Switched Capacitor Filter Pre-Charging for SNR
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Solution Overview
Problem
Current Solid State Area Array Imaging Devices (SSAAIDs) face challenges in providing acceptable images in both low and high light conditions due to limited dynamic range and signal-to-noise ratio (SNR) in their integration circuits, with switched capacitor filter circuits not optimally addressing these issues.
Innovation Solution
A new operating method for switched capacitor filter integration circuits that involves pre-charging the final filter capacitor with the full voltage gain value, combining integration and filter capacitors for the first subframe, and adjusting subframe timing to maintain effective well capacity and improve SNR, without requiring additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If switched capacitor filter circuits are used to increase effective well capacity, then the integration capacitor can be larger than the detector area allows, but the signal-to-noise ratio and gain flexibility are not optimal
Solution Approach 1:
The patent applies preliminary action by pre-charging the final filter capacitor with the full voltage gain value before the main integration process. This is achieved by running a first subframe with integration and filter capacitors combined as one larger integration capacitor, which pre-sets the sum capacitor to close to its final value, thereby improving signal-to-noise ratio while maintaining the increased well capacity benefit
Solution Approach 2:
The patent implements dynamics by using a more complex timing pattern that dynamically switches between different capacitor configurations. The circuit transitions from combining integration and filter capacitors in the first subframe to the conventional switched capacitor filter timing in subsequent subframes, allowing optimal performance across different operating conditions
2Adaptability or versatility
If prior art uses shorter integration times for better high light performance, then saturation is reduced, but sensitivity decreases and low light level conditions cannot be captured
Solution Approach 1:
The patent applies segmentation by dividing the integration process into multiple subframes with different timing patterns. The first subframe uses a longer integration time optimized for low light sensitivity, while subsequent subframes use the switched capacitor filter timing optimized for high light performance, allowing the system to capture both low and high light level conditions effectively
Solution Approach 2:
The patent implements multi-functionality by designing the switched capacitor filter circuit to perform both low light integration and high light filtering operations. The same circuit infrastructure supports different operating modes through timing control, making it universally applicable to both low light level detection and high light level saturation prevention
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 method enhances the signal-to-noise ratio and gain flexibility, suppressing readout noise while maintaining the advantage of larger effective well capacity, even with fewer subframes, and provides better performance compared to prior art methods.
Implementation Method 1
Each pixel of an SSAAID generates and holds an amount of charge proportionate to the intensity of light incident thereon and the length of time that light was allowed to fall on the pixel using an integration circuit
Implementation Method 2
The charge handling capacity of such a circuit is determined by voltage, integration time, and capacitance of its capacitor(s)
Data Source
AI summary
A method of operating switched capacitor filter integration circuits by pre-charging a final filter capacitor thereof with the final full voltage gain value during a first subframe to obtain an enhanced signal to noise ratio without changes to the circuit or components thereof.