amplification state that would limit other operational possibilities.
4Reliability
If separate components are used for different operational modes, then performance in each mode is optimized, but device complexity increases
Solution Approach 1:
The patent merges three different subcircuits (CTIA, SFD, and DI) into a single integrated unit cell structure. Rather than using separate physical components for each operational mode, the design combines multiple functional circuits within one unit cell, allowing them to share common elements such as the photodetector and output interface while maintaining distinct operational pathways for each mode.
Solution Approach 2:
The unit cell serves as a universal structure that accommodates multiple subcircuits and operational modes within a single integrated component. This multi-functional design eliminates the need for separate dedicated hardware for each mode, reducing overall device complexity while maintaining the ability to optimize performance for different scenarios through selective activation of appropriate subcircuits.
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 allows a single image sensor to operate effectively across a wide range of applications, achieving a total dynamic range greater than 110 dB and enabling operation mode changes without affecting accumulated charge, thus preserving light intensity data.
Implementation Method 1
Image sensors used in image capture devices generally generate charge in proportion to light intensity received at that location
Data Source
AI summary
In certain embodiments, a system is provided for image capture that includes a unit cell that includes a Capacitor TransImpedance Amplifier (CTIA) subcircuit, a Source Follower per Detector (SFD) subcircuit, and a Direct Injection (DI) subcircuit. The unit cell may operate using one of the subcircuits selected in response to a control signal. A column amplifier may be coupled to the unit cell. The column amplifier may be operable to receive an intermediate signal from the unit cell and couple components of the column amplifier corresponding to the selected subcircuit in response to the control signal. The column amplifier may generate an output signal from the intermediate signal using the coupled components of the column amplifier.