Photodetector Array Readout Using Matched Dark Current Subsets
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Solution Overview
Problem
Photodetector arrays, particularly those using quantum-dot graphene field-effect transistors (QD GFETs), face challenges in achieving uniform dark current levels across individual photodetectors, leading to variations in resistance and signal processing complexities, which hinder efficient image acquisition and processing.
Innovation Solution
The approach involves identifying and grouping photodetectors into subsets based on predetermined dark current components, ensuring each subset has a combined dark current level that is substantially the same, allowing for efficient signal readout and amplification by matching the combined dark current component to a predefined readout circuit offset level, and subsequently subtracting it from the photodetector output signals to isolate the image component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If individual photodetectors are used with varying dark current levels, then the array can capture image signals, but the variations in dark current lead to resistance variations and signal processing complexities
Solution Approach 1:
The photodetector array is divided into multiple subsets, where each subset contains photodetectors with matched combined dark current levels. This segmentation allows the readout circuit to process each subset independently with simplified signal processing, while still capturing the complete image through combination of subset signals.
Solution Approach 2:
The invention changes the parameter of dark current by grouping photodetectors into subsets with matched combined dark current levels. This parameter matching eliminates resistance variations and simplifies signal processing requirements, directly resolving the technical contradiction between image acquisition efficiency and signal processing complexity.
2Measurement precision
If photodetectors with non-uniform dark current are readout individually, then each photodetector signal can be processed, but programmable gain stages are required increasing circuit complexity
Solution Approach 1:
Multiple photodetectors are merged into subsets where their combined dark current levels are matched. This merging eliminates the need for individual programmable gain stages for each photodetector, as the combined signals from each subset can be processed with uniform gain settings, thereby reducing readout circuit complexity while maintaining signal readout accuracy.
3Ease of operation
If dark current variations are not suppressed, then the readout circuit can operate with simple settings, but the signal-to-noise ratio deteriorates and dynamic range management becomes difficult
Solution Approach 1:
The photodetectors are pre-grouped into subsets with matched combined dark current levels before the actual imaging process. This preliminary action of dark current matching ensures that when the readout circuit operates with simple uniform settings, the signal-to-noise ratio is optimized and dynamic range management is facilitated, resolving the contradiction between operational simplicity and signal quality.
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 enables effective suppression of dark current variations, allowing for better signal-to-noise ratio and dynamic range management in readout electronics, facilitating efficient image acquisition and processing with reduced need for programmable gain stages and improved image quality.
Implementation Method 1
each photodetector of the array configured to provide a photodetector output signal comprising the dark current component and an image component on exposure to incident electromagnetic radiation from a target scene
Data Source
AI summary
An apparatus comprising a processor and memory including computer program code, the memory and computer program code configured to, with the processor, enable the apparatus at least to: based on a predetermined dark current component for each photodetector in an array of photodetectors, identify a plurality of subsets of photodetectors from the array for signal readout and amplification by a readout circuit, each photodetector of the array configured to provide a photodetector output signal comprising the dark current component and an image component on exposure to incident electromagnetic radiation from a target scene, wherein each subset of photodetectors is identified such that the combined dark current component of the constituent photodetector output signals for each subset is substantially the same; and provide the identified plurality of subsets for use in signal readout and amplification by the readout circuit.