Bolometer Unit-Cell Integrity Checks Using Offset Circuits
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Solution Overview
Problem
Imaging systems, particularly thermal imagers, suffer from defective image detectors due to manufacturing variances or degradation, leading to inaccurate readouts and issues like dead or stuck pixels, which are critical in advanced applications.
Innovation Solution
Implementing offset circuits in a focal plane array to selectively superimpose fixed-pattern noise on output signals, allowing for robust detection of defective detectors by comparing modified output signals to expected ranges, and flagging non-functional detectors for remedial actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offset circuits are added to superimpose fixed-pattern noise on output signals, then detector integrity checking capability is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing expected output values for each detector element in a lookup table before actual operation. During integrity checking, the system simply retrieves pre-computed values and compares them with actual readings, avoiding complex real-time calculations. This allows the system to implement comprehensive detector monitoring without adding significant computational complexity to the operating system.
Solution Approach 2:
The patent introduces an intermediary component - a dedicated integrity checking module that acts as a mediator between the detector array and the main processing system. This module handles the complexity of integrity checking operations, including signal acquisition, processing, and comparison, while presenting a simplified interface to the rest of the system. The intermediary isolates the complexity of the checking mechanism from the main operational flow.
2Reliability
If comprehensive detector monitoring is implemented, then diagnostic coverage is improved, but processing time increases
Solution Approach 1:
The patent implements periodic action by conducting integrity checks at specific intervals rather than continuously monitoring all detectors at full resolution. The system can adjust the frequency and depth of checks based on operational conditions, performing rapid scans during normal operation and more thorough examinations when anomalies are detected. This periodic approach maintains high diagnostic coverage while minimizing average processing time.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing expected output values for each detector element in a lookup table before actual operation. During integrity checking, the system simply retrieves pre-computed values and compares them with actual readings, avoiding complex real-time calculations. This allows the system to implement comprehensive detector monitoring without adding significant computational complexity to the operating system.
3Manufacturing precision
If offset circuits are integrated into the focal plane array, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent applies universality by designing offset circuits with standardized, modular architectures that can be replicated across all detector elements using the same fabrication processes. The circuits are designed to perform multiple functions - normal signal processing and integrity checking - using the same hardware components. This multi-functionality reduces the need for specialized manufacturing steps while maintaining precise offset control across the array.
Solution Approach 2:
The patent implements parameter changes by making offset values programmable and adjustable after fabrication. Rather than requiring precise physical adjustment during manufacturing, the system allows offset parameters to be configured through digital control, enabling post-fabrication calibration. This approach decouples manufacturing precision requirements from operational precision, making the device easier to manufacture while maintaining high performance.
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
Ensures high diagnostic coverage for transient failures and accurate detection of defective detectors, enabling quick entry into a safe state for mission-critical systems.
Implementation Method 1
Each of the infrared detectors is configured to provide an output signal in response to externally received thermal radiation
Data Source
AI summary
Techniques to test infrared detectors are disclosed. In one example, a focal plane array for an imaging system includes a plurality of infrared detectors arranged in a plurality of rows and columns where each of the infrared detectors is configured to provide an output signal in response to externally received thermal radiation associated with a scene. A plurality of offset circuits of the imaging system may be electrically coupled to the focal plane array and configured to selectively superimpose fixed-pattern noise on the output signals to provide modified output signals. A readout integrated circuit of the imaging system may be configured to provide the modified output signals for processing to test an integrity of the infrared detectors. Modified output signals that are outside an expected output range based on the thermal radiation and known offset may be determined defective. Related methods, devices, and systems are also provided.